Thin-layer composite ultrafiltration membrane as well as preparation method and application thereof

Abstract

The invention provides a thin-layer composite ultrafiltration membrane as well as a preparation method and application thereof, and the preparation method of the thin-layer composite ultrafiltration membrane comprises the following steps: (1) dissolving a monomer containing an alcoholic hydroxyl group and a compound containing an amino group in an alkaline solution A to obtain a water-phase reactant; (2) dipping a porous support membrane in a water-phase reactant, then dipping in an oil-phase reactant, and carrying out heat treatment to obtain a porous support membrane of which the surface is covered with a polyesteramide separation layer; and (3) treating the porous support membrane with the polyesteramide separation layer covered on the surface obtained in the step (2) in an alkaline solution B to obtain the thin-layer composite ultrafiltration membrane. The thin-layer composite ultrafiltration membrane has the advantages of narrow pore size distribution, high porosity and ultrahigh pure water flux, and can be used for stable separation of biomacromolecules.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane materials, and in particular relates to a thin-layer composite ultrafiltration membrane and a preparation method and application thereof. Background Art

[0002] Membrane separation technology has been widely used in water treatment, food industry, biopharmaceuticals and other fields due to its green, environmentally friendly, economical and efficient characteristics. Among them, ultrafiltration membrane, as an important membrane material, can effectively separate macromolecules, colloidal particles and microorganisms in the solution through physical screening. The separation performance of the ultrafiltration membrane depends not only on the chemical composition and molecular structure of the membrane material itself, but also on the pore size and its distribution uniformity on the membrane surface. In addition, the surface properties of the membrane, such as hydrophilicity, roughness, and charge properties, will also significantly affect its pure water flux, retention rate and anti-pollution ability. With the increasing demand for high-efficiency and low-energy separation in various industries, how to further improve the permeation flux, anti-pollution performance and chemical stability of ultrafiltration membranes while taking into account high flux and high selectivity has become a research focus in academia and industry.

[0003] Currently, most research focuses on preparing ultrafiltration membranes using phase inversion technology. This method induces phase separation between a polymer solution and a nonsolvent bath, forming a porous membrane structure with a controllable pore size distribution. During the preparation process, membrane pore morphology and separation performance are influenced by multiple factors, including polymer concentration, solvent system, cosolvent type and dosage, coagulation bath formulation, and temperature.

[0004] In order to further improve the performance of ultrafiltration membranes, many scholars have achieved modification by means of surface functionalization modification or changing the blending monomer system. For example, CN119733392A discloses a method for preparing ultrafiltration membranes by blending polyester carbonate / cellulose acetate. The membrane forms an ordered asymmetric finger-like pore structure due to enhanced hydrophilicity, thereby significantly reducing pollution and improving long-term performance. CN11710120A discloses the introduction of functional hydrophilic molecules in the membrane making process, cross-linking them with each other, constructing a stable hydrophilic cross-linked network, and giving the membrane a more uniform pore structure and lasting hydrophilic properties. Although the membrane performance can be improved to a certain extent by additives and process optimization, in order to achieve precise control of pore size and higher consistency, more in-depth exploration and innovation in material design and preparation technology are still needed.

[0005] Interfacial polymerization is the core process for preparing thin-layer composite membranes (TFCs) and is widely used in the large-scale production of nanofiltration and reverse osmosis membranes. By utilizing its self-inhibition characteristics, a nanometer-scale ultra-thin polyamide separation layer can be grown in situ on the surface of the support membrane, thus showing obvious advantages in permeability. CN119701657A discloses a method for synthesizing a high-flux nanofiltration membrane based on a new diamine monomer of trans-2,5-dimethylpiperazine. Its methyl substituent slows down the diffusion rate of the organic phase to the aqueous phase through the steric effect, helps to form a thinner separation layer, and significantly improves the pure water flux; CN111229053A discloses a high-flux nanofiltration membrane preparation technology with a non-woven fabric as the support layer, eliminating the additional permeation resistance brought by the intermediate layer, further reducing the film thickness and improving the permeation flux, while maintaining excellent separation performance. Although certain progress has been made in improving the permeability of nanofiltration membranes by regulating the structure of the separation layer and the porosity of the support layer, since the interfacial polymerization reaction will continue spontaneously until the pore size is close to the monomer size, the adjustable range of the pore size is still limited, which restricts the significant improvement of the permeation flux. There is currently no literature reporting the extension of this method to a macroporous support layer to prepare a macroporous separation layer, and there is great potential for future research in this direction.

