改良磁性奈米銀觸媒進行異相催化臭氧去除水中腐植酸之研究

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Title:	改良磁性奈米銀觸媒進行異相催化臭氧去除水中腐植酸之研究
Other Titles:	Modified Magnetic Silver nano-catalysts for Heterogeneous Catalytic Ozonation to Remove Humic acid in water
Authors:	林世軒 Shih-Hsuan Lin
Contributors:	張鎮南 Cheng-Nan Chang 東海大學環境科學與工程學系
Keywords:	磁性顆粒;異相催化臭氧化;腐植酸;氫氧自由基;捕捉劑;coumarin;7-hydroxycoumarin;TBA magnetic particles;catalytic ozonation;humic acid;hydroxyl radicals;scavengers;coumarin;7-hydroxycoumarin;TBA
Date:	2012
Issue Date:	2013-01-03T06:00:54Z (UTC)
Abstract:	本研究使用改良之磁性銀奈米顆粒 (Fe3O4/SiO2/Ag) 進行異相催化臭氧化去除水中之腐植酸，並在系統中添加氫氧自由基捕捉劑以探討催化臭氧化之機制。已知coumarin與氫氧自由基反應後會形成中間產物7-hydroxycoumarin，藉由中間產物的生成可以用以表示系統中氫氧自由基的存在。結果顯示，Fe3O4/SiO2/Ag結合臭氧之中間產物產量高於單獨臭氧化系統，這是因為Fe3O4/SiO2/Ag能分解臭氧產生更多的氫氧自由基。而加入另一種氫氧自由基捕捉劑TBA後，可以觀察到中間產物的產量會因為氫氧自由基被捕捉而降低，而 Fe3O4/SiO2/Ag結合臭氧之中間產物產量仍高於單獨臭氧化。結果顯示Fe3O4/SiO2/Ag結合臭氧增加了系統中氫氧自由基的含量。以Fe3O4/SiO2/Ag結合臭氧去除水中腐殖酸，只有在水溶液為酸性時，催化臭氧之效果會優於於單獨臭氧化，這是由於水溶液在高pH值時，臭氧之自解反應抑制了催化劑的效果。而以一階反應式之Kd值比較各式催化臭氧化之臭氧分解能力，發現本研究使用之催化臭氧化之Kd值為7.0 10-4 s-1是單獨臭氧化Kd值之1.75倍。經由實驗證實Fe3O4/SiO2/Ag結合臭氧可以提升系統之氧化力並增加腐殖酸之去除率。 This study used modified magnetic silver nanoparticles (Fe3O4/SiO2/Ag) for the heterogeneous catalytic ozonation to remove humic acid (HA) in water. While hydroxyl radical (?OH) scavengers were added to the system in order to investigate the catalytic ozonation mechanisms. Coumarin is known to react with?OH to generate intermediate (7-hydroxycoumarin). The formation of the intermediate can be used to indicate the presence of?OH in the system. Compared to ozonation alone, Fe3O4/SiO2/Ag combined with ozone to produce more intermediate. This is due to the decomposition of ozone to produce more ?OH by Fe3O4/SiO2/Ag. Added another?OH scavengers of TBA can be observed production of intermediate will be reduced because the?OH was captured, while the intermediate produced in Fe3O4/SiO2/Ag combined with ozone is still higher than the ozonation alone. The results showed that Fe3O4/SiO2/Ag combined with ozone to improve the content of?OH in the system. To remove of humic acid by Fe3O4/SiO2/Ag combined with ozone, the humic acid removal rate is only higher than ozonation alone in acidic condition, this is due to the ozone self-decomposition inhibits the effect of the catalyst at high pH cases. Comparison of first-order ozone decay rate constants, the Kd values of this study of 7.0×10-4 s-1 and is 1.75 times than that of ozonation alone. The results indicated the presence of Fe3O4/SiO2/Ag could improve the oxidizing power of overall system and leading to the HA removal rate increased.
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