Photon Factory Activity Report 2018 #36 (2019)

BL-27B/2017G054

Local Structure of Zr(IV) in Nitric Acid Solutions

Akihiro UEHARA1, *, Toshiyuki FUJII2, and Yoshihiro OKAMOTO3National Institute for Quantum and Radiological Science and Technology,
4-9-1 Anagawa, Inage, Chiba, 263-8555, Japan
2
Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering,Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
3Nuclear Science Research Institute, Sector of Nuclear Science Research,
Japan Atomic Energy Agency, 1-1-1, Kouto, Sayo, Hyogo, 579-5148, Japan1

2. Experimental
ZrO(NO3)2 and ZrCl4 were dissolved in various
concentration of HNO3 from 0.1 to 10 M. Zr(IV)concentration was 0.05 M. ZrCl4 was treated in glove box,
where oxygen and moisture are controlled less than 1ppm,
to avoid its oxidation. Zr K-edge XAFS measurements
were performed at the beamline BL-27B of the Photon
Factory. A suite of principle component analysis, PCA,
including target transformation and iterative target
transformation was performed both on the acquired
EXAFS spectra using the program code ITFA developedby Rossberg [2].
3. Results
Our group has reported the ligand exchange ofhydroxide and halides to Au(III) ion occurred in aqueous
solution by PCA of EXAFS spectra[3,4]. These analyticalmethods were applied into the present Zr system. In themeasurement of XANES spectra, there are little
differences in each HNO3 concentration. In the data ofEXAFS spectra, there are slightly change in oscillation
pattern depending on the HNO3 concentration as shown in
Figure 1 (a). It was suggested that these spectra areconsisted of one or two components based on the PCA
results. Fitted spectrum was shown in dotted line ofFigure 1 (a). The calculated component fraction wasplotted as a function of HNO3 concentration as shown inFigure 1 (b). It was found that fraction of component 1,
which was mainly observed at 10 M HNO3 of ZrCl4,
increased with HNO3 concentration increasing whereas
the fraction of component 2 was main species at lower
HNO3 concentration. The results of Fouriertransformations suggested that Zr-O bond distanceslightly increased with increasing HNO3 concentration
due to different Zr-O coordinations such as Zr=O, Zr-OH,and Zr-OH2.
(a)10*
109k3χ (k)

753
10.1
246810k / Å-1

12(b) 1Fraction

1. Introduction
Zirconium has been used in the cladding material ofnuclear fuel. On the nuclear fuel reprocessing, uranium isseparated by solvent extraction mixing with organic
solution containing extractants and aqueous solution
containing nuclear fuel elements dissolved into nitric acid.
It is important to study chemical behavior of Zr ion in
those solutions to increase the extractability andselectivity of uranium. It has been reported thecoordination structure of Zr(IV) depends on theconcentration of H+ as well as that of Zr(IV). Takasaki
recently reported that Zr-Zr coordination number
decreased with increasing the hydrogen chloride
concentration, but did not change in case of perchloric
acid [1]. This indicates that counter anion also plays animportant role for the coordination of zirconium. On theother hand, the first coordination sphere of Zr(IV) andoxygen in aqueous acidic solution is not clear because ofthe similar Zr-O bond distance in the hydrolysis andzirconyl species. In the present study, local structure of Zr
in various concentration of nitric acid was analyzed.

0.500.1 13*5 7 9 10 10[HNO3]/Mcomponent 1component 2Figure 1. (a) Fitted EXAFS response of ZrO(NO3)3
dissolved into various concentration of HNO3. Sample *was prepared using ZrCl4 and 10 M HNO3. (b) Fractionof two components calculated by PCA.
References[1] Takasaki, et al, Bunseki Kagaku, 2010, 59, 447.
[2] Rossberg, et al., Anal. Bioanal. Chem., 2003, 376, 631.
[3] Booth, et al., Chem. Sci., 2017, 8, 7954.
[4] Uehara, et al., Electrochim. Acta, 2016, 190, 997.
*uehara.akihiro@qst.go.jp