Pollution-resistant separation membrane and preparation method thereof

Abstract

The invention provides a pollution-resistant separation membrane and a preparation method thereof, and the method comprises the following steps: preparing and uniformly mixing a buffer salt solution of protein and a hydrophilic polymer, then adding a reducing agent, and carrying out a stirring reaction for 1-20 min, so that the protein and the hydrophilic polymer are co-assembled in the solution to form an aggregate with an adhesion characteristic, thereby obtaining a modified solution; wherein the mass ratio of the protein to the hydrophilic polymer is not more than 5: 1 and not less than 1: 25; the surface of the porous filter material is coated with the prepared modification liquid for 10-200 s, the modification liquid adheres to the surface of the porous filter material to form a pollution-resistant coating, and the separation membrane with the pollution-resistant coating is obtained after washing; the preparation method of the pollution-resistant separation membrane provided by the invention has the advantages of environmental protection, simple operation, good pollution-resistant effect, easy industrial production and the like.

Description

Technical Field

[0001] The 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 the operation, the various complex components in the feed liquid will cause serious membrane pollution, resulting in a decrease in the separation membrane flux, and frequent cleaning will cause a decrease in the service life of the membrane. Therefore, the membrane pollution 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. Improving 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 is 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, it is of great research significance to develop anti-pollution separation membranes that are simple to operate, low cost, high stability, energy-saving and environmentally friendly.

[0004] Protein has good biocompatibility and hydrophilicity. After reducing disulfide-bonded proteins to amyloid proteins by reducing agents, the amyloid protein aggregates can be directly adhered to various substrate surfaces by simple coating methods and have good stability. Patent CN108854599B provides a method for phase transformation of lysozyme with disulfide bonds to form a two-dimensional nanofilm for hemodialysis. However, this method only uses amyloid proteins to prepare separation membranes. The formed membranes are only composed of amyloid proteins and do not contain other components. This makes the membrane surface hydrophilic and severely adsorbs proteins and other materials, resulting in limited membrane pollution resistance.

[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-pollution 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-hydrophobic forces), and promotes the hydrophilic polymer and the 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, and has permanent and continuous pollution resistance. This method has the advantages of strong universality, low cost, simple operation and green environmental protection. The obtained anti-pollution 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] Prepare and mix a buffered salt solution of protein and hydrophilic polymer, then add a reducing agent, stir and react for 1-20 minutes, so that the disulfide bonds of the protein are opened, the protein is completely reduced, and amyloid protein is formed, so that it has adhesion, and the protein and the hydrophilic polymer are co-assembled in the solution to form an aggregate with adhesion properties, thereby obtaining a modified solution; wherein the mass ratio of the protein to the hydrophilic polymer is not more than 5:1 and not less than 1:25;

[0009] The prepared modification liquid is coated on the surface of the porous filter material for 10-200 seconds. The modification liquid adheres to the surface of the porous filter material to form a pollution-resistant coating. After washing with water, a separation membrane with a 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] Further, 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] Further, 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 filtering characteristics.

[0017] The pollution-resistant separation membrane obtained by 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 water drops are completely absorbed within 1 second to 2 minutes when they are dropped on the pollution-resistant coating. 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 complicated surface pretreatment process and can obtain a separation membrane with high stability and good anti-pollution effect through simple coating. The preparation process is simple, environmentally friendly, biosafe, economically efficient and easy to industrialize. The preparation method is suitable for constructing surface coatings of microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, forward osmosis membranes and pervaporation membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only 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 of the present invention and Comparative Example 7. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail below in conjunction with the drawings in the embodiment of the present invention. The described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] 2mL of 50mmol / L cysteine ​​tris hydroxymethyl aminomethane buffer was adjusted to pH 5.0, 2mL of 2mg / mL bovine serum albumin (BSA) and 2mg / mL poly (sulfobetaine acrylate) (PSBMA) tris hydroxymethyl aminomethane buffer solution was adjusted to pH 5.0, and then the above two solutions were fully stirred and mixed, and the modified solution was formed after 20min of reaction. The modified solution was poured on the surface of a PES ultrafiltration membrane with a diameter of 50mm (molecular weight cutoff of 50kDa) for deposition for 120 seconds. After the deposition, the modified solution on the membrane surface was poured out, and the membrane was then 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] Example 2-15

