III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Online anion-exchange experiment of Zr in H2 SO4 for the chemical
study of Rf in H2 SO4T. Yokokita,∗1 Y. Shigekawa,∗1 Y. Wang,∗1 Y. Komori,∗1 Y. Kasamatsu,∗2 E. Watanabe,∗2 and H. Haba∗1The chemical properties of superheavy elements(SHEs) with atomic number Z ≥ 104 are expected todeviate from the periodicity of their lighter homologues
in the periodic table. Thus, chemical studies on SHEs
are interesting. These elements are produced at accelerators by using heavy-ion-induced nuclear reactions.
The production rates of these elements are low, andtheir half-lives are short (T1/2 ≤ 1 min). Thus, thechemical studies of SHEs are conducted on a singleatom basis. Therefore, performing, the chemical experiment of SHEs is diﬃcult. Thus far, the chemical
properties of SHEs have been discussed by comparing
them with those of their homologous elements.1)
In the solution chemistry of SHEs, ion exchange andsolvent extraction are often performed.1) To study thesulfate complexation of Rf, we plan to perform anionexchange experiments of Rf along with its homologous
elements. By using the batch-type solid-liquid extraction apparatus called AMBER2) , we measured the Kdvalues of Rf in 0.060–0.46 M H2 SO4 .3,4) In our previous study, to obtain the comparison data for Rf, weperformed an online anion-exchange experiment of Zrand Hf by using AMBER.5) However, the Kd values ofZr had large errors, because the radioactivity of 85 Zr
was very low. In this work, we re-examined the online
anion-exchange behavior of 89m Zr with higher radioactivities.
89m
Zr was produced in the 89 Y(d, 2n)89m Zr reaction
by using the K70 AVF cyclotron at RIKEN. The nuclear reaction products were transported to a chemistry room by a He/KCl gas-jet system. The transported products were deposited on the collection siteof the AMBER’s dissolution equipment for 1 min andwere then dissolved with 0.23 mL of 0.060, 0.11, 0.26,0.30, 0.46, and 0.72 M H2 SO4 . The solution sample
was injected into a chemical reaction container containing 1.4–3.8 mg of an anion-exchange resin (Mitsubishi
Chemical Co., MCI GEL CA08Y). After shaking thecontainer with a shaker for 10, 30, and 90 s, only thesolution phase was discharged from the container byusing a PTFE ﬁlter with compressed air. The discharged solution was collected in a PP tube, and wasassayed by γ-ray spectroscopy. We also performed control experiments with 10, 30, and 90 s shaking without
the resin to determine the standard radioactivity of thesolution sample. The Kd values were determined fromthe following equation:
Kd = Ar Vs /As wr = (Ac − As )Vs /As wr∗1∗2RIKEN Nishina Center
Graduate School of Science, Osaka University(1)

Fig. 1. The Kd values of Zr in anion exchange as a functionof H2 SO4 concentration.

where Ar , As , and Ac are radioactivities of the resin,
the solution, and the control solution, respectively; Vs
is the volume (mL) of the solution; and wr is the massof the dry resin (g).
Figure 1 shows the H2 SO4 -concentration dependence of the Kd values of Zr in the online and oﬄine
experiments. The Kd values of Zr in the online experiment are in agreement with those in the oﬄine experiment within the error range in 0.11–0.72 M H2 SO4 .
This indicates that the Kd values of Zr in equilibrium
are obtained in the online experiment at these H2 SO4concentrations. However, at 0.060 M H2 SO4 the Kdvalue of Zr in the online experiment was lower thanthat in the oﬄine experiment. A probable reason forthis disagreement is that the Kd value at this low concentration is too high to be determined with the AMBER system. Another possibility is that the chemical
reaction time is not suﬃcient for the anion-exchangeequilibrium. Therefore, it is important to directly investigate the reaction time dependence of the anionexchange behavior of Rf to conﬁrm the anion-exchange
reaction equilibrium of Rf.
From this work, we obtained the comparison datafor Rf. We will discuss the sulfate complexation of Rf
based on the anion-exchange behavior of Rf, Zr, Hf,and Th in a separate study.4)
References

1) A. Türler, V. Pershina., Chem. Rev. 113, 1273 (2013).
2) Y. Kasamatsu et al., Radiochim. Acta 103, 513 (2015).
3) T. Yokokita et al., RIKEN Accel. Prog. Rep. 53, 165 (2020).
4) T. Yokokita et al., in this report.
5) T. Yokokita et al., RIKEN Accel. Prog. Rep. 52, 187 (2019).

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