Copper Removal Using Rice Husk

i:/3b2/Jobs/clean/2009/Heft9/138.3d 24. 8. 2009
Clean 2009, 37 (9), 0000–0000 H. Jaman et al. 1
Hasanur Jaman1
Debarati Chakraborty1
Papita Saha1
1
Biotechnology Department, National
Institute of Technology, Durgapur, India.
Research Article
A Study of the Thermodynamics and Kinetics of
Copper Adsorption Using Chemically Modified Rice
Husk
The use of rice husk as a low cost adsorbent for the removal of copper from waste-
water has been explored in a laboratory scale experiment. The rice husk used for the
study was treated with alkali to increase the sorption properties. The influence of
metal ion concentration, weight of biosorbent, stirring rates, temperature and pH
were also evaluated, and the results are fitted using adsorption isotherm models.
From the experimental results it was observed that almost 90–98% of the copper
could be removed using treated rice husk. The Langmuir adsorption isotherm,
Freundlich isotherm and Tempkin isotherm models were used to describe the distri-
bution of copper between the liquid and solid phases in batch studies, and it was
observed that the Langmuir isotherm better represented the adsorption phenom-
enon. The experimental rate constant, activation energy, Gibbs free energy, enthalpy
and entropy of the reaction were calculated in order to determine the mechanism of
the sorption process.
Keywords: Adsorption isotherm; Adsorption kinetics; Biosorption; Copper; Thermodynamic
parameters;
Received: June 23, 2009; revised: July 14, 2009; accepted: August 6, 2009
DOI: 10.1002/clen.200900138
1 Introduction
Adsorption is defined as the process where a solute is removed from
the liquid phase through contact with a solid adsorbent which has a
special affinity for that particular solute [1]. When the solid adsorb-
ent is a biological product the adsorption is referred to as biosorp-
tion. Biosorbents are highly porous materials and adsorption pri-
marily takes place on the walls of the pores or at specific sites inside
the particles.
Copper is an essential trace nutrient in all higher plants and ani-
mals. It is found primarily in bloodstreams, in various enzymes and
in copper based pigments. But it can be poisonous to organisms and
humans if the amount of copper is high. Too much copper in water
has been found to damage marine life [2]. An inherited condition
called Wilson's disease causes the body to retain copper since it is
excreted by the liver into the bile. If untreated, this disease leads to
brain and liver damage. In addition, studies have shown that people
with mental illness such as schizophrenia have heightened levels of
copper in their system. The potential sources of copper contamina-
tion in wastewater are the metal cleaning and plating industry, fer-
tilizers, refineries, the tannery industry, paper and pulp, etc. Hence,
its removal from wastewater is of the utmost importance.
The removal of copper ions from wastewater can be achieved
using different methods like ion exchange, chemical precipitation,
reverse osmosis, chemical oxidation, electrodialysis, adsorption
using activated carbon or activated charcoal, fly ash, clayey soil, etc.
[3–10]. However, these treatment methods are costly and also suffer
from the disadvantages of incomplete removal, being a labor inten-
sive operation and having a high energy requirement. Disposal of
the sludge is also a problem. The search for new and cost effective
technologies involving the removal of heavy metals has been ori-
ented to biosorption based on the metal binding capacities of differ-
ent biological or agricultural materials [11–23]. The main advan-
tages of biosorption are the low operating cost, easily available sour-
ces, minimization of sludge volume to be disposed of, and the possi-
bility of the regeneration of metals from the biosorbents. A number
of natural and synthetic adsorbents have been studied by various
researchers for the removal of heavy metals.
Rice husk is an easily available agricultural waste material, and
from a literature survey it was revealed that the annual generation
of rice husk in India is 18 to 22 million tons. Rice husk is the outer
covering of paddy and accounts for 20–25% of its weight and is an
agricultural byproduct whose major constituents are organic mate-
rials and hydrated silicon. The organic materials present in rice
husk are cellulose (55–60 wt% including cellulose and hemicellu-
lose), lignin (22 wt%), crude protein (3%), etc. Carboxyl, hydroxyl
and amidogen etc. are some of the functional groups which make
the adsorption process possible.
For the present study, rice husk obtained from a food process was
treated with alkali to increase the sorption capacity and was used as
the biomaterial for the removal of copper from wastewater.
The objective of the present study is to investigate the metal bio-
sorption properties of treated rice husk as a biosorbent. For this,
batch and laboratory scale flow experiments were conducted. For
Correspondence: P. Saha, Biotechnology Department, National Institute
of Technology, Durgapur, India.
