Polyether sulfone flat sheet membrane with high flux and small molecular weight retention as well as preparation method and application of polyether sulfone flat sheet membrane

Abstract

The invention provides a polyether sulfone flat sheet membrane with high flux and small molecular weight interception as well as a preparation method and application thereof, and relates to the technical field of membrane materials. The preparation method of the polyethersulfone flat sheet membrane with high flux and small molecular weight interception comprises the following steps: mixing polyethersulfone, a pore-foaming agent, an additive and a good solvent to obtain a homogeneous membrane casting solution; mixing a linear hydrophilic polymer with water to obtain a high-viscosity coagulating bath; wherein the molecular weight of the linear hydrophilic polymer is more than 100kDa; coating a base material plate with the homogeneous casting membrane solution, and placing the base material plate in the high-viscosity coagulating bath to obtain a primary polyether sulfone flat sheet membrane; the primary polyether sulfone flat sheet membrane is rinsed and subjected to pore protection, and the polyether sulfone flat sheet membrane with high flux and small molecular weight interception is obtained. The high-viscosity coagulating bath is adopted, and the membrane casting liquid phase conversion time is delayed, so that a uniform and compact layer is constructed on the surface layer of the membrane casting liquid, the formation of all-medium sponge holes is promoted, and the separation precision of small-molecular-weight substances is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane materials, in particular to a high-flux, low-molecular-weight cut-off polyethersulfone flat membrane and a preparation method and application thereof. Background Art

[0002] Polyethersulfone is an engineering plastic with excellent high-temperature resistance, outstanding mechanical strength, and good chemical stability. Polyethersulfone membranes have good biocompatibility and a certain degree of hydrophilicity and are widely used in industries such as water treatment, biopharmaceuticals, and food and beverages. Researchers have conducted relatively in-depth and comprehensive research on ultrafiltration membranes, and polyethersulfone ultrafiltration membranes with various molecular weight cutoffs are available on the market. Currently, there are few ultrafiltration membranes with low molecular weight cutoffs on the market, and their pore size distribution is relatively wide, which may cause leakage of small molecules, making them unsuitable for scenarios requiring high separation precision. In addition, ultrafiltration membranes with low molecular weight cutoffs generally have a relatively low flux. Therefore, research on ultrafiltration membranes with higher precision and higher flux, low molecular weight cutoffs, is necessary. Low molecular weight cutoff ultrafiltration membranes can, to a certain extent, replace some nanofiltration membranes, thereby expanding the application range of ultrafiltration membranes.

[0003] Polyethersulfone (PES) ultrafiltration membranes are prepared using a non-solvent-induced phase separation technique. The membrane formation process involves both thermodynamic and kinetic processes. The precise control of molecular chain motion and bidirectional solvent diffusion during the phase transition of the casting solution is a key element in optimizing PES membrane materials.

[0004] CN117679954A discloses a method for preparing a high-flux, anti-pollution polyethersulfone flat microporous membrane. The preparation comprises the following steps: step 1, preparing a casting solution: dissolving dried polyethersulfone pellets, a porogen, and an amphiphilic polymer in an organic solvent, heating and stirring, cooling the mixture to room temperature, and standing for degassing to obtain a uniform casting solution; step 2, preparing a coagulation bath: dissolving an organic alcohol and an inorganic salt in water, uniformly mixing the mixture to form a uniform solution, and heating the solution to obtain a coagulation bath; the organic alcohol acts as a curing retarder to slow down the phase transformation of the polyethersulfone, and the inorganic salt acts as a modification inducer to promote local dehydration of the amphiphilic polymer; step 3, preparing a liquid film: casting the casting solution obtained in step 1 on a horizontal substrate to form a continuous and uniform liquid film of a certain thickness, which is then pre-gelled; and step 4, thin film curing: immersing the pre-gelled liquid film in step 3 together with the substrate in the coagulation bath to fully cure and form the liquid film and then fall off the substrate to obtain a high-flux, anti-pollution polyethersulfone flat microporous membrane. The components of the coagulation bath are organic alcohol and inorganic salt; among them, the organic alcohol is a small molecule alcohol, and the addition amount needs to reach 20-40% to achieve delayed phase separation. When the addition amount is low, the phase separation cannot be effectively delayed, resulting in instantaneous liquid-liquid phase separation, and a large finger-like pore structure may be formed; and the inorganic salt will promote the local dehydration and precipitation of the amphiphilic polymer through the "salting out effect", forming a heterogeneous nucleation point, and sharply increasing the chemical potential gradient of the coagulation bath. Therefore, there is a problem of uneven phase separation of the casting liquid, which may cause a decrease in the retention rate.

