Anti-fouling polyether sulfone ultrafiltration membrane and preparation method thereof

Abstract

The application discloses an anti-pollution polyether sulfone ultrafiltration membrane and a preparation method thereof, and relates to the technical field of ultrafiltration membrane preparation.The ultrafiltration membrane comprises a polyester non-woven fabric support layer and a porous functional membrane layer arranged on the surface of the polyester non-woven fabric support layer, the porous functional membrane layer is a porous membrane layer formed by blending polyether sulfone and end group sulfonated polyether sulfone, the chemical formula of the end group sulfonated polyether sulfone is shown in structural general formula (I), wherein the molecular weight of the end group sulfonated polyether sulfone is 25,000 g·mol ‑1 -55,000 g·mol ‑1 , and the mass ratio of the end group sulfonated polyether sulfone to the polyether sulfone is any value in the range of 0.05-0.20.The molecular structure, molecular weight and blending ratio of the end group sulfonated polyether sulfone are synergistically controlled, so that the obtained ultrafiltration membrane forms an asymmetric porous structure with relatively concentrated pore size distribution, and the hydrophilicity, pure water flux, retention performance, anti-pollution performance and structural stability of the membrane are considered.

Description

Technical Field

[0001] This invention relates to the field of ultrafiltration membrane preparation technology, specifically to an antifouling polyethersulfone ultrafiltration membrane and its preparation method. Background Technology

[0002] Polyethersulfone (PES) possesses advantages such as heat resistance, chemical corrosion resistance, high mechanical strength, and good film-forming properties, making it widely used as a membrane substrate material for ultrafiltration membranes. Existing PES ultrafiltration membranes are typically prepared using a solvent-inducing phase separation method. This involves preparing a casting solution using PES, a pore-forming agent, and an organic solvent. The casting solution is then coated onto the surface of a nonwoven fabric support layer and immersed in a coagulation bath. Through the exchange between the solvent and the non-solvent, the PES undergoes phase separation and solidifies to form a porous membrane layer.

[0003] However, the main chain of polyethersulfone molecules is composed primarily of aromatic rings, ether bonds, and sulfone groups, lacking hydrophilic functional groups capable of forming stable hydration with water molecules. Consequently, the resulting ultrafiltration membranes typically exhibit strong hydrophobicity. When treating feed solutions containing proteins or other organic contaminants, these contaminants easily adsorb onto the membrane surface or enter the membrane pores, causing pore blockage and a decrease in water flux. Furthermore, the membrane flux after fouling is difficult to recover, thus affecting the separation performance and operational stability of the ultrafiltration membrane.

[0004] To improve the hydrophilicity and antifouling properties of polyethersulfone (PES) ultrafiltration membranes, existing technologies have proposed modification methods such as surface grafting, plasma treatment, inorganic hydrophilic particle filling, and hydrophilic polymer blending. Surface grafting or plasma treatment usually requires additional processing steps after membrane formation, making the process relatively complex. Inorganic hydrophilic particles may aggregate in the PES matrix, forming interfacial defects between the inorganic particles and the polymer. When water-soluble hydrophilic polymers such as polyethylene glycol are used as long-term hydrophilic modification components, they may migrate or be lost from the membrane matrix during solidification or use, potentially increasing the membrane pore size or widening the pore size distribution, leading to a decrease in membrane retention performance.

[0005] Sulfonated polyethersulfone (PES) possesses an aromatic PES backbone similar to PES and contains sulfonic acid groups that enhance hydrophilicity, thus it can be blended with PES as a hydrophilic functional polymer to form films. However, existing PES modification schemes mostly focus on adjusting the degree of sulfonation or the amount added, paying insufficient attention to the spatial distribution of sulfonic acid groups in the polymer molecular chain, the molecular weight of PES, and the compatibility between PES and PES blending ratio. When sulfonic acid groups are randomly distributed on the aromatic rings of the repeating structural units of the polymer, the local polarity of the polymer molecular chain may change significantly, thus affecting the dispersion state of PES in the PES matrix and the phase separation behavior of the casting solution during solidification. At the same time, inappropriate molecular weight or amount of PES may also cause excessive viscosity of the casting solution, excessively rapid solvent-to-nonsolvent exchange, or excessively open membrane pore structure, making it difficult to simultaneously achieve high pure water flux, retention capacity, and antifouling performance of the membrane. Summary of the Invention

[0006] One objective of the first aspect of this invention is to provide an antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation, which solves the technical problems of insufficient hydrophilicity and antifouling performance of polyethersulfone ultrafiltration membranes in the prior art, and the difficulty in reasonably controlling the membrane pore structure by existing hydrophilic modification methods, resulting in the difficulty in simultaneously achieving the pure water flux, retention performance and flux recovery performance after fouling of ultrafiltration membranes.

[0007] Another objective of the first aspect of the present invention is to facilitate the formation of a continuous membrane pore structure with a relatively concentrated pore size distribution.

[0008] The second objective of this invention is to provide a method for preparing an antifouling polyethersulfone ultrafiltration membrane.

[0009] According to a first aspect of the present invention, the present invention provides an antifouling polyethersulfone ultrafiltration membrane based on the structure regulation of end-group sulfonated polyethersulfone, comprising a polyester nonwoven fabric support layer and a porous functional membrane layer disposed on the surface of the polyester nonwoven fabric support layer, wherein the porous functional membrane layer is a porous membrane layer formed by blending polyethersulfone and end-group sulfonated polyethersulfone, and the casting solution used to form the porous functional membrane layer comprises the polyethersulfone, the end-group sulfonated polyethersulfone, polyvinylpyrrolidone and an organic solvent, wherein the general structural formula (I) of the end-group sulfonated polyethersulfone is: ; The terminal sulfonated polyether sulfone has a molecular weight of 25000 g·mol⁻¹. -1 -55000g·mol -1 The mass ratio of the terminal sulfonated polyethersulfone to the polyethersulfone is any value between 0.05 and 0.20.

[0010] Optionally, the mass ratio of the end-group sulfonated polyethersulfone to the polyethersulfone is any value between 0.10 and 0.15.

[0011] Optionally, the molecular weight of the terminal sulfonated polyether sulfone is 40000 g·mol⁻¹. -1 The polyethersulfone has a molecular weight of 20,000 g·mol⁻¹. -1 -95000 g·mol -1 .

