Extraction of the fluoride-, chloride- and bromide complexes of the elements Nb, Ta, Pa, and 105 into aliphatic amines

Previous studies of the halide complex formation of element 105 in HCl–HF mixtures and extractions into triisooctyl amine (TIOA) have been performed with the Automated Rapid Chemistry Apparatus, ARCA II. Element 105 was shown to be absorbed on the column from 12 M HCl–0.02 M HF together with its lig...

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Bibliographic Details
Published in:	Journal of alloys and compounds Vol. 271; pp. 292 - 295
Main Authors:	Paulus, W., Kratz, J.V., Strub, E., Zauner, S., Brüchle, W., Pershina, V., Schädel, M., Schausten, B., Adams, J.L., Gregorich, K.E., Hoffman, D.C., Lane, M.R., Laue, C., Lee, D.M., McGrath, C.A., Shaughnessy, D.K., Strellis, D.A., Sylwester, E.R.
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 12-06-1998
Subjects:	Aliquat 336–HCl Aliquat 336–HF Extraction chromatography Niobium Protactinium and element 105 Tantalum Tantalum Aliquat 336–HCl Protactinium and element 105 Extraction chromatography Aliquat 336–HF Niobium
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Summary:	Previous studies of the halide complex formation of element 105 in HCl–HF mixtures and extractions into triisooctyl amine (TIOA) have been performed with the Automated Rapid Chemistry Apparatus, ARCA II. Element 105 was shown to be absorbed on the column from 12 M HCl–0.02 M HF together with its lighter homologues Nb, Ta and the pseudohomologue Pa. In elutions with 10 M HCl–0.025 M HF, 4 M HCl–0.02 M HF, and 0.5 M HCl–0.01 M HF, the extraction sequence Ta>Nb>105>Pa was observed and element 105 behaved very differently from its closest homologue Ta. As it is not possible within reasonable effort to model the many presumably mixed fluoride–chloride complexes involved in these studies, theoretical calculations were performed in the pure chloride system predicting a reversed sequence of extraction. To verify this experimentally, and in order to perform a systematic study of halide complexation of the group 5 elements, new batch extraction experiments for Nb, Ta, and Pa were performed with the quarternary ammonium salt Aliquat 336 in pure HF, HCl, and HBr solutions. Based on these results, new chromatographic column separations were elaborated to study separately the fluoride and chloride complexation of element 105 with ARCA II. In the system Aliquat 336–HF, after feeding of the activity onto the column in 0.5 M HF, element 105 did not elute in 4 M HF (Pa fraction) but showed a higher distribution coefficient close to that of Nb (and Ta). In the system Aliquat 336–HCl, after feeding onto the column in 10 M HCl, element 105 showed a distribution coefficient in 6 M HCl close to that of Nb establishing an extraction sequence Pa>Nb≥105>Ta which is theoretically predicted by considering the competition between hydrolysis and complex formation.
ISSN:	0925-8388 1873-4669
DOI:	10.1016/S0925-8388(98)00073-5