[0005] CN116036896A discloses a composite nanofiltration membrane with a low molecular weight cutoff and a narrow pore size distribution, and a method for preparing the same. The method comprises the following steps: mixing a support membrane material, an amphiphilic polymer, and an additive to prepare a casting solution; using an aqueous solution containing the hydrophilic polymer as a coagulation bath, and preparing a support membrane with a hydrophilic coating on its surface by an immersion precipitation phase conversion method; treating the surface of the support membrane with the hydrophilic coating with an aqueous solution of a polyamine and then an organic solution of a polyacyl chloride; and further constructing a polyamide selective separation layer on the surface of the support membrane by interfacial polymerization; and finally, heat treating the support membrane to obtain a composite nanofiltration membrane with a low molecular weight cutoff and a narrow pore size distribution. Although this invention uses an aqueous solution containing a hydrophilic polymer as a coagulation bath, its purpose is to obtain a support membrane with an excellent hydrophilic coating. However, the hydrophilic polymer used has a low molecular weight, insufficient coagulation bath viscosity, or poor solubility in pure water, preventing the formation of a homogeneous coagulation bath, which affects the uniform phase separation behavior of the casting solution.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The present invention aims to provide a high-flux, low-molecular-weight-retention polyethersulfone flat membrane, its preparation method, and application. The present invention effectively addresses the low flux and precision issues of existing polyethersulfone flat membranes with low molecular weight retention, providing a method for preparing a high-flux, low-molecular-weight-retention polyethersulfone flat membrane. The present invention also provides a method for preparing a low-molecular-weight-retention polyethersulfone flat membrane, utilizing dual-dimensional control of the casting solution and the coagulation bath to provide a method for preparing a high-flux, high-precision polyethersulfone flat membrane suitable for low-molecular-weight-retention.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] In a first aspect, the present invention provides a method for preparing a high-throughput, low-molecular-weight cutoff polyethersulfone flat membrane, the preparation method comprising:

[0010] mixing polyethersulfone, porogen, additives and good solvent to obtain a homogeneous film casting solution;

[0011] Mixing a linear hydrophilic polymer and water to obtain a high-viscosity coagulation bath; wherein the molecular weight of the linear hydrophilic polymer is greater than 100 kDa;

[0012] After coating the homogeneous casting solution on a substrate plate, the substrate plate is placed in the high viscosity coagulation bath to obtain a primary polyethersulfone flat membrane;

[0013] The nascent polyethersulfone flat membrane is rinsed and maintained to obtain the high-flux, small-molecular-weight-rejection polyethersulfone flat membrane.

[0014] Furthermore, the homogeneous casting solution comprises, by weight percentage, 23-27% polyethersulfone, 5-10% porogen, 0.1-3% additive, and the balance being a good solvent.

[0015] Furthermore, the molecular weight of the polyethersulfone is 58-95 kDa.

[0016] Furthermore, the porogen includes polyethylene glycol and / or polyvinyl pyrrolidone.

[0017] Furthermore, the molecular weight of the polyethylene glycol is 2 to 20 kDa.

[0018] Furthermore, the molecular weight of the polyvinyl pyrrolidone is 8 to 60 kDa.

[0019] Furthermore, the additive includes a non-temperature-sensitive block-type amphiphilic macromolecular polymer.

[0020] Furthermore, the non-temperature-sensitive block-type amphiphilic macromolecular polymer includes any one of methoxy polyethylene glycol-polycaprolactone, methoxy polyethylene glycol-polylactic acid or polyethyleneimine-polycaprolactone, or a combination of at least two thereof.

[0021] Furthermore, the molecular weight of the block amphiphilic macromolecule is 2 to 30 kDa.

[0022] Furthermore, the good solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, or a combination of at least two thereof.

[0023] Furthermore, the specific steps of preparing the homogeneous casting solution include:

[0024] The polyethersulfone, porogen and additives are placed in a good solvent, heated and stirred, and after all the raw materials are dissolved, the temperature is lowered and vacuum degassing is performed to obtain the homogeneous casting solution.

[0025] Furthermore, the temperature of the heating and stirring is 50 to 70° C., and the time of the heating and stirring is 12 to 24 hours.

[0026] Furthermore, the viscosity of the high-viscosity coagulation bath is 20 to 150 mPa·s.

[0027] Furthermore, the high-viscosity coagulation bath comprises, by mass percentage, 1 to 5% of a linear hydrophilic polymer and the remainder being water.

[0028] Furthermore, the linear hydrophilic polymer includes polyethylene oxide and / or polyvinyl pyrrolidone.

[0029] Furthermore, the molecular weight of the polyethylene glycol is 100 to 800 kDa.

[0030] Furthermore, the molecular weight of the polyvinyl pyrrolidone is 300 to 1300 kDa.

[0031] Furthermore, the temperature of the high viscosity coagulation bath is 20-30°C.

[0032] Furthermore, the coating is performed by a blade coating method.

[0033] Furthermore, the thickness of the blade used in the blade coating method is 20 to 300 μm.

[0034] Furthermore, the substrate plate includes a glass plate.

[0035] Furthermore, the specific steps of preparing the nascent polyethersulfone flat membrane include:

[0036] The homogeneous casting liquid is poured onto the substrate plate, and the scraper thickness is adjusted. When the scraper scrapes the homogeneous casting liquid to the required uniform thickness, the substrate plate carrying the homogeneous casting liquid is obtained; the substrate plate carrying the homogeneous casting liquid is placed in the high viscosity coagulation bath for coagulation, and after the membrane falls off the substrate plate, the primary polyethersulfone flat membrane is obtained.

[0037] Furthermore, the rinsing includes: placing the nascent polyethersulfone flat membrane in pure water for displacement rinsing.

[0038] Furthermore, the pore preservation comprises: placing the rinsed primary polyethersulfone flat membrane in a glycerol aqueous solution for soaking.

[0039] Furthermore, the glycerol aqueous solution comprises, by mass percentage, 30-50% glycerol and the remainder water.

[0040] Furthermore, the soaking temperature is 20 to 30° C., and the soaking time is 12 to 48 hours.

[0041] In a second aspect, the present invention provides a polyethersulfone flat membrane, which is prepared by the preparation method of the high-flux, low-molecular-weight-rejection polyethersulfone flat membrane according to the first aspect.

[0042] Furthermore, the water flux of the polyethersulfone flat membrane is 36L / m 2 ·h·bar and above.

