Preparation method and application of MOFs-based double-scale polyimide three-dimensional network nanofiber membrane

Abstract

The application discloses a preparation method and application of a MOFs-based double-scale polyimide three-dimensional network nanofiber membrane, and comprises the following steps: calcining a double-scale three-dimensional network PAA fiber membrane in an inert atmosphere to obtain a double-scale three-dimensional network PI fiber membrane; and immersing the double-scale three-dimensional network PI fiber membrane in a mixed solution of a zinc salt, an organic ligand and a solvent B, so that MOFs grow in situ on the fiber membrane, and then drying to prepare the MOFs-based double-scale polyimide three-dimensional network nanofiber membrane. The MOFs-based double-scale polyimide three-dimensional network nanofiber membrane is used as a filter layer to prepare a MOFs-based double-scale nanometer network radioactive iodine aerosol protective mask. The MOFs-based double-scale nanometer network radioactive iodine aerosol protective mask has the characteristics of good stability, high iodine gas adsorption capacity, excellent filtration efficiency and good air permeability. The mask has potential application prospects in the fields of adsorption and purification of radioactive iodine gas and protection of radioactive aerosol in the nuclear industry and nuclear accident emergency.

Description

Technical Field

[0001] This invention belongs to the technical field of polyimide nanofiber membrane filtration materials in nanofiber membranes. More specifically, this invention relates to a method for preparing and applying a MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane. Background Technology

[0002] Nuclear energy development and nuclear accident emergency response processes generate large amounts of radioactive aerosols, mainly composed of fission products and suspended solid dust, with a particle size distribution ranging from 0.3 μm to 10 μm; these aerosols contain various radionuclides, such as... 137 Cs、 3 H, 90 Sr、 14 C 129 I, 131 I, 133 Xe, etc. Among them, 131 I and 129 I has a higher output, especially 129 I, which has a long half-life (T 1 / 2 =1.6×10 7 a) The thyroid gland's targeted toxicity, high mobility, and ease of bioaccumulation pose a potential radiation threat to workers and the environment. In a nuclear accident, radioactive iodine is mainly released into the atmosphere in the form of aerosols, with a small amount released in gaseous form. Conventional protective measures are insufficient to address this type of multiphase contamination.

[0003] Currently, the methods for enriching and removing radioactive iodine and aerosols from radioactive waste gas are mainly divided into wet scrubbing and dry adsorption. Wet scrubbing, such as the Iodox process, Mercurex process, and alkaline solution scrubbing, has problems such as complex process systems, highly corrosive equipment, and high operating costs. It also easily generates secondary waste liquid containing radionuclides, posing environmental risks. However, mainstream dry adsorption materials face a dual technical bottleneck: (1) powder materials such as activated carbon and silver-based zeolite have limited iodine adsorption capacity (<500mg / g) and cannot intercept submicron aerosols; (2) although HEPA filters can trap 0.3μm particles (efficiency ≥99.97%), they lack radioactive iodine adsorption performance, leading to the risk of radioactive iodine gas penetration. Therefore, in nuclear emergency situations, it is of great significance to develop a fast and convenient radioactive iodine aerosol protective mask.

[0004] In recent years, researchers have revealed that metal-organic frameworks (MOFs) possess high specific surface areas (>2000 m²). 2The designable pore structure and functionalized sites (such as amino and thiol groups) exhibit excellent performance in radioactive iodine adsorption (ZIF-8 adsorption capacity reaches 1.25 g / g, and UiO-66-FA reaches 2.25 g / g). Meanwhile, electrospun fiber membranes, with their advantages of simple processing, controllable fiber diameter (50-500 nm), and high porosity (over 80%), have become one of the most promising and widely used air filtration membranes. Currently, electrospinning technology has been successfully applied to the preparation of various polymer fiber membranes, such as polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), and polyimide (PI).

[0005] In addition, currently available commercially available conventional protective masks have limited filtration efficiency when filtering aerosol particles with a diameter of 0.3μm and above, and cannot simultaneously adsorb radioactive iodine gas. This technical deficiency makes it difficult for conventional protective masks to effectively block the diffusion of radioactive iodine-containing aerosols under the complex operating conditions of nuclear power plants or in the event of a sudden accident, posing a potential risk to the health and safety of workers. Summary of the Invention

[0006] 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.

[0007] To achieve these and other advantages according to the present invention, a method for preparing a MOFs-based two-scale polyimide three-dimensional network nanofiber membrane is provided, comprising the following steps:

[0008] Step 1: Calcine the dual-scale three-dimensional network PAA fiber membrane in an inert atmosphere to achieve thermal imidization reaction, and obtain the dual-scale three-dimensional network PI fiber membrane.

[0009] Step 2: Immerse the dual-scale three-dimensional network PI fiber membrane in a mixed solution of zinc salt, organic ligand, and solvent B. Use a self-assembly method to allow MOFs to grow in situ on the fiber membrane. Then place it in an oven for drying to prepare MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane.

[0010] Preferably, in step one, the method for preparing the dual-scale three-dimensional network PAA fiber membrane includes:

[0011] S11. Weigh 4,4'-diaminodiphenyl ether, dodecyltrimethylammonium bromide and pyromellitic dianhydride and dissolve them in organic solvent A. Stir to dissolve and form a precursor spinning solution.

[0012] S12. Electrospin the precursor spinning solution to obtain a dual-scale three-dimensional network PAA fiber membrane.

[0013] Preferably, in S11, the organic solvent A is any one of N,N-dimethylformamide, ethanol, tetrahydrofuran, N,N-dimethylacetamide, acetone, and diethyl ether.

[0014] Preferably, in S11, the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride is 1-5:1-5; the total concentration of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride in organic solvent A is 10%-20%; the concentration of dodecyltrimethylammonium bromide in organic solvent A is 0-5%; the stirring and dissolving temperature is 0-10°C; the ambient humidity is 30-100%; and the stirring time is 1-24 hours.

