A fluorinated polyamide thin layer composite organic nanofiltration membrane and a preparation method thereof

Abstract

The application discloses a preparation method of a fluorinated polyamide thin-layer composite organic nanofiltration membrane, and comprises the following steps: an ion liquid solution containing fluorinated polyamine monomers and an alkane solution of polyacyl chloride monomers are subjected to polycondensation reaction on a free interface to form a fluorinated polyamide nanofilm; and then the fluorinated polyamide nanofilm is combined with a porous base membrane through a transfer printing method to obtain the fluorinated polyamide thin-layer composite organic nanofiltration membrane. The preparation method can widen the use range of the fluorinated polyamine monomers, so that a series of fluorinated polyamide nanofilms with customized structure and performance can be designed, and the fluorinated polyamide thin-layer composite organic nanofiltration membrane prepared has excellent separation performance in a non-polar solvent system.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a fluorinated polyamide thin-layer composite organic nanofiltration membrane and its preparation method. Background Technology

[0002] Organic nanofiltration is a novel membrane separation technology characterized by low energy consumption, simple operation, and high integration, showing great application potential in material purification, drug concentration, and solvent recovery. The core component of organic nanofiltration is the organic nanofiltration membrane, and polyamide thin-layer composite organic nanofiltration membranes have become a research hotspot in this field due to their ease of preparation and excellent selectivity. These membranes are typically aromatic polyamide thin-layer composite organic nanofiltration membranes prepared by interfacial polymerization, with the polyamide nanofilm playing a crucial role in separation. The structure of the polyamide nanofilm is critical to the performance of the composite membrane. Traditional polyamide nanofilms contain many polar groups, limiting their application to polar solvent systems. Their application in non-polar solvent systems has been a significant challenge. Introducing fluorinated groups into polyamide nanofilms can increase the affinity of the polyamide crosslinking network for non-polar solvents; therefore, the preparation of fluorinated polyamide nanofilms holds promise for advancing the application of polyamide thin-layer composite organic nanofiltration membranes in non-polar solvent systems.

[0003] For example, Chinese patent document CN111420566B discloses a method for preparing a solvent-resistant polyamide nanofiltration membrane containing fluorinated organic nanoparticles. Using polyamines, dopamine, and fluoroalkyl thiols as reactive monomers, fluorinated organic nanoparticles are formed through Michael addition and Schiff base reactions. These nanoparticles are then reacted with polyacrylamide chlorides via interfacial polymerization to form a polyamide nanofilm containing fluorinated organic nanoparticles on the surface of a porous support membrane. While introducing fluorinated organic nanoparticles is effective, this method is complex and involves cumbersome steps, and it cannot effectively regulate the chemical structure of the polyamide nanofilm.

[0004] Chinese patent document CN109351190B discloses a method for preparing fluorinated polyamide nanofiltration membranes. By adding a fluorinated monomer to an aqueous monomer solution for interfacial polymerization, the solvent flux and solvent resistance of the membrane are significantly improved. The fluorinated monomer, possessing the hydrophobic functional group -CF3, allows for greater diffusion of the aqueous active monomer into the organic phase. The accumulation of the aqueous active monomer mixture at the interface increases the specific surface area of ​​the polyamide membrane, thereby effectively improving the membrane flux. Simultaneously, the high bond energy of the CF bond ensures a stable fluoropolymer backbone, effectively enhancing the membrane's solvent resistance. However, the poor solubility of water as a solvent significantly limits the range of applicable concentrations and types of fluorinated monomers, severely hindering the interfacial synthesis and molecular design of fluorinated polyamide membrane materials. Summary of the Invention

[0005] This invention provides a fluorinated polyamide thin-layer composite organic nanofiltration membrane and its preparation method. The fluorinated polyamide thin-layer composite organic nanofiltration membrane exhibits excellent separation performance in non-polar solvent systems.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a fluorinated polyamide thin-layer composite organic nanofiltration membrane includes:

[0008] An ionic liquid solution containing fluorinated polyamine monomers and an alkane solution containing polyacrylamide monomers undergo a polycondensation reaction at a free interface to form a fluorinated polyamide nanofilm. The fluorinated polyamide nanofilm is then composited with a porous base membrane using a transfer composite method to obtain a fluorinated polyamide thin-layer composite organic nanofiltration membrane.

