The mechanism of zinc ion transport in cation-exchange membranes

Abstract

The mechanism of zinc ion transport across AMF-C-103 (sulfonated polyethylene styrene graft copolymer) cation-exchange membrane as a model for small ion transport in physiological membranes has been studied. The time dependence of zinc concentration in the receiving solution has been followed in the multi-ionic system: ZnCl 2, NaCl∥membrane∥NaCl. The behavior of the system has also been studied in presence of anionic, cationic, and nonionic detergents at low concentrations (10 −4 M). A simple and sensitive method of differential pulse polarography has been applied for the determination of zinc concentration. The interdiffusion of counterions (zinc and sodium) is proposed as a mechanism of zinc ion transport in the investigated system. Experiments in presence of detergents show that zinc transport is markedly reduced in presence of cationic detergent. Anionic and nonionic detergents do not affect zinc transport at these detergent concentrations. The passage of Zn 2+ or Na + ions is reduced because cationic detergent decreases membrane capacity through adsorption at the membrane surface. Electrophoretic experiments indicate that there is no formation of stable forms of zinc-detergent in the bulk of the solution.