Kun Shan University Institutional Repository:Item 987654321/3450
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    Title: 發展超音電解聯用系統處理五氯酚污染土壤
    Authors: 吳庭年
    Keywords: 五氯酚(PCP)
    Pentachlorophenol (PCP)
    Platinum electrode
    Electrochemical Detection
    Electochemical Reduction
    Date: 2007-10-31
    Issue Date: 2009-08-14 23:44:10 (UTC+8)
    Abstract: 五氯酚(Pentachlorophenol,PCP)常被使用於殺蟲劑、木材防腐劑等用途,歷經數十年來的大量廣泛使用,普遍存在於自然環境中,且因生物分解五氯酚的速率極為緩慢,因而成為土壤及地下水的指標性污染物。電解氧化技術可利用電化學反應來氧化污染物,此技術已成功應用於去除廢水中許多難分解污染物。此外,電化學技術亦為一項高靈敏度、快速測定的工具。本研究提出之構想為一多年期計畫,發展結合超音電解處理程序整治高污染五氯酚土壤,利用超音波萃取機制先將污染土壤中五氯酚自土壤吸附相萃取至水溶相,藉由超過濾機制將土壤與溶液分離,分離出之溶液於電解系統中應用電催化機制將五氯酚脫氯,並進一步氧化降解,而達到無害化程度。惟受限於計畫經費與期程,現階段的研究主要專注於電化學技術的應用,做為水中氯酚化合物的偵測工具,及使用於電還原脫氯的應用。電偵測實驗部分,以三極式白金電極系統,使用電化學分析儀,以線性掃描伏安法(LSV)測定水中微量氯酚化合物,使用的掃描速度為0.3V/s、電解質0.1M Na2SO4 及電壓掃描範圍-1.50V 至+1.80V,極譜圖中4-氯酚、2,4-二氯酚及五氯酚氧化波峰分別出現在1.228V、1.120V及1.037V左右,測定之三種氯酚化合物濃度與其對應之波峰電流值成良好線性關係,r2值為介於0.9964與0.9978之間。實驗品管分析作業包括重複分析及標準品查核分析之結果良好,4-氯酚、2,4-二氯酚、及五氯酚之偵測極限值可達0.13 mg/L、0.24 mg/L及0.09mg/L。由實驗結果驗證,電化學分析可做為水中微量氯酚化合物之快速測定方法。電還原脫氯實驗部分,使用三極式白金電極系統, 在0.1M Na2SO4電解質條件下,操作不同電壓對五氯酚進行還原脫氯實驗。比較降解電壓0.2 V、0.3 V與0.4V之操作,電解60 min後 五氯酚降解率分別為37%、56%與7%,脫氯率則達20%、56%及10%。由實驗結果可初步判定以0.3V之操作電壓降解效果最佳,且降解的五氯酚可達完全脫氯的情況。Pentachlorophenol (PCP) is widely used aspesticide and wood preservative. After broadlyapplied in a great quantity for several decades, PCPcan be found in most natural environments. Thus,PCP becomes one of most prevalent undergroundcontaminants due to its slow rate of biodegradation.Electrochemical oxidation has been applied as aremedy scheme for many refractory compounds suchas pesticides and chlorinated phenols. Besides,electrochemical technology can be applied as a toolfor highly sensitive and rapid measurement. Theoriginal objective of this research is to develop anassociated scheme of ultrasonic extraction andelectrochemical oxidation for removing PCP fromsoil. First, the mechanism of ultrasonic extraction isutilized to partition PCP from soil matrix to the slurrysolution. The extract is further filtered throughultra-filtration (UF) membrane and sequentiallysubjected to electrochemical oxidation for thepurpose of de-chlorination and degradation of PCP.However, the presented study is focused on theapplication of electrochemical technology as adetection tool and/or as a dechlorination scheme forchlorophenols due to the limitation of budget andtime.In the experiments of electrochemicalmeasurement, a tri-electrode system used a platinum(Pt) electrode as working electrode, a Pt wire ascounter electrode, and a saturated Ag/AgCl electrodeas reference electrode. Electrochemical analyzer isoperated in a linear sweep voltammetric (LSV) mode:scan rate 0.3 V/s, 0.1M Na2SO4 as electrolyte, and 4-chlorophenol (4-MCP), 2,4-dichlorophenol(2,4-DCP), and PCP occur at 1.228V, 1.120V, and1.037V in the cyclic voltammogram. A linearrelationship between concentration and peak currentexists based on r2 values ranging 0.9964 and 0.9978,and this linearity can be employed as calibrationcurve to measure the concentrations of chlorophenols.The results of QA/QC including duplication andstandard check are satisfied, and the detection limitsare 0.13 mg/L for 4-MCP, 0.24 mg/L for 2,4-DCP,and 0.09 mg/L for PCP. Consequently,electrochemical analysis can be employed as adetection tool for trace chlorophenols in water.In the experiments of electrochemicaldechlorination, the tri-electrode system was alsoemployed to compare the effect of PCP degradationand dechlorination under various operating potentials.The reaction cell was fed with 0.1M Na2SO4 aselectrolyte, and installed a Pt electrode as workingelectrode, a Pt wire as counter electrode, and asaturated Ag/AgCl electrode as reference electrode.The degradation of PCP was found 37 %, 56%, and 7% after 60mins under 0.2, 0.3, and 0.4 V, respectively;meanwhile, the dechlorination of PCP was 20 % for0.2V, 56% for 0.3V, and 10% for 0.4V. The resultshowed that 0.3 V could be the optimum potential forPCP degradation and dechlorination, and thedegraded PCP was found completely dechlorinated.Keywords:Pentachlorophenol (PCP), Platinumelectrode, Electrochemical Detection, ElectochemicalReduction, Dechlorination
    Appears in Collections:[Graduate School and Department of Environmental Engineering] Research Projects

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