On the Sustainable Utilization of Geopolymers for Safe Management of Radioactive Waste: A Review

The application of geopolymers for the safe management of radioactive waste has not been implemented on a large scale, where they are tirelessly examined with the purpose of facilitating the practicality and feasibility of the actual application towards the sustainable performance of these materials. This review therefore compiles the findings of the utilization of geopolymers as sorbents for removal of radio-contaminants from aqueous waste streams and as immobilization matrices for the containment of different radioactive wastes. The investigated geopolymer base materials encompass a wide range of reactive aluminosilicate precursor sources that include natural materials, industrial wastes, and chemicals. This work introduces to the reader the scientific interest in the field of geopolymer studies, their sustainability analysis, and their application in the nuclear industry, in particular in radioactive waste treatment and immobilization. The geopolymer classification, radiation stability, and structural characterizations were summarized with special reference to the characterization of the structure alteration due to the inclusion of functional materials or radioactive wastes. The effect of the application of metakaolin-based materials, fly ash-based materials and other base materials, and their blend on radio-contaminant removal from aqueous solutions and the immobilization of different problematic radioactive waste streams were reviewed and analyzed to identify the gaps in the sustainable performance of these materials. Finally, perspectives on geopolymer sustainability are presented, and the identified gaps in sustainable application included the need to investigate new areas of application, e.g., in pretreatment and membrane separation. The reusability and the regeneration of the geopolymer sorbents/exchangers need to be addressed to reduce the material footprints of this application. Moreover, there is a need to develop durability tests and standards based on the record of the application of the geopolymers.