Preparation of MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane materials and their application in the removal of radioactive iodine aerosols.

Abstract

This invention discloses the preparation of a MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material and its application in the removal of radioactive iodine aerosols. The method includes: dissolving at least two polymers in an organic solvent, then adding MOFs powder and stirring to form a precursor solution; electrospinning the precursor solution to obtain the MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material. This invention provides new ideas for the design and synthesis of electrospun fiber membranes and for the deep purification of iodine aerosols. Furthermore, compared with other fiber membrane materials, this fiber membrane material exhibits good radiation stability, high adsorption capacity, and excellent filtration efficiency. It has potential applications in the field of nuclear fuel reprocessing technology, including the adsorption of radioactive iodine gas and methyl iodine, as well as the filtration of radioactive aerosols.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel reprocessing technology, specifically to the preparation of a MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material and its application in the removal of radioactive iodine aerosols. Background Technology

[0002] Radioactive aerosols are small clusters of radioactive fission products that form on the surface of the atmosphere through solidification, condensation and chemical interactions. These clusters, about a few nanometers in size, attach to tiny particles in the atmosphere and are suspended in the gas as solid particles or tiny droplets.

[0003] Currently, various methods exist for removing radioactive aerosols from exhaust gases, primarily wet and dry purification technologies. Wet purification technologies include bubbling scrubbing, atomization fixation, pressurized dissolved air flotation, and oxidation electric field trapping; however, these methods are complex, costly to operate, can generate secondary pollution, and are not ideal for removing radioactive iodine. Dry purification technologies mainly use fiber or membrane filter media to trap aerosol particles; these technologies are highly mature and widely used in air purification for nuclear energy and non-nuclear industries. Currently, most high-efficiency air filters used in nuclear power plant air purification systems employ glass fiber filter media, but these have drawbacks such as high filtration resistance, easy clogging, and inability to directly adsorb radioactive iodine gas. Therefore, developing an effective filter material to enrich and remove radioactive iodine aerosols from exhaust gases is of great significance.

[0004] Many methods for preparing fiber membranes for air purification have been developed, commonly based on centrifugal spinning, melt-blown spinning, and electrospinning. Among these, electrospun fiber membranes possess excellent properties, such as superior surface adhesion, high porosity, high specific surface area, low basis weight, and uniform fiber size, enabling the preparation of high-performance filtration membrane materials. They have become one of the most promising and widely used air filtration media membranes. Currently, many electrospun polymer fiber membranes are used in air purification, including those made of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyimide (PI), polyethylene terephthalate (PET), polyamide, polyurethane (PU), polyethylene oxide (PEO), and polysulfone (PSU). Furthermore, much research focuses on modifying composite fiber membranes by adding different guest materials to prepare high-performance, multifunctional nanofiber membranes. However, no fiber membrane materials have been applied to remove radioactive iodine aerosols in the current technology, and existing fiber membrane materials exhibit poor adsorption performance for radioactive iodine aerosols. Summary of the Invention

[0005] In view of the above technical problems, the present invention needs to propose a MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material and its preparation method, which has good irradiation stability, easy recovery, high adsorption capacity, excellent filtration efficiency, and multifunctional removal of iodine gas, methyl iodine, and aerosol particles.

[0006] This invention develops a MOF-based composite fiber membrane for the efficient removal of radioactive iodine aerosols. The composite fiber membrane with uniform dimensions was prepared using a one-step electrospinning method. Adsorption and aerosol filtration experiments demonstrate that the composite fiber membrane exhibits high adsorption capacity for I₂ and CH₃I, and highly efficient filtration performance for radioactive aerosols. The composite fiber membrane demonstrates both high iodine removal performance and high aerosol filtration efficiency, showing great application potential in the deep treatment of radioactive iodine aerosols.

[0007] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0008] To achieve these objectives and other advantages according to the present invention, a method for preparing MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane materials is provided, comprising the following steps:

[0009] Step 1: Dissolve at least two polymers in an organic solvent, then add MOF powder and stir to dissolve and form a precursor solution;

[0010] Step 2: Electrospin the precursor solution to obtain MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material.

[0011] Preferably, the polymer is at least two of the following: polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylidene fluoride, polylactic acid, polyimide, polyethylene terephthalate, polyamide, polyurethane, polyethylene oxide, and polysulfone.

[0012] Preferably, the MOF powder is one of ZIF-8, UIO-66, ZIF-67, MIL-125, MOF-808, NU-1000, and Cu-BTC.

