Enhanced levofloxacin degradation via peroxodisulfate activation using a magnetic MnFe2O4/pumice catalyst: Mechanisms, toxicity assessment, and degradation pathways

Addressing the challenge of developing stable and highly efficient catalysts for peroxodisulfate (PDS) activation is crucial for advancing water pollution control technologies. This study introduced a novel magnetic MnFe 2 O 4 /pumice nanocomposite, synthesized through a simple method, aimed at the sustainable activation of PDS for the degradation of Levofloxacin (LEV). Leveraging pumice as a substrate not only enhanced the catalyst's stability and dispersibility but also increased MnFe 2 O 4 's activation sites. Employing a 2:1 mass ratio of MnFe 2 O 4 to pumice, the catalyst achieved a remarkable LEV removal efficiency of 96.69 % and a mineralization efficiency of 55.83 % within 30 min. This performance significantly surpasses that of pumice or MnFe 2 O 4 alone, with the MnFe 2 O 4 /pumice catalyst being 2.81 and 2.18 times more efficient, respectively. Additionally, the MnFe 2 O 4 /pumice + PDS system demonstrated outstanding stability and reusability, maintaining a LEV removal efficiency of 93.5 % after 120 min over ten cycles. Quenching experiments and Electron Paramagnetic Resonance (EPR) studies pinpointed singlet oxygen ( 1 O 2 ) as the primary reactive species, with notable contributions from sulfate and hydroxyl radicals. X-ray photoelectron spectroscopy (XPS) analyses attributed this enhanced activity to the Fe (III)/Fe (II) and Mn (II)/Mn (III) redox couples. The degradation pathways for LEV were further explored using density functional theory and high-resolution liquid chromatography-mass spectrometry (LC-MS), while the ecological toxicity of the degradation intermediates was assessed through quantitative structure–activity relationship (QSAR) analysis. These insights proposed a plausible mechanism for LEV degradation in the MnFe 2 O 4 /pumice activated PDS system, highlighting its potential for wastewater treatment applications.