The remediation of perfluoroalkyl substances (PFAS) from aqueous solution has received considerable interest due to their potential threat to the environment and human health. Degradations of PFAS in water by conventional methods are largely ineffective and particularly challenging because of the extremely strong C-F bonds of the PFASs. We demonstrated ultrasonic irradiation at 640 KHz can effectively degrade a variety of legacy and emerging PFAS, including perfluorobutanoic acid (PFBuA), perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluoro-2-propoxypropanoic acid (GenX), and perfluoro-4-methoxybutanoic acid (PFMeoBuA). Liquid Chromatography- Orbitrap High Resolution Mass Spectrometry (LC-HRMS) was used to monitor the degradation of target PFASs as a function of treatment time. Hydroxyl radical scavengers, coumarin, terephthalic acid, and t-butyl alcohol showed no significant effect on the rate of PFAS degradation, indicating the degradation likely proceeds through pyrolysis and not oxidation. Mineralization of individual PFAS to fluoride was measured using a fluoride ion selective electrode. The fluoride mass balance from PFBuA and PFOA after three hours of treatment was 40-50 %, while nearly 75 % mineralization to fluoride was observed for GenX, PFMeoBuA, PFPeA, and PFHpA. Ion chromatographic analysis of treated PFASs revealed production of formate ion, however others anions were not detectable under our conditions. Detailed product studies using an Orbitrap HRMS will be performed to tentatively identify the fluorinated degradation products formed during sonolysis. The obtained results suggest that sonolytic induced degradation is a promising method for the removal of PFASs from aqueous solutions.

Degradation of perfluoroalkyl substances (PFAS) in water by ultrasonic irradiation

2019 Spring National Meeting

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