An ultrafiltration membrane, its preparation method and application

Abstract

This invention belongs to the field of membrane preparation technology, specifically relating to an ultrafiltration membrane, its preparation method, and its applications. The method first prepares an organic / inorganic hybrid membrane containing inorganic nanoparticles. Then, the hybrid membrane is immersed in a dilute acid aqueous solution of chitosan, allowing the dilute acid to etch and remove the inorganic nanoparticles, thereby increasing the membrane porosity. Simultaneously, chitosan is deposited on the membrane surface to further improve the membrane's hydrophilicity and permeability, and to reduce the average pore size of the membrane surface. The ultrafiltration membrane prepared in this way has the characteristics of small pore size and high porosity, exhibiting both high permeability and selectivity, and shows broad application prospects in water treatment, biomedicine, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to an ultrafiltration membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation technology has gained widespread attention in water treatment, chemical engineering, hemodialysis, and drug separation due to its advantages such as high efficiency, low energy consumption, and high degree of automation. Ultrafiltration is an important form of membrane separation technology, with ultrafiltration membranes typically having pore sizes between 1 and 100 nanometers. Ultrafiltration technology is usually based on a pressure-driven principle. When a liquid passes through an ultrafiltration membrane, small molecules, inorganic salts, and water molecules can easily pass through the tiny pores on the membrane to the other end, forming the permeate. Meanwhile, larger molecules, colloidal particles, bacteria, and viruses are effectively retained on the membrane surface, thus achieving the separation of different substances.

[0003] Currently, ultrafiltration membranes are mostly made of polymer materials. In the preparation of ultrafiltration membranes, polymers are dissolved in a suitable solvent to prepare a casting solution. Simultaneously, to obtain ideal pore structure and permeation performance, porogens are usually added to the casting solution. As the phase transformation process proceeds, the porogen gradually detaches from the membrane, forming pores within the membrane. These pores endow the ultrafiltration membrane with its permeation separation function. However, existing technologies have two problems. First, relying solely on adding porogens to achieve membrane porosity is limited. Typically, membranes prepared solely by adding porogens have a porosity that rarely exceeds 80%. Second, for ultrafiltration membranes, existing technologies often sacrifice membrane selectivity when improving permeability. This is because current methods for improving membrane permeability often increase the pore size, which prevents the interception of some polymers and colloidal particles, thus reducing selectivity. Therefore, the ideal physical structure of an ultrafiltration membrane is one with small pore size and high porosity, achieving both high selectivity and high permeability simultaneously. Currently, there is no simple method for preparing ultrafiltration membranes that can simultaneously improve both permeability and selectivity. Summary of the Invention

[0004] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing an ultrafiltration membrane. This method generates more water channels and improves membrane permeability by acid etching of inorganic nanoparticles in an organic / inorganic hybrid membrane. Simultaneously, by depositing a layer of hydrophilic chitosan on the membrane surface, not only is the membrane permeability improved by increasing its hydrophilicity, but the deposition of chitosan also reduces the average pore size on the membrane surface, thereby enhancing the membrane's retention capacity. Ultimately, an ultrafiltration membrane exhibiting both high permeability and high selectivity is obtained.

[0005] Another object of the present invention is to provide an ultrafiltration membrane obtained by the above preparation method, which has the characteristics of small pore size and high porosity, and therefore has both high permeability and high selectivity.

[0006] Another object of the present invention is to provide an application of the above-mentioned ultrafiltration membrane.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows;

[0008] A method for preparing an ultrafiltration membrane includes the following steps:

[0009] (1) Inorganic particles are dispersed in a solvent to prepare a suspension;

[0010] (2) Add the polymer and pore-forming agent to the suspension to prepare a casting solution;

[0011] (3) The casting solution is phase-inverted to form a film;

[0012] (4) Immerse the membrane in an acidic solution of chitosan to etch the inorganic particles in the membrane and at the same time deposit chitosan on the membrane surface to obtain the ultrafiltration membrane.

