Nanofiber membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oil-water separation, and discloses a nanofiber membrane as well as a preparation method and application thereof. The nanofiber membrane is prepared through co-electrostatic spinning and comprises a first nanofiber and a second nanofiber which are mutually wound, the first nanofiber contains polypropylene and a hydrophobic polymer, the second nanofiber is polyacrylonitrile, and the first nanofiber and the second nanofiber are mutually wound. The hydrophobic polymer is at least one of polystyrene, polyvinylidene fluoride and polymethyl methacrylate. According to the technical scheme, water and oil are allowed to be conveyed through the membrane through the two channels, formation of intercepted oil pollutants in the whole separation process is fundamentally avoided, and lasting and excellent anti-pollution performance is provided for ultra-stable long-term separation of the oil pollutants from oil-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of oil-water separation technology, specifically to a nanofiber membrane, its preparation method, and its application. Background Technology

[0002] Oil extraction, transportation, and processing generate large amounts of oily wastewater, which can cause a series of ecological and environmental problems when it enters the environment's water bodies. Researching rapid and efficient oil-water separation materials has become a focus of current scientific research. Oily wastewater can be classified into four forms based on oil droplet size: floating oil (>150μm), dispersed oil (20–150μm), emulsified oil (<20μm), and dissolved oil (less than a few micrometers). Among these, the separation of emulsified and dissolved oils is currently the most challenging. Traditional oil-water separation methods, including gravity separation, centrifugation, flotation, flocculation, and electrolysis, are only effective for simple floating and dispersed oils. For complex emulsified oil-water mixtures, they suffer from low separation efficiency, high cost, potential secondary pollution, and low recycling rates. Membrane separation technology, with its advantages of good selectivity, ease of operation, and recyclability, has become an emerging technology in the field of oil-water separation.

[0003] Current research on separation membranes typically aims for a uniform distribution of hydrophilic components on the membrane surface or pore walls. However, emulsified oil, isolated outside the membrane, tends to accumulate on the surface of the membrane hydration layer due to its uniform wettability, forming a demulsified oil film. Once a large amount of oil film forms on the membrane surface or blocks the pores, the water channels will be occupied or even closed, leading to a sharp decrease in water content per unit area.

[0004] Therefore, it is necessary to rethink and redesign novel membrane structures and heterogeneous wettability to achieve continuous oil / water separation without causing scaling interruptions. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem in the prior art that once emulsified oil accumulates and forms a large oil film on the membrane surface during oil-water separation, it will block the pores. This invention provides a nanofiber membrane, its preparation method, and its application. This technical solution prepares the nanofiber membrane through co-electrospinning, which allows water and oil to permeate through their respective channels, effectively preventing the blockage of channels by the oil phase, and achieving ultra-stable separation of emulsified oil-water mixtures.

[0006] To achieve the above objectives, the first aspect of the present invention provides a nanofiber membrane, which is prepared by co-electrospinning and comprises a first nanofiber and a second nanofiber entangled with each other, wherein the first nanofiber contains polypropylene and a hydrophobic polymer, the second nanofiber is polyacrylonitrile, and the hydrophobic polymer is at least one selected from polystyrene, polyvinylidene fluoride and polymethyl methacrylate.

[0007] Preferably, the pore size of the nanofiber membrane is 1-10 μm, and the porosity is 85%-95%. Preferably, the mass ratio of the first nanofiber to the second nanofiber is (0.8-1.3):1.

[0008] Preferably, the mass ratio of the polypropylene to the hydrophobic polymer is 1:(0.2-5).

[0009] A second aspect of the present invention provides a method for preparing a nanofiber membrane, the method comprising the following steps:

[0010] (1) Mix the polypropylene solution and the hydrophobic polymer solution to obtain a mixed solution;

[0011] (2) The mixed solution and the polyacrylonitrile solution were electrospun together to obtain a nanofiber membrane;

[0012] The hydrophobic polymer in the hydrophobic polymer solution is at least one of polystyrene, polyvinylidene fluoride, and polymethyl methacrylate.

[0013] Preferably, the solvent in the polypropylene solution is at least one selected from n-heptane, dichloromethane, trichloromethane, carbon tetrachloride, xylene, tetrahydrofuran, and cyclohexane.

[0014] Preferably, the concentration of the polypropylene solution is 1-50 wt%.

