alexa Removal of Transition Metals from Dilute Aqueous Solution by Carboxylic Acid Group containing Absorbent Polymers
ISSN: 2157-7587
Hydrology: Current Research

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  • Research Article   
  • Hydrol Current Res 2011, Vol 2(1): 107
  • DOI: 10.4172/2157-7587.1000107

Removal of Transition Metals from Dilute Aqueous Solution by Carboxylic Acid Group containing Absorbent Polymers

Z S Liu1* and G L Rempel2
1National Center for Agricultural Utilization Research, ARS/USDA, 1815 N. University Street, Peoria, IL 61604, USA
2Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada
*Corresponding Author: Dr. Z S Liu, National Center for Agricultural Utilization Research, ARS/USDA, 1815 N. University Street, Peoria, IL 61604, USA, Tel: 1 309-681-6104, Fax: 1 309-681-6524, Email: [email protected]

Received Date: Feb 20, 2011 / Accepted Date: Mar 29, 2011 / Published Date: Apr 22, 2011

Abstract

A carboxylic acid group containing resin with cation exchange capacity, 12.67 meq/g, has been used to remove Cu2+, Co2+ and Ni2+ ions from dilute aqueous solution. The resin had Cu2+, Co2+ and Ni2+ removal capacity, 216 mg/g, 154 mg/g and 180 mg/g, respectively. The selectivity of the resin for Cu2+ over Co2+ and Ni2+ was investigated in the presence of 1.0 M or 0.5 M sodium chloride. The resin was found to offer high capacity and selectivity for Cu2+. The sorbed metal ions (Cu2+, Co2+ and Ni2+) were easily stripped with dilute HCl. The sorbed Co2+ and Ni2+ could also be stripped with 1.0M NaCl.

Keywords: Ion-exchange; Selectivity; Sodium chloride; Carboxylic acid group-containing absorbents

Introduction

During the past two decades, high water absorbing polymers have received considerable interest from both academic and applied research laboratories. These materials show very high water retention capacities, which make them useful for new industrial and biomedical applications [1-3]. The synthetic polyacrylate derived from acrylic acid has emerged as one important high water absorbing polymer, because acrylic acid is cheap and easy to polymerize to products with high molecular weight. The development of high water absorbing polymers prepared by reacting acrylic acid and acrylamide copolymer with formaldehyde (crosslinker) was reported in our previous publication [4]. This cross linked co-polymerization of acrylic acid and acrylamide, referred to as CCPAA absorbent, was found that its absorption capacity depends on the cross linking density. With high cross linking density, e.g. high acrylamide content, it shows relatively low swelling in water. However, these materials are suitable for use as ion-exchange resins, where some swelling is necessary but high swelling ratio must be avoided. It is well known that resin capacity, selectivity and rate behavior for loading and elution are three important functional properties of ion-exchange resins for influencing their applications. The equilibrium sorption capacity of a resin is often observed in practice to be much less than the theoretical capacity calculated from resin composition. This is attributed to the inaccessibility of the many sorption sites buried inside the resin matrix. It is expected that this swelling property of the CCPAA resin will benefit its sorption capacity for the metal ions.

Maxim and co-workers [5] recently reported the retention process of the Cu2+ and Ni2+ cations from CuSO4 and NiSO4 aqueous solution by eight acrylic ion exchangers. Liu and coworkers recently reported removal of Cu2+, Co2+and Ni2+ from aqueous solution using bio-based carboxylate containing resins [6]. Rivas and coworkers studied the metal retention properties of resins containing amino and carboxylic acid groups (cross linked poly[3-(methacryloylamino)propyl]dimethyl(3- sulfopropyl)ammonium hydroxide], P(MAPDSA), and poly[3- (methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide-co-acrylic acid], P(MAPDSA-co-AA). They investigated under competitive and noncompetitive conditions for Cu2+, Cd2+, Hg2+, Zn2+, Pb2+, and Cr2+ ions by batch and column equilibrium procedures. The resin showed that a maximum retention capacity value for Hg2+ at pH 2 was 1.89 meq/g. The resin also showed a high selectivity to Hg2+ion [7]. In this work, the water swellable CCPAA resin with 5% acrylamide has been used for studying sorption characteristics and selectivity for copper over cobalt and nickel. Consequently the distribution behavior of the Cu2+, Co2+ and Ni2+ in the presence of salt (NaCl) in the solution was calculated presented in this paper. This resin will be explored further for its application in waste water treatment.

