A solidified palygorskite ceramic body containing radioactive iodine, its preparation method and application

Abstract

This invention belongs to the field of radioactive iodine waste treatment technology, and discloses a palygorskite ceramic solidified body for solidifying radioactive iodine, its preparation method, and its application. The chemical formula of the ceramic solidified body is Mg5Si8O. 20‑X I X The process involves adding palygorskite to a sodium thiosulfate solution and stirring under reflux at 70-90°C. Radioactive silver iodide is then added and heated under stirring. The mixture is dried to obtain palygorskite powder adsorbed with radioactive iodide ions. Deionized water is then added and mixed. The resulting paste-like mixture is subjected to a pressure of 200-300 MPa and sintered at a uniaxial pressure of 500-700 MPa at 150-200°C. After demolding and drying, the mixture is annealed at 600-700°C and allowed to cool naturally. The resulting ceramic solidified body exhibits stable chemical properties, low cost, and can solidify radioactive iodine content ranging from 13-83 wt%, making it suitable for disposing of radioactive iodine waste.

Description

Technical Field

[0001] This invention belongs to the field of materials and radioactive waste treatment technology, and more specifically, relates to a palygorskite ceramic solidified body for solidifying radioactive iodine, its preparation method and application. Background Technology

[0002] Nuclear energy, as a highly efficient and clean energy source, has enormous development potential. However, the operation of nuclear energy facilities inevitably generates radioactive waste, which pollutes the atmosphere, water bodies, and soil, causing serious impacts on the ecological environment and human health. Therefore, it is necessary to solidify radioactive waste to prevent environmental damage. Radioactive iodine is a type of highly radioactive nuclear waste that is particularly difficult to handle. Radioactive iodine has a very long half-life (approximately 1.574 × 10⁻⁶). 7 (year), and is easily converted into radioactive iodine ions (I) - Radioactive iodine dissolves in water in the form of iodine vapor; at the same time, iodine easily accumulates in the thyroid gland of the human body, and its radioactivity can cause cell carcinogenesis, seriously endangering human health. In addition, during the reprocessing of fuel elements, radioactive iodine evaporates in the gaseous form of iodine vapor, and is then collected by silver-coated zeolite material. The radioactive iodine in silver-coated zeolite mainly exists in the form of silver iodide (AgI).

[0003] AgI has a low decomposition temperature, poor thermal stability, and is easily pyrolyzed, generally decomposing within the range of 70–90℃. Secondly, the solubility of silver iodide is 8.3 × 10⁻⁶. -17 Under geological burial conditions, AgI readily undergoes hydrolysis, resulting in the release of radioactive iodide ions (I₂O₃). - Because of the release of radioactive iodine, AgI cannot be directly used as a solidified form of radioactive iodine. It requires further processing to transform it into a stable solidified form that can be stored for extended periods to meet the long-term disposal requirements of radioactive iodine. Furthermore, the high cost of AgI due to its silver content hinders efforts to reduce disposal costs.

[0004] Currently, the main method for treating silver iodide is to solidify it using glass matrices, such as sodalite and phosphate glass. However, these methods suffer from high iodine leaching rates and high economic costs. Therefore, it is necessary to develop new solidification methods and solidification bodies to treat radioactive silver iodide.

[0005] On the other hand, palygorskite is an aquifer chain-like magnesium silicate mineral with an ideal chemical composition of Mg5Si8O. 20(OH)2(H2O)4·4H2O. Due to its special crystal structure and physicochemical properties, such as large specific surface area, high chemical activity, and good thermal stability, palygorskite can form covalent bonds with some adsorption molecules after Si-O-Si oxygen bridge bonds are broken after modification. This gives the mineral excellent adsorption performance and makes it a promising candidate for treating radioactive iodine. Summary of the Invention

[0006] To address the shortcomings of existing technologies for solidifying radioactive silver iodide, the primary objective of this invention is to provide a ceramic solidified body for solidifying radioactive iodide ions. First, palygorskite is modified by adding it to a sodium thiosulfate solution; then, silver iodide is added, and the sodium thiosulfate solution dissolves the silver iodide, allowing the palygorskite to effectively adsorb radioactive iodide ions (I₂O₃) from the solution. - Pallasite (Mg5Si8O3) adsorbed with radioactive iodide ions was obtained. 20-X I X (OH)2(H2O)4·4H2O) can also recover Ag ions dissolved in sodium thiosulfate solution, reducing disposal costs.

