Molecular brush modified anti-pollution polyamide membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of wastewater and sewage treatment, and particularly discloses a molecular brush modified anti-pollution polyamide membrane for sewage and wastewater treatment as well as a preparation method and application of the molecular brush modified anti-pollution polyamide membrane. The method comprises the following steps: S1, covalently grafting polyethyleneimine to the surface of an activated polyamide membrane to form an amino functional layer; the reaction concentration of the polyethyleneimine is 0.05 to 1.5 percent; s2, alpha-bromoisobutyric acid reacts with the amino functional layer to form an initiator layer; s3, the initiator layer is sequentially grafted with a zwitterionic polymer and a fluorine-containing polymer to form a zwitterionic hydrophilic layer and a low surface energy layer, and the molecular brush modified anti-pollution polyamide membrane is obtained. The polyamide membrane provided by the invention has better water flux, excellent organic pollution and inorganic scaling resistance and more excellent stability, and has excellent flux attenuation rate and flux recovery rate in simulated wastewater treatment; the device can be applied to sewage treatment equipment, seawater desalination equipment, industrial wastewater treatment and recycling equipment and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater and sewage treatment, and more specifically, relates to a molecular brush modified anti-fouling polyamide membrane for sewage and wastewater treatment, its preparation method and application. Background Art

[0002] Sewage and wastewater treatment and resource utilization are key measures to solve the fresh water resource crisis in China and are major strategic needs of the country. Due to advantages such as small floor area, good effluent quality, and high treatment efficiency, nanofiltration technology (NF) is widely used in fields such as water softening, organic matter removal, heavy metal removal, and sewage treatment and resource utilization. However, its practical application has long been restricted by the problem of membrane fouling. Currently, polyamide nanofiltration membranes occupy 60%-70% of the global nanofiltration membrane market due to their comprehensive performance advantages and mature modification technologies. The surface of existing polyamide nanofiltration membranes is prone to adsorbing particulate matter, colloids, and organic matter in wastewater, forming a fouling layer that leads to a decrease in flux and even causing irreversible membrane pore blockage.

[0003] To effectively alleviate this key problem of membrane fouling, the most common approach is to construct a hydrophilic anti-fouling buffer layer on the surface of the nanofiltration membrane to block the diffusion of pollutants towards the membrane surface. This buffer layer is rich in a large number of hydrophilic functional groups, such as carboxyl, hydroxyl, sulfonic acid, amino groups, etc. These functional groups can form a unique network structure with water molecules through hydrogen bonding, and immediately generate a dense hydration layer on the membrane surface to block the migration and aggregation of pollutants towards the membrane surface.

[0004] The new method of grafting hydrophilic polymers on the membrane surface has now received wide recognition in the academic community. Practice has shown that among numerous hydrophilic polymers, zwitterionic polymers have incomparable advantages in improving the anti-fouling performance of membranes compared to other hydrophilic compounds. The reason is that zwitterionic compounds can bind water molecules through electrostatic interaction, and the binding force strength is about 7-8 times that of ordinary hydrogen bonds, which is conducive to forming a denser hydration layer and efficiently blocking the deposition of pollutants on the membrane surface.

[0005] In the field of membrane science research, using SI-ATRP reaction (surface-initiated atom transfer radical polymerization) to trigger the polymerization of zwitterionic compound monomers on the membrane surface, enabling the in-situ growth of polymer molecular chains on the membrane surface to form a brush-shaped buffer layer with appropriate density and height, has become the most commonly used and effective method for grafting zwitterionic polymers on the membrane surface.

[0006] This method successfully overcomes the problem of uneven grafting caused by steric hindrance factors during the process of traditional grafting of long-chain polymers. The key step in implementing the SI-ATRP reaction is to precisely anchor α-bromoisobutyryl bromide as an initiator on the membrane surface. In practice, due to the lack of functional groups on the surface of the polyamide nanofiltration membrane that can form covalent bonds with acyl bromide groups. This has prompted researchers to adopt a specific strategy in practice: first, blend α-bromoisobutyryl bromide with dopamine hydrochloride salt, so that the acyl bromide group and the phenolic hydroxyl group combine to form an ester bond. By means of the self-polymerization of dopamine hydrochloride salt under alkaline conditions, the formed polydopamine coating with a "mussel-inspired structure" can form hydrogen bonds with the surface of the polyamide nanofiltration membrane, thereby introducing α-bromoisobutyryl bromide onto the membrane surface. As disclosed in the literature "Facile preparation of antifouling nanofiltration membrane by grafting zwitterions for reuse of shale gas wastewater" (Minli Hu, Separation and Purification Technology, https: / / doi.org / 10.1016 / j.seppur.2021.119310), a method for modifying the surface of the polyamide nanofiltration membrane NF90 is described. First, α-bromoisobutyryl bromide is used as an initiator and mixed with dopamine hydrochloride salt, and then a polydopamine coating is formed on the NF90 membrane. Subsequently, a zwitterionic polymer brush (PSBMA) is grafted on this basis through the SI-ATRP reaction.

[0007] However, the above method still has obvious defects, which limit its application in large-scale production. Specifically: (1) The stability of the polydopamine coating is relatively poor because there are a large number of non-covalent structures inside the coating, resulting in the coating being very unstable in acids, bases, and polar organic solvents; (2) The initiator α-bromoisobutyryl bromide and dopamine hydrochloride salt need to be blended in an organic solvent and a closed environment, and it is necessary to remove moisture and oxygen in the organic solvent in advance using nitrogen, and the operation is relatively complex; (3) The water flux of the finally prepared modified polyamide nanofiltration membrane is relatively low, only 0.83 L / (m 2 ·h·bar), which is difficult to meet the actual application requirements; (4) The initiator α-bromoisobutyryl bromide has high reactivity and is easily decomposed under light conditions. The acyl bromide group in its molecule is easily affected by water vapor in the air and hydrolyzed into a carboxyl group with low reactivity, losing the ability to react with dopamine hydrochloride, and the hydrobromic acid produced by hydrolysis is highly corrosive to equipment; (5) The reaction requires the addition of triethylamine as an acid-binding agent, and α-bromoisobutyryl bromide itself has the problems of being volatile and having a strong pungent smell. The above problems indicate that there are still many limitations in the application of zwitterionic polymers on polyamide nanofiltration membranes. Summary of the Invention

[0008] Aiming at the above existing technical problems, the primary object of the present invention is to provide a preparation method of a molecular brush modified anti-pollution polyamide membrane. The preparation method has simplicity in operation, can be carried out under room temperature, aqueous solution and air conditions, with mild reaction conditions, without the need to isolate air and water vapor, without using triethylamine as an acid-binding agent to participate in the reaction, and without the participation of organic solvents; and the reagents used are non-toxic and have no negative impact on the environment. The prepared molecular brush modified anti-pollution polyamide membrane has better water flux, excellent anti-organic pollution and inorganic fouling resistance, has more excellent stability, and is more conducive to long-term use. It can be used in sewage treatment, seawater desalination and industrial wastewater treatment and reuse membrane module equipment.

