Anti-pollution ultrafiltration membrane and preparation method thereof

Abstract

The invention relates to an anti-pollution ultrafiltration membrane based on a carbon nanotube photothermal effect, a preparation method of the anti-pollution ultrafiltration membrane and application of the anti-pollution ultrafiltration membrane in protein separation. The ultrafiltration membrane has a porous and loose structure, and is characterized in that high-dispersion carbon nanotubes are introduced, so that on one hand, the light absorption efficiency is improved by increasing light scattering and absorption paths, and on the other hand, heat transfer and accumulation in the membrane are promoted, and efficient temperature rise is realized. Under the illumination condition, the surface temperature of the ultrafiltration membrane is remarkably increased, denaturation of residual protein is promoted, denatured protein is effectively removed through a gas-liquid mixed flushing method, and flux recovery is achieved. The prepared ultrafiltration membrane has excellent anti-pollution performance and flux recovery rate, is suitable for the field of protein separation, and can remarkably prolong the service life and improve the separation efficiency of the membrane.

Description

Technical Field

[0001] The present invention relates to a method for preparing a small-aperture anti-pollution ultrafiltration membrane, specifically to a method for preparing a small-aperture anti-pollution ultrafiltration membrane for protein retention, belonging to the technical field of membrane preparation. Background Art

[0002] Proteins have important application values in the fields of biology, medicine, food, etc. At present, protein separation technologies based on characteristics such as molecular size, solubility, and charge have made certain progress, but still face problems such as multi-step purification, low target protein content, difficult separation, and easy contamination. Especially in trace protein analysis, proteins are easily denatured or aggregated due to environmental factors, limiting their applications.

[0003] Although ultrafiltration membrane technology has been widely used in the field of protein separation, there are still problems such as membrane pollution, protein adsorption, low flux, and poor retention effect on small-molecular-weight proteins. To overcome these limitations, researchers are committed to developing new ultrafiltration membrane materials, including precisely controlling the membrane aperture through nanotechnology and developing highly hydrophilic and anti-pollution materials. For example, Chinese Patent CN202311590182.8 in the prior art reports a carbon quantum dot polyethersulfone ultrafiltration membrane, but its preparation steps are cumbersome, the consumables are many, and the cost of using 700W microwave treatment is relatively high. At the same time, using non-woven fabric as a carrier is easily contaminated during long-term use. Therefore, developing a small-aperture anti-pollution ultrafiltration membrane with low cost, strong anti-pollution ability, and good long-term stability is of great significance to the field of protein separation.

[0004] Due to its polysaccharide structure and abundant hydroxyl functional groups, hyaluronic acid can form a stable hydrogen bond network with water molecules, reduce the energy barrier on the membrane surface, and reduce the non-specific adsorption of proteins to the membrane material. In addition, the biocompatibility of hyaluronic acid helps to maintain the native conformation and biological activity of proteins, making these characteristics an ideal material for reducing membrane pollution and improving protein recovery rate. Due to its unique nanoscale structure and electronic properties, carbon nanotubes have significant photothermal conversion ability. Under light illumination conditions, carbon nanotubes can efficiently absorb light energy and quickly convert it into heat energy, showing efficient and rapid photothermal response characteristics.

[0005] The present invention significantly improves the anti-pollution performance and flux recovery rate of the ultrafiltration membrane by introducing the photothermal effect of carbon nanotubes and combining with the gas-liquid mixing flushing technology, providing an efficient and stable solution for protein separation. Summary of the Invention

[0006] The problem to be solved by the present invention is: to provide a method for preparing a small-aperture anti-pollution ultrafiltration membrane for protein separation.

[0007] To solve the above problems, the present invention provides a method for preparing a small-aperture anti-pollution ultrafiltration membrane for protein separation, and the method comprises the following steps: (1) Weigh a certain amount of polyvinylidene fluoride, carbon nanotubes, dispersant, pore-forming agent, and the balance is solvent, and place them in different beakers respectively; (2) Mix the carbon nanotubes with the dispersant solvent, add them to the solvent and perform ultrasonic treatment to obtain a uniformly dispersed carbon nanotube dispersion. The ultrasonic time is 4 - 6 h; (3) Add the polyvinylidene fluoride and the pore-forming agent to the carbon nanotube dispersion, heat and stir, and then perform degassing treatment on the solution to obtain a blended casting solution. The heating temperature is 50 - 60 °C, the stirring time is 12 h - 14 h, and the degassing treatment time is 6 h - 8 h; (4) Pour the casting solution onto a carrier, perform blade coating, and then soak it in water to obtain the small-aperture anti-pollution ultrafiltration membrane for protein separation. The carrier for blade coating is a glass plate.

