Indian Journal of Chemical Technology
Vol. 22, May-July 2015, pp. 113-119
Adsorption of Indium(III) from aqueous solutions using SQD-85 resin
Hao Zhang1, Xinyi Chen1, Chunhua Xiong1,*, Caiping Yao1, Jiandin Li1, Xuming Zheng2 & Jianxiong Jiang3
1
Department of Applied Chemistry, Zhejiang Gongshang University, Hangzhou, 310012, China
2
Engineering Research Center for Eco-Dying & Finishing of Textiles, Ministry of Education,
Zhejiang Sci-Tech University, Zhejiang Province, 310018, China
3
Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education,
Hangzhou Normal University, Zhejiang Province, 310012, China
E-mail: [email protected]
Received 3 May 2013; accepted 16 January 2014
The feasibility of using SQD-85 resin as an adsorbent for indium(III) has been investigated. Various conditions such as
solution pH, temperature and contact time on the adsorption of indium(III) has also been examined. The results show that
the optimal adsorption condition of SQD-85 resin for indium(III) is achieved at the pH value of 5.5 in acetic acid-sodium
acetate (HAc-NaAc) buffer solution. The maximum uptake capacity of indium(III) is 297.2 mg/g at 298K at an initial pH
value of 5.5. The isotherms data fits well with Langmuir model better than Freundlich model. Kinetics on the adsorption of
indium(III) has been studied. The apparent activation energy Ea and adsorption rate constant k298 values are 12.11 kJ/mol
and 5.07×10-3 min-1, respectively. The thermodynamic parameters with the ǻS value of 106.61 J/(K·mol) and ǻH value of
13.55 kJ/mol indicate that the adsorption process is endothermic in nature. While the decrease of Gibbs free energy (ǻG)
with the temperature increasing indicates that the process occurred spontaneously. Finally, indium(III) can be eluted using
0.1 mol/L HCl solution and the elution percentage was relatively high (97%). Resins before and after indium(III) and
adsorbed and characterized by IR spectroscopy and thermo-gravimetric analysis.
Keywords: Adsorption, Indium(III), Kinetics, SQD-85 resin, Thermodynamics
Indium is a rare and valuable metal which is widely
used in a variety of industries, such as liquid crystal
displays (LCDs)1-2, semiconductors, low-temperature
solders and infrared photodetectors3. Though it is
widely distributed in the earth's crust, the reserves of
indium are very small and often appear in low
concentrations. Considering the current indium metal
consumption rates, it is estimated that the global
reserves of indium metal can only last for another 20
more years. Therefore, there is a growing interest in
the development of new indium metal recovery
methods6.
Most studies related to the extraction of indium(III)
have employed chemical precipitation7-9, solvent
extraction10, and liquid membrane11. However, for
solutions of low concentrations of indium(III), these
conventional methods have a lot of disadvantages,
such as high reagent/energy requirements, the
generation of toxic sludge or other waste products,
and high capital costs. Compared with the other
methods, ion exchange has received a considerable
attention in recent years because of its relatively low-
cost, effectiveness and easy handling. SQD-85 resin,
as one of the typical ion exchange resins, contain
functional group of –COOH, which possesses not
only protons that can exchange with cations, but also
oxygen atoms that can coordinate directly with metal
ion and form stable coordinate compound. Also, it is
easy to obtain since it’s commercially produced. Due
to the above mentioned properties, SQD-85 resin has
been preferred in indium(III) sorption for metal
recovering.
In this work, SQD-85 resin was used for the
recovery of indium(III) from aqueous solution using
batch and column adsorption methods. Some factors
affecting adsorption, such as initial pH of solution,
temperature and contact time have been examined.
Kinetics and isotherm adsorption experiments were
carried out. Thermodynamic parameters of adsorption
for indium(III) ion were calculated. The Thomas
model was applied to the experimental data that is
obtained from the column experiments. The
experimental results may provide a new pathway to
the recovery of indium(III) from aqueous solutions in
the hydrometallurgical systems.
INDIAN J. CHEM. TECHNOL., MAY-JULY 2015
114
Experimental Section
Apparatus
The concentrations of metal ion were determined
with
Shimadzu
UV-2550
ultraviolet-visible
spectrophotometer. The resin dosage was measured
by electronic balance of Sartorius BS 224s. Mettler
Toledo delta 320 pH meter was used for measuring
the pH values of solutions. The samples were shaken
in the DSHZ-300A and THZ-C-1 temperature
constant shaking machine. The water used in the
present work was purified using Mol Research
analysis-type ultra-pure water machine. The thermogravimetric analysis was investigated using Mettler
TGA/DSCl simultaneous thermal analyzer (with a
temperature range of 50-1000°C, heating rate of
20°C/min, atmosphere of N2). The sample for IR
spectroscopy was described by Nicolet 380 FT-IR.