[0013] Preferably, the inorganic particles mentioned in step (1) are nanoparticles, specifically one or more of calcium carbonate, barium carbonate, magnesium carbonate, zinc oxide, magnesium oxide, barium hydroxide, and magnesium hydroxide.

[0014] More preferably, the inorganic particle size in step (1) is 5 to 80 nm.

[0015] Preferably, the solvent in step (1) is one or more of N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide and 1,4-dioxane.

[0016] Preferably, the method for preparing the suspension in step (1) is ultrasonic treatment.

[0017] More preferably, the method for preparing the suspension in step (1) is to sonicate for 10 to 60 minutes.

[0018] Preferably, the polymer described in step (2) is a non-degradable polymer or a biodegradable polymer.

[0019] More preferably, the non-degradable polymer mentioned in step (2) is one or more of polyvinylidene fluoride, polysulfone, polyethersulfone, polypropylene, polyamide and polyacrylonitrile.

[0020] More preferably, the biodegradable polymer mentioned in step (2) is one or more of polylactic acid, poly-8-caprolactone, polyhydroxybutyrate, polybutylene succinate, polybutylene adipate, and cellulose acetate.

[0021] Preferably, the pore-forming agent in step (2) is one or more of polyvinylpyrrolidone, polyethylene glycol, propanol and lithium chloride.

[0022] Preferably, the casting solution in step (2) contains, by mass, 0.5 to 10 parts of inorganic particles, 40 to 75 parts of solvent, 12 to 25 parts of polymer and 2 to 18 parts of pore-forming agent.

[0023] More preferably, the casting solution in step (2) contains, by mass, 3-8 parts of inorganic particles, 55-70 parts of solvent, 16-20 parts of polymer and 6-12 parts of pore-forming agent.

[0024] Preferably, the method for preparing the casting solution in step (2) involves adding the polymer and pore-forming agent to the suspension and stirring at 50–90°C for 4–8 hours.

[0025] Preferably, the phase inversion film formation method in step (3) involves vacuum degassing the casting solution, scraping the film, and then placing it in a coagulation bath for phase inversion film formation.

[0026] More preferably, the phase inversion film formation method described in step (3) is to degas the film under vacuum for 10 to 30 minutes at the same temperature as the casting solution, scrape the film, and then place it in deionized water for phase inversion film formation.

[0027] Preferably, the dilute acid solution of chitosan in step (4) contains chitosan, acid, crosslinking agent and deionized water.

[0028] Preferably, the acid in the dilute acid solution of chitosan in step (4) is one or more of acetic acid, citric acid and hydrochloric acid.

[0029] More preferably, the crosslinking agent in step (4) is one or more of glutaraldehyde, glyoxal, epichlorohydrin and tripolyphosphate.

[0030] More preferably, the dilute acid solution of chitosan in step (4) contains, by mass, 1 to 10 parts of chitosan, 10 to 50 parts of acid, 0.1 to 1 part of crosslinking agent and 1000 parts of deionized water.

[0031] More preferably, the dilute acid solution of chitosan in step (4) contains, by mass, 3-7 parts chitosan, 15-40 parts acid, 0.3-0.6 parts crosslinking agent and 1000 parts deionized water.

[0032] Preferably, the immersion time of the membrane in the acidic chitosan solution in step (4) is 5 to 60 minutes.

[0033] Preferably, after etching the inorganic particles in the membrane and depositing chitosan on the membrane surface as described in step (4), the ultrafiltration membrane can be washed with deionized water.

[0034] The present invention further provides an ultrafiltration membrane obtained by the above preparation method, which has an ultrafiltration membrane with an ultra-high porosity, all reaching 86% or more, and a more preferred ultrafiltration membrane prepared under more favorable conditions can achieve a porosity of 90% or more. Meanwhile, due to the deposition of chitosan, the ultrafiltration membrane also has a small pore size.

