A method for preparing a polyamide membrane with a hierarchical pore structure mediated by a protein fiber network

Abstract

A method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network, which belongs to the field of seawater desalination and wastewater pollution control. The purpose of the present invention is to solve the problem that when the existing method is used to prepare a polyamide membrane, the porosity of the base membrane is low and the distribution of amine monomers is uneven, which affects the integrity and separation performance of the polyamide layer. Method: 1. Preparation of protein fibers; 2. Quenching and dialysis; 3. Loading the protein fiber network on the ultrafiltration membrane; 4. Preparing an aqueous phase solution and an organic phase solution; 5. Interfacial polymerization to obtain a polyamide membrane with a multi-level pore structure mediated by a protein fiber network. The polyamide membrane prepared by the present invention greatly improves the water flux while ensuring a high salt rejection rate, and the introduction of the protein fiber network also enhances the mechanical strength and anti-pollution ability of the membrane. The present invention can obtain a polyamide membrane with a multi-level pore structure mediated by a protein fiber network.

Description

Technical Field

[0001] The invention belongs to the field of seawater desalination and wastewater pollution control. Background Art

[0002] Membrane separation technology plays a vital role in the field of water treatment due to its high efficiency and environmentally friendly characteristics. Nanofiltration membranes, as the core component of this technology, have shown broad application potential in water purification, seawater desalination and wastewater treatment due to their unique pore size selectivity and low operating pressure. They effectively remove soluble organic matter, hardness components and specific ions in water through precise screening, while maintaining a high water flux. The preparation technology of nanofiltration membranes continues to advance, among which interfacial polymerization has become the mainstream due to its strong controllability and ease of operation. By forming an ultra-thin polyamide selective layer on the porous base membrane, efficient retention of the target substance is achieved. However, the traditional interfacial polymerization method still faces challenges in the preparation process, such as insufficient hydrophilicity and low porosity of the base membrane, resulting in uneven distribution of amine monomers, affecting the integrity and separation performance of the polyamide layer, and limiting the further improvement of the separation efficiency and selectivity of the nanofiltration membrane. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that when preparing polyamide membranes by existing methods, the porosity of the base membrane is low and the amine monomer is unevenly distributed, which affects the integrity and separation performance of the polyamide layer. The present invention provides a method for preparing a polyamide membrane with a multi-level porous structure mediated by a protein fiber network.

[0004] In order to overcome the defects of the prior art, the present invention proposes an innovative "method for preparing a polyamide membrane with a multi-level porous structure mediated by a protein fiber network". This method significantly improves the hydrophilicity and porosity of the base membrane by constructing a protein fiber network on the porous base membrane, provides a uniform reaction interface for interfacial polymerization, thereby promoting the uniform formation of the polyamide layer and effectively avoiding the generation of defects. By precisely controlling the polymerization conditions, the prepared nanofiltration membrane exhibits excellent separation performance, including higher water flux and better salt retention rate. In addition, the introduction of the protein fiber network also enhances the mechanical strength and anti-pollution ability of the membrane, providing a guarantee for the long-term stable operation of the nanofiltration membrane. This innovative method not only improves the performance of the nanofiltration membrane, but also provides a new direction for the development of water treatment technology, and is expected to be more widely used in fields such as water purification and sewage treatment.

[0005] The present invention optimizes the interfacial polymerization process through a protein fiber network, utilizes the high affinity of the protein fiber network with amine molecules, effectively slows down the diffusion rate of amine monomers, and achieves precise control of the polymerization reaction to prepare a nanofiltration membrane with a thinner and more uniform polyamide layer.

