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 Fe 3 O 4 @SiO 2 –NH 2 have been extensively investigated as advanced adsorbents; however, most studies on surface modification of Fe 3 O 4 @SiO 2 substances were of environmentally inefficient grafting methods. Herein, we demonstrated that mono-dispersed and spherical Fe 3 O 4 @SiO 2 –NH 2 nanomaterials can be facilely prepared by co-condensation of TEOS with APTMS employing a green sol–gel process. The as-prepared Fe 3 O 4 @SiO 2 –NH 2 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) ( q m   =   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 Fe 3 O 4 @SiO 2 –NH 2 , due to its easy synthesis and recovery and eco-friendliness, can be a potential adsorbent for Pb(II) removal.