High-performance anti-pollution zwitterionic nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention discloses a high-performance anti-pollution zwitter-ion nanofiltration membrane and a preparation method and application thereof, the method comprises the following steps: S1, immersing a support base membrane in deionized water, and then adhering the support base membrane to the bottom of a glass plate; s2, soaking the supporting base membrane in an inorganic phase solution, and then drying until no obvious water drops exist on the surface; s3, the supporting base membrane is soaked in an organic phase solution, a thin polyamide layer is formed on the surface of the supporting base membrane, then heat treatment is carried out, and the organic phase solution comprises multiple acyl chloride monomers and a solvent; s4, soaking the membrane prepared in the step S3 in a grafting solution for surface grafting, and then performing heat treatment to obtain the high-performance anti-pollution zwitter-ion nanofiltration membrane. Through a synergistic modification strategy, the microstructure and surface properties of the nanofiltration membrane are optimized, and the properties of the traditional nanofiltration membrane are improved.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a high-performance anti-pollution zwitterion nanofiltration membrane and a preparation method and application thereof. Background Art

[0002] Severe environmental pollution has made the protection and purification of water resources an urgent need. As a new pressure-driven separation technology between ultrafiltration and reverse osmosis, nanofiltration, due to its low cost, low operating pressure, and energy-saving characteristics, has been widely used in seawater desalination, wastewater treatment, dye removal, and industrial material separation, and is a current research hotspot.

[0003] High-performance separation membranes are at the core of nanofiltration technology. Thin-film composite polyamide membranes, which have been commercially used in nanofiltration processes, feature a highly porous polymer support layer and a polyamide active layer formed through interfacial polymerization (IP). Consequently, they exhibit excellent selective permeability and strong chemical and thermal stability. In recent years, research has focused on regulating the structure of polyamide nanofiltration membranes, improving separation performance through material doping (e.g., introducing functional materials such as titanium dioxide, graphene oxide, and polyvinyl alcohol into the aqueous phase for interfacial polymerization) or surface modification. Furthermore, numerous studies have explored enhancing the permeability and separation performance of nanofiltration membranes by adjusting the concentrations of different monomers in the interfacial polymerization reaction.

[0004] However, due to the large number of carboxyl groups produced by interfacial polymerization, traditional nanofiltration membranes usually have negative charges on their surfaces. In the process of treating complex dye wastewater, strong electrostatic interactions are generated with the large number of charged organic molecules in the dye wastewater, resulting in large amounts of adsorption and deposition of pollutants on the membrane surface, causing serious membrane fouling. The continuous accumulation of pollutants on the membrane surface reduces the effective filtration area of ​​the membrane and blocks the pore size, resulting in a significant decrease in the separation performance of the nanofiltration membrane. Frequent cleaning to restore membrane flux also significantly increases maintenance costs. Some studies have increased membrane flux by adjusting the monomer concentration ratio or surface modification to adjust the membrane pore size, but due to the limitation between permeability and selectivity, the separation performance of the membrane will also be greatly reduced, further limiting the widespread application of nanofiltration membranes in actual water treatment. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance anti-pollution zwitterionic nanofiltration membrane and its preparation method and application. Through a synergistic modification strategy, it optimizes the microstructure and surface properties of the nanofiltration membrane, improves the properties of traditional nanofiltration membranes, and to a certain extent improves the water flux, anti-pollution performance and dye removal efficiency of the membrane, effectively solving the membrane pollution problems and performance bottlenecks of traditional nanofiltration membranes when treating wastewater such as dyes.

