Membrane conductivity: Interpretation and application according to the model with a heterogeneous interstitial solution

The critical analysis of the bibliographic data shows that membrane conductivity interpretations by electrochemical and physical chemistry models based on a homogeneous interstitial solution are not satisfactory. We propose to compare membrane conductivity measurements with a model involving an electric equivalent scheme and using a heterogeneous representation of the interstitial solution. The calculated parameters enable to compute the relative importance of three possible behaviours of various ion exchange membranes (IEM) as a function of the concentration of NaCl solutions. The correlation between experimental and calculated data are validates the assumptions made. Practical applications of the proposed treatment are important. For example, it allows to define, for a given membrane, the concentration domain in which the electric conduction due to the electrolyte is negligible or to optimize the choice of the IEM for a given electromembrane process. (C) 1999 Elsevier Science Ltd. All rights reserved.