Synergistic activation of sulfite for As(III) oxidation by basic copper(II) carbonate in homogeneous and heterogeneous processes at near-neutral conditions

Arsenic is categorized as a class I carcinogen due to its strong biological toxicity. In this study, a novel treatment process with Cu 2 (OH) 2 CO 3 as catalyst is proposed, whereby As(III) in water is oxidized by activating sulfite to generate SO 4 − and SO 5 − radicals. Under conditions of [Cu 2 (OH) 2 CO 3 ] 0  = 0.01 g·L −1 , [sulfite] 0  = 0.3 mmol·L −1 , and initial pH 8.0, 94% of As(III) was converted into As(V) within 20 min, whereby dissolved oxygen had a pivotal impact on the reaction. However, HCO 3 − , humic acid, and fulvic acid all significantly inhibited the oxidation. Heterogeneous electron transfer on the catalyst surface and homogeneous dissolved Cu 2+ jointly activated sulfite in the Cu 2 (OH) 2 CO 3 /sulfite system, with the heterogeneous process predominating. Density functional theory (DFT) calculations disclose a dominate physical adsorption of sulfite on Cu 2 (OH) 2 CO 3 surface with 1.74 electrons transferred. >90% of As(III) was still oxidized after recycling the material five times, indicating excellent reusability. Overall, it shows good potential for application in the removal of As(III) from real water samples.