Efficient As(III) removal by magnetic CuO-Fe3O4 nanoparticles through photo-oxidation and adsorption under light irradiation.

A novel bifunctional CuO-Fe3O4 magnetic material was synthesized and characterized, to remove As(III) through photo-oxidation and adsorption. Photo-oxidation of As(III), adsorption characteristics of CuO-Fe3O4 nanoparticles, the effect of solution pH, ionic strength and coexisting ions on As(III) removal were investigated. Under light irradiation, As(III) could be completely oxidized to less toxic As(V) by CuO-Fe3O4 nanoparticles within 60min in the photo-oxidation reaction. Simultaneously, As(V) could be adsorbed onto the surface of nanoparticles with high efficiency. The adsorption of As(V) was well fitted by the pseudo-second-order model and the Freundlich isotherm model, respectively, and the maximum adsorption capacities of the nanoparticles was 118.11mg/g at pH 7.0. As(III) could be effectively removed by CuO-Fe3O4 nanoparticles at initial pH range from 4 to 8. Among all the common coexisting ions investigated, except for chloride and sulfate, carbonate, silicate and phosphate decreased the As(III) removal by competing with arsenic species for adsorption sites. The synthesized magnetic CuO-Fe3O4 combined the photocatalytic property of CuO and the high adsorption capacity of both CuO and Fe3O4, which make it have significant potential applications in the arsenic wastewater treatment.