[0035] The present invention further provides the application of the above-mentioned ultrafiltration membrane in the fields of water treatment or biomedicine.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] This invention proposes a novel membrane fabrication method that simultaneously increases porosity and reduces membrane pore size. First, an organic / inorganic hybrid membrane containing inorganic nanoparticles is prepared. Then, the hybrid membrane is immersed in a dilute acid aqueous solution of chitosan. During this process, the dilute acid acts as an etching agent, removing the inorganic nanoparticles from the membrane, thereby forming more water channels inside the membrane and significantly increasing its porosity, resulting in a substantial improvement in membrane permeability. Simultaneously, chitosan deposits on the membrane surface, not only enhancing permeability through hydrophilicity but also effectively reducing the average pore size of the membrane surface, thus significantly improving the membrane's retention capacity. Through this unique preparation method, we successfully obtained an ultrafiltration membrane with small pore size and high porosity. This novel ultrafiltration membrane not only exhibits excellent permeability but also outstanding selectivity, truly achieving a dual improvement in both permeability and selectivity. Therefore, the ultrafiltration membrane prepared by this invention shows broad application prospects in many fields such as water treatment and biomedicine, and has significant practical value. Attached Figure Description

[0038] Figure 1 The figures show the pore size distribution curves of the ultrafiltration membranes prepared in Examples 1-5 and 7. By filtering polyethylene glycol (PEG) and polyethylene oxide (PEO) of different molecular weights, the concentrations of PEG and PEO in the feed solution and permeate solution were analyzed using a total organic carbon analyzer to obtain the membrane's molecular weight cutoff, thereby further calculating the membrane's pore size. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. For process parameters not specifically specified, conventional techniques can be referred to.

[0040] Example 1

[0041] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0042] The specific steps are as follows:

[0043] (1) Disperse 0.5g of calcium carbonate particles with a particle size of 40nm into 40g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 10 minutes to form a suspension.

[0044] (2) Add 12g of polyethersulfone and 2g of polyethylene glycol to the suspension and stir at 70°C for 8 hours to prepare the casting solution.

[0045] (3) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0046] (4) Add 10g of acetic acid and 1g of chitosan to 1L of water, mix well, and then add 0.1g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 5 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0047] Example 2

[0048] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0049] The specific steps are as follows:

[0050] (1) Disperse 5g of calcium carbonate particles with a particle size of 40nm into 60g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 50 minutes to form a suspension.

[0051] (2) Add 18g of polyethersulfone and 10g of polyethylene glycol to the suspension and stir at 70°C for 8 hours to prepare the casting solution.

[0052] (3) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0053] (4) Add 30g of acetic acid and 5g of chitosan to 1L of water, mix well, and then add 0.5g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0054] Example 3

[0055] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0056] The specific steps are as follows:

[0057] (1) Disperse 10g of calcium carbonate particles with a particle size of 40nm into 75g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 60 minutes to form a suspension.

[0058] (2) Add 25g of polyethersulfone and 18g of polyethylene glycol to the suspension and stir at 70°C for 8 hours to prepare the casting solution.

[0059] (3) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0060] (4) Add 50g of acetic acid and 10g of chitosan to 1L of water, mix well, and then add 1g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 60 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0061] Example 4

[0062] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0063] The specific steps are as follows:

[0064] (1) Disperse 1g of barium hydroxide particles with a particle size of 70nm into 50g of dimethyl sulfoxide and treat with an ultrasonic cell disruptor for 20 minutes to form a suspension.

[0065] (2) Add 14g of polyvinylidene fluoride and 4g of polyvinylpyrrolidone to the suspension and stir at 60°C for 6 hours to prepare a casting solution.

[0066] (3) Place the prepared casting solution in a vacuum drying oven at 60°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0067] (4) Add 12g of citric acid and 2g of chitosan to 1L of water, mix well, and then add 0.2g of sodium tripolyphosphate to obtain a chitosan-citric acid aqueous solution. Take a membrane and immerse it in the above chitosan-citric acid aqueous solution. After 10 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0068] Example 5

[0069] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0070] The specific steps are as follows:

[0071] (1) Disperse 3g of magnesium oxide particles with a particle size of 5nm into 55g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 30 minutes to form a suspension.