[0012] Optionally, the sulfonated polyethersulfone is a hydrophilic functional polymer with a sulfonation degree of any value between 1% and 30%.

[0013] Optionally, the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

[0014] According to a second aspect of the present invention, the present invention also provides a method for preparing the antifouling polyethersulfone ultrafiltration membrane according to any one of the above claims, comprising the following steps: Polyethersulfone, end-group sulfonated polyethersulfone having the structure shown in formula (I), polyvinylpyrrolidone and organic solvent are mixed and stirred until the polyethersulfone, the end-group sulfonated polyethersulfone and the polyvinylpyrrolidone are dissolved to obtain a casting solution; The casting solution is subjected to vacuum degassing; The vacuum-degassed casting liquid is scraped onto the surface of the polyester nonwoven fabric support layer to form a wet film. The wet membrane is immersed in a water coagulation bath for non-solvent-induced phase separation, so that the polyethersulfone and the end-group sulfonated polyethersulfone form a porous functional membrane layer on the surface of the polyester nonwoven support layer, thus obtaining the nascent membrane. The nascent membrane is washed with water to obtain the antifouling polyethersulfone ultrafiltration membrane.

[0015] Optionally, the total mass of the polyethersulfone and the terminal sulfonated polyethersulfone accounts for 20wt%-35wt% of the total mass of the casting solution, and the polyvinylpyrrolidone accounts for 2wt%-10wt% of the total mass of the casting solution.

[0016] Optionally, the stirring temperature is 60℃-80℃ and the stirring time is 6h-8h.

[0017] Optionally, the casting solution is applied to the surface of the polyester nonwoven fabric support layer using a scraping machine, with a scraping gap of 100μm-300μm and a scraping speed of 1cm·s. -1 -20cm·s -1 The wet film is immediately immersed in the water coagulation bath after it is formed. The water coagulation bath is deionized water, the temperature of the water coagulation bath is 5℃-15℃, and the coagulation time is 10min-60min.

[0018] Optionally, the nascent membrane is rinsed with deionized water for at least 30 minutes; the rinsed membrane is stored in deionized water, or the rinsed membrane is immersed in a 10wt%-30wt% glycerol aqueous solution for 0.5h-4h and dried at 40℃-60℃ to obtain the wet or dry membrane of the antifouling polyethersulfone ultrafiltration membrane.

[0019] The end-group sulfonated polyethersulfone of this invention maintains structural compatibility with polyethersulfone through an aromatic polyethersulfone backbone similar to that of polyethersulfone, and utilizes sulfonic acid groups concentrated at the ends of the molecular chains to provide hydrophilicity, reducing the disturbance to the stability of the casting solution and the phase separation process caused by the local polarity differences caused by randomly distributed sulfonic acid groups; simultaneously, the molecular weight of the end-group sulfonated polyethersulfone is controlled at 25000 g·mol⁻¹. -1 -55000g·mol -1The mass ratio of polyethersulfone to polyethersulfone is controlled at 0.05-0.20 to maintain the appropriate dispersion and molecular chain entanglement of the end-sulfonated polyethersulfone in the polyethersulfone matrix. The content of hydrophilic groups in the casting solution and the exchange process between solvent and non-solvent are also adjusted to reduce the migration and loss of end-sulfonated polyethersulfone, excessive viscosity of the casting solution, excessively open membrane pores, or overly dense membrane pore structure. With the pore-forming effect of polyvinylpyrrolidone and the mechanical support of the polyester nonwoven fabric support layer, an asymmetric porous functional membrane layer with a dense skin layer, a layer of interconnected finger pores, and a relatively concentrated pore size distribution is formed. This improves the hydrophilicity of the membrane surface and the pure water flux, reduces the adsorption and blockage of proteins on the membrane surface and within the pores, and improves the flux recovery rate after fouling while maintaining the bovine serum albumin retention capacity. The resulting polyethersulfone ultrafiltration membrane balances permeability, separation performance, antifouling performance, and structural stability.

[0020] Furthermore, the terminal sulfonated polyether sulfone of the present invention has a molecular weight of 40000 g·mol⁻¹. -1 The molecular weight of polyethersulfone is 20000 g·mol⁻¹ -1 -95000g·mol -1 Polyethersulfone exhibits film-forming properties within the aforementioned molecular weight range and can form the main framework of porous functional membranes; its molecular weight is 40000 g·mol⁻¹. -1 The end-group sulfonated polyethersulfone can maintain the corresponding structural compatibility with polyethersulfone and participate in regulating the rheological state of the casting solution and the non-solvent-induced phase separation process, so that the end-group sulfonated polyethersulfone is dispersed in the polyethersulfone matrix, which is conducive to forming a continuous membrane pore structure with a relatively concentrated pore size distribution.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0022] The following sections will describe some specific embodiments of the invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing an antifouling polyethersulfone ultrafiltration membrane according to an embodiment of the present invention; Figure 2 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 1 of the present invention; Figure 3 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 2 of the present invention; Figure 4 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 3 of the present invention; Figure 5 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 4 of the present invention; Figure 6 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Comparative Example 1 of the present invention; Figure 7 These are scanning electron microscope images of the antifouling polyethersulfone ultrafiltration membranes prepared according to Example 1 and Comparative Example 2 of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0025] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] This invention provides an antifouling polyethersulfone ultrafiltration membrane based on the structure regulation of end-group sulfonated polyethersulfone. The antifouling polyethersulfone ultrafiltration membrane includes a polyester nonwoven fabric support layer and a porous functional membrane layer disposed on the surface of the polyester nonwoven fabric support layer. The porous functional membrane layer is a porous membrane layer formed by blending polyethersulfone and end-group sulfonated polyethersulfone. The casting solution used to form the porous functional membrane layer includes polyethersulfone, end-group sulfonated polyethersulfone, polyvinylpyrrolidone, and an organic solvent. The general structural formula (I) of end-group sulfonated polyethersulfone is: ; The molecular weight of the terminal sulfonated polyether sulfone is 25000 g·mol⁻¹. -1 -55000g·mol -1 The mass ratio of terminal sulfonated polyethersulfone to polyethersulfone is any value between 0.05 and 0.20. Here, the molecular weight of the terminal sulfonated polyethersulfone can be 25000 g·mol⁻¹. -1 30000g·mol -1 35000g·mol -1 40000g·mol -1 45000g·mol -1 50000g·mol -1 Or 55000g·mol -1 It can also be 25000 g·mol -1 -55000g·mol -1 The mass ratio of terminal sulfonated polyethersulfone to polyethersulfone can be 0.05, 0.10, 0.15 or 0.20, or any other value between 0.05 and 0.20.

