| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 94 === In this study, titanium tetra-chloride (TiCl4) was used as precursor to prepare titanium dioxide powders by the process involves two stages: precipitating and peptizing. Firstly, white precipitates of amorphous oxide were produced from the precipitation reaction of TiOCl2 with sodium hydroxide. Then the precipitates were redispersed in aqueous solution of HNO3 at 90oC for peptizing. Tailored titania photocatalysts, which consist biphase titania with various phase compositions of anatase and rutile, can then be synthesized by controlling the concentration of HNO3. With increasing the nitric acid concentration from 0 to 0.5M, the titania crystalline changed from single phase anatase to single phase rutile. With further increasing nitric acid concentration from 0.5 to 4.0M, titania crystalline changed over from single phase rutile to single phase anatase. The reverse trend of crystalline phase formation with HNO3 concentration were explained by pH and nitric ion concentration , respectively. Furthermore, photocatalystic degradation of methylene blue by the synthesized tailored titania catalysts under UV illumination was systematically studied. A synergetic effect between the anatase and rutile particles is observed. The optimal composition of catalyst is found to be 82.6 wt% anatase. Moreover, photocatalystic performance of mechanically mixed biphase titania catalysts was also studied.
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