[0072] (2) Add 16g of polysulfone and 6g of lithium chloride to the suspension and stir at 80°C for 5 hours to prepare casting solution.

[0073] (3) Place the prepared casting solution in an 80℃ vacuum drying oven for 10 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0074] (4) Add 15g hydrochloric acid and 3g chitosan to 1L of water, mix well, and then add 0.3g glyoxal to obtain a chitosan hydrochloric acid aqueous solution. Take a membrane and immerse it in the above chitosan hydrochloric acid aqueous solution. After 40 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0075] Example 6

[0076] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0077] The specific steps are as follows:

[0078] (1) Disperse 5g of magnesium carbonate particles with a particle size of 20nm into 60g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 40 minutes to form a suspension.

[0079] (2) Add 17g of poly(m-phenylene isophthalamide) and 9g of polyvinylpyrrolidone to the suspension and stir at 90°C for 4 hours to prepare a casting solution.

[0080] (3) Place the prepared casting solution in a vacuum drying oven at 90℃ for 20 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0081] (4) Add 30g hydrochloric acid and 5g chitosan to 1L of water, mix well, and then add 0.4g epichlorohydrin to obtain a chitosan hydrochloric acid aqueous solution. Take a membrane and immerse it in the above chitosan hydrochloric acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0082] Example 7

[0083] This embodiment provides a non-degradable ultrafiltration membrane and its preparation method.

[0084] The specific steps are as follows:

[0085] (1) Disperse 8g of magnesium hydroxide particles with a particle size of 50nm into 70g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 50 minutes to form a suspension.

[0086] (2) Add 20g of polyacrylonitrile and 12g of polyvinylpyrrolidone to the suspension and stir at 80°C for 7 hours to prepare the casting solution.

[0087] (3) Place the prepared casting solution in an 80℃ vacuum drying oven for 10 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0088] (4) Add 40g of citric acid and 7g of chitosan to 1L of water, mix well, and then add 0.6g of sodium tripolyphosphate to obtain a chitosan-citric acid aqueous solution. Take a membrane and immerse it in the above chitosan-citric acid aqueous solution. After 20 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0089] Example 8

[0090] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0091] The specific steps are as follows:

[0092] (1) Disperse 2g of barium hydroxide particles with a particle size of 30nm into 50g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 10 minutes to form a suspension.

[0093] (2) Add 15g of poly-ε-caprolactone and 5g of acetone to the suspension and stir at 50°C for 8 hours to prepare the casting solution.

[0094] (3) Place the prepared casting solution in a vacuum drying oven at 50°C for 10 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0095] (4) Add 14g hydrochloric acid and 2g chitosan to 1L of water, mix well, and then add 0.2g glyoxal to obtain a chitosan hydrochloric acid aqueous solution. Take a membrane and immerse it in the above chitosan hydrochloric acid aqueous solution. After 10 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0096] Example 9

[0097] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0098] The specific steps are as follows:

[0099] (1) Disperse 4g of zinc oxide particles with a particle size of 60nm into 58g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 20 minutes to form a suspension.

[0100] (2) Add 16g of polybutylene succinate and 7g of polyvinylpyrrolidone to the suspension and stir at 90°C for 4 hours to prepare a casting solution.

[0101] (3) Place the prepared casting solution in a vacuum drying oven at 90℃ for 20 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0102] (4) Add 20g of acetic acid and 4g of chitosan to 1L of water, mix well, and then add 0.4g of sodium tripolyphosphate to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0103] Example 10

[0104] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0105] The specific steps are as follows:

[0106] (1) Disperse 6g of barium carbonate particles with a particle size of 80nm into 60g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 40 minutes to form a suspension.

[0107] (2) Add 18g of polybutylene adipate and 8g of polyvinylpyrrolidone to the suspension and stir at 80°C for 6 hours to prepare a casting solution.

