Enhanced uranium extraction from seawater using bifunctional-modified molecular sieves with high selectivity and adsorption capacity

The extraction of uranium from seawater is not only crucial from a strategic standpoint but also poses significant technical challenges. In this work, a series of novel bifunctionalized mesoporous silicas were prepared through a straightforward method, utilizing the structural characteristics of SBA-15 and synergistic effect of functional groups. The impact of pH value, initial uranium concentration, temperature, and duration on uranium adsorption was investigated through a series of batch experiments. The bifunctional modified SBA-15 demonstrated rapid uranium adsorption, which was a spontaneous endothermic reaction and conformed to the pseudo-second-order model. Thereinto, SBA-15 modified with aldoxime and amino group (SBA-15-SAO-N) exhibited the best uranium adsorption performance, with a maximum adsorption capacity of 701.85 mg·g −1 at 298 K and pH 6, an increase of 146 % compared to SBA-15-SAO. SBA-15-SAO-N exhibits excellent U/V selectivity (selectivity coefficient of 30) in the coexistence of U and V solutions, and it still maintains high adsorption capacity after five adsorption-desorption cycles. In actual seawater conditions, the adsorption capacity of SBA-15-SAO-N was 135.26 μg·g −1 . By combining DFT calculations and characterization, the coordination model and interaction energy between functional groups and uranyl were elucidated, revealing that introducing bifunctional groups can enhance the binding strength of adsorbents to uranium and form more stable complexes, thereby improving adsorption capacity and selectivity. These results indicate that bifunctional modified mesoporous silica offers a promising strategy for recovering uranium resources from seawater.