Removal of uranium(VI) from aqueous solution by magnetic yolk-shell iron oxide@magnesium silicate microspheres

Yolk-shell microspheres with magnetic Fe3O4 cores and hierarchical magnesiumsilicate shells (Fe3O4@MS) have been successfully synthesized by combining the versatile sol-gel process and hydrothermal reaction. The as-prepared Fe3O4@MS microspheres were then assessed as the adsorbent for uranium(VI) removal from water, and could be easily separated by an external magnetic field. Influencing factors to adsorb uranium(VI) were investigated, including pH, ionic strength and coexisted ions, amount of adsorbent and equilibrium time. The results indicated that uranium(VI) adsorption on Fe3O4@MS microspheres was strongly dependent on pH and the ionic strength. The maximum adsorption capacity for uranium(VI) was calculated to be 1.51 x 10(-5) mol g(-1) based on the Langmuir model and the experimental data fitted the Langmuir model (R-2 = 0.999) better than the Freundlich model (R-2 = 0.954). The as-prepared sub-microspheres showed their potential applications as adsorbent for highly efficient removal of heavy metal ions from wastewater.