A composite layer polyether ether ketone organic solvent nanofiltration membrane, a preparation method and application thereof

Abstract

The application provides a composite layer polyether ether ketone organic solvent nanofiltration membrane, the nanofiltration membrane comprising a support layer and a selective separation layer; the support layer is a sulfonated polyether ether ketone base film, and the selective separation layer is a polyamide film formed by interfacial polymerization of a piperazine monomer, PDA-ZIF-8 nanoparticles and an acyl chloride monomer on the support layer interface.The application coats and modifies ZIF-8 by using polydopamine (PDA), improves the dispersibility of ZIF-8 in water, and avoids the non-selective defects caused by uneven dispersion of nanoparticles; further, a sulfonated polyether ether ketone film base film is used as the support layer, and the ultrafine PDA-ZIF-8 nanoparticles are introduced into the polyamide selective separation layer by an interfacial polymerization process, so that the prepared organic solvent nanofiltration membrane has excellent solvent resistance and high temperature resistance and is widely used in industry.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a composite layer polyether ether ketone organic solvent nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation technology is a green separation technology that utilizes the sieving properties of membrane materials to separate and purify target components. Compared with traditional separation technologies, membrane separation technology has advantages such as high efficiency, low energy consumption, and simple operation. Organic solvent nanofiltration (OSN), as an emerging membrane separation technology, separates organic solutions from target components by applying a pressure gradient on the membrane feed side, achieving the concentration and recovery of target components. In recent years, it has been widely used in processes such as solvent-containing wastewater treatment, organic waste liquid recovery, and biochemical synthesis and purification. Currently, most organic solvent nanofiltration membranes are mainly made of polymers such as polyimide (PI) and polybenzimidazole (PBI). Through cross-linking post-treatment, these polymer membranes have good solvent resistance in most aprotic solvents, but their thermal stability and chemical stability under harsh operating conditions are weak, which greatly limits their widespread application.

[0003] Polyetheretherketone (PEEK), a semi-crystalline polymer with a linear aromatic backbone structure, has attracted widespread attention due to its excellent heat resistance, chemical resistance, and high mechanical strength. However, PEEK is only soluble in some strong protic acids at room temperature, and its excellent solvent resistance makes its membrane processing more difficult. Peeva et al. first dissolved PEEK powder in methanesulfonic acid (MSA) and SA solutions at room temperature and prepared membranes via phase inversion. The results showed that the PEEK membrane prepared by the one-step MSA / SA solution method did not require crosslinking and could effectively separate N,N-dimethylformamide (DMF) solvent at 80°C, achieving a 93% recovery rate for the Pd catalyst in long-term continuous Heck coupling reactions. Da Silva Burgal et al. first used the PEEK membrane prepared by this method for organic solvent nanofiltration, achieving nanofiltration performance through annealing at 20°C. After annealing, the permeate flux of the PEEK membrane for tetrahydrofuran (THF) increased from 28 L / (h·m³). 2 The concentration of 0.22 L / (h·m) decreased to 0.22 L / (h·m). 2 The molecular cutoff was increased to 400–600 g / mol. Furthermore, Da Silva Burgal controlled the membrane's permeability by altering the solvent type of the membrane pores before annealing, achieving a WMCO range of 295–1400 g / mol. The preparation method of directly processing PEEK into membranes by dissolving it in sulfonic acid solvent is simple and inexpensive. The resulting PEEK membranes are not only heat-resistant but also capable of membrane separation in strong acids, strong bases, and harsh organic solvents.

[0004] However, since acidic solutions are used as coating solutions to prepare membranes, it is difficult to adjust the permeation performance of PEEK membranes by adding additives such as pore-forming agents and volatile co-solvents to such highly corrosive and highly oxidizing coating solutions. Summary of the Invention

[0005] In view of this, the present invention provides a composite layer polyether ether ketone organic solvent nanofiltration membrane, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A composite layer polyetheretherketone organic solvent nanofiltration membrane, the nanofiltration membrane comprising a support layer and a selective separation layer; the support layer is a sulfonated polyetheretherketone-based membrane, and the selective separation layer is a polyamide film formed by polymerization of piperazine monomers, PDA-ZIF-8 nanoparticles, and acyl chloride monomers at the interface of the support layer.

