Transport properties of a cation exchange membrane with sodium and potassium as counterions

The measured transport properties for the cation exchange membrane Ionics 61AZL389 in the Na+ + K+ mixed counterion states are presented. The transport numbers of counterions and of water as well as the specific conductivity of the membrane showed approximately linear behaviour as a function of ionic fraction in the membrane. It is therefore concluded that it is possible to estimate the transport numbers of counterions from known selectivity coefficients and concentrations in the external solution. The transport number of water and the specific conductivity of the membrane can also be evaluated reasonably accurately using data for membranes in pure homoionic states. The separation ratio was found to be constant over a wide range of concentration ratios under the hydrodynamic conditions used experimentally.