Studies on Biosorption for the removal of Cr (III) from
aqueous solution using marine macro algae
K.Dayana1*, Ch.V Ramachandramurthy2
1*Research scholar, Dept of Chemical Engineering, Andhra University, A.P, India,
Email id: karradayana@yahoo.co.in
2 Professor, Dept of Chemical Engineering, Andhra University, A.P, India,
Email id: prof.chvmurthy@sify.com
Abstract:
In recent days water pollution due to heavy metals is an issue of great environmental concern.
Heavy metal pollution occurs directly by effluents from industries, refineries and waste treatment
plants. Removal and recovery of heavy metals are very important with respect to environmental
and economical considerations. This investigation comprise of the equilibrium, kinetics and
thermodynamic study for Biosorption of Chromium(III) ions from aqueous solution using
Marine Macro Algae (Amphiroa Flagillisma) as a biosorbent in a batch process. The kineticsof
Chromium Biosorption was slow; approximately 90% of Biosorption takes place in 3 hours. The
percent adsorption increased with increase in pH, at near neutral pH 2.0 of the solution were
found to favour adsorption very strongly. The Biosorption equilibrium data were well described
by Langmuir and Freundlich adsorption isotherms. The biosorbent was characterized and
evaluated by the FTIR spectroscopy in the Biosorption process. Finally an empirical correlation
was proposed to estimate equilibrium metal concentration in the solid phase.
Key words: Biosorption, Equilibrium, Chromium, adsorption, Langmuir and Freundlich
1. Introduction:
A large number of industries including plating, petroleum refinery, battery
manufacturing, pigments and mining release heavy metals in waste streams which have negative
effects on water bodies. The chief threat of industrialization is emanation of large volumes of
effluents, especially as aqueous discharges. The discharges generally are loaded with heavy
metals that are persistent. Though most of these ions are “essential elements” required in traces
for the biota, their presence in excess amounts harms many forms of life and proves catastrophic
to the environment in the long run. Thus, environmental health governs the standard of human
life as well as the prosperity of the biosphere. Effective removal of heavy metal ions from
aqueous solution is important in the protection of environmental quality and public health
because heavy metal ions are not biodegradable. As almost all nations around the world are
increasingly concerned about the raising levels of toxic heavy metals in the environment, their
removal especially from aqueous systems occupies top priority among the various environmental
issues.
Technological developments for removal of these heavy metals through various processes
like Reverse Osmosis, Chemical Precipitation, Solvent Extraction, Ion exchange, etc., are noneco friendly and consist of inherent disadvantages such as incomplete metal removal, high
reagent or energy requirement and generation of toxic sludge or other wastes that require
disposal. These factors have lead to the search for improvisation of technologies that ultimately
resulted in a new innovative, economical and eco-friendly approach, namely, Biosorption
Technology.Biosorption has been successfully used in the treatment of metal contaminated water
using low cost materials such as marine algae, bacteria, fungi, etc. Biosorption is rapid
phenomenon of passive metal sequestration by the biomass. Biological resources such as
Bacteria, Cyanobacteria, yeasts, Algae and fungi are identified as potential sorbent candidates of
toxic heavy metals from the aqueous medium. Either live or dead biomass can be employed as a
sorbent material because of ease in harvesting and valorizing them.
Many algal species such as Heterosigma akashiwo(Hada) ,Spirogyra species, C.Vulgaris,
Sargassum baccularia and Gracilaria salicornia, Bifurcaria bifurcata, Brown seaweeds
Saccorhiza polyschide, Ascophyllum nodosum, Laminaria ochroleu1, and Pelvetia caniculat,
Caulerpa lentillifera, Chlamydomonas reinhardtii, Ulva reticulat, Chlorella miniata, Ulva lactuc
have been extensively studied for heavy metal Biosorption and the process mechanisms seems to
be different from species to species.
Our studies was amied at investigating the mechanism of metal uptake of Cr(III) ions from
aqueous solution and the role involved by the functional groups present in the biomass in
Biosorption process was examinedby FTIR analysis in addition to the environmental parameters
affecting the Biosorption process such as pH, time and initial concentration, biomass dosage(L/S
ratio) and temperature.
2. Materials and Methods:
The chemicals used are of AR/LR grade supplied by different standard manufacturing industries.
2.1. Preparation of biosorbent:
The algae was collected from sea in Visakhapatnam and are washed with water and then with
distilled water to remove the dust and soluble impurities. They are dried under sun for 20 days,
and the dried algae were kept in heater for 5 days. The dried algae are finely powdered and sized
by passing the powder through a set of sieves ranging from 53 to 152µ sizes. The powder is
collected separately and preserved in glass bottle for use as biosorbent.
2.2. Preparation of stock solution:
Chromium chloride solution was prepared by dissolving about 5.28 g chromium chloride salt in
1000 ml standard volumetric flask with de-mineralized water. From the stock solution,
experimental test solutions were prepared, to the specification of 25, 50, 75 and 100 ppm by
diluting the primary stock solution with de-mineralized water. The pH of the test solution was
altered by adding appropriate amount of mineral acids.