[0008] The PDA-ZIF-8 nanoparticles were prepared by the following method:

[0009] S11. Prepare zinc nitrate hexahydrate-methanol solution and 2-methylimidazole-methanol solution, mix, stir, centrifuge, remove supernatant and wash with methanol, and vacuum dry to obtain ZIF-8 nanosheets.

[0010] S12. Disperse ZIF-8 nanosheets in methanol, add Tris buffer and dopamine hydrochloride, stir, centrifuge, remove the supernatant and wash with methanol, and vacuum dry to obtain PDA-ZIF-8 nanoparticles.

[0011] Furthermore, in step S11, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:(5~10), the mixture is stirred for 0.5~4h, centrifuged at 6000~12000rpm, washed with methanol 2~5 times, and vacuum dried at 40~70℃.

[0012] In some specific embodiments, preferably, in step S11, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:8, the mixture is stirred for 1 hour, centrifuged at 10,000 rpm, washed with methanol three times, and vacuum dried at 60°C.

[0013] Furthermore, in step S12, the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride is (5~20):1, the concentration of Tris buffer is 10~30mM, stirring is performed for 4~6h, centrifugation speed is 6000~12000rpm, methanol washing is repeated 2~5 times, and vacuum drying temperature is 40~70℃.

[0014] In some specific embodiments, preferably, in step S12, the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride is 10:1, the concentration of Tris buffer is 10mM, the stirring is carried out for 5 hours, the centrifugation speed is 10000rpm, the methanol washing is repeated 3 times, and the vacuum drying temperature is 60℃.

[0015] Furthermore, the piperazine monomers include hexahydropyrazine, N-methylpiperazine, and N-ethylpiperazine; the acyl chloride monomers include pyromellitic trimethylolpropionate chloride.

[0016] In some specific embodiments, preferably, the piperazine monomer is hexahydropyrazine; and the acyl chloride monomer is pyromellitic trimethylolpropionate chloride.

[0017] A method for preparing the above-mentioned nanofiltration membrane includes the following steps:

[0018] S21. Dissolve polyetheretherketone in a mixed solution of methanesulfonic acid and sulfuric acid, stir, and let stand to remove air bubbles to obtain casting solution; coat the casting solution onto a non-woven fabric support, let stand, and then immerse it in a deionized water precipitation bath to form a phase inversion membrane; wash the membrane to obtain sulfonated polyetheretherketone-based membrane.

[0019] S22. PDA-ZIF-8 nanoparticles are dispersed in a piperazine monomer solution to prepare an aqueous solution, and an acyl chloride monomer is dissolved in n-hexane solution to prepare an organic solution.

[0020] S23. Pour the aqueous solution from step S22 onto the surface of the base membrane and let it stand. Use a rubber roller to remove excess aqueous solution from the membrane surface. Then, slowly pour the organic solution from step S22 onto the membrane surface, allow it to react, dry, and bake to obtain the nanofiltration membrane.

[0021] Furthermore, in step S21, the polyetheretherketone content in the sulfonated polyetheretherketone-based film is 5~20wt%; the molar ratio of methanesulfonic acid to sulfuric acid is (1~5):1.

[0022] In some specific embodiments, preferably, the content of polyetheretherketone in the sulfonated polyetheretherketone-based film in step S21 is 12wt%; the molar ratio of methanesulfonic acid to sulfuric acid is 2.5:1.

[0023] Furthermore, in step S22, the concentration of piperazine monomers in the aqueous solution is 0.0025~1.5 wt%; and the concentration of PDA-ZIF-8 nanoparticles in the aqueous solution is 0.001~0.02 wt%.

[0024] In some specific embodiments, preferably, the concentration of piperazine monomer in the aqueous solution of step S22 is 0.3 wt%, and the concentration of PDA-ZIF-8 nanoparticles in the aqueous solution is 0.012 wt%.

[0025] Furthermore, the concentration of acyl chloride monomers in the organic phase solution in step S22 is 0.001~1.0wt%.

