Emulsified Vegetable Oil Droplet Interfaces Sustain PFOA Defluorination in Groundwater through Carbon-Centered Radicals.

Perfluorooctanoic acid (PFOA) is highly resistant to degradation due to the extremely high bond energy of its C-F bonds. Current remediation approaches lead to incomplete defluorination and generally rely on external energy input, which limits their applicability for groundwater remediation. Here, we develop a novel emulsified vegetable oil (EVO)-Fe(II)/O2 system that achieves near-complete defluorination of PFOA (>99%) under dark conditions without external oxidants. Mechanistic investigations reveal that EVO droplets create droplet-associated interfaces that confine PFOA and reactive species and catalyze a distinct radical cascade, modulating the conversion of superoxide radicals (O2•-) into singlet oxygen (1O2) and subsequently carbon-centered radicals (CCR•). This sequence unlocks a novel defluorination pathway dominated by CCR• and 1O2. Furthermore, this reactivity is sustained by the structural evolution of EVO from linear degradation to cross-linked aromatic polymerization, which continuously replenishes redox-active functional groups. These findings establish a theoretical framework for low-energy, sustainable PFOA deep defluorination in groundwater.