RIKEN Accel. Prog. Rep. 50 (2017)

Ⅲ-3. Radiochemistry & Nuclear Chemistry

Extraction behavior of 93mMo and 179W from HF / HCl into Aliquat336 asmodel experiments for seaborgium (Sg)A. Mitsukai,䠆1,䠆2 A. Toyoshima,䠆2 Y. Komori,䠆3 S. Yano,䠆3 H. Haba,䠆3 M. Asai,䠆2 K. Tsukada,䠆2 T.K. Sato,䠆2and Y. Nagame䠆1,䠆2[HF] = 10-2 M, indicating that anionic fluoride complexes
are formed beyond that concentration. Above [HF] = 10 -1 M,
on the other hand, the D values of Mo and W decrease withincreasing [HF]. This is due to the increase of the HF2concentration; the extraction of HF2- is competed with thatof anionic fluoride complexes of Mo and W. Under thepresent conditions, we clearly observed the formation ofanionic fluoride complexes of Mo and W. In the next step,
the extraction behavior of Mo and W will be investigatedwhile varying the Aliquat336 concentration in the HF/HClsolution to obtain information on chemical forms of theanionic fluoride complexes of Mo and W

Chemical studies of superheavy elements with atomicnumbers Z  104 provide not only crucial and challenging
opportunities to advance our understanding of the propertiesof matter at the limits of existence but also elucidate theinfluence of relativistic effects on atomic electrons and thearchitecture of the farthest of the periodic table ofelemetnts.1,2) These elements are all artificial andsynthesized at accelerators using nuclear reactions ofheavy-ion beams with heavy element target materials. As
both the half lives and cross sections of these nuclides arerapidly decreasing with increasing Z, they are usuallyavailable in quantities of only a few atoms or often one
atom at a time.
Recently, we started studying the aqueous chemistry ofelement 106, seaborgium (Sg), to clarify its complex
formation and redox reactions in aqueous phases. In thiswork, the solvent extraction behavior of molybdenum (Mo)and tungsten (W), which are lighter homologs of Sg, from aHF/HCl mixed solution into toluene with an amine
extractant Aliquat336 is studied by a batch wise method toelucidate the complex formation of these homologs.
At the RIKEN AVF cyclotron, 93mMo and 179W were
produced in the 93Nb(d, 2n)93mMo and natTa(d, xn)179W
reactions, respectively. The reaction products weretransported to the laboratory by a gas-jet method anddeposited on a small Naflon® sheet. The deposited products
were dissolved with 700 ȝL of HF/HCl and the solution wascollected in a plastic tube. Then the same volume of
Aliquat336/toluene solution was added to this HF/HClsolution. The mixture was shaken for 60 s. (In a separate
experiment, we confirmed that the chemical equilibrium of
this reaction was accomplished within 60 s in the presentsystem.)3) After centrifugation, the aqueous and organic
solutions were separately taken in plastic tubes for Ȗ-ray
spectrometry with a Ge detector. The distribution ratio (D)is defined as the ratio of radioactivity per unit volume
between two phase as D = (Aorg / Vorg) / (Aaq / Vaq), whereAorg and Aaq denote radioactivities in the organic andaqueous phases, respectively, and Vorg and Vaq represent thevolumes of the organic and aqueous phases, respectively.
In the batch experiments, the concentration of HF wasvaried from 10-4 to 5 M, while those of HCl and Aliquat336
were fixed to be 1 M and 0.2 M, respectively. In Fig. 1,variations of the D values of Mo and W are shown as afunction of HF concentration, [HF]. The D values of bothelements start to increase steeply at approximately

1100

D

101010-1
179

W93m

Mo

100-2

10-510-4

10-3

10-2

10-1

101

[HF] / M
Fig. 1. Variation of the D values of Mo and W as afunction of [HF].
References
1) A. Türler, V. Pershina, Chem. Rev. 113, 1237 (2013).
2) M. Schädel, D. Schaughnessy (eds.): The Chemistry ofSuperheavy Elements, 2nd edition (Springer, Berlin,2014).
3) A. Mitsukai, Master’s Thesis (2017) (unpublished).

䠆1

Graduate School of Science and Technology, Ibaraki University
Advanced Science Research Center, Japan Atomic Energy Agency
䠆3
RIKEN Nishina Center䠆2- 248 -