[0007] Another objective of this invention is to provide a method for preparing the above-mentioned ceramic solidified body for solidifying radioactive iodine ions. This method prepares a palygorskite ceramic solidified body by cold sintering palygorskite that adsorbs radioactive iodine ions. This method can effectively solidify radioactive iodine ions, and the solidified body has a low leaching rate, stable chemical properties, and can be stored for a long time. This solves the problem of solidifying radioactive iodine in nuclear waste and has good practical significance.

[0008] Another object of the present invention is to provide the application of the above-mentioned ceramic solidified body for solidifying radioactive iodine ions.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A palygorskite ceramic solidified body for solidifying radioactive iodine, the chemical formula of the ceramic solidified body being Mg5Si8O 20- X I X (OH)₂(H₂O)₄·4H₂O, where x is 1~20, is palygorskite Mg₅Si₈O 20(OH)2(H2O)4·4H2O is added to a sodium thiosulfate solution and stirred under reflux at 70–90°C. Radioactive silver iodide is then added and stirred, filtered, and dried to obtain palygorskite powder adsorbed with radioactive iodide ions. This powder is then mixed with deionized water, and the resulting paste mixture is poured into a mold. A pressure of 200–300 MPa is first applied, followed by a uniaxial pressure of 500–700 MPa. The temperature is raised to 150–200°C for cold sintering. After cooling to room temperature, the mixture is demolded and dried. Finally, it is heated to 600–700°C for annealing and allowed to cool naturally to obtain the final product.

[0011] Preferably, the palygorskite has a particle size of 10–100 μm, and the radioactive silver iodide has a particle size of 10–100 μm.

[0012] Preferably, the concentration of the sodium thiosulfate solution is 1-2 mol / L, the mass ratio of palygorskite to sodium thiosulfate in the sodium thiosulfate solution is 1:(2-10), and the molar ratio of radioactive silver iodide to palygorskite is (1-20):1.

[0013] Preferably, the mass ratio of palygorskite powder adsorbing radioactive iodide ions to deionized water is (1-5):1.

[0014] Preferably, the iodine content in the palygorskite ceramic solidified body is 13–83 wt%.

[0015] The method for preparing the palygorskite ceramic solidified body with solidified radioactive iodine includes the following specific steps:

[0016] S1. Paleolithic Mg5Si8O 20 (OH)2(H2O)4·4H2O is added to sodium thiosulfate solution and stirred and refluxed at 70-90℃ to obtain sodium thiosulfate solution containing modified palygorskite.

[0017] S2. Radioactive silver iodide is added to a sodium thiosulfate solution containing modified palygorskite and heated and stirred at 70-90°C. After filtration and drying, palygorskite powder with adsorbed radioactive iodide ions is obtained.

[0018] S3. Add palygorskite powder that adsorbs radioactive iodine ions to deionized water to make a paste mixture. Pour the paste mixture into a mold, apply a pressure of 200-300 MPa, then apply a uniaxial pressure of 500-700 MPa to the mold, heat to 150-200℃ for cold sintering, cool to room temperature, demold, dry at 150-200℃, and finally heat to 600-700℃ for annealing. Allow to cool naturally to obtain a solidified palygorskite ceramic body with radioactive iodine.

[0019] Preferably, the stirring and reflux time in step S1 is 20-30 hours; the heating and stirring time in step S2 is 10-30 hours.

[0020] Preferably, the heating and cooling rates in step S3 are both 5-10°C / min, the sintering time is 120-150 min, the drying time is 10-20 h, and the annealing time is 5-15 h.

[0021] The application of the palygorskite ceramic solidified body containing solidified radioactive iodine in the field of solidification for the treatment of high-radioactive waste.

