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 charged microporous membranes. The effects of changes in solvent dielectric constant near the wall, ion hydration effects, finite ion sizes, and charge regulating surface effects, are incorporated into the governing electrohydrodynamic equations (i.e., Navier-Stokes (NSE), Nernst-Planck (NPE), and Poisson-Boltzmann (PBE) equations). Their effect on streaming potential, pore conductivity, excess conductivity, and maximum energy conversion efficiency for electro-osmosis is illustrated. It is shown that the dielectric saturation and ion hydration effects cause significant changes in the electric potential field and ion concentration inside the capillary tubes. Quantitative comparisons of model results with measured electrokinetic data reveal better agreement when compared with the existing model.