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IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 347
BIOSORPTION OF Hg (II) FROM AQUEOUS SOLUTIONS USING BUTEA MONOSPERMA
Mallappa A. Devani
1
, Basudeb Munshi
2
, John U. Kennedy Oubagaranadin
3
, Bipin Bihari Lal
4
1, 2
Department of Chemical Engineering, National Institute of Technology, Rourkela 769008, Orissa, INDIA
3
Department of Ceramic and Cement Technology, PDA College of Engineering, Gulbarga, Karnataka, INDIA:
4
Department of Civil Engineering, Bheemanna Khandre Institute of Technology, Bhalki, Karnataka, INDIA
mdevani003@gmail.com and basudebmyahoo.com, ju_kennedy@yahoo.co.in, bipinji@yahoo.com
Abstract
The objective of this study is to investigate the feasibility of using Butea monosperma leaves powder (BMLP) for the removal of mercury from aqueous solution at the normal pH of the solution and at room temperature (30
o
C). Results show that BMLP has a good biosorption capacity for mercury. The biosorption isotherms were analyzed using Freundlich, Langmuir and Temkin models. The Freundlich model yielded the best fit for the experimental biosorption equilibrium data. The maximum monolayer biosorption capacity as determined from the Langmuir model is 62.235 mg/g of biosorbent for initial concentration of 150 ppm mercury in the solution. The biosorption energy,
Δ
Q indicates that the biosorption reaction was endothermic. The kinetic data fitted the Ho’s pseudo-second-order model with correlation coefficient 0.9985 and 0.9620 for initial concentration of 100 ppm and 150 ppm mercury in the solution. The studies suggest that the sorbent can be used for the removal of mercury from aqueous solutions.
Keywords:
Biosorption, Mercury, Isotherms, Kinetics
---------------------------------------------------------------------***------------------------------------------------------------------------
1. INTRODUCTION
Today worldwide heavy metal pollution is a dangerous threat to human and animals both in developed and developing countries. The most toxic metals given in the report by the United States Environmental Protection Agency (USEPA, 1978) are antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium and zinc. These metals are neither biodegradable nor destroyable; therefore removal of them is extremely necessary from water/wastewater [1]. Biosorption is most emerging technique studied worldwide since last 10 years, due to its potential in treatment of wastewater [2-3]. Biosorbents of agricultural srcin have polar functional groups of protein lignin, carbohydrates and phenolic compounds that have carboxyl, hydroxyl, sulfate, and amino groups, polymeric groups like cellulose, hemi-cellulose, pectin, lignin and proteins as active centers for metal uptake [4]. Many researchers have made significant contributions in this area, utilizing a number of agro-based materials such as rice husk, coconut shell, walnut hazelnut and almond shell, cotton seed hull, bagasse pith, papaya wood, sun flower stem, etc. [5-7]. The objective of the present study was to explore the potential of
Butea monosperma leaves powder
(BMLP)
for the removal of Hg(II) from the aqueous solutions. The
Butea monosperma
leaves are in enormous supply, inexpensive and easily found around in forest.
2. EXPERIMENTAL 2.1 Biosorption Equilibrium Experiments
50 ml solutions of 100 ppm Hg(II) concentration were dosed with 0.05g, 0.1g, 0.15g, 0.2g, 0.25g, 0.3g, 0.35g, 0.4g and 0.45g of average size 0.5125mm biosorbent and was shaken in an orbital shaker for about 4 hrs for equilibration. The solutions were then filtered and the residual Hg(II) concentrations were determined spectrophotometrically as reported [8]. A similar set of experiments was performed with an initial Hg(II) concentration of 150 ppm.
2.2 Kinetic Experiments
Batch kinetic studies were carried out in a 250 ml glass beaker. 0.1g of average size 0.5125mm biomass was added to 25 ml metal solution of 100 ppm Hg(II) concentration and was shaken in an orbital shaker. Samples were withdrawn at different time intervals of 30 Sec, 1 min, 3 min, 6 min, 10 min, 25 min, 45 min, 60 min, 75 min, and 90 min. Samples were immediately vacuum filtered by using Gooch sintered ware grade G4 and the residual concentration of Hg(II) were determined spectophotometrically. A similar set of experiments was performed with an initial Hg(II) concentration of 150 ppm.
IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 348 3. RESULTS AND DISCUSSION 3.1 Equilibrium Studies
In this study three isotherm models were to used to test the equilibrium biosorption of Hg (II) onto
BMLP.
