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 nano-particles (MNPs) prepared under optimum conditions possessing uniform core-shell structure (similar to 200 nm in diameter), relatively high loading of amino-functionality (similar to 5.45 wt%), easy recovery by external magnet and effective removal of Pb(II)(q(m) = 243.9 mg/g, 25 degrees 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. (C) 2012 Elsevier B.V. All rights reserved.