[0006] Therefore, developing an ultrafiltration membrane with narrow pore size distribution, high porosity and large flux to ensure sustainable operation under conditions of high efficiency and low energy consumption is a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing a thin-layer composite ultrafiltration membrane. By regulating the interfacial diffusion-reaction synergistic mechanism of aqueous phase reactants, the polyamide segments and polyester segments are evenly distributed, thereby constructing a polyesteramide separation layer with a complete structure, uniform pore size distribution and no defects. The thin-layer composite ultrafiltration membrane has a narrow pore size distribution, high porosity, ultrahigh pure water flux and excellent protein and macromolecule separation performance.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a high-flux anti-pollution thin-layer composite ultrafiltration membrane, the method comprising the following steps:

[0010] (1) dissolving a monomer containing an alcoholic hydroxyl group and a compound containing an amino group in an alkaline solution A to obtain an aqueous phase reactant;

[0011] (2) immersing the porous support membrane in an aqueous phase reactant, and then immersing the porous support membrane in an oil phase reactant, and subjecting the porous support membrane to heat treatment to obtain a porous support membrane having a polyester amide separation layer on its surface;

[0012] (3) treating the porous support membrane with the polyester amide separation layer obtained in step (2) in alkaline solution B to obtain the thin layer composite ultrafiltration membrane;

[0013] The difference in molecular weight between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤100Da;

[0014] The difference in concentration between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤0.05%.

[0015] The present invention comprises the following steps: immersing a porous support membrane in a monomer containing an alcoholic hydroxyl group and an aqueous phase reactant containing an amino compound to obtain a support membrane with amino and hydroxyl aqueous phase reactants loaded on the surface; then immersing the support membrane in an oil phase reactant to perform an interfacial polymerization reaction to form an active separation layer of polyamide and polyester chain segments with a balanced distribution; and then treating the support membrane in an alkaline solution B to etch away the polyester structure with a low cross-linking degree and a loose structure with alkali, thereby finally obtaining the thin-layer composite ultrafiltration membrane.

[0016] The molecular weight difference between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤100 Da, for example, it can be 10 Da, 20 Da, 30 Da, 40 Da, 50 Da, 60 Da, 70 Da, 80 Da, 90 Da or 100 Da.

[0017] The difference in concentration between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤0.05%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04% or 0.05%.

[0018] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0019] Preferably, the monomer containing alcoholic hydroxyl groups includes any one or a combination of at least two of sophoroside, salidroside, dextran, β-cyclodextrin or gallic acid.

[0020] Preferably, the concentration of the alcoholic hydroxyl monomer in the aqueous phase reactant is 0.05-5 wt%, for example, 0.05 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%.

[0021] Preferably, the alkaline solution A comprises any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two of them.

[0022] Preferably, the pH of the alkaline solution A is 11-13.4, for example, 11, 12, 13 or 13.4.

[0023] The present invention controls the pH of the alkaline solution A at 11-13.4 to increase the reaction rate of the alcoholic hydroxyl group-containing monomer so that it matches the reaction rate of the amino compound, thereby enhancing the synergistic effect of interfacial polymerization, thereby constructing a polyester amide separation layer with a complete structure, uniform pore size distribution and no defects. The polyamide and polyester chain segments are evenly distributed, which is beneficial to subsequent alkaline etching treatment.

[0024] Preferably, the amino group-containing compound includes any one or a combination of at least two of polyethyleneimine, piperazine, ethylenediamine, tetraethylenepentamine, diethylenetriamine or triethylamine.