[0013] Preferably, the ZIF-8 powder is prepared as follows: zinc salt is dissolved in solvent A, denoted as solution A; 2-methylimidazole is also dissolved in solvent B, denoted as solution B, and solution B is quickly added to solution A. The resulting mixed solution is ultrasonically treated, covered with plastic wrap, and allowed to stand at room temperature for 12-36 hours. The resulting suspension is centrifuged, and the resulting white powder is dried in a drying oven to obtain ZIF-8 powder. Then, it is sealed in a sample bottle and stored in a desiccator.

[0014] Preferably, in the method for preparing the ZIF-8 powder, the zinc salt is any one of zinc nitrate hexahydrate, zinc chloride, and zinc sulfide; solvent A and solvent B are any one of methanol, ethanol, water, and N,N-dimethylformamide.

[0015] Preferably, the ratio of zinc salt to solvent A is 1-5:2-4; the ratio of 2-methylimidazole to solvent B is 1-5:2-4; the mass ratio of zinc salt to 2-methylimidazole is 1:1-4; and the ultrasonic treatment time is 5-30 min.

[0016] Preferably, in the preparation method of the ZIF-8 powder, the ultrasonic treatment time is 5-30 min; the drying temperature is 50-80℃; and the drying time is 6-36 h.

[0017] Preferably, in step one, the organic solvent is any one of N,N-dimethylformamide, tetrahydrofuran, isopropanol, and a mixture of tetrahydrofuran and dimethylformamide. More preferably, the organic solvent is N,N-dimethylformamide, as ZIF-8 exhibits the best solubility and spinning performance in N,N-dimethylformamide.

[0018] Preferably, in step one, the mass ratio of polymer, MOF powder, and organic solvent is 0.3–1.8:0.1–0.3:9. Within this ratio range, ZIF-8 powder can be uniformly dispersed in the polymer spinning solution, and the viscosity of the precursor spinning solution within this ratio range is also suitable for electrospinning.

[0019] Preferably, in step two, the electrospinning parameters are as follows: 20-30 gauge stainless steel needles; spinning voltage: 6-20KV; electrode distance: 5-20cm; injection pump feed rate: 0.5-2mL / h; ambient temperature: 5-40℃; ambient humidity: 30-100%. Only when the critical voltage is reached can the electric field force overcome the surface tension of the polymer droplets, thus causing the Taylor cone to eject and form a jet. Under the further stretching of the electric field force, the jet undergoes a solvent evaporation process to form fibers. Voltage, flow rate, and ambient temperature and humidity also affect fiber formation.

[0020] Preferably, an 18-24 gauge needle is used; the electrospinning voltage is 8-15KV; and the injection pump feed rate is 0.3-0.8mL / min. The ambient temperature is 5-20℃; and the ambient humidity is 40-80%. Within this range, the filaments are uniform and can provide uniform adhesion points for ZIF-8.

[0021] Preferably, in step one, the ZIF-8 powder is pretreated before use. The pretreatment process is as follows: ZIF-8 powder and ethylenediamine with a mass-to-volume ratio of 5-10g:500-800mL are added to a high-pressure reactor, sealed, and reacted at a pressure of 10-15MPa and a temperature of 300-315℃ for 3-5 minutes. After cooling to room temperature, the mixture is filtered and dried to obtain pretreated ZIF-8 powder.

[0022] The present invention also provides a MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material prepared according to the preparation method described above.

[0023] This invention also provides the application of MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material prepared according to the preparation method described above in the adsorption and filtration of radioactive iodine aerosols. This material exhibits excellent adsorption performance for iodine gas and ideal filtration efficiency for radioactive aerosols, while also demonstrating significant stability and radiation resistance.

[0024] Preferably, MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane materials are soaked in water and then applied to the adsorption and filtration of radioactive iodine aerosols.

[0025] Preferably, MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane materials are irradiated with radioactive cobalt and then applied to the adsorption and filtration of radioactive iodine aerosols.

[0026] The present invention has at least the following beneficial effects:

[0027] (1) The multifunctional three-dimensional network fiber membrane material of the present invention, compared with other fiber materials, is a MOFs-based three-dimensional network nanocomposite fiber membrane material, which has high adsorption performance for radioactive iodine gas and is a new type of high-efficiency fiber membrane material.

[0028] (2) The multifunctional three-dimensional network fiber membrane material of the present invention, compared with other fiber materials, is a MOFs-based three-dimensional network nanocomposite fiber membrane material, which has good adsorption performance for methyl iodine, making it a very promising strategy in the field of protection against radioactive environments.

