CN115044059B - A rapid preparation method and application of MOFs material for adsorption and separation of rhenium or technetium - Google Patents

Abstract

The invention relates to the technical field of nuclear fuel post-processing, in particular to a rapid preparation method and application of MOFs (metal-organic frameworks) materials for adsorbing and separating rhenium or technetium, wherein the preparation method comprises the following steps: mixing tetra (4-pyridine biphenyl) ethylene and silver nitrate in an organic solvent A for reaction, and filtering, washing and drying a product to obtain the MOFs material; the organic solvent A is a mixed solvent of acetonitrile and dimethyl sulfoxide; or, the tetra (4-pyridine biphenyl) ethylene is dissolved in the organic solvent B, the silver nitrate is dissolved in the acetonitrile, the MOFs material is obtained after the two solutions are mixed, the MOFs material can be generated in 5-10min by the method, even the adsorbing material product can be obtained by directly mixing, the yield can reach 94% at most, compared with the MOFs preparation process in the prior art, the method is usually more than several days, the speed is greatly improved, a novel method is provided for preparing the pertechnetate adsorbent in a large scale, and the material can efficiently remove the radioactive pollutant TcO ₄ ^‑ And ReO ₄ ^‑ The effect is excellent.

Description

A rapid preparation method and application of MOFs material for adsorption and separation of rhenium or technetium

technical field

The invention relates to the technical field of nuclear fuel reprocessing, in particular to a rapid preparation method and application of MOFs materials for adsorbing and separating rhenium or technetium.

Background technique

As a clean and efficient green energy, nuclear energy has gradually become one of the most promising clean energy sources. It provides a strong energy guarantee for the country's rapid economic development and also makes a great contribution to reducing carbon emissions. At the same time, with the development of nuclear energy, a large amount of radioactive waste has been produced. The safe disposal of these nuclear wastes and the elimination of nuclides leaked into the environment during nuclear accidents have always been the key issues for the safe development of nuclear energy. Among the long-lived elements produced in nuclear fission, the fission product Tc-99 is a typical long-lived fission product (t _1/2 = 2.13×10 ⁵ years), mainly composed of high technetium with strong water solubility and high stability It exists in the form of acid radical (TcO ₄ ^- ), which is a typical anionic radionuclide. The separation of TcO ₄ ^- from nuclear waste liquid and nuclear contaminated water system is of great significance to promote the reprocessing of spent fuel, restore the ecological environment and protect human health.

Among the currently developed separation methods, solid-phase adsorption technology has the advantages of simple operation, no secondary pollution, high adsorption capacity, and good selectivity. Compared with solvent extraction, precipitation, reduction, and membrane separation, it has been widely accepted. s concern. Among the many materials used for TcO ₄ ^-adsorption separation, metal-organic framework materials (MOF) have the characteristics of large specific surface area, high porosity, flexible structure and easy modification, and are widely favored by researchers, such as Wang Shuao of Soochow University. The reported SCU-103 cationic MOF material (Shen N, Yang Z, Liu S, et al.99TcO ₄ ^- removal from legacy defense nuclear waste by an alkaline-stable 2D cationic metal organicframework[J]. Nature communications, 2020, 11(1 ):1-12.) It can adsorb and remove radioactive pertechnetate from strong alkaline waste liquid. The preparation of MOF materials is mainly obtained by solvothermal method or hydrothermal method under high temperature and high pressure for a long time. The reports that can be rapidly synthesized at room temperature focus on the field of neutral MOF materials constructed by carboxyl and imidazole organic ligands. Cationic MOF The method of direct mixing synthesis at room temperature has not been reported in the field of materials.

In the researches reported so far, most of the cationic MOF materials that can be used for TcO ₄ ^-adsorption separation lack good acid-base stability, especially in the presence of a large number of competing ions, the adsorption capacity is greatly affected and cannot be achieved. Efficient and selective separation of TcO ₄ ^- . At the same time, the preparation of cationic MOF materials needs to be carried out in a reactor. The synthesis process has the characteristics of high temperature, high pressure and long reaction time. For example, in the applicant's early research results CN 112322282 A, although the reaction conditions are relatively mild, the reaction of MOFs materials The preparation time is as long as 48-128h, and the process is long. So far, there are no methods and related research reports that can rapidly prepare cationic MOF materials at room temperature, which greatly limits the industrial production and application of such materials.

