A method for rapidly preparing ZIF-8 / polypropylene melt-blown fiber membranes in batches at low cost

Abstract

The present invention relates to the field of air filtration, and in particular to a method for preparing ZIF-8 / polypropylene melt-blown fiber membranes in batches at low cost and fast. The present invention is aimed at the existing method of growing ZIF-8 on the surface of polypropylene melt-blown cloth to improve air filtration performance, which has the problems of high cost, long preparation time, and complex process, and provides a method for preparing ZIF-8 / polypropylene melt-blown fiber membranes in batches at low cost and fast. First, the surface of the polypropylene melt-blown cloth is pretreated with an inorganic alkali aqueous solution, and then, under ultrasonic conditions, the melt-blown cloth is successively placed in a zinc ion aqueous solution and a 2-methylimidazole / N, N-dimethylformamide mixed aqueous solution and dried to obtain a ZIF-8 / polypropylene melt-blown fiber membrane. The preparation method uses water as the main solvent, and a method of adding a small amount of N, N-dimethylformamide to water achieves rapid growth on polypropylene melt-blown cloth at a smaller molar ratio of 2-methylimidazole and zinc nitrate hexahydrate, thereby being suitable for large-scale industrial production for air filtration.

Description

Technical Field

[0001] The invention belongs to the field of membranes, and in particular relates to a method for rapidly preparing ZIF-8 / polypropylene melt-blown fiber membranes in batches at low cost. Background Art

[0002] The increasing content of pollutants in the air, such as PM2.5, formaldehyde, volatile organic compounds, and microorganisms such as bacteria and viruses, poses a serious threat to human health, while ordinary non-woven materials have relatively single functions. Zeolite imidazolate framework material-8 (ZIF-8), as a type of metal organic framework, has shown great potential in the field of air filtration due to its unique structure and performance: it has an ultra-high specific surface area and rich microporous structure that can adsorb various pollutant molecules in the air; it shows excellent tolerance under different temperature and humidity conditions, ensuring long-term and stable filtration efficiency; it is relatively easy to prepare and modify. Loading ZIF-8 on polypropylene meltblown cloth can broaden the scope of use of polypropylene meltblown cloth, and also solve the problem of difficult recycling of ZIF-8.

[0003] At present, there have been a large number of studies trying to grow ZIF-8 on substrates for industrial production, but due to its complex process, long preparation time and high cost, it is only limited to the experimental research stage. At present, solution immersion method for growing ZIF-8 is a common method. Chinese patent CN118788058A discloses a method for in-situ growth of ZIF-8 on the surface of non-woven materials in aqueous solution with the assistance of polydopamine. Although it shortens the reaction time of polydopamine to 40 to 150 minutes, it still does not meet the needs of industrialization. Chinese patent CN202410934122.1 immerses the fabric in a 2-methylimidazole aqueous solution, stirs at room temperature and slowly adds a zinc source aqueous solution, washes and dries, and obtains a fabric with ZIF-L / ZIF-8 nanorods on the surface. Similarly, the method of Chinese patent CN118807483A does not use additional adhesives, but ZIF-8 and fabrics are physically combined and have poor stability; the organic ligand solution and the metal ion solution react directly by mixing, which wastes raw materials. Chinese patent CN117867861A soaks the nonwoven material pretreated with dopamine hydrochloride / strong alkali solution in a zinc ion aqueous solution and then in a 2-methylimidazole aqueous solution under ultrasonic conditions to rapidly grow ZIF-8. Although it uses a room temperature immersion method to achieve rapid growth of ZIF-8 on the surface of the nonwoven material, it must ensure a large molar ratio of 2-methylimidazole to zinc nitrate hexahydrate, and a large amount of excess 2-methylimidazole causes a waste of raw materials, and the production cost is relatively high.

