Studies on Exchange Equilibria of Cations between Cation-Exchange Membranes and Electrolytic Solutions

Abstract

The variations of the selectivity coefficient KAB between Na+–H+, Na+–K+, and Na+–Cu2+ systems and the separation factor αAB between Na+–Cu2+ and K+–Cu2+ systems in cation-exchange membranes as functions of loading and particle size of resin have been measured. The exchange affinities of all the membranes increase as H+<Na+<K+<Cu2+. KAB is almost constant, independent of particle size and loading of resin in the membrane. αNaCu and αKCu increase with decrease in particle size but remain almost constant with loading of resin in the membranes. The order of selectivity is KNaH<KNaK≤KNaCu. The values of (αABQ0−1)other(αABQ0−1)−1M(300)C60 for the Na+–Cu2+ system are approximately 1.060 and for K+–Cu2+ are approximately 0.870. Q0 represents the exchange capacity of a dry membrane per unit volume (in milliequivalents per cubic centimeter).