[0015] Preferably, in step S12, the electrospinning parameters are as follows: spinning voltage: 5–25 kV; needle: 18–30 gauge stainless steel needle; electrode distance: 5–20 cm; injection pump feed rate: 0.3–1.5 mL / h; ambient temperature: 5–40 °C; ambient humidity: 30–100%.

[0016] Preferably, in step one, the inert atmosphere includes one of nitrogen, argon, and helium; the thermal imidization calcination temperature is 250–550°C, the heating rate is 1–10°C / min, and the holding time is 0.5–4h.

[0017] Preferably, in step two, solvent B includes one or more of methanol, deionized water, ethanol, and N,N-dimethylformamide; zinc salt includes any one or more of zinc nitrate hexahydrate, zinc chloride, zinc sulfate, zinc acetate, and zinc citrate; organic ligand includes any one of imidazole and 2-methylimidazole; the impregnation time is 1–48 h; the drying temperature is 30–80 °C, and the drying time is 1–10 h; the molar ratio of zinc salt to organic ligand is 1:8, and the ratio of organic ligand to solvent B is 0.04 mol of organic ligand dissolved per 100 mL of solvent B.

[0018] An application of a MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane is disclosed. This MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane is used to prepare a MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask. The specific method includes: selecting a breathable nonwoven fabric as the outer and inner layers of the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask; placing the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane as the filter layer of the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask between the outer and inner layers; and obtaining the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask through a composite process.

[0019] Preferably, the composite process includes hot pressing, sewing, and bonding.

[0020] Preferably, the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask is used to capture and filter radioactive iodine aerosols.

[0021] To improve the adsorption capacity of MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane for iodine and increase its saturated adsorption capacity for iodine gas, after obtaining the dual-scale three-dimensional network PI fiber membrane in step one, the membrane was immersed in a polyethyleneimine solution with 2-chloro-1-methylpyridine iodide added as an activator. The solution was heated to 50–80°C for 5–12 h and then dried to obtain a grafted modified dual-scale three-dimensional network PI fiber membrane. The polyethyleneimine solution had a mass fraction of 30–50 wt%, a molecular weight of 3500–12000 g / mol, and 2-chloro-1-methylpyridine iodide accounted for 1–4 wt% of the polyethyleneimine solution.

[0022] Meanwhile, in step two, bismuth nitrate pentahydrate is added to the mixed solution, with a molar ratio of bismuth nitrate pentahydrate to zinc salt of 1:1.

[0023] The present invention has at least the following beneficial effects:

[0024] (1) This invention reports three types of mask preparation methods, which are respectively applied to daily PM2.5 treatment. 2.5 Protection, Industrial PM 0.3 High-performance protection, and protection against radioactive iodine aerosols in nuclear emergency situations.

[0025] (2) The MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask of the present invention uses a dual-scale three-dimensional network nanofiber membrane as its core filter material. The fiber diameter and pore size can be controlled and adjusted through electrospinning, giving the mask excellent breathability and ideal PM2.5 levels. 0.3 Filtration performance.

[0026] (3) The MOFs-based dual-scale nano-network radioactive iodine aerosol protective mask of the present invention, compared with conventional masks, has a filter layer material of MOFs-based dual-scale three-dimensional network nanofiber membrane material, which achieves high adsorption capacity of radioactive iodine gas and has significant application potential in the field of radioactive iodine gas protection in nuclear fuel reprocessing.

[0027] (4) The MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask of the present invention has good hydrophobic properties and thermal stability compared with conventional masks. It can be used normally at high temperatures and has good application prospects in nuclear emergency situations.

[0028] (5) The MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask of the present invention has excellent antibacterial properties compared with conventional masks, providing strong protection for the health of personnel.

[0029] In preparing a MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask, this invention uses a MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane as the filter layer. During the preparation of the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane, the adsorption capacity of the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane for elemental iodine is further enhanced by polyethyleneimine graft modification and bismuth incorporation, thereby improving the saturated adsorption capacity for elemental iodine gas.

[0030] In summary, this invention combines electrospinning technology with the advantages of MOFs through the "adsorption-filtration" synergistic mechanism of MOFs-based dual-scale nanofiber membranes. It possesses high iodine capacity, high filtration efficiency, and environmental stability, providing nuclear power plant personnel with an efficient and lightweight integrated protection solution that significantly reduces the hazards of radioactive exposure.

[0031] 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 Figure Description

[0032] Figure 1 SEM images and fiber diameter distribution of the nano-three-dimensional network PAA fiber membrane prepared for Comparative Example 1;

[0033] Figure 2 SEM images and fiber diameter distribution of the nano-three-dimensional network PI fiber membrane prepared for Comparative Example 1;

[0034] Figure 3 SEM images and fiber diameter distribution diagrams of the PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared for Comparative Example 2;

[0035] Figure 4 SEM image of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1;

[0036] Figure 5 Optical images of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1 and the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane mask made in the laboratory;

[0037] Figure 6 The XRD patterns are of the three-dimensional network nanofiber membrane materials prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0038] Figure 7 FTIR infrared images of the three-dimensional network nanofiber membrane materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0039] Figure 8 XPS images of the three-dimensional network nanofiber membrane materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0040] Figure 9 This is a schematic diagram illustrating the iodine gas purification performance of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1.

[0041] Figure 10 A schematic diagram illustrating the purification capacity of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1 for flue gas aerosols.

[0042] Figure 11 The filtration efficiency of the nano-three-dimensional network PI fiber membrane in Comparative Example 1 for simulated radioactive aerosols of different particle sizes is shown.

[0043] Figure 12 To compare the filtration efficiency of the PI / DTAB dual-scale three-dimensional network nanofiber membrane in Example 2 for simulated radioactive aerosols of different particle sizes.

[0044] Figure 13 The filtration efficiency of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane in Example 1 for simulated radioactive aerosols of different particle sizes is shown.

