Method for solidifying silver iodide, ceramic solidified body and use

Abstract

This application discloses a method for curing silver iodide, a ceramic curing body, and its applications. The method for curing silver iodide provided in this application, considering the widespread use of silver iodide in the treatment of radioactive iodine, directly uses silver iodide as a raw material, mixes it with barium source salt and sodium iodide salt raw materials, and prepares a ceramic curing body through steps such as dry pressing, reaction, and sintering, thereby curing radioactive iodine within the ceramic curing body. This method is simple, low-cost, and highly applicable, and can cure silver iodide with a content of 4.44–35.40 wt%. Compared with traditional iodine curing methods, it is more practical and can be applied to the disposal of radioactive iodine waste.

Description

Technical Field

[0001] This application relates to the field of radioactive waste treatment technology, specifically to a method for solidifying silver iodide, a ceramic solidified body, and its application. Background Technology

[0002] Nuclear energy, as a highly efficient energy source, has been applied in many fields. However, the fission process of nuclear fuel generates various radioactive wastes, and the safe disposal of these radioactive wastes is crucial for the sustainable development of nuclear energy.

[0003] Radioactive iodine is a major radioactive waste product generated from the fission of nuclear power plant fuel. Furthermore, iodine is highly volatile. The main hazards of radioactive iodine include its high toxicity, volatility, easy diffusion, and easy absorption by the human body, particularly its accumulation in the thyroid gland, causing radiation damage and posing a serious threat to human health.

[0004] Currently, the generally accepted method for effectively treating and disposing of radioactive iodine waste is to effectively adsorb it to transform it into a stable solid, followed by further sintering to form a stable solidified body. Commonly used iodine adsorbents include silver-coated silica gel or silver-coated zeolite. Silver-coated zeolite has high iodine adsorption efficiency and wide application; the radioactive iodine adsorbed on silver-coated zeolite mainly exists in the form of silver iodide (AgI). AgI has a melting point of 558℃ and a boiling point of 1506℃, exhibiting poor thermal stability and prone to pyrolysis at high temperatures. Therefore, silver iodide cannot be directly used as a solidified form of radioactive iodine and requires further treatment to transform it into a stable solidified body that can be stored for a long time before deep geological burial to avoid polluting the ecological environment.

[0005] Given the high hazard of radioactive silver iodide (AgI), numerous measures have been implemented to solidify iodine adsorbents containing silver iodide, primarily using methods such as cement or glass solidification. While these methods can mitigate the radioactive iodine to some extent, the resulting solidified bodies still suffer from poor stability, susceptibility to secondary pollution, and low levels of radioactive iodine. Summary of the Invention

[0006] The purpose of this application is to solve the problems of poor stability, easy secondary pollution, and low radioactive iodine content of silver iodide curing bodies prepared in existing related technologies, and to provide a method for curing silver iodide, a ceramic curing body, and its application.

[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0008] In a first aspect, this application provides a method for curing silver iodide, comprising the following steps:

[0009] Silver iodide, barium source salt and sodium iodide salt are mixed and then dry-pressed to obtain the first rough blank;

[0010] The first rough embryo was subjected to an in-situ reaction at 400–600 °C to obtain the second rough embryo;

[0011] The second rough blank is sintered and densified.

[0012] In one optional embodiment, the molar ratio of the barium source salt, the silver iodide, and the sodium iodide salt, calculated based on barium, silver, and sodium elements, is 2:x:(1-x), where 0.1 ≤ x ≤ 0.9. Exemplarily, the value of x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0013] In one optional embodiment, the barium source salt includes at least one of barium carbonate, barium nitrate, anhydrous barium hydroxide, barium hydroxide octahydrate, and barium sulfate;

[0014] And / or, the sodium iodide salt includes at least one of sodium iodate, sodium periodate, and sodium iodide.

[0015] In an optional embodiment, the in-situ reaction conditions further include: a heating rate of 2–10 °C / min and an in-situ reaction time of 1–10 h. For example, the first rough preform is placed in a muffle furnace and heated to 400–600 °C at a heating rate of 2–10 °C / min, held at that temperature for 1–10 h to complete the in-situ reaction and generate Ba2(Ag) x Na 1-x IO6.

