貴金屬提高二氧化鈦對五氯酚光催化效應之研究

Effect of Precious Metals on the TiO2 Photocatalysis of Pentachlorophenol

曾聖倫(Sheng-Lun Tseng) ； 林耀堅(Yaw-Jian Lin) ； 吳梅芳(Mei-Fang Wu)

《界面科學會誌》 27卷1期 (2005/03) Pp. 17-24

https://doi.org/10.30020/JCCIS.200503.0002

摘要

五氯酚（pentachlorophenol, PCP）為人工合成物質，因具穩定的環狀結構、生物累積性及強烈的生物毒性，當濃度達0.6 mg/L 時，可造成多種生物的死亡。此外氯酚類亦為疑似環境賀爾蒙化合物，故被美國環保署列為毒性物質。二氧化鈦具有強氧化力、光穩定性、非毒性和價格低廉，故常用於處理難分解有機污染物，但因電子-電洞對的再結合使反應速率受到影響，因此本研究目的為添加貴金屬於二氧化鈦系統中，以遲緩電子-電洞的再結合而提高光催化反應速率。此試驗將TiCl4以溶膠凝膠法製備TiO2後（粒徑20~46 nm），添加1.0 wt%的貴金屬探討不同光源（自然日光、氙燈及紫外光燈）對五氯酚降解之影響，結果顯示自然日光為效果最佳之光源，因其具高光強度，並且證實添加貴金屬（Au、Ag、Pt 及Cu）於TiO2中可增進可見光的吸收（表面積：56~86 m^2/g）。對五氯酚的降解作用以添加貴金屬的TiO2速率比純TiO2佳，因貴金屬能捕捉電子而延遲電子電洞對再結合，有助於可見光的吸收亦幫助觸媒的活性。光催化反應過程中﹝Cl^-﹞濃度隨著光照時間的增加而增加，而五氯酚濃度相對隨光照時間增加而降低，顯示脫氯作用為五氯酚降解途徑之一。隨光照時間增加，五氯酚溶液之TOC濃度降低，顯示五氯酚及其產物經異相光催化後可迅速分解。

關鍵字

貴金屬 ； 五氯酚 ； 光催化 ； 二氧化鈦 ； 電子-電洞對

並列摘要

Pentachlorophenol (PCP) is a man-made synthesized compound. Due to its high stability of aromatic structure, it is not easily biodegradable. When the concentration of PCP reaches 0.6 ppm, it could be harmful to many organisms. Chlorophenol could be a compound of the environmental endocrine, so it is listed as one of the toxic materials by the US EPA. TiO2 has been characterized and used as a strong oxidant. Because of its photo-stability, non-toxic, and low price, it is used for the degradation of organic pollutants. The recombination of electron-electron hole pairs on TiO2 can reduce the reaction rates of photocatalysis. The purpose of this study is to use precious metals to enhance the TiO2 photocatalytic systems. TiO2 with the precious metals (1.0 wt%) was prepared by TiCl4 using a sol gel. Different light sources (solar, xenon lamp and UV lights) were compared. The result showed that solar light was the most effective light source. Its luminous intensity was also the highest. It also verified indirectly that the precious metals can promote the absorption of visible light on TiO2. The degradation of pentachlorophenol was faster using the precious metals than that without TiO2. It is becaused that the recombination of electron and electric hole was reduced. It helped the catalyst to absorb more of the visible light. The concentrations of Cl^- were increased with the extension of exposure time. The concentrations of pentachlorophenol were decreased with the increase of exposure time. The concentrations of TOC were detected in the same way. This concluded that photocatalysis of PCP was effective to reduce the toxicity of PCP contaminated samples.

並列關鍵字

Precious Metals ； Pentachlorophenol ； Photocatalysis ； Titanium Dioxide ； Electron-hole Pair