[0028] In this embodiment, through the above-described configuration, the sulfonic acid groups of the end-sulfonated polyethersulfone are concentrated at the ends of the polymer molecular chain, while its main chain segments maintain an aromatic polyethersulfone skeleton similar to that of polyethersulfone. This allows the end-sulfonated polyethersulfone to form a better structural compatibility with the polyethersulfone matrix. Compared to sulfonated polyethersulfone where the sulfonic acid groups are randomly distributed on the repeating structural unit aromatic ring, the end-sulfonated polyethersulfone can reduce the disturbance of local polarity differences in the molecular chain on the stability of the casting solution and the phase separation process. Furthermore, the hydrophilic effect of the end-sulfonic acid groups can regulate the exchange rate between the organic solvent and the non-solvent in the coagulation bath. This improves the hydrophilicity of the porous functional membrane while avoiding the formation of excessively large pores or local macropore defects due to excessively fast phase separation.

[0029] Meanwhile, the molecular weight of the end-group sulfonated polyether sulfone was controlled at 25000 g·mol⁻¹. -1 -55000g·mol -1This allows the sulfonated polyethersulfone to form a suitable entanglement with the polyethersulfone molecular chain, reducing the migration or loss of the end-group sulfonated polyethersulfone into the coagulation bath during film formation. It also avoids excessive viscosity of the casting solution, hindered solvent-solvent exchange, and overly dense membrane pores caused by excessively high molecular weight. Controlling the mass ratio of end-group sulfonated polyethersulfone to polyethersulfone at 0.05-0.20 ensures sufficient hydrophilic sulfonic acid groups in the porous functional membrane layer and limits the accelerated phase separation rate, widened pore size distribution, and decreased retention performance caused by excessively high end-group sulfonated polyethersulfone content. Therefore, the molecular structure, molecular weight, and mass ratio of end-group sulfonated polyethersulfone to polyethersulfone collectively determine its dispersion state, degree of molecular chain entanglement, and content of hydrophilic groups in the casting solution.

[0030] Based on this, polyvinylpyrrolidone (PVP) acts as a pore-forming agent, promoting pore formation and improving connectivity between pores during coagulation. Organic solvents are used to form a uniform casting solution from polyethersulfone (PES), sulfonated PES, and PES. The polyester nonwoven support layer provides mechanical support for the porous functional membrane, reducing shrinkage, deformation, or damage during preparation and use. The combined polymer structure, composition, and parameter ranges enable the porous functional membrane to form an asymmetric porous structure with a dense skin and interconnected finger-like pores. The pore distribution is relatively concentrated, improving pure water flux and membrane surface hydrophilicity while maintaining the retention capacity for bovine serum albumin (BSA), reducing protein adsorption and blockage on the membrane surface and within the pores, and improving flux recovery rate after fouling. This balances the permeation performance, separation performance, antifouling performance, and structural stability of the PES ultrafiltration membrane.

[0031] In a preferred embodiment, when the molecular weight of the end-group sulfonated polyether sulfone is 40000 g·mol⁻¹ -1 When the mass ratio of end-sulfonated polyethersulfone to polyethersulfone is 0.15, the resulting antifouling polyethersulfone ultrafiltration membrane has a water contact angle of 58.6° and a pure water flux of 196.3 L·m. -2 ·h -1 ·bar -1 The bovine serum albumin (BSA) rejection rate was 96.8%, and the flux recovery rate after fouling was 90.3%. Compared with ultrafiltration membranes prepared using randomly aromatic ring sulfonated polyethersulfone, this ultrafiltration membrane improved the BSA rejection rate while maintaining similar hydrophilicity and flux recovery rate after fouling. This indicates that the chain-end distribution of sulfonic acid groups, along with the molecular weight and blending ratio, can limit excessive opening of membrane pores and achieve a balance between water flux, rejection performance, and antifouling performance.

[0032] In a further embodiment, the mass ratio of end-group sulfonated polyethersulfone to polyethersulfone is any value between 0.10 and 0.15. Specifically, the mass ratio of end-group sulfonated polyethersulfone to polyethersulfone can be 0.10, 0.11, 0.12, 0.13, 0.14, or 0.15, or any value between 0.10 and 0.15. Controlling the mass ratio of end-group sulfonated polyethersulfone to polyethersulfone within the above range ensures that the porous functional membrane layer has an appropriate amount of hydrophilic sulfonic acid groups, and avoids the increase in membrane pore size, widening of pore size distribution, or loosening of membrane skeleton caused by excessive end-group sulfonated polyethersulfone content. This is beneficial for balancing the membrane's hydrophilicity, pure water flux, bovine serum albumin rejection rate, and flux recovery rate after fouling.

[0033] In a further embodiment, the molecular weight of the terminal sulfonated polyether sulfone is 40,000 g·mol⁻¹. -1 The molecular weight of polyethersulfone is 20000 g·mol⁻¹ -1 -95000g·mol -1 Specifically, the molecular weight of polyethersulfone can be 20000 g·mol⁻¹. -1 30000g·mol -1 40000g·mol -1 50000g·mol -1 60000g·mol -1 70000g·mol -1 80000g·mol -1 Or 95000g·mol -1 It can also be 20000 g·mol -1 -95000g·mol -1 Any value in the above range. Polyethersulfone exhibits film-forming properties within the above molecular weight range and can form the main framework of porous functional membranes; molecular weight of 40000 g·mol⁻¹ -1 The end-group sulfonated polyethersulfone maintains structural compatibility with polyethersulfone and participates in regulating the rheological state of the casting solution and the solvent-inducible phase separation process, allowing the end-group sulfonated polyethersulfone to disperse in the polyethersulfone matrix. This is beneficial for forming a continuous membrane pore structure with a relatively concentrated pore size distribution. Under the same membrane formation conditions, a molecular weight of 40000 g·mol⁻¹ was used. -1 Ultrafiltration membranes made from end-group sulfonated polyethersulfone can balance pure water flux, bovine serum albumin rejection rate, and flux recovery rate after fouling.

