Diffusion of electrolytes:

The coion (ion having same charge as in which of the fixed group of the membranes) transport is comparatively little and is dependent upon the quality of the ion selective membranes and brine concentration. Anion is the coion for cation associative membranes and cation is the coion for anion selective membranes. Water is also transported electroosmotically along with the coions.

Diffusion of electrolytes occurs from the brine to the dialysate since in the electrodialysis procedure the brine is commonly more concentrated than the dialysate. Water transport is also related along with electrolyte diffusion. Water transport because of osmosis takes place from the low concentration dialysate compartment within the higher concentration brine compartment.

The competence of electrodialysis process in the depletion of ionic substances from the dialysate might be considerably decreased through the adverse effects, free electrolyte diffusion, namely, coion transport, electroosmotic water transport related along with counter ion movement and osmosis. The effects of these unwanted transfer processes could, therefore, be reduced, through the selection of the membranes and through the operational procedure.