A method for preparing a self-contained microporous polymer nanofiltration membrane

Abstract

The invention discloses a method for preparing a self-microporous polymer nanofiltration membrane, the preparation method comprising: (1) preparing a PIMs base membrane by a phase inversion method; (2) dissolving TTSBI in an alkaline aqueous solution to form an aqueous phase; dissolving trimesoyl chloride and 4-trifluoromethylbenzoyl chloride in n-hexane to form an oil phase; obtaining a PIMs-F nanofiltration membrane by an interfacial polymerization method; (3) immersing the prepared PIMs-F nanofiltration membrane in a hexamethylenediamine isopropanol solution having a concentration of 12 to 25 g / L at room temperature for 12 to 36 hours to crosslink the composite membrane, and repeatedly washing with deionized water after the crosslinking is completed to obtain the self-microporous polymer nanofiltration membrane. The invention is based on the microporous structure of PIMs, and adjusts its structure by introducing 4-trifluoromethylbenzoyl chloride, thereby improving the retention rate of the composite membrane for dyes, and at the same time, the introduction of 4-trifluoromethylbenzoyl chloride increases the fluorine-containing groups of the selective layer, thereby improving the permeability of the composite membrane to non-polar solvents.

Description

Technical Field

[0001] The invention belongs to the field of membrane separation under pressure drive, and in particular relates to a method for preparing a self-microporous polymer nanofiltration membrane. Technical Background

[0002] Traditional separation processes, such as evaporation and distillation, are widely used in the oil and gas, energy, chemical and pharmaceutical industries, but they are energy-intensive processes that consume a lot of energy and cause serious pollution to the environment. As a new separation technology, the membrane separation process is a new, efficient, low-energy, stable and green separation process that can replace traditional high-energy separation engineering. In order to enable the wider application of membrane technology, selective separation membranes are required to be applicable to solvent systems, such as polar solvents or non-polar solvents. To this end, it is necessary to design the polymer structure at the molecular level to provide interconnected micropores that interact with the solvent and maintain long-term chemical stability.

[0003] Polymers of intrinsic microporosity (PIMs) are a type of organic microporous polymer. They are a special type of polymer that obtains micropores by relying on its own rigidity and the non-planar twisted structure of the molecule. The twisted structure of its molecular chain prevents chain stacking, which makes it have a higher free volume than general polymers. PIMs have a narrow pore size distribution and do not have the pore collapse problem when the pore template is removed from inorganic porous materials. They have been widely used in the field of membrane separation. However, the micropore size of PIMs is 1-2nm, the molecular sieving performance is poor, and the permeability to non-polar solvents is weak, which limits its application in organic solvent nanofiltration.

[0004] Therefore, the present invention is based on the microporous structure of PIMs, and by introducing 4-trifluoromethylbenzoyl chloride to adjust its structure, the retention rate of the composite membrane for three dyes, chrome black T, Coomassie brilliant blue R25 and Bengal rose red, is improved. At the same time, the introduction of 4-trifluoromethylbenzoyl chloride increases the fluorine-containing groups of the selective layer, and improves the permeability of the composite membrane to non-polar solvents. The present invention is conducive to the further development of PIMs membranes in solvent-resistant nanofiltration membranes and the application prospects in polar solvents and non-polar solvents. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a self-microporous polymer nanofiltration membrane.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0007] The present invention provides a method for preparing a self-microporous polymer nanofiltration membrane, the preparation method comprising:

[0008] (1) Preparing a PIMs base film by a phase inversion method: P84 powder and N,N-dimethylformamide (DMF) are mixed and stirred for 2 to 10 hours. After the mixture is completely dissolved, it is placed in a vacuum drying oven and vacuumed for 4 to 18 hours to remove bubbles to obtain a casting solution; a scraper with a thickness of 150 to 250 μm is selected to scrape the casting solution onto a non-woven fabric to form a film; the prepared film is placed in deionized water and phase inverted at 20 to 30° C. to obtain a formed base film; wherein, based on the total mass of P84 powder and N,N-dimethylformamide as 100%, the mass percentages of P84 powder and N,N-dimethylformamide are 12% to 22% and 78% to 88%, respectively;

