Preparation of amino-functionalized Fe₃O₄@mSiO₂ core-shell magnetic nanoparticles and their application for aqueous Fe³⁺ removal

Fe₃O₄ nanoparticle with magnetic properties and nanoscale features has provoked wide research interest and great potential application. Herein, a modified Stober and template-removing method was adopted to prepare magnetic mesoporous silica nanoparticles (MSNs), comprising a Fe₃O₄ core and a mesoporous silica shell. The shell was functionalized by amino-groups with tunable removal efficiency for aqueous heavy metals ions. Structural and magnetic properties were characterized by XRD, SEM, FT-IR, vibrating sample magnetometer (VSM) and BET (Brunauer-Emmertt-Teller) techniques. Also, the adsorbing efficiency for heavy metal ions was measured by UV-vis spectrometry. Results revealed that the pure magnetite is cubic with a side length of 40 - 70nm, while the silica-coated magnetite is spherical with a diameter of 220-260nm. The mesoporous silica shell has an average pore size of 2.6nm and a high surface area of 675m²·g^-1, which lead to a large adsorption capacity for Fe³⁺ (up to 20.66mg of Fe per g of adsorbent). Moreover, rapid magnetic separation and regeneration of as-prepared adsorbent were achieved conveniently. The distinctive structure and the heavy metal ions removal property of magnetic nanocomposites reflect their prospective application in water treatment.