Synergistic nanofibrous adsorbent for uranium extraction from seawater

Huge reserves of uranium (U) in seawater have been of interest to scientists and energy companies since the 1950s. However, extracting trace concentrations (3.3 ppb) of U from seawater is economically unfeasible without new, high-performance adsorbents. Here, a mat-like nanofibrous composite adsorbent containing binary coordination groups (amidoxime (AO) and carboxyl (AC(-))) in a highly porous network of nanofibers is constructed via a parallel-blend electrospinning method. Its U uptake in artificial seawater is more than double those of adsorbents containing AO or AC(-) groups alone. Density functional theory (DFT) calculations reveal that this synergistic effect is because the AC(-) group promotes both the U 5f/6d orbital contribution to U-AO bonding and the dissociation of uranyl tricarbonate ions in seawater. In a continuous flow-through experiment with simulated seawater, the nanofibrous adsorbent achieves an adsorption capacity up to 2.86 mg U g(ads)(-1) in 30 d but without saturation, indicating a high efficiency for U extraction.