[0008] Preferably, the mass fraction content ratio of polyvinylidene fluoride, pore-forming agent, solvent, carbon nanotubes, and dispersant in the raw materials in (2) is: (10% - 30%): (1% - 10%): (60% - 90%): (0.05% - 5%): (0.5% - 5%).

[0009] Preferably, the blade coating thickness in (4) is 100 μm - 300 μm.

[0010] Preferably, the pore-forming agent in (1) is one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; the solvent is one of N-N dimethylformamide, N-N dimethylacetamide, and N-methylpyrrolidone; the dispersant is one of sodium dodecylbenzenesulfonate, hyaluronic acid, and polyacrylic acid.

[0011] Preferably, the average pore diameter of the membrane is in the range of 10 kDa to 20 kDa, and a dead-end filtration device is used for performance testing. The specific steps are as follows: Pass N 2 into the system at a pressure of 0.1 MPa, and at the same time continuously add the protein solution (prepared from 2 L of phosphate buffer solution with a BSA protein concentration of 2 g / L) to the dead-end filter under atmospheric pressure. After continuously filtering the PBS solution with the ultrafiltration membrane prepared by the present invention for 48 hours, the BSA protein retention rate is measured to be ≥98%, and the flux reaches 800 Lm -2 h -1 bar -1 .

[0012] Preferably, at 1 kW / m 2After 30 minutes of illumination, the protein on the residual membrane was heated and denatured. The denatured protein was removed by the gas-liquid mixing flushing method (the gas-liquid ratio of nitrogen to water was controlled between 1:1 and 1:3, the nitrogen flow rate was 1 - 3 m³ / h, and the deionized water flow rate was 0.5 - 1.5 m / s), and the flushing duration was between 30 min and 150 min. The rejection rate of the cleaned ultrafiltration membrane for BSA protein was restored to ≥99.7%, and the flux recovery rate was ≥96%.

[0013] Compared with the existing technology, the beneficial effects of the present invention are as follows: 1. Excellent anti-pollution performance The present invention endows the ultrafiltration membrane with unique anti-pollution performance by utilizing the photothermal effect of carbon nanotubes. The one-dimensional nanostructure of carbon nanotubes can efficiently convert light energy into heat energy, forming a local high-temperature microenvironment on the membrane surface, with a temperature of up to 77.6 ± 2.2 °C, which happens to be within the denaturation threshold range of bovine serum albumin (BSA) (75 - 80 °C). This temperature promotes the denaturation of BSA adsorbed on the membrane surface, and the protein molecules unfold and aggregate to form a gel under continuous heating. Through the gas-liquid mixing flushing method, the denatured protein can be effectively removed. This phase change process converts the irreversible adsorption state of the protein in the membrane pores into a removable gel state, significantly extending the service life of the ultrafiltration membrane.

[0014] 2. Effective gas-liquid mixing flushing method The present invention uses the gas-liquid mixing flushing method to clean the ultrafiltration membrane. This method mixes compressed air with deionized water or buffer solution and introduces it into the ultrafiltration membrane module in a pulsed manner under a certain pressure. The gas pulse expands the membrane pores, and at the same time, local micro-impacts are generated when the bubbles break on the membrane surface, effectively disturbing the gel and removing the denatured protein. The gas-liquid mixed flow brings the pollutants out of the membrane pores, significantly improving the cleaning efficiency. This method has a significant cleaning effect on the protein pollution of ultrafiltration membranes in the field of protein separation or similar applications. Description of the Drawings

[0015] Figure 1 Schematic diagram of the mechanism of the protein-resistant ultrafiltration membrane. Detailed Embodiments Examples

[0016] (1) Preparation of the carbon nanotube dispersion material: 0.05% carbon nanotubes, 0.5% hyaluronic acid, and 80.5% dimethylacetamide solvent; after mixing the materials, ultrasonic treatment was carried out for 4 - 6 h to obtain the carbon nanotube dispersion; (2)Preparation of the casting solution: The material solution is prepared from the following components by mass percentage, where polyvinylidene fluoride is 18%, polyvinylpyrrolidone is 1%, and the rest is the carbon nanotube dispersion. Polyvinylidene fluoride and polyvinylpyrrolidone are added to the carbon nanotube dispersion, heated and stirred for 12 h to form a transparent casting solution, which is then allowed to stand for defoaming for 6 h and is ready for use; (3)Preparation of the small-pore anti-fouling ultrafiltration membrane for protein separation: The casting solution prepared in step (2) is scraped onto a glass plate with a doctor blade to form a 200-μm thin layer at a scraping speed of 30 mm / s; after scraping, it is soaked in water for 10 s until the membrane is formed and stabilized to obtain the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane is about 18 kDa, and the protein rejection rate is ≥99%.