[0043] Furthermore, the polyethersulfone flat membrane has a polyethylene glycol rejection rate of more than 94%.

[0044] Furthermore, the molecular weight of the polyethylene glycol is 5 to 10 kDa, preferably 6 kDa.

[0045] Furthermore, the surface porosity of the polyethersulfone flat membrane is greater than 1%.

[0046] In a third aspect, the present invention provides a use of the polyethersulfone flat membrane in intercepting small molecular weight compounds and / or small molecular weight polymers.

[0047] Furthermore, the molecular weight of the small molecular weight compound is below 10 kDa.

[0048] Furthermore, the molecular weight of the low molecular weight polymer is below 10 kDa.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The high viscosity coagulation bath used in the present invention can delay the phase transformation time of the casting liquid and convert the instantaneous phase separation into delayed phase separation. On the one hand, it constructs a uniform and dense layer on the surface of the casting liquid. On the other hand, it promotes the formation of full-medium sponge pores, avoids the formation of finger-like pores, and improves the separation accuracy.

[0051] (2) The non-temperature-sensitive segmented amphiphilic macromolecules with good biocompatibility and polymer compatibility adopted in the present invention, on the one hand, are not affected by temperature during the dissolution of the casting liquid, ensuring the uniformity and stability of the molecular morphology of each component in the casting liquid, thereby forming uniform induced micropores in the entire medium and ensuring the retention accuracy of the membrane; on the other hand, by forming a directional arrangement at the casting liquid-water interface with the hydrophobic end facing the casting liquid and the hydrophilic end facing the water, the interfacial free energy between the casting liquid and water is reduced, the hydrophilic end of the amphiphilic macromolecule induces water in the coagulation bath to enter the casting liquid, enhances the double diffusion effect between water and the casting liquid, opens the casting liquid interface, and causes the casting liquid to differentiate into smaller polyethersulfone concentrated phases. The channels induced by the hydrophilic end to enter the casting liquid will form channels of membrane pores, thereby increasing the membrane surface opening rate, thereby increasing the membrane flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0053] Figure 1 This is a scanning electron microscope image of the cross-sectional morphology of the polyethersulfone flat membrane provided in Example 1.

[0054] Figure 2 This is a scanning electron microscope image of the surface morphology of the polyethersulfone flat membrane provided in Example 1.

[0055] Figure 3 This is a scanning electron microscope image of the cross-sectional morphology of the polyethersulfone flat membrane provided in Comparative Example 2. DETAILED DESCRIPTION

[0056] Unless otherwise defined herein, scientific and technological terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0057] It should be noted that the following description sets forth specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art may make similar generalizations without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0058] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0059] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0060] In a first aspect, the present invention provides a method for preparing a high-throughput, low-molecular-weight cutoff polyethersulfone flat membrane, the preparation method comprising:

[0061] mixing polyethersulfone, porogen, additives and good solvent to obtain a homogeneous film casting solution;

[0062] Mixing a linear hydrophilic polymer and water to obtain a high-viscosity coagulation bath; wherein the molecular weight of the linear hydrophilic polymer is greater than 100 kDa;

[0063] After coating the homogeneous casting solution on a substrate plate, the substrate plate is placed in the high viscosity coagulation bath to obtain a primary polyethersulfone flat membrane;

[0064] The nascent polyethersulfone flat membrane is rinsed and maintained to obtain the high-flux, small-molecular-weight-rejection polyethersulfone flat membrane.

[0065] The present invention proposes a preparation method that achieves delayed phase separation of a polyethersulfone ultrafiltration membrane by regulating the kinetics of the non-solvent-induced phase separation process. By adding a linear hydrophilic polymer with a molecular weight of no less than 100 kDa to prepare a high-viscosity coagulation bath, the increased viscosity of the coagulation bath reduces the water diffusion and solvent exchange rates of the casting solution during the phase transition, thereby slowing the phase separation rate of the casting solution. This delays phase separation, creates a uniform and dense separation layer on the membrane surface, and reduces the formation of finger-like pores in the membrane cross-section.

[0066] As an optional embodiment, the homogeneous casting solution comprises, by mass percentage, 23-27% polyethersulfone, 5-10% porogen, 0.1-3% additive, and the balance being a good solvent.

[0067] As an optional embodiment, based on the total mass of the homogeneous casting liquid being 100%, the content of polyethersulfone in the homogeneous casting liquid is 23-27%, for example, 23%, 24%, 25%, 26%, 27%, etc.

[0068] As an optional embodiment, based on the total mass of the homogeneous casting liquid being 100%, the content of the porogen in the homogeneous casting liquid is 5-10%, for example, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0069] As an optional embodiment, based on the total mass of the homogeneous casting liquid as 100%, the content of the additive in the homogeneous casting liquid is 0.1-3%, for example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0070] As an optional embodiment, the molecular weight of the polyethersulfone is 58 to 95 kDa, for example, it can be 58 kDa, 60 kDa, 62 kDa, 64 kDa, 66 kDa, 68 kDa, 70 kDa, 72 kDa, 74 kDa, 76 kDa, 78 kDa, 80 kDa, 82 kDa, 84 kDa, 86 kDa, 88 kDa, 90 kDa, 92 kDa, 94 kDa, 95 kDa, etc.

[0071] As an optional embodiment, the porogen includes polyethylene glycol and / or polyvinyl pyrrolidone.

[0072] As an optional embodiment, the molecular weight of the polyethylene glycol used as the porogen is 2 to 20 kDa, for example, 2 kDa, 5 kDa, 10 kDa, 15 kDa, 20 kDa, etc.