[0009] The second object of the present invention is to provide a molecular brush modified anti-pollution polyamide membrane prepared by the above preparation method.

[0010] The third object of the present invention is to provide the application of the above molecular brush modified anti-pollution polyamide membrane in wastewater treatment.

[0011] The fourth object of the present invention is to provide the application of α-bromoisobutyric acid as an initiator in the preparation of polyamide membranes by surface-initiated atom transfer radical polymerization.

[0012] In order to achieve the above objects, the present invention is realized through the following technical solutions: The present invention claims a preparation method of a molecular brush modified anti-pollution polyamide membrane, comprising the following steps: S1. Covalently graft polyethyleneimine onto the surface of the activated polyamide membrane to form an amino-functionalized layer; the reaction concentration of polyethyleneimine is 0.05 - 1.5%. S2. React α-bromoisobutyric acid with the amino-functionalized layer to form an initiator layer. S3. Graft a zwitterionic polymer and a fluoropolymer onto the initiator layer in sequence to form a zwitterionic hydrophilic layer and a low surface energy layer, and obtain a molecular brush modified anti-pollution polyamide membrane.

[0013] In step S1 of the present invention, polyethyleneimine is used, which contains multiple amino groups in its molecule. A part of the amino groups can react with the carboxyl groups on the surface of the polyamide nanofiltration membrane to form multiple stable amide bonds, so that polyethyleneimine is firmly combined with the polyamide nanofiltration membrane, and the remaining amino groups can be used as new active groups for further grafting initiators; the polyethyleneimine adopted in the present invention can replace the most commonly used polydopamine coating in the existing method, and from the perspective of coating stability, the polydopamine coating that forms a covalent bond with the substrate is more stable than the one that adheres to the substrate through hydrogen bond interaction, and is more conducive to long-term use.

[0014] Furthermore, the present invention uses α-bromo isobutyric acid as an initiator. α-Bromo isobutyric acid can crosslink with the amino groups on the polyethyleneimine crosslinked bottom layer to form amide bonds to complete grafting and then form an initiator layer. Subsequently, through two SI-ATRP reactions, zwitterionic polymers (PSBMA) and fluorine-containing polymers (PHFBM) are grafted in sequence to form a hydrophilic hydration barrier and a low surface energy antifouling interface, forming a diblock molecular brush with "pollution defense" and "pollution release" functions.

[0015] Furthermore, the inventors found through research that for the amino-functionalized layer and the finally prepared molecular brush-modified antifouling polyamide membrane, in step S1, the reaction concentration of polyethyleneimine is relatively important. A higher reaction concentration of polyethyleneimine will increase the amount of polyethyleneimine grafted onto the membrane surface, thereby increasing the number of SI-ATRP reaction active sites and obtaining a denser molecular brush layer, which will in turn lead to a decrease in the pure water permeation flux. If the reaction concentration of polyethyleneimine is low, the amount of polyethyleneimine grafted onto the membrane surface is small, which will instead greatly affect the antifouling performance of the molecular brush-modified antifouling polyamide membrane. By controlling the reaction concentration of polyethyleneimine within a specific range, the present invention enables the molecular brush-modified antifouling polyamide membrane to have excellent water flux while also having excellent antifouling performance.

[0016] The present invention proposes a method for grafting zwitterionic polymers through covalent interaction. This method is superior to the traditional α-bromoisobutyryl bromide-poly dopamine method in terms of environmental friendliness and operational simplicity. The present invention innovatively uses α-bromo isobutyric acid as an environmentally friendly initiator, which is non-toxic, has excellent hydrolysis stability, and realizes the permanent fixation of the initiator through covalent grafting technology in combination with polyethyleneimine (PEI), avoiding the peeling risk of traditional non-covalent coatings.

[0017] Compared with the traditional polydopamine coating method and α-bromoisobutyryl bromide initiator, the method provided by the present invention has operational simplicity. It can be carried out at room temperature, in aqueous solution and air conditions. The reaction conditions are mild, without the need to isolate air and water vapor, without the need to use triethylamine as an acid-binding agent to participate in the reaction, and without the need for organic solvents; and the reagents used are non-toxic and have no negative impact on the environment.

[0018] Conventional α-bromoisobutyryl bromide initiators need to be first mixed with dopamine hydrochloride in an organic solvent (such as N,N-dimethylformamide) to form an ester group between the acyl bromide group and the phenolic hydroxyl group, and then initiate the self-polymerization of dopamine to form a polydopamine coating on the membrane surface. It should be emphasized that the blending process needs to react for several hours under a nitrogen atmosphere to avoid the hydrolysis of α-bromoisobutyryl bromide when encountering water vapor in the air and losing its reaction effect. Moreover, triethylamine with a similarly pungent odor needs to be added as an acid-binding agent to promote the reaction. This operation method requires air-insulated conditions, and the reagents used are highly toxic, having a negative impact on the environment. Therefore, the method provided by the present invention is superior to the conventional polydopamine coating and α-bromoisobutyryl bromide initiator in terms of environmental protection and operational simplicity.

[0019] Furthermore, the molecular brush-modified anti-fouling polyamide membrane prepared by the method of the present invention has better water flux, excellent anti-organic fouling and inorganic scaling properties, and more excellent stability, being more conducive to long-term use. The flux decline rate (FDR) after filtering in simulated wastewater for 24 hours is only 8.8%, and the flux recovery rate (FRR) is 96.6%. When treating the ultrafiltration water of a membrane bioreactor (MBR) for landfill leachate, after three cycles of filtration tests, the flux recovery rate (FRR) is still 94.2%. The present invention provides another green, efficient and simple solution for constructing a molecular brush coating on the surface of a polyamide nanofiltration membrane.

