Per- and poly-fluorinated alkyl substances (PFASs) are a group of recalcitrant contaminants containing a fully fluorinated carbon chain and one of several different end groups (e.g., sulfonate, carboxylate). They resist degradation including oxidation by hydroxyl radicals due to strong carbon-fluorine bonds. This study explored sonochemical degradation of perfluorononanoic acid (PFNA) and perfluorohexanesulfonic acid (PFHxS), two rarely studied among six PFASs in USEPA’s UCMR3 list. Sonication at 20 kHz and 480 W/L yielded the first order degradation rate of 0.0018 and 0.0138 min<sup>-1</sup> for PFHxS and PFNA, respectively. The result suggests thermolysis of PFNA and PFHxS occurred at the water-cavitation bubble interface, the major degradation site for sonolysis of PFASs. However, the degradation rate was enhanced with bubbling of argon gas, while reduced with the presence of 5 mg/L of Suwannee River natural organic matter. LC-MS-MS analysis identified the major degradation intermediates including perfluorohexanoic, perfluorobutanesulfonic, perfluoropentanoic, and perfluoropropanoic anions.

Sonochemical degradation of perfluorononanoic and perfluorohexanesulfonic acids in aqueous solutions

254th National Meeting (2017)

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