[0073] As an optional embodiment, the polyethylene glycol used as the porogen includes any one or a combination of at least two of polyethylene glycols having a molecular weight of 2 kDa, 4 kDa, 6 kDa, 8 kDa, 10 kDa, or 20 kDa.

[0074] As an optional embodiment, the molecular weight of polyvinyl pyrrolidone used as the porogen is 8 to 60 kDa, for example, 8 kDa, 16 kDa, 24 kDa, 32 kDa, 40 kDa, 48 kDa, 56 kDa, 60 kDa, etc.

[0075] As an optional embodiment, the polyvinyl pyrrolidone used as the porogen includes polyvinyl pyrrolidone-K17 and / or polyvinyl pyrrolidone-K30.

[0076] As an optional embodiment, the additive includes a block-type amphiphilic macromolecule.

[0077] As an optional embodiment, the additive includes a non-temperature-sensitive block amphiphilic macromolecular polymer with good biocompatibility and polymer compatibility.

[0078] In the present invention, the amphiphilic polymer selected is a linear block copolymer, with good biocompatibility, high polymer compatibility and non-temperature sensitivity, by forming a hydrophobic end towards the casting liquid at the casting liquid-water interface, the hydrophilic end towards the directional arrangement of water, reducing the interfacial free energy between the casting liquid and the water. The hydrophilic end of the amphiphilic macromolecule induces the water in the coagulation bath to enter the casting liquid, promotes the double diffusion effect between water and the casting liquid, opens the casting liquid interface, and causes the casting liquid to be divided into smaller polyethersulfone concentrated phases, and the hydrophilic end induces the passage of water entering the casting liquid to form the passage of film pores, improves the membrane surface open porosity, thereby improving membrane flux. Non-temperature sensitivity ensures the homogeneity and stability of the components of the casting liquid in the dissolution process and at room temperature, avoids the generation of local defects in the film forming process, forms a uniform induction micropore of the full medium, ensures the interception accuracy of the membrane.

[0079] As an optional embodiment, the block-type amphiphilic macromolecular polymer includes any one of methoxy polyethylene glycol-polycaprolactone, methoxy polyethylene glycol-polylactic acid or polyethyleneimine-polycaprolactone, or a combination of at least two thereof.

[0080] As an optional embodiment, the molecular weight of the block amphiphilic macromolecule is 2 to 30 kDa, for example, 2 kDa, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, etc.

[0081] As an optional embodiment, the good solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, or a combination of at least two thereof.

[0082] As an optional embodiment, the specific steps of preparing the homogeneous casting solution include:

[0083] The polyethersulfone, porogen and additives are placed in a good solvent, heated and stirred, and after all the raw materials are dissolved, the temperature is lowered and vacuum degassing is performed to obtain the homogeneous casting solution.

[0084] As an optional embodiment, the specific steps of preparing the homogeneous casting solution include:

[0085] The dried polyethersulfone, porogen and additives are placed in a good solvent, heated and stirred, and after the added powder is completely dissolved, the temperature is lowered and vacuum degassing is performed to obtain a homogeneous casting solution; wherein the mass fraction of polyethersulfone is 23-27%, the mass fraction of the porogen is 5-10%, and the mass fraction of the additive is 0.1-3%.

[0086] As an optional embodiment, the heating and stirring temperature is 50-70°C, for example, it can be 50°C, 52°C, 54°C, 55°C, 56°C, 58°C, 60°C, 62°C, 64°C, 65°C, 66°C, 68°C, 70°C, etc.

[0087] As an optional embodiment, the heating and stirring time is 12 to 24 hours, for example, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0088] As an optional embodiment, the viscosity of the high-viscosity coagulation bath is 20-150 mPa·s, for example, it can be 20 mPa·s, 40 mPa·s, 60 mPa·s, 80 mPa·s, 100 mPa·s, 120 mPa·s, 140 mPa·s, 150 mPa·s, etc.

[0089] As an optional embodiment, the high-viscosity coagulation bath comprises, by mass percentage, 1 to 5% of a linear hydrophilic polymer and the remainder being water.

[0090] As an optional embodiment, based on the total mass of the high viscosity coagulation bath as 100%, the content of the linear hydrophilic polymer in the high viscosity coagulation bath is 1-5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0091] As an optional embodiment, the linear hydrophilic polymer includes polyethylene oxide and / or polyvinyl pyrrolidone. As an optional embodiment, the molecular weight of the polyethylene oxide in the high viscosity coagulation bath is 100 to 800 kDa, for example, 100 kDa, 200 kDa, 300 kDa, 320 kDa, 400 kDa, 480 kDa, 500 kDa, 600 kDa, 640 kDa, 700 kDa, 800 kDa, etc.

[0092] As an optional embodiment, the molecular weight of the polyvinylpyrrolidone in the high viscosity coagulation bath is 300-1300 kDa, for example, it can be 300 kDa, 320 kDa, 400 kDa, 480 kDa, 500 kDa, 600 kDa, 640 kDa, 700 kDa, 800 kDa, 900 kDa, 960 kDa, 1000 kDa, 1120 kDa, 1280 kDa, 1300 kDa, etc.

[0093] As an optional embodiment, the polyvinyl pyrrolidone in the high-viscosity coagulation bath includes polyvinyl pyrrolidone-K60 and / or polyvinyl pyrrolidone-K90.

