Selective Removal of Radioactive Cesium from Nuclear Waste by Zeolites: On the Origin of Cesium Selectivity Revaealed by Systematic Crystallographic Studies

Ha Young Lee, Hu Sik Kim, Hae Kwon Jeong, Man Park, Dong Yong Chung, Keun Young Lee, Eil Hee Lee, Woo Taik Lim

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59 Scopus citations

Abstract

Selective ion-exchange with zeolites has been considered as one of the most promising means to remove a radioactive isotope of cesium, 137Cs, present in low concentration in seawater. However, there has been no report on the fundamental structure-property relation of zeolite-based Cs ion-exchangers. In this study, we investigate the origin of the selectivity of the radioactive cesium isotope in zeolite frameworks using zeolite A (LTA) as a model system. We prepared seven single crystals of fully dehydrated and partially cesium exchanged Zeolite A (LTA) with different Cs+/Na+ ratios. Their single-crystal synchrotron X-ray diffraction experiments revealed the significant differences in the degree of exchange and the site selectivity of Cs+ ions depending on the initial Cs+ concentrations in given ion exchange solutions. The degree of Cs+-ion exchange increases from 15.8 to 44.2% as the initial Cs+ concentration increases and the Na+ content decreases. In addition, it was found that Cs+ ions are energetically preferred and occluded in the center of eight-oxygen rings. With this finding, we tested the Cs adsorption capacity of pure zeolite Rho which has much more eight-oxygen rings than zeolite A along with commercial faujasite-type zeolite and titanosilicate from deionized water and seawater. Zeolite Rho showed significantly better performance on the Cs removal in the presence of high salt contents (i.e., seawater) than faujasite-type zeolite and titanosilicate.

Original languageEnglish
Pages (from-to)10594-10608
Number of pages15
JournalJournal of Physical Chemistry C
Volume121
Issue number19
DOIs
StatePublished - 18 May 2017

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