Method for synthesizing sodalite by hydrothermal method and application of the method for immobilizing and stabilizing hazardous metal nuclides

Abstract

The application discloses a method for synthesizing sodalite by a hydrothermal method and solidifying and stabilizing harmful metal elements and application thereof, and belongs to the technical field of solidification treatment of hazardous waste. In the method, raw materials for synthesizing the sodalite, such as silicon dioxide, are pretreated by ball milling, and then the sodalite solidification body is rapidly synthesized by hydrothermal synthesis at a low temperature for a certain time, and radioactive harmful substances, such as radioactive waste salt in the nuclear industry, are simultaneously solidified in the process. The sodalite synthesized under the optimized conditions can also be used as an adsorbent to be extended to environmental media such as aqueous solution and liquid salt and be used for adsorbing radioactive or other common heavy metal harmful elements. The method has the advantages of fast reaction rate, high immobilization rate, strong stability, low cost and environmental friendliness and the like, and has important application value in the field of treatment and disposal of radioactive waste salt and other hazardous waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste treatment and disposal, and particularly relates to a method for synthesizing sodalite by a hydrothermal method and solidifying and stabilizing harmful metal elements and application thereof. BACKGROUND

[0002] Nuclear energy is widely used in the world due to its high energy density, cleanliness, economy and other advantages. However, with the development of the nuclear energy industry, the final disposal of radioactive waste salt in spent fuel reprocessing has become a key problem to be solved. At present, after the spent fuel is treated by a wet method and a dry method, the waste still contains a certain amount of radioactive elements, and common representative elements include Cs, Sr, Ba, Ce and a large amount of chlorine elements. These elements have strong migration ability in the environment, and it is challenging to capture and fix them. Therefore, it is of great significance to capture radioactive elements from radioactive waste liquid or solid waste salt for environmental protection and human health.

[0003] Generally, some excellent immobilization materials are used to immobilize radioactive elements for final disposal. Some existing organic and inorganic immobilization materials have poor immobilization effect on some specific elements, and are not universally applicable. Moreover, the thermal stability, radiation stability, acid and alkali resistance and mechanical strength of the immobilization materials are low, which is not conducive to the capture and immobilization of target elements. In addition, the production of such immobilization materials has high raw material cost, high energy consumption, easy escape of target elements and secondary pollution problems in the synthesis process. Therefore, the traditional radioactive waste treatment materials have great limitations in the treatment of radioactive elements. For example, common glass and glass-ceramic immobilization materials use high-temperature treatment methods, which can achieve immobilization of elements to a certain extent, but the high-temperature process not only has high energy consumption, but also easily causes the escape of target elements and produces secondary pollution problems. Some low-temperature cement and asphalt materials have poor thermal stability and radiation stability, and low immobilization efficiency, which can only be used for the treatment of low-level radioactive waste and cannot effectively and comprehensively capture and immobilize various radioactive elements. Covalent organic framework (COF) and metal organic framework (MOF) have high adsorption, but the synthesis process has secondary pollution problems, and the acid and alkali resistance, radiation resistance and thermal stability of the adsorbent materials are poor, which greatly limits the application. Therefore, it is urgent to develop an efficient, economical, energy-saving and environmentally friendly radioactive waste salt immobilization material to realize the safe treatment and disposal of nuclear waste. SUMMARY

[0004] In view of the above-mentioned defects of the prior art, in a first aspect of the present application, a method for synthesizing sodalite and solidifying and stabilizing hazardous metal nuclides by a hydrothermal method is provided, comprising the following steps:

[0005] According to the element composition of sodalite (XAl6Si6O 24 Y), a silicon source, an aluminum source, a sodium source, and a chlorine source are prepared; the raw materials in stoichiometric ratio are treated by ball milling, mixed with water in a certain solid-liquid ratio to obtain a pre-reaction liquid; a template agent is added and mixed, and then a hydrothermal reaction is carried out in an alkaline environment to obtain sodalite.

[0006] X represents a cation, and Y represents an anion; the composition of X is sodium or a combination of sodium and a metal element, and 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 composition of Y is chlorine or a combination of chlorine and an inorganic anion, and the inorganic anion includes at least one of a hydroxyl ion, a halide ion, a phosphate ion, and a sulfate ion.

