Efficient degradation of industrial pollutants with sulfur (IV) mediated by LiCoO₂ cathode powders of spent lithium ion batteries: A “treating waste with waste” strategy

Strategies to maximize the reuse of electronic and industrial wastes have scientific, economic, social and environmental implications. We herein propose a strategy of “treating waste with waste” using LiCoO₂ cathode powders from spent lithium ion batteries to eliminate industrial pollutants led by sulfur (S) (IV) in waste water. By radical scavenging experiments and electron spin resonance (ESR) analysis, we identified singlet ¹O₂ as the dominant species while SO₄^[rad]− and ^[rad]OH as the secondary species for decontamination during the oxidization process mediated by LiCoO₂ powders. The intrinsic mechanism of S(IV) conversion was revealed to be two-step hydrogen migrations from HSO₃⁻ to O₂ occurring on LiCoO₂ surface by density functional theory (DFT) calculations. The surface of LiCoO₂ powders plays a key role in anchoring sulfur species and forming surface complex as an excellent medium, which is found to be stable and reusable by material characterizations and the recycling experiment. Free Co(II) ions in solvents have no catalysis effect on the conversion of pollutants. Our work offers a particularly vivid example for rational reuse of electronic wastes to eliminate industrial pollutants, and may raise economic benefits in environmental practice due to two aims achieved in once action.