Theoretical and Experimental Studies of the Membrane Permeabilities to Ions in Liquid Membrane

Abstract

Abstract A theory for the ion transport across liquid ion-exchange membrane was presented on the basis of nonequilibrium thermodynamics with the assumptions that the carrier ions and complexes were present only in the membrane phase, and that there was no volume flow and all chemical reactions were at equilibrium. The equations for “total” fluxes of membrane-permeable ions at steady state were derived from a set of the equations for “individual” fluxes of all mobile species present in the liquid membrane where the complexes were assumed to be partially dissociated. The “total” phenomenological coefficients were able to be expressed in terms of the “individual” coefficients. The diffusional and electroconductional membrane permeabilities to a selective ion in the liquid membrane–single electrolyte system were found to be in the same form as those in the fixed-site membrane–single electrolyte system, if the mean diffusion coefficient and mean mobility of the free species and its complex were used. The rate constants in the permeation process were also related to the diffusional membrane permeability. The experimental examination was made on a liquid cation-exchange membrane–aqueous single electrolyte system at 25 °C. The solution of calcium hexadecyl sulfate in 1-octanol and calcium chloride were used as the liquid membrane and the electrolyte, respectively. All the measured quantities were consistently interpreted by the presented theory.