Magnetic functionalized polyimide hybrid matrix membrane, method for preparing same, and use thereof

Abstract

The application discloses a kind of magnetic functional polyimide mixed matrix membrane and its preparation method and application, its preparation method includes preparing magnetic porous filler, preparing polyimide resin, magnetic porous filler is dispersed into organic solvent and is ultrasonically treated to obtain filler suspension, polyimide resin is added to organic solvent and is stirred and dissolved to obtain polyimide resin solution, filler suspension is added to polyimide resin solution, and mixed matrix casting fluid is obtained by stirring and ultrasonic treatment, and magnetic functional polyimide mixed matrix membrane is prepared by mixed matrix casting fluid.The magnetic functional polyimide mixed matrix membrane of the application contains the magnetic porous filler with paramagnetism and abundant nanopore structure inside, can greatly improve the gas permeability of membrane material itself, can greatly improve the selectivity of oxygen, and finally obtain the magnetic functional polyimide mixed matrix membrane with higher oxygen permeability and gas selectivity.

Description

Technical Field

[0001] This invention belongs to the field of polyimide gas separation membrane technology, specifically relating to a magnetically functionalized polyimide mixed matrix membrane, its preparation method, and its application. Background Technology

[0002] Oxygen plays a vital role in daily life and industrial production. For example, it is one of the essential gases for life, required for respiration in both humans and animals. Within the body, oxygen is transported to cells, participating in metabolic processes, generating energy, and maintaining normal bodily functions. In industrial production, oxygen is an important chemical raw material and additive. In industries such as steel, chemicals, and gas, it acts as an oxidant, increasing reaction rates and efficiency while reducing production costs. It is also used as a combustion aid in specialized welding. In aerospace, oxygen is a crucial fuel, with liquid oxygen and liquid hydrogen used as fuel in rocket engines. In the medical field, oxygen is frequently used to treat respiratory and cardiovascular diseases. Therefore, oxygen is consumed in enormous quantities in daily life and production, making it an irreplaceable necessity. The production, enrichment, separation, and purification of oxygen have always been important branches of industrial technology and scientific development, and the efficient enrichment and purification of oxygen has become a focus of widespread attention. Traditional oxygen enrichment, separation, and purification technologies generally include cryogenic separation, chemical or physical adsorption, etc. These methods are not only energy-intensive and costly, but also complex and dangerous. In contrast, using gas separation membrane technology for oxygen enrichment, separation, and purification can significantly reduce energy consumption, lower costs, require less investment, and produce high-efficiency, safe, and reliable products.

[0003] Polyimide polymers possess a variety of excellent properties, such as excellent corrosion resistance, high thermal stability, and mechanical strength, and are now widely used in the field of gas separation membranes, exhibiting superior gas separation performance. Furthermore, due to the diverse types of polyimides and their varied molecular structures, different types of polyimides possess different separation effects. Therefore, the performance of polyimide gas separation membranes can be precisely controlled by effectively regulating the polyimide molecular structure.

[0004] However, most existing polyimide mixed matrix membranes are designed for the separation of CO2 gas (mainly CO2 / CH4) [see Chinese patent references CN113413777A, CN113694747A, CN114950146A, CN115232026A, CN115715939A, CN117258562A, CN118286894A, etc.]. A few polyimide mixed matrix membranes designed for the separation of O2 gas (mainly O2 / N2) also suffer from low O2 / N2 gas selectivity (usually below 6) [see Chinese patent references CN107551835A, CN112717723A, CN118743932A, etc.]. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a magnetically functionalized polyimide mixed matrix membrane with O2 / N2 gas selectivity ≥8, its preparation method and application.

[0006] The technical solution to achieve the objective of this invention is: a method for preparing a magnetically functionalized polyimide mixed matrix membrane, comprising the following steps:

[0007] S1: Preparation of magnetic porous packing material.

[0008] S11: Disperse the nanoporous filler in deionized water, then add ferric compound, and sonicate to obtain ferric suspension.

[0009] S12: Add the ferrous compound to deionized water and stir to dissolve to obtain a ferrous solution.

