Of Tio <sub> 2 </ Sub> Photocatalysts Doped And The Degradation Of The Dye Wastewater

As a new environment-purifying technique, the photocatalysis decomposition technology is paid more attention while environment pollution is being more and more serious. Heterogeneous photocatalysis by semiconductors has unique advantages in water pollution control, especially in the treatment of wastewater containing poisonous organic compounds which are difficult to destroy.In this thesis, using the tetra-n-butyl titauate as main raw material, the TiO₂ and the TiO₂ doped with metal ions were prepared with the sol-gel hydrolytic method. The catalysts were characterized by means of BET area (BET), transmission election microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and solid ultraviolet absorbance spectroscopy. On this basis, using ultraviolet lamp with main wavelength of 254nm as light source, the contaminants removal efficiency in methyl orange was studied under the treatment of suspended TiO₂ and suspended TiO₂ doped with metal ions. Influences of several factors such as preparation conditions and doped metal ions were studied respectively. The kinetics of methyl orange decomposition was investigated under the treatment of suspended Cr-TiO₂ catalyst.The influencing factors, such as pH value, amount of water, solvent and calcination temperature, for the TiO₂ preparation were studied respectively. The optimal conditions for TiO₂ preparation were pH 3.0, 8.0mL water, 20.0mL ethanol and 550℃ calcination temperature. The average semi-diameter of the TiO₂ particles was 11.0nm and it was composed by anatase (22.7%) and rutile (77.3%). The catalytic decomposition rate of methyl orange with 10.0mg/L initial concentration was up to 94.4% after 10 hours by the TiO₂ catalyst.The transform temperature of anatase to rutile was changed when the TiO₂ was doped with different metal ion and the catalytic activity was also changed. The results showed that the catalytic activity order was Zn²⁺ (2.0 wt%) > Cr⁶⁺ (3.0 wt%) > Zr⁴⁺ (3.0 wt%) > Ni²⁺ (5.0 wt%) > Cu²⁺ (1.0 wt%) > Fe³⁺ (3.0 wt%) > Co²⁺ (1.0 wt%) . The reason that the TiO₂ doped with 2.0 w/% Zn²⁺ showed higher activity may be the Zn²⁺ enter in the TiO₂ crystal.The wavelength of ray absorbed by the TiO₂ doped with 3.0 wt% Cr⁶⁺ shifted from 387.5nm to 705.0nm. The influencing factors, such as amount of Cr⁶⁺, amount of acid and calcination temperature, for the Cr-TiO₂ preparation were studied respectively. The optimal conditions for Cr-TiO₂ preparation were 3.4w/% Cr⁶⁺,...