[0034] In a further embodiment, the sulfonated polyethersulfone is a hydrophilic functional polymer with a sulfonation degree of any value between 1% and 30%. Specifically, the sulfonation degree of the end-group sulfonated polyethersulfone can be 1%, 5%, 10%, 15%, 20%, 25%, or 30%, or any value between 1% and 30%. The sulfonation degree of the end-group sulfonated polyethersulfone can adjust the number of hydrophilic sulfonic acid groups it contains, thereby affecting the solvent-non-solvent exchange process between the casting solution and the coagulation bath, as well as the surface hydrophilicity and pore structure of the resulting porous functional membrane. Within the sulfonation degree range examined in this application, as the sulfonation degree increases, the water contact angle of the resulting ultrafiltration membrane generally decreases, and the pure water flux generally increases; when the sulfonation degree further increases, the membrane pore structure tends to open, and the bovine serum albumin rejection rate may decrease. Therefore, by controlling the sulfonation degree of the end-group sulfonated polyethersulfone, the hydrophilicity, pore structure, pure water flux, and rejection performance of the membrane can be adjusted. Among them, when the degree of sulfonation of the end-group sulfonated polyether sulfone is 5%, the resulting ultrafiltration membrane has better overall separation performance and antifouling performance.

[0035] In a further embodiment, the organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide. Specifically, the organic solvent can be N-methylpyrrolidone, N,N-dimethylacetamide, or N,N-dimethylformamide, or a mixture of N-methylpyrrolidone and N,N-dimethylacetamide, a mixture of N,N-dimethylacetamide and N,N-dimethylformamide, or a mixture of all three. The aforementioned organic solvent has a dissolving effect on polyethersulfone, end-group sulfonated polyethersulfone, and polyvinylpyrrolidone, which is beneficial for forming a uniform casting solution. After the casting solution is immersed in a water coagulation bath, the organic solvent can exchange with water, causing phase separation of the polyethersulfone and end-group sulfonated polyethersulfone and solidification to form a porous functional membrane layer. Therefore, by selecting one or more of the above-mentioned organic solvents, the dissolution and film formation requirements of different casting solution compositions can be met, and the exchange process between solvents and non-solvents and the membrane pore structure can be adjusted.

[0036] Figure 1 This is a schematic flowchart of a method for preparing an antifouling polyethersulfone ultrafiltration membrane according to an embodiment of the present invention.

[0037] like Figure 1 As shown, the present invention also provides a method for preparing the antifouling polyethersulfone ultrafiltration membrane according to any one of the above claims, comprising the following steps: Step S100: Mix polyethersulfone, end-group sulfonated polyethersulfone having the structure shown in formula (I), polyvinylpyrrolidone and organic solvent, and stir until polyethersulfone, end-group sulfonated polyethersulfone and polyvinylpyrrolidone are dissolved to obtain casting solution; Step S200: Vacuum degassing of the casting solution; Step S300: The vacuum-degassed casting liquid is scraped onto the surface of the polyester nonwoven fabric support layer to form a wet film; Step S400: Immerse the wet membrane in a water coagulation bath for non-solvent-induced phase separation, so that polyethersulfone and end-group sulfonated polyethersulfone form a porous functional membrane layer on the surface of the polyester nonwoven support layer, and obtain the nascent membrane. Step S500: Wash the nascent membrane with water to obtain an antifouling polyethersulfone ultrafiltration membrane.

[0038] In this embodiment, the above preparation steps are coordinated. First, polyethersulfone, terminal sulfonated polyethersulfone, and polyvinylpyrrolidone are dissolved in an organic solvent to form a homogeneous casting solution. Then, the solution is sequentially subjected to vacuum degassing, nonwoven fabric surface coating, non-solvent-induced phase separation in an aqueous coagulation bath, and water washing. This allows polyethersulfone and terminal sulfonated polyethersulfone to co-precipitate and solidify on the surface of the polyester nonwoven fabric support layer, forming a porous functional membrane layer. The main chain segments of terminal sulfonated polyethersulfone have a similar chemical structure to polyethersulfone, and its terminal sulfonic acid groups can regulate the mass transfer between the solvent and non-solvent. Polyvinylpyrrolidone participates in regulating the state of the casting solution and the membrane pore formation process. Thus, based on the mechanical support provided by the polyester nonwoven fabric, the porous functional membrane layer can form an asymmetric porous structure with a relatively uniform pore structure. This allows the resulting antifouling polyethersulfone ultrafiltration membrane to balance structural stability, pure water permeability, bovine serum albumin retention, and flux recovery performance after fouling. This preparation method forms a porous functional membrane layer through a single coating and phase separation process using the same casting solution. It eliminates the need for surface grafting or other chemical modification treatments after film formation, which simplifies the film-making process and improves the consistency of membrane structures across different batches.

[0039] In step S100, polyethersulfone, terminal sulfonated polyethersulfone, polyvinylpyrrolidone and organic solvent are mixed and stirred thoroughly to dissolve each polymer component. This helps to reduce undissolved polymer particles and distributes terminal sulfonated polyethersulfone and polyvinylpyrrolidone in the casting solution, providing conditions for the subsequent formation of a uniformly composed porous functional membrane.

[0040] In step S200, vacuum degassing of the casting solution can remove air bubbles that have been mixed into the casting solution during stirring and dissolving, reducing the possibility of pinholes, cavities, or local film defects during coating and solidification, thereby improving the continuity of the wet film and the quality of the film formation.

[0041] In step S300, the degassed casting liquid is scraped onto the surface of the polyester nonwoven fabric support layer, which allows the casting liquid to spread along the surface of the support layer to form a wet film, and allows some of the casting liquid to enter the surface pores of the polyester nonwoven fabric support layer, thereby increasing the contact area between the porous functional film layer and the polyester nonwoven fabric support layer, which is conducive to the formation of a stable composite relationship between the two; the scraping coating also makes it easier to control the coverage and thickness uniformity of the wet film.

[0042] In step S400, after the wet membrane is immersed in the water coagulation bath, the organic solvent in the casting solution diffuses into the water coagulation bath, while water enters the interior of the wet membrane, causing non-solvent-induced phase separation in the casting solution system, forming a polymer-rich phase and a polymer-depleted phase. The polymer-rich phase precipitates and solidifies to form the main framework of the porous functional membrane layer, while the polymer-depleted phase forms membrane pores. This step can fix the distribution of polyethersulfone and end-group sulfonated polyethersulfone in the porous functional membrane layer and form membrane pore channels for liquid permeation and macromolecule retention.

