High catalytic oxidation of As(III) by molecular oxygen over Fe-loaded silicon carbide with MW activation

The catalytic oxidation of arsenite (As(III)) to arsenate (As(V)) and the removal of arsenic (As) in an iron loaded silicon carbide (Fe/SiC) system under microwave (MW) irradiation were studied. Fe/SiC was synthesized by electro-deposition and its capability of activating molecular oxygen was also characterized. Highly efficient As(III) removal in a wide pH range of 2.5-9.5 was achieved, involving oxidation by reactive oxidation species (OH and O2−) induced by MW irradiation and adsorption by the generated Fe (hrdro)oxide precipitates. Significant enhancement of As(III) oxidation was achieved at acidic pH, where sequential fresh Fe(0) exposure with MW irradiation could improve the Fenton-like reactions and oxidation efficiency for As(III). As(III) removal was accelerated via adsorption at alkaline conditions, where the adsorbed Fe(II) on Fe/SiC showed significant catalytic activity for molecular oxygen and high pH further favored the formation of (hydro)oxides and the As sequestration by adsorption. Fe/SiC showed superior performance for the treatment of As in water with MW irradiation.