See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/318233689
Leaching Of A Commercial Vermiculite In H2SO4 Solutions
Conference Paper · October 2014
CITATIONS
READS
0
413
4 authors:
Ilhan Ehsani
Erika Tóthová
Sirnak Üniversitesi
Slovak Academy of Sciences
12 PUBLICATIONS 16 CITATIONS
44 PUBLICATIONS 410 CITATIONS
SEE PROFILE
SEE PROFILE
Matej Baláž
Abdullah Obut
Institute of Geotechnics, Slovak Academy of Sciences
Hacettepe University
126 PUBLICATIONS 2,127 CITATIONS
36 PUBLICATIONS 354 CITATIONS
SEE PROFILE
SEE PROFILE
Some of the authors of this publication are also working on these related projects:
SEMINANO - Mechanochemistry of Semiconductor Nanocrystals: from Minerals to Materials and Drugs View project
Mechanical Alloying, Mechanochemistry View project
All content following this page was uploaded by Ilhan Ehsani on 24 July 2017.
The user has requested enhancement of the downloaded file.
Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014
LEACHING OF A COMMERCIAL VERMICULITE IN H2SO4
SOLUTIONS
İ.Ehsani1, E.Turianicová2, M.Baláž2 and A.Obut1,a
1. Hacettepe University, Mining Engineering Department, Ankara, Turkey
2. Institute of Geotechnics, Slovak Academy of Sciences, Košice, Slovakia
a. Corresponding author (aobut@hacettepe.edu.tr)
ABSTRACT: In this study, the leaching behaviour of a commercial vermiculite sample, in
natural and heated forms, in 1 M aqueous sulphuric acid solutions at 20°C and 90°C was
investigated using chemical and X-ray diffraction analyses, Fourier transform infrared
spectroscopy and nitrogen adsorption measurements. Although small changes occurred in
the chemical compositions and surface area values following leaching at 20°C, great
reductions in the amounts of structural components, i.e. Al2O3, Fe2O3, MgO, and dramatic
increases in the surface area values were observed after leaching of both samples at 90°C,
indicating quantitative, but not total, dissolution of the samples. Similarly, acid leaching of
natural and heated vermiculite samples at 20°C resulted only small changes in the X-ray
diffraction patterns and infrared spectra, but with the increase of leaching temperature to
90°C, significant changes, i.e. the dissolution of vermiculite structures and the formation of
hydrous amorphous silica phase, were observed.
1. INTRODUCTION
Swelling clay minerals, such as smectites
and vermiculites, exhibit differences in
their layer charges, adsorptive properties,
cation exchange capacities, particle sizes
etc. Because of these differences, they
can be used in different areas such as
foundry, construction, agriculture or
chemical industries either directly or after
the application of different modification
processes. Leaching by inorganic acids,
i.e. sulphuric or hydrochloric acid, is one
of the useful modification processes for
these clay minerals and due to the
enhanced surface and catalytic behaviour
following acid leaching, they can be used
as bleaching earths, as catalysts or
catalyst supports, in the production of
carbonless copying paper or in the
preparation of pillared clays and
organoclays [Komadel et al., 1990;
Suquet et al., 1991; Mokaya and Jones,
1995; Breen et al., 1997; Ravichandran
and Sivasankar, 1997; Londo et al., 2001;
Gates et al., 2002; Jozefaciuk and
Bowanko, 2002; Önal et al., 2002; Kooli,
2009; Steudel et al., 2009a].
In contrast to numerous studies related
with acid leaching of smectites, the
number of studies investigating the
leaching behaviour of commercial
vermiculites in inorganic or organic acids
is low. Therefore, in this study, leaching
behaviour of a commercial vermiculite, in
natural and heated forms, in sulphuric
acid solutions was investigated and
comparative data were collected for
future studies. To identify the changes
caused by acid leaching, X-ray diffraction
(XRD), Fourier transform infrared (FTIR) and chemical analyses together with
nitrogen adsorption measurements were
performed on the natural, heated and
leached vermiculite samples.
2. MATERIALS AND METHODS
The natural sample used in this work is
commercial micron grade Palabora
(South Africa) vermiculite. According to
the data supplied by the producer, 80% of
the natural sample is in the size range of
-0.710+0.250 mm and the fraction of
-0.180 mm is maximum 10%. The natural
sample contains 85-95% ‘vermiculite’,
757
and phlogopite, apatite, diopside with
trace amounts of dolomite and quartz are
the impurities. Chemical composition of
the natural sample was given in Table 1.
Table 1: Chemical composition (%) of the
natural vermiculite sample.
