Hollow Fe₃O₄@mesoporous carbon core–shell microspheres for efficient sorption of radionuclides

Hollow Fe₃O₄@mesoporous carbon (h-Fe₃O₄@mC) microspheres have been synthesized using silica nanospheres as the sacrificial matrix. Physiochemical properties, surface morphology, and internal structures of the as-prepared products have been carefully characterized. The synthesized h-Fe₃O₄@mC microspheres have been applied to adsorb radionuclides from aqueous solutions and can be easily separated by an external magnetic field. Effects of contact time, pH, and initial concentrations on the interaction of h-Fe₃O₄@mC with U(VI), Eu(III), Co(II), and Sr(II) have been studied. The sorption is strongly dependent on pH and can reach equilibrium within 2 h. Dependence of sorption on pH is relevant to both the surface properties of sorbents and the relative distribution of radionuclides species in solutions. Due to the mesoporous structure, carboxyl-functionalized surface, and low density, h-Fe₃O₄@mC shows efficient sorption for radionuclides even in acidic solutions. The maximum sorption capacities of U(VI), Eu(III), Co(II), and Sr(II) on h-Fe₃O₄@mC at pH 3.0 and T = 298 K calculated from the Langmuir model are 0.566, 1.013, 0.860, and 0.733 mmol g⁻¹, respectively. Findings of the present work suggest that h-Fe₃O₄@mC can serve as a promising candidate for recovery and removal of radionuclides from aqueous solutions in the environmental pollution management.