Anti-fouling polyamide composite membrane, and preparation method and application thereof

Abstract

The application belongs to the field of separation membrane technology and relates to an anti-pollution polyamide composite membrane and a preparation method and application thereof.The anti-pollution polyamide composite membrane comprises a porous support layer and a polyamide separation layer, the surface of the polyamide separation layer is grafted with N-alkyl glucosamine compounds, and the N-alkyl glucosamine compounds are grafted by esterification reaction of hydroxyl groups contained in the N-alkyl glucosamine compounds and acyl chloride groups remaining on the surface of the polyamide separation layer.By introducing N-alkyl glucosamine compounds with a specific structure to graft the acyl chloride groups remaining on the surface of the polyamide separation layer through esterification reaction, the synergistic regulation of the hydrophilicity and charge characteristics of the membrane surface is realized, the anti-pollution property and separation efficiency of the membrane are significantly improved, the membrane can also be endowed with good chlorine resistance, the compactness and thickness of the membrane itself are not changed, the original interception performance can be maintained while the permeability is improved, and the trade-off effect between the permeability and selectivity of the traditional separation membrane is overcome.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane technology, and relates to an antifouling polyamide composite membrane, its preparation method, and its application. Background Technology

[0002] Polyamide composite membranes are widely used in seawater desalination, wastewater reuse, and industrial fluid treatment due to their excellent separation performance; however, membrane fouling has always been a key bottleneck restricting their large-scale application. The adsorption and deposition of pollutants on the membrane surface not only leads to a decrease in membrane flux and separation efficiency but also increases operating energy consumption and cleaning frequency, shortening the membrane's lifespan. Therefore, improving the antifouling properties of polyamide composite membranes is essential.

[0003] In recent years, a large amount of research on antifouling reverse osmosis membranes has been underway. For example, CN104226123A discloses a method for preparing a high-flux antifouling reverse osmosis membrane. This method involves an amidation reaction between the amino groups in a modifier and residual active acyl chloride groups, thereby terminating the reactivity of the acyl chlorides and reducing the hydrolysis ratio. Consequently, the content of negatively charged groups on the polyamide structure surface is significantly reduced, and the negative charge potential is lowered, thus reducing the shielding effect against fouling by charged substances with opposite charges on the membrane surface during operation. Another example is CN119186285A, which discloses an antifouling composite membrane, its preparation method, and a reverse osmosis membrane. This method grafts phosphonic acid groups containing amino groups onto the polyamide separation layer through a chemical reaction between the amino groups and acyl chloride groups on the nascent membrane surface. This improves the hydrophilicity of the polyamide separation layer, making it easier for the membrane to form a hydrated layer during separation, thereby preventing pollutants from adsorbing or depositing on the membrane surface and improving the membrane's antifouling ability. The prior art, including the invention mentioned above, mainly improves the antifouling ability of polyamide reverse osmosis membranes through the post-amidation reaction between the residual acyl chloride groups on the membrane surface and the amino groups of the grafted monomers. However, the amide bonds formed by the amidation reaction have poor chlorine resistance and are prone to degradation in chlorine-containing cleaning environments, affecting the long-term stability of the membrane. At the same time, it has limited effect on improving the hydrophilicity of the membrane surface and cannot control the surface charge characteristics.

[0004] Therefore, developing an antifouling polyamide composite membrane that can combine excellent surface hydrophilicity and charge property control with good chlorine resistance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an antifouling polyamide composite membrane, its preparation method, and its application. By introducing N-alkylglucosamine compounds to undergo esterification with the residual acyl chloride groups on the surface of the polyamide separation layer for grafting, the hydrophilicity and charge properties of the membrane surface are synergistically regulated, significantly improving the membrane's antifouling performance and separation efficiency. At the same time, it can endow the membrane with good chlorine resistance stability without affecting the membrane's retention performance, overcoming the trade-off effect between permeability and selectivity in traditional separation membranes.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides an antifouling polyamide composite membrane, the antifouling polyamide composite membrane comprising a porous support layer and a polyamide separation layer; The surface of the polyamide separation layer is grafted with N-alkylglucosamine compounds, and the N-alkylglucosamine compounds are grafted by esterification reaction between the contained hydroxyl groups and the residual acyl chloride groups on the surface of the polyamide separation layer.

