Defluorination phenomenon during CO2 methanation with Fe0 enhancement when PFOS coexists with microplastics

In this study, the effects of PFOA exposure on methanogenesis and defluorination properties were evaluated by the purification of biogas during PET and ZVI-mediated anaerobic digestion. The experimental results showed that after 5 cycles of culture, the proportion of methane in PFOA and PFOA_PET group still reached about 90% despite the toxicity of PFOA and PET to cells, proving that biogas purification under this system is effective. The proportion of methane in the group with zero-valent iron (ZVI) reached about 95%, showing good biomethanation performance. Measurements of protein and reactive oxygen species (ROS) suggest that ZVI may reduce the toxicity of PFOA to cells by promoting protein binding to PFOA. In addition, it was confirmed by molecular docking that PFOA can bind to bovine serum protein (BSA), which may be one of the mechanisms to reduce PFOA's cytotoxicity. PFOA, PET, and ZVI affect microbial growth to varying degrees, and the addition of ZVI and PET may increase the proportion of methane by upregulating key genes and enzymes. The addition of ZVI promotes the mineralization and degradation of PFOA, and the upregulation of crcB gene and palustris enzyme is the reason for this result, and the main pathway is H/F exchange and decarboxylation, and the CO2 produced can provide more carbon sources for biogas purification.