[0025] Preferably, the concentration of the amino compound in the aqueous phase reactant is 0.05-5 wt%, for example, 0.05 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%.

[0026] Preferably, the oil phase reactant is obtained by dissolving an acyl halide compound in an organic solvent.

[0027] Preferably, the functionality of the acyl halide compound is ≥2, for example, 2, 3, 4 or 5.

[0028] Preferably, the acyl halide compound includes an acyl chloride compound and / or an acyl bromide compound.

[0029] Preferably, the acyl halide compound includes any one of trimesoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, biphenyltetracarboxylic acid chloride or biphenyltricarboxylic acid chloride, or a combination of at least two thereof.

[0030] Preferably, the organic solvent includes any one of n-hexane, acetonitrile, acetone, cyclohexane, chloroform or isooctane, or a combination of at least two thereof.

[0031] Preferably, the concentration of the oil phase reactant is 0.1-1.0 wt%, for example, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt% or 1 wt%.

[0032] The thin-layer composite ultrafiltration membrane described in the present invention includes a porous support membrane and a polyesteramide separation layer arranged on the surface of the porous support membrane. By regulating the concentrations of aqueous phase reactants and oil phase reactants, the crosslinking degree and thickness of the polyesteramide separation layer formed during the interfacial polymerization process are regulated.

[0033] Preferably, the porous support membrane is a polymer separation membrane.

[0034] Preferably, the pore size of the polymer separation membrane is 0.01-0.22 μm, for example, 0.01 μm, 0.04 μm, 0.07 μm, 0.10 μm, 0.13 μm, 0.16 μm, 0.19 μm or 0.22 μm.

[0035] Preferably, the polymer separation membrane comprises any one of polysulfone, polyethersulfone, polyvinylidene fluoride, polyethylene or polypropylene.

[0036] Preferably, the porous support membrane is immersed in the aqueous reactant for 1-10 min, for example, 1 min, 2 min, 4 min, 6 min, 8 min or 10 min.

[0037] Preferably, the porous support membrane is immersed in the oil phase reactant for 1-5 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0038] Preferably, the heat treatment temperature is 40-80°C, for example, 40°C, 50°C, 60°C, 70°C or 80°C.

[0039] Preferably, the heat treatment time is 1-15 min, for example, 1 min, 4 min, 7 min, 10 min, 12 min or 15 min.

[0040] Preferably, the alkaline solution B includes any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two of them.

[0041] Preferably, the pH of the alkaline solution B is 11-13.4, for example, 11, 12, 13 or 13.4.

[0042] In the present invention, the pH value and soaking time of the alkaline solution B determine the pore size and thickness of the composite ultrafiltration membrane.

[0043] Preferably, the porous support membrane with the polyester amide separation layer on its surface is treated in the alkaline solution B for 5-40 min, for example, 5 min, 10 min, 20 min, 30 min or 40 min.

[0044] Preferably, the thickness of the polyester amide separation layer is 30-300 nm, for example, 30 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm.

[0045] In a second aspect, the present invention provides a thin-layer composite ultrafiltration membrane, which is prepared by the preparation method described in the first aspect.

[0046] In a third aspect, the present invention provides a use of the thin-layer composite ultrafiltration membrane described in the second aspect in the separation of biomacromolecules.

[0047] The biomacromolecule includes any one of enzyme protein, antibody protein, glycoprotein, virus or liposome, or a combination of at least two of them.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention constructs a polyester amide separation layer with a complete structure, uniform pore size distribution and no defects through interfacial polymerization reaction, and then etches away the polyester structure with low cross-linking degree and loose structure through alkaline solution B, successfully preparing a thin-layer composite ultrafiltration membrane with a narrow pore size distribution. The thin-layer composite ultrafiltration membrane has a narrow pore size distribution, high porosity, and ultrahigh pure water flux, and can be used for the stable separation of biomacromolecules; the pure water flux of the thin-layer composite ultrafiltration membrane is as high as 512 L·m -2 h -1 bar -1 The pore size distribution is less than 1.48, the retention rate of bovine serum albumin can reach 100%, and the pure water flux recovery rate can reach 87%; and its preparation process is simple, it can be reused, and has broad application prospects. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0051] Example 1

