A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers

Abstract

This invention relates to a method for preparing an ultrafiltration membrane based on spray-deposited block copolymer nanofibers, comprising: dispersing block copolymer nanofibers with a diameter of 15-30 nm and a length of 500-2000 nm in a solvent to prepare a block copolymer nanofiber solution with a mass percentage concentration of 0.075-0.75%; uniformly spraying the obtained block copolymer nanofiber solution onto the surface of a microfiltration substrate membrane, controlling the spraying amount of the block copolymer nanofiber solution to be 0.025-0.08 mL / cm². 2 A composite ultrafiltration membrane is obtained. The membrane fabrication method provided by this invention is simple, easy to implement, clean, and efficient. Furthermore, the pore size and thickness of the separation layer of the obtained ultrafiltration membrane are adjustable, and the flux can be adjusted within a certain range.

Description

Technical Field

[0001] This invention relates to a method for preparing an ultrafiltration membrane, and more particularly to a method for preparing an ultrafiltration membrane based on spray-deposited block copolymer nanofibers. Background Technology

[0002] Membrane separation is a technology that uses membrane materials as a medium to achieve efficient separation of substances based on the principle of selective permeation. Compared with other separation technologies, membrane separation has significant advantages in efficiency and energy saving, and has become a key technology for solving major problems in water resources, environmental protection, and energy. Membrane separation has a wide range of applications and therefore a huge market. Precisely controlling the pore structure of ultrafiltration membranes and reducing the pollution risks in the preparation process are important ways to expand its application areas, making the preparation of ultrafiltration membranes of great significance.

[0003] In the preparation of ultrafiltration membranes, a phase transformation process involving polymer solutions in water is generally employed. This pore-forming process is easily affected by minute kinetic disturbances, and the microstructure of the pores is difficult to control. The resulting membranes have a wide pore size distribution, leading to a trade-off between permeability and selectivity during separation. Furthermore, this process requires large amounts of organic solvents and generates difficult-to-treat wastewater, posing a significant pollution risk.

[0004] Therefore, it is of great significance to invent a simple, easy-to-implement, efficient and clean method for preparing ultrafiltration membranes. Summary of the Invention

[0005] The purpose of this invention is to improve existing membrane fabrication technology and provide a highly efficient, clean, and simple method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers.

[0006] The technical solution to achieve the above-mentioned objective of this invention is as follows: a method for preparing an ultrafiltration membrane based on spray-deposited block copolymer nanofibers; that is, using stacked block copolymer nanofibers as the selective separation layer and a microfiltration base membrane as the support layer, an ultrafiltration membrane is prepared by spray-depositing nanofibers, comprising the following steps:

[0007] 1) Block copolymer nanofibers with a diameter of 15-30 nm and a length of 500-2000 nm are dispersed in a solvent to prepare a block copolymer nanofiber solution with a mass percentage concentration of 0.075-0.75%.

[0008] 2) The block copolymer nanofiber solution obtained in 1) is uniformly sprayed onto the surface of the microfiltration membrane, with the spraying amount of the block copolymer nanofiber solution controlled at 0.025-0.08 mL / cm². 2 A composite ultrafiltration membrane was obtained.

[0009] In the scheme described in this invention, 1) the block copolymer nanofibers can be fibrous block copolymers prepared from various existing polymer monomers, provided that their diameter and length meet the range defined in this invention. For example, the block copolymer nanofibers can be poly(N,N-dimethylaminoethyl methacrylate)-block-polyethylene glycol, polyethylene glycol-block-benzyl methacrylate, etc., block copolymer nanofibers.

[0010] The performance of ultrafiltration membranes mainly depends on the thickness, pore size, and porosity of the separation layer deposited on the surface of the microfiltration substrate after spraying. Insufficient thickness, excessively large pore size, or excessively low porosity will not result in excellent retention rates, while excessive thickness, excessively large pore size, or excessively high porosity will not guarantee sufficient pure water flux. In the solution described in this invention, the thickness, pore size, and porosity of the prepared ultrafiltration membrane can be controlled by adjusting the concentration of the sprayed block copolymer nanofiber solution, the diameter and length of the block copolymer nanofibers, and the amount of block copolymer nanofiber solution sprayed.