[0007] When at least one of X and Y contains a radionuclide of radioactive waste salt, the radionuclide is solidified in situ; when X and Y do not contain a radionuclide of radioactive waste salt, the obtained sodalite is used to adsorb radioactive waste salt or other hazardous metal nuclides in an aqueous solution, a liquid molten salt, or a solid salt environment, to achieve solidification and stabilization of the hazardous nuclides.

[0008] Preferably, the silicon source includes silicon dioxide and sodium silicate; the aluminum source includes aluminum hydroxide, aluminum oxide, sodium aluminate, aluminum chloride, and a mixture of 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.

[0009] In the process of synthesizing sodalite, when radioactive waste salt (containing Cs, Sr, Ba, Ce, etc.) is simultaneously solidified, the following technical problems need to be overcome: first, a plurality of ions (such as Cs + , Sr 2+ , Ba 2+ , etc.) in the waste salt compete with Na + to occupy the lattice sites of sodalite, which easily leads to crystal distortion or a decrease in crystallinity, affecting the structural stability of the solidified body; second, some nuclides (such as Cs + ) are difficult to form a stable "sodalite phase", but may generate a by-product phase (such as Cs - carnegieite), which consumes effective components (such as SiO2) in the system, and further changes the chemical composition and performance of the solidified body; third, the high content of Cl -The compatibility with raw materials needs to be precisely controlled. For example, if the content of NaCl exceeds the stoichiometric amount, rock salt inclusions are easily produced, and the decomposition of sodalite generates nepheline, which consumes reactants and reduces the waste salt load. In addition, the uniform dispersion of nuclides in the system is crucial. Local high concentration can cause structural defects and increase the risk of long-term nuclide leaching. Finally, the conditions of hydrothermal synthesis and other conditions need to be precisely optimized to balance the crystallization of sodalite and the solidification of nuclides, avoid performance degradation of the solidified body due to incomplete crystallization or uneven distribution of nuclides, and ensure the long-term safety and stability of the solidified body in geological disposal. The solution of these problems is of great significance to the efficient and stable solidification of radioactive waste salt. Therefore, the conditions of the synthesis process need to be precisely controlled to achieve high crystallinity and high fixation efficiency of target nuclides.

[0010] 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.

[0011] Preferably, the ball milling treatment includes dry milling or wet milling. In the case of wet milling, the dispersion medium is selected from at least one of water, ethanol, and acetone.

[0012] Preferably, the solid-to-liquid ratio of the mixture with water is 1:5-30.

[0013] Preferably, the template agent is triethanolamine.

[0014] Preferably, the addition amount of the template agent is 1 wt.%-5 wt.% of the pre-reaction solution.

[0015] In the synthesis stage, the addition of 1 wt.%-5 wt.% of triethanolamine template agent in the aqueous solution helps to guide the rapid synthesis of mesoporous and macroporous sodalite. In addition, the synthesized sodalite is a composite organic-inorganic material dominated by inorganic crystals and assisted by organic materials. During the solidification of radioactive nuclides, chemical coordination can occur between the organic material and the target nuclide ions, enhancing the solidification of the target nuclide ions.

[0016] Preferably, the stirring rate of the mixing is 100-600 rpm, and the stirring time is 1-6 h.

[0017] 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 an alkaline environment, which is adjusted by the mineralizer sodium hydroxide. The molar ratio of sodium hydroxide to silicon dioxide is 0.5-6:1.

[0018] In the second aspect of the present application, the method for synthesizing sodalite by the hydrothermal method and solidifying and stabilizing harmful metal nuclides of the first aspect of the present application is used to fix radioactive nuclides or other harmful metal nuclides.

[0019] Based on the above technical scheme, the design concept and principle of the application are as follows:

[0020] The conventional heavy metals do not have radioactivity in the natural environment, and their migration, transformation ability, capture difficulty and harmfulness in media such as water and soil are far inferior to those of fissile nuclides, so general materials can be used to achieve the immobilization target for conventional heavy metals. For fissile elements, it is necessary to improve the immobilization efficiency and prevent further decay and release of secondary pollutants, so it is necessary to reasonably control and explore the precise immobilization of nuclide ions in the chemical bonds of the material or the closure in the internal structure of the material to effectively bind the target nuclides, which will play a positive role in reducing the secondary harm of radioactivity and further promote the closed loop cycle of nuclear energy.

