Adsorption and Reactions of Trihalomethane and Nitrobenzene on Powdered TiO2

• Main Authors: Meng-Tso Chen, 陳孟佐
• Other Authors: Jong-Liang Lin
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/31923690371172792909

碩士 === 國立成功大學 === 化學系碩博士班 === 91 === The adsorption and reactions of CHBr3, CHCl3 and C6H5NO2 on powdered TiO2 have been investigated by Fourier transform infrared spectroscopy. CHBr3 is adsorbed molecularly or dissociatively to form HCOO(a), (-OCHBr2), or (-OCHBrO-) at 35oC. Surface CHBr3 desorbs or decomposes into HCOO(a) more in vacuum at ~150oC. As TiO2 in contact with gaseous CHBr3 is heated in a closed cell, CO(g) and HBr(g) are detected. In the case of CHBr3(a) photodecomposition in the presence of O2, CO2(g), and HCOO(a) are generated. But CHBr3(a) photoreaction is almost terminated in the absence of O2. At 35oC, CHCl3 is adsorbed molecularly or dissociately to form CO(a), HCOO(a), (-OCHCl2), or (-OCHClO-). As temperature is raised above 150 oC, the absorbed CHCl3 is desorbed or transformed into HCOO(a) more. As TiO2 in contact with gaseous CHCl3 is heated in a closed cell, HCl from Cl(a) and OH(a) recombination, CO from CHCl3 or HCOO(a) decomposition are generated. Under UV irradiation in the presence of O2, adsorbed CHCl3 on TiO2 decomposes to form CO2(g) and HCOO(a). The CHCl3 photoreaction is terminated in the absence of O2. C6H5NO2 is adsorbed in a end-on geometry on TiO2 surface, with an interaction of the nitro-group with the Ti4+ ions or OH group at 35oC. As the TiO2 surface is heated to 400 oC, the infrared absorptions suggests the formation of azoxybenzene (C6H5N=NC6H5), nitrosobenzene(C6H5NO), or phenoxy group(C6H5O). Adsorbed C6H5NO2 decomposes to form CO(a), H2O(a), and carbonate(CO3) or NOx- under UV irradiation in O2. The photocomposition is accelerated with addition of H2O.