[0006] A method for preparing a polyamide membrane with a multi-level porous structure mediated by a protein fiber network is specifically completed by the following steps:

[0007] 1. Preparation of protein fiber:

[0008] The protein monomer is dissolved in ultrapure water to obtain a protein solution; the protein solution is placed in a refrigerator for a period of time, and after being taken out, the pH value thereof is adjusted to acidity using hydrochloric acid, and then heated and stirred in an oil bath for a period of time to obtain protein fibrils;

[0009] 2. Quenching and dialysis:

[0010] The protein fibrils are taken out from the oil bath, and the container containing the protein fibrils is immediately placed in an ice bath to quickly quench the reaction and prevent further assembly. After cooling to room temperature, the container is dialyzed in a refrigerator using water as a dialyzing fluid for a period of time to obtain a protein fiber solution;

[0011] 3. Loading protein fiber network on ultrafiltration membrane:

[0012] The ultrafiltration membrane is rinsed with deionized water for multiple times and then immersed in anhydrous ethanol. Before use, the ultrafiltration membrane is taken out from the anhydrous ethanol and immersed in deionized water. The protein fiber solution is poured onto the ultrafiltration membrane taken out from the deionized water, and then vacuum filtered to obtain an ultrafiltration membrane loaded with a protein fiber network.

[0013] 4. Prepare aqueous solution and organic solution:

[0014] ①, dissolving piperazine in water to obtain an aqueous solution;

[0015] ②, dissolve trimesoyl chloride in an organic solvent, stir evenly and let stand for a while to obtain an organic phase solution;

[0016] 5. Interface polymerization:

[0017] The ultrafiltration membrane loaded with the protein fiber network is immersed in the aqueous solution for a period of time and then taken out, the wetted ultrafiltration membrane is suspended, and after no water droplets can be observed on the surface, the wetted ultrafiltration membrane is immersed in the organic phase solution and then taken out after a period of time to obtain a multi-level pore structure polyamide membrane mediated by the protein fiber network, which is stored in ultrapure water.

[0018] Principle of the present invention:

[0019] 1. The present invention uses protein fibers to construct a network structure with high porosity on the base membrane, which significantly improves the porosity of the base membrane. The high affinity between the protein fiber network and the amine molecules enables the modified base membrane to efficiently adsorb and store the amine molecules. At the same time, during the interfacial polymerization process, this network structure effectively slows down the release rate of piperazine molecules. This controlled release strategy not only improves the uniformity of the polymerization reaction, but also significantly reduces the thickness of the polyamide layer. Compared with conventional nanofiltration membranes, the nanofiltration membrane prepared by the present invention has a significantly improved water flux while maintaining high salt retention performance.

[0020] 2. The nanofiltration membrane prepared by the present invention adopts a unique multi-level pore structure design, in which the first-level pore structure originates from the protein fiber network itself, providing a large number of fluid transmission channels; the second-level pore structure is a more delicate pore structure formed by the reaction of piperazine (PIP) and trimesoyl chloride (TMC) in the pores of the protein fiber network; the third-level pore structure is the dense polyamide selection layer finally formed, which has precise molecular screening capabilities. The design of this multi-level pore structure not only improves the water flux of the membrane, but also enhances the selectivity of the membrane, thereby realizing efficient separation of solutes of different sizes.

[0021] 3. The nanofiltration membrane prepared by the present invention has not only significant improvements in water flux and selectivity, but also additional structural stability and antibacterial properties. The introduction of the protein fiber network not only enhances the mechanical strength of the membrane, but also gives the membrane material itself good antibacterial properties because of the use of lysozyme with antibacterial properties in the preparation process. This antibacterial property helps to reduce biological contamination of the membrane during use, prolongs the service life of the membrane, and reduces the need for chemical cleaning. Combining these characteristics, the nanofiltration membrane prepared by the present invention not only improves the water treatment efficiency, but also provides a guarantee for the long-term stable operation of the membrane.

[0022] The present invention has the following effects:

[0023] 1. Compared with the nanofiltration membrane prepared by the traditional method, the water flux of the protein fiber network-mediated multi-level pore structure polyamide membrane prepared by the present invention is increased from 17.23Lm -2 h -1 bar -1 Increased to 30.4Lm -2 h -1 bar -1 , achieving a significant increase in water flux while maintaining the high retention performance of the membrane.

