Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 49 (2016)

Extraction behavior
behavior of Mo and W fromfrom sulfuric
Extraction
sulfuric acidacid into
intoAliquat336
Aliquat336 as
as modelmodel
experiments(Sg)
experiments for seaborgium
seaborgium (Sg)A. Mitsukai,＊1,＊2 A. Toyoshima,＊2 Y. Kaneya,＊1,＊2 Y. Komori,＊3 H. Haba,＊3 M. Asai,＊2 K. Tsukada,＊2 T.K Sato,＊2K. Ooe＊4 D. Sato, ＊4 M. Murakami, ＊4 and Y. Nagame＊1,＊2In Fig. 1, the variation of the distribution ratios of Mo andW are shown as a function of extraction time, which is thetime required to pass through the spiral PTFE tube. In theprevious batch-wise extraction experiments, the D values ofMo and W at the equilibrium are approximately 15 and 2.4)
It is found that, in the off-line experiment, the extraction of181
W reaches the equilibrium in less than 50 s because its Dvalue increases up to the equilibrated value of 2 within 50 s.
This equilibration time is much shorter than the time ofabout 120 s for W observed in our previous experiments.4)
This result indicates that the extraction kinetics of W wasenhanced with the FSE. However, in the on-line experiment,
the equilibration time of Mo of approximately 50 s wasmuch longer than that of less than 5 s, 4) and the extractionof W did not reach equilibrium within 50 s. This is probably
due to slow chemical reactions other than extraction in theMDG and FSE. In future, the kinetics of these elements will
be improved by using heating or supersonic systems.
210Org : 0.2 M Aliquat336-toluene
Aq : 6 M H SO
24110

㻰

It is known that for inorganic metal complexes such as asulfato, the ionic radius of the metal center plays animportant role in its complex formation. Unlike its lighter
homologs, Mo and W the sulfato complex of seaborgium ishard to form, because the theoretically predicted ionicradius of Sg is larger than those of the homologs.
Experimental assessment of the sulfato complex formationof Sg, therefore, provides information on its ionic radius,
which would be influenced by strong relativistic effects.1) A
rapid solvent extraction apparatus is, however, required tobe developed to explore the complex formation of Sg
because the half-lives (T1/2) of the 265a,bSg isotopes are soshort (around 10 s) and their production cross sections in
the 248Cm(22Ne, 5n)265a,bSg reaction are extremely small.2) In
the present study, we examined the extraction behavior ofcarrier-free 181W (T1/2 = 121.8 d) using a newly developed
Flow Solvent Extractor (FSE) to find suitable experimental
conditions for future Sg experiments. On-line experimentswith the short-lived 93mMo (T1/2 = 6.85 h) and 179W (T1/2 =37 min) nuclides were also carried out using the FSE
connected to a Membrane Degasser (MDG), which wasdeveloped for the dissolution of gas-jet transportedproducts.3)
At the RIKEN AVF cyclotron, 93mMo and 179W wereproduced in the natNb(d, 2n)93mMo and natTa(d, xn)179W
reactions, respectively. The reaction products weretransported to the chemistry laboratory by a gas-jet method
and were dissolved with 6 M sulfuric acid using the MDG.
This aqueous solution was then immediately mixed with anorganic solvent of 0.2 M Aliquat336 dissolved in toluene
using a spiral PTFE tube with 1-mm inner diameter. Themixture with a volume of 1.5 mL throughout the PTFE tube
was collected in a sample vial. After centrifuging, theaqueous and organic solutions were separately taken inmeasurement tubes for γ-ray spectrometry with a Gedetector. The distribution ratio (D) is defined as the ratio ofratio activity per volume between each phase as D = (Aorg/ Vorg) / (Aaq / Vaq), where Aorg and Aaq are radioactivities in
the organic and aqueous phases, respectively, and Vorg andVaq are the volume of the organic and aqueous phases,respectively. Off-line experiments with the relatively
long-lived 181W produced in the natTa(d, n)181W reaction
were also carried out to compare with the on-lineexperiments.
Graduate School of Science and Technology, Ibaraki University
Advanced Science Research Center, Japan Atomic Energy Agency＊3
RIKEN Nishina Center＊4
Graduate School of Science and Technology, Niigata University＊1＊2- 236 -010181-110179

WW93m

Mo-210010203040

Extraction Time / s50Fig. 1. Dependence of the distribution ratio (D) of Mo andW on extraction time in the spiral PTFE tube of the FSE
system.

References

1) V. Pershina: in The Chemistry of Superheavy Elements. 2ndedition, edited by M. Schädel and D.Shaughnessy (SpringerVerlag, Berlin, 2014), p. 158
2) H. Haba et al., Phys. Rev. C 85, 024611 (2012).
3) Y. Komori et al.: in this report.
4) A. Toyoshima et al,; RIKEN Accel. Prog. Rep. 48, 283 (2014).