Effect of Acetic Acid Dissociation Reaction on the Limiting Current Density in a System with a Rotating Membrane Disk

Abstract

At present, the nature of the limiting state of electromembrane systems in solutions of strong electrolytes (e.g., NaCl) is well known. The value of the limiting current in these systems with a rotating membrane disk (RMD) can be calculated quite accurately using the Levich equation. In cases where weak acids and/or their salts are present in the electromembrane system, this equation ceases to be satisfied and the electrodiffusion ion transport is complicated by proton-transfer chemical reactions between these acids, their anions, and water. In this work, the effect of these reactions on the limiting current density in a system with a rotating disk of a cation-exchange membrane and acetic acid has been experimentally studied. The results of voltammetry and their theoretical interpretation using the known mathematical model are presented. Conditions under which the mass transfer rate is limited by the diffusion delivery of acetic acid molecules to the membrane surface, as well as conditions under which the limiting stage is the reaction of their dissociation at the membrane/depleted solution interface, have been revealed.