[0026] In some specific embodiments, preferably, the concentration of acyl chloride monomer in the organic phase solution of step S22 is 0.2 wt%.

[0027] Furthermore, in step S23, the aqueous phase solution is allowed to stand on the base film for 0.5~5 min, and the organic phase solution is allowed to react on the base film for 0.5~2 min; baking conditions: 40~70℃, 5~30 min.

[0028] In some specific embodiments, preferably, in step S23, the aqueous phase solution is allowed to stand on the base film for 2 minutes, and the organic phase solution is allowed to react on the base film for 1 minute; baking conditions: 60°C, 15 minutes.

[0029] The above-mentioned nanofiltration membranes are used in the separation of organic solution systems.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention employs polydopamine (PDA) to coat and modify ZIF-8. Utilizing the numerous phenolic hydroxyl and amino functional groups in PDA, these groups are linked to the outer wall of ZIF-8, significantly improving its dispersibility in water and avoiding the non-selective defects caused by uneven nanoparticle dispersion. Furthermore, a sulfonated polyether ether ketone (PEEK) membrane is used as the support layer. Through a simple and reproducible interfacial polymerization process, ultrafine PDA-ZIF-8 nanoparticles are introduced into the polyamide selective separation layer. The resulting organic solvent nanofiltration membrane exhibits excellent solvent resistance. It is applicable in various polar proton, polar aprotic, and nonpolar solvent systems, and maintains its intact membrane structure even under high-temperature (80°C) conditions with organic solvents, demonstrating broad prospects for industrial applications. Attached Figure Description

[0032] Figure 1 This is a SEM image of the PDA-ZIF-8 nanoparticles prepared in this invention.

[0033] Figure 2 This is a SEM image of the sulfonated polyether ether ketone-based film prepared according to the present invention.

[0034] Figure 3 SEM image of the nanofiltration membrane prepared in Comparative Example 1.

[0035] Figure 4 This is a SEM image of the polyether ether ketone organic solvent nanofiltration membrane containing PDA-ZIF-8 nanoparticles prepared in this invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0037] Example 1

[0038] This embodiment provides a composite layer polyetheretherketone organic solvent nanofiltration membrane, and the specific preparation method is as follows:

[0039] Preparation of PDA-ZIF-8 nanoparticles:

[0040] Zinc nitrate hexahydrate-methanol solution and 2-methylimidazole-methanol solution were prepared and mixed at a molar ratio of 1:8. The mixture was magnetically stirred at room temperature for 1 h, centrifuged at 10000 rpm for 10 min, the supernatant was removed and the mixture was washed three times with methanol. The mixture was then vacuum dried at 60 °C to obtain ZIF-8 nanosheets.

[0041] The ZIF-8 nanosheets obtained in the previous step were added to methanol and sonicated for 2 hours to disperse them evenly. Then, 10 mM Tris buffer and dopamine hydrochloride (the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride was 10:1) were added. The mixture was stirred at room temperature for 5 hours, centrifuged at 10,000 rpm for 10 minutes, the supernatant was removed, and the mixture was washed three times with methanol. The PDA-ZIF-8 nanoparticles were obtained by vacuum drying at 60 °C.

[0042] Preparation of sulfonated polyetheretherketone (PEEK) based films:

[0043] Polyetheretherketone (PEEK) was dissolved in a mixed solution of methanesulfonic acid and sulfuric acid, stirred until homogeneous, and allowed to stand for 90 hours to remove air bubbles, thus obtaining the casting solution. The casting solution contained 12 wt% PEEK, and the molar ratio of methanesulfonic acid to sulfuric acid was 2.5:1.

[0044] Using a blade-type doctor blade with a thickness of 200 μm, the casting solution is poured under the doctor blade. The doctor blade spreads the casting solution onto the nonwoven fabric support at a transverse speed of 0.5 cm / s. After standing for 0.5 min, it is immersed in a deionized water precipitation bath to form a phase inversion membrane. The water is changed midway to keep the precipitation bath neutral, and excess residual reagents in the sulfonated polyether ether ketone-based membrane are washed away to obtain the sulfonated polyether ether ketone-based membrane.

