SA-DNA hydrogel microspheres for Ultra-Selective uranyl (VI) extraction from seawater

Extraction of uranium from seawater is vital for the advancement of nuclear energy. However, the synthesis of selective adsorbents remains challenging. In this study, affordable sodium alginate (SA) and functional DNA strands were selected to fabricate SA-DNA hydrogel microspheres for the selective adsorption of uranyl ions (UO22+) in an economically viable manner. The microspheres were approximately 2 mm in size and contained numerous micrometer-sized pores to enhance mass transfer and fully expose the active sites. With DNA functioning as selective adsorption sites, the microspheres showed a significantly high affinity for UO22+ with a selectivity of 43.6 times that of vanadium ions, achieving unprecedented selective adsorption of UO22+. From the results, the synthesized adsorbent has exceptional uranium adsorption capability and excellent resistance against co-existing ions in seawater, and it is easily accessible and cost-effective. Analysis of interactions between the functional groups and ions revealed the coordination environment of UO22+. Density functional theory (DFT) calculations suggested that DNA provides favorable energetics for UO22+ binding and illustrated the U with P-O coordination effect. The results of this study are crucial for advancing the selective extraction of uranium from seawater. Moreover, such adsorbents with ultrahigh selectivity may be applied to extract other resource ions from seawater.