In-situ fabrication of MOF-derived MnO-C modified graphite felt for electro-activation of peroxymonosulfate toward degradation of tetracycline: Performance, mechanism and degradation pathway

Peroxymonosulfate (PMS) activation by synergy of electrochemistry and catalyst has emerged as a promising technique for the degradation of organic contaminants. Herein, manganese oxide-carbon modified graphite felt (MnO-C/GF) electrodes are successfully synthesized by pyrolyzing Mn-MOF/GF composite. MnO-C/GF is employed as an anode to remove tetracycline (TC) in a process of PMS activation with the assistance of electrochemistry (EC). Under optimal conditions (50 mg/L TC, 10 mA·cm−2, pH 7, 0.80 mM PMS,0.05 M Na2SO4, 25 °C), MnO-C800/GF electrode (pyrolysis at 800 °C) achieves remarkable degradation efficiency of 90.48 % for TC after 60 min in EC-PMS system. The reaction rate constant (k) of MnO-C800/GF increases by 4.54 and 2.38 times compared to bare GF and MnO/GF in EC-PMS system, respectively. In addition, quenching test and electron paramagnetic resonance test reveal that ·OH, SO4−, O2− and 1O2 are involved in the degradation process at MnO-C800/GF-EC-PMS system. According to the results of density functional theory and liquid chromatography-mass spectrometry, the degradation of TC mainly includes hydrogenation, demethylation, deamidation, dehydroxylation and ring-opening reactions. This work demonstrates that the combination of electrochemistry and metal oxide-activated PMS is a highly efficient approach for the degradation of antibiotic contaminant.