[0020] Preferably, in the step S1, the polyethyleneimine is grafted onto the surface of the polyamide membrane through an EDC / NHS reaction.

[0021] More preferably, in the step S1, the specific operation of covalently grafting polyethyleneimine onto the surface of the polyamide membrane is: immersing the polyamide membrane in an aqueous solution containing EDC (N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride), NHS (N-hydroxysuccinimide) and polyethyleneimine for reaction, thereby forming an amino-functionalized layer on the surface of the polyamide membrane.

[0022] Preferably, the reaction concentration of NHS in the aqueous solution is 0.001 - 0.02 mol / L; more preferably, the reaction concentration of NHS in the aqueous solution is 0.008 - 0.015 mol / L.

[0023] Preferably, the reaction ratio of EDC to NHS is 1:2 - 4:1.

[0024] Preferably, in the step S1, at least one of the following (a)-(c) is selected: (a)The reaction concentration of polyethyleneimine is 0.1 - 1.5%; preferably, the reaction concentration is 0.8 - 1.3%; more preferably, the reaction concentration is 1 - 1.2%; most preferably, the reaction concentration is 1%. (b)The reaction time in aqueous solution is 30 - 300 min; preferably, the reaction time is 80 - 160 min; more preferably, the reaction time is 100 - 140 min; most preferably, the reaction time is 120 min. (c)The reaction temperature in aqueous solution is 15 - 60 °C; preferably, the reaction temperature is 20 - 30 °C; most preferably, the reaction temperature is 25 °C.

[0025] Preferably, the polyethyleneimine includes one or more of linear polyethyleneimine and branched polyethyleneimine.

[0026] Preferably, the molecular weight of the polyethyleneimine is 100 - 750000 Da. Further preferably, the molecular weight of the polyethyleneimine is 200 - 10000 Da; more preferably, the molecular weight of the polyethyleneimine is 300 - 1000 Da; most preferably, the molecular weight of the polyethyleneimine is 400 - 800 Da. More specifically, the molecular weight of the polyethyleneimine can be 100 Da, 200 Da, 300 Da, 400 Da, 500 Da, 600 Da, 700 Da, 800 Da, 900 Da, 1000 Da, 2000 Da, 4000 Da, 6000 Da, 8000 Da, 10000 Da, 50000 Da, 100000 Da, 200000 Da, 400000 Da, 600000 Da, etc., or the range formed by any of the above values, such as 200 - 800 Da, 400 - 5000 Da, etc., and the present invention is not limited thereto.

[0027] Preferably, the polyamide membrane can be a polyamide membrane conventionally used in the art or commercially available, such as DuPont NF90, etc. Preferably, the molecular weight cut-off of the polyamide membrane is 100-2000 Da; more preferably, the molecular weight cut-off is 120-1000 Da; even more preferably, the molecular weight cut-off is 140-500 Da; even more preferably, the molecular weight cut-off is 150-200 Da. More specifically, the molecular weight cut-off of the polyamide membrane can be 100 Da, 110 Da, 120 Da, 130 Da, 140 Da, 150 Da, 160 Da, 170 Da, 180 Da, 190 Da, 200 Da, 500 Da, 600 Da, 800 Da, 1000 Da, 1400 Da, 1800 Da, etc., or an interval range formed by any of the above values, such as 200-800 Da, 120-180 Da, etc., and the present invention is not limited thereto.

[0028] Preferably, in the step S2, the specific operation of α-bromoisobutyric acid reacting with the amino-functionalized layer to form an initiator layer is: immersing the polyamide membrane with the amino-functionalized layer formed in the step S1 into an aqueous solution containing EDC, NHS and α-bromoisobutyric acid for reaction, thereby forming an initiator layer.

[0029] More preferably, in the step S2, at least one of the following (d)-(f) is selected: (d) The mass fraction of α-bromoisobutyric acid in the aqueous solution is 0.1-1.5%; preferably, the mass fraction of α-bromoisobutyric acid is 0.5-1.2%; more preferably, the mass fraction of α-bromoisobutyric acid is 0.8-1.0%; (e) The reaction time in the aqueous solution is 30-300 min; preferably, the reaction time is 80-280 min; more preferably, the reaction time is 200-260 min; most preferably, the reaction time is 240 min; (f) The reaction temperature in the aqueous solution is 15-60 °C; preferably, the reaction temperature is 20-30 °C; most preferably, the reaction temperature is 25 °C.

[0030] Preferably, in the steps S1 and S2, the aqueous solution is a MES buffer aqueous solution. More specifically, the concentration of the MES buffer aqueous solution is 0.001-0.02 mol / L; more preferably, the concentration is 0.008-0.015 mol / L. More specifically, the pH of the MES buffer aqueous solution is 5.0-6.0; most preferably, the pH is 5.5.

[0031] Preferably, in some specific embodiments, the operation of step S3 is as follows: Immerse the polyamide membrane after the reaction in step S2 into the ATRP reaction solution 1 containing zwitterionic polymer monomers, add a reducing agent to initiate radical polymerization to form a zwitterionic hydrophilic layer (i.e., hydrophilic PSBMA layer); further, immerse the reacted polyamide membrane into the ATRP reaction solution 2 containing fluoropolymer monomers, add a reducing agent to initiate radical polymerization to form a low surface energy layer (i.e., low surface energy PHFBM layer).

[0032] Preferably, the ATRP reaction solution 1 and the ATRP reaction solution need to be deoxygenated by bubbling. More specifically, the total time for the deoxygenation by bubbling operation is 10 - 30 min; most preferably, the total time for the deoxygenation by bubbling operation is 20 min.

[0033] Preferably, the monomers of the zwitterionic polymer are selected from one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 2-methacryloyloxyethylphosphorylcholine; and / or, the monomers of the fluoropolymer are selected from one or more of hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, trifluoroethyl methacrylate.

[0034] Preferably, the ATRP reaction solution 1 and the ATRP reaction solution 2 further include: a solvent, copper chloride, and tris(2-pyridylmethyl)amine.

