MEMBRANE-POTENTIAL OF BIPOLAR MEMBRANES

The membrane potential of a bipolar membrane composed of a cation-exch ange layer in series with an anion-exchange layer is analyzed theoreti cally and experimentally. The theoretical approach is based on an exte nsion of the Nernst-Planck equations of monopolar charged membranes to the case of the two ion-exchange layers in series and the diffusion b oundary layers adjacent to the bipolar membrane. The experimental resu lts concern the transient behavior, stirring effects and concentration dependence of the membrane potential, and can be explained by means o f the above theoretical approach. It is shown that membrane potential measurements can contribute significantly to a better electrochemical characterization of bipolar membranes.