Physicochemical study of adsorption and photodegradation processes of methylene blue on copper-doped TiO2 films

Copper-doped TiO2 (Cu:TiO2) was synthesized by the sol-gel method. Likewise, studies with copper-impregnated TiO2 (TiO2/Cu imp) and undoped TiO2 were produced for comparative purposes. The Cu:TiO2 was subsequently characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), diffuse reflectance spectroscopy, total-reflection X-Ray fluorescence spectroscopy (TXRF), X-ray photoelectron spectroscopy (XPS), BET surface area analysis and a study of the formation of hydroxyl radical detected by monitor fluorescence emission spectrum. The physicochemical process of adsorption was analyzed by determining the time taken by Cu:TiO2 films to reach adsorption/desorption equilibrium at different concentrations of methylene blue (MB). A comparison of the isotherm was conducted using the mathematical models of Langmuir and Freundlich, and the best result was for the Freudlinch model. The photodegradation kinetics of three catalysts previously described in powder and film conditions was studied on the Langmuir-Hinshelwood pseudo-first order mathematical model. The best results were obtained by photodegradation of methylene blue on copper-doped TiO2 in powder or film form, degrading 42.6% and 25.1% of dye, respectively, under visible radiation at a time of 6 h.