[0017] (4)Through dead-end filtration testing, the protein rejection rate of the ultrafiltration membrane reached 98.4% at about 48 h. After 30 min of light irradiation at 1 kW / m 2 the protein remaining on the membrane was thermally denatured. The ultrafiltration membrane was rinsed for 30 min using the gas-liquid mixing rinsing method (the gas-liquid ratio of air to water is 1:1, the nitrogen gas flow rate is 1 m³ / h, and the deionized water flow rate is 0.5 m / s) to remove the denatured protein. After testing, it was found that the protein rejection rate of the ultrafiltration membrane increased to 98.6%, and the flux recovery rate reached 95%, showing good anti-fouling performance. Example

[0018] (1)Preparation of the carbon nanotube dispersion material: Carbon nanotubes are 0.05%, hyaluronic acid is 0.6%, and dimethylacetamide solvent is 80%; after the material solution is mixed, it is ultrasonically treated for 4 - 6 h to obtain the carbon nanotube dispersion; (2)Preparation of the casting solution: The material solution is prepared from the following components by mass percentage, where polyvinylidene fluoride is 18%, polyvinylpyrrolidone is 1.5%, and the rest is the carbon nanotube dispersion. Polyvinylidene fluoride and polyvinylpyrrolidone are added to the carbon nanotube dispersion, heated and stirred for 12 h to form a transparent casting solution, which is then allowed to stand for defoaming for 6 h and is ready for use; (3)Preparation of the small-pore anti-fouling ultrafiltration membrane for protein separation: The casting solution prepared in step (2) is scraped onto a glass plate with a doctor blade to form a 200-μm thin layer at a scraping speed of 30 mm / s; after scraping, it is soaked in water for 10 s until the membrane is formed and stabilized to obtain the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane is about 17 kDa, and the protein rejection rate is ≥99.1%.

[0019] (4)Through dead-end filtration testing, the protein rejection rate of the ultrafiltration membrane reached 98.5% at about 48 h. After 30 min of light irradiation at 1 kW / m 2After irradiation with light for 30 minutes, the protein remaining on the membrane was denatured by heating. The ultrafiltration membrane was flushed for 40 minutes using a gas-liquid mixed flushing method (gas-liquid ratio of air to water was 1:1.5, nitrogen flow rate was 1.5 m³ / h, and deionized water flow rate was 0.5 m / s) to remove the denatured protein. After testing, it was found that the ultrafiltration membrane had a protein retention rate of 98.7% and a flux recovery rate of 96%, indicating good anti-pollution performance. Example

[0020] (1) Preparation of carbon nanodispersion liquid material: 0.06% carbon nanotubes, 0.5% hyaluronic acid, 79.4% dimethylacetamide solvent; after mixing the material and liquid, ultrasonic treatment is performed for 4-6 hours to obtain a carbon nanodispersion liquid; (2) Preparation of casting solution: The material solution is prepared by the following components in percentage by mass, wherein polyvinylidene fluoride 19%, polyvinyl pyrrolidone 1%, and the rest is carbon nano-dispersion solution. Add polyvinylidene fluoride and polyvinyl pyrrolidone to the carbon nano-dispersion solution, heat and stir for 12 hours to form a transparent casting solution, and let it stand for degassing for 6 hours before use; (3) Preparation of a small-pore anti-fouling ultrafiltration membrane for protein separation: Use a scraper to scrape the casting solution prepared in step (2) onto a glass plate to form a 200 μm thin layer at a scraping speed of 30 mm / s; after scraping, soak it in water for 10 seconds until the membrane is formed and stabilized, thereby obtaining the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane is about 16 kDa, and the protein retention rate is ≥99.3%.