E-mail: papitasaha@gmail.com
i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com

2 H. Jaman et al. Clean 2009, 37 (9), 0000–0000
the batch experiment the effect of factors like initial pH value, influ-
ent concentration, agitation speed, temperature of the adsorption
reaction, etc. were investigated. An attempt was also made to under-
stand the kinetic rate constant of the reaction and thermodynamic
parameters.
2 Materials and Methods
2.1 Preparation of Raw Biosorbents
Rice husk was obtained from an agro industry of the local area and
washed properly with distilled water and dried at 608C in an oven
drier. After that it was subjected to 2% sodium hydroxide treatment
and then the solution was autoclaved for about 15 min to separate
the low molecular weight lignin compounds. After that the mate-
rial was washed properly with distilled water till the pH reached
close to neutrality. The solid particle was then separated from the
solution using a filtration process and dried at 608C. The particle
size of the treated rice husk was found to be less than 355 lm.
2.2 Preparation of Copper (II) Solutions (Adsorbates)
A stock solution of copper was prepared using A.R. grade copper sul-
phate pentahydrate in distilled water (E-Merck). The required quan-
tity of copper was accurately weighed and dissolved in a small
amount of distilled water and made up to 1 L in a volumetric flask
by adding distilled water. Experimental copper (II) solutions of dif-
ferent concentrations were prepared by diluting the stock solution
using distilled water.
2.3 Characterization of the Biomatrix
Particle size analysis of the biosorbents were carried out as per IS
2720 using standard sieves of different sizes.
Scanning electron micrographs were studied using a scanning
electron microscope, Model Hitachi S-3000N to understand the mor-
phology of the biosorbents before and after the adsorption of copper
using treated rice husk. The particles were coated with gold using a
sputter coater to give conductivity to the samples. The scanning
electron micrographs were then taken.
2.4 Determination of Copper (II) Content in the
Solutions
The free copper (II) content of the effluent solutions before and after
treatment was determined colorimetrically using a UV/VIS spectro-
photometer (Hitachi). 0.2 mL of a 1% w/v of sodium diethyl dithio-
carbamate solution, and 20 mL of 1.5 N ammonia solution were
added to the sample (1 mL) containing less than 60 mg/L of Cu (II)
ions and diluted to 25 mL with double distilled water. The absorb-
ance of the yellow colored solution was then read at 460 nm [11, 24].
2.5 Other Chemicals
All other chemicals used in the study such as acids, alkalis, sodium
diethyl dithiocarbamate, ammonia solutions etc. were supplied
Himedia Research laboratory and E-Merck India.
2.6 Influence of Agitation Speed
The copper biosorption capacity was determined at different agita-
tion speeds ranging from 60 to 400 rpm (Incubator shaker, Innova
42, New Brunswick Scientific) using a fixed amount (1 g) of treated
rice husk and a fixed amount of copper solution (50 ppm) at temper-
ature of 310 K. The initial and final concentrations of the solutions
were measured using UV/VIS spectrophotometry and the adsorption
capacities of the adsorbent were calculated.
2.7 Influence of pH
Adsorption experiments for copper (II) ions on rice husk were car-
ried out through a batch method. 0.1 N hydrochloric acid and 0.1 N
NaOH were used for adjusting the initial pH of solution after addi-
tion of biosorbent. The pH measurements were made using a pH
meter during all the experiments. 1 g of treated rice husk was added
to 100 mL of 50 ppm copper (II) solution in 0.25 L Erlenmeyer flasks.
The pH was maintained using hydrochloric acid and sodium
hydroxide. The pH values of the solutions were pH 2, 4, 5.5, 7, 8.5,
and 11.4. The flasks were stirred at a constant temperature (310 K)
in a digital incubator shaker at 200 rpm (using an Incubator shaker,
Innova 42, New Brunswick Scientific) and samples (about 3–4 mL)
were taken from the flasks at particular time intervals. Solution con-
centrations were analyzed using UV/VIS spectrophotometry.