[0035] Specifically, the solvent is a mixed solution of an alcohol solvent (such as isopropanol, etc.) and water; the volume ratio of the alcohol solvent to water is 1:1 - 1:3. Specifically, the concentration of copper chloride in the ATRP reaction solution 1 is 1 - 20 mmol / L; preferably, the concentration of copper chloride is 3 - 8 mmol / L; most preferably, the concentration of copper chloride is 5 mmol / L. Specifically, the concentration of tris(2-pyridylmethyl)amine in the ATRP reaction solution 1 is 0.01 - 0.12 mol / L; preferably, the concentration of tris(2-pyridylmethyl)amine is 0.02 - 0.06 mol / L; most preferably, the concentration of tris(2-pyridylmethyl)amine is 0.03 mol / L.

[0036] Preferably, the reducing agent can be a reducing agent conventionally used in the SI-ATRP reaction in the art. More specifically, the reducing agent includes but is not limited to L-ascorbic acid, etc. Specifically, the addition amount of the reducing agent is 1 - 10 g per liter of the reaction solution; preferably, the addition amount of the reducing agent is 4 - 8 g per liter of the reaction solution; most preferably, the addition amount of the reducing agent is 6 g per liter of the reaction solution.

[0037] Preferably, the reaction time in ATRP reaction solution 1 is 15 - 60 min; more preferably, the reaction time in ATRP reaction solution 1 is 30 - 50 min; most preferably, the reaction time in ATRP reaction solution 1 is 40 min. Preferably, the reaction temperature in ATRP reaction solution 1 is 15 - 60 °C. Most preferably, the reaction temperature is 25 °C.

[0038] Preferably, the reaction time in ATRP reaction solution 2 is 15 - 120 min; more preferably, the reaction time in ATRP reaction solution 1 is 20 - 50 min; most preferably, the reaction time in ATRP reaction solution 1 is 30 min. Preferably, the reaction temperature in ATRP reaction solution 2 is 15 - 60 °C. Most preferably, the reaction temperature is 25 °C.

[0039] Furthermore, the present invention claims the molecular brush modified anti - fouling polyamide membrane prepared by the above - mentioned preparation method.

[0040] Furthermore, the present invention claims the application of the above - mentioned molecular brush modified anti - fouling polyamide membrane in wastewater treatment.

[0041] Furthermore, the present invention claims the application of α - bromoisobutyric acid as an initiator in the preparation of polyamide membranes by surface - initiated atom transfer radical polymerization.

[0042] Compared with the prior art, the present invention has the following beneficial effects: (1) The method provided by the present invention has the simplicity in operation, can be carried out under room temperature, aqueous solution and air conditions, with mild reaction conditions, without the need to isolate air and water vapor, without using triethylamine as an acid - binding agent to participate in the reaction, and without using organic solvents; and the reagents used are non - toxic and have no negative impact on the environment.

[0043] (2) The molecular brush modified anti - fouling polyamide membrane prepared by the above - mentioned method of the present invention has better water flux, excellent anti - organic fouling and inorganic scaling properties, has more excellent stability, and is more conducive to long - term use. Description of the Drawings

[0044] Figure 1 It is the water contact angle of each polyamide membrane in Example 1.

[0045] Figure 2 It is the scanning electron microscope (SEM) characterization diagram of each polyamide membrane in Example 1.

[0046] Figure 3 It is the atomic force microscope (AFM) characterization diagram of each polyamide membrane in Example 1.

[0047] Figure 4 It is membrane N in Example 1Br High-resolution X-ray photoelectron spectroscopy (XPS) Br 3d spectrum.

[0048] Figure 5 Membrane fouling curves of each polyamide membrane in Example 1 applied to humic acid simulated wastewater.

[0049] Figure 6 Membrane fouling curves of each polyamide membrane in Example 1 applied to the advanced treatment of actual wastewater landfill leachate MBR effluent.

[0050] Figure 7 Long-term membrane fouling curve of membrane D3 prepared in Example 1 applied to the advanced treatment of actual wastewater landfill leachate MBR effluent.

[0051] Figure 8 Short-term fouling curves of polyamide membranes prepared in Examples 1-3, Comparative Examples 3 and 4 applied to bovine serum albumin simulated wastewater. Detailed implementation mode

[0052] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0053] Example 1 Preparation of molecular brush modified anti-fouling polyamide membrane (1) Commercial polyamide membrane Fimtec from DuPont TM After NF90 was rinsed with deionized water multiple times to remove preservatives and membrane pore retention agents, it was soaked in deionized water for later use, labeled as N0; (2) Prepare a 0.1 mol / L MES buffer aqueous solution with a pH of 5.5. Dissolve EDC and NHS in the MES buffer aqueous solution successively. The preparation concentrations of EDC and NHS are both 0.1 mol / L. Finally, add polyethyleneimine (PEI) with an average molecular weight of 600 Da, and the mass fraction of PEI is 1%; (3) Fix N0 in the reaction device, and ensure that the selective layer of the membrane faces upward; pour the solution prepared in step (2) into the reaction device, place it on a shaker, and react at a speed of 60 rpm under open air at room temperature for 2 h. After the reaction, pour out the solution, wash away the remaining reactants with deionized water, keep the membrane fixed in the reaction device, and label this PEI-modified membrane as N PEI membrane; (4)Prepare a 0.1 mol / L MES buffer aqueous solution with a pH of 5.5. Dissolve EDC and NHS successively in the MES buffer aqueous solution. The prepared concentrations of EDC and NHS are both 0.1 mol / L. Finally, add α-bromoisobutyric acid and dissolve it fully. The mass fraction of α-bromoisobutyric acid is 1%. (5)Pour the solution prepared in the above step (4) into a reaction device fixed with an N PEI membrane, place it on a shaker, and react at a rotation speed of 60 rpm under open air at room temperature for 4 h. After the reaction is completed, pour out the solution, wash away the remaining reactants with deionized water, and label it as the N Br membrane. (6)Prepare an ATRP reaction solution 1 containing zwitterionic monomers. The solvent is a mixed solution of isopropanol and water with a volume ratio of 1:1. The solutes are [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) at 270 mmol / L, copper chloride at 5 mmol / L, and tris(2-pyridylmethyl)amine (TPMA) at 0.03 mol / L. Cut the N Br membrane prepared in step (5) into appropriate sizes, add it to a three-necked flask together with the above ATRP reaction solution 1, and continuously introduce nitrogen for 20 min. (7)Prepare a reducing agent solution. The volume of the solution is 1 / 20 of the volume of the ATRP reaction solution 1 in step (6). The solvent is a mixed solution of isopropanol and water with a volume fraction ratio of 1:1. The solute is L-ascorbic acid, and the addition amount is 6 g of L-ascorbic acid added per liter of the ATRP reaction solution 1. (8)After the nitrogen introduction time in step (6) ends, pour the reducing agent solution in step (7) into the three-necked flask, then quickly seal the three mouths of the three-necked flask with rubber stoppers to make the reaction system in an anaerobic environment. The total reaction time is 40 min. After the reaction is completed, take out the membrane, wash it thoroughly with ultrapure water, soak it in ultrapure water, and store it in a refrigerator at 4°C. The membrane is labeled as the N1 membrane. (9)Perform a secondary ATRP reaction to graft a low surface energy fluorinated molecular brush. The operation is the same as that in the above steps (6)-(8), with the difference that: use ATRP reaction solution 2, in which the monomer is replaced with hexafluorobutyl methacrylate (HFBM) with a concentration of 5 mmol / L; the reaction time in step (8) is 30 min, and a molecular brush-modified anti-fouling polyamide membrane is prepared and labeled as the D3 membrane.