[0024] 2. After the protein fiber network is introduced into the base film, the polyamide layer formed by interfacial polymerization shows a smaller thickness and higher roughness. The formation of this structure is due to the multi-level pore characteristics of the protein fiber network, which provides more active sites for interfacial polymerization and promotes a more uniform polymerization reaction, thereby forming a more uniform polyamide layer. .

[0025] 3. The preparation method used in the present invention provides the membrane with additional structural stability and anti-fouling performance by introducing a protein fiber network, which is of great significance for improving the long-term operation stability of the membrane and reducing the cleaning frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The atomic force microscope images of the protein fibers prepared in Example 1, Example 6 and Example 7, the inset in the upper right corner is a height change diagram of the underlined portion, in which 1 is a protein fibril heated for 8 hours, 2 is 10 hours, and 3 is 12 hours;

[0027] Figure 2 To measure the fiber diameter using Nanoscope Analysis software, 100 fibers were randomly selected for measurement and a distribution graph was drawn. The numbers marked in the graph are the average values ​​of the diameters;

[0028] Figure 3 Fourier transform infrared spectra of the ultrafiltration membrane loaded with protein fiber network, polyethersulfone ultrafiltration membrane and lysozyme powder prepared after performing step 3 in Example 1 and Example 2;

[0029] Figure 4 The UV spectra of the protein fibers prepared in Example 1, Example 6 and Example 7 and the test after adding piperazine, both of which were measured after dilution with water, and the interaction between the protein fibers and piperazine was characterized by the peak change at a wavelength of 260-300nm. The dotted line is the sample with only protein fibers, and the solid line is the spectrum after adding piperazine. The concentration of the protein fibers used in the diluted test is 0.02wt%, and the concentration of piperazine is 0.04wt%;

[0030] Figure 5 The water flux and salt rejection of the membranes prepared in Examples 1-5 were tested. The water flux was measured at 0.4 MPa after a pre-pressure of 0.5 MPa for 1 h, and the salt rejection was measured using a 1000 ppm sodium sulfate solution. DETAILED DESCRIPTION

[0031] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0032] Specific implementation method 1: This implementation method is a method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network, which is specifically completed by the following steps:

[0033] 1. Preparation of protein fiber:

[0034] The protein monomer is dissolved in ultrapure water to obtain a protein solution; the protein solution is placed in a refrigerator for a period of time, and after being taken out, the pH value thereof is adjusted to acidity using hydrochloric acid, and then heated and stirred in an oil bath for a period of time to obtain protein fibrils;

[0035] 2. Quenching and dialysis:

[0036] The protein fibrils are taken out from the oil bath, and the container containing the protein fibrils is immediately placed in an ice bath to quickly quench the reaction and prevent further assembly. After cooling to room temperature, the container is dialyzed in a refrigerator using water as a dialyzing fluid for a period of time to obtain a protein fiber solution;

[0037] 3. Loading protein fiber network on ultrafiltration membrane:

[0038] The ultrafiltration membrane is rinsed with deionized water for multiple times and then immersed in anhydrous ethanol. Before use, the ultrafiltration membrane is taken out from the anhydrous ethanol and immersed in deionized water. The protein fiber solution is poured onto the ultrafiltration membrane taken out from the deionized water, and then vacuum filtered to obtain an ultrafiltration membrane loaded with a protein fiber network.

[0039] 4. Prepare aqueous solution and organic solution:

[0040] ①, dissolving piperazine in water to obtain an aqueous solution;

[0041] ②, dissolve trimesoyl chloride in an organic solvent, stir evenly and let stand for a while to obtain an organic phase solution;

[0042] 5. Interface polymerization:

[0043] The ultrafiltration membrane loaded with the protein fiber network is immersed in the aqueous solution for a period of time and then taken out, the wetted ultrafiltration membrane is suspended, and after no water droplets can be observed on the surface, the wetted ultrafiltration membrane is immersed in the organic phase solution and then taken out after a period of time to obtain a multi-level pore structure polyamide membrane mediated by the protein fiber network, which is stored in ultrapure water.

