Microwave-assisted synthesis of magnetic Fe3O4-mesoporous magnesium silicate core-shell composites for the removal of heavy metal ions

An ultrafast and facile microwave assisted hydrothermal approach was applied to synthesize magnetic Fe3O4-mesoporous magnesium silicate (FMMS) core-shell composites for effective removal of Cu2+, Cd2+ and Pb2+ from aqueous solutions. The FMMS composites have mesoporous magnesium silicate shells encapsulated Fe3O4 spheres core structures, and the mesoporous shell assembled by a large number of intercrossed nanosheets with a diameter of 4.0 nm pores, thus exhibited the excellent capability to remove Pb2+ (223.2 mg/g) and Cu2+ (53.5 mg/g) ions from aqueous solutions. The superior removal capacity of the FMMS composites can be ascribed to its mesoporous structures with abundant adsorption active sites. The competitive adsorption studies showed that the adsorbent affinity order of three metal ions by FMMS composites is Cu2+>Pb2+>Cd2+. It is noteworthy that the heavy metal ions could not only adsorb on the surface of FMMS composites, but also intercalate into the intercrossed nanosheets of mesoporous magnesium silicate shell, which reveals the synergistic effect of the electrostatic attraction, surface complexation and ion exchange coupled with the adsorption bonding with surface hydroxyl groups. Furthermore, the FMMS composites exhibited excellent sorption-regeneration performance, which can be easily separated and recovered by external magnet. All results demonstrated that the magnetic FMMS core-shell composite was a promising sorbent material for the preconcentration and separation of heavy metal ions from the waste water. (C) 2017 Elsevier Inc. All rights reserved.