A novel process to synthesize magnetic hollow silica microspheres

Magnetic hollow silica microspheres (MHSM) were successfully synthesized by combining a sol–gel technology with a low temperature drying. The oil-in-water Pickering emulsion droplets stabilized by the modified Fe3O4 nanoparticles (MFN) were used as the templates. It was found that a certain contact angle of MFN was required in the formation of oil-in-water Pickering emulsion. The average diameter of the oil droplets decreased with the increase for the amount of MFN. The MHSM obtained with strong magnetism were of hollow structures with a diameter of about 350 nm and an average thickness of 40 nm. Most of MFN arrayed in the interface compactly while the other MFN dispersed in the silica matrixes. It was noted that the magnetism of MFN was less affected during the preparation process. Each microsphere had a uniform magnetic fraction due to the template coming from the self-assembly of MFN at the oil–water interface. The as-prepared MHSM have potential application for adsorbent of heavy metal ions or organic pollutants.