2.8 Adsorption Experiments
The copper biosorption capacity was determined at different metal
concentrations ranging from 10 to 200 ppm and a fixed amount (1
g) of treated rice husk in order to calculate the biosorption constant
using different isotherms. 100 mL of different concentration of cop-
per (II) solutions ranging from 10–200 ppm were used. The dried
treated rice husk (1 g) was added to Erlenmeyer flasks and agitated
at 310 K and 200 rpm for 2 h. The initial and final concentrations of
the solutions were measured using UV/VIS spectrophotometry and
the adsorption capacities of the adsorbent were calculated. After
equilibrium was attained by each system, the metal uptake capacity
for each sample was calculated according to a mass balance on the
metal ion using Eq. (1):
qe ¼ ðCi À CeÞ V
m ð1Þ
where Ci is initial copper (II) concentration, Ce is equilibrium copper
(II) concentration (mg/L), V is volume of the solution (L), m is the
weight of the treated rice husk in g. The extent of sorption as a per-
centage was calculated using the Eq. (2):
Sorptionð%Þ ¼
Ci À Ce
Ci
6 100 ð2Þ
The Langmuir and Freundlich adsorption isotherm models were
used to analyze the experimental data.
For the Langmuir model the following equation was used:
Ce
qe
¼
1
Q 0 b
þ
Ce
Q o
ð3Þ
where qe is the amount of copper (II) adsorbed at equilibrium (mg/L),
Ce is the concentration of copper (II) in the aqueous phase at equili-
brium (mg/L). Q0
and b are the Langmuir constants related to adsorp-
tion capacity and the energy of adsorption.

Clean 2009, 37 (9), 0000–0000 Adsorption of Copper Using Chemically Modified Rice Husk 3
The Freundlich isotherm constants were calculated using the fol-
lowing equation:
lnqe = lnKF + (1/n) lnCe (4)
where qe is the amount of copper (II) adsorbed at equilibrium, and KF
and n are Freundlich constants related to adsorption capacity and
adsorption intensity, respectively.
For the Tempkin isotherm model the following equation was
used:
qe = BT lnKT + BT lnCe (5)
where qe is the amount of copper (II) adsorbed at equilibrium, Ce is
the concentration of copper (II) in the aqueous phase at equilibrium
(mg/L), and KT and BT are the constants.
2.9 The Intraparticle Diffusion Model
The fractional approach to the equilibrium varies according to the
function (Dt0.5
/r2
)0.5
, where r (m) is the particle radius and D (m2
/s) is
the diffusivity of solute within the particle. The initial rate of intra-
particle diffusion can be obtained by linearization of the curve [13]:
qt = f(t0.5
) (6)
The plot of qt vs. t0.5
may represent a multi-linearity which indi-
cates that two or more steps occur. The first step is the sharper step
which is external surface adsorption or the instantaneous adsorp-
tion stage. The second step is the gradual adsorption stage where
intraparticle diffusion is rate controlled. The third portion is the
final stage where intraparticle diffusion starts due to low solute con-
centration in solution.
2.10 Influence of Temperature and Kinetic Studies
To achieve the optimized temperature and determine the reaction
rate constant and activation energy, the sorption process was car-
ried out at different temperatures ranging from 298 to 330 K. 100
mL of copper (II) solution were put in an Erlenmeyer flask and a
fixed amount of rice husk was used. The mixture was then agitated
at 200 rpm for 1 h. Kinetic rate constants were calculated at the dif-
ferent temperatures. The rate constant activation energy of the
adsorption of copper (II) was determined using the Arrhenius equa-
tion [25]:
ln k2 ¼ ln A0 À
Ea
R T
ð7Þ
Ea is the activation energy in kJ/mol, R is the gas constant (8.314 J
mol– 1
K– 1
), A0 is the Arrhenius constant.
2.11 Error Analysis
In order to compare the applicability of different models, the nor-
malized standard deviation was calculated using Eq. (8):
Dq ð%Þ ¼ 100 6
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
R ½ðqexp À qcalÞ=qexpŠ2
N À 1
s
ð8Þ
where N is the number of data points, qexp and qcal (mg/g) are the
experimental and the calculated values of the equilibrium biosor-
bate solid concentration in the solid phase, respectively.
A non linear regression analysis method was used to calculate the
kinetic model. The statistics were basically the least sum of squares
of the differences between the experimental data and the data
obtained from the models. The value of SS was evaluated using the
equation [26]:
SS ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
½ðCt=CoÞc À ððCt=CoÞeŠ2
n
s
ð9Þ
where (Ct/C0)c is the ratio of effluent and influent concentrations
obtained from calculation according to the Langmuir model and
(Ct/C0)exp is the ratio of effluent and influent concentrations obtained
from experimental results. If the value of SS is a small number, the
model data is similar to the experimental data, and the model can
represent the experimental data. If the value of SS is higher, the
model is not similar to the experimental data, and therefore the
model cannot represent the experimental data.
