A covalent organic framework material for removing pertechnetate, preparation method and application

Abstract

The application discloses a covalent organic framework material for removing pertechnetate, a preparation method and application, and a structural formula I of the covalent organic framework material is as follows: The organic framework material can be used as an adsorbent to adsorb and separate TcO4 in spent fuel ‑ , has good crystallinity, hydrophilicity and a large specific surface area, and a proportion of exchanged pertechnetate of the same mass of the material is high, and can be applied to treatment of radioactive waste liquid.

Description

Technical Field

[0001] This invention relates to the field of organic materials technology, specifically to a covalent organic framework material for removing pertechnetate, its preparation method, and its application. Background Technology

[0002] With the sustained and rapid development of my country's economy and the continuous improvement of residents' living standards, energy consumption is increasing daily, leading to increasingly serious energy shortages, energy crises, and environmental pollution problems. Nuclear energy has the advantages of being clean and low-carbon, and can effectively replace the consumption of traditional energy sources such as coal and oil. Spent fuel reprocessing is the central link in the nuclear fuel cycle, and it is of great significance to environmental safety and the sustainable development of nuclear energy, becoming one of the key issues restricting the sustainable development of nuclear energy. 99 Tc is one of the most challenging radionuclides to handle in spent fuel reprocessing due to its long half-life and high toxicity. It also exhibits high toxicity in aqueous solutions. 99 TcO4 - It exists in various forms. In fields such as spent fuel reprocessing and nuclear environment remediation, the design and synthesis of [materials] exhibits excellent [potential]. 99 TcO4 - Separating materials with good capture properties is a major challenge.

[0003] Ion exchange is currently 99 TcO4 - The main means of removal. Currently, the adsorbent materials that are widely used are anion exchange resins (such as IRA-400, IRA-401 or Purolite-A-520E, etc.), but their adsorption rate is slow and their adsorption capacity is limited, which greatly restricts their practical application.

[0004] Related technologies include Chinese invention patent CN 112322282 B, which describes a MOF material for fluorescently recognizing pertechnetate or perrhenate, its preparation method, and its application. MOF materials can recognize and adsorb pertechnetate, but as metal-organic framework materials, they leave metal residues during use. Another example is Chinese invention patent CN 113214480 B, which describes a method for synthesizing a cationic framework material and its adsorption application. This cationic framework material has a high density of positively charged imidazole groups in its framework, which can bind to anionic perrhenate through electrostatic interactions, greatly improving the adsorption capacity for perrhenate. However, it has not been proven that it can remove pertechnetate. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a covalent organic framework material for removing pertechnetium ions, its preparation method, and its applications. This covalent organic framework material exhibits high chemical stability, good crystallinity, hydrophilicity, large specific surface area, low density, light weight, and a high exchange rate of pertechnetium ions per unit mass.

[0006] To achieve the above objectives, embodiments of the present invention, in a first aspect, provide a covalent organic framework material for removing pertechnetate, having the following structural formula I:

[0007]

[0008] According to an embodiment of the present invention, a covalent organic framework material for removing pertechnetium (PcO4) is disclosed. This organic framework material, Im-COF-PDSU, achieves selective removal of PcO4 because the anion of imidazole hydrochloride can undergo ion exchange with PcO4. It can be used as an adsorbent to adsorb and separate TcO4 from spent fuel. - Adsorption experiments showed that 5 mg of this organic framework material reached adsorption equilibrium in approximately 150 minutes in a 100 ppm sodium pertechnetate solution, with an adsorption capacity of 295 mg / g and a removal rate of over 96%. Due to its good crystallinity, hydrophilicity, and large specific surface area, the covalent organic framework material has a high exchange rate of pertechnetate for the same mass of material, making it suitable for treating radioactive waste liquids.

[0009] The second aspect of the present invention provides a method for preparing the above-described covalent organic framework material for removing pertechnetium, comprising:

[0010] Compound 5 and pyromellitic aldehyde were mixed and reacted with acetic acid as a catalyst at 30–150 °C for 2–7 days to obtain a covalent organic framework material of formula I.

