Method for synthesizing sodalite and solidifying and stabilizing harmful metal nuclide through hydrothermal method and application

Abstract

The invention discloses a method for synthesizing sodalite through a hydrothermal method and solidifying and stabilizing harmful metal nuclides and application, and belongs to the technical field of solidification treatment of hazardous wastes. According to the method, silicon dioxide and other raw materials for synthesizing sodalite are subjected to ball milling pretreatment and then subjected to heat preservation for a certain time at the low temperature, sodalite solidified bodies are rapidly subjected to hydro-thermal synthesis, and radioactive harmful substances such as nuclear industry radioactive waste salt are synchronously solidified in the process; the sodalite synthesized under optimized conditions can also be used as an adsorbent to be expanded and applied to environmental media such as aqueous solutions and liquid salts, and is used for adsorbing radioactive or other common heavy metal harmful elements. The method has the advantages of high reaction rate, high immobilization rate, strong stability, low cost, environmental friendliness and the like, and has important application value in the field of treatment and disposal of hazardous wastes such as radioactive waste salt and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of hazardous waste treatment and disposal, and in particular to a method for synthesizing sodalite by a hydrothermal method and solidifying and stabilizing harmful metal nuclides and an application thereof. Background Art

[0002] Nuclear energy is widely used worldwide due to its high energy density, cleanliness, and affordability. However, with the development of the nuclear energy industry, the final disposal of radioactive salts from spent fuel reprocessing has become a critical issue that needs to be addressed. Currently, after wet and dry treatment of spent fuel, the waste generated still contains a certain amount of radioactive nuclides. Common representatives include various fragmented elements such as Cs, Sr, Ba, and Ce, as well as a large amount of chlorine. These nuclides have strong mobility in the environment, making their capture and immobilization challenging. Therefore, capturing radioactive nuclides from radioactive waste liquids or solid waste salts is of great significance to environmental protection and human health.

[0003] Radionuclides are typically immobilized using high-performance immobilization materials to facilitate their final disposal. Existing organic and inorganic immobilization materials have poor immobilization properties for certain specific elements, making them not universally applicable. Furthermore, their inherent thermal stability, radiation stability, acid and alkali stability, and mechanical strength are low, making them unsuitable for capturing and immobilizing target nuclides. Furthermore, the production of these immobilization materials is associated with high raw material costs, high energy consumption, and the potential for escape of target nuclides, as well as secondary contamination during the synthesis process. Consequently, traditional radioactive waste treatment materials have significant limitations for the treatment of radionuclides. For example, common immobilization materials such as glass and glass-ceramics utilize high-temperature treatment methods. While these methods can achieve a certain degree of radionuclide immobilization, the high-temperature process is not only energy-intensive but also prone to escape of target nuclides, resulting in secondary contamination. Furthermore, some low-temperature cement and asphalt materials have poor thermal and radiation stability, resulting in low immobilization efficiency. They can only be used to treat low-level radioactive waste and are unable to effectively and comprehensively capture and immobilize multiple radionuclides. While covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) possess high adsorption properties, their synthesis processes pose secondary pollution challenges. Furthermore, these adsorbent materials inherently suffer from poor acid, alkali, radiation, and thermal stability, significantly limiting their application. Therefore, there is an urgent need to develop efficient, economical, energy-efficient, and environmentally friendly materials for immobilizing radioactive waste salts to ensure the safe and final treatment and disposal of nuclear waste. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for synthesizing sodalite by a hydrothermal method and solidifying and stabilizing harmful metal nuclides is provided, comprising the following steps: According to sodalite (XAl6Si6O 24 Y) elemental components, preparing silicon source, aluminum source, sodium source, and chlorine source; ball-milling the raw materials in a stoichiometric ratio, and then mixing them with water at a certain solid-liquid ratio to obtain a pre-reaction solution; adding a template and mixing, and then performing a hydrothermal reaction in an alkaline environment to obtain sodalite; X represents a cation, and Y represents an anion; X is composed of sodium or a combination of sodium and a metal element, wherein the metal element includes at least one of an alkali metal, an alkaline earth metal, an actinide element, a lanthanide element, and a transition metal element; Y is composed of chlorine or a combination of chlorine and an inorganic anion, wherein the inorganic anion includes at least one of a hydroxide ion, a halogen anion, a phosphate ion, and a sulfate ion; When at least one of X and Y contains radioactive nuclides from radioactive waste salts, the radioactive nuclides are solidified in situ; when X and Y do not contain radioactive nuclides from radioactive waste salts, the obtained sodalite is used to adsorb radioactive waste salts or other harmful metal nuclides in an aqueous solution, liquid molten salt, or solid salt environment to achieve solidification and stabilization of the harmful nuclides.

