Electroreduction of As(III) in acid environment

Abstract

The main reduction products of aqueous sulfuric acid solutions of As(III) are arsine and elemental arsenic, whose yields are substantially dependent on the electrolysis conditions. At a current density of 500 A m–2and an As(III) concentration of 0.25 M, the following current efficiencies (CE) for arsenic and arsine are obtained: Cd, 28.2 and 26.2; Pb, 29.3 and 22.9; Ti, 16.1 and 22.4; steel 3, 21.0 and 21.0; Cu, 20.3 and 19.9; and stainless steel, 24.9 and 16.9. For arsine, CE on a Pb cathode is virtually temperature-independent at 15–80°C. Multiple use of the same Pb cathode barely impacts its activity. The arsine CE considerably increases at 2500–3000 A m–2and reaches 75–78% and 50–53% on Pb and Cd, respectively.