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

The critical analysis of the bibliographic data shows that membrane conduct ivity interpretations by electrochemical and physical chemistry models base d on a homogeneous interstitial solution are not satisfactory. We propose t o compare membrane conductivity measurements with a model involving an elec tric equivalent scheme and using a heterogeneous representation of the inte rstitial 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 mad e. Practical applications of the proposed treatment are important. For example , it allows to define, for a given membrane, the concentration domain in wh ich the electric conduction due to the electrolyte is negligible or to opti mize the choice of the IEM for a given electromembrane process. (C) 1999 El sevier Science Ltd. All rights reserved.