UV/SO_3^(2-)体系还原降解全氟辛烷磺酸及其影响因素

Reductive degradation of perfluorooctanesulfonate in UV/sulfite system and related influencing factors

采用水合电子(e-aq)的还原技术降解水中的全氟辛烷磺酸(PFOS).结果表明,不同体系PFOS降解的脱氟率如下:SO_3^(2-)/N_2<UV/N_2<UV/SO_3^(2-)/O2<UV/SO_3^(2-)/Air<UV/SO_3^(2-)/N_2,通过刃天青荧光探针实验证实与体系e-aq的生成量有关.PFOS降解的脱氟动力学满足PEK模型,其快反应与慢反应分别对应于PFOS支链异构体与直链异构体的降解.增加SO_3^(2-)浓度可提高PFOS的脱氟率,碱性条件下的脱氟效果明显优于酸性和中性条件.此外,反应温度的提升可进一步提高PFOS的脱氟率.通过对中间产物的监测表明,除了端基断裂和氟原子直接脱除的方式外,PFOS亦可通过中间C—C键断裂的方式发生降解,从而使得短链全氟丙酸(PFPr A)和全氟丁酸(PFBA)的浓度明显高于其它产物.

A reductive method was developed for the effective defluorination of perfluorooctanesulfonate（ PFOS） by hydrated electrons（ eaq^-） in sulfite solution under UV irradiation. It was found that the defluorination rate of PFOS followed the order of SO3^2-/N2 UV/N2 UV/SO3^2-/O2 UV/SO3^2-/Air UV/SO3^2-/N2,which agrees well with the trend of e-aqproduction measured by using resazurin as a fluorogenic probe. The defluorination of PFOS was also accelerated by adding more sulfite, increasing reaction temperature or using an alkaline solution. The defluorination of PFOS followed the parallel exponential kinetics（ PEK） model,in which the fast and slow exponential processes were assigned to the degradation of branched PFOS and linear PFOS,respectively. The identification of intermediates showed that PFOS decomposition involved desulfonation,defluorination and centermost C—C bond scission,resulting in the generation of pentafluoropropionic acid（ PFPr A） and heptafluorobutyric acid（ PFBA） with concentrations higher than other significantly products.