ZSM-5-(C@Fe) activated peroxymonosulfate for effectively degrading ciprofloxacin: In-depth analysis of degradation mode and degradation path

Abstract

In this work, ZSM-5-(C@Fe), as a peroxymonosulfate (PMS) heterogeneous activator, was synthesized, characterized, and evaluated for activating PMS to degrade ciprofloxacin (CIP) in wastewater. Zeolite Socony Mobil-5 (ZSM-5) was utilized to enhance structural stability and provided a scaffold to graft Fe doping C nanocomposites activator. Pyrolytic metal-organic frameworks (MOFs) can use crystal structure to construct stable carbon-encapsulated Fe nanocomposites. The formation of C-O-Si, C-O-Al and C-Fe was the key to the stability of catalysts. Fe doping in ZSM-5-(C@Fe) formed non-radical degradation pathway was the key to improve the degradation efficiency. The experimental data indicated ZSM-5-(C@Fe) could completely remove 20 mg L−1 CIP within 15 min and achieve good results in the experiments of treating actual wastewater, which could reduce 40% COD of the paper mill aerobic pond effluent. The Fukui function calculation and UHPL C-H RMS/MS analysis elucidated that the 1O2-dominated electrophilic reaction and the ZSM-5-(C@Fe) complex PMS-dominated nucleophilic reaction were the main pathways for CIP degradation and the radical degradation pathway (·OH and SO4−˙) plays auxiliary role. In addition, two new degradation pathways of the N29 and C27 in quinolone ring and the N22 in piperazine ring were discovered. This finding had important implications for the removal of N from organic pollutants.