Iron-doped ordered mesoporous Co3O4 activation of peroxymonosulfate for ciprofloxacin degradation: Performance, mechanism and degradation pathway

Abstract

Ordered mesoporous Co3O4 (OM-Co3O4) displayed superior performance for peroxymonosulfate (PMS) activation. While, the separation and recovery of the catalyst after catalytic oxidation needed tedious operation. In this study, the as-synthesized iron-doped OM-Co3O4 not only inherited the merits of ordered mesoporous materials such as high surface area and abundant mesoporous structure, but endowed them with ferromagnetism, facilitating their separation from the solution. Compared with spinel Co3O4, iron-doped OM-Co3O4 showed superior catalytic activity, wide application scope, excellent reusability and long-term stability, fully validated that iron-doped OM-Co3O4 can be a promising heterogeneous PMS activator for environmental application. High catalyst loading and PMS concentration were both beneficial to CIP degradation. The best CIP degradation occurred under base conditions. Chlorine and bicarbonate presented completely opposite two-side effects. The mechanism of CIP degradation was primarily attributed to SO4− and OH to a lesser extent. The rapid redox cycles of M2+/M3+ (M = Co, Fe) and O2−/O2 ensured the continuous generation of reactive oxygen species and the efficient degradation of CIP. The cleavage of piperazine ring, hydroxylation and defluorination were identified as the main oxidation pathways for CIP degradation in iron-doped OM-Co3O4 activated PMS system.