Synergistic pyrogenic carbon-microbial dehalogenator taking the "forever" out of "forever chemicals"

Per- and polyfluoroalkyl substances (PFAS) exhibit pronounced resistance to microbial defluorination due to the exceptional stability of C-F bonds, their helical molecular configuration, and the dense shielding by fluorine atoms. These properties result in limited transformation and incomplete defluorination, thereby constraining the effectiveness of conventional bioremediation approaches. This study hypothesizes that C-F bond strength in PFASs can be modulated through adsorption to enhance their microbial defluorination. Density functional theory (DFT) calculations indicated an 8.9 % reduction in the C-F bond dissociation energy of perfluorooctanoic acid (PFOA) via electron transfer mediated by pyrogenic carbon. This weakening lowered the C-F bond strength to a level comparable to that of C-Cl bonds in chlorinated hydrocarbons, significantly increasing PFOA susceptibility to microbial cleavage. Experimentally, nearly complete removal of PFOA at an initial concentration of 1 mg/L was achieved within 40 days, supported by fluoride ion release and the formation of short-chain fluorinated intermediates. Microbial community analysis implicated Dehalobacter as a primary agent responsible for reductive defluorination. The enhanced defluorination was further attributed to sustained electron shuttling through quinone-hydroquinone redox cycling facilitated by pyrogenic carbon. This integrated approach offers a promising and scalable strategy for remediating PFAS-contaminated environments.