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

Abstract

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 (e) 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 CFCFCOOH and CFCOOH, which are stable intermediates of GenX degradation. Mechanistic investigations suggest that the etheric bond in the molecule is a favorable attack point for the e. Such finding is corroborated by quantum chemical calculations. The side CF- at the α-carbon probably acts as an effective barrier that prevents GenX from being cleaved by SO• 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.

LC-MS screening of poly- and perfluoroalkyl substances in contaminated soil by Kendrick mass analysis

“…For example, the KMD for PFHpA is − 1.96 × 10 −4 (Eq. 3) and exactly the same number for PFOA and PFNA or even larger PFCAs like perfluorohexadecanoic acid (C 16…”

“…Two of the best studied PFASs, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), accumulate in the liver, lung, and kidney of rats and are proposed to be a big threat to humans and biota [14,15]. Their major manufacturer 3M has hence phased out the production of these two substances between 2000 and 2002 [1], yet other P FA S s s u c h a s a m m o n i u m 2 , 3 , 3 , 3 -t e t r a f l u o r o -2-(heptafluoropropoxy)-propanoate (GenX) have replaced these compounds [16]. Studies performed by Gomis et al [17] and Sun et al [18] even indicate a higher toxicity and a lower sorption on activated carbon for GenX than for PFOA, highlighting the importance of both legacy and novel PFASs.…”

Evaluation of Maternal, Embryo, and Placental Effects in CD-1 Mice following Gestational Exposure to Perfluorooctanoic Acid (PFOA) or Hexafluoropropylene Oxide Dimer Acid (HFPO-DA or GenX)

“…Despite such efforts, exposure to PFOA remains a concern due to its long human half-life ( ∼ 3:5 y) (Olsen et al 2007), environmental persistence (Lindstrom et al 2011), and the fact that longer-chain/precursor PFAS chemicals can degrade and form PFOA. In response to restrictions on PFOA, manufacturers have increased production on replacement compounds with alternative chemistries aimed at making the compounds less bioaccumulative and with shorter serum half-lives; however, toxicity data for these alternative PFAS are limited (Bao et al 2018).…”

Per- and polyfluoroalkylether substances: identity, production and use

“…183 Beekman et al, for Netherlands National Institute of Public Health, (2016), Evaluation of substances used in the GenX technology by Chemours, Dordrecht. RIVM Letter report 2016-0174.184 Bao, Yixiang et al (2018). Degradation of PFOA Substitute -GenX (HFPO-DA ammonium salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite?.…”