[0005] Preferably, the silicon source includes silicon dioxide and sodium silicate; the aluminum source includes aluminum hydroxide, aluminum oxide, sodium aluminate, a mixture of aluminum chloride and aluminum hydroxide; the sodium source includes sodium aluminate, sodium chloride and sodium hydroxide; the chlorine source includes sodium chloride; and the metal element includes at least one of Cs, Sr, Ba, Ce, Ag, Cd, Cr and Ni.

[0006] When simultaneously solidifying radioactive waste salts (containing Cs, Sr, Ba, Ce, etc.) during the sodalite synthesis process, the following technical problems need to be overcome: First, the various ions in the waste salts (such as Cs + 、Sr 2+ 、Ba 2+ etc.) with Na + Competition for sodalite lattice sites can easily lead to crystal distortion or decreased crystallinity, affecting the structural stability of the solid body; secondly, some nuclides (such as Cs + ) is difficult to form a stable "sodalite phase", but may generate a secondary phase (such as Cs - Cesium garnet), consumes the effective components in the system (such as SiO2), and then changes the chemical composition and properties of the solidified body; Moreover, the high content of Cl in the waste salt -Compatibility with raw materials needs to be precisely controlled. For example, if the NaCl content exceeds the stoichiometric amount, rock salt inclusions are likely to form, and the decomposition of sodalite to form nepheline will consume reactants and reduce the waste salt loading. In addition, the uniform dispersion of nuclides in the system is crucial. Excessive local concentration will cause structural defects and increase the risk of long-term nuclide leaching. Finally, conditions such as hydrothermal synthesis need to be precisely optimized to balance sodalite crystallization and nuclide solidification, avoid degradation of the solidified body due to incomplete crystallization or uneven distribution of nuclides, and ensure its long-term safety and stability in geological disposal. Solving these problems is critical to achieving efficient and stable solidification of radioactive waste salts. Therefore, the condition parameters for sodalite synthesis need to be precisely controlled during the synthesis process to achieve the goals of high crystallinity and high immobilization efficiency of the target nuclides.

[0007] Preferably, the ball-to-material ratio of the ball milling treatment is 3-20:1, and the ball milling time is 0.5-6 h.

[0008] Preferably, the ball milling treatment includes dry milling or wet milling; under wet milling conditions, the dispersion medium is selected from at least one of water, ethanol, and acetone.

[0009] Preferably, the solid-to-liquid ratio of the mixture with water is 1:5~30.

[0010] Preferably, the template is triethanolamine.

[0011] Preferably, the amount of the template added is 1 wt.% to 5 wt.% of the pre-reaction solution.

[0012] During the synthesis stage, the addition of 1 to 5 wt.% triethanolamine as a template to the aqueous solution facilitates the rapid synthesis of mesoporous and macroporous sodalite. Furthermore, the synthesized sodalite is a composite organic-inorganic material, with inorganic crystals predominating and organic materials assisting. During the radionuclide immobilization process, the organic matter can chemically coordinate with the target nuclide ions, enhancing the immobilization of the target nuclide ions.

[0013] Preferably, the mixing is carried out at a stirring rate of 100 to 600 rpm and a stirring time of 1 to 6 h.