[0011] In a preferred embodiment of the present invention, 1) the block copolymer nanofibers have a diameter of 20-30 nm and a length of 500-2000 nm.

[0012] In a more preferred embodiment of the present invention, 1) the block copolymer nanofiber is composed of block A and block B, wherein block A is poly(N,N-dimethylaminomethyl methacrylate) and block B is polybenzyl methacrylate; wherein the number of structural units in block A is 29-38 and the number of structural units in block B is 60-70. Blocks A and B with the specified number of structural units can copolymerize to obtain block copolymer nanofibers with a diameter of 20-30 nm and a length of 500-2000 nm.

[0013] In a further preferred embodiment of the present invention, the concentration of the block copolymer nanofiber solution 1) is 0.075wt%-0.1wt%.

[0014] In a preferred embodiment of the present invention, the solvent described in 1) is ethanol or water.

[0015] In a preferred embodiment of the present invention, the spraying amount of the block copolymer nanofiber solution described in step 2) is 0.05-0.075 mL / cm². 2 .

[0016] In the present invention, the microfiltration membrane described in 2) is any membrane material that does not react with the solvent described in 1), preferably any one of polyethersulfone membrane, polyvinylidene fluoride membrane or polytetrafluoroethylene membrane.

[0017] This invention provides a process for preparing an ultrafiltration membrane: a specific concentration solution of block copolymer nanofibers of a specific size is sprayed and deposited onto a microfiltration base membrane in a specific amount to form an ultrafiltration membrane with densely stacked block copolymer nanofibers as the separation layer and the microfiltration base membrane as the support layer.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By controlling the size of block copolymer nanofibers and the concentration of block copolymer nanofiber solution, a new approach to preparing ultrafiltration membranes by one-dimensional nanofiber deposition through spraying to form a densely stacked block copolymer nanofiber separation layer has been realized. This method is more cost-effective, green and clean, and energy-efficient than existing technologies.

[0020] (2) The effective pore size of the prepared ultrafiltration membrane can be adjusted within a certain range by changing the diameter of the block copolymer nanofibers, the spraying concentration of the block copolymer nanofiber solution and the spraying volume, thereby controlling the separation performance of the prepared membrane.

[0021] (3) The film-making process does not require molds, the molding is fast, and the block copolymer nanofiber solution has a high utilization rate. Attached Figure Description

[0022] Figure 1A These are transmission electron microscopy (TEM) images of the block copolymer nanofibers used in Examples 1 to 3. Figures 1B to 1C These are scanning electron microscope (SEM) images of the surface and cross-section of membrane-II prepared in Example 2.

[0023] Figures 2A to 2C The images shown are scanning electron microscope (SEM) images of the cross sections of membranes I, II, and III prepared in Examples 1 to 3, respectively.

[0024] Figure 3 This demonstrates the changes in pure water flux and rejection rate of membranes I, II, and III prepared in Examples 1 to 3 as the coating amount increases.

[0025] Figure 4A These are transmission electron microscopy (TEM) images of the block copolymer nanofibers used in Examples 7-9. Figures 4B to 4C These are scanning electron microscope (SEM) images of the surface and cross-section of the membrane-VIII prepared in Example 8.

[0026] Figure 5 The changes in pure water flux and rejection rate of membranes-VII,-VIII and-IX prepared in Examples 7 to 9 with increasing coating amount are shown.

[0027] Figure 6AThese are transmission electron microscopy (TEM) images of the block copolymer nanofibers used in Comparative Examples 7-9. Figures 6B to 6D These are scanning electron microscope (SEM) images of the surfaces of the films prepared in Comparative Examples 7-9. Detailed Implementation

[0028] This invention provides a method for preparing an ultrafiltration membrane based on spray-deposited block copolymer nanofibers, comprising the following steps:

[0029] a) Disperse block copolymer nanofibers in a solvent to prepare a block copolymer nanofiber solution;

[0030] b) Cut the microfiltration membrane to 10×10cm. 2 The size is fixed on the heating table of the sprayer, and the spraying size is set according to the size of the base film;

[0031] c) Pour the block copolymer nanofiber solution prepared in step a into the syringe connected to the sprayer, start the sprayer and air pump, and the block copolymer nanofiber solution is atomized into droplets under the drive of compressed air. As the solvent gradually evaporates during the spraying of the droplets, the block copolymer nanofibers begin to solidify and finally deposit on the surface of the microfiltration membrane.