[0094] As an optional embodiment, the specific steps of preparing the high viscosity coagulation bath include:

[0095] A linear hydrophilic polymer is added into water and mixed evenly to obtain a high-viscosity coagulation bath; the linear hydrophilic polymer can be completely dissolved in water, and the mass fraction of the linear hydrophilic polymer is 0.1-5%.

[0096] As an optional embodiment, the temperature of the high viscosity coagulation bath is 20-30°C, for example, 20°C, 22°C, 24°C, 25°C, 26°C, 28°C, 30°C, etc.

[0097] As an optional embodiment, the coating is performed by a blade coating method.

[0098] As an optional embodiment, the scraper thickness used in the scraper coating method is 20 to 300 μm, for example, it can be 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, etc.

[0099] As an optional embodiment, the substrate plate includes a glass plate.

[0100] As an optional embodiment, the specific steps of preparing the nascent polyethersulfone flat membrane include:

[0101] The homogeneous casting liquid is poured onto the substrate plate, and the scraper thickness is adjusted. When the scraper scrapes the homogeneous casting liquid to the required uniform thickness, the substrate plate carrying the homogeneous casting liquid is obtained; the substrate plate carrying the homogeneous casting liquid is placed in the high viscosity coagulation bath for coagulation, and after the membrane falls off the substrate plate, the primary polyethersulfone flat membrane is obtained.

[0102] As an optional embodiment, the specific steps of preparing the nascent polyethersulfone flat membrane include:

[0103] Pour the uniform casting liquid onto the glass plate of the flat film scraping machine, adjust the scraper to a certain thickness, wait for the scraper to scrape the casting liquid to a uniform thickness, quickly place the glass plate in a high viscosity coagulation bath, and wait for the film to fall off the glass plate to obtain the primary polyethersulfone flat film.

[0104] As an optional embodiment, the rinsing includes: placing the nascent polyethersulfone flat membrane in pure water for displacement rinsing.

[0105] As an optional embodiment, the pore preservation includes: placing the rinsed primary polyethersulfone flat membrane in a glycerol aqueous solution for soaking.

[0106] As an optional embodiment, the glycerol aqueous solution comprises, by mass percentage, 30-50% glycerol and the remainder water.

[0107] As an optional embodiment, based on the total mass of the glycerol aqueous solution as 100%, the content of glycerol in the glycerol aqueous solution is 30-50%, for example, it can be 30%, 32%, 34%, 35%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, 50%, etc.

[0108] As an optional embodiment, the soaking temperature is 20-30°C, for example, it can be 20°C, 22°C, 24°C, 25°C, 26°C, 28°C, 30°C, etc., and the soaking time is 12-48h, for example, it can be 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, 48h, etc.

[0109] As an optional embodiment, the nascent polyethersulfone flat membrane is further subjected to the following post-treatment steps:

[0110] The nascent polyethersulfone flat membrane was placed in pure water for full replacement and rinsing, and then immersed in a glycerol aqueous solution to preserve the pores, and then taken out and dried at room temperature to obtain a polyethersulfone flat membrane with high filtration accuracy and small molecular weight retention.

[0111] In a second aspect, the present invention provides a polyethersulfone flat membrane, which is prepared by the preparation method of the high-flux, low-molecular-weight-rejection polyethersulfone flat membrane according to the first aspect.

[0112] As an optional embodiment, the water flux of the polyethersulfone flat membrane is 36L / m 2 ·h·bar and above.

[0113] As an optional embodiment, the retention rate of the polyethersulfone flat membrane for polyethylene glycol is above 94%.

[0114] As an optional embodiment, the molecular weight of the polyethylene glycol is 5 to 10 kDa, for example, 5 kDa, 6 kDa, 7 kDa, 8 kDa, 9 kDa, 10 kDa, etc., preferably 6 kDa.

[0115] As an optional embodiment, the surface open porosity of the polyethersulfone flat membrane is greater than 1%.

[0116] In a third aspect, the present invention provides a use of the polyethersulfone flat membrane in intercepting small molecular weight compounds and / or small molecular weight polymers.

[0117] As an optional embodiment, the molecular weight of the small molecular weight compound is less than 10 kDa, for example, it can be 5 kDa, 6 kDa, 7 kDa, 8 kDa, 9 kDa, 10 kDa, etc.

[0118] As an optional embodiment, the molecular weight of the small molecular weight polymer is less than 10 kDa, for example, it can be 5 kDa, 6 kDa, 7 kDa, 8 kDa, 9 kDa, 10 kDa, etc.

[0119] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0120] Example 1

[0121] This embodiment provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The preparation method of the polyethersulfone flat membrane comprises the following steps:

[0122] S1. Preparation of casting solution:

[0123] The dried polyethersulfone (73kDa), porogen polyethylene glycol (2kDa) and additive methoxy polyethylene glycol-polylactic acid (2kDa) are placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder is completely dissolved, the temperature is lowered and vacuum degassing is performed to obtain a homogeneous casting solution; the homogeneous casting solution includes, by mass percentage, 23% polyethersulfone, 10% porogen, 1% additive, and the balance is N,N-dimethylacetamide.

[0124] S2. Preparation of high viscosity coagulation bath:

[0125] Polyethylene oxide (300 kDa) was added to 25° C. water and mixed uniformly to obtain a high-viscosity coagulation bath. The high-viscosity coagulation bath comprised, by mass percentage, 1% polyethylene oxide (300 kDa) and the remainder water. The viscosity of the high-viscosity coagulation bath was 92 mPa·s.

