DOUBLE-LAYER EFFECT ON THE TRANSFER OF SOME MONOVALENT IONS ACROSS THE POLARIZED OIL-WATER INTERFACE

The apparent values of the standard ion-transfer rate constant k(app,i)-degrees and charge-transfer coefficient alpha(app,i) for ion transfer across the nitrobenzene-water interface at 25-degrees-C were measured using an ac impedance method for Me4N+, Et4N+, Pr4N+ and PF6- ions in aqueous solutions of LiCl at concentrations ranging from 0.01 to 0.8 mol dm-3. The change in the double-layer structure with LiCl concentration was deduced from the electrocapillary data. Taking account of the double-layer structure, we estimated the double-layer effect on the kinetic parameters within the framework of the classical Frumkin-type double-layer effect for the two types of current-potential characteristics for the ion transfer: the Butler-Volmer equation and the Goldman-type equation. The observed slight increase in k(app,i)-degrees and the practical invariance of alpha(app,i) with the LiCl concentration for all ions studied did not conform to the theoretical prediction from the Frumkin correction for both current-potential characteristics, suggesting that the contribution of the Frumkin-type double-layer effect on the observed values of the kinetic parameters is insignificant.