[0006] In one aspect of the present invention, a method for preparing a high-performance anti-fouling zwitterionic nanofiltration membrane is provided. According to an embodiment of the present invention, the preparation method comprises the following steps:

[0007] S1. Immerse the supporting base film in deionized water, and then stick the supporting base film to the bottom of the glass plate;

[0008] S2. Pour the inorganic phase solution evenly onto the surface of the supporting base film fixed on the glass plate, soak the supporting base film, and then dry it until there are no obvious water droplets on the surface;

[0009] S3, immersing the supporting base membrane in the organic phase solution again to form a thin polyamide layer on the surface, and then performing heat treatment;

[0010] S4, soaking the membrane obtained in step S3 in a grafting solution for surface grafting, and then performing heat treatment to obtain the high-performance anti-pollution zwitterionic nanofiltration membrane.

[0011] In addition, the method for preparing a high-performance anti-fouling zwitterionic nanofiltration membrane according to the above embodiment of the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, in step S1, the supporting base membrane is immersed in deionized water for more than 30 minutes; the supporting base membrane is one of a polyethersulfone (PES) ultrafiltration membrane, a polyvinylidene fluoride (PVDF) membrane, a polyacrylonitrile (PAN) membrane, and a polysulfone (PSf) membrane; and the pore size of the PES ultrafiltration membrane is one of 220 nm, 470 nm, 300 nm, and 500 nm. Water or a related solvent is used to fully wet the porous structure of the base membrane to expel air, promote moderate swelling of the base membrane to optimize the pore state, and remove residual impurities on the surface, thereby creating a stable and clean base environment for the subsequent uniform distribution of aqueous and oil phase monomers and interfacial polymerization reactions, thereby ensuring the integrity and separation performance of the composite membrane.

[0013] In some embodiments of the present invention, in the inorganic phase solution in step S2, the compound having a polyamine structure is one of tetraethylenepentamine, polyethyleneimine, and tri(2-aminoethyl)amine, the aqueous phase monomer is one of piperazine, m-phenylenediamine, and p-phenylenediamine, and the mass ratio of the compound having a polyamine structure, the aqueous phase monomer, and anhydrous sodium phosphate is (0.1-1.0): (0.5-2): (0.3-0.8); the inorganic phase solution also includes a pH adjuster, and the pH adjuster is one of anhydrous sodium phosphate, sodium carbonate, sodium bicarbonate, and disodium hydrogen phosphate.

[0014] Preferably, the compound having a polyamine structure is tris(2-aminoethyl)amine, the aqueous phase monomer is piperazine, and the solvent is deionized water.

[0015] Anhydrous sodium phosphate is used to adjust the pH and ionic strength of the inorganic phase solution, ensuring the stability of the polymerization reaction. Piperazine, the primary monomer in the inorganic phase, participates in the interfacial polymerization reaction to form the polyamide layer. TAEA and PIP are blended to modify the nanofiltration membrane and regulate the cross-linked network structure of the polyamide separation layer.

[0016] In some embodiments of the present invention, in step S2, the supporting base membrane is immersed in the inorganic phase solution for 2-10 minutes, and the drying temperature is 20-30°C. The inorganic phase solution is allowed to fully infiltrate the supporting base membrane, evenly loading the inorganic phase components throughout its pores and surface, laying a solid foundation for subsequent interfacial polymerization with the organic phase. The drying step prevents excess moisture from interfering with the polymerization reaction.

[0017] In some embodiments of the present invention, in the organic phase solution in step S3, the polyacyl chloride monomer is a mixture of one or more of 1,3,5-benzenetricarbonyl trichloride (TMC), isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, and biphenyltetracarboxylic acid chloride, and the solvent is a mixture of one or more of n-hexane, cyclohexane, n-heptane, toluene, and chloroform. Preferably, the polyacyl chloride monomer is 1,3,5-benzenetricarbonyl trichloride (TMC), and the solvent is n-hexane.

[0018] 1,3,5-Benzenetricarbonyl sodium trichloride is the core monomer in the organic phase. It undergoes an interfacial polymerization reaction with piperazine in the inorganic phase, forming a polyamide separation layer on the surface of the support membrane. This layer directly determines the nanofiltration membrane's performance, such as retention rate and water flux. Its concentration and reactivity affect the crosslinking degree and pore size of the polyamide layer, which in turn affects the dye separation effect. n-Hexane, as a solvent for TMC, allows for its uniform dispersion, forming a stable organic phase system and ensuring sufficient contact and reaction between TMC and the inorganic monomer.