[0029] (3) The multifunctional three-dimensional network fiber membrane material of the present invention, compared with other fiber materials, is a MOFs-based three-dimensional network nanocomposite fiber membrane material, which has high efficiency in filtering and capturing radioactive aerosol gases, and thus shows great application potential in the deep treatment of radioactive iodine aerosols.

[0030] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached image description:

[0031] Figure 1 The diagram shows the preparation process of the novel MOFs-based nanofiber composite membrane material of the present invention, and the SEM images of the PVP / PAN fiber membrane material of Example 1 (b, c, d) and the SEM images of the ZIF-8@PVP / PAN composite fiber membrane material of Example 2 (e, f, g).

[0032] Figure 2 The images show the XRD pattern (a), infrared pattern (b), and XPS image (c) of the MOFs-based nanofiber composite membrane materials of Examples 1 and 2.

[0033] Figure 3 The graph shows the adsorption curves (a), isothermal adsorption curves (b), and performance changes (c) of the MOFs-based nanofiber composite membrane materials prepared in Examples 1 and 2 for iodine gas.

[0034] Figure 4 The adsorption curves (a), isothermal adsorption curves (b), and performance changes (c) of the MOFs-based nanofiber composite membrane materials prepared in Examples 1 and 2 for methyl iodine gas are shown.

[0035] Figure 5 The adsorption curves of iodine gas (a) and methyl iodine gas (b) on the MOFs-based nanofiber composite membrane materials prepared in Examples 1 and 3 are shown.

[0036] Figure 6 The filtration efficiency curves (a), filtration efficiency curves (b), and pressure drop variation diagrams (c) of the MOFs-based nanofiber composite membrane materials prepared in Examples 1 and 2 for simulated radioactive aerosols of different particle sizes are shown.

[0037] Figure 7 The images show SEM images of the PVP / PAN fiber membrane materials filtered by Example 1 and the corresponding application examples 3 (a, b, c); and SEM images of the ZIF-8@PVP / PAN fiber membrane materials filtered by Example 2 and the corresponding application examples 3 (d, e, f). Detailed implementation method:

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] The raw materials used in the following examples, polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN) and N,N-dimethylformamide (DMF), were all purchased from Aladdin Chemical Co., Ltd. and were used directly without further purification.

[0041] Example 1:

[0042] (1) Preparation of PVP / PAN fiber membrane: First, a spinning solution was prepared by simultaneously adding 0.5g of PVP powder and 0.5g of PAN powder to 9g of DMF solution and stirring at room temperature for 6 hours to dissolve the powder. Electrospinning was then performed by placing the spinning solution into a plastic syringe and then into a syringe pump. A No. 22 metal needle was used during spinning, maintaining a speed of 0.5mL / h and a voltage of 10KV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150r / min. After 6 hours of spinning, the aluminum foil loaded with the fiber membrane was removed and dried in an oven at 60℃ for 12 hours to obtain the PVP / PAN nanocomposite fiber membrane.

[0043] Example 2:

[0044] A schematic diagram of the preparation process of MOFs-based nanocomposite fiber membrane materials is shown below. Figure 1 As shown in (a):

[0045] (1) Preparation of ZIF-8: 1.487 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, denoted as solution A. 3.284 g of 2-methylimidazole was also dissolved in 50 mL of methanol, denoted as solution B, and solution B was quickly added to solution A. The mixed solution was sonicated for 10 minutes, covered with plastic wrap, and allowed to stand at room temperature for 24 hours. The suspension was then centrifuged, and washed three times with methanol during centrifugation. The resulting white powder was dried at 60 °C for 12 hours to obtain ZIF-8 powder.

[0046] (2) Preparation of ZIF-8@PVP / PAN fiber membrane: First, a spinning solution was prepared by dissolving 0.5g of PVP powder and 0.5g of PAN powder in 9g of DMF solution, followed by the addition of 0.2g of ZIF-8 powder. The mixture was ultrasonicated for 1 hour and then stirred for 12 hours to obtain a composite spinning solution. The solution was then subjected to electrospinning. The spinning solution was first placed in a plastic syringe, which was then placed in a syringe pump. A No. 22 metal needle was used during spinning, maintaining a speed of 0.5mL / h and a voltage of 10KV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150r / min. After 6 hours of spinning, the aluminum foil loaded with the fiber membrane was removed and dried in an oven at 60℃ for 12 hours to obtain the ZIF-8@PVP / PAN fiber membrane.