In summary, in order to realize the large-scale preparation of cationic MOF as a pertechnetate adsorbent, those skilled in the art urgently need to develop a MOF material that can be rapidly prepared at room temperature, and the material must also have excellent acid-base stability. It has a series of advantages such as high specificity, fast adsorption kinetics, ultra-high selectivity, and recyclability.

Contents of the invention

The present invention aims at the problems in the prior art that the preparation process of cationic MOF adsorption materials used in the adsorption of pertechnetic acid is lengthy, time-consuming, difficult to prepare, etc., and provides a MOFs material for adsorbing and separating rhenium or technetium (ReO ₄ ^-does TcO ₄ ^-substitute A rapid preparation method for MOFs), which can start to produce MOFs materials within 5-10 minutes, and even directly mix them to obtain adsorption material products, with a yield of up to 94%. Compared with the preparation process of MOFs in the prior art, which often It lasts for more than a few days, and the speed is greatly improved, which provides a new method for large-scale preparation of pertechnetate adsorbent, and the material can efficiently remove radioactive pollutants TcO ₄ ^- and ReO ₄ ^- with excellent effect.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A rapid preparation method for adsorbing and separating rhenium or technetium MOFs material, comprising the steps of: tetrakis (4-pyridine biphenyl) ethylene and silver nitrate are mixed and reacted in an organic solvent A, and the product is filtered, washed, and dried to obtain the MOFs material ; The organic solvent A is a mixed solvent of acetonitrile and dimethyl sulfoxide. The ligand used in the present invention is a rigid planar ligand, and the pyridine functional group has a paired lone electron pair, which can form a coordination bond with a transition metal ion, and the nitrogen atom belongs to a soft atom ligand, based on the theory of soft and hard combination Guidance, coordinate with the transition metal silver to form a four-fold interpenetrated stable structure, so that the ligand tetrakis (4-pyridylbiphenyl) ethylene can quickly and stably produce MOFs materials in a solvent with silver nitrate.

The molar ratio of tetrakis (4-pyridine biphenyl) ethylene to silver nitrate is 1:0.8-1.2, and in the structure of MOFs, the ligand tetrakis (4-pyridine biphenyl) ethylene and silver nitrate are in a relationship of 1:1 Forming, so the two reaction raw materials are equipped at a ratio of about 1:1.

During the mixing reaction, any method including heating, stirring at room temperature or ultrasound is used to accelerate the reaction speed.

Wherein, the heating temperature is 60-120° C., the reaction time is more than 10 minutes, and the volume ratio of acetonitrile and dimethyl sulfoxide (DMSO) in the organic solvent A is 20:1-12. Through the method of the present invention, a hydrothermal kettle can be used in the heating process to prevent the solvent ratio from changing due to the excessive volatilization of the solvent at high temperature, and an ordinary glass container can also be selected for synthesis and preparation during low-temperature synthesis; the product MOFs will be produced after the reaction is carried out for 10 minutes . The heating temperature is preferably 70-90°C. At this temperature, energy consumption can be reduced, the use of a reaction kettle can be avoided, and the preparation process of the reaction can be simplified. More preferably 80°C. In this method, the product can be produced within the range of reaction temperature and solvent ratio, and has no obvious influence on the preparation result of the material, but beyond this range, the product cannot be effectively synthesized or the yield is significantly reduced.

For example, if the content of DMSO is further increased, the ligands are difficult to dissolve, and the yield of MOFs materials will decrease, and if it is further increased, MOFs materials will not be generated.

Preferably, the volume ratio of acetonitrile and DMSO in the organic solvent A is 5:2. Under this ratio, the rate of generating MOFs material is the fastest and the yield is higher.

