Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 47 (2014)

Extraction behavior of Nb and Ta with Aliquat 336 in HF solutions
D. Sato,*1 M. Murakami,*1,*2 K. Ooe,*1 H. Haba,＊2 S. Goto,*1 and H. Kudo*3
Studies on the chemical properties of transactinide
elements with atomic numbers Z ≥ 104 are extremelyinteresting. It is suggested that the chemical properties ofthese elements are different from those of their lighter
homologs because of the strong relativistic effects on thevalence electrons1). Therefore, comparative studies on thechemical behaviors of transactinide elements and theirlighter homologs are very important.
We are planning to investigate the chemical properties ofDb, which is the 105th element in the periodic table.
Because a fluoride ion is known as a strong complexing
reagent for group 5 elements2), ion-pair extractions of Nband Ta, which are the lighter homologs of Db, withquaternary ammonium (Aliquat 336) in HF solutions werecarried out to study complex formations of these elementswith fluoride ions.
Long-lived radiotracers, 95gNb (T1/2 = 34.97 d) and 179Ta(T1/2 = 665 d), were produced during proton bombardmentsof Zr and Hf metallic foil targets with natural isotopic
abundances, respectively, using the RIKEN AVF Cyclotron.
These radiotracers in the targets were chemically isolated
by ion-exchange separation. The tracers were dissolved in
600 μL of 1 M HF and then mixed with the same volume of
10-8-10-3 M Aliquat 336-1,2-dichloroethane solutions in a
polypropylene tube. After shaking the solutions for 5 min,followed by centrifugation, the two phases were separately
pipetted into sample tubes. The radioactivities of the two
samples were assessed with a Ge detector. Distribution
ratios (D) of Nb and Ta were obtained from the ratio of theradioactivities of the two phases.
The dependence of the distribution ratios of 95gNb and179
Ta in 1 M HF on the concentrations of Aliquat 336 areshown in Fig. 1. The results show a linear relation with aslope of ≈1 for both Nb and Ta, which indicates that
univalent anionic fluoride complexes are extracted by
Aliquat 336.
The dependences of D values of 95gNb and 179Ta on theHF concentration were also investigated for varying HF
concentrations (10-2-10 M) with 10-4 M Aliquat336-1,2-dichloroethane solution (Fig. 2). The maximum D
value of Ta is obtained in 0.27 M HF. On the other hand, theD value of Nb decreases gradually with HF concentrationfrom 10-2 M to 10 M, thus, there was a clear differences inthe extraction behaviors of Nb and Ta. The large
differencein the D values of Nb and Ta is probably due tothe fact that Ta forms fluoro-complexes TaFn5-n, while Nb is
predominantly present as oxo-fluoro complexes NbOFn3-n 3).

As mentioned above, the results obtained from Fig.1 showthat the extracted species of Nb and Ta are both univalentanionic complexes. Therefore, Nb and Ta exist as TaF6- andNbOF4- under these experimental conditions.
The fluoro-complex formation of Db needs to beinvestigated from the experimental result to dtermine
whether the extraction behavior of Db from HF solutions
into Aliquat 336-1,2-dichloroethane solution is closer to thatof Nb or Ta.

Fig. 1: Variation of the distribution ratio D of 95gNb and179
Ta vs. concentration of Aliquat 336 in 1 M HF

Fig. 2: Variation of the distribution ratio D of 95gNb and179
Ta vs. initial concentration of HF
References
1) P. Pyykko: Chem. Rev. 88, 563 (1988)
2) Y. Kasamatsu, A. Toyoshima, H. Toume, K. Tsukada, H. Haba,
Y. Nagame: J. Nucl. Radiochem. Sci., Vol. 8, No. 2, 69-72(2007)
3) F. Monroy Guzman, D. Trubert, L. Brillard, J. B. Kim, M.
Hussonnois, and O. Constantinescu: J. Radioanal. Nucl. Chem.
208, 461-466 (1996).

*1

Graduate School of Science and Technology, Niigata University
RIKEN, Nishina Center*3
Department of Chemistry, Faculty of Science, Niigata University*2- 271 -