STRUCTURAL FACTORS OF ZEOLITES DETERMINING THE CAPTURE CAPABILITY OF RADIOACTIVE CESIUM AND STRONTIUM

Abstract

Ion-exchange materials have been investigated for selective capturing of radioactive 137Cs+ and 90Sr2+ from low-concentration sources containing high concentrations of various competing ions (e.g., Na+, K+, Mg2+, and Ca2+). Inorganic materials have been more extensively investigated than organic resins because they can withstand the harsh conditions of nuclear sites, which produce immense heat and radiation. In particular, zeolites have been investigated the most, because of their low material cost, commercial availability, diverse structures and compositions, and high compatibility with cement and glass matrices that are used for the immobilization of radioactive waste. The ion-exchange properties of typical aluminosilicate zeolites strongly depend on their framework topologies and compositions. Therefore, for designing highperformance zeolites to capture Cs+/Sr2+, it is crucial to understand the effects of different zeolite structures and Si/Al ratios on the Cs+/Sr2+ ion-exchange properties. In previous studies, only a few zeolites have been tested under a wide range of ion-963 exchange conditions, with a major focus on searching materials with improved performances. Unfortunately, such studies have provided limited insight into how different structural parameters of zeolites affect their Cs+ and Sr2+ capture abilities. Understanding the structure-property correlation is necessary, not only for the design of high-performance ion-exchangers of radioactive isotopes, but also for widening our fundamental knowledge on the ion-exchange processes within zeolites.