Flame sprayed visible light-active Fe-TiO2 for photomineralisation of oxalic acid

Visible light-active Fe-doped TiO2 was prepared by a one-step flame spray pyrolysis (FSP) technique. The properties of the photocatalysts were characterised by UV–vis diffuse-reflectance spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption (BET), transmission electron microscope (TEM) and zeta potential techniques. Being a bottom-up approach, the short residence time coupled with rapid quenching during FSP resulted in homogeneous Fe-doped TiO2 for Fe/Ti ratios approximately up to 0.05. This is five times higher than that reported for particles synthesised by conventional wet techniques followed by high temperature annealing. Under visible light irradiation (λ > 400 nm), the rate of oxalic acid mineralisation by Fe-doped TiO2 (Fe/Ti = 0.05) was 6.4 times higher than that of similarly prepared bare TiO2 and Degussa P25. A unique Fe-leaching and re-adsorption properties were observed during the reaction. Unlike the system of bare TiO2 spiked with dissolved Fe(III) ions, the FSP Fe-doped TiO2 photocatalyst was found to be stable and reusable after each run with minimal loss of Fe from the surface.