III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Cation- and anion-exchange behavior and UV-vis spectroscopy of Zr in
HBr for chemical characterization of bromide complexes of Rf
T. Yokokita∗1 and H. Haba∗1
The chemical properties of superheavy elements(SHEs) with atomic number Z ≥ 104 deviate from theperiodicity of their lighter homologues in the periodic
table because of the strong relativistic eﬀects on valence
electron shells in these heavy atoms. Therefore, chemicalresearch studies on these elements are intriguing and ofgreat importance. However, the chemical study of theseelements is very diﬃcult because the half-lives of theseelements are short and the production rates of these elements are low.1)
Anion-exchange studies in HF and HCl have been reported for element 104, Rf.2,3) The observed adsorption
strength on the anion-exchange resin is Zr ≈ Hf > Rf in
1.9–13.9 M HF2) and Rf > Zr > Hf in 7.0–9.0 M HCl.3)
We are interested in the anion-exchange result of Rf in
HBr because the adsorption sequence is diﬀerent between
HF and HCl media. There is one report on the bromide
complex of Rf.4) In this report, the solvent extraction ofRf and its homologous elements were performed. Rf was
not extracted from 7.75–9.0 M HBr, while Zr and Hf wereextracted. Further study on the bromide complexationof Rf is required to understand the halide complexationof Rf in detail, In this work, cation and anion exchangesof Zr were performed to obtain the comparison data forRf. The UV-vis spectra of Zr in HBr solution was measured to discuss the ion-exchange behavior of Zr.
The 88 Z was produced in the 89 Y(d, 3n) reaction using the RIKEN AVF cyclotron; further, 88 Zr was puriﬁedby an anion-exchange method. The cation- and anionexchange of Zr were performed by employing the batch
method in 1.1–8.8 M HBr, which is the same procedure
an in Ref. 5). Further, control experiments without theresin were performed to determine the standard radioactivity of the solution sample. The distribution coeﬃcient(Kd ) was obtained according to Kd = (Ac − As )V /As w;
here, Ac and As denote the radioactivities in the control and exchanged solutions, respectively. V denotes
the volume of the solution, and w denotes the weight of
the ion-exchange resin.

Fig. 2. UV-vis spectra of Zr in 1.1–7.9 M HBr.

The UV-vis spectra of 0.016–0.33 M Zr in the 1.1–
7.9 M HBr solution were measured with UV-vis spectrospectrophotometer (JASCO Co., V-730) to obtain thestructural information on the Zr species in HBr.
In the anion exchange, the Kd values of Zr are low (<10 mL g−1 ) for all [HBr] studied in this work, indicating
which implies Zr does not form anionic species at 1.1–
8.8 M. This anion-exchange behavior is consistent withthat using macro amounts of Zr.6) The variation of theKd values of Zr on the cation exchange resin are shownin Fig. 1. The Kd values decrease with an increase in[HBr] in the range 1.1–7.0 M, and they increase above
7.0 M.
The UV-vis spectra of Zr in HBr solution are shownin Fig. 2. At 1.1–5.2 M, one adsorption band is seenat λmax = 410–421 nm, and its molar adsorption coefﬁcient (∆ε) increases with an increase of [HBr]. Above
6.0 M, the UV-vis spectra shows two adsorption bands atλmax = 390–391 and 463–467 nm, and both increase withan increase in [HBr], which indicates that the dominant
Zr species is changed. This spectral change at 6.0 M isreasonably reﬂected on the variation of the Kd values inFig. 1: bromide complexes are increasingly formed withan increase in [HBr], and above 7.0 M, a diﬀerent bromide complex is adsorbed on the cation-exchange resin.
It is possibility that the oxybromide complex of Zr is
protonated and the cationic species of Zr increases.
In the future, we plan to measure the Raman spectraof ZrBr4 in the HBr solution and the mass spectra of thesolvent extracted Zr species to determine the Zr species
in the HBr solution.
References

Fig. 1. Variation of the Kd values of Zr on the cation exchange resin as a function of [HBr].
∗1

RIKEN Nishina Center

1) A. Türler, V. Pershina., Chem. Rev. 113, 1273 (2013).
2) H. Haba et al., J. Am. Chem. Soc. 126, 5219 (2004).
3) H. Haba et al., J. Nucl. Radiochem. Sci. 3, 143 (2002).
4) D. C. Kacher et al., Radiochim. Acta 75, 127 (1996).
5) T. Yokokita et al., RIKEN Accel. Prog. Rep. 53, 164 (2020).
6) Gmelin Handbuch der Anorganishchen Chemie Uranium
Suppl. Vol. D3, edited by R. Warncke (Springer-Verlag,Berlin, Heidelberg, New York, 1982).

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