3. RESULTS AND DISCUSSION
3.1. Chemical Analyses, Surface Area
Measurements and Porous Properties
Some of the main chemical components
and surface area values of the natural and
heated samples together with their
corresponding leached counterparts were
presented in Table 2 and Table 3,
respectively.
SiO2
Al2O3
Fe2O3
MgO
41.02
8.90
8.36
19.91
CaO
Na2O
K2O
TiO2
6.27
0.07
4.63
0.97
Table 2: Main chemical components (%)
of the natural, heated and leached
vermiculites.
P2O5
MnO
Cr2O3
L.O.I
Sample
SiO2
Al2O3
Fe2O3
MgO
K 2O
2.41
0.06
0.05
6.97
NV
41.02
8.90
8.36
19.91
4.63
NV-20
44.22
9.32
8.77
20.21
4.65
NV-90
64.81
4.32
5.08
10.95
2.58
HV
44.39
10.09
9.31
21.69
5.20
HV-20
45.59
9.56
9.08
21.18
4.89
HV-90
62.10
4.94
5.54
13.18
3.03
In the leaching studies, natural and heated
(at 900°C, according to Turianicová et al.
[2014]) vermiculite samples were used.
Because surface area is one of the most
important parameters in leaching studies,
in this study, heated vermiculite was
compared with the natural vermiculite
due to its higher surface area. Sulphuric
acid was selected as the leaching reagent
due to its reported efficiency on
dissolution [Steudel et al., 2009a]. In a
representative experiment, 50 grams of
natural (NV) or heated (HV) vermiculite
was leached in 500 mL, 1 M aqueous
H2SO4 solution either at 20°C or 90°C for
60 minutes under constant rate of stirring.
Following leaching, the solid residues
were separated by filtration, washed and
finally dried at 105°C. The chemical
compositions, XRD patterns (Rigaku
with
CuKα
radiation,
following
equilibration under room atmosphere),
FT-IR spectra (Bruker, by KBr pellet
method), and B.E.T. surface area values
(Quantachrome Instruments, by nitrogen
adsorption following degas for two hours
at 105°C) of the natural, heated and
leached vermiculites were determined in
order to observe the changes caused by
acid leaching. The pore size distribution
of a selected leach residue was also
determined.
758
Table 3: Surface area values (m2/g) of the
natural, heated and leached vermiculites.
NV
NV-20
NV-90
3.322
5.632
251.844
HV
HV-20
HV-90
13.963
15.429
97.950
(Table 2) showed that when the natural
and heated samples were leached at 20°C
(NV-20 and HV-20, respectively), there
were only small changes in the values of
main chemical components, indicating
insignificant dissolution from the clay
samples. Due to the low amounts of
dissolution of the structural components,
i.e. Mg, Fe and Al, the increases in the
surface area values of the leached
vermiculites were also low (Table 3).
On the other hand, when leaching process
was performed at 90°C (samples NV-90
and HV-90), the amounts of magnesium,
iron and aluminum in the leach residues
became approximately half of their initial
Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014
values, which indicated quantitative, but
not total, dissolution of the clay structures
in both samples. Although surface area of
the heated sample is higher than the
natural one, the amount of residual
structural components in its leach
residues were higher in comparison to the
residues of the natural sample probably
due to the presence of dehydrated and
collapsed clay structures in the heated
sample [Okada et al., 2006; Steudel et al.,
2009a,b].
In the studies where micron grade South
African vermiculite was used; Okada et
al. [2006] were increased the surface area
from 1 to 265 m2/g by leaching the
natural sample in 1 M H2SO4 solution at
70°C for 60 minutes; Temuujin et al.
[2003] were increased the surface area
from 1.4 to 407 m2/g by leaching the
natural sample in 1 M HCl solution at
80°C for 60 minutes and to 553 m2/g by
leaching under same conditions for 120
minutes; and Temuujin et al. [2008] were
increased the surface area again from 1.4
to 547 m2/g by leaching the heated (at
600°C) sample in 2 M HCl solution at
80°C for 120 minutes. In this study, the
surface area of the natural (3.322 m2/g)
and heated (at 900°C, 13.963 m2/g)
micron grade South African vermiculite
samples were increased to 5.632 m2/g and
15.429 m2/g by low temperature (20°C),
and to 251.844 m2/g and 97.950 m2/g for
high temperature (90°C) leaching in 1 M
H2SO4 solution for 60 minutes,
respectively (Table 3).
