Electrochemical Acceleration of Redox Reaction Cycles on the Surface of Fe2O3-MnO2 Cathode to Activate the Peroxymonosulfate for the Efficient Removal of Levofloxacin

Abstract

Here, we establish an electrochemically promoted peroxymonosulfate (PMS) activation system based on Fe2O3-MnO2 cathode for the degradation of levofloxacin (LEV). Compared with the single materials Fe2O3 and MnO2, Fe2O3-MnO2 exhibits more active sites and excellent electrochemical characteristics, including faster electron transfer and lower overpotential of oxygen reduction reaction (ORR). The degradation efficiency of the system can reach 92.1% within 60 min under the optimal conditions of 30 mA cm−2, natural pH, 10 mM PMS, and 25 °C. The efficient degradation performance is due to the fact that electrochemistry can accelerate the electron transfer and further improve the cycle of the redox reactions of FeⅡ/FeⅢ and MnⅡ/MnⅢ/MnⅣ, thereby, activating PMS to generate more active species (e.g., ·OH, SO4 −· and 1O2 etc). And the 1O2 is found to be the main reactive substance. Besides, the degradation pathway of LEV is inferred based on the identification of reaction intermediates, including defluorination, decarboxylation, destruction of piperazinyl groups, and oxidation of quinolone rings. This research provides a reliable method for the effective removal of refractory organic pollutants.