Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 50 (2017)

Batch solid-liquid extraction of Nb and Ta
with 52 wt% Aliquat 336 resin from HF solutions
D. Sato,*1,*2 M. Murakami,*1 K. Ooe,*1 R. Motoyama,*1 H. Haba,*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 using theAutomated Rapid Chemical Apparatus (ARCA).1), 2) In
particular, an anion-exchange experiment of element 105,
Db was successfully performed in 13.9 M hydrofluoric acidsolution.2) However, the chemical species of Db in HF
solution were still not clear. Therefore, we studied theliquid-liquid extraction behavior of Nb and Ta, which arelighter homologues of Db, with Aliquat 336 forinvestigating the charge of complexes of these elements
extracted from HF solution.3) The results showed that
univalent anionic complexes such as NbOF4- and TaF6- wereextracted. Applying this extraction system to thesolid-liquid extraction with Aliquat 336 resin, on-line
column chromatography experiments of Nb and Ta with 32
wt% Aliquat 336 resin from HF solutions were conductedusing ARCA.4) In these experiments, the distribution
coefficients (Kd) of Nb and Ta in 1-27 M HF solution werecalculated from elution peak volume (Vp) and werecompared with the results of a batch experiment. The results
showed that the Kd values of Nb in 5.4 M HF and 10 M HFwith ARCA were lower than those obtained from the batchexperiment. This probably suggests that the Kd values of Nbin these HF concentrations were too low because thevolume of the resin in micro-columns of ARCA is verysmall. Therefore, it is necessary to increase the Kd values ofNb by increasing the amount of Aliquat 336 in the resin. In
this work, the batch solid-liquid extraction of Nb and Ta
with 52 wt% Aliquat 336 resin was performed.
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 ionexchange. A 52 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 drying
in an oven at 80 C.5) The 95gNb and 179Ta tracers weredissolved in 400 ȝL of 1-27 M HF and then mixed with
10-15 mg of the 52 wt% Aliquat 336 resin in a syringelessfilter tube. After shaking for 5 min, the solution wasseparated from the resin by filtration, and 250 ȝL of thesolution in each sample was pipetted into another sample
tube. For measurement of initial radioactivity, Aini, in theaqueous solutions, control experiments without the Aliquat
336 resin were also conducted. The radioactivities of thesesamples were measured with a Ge detector. The Kd of 95gNb
and 179Ta were obtained using the following equation:(1)Here, As is the radioactivity of the solution, mr is the weightof the 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 the52 wt% Aliquat 336 resin from 1-27 M HF solutions. The
obtained results are shown in Fig. 1. In addition, theprevious results with 32 wt% Aliquat 336 resin are also
shown in Fig. 1.The Kd values of 179Ta decreased withincreasing [HF]ini, while those of 95gNb show a minimum at
10 M HF. The obtained behaviors of both elements weresimilar to those with 32 wt% Aliquat 336 resin, andtherefore, the extraction species of those elements are thesame for both resins. The lowest Kd value obtained in thisstudy was about 34 at 10 M HF for Nb. In the previousexperiment, the Kd values obtained from the elution curves
in an on-line column experiment were in good agreementwith those obtained in a batch experiment in the Kd value
range of 30-80. Therefore, it is expected that consistent
results between on-line column and batch experiments
would be obtained with 52 wt% Aliquat 336 resin. Recently,
an on-line column experiment of Nb and Ta with 52 wt%
Aliquat 336 resin was performed using ARCA.6)

Fig. 1. Adsorption behavior of 95gNb and 179Ta on 32 wt%
and 52 wt% Aliquat 336 resin as a function of [HF]ini.
References
1) W. Paulus et al., Radiochim. Acta. 84, 69 (1999).
2) K. Tsukada et al., Radiochim. Acta. 97, 83 (2009).
3) D. Sato et al., Accel. Prog. Rep. 47, 247 (2014).
4) D. Sato et al., 59th Japan Society of Nuclear and RadiochemicalSciences, September 25-29, 2015, Sendai, Japan.
5) H. Haba et al., Radiochim. Acta. 95, 1 (2007).
6) D. Sato et al., In this report.

*1

Graduate School of Science and Technology, Niigata University
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*2- 249 -