[0011] The structural formula II of compound 5 is:

[0012]

[0013] According to the preparation method of the present invention, a covalent organic framework material of formula I can be synthesized. This covalent organic framework material, Im-COF-PDSU, can selectively remove pertechnetate ions because the anion of imidazole hydrochloride can undergo ion exchange with the pertechnetate ion. It can be used as an adsorbent to adsorb and separate TcO4 from spent fuel. - Adsorption experiments showed that 5 mg of this organic framework material reached adsorption equilibrium in approximately 150 minutes in a 100 ppm sodium pertechnetate solution, with an adsorption capacity of 295 mg / g and a removal rate of over 96%. Due to its good crystallinity, hydrophilicity, and large specific surface area, the covalent organic framework material has a high exchange rate of pertechnetate for the same mass of material, making it suitable for treating radioactive waste liquids.

[0014] Optionally, compound 5 and pyromellitic aldehyde are mixed and then added to a solvent, wherein the solvent is a mixture of pyromellitic aldehyde and 1,4-dioxane, and the volume ratio of pyromellitic aldehyde to 1,4-dioxane is 3 to 12:1.

[0015] Optionally, the molar ratio of acetic acid to compound 5 is 2 to 10:1.

[0016] Optionally, the reaction raw materials are loaded into a pressure-resistant reaction tube and subjected to 1 to 3 cycles of "freezing-vacuuming-thawing". The mixture is then placed at 30 to 150°C for 2 to 7 days. After the reaction is completed, the mixture is filtered, washed with acetone and / or tetrahydrofuran, and then vacuum dried at 60 to 100°C to obtain the covalent organic framework material of Formula I.

[0017] Optionally, compound 5 is synthesized via the following steps:

[0018] (1) Reaction of diethyl 2,5-dihydroxyterephthalate with 1,2-dichloroethane yields compound 2;

[0019] (2) Compound 2 was reacted with imidazole to obtain compound 3;

[0020] (3) Compound 3 was reacted with iodomethane to obtain compound 4;

[0021] (4) React compound 4 with hydrazine hydrate to obtain compound 5;

[0022] The synthesis path is as follows:

[0023]

[0024] Further, in step (1), diethyl 2,5-dihydroxyterephthalate and cesium carbonate are added to an organic solvent, and then 1,2-dichloroethane is added and heated under reflux to obtain compound 2; the organic solvent is one or more of DMF, DMSO, acetonitrile, acetone, and ethyl acetate.

[0025] Further, in step (2), compound 2 and cesium carbonate are added to an organic solvent, and then imidazole is added and heated to react, to obtain compound 3; the organic solvent is one or more of DMF, DMSO, acetonitrile, acetone, and ethyl acetate.

[0026] Further, in step (3), compound 3 is reacted with iodomethane under reflux in acetone to obtain compound 4; in step (4), compound 4 is reacted with hydrazine hydrate under reflux in anhydrous ethanol to obtain compound 5.

[0027] The embodiments of the present invention provide, in a third aspect, the application of the above-described covalent organic framework material for removing pertechnetate in the treatment of radioactive waste liquid.

[0028] This covalent organic framework material exhibits high chemical stability, good crystallinity, hydrophilicity, large specific surface area, low density, light weight, and a high proportion of technetium ions exchanged per unit mass, making it suitable for treating radioactive waste liquids.

[0029] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] Figure 1 This is the 1H NMR spectrum of compound 2 according to an embodiment of the present invention;

[0031] Figure 2 This is the carbon NMR spectrum of compound 2 according to an embodiment of the present invention;

[0032] Figure 3 This is the 1H NMR spectrum of compound 3 according to an embodiment of the present invention;

[0033] Figure 4 This is the carbon NMR spectrum of compound 3 according to an embodiment of the present invention;

[0034] Figure 5 This is the 1H NMR spectrum of compound 4 according to an embodiment of the present invention;

[0035] Figure 6 This is the carbon NMR spectrum of compound 4 according to an embodiment of the present invention;

[0036] Figure 7 This is the 1H NMR spectrum of compound 5 according to an embodiment of the present invention;

[0037] Figure 8 The carbon NMR spectrum of compound 5 according to an embodiment of the present invention;

[0038] Figure 9 This is the PXRD spectrum of Im-COF-PDSU, a covalent organic framework material of imidazole hydrochloride according to an embodiment of the present invention;

[0039] Figure 10 This is a thermogravimetric analysis diagram of Im-COF-PDSU, a covalent organic framework material of imidazole hydrochloride according to an embodiment of the present invention;

[0040] Figure 11 The attached diagram shows the nitrogen adsorption-desorption process of Im-COF-PDSU according to an embodiment of the present invention.

