Polyethylene glycol-enhanced CoFe alloy @biochar to boost Fenton-like reactions: A synergy of SO4·-, 1O2, Co(IV)/Fe(IV) and electron transfer.

This study constructed a CoFe alloy loaded biochar (CoFe@PBC) with polyethylene glycol-2000 (PEG-2000) to improve PMS activation and durability. Characterization analysis and theoretical calculations indicated that CoFe alloy changed the electrostatic surface potential (ESP) and spin-polarized density of states (DOS) distribution of the catalyst. This led to variations in the electron-donating ability and a smaller energy gap between HOMO and LUMO, thus further improving the electron-transfer rate and the generation of SO4·-, 1O2, and Co(IV)/Fe(IV) species. The significantly enhanced catalytic performance can be attributed to the synergistic effects of Co, Fe, and PEG-2000, where Co was identified as the primary active center, Fe played a role in accelerating electron transfer, while PEG-2000 functioned as a template, optimizing the hydrophilicity and alloy deposition on the catalyst. Toxicity evaluation and cytotoxicity assays confirmed that ciprofloxacin was transformed into less toxic byproducts. The LogP, ΔE, and degradation rate constants of various micropollutants exhibited strong linear correlations (R2 = 0.8579/0.8593), demonstrating the significant selectivity of CoFe@PBC/PMS system in pollutant degradation. Overall, this study contributes to the sustainable fabrication of carbon-alloy catalysts with enhanced waste valorization capabilities.