[0016] Preferably, the reaction equation for the in-situ reaction is at least one of the following equations:

[0017] 2Ba(OH)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 2H2O;

[0018] 2BaCO3+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 2CO2;

[0019] 2Ba(NO3)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 4NO2;

[0020] 2Ba(OH)2•8H2O + xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x I 1-x IO6+ 18H2O;

[0021] 2BaSO4+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x I 1-x IO6+ 2SO3;

[0022] 2Ba(OH)2+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x I 1-x IO6+ 2H2O;

[0023] 2BaCO3+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x I 1-x IO6+ 2CO2;

[0024] 2Ba(NO3)2+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x I 1-x IO6+ 4NO2;

[0025] 2Ba(OH)2•8H2O + xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x I 1-x IO6+ 18H2O;

[0026] 2BaSO4+ xAgI + (1-x) NaIO3+ (0.5+1.5x)2O2 = Ba2Ag x I 1-x IO6+ 2SO3;

[0027] 2Ba(OH)2+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x I 1-x IO6+ 2H2O;

[0028] 2BaCO3+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x I 1-xIO6+ 2CO2;

[0029] 2Ba(NO3)2+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 2NO2;

[0030] 2Ba(OH)2•8H2O + xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 18H2O;

[0031] 2BaSO4+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 2SO3.

[0032] In one optional embodiment, the sintering densification conditions include: a heating rate of 2–10 °C / min, a sintering temperature of 800–1100 °C, and a sintering time of 1–10 h. For example, after the in-situ reaction is completed, the temperature is further increased to 800–1100 °C at a heating rate of 2–10 °C / min, held for 1–10 h to complete sintering densification, and then cooled to room temperature to obtain solidified silver iodide Ba2(Ag) x Na 1-x )IO6 ceramic solidified body, wherein x is 0.1~0.9.

[0033] In one optional embodiment, the dry pressing conditions include a dry pressing pressure of 10–80 MPa.

[0034] In one optional embodiment, the silver iodide, the barium source salt, and the sodium iodide salt are all powders with a particle size of 10 nm to 100 μm. When mixing the silver iodide, barium source salt, and sodium iodide salt, the raw material powders can be ground and mixed uniformly to obtain a mixed raw material powder. The grinding and mixing method can be a commonly used method in the field, such as at least one of mortar and pestle grinding, planetary ball milling, or roller ball milling.

[0035] Secondly, this application provides a ceramic solidified body prepared by the above method, wherein the chemical formula of the ceramic solidified body is Ba2(Ag) x Na 1-xIO6, possessing a periodate double perovskite structure, wherein 0.1 ≤ x ≤ 0.9. For example, the value of x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. The pyrolysis temperature of the solidified ceramic body is 750℃~1000℃.

[0036] Thirdly, this application provides the application of the above-mentioned method in the treatment of radioactive iodine waste.

[0037] Fourthly, this application provides a method for treating radioactive iodine waste, comprising the following steps:

[0038] Radioactive iodine waste is adsorbed using a silver-containing adsorbent to convert the radioactive iodine waste into radioactive silver iodide.

[0039] The radioactive silver iodide was cured using the method described above.

[0040] In an alternative embodiment, the silver-containing adsorbent may be, for example, silver-coated silica gel particles and / or silver-coated zeolite.

[0041] In one alternative embodiment, after solidifying the radioactive silver iodide, a further step of treating the resulting solidified ceramic body may be included. For example, the resulting solidified ceramic body may be subjected to deep geological burial.

[0042] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0043] The method for solidifying silver iodide provided in this application, taking into account the widespread application of silver iodide (AgI) in the treatment of radioactive iodine, directly uses silver iodide as a raw material, mixes it with barium source salt and sodium iodide salt raw materials, and prepares a ceramic solidified body through steps such as dry pressing, reaction, and sintering, thereby solidifying radioactive iodine in the ceramic solidified body. This method is simple, low-cost, and highly applicable, and can solidify silver iodide with a content of 4.44~35.40 wt%. Compared with traditional iodine solidification methods, it is more practical and can be applied to the disposal of radioactive iodine waste.

[0044] Specifically, the method of this application can dissolve Ag in radioactive silver iodide (AgI) to the Na position in Ba2NaIO6, and replenish the iodine position in the matrix with the radioactive iodine (I) adsorbed in AgI, forming a periodate double perovskite structure Ba2(Ag) x Na 1-x An IO6 ceramic solidification body was developed to effectively solidify radioactive iodine. This ceramic solidification body exhibits stable chemical properties and good thermal stability, meeting the requirements for long-term deep geological burial. Therefore, it solves the problem of solidifying radioactive iodine in nuclear waste, demonstrating significant practical importance and promising application prospects.