[0009] (2) preparing an aqueous phase: dissolving 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI) in an alkaline aqueous solution to prepare an aqueous phase, wherein the mass ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to water is 0.5-2.0:100, the base in the alkaline aqueous solution is NaOH, KOH or ammonia, and the initial molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to the base is 1:3-6;

[0010] Prepare the oil phase: dissolve trimesoyl chloride (TMC) and 4-trifluoromethylbenzoyl chloride in n-hexane to prepare the oil phase, wherein the mass volume ratio of trimesoyl chloride to n-hexane is 0.02-0.08 g:100 mL, and the volume ratio of 4-trifluoromethylbenzoyl chloride to n-hexane is 0.05-0.4:100;

[0011] First, the bottom membrane is naturally dried and then fixed on the frame of the interfacial polymerization, and then the water phase is poured on the front side of the membrane, and the water phase on the membrane surface is poured out after 1 to 5 minutes, and it is naturally air-dried in the air until there is no water stain; then the oil phase is poured on the front side of the membrane, and the oil phase on the membrane surface is poured out after 1 to 5 minutes, and after it is naturally air-dried, the membrane after the interfacial polymerization is placed in a vacuum drying oven at 50 to 100° C. and dried for 5 to 15 minutes to obtain a PIMs-F nanofiltration membrane;

[0012] (3) Immersing the prepared PIMs-F nanofiltration membrane in a 12-25 g / L hexamethylenediamine isopropanol solution at room temperature for 12-36 h to crosslink the composite membrane. After the crosslinking is completed, the membrane is repeatedly washed with deionized water to remove excess solvent on the membrane surface to obtain the self-microporous polymer nanofiltration membrane, and then the self-microporous polymer nanofiltration membrane is stored in deionized water for further use.

[0013] Furthermore, in step (1), the mass percentages of P84 and dimethylformamide (DMF) are 16% to 22% and 78% to 84%, respectively, and more preferably 16% to 20% and 80% to 84%, respectively.

[0014] Furthermore, in step (1), the mechanical stirring time is 4 to 8 hours; and the time for vacuuming and degassing the mixed casting liquid is 6 to 12 hours.

[0015] Furthermore, in step (1), the thickness of the scraper is 200 μm-250 μm, more preferably 200 μm.

[0016] Furthermore, in step (2), the mass ratio of TTSBI to water is 0.5-1.5:100, more preferably 1.0:100.

[0017] Furthermore, in step (2), in the oil phase, the mass volume ratio of TMC to n-hexane is 0.04-0.06 g:100 mL, more preferably 0.05 g:100 mL; the volume ratio of 4-trifluoromethylbenzoyl chloride to n-hexane is 0.05-0.2:100, more preferably 0.05-0.15:100, and most preferably 0.10:100.

[0018] Furthermore, in step (2), the contact time between the aqueous phase and the front surface of the base film is 1 to 3 minutes, more preferably 2 minutes.

[0019] Furthermore, in step (2), the front contact time between the oil phase and the membrane is 1 to 3 minutes, more preferably 2 minutes.

[0020] Furthermore, in step (2), the film after the interfacial polymerization is placed in a vacuum drying oven and dried at 50-80° C., more preferably at 50° C., for 6-10 min, more preferably 10 min.

[0021] Furthermore, in step (3), the PIMs-F nanofiltration membrane is immersed in a hexamethylenediamine isopropanol solution with a concentration of 16 to 22 g / L, more preferably 20 g / L, for 18 to 36 hours, more preferably 24 hours, to cross-link the composite membrane.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) The preparation process of the present invention is simple, easy to operate, low in toxicity and environmentally friendly, and convenient for industrial application.

[0024] (2) Compared with the original PIMs membrane without 4-trifluoromethylbenzoyl chloride, the self-microporous polymer nanofiltration membrane prepared by the present invention has the above-mentioned retention rate for three negatively charged dyes with different molecular weights, namely, chrome black T (ET, Mw=461.4), Coomassie brilliant blue R25 (CBR, Mw=825.9) and Bengal rose red (RB, Mw=1017.6). Moreover, when the content of 4-trifluoromethylbenzoyl chloride is 0.10%, the performance of the membrane is more suitable.