[0010] S13: Heat the ferric suspension obtained in step S11 to 40-70°C, then slowly add the ferrous solution obtained in step S12, followed by slowly adding the alkaline solution until the reaction system becomes alkaline. After the addition is complete, raise the temperature to 80-100°C and crystallize for 1-3 hours.

[0011] S14: After crystallization, magnetic porous filler is obtained through post-processing.

[0012] In step S11 above, the nanoporous filler is one or two of the following: attapulgite, carbon nanotubes, zeolite, diatomite, illite, sepiolite, montmorillonite, and palygorskite.

[0013] The molar ratio of the ferric compound in step S11 to the ferrous compound in step S12 is 1:1.25 to 1:1.75.

[0014] In step S11 above, the trivalent iron compound is one or two of ferric chloride, ferric nitrate, and ferric sulfate; preferably ferric chloride.

[0015] In step S12 above, the divalent iron compound is one or two of ferrous sulfate, ferrous chloride, ferrous carbonate, and ferrous sulfide; preferably ferrous sulfate.

[0016] In step S13 above, the alkaline solution is sodium hydroxide solution or ammonia water, preferably ammonia water.

[0017] In step S13 above, the alkalinity is pH=10 to 12.

[0018] S2: Preparation of polyimide resin.

[0019] S21: Add the diamine monomer to an organic solvent, heat to 50-70°C, stir until the diamine monomer is completely dissolved, then add the dianhydride monomer, heat to 80-100°C, stir until the dianhydride monomer is completely dissolved, heat to 180-230°C, add the catalyst and toluene for reflux and water removal reaction to obtain polyimide slurry.

[0020] S22: The polyimide slurry obtained in step S21 is injected into the phase inversion liquid to obtain filamentous solids. The filamentous solids are then repeatedly washed with the phase inversion liquid and finally dried to obtain polyimide resin.

[0021] In step S21 above, the organic solvent is one or two of 1,3-dimethyl-2-imidazolinone (DMI), pentachlorophenol, p-chlorophenol (PCP), N-methylpyrrolidone (NMP), cresol, and m-cresol.

[0022] In step S21 above, the diamine monomer is one or two of 3,7-diamino-2,8-dimethyldibenzothiophene sulfone (OTS), 2,2',5,5'-tetrachlorobenzidine (TCB), and m-phenylenediamine (mPD).

[0023] In step S21 above, the dianhydride monomer is one or two of the following: hexafluorodianhydride (6FDA), biphenyl dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4'-oxobisphthalic anhydride (ODPA).

[0024] In step S21 above, the molar ratio of the diamine monomer to the dianhydride monomer is 1:0.95 to 1:1.05.

[0025] In step S21 above, the catalyst is one of isoquinoline, pyridine, methylpyridine, and triethylamine, preferably isoquinoline.

[0026] In step S21 above, the amount of catalyst used is 0.1 to 1% of the total weight of the diamine monomer and the dianhydride monomer.

[0027] In step S21 above, the volume ratio of toluene to the organic solvent is 1:5 to 1:30.

[0028] In step S21 above, the reflux water-carrying reaction time is 20-50 hours.

[0029] S3: Preparation of magnetically functionalized polyimide mixed matrix membrane.

[0030] S31: Disperse the magnetic porous packing material obtained in step S1 into an organic solvent and sonicate it to obtain a packing material suspension.

[0031] S32: Add the polyimide resin obtained in step S2 to an organic solvent and stir to dissolve it to obtain a polyimide resin solution.

[0032] S33: Add the filler suspension obtained in step S31 to the polyimide resin solution obtained in step S32, stir to mix evenly, and then perform ultrasonic treatment to obtain a mixed matrix casting solution.

[0033] S34: The mixed matrix casting solution obtained in step S33 is uniformly coated onto a clean glass plate, then placed in an oven, the temperature is increased by a program to remove the solvent, and finally the temperature is naturally reduced to room temperature. The glass plate with the film is then immersed in distilled water to peel it off, and a magnetically functionalized polyimide mixed matrix film is obtained.

