Degradation of flumequine in water by pulsed discharge plasma coupled with reduced graphene oxide/TiO2 nanocomposites

Herein, pulsed discharge plasma (PDP) was coupled with reduced graphene oxide (rGO)/TiO(2 )nanocomposites to degrade flumequine (FLU) in water. The rGO/TiO2 nanocomposites were prepared by hydrothermal method, which were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption apparatus. The characteristic results showed that the rGO/TiO2 nanocomposites could be synthesized successfully. The rGO/TiO2 nanocomposites had a larger specific surface area than pure TiO2. The degradation performance indicated that the removal efficiency could reach 99.4% with 60 min treatment in PDPrGO/TiO2 system, which was higher than in sole PDP system (64.8%) and PDP-TiO2 system (75.7%). Moreover, compared to pure TiO2, the kinetic constant, TOC removal, synergistic factor and energy efficiency could be also improved when rGO/TiO2 nanocomposites were added into PDP system. Besides, the effect of catalyst dosage, peak voltage, air flow rate and solution pH on FLU removal efficiency was investigated. Subsequently, response surface methodology (RSM) was adopted to inspect the interactional influences between catalyst dosage, peak voltage, air flow rate and solution pH, and the optimal parameters based on the result of single factor experiments. No matter reaction system was PDP system or PDP-rGO/TiO2 system, the O-3 and (OH)-O-center dot concentration in deionized water were higher than that in FLU solution, suggesting that O-3 and (OH)-O-center dot played major role in degrading FLU. The addition of rGO/TiO2 could consume O-3 and lead to more (OH)-O-center dot generation, which accelerated the degradation of FLU. The decline of pH value and the rise of conductivity deduced that many acid substances could be produced during FLU degradation, which could be mineralized into CO2 and H2O ultimately.