Pulsed discharge plasma assisted with graphene-WO3 nanocomposites for synergistic degradation of antibiotic enrofloxacin in water

Synergistic degradation of enrofloxacin (EFA) in water by pulsed discharge plasma (PDP) assisted with graphene-WO3 nanocomposites was investigated. The graphene-WO3 nanocomposites with different weight ratio of graphene were prepared by a hydrothermal method, which were characterized by various aspects, such as structure and morphology, chemical bonding state, optical property and electrochemical property. The results showed that graphene could be hybridized with WO3 nanoparticles successfully. Compared to the pure WO3, the specific surface area enhanced and the light absorption range extended in the graphene-WO3 nanocomposites. Moreover, the separation rate of electron-hole pairs accelerated apparently. The result of degradation performance showed that graphene-WO3 nanocomposites significant improved the removal efficiency and first-order kinetic constant of EFA in PDP system. Highest removal efficiency (99.1%) could be obtained with 60 min treatment in PDP system with 3% graphene-WO3 nanocomposite, which was 23.1% higher than that in the sole PDP system. Correspondingly, the synergistic factor could reach 2.82, suggesting that the synergistic effect could be established. In addition, the effect of various factors including catalyst dosage, peak voltage, air flow rate and initial solution concentration on EFA degradation was evaluated. The graphene-WO3 nanocomposite addition further decomposed O-3 and improved the generation of % OH and H2O2. The mineralization and three-dimensional fluorescence analysis verified that the EFA molecules could be destroyed and lead to the generation of intermediates. Subsequently, the degradation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC). Based on the above analysis, EFA degradation mechanism in the PDP system with graphene-WO3 nanocomposites was proposed finally.