SURFACTANT MODIFIED ZEOLITE Y AS A SORBENT FOR SOME
CHROMIUM AND ARSENIC SPECIES IN WATER
NIK AHMAD NIZAM NIK MALEK
A thesis submitted in fulfillment of the
requirements for the award of the degree of
Master of Science (Chemistry)
Faculty of Science
Universiti Teknologi Malaysia
JANUARY 2007
iii
To my beloved mother, father, brothers, sisters and my bestfriend
iv
ACKNOWLEDGEMENT
In the name of Allah the Almighty, thanks to Him for giving me the
opportunity and will to finish this research and to complete this thesis. I would like
to express my sincere appreciation and gratitude to my research supervisor, Prof Dr
Alias Mohd Yusof for his knowledge, acquaintance, guidance, supervision, critics,
evaluation, encouragement, and for supporting me throughout the undertaking of this
research. I am also very thankful to my research team friends, especially, to Mr
Mohamad Adil, Tan See Hua, Lee Kian Keat and Chia Chai Har for giving me the
motivation, knowledge, assistance, critics, information, opinion and for their kind
contribution for helping me to finish my research.
A thousand thanks also to all of the staffs in chemistry department, faculty of
science for helping me during this research, particularly, the lab assistants. Not
forgetting my lovely bestfriend, Ms Nor Suriani Sani for the motivation, support,
encouragement, friendship, advice and understanding. I greatly appreciate it.
I want to extend my utmost gratitude and appreciation to my parents, family,
fellow friends and those who provided assistance in this research either intentionally
or unintentionally at various conditions and occasions during the progress of this
research and the completion of this thesis. All of their supports towards the
completion of this thesis will be reciprocated by Allah the Almighty. Without their
supports and contributions, this thesis would not have been the same as presented
here. Thank you very much.
v
ABSTRACT
The removal of some chromium and arsenic species from water by the
surfactant-modified zeolite Y (SMZY) and unmodified zeolite Y was studied.
Zeolite NaY was successfully synthesized from rice husk ash via seeding method
involving the preparation of two separate gel formations. The synthesized and
commercial zeolite NaY were characterized with XRD, FTIR, surface area and
elemental analysis. The total cation exchange capacity (CEC) and external cation
exchange capacity (ECEC) for the synthesis was higher than the commercial one due
to the lower ratio of silica to alumina for the synthesized than the commercial zeolite
Y. The zeolite NaY was subsequently modified with hexadecyltrimethyl ammonium
(HDTMA) at the amount equal of 50%, 100% and 200% of ECEC of the zeolite. The
study of Cr(III) removal showed the synthesized zeolite NaY effectively removed
Cr(III) than the commercial one. The equilibrium sorption data fitted the Langmuir
and Freundlich isotherm models and the kinetic study was followed the pseudo
second order model. The slight decrease of the Cr(III) removal capacity for SMZY
indicated that the sorbed cationic surfactant blocked sorption sites for Cr(III). While
the unmodified zeolite had little affinity for the Cr(VI) and As(V) species, the
SMZY showed significant removal of both species. The adsorption equilibrium data
are best fitted to the Langmuir model. The removal of Cr(VI) was highest when the
synthesized zeolite NaY was modified such that HDTMA achieved 100% of its
ECEC. The SMZY-synthesis showed an adsorption of As(V) capacity higher than
the SMZY-commercial. Because the As(III) exists form as neutral species in water,
the removal of As(III) from water between unmodified and SMZY showed only a
slight difference. The effects of different surfaces coverage of HDTMA-zeolite on
the sorption of these species were insignificant. The SMZY was proven to be useful
in removing cationic and anionic forms of arsenic and chromium in water
simultaneously compared to the unmodified zeolite Y since it has the affinity for
both cations and anions.
vi
ABSTRAK
Penyingkiran beberapa spesies kromium dan arsenik daripada air oleh zeolit
Y yang diubahsuai dengan surfaktan (SMZY) dan zeolit Y yang tidak diubahsuai
telah dikaji. Zeolit NaY telah berjaya disintesis daripada abu sekam padi melalui
kaedah pembenihan yang melibatkan penyediaan dua pembentukan gel yang
berasingan. Zeolit NaY yang disintesis dan zeolit komersil dicirikan dengan XRD,
FTIR, luas permukaan dan analisis unsur. Kapasiti penukaran kation (CEC) dan
kapasiti penukaran kation luaran (ECEC) bagi zeolit yang disintesis didapati lebih
tinggi daripada zeolit komersil disebabkan oleh nisbah silika kepada alumina bagi
zeolit yang disintesis lebih rendah berbanding zeolit Y komersil. Zeolit NaY
kemudiannya diubahsuai dengan heksadesiltrimetil ammonium (HDTMA) pada
amaun 50%, 100% dan 200% daripada ECEC zeolit tersebut. Kajian menunjukkan
penyingkiran Cr(III) oleh zeolit NaY yang disintesis adalah lebih berkesan
berbanding zeolit komersil. Data penjerapan keseimbangan berpadanan dengan
model isoterma Langmuir dan Freundlich manakala kajian kinetik mengikuti model
pseudo tertib kedua. Penurunan sedikit terhadap kapasiti penyingkiran Cr(III) bagi
SMZY menunjukkan surfaktan kationik yang dijerap menghalang tapak penjerapan
bagi Cr(III). Zeolit yang tidak diubahsuai mempunyai sedikit sahaja afiniti terhadap
Cr(VI) dan As(V) manakala SMZY menunjukkan penyingkiran yang ketara bagi
kedua-dua spesies. Data penjerapan keseimbangan berpadanan dengan model
Langmuir. Penyingkiran Cr(VI) adalah paling tinggi apabila zeolit NaY yang
disintesis diubahsuai dengan HDTMA yang memenuhi 100% daripada ECEC zeolit
tersebut. SMZY-sintesis menunjukkan kapasiti penjerapan As(V) lebih tinggi
berbanding SMZY-komersil. Oleh kerana As(III) terbentuk dalam air sebagai spesies
yang neutral, penyingkiran As(III) daripada air antara zeolit tidak diubahsuai dan
SMZY menunjukkan perbezaan yang sedikit sahaja. Kesan perbezaan litupan
permukaan bagi HDTMA-zeolit terhadap penjerapan spesies-spesies ini tidak terlalu
ketara. SMZY terbukti berguna dalam penyingkiran logam yang membentuk
kationik dan anionik dalam air secara serentak berbanding zeolit Y yang tidak
diubahsuai kerana ia mempunyai sifat afiniti terhadap kation dan anion.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
THESIS STATUS DECLARATION
SUPERVISOR’S DECLARATION
1
TITLE PAGE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xii
LIST OF FIGURES
xiv
LIST OF SYMBOLS
xviii
LIST OF ABBREVIATIONS
xix
LIST OF APPENDICES
xxi
INTRODUCTION
1
1.1 Introduction
1
1.2 Rice Husk Ash
2
1.3 Zeolite
4
1.3.1 Zeolite NaY
7
1.3.2
Synthesis of Zeolite NaY
10
1.3.2.1
15
Seeding Technique
viii
1.3.2.2
1.3.3
Ageing
16
Characterization
17
1.3.3.1 X-Ray Diffraction Technique
17
1.3.3.2
Infrared Spectroscopy
20
1.3.3.3
Elemental Analysis
24
1.3.3.4
Ion Exchange Capacity
25
1.4 Surfactant Modified Zeolite
28
1.5 Toxic Metals in Water
33
1.5.1
Chromium
36
1.5.2
Arsenic
38
1.6 Removal of Toxic Metals in Water
1.6.1
Adsorption Theory
1.7 Research Background and Objectives of the
41
43
45
Study
2
MATERIALS AND METHODS
47
2.1 Preparation of Rice Husk Ash
47
2.2 Characterization of Rice Husk Ash
48
2.2.1 X-Ray Diffraction Technique
48
2.2.2
Infrared Spectroscopy
48
2.2.3
Elemental Analysis
49
2.3 Synthesis of Zeolite NaY
50
2.4 Characterization of Zeolite NaY
52
2.4.1
Surface Area and Porosity
52
2.4.2
Elemental Analysis
53
2.4.2.1
Decomposition of Zeolite
Samples
53
2.4.2.2
Determination of Sodium
54
2.4.2.3
Determination of Aluminum
54
2.4.2.4
Determination of Loss on
Ignition and Percentage of Silica
2.4.3
Determination of Unit Cell
55
56
ix
2.4.4
Determination of Cation Exchange
57
Capacity
2.4.4.1
Total Cation Exchange Capacity
2.4.4.2
External Cation Exchange
Capacity
57
58
2.5 Preparation of Surfactant Modified Zeolite Y
59
2.6 Characterization of Surfactant Modified Zeolite Y
61
2.6.1
Elemental Analysis
61
2.6.2
Dispersion Behavior
63
2.6.3
Maximum Adsorption of HDTMA
63
2.7 Adsorption Studies
2.7.1
Adsorption of Cr(III)
64
2.7.1.1
Kinetic Study
65
2.7.1.2
Effect of Initial pH
65
2.7.1.3
Isotherm Study
66
2.7.1.4
Determination of Cr(III) by
FAAS
2.7.2
67
2.7.2.1
Effect of Initial pH
68
2.7.2.2
Isotherm Study
68
2.7.2.3
SMZY-Chromate Structure
2.7.2.4
69
Determination of Cr(VI) by UVVis Spectrophotometer
2.7.4
66
Adsorption of Cr(VI)
Study
2.7.3
64
69
Adsorption of As(V) and As(III):
Preliminary Study
70
Adsorption of As(V)
71
2.7.4.1
Effect of Initial pH
71
2.7.4.2
Isotherm Study
72
2.7.4.3
Determination of Arsenic by
FAAS
72
x
3
RESULTS AND DISCUSSION: SORBENTS
DEVELOPMENT
73
3.1 Rice Husk Ash as a Source of Silica
73
3.2 Synthesis of Zeolite NaY
75
3.2.1
X-ray Diffraction Technique
75
3.2.2
Infrared Spectroscopy
80
3.2.3
Elemental Analysis
83
3.2.4
Physicochemical Properties
86
3.3 Characterization of Surfactant Modified Zeolite Y
4
88
3.3.1
X-ray Diffraction Technique
88
3.3.2
Infrared Spectroscopy
90
3.3.3
Elemental Analysis
91
3.3.4
Surface Area and Porosity
94
3.3.5
Dispersion Behavior
95
3.3.6
Maximum Adsorption of HDTMA
98
RESULTS AND DISCUSSION: APPLICATION
OF SORBENTS
101
4.1 Removal of Cr(III)
101
4.1.1
Kinetic Study
101
4.1.2
Effect of Initial pH
107
4.1.3
Isotherm Study
109
4.2 Removal of Cr(VI)
113
4.2.1
Effect of Initial pH
113
4.2.2
Isotherm Study
116
4.2.3
SMZY-Chromate Structure Study
119
4.3 Removal of Arsenic
4.3.1
4.3.2
122
Preliminary study: Adsorption of Arsenate
and Arsenite
122
Removal of Arsenate
125
4.3.2.1
125
Effect of Initial pH
xi
4.3.2.2
5
Isotherm Study
127
CONCLUSIONS AND SUGGESTIONS
132
5.1 Conclusions
132
5.2 Suggestions
136
REFERENCES
137
Appendices A - I
148-198
xii
LIST OF TABLES
TABLE NO.
TITLE
PAGE
1.1
Element sources in the zeolites and their function
5
1.2
Composition ratio of synthesis Zeolite NaY
10
1.3
The assignments of the main infrared bands for zeolites
22
2.1
The abbreviation of the surfactant modified zeolite Y
60
2.2
Solutions for calibrating flame photometer
62
3.1
Chemical composition of rice husk ash
74
3.2
Zeolite NaY infrared assignments
81
3.3
IR assignments for commercial, synthesized zeolite NaY
and zeolite Y (SiO2/Al2O3 4.87)
82
3.4
Percentage amount of major elements contained in the
zeolite samples from the first approach
84
3.5
Percentage amount of major elements contained in
zeolite samples by XRF technique
84
3.6
The physicochemical properties of the synthesized (ZeoNaY-S) and commercial zeolite NaY (Zeo-NaY-C)
86
3.7
Peak lists of SMZY infrared spectrum
90
3.8
The content of Na2O in the SMZY and their parent
zeolite
91
3.9
Elemental data of the SMZY obtained from the CHNS
analyzer
93
3.10
Surface area and porosity of the SMZY and unmodified
zeolites
94
xiii
3.11
Fitted Langmuir parameters for sorption of HDTMA by
synthesized zeolite Y
99
4.1
Values of the pseudo second order model parameters for
the adsorption of Cr(III) by synthesized and commercial
zeolite NaY
107
4.2
Fitted Langmuir and Freundlich parameters for Cr(III)
sorption on SMZY and the unmodified synthesized and
commercial zeolite NaY
111
4.3
Fitted Langmuir parameters for sorption of Cr(VI) by
SMZY
117
4.4
Values of the adsorption of As(III) and As(V) by SMZY
and respective parent zeolite Y
123
4.5
Values of the Langmuir parameters for sorption of As(V)
by SMZY
129
xiv
LIST OF FIGURES
FIGURE NO.
1.1
TITLE
PAGE
The sodalite cages (truncated octahedral) connected on
the hexagonal faces in zeolite Y. The three types of
cation sites are shown.
8
1.2
Derivation of Bragg’s law for X-ray diffraction
18
1.3
The illustration of the X-ray powder diffraction method
19
1.4
The structure of hexadecyltrimethyl
bromide (HDTMA-Br)
29
1.5
ammonium
Schematic diagram of HDTMA micelle formation in
solution and admicelle formation on the zeolite surface
and the uptake substance onto surfactant modified
zeolite
31
1.6
The structure of the anion form of arsenate (a, b, c and
d) and the neutral form of arsenite (e) species.
39
3.1
The XRD diffractogram of RHA
73
3.2
Infrared spectrum of rice husk ash
74
3.3
The X-ray diffraction patterns of the product obtained
from the synthesis without ageing and seeding
technique (NA-NS-Zeo) and the product from the
synthesized zeolite Y with ageing but without seeding
technique (A-NS-Zeo)
76
The X-ray diffraction pattern of mixed synthesized
zeolite NaY (Zeo-NaY-S) via seeding and ageing
techniques match up with the sodium aluminum silicate
hydrate NaY (Na2Al2Si4.5O13.xH2O) pattern existed in
PDF
77
3.4
xv
3.5
The compilation of X-ray diffractograms of the
synthesized zeolite NaY
78
The X-ray diffraction pattern of the commercial zeolite
NaY
79
3.7
The infrared spectrum of Zeo-NaY-S
80
3.8
The infrared spectrum of Zeo-NaY-C
80
3.9
The illustration of infrared spectrum of zeolite Y (Si/Al
= 2.5) in the region from 1250 to 420 cm-1
81
The comparison of the infrared spectrum of synthesized
zeolite NaY (Zeo-NaY-S) and rice husk ash (RHA)
83
The XRD patterns of the surfactant modified zeolite Y
together with the parent zeolites
89
The comparison of the Na2O amount (mg/g) present in
the SMZY and respective unmodified zeolite
92
The comparison of the specific surface area (m2/g),
total pore volume (cc/g) and average pore size (Ǻ) for
SMZY and unmodified zeolite Y
95
Photographs show the distribution of SMZY and
unmodified zeolite NaY solid particles when added to
hexane-water mixture
96
Photographs showing the distribution of SMZY and
unmodified zeolite Y solid particles
97
The sorption isotherm plotted of HDTMA onto the
synthesized zeolite Y
98
The plotted of 1/qe against 1/Ce where qe is the
HDTMA adsorbed at equilibrium (mmol/kg) and Ce is
concentration of HDTMA at equilibrium (mmol/L).
99
Schematic diagram of the theoretical HDTMA
formation on the zeolite Y structure
100
Sorption kinetics graph for synthesized zeolite NaY
from two different initial concentrations of Cr(III)
102
Sorption kinetics graph for commercial zeolite NaY
with two different initial concentrations
102
3.6
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
3.18
4.1
4.2
xvi
4.3
4.4
4.5
Percentage of the Cr(III) removal by synthesized (ZeoNaY-S) and commercial zeolite NaY with [Cr(III)]initial
= 250 mg/L.
103
Percentage of the Cr(III) removal by synthesized (ZeoNaY-S) and commercial zeolite NaY with [Cr(III)]initial
= 500 mg/L.
104
The effect of pH on the Cr(III) removal by synthesized
and commercial zeolite NaY
108
The adsorption isotherm of Cr(III) sorption on SMZY
from the synthesized zeolite NaY together with the
unmodified synthesized zeolite NaY
109
The adsorption isotherm of Cr(III) sorption on SMZY
from the commercial zeolite NaY together with the
unmodified commercial zeolite NaY
110
The adsorption isotherm of Cr(III) sorption on
unmodified synthesized and commercial zeolite NaY
110
The Kf (Freundlich constant) values for the adsorption
of Cr(III) by SMZY and unmodified zeolite Y
112
4.10
Effect of pH solution on Cr(VI) removal by SMZY
114
4.11
Sorption of Cr(VI) by SMZY and unmodified
synthesized zeolite Y
116
Sorption of Cr(VI) by SMZY and unmodified
commercial zeolite Y
116
The comparison of the maximum adsorption (Qo)
calculated from the Langmuir isotherm model for the
sorption of Cr(VI) by SMZY
118
XRD patterns of the unmodified synthesized zeolite
NaY (Zeo-NaY-S), SMZY-100-S and after contacting
with chromate solution (SMZY-100-S-Chromate)
120
IR spectra of SMZY-100-S and SMZY-100-SChromate
120
IR spectra of unmodified synthesized zeolite NaY
(Zeo-NaY-S) and SMZY-100-S-Chromate
121
Schematic diagram for the mechanism of Cr(VI)
sorption by SMZY
121
4.6
4.7
4.8
4.9
4.12
4.13
4.14
4.15
4.16
4.17
xvii
4.18
4.19
4.20
4.21
4.22
4.23
4.24
Adsorption of As(III) by the SMZY and unmodified
zeolite NaY
123
The adsorption of As(V) species from aqueous solution
by SMZY and unmodified zeolite NaY
124
Effect of the initial pH solution in the removal of
As(V) by SMZY
125
As(V) sorption from aqueous solution by SMZY-50-S,
SMZY-50-C and respective parent zeolite NaY
128
As(V) sorption from aqueous solution by SMZY-100S, SMZY-100-C and respective parent zeolite NaY
128
As(V) sorption from aqueous solution by SMZY-200S, SMZY-200-C and respective parent zeolite NaY
129
Comparison of the maximum adsorption (Qo) value
calculated from the Langmuir isotherm model for the
As(V) sorption by each of the SMZY
130
xviii
LIST OF SYMBOLS
°C
-
Degree Celsius
Co
-
Initial concentration
Ce
-
Equilibrium concentration
cm
-
Centi meter
dm
-
Deci meter
g
-
Gram
kg
-
Kilo gram
kV
-
Kilo Volt
L
-
Liter
m
-
Meter
M
-
Molar
mA
-
Mili ampere
meq
-
Mili equivalent
mg
-
Mili gram
min
-
Minute
mL
-
Mili Liter
mm
-
Mili meter
mmol
-
Mili mol
N
-
Normal
nm
-
Nano meter
ppm
-
Part per million
ppb
-
Part per billion
Å
-
Angstrom
μg
-
Micro gram
μL
-
Micro Liter
xix
LIST OF ABBREVIATIONS
AAS
-
Atomic Absorption Spectroscopy
APHA
-
American Public Health Association
ASTM
-
American Society for Testing and Materials
ATP
-
Adenosine Tri-Phosphate
BET
-
Brunauer, Emmet, and Teller
BTEX
-
Benzene, Toluene, Ethylene and Xylene
CCA
-
Chromated Copper Arsenate
CEC
-
Cation Exchange Capacity
CHNS
-
Carbon Hydrogen Nitrogen Sulphur
CMC
-
Critical Micelle Concentration
CQ
-
Chloroquin
CRM
-
Certified Reference Materials
DDTMA
-
Decadecyltrimethyl Ammonium
DHA
-
Dehydroabietic Acid
ECEC
-
External Cation Exchange Capacity
EPA
-
Environmental Protection Agency
FAAS
-
Flame Atomic Absorption Spectroscopy
FAU
-
Faujasite
FTIR
-
Fourier Transform Infrared
HDTMA
-
Hexadecyltrimethyl Ammonium
ICDD
-
International Centre for Diffraction Data
ICPMS
-
Inductively Coupled Plasma Mass Spectrometry
IEC
-
Ion Exchange Capacity
IR
-
Infrared
LEDs
-
Light Emitting Diodes
xx
LOI
-
Loss on Ignition
LTA
-
Linde Type A
MCL
-
Maximum Contaminant Levels
MTDC
-
Malaysian Technology Development Corporation
NAA
-
Neutron Activation Analysis
NIOSH
-
National Institute for Occupational Safety and
Health
NMR
-
Nuclear Magnetic Resonance
ODTMA
-
Octadecyltrimethyl Ammonium
OTS
-
Octadecyltrichlorosilane
PCE
-
Perchloroethylene
PDF
-
Powder Diffraction File
PFC
-
Plug Flow Combustor
PTFE
-
Polytetrafluoroethylene
QC
-
Quality Control
R&D
-
Research and Development
RHA
-
Rice Husk Ash
SIRIM
-
Standards and Industrial Research Institute of
Malaysia
SMC
-
Surfactant Modified Clinoptilolite
SMZ
-
Surfactant Modified Zeolite
SMZY
-
Surfactant Modified Zeolite Y
TCE
-
Trichloro Ethylene
TDTMA
-
Tetradecyltrimethyl Ammonium
TEA
-
Tetraethyl Ammonium
TOC
-
Total Organic Carbon
UV-Vis
-
Ultra Violet-Visible
WHO
-
World Health Organization
XRD
-
X-Ray Diffraction
XRF
-
X-Ray Flourescence
xxi
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
Elemental analysis for the zeolite NaY
148
A-1
Analysis data for the determination of sodium
in the zeolite NaY samples by AAS
148
Analysis data for the determination of Al by
ICP-MS
149
Analysis data for the determination of loss on
ignition (LOI) and the percentage of silica
(%SiO2)
150
A-4
X-Ray Fluorescence (XRF) accuracy
150
B
Physicochemical Properties of the Zeolite NaY
151
B-1
Surface area and porosity
151
B-2
Determination of the unit cell
152
B-3
Determination of CEC and ECEC
153
C
Infrared spectra of SMZY matching with
respective parent zeolite
155
Determination of sodium in SMZY and
unmodified zeolite Y
158
Surface area and porosity of the surfactant
modified zeolite Y
159
Maximum adsorption of HDTMA on the
zeolite Y
160
Removal of Cr(III) study
161
A-2
A-3
D
E
F
G
xxii
G-1
Kinetic study of the Cr(III) uptake by the
synthesized and commercial zeolite NaY
161
G-2
Effect of the initial pH for the Cr(III) removal
164
G-3
Isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite NaY
168
H
Removal of Cr(VI) study
174
H-1
Effect of the initial pH solution on the removal
of Cr(VI) by SMZY
174
Isotherm study of the removal of Cr(VI) by
SMZY
180
I
Removal of arsenic study
192
I-1
Preliminary study of the As(III) and As(V)
adsorption by SMZY and unmodified zeolite Y
192
Effect of the initial pH solution on the removal
of As(V) by SMZY
193
H-2
I-2
I-3
Isotherm study of the As(V) sorption by
SMZY
195
J
Presented papers and expected publications
from this study
198
CHAPTER 1
INTRODUCTION
1.1
Introduction
Water is not only ubiquitous in nature, but is a necessary ingredient for all forms
of life. The human embryo is approximately 90 percent water, and adults are 65 to 70
percent water; the percentage of water then decreases in old age (McCaull and
Crossland, 1974). Water is essential for life and no person can live more than a few days
without it. There are many sources of water such as lakes, rivers, oceans, groundwater,
rain and streams. In reality, water is not pure in nature because approximately half of the
known chemical elements have been found dissolved in nature. A clean running stream,
even in its unpolluted state, contains a complex mixture of organic and inorganic
substances. Today, as the population expands and industry evolves, there are many
different disease-causing microorganisms and complex human health hazards that can be
related to the organic and inorganic substances i.e. toxic metals, dumped in the water in
mammoth quantities by our fast-changing technological civilization. Because of this
problem, the regulations and laws for standard limitation of contaminants in water have
become the main priority for the environment institutional in every country and world
organization to overcome the exceeding value of contaminants in water for the
protection of human health. To ensure that wastewater treatment process in industrial
facilities and the water purification process for drinking water comply with the
2
regulations, these processes require the best technology to reduce the amount of
contaminants. The method of treatment required for the removal of contaminants or their
reduction to acceptable limits, depends in part on the fineness of the material. Therefore,
the development of cost effective alternative sorbents material for treatment of
contaminants in water is needed.
There are many sorbent materials exist in this world either occurring naturally or
produced synthetically. Nowadays, alternative cost effective technologies or sorbents are
greatly required to overcome the exceeding value of contaminants in water. The
materials produced from natural materials that are available in large quantities or certain
waste products from industrial or agricultural operations may have the potential to be
used as inexpensive sorbents. One of the natural products that produced in abundance in
Malaysia is the rice husk which can be used as a source of silica for the preparation of
the zeolite; the material which has adsorption properties.
1.2
Rice Husk Ash as a Source of Silica
Rice husk ash is the natural sheath that forms on rice grains during their growth
and it has no commercial value. In Malaysia, rice husk is produced in abundance after
every paddy harvesting season and contributes to major agricultural waste. The husks
are eliminated by burning them in the field at high temperature leaving behind a white
blackish powder which is the constituents of silica. The presence of the silica ash causes
a number of problems to the environment that causes pollution and disposal problems
because of its nonbiodegradable property. Therefore, useful applications of the rice husk
are desirable to solve this problem. The major constituent of rice husk after complete
burning at high temperature is silica (SiO2) in amorphous structure which formed as
white powder and some amount of metallic impurities (Yalcin and Serinc, 2001).
3
The utilization of rice husk ash as an alternative source of silica towards the
synthesization of zeolites has been reported nearly 20 years ago by Bajpal and Rao
(1981). They have synthesized mordenite type zeolite using silica from rice husk ash.
Besides that, rice husk ash was also used as a source of silica in the preparation of
zeolite NaX (Dalal and Rao, 1985). Apart from that, zeolite Y was also successfully
synthesized and was readily patented in Malaysia by Halimaton Hamdan and Yeoh Ann
Keat (1993). There are two forms of silica; amorphous and crystalline. The amorphous
form of silica is active towards the synthesis of zeolite but the crystalline form is
inactive. The combustion of rice husk under controlled atmosphere and temperature less
than 800 oC will generate the amorphous silica in the form of white powder and this
silica ash which is transformed from the husk by complete burning constitutes 15 to 20%
of the total weight of the husk. Hence, it is appropriate to employ rice husk ash from
combustion of rice husk at temperature lower than 800 oC as a source of silica in the
synthesis of zeolite.
It is important and essential to characterize rice husk ash before using it to
synthesis zeolite because the successful synthesis of zeolite rely on the reactive source of
raw materials especially silica. The main characterization methods of rice husk ash
involves X-ray diffraction technique (XRD), Infrared spectroscopy (IR) and elemental
analysis. The XRD diffractogram will indicate the phase of material, either crystalline or
amorphous. Source of silica obtained from rice husk ash that will be used to synthesis
zeolite must be in the complete amorphous form. This form of silica will be featureless
in the XRD diffractogram and the appearance of diffused maximum at 2θ = 23º
(Halimaton Hamdan et al., 1997). The IR spectroscopy is also an imperative tool to
characterize rice husk because the spectrum of material can support the data from XRD.
The IR spectrum of amorphous silica is illustrated by the intense peaks at 1100, 800 and
470 cm-1 which are contributed from the asymmetric, symmetric and bending vibration
frequencies for Si-O-Si bonds respectively (Cross and Jones, 1969). The information
about the quantity of silica contained in the rice husk ash is crucial prior to synthesizing
of the zeolite because one of the factors affecting the production of zeolite is the amount
4
of raw material (Robson, 2001). Therefore, the percentage of silica enclosed in the rice
husk ash must be determined.
1.3
Zeolite
Zeolite is a crystalline material and its structure consists of hydrated
aluminosilicates of metals from group I and group II, in particular, sodium, potassium,
magnesium and calcium. Structurally the zeolites are framework aluminosilicates which
are based on an infinitely extending three-dimensional network of AlO4 and SiO4
tetrahedra linked to each other by sharing all of the oxygen. The structural formula of a
zeolite is represented by the crystalline unit cell as:
Mx/n[(AlO2)x(SiO2)y].wH2O
Where:
M
:
cation
n
:
valence cation
w
:
the number of water molecule
y/x
:
the ratio of the tetrahedral silica to alumina
portion [ ]
:
framework composition
The framework contains channels and interconnected voids which are occupied
by the cation and water molecules. Zeolites consist of SiO2, Al2O3, alkali cation, water
and other substances with varying functions from one another. Table 1.1 summarizes the
function of each element in zeolites. The cations are quite mobile and may usually be
exchanged to varying degrees by other cations. Intracrystalline “zeolitic” water in
zeolites can be removed continuously and reversibly.
5
The appropriate definition of zeolites by Smith (Breck and Flanigen, 1964) is:
“A zeolite is an aluminosilicate with a framework structure enclosing cavities
occupied by large ions and water molecules, both of which have considerable
freedom of movement permitting ion exchange and reversible dehydration.”
Table 1.1: Element sources in the zeolites and their function.
Source
Function (s)
SiO2
Primary building units of the framework
AlO2
Origin of the framework charge
OH-
Mineralizer, guest molecule
Alkali cation
Counter ion of framework charge
Water
Solvent, guest molecule
Organic directing agent
Counter ion of framework charge, guest molecule,
template
Zeolites are often termed as “molecular sieve” because the zeolitic pores are
microscopically small with approximately molecular size dimensions. The windows and
channels of a zeolite allow it to discriminate among guest molecules and cations on the
basis of size. Zeolites are divided into two main classes, namely, mineral such as
clinoptilolite, mordenite and garronite and the synthetic zeolite such as zeolite A, X and
Y. The zeolite molecular sieve has three major functions, which are as catalyst, ion
exchanger and adsorbent material. In view of the fact that silicon typically exists in a 4+
oxidation state, the silicon-oxygen tetrahedral is electrically neutral. However, in the
framework of zeolite, aluminum typically exists in the 3+ oxidation state so that
aluminum-oxygen tetrahedral form a centre that is deficient of one electron. Thus,
zeolite framework is typically anionic and charge-compensating cations populate the
pores to maintain electrical neutrality. These cations can participate in ion exchange
processes and will yield important properties for zeolites. When charge-compensating
cation are “soft” cations such as sodium, zeolites are excellent water softeners because
6
they can pick up the “hard” magnesium and calcium cations as well as toxic metals
cation in the water living behind the soft cation.
The fundamental properties and applications of molecular sieve zeolites involve
many scientific disciplines and cross many of the traditional boundaries. Fields involved
are inorganic and physical chemistry with emphasis on surface and colloid chemistry
and catalysis, biochemistry, the geological sciences of geochemistry, geology,
mineralogy and physics, including crystallography, spectroscopy and solid state physics
(Breck, 1971). One of the main applications of zeolites is ion-exchanger. The ionexchanger can be classified into organic and inorganic ion-exchanger. Resin is the
organic form ion-exchanger while zeolites are classified as the synthetic inorganic ion
exchanger. The major application of ion-exchanger is to remove toxic metals in the
purification of water. The cation exchange behaviour depend on the nature of the cation
species, the size of ion or complex cation, charge of ion or complex cation and type of
zeolite structure (Breck, 1964). Thus, zeolites are capable for the removal of the toxic
metals from water due to the ion exchange properties of zeolites.
Adsorption and ion exchange are the most common and effective processes for
removing ions discharged into the environment, with resins being the most important
group of ion exchange materials followed by zeolites. However, resins are expensive
and must be regenerated and activated carbon is generally less effective for most metals
and also requires regeneration. Therefore, alternative effective and economic sorbents
are needed. Many authors have studied the application of both synthetic and natural
zeolites as sorbents for the removal of metals cation from water. Some authors have
reported the applications of the synthetic zeolite in removing heavy metals, for instance,
Shevade and Robert (2004) used zeolite Y for arsenate removal from pollutant water,
Veronica Badillo-Almaraz et al. (2003) used zeolite X for the adsorption of Zn(II)
species from aqueous solution and the utilization of Zeolite NaY as an ion-exchanger for
Co(II) and Fe(II) by Kim and Keane (2000). Among the natural zeolite, clinoptilolite is
the naturally occurring zeolite that mostly used as an ion-exchanger and adsorption in
the purification of water as clinoptilolite is probably the most abundant zeolite found in
7
nature because of its wide geographic distribution and large size of deposits (Peric et al.,
2004). There are many papers reporting on the application of clinoptilolite as an
adsorbent for toxic metals including the removal of lead and cadmium (Maliou et al.,
1992), arsenate and arsenite (Elizalde-Gonzalez et al., 2001b) and copper, zinc, cobalt,
nickel and mercury (Blanchard et al., 1984). Therefore, zeolite is one of the promising
inorganic materials in removing toxic metals in the purification of water.
1.3.1
Zeolite NaY
Synthetic zeolite NaY is the synthesized zeolite Y of which sodium cation
neutralize the framework structure of aluminosilicate and this material is in the same
group with zeolite X. Both zeolites exhibit a structure similar to naturally occurring
faujasite types. The differences between these zeolites are due to the composition and
other physical properties brought about by the compositional differences. The Si, Al
contents of zeolite Y are similar to that of faujasite whereas zeolite X is much more
aluminous. Zeolite Y exhibits the FAU (faujasite) structure which has a 3-dimensional
pore structure with pores running perpendicular to each other in the x, y and z planes
similar to LTA, and is made of secondary building units 4, 6 and 6-6. The pore diameter
is large at 7.4Ǻ since the aperture is defined by a 12 member oxygen ring, and leads into
a larger cavity of diameter 12Ǻ. The cavity is surrounded by ten sodalite cages
(truncated octahedral) connected on their hexagonal faces as shown in Figure 1.1. The
unit cell is cubic (a = 24.7Ǻ) with Fd-3m symmetry. Zeolite Y has a void volume
fraction of 0.48, with a Si/Al ratio of 2.43 (Bhatia, 1990).
8
Truncated
octahedral
(sodalite cage)
Hexagonal
faces
12 member
oxygen ring
Site I
Site II
Figure 1.1
Site III
The truncated octahedral (sodalite cage) connected on the hexagonal
faces in zeolite Y. The three types of cation sites are shown.
The framework of both zeolite Y and X consists of a tetrahedral arrangement of
the truncated octahedral, i.e. the octahedral are joined to the octahedral faces by
hexagonal prisms (Figure 1.1). The truncated octahedral is referred to as the sodalite unit
or sodalite cage. The cations in the structure occupy three types of positions. These are
type I, type II and type III which are in the centres of the hexagonal prism, on the six
membered rings and on the walls of the channels, respectively. In the sodium form of a
typical zeolite Y there are 56 sodium ions per unit cell while in the zeolite X, 86 cations
per unit cell. These are distributed in the 3 different sites where for the zeolite Y, 16 in
site I, 32 in site II and 8 in site III while for the zeolite X, 16 in site I, 32 in site II and 38
in site III. A major difference between zeolite X and Y is the non-occupancy of the type
III sites for zeolite Y (Breck, 1964). Zeolites can be grouped into six categories
according to the number of O-atoms in their largest ring. The faujasite family including
zeolite Y are categorized into the 12-membered oxygen ring systems (Chen et al., 1994).
Zeolites in this group system are also known as large pore zeolites.
9
Zeolite Y was discovered by Breck in 1961 when his group of researchers found
that it should be possible to synthesize the zeolite X structure with silica/alumina ratios
as high as 4.7 but his trial resulted in the zeolite that have a significant change in
properties at a ratio above 3.0. Since zeolite X had been defined in reported patent as
having silica/alumina ratios between 2.0 and 3.0, the isostructural zeolite with ratios
above 3.0 and up to 6.0 were named and patented as zeolite Y (Robson and Occeli,
1988). The chemical formula for zeolite Y expressed in terms of moles of oxides may be
written as (Breck, 1964):
0.9 ± 0.2 Na2O : Al2O3 : w SiO2 ; x H2O
Here w is a value greater than 3 up to about 6 and x may be a value up to about 9.
Among the numerous synthetic zeolite, the widely used in many field is the
zeolite Y. One of the important applications of zeolites is as a cracking catalyst. Zeolite
Y being more stable at high temperature due to the higher Si/Al ratio than other
synthetic zeolites is useful as a catalyst for the cracking of petroleum. That is why
zeolite Y had taken the place of zeolite X in the 1960s as a catalyst (Smart and Moore,
1993). Besides that, zeolite Y has also been used as the ion exchanger in order to remove
heavy metals from water because of its high surface area, cation exchange capacity and
stability. Kim and Keane (2000) reported the study on the ion exchange of divalent
cobalt and iron by zeolite NaY. They concluded that sodium-based zeolite Y is effective
in removing divalent iron and cobalt from aqueous solutions over the concentration
range 0.005-0.05 mol dm-3. Oliveira et al. (2004) had studied the removal of the metallic
contaminants using magnetic-zeolite Y which is a physical composite of iron and zeolite
Y, as a way of applying magnetic property to separate metals from water.
10
1.3.2 Synthesis of Zeolite NaY
The factors affecting the synthesis of zeolite Y is comparable to the synthesis of
other synthetic zeolite. A few main parameters, conditions and materials related to the
synthesis of zeolite must be recognized and moreover it is of utmost importance to know
the source of the materials and technical grade materials to be assayed and analyzed for
impurities before the synthesis of zeolite (Robson, 2001). The nature of the starting
materials, overall chemical composition of the reactant mixtures, factors affecting
nucleation, reaction time and pressure as well as temperature are also important in
determining the zeolite species (Breck, 1974; Barrer, 1982). These variables and
parameters do not necessarily determine the products obtained in hydrothermal reactions
because the reactant mixtures may be heterogeneous and nucleation appears to be
kinetically rather than thermodynamically determined and controlled (Barrer, 1982).
Breck and Tonawanda (1964) in their reported patent explained more about the
condition on how to synthesis zeolite Y. One of the conditions that should be followed is
when an aqueous colloidal silica sol or reactive amorphous solid silica is employed as
the major source of silica, zeolite Y may be prepared by preparing an aqueous sodium
aluminosilicate mixture having a composition, expressed in terms of oxide-mole-ratio,
which falls within one of the ranges shown in Table 1.2. Crystallization occurs readily
between 80 and 125 ºC. The temperature affects the size of the crystals, with the larger
crystals forming at lower temperatures.
Table 1.2 : Composition ratio of synthesis Zeolite NaY
Ratio
Range 1
Range 2
Range 3
Na2O/SiO2
0.20 to 0.40
0.41 to 0.60
0.61 to 0.80
SiO2/Al2O3
10 to 40
10 to 30
7 to 30
H2O/Na2O
25 to 60
20 to 60
20 to 60
11
In the synthesis of zeolite, source and starting materials are very crucial to
determine the production of zeolite. Three major source materials that should be
emphasized are the source of water, aluminium and silica according to the term zeolites
as an aluminosilicate. Zeolite NaY can be synthesized by many sources of silica. Silica
can be obtained from sodium silicate, silica gels, silicic acid, aqueous colloidal silica
sols and reactive amorphous solid silica. The source of silica in the synthesis of zeolite
Y can also be obtained from the natural products, for instance, from the coal fly ash
(Zhao et al., 1997) and rice husk ash (Halimaton Hamdan et al., 1997; Zainab Ramli et
al., 1996). In this study, we have used rice husk ash as a source of silica to synthesize
the zeolite NaY. There are researchers that have successfully synthesized zeolite NaY
from rice husk ash whereby when the dried rice husk is burnt in controlled atmosphere
and temperature below 800 ºC it will produce rice husk ash containing over 90%
reactive amorphous silica (Halimaton Hamdan et al., 1997). According to the Breck and
Tonawanda (1964), one of the conditions for successfully synthesized zeolite NaY is the
reactive amorphous silica. In addition, the application for the production of zeolite NaY
in this study is as a sorbent material less pure silica materials from rice husk ash can be
employed in order to reduce the cost instead of using the costly commercial silica.