1. Freundlich Isotherm
This model normally gives a better fit mainly for biosorption from liquids and can be expressed as [9]:
neF e
C K q
1
=
(1) Where
q
e
(mg/gm) is the amount of adsorbate biosorbed at equilibrium and C
e
(mg/L) is the equilibrium concentration of adsorbate in solution. In this model, the mechanism and the rate of adsorption are functions of the constants,
1/n
and
K
F
(L/mg) respectively. The value of the plots for the biosorption of Hg(II) on
BMLP
given in the table 1. The plots give good fit (R
2
= 0.9945 for 100 ppm and 0.9921 for 150 ppm). For a good biosorbent, 0.2 <
1/n
<0.8 (0.3368 for 100 ppm and 0.6036 for 150 ppm) A smaller value of
1/n
indicates better biosorption and formation of relatively strong bond between the adsorbate and biosorbent.
2. Langmuir Isotherm
This model is valid for monolayer biosorption onto surface having finite number of similar sorption sites which is presented by the following equation [10]:
e Le Lme
C K C K qq
+=
1
(2) In this model,
q
m
(mg/g) is the metal biosorbed corresponding to complete monolayer coverage, i.e., the maximum biosorption capacity, C
e
is equilibrium concentration of the solution (mg/L), and
K
L
(L/mg) is the Langmuir constant. From the values of
q
m
, as shown in the Table No. 1, it is observed that the maximum biosorption capacity of
BMLP
is 26.719 mg/g and 62.235 mg/g for initial concentration of mercury 100 ppm and 150 ppm respectively. For Langmuir type process, to determine if the biosorption is favorable or not, a dimensionless separation factor is defined as [11]:
0
11
C K R
L L
+=
(3) If
L
R
>1, the isotherm is unfavorable
L
R
=1, the isotherm is linear 0<
L
R
<1, the isotherm is favorable
L
R
= 0, the isotherm is reversible. The value of R
L
for Butea monosperma (0.01104 for 100 ppm mercury and 0.08025 for 150 ppm mercury) falls between 0 and 1, indicating that the isotherms are favorable. Fig.1 shows a plot of residual equilibrium concentration
C
e
(ppm) against adsorbate loading
q
e
(mg/g). The curves are convex upward and so they are favorable because a relatively high adsorbate loading can be obtained at low concentration in the solution.
01234567891011121314151605101520253035 C
0
= 100 ppm C
0
= 150 ppm
q
e
( m g / g )
C
e
(ppm)
Fig1.
Equilibrium data for the biosorption of Hg(II) on Butea monosperma
3. Temkin Isotherm
The derivation of the Temkin isotherm assumes that the fall in the heat of biosorption is linear rather than logarithmic, as implied in the Freundlich equation. The Temkin isotherm is expressed as [12]:
)ln(
eT e
C K Q RT q
∆=
(4) The parameters of the Temkin model, which takes into account the biosorbing species-biosorbent interactions, gave a satisfactory fit to the experimental data. The biosorption energy,
Δ
Q
(448 kJ/kmol for 100 ppm and 189 kJ/kmol for 150 ppm mercury in the solution), indicates that the biosorption reaction was endothermic.
K
T
is the equilibrium binding constant (L/mg) corresponding to the maximum binding energy. From the values of
K
T
(9.7496 and 0.7611 for an initial concentration of 100 ppm and 150 ppm mercury) it is observed that the binding energy is better for
BMLP
.
IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 349
Table1.
Isotherm modeling for the biosorption of Hg (II) onto Butea monosperma Model Equation R
χ
C
0
(ppm) Parameter values 1. Freundlich
n
eF e
C K q
1
=
0.9945 0.1486 100
1/n
= 0.3368;
K
F
= 12.80 0.9921 0.4574 150
1/n
= 0.6036;
K
F
= 6.599 2. Langmuir
e Le Lme
C K C K qq
+=
1
0.9894 0.6979 100
m
q
= 26.719;
L
K
= 0.8954 0.9912 1.2169 150
m
q
= 62.235;
L
K
= 0.0764 3. Temkin
)ln(
eT e
C K Q RT q
∆=
0.9903 0.2636 100
∆
Q
= 448 kJ/kmol; K
T
= 9.7496 0.9553 2.5904 150
∆
Q
= 189 kJ/kmol; K
T
= 0.7611
3.2 Kinetic Studies
Information about the biosorption mechanism is provided by kinetic study of biosorption. In this study, two different kinetic models were applied in order to establish which of them shows the best fit with experimentally obtained data.