[0007] The antifouling polyamide composite membrane provided by this invention introduces N-alkylglucosamine compounds, which can undergo esterification with the acyl chloride groups remaining on the surface of the polyamide separation layer. This successfully grafts N-alkylglucosamine compounds onto the surface of the polyamide separation layer, forming a high-density hydrophilic layer, thereby effectively improving the surface hydration capacity of the resulting polyamide composite membrane and effectively inhibiting the adsorption of hydrophobic pollutants. Simultaneously, the esterification of the acyl chloride groups remaining on the surface of the polyamide separation layer reduces the number of acyl chloride groups available for hydrolysis on the membrane surface, thus reducing the surface negative charge of the membrane at neutral pH. Furthermore, the amine groups contained in the grafted N-alkylglucosamine compounds have pH-responsive characteristics (pKa approximately 8.0~9.5), partially protonated and positively charged under neutral conditions, which can offset some of the negative charge of the carboxyl groups, effectively reducing the negative charge on the membrane surface. Under acidic conditions, complete protonation further reduces the negative charge on the membrane surface. The synergistic effect of the above-mentioned dual mechanisms of enhanced hydrophilicity and reduced electronegativity significantly improves the antifouling ability of the final polyamide composite membrane.

[0008] The antifouling polyamide composite membrane provided by this invention utilizes the esterification reaction between the hydroxyl groups in N-alkyl glucosamine compounds and the residual acyl chloride groups on the surface of the polyamide separation layer to achieve covalent grafting. The resulting ester bonds have stronger chlorine resistance than the amide bonds formed by traditional amino modification. In chlorine-containing cleaning environments, the ester bonds are less prone to chlorine degradation, ensuring the structural integrity of the hydrophilic layer. This guarantees the long-lasting antifouling performance of the obtained polyamide composite membrane and extends its service life.

[0009] The antifouling polyamide composite membrane provided by this invention grafts N-alkyl glucosamine compounds onto its surface without altering the density and thickness of the polyamide separation membrane. While improving permeability, it maintains the original retention performance, overcoming the trade-off between permeability and selectivity in traditional separation membranes.

[0010] Preferably, the N-alkylglucosamine compound includes any one or a combination of at least two of N-methylglucosamine, N-ethylglucosamine, N-propylglucosamine, N-butylglucosamine, or D-glucosamine.

[0011] Preferably, the porous support layer is made of any one or a combination of at least two of polysulfone, polysulfone, polyethersulfone, polyvinylidene fluoride, polyvinyl chloride, or polyacrylonitrile.

[0012] Preferably, the pore size of the porous support layer is 10~100 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm, etc.; the specific size can be selected according to different application scenarios.

[0013] Preferably, the raw materials for preparing the polyamide separation layer include polyamine monomers and polyacrylamide chloride monomers.

[0014] In this invention, there are no special requirements for the specific selection of the polyamine monomers. Conventional types in the art can be selected, including but not limited to piperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, polyetheramine, or polyethyleneimine, or any one or at least two combinations thereof. However, in order to ensure that the obtained antifouling polyamide composite membrane has better performance, piperazine is preferred for nanofiltration membrane preparation and m-phenylenediamine is preferred for reverse osmosis membrane preparation.

[0015] In this invention, there are no special requirements for the specific selection of the polyacryl chloride monomer. Conventional types in the art can be selected, including but not limited to aromatic acryl chloride compounds, such as 1,3,5-pyromellitic chloride, 1,3-isophthaloyl chloride, 1,4-terephthaloyl chloride, etc., with 1,3,5-pyromellitic chloride being preferred.

[0016] Preferably, the method for preparing the polyamide separation layer includes: fixing a porous support layer in a frame, surface-wetting the porous support layer with an aqueous solution containing polyamine monomers, removing the residual aqueous solution from the surface of the porous support layer, coating the surface of the porous support layer with an oil solution containing polyacrylamide monomers to carry out an interfacial polymerization reaction, removing the residual oil solution from the surface of the porous support layer, and heat-treating to obtain the polyamide separation layer.

[0017] Preferably, the mass percentage of polyamine monomer in the aqueous solution containing polyamine monomer is 1-3%, such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%.

[0018] Preferably, the solvent of the aqueous solution is water.

[0019] Preferably, the soaking time is 100~150 s, such as 100 s, 105 s, 110 s, 115 s, 120 s, 125 s, 130 s, 135 s, 140 s, 145 s or 150 s.

[0020] Preferably, the removal of residual aqueous solution from the surface of the porous support layer is performed using a rubber roller or a nitrogen gas knife.

