Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 49 (2016)

Solid-liquid
extractionof
of Nb
Nb andand Ta336
resin
from
Solid-liquid
extraction
TawithwithAliquat
Aliquat
336
resin
from
HFHF
solutionsexperimentofof
element
105,
solutionsfor
forchemicalchemical experimentelement
105,
DbDb
D. Sato,*1,*2 M. Murakami,*1 K. Ooe,*1 R. Motoyama,*1 H. Haba,䠆2 Y. Komori,*2A. Toyoshima,*3 A. Mitsukai,*3 H. Kikunaga,*4 S. Goto,*1 and H. Kudo*5
The elements with atomic number ≥ 104 are calledsuper-heavy elements. Aqueous chemistry experiments withthese elements have been performed often by a column
chromatographic method. In particular, an anion-exchange
experiment of element 105, Db was successfully performed
in 13.9 M hydrofluoric acid solution using AutomatedRapid Chemical Apparatus, ARCA.1) Chemical species of
Db in HF solution were, however, still not identified. We
have, therefore, studied liquid-liquid extraction behavior of
Nb and Ta, which are lighter homologues of Db, withAliquat 336 for investigating the charge of extracted
complexes of these elements from HF solution. From theseresults, it was found that, although the extraction behaviorof Nb was different from that of Ta, univalent anionic
fluoride complexes were extracted for both Nb and Ta byAliquat 336.2) Based on these results, it is expected that
information on the chemical species of Db in HF solution
would be obtained by applying this extraction system to thesolid-liquid extraction experiment with ARCA. The
solid-liquid extraction experiments of Nb and Ta with anAliquat 336 resin from HF solutions were conducted by abatch method for the column experiment with ARCA in thiswork.
Long-lived radiotracers, 95gNb (T1/2 = 34.97 d) and 179Ta(T1/2 = 665 d), were produced by deuteron irradiation on Zrand Hf metallic foil targets with natural isotopic abundance,
respectively, using the RIKEN K70 AVF Cyclotron. Theseradiotracers in the targets were chemically isolated by anion-exchange. A 32 wt% Aliquat 336 resin was prepared bymixing MCI GEL CHP20/P30 with Aliquat 336 dissolved
in methanol for about 1 day, which was followed by dryingin an oven at 80 .3) The 95gNb and 179Ta tracers weredissolved in 400 μL of 1-27 M HF, and then mixed with
10-15 mg of the 32 wt% Aliquat 336 resin in a syringelessfilter tube. After shaking for 5 min, the solution wasseparated from the resin by filtration, and 250 μL of thesolution in each sample was pipetted into another sample
tube. For measurement of initial radioactivity, Aini, in the
aqueous solutions, control experiments without the Aliquat
336 resin were also conducted. The radioactivities of thesesamples were measured with a Ge detector. The distribution
coefficients, Kd of 95gNb and 179Ta were obtained by thefollowing equation:(1)Here, As is the radioactivity of solution, mr is the weight ofthe resin used and Vs is the volume of a liquid phase.
The dependences of Kd values of 95gNb and 179Ta on theinitial HF concentration, [HF]ini were investigated with the32 wt% Aliquat 336 resin from 1-27 M HF solutions. The
obtained results were shown in Fig.1. It is revealed that theKd values of 179Ta are decreased with increasing [HF]ini,
while those of 95gNb show a minimum at 10 M HF. Thedecreases of the Kd values of both the elements are due toan increase of HF2- ion.1) Comparing with our earlier resultson liquid-liquid extraction of these elements,2) thissolid-liquid extraction behavior of 179Ta is found to be very
similar to that in liquid-liquid extraction. Thus, the samecomplex, TaF6- ion as that in liquid-liquid extraction isprobably extracted by the Aliquat 336 resin. However, thesolid-liquid extraction behavior of 95gNb was partlydifferent from that in Ref. [2]. While distribution ratios of95gNb in Ref. [2] decreased gradually with increasing [HF]ini,
a gradual increase of Kd values is observed above 10 M HF
in the present solid-liquid extraction. This suggests that theextracted complexes of 95gNb in solid-liquid extraction
might be different from those in liquid-liquid extraction.
Further investigation of the extracted species of 95gNb insolid-liquid extraction is needed for identification of the Nbspecies.

Fig.1 The adsorption behavior 95gNb and 179Ta
on Aliquat 336 resin as a function of [HF]iniReferences

Graduate School of Science and Technology, Niigata University*2
RIKEN Nishina Center*3
Japan Atomic Energy Agency*4
Research Center for Electron Photon Science, Tohoku University*5
Department of Chemistry, Faculty of Science, Niigata University*11) K. Tsukada et al.: Radiochim. Acta. 97, 83 (2009).
2) D. Sato et al.: Accel. Prog. Rep. 47, 247 (2014).
3) H. Haba et al.: Radiochim. Acta. 95, 1 (2007).

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