[0045] Figure 14 Figures showing the pressure drop variations of nanoscale three-dimensional network PI fiber membranes, PI / DTAB dual-scale three-dimensional network nanofiber membranes, and ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membranes.

[0046] Figure 15 This is a schematic diagram of the iodine gas adsorption and purification performance of the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask prepared in Example 1;

[0047] Figure 16 The adsorption curve of iodine gas on the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1 is shown.

[0048] Figure 17 The isothermal adsorption curve of iodine gas on the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1 is shown below.

[0049] Figure 18 The graph shows the performance changes of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared in Example 1 after high temperature and water treatment. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0051] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0052] The raw materials used in the following examples, 4,4'-diaminodiphenyl ether (ODA), dodecyltrimethylammonium bromide (DTAB), pyromellitic dianhydride (PMDA), N,N-dimethylformamide (DMF), zinc nitrate hexahydrate (Zn(NO3)2·6H2O), 2-methylimidazole, and methanol were all purchased from Aladdin Chemical Co., Ltd. and were used directly without further purification.

[0053] Example 1:

[0054] A ZIF-8@PI / DTAB dual-scale nanofiber membrane mask includes the following steps:

[0055] Step 1: Preparation of PAA / DTAB solution: Weigh 0.233g of DTAB, 1.0113g of ODA, and 1.146g of PMDA using an electronic balance and add them to 5mL of DMF solution respectively. Place the DMF solution containing dissolved ODA and DTAB in an ice bath and stir until homogeneous. After ODA / DTAB is completely dissolved, quickly add the PMDA suspension to the ODA / DTAB solution. Place the mixed solution in a 0℃ water bath and stir for 5 hours to obtain a pale yellow viscous PAA / DTAB electrospinning solution with a concentration of 18wt%.

[0056] Step 2: Preparation of PAA / DTAB fiber membrane: Electrospinning was performed. The PAA / DTAB electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. A 25-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 11 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 5 hours of spinning, the aluminum foil loaded with the PAA / DTAB fiber membrane was removed and set aside.

[0057] Step 3: Preparation of PI / DTAB dual-scale nanofiber membrane: The prepared PAA / DTAB fiber membrane was placed in a tube furnace under a nitrogen atmosphere, and the imidization process was completed in three stages by heating. After natural cooling, the PI / DTAB dual-scale nanofiber membrane was obtained.

[0058] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0059] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0060] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 minutes to complete the imidization.

[0061] Step 4: Preparation of ZIF-8@PI / DTAB dual-scale nanofiber membrane: Weigh 1.487 g of Zn(NO3)2·6H2O using an electronic balance and add it to 50 mL of methanol. After the zinc salt is completely dissolved, immerse 40 mg of the PI / DTAB dual-scale nanofiber membrane in the above solution for 12 h. Then, dissolve 3.284 g of 2-methylimidazole in 50 mL of methanol and pour it into the above impregnation solution for another 12 h to complete the in-situ self-assembly growth of ZIF-8. Finally, wash three times with methanol and ethanol respectively to remove unreacted impurities, and dry in an oven at 60 °C for 1 h to obtain the ZIF-8@PI / DTAB dual-scale nanofiber membrane.

[0062] Step 5: Production of ZIF-8@PI / DTAB dual-scale nanofiber membrane masks: Highly breathable fiber materials are selected as the outer and inner layers of the mask filter. The outer layer, ZIF-8@PI / DTAB dual-scale nanofiber membrane, and inner layer are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain ZIF-8@PI / DTAB dual-scale nanofiber membrane masks for nuclear emergency radioactive iodine aerosol protection.

[0063] Example 2

[0064] A ZIF-8@PI / DTAB dual-scale nanofiber membrane mask includes the following steps:

[0065] Step 1: Preparation of PAA / DTAB solution: Weigh 0.233g of DTAB, 1.0113g of ODA, and 1.146g of PMDA using an electronic balance and add them to 5mL of DMF solution respectively. Place the DMF solution containing dissolved ODA and DTAB in an ice bath and stir until homogeneous. After ODA / DTAB is completely dissolved, quickly add the PMDA suspension to the ODA / DTAB solution. Place the mixed solution in a 0℃ water bath and stir for 5 hours to obtain a pale yellow viscous PAA / DTAB electrospinning solution with a concentration of 18wt%.

[0066] Step 2: Preparation of PAA / DTAB fiber membrane: Electrospinning was performed. The PAA / DTAB electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. A 25-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 11 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 5 hours of spinning, the aluminum foil loaded with the PAA / DTAB fiber membrane was removed and set aside.

[0067] Step 3: Preparation of PI / DTAB fiber membrane: The prepared PAA / DTAB fiber membrane was placed in a tube furnace under a nitrogen atmosphere and the imidization process was completed in three stages by heating. After natural cooling, the PI / DTAB dual-scale nanofiber membrane was obtained.

[0068] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0069] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0070] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 min to complete imidization;

[0071] 40 mg of PI / DTAB dual-scale nanofiber membrane was impregnated in 100 mL of a 30 wt% polyethyleneimine solution with a molecular weight of 6000 g / mol. 2 wt% of 2-chloro-1-methylpyridine iodide was added as an activator to the polyethyleneimine solution. The mixture was heated to 60 °C and impregnated for 12 h. After impregnation, the membrane was dried at 60 °C to obtain the grafted modified PI / DTAB dual-scale nanofiber membrane.

[0072] Step 4: Preparation of ZIF-8@PI / DTAB dual-scale nanofiber membrane: 1.487 g of Zn(NO3)2·6H2O and 2.425 g of Bi(NO3)3·5H2O were weighed using an electronic balance and added to 50 mL of methanol. After the zinc and bismuth salts were completely dissolved, 40 mg of the grafted modified PI / DTAB dual-scale nanofiber membrane was immersed in the above solution for 12 h. Then, 3.284 g of 2-methylimidazole was dissolved in 50 mL of methanol and poured into the above impregnation solution for another 12 h, completing the in-situ self-assembly growth of ZIF-8. Finally, the membrane was washed three times with methanol and ethanol respectively to remove unreacted impurities, and then dried in an oven at 60 °C for 1 h to obtain the ZIF-8@PI / DTAB dual-scale nanofiber membrane.