Experimental Details

Preparation of the CCPAA resin

Details for the synthesis of the CCPAA resin (5% acrylamide) were given in the literature (4). Typically, a solution of 90 ml distilled water, 0.048 g (18 mmol) of potassium persulfite and 0.02 g (0.09 mmol) of potassium metabisulfite were added into a flask fitted with a mechanical stirrer, condenser, thermometer and dropping funnel. At 65°C, 11.40 g (0.16 mol) of acrylic acid and 0.60 g (0.008 mol) of acrylamide in 15 ml distilled water were added dropwise in 10 minutes, followed by adjusting pH to about 4.5 with sodium hydroxide solution. The mixture was heated to 75°C. The polymerization began in about 10 minutes. The system was maintained for 2 hrs at 70°C. 3.7 ml formaldehyde solution was then added at 45°C and maintained for 1 hr. The system was heated to 70°C and maintained for 3 hrs. The product was dewatered with ethanol and dried to solid product at 80°C overnight. The resin was ground to pass 60 mesh sieves. The cation exchange capacity of the CCPAA resin was measured according to the method described by Kunin [8] and was found to be 12.67 meq/g.

Reagents

Copper sulphate, CuSO4·5H2O and cobalt sulphate, CoSO4·7H2O were obtained from J. T. Baker, USA. They were Baker analyzed reagents. Nickel sulphate, NiSO4·6H2O was obtained from Fisher Scientific Company, USA. It was a Fisher certified reagent. Copper, cobalt and nickel atomic absorption standard solutions were obtained from Aldrich, USA. They were 1,000 ppm in 1% HNO3.

Analysis

Metal ions in aqueous solution were measured with ARL (applied Research Laboratories) SpectraSpan-7 DCP emission spectrometer.

Sorption experiments

In all equilibrium studies, measured amounts of sorbent was vigorously shaken with definite volumes of solution of known metal concentration for 20 hrs in tightly stoppered glass bottles at ambient temperature, using a gyratory shaker with 2 cm eccentricity at 300 rpm. The residual metal concentrations in solution were measured. A range of concentrations (1 mM/L to 10 mM/L) was employed for each of the metal species, Cu2+, Co2+ and Ni2+ chosen for the study. The pH values of the solution for CuSO4, CoSO4 and NiSO4 are 5.0-5.4, 5.1-5.3 and 5.7-6.0, respectively. The sorption was also measured as a function of time under vigorous agitation.

The sorption capacity of the CCPAA resin for Cu2+, Co2+ and Ni2+ was measured by agitating the resin (0.50 g) in excess of 0.1 M CuSO4, 0.1 M CoSO4 and 0.1 M NiSO4 solution (50 mL), respectively, for 20 hrs. The results showed that the sorption capacities of CCPAA resin for Cu2+, Co2+ and Ni2+ were 216 mg/g, 154 mg/g and 180 mg/g, respectively. The sorption capacity of the CCPAA resin showed higher than that of ion-exchange resin prepared by conversion of soybean oil, which are 192 mg/g, 78 mg/g and 96 mg/g, respectively [6]. The accessibility of functional groups on the resin may be a key factor because of swell ability of the resin.

Selectivity experiments

The selectivity of the sorption for Cu2+ over Co2+ and Ni2+ was studied. The measured amounts of the sorbent were vigorously shaken with definite volumes of solution of known metal concentration (combinations of 2 metals at a time) in the presence of varying concentrations of sodium chloride for 20 hrs at ambient temperature. The residual metal concentration in solution was determined. A range of concentrations (1 mM/L to10 mM/L) was employed for each pair of metal species.

pH Runs

Sulphuric acid was used to acidify the solution. The pH range employed for the pH profiles was from 1.85 - 6.84. Once 20 mL of the metal solution (4 mM/L) was added, the bottles were placed evenly on a platform shaker at 300 rpm for 20 hrs at ambient temperature. The residual metal concentration in solution was measured.

Stripping behavior

In the stripping experiments, 0.04 g of the CCPAA resin, on which sorbed 8.64 mg Cu2+, or 6.16 mg Co2+, or 7.2 mg Ni2+, was used. The bottles were placed evenly on a platform shaker at 300 rpm at ambient temperature. The time was started when the acid solution (HCl) first hit the resin particles. The bottles were removed at 15 min, 30 min, 1 hr, 2 hrs, 3 hrs and 4 hrs intervals. The metal concentrations in the solutions were measured. Sorbed Co2+ and Ni2+ ions were also stripped by using 1.0 M NaCl solution. The bottles were removed at 4 hrs, 12 hrs, 24 hrs and 30 hrs intervals.

