Hydrophilic treatment method for ultrafiltration membrane

Abstract

The invention provides an ultrafiltration membrane hydrophilic treatment method which comprises the following steps: S1, soaking an ultrafiltration membrane in an organic solvent for full wetting to obtain a wetted ultrafiltration membrane; s2, putting the wetted ultrafiltration membrane into a microcapsule emulsion, and carrying out first soaking treatment to obtain a first soaked ultrafiltration membrane; s3, placing the ultrafiltration membrane after the first soaking in an organic weak acid solution for second soaking treatment to obtain a hydrophilic modified ultrafiltration membrane; wherein the microcapsule emulsion is formed by dispersing a microcapsule into water, the microcapsule has a core-shell structure, the core-shell structure comprises a microcapsule core and a microcapsule shell, the microcapsule core is inorganic nanoparticles, and the microcapsule shell is chitosan. The method is mild in reaction condition, simple in operation step and easy to realize industrialization.

Description

Technical Field

[0001] This invention relates to the field of membrane separation and modification technology, and specifically to a method for hydrophilic treatment of ultrafiltration membranes. Background Technology

[0002] Membrane separation technology is widely used in water treatment, material separation, purification, and concentration. Currently, due to its energy-saving, high-efficiency, simple process, and convenient operation, membrane technology has gradually replaced traditional water treatment processes. Commonly used materials for preparing ultrafiltration membranes include cellulose, polysulfone, and fluoropolymers. Most ultrafiltration membrane materials are hydrophobic, and the strong hydrophobicity of the ultrafiltration membrane surface makes it susceptible to fouling during use, reducing membrane lifespan and separation performance. Therefore, hydrophilicity is a key factor affecting membrane separation performance, and hydrophilization is crucial for promoting the application of ultrafiltration membranes.

[0003] Common hydrophilic modification methods mainly include blending modification, surface grafting, and surface deposition, which enhance the hydrophilicity and performance of the membrane by introducing hydrophilic groups.

[0004] CN202410671706.4 discloses a method for hydrophilic modification of a polytetrafluoroethylene (PTFE) filter membrane, comprising the following steps: immersing the PTFE filter membrane in an organic solvent to fully wet it; immersing the wetted PTFE filter membrane in an oil-in-water emulsion; and then placing it in a crosslinking agent solution for a crosslinking reaction to obtain a hydrophilically modified PTFE filter membrane; wherein the oil-in-water emulsion is uniformly dispersed from a water-soluble polymer, a non-water-soluble organic solvent, an emulsifier, and water. In this method, the oil-in-water emulsion contains a large amount of organic solvent, and the oil-in-water exists in emulsion form, making it more difficult to remove than a pure solvent, potentially causing membrane fouling during subsequent removal processes.

[0005] Therefore, more hydrophilic modification methods are still needed. Summary of the Invention

[0006] To address the drawbacks of existing emulsions containing organic solvents, this invention provides a method for treating ultrafiltration membranes with organic-inorganic microcapsules, thereby improving the hydrophilicity and antibacterial properties of the ultrafiltration membrane while also enhancing its mechanical properties. The provided microcapsule wall material is chitosan, and the core material is inorganic particles. Because the microcapsules do not contain organic solvents, the possibility of ultrafiltration membrane fouling is avoided. Simultaneously, the chitosan wall material enhances the antibacterial properties of the ultrafiltration membrane, and the inorganic particles in the core material improve its strength. The ultrafiltration membrane obtained by this method exhibits excellent hydrophilicity and chemical stability, while simultaneously improving membrane flux, mechanical strength, and antibacterial properties. Furthermore, the reaction conditions are mild, the operation steps are simple, and it is easily industrialized.

[0007] In one aspect of the invention, a method for hydrophilic modification of an ultrafiltration membrane is provided. According to an embodiment of the invention, the method for hydrophilic modification of the ultrafiltration membrane includes the following steps: S1: Immerse the ultrafiltration membrane in an organic solvent to fully wet it, and obtain a wetted ultrafiltration membrane; S2: The wetted ultrafiltration membrane is placed in a microcapsule emulsion for a first immersion treatment to obtain a first-immersion ultrafiltration membrane; S3: The first soaked ultrafiltration membrane is placed in an organic weak acid solution for a second soaking treatment to obtain a hydrophilic modified ultrafiltration membrane; The microcapsule emulsion is formed by dispersing microcapsules in water. The microcapsules have a core-shell structure, comprising a microcapsule core and a microcapsule shell. The microcapsule core is an inorganic nanoparticle, and the microcapsule shell is chitosan. This method features mild reaction conditions, simple operation steps, and is easily industrialized. It also improves membrane flux, mechanical strength, and antibacterial properties. The hydrophilically modified ultrafiltration membrane obtained using this method exhibits excellent hydrophilicity and chemical stability.