There are some problems that occur during the synthesis of zeolite NaY since the
source of material used in this synthesis is amorphous silica and also the formation of
zeolite NaY is metastable. It is possible to produce two or more crystalline phases from
the same unreacted gel components. In the case of the formation zeolite Y, during the
crystallization sequence, the initial formation of the desired faujasite phase (NaY) occur
and subsequently followed by the evolution of a transient phase closely, gmelinite and
finally by the production of garronite (Zeolite NaP) (Chen et al., 1994). Beside that,
other phases identified to crystallize when the Na2O/SiO2 and H2O/Na2O were changed
include herschelite, noselite and zeolites P and A (Szostak, 1992). In order to avoid such
phenomena from occurring and to yield high purity of zeolite NaY, the seeding and
ageing methods during the synthesizing of zeolite NaY from rice husk ash will be
highlighted.
12
During the synthesis of the zeolite NaY, a number of parameters were
emphasized in order to obtain the product with high purity of crystalline zeolite NaY and
low impurities as well as the elimination of other undesirable phases. The synthesis of
zeolite is also a typical inorganic reaction procedure, therefore, the parameters that have
been highlighted and will affect the product are:
1) Type of starting materials.
2) Initial composition of the gel.
3) Alkalinity of the reaction.
4) Ageing period.
5) Crystallization temperature and time.
These parameters will be discussed below as all of them play important roles for
successful synthesis of zeolite NaY with a Faujasite structure.
1) Type of starting materials
The starting materials used in the synthesis were rice husk ash as a source of
amorphous silica (SiO2), sodium aluminate as a source of aluminate and sodium
hydroxide as a source for the alkaline condition. Hydrothermal synthesis of
aluminosilicate zeolites involved a mixture of Si and Al species that were obtained from
rice husk ash and sodium aluminate, respectively. The mixture was then converted via
an alkaline supersaturated solution from sodium hydroxide (NaOH) solution into
microporous crystalline aluminosilicates. Sodium hydroxide serves as a source of
sodium ions and also assisted in controlling the pH. Zeolite Y is synthesized only from
reactive amorphous silica while unreactive amorphous silica usually produces a mixture
of zeolite Y and P (Zainab Ramli et al., 1996). Sodium aluminate was supplied by
Riedel De Haen containing 50 to 56% of Al2O3 and rice husk ash containing 91.65% of
amorphous silica. Sodium aluminate was used to introduce aluminium in the anionic
form since alkali salts have a strong electrolytic effect on gel formation after addition of
alkali silicate solution (Robson, 2001). The high percentage of raw material will yield
high purity of product because the structure and properties of the molecular sieve
product are highly dependent on the physical and chemical nature of the reactants used
13
in preparing the reaction mixture, especially the composition of desired materials in the
raw materials. In addition, according to the original patent for the synthesis of zeolite Y
(Breck, 1964), amorphous silica from rice husk ash was indicated as one of the preferred
sources of silica for obtaining Zeolite NaY.
2) Initial composition of gel
The initial composition for the synthesis of zeolite NaY from RHA followed the
Na2O-Al2O3-SiO2-H2O system. The overall composition of gel is 4.62 Na2O: Al2O3: 10
SiO2: 180H2O when expressed in terms of oxide-mole-ratios, results in Na2O/SiO2 is
0.462, SiO2/Al2O3 is 10 and H2O/Na2O is 45. This composition falls into range 2,
referring to Table 1.2. Thus, the composition of initial gel was appropriate for the
synthesis of zeolite Y from reactive amorphous silica as suggested by Breck et al.
(1964).
3) Alkalinity of the reaction
The pH of the mixture was controlled by sodium hydroxide solution to provide
the alkaline pH of generally between 8 and 12. The alkaline condition is important in the
synthesis of zeolite because [Al(OH)4]- is most abundant in alkaline solution. The
oligomeric silicate species react with this monomer [Al(OH)4]- to produce
aluminosilicate structure. Furthermore, the increased pH will accelerate crystal growth
by shortening the induction period (period before formation of viable nuclei) (Wetkamp
et al., 1994). The crystallization generally proceeds via the solution phase because the
solubility of silicate, aluminate and aluminosilicate in the solution are important as
crystallization mechanisms. Thus, the elevated pH is important since the solubility
depends on the alkalinity. Besides that, the activity of SiO2 in the aluminosilicate
mixture also depends upon the alkalinity [OH-]. The higher the [OH-] the lower the
activity; therefore the synthesis of zeolite with low SiO2/Al2O3 requires high [OH-].
Hence, the increase of Al2O3 will provide more ion exchange sites necessary for ion
exchange property.
14
4) Ageing period.
After the aluminosilicate gel was prepared, the hydrogel was kept for 24 hours at
ambient temperature. This ageing process is crucial in obtaining a high purity product
especially in the synthesis of zeolite Y. The important step during the ageing period is
the dissolution or depolymeriztion of the silica sol that will increase the concentration of
dissolved silica promoted by the alkaline. The ageing time of 24 hours was selected
because Breck (1964) has proven that this period is optimum in producing a high yield
of zeolite Y that is 92%. Bo and Hongzhu (1998) also reported that the rate of
crystallization and composition of the crystalline products depend strongly on the ageing
time and temperature in the synthesis of zeolite Y. This fact is also supported by another
author, Zhao et al. (1997) which emphasized that ageing process was the important role
in achieving the favorable hydrothermal aluminosilicate chemistry for zeolite formation.
Along with this process and seeding method, they had successfully synthesized zeolite Y
without marked presence of other impurities especially the absence of the formation of
zeolite P.
5) Crystallization temperature and time.
The crystallization temperature in hydrothermal condition is around 100 ± 3 oC
since the crystallization is most satisfactorily effective at a temperature from 80 oC to
125 oC. At lower temperatures (below 200 oC), the crystals which are formed are smaller
in size than those generated at higher temperature (Breck, 1964). Whereas the increasing
temperature of crystallization favours the formation of the zeolite P followed ultimately
by analcime (Breck, 1974). The crystallinity of the product normally increases in time.
However, this is only partially true because zeolite synthesis is governed by the
occurrence of successive phase transformation (Ostwald rule of successive phase
transformation). As a result, the thermodynamically least favorable phase will crystallize
first and will be successively replaced in time by more stable phases. In case of the
Zeolite Y formation, the crystallization sequence is: amorphous Æ Faujasite Æ NaP
15
(Gismondine type) (Wetkamp et al., 1994). Therefore, with the aim to avoid such
formation from occuring; crystallization time was fixed for 24 hours.
In order to prevent contamination, Teflon and PTFE containers were used during
the preparation of all solutions, for the reaction mixture and for the crystallization
process. Glass vessels were not used and were avoided since glass participates in the
reaction and silica, alumina and boron are known to be leached out of glass (Robson,
2001). These containers were washed with hydrofluoric acid (5%) before and after
experiments to eliminate the silica and alumina as well as other contaminants contained
inside the containers as the HF is known to able to dissolve these substances. After
crystallization, it was necessary to filter the solid product immediately and washed with
hot water because there was so much unreacted base left which can destroy the structure
of the zeolite Y and reduce the degree of crystallinity. Washing with hot distilled water
will eliminate these undesired substances (Bo and Hongzhu, 1998). During the
synthesis, safety must be considered as the experiments involved hazardous materials.
Measures taken include wearing gloves and face mask when handling the caustic
materials. The reaction vessels were opened immediately after they were taken out from
the oven (100 oC) in order to prevent damage to the vessel.
1.3.2.1 Seeding Technique
Seeding and ageing are two important techniques in zeolite synthesis in order to
obtain a pure crystalline phase with high percentage of desirable product as well as low
impurities. Seeding is a technique in which the supersaturated system (seed gel) is
inoculated with small particles of materials to be crystallized. The seeding method
necessitates the preparation of two separate gels; seed gel is about 5 percent from overall
and the remaining is feedstock gel. These two gels will be mixed together in the final
part of the synthesis. Adding seed crystals to a crystallization system will result in
increased crystallization rate. The enhanced rate might be due to the increasing existing
16
surface area but also might be the result of enhanced nucleation of new crystals (Robson,
2001). The secondary nucleation mechanism referred to as initial breeding results from
microcrystalline dust being washed off of seed crystal surfaces in a new synthesis batch.
These microcrystalline fragments grow to observable sizes and result in greatly
enhanced crystallization rates due to the significantly increasing crystal surface area
compared to the unseeded system. Consequently, it is to be expected that addition of
seed to a synthesis system will introduce sub-micron sized crystallites into the system
which will serve as nuclei. Finally, the same particulates which appear to catalyze
zeolite nucleation in unseeded systems may remain in sufficient number to catalyze
nucleation in seeded systems, since they are inherently present in the seed crystal sample
and may be impossible to eliminate via typical filtration techniques. In the seeding
technique, if the surface area provided by the seed crystals is larger than the one
supplied by fresh nuclei, the seeding technique provides a favourable condition for
measuring linear growth rates (Barrer, 1982).
1.3.2.2 Ageing
Ageing is a process in which the mixture of aluminosilicate is left for a period of
time at room temperature or below the crystallization temperature. In case of the
formation of zeolite Y, the appropriate period of time is 24 hours. Preliminary ageing of
the reaction mixture at room temperature after gel formation followed by subsequent
crystallization at a higher temperature of 100 oC improves the crystallization process
because the ageing process will proceed more quickly than in the non aged case. During
the gel aging, germ nuclei will be formed within the solution and they grow to
observable sizes upon subsequent high-temperature synthesis (Cook and Thompson,
1988). After the initial gel formation, the aging step is necessary in order to equilibrate
the heterogeneous gel mixture with the solution, resulted in the lower SiO2/Al2O3 ratio
in the gel necessary to form zeolite Y (Breck, 1974). Therefore, the ageing process will
be emphasized during the synthesis progress as it can provide a major consequence in
17
successfully synthesizing zeolite NaY from rice husk ash with high percentage of zeolite
Y in resultant product.
1.3.3
Characterization
In general, the characterization of a zeolite has to provide information about
structure and morphology, the chemical composition, the ability to sorb and retain
molecules and the ability to chemically convert these molecules. Information on the
structural, chemical and catalytic characteristics of zeolites is essential for deriving
relations between their chemical and physicochemical properties on the one side and the
sorptive and catalytic properties on the other. Such relations are of high importance, as
they allow the rational development of sorbents, catalyst and advanced structural
materials. In this study, the zeolite was synthesized from rice husk ash and the main uses
are as cation exchangers and sorbent, thus only characterizations with respect to these
applications are being dealt with in depth. There are many characterization techniques
but the important ones in this study are X-ray diffractogram (XRD), infrared
spectroscopy (IR), elemental analysis and ion exchange capacity (IEC). Each of the
characterization techniques will be described below.
1.3.3.1 X-Ray Diffraction Technique
For zeolites produced in the laboratory, X-ray powder diffraction data is the most
commonly used to validate the synthesized zeolite and to identify a newly synthesized
material as well as to monitor the effects of a post-synthesis modification. X-ray powder
diffraction data is also the most commonly used technique as a ‘fingerprint’ in the
identification of a material because each crystalline solid has its own characteristic Xray powder pattern (West, 1988). The measured pattern is compared to an existing one,
18
whether it is a pattern in the Collection of Simulated XRD Powder Patterns for Zeolites,
the Powder Diffraction File (PDF) of the ICDD or an in-house data file (Robson, 2001).
In recent days, the use of X-ray diffraction technique is of utmost importance in
identifying the synthesized zeolite because of the general availability of powder X-ray
diffraction facilities and the increasing application of computers to automate sample
scanning and data analysis as well as to enable rapid collection of data on a large
number of samples essentially in the absence of an operator (Jarman, 1985). Besides for
identification material, XRD diffractogram provides much information such as the
degree of crystallinity, the presence of other phases or impurities and the determination
of crystal structure.
The X-ray diffraction technique is based on the Bragg’s Law. The Bragg
approach to diffraction is to regard crystals as built up of layers or planes such that each
acts as a semi-transparent mirror. Some of the X-rays are reflected of a plane with the
angle of reflection equal to the angle of incidence, but the rest are transmitted to be
subsequently reflected by succeeding planes. The derivation of Bragg’s law is shown in
Figure 1.3. The relation between lattice planes with a distance d, the angle of reflection,
θ and measured at wavelength, λ can be described by Bragg’s law in equation 1:
nλ = 2d sin θ
(1)
The primary use of Bragg’s law is in the determination of the spacing between the layers
in the lattice for, once the angle θ corresponding to a reflection has been determined, d
may readily be calculated.
θ
d
Figure 1.2
Derivation of Bragg’s law for X-ray diffraction
19
The mostly used XRD technique for zeolites is the powder diffraction technique
because zeolite is mainly in the powder form. Powder diffraction techniques are used to
identify a sample of a solid substance through the comparison of the positions of the
diffraction lines and their intensities with a large data bank which can be acquired from
the powder diffraction file, maintained by the International Centre for Diffraction Data
(ICDD) and contains information of about 50 000 crystalline phases. The principles of
the powder diffraction technique are shown in Figure 1.4. A monochromatic beam of Xrays strikes a finely powdered sample that, ideally, has crystals randomly arranged in
every possible orientation. In such a powder sample, the various lattice planes are also
present in every possible orientation. For each set of planes, therefore, at least some
crystals must be oriented at the Bragg angle, θ, to the incident beam and thus, diffraction
occurs for these crystals and planes. The diffracted beams may be detected by
surrounding the sample with a detector.
Source
sample
filter
Figure 1.3
Detector
The illustration of the X-ray powder diffraction method
The most important use of the powder method is in the qualitative identification
of crystalline phases or compounds. While most chemical methods of analysis give
information about the elements present in a sample, powder diffraction is very different
and perhaps unique that it tells which crystalline compounds or phases are present with
no direct information about their chemical constitution.
The determination of the unit cell dimension of zeolites can also be obtained
from the X-ray technique. Zeolites are in the form of crystal, thus its structure is built up
of regular arrangements of atoms in three dimensions; these arrangements can be
represented by a repeating unit or motif called the unit cell. The unit cell is defined as
20
the smallest repeating unit which shows the full symmetry of the crystal structure (West,
1988). The unit cell dimension of a freshly synthesized faujasite-type zeolite is a
sensitive measure of composition which, among other uses, distinguishes between the
two synthetic faujasite type zeolite, X and Y. The unit cell dimension, a of the zeolite
can be calculated from the equation:
a = {( d hkl ) (h + k + l )]
2
2
2
2
1
2
(2)
where
hkl
= the miller indices (Ǻ)
d
= distance between reflecting planes having the Miller indices.
The d-spacing can be derived from equation 1 as:
d hkl =
λ
2 sin θ
(3)
The wavelength of X-ray radiation ( λ ) for CuKα1 is 1.54060 Ǻ (0.154060 nm). The
value of unit cell dimension from this equation thus can be used to determine the Si/Al
ratio of zeolite Y by Breck’s equation (Breck, 1974):
1.66656
Si
=
−1
Al a − 24.191
(4)
Hence, it is useful to characterize the raw material, synthesized zeolite and the modified
zeolite by the X-ray diffraction technique as it can give many valuable information about
the materials that had been studied.
1.3.3.2 Infrared Spectroscopy
The fundamental basic theory of the infrared spectroscopy is that the infrared
radiation will promote transitions in a molecule between rotational and vibrational
21
energy levels of the ground (lowest) electronic energy state (Cross and Jones, 1969). The
vibrational modes, involving pairs or groups of bonded atoms can be excited at higher
energy states by the absorption of radiation of appropriate frequency. In the infrared
spectroscopy technique, the frequency of the incident radiation is varied and the quantity
of radiation absorbed or transmitted by the sample is obtained. The infrared spectra of
solids are usually complex with a large number of peaks corresponding to each
particular vibrational transition. In order for a particular mode to be active towards
infrared, the associated dipole moment must vary during the vibrational cycle
consequently centrosymmetric vibrational modes are infrared inactive.
Zeolites are crystalline aluminosilicates consisting of corner linked tetrahedral
where the Al and Si atom lie at the centres of tetrahedral and oxygen atom lie at the
corners. As a result, the vibrations of the framework of zeolites give rise to typical bands
in the mid and far infrared. The usually used region of infrared for the characterization
of zeolites is the mid-infrared region which is from 200 to 1300 cm-1 since it contains
the fundamental vibrations of the Si, AlO4 or TO4 units in all zeolites framework (Rabo,
1976). In this region, there is a specific range for a typical band related to the zeolites
structure that was studied by many earlier researchers in order to provide the information
for the structural characteristics. Rabo (1976) reported that Flanigen, Khatami and
Szymanski are the earlier researchers who studied the mid-IR spectroscopy in the
characterizations of zeolite. The original assignments of the main IR bands were
described in Table 1.3. (Robson, 2001). They classified the mid-IR vibrations for the
zeolites structure into two types of vibrations which are related to the internal vibrations
of the TO4 tetrahedra and the vibrations primarily related to external linkages between
tetrahedral. The internal vibrations mainly in the primary building unit in zeolite
frameworks tend to be insensitive to variations in framework structure, while the
external linkages are sensitive to the framework topology and to the presence of
symmetrical clusters of tetrahedral in the form of larger polyhedra.
22
Table 1.3 : The assignments of the main infrared bands for zeolites
i)
Internal tetrahedral
(Structure insensitive vibrations)
a)
1250 – 920 cm-1
Asymmetrical stretch of Si-O-T
b)
720 – 650 cm-1
Symmetrical stretch of Si-O-T
c)
500 – 420 cm-1
T-O bend
ii)
External linkages
(Structure sensitive vibrations)
a)
650 – 500 cm-1
Double ring vibrations
b)
420 – 300 cm-1
Pore opening vibrations
c)
1150 – 1050 cm-1
Asymmetrical stretch of Si-O-T
d)
820 – 750 cm-1
Symmetrical stretch of Si-O-T
T = Si, Al
The strongest band is in the region of 1250 to 920 cm-1 related to the T-O stretch and the
next strongest band in the 420 to 500 cm-1 is from the T-O bending mode while
stretching modes involving mainly the tetrahedral atoms are in the region of 650 to 820
cm-1. A band in the 500 to 650 cm-1 region related to the presence of the double rings in
the framework structures which is observed in all of the zeolite structures that contain
the double 4- and double 6-ring that can be found in zeolite Y (Breck, 1974).
Although organic chemists are frequently concerned with the use of infrared
spectroscopy data for the identification of compounds, it is also helpful for inorganic
chemists to characterize the inorganic materials. However, the infrared spectroscopy
data is barely used to support data from X-ray diffractogram which is the ‘fingerprint’
for the identification of zeolites and its new derivatives. Besides that, the spectra is also
used to compare between raw material (silica) and the synthesized zeolite. Flanigen
(Rabo, 1976) from Union Carbide Corporation reported that the infrared spectroscopy
can yield information not only on short range bond order and characteristics but also on
long range order in crystalline solid caused by lattice coupling, electrostatic and other
effects and can serve as very rapid and useful structural techniques. Additionally,
infrared spectroscopy is also a valuable technique for exploring and studying the nature
23
of hydroxyl groups in zeolite, the interaction of cations with adsorbed molecules and the
fundamental framework structure of zeolites (Gould, 1974).
In the infrared spectrum of zeolites in the range of 300 to 1300 cm-1, for some of
the structure sensitive and insensitive bands, a linear relation between the wavenumber
and the number of lattice aluminum atoms (NAl) is reported (Rabo, 1976). After
calibration, it is possible to use this relation to derive the number of lattice aluminum
atoms from the band positions. Since the structure insensitive asymmetric stretch (σ1)
(950 – 1250 cm-1) and the structure sensitive symmetric stretch band (σ2) (750 – 820
cm-1) frequencies increase with decreasing Al content in a linear manner, these
frequencies can be used in the determination of the number of lattice aluminum atoms
(NAl) for zeolite Y. The number of Al in the framework of zeolite NaY sample can be
calculated according to the following equation derived by Kubelkova et al. (1988)
N Al = [4.425 − 4.054−3σ 1 ] × [ N Al + N Si ]
(5)
N Al = [4.468 − 5.299−3σ 2 ] × [ N Al + N Si ]
(6)
where [NAl + NSi] for zeolite Y is equal to 192. The value of the number of lattice
aluminium atoms from equation 5 and 6 can be used for the calculation of Si/Al and
SiO2/Al2O3 ratio according to the equation 7 and 8, respectively:
Si 192 − N Al
=
Al
N Al
192 − N Al
SiO2
=
N Al
Al 2 O3
2
(7)
(8)
24
1.3.3.3 Elemental Analysis
The structure of zeolite NaY consist of a three dimensional framework of SiO4
and AlO4 tetrahedra with the sodium cation to balance the framework charge while the
water molecule is enclosed in the large cavities of the framework. Thus, the
determination of the bulk elemental composition of zeolites is important in many aspects
of zeolite synthesis, characterization and applications. This information is used to verify
the synthesis formulation, the bulk of silica and alumina ratio (Si/Al ratio), the cations
concentration, degree of ion exchange and the detection of contaminant elements such as
impurities and poison (Robson, 2001). Corbin et al. (1987) had studied the comparison
of analytical techniques for the determination of silicon and aluminium content in
zeolites. The techniques include atomic absorption spectroscopy (AAS), neutron
activation analysis (NAA), proton inelastic scattering, X-ray fluorescence (XRF), wet
chemical, inductively coupled plasma-mass spectrometry (ICP-MS) and nuclear
magnetic resonance (NMR). They concluded that the effectiveness of each of the
technique differs from each other and requires the appropriate modification of the
sample preparation prior to measurements. From their study it can be summarized that
there are many techniques for the determination of elemental composition in zeolites.
The elements and species that are important to be determined are sodium,
aluminum, silica and water. The instrumental method to determine these elements
involves inductively coupled plasma mass spectroscopy (ICPMS) for the determination
of aluminium and flame atomic absorption spectroscopy (FAAS) for the determination
of sodium cation. These instrumental techniques are the most common techniques
employed for the determination of compositional metals because they offer the
advantage of reducing interferences and matrix effects and have advanced accuracy,
precision and speed well than “classical wet chemistry”. In general, the sensitivity of
ICP-MS is better than the conventional flame AAS. However, flame AAS has rather
better sensitivity for group IA elements, including sodium, hence the reason for the
determination of sodium using AAS and aluminum with ICP-MS. Both ICP-MS and
AAS necessitate that the sample be introduced as liquid, thus decomposition is necessary
25
prior to analysis and similar preparation schemes apply for both techniques. The
approach for decomposition sample that are used in this research is the beaker digestion
with hydrofluoric acid. The digestion requires the addition of hydrofluoric acid in order
to solubilize the Si. Besides ICP-MS and AAS, the X-ray fluorescence (XRF) also can
be used for the determination of composition in zeolites. As compared to ICP and AAS,
the wavelength dispersive XRF had the benefit which include the ability to determine
some non-metals, conceptually require simpler sample preparation and with improved
precision. However, in many cases XRF cannot perform the complete characterization
due to its poor sensitivity for light elements and sensitivity to changes in the matrix
composition. While XRF has its greatest use in a controlled manufacturing environment,
ICP and AAS is often the technique of choice in the research and development (R&D)
environment. The determination of loss on ignition at a specified temperature and time
will be used to determine the percentage of water.
The results from the elemental analysis can provide information to calculate the
ratio of silica to alumina which determines the thermal and chemical stability of the
zeolite, the hydrophilic nature of the zeolite, the numbers and strength of the acid sites in
the acid form and the capacity of the ion exchange. Breck and Tonawanda (1964) who
was the first person to discover the zeolite Y had patented the zeolite Y having
silica/alumina ratio above 3.0 and up to 6.0 since zeolite X had been defined as having
silica/alumina ratios between 2.0 and 3.0. Changing the Si/Al ratio also changes its
cation content and the stability. Fewer Al atoms means that the zeolites are more
siliceous, thus fewer exchangeable cations will be present and the thermal stability
improves.
1.3.3.4 Ion Exchange Capacity
Because of zeolites are composed of crystalline aluminosilicates with the
structure based on tetrahedral SiO4 and AlO4 units, connected by shared oxygen atoms,
26
they are one of the synthetics inorganic cation-exchangers. This kind of threedimensional structure has small pores where the exchangeable ions are located and
where the ion exchange reactions take place. Silicon is tetravalent and aluminium is
trivalent, which result in negatively charged framework structures. Thus each mole of
aluminium produces one equivalent of cation exchange capacity for the zeolite
framework. Ion exchange is a chemical reaction in which free mobile ions of a solid, the
ion exchanger, are exchanged for different ions of similar charge in solution. The
exchange reactions in typical zeolite can be written as follows:
M+X- + N+ Æ N+X- + M+
(9)
Where:
M+X- =
Zeolite with M+ is framework and X- is counterion.
N+
Cation in the solution
=
The ion exchange properties of zeolites are mainly based on the charge density
and pore size of the materials (Breck, 1974). In zeolites where the internal void space
consists of portions accessible only through smaller pores, the total ion exchange
capacity may be available to the smallest ions but only part to larger ions. However, the
majority of the total ion exchange capacity is available to the most common cations.
Furthermore, the cation exchange behaviour also depends on the temperature,
concentration of the cation species in solution, the anion species associated with the
cation, the solvent, the structural characteristics of the particular zeolite and the nature of
the cation species, size, both anhydrous and hydrated and cation charge (Breck, 1974).
In addition, the chemical composition is also the factor governing the cation exchange of
zeolite as a higher exchange capacity. This is observed with zeolites of low silica per
alumina ratio since each AlO4 tetrahedra in the zeolite framework provides a single
cation exchange sites. Zeolite X exhibits higher cation exchange capacity than zeolite Y
because it has lower silica to alumina ratio hence higher framework charge.
Cation exchange capacity (CEC) can be defined as the sum of the exchangeable
cations that a mineral can adsorb at a specific pH, i.e. a measurement of the negative
27
charges carried by the mineral (Wilson, 1994). The ion exchange capacity of zeolite ion
exchanger is a function of their silicon oxide/aluminium oxide mole ratio, since AlO4
tetrahedra in the zeolite framework provides a single cation exchange sites (Sherman,
1978) and its commonly measured in terms of moles of exchangeable cation per gram
(or 100 grams) of zeolites, moles/g or in terms of equivalents of exchangeable cation per
gram (or 100 grams) of zeolites, meq/g. Using CEC expressed in terms of
miliequivalents per gram (meq/g) makes it easy to compare how much of any cation can
be exchanged by a particular zeolite, without having to worry about the charge on the
cation involved. The exchange process involves replacing one singly-charged
exchangeable atom in the zeolite by one singly-charged atom from the solution, in this
study; the singly-charged atom that is used to exchange sodium cations in zeolite NaY is
ammonium cation, NH4+ which possesses single charged ion. So, it is of utmost
importance to know and verify the ion exchange capacity of the synthesized zeolite
because the main function of the zeolite in this study is for ion exchange with heavy
metals in the aqueous phase.
The total cation exchange capacity is the sum of external cation exchange
capacity (ECEC) and internal cation exchange capacity. Because of large molecule of
hexadecyltrimethyl ammonium, HDTMA, this molecule cannot enter the angstrom size
of pore zeolite and will exchange on the surface of zeolite. The measurement ECEC is to
differentiate between internal and external cation exchange sites that would enable better
investigation of changes in modified mineral properties as a function of surfactant
loading and also to characterize the exchange capacity of the mineral surface for
HDTMA (Li and Bowman, 1997). Therefore, it is essential to determine the external
cation exchange capacity by using HDTMA cation as the exchanged cation before the
modification of zeolite surface. From the measured external cation exchange capacity,
the maximum uptake of the HDTMA will be known and will provide information for
internal cation exchange capacity.
28
1.4
Surfactant Modified Zeolite
Some of the toxic metals may exist as cations, anions, non-ionized species and
complex macromolecules in the aqueous phase (Sengupta, 2002), for instance, arsenic
which is prominently carcinogen, can form anion as arsenate (As(V)) and non-ionized
species as arsenite (As(III)). Another known toxic metal in water is chromium (Cr)
which can also form Cr3+ cation (Cr(III)) and the anionic form as chromate, CrO42- for
Cr(VI). Therefore, the materials that can remove this kind of toxic metals
simultaneously in the water body are of great importance with regards to the water
purification or wastewater treatment. To achieve this result, the composite ion exchanger
has to be developed, for which it shall contain the properties of cation and anion
exchanger at the same time. In order to sorb anion and cation, the modified surface must
possess positively and negatively charged exchange sites. However, a typical zeolite
cannot remove or sorb the anion species as its surface is in the anionic charges. By
treating the zeolite with a cationic surfactant, an organic covering is created on the
external zeolite surfaces and the charge is reversed to positive charge. Therefore, the
modification surface of zeolite by cationic surfactant (i.e. HDTMA) can be made
according to the successful clinoptilolite modified with HDTMA by Li and Bowman
(1997) and they called it surfactant-modified zeolite (SMZ). Laboratory batch and
column tests demonstrate that SMZ can simultaneously remove multiple types of
contaminants from water, including inorganic anions such as chromate and hydrophobic
organics such as chlorinated solvents and fuel components (Li et al., 1998b). Zeolite
NaY resembles natural zeolite minerals that have permanent negative charges on their
surface and large cation exchange capacity (CEC) which enables them to be modified by
cationic surfactant to enhance their sorption of organic and anionic contaminants in
water.
The surfactant that is commonly employed to be attached on the zeolite surface
in the previous studies is HDTMA, the quaternary amine hexadecyltrimethylammonium
cation which is a long chain cationic surfactant that possesses a permanent positive
charge. The HDTMA is in the group of cationic surfactant where they have positively
29
charged hydrophilic head group generally amine, attached to a hydrophobic tail of
hydrocarbon moiety. The structure of the HDTMA is shown in Figure 1.5. The HDTMA
structure consists of permanently charged trimethyl ammonium head group attached to a
16-carbon chain. It can be obtained as common salts such as HDTMA-bromide and
HDTMA-chloride. Since the uses of this surfactant are mainly as hair conditioner,
mouthwash and fabric softeners, it is assumed that low levels of HDTMA will not be
harmful to the environment. The critical micelle concentration (CMC) is the minimum
concentration of the surfactant needed to form a micelle and for HDTMA-Br is 0.9
mmol/L. The individual surfactant molecules will self associate into micellular clusters
above the CMC.
+
N Br
Æ Hydrophobic tail
Æ 16 chain
hydrocarbon
Æ Hexadecyl
Figure 1.4
Æ Bromide anion
Æ Negative charge
Æ Balance the
ammonium charge
Æ Hydrophilic head
Æ Trimethyl ammonium
Æ Positive charge
The structure of hexadecyltrimethyl ammonium bromide (HDTMA-Br)
Depending on the chemical structure of the cationic surfactant, it is possible to
make a hydrophilic solid behaves as if it was hydrophobic or (less usual) to make a
hydrophobic solid behave as if it were hydrophilic (Porter, 1994). When the adsorption
of a surfactant onto a solid surface is considered, there are several quantitative points
that are of interest. They include:
i)
The amount of surfactant adsorbed per unit mass of solid.
ii)
The solution surfactant concentration required to produce a given surface
coverage or degree of adsorption.
iii)
The surfactant concentration at which surface saturation occurs.
iv)
The orientation of the adsorbed molecules relative to the surface
saturation occurs.
30
v)
The effect of adsorption on the properties of the solid relative to the rest
of system
In all of the above, it is assumed that such factors as temperature and pressure are held
constant. The maximum surfactant loading on zeolite surface is a function of surfactant
type, chain length and counter ion type (Li and Bowman, 2001a).Thus, the surface
properties of zeolite can be modified by using cationic surfactants HDTMA because the
surface of zeolite is the net negative charged resulting from isomorphic substitution of
cations in the crystal lattice.
Theoretically, when the zeolite contacting with HDTMA above the CMC in the
aqueous phase, the HDTMA cation will selectively exchange with the inorganic cations
on the external surface of zeolite framework. In the case of zeolite NaY, sodium cation
(Na+) will be exchanged and forms a surfactant bilayer with anion exchange properties.
The equation of the exchange can be described below:
2M-Na+ +
HDTMA+
↔ M-Na+HDTMA+
+
Na+
(10)
where M is the framework of zeolite having negatively charge. The HDTMA molecule
will be exchanged with the zeolite’s cation in the external framework and limited
exclusively to external surface of zeolite particles because the HDTMA molecule is too
large to penetrate the internal pore spaces of the zeolite or to access the internal cation
exchange positions since it has a long chain quaternary ammonium cations.
The sorption of cationic surfactant onto a negatively charged surface of zeolite
involves both cation exchange and hydrophobic bonding (Li and Bowman, 1997). It was
suggested that at low loading levels of HDTMA exposed to a negatively charged zeolite
surface, it will be retained by ion exchange and eventually form a monolayer at the
solid-aqueous interface. At this stage, the surfactant molecules exist as monomers in
aqueous solution at concentrations below the CMC which is typically below 1 mmol/L.
When the surfactant concentration is greater than CMC, the surfactant molecules
31
associate to form solution micelles in addition to monomers. As the amount of HDTMA
increases and the initial surfactant concentration is greater than CMC, the interaction
among the hydrocarbon tails causes the formation of a bilayer or patchy bilayer with the
first layer retained by cation exchange and the second layer by hydrophobic bonding and
stabilized by counter ions. The sorbed surfactant creates an organic-rich layer on the
zeolite surface and the charge on the surface is reversed from negative to positive. The
positively charged head groups are then balanced by counter ions. A model for the
interaction of HDTMA on the external surface of zeolite is shown in Figure 1.6. This
theoretical phenomenon shows that the anion that counterbalanced the positive charge
from HDTMA will be exchanged by more strongly held counter ions while the organic
partitioning will absorb organic substances and the outer cations will be replaced with
cation that neutralizes zeolite from the internal pore.
CrO3-
Br-
CrO3Br-
Br-
+
+ +
+
Na+
Br-
+
Br-
Br-
Br-
H3AsO3
Cation
+
exchange
Na+
Figure 1.5
Organic
partitioning
H3AsO3
Cr3+
Anion
exchange
+ +
Br-
CrO3-
+ + + + +
+
Zeolite surface
Schematic diagram of HDTMA micelle formation in solution and
admicelle formation on the zeolite surface and the uptake substance onto surfactant
modified zeolite.
Along with its unique properties, the resultant surfactant modified zeolite (SMZ) is
capable of simultaneous sorption of anions, cation and non-polar organic molecules
from water.
32
The advantages of surfactant modified material are that it can be used to
eliminate multiple types of undesired contaminants elements in water which are
inorganic cation (e.g.; Pb2+, Cd2+, Cr3+) and inorganic anion (e.g.; chromate, selenate,
arsenate) as well as organic substances (e.g.; perchloroethylene (PCE), trichloro ethylene
(TCE), benzene, toluene, ethylene and xylene (BTEX)) all together. The surfactant
modified zeolite proved to be chemically and biologically stable at a long term period.
Li et al. (1998b) studied the long term chemical and biological stability of surfactant
modified natural zeolite, and they concluded that the SMZ was stable in high ionic
strength, high and low pH environments, under both aerobic and anaerobic conditions
and moreover resistant to microbial degradation.
Recently, clinoptilolite is the natural zeolite that is mostly used in order to create
the SMZ for the adsorption and removal of many types of contaminants in water and it
has been working successfully. The studies on the use of SMZ from clinoptilolite for
environmental remediation were limited to the removal of organic contaminants from
water until Haggerty and Bowman (1994) showed that SMZ significantly increased the
sorption of chromate. The sorption of chromate was attributed to anion exchange on the
outermost surface created by the sorbed surfactant bilayer (Li et al., 1998a). Besides
sorption of chromate, SMZ has also been proven to sorb other oxyanions such as
sulphate (SO42-) and selenate (SeO42-) (Haggerty and Bowman, 1994), nitrate (NO32-)
(Li, 2003) and also dihydrogenphosphate (H2PO4-) (Vujakovic et al., 2000). Li et al.
(2002) also reported that cation exchange by SMZ is reduced compared to the
unmodified zeolite. They observed that the reduction in metal cation uptake by the SMZ
is controlled by the surfactant loading on the zeolite surface and by the type of metal
cations. There are many papers which reported on the sorption of organic contaminants
in water by SMZ. Bouffard and Duff (2000) applied SMZ as adsorbents for the removal
of dehydroabietic acid (DHA) from a model process white-water, Li and Bowman
(2001a) studied the regeneration of SMZ after saturation with perchloroethylene,
Hayakawa et al. (2000) used zeolite P and X that had been attached with hexadecyl-,
tetradecyl- and dodecyltrimethylammonium bromides as a drug carrier and the release of
chloroquin (CQ), besides that, SMZ as the new efficient adsorbents for mycotoxins was
33
studied by Tomasevic-Canovic et al. (2003). These literature reviews show that SMZ
has many uses in the purification of water as the contaminants exist in many forms,
cationic, anionic, neutral and organic form.
1.5
Toxic Metals in Water
Heavy metals are metallic elements that have a high atomic number and are toxic
to living organisms. Because they are toxic, heavy metals are sometimes referred to as
toxic metals (Young, 2000). There are approximately 30 different toxic metals that have
impacts upon human health and each of them will produce different behavioral,
physiological and cognitive changes in an exposed individual. Examples of toxic metals
are chromium (Cr), arsenic (As), selenium (Se), cadmium (Cd), nickel (Ni), lead (Pb),
mercury (Hg), manganese (Mn), cobalt (Co), zinc (Zn) and copper (Cu). Although
arsenic (As) and selenium (Se) are the elements on the border between metals and nonmetals and are known as metalloids, they are also considered as toxic metals because of
their toxicity and well-known carcinogence since they exhibits some metallic properties.
Heavy metals in natural waters may be suspended (particles >100 nm in size),
colloidal (particles in the intermediate range between suspended and soluble) or soluble
(particles <1 nm) (Rubin, 1974). The suspended and colloidal particles may consist of
individual or mixed metals in the form of their hydroxides, oxides, silicates, sulfides or
as other compounds, or they may consist of clay, silica or organic matter to which metals
are bound by adsorption, ion exchange and complexation. The soluble metals may be
ions, simple or complex or un-ionized organometallic chelates or complexes.
Heavy metals enter the water systems; surface water, groundwater, supplied tap
water and rain water from a variety of sources and can be divided into three major
sources which are nature, human activities and agriculture. The largest natural source
exposed to surface water is directly from rocks and soils. Dead and decomposing
34
vegetation and animal matters, also contribute small amounts of metals to adjacent
waters. Large quantities of metals in water are also contributed from wet and dry fallout
of atmospheric particulate matters derived from natural sources, for instance, the dust
from the weathering of rock, from volcanic eruption and the smoke from forest fires and
micrometeorites dust (Young, 2000). The second major source of heavy metals in the
water system is from human activities that pollute and contaminate the water bodies
through direct discharge of various treated or untreated municipal, residential or
industrial effluents. Many of the toxic metals discharged in surface and groundwater are
from the industrial wastes such as from the industries of metal mining operations,
metallurgical, electroplating industries and tanneries (Rubin, 1974) mostly from
wastewater treatment process especially located in big town areas. The concentration of
various metals in industrial discharges depends upon the type of industries, specific
processes operations and the wastewater treatment system. Besides that, the
contamination of heavy metals in water is also contributed from illegal disposal of
industrial effluents. The source of heavy metals in the natural water by human activities
also include land clearing which is primarily related to the lumbering industry and the
construction industry as well as for agricultural purposes. The clearing of land can be
subjected to extreme erosion particularly during the construction period; hence
increasing the potential for the carrying of heavy metals to the aquatic environment. In
the domestic sewage, the amounts of metals may vary according to water usage, quantity
and types of food eaten, time of year, economic status and the sewage system (Rubin,
1974). In supplied tap water, heavy metals come from the corrosion of the metal pipes
used to carry water to consumers (Bailey et al., 1999). Agricultural activities also affect
the source of metals in water particularly in the rural region. The used of fertilizers by
humans applied to the soil and the death and subsequent decomposition of plants can
affect the distribution of metals in groundwater. In addition to these sources, the
lowering of pH in rain and surface water and the increased and widely used surfactants
in consumer and industrial product have greatly enhanced the mobility of heavy metals
in the environment (Sengupta, 2002).