2.11 Thermodynamic Parameters
The thermodynamic parameters of the adsorption of copper were
determined using the following basic equations:
KC ¼
Ca
Ce
ð10Þ
DG0
= –RT lnKC (11)
ln Kc ¼ DS0
R À
DH0
RT
ð12Þ
where KC is the distribution coefficient for the adsorption, DH0
is the
enthalpy change, DS0
is the entropy change, DG0
is the Gibb's free
energy change, R is the gas constant, T is the absolute temperature,
Ca is the copper adsorbed per unit mass of the adsorbent, and Ce is
the equilibrium adsorbate concentration in the aqueous phase.
2.12 Column Adsorption Studies
Continuous column adsorption experiments were conducted using
a glass column of diameter 30 mm and height 1 m to evaluate the
removal of copper (II) from solution. 10 g of rice husk was put in the
column and the height of the bed was maintained at 15.5 cm. The
column was shaken while being packed with rice husk to minimize
void volume and air gaps. The flow rate was maintained at 2 mL/
min. Solutions of different concentration of copper (II) were passed
through the column. Then, the concentrations of the exit solutions
passing through the bed were determined using UV/VIS spectropho-
tometry.
3 Results and Discussion
3.1 Effect of Agitation Speed
From Fig. 1, it is observed that as the agitation speed increased from
60 to 200 rpm, the adsorption capacity of the rice husk increased,
but if the agitation speed was further increased beyond 200 rpm the
adsorption capacity decreased. The reason behind this phenomenon
is that as agitation speed increased, some of the copper (II) adsorbed
by the treated rice husk was desorbed and so the concentration of
copper in the solution increased. When the agitation speed used
was higher than 200 rpm, an amount of copper adsorbed by rice

husk was desorbed, and as a result the concentration of the copper
solution increased due to the high speed of rotation of the solution.
From Fig. 1, it is also observed that the sorption capacity for the
removal of copper was higher when treated rice husk was used,
rather than using untreated raw rice husk. So, from the experimen-
tal results it can be inferred that treated rice husk has a better effi-
ciency than untreated rice husk due to the chemical modification
of the functional group using alkali.
3.2 Effect of Different Initial Concentrations
From Fig. 2 it is observed that as the initial concentration of copper
(II) increased, the biosorption capacity of the rice husk increased,
with the sorption percentage increasing first to about 99% and then
decreasing to about 63%. At higher metal concentrations, the metal
ions were adsorbed more than at low metal concentrations as more
biosorbent binding sites were free for interaction at low metal con-
centrations. At low ion concentrations, the available metal
adsorbed more quickly, and at higher ion concentrations the metal
needed to diffuse to the surface of the adsorbent by intraparticle dif-
fusion, and greatly hydrolyzed ions will diffuse at a slower rate.
From the experimental results it was also observed that a large
amount of solution was removed in the first 10–20 min of contact
time and equilibrium was attained within 30–60 min.
3.3 Effect of pH
Biosorption of copper (II) was measured at given contact times for
four different pH solutions (pH 2, 4, 5.5, 7, 8.5 and 11.4). At higher
pH values (higher than pH 5.5), the copper (II) precipitated from sol-
ution because of the high concentrations of OH–
in the medium.
From the experimental results it was observed that at pH 5.5 the
maximum sorption capacity was obtained for 50 ppm initial metal
concentration and 1 g of biosorbent (see Fig. 3).
3.4 Adsorption Isotherms
An adsorption isotherm is characterized by certain constants which
express the surface properties and affinity of an adsorbent. Experi-
mental data was fitted to Langmuir, Freundlich and Tempkin mod-
els. From Fig. 4 it can be seen that the Langmuir isotherm represents
the experimental data better than the Freundlich and Tempkin iso-
therms with initial metal concentration of 50 ppm, 100 mL solu-
tion, agitation speed 200 rpm, temperature 378C, and biosorbent
dose 1 g. The Langmuir constant Q0
is 4.766 mg/g, b is 14.37 L/mg
with a regression coefficient of 0.9997, whereas in the Freundlich
model KF is 4.72 mg/g, n is 32.88 and the regression coefficient is
0.8885. For the Tempkin isotherm, BT is 0.2436, KT is 1.04 (L g m– 1
)
and the regression coefficient is 0.89. The experimental results indi-
cate that copper (II) ions adsorbtion on rice husk is monolayer
adsorption. As the temperature increased, the adsorption capacity
increased, indicating that the process was endothermic in nature.