[0032] As the nozzle moves repeatedly from left to right and from front to back, a thin, dense block copolymer nanofiber membrane layer is formed on the surface of the microfiltration base membrane, which combines with the microfiltration base membrane to form an ultra-microfiltration membrane.

[0033] The block copolymer nanofibers are composed of block A and block B, where block A is poly(N,N-dimethylaminomethyl methacrylate) and block B is benzyl methacrylate; the number of structural units in block A is 29-38 and the number of structural units in block B is 60-70; the diameter of the block copolymer nanofibers is 15-30 nm.

[0034] d) Preferably, the solvent in step a) is ethanol or water; preferably, the mass percentage concentration of the block copolymer nanofiber solution is 0.05-0.75%.

[0035] The preferred microfiltration base membrane in step b) is a polyethersulfone membrane, a polyvinylidene fluoride membrane, a polytetrafluoroethylene membrane, etc., and the base membrane used should not react with the block copolymer nanofiber solution or with the solvent in the block copolymer nanofiber solution.

[0036] In preferred step c), the spraying volume of the block copolymer nanofiber solution is mainly 2.5 mL, 5 mL and 7.5 mL, and the solution should be able to uniformly cover the surface of the base film.

[0037] The present invention will be further described below with reference to specific embodiments, but the given embodiments do not constitute a limitation on the scope of protection of the claims of the present invention.

[0038] Examples 1-3

[0039] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0040] a) Weigh 0.3 g of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 70 structural units), nanofibers with a diameter of 20-30 nm and a length of 1000-2000 nm, disperse in 80 g of ethanol, and prepare a solution with a polymer mass fraction of 0.075 wt%;

[0041] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0042] c) Take 5 ml, 7.5 ml, and 10 ml of the block copolymer nanofiber solution prepared in a) respectively, add them into a syringe, and use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.05 ml / cm², 0.075 ml / cm², and 0.1 ml / cm² respectively.

[0043] d) Three membranes coated with block copolymer nanofiber solution were placed in a ventilated area and allowed to air dry naturally, resulting in three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and a PES membrane as the support layer. These membranes are designated as membrane-I, membrane-II, and membrane-III. Their transmission electron microscopy (TEM) images are shown below. Figure 1A As shown.

[0044] Depend on Figures 1A to 1C It can be seen that the diameter of the block copolymer nanofibers sprayed in Example 2 is between 20-30 nm. The prepared membrane-II is an ultrafiltration membrane with a spraying amount of 0.075 ml / cm² of base membrane. The selective separation layer formed by the close stacking of nanofibers on the base membrane surface is flat and has a thickness of 700-730 nm, and is uniform and flat.

[0045] Depend on Figures 2A to 2C It can be seen that as the amount of block copolymer nanofibers sprayed and deposited in Examples 1 to 3 increases, the film thickness of Membrane-I, Membrane-II and Membrane-III gradually increases.

[0046] Depend on Figure 3It can be seen that the pure water flux of the ultrafiltration membranes (membrane-I, membrane-II, and membrane-III) prepared in Examples 1 to 3 are 2363.33 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 660.67 L·m -2 ·h -1 ·bar -1 267.33 L·m -2 ·h -1 ·bar -1 The retention rates for 50nm gold nanoparticles were 93%, 97%, and 99%, respectively. As the thickness of the block copolymer nanofiber separation layer increased, the water flux gradually decreased, while the retention rate gradually increased.

[0047] Comparative Examples 1-3

[0048] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0049] a) Weigh 0.25 g of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 70 structural units), nanofibers with a diameter of 20-30 nm and a length of 1000-2000 nm, disperse in 100 g of ethanol, and prepare a solution with a polymer mass fraction of 0.05 wt%;

[0050] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0051] c) Take 5 ml, 7.5 ml, and 10 ml of the block copolymer nanofiber solution prepared in a) respectively, add them into a syringe, and use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.05 ml / cm², 0.075 ml / cm², and 0.1 ml / cm² respectively.

