Role of Ligand Structure and Basicity on the Extraction of Uranyl Isoxazolonate Adducts

Abstract

The extraction behavior of uranium(VI) from dilute nitric acid was investigated employing 3‐phenyl‐4‐acetyl‐5‐isoxazolone (HPAI) as the chelating ligand and several amides with varying degree of branching such as di‐2‐ethylhexylacetamide (D2EHAA), di‐2‐ethylhexylpropanamide (D2EHPrA), di‐2‐ethylhexylisobutyramide (D2EHiBA), and di‐2‐ethylhexylpivalamide (D2EHPvA) as neutral donors in toluene medium. The two‐phase extraction constant (log K _ex) for the binary species UO₂(PBI)₂H₂O was found to be 0.66. The overall equilibrium constants (log K ) for the ternary species of the type UO₂(PAI)₂B are estimated to be 5.29 (D2EHAA), 5.02 (D2EHPrA), 4.86 (D2EHiBA), and 4.28 (D2EHPvA), respectively, which vary linearly with the basicity of the amides. The role of steric factors in the co‐ordination of the amides to the uranyl β‐diketones and the adduct formation in the case of the ternary complexes was explained on the basis of molecular modeling.

Keywords:

• Uranium(VI)
• Solvent extraction
• Beta‐diketone
• Isoxazolone
• Amide

Acknowledgments

One of the authors (Shrabanti Banerjee) wishes to record her gratitude to The University of Burdwan for providing Senior Research Fellowship to her. We are also grateful to Dr. S. B. Manohar, Head, Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India for providing valuable suggestions in this work.