A pollution-resistant separation membrane and a method for manufacturing the same

Abstract

The application provides a kind of pollution-resistant separation membrane and its preparation method, method includes as follows: configuration and mix evenly protein and hydrophilic polymer buffer salt solution, then join reducing agent, stirring reaction 1-20min, so that protein and hydrophilic polymer co-assemble in solution and form aggregate with adhesion characteristics, to obtain modified liquid;Wherein, the mass ratio of protein and hydrophilic polymer is not more than 5:1, and not less than 1:25;The prepared modified liquid is coated on the surface of porous filter material for 10-200 seconds, and the modified liquid adheres to form a pollution-resistant coating on the surface of the porous filter material. After water washing, a separation membrane with a pollution-resistant coating is obtained. The preparation method of the pollution-resistant separation membrane has the advantages of green environmental protection, simple operation, good pollution resistance, easy industrialization and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, in particular to a pollution-resistant separation membrane and a preparation method thereof. Background Art

[0002] Membrane separation technology has the advantages of high separation efficiency, simple operation, high economic benefits and no secondary pollution. It has become one of the most important means in separation science and is widely used in sewage treatment, biomedicine, food processing and seawater desalination. However, during operation, the various complex components in the feed liquid can cause serious membrane fouling, resulting in a decrease in the separation membrane flux, and frequent cleaning will cause a decrease in the membrane service life. Therefore, the membrane fouling problem has always restricted the application of membrane separation technology in many industrial fields.

[0003] Modifying the membrane surface to solve the membrane fouling problem is a simple, efficient and adaptable method. Increasing the hydrophilicity of the membrane surface and reducing the roughness and charge of the membrane surface can improve the phenomenon of membrane fouling. However, it was found from dynamic filtration that the hydrophilicity of the membrane surface plays the most important role in membrane fouling. At present, in order to improve the hydrophilicity of the membrane surface, there are many methods for constructing surface hydrophilic coatings, such as surface grafting, surface plasma treatment, chemical deposition, blending modification and surface coating. However, these current surface coating construction methods have the defects of expensive equipment, complex operation, poor stability, limited processing area, and unsuitability for large-scale industrial applications. Therefore, the development of anti-pollution separation membranes that are simple to operate, low cost, high stability, energy-saving and environmentally friendly has important research significance.

[0004] Proteins have excellent biocompatibility and hydrophilicity. After disulfide-bonded proteins are reduced to amyloid proteins using a reducing agent, the resulting amyloid aggregates can be directly adhered to various substrate surfaces through a simple coating method and exhibit good stability. Patent CN108854599B provides a method for phase-transforming disulfide-bonded lysozyme into a two-dimensional nanofilm for use in hemodialysis. However, this method uses only amyloid proteins to prepare the separation membrane. The resulting membrane is composed solely of amyloid proteins and contains no other components. This results in poor hydrophilicity of the membrane surface, severe adsorption of proteins and other materials, and limited resistance to contamination.

[0005] The present application provides a method for constructing a pollution-resistant coating on the surface of a separation membrane. The method has the advantages of high universality, simple operation, high efficiency, low cost, green environmental protection and easy industrialization. The obtained pollution-resistant separation membrane has the advantages of good stability and good anti-pollution effect, and has important innovative value. Summary of the Invention

[0006] In order to overcome the membrane fouling problem existing in the existing membrane separation technology, the present invention provides a method for co-assembling and depositing proteins and hydrophilic polymers on the surface of a porous filter membrane under the action of a reducing agent to construct an anti-fouling coating: In order to improve the hydrophilicity and pollution resistance of the membrane surface, the present application adds a hydrophilic polymer to a protein solution, regulates the intermolecular forces (electrostatic forces and hydrophilic and hydrophobic forces), and promotes the hydrophilic polymer and protein to co-assemble into a membrane under the action of a reducing agent to construct a pollution-resistant coating. The added hydrophilic polymer greatly improves the hydrophilicity and pollution resistance of the coating, and can quickly and firmly adhere to the membrane surface, with permanent and continuous pollution resistance. This method has the advantages of strong universality, low cost, simple operation and green environmental protection. The obtained anti-fouling separation membrane has the advantages of good stability and good anti-pollution effect.

