UV-assisted Catalytic Wet Peroxide Oxidation and adsorption as efficient process for arsenic removal in groundwater

Abstract

Arsenic is a toxic and carcinogenic element present in groundwater as arsenite, As(III) and/or arsenate, As(V), due to natural lixiviation or because of anthropogenic activities. The World Health Organization threshold in drinking water is 10 μg/L, well below the concentration found in the water resources of numerous populations, as in the Duero basin (Spain). As(V) can be easily removed by adsorption onto iron-based adsorbents, whereas As(III) is harder to remove. Therefore, in this work we propose the use of ilmenite (FeTiO3), a low-cost catalyst, as both photocatalyst and adsorbent in the UV-A assisted Catalytic Wet Peroxide Oxidation process. The main aim of this technology is to oxidize arsenite into arsenate, for its subsequent adsorption onto the Fe sites of the catalyst. This technology has proven to be effective for the oxidation and removal of 10 mg/L As(III) working at 1000 mg/L ilmenite, 60 mg/L H2O2, 0, pH0: 7 and room temperature (25 °C), in both ultrapure water and groundwater collected from Lastras de Cuéllar (Segovia, Spain). Furthermore, we propose a complete kinetic model which comprises the H2O2 decomposition, As(III) oxidation and As(V) adsorption, which is in agreement with the experimental data.