[0126] S3. Preparation of nascent polyethersulfone flat membrane:

[0127] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0128] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0129] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0130] Figure 1 This is a scanning electron microscope image of the cross-sectional morphology of the polyethersulfone flat membrane provided in Example 1. Figure 1 As shown, the polyethersulfone flat membrane obtained by the preparation method of the present invention has full dielectric sponge pores, uniform cross-section, no macroscopic stratification, and no formation of finger-like pores.

[0131] Figure 2 This is a scanning electron microscope image of the surface morphology of the polyethersulfone flat membrane provided in Example 1. Figure 2 As shown, the surface of the polyethersulfone flat membrane obtained by the preparation method of the present invention has uniform small pores and a dense structure.

[0132] Example 2

[0133] This embodiment provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The preparation method of the polyethersulfone flat membrane comprises the following steps:

[0134] S1. Preparation of casting solution:

[0135] The dried polyethersulfone (73kDa), porogen polyethylene glycol (2kDa) and additive methoxy polyethylene glycol-polylactic acid (2kDa) are placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder is completely dissolved, the temperature is lowered and vacuum degassing is performed to obtain a homogeneous casting solution; wherein the homogeneous casting solution includes, by mass percentage, 23% polyethersulfone, 10% porogen, 1% additive, and the balance is N,N-dimethylacetamide.

[0136] S2, preparation of high viscosity coagulation bath:

[0137] Polyvinyl pyrrolidone-K90 was added to 25° C. water and mixed uniformly to obtain a high-viscosity coagulation bath. The high-viscosity coagulation bath comprised, by weight percentage, 1% polyvinyl pyrrolidone-K90 and the remainder water. The viscosity of the high-viscosity coagulation bath was 65 mPa·s.

[0138] S3. Preparation of nascent polyethersulfone flat membrane:

[0139] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0140] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0141] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0142] Example 3

[0143] This embodiment provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The preparation method of the polyethersulfone flat membrane comprises the following steps:

[0144] S1. Preparation of casting solution:

[0145] The dried polyethersulfone (73kDa), porogen polyethylene glycol (2kDa) and additive polyethyleneimine-polycaprolactone (4kDa) are placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder is completely dissolved, the temperature is lowered and vacuum degassing is performed to obtain a homogeneous casting solution; wherein the homogeneous casting solution includes, by mass percentage, 23% polyethersulfone, 10% porogen, 1% additive, and the balance is N,N-dimethylacetamide.

[0146] S2. Preparation of high viscosity coagulation bath:

[0147] Polyethylene glycol (100 kDa) was added to 25° C. water and mixed uniformly to obtain a high-viscosity coagulation bath. The high-viscosity coagulation bath comprised, by mass percentage, 1% polyethylene oxide (300 kDa) and the remainder water. The viscosity of the high-viscosity coagulation bath was 92 mPa·s.

[0148] S3. Preparation of nascent polyethersulfone flat membrane:

[0149] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0150] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0151] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0152] Example 4

[0153] This embodiment provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The preparation method of the polyethersulfone flat membrane comprises the following steps:

[0154] S1. Preparation of casting solution:

[0155] The dried polyethersulfone (73kDa), porogen polyethylene glycol (2kDa) and additive methoxy polyethylene glycol-polylactic acid (2kDa) are placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder is completely dissolved, the temperature is lowered and vacuum degassing is performed to obtain a homogeneous casting solution; the homogeneous casting solution includes, by mass percentage, 27% polyethersulfone, 5% porogen, 1% additive, and the balance is N,N-dimethylacetamide.

[0156] S2. Preparation of high viscosity coagulation bath:

[0157] Polyethylene oxide (300 kDa) was added to 25° C. water and mixed uniformly to obtain a high-viscosity coagulation bath. The high-viscosity coagulation bath comprised, by mass percentage, 1% polyethylene oxide (300 kDa) and the remainder water. The viscosity of the high-viscosity coagulation bath was 92 mPa·s.

[0158] S3. Preparation of nascent polyethersulfone flat membrane:

[0159] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0160] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0161] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0162] Example 5

[0163] This example provides a high-throughput, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that the porogen polyethylene glycol (2 kDa) provided in S1 is replaced with polyvinylpyrrolidone-K17. The other steps are exactly the same as in Example 1.

[0164] Example 6

[0165] This example provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that the porogen polyethylene glycol (2 kDa) provided in S1 is replaced with polyethylene glycol (1 kDa). Other steps are exactly the same as in Example 1.

[0166] Example 7

[0167] This example provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that the porogen polyethylene glycol (2 kDa) provided in S1 is replaced with polyethylene glycol (20 kDa). Other steps are exactly the same as in Example 1.

[0168] Example 8

[0169] This example provides a high-throughput, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that the high-viscosity coagulation bath is prepared with 0.1% polyethylene oxide (800 kDa), and the viscosity of the high-viscosity coagulation bath is 26 mPa·s. (Other steps are identical to those in Example 1.)

[0170] Example 9

[0171] This embodiment provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that S3 is immersed in a 50% glycerol aqueous solution (at 25° C. for 24 h). Other steps are identical to those in Example 1.

[0172] Comparative Example 1

[0173] This comparative example provides a polyethersulfone flat membrane, and the preparation method of the polyethersulfone flat membrane comprises the following steps:

[0174] S1. Preparation of casting solution:

[0175] Dried polyethersulfone (73kDa) and polyethylene glycol (2kDa) were placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder was completely dissolved, the temperature was lowered and vacuum degassing was performed to obtain a homogeneous casting solution; wherein the mass fraction of polyethersulfone was 23% and the mass fraction of the porogen was 10%.

