Construction of cobalt-embedded magnetic yolk-shell magic cube nanoreactors for metronidazole wastewater purification.

Developing low-catalyst-dosage technologies for metronidazole (MTZ) wastewater treatment is a pressing task. In this study, a novel magnetic yolk-shell magic-cube-structured catalyst was constructed, which combines highly exposed active sites with a nanoconfinement effect. At a catalyst dosage as low as 50 µg/mL, with peroxymonosulfate (PMS) concentration optimized to 0.2 g/L (yielding an optimal catalyst-to-PMS ratio of 1:4), activation of PMS enables 97.0 % degradation of MTZ within 15 min. In continuous-flow experiments, a MTZ degradation rate of 97 % was achieved within 1440 min. Theoretical calculations indicate that the carbon-rich shell promotes the generation of ¹O2, whereas the cobalt core induces radical pathways. Comprehensive experimental measurements collectively confirm the dominant contribution of ¹O2, while Co(IV)=O, SO4•-, ∙OH, and O2•- play synergistic roles. Ecotoxicity assessment and life-cycle assessment validate the environmental friendliness of the process. This study provides new strategies for the design and application of high-performance, low-dose catalytic nanoreactors for the remediation of antibiotic pollution in water systems.