Synthesis of Fe3O4-decorated SiO2 nanostructure using rice husk as a source by microwave combustion for the development of a magnetically recoverable adsorbent

Abstract

In this study, we prepared Fe3O4-decorated SiO2 (Fe3O4@SiO2) nanostructure using rice husk as a silica source through a microwave-assisted combustion process. The results of the X-ray diffraction, Fourier transform infrared, energy-dispersive X-ray, scanning electron microscopy, and transmission electron microscope analyses corroborate that polycrystalline Fe3O4 nanoparticles with 5–10 nm size were decorated on the amorphous SiO2 nanosphere having a size of 50 nm in diameter. A vibrating sample magnetometer indicated that Fe3O4 decoration on rice husk–derived SiO2 (RH SiO2) was able to transform nonmagnetic into ferromagnetic material with saturation magnetization of 45 emu/g. The effects of pH, adsorbent dosage, and time on the removal of Hg2+ by RH SiO2 and Fe3O4@SiO2 samples were investigated and it was found that 100 mg adsorbent dosage at pH 6 for 20 min contact time is suitable for the sufficient removal (>90%) of Hg2+ ions with 100 mg/L concentration. The ferromagnetic characteristic, mesoporous structure, and high specific surface area (174.930 m2g−1) of Fe3O4@SiO2 nanostructure help develop a magnetically recoverable adsorbent for removal of Hg2+ ions from an aqueous solution.