[0034] In steps S31 and S32 above, the organic solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and 1,3-dimethyl-2-imidazolinone (DMI).

[0035] In step S33 above, the polyimide resin in the mixed matrix casting solution has a weight percentage of 10-30 wt%.

[0036] In step S33 above, the weight percentage (i.e., doping amount) of the magnetic porous filler in the mixed matrix casting solution is 1 to 5 wt%.

[0037] The thickness of the magnetically functionalized polyimide mixed matrix film of the present invention can be adjusted by adjusting the solid content of the casting liquid or by adjusting the opening height of the scraper.

[0038] The magnetically functionalized polyimide mixed matrix membrane of the present invention is used for the enrichment, separation and purification of industrial oxygen.

[0039] The positive effects of this invention are:

[0040] (1) The magnetically functionalized polyimide mixed matrix membrane of the present invention contains magnetic porous filler with both paramagnetism and rich nanopore structure. On the one hand, the rich nanopore structure can provide abundant transport channels for gas transport, thereby greatly improving the gas permeability of the membrane material itself. On the other hand, under the influence of paramagnetic properties, the adsorption of oxygen by the membrane material is greatly increased, thereby greatly improving the oxygen selectivity, and finally obtaining a magnetically functionalized polyimide mixed matrix membrane with both high oxygen permeability and gas selectivity.

[0041] (2) The magnetically functionalized polyimide mixed matrix membrane of the present invention has an O2 / N2 gas selectivity of ≥7, and in some cases even ≥10, while the glass transition temperature is still guaranteed to be above 200℃, which has good thermal stability.

[0042] (3) The magnetically functionalized polyimide mixed matrix membrane of the present invention can be used for the enrichment, separation and purification of industrial oxygen, such as the preparation of high-purity oxygen. This can effectively reduce the high energy consumption in the oxygen production process, solve the disadvantages of complex and dangerous operation in the high-purity oxygen production process, and significantly reduce the investment and production costs of the oxygen enrichment industry. Detailed Implementation

[0043] (Example 1)

[0044] The method for preparing the magnetically functionalized polyimide mixed matrix film in this embodiment includes the following steps:

[0045] S1: Preparation of magnetic porous packing material.

[0046] S11: Disperse 40g of attapulgite into 200g of deionized water, then add 29.4g of ferric chloride (0.18mol), and sonicate for 1h to obtain a ferric chloride suspension.

[0047] S12: Add 40g of ferrous sulfate (0.26mol) to 200g of deionized water, stir to dissolve, and obtain ferrous sulfate solution.

[0048] S13: Heat the ferric chloride suspension obtained in step S11 to 55°C, then slowly add the ferrous sulfate solution obtained in step S12, followed by slowly adding ammonia water until the pH of the reaction system is 11. After the addition is complete, raise the temperature to 90°C and crystallize for 2 hours.

[0049] S14: After crystallization, the reaction system was cooled to room temperature, filtered, the filter cake was washed three times with ethanol, dried in a 60℃ oven, and passed through a 200-mesh sieve to obtain 50.18g of magnetic porous filler, denoted as Fe3O4@attapulgite.

[0050] S2: Preparation of polyimide resin.

[0051] S21: In a four-necked flask equipped with a mechanical stirrer, thermometer, and nitrogen purging tube, add 400 mL of 1,3-dimethyl-2-imidazolinone (DMI), 27.4034 g of 3,7-diamino-2,8-dimethyldibenzothiophene sulfone (OTS), and 32.1661 g of 2,2',5,5'-tetrachlorobenzidine (TCB). Heat to 60°C and stir until the diamine monomer is completely dissolved. Then add 44.3745 g of hexafluorodianhydride (6FDA) and 29.3892 g of biphenyl dianhydride (BPDA). Heat to 100°C and stir until the dianhydride monomer is completely dissolved. Heat to 210°C, add 0.5 g of isoquinoline and 20 mL of toluene, and reflux to remove water for 40 h.

