Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Anion-exchange behaviour of Nb, Ta and Pa in H2 SO4M. Kato,∗1,∗2 K. Tsukada,∗3 H. Haba,∗1 Y. Komori,∗1 T. Yokokita,∗1 D. Mori,∗1 S. Adachi,∗1,∗4A. Kashihara,∗1,∗4 and K. Sueki∗1,∗5Studies on the behavior of the group-4 elements Zrand Hf, which are homologous elements of Rf, havebeen conducted in H2 SO4 .1) It was found that the ionexchange reaction of Zr and Hf is slow in H2 SO4 andcannot reach equilibrium in current superheavy element studies. On the other hand, there are not many
researches on the group-5 elements in H2 SO4 . Similarly to the group-4 elements, the ion-exchange reaction of the group-5 elements Nb and Ta, and theirpseudo homologue Pa may be slow. To elucidate thebehaviour of Db in H2 SO4 , it is necessary to clarify thebehaviour of Nb, Ta and Pa in H2 SO4 .
95
Nb (T1/2 = 35.0 d) and 179 Ta (T1/2 = 1.82 y) were
produced in the nat Zr(d, xn) and nat Hf(d, xn) reaction,respectively, by bombarding metallic nat Zr and nat Hffoils with a 24-MeV deuteron beam using the RIKEN
AVF cyclotron.
Each target material was dissolved in 0.2 mL ofconcentrated HF solution in a PTFE beaker. After evaporation to dryness, the residue was dissolved
with 0.2 mL of 1 M HF and then dried up. Theresidue was dissolved with 0.3 mL of 1 M HF and fed
onto a chromatographic column ﬁlled with the anionexchange resin (BIO RAD AG 1 × 8 100–200 mesh,F− form 5 mm i.d. × 45 mm). After washing the column with 2.5 mL of 1 M HF, Zr and Hf were eluted
from the column with 5 mL of the mixed solution of9 M HCl/0.004 M HF. Then, Nb was eluted with 5 M
HNO3 /0.2 M HF, while Ta was eluted with 4 M HCl.2)
233
Pa (T1/2 = 27.0 d) was chemically separated from237
Np (T1/2 = 2.144×106 y). 237 Np was dissolved with0.2 mL of 9 M HCl, and fed onto the chromatographic
column ﬁlled with the 100–150 mesh of the TK400
resin. Np was eluted with 20 mL of 9 M HCl, then
Pa was eluted subsequently with 1.8 mL of 1 M HCl.
The solution was evaporated to dryness to fume out
HCl. Then, the residue was dissolved with pure waterand evaporated to dryness 3 times. Then, radio tracers
were stocked in a polypropylene vessel in 1 M H2 SO4 .
For the batch experiments with low H2 SO4 concentrations, the radiotracer was diluted to 0.2 M H2 SO4 withpure water.
The anion-exchange resin used was the strongly
basic anion exchanger, MCI GEL CA08Y suppliedby Mitsubishi Chemical Corporation. The resin waswashed with 2.0 M NaOH and 2.0 M H2 SO4 alterna∗1∗2∗3∗4∗5RIKEN Nishina Center
Science and Engineering, University of Tsukuba
JAEA, Advanced Science Research Center
Graduated school of Pure and Applied Sciences, Universityof Tsukuba
Faculty of Pure and Applied Sciences, University of Tsukuba- 163 -Fig. 1. Variation of the Kd values of 95 Nb, 179 Ta and 233 Pa
on the anion-exchanger CA08Y as a function of HSO−
4
concentration [HSO−4 ].

tively 3 times to replace Cl− ion in CA08Y with HSO−
4.
Finally, the resin was washed with distilled water anddried up to a constant weight at 70◦ C in an oven.1)
We determined the distribution coeﬃcient (Kd ) values of Nb, Ta, and Pa on CA08Y in H2 SO4 at various concentrations. 5–25 mg of the resin and 3 mLof H2 SO4 solutions with 50 µL of the radiotracer wereplaced in a polystyrene centrifuge tube and shaken for
120 min at 22◦ C. After centrifugation, a 1 mL of thesolution was pipetted and subjected to γ-ray spectrometry with a Ge detector The same treatment was conducted without the resin to determine the reference radioactivity. The radioactivity on the resin was determined by subtracting the solution radioactivity fromthe reference activity.
Figure 1 shows a variation of the Kd values of Nb,
Ta, and Pa as a function of [HSO−4 ]. Especially in thecase of Nb, the Kd values varies greatly. Therefore, it’snecessary to check the reproducibility of the data.
It was reported that the ion-exchange reaction of thegroup-4 elements is slow.1) However, we found that thereaction of the group-5 elements reach the equilibrium
faster, within 20 s.
References

1) Z. J. Li et al., Radiochim. Acta 100, 157 (2012).
2) Y. Kasamatsu et al., J. Nucl. Radiochem. Sci. 8, 2(2007).