[0044] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the protein monomer described in step 1 is β-lactoglobulin, lysozyme or bovine serum albumin; the mass ratio of the protein monomer described in step 1 to ultrapure water is (0.2-0.4):(20-30). The other steps are the same as those in specific embodiment 1.

[0045] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: the refrigeration temperature in step 1 is 3°C to 4°C, and the refrigeration time is 24h to 32h; in step 1, hydrochloric acid with a mass fraction of 1mol / L to 5mol / L is used to adjust the pH value of the protein solution to 2 to 3. The other steps are the same as those in specific implementation method 1 or 2.

[0046] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the temperature of the oil bath heating and stirring in step 1 is 80°C to 90°C, the stirring speed is 40rpm to 60rpm, and the time is 8h to 24h. The other steps are the same as those of specific embodiments 1 to 3.

[0047] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the dialysis time in step 2 is 20h to 30h, and the dialysate does not need to be replaced during the dialysis period; the mass fraction of the protein fiber solution in step 2 is 0.05% to 0.2%. The other steps are the same as those in specific embodiments 1 to 4.

[0048] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that: in step 3, the ultrafiltration membrane is rinsed with deionized water for 3 to 4 times; in step 3, the ultrafiltration membrane is immersed in anhydrous ethanol for more than 24 hours. The other steps are the same as those of specific implementation methods 1 to 5.

[0049] Specific embodiment 7: The difference between this embodiment and any one of the specific embodiments 1 to 6 is that the ultrafiltration membrane described in step 3 is a polyethersulfone membrane, a polysulfone membrane, a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a polyvinylidene fluoride membrane or a cellulose acetate membrane; the volume ratio of the protein fiber solution described in step 3 to the surface area of ​​the ultrafiltration membrane is (10 mL to 40 mL): (20 cm 2 ~30cm 2 ). The other steps are the same as those in Specific Embodiments 1 to 6.

[0050] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the mass fraction of the aqueous solution in step 4 ① is 0.1% to 0.3%; the mass fraction of trimesoyl chloride in the organic solution in step 4 ② is 0.1% to 0.5%. The other steps are the same as those in specific embodiments 1 to 7.

[0051] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the standing time in step 4 ② is 0.5h to 1h; the organic solvent in step 4 ② is Isopar-G or n-hexane. The other steps are the same as those in specific embodiments 1 to 8.

[0052] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: in step 5, the ultrafiltration membrane loaded with the protein fiber network is immersed in the aqueous solution for 5 min to 10 min; in step 5, the wetted ultrafiltration membrane is immersed in the organic solution for 30 s to 60 s. The other steps are the same as those of specific embodiments 1 to 9.

[0053] The following examples are used to verify the beneficial effects of the present invention:

[0054] Example 1: A method for preparing a polyamide membrane with a multi-level porous structure mediated by a protein fiber network is specifically completed by the following steps:

[0055] 1. Preparation of protein fiber:

[0056] ① Dissolve 0.2g lysozyme in 20g ultrapure water to obtain a protein solution; put the protein solution into a refrigerator at 4°C for 24h, take it out and adjust its pH value to 2 with 5mol / L hydrochloric acid, then heat and stir in an oil bath for a period of time to obtain protein fibrils;

[0057] The temperature of the oil bath heating and stirring in step 1 is 90°C, the stirring speed is 60 rpm, and the time is 10 h;

[0058] 2. Quenching and dialysis:

[0059] The protein fibrils were taken out from the oil bath, and the container containing the protein fibrils was immediately placed in an ice bath to quickly quench the reaction and prevent further assembly. After cooling to room temperature, water was used as a dialysate and dialyzed in a refrigerator for 24 hours without changing the dialysate to obtain a protein fiber solution.