[0007] A method for preparing a pollution-resistant separation membrane comprises the following steps:

[0008] A buffered salt solution of protein and hydrophilic polymer is prepared and mixed, and then a reducing agent is added and stirred for 1-20 minutes to open the disulfide bonds of the protein, completely reduce the protein, form amyloid protein, and make it adhesive. The protein and the hydrophilic polymer are co-assembled in the solution to form aggregates with adhesive properties, thereby obtaining a modified solution; wherein the mass ratio of the protein to the hydrophilic polymer is not greater than 5:1 and not less than 1:25;

[0009] The prepared modifying liquid is applied to the surface of the porous filter material for 10-200 seconds. The modifying liquid adheres to the surface of the porous filter material to form a pollution-resistant coating. After washing with water, a separation membrane with the pollution-resistant coating is obtained.

[0010] Furthermore, the concentration of protein in the modified solution is 1 mg / mL-50 mg / mL, and the concentration of the hydrophilic polymer is 1 mg / mL-50 mg / mL.

[0011] Furthermore, the protein is a protein that can undergo amyloid assembly under the action of a reducing agent, including but not limited to any one or more of fibrinogen, bovine serum albumin, lysozyme, keratin, papain, lactoferrin, hemolysin, cytochrome C, pectinase, cellulase, lipase, epidermal protein, and trypsinogen; the hydrophilic polymer includes one or more of polyphosphorylcholine zwitterionic polymers, poly(sulfobetaine acrylate), polysulfobetaine zwitterionic polymers, poly-N,N-dimethyl-2-methylacrylamide zwitterionic polymers, polyacrylamide zwitterionic polymers, poly(2-ethyl-2-oxazoline), poly(2-methyl-2-oxazoline), and other poly(2-oxazoline)s, polyethyleneimine, chitosan, agar, polyacrylic acid, polyglutamic acid, polyaspartic acid, and their derivatives.

[0012] Furthermore, the reducing agent includes but is not limited to one or more of tris-(2-carboxyethyl)phosphine hydrochloride, cysteine, mercaptoethanol, and dithiothreitol, wherein the concentration of the reducing agent is 10-100 mmol / L.

[0013] Furthermore, the pH range of the buffer solution of the protein and the hydrophilic polymer is 4-10, and the concentration of the buffer solution is 0.5-3 mol / L;

[0014] Furthermore, commonly used buffer salts include, but are not limited to, one or more of phosphate, tris(hydroxymethyl)aminomethane hydrochloride, (2-hydroxyethyl)-1-piperazineethanesulfonate, and 3-(N-morpholinyl)propanesulfonate.

[0015] Furthermore, the reducing agent includes but is not limited to one or more of tris-(2-carboxyethyl)phosphine hydrochloride, cysteine, mercaptoethanol, and dithiothreitol, wherein the concentration of the reducing agent is 10-100 mmol / L.

[0016] Furthermore, the porous filter material can be divided into organic separation membrane, inorganic separation membrane and organic-inorganic hybrid separation membrane according to the material; and can be divided into microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, reverse osmosis membrane, forward osmosis membrane, membrane distillation membrane, pervaporation membrane, etc. according to the filtration characteristics.

[0017] The pollution-resistant separation membrane obtained based on the above-mentioned pollution-resistant separation membrane preparation method has the ability to resist protein adsorption on the surface, and the protein adsorption amount is less than 20ug / cm 2 , and does not change with the use time of the separation membrane; the separation membrane has a porous filter material and a pollution-resistant coating formed thereon; the pollution-resistant coating has a strong hydrophilicity, and when water droplets are dropped on the pollution-resistant coating, the water droplets are completely absorbed within 1 second to 2 minutes. The hydrophilicity of the pollution-resistant coating is permanent and does not change with the use time of the separation membrane.

[0018] The advantages and positive effects of the present invention are:

[0019] The present invention provides a method for constructing an anti-pollution coating on the surface of a separation membrane. The method does not require a complex surface pretreatment process, and a separation membrane with high stability and good anti-pollution effect can be obtained through simple coating. The preparation process is simple, environmentally friendly, biosafe, economically efficient and easy to industrialize. In addition, the preparation method is suitable for constructing surface coatings for microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, forward osmosis membranes and pervaporation membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The technical solutions of the present application will be described in further detail below in combination with the drawings and examples, but it should be understood that these drawings are designed for explanatory purposes only, and thus do not limit the scope of the present application. In addition, unless specifically indicated, these drawings are only intended to conceptually illustrate the structural configurations described herein, and are not necessarily drawn to scale.

