Porous organic polymer adsorbent for iodine capture as well as preparation method and application of porous organic polymer adsorbent

Abstract

The invention discloses a porous organic polymer adsorbent for iodine capture and a preparation method and application thereof, and relates to the field of resources and environments. The porous organic polymer adsorbent POPs-4 is prepared by taking biimidazole and 1, 2, 4, 5-tetrabromomethyl benzene as monomers to react. The obtained POPs-4 adsorbent can show the ultrahigh adsorption capacity of 0.98 g / g on iodine under the simulated practical application conditions (the temperature is smaller than or equal to 150 DEG C, and the I2 is larger than or equal to 150 ppmv), and the ultrahigh adsorption capacity is far higher than that of an Ag-coated MOR adsorbent (-0.17 g / g) commonly used in the industry. And meanwhile, the adsorbent has relatively good thermal stability and can meet the requirement that the adsorbent has considerable adsorption capacity under a high-humidity condition (RH is equal to 50%). And the adsorbent is simple to synthesize and easy to operate, can be prepared on a large scale, and is a radioactive iodine adsorbent with industrial application potential.

Description

Technical Field

[0001] The invention relates to the field of resources and environment, and in particular to a porous organic polymer adsorbent for iodine capture, and a preparation method and application thereof. Background Art

[0002] As global energy demand increases, nuclear energy as a clean energy source has received more attention. Iodine (I2) is one of the byproducts of nuclear fission, and its isotopes exist in 129 I and 131 I, where 129 I has a long half-life (about 1.57×10 7 years) and high toxicity, 131 I can harm the thyroid gland and affect metabolism. Using adsorbents to achieve efficient capture of radioactive iodine is considered to be one of the most effective methods. Porous organic polymers are a class of porous materials formed by the polymerization of organic units. Their rich specific surface area is conducive to providing more adsorption sites. However, traditional adsorbents usually have the characteristics of low adsorption capacity, poor regeneration performance, and poor practical application capabilities. In particular, it is challenging to effectively capture radioactive iodine from nuclear tail gas under industrial conditions (temperature ≥150℃, concentration ≤150 ppmv I2). Therefore, the development of a new and efficient adsorbent has important industrial value. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned problems in the prior art, and to provide a porous organic polymer adsorbent for iodine capture, and a preparation method and use thereof, wherein the adsorbent is formed by reacting a mixture containing biimidazole and 1,2,4,5-tetrabromomethylbenzene. The biimidazole in the adsorbent has abundant nitrogen sites, and such nitrogen sites containing lone pairs of electrons can form strong interactions with electron-deficient iodine through charge transfer interactions, thereby achieving efficient adsorption of iodine. At the same time, the introduction of benzene rings into the adsorbent can increase the pore structure of the skeleton, while exposing more adsorption sites, promoting the mass transfer of molecular iodine, thereby further increasing the iodine adsorption capacity. The porous organic polymer adsorbent can capture radioactive iodine at high temperature and low concentration (≥150°C, ≤150 ppmv), and can effectively reduce environmental pollution caused by radioactive iodine. In addition, the preparation method and application of the adsorbent provided by the present invention are simple and easy to operate.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] A porous organic polymer adsorbent for iodine capture, wherein the chemical structure of the porous organic polymer adsorbent is as follows:

[0006] ;

[0007] The specific surface area of ​​the porous organic polymer adsorbent is as high as 400 m 2 / g, pore volume up to 0.5 cm 3 / g.

[0008] The porous organic polymer adsorbent is prepared by reacting a mixture containing a biimidazole monomer and 1,2,4,5-tetrabromomethylbenzene, and the reaction formula is as follows:

[0009] .

[0010] The method for preparing the porous organic polymer adsorbent comprises the following steps:

[0011] 1) mixing biimidazole and an alkali metal catalyst in a solvent to prepare a mixed solution;

[0012] 2) dispersing 1,2,4,5-tetrabromomethylbenzene in a solvent to prepare a 1,2,4,5-tetrabromomethylbenzene solution;

[0013] 3) adding the mixed solution of step 1) dropwise into the 1,2,4,5-tetrabromomethylbenzene solution, reacting in a sealed and heated environment, and then cooling to room temperature, filtering, purifying, washing, and drying to obtain the porous organic polymer adsorbent.

[0014] The solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran; the alkali metal catalyst includes at least one of sodium hydride, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0015] The solvents required for washing in the present invention include, but are not limited to, one or more of tetrahydrofuran, methanol, ethanol, and water.

[0016] In the present invention, the molar ratio of biimidazole to alkali metal catalyst is 1:2-4, preferably 1:2; the molar ratio of biimidazole to 1,2,4,5-tetrabromomethylbenzene is 1-3:1, preferably 2:1.

[0017] In step 3), the reaction temperature is 20-120° C. and the reaction time is 2-72 hours.

