PROPERTIES OF COMPOSITE MEMBRANES FORMED FROM ION-EXCHANGE MEMBRANES AND CONDUCTING POLYMERS .4. CHANGE IN MEMBRANE RESISTANCE DURING ELECTRODIALYSIS IN THE PRESENCE OF SURFACE-ACTIVE AGENTS

One of the unsolved problems in electrodialysis is organic fouling of the ion-exchange membrane. Sodium n-dodecyl sulfate and sodium n-dodecylbenzenesulfonate were used as a model of foulant ions against the anion-exchange membrane. The voltage drop across the anion-exchange membrane increased extremely during electrodialysis in the presence of sodium n-dodecyl sulfate and showed an unstable value similar to voltage oscillation. This was explained on the basis of the morphology of the membrane. On the other hand, the electric resistance of the composite membrane comprising the anion-exchange membrane and polypyrrole never increased in the presence of sodium n-dodecyl sulfate. The composite membrane was prepared by immersing the anion-exchange membrane, which had been equilibrated with a ferric chloride solution of high concentration, into an aqueous pyrrole solution. (Pyrrole was polymerized with Donnan-absorbed ferric ions in the membrane matrix.) The anion-exchange membrane and the composite membrane also showed a similar behavior against sodium n-dodecylbenzenesulfonate. However, the electric resistance of the composite membrane was somewhat higher than that of the untreated anion-exchange membrane.