More preferably, the reaction time under heating conditions is 10 min-24 h; further preferably, the reaction time is 10 min-3 h, and the reaction yield increases little after 3 h, and basically no increase after 24 h.

Wherein, the reaction time under stirring at room temperature is more than 10 minutes; the volume ratio of acetonitrile and dimethyl sulfoxide in the organic solvent A is 20:1-4. Preferably, the reaction time is 10 min-3 h under stirring at room temperature. The product was produced after stirring for 10 minutes, and the reaction was complete when the stirring was continued for 3 hours. Heating can also be carried out during the stirring process, which can accelerate the reaction process and increase the reaction yield, but increases the energy consumption in the preparation of MOF.

Wherein, the reaction is under the action of ultrasound for more than 5 minutes, and the volume ratio of acetonitrile and dimethyl sulfoxide in the organic solvent A is 20:1-4. Preferably, the reaction time under ultrasonic conditions is 5min-1h. The product was produced after 5 minutes of ultrasonication, and the reaction was complete after 1 hour of ultrasonication. Prolonging the reaction time did not significantly improve the yield.

In the above methods of heating, stirring at room temperature or ultrasonication, the tetrakis(4-pyridylbiphenyl)ethylene ligand does not need to be completely dissolved in the mixed solution, but only needs to have a certain solubility.

The present invention also provides another rapid preparation method for adsorbing and separating rhenium or technetium MOFs materials, comprising the steps of dissolving tetrakis (4-pyridine biphenyl) ethylene in organic solvent B, dissolving silver nitrate in acetonitrile, two solutions The mixed product is filtered, washed and dried to obtain the MOFs material;

The organic solvent B is a mixed solvent with a volume ratio of dichloromethane to acetonitrile of 20:1-4; the volume ratio of the organic solvent B to acetonitrile for dissolving silver nitrate is 20:0.5-1.

In this method, after the two solutions are mixed, simple stirring can be carried out to make the two evenly mixed. The reaction time of the mixing process hardly needs to wait, and the precipitation of the product MOFs can be seen directly after mixing, and the preparation process can be completed within 1 minute at the longest. , the MOFs material can be obtained by filtering, washing and drying, and the tested yield is as high as 94%, and the effect is excellent. And the preparation basically does not require the consumption of external energy, which is very suitable for large-scale industrial production.

The filtration, washing and drying process of the product obtained in the above rapid preparation method means that the MOFs material is produced in the form of precipitation in the solution, after filtration, cleaning and centrifugation with methanol, acetonitrile or ethanol and other solutions, and drying to remove excess solvent to obtain the final MOFs Material.

In the heating reaction method, since the cooling process will still increase the yield of MOF materials, the cooling method can be selected to turn off the heating and cool naturally, and then perform the post-processing process.

The invention also provides the application of the MOFs material prepared according to the preparation method in adsorption and separation of rhenium or technetium.

The application of the MOFs material in adsorption and separation of rhenium or technetium includes the steps of: placing the MOFs material in a solution containing rhenium or technetium for 40min-24h to achieve the effect of removing rhenium or technetium in the solution;

The solid-liquid ratio of the MOFs material to the solution containing rhenium or technetium is 1-10:1; the removal rate of rhenium is more than 35%, and the removal rate of technetium is more than 80%, and excellent technetium can be obtained with a low solid-liquid ratio. Or the removal rate of rhenium.

Preferably, the solid-liquid ratio is 2-10:1, the removal rate of rhenium is more than 55%, and the removal rate of technetium is more than 95%; more preferably, the solid-liquid ratio is 5-10:1, and the removal rate of rhenium is 75%. % or more, the removal rate of technetium is more than 99%.

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

(1) The present invention finds a rapid preparation method for cationic MOFs materials that can be used to adsorb and separate rhenium or technetium. In a mixed solvent of acetonitrile and DMSO, the ligand tetrakis (4-pyridine biphenyl) ethylene and silver nitrate can be used in a short time The MOFs material can be quickly prepared in-house, and the ultrasonic process only takes 5 minutes to produce the product, and the reaction can be completed after 1 hour. Compared with other studies, the MOF synthesis requires dozens of hours of high-temperature heating requirements, which greatly simplifies the synthesis method. It is expected to be used in the production and preparation of industrialized MOFs.

