Polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to a polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane as well as a preparation method and application thereof, and belongs to the technical field of nanofiltration membranes. The problems of low flux and poor selectivity of a hollow fiber solvent-resistant nanofiltration membrane in the prior art are solved. The preparation method comprises the following steps: dissolving a dried soluble polyaryletherketone precursor containing a ketimine structure and a pore-foaming agent in an organic solvent, uniformly mixing, and carrying out vacuum defoaming to obtain a spinning solution; uniformly mixing deionized water and an organic solvent to obtain core liquid; and respectively extruding the spinning solution and the core solution from a shell layer and a core layer of a coaxial spinning nozzle, passing through an air layer, immersing in a coagulating bath for curing to obtain a polyaryletherketone precursor primary hollow fiber membrane, and sequentially immersing in deionized water for curing and immersing in an acid solution for acidification to obtain the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane. The polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane has good solvent resistance, heat resistance, chemical resistance and permeation selectivity.

Description

Technical Field

[0001] This invention belongs to the field of nanofiltration membrane technology, specifically relating to a polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] In the food, pharmaceutical, and petrochemical industries, organic solvents are used extensively as raw materials, solvents, or cleaning agents during production. The pharmaceutical and fine chemical industries, in particular, use solvents in enormous quantities, sometimes accounting for as much as 90% of total chemical consumption. Simultaneously, these production processes generate large amounts of mixed organic solvent waste liquids. Direct discharge of such waste liquids leads to resource waste and environmental pollution; therefore, the separation and recycling of organic solvents is essential. Common industrial methods for solvent separation include distillation, evaporation, and liquid-liquid extraction. These methods, however, require significant heat consumption, are complex to operate, and have relatively low separation efficiency.

[0003] Organic solvent nanofiltration membrane technology boasts advantages such as high separation efficiency, low energy consumption, simple operation, and no phase change, gradually becoming a primary method for organic solvent separation and recovery. The core component of organic solvent nanofiltration membrane technology is the solvent-resistant nanofiltration membrane. The selection of membrane materials is particularly important depending on the membrane separation process and the separated medium. Commonly used polymer materials for membrane fabrication include: polyacrylonitrile (PAN), polyimide (PI), polyamide-imide (PAI), polybenzimidazole (PBI), polydimethylsiloxane (PDMS), polypyrrole (PPy), and polyaryletherketone (PAEK). Among these, PAEK is a semi-crystalline polymer with excellent solvent resistance, chemical resistance, and mechanical stability, making it particularly suitable for harsh organic solvent systems such as high-temperature, strong acid, and strong alkali environments. Although there has been considerable research on flat-sheet organic solvent nanofiltration membranes, their large footprint, complex operation, and low separation efficiency limit their application. Hollow fiber membranes not only possess advantages such as high packing density, high specific surface area, small footprint, and high separation efficiency, but also have stable production processes, good reproducibility, and are easier to industrialize, showing great application potential in the field of organic solvent nanofiltration. However, due to the semi-crystalline nature of polyaryletherketones (PAEs) and their regularly arranged molecular chains, they are difficult to dissolve in conventional solvents. Therefore, thermally induced phase separation (TIPS) is commonly used to prepare PAE hollow fiber membranes. However, this method is not only energy-intensive, but also produces nanofiltration membranes with low flux and poor separation accuracy, making it unsuitable for sieving low molecular weight solutes. A Chinese patent discloses a method for preparing a solvent-resistant PAE hollow fiber nanofiltration membrane with a narrow pore size distribution (CN114870639B). This method involves dissolving PAEs in a diluent to prepare a polymer solution at 200-350°C to prepare the PAE hollow fiber membrane. This method requires high dissolution temperatures and long dissolution times, resulting in high energy consumption and a thick membrane layer with low flux and poor selectivity. Therefore, it is necessary to develop a high-flux and highly selective polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane under mild conditions. Summary of the Invention

[0004] This invention addresses the technical problems of low flux and poor selectivity in existing hollow fiber solvent-resistant nanofiltration membranes by providing a polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane, its preparation method, and its applications. The polyaryletherketone hollow fiber membrane of this invention exhibits high flux and high selectivity, while also possessing good solvent resistance, heat resistance, chemical resistance, and permeation selectivity.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.

