Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 48 (2015)

Reversed-phase chromatography of Nb and Ta with TBP forconducting a chemical experiment on the 105th element, Db
M. Murakami,∗1,∗2 S. Tsuto,∗1 K. Ooe,∗1 S. Goto,∗1 D. Sato,∗1 N. Goto,∗1 T. Koyama,∗1 T. Nagaoka,∗1R. Motoyama,∗1 H. Haba,∗2 Y. Komori,∗2 A. Toyoshima,∗3 A. Mitsukai,∗3,∗4 Y. Kitayama,∗5 Y. Fukuda,∗5and H. Kudo∗1∗1∗2∗3∗4∗5Department of Chemistry, Niigata University
RIKEN Nishina Center
Advanced Science Research Center, Japan Atomic Energy
AgencyFaculty of Science, Ibaraki University
Graduate School of Natural Science and Technology,Kanazawa University

Radioactivity per each fraction (arb. unit)of the total activity of 178a Ta). Similar elution behavior of 90g Nb was also observed at higher [HF]ini . The
peak volume of the elution curves of 178a Ta graduallydecreased, corresponding to the decreasing distribution coefficient (Kd ) of 178a Ta on the TBP resin. InFig. 1, the elution curve of 178a Ta was fitted by theGlückauf formula of chromatography4) except for thefirst leakage fraction. The Kd values are described as
Kd = vp /mr , where vp and mr are the peak volume andmass of dry resin (6.31 mg), respectively. The evaluated Kd values of 178a Ta are shown in Fig. 2 together
with those of 179 Ta previously obtained by the batchexperiments.1) The good agreement between the online and off-line results indicates that the extraction
equilibrium is reached in the present column experiment. Recently, we performed an extraction experiment of Db with the studied system.5)
10010090g
90g
NbNb
178a178a80
80

TaTa6060404020200000

500
500

1000
1000

1500
1500

Volume (µL)(�L)
VolumeFig. 1. Elution curves of 90g Nb and 178a Ta in 1.0 M HF on
the column of 62 wt%TBP resin.
310103178a178aTa
Ta(on-line)(on-line)
90g
90g
NbNb(batch)(batch)179
179

Ta
Ta(batch)(batch)2
10102

Kd (mL/g)(mL/g)
Kd

Detailed chemical properties of superheavy elements(SHEs) have not been elucidated owing to the difficultyin conducting chemical experiments because of theirshort half-lives and extremely low production rates.
For investigating the chemical properties of the 105thelement, Db, we studied the extraction behavior of
the group-5 homolog elements Nb and Ta from HF
media with tributyl phosphate (TBP), which is usedin the industrial separation of Nb and Ta. In ourprevious study using batchwise solvent extraction,1)
we observed the differences between the 95g Nb and179
Ta extraction behaviors; the distribution ratios of179
Ta reach a maximum at the initial HF concentration, [HF]ini = 0.27 M, whereas those of 95g Nb increase
with increasing [HF]ini . To examine the applicabilityof this extraction system to the short-lived 262 Db with
T1/2 = 33.8 s, we performed an on-line reversed-phase
chromatographic experiment on Nb and Ta using Automated Rapid Chemistry Apparatus (ARCA).2)
The nuclides 90g Nb (T1/2 = 14.6 h) and 178a Ta(T1/2 = 2.45 h) were produced via the nat Zr(d,xn)
and nat Hf(d,xn) reactions, respectively, with a 24-MeV
deuteron beam supplied from the RIKEN AVF cyclotron. The nuclides produced were transported witha He/KCl gas-jet system and were deposited on a collection site in ARCA for 60 s. Then, the products
were dissolved in 1–10 M HF solutions and were loaded
onto a column (1.6 mm i.d. × 7.0 mm height) filledwith a 62-wt% TBP-laden resin, which was preparedin the procedure described in Ref. 3. The flow rateof the eluent was 1.0 mL/min. The effluent fractions
were consecutively collected in 7 polypropylene (PP)tubes. The remaining products in the column werestripped with 330 µL of 10 M HF at a flow rate of 1.0mL/min, and the effluent was collected in another PPtube. Each fraction was subjected to γ-ray spectrometry with a Ge detector.
Figure 1 shows the elution curves of 90g Nb and178aTa in 1.0 M HF as an example, in which correction for a dead volume of ARCA (40 µL) was made forthe effluent volume. 90g Nb was eluted immediately,
whereas 178a Ta showed a broad peak around 770 µL
with a small leakage in the first effluent (less than 5%110101010
100-11010-1

010100110101210102[HF][HF]iniini(M)(M)

Fig. 2. Variation in Kd values of 178a Ta as a functionof [HF]ini (closed symbols). The Kd values of 95g Nb
and 179 Ta obtained by the batch experiment1) are also
shown as open symbols.

References

1) S. Tsuto et al.: RIKEN Accel. Prog. Rep. 47, 270
in press.
(2014).
2) Y. Nagame et al.: Radiochim. Acta 93, 519 (2005).
3) H. Haba et al.: Radiochim. Acta 95, 1 (2007).
4) E. Glückauf: Trans. Faraday Soc. 51, 34 (1955).
5) M. Murakami et al.: In this report.

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