Results and Discussion

Sorption isotherm

The sorption isotherm was studied using metal concentrations between 1 mM/L to 10 mM/L at pH 5.0-6.0 and ambient temperature. The equilibrium data for the sorption of Cu2+, Co2+ and Ni2+from aqueous solutions by the CCPAA resin was plotted against equilibrium solution in Figure 1. The results showed that the CCPAA resin could take up significant quantities of Cu2+, Co2+ and Ni2+. At lower metal concentrations (< 6 mM/L), the sorption capacity of the CCPAA resin for Cu2+, Co2+ and Ni2+ did not change significantly. However, at higher concentrations (> 8 mM/L), the metal ions were adsorbed in roughly the order Cu2+ > Ni2+ > Co2+.

hydrology-current-research-sorption

Figure 1: Equilibrium sorption of Cu2+, Co2+ and Ni2+ from sulphate solutions on CCPAA resin (resin loading: 1.5g/L).

The equilibrium sorption data of copper in Figure 1 fitted well to the Freundlich isotherm, whereas they were fitted poorly by a Langmuir isotherm. The equilibrium sorption data of cobalt and nickel fitted well both to the Freundlich isotherm and to the Langmuir isotherm. Thus, for the sorption of Cu2+, Co2+ and Ni2+, the Freundlich isotherm might be written as:

              X* = mC*n                         (1)

where X* and C* are the equilibrium sorption and equilibrium concentration of sorbate, respectively, and m (mmol/g dry resin) and n are adjustable parameters. To solve for the isotherm constants, the function may be linearized by taking the natural logarithm of each side (eq .2).

      ln X* = lnm+ nlnC *                   (2)

Values of m and n were determined by least-squares fit of the sorption data in Figure 1 and were presented in Table 1. For the sorption of Co2+ and Ni2+, the Langmuir isotherm may be written as:

      C*A/X*=1/KbKs+C*As                (3)

where X* and C*A are the equilibrium sorption (mmol/g dry resin) and equilibrium concentration (mM/l) of metal ion in solution, respectively. The values of the saturation constant, AS (mmol/g dry resin), and the binding constant, Kb (l mM-1) were determined by least-squares fit and were presented in Table 1.

Sorbate Freundlich isotherm eq. (2) Langmuir isotherm, eq. (3)
  m
(mmol/g dry resin)
 n corr. coeff. As (mmol/g dry resin) Kb (l mmol-1) corr. coeff.
CuSO4 0.4041 1.139 0.998      
CoSO4 0.5455 0.900 0.989 47.62 0.011 0.996
NiSO4 0.6703 0.764 0.959 10 0.065 0.995

Table 1: Parameters of Freundlich and Langmuir isotherm for sorption on the CCPAA resin.

Effect of salt

Experiments were conducted to determine the effect of high background concentration of sodium chloride. It was found that neither of NaCl concentrations of 0.5 M and 1.0 M has any significant effect on the Cu2+ sorption capacity of the CCPAA resin as seen in Figure 2. However the Co2+ and Ni2+ sorptions capacity on the CCPAA resin decreased drastically over the whole range of sorbate concentrations employed as seen in Figure 3 and Figure 4. This may lead to a method of separating Cu2+ from Co2+ and Ni2+, since commercial cation-exchange resins containing sulfonic or carboxylic functional groups have limited potential for removal and recovery of heavy metals from process solutions and waste streams because of their low selectivity.

hydrology-current-research-equilibrium

Figure 2: Equilibrium sorption of Cu2+from CuSO4 solution with 0.5 M NaCl and 1.0 M NaCl on CCPAA resin (resin loading: 1.5g/L).

hydrology-current-research-resin

Figure 3: Equilibrium sorption of Co2+ from CoSO4 solution with 0.5 M NaCl and 1.0 M NaCl on CCPPAA resin (resin loading: 1.5g/L).

hydrology-current-research-loading

Figure 4: Equilibrium sorption of Ni2+ from NiSO4 solution with 0.5 M NaCl and 1.0 M NaCl on CCPAA resin (resin loading: 1.5g/L).

