Photocatalytic Degradation of Methylene Blue by Fe3O4@MAl-Layered Double Hydroxides (M=Zn, Co, Ni) Composite: Performance, Kinetics, and Mechanism

Based on low-cost, non-toxic, and strong light absorption ferric oxide (Fe3O4) and layered double hydroxides (LDHs) with large specific surface and high stability, Fe3O4@MAl-LDHs (M=Zn, Co, Ni) composites were prepared and used for photocatalytic degradation of methylene blue. The composition and structure of the composites were characterized by X-ray powder diffraction (XRD), UV-Vis absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N-2 adsorption-desorption test. The optimum conditions were as follows: the amount of catalyst was 50 mg, the light intensity was 500 W, the pH value was 9, and the reaction temperature was 40 degrees C. The degradation rate of methylene blue increased significantly from 23.2% of LDHs to 87.0% of Fe3O4@MAl-LDHs. The degradation of methylene blue by LDHs mainly comes from center dot OH, while the photo-degradation activity of Fe3O4@MAl-LDHs is mainly contributed by both center dot OH and holes. In addition, there were also great differences in the electrochemical properties of LDHs and Fe3O4@MAl-LDHs.