TiO2 modifications by hydrothermal treatment and doping to improve its photocatalytic behaviour under visible light

Heterogeneous photocatalysis based on TiO2 materials is an interesting method for the treatment of polluted water because it allows degradation of a wide variety of organic contaminant compounds. The performance of TiO2 based photocatalysts was studied by aqueous solutions of methylene blue (MB) as a model contaminant compound by using 50 mg L−1 as initial water contaminant concentration in order to compare the photocatalytic behaviour of TiO2 Degussa P25 and some synthesized photocatalysts by hydrothermal treatment (nanostructured TiO2 and metal-doped nanostructured TiO2 photocatalysts: nanostructured Co–TiO2, nanostructured Fe–TiO2 and nanostructured Mn–TiO2) under UV and visible light irradiation. Photocatalytic materials characterization was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption, mercury porosimetry, XPS and diffuse reflectance UV–vis spectra. An improvement of the photocatalytic activity has been observed when nanostructured and doped photocatalysts were used under visible light irradiation, concluding that the hydrothermal treatment produces a nanostructuration of commercial titania by the formation of nanoparticles, which results in a large decrease of average crystallite size of undoped and doped titania, and in an important increase of BET specific area and total pore area.