[0041] Figure 12 This is a pore size distribution diagram of Im-COF-PDSU according to an embodiment of the present invention;

[0042] Figure 13This is the infrared spectrum of Im-COF-PDSU according to an embodiment of the present invention;

[0043] Figure 14 The adsorption kinetics of Im-COF-PDSU according to embodiments of the present invention;

[0044] Figure 15 This is the adsorption isotherm of Im-COF-PDSU according to an embodiment of the present invention;

[0045] Figure 16 This describes the selective adsorption of Im-COF-PDSU under different nitrate ion concentrations according to embodiments of the present invention;

[0046] Figure 17 This describes the selective adsorption of Im-COF-PDSU under different sulfate ion concentrations according to embodiments of the present invention;

[0047] Figure 18 This is an adsorption diagram of Im-COF-PDSU recycling according to an embodiment of the present invention. Detailed Implementation

[0048] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0049] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0050] The test materials used in this invention are all common commercial products and can be purchased on the market.

[0051] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0052] Example 1

[0053] (1) Synthesis of compound 2

[0054] Diethyl 2,5-dihydroxyterephthalate (2.0 g) and cesium carbonate (6 g) were added to a 250 mL flask, followed by 30 mL of acetonitrile as a solvent. Finally, 3.15 mL of 1,2-dichloroethane was added, and the mixture was heated to 100 °C and refluxed overnight. After cooling to room temperature, the mixture was filtered through diatomaceous earth and distilled under reduced pressure to obtain a white solid. This solid was then separated using a hexane and ethyl acetate (5:1) column chromatography to obtain 2.9 g of a white solid, compound 2, with a yield of 77%. 1 H NMR and 13 C NMR such as Figure 1 and Figure 2 As shown.

[0055] (2) Compound 2 (3.0 g) was added to a 50 mL single-necked flask, along with cesium carbonate (1.0 g), imidazole (1.1 g), and 40 mL of acetonitrile as solvents. The mixture was refluxed at 100 °C for 6 h, cooled to room temperature, and distilled under reduced pressure to obtain a white solid. The solid was then passed through a silica gel column using ethyl acetate as the eluent to obtain 3.06 g of a white solid, compound 3, with a yield of 90%. 1 H NMR and 13 C NMR such as Figure 3 and Figure 4 As shown.

[0056] (3) Synthesis of compound 4

[0057] First, compound 3 (4.42 g) was dissolved in 50 mL of anhydrous acetone, then 6 mL of iodomethane was added, and the mixture was refluxed at 80 °C for 20 h. After cooling to room temperature, a large amount of pale yellow solid was obtained. The solid was filtered, washed, and dried under vacuum to give 7.05 g of pale yellow solid compound 4, with a yield of 97%. 1 H NMR and 13 C NMR such as Figure 5 and Figure 6 As shown.

[0058] (4) Synthesis of compound 5

[0059] First, compound 4 (3 g) was dissolved in 50 mL of anhydrous ethanol, then 10 mL of hydrazine hydrate was added, and the mixture was refluxed at 100 °C for 6 h. After cooling to room temperature, the ethanol and hydrazine hydrate were removed under reduced pressure to obtain a pale yellow solid. The solid was washed with a small amount of cold ethanol and dried to obtain 2.74 g of a pale yellow solid, compound 5, with a yield of 95%. 1 H NMR and 13 C NMR such as Figure 7 and Figure 8 As shown.