(2) In the present invention, it is also found that the ligand tetrakis (4-pyridine biphenyl) ethylene is dissolved in the mixed solution of dichloromethane and acetonitrile, and is directly mixed with the acetonitrile solution that is dissolved with silver nitrate, and immediately can obtain Products, the preparation of MOFs can be completed within 1 min at the longest, and there is basically no need for external energy consumption, which is very suitable for large-scale industrial production.

(3) The MOFs material prepared by the present invention is used to adsorb rhenium or technetium, and the effect is remarkable, and the highest adsorption rate can reach 99%.

Description of drawings

Figure 1 is the X-ray powder diffraction patterns of cationic MOF materials synthesized under different conditions.

FIG. 2 is a SEM image of the cationic MOF material synthesized by heating in Example 1. FIG.

Fig. 3 is the SEM image of the cationic MOF material synthesized by stirring at room temperature in Example 2.

Fig. 4 is the SEM image of the ultrasonically synthesized cationic MOF material in Example 3.

Fig. 5 is the SEM image of the cationic MOF material synthesized by the direct mixing method in Example 4.

Fig. 6 is a graph showing the percentage ^of TcO ₄ adsorbed by the cationic MOF material in Application Example 1.

Fig. 7 is a graph showing the percentage of adsorption ^of ReO ₄ on the cationic MOF material in application example 2.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. Modifications or equivalent replacements made by those skilled in the art on the basis of understanding the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall fall within the protection scope of the present invention.

Raw materials silver nitrate, tetrakis (4-pyridylbiphenyl) ethylene, methanol, ethanol, dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, sodium hydroxide, sodium nitrate used in the following specific embodiments Reagents such as can be purchased from Sarn Chemical Company and used without further purification.

Example 1

Weigh 40mg of tetrakis(4-pyridylbiphenyl)ethylene and 10.6mg of silver nitrate in a reaction test tube, measure _14mL of CH CN and DMSO mixed solvent (v/v, 10/4) into it and seal it, Put it into an oven and raise the temperature to 80°C for 3 hours, and then close the oven to cool down naturally after the heating is completed. The reaction solution was filtered, and the filtered product was washed with methanol and deionized water respectively, and then dried. The obtained light yellow powder was the cationic MOF material, and the yield was 80%.

Figure 1 shows the X-ray powder pattern of the MOF material after the reaction at 80°C for 3 hours, in which there is no raw material peak of the organic ligand, indicating that the reaction of the substrate is complete. Figure 2 is the SEM image of the product obtained by the heating method. It can be seen that the MOF material obtained by this method is an octahedral particle.

Example 2

Weigh 40mg of tetrakis(4-pyridylbiphenyl)ethylene and 10.6mg of silver nitrate in a reaction test tube, add 14mL of CH ₃ CN and DMSO mixed solvent (v/v, 10/4), and then stir 10min, at this time, the product has been produced in the reaction, but there are still a large amount of raw materials not completely reacted, as can be seen from the PXRD pattern in Figure 1, the diffraction peaks of the raw materials that exist when the reaction time is short. After continuous stirring for 3 hours, filter the reaction solution, wash the filtered product with methanol and deionized water, and then dry it. The obtained light yellow powder is the cationic MOF material. At this time, there is no PXRD diffraction peak of the raw material in the product. After testing The calculated yield was 92%.

Shown in Fig. 1 is to stir 10min, 30min and the PXRD diffraction peak of 3 hours product, wherein still have obvious substrate peak after stirring 10min and 30min, and also have product peak, show that there is the production of product in the shorter reaction time, However, the substrate was not completely reacted, and the yield was low, but there was no substrate peak when the reaction was extended to 3 hours, indicating that the substrate was completely reacted, and all the obtained products were MOF materials.

