A novel removal strategy for copper and arsenic by photooxidation coupled with coprecipitation: Performance and mechanism

Arsenic and copper causing water pollution is a worldwide problem, and simultaneously achieving water decontamination from arsenic and copper is immensely attractive. In this study, an economical and eco-friendly light-enhanced removal system was proposed to simultaneously alleviate water contamination from arsenic and copper, where nascent copper hydroxides (CHO) acted as nano-absorbers and electron acceptors for As(III) removal. According to the mechanism studies, the nascent CHO effectively capture As(III) forming surface Cu (II)-As(III) complex (formation constant, log K-f1 = 6.0). Then, light induced the ligand-to-metal charge transfer (LMCT) from As(III) to Cu(II) inside the Cu(II)-As(III) complex, thus leading to both As(III) oxidation and Cu(II) reduction under anoxic conditions. The quantum yield of As(III) photooxidation at 365 nm was ascertained as (2.3 +/- 0.2) x 10(-2). The final photoproducts can be easily recycled as stabilized Cu(II)-As(V) complex and deposit. Real sunlight-driven photooxidation of As(III) in the presence of CHO and As(III) photooxidation to As (V) in solid Cu(II)-As(III) complex were also confirmed, which implying the promising application in practical water treatment. Accordingly, the oxygen-independent and light-enhanced removal of arsenic and copper can help develop recovery strategies for copper and arsenic.