LAUSR

Abstract Non-thermal plasma coupled with graphene-TiO2-Fe3O4 nanocomposites was applied to promote oxytetracycline (OTC) degradation in water. Graphene-TiO2-Fe3O4 nanocomposites were systematically characterized and calculated based on the density functional theory (DFT). Graphene-TiO2-Fe3O4 nanocomposites exhibited higher specific surface area, carrier separation rate and magnetic intensity. More importantly, graphene-TiO2-Fe3O4 nanocomposites were very prone to separation from solution. Compared to Fe3O4 and graphene-TiO2, graphene-TiO2-Fe3O4 nanocomposites further enhanced the removal efficiency of OTC. The highest removal efficiency could reach 98.1% when the doping amount of Fe3O4 was 20 wt%. The optimal parameters of catalyst dosage, peak voltage, air flow rate and pH value were 0.24 g/L, 18 kV, 4 L/min and 3.2, respectively. Compared with graphene-TiO2, the addition of graphene-TiO2-Fe3O4 nanocomposites decreased the concentration of O3 and H2O2, but increased the production of ·OH. ·OH, O3 and H2O2 played certain role for OTC elimination. The degradation process was explored by UV–Vis spectrum, three dimensional fluorescence, liquid chromatography-mass spectrometry (LC-MS), ion chromatography (IC) and discrete Fourier transform (DFT) analysis. Reactive molecular dynamical (MD) simulation was also performed to further investigate the reaction mechanisms, and the simulation show a good agreement with the experimental observation by analyzing the bond breaking and formation. The actual toxicity of OTC was alleviated after plasma-catalytic treatment.