EFFECT OF POLYMER MATERIALS ON MEMBRANE-POTENTIAL, RECTIFICATION AND WATER-SPLITTING IN BIPOLAR MEMBRANES

Bipolar membranes are of practical interest in a new process for the c ommercial production of acids and bases. In this study, the effect of polymer components and structure on membrane potential, rectification and water splitting in bipolar membranes was discussed. The experiment al results for the membrane potential agree well with the theoretical predictions if the effective charge densities of bipolar membranes wer e assumed to be 0.0001 times smaller than those which were estimated f or each layer separately. The results of the water splitting and recti fication effects show that a membrane exhibiting a high rectification effect has a low water splitting effect. The water splitting ability d epends on the thickness of the anion exchange layer. Though it has bee n pointed out that the state of the intermediate boundary region is al so responsible for water splitting, the results indicate that the chem ical composition of the anion exchange layer plays an important role. If the membrane structure is similar to an ionomer, the water splittin g is also more effective. It is very important to prevent water swelli ng as far as possible, not only by polymer crosslinking but also by su pporting the membrane with woven cloth. Copyright (C) 1996 Elsevier Sc ience Ltd.