[0052] d) Place the three membranes coated with block copolymer nanofiber solution in a ventilated place to dry naturally, and obtain three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and PES membrane as the support layer, denoted as control membrane-I, control membrane-II and control membrane-III.

[0053] Compared to Examples 1 to 3, the concentration of the block copolymer nanofiber solution sprayed in Comparative Examples 1 to 3 decreased to 0.05 wt%, failing to effectively cover the base membrane surface, resulting in a separation layer with a pore size of 200-300 nm. Therefore, the performance of the ultrafiltration membranes prepared in Comparative Examples 1 to 3 (Comparative Membrane-I, Comparative Membrane-II, and Comparative Membrane-III) was significantly worse than that of Membrane-I, Membrane-II, and Membrane-III, with pure water fluxes of 18625 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 14256 L·m -2 ·h -1 ·bar -1 13471 L·m -2 ·h -1 ·bar -1 The retention rates of 50nm gold nanoparticles were only 7%, 12%, and 15%, respectively.

[0054] Examples 4-6

[0055] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0056] a) Weigh 0.4 g of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 70 structural units), nanofibers with a diameter of 20-30 nm and a length of 1000-2000 nm, disperse in 80 g of ethanol, and prepare a solution with a polymer mass fraction of 0.1 wt%;

[0057] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0058] c) Take 2.5 ml, 5 ml, and 7.5 ml of the block copolymer nanofiber solution prepared in a) respectively, add them into a syringe, and use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.025 ml / cm², 0.05 ml / cm², and 0.075 ml / cm² respectively.

[0059] d) Place the three membranes coated with block copolymer nanofiber solution in a ventilated place to dry naturally, and obtain three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and PES membrane as the support layer, denoted as membrane-IV, membrane-V and membrane-VI.

[0060] Compared to Examples 1 to 3, Examples 4 to 6 used a higher concentration of block copolymer nanofiber solution, achieving performance comparable to Membrane-I, Membrane-II, and Membrane-III with a relatively lower coating amount. The pure water flux of the prepared ultrafiltration membranes (Membrane-IV, Membrane-V, and Membrane-VI) was 1828.51 L·m⁻¹. -2 ·h -1 ·bar -1 699.54 L·m -2 ·h -1 ·bar -1 399.01 L·m -2 ·h -1 ·bar -1 The retention rates of 50nm gold nanoparticles were 95%, 97%, and 99%, respectively.

[0061] Examples 7-9

[0062] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0063] a) Weigh 2.4 g of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 60 structural units), nanofibers with a diameter of 15-20 nm and a length of 500-800 nm, disperse in 80 g of ethanol, and prepare a solution with a polymer mass fraction of 0.6 wt%;

[0064] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0065] c) Take 2.5 ml, 5 ml, and 7.5 ml of the block copolymer nanofiber solution prepared in a) respectively, add them into a syringe, and use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.025 ml / cm², 0.05 ml / cm², and 0.075 ml / cm² respectively.

[0066] d) Three membranes coated with block copolymer nanofiber solution were placed in a ventilated area and allowed to air dry naturally, resulting in three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and a PES membrane as the support layer. These membranes are designated as membrane-VII, membrane-VIII, and membrane-IX. Their transmission electron microscopy (TEM) images are shown below. Figure 4A As shown.

[0067] Depend on Figures 4A to 4CIt can be seen that the diameter of the block copolymer nanofibers sprayed in Example 8 is between 15-20 nm. The prepared membrane-VIII is an ultrafiltration membrane with a spraying amount of 0.075 ml / cm² of base membrane. The selective separation layer formed by the close stacking of its nanofibers on the base membrane surface is flat and has a thickness of 1300-1538 nm, and is uniform and flat.

[0068] Compared to Examples 1 to 6, Examples 7 to 9 used block copolymer nanofibers with smaller diameters and lengths, resulting in thinner separation layers deposited after spraying with the same or smaller spraying amounts. Although the concentration of the spraying solution was significantly increased compared to Examples 1 to 6, the rejection performance of membranes-VII, VIII, and IX was relatively reduced, but the pure water flux remained within the ideal range. The pure water fluxes of the ultrafiltration membranes (membranes-VII, VIII, and IX) prepared in Examples 7 to 9 were 6874 L·m⁻²·h⁻¹·bar⁻¹, 1731 L·m⁻²·h⁻¹, and 1731 L·m⁻²·bar⁻¹, respectively. -2 ·h -1 ·bar -1 616 L·m -2 ·h -1 ·bar -1 The retention rates for 50nm gold nanoparticles were 83.33%, 93.8%, and 98%, respectively.

