Chromium (III) recovery from waste acid solution by ion
exchange processing using Amberlite IR-120 resin: batch and
continuous ion exchange modelling
Francisco José Alguacila, Manuel Alonsoa, Luis Javier Lozanob
a
Centro Nacional de Investigaciones Metalúrgicas (CSIC), Avda. Gregorio del Amo 8,
Ciudad Universitaria, 28040 Madrid, Spain. E-mail: fjalgua@cenim.csic.es
b
Departamento de Ingenieria Química y Ambiental, E.T.S.I.I., Campus Muralla del
Mar; c/Doctor Fleming s/n, 30202 Cartagena, Spain
Abstract
The use of ion exchange technology was studied to remove chromium (III) from acidic
waste solution by Amberlite IR-120 resin. Batch and column experimental tests were
conducted to provide data for theoretical models and verify the system performance of
the adsorption process. Results of batch equilibrium tests indicated that Langmuir
isotherm describes well the adsorption process, whereas experimental data also provide
evidence that, under the present experimental conditions, chromium (III) adsorption by
Amberlite IR-120 resin is film-diffusion controlled; on the other hand, the theoretical
model used in the present investigation was found to predict reasonably well the ion
exchange breakthrough performance.
Keywords: Chromium (III) adsorption; Amberlite IR-120; Batch and column operations
1.Introduction
Heavy metals are considered as non-biodegradable toxic pollutants which may be
released in the environment by various activities, thus, they removal represents a
necessary environmental challenge. In the case of liquid effluents, there are many
methods available for the removal of these metals: chemical precipitation, coagulation,
solvent extraction and membrane processes, etc.; adsorption has been shown to be an
economically feasible alternative (Haas and Vamos, 1995; Suarez et al., 2002; ElShafey et al., 2002; Zouboulis et al., 2002; Alguacil and Villegas, 2002; Lee et al.,
2003; López et al., 2003).
Ion exchange is one of the most popular methods for the removal of metal ions from
aqueous solution (Kentish and Stevens, 2001; Rao et al., 2002; Kim and Keane, 2002;
Alguacil et al., 2002).
Different industrial applications call for various forms of chromium. Such as chromite,
ferrochromium, chromium metal, chromite refractory bricks, chromite foundry sands,
chromic acid, and other chromium compounds, while the principal industrial
applications of chromium and its compounds included non-ferrous and ferroalloys,
refractories, chemicals (metal finishing and corrosion control, leather tanning and
finishing, pigments, wood preservative, etc.). This element occurs in aqueous systems in
both the trivalent form (Cr3+) and the hexavalent form (chromate CrO42- and dichromate
Cr2O72-), and whereas Cr(VI) has long been recognized as a toxic substance to animal
and plants, Cr(III) is considered to be less toxic, though its elimination from
contaminated waters is also of a primarily necessity in industrializated countries (Nriagu
and Nieboer, 1988; Sarkar, 2002).
2
The objective of the present study is to address the performance of Amberlite IR-120
ion exchange resin in the removal of Cr(III) from wastewaters. Various parameters were
studied, in both batch and continuous operational modes, to optimize conditions for
effective removal of this metal ion from water containing it.
2.Experimental
Amberlite IR-120 (Fluka) is a macroporous cation exchange resin, which main
characteristics are given in Table 1. All other chemicals used in the present work were
of AR grade. Aqueous solutions were analysed for chromium by using a Perkin Elmer
1100B AAS.
Batch operation: equilibrium adsorption experiments were carried out by the use of a
weighed amount of resin (1 g) which were contacted (1200 min-1) in a glass reactor with
200 ml aqueous solution containing chromium (III) chloride at 20º C and for various
times. The residual Cr(III) concentrations in the aqueous solution after the desired
treatment and time were measured by AAS. The metal uptake by the resin was
calculated from the residual concentration of chromium in the aqueous phase. The
fractional approach to equilibrium (F) was calculated by:
F
Cr0  Crt
Cr0  Cre
(1)
where [Cr]0 is the initial solution concentration, [Cr]t is the concentration at an elapsed
time and [Cr]e is the chromium concentration in the aqueous solution at equilibrium.
Continuous operation: column trials were carried out with 1 g resin, which was loaded
into the column with a nominal capacity of 5 ml and fitted with 20 μm polyethylene frit
as bed support. Aqueous phases containing chromium (III) were passed through the bed
using a peristaltic pump. The effluent from the column was either directed to the
fraction collector or to the waste. Samples were collected regularly and analysed (AAS)
to monitor the chromium concentration leaving the column.
3.Results and discussion
3.1.Batch experiments
The Langmuir and Freundlich models (Tani et al., 1998) are two general isotherms
commonly used to describe the equilibrium ion exchange relation between the solid and
liquid phases; these models are represented respectively by:
Mr 
Mr
abMe
1  bMe
 kM e
n
(2)
(3)
where [M]r and [M]e are the equilibrium ion exchange capacity of the resin and the
equilibrium metal concentration in the aqueous solution, respectively, and a, b, k and n
are the constant isotherm parameters. The observed data of the equilibrium ion
exchange tests are shown in Fig.1. This figure also shows the model fit using the two
isotherms. The model fit (Table 2) reveals that the Langmuir isotherm represents
Amberlite IR-120 adsorption of Cr(III) better the Freundlich isotherm. The isotherm
3
parameters obtained by the model fit are listed in the same table, these isotherm
parameters allow easy determination of the equilibrium ion exchange capacity of the ion
exchange resin for different Cr(III) initial concentrations.