[0052] This embodiment provides a thin-layer composite ultrafiltration membrane and a preparation method thereof, the preparation method comprising the following steps:

[0053] (1) 0.5 g of dextran (number average molecular weight 10,000 Da, McLean, D806714) and 0.5 g of polyethyleneimine (number average molecular weight 10,000 Da, Aladdin, E107079) were dissolved in 100 mL of 0.2 wt% sodium hydroxide solution to prepare an aqueous phase reactant; 0.2 g of trimesoyl chloride was dissolved in 100 g of n-hexane solvent to prepare a 0.2 wt% oil phase reactant;

[0054] (2) The porous support membrane (Zhongke Ruiyang PVDF 100K, UF100) was immersed in the aqueous phase reactant, taken out after 5 minutes, and the residual solution on the surface was removed, and then immersed in the oil phase reactant to cause interfacial polymerization reaction. After 1 minute, it was taken out and the organic solution on the surface was removed. It was heat-treated at 60 ° C for 5 minutes to obtain a porous support membrane with a polyester amide separation layer on the surface;

[0055] (3) The porous support membrane with the polyester amide separation layer obtained in step (2) was immersed in 50 mL of a 0.2 wt % sodium hydroxide aqueous solution for 30 min to obtain the thin layer composite ultrafiltration membrane.

[0056] Example 2

[0057] This embodiment provides a method for preparing the thin-layer composite ultrafiltration membrane. The only difference between the preparation method and Example 1 is that 0.5 g of β-cyclodextrin (molecular weight of 1135 Da, McLean, C804562) and 0.5 g of polyethyleneimine (number average molecular weight of 1200 Da, Aladdin, E670260) are used in step (1), and the rest are the same as Example 1.

[0058] Example 3

[0059] This embodiment provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that of Example 1 only in that, in step (1), 0.25 g of dextran (number average molecular weight of 10,000 Da, McLean, D806714) and 0.25 g of polyethyleneimine (number average molecular weight of 10,000 Da, Aladdin, E107079) are dissolved in 100 mL of 0.2 wt % sodium hydroxide solution to prepare an aqueous phase reactant. The rest is the same as in Example 1.

[0060] Example 4

[0061] This embodiment provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method is different from that of Example 1 only in that in step (2), the porous support membrane is immersed in the aqueous reactant and taken out after 2 minutes. The rest is the same as that of Example 1.

[0062] Example 5

[0063] This embodiment provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that of Example 1 only in that the porous support membrane covered with the polyester amide separation layer in step (3) is soaked in 50 mL of a 0.2 wt% sodium hydroxide aqueous solution for 15 min. The rest is the same as that of Example 1.

[0064] Comparative Example 1

[0065] This comparative example provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that in Example 1 only in that step (1) uses 0.5 g of polyethyleneimine (number average molecular weight of 10,000 Da, Aladdin, E107079) and 0.5 g of β-cyclodextrin (molecular weight of 1,135 Da, McLean, C804562), and the rest is the same as in Example 1.

[0066] Comparative Example 2

[0067] This comparative example provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that in Example 1 only in that step (1) uses 0.5 g of polyethyleneimine (number average molecular weight of 10,000 Da, Aladdin, E107079) and 0.25 g of dextran (number average molecular weight of 10,000 Da, McLean, D806714), and the rest are the same as in Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that of Example 1 only in that the sodium hydroxide solution in step (1) is replaced with 100 mL of pure water, and the rest is the same as that of Example 1.

[0070] Comparative Example 4

[0071] This comparative example provides a thin-layer composite ultrafiltration membrane and a preparation method thereof. The preparation method differs from that of Example 1 only in that, in step (3), the porous support membrane with a polyester amide separation layer on its surface is soaked in 50 mL of pure water for 12 h. The rest is the same as that of Example 1.