[0008] According to embodiments of the present invention, the above-described method for hydrophilic modification of ultrafiltration membranes may further include at least one of the following additional technical features: According to an embodiment of the present invention, the first soaking treatment time is 3h to 18h. If it is less than 3h, the surface of the ultrafiltration membrane cannot be fully wetted with microcapsule emulsion. If it is more than 18h, the production cycle will inevitably be extended, but it will not have an adverse effect on the performance of the ultrafiltration membrane.

[0009] According to an embodiment of the present invention, the first soaking treatment time is 3h to 5h.

[0010] According to an embodiment of the present invention, the organic weak acid solution is a citric acid solution, a succinic acid solution, or an oxalic acid solution.

[0011] According to embodiments of the present invention, the organic weak acid solution is a citric acid solution with a mass concentration of 0.2% to 2%, a succinic acid solution with a mass concentration of 0.2% to 2%, or an oxalic acid solution with a mass concentration of 0.2% to 2%. The concentration of 0.2% to 2% is chosen to control the degree of cross-linking with the microcapsule emulsion. If the concentration is below 0.2%, the reaction rate will be too slow and the reaction will be insufficient; if the concentration is above 2%, the reaction rate will be too fast, easily leading to over-cross-linking and decreased hydrophilicity.

[0012] According to an embodiment of the present invention, the second soaking time is 20 min to 90 min. If the soaking time is less than 20 min, the microcapsule emulsion cannot be fully cross-linked, resulting in poor adhesion of the microcapsule emulsion to the ultrafiltration membrane surface; if the soaking time is more than 90 min, the microcapsule emulsion will be over-cross-linked, resulting in poor hydrophilicity.

[0013] According to an embodiment of the present invention, the organic solvent is selected from methanol, ethanol, isopropanol and acetone.

[0014] According to embodiments of the present invention, the inorganic nanoparticles include silicon dioxide, aluminum oxide, calcium carbonate, aluminum nitride, titanium dioxide, carbon nanotubes, or graphene.

[0015] According to an embodiment of the present invention, the microcapsule emulsion comprises, by weight: 0.5-10 parts microcapsule shell, 10-40 parts microcapsule core, and 44-89 parts water.

[0016] According to an embodiment of the present invention, the microcapsule emulsion further comprises a dispersant.

[0017] According to embodiments of the present invention, the dispersant comprises one or more selected from Span 80, Span 60, Span 40, Span 20, Tween 80, Tween 60, Tween 40, Tween 20, OP-10, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, or polycarboxylate ammonium salts.

[0018] According to an embodiment of the present invention, the microcapsule emulsion comprises, by weight: 0.5-10 parts microcapsule shell, 10-40 parts microcapsule core, 0.5-1 part dispersant, and 44-89 parts water.

[0019] According to an embodiment of the present invention, the microcapsule emulsion further includes a binder.

[0020] According to embodiments of the present invention, the adhesive comprises one or more of polyvinyl alcohol, polyethylene oxide, and polyvinylpyrrolidone.

[0021] According to an embodiment of the present invention, the microcapsule emulsion comprises, by weight: 0.5-10 parts microcapsule shell, 10-40 parts microcapsule core, 0-5 parts binder, and 44-89 parts water.

[0022] According to an embodiment of the present invention, the microcapsule emulsion comprises, by weight: 0.5-10 parts microcapsule shell, 10-40 parts microcapsule core, 0.5-1 part dispersant, 0-5 parts binder, and 44-89 parts water.

