五氯酚( Pentachlorophenol, PCP )是為一毒性甚大之物質，由於五氯酚化學性質安定難溶於水又不易被生物分解，在環境中累積到一定程度將會造成嚴重的危害。本研究係以臭氧氧化分解五氯酚，針對臭氧濃度、溶液pH值與添加自由基捕捉劑等，對臭氧分解五氯酚反應之影響與其生成之中間產物進行探討。結果顯示，在高濃度臭氧分解五氯酚之後，會產生三種中間產物，分別為：Tetrachloro-p-hydroquinone (TCHQ)，Tetrachlorocatechol (TCCA)，Tetrachloro-p-benzoquinon (TCBQ)。在pH=6，反應時間2分鐘，對五氯酚降解效率可達95 %，由實驗結果可計算出其初使反應速率為4.98 ×10-2 (1/S)，且此一反應為二次反應。另一方面，當溶液pH值低時，臭氧降解五氯酚效果並不理想，在高臭氧濃度的情況下，對五氯酚降解效率僅30 %。臭氧處理五氯酚在未添加自由基捕捉劑的情況下，在不同的臭氧濃度的情況下，當反應時間達0.08分鐘之後，所有反應均達平衡狀態，而在高濃度臭氧反應下僅生成TCHQ與TCCA兩種中間產物；亦可由實驗結果計算出其初使反應速率為1.82 × 10-1 (1/S)。 Pentachlorophenol (PCP) is a highly toxicity material. Owing to its chemical property, it is difficult to dissolve in water and is recalcitrant to biological degradation. It can accumulate in the environment and can cause serious soil and groundwater contaminations. The objective of this study focused on the oxidation of PCP by ozone. Parameters studied in this investigation include ozone concentration, solution pH, and radical scavenger. It was found that under higher ozone concentration, the degradation of PCP will lead to three intermediates: tetrachloro-p- hydroquinone, tetrachloro-p-benzoquinon, and tetrachlorocatechol. Within 2 minutes of reaction at pH 6, the degradation of PCP were around 95%. From the experimental data, it was found that the reaction followed second-order kinetics and its initial rate was 4.98 ×10-2 S-1. On the other hand, at 2 minutes of reaction at pH 3 the degradation of PCP was only 30%. The degradation of PCP by ozone without the addition of the scanvenger, under different ozone concentrations at 0.08 min of reaction, reached a steady concentration. Under higher ozone concentrations, the degradation of PCP was around 90%. Under these conditions, PCP degradation also produce two intermediates: tetrachlorocatechol and tetrachloro-p-hydroquinone and its initial rate was 1.82 × 10-1 S-1.
