Multi-catalysis induced by pulsed discharge plasma coupled with graphene-Fe3O4 nanocomposites for efficient removal of ofloxacin in water: Mechanism, degradation pathway and potential toxicity

Abstract

Herein, degradation of ofloxacin (OFX) by pulsed discharge plasma (PDP) coupled with multi-catalysis using graphene-Fe₃O₄ nanocomposites was inspected. The graphene-Fe₃O₄ nanocomposites were prepared by hydrothermal synthesis, and their morphology, specific surface area, chemical bond structure and magnetic property were characterized systematically. Compared with sole Fe₃O₄, the specific surface area of graphene-Fe₃O₄ nanocomposites increased from 26.34 m²/g to 125.04 m²/g. The prepared graphene-Fe₃O₄ nanocomposites had higher paramagnetism and the magnetic strength reached 66.05 emu/g, which was prone to separate from solution. Graphene-Fe₃O₄ nanocomposites could further accelerate OFX degradation compared to sole Fe₃O₄. When graphene content was 18 wt%, graphene-Fe₃O₄ nanocomposites exhibited the highest catalytic activity, and the removal efficiency of OFX enhanced from 65.0% (PDP alone) to 99.9%. 0.23 g/L dosage and acid solution were beneficial for OFX degradation. Higher stability of graphene-Fe₃O₄ nanocomposites could be maintained although four times use. Graphene-Fe₃O₄ nanocomposites could catalyze H₂O₂ and O₃ to produce more ·OH. The degradation products of OFX were identified by liquid chromatography mass spectrometry (LC-MS) and ion chromatography (IC). According to the identified products and discrete Fourier transform (DFT), the degradation pathway was inferred. Further toxicity assessment of products manifested that the toxicity of oral rat 50% lethal dose (LD₅₀) and the developmental toxicity of OFX were reduced.

Keywords: Degradation; Graphene-Fe(3)O(4); Mechanism; Ofloxacin; Pulsed discharge plasma.