Improved visible-light activity for oxidative discolouration of methyl orange by TiO2/thiourea photocatalyst prepared via ball-milling/low thermal treatment

In this work, it is demonstrated that visible-light photocatalytic activity for degrading methyl orange (MO) could be improved by co-milling of TiO2 (Degussa P25) with thiourea. The photocatalysts have been prepared by combined mechanochemical/thermal synthesis. Structures and morphology of the as-prepared TiO2 nanoparticles were characterized by X-ray powder diffraction, N2 adsorption–desorption isotherms, UV‒Vis diffuse reflectance spectroscopy and scanning electron microscopy. It is shown that co-milling of TiO2 with thiourea favours formation of brookite phase and it results in the occurrence of more porous structures. The optical properties are modified and the band gap energy values of the samples become smaller, when thiourea is introduced. Ball-milled samples show better photocatalytic activities during oxidative discolouration of MO than that of the initial TiO2. The discolouration degree is above 99% for ball-milled TiO2/thiuourea nanoparticles, while it is 2% for pure and 15% for ball-milled TiO2.