[0004] Due to its large molecular size, N,N-dimethylformamide has strong affinity for metal ions and structural guidance ability, which can induce zinc ion nucleation, making it easier for ZIF-8 to form a dodecahedral three-dimensional structure, promoting the growth of ZIF-8 on the substrate. N,N-dimethylformamide has been used to grow ZIF-8 on a substrate for modification. For example, the paper published by Sile Ren et al., "An industrial synthesis method of Zeolitic Imidazolate Framework-8-based composites for formaldehyde adsorption application", mixed zinc acetate dihydrate and 2-methylimidazole in an aqueous solution at a molar ratio of 1:4, and then added N,N-dimethylformamide to synthesize ZIF-8 crystals, which were then grown on silica gel. The paper "Preparation of the Carbonized Zif-8@PAN Nanofiber Membranefor Cadmium Ion Adsorption" published by Sun et al. immersed the zinc oxide / polyacrylonitrile nanofiber membrane in a mixed solution of N,N-dimethylformamide and 2-methylimidazole with a concentration of 1%, and reacted at 100°C for 7h in the inner cavity of a high-pressure reactor, and then dried in vacuum at 80°C for 2h to obtain the ZIF-8 / polyacrylonitrile nanofiber membrane. The paper "Confined-Coordination Induced Intergrowth of Metal-Organic Framework into PreciseMolecular Sieving Membranes" published by Guozhen Liu et al. used a restricted coordination-induced intergrowth strategy to make the metal-organic framework without lattice defects on the membrane surface to achieve precise molecular separation. By controlling the back diffusion of the metal-organic framework precursor, regulating its spatial properties (size and shape) and environment (water or N,N-dimethylformamide) to slow down the coordination reaction rate, the metal-organic framework crystals grow into an integrated membrane. Chinese patent CN115434148A dissolves zinc nitrate hexahydrate in N,N-dimethylformamide solution of polyacrylonitrile, and the fiber membrane obtained by electrospinning is dried to obtain zinc ion / polyacrylonitrile nanofiber membrane. The fiber membrane is added to 2-methylimidazole methanol solution for microwave reaction, and then washed and dried to obtain ZIF-8 / polyacrylonitrile composite nanofiber membrane. This process is prepared by electrospinning, and some ZIF-8 crystals are coated inside the fiber, which cannot fully exert the unique advantages of ZIF-8.Chinese patent CN117085647A adds zinc nitrate hexahydrate, 2-methylimidazole and solvent (ethanol solution mixed with ethanol and deionized water in a volume ratio of 1:1) to a suspension mixed with activated carbon and N,N-dimethylformamide to react to obtain a ZIF-8 activated carbon composite material. The composite material is added with hydrogen peroxide solution and polypropylene non-woven fabric, and soaked and dried to obtain a modified ZIF-8 / polypropylene non-woven fiber membrane. The process is complex and the preparation cycle is long. The organic solvent accounts for a high proportion of the solvent used in this method, and the organic ligand solution is directly mixed with the metal ion solution to grow ZIF-8 on the fiber surface in situ, resulting in a waste of raw materials and high cost. Chinese patent CN114247307A mixes an inhibitor (triethylamine or pyridine) and a 2-methylimidazole solution to form a prepolymer colloid, then adds a zinc ion N,N-dimethylformamide solution, reacts to obtain a prepolymer colloid solution, centrifuges and concentrates it, and coats it on a substrate material to volatilize at room temperature to obtain a membrane with ZIF-8 grown on it. Although this method can control the thickness of the ZIF-8 functional layer, the reaction steps are complicated due to the centrifugal concentration step, making it difficult to apply industrially. Chinese patent CN118240385A pre-treats the carbon nanotube film in an inorganic alkali or strong acid solution at room temperature, then soaks it in a zinc acetate solution, washes and dries it. The dried carbon nanotube film is then soaked in a 2-methylimidazole solution, washed and dried to obtain a ZIF-8 / carbon nanotube flexible composite material. This method can grow a relatively dense layer of ZIF-8 with good crystal phase and uniformity, but it needs to be immersed in a zinc ion solution for 12 to 24 hours and in an organic ligand solution for 10 to 90 minutes, and the reaction time is relatively long; the solvent of the 2-methylimidazole solution is formed by mixing water and an organic solvent including N,N-dimethylformamide in a volume ratio of 5 to 25:75 to 95, and the excessive proportion of organic solvent in the solvent leads to a high raw material cost. Therefore, a method with faster reaction speed and lower cost is needed to stably grow ZIF-8 on a substrate. Summary of the invention

