AN IMPROVED SPACE-CHARGE MODEL FOR FLOW-THROUGH CHARGED MICROPOROUS MEMBRANES

The Space-Charge model is modified to better analyze the steady-state electrohydrodynamic behavior of aqueous monovalent electrolytes in cha rged microporous membranes. The effects of changes in solvent dielectr ic constant near the wall, ion hydration effects, finite ion sizes, an d charge regulating surface effects, are incorporated into the governi ng electrohydrodynamic equations (i.e., Navier-Stokes (NSE), Nernst-Pl anck (NPE), and Poisson-Boltzmann (PBE) equations). Their effect on st reaming potential, pore conductivity, excess conductivity, and maximum energy conversion efficiency for electro-osmosis is illustrated. It i s shown that the dielectric saturation and ion hydration effects cause significant changes in the electric potential field and ion concentra tion inside the capillary tubes. Quantitative comparisons of model res ults with measured electrokinetic data reveal better agreement when co mpared with the existing model.