[0047] Example 3:

[0048] (1) Preparation of ZIF-8: 1.487 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, denoted as solution A. 3.284 g of 2-methylimidazole was also dissolved in 50 mL of methanol, denoted as solution B, and solution B was quickly added to solution A. The mixed solution was sonicated for 10 minutes, covered with plastic wrap, and allowed to stand at room temperature for 24 hours. The suspension was then centrifuged, and washed three times with methanol during centrifugation. The resulting white powder was dried at 60 °C for 12 hours to obtain ZIF-8 powder.

[0049] (2) Add 1g of ZIF-8 powder and 100mL of ethylenediamine to a high-pressure reactor, seal it, and react it for 5min at a pressure of 12MPa and a temperature of 310℃. After cooling to room temperature, filter and dry to obtain pretreated ZIF-8 powder (P-ZIF-8).

[0050] (3) Preparation of P-ZIF-8@PVP / PAN fiber membrane: First, a spinning solution was prepared by dissolving 0.5g of PVP powder and 0.5g of PAN powder in 9g of DMF solution, followed by the addition of 0.2g of pretreated ZIF-8 powder. The mixture was ultrasonicated for 1 hour and then stirred for 12 hours to obtain a composite spinning solution. The solution was then subjected to electrospinning. The spinning solution was first placed in a plastic syringe, which was then placed in an injection pump. A No. 22 metal needle was used during spinning, maintaining a speed of 0.5mL / h and a voltage of 10KV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150r / min. After 6 hours of spinning, the aluminum foil loaded with the fiber membrane was removed and dried in an oven at 60℃ for 12 hours to obtain the P-ZIF-8@PVP / PAN fiber membrane.

[0051] Example 4:

[0052] Preparation of UIO-66@PVP / PAN fiber membrane: First, a spinning solution was prepared by dissolving 0.5g of PVP powder and 0.5g of PAN powder in 9g of DMF solution, followed by the addition of 0.2g of UIO-66 powder. The mixture was ultrasonicated for 1 hour and then stirred for 12 hours to obtain a composite spinning solution. The solution was then subjected to electrospinning. The spinning solution was first placed in a plastic syringe, which was then placed in a syringe pump. A 22-gauge metal needle was used during spinning, maintaining a speed of 0.5mL / h and a voltage of 10KV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150r / min. After 6 hours of spinning, the aluminum foil loaded with the fiber membrane was removed and dried in an oven at 60℃ for 12 hours to obtain the UIO-66@PVP / PAN fiber membrane.

[0053] Example 5:

[0054] Preparation of MIL-125@PVP / PAN fiber membrane: First, a spinning solution was prepared by dissolving 0.5g of PVP powder and 0.5g of PAN powder in 9g of DMF solution, followed by the addition of 0.2g of MIL-125 powder. The mixture was ultrasonicated for 1 hour and then stirred for 12 hours to obtain a composite spinning solution. The solution was then subjected to electrospinning. The spinning solution was first placed in a plastic syringe, which was then placed in a syringe pump. A 22-gauge metal needle was used during spinning, maintaining a speed of 0.5mL / h and a voltage of 10KV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150r / min. After 6 hours of spinning, the aluminum foil loaded with the fiber membrane was removed and dried in an oven at 60℃ for 12 hours to obtain the MIL-125@PVP / PAN fiber membrane.

[0055] The composite fiber membrane materials prepared in Examples 1 and 2 were characterized by SEM, XRD, and infrared spectroscopy. Macroscopically, they are nonwoven membranes, and the surface morphologies of PVP / PAN and ZIF-8@PVP / PAN are as follows. Figure 1 As shown, under an electron microscope, they appear to be fibrous membranes composed of long, continuous fibers randomly interwoven together. Figure 1 As shown in (b) and (c), the original PVP / PAN fibers are cylindrical with a smooth surface and an average fiber diameter of 350 nm. Figure 1(e, f) are SEM images of ZIF-8@PVP / PAN. It can be seen that after loading ZIF-8, ZIF-8 crystals appeared on the surface of the fiber membrane, and the fiber diameter distribution did not change significantly, with an average diameter of 0.32 nm. The ZIF-8 nanoparticles embedded in the PVP / PAN fiber membrane composite seem to retain their original rhombic dodecahedral crystal structure, further improving the accessibility of ZIF-8 in the nanofiber composite material, which is crucial for I2 capture and retention. EDS images show the elemental distribution of pure PVP / PAN and ZIF-8@PVP / PAN. Figure 1 As shown in d, pure PVP / PAN fiber membranes are composed of C, N, and O. After adding ZIF-8, as shown in the elemental mapping image ( Figure 1 As shown in g), Zn and N elements are uniformly distributed on the fibers, indicating that ZIF-8 particles are uniformly loaded onto the surface and interior of the fibers. The loading of ZIF-8 crystals increases the surface roughness of the PVP / PAN nanofibers, which not only increases the effective surface area for iodine gas action but also makes it more advantageous for filtration applications using nanofiber membranes and enhances their particle capture performance.