[0009] Ionic liquids are green, environmentally friendly solvents with strong dissolving power, capable of forming two immiscible phases with alkanes. Using ionic liquids to dissolve fluorinated polyamine monomers can significantly broaden the selection range of fluorinated polyamine monomers, facilitating the regulation and optimization of the molecular structure of polyamide nanofilms. The high viscosity of ionic liquids enhances the stability of the interface formed with alkane solutions and regulates the diffusion rate of fluorinated polyamines, improving the stability and controllability of the interfacial polymerization reaction. This lays the foundation for improving the separation performance of polyamide nanofilms in non-polar solvent systems.

[0010] Preferably, the ionic liquid is at least one of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0011] Preferably, the fluorinated polyamine monomer is at least one selected from 2,2'-bis(trifluoromethyl)benzidine, 2,2'-bis(4-aminophenyl)hexafluoropropane, 5'-(4-amino-3,5-difluorophenyl)-3,3”,5,5”-tetrafluoro-[1,1':3',1”-terphenyl]-4,4”-diamine, 2,2'-difluoro-4,4'-diaminobiphenyl, 4,4'-diaminooctafluorobiphenyl, 3,3'-bistrifluoromethyl-4,4-benzidinediamine, 5-(trifluoromethyl)-1,3-phenylenediamine, and 4,4'-(hexafluoroisopropyl)bis(p-phenoxy)diphenylamine.

[0012] The concentration of fluorinated polyamine monomers is one of the key factors affecting the structure of fluorinated polyamide nanofilms. When the monomer concentration is too low, the prepared fluorinated polyamide film is relatively porous; when the monomer concentration is moderate, diffusion and reaction are well matched, and the prepared fluorinated polyamide nanofilm has excellent separation performance; however, when the monomer concentration is too high, the diffusion depth of the monomer at the interface increases, resulting in a larger thickness of the prepared fluorinated polyamide nanofilm, which leads to lower solvent permeability.

[0013] Preferably, in the ionic liquid solution of the fluorinated polyamine monomer, the concentration of the fluorinated polyamine monomer is 0.01–100 g / L.

[0014] More preferably, in the ionic liquid solution of the fluorinated polyamine monomer, the concentration of the fluorinated polyamine monomer is 5–50 g / L.

[0015] Preferably, the polyacrylamide chloride monomer is at least one selected from phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, and trimesoyl chloride.

[0016] Preferably, the alkane is at least one selected from n-hexane, cyclohexane, trifluorotrichloroethane, isoalkanes, cyclohexane, and heptane.

[0017] The concentration of polyacrylamide monomers is also one of the key factors affecting fluorinated polyamide nanofilms. Neither excessively high nor excessively low concentrations of polyacrylamide monomers can form fluorinated polyamide nanofilms with excellent permeation selectivity.

[0018] Preferably, in the alkane solution of the polyacryl chloride monomer, the concentration of the polyacryl chloride monomer is 0.05–10 g / L.

[0019] More preferably, the polyacrylamide chloride monomer is pyromellitic trimethylolpropionate chloride; the alkane is an isoparaffin; and the concentration of the polyacrylamide chloride monomer in the alkane solution is 0.5–5 g / L.

[0020] A short reaction time is insufficient to form a dense fluorinated polyamide nanofilm; an excessively long reaction time leads to decreased film formation efficiency and reduced film permeability.

[0021] Preferably, the time for the polycondensation reaction to occur at the free interface is 10 to 1000 s.

[0022] Further preferably, the time for the polycondensation reaction to occur at the free interface is 30–600 s.

[0023] The porous base membrane is one of the following: nylon 66 microfiltration membrane, polytetrafluoroethylene microfiltration membrane, polyimide ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, polyetheretherketone ultrafiltration membrane, and polybenzimidazole ultrafiltration membrane.

[0024] Preferably, the preparation method of the fluorinated polyamide thin-layer composite organic nanofiltration membrane further includes: immersing the fluorinated polyamide thin-layer composite membrane in an organic solvent for activation treatment.

[0025] Organic solvents have the following functions: dissolving oligomers in fluorinated polyamides, increasing free volume; swelling pore size and increasing pore connectivity; and exposing fluorinated groups in the pores. The synergistic effects of organic solvents can enhance the permeation flux of fluorinated polyamide thin-film composite membranes to non-polar solvents.