[0022] The chemical equations for the reaction process in this invention are as follows:

[0023] (1) Dissolution reaction: AgI + 2Na₂S₂O₃ = Na₃[Ag(S₂O₃)₂] + NaI

[0024] (2) Adsorption reaction: Mg5Si8O 20 (OH)₂(H₂O)₄H₂O + XI - =Mg5Si8O 20-X I X (OH)₂(H₂O)₄H₂O + XO 2- x takes values ​​from 1 to 20.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention uses sodium thiosulfate to modify palygorskite, enabling the dissolution of radioactive silver iodide. This allows palygorskite to effectively adsorb radioactive iodide ions, and the silver can be recovered through the solution, effectively reducing the cost of using silver-coated silica gel and silver-containing zeolites for iodine adsorption. Through the modification of palygorskite, the Si-O-Si oxygen bridge bonds are broken, allowing it to form covalent bonds with radioactive iodide ions; simultaneously, Na… + With the metal cations (Mg) in the crystal 2+ The substitution process causes an imbalance in the charge distribution within the crystal, giving palygorskite a stronger adsorption capacity for radioactive iodine ions. Furthermore, my country has large reserves of palygorskite at low cost, which can effectively reduce raw material costs.

[0027] 2. This invention uses cold sintering to effectively reduce the sintering temperature. Densification can be achieved simply by adding deionized water and applying sintering pressure. It can effectively suppress the volatilization of radioactive iodine ions at high temperatures. The process is simple, energy consumption is low, and manufacturing cost is low.

[0028] 3. The ceramic solidified body of the present invention has excellent thermal and chemical stability, which can meet the requirements for long-term storage of radioactive materials and has broad application prospects for the solidification of radioactive iodine. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0030] Example 1

[0031] Let Mg5Si8O 20-X I X In the (OH)2(H2O)4·4H2O(x=1) ceramic solidified body, the molar ratio of palygorskite to silver iodide is 1:1, and the total mass of each raw material powder is 50g.

[0032] 1. Weigh 39.12g of palygorskite (Mg5Si8O) 20 (OH)2(H2O)4·4H2O) was added to 80 mL of 1 mol / L sodium thiosulfate solution and stirred and refluxed at 70 °C to obtain a sodium thiosulfate solution containing modified palygorskite.

[0033] 2. Weigh 10.88g of silver iodide and add it to a sodium thiosulfate solution containing modified palygorskite. Heat and stir at 70℃ for 10 hours to allow the palygorskite to fully adsorb iodide ions. Filter the palygorskite Mg5Si8O that has adsorbed radioactive iodide ions. 20-x I x (OH)2(H2O)4·4H2O was stirred and washed at 70℃ for 20h, filtered, and dried at 70℃ for 30h to obtain palygorskite powder adsorbed with radioactive iodide ions.

[0034] 3. Add palygorskite powder that has adsorbed radioactive iodine ions to 25 mL of deionized water, grind and obtain a paste-like mixture;

[0035] 4. Pour the paste mixture into a stainless steel mold. First, apply a pressure of 200 MPa using a tablet press and hold it. Then, heat the mixture to 150°C at a rate of 5°C / min for cold sintering, while simultaneously applying a uniaxial pressure of 700 MPa to the mold. Sinter for 120 min, then cool to room temperature at a rate of 5°C / min. Remove the mold, demold the sample, and dry it in a constant temperature drying oven at 150°C for 10 h to remove any residual liquid phase. Place the cold-sintered sample into a high-temperature furnace and anneal it at 600°C at a rate of 5°C / min for 5 h. Allow it to cool naturally to obtain Mg5Si8O. 19 The ceramic solidified body containing I(OH)2(H2O)4·4H2O has an iodine mass fraction of 13.29 wt%.

[0036] Example 2

[0037] The difference from Example 1 is that the masses of palygorskite and silver iodide in steps 1 and 2 are 27.26 g and 22.74 g, respectively, the molar ratio of palygorskite to silver iodide is 1:3, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)₂(H₂O)₄·4H₂O (x=3)

[0038] The Mg5Si8O in this embodiment 17 The mass fraction of iodine in the I3(OH)2(H2O)4·4H2O ceramic solidified body is 32.34 wt%. Iodine exists in palygorskite in an adsorbed ionic state, which is very firmly bound, difficult to separate, and chemically stable. Palygorskite also exhibits heat resistance and good thermal stability; at certain temperatures, it only loses its surface water structure without damaging its internal structure.

