Relationship between zeolite structure and capture capability for radioactive cesium and strontium
- Authors
- Kwon, Songhyeon; Kim, Chaehoon; Han, Eunhye; Lee, Hoin; Cho, Hae Sung; Choi, Minkee
- Issue Date
- Apr-2021
- Publisher
- Elsevier B.V.
- Keywords
- Cesium; Ion exchange; Strontium; Structural dependence; Zeolite
- Citation
- Journal of Hazardous Materials, v.408
- Journal Title
- Journal of Hazardous Materials
- Volume
- 408
- URI
- https://scholarworks.bwise.kr/cau/handle/2019.sw.cau/62475
- DOI
- 10.1016/j.jhazmat.2020.124419
- ISSN
- 0304-3894
1873-3336
- Abstract
- Zeolites are widely used for capturing radioactive Cs+ and Sr2+, but the important structural factors determining their performance have not been clearly understood. To investigate the structure-property relationship, we prepared thirteen zeolites with various structures and Si/Al ratios. Ion-exchange experiments revealed that Cs+ exhibited an enhanced affinity to zeolites with high Si/Al ratios, which could be explained by the dielectric theory. Notably, zeolites containing 8-membered ring (8MR) showed extra-high Cs+ selectivity. Structural analysis using X-ray diffraction proved that Cs+ with an ionic diameter of 3.6 Å was selectively coordinated within 8MR having a cavity diameter of 3.6–4.1 Å. Such unique size-selective Cs+ coordination is analogous to ion complexation by macrocyclic organic ligands (e.g., crown ethers). Divalent Sr2+ showed decreasing affinity to zeolites as the Si/Al ratio increased, because of the increasing average Al–Al distance distribution. Sr2+ exchange exhibited an insignificant dependence on zeolite structures due to its strong hydration, which inhibited close interaction with zeolite frameworks. In terms of kinetics, Sr2+ exchange was significantly slower than Cs+ exchange because of the bulkiness of hydrated Sr2+ ions. Therefore, the micropore channels with large apertures (e.g., 12-membered ring) were beneficial for achieving fast ion-exchange kinetics, especially in the case of Sr2+.
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