US EPA

5024249 

Journal Article 

Degradation of PFOA Substitute: GenX (HFPO-DA Ammonium Salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite? 

Bao, Y; Deng, S; Jiang, X; Qu, Y; He, Y; Liu, L; Chai, Q; Mumtaz, M; Huang, J; Cagnetta, G; Yu, G 

2018 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

52 

20 

11728-11734 

English 

30207460 

10.1021/acs.est.8b02172 

WOS:000447816100030 

Hexafluoropropylene oxide dimer acid (HFPO-DA, ammonium salt with trade name: GenX) has been recently detected in river water worldwide. There are significant concerns about its persistence, and potential adverse effects to the biota. In this study, the degradability of GenX by typical advanced redox technologies (UV/persulfate and UV/sulfate) is investigated. Results demonstrate that <5% GenX is oxidized after 3 h in UV/persulfate system, which is much lower than ∼27% for PFOA. In comparison, GenX can be readily degraded and defluorinated by hydrated electron (eaq-) generated by UV/sulfite system. Specifically, GenX is not detectable after 2 h, and >90% of fluoride ion is recovered 6 h later. This is attributed to the accumulation and subsequent degradation of CF3CF2COOH and CF3COOH, which are stable intermediates of GenX degradation. Mechanistic investigations suggest that the etheric bond in the molecule is a favorable attack point for the eaq-. Such finding is corroborated by quantum chemical calculations. The side CF3- at the α-carbon probably acts as an effective barrier that prevents GenX from being cleaved by SO4-• or OH• at its most sensible point (i.e. the carboxyl group). This study illustrates that reduction by UV/sulfite might be a promising technology to remove GenX from contaminated water. 

environmental studies; ultraviolet radiation; organic contaminants; water pollution; oxidation; degradation; reduction; fluoride; ammonium; quantum chemistry; carboxyl group; ammonium salts; chemical bonds; degradability; organic chemistry; intermediates; chemical attack; sulfate; sulfite