The rate law governing the adsorption of chromium (III) by Amberlite IR-120 had been
determined by using various experimental conditions. Three possible adsorption
mechanism had been evaluated if the adsorption of chromium (III) into the resin must
be considered as a liquid-solid phase reaction which includes diffusion of chromium
ions from the aqueous phase to the resin surface, the diffusion of ions within the resin
and the chemical reaction between ions and resin functional groups. The rate equations
for the above three cases are (Alguacil, 2003):
i) film-diffusion controlled process, the rate equation is:
ln( 1  F)  kt
(4)
ii) particle-diffusion controlled process, with the equation as:
ln( 1  F 2 )  kt
(5)
and iii) moving boundary process:
3  3(1  F) 2 / 3  2F  kt
(6)
in all the above equations, F is the fractional approach to equilibrium, whereas k is the
corresponding rate constant. Results from the present investigation are shown in Table
3, and shows that the metal uptake by Amberlite IR-120 resin is best fitted by the filmdiffusion controlled mechanism.
3.2.Continuous experiments
Similarly to other unit operations, ion exchange is a process whose performance is
affected by a number of operational parameters, including the equilibrium resin
adsorption capacity and the mass transfer rate (Malakul et al., 1998). Prediction of
column performance usually involves the resolution of a set of nonlinear partial
differential equations, though as an alternative, a macroscopic version from the above
was suggested (Lin and Kiang, 2003) for describing the behaviour of a column
adsorber. In most instances the equation which represented the macroscopic model is
written as:
ln
Mt
M0  Mt
 Me m 

 KM0  t 


M
f
0


(7)
where [M]t is the solute concentration in the outlet solution at time t, [M]0 is the inlet
solute concentration, K the rate constant of adsorption, [M]e the equilibrium solid-phase
(i.e. resin) concentration of sorbed solute, m the mass of adsorbent, f the flow rate and t
the time. According to the above equation, the left-hand quantity is a linear function of
time, and in fact, the above equation is essentially the same as the simplified logistic
function that describes the biological or population growth and distribution:
4
ln
Mt
M0  Mt
 k( t  )
(8)
The two parameters in eq.(8) can be readily estimated from the slope (k) and the
intercept (τ) when plotting ln [M]t/[M]0-[M]t versus time. Fig.2 shows this plot for
various inlet Cr(III) concentrations, whereas the estimated parameters for Amberlite IR120 adsorption of Cr(III) for different inlet metal concentrations and flow rates are
listed in Table 4. Using the estimated parameters, the breakthrough curves for various
inlet concentrations and flow rates could be predicted for Cr(III) adsorption. Figs. 3 and
4 compare the predicted and experimental data for various inlet Cr(III) concentrations
and flow rates, respectively. It can be observed that the model predictions compare
reasonably well with the experimental data, thus, eq.(8) can be used for convenient
representation of the column ion exchange process under the present experimental
conditions.
4.Conclusions
Amberlite IR-120 resin had been used to remove chromium (III) from aqueous chloride
solutions. The Langmuir isotherm was found to adequately describe the equilibrium
relation between the resin and liquid phases of the ion exchange process, whereas
kinetics experiments showed that chromium adsorption by Amberlite IR-120 resin is
film-diffusion controlled. Under dynamic conditions, the increase in the metal
concentration and the flow rate cause a decrease of the breakthrough performance. A
theoretical model was adopted for representing the column performance. The model
with its model parameters properly identified was observed to predict reasonably well
the experimental breakthrough curves.
Acknowledgements
To CSIC (Spain) for support. Also to Mr. Bascones and Mr. López for technical
assistance.
5.References
Alguacil,F.J., Villegas,M.A., 2002. Liquid membranes and the treatment of metalbearing wastewaters. Rev. Metal. MADRID 38, 45-55.
Alguacil,F.J., Coedo,A.G., Dorado,T., Padilla,I., 2002. The renoval of toxic metals from
liquid effluents by ion exchange resins. Part I: Chromium (VI)/Sulphate/Dowex 1x8.
Rev. Metal. MADRID 38, 306-311.
Alguacil,F.J., 2003. The removal of toxic metals from liquid effluents by ion exchange
resins. Part III: Copper/Sulphate/Amberlite 200. Rev. Metal. MADRID 39, 205-209.
El-Shafey,E., Cox,M., Pichugin,A.A., Appleton,Q., 2002. Application of carbon sorbent
for the removal of cadmium and other heavy metal ions from aqueous solution. J.
Chem. Technol. Biotechnol. 77, 429-436.
Haas,C.N., Vamos,R.J., 1995. Hazardous and industrial waste treatment. Prentice Hall,
New Jersey.
