Selective Generation of Co(IV)–Oxo Species in Catalytic Ozonation Process for Effective Decontamination of High-Salinity Wastewater

Heterogeneous catalytic ozonation (HCO) is widely used for degrading organic contaminants in wastewater, yet its efficiency is severely compromised in high-salinity environments due to the quenching of hydroxyl radicals (HO•) by common background anions. Herein, we report the rational evolution from single-atom to diatomic Co catalysts (Co-DAC), which precisely regulate the adsorption configuration of O₃ and switch the dominant reactive oxygen species from nonselective HO• to highly selective Co(IV)═O species. In contrast to the end-on O₃ adsorption on an isolated single-atom site, the adjacent dual Co atoms favor a bridge-like O₃ adsorption configuration with a more symmetric charge distribution, which facilitates homolytic O-O bond cleavage and thus promotes Co(IV)═O formation. Consequently, the Co-DAC/O₃ system exhibits exceptional resistance to high salinity (100 mM Cl⁻) and achieves a record-high mass activity (0.90 mmol g⁻¹ min⁻¹) of oxalic acid removal. As a proof of concept, a carbon nanotube-supported Co-DAC membrane is equipped in a flow-through reactor to intensify convective mass transfer, yielding a 162-fold increase in the decontamination rate over a conventional batch configuration. This work not only advances the mechanistic understanding of O₃ activation on diatomic sites but also provides a scalable solution for treating refractory organic pollutants in high-salinity wastewater.