[0073] Step 5: Production of ZIF-8@PI / DTAB dual-scale nanofiber membrane masks: A breathable non-woven fabric is selected as the outer and inner layer material for the mask filter. The outer layer, ZIF-8@PI / DTAB dual-scale nanofiber membrane, and inner layer are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain ZIF-8@PI / DTAB dual-scale nanofiber membrane masks for nuclear emergency radioactive iodine aerosol protection.

[0074] Comparative Example 1:

[0075] A method for preparing a nano-three-dimensional network PI fiber membrane includes the following steps:

[0076] Step 1: Preparation of PAA solution: Weigh 1.0113 g of ODA and 1.146 g of PMDA using an electronic balance and add them separately to 5 mL of DMF solvent. Place both solutions in an ice bath and stir until homogeneous. After the ODA is completely dissolved, quickly add the PMDA suspension to the ODA solution. Place the mixed solution in a 0°C water bath and stir for 5 h to obtain a pale yellow viscous PAA electrospinning solution with a concentration of 18 wt%.

[0077] Step 2: Preparation of the three-dimensional nano-network PAA fiber membrane: Electrospinning was performed. The PAA electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. An 18-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 18 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 2 hours of spinning, the aluminum foil from the three-dimensional nano-network PAA fiber membrane was removed for later use.

[0078] Step 3: Preparation of the nano-three-dimensional network PI fiber membrane: The prepared nano-three-dimensional network PAA fiber membrane was placed in a tube furnace under a nitrogen atmosphere, and the imidization process was completed by heating in three stages, followed by natural cooling to obtain a dual-scale three-dimensional network PI fiber membrane. The three-stage heating process was as follows:

[0079] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0080] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0081] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 minutes to complete the imidization.

[0082] Step 4: Production of Nano-3D Network PI Fiber Membrane Masks: Using breathable non-woven fabric as the outer and inner layers of the mask filter, and a nano-3D network PI fiber membrane as the filter layer, the outer, nano-3D network PI fiber membrane, and inner layers are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain the mask for PM2.5 application. 2.5 Nanoscale three-dimensional network PI fiber membrane for daily protection.

[0083] Comparative Example 2:

[0084] A method for preparing a PI / DTAB dual-scale nanofiber membrane mask includes the following steps:

[0085] Step 1: Preparation of PAA / DTAB solution: Weigh 0.233g of DTAB, 1.0113g of ODA, and 1.146g of PMDA using an electronic balance and add them to 5mL of DMF solution respectively. Place the DMF solution containing dissolved ODA / DTAB in an ice bath and stir until homogeneous. After the ODA / DTAB is completely dissolved, quickly add the PMDA suspension to the ODA / DTAB solution. Place the mixed solution in a 0℃ water bath and stir for 5 hours to obtain a pale yellow viscous PAA / DTAB electrospinning solution with a concentration of 18wt%.

[0086] Step 2: Preparation of PAA / DTAB fiber membrane: Electrospinning was performed. The PAA / DTAB electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. A 25-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 18 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 2 hours of spinning, the aluminum foil loaded with the PAA / DTAB fiber membrane was removed and set aside.

[0087] Step 3: Preparation of PI / DTAB dual-scale nanofiber membrane: The prepared PAA / DTAB fiber membrane was placed in a tube furnace under a nitrogen atmosphere, and the imidization process was completed in three stages by heating. After natural cooling, the PI / DTAB dual-scale nanofiber membrane was obtained.

[0088] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0089] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0090] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 minutes to complete the imidization.

[0091] Step 4: Production of PI / DTAB dual-scale nanofiber membrane masks: A breathable non-woven fabric is selected as the outer and inner layer material for the mask filter. The outer layer, PI / DTAB dual-scale nanofiber membrane, and inner layer are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain industrial PM2.5. 0.3 Protective PI / DTAB dual-scale nanofiber membrane mask.

[0092] Comparative Example 3

[0093] A ZIF-8@PI / DTAB dual-scale nanofiber membrane mask includes the following steps:

[0094] Step 1: Preparation of PAA / DTAB solution: Weigh 0.233g of DTAB, 1.0113g of ODA, and 1.146g of PMDA using an electronic balance and add them to 5mL of DMF solution respectively. Place the DMF solution containing dissolved ODA and DTAB in an ice bath and stir until homogeneous. After ODA / DTAB is completely dissolved, quickly add the PMDA suspension to the ODA / DTAB solution. Place the mixed solution in a 0℃ water bath and stir for 5 hours to obtain a pale yellow viscous PAA / DTAB electrospinning solution with a concentration of 18wt%.

[0095] Step 2: Preparation of PAA / DTAB fiber membrane: Electrospinning was performed. The PAA / DTAB electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. A 25-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 11 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 5 hours of spinning, the aluminum foil loaded with the PAA / DTAB fiber membrane was removed and set aside.

[0096] Step 3: Preparation of PI / DTAB fiber membrane: The prepared PAA / DTAB fiber membrane was placed in a tube furnace under a nitrogen atmosphere and the imidization process was completed in three stages by heating. After natural cooling, the PI / DTAB dual-scale nanofiber membrane was obtained.

[0097] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0098] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0099] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 min to complete imidization;

[0100] 40 mg of PI / DTAB dual-scale nanofiber membrane was impregnated in 100 mL of a 30 wt% polyethyleneimine solution with a molecular weight of 6000 g / mol. 2 wt% of 2-chloro-1-methylpyridine iodide was added as an activator to the polyethyleneimine solution. The mixture was heated to 60 °C and impregnated for 12 h. After impregnation, the membrane was dried at 60 °C to obtain the grafted modified PI / DTAB dual-scale nanofiber membrane.

