Predicting the thermal decomposition behaviour of perfluorooctane sulfonamidoacetic acid (FOSAA): An emerging heteroatomic PFAS

Perfluorooctane sulfonamidoacetic acid (FOSAA) is an emerging heteroatomic perfluorinated alkyl substance (PFASs) compound. FOSAA acts as a xenobiotic and an environmental contaminant, and serves as a precursor to perfluorooctane sulfonate, similar to N-ethylperfluorooctane sulfonamidoacetic acid. The production of this compound has increased due to its use in several strategic applications, despite of proven toxicity. Our investigation employs computational analysis to explore the fate of FOSAA once subjected to thermal stress, aiming to develop comprehensive decomposition pathways. Comprehending the decomposition pathways of FOSAA is instrumental to design real operations that ultimately leads to its fluorine mineralization. The study encompasses 53 species and around 71 reactions, covering bond dissociation energies (BDEs), unimolecular reactions, the formation and fragmentation of the parent C₈F₁₇ radical, and bimolecular reactions beginning with the hydrofluorination of FOSAA. Additionally, it examines the abstraction of hydrogen from various functional groups of FOSAA by H/OH/F radicals. Our theoretical conditions for the thermal destruction of FOSAA span a wide temperature range of 300–2000 K. The kinetics and mechanisms revealed in this study aim to facilitate the development of innovative FOSAA thermal disposal technologies and other degradation processes, thereby accelerating research progress in modelling gas/solid reactions that mineralize FOSAA-derived fluorine.