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

Siyu Yang,Lei Wang,Jianping Qiu,Mingmin Jia,Zhigang Zhou,Zipeng Zou,Zhongbo Lv,Yuhai Yang,Haonan Zhu,Fangyuan Wang

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.