[0176] S2. Preparation of high viscosity coagulation bath:

[0177] Polyethylene glycol (100 kDa) was added to 25° C. water and mixed uniformly to obtain a high-viscosity coagulation bath. The high-viscosity coagulation bath comprised, by mass percentage, 1% polyethylene oxide (300 kDa) and the remainder water. The viscosity of the high-viscosity coagulation bath was 92 mPa·s.

[0178] S3. Preparation of nascent polyethersulfone flat membrane:

[0179] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0180] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0181] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0182] Comparative Example 2

[0183] This comparative example provides a polyethersulfone flat membrane, and the preparation method of the polyethersulfone flat membrane comprises the following steps:

[0184] S1. Preparation of casting solution:

[0185] The dried polyethersulfone (73kDa) and porogen polyethylene glycol (2kDa) were placed in N,N-dimethylacetamide and stirred at 60°C for 18 hours. After the added powder was completely dissolved, the temperature was lowered and vacuum degassing was performed to obtain a homogeneous casting solution; wherein the mass fraction of polyethersulfone was 23% and the mass fraction of the porogen was 10%.

[0186] S2. Preparation of coagulation bath:

[0187] The coagulation bath is pure water at 25° C., without adding a hydrophilic polymer.

[0188] S3. Preparation of nascent polyethersulfone flat membrane:

[0189] Pour the uniform casting liquid obtained in S1 onto the glass plate of a flat-plate scraper, adjust the scraper to 250 μm, and wait for the scraper to scrape the casting liquid to a uniform thickness. Quickly place the glass plate in the high viscosity coagulation bath of S2. After the film falls off the glass plate, the primary polyethersulfone flat plate membrane is obtained.

[0190] Figure 3 This is a scanning electron microscope image of the cross-sectional morphology of the polyethersulfone flat membrane provided in Comparative Example 2. Figure 3 As shown, the polyethersulfone flat membrane obtained in this comparative example has a large number of finger-like pores.

[0191] S4. Post-treatment of nascent polyethersulfone flat membrane:

[0192] The nascent polyethersulfone flat membrane obtained in S3 was placed in pure water for thorough replacement and rinsing, and then immersed in a 40% glycerol aqueous solution (at 25°C for 24 hours), and then taken out and dried at room temperature to obtain a high-flux, small molecular weight retention polyethersulfone flat membrane.

[0193] Comparative Example 3

[0194] This comparative example provides a polyethersulfone flat membrane, which differs from Example 1 only in that a low-viscosity coagulation bath is provided: the polyethylene oxide (300 kDa) in the S3 coagulation bath is replaced with polyethylene glycol (2 kDa), and the other steps are exactly the same as Example 1.

[0195] Comparative Example 4

[0196] This comparative example provides a polyethersulfone flat membrane, which differs from Example 1 only in that the S4 pore preservation step is not performed: the rinsed primary polyethersulfone flat membrane is directly dried, and the other steps are exactly the same as Example 1.

[0197] Comparative Example 5

[0198] This example provides a high-flux, low-molecular-weight cutoff polyethersulfone flat membrane. The only difference from Example 1 is that the additive methoxypolyethylene glycol-polylactic acid provided in S1 is replaced with Pluronic P123. Other steps are exactly the same as in Example 1.

[0199] Test Example 1

[0200] Test samples: polyethersulfone flat membranes provided in Examples 1 to 9 and polyethersulfone flat membranes provided in Comparative Examples 1 to 5.

[0201] Test method:

[0202] (1) Water flux test: The test was conducted using a cross-flow membrane test bench. The pure water temperature was 25°C and the operating pressure was 1.0 bar, which was then stabilized for 1 hour. The amount of water permeating per unit membrane area per unit time was then calculated under a test pressure of 1 bar.

[0203] (2) Retention test: A cross-flow membrane test bench was used for testing. The concentration of 6kDa polyethylene glycol was 1000ppm and the sample was stabilized at an operating pressure of 1.0 bar for 1 hour. Then, a water sample was taken at a test pressure of 1 bar. The TOC concentration was compared with that of the raw water, and the retention rate of the membrane for polyethylene glycol 6kDa was calculated.

[0204] (3) Morphological Structure Testing: Cross-sectional samples of the membrane were prepared using the liquid nitrogen freeze-fracture method. After sufficient drying, they were gold-sprayed for 40 seconds and then tested under a field emission scanning electron microscope. The measured cross-sectional morphology is shown in the figure. The surface porosity was further quantified using Image J software.

[0205] The specific test results are shown in Table 1 below:

[0206] Table 1

[0207]

[0208]

[0209] As shown in Table 1, after using a high-viscosity coagulation bath, the retention rate of the polyethersulfone flat membrane for 6kDa polyethylene glycol increased from 78.45% in a pure water coagulation bath to over 94%; after introducing hydrophilic macromolecules into the casting solution, the membrane surface porosity increased from the initial ~0.5% to over 1%, and the pure water flux of the membrane also increased by ~27%~31%.

[0210] Within the limits of the present invention, higher coagulation bath viscosity results in a relatively higher PES membrane retention rate. This demonstrates that the high-viscosity coagulation bath employed in the present invention can delay the phase transition time of the casting liquid, transforming instantaneous phase separation into delayed phase separation. This not only creates a uniform, dense layer on the surface of the casting liquid, but also promotes the formation of fully dielectric sponge pores, avoiding the formation of finger-like pores and improving separation accuracy. The use of amphiphilic macromolecular additives can effectively increase the membrane's surface porosity, thereby enhancing membrane flux.