[0101] Step 4: Preparation of ZIF-8@PI / DTAB dual-scale nanofiber membrane: 1.487 g of Zn(NO3)2·6H2O was weighed using an electronic balance and added to 50 mL of methanol. After the zinc salt was completely dissolved, 40 mg of the grafted modified PI / DTAB dual-scale nanofiber membrane was immersed in the above solution for 12 h. Then, 3.284 g of 2-methylimidazole was dissolved in 50 mL of methanol and poured into the above impregnation solution for another 12 h, completing the in-situ self-assembly growth of ZIF-8. Finally, the membrane was washed three times with methanol and ethanol respectively to remove unreacted impurities, and then dried in an oven at 60 °C for 1 h to obtain the ZIF-8@PI / DTAB dual-scale nanofiber membrane.

[0102] Step 5: Production of ZIF-8@PI / DTAB dual-scale nanofiber membrane masks: A breathable non-woven fabric is selected as the outer and inner layer material for the mask filter. The outer layer, ZIF-8@PI / DTAB dual-scale nanofiber membrane, and inner layer are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain ZIF-8@PI / DTAB dual-scale nanofiber membrane masks for nuclear emergency radioactive iodine aerosol protection.

[0103] Comparative Example 4

[0104] A ZIF-8@PI / DTAB dual-scale nanofiber membrane mask includes the following steps:

[0105] Step 1: Preparation of PAA / DTAB solution: Weigh 0.233g of DTAB, 1.0113g of ODA, and 1.146g of PMDA using an electronic balance and add them to 5mL of DMF solution respectively. Place the DMF solution containing dissolved ODA and DTAB in an ice bath and stir until homogeneous. After ODA / DTAB is completely dissolved, quickly add the PMDA suspension to the ODA / DTAB solution. Place the mixed solution in a 0℃ water bath and stir for 5 hours to obtain a pale yellow viscous PAA / DTAB electrospinning solution with a concentration of 18wt%.

[0106] Step 2: Preparation of PAA / DTAB fiber membrane: Electrospinning was performed. The PAA / DTAB electrospinning solution was placed in a plastic syringe, which was then placed in a syringe pump. A 25-gauge metal needle was used during spinning, maintaining a speed of 0.5 mL / h and a voltage of 11 kV. A metal roller receiver wrapped with aluminum foil was used, rotating at 150 r / min. After 5 hours of spinning, the aluminum foil loaded with the PAA / DTAB fiber membrane was removed and set aside.

[0107] Step 3: Preparation of PI / DTAB fiber membrane: The prepared PAA / DTAB fiber membrane was placed in a tube furnace under a nitrogen atmosphere and the imidization process was completed in three stages by heating. After natural cooling, the PI / DTAB dual-scale nanofiber membrane was obtained.

[0108] ① Heat from 25℃ to 150℃ at a rate of 5℃ / min, anneal for 30 min, and remove residual solvent.

[0109] ② Heat from 150℃ to 250℃ at a rate of 5℃ / min, anneal for 30 min, and dehydrate and cyclize the hydroxyl groups.

[0110] ③ Increase the temperature from 250℃ to 350℃ at a rate of 10℃ / min, and anneal for 60 minutes to complete the imidization.

[0111] Step 4: Preparation of ZIF-8@PI / DTAB dual-scale nanofiber membrane: Weigh 1.487 g of Zn(NO3)2·6H2O and 2.425 g of Bi(NO3)3·5H2O using an electronic balance and add them to 50 mL of methanol. After the zinc salt and bismuth salt are completely dissolved, immerse 40 mg of PI / DTAB dual-scale nanofiber membrane in the above solution for 12 h. Then dissolve 3.284 g of 2-methylimidazole in 50 mL of methanol and pour it into the above impregnation solution for another 12 h to complete the self-assembly in-situ growth of ZIF-8. Finally, wash three times with methanol and ethanol respectively to remove unreacted impurities, and dry in an oven at 60 °C for 1 h to obtain the ZIF-8@PI / DTAB dual-scale nanofiber membrane.

[0112] Step 5: Production of ZIF-8@PI / DTAB dual-scale nanofiber membrane masks: A breathable non-woven fabric is selected as the outer and inner layer material for the mask filter. The outer layer, ZIF-8@PI / DTAB dual-scale nanofiber membrane, and inner layer are placed together in sequence and rolled together to obtain the mask filter. According to the mask design requirements, the mask filter is cut into different shapes and sizes and fed into the mask production line to obtain ZIF-8@PI / DTAB dual-scale nanofiber membrane masks for nuclear emergency radioactive iodine aerosol protection.

[0113] The three-dimensional network nanofiber membrane materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 were characterized by SEM, XRD, FTIR infrared, and XPS. Figures 1-4 The microstructure characteristics of PAA (prepared in step two of Comparative Example 1), PI (prepared in step four of Comparative Example 1), PI / DTAB (prepared in step four of Comparative Example 2), and ZIF-8@PI / DTAB (prepared in Example 1) fiber membranes are shown respectively. In Comparative Example 1, the original PAA and PI fibers are regular cylindrical (e.g., ...). Figure 1 and Figure 2 As shown), the surface is smooth, and the fiber diameter follows a normal distribution, with fiber diameters approximately 238 nm and 193 nm, respectively. After introducing DTAB (as shown...), the surface is smooth, and the fiber diameters follow a normal distribution, with fiber diameters around 238 nm and 193 nm, respectively. Figure 3 As shown), the fiber diameter is significantly reduced to approximately 111 nm. More importantly, a finer secondary fiber network (37 nm in diameter) forms on the fiber surface, creating a two-scale three-dimensional nanofiber network structure. Furthermore, the fiber arrangement is denser, and the pore size is reduced, which is more conducive to improving aerosol retention efficiency. ZIF-8@PI / DTAB fibers (such as...) Figure 4 As shown, ZIF-8 crystals grow uniformly on the fiber surface in a typical rhombic dodecahedral morphology (approximately 32 nm in size). While maintaining the integrity of the fiber structure, this significantly improves the accessibility of MOF active sites, providing structural assurance for the efficient chemisorption of radioactive iodine. Furthermore, it further reduces the pore size of the fiber, which is more conducive to improving the filtration efficiency of aerosols.