[0054] Example 2 Preparation of Molecular Brush-Modified Anti-Fouling Polyamide Membrane The difference between this example and Example 1 is that: in step (2), the mass fraction of polyethyleneimine is 0.1%, and the finally prepared molecular brush-modified anti-fouling polyamide membrane is labeled as D1.

[0055] Example 3 Preparation of Molecular Brush Modified Anti-Pollution Polyamide Membrane The difference between this example and Example 1 is that: in step (2), the mass fraction of polyethyleneimine is 0.5%, and the finally prepared molecular brush modified anti-pollution polyamide membrane is labeled as D2.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is that: in step (2), ethylenediamine (EDA) is used to replace polyethyleneimine, and the mass fraction remains 1%. The membrane grafted only with ethylenediamine is labeled as N EDA , and the finally prepared molecular brush modified anti-pollution polyamide membrane is labeled as D6.

[0057] Comparative Example 2 This comparative example compares the stability of polyethyleneimine coatings and polydopamine coatings fixed with initiators. The specific steps are as follows: (1) The commercial polyamide membrane NF90 was rinsed with deionized water multiple times to remove preservatives and membrane pore retention agents, and then soaked in deionized water for standby; (2) Prepare a 1 mol / L Tris buffer solution with a pH of 8.5, add an appropriate amount of hydrochloric acid dopamine to dissolve it, and prepare a 4 g / L hydrochloric acid dopamine modification solution; (3) Fix the membrane in the reaction device, ensure that the selective layer of the membrane faces upward, pour the modification solution in step (2) on the membrane surface, and the self-polymerization process of dopamine on the membrane surface is 10 minutes. After the reaction, pour out the activation solution, wash away the remaining reactants with deionized water, keep the membrane fixed in the reaction device, and label the two prepared membranes as N PDA-1 and N PDA-2 ; (4) Prepare two PEI modified membranes according to steps (1) - (3) of Example 1, and label them as N PEI-1 and N PEI-2 ; (5) Prepare hydrochloric acid with a pH = 2 and sodium hydroxide solution with a pH = 13 respectively, and soak the prepared membranes N PEI-1 and N PDA-1 in hydrochloric acid at the same time, and soak the membranes N PEI-2 and N PDA-2 in sodium hydroxide solution at the same time. The soaking time is 12 hours. The membranes after acid treatment are labeled as N PEI-1A , N PDA-1A , and the membranes after alkali treatment are labeled as N PEI-2B , N PDA-2B . Compare the membranes N PEI-1 , N PDA-1 , N PEI-2 and N PDA-2The changes in the pure water permeation flux and the rejection performance of sodium sulfate and magnesium chloride before and after acid-base immersion were used to evaluate the coating stability.

[0058] Comparative Example 3 Preparation of molecular brush modified anti-fouling polyamide membrane The difference between this comparative example and Example 1 is that the mass fraction of polyethyleneimine in step (2) is 2.0%, and the finally prepared molecular brush modified anti-fouling polyamide membrane is labeled as D4.

[0059] Comparative Example 4 Preparation of molecular brush modified anti-fouling polyamide membrane The difference between this comparative example and Example 1 is that the mass fraction of polyethyleneimine in step (2) is 3.0%, and the finally prepared molecular brush modified anti-fouling polyamide membrane is labeled as D5.

[0060] Test Example I. Experimental objects The polyamide nanofiltration membranes prepared in the examples and comparative examples were used.

[0061] II. Experimental methods The prepared polyamide nanofiltration membranes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the hydrophilic-hydrophobic properties were measured, and the pure water flux, salt rejection rate, and anti-fouling performance during the filtration of simulated wastewater containing humic acid, simulated wastewater containing bovine serum albumin, and the ultrafiltration effluent of the actual wastewater landfill leachate membrane bioreactor (MBR) were measured. Among them, (1) Determination of pure water flux: In this experiment, a cross-flow filtration device was used for determination. The effective area of the membrane was 16 cm 2 , the filtration temperature was controlled at 25 °C, the test pressure was 6 bar, and the membrane surface flow rate was controlled at 0.1 m / s. The polyamide nanofiltration membrane was pre-pressed with pure water. After the flux was stable, the water permeation flux J of the polyamide nanofiltration membrane was recorded. The calculation formula is:

[0062] Among them, V represents the volume of leachate (L), A represents the effective membrane area (m 2 ), represents the filtration duration (h).

[0063] (2) Determination of membrane rejection rate: The rejection rate of the polyamide nanofiltration membrane for salts in 2000 mg / L MgCl2 and Na2SO4 solutions was measured. The rejection rate of the polyamide nanofiltration membrane was calculated according to the following formula:

[0064] Among them, CF and C P respectively represent the conductivity of the concentrate and the permeate.

