Third phase formation revisited: The U(VI), HNO3-TBP, n-dodecane system

R. Chiarizia; M. P. Jensen; M. Borkowski; J. R. Ferraro; P. Thiyagarajan; K. C. Littrell

doi:10.1081/SEI-120017545

Third phase formation revisited: The U(VI), HNO₃-TBP, n-dodecane system

R. Chiarizia, M. P. Jensen, M. Borkowski, J. R. Ferraro, P. Thiyagarajan, K. C. Littrell

Research output: Contribution to journal › Article › peer-review

142 Scopus citations

Abstract

In this work, the system U(VI), HNO₃-tri-n-butylphosphate (TBP), n-dodecane has been revisited with the objective of gaining information on the coordination chemistry and structural evolution of the species formed in the organic phase before and after third phase formation. Chemical analyses, spectroscopic and EXAFS data indicate that U(VI) is extracted as the UO₂(NO₃)₂ · 2TBP adduct, while the third phase species have the average composition UO₂(NO₃)₂ · 2TBP · HNO₃. Small-angle neutron scattering (SANS) measurements on TBP solutions loaded with only HNO₃ or with increasing amounts of U(VI) have revealed the presence, before phase splitting, of ellipsoidal aggregates with the major and minor axes up to about 64 and 15 Å, respectively. The formation of these aggregates, very likely of the reverse micelle-type, is observed in all cases, that is, when only HNO₃, only UO₂(NO₃)₂, or both HNO₃ and UO₂(NO₃)₂ are extracted by the TBP solution. Upon third phase formation, the SANS data reveal the presence of smaller aggregates in the light organic phase, while the heavy organic phase contains pockets of diluent, each with an average of about two molecules of n-dodecane.

Original language	English
Pages (from-to)	1-27
Number of pages	27
Journal	Solvent Extraction and Ion Exchange
Volume	21
Issue number	1
DOIs	https://doi.org/10.1081/SEI-120017545
State	Published - Jan 2003
Externally published	Yes

Funding

This work was funded by the U. S. Department of Energy, Office of Basic Energy Science (for use of the Advanced Photon Source), Division of Chemical Science (for the part performed at the Chemistry Division of ANL) and Division of Material Science (for the part performed at INPS), under contract No. W-31-109-ENG-38. In this work, the system U(VI), HNO3–tri-n-butylphosphate (TBP), n-dodecane has been revisited with the objective of gaining information on the coordination chemistry and structural evolution of the species #Work performed under the auspices of the U. S. Department of Energy, Office of Basic Energy Science, Division of Chemical Science (for the part performed at the Chemistry Division of ANL) and Division of Material Science (for the part performed at INPS), under contract No. W-31-109-ENG-38. §The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (‘‘Argonne’’) under Contract No. W-31-109-ENG-38 with the US Department of Energy. The US Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. *Correspondence: R. Chiarizia, Chemistry Division, Argonne National Laboratory, Argonne, IL 60439, USA. E-mail: [email protected].

Funders	Funder number
Division of Chemical Science
Division of Material Science
Office of Basic Energy Science
U. S. Department of Energy
University of Chicago as Operator of Argonne National Laboratory
Argonne National Laboratory

Keywords

EXAFS
Scattering
Small angle neutron
Third phase formation
Tributylphosphate
Uranyl nitrate

Access to Document

10.1081/SEI-120017545

Cite this

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abstract = "In this work, the system U(VI), HNO3-tri-n-butylphosphate (TBP), n-dodecane has been revisited with the objective of gaining information on the coordination chemistry and structural evolution of the species formed in the organic phase before and after third phase formation. Chemical analyses, spectroscopic and EXAFS data indicate that U(VI) is extracted as the UO2(NO3)2 · 2TBP adduct, while the third phase species have the average composition UO2(NO3)2 · 2TBP · HNO3. Small-angle neutron scattering (SANS) measurements on TBP solutions loaded with only HNO3 or with increasing amounts of U(VI) have revealed the presence, before phase splitting, of ellipsoidal aggregates with the major and minor axes up to about 64 and 15 {\AA}, respectively. The formation of these aggregates, very likely of the reverse micelle-type, is observed in all cases, that is, when only HNO3, only UO2(NO3)2, or both HNO3 and UO2(NO3)2 are extracted by the TBP solution. Upon third phase formation, the SANS data reveal the presence of smaller aggregates in the light organic phase, while the heavy organic phase contains pockets of diluent, each with an average of about two molecules of n-dodecane.",

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