Hexafluoropropylene Oxide Dimer Acid (HFPODA or GenX), a short-chain organofluorine compound, was developed by DuPont in 2009 as a ‘safer’ alternative to the highly toxic and persistent perfluorooctanoic acid (PFOA). However, emerging evidence suggests that GenX itself presents significant health risks, leading the US EPA to set a health advisory level of 10 parts per trillion (ppt) in water. GenX, like most PFAS compounds, do not degrade under traditional wastewater treatments due to the strong C-F bond energy of 530 kJ/mol. Ultrasonication has promise as a viable treatment owing to the rapid collapse cavitation bubbles undergo that create localized temperatures of 15000 K and pressures of 1000 atm. Our research incorporated ultrasonication into an advanced reduction process (ARP) treatment system and utilized non-targeted analysis on a high-performance mass spectrometer to determine ultrasonication's role in breaking down GenX. Starting with a GenX concentration of 2.0 ppb, the system achieved 99.2% degradation of GenX, reducing its concentration to 9.5 ppt at a rate of 0.1112 min^-1. Non-targeted analysis identified pathways for GenX degradation revealing that without ultrasonication, CF₃COO^- (trifluoroacetic acid, TFA) is significantly higher than all other products, occupying 93% of total counts. TFA belongs to the subclass of PFAS known as ultrashort-chain perfluoroalkyl acids (PFAAs) and is classified as having low to moderate toxicity. In contrast, non-toxic CH₃SO₃^- is the most dominant product in the presence of ultrasonication, occupying 99.9% of total counts of final products, providing evidence for the enhanced effectiveness of degradation of GenX to non-toxic byproducts. Preliminary assessment of other PFAS compounds within this system revealed fluorotelomer sulfonic acids and short-chain polyfluoroalkyl carboxylic acids were also effectively degraded, but longer-chain PFAs showed less promising results, highlighting the opportunity for improvement.

Kelsey OMalley

Appearances