The adsorption-desorption isotherms and
pore size distribution of the leach residue
HV-90 were given in Figures 1 and 2,
respectively. As can be seen from Figure
1, there is a hysteresis loop which
suggests the presence of mesopores in the
sample. There are no micropores present
in the sample. Due to the shape of the
isotherm in the region of higher relative
pressures, it can be said that there could
be some small amount of macropores
present in the sample. The total pore
volume of HV-90 was 0.1326 cm3·g-1.
The presence of mesopores was
confirmed by the pore size distribution
study. As can be seen from Figure 2, the
structure contains almost no other type of
pores than mesopores with radii between
1.5 and 10 nm (the diameters between 3
and 20 nm). The measurement from
adsorption isotherm confirmed the
presence of so-called tensile strength
effect, because the peak with maximum
around 2 nm present in case of pore size
distribution
calculated
from
the
desorption isotherm does not present.
Figure 1: Nitrogen adsorption/desorption
isotherm for HV-90.
Figure 2: Pore size distribution for HV90.
759
3.2. XRD Analyses
XRD patterns of the natural and heated
samples together with their leached
counterparts were given in Figures 3 and
4, respectively.
NV-90
NV-20
NV
2θ(°)
Figure 3: XRD patterns of the natural
vermiculite and its leach residues.
HV-90
HV-20
HV
2θ(°)
Figure 4: XRD patterns of the heated
vermiculite and its leach residues.
XRD pattern of the natural sample (NV
in Figure 3) shows diffraction peaks at
6.22°, 7.18° and 7.48°, indicating the
presence of both two- and one-water760
layer hydration states and interstratified
phases [Ruiz-Conde et al., 1996; Marcos
et al., 2009; Muiambo et al., 2010]. High
content of potassium (see Table 1) in the
natural sample in comparison to true
vermiculites also indicated the presence
of interstratification [Muiambo and
Focke, 2012]. Very small intensity peak
at 8.80° was attributed to mica impurity
[Muiambo et al., 2010]. The main and
single basal peak at 8.86° in XRD pattern
of the heated sample indicated the
existence of dehydrated and collapsed
clay structures.
Leaching of the natural and heated
samples at 20°C in 1 M H2SO4 solution
caused small changes and only
insignificant differences in the peak
intensities of clay structures were
observed, in accord with the chemical
analyses results. On the other hand,
leaching of the natural sample at 90°C
caused major dissolution of the
vermiculite structures as observed by the
disappearance of peak at 6.22° (compare
NV or NV-20 with NV-90 in Figure 3).
The intensities of the basal peaks were
also greatly reduced and background of
the pattern was increased, both
suggesting amorphization by dissolution
of the clay structures.
Heating of the natural sample at 900°C
produced dehydrated and collapsed clay
structures, which resemble micas, as
observed by the main peak at 8.86° (see
pattern HV in Figure 4). Although the
changes caused by acid leaching in the
natural sample were easily observable by
the analyses of XRD peaks in the related
patterns, almost no changes were
observed in case of the heated samples.
Only very small increase was observed in
the background intensity in XRD pattern
of the leach residue obtained by leaching
of heated vermiculite sample in 1 M
H2SO4 for 60 minutes (see HV-90 in
Figure
4).
Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014
3.2. FT-IR Analyses
FT-IR spectra of the natural and heated
samples together with their corresponding
leached counterparts were given in
Figures 5 and 6, respectively.
NV
NV-20
NV-90
Wavenumber (cm-1)
Figure 5: FT-IR spectra of natural
vermiculite and its leach residues.
HV
HV-20
HV-90
Wavenumber (cm-1)
Figure 6: FT-IR spectra of heated
vermiculite and its leach residues.
FT-IR spectrum of the natural sample
shows a broad and very strong intensity
absorption band at 999 cm-1 belonging to
Si-O-Si and Si-O-Al vibrations. The
strong intensity band (with a shoulder)
centered at 457 cm-1 may be associated
with Si-O-Si and Si-O-Mg. The medium
intensity absorption at 1632 cm-1 is
attributed to the OH bend deformation of
water. The medium band observed at 687
cm-1 may be related with R-O-Si, where
R=Mg, Al or Fe. The weak bands at 602,
729 and 818 cm-1 may be assigned to
mixed Al-O/Si-O and hydroxyl groups
[Suquet et al., 1991; Ravichandran and
Sivasankar, 1997; da Fonseca et al., 2006;
Steudel et al., 2009a; Chmielarz et al.,
2010; Muiambo et al., 2010; Hongo et al.,
2012; Muiambo and Focke, 2012].