[0114] Figure 5 Optical images of the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane prepared for Example 1 and the ZIF-8@PI / DTAB dual-scale three-dimensional network nanofiber membrane mask made in the laboratory are shown. It can be seen that the fiber membrane has excellent mechanical properties and can be used for mask production.

[0115] Figure 6 XRD images of PI fiber membrane, PI / DTAB and ZIF-8@PI / DTAB dual-scale nanofiber membrane are shown. The PI fiber membrane and PI / DTAB dual-scale nanofiber membrane show amorphous phase images. In the XRD spectrum of ZIF-8@PI / DTAB dual-scale nanofiber 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 spectrum of ZIF-8, which proves that ZIF-8 was successfully self-assembled and grown in situ in PI / DTAB dual-scale nanofiber membrane.

[0116] The chemical bond structure of the sample obtained by FTIR spectroscopy analysis (e.g. Figure 7 (As shown). Typical characteristic peaks that can be observed in the spectrum of PAA / DTAB fiber membranes, with 1710 cm⁻¹ being the most prominent. -1 A strong absorption peak appears at 1240 cm⁻¹, corresponding to the stretching vibration of C=O in carboxylic acid (-COOH). -1 The CO stretching vibration of the catechol group is observed at 1544 cm⁻¹. -1 This is the NH stretching vibration of the catechol group. However, after the thermal imidization reaction, these characteristic peaks of the PAA / DTAB fiber membrane disappear, and a peak at 1780 cm⁻¹ appears. -1 and 1720cm -1 The new characteristic peaks, corresponding to the asymmetric and symmetric stretching vibrations of C=O in the imide ring, are typical characteristic peaks of PI, and are particularly prominent at 1380 cm⁻¹. -1 A new characteristic peak appeared, attributed to the stretching vibration of CN in the imide ring, further confirming the completion of the cyclization reaction. Following in-situ self-assembly growth of ZIF-8, a peak of 1146 cm⁻¹ appeared in the FTIR spectrum of the ZIF-8@PI / DTAB dual-scale nanofiber film. -1 994cm -1 759cm -1 694cm -1 and 420cm -1 Several characteristic peaks were observed at this point, which are attributed to the characteristic peaks of ZIF-8, including the one at 420 cm⁻¹. -1 The peak shown is a characteristic Zn-N stretching peak of ZIF-8, at 1146 cm⁻¹. -1 and 994cm -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 making it a key functional group in ZIF-8. To further confirm the chemical composition, XPS analysis was performed on PI / DTAB and ZIF-8@PI / DTAB dual-scale nanofiber membranes. The full spectrum analysis is shown below. Figure 8 As shown, the PI / DTAB plot reveals peaks for C1s, N1s, and O1s, while the ZIF-8@PVP / PAN plot shows peaks for C1s, N1s, O1s, and Zn2p. The chemical structures of several fiber membranes are illustrated by comparing the FTIR, XPS, and XRD patterns of the PAA fiber membrane, the PI / DTAB dual-scale fiber membrane, and the ZIF-8@PI / DTAB dual-scale fiber membrane, and the successful in-situ self-assembly of MOF crystal ZIF-8 on the fiber membrane is demonstrated.

[0117] Application Example 1

[0118] To evaluate the breathability of the prepared mask, an ammonia water breathability test was conducted. The ZIF-8@PI / DTAB dual-scale fiber membrane filter material of the mask prepared in Example 1 was cut into circular samples with a diameter of 5 cm and tightly attached to a wide-mouth bottle containing ammonia water. A pH test paper was taken and quickly placed at the mouth of the bottle, and the change of pH test paper was observed.

[0119] like Figure 9 As shown, the pH test paper changed color rapidly after being placed on the surface for 1 second, which directly demonstrates that the prepared ZIF-8@PI / DTAB dual-scale fiber membrane filter material has significant air permeability. Therefore, the prepared ZIF-8@PI / DTAB dual-scale fiber membrane mask has obvious air permeability and comfort.

[0120] Application Example 2

[0121] To further evaluate the filtration performance of the prepared ZIF-8@PI / DTAB dual-scale fiber membrane mask, the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material prepared in Example 1 was first placed in an interconnected volumetric flask interlayer, with flue gas simulating the generation of aerosols on one side. The purification capacity of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material for aerosols was then determined by observing the concentration changes of the gases on both sides.

[0122] from Figure 10 As can be seen, the volumetric flask containing flue gas aerosols was filled with aerosol particles, while the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material significantly blocked the passage of aerosols, thus the volumetric flask on the right remained transparent. This indicates that the ZIF-8@PI / DTAB dual-scale nanofiber membrane has excellent aerosol filtration performance and can meet the purpose of aerosol purification. This ZIF-8@PI / DTAB dual-scale nanofiber membrane mask has significant application potential for protection against industrial flue gas pollution.