35
Toxic metals can be distinguished from other toxic pollutants, since they are nonbiodegradable and can accumulate in living tissues, thus becoming concentrated
throughout the food chain (Korngold et al., 1996). It is well known that toxic elements
and their discharge into receiving waters cause detrimental effects on human health and
will constitute a great risk for the aquatic and environment system. The health hazards
presented by heavy metals depend on the level of exposure which are generally divided
into two classes: acute exposure and chronic exposure. Acute exposure refers to contact
with a large amount of the heavy metals in a short period of time whereas chronic
exposure refers to contact with low levels of the heavy metals over a long period of time
(Young, 2000). The toxicity of heavy metals is attributed to harmful and even lethal
effects on the human body, particularly on the central nervous system, causing mental
disorders such as fatigue, insomnia, decreased concentration, aggressive behaviour,
memory loss, learning deficits, depression, irritability, gastric symptom, sensory
symptom and motor symptom, and to the physical manifestations such as liver and
kidney dysfunction, infertility, gout, hypertension, headache and Candida (yeast)
infections (An et al., 2001). One of the papers reported from India, which is one of the
countries having problems of increasing toxic metals in water system affecting many
people; Singh et al. (2004) had studied the impact of the toxicants discharged from
sewage treatment plants on the health, agricultural and environmental quality in the
wastewater disposal area. The impact of the wastewater toxicants (metals and pesticide)
on human health in the areas receiving wastewater was assessed through a standard
questionnaire containing a total of 35 items, which cover eight neurobehavioral
functions established to be affected by the chemicals exposures. The studied population
was divided into exposed and unexposed groups. They found that there was a significant
difference in the overall analysis between the exposed and unexposed population group.
The levels of the metals in the human blood and urine samples of the exposed and
unexposed groups were also studied to confirm the analysis of the questionnaire and
they found that the levels of metals in the samples were higher in exposed population
than those unexposed population groups. Thus, they concluded that there has been a
considerable impact of these toxicants on human health in the exposed area.
36
The problems of toxic metals distribution and its toxicity in aquatic system are
global problems which give pressure to the federal and state governments to overcome
this issue. Growing levels of toxic metals pollution in the natural water system related to
the evolution of the industrial and agricultural activities demand effective approach to
overcome this problem.
1.5.1
Chromium
Chromium is a transition metal, one of the elements found between group II and
III in rows 4 through 6 of the periodic table. Its atomic number is 24, its atomic mass is
51.996 and its chemical symbol is Cr. Chromium is one of the toxic metals that has been
studied because it can be formed in both cationic and anionic in water. Chromium exists
in oxidation states +2, +3, +4, +5 and +6, but the most common, stable and abundant
forms are chromium (III) and chromium (VI) (Katz and Salem, 1994). Chromium (III)
exists in the form of cation, Cr3+ and it occurs naturally in the environment while
chromium (VI) exists in the anionic form (chromate) produced by industrial process for
laboratory reagents and manufacturing intermediates. Each of both forms has a unique
chemistry and behaviour; for example, the chemical form of chromium is largely
determined by their potential toxicity as Cr(VI) is believed to be carcinogenic in humans
while Cr(III) is actually an essential micronutrient (Katz and Salem, 1993). In the
aqueous solutions, Cr(VI) is very soluble and exists in the form of chromic acid
(H2CrO4) and in the form of dichromate (Cr2O72-) while in neutral solutions, Cr(VI) is
present in the form of HCrO4- and CrO42- (Korngold et al., 2003).
Chromium is an ubiquitous element, not only because of its occurrence in nature,
but also due to the many anthropogenic sources resulting from its widespread industrial
application (Martinez-Bravo et al., 2001). Chromium and its compounds are used in
refractories, drilling mud, electroplating cleaning agents in the metal finishing industry,
mordants in the textile industry, catalytic manufacture, fungicides and wood
37
preservatives, in the production of chromic acid and specialty chemicals. They are also
used as a constituent of inorganic pigments, as a sensitizer in the photographic industry,
as dyes and pigments and in medicinal astringents and antiseptics. Other uses for
chromium and its compounds include organic chemical synthesis, leather treatment,
photomechanical processing and industrial treatment, including treatment of cooling
tower water (Katz and Salem, 1994). As chromium is very widely used, there are many
sources of leaching the chromium into the natural water system and it should be
removed practically.
Cr(VI) is toxic and a carcinogenic. It is quite soluble in the aqueous phase almost
in the entire pH range and mobile in the natural environment. The carcinogence and
toxicity of Cr(VI) is based on its state where the chromate anion resembles the form of
sulfates and phosphate (Costa, 2003). In addition, the toxic nature of the Cr(VI) ions is
attributed to their high oxidation potential and their relatively small size, which enables
them to penetrate through biological cell membranes (Balarama-Krishna et al., 2005). At
physiological pH, Cr(VI) exists as an oxyanion, with an overall charge of minus 2
having borrowed electrons from oxygen. In this form, Cr(VI) resembles oxyanions, such
as sulfates and phosphates, which are used extensively in humans for many diverse
biochemical processes. The individual cells of the body need to take up sulfate and
phosphate and have active systems that transport these nutrients. However, chromate
fools the cell’s anion uptake system into thinking that Cr(VI) is sulfate or phosphate and
the cells transport chromate from the outside of the cell into its interior. Thus, if
chromate is delivered to any cell in the body regardless of the route of exposure it will
be taken up into the cell. In contrast, Cr(III) does not resemble any biological nutrient
and has no similar way to enter the cell. However, it is possible that Cr(III) may be
oxidized into Cr(VI) in the appropriate condition, hence the toxicity of Cr(VI) take
place. Usually, Cr(III) is readily oxidized to the hexavalent state at high pH (Katz and
Salem, 1993). Presently, Cr(VI) has been recognized as a probable agent of lung cancer
and it also produces gastrointestinal disorders, dermatitis and ulceration of skin in man
(Balasubramanian and Pugalenthi, 1999).
38
The regulation for the limitation of the chromium concentration in water should
be highlighted and emphasized in every country due to the toxicity, reactivity and
probable carcinogens of chromium. Acceptable limits for the chromium in water differ
in almost every country. As a guideline, the World Health Organization (WHO)
recommends a maximum level of 50 μg/L (ppb) for Cr(VI) in drinking water (Zu, 1993)
and the National Institute for Occupational Safety and Health (NIOSH) recommends that
the levels of chromium should be reduced to 10-3 mg/m3 (Rengaraj et al., 2003). The
Environmental Protection Agency (EPA) has set the MCL (Maximum Contaminant
Levels) at 0.1 ppm in drinking water because EPA believes, given the present
technology and resources, this is the lowest level where the removal of this contaminant
can be achieved in drinking water.
1.5.2
Arsenic
Arsenic is the third member of the nitrogen family, which consists of elements in
group 15 of the periodic table. Its atomic number is 33, its atomic mass is 74.9216 and
its chemical symbol is As. Arsenic is characterized more by its ubiquity than by its
abundance. Arsenic is a naturally occurring metalloid element, the 20th most abundant
element in the earth’s crust and is the 12th most abundant element in the human body
(King, 1994). As a metalloid, arsenic has both metallic and nonmetallic properties.
Arsenic displays various oxidation states that are -3, 0, +3 and +5. The commonly
encountered oxidation states of arsenic in water are +3 (As(III) or arsenite) and +5
(As(V) or arsenate) of which the former mostly exist in the neutral form while the latter
exist in the anionic form. The major chemical form in which arsenic appears to be
thermodynamically stable is arsenate ion. At moderate or high redox potentials arsenic
can be stabilized as a series of pentavalent (arsenate) oxyanions, H3AsO4, H2AsO4-,
HAsO42- and AsO43-. However, under most reducing (acid and mildly alkaline)
conditions and lower redox potential, the trivalent arsenite species (H3AsO3)
39
predominate (Mandal and Suzuki, 2002). The structures for arsenates and arsenite
species are shown in Figure 1.6.
O
As
As
HO
HO
OH
OH
(a) H3AsO4
OH
2-
3-
O
As
O
O
(b) H2AsO4-
O
HO
-
O
As
O
O
O
O
(d) AsO43-
(c) HAsO42HO
As
OH
OH
(e) H3AsO3
Figure 1.6
The structure of the anion form of arsenate (a, b, c and d) and the neutral
form of arsenite (e) species.
Arsenic is very widely distributed in nature with its abundance on earth is
thought to be about 5 parts per million (Young, 2000). In waters, it occurs in rivers,
lakes, streams, groundwater and in the seas and oceans. The arsenic concentration of
most potable waters seldom exceeds 10 ppb, although values as high as 100 ppb have
been reported (Cleseri et al., 1989). Exposure to arsenic may come from natural sources,
from industrial sources or from food or beverages. Arsenic is increasingly being found
in water in many parts of the world such as Bangladesh, Taiwan, Chile, West BengalIndia, Mexico, Argentina, Canada, Hungary and some parts of USA; Utah, Western
Oregon and California (Mandal and Suzuki, 2002). The arsenic polluted areas of the
world can be geologically subdivided into areas made of sediments derived from water
or volcanic rocks characterized by the presence of geysers, gold and uranium mining
areas (Kundu, 2004). These elevated arsenic concentrations are mostly of natural origin.
40
Most arsenic is used in the form of compounds of which As2O3 is the sole basic
material. The largest consumers of arsenic trioxide are the USA, Malaysia and the UK
(Merian, 2004). The uses of arsenic are to make alloys mostly with lead, transistor and
light-emitting diodes (LEDs) and also in wood preservatives as CCA (Chromated
Copper Arsenate) (Young, 2000).
Arsenic and its compounds are toxic, poison and carcinogenic to animals and
human with Arsenite (As(III)) is generally considered more acutely toxic than arsenate
(As(V)). Arsenate and arsenite are thought to elicit acute toxicity via different
mechanisms where arsenate mimicks phosphate and interfering with ATP production in
the mitochondria while arsenite binds to and inactivates sulfhydryl-containing enzymes
(Lantz et al., 1994). In low doses, arsenic produces nausea, vomiting and diarrhoea
while in larger doses, it causes abnormal heart beat, damage to blood vessels and a
feeling of ‘pins and needles’ in hand and feet. Long term exposure to arsenic and its
compounds can cause cancer where the inhalation can result in lung cancer and if
swallowed, cancer is likely to develop in the bladder, kidneys, liver and lungs (Newton,
1999). Large doses of inorganic arsenic can cause death. The specific disease called
arsenocosis that be related only if the doses of inorganic arsenic compounds are higher
in the human body.
Since arsenic is well known as toxic and carcinogenic that affects many people
around the world, the Safe Drinking Water Act requires Environmental Protection
Agency (EPA) to revise the existing 50 ppb standard for arsenic in drinking water. On
January 22, 2001 EPA adopted a new standard and public water must comply with the
10 ppb standard beginning January 23, 2006 (EPA, 2001). In addition, arsenic is the one
substance that is considered to be potential occupational carcinogens by National
Institute for Occupational Safety and Health (NIOSH). In addition, the provisional
guideline value recommended by the World Health Organization is 10 ppb (WHO,
1993).
41
1.6
Removal of Toxic Metals in Water
As discussed in the previous sections chromium and arsenic are very toxic,
carcinogenic and very harmful to human beings, in addition, the requirement to comply
with the regulation made by the governments, the importance of removing both toxic
metals in various sources before discharging them into surface water streams or for
drinking water are very crucial. With the purpose to reduce or eliminate the
concentration and quantity of both metals, the treatment of the affected water can be
done by using many types of techniques and methods such as filtration, chemical
precipitation, coagulation, ion exchange, adsorption, electrodeposition, reverse osmosis,
cementation, solvent extraction and biological processing. All these approaches have
their inherent advantages and limitation. The oldest and most frequently used method for
removal those toxic metals from wastewater are precipitation. Although this process is
effective to remove a large amount of toxic metals, it has some disadvantages. It
produces a large amount of sludge which has a long settling time and harmful to the soil.
For this reason, adsorption processes has been and actually are the most frequently
applied method in the industries instead of precipitaion and consequently the most
extensively studied.
Recently, a wide range of sorbent is available for the removal of chromium from
water especially the hexavalent chromium (chromate) since the toxicity and solubility of
chromate anion is well-known to be extremely higher than trivalent chromium. The
surfactant modified zeolite from the natural zeolite, i.e. clinoptilolite, is widely used to
remove chromate from water (Ghiaci et al., 2004; Li, 2004; Haggerty and Bowman,
1994; Vujakovic et al., 2000). The other sorbent used for the removal of chromate
includes biosorbent, for instance, chitosan (Schumi et al., 2001; Bodu et al., 2003),
hazelnut shell (Cimino et al., 2000), sargassum sp. biomass (Cossich et al., 2002),
Aeromonas cavidae (Loukidou et al., 2004) and bacillus sp. (Nourbakhsh et al., 2002),
the ion exchanger resins in the anionic form (Korngold et al., 2003), the activated carbon
(Selvi et al., 2001; Babel and Kurniawan, 2004) and coals (Lakatos et al., 2002). Since
the toxicity of trivalent chromium is greatly less than hexavalent chromium, only a little
42
has been reported in the removal of trivalent chromium from water. The sorbent for the
trivalent chromium includes biosorbent such as brown seaweed biomass (Yun et al.,
2001) and Saccharomycess cerevisiae (Ferraz et al., 2004). Besides that, the ion
exchanger resin in the cation form (Rengaraj et al., 2001; Rengaraj et al., 2003), zeolite
(Barros et al., 2004; Bosco et al., 2005), bentonite (Chakir et al., 2002) and activated
carbon (Cordero et al., 2002) have been used to remove trivalent chromium from water.
Numerous sorbents have been developed to remove arsenic from water. The
sorbent used for the removal of arsenate and arsenite from water are natural zeolitesclinoptilolite (Elizalde-Gonzalez et al., 2001b), cement (Kundu et al., 2004), granular
ferric hydroxide (Thirunavukkarasu et al., 2003), zero-valent iron (Bang et al., 2005),
iron hydroxide-coated alumina (Hlavay and Polyák, 2005), iron oxide-loaded slag
(Zhang and Itoh, 2005), ferruginous manganese ore (Chakravarty et al., 2002), red mud
(Altundogan et al., 2000), iron(III) phosphate (Lenoble et al., 2005), Zr-loaded lysine
diacetic acid chelating resin (Balaji et al., 2005), nanocrystalline titanium dioxide (Pena
et al., 2005) and mesoporous alumina (Kim et al., 2004). Since the arsenate and arsenite
exist in different forms in water, some sorbents cannot remove both species
simultaneously. The commonly used sorbent for arsenate removal from water recently
are synthetic zeolite (Shevade and Robert, 2004), natural zeolites (Xu et al., 2002),
natural iron ores (Zhang et al., 2004), synthetic akaganeite (Deliyanni et al., 2003),
strong-base anion-exchange resins (Korngold et al., 2001), metal-loaded clay (Lazaridis
et al., 2002), Ce(IV)-doped iron oxide (Zhang et al., 2003) and biosorbents such as P.
chrysogenum biomass (Loukidou et al., 2003). Papers reported on the removal of
arsenite from water is limited since arsenite (As(III)) is difficult to be removed from
water using normal available treatment process. It is usually necessary to change the
trivalent arsenic to the pentavalent form by adding an oxidant, generally chlorine
(Kartinen and Martin, 1995). There is no paper found reporting the removal of arsenic
from water by surfactant-modified zeolite, however, Sullivan et al. (2003) had reported
the sorption of arsenic from water soil-washing leachate since the pentavalent arsenic
resembles chromate that can undergo anion exchange by surfactant modified zeolite.
43
1.6.1
Adsorption Theory
The removal of toxic metals from sorbent is based on the adsorption at solidliquid interfaces. Adsorption from dilute aqueous solution onto the particulate matter
present in suspension may involve specific chemical interaction between adsorbate and
adsorbent. The most common interactions of this type include an ion exchange process
in which the counter ions of the substrate are replaced by ions of similar charge. The
experimental determination of the extent of adsorption usually involves shaking a known
mass of adsorbent with a solution of known concentration at a fixed temperature and
fixed period of time. The concentration of the supernatant solution is then determined by
chemical means, which equilibrium conditions have been established. An adsorption
isotherm is a graphical representation showing the relationship between the amounts
adsorbed by a unit weight of adsorbent and the amount of adsorbate remaining in test
media at equilibrium and at a fixed of temperature. The major factors determining the
shape of an isotherm are the number of compounds in the solution, their relative adsorb
abilities, the initial concentration in the solution, the degree of competition among solute
for adsorption sites and the characteristic of the adsorbent. Equilibrium studies on
adsorption provide information about the capacity of the adsorbent or the amount
required to remove a unit mass of pollutant. The most widely used isotherm equation for
modelling the adsorption are the Langmuir and Freundlich models.
The simplest theoretical model that can be used to describe monolayer adsorption
is the Langmuir equation. The Langmuir equation is based on a kinetic approach and
assumes a uniform surface, a single layer adsorbed material at constant temperature. The
Langmuir equation is:
x bQo C e
=
m 1 + bC e
where:
x
: mass of adsorbate adsorbed (mg or mmol)
m
: mass of adsorbent (g or kg)
Ce
: equilibrium concentration (mg/L or mmol/L)
(11)
44
b
: langmuir constant related to the affinity of the binding site.
Qo
: maximum adsorption at monolayer coverage (mg/g or mmol/kg)
The equation (11) can be simplified, if:
x
= q e = amount adsorbed at equilibrium (mg/g or mmol/kg)
m
(12)
Therefore:
qe =
bQo C e
1 + bC e
(13)
The nonlinear form (equation 13) can be evaluated by transforming to the linear
equation:
m 1
1
1
=
=
+
x qe Qo bQo C e
When
m
x
or
intercept-Y is
(14)
1
1
1
against
, a straight line graph is obtained with slope is
and
qe
Ce
bQo
1
.
Qo
The Freundlich is an empirical equation based on the distribution of solute
between solid phase and aqueous phase at equilibrium. The basic Freundlich equation is:
1
x
= q e = K f C en
m
(15)
The abbreviation in equation 15 is similar to the Langmuir equation except for K f and n
is the empirical Freundlich constant. Equation 15 can be rearranged into a linear form:
log
x
1
= log q e = log K f + log C e
m
n
(16)
45
When log
x
or log q e against log C e , a straight line graph is obtained where the slope is
m
1
and the intercept-Y is log K f .
n
1.7
Research Background and Objectives of the Study.
In order to remove the toxic metals, i.e. chromium and arsenic that can exists in
the form of cation (Cr(III)), anions (Cr(VI) and As(V)) and neutral (As(III)) species as
H3AsO3 in water depending on the oxidation states and the condition of water especially
the pH of
solution, the materials which have the properties of anion and cation
exchanger simultaneously are essential and have to be developed. Therefore, the most
important aim of this study is to develop such materials by attaching the zeolite with the
cationic surfactant. Prior to modify the zeolite surface by cationic surfactant, the highly
pure zeolite NaY must be produced and characterized by various characterizations
techniques. The synthesis of the zeolite NaY requires a source of silica as a main raw
material, hence, the rice husk ash which is known to have high content of silica can be
used. In addition, the rice husk is produced in abundance in Malaysia as agro-waste and
which needs to reprocess to value added product and thus to solve the environmental
problem. The zeolite is well-known having permanent negative net charges allowed to
cation exchanger and by attaching it to cationic surfactant, the external surface of zeolite
may have positive charges resulting from the double layers provided by the hydrophobic
bonding of surfactant at the external surface of zeolite enabling anion exchange. Thus, it
can be used to sorb cation and anion species in aqueous solution.
The objectives of the study are as follows:
1) To prepare and characterize the rice husk ash as a raw material.
2) To synthesize zeolite NaY from rice husk ash as a source of silica.
3) To characterize the synthesized zeolite NaY by various methods.
46
4) To prepare the surfactant-modified zeolite Y by modifying the surface of zeolite
NaY with cationic surfactant (HDTMA).
5) To characterize the surfactant-modified zeolite Y by a variety of methods.
6) To study the effectiveness of the modified and unmodified zeolite for the
removal of Cr(III), Cr(VI), As(III) and As(V) from water.
CHAPTER 2
MATERIALS AND METHODS
2.1
Preparation of Rice Husk Ash
The raw material, rice husk was obtained from Bernas (Beras Nasional) milling,
Selangor. Rice husk ash that was used as a source of silica in the synthesis of zeolite was
prepared through physical combustion in a Plug Flow Combustor (PFC), located at the
Solid State Laboratory, MTDC Building at Universiti Teknologi Malaysia (UTM). Prior
to burning, the rice husk was washed by immersing them in distilled water to eliminate
undesirable materials such as rice, sand and other agricultural wastes. The rice husk was
then dried under sunlight for a period of time until the entire rice husk was completely
dried. Then, the dried rice husk was burnt in the PFC at a constant temperature of 600 oC
and constant pressure for an hour to ensure that the product is in an amorphous silica
phase. The product obtained was white with slightly blackish powder form. The rice
husk ash was ground using a mortar to homogenize and to get a powdered form of the
material. The rice husk ash obtained from this process was labeled as RHA and it can be
readily characterized and used as a source of silica in the synthesis of zeolite NaY.
48
2.2
Characterization of Rice Husk Ash.
The preparation of the rice husk ash is to provide a source of silica for the
synthesis of zeolite, thus a few characterization techniques related to the structure and
the amount of silica produced were carried out. The characterization of the rice husk ash
was done involving X-ray diffraction technique (XRD), infrared spectroscopy (IR) and
X-ray fluorescence technique (XRF) for the elemental analysis.
2.2.1
X-Ray Diffraction Technique
The phase identification of silica in the rice husk ash was determined using X-ray
Diffraction (XRD) method on a Bruker AXS GmbH (German) machine. X-Ray
diffraction patterns were recorded with a CuKα radiation at λ = 1.5418 Å at 40 kV and
20 mA in the range of 2θ = 5o to 50 o with a scanning speed of 0.05o per second.
2.2.2
Infrared Spectroscopy
Rice husk ash sample was characterized with a Fourier Transform Infrared
(FTIR) Spectrophotometer (model FTIR-8300, Shimadzu, Japan) using the KBr method.
Approximately 0.001 g of the rice husk ash was taken as a representative from the
overall sample and transferred to the mortar crucible. A little KBr was then added in the
ratio of sample to KBr of 1:100 and mixed thoroughly. These two substances were
ground together using a mortar. The mixture was then pressed at a pressure of 7 tonnes
for a minute to obtain the KBr sample disk. Finally, the disk was placed at the sample
holder for the FTIR scanning from 400 cm-1 to 4000 cm-1.
49
2.2.3
Elemental Analysis
The X-ray fluorescence (XRF) technique was used to determine the elements
present in the rice husk ash quantitatively. The samples were further ground to 20-30
microns grain size prior to the XRF analysis and for the determination of loss on ignition
(%LOI). In the preparation of the specimen, firstly a mixture of 0.5 g sample and 5 g of
spectroflux (Johnson & Mathey, London), giving a dilution ratio of 1:10 was prepared.
The homogenous mixtures, placed in Pt-Au crucibles, were burnt for 20 min at 1000 ºC
in an automatic glass bead preparation machine (Claisse Bis 10 Fluxer model). The
homogenous melts were shaped into 3 mm thick, 32 mm diameter glass beads using PtAu moulds. Standards were also prepared by using the same procedure. For the XRF
analysis, a set of standard parameter for 10 major elements was set on a fully automated
Phillips PW 1480 Spectrometer. A standard calibration method was used, using 10
concentration-intensity curves, one for each element, constructed from 22 certified
reference materials (CRM) of rocks, minerals, ores, soils, sediments, bricks, etc. It is
believed that the matrix of the unknown is reasonably similar to those of CRM’s, giving
reasonably accurate results. The X-ray intensity of an element in a sample is compared
to the appropriate standard curve, giving its concentration. The concentrations of major
elements are reported as the weight percentages of the oxides, recalculated to 100%. Ten
major elemental components determined by XRF are SiO2, TiO2, Fe2O3, Al2O3, MnO,
CaO, MgO, Na2O, K2O and P2O5.
L.O.I. (loss on ignition) is the percentage of volatile components, mainly crystalbound water and organic carbon (as CO2), driven off from a sample when heated at 1000
ºC. An accurate weight of 1.000 g sample was placed in the muffle furnace,
subsequently heated at 1000 ºC for an hour. The loss of weight of the sample after the
combustion was compared to the weight of sample before the combustion to get the
value of the percentage of loss on ignition.
50
2.3 Synthesis of Zeolite NaY
The starting materials employed in the synthesis of zeolite NaY were sodium
aluminate supplied by Riedel De Haen, sodium hydroxide (NaOH) pellets from Merck
and silica from RHA. In order to prevent contamination, Teflon bottles and PTFE
beakers were used for the preparation of all solutions and for the reaction mixture. For
crystallization, Teflon bottles were employed. Glass vessels have been avoided as glass
participates in the reaction because silica and alumina can leach out of glass. Teflon
bottles and PTFE beakers were cleaned by immersing them in hydrofluoric acid 5% and
left overnight prior to the synthesis of the zeolite NaY.
The procedure for the synthesis of zeolite NaY was done according to Ginter, D.
M. (Robson, 2001) but with different compositions and types of raw materials. They had
successfully synthesized zeolite NaY by means of the seeding method. The preparation
involved three major steps namely the preparation of seed gel, followed by feedstock gel
and finally, the overall gel.
Batch composition for seed gel is 10.67 Na2O :Al2O3 : 10SiO2 :180 H2O and it
contributed 5% from the overall gel composition. Firstly, NaOH pellets were weighed
(1.6616 g) and transferred to the PTFE beaker; added with H2O (7.5 mL) and
continuously stirred with a magnetic stirrer until a clear solution is obtained after
dissolving the pellets. To prepare the aluminate solution, the prepared NaOH solution
(2.0 mL) was added to the sodium aluminate, NaAlO2 (0.7517 g) followed by stirring
and heating it gently until the mixture became an apparent solution. For the preparation
of silicate solution, RHA (1.5361 g) was mixed with the prepared NaOH solution in the
PTFE beaker and subsequently stirred and heated in the water bath at boiling water
temperature. The aluminate and silicate were then mixed in the PTFE beaker and stirred
for half an hour to achieve homogenization. Then, the mixture was transferred to the
Teflon bottle and capped for the ageing process to take place by leaving it at room
temperature for 24 hours. After 24 hours of ageing, the loose brown gel would appear
and it will be applied as seed gel for the seeding of the feedstock gel.
51
The second step is the preparation of feedstock gel which comprises 95% of the
whole gel. The methodology is similar to the preparation of seed gel but different in the
quantity of starting materials and required a larger PTFE beaker. Batch composition
used in the preparation of the feedstock gel is 4.30 Na2O :Al2O3 :10 SiO2 :180 H2O.
Initially, NaOH solutions were prepared by dissolving NaOH pellets (7.7585 g) with
distilled water (142.5 mL) in the PTFE beaker, stirred with magnetic stirrer until a clear
solution appeared. For the preparation of aluminate solution, sodium aluminate (13.7711
g) was dissolved in NaOH solution (42.5 mL) by stirring and heated gently on a hot
plate until a clear solution appeared. In the preparation of silicate solution, NaOH
solution (100 mL) was added to the RHA (28.1463 g) in the PTFE beaker. The mixture
was then stirred and heated in a hot water bath. Then the aluminate and silicate solution
were mixed in the PTFE beaker, subsequently stirred for 2 hours with the purpose of
making it completely homogenized. This combination of solution was used as the
feedstock gel.
Lastly, the overall gel comprising the batch composition of 4.62 Na2O :Al2O3 :10
SiO2 :180 H2O was prepared by mixing the feedstock gel and seed gel. The feedstock
gel was stirred magnetically and at the same time, the seed gel was added slowly and the
mixture was continuously stirred for 2 hours. The mixture was then transferred into a
Teflon bottle and left for ageing for 24 hours at room temperature. After ageing the
mixture for 24 hours, the mixture in the Teflon bottle was heated in an oven at 100 oC
for 22 hours. Teflon bottle was taken out, the cap was quickly opened and left to cool to
room temperature. Subsequently, the solid product was separated by suction filtration
and followed by washing with hot distilled deionized water and then dried overnight in
the oven at 100 oC. Finally, the dried zeolite NaY was weighed and placed in the plastic
bottle. The synthesis was repeated for 10 batches and labeled according to Zeo-NaY-S1
to S10. All of the synthesized zeolite NaY samples were mixed together in the plastic
bottle and was closed tightly. The mixture was then homogenized for 12 hours to ensure
good homogenization of the samples. The homogenized sample was sieved (250 mesh)
to obtain desired size of zeolite samples and ready to be used for the characterizations
and modifications steps and labeled as Zeo-NaY-S.
52
2.4 Characterization of Zeolite NaY
The synthesized zeolite NaY, together with the commercial zeolite NaY was
characterized by various characterization techniques including the X-ray diffraction
(XRD) technique, infrared spectroscopy (IR), surface area and porosity, elemental
analysis, the determination of unit cell and the ion exchange capacity (CEC and ECEC).
The commercial zeolite NaY was supplied by Zeolyst International (CBV 100) having
the SiO2/Al2O3 ratio of 5.1. The procedure for XRD technique is similar to the one in
Section 2.2.1 but after the diffractogram pattern was obtained, it was compared to an
existing pattern of zeolite Y from the powder diffraction files (PDF). For the infrared
spectroscopy, since the samples are in powder form, the KBr technique was used as
describe in Section 2.2.2.
2.4.1
Surface Area and Porosity
The specific surface area and porosity of synthesized and commercial zeolite
NaY were determined by using the QuantaChrome Autosorb-IC machine. Firstly, all of
the samples were ground in a mortar to generate the smaller sized solid sample.
Approximately 0.04 g sample was taken as the representative of the overall sample and
was then transferred to the sample holder. Prior to the adsorption of N2 gases, the sample
was degassed at 350 oC for three hours. The analyses of samples were done according to
the multipoint measurements provided by the BET surface area technique, total pore
volume and average pore size.
53
2.4.2
Elemental Analysis
As described in the Chapter 1, the sample must be in the liquid form prior to the
analysis of sodium and aluminum by AAS and ICP-MS, respectively. Thus, the
decomposition of sample through the digestion of solid sample with hydrofluoric acid
was carried out. The procedure for the elemental analysis using XRF was performing
according to the procedure stated in Section 2.4.3.
2.4.2.1 Decomposition of Zeolite Samples
Prior to the elemental analysis by atomic absorption spectroscopy (AAS) and
inductively coupled plasma mass spectrometry (ICP-MS), the solid samples must be
decomposed to produce the liquid form. In this research, the decomposition procedure of
the zeolite sample was adopted from the procedure used for clay as both have similar
elemental composition in their structure (Wilson, 1994). During the decomposition
process, the use of glassware was avoided because the hydrofluoric acid can react with
the silica from the glassware. For the decomposition, 50 (± 0.01) mg of the prepared,
representative sample was placed in a PTFE bottle with 0.5 mL aqua regia. The aqua
regia solution is the solution in which 3 volumes of concentrated HCl was mixed with 1
volume of concentrated HNO3 and this solution was used immediately after the
preparation. The concentrated hydrofluoric acid (48%) (3 mL) was then added and the
vessel was sealed tight instantaneously and was placed in an oven at 100 ± 5 oC for one
hour. After cooling, the solution was transferred to a 50 mL plastic beaker containing
boric acid (H3BO3) (2.8 g) followed by the addition of distilled water (10 mL) and
subsequently the mixture was stirred magnetically to dissolve any insoluble fluorides.
The solution was diluted to 100 mL in the plastic volumetric flask and stored in a
polyethylene bottle. This solution was ready for major elemental analysis.
54
2.4.2.2 Determination of Sodium
The amount of sodium present in the synthesized samples and commercial
zeolite NaY were determined with a flame atomic absorption spectroscopy (FAAS)
(GBC, model Avanta, Australia) after the decomposition of the samples with
hydrofluoric acid (HF). The glassware and plastic sample holder used in this procedure
were washed with nitric acid 10%, (HNO3) by immersing them overnight in order to
dissolve and eliminate the contamination inside the apparatus, in particular the heavy
metals as these elements will cause interferences during measurement with AAS. All of
the decomposed samples were diluted 100 times with distilled water since the range of
series standard solution is in low concentration, 0.4 to 2.0 ppm. The standard solution
was prepared by diluting 1000 mg/L of stock sodium solution to the required series of
standard solution using distilled water in a 100 mL volumetric flask. The standard and
decomposed samples solutions were aspirated into the flame and the absorbance was
recorded at 589.6 nm, the specific absorbance for sodium. Water was aspirated between
each sample. The standard calibration curve was prepared automatically by plotting the
absorbance versus concentration for each standard and the concentration of sodium in
samples was calculated automatically by the instrument, in mg/L. Quality control and
spike recovery solution were measured after every five samples solution in order to
evaluate and verify the data during the measurement of sodium in samples.
2.4.2.3 Determination of Aluminum
Aluminum content in zeolite was determined by using inductively coupled
plasma-mass spectrometry (ICP-MS) (Perkin Elmer, model Elan 6000) instrumental
technique. Due to the high sensitivity of ICP-MS, double distilled deionized water and
high purity reagents and acid were used in the preparation of samples and standard
solution. All of the apparatus were washed with 10% nitric acid (HNO3) by immersing
them in this acid overnight with the aim to eliminate and dissolve the metals
55
contaminant. A series of standard solution ranging from 50 to 250 µg/L were prepared
by diluting the stock multi-element ICPMS calibration standard solution, 1000 µg/L
(Perkin Elmer) with addition of 2 mL of Ultra-pure nitric acid concentrated from subboiling distillation that was supplied from Fischer (optima grade). Nitric acid is
preferred for ICP-MS in order to minimize polyatomic ion interferences. Each of the
sample was prepared in three replicates and was diluted 1000 times prior to the
determination by ICP-MS. Spike recovery studies and quality control were set up to
verify the accuracy and precision of the instrument while measurements of samples were
taken.
2.4.2.4 Determination of Loss on Ignition and Percentage of Silica
The loss on ignition (LOI) method was carried out following Malaysian Standard
procedure, MS ISO 3262: 1975. Certain weights of dried samples (about 0.2 g) were
placed in small ceramic crucibles and placed in the oven at 100 oC overnight. The dried
samples were then weight (about 0.1 g), m0, placed in a platinum crucible and ignited in
a muffle furnace (Carbolite muffle furnace, model: ELF 11/6B, Barloworld Scientific,
England) at 1000 oC for 30 minutes, followed by cooling in a desiccator. After the
temperature of the sample was in equilibrium with the room temperature, the sample
was weighed (m1). The LOI, as a percentage by mass, is given by the formula below:
% LOI =
m0 − m1
× 100 %
m0
(17)
Silica content was determined using the standard SIRIM method (ISO 32621975). The residue from the determination of LOI was used to determine the percentage
of SiO2 content. The residue in the platinum crucible was added gradually with 1 ml of
50% sulfuric acid (H2SO4). The crucible was heated gently until fuming has ceased in
the fume cupboard. The crucible was then placed in a muffle furnace set at 900 oC for 30
minutes to continue heating. The residue was then removed from the furnace, cooled in
56
the desiccator and weighed (m2). Later, the residue in the platinum crucible was added
slowly with a mixture of H2SO4 : HF (1:5) and heated on a hot plate until the white
fumes no longer evolved. The heating was continued in the muffle furnace at 900 oC.
The crucible was removed after 30 minutes from the muffle furnace, cooled in the
dessicator and weighed (m3). The calculation on the percentage silica present is based on
this equation:
% SiO 2 =
2.4.3
m 2 − m3
× 100 %
m1
(18)
Determination of Unit Cell
The determination of the unit cell of zeolites was carried out according to the
standard test method for the determination of the unit cell dimension of a Faujasite-type
zeolite (D 3942-03) provided by the international standard test method (ASTM
International, 2003). As a summary of the method, a sample of the zeolite Y was mixed
with powdered silicon and the zeolite unit cell dimension was calculated from the X-ray
diffraction pattern of the mixture, using the silicon reflections as a reference. Firstly,
about 1.5 g of powdered zeolite samples was placed in the drying oven at 110 ºC for 1
hour. The dried zeolite was then blended with about 0.05 g of silicon in a mortar and
was ground until intimately mixed. The sample was put in the sample holder for the
measurement of X-ray diffraction. The determination of the X-ray diffraction pattern
was done as referred to the procedure in section 2.2.1. The angle of the zeolite
reflections at about 53.4º and 57.8º 2θ and that of the 56.1º silicon reflection to at least
two decimal places were measured. The measured reflection angles for the zeolite were
corrected by adding to each of the quantity (calculated minus measured angle of the
silicon reflection). The unit cell dimension was then calculated in accordance with
equations 2 and 3 in Section 1.3.3.1.
57
2.4.4
Determination of Cation Exchange Capacity
In order to determine the total cation exchange capacity (CEC) in the zeolites,
the sodium cations which neutralize the framework of aluminosilicates are exchanged
with other cation having a similar size of sodium. In contrast, the external cation
exchange capacity (ECEC) of zeolite was done by exchanging the sodium cation with
the larger cation of surfactant, i.e. HDTMA that could hardly penetrate into the pore of
zeolite.
2.4.4.1 Total Cation Exchange Capacity
The procedure for the determination of CEC was based on Chapman, 1965
(Wilson, 1994). This method was applicable to most soil and zeolite samples. The
zeolite sample was mixed with an excess of sodium acetate solution, resulting in an
exchange of the added sodium cations for the matrix cations. Subsequently, the sample
was washed with isopropyl alcohol. An ammonium acetate solution was then added
which replaced the adsorbed sodium with ammonium. The concentration of displaced
sodium was then determined by AAS. The reagents used for this procedure were sodium
acetate (NaOAc), 1.0 N, ammonium acetate (NH4OAc), 1.0 N and isopropyl alcohol
supplied by Merck. Sodium acetate (NaOAc), 1.0 N was prepared by dissolving NaOAc
(136 g) in water and diluted to 1000 ml in a volumetric flask. The pH of this solution
was adjusted by adding a few drops of acetic acid or NaOH to the solution to pH 8.2.
The 1.0 N of ammonium acetate (NH4OAc) was prepared by diluting glacial acetic acid
(99.5%) (114 mL) with distilled water to a volume approximately one liter in a 2 L
volumetric flask. The concentrated ammonium hydroxide (NH4OH) (138 mL) was then
added and mixed with water to obtain an amount of about 1980 mL. The pH was
adjusted with NH4OH to obtain a pH of 7 and this solution was diluted to the 2 L mark
with distilled water.
58
For the preliminary step, about 0.2 g of the sample was weighed accurately and
transferred to a 50 mL centrifuge tube. The sodium acetate, 1.0 N (6.6 mL) was added to
the sample and the tube was closed tightly. This tube was shaken with an orbital shaker
(150 rpm) for 10 minutes. The tube was then centrifuged to separate the solid and the
solution into two phases until the supernatant liquid was clear. The liquid was decanted
and this procedure was repeated three more times. Subsequently, about 6.6 mL of 99%
isopropyl alcohol was added to the sample, the tube closed tightly, shaken for 10
minutes, centrifuged and finally, the liquid was decanted. This procedure was repeated
two more times. The final step was the addition of ammonium acetate, 1.0 N (6.6 mL)
into the solid sample in the centrifuge tube, stoppered tightly, and shaken with a
mechanical shaker for 10 minutes and centrifuged for 10 minutes. The supernatant was
kept in a 100 mL volumetric flask. This procedure was repeated three times. The
combined solution was diluted to the 100 mL mark with ammonium acetate solution.
The determination of the sodium concentration was analyzed by AAS (GBC, model
Avanta, Australia).
2.4.4.2 External Cation Exchange Capacity
The procedure for the determination of ECEC was adopted from Bouffard
(1998). The procedure for ECEC is similar to the determination of CEC but differs in the
last step in which the sodium cation was replaced by HDTMA cation. The procedure for
ECEC determination involved: (1) saturation of the sample with sodium cations, (2)
exchanging the sodium cation by HDTMA and (3) analyzing the concentration of
sodium using AAS.
Chemicals used in this procedure were sodium acetate (NaOAc), isopropyl
alcohol 99% and hexadecyltrimethyl ammonium bromide (HDTMA-Br) which were
supplied by Merck. First, each sample was weighed accurately (0.2 g) and transferred to
a 50 mL centrifuge tube. The saturation sample with sodium cations and wash with
59
isopropyl alcohol steps were followed the procedure for the determination of total cation
exchange capacity (CEC) described in Section 2.4.4.1. The last step involved the
exchange of sodium cations with hexadecyltrimethyl ammonium cations. The HDTMA
solution, 0.5 mmol L-1 (6.6 ml) was added to each sample taken from the previous step.
