Transport competition between proton and cupric ion through a cation-exchange membrane.

Abstract The CMS-Neosepta membrane has been developed for the production of brine from sea water by electrodialysis. The monovalent cation permselective membrane is more permeable for Na+ ions than for alkaline earth cations. This paper deals with the equilibrium properties of this membrane in contact with an aqueous solution containing sulfuric acid and cupric sulfate. The exchange isotherm between Cu2+ ions and H+ ions shows a higher affinity of the Cu2+ ion towards the membrane material. This valence effect is quantified by the variations of the ratio of the activity coefficients of the two individual cations. The individual mobilities of protons and cupric ions in the membrane have been determined.