[0072] Performance testing:

[0073] The thin-layer composite ultrafiltration membranes provided in the above examples and comparative examples were tested for pure water permeation flux, bovine serum albumin retention rate, pore size distribution and average effective pore size at 25°C.

[0074] The cross-flow filtration device was used to test the pure water permeation flux, bovine serum albumin retention rate, pure water flux recovery rate, pore size distribution and average effective pore size of the composite ultrafiltration membrane. The effective membrane area of ​​the membrane chamber was 8 cm 2 .

[0075] (1) The pure water permeation flux is expressed by formula I:

[0076]

[0077] In formula I, PWP is the pure water permeation flux (L m -2 h -1 bar -1 );V p A is the volume of permeate collected in time t (L); m is the effective membrane area (m 2 ); t is the running time (h); TMP is the transmembrane pressure (bar).

[0078] (2) The retention rate of bovine serum albumin is expressed as formula II:

[0079]

[0080] In Formula II, C p and C r represent the concentration of solute in the permeate and retentate, respectively.

[0081] (3) Pure water flux recovery rate: This represents the anti-pollution performance of the thin-layer composite ultrafiltration membrane and is expressed by Formula III:

[0082]

[0083] In formula III, J R is the pure water flux restored after protein filtration and deionized water washing; J0 is the pure water flux before protein filtration operation.

[0084] (4) Pore size distribution and average effective pore size: Four neutral molecules (dextran 10,000 Da, dextran 20,000 Da, dextran 40,000 Da, dextran 70,000 Da) were used as molecular probes to measure the membrane pore size distribution, which is expressed as Formula IV:

[0085]

[0086] In Formula IV, d p represents the Stokes diameter of the solute; σ p represents the geometric standard deviation, which is determined by the d when R = 84.13% and R = 50%. p Compared to the calculation; μ p Represents the average effective pore size, obtained when R=50%.

[0087] The specific test results are shown in Table 1:

[0088] Table 1

[0089]

[0090] As can be seen from the data in Table 1, the thin-layer composite ultrafiltration membrane obtained by the preparation method of the present invention has ultra-high pure water flux, almost completely retains bovine serum albumin, has a narrow pore size distribution, and has strong resistance to protein contamination.

[0091] In the composite ultrafiltration membranes provided in Examples 1-5, the aqueous phase reactants are all monomers containing alcoholic hydroxyl groups and compounds containing amino groups of the same molecular weight, with similar diffusion rates and reaction activities. The ultrafiltration membranes finally formed all have larger membrane pores, achieving high-purity water flux and retention of bovine serum albumin.

[0092] From the comparison between Example 1 and Comparative Example 1, it can be seen that the molecular weights of the alcoholic hydroxyl-containing monomer and the amino-containing compound in Comparative Example 1 are quite different, the reaction is unbalanced, the average pore size of the prepared thin-layer composite ultrafiltration membrane is reduced, and the uniformity of the pore size distribution is poor, resulting in a decrease in the pure water permeation flux and a decrease in the retention rate of bovine serum albumin. In addition, due to protein contamination, the pure water flux of the thin-layer composite ultrafiltration membrane cannot be restored by cleaning with deionized water.

[0093] From the comparison of Example 1 and Comparative Example 2, it can be seen that the concentrations of the alcoholic hydroxyl-containing monomer and the amino-containing compound in Comparative Example 2 are quite different, the reaction is unbalanced, the average pore size of the prepared thin-layer composite ultrafiltration membrane is reduced, and the uniformity of the pore size distribution is poor, resulting in a decrease in the pure water permeation flux and a decrease in the retention rate of bovine serum albumin. In addition, due to protein contamination, the pure water flux of the thin-layer composite ultrafiltration membrane cannot be restored by cleaning with deionized water.

[0094] From the comparison between Example 1 and Comparative Example 3, it can be seen that in step (1) of Comparative Example 3, the monomer containing alcoholic hydroxyl groups and the compound containing amino groups are dissolved in pure water (pH is 6.5), which changes the pH of the solution, resulting in uneven reaction activity of the aqueous phase reactants, a decrease in the average pore size of the prepared thin-layer composite ultrafiltration membrane, a decrease in pure water flux, and a low pure water flux recovery rate.