[0005] In summary, the present invention provides a method for preparing a ZIF-8 / polypropylene melt-blown fiber membrane in view of the problems that the existing ZIF-8 grown on a substrate has a complex process, a long preparation time, and a high cost. The specific steps are as follows:

[0006] Step 1: The weight of the deionized water after washing is 10g / m 2 ~25g / m 2 The polypropylene meltblown cloth is alkalized for 3 to 20 minutes in an aqueous solution of an inorganic alkali (potassium carbonate, sodium carbonate, sodium hydroxide, potassium hydroxide) with a concentration of 0.1 to 0.3 mol / L at a temperature of 15 to 40°C and an ultrasonic power of 200 to 600 W.

[0007] Step 2: Ultrasonicate the pretreated polypropylene meltblown cloth in a zinc nitrate aqueous solution for 5 to 30 seconds at a temperature of 15 to 40° C. and an ultrasonic power of 200 to 600 W to load zinc ions on the surface of the polypropylene meltblown cloth fibers.

[0008] Step 3: After taking out the polypropylene meltblown cloth loaded with zinc ions, ultrasonicate it again in a mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide for 5 to 30 seconds at a temperature of 15 to 40°C and an ultrasonic power of 200 to 600 W to grow ZIF-8 crystals on the fiber surface in situ, and dry it in a forced air oven at 80°C for 5 minutes.

[0009] The molar ratio of zinc nitrate hexahydrate, 2-methylimidazole, N,N-dimethylformamide and deionized water in step 2 and step 3 is zinc nitrate hexahydrate: 2-methylimidazole: N,N-dimethylformamide: deionized water = 1:2-10:1-6:200-500.

[0010] The present invention has the following outstanding advantages:

[0011] 1) The preparation cost is low. Expensive conventional solvents such as methanol, ethanol, acetone, etc. are replaced with deionized water, and a small amount of N,N-dimethylformamide is added to the deionized water. Since the price of industrial 2-methylimidazole is about 10 times that of zinc nitrate hexahydrate and N,N-dimethylformamide, the present invention avoids using a larger molar ratio of 2-methylimidazole to zinc ions, and ZIF-8 can be uniformly grown on the surface of polypropylene meltblown cloth under the condition of zinc nitrate hexahydrate: 2-methylimidazole = 2 to 10. Therefore, the raw material cost of the present invention is 60 to 80% of the preparation methods of patents CN117867861A and CN118240385A. At the same time, due to the relatively short preparation time, other required costs such as energy consumption and equipment depreciation can also be reduced.

[0012] 2) Short preparation time. The pretreated polypropylene meltblown cloth only needs to be ultrasonicated for 5 to 30 seconds in a zinc nitrate aqueous solution and a 2-methylimidazole / N,N-dimethylformamide mixed aqueous solution at a temperature of 15 to 40°C to grow ZIF-8 on the surface, while most methods of growing ZIF-8 on substrates take more than 5 minutes. For example, the ultrasonic time in the zinc ion aqueous solution and the 2-methylimidazole aqueous solution in patent CN117867861A reached 5 minutes.

[0013] 3) The process is simple and easy. ZIF-8 can be grown on the surface of polypropylene meltblown cloth under low reaction temperature conditions (temperature 15-40°C), low ultrasonic power (200-600W) and short reaction process (sonication in zinc ion aqueous solution and 2-methylimidazole / N,N-dimethylformamide mixed aqueous solution successively). Industrial production only requires an ultrasonic cleaner and an oven, which effectively simplifies the production process while ensuring a faster production speed. Relatively simple production equipment is used, which is conducive to reducing the equipment requirements for industrialization and avoiding the use of equipment with high purchase and maintenance costs such as electrospinning machines required by patent CN115434148A and centrifuges required by patent CN114247307A. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a scanning electron microscope (SEM) image of polypropylene fiber after washing with deionized water;

[0015] Figure 2 is the scanning electron microscope (SEM) image of the alkalized polypropylene fiber;

[0016] Figure 3a The scanning electron microscope (SEM) image of Example 1;

[0017] Figure 3b The scanning electron microscope (SEM) image of Example 2;

