Fig. 1

Kinetics of As(III) oxidation on CuO NPs surface at pH 6 (a), pH 9 (b), and pH 11 (c) in the open system, and pH 11 in the N₂ atmosphere (d). These figures showed the concentration distribution of As(III) and As(V) species in solution, on CuO NPs surface, and total oxidized As(III) amount during the As(III) oxidation reaction