In accord with the results of XRD
analyses, low temperature acid leaching
caused only small changes in the FT-IR
spectra of both the natural and heated
vermiculites. But, high temperature acid
leaching changed the corresponding IR
spectra dramatically, because of the
sensitivity of FT-IR spectroscopy for
detecting the possible changes (or
destruction) in the crystalline structure of
clay minerals following any modification
process [Suquet et al., 1991]. By high
temperature leaching of the natural
sample, bands at 602, 687, 729 and 818
cm-1 disappeared and new absorption
peaks of Si-O at 1088 (with shoulder
~1200 cm-1), 800 and 461 cm-1, and
SiOH at 968 cm-1 belonging to hydrous
amorphous silica phase were revealed
[Pálková et al., 2003; Wypych et al.,
2005; Yu et al., 2012]. This indicates the
formation of hydrous amorphous silica
phase by acid dissolution of the structural
components from the natural and heated
vermiculites. Similar changes were also
observed by high temperature acid
leaching of heated vermiculite sample but
the effect of acid leaching is somewhat
lower when compared to the natural
761
sample. The absorption band at 1007 cm-1
belonging to the heated sample also
indicated the higher resistance of
collapsed mica like layers against acid
attack, which is consistent with the
results obtained by chemical and XRD
analyses.
4. CONCLUSIONS
In this work, the leaching behaviours of a
natural and a heated vermiculite sample
in 1 M H2SO4 solution at 20°C and 90°C
for 60 minutes were investigated using
different analyses methods. Although no
or small changes occurred in chemical
compositions, in XRD/FT-IR patterns and
surface area values of the leach residues
obtained by low temperature (20°C) acid
leaching, significant reductions in the
amounts of structural components,
important changes in XRD and especially
in FT-IR patterns and great increases in
surface area values of the leach residues
obtained by high temperture (90°C) acid
leaching of the natural and heated
vermiculites were observed. All results of
the analyses methods indicated that
hydrous amorphous silica phase was
formed following high temperature acid
leaching of the natural and heated
vermiculites due to the dissolution of
structural components from the clay
structures. Under any leaching condition
studied, the heated vermiculite showed
higher resistance against acid leaching
probably due to the presence of collapsed
mica like layers. According to the data
collected in this work, a new leaching
study was initiated for determining the
high temperature (90°C) acid leaching
behaviour of the vermiculite samples at
different sulphuric acid concentrations
and for the preparation of higher surface
area and purer hydrous amorphous silica
phases suitable for various applications.
Acknowledgements: The authors wish to
acknowledge Mike Darling (Palabora
Europe Ltd.) for the supply of natural
762
vermiculite sample. Two of the authors
(E.T. and M.B.) thanks the Slovak Grant
Agency VEGA (project 2/0064/14) and
the Agency for Science and Development
(APVV-0189-10) for the partial support.
REFERENCES
Breen, C., Watson, R., Madejová, J., Komadel, P.
and Klapyta, Z., 1997. Acid-activated
organoclays: Preparation, characterization
and catalytic activity of acid-treated
tetraalkylammonium-exchanged
smectites,
Langmuir, 13, 6473.
Chmielarz, L., Kowalczyk, A., Michalik, M.,
Dudek, B., Piwowarska, Z. and Matusiewicz,
A., 2010. Acid-activated vermiculites and
phlogopites as catalysts for the DeNOx
process, Applied Clay Science, 49, 156.
da Fonseca, M.G.,Wanderley, A.F., Sousa, K.,
Araraki, L.N.H. and Espinola, J.G.P., 2006.
Interaction of aliphatic diamines with
vermiculite in aqueous solution, Applied Clay
Science, 32, 94.
Gates, W.P., Anderson, J.S., Raven, M.D. and
Churchman, G.J., 2002. Mineralogy of a
bentonite from Miles, Queensland, Australia
and characterisation of its acid activation
products, Applied Clay Science, 20, 189.
Hongo, T., Yoshino, S., Yamazaki, A., Yamasaki,
A.
and
Satokawa,
S.,
2012.
Mechanochemical treatment of vermiculite in
vibration milling and its effect on lead(II)
adsorption ability, Applied Clay Science, 70,
74.
Jozefaciuk, G. and Bowanko, G., 2002. Effect of
acid and alkali treatments on surface areas
and adsorption energies of selected minerals,
Clays and Clay Minerals, 50, 771.
Komadel, P., Schmidt, D., Madejova, J. and Čičel,
B., 1990. Alteration of smectites by
treatments with hydrochloric acid and sodium
carbonate solutions, Applied Clay Science, 5,
113.
