Electrochemical characterization of charged membranes and membrane systems

Abstract

The electrochemical behaviour of polyelectrolyte complex (PELC) membranes, prepared by simultaneous interfacial reaction between aqueous solutions of Na-cellulose sulphate (CS) on the one side and different polycations as well as cationic macroions on the other side, was investigated. Tangential streaming potential and concentration potential measurements were carried out in order to obtain a complete information on the nature and density of their effective surface charges. In the case of PELC membranes obtained from CS and polycations, their weak ion exchange properties are confirmed. On the other hand, in the case of PELC membranes obtained from CS and cationic surfactants, the results of tangential streaming potential measurements lead to a reinterpretation of earlier observations based on concentration potential measurements: Their properties are governed by specific sorption of anions from surrounding solutions. For the case of membrane systems obtained by laminating both types of PELC membranes one over the other, the characterization of gradients with respect to fixed charge density and/or morphology is demonstrated.