Adsorbent for capturing radioactive iodine and preparation method thereof

Abstract

The invention provides an adsorbent for capturing radioactive iodine and a preparation method of the adsorbent. The adsorbent disclosed by the invention is composed of the silver-loaded polystyrene-based conjugated microporous polymer, and compared with common nuclear-grade activated carbon in the prior art, the cost of the adsorbent disclosed by the invention is lower. The preparation method of the adsorbent provided by the invention is simple and efficient, the conjugated microporous polymer with excellent performance can be prepared, the prepared polymer has relatively high pore volume, the adsorption capacities of elemental iodine and methyl iodide can respectively reach 273 wt% and 22 wt%, and the adsorbent can be regenerated and recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of functional polymer materials. More specifically, the present invention relates to an adsorbent for radioactive iodine capture and a preparation method of the adsorbent. Background Art

[0002] Radioactive iodine (such as iodine-131) is one of the common radioactive nuclides in nuclear reactors and nuclear accidents. It has high radiotoxicity and bioaccumulation, posing a serious threat to the environment and human health. In the operation of nuclear power plants, nuclear medicine applications, and nuclear accident handling, the effective removal of radioactive iodine has become an important research topic. Currently, the removal techniques of radioactive iodine mainly include physical adsorption, chemical adsorption, and biological adsorption methods. The physical adsorption method usually uses materials such as activated carbon and molecular sieves to adsorb iodine and its compounds through physical actions; the chemical adsorption method uses chemical reactions to fix iodine on the adsorbent, such as silver-based materials and copper-based materials; the biological adsorption method uses microorganisms or biological materials to adsorb radioactive iodine.

[0003] Although the prior art has made certain progress in the removal of radioactive iodine, there are still some deficiencies. For example, the physical adsorption method is a reversible adsorption, with limited adsorption capacity and easy saturation; the chemical adsorption method has a high cost, and the regeneration of the adsorbent is difficult; the biological adsorption method has complex operations and limited application scope. Therefore, it is of great practical significance to develop an efficient, economical, and easy-to-operate adsorbent for removing radioactive iodine. Summary of the Invention

[0004] The present invention aims to provide an adsorbent for radioactive iodine capture and a preparation method thereof to overcome the disadvantages of the prior art.

[0005] The adsorbent of the present invention is composed of a silver-loaded polystyrene-based conjugated microporous polymer, which is more cost-effective than the commonly used nuclear-grade activated carbon in the prior art. The cost of the adsorbent disclosed in the present invention is about 6.12 $ / kg, while the cost of nuclear-grade activated carbon GAC1240 is about 12 $ / kg.

[0006] The present invention also provides a preparation method of the above-mentioned adsorbent. The method is simple and efficient, and can prepare a conjugated microporous polymer with excellent performance. The prepared polymer has a high pore volume, and the adsorption capacities for elemental iodine and methyl iodide can reach 273 wt% and 22 wt% respectively, and can be regenerated and recycled. After loading silver, its adsorption capacity is further improved, and the adsorption capacities for elemental iodine and methyl iodide can reach 358 wt% and 26 wt% respectively.

[0007] According to the first aspect of the present invention, the present invention provides an adsorbent for removing radioactive iodine, which is composed of a silver-loaded polystyrene-based conjugated microporous polymer, and the polystyrene-based conjugated microporous polymer has the following structure:

[0008]

[0009] Preferably, the molecular weight of the polystyrene-based conjugated microporous polymer is about 3500

[0010] Preferably, in the adsorbent, the weight ratio of silver to the polystyrene-based conjugated microporous polymer is 1-20 wt.%.

[0011] Preferably, the BET specific surface area of the polystyrene-based conjugated microporous polymer is 850-1200 m 2 / g, the pore volume reaches 1.05 cm 3 / g, and the average pore diameter is 4.48 nm.

[0012] According to the second aspect of the present invention, the present invention provides a preparation method of the above-mentioned adsorbent. The preparation method includes: dissolving expanded polystyrene in an organic solvent, then adding a Lewis acid and dimethoxymethane, and under the catalysis of the Lewis acid, using dimethoxymethane to carry out a cross-linking reaction to obtain a polystyrene conjugated microporous polymer. The polystyrene conjugated microporous polymer is washed and extracted, and then blended with a silver salt solution and allowed to stand to obtain a silver ion-loaded polystyrene conjugated microporous polymer, which is obtained as the adsorbent of the present invention after vacuum drying.

