An anti-fouling block copolymer polyamide nanomembrane, and a preparation method and application thereof

Abstract

The application discloses an anti-pollution block copolymer polyamide nanometer membrane and a preparation method and application thereof, and belongs to the field of membrane separation technology. The preparation method comprises the following steps: taking a water-soluble block copolymer aqueous solution as a water phase, taking an organic solvent of a polyacyl chloride as an oil phase, and adopting self-supporting interfacial polymerization to prepare a double-face heterogeneous anti-pollution block copolymer polyamide nanometer membrane. The length of a block unit in the block copolymer is adjusted, so that the diffusion rate of the block copolymer at the interface is controlled, the surface morphology and micropore structure of the nanofiltration membrane are effectively controlled, and the application of the nanofiltration membrane to efficient and stable treatment of natural water shows extremely strong anti-pollution capacity and high selective separation performance. The preparation method is simple, controllable and easy for large-scale production, and shows good application prospect in the field of natural water purification.

Description

Technical Field

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

[0002] In recent years, water pollution has attracted widespread attention from all sectors of society. Existing remediation measures are no longer sufficient to meet people's demands for environmental protection. Compared with traditional separation technologies, membrane separation processes have advantages such as energy saving, environmental protection, high efficiency, and no phase change during the separation process, and can effectively improve water quality, thus gaining rapid adoption.

[0003] Among numerous membrane separation products, nanofiltration membranes, as a novel drinking water purification technology, not only possess excellent turbidity removal capabilities but also allow water and small molecules of monovalent inorganic salts to permeate while almost completely removing bacteria, viruses, and aquatic organisms from the water, achieving the harmless and resource-based treatment of surface water. Furthermore, nanofiltration membranes offer advantages such as simple equipment and convenient operation, and are currently widely used in various fields. However, membrane fouling and the trade-off effect significantly limit the application potential of nanofiltration membranes. Particularly noteworthy is the serious membrane fouling problem caused by the non-specific or specific adsorption of suspended particles, colloids, and microorganisms in the feed liquid onto the membrane. This leads to membrane pore blockage, resulting in decreased membrane separation performance, increased operating pressure, increased maintenance costs, and shortened service life, thus severely restricting the long-term development of nanofiltration membranes. Therefore, the key to membrane separation technology lies in preparing separation membrane products with excellent selectivity, antifouling properties, and stability.

[0004] Based on the types of contaminants in the feed liquid, nanofiltration membranes are classified into three types: inorganic, organic, and microbial contamination. These three types of contamination generally do not exist in individual forms but rather in a combined manner. Over long-term operation, this can lead to membrane pore blockage, resulting in decreased membrane separation performance, increased maintenance costs, and shortened lifespan. Therefore, improving the separation capacity and antifouling performance of nanofiltration membranes to meet more diverse separation requirements and reduce production costs is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the main objective of this invention is to provide an antifouling block copolymer polyamide nanomembrane, which has a bifacial heterogeneous structure, good nanofiltration performance and antifouling performance, and can meet the water treatment requirements under various conditions.

[0006] Another objective of this invention is to provide a method for preparing the antifouling block copolymer polyamide nanofilm, which controls the diffusion rate of the block copolymer at the interface by adjusting the length of the block unit in the block copolymer, thereby achieving effective control over the surface morphology and microporous structure of the polyamide nanofilm.

[0007] Another object of the present invention is to provide the application of the aforementioned antifouling block copolymer polyamide nanofilm in water purification.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] This invention provides an antifouling block copolymer polyamide nanofilm, comprising a supporting base film and a polyamide nanofilm located on the surface of the supporting base film, wherein: the polyamide nanofilm is grafted with a high-density polyethylene glycol brush, which is a polymer of block copolymer and polyacrylamide chloride at the water-oil interface.

[0010] Preferably, the molecular weight cutoff (MWCO) of the supporting base membrane is 50 kDa.