The separation factor (RL) [24] can be calculated using this equation:
Figure 1. The effect of agitation speed on copper (II) biosorption in
respect to time.
Figure 2. The effect of initial metal ion concentration on the adsorption of
copper using treated rice husk.
Figure 3. The adsorption capacity of copper (II) solution at different pH
using chemically modified rice husk.

RL ¼
1
1 þ b C0
ð13Þ
where C0 is the initial concentration (mg/L) and b is the Langmuir
constant. From Fig. 4 and value of b, RL is calculated to be 0.0014,
which is less than 1 and greater than 0. From the slope of the plot of
qt vs. t0.5
, the external surface intraparticle diffusion rate kid was
determined as 2 mg g– 1
min– 0.5
at 378C. This diffusion rate is attrib-
uted to the instantaneous utilization of the most readily available
sites on the adsorbents external surface.
3.5 Influence of Temperature and Kinetic Studies
The effect of temperature on copper (II) adsorption kinetics can be
seen in Tab. 1. As the temperature of the solution is changed from
298 to 330 K, the amount of copper (II) adsorbed on the treated rice
husk increased from 3.8 to 4.95 mg/g for 100 mL of 50 ppm copper
solution. This may be a result of an increase in the mobility of cop-
per (II) ions with temperature. But it is also observed that as the tem-
perature rose higher than 458C, some copper (II) ion was desorbed
from the rice husk due to the increase in temperature.
The pseudo first order rate expression is generally described by
the following equation:
dqt
dt
¼ k1ðqe À qtÞ ð14aÞ
where, qe is the amount of copper adsorbed at equilibrium per unit
weight of adsorbent (mg/g), qt is the amount of copper adsorbed at
any time (mg/g) and k1 is the rate constant (min– 1
).
Integrating and applying boundary conditions as t = 0 and qt = 0 to
t = t and qt = qt, the final equation is:
logðqe À qtÞ ¼ log qe À k1
t
2:303
ð14bÞ
The pseudo second order kinetic model equation is:
t
qt
¼
1
k2 q2
e
þ
t
qe
ð15Þ
Where k2 is the pseudo second order rate constant of adsorption
(g mg– 1
min– 1
) and qe and qt are the amounts of copper (II) adsorbed
(mg/g) at equilibrium and at time t, respectively. The initial adsorp-
tion rate, h (mg g– 1
min– 1
) as t ﬁ 0 can be calculated as [22]:
h ¼ k2 q2
e ð16Þ
Calculations show for adsorption of copper using biosorbents,
pseudo second order models represent the phenomenon better
than first order models.
The linear plots of t/qt vs. t for different temperatures are shown
in Fig. 5. At a temperature of 378C, the rate constant was 0.3109 g
mg– 1
min– 1
and the initial adsorption rate was 7.32 mg g– 1
min– 1
.
Figure 4. a) Langmuir isotherm plots for the adsorption of copper onto
treated rice husk; b) Freundlich isotherm plots for the adsorption of cop-
per onto treated rice husk; c) Tempkin isotherm plots for the adsorption of
copper onto treated rice husk.
Table 1. Results of theoretical and experimental metal uptake capacity at
different temperatures.
T,8C Qe (Calculated ),
mg/g
Qe (Experi-
ment), mg/g
R2
q (%) SS
30 4.44 4.516 0.999 5.374 0.038
37 4.86 4.88 0.999 1.414 0.01
40 4.69 4.88 0.991 1.343 0.095
45 4.962 4.93 0.999 2.255 0.015
57 4.90 4.88 0.999 1.414 0.01

From the pseudo second order rate constant k2 at different temper-
atures, the activation energy Ea is calculated using the Arrhenius
equation (Eq. (7)). By plotting logk2 versus 1/t (see Fig. 6) the activa-
tion energy for copper adsorption is calculated from the slope and
was found to be 38.77 kJ/mol. As the activation energy was less than
40 kJ/mol, it follows that the reaction is a diffusion controlled proc-
ess in which there is a physical step in the adsorption process.
