Synthesis and characterization ZnFe2O4@MnO and MnFe2O4@ZnO magnetic nanocomposites: Investigation of photocatalytic activity for the degradation of Congo Red under visible light irradiation

In the present investigation, ZnFe2O4@MnO and MnFe2O4@ZnO magnetic nanocomposites were fabricated via a facile hydrothermal method and were calcined at 300 °C for 3 h. Synthesis of ZnFe2O4@MnO and MnFe2O4@ZnO magnetic nanocomposites optimized by the different weight percentages. The synthesized photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Vibrating Sample Magnetometer (VSM), EDAX (Energy dispersive X-ray Analysis), diffuse reflectance UV-vis spectroscopy (DRS)  and field emission scanning electron microscopy (FESEM). The ZnFe2O4@MnO nanoparticles were found to have 20-50 nm. Magnetic studies revealed that the ZnFe2O4@MnO and MnFe2O4@ZnO nanocomposites can be easily separated from the solution by an external magnetic field. The photocatalytic degradation of Congo red dye (CR) was investigated based on the removal of Congo red (CR) in aqueous solution in 35 min of visible light irradiation. Compared with MnFe2O4@ZnO nanocomposite, the ZnFe2O4@MnO nanocomposite showed high photocatalytic performance on the photodegradation of Congo red. Effect of reaction time, pH, and loading of ZnO on degradation of CR was studied,The results demonstrated that the degradation efficiency of ZnFe2O4@MnO nanocomposite (98.5%) was better than that of MnFe2O4@ZnO nanocomposite (90.32%), which is due to the presence of narrow band gap energy of ZnFe2O4@MnO.Kinetics studies have displayed  that the degradation of CR by the prepared of photocatalysts follows the pseudo-first-order kinetics and the rate constant achieved for ZnFe2O4@MnO (k=0.0371 min−1) was much greater than of MnFe2O4@ZnO (k=0.0321 min−1). The synthesized ZnFe2O4@MnO nanocomposite can be potentially applied as a magnetically separable photocatalyst to deal with water pollution problems.