[0056] Figure 2 (a) shows the XRD patterns of ZIF-8 powder, PVP / PAN fiber membrane, and ZIF-8@PVP / PAN fiber membrane. The PVP / PAN fiber membrane shows an image of the amorphous phase. The image of the synthesized ZIF-8 nanocrystals is identical to the standard ZIF-8 image, confirming the successful synthesis of ZIF-8 powder. In the spectrum of the ZIF-8@PVP / PAN fiber membrane, characteristic peaks of ZIF-8 nanocrystals were observed at 7.3, 10.4, 12.7, 14.7, 16.7, 18.0, and 26.7. The strong diffraction peaks corresponding to the (011), (002), (112), (022), (013), (222), and (134) crystal planes of ZIF-8 are consistent with the standard ZIF-8 spectrum, further demonstrating the successful loading of ZIF-8 in PVP / PAN.

[0057] The chemical bond structure of the sample obtained by FTIR spectroscopy analysis ( Figure 2 (b) ) Typical characteristic peaks of PAN and PVP can be observed in the spectrum of the PVP / PAN fiber membrane, with the peak at 2244 cm⁻¹. -1 The peak at 1350-1500 cm⁻¹ is due to the C≡N bond vibration of the PAN cyano group. -1 The characteristic absorption peak of PAN cyano cyclization is stretched at 1653 cm⁻¹. -1 The position is due to the -C=O stretching vibration transition of PVP, 1291cm -1The stretching vibrations are attributed to the tertiary amine groups derived from PVP. Additionally, the FTIR spectra of ZIF-8@PVP / PAN are observed at 1146, 994, 759, 694, and 420 cm⁻¹. -1 Several characteristic peaks were observed, attributed to the characteristic peaks of ZIF-8. Compared to pure PAN / PVP, the ZIF-8@PVP / PAN spectrum contained a 420 cm⁻¹ peak. -1 The peaks shown are characteristic Zn-N stretching peaks of ZIF-8, at 1146 and 994 cm⁻¹. -1 The peak at 759 cm⁻¹ is attributed to the CN stretching mode of 2-methylimidazole. -1 The peak at [value] corresponds to the CN bending vibration and CH bending mode in 2-methylimidazole. The Zn-N bond is a functional group connecting the metal site and the organic framework in ZIF-8, thus it is a key functional group in ZIF-8. XPS analysis was performed on the PVP / PAN nanofiber membrane and the ZIF-8@PVP / PAN composite fiber membrane; the full spectrum analysis is shown below. Figure 2 As shown in (c), the PVP / PAN spectrum exhibits peaks at C1s, N1s, and O1s, while the ZIF-8@PVP / PAN spectrum shows peaks at C1s, N1s, O1s, and Zn2p, consistent with the EDS results. The successful synthesis of ZIF-8@ / PVP / PAN NM is confirmed by comparing the FTIR, XPS, and XRD patterns of the PVP / PAN fiber membrane and the ZIF-8 / PVP / PAN fiber membrane.

[0058] Application Example 1:

[0059] To test the adsorption performance of the obtained nanocomposite fiber membrane material for iodine gas, 20 mg of the fiber membrane sample and excess iodine were placed in a glass container and placed in a 75°C oven under normal pressure. After a certain contact time, the container was removed and cooled to room temperature. The mass change of the nanocomposite fiber membrane was then measured after different reaction times to calculate its iodine adsorption capacity. The calculation was performed according to the following formula:

[0060] Iodine adsorption capacity = (mass after reaction - mass before reaction) / mass before reaction;

[0061] To investigate the adsorption performance of this nanofiber composite membrane material for iodine gas at different concentrations, a series of isothermal adsorption experiments were conducted. 20 mg of the nanofiber composite membrane materials prepared in Examples 1 and 2 were taken, and different concentrations of iodine gas were obtained by adding different masses of iodine. The experiments were then conducted at 75°C to study the material's ability to adsorb iodine gas at different iodine concentrations. The iodine capture performance was calculated by weighing the material after 12 hours of adsorption and measuring the mass change.