[0014] Preferably, the pH of the hydrothermal reaction is 7-14, the reaction temperature is 60-200° C., and the reaction time is 6-48 h. The hydrothermal synthesis system needs to be carried out in a certain alkalinity environment, and the mineralizer sodium hydroxide is used for adjustment, and the molar ratio of sodium hydroxide to silicon dioxide is 0.5-6:1.

[0015] In the second aspect of the present invention, the method for synthesizing sodalite by the hydrothermal method and solidifying and stabilizing harmful metal nuclides according to the first aspect of the present invention is used to immobilize radioactive nuclides or other harmful metal nuclides.

[0016] Based on the above technical solutions, the design concept and principle of the present invention are as follows: Conventional heavy metals are not radioactive in the natural environment, and their migration and transformation capabilities in media such as water and soil, as well as their difficulty in capture and hazard, are far less than those of fission nuclides. Therefore, conventional heavy metals can be immobilized using standard materials. However, for fission elements, it is necessary to improve the immobilization efficiency and prevent their further decay and release of secondary pollutants. Therefore, rational regulation and exploration should be conducted to precisely fix the nuclide ions in the chemical bonds of the material, or to enclose them within the internal structure of the material, in order to effectively bind the target nuclides. This will play a positive role in reducing the secondary hazards of radioactivity and further promote the closed-loop circulation of nuclear energy.

[0017] Compared with conventional solidification materials, artificial rock solidification mineral materials have the advantages of high fixation efficiency, low production cost, and easy operation. They can fix fission elements and other radioactive substances in the mineral lattice or adsorb them inside the mineral skeleton through ion exchange, chemical bonding, adsorption, etc., thus effectively binding radioactive substances. Sodalite (Na8Al6Si6O 24 Cl2) is a mineral material for solidifying radioactive waste salts with excellent properties such as good chemical stability, thermal stability, radiation stability, acid stability and mechanical strength. Its stable crystal structure can simultaneously embed target nuclides (cations) and chlorine elements (anions) into its skeleton structure, thereby achieving targeted, precise and efficient solidification of radioactive waste salts.

[0018] The present invention uses silicon source, aluminum source, sodium source, chlorine source (such as silicon dioxide, sodium metaaluminate, sodium chloride, etc.), the stoichiometric ratio of the three is 6:6:2 under this material selection, and the reaction formula is ; Under other options, those skilled in the art can adjust according to the type of raw materials and ion valence, for example ) as a raw material, leveraging the homogeneous and highly dispersed nature of aqueous solutions, a highly efficient, integrated treatment method has been developed to simultaneously adsorb and immobilize radionuclides in a sealed container at low temperature and pressure, eliminating the need for high-temperature treatment. This method synthesizes sodalite at relatively low temperatures and simultaneously solidifies radioactive waste salts in situ. To expand sodalite's applications, it can be applied in aqueous, molten, and solid salt media, not only to adsorb and solidify radionuclides but also to other common heavy metals and harmful elements in the environment.

[0019] The mechanism of action of the sodalite solidification base material involved in the present invention can be flexibly adjusted based on different actual conditions or needs. First, the sodalite itself synthesized under the optimized conditions of the hydrothermal method can be used as an adsorbent to achieve the adsorption of radioactive waste salt or other harmful metal elements in a solution or molten salt environment. Second, the reaction route of the hydrothermal method for synthesizing sodalite can be utilized, with waste salt containing radioactive nuclides as the synthetic raw material, to synthesize a sodalite-type solidified body and simultaneously achieve the solidification of radioactive nuclides. Due to the in-situ synthesis synchronous solidification process, the target nuclide ions adopt processes such as lattice solidification, adsorption, chemical coordination, ion exchange, etc. to embed the fragment elements and chlorine in the waste salt into the artificial rock skeleton, lattice, or be adsorbed inside and outside the structure, etc., and its effect is better than the solidification form of adsorption.