[0023] According to an embodiment of the present invention, the microcapsule emulsion is a microcapsule emulsion formed by dispersing microcapsules in water, which is achieved by the following method: The microcapsule emulsion, which is a microcapsule emulsion formed by dispersing microcapsules in water, is prepared in the following manner: Inorganic nanoparticles, dispersants, and water are dispersed to form an inorganic nanoparticle dispersion. Chitosan was added to acetic acid and dissolved. Then, the inorganic nanoparticle dispersion was added and subjected to high-speed shearing treatment to obtain a solution after high-speed shearing treatment. A cross-linking agent is added to the solution after high-speed shearing treatment to perform cross-linking treatment, thereby obtaining the microcapsule emulsion.

[0024] According to an embodiment of the present invention, the dispersion process is performed by ultrasonic or high-speed shearing.

[0025] According to an embodiment of the present invention, the dispersion treatment is carried out by ultrasonic dispersion for 0.5 h to 2 h. The ultrasonic dispersion time is 0.5 h to 2 h because if the ultrasonic dispersion time is less than 0.5 h, the inorganic particles cannot be dispersed well, and if the ultrasonic dispersion time is greater than 2 h, the inorganic particles may further agglomerate due to the Austaunch ripening effect.

[0026] According to an embodiment of the present invention, the high-speed shearing treatment is carried out by dispersing the emulsifier at 2000-10000 rpm for 15-60 minutes. If the rotation speed is lower than 2000 rpm and the dispersion time is lower than 15 minutes, the inorganic particles cannot achieve good dispersion. If the rotation speed is higher than 10000 rpm and the dispersion time is higher than 60 minutes, the inorganic particles may further agglomerate due to the Austmann ripening effect. According to an embodiment of the present invention, the mass concentration of the first crosslinking agent solution is 0.5% to 2%. If the mass concentration of the crosslinking agent solution is less than 0.5%, the reaction will be too slow and ineffective coating will not be achieved. If the mass concentration of the crosslinking agent solution is greater than 2%, the reaction will be too fast, leading to agglomeration and sedimentation.

[0027] According to an embodiment of the present invention, the first crosslinking agent is selected from one or more of glyoxal, malondialdehyde, succinal, glutaraldehyde, oxalic acid, succinic acid, and citric acid.

[0028] According to an embodiment of the present invention, the crosslinking reaction temperature is 50°C to 80°C. If the reaction temperature is below 50°C, the reaction will be too slow, and the microcapsules will not be effectively encapsulated. If the reaction temperature is above 80°C, the reaction rate will be too fast, leading to aggregation and sedimentation.

[0029] According to an embodiment of the present invention, the cross-linking reaction time is 2–5 hours. A cross-linking time less than 2 hours will result in ineffective microcapsule encapsulation. A cross-linking time greater than 5 hours will inevitably lead to wasted energy and labor, but will not adversely affect the performance of the microcapsules.

[0030] According to an embodiment of the present invention, the mass ratio of the inorganic nanoparticles, dispersant and water is (10~40):(0.5~1):(44~89). According to an embodiment of the present invention, the mass ratio of chitosan to acetic acid is (0.5~10):(0.1~1.0).

[0031] According to an embodiment of the present invention, the mass ratio of the inorganic nanoparticles, dispersant, water, chitosan and second crosslinking agent is (10~40):(0.5~1):(44~89):(0.5~10):(0.10~1.0).

[0032] According to an embodiment of the present invention, the particle size of the microcapsules is 5 nm to 100 nm. The minimum particle size of the microcapsules is 5 nm due to the limitation of the particle size of inorganic particles, and the particle size of the microcapsules cannot be greater than 100 nm because if the particle size of the microcapsules is greater than 100 nm, it may clog the pores of the ultrafiltration membrane, resulting in a decrease in the porosity and flux of the ultrafiltration membrane.

[0033] In another aspect, the present invention also provides an ultrafiltration membrane. According to an embodiment of the present invention, the ultrafiltration membrane is prepared by the hydrophilic modification method of the ultrafiltration membrane described above.

[0034] In another aspect of the invention, the invention also proposes the preparation of an ultrafiltration membrane according to the hydrophilic modification method of the ultrafiltration membrane described above, or the application of the ultrafiltration membrane described above in membrane separation technology.

