MOFs-derived Mn/C composites activating peroxymonosulfate for efficient degradation of sulfamethazine: Kinetics, pathways, and mechanism

Both manganese oxides (MnOx) and carbon materials hold promise for persulfate activation to remediate polluted waterbodies. However, the aggregation of MnOx during the calcination synthesis and lower activity to persulfate of carbon materials seriously limit their industrial application. In this work, two Mn/C composites (MnOx-NA and MnOx-A) were synthesized from manganese-metal organic frameworks (MOFs) under nitrogen atmosphere and air atmosphere calcination respectively. The prepared MnOx-NA exhibited more excellent peroxymonosulfate (PMS) activation performance than MnOx-A, and almost 100% sulfamethazine (SMT) could be removed by the MnOx-NA/PMS system within 30 min. Moreover, the MnOx-NA/PMS system exhibited impressive stability even after 10 cycles and displayed high anti-interference ability to Cl−, ClO4−, CO32−, SO42−, NO3− and humic acid (HA). In addition, the oxidation system could efficiently remove SMT in different aqueous matrices. Three possible pathways of SMT degradation were proposed according to the LC-MS analysis. Electron paramagnetic resonance (EPR), quenching experiments, and cyclic voltammetry experiments revealed that SMT degradation predominantly occurred through a catalyst-mediated electron transfer pathway. Material characterization and electrochemical impedance spectroscopy (EIS) analysis showed that the derived carbon species strengthened the MnOx-NA's electron-transfer capability and promoted the uniform distribution of MnOx particles on the carbon materials surface, which significantly improved MnOx-NA's PMS activation performance. This study introduces a facile method for the design of Mn/C composites PMS activator and provides theoretical guidance for water pollution remediation.