[0108] (3) Place the prepared casting solution in an 80°C vacuum drying oven for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0109] (4) Add 30g of acetic acid and 5g of chitosan to 1L of water, mix well, and then add 0.5g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0110] Example 11

[0111] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0112] The specific steps are as follows:

[0113] (1) Disperse 7g of magnesium carbonate particles with a particle size of 10nm into 68g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 40 minutes to form a suspension.

[0114] (2) Add 19g of cellulose acetate and 10g of lithium chloride to the suspension and stir at 80°C for 7 hours to prepare the casting solution.

[0115] (3) Place the prepared casting solution in an 80℃ vacuum drying oven for 20 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0116] (4) Add 25g of citric acid and 6g of chitosan to 1L of water, mix well, and then add 0.5g of epichlorohydrin to obtain a chitosan-citric acid aqueous solution. Take a membrane and immerse it in the above chitosan-citric acid aqueous solution. After 25 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0117] Example 12

[0118] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0119] The specific steps are as follows:

[0120] (1) Disperse 8g of zinc oxide particles with a particle size of 50nm into 30g of N-methylpyrrolidone and 30g of 1,4-dioxane, and treat with an ultrasonic cell disruptor for 30 minutes to form a suspension.

[0121] (2) Add 18g of polylactic acid and 8g of polyethylene glycol to the suspension and stir at 70°C for 5 hours to prepare the casting solution.

[0122] (3) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0123] (4) Add 30g hydrochloric acid and 7g chitosan to 1L of water, mix well, and then add 0.5g epichlorohydrin to obtain a chitosan hydrochloric acid aqueous solution. Take a membrane and immerse it in the above chitosan hydrochloric acid aqueous solution. After 20 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0124] Example 13

[0125] This embodiment provides a biodegradable ultrafiltration membrane and its preparation method.

[0126] The specific steps are as follows:

[0127] (1) Disperse 10g of magnesium oxide particles with a particle size of 20nm into 75g of N-methylpyrrolidone and treat with an ultrasonic cell disruptor for 50 minutes to form a suspension.

[0128] (2) Add 23g of polyhydroxybutyrate and 16g of polyvinylpyrrolidone to the suspension and stir at 80°C for 6 hours to prepare a casting solution.

[0129] (3) Place the prepared casting solution in an 80℃ vacuum drying oven for 20 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0130] (4) Add 50g of acetic acid and 9g of chitosan to 1L of water, mix well, and then add 0.8g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 20 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane.

[0131] Comparative Example 1

[0132] This embodiment serves as a comparison with Examples 1-3, providing an ultrafiltration membrane that does not etch or deposit chitosan and its preparation method.

[0133] The specific steps are as follows:

[0134] (1) Take 60g of N,N-dimethylacetamide, add 18g of polyethersulfone and 10g of polyethylene glycol to N,N-dimethylacetamide, and stir at 70°C for 8 hours to prepare casting solution.

[0135] (2) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0136] (3) Add 30g of acetic acid to 1L of water and mix well to obtain an acetic acid aqueous solution. Take a membrane and immerse it in the above acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane that does not etch inorganic particles and does not deposit chitosan.

[0137] Comparative Example 2

[0138] This embodiment serves as a comparison with Embodiment 2, providing an ultrafiltration membrane that only etches inorganic particles and does not deposit chitosan, and its preparation method.

[0139] The specific steps are as follows:

[0140] (1) Disperse 5g of calcium carbonate particles with a particle size of 40nm into 60g of N,N-dimethylacetamide and treat with an ultrasonic cell disruptor for 50 minutes to form a suspension.

[0141] (2) Add 18g of polyethersulfone and 10g of polyethylene glycol to the suspension and stir at 70°C for 8 hours to prepare the casting solution.

[0142] (3) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0143] (4) Add 30g of acetic acid to 1L of water and mix well to obtain an acetic acid aqueous solution. Take a membrane and immerse it in the above acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane that only etches inorganic particles and does not deposit chitosan.

