Efficient Removal of U(VI) Using Functionalized Hollow Mesoporous Silica Nanospheres

The capture and recycle uranium from wastewater is very important for the environmental protection and sustainable nuclear energy development. In this work, functionalized hollow mesoporous silica nanospheres bearing aminopropyl and Schiff base groups, abbreviated as HMSNs-NH2 and HMSNs-SA, respectively, were prepared for the removal of U(VI) from aqueous solution. The effects of solution pH, adsorption kinetics, thermodynamics and isotherms, as well as the presence of competing metal ions on the uranium adsorption onto the two adsorbents were investigated in detail. It was found that both adsorbents showed largely enhanced adsorption capacity and good selectivity towards U(VI) than unfunctionalized HMSNs. The maximum adsorption capacities reach 499.72 mg/g for HMSNs-NH2 and 317.29 mg/g for HMSNs-SA, which are at a high level compared with the reported functionalized mesoporous silica materials. Furthermore, both adsorbents can rapidly remove uranium with the removal rate more than 97% from tap water and 85% from seawater with injected uranium of 5 ppm. The findings of the present work provide new actinide adsorbents by combining organic ligands with hollow mesoporous matrixes.