[0013] Limitedly, the polystyrene conjugated microporous polymer is washed 1-3 times with acetone, dilute hydrochloric acid and ultrapure water respectively, and Soxhlet extracted with methanol at 80-105 °C for 40-60 hours for further purification.

[0014] Preferably, the organic solvent is dichloroethane.

[0015] Preferably, the Lewis acid is anhydrous ferric chloride.

[0016] Preferably, the molar ratio of expanded polystyrene: Lewis acid: dimethoxymethane is 1:2-5:12-15.

[0017] Preferably, the silver salt solution is one of 1-20 wt.% silver nitrate and silver acetate solution.

[0018] Preferably, the molar ratio of silver ions in the salt solution to the polystyrene conjugated microporous polymer is 0.1-2.5:1. Description of the Drawings

[0019] Figure 1 is the infrared spectrum diagram of the polystyrene-based conjugated microporous polymer;

[0020] Figure 2 It is the isothermal nitrogen adsorption - desorption curve of polystyrene - based conjugated microporous polymer;

[0021] Figure 3 It is a schematic diagram of the adsorption capacity of conjugated microporous polymer for cyclic adsorption - desorption of iodine and methyl iodide. Specific embodiments

[0022] To make the technical solutions and advantages of this application clearer, the following will clearly and completely describe the technical solutions of this application in combination with the drawings of the embodiments of this application. Obviously, the described embodiments are exemplary embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.

[0023] Example 1

[0024] Add 100 mL of 1,2 - dichloroethane to 1.5 g of expanded polystyrene, stir to fully dissolve the expanded polystyrene, then let it stand for 30 minutes to fully swell, and add 6 g of anhydrous ferric chloride and 15 mL of dimethoxymethane. The mixture reacts at 80 °C for 20 hours. The obtained solid product is washed three times with acetone, dilute hydrochloric acid, and ultrapure water respectively. Then, the crude product is further purified by Soxhlet extraction with methanol at 100 °C for 48 hours. Next, dissolve 0.1 g of silver nitrate in water, mix it with the polymer, and let it stand for 18 hours. Finally, the obtained product is dried in vacuo at 120 °C to obtain brick - red solid particles.

[0025] Example 2

[0026] Add 80 mL of tetrahydrofuran to 1.5 g of expanded polystyrene, stir to fully dissolve the expanded polystyrene, then let it stand for 50 minutes to fully swell, and add 6 g of anhydrous ferric chloride and 15 mL of dimethoxymethane. The mixture reacts at 60 °C for 48 hours. The obtained solid product is washed three times with acetone, dilute hydrochloric acid, and ultrapure water respectively. Then, the crude product is further purified by Soxhlet extraction with methanol at 100 °C for 60 hours. Next, dissolve 0.1 g of silver acetate in water, mix it with the polymer, and let it stand for 18 hours. Finally, the obtained product is dried in vacuo at 120 °C to obtain brick - red solid particles.

[0027] Example 3

[0028] 1.5 g of expanded polystyrene was added with 120 mL of xylene, and stirred to fully dissolve the expanded polystyrene. Subsequently, it was left standing for 60 minutes to fully swell, and 6 g of anhydrous ferric chloride and 15 mL of dimethoxymethane were added. The mixture was reacted at 100 °C for 12 hours. The obtained solid product was washed three times with acetone, dilute hydrochloric acid and ultrapure water respectively. Then, the crude product was further purified by Soxhlet extraction with methanol at 100 °C for 40 hours. Next, 0.15 g of silver acetate was dissolved in water and blended with the polymer, and left standing for 18 hours. Finally, the obtained product was dried in vacuo at 120 °C to obtain brick-red solid particles.

[0029] Characterization of the intermediate polystyrene conjugated microporous polymer

[0030] The intermediate product obtained in Example 1 (the polymer before blending with silver nitrate) was characterized.

[0031] In Figure 1 the infrared spectrum, the peaks at 758 and 700 cm -1 wave numbers belong to the stretching vibration peaks of monosubstituted benzene rings, which are weaker than those of polystyrene before crosslinking. This is because the proton hydrogen atoms on the benzene ring are replaced by dimethoxymethane, indicating that the crosslinking reaction has proceeded successfully.

