|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 as pesticide and wood preservative. After broadly applied in a great quantity for several decades, PCP can be found in most natural environments. Thus, PCP becomes one of most prevalent underground contaminants due to its slow rate of biodegradation. Electrochemical oxidation has been applied as a remedy scheme for many refractory compounds such as pesticides and chlorinated phenols. Besides, electrochemical technology can be applied as a tool for highly sensitive and rapid measurement. The original objective of this research is to develop an associated scheme of ultrasonic extraction and electrochemical oxidation for removing PCP from soil. First, the mechanism of ultrasonic extraction is utilized to partition PCP from soil matrix to the slurry solution. The extract is further filtered through ultra-filtration (UF) membrane and sequentially subjected to electrochemical oxidation for the purpose of de-chlorination and degradation of PCP. However, the presented study is focused on the application of electrochemical technology as a detection tool and/or as a dechlorination scheme for chlorophenols due to the limitation of budget and time. In the experiments of electrochemical measurement, a tri-electrode system used a platinum (Pt) electrode as working electrode, a Pt wire as counter electrode, and a saturated Ag/AgCl electrode as reference electrode. Electrochemical analyzer is operated in a linear sweep voltammetric (LSV) mode: scan rate 0.3 V/s, 0.1M Na2SO4 as electrolyte, and scan range -1.5 to 1.8 V. The oxidative peaks of 4-chlorophenol (4-MCP), 2,4-dichlorophenol (2,4-DCP), and PCP occur at 1.228V, 1.120V, and 1.037V in the cyclic voltammogram. A linear relationship between concentration and peak current exists based on r2 values ranging 0.9964 and 0.9978, and this linearity can be employed as calibration curve to measure the concentrations of chlorophenols. The results of QA/QC including duplication and standard check are satisfied, and the detection limits are 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 a detection tool for trace chlorophenols in water. In the experiments of electrochemical dechlorination, the tri-electrode system was also employed to compare the effect of PCP degradation and dechlorination under various operating potentials. The reaction cell was fed with 0.1M Na2SO4 as electrolyte, and installed a Pt electrode as working electrode, a Pt wire as counter electrode, and a saturated 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 % for 0.2V, 56% for 0.3V, and 10% for 0.4V. The result showed that 0.3 V could be the optimum potential for PCP degradation and dechlorination, and the degraded PCP was found completely dechlorinated.