Uranyl extraction by N,N-dialkylamide ligands studied using static and dynamic DFT simulations.

Area of Science:

• Computational Chemistry
• Solution Chemistry
• Coordination Chemistry

Background:

• Uranyl extraction from aqueous solutions to organic phases is crucial for nuclear fuel reprocessing.
• Amide ligands are effective extractants for uranyl ions, but their complexation mechanisms require detailed investigation.
• Understanding the role of solvent and ligand coordination is key to optimizing extraction efficiency.

Purpose of the Study:

• To investigate the structure, stability, and solvent effects on uranyl complexes during extraction using DFT.
• To elucidate the binding modes of nitrate and water ligands in different environments.
• To propose mechanisms for uranyl extraction by amide ligands at the water-hexane interface.

Main Methods:

• Density Functional Theory (DFT) static calculations with continuum solvation models (SMD).
• DFT-based Molecular Dynamics (DFT-MD) simulations in explicit solvent environments (water, hexane, interface).
• Metadynamics simulations to explore ligand binding dynamics.

Main Results:

• Stepwise formation of uranyl-nitrate-amide complexes is energetically favorable.
• Solvent-dependent binding modes of nitrate ligands were observed, switching between bidentate and monodentate.
• Uranyl complexes at the water-hexane interface exhibit water-like structural characteristics, inverting gas-phase bond distance trends.
• Complex structures and stability are significantly influenced by the solvent environment and dynamics.

Conclusions:

• DFT studies provide insights into uranyl complexation and extraction mechanisms.
• Complexation of amide ligands at the interface is a likely step in the extraction process.
• Solvent effects and molecular dynamics are critical for understanding uranyl extraction efficiency.