Mechanism of formation of peroxomonosulphuric acid during electrolytic preparation of peroxodisulphates

Abstract

The content of peroxomonosulphuric acid in the anolyte flowing out from a continual flow-through laboratory electrolyser for the preparation of concentrated ammonium peroxodisulphate solutions was always lower than would correspond to its rate of formation by spontaneous hydrolysis of S2O82- ions in acid medium. Hence, peroxomonosulphuric acid is formed during electrosynthesis of peroxodisulphates only by reactions taking place also in hydrolysis of S2O82- ions. The formation of peroxomonosulphuric acid by direct anodic discharge of HSO4- ions is improbable. A modified mechanism of the formation of H2SO5 either during hydrolysis or during electrolytic manufacture of peroxodisulphates is proposed.