Preparation Of Nano-TiO₂ Thin Film And Study On Coupled Photocatalysis For Nitrogen Removal

The photocatalytic oxidation technique of TiO₂ has been paid more and more attention for the advantages of less energy cost, mild reaction condition, easy operation and less secondary pollution, so it is abroad researched in the field of environment pollution control now. Aiming at the actuality of disadvantages of TiO₂ powder, difficult to be separated effectively, and easy to deposit and agglomerate, preparation process of nanosized TiO₂ thin film is studied, and the firm TiCVglass thin films with anatase nano-crystalline have been prepared by the sol-gel processing using tetrabutyl titanate as a precursor in this paper. On this basis, using ultraviolet germicidal lamp with main wavelength of 253.7 run as light source, the oxidation and reduction effect for nitrogen removal in water is studied under the treatment of fixed nanosized TiO₂ photocatalytic reactor, and the mechanism of photocatalytic nitrogen removal is described. Moreover, the photocatalyst will be modified in order to enhance the photocatalytic capability of TiO₂, Ag is photocatalytically deposited on the TiO₂ thin film and the Nitrogen is doped into TiO₂. Finally, the nanosized TiO₂ which loaded on the fiberglass cloth also is attempted.The main results show, the nanosized TiO₂ semiconductor photocatalyst can be obtained, by the sol-gel processing using tetrabutyl titanate as a precursor. The reaction condition is easy to control and the process is stable, thus the distribution uniformity can reach molecule level, and highly quality sol and gel can be acquired, and obtain the nanosized particles. Surface appearance and particle size of TiO₂ crystal can be obtained by SEM, TEM analysis, and they can be controlled by optimizing reaction conditions. TiO₂ prepared in this experiment is anatase, and the average size of TiO₂ particles in the thin film is 10²0nm. The oxidation and reduction capability of the thin film have been studied comprehensively from some important factors of the photocatalytic nitrogen removal in the reaction, such as the initial concentration of nitrogenous compounds, N₂ flow rate, thin film thickness, pH value and so on. After the irradiation about 2 hours, the removal of TN in the photocatalytic reaction is more than 50%.The modified methods which photocatalytically deposit Ag on the TiO₂ thin film and mix the nitrogen into TiO₂ can prevent the recombination of photo-induced electrons and holes, besides enlarge the responding area of TiO₂ to visible light area, and enhance the photocatalytic capability of TiO₂, so the availability of solar energy becomes bigger. In addition, the result of the experimentwith the fiberglass shows, the transmissivity is better, the fiberglass is easy to be made into film and processed to some shapes, and it is convenient for application.