The facile synthesis of a magnetic OMS-2 catalyst for decomposition of organic dyes in aqueous solution with peroxymonosulfate

A magnetically recyclable nanocomposite, manganese oxide octahedral molecular sieve (OMS-2) coated Fe3O4 nanoparticles, was prepared using a facile solvent-free process with manganese salts and Fe3O4 at a low temperature. XRD, SEM, TEM, FT-IR, XPS and N2 adsorption–desorption isotherm analysis showed that in the core–shell nanocomposite, OMS-2 was homogeneously distributed on the Fe3O4 surface with similar structures to that of pure OMS-2 but a much higher surface area of 251 m2 g−1. The catalyst exhibited excellent activity toward the degradation of Acid Orange 7 (AO7), Reactive Brilliant Blue KN-R, Reactive Brilliant Red X-3B, methylene blue, methyl orange, and rhodamine B in the presence of peroxymonosulfate (PMS), with nearly complete decolorization within 15 min. The catalyst could also be easily recovered with the assistance of an external magnetic field, and could be reused for ten successive cycles without any change of structure. The loss of Mn ions in solution was lower than 0.05 mg L−1 and no Fe ions were detected. The effect of several parameters, including the OMS-2 content in the nanocomposites, the concentration of AO7, PMS and the catalyst, and solution pH, on the degradation efficiency was also discussed.