Synthesis of Fe 3 O 4 @SiO 2 @MnO 2 composite magnetic submicrospheres as adsorbent for methyl orange decolouration

Abstract

Core–shell–shell composite (Fe3O4@SiO2@MnO2) submicrospheres were successfully synthesised by homogeneous precipitation of MnO2 on Fe3O4@SiO2 spheres, which were prepared by a modified sol–gel method with the presence of Fe3O4 particles. The synthesised multilayer-structured nanocomposites were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and using a vibrating sample magnetometer. The results show that the magnetic Fe3O4 cores were well wrapped by the intermediate layer of SiO2 with a thickness of 40 nm in the amorphous phase, and the MnO2 nanoparticles with a diameter not exceeding 10 nm were attached on the SiO2 shell. The magnetic measurements indicated that the Fe3O4@SiO2@MnO2 submicrospheres were of superparamagnetism with the saturation magnetisation of 29.41 eum/g. At the same time, the submicrospheres demonstrated a high chemical adsorption activity for methyl orange (MO) decolouration with efficiency of up to 93.76% within 1 h. Moreover, the submicrospheres were found to be stable under repeated applications of up to five successive cycles with a near constant adsorption activity after regeneration. It is expected that the adsorbent could be used for trace pollutants (MO) removal from water and recycled owing to its superparamagnetism properties and high adsorption activity.