[0052] S22: After the reaction is complete, toluene is distilled off and cooled to room temperature. The resulting polyimide slurry is injected into ethanol to obtain filamentous solids. The filamentous solids are then repeatedly washed with ethanol and finally dried in an oven at 65°C for 6 hours to obtain polyimide resin.

[0053] S3: Preparation of magnetically functionalized polyimide mixed matrix membrane.

[0054] S31: Disperse 1g of the magnetic porous filler Fe3O4@attapulgite prepared in step S1 into 39g of DMAc solvent, and sonicate for 2h to obtain a filler suspension.

[0055] S32: Add 20g of the polyimide resin obtained in step S2 to 40g of DMAc solvent, stir to dissolve, and obtain a polyimide resin solution.

[0056] S33: Add the filler suspension obtained in step S31 to the polyimide resin solution obtained in step S32, stir to mix evenly, and then sonicate for 1 hour to obtain a mixed matrix casting solution with a doping amount of 1 wt%.

[0057] S34: The mixed matrix casting solution obtained in step S33 is uniformly coated onto a clean glass plate, and then placed in a forced-air drying oven. The solvent is removed by heating according to the program of 80℃ / 6h, 150℃ / 2h, and 200℃ / 2h. Finally, the temperature is naturally reduced to room temperature, and the glass plate with the film is immersed in distilled water for peeling to obtain a magnetically functionalized polyimide mixed matrix film.

[0058] (Examples 2-3)

[0059] The preparation methods of the magnetically functionalized polyimide mixed matrix membranes in each embodiment are basically the same as those in Example 1, except that the amount of magnetic porous filler Fe3O4@attapulgite added in step S31 and the corresponding doping amount of the mixed matrix casting solution in step S33 are shown in Table 1.

[0060] (Comparative Examples 1 to 6)

[0061] The preparation methods of the magnetically functionalized polyimide mixed matrix membranes in each comparative example are basically the same as those in Example 1, except that the amount of magnetic porous filler Fe3O4@attapulgite added in step S31 and the corresponding doping amount of the mixed matrix casting solution in step S33 are shown in Table 1.

[0062] (Comparative Example 7)

[0063] The difference between the comparative example and Example 1 is that step S1, which involves preparing magnetic porous fillers, is omitted. In step S3, 20g of the polyimide resin obtained in step S2 is directly added to 80g of DMAc solvent and stirred to dissolve, resulting in a mixed matrix casting solution (equivalent to a doping amount of 0wt%).

[0064] (Test example)

[0065] The gas separation performance and glass transition temperature of the polyimide mixed matrix membranes prepared in each embodiment and comparative example were tested, and the results are shown in Table 1.

[0066] Among them: the test conditions for gas permeability coefficient are 25℃ and 0.25MPa, and the unit is Barrer[(10 -5 ×cm 3 (STP) / (cm) 2 ·S·cmHg).

[0067] Table 1

[0068] In step S31, the filler + DMAc Doping amount <![CDATA[O2 Permeability]]> <![CDATA[N2 Permeability]]> <![CDATA[O2 / N2 selectivity]]> Tg / ℃ Example 1 1g + 39g 1wt% 10.38 1.26 8.24 303 Example 2 2g+38g 2wt% 14.41 1.53 9.42 286 Example 3 5g+35g 5wt% 17.11 1.75 9.78 269 Comparative Example 1 0.1g + 39.9g 0.1wt% 6.03 1.17 5.15 314 Comparative Example 2 0.2g + 39.8g 0.2wt% 6.11 1.18 5.18 312 Comparative Example 3 0.5g + 39.5g 0.5wt% 6.43 1.23 5.23 308 Comparative Example 4 8g+32g 8wt% 19.43 3.80 5.11 258 Comparative Example 5 10g + 30g 10wt% 21.34 4.87 4.38 251 Comparative Example 6 15g + 25g 15wt% 28.31 9.41 3.01 224 Comparative Example 7 / 0wt% 5.89 1.15 5.12 315

[0069] (Examples 4 to 12)

[0070] The preparation methods of the magnetically functionalized polyimide mixed matrix membranes in each embodiment are basically the same as those in Example 1, except that the types of nanoporous fillers in step S1 and the corresponding types of magnetic porous fillers are shown in Table 2.