3.6 Thermodynamic Parameters
The values of DH0
and, DS0
were determined from the slopes and
intercept of the plot of lnKc vs. (1/T) (Fig. not shown) and listed in
Tab. 2. The negative value of DG0
at all temperatures indicate that
the copper adsorption reaction was spontaneous in nature and it
was also observed that as the temperature increases, DG0
decreases
up to 458C indicating the feasibility of adsorption at higher temper-
atures. So, it can be inferred that the reaction is spontaneous in
nature. As the DG0
ranges from –4.63 to –12.27 kJ/mol, the adsorp-
Figure 5. Pseudo 2nd order kinetics at different temperature.
Figure 6. Rate constant vs temperature relation to determine the activa-
tion energy of the reaction.
Figure 7. a) Scanning electron micrograph of rice husks, b) scanning
electron micrograph of treated rice husk, and c) scanning electron micro-
graph of treated rice husk after biosorption of copper (II).

tion process is predominantly a physical adsorption process. The
calculated positive value of enthalpy (see Tab. 2) demonstrated that
the reaction was an endothermic process and so the reaction con-
sumes energy. For copper adsorption on rice husks in an aqueous
system, initially copper ions have to displace more than one water
molecule previously adsorbed on the rice husk. As the diffusion
process was endothermic in nature, it is expected that increased sol-
ution temperature would result in increased uptake of copper ions
from aqueous solution. But as the temperature increased above
458C, desorption from biosorbents may occur and so the concentra-
tion of copper in aqueous solution increased by a small amount.
The entropy of the reaction was positive as the displaced water mol-
ecules gain more translational entropy than was lost by the copper
ions and so as a result there will be increased randomness at the
solid/solution interface.
The surface morphology of rice husk before and after adsorption
of copper was also studied with a scanning electron microscope (see
Fig. 7). These figures reveal the surface texture and porosity of the
treated (see Fig. 7b)), untreated (see Fig. 7a)) and adsorbed treated
rice husk (see Fig. 7c)). It was observed that the surface texture of
treated rice husk and untreated rice husk was different due to the
chemical modification of the untreated rice husk. It was also
observed that the surface texture of the treated adsorbent changed
drastically after the loading of copper.
3.6 Column Experiment
From the column experiment (Fig. 8a)) it was observed that as time
increased, the efficiency of the reduction of copper increased as
well as the sorption capacity, and after a certain time period (5.30 h)
almost 99.99% removal of copper was achieved.
From Fig. 8b) it was observed that as concentration of the copper
(II) solution increased from 50 to 200 ppm the adsorption capacity
increased but the sorption percentage of copper (II) ions decreased
at high concentrations of copper (II) in solution.
The column experimental data was fitted to a Langmuir adsorp-
tion model and it was observed that the regression coefficient was
0.9984. This phenomenon indicates that the Langmuir adsorption
model also represents the adsorption criteria in column experi-
ments, and treated rice husk can be effectively used for copper
removal in column operation also.
4 Conclusions
The experimental results show that in batch and column experi-
ments almost 90–98% copper (II) can be removed from wastewater.
The rice husk has the potential biosorption capacity to remove cop-
per (II). Furthermore, the results show that the adsorption equili-
brium data fitted the Langmuir adsorption model very well at differ-
ent temperatures. Also, the pseudo second order kinetic model pro-
vided the best correlation with the experimental data, whereas the
pseudo first order model did not fit the experimental data well. Due
to the low cost of rice husk this may be an effective material for the
treatment of wastewater containing copper, and this material is bio-
degradable and ecofriendly. So, it can be concluded that treated rice
husk can be recommended as a biosorbent for the removal copper
(II).
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Table 2. Thermodynamic parameters for the adsorption of copper onto
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Sr No. T, K DG, kJ/mol DH, kJ/mol DS, J mol– 1
K– 1
1 303 –4.63 67.051 15.51
2 313 –10.127
3 318 –12.27
4 330 –10.24

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DOI: 10.1002/clen.200900138
Research Article: The use of alkali
treated rice husk as a low cost adsorb-
ent for the removal of copper from
wastewater was explored in a laboratory
scale experiment. The influence of
some of the factors affecting biosorption
is evaluated, and the results were fitted
using Langmuir, Freundlich and Temp-
kin adsorption isotherms. It was found
that 90–98% of the copper could be
removed using treated rice husk.
A Study of the Thermodynamics and Kinetics
of Copper Adsorption Using Chemically
Modified Rice Husk
H. Jaman, D. Chakraborty, and P. Saha*
Clean 2009, 37 (9), 00– 00

Copper Removal Using Rice Husk

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