[0018] Figure 3c The scanning electron microscope (SEM) image of Example 3;

[0019] Figure 3d The scanning electron microscope (SEM) image of Example 4 is shown;

[0020] Figure 4a The scanning electron microscope (SEM) image of Comparative Example 1;

[0021] Figure 4b This is the scanning electron microscope (SEM) image of Comparative Example 2. DETAILED DESCRIPTION

[0022] The following is a further detailed description of a method for rapidly preparing ZIF-8 / polypropylene melt-blown fiber membranes in batches at low cost provided by the present invention in conjunction with specific examples and comparative examples. It should be understood that the specific examples and comparative examples are only used to explain and introduce the invention and cannot limit the scope of application of the present invention. Any modifications and changes made to the present invention fall within the scope of protection of the present invention without departing from the purpose and scope of the present invention.

[0023] The schemes of Examples 1 to 4 are shown in Table 1:

[0024] Table 1

[0025] Example <![CDATA[Gram weight of polypropylene meltblown cloth (g / m 2 )]]> Zinc nitrate hexahydrate: 2-methylimidazole: N,N-dimethylformamide: deionized water (molar ratio) Growth time of ZIF-8 1 18 1:3.5:1:340 15 seconds 2 18 1:4:2.5:500 20 seconds 3 12 1:4.5:4:500 15 seconds 4 12 1:3:6:340 20 seconds

[0026] Comparative Examples 1 and 2 are shown in Table 2:

[0027] Table 2

[0028] Comparative Example <![CDATA[Gram weight of polypropylene meltblown fabric (g / m 2 )]]> Zinc nitrate hexahydrate: 2-methylimidazole: deionized water (molar ratio) Growth time of ZIF-8 1 18 1:40:1000 5 minutes 2 12 1:40:1000 5 minutes

[0029] Embodiment 1:

[0030] Step 1: Take a piece of paper weighing 18g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0031] Step 2: Accurately weigh 0.4g of sodium hydroxide and dissolve it in 50mL of deionized water. Place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400W. Then take out the sample and wash it 3 times with distilled water for later use.

[0032] Step 3: Accurately weigh 2.9 g of zinc nitrate hexahydrate and dissolve it in 60 mL of deionized water. Place the sample washed in step 2 into the zinc ion aqueous solution, and then transfer it to an ultrasonic cleaner for 15 seconds at a temperature of 20° C. and an ultrasonic power of 400 W.

[0033] Step 4: Accurately weigh 2.84 g of 2-methylimidazole and put it into 60 mL of deionized water, and add 0.72 ml of N,N-dimethylformamide, and stir until dissolved. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide, and then transfer it to an ultrasonic cleaner at a temperature of 20°C and an ultrasonic power of 400 W for 15 seconds.

[0034] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0035] Embodiment 2:

[0036] Step 1: Take a piece of paper weighing 18g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0037] Step 2: Accurately weigh 0.4g of sodium hydroxide and dissolve it in 50mL of deionized water. Place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400W. Then take out the sample and wash it 3 times with distilled water for later use.

[0038] Step 3: Accurately weigh 2.0 g of zinc nitrate hexahydrate and dissolve it in 60 mL of deionized water. Place the sample washed in step 2 into the zinc ion solution and then transfer it to an ultrasonic cleaner for 20 seconds at a temperature of 20°C and an ultrasonic power of 400 W.

[0039] Step 4: Accurately weigh 2.2 g of 2-methylimidazole and put it into 60 mL of deionized water, and add 1.2 ml of N,N-dimethylformamide, and stir until dissolved. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide, and then transfer it to an ultrasonic cleaner at a temperature of 20°C and an ultrasonic power of 400 W for 20 seconds.

[0040] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0041] Embodiment 3:

[0042] Step 1: Take a piece of paper with a weight of 12g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0043] Step 2: Accurately weigh 0.4 g of sodium hydroxide and dissolve it in 50 mL of deionized water; place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400 W. Then take out the sample and wash it with distilled water for 3 times for later use.