[0045] Furthermore, this method fully utilizes the characteristics of silver iodide exothermic and reactive properties during heating, enabling in-situ reaction and densification at lower temperatures, effectively reducing the volatilization of iodine during sintering. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 The Ba2(Ag) obtained by reaction sintering when x=0.1 in the embodiments of this application is... 0.1 Na 0.9 X-ray diffraction pattern of IO6 ceramic solidified body;

[0048] Figure 2 The Ba2(Ag) obtained by reaction sintering when x=0.1 in the embodiments of this application is... 0.1 Na 0.9 Scanning electron microscope image of IO6 ceramic solidified body. Detailed Implementation

[0049] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0051] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0052] Example 1

[0053] Curing silver iodide is performed using the following method:

[0054] (1) Raw material mixing: Pour the raw material powders of silver iodide, anhydrous barium hydroxide and sodium periodate into a grinding mortar and grind until they are evenly mixed to obtain a uniform raw material powder; wherein, based on barium, silver and sodium elements, the molar ratio of anhydrous barium hydroxide, silver iodide and sodium periodate is 2:0.1:0.9; the particle size of anhydrous barium hydroxide, silver iodide and sodium periodate is 100 nm;

[0055] (2) Dry pressing: The mixed raw material powder is dry pressed under a pressure of 10MPa to obtain a rough blank with a certain shape;

[0056] (3) In-situ reaction: The rough embryo obtained in step (2) is placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min. The temperature is held for 1 hour to complete the in-situ reaction and generate Ba2(Ag) 0.1 Na 0.9 )IO6; where the in-situ reaction equation is:

[0057] 2Ba(OH)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO⁶⁺ ⇌ 2H₂O, x=0.1;

[0058] (4) Sintering: After the in-situ reaction in step (3) is completed, the temperature is increased to 1100℃ at a rate of 5℃ / min and held for 5h to complete the sintering densification. Then, it is cooled to room temperature to obtain Ba2(Ag) solidified silver iodide. 0.1 Na 0.9 The IO6 ceramic cured body contains 4.44 wt% silver iodide and has a pyrolysis temperature of approximately 1000℃.

[0059] X-ray diffraction analysis was performed on the ceramic solidified body prepared in this embodiment, and the results are as follows: Figure 1 As shown, from Figure 1 As can be seen from the data, the solidified ceramic body has a periodate double perovskite crystal structure and exhibits good stability.

[0060] The ceramic solidified body prepared in this embodiment was observed by scanning electron microscopy, and the results are as follows: Figure 2 As shown, from Figure 2 As can be seen, the microstructure of the ceramic solidified body is relatively dense, exhibiting good sintering activity.

[0061] Example 2

[0062] Curing silver iodide is performed using the following method:

[0063] (1) Raw material mixing: Pour the raw material powders of silver iodide, anhydrous barium hydroxide and sodium periodate into a grinding jar and mix them evenly using a planetary ball mill to obtain a uniform raw material powder; wherein, based on barium, silver and sodium elements, the molar ratio of anhydrous barium hydroxide, silver iodide and sodium periodate is 2:0.5:0.5; the particle size of anhydrous barium hydroxide, silver iodide and sodium periodate is 10 nm;

[0064] (2) Dry pressing: The mixed raw material powder is dry pressed under a pressure of 50MPa to obtain a rough blank with a certain shape;

[0065] (3) In-situ reaction: The rough embryo obtained in step (2) is placed in a muffle furnace and heated to 500°C at a heating rate of 10°C / min. The temperature is held for 3 hours to complete the in-situ reaction and generate Ba2(Ag) 0.5 Na 0.5 )IO6; where the in-situ reaction equation is:

[0066] 2Ba(OH)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO⁶⁺ ⇌ 2H₂O, x=0.5;

[0067] (4) Sintering: After the in-situ reaction in step (3) is completed, the temperature is increased to 900℃ at a rate of 10℃ / min and held for 1 hour to complete the sintering densification. Then, the temperature is lowered to room temperature to obtain Ba2(Ag) 0.5 Na 0.5 The IO6 ceramic cured body contains 20.85 wt% silver iodide and has a pyrolysis temperature of approximately 880 °C.