[0035] According to embodiments of the present invention, an ultrafiltration membrane is immersed in a microcapsule emulsion. The water-soluble wall material on the microcapsules reacts with a crosslinking agent to form a crosslinked network that wraps around the ultrafiltration membrane, thereby enhancing the hydrophilicity and durability of the ultrafiltration membrane. The inorganic particles of the microcapsule core material can improve the strength and pressure resistance of the ultrafiltration membrane. The hydrophilic modification method according to embodiments of the present invention can reduce the contact angle of water on the surface of the ultrafiltration membrane, resulting in an ultrafiltration membrane with excellent hydrophilicity, durability, and higher water flux, as well as excellent mechanical strength and pressure resistance. Furthermore, the modification is uniform, broadening the application of ultrafiltration membranes in the field of water treatment and demonstrating broad application prospects. According to an embodiment of the present invention, the microcapsule shell is chitosan and the microcapsule core is inorganic nanoparticles, which do not contain organic solvents and are safe and environmentally friendly.

[0036] The hydrophilic modification method according to embodiments of the present invention has relatively mild reaction conditions, simple operation steps, and is easy to industrialize. Detailed Implementation

[0037] The following examples are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] Example 1 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of isopropanol and immerse the ultrafiltration membrane to fully wet it; (2) Weigh 50g of nano silica and 5g of polycarboxylic acid ammonium salt dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 20min to form a nano silica dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add nano-silica dispersion, and after uniform dispersion, add 2 mg of glutaraldehyde. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVA205 (5%) solution to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the treatment solution for 5 hours; (5) Remove and immerse in 1% citric acid solution for 90 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0039] Example 2 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of ethanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of nano titanium dioxide and 8g of Span 80 dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 10min to form a nano titanium dioxide dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add nano titanium dioxide dispersion, and after it is evenly dispersed, add 2 mg of glyoxal and react at 80 °C for 2 h under stirring to obtain microcapsule emulsion. Add 10 g of PEO-8 (5%) solution to reach the treatment solution.

[0040] (4) Immerse the ultrafiltration membrane in the microprocessing solution for 3 hours; (5) Remove and immerse in 1% succinic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0041] Example 3 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of methanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of carbon nanotubes and 3g of sodium dodecyl sulfonate dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 20min to form a carbon nanotube dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add carbon nanotube dispersion, and after uniform dispersion, add 2 mg of malondialdehyde. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVP (6%) to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the treatment solution for 5 hours; (5) Remove and immerse in 1% oxalic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0042] Example 4 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of acetone to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of graphene and 5g of Tween 80 dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 50min to form a graphene dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add graphene dispersion, and after it is evenly dispersed, add 2 mg of oxalic acid. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVA217 (5%) to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the treatment solution for 3 hours; (5) Remove and immerse in 1% citric acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0043] Comparative Example 1 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of isopropanol and immerse the ultrafiltration membrane to fully wet it; (2) Weigh 50g of nano silica and 5g of polycarboxylic acid ammonium salt dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 20min to form a nano silica dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add nano-silica dispersion, and after uniform dispersion, add 2 mg of glutaraldehyde. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVA205 (5%) solution to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the treatment solution for 1 hour; (5) Remove and immerse in 1% citric acid solution for 90 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0044] Comparative Example 2 This embodiment discloses a method for hydrophilic modification of an ultrafiltration membrane, the specific steps of which are as follows: (1) Take an appropriate amount of acetone to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of graphene and 5g of Tween 80 dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 50min to form a graphene dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add graphene dispersion, and after it is evenly dispersed, add 2 mg of oxalic acid. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVA217 (5%) to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the microcapsule emulsion for 1 hour; (5) Remove and immerse in 3% citric acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0045] Comparative Example 3 (1) Take an appropriate amount of methanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of carbon nanotubes and 3g of sodium dodecyl sulfonate dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 10min to form a carbon nanotube dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add carbon nanotube dispersion, and after uniform dispersion, add 2 mg of malondialdehyde. React at 50 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVP (6%) to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the microcapsule emulsion for 5 hours; (5) Remove and immerse in 1% oxalic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0046] Comparative Example 4 (1) Take an appropriate amount of methanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of carbon nanotubes and 3g of sodium dodecyl sulfonate dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 20min to form a carbon nanotube dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add carbon nanotube dispersion, and after uniform dispersion, add 2 mg of malondialdehyde. React at 40 °C for 3 h under stirring to obtain microcapsule emulsion. Add 10 g of PVP (6%) to obtain treatment solution. (4) Immerse the ultrafiltration membrane in the treatment solution for 5 hours; (5) Remove and immerse in 1% oxalic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0047] Comparative Example 5 (1) Take an appropriate amount of ethanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Weigh 50g of nano titanium dioxide and 8g of Span 80 dispersant and disperse them in 200g of deionized water. Disperse them by ultrasonication for 10min to form a nano titanium dioxide dispersion. (3) Dissolve 2 g of chitosan in 198 g of acetic acid, then add nano titanium dioxide dispersion, disperse evenly, add 20 mg of glyoxal, react at 80 °C for 2 h under stirring, add 10 g of PEO-8 (5%) solution to obtain microcapsule emulsion; (4) Immerse the ultrafiltration membrane in the microcapsule emulsion for 3 hours; (5) Remove and immerse in 1% succinic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0048] Comparative Example 6 (1) Take an appropriate amount of ethanol to immerse the ultrafiltration membrane and wet it thoroughly; (2) Dissolve 2 grams of chitosan in 198 grams of acetic acid to obtain liquid A; (4) Immerse the ultrafiltration membrane in liquid A for 3 hours; (5) Remove and immerse in 1% succinic acid solution for 20 minutes; (6) Remove and dry to obtain a hydrophilic modified ultrafiltration membrane.

