Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 48 (2015)

Extraction behavior of Mo and W from H2SO4 using amine-extractant(Aliquat336) as homologs of seaborgium
A. Toyoshima,*1 A. Mitsukai,*1,*2 A. Vascon,*1 Y. Kaneya,*1,*3 M. Murakami,*4,*5 K. Ooe,*4 N. Goto,*4 D. Sato,*4 Y. Komori,*5H. Haba,*5 K. Tsukada,*1 M. Asai,*1 T. K. Sato,*1 Y. Nagame,*1 and M. Schädel*1,*6Advanced Science Research Center, Japan Atomic Energy Agency
Faculty of Science, Ibaraki University＊3Graduate School of Science and Engineering, Ibaraki University＊4
Graduate School of Science and Technology, Niigata University＊5
RIKEN Nishina Center＊6
GSI Helmholtzzentrum für Schwerionenforschung GmbH
＊1
＊2

volumes of the organic and aqueous phases, respectively.
In the experiments of W, 181W was produced in the181
Ta(d, xn)181W reaction at the RIKEN K70 AVF cyclotron.
After the chemical separation of 181W from a Ta target
material through an ion-exchange, carrier-free 181W wasstocked in H2SO4 solutions. The procedure of thesubsequent batch experiment was the same as that for93mMo described above.
Results of kinetics experiments showed that theextraction equilibrium of 93mMo was reached within 5 s in
the range of 0.1 M < [H2SO4] < 8.6 M, while that of W wasdependent on [H2SO4]; the equilibrium was attained within
40 s at [H2SO4] < 1 M and within 2 min at 1 M < [H2SO4] <8.6 M. In Fig. 1, the D values of Mo and W underequilibrated conditions are shown as a function of [H2SO4].
The D values of Mo and W decrease up to 3 M and 2 M,
respectively, with increasing [H2SO4]. This is probably due
to protonation reactions of hydrolyzed Mo and W species.
On the other hand, when [H2SO4] > 3 M and > 4 M, the Dvalues of W and Mo, respectively, show a sharp increase.
This clearly indicates the formation of anionic sulfate
complexes of Mo and W. Sulfate complexation of Sg under
the present experimental conditions will be clarified in ourfuture experiments.
10293mMo

101

D

Recently, we began to study the aqueous chemistry of agroup-6 transactinide element, Sg. At present, we focus on
the formation of anionic sulfate complexes of Mo and W,
which are lighter homologs of Sg, by means ofamine-extraction in H2SO4 as a preparatory experiment forSg. Previously, we have found that the group-4transactinide, Rf, has a weaker preference to form a sulfate
complex than its lighter homologs, Zr and Hf.1) This isconsistent with its predicted, larger ionic radius comparedto the measured radii of Zr and Hf; moreover, this is ingood agreement with a theoretical prediction2) that thestability of Rf complexes is lower because of the smaller
ionic contribution to the chemical bond. The investigationof sulfate complex formation of Sg is, therefore, expected toprovide valuable information on its ionic radius andchemical bonding.
This paper reports on the extraction behavior of thecarrier-free radioisotopes 93mMo and 181W from aqueous
H2SO4 solution using an amine extractant, Aliquat336, by abatch method to ensure that the chemical behavior ofmononuclear complexes of these homologs is retained. First,
the extraction kinetics of these radioisotopes in 0.1, 4.3 and
8.6 M H2SO4 with 0.2 M Aliquat336 were studied. Then,
extraction probabilities were investigated as a function ofH2SO4 concentration, [H2SO4].
In the experiments of Mo, 93mMo was produced in thenatZr(, xn) reaction at the RIKEN K70 AVF cyclotron.
Nuclear reaction products transported by a KCl/He gas-jet
at a flow rate of 2.5 L/min were deposited on a small pieceof plastic (Naflon®, ~2 cm × 1.5 cm) for 3 min. KCl
aerosols were produced by sublimation at 640oC. Then, thedeposited products were dissolved win 100 L of 0.1 – 8.6
M H2SO4 solution. The solution was then added to 600 Lof H2SO4 solution with the same concentration in a plasticvial. Subsequently, 700 L of the toluene solution ofAliquat336 was added. After shaking with a Vortex mixer
for 360 s, the mixed sample was centrifuged for 30 s. From
both the phases, 500 L solutions were collected separatelyin 2 vials. These 2 samples were then subjected to -ray
spectrometry with a Ge detector. The distribution ratio, D,
was evaluated with the equation, D = (Aorg / Vorg) / (Aaq / Vaq),
where Aorg and Aaq are the radioactivities in organic andaqueous phases, respectively, and Vorg and Vaq are the181

W100

10-1

10-2
10-1

100
[H2SO4] / M

101Fig. 1. Variation of D value of Mo and W as a function of
H2SO4 concentration, [H2SO4].
References

1) Z. J. Li et al.: Radiochim. Acta 100, 157 (2012).
2) V. Pershina et al.: Radiochim. Acta 94, 407 (2006).

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