Immobilization Behavior Of Cs⁺&Sr²⁺ By Geopolymer

Geopolymer is chemically stable and has a "zeolite-like" structure,which can effectively surround the radioactive cations in a cage-shaped closed cavity structure formed by the combination of ring molecules for the purpose of immobilization.The porous aluminosilicate polymer prepared by the foaming method has many advantages,such as low cost,green and pollution-free,large specific surface area,and high porosity.So it can be used as an excellent inorganic adsorbent to absorb radioactive ions in nuclear waste liquid.It also has broad application prospects in the industrial field.In this paper,first,metakaolin,alkali excitation solution,and Cs NO₃/Sr（NO₃）₂ solution are used as the main raw materials to synthesize aluminosilicate polymer solidified body containing simulated radionuclide and compare the sealing performance with cement solidified body.Then the foaming method was used to prepare porous aluminosilicate polymer and its composite material with graphene oxide（GO）.The effects of different types of poreforming agents on pore structure and distribution were studied.The focus was on H₂O₂,Triton,The effect of the amount of graphene oxide used on the sample porosity,pore structure and mechanical properties.Finally,through the design adsorption experiment,the effect of Cs⁺ adsorption by porous samples was observed and the feasibility of cesium garnet produced by high temperature treatment of porous aluminosilicate polymer samples to improve the sealing effect was verified.The leaching experiments in 25℃,60℃ deionized water and 5wt% Na Cl solution were used to compare the sealing effect of aluminosilicate polymer and cement cured body on Cs⁺ and Sr²⁺.The dissolution rate of Cs⁺ and Sr²⁺ under different conditions was plotted.The change curve of cumulative dissolution fraction with time analyzes the dissolution behavior and dissolution mechanism.The results show that the cured aluminosilicate polymer has better sealing effect than cement.Under deionized water conditions,the dissolution rate of Cs⁺ and Sr²⁺ in the solidified body of aluminosilicate polymer polymer for 42 d was much lower than that of cemented body no matter it was 25 ℃ or 60 ℃.As the temperature increases,the dissolution rate and cumulative dissolution fraction increase to some extent,but the aluminosilicate polymer cured body is still much lower than the cement cured body.Under the environment of Na Cl aqueous solution,the dissolution rate and cumulative dissolution fraction of the cured aluminosilicate polymer and cement cured body are increased,and the corrosion resistance of the aluminosilicate polymer is better than cement.Porous aluminosilicate polymer was prepared by adjusting Triton and H₂O₂ mass ratio to 0.2,0.4,0.6,0.8 and 1.0.As the amount of H₂O₂ increases,the pore size increases and the porosity increases,but the compressive strength decreases.When the ratio of Triton to H₂O₂ is 0.6,the porosity is 72.07% and the compressive strength is 1.76±0.19 MPa.The addition of graphene oxide solution can improve the mechanical properties of porous samples.When 3g of GO aqueous solution is added,the compressive strength of the sample is 2.6MPa,which is 1.5 times the strength of the sample without GO.The Cs⁺ adsorption experiment showed that the adsorption efficiency of porous aluminosilicate polymer was significantly improved,approaching 100%.The addition of GO would cover the surface of the aluminosilicate polymer,making the adsorption efficiency slightly lower.The porous sample after adsorption of Cs⁺ was subjected to high-temperature treatment at 900℃,and the diffraction peaks of cesium garnet（PDF#29-0407 and PDF#88-0055）appeared,proving that high temperature can be used to generate cesium-containing aluminum silicate polymer in situ The cesium garnet method improves the sealing effect to better suit the actual application.