利用含碳二氧化鈦光催去除微量氣態元素汞之研究

Photocatalytic Removal of Low-Concentration Elemental Mercury with Carbon-Doped TiO2

潘郁采(Yu-Tsai Pan)

指導教授 ： 席行正

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2013年)

https://doi.org/10.6841/NTUT.2013.00385

摘要

由於汞具生物累積性、於自然界中具有持久性，且能於大氣中進行廣泛傳輸，故汞物質的排放受到全球性的關注與重視。二氧化鈦 (TiO2) 光觸媒為能氧化與吸附元素汞的一種新興方法。本研究以含浸法 (impregnation) 製備以碳覆載於100％銳鈦礦晶相之二氧化鈦 (Ishihara, ST-01 TiO2) 合成C-TiO2，且藉由SEM、TEM、BET、FTIR與XPS分析觸媒改質前後之特性。並探討於不同氧氣、水分、光線種類及反應溫度之實驗條件下，比較改質前後觸媒對氣態元素汞吸附去除效率之差異，並探討單一煙道氣體對汞之吸附及氧化之影響。
由SEM與TEM之結果可觀察到TiO2與C-TiO2之粉末粒徑與晶相結構並無明顯改變；但由於C-TiO2經碳摻雜故其比表面積下降，而平均孔徑與總孔體積也略微減少；而FTIR與XPS之數據也進一步證明C-TiO2具含碳官能基團於表面。
光催化實驗結果部分，其改質與未改質觸媒無論於何時驗條件下，於紫外光的照射下，皆有吸附效果。而氧氣濃度的增加其吸附效率也隨之增加，在25℃，21% O2、水氣及可見光下，由於氧氣暴露時間增加以及水氣的加入TiO2與C-TiO2之吸附效率可分別達到51.5%及51.6%。然而於溫度愈高兩種觸媒之吸附效率也愈趨下降，脫附率也逐漸上升，於100℃下，21% O2、水氣、照紫外光下TiO2與C-TiO2吸附效率仍分別可達到33.9%、31.8%。而由於C-TiO2表面具含碳官能基的形成，具疏水性且與汞鍵結較強，故不易受溫度上升而脫附，能提高對水氣之抵抗性。
常溫下，模擬單點煙道氣體 (NO, SO2 and HCl) 實驗之結果顯示，由於煙道氣體與汞之會於觸媒表面之吸附位置產生競爭吸附的效應，故其吸附效率均不高；且因煙道氣體的影響使得氧化汞效率上升，在SO2與HCl時尤其明顯。

關鍵字

元素氣態汞 ； 含碳二氧化鈦 ； 吸附效率 ； 氧化汞出流率

並列摘要

Mercury emissions are of global concern because of their persistence, bioaccumulation in ecosystems, and their neurotoxic impact on human health. TiO2 photocatalysis is a novel method for elemental mercury oxidation/removal. A carbon-doped titania photocatalyst was prepared via impregnation using Ishihara ST-01 TiO2 powder (100% anatase) as the raw material and ethanol as the carbon source. The raw and carbon-doped TiO2 samples were characterized with SEM, TEM, XRD, FTIR, XPS, and N2 adsorption. The removal efficiency of gaseous Hg0 at ppb level using TiO2 and C-TiO2 was evaluated under various conditions. The SEM and TEM test results indicated that the raw and C-doped ST-01 TiO2 was in similarly globular shape, with a size of 20-30 nm. The FTIR and XPS examinations further suggested the presence of carbon functional groups on the C-TiO2 surface. The N2 adsorption isotherms suggested that carbon doping on the TiO2 surface caused a slight decrease in BET surface area, average pore size, and total pore volume.
The Hg0 removal increased with increasing oxygen concentration. Under UV irradiation, both catalysts showed appreciated photocatalytic removal of Hg0. The optimal removal efficiencies of TiO2 and C-TiO2 at 25℃, 21% O2, humid condition, and VL irridation were 51.5% and 51.6%, respectively. The Hg0 adsorption efficiency decreased and the desorption rate increased with increasing test temperature. Nevertheless, at 100℃, 21% O2, humid condition, and UV irradiation, the Hg0 removal efficiency of raw TiO2 and C-TiO2 reached 33.9% and 31.8%, respectively. Due to the carbon function groups on the C-TiO2 surface, the hydrophilicity of TiO2 surface appears to decrease, causing less adsorption competition from H2O for Hg0 adsorption at higer temperature. The presence of flue gas components including NO, SO2, and HCl reduced the Hg0 adsorption, indicating that the active sites on the catalysts surface were occupied by the flue gas components.

並列關鍵字

Carbon-doped TiO2 ； photocatalysis ； elemental mercury ； mercury adsorption efficiency ； mercury oxidation efficiency

參考文獻

95. 黃竣鴻，以鉑、碳對二氧化鈦改質之可見光降解氮氧化合物研究及鑑定分析，博士論文，國立清華大學化學工程研究所，新竹，2010。

4. 李淑莉，臺灣地區燃煤發電廠含汞物質流布與管理之研究，碩士論文，國立臺北科技大學環境工程與管理研究所，臺北，2008。

80. 粘聖宏、席行正、陳孝行，「奈米級含氮二氧化鈦應用於微量元素汞蒸氣去除之研究」，第19屆國際氣膠科技研討會暨細懸浮微粒 (PM2.5) 管制策略研討會，臺中，2012，第191-194頁。

2010，第68-77頁。

5. P. Holmes, K.A.F. James, L.S. Levy, “Is low-level environmental mercury exposure of concern to human health?,” Science of the Total Environment, vol. 408, 2009, pp. 171-182.