The centrifuge tube was then closed tightly, shaken for 10 minutes and centrifuged.
Liquid was then decanted into a volumetric flask (100 mL). This last procedure was
repeated three times. The combined solution taken from the last step was diluted to the
mark of volumetric flask with HDTMA solution. The concentration of displaced sodium
was then determined by atomic absorption spectroscopy (GBC, model Avanta,
Australia).
2.5
Preparation of Surfactant Modified Zeolite Y
Three series of surfactant modified zeolite Y (SMZY) were prepared by reacting
zeolite with aqueous solutions containing a single type of HDTMA. Hexadecyltrimethyl
ammonium (HDTMA) bromide was supplied by Merck-Schuchardt. HDTMA was
added in an amount equal to 50%, 100% or 200% of external cation exchange capacity
(ECEC) of zeolite. This experiment was to study the effect of different surface coverage
of HDTMA onto zeolite in the sorption of anions in water. The SMZY was identified by
a prefix that stated the percentage of zeolite’s ECEC which was supposedly to be
occupied, followed by the abbreviation for the type of zeolite; i.e. S and C, for the
synthesized zeolite NaY and commercial zeolite NaY, respectively. The abbreviation of
each modified zeolites are listed in the Table 2.1.
60
Table 2.1: The abbreviation of the surfactant modified zeolite Y
Precursor
Percent surface coverage
Abbreviation
Synthesized Zeolite NaY
50%
SMZY-50-S
100%
SMZY-100-S
200%
SMZY-200-S
50%
SMZY-50-C
100%
SMZY-100-C
200%
SMZY-200-C
Commercial Zeolite NaY
For example, the preparation of SMZY-50-S needed 0.9788 g of HDTMAbromide to saturate 50% of the ECEC synthesized zeolite NaY (8 g). The calculation of
the amount of HDTMA needed was shown below:
ECEC of synthesized zeolite NaY
= 67.14 meq/100g
Molecular weight of HDTMA bromide
= 364.46 g/mol
For 1 meq/100g
=
6.02 × 1020 adsorption sites.
=
1 mmol/100g
=
0.01 mmol/g
=
1.0 × 10-5 mol/g
Hence, 1 g of synthesized zeolite with ECEC
= 67.14 meq/100 g can be satisfied by 6.714 ×10-4 mol of cations to
achieve 100% satisfaction
Amount of HDTMA bromide needed
= 0.50 × 8 g × 6.714 × 10-4 × 364.46 g/mol
= 0.9788 g HDTMA-bromide
After the aqueous solutions were mixed with zeolite, the mixture was stirred
using a magnetic stirrer for 5 days at room temperature. The mixture was then filtered by
61
vacuum filtration and the solid sample was dried at 60 ºC for overnight. The resultants
SMZY were readily characterized and used for the adsorption study.
2.6
Characterization of Surfactant Modified Zeolite Y
The surfactant modified zeolite Y was characterized by various techniques in
order to study their structure, the elemental compositions and the other properties related
to the modifications. The characterizations included X-ray diffraction technique, infrared
spectroscopy, elemental analysis, surface area and porosity, dispersion behavior and the
maximum adsorption of HDTMA onto the zeolite. The XRD technique and IR
spectroscopy methods were done as described in Sections 2.2.1 and 2.2.2, respectively.
The elemental analyses involved the determination of sodium cation by flame
photometer after the decomposition of samples and the analysis of carbon, hydrogen and
nitrogen by Carbon-Hydrogen-Nitrogen-Sulfur analyzer (CHNS). The procedure for
determining the surface area and porosity has been discussed in Section 2.4.1.
2.6.1
Elemental Analysis
The determinations of sodium cation contained in the SMZY were carried out
after the samples were decomposed using hydrofluoric acid. The procedure for the
decomposition samples is described in the section 2.4.2.1. The sodium content in the
surfactant modified zeolite Y was determined by flame photometer (model PFP7,
Burkard Scientific, UK). The determination procedure was done according to the
method described for the chemical tests for cement proposed by the British Standards
Institution (1970). The sodium stock solution (100 mg/L Na2O) was prepared by
dissolving 0.1886 g of dried analytical reagent grade NaCl in distilled water and diluted
62
to 1000 mL. The calibration solutions were prepared using the quantities given in Table
2.2.
Table 2.2: Solutions for calibrating flame photometer
Calibration
Sodium stock
HNO3
Water to make
Equivalent concentrations,
solution
solution (mL)
(mL)
(mL)
Na2O (mg/L)
Scale-zero
0
10
1000
0
Scale-100
50
10
1000
5
Standard 1
5
5
500
1
Standard 2
10
5
500
2
Standard 3
15
5
500
3
Standard 4
20
5
500
4
The sodium light filter was set in the flame photometer to read 0 with scale-zero
solution and 100 with scale-100 solution. The readings obtained for each of the
intermediate calibration solutions was recorded and the calibration graph of instrument
reading against mg per liter of Na2O was constructed. The decomposed samples
solutions were then aspirated into the flame and the reading was recorded. The value of
the concentration Na2O in the samples was calculated from the standard calibration
curve.
For the determination of the percentage of the amount of carbon, hydrogen and
nitrogen in the zeolite and surfactant modified zeolite samples, CHNS analyzer model
FlashEA 1112 series (Thermo Finnigan, Italy) was used. Helium was used as carrier gas
whereas oxygen was the gas for sample oxidation. The furnace temperature was
maintained at 900 ºC. About 2.5-3.0 mg of the sample was weighed and introduced into
the universal tin container with a spatula. The container was then closed using two
spring tweezers. The tin container containing the sample was stored in the autosampler
and dropped into the combustion reactor after a few seconds. Atropina (C17H23NO3) was
63
used as the standard in the analyses. The amount of carbon, hydrogen, nitrogen and
sulfur present in the samples were measured as a percentage (%) amount.
2.6.2
Dispersion Behavior
In order to study the relative position in an oil-water mixture of unmodified and
modified zeolites, an approximately 0.06 g of sample was added in the mixture of
distilled water (2 mL) and n-hexane (2 mL) in a 10 mL glass bottle with stopper. The
images of each glass bottle were taken immediately after the addition of sample. The
relative positions of the particles in the mixture were compared. The dispersion
behaviour study was to acquire information in relation to the spreading behaviour of the
surfactant modified zeolite Y and the unmodified zeolite in aqueous solutions; either
they disperse well in water or in the organic phase. The samples from the relative
position study were shaken for 2 hours at room temperature. The images of each sample
were taken instantaneously after the shaking. The emulsions formed were then left at
ambient conditions for the coalescence of droplets to occur. The images were captured at
an appropriate time. The dispersion behavior of each samples were compared.
2.6.3
Maximum Adsorption of HDTMA
Prior to the isotherm study of uptaking HDTMA onto synthesized zeolite NaY,
the synthesized zeolite were ground and sieved to the desired aggregate size (250 mesh).
The synthesized zeolite NaY (0.5 g) was weighed accurately and added with the
HDTMA solutions to yield cation dosages in the range from 25 to 250% of zeolite
external cation exchange capacity (ECEC) in the 50 mL centrifuge tube. The
suspensions of zeolites and HDTMA cation were shaken in an orbital shaker for 24
hours using an orbital shaker (Protech, model no. 722) at a constant agitation rate at the
64
ambient temperature. For the well separation of solid and liquid, the tube was then
centrifuged (5000 rpm, 15 minutes) and subsequently the supernatant was decanted by
the filtration technique using a Whatman filter paper (125 mm). The liquid supernatant
was then analyzed for the determination of the concentration of the remaining HDTMA
in the solution using the total organic carbon analyzer (TOC-Ve, Shimadzu, Japan).
About 20 μL of the supernatant was taken with a syringe and injected into the injection
port of TOC instrument. The concentration of the total organic carbon was determined
automatically by the instrument. Assuming complete conversion of organic cations to
CO2 during TOC analysis, the TOC content of samples were converted to the
equilibrium concentration of HDTMA (mmol/L).
2.7
Adsorption Studies
The series of the surfactant modified zeolite Y (SMZY) were evaluated
systematically using the isotherm equilibrium study for acquiring the value of the
maximum adsorption of the toxic metals. In addition, the initial pH of the solution can
also affect the adsorption process, thus the adsorption studies also include the effect of
the initial pH of each species. Because the SMZY is possible to adsorb cation and anion,
the adsorption studies for the Cr3+ (Cr(III)), chromate anion (Cr(VI)), arsenate (As(V))
and arsenite (As(III)) were chosen.
2.7.1
Adsorption of Cr(III)
The Cr(III) species exists in the form of cation , Cr3+, thus the zeolite NaY can
effectively remove this species from water because of its cation exchange property.
Therefore, this study was highlighted in the adsorption studies of Cr3+ by the unmodified
synthesized and the unmodified commercial zeolite NaY. Studies done included the
65
kinetic study based on the different agitation time, the effect of the initial solution pH
and the isotherm study. The isotherm study was done using the unmodified zeolite Y and
SMZY. The determination of the concentration of chromium in the initial and final
solution was carried out using the AAS technique and will be explained in Section
2.7.1.4.
2.7.1.1 Kinetic Study
There are several parameters affecting the adsorption rate including stirring time.
The kinetic study which was based on the effect of stirring time for the Cr(III) removal
was carried out for the unmodified synthesized and the commercial zeolite NaY via the
batch method and with different contact times. The stock solution of 250 and 500 mg/L
of Cr(III) was prepared by dissolving an appropriate amount of Cr(NO3)3.9H2O (Merck)
in 250 mL distilled deionized water. A constant amount of zeolite samples (0.1000 g)
was mixed with 25 mL Cr(III) solution in 50 mL centrifuge tube. The suspension was
shaken for varying periods of time starting from 10 minutes to 48 hours using an orbital
shaker (Hotech) with constant agitation rate (120 rpm) and at room temperature. The
solid phase was then separated by filtration through a Whatman filter paper (125 mm).
The concentrations of chromium in the supernatant solution after adsorption were
determined with the AAS technique.
2.7.1.2 Effect of Initial pH
The pH of the solution also determines the ionic species present in the solution
and the structure of zeolite. The effects of initial pH studies on the removal of Cr(III)
was performed by the initial concentration of Cr(III) of 300 mg/L and 0.1000 g of both
unmodified zeolite Y. The initial pH of the solution (2, 3, 4, 5) was adjusted using HNO3
66
solution or diluted NaOH solution measured with a pH meter model CyberScan pH/Ion
510 (Eutech Instruments). The solution was shaken for an appropriate time in the orbital
shaker with constant agitation rate (120 rpm). The mixture was then withdrawn and
filtered through a Whatman filter paper and the pH of the liquid checked. The filtrate
was analyzed by flame atomic absorption spectroscopy (FAAS) after an appropriate
dilution of the filtrate solution for the determination of Cr(III).
2.7.1.3 Isotherm Study
The adsorption equilibrium experiments on chromium were conducted to
determine the adsorption capacity of Cr(III) under a given set of conditions. The
sorption isotherm study was carried out via the batch method for the unmodified and
modified zeolite Y. Essentially, 25 mL of a solution containing the trivalent chromium
with an initial concentration ranging from 100 to 600 mg/L (pH 3.5) was mixed with
precisely 0.1000 g of samples in a 50 mL centrifuge tube. The tubes were sealed and
shaken for an appropriate time (according to the kinetic studies) with an orbital shaker
(120 rpm) at room temperature. Finally, the solution was filtered through a Whatman
filter paper (125 mm). The pH of the solution was measured before and after shaking.
The concentration of the remaining Cr(III) in the solutions after contact with the samples
was determined by FAAS. The Freundlich and Langmuir adsorption isotherms were
then used to analyze the results as these isotherms have been shown as being useful in
describing adsorption behaviour of metals on zeolites.
2.7.1.4 Determination of Cr(III) by FAAS
The concentration of Cr(III) in the initial and final solutions were determined by
the flame atomic absorption spectroscopy (FAAS) (Perkin Elmer, model AAnalyst 400).
67
The standard calibration solution was prepared from the appropriate dilution of the stock
solution chromium nitrate, Cr(NO3)3.9H2O (Merck) 1000 mg/L. The concentrations of
the standard solutions were prepared in the range from 0.1 to 5.0 mg/L. In order to get
the precise value of the amount Cr(III) in the solution, the correlation coefficient of the
standard calibration curve should be above 0.98. The standard samples solutions were
aspirated into the flame and the absorbance acquired at 357.87 nm, the exact absorbance
for chromium. An amount of distilled water was aspirated between each sample. The
automatic plotting of the standard calibration curve was done by the instrument by
plotting the absorbance against concentration for every standard measured. The series of
the samples solution were diluted with an appropriate dilution before the samples were
aspirated in the flame. The solutions containing known amounts of Cr(III) were
introduced to the flame for every 5 to 10 samples for the quality control to avoid
inaccurate value of the Cr(III) concentration. The concentrations of chromium in the
solution were then automatically calculated by the instrument, in mg/L.
2.7.2
Adsorption of Cr(VI)
The property of anion exchanger in the SMZY enabled them to adsorb the
species of hexavalent chromium, Cr(VI) as it can exist in the form of chromate anions.
Hence, the evaluation on the removal capacity of the chromate anion by SMZY was
studied involving the effect of the initial pH of the Cr(VI) solution and the isotherm
study. The Cr(VI) solution was prepared by dissolving a suitable amount of potassium
dichromate, K2Cr2O7 (Merck, Darmstadt, Germany) in distilled water. In order to prove
that the structure of the framework zeolite did not collapse after the adsorption and to
construct the adsorption model, the SMZY-chromate was prepared by contacting the
SMZY in elevated concentration of chromate and subsequently their structure was
studied. The determination of Cr(VI) in the solution will be described in Section 2.7.2.4.
68
2.7.2.1 Effect of Initial pH
The pH of the Cr(VI) solution (10 mg/L) was adjusted with the addition of
NaOH or HNO3 solution to obtain the pH 3, 5, 7, 8 and 10. The pH of the solution was
measured by pH meter CyberScan pH/Ion 510 pH meter (Eutech Instruments). An
accurate amount of SMZY (0.2000 g) samples were mixed with the previously prepared
Cr(VI) solution (20 mL) in a 50 mL centrifuge tube. The samples were then shaken for
48 hours. The supernatant was filtered through a Whatman filter paper (125 mm); the pH
was checked and diluted prior to the determination of Cr(VI). The diluted supernatant
was then analyzed for Cr(VI) left in the solution by UV-Vis spectrophotometer.
2.7.2.2 Isotherm study
Isotherm study of Cr(VI) adsorption was conducted in aqueous solution and by
batch studies. An accurate amount of the unmodified and modified zeolite (0.5 g) was
placed in a centrifuge tube 50 mL and added with Cr(VI) solution having concentrations
in the range of 10 to 70 mg Cr(VI)/L. The pH of the Cr(VI) solutions were kept between
3 and 4. The mixtures were shaken at room temperature at the agitation rate of 150 rpm
using an orbital shaker (Hotech) for 48 hours (a period shown to be sufficient to reach
adsorption equilibrium). The mixture was then filtered and the extracted solution was
analyzed to determine the Cr(VI) concentration by UV-Vis spectrophotometer. The
Langmuir isotherm was used to determine the maximum adsorption capacity of Cr(VI)
onto the SMZY.
69
2.7.2.3 SMZY-Chromate Structure Study
Approximately 5 g of the SMZY was weighed and placed in the PTFE beaker
(250 mL). The samples were then mixed with 50 mL Cr(VI) solution (1000 mg/L). The
suspension was stirred with a magnetic stirrer for 5 hours at room temperature. The
suspension was then filtered and the solid residue was heated in the oven at 60 ºC for 24
hours in order to dry it. Subsequently, the solid sample was ground prior to the study of
its structure. The identification of its structure was determined by X-ray diffraction
(XRD) technique and infrared (IR) spectroscopy, summarized in the Sections 2.2.1 and
2.2.2, respectively. The diffractogram of XRD and the spectrum of IR were compared
before and after the adsorption of Cr(VI).
2.7.2.4 Determination of Cr(VI) by UV-Vis Spectrophotometer
The procedure for the determination of the hexavalent chromium, Cr(VI) in the
solution was based on the standard method set up by American Public Health
Association (APHA) (Cleseri et al., 1989). This procedure measured only hexavalent
chromium (Cr(VI)) in which the hexavalent chromium was determined colorimetrically
by reaction with diphenylcarbazide in acid solution. A stock chromium solution (50
mg/L) was prepared by dissolving potassium dichromate, K2Cr2O7 (141.4 g) in water
and diluted to 1000 mL. The diphenylcarbazide solution was prepared by dissolving 1,5diphenycarbazide (250 mg) in acetone (50 mL). In the preparation of standard
calibration curve, Cr(VI) standard solution was treated by the same procedure as the
sample to compensate the slight losses of Cr(VI) during digestion or other analytical
operations. The volume of standard chromium solution (5 mg/L) ranging from 2.00 to
20.0 mL was pipetted to give standards of 10 to 100 mg Cr, into 250 mL conical flasks.
After the development of color, a suitable portion of each solution was transferred to a
1-cm absorption cell, the absorbance was measured at 540 nm. Distilled water was used
as a reference. In order to get the accurate value of the concentration of Cr(VI) in the
70
solution, the correlation coefficient of standard calibration curve should be above 0.98.
For the development of color, an appropriate volume of sample solution (initial and final
solution) was diluted by 1 M H2SO4 in 25 mL volumetric flasks. It was then added with
0.5 mL 0.25% diphenylcarbazide solution, shaken and kept for full color development in
5 min. After the development of color, the solution was transferred to a 1-cm absorption
cell and the absorbance was measured at 540 nm using an ultra violet-visible (UV-Vis)
spectrophotometer (Perkin Elmer, model Lambda 25) and distilled water was used as a
reference. Cr(VI) adsorption was determined from the difference between the initial and
final concentrations using the unit mmol Cr(VI)/kg zeolite.
2.7.3
Adsorption of As(V) and As(III): Preliminary Study
Prior to further adsorption study of arsenic by SMZY, the adsorptions of the
single component of arsenate (As(V)) and arsenite (As(III)) solution were determined.
The unmodified and modified zeolites samples were used in this preliminary study. The
stock solution of As(III) (1000 mg/L) was prepared by dissolving As2O3 (1.32 g) in a
solution containing 4 g of NaOH pellet in 100 mL and after the dissolution was
completed, the mixture was then added with 20 mL concentrated HNO3 and finally
diluted to the 1000 mL mark. The stock solution of As(V) was prepared by dissolving
Na2HAsO4 (0.0416 g) in a solution containing 0.2 g of NaOH in 10 mL and finally
diluted to the 50 mL by distilled water. The stock solutions of both species were diluted
to the desired concentrations with distilled water for the adsorption study.
For the preliminary adsorption study, 0.1 g of samples were weighed accurately
and placed in the 50 mL centrifuge tube containing the single component of As(III) (20
mL, 20 mg/L) or As(V) (pH 8, 20 mL, 20 mg/L) species. The centrifuge tube was then
shaken for 24 hours by orbital shaker at a constant agitation rate (120 rpm). The solid
sample and solution was filtered with a Whatman filter paper (125 mm). The filtrate was
analyzed for the concentrations of the remaining As(V) or As(III) in the solution. FAAS
71
was used to determine the concentration of As(V) and As(III) and this procedure will be
described in Section 2.7.4.3. The adsorption capacities of both species were stated as the
percentage of the adsorption.
2.7.4
Adsorption of As(V)
The additional adsorption study was done for the adsorption of As(V) by
modified and unmodified zeolite Y. The study also included the investigation on the
effect of the initial pH and the isotherm patterns. The preparation of stock solution of the
As(V) was described in Section 2.7.3 and the determination of As(V) concentration
followed the procedure in Section 2.7.4.3.
2.7.4.1 Effect of Initial pH
The samples for this study comprised the SMZY from both type of zeolites.
About 0.2 g of the sample was weighed precisely and placed in the 50 mL centrifuge
tube. The solution containing 20 mg/L of As(V) (20 mL) having a different initial pH
was added to the sample. The adjustment of the pH solution was carried out by the
addition of NaOH or HNO3 solution to obtain the pH 2, 4, 6, 7, 8, 10 and 12. The pH
was measured using a CyberScan pH/Ion 510 pH meter (Eutech Instruments). The
mixture in the tube was shaken for 5 hours at a constant agitation rate (120 rpm) and at
ambient temperature. The mixture was then separated by filtration and the pH of the
filtrate was determined. Finally, the filtrate was analyzed for the concentration of As(V)
using FAAS.
72
2.7.4.2 Isotherm Study
For the purpose of acquiring the value of the maximum adsorption capacity of
As(V) by surfactant modified zeolite Y and unmodified zeolite Y, the isotherm study
was carried out with adsorption at different initial concentrations of As(V) solution. The
As(V) solution was prepared with the appropriate dilution of the stock solution to get the
required concentrations of As(V) of 10, 20, 30, 40 and 50 mg/L. About 0.2 g of sample
was weighed precisely and added with 20 mL As(V) solution (pH 6) in the centrifuge
tube 50 mL. The tubes were then shaken for 5 hours and the supernatant subsequently
filtered. The filtrate was analyzed for the concentration of As(V) using FAAS technique
(Section 2.7.4.3).
2.7.4.3 Determination of Arsenic by FAAS
Because of the high concentration of both arsenic species used to construct the
isotherm study and to study the effect of initial pH, the flame atomic absorption
technique spectroscopy (Perkin Elmer, model AAnalyst 400) was utilized. The
electrodeless lamp with the exact wavelength of 234.98 nm for arsenic was used.
Standard solutions of arsenic were prepared in the range of 15 to 60 mg/L by diluting the
stock solution of arsenic (1000 mg/L) (BDH, Poole, England). The sample solution was
aspirated in the flame followed by the solution having a known concentration of arsenic
for the evaluation of quality control (QC). The concentration of the arsenic was
calculated automatically by the instrument.
CHAPTER 3
RESULTS AND DISCUSSION: SORBENTS DEVELOPMENT
3.1
Rice Husk Ash as a Source of Silica
Rice husk ash (RHA) was obtained from the combustion of rice husk at 600 °C
using the rice husk burner. The X-ray diffractogram pattern of RHA is shown in Figure
3.1. This diffractogram reveals that the silica present in RHA was completely
amorphous to XRD as indicated by the featureless pattern and the absence of significant
peak and the appearance of diffuse maximum at 2θ = 23° typical for amorphous silica
(Halimaton Hamdan et al., 1997).
10
20
30
2-Theta-Scale
Figure 3.1
The XRD diffractogram of RHA
40
50
74
The infrared spectrum for RHA is shown in Figure 3.2. This spectrum
demonstrates a very strong, intense and broad peak at 1100 cm-1 which corresponds to
the Si-O-Si asymmetric vibration and due to the greater ionic character of the Si-O
group, this band is much more intense than the corresponding C-O band for ether
(Socrates, 1994). This spectrum also exhibits bands at 804 cm-1 and 470 cm-1 which
correspond to the symmetric stretching of SiO4 tetrahedra and Si-O bending band
vibrations, respectively. This data indicates that the silica phase found in RHA was
completely amorphous due to the absence of bands near 622 cm-1 which is identical to
tridymite (crystalline phase) that shows the presence of the cristobalite phase (Willis et
al., 1987). This observation also supports the results obtained from XRD that the RHA
contains the amorphous form of silica.
45.0
%T
40.0
804.3
470.6
35.0
30.0
1192.9
RHA-P
25.0
1102.2
3465.8
20.0
2000.0
Figure 3.2
1500.0
1000.0
500.0
1/cm
Infrared spectrum of rice husk ash
The composition of major elements present in the RHA as analyzed by X-ray
fluorescence (XRF) technique can be seen in Table 3.1. The silica content in RHA is
somewhat higher because most of the impurities were eliminated during combustion at
that temperature.
Table 3.1 : Chemical composition of rice husk ash
Oxide SiO2
%
TiO2 Fe2O3 Al2O3 MnO CaO MgO Na2O K2O P2O5 LOI
91.65 0.03
0.27
0.27
0.07
0.58
0.58
0.74
0.74
0.19
4.88
75
3.2
Synthesis of Zeolite NaY
The synthesized zeolite NaY (Zeo-NaY-S) together with the commercial zeolite
NaY (Zeo-NaY-C) acting as comparison was characterized using XRD and FTIR for the
identification of the structure; the XRF, ICPMS, AAS and classical wet methods for
elemental analysis; and the physicochemical properties which are unit cell, ratio of
silica/alumina, surface area and porosity, cation exchange capacity (CEC) and external
cation exchange capacity (ECEC).
3.2.1
X-Ray Diffraction Technique
In order to prevent the formation of other zeolites or phases during the synthesis
of zeolite Y and to get highly pure zeolite NaY from RHA, the seeding and ageing
techniques were highlighted. As a comparison, the procedure for the synthesis of zeolite
NaY from RHA either without ageing or seeding techniques was carried out and the
products were characterized by XRD technique. This was done to study the effect of
ageing and seeding techniques in the synthesis of zeolite NaY.
The preliminary preparation of zeolite NaY from RHA without ageing and
seeding techniques revealed that the mixture consisted of the zeolite Y and A. Besides
that, we also prepared the zeolite NaY from RHA with ageing but without the seeding
technique. It is clear that the main impurity in the synthesis of zeolite Y without the
seeding technique was attributed to the formation of zeolite P. The XRD patterns of both
products were assembled in Figure 3.3 while Figure 3.4 shows the XRD pattern of the
zeolite NaY that was synthesized via the seeding and ageing techniques. The
diffractogram of the zeolite NaY from the seeding and ageing techniques exhibit many
significant peaks from 2θ = 5° to 50º indicating that the samples are in the crystalline
form. Furthermore, when this pattern was matched up with the peaks corresponding to
the zeolite NaY structure as shown in Figure 3.4, it shows that the product formed from
76
the synthesized zeolite NaY by seeding and ageing techniques was highly pure zeolite
NaY because all of the peaks were well matched with the peaks of zeolite NaY structure.
In addition, the diffractogram also demonstrates that no other significant peaks
correspond to zeolite A and P emerged, which confirmed the elimination of the
formation of zeolite A and P. There were also no impurities and other phases formed in
the synthesized zeolite NaY.
Y
I
n
t
e
n
s
i
t
y
A
Y
Y
Y
Figure 3.3
Y
A
Y Y
P
(a.u.)
5
A
Y
P
Y
Y
A
Y
A
P
Y
Y
Y
Y
Y
NA-NS-Zeo
Y
P
Y
Y
Y
A
A
Y
Y
Y
2-Theta - Scale
P
Y
Y
Y
A-NS-Zeo
5
The X-ray diffraction patterns of the product obtained from the synthesis
without ageingand seeding technique (NA-NS-Zeo) and the product from the
synthesized zeolite Y with ageing but without seeding technique (A-NS-Zeo). The
diffractograms were marked with zeolite A (A), zeolite P (P) and zeolite Y (Y) patterns
which existed in the powder diffraction file (PDF).
77
I
n
t
e
n
s
i
t
y
(a.u.)
2-Theta-Scale
Figure 3.4
The X-ray diffraction pattern of mixed synthesized zeolite NaY (Zeo-
NaY-S) via seeding and ageing techniques match up with the sodium aluminum silicate
hydrate NaY (Na2Al2Si4.5O13.xH2O) pattern existed in PDF.
It was proven that zeolite NaY with high purity was successfully synthesized
from RHA by seeding and ageing techniques without marked presence of impurities, i.e.
zeolite P and A. This result revealed that the seeding and ageing techniques will induce
the zeolite Y formation. In previous reports, Zhao et al. (1997) used these seeding and
ageing techniques to generate zeolite Y with a maximum crystalinity of 72% from coal
fly ash through hydrothermal treatment. In the absence of seed, zeolite P was found to be
a competitive phase and the main impurity present in the resulting products. In the
synthesis of zeolite Y, when a source of silica is from rice husk ash which is less pure
than the commercial silica, this requires the addition of seeds or initial solution to
provide nuclei, which can selectively induce the formation of zeolite Y and eliminate the
processes of induction and nucleation.
Without ageing, the period of crystallization became shorter resulting in the
formation of zeolite A. The silica-rich zeolite A appears to crystallize well in a period of
one hour which is followed by rapid conversion in many instances to hydroxysodalite
(Breck, 1974). Breck and Flanigen (1964), in their early experiment showed that the
synthesized product with 92% of zeolite Y was produced after ageing for 24 hours at
78
room temperature compared to the product produced without ageing was only 63% of
zeolite Y. In addition, Ginter et al. (1992) who studied the effects of gel ageing on the
synthesis of zeolite NaY from colloidal silica also reported that prolonged ageing led to
incorporation of additional Si into the aluminosilicate solid and this gave rise to a larger
number of smaller nuclei and resulted in a higher final yield of Zeolite NaY. They also
found that in the absence of ageing, zeolite phases other than NaY were formed.
Zeo-NaY-S10
Zeo-NaY-S9
Zeo-NaY-S8
I
n
t
e
n
s
i
t
y
Zeo-NaY-S7
Zeo-NaY-S6
Zeo-NaY-S5
(a.u.)
Zeo-NaY-S4
Zeo-NaY-S3
Zeo-NaY-S2
Zeo-NaY-S1
2-Theta-Scale
Figure 3.5
The compilation of X-ray diffractograms of the synthesized zeolite NaY
79
Because of the successful production of highly pure zeolite NaY and the
elimination of other phases and impurities via seeding and ageing techniques, the
procedure was repeated ten more times and was labeled as Zeo-NaY-S1 to S10. Each of
the synthesized samples was characterized by XRD to obtain the X-ray diffractogram as
this is the crucial and important characterization technique in the identification of the
synthesized crystalline zeolite NaY and for the observation if any impurities or other
phases in the product. Figure 3.5 shows the X-ray diffraction patterns of 10 batches of
the synthesized zeolite NaY through the seeding and ageing techniques. This figure
reveals that the seeding and ageing techniques for the synthesis of zeolite NaY from
RHA has successfully produced a pure zeolite NaY with high reproducibility. These
products were mixed together and homogenized to get Zeo-NaY-S that were used for
further characterizations and modification.
Matching the diffractogram from the commercial zeolite NaY, it was found that
the patterns are nearly the same as those of the synthesized zeolite but the crystallinity is
higher and observable sharpness of the peaks is better for the commercial zeolite. The
reason is that the commercial zeolite Y is typically prepared from highly pure starting
materials, equipped with more expensive apparatus and utilization of high technology
devices, while the synthesized zeolite NaY was produced from less pure silica contained
in RHA and inexpensive lab scale devices and apparatus were employed. The XRD
pattern of commercial zeolite NaY is shown in Figure 3.6.
I
n
t
e
n
s
i
t
y
(a.u.)
10
20
30
2 - Theta
Figure 3.6
40
- Scale
The X-ray diffraction pattern of the commercial zeolite NaY
50
80
3.2.2
Infrared Spectroscopy
To support the XRD analysis, the mid infrared (IR) region of the spectrum was
used (1300 to 400 cm-1) since this region contained the fundamental vibrations of the
framework (Si,Al)O4 tetrahedra and should expose the framework structure (Gould,
1974). The infrared spectrum for the synthesized zeolite NaY (Zeo-NaY-S) and
commercial zeolite NaY (Zeo-NaY-C) are illustrated in the Figures 3.7 and 3.8,
respectively.
50.0
%T
Zeo-NaY-S
40.0
773.4 694.3
569.9 500.5
30.0
463.8
1101.3
20.0
1005.8
10.0
1300.0
Figure 3.7
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
The infrared spectrum of Zeo-NaY-S
60.0
%T
792.7 717.5
578.6 505.3
Zeo-NaY-C
50.0
462.9
40.0
1141.8
30.0
20.0
1300.0
Figure 3.8
1200.0
1100.0
1000.0
900.0
800.0
The infrared spectrum of Zeo-NaY-C
700.0
600.0
500.0
400.0
1/cm
81
The infrared spectra for the synthesized and commercial zeolite NaY show six
significant peaks from 1250 to 400 cm-1 comparable to the spectrum zeolite NaY which
was assigned by Flanigen and Khatami (Gould, 1974: Rabo, 1976). They explained that
the IR spectrum for zeolite NaY in the region of 1300 to 400 cm-1, six significant peaks
emerged which were related to zeolite NaY structure. A summary of the infrared
assignments is contained in Table 3.2 and illustrated in Figure 3.9.
Table 3.2 : Zeolite NaY infrared assignments
Wavelength (cm-1)
Vibration mode
1) Internal tetrahedra
Asymmetric stretch
1250-950
Symmetric stretch
720-650
T-O bend
420-500
2) External linkages
Double ring
650-500
Symmetric stretch
750-820
Asymmetric stretch
1050-1150
Symm. stretch
Asymm. stretch
950
1250
650
2
2
1
T-O bend
Dbl. ring
500
420
2
1
1
Figure 3.9
1 = Internal tetrahedra –structure insensitive
2 = external linkages– structure sensitive
The illustration of infrared spectrum of zeolite Y (Si/Al = 2.5) in the
region from 1250 to 420 cm-1
82
Wright (Rabo, 1976) also studied the infrared spectra in the region of 300-1200
cm-1 for a series of type X and Y zeolites with varying Si/Al ratios. They assigned bands
near 1140 cm-1 to a symmetric Si-O-Si stretching mode, 1075 cm-1 to a symmetric Si-OAl stretching mode, the strongest band near 1000 cm-1 to both Si-O-Si and Si-O-Al
asymmetric stretching modes. The shoulder near 500 cm-1 was found in NaY zeolite but
absent in NaX, as assigned to an Si-O-Al out-of-plane bending mode.
All of the peaks in the IR spectrum of the synthesized and commercial zeolite
NaY are in the region discussed above and the presence of the shoulder peak near 500
cm-1 indicates that the zeolite NaY has been successfully synthesized. The IR spectra
also shows strong, intense bands at 3500 cm-1 regions exhibited by discrete water
absorption because of the hydrated property of zeolite. A summary of the synthesized
and commercial infrared assignments is contained in Table 3.3.
Table 3.3 : IR assignments for commercial, synthesized zeolite NaY and zeolite
Y (SiO2/Al2O3 4.87)
Vibration mode
a
Zeolite Y
Zeo-NaY-C
Zeo-NaY-S
1130 (msh)
1141.8 (msh)
1125.4 (msh)
1005 (s)
1022.2 (s)
1005.8 (s)
784 (m)
790.8 (m)
773.4 (m)
714 (m)
721.3 (m)
694.3 (m)
Double rings
572 (m)
578.6 (m)
569.9 (m)
Out-of-plane bending
500 (msh)
499.5 (msh)
500.5 (msh)
T-O bend
455 (ms)
462.9 (ms)
463.8 (ms)
Asymmetric Stretch
Symmetric stretch
Notes: a: SiO2/Al2O3 4.87 (Gould, 1971: Rabo, 1976), s: strong, ms: medium strong, m: medium,
sh: shoulder
From Table 3.3, it can be seen that each of peaks for Zeo-NaY-S is identical with
the peaks from the zeolite Y which had been studied by Flanigen and Khatami (Gould,
1974: Rabo, 1976). Beside that, the spectra also explains the changes that occurred in the
83
structure of raw material, silica from RHA to a zeolite structure. This phenomenon is
shown by the shifting of peak near 1000 cm-1 contributed from the transformation of SiO-Si to Si-O-Al bonding as shown in Figure 3.10. The intensity of the peak of the
synthesized zeolite NaY is somewhat higher than silica since the zeolite structure is
more rigid. From these infrared spectra and the assignments of peak, it can be concluded
that infrared spectroscopy can assist the data from XRD diffractogram in the
identification of zeolite and proved that the zeolite NaY was successfully synthesized.
50.0
%T
40.0
804.3
773.4 694.3
470.6
569.9 500.5
RHA
30.0
1192.9
1102.2
Zeo-NaY-S
463.8
1101.3
20.0
1005.8
10.0
1300.0
Figure 3.10
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
The comparison of the infrared spectrum of synthesized zeolite NaY
(Zeo-NaY-S) and rice husk ash (RHA)
3.2.3
Elemental Analysis
The quantitative determinations of major elements contained in the zeolite
samples were carried out using two different approaches. The first approach was the
combination of the analysis after complete dissolution of the samples and the classical
gravimetric method while the second approach was physical analysis method using the
wavelength dispersive X-ray fluorescence (XRF) technique. These comparisons were
done because there is no ‘best’ technique for the elemental analysis of zeolite although
there are a wide variety of techniques reported in the previous literature (Corbin et al.,
1987). Table 3.4 gives the data of the Na2O, Al2O3, SiO2 and H2O amounts from the first
84
approach. As a comparison, the percent amount of these elements and other oxide
elements from XRF technique is given in Table 3.5.
Table 3.4 : Percentage amount of major elements contained in the zeolite
samples from the first approach
Elements
Zeo-NaY-S
Zeo-NaY-C
Na2O (%)
16.91
8.8
Al2O3 (%)
14.6619
13.99
SiO2 (%)
47.2581
56.46
H2O (%)
21.17
20.75
Table 3.5 : Percentage amount of major elements contained in zeolite samples
by XRF technique
Elements
Zeo-NaY-S
Zeo-NaY-C
SiO2
43.74
47.63
TiO2
0.04
0.09
Fe2O3
0.17
<0.01
Al2O3
18.35
15.66
MnO
0.04
<0.01
CaO
0.45
0.19
MgO
<0.01
0.02
Na2O
12.4
8.47
K2O
0.37
0.03
P2O5
0.12
0.06
L.O.I.
24.32
27.85
It is necessary to convert the quantity of sodium and aluminum to the oxide form
in the samples because the preparation of zeolite was derived from the oxide moles of
sodium and aluminum. Data from AAS and ICP-MS was accurate and reliable due to the
85
values from the quality control (QC) and spike recovery study. Furthermore, the
correlation coefficient (r2) for the standard calibration curve was nearly one indicating
that the value of the amounts of sodium and aluminum were trustworthy and consistent.
The data from AAS and ICP-MS together with the respective QC and spike recovery can
be seen in Appendix A-1 and A-2 while the data for the determination of %LOI and
%SiO2 is in Appendix A-3. For the XRF technique, the measurement of accuracy is the
relative error, i.e. the difference between the recommended value (given by the CRM’s
producer) and the observed value (given by UKM’s XRF machine) of a certified
reference material, stated as percentage. The CRM has been analyzed along with the
samples. It is assumed that the relative errors of the CRM are equivalent to those of the
17 unknowns as indicated in Appendix A-4.
The variation value of the major elements amount in zeolites for both approaches
is due to the different way in which the treatment of the samples was done and the
instrumental techniques used. For the first approach, the dissolution samples might not
completely solubilize the solid samples and the slight losses of silicon from the digestion
step by HF acid might be possibly due to the volatility of the resulting fluorides. As
compared to AAS and ICPMS, the benefits of XRF include the ability to determine
some non-metals, conceptually simpler sample preparation and improved precision. The
disadvantages include poor sensitivity of light elements and sensitivity to changes in the
matrix composition. Corbin et al. (1987) in their paper found that the atomic absorption
spectroscopy data was to be the most reliable but the data obtained from XRF, wet
chemical and ICP spectrometric analysis showed that alteration in the methodology of
these techniques was needed to improve their precision. In addition, the utilization of
AAS, ICP and XRF were found better than the classical wet chemistry methods because
these methods offer the benefit of reduced interferences and matrix effects, and have
improved accuracy, precision and speed.
Besides that, a particular problem with zeolites is that the ambient humidity may
affect the amount of sample moisture which can lead to uncertainties in the sample
weights. As a conclusion, since these two approaches have their benefits and
86
disadvantage as well as the problem with zeolites itself, both data for the amount of
major elemental analysis can be used.
3.2.4
Physicochemical Properties
The information regarding the physicochemical properties of the synthesized and
commercial zeolite NaY is very important and essential since the zeolites were used for
surface modification and utilized as sorbents for toxic metals. The properties that had
been studied are surface area, porosity, unit cell, silica per alumina ratio, total cation
exchange capacity and the external cation exchange capacity. Table 3.6 gives a list of
the physicochemical properties and respective values for the synthesized and
commercial zeolite NaY. The analysis data for each properties study are in Appendix B.
Table 3.6 : The physicochemical properties of the synthesized (Zeo-NaY-S) and
commercial zeolite NaY (Zeo-NaY-C).