[0043] In step S500, the nascent membrane is washed with water to further remove residual organic solvents and at least some polyvinylpyrrolidone from the porous functional membrane layer and the polyester nonwoven support layer. This allows the membrane pores formed after the polyvinylpyrrolidone dissolves to become interconnected, and reduces the impact of residual solvents and free pore-forming agents on the subsequent membrane performance, thereby obtaining an antifouling polyethersulfone ultrafiltration membrane that can be used for liquid separation.

[0044] In a further embodiment, the total mass of polyethersulfone (PES) and terminal sulfonated PES accounts for 20 wt%-35 wt% of the total mass of the casting solution, and polyvinylpyrrolidone (PVP) accounts for 2 wt%-10 wt% of the total mass of the casting solution. In this embodiment, the total content of PES and terminal sulfonated PES is coordinated with the content of PES; the former provides a continuous film-forming framework for the porous functional membrane layer, while the latter regulates the formation and connectivity of membrane pores within the film-forming framework. This allows the casting solution to possess both the fluidity required for blade coating and the compositional conditions required for solvent-induced phase separation. By controlling the contents of these two groups, it is beneficial to form an asymmetric porous functional membrane layer with both a dense skin and a through-pore structure, reducing the occurrence of local membrane layer defects, excessively dense pores, or excessively loose pore structures. This, in turn, balances the structural stability, permeability, and retention performance of the antifouling PES ultrafiltration membrane.

[0045] In one specific embodiment, the total mass of polyethersulfone and end-group sulfonated polyethersulfone can account for 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, or 35wt% of the total mass of the casting solution, or any value within the range of 20wt%-35wt%. Polyethersulfone and end-group sulfonated polyethersulfone constitute the film-forming polymer of the porous functional membrane layer. The total content of both in the casting solution can adjust the viscosity, flow state, and density of the polymer skeleton formed after phase separation. Controlling the total content of both within the above range helps to maintain the casting solution's suitable flowability and film-forming properties for coating, enabling the casting solution to continuously cover the surface of the polyester nonwoven fabric support layer, and ensuring that the porous functional membrane layer formed after phase separation has a continuous polymer skeleton and corresponding structural stability, while reserving appropriate space for membrane pore formation.

[0046] In one specific embodiment, polyvinylpyrrolidone (PVP) can account for 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 10 wt% of the total mass of the casting solution, or any value within the range of 2 wt% to 10 wt%. As a water-soluble pore-forming agent, PPVP can influence the viscosity of the casting solution and the distribution of polymer molecular chains within it. After the wet film enters the water coagulation bath, PPVP can at least partially enter the aqueous phase through solvent-non-solvent exchange, forming pores in the porous functional membrane layer. Controlling the PPVP content within the aforementioned range is beneficial for adjusting the number of pores, pore connectivity, and the density of the porous functional membrane layer. This reduces the likelihood of insufficient pore number or connectivity due to low pore-forming agent content, and also reduces the likelihood of excessive viscosity changes in the casting solution or compromised polymer backbone continuity due to high pore-forming agent content.

[0047] Further, in one embodiment, the total mass of polyethersulfone and terminally sulfonated polyethersulfone accounts for 20wt%-35wt% of the total mass of the casting solution. Specifically, the total mass of polyethersulfone and terminally sulfonated polyethersulfone can account for 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, or 35wt% of the total mass of the casting solution, or any value within the range of 20wt%-35wt%. The total content of polyethersulfone and terminally sulfonated polyethersulfone can adjust the polymer concentration and flow state of the casting solution, and determine the polymer content used to form the main framework of the porous functional membrane after phase separation. Controlling the total content within the above range is beneficial for the casting solution to have a state suitable for blade coating, and for maintaining the continuity and corresponding structural strength of the formed porous functional membrane, while reserving appropriate space for the formation of membrane pores.

[0048] Further, in one embodiment, polyvinylpyrrolidone accounts for 2wt%-10wt% of the total mass of the casting solution. Specifically, polyvinylpyrrolidone can account for 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or 10wt% of the total mass of the casting solution, or any value within the range of 2wt%-10wt%. Polyvinylpyrrolidone can participate in the solvent-induced phase separation process as a pore-forming agent. During coagulation and washing, it at least partially enters the aqueous phase and forms pores in the porous functional membrane layer. Controlling the amount of polyvinylpyrrolidone within the above range is beneficial for adjusting the number of pores, pore connectivity, and density of the porous functional membrane layer, avoiding limited pore connectivity due to insufficient pore-forming agent dosage, or adverse effects on the state of the casting solution and the continuity of the porous functional membrane layer due to excessive pore-forming agent dosage.

[0049] Further, in one embodiment, the stirring temperature is 60–80°C, and the stirring time is 6–8 hours. Specifically, the stirring temperature can be 60°C, 62°C, 65°C, 68°C, 70°C, 75°C, or 80°C, or any value within the range of 60°C–80°C; the stirring time can be 6 hours, 6.25 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, or any value within the range of 6 hours–8 hours. Stirring within the above temperature and time range promotes the dissolution of polyethersulfone, end-group sulfonated polyethersulfone, and polyvinylpyrrolidone in the organic solvent, and ensures uniform distribution of each component in the casting solution, thereby reducing undissolved polymer particles and local component concentration differences, providing a uniformly composed casting solution for subsequent coating to form a continuous wet film. Simultaneously, controlling the stirring temperature and time within the above range helps to ensure sufficient dissolution of each component while reducing organic solvent evaporation and changes in the casting solution composition caused by prolonged high-temperature treatment.

[0050] Furthermore, in one embodiment, a scraping machine is used to apply the casting solution to the surface of the polyester nonwoven fabric support layer, with a scraping gap of 100μm-300μm and a scraping speed of 1cm·s. -1 -20cm·s -1 Specifically, the doctor blade gap can be 100μm, 125μm, 150μm, 175μm, 200μm, 250μm, or 300μm, or any value between 100μm and 300μm; the doctor blade speed can be 1cm·s. -1 3cm·s -1 5cm·s -1 10cm·s -1 15cm·s -1 18cm·s -1 Or 20cm·s -1 It can also be 1 cm·s -1 -20cm·s -1 Any value within the range. The doctor blade gap can adjust the thickness of the wet film and the amount of casting solution per unit area, while the casting speed can affect the spreading state of the casting solution on the surface of the polyester nonwoven fabric support layer and the consistency of the wet film thickness. Controlling the doctor blade gap and casting speed within the above range is beneficial for the continuous coverage of the polyester nonwoven fabric support layer by the casting solution, and for allowing some of the casting solution to enter the surface pores of the polyester nonwoven fabric support layer, thereby improving the coverage uniformity of the porous functional film layer and its bonding stability with the polyester nonwoven fabric support layer.