[0019] In some embodiments of the present invention, in step S3, the supporting base membrane is immersed in the organic phase solution for 1-3 minutes; the heat treatment is performed in a forced air drying oven at a temperature of 40-60°C for 5-15 minutes. Step S3 allows the organic phase molecules to fully adhere to the surface and pores of the inorganic phase-loaded base membrane, ensuring full contact between the two phases at the interface, leading to efficient and uniform interfacial polymerization, thereby forming a polyamide layer with excellent separation properties.

[0020] In some embodiments of the present invention, in step S4, the grafting solution is an anhydrous ethanol solution containing 1,3-propane sultone (1,3PS). 1,3PS is used to undergo a quaternization reaction with TAEA to construct zwitterionic sulfonic acid groups on the membrane surface.

[0021] In some embodiments of the present invention, in step S4, the membrane prepared in step S3 is immersed in the grafting solution for 10-40 minutes; the heat treatment temperature is 40-60°C and the heat treatment time is 5-15 minutes. Soaking the prepared membrane in the grafting solution for surface grafting allows the zwitterionic groups to be firmly bonded to the membrane surface, imparting hydrophilicity and charge regulation capabilities to the membrane. Subsequent heat treatment stabilizes the grafted structure, ultimately yielding a zwitterionic nanofiltration membrane with both efficient separation performance and excellent anti-fouling capabilities.

[0022] In another aspect of the present invention, the present invention provides a method for preparing a high-performance anti-pollution zwitterion nanofiltration membrane to obtain a high-performance anti-pollution zwitterion nanofiltration membrane.

[0023] In another aspect of the present invention, the present invention provides a use of the high-performance anti-fouling zwitterionic nanofiltration membrane. In an embodiment of the present invention, the high-performance anti-fouling zwitterionic nanofiltration membrane is used to remove dyes or treat wastewater.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) This invention combines co-modification with surface grafting to construct a novel zwitterionic nanofiltration membrane. The co-modification increases membrane flux; the zwitterion grafting effectively reduces electrostatic interactions between charged organic molecules and the membrane surface, enhancing the membrane's anti-fouling properties and reducing fouling levels. This method avoids the problems of existing methods, such as altered pore size distribution, reduced water permeability, and difficulty in scalability. It achieves improvements in membrane flux and retention, permeability, separation performance, and anti-fouling properties, enhancing the efficiency and stability of nanofiltration membranes in treating dye wastewater and other applications.

[0026] 2) This invention utilizes tris(2-aminoethyl)amine (TAEA) and 1,3-propane sultone (1,3-PS) to synergistically modify the nanofiltration membrane. TAEA, through interfacial polymerization, introduces its branched molecular structure into the polyamide separation layer. This unique introduction effectively modulates the polymer's cross-linked network, smoothing water transport through the membrane and reducing water transport resistance. Furthermore, during the surface grafting process, 1,3-PS reacts with the tertiary amine groups of TAEA to form zwitterionic sulfonic acid groups on the membrane surface. These zwitterionic groups strongly interact with water molecules, forming a strongly hydrated layer. This layer acts as a barrier, significantly reducing electrostatic interactions between charged organic molecules and the membrane surface, preventing direct contact. This fundamentally addresses the problem of electrostatic adsorption leading to membrane fouling in traditional nanofiltration membranes. Over long-term operation, this strongly hydrated layer enhances the membrane's retention performance, effectively ensuring stable operation. Experiments show that the pure water flux of the nanofiltration membrane modified by the method of the present invention is 2.48 times that of the unmodified membrane, which significantly improves the water flux of the membrane.