[0015] Preferably, the solvent in the hydrophobic polymer solution is at least one of dimethylformamide, acetone, toluene, dimethylacetamide, and dimethyl sulfoxide.

[0016] Preferably, the concentration of the hydrophobic polymer solution is 1-50 wt%.

[0017] Preferably, in the mixed solution, the mass ratio of the polypropylene to the hydrophobic polymer is 1:(0.2-5).

[0018] Preferably, the solvent in the polypropylene solution is at least one of dimethylformamide, acetone, chloroform, and carbon tetrachloride.

[0019] Preferably, the concentration of the polyacrylonitrile solution is 1-10 wt%.

[0020] Preferably, the method further includes immersing the nanofiber membrane obtained in step (2) in a methanol solution of sodium hydroxide.

[0021] Preferably, the concentration of the sodium hydroxide methanol solution is 8-15 wt%.

[0022] A third aspect of the present invention provides a nanofiber membrane prepared by the method described above.

[0023] The fourth aspect of the present invention provides the application of the above-mentioned nanofiber membrane in emulsified oil-water separation.

[0024] The above technical solution involves preparing a nanofiber membrane via co-electrospinning. The resulting nanofiber membrane comprises a hydrophobic first nanofiber and a hydrophilic second nanofiber, forming a dual-channel system. This independent dual-channel system allows water and oil to pass through the membrane separately, exhibiting high permeability and stability for surfactant-stabilized oil-in-water emulsions. The intertwined hydrophobic first nanofiber and hydrophilic second nanofiber form channels through micro / nanospaces. The hydrophilic second nanofiber acts as a water channel, while the hydrophobic first nanofiber serves as agglomeration sites and oil transport channels. Furthermore, the difference in interfacial tension allows oil droplets to deposit, migrate, coalesce, and be removed between the nanofibers. This invention fundamentally avoids the formation of trapped oil contaminants during the entire separation process, providing durable and excellent anti-fouling performance for the ultra-stable long-term separation of oil contaminants from oily wastewater. It solves the problem of reduced flux and unstable use that existing technologies cannot address, and has broad application prospects in the field of oil-water separation. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the nanofiber membrane described in this invention. Detailed Implementation

[0026] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] The nanofiber membrane of this invention is prepared by co-electrospinning and comprises a first nanofiber and a second nanofiber entangled together. The first nanofiber contains polypropylene and a hydrophobic polymer, and the second nanofiber is polyacrylonitrile. The hydrophobic polymer is at least one selected from polystyrene, polyvinylidene fluoride, and polymethyl methacrylate. The nanofiber membrane of this invention, composed of a hydrophobic first nanofiber and a hydrophilic second nanofiber, forms a dual-channel structure, allowing water and oil to permeate through their respective channels. This effectively prevents the oil phase from blocking the channels, achieving ultra-stable separation of emulsified oil-water mixtures.

[0029] In the nanofiber membrane of the present invention, in order to improve the efficiency of emulsified oil-water separation, the pore size of the nanofiber membrane is preferably 1-10 μm, more preferably 3-8 μm; the porosity is preferably 85%-95%, more preferably 88%-93%.

[0030] In the nanofiber membrane of the present invention, in order to ensure that water and oil permeate through their respective channels, the mass ratio of the first nanofiber to the second nanofiber is preferably (0.8-1.3):1, more preferably (0.9-1.2):1.

[0031] In the nanofiber membrane of the present invention, in order to increase the hydrophobicity of the first nanofiber, the hydrophobic polymer is preferably polystyrene. The mass ratio of the polypropylene to the hydrophobic polymer is preferably 1:(0.2-5), more preferably 1:(0.375-0.5), and specifically, for example, 8:3, 1:0.4, 9:4 or 1:0.5.

[0032] In some embodiments, the nanofiber membrane of the present invention is prepared by co-electrospinning and comprises a first nanofiber and a second nanofiber entangled with each other, wherein the first nanofiber contains polypropylene and polystyrene, and the second nanofiber is polyacrylonitrile. The pore size of the nanofiber membrane is 1-10 μm, and the porosity is 85%-95%. The mass ratio of the first nanofiber to the second nanofiber is (0.8-1.3):1. The mass ratio of the polypropylene to the polystyrene is 1:(0.2-5).

