Degradation of butyl xanthate via peroxydisulfate activation using a magnetic CoFe2O4/chestnut shell biochar composite catalyst

Abstract Residual flotation reagents in mineral-processing wastewater pose persistent environmental risks, creating a need for efficient and reusable treatment technologies. Here we show that a magnetic composite of cobalt ferrite and chestnut-shell-derived porous biochar efficiently activates peroxydisulfate to degrade sodium butyl xanthate in water. Under optimized conditions, the composite removes 99.5% of sodium butyl xanthate within 120 minutes, with a pseudo-first-order rate constant of 0.041 per minute. It maintains effective removal in real water matrices, is readily recovered using a magnet, and remains stable over five successive cycles. Mechanistic analyses identify superoxide radicals and singlet oxygen as the dominant reactive species, while cobalt and iron redox cycling supports peroxydisulfate activation. The porous biochar framework also promotes pollutant enrichment, active-site dispersion, and interfacial electron transfer. These results demonstrate a reusable catalyst for treating flotation-reagent-contaminated wastewater.