SANS study of third phase formation in the Th(IV)-HNO{sub 3}/ TBP-n-octane system.
Formation of a third organic phase at high metal loading in the extraction of tetravalent actinides by TBP in aliphatic diluents has been investigated mostly from the standpoint of the composition of the organic phase species before and after phase splitting. Very little is known of the structure and morphology of the organic phase species. In this work, a study of third phase formation upon either dissolution of Th(NO{sub 3}){sub 4} in 20% TBP in n-octane or Th(NO{sub 3}){sub 4} extraction from 1 M HNO{sub 3} by 20% TBP in n-octane is reported. Chemical analyses have shown that, under the conditions of this work, Th(IV) exists in the organic phase mainly as the trisolvate Th(NO{sub 3}){sub 4}.(TBP){sub 3}. The third phase species also contains a small amount of HNO{sub 3}, presumably hydrogen-bonded to the trisolvate complex. Small-angle neutron scattering measurements on TBP solutions loaded with only HNO{sub 3} or with increasing amounts of Th(IV) revealed the presence, before phase splitting, of large ellipsoidal aggregates with the parallel and perpendicular axes having lengths up to about 230 and 24 Angstroms, respectively. Although the formation of these aggregates is observed in all cases, that is, when only HNO{sub 3}, only Th(NO{sub 3}){sub 4}, or both HNO{sub 3} and Th(NO{sub 3}){sub 4} are extracted by the TBP solution, the size of the aggregates is largest in the latter case. Formation of these aggregates is probably the main reason for phase splitting.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 949448
- Report Number(s):
- ANL/CHM/JA-41014
- Journal Information:
- Sep. Sci. Technol., Journal Name: Sep. Sci. Technol. Journal Issue: 12-13 ; 2003 Vol. 38; ISSN 0149-6395; ISSN SSTEDS
- Country of Publication:
- United States
- Language:
- ENGLISH
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