Manipulating High-Valent Cobalt-Oxo Generation on Co/N Codoped Carbon Beads via PMS Activation for Micropollutants Degradation

Manipulating high-valent cobalt-oxo [Co(IV)═O] species in a catalytic system is pivotal; however, it is challenging due to the inefficiency and unsustainability of Co(IV)═O generation. In this study, we fabricated macroscopic porous Co/N codoped carbon beads (Co–NC) and identified Co(IV)═O as the prominent species in peroxymonosulfate (PMS) activation. Specifically, Co(IV)═O species on a Co–NC-900/PMS system was regarded as the crucial driver of tetracycline (TC) removal (with a degradation efficiency of 97.3% and an initial concentration of 20 mg L–1) through quenching experiments, methyl phenyl sulfoxide (PMSO) degradation, and methyl phenyl sulfone (PMSO2) generation. Importantly, Co–Nx active sites are responsible for the formation of Co(IV)═O species, which contribute as much as 98.33% to TC degradation based on the calculation of the steady-state concentration. In addition, the relative contributions of Co(IV)═O toward various micropollutants are substrate-specific and related to their ionization potential (IP). The practical application of Co–NC-900 was further evaluated in the continuous flow mode, and it showed excellent durability and performance. Overall, we have aroused the importance of Co(IV)═O on micropollutants removal in heterogeneous systems and provided an alternative macroscopic catalyst that can be potentially exploited in real water decontamination scenarios.