Amino-functionalization of hydroxylated SBA-15 for enhanced uranium adsorption from seawater

Abstract Uranium extraction from seawater is a strategic deployment to the sustainable development of nuclear energy. However, challenges exist in uranium enrichment because of the extremely low U(VI) concentration and the complexity of seawater. Herein, a novel NH2-functionalized mesoporous hydroxylated SBA-15 (NH2-H-SBA-15), synthesized via post-grafting method was used as the adsorbent in uranium adsorption field. The adsorbent was prepared by reacting between aminosilane and the surface silanol groups of hydroxylated SBA-15. It shows stable adsorption properties in a wider applicable pH range (6-8) because amino groups have better adaptability both in weakly acidic and alkaline environment. Moreover, adsorption kinetic data better fitted pseudo-second-order model, which indicated that the uranium adsorption process belongs to chemical adsorption. Isothermal data better followed the Langmuir model, suggesting a monolayer coverage adsorption mode. Additionally, the adsorption capacity of the NH2-H-SBA-15 is approximatively 115 mg·g-1 within 7 days at pH = 8.1 and 25 ℃ in uranium-spiked natural seawater. Therefore, the NH2-H-SBA-15 shows the excellent selectivity of uranium in the natural seawater (αU/M > 1) which provides a promising prospect in extracting uranium from seawater.