Materials
SQD-85 resin was supplied by Jiangsu Suqing
Water Treatment Engineering Group Co., Ltd
(Jiangsu, China). And the properties were shown in
Table 1. The standard stock solutions were prepared
by dissolving an appropriate amount of indium (AR)
in 6 mol/L HCl. HAc-NaAc (1 mol/L) solutions with
pH 3.5~6.0 and C6H12N4-HCl buffer solutions with
pH 5.4 were prepared from the HAc, NaAc, C6H12N4
and HCl solutions. The chromophoric reagent of 0.2%
xylenol orange solution was obtained by dissolving
0.2000 g xylenol orange powder into 100 mL purified
water. All other chemicals were of analytical grade
and purified water was used throughout.
Batch experiments
Experiments were conducted in a certain range of
pH, temperature and contact time. The operation for
the adsorption of indium(III) is usually carried out in
batch vessels12.
Batch experiments were performed under kinetic
and equilibrium conditions. A desired amount of
pretreated SQD-85 resin was weighed and added into
a conical flask, in which a desired volume of buffer
solution with pH 5.5 was added. After 24 h, a required
amount of standard solution of indium(III) was put in.
The flask was shaken in a shaker at a given constant
temperature. The upper layer of clear solution was
taken for analysis until adsorption equilibrium was
reached. The procedure of kinetic tests was identical
to that of the equilibrium tests. The aqueous samples
were taken at preset time intervals and the
concentrations of indium(III) were similarly measured.
Column experiments
In the column experiments, continuous packed bed
studies were performed in a fixed bed mini glass
column (ĭ6 mm×30 cm) with 300 mg resin. The
SQD-85 resin in the column was pre-soaked for 24 h
before starting the experiment. The indium(III)
solution at a known concentration and flow rate was
passed continuously through the stationary bed of
sorbent in up-flow mode to avoid diluting the effluent.
The experiment was continued until a constant
indium(III) ions concentration was obtained. The
column studies were performed at the optimum pH
value determined from batch studies and at a constant
temperature of 25°C to be representative of
environmentally relevant condition.
Analytical method
A solution containing of indium(III) was accurately
added into a 10 mL colorimetric tube, and then 1.0
mL visualization reagent of 0.2% xylenol orange and
4 mL C6H12N4-HCl buffer solution were added. After
the addition of purified water to the mark of
colorimetric tube, the absorbency was determined in a
1 cm colorimetric vessel at a wavelength of 515 nm
and compared with the blank test. The adsorption
capacity (Q) and distribution coefficient (D) were
calculated according to the following formulas:
Q=
C0 − Ce
V
W
Macroporous weak
acid resin
D=
C0 − Ce V
×
Ce
W
凟COOH
Macroporous
45~50
14.0
0.70~0.80
1.10~1.20
where C0 is the initial concentration in solution
(mg/mL); Ce is the equilibrium concentration in
solution (mg/mL); V is the total volume of solution
(mL); W is the dry mass of resin (g).
Table 1 — General description and properties of resin
Resin
Functional group
Structure
Containing moisture/%
Capacity/(mmol·g−1)
Wet superficial density/(g·mL−1)
True wet density/(g·mL−1)
… (1)
… (2)
ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN
Results and Discussion
Influence of pH on the adsorption for indium(III)
The pH of aqueous solution has been identified as
the most important variable governing the adsorption
capacity of resins. In order to investigate the effect of
pH on the adsorption of indium(III) ions on the SQD85 resin, the adsorption experiments were carried out
by varying the initial pH value of the solution over
range of 3.5~6.0.
The distribution coefficient was very small in the
pH range of 3.5~5.0 and a sharp increase of the
distribution coefficient occurred in the pH range of
5.0~5.5. The pH value affected the surface charge of
the adsorbent and the degree of ionization and
speciation of the adsorbate in aqueous solution13. The
indium(III) uptake increased as the pH went up, and it
can be explained based on a decrease in competition
between protons (H+ ) and indium(III) for the same
adsorption sites and by the decrease of the positive
surface charge on the resin resulting in a lower
electrostatic repulsion between the surface of resin
and indium(III). While at pH 6.0, the metal ion was
prone deposit. Hence the adsorption pH value was
optimized as 5.5.