The microscopic morphology of the prepared MOFs material SEM is shown in Figure 3. The MOF material obtained by stirring at room temperature is also an octahedral particle, which shows that the morphology of the material prepared by method 1 is consistent.

Example 3

Weigh 40mg of tetrakis (4-pyridine biphenyl) ethylene and 10.6mg of silver nitrate in a reaction test tube, measure 14mL of CH ₃ CN and DMSO mixed solvent (v/v, 10/4) to add it, then room temperature Ultrasonic 5min, this moment reaction also has product production in this moment, but still a large amount of raw materials are not fully reacted, can see the diffraction peak of the raw material that exists when reaction time is short from the PXRD figure in accompanying drawing 1. After continuous ultrasonication for 1 hour, the reaction solution was filtered, and the filtered product was washed with methanol and deionized water respectively, and then dried. The obtained light yellow powder was the cationic MOF material, and the yield was 95%.

Figure 1 shows the PXRD diffraction peaks of the product for 5 minutes, 30 minutes and 1 hour of ultrasonication, and the product is produced when reacting for 5 minutes and 30 minutes respectively, while the raw material peak still exists, and there is no substrate peak after the reaction is extended to 1 hour, indicating that the reaction is complete , no raw materials left. It can be seen from Figure 4 that the morphology of the MOF material prepared by the ultrasonic method is octahedral, which is consistent with the morphology of the material obtained by heating and stirring at room temperature.

Example 4

Weigh 40mg of tetrakis(4-pyridylbiphenyl)ethylene and dissolve in 20mL of dichloromethane and acetonitrile mixed solution (v/v, 10/4), and dissolve silver nitrate containing equimolar amount in 1mL of CH ₃ CN solution , and added dropwise to the organic ligand, and stirred, the stirring was stopped after mixing evenly for 1 min, the reaction solution was filtered, and the filtered product was washed with methanol and deionized water respectively, and then dried, the obtained light yellow powder was cationic MOF material, the yield was 94%.

Figure 1 shows the PXRD diffraction peaks of the product prepared by direct mixing, wherein there is no diffraction peak of the organic ligand raw material, it can be seen that this method can effectively and quickly prepare the cationic MOFs material, and the reaction speed is obviously faster than other methods. Maintain very high productivity. The SEM microscopic morphology of the prepared MOFs material is shown in Figure 5, which is consistent with the material morphology shown in Figure 2-4, all of which are octahedral particles, indicating that the material prepared by direct mixing is consistent with the product prepared by other methods.

Application example 1

According to the reported concentration of each component in the low-level radioactive waste liquid in a certain area, the simulated waste liquid is configured. The waste liquid contained TcO ₄ ^- . Weighed 2.49, 5.03, 12.58, and 19.99 mg MOFs samples respectively and placed them in 2.5 mL of simulated waste liquid. After stirring for 24 hours, samples were taken, filtered through a 0.22 μm water filter membrane, and the remaining The concentration of technetium is detected, and the change of TcO ₄ ^- concentration is detected to obtain the adsorption and removal ability properties of MOF materials for TcO ₄ ^- in the simulated waste liquid. The results are shown in Figure 6. When the solid-liquid ratio is 1/1, 2/1, 5/1 and 8/1, the adsorption and removal rates of TcO ₄ ^- by cationic MOF materials are 83%, 96%, and 99%. and 99%. It shows that the cationic MOF material has a very strong ability to adsorb and remove TcO ₄ ^- in the waste liquid, and this MOF is currently the material with the highest removal ability for TcO ₄ ^- in the waste liquid under the condition of low solid-liquid ratio. Conventional adsorption materials usually have a removal rate of more than 90% when the solid-liquid ratio is above 10/1, but only a few materials can increase the solid-liquid ratio to 5/1, and the removal rate reaches 97%, while the MOFs of the present invention can Removal rates up to 96% at 2/1 and 99% at 5/1.