[0011] Preferably, the supporting base film comprises an asymmetric composite film, wherein one side of the asymmetric composite film comprises a nonwoven fabric and the other side comprises a polymer layer, wherein the polymer layer is formed by one or more of polysulfone, polyethersulfone, polysulfone, polyimide, polyamide, polyetherimide, polyacrylonitrile, polymethyl methacrylate, polyethylene, polypropylene, and polyvinylidene fluoride.

[0012] Preferably, the method for preparing the block copolymer includes:

[0013] (a) A macromolecular initiator and monomer are dissolved in an organic solvent, and a catalyst and ligand are added to initiate atom transfer radical polymerization. After the reaction is completed, the product is acid-treated to obtain a water-soluble block copolymer.

[0014] (b) The water-soluble block copolymer is composed of film-forming blocks rich in primary amines and polyethylene glycol antifouling blocks. The degree of polymerization of the block units is adjusted to obtain the block copolymer.

[0015] The macromolecular initiator is a brominated polyethylene glycol;

[0016] The organic solvent is anhydrous anisole;

[0017] The atom transfer radical polymerization reaction was carried out in situ for 24 hours under an inert gas atmosphere, at a temperature of 80°C, with magnetic stirring and in the presence of a catalyst.

[0018] The catalyst is a mixture of CuBr and N,N,N',N',N”-pentamethyldiethylenetriamine (PMDETA) ligand;

[0019] The molar ratio of macromolecular initiator, monomer, CuBr and PMDETA is 1:30:3:6;

[0020] The acid reagent used in the acid treatment is trifluoroacetic acid.

[0021] More preferably, the macromolecular initiator is a compound of formula (1): m = 45 or m = 16.

[0022] More preferably, the monomer is a compound represented by formula (2):

[0023] Preferably, the polyacryl chloride is added to an organic solvent and dissolved by ultrasonication to obtain an oil phase solution with a mass concentration of 0.5 wt%. The polyacryl chloride is selected from one or more of pyromellitic triacryl chloride, isophthalic chloride, terephthalic chloride, cyclohexane triacryl chloride, and cyclopentane triacryl chloride. The organic solvent is one of n-hexane, n-heptane, dodecane, and toluene.

[0024] Preferably, the block copolymer is dissolved in water by ultrasonication to obtain an aqueous solution with a mass concentration of 0.2 wt%.

[0025] Preferably, in step (1), the in-situ amide reaction time is 5 min.

[0026] This invention also provides a method for preparing an antifouling block copolymer polyamide nanofilm, comprising the following steps:

[0027] (1) Using polyamines and polyacryl chlorides as polymerization raw materials, an amidation reaction was carried out at the water-oil interface by interfacial polymerization to obtain an unsupported antifouling block copolymer polyamide nanofilm.

[0028] (2) Take out the anti-pollution unsupported block copolymer polyamide nanofilm, release it into deionized water, and then place it on the supporting base film to air dry naturally for 3 hours to obtain the anti-pollution block copolymer polyamide nanofilm composite film.

[0029] Invention Principle Description: The block copolymer prepared by this invention consists of film-forming blocks rich in primary amines and polyethylene glycol antifouling blocks. During interfacial polymerization, the primary amines of the block copolymer react with acyl chloride groups in the organic phase solution at the water-oil interface via an amide reaction. Through in-situ polymerization, dense hydrophilic polyethylene glycol (PEG) brushes are grafted onto the polyamide nanomembrane, constructing a hydrophilic surface layer during water treatment. Under the influence of the hydrophilic regions, various pollutants, especially microbial pollutants such as bacteria and proteins, and organic pollutants, can be effectively inhibited. The prepared antifouling block copolymer polyamide nanomembrane exhibits excellent nanofiltration and antifouling performance, meeting water treatment requirements under various conditions. Furthermore, in composite membranes prepared by traditional interfacial polymerization processes, the organic phase layer (front side) is exposed on the surface. By flipping the polyamide layer, exposing the aqueous phase layer (back side) on the surface of the composite membrane, the antifouling performance of the block copolymer polyamide nanomembrane is optimized.

