選擇性光催化氧化水中氨氮為氮氣之研究

Selective Photocatalytic Oxidation of Ammonia to Nitrogen on Metal/TiO2 in Water

楊鈞期(Chun-Chi Yang)

指導教授 ： 駱尚廉

國立臺灣大學/工學院/環境工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.02497

摘要

本研究以光催化法氧化水中氨氮，光源為365 nm之UV光，催化劑為陽極氧化法製備之奈米鈦管與商用的二氧化鈦；此外，亦利用光沉積法披覆鉑金屬於奈米鈦管表面，以及在二氧化鈦上披覆鈀、鉑、金和銅等四種金屬，使氨氮氧化速率提高，且促使氨氮氧化為氮氣；並進一步探討在不同條件下的反應活性、中間產物、最終產物濃度和氮氣產率，以決定最佳氮氣產率之條件。
研究結果為：（1）由背景實驗得知，氨氮不會吸收波長365 nm之UV光而直接光解，且在pH值為10.5時有15.9 %的氨氮逸散，pH值為9.5則為9.3 %；（2）自製奈米鈦管之內徑約20 ~ 100 nm不等，管壁厚度為10 nm，並由側面圖得知管長約為276 nm；（3）以奈米鈦管光催化24小時可降解20 %之氨氮，而二氧化鈦可在3小時內降解超過50 %之氨氮，並於14小時內將95 %氨氮完全氧化為最終產物；（4）披覆型二氧化鈦之氨氮氧化速率皆高於二氧化鈦，如披覆鈀且於pH=10.5時，於5至7小時內即可完全氧化；（5）隨pH值降低，氨氮氧化速率減慢，產物分佈亦有所改變，而Au/TiO2之氧化速率較不受pH影響，在pH=8時其氧化速率比其他催化劑快速，速率常數為0.0025 min-1，但氮氣產率僅有10 %；（6）當pH值下降，氮氣產率有提升之趨勢，尤以Cu/TiO2最為明顯，當pH由10.5下降至8，氮氣產率由3.3 %提升至43.1 %。

關鍵字

氨氮 ； 光催化氧化 ； 二氧化鈦 ； 奈米鈦管 ； 披覆型二氧化鈦

並列摘要

This research is about treating ammonia in water by photocatalysis under UV illumination (λ= 365 nm), and the catalysts used are titanium nanotube and titanium dioxide (TiO2). In order to enhance ammonia oxidation rate and nitrogen yields, some metals such as Pd, Pt, Au, Cu was coated on TiO2 by photodeposition method. Effects of pH value were also tested for the optimal reaction conditions.
The results showed that direct photodegradation of ammonia did not occurr under UV illumination (λ= 365 nm). The amount of ammonia volatilization was 15.9 % and 9.3 % at pH value of 10.5 and 9.5, respectively. The diameter of titanium nanotube varied from 20 to 100 nm, its length was about 276 nm, and thickness was about 10 nm. Through photocatalyzing by titanium nanotube after 24 hours, only 20% of ammonia degraded. However, 95% of ammonia degraded within 14 hours while the catalyst was titanium dioxide. Metal loaded on TiO2, especially Pd, improved effectively the ammonia oxidation rate; more than 99% of ammonia was degraded into nitrate during 7 hours. With the pH value decreasing, the ammonia oxidation rate decreased. Furthermore, the ammonia degradation rate using Au/TiO2 was not affected by the pH. For Cu/TiO2, nitrogen yields raised from 3.3 % to 43.1 %, with the pH value decreased from 10.5 to 8.

並列關鍵字

ammonia ； photocatalysis ； titanium nanotube ； titanium dioxide

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