Glycine Permeation through Na+, Ag+, and Cs+ Forms of Perfluorosulfonated Ion-Exchange Membranes

Abstract

We have studied the effect of counterions in perfluorosulfonated ion-exchange membranes on glycine permeation and found that counterions controlled permeation behavior. The Na⁺ form of the membrane exhibited saturation kinetics of the Michaelis-Menten type; that is, the flux rapidly increased with concentration and reached a limiting flux at a concentration of about 2 mol/L. The Cs⁺ form exhibited markedly lower fluxes which were nearly Fickian. For the Ag⁺ form, however, the fluxes increased rapidly and nonlinearly at low concentrations, but attained Fickian linearity at high concentrations. Ionizability of the sulfonate groups and hydration numbers of the counterions appeared to cause departure from Fickian behavior.