[0025] (3) The self-microporous polymer nanofiltration membrane prepared by the present invention, among which the optimal PIMs-F membrane (fluorinated chloride content of 0.10%) prepared in the example, has a slightly lower permeability coefficient for three different dyes than the original PIMs membrane, but the retention rates of different dyes all show a significant upward trend, showing a strong dye retention rate. In addition, the separation performance of the PIMs-F nanofiltration composite membrane is related to the molecular weight of the dye, and the retention rate shows a significant increase with the increase of the molecular weight.

[0026] (4) For the self-microporous polymer nanofiltration membrane prepared by the present invention, for three different types of solvents (polar ethanol, non-polar n-hexane, and polar non-protonic solvent dimethylformamide DMF), as the concentration of fluoroacyl chloride increases, the permeability coefficients of ethanol and dimethylformamide DMF show a decreasing trend with the increase of fluoroacyl chloride concentration, while the permeability coefficient of non-polar solvent n-hexane shows a trend of first increasing and then decreasing.

[0027] (5) The self-microporous polymer nanofiltration membrane prepared by the present invention, among which the optimal PIMs-F membrane (fluorinated chloride content of 0.10%) prepared in the example, compared with the original PIMs membrane in different solvents (methanol, ethanol, acetone, dimethylformamide DMF, tetrahydrofuran THF, n-hexane, toluene), has higher permeability in non-polar solvents (n-hexane, toluene) than the original membrane, while its permeability in polar solvents (methanol, ethanol) and polar aprotic solvents (acetone, dimethylformamide DMF and tetrahydrofuran THF) is lower than the original membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1a , 1b 1c and 1c are the permeability coefficients and retention rates of the PIMs-F nanofiltration composite membranes with different 4-trifluoromethylbenzoyl chloride contents prepared in the examples of the present invention for three dye aqueous solutions;

[0029] Figure 2 The permeability coefficients of the optimal PIMs-F membrane (with a fluorinated chloride content of 0.10%) prepared in Example 1 of the present invention and the original PIMs membrane prepared in Example 2 to dyes of different molecular weights;

[0030] Figure 3The retention rates of the optimal PIMs-F membrane (with a fluorinated chloride content of 0.10%) prepared in Example 1 of the present invention and the original PIMs membrane prepared in Example 2 for dyes of different molecular weights;

[0031] Figure 4 The permeability coefficients of the PIMs-F nanofiltration composite membranes with different 4-trifluoromethylbenzoyl chloride contents prepared in the embodiments of the present invention in different organic solvents;

[0032] Figure 5 The permeability coefficients of the PIMs-F optimal membrane with 4-trifluoromethylbenzoyl chloride content (fluorinated chloride content of 0.10%) prepared in Example 1 of the present invention and the original PIMs membrane prepared in Example 2 in different organic solvents.

[0033] Figure 6 The organic solvent permeability coefficients of the films prepared in Example 1 and Comparative Example 1 of the present invention under the conditions of cross-linking of the front and rear base films.

[0034] Figure 7 The SEM images (scale 100 nm) of Example 1 and Comparative Example 2 of the present invention using different fluorine-containing monomers are shown below: left: Example 1; right: Comparative Example 2. DETAILED DESCRIPTION

[0035] The content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples. The following examples describe in more detail a method for preparing a self-microporous polymer nanofiltration membrane in the present invention, and these examples are provided by way of illustration, but these examples do not limit the scope of the present invention. Unless otherwise specified, the experimental method adopted in the present invention is a conventional method, and the experimental equipment, materials, reagents, etc. used can be purchased from chemical companies.

[0036] The PI (Lenzing P84) used in the examples of the present invention was purchased from HP polymer GMbH in Austria.

[0037] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0038] Embodiment 1:

[0039] (1) Preparation of fluorine-containing self-porous nanofiltration membrane: At room temperature, weigh 18g P84 powder and 82g dimethylformamide DMF into a 150mL round-bottom flask, mix and stir for 5h, and after complete dissolution, place it in a vacuum drying oven and vacuum remove bubbles for 6 hours to obtain a casting solution. Select a scraper with a thickness of 200μm to scrape the casting solution onto the non-woven fabric to form a film. The prepared film is placed in deionized water and phase-inverted at 25°C to obtain a formed base film. The prepared base film is replaced with deionized water twice for the purpose of cleaning, and then stored in deionized water, waiting for the next step.

