Optimized removal of arsenate(III) by adaptation of oxidation and precipitation processes to the filtration step

Abstract

Processes for the removal of arsenic from water have been widely studied. Realizable and reliable concepts, however, exist only for the removal of inorganic arsenate(V). The question of how to optimize removal of arsenate(III) has not yet been addressed sufficiently. To improve this specific knowledge, the potential of coupled oxidation and precipitation processes to eliminate arsenate(III) was examined in pilot-scale experiments. Potassium permanganate and manganese dioxide coated quartz sand filter grains have been found to be highly effective agents for the oxidation of arsenate(III). Iron(II) in combination with oxygen proved to be comparable to iron(III) with respect to arsenate(V) binding capacity. The entire process can be optimized by selecting oxidation and precipitation agents with regard to the final filtration step. The best and most reliable of the investigated combinations was the coupling of manganese dioxide coated quartz sand for arsenate(III) oxidation with iron(II) / oxygen to bind the generated arsenate(V) molecules.