[0021] Preferably, the mass percentage of the polyacryl chloride monomer in the oil phase solution containing the polyacryl chloride monomer is 0.1% to 1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0022] Preferably, the solvent of the oil phase solution includes any one or a combination of at least two of the following: n-hexane, cyclohexane, n-heptane, n-decane, toluene, Isopar E, or Isopar G.

[0023] Preferably, the heat treatment process further includes a step of cleaning the membrane surface with an organic solvent.

[0024] Preferably, the heat treatment temperature is 50~100℃, such as 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃.

[0025] Preferably, the heat treatment time is 200~400 s, such as 200 s, 240 s, 260 s, 280 s, 300 s, 320 s, 340 s, 360 s, 380 s or 400 s.

[0026] Preferably, the time for the interfacial polymerization reaction is 30~100 s, such as 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s or 100 s.

[0027] In a second aspect, the present invention provides a method for preparing an antifouling polyamide composite membrane as described in the first aspect, the method comprising: reacting a separation membrane comprising a porous support layer and a polyamide separation layer with an aqueous solution of an N-alkylglucosamine compound under alkaline conditions to obtain the antifouling polyamide composite membrane.

[0028] Preferably, the mass percentage of the N-alkylglucosamine compound in the aqueous solution is 0.1% to 5%, for example, 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0029] Preferably, the alkaline conditions are alkaline conditions with a pH value of 10 to 12 (e.g., 10, 10.5, 11, 11.5 or 12, etc.).

[0030] Preferably, the temperature of the contact reaction is 20~40℃, such as 20℃, 22℃, 24℃, 26℃, 28℃, 30℃, 32℃, 34℃, 36℃, 38℃ or 40℃.

[0031] Preferably, the contact reaction time is 1 to 10 minutes, such as 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes.

[0032] Preferably, the reaction further includes a cleaning step after the contact reaction is completed. The cleaning can remove unreacted N-alkylglucosamine compounds.

[0033] Preferably, the antifouling polyamide composite membrane is stored in pure water for later use, or subjected to heat treatment to enhance the grafting stability of N-alkylglucosamine compounds.

[0034] Thirdly, the present invention provides an application of the antifouling polyamide composite membrane as described in the first aspect in seawater desalination or wastewater recycling.

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) The antifouling polyamide composite membrane provided by the present invention has both excellent hydrophilicity (water contact angle of 40~77°) and charge controllability (zeta potential of -42~-29 mV at pH=7 and -35~-5 mV at pH=3), which can effectively reduce the adsorption and deposition of hydrophobic pollutants, realize dynamic control of membrane surface charge, and enhance the selective repulsion ability of charged pollutants; and through the synergistic effect of hydrophilic repulsion and charge repulsion, the antifouling ability of the membrane is significantly improved, so that the flux decay rate of the membrane after bovine serum albumin pollution is only 9.6~24.%, and the flux recovery rate is as high as 90.4~96.8%; (2) The antifouling polyamide composite membrane provided by the present invention can maintain the original molecular weight cutoff and salt rejection rate while improving permeability, with a water flux of up to 50.4~56.4 LMH and a NaCl rejection rate of up to 99.18~99.27%; (3) The anti-fouling polyamide composite membrane provided by the present invention has better chemical stability and long-term operational stability in chlorine-containing cleaning environments. The NaCl retention rate after chlorination is still as high as 64.6~78.4%, which plays an important role in ensuring the long-term performance of anti-fouling. Detailed Implementation

