Concentration Polarisation in the Electrodialysis Process and the Polarisation Characteristics of Ion-selective Membranes

Complications in the electrodialysis process, due to the occurrence of concentration polarisation, are analysed. It is shown that most present-day methods for measuring the electrochemical characteristics of ion-selective membranes are not suitable for monitoring the behaviour of these membranes over a wide range of polarising current densities. An analysis of the polarisation characteristics of electromembrane systems shows the advantages of a system with a rotating membrane disc. It is shown that in the polarisation process there is a significant deterioration of the electrochemical properties of heterogeneous membranes whereas the properties of homogeneous perfluorinated sulpho-cation-exchange membranes remain almost unchanged. The bibliography includes 43 references.