Physicochemical properties
Zeo-NaY-S
Zeo-NaY-C
Unit cell, ao (Ǻ)
24.759
24.669
3.22
4.04
SiO2/Al2O3
2.384
3.042
SiO2/Al2O3
3.871
4.978
SiO2/Al2O3
3.756
5.117
SiO2/Al2O3
3.409
5.206
1.94
2.49
Si/Al
1.88
2.57
Si/Al
1.70
2.60
a
SiO2/Al2O3
b
c
d
e
c
Si/Al
d
e
Notes: a: from elemental analysis, b: from XRF, c: from unit cell, d; from infrared spectrum
(equation 5), e: from infrared spectrum (equation 6)
87
Table 3.6 (continue): The physicochemical properties of the synthesized (ZeoNaY-S) and commercial zeolite NaY (Zeo-NaY-C).
Physicochemical properties
Zeo-NaY-S
Zeo-NaY-C
Surface area (m2/g)
506.6
484.9
Total pore volume (cc/g)
0.2748
0.2639
Average pore diameter (Ǻ)
21.70
21.77
Cation exchange capacity , CEC (meq/g)
3.15
2.55
External cation exchange capacity, ECEC (meq/g)
0.671
0.533
Since the ratio of Si/Al was calculated from unit cell, it was defined as the ratio
of the framework which corresponds to all tetrahedrally coordinated Si or Al atoms
within the crystal lattice. In contrast, the bulk or elemental SiO2/Al2O3 ratio comprises
nonframework Al and Si atoms in addition to the entire framework Si and Al atoms. The
value of SiO2/Al2O3 in Table 3.6 shows that zeolite Y was successfully synthesized from
RHA because zeolite Y was recognized in reported patent as having silica/alumina ratios
between 3.0 and 6.0 as said by the Breck’s patent (Breck, 1964).
In general, thermal, hydrothermal and acid stability of zeolites improve as they
become more siliceous or having the increasing value of silica to alumina ratio (Siantar
et al., 1995). According to Flanigen’s notation, low silica zeolites are defined as having
2<SiO2/Al2O3<4; intermediate SiO2/Al2O3 zeolites as having 4<SiO2/Al2O3<10 and high
silica materials as generally having SiO2/Al2O3 ratios more than 10 (Chen et al., 1994).
Thus, synthesized and commercial zeolite NaY are the low silica zeolites with the
commercial zeolite NaY as is more siliceous than synthesized zeolite NaY.
The synthesized zeolite NaY has higher CEC and ECEC than the commercial
zeolite NaY due to the higher amount of Na2O contained in the synthesized as well as
the lower ratio of SiO2/Al2O3 since each AlO4 tetrahedra in the zeolite framework
provides a single cation exchange sites (Sherman, 1978).
88
3.3
Characterization of Surfactant Modified Zeolite Y
The surfaces of the synthesized and commercial zeolite Y were modified by the
cationic surfactant, HDTMA by way of exchanging the sodium cation that neutralized
the external framework of aluminosilicate of the zeolite. The HDTMA molecule is too
large to enter the angstrom size of zeolite Y’s pore that will consequently exchange with
sodium cation in the exterior framework. For that reason, the structure of the zeolite did
not have an alteration after the modification process. In order to prove this hypothesis,
each of the SMZY was characterized by XRD and IR techniques to obtain the structure
information. Due to the exchange of the cation that neutralized the framework zeolite,
the elemental analysis was done including the determination of sodium cation using
flame photometer after the decomposition of samples and the elements that created the
HDTMA molecule, i.e. carbon, hydrogen and nitrogen using CHNS analyzer.
Other characterizations include the surface area and porosity, the dispersion
behavior and the maximum adsorption of HDTMA onto zeolite that were related to the
utilization of the SMZY as a sorbent for toxic metals in water. The dispersion behavior
study was to observe the relative position and the behavior of the SMZY in the mixture
of oil and water since the surface of the SMZY turns into partially hydrophobic. Lastly,
it was essential to get the value of the maximum adsorption of HDTMA onto zeolite
which can be used to study the orientation of the adsorbed HDTMA relative to the
surface and solution in order to construct the schematic diagram of the theoretical
adsorption study of HDTMA onto zeolite Y. The Langmuir isotherm was used to obtain
the maximum adsorption value of HDTMA onto the zeolite.
3.3.1
X-Ray Diffraction Technique
Because the XRD technique is found to be crucial and suitable for the
determination of the zeolites structure, this technique was applied for the determination
89
of the SMZY structure in order to prove that the structure of zeolite Y has not changed
after the modification. Figure 3.11 shows the compilation of XRD diffractograms for
each of the SMZY together with the respective unmodified zeolite Y. This figure
revealed that the structure of the zeolite was not changed after the modification process,
thus proving the theoretical explained in previous section. The XRD patterns of each
SMZY were nearly identical with the pattern of the parent zeolite. Furthermore, it can be
seen that no other peaks emerged which confirmed that there are no impurities and other
phases inside the structure after the modification process.
SMZY-200-C
I
n
t
e
n
s
i
t
y
SMZY-100-C
SMZY-50-C
Zeo-NaY-C
SMZY-200-S
(a.u.)
SMZY-100-S
SMZY-50-S
Zeo-NaY-S
5
10
Figure 3.11
parent zeolites
20
2-Theta - Scale 30
40
50
The XRD patterns of the surfactant modified zeolite Y together with the
90
3.3.2
Infrared Spectroscopy
The infrared spectra for all SMZY together with the respective original zeolite Y
can be seen in Appendix C. Every infrared spectrum of the SMZY was almost identical
with their unmodified zeolites which only corresponded to the structure of the zeolite Y
as described previously thus the structure was not changed after the modification
process. Additionally, no other peaks emerged, hence there were no impurities or other
formations and phases occured during the modification. The peak assignments of SMZY
infrared spectrum are listed in Table 3.7. The infrared spectrum of each SMZY shows 6
peaks emerged which corresponds to the structure of zeolite Y as stated previously in
Section 3.2.2. The values of each peak wavenumber for SMZY are slightly different
with the parent zeolite due to the sample preparation and the instruments factor.
Table 3.7 : Peak lists of SMZY infrared spectrum
Sample
SMZY-50-S
SMZY-100-S
SMZY-200-S
SMZY-50-C
SMZY-100-C
SMZY-200-C
Asymmetric
Symmetric
Double
Out of plane
T-O
Stretch
stretch
Rings
bending mode
bend
1102.2msh
771.5m
569m
496.6msh
461.9ms
1008.7s
692.4m
1102.2msh
771.5m
569m
499.5msh
461.9ms
1005.8s
696.3m
1102.2msh
771.5m
569m
499.5msh
461.9ms
1005.8s
696.3m
1139.8msh
792.7m
578.6m
503.4msh
461.9ms
1023.2s
720.4m
1139.8msh
792.7m
578.6m
49.5msh
461.9ms
1023.2s
720.4m
1139.8msh
792.7m
575.7m
503.4msh
461.9ms
1023.2s
723.3m
Notes: s: strong, ms: medium strong, m: medium, sh: shoulder
91
3.3.3
Elemental Analysis
The preparation of the series of SMZY was based on partially exchanging the
HDTMA cation with sodium cation in the external framework of zeolite Y as described
in the equation below:
[Al-O-Si]-Na+ + HDTMA+Br- ↔ [Al-O-Si]-Na+HDTMA+ +
Br-
(17)
Where the portion of [Al-O-Si]- represents the aluminosilicate framework of zeolite Y
having a negative charge where the framework is neutralized by Na+. For this reason, the
elemental analysis of sodium and HDTMA cation present in the SMZY and the
unmodified zeolite Y was crucial in determining the decreasing amount of sodium and
the increasing amount of HDTMA in the SMZY after the modification. The values of
the Na2O content in the SMZY and the unmodified zeolite are listed in Table 3.8 while
the graph bar showing the variations of these amounts were illustrated in Figure 3.12.
The analysis data are attached in Appendix D.
Table 3.8 : The content of Na2O in the SMZY and their parent zeolite
Samples
[Na2O] (mg/g) [Na2O] (mmol/g)
Zeo-NaY-S
138.46
2.2333
SMZY-50-S
116.67
1.8817
SMZY-100-S
113.46
1.8300
SMZY-200-S
117.95
1.9024
Zeo-NaY-C
96.47
1.5560
SMZY-50-C
88.14
1.4216
SMZY-100-C
89.10
1.4371
SMZY-200-C
92.63
1.4940
92
140
[Na2O], mg/g
120
100
80
60
40
20
0
ZeoNaY-S
Figure 3.12
SMZY50-S
SMZY100-S
SMZY200-S
ZeoNaY-C
SMZY50-C
SMZY100-C
SMZY200-C
The comparison of the Na2O amount (mg/g) present in the SMZY and
respective unmodified zeolite
Table 3.8 and Figure 3.12 reveal that the amounts of sodium in the SMZY were
lower than the unmodified zeolite NaY, demonstrating that the sodium in the parent
zeolite was partially removed and exchanged with the HDTMA cation after the
modification process.
The carbon-hydrogen-nitrogen-sulfur (CHNS) analyzer was used to determine
the three elements (carbon, hydrogen and nitrogen) contained in the SMZY and also raw
zeolite. The existence of carbon and hydrogen was due to the organic moieties in the
samples whereas nitrogen was due to the existence of ammonium cations. Therefore, it
was essential to determine the percentage of this element due to the surfactant that was
used to modify zeolite possessing long chains of hydrocarbon tail and the ammonium as
the charge head.
93
Table 3.9 : Elemental data of the SMZY obtained from the CHNS analyzer
Samples
Carbon (%)
Hydrogen (%)
Nitrogen (%)
Sulfur (%)
Zeo-NaY-S
0.46 ± 0.06
2.25 ± 0.02
n.d
0.03 ± 0.01
SMZY-50-S
1.12 ± 0.41
2.03 ± 0.10
n.d
0.04 ± 0.01
SMZY-100-S
3.88 ± 0.17
2.92 ± 0.05
n.d
0.05 ± 0.01
SMZY-200-S
3.46 ± 0.12
2.81 ± 0.11
n.d
0.04 ± 0.01
Zeo-NaY-C
0.07 ± 0.01
2.45 ± 0.06
n.d
0.12 ± 0.06
SMZY-50-C
1.77 ± 0.07
2.62 ± 0.04
n.d
0.04 ± 0.01
SMZY-100-C
2.06 ± 0.15
2.64 ± 0.06
n.d
0.04 ± 0.01
SMZY-200-C
1.89 ± 0.07
2.64 ± 0.08
n.d
0.04 ± 0.02
Note: n.d = not detected
The carbon and hydrogen were supposedly not to be present in both of the
unmodified zeolite Y. However, since some organic impurities and moisture were
present in the zeolites, the variation of the results was acceptable. The percentage of
carbon was somewhat higher in the synthesized zeolite Y than the commercial one
because the source of silica in the synthesized zeolite was from the natural products, rice
husk ash, which contained organic impurities that were not fully removed. The
instrument could not detect the presence of the nitrogen in the samples because the
concentration of this element was relatively too low as there is only one nitrogen for
every surfactant. The insignificant values of the percentage of hydrogen in those samples
were due to the possibility of the zeolites allowing the adsorption of water (H2O) from
the environment. This data showed that the amount of carbon and hydrogen in the
SMZY was higher than the respective unmodified zeolite Y validated that the HDTMA
cation was exchanged with sodium in the zeolite Y after the modification process. The
quantity of sodium and HDTMA was found to vary among the SMZY due to the
different amounts of starting HDTMA used in the modification.
94
3.3.4
Surface Area and Porosity
In general, the adsorption of metals onto the sorbents depends on its surface area
and porosity. Bigger pore size creates wider surface area of the materials hence giving
more exchange sites and resulted in higher adsorption capacity. Therefore, it is
important to get the information about the surface area and porosity of the sorbents.
Table 3.10 gives the value of the surface area and porosity for each SMZY together with
their parent zeolite Y and the variation of these values was illustrated in Figure 3.13. The
analysis data are attached in Appendix E. Although the preparation of SMZY was based
on the surface modifications of the zeolite, the HDTMA cation did not alter the area of
the external surface of the zeolite since the HDTMA molecules did not have a long chain
hydrocarbon tail compared of other cationic surfactant, for instance OTS
(octadecyltrichlorosilane). Hadi Nur et al. (2005) had used OTS for covering the surface
of zeolite NaY, and they found that the specific surface area of the modified zeolite NaY
was lower than the unmodified because the OTS have the long chain hydrocarbon tail
that tend to accumulate at the exterior framework of the zeolite. In contrast, the surface
area of the SMZY became higher than the unmodified zeolite that tends to give more
adsorption capacity for toxic metals in water.
Table 3.10 : Surface area and porosity of the SMZY and unmodified zeolites.
Surface area
Total pore volume
Average pore size
Samples
(m2/g)
(cc/g)
(Ǻ)
Zeo-NaY-S
506.6
0.2748
21.70
SMZY-50-S
502.1
0.2722
21.69
SMZY-100-S
553.1
0.2998
21.68
SMZY-200-S
540.3
0.2922
21.63
Zeo-NaY-C
484.9
0.2639
21.77
SMZY-50-C
563.8
0.3060
21.71
SMZY-100-C
602.2
0.3267
21.70
SMZY-200-C
545.6
0.2960
21.70
95
70
60
50
40
30
20
10
0
ZeoNaY-S
SMZY50-S
SMZY100-S
SMZY200-S
ZeoNaY-C
SMZY50-C
SMZY100-C
SMZY200-C
Surface area x 10 (m2/g)
Total pore volume x 10E-2 (cc/g)
average pore size (Angstrom)
Figure 3.13
The comparison of the specific surface area (m2/g), total pore volume
(cc/g) and average pore size (Ǻ) for SMZY and unmodified zeolite Y
3.3.5
Dispersion Behavior
The relative positions of SMZY and unmodified zeolite Y solid particles in an
oil-water mixture when added to hexane-water mixture are shown in Figure 3.14. The
different distribution of modified and unmodified zeolite Y in the hexane water mixture
can be seen in this figure where the SMZY forms a colloidal dispersion in the organic
phase (dispersed in hexane) while the unmodified zeolite Y was dispersed well in
aqueous phase (dispersed in water). It proves that the distinctive behavior of the SMZY
from unmodified zeolite Y was due to the modification of zeolite surface by HDTMA
that created a partially hydrophobic zeolite Y.
96
Synthesized zeolite Y
(1)
Figure 3.14
(2)
(3)
Commercial zeolite Y
(4)
(5)
(6)
(7)
(8)
Photographs show the distribution of SMZY and unmodified zeolite NaY
solid particles when added to hexane-water mixture. The hexane solution is located at
upper phase and the water was situated at lower phase.
Legend:
(1) Zeo-NaY-S,
(2) SMZY-50-S,
(3) SMZY-100-S,
(4) SMZY-200-S,
(5) Zeo-NaY-C,
(6) SMZY-50-C,
(7) SMZY-100-C,
(8) SMZY-200-C
In order to study the dispersion behavior of SMZY and unmodified zeolite NaY,
the samples from the relative position in an oil-water mixture were stirred and
subsequently the solid particles distribution was observed instantaneously after the
stirring and after the static condition. Figure 3.15 shows the image of SMZY and
unmodified zeolite NaY in hexane-water before stirring, after stirring for 2 hours and
after static condition for 30 minutes and for 24 hours.
97
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(a)
Stirring for 2 hours
(b)
Static for 30 minutes
(c)
Static for 24 hours
(d)
Figure 3.15
Photographs showing the distribution of SMZY and unmodified zeolite Y
solid particles; (a) when added to hexane-water mixture, (b) after stirring for 2h, (c) after
keeping under static conditions for 30 minutes and (d) 24 hours. The legends are same
with Figure 3.14.
98
The observation from Figure 3.15 confirms that the samples of SMZY were
dispersed in aqueous solution (water) and in organic phase as well (hexane) after stirring
for 2 hours due to the contact of the water molecule in the zeolite Y structure since the
water molecules were able to enter the pore size of the zeolite structure. After 24 hours,
the solid particles of both unmodified zeolite NaY settled out, whereas the samples
SMZY remained well dispersed in aqueous water. This observation revealed that the
dispersion behavior of zeolite Y was changed after the modifications of its surface by
HDTMA. The modified zeolite Y with HDTMA became partially hydrophobic and
hydrophilic. From these photographs as well, the dispersion behavior of the SMZY was
not different among them because of the insignificant amounts of HDTMA in the series
of the SMZY according to the elemental analysis.
3.3.6
Maximum Adsorption of HDTMA
Sorption of cationic surfactants from solution onto solid surfaces can be
described by the Langmuir isotherm. The sorption isotherm for HDTMA on the
synthesized zeolite Y is presented in Figure 3.16 and the analysis data for this study can
[HDTMA] sorbed, (mmol/kg
be seen in Appendix F.
700
600
500
400
300
200
100
0
0
Figure 3.16
1
2
3
4
[HDTMA]e, (mmol/L)
5
6
7
The sorption isotherm plotted of HDTMA onto the synthesized zeolite Y
99
When fitting the data (Figure 3.16) into equation 14 in Section 1.6.1, it was
found that the high coefficient of determination (r2) as shown in Figure 3.17 indicating
good agreement with Langmuir model. The maximum of the HDTMA adsorbed onto
zeolite (Qo) can be calculated from the equation given in the graph (Figure 3.17) and
was tabulated in Table 3.11. Li and Bowman (1997) also found the same result where
the adsorption isotherms of HDTMA-Br, HDTMA-Cl and HDTMA-HSO4 on the
clinoptilolite surface were followed Langmuir isotherm.
0.012
0.01
1/qe
0.008
0.006
y = 0.0056x + 0.0009
0.004
2
R = 0.9754
0.002
0
0
Figure 3.17
0.5
1/Ce
1
1.5
The plotted of 1/qe against 1/Ce where qe is the HDTMA adsorbed at
equilibrium (mmol/kg) and Ce is concentration of HDTMA at equilibrium (mmol/L).
Table 3.11 : Fitted Langmuir parameters for sorption of HDTMA by synthesized
zeolite Y
Slope (1/bQo)
intercept (1/Qo)
Qo (mmol/kg)
b (1/kg)
r2
0.0056
0.0009
1111.1
0.1607
0,9754
The HDTMA molecule is sorbed (1111.1 mmol/kg) essentially quantitatively up
to nearly twice the ECEC value of the synthesized zeolite Y (671.4 mmol/kg). Sullivan
et al. (1998) also found the same results when they used clinoptilolite, the naturally
occurring zeolite tailoring with HDTMA. It thus proved that the HDTMA molecule with
100
concentration above CMC creates an organic-rich layer on the zeolite surface and the
charge on the surface is reversed from negative to positive. The positive charge on the
outward-pointing HDTMA head groups is balanced by anions from the solution,
forming an electrical double layer. The schematic diagram for this theory can be seen in
Figure 3.18. The anion properties in the surface of SMZY allow them to exchange the
counter ions by other anions.
•
•
•
Pore
Cation (Na+)
balance the
charge inside
Internal area
Br-
Br-
Br-
Br-
+
BrBr-
+
HDTMA Bromide
structure
Br-
Br-
Zeolite NaY
Figure 3.18
Br-
Br-
Br-
Br-
Br-
Br-
Surfactant modified zeolite Y
(SMZY)
Schematic diagram of the theoretical HDTMA formation on the zeolite Y
CHAPTER 4
RESULTS AND DISCUSSION: APPLICATION OF SORBENTS
4.1
Removal of Cr(III)
Since the trivalent chromium, Cr(III) species particularly exist in water as
cations, the unmodified zeolite Y can be used to remove them from water based on the
cation exchange property of this material. The removal of Cr(III) which involve the
kinetic study and the effect of initial pH were performed by using the unmodified
synthesized and commercial zeolite NaY. The SMZY and unmodified zeolite Y were
used for the isotherm study of the Cr(III) uptake from water. The analysis data for the
removal of Cr(III) studies are given in Appendix G.
4.1.1
Kinetic Study
In order to accomplish the kinetic study, the effect of contact time experiments of
Cr(III) removal by the synthesized and commercial zeolite Y were carried out with two
different initial concentrations of Cr(III) which are 250 mg/L and 500 mg/L ranging
from 10 minutes to 48 hours. The initial concentration, Co (mg/L) and metal
102
concentrations at preset time intervals, Ct (mg/L) were determined and the Cr(III)
uptake, q (mg Cr(III) sorbed/g zeolite) was calculated from the equation as follows:
q=
(Co − Ct )v
1000 w
(19)
where v is the volume of the solution (mL) and w is the mass of the sorbent (g). The
uptake values of Cr(III) from the solution as a function of contact time are presented in
[Cr(III)] Sorbed (mg/g)
Figures 4.1 and 4.2 for synthesized and commercial zeolite Y, respectively.
100
80
60
40
250 ppm
20
500 ppm
0
0
Figure 4.1
10
20
30
Time (hour)
40
50
60
Sorption kinetics graph for synthesized zeolite NaY from two different
[Cr(III)] Sorbed (mg/g)
initial concentrations of Cr(III). (Condition: 0.1 g sorbents, 25 mL Cr(III) solution)
70
60
50
40
30
20
250 ppm
500 ppm
10
0
0
Figure 4.2
10
20
30
Time (hour)
40
50
60
Sorption kinetics graph for commercial zeolite NaY with two different
initial concentrations. (Condition: 0.1 g sorbents, 25 mL Cr(III) solution)
103
As shown in Figures 4.1 and 4.2, the Cr(III) removal increases with time and
attains equilibrium in 8 hours for both zeolites. This trend emphasizes that sorption
times have important effects on the removal efficiency, which increases significantly
with increasing zeolites contact time with the Cr(III) solution. This is a consequence of
the molecular sieve property of the zeolites where the larger size of Cr(III) species
needed more time to exchange with sodium cation that is neutralized in the pore of the
zeolite framework. At a low concentration (250 mg/L), the duration for the uptake of
Cr(III) by synthesized zeolite NaY to reach the equilibrium state was faster than the
commercial one. In addition, the Cr(III) uptake versus time curves for this initial
concentration are single, smooth and continuously leading to saturation, suggesting the
possible monolayer coverage of Cr(III) on the surface of the sorbent (Rengaraj et al.,
2001).
In order to compare the efficiency of uptake Cr(III) by both zeolites from
different initial concentrations of Cr(III), the percentage of the removal of Cr(III) from
the solution as a function of shaking time were performed. The definition of percent
removal is as follow:
%removal =
(C o − C t )
× 100
Co
(20)
120
% Removal
100
80
60
40
Zeo-NaY-S
20
Zeo-NaY-C
0
0
Figure 4.3
10
20
30
Time (hour)
40
50
60
Percentage of the Cr(III) removal by synthesized (Zeo-NaY-S) and
commercial zeolite NaY (Zeo-NaY-C) with [Cr(III)]initial = 250 mg/L. (Condition: 0.1 g
sorbent, 25 mL Cr(III) solution)
104
100
% Removal
80
60
40
Zeo-NaY-S
20
Zeo-NaY-C
0
0
Figure 4.4
10
20
30
Time (hour)
40
50
60
Percentage of the Cr(III) removal by synthesized (Zeo-NaY-S) and
commercial zeolite NaY (Zeo-NaY-C) with [Cr(III)]initial = 500 mg/L. (Condition: 0.1 g
sorbent, 25 mL Cr(III) solution)
A plot of the percentage of the Cr(III) removal against contact time is shown in
Figures 4.3 and 4.4 for Cr(III) initial concentration of 250 mg/L and 500 mg/L,
respectively. These figures indicate that the synthesized zeolite NaY is more efficient in
removing the Cr(III) species from the aqueous solution than the commercial one. The
synthesized zeolite NaY completely removed Cr(III) from the solution of 250 mg/L after
8 hours of shaking period while the commercial zeolite NaY removed only 65% of
Cr(III) having the concentration of 250 mg/L. Both zeolites removed only half the
Cr(III) species from the initial concentration of 500 mg/L.
Experiments were also established in order to understand the kinetics of Cr(III)
removal by both zeolites from two different initial concentrations. The kinetics of
sorption describing the solute uptake rate which in turn governs the residence time of
sorption reaction is one of the important characteristics defining the efficiency of
sorption. Mathematical models that are used most frequently to describe kinetics of
sorption in a free suspension in a well agitated batch system are pseudo-first and pseudosecond order equations (Aksu, 2000).
105
Generally, the adsorption of adsorbate (A) on the surface site can be represented
by the following equation:
A
+
surface site
↔
A-surface site
(21)
where A-surface site is the product. From this equation, the rate of adsorption is first
order concerning the concentration of adsorbate in the solution, [A] and is also
proportional to the amount of active surfaces on the sorbent (Mortimer, 1993). If θ is the
coverage fraction of the sorbent surface by the adsorbate, the rate of adsorption can be
written as:
rads = k ads [ A](1 − θ )
(22)
where k ads is the adsorption rate constant. The concentration of adsorbate, [A] is usually
used in large amount while the sorbent is in deficient amount in batch adsorption
experiment so that the amount of sorbent can be negligible. Hence, the equation (22) is
changed as follows:
rads = k ads (1 − θ )
(23)
since the adsorption rate is independent towards the concentration of adsorbate [A].
If the adsorption keeps on up to the maximum monolayer coverage and reaches the
equilibrium, the equation (23) can be written as:
rads =
dqt
k1,ads (qe − qt )
dt
(24)
where, qt is the amount of adsorbate sorbed (mg/g) at any time, t and is equivalent to the
coverage fraction, θ on the sorbent by the adsorbate and q e is the amount of adsorbate
sorbed at equilibrium which is equivalent to unit coverage. From this equation, since
106
there is only one product ( q e − qt ), the order of the adsorption is forced to one. Because
of the order of the adsorption is approximated to the first order, it is called pseudo-first
order with the pseudo- means apparently similar to. If the adsorption reaction is
approximated to the second order with respect to ( q e − qt )2, it is called pseudo-second
order and the equation is as follows:
dqt
= k 2,ads (qe − qt ) 2
dt
(25)
where k1,ads and k 2,ads is the adsorption rate constants for pseudo-first and pseudosecond order, respectively. When equation (24) and (25) is integrated between the limits,
t = 0 to t = t and qt = 0 to qt = qt, it becomes
log(q e − qt ) = log q e −
t
1
1
=
+ t
2
q k 2,ads q e q e
k1,ads
2.303
t
(26)
(27)
Equation (26) is for pseudo-first order and equation (27) is for pseudo-second order. A
plot of log(q e − qt ) against t will gives linear lines if the adsorption follows the first
order. If the adsorption follows the second order, a plot of t/q against t will yield straight
lines. Hence, the rate constant and the amount of adsorbate sorbed on the sorbents at the
equilibrium can be determined.
In this study whereby the adsorbate is Cr(III) cations and the sorbent is zeolite
Y, when fitting the experiment data to the equation (26) and (27), the correlation
coefficients indicated that the adsorption of Cr(III) on the synthesized and commercial
zeolite NaY were well fitted with equation (27) (pseudo second order) rather than that of
for equation (26) (pseudo first order). As a results, the mechanism of the adsorption of
Cr(III) on the zeolite NaY was based on the pseudo second order model. The values of
107
the rate constant and the amount of Cr(III) sorbed on the zeolite at the equilibrium
together with the correlation coefficients for the adsorption of Cr(III) on synthesized and
commercial zeolite NaY are listed in Table 4.1.
Table 4.1: Values of the pseudo-second order model parameters for the
adsorption of Cr(III) by synthesized and commercial zeolite NaY
[Cr(III)]initial,
Y-
k2, ads
qe
Zeolite
(mg/L)
slope
intercept
r2
(g/mg/h)
(mg/g)
Zeo-NaY-S
250
0.0154
0.003
0.9999
0.0791
64.9350
500
0.0102
0.0211
0.9976
0.00493
98.0392
250
0.0222
0.0110
0.9997
0.0448
45.0450
500
0.0167
0.0223
0.9912
0.0125
59.8802
Zeo-NaY-C
The results from Table 4.1 prove that the uptake of Cr(III) by the zeolite NaY
fitted well with the pseudo-second order model since the correlation coefficient (r2) was
higher than 0.99. Bosco et al (2005) also found that the adsorption of Mn, Cr, Ni and Cd
on the Brazilian natural scolecite, which is the natural zeolte, followed the pseudosecond order model. The sorption of Cr(III) by both zeolites increased with increasing
Cr(III) concentrations. The uptake of Cr(III) by synthesized zeolite NaY at equilibrium
is higher than the commercial ones for both initial concentration possibly due to the
lower ratio of silica to alumina of the synthesized zeolite NaY than the commercial one
that tends to give more exchange sites for the synthesized zeolite NaY.
4.1.2
Effect of Initial pH
pH values of 2, 3, 4 and 5 of the Cr(III) solutions were selected in order to
study the effect of initial pH solution in the adsorption of Cr(III) by zeolite NaY. This
study was performed at such pH values because the presence of OH- when the pH
108
increased above 6 will induce the formation of the hydroxyl complexes of chromium
Cr(OH)3 which tend to precipitate. Figure 4.5 presents the effect of initial pH on the
Percent Cr(III) removal
Cr(III) removal by synthesized and commercial zeolite NaY.
100
90
80
70
60
50
40
30
20
10
0
2
Zeo-NaY-C
Figure 4.5
3
Zeo-NaY-S
4
5
pH
The effect of pH on the Cr(III) removal by synthesized and commercial
zeolite NaY (Condition: 0.1 g of sorbents; 25 mL of 300 mg/L Cr(III) solution)
As seen in Figure 4.5, the removal efficiency of Cr(III) by both zeolites is
reasonably high in the pH range from 2 to 5 caused by the possible Cr species in this
range of pH. According to the theoretical distribution of the chromium species at
different pH values in aqueous solutions, the predominant species below pH 2 is Cr3+, at
pH 4, the Cr3+ and Cr(OH)2+ species are present in an approximate distribution of 40%
and 60%, respectively and at pH 5, the Cr(OH)2+ species will dominate accounting for
nearly 70% of the chromium present with the other major forms as Cr3(OH)45+
accounting around 20% while at pH between 6.5 and 10, the predominant species is
Cr(OH)3 (Leyva-Ramos et al., 1995). Because all of the species are in the cation forms,
they can be exchanged with Na+ that neutralized the framework of zeolite.
Although the removal percentage of Cr(III) seems to be similar in both
zeolites, the synthesized zeolite NaY actually exhibits higher removal percentage than
the commercial for each of the initial pH. The highest removal percentage of Cr(III) by
both zeolites can be seen occurring at pH 4. The removal percentage of Cr(III) decreased
109
when pH decreased (pH 2) because the competitive exchange of H+ is considered to be
the reason for the lower uptake in more acidic environments. Bosco et al. (2005) also
observed the same results when using the natural occurring zeolite, Brazilian natural
scolecite to remove Cr(III) from wastewater.
4.1.3
Isotherm Study
The adsorption capacity of the SMZY and the unmodified zeolite NaY for the
Cr(III) removal was determined through the adsorption isotherm studies. The isotherm
graph for the adsorption of Cr(III) by SMZY from synthesized and commercial zeolites
are given in Figures 4.6 and 4.7, respectively and the comparison of the isotherm graph
for the unmodified synthesized and commercial zeolite NaY can be seen in Figure 4.8.
In order to get the information regarding the adsorption capacity of Cr(III) by
each sorbents, the Langmuir and Freundlich isotherm adsorption models were used. The
theoretical calculations for these models are explained in Chapter 1. The values of the
isotherm models parameters are given in Table 4.2.
[Cr(III)] Sorbed (mg/g)
80
70
60
50
40
30
20
10
Zeo-NaY-S
SMZY-100-S
SMZY-50-S
SMZY-200-S
100
[Cr(III)]e (mg/L)
150
0
0
Figure 4.6
50
200
The adsorption isotherm of Cr(III) sorption on SMZY from the
synthesized zeolite NaY together with the unmodified synthesized zeolite NaY.
110
(Condition: 0.1 g Zeolite, [Cr(III)]initial = 100 mg/L to 600 mg/L, 25 mL of Cr(III)
solution, pH 4).
[Cr(III)] Sorbed (mg/g)
60
50
40
30
20
10
Zeo-NaY-C
SMZY-50-C
SMZY-100-C
SMZY-200-C
0
0
50
100
150
200
250
[Cr(III)]e (mg/L)
Figure 4.7
The adsorption isotherm of Cr(III) sorption on SMZY from the
commercial zeolite NaY together with the unmodified commercial zeolite NaY.
(Condition: 0.1 g Zeolite, [Cr(III)]initial = 100 mg/L to 600 mg/L, 25 mL of Cr(III)
solution, pH 4).
[Cr(III)] Sorbed (mg/g)
80
70
60
50
40
30
20
10
Zeo-NaY-S
Zeo-NaY-C
0
0
50
100
150
[Cr(III)]e (mg/L)
200
250
111
Figure 4.8
The adsorption isotherm of Cr(III) sorption on unmodified synthesized
and commercial zeolite NaY. (Condition: 0.1 g Zeolite, [Cr(III)]initial = 100 mg/L to 600
mg/L, 25 mL of Cr(III) solution, pH 4).
Table 4.2: Fitted Langmuir and Freundlich parameters for Cr(III) sorption on
SMZY and the unmodified synthesized and commercial zeolite NaY
Freundlich
Langmuir
Samples
Kf (mg/g)
n (1/g)
r2
Qo (mg/g)
b (1/g)
r2
Zeo-NaY-S
50.084
12.315
0.9856
68.493
0.924
0.6707
SMZY-50-S
32.337
9.372
0.9364
63.291
0.075
0.9137
SMZY-100-S
41.410
14.793
0.9189
58.140
0.061
0.8259
SMZY-200-S
36.266
11.274
0.9062
55.249
0.052
0.9306
Zeo-NaY-C
24.395
6.536
0.9874
61.350
0.063
0.9149
SMZY-50-C
20.994
5.814
0.9699
62.893
0.050
0.9499
SMZY-100-C
19.760
5.624
0.9767
51.813
0.081
0.9532
SMZY-200-C
20.338
5.862
0.9834
51.813
0.065
0.9137
The values of the correlation coefficients (r2) for Freundlich isotherms indicate
that this model fits all the experimental data better than the Langmuir isotherm. This is
because the surface of the zeolite NaY is not uniform since its structure has a large
central cavity volume and the assembly of many polyhedral building units to construct
the crystal structure of zeolite. Due to these factors, the surface of the zeolite Y creates
the heterogeneity sites for Cr(III) to be adsorbed onto zeolite Y. In addition, the
adsorption of Cr(III) on zeolite is not only involves cation exchange but can also be
adsorbed physically onto the surface of the zeolite since the surface area of the zeolite is
very high. This explains the multilayer adsorption occurs during the adsorption, hence,
identical to the assumptions of the Freundlich isotherm. Figure 4.9 showed the
comparison of the Kf (Freundlich constant) value for each sorbents.
112
60
Kf (mg/g)
50
40
30
20
10
Ze
oN
aY
-S
Ze
oN
aY
-C
SM
ZY
-5
0SM
S
ZY
-5
0SM
C
ZY
-1
00
SM
-S
ZY
-1
00
SM
-C
ZY
-2
00
SM
-S
ZY
-2
00
-C
0
Figure 4.9
The Kf (Freundlich constant) values for the adsorption of Cr(III) by
SMZY and unmodified zeolite Y
The adsorption of the Cr(III) by zeolite Y that had been modified with the
HDTMA cation (SMZY) was observed to be lower than the unmodified zeolite. The
decreased value of Kf for the modified zeolite Y with HDTMA was due to the
competition for sorption sites between Cr(III) cation and cationic surfactant molecules
(HDTMA). Li et al. (2002) also observed the same results regarding the sorption of
selected metal cations onto surfactant modified clinoptilolite (SMC). They concluded
that the reduction in metal cation uptake by the clinoptilolite modified with cationic
surfactant is controlled by the surfactant loading on the zeolite surface. The Kf value
among the SMZY from both zeolites are insignificantly different because there are only
a slight different in the amounts of HDTMA on the zeolite Y for each SMZY samples.
The adsorption of the Cr(III) by the synthesized zeolite NaY was higher than the
commercial one because the synthesized zeolite NaY has a higher cation exchange
capacity (CEC) and lower ratio of SiO2/Al2O3 as well as higher surface area than the
commercial one, hence giving more exchange sites for adsorption to occur. Compared to
the previous literature, the sorption of Cr(III) onto the synthesized zeolite NaY is higher
than the resin type 1200H (Kf=3.28 mg/g), 1500H (Kf=4.99 mg/g), IRN97H (Kf=6.31
mg/g) (Rengaraj et al., 2003), IRN77 (Kf=35.38 mg/g) and SKN1 (Kf=46.34 mg/g)
113
(Rengaraj et al., 2001). As a conclusion, the zeolite NaY synthesized from RHA is
efficient and suitable in removing Cr(III) species from water.
4.2
Removal of Cr(VI)
As explained in the Chapter 1, the zeolite NaY that had been modified by
cationic surfactant, HDTMA (SMZY) above the critical micelle concentration (CMC)
level generates the zeolite having the property which is partially anion exchanger. Thus,
the SMZY are able to remove hexavalent chromium (Cr(VI)) species from water since
this species particularly exists in water as the chromate anion. This study involved the
effect of the pH solution on the removal of chromate by SMZY. Then, the adsorption
capacity of SMZY was determined through isotherm study and the unmodified zeolite Y
was used as comparison.
For the determination of Cr(VI), the solution was added with diphenylcarbazide.
A measurement was performed by ultraviolet-visible (UV-Vis) spectrophotometer since
the diphenylcarbazide forms complexes only with Cr(VI) species. Lastly, the production
of SMZY-chromate solid particle was characterized by XRD and IR spectroscopy to
study their structure in order to construct the theoretical adsorption of chromate on the
SMZY. The analysis data for the removal of Cr(VI) study are given in Appendix H.
4.2.1
Effect of Initial pH.
The removal of chromate from water by adsorbent is highly dependent on the pH
of the solution, which subsequently affects the surface charge of the adsorbent, the
degree of ionization and the speciation of the adsorbate species (Schumi et al., 2001). In
water as well, the chromate anion is not a simple monovalent anion but rather a series of
114
chromate anions depending upon the pH and the concentration of the solution.
Therefore, it was important to study the effect of pH on the adsorption of chromate onto
SMZY. Adsorption of chromate by SMZY was determined by the different initial pH of
the chromate solution, namely pH 3, 5, 7, 8 and 10, using 0.2 g of each SMZY and 20
mL of 10 mg/L Cr(VI) solution. The results obtained were demonstrated in the bar chart
shown in Figure 4.10.
60
% removal
50
40
pH 3
30
pH 5
pH 7
20
pH 8
pH 10
10
0
SMZY- SMZY- SMZY50-S
100-S
200-S
Figure 4.10
SMZY- SMZY- SMZY50-C
100-C 200-C
Effect of pH solution on Cr(VI) removal by SMZY. (Condition: 0.2 g
sorbent, 20 mL Cr(VI) solution, [Cr(VI)]initial=10 mg/L).
Figure 4.10 showed the effect of pH, ranging from 3 to 10 on the adsorption of
chromate by each SMZY. It is thus observed that chromate adsorption is pH dependable.
The Cr(VI) species may be represented in various forms such as H2CrO4, HCrO4-, CrO42and Cr2O72- in the solution phase as a function of pH. Chromate speciation is affected by
solution pH through the following equilibrium (Cotton and Wilkinson, 1998):
HCrO4-
↔
CrO42- + H+
K=10-5.9
(26)
H2CrO4-
↔
HCrO4- + H+
K=4.1
(27)
Cr2O72- + H2O
↔
2HCrO4
K=10-2.2
(28)
115
Above pH 6, the dominant species is yellow chromate anion, (CrO4)2-, between
pH 2 and 6, HCrO4- and dichromate ion, Cr2O72- are in equilibrium. From Eq. (26), the
major species are HCrO4- at pH 5 and CrO42- at pH 7. Because of the distribution of
Cr(VI) in water which is in the form of anion, it is clearly indicated that the zeolite Y
that has been modified with cationic surfactant are suitable to adsorb Cr(VI) species in
water at suitable pH. The adsorption efficiency of chromate was highest at pH 3 for each
of the SMZY while the adsorption decreased when the pH increased. It is due to the
dominant species of Cr(VI) exist in water and the exchange capacity of the SMZY for
that species. As described above, at lower pH, the Cr(VI) species mostly is in univalent
form (HCrO4-) and thus requires one exchange site for one molecule of Cr(VI) species at
that pH . In contrast, at high pH, the divalent form of Cr(VI) species (Cr2O72-,CrO42-) is
mostly existed and necessitate two exchange site from SMZY for the adsorption to
occur. This resulted in higher removal capacity of Cr(VI) species by SMZY at lower pH
than that of at higher pH
In addition, the lower affinity of chromate sorption at pH 10 may also be
influenced by the strong competition of OH- with Br- or chromate anion for the sorption
sites since more OH- anion present at the high pH. Li (2004) also found similar
observations at pH 11 as more Cl- is desorbed at this pH. In addition, at pH values
greater than 6, the presence of OH- ions forms the hydroxyl complexes of chromium.
