Abstract
Ion flux across an ion exchange membrane in multicomponent ion systems has been described by a theory based on the Donnan equilibrium and the Nernst-Planck equation of flux. The permeation cofficients of ions and membrane potential in various kinds of electrolyte systems were calculated by this theory and measured experimentally as a function of membrane change density. The results show that the counterion with the highest valence is the most important for ion permeation phenomena in a multicomponent ion system and that uphill transport of a bivalent counterion occurs because its concentration gradient in a changed membrane is in the opposite direction to its concentration gradient of external solutions. This phenomenon is applicable in a new mechanism to control ion transport direction.