[0065] (3)Anti-fouling performance test: The humic acid HA simulated wastewater simulated the composition of the actual landfill leachate, and was prepared from 6 g / L NaCl, 0.15 g / L CaCl2 and 0.1 g / L humic acid, with the pH adjusted to 7.0. Before the test, the polyamide nanofiltration membrane was pre-pressed overnight with 30 bar ultrapure water, and the initial flux was adjusted with a 6 g / L NaCl solution J 0 to 30 L·m -2 ·h -1 . The fouling test lasted for 24 hours. During this period, the permeate was refluxed every hour to keep the total osmotic pressure of the feed liquid constant, and the membrane surface flow rate was maintained at 0.44 m·s -1 and the temperature at 25 ± 3°C. After the test, the membrane was rinsed with ultrapure water for 30 minutes, and the flux after cleaning was tested with a NaCl solution having the same conductivity J 2, and then the flux recovery rate (FRR) was evaluated. The flux decline ratio (FDR) and the flux recovery rate (FRR) were calculated respectively through the initial flux ( J 0), the flux after fouling ( J t ), and the flux after cleaning ( J 2), and the formulas are as follows:

[0066]

[0067] where, J 0 and J t are respectively the initial flux and the final flux during the test process, J 2 is the NaCl flux after physical cleaning after fouling filtration.

[0068] The bovine serum albumin (BSA) simulated wastewater was used to evaluate the treatment effect of the wastewater treatment process and equipment on protein-containing wastewater, and was prepared from 2 g / L NaCl, 0.15 g / L CaCl2 and 0.1 g / L bovine serum albumin. Before the test, the polyamide nanofiltration membrane was pre-pressed overnight with 30 bar ultrapure water, and the initial flux was adjusted to 30 L·m -2 ·h -1 . The fouling test lasted for 6 hours. During this period, the permeate was refluxed every hour to keep the total osmotic pressure of the feed liquid constant, and the transmembrane flow rate was maintained at 0.44 m·s -1And at a temperature of 25 ± 3 °C. After the test, the membrane was rinsed with ultrapure water for 30 minutes, and the flux recovery rate (FRR) of the membrane was evaluated with a NaCl solution having the same conductivity.

[0069] The actual wastewater was taken from the ultrafiltration effluent treated by MBR in a waste incineration plant in Guangzhou. The water sample was stored at 4 °C. The pretreatment included filtering and removing suspended particulate matter with a 0.22 μ m polyethersulfone microfiltration membrane, and detecting the concentrations of metal ions and organic matters by ICP-OES and TOC analysis. During the test, first, a sodium chloride solution with the same conductivity as the actual water was used for pre-pressurization and the initial flux was adjusted to 40 ± 2 L·m -2 ·h -1 , with 4.5 L of wastewater as the feed liquid, continuously filtered until the cumulative permeate volume reached 3 L or the FDR exceeded 80%. After the test, the membrane was rinsed with ultrapure water for 30 minutes, and the flux recovery rate (FRR) was evaluated with a NaCl solution having the same conductivity.

[0070] III. Experimental Results Table 1

[0071] Table 1 is a summary table of the pure water permeation flux and inorganic salt rejection rate of the polyamide nanofiltration membranes prepared in Examples 1-3 and Comparative Examples 1-4 of this application. From the results in Table 1, it can be seen that after grafting PEI on the original membrane, the pure water permeation flux decreased to 5.0 LMH / bar, the sodium sulfate rejection rate decreased to 95.0%, and the magnesium chloride rejection rate increased to 97.7%. This is mainly because the grafting of PEI caused the membrane pores to shrink, the membrane pores became denser, and the pure water permeation flux decreased. At the same time, the positive charge of the membrane increased, resulting in a weakened repulsion to sulfate ions and an enhanced repulsion to magnesium ions. After grafting zwitterionic molecular brushes and diblock molecular brushes through SI-ATRP reaction, the pure water permeation flux further decreased to 2.6 LMH / bar and 2.3 LMH / bar, the sodium sulfate rejection rate increased to 97.6% and 98.6% respectively, while the magnesium chloride rejection rate decreased to 94.2% and 96.7% respectively. This is because the dense molecular brush layer increased the resistance of water molecules passing through the membrane, and at the same time, the grafting of the initiator consumed the amino groups on the membrane surface, weakening the positive charge of the membrane. N PEI Compared with N0, the changes in the pure water permeation flux and salt rejection performance of N, N1, and D3 membranes indicate that the new initiator and diblock molecular brush coating were successfully grafted on the membrane surface.

[0072] In addition, compared with the existing polyamide membrane synthesized by the method of dopamine hydrochloride + α-bromoisobutyryl bromide, its water flux is relatively low, only 0.83 L m -2 h -1 bar -1, the polyamide membrane prepared by the polyethyleneimine + α-bromoisobutyric acid scheme adopted in the present invention has excellent water flux, and the water flux ≥ 2.3 L m -2 h -1 bar -1 . It is significantly better than the existing schemes.

[0073] The pure water permeation fluxes of the membranes D1 - D5 obtained in Examples 1 - 3, Comparative Examples 3 and 4 are 3.1, 2.7, 2.3, 1.8, 1.3 L m -2 h -1 bar -1 respectively, and there are also differences in the inorganic salt rejection rate. This shows that increasing the mass fraction (reaction concentration) of polyethyleneimine can increase the amount of polyethyleneimine grafted onto the membrane surface, thereby increasing the number of SI-ATRP reaction active sites, obtaining a denser molecular brush layer, and further resulting in a decrease in the pure water permeation flux.

[0074] For the ethylenediamine-modified membrane N prepared in Comparative Example 1 EDA and the molecular brush-modified membrane D6, the pure water permeation fluxes are 5.3 and 1.6 L m -2 h -1 bar -1 respectively. The sodium sulfate rejection rate of the membrane D6 is slightly lower than that of the original membrane N0, while the magnesium chloride rejection rate increases significantly to 97.0% and 95.5% respectively, indicating the successful grafting of ethylenediamine onto the membrane surface and the successful construction of the molecular brush. At the same time, compared with the membrane D3 prepared in Example 1, the membrane D6 has a lower pure water permeation flux, which may be because the molecular weight of ethylenediamine is only 60.1 Da, much lower than the polyethyleneimine (600 Da) used in Example 1. The smaller molecular weight ethylenediamine is more likely to be grafted into the membrane pores, resulting in the growth of the molecular brush inside the membrane pores and blocking the membrane pores, thus having a lower pure water permeation flux.

