Electroassisted Transport Phenomenon of Strong and Weak Electrolytes across Ion-Exchange Membranes: Chronopotentiometric Study on Deactivation of Anion Exchange Membranes by Higher Homologous Monocarboxylates

Abstract

The electrical responses of two interpolymer ion-exchange (anion and cation) membranes have been investigated by chronopotentiometry in dilute solutions of NaCl, KCl, and HCl as strong electrolytes and a 75:25 mixture of (1 mM) RCOOH−RCOONa, where R = −H, −CH3, −CH2CH3, −CH2CH2CH3, and −CH(CH3)2 as weak electrolytes. The behavior of both of these membranes was nearly ideal in strong electrolytes. The performance of a cation membrane in weak electrolytes R = −H and −CH3 was as good as in NaCl/KCl and less satisfactory in others. On the other hand, the performance of an anion membrane in electrolytes R = −H and −CH3 was nearly identical to that in NaCl/KCl, but it steadily decreased as the length and size of the alkyl (−R) chain increased. The poor performance of the anion membrane in higher homologous carboxylates with R = −CH2CH3, −CH2CH2CH3, and −CH(CH3)2 has been attributed to fouling of the surface by the RCOO− groups next to the membrane in the interfacial zone on the diluate side and/or the choking o...