[0040] After that, weigh 0.47g of sodium hydroxide and dissolve it in 100mL of deionized water, sonicate for several minutes to fully dissolve it to obtain an alkaline solution. Then dissolve 1g of TTSBI in a dilute sodium hydroxide solution, where the molar ratio of TTSBI:NaOH is 1:4, sonicate for 2h to ensure that it is completely dissolved, and prepare a 1wt% TTSBI aqueous phase. Then weigh 0.05g of TMC, use a pipette to transfer 0.10mL of 4-trifluoromethylbenzoyl chloride and dissolve it in 100mL of n-hexane, sonicate for 2h, and prepare a 0.10w / v% concentration of acyl chloride solution.

[0041] After the base film is naturally dried, it is fixed on the frame of the interfacial polymerization, and then the water phase is poured on the front of the membrane, the time is 2 minutes, the water phase on the surface of the membrane is poured out, and it is naturally air-dried in the air until there is no water stain. Then the oil phase is poured on the front of the membrane, the time is 2 minutes, the oil phase on the surface of the membrane is poured out, and it is left to air-dry naturally. The membrane after interfacial polymerization is then placed in a vacuum drying oven at 50°C and dried for 10 minutes to obtain a fluorine-containing self-microporous nanofiltration membrane. The prepared PIMs-F nanofiltration membrane is immersed in a 20g / L hexamethylenediamine isopropanol solution for 24 hours to crosslink the composite membrane. After the crosslinking is completed, it is repeatedly washed with deionized water to remove excess solvent on the membrane surface to obtain a nanofiltration membrane with excellent performance, which is named PIMs-0.10%F.

[0042] (2) Evaluation of nanofiltration membrane separation performance: The fluorine-containing microporous nanofiltration membrane prepared by the preparation method of the present invention was used as a filtration membrane and placed in a cross-flow filtration device, wherein the test area was 7.07 cm 2 The flux and retention rate of the prepared membrane were measured at 25°C and 0.4 MPa, and the solvent was 0.05 g / L dye aqueous solution. The permeability coefficient of PIMs-0.10% F to chrome black T solution was 92.8 L / (m 2 ·h·MPa), the retention rate of chrome black T was 92.5%; the permeability coefficient of PIMs-0.10%F to Coomassie brilliant blue R25 solution was 99.4L / (m 2·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 94.8%; the permeability coefficient of PIMs-0.10%F to Bengal Rose Red liquid was 100.5L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 97.4%.

[0043] Embodiment 2:

[0044] The 0.10 mL 4-trifluoromethylbenzoyl chloride in Example 1 was replaced with 0 mL 4-trifluoromethylbenzoyl chloride and named PIMs-0%F. The other steps remained unchanged to obtain a fluorine-containing self-microporous nanofiltration membrane. The separation performance of the nanofiltration membrane was tested using the performance testing method of Example 1. The results showed that the permeability coefficient of PIMs-0%F to the chrome black T liquid was 96.8 L / (m 2 ·h·MPa), the retention rate of chrome black T was 81.6%; the permeability coefficient of PIMs-0%F to Coomassie brilliant blue R25 solution was 101.7L / (m 2 ·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 83.8%; the permeability coefficient of PIMs-0%F to Bengal Rose Red liquid was 108.8L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 85.4%.

[0045] Embodiment 3:

[0046] The 0.10 mL 4-trifluoromethylbenzoyl chloride in Example 1 was replaced with 0.05 mL 4-trifluoromethylbenzoyl chloride and named PIMs-0.05% F. The other steps remained unchanged to obtain a fluorine-containing self-microporous nanofiltration membrane. The separation performance of the nanofiltration membrane was tested using the performance test method of Example 1. The results showed that the permeability coefficient of PIMs-0.05% F to the chrome black T liquid was 92.6 L / (m 2 ·h·MPa), the retention rate of chrome black T was 83.8%; the permeability coefficient of PIMs-0.05%F to Coomassie brilliant blue R25 solution was 97.8L / (m 2 ·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 88.5%; the permeability coefficient of PIMs-0.05%F to Bengal Rose Red liquid was 103.7L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 89.6%.