[0071] Table 2

[0072] Examples 4 to 6 Examples 7 to 9 Examples 10 to 12 Nanoporous packing 40g of sepiolite 40g of montmorillonite 40g of Polu Stone Magnetic porous packing <![CDATA[Fe3O4@Sepiolite 49.88 g]]> <![CDATA[Fe3O4@montmorillonite 52.64 g]]> <![CDATA[Fe3O4@Halloysite 48.94g]]>

[0073] The gas separation performance and glass transition temperature of the polyimide mixed matrix membranes prepared in Examples 4 to 12 were tested, and the results are shown in Table 3.

[0074] Table 3

[0075] Magnetic porous packing Doping amount <![CDATA[O2 Permeability]]> <![CDATA[Permeability of N2]]> <![CDATA[O2 / N2 selectivity]]> Tg / ℃ Example 4 <![CDATA[Fe3O4@Sepiolite]]> 1wt% 10.83 1.32 8.20 311 Example 5 <![CDATA[Fe3O4@Sepiolite]]> 2wt% 14.77 1.64 9.00 303 Example 6 <![CDATA[Fe3O4@Sepiolite]]> 5wt% 17.56 1.87 9.39 297 Example 7 <![CDATA[Fe3O4@Montmorillonite]]> 1wt% 9.86 1.27 7.76 293 Example 8 <![CDATA[Fe3O4@Montmorillonite]]> 2wt% 8.53 1.04 8.20 290 Example 9 <![CDATA[Fe3O4@Montmorillonite]]> 5wt% 12.18 1.33 9.16 281 Example 10 <![CDATA[Fe3O4@Halloysite]]> 1wt% 8.16 1.29 6.32 303 Example 11 <![CDATA[Fe3O4@Halloysite]]> 2wt% 8.98 1.28 7.02 297 Example 12 <![CDATA[Fe3O4@Halloysite]]> 5wt% 9.45 1.23 7.68 291

[0076] (Examples 13 to 21).

[0077] The preparation methods of the magnetically functionalized polyimide mixed matrix membranes in each embodiment are basically the same as those in Example 1, except that the types and amounts of diamine monomers and dianhydride monomers used to prepare the polyimide resin in step S2 are shown in Table 4.

[0078] Table 4

[0079] Examples 13 to 15 Examples 16 to 18 Examples 19 to 21 Diamine monomer OTS 28.0334g 33.8880g 29.7202g diamine monomer TCB 32.9056g 26.5184g 34.8856g Dihydride monomer 6FDA 38.3159g 36.5833g 38.5008g Dihydride monomer BPDA 36.0778g 36.3436g 25.4991g Dihydride monomer PMDA / / 4.7259g

[0080] The gas separation performance and glass transition temperature of the polyimide mixed matrix membranes prepared in Examples 13 to 21 were tested, and the results are shown in Table 5.

[0081] Table 5

[0082] Doping amount <![CDATA[O2 Permeability]]> <![CDATA[N2 Permeability]]> <![CDATA[O2 / N2 selectivity]]> Tg / ℃ Example 13 1wt% 8.89 0.88 10.10 284 Example 14 2wt% 8.93 0.81 11.02 279 Example 15 5wt% 9.37 0.80 11.71 258 Example 16 1wt% 6.12 0.54 11.33 292 Example 17 2wt% 6.90 0.56 12.32 284 Example 18 5wt% 7.84 0.59 13.29 271 Example 19 1wt% 11.18 1.48 7.55 319 Example 20 2wt% 15.97 2.05 7.79 307 Example 21 5wt% 18.12 2.20 8.24 300

[0083] (Examples 22 to 30)

[0084] The preparation methods of the magnetically functionalized polyimide mixed matrix membranes in each embodiment are basically the same as those in Example 1, except that: the types of nanoporous fillers and corresponding magnetic porous fillers in step S1, and the types and amounts of diamine monomers and dianhydride monomers used to prepare polyimide resin in step S2 are shown in Table 6.

