MODELING OF PRESSURE-DRIVEN MEMBRANE SEPARATION OF ELECTROLYTES - HIGH-TEMPERATURE APPROXIMATION

A model of pressure-driven membrane process of electrolyte separation is presented. The electric held potential assumed as being known, exac t solution for permeate composition is readily obtained. All species a re assumed to have the same convection velocity. Local electroneutrali ty condition is not used. The electric potential has been taken into a ccount under high temperature approximation, thus reducing the problem to algebraic equation in exp(Psi), where Psi is dimensionless how pot ential, and making it possible to calculate concentrations of ions in permeate. Negative retention is shown to be possible for one-component electrolyte solution. For electrolyte mixtures, concentration of ion with high charge is shown to ''govern'' the membrane selectivity in re spect to low-charge ions. Results obtained are in qualitative accordan ce with the earlier experimental data on membrane separation of reacti on mixtures in homogeneous catalysis. (C) 1998 Elsevier Science B.V.