Synthesis of visible light-driven graphene based ZnFe mixed metal oxide for efficient degradation of tetracycline

Magnetically separable reduced graphene oxide (RGO)-based ZnFe mixed metal oxide (MMO) nanocomposite (MMO/RGO) was prepared via a scalable and low energy-consuming co-precipitation-calcination process. The preparation procedure can be easily carried out at lower temperature in shorter time compared with those reported in literatures. The structural characterization indicates that ZnFe MMO (i.e., ZnO/ZnFe₂O₄) heterojunctions are homogeneously distributed as particles with a size in the range of 5–30 nm on the surface of RGO. The ZnFe MMO/RGO nanocomposite exhibits superior photocatalytic performance and stability for the degradation of tetracycline (TC) under visible-light illumination. 100% of the TC molecules is removed after visible-light irradiation for 120 min at 25 °C in the presence of ZnFe MMO/RGO. The photodegradation rate constant is 3.4 times that of ZnFe MMO, suggesting that the synergistic effect between ZnFe MMO and RGO improves the photocatalytic degradation performance of the nanocomposites. Neither toxic chemical reductants nor additional solvents were used during the preparation. More importantly, ZnFe MMO/RGO nanocomposite can be easily recycled by applying an external magnet. This work may provide an environment-friendly low-energy consuming method for large-scale production of MMO/RGO photocatalysts toward the degradation of TC. The photocatalytic mechanism of the ZnFe MMO/RGO nanocomposite was also investigated.