Magnetically separable MnFe2O4/TA/ZnO nanocomposites for photocatalytic degradation of Congo Red under visible light

Recently, the use of carbon based materials and magnetic nanoparticles for supporting or coupling with metal oxides such as ZnO is a promising axis. The use of carbon materials enhances the photocatalytic performance of ZnO for the degradation of organic pollutants because of their properties. The introduction of magnetic nanoparticles such as manganese ferrite (MnFe2O4) to non-magnetic ZnO provides the easy separation of the photocatalyst from the treated water using a magnet and to improve its photoactivity in the visible region of the solar spectrum. This work was focused on the synthesis of a new magnetically separable composite photocatalyst including ZnO, MnFe2O4 and tannic acid (TA) by hydrothermal method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and vibration sample magnetometer (VSM). The photocatalytic activities of the prepared photocatalysts were evaluated through the photocatalytic degradation of Congo Red (CR) under visible light and MnFe2O4/TA/ZnO exhibits the best photoactivity. The degradation yield of CR is 84.2% of CR over the MnFe2O4/TA/ZnO under the visible light for 90 min. At the end of five times recycling, the photocatalytic performance of CR presence the MnFe2O4/TA/ZnO can even reach nearly 77.5%. Such results demonstrate that the MnFe2O4/TA/ZnO exhibits great photocatalytic efficiency for CR compared to their constituent photocatalysts and easy separation from the dye solution by applying an external magnetic field.