Pb(II) removal of Fe3O4@SiO2–NH2 core–shell nanomaterials prepared via a controllable sol–gel process

Contamination of natural water with heavy metals (especially lead ions) is a problem of major concern and thus great demand of effective adsorbents for removal of toxic ions is increasing. Due to the task-specific properties of amino groups, core–shell nanostructures of Fe3O4@SiO2–NH2 have been extensively investigated as advanced adsorbents; however, most studies on surface modification of Fe3O4@SiO2 substances were of environmentally inefficient grafting methods. Herein, we demonstrated that mono-dispersed and spherical Fe3O4@SiO2–NH2 nanomaterials can be facilely prepared by co-condensation of TEOS with APTMS employing a green sol–gel process. The as-prepared Fe3O4@SiO2–NH2 magnetic nanoparticles (MNPs) prepared under optimum conditions possessing uniform core–shell structure (∼200 nm in diameter), relatively high loading of amino-functionality (∼5.45 wt%), easy recovery by external magnet and effective removal of Pb(II) (qm = 243.9 mg/g, 25 °C). The adsorption was shown to be effective and a higher temperature was more favorable for the adsorption. The adsorption equilibrium data obeyed the Langmuir model and the kinetic data were well fitted to the pseudo-second-order model. Thermodynamic studies revealed the feasibility and endothermic nature of the system. These results demonstrated that the sol–gel produced Fe3O4@SiO2–NH2, due to its easy synthesis and recovery and eco-friendliness, can be a potential adsorbent for Pb(II) removal.