[0047] Embodiment 4:

[0048] The 0.10 mL 4-trifluoromethylbenzoyl chloride in Example 1 was replaced with 0.15 mL 4-trifluoromethylbenzoyl chloride and named PIMs-0.15% F. The other steps remained unchanged to obtain a fluorine-containing self-microporous nanofiltration membrane. The separation performance of the nanofiltration membrane was tested using the performance test method of Example 1. The results showed that the permeability coefficient of PIMs-0.15% F to the chrome black T liquid was 88.7 L / (m 2 ·h·MPa), the retention rate of chrome black T was 91.6%; the permeability coefficient of PIMs-0.15%F to Coomassie brilliant blue R25 solution was 86.5L / (m 2 ·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 92.8%; the permeability coefficient of PIMs-0.15%F to Bengal Rose Red liquid was 87.6L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 97.1%.

[0049] Embodiment 5:

[0050] The 0.10 mL 4-trifluoromethylbenzoyl chloride in Example 1 was replaced with 0.20 mL 4-trifluoromethylbenzoyl chloride and named PIMs-0.20% F. The other steps remained unchanged to obtain a fluorine-containing self-microporous nanofiltration membrane. The separation performance of the nanofiltration membrane was tested using the performance test method of Example 1. The results showed that the permeability coefficient of PIMs-0.20% F to the chrome black T liquid was 85.6 L / (m 2 ·h·MPa), the retention rate of chrome black T was 91.8%; the permeability coefficient of PIMs-0.20%F to Coomassie brilliant blue R25 solution was 83.6L / (m 2 ·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 93.2%; the permeability coefficient of PIMs-0.20%F to Bengal Rose Red liquid was 85.5L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 97.9%.

[0051] Embodiment 6:

[0052] The PIMs-0.10%F and PIMs-0%F nanofiltration membranes prepared according to the methods of Example 1 and Example 2 were selected, and the permeability coefficients of the two nanofiltration membranes to dyes of different molecular weights were tested respectively using the performance testing method of Example 1. The initial feed liquid was set to be 50 ppm of chrome black T, Coomassie brilliant blue R25, and Bengal rose red aqueous solution, the test pressure was 0.4 MPa, cross-flow filtration, and the test area was 7.07 cm 2 The results show that the permeability coefficient of PIMs-0%F to chrome black T is about 96.8L / (m 2 ·h·MPa), and the permeability coefficient to Coomassie Brilliant Blue R25 is about 101.7L / (m 2·h·MPa), the permeability coefficient of Bengal rose is about 108.8L / (m 2 ·h·MPa); the permeability coefficient of PIMs-0.10%F to chrome black T is 92.8L / (m 2 ·h·MPa), and the permeability coefficient to Coomassie Brilliant Blue R25 is 99.4L / (m 2 ·h·MPa), the permeability coefficient of Bengal rose is 100.5L / (m 2 ·h·MPa). See the attached Figure 2 .

[0053] Embodiment 7:

[0054] The PIMs-0.10%F and PIMs-0%F nanofiltration membranes prepared according to the methods of Example 1 and Example 2 were selected, and the retention rates of the two nanofiltration membranes for dyes of different molecular weights were tested respectively using the performance test method of Example 1. The initial feed liquid was set to be 50 ppm of chrome black T, Coomassie brilliant blue R25, and Bengal rose red aqueous solution, the test pressure was 0.4 MPa, cross-flow filtration, and the test area was 7.07 cm 2 The results showed that the retention rate of nanofiltration membrane PIMs-0%F for chrome black T was about 81.6%, the retention rate for Coomassie brilliant blue R25 was about 83.8%, and the retention rate for Bengal rose was about 85.4%; the retention rate of nanofiltration membrane PIMs-0.10%F for chrome black T was about 92.5%, the retention rate for Coomassie brilliant blue R25 was about 94.8%, and the retention rate for Bengal rose was about 97.4%. See the attached Figure 3 .

[0055] Embodiment 8:

[0056] The PIMs-0.10%F nanofiltration membrane prepared according to the method of Example 1 was selected to test the permeability coefficient of the PIMs-0.10%F nanofiltration membrane to three different types of solvents (polar ethanol, non-polar n-hexane, and polar aprotic solvent dimethylformamide DMF). Among them, the test pressure was 0.4Mpa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07cm 2 The permeability coefficient of PIMs-0.10%F membrane to ethanol was measured to be about 33.8L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide DMF is about 105.8L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 102.5L / (m 2 ·h·MPa).