[0020] Specifically, taking Cs, Sr, Ba, and Ce as examples, the stage evolution process of reconstruction at the interface of precursor raw materials and the formation of sodalite cage structure is as follows: Under the hydrothermal synthesis parameters, Si, O, and Al combine to form the β cage structure unique to sodalite. The solidification mechanism of sodalite for Cs, Sr, Ba, and Ce is derived from the specific coordination effect and lattice adaptability of its cubic cage structure and multi-element nuclides. In the multi-element coexistence system, the alkali metal Cs + It occupies the cubic coordination site in the center of the sodalite β cage through ion exchange and combines with the cage wall oxygen atoms in an octa-coordinate form (coordination number 8.2 ± 0.3, bond length 2.95 Å). The size adaptability of its 0.167 nm ion radius and the cage cavity diameter (0.66 nm) makes its curing efficiency reach 98.7%; the alkaline earth metal Sr 2+ 、Ba 2+ It is embedded in the aluminosilicate framework in a six-coordinated manner to form [SrO6] 4- 、[BaO6] 4- Coordination unit, excessive introduction leads to lattice parameter expansion, and enhances structural stability through lattice energy matching; Lanthanide Ce 3+ By utilizing the strong coordination ability of the 4f electron layer, [CeO8] is formed at the double six-membered ring connection site. 13- The twelve-coordinate structure, the synergistic effect of covalent bond components and ionic bonds makes its leaching activation energy 30% higher than that of the bulk phase. The four nuclides are ion exchanged (Cs + ), lattice expansion (Sr 2+ 、Ba 2+ ), coordination chelation (Ce 3+ ) and the synergistic effect of cage-like structure spatial confinement, forming a triple solidification barrier at the intracrystalline (cage coordination), grain boundary (interface chemistry) and macrostructural (dense grain boundary) levels, ultimately achieving a normalized leaching rate (28 days) of <5×10 -4 g / (cm 2 d) Efficient fixation.

[0021] In summary, in particular, in the process of synthesizing sodalite, such as Ce 3+ 、Ce 4+ Can replace Al in the sodalite framework structure 3+ Or Si 4+ , and then enter the sodalite skeleton structure to achieve the goal of efficient solidification. The adsorption and solidification process in aqueous media and molten salt media mainly uses ion exchange, adsorption, chemical coordination and other effects to solidify the target nuclides. In the above application scenarios, sodalite achieves lattice solidification of different nuclides through targeted capture and isomorphous substitution, thereby converting waste salt into a stable and harmless solid form, effectively reducing the risk of migration, diffusion, and leakage of radioactive substances, which is conducive to long-term geological storage. The method of the present invention can be better connected and applied in the treatment of spent fuel wet and dry post-processing waste in terms of process, providing a new technical approach for the safe treatment of radioactive waste salt, thereby realizing the closed-loop sustainable development of nuclear energy.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention provides a method for synthesizing sodalite and solidifying and stabilizing harmful metal nuclides using a hydrothermal method. The method not only has good compatibility with fragmented elements and chlorine, but can also effectively encapsulate other harmful metal elements, including various harmful metal nuclides contained in radioactive waste salt, to prevent their release and migration. Compared with existing glass, ceramic, and glass solidification technologies, the method can achieve efficient synthesis of sodalite and simultaneous solidification of harmful metal nuclides at a lower temperature, has a wide range of application scenarios, and has a simple operation process. It does not require the addition of additional binders or secondary glass coating, has no secondary pollution problems, and is environmentally friendly.

[0023] The present invention provides an application of a method for synthesizing sodalite by a hydrothermal method and solidifying and stabilizing harmful metal nuclides, namely, a highly efficient, low-energy-consuming, economical and highly safe ultra-stable inorganic solid acid-resistant material. It captures and immobilizes radioactive nuclides through an integrated processing method and has wide industrial applicability. It can be used not only in nuclear power plants, nuclear fuel reprocessing plants and other scenarios where radioactive waste salts are generated, but also in the adsorption of harmful metal nuclides in environmental media. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 X-ray diffraction (XRD) pattern of sodalite synthesized under optimal conditions Figure 2 Fourier transform infrared (FTIR) spectrum of sodalite synthesized under optimal conditions; Figure 3Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) spectrum of sodalite solidified body synthesized under the preferred conditions; Figure 4 Thermogravimetric (TG) spectrum of sodalite solidified body; Figure 5 XRD spectrum after soaking in aqueous solution of different pH values; Figure 6 Normalized leaching rate graph; Figure 7 Graphs related to the adsorption effect of sodalite on target nuclides in aqueous solution, molten salt, and solid salt media. DETAILED DESCRIPTION

