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

• A photo-enhanced removal of As(III) and Cu(II) was achieved. • As(III) removal was through a combination of photooxidation and coprecipation. • As(III) photooxidation relied on the formation of the Cu(II)–As(III) complex. • As(III) complexed with Cu(II) is photooxidized via direct electron transfer. • Procedures to realize the light-enhanced water's purification were proposed. 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) × 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. [ABSTRACT FROM AUTHOR]