The goal of chemical destruction of perfluoroalkyl substances (PFAS) is mineralization of fluorine as free aqueous fluoride. The carbon–fluorine (C–F) bond has relatively high kinetic stability but is thermodynamically unstable with respect to hydrofluoric acid (HF) at moderate partial pressures of hydrogen. If the activation barrier can be overcome, then hydrogen gas is capable of completely mineralizing the fluorine from fluorocarbons. As an example, in this work we explore the mineralization of fluorine from bulk polytetrafluoroethylene (PTFE), which is one of the most inert fluorocarbons known. Hydrogen gas (H2) activated by a nonequilibrium plasma in the temperature range from 330 to 470 °C results in PTFE destruction rates from 1 to 10 g h–1 and batch conversion as high as 80% in 12 h. Greater than 90% fluorine mineralization was reproducibly achieved. For comparison, thermal reaction without plasma at 500 °C using the same hydrogen gas composition and pressure resulted in similar mass loss rate from the PTFE feedstock but negligible fluorine mineralization. The results support the perspective that PFAS destruction in reducing environments is about overcoming a reaction barrier to allow the exergonic reaction to proceed toward HF. HF is then straightforward to neutralize.
Sudagar et al. (Mon,) studied this question.