[0039] Example 3

[0040] The difference from Example 1 is that the masses of palygorskite and silver iodide in steps 1 and 2 are 18.74 g and 31.26 g, respectively, the molar ratio of palygorskite to silver iodide is 1:6, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=6).

[0041] The Mg5Si8O in this embodiment 14 The mass fraction of iodine in the I6(OH)2(H2O)4·4H2O ceramic solidified body is 50.43 wt%.

[0042] Example 4

[0043] The difference from Example 1 is that: in steps 1 and 2, the masses of palygorskite and silver iodide are 27.26 g and 22.74 g, respectively; the molar ratio of palygorskite to silver iodide is 1:3; in step 4, the annealing temperature is 700℃, the annealing time is 10 h, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=3).

[0044] The Mg5Si8O in this embodiment 17 The mass fraction of iodine in the I3(OH)2(H2O)4·4H2O ceramic solidified body is 32.34 wt%.

[0045] Example 5

[0046] The difference from Example 1 is that: in steps 1 and 2, the masses of palygorskite and silver iodide are 27.26 g and 22.74 g, respectively; the molar ratio of palygorskite to silver iodide is 1:3; in step 4, the annealing temperature is 700℃, the annealing time is 15 h, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=3).

[0047] The Mg5Si8O in this embodiment 17 The mass fraction of iodine in the I3(OH)2(H2O)4·4H2O ceramic solidified body is 32.34 wt%.

[0048] Example 6

[0049] The difference from Example 1 is that: the masses of palygorskite and silver iodide in steps 1 and 2 are 18.74 g and 31.26 g, respectively; the molar ratio of palygorskite to silver iodide is 1:6; the concentration of sodium thiosulfate in step 1 is 2 mol / L; and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=6).

[0050] The Mg5Si8O in this embodiment 14 The mass fraction of iodine in the I6(OH)2(H2O)4·4H2O ceramic solidified body is 50.43 wt%.

[0051] Example 7

[0052] The difference from Example 1 is that: the mass of palygorskite and silver iodide in steps 1 and 2 are 20.92 g and 29.08 g, respectively; the heating, stirring, and drying temperatures are all 90°C; the molar ratio of palygorskite to silver iodide is 1:5; and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=5).

[0053] The Mg5Si8O in this embodiment 15 The mass fraction of iodine in the I5(OH)2(H2O)4·4H2O ceramic solidified body is 45.36 wt%.

[0054] Example 8

[0055] The difference from Example 1 is that: the mass of palygorskite and silver iodide in steps 1 and 2 are 16.97 g and 33.03 g, respectively; the annealing temperature in step 4 is 700 °C, the annealing time is 15 h, the molar ratio of palygorskite to silver iodide is 1:7, and the ceramic solidified body is Mg5Si8O. 20-X I X(OH)2(H2O)4·4H2O (x=7).

[0056] The Mg5Si8O in this embodiment 13 The mass fraction of iodine in the I7(OH)2(H2O)4·4H2O ceramic solidified body is 54.81 wt%.

[0057] Example 9

[0058] The difference from Example 1 is that: the mass of palygorskite and silver iodide in steps 1 and 2 are 11.53 g and 38.47 g, respectively; the annealing temperature in step 4 is 600 °C, the annealing time is 10 h, the molar ratio of palygorskite to silver iodide is 1:15, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=15).

[0059] The Mg5Si8O5I in this embodiment 15 The mass fraction of iodine in the (OH)2(H2O)4·4H2O ceramic solidified body is 70.01 wt%.

[0060] Example 10

[0061] The difference from Example 1 is that: in steps 1 and 2, the masses of palygorskite and silver iodide are 7.62 g and 42.38 g, respectively; the molar ratio of palygorskite to silver iodide is 1:20; in step 4, the annealing temperature is 700℃, the annealing time is 15 h, and the ceramic solidified body is Mg5Si8O. 20-X I X (OH)2(H2O)4·4H2O (x=20).