[0211] In addition, after the temperature-sensitive amphiphilic macromolecular additive was used in Comparative Example 5, the surface porosity of the membrane did not change significantly, but the retention rate decreased by ~9%, which fully demonstrated that the non-temperature-sensitive amphiphilic macromolecular additive used in the present invention maintains uniformity and stability with the molecular chain state of each component in the casting liquid during the dissolution process, and no local defects are formed during the phase transition to membrane process.

[0212] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-throughput, low-molecular-weight cutoff polyethersulfone flat membrane, characterized in that: The preparation method comprises: mixing polyethersulfone, porogen, additives and good solvent to obtain a homogeneous film casting solution; Mixing a linear hydrophilic polymer and water to obtain a high-viscosity coagulation bath; wherein the molecular weight of the linear hydrophilic polymer is greater than 100 kDa; After coating the homogeneous casting solution on a substrate plate, the substrate plate is placed in the high viscosity coagulation bath to obtain a primary polyethersulfone flat membrane; The nascent polyethersulfone flat membrane is rinsed and maintained to obtain the high-flux, small-molecular-weight-rejection polyethersulfone flat membrane.

2. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1, wherein: The homogeneous casting solution comprises, by weight percentage, 23-27% polyethersulfone, 5-10% porogen, 0.1-3% additive, and the balance being a good solvent; Preferably, the molecular weight of the polyethersulfone is 58 to 95 kDa; Preferably, the porogen comprises polyethylene glycol and / or polyvinyl pyrrolidone; Preferably, the molecular weight of the polyethylene glycol is 2 to 20 kDa; Preferably, the molecular weight of the polyvinylpyrrolidone is 8 to 60 kDa; Preferably, the additive comprises a non-temperature-sensitive block-type amphiphilic macromolecular polymer; Preferably, the non-temperature-sensitive block amphiphilic macromolecular polymer includes any one or a combination of at least two of methoxy polyethylene glycol-polycaprolactone, methoxy polyethylene glycol-polylactic acid or polyethyleneimine-polycaprolactone; Preferably, the molecular weight of the non-temperature-sensitive block amphiphilic macromolecule is 2 to 30 kDa; Preferably, the good solvent includes any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, or a combination of at least two thereof.

3. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1 or 2, characterized in that: The specific steps of preparing the homogeneous casting solution include: The polyethersulfone, porogen and additives are placed in a good solvent, heated and stirred, and after all the raw materials are dissolved, the temperature is lowered and vacuum degassing is performed to obtain the homogeneous casting solution; Preferably, the heating and stirring temperature is 50 to 70° C., and the heating and stirring time is 12 to 24 hours.

4. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1, wherein: The viscosity of the high viscosity coagulation bath is 20 to 150 mPa·s; Preferably, the high viscosity coagulation bath comprises, by mass percentage: 0.1-5% of a linear hydrophilic polymer and the balance water; Preferably, the linear hydrophilic polymer comprises polyethylene oxide and / or polyvinyl pyrrolidone; Preferably, the molecular weight of the polyethylene oxide is 100 to 800 kDa; Preferably, the molecular weight of the polyvinylpyrrolidone is 300 to 1300 kDa; Preferably, the temperature of the high viscosity coagulation bath is 20-30°C.

5. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1, wherein: The coating adopts a doctor blade coating method; Preferably, the thickness of the blade used in the blade coating method is 20 to 300 μm; Preferably, the substrate plate comprises a glass plate; Preferably, the specific steps of preparing the nascent polyethersulfone flat membrane include: The homogeneous casting liquid is poured onto the substrate plate, and the scraper thickness is adjusted. When the scraper scrapes the homogeneous casting liquid to the required uniform thickness, a substrate plate carrying the homogeneous casting liquid is obtained; the substrate plate carrying the homogeneous casting liquid is placed in the high viscosity coagulation bath for coagulation, and after the membrane falls off the substrate plate, the primary polyethersulfone flat membrane is obtained.

6. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1, wherein: The rinsing comprises: placing the nascent polyethersulfone flat membrane in pure water for displacement rinsing.

7. The method for preparing a high-throughput, low-molecular-weight cut-off polyethersulfone flat membrane according to claim 1, wherein: The pore preservation method comprises: placing the rinsed primary polyethersulfone flat membrane in a glycerol aqueous solution for soaking; Preferably, the glycerol aqueous solution comprises, by mass percentage, 30-50% glycerol and the remainder water; Preferably, the soaking temperature is 20-30° C., and the soaking time is 12-48 hours.

8. A polyethersulfone flat membrane, characterized in that The polyethersulfone flat membrane is prepared by the method for preparing a high-flux, low-molecular-weight-cutoff polyethersulfone flat membrane according to any one of claims 1 to 7.

9. The polyethersulfone flat membrane according to claim 8, characterized in that The water flux of the polyethersulfone flat membrane is 36L / m 2 ·h·bar or above; Preferably, the retention rate of the polyethersulfone flat membrane for polyethylene glycol is above 94%; Preferably, the molecular weight of the polyethylene glycol is 5 to 10 kDa, preferably 6 kDa; Preferably, the surface porosity of the polyethersulfone flat membrane is greater than 1%.

10. Use of the polyethersulfone flat membrane according to claim 8 or 9 for retaining small molecular weight compounds and / or small molecular weight polymers; in, The molecular weight of the small molecular weight compound is less than 10 kDa; Wherein, the molecular weight of the small molecular weight polymer is below 10 kDa.

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