[0062] Application Example 2:

[0063] To test the adsorption performance of the obtained nanocomposite fiber membrane material for methyl iodine gas, 20 mg of the fiber membrane sample and excess methyl iodine were placed in a glass container and placed in a 75°C oven under normal pressure. After a certain contact time, the container was removed and cooled to room temperature. The mass change of the nanocomposite fiber membrane was then measured after different reaction times to calculate its methyl iodine adsorption capacity. The calculation was performed according to the following formula:

[0064] Methyl iodine adsorption capacity = (mass after reaction - mass before reaction) / mass before reaction;

[0065] To investigate the adsorption performance of this nanocomposite fiber membrane material at different concentrations of methyl iodine gas, a series of isothermal adsorption experiments were conducted. 20 mg of the nanocomposite fiber membrane materials prepared in Examples 1 and 2 were taken, and different concentrations of methyl iodine gas were obtained by adding different masses of methyl iodine. The experiments were then conducted at 75°C to study the material's ability to adsorb methyl iodine gas at different methyl iodine concentrations. The methyl iodine capture performance was calculated by weighing the material after 12 hours of adsorption and measuring the mass change.

[0066] The capture capabilities of PVP / PAN and ZIF-8@PVP / PAN for elemental iodine gas and methyl iodine gas were studied by different adsorption times. Figure 3 As shown, the saturated adsorption capacity of pure PVP / PAN fiber membrane for iodine gas is 1492 mg / g, while the saturated adsorption capacity of ZIF-8@PVP / PAN composite fiber membrane for iodine gas reaches 2898 mg / g, representing a 94% improvement in adsorption performance. Both membranes reached adsorption equilibrium in approximately 120 min. Both types of fiber membranes also exhibit good adsorption performance for methyl iodine, such as... Figure 4 As shown, the saturated adsorption capacity of pure PVP / PAN for methyl iodine is 241 mg / g, while the saturated adsorption capacity of ZIF-8@PVP / PAN composite fiber membrane for methyl iodine gas reaches 456 mg / g, with an adsorption performance improvement of 89%. The adsorption kinetics of both membranes reach adsorption equilibrium at around 360 min.

[0067] The capture capabilities of P-ZIF-8@PVP / PAN and ZIF-8@PVP / PAN for elemental iodine gas and methyl iodine gas were studied by different adsorption times. Figure 5 As shown in (a), the ZIF-8@PVP / PAN composite fiber membrane exhibits a saturated adsorption capacity of 2898 mg / g for iodine gas, while the P-ZIF-8@PVP / PAN composite fiber membrane shows a significant improvement with a saturated adsorption capacity of 3004 mg / g. Both fiber membranes also demonstrate good adsorption performance for methyl iodine. Figure 5As shown in (b), the saturated adsorption capacity of the ZIF-8@PVP / PAN composite fiber membrane for methyl iodine gas reached 456 mg / g, while the saturated adsorption capacity of the P-ZIF-8@PVP / PAN composite fiber membrane for methyl iodine gas reached 485 mg / g, showing a significant improvement. From the above experimental results, it can be seen that by pretreating the ZIF-8 powder, the surface groups of ZIF-8 were changed, and the mixing effect of ZIF-8 with PVP and PAN was improved. As a result, the prepared P-ZIF-8@PVP / PAN composite fiber membrane has richer surface groups, which improves the adsorption of iodine gas and methyl iodine gas.

[0068] Isothermal adsorption curve ( Figure 3 As shown in (b) and (4b), the iodine adsorption capacity per unit weight of adsorbent increases with increasing concentrations of I₂ and CH₃I until equilibrium is reached. This phenomenon indicates that the concentration gradient promotes the adsorption of iodine gas onto the nanofiber composite membrane until the binding sites of the nanofiber composite membrane reach adsorption saturation. Based on the fitting results of two adsorption models, the Langmuir model (R) 2 >0.99) compared to the Freundlich model (R 2 >0.89) is more consistent. This indicates that the capture of iodine by the two fiber membrane materials is independent, and the adsorption process tends to be monolayer adsorption.

