| In recent years, the heterogeneous photocatalysis for the degradation of organic pollutants using nano-TiO2 semiconductors has been extensively studied in environmental science. The photocatalytic degradation technique has many advantages, such as operating under ambient temperature and normal pressure, decomposing organic pollutants completely without second pollution. Except for those advantages, nano-TiO2 powders have some deficiencies, so it is necessary to modify TiO2 by the adulteration to improve their photocatalytic activity.The pure and Ce doped TiO2 nanoparticles were prepared by a sol-gel method with Ti(0Bu)4 as raw material, HAc as complexagent and alcohol as the solvent, and characterized by XRD and UV-VIS. Influence of roasting temperature on the crystal phase composition, the particle size and the catalytic activity was also researched. In addition, the phase transition of the TiO2 powder was studied in the roasting process. The photocatalytic activities of the prepared samples and the effect of doped Ce content on activities were investigated by the degradation reaction of methylene blue under the sunlight.The results showed the doped Ce could greatly restrain the increase of crystallite size and the change of crystal phase of TiO2 in high calcinations temperature from anatase phase to rutile phase, and it also can extend the light response of TiO2 nanoparticlcs to the visible region. The concentration of the doped Ce and calcination temperature showed remarkable effect to photodegradation. When the concentration of the Ce dopant was 0.5% and the calcination temperature was 800℃, prepared composition photocatalyst showed highest catalytic activity to methylene blue degradation.To improve further the degradation efficiency to methylene blue, the photocatalytic degradation of TiO2 combined with other advanced oxidation technology - ultrasonic wave irradiation and contact glow discharge electrolysis was studied. A variety of affecting factors on ultrasonic degradation of methylene blue in the presence of sol-gel nano TiO2 were studied. The results indicated that the degradation efficiency of methylene blue rose with the rise of reaction time. The initial pH of reaction solution had little influence to the degradationefficiency, but in alkali solution, methylene blue degraded easier than in acid or neutral solution. The degradation efficiency of methylene blue reached up to 92% in 60min when ultrasonic frequency was 40KHz, power input was 50W, amount of the catalyst 450～500mg/L, pH=8.0 and the initial dye concentration was 20mg/L.In the test of the degradation of methylene blue with nano-TiO2 film combining with contact glow discharge electrolysis, it was found that when the number of layers is 5, the photocatalytic activity is highest. The developed new method can degrade methylene blue more efficiently. And the composition catalyst had long using life and could be used repetitiously. |