[0026] Preferably, the organic solvent is at least one selected from methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, acetone, butanone, cyclobutanone, pentanone, cyclopentanone, hexanone, and cyclohexanone.

[0027] Preferably, a method for preparing a fluorinated polyamide thin-layer composite organic nanofiltration membrane includes:

[0028] (1) A fluorine-containing polyamine monomer ionic liquid solution is coated onto the substrate surface to form a fluorine-containing polyamine solution liquid film;

[0029] (2) The substrate carrying the liquid film of fluorinated polyamine solution is placed in the alkane solution of polyacrylamide monomer. The fluorinated polyamine and polyacrylamide undergo a polycondensation reaction at the interface of ionic liquid and alkane to generate fluorinated polyamide nanofilm.

[0030] (3) Cover the porous base film on the surface of the fluorinated polyamide nanofilm to make it composite with the fluorinated polyamide nanofilm. Immerse the substrate in constant temperature water and the fluorinated polyamide thin film composite film is separated from the substrate.

[0031] (4) The fluorinated polyamide thin-film composite film is immersed in an organic solvent for activation treatment to obtain the final product.

[0032] In step (1), if the liquid film of the fluorinated polyamine solution is too thin, the total amount of fluorinated polyamine monomers will be insufficient, which will easily cause damage and defects to the fluorinated polyamide nanofilm; if the liquid film of the fluorinated polyamine solution is too thick, the liquid film will easily flow, causing interface disturbance and interface inhomogeneity.

[0033] Preferably, in step (1), the thickness of the liquid film of the fluorinated polyamine solution is 10 to 1000 μm.

[0034] More preferably, in step (1), the thickness of the liquid film of the fluorinated polyamine solution is 50-200 μm.

[0035] The present invention also provides a fluorinated polyamide thin-layer composite organic nanofiltration membrane prepared by the above preparation method.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) This invention develops a method for constructing fluorinated polyamide thin-layer composite organic nanofiltration membranes; by utilizing ionic liquids, the application range of fluorinated polyamine monomers can be broadened, thereby designing a series of fluorinated polyamide nanofilms with customized structure and performance;

[0038] (2) High-viscosity ionic liquids are beneficial for controlling the monomer diffusion rate and providing a stable reaction interface, thereby improving the controllability and stability of the interfacial polymerization reaction, which is conducive to generating a fluorinated polyamide thin-layer composite organic nanofiltration membrane with controllable and uniform structure.

[0039] (3) By treating fluorinated polyamide thin-layer composite organic nanofiltration membranes with different organic solvents, the permeation flux of fluorinated polyamide thin-layer composite organic nanofiltration membranes to different types of non-polar solvents can be effectively improved, and organic nanofiltration membranes suitable for different non-polar solvent systems can be developed, which greatly expands the application field of polyamide thin-layer composite organic nanofiltration membranes.

[0040] This invention, based on ionic liquid-mediated interfacial polymerization, overcomes the bottleneck in the preparation of polyamide nanofilms with special separation properties, pioneers multi-level cutting-edge separation application research, and is the first in the world to achieve a breakthrough in the preparation and application of special functional polyamide nanofilms. Attached Figure Description

[0041] Figure 1 The image shows a scanning electron microscope (SEM) image of the fluorinated polyamide thin-film composite film prepared in Example 1. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0043] The preparation method of the fluorinated polyamide thin-layer composite organic nanofiltration membrane of the present invention includes: firstly, coating a substrate surface with an ionic liquid solution of fluorinated polyamine monomers of a certain thickness using a doctor blade, and then immersing it in an alkane solution containing polyacrylamide chlorides for a certain period of time. The fluorinated polyamide nanofilm generated at the free interface is then composited with a porous base membrane, and then immersed in constant temperature water, where the fluorinated polyamide thin-layer composite organic nanofiltration membrane automatically floats on the water surface. The fluorinated polyamide thin-layer composite organic nanofiltration membrane is then removed, dried, treated with an organic solvent, and its separation performance is tested.

[0044] In this embodiment, rejection rate and permeation flux are two important parameters for evaluating organic nanofiltration membranes. The rejection rate is defined as:

[0045]

[0046] Among them, C f Indicates the concentration of solute in the feed solution before treatment; C pThis indicates the concentration of the solute in the filtrate after treatment.

