Ferrate-assisted nonthermal plasma for efficient PFOA degradation in landfill leachate: Mitigating bulk organic...

Per- and polyfluoroalkyl substances (PFAS) in complex wastewater are highly persistent due to the strength of the C-F bonds and the presence of coexisting organic and inorganic constituents, which strongly inhibit their degradation performance. In this study, a synergistic plasma-ferrate process was developed to achieve efficient PFAS removal in both synthetic and real landfill leachate wastewater. Under optimized conditions (discharge power of 150 W, ferrate dosage of 2.1 mg/L and pH 9), the process achieved PFOA degradation efficiencies up to 95% and a reduced energy consumption (EE/O ≈ 95 kWh/m³). The enhanced performance arises from a combination of factors: first, plasma-generated electrons and reactive species activate ferrate to form high-valent iron species (Fe(IV)/Fe(V)), substantially increasing oxidative capacity; second, plasma directly produces e_aq⁻ and H•, which dominate the reductive defluorination of PFAS; third, ferrate selectively oxidizes and coagulates background organic matter, reducing the quenching of e_aq⁻ and improving the reduction of PFAS. This multi-faceted synergy enables PFAS degradation in real wastewater to approach the efficiency observed in synthetic wastewater (>90%). Compared with other ferrate-based advanced oxidation processes, the required ferrate dosage is markedly lower (only a few mg/L versus tens of mg/L typically reported). Overall, the plasma-ferrate synergistic process offers a promising, energy-efficient, and scalable approach for treating PFAS-contaminated complex wastewater, overcoming matrix interference, and enabling high degradation performance with minimal chemical consumption.