PROCESS FOR PREPARING A TITANE DIOXIDE PHOTOCATALYST AS A FILM OR POWDER AND PHOTOCATALYST OBTAINED THEREBY

The invention relates to a titanium dioxide photocatalyst and to a process for preparing the same, employed for purifying polluted water containing organic pollutants. According to the invention, the photocatalyst is presented as a thin nanostructured titanium dioxide film doped with 1.5...6% sulphur deposited on a soda-lime-silica glass carrier, at a coating thickness of 800 A, at the most, or as a powder at a crystallite size of 350 A, at the most, and has photocatalytic activity in the visible range. The process claimed by the invention consists in contacting, within a hydrolysis medium, a tetraethyl orthotitanate and thiourea solution in absolute ethyl alcohol, at a reaction temperature of 20...50°C for 60...120 min, at a pH value of 3...5. By concentrating the precipitate solution at 80°C, there is obtained the catalyst as powder. When it is made as a film, the hydrolysis process takes place in a closed system, under nitrogen atmosphere, in the presence of azotic acid catalyst; from the clear solution obtained, two film coats are deposited on the carrier by immersion, the second coat being applied after densification of the first coat at a temperature of 300°C.