[0044] Step 3: Accurately weigh 1.98 g of zinc nitrate hexahydrate and dissolve it in 60 mL of deionized water. Place the sample washed in step 2 into the zinc ion solution and then transfer it to an ultrasonic cleaner for 15 seconds at a temperature of 20° C. and an ultrasonic power of 400 W.

[0045] Step 4: Accurately weigh 2.47 g of 2-methylimidazole and put it into 60 mL of deionized water, and add 1.92 ml of N,N-dimethylformamide, and stir until dissolved. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide, and then transfer it to an ultrasonic cleaner at a temperature of 20°C and an ultrasonic power of 400 W for 15 seconds.

[0046] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0047] Embodiment 4:

[0048] Step 1: Take a piece of paper with a weight of 12g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0049] Step 2: Accurately weigh 0.4g of sodium hydroxide and dissolve it in 50mL of deionized water. Place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400W. Then take out the sample and wash it 3 times with distilled water for later use.

[0050] Step 3: Accurately weigh 2.9 g of zinc nitrate hexahydrate and dissolve it in 60 mL of deionized water. Place the sample washed in step 2 into the zinc ion solution and then transfer it to an ultrasonic cleaner for 20 seconds at a temperature of 20°C and an ultrasonic power of 400 W.

[0051] Step 4: Accurately weigh 2.43 g of 2-methylimidazole and put it into 60 mL of deionized water, and add 4.32 ml of N,N-dimethylformamide, and stir until dissolved. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide, and then transfer it to an ultrasonic cleaner at a temperature of 20°C and an ultrasonic power of 400 W for 20 seconds.

[0052] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0053] Comparative Example 1:

[0054] Step 1: Take a piece of paper weighing 18g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0055] Step 2: Accurately weigh 0.4g of sodium hydroxide and dissolve it in 50mL of deionized water. Place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400W. Then take out the sample and wash it 3 times with distilled water for later use.

[0056] Step 3: Accurately weigh 0.825 g of zinc nitrate hexahydrate and dissolve it in 50 mL of deionized water. Place the sample washed in step 2 into the zinc ion aqueous solution and then transfer it to an ultrasonic cleaner for 5 minutes at a temperature of 20° C. and an ultrasonic power of 400 W.

[0057] Step 4: Accurately weigh 9.11 g of 2-methylimidazole and dissolve it in 50 mL of deionized water. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the 2-methylimidazole aqueous solution, and then transfer it to an ultrasonic cleaning machine for 5 minutes at a temperature of 20° C. and an ultrasonic power of 400 W.

[0058] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0059] Comparative Example 2:

[0060] Step 1: Take a piece of paper with a weight of 12g / m 2 The polypropylene meltblown fabric sample was rinsed with deionized water for 3 times to remove impurities on the fiber surface, and then placed in an oven for drying at 70°C.

[0061] Step 2: Accurately weigh 0.4g of sodium hydroxide and dissolve it in 50mL of deionized water. Place the polypropylene meltblown fabric sample dried in step 1 into the sodium hydroxide solution, and then transfer it to an ultrasonic cleaner for 10 minutes at a temperature of 20°C and an ultrasonic power of 400W. Then take out the sample and wash it 3 times with distilled water for later use.

[0062] Step 3: Accurately weigh 0.825 g of zinc nitrate hexahydrate and dissolve it in 50 mL of deionized water. Place the sample washed in step 2 into the zinc ion aqueous solution and then transfer it to an ultrasonic cleaner for 5 minutes at a temperature of 20° C. and an ultrasonic power of 400 W.

[0063] Step 4: Accurately weigh 9.11 g of 2-methylimidazole and dissolve it in 50 mL of deionized water. Put the polypropylene melt-blown cloth loaded with zinc ions in step 3 into the 2-methylimidazole aqueous solution, and then transfer it to an ultrasonic cleaning machine for 5 minutes at a temperature of 20° C. and an ultrasonic power of 400 W.

[0064] Step 5: The ZIF-8 / polypropylene melt-blown fiber membrane prepared in step 4 was directly transferred to a forced air oven and dried at 80° C. for 5 minutes.