[0045] Preparation of polyetheretherketone organic solvent nanofiltration membrane containing PDA-ZIF-8 nanoparticles:

[0046] The prepared PDA-ZIF-8 nanoparticles were dispersed in a hexahydropyrazine monomer solution and ultrasonically treated for 2 hours to obtain an aqueous solution. Tristyrene chloride (TMC) was dissolved in n-hexane to obtain an organic solution. The aqueous solution contained 0.003 wt% PDA-ZIF-8 nanoparticles and 0.3 wt% hexahydropyrazine monomer; the organic solution contained 0.2 wt% tristyrene chloride.

[0047] The aqueous solution prepared above was poured onto the surface of the sulfonated polyether ether ketone membrane and allowed to stand for 2 minutes. Excess aqueous solution on the membrane surface was removed using a rubber roller. Then, the organic solution prepared above was slowly poured onto the membrane surface, reacted for 1 minute, dried for 2 minutes, and then placed in an oven to anneal at 60°C for 15 minutes to obtain the nanofiltration membrane.

[0048] Example 2

[0049] This embodiment provides a composite layer polyether ether ketone organic solvent nanofiltration membrane. The specific preparation method is basically the same as that in Example 1, except that the content of PDA-ZIF-8 nanoparticles in the aqueous solution is 0.006wt%, and the rest remain unchanged.

[0050] Example 3

[0051] This embodiment provides a composite layer polyether ether ketone organic solvent nanofiltration membrane. The specific preparation method is basically the same as that in Example 1, except that the content of PDA-ZIF-8 nanoparticles in the aqueous solution is 0.012wt%, and the rest remain unchanged.

[0052] Example 4

[0053] This embodiment provides a composite layer polyether ether ketone organic solvent nanofiltration membrane. The specific preparation method is basically the same as that in Example 1, except that the content of PDA-ZIF-8 nanoparticles in the aqueous solution is 0.036wt%, while the rest remain unchanged.

[0054] Example 5

[0055] This embodiment provides a composite layer polyetheretherketone organic solvent nanofiltration membrane, and the specific preparation method is as follows:

[0056] Preparation of PDA-ZIF-8 nanoparticles:

[0057] Zinc nitrate hexahydrate-methanol solution and 2-methylimidazole-methanol solution were prepared and mixed at a molar ratio of 1:5. The mixture was magnetically stirred at room temperature for 1 h, centrifuged at 6000 rpm for 15 min, the supernatant was removed and washed three times with methanol, and then vacuum dried at 40 °C to obtain ZIF-8 nanosheets.

[0058] The ZIF-8 nanosheets obtained in the previous step were added to methanol and sonicated for 2 hours to disperse them evenly. Then, 20 mM Tris buffer and dopamine hydrochloride (the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride was 5:1) were added. The mixture was stirred at room temperature for 4 hours, centrifuged at 6000 rpm for 15 minutes, the supernatant was removed, and the mixture was washed three times with methanol. The PDA-ZIF-8 nanoparticles were obtained by vacuum drying at 40 °C.

[0059] Preparation of sulfonated polyetheretherketone (PEEK) based films:

[0060] Polyetheretherketone (PEEK) was dissolved in a mixed solution of methanesulfonic acid and sulfuric acid, stirred until homogeneous, and allowed to stand for 90 hours to remove air bubbles, thus obtaining the casting solution. The casting solution contained 5 wt% PEEK, and the molar ratio of methanesulfonic acid to sulfuric acid was 1:1.

[0061] Using a blade-type doctor blade with a thickness of 200 μm, the casting solution is poured under the doctor blade. The doctor blade spreads the casting solution onto the nonwoven fabric support at a transverse speed of 0.5 cm / s. After standing for 2 minutes, the film is immersed in a deionized water precipitation bath to form a phase inversion film. The water is changed midway to keep the precipitation bath neutral, and excess residual reagents in the sulfonated polyether ether ketone-based film are washed away to obtain the sulfonated polyether ether ketone-based film.