[0033] In other embodiments, the nanofiber membrane of the present invention is prepared by co-electrospinning and comprises a first nanofiber and a second nanofiber entangled with each other, wherein the first nanofiber contains polypropylene and polyvinylidene fluoride, and the second nanofiber is polyacrylonitrile. The pore size of the nanofiber membrane is 3-8 μm, and the porosity is 88%-93%. The mass ratio of the first nanofiber to the second nanofiber is (0.9-1.2):1. The mass ratio of the polypropylene to the polyvinylidene fluoride is 1:(0.375-5).

[0034] A second aspect of the present invention provides a method for preparing a nanofiber membrane, the method comprising the following steps:

[0035] (1) Mix the polypropylene solution and the hydrophobic polymer solution to obtain a mixed solution;

[0036] (2) The mixed solution and the polyacrylonitrile solution were electrospun together to obtain a nanofiber membrane;

[0037] The hydrophobic polymer in the hydrophobic polymer solution is at least one of polystyrene, polyvinylidene fluoride, and polymethyl methacrylate.

[0038] According to the method described in this invention, a polypropylene solution and a hydrophobic polymer solution form hydrophobic first nanofibers, and a polyacrylonitrile solution forms hydrophilic second nanofibers. The first and second nanofibers are intertwined to form a nanofiber membrane, allowing water and oil to permeate through their respective channels, effectively preventing the blockage of channels by the intercepting phase, and achieving ultra-stable separation of emulsified oil-water mixtures.

[0039] In the method described in this invention, the solvent in the polypropylene solution can be a commonly used organic solvent in the art, specifically, at least one selected from n-heptane, dichloromethane, trichloromethane, carbon tetrachloride, xylene, tetrahydrofuran, and cyclohexane. To ensure the formation of nanofibers, the solvent in the polypropylene solution is preferably n-heptane, dichloromethane, trichloromethane, or cyclohexane. The concentration of the polypropylene solution can be 1-50 wt%, preferably 8-10 wt%, specifically, for example, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%.

[0040] In the method described in this invention, the preparation process of the polypropylene solution may include: mixing polypropylene and an organic solvent and stirring by ultrasound. The stirring time may be 10-15 hours, preferably 11-13 hours.

[0041] In the method described in this invention, the solvent in the hydrophobic polymer solution can be a commonly used organic solvent in the art, specifically, at least one selected from dimethylformamide, acetone, toluene, dimethylacetamide, and dimethyl sulfoxide, preferably dimethylformamide. The concentration of the hydrophobic polymer solution can be 1-50 wt%, preferably 8-10 wt%, specifically, for example, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%. To improve the hydrophobicity of the nanofiber membrane, the hydrophobic polymer in the hydrophobic polymer solution is preferably polystyrene.

[0042] In the method described in this invention, the preparation process of the hydrophobic polymer solution may include: mixing the hydrophobic polymer and an organic solvent and stirring by ultrasound. The stirring time may be 10-15 hours, preferably 11-13 hours.

[0043] In the method described in this invention, the mass ratio of the polypropylene to the hydrophobic polymer in the mixed solution can be 1:(0.2-5). To ensure the hydrophobicity of the nanofiber membrane, the mass ratio of the polypropylene to the hydrophobic polymer is preferably 1:(0.375-0.5), specifically, for example, 8:3, 1:0.4, 9:4, or 1:0.5.

[0044] In the method described in this invention, the solvent in the polyacrylonitrile solution can be a commonly used organic solvent in the art, specifically, for example, at least one of dimethylformamide, acetone, chloroform, and carbon tetrachloride, preferably dimethylformamide. The concentration of the polyacrylonitrile solution can be 1-50 wt%, preferably 8-10 wt%, specifically, for example, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%.

[0045] In the method described in this invention, the preparation process of the polyacrylonitrile solution may include: mixing polyacrylonitrile and an organic solvent and stirring by ultrasound. The stirring time may be 10-15 hours, preferably 11-13 hours.

[0046] In the method described in this invention, step (2) may include fixing the mixed solution and the polyacrylonitrile solution on both sides of the electrospinning receiving roller. The electrospinning conditions include: a rotational speed of 70-90 rpm, preferably 75-85 rpm; a distance from the needle tip to the receiving device of 12-18 cm, preferably 14-16 cm; a translational speed of 100-140 mm / min, preferably 110-130 mm / min; and a translational distance of 250-300 mm, preferably 260-280 mm. By adjusting the spray speed of the electrospinning solution, nanofiber membranes with different mass ratios can be obtained. The mass percentage of polyacrylonitrile in the nanofiber membrane is 45-55%.

