A generic solvothermal defluorination method for carboxylate and sulfonate PFAS

We report a solvothermal method that enables complete mineralization of structurally diverse per- and polyfluoroalkyl substances (PFAS) under substantially milder conditions than established hydrothermal treatments. The method's scope includes perfluorocarboxylic acids (PFCAs), perfluorosulfonic acids (PFSAs), and the perfluoroether carboxylic acid (PFECA) GenX. At 220 °C and with 8 M KOH, the addition of alcohol co-solvents (50 vol% methanol) markedly enhances defluorination, enabling >99% conversion of PFAS to inorganic fluoride. Performing the reactions in sealed pressure batch reactors ensures closed fluorine mass balances and prevents loss of hazardous fluorinated gases, allowing complete recovery of inorganic fluoride. Alcohol co-solvents promote mineralization through a dual role by enhancing retention of volatile fluorinated intermediates in the reactive liquid phase and enabling hydride-assisted degradation pathways. The method is further demonstrated on PFAS-loaded granular activated carbon (GAC), achieving high mineralization yields in a real-life waste matrix. Combined multinuclear NMR, FTIR and chromatographic analyses identify in detail intermediates and reaction networks in this PFAS destruction approach.