UV/nitrilotriacetic acid process as a novel strategy for efficient photoreductive degradation of perfluorooctanesulfonate

Abstract

Perfluorooctanesulfonate (PFOS) is a toxic, bioaccumulative and highly persistent anthropogenic chem. Hydrated electrons ( e(aq)(-) ) are potent nucleophiles that can effectively decomp. PFOS. In previous studies, e(aq)(-) are mainly produced by photoionization of aq. anions or arom. compds. In this study, we proposed a new photolytic strategy to generate e(aq)(-) and in turn decomp. PFOS, which utilizes nitrilotriacetic acid (NTA) as a photosensitizer to induce water photodissocn. and photoionization, and subsequently as a scavenger of hydroxyl radical ((OH)-O-center dot) to minimize the geminate recombination between (OH)-O-center dot and e(aq)(-) . The net effect is to increase the amt. of e(aq)(-) available for PFOS degrdn. The UV/NTA process achieved a high PFOS degrdn. ratio of 85.4% and a defluorination ratio of 46.8% within 10 h. A pseudo first-order rate const. (k) of 0.27 h^(-1) was obtained. The laser flash photolysis study indicates that e(aq)(-) is the dominant reactive species responsible for PFOS decompn. The generation of e(aq)(-) is greatly enhanced and its half-life is significantly prolonged in the presence of NTA. The ESR (ESR) measurement verified the photodissocn. of water by detecting (OH)-O-center dot. The model compd. study indicates that the acetate and amine groups are the primary reactive sites.