Efficient Catalytic Process Induced by Lithium-Deficient Spent LiNi_1/3Co_1/3Mn_1/3O₂: Toward Both Organic Pollutant Decontamination and E-Waste Reuse

Spent LiNi_xCo_yMn_zO₂ (SNCM) still suffers from high recycling costs and secondary contamination, whereas materials containing nickel, cobalt, or manganese have been demonstrated to have excellent catalytic ability in the activation of sulfite [S(IV)]. The effective combination of SNCM and S(IV) is therefore expected to maximize the value of e-waste recycling. In this study, lithium defects and oxygen vacancies were found in SNCM, rather than in pristine nickel cobalt manganese oxide, which greatly enhanced the efficiency of S(IV) activation. Six typical pollutants can be efficiently degraded in the SNCM/S(IV) system, and their degradation efficiencies were all above 75% within 60 min. Interestingly, different from the alkaline conditions, an induction period of 3 min was observed under acidic conditions. HSO₃^- was slowly adsorbed to release SO₃^•- over 3 min. This conclusion has been validated through quenching experiments, S(IV) consumption profiles, and density functional theory calculations. SO₄^•- and ^•OH are the main reactive oxidative species in the SNCM/S(IV) system, and the generation of SO₅^•- by O₂ with SO₃^•- may be a key step for the further production of SO₄^•-•OH, and ¹O₂. Moreover, the excellent stability and practical application prospects of the SNCM/S(IV) system are also discussed.