Selective removal and long-term immobilization of uranium by ultralow content Fe0 in the pores of amino functionalized silica gel

Developing a materials to realize the selective adsorption and long-term immobilization of uranium is of great significance for the effective remediation of uranium-containing wastewater. Herein, we half-filled Fe 0 into SGB-NH 2 mesoporous channels to prepare a composite of Fe 0 and amino-functionalized silica (Fe 0 @SGB-NH 2 ), and used to the selective removal of uranium in solution under aerobic conditions . It was found that solutions containing 10 mg/L U(VI) could be purified 98.96% by Fe 0 @SGB-NH 2 in the presence or absence of Na + , K + , Mg 2+ , SO 4 2 − , NO 3 − , HCO 3 − and Cl − at pH 5–9. Compared with Fe 0 , its saturation magnetization decreased from 81.24 emu/g to 0.78 emu/g, while the specific surface area increased from 47.895 m 2 /g to 504.404 m 2 /g, successfully preventing the agglomeration and rapid corrosion of Fe 0 without reducing its activity. More interestingly, the consumption of Fe 0 @SGB-NH 2 was only 1/28 of untreated Fe 0 when identical uranium removal efficiency was achieved. Further mechanistic studies indicated that U(VI) was firstly selectively captured by amino groups on the surface of the material and then reduction or adsorption in the pore, the long and narrow mesoporous channels reduce the possibility of uranium re-oxidation, thereby significantly reducing its re-release efficiency from 21.5% to only 1.73%. Encapsulation of Fe 0 within SGB-NH 2 channels was found to facilitate faster removal rate and higher U(VI) reduction ratio, and reduce uranium re-oxidation, thus benefit the long-term immobilization of uranium in contaminated groundwater.