Solar-Driven Arsenic(V) Transformation, Speciation, and Adsorption on the Chalcopyrite Surface

Understanding the dynamics of arsenic species (As(V) and As(III)) in water is crucial for mitigating their significant health risks. Here, we demonstrate the exceptional ability of chalcopyrite minerals to convert As(V) into As(III), and achieve 100% removal over a broad range of concentrations (0.005-50 mg/L). This unique process combines adsorption with photocatalytic redox reactions, where As(V) is first adsorbed on the mineral surface and then reduced to As(III) by photogenerated electrons. Density functional theory calculations reveal the "Cu(I)-Fe(III) redox-couple" within chalcopyrite as the key driver of this efficient photocatalysis. This redox-couple exhibits excellent light absorption and excitation dynamics, facilitating the rapid transfer of photogenerated electrons to the Fe site for As(V) reduction. This research unveils a previously unknown pathway for arsenic adsorbed and reduction in the natural environment, potentially impacting our comprehension of the global geochemical cycle of the toxic As element.