[0047] Permeation flux is defined as the volume of organic solvent that permeates through a unit membrane area per unit time under a given operating pressure; its unit is L / m². 2 The formula for h·bar is:

[0048]

[0049] Where V represents the volume of filtrate passing through the organic nanofiltration membrane, in L; and A represents the effective membrane area, in m². 2 t represents time, in hours (h); P represents the pressure used in the test, in bar.

[0050] Example 1

[0051] 2,2'-bis(trifluoromethyl)benzidine was selected as the polyamine monomer. It was dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate, and the concentration of 2,2'-bis(trifluoromethyl)benzidine was 15 g / L. Tristyrene chloride was selected as the polyacrylamide monomer. It was dissolved in isoalkanes, and the concentration of tristyrene chloride was 0.5 g / L.

[0052] A 100 μm thick 2,2'-bis(trifluoromethyl)benzidine ionic liquid solution film was coated onto a wide substrate using a doctor blade in a container containing the solution. The substrate was then immersed in an isoalkane solution containing trimesoyl chloride. Contact between the 2,2'-bis(trifluoromethyl)benzidine ionic liquid solution film and the trimesoyl chloride solution triggered interfacial polymerization. After 180 s of reaction, the resulting fluorinated polyamide nanofilm was composited with a nylon 66 porous base membrane. Subsequently, the polyamide thin-layer composite organic nanofiltration membrane and the substrate were placed in warm water, resulting in separation. The fluorinated polyamide thin-layer composite organic nanofiltration membrane was treated with acetone for 10 min, and its separation performance in a non-polar solvent system was then tested. The organic nanofiltration test results are shown in Table 1.

[0053] The scanning electron microscope image of the polyamide thin-layer composite organic nanofiltration membrane prepared in Example 1 is shown below. Figure 1 As shown.

[0054] Examples 2-4

[0055] The thicknesses of the polyamine ionic liquid solution film uniformly coated on the substrate were adjusted to 50 μm, 150 μm, and 200 μm, respectively, with the other conditions being the same as in Example 1.

[0056] Test Example 1

[0057] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 1-4 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 1.

[0058] Table 1. Dye rejection rate and n-hexane permeation flux of polyamide thin-film composite organic nanofiltration membranes prepared in Examples 1-4

[0059]

[0060] Examples 5-11

[0061] The polyamine monomers were adjusted to be 2,2'-bis(4-aminophenyl)hexafluoropropane, 5'-(4-amino-3,5-difluorophenyl)-3,3”,5,5”-tetrafluoro-[1,1':3',1”-terphenyl]-4,4”-diamine, 2,2'-difluoro-4,4'-diaminobiphenyl, 4,4'-diaminooctafluorobiphenyl, 3,3'-bistrifluoromethyl-4,4-biphenyldiamine, 5-(trifluoromethyl)-1,3-phenylenediamine, and 4,4'-(hexafluoroisopropyl)bis(p-phenoxy)diphenylamine, with the remaining conditions the same as in Example 1.

[0062] Comparative Example 1

[0063] The polyamine monomer was adjusted to 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, and the other conditions were the same as in Example 1.

[0064] Test Example 2

[0065] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 5-11 and Comparative Example 1 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent Yellow 98 n-hexane solution were tested at 25°C and 6 bar. The results are shown in Table 2.

[0066] Table 2. Dye rejection rate and n-hexane permeation flux of the polyamide thin-film composite organic nanofiltration membranes prepared in Examples 5-11 and Comparative Example 1.

[0067]

[0068] Examples 12-16

[0069] The ionic liquids were adjusted to be 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and the other conditions were the same as in Example 1.

[0070] Test Example 3

[0071] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 12-16 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 3.

[0072] Table 3. Dye rejection rate and n-hexane permeation flux of the polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 12-16

[0073]

[0074] Examples 17-20

[0075] The concentrations of the fluorinated polyamine monomers were adjusted to 5 g / L, 10 g / L, 30 g / L, and 50 g / L, respectively, with the other conditions being the same as in Example 1.

[0076] Test Example 4

[0077] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 17-20 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 4.

[0078] Table 4. Dye rejection rate and n-hexane permeation flux of the polyamide thin-film composite films prepared in Examples 17-20

[0079]

[0080] Examples 21-24

[0081] The interfacial polymerization reaction time was adjusted to 30s, 120s, 360s, and 600s, with the other conditions being the same as in Example 1.