1. Pseudo-first-order (Lagergren) model
This model is frequently used in kinetic studies and is the earliest known one explaining the rate of biosorption based on the biosorption capacity [13]. It is given by:
)(
1
t et
qqk dt dq
−=
(5)
Where, q
t
is uptake at any time‘t’, q
e
is equilibrium uptake and k
1
is first order rate constant. The experimental data gives good fit for
BMLP
(R
2
= 0.9963 and 0.9247 for 100 ppm and 150 ppm mercury concentration). The values of the first-order rate constant (
k
1
)
are 4.898 and 2.457min
-1
for 100 ppm and 150 ppm mercury.
2. Pseudo second-order (Ho) model
The kinetic equation is written in the form [14]:
t k qt k qq
eet
222
1
+=
(6) The data gives perfect fit for this model for
BMLP
(R
2
= 0.9985 and 0.9625 for initial concentration of 100 ppm and 150 ppm mercury) as shown in Fig.2 compared to Lagergren’s first-order rate equation. The values of the second-order rate constants found from of the graphs for
BMLP
(
k
2
= 0.8261 gm/(mg-min) and 0.1490 gm/(mg-min) for 100 ppm and 150 ppm mercury) indicate that Hg(II) removal rate is very fast.
02040608010005101520253035
C
0
= 100 ppm C
0
= 150 ppm
q
t
( m g / g )
t (min)
Fig2.
Kinetic data for the biosorption of Hg(II) on Butea monosperma
Table2.
Kinetic modeling of biosorption of Hg (II) by Butea monosperma Model Equation R
2
χ
2
C
0
(ppm) Parameter values 1. Pseudo- first-order (Lagergren)
)1(
1
t k et
eqq
−
−=
0.9963 0.2087 100
q
e
= 23.66;
k
1
= 4.898
0.9247 7.3495 150
q
e
= 30.15;
k
1
= 2.457 2. Pseudo- second- order (Ho)
t k qt k qq
eet
222
1
+=
0.9985 0.0870 100
q
e
= 23.86;
k
2
= 0.8261 0.9620 3.7061 150
q
e
= 30.97;
k
2
= 0.1490
IJRET: International Journal of Research in Engineering and Technology
eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 350 CONCLUSIONS
In the present study, the potential of using
BMLP
was assessed for the removal of Hg(II) from aqueous solutions. The Freundlich model fitted the experimental data well. The
BMLP
exhibits a maximum biosorption capacity of 62.235mg/g for initial metal concentration of 150 ppm. Biosorption followed pseudo-second order rate model as indicated by very high value of coefficient of correlation 0.9912. Since the raw material (Butea monosperma) is freely available in large quantities as a waste, it can be used economically for Hg(II) removal from polluting waters.
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Minerals Engineering,
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K. H. Chong and B. Volesky, “Description of Two Metal Biosorption Equilibria by Langmuir type Models”,
Biotechnology and Bioengineering,
Vol. 47, 1995, pp. 451-60. [3]
[3] A. D. Crowall, “Surface and Solid Gas Interface”, New York,
Marcel Dekker
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F. Pagnanelli, S. Mainelli, F. Veglio and L. Toro, “Heavy Metal Removal by Olive Pomace: Biosorbent Characterization and Equilibrium Modeling,”
Chemical Engineering Sci
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Bioresource Technol
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N. A. Khan, S. Ibrahim, P. Subramaniam, “Elimination of Heavy Metals from Wastewater using Agricultural Wastes as Adsorbents,”
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T. W. Weber and R. K. Chakkravorti, “Pore and Solid Diffusion Models for Fixed Bed Adsorbents”,
American Institute of Chemical Eng. Journal,
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John U. Kennedy Oubagaranadin and Z.V.P. Murthy, “Modeling of Adsorption of Chromium(VI) on Activated Carbons Derived from Corn (Zea mays) Cob,”
Chemical Product and Process Modeling,
Vol. 4, Issue 1, 2009. [14]
Y. Ho, and A. E. Ofemaja, Pseudo – Second order Model for Lead Ion Sorption from Aqueous Solutions onto Palm Kernel fiber,”
Journal of Hazardous Materials,
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