[0060] (5) Synthesis of imidazole hydrochloride covalent organic framework materials

[0061] Trimethylbenzaldehyde (16 mg, 0.1 mol) and compound 5 (104.7 mg, 0.15 mol) were added to a pressure-resistant reaction tube (volume: 25 mL, tube height: 20 cm, tube diameter: 15 cm). Then, 1.8 mL of trimethylbenzylene and 0.2 mL of 1,4-dioxane were added. After sonication (power: 120 W, 10 min), 0.2 mL of acetic acid aqueous solution (6 M) was added. The system was then frozen and evacuated with liquid nitrogen, and the "freezing-evacuation-thawing" operation was repeated three times. The system was sealed with a polytetrafluoroethylene stopper and placed in an oil bath. The reaction was carried out at 120 °C for 3 days. After cooling to room temperature, the mixture was filtered and washed multiple times with acetone and tetrahydrofuran, respectively. Soxhlet extraction was performed with 150 mL of acetone and 150 mL of tetrahydrofuran solution (100 °C overnight). Finally, the product was vacuum dried at 80 °C for 24 h to obtain the imidazole hydrochloride covalent organic framework material Im-COF-PDSU.

[0062] X-ray powder diffraction analysis of imidazole hydrochloride covalent organic framework materials yielded the following results: Figure 9 As shown, Im-COF-PDSU is a two-dimensional sheet material with good crystallinity.

[0063] The thermal stability of Im-COF-PDSU was verified by thermogravimetric analysis (TGA), and the results are as follows: Figure 10 As shown, Im-COF-PDSU maintains good stability at 200℃, indicating that Im-COF-PDSU has good thermal stability.

[0064] Pore ​​size testing was performed on Im-COF-PDSU, and the results are as follows: Figure 11 and Figure 12 As shown, the specific surface area of ​​Im-COF-PDSU is 388 m². 2 / g, its pore size is mainly distributed at 1.98nm, which is a nanometer-scale pore.

[0065] Infrared spectroscopy was performed on Im-COF-PDSU, and the results are as follows: Figure 13 As shown, the aldehyde group of the substrate disappears and an imine bond is formed. Infrared characterization confirmed the structure of Formula I of the Im-COF-PDSU material.

[0066] Example 2

[0067] Sodium pertechnetate was prepared into aqueous solutions of various concentrations to test the adsorption capacity of Im-COF-PDSU.

[0068] Adsorption kinetics experiment: 2 mg of adsorbent was added to 10 mL of sodium pertechnetate aqueous solution (56 ppm). Adsorption experiments were conducted under the conditions of pH 7, temperature 25℃, and rotation speed 5000 rpm. Samples were taken at different time points, and the adsorbed liquid was separated using a 0.22 μm aqueous filter membrane. The results are as follows: Figure 14 As shown, in a sodium pertechnetate solution with a concentration of 100 ppm, 5 mg of Im-COF-PDSU material reached adsorption equilibrium in about 150 min, with an adsorption capacity of 272 mg / g.

[0069] Adsorption isotherm experiment: 2 mg of adsorbent was added to 10 mL of sodium pertechnetate aqueous solution of different concentrations. Adsorption experiments were conducted under the conditions of pH 7, temperature 25℃, and rotation speed 5000 rpm. Samples were taken at the 150 min time point, and the adsorbed liquid was separated using a 0.20 μm aqueous filter membrane. The results are as follows: Figure 15 As shown, Figure 15 This is the adsorption isotherm of Im-COF-PDSU, with a maximum adsorption capacity of 1008 mg / g.

[0070] Competitive ion experiment: 2 mg of adsorbent was added to 10 mL of a 56 ppm sodium pertechnetate aqueous solution. NaNO3 solutions with concentrations of 56 ppm, 560 ppm, 2.8 mg / mL, and 5.6 mg / mL were added 1:1 to the 56 ppm sodium pertechnetate solution to investigate the effects of different NO3 concentrations. - The effect on adsorption was investigated by adding Na₂SO₄ solutions at concentrations of 56 ppm, 560 ppm, 5.6 mg / mL, and 56 mg / mL, respectively, to a 56 ppm sodium pertechnetate solution at a 1:1 ratio. 2- Effect on adsorption. Adsorption experiments were conducted at pH 7, temperature 25℃, and rotation speed 5000 rpm. The adsorbed liquid was then separated using a 0.20 μm aqueous filter membrane. Figure 16 and 17 The selective adsorption of Im-COF-PDSU under different anion concentrations was demonstrated, and the results showed that Im-COF-PDSU still maintained high selectivity even in the presence of nitrate concentrations of two orders of magnitude and sulfate concentrations of three orders of magnitude.