[0057] Embodiment 9:

[0058] The PIMs-0%F nanofiltration membrane prepared according to the method of Example 2 was selected to test the permeability coefficient of the PIMs-0%F nanofiltration membrane to three different types of solvents (polar ethanol, non-polar n-hexane, and polar aprotic solvent dimethylformamide DMF). The test pressure was 0.4 MPa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07 cm 2 The permeability coefficient of PIMs-0%F membrane to ethanol was measured to be about 38.6L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide DMF is about 111.3L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 85.8L / (m 2 ·h·MPa).

[0059] Embodiment 10:

[0060] The PIMs-0.05%F nanofiltration membrane prepared according to the method of Example 3 was selected to test the permeability coefficient of the PIMs-0.05%F nanofiltration membrane to three different types of solvents (polar ethanol, non-polar n-hexane, and polar aprotic solvent dimethylformamide DMF). Among them, the test pressure was 0.4Mpa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07cm 2 The permeability coefficient of PIMs-0.05%F membrane to ethanol was measured to be about 35.7 L / (m 2 ·h·MPa), and the permeability coefficient to DMF is about 107.2L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 95.3L / (m 2 ·h·MPa).

[0061] Embodiment 11:

[0062] The PIMs-0.15%F nanofiltration membrane prepared according to the method of Example 4 was selected to test the permeability coefficient of the PIMs-0.05%F nanofiltration membrane to three different types of solvents (polar ethanol, non-polar n-hexane, and polar aprotic solvent dimethylformamide DMF). Among them, the test pressure was 0.4Mpa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07cm 2 The permeability coefficient of PIMs-0.15%F membrane to ethanol was measured to be about 27.8L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide (DMF) is about 89.7L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 94.8L / (m 2 ·h·MPa).

[0063] Embodiment 12:

[0064] The PIMs-0.20%F nanofiltration membrane prepared according to the method of Example 5 was selected to test the permeability coefficient of the PIMs-0.05%F nanofiltration membrane to three different types of solvents (polar ethanol, non-polar n-hexane, and polar aprotic solvent dimethylformamide DMF). Among them, the test pressure was 0.4Mpa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07cm 2 The permeability coefficient of PIMs-0.20%F membrane to ethanol was measured to be about 24.9 L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide (DMF) is about 84.6L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 88.9L / (m 2 ·h·MPa).

[0065] Embodiment 13:

[0066] The PIMs-0.10%F and PIMs-0%F nanofiltration membranes prepared according to the methods of Example 1 and Example 2 were selected to test the permeability of these two nanofiltration membranes to 7 different solvents: polar solvents (methanol, ethanol), polar aprotic solvents (acetone, dimethylformamide DMF and tetrahydrofuran THF), and non-polar solvents (n-hexane, toluene). Among them, the test pressure was 0.4Mpa, the test temperature was 25°C, the cross-flow filtration was performed, and the test area was 7.07cm 2 The permeability coefficient of PIMs-0.10%F membrane to methanol was measured to be about 46.0L / (m 2 ·h·MPa), and the permeability coefficient to ethanol is about 33.8L / (m 2 ·h·MPa), and the permeability coefficient to acetone is about 72.8L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide DMF is about 105.8L / (m 2 ·h·MPa), and the permeability coefficient to tetrahydrofuran (THF) is about 38.6L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 102.5L / (m 2 ·h·MPa), and the permeability coefficient to toluene is about 42.6L / (m 2 ·h·MPa); The permeability coefficient of PIMs-0%F membrane to methanol was measured to be about 48.2L / (m 2 ·h·MPa), and the permeability coefficient to ethanol is about 38.6L / (m 2 ·h·MPa), and the permeability coefficient to acetone is about 72.8L / (m 2 ·h·MPa), the permeability coefficient of dimethylformamide DMF is about 111.3L / (m2 ·h·MPa), and the permeability coefficient to tetrahydrofuran (THF) is about 39.8L / (m 2 ·h·MPa), and the permeability coefficient to n-hexane is about 85.8L / (m 2 ·h·MPa), and the permeability coefficient to toluene is about 28.4L / (m 2 ·h·MPa). See the attached Figure 5 .