[0030] In some embodiments, the block copolymer possesses properties such as antifouling, hydrophilicity, acid resistance, and alkali resistance, all of which can be obtained through the block copolymer preparation method proposed in this invention. The antifouling functional block units include: zwitterions, such as quaternary ammonium salt cations combined with different types of anions to obtain sulfonate betaine, carboxylate betaine, and linylcholine; hydrophilic molecules, such as polyethylene glycol methacrylate (PEGMA), 2-methacrylate oxyethyl phosphocholine (MPC), methacrylate carboxylate betaine (CB-MA), and methacrylate sulfate betaine (SBMA); and antibacterial molecules, such as tannic acid (TA), chitosan, capsaicin, and guanidine. By controlling the diffusion rate of the water-soluble block copolymer at the water-oil interface, the microporous structure and surface morphology of the composite membrane can be effectively controlled.

[0031] The present invention also provides the application of the antifouling block copolymer polyamide nanofilm in water purification.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The functional block copolymer preparation method used in this invention is simple, and its application in the production of antifouling block copolymer polyamide nanofilms is simple, controllable, and easy to scale up.

[0034] 2. The antifouling block copolymer polyamide nanofilm prepared by this invention has extremely strong hydrophilicity on its surface. It improves the antifouling performance by forming a dense hydration layer and prevents the adsorption of pollutants on the membrane surface and in the membrane pores.

[0035] 3. The antifouling block copolymer polyamide nanomembrane prepared by this invention has high water flux and high retention rate, and is effective in water treatment processes.

[0036] 4. By increasing the degree of polymerization of polyethylene glycol in the block copolymer, i.e., extending the length of the polyethylene glycol hydrophilic brush, this invention can effectively improve the antifouling efficiency and permeation selectivity of the antifouling block copolymer polyamide nanofilm.

[0037] 5. By flipping the polyamide functional layer, this invention can effectively improve the antifouling efficiency of the antifouling block copolymer polyamide nanofilm, thereby maximizing water treatment efficiency. Attached Figure Description

[0038] Figure 1 The synthetic route for the functional block copolymers in the examples is shown below.

[0039] Figure 2 This is a schematic diagram illustrating the preparation of the antifouling block copolymer polyamide nanofilm in the examples.

[0040] Figure 3AFM images of the surface of the heterogeneous antifouling block copolymer polyamide nanofilm (RM-PEG2k) in the examples: (a) front side; (b) back side.

[0041] Figure 4 The results of solid surface zeta potential analysis of the antifouling block copolymer polyamide nanofilm in the examples are shown.

[0042] Figure 5 The static water contact angle (WCA) analysis results of the antifouling block copolymer polyamide nanofilm in the examples are shown.

[0043] Figure 6 The salt rejection rate and water flux of the antifouling block copolymer polyamide nanomembrane in the examples are shown under simulated river water conditions.

[0044] Figure 7 For the analysis of the antibacterial properties of the antifouling block copolymer polyamide nanofilm in the examples: (a) the antibacterial properties of the nanofilm were analyzed by Escherichia coli and the paper disc diffusion method; (b) SEM image of the surface of the RM-PEG2k membrane after the antibacterial experiment; (c) SEM image of the surface of the RM-PIP membrane after the antibacterial experiment.

[0045] Figure 8 The results of the dynamic cyclic anti-adhesion experiment of the anti-fouling block copolymer polyamide nanofilm in the examples are shown in simulated river water conditions.

[0046] Figure 9 The image shows the UV absorption spectra of the anti-pollution block copolymer polyamide nanofilm before and after river water purification in the examples. Detailed Implementation

[0047] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0048] Example 1:

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0050] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0051] Example 1: Preparation of a diblock copolymer with two different block units, the synthetic route is as follows: Figure 1 As shown.