[0069] Comparative Examples 4-6

[0070] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0071] a) Weigh 2 grams of block copolymer nanofiber solution (poly(N,N-dimethylaminomethacrylate with 30 structural units and poly(benzyl methacrylate with 60 structural units), nanofibers with a diameter of 15-20 nm and a length of 500-800 nm, disperse in 80 grams of ethanol, and prepare a solution with a polymer mass fraction of 0.5 wt%.

[0072] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0073] c) Take 5 ml and 7.5 ml of the block copolymer nanofiber solution prepared in a) respectively, add them into a syringe, and use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes respectively, that is, the amount of block copolymer nanofibers covering the base membrane is 0.05 ml / cm² and 0.075 ml / cm² respectively.

[0074] d) Place the three membranes coated with block copolymer nanofiber solution in a ventilated place to dry naturally, and obtain three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and PES membrane as the support layer, denoted as control membrane-IV, control membrane-V and control membrane-VI.

[0075] Compared to Examples 1 to 6, Comparative Examples 4 to 6 used block copolymer nanofibers with smaller diameters and lengths, resulting in a thinner separation layer after spraying with the same amount of coating. Although the concentration of the spraying solution was significantly increased compared to Examples 1 to 6, the retention performance of Comparative Membrane-IV, Comparative Membrane-V, and Comparative Membrane-VI was still significantly reduced. Compared to Examples 7 to 9, Comparative Examples 4 to 6 used block copolymer nanofiber solutions with even lower concentrations for spraying, resulting in ineffective coverage of the base membrane surface. The thickness of the resulting separation layer was only tens of nanometers, with a surface pore size of around 200 nm. Therefore, the performance of the ultrafiltration membranes (Comparative Membrane-IV, Comparative Membrane-V, and Comparative Membrane-VI) prepared in Comparative Examples 4 to 6 was significantly worse than that of Membranes-I to IX, with pure water fluxes of 23420 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 17553 L·m -2 ·h -1 ·bar -1 16908 L·m -2 ·h -1 ·bar -1 The retention rates of 50nm gold nanoparticles were 5%, 6%, and 15%, respectively.

[0076] Examples 10-12

[0077] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0078] a) Weigh 3 grams of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 60 structural units), nanofibers with a diameter of 15-20 nm and a length of 500-800 nm, disperse in 80 grams of ethanol, and prepare a solution with a polymer mass fraction of 0.75 wt%.

[0079] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0080] c) Take 2.5 ml, 4 ml, and 5 ml of the block copolymer nanofiber solution prepared in a) and add them into a syringe. Use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes, respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.025 ml / cm², 0.04 ml / cm², and 0.05 ml / cm², respectively.

[0081] d) Place the three membranes coated with block copolymer nanofiber solution in a ventilated place to dry naturally, and obtain three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and PES membrane as the support layer, denoted as membrane-X, membrane-XI and membrane-XII.

[0082] Compared to Comparative Examples 4 to 6, Examples 10 to 12 used a high-concentration block copolymer nanofiber solution for spraying. Although the spraying amount was comparable or even smaller, a significantly increased separation layer thickness was still achieved, resulting in a significant improvement in retention rate, and the water flux remained within the ideal range. Compared to Examples 7 to 9, Examples 10 to 12 also achieved relatively better performance due to the use of a higher concentration of block copolymer nanofiber solution for spraying. The pure water flux of the prepared ultrafiltration membranes (membrane-X, membrane-XI, and membrane-XII) was 4341 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 657 L·m -2 ·h -1 ·bar -1 304 L·m -2 ·h -1 ·bar -1 The retention rates for 50nm gold nanoparticles were 92%, 95%, and 98.6%, respectively.