[0067] Comparative Example 1:

[0068] (1) Preparation of fluorine-containing self-porous nanofiltration membrane: At room temperature, weigh 18g P84 powder and 82g dimethylformamide DMF in a 150mL round-bottom flask, mix and stir for 5h, and after complete dissolution, place it in a vacuum drying oven and vacuum remove bubbles for 6 hours to obtain a casting solution. Select a scraper with a thickness of 200μm to scrape the casting solution onto a non-woven fabric to form a film. The prepared film is placed in deionized water and phase-inverted at 25°C to obtain a formed base film. The prepared base film is replaced with deionized water twice to achieve the purpose of cleaning, and then immersed in a 20g / L hexamethylenediamine isopropanol solution for 24h for cross-linking. After the cross-linking is completed, it is repeatedly washed with deionized water to remove excess solvent on the membrane surface and stored in deionized water, waiting for the next step.

[0069] After that, weigh 0.47g of sodium hydroxide and dissolve it in 100mL of deionized water, sonicate for several minutes to fully dissolve it to obtain an alkaline solution. Then dissolve 1g of TTSBI in a dilute sodium hydroxide solution, where the molar ratio of TTSBI:NaOH is 1:4, sonicate for 2h to ensure that it is completely dissolved, and prepare a 1wt% TTSBI aqueous phase. Then weigh 0.05g of TMC, use a pipette to transfer 0.10mL of 4-trifluoromethylbenzoyl chloride and dissolve it in 100mL of n-hexane, sonicate for 2h, and prepare a 0.10w / v% concentration of acyl chloride solution.

[0070] The cross-linked bottom membrane was naturally dried and fixed on the interfacial polymerization frame, and then the water phase was poured on the front of the membrane, and the time was 2 minutes. The water phase on the membrane surface was poured out and dried naturally in the air until there was no water stain. Then the oil phase was poured on the front of the membrane, and the time was 2 minutes. The oil phase on the membrane surface was poured out and waited for it to dry naturally. The membrane after interfacial polymerization was placed in a vacuum drying oven at 50°C for 10 minutes to obtain a fluorine-containing self-microporous nanofiltration membrane, which was recorded as PIMs-0.10% F-1.

[0071] (2) Evaluation of nanofiltration membrane separation performance: The fluorine-containing microporous nanofiltration membrane prepared by the preparation method of the present invention was used as a filtration membrane and placed in a cross-flow filtration device, wherein the test area was 7.07 cm 2The flux and rejection of the prepared membrane were measured at 25 °C and 0.4 MPa. The separation stability performance of pre-crosslinked PIMs-0.10% F-1 and post-crosslinked PIMs-0.10% F was compared. Figure 6 shown.

[0072] Compared with the pre-crosslinking method, the PIMs-0.10%F membrane showed better performance under long-term ethanol testing.

[0073] Comparative Example 2:

[0074] The 4-trifluoromethylbenzoyl chloride in Example 1 was replaced with perfluorooctanoyl chloride, and the other steps remained unchanged to obtain a defective fluorine-containing self-microporous nanofiltration membrane PIMs-SF. The performance test method of Example 1 was used to test the separation performance of the nanofiltration membrane. The results showed that the permeability coefficient of PPIMs-SF to the chrome black T liquid was 198.7 L / (m 2 ·h·MPa), the retention rate of chrome black T was 12.6%; the permeability coefficient of PIMs-SF to Coomassie brilliant blue R25 solution was 210.5L / (m 2 ·h·MPa), the retention rate of Coomassie Brilliant Blue R25 was 11.2%; the permeability coefficient of PIMs-SF to Bengal Rose Red liquid was 187.6L / (m 2 ·h·MPa), the retention rate of Bengal rose red was 5.1%. Figure 7 It was found that PIMs-SF had membrane defects, which might be due to the fact that the interface process did not react completely, resulting in the inability to form a good nanofiltration selectivity layer. At that time, the dye retention was greatly reduced and could not meet the normal organic solvent nanofiltration membrane separation requirements.