[0021] Figure 1 Dynamic anti-pollution data provided for Example 11 and Comparative Example 7 of the present application. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the examples of the present application will be described in further detail below in combination with the drawings of the examples of the present application. The described examples are part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0023] The examples of the present application will be described in detail below in combination with the drawings.

[0024] Example 1

[0025] 2 mL of 50 mmol / L cysteine tris buffer was adjusted to pH 5.0, 2 mL of 2 mg / mL bovine serum albumin (BSA) and 2 mg / mL poly(sulfobetaine acrylate) (PSBMA) mixed tris buffer solution was adjusted to pH 5.0, then the above two solutions were thoroughly stirred and mixed uniformly, and a modified solution was formed after 20 min of reaction. The modified solution was poured onto the surface of a PES ultrafiltration membrane sheet (molecular weight cut-off 50 kDa) with a diameter of 50 mm for deposition, and the time was 120 seconds. After the deposition was completed, the modified solution on the surface of the membrane was poured out, and then the membrane was washed with deionized water to obtain a separation membrane with a pollution-resistant coating. The water contact angle data and protein adsorption data of the prepared pollution-resistant separation membrane are shown in Table 1.

[0026] Examples 2-15

[0027] The preparation process of the pollution-resistant surface coating is similar to that of Example 1, wherein the required protein, hydrophilic polymer, reducing agent, porous filter material, reaction pH, reaction conditions and other variables are shown in Table 1, and the water contact angle data and protein adsorption data of the prepared pollution-resistant separation membrane are shown in Table 1; the dynamic anti-pollution data of Example 11 are shown in Table 1 (using a tangential flow filtration device for the experiment, wherein the pollutant is BSA, the pressure is 2 bar, and the cleaning solution is 0.1 mol / L sodium hydroxide solution); Figure 1 ​

[0028] Comparative Examples 1-10

[0029] The preparation process of the anti-fouling surface coating in the comparative example is similar to that of Example 2, wherein the required variables such as protein, hydrophilic polymer, reducing agent, porous filter material, reaction pH, reaction conditions, etc. are shown in Appendix 1, and the water contact angle data and protein adsorption data of the prepared anti-fouling separation membrane surface are shown in Appendix 1. The dynamic anti-fouling data of Comparative Example 7 are shown in Appendix 1. Figure 1 shown.

[0030] From the data in Table 1, it can be found that the anti-pollution coating prepared by the modified solution in the embodiment effectively reduces the water contact angle of the porous filter material to no more than 60°, significantly improving its hydrophilicity. At the same time, the protein adsorption capacity of the anti-pollution coating is no more than 20ug / cm 2 , especially Example 11, its protein adsorption capacity is 5ug / cm 2 , which is much lower than the porous filter substrate and the coating membranes prepared with other formulations in the comparative examples, indicating that the coating prepared by this method has very excellent anti-fouling properties. The accompanying figures also show that when using this anti-fouling separation membrane for filtration experiments, when using BSA solution as the feed liquid, the flux of Comparative Example 7 decayed to 50%, while that of Example 11 decayed to 71%. After cleaning with sodium hydroxide solution, the flux of Example 11 recovered to 98%, while that of Comparative Example 7 recovered to 67%. This shows that Example 11 has excellent anti-fouling properties, can significantly increase the production rate when concentrating and purifying substances such as proteins, and is easy to clean.

[0031] Table 1

[0032]

[0033]

[0034]

[0035] Note:

[0036] 1. PSBMA is poly(sulfobetaine acrylate), PEI is polyethyleneimine, PAA is polyacrylic acid, TCEP is tris(2-carboxyethyl)phosphine, BSA is bovine serum albumin, and Lyz is lysozyme protein;

[0037] 2. In the porous filter material, PES is polyethersulfone membrane, PSf is polysulfone membrane, and PVDF is polyvinylidene fluoride membrane;

[0038] 3. The porous filter materials are all membranes with a diameter of 50mm.