[0144] Comparative Example 3

[0145] This embodiment serves as a comparison with Embodiment 2, providing an ultrafiltration membrane that does not etch inorganic particles but only deposits chitosan and its preparation method.

[0146] The specific steps are as follows:

[0147] (1) Take 60g of N,N-dimethylacetamide, add 18g of polyethersulfone and 10g of polyethylene glycol to N,N-dimethylacetamide, and stir at 70°C for 8 hours to prepare casting solution.

[0148] (2) Place the prepared casting solution in a vacuum drying oven at 70°C for 30 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0149] (3) Add 30g of acetic acid and 5g of chitosan to 1L of water, mix well, and then add 0.5g of glutaraldehyde to obtain a chitosan-acetic acid aqueous solution. Take a membrane and immerse it in the above chitosan-acetic acid aqueous solution. After 30 minutes, take out the membrane and wash it with deionized water to obtain an ultrafiltration membrane that only deposits chitosan and does not etch chitosan.

[0150] Comparative Example 4

[0151] This embodiment serves as a comparison with Example 9, providing a biodegradable ultrafiltration membrane that does not etch or deposit chitosan and its preparation method.

[0152] The specific steps are as follows:

[0153] (1) Take 58g of N-methylpyrrolidone, add 16g of polybutylene succinate and 7g of polyvinylpyrrolidone to N-methylpyrrolidone, and stir at 90°C for 4 hours to prepare casting solution.

[0154] (2) Place the prepared casting solution in a vacuum drying oven at 90°C for 20 minutes to degas. After scraping the film, place the liquid film in deionized water to convert it into a membrane.

[0155] (3) Add 20g of acetic acid to 1L of water and mix well to obtain an acetic acid aqueous solution. Immerse a membrane in the above acetic acid aqueous solution, remove the membrane after 30 minutes, and wash it with deionized water to obtain an ultrafiltration membrane.

[0156] The membrane porosity was tested using the wet-dry gravimetric method. The wet membrane was cut into 3×4 cm rectangles and weighed. It was then placed in a 50℃ forced-air drying oven for 48 hours to dry. The weight of the dry membrane was measured, and the membrane porosity was calculated using the following formula:

[0157]

[0158] Where ε is the overall porosity of the membrane, W w It is the weight of the wet film (g), W d It is the weight of the dry film (g), ρ w The density of deionized water (g / cm³) 3 A is the area of ​​the membrane (cm²) 2 ), where δ is the thickness of the membrane (cm).

[0159] The molecular weight cutoff (MWCO) of the membrane is obtained by filtering polyethylene glycol (PEG) and polyethylene oxide (PEO) with different molecular weights, which is the molecular weight corresponding to a solute rejection rate of 90%, and the pore size of the membrane can then be calculated.

[0160] Retention tests were conducted on 0.1 g / L PEG and PEO solutions of different molecular weights using a cross-flow filtration device. The concentrations of PEG and PEO in the feed solution and permeate solution were analyzed using a total organic carbon analyzer. Retention rates were calculated, and the Stokes diameter (d) corresponding to different molecular weights was calculated using the appropriate formula. s ).

[0161]

[0162]

[0163] Where M w It is the molecular weight of PEG or PEO.

[0164] The surface pore size distribution of the membrane is represented by a probability density function using the log-normal distribution.

[0165]

[0166] Where d p It is the pore size of the membrane; μ p It is the average aperture; d s The diameter of the solute when R = 50%; σ p It is the geometric standard deviation of the solute, defined as the ratio of the solute size at R = 84.13% to the solute size at R = 50%.

[0167] Filtration and permeation tests were performed using a cross-flow apparatus. The PBS membrane was first pre-stressed at 1 bar for 30 minutes to stabilize, and then tested every 10 minutes to obtain a stable pure water flux. Membranes with different compositions were tested at least five times to obtain average flux data. The pure water flux was calculated using the following formula:

[0168]

[0169] Where J is the membrane water flux (L·m) -2 .h -1 .bar - 1). V is the permeate volume (L), and A is the effective membrane area (7.07 cm²). 2 ). t represents the test time (h) for each test, and P represents the transmembrane pressure (bar).