Determination of adsorption rate constant and apparent
activation energy
The influence of contact time on the adsorption of
indium(III) onto SQD-85 resin (Fig. 1) was
investigated at the temperature of 288, 298 and 308 K.
It is clear that the adsorption amount of indium(III)
increased as the contact time elapsed. The adsorption
amount of metal ions increased rapidly during the first
few hours, and then increased slowly until
equilibrium state was reached. The equilibrium for the
adsorption of indium(III) was reached in 13 h. Due to
the existence of greater number of resin sites available
for metal ions adsorption, the initial adsorption rate
was very fast. As the remaining vacant surface sites
decreased and due to formation of repulsive forces
between the metals on the solid surface and in the
liquid phase, the adsorption rate slowed down. The
kinetic curves are single, smooth, and continuous,
indicating the possible monolayer coverage of metal
ions on the surface of the resins14.
The kinetics of adsorption can be described by the
first-order kinetic model expression15 that is given by:
log(Qe − Qt ) = log Q1 −
k1
t
2.303
… (3)
The second-order kinetic model equation is given
as :
16
t
1
t
=
+
2
Qt k 2Q2
Q2
… (4)
where Qt and Qe are the adsorption amounts of
indium(III) at certain time and at equilibrium time
(mg/g), Q1 and Q2 are the calculated adsorption
capacities of first-order kinetic model and secondorder kinetic model (mg/g), respectively, and k1 and k2
are is the adsorption rate constant of first-order kinetic
model and second-order kinetic model (g/(mg·min)).
As shown in Table 2, the correlation coefficient
(R12) for the first-order kinetic model is better than the
the correlation coefficient (R22) for the second-order
kinetic model. Moreover, the calculated adsorption
capacity of first-order kinetic model produces good
fittings which indicated that the interactions would
follow the first-order kinetic model. This meant that
the liquid film spreading was the predominating step
of the adsorption process17.
According to the Arrhenius equation18:
lg k = −
Fig. 1 — Effect of contact time on adsorption
115
Ea
+ lg A
2.303RT
... (4)
where Ea is the Arrhenius activation energy for the
adsorption process indicating the minimum energy
that reactants must have for the reaction to proceed, A
is the Arrhenius factor, R is the gas constant (8.314
J/(mol·K), k is the adsorption rate constant and T is
the solution temperature. Ea and A values can be
INDIAN J. CHEM. TECHNOL., MAY-JULY 2015
116
Table 2 ʊ Kinetics model constants for adsorption of indium(III) by SQD-85 resin
T (K)
288
298
308
Qe (mg/g)
204.3
297.2
337.5
First-order kinetic model
Q1 ( mg/g)
k1 (min−1)
223.9
4.15×10−3
311.8
5.07×10−3
345.1
5.76×10−3
estimated from slope and intercept value of this plot
lgk vs 1/T, respectively. The correlation coefficient of
the straight line R2=0.9993 was achieved. The
apparent activation energy Ea was 12.11 kJ/mol,
which could be considered as a low energy barrier in
this study. It can be deduced that the adsorption speed
accelerated when the temperature rose within the
scope of experimental temperature.
Isotherm adsorption curve
The Langmuir and Freundlich models are the most
frequently employed models that have been published
in the literature to describe experimental data of
adsorption isotherms. The Langmuir and Freundlich
isotherms are studied in 30 mL solutions with the
initial metal ions concentration varying in the range of
6 mg/30 mL~12 mg/30mL with 15.0 mg resin at
desired pH, 100 rpm and 288, 298 and 308 K.
The adsorption data are analyzed to see whether the
isotherm obeyed the Langmuir19 and Freundlich20
isotherm models. The linear forms of the Langmuir
and Freundlich isotherms are represented by the
following equations:
Langmuir isotherm:
Ce Ce
1
=
+
Qe Qm bQm
... (5)
Freundlich isotherm:
1
log = log K f + log Ce
n
R2
0.9219
0.9458
0.9672
Second-order kinetic model
Q2 (mg/g)
k1( min−1)
156.3
5.47×10−6
212.5
6.38×10−6
267.4
6.12×10−6
obtained from Langmuir model than from the
Freundlich model (R2288K =0.9881, R2298K =0.9671,
R2308K =0.9875), suggesting the applicability of
Langmuir model to this system. The Langmuir
isotherms model assumes that adsorption takes place
at specific homogeneous sites within the adsorbents
and has been successfully applied to many other real
adsorption processes. It is evident that the adsorption
of indium(III) ion onto SQD-85 resin is fitted better to
the Langmuir isotherm than that of the Freundlich
isotherm models.