[0060] The mass fraction of the protein fiber solution in step 2 is 0.1%;

[0061] 3. Loading protein fiber network on ultrafiltration membrane:

[0062] The ultrafiltration membrane was rinsed three times with deionized water and then immersed in anhydrous ethanol for 24 h. Before use, it was taken out of anhydrous ethanol and immersed in deionized water. 10 mL of protein fiber solution was poured into the membrane with a surface area of ​​20 cm taken out from deionized water. 2 The ultrafiltration membrane is then vacuum filtered to obtain an ultrafiltration membrane loaded with a protein fiber network;

[0063] The ultrafiltration membrane described in step 3 is a polyethersulfone membrane;

[0064] 4. Prepare aqueous solution and organic solution:

[0065] ①, dissolving piperazine (PIP) in water to obtain an aqueous solution;

[0066] The mass fraction of the aqueous solution described in step 4① is 0.1%;

[0067] ② Dissolve trimesoyl chloride (TMC) in an organic solvent, stir evenly and let stand for 1 hour to obtain an organic phase solution;

[0068] The organic solvent described in step 4② is Isopar-G;

[0069] 5. Interface polymerization:

[0070] The ultrafiltration membrane loaded with the protein fiber network was immersed in the aqueous solution for 10 minutes, the wetted ultrafiltration membrane was suspended, and after no water droplets could be observed on the surface, the wetted ultrafiltration membrane was immersed in the organic solution for 30 seconds and then taken out to obtain a multi-level pore structure polyamide membrane mediated by the protein fiber network, which was stored in ultrapure water.

[0071] Example 2: The difference between this example and Example 1 is that in step 3, 20 mL of protein fiber solution is poured into the deionized water with a surface area of ​​20 cm 2 The other steps and parameters are the same as those in Example 1.

[0072] Example 3: The difference between this example and Example 1 is that in step 3, 30 mL of protein fiber solution is poured into the deionized water with a surface area of ​​20 cm 2 The other steps and parameters are the same as those in Example 1.

[0073] Example 4: The difference between this example and Example 1 is that in step 3, 40 mL of protein fiber solution is poured into the deionized water with a surface area of ​​20 cm 2 The other steps and parameters are the same as those in Example 1.

[0074] Example 5: This example is different from Example 1 in that the loading of the protein fiber on the ultrafiltration membrane in step 3 is omitted, and the unmodified ultrafiltration membrane is directly used for interfacial polymerization. The other steps and parameters are the same as those in Example 1.

[0075] Example 6: This example is different from Example 1 in that the oil bath heating and stirring time in step 1 is 8 hours. The other steps and parameters are the same as those in Example 1.

[0076] Example 7: This example is different from Example 1 in that the oil bath heating and stirring time in step 1 is 12 hours. The other steps and parameters are the same as those in Example 1.

[0077] The membranes prepared in Examples 1 to 4 are mainly used to explore the effects of different protein fiber network thicknesses and densities on the preparation method of a polyamide membrane with a multi-level pore structure mediated by a protein fiber network. Example 5 is a polyamide nanofiltration membrane prepared without a protein fiber network, which is mainly used for comparison with a polyamide membrane with a multi-level pore structure mediated by a protein fiber network; Example 1, Example 6 and Example 7 are mainly used to explore the effects of different heating times on the protein fiber structure.

[0078] Figure 1 The atomic force microscope images of the protein fibers prepared in Example 1, Example 6 and Example 7, the inset in the upper right corner is a height change diagram of the underlined portion, in which 1 is a protein fibril heated for 8 hours, 2 is 10 hours, and 3 is 12 hours;

[0079] Depend on Figure 1 It can be seen that the prepared protein fibrils can be clearly observed, in the form of linear fibers with a length of about several microns. From the inset diagram, it can be seen that with the increase of heating time, the height of the fiber gradually increases, which is about 2.8nm after 8h heating time, about 3.1nm after 10h heating, and about 3.3nm after 12h heating, indicating that the heating time has a certain effect on the fiber size. Different fiber networks can be prepared by controlling the heating time to prepare a multi-level porous structure polyamide membrane mediated by a protein fiber network.

