MOF-derived FeCo carbon nanomaterials with abundant oxygen vacancies as highly efficient peroxymonosulfate catalyst for ciprofloxacin degradation

In this work, the FeCo-NB@C catalysts were prepared via calcination with FeCo-MOF as a precursor for highly efficient activation of peroxymonosulfate (PMS). SEM and XPS indicated that FeCo-NB@C possesses mass metal active sites and abundant oxygen vacancies. A synergistic effect (synergy indices 4.6) was observed in the FeCo-NB@C600/PMS process. The ciprofloxacin (CIP) could be almost degraded completely within 15 min in the optimal conditions. It was noted that FeCo-NB@C600/PMS process still performed well on CIP removal under multiple inorganic anions and real water matrix conditions. Radical quenching experiments, EPR analysis, and contribution calculation identified that SO4•−, •OH, and other ROS (O2•− and 1O2) played dominant role in CIP degradation, accounting for 60.24%, 20.19%, and 17.46%, respectively. The redox cycle of Co2+/Co3+ and Fe2+/Fe3+ induced the production of SO4•− and further formed •OH, etc. In addition, the formation of O2•− was confirmed by the role of oxygen vacancies rather than O2 through a series of designed experiments. Furthermore, the characterization results illustrated that FeCo-NB@C600 was largely unchanged with low ion leaching after three times cycles in PMS activated process, indicating the excellent stability and reusability of FeCo-NB@C600. Finally, the results of CIP degradation pathways and toxic evaluation revealed the low ecotoxicity of the intermediate products. This study demonstrates the synergistic catalytic mechanism of bimetallic catalysts in the persulfate activation, promising to realize sustainable and efficient water treatment technology.