[0025] The present application will be further described by way of examples, but the present application is not limited to the scope of the examples. In the following examples, the experimental methods not specified in the specific conditions are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0026] Example 1 This example uses in-situ solidification to solidify radioactive waste salt, and the steps are as follows: (1) Dry the raw materials such as silicon dioxide, sodium chloride, and sodium aluminate in a forced air drying oven to remove the water therein; (2) Pass the silicon dioxide through a 50-200 mesh screen to obtain silicon dioxide powder; (3) Dry the individual raw material components of the radioactive waste salt in a forced air drying oven to remove the water therein; (4) Synthesize sodalite, weigh the required amount of silicon dioxide, sodium aluminate, and sodium chloride according to the stoichiometric ratio of 6:6:2, and mix the three in a ball mill until uniform; the molar ratio of sodium hydroxide to silicon dioxide is 6:1; (5) Mix with water according to a solid-liquid ratio of 1:10 to obtain a pre-reaction liquid; add 1 wt.% of triethanolamine and stir at 200 rpm for 1 h, and perform a hydrothermal reaction in an alkaline environment; place the sealed container containing the sodalite synthesis raw materials in a muffle furnace, heat at a rate of 5 ℃ / min to the target temperature of 160 ℃, and then maintain the temperature for 24 h; after the reaction is complete, naturally cool to room temperature and then remove to obtain the corresponding sodalite solidified body.

[0027] This example synthesizes sodalite in-situ and simultaneously solidifies radioactive waste salt. The main components of the simulated radioactive waste salt are shown in Table 1, and the addition amount is calculated according to the waste salt containment rate of 15 wt.% after solidification.

[0028] Table 1: Composition of radioactive waste salt

[0029] The sodalite solidified body was dried at 80°C for 8 h, ground, and sieved through a 100 mesh screen to obtain a solidified body powder and perform various performance tests.

[0030] Material characterization analysis was performed on the solidified body, and the test analysis methods were as follows: X-ray diffraction (XRD) was used for solidified body phase identification; scanning electron microscopy (SEM, Zeiss SIGMA) and energy dispersive spectroscopy (EDS, Oxford X-max 55) were used to observe the microstructure and element distribution of the sample; Fourier transform infrared spectroscopy analysis (FTIR) was used to test the functional groups of the material; a simultaneous thermal analyzer (HITACHI STA200) was used to determine the thermal stability of the sample, with an Ar atmosphere from room temperature to 900°C at a heating rate of 5°C / min; water immersion experiments were performed on the sodalite with different pH aqueous solutions to test its acid and alkali resistance.

[0031] ICP-MS (PQ-MS) was used to test the concentrations of Cs, Sr, Ba, and Ce in the leaching solution (PCT-A method). According to the PCT-A method of the American Society for Testing and Materials (ASTM), the prepared solidified body was ground in a marble mortar for 30 min and sieved through a 100-200 mesh screen. 2 g of solidified body powder was taken into a reaction kettle, 20 mL of deionized water was added, and it was immersed at 90°C. The leaching solution was taken on the 1st, 3rd, 7th, 14th, and 28th day, and the ion concentration in the leaching solution was determined by inductively coupled plasma mass spectrometry (ICP-MS). The normalized leaching rate was calculated.

[0032] Example 2 Adsorption and solidification application in high-level radioactive waste liquid: This example is basically the same as Example 1, except that no radioactive waste salt is added during the preparation of the sodalite, and the sodalite obtained from the reaction is used as an adsorbent for adsorption and solidification in a high-level radioactive aqueous solution.

