PFOA and PFOS Are Generated from Zwitterionic and Cationic Precursor Compounds during Water Disinfection with Chlorine or Ozone

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are anionic organic pollutants, which are widespread in the environment. They have become a global concern due to their persistence in the environment as well as their toxicity and bioaccumulative properties. In this study, we demonstrate that PFOA, PFOS, or both are produced from a group of four zwitterionic/cationic polyfluoroalkyl amide (FA) and sulfonamide (FS) compounds during conventional drinking-water disinfection with chlorine or ozone. FA compounds were readily degraded by chlorine and converted primarily to PFOA, likely by a Hofmann-type rearrangement. FS compounds were much less reactive toward chlorine; the generation of PFOS from the FSs was not significant. All four FA and FS compounds were degraded rapidly during ozonation, generating PFOA, PFOS, and a number of infrequently reported products for which chemical structures were either confirmed or tentatively proposed using high-resolution mass spectrometry. FSs generated both PFOS and PFOA during ozonation with the yield of PFOA even higher than that from the FAs. The results of this study may provide important insight into the degradation mechanisms of FAs and FSs and shed light on their contribution to the secondary formation of PFOA and PFOS in natural and engineered systems.