We are one of the local labs that primarily focus on the uranium resource utilization, located within State Key Laboratory of Environment-friendly Energy Materials, Southwest University of Science & Technology, in Mianyang, China. We are delighted to share the stories behind the paper while also provide fresh insights for electrochemical uranium extraction.

Uranium extraction in nuclear wastewater from the production of nuclear fuel is an efficient means to realize the secondary supply of uranium resources. In practical terms, the majority of uranium-containing nuclear wastewater is generated through fuel production processes which involve extensive use of uranium fluoride. In real nuclear wastewater, F⁻ commonly co-exists with UO₂²⁺, resulting in the complex species of UO₂F_x and thus the decreased extraction efficiency. Accordingly, the traditional adsorption or ion exchange strategy requires the pre-precipitation of F⁻ by Ca²⁺, resulting in the formation of uranium-containing CaF₂ as radioactive solid waste.

Parallel to traditional strategy, electrochemical uranium extraction has attracted increasing attention because of the fast kinetics, increased extraction capacity, and resistance to the interference of anions. However, current progress on electrochemical extraction of U(VI) is limited to the aqueous solution systems without F⁻, which lack the strategy in real nuclear wastewater from nuclear fuel production. In real nuclear wastewater, the main bottlenecks of uranium extraction lie in the competitive coordination between U(VI) and F⁻, thus resulting in the poor extraction efficiency of uranium under the interference of high concentrations of F⁻.

Therefore, we developed an ion pair sites strategy of for selective binding of UO₂F_x and efficient electrochemical uranium extraction in real nuclear wastewater. The UO₂F_x was adsorbed on the ion pair sites of without the separation of the U-F bond. After that, the uranyl was reduced to low-valent species, which weakened the Coulombian force of uranyl and F⁻, thus resulting in the formation of an intermediate UO_2+x product. The metastable low-valent uranium was then oxidized, followed by crystallizing with F⁻ and forming the final K₃UO₂F₅ (Figure 1). In real nuclear wastewater, the uranium was extracted as oxide powder with high purity. Therefore, the uranium was able to be efficiently extracted from the electrode.

We hope that our strategy of ion pair sites in the electrochemical extraction of nuclear wastewater can serve as a beacon of inspiration for other researchers in the field. By revealing the potential applications of ion pair sites in the field of electrochemical uranium extraction, we will be more than delighted to witness further exploration into innovative coordination sites strategies for not only uranium extraction but also other complex nuclide.

Please feel free to contact Prof. Wenkun Zhu, corresponding author of this article, if you have any questions or comments about the work: zhuwenkun@swust.edu.cn.