Ultra-small Co3O4 particles embedded into N-doped carbon derived from ZIF-9 via half-pyrolysis for activating peroxymonosulfate to degrade sulfamethoxazole

Abstract

The fabrication of novel and efficient transition metal-based catalysts for peroxymonosulfate (PMS) activation is of great significance for environmental remediation. Concerning energy consumption, the Co₃O₄@N-doped carbon (Co₃O₄@NC-350) was constructed via a half-pyrolysis strategy. The relatively low calcination temperature (350 °C) caused Co₃O₄@NC-350 to exhibit ultra-small Co₃O₄ nanoparticles, rich functional groups, uniform morphology, and a large surface area. For PMS activation, Co₃O₄@NC-350 could degrade 97% of sulfamethoxazole (SMX) in 5 min with a high k value of 0.73364 min⁻¹, which was superior to the ZIF-9 precursor and other derived materials. Besides, Co₃O₄@NC-350 could be re-used over 5 times without obvious performance and structure change. The investigation of the influencing factors containing co-existing ions and organic matter demonstrated the Co₃O₄@NC-350/PMS system has satisfactory resistance. The quenching experiments and electron paramagnetic resonance (EPR) tests showed ˙OH, SO₄˙⁻, ˙O₂⁻ and ¹O₂ participated in the degradation process. Moreover, the structure and toxicity of intermediates during the SMX decomposing process have been evaluated. Overall, this research provides new prospects for exploring efficient and recycled MOF-based catalysts for PMS activation.