Multi-catalysis induced by pulsed discharge plasma coupled with graphene-FeO 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-FeO nanocomposites was inspected. The graphene-FeO nanocomposites were prepared by hydrothermal synthesis, and their morphology, specific surface area, chemical bond structure and magnetic property were characterized systematically. Compared with sole FeO, the specific surface area of graphene-FeO nanocomposites increased from 26.34 m/g to 125.04 m/g. The prepared graphene-FeO nanocomposites had higher paramagnetism and the magnetic strength reached 66.05 emu/g, which was prone to separate from solution. Graphene-FeO nanocomposites could further accelerate OFX degradation compared to sole FeO. When graphene content was 18 wt%, graphene-FeO 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-FeO nanocomposites could be maintained although four times use. Graphene-FeO nanocomposites could catalyze HO and O 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 (LD) and the developmental toxicity of OFX were reduced.