Evaluation of the Effect of Electroosmosis on the Efficiency of Electrobaromembrane Separation with Track-Etched Membranes

The results of a theoretical analysis of the influence of the electroosmotic flow on the electromigration and convective transport of competing ions separated by the electrobaromembrane process are presented. Separated ions of the same charge sign move in an electric field through the pores of a track-etched membrane to the corresponding electrode, while a commensurate convective counterflow being created by the pressure drop across the membrane. A simplified model based on the convective electrodiffusion equation and the Hagen–Poiseuille equation allows the analysis of experimental data using only the effective transport numbers of ions in the membrane as fitting parameters. Using a 2D mathematical model described by the system of Nernst–Planck, Navier–Stokes, and Poisson equations, it is shown that the electroosmotic flow can cause the effective transport numbers of competing ions to exceed their values in solution, even if these ions are coions for the membrane.