[0051] Further, in one embodiment, the wet film is immediately immersed in a coagulation bath after formation. The coagulation bath is deionized water, and the temperature of the coagulation bath is 5°C-15°C, with a coagulation time of 10 min-60 min. Specifically, the temperature of the coagulation bath can be 5°C, 7°C, 8°C, 10°C, 12°C, 13°C, or 15°C, or any value within the range of 5°C-15°C; the coagulation time can be 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, or any value within the range of 10 min-60 min. Immediately immersing the wet film in the coagulation bath after formation reduces the residence time of the wet film in air and the changes in surface composition caused by the evaporation of organic solvents, allowing the wet film to undergo non-solvent-induced phase separation in a relatively uniform initial state. Deionized water, as a non-solvent, can exchange with the organic solvent in the casting solution and reduce the interference of dissolved impurities in the water on the phase separation process. The coagulation bath temperature can regulate the mass transfer rate between organic solvent and water. Controlling the coagulation bath temperature at 5℃-15℃ is beneficial for controlling the polymer precipitation and solidification process and reducing the possibility of forming local macropores or widening of pore size distribution due to excessively rapid exchange between solvent and non-solvent. Coagulation for 10min-60min can provide sufficient time for phase separation and solidification of porous functional membranes, thus fixing the formed membrane pore structure.

[0052] Furthermore, in one embodiment, the nascent membrane is rinsed with deionized water for at least 30 minutes. Specifically, the deionized water rinsing time can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, 90 minutes, or 120 minutes, or any other time not less than 30 minutes. Rinsing the nascent membrane with deionized water can further remove residual organic solvents and at least some polyvinylpyrrolidone from the porous functional membrane layer and the polyester nonwoven support layer, reducing the impact of residual organic solvents and free pore-forming agents on the membrane pore structure and subsequent separation process, and allowing the membrane pores formed after the polyvinylpyrrolidone dissolves to become interconnected.

[0053] Furthermore, in one embodiment, the rinsed membrane is stored in deionized water to obtain a wet membrane of the antifouling polyethersulfone ultrafiltration membrane. Storing the rinsed membrane in deionized water can keep the porous functional membrane layer moist, reduce the possibility of the membrane pores shrinking or closing due to water evaporation, and thus maintain the membrane pore structure and the water-wet state of the wet membrane before use.

[0054] Further, in another embodiment, the rinsed membrane is immersed in a glycerol aqueous solution with a mass concentration of 10wt%-30wt% for 0.5h-4h, and then dried at 40℃-60℃ to obtain a dry membrane of the antifouling polyethersulfone ultrafiltration membrane. Specifically, the mass concentration of the glycerol aqueous solution can be 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 25wt%, or 30wt%, or any value within the range of 10wt%-30wt%; the immersion time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or 4h, or any value within the range of 0.5h-4h; the drying temperature can be 40℃, 42℃, 45℃, 50℃, 55℃, or 60℃, or any value within the range of 40℃-60℃. Glycerol can enter the pores of the porous functional membrane layer with the glycerol aqueous solution, and slow down the rapid evaporation of water in the pores during the subsequent drying process, reducing the capillary pressure on the pore walls, thereby reducing pore shrinkage or collapse. Controlling the mass concentration and soaking time of the glycerol aqueous solution within the above range is beneficial for glycerol to enter the interior of the porous functional membrane and be distributed in the membrane pores. Drying at 40℃-60℃ can remove moisture from the membrane while reducing the impact of higher temperatures on the morphology of the porous functional membrane and the dimensional stability of the polyester nonwoven support layer, so that the dry membrane can maintain the corresponding membrane pore structure during storage and transportation.

[0055] The technical solution of this application will be further described below with reference to specific embodiments.

[0056] Example 1

[0057] Weigh 24.0 g of polyethersulfone, 3.6 g of sulfonated polyethersulfone, and 5.0 g of polyvinylpyrrolidone, and add them to 67.4 g of N,N-dimethylformamide. The sulfonated polyethersulfone has a sulfonation degree of 5% and a molecular weight of 40,000 g·mol⁻¹. -1 The end-group sulfonated polyethersulfone has a mass ratio of sulfonated polyethersulfone to polyethersulfone of 0.15.

[0058] The above raw materials were added to a sealed reactor and mechanically stirred at 60°C for 8 hours to obtain a blended, transparent casting solution. The casting solution was then transferred to a vacuum degassing reactor and degassed at room temperature for 2 hours. The doctor blade gap was set to 200 μm and the doctor blade speed to 20 cm·s. -1 The casting solution was coated onto the surface of a polyester nonwoven fabric support layer to form a wet film, which was then immediately immersed in a 10°C deionized water coagulation bath for phase inversion to form a membrane. The resulting nascent membrane was then rinsed with deionized water to thoroughly remove residual N,N-dimethylformamide and polyvinylpyrrolidone. The membrane was then immersed in a 30wt% glycerol aqueous solution for 2 hours, followed by gradient drying at 40°C–60°C to obtain an antifouling polyethersulfone ultrafiltration membrane.

[0059] Example 2

[0060] The only difference between Example 2 and Example 1 is that the mass ratio of sulfonated polyethersulfone to polyethersulfone is 0.05.

[0061] Example 3

[0062] The only difference between Example 3 and Example 1 is that the mass ratio of sulfonated polyethersulfone to polyethersulfone is 0.10.

[0063] Example 4

[0064] The only difference between Example 4 and Example 1 is that the mass ratio of sulfonated polyethersulfone to polyethersulfone is 0.20.

[0065] Example 5

[0066] The only difference between Example 5 and Example 1 is that the molecular weight of the sulfonated polyether sulfone is 25000 g·mol⁻¹. -1 .

[0067] Example 6

[0068] The only difference between Example 6 and Example 1 is that the molecular weight of the sulfonated polyether sulfone is 55000 g·mol⁻¹. -1 .

[0069] Example 7

[0070] The only difference between Example 7 and Example 1 is that the degree of sulfonation of the sulfonated polyether sulfone is 1%.