[0123] Application Example 3

[0124] To further verify the filtration performance of the masks prepared in the examples, this study used a nanoparticle aerosol generator to conduct aerosol interception efficiency tests. The experimental procedure is as follows: Fiber membrane filter materials from the three types of masks prepared in Example 1, Comparative Example 1, and Comparative Example 2 were taken and cut into circular samples with a diameter of 5 cm. These samples were then fixed in the test chamber using precision clamps. The actual effective filtration area was 15.904 cm². 2The testing system employed a dual-channel particle counter to monitor upstream and downstream aerosol concentrations. Nano-sized silica particles with a diameter range of 300 nm to 10 μm were selected as the test medium to simulate radioactive aerosols. During the experiment, the surface velocity was controlled by adjusting the airflow parameters, and the concentration changes of particles of different sizes before and after filtration were recorded simultaneously. The pressure loss value was obtained in real time by a differential pressure sensor, acquiring the pressure drop parameters across the membrane structure. Each set of data was averaged after three parallel experiments. Filtration performance parameters were calculated using the following mathematical formula:

[0125] Filtration efficiency = 1 - (number of upstream aerosol particles) / (number of downstream aerosol particles)

[0126] The quality factor is calculated using the following formula:

[0127] Quality factor = -ln(1 - filtration efficiency) / pressure drop

[0128] in Figure 11 The image shows the variation in filtration efficiency of the PI mask filter material prepared in Comparative Example 1 for aerosol particles of different sizes at a surface velocity of 5 cm / s. It can be seen that the PI mask filter material effectively filters PM... 0.3 The filtration efficiency is 97.61%. As the particle size of aerosol particles increases, the filtration efficiency also gradually increases. For aerosol particles with a particle size greater than 3μm, the filtration efficiency reaches 99.99%. Therefore, PI masks have obvious advantages and application potential for daily protection. Figure 12 The filtration efficiency of the PI / DTAB dual-scale nanofiber membrane mask filter material prepared in Comparative Example 2 for aerosol particles of different sizes was shown to be different at a surface velocity of 5 cm / s. This demonstrates the filtration efficiency of the PI / DTAB dual-scale nanofiber membrane mask for PM2.5 particles. 0.3 The filtration efficiency is 99.99%, and it reaches 100% for aerosol particles larger than 1 μm. This is because the addition of DTAB enhances the charge of the spinning solution, significantly reducing the fiber diameter and thus the fiber pore size, thereby significantly improving the filtration efficiency of the PI / DTAB dual-scale nanofiber membrane mask. Therefore, the PI / DTAB dual-scale nanofiber membrane mask has significant advantages and application potential for protection against industrial nanoscale aerosol particles. Figure 13 The filtration efficiency of the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask filter material prepared in Example 1 for aerosol particles of different sizes was shown to be different at a surface velocity of 5 cm / s. This demonstrates the filtration efficiency of the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask for PM2.5. 0.3The filtration efficiency is 99.99%, and it reaches 100% for aerosol particles larger than 1 μm. More importantly, due to the excellent iodine adsorption functionality of MOF crystal ZIF-8, the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask has excellent application potential for nanoscale radioactive iodine aerosols in nuclear accident emergency situations. The pressure drop changes of three types of masks were also measured. Figure 14 As shown, at a surface velocity of 5 cm / s, the pressure drop of the PI mask is only 97 Pa, indicating excellent breathability. Adding DTAB enhances the charge of the spinning solution, significantly reducing the fiber diameter and thus the fiber pore size, resulting in a slightly higher pressure drop of the PI / DTAB dual-scale nanofiber membrane mask, but still only 119 Pa. After in-situ self-assembly growth of ZIF-8 crystals, the pore size of the fiber membrane continues to decrease, and the pressure drop slowly increases, but still only 131 Pa. The three mask models of this invention not only have significant filtration efficiency but also excellent pressure drop performance. They have significant application potential in daily protection, industrial nanoscale aerosol protection, and nuclear power plant applications and nuclear accident emergency iodine aerosol protection.

[0129] Application Example 4:

[0130] To visually demonstrate the iodine gas adsorption and purification performance of the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask prepared in Example 1, the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material prepared in Example 1 was placed in an interconnected volumetric flask interlayer, with 20 mg of iodine placed on one side, and then simultaneously placed in a 75°C oven. The purification capacity of the fiber membrane for iodine gas was determined by observing the color changes of the gases on both sides.

[0131] like Figure 15 As shown, after iodine was added to the volumetric flask on the left, a distinct purple gas was formed. However, after passing through the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material in the interconnected volumetric flask layers, the iodine gas was rapidly adsorbed and purified by the fiber membrane, allowing the volumetric flask on the right to remain transparent and uncontaminated by iodine gas. This demonstrates that the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material has significant iodine gas purification performance and excellent application potential in nuclear emergency situations.

[0132] Application Example 4:

[0133] To further investigate the adsorption kinetics of iodine gas on the ZIF-8@PI / DTAB dual-scale nanofiber membrane material, this invention uses a stable isotope of non-radioactive iodine (I₂) with almost identical chemical properties instead of radioactive iodine. 20 mg of the fiber membrane sample and I₂ were placed together in a glass container and placed in a 75°C constant-temperature oven under normal pressure to simulate the ambient temperature of waste gas treatment in a post-treatment plant. After a certain period of adsorption, the container was removed and cooled to room temperature. The iodine adsorption performance of the two fiber membrane samples was calculated and compared using the following formula.

[0134] Iodine adsorption capacity = (mass after reaction - mass before reaction) / mass before reaction;

[0135] To further investigate the I2 gas adsorption performance of this nanofiber membrane material at different concentrations, a series of isothermal adsorption experiments were conducted. 20 mg of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material prepared according to Example 1 was used, and different masses of iodine were added to create iodine gas environments of varying concentrations. The experiments were then conducted at 75°C to explore the material's adsorption capacity for iodine gas under different iodine concentrations. After 12 hours of experimentation, the mass change was measured, and the iodine capture performance was calculated.

[0136] The capture and purification capacity of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material prepared in Example 1 for iodine gas was studied by different adsorption times. Figure 16 As shown, the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material achieved a saturated adsorption capacity of 2931 mg / g for elemental iodine gas, which is twice the reported adsorption capacity of ZIF-8 powder. This is attributed to the fiber structure preventing the aggregation of ZIF-8 crystals, and more importantly, improving the diffusion pathway of iodine, enhancing the charge transfer process, and further improving the adsorption kinetics, reaching adsorption equilibrium in about 120 min. The fitting curves from the two adsorption kinetic models show that the adsorption curve better conforms to pseudo-second-order adsorption kinetics.

