Photon Factory Activity Report 2018 #36 (2019)

BL-27B/2018G573

Structural analysis for development of minor actinide recovery process using
diglycolamide extractants
Makoto Okada1, Sou Watanabe2, Tsuyoshi Arai3, Haruaki Matsuura1*
1

Cooperative Major in Nuclear Energy, Tokyo City University, 1-28-1, Tamazutsumi,
Setagaya-ku, Tokyo, 1588557, Japan
2
Japan Atomic Energy Agency, 2-4, Shirakata, Nakagun,Tokai-mura, Ibaraki, 3191195, Japan3
Shibaura Institute of Technology, 3-7-5, Toyosu, Koto-ku, Tokyo, 1358548, Japan
1

Introduction
Development has been carried out for the realization of arecovery system for trivalent minor actinides (MA: Amand Cm) by separation processes such as solvent
extraction and extraction chromatography for high-level
radioactive liquid waste. At present, a process using
diglycolamide (DGA) extractant in group separation
process has been considered. For tetraoctyl diglycolamide(TODGA) impregnated adsorbents, the problem was thatthe elution rate of adsorbed MA and rare earth elements
was low [1]. It is necessary to establish the optimum
conditions when using each extractant in order to reducethe volume and the harmfulness of radioactive waste. In
this research, focusing on tetraethylhexyl diglycolamide(TEHDGA), which is expected to have higher elution
performance than TODGA, the nitric acid concentration
dependence of the complex structure in the adsorbent
impregnated with both DGA extractants was investigatedby EXAFS.

Eu2

3

Results and Discussion
By the previous research of solvent extraction, it has
been confirmed that the adsorption degree of the twoadsorbents is different, so we considered the factors thatcause the difference from the structural change [2]. Theabsorption edge jump of the X-ray absorption spectrum
by EXAFS measurement does not show a difference athigh nitric acid concentration as shown in the ICP-OES
analysis, but the difference between these variation trend
is larger at low nitric acid concentration. And it turned outthat the adsorption degree becomes larger with theFT|(k)·k | [arb.unit]

TEHDGA
TODGA

3M
1M

3

Experiment
An adsorbent was prepared by impregnating porous
silica particles coated with a styrene-divinylbenzene
copolymer (referred to as SiO2-P) with 33 wt% ofTODGA and TEHDGA extractant, respectively. As anadsorption test, it was shaken for 3 hours at a ratio of 1:20
of an adsorbent and a metal solution containing Eu andNd, using nitric acid concentration as a parameter. Afterthe shaking test, the supernatant was subjected toICP-OES analysis, and the dried adsorbent was subjected
to EXAFS analysis. EXAFS measurement was carried out
at High Energy Accelerator Research Organization
Photon Factory BL-27B, in transmission mode, usingEuLⅢ and NdLⅢ absorption edges.

TODGA adsorbent.
Figure 1 shows the nitric acid concentration dependenceof the structural functions in the case of Eu. Since thenitric acid concentration dependency of the structuralfunctions of the two adsorbents was confirmed from Fig.
1, the fitting analysis was performed using the firstcoordination element as oxygen. As a result, the nearest
oxygen coordination number was confirmed to have thesame nitric acid concentration dependency as increasing
the absorption edge jump. Therefore, there is acorrelation between the amount of adsorption and thecontribution of oxygen atoms around the rare earth
element. From these results, it is considered that the twoadsorbents differ in the acid concentration dependency ofthe extractant contributing to the extraction depending on
the structure of the side chain, and the TEHDGAadsorbent has higher elution degree.

0.1M
0.05M
0.01M

012R [Å]34Fig. 1 Nitrate concentration dependence ofthe structural functions of Eu.
References[1] S. Watanabe, et al., Procedia Chemistry 21,
101-108 (2016)[2] H. Suzuki, et al., Annual meeting of the Japan
Atomic Energy Society, 2K08 (2017)*hmatuura@tcu.ac.jp