[0052] (1) Synthesis of the polymer monomer (N-Boc-AEAA)

[0053] Under ice bath conditions, monosubstituted N-Boc-ethylenediamine (3.20 g, 20 mmol, 1.0 equiv.) and triethylamine (3.06 g, 30 mmol, 1.5 equiv.) were dissolved in 50 mL of anhydrous CH2Cl2. Then, 20 mL of anhydrous CH2Cl2 solution containing acryloyl chloride (2.72 g, 30 mmol, 1.5 equiv.) was added dropwise over approximately 1 hour. After the addition was complete, the reaction mixture was stirred overnight at room temperature. After the reaction was complete, the reaction mixture was washed three times with semi-saturated brine to remove the triethylamine salt. The organic layer was collected, dried over anhydrous Na2SO4, and concentrated to obtain a pale yellow or white solid. The crude product was further purified by silica gel chromatography, eluting with a mixture of ethyl acetate and n-hexane in a ratio of 7:3 (v / v). The fraction containing the target product was collected and concentrated to give 3.39 g of the target product (yield: 79%) as a white solid. 1 H NMR (400MHz, CDCl3, 298K) δ = 6.28 (s, 1H), 6.24 (d, J = 17.16Hz, 1H), 6.10 (m, 1H) ,5.63(dd,J=10.35Hz,1H),5.92(s,1H),3.44(m,2H),3.31(m,2H),1.43(s,9H).

[0054] (2) Synthesis of macromolecular initiator PEG2k-Br

[0055] Under ice bath conditions, PEG2k (2.00 g, 1.0 mmol, 1.0 equivalent) and triethylamine (612 mg, 6.0 mmol, 6.0 equivalent) were dissolved in 30 mL of anhydrous CH2Cl2. Then, 20 mL of anhydrous CH2Cl2 solution containing 2-bromoisobutyryl bromide (690 mg, 3.0 mmol, 3.0 equivalent) was added dropwise over approximately 1 hour. After the addition was complete, the reaction mixture was stirred overnight at room temperature. After the reaction was complete, the reaction mixture was washed three times with semi-saturated brine to remove the triethylamine salt. The organic layer was collected, dried over anhydrous Na2SO4, concentrated to 20 mL, and then precipitated in 300 mL of ice-cold diethyl ether to give 1.78 g of the target product (yield: 83%) as a white solid. 1H NMR (400MHz, CDCl3, 298K) δ=4.34(m,-CH2OOC-,2H), 3.64(m,-OCH2CH2O-,176H), 3.38(s,CH3O-,3H), 1.94(s,-OOCC(CH3)2-,6H).

[0056] (3) Synthesis of macromolecular initiator PEG750-Br

[0057] Under ice bath conditions, PEG750 (3.75 g, 5.0 mmol, 1.0 equivalent) and triethylamine (3.06 g, 30.0 mmol, 6.0 equivalent) were dissolved in 80 mL of anhydrous CH2Cl2. Then, 400 mL of anhydrous CH2Cl2 solution containing 2-bromoisobutyryl bromide (3.45 g, 15.0 mmol, 3.0 equivalent) was added dropwise over approximately 1 h. After the addition was complete, the reaction mixture was stirred overnight at room temperature. After the reaction was complete, the reaction mixture was washed three times with semi-saturated brine to remove the triethylamine salt. The organic layer was collected, dried over anhydrous Na2SO4, concentrated to 20 mL, and precipitated in 300 mL of ice-cold diethyl ether to give 3.56 g of the target product (yield: 79%) as a white solid. 1 H NMR (400MHz, CDCl3, 298K) δ=4.31(m,-CH2OOC-,2H), 3.62(m,-OCH2CH2O-,60H), 3.35(s,CH3O-,3H), 1.92(s,-OOCC(CH3)2-,6H).

