Subject Number : S-16-MS-2001, 2020
Support Type : Common use
Proposal Title (English) : STXM analysis of adsorbent for effective recovery of radioactive elements
Username (English) : Y. Sano1), S. Watanabe1), Y. Miyazaki1), S. Kibe1), H. Matsuura2), T. Uchiyama2), Y. Katai2)
Affiliation (English) : 1) Japan Atomic Energy Agency (JAEA), 2) Tokyo City University

1. Summary
JAEA has been developing the selective recovery process of radioactive elements, which uses adsorbents of SiO2 supports coated with styrene-divinylbenzene copolymer (SiO2-P) and extractants on its surface. In this study, the change of adsorbent surface, such as thickness of polymer and uniformity of extractants, after adsorbing metal ions was investigated by scanning transmission X-ray microscope (STXM).

2. Experimental
The adsorbents in which Di-(2-ethylhexyl) phosphoric acid (HDEHP) was impregnated as an extractant were synthesized. The average diameter and pore size of the synthesized adsorbents were 50μm and 600nm, respectively. Some adsorbents were mixed with Zr/HNO3 solution and filtered to prepare the adsorbents adsorbing Zr. These adsorbents were sliced to 300nm in thickness by focused ion beam (FIB), and were supplied to STXM analysis in BL4U.

3. Results and Discussion
The O-NEXAFS spectra observed for the adsorbents before and after adsorbing Zr showed that the intensity of pre-edge peak at 532eV increased after Eu adsorption at any position in the adsorbent. Figure 1 shows the colorized composition maps of sliced adsorbents before and after adsorbing Zr, which were calculated by fitting C-NEXAFS spectra with those of SDB polymer and HDEHP. The SDB polymer and HDEHP were distributed within several hundred nanometers from the pore surface, and their distributions, especially SDB polymer, were spread uniformly over the adsorbent adsorbing Zr.
The increase of pre-edge peak at 532eV in O-NEXAFS spectra after Zr adsorption indicates the adsorption of some kinds of molecules contained in Zr/HNO3 solution, such as H2O. The adsorption of Zr and these molecules will bring the swelling of SDB polymer in the pore of SiO2 support, which was observed in Fig. 1.

Fig. 1. Colorized composition maps (black; SiO2, white; pore, red; SDB, blue; HDEHP (purple; mixture of red and blue) )

4. Others
The authors wish to thank Dr. Ohigashi for his helpful supports to have STXM analyses.

5. Publication/Presentation
(1) Y. Sano, S. Watanabe, H. Matsuura, T. Arai, 2017 Annual Meeting of AESJ, 2017/03/29.

6. Patent
N/A