Selectivity for copper (II)

In hydrometallurgy, considerable interest exists in the separation of Cu2+from Co2+ and Ni2+, therefore, the selectivity of the CCPAA resin for Cu2+ over Co2+ or Ni2+ with presence of 1.0 M NaCl in the solution was investigated. Figure 5 and Figure 6 showed the results of two mixed solutions, in which each metal ion concentration was varied from 4 mM/L to 12 mM/L. It can be seen from Figure 5 and Figure 6 that the CCPAA resin is able to absorb about 10 times more Cu2+ than Co2+ and Ni2+ at higher metal concentrations (> 8 mM/L). However, the sorption capacity differences between Cu2+, Co2+ and Ni2+ were also rather large at lower metal concentrations (< 6 mM/L). It may be predicted that the separation of Cu2+ from Co2+ and Ni2+ is possible with the CCPAA resin in the presence of salt in solution.

hydrology-current-research-sulphate-solution

Figure 5: Equilibrium sorption of Cu2+/Co2+ from sulphate solution with 1.0 M NaCl on CCPAA resin (resin loading: 1.5g/L).

hydrology-current-research-sulphate

Figure 6: Equilibrium sorption of Cu2+/Ni2+ from sulphate solution in 1.0 M NaCl solution on CCPAA resin (resin loading: 1.5g/L).

Fraction of copper, nickel and cobalt among several complex species

It is well known that in the presence of Cl- in solution, the four coordinate M (II) complexes are formed, which reported in literature [6,9]. Taking copper as an example, the stepwise formation constant Ki , which stands for K1 to K4, associated with each of four equilibria, may be obtained from the book of "Stability Constants," edited by Sill´n et al. [10] and literature [11], it was found that the values of stepwise formation constants Ki are 2.80, 1.60, 0.49 and 0.73, respectively. Considering the overall formation, the equation may be written as follows:

equation (4)

From equation (4), the mass balance equation for each species of complex can be obtained as equation 5.

equation (5)

The formation constants, ß1, ß2, ß3, and ß4, are found to have relationships to K constants as follows:

ß1 = K1, ß2 = K1K2, ß3 = K1K2K3, and ß4 = K1K2K3K4.

By substituting the K values (already known from the literature), the numerical values for ß1, ß2, ß3 and ß4 may be calculated. If [C] is the total concentration of copper, then

[C] = [Cu2+] + [CuCl+] + [CuCl2] + [CuCl3-] + [CuCl42-]

Substitution in terms of the formation constants, listed in equation 5, it gives

[C] = [Cu2+] (1 + β1 [Cl-] + β2 [Cl-]2 + β3 [Cl-]3 + β4 [Cl-]4)

The fraction of Cu (α) presented as each species may be calculated as a function of [Cl-] alone:

α0 = [Cu2+] / C = (1 + ß1 [Cl-] + β2 [Cl-]2 + β3 [Cl-]3 + β4 [Cl-]4)-1

α1 = [CuCl+]/C = β1 [Cl-] α0

α2 = [CuCl2] / C = β2 [Cl-]2 α0

α3 = [CuCl3 -] / C = ß3 [Cl-]3 α0

α4 = [CuCl4 2-] / C = ß4 [Cl-]4 α0

By substituting of β values and concentrations of 1.0 M and 0.5 M [Cl-], respectively, the fractions of Cu (α) were calculated and summarized in Table 2.

Fraction Copper Nickel Cobalt
[Cl-] 1.0M [Cl-] 0.5 M [Cl-] 1.0M [Cl-] 0.5 M [Cl-] 1.0M [Cl-] 0.5 M
α0 1.92×10-6 2.36×10-5 0.206 0.56 0.455 0.68
α1 1.21×10-3 7.45×10-3 0.153 0.21 0.314 0.23
α2 4.80×10-2 1.48×10-1 0.161 0.11 0.232 0.087
α3 0.15 0.23 0.243 0.083    
α4 0.80 0.61 0.237 0.04    

Table 2: The fraction of metal ions presented as each species.

The formation constants for β1, β2, β3, and β4 of Ni and the formation constants for β1 and β2 of cobalt may also be obtained from literature [10,12,13]. For the nickel, they were respectively, 0.74, 0.78, 1.18, and 1.15. For the Co, they were 0.69 and 0.51. The same procedure discussed above was used to calculate the fractions of Ni (α) and Co (α). The results were summarized in Table 2.

