Third phase formation revisited: the U(VI), HNO{sub 3} - TBP, n-dodecane system.
In this work, the system U(VI), HNO{sub 3}-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 UO{sub 2}(NO{sub 3}){sub 2}{center_dot}2TBP adduct, while the third phase species have the average composition UO{sub 2}(NO{sub 3}){sub 2}{center_dot}2TBP{center_dot}HNO{sub 3}. Small-angle neutron scattering (SANS) measurements on TBP solutions loaded with only HNO{sub 3} 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 A, respectively. The formation of these aggregates, very likely of the reverse micelle-type, is observed in all cases, that is, when only HNO{sub 3}, only UO{sub 2}(NO{sub 3}){sub 2}, or both HNO{sub 3} and UO{sub 2}(NO{sub 3}){sub 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.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 949724
- Report Number(s):
- ANL/CHM/JA-43735; SEIEDB; TRN: US1003626
- Journal Information:
- Solvent Extr. Ion Exch., Vol. 21, Issue 1 ; 2003; ISSN 0736-6299
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
New insights in third phase formation in the U(VI)-HNO{sub 3}, TBP-alkane system.
Application of the Baxter model for hard-spheres with surface adhesion to SANS data for the U(VI) - HNO{sub 3}, TBP-n-dodecane system.