[0021] (4) Through the dead-end test, the protein retention rate of the ultrafiltration membrane reached 98.6% in about 48 hours. 2 After irradiation with light for 30 minutes, the protein remaining on the membrane was denatured by heating. The ultrafiltration membrane was flushed for 50 minutes using a gas-liquid mixed flushing method (gas-liquid ratio of air to water was 1:1.8, nitrogen flow rate was 1.5 m³ / h, and deionized water flow rate was 1 m / s) to remove the denatured protein. After testing, it was found that the ultrafiltration membrane had a protein retention rate of 98.8% and a flux recovery rate of 95.5%, indicating good anti-pollution performance. Example

[0022] (1) Preparation of carbon nanodispersion liquid material: 0.06% carbon nanotubes, 0.6% hyaluronic acid, 79% dimethylacetamide solvent; after mixing the material and liquid, ultrasonic treatment is performed for 4-6 hours to obtain a carbon nanodispersion liquid; (2) Preparation of casting solution: The material solution is prepared by the following components in percentage by mass, wherein 19% polyvinylidene fluoride, 1.5% polyvinyl pyrrolidone, and the rest is carbon nano-dispersion solution. Add polyvinylidene fluoride and polyvinyl pyrrolidone to the carbon nano-dispersion solution, heat and stir for 12 hours to form a transparent casting solution, and let it stand for degassing for 6 hours before use; (3) Preparation of a small-pore anti-fouling ultrafiltration membrane for protein separation: Use a scraper to scrape the casting solution prepared in step (2) onto a glass plate to form a 200 μm thin layer at a scraping speed of 30 mm / s; after scraping, soak it in water for 10 seconds until the membrane is formed and stabilized, thereby obtaining the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane is about 15 kDa, and the protein retention rate is ≥99.4%.

[0023] (4) Through the dead-end test, the protein retention rate of the ultrafiltration membrane reached 98.7% in about 48 hours. 2 After irradiation with light for 30 minutes, the protein remaining on the membrane was denatured by heating. The ultrafiltration membrane was flushed for 60 minutes using a gas-liquid mixed flushing method (gas-liquid ratio of air to water was 1:2, nitrogen flow rate was 2 m³ / h, and deionized water flow rate was 1 m / s) to remove the denatured protein. After testing, it was found that the ultrafiltration membrane had a protein retention rate of 98.9% and a flux recovery rate of 95%, indicating good anti-pollution performance. Example

[0024] (1) Preparation of carbon nanodispersion liquid material: 0.05% carbon nanotubes, 0.5% hyaluronic acid, 78.5% dimethylacetamide solvent; after mixing the material and liquid, ultrasonic treatment is performed for 4-6 hours to obtain a carbon nanodispersion liquid; (2) Preparation of casting solution: The material solution is prepared by the following components in percentage by mass, wherein polyvinylidene fluoride 19%, polyvinyl pyrrolidone 2%, and the rest is carbon nano-dispersion solution. Add polyvinylidene fluoride and polyvinyl pyrrolidone to the carbon nano-dispersion solution, heat and stir for 12 hours to form a transparent casting solution, and let it stand for degassing for 6 hours before use; (3) Preparation of a small-pore anti-fouling ultrafiltration membrane for protein separation: Use a scraper to scrape the casting solution prepared in step (2) onto a glass plate to form a 200 μm thin layer at a scraping speed of 30 mm / s; after scraping, soak it in water for 10 seconds until the membrane is formed and stabilized, thereby obtaining the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane is about 14 kDa, and the protein retention rate is ≥99.6%.

[0025] (4) Through the dead-end filtration test, the protein retention rate of the ultrafiltration membrane reached 98.8% in about 48 hours. 2After 30 minutes of illumination, the proteins remaining on the membrane were denatured by heating. The denatured proteins were removed by flushing the ultrafiltration membrane for 70 minutes using a gas-liquid mixing flushing method (the gas-liquid ratio of air to water was 1:2.5, the nitrogen gas flow rate was 2 m³ / h, and the deionized water flow rate was 1.5 m / s). After testing, it was found that the protein rejection rate of the ultrafiltration membrane increased to 99.3%, and the flux recovery rate reached 96.5%, indicating good anti-fouling performance. Example

[0026] (1) Preparation of carbon nanotube dispersion material: 0.05% carbon nanotubes, 0.6% hyaluronic acid, and 78% dimethylacetamide solvent; after mixing the materials and liquids, ultrasonic treatment was carried out for 4 - 6 hours to obtain the carbon nanotube dispersion. (2) Preparation of casting solution: The material solution was prepared from the following components by mass percentage. Among them, 19% polyvinylidene fluoride, 2.5% polyvinylpyrrolidone, and the remaining was the carbon nanotube dispersion. Polyvinylidene fluoride and polyvinylpyrrolidone were added to the carbon nanotube dispersion, heated and stirred for 12 hours to form a transparent casting solution, and then left to stand for defoaming for 6 hours for later use. (3) Preparation of a small-pore anti-fouling ultrafiltration membrane for protein separation: The casting solution prepared in step (2) was scraped onto a glass plate using a doctor blade to form a 200 μm thin layer, and the scraping speed was 30 mm / s; after scraping, it was immersed in water for 10 s until the membrane was formed and stabilized to obtain the small-pore anti-fouling ultrafiltration membrane for protein separation; the average pore size of the ultrafiltration membrane was about 13 kDa, and the protein rejection rate was ≥99.8%.