In the presence of Cu2+ and Ni2+ in mixed system, the total metal concentration was defined as follows:

[C] = {[Cu2+] (1 + β1,Cu [Cl-] + β2,Cu [Cl-]2 + β3,Cu [Cl-]3 + β4,Cu [Cl-]4 )} + {[Ni2+] (1 + β1,Ni [Cl-] + β2,Ni [Cl-]2 + β3,Ni [Cl-]3 + β4,Ni [Cl-]4)}

when concentrations of Cl-, Cu2+ and Ni2+ are 1.0 M, 0.01 M and 0.01 M, respectively, the fractions of copper and nickel complexes may be calculated using the same procedure discussed above. The results were summarized in Table 3. When Cl- was changed to 0.5 M, the calculated fractions of copper and nickel complexes in the mixed system were shown in Table 3. The same procedure was used to calculate the fractions of copper and cobalt and results were summarized in Table 3. Because CCPAA resin is a weak acid cation exchange resin, once resin in the protonated form contacted water, a small percentage of carboxylic groups were ionized, which was reported in the article [6]. When it reacted with base, NaOH, (the CCPAA resin was neutralized during the preparation), some of the carboxylic groups would be converted to a more highly ionized form (eq. 6).

equation (6)

Scheme 1 showed the proposed exchanging process of the CCPAA resin with Cu2+.

hydrology-current-research-exchange

Scheme 1: Ion exchange process of resin with Cu2+ ion.

In contrast, the CCPAA resin reacted with a neutral salt (NaCl) to a very minor degree. This is because one of the products is a highly ionized acid. Therefore pH value of the solution will be low, and as a result the ionization of the resin will be depressed and driven to the left, as seen from equation 7.

equation (7)

Consequently, it only exchanges with CuCl+. Scheme 2 showed the proposed exchange process of the resin with CuCl+.

hydrology-current-research-process

Scheme 2: Ion exchange process of resin with CuCl+.

Fraction [Cl-]1.0M [Cl-] 0.5 M [Cl-]1.0M [Cl-] 0.5 M
copper nickel copper nickel copper cobalt copper cobalt
α0 1.92×10-6 1.92×10-6 2.36×10-5 2.36×10-5 1.92×10-6 1.92×10-6 2.36×10-5 2.36×10-5
α1 1.21×10-3 1.42×10-6 7.45×10-3 8.70×10-6 1.21×10-3 1.32×10-6 7.45×10-3 8.10×10-6
α2 4.80×10-6 1.50×10-6 1.48×10-1 4.60×10-5 4.80×10-2 9.80×10-7 1.48×10-1 3.00×10-6
α3 1.49×10-1 2.27×10-6 0.23 3.50×10-6 1.49×10-1 N/A 0.23 N/A
α4 0.8 2.21×10-6 0.61 1.70×10-6 0.8 N/A 0.61 N/A

Table 3: The fraction of metal ions presented in the mixture of metal ion system.

By comparison of α1 values (corresponding to CuCl+, CoCl+, and NiCl+ species, respectively) from Table 3, it was clear that a1 values for CuCl+ are much larger than those for CoCl+ and NiCl+ at 0.5 M and 1.0 M NaCl solution. This is one of the possible explanations of separation of Cu2+ from Co2+ and Ni2+. It is well known that other factors such as ionic radius and hydration energies of metal ions also affect selectivity and stability of metal complexes, which were reported by other authors [14,15].

Effect of pH

The effect of pH on Cu2+, Co2+ and Ni2+ sorption by the CCPAA resin was shown in Figure 7. The sorption of these metal ions was relatively unaffected by pH value above 3. However, the sorption of metal ions was found to fall drastically at pH levels below 3. This is attributed to acidic pH, -COO groups are protonated preferably and metal uptake is decreased consequently. The results indicated that the sorbed Cu2+, Co2+ and Ni2+ could be easily stripped by dilute acid.

hydrology-current-research-sulphate-equilibrium

Figure 7: Effect of pH on equilibrium sorption of Cu2+, Co2+ and Ni2+ from sulphate solution (4.0 mM/L) on CCPAA resin (resin loading: 1.5g/L).

Sorption rate behavior

The sorption of Cu2+, Co2+ and Ni2+ on the CCPAA resin was measured as a function of time at ambient temperature. Taking copper as an example plotted in Figure 8, it can be seen that the rate of sorption on the CCPAA resin was very high for CuSO4. 80% of the equilibrium sorption was being attained within 15 minutes from 10 mM solution. However, the rate of sorption on the CCPAA resin was relatively lower for CoSO4 and NiSO4, with only 41.7% and 58.9% of the equilibrium sorption being attained within 15 minutes from 10 mM CoSO4 and 8 mM NiSO4 solution, respectively. The rate of attainment of equilibrium sorption appeared to be dependent on the solution concentrations of Cu2+, Co2+ and Ni2+.

hydrology-current-research-solution-equilibrium

Figure 8: Rate of sorption of Cu2+ from sulphate solutionimage 6.0 mM/L, image 10.0 mM/L) by CCPAA resin (resin loading: 1.5g/L).