[0062] Preparation of polyetheretherketone organic solvent nanofiltration membrane containing PDA-ZIF-8 nanoparticles:

[0063] The prepared PDA-ZIF-8 nanoparticles were dispersed in an N-methylpiperazine solution and ultrasonically treated for 2 hours to obtain an aqueous solution. Tristyrene chloride (TMC) was dissolved in n-hexane to obtain an organic solution. The aqueous solution contained 0.012 wt% PDA-ZIF-8 nanoparticles and 0.05 wt% N-methylpiperazine monomers; the organic solution contained 0.01 wt% tristyrene chloride.

[0064] The aqueous phase solution prepared above was poured onto the surface of the sulfonated polyether ether ketone membrane and allowed to stand for 2 minutes. Excess aqueous phase solution on the membrane surface was removed using a rubber roller. Then, the organic phase solution prepared above was slowly poured onto the membrane surface, reacted for 2 minutes, dried, and then placed in an oven to anneal at 40°C for 25 minutes to obtain the nanofiltration membrane.

[0065] Example 6

[0066] This embodiment provides a composite layer polyetheretherketone organic solvent nanofiltration membrane, and the specific preparation method is as follows:

[0067] Preparation of PDA-ZIF-8 nanoparticles:

[0068] Zinc nitrate hexahydrate-methanol solution and 2-methylimidazole-methanol solution were prepared and mixed at a molar ratio of 1:10. The mixture was magnetically stirred at room temperature for 1 h, centrifuged at 12000 rpm for 10 min, the supernatant was removed and the mixture was washed three times with methanol. The mixture was then vacuum dried at 70 °C to obtain ZIF-8 nanosheets.

[0069] The ZIF-8 nanosheets obtained in the previous step were added to methanol and sonicated for 2 hours to disperse them evenly. Then, 30 mM Tris buffer and dopamine hydrochloride (the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride was 20:1) were added. The mixture was stirred at room temperature for 6 hours, centrifuged at 12000 rpm for 10 minutes, the supernatant was removed, and the mixture was washed three times with methanol. The PDA-ZIF-8 nanoparticles were obtained by vacuum drying at 70 °C.

[0070] Preparation of sulfonated polyetheretherketone (PEEK) based films:

[0071] Polyetheretherketone (PEEK) was dissolved in a mixed solution of methanesulfonic acid and sulfuric acid, stirred until homogeneous, and allowed to stand for 90 hours to remove air bubbles, thus obtaining the casting solution. The casting solution contained 20 wt% PEEK, and the molar ratio of methanesulfonic acid to sulfuric acid was 5:1.

[0072] Using a blade-type doctor blade with a thickness of 200 μm, the casting solution is poured under the doctor blade. The doctor blade spreads the casting solution onto the nonwoven fabric support at a transverse speed of 0.5 cm / s. After standing for 0.5 min, it is immersed in a deionized water precipitation bath to form a phase inversion membrane. The water is changed midway to keep the precipitation bath neutral, and excess residual reagents in the sulfonated polyether ether ketone-based membrane are washed away to obtain the sulfonated polyether ether ketone-based membrane.

[0073] Preparation of polyetheretherketone organic solvent nanofiltration membrane containing PDA-ZIF-8 nanoparticles:

[0074] The prepared PDA-ZIF-8 nanoparticles were dispersed in an N-ethylpiperazine solution and ultrasonically treated for 2 hours to obtain an aqueous solution. Tristyrene chloride was dissolved in n-hexane to obtain an organic solution. The aqueous solution contained 0.012 wt% PDA-ZIF-8 nanoparticles and 1.5 wt% N-ethylpiperazine monomer; the organic solution contained 1.0 wt% tristyrene chloride.

[0075] The aqueous solution prepared above was poured onto the surface of the sulfonated polyether ether ketone membrane and allowed to stand for 2 minutes. Excess aqueous solution on the membrane surface was removed using a rubber roller. Then, the organic solution prepared above was slowly poured onto the membrane surface, reacted for 1 minute, dried for 2 minutes, and then placed in an oven to anneal at 60°C for 15 minutes to obtain the nanofiltration membrane.

[0076] Comparative Example 1

[0077] This comparative example provides a nanofiltration membrane, and the specific preparation method is basically the same as that in Example 1, except that the aqueous solution does not contain PDA-ZIF-8 nanoparticles, while the rest remain unchanged.

