Efficient antibiotic degradation via peroxymonosulfate activation by a biochar-supported cobalt single-atom catalyst:...

Single-atom catalysts (SACs) have attracted considerable attention owing to their high catalytic activity and atom utilization. Nevertheless, their application to antibiotic removal and associated biosafety remains insufficiently explored. In this work, a single-atom Co catalyst supported on N-doped biochar (SA-Co-NC) was synthesized by impregnation-pyrolysis to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The porous biochar stabilized atomically dispersed Co-N₃ sites. The experimental results demonstrate that the SA-Co-NC/PMS system removed 96.6% of TC within 18 min and achieved 75.7% mineralization. X-ray absorption spectroscopy and density functional theory calculations indicate that coordinatively unsaturated Co-N₃ sites regulate the local electronic structure, strengthen TC and PMS adsorption, and promote PMS activation, with ¹O₂ dominating the nonradical pathway and Co(IV)=O possibly contributing. Phytotoxicity assessments demonstrate that the treated solution is less phytotoxic than untreated TC solution. Animal toxicity tests reveal that a 24-h oral exposure to SA-Co-NC caused no overt histopathological damage in the mouse liver, kidney, or thyroid and produced only limited changes in the measured oxidative-stress and inflammatory markers. These results demonstrate the catalytic effectiveness and preliminary biosafety of SA-Co-NC for antibiotic-contaminated water treatment.