ELECTROCHEMICAL OXIDATION OF SULFITE IONS AT GRAPHITE-ELECTRODES

The electrochemical oxidation of sodium sulphite has been studied in aqueous sodium sulphate solution at two different graphite electrodes, one being of natural graphite (EC) and the other impregnated with phenol (ECK). The objective of the present work was to obtain some insight into the direct oxidation as well as the indirect oxidation, via produced oxygen radical species, of sulphite on non-metal electrodes. For this reason a study of the oxidation of sulphite in the concentration range between 0-0.10 M in aqueous sodium sulphate using a batch electrochemical reactor, operating potentiostatically, was undertaken. The potential range was chosen between 1.0 to 2.5 V/SCE, and the concentration of the supporting electrolyte, sodium sulphate, was kept constant at 0.5 M. A kinetic Tafel type law, considering irreversible behaviour for the direct sulphite oxidation and the mass transfer performance in regards to the experimental conditions were applied to predict the time variations of the sulphite conversion.