[0047] In the method described in this invention, in order to improve the hydrophilicity of polyacrylonitrile, the method preferably further includes immersing the nanofiber membrane obtained in step (2) in a methanol solution of sodium hydroxide and placing it in a shaking incubator for reaction. The reaction conditions include: the rotation speed can be 100-150 rpm, preferably 110-130 rpm; the time can be 35-45 h, preferably 37-42 h.

[0048] In the method described in this invention, the method may further include washing and drying the nanofiber membrane after immersion in sodium hydroxide. The washing is performed by solvent exchange to remove any residual byproducts and amine molecules. The specific washing process may include: sequentially immersing the nanofiber membrane after immersion in sodium hydroxide in nitric acid, water, methanol, and n-hexane. The concentration of the nitric acid may be 0.8-1.2 mol / L. The nanofiber membrane is immersed in nitric acid for 0.8-1.2 h, in water for 5.5-6.5 h and repeated 3-4 times, in methanol for 1.8-2.2 h and repeated 3-4 times, and in n-hexane for 1.8-2.2 h and repeated 3-4 times. The drying conditions include: a temperature of 75-90°C, preferably 75-85°C; a vacuum of -0.08 to -0.1 MPa, preferably -0.09 to -0.1 MPa; and a drying time of 12-24 h, preferably 14-16 h. In this paper, vacuum degree is defined as atmospheric pressure minus absolute pressure.

[0049] In the method described in this invention, in order to further improve the hydrophilicity of polyacrylonitrile, the concentration of the methanol solution of sodium hydroxide is preferably 8-15 wt%, more preferably 8-12 wt%.

[0050] In some embodiments, the method for preparing the nanofiber membrane of the present invention includes the following steps:

[0051] (1) A polypropylene solution with a concentration of 1-50 wt% and a hydrophobic polymer solution with a concentration of 1-50 wt% are mixed and stirred by ultrasound for 10-15 h to obtain a mixed solution, wherein the mass ratio of the polypropylene to the hydrophobic polymer is 1:(0.2-5).

[0052] (2) The mixed solution and the polyacrylonitrile solution with a concentration of 1-50wt% are fixed on both sides of the electrostatic spinning receiving roller, the rotation speed is 70-90rpm, the distance from the needle tip to the receiving device is 12-18cm, the translation speed is 100-140mm / min, and the translation distance is 250-300mm, to obtain a nanofiber membrane.

[0053] (3) The nanofiber membrane obtained in step (2) is immersed in a methanol solution of sodium hydroxide with a concentration of 8-15 wt% and placed in a shaking incubator at a speed of 100-150 rpm for 35-45 h. The nanofiber membrane after being immersed in sodium hydroxide is then washed sequentially in nitric acid with a concentration of 0.8-1.2 mol / L for 0.8-1.2 h, in water for 5.5-6.5 h and repeated 3-4 times, in methanol for 1.8-2.2 h and repeated 3-4 times, and in n-hexane for 1.8-2.2 h and repeated 3-4 times. Finally, it is dried for 12-24 h at a temperature of 75-90℃ and a vacuum degree of -0.08 to -0.1 MPa.

[0054] The hydrophobic polymer in the hydrophobic polymer solution is at least one of polystyrene, polyvinylidene fluoride, and polymethyl methacrylate.

[0055] In other embodiments, the method for preparing the nanofiber membrane of the present invention includes the following steps:

[0056] (1) A polypropylene solution with a concentration of 8-10 wt% and a polystyrene solution with a concentration of 8-10 wt% are mixed and stirred by ultrasound for 11-13 hours to obtain a mixed solution, wherein the mass ratio of the polypropylene to the polystyrene is 1:(0.375-0.5).

[0057] (2) The mixed solution and the polyacrylonitrile solution with a concentration of 8-10wt% are fixed on both sides of the electrostatic spinning receiving roller, the rotation speed is 75-85rpm, the distance from the needle tip to the receiving device is 14-16cm, the translation speed is 110-130mm / min, and the translation distance is 260-280mm, to obtain a nanofiber membrane.

