Bimetallic CoMn-MOF decorated biochar as peroxymonosulfate activator for efficient ofloxacin degradation: Performance and mechanism insights

Abstract

The application of metal-organic framework (MOF)-based peroxymonosulfate (PMS) catalysts in heterogeneous reactions has attracted widespread interests. However, improving the efficiency and stability of the catalysts remains considerable challenges. Herein, bimetallic CoMn-MOF was constructed on the surface of biochar derived from peanut shell to fabricate the CoMn-MOF/biochar (CMB) composite as PMS catalyst using a simple hydrothermal process. Under optimal degradation conditions, i.e., [CMB] = 1 g/L, [PMS] = 1 mM, the ofloxacin (OFL) degradation efficiency can reach 92.9 % in 120 min in CMB/PMS system, and in which the reaction rate constant (0.1075 min⁻¹) was 82 times higher than that in CoMn-MOF/PMS (0.0013 min⁻¹). The remarkable improved catalytic performance was attributed to the multi active sites CMB composite enhanced electron transfer rate to produce abundant reaction active species. Besides, CMB exhibited high OFL degradation efficiency (77.8 %) after five cycles and strong mineralization efficiency (66.2 %) by effectively activating PMS. Moreover, the toxicity of OFL and its intermediates after degradation was greatly reduced based on the TEST results. The primary active species identified in this study were O₂^•-, ¹O₂ and SO₄^•- for OFL degradation in the CMB/PMS system. Furthermore, based on the results of the quenching experiments and HPLC-MS analysis, a catalytic degradation mechanism for OFL was proposed along with three potential degradation pathways. This research proposes a novel reference to develop an effective PMS catalyst for wastewater treatment through the combination of biochar and bimetallic MOFs.