[0006] In a first aspect, the present invention provides a method for preparing a solvent-resistant polyaryletherketone hollow fiber nanofiltration membrane, comprising the following steps:

[0007] S1. At room temperature, a dry soluble polyarylether ketone precursor containing a ketimine structure and a pore-forming agent are dissolved and mixed evenly in a mixed organic solvent, and after vacuum degassing, a spinning solution is obtained.

[0008] In the spinning solution, the mass fraction of the soluble polyaryletherketone precursor containing a ketimine structure is 15wt%~25wt%, and the mass fraction of the pore-forming agent is 1wt%~10wt%.

[0009] The mixed organic solvent is a mixture of a first organic solvent and a second organic solvent in a mass ratio of (0.1~1):(0.1~1). The first organic solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, and diphenyl sulfone. The second organic solvent is a mixture of one or more of 1,4-dioxane, acetone, and tetrahydrofuran.

[0010] S2. Mix deionized water and organic solvent at a mass ratio of (0.1~1):(0.1~1) to obtain core solution;

[0011] S3. Under the conditions of room temperature and relative humidity of 40RH%~60RH%, the spinning solution is extruded from the shell layer and core layer of the coaxial spinneret at a rate of 2~4mL / min and the core solution at a rate of 1~2mL / min, respectively. After passing through an air layer height of 1~20cm, it is immersed in a coagulation bath at 20~25℃ to solidify and obtain a polyaryletherketone precursor nascent hollow fiber membrane.

[0012] S4. Soak the polyaryletherketone precursor nascent hollow fiber membrane in deionized water for 24-48 hours, and change the deionized water every 6-10 hours to obtain the precursor polyaryletherketone hollow fiber membrane.

[0013] S5. The precursor polyaryletherketone hollow fiber membrane is immersed in an acid solution and acidified at 30~60℃ for 24~48h. After washing with deionized water, a solvent-resistant polyaryletherketone hollow fiber nanofiltration membrane is obtained.

[0014] Preferably, in S1, the number-average molecular weight of the soluble polyaryletherketone precursor containing a ketimine structure is 20,000 to 100,000 g / mol.

[0015] Preferably, in S1, the soluble polyaryletherketone precursor containing a ketimine structure is one or a mixture of ketimine polyether etherketone, ketimine polyether etherketone ketone, ketimine polyether etherketone, ketimine biphenyl type polyether etherketone, and ketimine biphenyl type polyether etherketone ketone.

[0016] The chemical structural formulas of the ketimine polyether ether ketone, ketimine polyether ether ketone ketone, ketimine polyether ketone, ketimine biphenyl type polyether ether ketone, and ketimine biphenyl type polyether ether ketone ketone are shown in (1), (2), (3), (4), and (5), respectively:

[0017] .

[0018] Preferably, in S1, the pore-forming agent is one or a mixture of lithium chloride, calcium chloride, lithium bromide, lithium nitrate, calcium nitrate, ethylene glycol, propylene glycol, butanediol, polyethylene glycol, and polyvinylpyrrolidone.

[0019] Preferably, in S1, the method of achieving uniform mixing is to stir for 48-72 hours.

[0020] Preferably, in S1, the vacuum degassing time is 48~72h.

[0021] Preferably, in S1, the mass fraction of the soluble polyaryletherketone precursor containing a ketimine structure in the spinning solution is 15wt%~21wt%, and the mass fraction of the pore-forming agent is 1wt%~7wt%.

[0022] More preferably, in the spinning solution, the mass fraction of the soluble polyaryletherketone precursor containing the ketimine structure is 19wt%~21wt%, and the mass fraction of the pore-forming agent is 3wt%~5wt%.

[0023] Preferably, in S2, the organic solvent is one or a mixture of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, methanol, and ethanol.

[0024] Preferably, in S2, the mass ratio of the deionized water to the organic solvent is (0.3~0.8):(0.3~0.8).

[0025] More preferably, the mass ratio of the deionized water to the organic solvent is (0.5~0.7):(0.5~0.7).