Thermodynamic parameters
In any adsorption procedure, both energy and
entropy considerations should be taken into account in
order to determine which process will take place
spontaneously. Values of thermodynamic parameters
are the actual indicators for practical application of a
process. The effect of temperature on the adsorption
characteristics of indium(III) onto SQD-85 resin was
investigated in the range of 288~308 K.
Thermodynamic parameters such as standard free
energy change (ǻG), standard enthalpy changes (ǻH)
and standard entropy changes (ǻS) were calculated by
using the following equation:
lg D =
∆S
∆H
−
2.303R 2.303RT
∆G = ∆H − T ∆S
... (6)
where Qe is the equilibrium indium(III) ions
concentration on the adsorbent (mg/g), Ce is the
equilibrium indium(III) ions concentration in solution
(mg/mL), Qm is the monolayer capacity of the
adsorbent (mg/g), b is the Langmuir constant and
related to the free energy of adsorption, Kf is
Freundlich constant and n (dimensionless) is the
heterogeneity factor.
According to the results, higher R2 values (R2288K
=0.9902, R2298K =0.9712, R2308K =0.9945) were
R2
0.8931
0.9320
0.9387
... (7)
... (8)
where D is distribution coefficient; R is the gas
constant (8.314 J/(mol·K)); and T is the absolute
temperature. The plot of lgD vs 1/T gives the straight
line from which ǻH and ǻG is estimated by the slope
and intercept of the linear form and the ǻG values at
different temperatures were calculated using Eq.(8),
respectively. Table 3 shows the values of
thermodynamic parameters of indium(III) ions
adsorption on SQD-85 resin. As presented in the
table, the negative ǻG values at given temperatures
indicate the spontaneous nature of the adsorption and
confirm the feasibility of the adsorption process. The
positive values of ǻS referred to the increased
ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN
117
Table 3ʊThermodynamic parameters calculated for adsorption
of indium(III) on SQD-85 resin at different temperatures
ǻG (kJ/mol)
ǻH
kJ/mol
ǻS
J/K·mol
T = 288 K
T = 298 K
13.55
106.61
-17.152
-18.218
T = 308 K
-19.284
randomness at the solid-solution interface. The
positive values of ǻH reveal that the adsorption is
endothermic in nature. The enthalpy change value is
13.55 kJ/mol, indicating that physisorption and
chemisorption coexist during adsorption process21,22.
Fig. 2 — Breakthrough curve for indium(III) on SQD-85 resin
Elution test
Whether an adsorbent is economically attractive in
removal of metal ions from aqueous solution depends
not only on the adsorptive capacity, but also on how
well the adsorbent can be regenerated again. For
repeated use of an adsorbent, adsorbed metal ions
should be easily desorbed under suitable conditions.
In this work, desorption of indium(III) ions with
various concentration of HCl eluent solution was
carried out. The percentages of elution are 89, 97, 95
and 91% for 0.05, 0.1, 0.2 and 0.3 mol/L HCl
concentration, respectively. The results show that the
indium(III) adsorbed by SQD-85 resin can easily be
desorbed, which indicates that SQD-85 resin can be
employed repeatedly in indium(III) adsorption.
Column study
Dynamic adsorption curve
The breakthrough curve shows the loading behavior
of indium(III) to be removed from solution in a fixed
bed23. Total adsorbed indium(III) quantity (Q; mg/g) in
the column for a given feed concentration and flow rate
is calculated from equation24:
Q=
³
v
0
(C0 − Ce )
dV
m
... (9)
where C0 and Ce are metal ion concentrations in the
influent and effluent, respectively, m is the total mass
of the sorbent loaded in the column and V is the
volume of metal solution passed through the column.
Q is the experimental maximum sorption capacity
value obtained by graphical integration. The
experimental breakthrough curves of indium(III) by
SQD-85 resin are shown in Fig. 2. Successful design
of a column adsorption process requires prediction of
the concentration vs time profile or breakthrough
curve for the effluent. The maximum sorption
Fig. 3 — Thomas model for the continuous adsorption of
indium(III)
capacity of resin is also needed in design.