[0027] 3) The zwitterionic nanofiltration membrane prepared by this invention, due to its unique structure and properties, exhibits high retention and flux for various dyes. On the one hand, the zwitterionic structure on the membrane surface reduces nonspecific adsorption of dye molecules to the membrane, enabling more efficient retention of dye molecules. On the other hand, the excellent water flux ensures sufficient water flow to carry dye molecules through the membrane, further improving dye removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Corresponding water flux diagrams of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0029] Figure 2 Graphs showing the corresponding sodium sulfate rejection and flux of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0030] Figure 3 The corresponding sodium chloride rejection and flux diagrams of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0031] Figure 4 Graphs showing the corresponding magnesium chloride rejection and flux of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0032] Figure 5 Graphs showing the corresponding magnesium sulfate rejection and flux of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0033] Figure 6The corresponding Congo red rejection and flux diagrams of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0034] Figure 7 The corresponding rhodamine B retention rate and flux diagram of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0035] Figure 8 The corresponding basic blue 24 retention rate and flux diagram of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0036] Figure 9 Graph showing the flux recovery ratio of humic acid for different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1;

[0037] Figure 10 Fourier transform infrared spectra (left) and magnified images (right) of different nanofiltration membranes prepared in Examples 1-4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane, the specific steps are as follows:

[0041] S1. Preparation of inorganic phase solution

[0042] A deionized aqueous solution containing piperazine (PIP), anhydrous sodium phosphate (Na3PO4), and tris(2-aminoethyl)amine (TAEA) was prepared as the inorganic phase and sonicated for 20 minutes. The concentration of PIP was 1.0 wt% (1 g), the concentration of Na3PO4 was 0.5 wt% (0.5 g), and the concentration of TAEA was 0.2 wt% (0.2 g). The solvent was 100 ml of deionized water.

[0043] S2. Preparation of organic phase solution

[0044] A n-hexane solution containing 1,3,5-phenyltricarbonyl trichloride (TMC) was prepared as an organic phase solution and ultrasonically treated for 20 min, wherein the concentration of TMC was 0.5 wt %, the mass was 0.33 g, and the amount of n-hexane used was 100 ml.

[0045] S3. Preparation of grafting solution

[0046] A 0.2 g / L 1,3-propane sultone (1,3PS) anhydrous ethanol solution was prepared, wherein 0.2 g of 1,3PS and 1 L of anhydrous ethanol were used.

[0047] S4. Preparation of blended modified nanofiltration membrane

[0048] (1) A PES-based membrane with a pore size of 220 nm was immersed in deionized water for more than 30 min, and then the surface water on the substrate was thoroughly removed using a rubber roller before the interfacial polymerization process.

[0049] (2) Attach the PES membrane to the bottom of the glass plate. Pour at least 10 ml of the prepared inorganic phase solution evenly onto the surface of the PES membrane fixed on the glass plate. Soak the membrane for 3 minutes. Remove excess solution and air-dry the membrane at room temperature for at least 10 minutes until no water droplets are visible on the surface.

[0050] (3) The PES-based membrane was immersed in the organic phase solution for 1 min. After a thin polyamide layer was formed on the surface, the PES-based membrane was placed in a 50°C forced air drying oven for 10 min to obtain an FCM-0.2 membrane. Before testing, the nanofiltration membrane was stored in a refrigerator at 4°C.

[0051] S5. Preparation of zwitterion-modified membrane

[0052] The membrane prepared in step S4 was immersed in the grafting solution for 20 minutes for surface grafting. It was then heat-treated in a 50°C forced air drying oven for 10 minutes to obtain a ZTFCM-0.2 membrane. The nanofiltration membrane was stored in a refrigerator at 4°C prior to testing.

