Studies of Transport Processes in Porous and Ion Exchange Membranes

摘要

The Nernst-Planck equations are applied to describe systems where diffusion, migration, and solvent flow contribute to the mass transport of strong electrolytes across porous membranes. Countercurrent electrolysis in a porous membrane used to separate ions from mixtures is studied. The ability of the Nernst-Planck model to predict the behavior of strong electrolytes in porous membranes at low concentrations is shown. The transport of cations in a cation exchange membrane is examined to develop a continuous model for the transport processes in an ion exchange membrane. The membrane used is a polystyrene-sulfonate cation exchange membrane and the total concentration of the solution is so low that the concentration of coions is negligible. A method for measuring the transport numbers of counterions as a function of the concentration of the counterions in the membrane in multi-ionic systems is assessed. The determination of the tracer diffusion coefficients of counterions is considered.