[0027] (4) Through dead-end testing, the protein rejection rate of the ultrafiltration membrane reached 99.5% at about 48 hours. After 30 minutes of illumination at 1 kW / m 2 the proteins remaining on the membrane were denatured by heating. The denatured proteins were removed by flushing the ultrafiltration membrane for 100 minutes using a gas-liquid mixing flushing method (the gas-liquid ratio of air to water was 1:3, the nitrogen gas flow rate was 3 m³ / h, and the deionized water flow rate was 1 m / s). After testing, it was found that the protein rejection rate of the ultrafiltration membrane increased to 99.7%, and the flux recovery rate reached 97%, indicating good anti-fouling performance.

Claims

1. A method for preparing a small-pore anti-pollution ultrafiltration membrane for protein separation, characterized in that: The following steps are involved: (1) Weigh a certain amount of polyvinylidene fluoride, carbon nanotubes, dispersant, porogen, and the remainder as solvent, and place them in different beakers; (2) Mixing carbon nanotubes with a dispersant solvent, adding the mixture to the solvent for ultrasonic treatment, and obtaining a uniform carbon nanotube dispersion. The ultrasonic treatment time is 4-6 hours; (3) Adding polyvinylidene fluoride and porogen to the carbon nanotube dispersion, heating and stirring, and then degassing the solution to obtain a blended casting solution. The heating temperature is 50-60°C, the stirring time is 12h-14h, and the degassing time is 6h-8h; (4) Pour the casting solution onto a carrier, apply a scraper coating, and then soak the membrane in water to obtain the small-pore anti-fouling ultrafiltration membrane for protein separation. The carrier for the scraper coating is a glass plate.

2. The method for preparing a small-pore anti-pollution ultrafiltration membrane for protein separation according to claim 1, characterized in that: In step (1), the mass fraction ratios of polyvinylidene fluoride, porogen, solvent, carbon nanotubes and dispersant in the raw materials are: (10%-30%): (1%-10%): (60%-90%): (0.05%-5%): (0.5%-5%).

3. The method for preparing a small-pore anti-pollution ultrafiltration membrane for protein separation according to claim 1, characterized in that: The coating thickness is 100 μm-300 μm.

4. A small-pore anti-pollution ultrafiltration membrane for protein separation, characterized in that: The film-forming agent is one of polyethersulfone, polyvinylidene fluoride, and polysulfone; the porogen is one of polyethylene glycol, polyvinyl pyrrolidone, and polyvinyl alcohol; the solvent is one of NN dimethylformamide, NN dimethylacetamide, and N-methylpyrrolidone; and the dispersant is one of sodium dodecylbenzene sulfonate, hyaluronic acid, and polyacrylic acid.

5. The film prepared by the method according to claim 1, characterized in that The average pore size of the membrane is in the range of 10 kDa to 20 kDa. The performance test is carried out using a dead-end filtration device. N2 is introduced into the system at a pressure of 0.1 MPa, and a protein solution (prepared with 2 L of phosphate buffer solution, in which the BSA protein concentration is 2 g / L) is continuously added to the dead-end filter under atmospheric pressure. After the PBS solution is continuously filtered for 48 hours using the ultrafiltration membrane prepared by the present invention, the BSA protein retention rate is measured to be ≥98%, and the flux reaches 800 Lm -2 h -1 bar -1 .

6. At 1 kW / m 2 After irradiation with light for 30 minutes, the protein on the residual membrane was heated and denatured, and the denatured protein was removed by gas-liquid mixed flushing method (the gas-liquid ratio of nitrogen to water was controlled between 1:1-1:3, the nitrogen flow rate was 1-3 m³ / h, and the deionized water flow rate was 0.5-1.5 m / s), and the flushing time was between 30 min-150 min. The retention rate of BSA protein of the washed ultrafiltration membrane was restored to ≥99.7%, and the flux recovery rate was ≥96%.

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