Dual-channel electron transfer boosting Fe/Co redox cycling in Co9S8/FeS catalyst for sustainable Fenton-like degradation

A dual-channel electron-donation pathway enables reductant-free Fe 2+ /Co 2+ regeneration. • Pollutants and S 2- synergistically drive reversible M(III)/M(II) redox cycling. • Co 9 S 8 /FeS/PMS achieves rapid and complete levofloxacin degradation within 10 min. A magnetic Co 9 S 8 /FeS composite derived from cobalt slag was developed for reductant-free PMS activation through a novel dual-channel electron-donation pathway involving S 2- species and levofloxacin (LEV). The catalytic performance and mechanism were investigated through degradation kinetics, reactive-species identification, X-ray absorption fine spectroscopy (XAFS), X-ray photo­electron spectroscopy (XPS) analyses, density functional theory (DFT) and life cycle assessment. The Co 9 S 8 /FeS/PMS system completely degraded LEV within 10 min (k = 0.4498 min −1 ), maintained efficient removal over pH 3.0–11.0 and after five cycles (>95%), with 1 O 2 as the dominant reactive species. DFT calculations, together with XAFS/XPS analyses, revealed that S 2− and LEV serve as dual electron donors to facilitate Fe 3+ /Co 3+ reduction, achieving nearly complete Fe/Co redox cycling and sustained PMS activation. Compared with conventional single-electron-donor Fenton-like systems, this strategy eliminates the need for external reductants and substantially reduces environmental impacts, offering a sustainable route for converting cobalt slag into recyclable catalysts for antibiotic wastewater treatment. Download: Download high-res image (176KB) Download: Download full-size image