Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 51 (2018)

Anion and cation exchanges of Zr, Hf, and Th in H2 SO4
for chemical study of Rf
T. Yokokita,∗1 S. Yano,∗1 Y. Komori,∗1 and H. Haba∗1
Clarifying the chemical properties of superheavy elements with atomic number Z ≥ 104 is an intriguing
and important subject. These elements are produced ataccelerators using heavy-ion-induced nuclear reactions.
The production rates of these elements are low, and theirhalf-lives are short (T1/2 ≤ 1 min). Thus, chemical studies on these elements are conducted on a single-atombasis.1)
The solution chemistry of superheavy elements has
been studied mainly for element 104, Rf. In these studies, experiments on Rf and homologous elements havebeen carried out under the same conditions, but for evenhomologous elements, equilibrated data were obtainedin few conditions. Particularly, it was reported that thechemical reaction kinetics between Zr and Hf are diﬀerent in H2 SO4 .2) Thus, the observation of equilibrationand the equilibrated distribution data are very important to characterize the sulfate complex formation of Rf.
In this work, we performed anion and cation exchange ofZr, Hf, and Th by using ion-exchange resin and ﬁber tosearch the rapid reaction system for the chemical studyof Rf.
We produced 88 Zr and 175 Hf in the 89 Y(d, 3n) andnatLu(d, xn)175 Hf reactions (nat = natural isotopicabundance), respectively, by using the RIKEN AVF cyclotron. 234 Th was obtained as an α-decay daughter
nuclide of 238 U. These radiotracers were puriﬁed by ananion-exchange method.
The ion-exchange experiments of Zr, Hf, and Th wereperformed by the batch method using 0.1–36.3 mg of theion exchanger (anion-exchange resin (Mitsubishi Chemical, MCI GEL AC08Y), anion-exchange ﬁber (Nichibi,IEF-BrA-SA), cation-exchange resin (Mitsubishi Chemical, MCI GEL CK08Y), or cation-exchange ﬁber(Nichibi, IEF-MR-SC)) and 0.25 mL of 0.12–1.0 M
H2 SO4 . We also performed control experiments without the resin. The distribution ratio (Qd ) was obtained
according to Qd = (Ac − As )V /As w, where Ac and As
denote the radioactivities in the control and extractedsolutions, respectively; V is the volume of the solution;
and w is the weight of the ion exchanger.
The dependence of the Qd values of Zr, Hf, and Th on
the shaking time is shown in Figs. 1(a), (b), and (c), respectively. When using the anion-exchange resin, the Qdvalues of Zr, Hf, and Th are constant in the entire time
range studied. When using the anion-exchange ﬁber, theQd values of Zr, Hf, and Th become constant after 1 h,
2 h, and 10 s for Zr, Hf, and Th, respectively. Whenusing the cation-exchange resin, the Qd values become
constant after 10 min for Zr and Hf and after 10 s for Th.
When using the cation-exchange ﬁber, the Qd values of∗1Fig. 1. Variations of the Qd values of (a) 88 Zr, (b) 175 Hf, and(c) 234 Th on the shaking time in 0.1 M H2 SO4 .

Zr, Hf, and Th become constant after 2 h, 10 min, and4 h, respectively. These results suggest that the anionexchange reaction reaches equilibrium within 10 s whenusing the anion- exchange resin, and this reaction system would be applicable for 261 Rf (T1/2 = 68 s). On
the other hand, the time required to reach equilibria in
the ion-exchange reaction with the other ion exchangers
used in this work are relatively long compared to thatwith the short-lived 261 Rf. We found that the time required to reach the equilibrium with the ion-exchange
resin is shorter than that with the ﬁber for both anion and cation exchange. We concluded that the ionexchange ﬁbers are unavailable for experiments with theshort-lived 261 Rf.
We also studied the variations of the distribution coeﬃcients (Qd values in equilibrium condition) of Zr, Hf,and Th on the anion-exchange resin to obtain comparison data and to determine the appropriate experimental condition for Rf experiment. We would like to perform a similar experiment on Rf experiments by using
AMBER,3) to observe the equilibration of the anionexchange reaction, and to investigate the chemical properties of the sulfate complex of Rf.
References
1) A. Turler, V. Pershina, Chem. Rev. 113, 1273 (2013).
2) Z. J. Li et al., Radiochim. Acta 100, 157 (2012).
3) Y. Kasamatsu et al., Radiochim. Acta 103, 513 (2015).

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