[0026] Preferably, in S3, the coagulation bath is one or a mixture of deionized water, methanol, ethanol, propanol, ethylene glycol, and diethylene glycol.

[0027] Preferably, in S3, the inner diameter (core layer) of the coaxial spinneret is 500~700μm and the outer diameter (shell layer) is 1000~2000μm.

[0028] Preferably, in S3, the height of the air layer is 5~18cm;

[0029] More preferably, the height of the air layer is 7~15cm;

[0030] Preferably, the height of the air layer is 9-12 cm.

[0031] Preferably, in step S3, the obtained polyaryletherketone precursor nascent hollow fiber membrane is wound onto a take-up roller at a speed of 20-30 rpm, and in step S4, the polyaryletherketone precursor nascent hollow fiber membrane on the take-up roller is immersed in deionized water.

[0032] Preferably, in S4, the deionized water is replaced every 8 hours.

[0033] Preferably, in S5, the acid solution is one or a mixture of more than one of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid.

[0034] Preferably, in step S5, the concentration of the acid solution is 1~9 mol / L.

[0035] Preferably, in step S5, deionized water is used for 3 to 5 cleaning cycles.

[0036] Secondly, the present invention also provides a polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane prepared by the above-mentioned method for preparing polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane.

[0037] Thirdly, the present invention also provides the application of the above-mentioned polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane in the separation of pure organic solvent systems and aqueous organic solvent systems.

[0038] In this invention, room temperature is defined as 23~30℃.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The polyaryletherketone hollow fiber membrane of the present invention has good solvent resistance, heat resistance, chemical resistance and permeation selectivity.

[0041] The polyaryletherketone hollow fiber membrane of the present invention utilizes the good solubility of soluble polyaryletherketone precursors containing ketimine structures at room temperature and their recrystallization after acidification, which simplifies the dry-spray wet spinning process and reduces manufacturing costs.

[0042] The polyaryletherketone hollow fiber membrane of this invention was prepared through synergistic optimization of the spinning solution formulation and spinning process parameters. Firstly, by adjusting the spinning solution concentration and the content of the pore-forming agent, the thermodynamic stability of the spinning solution was reduced, and the phase transformation rate in the coagulation bath was accelerated, which is beneficial for obtaining a separation skin with high surface porosity and thin thickness. Secondly, by controlling the air layer height, the evaporation of low-boiling-point solvents from the outer surface of the nascent fibers was increased, leading to a higher local polymer concentration and a reduction in the membrane surface pore size. Separation tests showed that the membrane had a rejection rate of up to 99.9% for methyl orange (327.3 g / mol) in ethanol solution, indicating that the polyaryletherketone hollow fiber membrane not only has good solvent resistance but also possesses the advantages of high throughput and high selectivity, showing excellent application and promotion prospects in the separation of pure organic solvent systems and aqueous organic solvent systems. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The images shown are scanning electron microscope (SEM) images of the cross-section of the polyether ether ketone hollow fiber solvent-resistant nanofiltration membrane prepared in Example 1 of the present invention. (a) is a cross-sectional view at a magnification of 100, and (b) is a cross-sectional view at a magnification of 300.

[0045] Figure 2 The images shown are scanning electron microscope (SEM) images of the cross-section of the biphenyl-type polyether ether ketone hollow fiber solvent-resistant nanofiltration membrane prepared in Example 10 of the present invention. (a) is a cross-sectional view at a magnification of 100, and (b) is a cross-sectional view at a magnification of 400.

[0046] Figure 3 The graph shows the relationship between the ethanol permeability and methyl orange rejection rate of the polyether ether ketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 1-4 of this invention and the solid content of the spinning solution.

[0047] Figure 4 The graph shows the relationship between the ethanol permeability and methyl orange rejection rate of the biphenyl-type polyether ether ketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 5-8 of this invention and the mass fraction of polyvinylpyrrolidone (PVP).

[0048] Figure 5 The graph shows the relationship between ethanol permeability and methyl orange rejection rate of the biphenyl-type polyether ether ketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 9-12 of this invention and air layer height (H). Detailed Implementation

[0049] The terminology used in this invention generally has the meanings commonly understood by those skilled in the art, unless otherwise stated.