[0058] (4) Synthesis of block copolymer PEG2k-b-(N-Boc-AEAA)n

[0059] PEG2k-Br (1.00 g, 0.47 mmol, 1.0 equivalent) and N-Boc-AEAA (3.0 g, 13.95 mmol, 30.0 equivalent) were dissolved in 10.0 mL of anhydrous anisole. After five cycles of nitrogen purging, PMDETA (550 μL, 2.8 mmol, 6.0 equivalent) and Cu(I)Br (200 mg, 1.40 mmol, 3.0 equivalent) were added sequentially. Finally, the reaction system was placed in an oil bath preheated to 80 °C and reacted under nitrogen protection for 24 h. The reaction mixture was then stopped by stirring in air and washed three times with semi-saturated brine to remove the Cu(II) catalyst and salt. After drying with Na2SO4, the organic phase was concentrated to 10 mL and precipitated twice in 200 mL of ice-cold diethyl ether to give 1.12 g of the target product (yield: 56%) as a light brown solid. 1H NMR (400MHz, CDCl3, 298K) δ = 3.64 (m, -OCH2CH2O-, 180H), 3.38 (s, CH3O-, 3H), 1.73 (m, 90H), 1.38 (m, 60H), 1.25 (m, 16H).

[0060] (5) Synthesis of block copolymer PEG750-b-(N-Boc-AEAA)n

[0061] PEG750-Br (0.90 g, 1 mmol, 1.0 equiv.) and N-Boc-AEAA (6.43 g, 30 mmol, 30.0 equiv.) were dissolved in 15.0 mL of anhydrous anisole. After five cycles of nitrogen purging, PMDETA (1170 μL, 6 mmol, 6.0 equiv.) and Cu(I)Br (430.50 mg, 3 mmol, 3.0 equiv.) were added sequentially. Finally, the reaction system was placed in an oil bath preheated to 80 °C and reacted under nitrogen protection for 24 h. The reaction mixture was then placed in air and stirred to terminate the reaction. The mixture was washed three times with semi-saturated brine to remove the Cu(II) catalyst and salt. After drying with Na2SO4, the organic phase was concentrated to 10 mL and precipitated twice in 200 mL of ice-cold diethyl ether to obtain 1.56 g of the target product (yield: 45%) as a light brown solid. 1 H NMR (400MHz, CDCl3, 298K) δ=3.64(m,-OCH2CH2O-,64H), 3.38(s,CH3O-,3H), 3.40-3.10(m,24H), 1.43(m,108H), 1.48-1.20(m,48H), 0.86(m,42H).

[0062] (6) Synthesis of the target block copolymer PEG2k-b-(N-Boc-AEAA)n

[0063] PEG2k-b-(N-Boc-AEAA)n (2.00 g, 0.47 mmol, 1.0 equiv.) was dissolved in 20.0 mL of anhydrous CH2Cl2. Then, trifluoroacetic acid (5.30 g, 46.51 mmol, 100 equiv.) was added dropwise. After the addition was complete, the reaction mixture was allowed to react at room temperature for 4 h. Finally, the reaction solution was concentrated to 15.0 mL and precipitated twice in 200 mL of ice-cold diethyl ether to give 1.17 g of the target product (yield: 76%), which was a light brown waxy substance. 1H NMR (400MHz, CDCl3, 298K) δ = 3.64 (m, -OCH2CH2O-, 180H), 3.38 (s, CH3O-, 3H), 2.75-2.25 (m, 40H), 1.24 (m, 30H), 0.87 (m, 6H).

[0064] (7) Synthesis of the target block copolymer PEG750-b-(N-Boc-AEAA)n

[0065] PEG750-b-(N-Boc-AEAA)n (2.00 g, 0.58 mmol, 1.0 equiv.) was dissolved in 20.0 mL of anhydrous CH2Cl2, and then trifluoroacetic acid (6.60 g, 57.85 mmol, 100 equiv.) was added dropwise. After the addition was complete, the reaction mixture was allowed to react at room temperature for 4 h. Finally, the reaction solution was concentrated to 15.0 mL and precipitated twice in 200 mL of ice-cold diethyl ether to give 0.93 g of the target product (yield: 71%), which was a light brown waxy substance. 1 H NMR (400MHz, CDCl3, 298K) δ = 3.64 (m, -OCH2CH2O-, 64H), 3.38 (s, CH3O-, 3H), 2.75-2.25 (m, 48H), 1.24 (m, 36H), 0.87 (m, 6H).

