2007-08-012024-05-16https://scholars.lib.ntu.edu.tw/handle/123456789/669224摘要：硝酸鹽與亞硝酸鹽為地下水中常見污染物，以含氮肥料為主要滲入來源，若此污染物濃度過高將危害環境生態與人體健康。現行處理技術包括薄膜逆滲透、離子交換法、生物脫硝法、化學還原法等。本研究主要探討成本低、時間短，以零價金屬為反應材料之化學還原技術來去除水中硝酸鹽氮(NO3-)。研究指出零價金屬擁有強大還原能力，以零價鐵與零價鋅為代表。然而，在降解硝酸鹽反應中發現零價鐵系統之產物幾乎皆為氨氮；零價鋅系統之產物為氮氣與氨氮。因此，本研究主要探討零價鋅系統降解硝酸鹽氮之產氮比例。 雙金屬技術藉由金屬表面的直接接觸產生電子轉移的反應，可改善單一零價金屬之低反應活性與改變反應途徑，進一步提升產氮比例。本研究選取銅、鈀、鎳、鉑等金屬作為與零價鋅合成雙金屬之觸媒，實驗證明鋅/鈀雙金屬可產生兩階段反應途徑:一、零價鋅將硝酸鹽氮降解為大量亞硝酸鹽與少量氨氮；二、雙金屬機制將亞硝酸鹽降解為氮氣及氨氮，產氮比例優於單一零價鋅系統。 本研究顯示硝酸鹽溶液為了去除水中溶氧影響，曝氮氣的溶液產氮比例優於曝氬氣的溶液；也發現若零價鋅/鈀負載之比例越高則產氮之比例亦越高；硝酸鹽溶液濃度約在45ppm時有最佳之產氮比例；加藥量在0.5g零價鋅/70ml硝酸鹽溶液時亦有最佳產氮比例與最高之產氮選擇性。 <br> Abstract: In the case of the reduction of nitrate in groundwater, the problem is how to convert nitrate [N(+V)] selectively to nontoxic dinitrogen [N(0)], not to completely reduced ammonia [N(-III)]. Unfortunately, ammonia has been reported to be the main product in all of cases through abiotic denitrification using zero valent iron. In this work, the selective reduction of nitrate over zinc alone and four bimetallic Cu/Zn, Pd/Zn, Pt/Zn, and Ni/Zn in buffered water (pH=7-8) saturated with nitrogen were investigated. Identification of the nitrogen containing species during the chemical reduction of nitrate was via a high-vacuum system equipped with quaploar mass spectrometer. While the slow and complete reduction of nitrate to ammonia is the only pathway for decomposition of nitrate over zinc alone, a new pathway, which of selective reduction of nitrate to dinitrogen, opens up on four bimetallic Cu/Zn, Pd/Zn, Pt/Zn, and Ni/Zn. The properties of Cu, Pd, Pt, and Ni including concentration of atomic hydrogen (H&#8226;) and free electron (e-) on their surface and their affinity for atomic nitrogen accounted for much difference in the distribution of the nitrogen-containing products for the four bimetallic systems. In the system of 5 wt% Pd/Zn, a nitrate conversion of 90% and selectivity for nitrogen of 60%, representing well over an order of magnitude increase in selectivity thus far reported.硝酸鹽亞硝酸鹽鋅/鈀雙金屬nitratenitritePd/Zn bimetal