[0050] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. The embodiments described are merely specific descriptions of the claims of the present invention, and the claims include, but are not limited to, the content of the described embodiments.

[0051] Unless otherwise specified, all reagents and materials used in the following examples and comparative examples are commercially available; all test methods are conventional unless otherwise specified. The spinneret model is HZ-SF-01; power supply: 220V-50Hz; total power: 1400W.

[0052] Example 1

[0053] The preparation method of polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0054] S1. Add 15g of ketimine polyether ether ketone, 1g of polyvinylpyrrolidone, 12.7mL of acetone and 72.0mL of N-methylpyrrolidone to a three-necked flask, and stir magnetically for 48h to fully dissolve and mix, so as to prepare a mixed solution with a polyarylether ketone precursor mass fraction of 15wt% and a polyvinylpyrrolidone mass fraction of 1wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0055] S2. Dissolve 50 mL of deionized water and 63 mL of ethanol thoroughly to prepare a core solution with a mass ratio of deionized water to ethanol of 1:1, and pour it into the core solution storage tank.

[0056] S3. Under conditions of 25℃ and 50% RH, the spinning solution is extruded from the shell and core layers of the coaxial spinneret at a rate of 3 mL / min and the core solution at a rate of 1 mL / min, respectively. The inner diameter of the coaxial spinneret is 500 μm and the outer diameter is 1000 μm. After passing through an air layer height of 5 cm, it is immersed in a deionized water coagulation bath at 25℃ to form a ketimine polyether ether ketone nascent hollow fiber membrane. It is then wound onto a take-up roller at a speed of 30 rpm.

[0057] S4. Immerse the nascent ketimide polyether ether ketone hollow fiber membrane on the take-up roller in deionized water for 48 hours, and change the deionized water every 8 hours to ensure that the organic solvent in the membrane is fully exchanged with the deionized water, so as to obtain the ketimide polyether ether ketone hollow fiber membrane.

[0058] S5. Immerse the ketimine polyether ether ketone hollow fiber membrane in a 5 mol / L sulfuric acid solution, heat to 40℃, acidify for 24 h, remove the membrane fibers, and rinse repeatedly with deionized water 5 times to obtain a polyarylether ketone hollow fiber solvent-resistant nanofiltration membrane.

[0059] The polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 12.0 L / m³. 2. h . The rejection rate of methyl orange was 89.5%. This indicates that the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this invention has excellent permeation selectivity in organic solvent systems, making it very suitable for the separation and purification of organic solvent systems.

[0060] Example 2

[0061] The preparation method of polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0062] S1. Add 17g of ketimine polyether ether ketone, 1g of polyvinylpyrrolidone, 12.7mL of acetone and 70.0mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 17wt% and a polyvinylpyrrolidone mass fraction of 1wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0063] S2-S5 are the same as in Example 1.

[0064] The polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 11.5 L / m³. 2. h . The rejection rate for methyl orange was 92.0%.

[0065] Example 3

[0066] The preparation method of polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0067] S1. Add 19g of ketimine polyether ether ketone, 1g of polyvinylpyrrolidone, 12.7mL of acetone and 68.0mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 19wt% and a polyvinylpyrrolidone mass fraction of 1wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0068] S2-S5 are the same as in Example 1.

[0069] The polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 11.4 L / m³. 2. h . The rejection rate for methyl orange was 99.0%.

[0070] Example 4

[0071] The preparation method of polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0072] S1. Add 21g of ketimine polyether ether ketone, 1g of polyvinylpyrrolidone, 12.7mL of acetone and 66.1mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 21wt% and a polyvinylpyrrolidone mass fraction of 1wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0073] S2-S5 are the same as in Example 1.

[0074] The polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 8.6 L / m³. 2. h . The rejection rate for methyl orange was 99.2%.

[0075] Example 5

[0076] The preparation method of biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0077] S1. Add 19g of ketimine-biphenyl polyether ether ketone, 3g of polyvinylpyrrolidone, 12.7mL of acetone and 66.1mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 19wt% and a polyvinylpyrrolidone mass fraction of 3wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0078] S2-S5 are the same as in Example 1.

