Ion Exchange Equilibrium between DOWEX 1X8 Resin Modified by Polyethyleneimine and Electrolyte Solutions

Abstract

In order to improve the selectivity of anion exchange resin, the surface of gel type anion exchange resin was modified with polyethyleneimine (PEI). In the proposed work an attempt to the utilization of commercial anion exchange resin modified by adsorption of polyethyleneimine was investigated. Many conditions of modification of anion exchange resin surface were studied. The influent parameters on the DOWEX 1X8 resin modification were determined using a factorial experimental design. The ion exchange reactions were studied for modified and unmodified resin and electrolyte solutions containing 2 3 Cl , NO and SO 4    . All experiments were performed at constant ionic strength I = 0.3 mol·L −1 and constant temperature T = 298 K. Ionic exchange isotherms were established for the binary systems: 2 2 3 4 NO SO .   3 4Cl NO , Cl SO andThe obtained results show that nitrate ion was more sorbed than chloride and sulfate. The order of preference for the anions studied in this investigation is:All the results given by this resin were compared with those obtained with the AMX anion exchange membrane. Selectivity coefficients and thermodynamic constants for the three binary systems and for the two resins were determined. The modified resin became more selective towards monovalent anions.

Modification of the AMX membrane surface by polyethyleneimine: Effect of ionic strength on the membrane ion exchange selectivity

“…These results are in agreement with several studies, [21,22,30] using either anion exchange membrane or resin. Sata et al [30] proved that the modification of the anionic membrane surface by polyethyleneimine makes the membrane more selective for nitrate than chloride and sulphate ions.…”

“…Hannachi et al studied the ion exchange equilibrium between Dowex 1 × 8 resin modified by PEI and electrolyte solutions. They found that the modified resin has a greater affinity for monovalent anions.…”

“…To modify the surface of the AMX membrane, a 5 × 5 cm sample of membrane was immersed in 250 mL of PEI solution at initial concentration equal to 1.5 g/ L, pH equal to 8.8, and at room temperature for 7 days as announced in previous studies …”

“…[20] Due to the water-soluble nature of this polymer, its adsorption on insoluble polymers such as ion exchange membranes and ion exchange resins was investigated. [10][11][12][13][14][21][22][23] The principal characteristics of PEI used in this study were illustrated in Table 1.…”

“…To modify the surface of the AMX membrane, a 5 Â 5 cm sample of membrane was immersed in 250 mL of PEI solution at initial concentration equal to 1.5 g/ L, pH equal to 8.8, and at room temperature for 7 days as announced in previous studies. [11,13,21] By determining the polyethyleneimine concentration remaining in the solution after equilibrium was reached, it was possible to calculate the adsorption capacity at equilibrium q e according to the following equation:…”