Direct Electrocatalytic Reduction of As(III) on CuSn Alloy Electrode: A Green and Sustainable Strategy to Recover Elemental Arsenic from Arsenic Wastewater

Arsenic contamination in groundwater and industrial wastewater poses a significant threat to human health and the ecosystem. Electrochemical reduction of highly mobile As(III) species into less toxic elemental arsenic (As(0)) has emerged as a promising method to effectively recover arsenic from water. In this study, a novel CuSn alloy nanowire array-modified copper foam (CuSn NAs/CF) electrode was fabricated for the direct electrochemical reduction of As(III) to As(0). The electrocatalytic reduction of As(III) was systematically investigated under various reaction conditions, including current densities, solution pH, electrolytes, and initial As(III) concentrations. The CuSn NAs/CF electrode was proven to effectively suppress the hydrogen evolution reaction and greatly enhance the electrochemical reduction of As(III). The recovery yield of As(0) on the CuSn NAs/CF electrode reached 3.67 mg/cm2 at 90 min of electrolysis in a 0.1 M Na2SO4 at pH 11, which was 2.75 times higher than that of the Cu NAs-modified electrode. Furthermore, the as-prepared electrode also demonstrated excellent electrochemical stability and a longer service life, maintaining a recovery yield of As(0) at 2.62 mg/cm2 even after 6 cycles. The reduction reaction mechanism of As(III) was ascribed to the synergistic effect of direct electrolysis and hydrogen radicals (·H) formation, as revealed by ESR and radical scavenger experimental results. This study not only provides convincing evidence for the direct electrochemical conversion of As(III) to As(0) on an innovative CuSn alloy electrode, but also offers a promising strategy to recover and reuse waste arsenic resources. This contributes to a sustainable and environmentally friendly approach to arsenic-containing wastewater treatment.