An application of the space charge model to the electrolyte conductivity inside a charged microporous membrane

In this study, we test the validity of the space charge model in the case of a ceramic microporous membrane. To this end, experimental measurements of the electrical resistance in pores are performed with the membrane filled with KCI solutions of various concentrations. The electrolyte conductivity within the membrane pores is deduced from these experiments. In situations where the contribution of the surface conduction is important (i.e. at low salt concentration or/and high zeta potential), the conductivity of the electrolyte inside pores substantially exceeds the conductivity of the external solution. Experimental results are compared with the theoretical predictions based on the Nernst-Planck and Navier-Stokes equations for flow in pores and the non-linear Poisson-Boltzmann equation for the electrostatic potential profile. For numerical calculations, the membrane is assumed to be a set of parallel cylindrical pores having an identical mean radius. The zeta potential is determined numerically from streaming potential measurements and used in the model to compute the electrolyte conductivity within the membrane pores. The space charge model provides rather good predictions for all the concentrations under consideration. (C) 1999 Elsevier Science B.V. All rights reserved.