[0049] Performance testing: The ultrafiltration membranes prepared in the examples and comparative examples were tested; (1) Contact angle test: The hydrophilicity of the ultrafiltration membrane was tested by the droplet method using a contact angle analyzer. First, the upper surface of the membrane was fixed on a glass slide, and 2.0 μL of water was dropped onto the upper surface of the membrane. The contact angle was recorded at the same time.

[0050] (2) Antifouling: The antifouling performance of the ultrafiltration membrane was tested using BSA target pollutants. After the pure water flux test of the ultrafiltration membrane was completed, the rejection rate test was performed. Then, the surface of the fouled ultrafiltration membrane was cleaned with deionized water for 1 hour, and then the cleaned membrane was tested for pure water flux.

[0051] The recovery rate of water flux after one cycle is used as a period to evaluate the membrane's antifouling performance. Therefore, flux is calculated. The formula for the recovery rate is as follows: x100% In the formula, FRR—flux recovery rate, in (%); J W Pure water flux before pollution J Wi-1 —Pure water flux after cleaning i- represents the loop count, denoted as 1, 2, 3. …… .

[0052] (3) Flux and rejection rate test: The water flux and protein rejection rate of the ultrafiltration membrane were tested according to the test standards in GB / T 32360 2015. (4) Antibacterial properties: determined according to AATCC 100-2004 standard.

[0053] (5) Tensile strength and elongation at break: Tested according to the "HY / T213-2016 Method for Determination of Tensile Strength of Hollow Fiber Ultrafiltration Membrane". The results are shown in Table 1.

[0054] Table 1

[0055] 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. In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A method for hydrophilic modification of an ultrafiltration membrane, characterized by, The method comprises the following steps: S1: soaking the ultrafiltration membrane in an organic solvent to sufficiently wet the ultrafiltration membrane, to obtain a wetted ultrafiltration membrane; S2: placing the wetted ultrafiltration membrane in a microcapsule emulsion for first soaking treatment, to obtain a first-soaked ultrafiltration membrane; S3: placing the first-soaked ultrafiltration membrane in an organic weak acid solution for second soaking treatment, to obtain a hydrophilic modified ultrafiltration membrane; The microcapsule emulsion is formed by dispersing microcapsules in water, the microcapsules have a core-shell structure, the core-shell structure comprises a microcapsule core and a microcapsule shell, the microcapsule core is an inorganic nanoparticle, and the microcapsule shell is chitosan.

2. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1, characterized by, The first soaking treatment is performed for 3-18 hours; Preferably, the first soaking treatment is performed for 3-5 hours.

3. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1, characterized by, The organic weak acid solution is a citric acid solution, a succinic acid solution, or an oxalic acid solution; Optionally, the organic weak acid solution is a citric acid solution with a mass concentration of 0.2%-2%, a succinic acid solution with a mass concentration of 0.2%-2%, or an oxalic acid solution with a mass concentration of 0.2%-2%; Optionally, the second soaking treatment is performed for 20-90 minutes.

4. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1, characterized by, The organic solvent is selected from one of methanol, ethanol, isopropanol, and acetone; Optionally, the inorganic nanoparticle comprises silicon dioxide, aluminum oxide, calcium carbonate, aluminum nitride, titanium dioxide, carbon nanotubes, or graphene; Optionally, in the microcapsule emulsion, the microcapsule shell accounts for 0.5-10 parts by mass, the microcapsule core accounts for 10-40 parts by mass, and the water accounts for 44-89 parts by mass.

5. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1, wherein The microcapsule emulsion further comprises a dispersant; Optionally, the dispersant comprises one or more selected from Span 80, Span 60, Span 40, Span 20, Tween 80, Tween 60, Tween 40, Tween 20, OP-10, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, or polycarboxylic acid ammonium salt; Optionally, in the microcapsule emulsion, the microcapsule shell accounts for 0.5-10 parts by mass, the microcapsule core accounts for 10-40 parts by mass, the dispersant accounts for 0.5-1 parts by mass, and the water accounts for 44-89 parts by mass.

6. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1 or 5, characterized by, The microcapsule emulsion further comprises a binder; Optionally, the binder comprises one or more of polyvinyl alcohol, polyethylene oxide, and polyvinylpyrrolidone; Optionally, in the microcapsule emulsion, the microcapsule shell accounts for 0.5-10 parts by mass, the microcapsule core accounts for 10-40 parts by mass, the binder accounts for 0-5 parts by mass, and the water accounts for 44-89 parts by mass. Optionally, in the microcapsule emulsion, the microcapsule shell accounts for 0.5-10 parts by mass, the microcapsule core accounts for 10-40 parts by mass, the dispersant accounts for 0.5-1 parts by mass, the binder accounts for 0-5 parts by mass, and the water accounts for 44-89 parts by mass.

7. The method for hydrophilic modification of an ultrafiltration membrane according to claim 5, wherein The microcapsule emulsion is formed by dispersing microcapsules in water, and the microcapsule emulsion is prepared in the following manner: dispersing the inorganic nanoparticles, the dispersant, and the water to form an inorganic nanoparticle dispersion; adding chitosan to acetic acid, dissolving the chitosan, adding the inorganic nanoparticle dispersion, and performing high-speed shearing treatment to obtain a high-speed shearing treated solution; The cross-linking agent is added into the solution after the high-speed shearing treatment, and the cross-linking treatment is carried out in the process of slow stirring to obtain the microcapsule emulsion; Optionally, the dispersion treatment is carried out by ultrasonic or high-pressure homogenization; Optionally, the dispersion treatment is carried out by ultrasonic dispersion of 200-600W for 30-60min; Optionally, the high-speed shearing treatment is carried out by high-speed shearing emulsification of 2000-10000rpm for 15-60min; Optionally, the mass concentration of the cross-linking agent solution is 0.5%-2%; Optionally, the cross-linking agent is selected from one or more of glyoxal, malondialdehyde, succinic dialdehyde, glutaraldehyde, oxalic acid, succinic acid and citric acid; Optionally, the temperature of the cross-linking reaction is 50-80℃; Optionally, the time of the cross-linking reaction is 2-5h; Optionally, the stirring speed of the cross-linking reaction is 200-1000rpm; Optionally, the mass ratio of the inorganic nanoparticles, the dispersant and water is (10-40):(0.5-1):(44-89); Optionally, the mass ratio of the chitosan and acetic acid is (0.5-10):(0.1-1.0); Optionally, the mass ratio of the inorganic nanoparticles, the dispersant, water, chitosan and the second cross-linking agent is (10-40):(0.5-1):(44-89):(0.5-10):(0.10-1.0).

8. The method for hydrophilic modification of an ultrafiltration membrane according to claim 1, wherein The particle size of the microcapsule is 5-100nm.

9. An ultrafiltration membrane, characterized by, The ultrafiltration membrane is prepared by the hydrophilic modification method of the ultrafiltration membrane according to any one of claims 1-8.

10. The ultrafiltration membrane prepared by the hydrophilic modification method of the ultrafiltration membrane according to any one of claims 1-8 or the ultrafiltration membrane according to claim 9 in the application of membrane separation technology.

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