[0036] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0037] The anti-fouling polyamide composite film provided by the present invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1 An antifouling polyamide composite membrane includes a porous support layer and a polyamide separation layer. The surface of the polyamide separation layer is grafted with N-methylglucosamine, and the grafting of N-methylglucosamine is achieved by esterification reaction between the contained hydroxyl groups and the residual acyl chloride groups on the surface of the polyamide separation layer. Its preparation method includes the following steps: (1) Prepare a polysulfone casting solution with a mass percentage of 12% in N,N-dimethylformamide. After stirring evenly, place the obtained polysulfone casting solution in a vacuum oven for degassing treatment. Then, cast the polysulfone casting solution and apply it to a polyester nonwoven fabric with a scraper. Immediately after application, immerse the fabric in a 25°C deionized water coagulation bath to solidify and obtain a polysulfone ultrafiltration membrane. Place the membrane in pure water for immersion and use. (2) Dissolve m-phenylenediamine in water to obtain an aqueous solution with a mass percentage of 3%; dissolve pyromellitic chloride in Isopar G isoalkanes to prepare an organic solution with a mass percentage of 0.15%. (3) Fix the polysulfone ultrafiltration membrane obtained in step (1) onto an organic glass plate frame, immerse the membrane surface in the aqueous phase solution obtained in step (2) for 120 s, and remove the excess aqueous phase solution on the surface of the polysulfone ultrafiltration membrane using a nitrogen gas knife; then contact the polysulfone ultrafiltration membrane with the organic phase solution obtained in step (2) for 60 s to carry out interfacial polymerization reaction, pour off the excess organic phase solution, rinse the surface of the polysulfone ultrafiltration membrane with Isopar G, and then blow it evenly until there is no residual solvent on the membrane surface. Then place it in an 80℃ oven for heat treatment for 5 min, take it out of the oven and rinse it with pure water to obtain a polyamide separation membrane; (4) Prepare an aqueous solution of N-methylglucosamine with a mass percentage of 0.5%, adjust its pH to 11.0 with triethylamine, contact the polyamide separation membrane obtained in step (3) with the above N-methylglucosamine aqueous solution and react at 25°C for 5 min, thoroughly clean the membrane surface with deionized water to obtain the antifouling polyamide composite membrane.

[0039] Example 2 An antifouling polyamide composite membrane differs from Example 1 only in that the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine in step (3) of the preparation method is 1%, while the other substances, structures and preparation methods are the same as in Example 1.

[0040] Example 3 An antifouling polyamide composite membrane differs from Example 1 only in that the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine in step (3) of the preparation method is 1.5%, while the other substances, structures and preparation methods are the same as in Example 1.

[0041] Example 4 An antifouling polyamide composite membrane differs from Example 1 only in that the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine in step (3) of the preparation method is 2%, while the other substances, structures and preparation methods are the same as in Example 1.

[0042] Example 5 An antifouling polyamide composite membrane differs from Example 1 only in that the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine in step (3) of the preparation method is 5%, while the other substances, structures and preparation methods are the same as in Example 1.

[0043] Example 6 An antifouling polyamide composite membrane differs from Example 1 only in that the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine in step (3) of the preparation method is 0.1%, while the other substances, structures and preparation methods are the same as in Example 1.

[0044] Example 7 An antifouling polyamide composite membrane, which differs from Example 1 only in that the pH of the N-methylglucosamine aqueous solution is adjusted to 10 with triethylamine in step (3) of the preparation method, while the other substances, structures and preparation methods are the same as in Example 1.

[0045] Example 8 An antifouling polyamide composite membrane differs from Example 1 only in that the pH of the N-methylglucosamine aqueous solution is adjusted to 12 with triethylamine in step (3) of the preparation method. All other substances, structures and preparation methods are the same as in Example 1.

[0046] Example 9 An antifouling polyamide composite membrane differs from Example 1 only in that D-glucosamine is used instead of N-methylglucosamine; all other materials, structures, and preparation methods are the same as in Example 1.

[0047] Comparative Example 1 A polyamide reverse osmosis membrane is prepared by the following steps: (1) Prepare a polysulfone casting solution with a mass percentage of 12% in N,N-dimethylformamide. After stirring evenly, place the obtained polysulfone casting solution in a vacuum oven for degassing treatment. Then, cast the polysulfone casting solution and apply it to a polyester nonwoven fabric with a scraper. Immediately after application, immerse the fabric in a 25°C deionized water coagulation bath to solidify and obtain a polysulfone ultrafiltration membrane. Place the membrane in pure water for immersion and use. (2) Dissolve m-phenylenediamine in water to obtain an aqueous solution with a mass percentage of 3%; dissolve pyromellitic chloride in Isopar G isoalkanes to prepare an organic solution with a mass percentage of 0.15%. (3) Fix the polysulfone ultrafiltration membrane obtained in step (1) in an organic glass plate frame, immerse the membrane surface in the aqueous phase solution obtained in step (2) for 120 s, and remove the excess aqueous phase solution on the surface of the polysulfone ultrafiltration membrane using a nitrogen gas knife; then react the polysulfone ultrafiltration membrane with the organic phase solution obtained in step (2) for 60 s, pour off the excess organic phase solution, rinse the surface of the polysulfone ultrafiltration membrane with Isopar G, and then blow it evenly until there is no residual solvent on the membrane surface. Then place it in an 80℃ oven for heat treatment for 5 min, take it out of the oven and rinse it with pure water to obtain the polyamide reverse osmosis membrane.