[0033] In an aqueous solution medium (the single concentration of Cs, Sr, Ba, and Ce was 250 mg / L), 50 mg of synthetic sodalite was mixed with 25 mL of solution, and the solution adsorption was performed at room temperature and initial pH conditions with 200 rpm shaking for 60 min. The adsorption efficiency was calculated to illustrate the solidification effect.

[0034] Example 3 Adsorption and solidification application in molten salt: In this example, the sodalite prepared without adding radioactive waste salt as in Example 2 is used as an adsorbent for adsorbing and fixing target nuclides in a molten salt medium.

[0035] In LiCl-KCl or LiCl-Li2O molten salt medium, 1 g of synthetic sodalite was mixed with 5 g of LiCl-KCl salt (molar ratio 0.592:0.408) containing 8 wt.% of radioactive nuclides, Cs, Sr, Ba and Ce each accounting for 2 wt.% for 30 min, and molten salt adsorption was carried out at 700°C in a high-temperature furnace for 60 min.

[0036] Example 4 Adsorption solidification application in solid salt: This example uses the sodalite prepared in Example 2 without adding radioactive waste salt as the adsorbent, which is applied in solid salt medium. After mixing the adsorbent with the salt, the target nuclides are adsorbed and fixed.

[0037] In LiCl-KCl or LiCl-Li2O solid salt medium, 1 g of synthetic sodalite was mixed with 5 g of LiCl-KCl salt (molar ratio 0.592:0.408) containing 8 wt.% of radioactive nuclides, Cs, Sr, Ba and Ce each accounting for 2 wt.% for 30 min, and solid salt adsorption was carried out at 300°C in a high-temperature furnace for 60 min.

[0038] Example 5 The XRD pattern of the sodalite synthesized in Example 2 is shown in Figure 1 , and the infrared spectrum is shown in Figure 2 . Figure 1 , and Figure 2 The results prove that the framework structure of the target sodalite is obtained, indicating that the hydrothermal method of the present application can successfully synthesize sodalite.

[0039] The SEM-EDS pattern of the sodalite solidified body is shown in Figure 3 . The SEM characterization result shows that the sodalite solidified body synthesized and simultaneously solidified with radioactive waste salt presents a cubic block shape in a state of agglomeration, with a smooth surface and no defects. The EDS analysis result shows that the signal intensity of Cs, Sr, Ba and Ce elements on the surface of the sodalite solidified body is uniformly distributed, confirming that the above-mentioned four kinds of fragment elements have been effectively solidified in the sodalite solidified body.

[0040] The thermogravimetric analysis result of the sodalite solidified body is shown in Figure 4 . The first stage of weight loss corresponds to the removal of adsorbed water, the second stage of weight loss corresponds to the removal of adsorbed water or bound water on the surface or inside, and the third stage corresponds to the decomposition of sodalite, accompanied by the volatilization of lithium chloride salt. These results show that the synthesized sodalite solidified body has good thermal stability within 800°C.

[0041] The test results of the sodalite solidified body after soaking in different pH aqueous solutions are shown in Figure 5 . Figure 5 This shows that its phase has not changed, proving that the sodalite mineral matrix has excellent acid and alkali resistance.

[0042] The normalized leaching rate test results of sodalite solidification body are shown in Figure 6 The normalized leaching rate showed that the normalized leaching rate of the four splinter elements was less than 5×10 -4 g / (cm 2 / d), indicating that sodalite effectively solidified the fragmented elements in the waste salt.

[0043] Figure 7 The adsorption effect of sodalite on target nuclides in aqueous solution, molten salt and solid salt medium. Adsorption application experiments show that this method can effectively adsorb four target nuclides in aqueous solution, molten salt and solid salt medium.

[0044] Example 6 This embodiment uses sodalite prepared without adding radioactive waste salt as in Example 2 as an adsorbent to be applied to an aqueous solution medium to adsorb and fix transition metal elements.

[0045] In an aqueous solution (initial Ag concentration of 250 mg / L), 50 mg of synthetic sodalite was mixed with 25 mL of solution and adsorbed at room temperature and initial pH conditions with shaking at 200 rpm for 60 min. The adsorption efficiency was calculated to illustrate the curing effect. The results showed that Ag + The adsorption capacity is 80 mg / g.

