Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 51 (2018)

Solid-liquid extraction of Mo and W by Aliquat 336 from HClsolutions toward extraction chromatography experiments of Sg†
Y. Komori,∗1,∗2 T. Yokokita,∗1,∗2 Y. Kasamatsu,∗2 H. Haba,∗1 A. Toyoshima,∗3 K. Toyomura,∗1 K. Nakamura,∗1J. Kaneya,∗2 M. Huang,∗2 Y. Kudou,∗2 N. Takahashi,∗1 and A. Shinohara∗1†∗1∗2∗3

Condensed from J. Radioanal. Nucl. Chem. 303, 1385
(2015).
Graduate School of Science, Osaka University
RIKEN Nishina Center
Advanced Science Research Center, Japan Atomic Energy
Agency- 215 -100
90Mo
173 W

80%ExtChemical characterization of transactinide elementswith atomic number ≥ 104 is an attractive and challenging subject in the ﬁeld of radiochemistry. Twodecades ago, Schädel et al. performed the pioneering cation-exchange experiment of seaborgium (Sg) in
5 × 10−4 M HF/0.1 M HNO3 1) and 0.1 M HNO3 2) using an automated rapid chemistry apparatus (ARCA).
In the literature, it was reported that the ﬂuoride
complexation of Sg was similar to that of its lighter
homologs, Mo and W. In their experiment, however,Schädel et al. observed only four time-correlated eventsfrom the daughters and granddaughters of 265 Sga,b1,2)
produced in the 248 Cm(22 Ne, 5n)265 Sga,b reaction because of the time-consuming α-sample preparation.
One of the possible methods of unambiguous identiﬁcation through detection of α-correlations from 265 Sga,band its descendants is to adopt liquid scintillation
counting for the physically pre-separated 265 Sga,b withGARIS.3) This approach has high detection eﬃciency
and the sample preparation time is short. In parallelwith the development of the measurement apparatus,
it is also necessary to search for experimental conditions applicable to 265 Sga,b . In this study, we examined solid-liquid extraction of Mo and W in the Aliquat
336/HCl system as a model experiment for Sg.
90
Mo (T1/2 = 5.7 h) and 173 W (T1/2 = 7.6 min) were
simultaneously produced via the nat Ge(22 Ne, xn)90 Mo
and nat Gd(22 Ne, xn)173 W reactions, respectively, using Gd/Ge targets at the RIKEN K70 AVF cyclotron.
Reaction products recoiling out of the targets were continuously transported to the chemistry laboratory using a He/KCl gas-jet method. The transported products were deposited on the ARCA collection site for5 min. The products were then dissolved in HCland subsequently fed into a microcolumn (1.0 mm i.d.
and 3.5 mm) ﬁlled with 52-wt.% Aliquat 336/CHP20Y
resin at a ﬂow rate of 1 mL/min. The eﬄuents werecollected in polypropylene (PP) tubes for every 50or 80-µL fraction. Then, the remaining products inthe column were stripped with 400–500 µL of 6 M
HNO3 /0.01 M HF and collected in another PP tube.
These samples were assayed through γ-ray spectrometry with Ge detectors. We also performed batch experiments with 93m Mo and 181 W using the Aliquat
336/CHP20Y resin in HCl solutions.

6040
20002468HCl concentration / M

10Fig. 1. Variation of %Ext values of 90 Mo and 173 W on 52wt. % Aliquat 336/CHP20Y column (1.0 mm i.d. and3.5 mm) as a function of HCl concentration.

In the experiments involving the transactinide elements and performed using the ARCA, chromatographic separation was conducted with approximately
200 µL of the eluent (ﬁrst fraction) and the remaining
radioactivities in the column were eluted by a stripping solution as the second fraction.4) To evaluate theextraction behaviors of Mo and W by this method, thepercent extraction (%Ext) on the resin was deﬁned as%Ext =

100A2
A1 + A 2(1)where A1 indicates the amount of radioactivity eluted
with 200 µL of the eﬄuent and A2 is that remaining
in the column with the eﬄuent. The variation of the%Ext values as a function of HCl concentration areshown in Fig. 1.
In the ﬁgure, the %Ext values of Mo increase to 70%in 2–4 M HCl and then decrease in 4–6 M, while thoseof W are less than 20% for all examined concentrations.
The trend of the %Ext values, Mo > W, is qualitatively
consistent with the results of the batch experiments
performed with 93m Mo and 181 W. This indicates thatthe extraction behaviors of Mo and W obtained withARCA reﬂect the chloride complex formation of theseelements, i.e., formation of the anionic oxochloro complexes [MO2 Cl3 ]− (M = Mo and W) in 1–6 M HCl.5,6)
Under the present conditions, therefore, it is expectedthat information on the chloride complexation of Sg
can be obtained by comparing its %Ext values withthose of Mo and W using our developed systems.
References
1) M. Schädel et al., Radiochim. Acta 77, 149 (1997).
2) M. Schädel et al., Radiochim. Acta 83, 163 (1998).
3) H. Haba et al., Phys. Rev. C 85, 024611, (2012).
4) H. Haba et al., Radiochim. Acta 95, 1 (2007).
5) C. Heinter-Wirguin, R. Cohen, J. Inorg. Nucl. Chem.
27, 1989 (1965).
6) T. Sato, K. Sato, Hydrometallurgy 37, 253 (1995).