[0170] In the filtration experiment, the feed solution was changed to 1 g·L⁻¹. -1 Bovine serum albumin (BSA) dissolved in phosphate buffer (0.1 mol·L⁻¹) -1 BSA solution was prepared in a solution at pH 7.4. BSA filtration was performed at 1 bar pressure. The absorbance of the feed solution and permeate was measured at 280 nm using a UV spectrophotometer to characterize the BSA concentration in the feed and permeate solutions, respectively. The membrane rejection rate (R, %) can be calculated using the following formula:

[0171]

[0172] Where C p and C f The values ​​represent the BSA concentration (g / L) in the permeate and feed solutions, respectively.

[0173] Analyzing the structural and performance data of the polyethersulfone membranes in Examples 2, 1, 2, and 3, in Comparative Example 1, without etching inorganic particles or depositing chitosan, the pure water flux of the ultrafiltration membrane was only 322.8 L·m⁻²·h⁻¹·bar⁻¹, and the retention rate for bovine serum albumin was 94.2%, indicating that its permeability was not ideal. In Comparative Example 2, only inorganic particles were etched without depositing chitosan, resulting in increased porosity and pore size of the ultrafiltration membrane, thus increasing the pure water flux to 1125.3 L·m⁻²·h⁻¹·bar⁻¹, but the retention rate for bovine serum albumin decreased to 34.7%. Permeability improved, but selectivity was poor. In Comparative Example 3, without etching inorganic particles and only depositing chitosan, the ultrafiltration membrane had low porosity, resulting in a pure water flux of 368.5 L·m⁻²·h⁻¹·bar⁻¹, and its permeability was still not ideal. In Example 2, the ultrafiltration membrane prepared by simultaneously etching inorganic particles and depositing chitosan has high porosity and small pore size, with a pure water flux of 826.6 L·m⁻²·h⁻¹·bar⁻¹ and a bovine serum albumin rejection rate of 96.9%. Overall, it has excellent permeation separation performance.

[0174] Analyzing the membrane structure and performance data of Examples 1, 2, 3, and Comparative Example 1, in Example 1, the acid etching of the inorganic nanoparticles and chitosan deposition resulted in higher permeability and selectivity of the ultrafiltration membrane compared to Comparative Example 1 (no etching, no deposition). However, due to the relatively small amount of nanoparticles and chitosan deposition in Example 1, the improvement in flux and retention was less than that in Example 2. In Example 3, the excessive amount of chitosan deposition reduced the membrane pore size to 13.3 nm, thus decreasing the permeation flux compared to Example 2.

[0175] The structural and performance data of the biodegradable polybutylene succinate membranes in Example 9 and Comparative Example 4 were analyzed. In Comparative Example 4, the ultrafiltration membrane of polybutylene succinate without etching of inorganic particles and without chitosan deposition had a pure water flux of only 8.5 L·m⁻²·h⁻¹·bar⁻¹ and a bovine serum albumin (BSA) rejection rate of 93.9%, indicating very poor permeability. In Example 9, after acid etching of inorganic particles and chitosan deposition, the flux of the ultrafiltration membrane increased to 204.8 L·m⁻²·h⁻¹·bar⁻¹, and the BSA rejection rate increased to 96.4%. Although the permeability of the biodegradable membrane is slightly worse than that of the traditional non-biodegradable membrane, for the same membrane material, the membrane prepared using the technology of this invention still shows a significant improvement in performance.

[0176] Table 1. Porosity, pore size, pure water flux, and retention of the examples and comparative examples.

