The study of preparing and modifying circular tube TiO2 thin film and degradation of dichlorophenol photocatalysis

• Main Authors: Chin-Chuan Liu, 劉謹銓
• Other Authors: 謝永旭
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/54045718243999828160

博士 === 國立中興大學 === 環境工程學系所 === 96 === The study include of three parts: (1). Using Taguchi method to investigate the preparation of titanium dioxide thin film by chemical vapor deposition method (CVD); (2). Photocatalysis of dichlorophenol by previous reactor and discussion of reaction character and intermediates; (3).Platinum and silver modify the photocatalyst by photoreduction deposition. The first part of experiments discussed the salicylic acid conversion efficiency with the different preparing parameters by chemical vapor deposition (CVD) method. The results indicated that the optimum preparing parameters for TiO2 photocatalysis were carrier gas flow rate = 550 ml/min, oxidation/calcinations temperature = 400℃/550℃, rotating speed of furnace = 20 rpm. Among the parameters, carrier gas flow rate and oxidation/calcination temperature were significant in salicylate conversion. The result of directly photolysis (only 365nm UV without photocatalyst) showed obvious degradation and dechlorolation of dichlorophenol at higher pH. To compare HPLC diagrams, kinds of the intermediate are similar at different pH. The quantities of intermediates increase with pH rising and form spices that are broken 2 chlorine. The result of photocatalysis show that degradation of dichlorophenol is best at pH=10. Photocatalysis degradation at pH=4 and pH=7 are similar, but higher ratio of low molecular acids at pH=7 and most intermediates at pH=4 are aromatic spices. We inferred that the high pH have advantage of hydroxyl radical production and break aromatic structure of primary intermediates. Although different reacting pathway of hydroxyl radial, chlorohydroquinone, was all identified in 2,3-DCP, 2,5-DCP and 3,4-DCP photocatalysis. It was found that the dechlorination intermediate, like phenoxyl product, would rechlorinate again. This was supported by the identified intermediate products: 2,6-DCP from 3,4-DCP and 3,4-DCP from 2,3-DCP. The third part of experiments discussed the conversion effect of salicylic acid with different modifying parameters including the concentration of metal, irradiation intensity and irradiation time by photoreduction deposition method. The results indicated that the optimum preparing parameters for Ag/TiO2 photocatalyst were 1.5mM Ag+, for Pt/TiO2 photocatalyst were 8 hrs irradiation time. Among the parameters, irradiation time was not important in Ag/TiO2 process, and the concentration of metal was not important in Pt/TiO2 process. By the results of XRD, SEM-EDS and ESCA could confirm that modified Ag and Pt on TiO2 thin film wouldn’t change the TiO2 crystal type (Anatase). The enhanced photoactivity of Ag/TiO2 and Pt/TiO2 compared to TiO2 under experimental results suggested that loaded Ag and Pt on TiO2 thin film are feasible.