[0046] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for hydrothermally synthesizing sodalite and solidifying and stabilizing harmful metal nuclides, characterized in that: The steps include: According to sodalite (XAl6Si6O 24 Y) elemental components, preparing silicon source, aluminum source, sodium source, and chlorine source; ball-milling the raw materials in a stoichiometric ratio, and then mixing them with water at a certain solid-liquid ratio to obtain a pre-reaction solution; adding a template and mixing, and then performing a hydrothermal reaction in an alkaline environment to obtain sodalite; X represents a cation, and Y represents an anion; the element type of X is sodium or a combination of sodium and a metal element, wherein the metal element includes at least one of an alkali metal, an alkaline earth metal, an actinide element, a lanthanide element, and a transition metal element; the element type of Y is chlorine or a combination of chlorine and an inorganic anion, wherein the inorganic anion includes at least one of a hydroxide ion, a halogen anion, a phosphate ion, and a sulfate ion; When at least one of X and Y contains radioactive nuclides from radioactive waste salts, the radioactive nuclides are solidified in the form of in-situ solidification; when X and Y do not contain radioactive nuclides from radioactive waste salts, the obtained sodalite is used to adsorb radioactive waste salts or other harmful metal nuclides in an aqueous solution, liquid molten salt, or solid salt environment to achieve solidification and stabilization of the harmful nuclides.

2. The method for hydrothermal synthesis of sodalite and solidification and stabilization of harmful metal nuclides according to claim 1, characterized in that: The silicon source includes silicon dioxide and sodium silicate; the aluminum source includes aluminum hydroxide, aluminum oxide, sodium metaaluminate, aluminum chloride and a mixture of aluminum hydroxide; the sodium source includes sodium metaaluminate, sodium chloride and sodium hydroxide; the chlorine source includes sodium chloride; and the metal element includes at least one of Cs, Sr, Ba, Ce, Ag, Cd, Cr and Ni.

3. The method for synthesizing sodalite by hydrothermal method and solidifying and stabilizing harmful metal nuclides according to claim 1, characterized in that: The ball-to-material ratio of the ball milling process is 3-20:1, and the ball milling time is 0.5-6 h.

4. The method for hydrothermal synthesis of sodalite and solidification and stabilization of harmful metal nuclides according to claim 1, characterized in that: The ball milling treatment includes dry milling or wet milling; under the wet milling condition, the dispersion medium is selected from at least one of water, ethanol, and acetone.

5. The method for synthesizing sodalite and solidifying and stabilizing harmful metal nuclides by hydrothermal method according to claim 1, characterized in that: The solid-liquid ratio of the mixture with water is 1:5~30.

6. The method for hydrothermal synthesis of sodalite and solidification and stabilization of harmful metal nuclides according to claim 1, characterized in that: The template agent is triethanolamine.

7. The method for synthesizing sodalite and solidifying and stabilizing harmful metal nuclides by hydrothermal method according to claim 1, characterized in that: The addition amount of the template is 1 wt.% to 5 wt.% of the pre-reaction solution.

8. The method for hydrothermal synthesis of sodalite and solidification and stabilization of harmful metal nuclides according to claim 1, characterized in that: The mixing is performed at a stirring rate of 100-600 rpm and a stirring time of 1-6 h.

9. The method for synthesizing sodalite by hydrothermal method and solidifying and stabilizing harmful metal nuclides according to claim 1, characterized in that: The pH of the hydrothermal reaction is 7-14, the reaction temperature is 60-200°C, and the reaction time is 6-48 hours. The hydrothermal synthesis system needs to be carried out in a certain alkalinity environment and is adjusted using the mineralizer sodium hydroxide. The molar ratio of sodium hydroxide to silicon dioxide is 0.5-6:

1.

10. An application of the method for hydrothermal synthesis of sodalite and solidification and stabilization of harmful metal nuclides according to any one of claims 1 to 9, characterized in that: Used to solidify and stabilize radioactive nuclides and other common heavy metal harmful elements.

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