[0018] The porous organic polymer adsorbent is used for adsorbing iodine.

[0019] Specifically, the adsorption temperature is 0~350°C, the iodine concentration is 10~16000 ppmv, and the relative humidity is 0~50%.

[0020] The porous organic polymer adsorbent has a saturated adsorption capacity of iodine of 0.98 g / g under nuclear tail gas conditions (150° C., 150 ppmv I2).

[0021] The porous organic polymer adsorbent after iodine adsorption of the present invention is reused after desorption and regeneration; the specific steps are: washing the porous organic polymer adsorbent after iodine adsorption with anhydrous ethanol for multiple times, filtering and drying.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] 1. The biimidazole-based porous organic polymer adsorbent POPs-4 prepared by the present invention has rich site content and pore structure, and has high thermal stability, and is suitable for use under industrial high temperature conditions;

[0024] 2. The porous organic polymer adsorbent of the present invention exhibits an ultra-high dynamic adsorption capacity (0.98 g / g) for iodine under simulated industrial conditions (150°C, 150 ppmv I2), which is much higher than the commonly used Ag@MOR adsorbent in industry (~0.17 g / g), providing a new idea for the research of new adsorbents;

[0025] 3. The preparation conditions of the present invention are mild, the operation is simple, the yield is high, and it can be prepared on a large scale to meet actual industrial needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the nitrogen adsorption curve of the porous organic polymer adsorbent POPs-4 prepared in Example 1 at 77 K;

[0027] Figure 2 Thermogravimetric curve of the porous organic polymer adsorbing POPs-4 prepared in Example 1;

[0028] Figure 3 The adsorption kinetic curve of POPs-4 on porous organic polymer adsorbent under static conditions at 75°C;

[0029] Figure 4 The iodine breakthrough curve of POPs-4 on porous organic polymer adsorbent at 150 °C and 150 ppmv I2.

[0030] Figure 5 Iodine breakthrough curve of porous organic polymer adsorbent POPs-4 at 150°C, 150 ppmv I2 and RH=50%;

[0031] Figure 6 This is the iodine breakthrough curve of the porous organic polymer adsorbent POPs-4 at 150°C and 150 ppmv I2 after 5 adsorption regeneration cycles. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0033] Example 1

[0034] 2,2'-biimidazole (15.0 mmol, 2.0 g) and NaH (30.0 mmol, 1.2 g) were added to 20 mL DMF and stirred at room temperature for 2 hours. 1,2,4,5-tetrabromomethylbenzene (7.5 mmol, 3.4 g) was dispersed in 30 ml DMF, and then the above solution was slowly added dropwise. The mixture was placed in an oven and reacted at 60 °C for 48 hours. The product was filtered, purified by Soxhlet extraction with tetrahydrofuran as solvent for 24 hours, washed with ethanol, and dried with supercritical carbon dioxide to obtain a porous organic polymer adsorbent POPs-4. The obtained porous organic polymer adsorbent POPs-4 has a relatively rich pore structure, and its BET specific surface area is measured to be 115.3 m 2 / g, pore volume is 0.36 cm 3 / g. The nitrogen adsorption-desorption curve of the porous organic polymer adsorbent POPs-4 is as follows Figure 1 Thermogravimetric curve is shown as Figure 2 As shown, it indicates that the synthesized porous organic polymer adsorbent POPs-4 has good thermal stability.

[0035] Example 2

[0036] Static Iodine Vapor Capture

[0037] Three 5 mL glass vials were placed in a 100 mL wide-mouth bottle. The first vial contained 30 mg of 3 ·min -1 ) after being activated for 8 hours under 40 ° C. The second vial contains elemental iodine, and the third vial is for reference only. The wide-mouth bottle is then sealed and placed in an oven at 75 ° C. After a period of contact, the wide-mouth bottle is taken out of the oven and cooled to room temperature. The glass vial containing the sample is taken out and weighed, and then put back into the wide-mouth bottle to continue adsorbing elemental iodine. When the weight reaches stability, the maximum adsorption amount of the sample is measured by the increase in mass. The static adsorption kinetic curve of the adsorbent POPs-4 under this condition is shown as follows: Figure 3 As shown, the results showed that the adsorbent POPs-4 achieved adsorption equilibrium within 94 hours, and the saturated adsorption capacity was 4.8 g / g.

