Photon Factory Activity Report 2019 #37 (2020)

BL-27B/2018G573

Structural analysis on complexes of rare earths formed in the adsorbent impregnatedwith NTA amides extractant for recovery of minor actinides
Makoto Okada1*, Masataka Takeuchi1, Sou Watanabe2, Yuichi Sano2,Tsuyoshi Arai3, Haruaki Matsuura1
12

Tokyo City University, 1-28-1, Tamazutsumi, Setagaya-ku, Tokyo, 1588557, Japan
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
Trivalent minor actinides (MA(III): Am and Cm) in highlevel radioactive liquid waste (HLLW) have long half-lives
and decay heat, thus those elements should be recovered inorder to reduce radiotoxic impact to global environment[1]. Separation of MA (III) from trivalent lanthanide (Ln(III)) is a main issue due to their chemical similarity. In thisresearch, we aim to construct a hybrid type process thatcomplements the shortcomings while maximizing thefeatures of both the solvent extraction method and theextraction chromatography method. One of promisingflow-sheets consists of two steps of MA(III)+Ln(III) corecovery and MA(III)/Ln(III) separation, the latter adopts
extraction chromatography in order to achieve higher
separation performance in a compact system, NTA amide
with uniform diameter and large pore diameter that aims toachieve rapid adsorption and elution while suppressing
pressure loss, which is a problem of the same technology.
By applying an adsorbent, the operating conditions will beeased and the amount of waste liquid generated will besuppressed. In this study, influence of side chain structuresof the extractants on local structure of rare earths
complexes and adsorption/desorption behavior wereinvestigated to gather valuable information for optimum ofprocess design.
2 Experiment
An adsorbent was prepared by impregnating porous silica
particles coated with a styrene-divinylbenzene copolymer(referred to as SiO2-P) with 33 wt% of HONTA andH2EHNTA extractant, respectively. As an adsorption test,
it was shaken for 3 hours at a ratio of 1:10 of an adsorbent
and a solution containing Eu or Nd, using nitric acidconcentration as a parameter. After the shaking, solidliquid separation, the supernatant was subjected to ICPOES analysis, and the dried adsorbent was subjected toEXAFS analysis. EXAFS measurement was carried out at
High Energy Accelerator Research Organization Photon
Factory BL-27B, in transmission mode, using NdL3 andEuL3 absorption edge.
3 Results and Discussion
Fig. 1 shows the adsorption rates of Eu3+ and Nd3+ on
NTA amides adsorbents. It can be seen that adsorption
rates decreases in both cases as the nitric acidconcentration increases. In addition, HONTA showed alarge difference in the adsorption rate of Eu used as asurrogate of Am and the adsorption rate of Nd that is RE
in comparison with HEHNTA when the nitric acidconcentration is low. Thus, HONTA is expected to havebetter separation performance than HEHNTA. In addition,
EXAFS revealed that HONTA had a clear difference in thenumber of nearest oxygen coordination numbers aroundEu3+ and Nd3+ compared to HEHNTA for each element,suggesting that this tendency affects the adsorption rates.
This work is supported by the Innovative Nuclear Researchand Development Program from the Ministry of Education,Culture, Sports, Science and Technology of Japan.

Fig. 1 Adsorption rates of Eu3+ and Nd3+References[1] International Atomic Energy Agency, “TechnicalReports Series No. 435; Implications of Partitioning andTransmutation in Radioactive Waste Management”, IAEA,Vienna (2004).
*g1981503@tcu.ac.jp,hmatsuura@tcu.ac.jp