Application example 2

According to the reported concentration of each component in a certain river, ReO ₄ ^- was used instead of TcO ₄ ^- to configure the simulated waste liquid. Weigh 5, 10, 15, 20, 25 and 50mg samples respectively and place them in 5mL simulated waste liquid, take samples after stirring for 12 hours, filter them with a 0.22μm water filter membrane, measure the concentration of remaining rhenium in them by ICP-MS, and detect the The change of ReO ₄ ^{-concentration} was used to obtain the properties of MOF materials for the adsorption and removal of ^ReO ₄ -in river waste liquid. The results are shown in Figure 7. When the solid-liquid ratio is 1/1, 2/1, 3/1, 4/1, 5/1 and 10/1, the adsorption and removal rates of ReO ₄ ^- by ionic MOF materials are divided into 37%, 59%, 68%, 72%, 76% and 90%. It shows that the cationic MOF material has very strong adsorption and removal ability for simulating ReO ₄ ^- in this river, and this MOF is currently the material with the highest removal ability for simulating ReO ₄ ^- in this river. As above, only a very small number of materials can achieve a removal rate of 90% by increasing the solid-to-liquid ratio to 40/1.

Claims (10)

1. A fast preparation method for adsorbing and separating rhenium or technetium MOFs material, is characterized in that, comprises steps: tetrakis (4-pyridine biphenyl) ethylene and silver nitrate mixed reaction in organic solvent A, product filtration, washing, Dry to obtain the MOFs material; the organic solvent A is a mixed solvent of acetonitrile and dimethyl sulfoxide. 2. the rapid preparation method of the MOFs material of absorbing and separating rhenium or technetium according to claim 1, is characterized in that, tetrakis (4-pyridine biphenyl) ethylene and silver nitrate mol ratio are 1:0.8-1.2. 3. The rapid preparation method for adsorbing and separating rhenium or technetium MOFs materials according to claim 1, characterized in that, during the mixed reaction process, any method including heating, stirring at room temperature or ultrasound is used to speed up the reaction speed. 4. the rapid preparation method of the MOFs material of absorbing and separating rhenium or technetium according to claim 3, it is characterized in that, the temperature of heating is 60-120 ℃, and the reaction time is more than 10min, acetonitrile and two The volume ratio of methyl sulfoxide is 20:1-12. 5. the rapid preparation method of the MOFs material of adsorbing and separating rhenium or technetium according to claim 3, is characterized in that, the reaction times is more than 10min under stirring at room temperature; In organic solvent A, acetonitrile and dimethyl sulfoxide volume ratio are 20: 1-4. 6. the rapid preparation method of the MOFs material of adsorbing and separating rhenium or technetium according to claim 3, it is characterized in that, under ultrasonic action, react more than 5min, acetonitrile and dimethyl sulfoxide volume ratio are 20:1- in the organic solvent A 4. 7. The rapid preparation method of the MOFs material of adsorbing and separating rhenium or technetium according to claim 3, characterized in that, the reaction time under heating conditions is 10min-3h; and/or, the reaction time under stirring at room temperature is 10min-3h; And/or, the reaction time under ultrasonic conditions is 5min-1h. 8. A fast preparation method for adsorbing and separating rhenium or technetium MOFs material, is characterized in that, comprises the steps: tetrakis (4-pyridine biphenyl) ethylene is dissolved in organic solvent B, and silver nitrate is dissolved in acetonitrile, two kinds After the solution is mixed, the product is filtered, washed, and dried to obtain the MOFs material; The organic solvent B is a mixed solvent with a volume ratio of dichloromethane to acetonitrile of 20:1-4; the volume ratio of the organic solvent B to acetonitrile for dissolving silver nitrate is 20:0.5-1. 9. The application of the MOFs material prepared by the preparation method according to any one of claims 1-8 in adsorption and separation of rhenium or technetium. 10. The application of the MOFs material in adsorption and separation of rhenium or technetium according to claim 9, characterized in that it comprises the step of: placing the MOFs material in a solution containing rhenium or technetium for 40min-24h to realize removal of the solution The role of rhenium or technetium in The solid-to-liquid ratio of the MOFs material to the solution containing rhenium or technetium is 1-10:1; the removal rate of rhenium is over 35%, and the removal rate of technetium is over 80%.

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