[0085] Table 6

[0086] Examples 22 to 24 Examples 25 to 27 Examples 28 to 30 Nanoporous packing illite 40g 40g of carbon nanotubes 40g of zeolite Magnetic porous packing <![CDATA[Fe3O4@Illite 56.02 g]]> <![CDATA[53.22 g of Fe3O4@carbon nanotubes]]> <![CDATA[Fe3O4@Zeolite 57.10 g]]> Diamine monomer OTS 27.0791g 27.8968g 27.7948g diamine monomer TCB 31.7854g 32.7452g 32.6255g Dihydride monomer 6FDA 43.8492g 36.1388g 36.0067g Dihydride monomer BPDA / 23.9347g 23.8471g Dihydride monomer ODPA 30.6197g 12.6177g / Dihydride monomer BTDA / / 13.0587g

[0087] The gas separation performance and glass transition temperature of the polyimide mixed matrix membranes prepared in Examples 22 to 30 were tested, and the results are shown in Table 7.

[0088] Table 7

[0089] Magnetic porous packing Doping amount <![CDATA[O2 Permeability]]> <![CDATA[N2 Permeability]]> <![CDATA[O2 / N2 selectivity]]> Tg / ℃ Example 22 <![CDATA[Fe3O4@Illite]]> 1wt% 7.53 0.82 9.18 301 Example 23 <![CDATA[Fe3O4@Illite]]> 2wt% 12.15 1.13 10.75 292 Example 24 <![CDATA[Fe3O4@Illite]]> 5wt% 16.83 1.24 13.57 286 Example 25 <![CDATA[Fe3O4@Carbon nanotubes]]> 1wt% 7.23 0.64 11.30 273 Example 26 <![CDATA[Fe3O4@Carbon nanotubes]]> 2wt% 8.12 0.67 12.12 261 Example 27 <![CDATA[Fe3O4@Carbon nanotubes]]> 5wt% 9.38 0.68 13.79 248 Example 28 <![CDATA[Fe3O4@Zeolite]]> 1wt% 11.09 1.38 8.04 338 Example 29 <![CDATA[Fe3O4@Zeolite]]> 2wt% 12.15 1.46 8.32 329 Example 30 <![CDATA[Fe3O4@Zeolite]]> 5wt% 13.31 1.47 9.05 323

Claims

1. A method for preparing a magnetically functionalized polyimide hybrid matrix membrane, characterized in that Has the following steps: S1: preparation of magnetic porous filler; S11: the nanoporous filler is dispersed into deionized water, then a trivalent iron compound is added, and ultrasonic treatment is performed to obtain a trivalent iron suspension; S12: a divalent iron compound is added to deionized water, and stirring and dissolution are performed to obtain a divalent iron solution; S13: the trivalent iron suspension obtained in step S11 is heated to 40-70℃, then the divalent iron solution obtained in step S12 is slowly added dropwise, then lye is slowly added dropwise until the reaction system is alkaline, and after the dropwise addition is completed, the temperature is raised to 80-100℃ for crystallization for 1-3h; S14: after the crystallization is completed, the magnetic porous filler is obtained through post-treatment; S2: preparation of polyimide resin; S21: diamine monomer is added to an organic solvent, the temperature is raised to 50-70℃, and stirring is performed until the diamine monomer is completely dissolved, then dianhydride monomer is added, the temperature is raised to 80-100℃, and stirring is performed until the dianhydride monomer is completely dissolved, the temperature is raised to 180-230℃, a catalyst and toluene are added for reflux water removal reaction, and polyimide slurry is obtained; the diamine monomer is one or two of 3,7-diamino-2,8-dimethyl dithiophene sulfone, 2,2',5,5'-tetrachlorobenzidine, and m-phenylenediamine; the dianhydride monomer is one or two of hexafluoro dianhydride, biphenyl dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, pyromellitic dianhydride, and 4,4'-oxybisphthalic anhydride; and the molar ratio of the diamine monomer to the dianhydride monomer is 1:0.95-1:1.05; S22: the polyimide slurry obtained in step S21 is injected into a phase inversion liquid to obtain a filamentous solid, the filamentous solid is repeatedly washed with a phase inversion liquid, and finally drying is performed to obtain polyimide resin; S3: preparation of magnetic functionalized polyimide mixed matrix membrane; S31: the magnetic porous filler prepared in step S1 is dispersed into an organic solvent, and ultrasonic treatment is performed to obtain a filler suspension; S32: the polyimide resin prepared in step S2 is added to an organic solvent, and stirring and dissolution are performed to obtain a polyimide resin solution; S33: the filler suspension obtained in step S31 is added to the polyimide resin solution obtained in step S32, stirring is performed to uniformly mix them, then ultrasonic treatment is performed, and a mixed matrix casting solution is obtained; S34: the mixed matrix casting solution prepared in step S33 is uniformly coated on a clean glass plate, then the glass plate is placed in an oven, programmed temperature rising is performed to remove the solvent, and finally natural temperature reduction is performed to room temperature, the glass plate with the membrane is immersed in distilled water for peeling, and a magnetic functionalized polyimide mixed matrix membrane is obtained.

