Facile synthesis of polyethyleneimine functionalized magnetic silicon nanocomposite for enhanced and rapid removal and recovery of hexavalent molybdenum ions

Molybdenum is an expensive rare metal with many application, however discharged effluents containing Mo(VI) ions from various industries constitute potential hazards to human health and the ecosystem. Thus, it is demanded to develop appropriate methods to separate and recover molybdenum from industrial wastewater. In the present work, polyethyleneimine (PEI) functionalized magnetic silicon (PEI@SiO₂@Fe₃O₄) nanocomposite was synthesized by a facile approach (60 °C, 1 h), and then for the first time used as the sorbent for efficient removal and recovery of Mo(VI) ions. The prepared PEI@SiO₂@Fe₃O₄ nanocomposite was then characterized using Fourier transform-infrared spectrometer, scanning electron microscoper, etc. Investigations of adsorption performances of the PEI@SiO₂@Fe₃O₄ demonstrated its high adsorption capacity of 409.8 mg/g at 298 K and fast adsorption kinetics with an equilibrium time of 45 min, while the sorption process was spontaneous, endothermic and well fitted by Langmuir isotherm and the pseudo-second order kinetic model. The possible adsorption mechanisms include coordinate bonds and electrostatic interaction. The sorbed Mo(VI) ions were completely eluated off from PEI@SiO₂@Fe₃O₄ sorbent using a Na₃PO₄ solution (20 g/L) within only 2 min. Outstanding reusability of PEI@SiO₂@Fe₃O₄ was illustrated after seven adsorption–desorption cycles with only 7 % loss in sorption capacity. The PEI@SiO₂@Fe₃O₄ was then applied to the treatment of real wastewaters containing Mo(VI), and very satisfactory results were achieved. These results suggest that the PEI@SiO₂@Fe₃O₄ nanocomposite is a potential sorbent for removing and recovery of Mo(VI) from wastewater.