Stripping behavior

Since the metal sorption capacity of the CCPAA resin is very low at lower pH values, for example, Ni2+sorption nearly zero at pH level below 2, therefore, 1.0 N HCl was used as a stripping agent. The resin was mixed with the stripping agent at ambient temperature and the solutions were analyzed for Cu2+, Co2+ and Ni2+, respectively. The stripping characteristics of metal loaded resin were show in Figure 9. Very rapid stripping of sorbed Cu2+, Co2+ and Ni2+ on the CCPAA resin was obtained. The sorbed Co2+ and Ni2+ sorbed could be stripped completely within 1 hour. However sorbed Cu2+ was stripped to 89% in 4 hours. This is in accord with the resin showing relatively higher sorption capacity of Cu2+ than Co2+ and Ni2+.

hydrology-current-research-containing-metal

Figure 9: Rates of stripping of CCPAA resin containing metal ions with 1.0 N HCl (resin loading: 2g/L).

Based on the study results of salt effect, it is assumed that sorbed Co2+ and Ni2+ could be stripped by NaCl solution. The results showed that the sorbed Co2+ and Ni2+ could be successfully stripped using 1.0 M NaCl. However, the stripping rate was relatively low. 85% of sorbed Ni2+ and 97% of sorbed Co2+ was stripped in 30 hours.

The CCPAA resin showed high sorption capacity for Cu2+, Co2+ and Ni2+ ions, but in order to be useful on a commercial scale, the resin would have to be reusable. As mentioned above, sorbed metals on the CCPAA resin could be easily stripped. The recycled CCPAA resin was treated with 0.1 N sodium hydroxide solutions and used to adsorb Cu2+. The profiles of fresh and reused resin have shown that the first recycling of the resin decayed around 5%. That means the resin could be reusable, but might have a finite number of regeneration cycles.

Conclusions

The carboxylic acid group containing CCPAA resin could be used for efficiently removing Cu2+, Co2+ and Ni2+ from dilute aqueous solutions. This resin with cation exchange capacity, 12.67 meq/g, has Cu2+ sorption capacity, 216 mg/g, Co2+ sorption capacity, 154 mg/g and Ni2+ capacity, 180 mg/g, respectively. It was found that pH affected the equilibrium sorption of the metals on the resin at lower pH values. The sorption of Cu2+, Co2+ and Ni2+ ions on the resin fell drastically at pH levels below 2.3, 2.8 and 3.6, respectively, which indicated the sorbed metals could be stripped by dilute acid. The stripping behaviour of the sorbed metals on the CCPAA resin was studied. It was found that the sorbed Co2+ and Ni2+ could be completely removed by stripping with 1 N HCl in 1 hour. The sorbed Cu2+ was stripped to 89% in 4 hours. This was in accord with the relatively higher absorption strength of Cu2+ than Co2+ and Ni2+. The sorbed Co2+ and Ni2+ were also removed by 1.0 M NaCl after a longer time.

After studying the effect of NaCl on the sorption capacity of the resin, it was found that NaCl hardly affects Cu2+ sorption on the resin over the whole range of sorbate concentrations employed, whereas the Co2+ and Ni2+ sorption on the resin decreased drastically over the whole range of sorbate concentrations employed. Based on this information, the possibility of separation of Cu2+ from mixture of Cu2+/Co2+, or from mixture of Cu2+/Ni2+ in the presence of NaCl were studied. The results showed that the resin could take 10 times more Cu2+ than Co2+ and Ni2+ at higher metal concentrations (> 8 mM/L). However the sorption capacity difference between Cu2+, Co2+ and Ni2+ were also rather large at lower metal concentrations (< 6 mM/L). The CCPAA resin could be reusable, but it was noted that the resin had a finite number of regeneration cycles, because of the decrease in sorption capacity of the resin.

References

Citation: Liu ZS, Rempel GL (2011) Removal of Transition Metals from Dilute Aqueous Solution by Carboxylic Acid Group containing Absorbent Polymers. Hydrol Current Res 2: 107. Doi: 10.4172/2157-7587.1000107

Copyright: © 2011 Liu ZS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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