[0066] Example 2: Preparation of antifouling block copolymer polyamide nanofilms

[0067] Antifouling block copolymer polyamide nanofilms were prepared using conventional interfacial polymerization: Block copolymers (PEG2k-b-(N-AEAA)n and PEG750-b-(N-AEAA)n, and commercially available piperazine molecules (PIP)) were dissolved in deionized water to prepare a 0.2 wt% aqueous solution, while trimesoyl chloride was dissolved in n-hexane to prepare a 0.5 wt% organic solution. 15 mL of the aqueous and organic solutions were sequentially added to a petri dish, and after a certain time, an antifouling polyamide nanofilm was obtained at the water-oil interface. To ensure sufficient reaction between the block copolymers and trimesoyl chloride, the interfacial polymerization time was set to 5 min. The individual polyamide nanofilms were then released into a container filled with deionized water, transferred to a support substrate, and air-dried for 3 h before subsequent testing and characterization.

[0068] Currently, membranes prepared using traditional interfacial polymerization processes have the organic phase (front side) facing upwards, resulting in suboptimal antifouling performance. This invention proposes a simple and effective method to obtain a defect-free polyamide membrane with the aqueous phase layer exposed on the outside (back side). For example... Figure 2As shown, the substrate is pushed toward the polyamide nanofilm at a constant rate and a certain angle. At this time, the reverse side of the block copolymer polyamide layer faces upward, which can optimize the performance of the composite film. According to the type of film-forming monomer and the preparation method of the nanofilm, the obtained nanofilms are labeled as M-PEG2k, M-PEG750, M-PIP and the corresponding RM-PEG2k, RM-PEG750, RM-PIP.

[0069] Example 3: Physicochemical characterization of antifouling block copolymer polyamide nanofilms

[0070] Unless otherwise specified, the quantitative experiments in the following examples were performed at least three times, and the results were averaged.

[0071] Table 1: X-ray photoelectron spectroscopy (XPS) analysis results of antifouling block copolymer polyamide nanofilms

[0072]

[0073] Analysis by atomic force microscopy (AFM) Figure 3 X-ray photoelectron spectroscopy (XPS) analysis (Table 1), solid surface zeta potential analysis ( Figure 4 ) and static water contact angle meter (WCA) analysis ( Figure 5 A bifacial heterogeneous antifouling block copolymer polyamide nanofilm was successfully obtained. The nanofilm surface has a high PEG grafting density, and the surface function can be maximized by flipping the polyamide layer or increasing the length of the PEG block.

[0074] Example 4: Separation Selectivity Analysis of Antifouling Block Copolymer Polyamide Nanofilms

[0075] The purification performance of the block copolymer polyamide nanomembranes prepared in Examples 1-3 was tested using simulated water. In a laboratory-customized cross-flow apparatus, the test sample was pre-pressurized with pure water at 8 bar for at least 30 minutes. After the water flux stabilized, pure water was continued to permeate the membrane at a test pressure of 6 bar. The pure water flux corresponding to the membrane was recorded and calculated. To better simulate natural water, under a fixed stirring speed of 500 rpm, 10 ppm humic acid (HA) and 100 ppm bovine serum albumin (BSA) were additionally introduced as representative pollutants into the feed solution in a single salt solution of 2000 ppm NaCl or 2000 ppm Na2SO4. During the test, the concentrations of inorganic salts in the feed solution and the inorganic salt concentrations in the permeate after membrane filtration were recorded, and the corresponding rejection rates of the membrane were calculated. The solubility of the inorganic salt solution was measured using a conductivity meter. The rejection rates of NaCl and Na2SO4 reflected the membrane's selectivity for monovalent and divalent ions. Figure 6 As shown.

