A urea-based approach to synthesize single atom iron catalysts for catalyzing peroxymonosulfate to degrade antibiotics

Abstract

Understanding the role and catalytic mechanism of single atomic catalysts (SACs) in activating peroxymonosulfate (PMS) and subsequently eliminating antibiotics in environmental water is crucial for designing more efficient catalysts. Despite C-N-metal SACs exhibiting excellent performance, their application is constrained by the intricate N-doped pretreatment process and the high cost of carrier materials. To handle these challenges effectively, a new approach, by using molten urea as both solvent and nitrogen source and polyethylene glycol as carbon source, was employed to synthesize the u-Fex-N-C (x = 1, 2, 3) catalysts. In which, u-Fe1-N-C had achieved an impressive 92 % degradation ratio for oxytetracycline (OTC) and remains unaffected by pH in the range of 3–11. It further exhibited catalytic degradation activity towards a broad spectrum of environmental pollutants, including sulfamethoxazole (SMZ), naproxen (NPX), ofloxacin (OFL), rhodamine B (RhB), and bisphenol A (BPA), and the degradation efficiencies reached 67 %, 83 %, 77 %, 99 %, and 93 %, respectively. According to a series of the characterization, the prepared u-Fe1-N-C possessed a unique FeN4 structure. Electron paramagnetic resonance (EPR) and radical quenching experiments proved that 1O2 and Fe (Ⅳ) played a key role in the current reaction system. In-situ Raman and electrically coupled oxidation systems also proved that the non-radical degradation pathway involving electron transfer in the u-Fe1-N-C/PMS system was the primary way for activating PMS. The degradation efficiency of OTC from real water samples still reached 84 %. This work provides a simple and cost-effective strategy for synthesizing SACs, offering promising applied prospects in the field of water treatment and environmental remediation.