[0080] In order to more accurately determine the diameter of amyloid fibers, the fiber diameter in the AFM image was measured using Nanoscope Analysis software. 100 fibers were randomly selected for measurement and a distribution diagram was drawn. The numbers marked in the diagram are the average diameters.

[0081] Figure 2 To measure the fiber diameter using Nanoscope Analysis software, 100 fibers were randomly selected for measurement and a distribution graph was drawn. The numbers marked in the graph are the average values ​​of the diameters;

[0082] Depend on Figure 2 It can be seen that: with the extension of heating time, the diameter distribution of protein fibers changes from scattered to more concentrated, indicating that there are amyloid fibers of various sizes when the time is short, and with the increase of heating time, the size of protein fibers increases while gradually becoming more uniform. As the heating time is extended from 8h to 10h, and then to 12h, the diameter increases from 9.38±2.04nm to 9.77±1.55nm, and then to 10.94±2.43nm.

[0083] The protein fiber-loaded ultrafiltration membrane, polyethersulfone ultrafiltration membrane, and lysozyme powder prepared after step 3 in Example 1 and Example 2 were subjected to Fourier transform infrared spectra; and the polyethersulfone ultrafiltration membrane and lysozyme powder were subjected to infrared testing to obtain four Fourier transform infrared spectra as shown in FIG. Figure 3 As shown;

[0084] Figure 3 Fourier transform infrared spectra of the ultrafiltration membrane loaded with protein fiber network, polyethersulfone ultrafiltration membrane and lysozyme powder prepared after performing step 3 in Example 1 and Example 2;

[0085] Depend on Figure 3 It can be seen that: 1650cm -1 The peak at 2960cm-1 gradually becomes stronger with the increase of protein fiber deposition volume, which is caused by the C=O stretching vibration of the peptide bond in the protein; -1 The peak at 1540cm may be related to the aliphatic part of the protein; -1 The peak at 3300 cm is caused by the peptide bonds in the protein (NH bending and CN stretching vibration); -1 The broad band centered on , involving other groups in lysozyme (such as O—H groups), demonstrated the successful loading of the protein fiber network on the ultrafiltration membrane.

[0086] Figure 4 The UV spectra of the protein fibers prepared in Example 1, Example 6 and Example 7 and the test after adding piperazine, both of which were measured after dilution with water, and the interaction between the protein fibers and piperazine was characterized by the peak change at a wavelength of 260-300nm. The dotted line is the sample with only protein fibers, and the solid line is the spectrum after adding piperazine. The concentration of the protein fibers used in the diluted test is 0.02wt%, and the concentration of piperazine is 0.04wt%;

[0087] from Figure 4 It can be seen that: since the ultraviolet spectrum peak of piperazine is mainly distributed at 200-250nm, in order to more accurately illustrate the interaction between piperazine and protein, the wavelength of 260-300nm where there is no piperazine peak distribution is selected for analysis. It can be seen that after adding piperazine (solid line in the figure), the peak value of the protein fiber has increased significantly, indicating that there is an interaction between piperazine and protein, and with the increase of heating time during preparation, the interaction between protein fiber and piperazine gradually increases.

[0088] Figure 5 The water flux and salt rejection of the protein fiber network-mediated hierarchical pore structure polyamide membrane prepared in Examples 1-4 (corresponding to 10-40 on the horizontal axis) are compared with the original polyamide membrane without the protein fiber network subjected to interfacial polymerization (corresponding to 0 on the horizontal axis);

[0089] from Figure 5It can be seen that with the increase of the loading amount of protein fiber on the ultrafiltration membrane, the water flux of the polyamide nanofiltration membrane prepared on this basis gradually increases, which can be attributed to the fact that the protein fiber network structure increases the roughness of the polyamide membrane and provides richer porosity; while the salt rejection rate decreases when the filtration volume is 30-40mL, which may be caused by the thicker network structure that makes the formed polyamide membrane defective. Therefore, the filtration volume of 20mL is selected as the optimal condition, at which time the water flux increases from 17.23Lm -2 h -1 bar -1 Increased to 30.4Lm -2 h -1 bar -1 , achieving a significant increase in water flux while maintaining the high retention performance of the membrane.