2. The method for preparing the magnetically functionalized polyimide mixed matrix membrane according to claim 1, characterized in that: In the above step S11, the nanoporous filler is one or two of attapulgite, carbon nanotube, zeolite, diatomite, illite, sepiolite, montmorillonite, and palygorskite; and the trivalent iron compound is one or two of ferric chloride, ferric nitrate, and ferric sulfate.

3. The method of claim 1, wherein the magnetic functionalized polyimide hybrid matrix membrane is prepared by the steps of: (a) mixing a polyimide precursor solution with a magnetic nanoparticle solution; (b) coating the mixture on a substrate; (c) drying the coated mixture; and (d) curing the coated mixture. In the above step S12, the divalent iron compound is one or two of ferrous sulfate, ferrous chloride, ferrous carbonate, and ferrous sulfide.

4. The method of claim 1, wherein the magnetic functionalized polyimide hybrid matrix membrane is prepared by the steps of: (a) mixing a polyimide precursor solution with a magnetic nanoparticle solution; (b) coating the mixture on a substrate; (c) drying the coated mixture; and (d) curing the coated mixture. In the above step S13, the lye is sodium hydroxide solution or ammonia water, and the alkalinity is pH=10-12.

5. The method of claim 1, wherein the magnetic functionalized polyimide hybrid matrix membrane is prepared by the steps of: (a) mixing a polyimide precursor solution with a magnetic nanoparticle solution; (b) coating the mixture on a substrate; (c) drying the coated mixture; and (d) curing the coated mixture. In step S21, the organic solvent is one or two of 1,3-dimethyl-2-imidazolidinone, pentachlorophenol, p-chlorophenol, N-methylpyrrolidone, cresol, m-cresol.

6. The method of claim 1, wherein the magnetic functionalized polyimide hybrid matrix membrane is prepared by the steps of: a) mixing a polyimide precursor solution with a magnetic nanoparticle solution; b) coating the mixture on a substrate; c) drying the coated mixture; d) curing the coated mixture; and e) removing the substrate. In step S21, the catalyst is one of isoquinoline, pyridine, methylpyridine, triethylamine, and the amount of the catalyst is 0.1-1% of the total weight of the diamine monomer and the dianhydride monomer; the volume ratio of the toluene to the organic solvent is 1:5-1:

30.

7. The method for preparing the magnetically functionalized polyimide mixed matrix membrane according to claim 1, characterized in that: In step S31 and step S32, the organic solvent is one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone.

8. The method for preparing the magnetically functionalized polyimide mixed matrix membrane according to claim 1, characterized in that: In step S33, the weight percentage of the polyimide resin in the mixed matrix casting solution is 10-30wt%, and the weight percentage of the magnetic porous filler in the mixed matrix casting solution is 1-5wt%.

9. A magnetic functionalized polyimide mixed matrix membrane prepared by the method of any one of claims 1-8.

10. Use of the magnetic functionalized polyimide mixed matrix membrane of claim 9 in enrichment, separation and purification of industrial oxygen.