[0071] Figure 18 This is an adsorption diagram of Im-COF-PDSU after recycling. Experimental results show that this adsorbent material retains 94% of its removal capacity even after being recycled five times.

[0072] In summary, according to embodiments of the present invention, a covalent organic framework material Im-COF-PDSU was prepared. Because the imidazole hydrochloride anion of Im-COF-PDSU can undergo ion exchange with pertechnetate, selective removal of pertechnetate can be achieved. Therefore, it can be used as an adsorbent to adsorb and separate TcO4 from spent fuel. - The above adsorption experiments show that 2 mg of this organic framework material placed in 10 mL of 56 ppm sodium pertechnetate aqueous solution exhibits an adsorption capacity of 272 mg / g after 150 min, with a removal rate exceeding 97%. Therefore, the covalent organic framework material Im-COF-PDSU, due to its good crystallinity, stability, hydrophilicity, and large specific surface area, can be applied to the treatment of radioactive waste liquid due to its high pertechnetate exchange ratio for the same mass of material.

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0074] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A covalent organic framework material for removing pertechnetate, wherein structural formula I is: I。 2. A method for preparing a covalent organic framework material for removing pertechnetate as described in claim 1, characterized in that, include: Compound 5 and pyromellitic aldehyde were mixed, and acetic acid was used as a catalyst. The molar ratio of acetic acid to compound 5 was 2~10:

1. The mixture was placed at 30~150℃ for 2~7 days to obtain the covalent organic framework material of formula I. The structural formula II of compound 5 is: Ⅱ。 3. The preparation method according to claim 2, characterized in that, Compound 5 and pyromellitic aldehyde were mixed and then added to a solvent, which was a mixture of pyromellitic aldehyde and 1,4-dioxane, with a volume ratio of pyromellitic aldehyde to 1,4-dioxane of 3 to 12:

1.

4. The preparation method according to claim 2, characterized in that, The reactants are loaded into a pressure-resistant reaction tube and subjected to 1 to 3 cycles of "freezing-evacuation-thawing". The tube is then placed at 30 to 150°C for 2 to 7 days. After the reaction is completed, the tube is filtered, washed with acetone and / or tetrahydrofuran, and then vacuum dried at 60 to 100°C to obtain the covalent organic framework material of Formula I.

5. The preparation method according to any one of claims 2-4, characterized in that, Compound 5 was synthesized via the following steps: (1) Reaction of diethyl 2,5-dihydroxyterephthalate with 1,2-dichloroethane yields compound 2; (2) Compound 2 was reacted with imidazole to obtain compound 3; (3) Compound 3 was reacted with iodomethane to give compound 4; (4) Compound 4 was reacted with hydrazine hydrate to obtain compound 5; The synthesis path is as follows: 。 6. The preparation method according to claim 5, characterized in that, In step (1), diethyl 2,5-dihydroxyterephthalate and cesium carbonate are added to an organic solvent, and then 1,2-dichloroethane is added and heated under reflux to obtain compound 2; The organic solvent is one or more of DMF, DMSO, acetonitrile, acetone, and ethyl acetate.

7. The preparation method according to claim 5, characterized in that, In step (2), compound 2 and cesium carbonate are added to an organic solvent, and then imidazole is added and heated to react, to obtain compound 3; the organic solvent is one or more of DMF, DMSO, acetonitrile, acetone, and ethyl acetate.

8. The preparation method according to claim 5, characterized in that, In step (3), compound 3 is reacted with iodomethane under reflux in acetone to obtain compound 4; In step (4), compound 4 is reacted with hydrazine hydrate under reflux in anhydrous ethanol to obtain compound 5.

9. The application of the covalent organic framework material for removing pertechnetate as described in claim 1 in the treatment of radioactive waste liquid.

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