[0058] (3) The nanofiber membrane obtained in step (2) is immersed in a methanol solution of sodium hydroxide with a concentration of 8-12 wt% and placed in a shaking incubator to react at a speed of 110-130 rpm for 37-42 h. The nanofiber membrane after being immersed in sodium hydroxide is then washed sequentially by soaking in nitric acid with a concentration of 0.8-1.2 mol / L for 0.8-1.2 h, soaking in water for 5.5-6.5 h and repeating 3-4 times, soaking in methanol for 1.8-2.2 h and repeating 3-4 times, and soaking in n-hexane for 1.8-2.2 h and repeating 3-4 times. Finally, it is dried for 14-16 h at a temperature of 75-85℃ and a vacuum degree of -0.09 to -0.1 MPa.

[0059] A third aspect of this invention provides a nanofiber membrane prepared by the method described above. The nanofiber membrane of this invention, through the formation of dual channels, allows water and oil to permeate through their respective channels, effectively preventing the blockage of channels by the intercepting phase, and achieving high-throughput, ultra-stable, long-term separation of emulsified oil-water mixtures.

[0060] The fourth aspect of this invention provides the application of the aforementioned nanofiber membrane in emulsified oil-water separation. The nanofiber membrane described in this invention can improve the efficiency of emulsified oil-water separation, solving the problem of reduced flux and unstable use that cannot be addressed by existing technologies, and has broad application prospects in the field of oil-water separation.

[0061] The following examples further illustrate the nanofiber membrane, its preparation method, and its applications according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0062] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples are commercially available. In Examples 1-7 and Comparative Examples 1-4, atactic polypropylene and polyacrylonitrile were purchased from Sigma-Aldrich, polystyrene and sodium dodecyl sulfonate were purchased from Aladdin Biochemical Technology Co., Ltd., and sodium hydroxide, nitric acid, methanol, dimethylformamide, ethanol, n-hexane, chloroform, and isooctane were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0063] Example 1

[0064] (1) Dissolve 10g of random polypropylene in 90g of chloroform and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0065] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0066] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0067] Scanning electron microscope (SEM) images of the nanofiber membranes prepared according to this embodiment are shown below. Figure 1 As shown.

[0068] Example 2

[0069] (1) Dissolve 10g of random polypropylene in 90g of chloroform and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 8g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0070] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0071] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 15 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0072] Example 3

[0073] (1) Dissolve 9g of random polypropylene in 91g of dichloromethane and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 8g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0074] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0075] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0076] Example 4

[0077] (1) Dissolve 8g of random polypropylene in 92g of n-heptane and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 6g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0078] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0079] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0080] Example 5

[0081] (1) Dissolve 10g of random polypropylene in 90g of cyclohexane and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0082] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0083] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0084] Example 6

[0085] (1) Dissolve 1g of random polypropylene in 99g of chloroform and stir ultrasonically for 10h to form a polypropylene solution. Dissolve 1g of polystyrene in 99g of dimethylformamide and stir ultrasonically for 10h to form a polystyrene solution. Mix 50g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 10h to obtain a mixed solution.

[0086] (2) Dissolve 1g of polyacrylonitrile in 99g of dimethylformamide and ultrasonically stir for 10h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 75rpm, the distance from the needle tip to the receiving device is 14cm, the translation speed is 110mm / min, the translation distance is 260mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0087] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 8 wt% and placed in a shaking incubator to react at a speed of 110 rpm for 35 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 0.8 mol / L for 0.8 h, soaking in water for 5.5 h and repeating 4 times, soaking in methanol for 1.8 h and repeating 4 times, and soaking in n-hexane for 1.8 h and repeating 4 times. Finally, it was dried for 14 h at a temperature of 75 °C and a vacuum degree of -0.09 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0088] Example 7

[0089] (1) Dissolve 50g of random polypropylene in 50g of chloroform and stir ultrasonically for 13h to form a polypropylene solution. Dissolve 50g of polystyrene in 50g of dimethylformamide and stir ultrasonically for 13h to form a polystyrene solution. Mix 10g of polypropylene solution and 50g of polystyrene solution and stir ultrasonically for 13h to obtain a mixed solution.

