RIKEN Accel. Prog. Rep. 48 (2015)

Ⅲ-3. Radiochemistry & Nuclear Chemistry

Solid-liquid extraction of 261Rf from hydrochloric acid with Aliquat 336 resin
T. Yokokita,＊1,＊2 Y. Kasamatsu,＊2 Y. Shigekawa,＊1,＊2 Y. Yasuda,＊1,＊2 K. Nakamura,＊1,＊2 H. Haba,＊1 Y. Komori,＊1M. Murakami,＊1 and A. Shinohara＊1,＊2
The chemical properties of transactinide elements(atomic numbers Z ≥ 104) are considered to differ fromthose of its homologues because of the increasingly strong
relativistic effects on the valence shell electrons of heavyatoms. The transactinide nuclei are produced at accelerators
using heavy-ion-induced nuclear reactions. These nuclei
have low production rates and short half-lives (T1/2 ≤ ~1min). Therefore, the chemical experiments of transactinides
must be carried out rapidly on one-atom-at-a-time basis
using nuclear reaction products transported from the target
chamber by a He/KCl gas-jet system. The chemical
properties of transactinides have so far been investigatedmainly by a partition method based on a comparison of theirchemical behavior with those of lighter homologous
elements.
Solution chemistry experiments have been often
conducted on element 104, rutherfordium (Rf). Anion- andcation-exchange experiments of Rf in HF and HF/HNO3
were successfully performed under conditions such that thedistribution behaviors in equilibria were observed for thehomologues of Rf. Clearly different behavior of Rf from its
homologues Zr and Hf was reported.1) On the other hand, inthe cation exchange in H2SO4/HNO3, the Kd values of Hf in
the online experiment were in good agreement with those in
the offline batch experiment, whereas the Kd values of Zr in
the online experiment were not.2) Therefore, it is important
to investigate the time dependence of the distribution
behaviors of transactinides to obtain their equilibrated data
because the time required to reach distribution equilibrium
would be different among homologues. Thus, we developed
a batch-type solid-liquid extraction apparatus to evaluate
the time dependence of the distribution behavior of Rf andto obtain the equilibrated Kd values.3) To determine theexperimental condition and obtain comparison data for Rf,
we also performed solid-liquid extraction of Zr and Hf andTh (pseudo homologue) with a quaternary ammonium
chloride, Aliquat 336, from HCl.4) In this work, we
performed an online solid-liquid extraction experiment on261
Rf and 169Hf using the developed apparatus at RIKEN.
The 261Rf (T1/2 = 68 s) and 169Hf (T1/2 = 3.25 min)nuclides were produced in the 248Cm(18O,5n)261Rf andnatGd(18O,xn)169Hf reactions, respectively, by the RIKEN
K70 AVF cyclotron. The nuclear reaction products thatrecoiled out from the target were caught by KCl aerosols inHe gas and were transported by the gas-jet system to thechemistry laboratory. In the solid-liquid extraction
experiments, the reaction products in the gas-jet weredeposited on a collection site on a dissolution apparatus.
＊1＊2

RIKEN Nishina Center
Graduate School of Science, Osaka University

Then, the deposited sample was dissolved in about 0.25 mL
of 7.9 and 9.0 M HCl. The solution sample entered thechemical reaction container containing the 28 wt% Aliquat
336 resin (1.11–1.62 mg). After shaking the container witha vortex mixer for 10–60 s, only the solution phase waspushed out of the container by compressed air and collectedon the Ta dish. Then the solution sample was evaporated todryness with hot He gas and a halogen lamp to prepare asample for α-spectrometry. Subsequently, the Ta dish wastransferred to a Si PIN photodiode detector, and α-particle
measurement was performed. After the measurement, theγ-ray activity of 169Hf was monitored using a Ge detector todetermine its Kd value and chemical yield.
In Fig. 1, the Kd values of Zr, Hf, and Th with the 28wt%
Aliquat 336 resin4) are shown as a function of the HClconcentration. The Kd values of Hf in this work wereconsistent with those in the offline batch experiment (≥4 hof shaking), indicating that the Kd values of Hf in equilibria
could be obtained using batch-type solid-liquid extraction
apparatus. The 24 and 3 α events were observed in theexperiments at 7.9 M HCl (38 extractions, chemical yield:56%) and at 9.0 M HCl (68 extractions, chemical yield:47%), respectively, in the α energy region of 261Rf and its
daughter 257No. The detected α counts for eluent clearlydecreased with an increase in the HCl concentration. Thissuggests that Rf forms anionic chloride complexes with Cl−ions, similar to the case of Zr and Hf and different from thecase of Th. The present results are consistent with theprevious report.5) We will report the Kd values of Rf in thepresent experiment in the future.

Fig. 1. The Kd values of Zr, Hf, and Th as a function of theHCl concentration with 28 wt% Aliquat 336 resin.
References

1) Y. Ishii et al.: Bull. Chem. Soc. Jpn. 84, 903 (2011).
2) Z. J. Li et al.: Radiochim. Acta 100, 157 (2012).
3) A. Kino et al.: RIKEN Accel. Prog. Rep. 46, 241 (2013).
4) T. Yokokita et al.: 6th International Conference of Ion Exchange,Ginowan, November 12 (2014).
5) H. Haba et al.: J. Nucl. Radiochem. Sci. 3, 143 (2002).

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