Fixed-Bed Catalytic Antibiotics Detoxification through Singlet Oxygen-Mediated Nonradical Oxidation: Mechanisms and Long-Term Performance

Abstract

This study presents an immobilized ZIF-67-derived catalyst, Co-N/C@EP-600, designed for efficient antibiotic detoxification via singlet oxygen (¹O₂)-mediated nonradical oxidation. The catalyst features a unique Co-N₃ combined with Co nanocluster (Co-N_3-NCs) structure, as confirmed by X-ray absorption fine structure (XAFS) and density functional theory (DFT) analyses. This structure enhances peroxymonosulfate (PMS) activation by reducing the energy barrier and promoting electron transfer, achieving ultrafast and complete degradation of ofloxacin (OFC, initial concentration of 10 mg L⁻¹) and other refractory organic pollutants within 20 minutes. Mechanistic studies revealed that ¹O₂ dominates the oxidation process, affirmed by quenching tests, electron spin resonance (ESR), and isotopic experiments. The catalyst exhibited exceptional stability, maintaining >90% efficiency over 30 cycles with minimal cobalt leaching (<1.0 mg L⁻¹). Practical application in a continuous-flow fixed-bed reactor demonstrated long-term performance, degrading fluoroquinolone antibiotics (OFC and enrofloxacin (ENR)) at high (10.0 mg L⁻¹) and low (1.0 mg L⁻¹) concentrations up to 30 and 20 days, respectively. Comprehensive toxicity assessments, encompassing microbial viability, activated sludge activity, and phytotoxicity assays, confirmed substantial detoxification toward fluoroquinolone antibiotics. This work provides a strategic blueprint for developing immobilized, eco-friendly catalysts that unite high performance, durability, and environmental compatibility in advanced wastewater treatment.