- 學位論文
硫酸根離子及界面活性劑輔助超音波去除水中全氟辛酸之影響
Effects of surfactants and sulfate ions on the degradation of perfluorooctanoic acid (PFOA) by ultrasonic (US)
若您是本文的作者，可授權文章由華藝線上圖書館中協助推廣。
摘要
全氟辛酸（C7F15COOH，PFOA）為一種陰離子界面活性劑，且為持久性有機污染物。本研究之第一部分以超音波化學降解法添加硫酸根離子針對全氟辛酸之降解進行探討。硫酸可透過超音波產生的空蝕效應(Cavitation effect)發生熱裂解反應，而釋放出具有強氧化性的自由基，如硫酸自由基及氫氧自由基等，這些氧化性物質可促進全氟辛酸之氧化分解，本研究欲探討不同的操作參數對於超音波降解全氟辛酸的影響效應，其包括過硫酸添加濃度效應、溶液初始pH值效應、初始溫度效應、及溶液表面張力之影響。全氟辛酸在單一超音波系統照射下，全氟辛酸降解效率隨硫酸根離子濃度增加而增加，當添加117 mM濃度之硫酸自由基時，可於室溫下、90分鐘內幾乎完全降解溶液中之全氟辛酸，其降解機制主要為超音波於水中所產生之空化作用以及其激發水中硫酸根離子轉化為硫酸自由基而破壞全氟辛酸之化學鍵結。其降解之動力大致符合擬一階反應動力模式，無論在酸性或鹼性的初始環境下，其降解全氟辛酸之差異性並不大，但隨溫度升高而下降，主要受到溫度升高時全氟辛酸溶液之表面張力的下降。為深入探討表面張力對於全氟辛酸之影響，本研究第二部分之目的為添加不同性質之界面活性劑觀察其對於超音波降解水中全氟辛酸之結果，全氟辛酸在水中解離後的主要以陰離子形式存在，為陰離子界面活性劑，易吸附在水中氣泡之氣液介面上，故可藉由超音波產生空蝕效應產生之局部高溫將其礦化。本研究以添加陽離子界面活性劑的方式，降低全氟辛酸吸附後氣液界面上的電斥力，提升超音波降解法去除PFOA的效果，實驗時主要探討陽離子界面活性劑的疏水基碳數多寡對全氟辛酸去除效果的影響，並觀察三種界面活性劑混合系統中的表面張力及臨界微胞濃度(Critical micelle concentration, CMC)的變化情形以了解其去除機制。包含分別添加陽離子型界面活性劑（十六烷基三甲基溴化銨，CTAB）、非離子型界面活性劑（辛基苯酚乙氧基化物，TritonX-100），及陰離子型界面活性劑（十二烷基硫酸鈉，SDS）的界面活性劑，結果發現CTAB可增加超音波於水中降解全氟辛酸之效果，其次為TritonX-100，而SDS則具抑制其降解速率之效應，此外，亦改變CTAB之添加濃度、溶液初始pH值、臨界微胞濃度以了解其對全氟辛酸去除效率之影響。
並列摘要
Perfluorooctanoic acid (C7F15COOH, PFOA) is an aqueous anionic surfactant and a persistent organic pollutant. It can be easily adsorbed onto the bubble-water interface and both mineralized and degraded by ultrasonic (US) cavitation at room temperature. The first part of this study is to investigate the effects of sulfate ions on the decomposition of perfluorooctanoic acid (PFOA) by ultrasonic (US) irradiation at various pHs, sulfate doses, powers and temperatures. The removal of PFOA was augmented with an increased sulfate ion concentration, with PFOA being almost completely decomposed in 90 min at 25 OC with a sulfate dose of 117 mM. The two major mechanisms in the sulfate- assisted sonochemical system are the direct destruction of PFOA by cavitation and the indirect destruction of PFOA by sulfate free radicals. The decomposition of PFOA followed pseudo-first-order kinetics and was not influenced by pH. The reaction rate constants decreased with increases in temperature due to decreases in the surface tension of the solution. The second part of this study is to investigate whether the effect of US on the degradation of PFOA in solution can be enhanced by the addition of surfactant. To achieve this aim, we first investigated the addition of a cationic (hexadecyl trimethyl ammonium bromide, CTAB), a nonionic (octyl phenol ethoxylate, TritonX-100), and an anionic (sodium dodecyl sulfate, SDS) surfactant. We found the addition of CTAB to have increased the degradation rate the most, followed by TritonX-100. SDS inhibited the degradation rate. We then conducted further experiments characterizing the removal efficiency of CTAB at varying surfactant concentrations and solution pHs. The removal efficiency of PFOA increased with CTAB concentration, with the efficiency reaching 79% after 120 min at 25 OC with a 0.12 mM CTAB dose.
參考文獻
Abbasi, Mahmood and Nima Razzaghi Asl (2008). "Sonochemical degradation of Basic Blue 41 dye assisted by nano TiO2 and H2O2." Journal of Hazardous Materials 153(3): 942-947.
Abe, Masahiko, Kazuo Kato and Keizo Ogino (1989). "Effects of inorganic electrolytes and of ph on micelle formation of amphoteric anionic mixed surfactant systems." Journal of Colloid and Interface Science 127(2): 328-335.
Acosta, E., M. Bisceglia and D. H. Kurlat (2005). "Self-aggregation in aqueous TRITON X-100 solutions near CMC." Physics and Chemistry of Liquids 43(3): 269-275.
Adewuyi, Yusuf G. (2005). "Sonochemistry in environmental remediation. 1. Combinative and hybrid sonophotochemical oxidation processes for the treatment of pollutants in water." Environmental Science & Technology 39(10): 3409-3420.
Adewuyi, Yusuf G. (2005). "Sonochemistry in environmental remediation. 2. Heterogeneous sonophotocatalytic oxidation processes for the treatment of pollutants in water." Environmental Science & Technology 39(22): 8557-8570.