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

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 m(2)/g to 125.04 m(2)/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 O-3 to produce more center dot 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. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study investigated the degradation of ofloxacin (OFX) using pulsed discharge plasma (PDP) combined with multi-catalysis of graphene-Fe3O4 nanocomposites. It was found that the graphene-Fe3O4 nanocomposites had higher catalytic activity compared to sole Fe3O4, leading to a significant enhancement in the removal efficiency of OFX. The addition of graphene content at 18 wt% showed the highest catalytic activity, achieving a removal efficiency of 99.9% for OFX. Acidic solution and optimal dosage were beneficial for OFX degradation, and the graphene-Fe3O4 nanocomposites exhibited increased stability after multiple uses.