[0068] Example 3

[0069] Curing silver iodide is performed using the following method:

[0070] (1) Raw material mixing: Pour the raw material powders of silver iodide, anhydrous barium hydroxide and sodium periodate into a grinding jar and mix them evenly using a roller mill to obtain a uniform raw material powder; wherein, based on barium, silver and sodium elements, the molar ratio of anhydrous barium hydroxide, silver iodide and sodium periodate is 2:0.9:0.1; the particle size of anhydrous barium hydroxide, silver iodide and sodium periodate is 100μm;

[0071] (2) Dry pressing: The mixed raw material powder is dry pressed under a pressure of 80MPa to obtain a rough blank with a certain shape;

[0072] (3) In-situ reaction: The crude preform obtained in step (2) is placed in a muffle furnace and heated to 400℃ at a heating rate of 2℃ / min. The temperature is held for 10h to complete the in-situ reaction and generate Ba2(Ag) 0.9 Na 0.1 )IO6; where the in-situ reaction equation is:

[0073] 2Ba(OH)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO⁶⁺ ⇌ 2H₂O, x = 0.9;

[0074] (4) Sintering: After the in-situ reaction in step (3) is completed, the temperature is increased to 800℃ at a rate of 2℃ / min and held for 10h to complete the sintering densification. Then, the temperature is lowered to room temperature to obtain Ba2(Ag) 0.9 Na 0.1 The IO6 ceramic cured body contains 35.40 wt% silver iodide and has a pyrolysis temperature of approximately 750 °C.

[0075] Example 4

[0076] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium carbonate; the molar ratio of barium carbonate, silver iodide, and sodium periodate is 2:0.2:0.8 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0077] 2BaCO3+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 2CO2, x=0.2.

[0078] The Ba2(Ag) prepared in this embodiment 0.2 Na 0.8 The content of silver iodide in the cured IO6 ceramic solidified body is 8.74 wt%, and the pyrolysis temperature of the ceramic solidified body is about 970℃.

[0079] Example 5

[0080] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium nitrate; the molar ratio of barium nitrate, silver iodide, and sodium periodate, calculated by barium, silver, and sodium elements, is 2:0.3:0.7; the reaction equation for the in-situ reaction in step (3) is:

[0081] 2Ba(NO3)2+ xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6 + 4NO2, x = 0.3.

[0082] The Ba2(Ag) prepared in this embodiment 0.3 Na 0.7 The mass fraction of silver iodide in the IO6 ceramic solidified body is 12.90 wt%, and the pyrolysis temperature of the ceramic solidified body is approximately 940 °C.

[0083] Example 6

[0084] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium sulfate; the molar ratio of barium sulfate, silver iodide, and sodium periodate is 2:0.4:0.6 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0085] 2BaSO4+ xAgI + (1-x) NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 2SO3, x=0.4.

[0086] The Ba2(Ag) prepared in this embodiment 0.4 Na 0.6 The mass fraction of silver iodide in the IO6 ceramic cured body is 16.94 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 910 °C.

[0087] Example 7

[0088] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium hydroxide octahydrate; the molar ratio of barium hydroxide octahydrate, silver iodide, and sodium periodate, calculated by barium, silver, and sodium elements, is 2:0.6:0.4; the reaction equation for the in-situ reaction in step (3) is:

[0089] 2Ba(OH)2•8H2O + xAgI + (1-x)NaIO4+ 2xO2 = Ba2Ag x Na 1-x IO6+ 18H2O, where x=0.6.

[0090] The Ba2(Ag) prepared in this embodiment 0.6 Na 0.4 The mass fraction of silver iodide in the IO6 ceramic cured body is 24.65 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 840 °C.

[0091] Example 8

[0092] The method for curing silver iodide according to Example 1 differs in that the sodium iodide salt used in step (1) of this example is sodium iodate; the molar ratio of anhydrous barium hydroxide, silver iodide, and sodium iodate, calculated by barium, silver, and sodium elements, is 2:0.7:0.3; the reaction equation for the in-situ reaction in step (3) is:

[0093] 2Ba(OH)2+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x Na 1-x IO6+ 2H2O, where x=0.7.

[0094] The Ba2(Ag) prepared in this embodiment 0.7 Na 0.3 The mass fraction of silver iodide in the IO6 ceramic cured body is 28.34 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 810℃.

