Solvent-Free, Ambient Temperature and Pressure Destruction of Perfluorosulfonic Acids under Mechanochemical Conditions: Degradation Intermediates and Fluorine Fate

Perfluorosulfonic acids (PFSAs) are a recalcitrant subclass of per-and polyfluoroalkyl substances (PFASs) linked to numerous negative health effects in humans. Scalable technologies that effectively destroy PFSAs will greatly reduce the future health and ecological impact of these forever chemicals. Herein, we show that several PFSAs undergo facile mechanochemical destruction (MCD) in the presence of quartz sand (SiO2). This process operates in the absence of solvent, at ambient temperature and pressure, generating a benign solid byproduct. Quantitative analysis of milled samples revealed high destruction efficiencies of 99.95% to 100% for five different PFSAs subjected to MCD conditions in the presence of SiO2 only. Extensive nontargeted analysis showed that, during degradation, other PFASs form and are ultimately destroyed upon extended mechanochemical treatment. Direct polarization (DP) and cross-polarization (CP) solid-state nuclear magnetic resonance (SSNMR) spectroscopy showed abundant silicon-fluorine (Si-F) bond formation post-MCD, indicating that fluorine was secured in a stable reservoir. Collectively, these results identified the degradation profile for an environmentally sound and effective PFSA degradation process that is amenable to scale-up.

Automated summary

Perfluorosulfonic acids (PFSAs), a subclass of PFASs, can be effectively destroyed through mechanochemical destruction (MCD) in the presence of quartz sand (SiO2), without the need for solvents and under ambient conditions. The destruction efficiency of five different PFSAs subjected to MCD conditions with SiO2 reached 99.95% to 100%. Other PFASs were formed and ultimately destroyed during the degradation process. Solid-state nuclear magnetic resonance spectroscopy confirmed the formation of silicon-fluorine (Si-F) bonds post-MCD, indicating the stable sequestration of fluorine.