[0177]

[0178]

[0179] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an ultrafiltration membrane, characterized in that, Includes the following steps: (1) Disperse inorganic particles in a solvent to prepare a suspension; the inorganic particles are nanoparticles, specifically one or more of calcium carbonate, barium carbonate, magnesium carbonate, zinc oxide, magnesium oxide, barium hydroxide and magnesium hydroxide. (2) The polymer and the pore-forming agent are added to the suspension to prepare a casting solution; the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, propanol and lithium chloride; (3) The casting solution is phase-inverted to form a film; (4) The membrane is immersed in a dilute acid solution of chitosan to etch the inorganic particles in the membrane and at the same time to deposit chitosan on the membrane surface, thus obtaining the ultrafiltration membrane; the dilute acid solution of chitosan contains chitosan, acid, crosslinking agent and deionized water.

2. The method for preparing the ultrafiltration membrane according to claim 1, characterized in that: The solvent mentioned in step (1) is one or more of N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide and 1,4-dioxane; The polymer mentioned in step (2) is a non-degradable polymer or a biodegradable polymer.

3. The method for preparing the ultrafiltration membrane according to claim 2, characterized in that: The acid in the dilute acid solution of chitosan mentioned in step (4) is one or more of acetic acid, citric acid and hydrochloric acid; The crosslinking agent mentioned in step (4) is one or more of glutaraldehyde, glyoxal, epichlorohydrin and tripolyphosphate.

4. The method for preparing the ultrafiltration membrane according to claim 2 or 3, characterized in that: The inorganic particle size mentioned in step (1) is 5–80 nm; The casting solution described in step (2) contains, by mass, 0.5 to 10 parts of inorganic particles, 40 to 75 parts of solvent, 12 to 25 parts of polymer and 2 to 18 parts of pore-forming agent; The dilute acid solution of chitosan described in step (4) contains, by mass, 1-10 parts chitosan, 10-50 parts acid, 0.1-1 parts crosslinking agent and 1000 parts deionized water.

5. The method for preparing the ultrafiltration membrane according to claim 4, characterized in that: The casting solution described in step (2) contains, by mass, 3-8 parts of inorganic particles, 55-70 parts of solvent, 16-20 parts of polymer and 6-12 parts of pore-forming agent; The dilute acid solution of chitosan described in step (4) contains, by mass, 3-7 parts chitosan, 15-40 parts acid, 0.3-0.6 parts crosslinking agent and 1000 parts deionized water.

6. The method for preparing the ultrafiltration membrane according to claim 2 or 3, characterized in that: The non-degradable polymer mentioned in step (2) is one or more of polyvinylidene fluoride, polysulfone, polyethersulfone, polypropylene, polyamide and polyacrylonitrile; The biodegradable polymer mentioned in step (2) is one or more of polylactic acid, poly-ε-caprolactone, polyhydroxybutyrate, polybutylene succinate, polybutylene adipate, and cellulose acetate.

7. The method for preparing an ultrafiltration membrane according to claim 1, characterized in that: The method for preparing the suspension in step (1) is ultrasonic treatment; The method for preparing the casting solution in step (2) involves adding the polymer and pore-forming agent to the suspension and then stirring. The phase inversion film formation method described in step (3) involves vacuum degassing the casting solution, scraping the film, and then placing it in a coagulation bath for phase inversion film formation.

8. The method for preparing the ultrafiltration membrane according to claim 7, characterized in that: The method for preparing the suspension in step (1) involves ultrasonic treatment for 10 to 60 minutes; The method for preparing the casting solution in step (2) is to add the polymer and pore-forming agent to the suspension and stir at 50-90°C for 4-8 hours. The phase inversion film formation method described in step (3) is to degas the film under vacuum for 10 to 30 minutes at the same temperature as the casting solution, scrape the film, and then place it in deionized water to form a phase inversion film. The immersion time of the membrane in the dilute acid solution of chitosan in step (4) is 5 to 60 minutes.

9. An ultrafiltration membrane, characterized in that: It is obtained by the preparation method described in claims 1 to 8.

10. The ultrafiltration membrane according to claim 9, characterized in that: The ultrafiltration membrane can be used in water treatment or biomedical fields.

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