PMS activation by MOF-derived bimetallic Mn0.8Co2.2O4 spinel: Efficient ofloxacin mineralization and synergistic mechanism elucidation

A bimetallic spinel Mn 0.8 Co 2.2 O 4 catalyst was successfully synthesized for PMS activation • Mn 0.8 Co 2.2 O 4 /PMS gains 100% OFX removal (25 min), 76.96% PMS use, 96.9% TOC removal • Coexisting radical and nonradical pathways via Co/Mn redox and oxygen vacancies • DFT confirmed Mn doping improved PMS adsorption, O O bond elongation, and d-band upshift • The catalyst exhibited excellent stability, reusability, and broad-spectrum applicability Ofloxacin (OFX), a recalcitrant fluoroquinolone antibiotic, poses significant risks to ecosystems and human health, necessitating the development of efficient remediation technologies. In this study, a bimetallic spinel Mn 0.8 Co 2.2 O 4 catalyst was successfully synthesized via pyrolysis of a CoMn-BTC metal-organic framework precursor and employed for peroxymonosulfate (PMS) activation toward OFX degradation. The incorporation of Mn into the Co 3 O 4 lattice induced lattice distortion, enlarging specific surface area (45.3 m 2 /g), and enriching Co 2+ content (58.34%), oxygen vacancies, and hydroxyl groups, thereby enhancing electron transfer capability and redox activity. The Mn 0.8 Co 2.2 O 4 /PMS system achieved complete OFX removal within 25 min (k = 0.14219 min −1 ), 1.78 times higher than pristine Co 3 O 4 , with high PMS utilization (75.96%) and near-complete mineralization (96.9% TOC removal). The catalyst exhibited excellent stability over five cycles with minimal metal leaching (Co: 0.365 mg/L, Mn: 0.079 mg/L) and maintained high efficiency (≥88.81%) across pH 3–11. Both radical (•O 2 − , SO 4 •- , •OH) and non-radical ( 1 O 2 , Co(IV) = O) pathways contributed, with 1 O 2 and •O 2 − predominant, with Co/Mn redox cycles and oxygen vacancies serving as key active sites. Electrochemical analysis and density functional theory calculations further confirmed that Mn doping enhanced PMS adsorption energy, elongated the O O bond, facilitated interfacial electron transfer, and shifted the d-band center closer to the Fermi level, thereby boosting catalytic activity. Three plausible degradation pathways were proposed based on reactive site analysis and intermediate identification. This work provides fundamental insights into Mn-doped cobalt spinel for Fenton-like PMS activation and demonstrates their potential as efficient, stable catalysts for antibiotic-contaminated wastewater remediation. Download: Download high-res image (296KB) Download: Download full-size image