[0069] To test the stability of the materials in a high-humidity environment, the two fiber membrane materials were immersed in pure water for 1 h, 3 h, 6 h, 12 h, 24 h, and 48 h, and then air-dried in a fume hood. Iodine adsorption experiments were then conducted using the methods described in Application Examples 1 and 2. Figure 3 (c) and Figure 4 (c) shows the adsorption performance of iodine gas and methyl iodine on the two fiber membranes after soaking in pure water for different times. As can be seen from the figure, after 1 hour of soaking, the adsorption performance of the PVP / PAN fiber membrane for iodine gas decreased to 762 mg / g, and the adsorption performance for methyl iodine decreased to 198 mg / g. The adsorption performance remained relatively stable with increasing soaking time, which is due to the decomposition of PVP in water. The capture performance of iodine gas and methyl iodine on the ZIF-8@PVP / PAN membrane also decreased after soaking in water. After 3 hours of soaking, the adsorption performance for iodine gas decreased to 1071 mg / g, and the adsorption performance for methyl iodine decreased to 239 mg / g. The capture performance for iodine remained relatively unchanged with increasing soaking time. Therefore, although the adsorption performance of the two fiber membranes decreased in an aqueous environment due to the decomposition of PVP, it still maintained a relatively high level. To verify the radiation stability of the materials, the two fiber membranes were irradiated with different doses (100 KGy, 150 KGy, 200 KGy) using radioactive cobalt, and iodine adsorption experiments were conducted using the methods described in Examples 1 and 2. Figure 3 (c) and Figure 4 As shown in (c), after irradiation with 100 kGy, 150 kGy, and 200 kGy, respectively, the capture performance of iodine gas and methyl iodine gas by PVP / PAN and ZIF-8@PVP / PAN fiber membranes showed no significant change. The adsorption capacity for iodine gas remained at approximately 1442 mg / g and 2773 mg / g, respectively, while the adsorption capacity for methyl iodine gas remained at approximately 237 mg / g and 451 mg / g, respectively. This indicates that both fiber membranes exhibit good radiation stability.

[0070] Application Example 3

[0071] To verify the filtration performance of the fiber membrane for radioactive aerosol particles, the filtration performance of Examples 1 and 2 was tested using a laboratory aerosol filtration testing platform. First, the fiber membrane was cut into circular filter membranes with a diameter of 5 cm, and then fixed in the fixture of the aerosol generator. The effective test area of ​​the nanofiber membrane was 15.904 cm². 2 Then, a particle counter was connected upstream of the filter membrane in the ventilation duct, and another particle counter was connected downstream. Nano-SiO2 was used as the aerosol source to simulate radioactive aerosols, with most particles having a diameter of 300 nm. The surface velocity was controlled by adjusting the airflow, and the number of particles before and after filtration was recorded using the particle counters. Simultaneously, the pressure drop across the membrane was measured. Each filtration experiment was repeated three times, and the average value was calculated. The filtration efficiency of different fiber membranes was calculated using the following formula:

[0072] Filtration efficiency = 1 - (number of upstream aerosol particles) / (number of downstream aerosol particles)

[0073] The quality factor is calculated using the following formula:

[0074] Quality factor = -ln(1 - filtration efficiency) / pressure drop

[0075] in Figure 6 (a) shows the filtration efficiency curves of two fiber membrane materials for aerosol particles of different diameters. The PVP / PAN fiber membrane for PM... 0.3 The filtration efficiency is 97.52%, and it gradually increases with the increase of pollutant diameter. For particles with a diameter greater than 3μm, the filtration efficiency can reach 100%. After loading with ZIF-8, due to the blocking adsorption effect of ZIF-8, the ZIF-8@PVP / PAN fiber membrane has a significant improvement in filtration efficiency for PM2.5. 0.3 The filtration efficiency is 99.91%, and it can reach 100% for particles with a diameter greater than 3 μm. To investigate the effect of different wind velocities on the filtration efficiency, the filtration efficiency at different surface velocities was further tested, such as... Figure 6As shown in (b), the filtration efficiency shows a slow decreasing trend with increasing surface velocity. At a surface velocity of 10 cm / s, the filtration efficiency of PVP / PAN for PM... 0.3 With a filtration efficiency of 97.02%, the ZIF-8@PVP / PAN still maintains a relatively high filtration efficiency of 99.62%. Figure 6 (c) shows the pressure drop and quality factor variation curves of the two fiber membranes at different face velocities. The figure shows that the pressure drops of PVP / PAN and ZIF-8@PVP / PAN at a face velocity of 5 cm / s are 181 Pa and 79 Pa, respectively, indicating that the loading of ZIF-8 not only improves the filtration efficiency of particulate matter but also reduces the pressure drop resistance of the fiber membrane. With increasing face velocity, the resistance to air increases, and the pressure drop rises slowly. The quality factor determines the overall performance of the filter in terms of filtration efficiency and pressure drop. Figure 6 As can be seen in (c), the quality of ZIF-8@PVP / PAN is therefore as high as 0.089 Pa. -1 It is a PVP / PAN fiber membrane (0.02 Pa). -1 The ZIF-8 loading significantly improves the filtration performance of the fiber membrane, being 4.45 times that of the standard membrane. This indicates that the ZIF-8 loading significantly enhances the filtration performance of the fiber membrane. While the quality factor decreases slowly with increasing surface velocity, it remains at a high level overall. In conclusion, ZIF-8@PVP / PAN exhibits good filtration efficiency and low pressure drop, making it a promising candidate for filtering and protecting against radioactive aerosols in nuclear emergency situations.