[0039] The present invention involves breaking the disulfide bonds of a protein containing disulfide bonds under the action of a reducing agent, causing the protein to fold and form an amyloid protein with adhesion. A hydrophilic polymer is then introduced before the protein is reduced by the reducing agent. The hydrophilic polymer and protein are co-assembled in a solution. Under the action of the reducing agent, a novel anti-fouling material, in which the protein and the hydrophilic polymer are bound to each other, is deposited on the substrate surface. The amyloid protein provides strong adhesion to the anti-fouling material, allowing the novel anti-fouling material to remain stably on the substrate surface without being lost during testing. The ratio of protein to hydrophilic polymer affects the anti-fouling performance of the material. While the amyloid protein provides adhesion, it also improves the anti-fouling effect of the coating. However, the main improvement in anti-fouling performance comes from the addition of the hydrophilic polymer. The ratio of the hydrophilic polymer is adjusted based on the interaction between the two, hydrophilicity, and other characteristics. When the binding force between the two is the strongest and the hydrophilic polymer content in the system is the highest, the material has the best anti-fouling effect and stability. (For example, Example 11 has very high hydrophilicity and anti-protein adsorption ability when the ratio of Lyz to PEOX reaches 1 / 10, which is much higher than that of Example 12 and Comparative Example 3)

[0040] In addition, the pH value of the solution affects the reduction reaction rate. When the pH value of the solution is near the isoelectric point of the protein system, the electrostatic repulsion between the protein molecules is weakest, making the reducing agent more capable of reducing disulfide bonds in the protein and the reaction rate higher. At the same time, some hydrophilic polymers have different electrical properties (pH response characteristics) at different pH values. By regulating the pH value of the solution to change the electrical properties of the hydrophilic polymer, the electrical properties of the hydrophilic polymer are opposite to those of the protein in the system, which can enhance the interaction between the two and thus improve the stability of the coating film. At the same time, the coating time of the modified solution on the surface of the porous filter material in the present invention is 10-200 seconds, which is much lower than the coating time of most current coating film preparations, effectively improving production efficiency.

[0041] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will appreciate that modifications may be made to the technical solutions described in the above embodiments, or that some of the technical features may be replaced with equivalents; such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a pollution-resistant separation membrane, characterized in that: The steps include: A buffered salt solution of protein and hydrophilic polymer is prepared and mixed, and then a reducing agent is added and stirred for 1-20 minutes, so that the protein and hydrophilic polymer co-assemble in the solution to form aggregates with adhesive properties, thereby obtaining a modified solution; wherein the mass ratio of the protein to the hydrophilic polymer is not greater than 5:1 and not less than 1:25; Applying the prepared modifying liquid to the surface of the porous filter material for 10-200 seconds, the modifying liquid adheres to the surface of the porous filter material to form a pollution-resistant coating, and after washing with water, a separation membrane with the pollution-resistant coating is obtained; The protein is a protein that can undergo amyloid assembly under the action of a reducing agent.

2. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The concentration of protein in the modified solution is 1 mg / mL-50 mg / mL, and the concentration of the hydrophilic polymer is 1 mg / mL-50 mg / mL.

3. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The protein includes any one or more of fibrinogen, bovine serum albumin, lysozyme, keratin, papain, lactoferrin, hemolysin, cytochrome C, pectinase, cellulase, lipase, epidermal protein, and trypsinogen; the hydrophilic polymer includes one or more of polyphosphorylcholine zwitterionic polymers, poly(sulfobetaine acrylate), polysulfobetaine zwitterionic polymers, poly-N,N-dimethyl-2-methylacrylamide zwitterionic polymers, polyacrylamide zwitterionic polymers, poly(2-ethyl-2-oxazoline), poly(2-methyl-2-oxazoline), polyethyleneimine, chitosan, agar, polyacrylic acid, polyglutamic acid, polyaspartic acid, and their derivatives.

4. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The pH range of the buffered salt solution of the protein and the hydrophilic polymer is 4-10, the concentration of the buffered salt solution is 0.5-3 mol / L, and the buffer salt includes one or more of phosphate, tris(hydroxymethylaminomethane) hydrochloride, (2-hydroxyethyl)-1-piperazineethanesulfonate and 3-(N-morpholinyl)propanesulfonate.

5. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The reducing agent includes one or more of tris-(2-carboxyethyl)phosphine hydrochloride, cysteine, mercaptoethanol, and dithiothreitol, wherein the concentration of the reducing agent is 10-100 mmol / L.

6. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The porous filter material includes an organic separation membrane, an inorganic separation membrane or an organic-inorganic hybrid separation membrane.

7. The method for preparing a pollution-resistant separation membrane according to claim 1, wherein: The porous filter materials include microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, forward osmosis membranes, membrane distillation membranes, and pervaporation membranes.

8. A pollution-resistant separation membrane prepared by the method according to any one of claims 1 to 7, characterized in that: The surface of the separation membrane has anti-protein adsorption ability, and the protein adsorption amount is less than 20 ug / cm 2 , and does not change with the use time of the separation membrane.

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