2.3. Preparation of standard solutions for Atomic Absorption Spectrophotometer Analysis:
1000 ppm Merck standard Chromium solutions was used to prepare standard solution for Atomic
Absorption Spectrophotometer analysis.primary standard solution was prepared by appropriate
dilution of 1000 ppm standard solution in accordance with the selected wavelength and
sensitivity check. The concentrations of unabsorbed Chromium ions in the sample supernatant
liquid were determined using an atomic absorption spectrophotometer(Perkin Elmer model
AA200) with an air-acetylene flame. Chromium hollow cathode lamp was used. Metal uptake (q)
was calculated using the general definition:
Q (mg or m mol g-1) = V(CT – CA)/M
Where CT and CA are the initial and final (equilibrium) metal concentrations in the solution
respectively, V is the solution volume and M is the mass of the biosorbent used.
2.4. pH adjustment of aqueous metal solutions:
The adsorption of metals decrease at low pH values because of competition for binding sites
between cations and protons, while at pH higher than 7, hydroxo species of the metals can be
formed and do not bind to the adsorption sites on the surface of the adsorbent. So, pH was
adjusted with the range of 3-7 by adding the 0.1 N HCl and 0.1 NaOH for acidic and basic pH
respectively. Chromium equilibrium studies with biomass, the pH was maintained with the range
of 3-6 only, because at te near to neutral pH and at basic pH the metal ions were precipitated. So,
in all experiments with chromium the maximum pH 6 was studied.
2.5. Initial concentration of the chromium in a aqueous solution:
50 ml of aqueous solution containing 20 mg/L chromium is taken in a 250 mL conical flask and
1.0g of 53 µm size biosorbent is added. The sample is kept in continuous contact for equilibrium
agitation time by shaking on an orbital shaker at room temperature. The sample is allowed to
settle and then filtered. The final chromium concentration of the filtrate is determined in an AAS.
The same procedure is repeated for other intial concentrations of chromium in aqueous solution (
25, 50, 75 and 100 ppm).
2.6. Equilibrium studies:
Equilibrium studieswere carried out at 200C, 300C, 400C and 500C temperature. The conical
flasks were kept in the orbital shaker, which was set at 180 rpm and shaken for required amount
of time to attain equilibrium. Sample solutions were collected periodically and analyzed in the
Atomic Absorption Spectrophotometer for the metal content in the test solution after adsorption;
the procedure was continued till the equilibrium conditions were obtained. Time required to
attain equilibrium was thus established.
3. Results and Discussions:
Experiments were conducted to estimate the time required to reach the equilibrium by taking an
initial charge of 100 ml of aqueous solution containing chromium ions and the biomass algae and
thoroughly shaking the mixture using orbital shaking machine. The samples were drawn at
different intervals of time and the metal concentration was estimated using Atomic Absorption
Spectrophotometer (AAS). The time required to reach equilibrium was found to 3 hours for
chromium.
3.1. Effect of agitation time:
Concentration (mg/L)
Agitation Time
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
0
30
60
90 120 150 180 210 240 270 300 330 360 390
Time (mins)
3.2. Effect of initial concentration of chromium
The graph is drawn as the percentage removal of chromium versus initial concentration of
chromium. The percentage removal of chromium is 97%.
% Removal
Concentration vs % removal
100
99
98
97
96
95
94
93
92
91
90
89
Series1
Series2
0
20
40
60
80
100
120
Concentration
3.3. Effect of pH:
The percent adsorption increased with increase in pH, at near neutral pH 4 the solution were
found to favour adsorption very strongly. At lower pH the percentage adsorption was very low; it
may be due to preferential adsorption of hydrogen ions.
30
pH Vs Conc
Conc
27
24
21
18
15
3
3.5
4
4.5
5
pH
3.4. Effect of Temperature:
The effect of temperature on percent adsorption of chromium using marine macro algae. It can
be observed that temperature was found to favor Biosorption. This may probably due to increase
in activity of biomass as the temperature increases.
% of removal
Temperature Vs % of Removal
100
90
80
70
60
50
40
30
20
10
0
290
295
300
305
310
315
320
325
Temperature in Kelvin
3.5. Freundlich isotherm for adsorption of chromium:
The Freundlich relationship is an empirical equilibrium relationship. It does not indicate a finite
uptake capacity of the adsorbent and can thus only be applied in case of low and intermediate
concentration ranges. However, it is easier to handle mathematically as it is a simple
relationship.
The Freundlich isotherm is given by
qe
=
Kf Cen
taking logarithms on bothsides, we get
ln qe = ln Kf + n ln Ce
where Kf and n are known as Freundlich constants obtainable from the plots of
ln qe vs ln Ce on the basis of the linear form of the equation.
4
R² = 0.9612
Freundlich isotherrm
3.5
R² = 0.9948
3
R² = 0.9993
log qe
2.5
R² = 1
2
1.5
1
0.5
0
0
0.5
1
1.5
log ce
2
2.5
s
CONCLUSIONS
This work explained the possibility of usage of themarine macro algae for chromium removal
from industrial effluents. Taking the values of parameters mentioned in Freundlich equation,
macro algae showed better biosorption. The maximum removal of Cr (III) metal (97.76%) for
micro-algae was obtained at concentration of 100 mg L -1. Initial metal concentration was
89.94mg/L at pH 3.92 and at temperature 30 °C. The maximum metal loading is found to be
18.9932 mg/gm . These data proved that initial pH strongly affected the uptake capacity of
biosorbent rather temperature. The biomass concentration had also effective impact.
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