[0076] Example 5: Analysis of the antibacterial properties of antifouling block copolymer polyamide nanofilms

[0077] The antibacterial properties of the block copolymer polyamide nanofilms prepared in Examples 1-3 were tested. Gram-negative Escherichia coli was used as the model bacteria in the test samples to evaluate the antibacterial activity of the prepared block copolymer polyamide nanofilms. Figure 7 This is a visualization of bacterial distribution on the membrane surface after paper diffusion. Compared with the nanomembrane fabricated by PIP, the antibacterial rings of RM-PEG2k, M-PEG2k, RM-PEG750, and M-PEG750 gradually become clearer. Subsequently, after scanning electron microscopy analysis of RM-PEG2k and RM-PIP, the latter's surface was covered with colonies, while no colonies were observed on the surface of the RM-PEG2k membrane. This indicates that the introduction of the PEG hydrophilic layer effectively prevented the adsorption and deposition of bacteria on the membrane surface.

[0078] Example 6: Analysis of the anti-adhesion properties of anti-fouling block copolymer polyamide nanofilms

[0079] Dynamic cyclic anti-adhesion experiments were conducted using the block copolymer polyamide nanomembranes prepared in Examples 1-3. In a laboratory-customized dead-end filtration system, the test samples were pre-pressurized with pure water at 8 bar for at least 30 minutes. After the water flux stabilized, the initial water flux (JW1) was recorded at a test pressure of 6 bar. To better simulate natural water, 50 ppm humic acid (HA), 1000 ppm bovine serum albumin (BSA), and 50 ppm *E. coli* were introduced as representative contaminants into the feed solution at a fixed stirring speed of 500 rpm. Filtration was performed continuously for 5 hours, with the permeation flux (JW2) monitored periodically every 15 minutes. After 5 hours of continuous testing, the membrane was washed with deionized water until the permeation performance stabilized, and the permeation flux (JW3) was recorded to evaluate the degree of water flux recovery and antifouling performance. This process was repeated for approximately 24 hours of continuous testing. Figure 8 As shown, the water flux of the block copolymer polyamide nanomembrane in each cycle is above 96%, which is much higher than that of RM-PIP (45.81%).

[0080] Example 7: Analysis of the purification capacity of antifouling block copolymer polyamide nanomembranes for domestic sewage

[0081] The purification capacity of the block copolymer polyamide nanomembrane prepared in Examples 1-3 was further evaluated for river wastewater. The water source for this invention was the Licun River in Qingdao City. After collecting natural water, it was first pre-filtered using 0.7 μm glass fiber filter paper to remove suspended particles. In a laboratory-customized dead-end filtration system, using the pretreated river water as the feed liquid, the test membrane sample was pre-pressurized with pure water at 8 bar for at least 30 minutes. After the water flux stabilized, the initial water flux was recorded at a test pressure of 6 bar. The permeate flux and UV 254 nm values ​​were recorded periodically every 1 hour, and the test was conducted continuously for 16 hours under the same test conditions to evaluate the separation stability of the nanomembrane. Figure 9 As shown, after RM-PEG2k separation treatment, the UV254 nm value increased from 0.1718 cm⁻¹. -1 It decreased significantly to 0.0116 cm. -1 The purification efficiency was 93%, indicating that the block copolymer polyamide nanofilm has the potential to be applied to efficient and sustainable separation processes such as river water purification.

[0082] In summary, the block copolymer prepared by this invention possesses both film-forming properties (rich in terminal amino groups) and functionality (hydrophilic polyethylene glycol). Antifouling block copolymer polyamide nanofilms can be synthesized in situ in a one-step manner using traditional interfacial polymerization methods. This provides a new approach for the large-scale, low-cost production of functional membrane materials for applications in multiple fields. The block copolymer preparation method proposed in this invention can be used to customize the synthesis of novel multifunctional membrane materials.