[0021] Compared with conventional solidification materials, artificial rock solidification mineral materials have the advantages of high immobilization efficiency, low production cost and convenient operation, and can immobilize fissile elements and other radioactive substances in the mineral lattice or adsorb them in the internal structure of the mineral framework through ion exchange, chemical bonding and adsorption, thereby effectively binding the radioactive substances. Sodalite (Na8Al6Si6O 24 Cl2) is a solidification radioactive waste salt mineral material with excellent properties such as chemical stability, thermal stability, irradiation stability, acid stability and mechanical strength, and its stable crystal structure can simultaneously embed target nuclides (cations) and chlorine elements (anions) in its framework structure, thereby achieving targeted and precise efficient solidification of radioactive waste salt.

[0022] The present application uses silicon source, aluminum source, sodium source and chlorine source (such as silicon dioxide, sodium metaaluminate, sodium chloride, etc., the stoichiometric ratio of the three is 6:6:2 under the selected materials, and the reaction formula is ; and under other choices, those skilled in the art can adjust according to the type of raw materials and the valence state of ions, for example ) as raw materials, using the characteristics of uniformity and high dispersion of aqueous solution medium, a high-efficiency integrated treatment method for simultaneously adsorbing and immobilizing radioactive nuclides without high-temperature treatment is developed under low temperature and low pressure conditions in a sealed container. The present application synthesizes sodalite at a lower temperature and simultaneously solidifies radioactive waste salt in situ, and in order to expand the application scenarios of sodalite, it is applied in aqueous solution medium, molten salt medium and solid salt medium, not only for adsorption and solidification of radioactive nuclides, but also for adsorption of other common heavy metal harmful elements in the environment medium.

[0023] The mechanism of action of the sodalite-based solidified material involved in this invention can be flexibly adjusted based on different practical conditions or needs. Firstly, sodalite synthesized under optimized hydrothermal conditions can itself be used as an adsorbent to adsorb radioactive waste salts or other harmful metal elements in solution or molten salt environments. Secondly, the hydrothermal synthesis route for sodalite can be utilized, using waste salts containing radioactive nuclides as raw materials to synthesize a sodalite-type solidified body while simultaneously solidifying the radioactive nuclides. Because during the in-situ synthesis and simultaneous solidification process, the target nuclide ions undergo lattice solidification, adsorption, chemical coordination, and ion exchange, causing fragmented elements and chlorine in the waste salt to be embedded in the artificial rock framework, lattice, or adsorbed inside or outside the structure, its effect is superior to adsorption-based solidification.

[0024] Specifically, taking Cs, Sr, Ba, and Ce as examples, the evolutionary process of sodalite cage structure formation during precursor interface reconstruction is as follows: Under hydrothermal synthesis parameters, Si, O, and Al combine to form the unique β-cage structure of sodalite. The solidification mechanism of sodalite on Cs, Sr, Ba, and Ce originates from the specific coordination effect and lattice compatibility between its cubic cage structure and multiple nuclides. In multi-element coexistence systems, alkali metal Cs... + By occupying the cubic coordination site at the center of the sodalite β-cage through ion exchange, it bonds with the oxygen atoms of the cage wall in an octetal coordination manner (coordination number 8.2 ± 0.3, bond length 2.95 Å). Its 0.167 nm ionic radius and the size fit between the cage cavity diameter (0.66 nm) result in a solidification efficiency of 98.7%. Alkali earth metal Sr... 2+ Ba 2+ It then incorporates a six-coordinated aluminosilicate framework to form [SrO6]. 4- [BaO6] 4- Coordination units, when introduced in excess, cause lattice parameter expansion, which is enhanced by lattice energy matching to improve structural stability; lanthanides Ce 3+ [CeO8] is formed at the double six-membered ring connection site by utilizing the strong coordination ability of the 4f electron shell. 13- The twelve-coordinate structure, with the synergistic effect of covalent and ionic bonds, increases its leaching activation energy by 30% compared to the bulk phase. Four nuclides are leached via ion exchange (Cs... + ), lattice expansion (Sr) 2+ Ba 2+ Coordination chelation (Ce) 3+ The synergistic effect of the cage-like spatial confinement creates a triple solidification barrier at the intragranular (cage cavity coordination), grain boundary (interfacial chemistry), and macroscopic (dense grain boundary) levels, ultimately achieving a normalized leaching rate (28 days) of <5×10⁻⁶. -4 g / (cm 2 ·d) Efficient fixation.

