Investigation of the Performance and Mechanism of an N-Doped Monolithic Fe/Ni-Based Catalyst for PMS Activation Toward Chlortetracycline Degradation in Water

MOF-derived catalysts have considerable potential for aqueous contaminant control, but their practical application is often constrained by the aggregation and difficult recovery of powder catalysts. In this study, a self-supporting N-doped Fe/Ni-based monolithic catalyst, denoted N-101-NFF, was fabricated through the in situ growth of an Fe-based MOF precursor on nickel–iron foam followed by pyrolysis. Under the conditions of 50 mg/L chlortetracycline (CTC), 0.08 mmol/L peroxymonosulfate (PMS), and an effective catalyst area of 1 cm2, N-101-NFF degraded 90.3% of CTC within 60 min and maintained a degradation efficiency of 88.6% after five consecutive cycles. Quenching experiments and EPR analysis indicated the involvement of •OH, SO4•−, O2•−, and 1O2 in CTC degradation. Electrochemical measurements indicated improved interfacial charge-transfer characteristics, while post-reaction XPS analysis revealed changes in the Fe and Ni valence states and surface N- and O-containing groups, supporting the involvement of Fe and Ni redox cycling and these surface functionalities in PMS activation. In a fixed-bed reactor, the system maintained more than 86% CTC removal over 24 h of continuous-flow operation at a CTC feed rate of 200 mL/h. These results highlight the potential of N-101-NFF as a recoverable monolithic catalyst for PMS-based treatment of antibiotic-contaminated water.