[0079] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 12.1 L / m³. 2. h .The rejection rate for methyl orange was 99.2%.

[0080] Example 6

[0081] The preparation method of biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0082] S1. Add 19g of ketimine-biphenyl polyether ether ketone, 5g of polyvinylpyrrolidone, 12.7 mL of acetone and 64.2 mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 19wt% and a polyvinylpyrrolidone mass fraction of 5wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0083] S2-S5 are the same as in Example 1.

[0084] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 13.5 L / m³. 2. h . The rejection rate for methyl orange was 99.1%.

[0085] Example 7

[0086] The preparation method of biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0087] S1. Add 19g of ketimine-biphenyl polyether ether ketone, 7g of polyvinylpyrrolidone, 12.7 mL of acetone and 62.3 mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 19wt% and a polyvinylpyrrolidone mass fraction of 7wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0088] S2-S5 are the same as in Example 1.

[0089] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 15.0 L / m³. 2. h . The rejection rate for methyl orange was 85.5%.

[0090] Example 8

[0091] The preparation method of biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane is as follows:

[0092] S1. Add 19g of ketimine-biphenyl polyether ether ketone, 9g of polyvinylpyrrolidone, 12.7mL of acetone and 60.3mL of N-methylpyrrolidone to a three-necked flask; stir magnetically for 48h to fully dissolve, and prepare a mixed solution with a polyarylether ketone precursor mass fraction of 19wt% and a polyvinylpyrrolidone mass fraction of 9wt%. Transfer the mixed solution to a spinning storage tank and degas under vacuum for 24h to obtain the spinning solution.

[0093] S2-S5 are the same as in Example 1.

[0094] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 20.4 L / m³. 2. h . The rejection rate for methyl orange was 84.7%.

[0095] Example 9

[0096] S1, S2, and S4-S5 are the same as in Example 6.

[0097] S3. Under conditions of 25℃ and 50% RH, the spinning solution is extruded from the shell and core layers of the coaxial spinneret at a rate of 2 mL / min and the core solution at a rate of 1 mL / min, respectively (the inner diameter of the coaxial spinneret is 700 μm and the outer diameter is 1000 μm). After passing through an air layer height of 7 cm, it is immersed in a deionized water coagulation bath at 25℃ to form a biphenyl-type polyether ether ketone nascent hollow fiber membrane, which is then wound onto a take-up roller at a speed of 30 rpm.

[0098] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 13.2 L / m³. 2. h . The rejection rate for methyl orange was 99.3%.

[0099] Example 10

[0100] S1, S2, and S4-S5 are the same as in Example 6.

[0101] S3. Under conditions of 25℃ and 50% RH, the spinning solution is extruded from the shell and core layers of the coaxial spinneret at a rate of 2 mL / min and the core solution at a rate of 1 mL / min, respectively (the inner diameter of the coaxial spinneret is 700 μm and the outer diameter is 1100 μm). After passing through an air layer height of 8 cm, it is immersed in a deionized water coagulation bath at 25℃ to form a biphenyl-type polyether ether ketone nascent hollow fiber membrane, which is then wound onto a take-up roller at a speed of 30 rpm.

[0102] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 13.1 L / m³. 2. h . The rejection rate for methyl orange was 99.5%.

[0103] Example 11

[0104] S1, S2, and S4-S5 are the same as in Example 6.

[0105] S3. Under conditions of 25℃ and 50% RH, the spinning solution is extruded from the shell and core layers of the coaxial spinneret at a rate of 2 mL / min and the core solution at a rate of 1 mL / min, respectively. The inner diameter of the coaxial spinneret is 500 μm and the outer diameter is 1400 μm. After passing through an air layer height of 9 cm, it is immersed in a deionized water coagulation bath at 25℃ to form a biphenyl-type polyether ether ketone nascent hollow fiber membrane. It is then wound onto a take-up roller at a speed of 30 rpm.

[0106] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 12.0 L / m³. 2. h . The rejection rate for methyl orange was 99.5%.

[0107] Example 12

[0108] S1, S2, and S4-S5 are the same as in Example 6.