[0095] Example 9

[0096] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium carbonate, and the sodium iodide salt is sodium iodate; the molar ratio of barium carbonate, silver iodide, and sodium iodate is 2:0.8:0.2 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0097] 2BaCO3+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x Na 1-x IO6+ 2CO2, where x=0.8.

[0098] The Ba2(Ag) prepared in this embodiment 0.8 Na 0.2 The mass fraction of silver iodide in the IO6 ceramic cured body is 31.92 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 780℃.

[0099] Example 10

[0100] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium nitrate, and the sodium iodide salt is sodium iodate; the molar ratio of barium nitrate, silver iodide, and sodium iodate is 2:0.2:0.8 based on the elements of barium, silver, and sodium; the reaction equation for the in-situ reaction in step (3) is:

[0101] 2Ba(NO3)2+ xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x Na 1-x IO6 + 4NO2, where x = 0.2.

[0102] The Ba2(Ag) prepared in this embodiment 0.2 Na 0.8 The mass fraction of silver iodide in the IO6 ceramic cured body is 8.74 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 970 °C.

[0103] Example 11

[0104] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium hydroxide octahydrate, and the sodium iodide salt is sodium iodate; the molar ratio of barium hydroxide octahydrate, silver iodide, and sodium iodate, calculated by barium, silver, and sodium elements, is 2:0.3:0.7; the reaction equation for the in-situ reaction in step (3) is:

[0105] 2Ba(OH)2•8H2O + xAgI + (1-x)NaIO3+ (0.5+1.5x)O2 = Ba2Ag x Na 1-x IO6+ 18H2O, where x=0.3.

[0106] The Ba2(Ag) prepared in this embodiment 0.3 Na 0.7 The mass fraction of silver iodide in the IO6 ceramic solidified body is 12.90 wt%, and the pyrolysis temperature of the ceramic solidified body is approximately 940 °C.

[0107] Example 12

[0108] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium sulfate, and the sodium iodide salt is sodium iodate; the molar ratio of barium sulfate, silver iodide, and sodium iodate is 2:0.4:0.6 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0109] 2BaSO4+ xAgI + (1-x) NaIO3+ (0.5+1.5x)2O2 = Ba2Ag x Na 1-x IO6+ 2SO3, where x=0.4.

[0110] The Ba2(Ag) prepared in this embodiment 0.4 Na 0.6The mass fraction of silver iodide in the IO6 ceramic cured body is 16.94 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 910 °C.

[0111] Example 13

[0112] The method for curing silver iodide according to Example 1 differs in that the sodium iodide salt used in step (1) of this example is sodium iodide; the molar ratio of anhydrous barium hydroxide, silver iodide, and sodium iodide, calculated by barium, silver, and sodium elements, is 2:0.5:0.5; the reaction equation for the in-situ reaction in step (3) is:

[0113] 2Ba(OH)2+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 2H2O, where x=0.5.

[0114] The Ba2(Ag) prepared in this embodiment 0.5 Na 0.5 The mass fraction of silver iodide in the IO6 ceramic cured body is 20.85 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 880℃.

[0115] Example 14

[0116] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium carbonate, and the sodium iodide salt is sodium iodide; the molar ratio of barium carbonate, silver iodide, and sodium iodide is 2:0.6:0.4 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0117] 2BaCO3+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 2CO2, where x=0.6.

[0118] The Ba2(Ag) prepared in this embodiment 0.6 Na 0.4 The mass fraction of silver iodide in the IO6 ceramic cured body is 24.65 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 840 °C.

[0119] Example 15

[0120] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium nitrate, and the sodium iodide salt is sodium iodide; the molar ratio of barium nitrate, silver iodide, and sodium iodide, calculated by barium, silver, and sodium elements, is 2:0.7:0.3; the reaction equation for the in-situ reaction in step (3) is:

[0121] 2Ba(NO3)2+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6 + 2NO2, where x = 0.7.

[0122] The Ba2(Ag) prepared in this embodiment 0.7 Na 0.3 The mass fraction of silver iodide in the IO6 ceramic cured body is 28.34 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 810℃.

[0123] Example 16

[0124] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium hydroxide octahydrate, and the sodium iodide salt is sodium iodide; the molar ratio of barium hydroxide octahydrate, silver iodide, and sodium iodide, calculated by barium, silver, and sodium elements, is 2:0.8:0.2; the reaction equation for the in-situ reaction in step (3) is:

[0125] 2Ba(OH)2•8H2O + xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 18H2O, where x=0.8.

