選擇性光催化還原水中硝酸鹽為氮氣之研究

Selective photocatalytic reduction of nitrate to nitrogen on Pd-Cu/TiO2 catalysts

曾雨凡(Yu-Fan Tseng)

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.2007.01005

摘要

硝酸鹽為地下水體中主要的污染物之一，近年來由於農業過量使用含氮肥料造成地下水中硝酸鹽濃度逐漸上升，若累積將對人體健康造成危害。現行處理技術包括離子交換、薄膜逆滲透、化學還原、生物脫硝等方法不僅操作維護成本高且出流水皆需要後續處理。本研究利用光沉積法將鈀、銅負載於二氧化鈦上作為光催化劑，並以甲酸為電洞捕抓劑進行硝酸鹽之光催化降解反應。
　　光催化還原法是利用UV光催化二氧化鈦而產生電子電洞分離 (e－-h+)，藉由電洞捕抓劑移除帶正電的電洞(h+)，讓電子(e－)有效導引至催化劑表面，負載金屬將進一步還原硝酸鹽。實驗結果證明光催化反應能快速且有效的降解硝酸鹽，且負載複合金屬之光催化劑比單金屬擁有更高的催化活性及產氮氣選擇性。此外，本研究亦探討不同電洞捕抓劑種類及濃度和不同金屬負載比例對於硝酸鹽還原反應速率及選擇性的影響。
　　本研究結果顯示光催化脫硝系統在最適操作條件下有最佳氮氣生成效果：(1)以濃度0.04 mol/L的甲酸作為電洞捕抓劑，(2)以負載比例1% Cu-1% Pd/TiO2為光催化劑時能將40 mg-N/L之硝酸鹽完全降解，並擁有高達80%之產氮氣選擇率。

關鍵字

光催化還原 ； 硝酸鹽 ； 二氧化鈦 ； 複合金屬催化劑

並列摘要

Nitrate is one of the significant pollutants in the groundwater system which concentration in groundwater is gradually increasing in recent years mainly due to overusing of nitrogenous fertilizer, and it would cause serious health risks. Current technologies such as ion exchange, reverse osmosis, chemical reduction and biological denitrification usually cost highly and need post-treatment of the produced effluents.
In this study, titania supported palladium-copper bimetallic catalysts prepared by photodeposition are applied to the photocatalytic reduction of nitrate in the presence of formic acid as a hole scavenger. Under illumination of UV light, the photoexcitation of TiO2 leads to the formation of electron-hole pairs. After the photogenerated holes were captured by hole scavenger, the electrons are transferred to the surface of photocatalysts, then loaded metal could carry out the nitrate reduction. The experimental results show great catalytic performance, and compared with monometallic catalysts, bimetallic catalysts exhibit more excellent photocatalytic reduction activity and selectivity. Furthermore, the effects of different type and concentration of hole scavengers and metal loading ratio on conversion of nitrate and selectivity for nitrogen are also systematically investigated.
Abundance of data from experimental factors reveal that photodeposited 1%Cu-1%Pd/TiO2 bimetallic catalysts exhibit 100% nitrate conversion for 40 mg-N/L nitrate solution and as much as 80% selectivity for nitrogen under the modification of 0.04 mol/L formic acid as a hole scavenger. The results demonstrate that the photocatalytic reduction of nitrate is a potent denitrification technique, especially with the development of applications involving sunlight.

並列關鍵字

Photocatalytic reduction ； Nitrate ； Titania ； bimetallic catalyst

參考文獻

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