[0095] From the comparison between Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 does not have the step of treating in alkaline solution B, resulting in the presence of polyester with low crosslinking degree and loose structure, thereby reducing the pore size of the thin layer composite ultrafiltration membrane and resulting in a decrease in pure water permeation flux.

[0096] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a thin layer composite ultrafiltration membrane, characterized in that: The preparation method of the thin layer composite ultrafiltration membrane comprises the following steps: (1) dissolving a monomer containing an alcoholic hydroxyl group and a compound containing an amino group in an alkaline solution A to obtain an aqueous phase reactant; (2) immersing the porous support membrane in an aqueous phase reactant, and then immersing the porous support membrane in an oil phase reactant, and subjecting the porous support membrane to heat treatment to obtain a porous support membrane having a polyester amide separation layer on its surface; (3) treating the porous support membrane with the polyester amide separation layer obtained in step (2) in alkaline solution B to obtain the thin layer composite ultrafiltration membrane; The difference in molecular weight between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤100Da; The difference in concentration between the monomer containing alcoholic hydroxyl groups and the compound containing amino groups is ≤0.05%.

2. The preparation method according to claim 1, characterized in that The monomer containing alcoholic hydroxyl group includes any one or a combination of at least two of sophoroside, salidroside, dextran, β-cyclodextrin or gallic acid; Preferably, the concentration of the alcoholic hydroxyl monomer in the aqueous phase reactant is 0.05-5 wt%; Preferably, the alkaline solution A comprises any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two thereof; Preferably, the pH of the alkaline solution A is 11-13.

4.

3. The preparation method according to claim 1 or 2, characterized in that The amino group-containing compound includes any one or a combination of at least two of polyethyleneimine, piperazine, ethylenediamine, tetraethylenepentamine, diethylenetriamine or triethylamine; Preferably, the concentration of the amino compound in the aqueous phase reactant is 0.05-5 wt %.

4. The preparation method according to any one of claims 1 to 3, characterized in that The oil phase reactant is obtained by dissolving an acyl halide compound in an organic solvent; Preferably, the functionality of the acyl halide compound is ≥2; Preferably, the acyl halide compound comprises an acyl chloride compound and / or an acyl bromide compound; Preferably, the acyl halide compound comprises any one of trimesoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride, biphenyltetracarboxylic acid chloride or biphenyltricarboxylic acid chloride, or a combination of at least two thereof; Preferably, the organic solvent comprises any one or a combination of at least two of n-hexane, acetonitrile, acetone, cyclohexane, chloroform or isooctane; Preferably, the concentration of the oil phase reactant is 0.1-1.0 wt%.

5. The preparation method according to any one of claims 1 to 4, characterized in that The porous support membrane is a polymer separation membrane; Preferably, the pore size of the polymer separation membrane is 0.01-0.22 μm; Preferably, the polymer separation membrane comprises any one of polysulfone, polyethersulfone, polyvinylidene fluoride, polyethylene or polypropylene.

6. The preparation method according to any one of claims 1 to 5, characterized in that The porous support membrane is immersed in the aqueous phase reactant for 1-10 minutes; Preferably, the porous support membrane is immersed in the oil phase reactant for 1-5 minutes.

7. The preparation method according to any one of claims 1 to 6, characterized in that The temperature of the heat treatment is 40-80°C; Preferably, the heat treatment time is 1-15 minutes.

8. The preparation method according to any one of claims 1 to 7, characterized in that The alkaline solution B includes any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two thereof; Preferably, the pH of the alkaline solution B is 11-13.4; Preferably, the porous support membrane covered with the polyester amide separation layer is treated in the alkaline solution B for 5-40 minutes; Preferably, the polyester amide separation layer has a thickness of 30-300 nm.

9. A thin layer composite ultrafiltration membrane, characterized in that: The thin-layer composite ultrafiltration membrane is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the thin-layer composite ultrafiltration membrane according to claim 9 in separation of biomacromolecules.

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