pH-regulated hydrolysis strategy for the construction of stable Co₃O₄/NC@BC composite catalyst for antibiotic...

The practical application of peroxymonosulfate (PMS) in water remediation is contingent on developing stable and highly efficient catalysts. Conventional cobalt-based catalysts, however, often suffer from active site agglomeration, sluggish electron transfer, and poor cycling stability, which hinder their scalability. To address these limitations, we engineered a composite of Co₃O₄ nanosheets anchored on nitrogen-doped carbon and highly graphitized biochar (Co₃O₄/NC@BC). This was achieved through a pH-regulated hydrolysis of ZIF-67/BC precursors into a layered Co(OH)₂/NC@BC intermediate, followed by calcination. This unique configuration not only exposes abundant active sites but also facilitates electron transfer and mitigates Co₃O₄ agglomeration via the conductive BC network. The optimized catalyst demonstrated exceptional performance, achieving 98.91% removal of ciprofloxacin (CIP) within 60 min, alongside robust anti-interference capability and reusability. Mechanistic studies revealed that both radical (SO₄^-• and •OH) and non-radical (¹O₂ and electron transfer) pathways contribute to CIP degradation. Assessment by the Ecological Structure-Activity Relationship (ECOSAR) model indicated a significant reduction in the acute and chronic toxicity of the degradation intermediates compared to the parent CIP. This work provides a strategic design for high-performance cobalt-based catalysts and underscores the application potential of the Co₃O₄/NC@BC composite for mitigating antibiotic contamination.