LIQUID-PHASE MASS-TRANSFER IN MULTICOMPONENT ION-EXCHANGE .1. SYSTEMSWITHOUT CHEMICAL-REACTIONS IN THE FILM

Liquid-phase mass transfer in ion exchange controlled by diffusion acr oss a Nernst film was studied for the general case of any arbitrary nu mber of counterions and coions. The Nernst-Planck equations are solved analytically for the momentary fluxes. The solution reduces to all ex act solutions available in the literature for special cases and provid es an approximation in the general case of arbitrary systems. The qual ity of the approximation is demonstrated by comparison with the genera l numerical solution. For most applications the errors can be neglecte d compared with those caused by the idealising assumptions of the film model. Experimental results obtained with a short column demonstrate the applicability of the solution to multi-component systems, thus ill ustrating that the electric potential has a strong effect on the fluxe s. In extreme cases, one or several species can be transferred against their concentration gradients.