Manganese oxide on activated carbon with peroxymonosulfate activation for enhanced ciprofloxacin degradation: Activation mechanism and degradation pathway

Ciprofloxacin, a threat to the ecosystem, can be effectively eliminated through heterogeneous activation of peroxymonosulfate (PMS) by metallic oxide catalyst-based advanced oxidation processes (AOPs). Manganese oxide (MnOx) is one of the most promising metallic oxide catalysts and deserves in-depth research. Herein, a MnOx catalyst loaded on activated carbon (MnOx/AC) was synthesized for the PMS activation in ciprofloxacin degradation. Due to the anchoring effect of AC on MnOx, the MnOx/AC catalyst demonstrated excellent performance and good reusability in ciprofloxacin degradation. Characterizations indicated that redox circles among valence states of Mn(II, III, and IV) species on the catalyst surface triggers the generation of reactive oxygen species (ROS), including 1O2, HO and SO4−. Notably, predominant species was 1O2 (63.75%), which ascribed to the increment of Mn(II) and the consumption of lattice oxygen. Moreover, the PMS adsorption on the MnOx/AC catalyst was a crucial step in ciprofloxacin degradation, and the acidic condition was favored. Furthermore, seven intermediates were detected by liquid chromatograph mass spectrometer during the ciprofloxacin degradation, thus establishing the degradation pathway of the ciprofloxacin. This study provided insights into activation mechanism and degradation pathway for the ciprofloxacin degradation by MnOx in water treatment using PMS–AOPs reaction system.