[0109] S3. Under conditions of 25℃ and 50% RH, the spinning solution is extruded from the shell and core layers of the coaxial spinneret at a rate of 2 mL / min and the core solution at a rate of 1 mL / min, respectively (the inner diameter of the coaxial spinneret is 600 μm and the outer diameter is 1500 μm). After passing through an air layer height of 10 cm, it is immersed in a deionized water coagulation bath at 25℃ to form a biphenyl-type polyether ether ketone nascent hollow fiber membrane, which is then wound onto a take-up roller at a speed of 30 rpm.

[0110] The biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in this embodiment was used to separate an ethanol solution containing 100 ppm methyl orange. The ethanol permeation flux of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was measured to be 10.7 L / m³. 2. h . The rejection rate for methyl orange was 99.9%.

[0111] Figure 1 A scanning electron microscope (SEM) image of the cross-section of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in Example 1 of this invention. Figure 1 As shown in (a), the polyetheretherketone hollow fiber membrane has a very uniform wall thickness, and its cross-section consists of double rows of finger-like pores and sponge-like pores. Figure 1 As shown in (b), the outer surface of the fiber membrane has a thin, dense layer that can effectively separate ethanol and methyl orange, exhibiting high selective sieving ability. Therefore, this work demonstrates the successful preparation of a polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane.

[0112] Figure 2 This is a scanning electron microscope (SEM) image of the cross-section of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane prepared in Example 10 of the present invention. Figure 1 As shown in (a), the biphenyl-type polyetheretherketone hollow fiber membrane has a very uniform wall thickness, and its cross-section consists of double rows of finger-like pores and sponge-like pores. Figure 1 As shown in (b), the outer surface of the fiber membrane has a thin, dense layer. This is because after the nascent fiber membrane is ejected from the spinneret, it passes through an air layer, causing the acetone on the membrane surface to evaporate, increasing the polymer concentration on the membrane surface and forming smaller pores. Therefore, this work proves that the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membrane was successfully prepared.

[0113] Figure 3 This is a graph showing the relationship between the ethanol permeability and methyl orange rejection rate of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 1-4 of this invention and the solid content of the spinning solution (15 wt%, 17 wt%, 19 wt%, and 21 wt% in Examples 1-4, respectively). As can be seen from the graph, with the increase of the solid content of the spinning solution, the ethanol permeability decreases from 12.0 L / m³. 2. h . bar dropped to 8.6 L / m 2. h . The methyl orange rejection rate increased from 89.5% to 99.2% due to the increased solid content, which raised the viscosity of the spinning solution, slowed the solvent-to-non-solvent phase transition rate, resulting in smaller skin pore size, decreased porosity, and increased solvent mass transfer resistance. Therefore, this demonstrates that the solid content of the spinning solution is a key parameter for adjusting membrane structure and performance.

[0114] Figure 4 This is a graph showing the relationship between the ethanol permeability and methyl orange rejection rate of the polyetheretherketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 5-8 of this invention and the solid content of polyvinylpyrrolidone (the mass fraction of polyvinylpyrrolidone in Examples 5-8 is 3 wt%, 5 wt%, 7 wt%, and 9 wt%, respectively). As can be seen from the graph, with the increase of polyvinylpyrrolidone content, the solvent permeability decreases from 12.1 L / m³. 2. h . bar increased to 20.4 L / m 2. h . The methyl orange rejection rate decreased from 99.2% to 84.7% due to the strong hydrophilicity of polyvinylpyrrolidone, which accelerates the solvent-to-non-solvent phase transition rate, causing instantaneous phase separation, forming more micropores, and reducing mass transfer resistance. Therefore, this indicates that the addition of polyvinylpyrrolidone as a porogen is beneficial for improving the permeability of polyaryletherketone hollow fiber membranes.

