Nanopockets with a Thermoresponsive Nitrate Ionic Liquid for Highly Efficient Uranium Extraction at High Acidity

The use of high-acidity nitric acid presents many challenges in designing extractants for uranium reprocessing. If nitrate is used as the anion in an ionic liquid (IL) extractant, the extraction efficiency and leakage behavior will improve due to the common-ion effect. However, nitrate ILs are usually hydrophilic, making their applications in uranium reprocessing difficult. In this study, nanopockets with a thermoresponsive nitrate IL Tyr(C₁₀)₂NO₃ were designed and applied in the extraction of uranium. Tyr(C₁₀)₂NO₃ is hydrophobic at room temperature but can homogenize with water when the temperature exceeds 80 °C. This upper critical solution temperature behavior facilitates sufficient contact between Tyr(C₁₀)₂NO₃ and uranium, causing an extremely short equilibration time. Tyr(C₁₀)₂NO₃ is stable in high-acidity nitric acid and shows good affinity toward uranyl ions. The extraction of uranyl using Tyr(C₁₀)₂NO₃ exhibited remarkable extraction efficiency, excellent extraction capacity under a 4 M HNO₃ condition, and good reusability. A hierarchical assembly mechanism has been proposed to rationalize the extraction system.