[0025] In summary, especially in the process of synthesizing sodalite, such as Ce 3+ , Ce 4+ may replace Al 3+ or Si 4+ in the sodalite framework structure, and then enter the sodalite framework structure to achieve the goal of efficient immobilization. In the adsorption and immobilization process in aqueous solution medium and molten salt medium, the target nuclides are mainly immobilized by ion exchange, adsorption and chemical coordination. In the above application scenarios, sodalite realizes lattice immobilization of different nuclides through targeted capture and isomorphous replacement, thereby converting waste salt into stable and harmless solid form, effectively reducing the risk of migration, diffusion and leakage of radioactive substances, and being conducive to long-term geological storage. The method can better connect the application in the treatment of spent fuel wet and dry reprocessing waste, provide a new technical approach for the safe treatment of radioactive waste salt, and realize the closed-loop sustainable development of nuclear energy.

[0026] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0027] The present application provides a method for synthesizing sodalite by hydrothermal method and immobilizing and stabilizing harmful metal nuclides. The method not only has good compatibility with fission fragment elements and chlorine elements, but also can effectively encapsulate other harmful metal elements containing various harmful metal nuclides in radioactive waste salt to prevent their release and migration. Compared with existing glass, ceramic and glass immobilization technologies, the method can realize efficient synthesis of sodalite at a lower temperature and simultaneously immobilize harmful metal nuclides, has a wide range of application scenarios, and is simple to operate without the need for additional binder or secondary glass coating, secondary pollution and environmental friendliness.

[0028] The present application provides an application of a method for synthesizing sodalite by hydrothermal method and immobilizing and stabilizing harmful metal nuclides, i.e. a highly efficient, low-energy, economical and highly safe super-stable inorganic solid acid-resistant material, which captures and immobilizes radioactive nuclides through an integrated treatment method, has wide industrial applicability, and can be applied not only to nuclear power plants, nuclear fuel reprocessing plants and other scenarios where radioactive waste salt is generated, but also to adsorption of harmful metal nuclides in environmental media. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 X-ray diffraction (XRD) spectrum of the sodalite synthesized under the preferred conditions

[0030] Figure 2 Fourier transform infrared (FTIR) spectrum of the sodalite synthesized under the preferred conditions

[0031] Figure 3Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) spectrum of the sodalite solidified body synthesized under the preferred conditions;

[0032] Figure 4 Thermogravimetric (TG) spectrum of the sodalite solidified body;

[0033] Figure 5 XRD spectrum after soaking in aqueous solution of different pH values;

[0034] Figure 6 Normalized leaching rate graph;

[0035] Figure 7 Graphs related to the adsorption effect of sodalite on target nuclides in aqueous solution, molten salt and solid salt media. DETAILED DESCRIPTION

[0036] The present application will be further described by way of examples, but the present application is not limited to the scope of the examples. The experimental methods in the following examples are not specified, and are selected according to conventional methods and conditions, or according to the instructions of the products.

[0037] Example 1

[0038] This example uses in-situ solidification to solidify radioactive waste salt, and the steps are as follows:

[0039] (1) The raw materials such as silicon dioxide, sodium chloride and sodium metaaluminate are dried in a forced air drying oven to remove the water therein;

[0040] (2) The silicon dioxide is passed through a 50-200 mesh screen to obtain silicon dioxide powder;

[0041] (3) The raw material components of the radioactive waste salt are dried in a forced air drying oven to remove the water therein;

[0042] (4) Synthesis of sodalite: the required amount of silicon dioxide, sodium metaaluminate and sodium chloride are weighed according to the stoichiometric ratio of 6:6:2, and the three are mixed uniformly in a ball mill; the molar ratio of sodium hydroxide to silicon dioxide is 6:1;

[0043] (5) mixed with water at a solid-liquid ratio of 1:10 to obtain a pre-reaction solution; 1 wt.% of triethanolamine was added and stirred at 200 rpm for 1 h to perform a hydrothermal reaction in an alkaline environment; a sealed container containing the sodalite raw material was placed in a muffle furnace, heated to a target temperature of 160°C at a rate of 5°C / min, and then kept at the target temperature for 24 h; after the reaction was completed, the corresponding sodalite solidified body was obtained after natural cooling to room temperature.

