Release of Fluoro-Contained Free Radicals and Polyfluorinated-Like Molecules from Photoaged Fluorinated Microplastics: Identification and Formation Mechanisms

Fluorinated microplastics (F-MPs), such as poly(vinylidene fluoride) (PVDF) and polytetrafluoroethylene (PTFE), are increasingly prevalent in environmental matrices due to their extensive industrial use, yet their chemical transformation under environmental aging remains unresolved. Here, we systematically elucidate the photochemical pathways governing radical formation, molecular fragmentation, and redox reactivity of F-MPs exposed to UV-A/H₂O₂ irradiation. Solid-state and spin-trapping electron-paramagnetic-resonance analyses reveal that the formation of persistent carbon-centered and fluorine-coupled radicals reaches 10¹⁵ spins g⁻¹ on PVDF, accompanied by the generation of ten short-lived reactive species, including ·OH, O₂·⁻, and CF₂·. Subsequent C-F bond scission releases fluoride ions (up to 50 μmol g⁻¹) and fluorinated molecular fragments structurally analogous to polyfluoroalkyl (PFAS) precursors (e.g., tetrafluoroethylene oxide, difluoroacetic acid, and trifluoroacetaldehyde). Concurrently, oxidative surface functionalization narrows the PVDF band gap and bolsters its oxidative potential by 5-fold, enabling the catalytic transformation of atrazine (a typical contaminant in water and soil) with a removal efficiency of 43.7 ± 3.2%. In contrast, PTFE exhibits minimal radical accessibility due to higher C-F bond dissociation energies and limited surface oxidation. These findings demonstrate that Photoaged F-MPs function as redox-active interfaces, vectors, and secondary PFAS sources, rather than presumed inert particulates, thus substantially expanding the paradigms of MPs' environmental reactivity and the contaminant fate.