Fe3+-doped TiO2 nanopowders for photocatalytic mineralization of oxalic acid under solar light irradiation

Iron (III) doped TiO2 nanopowders were synthesized by solgel method starting from the concentrated alcoholic solutions of tetraethyl (TET) and tetraisopropyl (TIP) orthotitanate precursors. TET precursor leads to gel formation while TIP precursor conducted to powder generation. The optimized thermal treatments, derived from TG/DTA analysis, allowed the transformation of precursor powders and gels into crystalline powders with anatase structure, as determined by X-ray diffraction (XRD). Corroboration of XRD, FT-IR and Raman investigations lead to the conclusion that Fe3+ was introduced substitutionally into TiO2 matrix. TEM analysis revealed similar morphology for all prepared samples, consisting of nanometric particles. UV-vis spectroscopy evidenced that Fe3+ dispersed into TiO2 matrix shifts the optical bandgap to the visible range. The photocatalytic mineralization of oxalic acid over Iron (III) doped TiO2 nanopowders under simulated solar irradiation was studied to assess the application potential of these materials in depollution field. CO2 production was identified as main product of photocatalytic reaction. The CO2 output was proportional to the surface area of the photocatalysts. In mean time, the lower was the optical band-gap of tested materials the higher was the photocatalytic activity for mineralization of oxalic acid. Introduction of Fe3+ into TiO2 lattice leads to creation of optically active redox sites, able to absorb the visible component of solar light. A reaction mechanism was advanced based on experimental facts. The role of substitutional Fe3+ in mechanism of oxalic acid photomineralization was examined in relationship with generation of e(-) and h(+) charges and O-2(-) and (OH)-O-center dot radicals. The optimized preparation method, requiring lower amounts of reagents and milder synthesis conditions, lead to homogeneous Fe3+/TiO2 materials with promising potential for depollution applications. (C) 2017 Elsevier B.V. All rights reserved.