Effect of the magnetic core size of amino-functionalized Fe3O4-mesoporous SiO2 core-shell nanoparticles on the removal of heavy metal ions

Abstract

Magnetite (Fe3O4)-mesoporous silica (mSiO2) core-shell nanoparticles are attractive heavy metal ion adsorbents. However, most studies have focused on the use of superparamagnetic Fe3O4 nanoparticles as core materials, resulting in low magnetic field responses due to their low susceptibility and saturation magnetization (Ms) values. Here, we report the synthesis, microstructure, and properties of ferrimagnetic Fe3O4-mSiO2 core-shell nanoparticles, focusing on the effects of the magnetic core size on their removal efficiency. We analyzed the magnetic properties and structural changes of the surface according to the magnetic core size and elucidated the correlation with the removal efficiency of heavy metal ions. Fe3O4 cores with diameters of 103, 123, or 207nm were synthesized by a modified polyol method, while the silica layer with a porous structure was coated using a sol-gel reaction. Amino-functionalized ferromagnetic Fe3O4-mSiO2 nanoparticles with different core sizes exhibited a faster and more efficient removal behavior of heavy metal ions than other reported superparamagnetic nanoparticles. The highest removal capacity of 84.4 mgg−1 for Cu2+ ions was observed with the nanoparticles having the largest specific surface area of 483.78m2g−1.