Traditionally, the Thomas model is used to fulfill the
purpose. The model has the following form25:
Ce
1
=
C 0 1 + exp [ KT (Qm − C0V ) / θ ]
…(10)
where KT is the Thomas rate constant
(mL·min−1·mg−1) and ș is the volumetric flow rate
(mL·min−1). The linearized form of the Thomas
model is as follows:
§C
· K Qm KT C0
−
ln ¨ 0 − 1¸ = T
V
θ
θ
© Ce
¹
…(11)
The kinetic coefficient KT and the adsorption
capacity of the column Q can be determined from a
plot of ln[(C0/Ce-1] vs t at a certain flow rate as shown
in Fig. 3. The outlet time t is from V/ș. The Thomas
equation coefficients for indium(III) adsorption were
KT = 9.02×10−3 mL/(min·mg) and Q = 269.77 mg/g.
118
INDIAN J. CHEM. TECHNOL., MAY-JULY 2015
Dynamic desorption curve
Efficient elution of adsorbed solute from SQD-85
resin in column was essential to ensure the reuse of
SQD-85 for repeated adsorption/desorption cycles.
With respect to the stripping of indium(III) from
SQD-85, 0.1 mol/L HCl eluant was employed. A
sharp increase of indium(III) concentration at the
beginning of acid elution was observed. Desorption
curve was plotted the effluent concentration (Ce) vs
elution volume (V) from the column at a certain flow
rate. It is seen that, 60 mL 0.1 mol/L HCl eluent
solution provided effectiveness of the desorption of
indium(III) from SQD-85, after which further
desorption was negligible. These results show that
efficient elution of indium(III) from SQD-85 in
column is practical, which indicates that the resin has
a potential repeatedly in removing indium(III) from
aqueous solutions.
TG analysis
The thermo-gravimetric analysis (TGA) curves for
SQD-85 resin before and after adsorption of
indium(III) were detected at the range of 0~1000°C
and the TGA curves are illustrated in Fig. 4. When the
temperature is lower than 250°C, the SQD-85 resin
presents an outstanding thermal stability. However, at
the temperature range of 100°C to 500°C, SQD-85indium(III) demonstrate two decomposition steps: one
is at 200°C and the other one is at 450°C. These
results mentioned above indicate that the SQD-85
resin within the adsorption of indium(III) ions can
lower the thermal stability and accelerate the
decomposition rate. The higher residue (38.6%) of
SQD-85-indium(III) compared with that of SQD-85
(10.2%) revealed that indium(III) ions were adsorbed
onto SQD-85 resin.
IR Spectra
IR analysis is an important analytical tool
determination of adsorption mechanism. The results
about structural caused by SQD-85 resin loading with
indium(III) was given by FTIR spectra. From the
experimental results above, the functional groups of
SQD-85 resin, –COOH and indium(III) were
supposed to form bonds. In order to confirm this, the
spectra of resin, before and after indium(III) was
adsorbed, were compared. It was found that the
characteristic adsorption peak of bond –C=O
(1712 cm-1) decreased in intensity after indium(III)
adsorption, and the new peak 1627 cm-1 formed. After
the adsorption, the characteristic peak of the bond
Fig. 4 — Thermo-gravimetric analysis (TGA) for the SQD-85
resin before and after the adsorption of indium(III) ions
–OH shifts from 3437 to 3420 cm −1. The results
showed that the hydrogen and oxygen atoms in the
–OH and –C=O groups were involved in indium(III)
adsorption. The adsorption mechanism might be
partly a result of the ion exchange or complexation
between the ions and carboxyl groups of SQD-85
resin.
Conclusion
The adsorption onto SQD-85 resin is highly
dependent on the pH value. In addition, contact time
and system temperature also influences the adsorption
processes. The maximum adsorption capacity of the
resin for indium(III) is 297.2 mg/g in pH 5.5 HAcNaAc system at 298 K. And it is found that 0.1 mol/L
HCl solution provides effectiveness for desorption of
indium(III) from SQD-85 resin. Isotherm studies
show that the adsorption process of SQD-85 resin for
indium(III) follows both the Langmuir and Freundlich
isotherm model. The apparent activation energy Ea
was 12.11 kJ/mol, indicating that the adsorption had a
low potential barrier. Thermodynamic parameters
(¨H, ¨S, ¨G) indicate that the adsorption of
indium(III) on SQD-85 resin is a spontaneous reaction
and is endothermic in nature. Column experiments
show that it is possible to remove indium(III) ions
from aqueous medium dynamically. And the resin can
be used in the environmental protection and
hydrometallurgical system.
Acknowledgement
The project was supported by the National Natural
Science Foundation of China (No.21276235) and the
ZHANG et al.: ADSORPTION OF INDIUM(III) FROM AQUEOUS SOLUTIONS USING SQD-85 RESIN
Special Major Science and Technology Project of
Zhejiang Province, China (No. 2011C11098).
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