[0044] In this example, sodalite was synthesized in situ and radioactive waste salt was simultaneously solidified. The main components of the simulated radioactive waste salt are shown in Table 1. The addition amount was calculated based on the waste salt containment rate of 15 wt.% after solidification.

[0045] Table 1: Composition of Radioactive Waste Salt

[0046]

[0047] The sodalite solidified body was dried at 80°C for 8 h, ground, and sieved through a 100-mesh sieve to obtain a solidified body powder, which was then subjected to various performance tests.

[0048] Material characterization analysis was performed on the solidified body, and the test analysis methods are as follows:

[0049] 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; simultaneous thermal analyzer (HITACHI STA200) was used to determine the thermal stability of the sample, which was heated from room temperature to 900°C at a rate of 5°C / min under an Ar atmosphere; water immersion experiments were performed on the sodalite with different pH aqueous solutions to test its acid and alkali resistance.

[0050] 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 sieve. 2 g of solidified body powder was taken into a reaction kettle, 20 mL of deionized water was added, and the kettle was kept at a constant temperature of 90°C. The leaching solution was taken out 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.

[0051] Example 2

[0052] Adsorption and solidification application in high-level radioactive waste liquid:

[0053] The embodiment is basically the same as embodiment 1, and the only difference is that no radioactive waste salt is added in the preparation process of sodalite, and the sodalite obtained by the reaction is used as an adsorbent to be applied in the adsorption and solidification of a high-radioactivity aqueous solution.

[0054] In an aqueous solution medium (the single concentration of Cs, Sr, Ba and Ce is 250 mg / L), 50 mg of the synthesized sodalite is mixed with 25 mL of the solution, and the solution adsorption is carried out at room temperature and under the initial pH condition, and the oscillation is 200 rpm for 60 min. The adsorption efficiency is calculated to indicate the solidification effect.

[0055] Embodiment 3

[0056] Adsorption and solidification application in molten salt:

[0057] In this embodiment, the sodalite prepared without adding radioactive waste salt in embodiment 2 is used as an adsorbent to be applied in the adsorption and fixation of target nuclides in a molten salt medium.

[0058] In a LiCl-KCl or LiCl-Li2O molten salt medium, 1 g of the synthesized sodalite is mixed with 5 g of LiCl-KCl salt (molar ratio 0.592:0.408) (containing 8 wt.% of radioactive nuclides, and Cs, Sr, Ba and Ce account for 2 wt.% respectively) for 30 min, and the molten salt adsorption is carried out in a high-temperature furnace at 700℃ for 60 min.

[0059] Embodiment 4

[0060] Adsorption and solidification application in solid salt:

[0061] In this embodiment, the sodalite prepared without adding radioactive waste salt in embodiment 2 is used as an adsorbent to be applied in a solid salt medium, and the adsorbent is mixed with the salt to adsorb and fix the target nuclides.

[0062] In a LiCl-KCl or LiCl-Li2O solid salt medium, 1 g of the synthesized sodalite is mixed with 5 g of LiCl-KCl salt (molar ratio 0.592:0.408; containing 8 wt.% of radioactive nuclides, and Cs, Sr, Ba and Ce account for 2 wt.% respectively) for 30 min, and the solid salt adsorption is carried out in a high-temperature furnace at 300℃ for 60 min.

[0063] Embodiment 5

[0064] The XRD pattern of the sodalite synthesized in embodiment 2 is shown in Figure 1 , and the infrared spectrum is shown in Figure 2 . Figure 1 , and the results of Figure 2 prove that the skeleton structure of the target sodalite is obtained, and it is indicated that the hydrothermal method of the present application can successfully synthesize sodalite.

[0065] The SEM-EDS spectrum of the sodalite solidified body is shown in Figure 3 The SEM characterization result shows that the sodalite solidified body synthesized and simultaneously solidified the radioactive waste salt presents a cubic block shape in a state of agglomeration, and the surface is flat and defect-free. The EDS analysis result shows that the signal intensity of Cs, Sr, Ba, Ce and other elements on the surface of the sodalite solidified body is uniformly distributed, which confirms that the above four kinds of fissile elements have been effectively solidified in the sodalite solidified body.