[0032] According to Figure 2 , it can be seen that the BET specific surface area of the product obtained by isothermal nitrogen adsorption is 890 m 2 / g, the pore volume reaches 1.14 cm3 / g, and the average pore diameter is about 5.09 nm.

[0033] Iodine and methyl iodide adsorption performance tests of adsorbents

[0034] The iodine and methyl iodide adsorption performances of the intermediate product (the polymer before blending with silver nitrate) and the final product obtained in Example 1 were tested.

[0035] Iodine and methyl iodide adsorption performance test: Twenty-milliliter glass bottles containing iodine or methyl iodide were respectively placed in a desiccator loaded with conjugated microporous polymer or silver-attached conjugated microporous polymer and sealed. The conjugated microporous polymer was weighed at regular intervals and then put back until its weight reached a stable value. The adsorption capacity of iodine or methyl iodide was measured by the weight change of the conjugated microporous polymer. The adsorption capacity of the material was calculated according to the following formula:

[0036]

[0037] where: q t represents the adsorption capacity of the material at time t, mg / g; m t represents the weight of the conjugated microporous polymer at time t, g; m0 represents the initial weight of the conjugated microporous polymer, g.

[0038] The experimental results show that: the adsorption capacities of the conjugated microporous polymer mesoporous nanospheres for iodine and methyl iodide are 273 wt% and 22 wt% respectively. The adsorption capacities of the silver-loaded microporous polymer for iodine and methyl iodide are 358 wt% and 26 wt% respectively, but its preparation cost is only 6.12 $ / kg. The adsorption capacity of the modified nuclear-grade activated carbon for elemental iodine is 376%, but its cost is about 13 $ / kg. The adsorption performance of the adsorbent disclosed in this patent is comparable to that of nuclear-grade activated carbon, but the cost is lower, so it is a favorable alternative product.

Claims

1. An adsorbent for radioactive iodine capture, the adsorbent being composed of a polystyrene-based conjugated microporous polymer loaded with silver, wherein the polystyrene-based conjugated microporous polymer has the following structure:

2. The adsorbent according to claim 1, wherein The molecular weight of the polystyrene-based conjugated microporous polymer is about 3500.

3. The adsorbent according to claim 1, wherein In the adsorbent, the molar ratio of silver ions to polystyrene conjugated microporous polymer is 0.1-2.5:

1.

4. The adsorbent according to claim 1, wherein The BET specific surface area of ​​polystyrene-based conjugated microporous polymers is 850-1200 m 2 / g, pore volume up to 1.05cm 3 / g, and the average pore size is 4.48nm.

5. A method for preparing an adsorbent for capturing radioactive iodine, the method comprising the following steps: (1) dissolving expanded polystyrene in an organic solvent, then adding Lewis acid and dimethoxymethane, and using dimethoxymethane to undergo a cross-linking reaction under the catalysis of Lewis acid to obtain a polystyrene conjugated microporous polymer; (2) washing and extracting the obtained polystyrene conjugated microporous polymer, and then blending with a silver salt solution and letting it stand to obtain a polystyrene conjugated microporous polymer loaded with silver ions, (3) The obtained silver-loaded polystyrene conjugated microporous polymer is vacuum dried to obtain an adsorbent for radioactive iodine capture.

6. The method according to claim 5, wherein: In step (2), the polystyrene conjugated microporous polymer is washed with acetone, dilute hydrochloric acid and ultrapure water for 1-3 times respectively, and further purified by Soxhlet extraction with methanol at 80-105° C. for 40-60 hours.

7. The method according to claim 5, wherein: In step (1), the organic solvent is ethylene dichloride, tetrahydrofuran or xylene, and the Lewis acid is anhydrous ferric chloride.

8. The method according to claim 5, wherein: In step (1), the molar ratio of expanded polystyrene:Lewis acid:dimethoxymethane is 1:2-5:12-15.

9. The method according to claim 5, wherein: The silver salt solution is 1-20wt.% silver nitrate or silver acetate solution.

10. The method according to claim 5, wherein: The molar ratio of silver ions in the silver salt solution to the polystyrene conjugated microporous polymer is 0.1-2.5:1.

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