Efficient Uranium Capture by Polysulfide/Layered Double Hydroxide Composites

• Published in: Journal of the American Chemical Society Vol. 137; no. 10; pp. 3670 - 3677
• Main Authors: Ma, Shulan, Huang, Lu, Ma, Lijiao, Shim, Yurina, Islam, Saiful M, Wang, Pengli, Zhao, Li-Dong, Wang, Shichao, Sun, Genban, Yang, Xiaojing, Kanatzidis, Mercouri G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.03.2015
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.5b00762

There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2 2+) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of S x -LDH composites (LDH is Mg/Al layered double hydroxide, [S x ]2– is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (q m = 330 mg/g), large K d U values (104–106 mL/g at 1–300 ppm U concentration), and high % removals (>95% at 1–100 ppm, or ∼80% for ppb level seawater) for UO2 2+ species. The S x -LDHs are exceptionally efficient for selectively and rapidly capturing UO2 2+ both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value K d U of 3.4 × 106 mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca2+/Na+, S x -LDH exhibits superior selectivity for UO2 2+, over previously reported sorbents. Under low U concentrations, (S4)2– coordinates to UO2 2+ forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)2– binds to UO2 2+ to generate neutral UO2S4 salts outside the gallery, with NO3 – entering the interlayer to form NO3-LDH. In the presence of high Cl– concentration, Cl– preferentially replaces [S4]2– and intercalates into LDH. Detailed comparison of U removal efficiency of S x -LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of S x -LDH materials for selective uranium capture.