Applications of Zeolites in The Nuclear Industry

Abstract

Zeolites are porous aluminosilicate which are deployed in different applications including their use in catalytic reactions, adsorption, and ion exchange processes. In the nuclear industry, zeolites have been applied widely in the treatment of different waste streams by ion exchange processes to remove radioactive elements. In this dissertation project, the applications of zeolites in the nuclear industry are reviewed. The most commonly applied zeolites in the nuclear industry (clinoptilolite, zeolite A, mordenite, chabazite, and faujasite X and Y) are identified with a description of their properties, structures, and applications. The treatment of aqueous waste streams by zeolites is discussed; typically, zeolites are applied for the removal of caesium and strontium from aqueous waste. Hierarchical and synthetic zeolites are found to have higher capacity and kinetics to remove caesium and strontium compared to natural zeolites. The effects of pH level, temperature, initial concentrations of caesium and strontium, and competing ions on the performance of zeolites were analysed based on data reported in the literature. The possibility of removing other radionuclides including heavy metals, actinides, and iodine from aqueous waste streams was reported. Other application of zeolites is the treatment of gaseous waste streams, silver mordenite and faujasite are the most accepted candidates to remove iodine from gaseous waste streams. Moreover, zeolites have been also applied for the treatment of molten salt waste from pyroprocessing, zeolite A is the main candidate for this process. An overview of the applications of zeolites for the clean-up of nuclear accidents such as Chernobyl and Fukushima is presented, where zeolites were applied for the decontamination of nuclear power plants, soil, and organisms. Finally, the use of zeolites as engineering barriers to contain radionuclides after their disposal in geological repositories is discussed. After the treatment of waste streams by zeolites, zeolites must be immobilised in solid wasteforms for final disposal. The possible wasteforms to contain zeolites include glass and cement wasteforms which are applied for the immobilisation of zeolites treating aqueous effluents. Additionally, for zeolites treating gaseous waste streams, a glass wasteform created by hot isostatic pressing is the typical solution. Finally, glass bonded sodalite is applied for the immobilisation of zeolites treating molten salt streams.