Redox-coupled coordination strategy for xanthate detoxification via self-catalysis over a broad pH range

This study developed an effective strategy to construct a Cu(II)/Cu(I) redox cycle catalytic system by anchoring Cu(II)/Cu(I) onto multi-walled carbon nanotubes (MWCNTs) via wet ball milling for the efficient degradation of xanthate compounds. The catalyst exhibited dual functionality: Cu(II) coordinated with electron-rich S-CS moiety in xanthate molecules, facilitating strong adsorption of xanthate and generation of stable Cu(I), which subsequently activated H₂O₂ to regenerate Cu(II) and generate reactive oxygen species (•OH, •O₂⁻, and ¹O₂). DFT calculations verified the enhanced adsorption of xanthate. This Cu(II)/Cu(I) redox cycle enabled simultaneous adsorption and degradation of PBX. Under optimal conditions (pH 7.0, 12 mM H₂O₂, 0.1 g/L catalyst), over 90 % PBX was degraded. The catalyst maintained high activity over wide pH range (pH 4-9) and five cycles with negligible Cu leaching (<0.05 mg/L), indicating excellent stability. The catalyst exhibits excellent resistance to interference from coexisting anions and organic acids, demonstrating strong practical performance. The catalyst also exhibited strong degradation efficiency toward diethyl dithiophosphate (DTP), achieving a removal rate of 71.7 %, highlighting its broader applicability to sulfur-containing flotation reagents. UHPLC-MS analysis identified key degradation intermediates, and two major degradation pathways were proposed. ECOSAR toxicity modeling revealed a significant reduction in aquatic toxicity from parent PBX to its final mineralized products (CO₃²⁻ and SO₄²⁻). The results demonstrate that the catalyst effectively degrades PBX through a redox-coupled mechanism and remains stable under repeated use. This work provides new insight into advanced oxidative removal of xanthates and offers a promising strategy for the treatment of sulfur-containing pollutants in neutral pH industrial effluents.