ELECTROCHEMICAL CHARACTERIZATION OF CHARGED MEMBRANES AND MEMBRANE SYSTEMS

The electrochemical behaviour of polyelectrolyte complex (PELC) membra nes, prepared by simultaneous interfacial reaction between aqueous sol utions of Na-cellulose sulphate (CS) on the one side and different pol ycations as well as cationic macroions on the other side, was investig ated. Tangential streaming potential and concentration potential measu rements 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 ex change properties are confirmed. On the other hand, in the case of PEL C 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 su rrounding solutions. For the case of membrane systems obtained by lami nating both types of PELC membranes one over the other, the characteri zation of gradients with respect to fixed charge density and/or morpho logy is demonstrated.