Abstract
Alkali-activated metakaolin geopolymers are attracting interest in the conditioning of nuclear wastes, especially for their ability to immobilise cationic species. However, there is limited understanding of the chemical interactions between the encapsulated spent ion-exchangers, used for decontaminating waste water, and the host aluminosilicate matrix. The lack of such understanding makes it difficult to predict the long-term stability of the waste form. In this study, the suitability of using metakaolin based geopolymer as a matrix for encapsulation of titanate-type ion-exchangers loaded with non-radioactive Sr was investigated for the first time, via spectroscopic and microstructural inspection of the encapsulated ion-exchangers and the aluminosilicate gel matrix. The microstructural and chemical properties of metakaolin geopolymers remained stable after encapsulating titanate type spent ion-exchangers, performed desirably as host materials for conditioning of Sr-loaded titanate ion-exchangers.
Highlights
Soon after the accident at the Fukushima Daiichi Nuclear Power Station on the 11th of March 2011, sea water was injected into the reactor core for emergency cooling.[1]
The present study investigates geopolymer cements based on metakaolin
Crystalline anatase (TiO2, Powder Diffraction File (PDF) # 01-084-1286) and quartz (SiO2, PDF# 01-078-2315) were observed from the metakaolin precursor, which stayed as inert phases in the alkali-activated metakaolin gel binder
Summary
Soon after the accident at the Fukushima Daiichi Nuclear Power Station on the 11th of March 2011, sea water was injected into the reactor core for emergency cooling.[1]. Sodium titanate, consisting of layered edge-sharing TiO6 octahedral chains linked with exchangeable interlayer sodium cations, was selected at the Fukushima Daiichi site for selective exchange of strontium ions from the waste water.[5,6,7,8,9] An alkaline aqueous environment is preferred for the functionality of sodium titanate as an ion-exchanger, as in a non-basic aqueous environment ( pH < 8), protonation of the surface cation-exchangeable site is preferred, which significantly reduces ion-exchange capacity.[7]
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