Claims

1. A method for preparing a self-contained microporous polymer nanofiltration membrane, characterized in that: The preparation method is: (1) Preparation of PIMs base film by phase inversion method: P84 powder and N,N-dimethylformamide were mixed and stirred for 2-10 h. After the mixture was completely dissolved, it was placed in a vacuum drying oven and vacuum-dried for 4-18 h to remove bubbles to obtain a casting solution; a scraper with a thickness of 150-250 μm was selected to scrape the casting solution onto a non-woven fabric to form a film; the prepared film was placed in deionized water and phase inverted at 20-30°C to obtain a formed base film; wherein, based on the total mass of P84 powder and N,N-dimethylformamide as 100%, the mass percentages of P84 powder and N,N-dimethylformamide were 12%-22% and 78%-88%, respectively; (2) preparing an aqueous phase: dissolving 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane in an alkaline aqueous solution to prepare an aqueous phase, wherein the mass ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to water is 0.5-2.0:100, the base in the alkaline aqueous solution is NaOH, KOH or ammonia, and the initial molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to the base is 1:3-6; Prepare the oil phase: dissolve trimesoyl chloride and 4-trifluoromethylbenzoyl chloride in n-hexane to prepare the oil phase, wherein the mass volume ratio of trimesoyl chloride to n-hexane is 0.02-0.08 g:100 mL, and the volume ratio of 4-trifluoromethylbenzoyl chloride to n-hexane is 0.05-0.15:100; First, the bottom membrane is naturally dried and then fixed on the frame of the interfacial polymerization. Then, the water phase is poured on the front of the membrane. After 1 to 5 minutes, the water phase on the membrane surface is poured out and dried naturally in the air until there is no water stain. Then, the oil phase is poured on the front of the membrane. After 1 to 5 minutes, the oil phase on the membrane surface is poured out. After it is naturally dried, the membrane after interfacial polymerization is placed in a vacuum drying oven at 50 to 100 ° C for 5 to 15 minutes to obtain a PIMs-F nanofiltration membrane. (3) The prepared PIMs-F nanofiltration membrane is immersed in a 12-25 g / L hexamethylenediamine isopropanol solution at room temperature for 12-36 h to cross-link the composite membrane. After the cross-linking is completed, the membrane is repeatedly washed with deionized water to remove excess solvent on the membrane surface, thereby obtaining the self-microporous polymer nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass percentages of the P84 powder and N,N-dimethylformamide are 16%-22% and 78%-84%, respectively.

3. The preparation method according to claim 2, characterized in that: In step (1), the mass percentages of the P84 powder and N,N-dimethylformamide are 16%-20% and 80%-84%, respectively.

4. The preparation method according to claim 1, characterized in that: In step (1), the mixing and stirring time is 4 to 8 hours; and the vacuum degassing time is 6 to 12 hours.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to water is 0.5-1.5:

100.

6. The preparation method according to claim 1, characterized in that: In step (2), in the oil phase, the mass volume ratio of trimesoyl chloride to n-hexane is 0.04-0.06 g:100 mL.

7. The preparation method according to claim 6, characterized in that: In step (2), in the oil phase, the mass volume ratio of trimesoyl chloride to n-hexane is 0.05 g:100 mL.

8. The preparation method according to claim 6, characterized in that: In step (2), the volume ratio of 4-trifluoromethylbenzoyl chloride to n-hexane is 0.10:

100.

9. The preparation method according to claim 1, characterized in that: In step (2), the water phase is in contact with the bottom membrane for 1 to 3 minutes; the oil phase is in contact with the membrane for 1 to 3 minutes.

10. The preparation method according to claim 9, characterized in that: In step (2), the contact time between the aqueous phase and the front surface of the base film is 2 minutes.

11. The preparation method according to claim 9, characterized in that: In step (2), the front contact time between the oil phase and the membrane is 2 min.

12. The preparation method according to claim 1, characterized in that: In step (2), the film after interfacial polymerization is placed in a vacuum drying oven at 50-80° C. for 6-10 min.

13. The preparation method according to claim 1, characterized in that: In step (3), the PIMs-F nanofiltration membrane is immersed in a hexamethylenediamine isopropanol solution with a concentration of 16-22 g / L for 18-36 h to perform composite membrane cross-linking.

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