[0115] Figure 5 This is a graph showing the relationship between the ethanol permeability and methyl orange rejection rate of the biphenyl-type polyetheretherketone hollow fiber solvent-resistant nanofiltration membranes prepared in Examples 9-12 of this invention and the air layer height (7 cm, 8 cm, 9 cm, and 10 cm in Examples 9-12, respectively). As can be seen from the graph, with the increase of air layer height, the ethanol permeability decreases from 13.2 L / m². 2. h . bar dropped to 10.7 L / m 2. h . The methyl orange rejection rate increased from 99.3% to 99.9% due to increased evaporation of low-boiling-point solvents from the outer surface of the nascent fibers, leading to a higher local polymer concentration and consequently a smaller pore size on the membrane surface. This indicates that changing the air layer height is beneficial for improving the selectivity of polyaryletherketone hollow fiber membranes.

[0116] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane, characterized in that, The steps are as follows: S1. At room temperature, a dry soluble polyarylether ketone precursor containing a ketimine structure and a pore-forming agent are dissolved and mixed evenly in a mixed organic solvent, and after vacuum degassing, a spinning solution is obtained. In the spinning solution, the mass fraction of the soluble polyaryletherketone precursor containing a ketimine structure is 15wt%~25wt%, and the mass fraction of the pore-forming agent is 1wt%~10wt%. The mixed organic solvent is a mixture of a first organic solvent and a second organic solvent in a mass ratio of (0.1~1):(0.1~1). The first organic solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, and diphenyl sulfone. The second organic solvent is a mixture of one or more of 1,4-dioxane, acetone, and tetrahydrofuran. S2. Mix deionized water and organic solvent at a mass ratio of (0.1~1):(0.1~1) to obtain core solution; S3. Under the conditions of room temperature and relative humidity of 40RH%~60RH%, the spinning solution is extruded from the shell layer and core layer of the coaxial spinneret at a rate of 2~4mL / min and the core solution at a rate of 1~2mL / min, respectively. After passing through an air layer height of 1~20cm, it is immersed in a coagulation bath at 20~25℃ to solidify and obtain a polyaryletherketone precursor nascent hollow fiber membrane. S4. Soak the polyaryletherketone precursor nascent hollow fiber membrane in deionized water for 24-48 hours, and change the deionized water every 6-10 hours to obtain the precursor polyaryletherketone hollow fiber membrane. S5. The precursor polyaryletherketone hollow fiber membrane is immersed in an acid solution and acidified at 30~60℃ for 24~48h. After washing with deionized water, a solvent-resistant polyaryletherketone hollow fiber nanofiltration membrane is obtained.

2. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, S1 possesses one or more of the following characteristics: The number-average molecular weight of the soluble polyaryletherketone precursor containing a ketimine structure is 20,000 to 100,000 g / mol. The soluble polyaryletherketone precursor containing a ketimine structure is one or a mixture of ketimine polyether etherketone, ketimine polyether etherketone ketone, ketimine polyether etherketone, ketimine biphenyl polyether etherketone, and ketimine biphenyl polyether etherketone ketone. The pore-forming agent is one or a mixture of lithium chloride, calcium chloride, lithium bromide, lithium nitrate, calcium nitrate, ethylene glycol, propylene glycol, butanediol, polyethylene glycol, and polyvinylpyrrolidone.

3. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, In S1, the method for achieving uniform mixing is to stir for 48-72 hours; And / or, the vacuum degassing time is 24~72h.

4. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, In S2, the organic solvent is one or a mixture of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, methanol, and ethanol.

5. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, In S3, the coagulation bath is one or a mixture of deionized water, methanol, ethanol, propanol, ethylene glycol, and diethylene glycol.

6. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, In S3, the inner diameter of the coaxial spinneret is 500~700μm and the outer diameter is 1000~2000μm.

7. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, In step S3, the obtained polyaryletherketone precursor nascent hollow fiber membrane is wound onto a take-up roller at a speed of 20-30 rpm. In step S4, the polyaryletherketone precursor nascent hollow fiber membrane on the take-up roller is immersed in deionized water.

8. The method for preparing the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 1, characterized in that, S5 possesses one or more of the following characteristics: The acid solution is one or a mixture of more than one of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid; The concentration of the acid solution is 1~9 mol / L; Rinse with deionized water 3-5 times.

9. The polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane prepared by the method according to any one of claims 1 to 8.

10. The application of the polyaryletherketone hollow fiber solvent-resistant nanofiltration membrane according to claim 9 in the separation of pure organic solvent systems and aqueous organic solvent systems.

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