Direct recovery of high-purity uranium from fluoride-containing nuclear wastewater via extraction materials with ensemble Lewis sites and a tandem electrochemical device

Electrochemical uranium extraction from real nuclear wastewater with a high concentration of fluoride ions (F-) represents a promising strategy for the efficient treatment of radioactive wastewater and the recovery of the valuable uranium resource. However, the current progress suffers from the interference of extremely high concentration of F- and undesired purity of the final uranium product. Herein, we constructed the neighboring ensemble Lewis acid-base pair sites (ensemble Lewis sites) in bismuth oxides as the extraction material, which was integrated into a designed tandem electrochemical device for efficient recovery of high-purity uranium from real nuclear wastewater. The mechanistic study revealed that the ensemble Lewis sites dramatically enhance the binding of all dominant uranyl fluoride (UO2Fx) species through the simultaneous strengthened chemical bonds with U, O, and F atoms. Besides, the tandem electrochemical device rationally controlled the reaction period to U3O8, avoiding the undesired crystalline transformation to K2U2O7. Through 3 h electrolysis in 1 L of real nuclear wastewater, the extraction efficiency of uranium reached 99.9 % with only 2.2 % impurities of alkali metals in extracted uranium product, outperforming the previous work. This study offers an effective method for the recovery of uranium resources in real nuclear wastewater.