[0066] 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 surface or internal adsorbed water and bound water, 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.

[0067] The test results of the sodalite solidified body after soaking in aqueous solutions of different pH values are shown in Figure 5 Figure 5 It shows that the phase does not change, which proves that the sodalite mineral substrate has excellent acid and alkali resistance.

[0068] The normalized leaching rate test results of the sodalite solidified body are shown in Figure 6 The normalized leaching rate shows that the normalized leaching rate of the four kinds of fissile elements is less than 5×10 -4 g / (cm 2 / d) after 28 days, indicating that the sodalite has effectively solidified the fissile elements in the waste salt.

[0069] Figure 7 The sodalite was synthesized without adding radioactive waste salt as in Example 2, and was used as an adsorbent to adsorb target nuclides in aqueous solution, molten salt and solid salt media.

[0070] Example 6

[0071] In this example, the sodalite synthesized without adding radioactive waste salt as in Example 2 was used as an adsorbent to adsorb excess metal elements in aqueous solution medium.

[0072] In the aqueous solution medium (the initial concentration of Ag is 250 mg / L), 50 mg of synthesized sodalite was mixed with 25 mL of solution, and the solution adsorption was carried out at room temperature and initial pH conditions, with 200 rpm shaking for 60 min. The adsorption efficiency was calculated to illustrate the solidification effect. The results show that the Ag + adsorption capacity is 80 mg / g.

[0073] ​The preferred embodiments of the present application have been described above in detail. It should be understood that modifications and variations to the present application can be affected by those skilled in the art without departing from the scope of the application. Accordingly, it is intended that all of the subject matter of the above description and the claims be interpreted to encompass all such modifications and changes.

Claims

1. A method for synthesizing sodalite and immobilizing a hazardous metal isotope by a hydrothermal method, characterized by, The method comprises the following steps: According to the sodalite XAl6Si6O 24 The element components of Y are prepared as silicon source, aluminum source, sodium source and chlorine source. The raw materials in stoichiometric ratio are treated by ball milling, mixed with water in a certain solid-liquid ratio to obtain a pre-reaction liquid. A template agent is added and mixed, and then a hydrothermal reaction is carried out in an alkaline environment to obtain sodalite. X represents a cation, Y represents an anion; the element type of X is sodium or a combination of sodium and a metal element, the metal element being at least one of Cs, Sr, Ba, Ce, Ag, Cd, Cr, Ni; the element type of Y is chlorine or a combination of chlorine and an inorganic anion, the inorganic anion being at least one of a hydroxyl ion, a halogen anion, a phosphate ion, and a sulfate ion; At least one of X and Y contains a radionuclide of radioactive waste salt, which solidifies the radionuclide in situ; The silicon source is silicon dioxide; the aluminum source is one of aluminum hydroxide, aluminum oxide, sodium metaaluminate, aluminum chloride, and a mixture of aluminum hydroxide; the sodium source is at least one of sodium metaaluminate, sodium chloride, and sodium hydroxide; the chlorine source is sodium chloride; The solid-liquid ratio of the mixture with water is 1:5-30; The template agent is triethanolamine, and the addition amount of the template agent is 1 wt.%-5 wt.% of the pre-reaction liquid; The pH of the hydrothermal reaction is 7 2. The method for synthesizing sodalite and immobilizing hazardous metal nuclides by hydrothermal synthesis according to claim 1, characterized in that: The ball-to-material ratio of the ball milling treatment is 3-20:1, and the ball milling time is 0.5-6 h.

3. The method for synthesizing sodalite and solidifying and stabilizing a hazardous metal nuclide by a hydrothermal method according to claim 1, characterized by: The ball milling treatment includes dry milling or wet milling; under the condition of wet milling, the dispersion medium is selected from at least one of water, ethanol, and acetone.

4. The method for synthesizing sodalite and immobilizing hazardous metal nuclides by hydrothermal synthesis according to claim 1, characterized in that: The stirring rate of the mixing is 100-600 rpm, and the stirring time is 1-6 h.

5. Use of a method according to any one of claims 1 to 4 for the synthesis of sodalite and the immobilization of hazardous metal nuclides by hydrothermal synthesis. The method is used for solidifying and stabilizing radionuclides and other common heavy metal harmful elements.

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