The sorption of chromate anion on the SMZY-100-S (100% of HDTMA from ECEC of
synthesized zeolite Y) is clearly favorable at pH values between 3 and 8. The Cr(VI)
species are very soluble in aqueous solutions and their solubility increases with pH;
therefore, it was practical to employ these series of SMZY in solutions with pH values
of 8 and below.
116
4.2.2
Isotherm Study
Previous results showed that sorption of chromate anion (Cr(VI)) on the
surfactant modified zeolite followed a typical Langmuir-type isotherm (Haggerty and
Bowman, 1994).
[Cr(VI)]sorbed (mmol/kg)
34.95
29.95
24.95
19.95
14.95
9.95
50-S
4.95
100-S
200-S
Zeo-NaY-S
-0.05
0
Figure 4.11
0.2
0.4
0.6
[Cr(VI)]e (mg/L)
0.8
1
Sorption of Cr(VI) by SMZY and unmodified synthesized zeolite Y.
(Condition: 0.5 g sorbent, 20 mL Cr(VI) , [Cr(VI)]initial=10 mg/L to 70 mg/L, pH ~3.5).
[Cr(VI)] sorbed (mmol/kg)
29.95
24.95
19.95
14.95
9.95
50-C
200-C
4.95
100-C
Zeo-NaY-C
-0.05
0
Figure 4.12
0.2
0.4
0.6
[Cr(VI)]e (mg/L)
0.8
1
Sorption of Cr(VI) by SMZY and unmodified commercial zeolite Y.
(Condition: 0.5 g sorbent, 20 mL Cr(VI), [Cr(VI)]initial=10 mg/L to 70 mg/L, pH ~3.5).
117
Figures 4.11 and 4.12 show the sorption of Cr(VI) on the SMZY from
synthesized and commercial zeolites, respectively. As a comparison, the sorption of
Cr(VI) by the unmodified zeolites is also present at that value. As shown in these
figures, the unmodified zeolite NaY had little affinity for Cr(VI). Zeolite Y posseses a
net negative structural charge resulting from isomorphic substitution of cations in the
crystal lattice. Due to this negative charge, zeolite Y has little or no affinity for anionic
species. In contrast, zeolite Y that had been modified with HDTMA effectively
removing Cr(VI) from aqueous solutions. The sorption of Cr(VI) by SMZY are varied
based on the surfactant loading onto zeolite Y. When this data are plotted as the linear
form of the Langmuir equation (eq. 14), the straight line graph was obtained showing
that the isotherm data for the sorption of Cr(VI) by SMZY were well-described by the
Langmuir isotherm equilibrium model. Table 4.3 presents the fitted Langmuir
parameters for all the batch sorption isotherm experiments.
Table 4.3: Fitted Langmuir parameters for sorption of Cr(VI) by SMZY
slope
intercept
Qo
b
Samples
(1/bQo)
(1/Qo)
(mmol/kg)
(1/kg)
r2
SMZY-50-S
0.0069
0.0476
21.0084
6.8986
0.9964
SMZY-100-S
0.0037
0.0266
37.5940
7.1892
0.9778
SMZY-200-S
0.0051
0.0325
30.7693
6.3725
0.9604
SMZY-50-C
0.0053
0.0384
26.0417
7.2453
0.9653
SMZY-100-C
0.0049
0.0319
31.3480
6.5102
0.9935
SMZY-200-C
0.0050
0.0369
27.1003
7.3800
0.9941
118
40
35
Qo (mmol/kg)
30
25
20
15
10
5
0
50-S
Figure 4.13
50-C
100-S
100-C
200-S
200-C
The comparison of the maximum adsorption (Qo) calculated from the
Langmuir isotherm model for the sorption of Cr(VI) by SMZY
The results from the Langmuir isotherm study clearly show that both zeolites
treated with HDTMA at amounts equal to 100% of the ECEC of the zeolites resulted in
the highest adsorption capacity for both types of zeolite Y. In the zeolite treated with
HDTMA at amounts equal to 50% and 200% of the external cation exchange capacity
(ECEC), the removal capacity of Cr(VI) from aqueous solutions was reduced. The
reduced sorption observed at higher HDTMA level may be due to the release of excess,
loosely bound HDTMA from admicelles on the SMZY into the aqueous solution. This
has subsequently resulted in the competition of the chromate with HDTMA in solution
to attach onto the surface of the zeolite. Haggerty and Bowman (1994) also reported that
the same observation occurred when the natural zeolite, clinoptilolite treated with
HDTMA at an amount of 200% of the ECEC was used to remove chromate anions in
water.
Table 4.3 and Figure 4.13 also revealed that the SMZY from the synthesized
zeolite Y adsorbed more Cr(VI) species than the commercial one because the
synthesized zeolite Y exhibited lower ratio of SiO2/Al2O3 and higher CEC than the
119
commercial zeolite Y. In addition, the surface area of the synthesized zeolite Y was
higher than the commercial one. The lower ratio of SiO2/Al2O3 tends to offer higher
exchange sites which enabled the synthesized zeolite Y to adsorb more HDTMA to
cover its surface, and thus presented a higher value of adsorption capacity of Cr(VI).
When compared to the organo-zeolite from the naturally occurring zeolite, clinoptilolite,
the SMZY in this study showed higher sorption capacity. From the previous literature,
Haggerty and Bowman (1994) showed that the surfactant modified zeolite from
clinoptilolite at amounts equal to 50%, 100% and 200% of the ECEC have maximum
adsorption of Cr(VI) which are 2.35, 4.08 and 3.6 mmol/kg, respectively.
4.2.3
SMZY-Chromate Structure Study
The SMZY-Chromate study was to construct the mechanism for the sorption of
chromate anion by SMZY. From the previous chapter, it is known that the mechanism of
the sorption of chromate anion occurred by anion exchange contributed by the reversed
surface charge from positive to negative resulting from the double layer of the HDTMA
on the surface of the zeolite Y. Thus, the structure of the zeolite Y should not collapse or
change to other phases after contact with the chromate solution. In order to prove this
theory, the SMZY-chromate was prepared by contacting the SMZY with elevated
concentrations of chromate solution. The product was characterized using XRD and IR
techniques, and subsequently compared to the unmodified Y and the SMZY. The XRD
patterns for the SMZY-chromate, SMZY-100-S and unmodified synthesized zeolite Y
are presented in Figure 4.14.
120
I
n
t
e
n
s
i
t
y
Zeo-NaY-S
SMZY-100-S
(a.u.)
SMZY-100-S-Chromate
2-Theta-Scale
Figure 4.14
XRD patterns of the unmodified synthesized zeolite NaY (Zeo-NaY-S),
SMZY-100-S and after contacting with chromate solution (SMZY-100-S-Chromate)
To support the results from the XRD diffractogram, infrared spectroscopy was
used to evaluate the SMZY-chromate product. The IR spectrum of SMZY-chromate was
compared to SMZY-100-S and unmodified zeolite Y in Figures 4.15 and 4.16,
respectively. The XRD diffractogram and the IR spectra for the SMZY after contact
with high concentration of chromate solution show that the structure of the zeolite NaY
did not collapse or changed to other phases and revealed that there were no impurities in
the product, hence proving the theory explained earlier. These results together with the
discussion in section 3.4.6 regarding the maximum adsorption of HDTMA onto zeolite
and the capability of the SMZY to adsorb chromate anion from water and, the
mechanism of the uptake chromate by SMZY can be illustrated in Figure 4.17.
70.0
%T
SMZY-100-S-Chromate
60.0
SMZY-100-S
50.0
771.5
771.5
696.3
569.0
569.0
40.0
499.5
461 9
30.0
20.0
10.0
1300.0
Figure 4.15
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
IR spectra of SMZY-100-S and SMZY-100-S-Chromate
500.0
400.0
1/cm
121
70.0
%T
60.0
SMZY-100-S-Chromate
50.0
Zeo-NaY-S
771.5
696.3
773.4
694.3
569.0
40.0
30.0
1101.3
20.0
1101.3
569.9
500.5
462.9
463.8
1002.9
1005.8
10.0
1300.0
Figure 4.16
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
IR spectra of unmodified synthesized zeolite NaY (Zeo-NaY-S) and
SMZY-100-S-Chromate
Br
Br
Br
Br
Br
Br
Br
Chromate-
Chromate-
Br
Br
Br
Br
Br
Surfactant modified zeolite Y
(SMZY)
Chromate-
Chromate-
Chromate-
ChromateChromate-
+
ChromateFigure 4.17
Chromate-
Chromate-
ChromateChromate-
ChromateChromate-
Schematic diagram for the mechanism of Cr(VI) sorption by SMZY
As illustrated in the schematic diagram in Figure 4.17, the sorption of chromate
anions by the cationic surfactant modified zeolite Y (SMZY) is contributed from surface
anion exchange on the positively charged outermost surface of the zeolite. The
positively charged outermost surface of SMZY was created by the surfactant bilayer
sorption when the amount of the surfactant loading exceeded the external cation
exchange capacity (ECEC) of the zeolite. In addition, the sorption of chromate anion
involved on the replacement of weakly held counterions by strongly held counterions
will eventually lead to the formation of a surface-anion complex. The formation of the
SMZY-chromate is insoluble, thus it will remain as solid particles in the solution that
122
can be separated by a simple filtration technique. As a brief conclusion, the modified
zeolite Y with cationic surfactant, HDTMA (SMZY) was successfully prepared and its
capability in removing chromate shows that the property of the SMZY is significantly
different from the unmodified zeolite NaY.
4.3 Removal of Arsenic
As explained in Chapter 1, the commonly oxidation state for arsenic species in
water are trivalent (As(III)) and pentavalent (As(V)) arsenic in which the former usually
exists as neutral species and the later particularly forms anion. Since the SMZY is
capable of adsorbing cation, anion and neutral species, it can be used to remove those
arsenic species in water. In order to prove that SMZY can adsorb As(III) and As(V)
species from water, the preliminary assessment involving the removal of both arsenic
species by SMZY was carried out by contacting the sorbent with a single concentration
of the species. The use of FAAS for the determination of arsenic species is due to the
high concentration in the initial concentration for both arsenic species. The initial
concentration that was used in this study is more than 10 mg/L. The analysis data for the
removal of arsenic are given in Appendix I.
4.3.1
Preliminary Study: Adsorption of Arsenate and Arsenite
The series of the SMZY and both unmodified zeolite Y were contacted with the
single solute in single concentration of As(V) and As(III). The sorbed concentration of
As(III) and As(V) was calculated from the difference between the final concentration
that is after the adsorption and the initial concentration of both arsenics species. The
results from these experiments are present in Table 4.4 and compared in the graph bar
shown in Figures 4.18 and 4.19 for adsorption of As(III) and As(V), respectively.
123
Table 4.4: Values of the adsorption of As(III) and As(V) (pH=8) by SMZY and
respective parent zeolite Y.
Samples
[As(III)]sorbed, mg/g
[As(V)]sorbed, mg/g
Zeo-NaY-S
0.127
0.047
SMZY-50-S
0.166
0.8869
SMZY-100-S
0.184
0.923
SMZY-200-S
0.162
1.085
Zeo-NaY-C
0.08
0.011
SMZY-50-C
0.142
0.481
SMZY-100-C
0.161
0.512
SMZY-200-C
0.207
0.443
[As(III)]sorbed (mg/g)
0.25
0.2
0.15
0.1
0.05
Ze
oN
a
SM Y-S
ZY
SM -50
-S
ZY
-1
00
SM
-S
ZY
-2
00
Ze
-S
oN
a
SM Y-C
ZY
-5
SM
0C
ZY
-1
00
SM
ZY -C
-2
00
-C
0
Figure 4.18
Adsorption of As(III) by the SMZY and unmodified zeolite NaY.
(Condition: 0.1 g sorbent, 20 mL As(III) solution, [As(III)]initial=20 mg/L).
As shown in Figure 4.18, it is clearly observed that the SMZY adsorbs more
As(III) than the unmodified zeolite Y but not as significant as the adsorption of As(V)
by SMZY (Figure 4.19). Arsenite (H3AsO3) has three constant of dissociation (pKa)
which is 9.2, 14.22 and 19.22 for pK1, pK2 and pK3, respectively. The pKa of As(III)
shows that the ionization step for this species to occur at elevated high pH. At pH 8,
124
As(III) exist in the form of neutral species in water. Since the As(III) mostly forms
neutral species in water (H3AsO3), the adsorption of As(III) on SMZY is due to the
partition of these species into the organic partitioning created from the bilayer of
HDTMA onto the surface of the zeolite Y at HDTMA loading greater than the external
cation exchange capacity (ECEC). The organic partitioning of the HDTMA can be seen
in Figure 1.6 in section 1.4. Furthermore, the zeolite itself can adsorb the arsenite
through the adsorption in the surface of zeolite since both zeolite Y having high specific
surface area. Besides that, the higher As(III) removal by unmodified synthesized zeolite
Y compared to the commercial one indicates that the structure, including Si/Al ratio and
the specific surface area, plays an important role in the arsenic removal process. As a
comparison from previous literature, the sorption of As(III) by zeolite Y was more than
the natural zeolite, clinoptilolite (0.014 mg/g) (Elizalde-Gonzalez et al., 2001b), due to
the higher CEC of the synthetic zeolite Y.
[As(V)]sorbed (mg/g)
1.2
1
0.8
0.6
0.4
0.2
Ze
oN
a
SM Y-S
ZY
SM -50
-S
ZY
-1
00
SM
-S
ZY
-2
00
Ze
-S
oN
a
SM Y-C
ZY
-5
SM
0C
ZY
-1
00
SM
-C
ZY
-2
00
-C
0
Figure 4.19
The adsorption of As(V) species from aqueous solution by SMZY and
unmodified zeolite NaY. (Condition: 0.1 g sorbent, 20 mL As(V) solution,
[As(V)]initial=10 mg/L).
Figure 4.19 shows that the adsorption of single solute and single concentration of
As(V) by SMZY varied significantly with the unmodified zeolite NaY. Therefore, it is
crucial to study further the adsorption of As(V) in order to get more information
125
regarding the effect of solution pH, the sorption behavior and the maximum adsorption
of the As(V) species by SMZY.
4.3.2
Removal of Arsenate
As reviewed in the previous section (Section 4.3.1), the adsorption of arsenate
(As(V)) by SMZY was obviously high compared to the unmodified zeolite Y thus
requiring more information regarding the effect of initial solution pH on the adsorption
of As(V) and the value of the maximum adsorption capacity through the isotherm study.
4.3.2.1 Effect of Initial pH
The SMZY were put into contact with As(V) solutions having pH 4, 6, 7, 8, 10
and 12 in order to study the effect of the solution pH in the removal of As(V). The
percentage of the removal as function of solution pH is illustrated at Figure 4.20.
60
pH 4
% removed
50
pH 6
40
pH 7
30
pH 8
20
pH 10
10
pH 12
0
50-S
Figure 4.20
100-S
200-S
50-C
100-C
200-C
Effect of the initial pH solution in the removal of As(V) by SMZY.
(Condition: 0.2 g sorbent, 20 mL As(V) solution, [As(V)]initial=20 mg/L).
126
The removal of As(V) by each SMZY occurred over a wide range of solution pH
and was clearly affected by the initial pH of the solution, similar to the observation for
the removal of Cr(VI) by SMZY. The trend for the removal of As(V) in different pH of
the solution ranging from 4 to 12 was nearly identical for each of the SMZY. In general,
it can be seen that the removal of As(V) by SMZY is dependent on the initial solution
pH and that the As(V) removal was highest at pH 8 for SMZY from the synthesized and
the commercial zeolite Y. The As(V) removal capacity was low at lower pH and
increased and at elevated pH, the As(V) removal was again decreased. Favorable
sorption of As(V) with SMZY from synthesized zeolite Y was found to take place at the
pH region of 6-8 which considered to be the pH for most drinking water.
Arsenate speciation is affected by the solution pH through the following
equilibrium:
HB3AsO4
↔
H2AsO4-
+
H+
pKa1 = 2.3
(29)
H2AsO4-
↔
HAsO42-
+
H+
pKa2 = 6.8
(30)
+
+
pKa3 = 11.6
(31)
HAsO4
2-
↔
AsO4
3-
H
From the equation 29, 30 and 31, the As(V) species occurs mainly in the form of
H2AsO4- in the pH range between 3 and 6, while a divalent anion HAsO42- dominates at
higher pH values (such as between pH 8 and pH 11). In the intermediate region which is
in the pH range between 6 and 8, both species coexist with one another (Kim et al.,
2004). Thus, it is evident the adsorption of arsenate by SMZY is pH dependent.
According to the equation 29, the As(V) species at pH 4 exists mostly as neutral
form (H3AsO4) and univalent form but the neutral form is much more common. As a
result, the removal capacity at pH 4 is lower than that of at pH 6 since the mechanism of
the removal by SMZY mainly by ion exchange and only a little for the adsorption to
occur. The removal of As(V) was the lowest at pH 12 because at this stage, the
dominants arsenate species exist as divalent (HAsO42-) and trivalent (AsO43-) forms
which need two and three exchange sites from SMZY for the adsorption to occur. In
127
contrast, at pH 8, the univalent (H2AsO4-) form of As(V) is dominants which only need
one exchange sites from SMZY, hence, more As(V) species can be adsorbed by SMZY.
In addition, there are many OH- existing in this solution at pH 12 that strongly compete
with the As(V) anions at the exchanges sites. Shevade and Robert (2004) also obtained
the same results when they used zeolite NH4Y to remove As(V) at pH 13.2. They had
studied the structure of this zeolite after contacting with the As(V) at pH 13.2 and found
that the structure was unstable resulting in the formation of a poorly crystalline
aluminosilicate, but the aluminosilicate solid was still present at this pH, thus, the
reduced As(V) sorption was due to the competition with aqueous OH-. The sorption
capacities of SMZY from synthesized zeolite Y were much higher than that of SMZY
from the commercial one. This observation was analogous with the removal of Cr(III)
and Cr(VI) by SMZY where the lower ratio of Si/Al of the synthesized zeolite Y might
influence and control the removal capacity.
The As(V) exists mainly in the anion form over a wide range of pH, thus proving
that the sorption of As(V) is attributable to the anion exchange provided from the
reversed charged from negative to positive that was created by the double layer of
HDTMA at the zeolite Y surface in SMZY. This observation is comparable with the
sorption of chromate anion by SMZY.
4.3.2.2 Isotherm Study
Previous work (Haggerty and Bowman, 1994: Li and Bowman, 1997: Li et al.,
1998a) have shown that anion sorption by surfactant modified zeolite is well described
by the Langmuir isotherm. The Langmuir isotherm had been described in section 1.6.1
in Chapter I. The sorption isotherms of As(V) from aqueous solutions by SMZY-50
(50% from ECEC), SMZY-100 (100% from ECEC) and SMZY-200 (200% from
ECEC) are given in Figures 4.21, 4.22 and 4.23, respectively. The sorption of As(V) by
unmodified zeolite Y is also given in each figures as comparison.
[As(V)]sorbed (mmol/kg)
128
19.5
14.5
9.5
4.5
-0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
[As(V)]e (mmol/L)
SMZY-50-S
Zeo-NaY-S
Figure 4.21
SMZY-50-C
Zeo-NaY-C
As(V) sorption from aqueous solution by SMZY-50-S, SMZY-50-C
and respective parent zeolite NaY. (Condition: 0.2 g sorbent, 20 mL As(V) with
[As(V)]initial=10 mg/L to 50 mg/L, pH 6).
[As(V)]sorbed (mmol/kg)
19.5
14.5
9.5
4.5
-0.5
0
0.1
0.2
0.3
0.4
0.5
[As(V)]e (mmol/L)
SMZY-100-S
Zeo-NaY-S
Figure 4.22
SMZY-100-C
Zeo-NaY-C
As(V) sorption from aqueous solution by SMZY-100-S, SMZY-100-C
and respective parent zeolite NaY. (Condition: 0.2 g sorbent, 20 mL As(V) with
[As(V)]initial=10 mg/L to 50 mg/L, pH 6).
[As(V)]sorbed (mmol/kg)
129
19.5
14.5
9.5
4.5
-0.5
0
0.1
0.2
0.3
0.4
[As(V)]e (mmol/L)
SMZY-200-S
Zeo-NaY-S
Figure 4.23
0.5
SMZY-200-C
Zeo-NaY-C
As(V) sorption from aqueous solution by SMZY-200-S, SMZY-200-C
and respective parent zeolite NaY. (Condition: 0.2 g sorbent, 20 mL As(V) with
[As(V)]initial=10 mg/L to 50 mg/L, pH 6).
The sorption of As(V) by SMZY fitted very well with the Langmuir isotherm
model because the straight line graph is obtained when these data are plotted according
to equation 8 (section 1.6.1) with the coefficient of determination (r2) for each set of the
linearized data exceeding 0.96 as shown in Table 4.5. The comparisons of the maximum
adsorption value (Qo) for each of the SMZY are exemplified in Figure 4.24.
Table 4.5: Values of the Langmuir parameters for sorption of As(V) by SMZY
Slope
Intercept
Qo
b
Samples
(1/bQo)
(1/Qo)
(mmol/kg)
(1/kg)
r2
SMZY-50-S
0.0026
0.0558
17.9211
21.4615
0.9949
SMZY-100-S
0.0010
0.0559
17.8891
55.9000
0.9696
SMZY-200-S
0.0003
0.0587
17.0358
195.6667
0.9981
SMZY-50-C
0.0044
0.1118
8.9445
25.4091
0.9951
SMZY-100-C
0.0048
0.0982
10.1833
20.4583
0.9980
SMZY-200-C
0.0098
0.1092
9.1575
11.1429
0.9970
130
20
18
16
Qo (mmol/kg)
14
12
10
8
6
4
2
0
SMZY50-S
Figure 4.24
SMZY100-S
SMZY200-S
SMZY50-C
SMZY100-C
SMZY200-C
Comparison of the maximum adsorption (Qo) value calculated from the
Langmuir isotherm model for the As(V) sorption by each of the SMZY.
Figures 4.21, 4.22 and 4.23 demonstrate that both unmodified zeolite NaY have
little affinity for As(V), in contrast, the SMZY shows significant sorption of As(V) from
aqueous solution. The ability of the SMZY to sorb As(V) is due to the anion exchange at
the positive sites brought about by the reversed charged resulting from the HDTMA
double layer onto the zeolite surface. Because the As(V) exists in water as the anion
form and analogous with the Cr(VI) species, the SMZY is able to sorb As(V) by the
anion exchange. On the contrary, the unmodified zeolite NaY having a net negative
charge in the structure tends to repulse the anion form of As(V) species. The SMZY
prepared from the synthesized zeolite Y sorb more As(V) than the SMZY from the
commercial one. The noteworthy difference of the As(V) sorption by SMZY from the
synthesized zeolite compared to the SMZY from the commercial is due to the properties
of the parent synthesized zeolite Y which has higher CEC, higher surface area and lower
ratio of silica per alumina than the commercial zeolite Y. These properties strongly
affect the adsorption capacity of the As(V) by SMZY.
131
From the Langmuir analysis, the sorption of As(V) by SMZY from the
synthesized zeolite Y varied slightly with each other in an ascending series as SMZY50-S > SMZY-100-S > SMZY-200-S. This is because the uptakes of HDTMA on the
zeolite are almost similar to each other according to the elemental analysis of the SMZY
(Section 3.3.3). For the SMZY prepared from the commercial zeolite Y, the zeolite
treated by HDTMA which attained of 100% of the ECEC of the zeolite showed the
highest sorption capacity. The reason for the decreasing As(V) sorption capacity for
zeolite treated with HDTMA which attained of 200% of the ECEC of the zeolite is same
with the sorption of Cr(VI). These results are caused by the release of excess, loosely
bound HDTMA from admicelles on the SMZY into the aqueous solution resulted in the
competition of the As(V) with HDTMA in the solution to attach onto the zeolite Y
surface.
Since the As(V) exists as anions in water and quite similar to the Cr(VI) species,
the theoretical mechanism for the adsorption of As(V) by SMZY can be seen in the
schematic diagram illustrated in Figure 4.17 with the chromate anion exchanged with
arsenate anion. Compared to the previous literature, the SMZY removed As(V) more
than the other sorbent, for instance, the red mud (6.86 mmol/kg) (Altundogan et al.,
2000), clinoptilolite (0.13347 mmol/kg) (Elizalde-Gonzalez et al., 2001) and the natural
iron ores (5.38 mmol/kg) (Zhang et al., 2004). As a brief conclusion, the zeolite Y that
was treated by HDTMA has the capability to remove As(V) from aqueous solutions
more than the unmodified zeolite Y and other sorbents.
CHAPTER 5
CONCLUSIONS AND SUGGESTIONS
5.1
Conclusions
Rice husk ash (RHA) which contained high quantity of the amorphous silica
(more than 95%) was prepared by the combustion of dried rice husk at 600 °C in an
hour. The amorphous form of RHA was indicated from the XRD diffractogram and IR
spectrum while the silica content was determined by the XRF technique. The RHA was
also reactive towards the synthesis of the zeolite hence was used as the source of silica
for the synthesis of the zeolite NaY.
The high purity of the zeolite NaY has been successfully synthesized from RHA
by seeding and ageing techniques during the synthesis process. On the other hand, the
product obtain from RHA without seeding and ageing techniques comprised of the
mixture of zeolite A and Y while the synthesized by ageing and without seeding
techniques was the mixture of zeolite P and Y. These two type of zeolites (i.e. Zeolite A
and P) were found to be the impurities in the synthesized zeolite NaY that must be
eliminated. Therefore, the seeding and ageing techniques were found inevitable in the
synthesis of highly pure zeolite NaY with the elimination of other phases and other
zeolites from the reactive source of silica taken from RHA. In addition, the production
of the synthesized zeolite NaY by these techniques was highly reproducible.
133
The synthesized zeolite NaY from RHA through seeding and ageing techniques
together with the commercial zeolite NaY were characterized using the XRD technique,
IR spectroscopy, elemental analysis and the physicochemical properties. The XRD
technique was found to be very useful to identify the zeolite in the solid products and the
IR spectrum was found suitable in supporting the results from XRD since the structure
of the zeolite NaY exhibited the specific six peaks of the IR spectrum (400 to 1000 cm1
). For the elemental analysis, two different approaches were used namely the physical
method (XRF) and the combination of the wet chemical technique and the analysis after
the dissolution of the solid samples. Since these two approaches have their benefits and
disadvantages as well as the problems with the zeolite itself, the results from these two
approaches can be used. The physicochemical properties that had been studied for the
synthesized zeolite NaY from RHA and the commercial zeolite NaY were unit cell,
silica per alumina ratio, surface area and porosity, total cation exchange capacity (CEC)
and external cation exchange capacity (ECEC). These physicochemical properties were
related to the application of the zeolite as a sorbent for toxic metals in water. It was
found that the synthesized zeolite NaY have higher CEC and ECEC than the commercial
ones due to the lower silica/alumina ratio and higher surface area for the synthesized
zeolite NaY which tends to give more exchange sites. The silica per alumina ratio of the
synthesized zeolite NaY was found in the range for zeolite Y proposed by Breck (Breck
and Tonawanda, 1964) proved that the zeolite Y had been successfully synthesized.
A series of the surfactant modified zeolite NaY (SMZY), the 50%, 100% and
200% of the ECEC zeolite were prepared by attaching the appropriate amount of
HDTMA molecule on the zeolite surface. From the XRD diffractogram and IR spectra,
the structure of the zeolite NaY did not collapse and was not converted to other phases,
and there were no impurities in the product after the modification. In addition, the
amount of sodium decreased and the amount of hydrogen and carbon increased, proving
that the HDTMA had successfully been attached onto the zeolite surface by cation
exchange with sodium cation. The surface area and porosity for each of the SMZY was
not changed after the modification since the HDTMA molecule was not too large to alter
the surface area of the zeolite Y. The dispersion behaviors of the SMZY were found to
134
be different from the parent zeolite Y since the SMZY became partially hydrophobic
that had the tendency to disperse in organic phase and water in contrast to the
unmodified zeolite Y that were dispersed only in water. Lastly, the adsorption of
HDTMA onto the zeolite NaY was based on the Langmuir isotherm showing that the
monolayer coverage was achieved after the zeolite Y was treated with HDTMA. The
maximum adsorption of HDTMA onto zeolite Y was nearly twice the ECEC value of
the synthesized zeolite Y revealing that the adsorption of HDTMA onto the zeolite NaY
above the CMC value created the bilayer formation on the zeolite surface and hence the
charge of the zeolite was reversed from negative to positive.
The SMZY together with the unmodified zeolite NaY from both zeolite NaY, i.e.
synthesized and commercial were applied in removing the trivalent chromium (Cr(III)),
hexavalent chromium or chromate (Cr(VI)), trivalent arsenic or arsenite (As(III)) and
pentavalent arsenic or arsenate (As(V)) species from the aqueous solution. The sorption
of Cr(III) by the synthesized zeolite Y was rapid and more efficient than the commercial
one. The kinetic of Cr(III) uptake by both zeolites was based on the pseudo second order
kinetic model with the amount of sorbed Cr(III) ions on the synthesized zeolite NaY at
the equilibrium much higher than the commercial one. The sorption efficiency of Cr(III)
by both zeolites were found reasonably high in the pH range from 2 to 5 and the highest
removal percentage occurred at pH 4. The isotherm study showed that the sorption of the
Cr(III) by the unmodified and modified zeolite NaY were described very well through
the Freundlich isotherm study in comparison to the Langmuir isotherm. The synthesized
zeolite NaY sorbed more Cr(III) from aqueous solution than the commercial one due to
the physicochemical properties of the synthesized zeolite NaY which governs the
sorbent efficiency. It was observed that the zeolite Y modified with surfactant reduced
the uptake of Cr(III).
The sorption of Cr(VI) and As(V) study showed that the modified zeolite Y with
surfactant was able to remove the anionic forms of contaminants in aqueous solution.
The sorption of these two anions occurred at a wide range of initial solution pH and
found to follow the Langmuir isotherm study. The sorption of Cr(VI) and As(V) were
135
highest when synthesized and commercial zeolite Y were treated with HDTMA equal to
100% of the zeolite’s ECEC. For the As(III) sorption study, since the As(III) exists in
water as neutral species, the sorption of As(III) by SMZY showed a little bit higher than
the unmodified zeolite Y but not as significant as the sorption of As(V). The sorption of
As(III) was observed highest when the zeolite’s external CEC has been fully satisfied by
HDTMA. It was also proven that the physicochemical properties of the parent zeolite Y
strongly controlled the sorption efficiency which the lower ratio of silica per alumina,
higher surface area and higher CEC and ECEC of the synthesized zeolite NaY than the
commercial giving more sorption of Cr(III), Cr(VI), As(III) and As(V).
As a general conclusion, zeolite NaY has the ability to remove cation species
(Cr(III)) from water but they have no or little affinity towards the anion (Cr(VI) and
As(V)) and neutral species (As(III)), in contrast, the surfactant modified zeolite Y
(SMZY) which was prepared by contacting the cationic surfactant, HDTMA on the
zeolite Y was useful and efficient to remove three types of inorganic contaminants of
cation, anion and neutral species. The capability of SMZY to sorb cation species was
due to the cation exchange by the sodium cation which neutralized the internal
framework particularly in the pore of the zeolite structure since the HDTMA molecule
are too large to enter the pore size of zeolite and will exchange with sodium in the
exterior framework. The HDTMA which created the bilayer formation through the tailtail interaction via columbic forces on the surface of zeolite Y resulting the reversed
charge from negative to positive charge was found to be the factors governing the
inorganic anion and neutral species sorbed by the SMZY. The sorption of the inorganic
anions (Cr(VI) and As(V)) involved the replacement of weakly held counterions by
strongly held counterions while the neutral species (As(III)) are partitioned at the
organic detachment produced from the bilayer of HDTMA. In addition, the sorptions of
these inorganic species were maximized when the zeolite’s ECEC have been fully
covered by HDTMA (100% from ECEC). Therefore, the zeolite treated with HDTMA
with fully satisfied ECEC of the zeolite can be used as alternative sorbents in removing
multiple types of contaminants from water for drinking water and waste water treatment.
136
5.2
Suggestions
Since the modified zeolite NaY with surfactant having the ability to remove
multiple contaminants has been successfully prepared, it is assumed that zeolites other
than zeolite Y can be used. There are enormous types of zeolites in this world either
occurring naturally or synthetically and they have similar properties with zeolite Y such
as cation exchange, having high surface area and having molecular sieve properties.
Besides that, the zeolites that have been successfully synthesized from the rice husk ash
are also suitable to generate the surfactant modified zeolite, for instance, zeolite X, A, P,
ZSM and MCM-41. On the other hand, the cationic surfactant that are attached in the
zeolite surface can also be changed. There are many types of cationic surfactant that can
be attached on the zeolite surface instead of the HDTMA, for instance, TDTMA,
ODTMA, DDTMA and TEA which are in the same family with HDTMA. It is
suggested that this surfactant is to be used in order to study the effect of the length of
hydrocarbon tail in removing contaminants.
The success of the SMZY in removing Cr(III) as cation, Cr(VI) and As(V) as
anions and As(III) as the neutral species shows that it has the capability to remove
multiple species in water. There are many toxic elements existing in water that should be
removed. These toxic elements are found in various forms, i.e. inorganic cation,
inorganic anion and organic substances. Therefore, it is suggested that to further the
study on the usage of SMZY in removing multiple types of contaminants, for instance,
the inorganic cation of heavy metals (Pb2+, Cu2+, Ni2+ and Zn2+), the inorganic anion
(selenate, selenite, nitrate, phosphate and sulfate) and the organic substance (benzene,
toluene, xylene and chlorinated hydrocarbon).
The adsorption study in this research was done through batch adsorption study,
thus, in order to examine the capability of the SMZY in removing contaminants through
the flow, it is required to continue the study using the column approach. There are still
many work to be done before it can be used in a filtering unit for drinking water purpose
or for waste water treatment process.
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APPENDIX A
Elemental analysis for the zeolite NaY
A-1: Analysis data for the determination of sodium in the zeolite NaY samples by
AAS
Table A.1.1: Standard calibration curve
Mean Abs
0
0.015
0.036
0.052
0.069
0.084
Standard calibration curve (Na)
Mean Absorbance
[Na] (ppm)
0
0.4
0.8
1.2
1.6
2.0
0,1
0,08
0,06
0,04
0,02
0
y = 0,0427x
2
R = 0,9979
0
0,5
1
1,5
2
2,5
[Na], ppm
Table A.1.2: Quantity of sodium contents in zeolite NaY samples
samples
Zeo-NaY-C
Zeo-NaY-S
Na content
(mg Na/g zeo)
71.40
125.46
(mmol Na/g zeo)
3.10
5.45
Na2O content
(%Na2O in
(g Na2O/g zeo)
1g zeo)
0.0961
9.61
0.1691
16.91
Table A.1.3: Value of the quality control (QC) for the determination of sodium
QC
QC1
QC2
QC3
Known [Na] (ppm)
0.8
1.2
1.6
[Na] from AAS (ppm)
0.828
1.219
1.616
Percent recovery (%)
103.50
101.58
101.00
Table A.1.4: Analysis of the spike recovery (Sp) for the determination of sodium
spike
[Na]AAS,
concentration sample +
[Na]added,
Recovery
ppm (A)
[Na]known, ppm (B)
ppm (C)
(%)
spike 1
0.253
1.421
1.0
116.8
spike 2
0.296
1.488
1.0
119.2
149
A-2: Analysis data for the determination of Al by ICP-MS
Table A.2.1: Standard calibration curve
Net int
0
297881.50
511796.96
1247255.79
Standard calibration curve for determination Al by ICP-MS
Net intensity
standard
(ppb)
0
50
100
250
1500000
y = 5038,5x
R2 = 0,9973
1000000
500000
0
0
50
100
150
200
250
Al concentration (ppb)
Table A.2.2: Quantity of Aluminum contents in zeolite NaY samples
Sample
Zeo-NaY-C
Zeo-NaY-S
Al content
(mg Al/g)
80.852
78.230
(mmol Al/g)
2.995
2.875
Al2O3 content
(percentage Al2O3
(g Al2O3/g)
in 1 g zeolite)
0.1527
15.2745
0.1466
14.6619
Table A.2.3: Analysis of the quality control (QC) for the determination of
Aluminum by ICP-MS
QC
Known [Al] (ppb)
[Al] from ICPMS (ppb)
percent recovery (%)
QC1
100
84.1742
84.1742
QC2
50
46.5387
93.0774
QC3
150
132.5702
88.3800
Table A.2.4: Analysis of the spike recovery study
spike
spike 1
[Al]ICP,
concentration sample +
[Al]added,
Recovery
ppb (A)
[Al]known, ppb (B)
ppb (C)
(%)
343.404
399.060
50
111.312
300
150
A-3: Analysis data for the determination of loss on ignition (LOI) and the
percentage of silica (%SiO2)
Table A.3.1: Results for the determination of percent loss on ignition (%LOI)
Samples
Mcrucibles
(g)
Zeo-NaY-C
Zeo-NaY-S
17.9649
18.5107
Msample ,mo
(before ignition)
(g)
0.1095
0.1261
Msample ,m1
(after ignition)
(g)
0.0847
0.0992
%LOI
22.65
21.33
Table A.3.2: Results for the determination of percent silica (%SiO2)
Samples
Mcrucibles+samples
(g)
Zeo-NaY-C
Zeo-NaY-S
18.0503
18.6114
Msample ,m2
(before ignition)
(g)
0.0854
0.1007
Msample ,m2
(after ignition)
(g)
0.0332
0.0274
%SiO2
61.63
73.59
A-4: X-Ray Fluorescence (XRF) accuracy
Table A.4.1: Relative error of major elements determination based on the
measurement on a certified reference material (CRM)
Elements
SiO2
TiO2
Fe2O3
Al2O3
MnO
CaO
MgO
Na2O
K2O
P2O5
Recommended
value
69.96
0.38
2.77
14.51
0.09
2.45
0.95
3.55
4.03
0.12
Observed
value
69.72
0.39
2.67
14.77
0.09
2.46
1.05
3.53
4.04
0.12
Absolute
difference
- 0.24
+ 0.01
- 0.10
+ 0.26
0
+ 0.01
+ 0.10
- 0.02
+ 0.01
0
Relative
error
0.3
2.6
3.6
1.8
0
0.4
10.5
0.6
0.2
0
151
APPENDIX B
Physicochemical Properties of the Zeolite NaY
B-1: Surface area and porosity
Table B.1.1: Analysis data for the determination of the specific surface area
Sample
Sample
weight (g)
Zeo-NaY-S
0.0454
Zeo-NaY-C
0.0302
MULTI
POINT
BET
P/Po
Volume
[cc/g] STP
172.6852
175.7438
177.6826
166.7507
169.0215
170.6063
1/
(W((Po/P)-1))
0.5407
1.1550
1.9270
0.5535
1.1880
2.0210
0.1045
0.2023
0.2996
0.1034
0.2006
0.3011
Surface
area
(m²/g)
506.6
484.9
Table B.1.2: Value of the pore volume and pore size
Samples
Zeo-NaY-S
Zeo-NaY-C
Total pore volume (cc/g)
0.2748
0.2639
Average pore diameter (Å)
21.70
21.77
152
B-2: Determination of the unit cell
Table B.2.1: Analysis data for the determination of the unit cell for ZeoNaY-S.