[0065] The scanning electron microscope images of the substrate after cleaning and alkalization of the present invention and the embodiments and comparative examples are shown in the attached drawings. Figure 1 This is a scanning electron microscope (SEM) image of the polypropylene meltblown cloth after washing with deionized water; Figure 2 This is a scanning electron microscope image (SEM) of the alkalized polypropylene meltblown cloth; Figure 3a , Figure 3b , Figure 3c and Figure 3d The scanning electron microscope images (SEM) of Example 1, Example 2, Example 3 and Example 4 are respectively; Figure 4a and Figure 4b The scanning electron microscope (SEM) images of Comparative Example 1 and Comparative Example 2 are shown. By comparing Examples 1 and 2 with Comparative Example 1, and Examples 3 and 4 with Comparative Example 2, it can be seen that with the help of N,N-dimethylformamide, it is possible to reduce costs, save time, and ensure the growth of dense ZIF-8 on the surface of the polypropylene meltblown cloth.

[0066] Test method:

[0067] The "GB / T 6165-2021 High Efficiency Air Filter Performance Test Method Efficiency and Resistance" method was used to test the filtration accuracy of ZIF-8 / polypropylene melt-blown fiber membrane for PM0.3.

[0068] The test results of the PM0.3 filtration accuracy of the ZIF-8 / polypropylene melt-blown fiber membrane prepared in the embodiment of the present invention and the production cost per square meter are shown in Table 3.

[0069] Table 3

[0070] Examples PM0.3 filtration accuracy <![CDATA[Production cost (yuan / m 2 )]]> Example 1 64.9 0.256 Example 2 66.4 0.244 Example 3 63.6 0.252 Example 4 67.2 0.260 Comparative Example 1 66.5 0.375 Comparative Example 2 64.4 0.346

[0071] Conclusion: By comparing Examples 1 and 2 with Comparative Example 1, and Examples 3 and 4 with Comparative Example 2, the ZIF-8 / polypropylene melt-blown fiber membrane prepared in 15 or 20 seconds with the assistance of N,N-dimethylformamide has the same PM0.3 filtration accuracy as the ZIF-8 / polypropylene melt-blown fiber membrane prepared in 5 minutes in a deionized water solution, but the production cost per square meter is reduced by 20-40%. The ZIF-8 / polypropylene melt-blown fiber membrane prepared by the present invention has good filtration performance while ensuring low production cost and short reaction time.

Claims

1. A method for rapidly preparing a ZIF-8 / polypropylene melt-blown fiber membrane, characterized in that: Here are the steps: S1: pre-treating the polypropylene meltblown cloth washed with deionized water by alkalization in an inorganic alkali aqueous solution; S2: placing the pretreated polypropylene meltblown cloth in an aqueous solution of zinc nitrate and ultrasonicating the surface of the polypropylene meltblown cloth fibers to load zinc ions; S3: The polypropylene melt-blown fabric loaded with zinc ions is taken out and placed in a mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide for ultrasonication again to grow ZIF-8 crystals on the fiber surface in situ, and then directly dried. In steps S2 and S3, the molar ratio of zinc nitrate hexahydrate, 2-methylimidazole, N,N-dimethylformamide and deionized water is zinc nitrate hexahydrate: 2-methylimidazole: N,N-dimethylformamide: deionized water = 1:2-10:1-6:200-500.

2. The method for preparing the ZIF-8 / polypropylene melt-blown fiber membrane according to claim 1, characterized in that: In the step S2, the polypropylene meltblown cloth is ultrasonically treated in the zinc ion aqueous solution for 5 to 30 seconds, at a temperature of 15 to 40° C., and at an ultrasonic power of 200 to 600 W.

3. The method for preparing the ZIF-8 / polypropylene melt-blown fiber membrane according to claim 1, characterized in that: In the step S3, the polypropylene meltblown cloth is ultrasonically treated in a mixed aqueous solution of 2-methylimidazole / N,N-dimethylformamide for 5 to 30 seconds, at a temperature of 15 to 40° C., and at an ultrasonic power of 200 to 600 W.

4. The method for preparing the ZIF-8 / polypropylene melt-blown fiber membrane according to claim 1, characterized in that: In step S3, the fiber membrane is dried in a forced air oven at 80° C. for 5 minutes.

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