Kentish,J.S., Stevens,G.W., 2001. Innovations in separation technology for the
recycling and re-use of liquid waste streams. Chem. Eng. J. 84, 149-159.
Kim,J.S., Keane,M.A., 2002. The removal of iron and cobalt from aqueous solutions by
ion exchange with Na-Y zeolite: batch, semi-batch and continuous operation. J. Chem.
Technol. Biotechnol. 77, 633-640.
5
Lee,T., Lim,H., Lee,Y., Park,J.-W., 2003. Use of waste iron metal for removal of
Cr(VI) from water. Chemosphere 53, 479-485.
Lin,S.H., Kiang,C.D., 2003. Chromic acid recovery from waste acid solution by an ion
exchange process: equilibrium and column ion exchange modeling. Chem. Eng. J. 92,
193-199.
Lopez,F.A., Martin,M.I., Perez,C., Lopez-Delgado,A., Alguacil,F.J., 2003. Removal of
copper ions from aqueous solutions by a steel-making by-product. Water Research 37,
3883-3890.
Malakul,P., Srinivasan,D., Wang,H.Y., 1998. Metal adsorption and desorption
characteristics of surfactant-modified clay complexes. Ind. Eng. Chem. Res. 37, 42964301.
Nriagu,J.O., Nieboer,E., 1988. Chromium in the natural and human environment. J.
Wiley and Sons, New York.
Rao,K.S., Sarangi,D., Dash,P.K., Chandhury,G.R., 2002. Treatment of wastewater
containing copper, zinc, nickel and cobalt using Duolite ES-467. J. Chem. Technol.
Biotechnol. 77, 1107-1113.
Sarkar,B., 2002. Heavy metals in the environment. Marcel Dekker, New York.
Suarez,C., Ahumada,E., Orellana,F., Hein,H. Cote,G., Lizama,H., 2002. Extraction of
iron (III) from acidic sulfate solutions with bis(2-ethylhexyl)phosphoric acid in
PENRECOR 170 ES, a new friendly diluent. J. Chem. Technol. Biotechnol. 77, 183189.
Tani,K., Ohta,T., Nii,S., Takashi,K., 1998. Copper renoval from dilute aqueous solution
by extraction with countercurrent multistage column. J. Chem. Eng. Japan 31, 394-406.
Zouboulis,A., Lazaridis,N.K., Matis,A.K., 2002. Removal of toxic metals ions from
aqueous systems by biosorptive flotation. J. Chem. Technol. Biotechnol. 77, 958-964.
6
Table 1
Characteristics of Amberlite IR-120 ion exchange resin
Polymer matrix
styrene-DVB
Functional group
sulfonic acid
Ionic form
H+
Exchange capacity
4.4 meq/g (dry)
Operating temperature
120º C (maximum
Effective size
0.45-0.60 mm
7
Table 2
Parameters of the Freundlich and Langmuir isotherms
r2
k
n
Freundlich
0.912
16.3
0.23
Langmuir
0.996
a
b
67.7
0.09
8
Table 3
The regression coefficients and rate constants for the tested adsorption mechanisms of
chromium onto Amberlite IR-120 resin
[Cr]0 (g/l)
[HCl]0 (M)
Equation
r2
k (min-1)
0.04
0.24
ln(1-F)
0.999
0.18
ln(1-F2)
0.977
0.14
3-3(1-F)2/3-2F
0.986
0.04
0.32
0.24
ln(1-F)
0.996
0.15
ln(1-F2)
0.965
0.11
2/3
3-3(1-F) -2F
0.974
0.04
0.01
0.12
ln(1-F)
0.990
0.19
2
ln(1-F )
0.959
0.15
3-3(1-F)2/3-2F
0.985
0.05
0.01
0.96
ln(1-F)
0.989
0.14
ln(1-F2)
0.982
0.10
3-3(1-F)2/3-2F
0.975
0.03
9
Table 4
Parameters of eq.(8)
Flow rate
(cm3/min)
8
4
2
8
8
a
Inlet concentrationa
(g/l)
0.5
0.5
0.5
1.0
0.25
In 0.12 M HCl aqueous medium
k (min-1)
τ (min)
0.15
0.085
0.040
0.21
0.096
14.9
30.9
60.8
11.2
22.7
10
Fig.1. Isotherm model fits of experimental equilibrium ion exchange data of Amberlite
IR-120 at 20º C.
Fig.2. Plot of ln [C]t/[C]0-[C]t vs. time for Cr(III) adsorption by Amberlite IR-120. Flow
rate 8 cm3/min. Temperature 20º C. Inlet solution Cr(III) and 0.12 M HCl.
Fig.3. Comparison of predicted (lines) and experimental (symbols) Cr(III) adsorption
breakthrough curves of Amberlite IR-120 for different inlet metal concentrations. Flow
rate 8 cm3/min. Temperature 20º C. Inlet solution Cr(III) and 0.12 M HCl.
Fig.4. Comparison of predicted (lines) and experimental (symbols) Cr(III) adsorption
breakthrough curves of Amberlite IR-120 for different flow rates. Temperature 20º C.
Inlet solution 0.5 g/l Cr(III) and 0.12 M HCl.