Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 47 (2014)

Solvent extraction of tungsten from oxalic acid solution with Aliquat 336
toward chemical studies of seaborgium
N. Goto,＊1 K. Ooe,＊1 M. Murakami, *1, 2 H. Haba,＊2 S. Goto,＊1 and H. Kudo＊3

D = (Aorg / Vorg) / (Aaq / Vaq),
where Aorg and Aaq are the radioactivities of organic andaqueous phases, respectively, and Vorg and Vaq are thevolumes of organic and aqueous phases, respectively. The
extraction kinetics was also investigated from 1.0 × 10-2 M
oxalic acid with 0.1 M HCl/0.9 M LiCl into 2.0 × 10-3 M
Aliquat 336/toluene solution by changing the shaking timefrom 3 to 3600 s.

In the experiment of the investigation of extraction
kinetics, the D value of 181W became constant in shaking
time longer than 30 s. This result shows that the extractionof W from oxalic acid solution with Aliquat 336 is fast. The
dependence of the D values of 181W on the Aliquat 336
concentration from 1.0 × 10-2 M oxalic acid with 0.1 M
HCl/0.9 M LiCl is shown in Fig. 1. The D value of W
increases with increasing [Aliquat 336]. The slope of the Dvalue of W vs. [Aliquat 336] plot in logarithmic scale isestimated to be 0.95 ± 0.08 with a weighted least-squares
fitting. This indicates that extracted anionic oxalate
complex of W is associated with one molecule of Aliquat
336. However, in macro scale, it was reported that W isextracted as (R3NH)2WO2(C2O4)2, where R3N shows a
trioctylamine (TOA) molecule, when the mole ratio(Oxalate / WO42-) in the aqueous phase was higher than4.54). This discrepancy might be caused by the protonation
to the W complex in the present experimental condition.
Further experiments such as an investigation of dependenceof D value on H+ concentration would be performed for thespeciation of the extracted species.

102
101
100

D

The aqueous chemical experiments of element 106,
seaborgium (Sg), have been reported by Schädel et al. in19971) and 19982). In these experiments, the cationexchange chromatography of Sg was conducted in
HF/HNO31) and HNO32) solutions. However, no chemicalexperiments for Sg have been reported since theseexperiments. Therefore, further experimental results arerequired for detailed discussion of chemical properties of Sg
in aqueous solutions. We are planning to investigate solvent
extraction behavior of Sg. Oxalic acid is a typical organicacid used as ligand for transition metals. It is reported thatmolybdenum (Mo) and tungsten (W), which are lighter
homologs of Sg, form anionic oxalate complexes and areextracted into an organic phase with ion-pair extractant. In
this work, we investigated the extraction behavior andextracted species of W from oxalic acid solution intotoluene with Aliquat 336 toward the chemical studies of Sg.
The experiments were performed using 181W in tracer scale
to prevent the formation of polyoxometalate complexes ofW.
The radiotracer 181W (T1/2 = 121.2 d) was produced in thebombardments of 24-MeV deuteron beam supplied by theRIKEN AVF cyclotron on natTa target foils. The 181W tracer
was chemically separated from the target material by ananion exchange method and stored in 1 M HCl solution.
The solvent extraction of 181W was carried out asfollowing procedure. One μL of the tracer solution waspipetted to a 1.5 mL polypropylene tube. Then, 700 μL of
the oxalic acid solution containing 0.1 M HCl/0.9 M LiClfor keeping ionic strength constant was added. The same
volume of Aliquat 336/toluene solution was mixed to theaqueous solution, and the mixture was shaken by amechanical shaker for 5 min. After centrifuging for 30 s,
500 μL aliquot of each phase was separately taken into vials,
and radioactivities of both phases were measured with a Ge
detector. The distribution ratio (D) of 181W was calculatedusing the following equation:

10-110-2 -5
1010-410-310-2[Aliquat336] / M

10-1Fig. 1. Variation of the distribution ratio of 181W from 1.0 ×10-2 M oxalic acid with 0.1 M HCl/0.9 M LiCl as a functionof the concentration of Aliquat 336.
References

1) M. Schädel et al.: Radiochim. Acta 77, 149 (1997).
2) M. Schädel et al.: Radiochim. Acta 83, 163 (1998).
3) K. Yakabe and S. Minami: Nippon Kagaku Kaishi 1983, 1045(1983).
4) K. Yakabe, K. Iwamoto and S. Minami: Nippon Kagaku Kaishi
1985, 714 (1985).

Graduate School of Science and Technology, Niigata University
RIKEN Nishina Center＊3
Department of Chemistry, Faculty of Science, Niigata University＊1＊2- 269 -