COMBINED FILM AND MEMBRANE DIFFUSION-CONTROLLED TRANSPORT OF IONS THROUGH CHARGED MEMBRANE

A mathematical model based on the Nernst-Planck equation has been sugg ested for predicting the ionic transport rate in a bi-ionic system und er the condition controlled by combined film and membrane diffusion. T he Na+-H+ system with a cation-exchange membrane was studied experimen tally as a test of the model, and the mass transfer coefficients in th e liquid film that yielded an optimum fit of the experimental data to the theoretical curves were determined. The obtained mass transfer coe fficients were found to be function of the stirring speed and solution composition. The theoretical time course of the concentration calcula ted using the obtained diffusion coefficients and mass transfer coeffi cients agreed well with the experimental results.