[0078] Comparative Example 2

[0079] This comparative example provides a nanofiltration membrane, which is prepared in a manner that is basically the same as that in Example 1. The difference is that the base membrane is prepared from commercial polysulfone with a molecular weight cutoff of 20,000 Da (purchased from Guochu Technology (Xiamen) Co., Ltd.), while all other aspects remain unchanged.

[0080] Furthermore, to understand the performance of the nanofiltration membranes prepared in the above embodiments and comparative examples, the following tests were also conducted:

[0081] Separation performance in different solution systems:

[0082] The separation performance of the membrane under different solution systems was tested using a cross-flow filtration device at 25℃ and a transmembrane pressure difference of 3.0 MPa. The final separation performance results are shown in Table 1. The specific solution systems are as follows: 1000 mg / L sodium sulfate solution-aqueous solution, 50 mg / L rhodamine B (positive charge, Mw=479.02 Da)-ethanol solution, 50 mg / L roxacin (negative charge, Mw=1017.64 Da)-ethanol solution, and 50 mg / L rhodamine B (positive charge, Mw=479.02 Da)-dimethylformamide solution.

[0083] Table 1. Separation performance of various nanofiltration membranes in different solution systems.

[0084]

[0085] It can be seen from the above table:

[0086] The nanofiltration membranes prepared in Examples 1-6 exhibited good retention rates for Na₂SO₄ in a sodium sulfate-water solution system (95.9-99.6%), Rhodamine B in a Rhodamine B-ethanol solution system (93.1-98.3%), Rosin in a Rosin-ethanol solution system (98.4-99.8%), and Rhodamine B in a Rhodamine B-dimethylformamide solution system (90.1-98.0%). These nanofiltration membranes demonstrated good retention rates for solutes in various systems. The comparison showed that the retention rate initially increased and then decreased with increasing PDA-ZIF-8 nanoparticle doping concentration, reaching its maximum at a doping concentration of 0.012 wt%.

[0087] By comparing with Comparative Example 1, it was found that Rhodamine B had a good rejection rate under all nanofiltration membranes because of its large molecular weight. However, when Rhodamine B with a smaller molecular weight was used, the rejection rate in Comparative Example 1 decreased significantly.

[0088] Permeation flux performance of different solvents:

[0089] Under conditions of 25℃ and a transmembrane pressure difference of 3.0 MPa, the permeation flux of the membrane for different solvents was tested using a cross-flow filtration device. The results are shown in Table 2.

[0090] Table 2. Permeation flux of each nanofiltration membrane to different solutions

[0091]

[0092] It can be seen from the above table:

[0093] The nanofiltration membranes prepared in Examples 1-6 had an ethanol flux of 106.55~242.11 L·h. -1 m -2 The flux for acetone was 45.69–93.8 L·h. -1 m -2 The flux of p-dimethylformamide was 78.98–155.6 L·h. -1 m -2 The flux for n-hexane is 3.12–11.2 L·h. -1 m -2 The nanofiltration membranes prepared in Examples 1-6 all exhibited high fluxes to solvents in different systems. The comparison shows that the permeation flux initially increases and then decreases with increasing PDA-ZIF-8 nanoparticle doping concentration, reaching its maximum at a doping concentration of 0.012 wt%.

[0094] Compared with Comparative Example 1, it was found that the addition of PDA-ZIF-8 nanoparticles significantly improved the permeation flux of the composite membrane to the non-polar solvent n-hexane.

[0095] Compared with Comparative Example 2, the composite membrane using sulfonated polyether ether ketone as the base film showed better tolerance.

[0096] Furthermore, to understand the stability of each nanofiltration membrane, the following tests were also conducted:

[0097] The nanofiltration membranes prepared in Examples and Comparative Example 2 were immersed in ethanol, acetone and n-hexane solvents at 25°C for 14 days, and in phosphoric acid and dimethylformamide at 80°C for 14 days, respectively. The results are shown in Table 3.

