EFFECTS OF STRUCTURE AND CHARGE ON THE DIFFUSIVE SALT PERMEATION ACROSS MICROPOROUS MEMBRANE FILTERS

Diffusion of LiCl through various types of polycarbonate track-etched membranes has been studied at different temperatures between 25 degree C and 50 degree C. From these results, the salt permeability, P//m//s, of the membrane system formed by the membrane itself and the two adjacent boundary layers has been obtained. The results conform to a simple relation between 1/P//m//s and l/ epsilon , l being the thickness of the membrane and epsilon its porosity. From this relation an estimation of the thickness of the boundary layers is obtained. Taking into account these results, a capillary charged membrane model has been used in order to estimate the charge density inside the pore in the range of concentrations studied.