N-S co-doped TiO2 synthesized by microwave precipitation method: Effective photocatalytic performance for the removal of organoarsenic compounds

The N-S co-doped TiO2 (N-S/TiO2) photocatalyst was successfully prepared by microwave precipitation method using titanium oxysulfate and urea precursors. The material was characterized by XRD, UV-Vis diffuse reflectance spectroscopy, FTIR, SEM, TEM, N2 physisorption, elemental chemical analysis, photoluminescence (PL), and zetametry. The removal of p-arsanilic acid (p-ASA), and roxarsone (ROX) solution in a mixture at pH 9 under UV light (365 nm) evaluated the photocatalytic activity of N-S/ TiO2. The commercial TiO2 P25 was additionally assessed for comparative purposes. The N-S/TiO2 showed the anatase crystalline phase, mesoporous structure, and surface area of 27.1 m2/g. The N-S/TiO2 material presented surface hydroxyl groups, adsorbed NH3 species, and N and S impurities incorporated in an interstitial and substitutional way, respectively (0.54 and 6.74 wt. %). The non-metals doping into TiO2 extended the absorption spectra towards the visible region (λ = 409 nm) and produced defects that improved the adsorption and photocatalytic properties of the prepared catalyst. The N-S/TiO2 material exhibited a significantly enhanced activity than pure TiO2 P25 under UV and visible light. The N-S/TiO2 material resulted in the highest photocatalytic activity allowing the complete removal of p-ASA, and ROX species, 67% mineralization, and simultaneous adsorption of released inorganic arsenic (AsO43-, 96.2%) within 240 min. A decrease in the toxicity of the effluent evaluated by the in vitro Vibrio fischeri toxicity test was observed (13%) at the end of the reaction compared with its initial value (25%), evidencing the potential application of the photocatalytic treatment using N-S/TiO2 catalyst in the removal of phenylated arsenic compounds. [Display omitted] •N-S/TiO2 was successfully prepared by microwave precipitation method using titanium oxysulfate and urea precursors.•Surface hydroxyl groups and interstitial and substitutional impurities of N and S enhanced the N-S/TiO2 activity.•N-S/TiO2 showed enhanced photocatalytic activity under UV and visible light.•N-S/TiO2 catalyst allowed simultaneous photocatalytic removal of organoarsenic and adsorption of released inorganic As.