Performance And Mechanism For The Immobilization Of Simulated Radionuclide Sr And Cs In The Geopolymer Ceramics

Although nuclear energy can alleviate the energy crisis,the radioactive waste brings a seriously threat to human life.At present,how to treat high-level liquid waste?HLW?effectively has attracted widespread attention from domestic and foreign scholars.Geopolymers with unique network structure can be used for curing radioactive waste liquor,but few scholars have made further research on its ceramization.In this paper,the characterization of geopolymer under high temperature was investigated,such as physical properties and mineral composition of fly ash and metakaolin-based geopolymers.The physical properties and leaching resistance of the ceramic solidification bodies that prepared by 4A zeolite,potassium silicate and metakaolin were studied.Combined with the mineral composition,micromorphology and molecular structure results,the properties and mechanism of the geopolymer ceramic solidification body were analysed.Meanwhile,the influence of zeolite content on the properties of ceramic solidification was further discussed.The results can provide a theoretical basis for the large-scale industrial application of high polymer liquid solidification waste liquid.The research of this paper shows that the metakaolin-based geopolymer has better resistance to high temperature han the fly ash-based geopolymer.At high temperature of 1200?,the metakaolin-based geopolymer has a large amount of leucite phase,and the sample structure is temper and compact.The compressive strength of the sample is sharply increased.Since the K-based metakaolin-based geopolymer sample first appears peak of the leucite ceramic crystal phase at the 1100? for the ionic radius of the alkali metal K⁺is larger than the Na⁺ion radius,the metal bond is weakened.The porosity is 1.21%,and the compressive strength is improved to 47.76 MPa,which is 12.98 MPa higher than the Na-based metakaolin-based geopolymer sample,and that can be used to prepare ceramic solidification bodies.The two groups of geopolymer ceramic solidification bodies prepared by the cerium-containing zeolite and the cerium-containing zeolite have good compactness,mechanical strength and leaching resistance.At 900?,The porosity of the sample is decreased significantly,the bulk density increased,and a large number of smooth and stable ceramic phase structures were formed at 1100? for the internal structure is dense,and the strength of the two sets of ceramic solidification samples were respectively increased to 81.33 MPa and 91.45 MPa.In addition,it shows better leaching resistance in deionized water,brine and silicate water.The leaching rate is lower than the industry standard value and has good long-term stability.The effect of the radionuclide zeolite on the performance of the ceramic solidification body is obvious.When the content of the radionuclide zeolite is 60%,the alkali metal in the zeolite participates in the reaction to reduce the melting temperature of the sample.The new nepheline phase is produced at 1100? for local melting of the sample,and the porosity increases,resulting in a sharp decrease in compressive strength.When the amount of radionuclide added is between 70%and 90%,a large number of ceramic phases are generated,such as nepheline and leucite.Phase analysis showed that free SiO₂ participates in the reaction and melts into a glass phase to filling the pores due to the molten,and increasing the compressive strength of the sample.In the high concentration brine solution,when the content of the radionuclide zeolite is90%,the leaching rate of the sample in the entire leaching period satisfies the industrial limit.The safe disposal of high-level liquid waste can be realized.