Study On Degradation Of Industrial Waste Water Of High Concentrations By Photocatalytic Oxidation

Since last decade, environmental pollution has been becoming more and more serious around the world. With the development of Nanometer preparation technology, nanometer TiO2catalyst has been a promising aspect in material science, catalysis chemistry or environmental science, and so on. Due to the high activity, well chemical stability, friendly protection in environment and many other virtues, nanometer TiO2has been widely used in organic pollutant degradation, waste water disposal, and air cleaning. Therefore photo-catalysis has been a promising environmental cleaning technique.According to the coprecipitation method and sol-gel method, the supported nanocomposite photocatalysts TixSn1-xO2/AC were synthesized and meanwhile the preparation conditions and application processes were successfully improved. Its photocatalytic activity on the degradation of acrylic acid with a high concentration of30000mg-L"1under UV light irradiation was studied. The best preparation conditions were as follows:active carbon as support, SnO2-dopped of15%, TiO2content rate with30%, calcination temperature at500℃, pH=2. In the conditions, the prepared catalyst showed the best photocatalysis activity. And the degradation rate of acrylic acid wastewater could reach up to93.3%under UV-light. The structures of photocatalyst were tested by XRD, and the characterization results proved the presence of anatase TiO2and TixSn1-xO2of substitution solid solution.SO42-was used for the surface modification of Fe2O3-TiO2/AC. The results indicated that:active carbon as support, Fe2O3-dopped of0.2%、1mol/L of sulfuric acid, TiO2content rate with25%、calcination temperature at500℃, pH3-4of the solution. In the conditions the prepared catalyst showed the best photocatalysis activity. Taking the dyeing waster (42000ppm) as the degradation material, we tested the catalyst activity, and found the degradation ratio reached to95.2%in10h under Vis-light. Because of catalyst’s special acidic structure, the photoelectron could accelerate the translation speed from the conduction band of the TiO2to the acidic center on the surface by the charge induction effect. The translation restrained the recombination of e" and h+, and increased visible light catalytic activity.The supported nanocomposite photocatalyst Fe2O3-TiO2-xNx/AC was prepared and the effects of composition and the preparation methods on the catalytic activity were sdudied. The best preparation conditions were as follows:(1) Active carbon as support,0.3mol/L of NH3H2O, Fe2O3-dopped of0.2%, TiO2content rate with25%、calcination temperature at500℃. In the conditions the prepared catalyst of the UV photo-catalyst showed the best photo-catalysis activity.(2) Active carbon as support,0.3mol/L of NH3·H2O, Fe2O3-dopped of0.2%, TiO2content rate with25%, calcination temperature at550℃. In the conditions the prepared catalyst of the visible light photo-catalyst shows the best photo-catalysis activity.According to the coprecipitation method and sol-gel method, the supported nanocomposite photocatalysts Fe2O3-TiO2-xNx/AC which could make effective use of sunlight were synthesized. The XRD results indicated that the nitrogen entered into the body of TiO2particle and replaced the lattice oxygen. Fe2O3were well-dispersed at the surface of the crystal particles in the forms of small clusters rather than independent crystalline phase. Photocatalysis activity of catalyst was observed in this paper. The results indicated:the concentration of sulfuric acid soaking, usage of catalyst and pH value of the solution would influence the photocatalysis effect. The results also indicated:when catalyst dosage, was12g·L-1and the solution pH was1-2, the catalyst shows the best photocatalytic activity and the degradation rate could reach98%.By common drying, vaccum refrigeration drying and SCFD drying, N-dopped TiO2with different particles could be prepared. The results obtained from XPS and IR testified:because nitrogen replaced the lattice oxygen, the width of forbidden band declined, and meanwhile the UV-light wave of the catalyst moved to the visible light (could reach to570nm). At the same time, the access of nitrogen made the oxygen-spaces increase, which increased the photo-catalytic activities greatly. The catalytic performance of the catalyst individually prepared by the three methods was equally better than that of P-25.