[0048] Comparative Example 2 A polyamide reverse osmosis membrane, which differs from Example 4 only in that ethylenediamine is used instead of N-methylglucosamine, while the other substances, structures and preparation methods are the same as in Example 1.

[0049] Comparative Example 3 A polyamide reverse osmosis membrane, which differs from Example 4 only in that D-sorbitol is used instead of N-methylglucosamine, while the other substances, structures and preparation methods are the same as in Example 1.

[0050] Comparative Example 4 A polyamide reverse osmosis membrane is prepared by the following steps: (1) Prepare a polysulfone casting solution with a mass percentage of 12% in N,N-dimethylformamide. After stirring evenly, place the obtained polysulfone casting solution in a vacuum oven for degassing treatment. Then, cast the polysulfone casting solution and apply it to a polyester nonwoven fabric with a scraper. Immediately after application, immerse the fabric in a 25°C deionized water coagulation bath to solidify and obtain a polysulfone ultrafiltration membrane. Place the membrane in pure water for immersion and use. (2) Dissolve m-phenylenediamine in water to obtain an aqueous solution with a mass percentage of 3%; dissolve pyromellitic chloride in Isopar G isoalkanes to prepare an organic solution with a mass percentage of 0.15%. (3) Fix the polysulfone ultrafiltration membrane obtained in step (1) onto an organic glass plate frame, immerse the membrane surface in the aqueous phase solution obtained in step (2) for 120 s, and remove the excess aqueous phase solution on the surface of the polysulfone ultrafiltration membrane using a nitrogen gas knife; then contact the polysulfone ultrafiltration membrane with the organic phase solution obtained in step (2) for 60 s to carry out interfacial polymerization reaction, pour off the excess organic phase solution, rinse the surface of the polysulfone ultrafiltration membrane with Isopar G, and then blow it evenly until there is no residual solvent on the membrane surface. Then place it in an 80℃ oven for heat treatment for 5 min, take it out of the oven and rinse it with pure water to obtain a polyamide separation membrane; (4) Prepare an aqueous solution of N-methylglucosamine with a mass percentage of 2%, and react the polyamide separation membrane obtained in step (3) with the above-mentioned N-methylglucosamine aqueous solution at 25°C for 5 min. Thoroughly clean the membrane surface with deionized water to obtain the polyamide reverse osmosis membrane.

[0051] Performance testing: (1) Basic performance test: The NaCl salt rejection rate R and water flux J of the reverse osmosis membrane were tested using a cross-flow membrane performance evaluation device. The feed solution was a 2000 ppm sodium chloride aqueous solution with pH=7.0±0.5, the operating pressure was 225 psi (1.55MPa), and the operating temperature was 25±1℃. The formula for calculating flux J is as follows: ; Where J is the permeate volume (L) and S is the effective membrane area (m²). 2 ), where t is time (h); The formula for calculating the NaCl salt rejection rate R is as follows: ; in, This represents the concentration of NaCl in the original solution. This represents the concentration of NaCl in the filtrate.

[0052] (2) Evaluation of antifouling ability: The antifouling performance of the reverse osmosis membrane was tested using the cross-flow membrane performance evaluation device described above. First, the feed liquid was pre-pressurized for 0.5 h at the above-mentioned operating pressure and temperature to obtain a stable flux, denoted as J0. In the second stage, 100 ppm bovine serum albumin was used to replace the sodium chloride solution. After filtration for a period of time, the final stable flux was recorded as J0. b Finally, clean the fouled membrane and then remeasure the flux under the same conditions as in the first step, denoted as J1. Finally, calculate the flux recovery rate (FRR) and flux decay rate (DRt) using the following formulas: ; ; Among them, J1, J0 and J b These represent the membrane flux after physical cleaning, the initial membrane flux before fouling, and the membrane flux after fouling, respectively.

[0053] (3) Membrane surface hydrophilicity: The contact angle is a measure of the degree of wettability of a solid surface, which indirectly reflects the hydrophilicity and hydrophobicity of the material. The degree of wettability of the membrane surface is characterized by the static contact angle. Sample preparation: The membrane sample was repeatedly rinsed with deionized water and dried in a vacuum oven at 40°C for 24 h, and then the water contact angle was tested.

