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, N-2 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 m(2)/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 (lambda = 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 NS/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.

Automated summary

The N-S co-doped TiO2 photocatalyst was successfully prepared and showed enhanced photocatalytic activity compared to commercial TiO2 P25 under UV and visible light. It exhibited high removal efficiency of organic arsenic compounds and reduced effluent toxicity, demonstrating great potential for water treatment applications.