The Electrochemical Characterization of Ion Exchange Membranes in Different Electrolytic Environments: Investigation of Concentration and pH Effects

Abstract

In this research, the effect of electrolyte concentration and environmental pH variations on electrochemical properties of two commercial heterogeneous ion exchange membranes was studied. Membrane structure investigation was carried out using the SEM method. Obtained images showed that the anion-exchange membrane possesses a rough surface while the cation-exchange one has mainly a smooth surface with effect on ions transportation ability. Membrane potential, transport number, and permselectivity were initially improved in cation-exchange membrane with an increase of electrolyte concentration from 0.1 to 0.5 M and then began to decrease with higher concentration increase from 0.5 to 1.0 M. Also, membrane potential, transport number, and permselectivity were decreased in anion-exchange membrane with increase of electrolyte concentration. Results revealed that cation-exchange membrane had higher potential, transport number, and selectivity at pH 7 and the anion-exchange one showed better performance at pH 10 compared to other pH values. Membrane resistance was decreased in both membranes due to increase of electrolyte concentration. Resistance also increased initially with increase of pH value but then began to decrease with higher increase in pH value. Membranes exhibited higher selectivity for monovalent ions compared to bivalent one. The results demonstrate that the anion-exchange membrane has lower selectivity and electrical resistance compared to the cation-exchange membrane.