Coal tar pitch-derived porous carbon activates persulfate for non-radical levofloxacin degradation

Abstract

The persistent presence of levofloxacin (LEV) residues in aquatic environments considerably threatens ecological safety and human health, owing to the potential spread of microbial resistance genes, creating an urgent need for effective removal technologies. In this study, porous carbon materials with high specific surface areas were synthesized using a one-step KOH activation method, with medium-low-temperature coal tar pitch serving as a carbon precursor. In addition, the performance and mechanism of LEV degradation via peroxydisulfate (PDS) activation were systematically explored. Characterization techniques such as X-ray diffraction, Raman spectroscopy, N₂ adsorption-desorption analysis, and field-emission scanning electron microscopy revealed that K11 possessed abundant pores, a specific surface area of up to 1220 m²·g^–1, and numerous defects, which collectively provided a structural basis for its catalytic activity. Degradation experiments demonstrated that the LEV removal rate exceeded 91% under conditions of a 0.2 g·L^–1 PDS dosage, a 0.1 g·L^–1 K11 dosage, pH levels ranging from 3 to 9, and a temperature of 30 °C, with robust resistance to interference from co-existing ions and humic acid. Even in real water bodies, a removal rate of over 77.84% was maintained. Free-radical quenching experiments and electron spin resonance assays confirmed that the reaction proceeded predominantly via non-radical pathways, primarily involving the generation of singlet oxygen by PDS, along with a minor contribution from direct electron transfer pathways. High-performance liquid chromatography-mass spectrometry identified LEV degradation intermediates, suggesting that the degradation pathways include piperazine ring cleavage, defluorination, and oxidation of the quinolone backbone. This study offers theoretical insights and technical guidance for the resource utilization of coal tar pitch and the control of antibiotic pollution.

Graphical abstract

Keywords

levofloxacin / degradation / peroxydisulfate / mechanism

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