[0054] (4) Charge characterization: Zeta potential is the potential on the shear surface when the solid and liquid phases move relative to each other in the electrokinetic effect of the solid surface. It can be used to characterize the charge status of the membrane surface. The Zeta potential of the membrane surface in 1mM KCl solution under different pH conditions was tested and calculated using a Zeta potential meter. Sample preparation: The membrane sample was repeatedly rinsed with deionized water.

[0055] (5) Chlorine resistance: The membrane was soaked in 1000 mg / L HClO solution for 24 h, and the flux and NaCl rejection rate were retested under the conditions of 15.5 bar pressure, pH=7.5 and 25±0.4℃.

[0056] The membranes provided in Examples 1-9 and Comparative Examples 1-4 were tested according to the above test methods, and the test results are shown in Table 1: Table 1 According to the data in Table 1: The antifouling polyamide composite membranes provided in Examples 1-9 possess excellent basic membrane properties (water flux of 50.4-56.4 LMH, NaCl rejection rate of 99.18-99.57%), hydrophilicity (water contact angle of 40-77°), charge controllability (zeta potential of -42 to -29 mV at pH=7, and -35 to -5 mV at pH=3), antifouling properties (membrane flux decay rate after bovine serum albumin contamination is only 9.6-24.%, and flux recovery rate is as high as 90.4-96.8%), and chlorine resistance (NaCl rejection rate after chlorination is still as high as 64.6-78.4%), all of which are significantly better than those in Comparative Examples 1-4.

[0057] Specifically, as can be seen from Examples 1-6, as the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine gradually increases, the water flux of the resulting antifouling polyamide composite membrane increases, while the NaCl rejection rate remains basically unchanged. However, if the mass percentage of N-methylglucosamine in the aqueous solution of N-methylglucosamine is too high, the water flux will decrease. This may be because high concentrations of N-methylglucosamine are more prone to aggregation, which will inhibit the diffusion rate from the aqueous solution to the oil solution, thereby affecting the formation rate and crosslinking degree of the polyamide separation layer. Secondly, as can be seen from Examples 1 and Examples 7-8, the water flux and NaCl rejection rate of the membrane are best at pH=11.

[0058] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A pollution-resistant polyamide composite film, characterized in that, The antifouling polyamide composite membrane includes a porous support layer and a polyamide separation layer; The surface of the polyamide separation layer is grafted with N-alkylglucosamine compounds, and the N-alkylglucosamine compounds are grafted by esterification reaction between the contained hydroxyl groups and the residual acyl chloride groups on the surface of the polyamide separation layer.

2. The antifouling polyamide composite film according to claim 1, characterized in that, The N-alkylglucosamine compounds include any one or a combination of at least two of N-methylglucosamine, N-ethylglucosamine, N-propylglucosamine, N-butylglucosamine, or D-glucosamine.

3. The antifouling polyamide composite film according to claim 1 or 2, characterized in that, The porous support layer is made of any one or a combination of at least two of the following: polysulfone, polyethersulfone, polyvinylidene fluoride, polyvinyl chloride, or polyacrylonitrile.

4. The antifouling polyamide composite film according to any one of claims 1 to 3, characterized in that, The raw materials for preparing the polyamide separation layer include polyamine monomers and polyacrylamide chloride monomers.

5. A method for preparing an antifouling polyamide composite film as described in any one of claims 1 to 4, characterized in that, The preparation method includes: reacting a separation membrane containing a porous support layer and a polyamide separation layer with an aqueous solution of an N-alkylglucosamine compound under alkaline conditions to obtain the antifouling polyamide composite membrane.

6. The preparation method according to claim 5, characterized in that, The aqueous solution of the N-alkylglucosamine compound contains 0.1% to 5% N-alkylglucosamine compound by mass.

7. The preparation method according to claim 5 or 6, characterized in that, The alkaline conditions are those with a pH value of 10 to 12.

8. The preparation method according to any one of claims 5 to 7, characterized in that, The temperature of the contact reaction is 20~40℃; Preferably, the contact reaction time is 1 to 10 minutes.

9. The preparation method according to any one of claims 5 to 7, characterized in that, The contact reaction is followed by a cleaning step.

10. The application of an antifouling polyamide composite membrane as described in any one of claims 1 to 4 in seawater desalination or wastewater recycling.

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