[0137] Meanwhile, the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter materials prepared in Example 2, Comparative Example 3, and Comparative Example 4 showed saturated adsorption capacities of iodine gas of 3375 mg / g, 2952 mg / g, and 3019 mg / g, respectively. It can be seen that the saturated adsorption capacity of the ZIF-8@PI / DTAB dual-scale nanofiber membrane prepared in Example 2 for iodine gas is significantly higher than that in Example 1, and also significantly higher than that in Comparative Example 3 and Comparative Example 4.

[0138] Isothermal adsorption curve ( Figure 17As shown in the figure, with increasing I2 concentration, the adsorption capacity of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material for iodine gas significantly increases until equilibrium is reached. This phenomenon indicates that the concentration difference promotes the rapid adsorption of iodine gas onto the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material until the binding sites of ZIF-8 reach adsorption saturation. Based on the fitting results of two adsorption models, the Langmuir model is more suitable. This suggests that the capture of iodine by the two ZIF-8@PI / DTAB dual-scale nanofiber membrane filter materials is independent, and the adsorption process tends to be monolayer adsorption.

[0139] To test the adsorption stability of the material in high temperature and high humidity environments, the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material was treated in ovens at 75℃, 100℃, and 200℃ for 2 hours before iodine gas adsorption experiments were conducted. Figure 18 As shown, the adsorption performance of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material remained unchanged at around 2900 mg / g under different temperature treatments. To verify the water stability of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material, it was soaked in pure water for 6 h, 12 h, and 48 h, then air-dried in a fume hood before adsorption experiments were conducted. Figure 18 It can be seen that the adsorption performance of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material remains unchanged after immersion in pure water for different times, still maintaining around 2900 mg / g, indicating that the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material has excellent water stability. High temperature and high humidity environments do not affect the iodine gas adsorption performance of the ZIF-8@PI / DTAB dual-scale nanofiber membrane filter material. The experimental results of the above application examples demonstrate that the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask not only has excellent filtration performance, low air permeability and pressure drop, but also a significant iodine gas adsorption and purification capacity. Therefore, the ZIF-8@PI / DTAB dual-scale nanofiber membrane mask has excellent application potential for protection against iodine-containing radioactive iodine aerosols in nuclear energy development and nuclear accident emergency situations.

[0140] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0141] 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. A method for preparing a MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane, characterized in that, Includes the following steps: Step 1: Calcine the dual-scale three-dimensional network PAA fiber membrane in an inert atmosphere to achieve thermal imidization reaction, and obtain the dual-scale three-dimensional network PI fiber membrane. Step 2: Immerse the dual-scale three-dimensional network PI fiber membrane in a mixed solution of zinc salt, organic ligand, and solvent B. Use a self-assembly method to allow MOFs to grow in situ on the fiber membrane. Then place it in an oven for drying to prepare MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane. In step one, the method for preparing the dual-scale three-dimensional network PAA fiber membrane includes: S11. Weigh 4,4'-diaminodiphenyl ether, dodecyltrimethylammonium bromide and pyromellitic dianhydride and dissolve them in organic solvent A. Stir to dissolve and form a precursor spinning solution. S12. Electrospin the precursor spinning solution to obtain a dual-scale three-dimensional network PAA fiber membrane.

2. The method for preparing MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 1, characterized in that, In S11, the organic solvent A is any one of N,N-dimethylformamide, ethanol, tetrahydrofuran, N,N-dimethylacetamide, acetone, and diethyl ether.

3. The method for preparing MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 1, characterized in that, In S11, the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride is 1~5:1~5; the total concentration of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride in organic solvent A is 10%~20%; the concentration of dodecyltrimethylammonium bromide in organic solvent A is 0~5%; the stirring and dissolving temperature is 0~10 ℃; the ambient humidity is 30~100%; and the stirring time is 1~24 h.

4. The method for preparing MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 1, characterized in that, In S12, the electrospinning parameters are as follows: spinning voltage: 5~25kV; needle: 18~30 stainless steel needle; electrode distance: 5~20cm; injection pump push rate: 0.3~1.5mL / h; ambient temperature: 5~40℃; ambient humidity: 30~100%.

5. The method for preparing MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 1, characterized in that, In step one, the inert atmosphere includes one of nitrogen, argon, and helium; the thermal imidization calcination temperature is 250~550℃, the heating rate is 1~10℃ / min, and the holding time is 0.5~4 h.

6. The method for preparing MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 1, characterized in that, In step two, solvent B includes one or more of methanol, deionized water, ethanol, and N,N-dimethylformamide; zinc salt includes any one or more of zinc nitrate hexahydrate, zinc chloride, zinc sulfate, zinc acetate, and zinc citrate; organic ligand includes any one of imidazole and 2-methylimidazole; the impregnation time is 1~48h; the drying temperature is 30~80℃, and the drying time is 1~10h; the molar ratio of zinc salt to organic ligand is 1:8, and the ratio of organic ligand to solvent B is 0.04mol of organic ligand dissolved in 100mL of solvent B.

7. An application of a MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane, wherein the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane is prepared from the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to any one of claims 1-6, characterized in that, The MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane is used to prepare MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective masks. The specific method includes: selecting a breathable non-woven fabric as the outer and inner layers of the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask; placing the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane as the filter layer of the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask between the outer and inner layers; and obtaining the MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask through a composite process.

8. The application of the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 7, characterized in that, Composite processes include hot pressing, sewing, and bonding.

9. The application of the MOFs-based dual-scale polyimide three-dimensional network nanofiber membrane according to claim 7, characterized in that, The MOFs-based dual-scale nanonetwork radioactive iodine aerosol protective mask is used to capture and filter radioactive iodine aerosols.

Images