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王莉,喻泽斌,李明樾,孙蕾,陈颖,彭振波,孙玲芳,项国梁.介质阻挡放电等离子去除PFOA的影响因素及机制研究[J].环境科学学报,2015,35(3):764-772

Degradation and mechanism of perfluorooctanoic acid (PFOA) in a dielectric barrier discharge system

基金项目：国家自然科学基金项目(No.21367002,51368004);广西自然科学基金项目(No.2014GXNSFAA118294);广西研究生教育创新计划资助项目(No.YCSZ2014044)

摘要：采用介质阻挡放电等离子对全氟辛酸(PFOA)进行降解研究,考察了PFOA初始浓度、放电峰-峰值电压、溶液初始pH及初始电导率对PFOA降解的影响.结果表明介质阻挡放电等离子对PFOA具有良好的降解效果.在峰-峰值电压为14 kV,初始电导率为50 μS·cm^-1条件下,2 h脱氟率可达48.43%.TOC去除符合伪一级反应动力学,速率常数为0.4075 h^-1,去除率达53.30%,投加羟基自由基(·OH)捕获剂实验表明:·OH是主要的活性物质,对PFOA脱氟贡献率78.30%.采用UPLC-QTOF/MS对反应产物进行检测,并推测PFOA可能的降解路径:①·OH氧化PFOA进行脱氟反应生成C₆F₁₃C(OH)₂COOH,经分子内脱H₂O生成C₆F₁₃COCOOH;②·OH氧化PFOA分子,使羧酸键—COOH断裂,生成醛类C₇F₁₃HO,最后两者都经·OH氧化成C₆F₁₃COOH,然后按上述过程逐级脱去CF₂生成短链全氟羧酸.

Abstract：A dielectric barrier discharge reactor was developed for the degradation of perfluorooctanoic acid (PFOA). The effect of key factors on defluorination of PFOA including initial PFOA concentration, peak voltage, initial pH and conductivity were investigated. Results showed that dielectric barrier discharge plasma was an effective way to degrade and mineralize PFOA. The optimum conditions were found to be 50 μS·cm^-1of initial conductivity at voltage 14 kV, defluorination reaching 48.43% and TOC removal of 53.30% with a pseudo-first-order rate constants of 0.4075 h^-1 within 2 h. Scavenger was added to investigate the contribution of hydroxyl radical (·OH) in this system and it was found that·OH contributed to 78.30% of the defluorination. Two possible mechanisms were proposed by the intermediates identified with UPLC-QTOF/MS. One was the PFOA molecule attacked by·OH to form C₆F₁₃COCOOH with HF removal, and the other was the broken of carboxyl group from PFOA to form C₇F₁₃HO. Both products were oxidized by·OH to form C₆F₁₃COOH and then CF₂ was removed stepwise to form short chain of perfluorocaboxylic acid.