[0071] Example 8

[0072] The only difference between Example 8 and Example 1 is that the degree of sulfonation of the sulfonated polyether sulfone is 10%.

[0073] Example 9

[0074] The only difference between Example 9 and Example 1 is that the degree of sulfonation of the sulfonated polyether sulfone is 15%.

[0075] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that pure polyethersulfone was used as the film-forming polymer, and sulfonated polyethersulfone was not added.

[0076] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that a random aromatic ring sulfonated polyether sulfone (Structural Formula II) is used instead of the main chain end-group sulfonated polyether sulfone in Example 1. Structural Formula II is as follows: .

[0077] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that polyethylene glycol is used as a hydrophilic additive, that is, polyethylene glycol is used instead of sulfonated polyethersulfone.

[0078] Figure 2 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 1 of the present invention. Figure 3 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 2 of the present invention. Figure 4 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 3 of the present invention. Figure 5 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Example 4 of the present invention. Figure 6 This is a cross-sectional scanning electron microscope image of the antifouling polyethersulfone ultrafiltration membrane prepared according to Comparative Example 1 of the present invention. Figure 7 These are scanning electron microscope images of the antifouling polyethersulfone ultrafiltration membranes prepared according to Example 1 and Comparative Example 2 of the present invention.

[0079] The antifouling polyethersulfone ultrafiltration membranes prepared in Examples 1-4 and Comparative Examples 1-2 were characterized by cross-sectional scanning electron microscopy, and the results were as follows: Figures 2 to 7 The test results are shown.

[0080] Next, the antifouling polyethersulfone ultrafiltration membranes prepared in Examples 1-9 and Comparative Examples 1-3 were subjected to performance and structural characterization tests, and the test results are shown in Table 1. The test methods for each parameter in Table 1 are as follows: (1) Pure water flux test: The pure water flux was measured using a cross-flow filtration device at 25°C and 0.20 MPa, with the unit being L·m. -2 ·h -1 Bar -1 .

[0081] (2) Water contact angle test: The static water contact angle of the membrane surface was determined by the static drop method at room temperature using a contact angle measuring instrument. Three different locations were tested for each sample, and the average value was taken.

[0082] (3) Morphological characterization: The surface and cross-sectional morphology of the film were observed using a scanning electron microscope.

[0083] (4) Anti-pollution performance test: using 1 g·L -1 Bovine serum albumin (BSA) solution was used as the contaminant solution and filtered at 0.20 MPa to calculate the flux recovery rate (FRR) after membrane fouling.

[0084] All performance tests were repeated at least 3 times, and the average of the results was taken.

[0085] Table 1. Performance and structural test results of the antifouling polyethersulfone ultrafiltration membranes obtained in the above embodiments and comparative examples.

[0086] Depend on Figures 2 to 6 As shown in Table 1, the amount of terminal sulfonated polyethersulfone added can simultaneously affect the cross-sectional pore structure, surface hydrophilicity, pure water permeability, and macromolecular retention performance of the polyethersulfone ultrafiltration membrane. In Examples 2, 3, 1, and 4, the mass ratios of terminal sulfonated polyethersulfone to polyethersulfone were 0.05, 0.10, 0.15, and 0.20, respectively. As the mass ratio increased from 0.05 to 0.20, the water contact angle of the resulting ultrafiltration membrane gradually decreased from 66.3° to 55.8°, and the pure water flux increased from 160.5 L·m⁻¹. -2 ·h -1 ·bar -1 Gradually increase to 213.0 L·m -2 ·h -1 ·bar -1 This indicates that end-group sulfonated polyether sulfone can improve the hydrophilicity of the membrane surface and reduce the resistance to water transport in the membrane pores.

[0087] When the mass ratio of end-sulfonated polyethersulfone to polyethersulfone increased from 0.05 to 0.15, the finger-like pores in the membrane cross-section gradually extended and tended to be continuous, improving the regularity and connectivity of the pore structure. Example 1, with a mass ratio of 0.15, exhibited a relatively uniform asymmetric pore structure, and its pure water flux was 196.3 L·m⁻¹. -2 ·h -1 ·bar -1 The BSA rejection rate was 96.8%, and the flux recovery rate was 90.3%. When the mass ratio was further increased to 0.20, although the water contact angle further decreased and the pure water flux increased to 213.0 L·m⁻¹, the overall efficiency remained relatively high. -2 ·h -1 ·bar -1 However, the presence of locally large pores in the membrane cross-section and the decrease in BSA rejection rate to 93.1% indicate that excessively high end-group sulfonated polyethersulfone content tends to open the membrane pore structure. Therefore, controlling the mass ratio of end-group sulfonated polyethersulfone to polyethersulfone at 0.10-0.15 is beneficial for balancing membrane hydrophilicity, pure water flux, BSA rejection rate, and flux recovery rate after fouling.

[0088] The molecular weight of end-sulfonated polyethersulfone primarily affects the flow state of the casting solution and the density of the membrane pores formed after phase separation, while its impact on the hydrophilicity of the membrane surface is relatively small. Molecular weights of 25000 g·mol⁻¹ are shown. -1 40000g·mol -1 and 55000g·mol -1 The water contact angle of all three ultrafiltration membranes was approximately 58°, but as the molecular weight increased, the pure water flux decreased from 208.8 L·m⁻¹. -2 ·h-1 ·bar -1 Reduced to 125.8 L·m -2 ·h -1 ·bar -1 The BSA rejection rate increased from 94.5% to 97.9%. Among them, the molecular weight was 40000 g·mol⁻¹. -1 The end-group sulfonated polyethersulfone enables the resulting ultrafiltration membrane to simultaneously achieve 196.3 L·m -2 ·h -1 ·bar -1 With a pure water flux of 96.8%, a BSA rejection rate of 96.8%, and a flux recovery rate of 90.3%, it exhibits good overall performance.

[0089] Within the sulfonation degree range of 1%-15% observed in the examples, as the sulfonation degree of the end-group sulfonated polyethersulfone increased, the water contact angle of the resulting ultrafiltration membrane gradually decreased, and the pure water flux gradually increased, but the BSA rejection rate generally decreased. When the sulfonation degree increased from 1% to 5%, the water contact angle decreased from 74.4° to 58.6°, and the pure water flux increased from 137.0 L·m -2 ·h -1 ·bar -1 Increased to 196.3 L·m -2 ·h -1 ·bar -1 The flux recovery rate increased from 82.1% to 90.3%, while the BSA rejection rate remained at 96.8%. When the degree of sulfonation was further increased to 15%, the pure water flux increased to 214.5 L·m³. -2 ·h -1 ·bar -1 However, the BSA rejection rate decreased to 92.8%. This indicates that a sulfonation degree of around 5% can effectively balance the membrane's hydrophilicity, permeability, rejection, and antifouling properties.