[0038] Example 3

[0039] Dynamic Iodine Vapor Capture

[0040] 30 mg of POPs-4 adsorbent was loaded into a quartz column with an inner diameter of 5.8 mm and a length of 150 mm. The gap was filled with quartz wool treated with silane. The column was heated to 40 ℃ and then cooled to 37 ℃ under a nitrogen flow (10 cm 3 ·min -1 ) for 8 hours. 3 ·min -1 The nitrogen gas at the rate of 16.7 cm 3 ·min -1 The iodine concentration of the adsorbent was 150 ppmv. After the iodine with this concentration passed through the adsorption column, the tail gas was received by 0.3 M sodium hydroxide solution. The iodine concentration in the absorption liquid was measured by inductively coupled plasma emission spectrometry to obtain the penetration curve. The penetration curve of POPs-4 adsorbent under this condition is shown in Figure 2. Figure 4 As shown, the POPs-4 adsorbent exhibited an ultra-high adsorption capacity of 0.98 g / g for iodine under this condition, far exceeding the Ag@MOR adsorbent commonly used in industry (~0.17 g / g).

[0041] Example 4

[0042] Dynamic iodine vapor capture under humid conditions

[0043] 30 mg of POPs-4 adsorbent was loaded into a quartz column with an inner diameter of 5.8 mm and a length of 150 mm. The gap was filled with quartz wool treated with silane. The column was heated to 40 ℃ and then cooled to 37 ℃ under a nitrogen flow (10 cm 3 ·min -1 ) for 8 hours. Under humidity conditions (RH=50%), 10 cm 3 ·min -1 The rate of nitrogen passing through the iodine column, 13.4 cm 3 ·min -1 The nitrogen gas at the rate of 1.5 t / min passes through the water generator. The two gas streams are 3.3 cm 3 ·min -1 The iodine vapor concentration was 150 ppmv and the relative humidity was 50%. After the iodine under this condition passed through the adsorption column, the tail gas was received by 0.3 M sodium hydroxide solution, and the iodine concentration in the absorption liquid was measured by inductively coupled plasma emission spectrometry to obtain the penetration curve. The penetration curve of POPs-4 adsorbent under this condition is shown in Figure 2. Figure 5 The results show that water vapor conditions do not affect the performance of the adsorbent and it can be recycled.

[0044] Example 5

[0045] Regeneration performance test

[0046] The iodine-saturated POPs-4 adsorbent was washed with ethanol (50 mL×3) to ensure that the adsorbed iodine was completely desorbed and used for the next cycle test after supercritical drying for 3 hours. The iodine breakthrough curve of the POPs-4 adsorbent at 150°C and 150 ppmv I2 after 5 regeneration cycles is shown in Figure 2. Figure 6 As shown, the results indicate that the POPs-4 adsorbent has good regeneration performance.

[0047] In summary, the bisimidazolyl-based porous organic polymer POPs-4 adsorbent of the present invention has a high specific surface area, can achieve high iodine adsorption performance under static and dynamic conditions, and can meet practical application conditions such as high temperature, high humidity and low concentration, and has the potential for radioactive iodine capture under industrial application conditions.

Claims

1. A porous organic polymer adsorbent for iodine capture, characterized in that: The chemical structure of the porous organic polymer adsorbent is as follows: 。 2. The method for preparing a porous organic polymer adsorbent for iodine capture according to claim 1, characterized in that: The porous organic polymer adsorbent is prepared by reacting a mixture containing biimidazole monomer and 1,2,4,5-tetrabromomethylbenzene.

3. The preparation method according to claim 2, characterized in that: The following steps are involved: 1) mixing biimidazole and an alkali metal catalyst in a solvent to prepare a mixed solution; 2) dispersing 1,2,4,5-tetrabromomethylbenzene in a solvent to prepare a 1,2,4,5-tetrabromomethylbenzene solution; 3) adding the mixed solution of step 1) dropwise into the 1,2,4,5-tetrabromomethylbenzene solution, reacting in a sealed and heated environment, and then cooling to room temperature, filtering, purifying, washing, and drying to obtain the porous organic polymer adsorbent.

4. The preparation method according to claim 3, characterized in that: The solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran; the alkali metal catalyst includes at least one of sodium hydride, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

5. The preparation method according to claim 3, characterized in that: The molar ratio of biimidazole to the alkali metal catalyst is 1:2-4; the molar ratio of biimidazole to 1,2,4,5-tetrabromomethylbenzene is 1-3:

1.

6. The preparation method according to claim 3, characterized in that: In step 3), the reaction temperature is 20-120° C. and the reaction time is 2-72 hours.

7. Use of the porous organic polymer adsorbent according to claim 1 or the porous organic polymer adsorbent prepared by the preparation method of any one of claims 2 to 6, characterized in that: Used to adsorb iodine.

8. The use according to claim 7, characterized in that: The adsorption temperature is 0~350℃, the iodine concentration is 10~16000ppmv, and the relative humidity is 0~50%.

9. The use according to claim 7, characterized in that: The saturated adsorption capacity of iodine by the porous organic polymer adsorbent under nuclear tail gas conditions reaches 0.98 g / g.

10. The use according to claim 7, characterized in that: The porous organic polymer adsorbent after adsorbing iodine is regenerated and reused after desorption.

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