Reverse Microemulsion Preparation Of Tio2 And Its Properties

This dissertation studied the preparation, characterization of nanometer sized TiO2 and its uv-vis absorption and photocatalytic properties. The precusor of nanometer sized TiO2 was prepared in the water-in-oil microemulsion, which was characterized for the structure, morphology, particle size and size distribution etc. Uv-vis absorption properties of nanometer sized TiO2 were studied. And the degradations of methylene blue by use of nanometer sized TiO2 or the loaded TiO2 as photocatalysts also were studied.The water-in-oil microemulsion was chosen, which consisted of Triton X-100/hexanol/cyclohexane/water. The size and distribution of water-cell in water-in-oil microemulsion was investigated by laser scattering technology. It can be shown from experimental results that the diameter of the droplet is between 5.5 nm and 8.8 nm and the average diameter is 7.0 nm when the water-to-surfactant molar ratio is 6.1. The experiment showed that the water-to-surfactant molar ratio (w=[H2O]/[surfactant]) was the predominant factor to the particle size of TiO2 and the concentration of titanium butoxide was in the next place. As the value of w increased, the average particle size of TiO2 increased subsequently. The relation between the average particle size (D) and the value of w could be shown: D=5.60+2.40w. On the other hand, the effect of titanium butoxide was complex. As the concentration of titanium butoxide increased from 0.120 molkg-1to 0.246 molkg"1, the TiO2 particle size decreased firstly and increased subsequently. TEM showed that the prepared titania particles with diameter in the range of 10-30 nm had narrow distribution and light agglomeration. The increase of the water-to-surfactant molar ratio in water-in-oil microemulsion had an obvious influence on conglomeration of titania nanoparticles. Besides, it was shown in DTA graph that anatase phase had transformed to rutile phase gradually and in the infrared spectrum that absorption peak obviously had broadened and moved to long wave.Uv-vis absorption results showed that nanometer sized TiO2 suspensions could intensively absorb ultraviolet light (190-400 nm), especially when its mass fractionwas beyond 0.075%. On the other hand, nanometer sized TiO2 suspensions' absorbability to visible light was appreciably lower than ordinary TiO2 suspensions.This dissertation finally studied the degradations of methylene blue by use of nanometer sized TiOi or the loaded TiOi supported by molecular sieve MCM41 and silica gel respectively as photocatalysts. Nanometer sized TiOi showed high photocatalytic activity. But the loaded TiOa catalysts showed higher photocatalytic activity than nanometer sized TiO2. Then, the mechanism and rate constant(k) of the photocatalytic degradation of the methylene blue solution were investigated.