[0090] Compared with Comparative Example 1 without sulfonated polyethersulfone, Example 1 showed a 20.8° decrease in water contact angle, an approximately 98.5% increase in pure water flux, a 15.5 percentage point increase in flux recovery rate, and a only 0.8 percentage point decrease in BSA rejection rate. This indicates that end-group sulfonated polyethersulfone can significantly improve the hydrophilicity, water permeability, and antifouling properties of the membrane while essentially maintaining the macromolecular rejection capacity.

[0091] Figure 7 This further illustrates the effect of the spatial distribution of sulfonic acid groups on the pore structure of the membrane surface. Example 1 uses end-sulfonated polyethersulfone. Figure 7 The surface pore size indicated in (a) is approximately 9.58 nm–11.6 nm; Comparative Example 2 uses random aromatic ring sulfonated polyethersulfone. Figure 7The surface pore sizes indicated in (b) range from approximately 8.47 nm to 16.9 nm, showing a relatively wide variation range. The water contact angle and flux recovery rate of Example 1 and Comparative Example 2 are essentially equivalent, but the BSA rejection rate of Example 1 is 96.8%, which is 10.8 percentage points higher than the 86.0% of Comparative Example 2. This indicates that, under similar degrees of sulfonation, molecular weight, and addition ratios, the chain-end distribution of sulfonic acid groups is beneficial in limiting the excessive opening of the membrane surface pore structure, enabling the resulting ultrafiltration membrane to maintain hydrophilicity and antifouling properties while exhibiting higher macromolecular rejection capacity.

[0092] In summary, this application achieves a porous functional membrane layer with a dense skin and interconnected finger-like pores by blending end-group sulfonated polyethersulfone having the structure shown in Formula (I) with polyethersulfone, and by controlling the molecular weight, degree of sulfonation, and mass ratio of the end-group sulfonated polyethersulfone to polyethersulfone, combined with a solvent-inducing phase separation process. Examples and comparative data show that end-group sulfonated polyethersulfone can improve the membrane's hydrophilicity, pure water permeability, and flux recovery performance after fouling, and maintains a high BSA rejection rate with similar hydrophilicity and antifouling performance by limiting excessive opening of the membrane pore structure.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation, characterized in that, The membrane includes a polyester nonwoven fabric support layer and a porous functional membrane layer disposed on the surface of the polyester nonwoven fabric support layer. The porous functional membrane layer is a porous membrane layer formed by blending polyethersulfone and end-group sulfonated polyethersulfone. The casting solution used to form the porous functional membrane layer includes the polyethersulfone, the end-group sulfonated polyethersulfone, polyvinylpyrrolidone, and an organic solvent. The general structural formula (I) of the end-group sulfonated polyethersulfone is: ； The terminal sulfonated polyether sulfone has a molecular weight of 25000 g·mol⁻¹. -1 -55000g·mol -1 The mass ratio of the terminal sulfonated polyethersulfone to the polyethersulfone is any value between 0.05 and 0.

20.

2. The antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation according to claim 1, characterized in that, The mass ratio of the terminal sulfonated polyethersulfone to the polyethersulfone is any value between 0.10 and 0.

15.

3. The antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation according to claim 1, characterized in that, The molecular weight of the terminal sulfonated polyether sulfone is 40,000 g·mol⁻¹. -1 The polyethersulfone has a molecular weight of 20,000 g·mol⁻¹. -1 -95000 g·mol -1 .

4. The antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation according to claim 1, characterized in that, The sulfonated polyethersulfone is a hydrophilic functional polymer with a sulfonation degree of any value between 1% and 30%.

5. The antifouling polyethersulfone ultrafiltration membrane based on end-group sulfonated polyethersulfone structure regulation according to claim 1, characterized in that, The organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide.

6. A method for preparing an antifouling polyethersulfone ultrafiltration membrane according to any one of claims 1-5, characterized in that, Includes the following steps: Polyethersulfone, end-group sulfonated polyethersulfone having the structure shown in formula (I), polyvinylpyrrolidone and organic solvent are mixed and stirred until the polyethersulfone, the end-group sulfonated polyethersulfone and the polyvinylpyrrolidone are dissolved to obtain a casting solution; The casting solution is subjected to vacuum degassing; The vacuum-degassed casting liquid is scraped onto the surface of the polyester nonwoven fabric support layer to form a wet film. The wet membrane is immersed in a water coagulation bath for non-solvent-induced phase separation, so that the polyethersulfone and the end-group sulfonated polyethersulfone form a porous functional membrane layer on the surface of the polyester nonwoven support layer, thus obtaining the nascent membrane. The nascent membrane is washed with water to obtain the antifouling polyethersulfone ultrafiltration membrane.

7. The preparation method according to claim 6, characterized in that, The total mass of the polyethersulfone and the terminal sulfonated polyethersulfone accounts for 20wt%-35wt% of the total mass of the casting solution, and the polyvinylpyrrolidone accounts for 2wt%-10wt% of the total mass of the casting solution.

8. The preparation method according to claim 6, characterized in that, The stirring temperature is 60℃-80℃, and the stirring time is 6h-8h.

9. The preparation method according to claim 6, characterized in that, The casting solution is applied to the surface of the polyester nonwoven fabric support layer using a scraping machine with a blade gap of 100μm-300μm and a scraping speed of 1cm·s. -1 -20cm·s -1 The wet film is immediately immersed in the water coagulation bath after it is formed. The water coagulation bath is deionized water, the temperature of the water coagulation bath is 5℃-15℃, and the coagulation time is 10min-60min.

10. The preparation method according to any one of claims 6-9, characterized in that, The nascent membrane is rinsed with deionized water for at least 30 minutes; the rinsed membrane is then stored in deionized water, or the rinsed membrane is immersed in a 10wt%-30wt% glycerol aqueous solution for 0.5h-4h and dried at 40℃-60℃ to obtain the wet or dry membrane of the antifouling polyethersulfone ultrafiltration membrane.

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