Preparation of TiO2 coatings and their photocatalytic activities

Titanium dioxide powders were obtained by the homogeneous precipitation technique by using two different titanium precursors, namely, titanium (IV) butoxide and titanium (IV) isopropoxide. The solution was prepared by mixing the Ti precursors in methanol, after that, acetic and sulfuric acid were slowly added. The solution was kept under constant magnetic stirring until obtaining a white precipitate. The white precipitate was centrifuged and dried and thermally annealed at 650 degrees C for 6 h, giving rise to TiO2 powders. From these powders a homogeneous fluid paste, by using a mixture of water and lactic acid, was prepared. Finally, from this paste, glass substrates were coated by using the Doctor Blade technique. The resultant coatings were annealed at 350 and 450 degrees C for 3h. The photocatalytic activity of the coatings were tested by the degradation of both aniline blue (AB) and methylene blue (MB) solutions, under UV light. The degradation efficiency was monitored by UV-vis spectrophotometry. The TiO2 powders were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The anatase phase was confirmed by XRD. The particles showed a round morphology, presenting smaller particle size in the samples processed from the butoxide precursor. The samples prepared from butoxide showed a better methylene blue degradation and samples prepared from isopropoxide presented the best aniline blue degradation.