Interfacial complex formation in uranyl extraction by tributyl phosphate in dodecane diluent: a molecular dynamics...

Area of Science:

• Nuclear Chemistry
• Materials Science
• Physical Chemistry

Background:

• Uranyl extraction is crucial for nuclear fuel reprocessing and waste management.
• Understanding interfacial mechanisms is key to optimizing solvent extraction processes.
• Atomistic simulations offer detailed insights into molecular interactions at interfaces.

Purpose of the Study:

• To investigate the molecular mechanisms of uranyl extraction at the aqueous-organic interface.
• To elucidate the role of nitric acid and extractant molecules in uranyl complex formation.
• To determine the coordination environment of uranyl ions during extraction.

Main Methods:

• Atomistic simulations of a multicomponent two-phase system.
• Modeling aqueous phase with uranyl, nitrate, and hydronium ions in water.
• Modeling organic phase with tributyl phosphate (TBP) extractant in dodecane diluent.

Main Results:

• The interface facilitates the formation of various uranyl complexes: UO2(2+)(NO3-)n *mTBP*kH2O (n+m+k=5).
• A common coordination feature involves oxygen binding to the uranium atom, forming a 5-fold symmetry plane.
• Nitric acid strongly enhances the formation of extractable uranyl species.

Conclusions:

• The study elucidates the interfacial molecular mechanisms governing uranyl extraction.
• The findings highlight the significant role of nitric acid in enhancing extractable species formation.
• The observed 5-fold coordination provides a detailed understanding of uranyl complexation during extraction.