Optimizing mixed activation pathway by high-spin spinel oxide for low-electrophilicity pollutants removal

Although PMS-based advanced oxidation processes (AOPs) represent an attractive water purification technology, achieving efficient oxidation of low-electrophilicity pollutants and their effective removal from real wastewater still remain challenges. Here, we designed a synergistic degradation system involving the electrophilic species Co (IV)=O and SO₄^•- induced by oxygen vacancies. There is a strong linear correlation between the degradation rate and the electrophilic index of the pollutant (R² = 0.93). The construction of the asymmetric coordination environment changed the spin state at the Co site, promoted the breakage of O-H bonds and the desorption of the *SO₄ intermediate, thereby facilitated the generation of Co (IV)=O and SO₄^•-. In the optimized catalyst (CAO-400) system, the degradation rate constant of carbamazepine reached 238.33 min^-1 M^-1, which was 22 times higher than that of catalyst without oxygen vacancies. In an enlarged-scale continuous flow reactor, the hydrogel ball (CAO-400@Alg) system maintained an 81% removal rate of the chemical oxygen demand (COD) of the wastewater, satisfying the regulatory discharge standards. This work provides valuable references for guiding the design of Fenton-like catalysts and realizing sustainable water purification applications.