[0082] Test Example 5

[0083] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 21-24 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., Yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 5.

[0084] Table 5. Dye rejection rate and n-hexane permeation flux of the polyamide thin-film composite films prepared in Examples 21-24

[0085]

[0086] Examples 25-29

[0087] The porous base membranes were adjusted to be polyimide porous membrane, polytetrafluoroethylene porous membrane, polyacrylonitrile porous membrane, polyetheretherketone porous membrane, and polybenzimidazole porous membrane, respectively, with the other conditions being the same as in Example 1.

[0088] Test Example 6

[0089] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 25-29 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 6.

[0090] Table 6. Dye rejection rate and n-hexane permeation flux of the polyamide thin-film composite films prepared in Examples 25-29

[0091]

[0092] Examples 30-40

[0093] The organic solvents used for the treatment were methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, butanone, cyclobutanone, pentanone, cyclopentanone, hexanone, and cyclohexanone, with the remaining conditions the same as in Example 1.

[0094] Test Example 7

[0095] The polyamide thin-layer composite organic nanofiltration membranes prepared in Examples 30-40 were tested for their rejection rate and n-hexane flux. The test method was as follows: the prepared organic nanofiltration membranes were placed in a standard organic nanofiltration testing apparatus, and the rejection rate and n-hexane flux of the organic nanofiltration membranes for a 50 ppm solvent (e.g., yellow 98) hexane solution were tested at 25°C and 6 bar. The results are shown in Table 7.

[0096] Table 7. Dye rejection rate and n-hexane permeation flux of the polyamide thin-film composite films prepared in Examples 30-40

[0097]

[0098] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluorinated polyamide thin-layer composite organic nanofiltration membrane, characterized in that, include: A condensation reaction occurs at the free interface between an ionic liquid solution containing fluorinated polyamine monomers and an alkane solution containing polyacrylamide chloride monomers to form a fluorinated polyamide nanofilm. The fluorinated polyamide nanofilm is then composited with a porous base membrane using a transfer composite method to obtain a fluorinated polyamide thin-layer composite organic nanofiltration membrane. The fluorinated polyamide thin-layer composite organic nanofiltration membrane is then activated by immersing it in an organic solvent. The organic solvent is at least one selected from acetone, butanone, cyclobutanone, pentanone, cyclopentanone, hexanone, and cyclohexanone. The fluorinated polyamine monomer is at least one of 2,2'-bis(trifluoromethyl)benzidine, 2,2'-bis(4-aminophenyl)hexafluoropropane, 5'-(4-amino-3,5-difluorophenyl)-3,3'',5,5''-tetrafluoro-[1,1':3',1''-terphenyl]-4,4''-diamine, 2,2'-difluoro-4,4'-diaminobiphenyl, 4,4'-diaminooctafluorobiphenyl, 3,3'-bistrifluoromethyl-4,4-benzidinediamine, 5-(trifluoromethyl)-1,3-phenylenediamine, and 4,4'-(hexafluoroisopropyl)bis(p-phenoxy)diphenylamine.

2. The method for preparing the fluorinated polyamide thin-layer composite organic nanofiltration membrane according to claim 1, characterized in that, The ionic liquid is at least one of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

3. The method for preparing the fluorinated polyamide thin-layer composite organic nanofiltration membrane according to claim 1, characterized in that, In the ionic liquid solution of fluorinated polyamine monomers, the concentration of the fluorinated polyamine monomers is 0.01~100 g / L.

4. The method for preparing the fluorinated polyamide thin-layer composite organic nanofiltration membrane according to claim 1, characterized in that, The polyacryl chloride monomer is at least one of phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, and trimesoyl chloride; the alkane is at least one of n-hexane, cyclohexane, trifluorotrichloroethane, isoalkanes, cyclohexane, and heptane.

5. The method for preparing the fluorinated polyamide thin-layer composite organic nanofiltration membrane according to claim 1, characterized in that, In the alkane solution of polyacryl chloride monomer, the concentration of polyacryl chloride monomer is 0.05~10 g / L.

6. The method for preparing the fluorinated polyamide thin-layer composite organic nanofiltration membrane according to claim 1, characterized in that, The time for condensation reaction to occur at the free interface is 10~1000 s.

7. A fluorinated polyamide thin-layer composite organic nanofiltration membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

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