[0062] The Mg5Si8I in this embodiment 20 The mass fraction of iodine in the (OH)2(H2O)4·4H2O ceramic solidified body is 82.88 wt%.

[0063] The ceramic solidified body of the present invention has stable chemical properties and low cost. After converting radioactive iodine waste into silver iodide using an adsorbent containing silver, the content of radioactive iodine that can be solidified is 13-83 wt%, which is suitable for the solidification of radioactive iodine and can dispose of radioactive iodine waste.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A palygorskite ceramic solidified body for curing radioactive iodine, characterized in that, The chemical formula of the ceramic solidified body is Mg5Si8O 20-X I X (OH)2(H2O)4•4H2O, where x is 1~20, is palygorskite Mg5Si8O 20 (OH)2(H2O)4•4H2O is added to a sodium thiosulfate solution and stirred under reflux at 70-90°C. Radioactive silver iodide is then added and stirred, filtered, and dried to obtain palygorskite powder adsorbed with radioactive iodide ions. This powder is then mixed with deionized water, and the resulting paste mixture is poured into a mold. A pressure of 200-300 MPa is applied first, followed by a uniaxial pressure of 500-700 MPa. The temperature is raised to 150-200°C for cold sintering. After cooling to room temperature, the mixture is demolded and dried. Finally, it is heated to 600-700°C for annealing and allowed to cool naturally to obtain the final product.

2. The palygorskite ceramic solidified body with solidified radioactive iodine according to claim 1, characterized in that, The palygorskite has a particle size of 10~100μm, and the radioactive silver iodide has a particle size of 10~100μm.

3. The palygorskite ceramic solidified body with solidified radioactive iodine according to claim 1, characterized in that, The concentration of the sodium thiosulfate solution is 1~2 mol / L, the mass ratio of palygorskite to sodium thiosulfate in the sodium thiosulfate solution is 1:(2~10), and the molar ratio of radioactive silver iodide to palygorskite is (1~20):

1.

4. The palygorskite ceramic solidified body with solidified radioactive iodine according to claim 1, characterized in that, The mass ratio of palygorskite powder that adsorbs radioactive iodide ions to deionized water is (1~5):

1.

5. The palygorskite ceramic solidified body with solidified radioactive iodine according to claim 1, characterized in that, The iodine content in the palygorskite ceramic solidified body is 13~83wt%.

6. The method for preparing palygorskite ceramic solidified body with solidified radioactive iodine according to any one of claims 1-5, characterized in that, The specific steps include the following: S1. Palaequa Mg5Si8O 20 (OH)2(H2O)4•4H2O is added to sodium thiosulfate solution and stirred and refluxed at 70~90℃ to obtain sodium thiosulfate solution containing modified palygorskite. S2. Radioactive silver iodide is added to a sodium thiosulfate solution containing modified palygorskite, and the mixture is heated and stirred at 70-90°C, filtered and dried to obtain palygorskite powder that adsorbs radioactive iodide ions. S3. Add palygorskite powder that adsorbs radioactive iodine ions to deionized water to make a paste mixture. Pour the paste mixture into a mold, apply a pressure of 200-300 MPa, then apply a uniaxial pressure of 500-700 MPa to the mold, heat to 150-200℃ for cold sintering, cool to room temperature, demold, dry at 150-200℃, and finally heat to 600-700℃ for annealing. Allow to cool naturally to obtain a solidified palygorskite ceramic body with radioactive iodine.

7. The method for preparing palygorskite ceramic solidified body with solidified radioactive iodine according to claim 6, characterized in that, The stirring and reflux time in step S1 is 20-30 hours; the heating and stirring time in step S2 is 10-30 hours.

8. The method for preparing palygorskite ceramic solidified body with solidified radioactive iodine according to claim 6, characterized in that, In step S3, the heating and cooling rates are both 5~10℃ / min, the sintering time is 120~150min, the drying time is 10~20h, and the annealing time is 5~15h.

9. The application of the palygorskite ceramic solidified body with solidified radioactive iodine as described in any one of claims 1-5 in the field of solidification for the treatment of high-radioactive waste.