Si std
Zeo
average
d value
3.128
5.664
3.768
2.855
2θ
(measured)
28.507
15.633
23.587
31.300
2θ
(correction)
28.467
15.593
23.547
31.260
θ
(correction)
dhkl
7.796
11.773
15.630
5.679
3.775
2.859
h2+k2+l2
19
43
75
average
a, (Ǻ)
24.755
24.759
24.763
24.759
R (Si/Al)
1.96
1.93
1.91
1.93
SiO2/Al2O3
3.916
3.871
3.828
3.871
a, Ǻ
24.755
24.759
24.763
24.759
R (Si/Al)
1.96
1.93
1.91
1.93
SiO2/Al2O3
3.916
3.871
3.828
3.871
h k
l
3
5
7
1
3
1
3
3
5
Table B.2.2: Analysis data for the determination of the unit cell for ZeoNaY-C.
Si std
Zeo
average
d value
3.128
3.293
3.752
2.844
2θ
(measured)
28.505
27.054
23.708
29.693
2θ
(correction)
28.467
27.016
23.670
29.655
θ
(correction)
dhkl
13.508
11.835
14.828
3.293
3.750
3.006
h2+k2+l2
19
43
75
average
a, (Ǻ)
24.699
24.653
24.657
24.670
R (Si/Al)
2.28
2.61
2.58
2.49
SiO2/Al2O3
4.563
4.216
4.155
4.978
a, (Ǻ)
24.699
24.653
24.657
24.670
R (Si/Al)
2.28
2.61
2.58
2.49
SiO2/Al2O3
4.563
4.216
4.155
4.978
h k
l
6
5
7
2
3
3
4
3
3
153
B-3: Determination of CEC and ECEC
Table B.3.1: Analysis data for the determination of the total cation exchange
capacity
No sample label
sample 1
sample 2
sample 3
sample 4
sample 5
sample 6
sample 7
sample 8
sample 9
sample 10
sample 11
sample 12
sample 13
sample 14
sample 15
sample 16
sample 17
sample 18
sample 19
sample 20
sample ID
C-CEC-1-1
C-CEC-1-2
C-CEC-1-3
C-CEC-1-4
C-CEC-100
Sp-C-CEC-1
C-CEC-2-1
C-CEC-2-2
C-CEC-2-3
QC (0.8 ppm)
S-CEC-1-1
S-CEC-1-2
S-CEC-1-3
S-CEC-1-4
S-CEC-100
Sp-S-CEC-1
S-CEC-2-1
S-CEC-2-2
S-CEC-2-3
QC(1.2 ppm)
% Recovery
% Quality control
67.90%
119.50%
105.75%
Type of zeolite NaY
Synthesized
Commercial
[Na], mg/L
145.1125
117.0750
[Na], AAS, (mg/L)
1.328
1.174
1.143
1.187
1.179
1.858
1.257
1.355
1.288
0.956
1.652
1.553
1.545
1.623
1.362
1.898
1.334
1.263
1.277
1.269
CEC, meq/g
3.150
2.545
Dilution
factor
100
100
100
100
100
100
100
100
100
[Na] (mg/L)
132.8
117.4
114.3
118.7
117.9
185.8
125.7
135.5
128.8
100
100
100
100
100
100
100
100
100
165.2
155.3
154.5
162.3
136.2
189.8
133.4
126.3
127.7
154
Table B.3.2: Analysis data for the determination of external cation exchange
capacity (ECEC)
No sample label
sample 1
sample 2
sample 3
sample 4
sample 5
sample 6
sample 7
sample 8
sample 9
sample 10
sample 11
sample 12
sample 13
sample 14
sample 15
sample 16
sample 17
sample 18
sample 19
sample 20
sample ID
C-ECEC-1-1
C-ECEC-1-2
C-ECEC-1-3
C-ECEC-1-4
C-ECEC-100
Sp-C-ECEC-1
C-ECEC-2-1
C-ECEC-2-2
C-ECEC-2-3
QC (0.8 ppm)
S-ECEC-1-1
S-ECEC-1-2
S-ECEC-1-3
S-ECEC-1-4
S-ECEC-100
Sp-S-ECEC-1
S-ECEC-2-1
S-ECEC-2-2
S-ECEC-2-3
QC(1.2 ppm)
% Recovery
% Quality control
85.90%
114.75%
102.20%
Type of
zeolite NaY
Synthesized
Commercial
[Na], mg/L
61.77
49.05
[Na], AAS, (mg/L)
0.504
0.468
0.468
0.502
0.558
1.417
0.595
0.492
0.509
0.918
0.621
0.590
0.640
0.613
0,565
1.330
0.405
0.591
0.651
1.226
ECEC, meq/g
0.6714
0.5330
Dilution
factor
100
100
100
100
100
100
100
100
100
[Na] (mg/L)
50.4
46.8
46.8
50.2
55.8
141.7
59.5
49.2
50.9
100
100
100
100
100
100
100
100
100
62.1
59.0
64.0
61.3
56.5
133
40.5
59.1
65.1
155
APPENDIX C
Infrared spectra of SMZY matching with respective parent zeolite
60.0
SMZY-50-S
%T
771.5 692.4
50.0
569.0 496.6
461.9
1102.2
40.0
773.4 694.3
569.9 500.5
Zeo-NaY-S
30.0
1008.7
463.8
1101.3
20.0
1005.8
10.0
1300.0
Figure C.1
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
Infrared spectrum of SMZY-50-S and Zeo-NaY-S
SMZY-50-C
60.0
578.6 503.4
578.6 505.3
792.7 720.4
792.7 717.5
%T
50.0
40.0
461.9
462.9
Zeo-NaY-C
1139.8
1141.8
30.0
1022.2
1023.2
20.0
1300.0 1200.0 1100.0 1000.0
Figure C.2
900.0
800.0
700.0
600.0
Infrared spectrum of SMZY-50-C and Zeo-NaY-C
500.0
400.0
1/cm
156
60.0
%T
SMZY-100-S
50.0
771.5 696.3
40.0
30.0
569.0 499.5
773.4 694.3
461.9
569.9 500.5
1102.2
Zeo-NaY-S
463.8
1101.3
20.0
1005.8
10.0
1300.0
Figure C.3
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
Infrared spectrum of SMZY-100-S and Zeo-NaY-S
60.0
Zeo-NaY-C
%T
792.7 717.5
578.6 505.3
792.7 720.4
578.6 499.5
462.9
50.0
40.0
461.9
1141.8
SMZY-100-C
1139.8
30.0
1023.2
1022.2
20.0
1300.0
Figure C.4
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
Infrared spectrum of SMZY-100-C and Zeo-NaY-C
500.0
400.0
1/cm
157
60.0
%T
SMZY-200-S
50.0
771.5 696.3
40.0
569.0 499.5
773.4 694.3
569.9 500.5
461.9
30.0
Zeo-NaY-S 1102.2
463.8
1101.3
20.0
1005.8
10.0
1300.0
Figure C.5
1005.8
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
500.0
400.0
1/cm
Infrared spectrum of SMZY-200-S and Zeo-NaY-S
60.0
%T
Zeo-NaY-C
792.7 717.5
578.6 505.3
792.7 723.3
575.7 503.4
462.9
50.0
40.0
1141.8
461.9
SMZY-200-C
1139.8
30.0
1023.2
1022.2
20.0
1300.0
Figure C.6
1200.0
1100.0
1000.0
900.0
800.0
700.0
600.0
Infrared spectrum of SMZY-200-C and Zeo-NaY-C
500.0
400.0
1/cm
158
APPENDIX D
Determination of sodium in SMZY and unmodified zeolite Y.
Table D.1: Standard Calibration curve
Na2O (mg/L)
0
1
2
3
4
5
Absorbance
0
0.021
0.043
0.064
0.083
0.103
Standard calibration curve (flame photometer)
0,12
0,1
Absorbance
Scale
0
20
40
60
80
100
y = 0,0208x
R2 = 0,9993
0,08
0,06
0,04
0,02
0
0
2 Na2O (mg/L) 4
6
Table D.2: Analysis data for the determination of sodium in SMZY
Sample ID
Dilution
Abs 1
Abs 2
Abs 3
Average Abs
Std Dev
ZeoNaY-S
20
0.072
0.071
0.073
0.072
0.001
SMZY50-S
20
0.061
0.060
0.061
0.0606
0.00058
SMZY100-S
20
0.059
0.058
0.06
0.059
0.001
SMZY200-S
20
0.062
0.061
0.061
0.0613
0.00058
QC
(3 ppm)
0.065
0.068
0.067
0.0666
0.001527525
[Na2O], mg/L
[Na2O], mg/L *
dilution
[Na2O], mg/g
[Na2O], mmol/g
3.4615
2.9166
2.8366
2.9487
3.2051
69.2307
138.4615
2.2332
58.3333
116.6666
1.8817
56.7307
113.4615
1.8300
58.9743
117.9487
1.9023
104.70%
Sample ID
Dilution
Abs 1
Abs 2
Abs 3
Average Abs
Std Dev
ZeoNaY-C
10
0.100
0.101
0.100
0.1003
0.0005
SMZY50-C
10
0.092
0.092
0.091
0.0916
0.0006
SMZY100-C
10
0.092
0.094
0.092
0.0926
0.0011
SMZY200-C
10
0.097
0.097
0.095
0.0963
0.0011
QC
(3 ppm)
4.8237
4.4070
4.4551
4.6314
3.1410
48.2371
96.4743
1.5560
44.0705
88.1410
1.42162
44.5512
89.1025
1.4371
46.3141
92.6282
1.4940
104.70%
[Na2O], mg/L
[Na2O], mg/L *
dilution
[Na2O], mg/g
[Na2O], mmol/g
0.065
0.064
0.067
0.06533
0.0016
159
APPENDIX E
Surface area and porosity of the surfactant modified zeolite Y
Table E.1: Analysis data for the determination of the surface area
Sample
Sample
weight (g)
SMZY-50-S
0.0288
SMZY-100-S
0.0268
SMZY-200-S
0.0247
SMZY-50-C
0.0221
SMZY-100-C
0.0294
SMZY-200-C
0.0290
MULTI
POINT
BET
P/Po
Volume
[cc/g] STP
168.4996
172.6423
176.0056
185.0937
189.8709
193.8231
179.6607
184.6891
188.9336
191.4353
195.0367
197.8466
204.0599
207.5684
211.1765
185.5383
188.9169
191.3728
1/
(W((Po/P)-1))
0.5497
1.1760
1.9710
0.4995
1.0670
1.7920
0.5125
1.0960
1.8340
0.4915
1.0440
1.7370
0.4442
0.9611
1.6360
0.5040
1.0760
1.7940
0.1037
0.2024
0.3024
0.1035
0.2020
0.3027
0.1032
0.2019
0.3021
0.1052
0.2028
0.3004
0.1017
0.1995
0.3015
0.1046
0.2026
0.3002
Surface
area
(m²/g)
502.1
553.1
540.3
563.8
602.2
545.6
Table E.2: Value of the pore volume and size
Samples
SMZY-50-S
SMZY-100-S
SMZY-200-S
SMZY-50-C
SMZY-100-C
SMZY-200-C
Total pore volume (cc/g)
0.2722
0.2998
0.2922
0.3060
0.3267
0.2960
Average pore diameter (Å)
21.69
21.68
21.63
21.71
21.70
21.70
160
APPENDIX F
Maximum adsorption of HDTMA on the zeolite Y.
Table F.1: Analysis data for the determination of maximum adsorption of
HDTMA on the zeolite Y
%
25
65
100
200
250
[C]initial, ppm
348.8
752.0
1245.0
2532.0
3036.0
[C]final, ppm
43.64
11.26
15.36
91.07
105.70
dilution
factor
3
30
30
15
15
[C]final, ppm
130.92
337.80
460.80
1366.05
1585.50
([C]i-[C]f) ppm
217.88
414.20
784.20
1165.95
1450.50
Table F.2: Analysis data for the determination of maximum adsorption of
HDTMA on the zeolite Y (continue).
[HDTMA]p%
25
65
100
200
250
initial,
mmol/L
1.6785
4.3641
6.7140
13.4280
16.7850
[C]initial,
mmol /L
29.067
62.667
103.750
211.000
253.000
[HDTMA]initial,
mmol/L
1.5298
3.2982
5.4605
11.1053
13.3158
[C]final,
ppm
130.92
337.80
460.80
1366.05
1585.50
[C]final,
mmol /L
10.9100
28.1500
38.4000
113.8375
132.1250
Table F.3: Analysis data for the determination of maximum adsorption of
HDTMA on the zeolite Y (continue).
%
25
65
100
200
250
[HDTMA]e, mmol/L
0.5742
1.4815
2.0210
5.9914
6.9539
[HDTMA] sorbed,
mmol/L
0.95561
1.8166
3.4394
5.1138
6.3618
[HDTMA] sorbed, mmol/kg
95.5614
181.6667
343.9474
511.3815
636.1842
161
APPENDIX G
Removal of Cr(III) study
G-1: Kinetic study of the Cr(III) uptake by the synthesized and commercial
zeolite NaY
Table G.1.1: Analysis data for the removal of Cr(III) by synthesized zeolite
Y ([Cr(III)]initial = 250 mg/L)
Time
(hour)
0
0.17
0.5
2
5
8
16
24
40
48
[Cr(III)] AAS,
mg/L
257.664
190.114
110.720
9.177
0
0
0
0
0
0
[Cr(III)] sorbed,
mg/L
[Cr(III)] sorbed,
mg/g
% removed
67.550
146.944
248.487
257.664
257.664
257.664
257.664
257.664
257.664
16.888
36.736
62.122
64.416
64.416
64.416
64.416
64.416
64.416
26.216
57.030
96.438
100.000
100.000
100.000
100.000
100.000
100.000
Table G.1.2: Analysis data for the removal of Cr(III) by synthesized zeolite
Y (Kinetic second order data)
[Cr(III)] sorbed (mg/g), q
16.888
36.736
62.123
64.416
64.416
64.416
64.416
64.416
64.416
time (hour), t
0.17
0.5
2
5
8
16
24
40
48
t/q (h/mg/g)
0.0101
0.0136
0.0322
0.0776
0.1242
0.2484
0.3726
0.6210
0.7452
162
Table G.1.3: Analysis data for the removal of Cr(III) by commercial zeolite
Y ([Cr(III)]initial = 250 mg/L)
Time
(hour)
0
0.17
0.5
2
5
8
16
24
40
48
[Cr(III)] AAS,
mg/L
257.664
79.167
55.706
60.760
91.172
95.832
87.122
81.864
79.893
78.408
[Cr(III)] sorbed,
mg/L
[Cr(III)] sorbed,
mg/g
% removed
99.330
146.252
136.144
166.492
161.832
170.542
175.800
177.771
179.256
24.833
36.563
34.036
41.623
40.458
42.636
43.950
44.443
44.814
38.550
56.761
52.838
64.616
62.807
66.188
68.228
68.993
69.570
Table G.1.4: Analysis data for the removal of Cr(III) by synthesized zeolite
Y (Kinetic second order data)
[Cr(III)] sorbed (mg/g), q
24.833
36.563
34.036
41.623
40.458
42.636
43.950
44.443
44.814
time (hour), t
0.17
0.5
2
5
8
16
24
40
48
t/q (h/mg/g)
0.0068
0.0137
0.0588
0.1201
0.1977
0.3753
0.5461
0.9000
1.0711
Table G.1.5: Analysis data for the removal of Cr(III) by synthesized zeolite Y
([Cr(III)]initial = 500 mg/L)
Time
(hour)
0
0.17
0.5
2
5
8
16
24
40
48
[Cr(III)] AAS,
mg/L
574.43
567.10
459.74
428.12
327.29
209.64
316.76
394.59
200.65
197.68
[Cr(III)] sorbed,
mg/L
[Cr(III)] sorbed,
mg/g
% removed
7.330
114.690
146.310
247.140
364.788
257.670
179.840
373.780
376.754
1.833
28.673
36.578
61.785
91.197
64.418
44.960
93.445
94.189
1.276
19.966
25.471
43.024
63.504
44.857
31.308
65.070
65.588
163
Table G.1.6: Analysis data for the removal of Cr(III) by synthesized zeolite
Y (Kinetic second order data)
[Cr(III)] sorbed (mg/g), q
1.833
28.673
36.578
61.785
91.197
93.445
94.189
time (hour), t
t/q (h/mg/g)
0.5
2
5
8
40
48
0.0174
0.0547
0.0810
0.0877
0.4281
0.5097
Table G.1.7: Analysis data for the removal of Cr(III) by commercial zeolite
Y ([Cr(III)]initial = 500 mg/L)
Time
(hour)
0
0.17
0.5
2
5
8
16
24
40
48
[Cr(III)] AAS,
mg/L
574.43
409.80
396.68
388.68
397.81
401.43
381.86
350.12
326.04
347.26
[Cr(III)] sorbed,
mg/L
[Cr(III)] sorbed,
mg/g
% removed
164.63
177.75
185.49
176.62
173.00
192.57
224.31
248.39
227.17
41.158
44.438
46.373
44.155
43.250
48.143
56.078
62.098
56.793
28.660
30.944
32.291
30.747
30.117
33.523
39.049
43.241
39.547
Table G.1.8: Analysis data for the removal of Cr(III) by commercial zeolite
Y (Kinetic second order data)
[Cr(III)] sorbed (mg/g), q
41.158
44.438
46.438
44.155
43.250
48.143
56.078
62.098
56.793
time (hour), t
0.17
0.5
2
5
8
16
24
40
48
t/q (h/mg/g)
0.0041
0.0112
0.0431
0.1132
0.1850
0.3323
0.4280
0.6441
0.8452
164
G-2: Effect of the initial pH for the Cr(III) removal
Table G.2.1: Analysis data for the effect of the pH for the Cr(III) removal by
synthesized zeolite NaY (pH 2)
sample
300 ppm
2-S-1
2-S-2
2-S-3
2-S-1
2-S-2
2-S-3
average
Std Dev
[Cr(III)] AAS (mg/L)
2.625
1.281
1.494
1.424
Dilution factor
100
20
20
20
average
Std Dev
[Cr(III)]i - [Cr(III)]f (mg/L)
236.88
232.62
234.02
234.51
[Cr(III)] Sorbed, q (mg/g)
59.220
58.155
58.505
58.627
0.543
[Cr(III)]e (mg/L)
262.50
25.62
29.88
28.48
28.00
2.17
Table G.2.2: Analysis data for the effect of the pH for the Cr(III) removal by
commercial zeolite NaY (pH 2)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.625
Dilution factor
100
[Cr(III)]e (mg/L)
262.5
2-C-1
2-C-2
2-C-3
0.915
0.817
0.776
30
30
30
average
Std Dev
27.45
24.51
23.28
25.08
2.14
[Cr(III)]i - [Cr(III)]f (mg/L)
235.05
237.99
239.22
237.42
[Cr(III)] Sorbed, q (mg/g)
58.7625
59.4975
59.805
59.355
0.535
2-C-1
2-C-2
2-C-3
average
Std Dev
Quality Control (4ppm)
3.459
% QC
86.475
165
Table G.2.3: Analysis data for the effect of the pH for the Cr(III) removal by
synthesized zeolite NaY (pH 3)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.809
Dilution factor
100
[Cr(III)]e (mg/L)
280.9
3-S-1
3-S-2
3-S-3
1.168
1.091
1.167
15
15
15
average
Std Dev
17.52
16.365
17.505
17.13
0.66
[Cr(III)]i - [Cr(III)]f (mg/L)
263.380
264.535
263.395
263.770
[Cr(III)] Sorbed, q (mg/g)
65.845
66.134
65.849
65.943
0.166
3-S-1
3-S-2
3-S-3
average
Std Dev
Table G.2.4: Analysis data for the effect of the pH for the Cr(III) removal by
commercial zeolite NaY (pH 3)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.809
Dilution factor
100
[Cr(III)]e (mg/L)
280.9
3-C-1
3-C-2
3-C-3
0.704
0.508
0.554
30
30
30
average
Std Dev
21.12
15.24
16.62
17.66
3.07
[Cr(III)]i - [Cr(III)]f (mg/L)
259.78
265.66
264.28
263.24
[Cr(III)] Sorbed, q (mg/g)
64.945
66.415
66.070
65.810
0.768
3-C-1
3-C-2
3-C-3
average
Std Dev
Quality Control (4ppm)
% QC
4.223 105.575
3.863
96.575
166
Table G.2.5: Analysis data for the effect of the pH for the Cr(III) removal by
synthesized zeolite NaY (pH 4)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.335
Dilution factor
100
[Cr(III)]e (mg/L)
233.5
4-S-1
4-S-2
4-S-3
1.88
1.489
1.517
10
10
10
average
Std Dev
18.8
14.89
15.17
16.29
2.18
[Cr(III)]i - [Cr(III)]f (mg/L)
214.70
218.61
218.33
217.21
[Cr(III)] Sorbed, q (mg/g)
53.6750
54.6525
54.5825
54.3033
0.5453
4-S-1
4-S-2
4-S-3
average
Std Dev
Table G.2.6: Analysis data for the effect of the pH for the Cr(III) removal by
commercial zeolite NaY (pH 4)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.335
Dilution factor
100
[Cr(III)]e (mg/L)
233.5
4-C-1
4-C-2
4-C-3
1.171
1.162
1.195
15
15
15
average
Std Dev
17.57
17.43
17.93
17.64
0.26
[Cr(III)]i - [Cr(III)]f (mg/L)
215.935
216.070
215.575
215.860
[Cr(III)] Sorbed, q (mg/g)
53.984
54.018
53.894
53.965
0.063
4-C-1
4-C-2
4-C-3
average
Std Dev
Quality Control ( 4ppm)
% QC
4.223
105.575
3.863
96.575
167
Table G.2.7: Analysis data for the effect of the pH for the Cr(III) removal by
synthesized zeolite NaY (pH 5)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.631
Dilution factor
100
[Cr(III)]e (mg/L)
263.1
5-S-1
5-S-2
0.484
0.435
10
10
average
Std Dev
4.84
4.35
4.60
0.35
[Cr(III)]i - [Cr(III)]f (mg/L)
258.26
258.75
258.51
[Cr(III)] Sorbed, q (mg/g)
64.565
64.688
64.626
0.086
5-S-1
5-S-2
average
Std Dev
Table G.2.8: Analysis data for the effect of the pH for the Cr(III) removal by
commercial zeolite NaY (pH 5)
sample
300 ppm
[Cr(III)] AAS (mg/L)
2.631
Dilution factor
100
[Cr(III)]e (mg/L)
263.1
5-C-1
5-C-2
5-C-3
4.574
5.120
4.864
10
10
10
average
Std Dev
45.74
51.20
48.64
48.53
2.73
[Cr(III)]i - [Cr(III)]f (mg/L)
217.36
211.90
214.46
214.57
[Cr(III)] Sorbed, q (mg/g)
54.340
52.975
53.615
53.643
0.683
5-C-1
5-C-2
5-C-3
average
Std Dev
Quality Control (4ppm)
4.022
3.484
% QC
100.55
87.1
168
G-3: Isotherm adsorption study of the Cr(III) by modified and unmodified
zeolite NaY
Table G.3.1: Standard calibration standard
[Cr(III)]
mg/L
0
0.1
0.5
1
3
5
6
standard calibration curve
5
Absorbance
Abs
0
0.0052
0.0213
0.0433
0.1215
0.1841
4
3
y = 26.259x
2
2
R = 0.9956
1
0
0
0.05
0.1
[Cr(III)] mg/L
0.15
0.2
Table G.3.2: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=100 mg/L)
Samples
100ppm
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC (2 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
QC (2 ppm)
Commercial
QC(1 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC (2 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC (2 ppm)
[Cr(III)] final AAS,
(mg/L)
0.762
0.191
0.132
0.001
0.011
1.438(71.9%)
0.010
0.021
0.007
0.004
1.457(72.85%)
0,705(70,5%)
0.055
0.058
0.028
0.014
1,449(72,45%)
0.020
0.046
0.016
0.026
1,451(72,55%)
dilution
100
[Cr(III)]e
(mg/L)
76.2
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
1
1
1
1
0.191
0.132
0.001
0.011
76.068
76.199
76.189
76.190
15.214
15.240
15.238
15.238
1
1
1
1
0.010
0.021
0.007
0.004
76.179
76.193
76.196
76.196
15.236
15.239
15.240
15.240
1
1
1
1
0.055
0.058
0.028
0.014
76.145
76.142
76.172
76.186
15.229
15.228
15.234
15.237
1
1
1
1
0.020
0.046
0.016
0.026
76.180
76.154
76.184
76.174
15.236
15.231
15.237
15.235
169
Table G.3.3: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=250 mg/L)
Samples
250ppm
QC(1 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(1 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
QC(1 ppm)
Commercial
QC(3 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(3 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC(3 ppm)
[Cr(III)]final AAS,
(mg/L)
2.5
1,194(119,4%)
0.108
0.107
2.150
1.723
1,194(119,4%)
1.062
0.745
1.390
1.613
1,194(119,4%)
3,217(107,23%)
2.057
1.911
2.247
2.253
3,217(107,23%)
2.483
2.459
2.564
2.475
3,217(107,23%)
dilution
100
[Cr(III)]e
(mg/L)
250
[Cr(III)]sorbed [Cr(III)]sorbed
(mg/L)
(mg/g)
10
10
10
10
1.08
1.07
21.50
17.23
248.92
248.93
228.50
232.77
49.784
49.786
45.700
46.554
10
10
10
10
10.62
7.45
13.90
16.13
239.38
242.55
236.10
233.87
47.876
48.510
47.220
46.774
20
20
20
20
41.14
38.22
44.94
45.06
208.86
211.78
205.06
204.94
41.772
42.356
41.012
40.988
20
20
20
20
49.66
49.18
51.28
49.50
200.34
200.82
198.72
200.50
40.068
40.164
39.744
40.100
Table G.3.4: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=300 mg/L)
Sample
300ppm
QC(1 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(1 ppm)
[Cr(III)]finalAAS,
(mg/L)
3
1,215(121,5%)
0.167
0.197
2.351
2.302
1,215(121,5%)
dilution
100
[Cr(III)]e
(mg/L)
300
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
25
25
25
25
4.175
4.925
58.775
57.550
295.825
295.075
241.225
242.450
59.165
59.015
48.245
48.490
170
Table G.3.4: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=300 mg/L)
(continue)
Sample
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
QC(1 ppm)
Commercial
QC(3 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(3 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC(3 ppm)
[Cr(III)]finalAAS,
(mg/L)
1.987
2.019
2.470
2.432
1,215(121,5%)
3,252(108,4%)
3.177
3.147
3.217
3.204
3,252(108,4%)
3.474
3.373
3.498
3.358
3,252(108,4%)
dilution
25
25
25
25
[Cr(III)]e
(mg/L)
49.675
50.475
61.750
60.800
[Cr(III)]sorbed
(mg/L)
250.325
249.525
238.250
239.200
[Cr(III)]sorbed
(mg/g)
50.065
49.905
47.650
47.840
25
25
25
25
79.425
78.675
80.425
80.100
220.575
221.325
219.575
219.900
44.115
44.265
43.915
43.980
25
25
25
25
86.850
84.325
87.450
83.950
213.150
215.675
212.550
216.050
42.630
43.135
42.510
43.210
Table G.3.5: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=350 mg/L)
Samples
350ppm
QC(1 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(1 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
QC(1 ppm)
[Cr(III)]final AAS,
(mg/L)
3.5
1,187(118,7%)
0.470
0.448
1.809
1.934
1,187(118,7%)
1.690
1.788
1.924
1.817
1,187(118,7%)
dilution
100
[Cr(III)] e
(mg/L)
350
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
50
50
50
50
23.50
22.40
90.45
96.70
326.50
327.60
259.55
253.30
65.30
65.52
51.91
50.66
50
50
50
50
84.50
89.40
96.20
90.85
265.50
260.60
253.80
259.15
53.10
52.12
50.76
51.83
171
Table G.3.5: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=350 mg/L)
(continue).
Samples
QC(3 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(3 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC(3 ppm)
[Cr(III)]final AAS,
(mg/L)
3,252(108,4%)
2.035
2.354
2.323
2.282
3,252(108,4%)
3.403
2.448
2.483
2.565
3,252(108,4%)
dilution
[Cr(III)] e
(mg/L)
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
50
50
50
50
101.75
117.70
116.15
114.10
248.25
232.30
233.85
235.90
49.65
46.46
46.77
47.18
50
50
50
50
170.15
122.40
124.15
128.25
179.85
227.60
225.85
221.75
35.97
45.52
45.17
44.35
Table G.3.6: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=400 mg/L)
Samples
400ppm
QC(1 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(1 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
QC(1 ppm)
Commercial
QC(3 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(3 ppm)
[Cr(III)]final AAS,
(mg/L)
4
1,233(123,3%)
1.151
1.238
2.472
2.361
1,233(123,3%)
2.164
2.101
2.035
2.299
1,233(123,3%)
3,214(107,13%)
2.676
2.625
2.808
2.661
3,214(107,13%)
dilution
100
[Cr(III)]e
(mg/L)
400
[Cr(III)]sorbed [Cr(III)]sorbed
(mg/L)
(mg/g)
50
50
50
50
57.55
61.90
123.60
118.05
342.45
338.10
276.40
281.95
68.49
67.62
55.28
56.39
50
50
50
50
108.20
105.05
101.75
114.95
291.80
294.95
298.25
285.05
58.36
58.99
59.65
57.01
50
50
50
50
133.80
131.25
140.40
133.05
266.20
268.75
259.60
266.95
53.24
53.75
51.92
53.39
172
Table G.3.6: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=400 mg/L)
(continue)
Samples
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC(3 ppm)
[Cr(III)]final AAS,
(mg/L)
2.912
2.893
2.837
3.016
3,214(107,13%)
dilution
50
50
50
50
[Cr(III)]e
(mg/L)
145.60
144.65
141.85
150.80
[Cr(III)]sorbed
(mg/L)
254.40
255.35
258.15
249.20
[Cr(III)]sorbed
(mg/g)
50.88
51.07
51.63
49.84
Table G.3.7: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=450 mg/L).
Samples
450ppm
QC(1 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(1 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
Commercial
QC(1 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(1 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
[Cr(III)]final AAS,
(mg/L)
4.5
1,223(122,3%)
0.903
1.170
1.741
1.800
1,223(122,3%)
1.618
1.669
1.738
1.678
1,207(120,7%)
1.861
1.860
1.993
2.071
1,207(120,7%)
1.978
1.959
1.997
2.043
dilution
100
[Cr(III)]e
(mg/L)
450
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
100
100
100
100
90.3
117.0
174.1
180.0
359.7
333.0
275.9
270.0
71.94
66.60
55.18
54.00
100
100
100
100
161.8
166.9
173.8
167.8
288.2
283.1
276.2
282.2
57.64
56.62
55.24
56.44
100
100
100
100
186.1
186.0
199.3
207.1
263.9
264.0
250.7
242.9
52.78
52.80
50.14
48.58
100
100
100
100
197.8
195.9
199.7
204.3
252.2
254.1
250.3
245.7
50.44
50.82
50.06
49.14
173
Table G.3.8: Analysis data for the isotherm adsorption study of the Cr(III) by
modified and unmodified zeolite Y ([Cr(III)]initial=500 mg/L)
Samples
500ppm
QC(3 ppm)
Synthesized
Zeo-NaY-S-1
Zeo-NaY-S-2
SMZY-50-S-1
SMZY-50-S-2
QC(3 ppm)
SMZY-100-S-1
SMZY-100-S-2
SMZY-200-S-1
SMZY-200-S-2
Commercial
QC(3 ppm)
Zeo-NaY-C-1
Zeo-NaY-C-2
SMZY-50-C-1
SMZY-50-C-2
QC(3 ppm)
SMZY-100-C-1
SMZY-100-C-2
SMZY-200-C-1
SMZY-200-C-2
QC(3 ppm)
[Cr(III)]final AAS,
(mg/L)
5
3,219(107,3%)
1.568
1.594
1.864
2.088
3,219(107,3%)
1.989
1.996
1.944
2.044
3,221(107,367%)
2.178
2.192
2.267
2.178
3,221(107,367%)
2.210
2.339
2.322
2.370
3,221(107,367%)
dilution
100
[Cr(III)]e
(mg/L)
500
[Cr(III)]sorbed
(mg/L)
[Cr(III)]sorbed
(mg/g)
100
100
100
100
156.8
159.4
186.4
208.8
343.2
340.6
313.6
291.2
68.64
68.12
62.72
58.24
100
100
100
100
198.9
199.6
194.4
204.4
301.1
300.4
305.6
295.6
60.22
60.08
61.12
59.12
100
100
100
100
217.8
219.2
226.7
217.8
282.2
280.8
273.3
282.2
56.44
56.16
54.66
56.44
100
100
100
100
221.0
233.9
232.2
237.0
279.0
266.1
267.8
263.0
55.80
53.22
53.56
52.60
174
APPENDIX H
Removal of Cr(VI) study
H-1: Effect of the initial pH solution on the removal of Cr(VI) by SMZY
Table H.1.1: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-50-S.
sample ID
pH 3 initial
3-50S-1
3-50S-2
3-50S-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-50S-1
5-50S-2
5-50S-3
Average
S.Dev
QC(0,5ppm)
pH 7 initial
7-50S-1
7-50S-2
7-50S-3
Average
S.Dev
QC(0,5ppm)
pH 8 initial
8-50S-1
8-50S-2
8-50S-3
Average
S.Dev
QC(0,5ppm)
pH 10 initial
10-50S-1
10-50S-2
10-50S-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.80
6.247
6.468
6.402
0,487(97,4%)
10.571
6.632
6.544
6.477
0,471(94,12%)
10.993
6.963
6.840
6.827
0,459(91,7%)
9.978
6.603
6.608
6.487
0,482(96,4 %)
9.596
7.270
7.280
7.504
0,470(93,94%)
[Cr(VI)]sorbed,
mg/L
[Cr(VI)]sorbed,
mg/g
% Remove
4.553
4.332
4.398
0.228
0.217
0.220
0.221
0.006
42.160
40.109
40.723
40.998
1.052
0.197
0.201
0.205
0.201
0.004
37.267
38.092
38.730
38.030
0.734
0.201
0.208
0.208
0.206
0.004
36.657
37.777
37.893
37.442
0.682
0.169
0.168
0.175
0.171
0.003
33.824
33.772
34.990
34.195
0.689
0.116
0.116
0.105
0.112
0.007
24.245
24.138
21.798
23.394
1.383
pH
3.4
6.34
5.1
3.940
4.027
4.094
6.61
7
4.030
4.153
4.166
5.68
8
3.375
3.370
3.491
6.73
10.09
2.327
2.316
2.092
8.22
175
Table H.1.2: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-100-S.
sample ID
pH 3 initial
3-100S-1
3-100S-2
3-100S-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-100S-1
5-100S-2
5-100S-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.80
5.920
6.091
5.865
[Cr(VI)]sorbed,
mg/g
% Remove
4.880
4.710
4.935
0.244
0.235
0.247
0.242
0.006
45.187
43.605
45.694
44.828
1.090
0.227
0.233
0.236
0.232
0.004
42.892
44.129
44.685
43.902
0.918
0.235
0.222
0.235
0.231
0.007
42.754
40.453
42.717
41.975
1.318
pH
3.4
6.28
0,487(97,4%)
10.571
6.037
5.906
5.847
5.1
4.534
4.665
4.724
6.09
0,471(94,12%)
pH 7 initial
7-100S-1
7-100S-2
7-100S-3
Average
S.Dev
QC(0,5ppm)
0,459(91,7%)
pH 8 initial
9.978
8-100S-1
8-100S-2
8-100S-3
Average
S.Dev
QC(0,5ppm)
5.261
5.279
5.343
pH 10 initial
10-100S-1
10-100S-2
10-100S-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]sorbed,
mg/L
10.993
6.293
6.546
6.297
7
4.700
4.447
4.696
6.6
8
4.717
4.700
4.635
0.237
0.235
0.232
0.234
0.002
47.278
47.098
46.455
46.943
0.433
0.123
0.122
0.121
0.122
0.001
25.654
25.360
25.267
25.427
0.202
6.4
0,482(96,4 %)
9.596
7.134
7.163
7.172
0,469(93,94%)
10.1
2.462
2.434
2.425
7.32
176
Table H.1.3: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-200-S.
sample ID
pH 3 initial
3-200S-1
3-200S-2
3-200S-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-200S-1
5-200S-2
5-200S-3
Average
S.Dev
QC(0,5ppm)
pH 7 initial
7-200S-1
7-200S-2
7-200S-3
Average
S.Dev
QC(0,5ppm)
pH 8 initial
8-200S-1
8-200S-2
8-200S-3
Average
S.Dev
QC(0,5ppm)
pH 10 initial
10-200S-1
10-200S-2
10-200S-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.800
5.649
5.635
5.637
[Cr(VI)]sorbed,
mg/L
[Cr(VI)]sorbed,
mg/g
% Remove
5.151
5.165
5.163
0.258
0.258
0.258
0.258
0.000
47.696
47.822
47.802
47.773
0.067
0.243
0.244
0.246
0.245
0.001
45.994
46.163
46.634
46.264
0.332
0.236
0.234
0.217
0.229
0.011
42.915
42.589
39.435
41.647
1.922
0.193
0.192
0.197
0.194
0.002
38.769
38.498
39.579
38.949
0.563
0.126
0.125
0.124
0.125
0.001
26.311
25.995
25.893
26.066
0.218
pH
3.4
6.04
0,487(97,4%)
10.571
5.709
5.691
5.641
5.1
4.862
4.880
4.930
6.51
0,471(94,12%)
10.993
6.275
6.311
6.658
7
4.718
4.682
4.335
6.53
0,4585(91,7%)
9.978
6.110
6.137
6.029
8
3.868
3.841
3.950
6.5
0,482(96,4 %)
9.596
7.071
7.102
7.112
0,470(93,94%)
10.09
2.525
2.495
2.485
8.02
177
Table H.1.4: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-50-C.
sample ID
pH 3 initial
3-50C-1
3-50C-2
3-50C-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-50C-1
5-50C-2
5-50C-3
Average
S.Dev
QC(0,5ppm)
pH 7 initial
7-50C-1
7-50C-2
7-50C-3
Average
S.Dev
QC(0,5ppm)
pH 8 initial
8-50C-1
8-50C-2
8-50C-3
Average
S.Dev
QC(0,5ppm)
pH 10 initial
10-50C-1
10-50C-2
10-50C-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.8
5.421
5.450
5.441
[Cr(VI)]sorbed,
mg/L
[Cr(VI)]sorbed,
mg/g
% Remove
5.380
5.350
5.360
0.269
0.268
0.268
0.268
0.001
49.806
49.538
49.625
49.656
0.137
0.204
0.201
0.183
0.196
0.012
38.655
38.018
34.540
37.071
2.215
0.203
0.201
0.202
0.202
0.001
36.961
36.591
36.742
36.765
0.186
0.154
0.154
0.151
0.153
0.002
30.897
30.897
30.320
30.705
0.333
0.101
0.105
0.103
0.103
0.002
21.081
21.825
21.516
21.474
0.374
pH
3.4
5.92
0,475(94,96%)
10.571
6.485
6.552
6.920
5.1
4.086
4.019
3.651
5.68
0,475(95,06%)
10.993
6.930
6.971
6.954
7
4.063
4.022
4.039
6.05
0,499(99,7%)
9.978
6.895
6.895
6.953
8
3.083
3.083
3.025
6.31
0,488(97,56 %)
9.596
7.573
7.502
7.532
0,471(94,2%)
10.09
2.023
2.094
2.065
7.99
178
Table H.1.5: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-100-C.
sample ID
pH 3 initial
3-100C-1
3-100C-2
3-100C-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-100C-1
5-100C-2
5-100C-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.800
5.581
5.638
5.441
[Cr(VI)]sorbed,
mg/g
% Remove
5.219
5.163
5.360
0.261
0.258
0.268
0.262
0.005
48.325
47.801
49.621
48.582
0.937
0.209
0.210
0.212
0.210
0.001
39.588
39.775
40.091
39.818
0.254
0.231
0.235
0.235
0.234
0.002
42.018
42.707
42.770
42.499
0.417
pH
3.4
5.79
0,475(94,96%)
10.571
6.386
6.366
6.333
5.1
4.185
4.205
4.238
5.7
0,475(95,06%)
pH 7 initial
7-100C-1
7-100C-2
7-100C-3
Average
S.Dev
10.993
6.374
6.298
6.291
QC(0,5ppm)
0,499(99,7%)
pH 8 initial
8-100C-1
8-100C-2
8-100C-3
Average
S.Dev
QC(0,5ppm)
9.978
5.842
5.874
5.850
pH 10 initial
10-100C-1
10-100C-2
10-100C-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]sorbed,
mg/L
7
4.619
4.695
4.702
4.08
8
4.136
4.104
4.128
0.207
0.205
0.206
0.206
0.001
41.454
41.135
41.368
41.319
0.165
0.068
0.069
0.071
0.069
0.001
14.190
14.335
14.738
14.421
0.284
6.14
0,488(97,56 %)
9.596
8.235
8.221
8.182
0,471(94,2%)
10.09
1.362
1.376
1.414
7.39
179
Table H.1.6: Analysis data for the effect of the initial pH solution on the
removal of Cr(VI) by SMZY-200-C.
sample ID
pH 3 initial
3-200C-1
3-200C-2
3-200C-3
Average
S.Dev
QC(0,5ppm)
pH 5 initial
5-200C-1
5-200C-2
5-200C-3
Average
S.Dev
QC(0,5ppm)
pH 7 initial
7-200C-1
7-200C-2
7-200C-3
Average
S.Dev
QC(0,5ppm)
pH 8 initial
8-200C-1
8-200C-2
8-200C-3
Average
S.Dev
QC(0,5ppm)
pH 10 initial
10-200C-1
10-200C-2
10-200C-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e,
mg/L
10.800
5.336
5.471
5.052
[Cr(VI)]sorbed,
mg/L
[Cr(VI)]sorbed,
mg/g
% Remove
5.464
5.329
5.748
0.273
0.266
0.287
0.276
0.011
50.596
49.339
53.224
51.053
1.982
0.232
0.232
0.232
0.232
0.000
43.954
43.971
43.943
43.956
0.014
0.236
0.236
0.223
0.232
0.008
42.996
43.006
40.554
42.185
1.413
0.223
0.222
0.222
0.222
0.000
44.609
44.472
44.438
44.506
0.090
0.119
0.119
0.119
0.119
0.000
24.842
24.820
24.760
24.807
0.043
pH
3.4
5.49
0,475(94,96%)
10.571
5.925
5.923
5.926
5.1
4.646
4.648
4.645
5.78
0,475(95,06%)
10.993
6.267
6.265
6.534
7
4.727
4.728
4.458
5.74
0,499(99,7%)
9.978
5.527
5.541
5.544
8
4.451
4.437
4.434
6.1
0,488(97,56 %)
9.5962
7.212
7.214
7.220
0,471(94,2%)
10.09
2.384
2.382
2.376
6.78
180
H-2: Isotherm study of the removal of Cr(VI) by SMZY
[Cr(VI)]
mg/L
0
0.25
0.50
0.75
1.00
Absorbance
0
0.1742
0.3575
0.5344
0.7192
Absorbance
Table H.2.1: Standard calibration data.