[0098] Table 3. Results of each nanofiltration membrane soaked under different conditions for 14 days

[0099]

[0100] It can be seen from the above table:

[0101] The nanofiltration membrane prepared in this embodiment exhibits good stability, remaining intact after immersion in different solvents at room temperature (25°C) for 14 days, ensuring its service life. It also remained intact after immersion in different solvents at high temperature (80°C) for 14 days. In contrast, the nanofiltration membrane in Comparative Example 2 only remained intact at room temperature, failing to meet the requirements for high-temperature applications.

[0102] As can be seen from the above tests, the nanofiltration membrane prepared by this invention has good separation performance, is suitable for different solution systems, and can maintain efficient retention of small molecular weight organic matter. At the same time, the stability of the nanofiltration membrane is also guaranteed, and it can adapt to high-temperature operating scenarios, thus further expanding its application range.

[0103] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0104] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite-layer polyetheretherketone organic solvent nanofiltration membrane, characterized in that, The nanofiltration membrane includes a support layer and a selective separation layer; the support layer is a sulfonated polyether ether ketone-based membrane, and the selective separation layer is a polyamide film formed by polymerizing piperazine monomers, PDA-ZIF-8 nanoparticles, and acyl chloride monomers at the interface of the support layer. The PDA-ZIF-8 nanoparticles were prepared by the following method: S11. Prepare zinc nitrate hexahydrate-methanol solution and 2-methylimidazole-methanol solution, mix, stir and react, centrifuge, remove supernatant and wash with methanol, and vacuum dry to obtain ZIF-8 nanosheets. S12. Disperse ZIF-8 nanosheets in methanol, add Tris buffer and dopamine hydrochloride, stir the reaction, centrifuge, remove the supernatant and wash with methanol, and vacuum dry to obtain PDA-ZIF-8 nanoparticles. The method for preparing the nanofiltration membrane includes the following steps: S21. Dissolve polyetheretherketone in a mixed solution of methanesulfonic acid and sulfuric acid, stir, and let stand to remove air bubbles to obtain casting solution; coat the casting solution onto a non-woven fabric support, let stand, and then immerse it in a deionized water precipitation bath to form a phase inversion membrane; wash the membrane to obtain sulfonated polyetheretherketone-based membrane. S22. PDA-ZIF-8 nanoparticles are dispersed in a piperazine monomer solution to prepare an aqueous solution, and an acyl chloride monomer is dissolved in n-hexane solution to prepare an organic solution. S23. Pour the aqueous solution from step S22 onto the surface of the base membrane and let it stand. Use a rubber roller to remove excess aqueous solution from the membrane surface. Then, slowly pour the organic solution from step S22 onto the membrane surface, allow it to react, dry, and bake to obtain the nanofiltration membrane. In step S22, the concentration of PDA-ZIF-8 nanoparticles in the aqueous solution was 0.012 wt%. In step S11, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:8, the reaction time is 1 h, the centrifugation speed is 10000 rpm, the washing with methanol is repeated 3 times, and the vacuum drying temperature is 60℃. In step S12, the mass ratio of ZIF-8 nanosheets to dopamine hydrochloride was 10:1, the concentration of Tris buffer was 10 mM, the reaction time was 5 h, the centrifugation speed was 10000 rpm, the washing with methanol was repeated 3 times, and the vacuum drying temperature was 60℃. The piperazine monomer is a hexahydropyrazine; The acyl chloride monomers include benzotrimethyl chloride; In step S21, the polyetheretherketone content in the sulfonated polyetheretherketone-based film is 12 wt%; the molar ratio of methanesulfonic acid to sulfuric acid is 2.5:

1. In step S22, the concentration of piperazine monomers in the aqueous solution was 0.3 wt%; the concentration of PDA-ZIF-8 nanoparticles in the aqueous solution was 0.003 wt%. In step S22, the concentration of acyl chloride monomers in the organic phase solution is 0.2 wt%. In step S23, the aqueous phase solution is allowed to stand on the base membrane for 2 minutes, and the organic phase solution is allowed to react on the base membrane for 1 minute; baking conditions: 60℃, 15 minutes.

2. The application of the nanofiltration membrane according to claim 1 in the separation of organic solution systems.

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