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 o f 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 ele ctrolyte inside pores substantially exceeds the conductivity of the externa l solution. Experimental results are compared with the theoretical predicti ons based on the Nernst-Planck and Navier-Stokes equations for flow in pore s and the non-linear Poisson-Boltzmann equation for the electrostatic poten tial profile. For numerical calculations, the membrane is assumed to be a s et of parallel cylindrical pores having an identical mean radius. The zeta potential is determined numerically from streaming potential measurements a nd used in the model to compute the electrolyte conductivity within the mem brane pores. The space charge model provides rather good predictions for al l the concentrations under consideration. (C) 1999 Elsevier Science B.V. Al l rights reserved.