| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 92 === In this study, we decompose the dichloromethane over The TiO2 and modified-Fe/TiO2 photocatalysts prepared by the sol-gel methods. We found that the photoactivity of the photocatalysts dried at 393 K for 24 hrs decrease with the ratio of Fe/Ti. The efficiency of the photocatalyst dropped significantly while the ratio of Fe/Ti was over 0.5 mol %. After calcining at 723 K for 4 hrs, the photocatalyst Fe/Ti=0.0005 mol% showed the higher photoactivity for the dichloromethane decomposition than that of TiO2.
The nitrogen-containedompound was detected through a FTIR in the case of the uncalcined photocatalyst. On the basis of this result, it was thought that the NO3- may act as the media to partake the photocatalytic reaction. No nitrogen-contained compounds were detected for the calcined photocatalyst in the FTIR patterns. Additionally, a significant amount of Cl2 gas was analyzed by a Cl2-analyzer during the photocatalytic experiment while no water was fed into the influent gases.
From the BET analysis, the surface area of the uncalcined photocatalyst decreased significantly. This may be due to that FeNO3•9H2O occupied the pores in the photocatalyst and cause low conversion. The formation temperatures of the anatase and rutile decreased with the ratio of Fe/Ti through the XRD and TGA analysis.
For the Fe/Ti=5 mol% photocatalysts, Fe2TiO5 may form at a high calcining temperature. After 24 hrs dried at 393K, the UV-Visible analysis indicated that the distinct absorption region was within the visible-wavelength and was attributed to FeNO3•9H2O, which is low/no photoactivity. However, after 4 hrs calcined at 723 K, the Fe/TiO2 photocatalysts resulted in a definite shift in the absorption spectra toward visible light regions.
In this study, we found the photoactivity decreased at high calcining temperatures and the presence of water resulted in decreasing conversion.
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