[0083] The above description represents a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. A pollution-resistant block copolymer polyamide nanofilm, characterized in that, It includes a supporting base film and a polyamide nanofilm located on the surface of the supporting base film, wherein: the polyamide nanofilm is grafted with high-density polyethylene glycol brushes, which are a block copolymer and a polymer of polyacrylamide chloride at the water-oil interface; The block copolymer is composed of film-forming blocks rich in primary amino groups and polyethylene glycol antifouling blocks. During interfacial polymerization, the primary amino groups of the block copolymer react with acyl chloride groups in the organic phase solution at the water-oil interface to undergo an amide reaction. Through in-situ polymerization, dense hydrophilic polyethylene glycol brushes are grafted onto the polyamide nanofilm.

2. The antifouling block copolymer polyamide nanofilm according to claim 1, characterized in that, The molecular weight cutoff of the supporting base membrane is 50 kDa.

3. The antifouling block copolymer polyamide nanofilm according to claim 1 or 2, characterized in that, The supporting base membrane includes an asymmetric composite membrane, one side of which includes a nonwoven fabric and the other side includes a polymer layer, wherein: The polymer layer is formed from one or more of the following materials: polysulfone, polyethersulfone, polysulfone, polyimide, polyamide, polyetherimide, polyacrylonitrile, polymethyl methacrylate, polyethylene, polypropylene, and polyvinylidene fluoride.

4. The antifouling block copolymer polyamide nanofilm according to claim 1, characterized in that, The method for preparing the block copolymer includes: (a) Atom transfer radical polymerization reaction is initiated by a macromolecular initiator and monomer in an organic solvent. After the reaction is completed, the product is acid-treated to obtain a water-soluble block copolymer. (b) The water-soluble block copolymer is composed of film-forming blocks rich in primary amines and polyethylene glycol antifouling blocks. The degree of polymerization of the block units is adjusted to obtain the block copolymer. The macromolecular initiator is a brominated polyethylene glycol; The organic solvent is anhydrous anisole; The atom transfer radical polymerization reaction was carried out in situ for 24 hours under an inert gas atmosphere, at a temperature of 80°C, with magnetic stirring and in the presence of a catalyst. The catalyst is a mixture of CuBr and PMDETA; The molar ratio of macromolecular initiator, monomer, CuBr and PMDETA is 1:30:3:6; The acid reagent used in the acid treatment is trifluoroacetic acid.

5. The antifouling block copolymer polyamide nanofilm according to claim 4, characterized in that, The macromolecular initiator is a compound represented by formula (1): (1), m=45 or m=16.

6. The antifouling block copolymer polyamide nanofilm according to claim 4, characterized in that, The monomer is a compound represented by formula (2): (2).

7. The antifouling block copolymer polyamide nanofilm according to claim 1, characterized in that, The polyacryl chloride is selected from one or more of pyromellitic trichloroisocyanurate, isophthaloyl chloride, terephthaloyl chloride, cyclohexanetriacryl chloride, and cyclopentanetriacryl chloride, and the organic solvent is selected from one of n-hexane, n-heptane, dodecane, and toluene.

8. The antifouling block copolymer polyamide nanofilm according to any one of claims 4-6, characterized in that, Polyacyl chlorides were added to an organic solvent and dissolved by ultrasonication to obtain an oil phase solution with a mass concentration of 0.5 wt%. And / or the block copolymer is added to water and dissolved by ultrasonication to obtain an aqueous solution with a mass concentration of 0.2 wt%.

9. A method for preparing the antifouling block copolymer polyamide nanofilm according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Using polyamines and polyacryl chlorides as polymerization raw materials, in-situ amide reaction was carried out at the water-oil interface for 1-10 min by interfacial polymerization to obtain polyamide nanofilms; (2) The polyamide nanofilm is taken out, first released into deionized water, and then placed on the supporting base film to air dry naturally for 1-4 hours to obtain the anti-fouling block copolymer polyamide nanofilm.

10. The application of the antifouling block copolymer polyamide nanofilm according to any one of claims 1 to 8 in water purification.

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