Claims

1. A method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of protein fiber: The protein monomer is dissolved in ultrapure water to obtain a protein solution; the protein solution is placed in a refrigerator for a period of time, and after being taken out, the pH value thereof is adjusted to acidity using hydrochloric acid, and then heated and stirred in an oil bath for a period of time to obtain protein fibrils; The protein monomer in step 1 is β-lactoglobulin, lysozyme or bovine serum albumin; The mass ratio of the protein monomer to ultrapure water described in step 1 is (0.2-0.4):(20-30); 2. Quenching and dialysis: The protein fibrils are taken out from the oil bath, and the container containing the protein fibrils is immediately placed in an ice bath to quickly quench the reaction and prevent further assembly. After cooling to room temperature, the container is dialyzed in a refrigerator using water as a dialyzing fluid for a period of time to obtain a protein fiber solution; 3. Loading protein fiber network on ultrafiltration membrane: The ultrafiltration membrane is rinsed with deionized water for multiple times and then immersed in anhydrous ethanol. Before use, the ultrafiltration membrane is taken out from the anhydrous ethanol and immersed in deionized water. The protein fiber solution is poured onto the ultrafiltration membrane taken out from the deionized water, and then vacuum filtered to obtain an ultrafiltration membrane loaded with a protein fiber network. The ratio of the volume of the protein fiber solution described in step 3 to the surface area of ​​the ultrafiltration membrane is (10 mL to 40 mL): (20 cm 2 ~30cm 2 ); 4. Prepare aqueous solution and organic solution: ①, dissolving piperazine in water to obtain an aqueous solution; ②, dissolve trimesoyl chloride in an organic solvent, stir evenly and let stand for a while to obtain an organic phase solution; 5. Interface polymerization: The ultrafiltration membrane loaded with the protein fiber network is immersed in the aqueous solution for a period of time and then taken out, the wetted ultrafiltration membrane is suspended, and after no water droplets can be observed on the surface, the wetted ultrafiltration membrane is immersed in the organic phase solution and then taken out after a period of time to obtain a multi-level pore structure polyamide membrane mediated by the protein fiber network, which is stored in ultrapure water.

2. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The refrigeration temperature in step 1 is 3°C to 4°C, and the refrigeration time is 24h to 32h; in step 1, the pH value of the protein solution is adjusted to 2 to 3 using hydrochloric acid with a mass fraction of 1 mol / L to 5 mol / L.

3. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The temperature of the oil bath heating and stirring in step 1 is 80° C. to 90° C., the stirring speed is 40 rpm to 60 rpm, and the time is 8 h to 24 h.

4. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The dialysis time in step 2 is 20 hours to 30 hours, during which the dialysis solution does not need to be replaced; the mass fraction of the protein fiber solution in step 2 is 0.05% to 0.2%.

5. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that In step 3, the ultrafiltration membrane is rinsed with deionized water for 3 to 4 times; in step 3, the ultrafiltration membrane is immersed in anhydrous ethanol for more than 24 hours.

6. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The ultrafiltration membrane described in step three is a polyethersulfone membrane, a polysulfone membrane, a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a polyvinylidene fluoride membrane or a cellulose acetate membrane.

7. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The mass fraction of the aqueous phase solution described in step 4① is 0.1% to 0.3%; the mass fraction of trimesoyl chloride in the organic phase solution described in step 4② is 0.1% to 0.5%.

8. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that The standing time in step 4 ② is 0.5h to 1h; the organic solvent in step 4 ② is Isopar-G or n-hexane.

9. The method for preparing a polyamide membrane with a multi-level pore structure mediated by a protein fiber network according to claim 1, characterized in that In step 5, the ultrafiltration membrane loaded with the protein fiber network is immersed in the aqueous solution for 5 minutes to 10 minutes; in step 5, the wetted ultrafiltration membrane is immersed in the organic solution for 30 seconds to 60 seconds.

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