Kooli, F., 2009. Exfoliation properties of acidactivated montmorillonites and their resulting
organoclays, Langmuir, 25, 724.
Londo, M.G., Yang, X. and Young, R.H., 2001.
Mesoporous silicoaluminate pigments for use
in inkjet and carbonless paper coatings, US
Patent 6274226B1.
Marcos, C., Arango, Y.C. and Rodriguez, I., 2009.
X-ray diffraction studies of the thermal
behaviour of commercial vermiculites,
Applied Clay Science, 42, 368.
Mokaya, R. and Jones, W., 1995. Pillared clays
and pillared acid-activated clays: A
comparative study of physical, acidic, and
Proceedings of 14th International Mineral Processing Symposium – Kuşadası, Turkey, 2014
catalytic properties, Journal of Catalysis, 153,
76.
Muiambo, H.F. and Focke, W.W., 2012. Ion
exchanged vermiculites with lower expansion
onset temperatures, Molecular Crystals and
Liquid Crystals, 555, 65.
Muiambo, H.F., Focke, W.W., Atanasova, M., van
der Westhuizen, I. and Tiedt, L.R., 2010.
Thermal properties of sodium-exchanged
Palabora vermiculite, Applied Clay Science,
50, 51.
Okada, K., Arimitsu, N., Kameshima, Y.,
Nakajima, A. and MacKenzie, K.J.D., 2006.
Solid acidity of 2:1 type clay minerals
activated by selective leaching, Applied Clay
Science, 31, 185.
Önal, M., Sarıkaya, Y., Alemdaroğlu, T. and
Bozdoğan, İ., 2002. The effect of acid
activation
on
some
physicochemical
properties of a bentonite, Turkish Journal of
Chemistry, 26, 409.
Pálková, H., Madejová, J. and Righi, D., 2003.
Acid dissolution of reduced-charge Li- and
Ni-montmorillonites, Clays and Clay
Minerals, 51, 133.
Ravichandran, J. and Sivasankar, B., 1997.
Properties and catalytic activity of acidmodified montmorillonite and vermiculite,
Clays and Clay Minerals, 45, 854.
Ruiz-Conde, A., Ruiz-Amil, A., Pérez-Rodríguez,
J.L. and Sánchez-Soto, P.J., 1996.
Dehydration-rehydration
in
magnesium
vermiculite: conversion from two-one and
one-two water layer hydration states through
the formation of interstratified phases,
Journal of Materials Chemistry, 6, 1557.
Steudel, A., Batenburg, L.F., Fischer, H.R.,
Weidler, P.G. and Emmerich, K., 2009a.
Alteration of swelling clay minerals by acid
activation, Applied Clay Science, 44, 105.
Steudel, A., Batenburg, L.F., Fischer, H.R.,
Weidler, P.G. and Emmerich, K., 2009b.
Alteration of non-swelling clay minerals and
magadiite by acid activation, Applied Clay
Science, 44, 95.
Suquet, H., Chevalier, S., Marcilly, C. and
Barthomeuf, D., 1991. Preparation of porous
materials by chemical activation of the Llano
vermiculite, Clay Minerals, 26, 49.
Temuujin, J., Minjigmaa, A., Jadambaa, Ts.,
Tsend-Ayush, S. and MacKenzie, K.J.D.,
2008. Porous properties of silica prepared by
selective acid leaching of heat-treated
vermiculite, Chemistry for Sustainable
Development, 16, 221.
Temuujin, J., Okada, K. and MacKenzie, K.J.D.,
2003. Preparation of porous silica from
vermiculite by selective leaching, Applied
Clay Science, 22, 187.
Turianicová, E., Obut, A., Tuček, Ľ., Zorkovská,
A., Girgin, İ., Baláž, P., Németh, Z., Matik,
M. and Kupka, D., 2014. Interaction of
natural and thermally processed vermiculites
with gaseous carbon dioxide during
mechanical activation, Applied Clay Science,
88&89, 86.
Wypych, F., Adad, L.B., Mattoso, N., Marangon,
A.A.S. and Schreiner, W.H., 2005. Synthesis
and characterization of disordered layered
silica obtained by selective leaching of
octahedral sheets from chrysotile and
phlogopite structures, Journal of Colloid and
Interface Science, 283, 107.
Yu, X.-b., Wei, C.-h., Ke, L., Wu, H.-z., Chai, X.s. and Hu, Y., 2012. Preparation of
trimethylchlorosilane-modified
acid
vermiculites for removing diethyl phthalate
from water, Journal of Colloid and Interface
Science,
369,
344.
763
View publication stats