[0075] For the membranes N grafted with polyethyleneimine coatings in Comparative Example 2 PEI-1 and N PEI-2 , the pure water permeation fluxes are 4.5 and 4.6 L m -2 h -1 bar -1 , while for the membranes N deposited with polydopamine coatings PDA-1 and N PDA-2 , the pure water permeation fluxes are 3.8 and 4.0 L m -2 h -1 bar -1 respectively. This is mainly because the polyethyleneimine-grafted coating forms a nanoscale coating, while the dopamine self-polymerized coating has a certain thickness, so it has a greater resistance to water molecule transmission and a lower pure water permeation flux. After soaking in hydrochloric acid with pH = 2 for 12 hours, the membrane N PDA-1AThe pure water permeation flux of PDA-1 significantly increased to 4.5 L m -2 h - 1 bar -1 compared with N. The rejection rates of sodium sulfate and magnesium chloride decreased to 97.4% and 93.6% respectively, indicating that the polydopamine coating partially decomposed after acid immersion. In contrast, membrane N PEI-1A maintained a pure water permeation flux and an inorganic salt rejection rate similar to those of N PEI-1 , both being 4.6 L m -2 h -1 bar -1 . The rejection rates of sodium sulfate and magnesium chloride were 97.0% and 96.5% respectively. Similarly, after soaking in a sodium hydroxide solution with pH = 13 for 12 hours, the pure water permeation flux of membrane N PDA-2B significantly increased to 4.5 L m PDA-2 compared with N -2 h - 1 bar -1 . The rejection rate of sodium sulfate decreased to 97.1%, indicating that the polydopamine coating partially decomposed after alkali immersion. In contrast, membrane N PEI-2B maintained a pure water permeation flux and an inorganic salt rejection rate similar to those of N PEI-2 , which were 4.7 L m -2 h -1 bar -1 respectively. The rejection rates of sodium sulfate and magnesium chloride were 96.2% and 97.1% respectively. In summary, the polyethyleneimine coating is more stable than the polydopamine coating in both acidic and alkaline environments.

[0076] Figure 1 are the water contact angles of each polyamide membrane in Example 1. From the Figure 1 results, it can be seen that after grafting the PEI hydrophilic layer on the membrane surface, the contact angle of the membrane did not change significantly. This may be because the base membrane has strong hydrophilicity, and the membrane surface still maintains good hydrophilicity after PEI modification. After grafting the initiator α-bromoisobutyric acid, the water contact angle of membrane N Br significantly increased to 50.9°, indicating the successful grafting of α-bromoisobutyric acid on the PEI bottom layer. The hydrophobic methyl groups contained in the molecular structure of α-bromoisobutyric acid increased the hydrophobicity of the membrane. After grafting the zwitterionic molecular brush through SI-ATRP reaction, the contact angle of N1 decreased to 24.9°, indicating the successful grafting of the superhydrophilic zwitterionic molecular brush on the membrane surface. After further grafting the fluorinated molecular brush, the contact angle of D3 increased to 38.5°. This is mainly due to the certain hydrophobicity of the fluorinated molecular brush. Figure 1 Indicates the successful grafting of the novel initiator coating and the molecular brush.

[0077] Figure 2 Scanning electron microscope (SEM) characterization diagrams of each polyamide membrane in Example 1. After PEI modification on the membrane surface, the surface morphology did not change significantly, indicating that the grafting of PEI was limited to the molecular level and no stacking occurred to form a coating with a certain thickness. After grafting zwitterionic molecular brushes, more ridge-like protrusions appeared on the surface. These were mainly clusters formed by the polyelectrolyte effect of the zwitterionic polymer brushes on the surface. After further grafting fluorinated molecular brushes, large dark areas appeared, indicating that the fluorinated molecular brushes formed a dense coating on the surface.

[0078] Figure 3 Atomic force microscope (AFM) characterization diagrams of each polyamide membrane in Example 1. After PEI modification on the membrane surface, the surface roughness did not change significantly. This was mainly because the grafting of PEI was limited to the molecular level, forming a coating with a nanoscale thickness, so the influence on the roughness of the original membrane was small. The introduction of zwitterionic molecular brushes did not cause an obvious change in roughness either. Although the zwitterionic molecular brushes formed clusters due to the polyelectrolyte effect under dry conditions, which might cause an increase in roughness, some of the zwitterionic molecular brushes filled in some uneven areas of the original membrane, and the effects of the two on roughness offset each other, keeping the roughness unchanged. After the membrane was further grafted with fluorinated molecular brushes, the roughness increased significantly, mainly because the fluorinated molecular brushes formed clusters of uneven sizes through hydrophobic interactions.

[0079] Figure 4 For membrane N in Example 1 Br High-resolution X-ray photoelectron spectroscopy (XPS) Br 3d spectrum. An obvious absorption peak corresponding to Br 3d appeared near the binding energy of 68 eV in the figure, indicating the successful grafting of the initiator α-bromoisobutyric acid (Biba) on the membrane surface and proving the feasibility of the novel initiator in the present invention.

[0080] Table 2

[0081] Table 2 is a summary table of FDR and FRR in the filtration experiments of the modified anti-fouling polyamide nanofiltration membranes prepared in Examples 1-3, Comparative Examples 3 and 4 of this application for short-cycle humic acid simulated wastewater, bovine serum albumin simulated wastewater, and landfill leachate MBR ultrafiltration effluent. Figure 5 Membrane fouling curves of each polyamide membrane in Example 1 applied to humic acid simulated wastewater. Using the original membranes N0 and N PEI as the control groups, from Figure 5It can be seen that the nanofiltration membranes N1 and D3 after molecular brush modification have excellent anti-fouling performance. After 24 hours of filtration, the flux decline rates (FRR) of the membranes are 23.7% and 8.8% respectively, and the flux recovery rates after cleaning can reach 82.6% and 96.6% (Table 2). This result indicates that the novel initiator coating proposed in the present invention can be used to prepare modified nanofiltration membranes with remarkable anti-fouling effects.

