Facile synthesis of carbon-doped CoMn2O4/Mn3O4 composite catalyst to activate peroxymonosulfate for ciprofloxacin degradation

Abstract

In this work, carbon-doped CoMn2O4/Mn3O4 (C-CoMnO) composite catalyst were prepared via calcining solvothermal product of Mn2+, Co2+, and 2-methylimidazole in air. The catalytic performance of activating peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation was discussed. The results showed that the 0.1 g L−1C-2CoMnO could effectively activate PMS, resulting in 96.18% CIP was degraded within 60 min. The corresponding total organic carbon removal ratio and apparent rate constant were 81.33% and 0.043 min−1, respectively. The influencing factors, such as Co/Mn molar ratios, calcination temperature, PMS concentration, solution pH, and coexisting ions were explored. The optimal catalytic system exhibited good recycling performance, wide pH adaptation and high resistance to salt interference. SO4⋅−, ⋅OH, and ⋅O2−-based radicals, as well as 1O2 and surface complexes-based nonradicals were participated in CIP degradation. The CIP degradation pathways were proposed. Density functional theory calculations (DFT) indicated that PMS was more easily activated via Co/Mn synergism. The doped carbon was also contributed to PMS activation via facilitating electron transfer. This study may shed light toward the synergistic effect of metal oxides in PMS activation.