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p H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 k V,初始电导率为50μS·cm-1条件下,2h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.
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 p H 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 k V,defluorination reaching 48. 43% and TOC removal of 53. 30% with a pseudo-first-order rate constants of 0. 4075 h- 1within2 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 C6F13 COCOOH with HF removal,and the other was the broken of carboxyl group from PFOA to form C7F13 HO. Both products were oxidized by ·OH to form C6F13COOH and then CF2 was removed stepwise to form short chain of perfluorocaboxylic acid.
出处
《环境科学学报》
CAS
CSCD
北大核心
2015年第3期764-772,共9页
Acta Scientiae Circumstantiae
基金
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)~~
关键词
PFOA
介质阻挡放电
活性物质
机制
PFOA
dielectric barrier discharge
reactive species
mechanism