[0082] Figure 6 This is the membrane fouling curve of each polyamide membrane in Example 1 applied to the actual wastewater landfill leachate MBR ultrafiltration effluent. Using the original membranes N0 and N PEI as the control groups, it can be seen from Figure 6 that the nanofiltration membranes N1 and D3 after molecular brush modification have excellent anti-fouling performance. When the membrane flux drops below 20% of the initial flux, the cumulative permeate volume can reach 2900 mL and 3000 mL, while the effluent volumes of the control N0 and N PEI are only 2600 mL each. This result shows that the novel initiator coating proposed in the present invention can be used to prepare modified nanofiltration membranes with remarkable anti-fouling effects and applied to the treatment of actual wastewater.

[0083] Table 3

[0084] Table 3 is a summary table of FDR and FRR for each cycle in the long-term landfill leachate MBR ultrafiltration effluent filtration experiment of the modified anti-fouling polyamide nanofiltration membrane prepared in Example 1 of this application. Figure 7 This is the long-term membrane fouling curve of the membrane D3 prepared in Example 1 applied to the actual wastewater landfill leachate MBR ultrafiltration effluent. It can be seen from the results that the flux decline rate of the membrane gradually increases in each filtration cycle. This is mainly because the pollutant concentration in the feed liquid gradually increases as the wastewater is continuously concentrated, resulting in an increasing rate of pollutant migration to the membrane surface. At the same time, the osmotic pressure also increases. Under the combined action of concentration polarization and increasing osmotic pressure, the membrane flux inevitably decreases. However, as can be seen from Table 3, finally, after three cycles of anti-fouling tests, after simple pure water physical cleaning, the modified membrane can still reach a flux recovery rate of 94.2%. This shows that the dual-defense functional molecular brush coating can significantly prevent the formation of irreversible fouling and extend the service life of the membrane.

[0085] Figure 8 This is the short-term fouling curve graph of the polyamide membranes prepared in Examples 1-3, Comparative Examples 3 and 4 applied to bovine serum albumin simulated wastewater. Using the original membrane N0 as the control group, it can be seen from Figure 8It can be seen that the flux decline of the molecular brush modified polyamide nanofiltration membranes D1-D5 during the filtration process is slower than that of the original membrane N0, indicating that the molecular brush modified membranes have better anti-fouling performance. After 6 hours of fouling filtration, the flux decline rate (FDR) of the original membrane N0 reached 35.5%, and the flux recovery rate (FRR) was only 85.6%. With the increase of the grafting concentration of polyethyleneimine, the FDR of D1-D5 gradually decreased, while the FRR gradually increased, which indicates that increasing the grafting amount of polyethyleneimine can improve the grafting density of the molecular brush and further enhance the anti-fouling performance (Table 3). From Table 1, it can be concluded that there is a trade-off effect between the anti-fouling performance and the pure water permeation flux of the molecular brush modified membranes, which needs to be considered comprehensively.

[0086] In summary, the novel initiator coating proposed in the present invention, namely the coating formed by combining polyethyleneimine and α-bromoisobutyric acid, not only has environmental friendliness and operational simplicity, but also has excellent stability, which is mainly reflected in the fact that polyethyleneimine and α-bromoisobutyric acid are combined with the membrane surface through covalent bonding. At the same time, in the anti-fouling test, the molecular brush modified membranes have excellent anti-fouling performance, indicating that the novel initiator coating can not only replace the traditional polydopamine initiator coating in terms of the coating grafting method, but also achieve similar effects to the polydopamine initiator coating in the subsequent anti-fouling modification process of the membrane, and also has applicability.

[0087] The foregoing examples are illustrative only and are used to explain some of the features of the method described in the present invention. The appended claims are intended to claim the broadest scope possible, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims should not be limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be construed as being covered by the appended claims where possible.

Claims

1. A preparation method of a molecular brush modified anti-fouling polyamide membrane, characterized in that, It includes the following steps: S1. Covalently graft polyethyleneimine onto the surface of the activated polyamide membrane to form an amino-functionalized layer; the reaction concentration of polyethyleneimine is 0.05 - 1.5%; S2. React α-bromoisobutyric acid with the amino-functionalized layer to form an initiator layer; S3. Graft a zwitterionic polymer and a fluoropolymer onto the initiator layer in sequence to form a zwitterionic hydrophilic layer and a low surface energy layer, and prepare a molecular brush modified anti-fouling polyamide membrane.

2. The preparation method according to claim 1, characterized in that, In step S1, the polyethyleneimine is grafted onto the surface of the polyamide membrane through the EDC / NHS reaction.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the specific operation of covalently grafting polyethyleneimine onto the surface of the polyamide membrane is: Immerse the polyamide membrane in an aqueous solution containing EDC, NHS, and polyethyleneimine for reaction, thereby forming an amino-functionalized layer on the surface of the polyamide membrane.

4. The preparation method according to claim 3, characterized in that, Selected from at least one of the following (a)-(c): (a) The reaction concentration of polyethyleneimine is 0.1 - 1.2%; (b) The reaction time in the aqueous solution is 30 - 240 min; (c) The reaction temperature in the aqueous solution is 15 - 60 °C.

5. The preparation method according to claim 1, characterized in that, In step S2, the specific operation of reacting α-bromoisobutyric acid with the amino-functionalized layer to form an initiator layer is: Immerse the polyamide membrane with the amino-functionalized layer formed in step S1 in an aqueous solution containing EDC, NHS, and α-bromoisobutyric acid for reaction, thereby forming an initiator layer.

6. The preparation method according to claim 5, wherein, Selected from at least one of the following (d)-(f): (d) The mass fraction of α-bromoisobutyric acid in the aqueous solution is 0.1 - 1.5%; (e) The reaction time in the aqueous solution is 30 - 300 min; (f) The reaction temperature in the aqueous solution is 15 - 60 °C.

7. According to the preparation method described in claim 1, it is characterized in that, The monomer of the zwitterionic polymer is selected from one or more of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 2-methacryloyloxyethylphosphorylcholine; and / or The monomer of the fluoropolymer is selected from one or more of hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate, trifluoroethyl methacrylate.

8. The molecular brush modified anti-fouling polyamide membrane prepared by the preparation method according to any one of claims 1 - 7.

9. The application of the molecular brush modified anti-fouling polyamide membrane according to claim 8 in wastewater treatment.

10. The application of α-bromoisobutyric acid as an initiator in the surface-initiated atom transfer radical polymerization for preparing a polyamide membrane.

Images