UV-induced photoactive adsorption mechanism of arsenite by anatase TiO2 with high surface hydroxyl group density

Abstract

Adsorption and photo-oxidation using anatase TiO2 is a promising technique for arsenite removal from aqueous solution. However, adsorption and photo-oxidation at the solid/liquid interface of TiO2 in aqueous suspensions is a complex reaction process. In this study, we use a simple and inexpensive synthesis method for this type of TiO2 and assess its arsenite adsorption and photo-oxidation performance. The prepared anatase TiO2 is rich in hydroxyl groups, with a hydroxyl concentration of approximately 12.84nm−2. Under irradiation with UV light, the adsorption capacity increases and the residual concentration of arsenic in the solution is lower than 10μgL−1. According to zeta potential, FTIR, and XPS analyses, the hydroxyl groups on the anatase TiO2 surface are responsible for arsenic adsorption. The effect of hydroxyl radicals is investigated through scavenger experiments, the results of which indicate that hydroxyl radicals play a key role in the oxidation of arsenite on anatase TiO2 under UV irradiation. The number of hydroxyl groups on the anatase TiO2 increases upon UV illumination, indicating that these are the photoactive species for arsenic adsorption.