[0090] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 13h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 85rpm, the distance from the needle tip to the receiving device is 16cm, the translation speed is 130mm / min, the translation distance is 280mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.4kV, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0091] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 8 wt% and placed in a shaking incubator to react at a speed of 130 rpm for 45 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.2 mol / L for 1.2 h, soaking in water for 6.5 h and repeating 3 times, soaking in methanol for 2.2 h and repeating 3 times, and soaking in n-hexane for 2.2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 85 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0092] Comparative Example 1

[0093] (1) Dissolve 10g of random polypropylene in 90g of chloroform and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0094] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +14kV, the spray speed of the polyacrylonitrile solution is 0.023mm / min, and the voltage of the polyacrylonitrile solution is -8kV to obtain a nanofiber membrane.

[0095] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0096] Comparative Example 2

[0097] (1) Dissolve 10g of random polypropylene in 90g of cyclohexane and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0098] (2) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution and the mixed solution obtained in step (1) on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the mixed solution is 0.115mm / min, the voltage of the mixed solution is +15.7kV, the spray speed of the polyacrylonitrile solution is 0.059mm / min, and the voltage of the polyacrylonitrile solution is -17kV to obtain a nanofiber membrane.

[0099] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa. The mass ratio of polyacrylonitrile in the nanofiber membrane was recorded in Table 1.

[0100] Comparative Example 3

[0101] (1) Dissolve 10g of random polypropylene in 90g of chloroform and stir ultrasonically for 12h to form a polypropylene solution. Dissolve 10g of polystyrene in 90g of dimethylformamide and stir ultrasonically for 12h to form a polystyrene solution. Mix 20g of polypropylene solution and 10g of polystyrene solution and stir ultrasonically for 12h to obtain a mixed solution.

[0102] (2) Fix the mixed solution obtained in step (1) on the electrostatic spinning receiving roller with a rotation speed of 80 rpm, a distance of 15 cm from the needle tip to the receiving device, a translation speed of 120 mm / min, a translation distance of 270 mm, a spray speed of 0.115 mm / min, and a voltage of +15.4 kV to obtain a nanofiber membrane.

[0103] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa.

[0104] Comparative Example 4

[0105] (1) Dissolve 10g of polyacrylonitrile in 90g of dimethylformamide and ultrasonically stir for 12h to form a polyacrylonitrile solution. Fix the polyacrylonitrile solution on both sides of the electrostatic spinning receiving roller. The rotation speed is 80rpm, the distance from the needle tip to the receiving device is 15cm, the translation speed is 120mm / min, the translation distance is 270mm, the spray speed of the polyacrylonitrile solution is 0.012mm / min, and the voltage of the polyacrylonitrile solution is -5.1kV to obtain a nanofiber membrane.

[0106] (3) The nanofiber membrane obtained in step (2) was immersed in a methanol solution of sodium hydroxide with a concentration of 10 wt% and placed in a shaking incubator to react at a speed of 120 rpm for 40 h. The nanofiber membrane after being immersed in sodium hydroxide was washed sequentially by soaking in nitric acid with a concentration of 1.0 mol / L for 1 h, soaking in water for 6 h and repeating 3 times, soaking in methanol for 2 h and repeating 3 times, and soaking in n-hexane for 2 h and repeating 3 times. Finally, it was dried for 16 h at a temperature of 80 °C and a vacuum degree of -0.1 MPa.

[0107] Test Example 1

[0108] The pore size and porosity of the nanofiber membranes prepared according to Examples 1-7 and Comparative Examples 1-4 were tested and recorded in Table 1. The test method was in accordance with the national standard GB / T 42697-2023 "Test Method for Porosity of Nonwoven Fabrics".

[0109] Test Example 2

[0110] The separation efficiency of the nanofiber membranes prepared according to Examples 1-7 and Comparative Examples 1-4 in emulsified oil-water separation after 1 hour was tested and recorded in Table 1. The test method is as follows:

[0111] An emulsion with an oil content of 1% by volume was prepared by dissolving the anionic surfactant sodium dodecyl sulfate (SLS) in 2000 mL of deionized water to form a 0.1 g / L sodium dodecyl sulfate aqueous solution. Then, 20 mL of isooctane was added, and the mixture was ultrasonically stirred for 6 hours to obtain the final mixture. Emulsion separation experiments were performed using a cross-flow apparatus (purchased from Shandong Bona Biotechnology Group Co., Ltd.) (diameter 2.8 cm, height 1 cm), with an effective membrane area of ​​6.15 cm². 2 The pressure was 0.5 bar. Before separation, the nanofiber membrane was pre-wetted with a 10 wt% ethanol aqueous solution, then installed in a cross-flow apparatus. A peristaltic pump was used to perform emulsion separation of the resulting mixture under a certain pressure, yielding a layered aqueous and oil phase (cross-flow velocity 2.65 L / m). 2 / s). Continuous stirring during the separation process ensures the stability of the emulsion, and timely replenishment of the emulsion ensures a constant feed rate. The oil content in the aqueous phase (filtrate) is determined by infrared spectrophotometry, with specific methods referring to the national standard HJ637-2018 "Determination of Petroleum and Animal Oils in Water".

