反應性元素鐵濾床結合過氧化氫進行水及土壤中五氯酚之還原氧化脫氯

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Title:	反應性元素鐵濾床結合過氧化氫進行水及土壤中五氯酚之還原氧化脫氯 Redox Dechlorination of Pentachlorophenol in Water and Soil by Reactive Zero-Valent Iron Filter Coupled with Hydrogen Peroxide
Authors:	黃瑞淵 Jui-Yuan Huang
Contributors:	盧明俊嘉南藥理科技大學：環境工程與科學系碩士班
Keywords:	五氯酚元素鐵過氧化氫二氧化碳脫氯地下水污染 Dechlorination Carbon dioxide Hydrogen Peroxide Zero-Valent Iron(ZVI) Pentachlorophenol(PCP)
Date:	2005
Issue Date:	2008-10-31 16:14:37 (UTC+8)
Abstract:	由於意外滲漏或不當的處置下，造成我國部分地區土壤及地下水受五氯酚嚴重污染的問題。本研究針對過氧化氫存在時，元素鐵反應系統對土壤及地下水中五氯酚還原脫氯及氧化去除之影響進行探討，期能發展以元素鐵為本之現地處理技術。研究過程發現，五氯酚分子受環境中pH值之變化而改變其水中溶解度，當pH = 4時五氯酚之溶解度約為0.5 mg/L。於系統中添加元素鐵參與反應時，在pH = 4的環境下，元素鐵迅速氧化為二價鐵，導致反應系統之氧化還原電位及溶氧有逐漸降低之趨勢；然而在pH = 7的操作環境下，可由反應濾床外觀明顯看出，元素鐵亦有逐漸氧化的現象，當過氧化氫加入系統時，分別與二價鐵及三價鐵形成Fenton與Fenton-like之反應程序，由實驗結果可明顯看出，該程序可破壞去除水相中之五氯酚。然而針對元素鐵效能持久性之研究中發現，在pH=4的環境下二價鐵之生成量隨時間不斷的累積，當反應進行約72小時後，由氧化還原電位、溶氧及二價鐵累積曲線之結果，可知二價鐵之生成速率漸趨緩慢。由人工污土實驗中發現，污染土壤中之五氯酚易被沖洗水所洗出，且經長時間沖洗後，五氯酚濃度會達到該沖洗水pH值之飽和溶解度，若添加元素鐵於污土中，並在第一階段進行酸洗且配合三段式過氧化氫之添加，可有效去除土壤中之五氯酚約80％。另一方面，利用二氧化碳的曝氣，可在短時間內有效降低反應環境之pH達4.05，然在此低pH值下，元素鐵迅速氧化生成二價鐵，此時搭配過氧化氫之添加，可有效破壞去除五氯酚。在連續批次實驗中發現，經過8批次的反應後，五氯酚及之氯離子濃度分別為0.21 mg/L及23.52 mg/L。在三小時連續批次實驗中發現，經過6批次的反應後，五氯酚及之氯離子濃度分別為5.87 mg/L及7.0 mg/L。在添加不同濃度過氧化氫之三小時連續批次實驗中發現，經過6批次的反應後，五氯酚及之氯離子濃度分別為0.5 mg/L及9.0 mg/L。在90分鐘連續批次實驗中發現，經過9批次的反應後，五氯酚及之氯離子濃度分別為0.06 mg/L及17.17 mg/L。由固相萃取實驗之結果，可發現315 g濾材對五氯酚之吸附量約為2 mg/L；而反應系統對五氯酚之破壞去除率，以連續批次實驗最佳，其次為90分鐘連續批次實驗，其去除率分別為99.47%及97.20%。若以短時間去除大量五氯酚為目標，則90分鐘連續批次實驗（97.20%）之操作方式是值得推薦的。 In this study, zero valent iron (ZVI)/quartz sand (QS) filter bed combined with hydrogen peroxide were used for the removal of aqueous pentachlorophenol (PCP) by the redox process. It was found that solution pH was an important parameter for the removal of PCP. At a neutral pH (pH=7) and alkaline pH (pH=9), most PCP tends to remain in the aqueous solution. With an acidic pH, the PCP with molecular form appears to precipitate out from the aqueous solution. The maximum solubility at controlled pH 4 was monitored at around 0.5 mg/L. In addition, PCP can be dechlorinated through the pathway of Fenton reaction, which was created by controlling the pH at acidic condition and by adding H2O2 into the filter bed at a later reaction stage. In this research, H2SO4 and CO2 gas were selected for adjusting pH to acidic condition. As a result, ZVI was efficient for operating with the step additions of H2O2 in the system for PCP removal. Regarding Fe0/H2SO4/H2O2 system, PCP contamination in the soil sample was removed by 80% at 72 hrs under three step additions of H2O2. From the Fe0/CO2/H2O2 system, PCP removal efficiency in the aqueous was 97% at the reaction time of 90 min under nine step additions of PCP and H2O2.
Relation:	校內外完全公開
Appears in Collections:	[Dept. of Environmental Engineering and Science (including master's program)] Dissertations and Theses

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