利用氧化劑處裡含phenanthrene及pyrene污染土壤之研究

台灣地區之主要能源之一為石油，其於運送、貯存及煉製過程中可能產生洩漏或不當排放造成污染。依據環保署調查結果台灣南部地區某些之地下含水層，含有來自油品中之苯、甲苯及多環碳氫化物(polycyclic aromatic hydrocarbons, PAHs)等致癌物，危害人體健康及生態環境。由於PAHs不利於微生物分解，對於受油品污染土壤中含PAHs處理方式，已有研究證實採用其它方式如化學氧化法可有效降低土中有機物。本研究目的為提出以模擬化學氧化反應處理含PAHs土壤之最佳化操作條件如時間及劑量等，並比較不同氧化劑如Fenton試劑(Fe^(+2) + H_2O_2)與過硫酸鹽(S_2O_8^(-2))對於具三苯環之phenanthrene及四苯環之pyrene各別之處理效率。由實驗結果得知，以本研究條件下，PAHs之初濃度為100 mg/L，約於10分鐘內，此二種氧化劑皆可有效氧化土壤中之生物難分解之PAHs。Fenton試劑之最佳劑量與phenanthrene之莫耳數比為phenanthrene/Fe_2+/H_2O_2 = 7: 14.4: 412，達到phenanthrene去除率為42%；最佳劑量與pyrene之莫耳數比pyrene/Fe_2+/H_2O_2 = 6: 14.4: 206，對於pyrene去除率為30%。此外，過硫酸鈉之最佳劑量分別為1680 及2099mM時，對於phenanthrene 及pyrene 去除率分別為50 及40 %，故莫耳數比為phenanthrene/S_2O_8^(2-) = 7: 1680，pyrene/S_2O_8^(2-) = 6: 2099。因此在本研究條件下，三環之phenanthrene比四環之pyrene之最佳去除效率較高，可能由於phenanthrene結構較簡單及其溶解度較大，釋放於溶液中有助於氧化劑反應。此外，Fenton試劑使用劑量較少，但有效時間較短，且須顧慮現場操作過氧化氫之安全問題。過硫酸鈉則需較高劑量，操作成本較高，但是延時效果較佳，故規劃於實場應用時需視狀況而選擇適當氧化劑。

關鍵字

多環碳氫化合物；化學氧化；過硫酸鹽

並列摘要

In Taiwan, petroleum is one of the major energy source, which can be accordingly contaminated in the process of illegally leakage or improper discharge of transportation, storage, or refinery. Taiwan EPA has investigated that some groundwater in southern area has been contaminated by carcinogens such as benzene, toulene and polycyclic aromatic hydrocarbons (PAHs) in damaging human health and the environment. Previous studies concluded that PAHs were effectively removed by chemical oxidation reaction from contaminated soil. The objective of this study is to propose a simulated site remediation for PAHs contamination such as phenanthrene and pyrene by two oxidation reagents including Fenton and persulfate (S_2O_8^(2-)) for optimizing the operating conditions in time and dosage to compare the treatment efficiencies. From the experimental results, under this research conditions while the concentrations of PAHs were 100 mg/L, the oxidants studied can both remove PAHs effectively. The removal rates of phenanthrene and pyrene of 42 and 30% were obtained by the optimal doses more ratio of Fenton reagents with phenanthrene/Fe^(2+)/H_2O_2 = 7: 14.4: 412 and pyrene/Fe^(2+)/H_2O_2 = 6: 14.4: 206, respectively. The removal efficiencies of phenanthrene and pyrene were 50 and 40 % adding S_2O_8^(2-) concentrations of 1680 and 2099 mM, respectively so that the optimal more ratios were phenanthrene/S_2O_8^(2-) = 7: 1680 and pyrene/S_2O_8^(2-) = 6: 2099. Therefore, the removal efficiencies of phenanthrene were higher than that of pyrene may result from less benzene-rings and higher water solubility for enhancing the oxidation under the experimental conditions. Moreover, less Fenton reagents, shorter reaction time and the safety issue are necessary to be considered. The persulfate demand more dose, higher cost and extend reaction time. It's necessary to evaluate the better choices of oxidation reagents for field application depending on the specific site problem.