A novel layered and cauliflower-like Fe3O4@MgAl-LDH@Ce3W18 nanocomposite has been synthesized by the selective ion-exchange method. The nanocomposite contains sandwich-type polyoxometalate (STPOM) anion [(OCe)3(PW9O34)2]12ÿ intercalated Mg–Al layered double hydroxides (LDHs) coated on the surface of the Fe3O4 particles. The obtained nanocomposite was used as a catalyst for decomposition of methylene blue solution with the assistance of H2O2 at room temperature. To investigate the catalytic properties and efficiency of the nanocatalyst, a MgAl-LDH@Ce3W18 nanocomposite was also prepared. The physicochemical properties of the products were elucidated based on FTIR, SEM, TEM, EDS, TGA, XRD, VSM, and N2 adsorption–desorption studies. The obtained results for Fe3O4@MgAl-LDH@Ce3W18 in the catalytic degradation of methylene blue (MB) dye, compared to other similar reported studies based on POMs and LDHs, represented a significant enhancement in the decomposition reaction rate owning to its high BET surface area and high charge density on selected STPOMs. The results indicated that the magnetic nanocatalyst has good selectivity toward methylene blue in the presence of rhodamine B (RB) and methyl orange (MO) with a high degradation efficiency of 90% within 5 minutes and excellent reusability in 6 cycles. Additionally, the magnetic nanocatalyst is readily separated and recycled from the reaction system by using an external magnetic field.