0.8
Standard calibration curve
0.6
0.4
2
R = 0.9999
0.2
0
0
0.2
0.4
0.6
0.8
1
1.2
[Cr(VI)] (mg/L)
Table H.2.2: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-50-S
sample ID
15 ppm initial
15-50S1-1
15-50S1-2
15-50S1-3
Average
S.Dev
15 ppm initial
15-50S2-1
15-50S2-2
15-50S2-3
Average
S.Dev
20 ppm initial
20-50S1-1
20-50S1-2
20-50S1-3
Average
S.Dev
20 ppm initial
20-50S2-1
20-50S2-2
20-50S2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
15.179
4.833
4.802
4.706
4.780
0.066
15.179
4.571
4.560
4.680
4.603
0.066
20.753
7.359
7.497
7.519
7.458
0.086
20.753
6.676
6.682
6.766
6.708
0.0504
0,496(99,16%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
10.347
10.377
10.474
0.0929
0.0923
0.0905
0.0919
0.0013
7.9595
7.9828
8.0572
7.9998
0.0510
10.608
10.620
10.500
0.0879
0.0877
0.0900
0.0885
0.0013
8.1610
8.1692
8.0774
8.1359
0.0508
13.394
13.256
13.234
0.1415
0.1442
0.1446
0.1434
0.0017
10.3036
10.1978
10.1809
10.2274
0.0665
14.077
14.071
13.987
0.1284
0.1285
0.1301
0.1290
0.0010
10.8291
10.8244
10.7598
10.8044
0.03876
181
Table H.2.2: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-50-S (continue)
sample ID
40 ppm initial
40-50S1-1
40-50S1-2
40-50S1-3
Average
S.Dev
40 ppm initial
40-50S2-1
40-50S2-2
40-50S2-3
Average
S.Dev
50 ppm initial
50-50S1-1
50-50S1-2
50-50S1-3
Average
S.Dev
50 ppm initial
50-50S2-1
50-50S2-2
50-50S2-3
Average
S.Dev
70 ppm initial
70-50S1-1
70-50S1-2
70-50S1-3
Average
S.Dev
70 ppm initial
70-50S2-1
70-50S2-2
70-50S2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
42.301
21.922
22.143
22.218
22.094
0.154
42.301
21.546
21.730
21.530
21.602
0.1114
52.525
30.605
31.011
30.880
30.832
0.2072
52.525
30.723
30.310
30.117
30.383
0.310
74.837
45.602
45.418
46.466
45.829
0.560
74.837
46.260
46.141
46.100
46.167
0.0831
0,494(98,76%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
20.379
20.158
20.083
0.4216
0.4259
0.4273
0.4249
0.0030
15.6774
15.5073
15.4496
15.5448
0.1183
20.755
20.571
20.771
0.4144
0.4179
0.4140
0.4155
0.0021
15.9667
15.8250
15.9790
15.9235
0.0855
21.920
21.514
21.645
0.5886
0.5964
0.5939
0.5930
0.0040
16.8628
16.5505
16.6513
16.6882
0.1594
21.802
22.215
22.408
0.5909
0.5829
0.5792
0.5843
0.0059
16.7721
17.0898
17.2382
17.0334
0.2382
29.235
29.419
28.371
0.8770
0.8735
0.8936
0.8814
0.0108
22.4902
22.6317
21.8256
22.3158
0.4305
28.577
28.696
28.737
0.8897
0.8874
0.8866
0.8879
0.0016
21.9840
22.0755
22.1071
22.0555
0.0639
182
Table H.2.3: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-100-S
sample ID
15 ppm initial
15-100S1-1
15-100S1-2
15-100S1-3
Average
S.Dev
15 ppm initial
15-100S2-1
15-100S2-2
15-100S2-3
Average
S.Dev
QC(0,6ppm)
20 ppm initial
20-100S1-1
20-100S1-2
20-100S1-3
Average
S.Dev
20 ppm initial
20-100S2-1
20-100S2-2
20-100S2-3
Average
S.Dev
QC(0,8ppm)
30 ppm initial
30-100S1-1
30-100S1-2
30-100S1-3
Average
S.Dev
30 ppm initial
30-100S2-1
30-100S2-2
30-100S2-3
Average
S.Dev
QC(0,8ppm)
[Cr(VI)]e, mg/L
15.896
2.516
2.511
2.517
2.514
0.003
15.896
2.788
2.787
2.753
2.776
0.019
0,629(104,83%)
20.897
4.395
4.426
4.426
4.416
0.018
20.897
3.875
3.764
3.783
3.807
0.060
0,813(101,64%)
28.471
8.014
8.153
8.421
8.196
0.206
28.471
7.810
7.898
7.752
7.819
0.073
0,745(93,11%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
13.380
13.385
13.379
0.0484
0.0483
0.0484
0.0484
0.0000
10.2934
10.2971
10.2926
10.2943
0.0023
13.108
13.109
13.143
0.0536
0.0536
0.0530
0.0534
0.0004
10.0839
10.0843
10.1105
10.0929
0.0153
16.502
16.471
16.471
0.0845
0.0851
0.0851
0.0849
0.0003
12.6947
12.6710
12.6710
12.6789
0.0137
17.021
17.133
17.114
0.0745
0.0724
0.0727
0.0732
0.0011
13.0945
13.1802
13.1659
13.1469
0.0459
20.458
20.318
20.051
0.1541
0.1568
0.1619
0.1576
0.0040
15.7377
15.6307
15.4246
15.5977
0.1591
20.661
20.573
20.719
0.1502
0.1519
0.1491
0.1504
0.0014
15.8946
15.8269
15.9389
15.8868
0.0564
183
Table H.2.3: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-100-S (continue).
sample ID
40 ppm initial
40-100S1-1
40-100S1-2
40-100S1-3
Average
S.Dev
40 ppm initial
40-100S2-1
40-100S2-2
40-100S2-3
Average
S.Dev
QC(0,6ppm)
50 ppm initial
50-100S1-1
50-100S1-2
50-100S1-3
Average
S.Dev
50 ppm initial
50-100S2-1
50-100S2-2
50-100S2-3
Average
S.Dev
QC(0,6ppm)
70 ppm initial
70-100S1-1
70-100S1-2
70-100S1-3
Average
S.Dev
70 ppm initial
70-100S2-1
70-100S2-2
70-100S2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
36.484
12.835
12.748
12.576
12.720
0.132
36.484
12.787
12.644
12.584
12.672
0.1043
0,558(93,05%)
55.512
18.200
18.970
18.328
18.499
0.413
55.512
17.680
18.127
17.508
17.772
0.3195
0,558(92,97%)
76.099
33.854
35.093
33.853
34.2667
0.7157
76.099
36.685
37.241
38.233
37.3863
0.7842
0,506(101,22%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
23.649
23.736
23.908
0.2468
0.2452
0.2419
0.2446
0.0026
18.1929
18.2599
18.3921
18.2816
0.1014
23.697
23.840
23.900
0.2459
0.2432
0.2420
0.2437
0.0020
18.2299
18.3399
18.3860
18.3186
0.0802
37.312
36.542
37.184
0.3500
0.3648
0.3525
0.3558
0.0079
28.7037
28.1114
28.6053
28.4735
0.3174
37.832
37.385
38.004
0.3400
0.3486
0.3367
0.3418
0.0061
29.1038
28.7599
29.2361
29.0333
0.2458
42.245
41.006
42.246
0.6511
0.6749
0.6511
0.6590
0.0138
32.4987
31.5455
32.4994
32.1812
0.5505
39.414
38.858
37.866
0.7055
0.7162
0.7353
0.7190
0.0150
30.3207
29.8930
29.1299
29.7812
0.6032
184
Table H.2.4: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-200-S.
sample ID
15 ppm initial
15-200S1-1
15-200S1-2
15-200S1-3
Average
S.Dev
15 ppm initial
15-200S2-1
15-200S2-2
15-200S2-3
Average
S.Dev
QC(0,6ppm)
20 ppm initial
20-200S1-1
20-200S1-2
20-200S1-3
Average
S.Dev
20 ppm initial
20-200S2-1
20-200S2-2
20-200S2-3
Average
S.Dev
QC(0,8ppm)
30 ppm initial
30-200S1-1
30-200S1-2
30-200S1-3
Average
S.Dev
30 ppm initial
30-200S2-1
30-200S2-2
30-200S2-3
Average
S.Dev
QC(0,8ppm)
[Cr(VI)]e, mg/L
15.896
3.589
3.593
3.595
3.592
0.003
15.896
3.673
3.667
3.671
3.670
0.002
0,629(104,83%)
20.897
6.217
6.237
6.414
6.289
0.1088
20.897
6.367
6.609
6.402
6.459
0.131
0,772(96,51%)
28.471
7.610
7.769
7.791
7.7234
0.0988
28.471
7.526
7.932
7.884
7.780
0.221
0,738(92,29%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
12.306
12.302
12.301
0.0690
0.0691
0.0691
0.0690
0.0000
9.4674
9.4640
9.4628
9.4647
0.0023
12.222
12.228
12.225
0.0706
0.0705
0.0705
0.0705
0.0000
9.4029
9.4074
9.4048
9.4050
0.0022
14.679
14.659
14.482
0.1195
0.1199
0.1233
0.1209
0.0021
11.2930
11.2777
11.1409
11.2372
0.0837
14.529
14.287
14.494
0.1224
0.1271
0.1231
0.1242
0.0025
11.1771
10.9909
11.1507
11.1062
0.1007
20.861
20.702
20.679
0.1463
0.1494
0.1498
0.1485
0.0019
16.0481
15.9258
15.9086
15.9608
0.0760
20.944
20.539
20.586
0.1447
0.1525
0.1516
0.1496
0.0042
16.1126
15.8004
15.8372
15.9167
0.1706
185
Table H.2.4: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-200-S (continue).
sample ID
40 ppm initial
40-200S1-1
40-200S1-2
40-200S1-3
Average
S.Dev
40 ppm initial
40-200S2-1
40-200S2-2
40-200S2-3
Average
S.Dev
QC(0,8ppm)
50 ppm initial
50-200S1-1
50-200S1-2
50-200S1-3
Average
S.Dev
50 ppm initial
50-200S2-1
50-200S2-2
50-200S2-3
Average
S.Dev
QC(0,6ppm)
70 ppm initial
70-200S1-1
70-200S1-2
70-200S1-3
Average
S.Dev
70 ppm initial
70-200S2-1
70-200S2-2
70-200S2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
36.484
14.156
14.433
14.176
14.255
0.154
36.484
14.646
14.699
14.614
14.653
0.042
0,72(90%)
55.512
21.786
21.633
22.197
21.872
0.291
55.512
21.839
22.332
22.191
22.120
0.253
0,558(93,067%)
76.099
42.712
42.564
42.584
42.620
0.0802
76.099
43.300
44.026
43.153
43.493
0.467
0,514(102,84%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
22.328
22.051
22.308
0.2722
0.2775
0.2726
0.2741
0.0029
17.1767
16.9636
17.1613
17.1005
0.1188
21.838
21.785
21.870
0.2816
0.2826
0.2810
0.2818
0.0008
16.7997
16.7589
16.8243
16.7943
0.0330
33.726
33.879
33.315
0.4189
0.4160
0.4268
0.4206
0.0056
25.9450
26.0627
25.6288
25.8789
0.2243
33.673
33.180
33.321
0.4200
0.4294
0.4267
0.4254
0.0048
25.9043
25.5250
25.6335
25.6876
0.1953
33.387
33.535
33.515
0.8214
0.8186
0.8189
0.8196
0.0015
25.6842
25.7981
25.7827
25.7550
0.0617
32.799
32.073
32.946
0.8327
0.8467
0.8299
0.8364
0.0090
25.2319
24.6734
25.3450
25.0834
0.3595
186
Table H.2.5: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-50-C.
sample ID
10 ppm initial
10-50C1-1
10-50C1-2
10-50C1-3
Average
S.Dev
10 ppm initial
10-50C2-1
10-50C2-2
10-50C2-3
Average
S.Dev
15 ppm initial
15-50C1-1
15-50C1-2
15-50C1-3
Average
S.Dev
15 ppm initial
15-50C2-1
15-50C2-2
15-50C2-3
Average
S.Dev
QC(0,5ppm)
20 ppm initial
20-50C1-1
20-50C1-2
20-50C1-3
Average
S.Dev
20 ppm initial
20-50C2-1
20-50C2-2
20-50C2-3
Average
S.Dev
30 ppm initial
30-50C1-1
30-50C1-2
30-50C1-3
Average
S.Dev
[Cr(VI)]e, mg/L
10.516
2.132
2.195
2.143
2.157
0.033
10.516
2.216
2.217
2.210
2.214
0.004
15.179
4.625
4.884
5.122
4.877
0.248
15.179
4.983
5.068
5.036
5.029
0.042
0,535(107,18%)
20.753
6.630
6.623
6.619
6.624
0.005
20.753
6.639
6.631
6.439
6.570
0.113
29.906
10.464
10.456
10.433
10.451
0.016
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
8.383
8.320
8.372
0.0410
0.0422
0.0412
0.0414
0.0006
6.4494
6.4005
6.4407
6.4302
0.0260
8.299
8.298
8.305
0.0426
0.0426
0.0425
0.0425
0.0000
6.3844
6.3840
6.3896
6.3860
0.0031
10.553
10.294
10.056
0.0889
0.0939
0.0985
0.0938
0.0048
8.1183
7.9193
7.7365
7.9247
0.1909
10.195
10.111
10.142
0.0958
0.0974
0.0968
0.0967
0.0008
7.8433
7.7782
7.8026
7.8081
0.0328
14.122
14.129
14.133
0.1275
0.1273
0.1273
0.1274
0.0001
10.8644
10.8698
10.8728
10.8690
0.0042
14.113
14.121
14.313
0.1276
0.1275
0.1238
0.1263
0.0021
10.8571
10.8634
11.0110
10.9105
0.0871
19.442
19.450
19.473
0.2012
0.2010
0.2006
0.2009
0.0003
14.9565
14.9626
14.9803
14.9665
0.0123
187
Table H.2.5: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-50-C (continue).
sample ID
30 ppm initial
30-50C2-1
30-50C2-2
30-50C2-3
Average
S.Dev
QC(0,5ppm)
40 ppm initial
40-50C1-1
40-50C1-2
40-50C1-3
Average
S.Dev
40 ppm initial
40-50C2-1
40-50C2-2
40-50C2-3
Average
S.Dev
50 ppm initial
50-50C1-1
50-50C1-2
50-50C1-3
Average
S.Dev
50-50C2-1
50-50C2-2
50-50C2-3
Average
S.Dev
QC(0,5ppm)
70 ppm initial
70-50C1-1
70-50C1-2
70-50C1-3
Average
S.Dev
70 ppm initial
70-50C2-1
70-50C2-2
70-50C2-3
Average
S.Dev
[Cr(VI)]e, mg/L
29.906
10.453
10.476
10.575
10.501
0.064
0,504(100,86%)
42.301
17.840
17.835
17.596
17.757
0.139
42.301
17.818
17.815
18.479
18.037
0.382
52.525
24.889
25.064
25.406
25.119
0.262
24.291
24.357
24.205
24.284
0.076
0,501(100,32%)
74.834
41.71
41.885
41.825
41.806
0.088
74.834
42.168
39.733
40.644
40.848
1.230
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
19.453
19.430
19.331
0.2010
0.2014
0.2033
0.2019
0.0012
14.9649
14.9473
14.8711
14.9278
0.0498
24.461
24.466
24.705
0.3431
0.3430
0.3384
0.3415
0.0026
18.8176
18.8214
19.0053
18.8814
0.1072
24.483
24.486
23.822
0.3426
0.3426
0.3553
0.3468
0.0073
18.8345
18.8368
18.3260
18.6657
0.2942
27.636
27.461
27.119
0.4786
0.4820
0.4886
0.4831
0.0051
0.4671
0.4684
0.4655
0.4670
0.0014
21.2600
21.1254
20.8623
21.0826
0.2022
21.7201
21.6693
21.7862
21.7252
0.0586
33.124
32.949
33.009
0.8021
0.8055
0.8043
0.8040
0.0017
25.4819
25.3473
25.3934
25.4075
0.0684
32.666
35.101
34.190
0.8109
0.7641
0.7816
0.7856
0.0236
25.1296
27.0028
26.3020
26.1448
0.9464
28.234
28.168
28.320
188
Table H.2.6: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-100-C.
sample ID
15 ppm initial
15-100C1-1
15-100C1-2
15-100C1-3
Average
S.Dev
15 ppm initial
15-100C2-1
15-100C2-2
15-100C2-3
Average
S.Dev
QC(0,6ppm)
20 ppm initial
20-100C1-1
20-100C1-2
20-100C1-3
Average
S.Dev
20 ppm initial
20-100C2-1
20-100C2-2
20-100C2-3
Average
S.Dev
QC(0,8ppm)
30 ppm initial
30-100C1-1
30-100C1-2
30-100C1-3
Average
S.Dev
30 ppm initial
30-100C2-1
30-100C2-2
30-100C2-3
Average
S.Dev
QC(0,8ppm)
[Cr(VI)]e, mg/L
15.896
3.837
3.842
3.797
3.826
0.024
15.896
3.601
3.534
3.524
3.553
0.0422
0,619(103,27%)
20.315
4.816
4.961
4.835
4.871
0.079
20.315
6.315
5.411
5.756
5.828
0.456
0,778(97,36%)
28.471
7.829
7.767
7.889
7.828
0.061
28.471
7.542
7.819
7.887
7.750
0.1826
0,734(91,75%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
12.058
12.053
12.098
0.0738
0.0739
0.0730
0.0735
0.0005
9.2762
9.2724
9.3071
9.2852
0.0190
12.294
12.361
12.371
0.0692
0.0679
0.0677
0.0683
0.0008
9.4577
9.5097
9.5175
9.4950
0.0325
15.498
15.353
15.479
0.0926
0.0954
0.0929
0.0936
0.0015
11.9227
11.8109
11.9082
11.8806
0.0607
13.999
14.903
14.558
0.1214
0.1040
0.1107
0.1120
0.0087
10.7694
11.4650
11.1996
11.1447
0.3510
20.641
20.703
20.581
0.1505
0.1493
0.1517
0.1505
0.0011
15.8792
15.9271
15.8329
15.8797
0.0470
20.928
20.651
20.583
0.1450
0.1503
0.1517
0.1490
0.0035
16.0997
15.8870
15.8343
15.9404
0.1405
189
Table H.2.6: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-100-C (continue).
sample ID
40 ppm initial
40-100C1-1
40-100C1-2
40-100C1-3
Average
S.Dev
40 ppm initial
40-100C2-1
40-100C2-2
40-100C2-3
Average
S.Dev
QC(0,6ppm)
50 ppm initial
50-100C1-1
50-100C1-2
50-100C1-3
Average
S.Dev
50 ppm initial
50-100C2-1
50-100C2-2
50-100C2-3
Average
S.Dev
QC(0,5ppm)
70 ppm initial
70-100C1-1
70-100C1-2
70-100C1-3
Average
S.Dev
70 ppm initial
70-100C2-1
70-100C2-2
70-100C2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
39.83
13.872
13.764
13.691
13.775
0.091
39.83
13.613
13.670
13.616
13.633
0.0320
0,554(92,43%)
50.621
22.224
22.027
22.383
22.211
0.178
50.621
22.726
22.579
22.286
22.530
0.224
0,483(96,64%)
74.077
41.628
39.753
39.168
40.183
1.285
74.077
39.209
38.851
38.728
38.929
0.249
0,500(100,04%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
25.958
26.066
26.139
0.2667
0.2647
0.2633
0.2649
0.0017
19.9692
20.0523
20.1084
20.0433
0.0700
26.217
26.160
26.214
0.2618
0.2629
0.2618
0.2621
0.0006
20.1684
20.1246
20.1661
20.1530
0.0246
28.397
28.594
28.238
0.4274
0.4236
0.4304
0.4271
0.0034
21.8455
21.9970
21.7232
21.8552
0.1371
27.895
28.042
28.335
0.4370
0.4342
0.4286
0.4333
0.0043
21.4593
21.5724
21.7978
21.6098
0.1723
32.449
34.324
34.909
0.8006
0.7645
0.7532
0.7728
0.0247
24.9626
26.4051
26.8551
26.0743
0.9886
34.868
35.226
35.349
0.7540
0.7471
0.7448
0.7486
0.0048
26.8236
27.0990
27.1936
27.0387
0.1922
190
Table H.2.7: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-200-C.
sample ID
15 ppm initial
15-200C1-1
15-200C1-2
15-200C1-3
Average
S.Dev
15 ppm initial
15-200C2-1
15-200C2-2
15-200C2-3
Average
S.Dev
QC(0,6ppm)
20 ppm initial
20-200C1-1
20-200C1-2
20-200C1-3
Average
S.Dev
20 ppm initial
20-200C2-1
20-200C2-2
20-200C2-3
Average
S.Dev
QC(0,8ppm)
30 ppm initial
30-200C1-1
30-200C1-2
30-200C1-3
Average
S.Dev
30 ppm initial
30-200C2-1
30-200C2-2
30-200C2-3
Average
S.Dev
QC(0,8ppm)
[Cr(VI)]e, mg/L
15.896
3.717
3.768
3.762
3.749
0.027
15.896
2.995
2.961
2.993
2.983
0.019
0,619(103,27%)
20.315
6.052
6.405
6.170
6.209
0.179
20.315
4.968
5.220
5.333
5.173
0.186
0,778(97,36%)
28.471
10.715
11.242
11.171
11.042
0.285
28.471
11.057
11.050
10.959
11.022
0.054
0,691(86,38%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
12.178
12.127
12.133
0.0715
0.0724
0.0723
0.0721
0.0005
9.3684
9.3292
9.3339
9.3438
0.0214
12.900
12.934
12.902
0.0576
0.0569
0.0575
0.0573
0.0003
9.9240
9.9503
9.9259
9.9334
0.0146
14.262
13.909
14.145
0.1164
0.1231
0.1186
0.1194
0.0034
10.9716
10.7005
10.8816
10.8512
0.1380
15.346
15.094
14.981
0.0955
0.1003
0.1025
0.0995
0.0035
11.8061
11.6123
11.5251
11.6478
0.1438
17.756
17.229
17.300
0.2060
0.2162
0.2148
0.2123
0.0055
13.65951227
13.25409647
13.30871606
13.4074416
0.220001233
17.414
17.421
17.512
0.2126
0.2125
0.2107
0.2119
0.0011
13.3964
13.4018
13.4718
13.4233
0.0421
191
Table H.2.7: Analysis data for the isotherm adsorption for Cr(VI) removal
study by SMZY-200-C (continue).
sample ID
40 ppm initial
40-200C1-1
40-200C1-2
40-200C1-3
Average
S.Dev
40 ppm initial
40-200C2-1
40-200C2-2
40-200C2-3
Average
S.Dev
QC(0,6ppm)
50 ppm initial
50-200C1-1
50-200C1-2
50-200C1-3
Average
S.Dev
50 ppm initial
50-200C2-1
50-200C2-2
50-200C2-3
Average
S.Dev
QC(0,5ppm)
70 ppm initial
70-200C1-1
70-200C1-2
70-200C1-3
Average
S.Dev
70 ppm initial
70-200C2-1
70-200C2-2
70-200C2-3
Average
S.Dev
QC(0,5ppm)
[Cr(VI)]e, mg/L
39.83
12.604
12.538
12.759
12.633
0.113
39.830
12.777
12.745
12.871
12.797
0.065
0,547(91,27%)
50.621
24.650
25.342
24.709
24.900
0.383
50.621
24.284
24.097
24.008
24.129
0.140
0,474(94,9%)
74.077
41.391
43.138
43.260
42.596
1.045
74.077
41.637
42.202
42.986
42.275
0.677
0,5002(100,04%)
[Cr(VI)] sorbed,
mg/L
[Cr(VI)]e,
mmol/L
[Cr(VI)] sorbed,
mmol/kg
27.226
27.292
27.071
0.2424
0.2411
0.2453
0.2429
0.0021
20.9446
20.9954
20.8254
20.9218
0.0872
27.053
27.085
26.959
0.2457
0.2451
0.2475
0.2461
0.0012
20.8116
20.8362
20.7392
20.7957
0.0503
25.971
25.279
25.912
0.4740
0.4873
0.4752
0.4788
0.0074
19.9792
19.4468
19.9338
19.7866
0.2951
26.337
26.524
26.613
0.4670
0.4634
0.4617
0.4640
0.0027
20.2607
20.4046
20.4731
20.3795
0.1083
32.686
30.939
30.817
0.7960
0.8296
0.8319
0.8192
0.0201
25.1450
23.8010
23.7072
24.2177
0.8043
32.440
31.875
31.091
0.8007
0.8116
0.8267
0.8130
0.0130
24.9557
24.5211
23.9179
24.4649
0.5211
192
APPENDIX I
Removal of arsenic study
I-1: Preliminary study of the As(III) and As(V) adsorption by SMZY and
unmodified zeolite Y
Table I.1.1: Analysis data for the preliminary study of the As(III) adsorption
by SMZY and unmodified zeolite Y.
samples
AsIII 20ppm
Zeo-NaY-S
SMZY-50-S
QC(25ppm)
SMZY-100-S
SMZY-200-S
QC(25ppm)
Zeo-NaY-CC
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(25ppm)
[As(III)]final, mg/L
19.95
18.68
18.29
26.17(104.68%)
18.11
18.33
27.14(108.56%)
19.15
18.53
18.34
17.88
26.23(104.92%)
[As(III)]final,
mmol/L
0.2662
0.2493
0.2441
[As(III)]sorbed,
mg/g
[As(III)]sorbed,
mmol/kg
0.127
0.166
1.6951
2.2156
0.2417
0.2446
0.184
0.162
2.4559
2.1623
0.2556
0.2473
0.2447
0.2386
0.080
0.142
0.161
0.207
1.0678
1.8953
2.1489
2.7629
Table I.1.2: Analysis data for the preliminary study of the As(V) adsorption
by SMZY and unmodified zeolite Y.
[As(V)]final,
mmol/L
0.2517
0.2454
0.1333
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
0.047
0.886
0.6273
11.8379
9.63
8.01
24.77(99.08%)
0.1285
0.1069
0.923
1.085
12.3198
14.4821
18.09
17.98
13.28
11.65(116.5%)
12.97
13.66
24.83(99.32%)
0.2414
0.2399
0.1772
0.011
0.481
0.1468
6.4201
0.1731
0.1823
0.512
0.443
6.8339
5.9129
samples
AsV pH 8
Zeo-NaY-S
SMZY-50-S
QC(10ppm)
[As(V)]final, mg/L
18.86
18.39
9.99
11.75(117.5%)
SMZY-100-S
SMZY-200-S
QC(25ppm)
AsV pH 8
Zeo-NaY-C
SMZY-50-C
QC(10ppm)
SMZY-100-C
SMZY-200-C
QC(25ppm)
193
I-2: Effect of the initial pH solution on the removal of As(V) by SMZY
Table I.2.1: Analysis data for the effect of pH (pH 2, 4, 6 and 7) on the
removal of As(V) by SMZY.
samples
AsV pH 2
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
AsV pH 2
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
[As(V)]final, mg/L
23.96
9.92
9.55
9.07
22.72(113.6%)
23.28
18.29
17.83
18.40
22.72(113.6%)
AsV pH4
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
24.50
15.18
15.76
15.02
22.86(114.3%)
19.92
20.39
20.86
22.72(113.6%)
AsV pH 6
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
AsV pH 6
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
22.97
13.67
13.05
11.74
23.53(117.65%)
23.81
17.97
17.68
19.01
23.24(116.2)
AsV pH 7
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
23.55
13.24
12.62
11.97
23.34(116.7%)
[As(V)]removed,
mg/L
% removal
pH final
14.04
14.41
14.89
58.58
60.13
62.12
5.30
5.29
5.14
4.99
5.45
4.88
21.43
23.41
20.96
4.28
4.11
3.91
9.32
8.74
9.48
38.04
35.67
38.69
6.66
6.39
6.29
4.58
4.11
3.64
18.69
16.77
14.85
5.70
5.63
9.30
9.92
11.23
40.48
43.18
48.88
6.53
6.27
6.21
5.84
6.13
4.80
24.52
25.74
20.15
5.88
5.76
5.61
10.31
10.93
11.58
43.77
46.41
49.17
6.66
6.38
6.22
194
Table I.2.2: Analysis data for the effect of pH (pH 7, 8, 10 and 12) on the
removal of As(V) by SMZY.
samples
AsV pH 7
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
[As(V)]final, mg/L
22.68
16.83
16.70
17.86
23.38(116.9%)
AsV pH 8
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(25ppm)
AsV pH 8
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(25ppm)
18.86
9.99
9.63
8.55
24.77(99.08%)
18.09
13.28
12.97
13.66
24.83(99.32%)
AsV pH 10
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
AsV pH 10
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
24.48
15.11
14.54
13.85
23.27(116.35%)
24.88
18.61
17.68
18.81
22.94(114.7%)
AsV pH 12
SMZY-50-S
SMZY-100-S
SMZY-200-S
QC(20ppm)
AsV pH 12
SMZY-50-C
SMZY-100-C
SMZY-200-C
QC(20ppm)
25.44
16.86
16.64
16.37
23.32(116.6%)
25.34
21.55
21.19
21.91
23.12(115.6%)
[As(V)]removed,
mg/L
% removal
pH final
5.85
5.98
4.82
25.79
26.36
21.25
6
5.86
5.80
8.86
9.23
10.30
47.02
48.93
54.65
6.90
6.40
6.31
4.81
5.12
4.43
26.58
28.30
24.48
6.21
6.09
5.67
9.37
9.94
10.63
38.27
40.60
43.42
7.98
6.82
6.77
6.27
7.20
6.07
25.20
28.93
24.39
6.68
6.54
6.40
8.58
8.80
9.07
33.72
34.59
35.65
3.79
4.15
3.43
14.95
16.37
13.53
195
I-3: Isotherm study of the As(V) sorption by SMZY
Conc.
(mg/L)
0
5
10
25
40
50
Absorbance
0
0.0483
0.0967
0.2124
0.3166
0.3826
absorbance
Table I.3.1: Standard calibration data
standard calibration curve
0.5
0.4
0.3
0.2
0.1
0
2
R = 0.9964
0
20 [As] (mg/L) 40
60
Table I.3.2: Analysis data for the isotherm study of the As(V) sorption by
SMZY ([As(V)]initial=10 mg/L)
samples
AsV 10ppm
50-S-1
50-S-2
100-S-1
100-S-2
200-S-1
200-S-2
QC(5ppm)
AsV 10ppm
50-C-1
50-C-2
100-C-1
100-C-2
200-C-1
200-C-2
QC(5ppm)
QC(20ppm)
[As(V)]final,
mg/L
9.53
0
0
0
0
0
0
4.76(95.2%)
9.53
0.90
1.27
1.13
1.20
2.54
3.60
5.14(102.98%)
20.95(104.75%)
[As(V)]final,
mmol/L
0.1272
0
0
0
0
0
0
0.1272
0.0121
0.0170
0.0150
0.0161
0.0339
0.0480
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
0.7147
0.7147
0.7147
0.7147
0.7147
0.7147
9.5401
9.5401
9.5401
9.5401
9.5401
9.5401
0.6466
0.6189
0.6300
0.6240
0.5239
0.4446
8.6312
8.2618
8.4089
8.3298
6.9934
5.9343
196
Table I.3.3: Analysis data for the isotherm study of the As(V) sorption by
SMZY ([As(V)]initial=20 mg/L)
samples
AsV 20ppm
50-S-1
50-S-2
100-S-1
100-S-2
200-S-1
200-S-2
QC(5ppm)
AsV 20ppm
50-C-1
50-C-2
100-C-1
100-C-2
200-C-1
200-C-2
QC(10ppm)
QC(40ppm)
[As(V)]final,
mg/L
18.600
5.20
5.24
4.57
4.23
3.65
3.41
5.43(108.66%)
18.64
11.52
10.28
11.01
10.66
12.66
12.01
10.5(105%)
38.47(96.175%)
[As(V)]final,
mmol/L
0.2482
0.0694
0.0701
0.0611
0.0565
0.0487
0.0455
0.2487
0.1537
0.1372
0.1469
0.1422
0.1689
0.1603
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
1.0045
1.00132
1.0518
1.0774
1.1211
1.1390
13.4083
13.3652
14.0389
14.3813
14.9649
15.2032
0.5340
0.6270
0.5722
0.5985
0.4485
0.4972
7.1276
8.3689
7.6381
7.9885
5.9863
6.6370
Table I.3.4: Analysis data for the isotherm study of the As(V) sorption by
SMZY ([As(V)]initial=30 mg/L)
samples
AsV 30ppm
50-S-1
50-S-2
100-S-1
100-S-2
200-S-1
200-S-2
QC(20ppm)
AsV 30ppm
50-C-1
50-C-2
100-C-1
100-C-2
200-C-1
200-C-2
QC(20ppm)
[As(V)]final,
mg/L
29.21
14.76
14.91
13.30
13.66
13.27
12.69
21.87(109.35%)
30.02
21.75
21.25
21.39
21.32
21.96
23.01
22.07(110.35%)
[As(V)]final,
mmol/L
0.3898
0.1970
0.1990
0.1775
0.1823
0.1771
0.1693
0.4006
0.2903
0.2836
0.2855
0.2845
0.2931
0.3071
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
1.0837
1.0725
1.1932
1.1662
1.1955
1.2390
14.4654
14.3152
15.9269
15.5666
15.9570
16.5376
0.6202
0.6577
0.6472
0.6525
0.6045
0.5257
8.2788
8.7793
8.6392
8.7092
8.0686
7.0174
197
Table I.3.5: Analysis data for the isotherm study of the As(V) sorption by
SMZY ([As(V)]initial=40 mg/L)
samples
AsV 40ppm
50-S-1
50-S-2
100-S-1
100-S-2
200-S-1
200-S-2
QC(20ppm)
AsV 40ppm
50-C-1
50-C-2
100-C-1
100-C-2
200-C-1
200-C-2
QC(25ppm)
[As(V)]final,
mg/L
37.55
23.86
22.15
20.44
22.41
21.75
22.70
21.35(106.75%)
37.52
29.45
28.70
28.95
28.90
30.52
31.37
25.36(101.44%)
[As(V)]final,
mmol/L
0.5012
0.3184
0.2956
0.2728
0.2991
0.2903
0.3029
0.5008
0.3930
0.3830
0.3864
0.3857
0.4073
0.4187
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
1.0267
1.1550
1.2832
1.1355
1.1850
1.1137
13.7046
15.4164
17.1282
15.1561
15.8168
14.8658
0.6052
0.6615
0.6427
0.6465
0.5250
0.4612
8.0786
8.8294
8.5791
8.6292
7.0074
6.1565
Table I.3.6: Analysis data for the isotherm study of the As(V) sorption by
SMZY ([As(V)]initial=50 mg/L)
samples
AsV 50ppm
50-S-1
50-S-2
100-S-1
100-S-2
200-S-1
200-S-2
QC(20ppm)
AsV 50ppm
50-C-1
50-C-2
100-C-1
100-C-2
200-C-1
200-C-2
QC(25ppm)
[As(V)]final,
mg/L
47.95
31.75
31.21
31.92
30.73
31.20
31.56
38.37(95.925%)
46.87
38.52
39.72
37.95
37.59
37.94
39.02
38.33(95.825%)
[As(V)]final,
mmol/L
0.6400
0.4237
0.4165
0.4260
0.4101
0.4164
0.4212
0.6256
0.5141
0.5301
0.5065
0.5017
0.5064
0.5208
[As(V)]sorbed,
mg/g
[As(V)]sorbed,
mmol/kg
1.2150
1.2555
1.2022
1.2915
1.2562
1.2292
16.2172
16.7578
16.0471
17.2380
16.7678
16.4075
0.6262
0.5362
0.6690
0.6960
0.6697
0.5887
8.3589
7.1576
8.9295
9.2899
8.9395
7.8583
198
APPENDIX J
Presented papers and expected publications from this study
1.
Nik Ahmad Nizam Nik Malek and Alias Mohd Yusof. “Adsorption of Chromate
Anion from Aqueous Solution by Surfactant Modified Zeolite Y”. Orally presented
at 18th Malaysian Analytical Chemistry Symposium (SKAM-18) 2005, 12-14
September 2005, Johor Bahru, Johor, Malaysia.
2.
Nik Ahmad Nizam Nik Malek and Alias Mohd Yusof. “The Effect of Seeding and
Ageing Techniques in the Synthesis of the Zeolite NaY from Rice Husk Ash”. Orally
presented at the Regional Conference on Solid State Science and Technology 2005
(RCSST’05), 18-21 December 2005, Kuantan, Pahang, Malaysia.
3.
Nik Ahmad Nizam and Alias Mohd Yusof. “The Use of Surfactant Modified Zeolite
Y as a Sorbent for Arsenic Species in Aqueous Solution”. Orally presented at
Regional Postgraduate Conference on Engineering and Science (RPCES 2006), 2627 July 2006, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia.
4.
Nik Ahmad Nizam and Alias Mohd Yusof. “Removal of Cr(III) from Aqueous
Solution by Zeolite NaY Prepared From Rice Husk Ash”, Orally presented at 19th
Malaysian Analytical Chemistry Symposium (SKAM-19), 21-24 August 2006,
Melaka, Malaysia. Will be submitted to Water Research.
5.
Nik Ahmad Nizam Nik Malek and Alias Mohd Yusof. “The Modification of Zeolite
NaY by Cationic Surfactant for the Sorption of Inorganic Anions from Aqueous
Solutions”. Orally presented at International Conference on Environment 2006
(ICENV2006), 13-15 November 2006, Penang, Malaysia. Will be submitted to
Journal of Hazardous Materials.