[0027] The preparation process of the anti-fouling 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 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; wherein the dynamic anti-fouling data of Example 11 are shown in Figure 1 As shown (a tangential flow filtration device was used for the experiment, where the pollutant was BSA, the pressure was 2 bar, and the cleaning solution was 0.1 mol / L sodium hydroxide solution);

[0028] Comparative Examples 1-10

[0029] The preparation process of the anti-fouling surface coating in the comparative example is similar to that in Example 2, wherein the required protein, hydrophilic polymer, reducing agent, porous filter material, reaction pH, reaction conditions and other variables 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, wherein the dynamic anti-fouling data of Comparative Example 7 are shown in 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 amount of the anti-pollution coating is no more than 20ug / cm 2 , especially Example 11, whose protein adsorption capacity is 5ug / cm 2 , which is much lower than the porous filter substrate and the coating membrane prepared by other formulas in the comparative example, which shows that the coating prepared by this method has very excellent anti-pollution performance. It can also be found from the attached figure that when the anti-pollution separation membrane is used for filtration experiments, it is found that when the BSA solution is used as the feed liquid, the flux of comparative example 7 decays to 50%, while that of example 11 decays to 71%; after washing with sodium hydroxide solution, the flux of example 11 recovers to 98%, while that of comparative example 7 recovers to 67%, which shows that example 11 has excellent anti-pollution performance, can significantly improve 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 tri(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 application breaks the disulfide bonds of proteins containing disulfide bonds under the action of a reducing agent, and the proteins fold to form amyloid proteins with adhesion ability. A hydrophilic polymer is introduced before the reducing agent reduces the proteins. The hydrophilic polymer and the protein are co-assembled in a solution. Under the action of the reducing agent, a new type of anti-pollution material in which the protein and the hydrophilic polymer are combined with each other is deposited on the surface of the substrate. The amyloid protein provides a strong adhesion ability for the anti-pollution material, so that the new type of anti-pollution material can stably exist on the surface of the substrate without being lost during the test. The ratio of protein to hydrophilic polymer affects the anti-pollution performance of the material. While amyloid protein provides adhesion, it also improves the anti-pollution effect of the coating to a certain extent. However, the main improvement in anti-pollution performance comes from the addition of hydrophilic polymers. The ratio is adjusted according to the interaction force between the two, hydrophilicity and other characteristics. When the binding force between the two is the strongest and the content of hydrophilic polymer in the system is the highest, the material has the best anti-pollution 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 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 the 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. The pH value of the solution is regulated to change the electrical properties of the hydrophilic polymer, so that the electrical properties of the hydrophilic polymer are opposite to the electrical properties of the protein in the system, which can enhance the interaction between the two, thereby improving 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 coating film preparations currently, effectively improving production efficiency.

[0041] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a pollution-resistant separation membrane, characterized in that: The steps include: Prepare and mix a buffered salt solution of protein and hydrophilic polymer, then add a reducing agent, and stir the reaction for 1-20 minutes, so that the protein and the hydrophilic polymer are co-assembled in the solution to form aggregates with adhesion 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; The prepared modification liquid is coated on the surface of the porous filter material for 10-200 seconds. The modification 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.

2. The method for preparing a pollution-resistant separation membrane according to claim 1, characterized in that: 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, characterized in that: 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.

4. The method for preparing a pollution-resistant separation membrane according to claim 1, characterized in that: 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 buffered salt includes but is not limited to 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, characterized in that: 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.

6. The method for preparing a pollution-resistant separation membrane according to claim 1, characterized in that: The porous filter material includes but is not limited to 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, characterized in that: The porous filter material includes, but is not limited to, a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a forward osmosis membrane, a membrane distillation membrane, and a pervaporation membrane.

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 the ability to resist protein adsorption, and the protein adsorption amount is less than 20ug / cm 2 , and does not change with the use time of the separation membrane.

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