From ambient to extreme conditions: a systematic investigation of actinides chemistry in fission products based oxo-salt systems

• Applicant: Dr. Evgeny V. Alekseev
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Mineralogy, Petrology and Geochemistry
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 390461079

• Final Report Year: 2022

Final Report Abstract

The project resulted in a systematic study of several systems containing actinides at different conditions including extreme conditions of pressure and temperature, as it was proposed in DFG-CNSF application. The work has been done in close cooperation with Chinese counterpart (Prof. Shuao Wang) which allow us perform a significant amount of work with transuranic elements. The most significant results of the research within the projects: 1. Understanding of structural incorporation of I into U-based oxides and oxo-hydroxides at normal and mild hydrothermal conditions. 2. Synthesis and study of first U-polyiodate from concentrated nitric acid aqueous solutions. 3. Understanding of acidity role on formation of U and Np selenates/selenites and nitrates. 4. Study of mixed anionic Se-based polyoxometalates with U, Np, Pu ad Am and development of new, very effective and less costly separation methodology for Ln((III) and An(VI) separation in acidic solutions. 5. Study of thermodynamics of U-Mo and U-W systems and verification of DFT+U methods for prediction of thermodynamics of complex solid-state chemical reactions involving U and d-elements. 6. Synthesis of several new phases in U-Mo systems under extreme conditions (high pressure/high temperature) and analysis of structural dimensionally change as a factor of synthetic pressure. 7. Synthesis and study of first HP divalent U-tellurates/tellurites and several new HP uranium selenates. 8. High-pressure synthesis of first hexagonal, fully uranium-bronze materials with mixed V-VI oxidation states of uranium. 9. Understanding of how the pressure can affect the linearity of uranyl group UO22+ on example of unique high-pressure uranyl sulfate. Using methods of DFT+U for understanding of linearity distortion energetics. 10. We summarize current state of the art in An-chemistry from ex-situ HP/HT conditions in a single work (prospective article at Dalton Transactions). The project was significantly affected by COVID-19 pandemic. However, obtained results are solid and bring new light for the inorganic chemistry of actinide elements in oxidic and oxo-salt systems.

Publications

• (2020) Extreme condition high temperature and high pressure studies of the K-U-Mo-O system. Dalton Transactions, 49(44), 15843–15853
  Murphy, G.L., Kegler, P., Klinkenberg, M., Wang, S., Alekseev, E.V.
  
• (2020) Insights into the Structural Chemistry of Anhydrous and Hydrous Hexavalent Uranium and Neptunium Dinitrato, Trinitrato, and Tetranitrato Complexes. Inorg.Chem. 59(10), 7204–7215
  Murphy G.L., Langer E.M., Walter O., Wang Y., Wang S., Alekseev E.V.
  
• (2021) Incorporation of iodine into uranium oxyhydroxide phases. Dalton Transactions, 50, 46, 17257-17264
  Murphy, G.L., Kegler, P., Klinkenberg M., Wilden A., Henkes M., Schneider D., Alekseev, E.V.
  
• (2021) The First Actinide Polyiodate: A Complex Multifunctional Compound with promising X-ray Luminescence Properties and Proton Conductivity. ChemComm. 57, 496
  Murphy, G.L., Wang Y. Kegler, P., Wang, S., Alekseev, E.V.
  
• (2021) The Role of Acidity in the Synthesis of Novel Uranyl Selenate and Selenite Compounds and Their Structures. Crystals, 11, 965
  Murphy, G.L., Kegler, P., Langer, E.M., Alekseev, E.V.
  
• (2021). Achieving and Stabilizing Uranyl Bending via Physical Pressure. Inorg.Chem. 60(12), 8419–8422
  Langer E., Kegler, P., Wang, S., Alekseev, E.V.