Atomic-Scale Analysis of Cs⁺ within Zeolitic Framework by AC-(S)TEM and First Principle Calculation

Kaname Yoshida, Kazuaki Toyoura, Katsuyuki Matsunaga, Hiroki Kurata, Atsushi Nakahira, Yumi H. Ikuhara and Yukichi Sasaki

Abstract: Zeolites have a great potential for application in various fields. Now, zeolites are again at a center of public attention in Japan as stable adsorbents and solidification materials of fission products, such as ¹³⁷Cs coming from damaged nuclear-power plants. Although ion-exchange mechanism within zeolitic nanocavities have been poorly understood. There are still open questions, at the atomic-level regime, on physical and chemical origins of ion-exchange selectivity and detailed atomic structures of counter cations inside the nanocavities. For practical application of zeolite as adsorbent of fission products, atomic-scale structural information of zeolites are indispensable. Here, precise locations of Cs⁺ captured within NaA-type zeolite were analyzed by high-resolution electron microscopy and theoretical calculation. Stable positions of adsorbed Cs⁺ in the nanocavities were identified, and the bonding environment with the zeolitic framework are revealed to be a key factor for the adsorbed cation locations.

Key words: Zeolite, ion-exchange, Caesium, AC-(S)TEM, Ab initio molecular dynamics simulation