[0076] To investigate the filtration mechanism of fiber membranes for radioactive aerosols, SEM was performed on the filtered material, such as... Figure 7 As shown in (a, b, c), the fiber membrane skeleton plays a crucial role in aerosol filtration. The high specific surface area and porous structure of the PVP / PAN fiber membrane provide a large contact surface for aerosol particles, promoting particle interception and capture. Secondly, the PVP / PAN fibers possess electrostatic charges, which attract charged aerosol particles, increasing their capture efficiency. Furthermore, the fine gaps and defects between the fibers of the PVP / PAN electrospun fiber membrane allow for the interception of particles of different sizes and types through inertial deposition and diffusion. Notably, after loading ZIF-8, the highly porous crystal structure of ZIF-8 provides a large surface area and adsorption sites, which is beneficial for the adsorption and capture of aerosol particles, especially smaller PM particles. 0.3 Most of them are adsorbed and enriched on the surface and inside of ZIF-8. Figure 7(d, e, f). ZIF-8 material, due to its inherent specific adsorption properties, effectively intercepts particles from the airflow. The combination of ZIF-8 with electrospun fiber membranes further improves the surface properties of the fiber membrane, increasing its affinity for aerosol particles. Consequently, ZIF-8@PVP / PAN further enhances filtration efficiency, consistent with experimental data. Therefore, ZIF-8@PVP / PAN electrospun fiber membranes achieve highly efficient filtration and capture of aerosol particles through the interception effect of the fiber structure, adsorption properties, and electrostatic attraction.

[0077] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. The application of a MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material in the adsorption and filtration of radioactive iodine aerosol, characterized in that, MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material was irradiated with radioactive cobalt and then applied to the adsorption and filtration of radioactive iodine aerosol. The preparation method of the MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material includes the following steps: Step 1: Dissolve at least two polymers in an organic solvent, then add MOF powder and stir to dissolve and form a precursor solution; Step 2: Electrospin the precursor solution to obtain MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material. The polymer is at least two of the following: polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylidene fluoride, polylactic acid, polyimide, polyethylene terephthalate, polyamide, polyurethane, polyethylene oxide, and polysulfone. The MOF powder is ZIF-8; The ZIF-8 powder is used after pretreatment. The pretreatment process is as follows: ZIF-8 powder and ethylenediamine with a mass-to-volume ratio of 5~10g:500~800mL are added to a high-pressure reactor, sealed, and reacted at a pressure of 10~15MPa and a temperature of 300~315℃ for 3~5min. After cooling to room temperature, the mixture is filtered and dried to obtain pretreated ZIF-8 powder.

2. The application of the MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material according to claim 1 in the adsorption and filtration of radioactive iodine aerosol, characterized in that, In step one, the organic solvent is any one of N,N-dimethylformamide, tetrahydrofuran, isopropanol, and a mixture of tetrahydrofuran and dimethylformamide.

3. The application of the MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material according to claim 1 in the adsorption and filtration of radioactive iodine aerosol, characterized in that, In step one, the mass ratio of polymer, MOF powder, and organic solvent is 0.3~1.8:0.1~0.3:

9.

4. The application of the MOFs-based multifunctional three-dimensional network nanocomposite fiber membrane material according to claim 1 in the adsorption and filtration of radioactive iodine aerosol, characterized in that, In step two, the electrospinning parameters are as follows: needles are 20-30 gauge stainless steel needles; spinning voltage: 6-20 KV; electrode distance: 5-20 cm; injection pump feed rate: 0.5-2 mL / h; ambient temperature: 5-40℃; ambient humidity: 30-100%.

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