[0126] The Ba2(Ag) prepared in this embodiment 0.8 Na 0.2 The mass fraction of silver iodide in the IO6 ceramic cured body is 31.92 wt%, and the pyrolysis temperature of the ceramic cured body is approximately 780℃.

[0127] Example 17

[0128] The method for curing silver iodide according to Example 1 differs in that the barium source salt used in step (1) of this example is barium sulfate, and the sodium iodide salt is sodium iodide; the molar ratio of barium sulfate, silver iodide, and sodium iodide is 2:0.9:0.1 based on barium, silver, and sodium elements; the reaction equation for the in-situ reaction in step (3) is:

[0129] 2BaSO4+ xAgI + (1-x)NaI + 2O2 = Ba2Ag x Na 1-x IO6+ 2SO3, where x=0.9.

[0130] The Ba2(Ag) prepared in this embodiment 0.9 Na 0.1 The mass fraction of silver iodide in the IO6 ceramic cured body is 35.40 wt%, and the pyrolysis temperature of the ceramic cured body is about 750℃.

[0131] Ba2Ag prepared by Examples 2-17 x Na 1-x The phase composition and microstructure of the IO6 (x=0.1-0.9) ceramic solidified body are basically the same as those in Example 1. It effectively solidifies radioactive silver iodide, achieving the purpose of ceramic solidification. The ceramic solidified body has stable chemical properties and good thermal stability, which can meet the requirements of long-term deep geological burial.

[0132] Comparative Example 1

[0133] The silver iodide was cured according to the method of Example 1, except that the temperature of the in-situ reaction in step (3) of this embodiment is 300°C.

[0134] The content of silver iodide in the ceramic solidified body prepared in this embodiment is 3.27 wt%, and the pyrolysis temperature of the ceramic solidified body is about 930℃.

[0135] Comparative Example 2

[0136] The silver iodide was cured according to the method of Example 1, except that the temperature of the in-situ reaction in step (3) of this embodiment is 700°C.

[0137] The content of silver iodide in the ceramic solidified body prepared in this embodiment is 2.94 wt%, and the pyrolysis temperature of the ceramic solidified body is about 910℃.

[0138] The above description is merely a preferred embodiment of this application; however, the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and its improved concept, should be covered within the scope of protection of this application.

Claims

1. A method for curing silver iodide, characterized in that, Includes the following steps: Silver iodide, barium source salt and sodium iodide salt are mixed and then dry-pressed to obtain the first rough blank; The first crude embryo was subjected to an in-situ reaction at 400–600 °C to obtain a product containing Ba2(Ag) x Na 1-x The second coarse embryo of IO6; The second rough blank is sintered and densified. The above-mentioned barium source salt is one of barium carbonate, anhydrous barium hydroxide, and barium hydroxide octahydrate; The aforementioned sodium iodate salt is one of sodium iodate, sodium periodate, or sodium iodide; The molar ratio of the above barium source salt, silver iodide, and sodium iodide salt is 2:x:(1-x), where 0.1≤x≤0.

9.

2. The method according to claim 1, characterized in that, The conditions for the in-situ reaction also include: a heating rate of 2–10 °C / min and an in-situ reaction time of 1–10 h.

3. The method according to claim 1, characterized in that, The conditions for sintering densification include: a heating rate of 2–10 °C / min, a sintering temperature of 800–1100 °C, and a sintering time of 1–10 h.

4. The method according to claim 1, characterized in that, The conditions for dry pressing include: a dry pressing pressure of 10–80 MPa.

5. The method according to claim 1, characterized in that, The silver iodide, the barium source salt, and the sodium iodide salt are all powders with a particle size of 10 nm to 100 μm.

6. A ceramic solidified body prepared by the method according to any one of claims 1 to 5, wherein the chemical formula of the ceramic solidified body is Ba2(Ag) x Na 1-x IO6 possesses a periodate double perovskite structure, in which, 0.1≤x≤0.9。 7. The application of the method according to any one of claims 1 to 5 in the treatment of radioactive iodine waste.

8. A method for treating radioactive iodine waste, characterized in that, Includes the following steps: Radioactive iodine waste is adsorbed using a silver-containing adsorbent to convert the radioactive iodine waste into radioactive silver iodide. The radioactive silver iodide is cured using the method described in any one of claims 1 to 5.

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