[0083] Comparative Examples 7-9

[0084] A method for preparing ultrafiltration membranes based on spray-deposited block copolymer nanofibers includes the following steps:

[0085] a) Weigh 4 grams of block copolymer nanofiber solution (poly(N,N-dimethylaminomethyl methacrylate with 30 structural units and poly(benzyl methacrylate with 50 structural units). The prepared nanofibers are spherical micelles with a diameter of 20-40 nm. Disperse them in 80 grams of ethanol to prepare a solution with a polymer mass fraction of 1 wt%.

[0086] b) Take 3 polyethersulfone (PES) films (film area 100 square centimeters) and place them on the heating table of the sprayer;

[0087] c) Take 2.5 ml, 5 ml, and 7.5 ml of the block copolymer nanofiber solution prepared in a) and add them into a syringe. Use a sprayer to spray and deposit the three doses of block copolymer nanofiber solution onto the surface of three PES membranes, respectively. That is, the amount of block copolymer nanofibers covering the base membrane is 0.025 ml / cm², 0.05 ml / cm², and 0.075 ml / cm², respectively.

[0088] d) Three membranes coated with block copolymer nanofiber solution were placed in a ventilated area and allowed to air dry naturally, resulting in three ultrafiltration membranes with densely stacked block copolymer nanofibers as the separation layer and a PES membrane as the support layer. These membranes are denoted as membrane-XIII, membrane-XIV, and membrane-XV. Their transmission electron microscopy (TEM) images are shown below. Figure 6A As shown.

[0089] Compared to Examples 1 to 12, Comparative Examples 7 to 9 used block copolymer spherical nanofibers with smaller fiber diameter and length, such as... Figures 6B to 6D As shown, due to the reduced number of block B structural units in the block copolymer nanofibers used, the nanofibers are spherical with a diameter smaller than the average pore size of the polyethersulfone (PES) membrane (220 nm). Therefore, most of the spherical fibers penetrate into the interior of the base membrane and cannot completely cover its surface. Even with increased spray concentration and spray volume, a separation layer cannot be formed on the PES membrane surface. The pure water flux of the prepared ultrafiltration membranes (membrane-XIII, membrane-XIV, and membrane-XV) is 8343 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 7534 L·m -2 ·h -1 ·bar -1 5196 L·m -2 ·h -1 ·bar -1 The retention rates for 50nm gold nanoparticles were 42%, 55%, and 58.6%, respectively.

[0090] Comparative Example 10

[0091] Weigh 4 grams of block copolymer nanofiber solution (poly(N,N-dimethylaminomethacrylate with 30 structural units and poly(benzyl methacrylate with 80 structural units)). The nanofibers prepared have too many B blocks, which causes the nanowires to become entangled and cannot be dispersed, so they cannot be sprayed to form a film.

Claims

1. A method for preparing an ultrafiltration membrane based on spray-deposited block copolymer nanofibers, comprising the following steps: 1) Block copolymer nanofibers with a diameter of 20-30 nm and a length of 500-2000 nm are dispersed in a solvent to prepare a block copolymer nanofiber solution with a mass percentage concentration of 0.075-0.75%. 2) Uniformly spray the block copolymer nanofiber solution obtained in 1) onto the surface of the microfiltration membrane, controlling the spraying amount of the block copolymer nanofiber solution to be 0.025-0.08 mL / cm. 2 A composite ultrafiltration membrane was obtained, with block copolymer nanofiber stacks as the selective separation layer and a microfiltration base membrane as the support layer.

2. The method as described in claim 1, characterized in that: 1) The block copolymer nanofiber is composed of block A and block B, wherein block A is poly(N,N-dimethylaminomethyl methacrylate) and block B is polybenzyl methacrylate; wherein the number of structural units in block A is 29-38 and the number of structural units in block B is 60-70.

3. The method as described in claim 1, characterized in that: 1) The concentration of the block copolymer nanofiber solution is 0.075wt%-0.1wt%.

4. The method as described in claim 1, characterized in that: 1) The solvent is ethanol or water.

5. The method as described in claim 1, characterized in that: 2) The spraying amount of the block copolymer nanofiber solution is 0.05-0.075 mL / cm². 2 .

6. The method as described in claim 1, characterized in that: 2) The microfiltration base membrane is any one of polyethersulfone membrane, polyvinylidene fluoride membrane or polytetrafluoroethylene membrane.

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