[0112] Separation efficiency is calculated using the following formula:

[0113]

[0114] C1 and C2 represent the oil content in the emulsion and aqueous phase (filtrate), respectively.

[0115] The mass percentage M of polyacrylonitrile in the nanofiber membranes prepared in Examples 1-7 and Comparative Examples 1-4 was calculated using the following formula and recorded in Table 1:

[0116]

[0117] Q X =π·r n 2 ·v X ·t

[0118] Where ρ1 and ρ2 are the densities of the polyacrylonitrile solution and the mixed solution of polypropylene and polystyrene, respectively; m1 and m2 are the mass fractions of the polyacrylonitrile solution and the mixed solution of polypropylene and polystyrene, respectively; and r... n v is the radius of the needle tip. x t represents the injection speed, and t represents the spinning time.

[0119] Table 1

[0120]

[0121] As can be seen from the results in Table 1, the embodiments using the nanofiber membrane described in this invention have high emulsification oil-water separation efficiency.

[0122] according to Figure 1 It can be seen that the hydrophilic and hydrophobic fibers in the prepared nanofiber membrane are intertwined to form an oil-water dual channel.

[0123] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A nanofiber membrane, characterized in that, The nanofiber membrane is prepared by co-electrospinning and includes a first nanofiber and a second nanofiber entangled with each other. The first nanofiber contains polypropylene and a hydrophobic polymer, and the second nanofiber is polyacrylonitrile. The hydrophobic polymer is at least one of polystyrene, polyvinylidene fluoride and polymethyl methacrylate.

2. The nanofiber membrane according to claim 1, characterized in that, The nanofiber membrane has a pore size of 1-10 μm and a porosity of 85%-95%.

3. The nanofiber membrane according to claim 1 or 2, characterized in that, The mass ratio of the first nanofiber to the second nanofiber is (0.8-1.3):1; Preferably, the mass ratio of the polypropylene to the hydrophobic polymer is 1:(0.2-5).

4. A method for preparing a nanofiber membrane, characterized in that, The method includes the following steps: (1) Mix the polypropylene solution and the hydrophobic polymer solution to obtain a mixed solution; (2) The mixed solution and the polyacrylonitrile solution were electrospun together to obtain a nanofiber membrane; The hydrophobic polymer in the hydrophobic polymer solution is at least one of polystyrene, polyvinylidene fluoride, and polymethyl methacrylate.

5. The method according to claim 4, characterized in that, The solvent in the polypropylene solution is at least one selected from n-heptane, dichloromethane, trichloromethane, carbon tetrachloride, xylene, tetrahydrofuran, and cyclohexane. Preferably, the concentration of the polypropylene solution is 1-50 wt%.

6. The method according to claim 4 or 5, characterized in that, The solvent in the hydrophobic polymer solution is at least one of dimethylformamide, acetone, toluene, dimethylacetamide, and dimethyl sulfoxide; Preferably, the concentration of the hydrophobic polymer solution is 1-50 wt%.

7. The method according to any one of claims 4-6, characterized in that, In the mixed solution, the mass ratio of the polypropylene to the hydrophobic polymer is 1:(0.2-5).

8. The method according to any one of claims 4-7, characterized in that, The solvent in the polypropylene solution is at least one of dimethylformamide, acetone, chloroform, and carbon tetrachloride; Preferably, the concentration of the polyacrylonitrile solution is 1-10 wt%.

9. The method according to any one of claims 4-8, characterized in that, The method also includes immersing the nanofiber membrane obtained in step (2) into a methanol solution of sodium hydroxide; Preferably, the concentration of the sodium hydroxide methanol solution is 8-15 wt%.

10. A nanofiber membrane prepared by the method according to any one of claims 4-9.

11. The application of the nanofiber membrane according to any one of claims 1-3 and 10 in emulsified oil-water separation.

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