[0053] Example 2

[0054] A method for preparing a high-performance anti-fouling zwitterionic nanofiltration membrane is disclosed, which differs from Example 1 only in that: in step S1, the concentration of TAEA is 0.5 wt% (0.5 g); the blended modified nanofiltration membrane obtained in step S4 is recorded as TFCM-0.5 membrane, and the zwitterionic modified membrane obtained in step S4 is recorded as ZTFCM-0.5 membrane. The other steps and parameters are the same.

[0055] Example 3

[0056] A method for preparing a high-performance anti-fouling zwitterionic nanofiltration membrane is disclosed, which differs from Example 1 only in that: in step S1, the concentration of TAEA is 0.8 wt% (0.8 g); the blended modified nanofiltration membrane obtained in step S4 is recorded as TFCM-0.8 membrane, and the zwitterionic modified membrane obtained in step S4 is recorded as ZTFCM-0.8 membrane. The other steps and parameters are the same.

[0057] Example 4

[0058] A method for preparing a high-performance anti-fouling zwitterionic nanofiltration membrane is disclosed, which differs from Example 1 only in that: in step S1, the concentration of TAEA is 1.0 wt% (1.0 g); the blended modified nanofiltration membrane obtained in step S4 is recorded as TFCM-1.0 membrane, and the zwitterionic modified membrane obtained in step S4 is recorded as ZTFCM-1.0 membrane. The other steps and parameters are the same.

[0059] Comparative Example 1

[0060] A control group was set up, and a method for preparing a nanofiltration membrane was used, which differed from Example 1 only in that: in step S1, the PIP concentration was 2.0 wt% (2.0 g), and TAEA was not added; the blended modified nanofiltration membrane obtained in step S4 was recorded as PA membrane.

[0061] The nanofiltration membranes prepared in Examples 1-4 and Comparative Example 1 were subjected to performance tests:

[0062] 1. Basic membrane flux test

[0063] The water flux of the nanofiltration membrane was tested using a cross-flow filtration device at an operating pressure of 5.0 bar. The water flux J of the membrane was calculated based on the mass of water that could pass through the membrane per unit time under a pressure of 5.0 bar. w :

[0064] Pure water flux J w (L / m 2 / h or LMH) is calculated by formula (1).

[0065] (1)

[0066] In formula (1), V is the permeable volume (L); Δt (h) is the permeable collection time interval; A is the effective area of ​​the membrane being tested (m 2 ).

[0067] like Figure 1 As shown, Figure 1The corresponding water flux of membranes prepared with different TAEA mass ratios is shown. Based on the experimental results, the TFCM-0.2 membrane prepared in Example 1 showed the highest flux among the blended modified membranes. Therefore, the TFCM-0.2 membrane was surface-grafted to obtain a new zwitterionic nanofiltration membrane (ZTFCM-0.2 membrane) with the best performance.

[0068] The incorporation of tri(2-aminoethyl)amine with a branched, strong structure increases membrane porosity and flux. By grafting 1,3-propane sultone (1,3-PS) onto the tertiary amine of triethylamine, surface modification introduces a zwitterionic structure, enhancing hydrophilicity. Generally, due to a "trade-off" effect, higher flux decreases retention, and lower flux increases retention. The incorporation of tri(2-aminoethyl)amine modulates the pore size of the nanofiltration membrane, increasing the membrane pore size and flux, resulting in a slight decrease in retention. However, the introduction of a zwitterionic structure on the surface further improves retention. A systematic analysis of the pure water flux performance of six nanofiltration membranes revealed that the nanofiltration membrane (ZTFCM-0.2 membrane) synergistically modified with tri(2-aminoethyl)amine (TAEA) and 1,3-propane sultone (1,3-PS) exhibited significantly enhanced separation performance. Specifically, the pure water flux of the modified membrane reached 2.48 times that of the unmodified membrane. This significant performance improvement was mainly attributed to the synergistic mechanism.

[0069] 2. Salt retention rate test

[0070] The separation performance of the membrane was tested at an operating pressure of 5.0 bar using 2000 ppm of Na2SO4, NaCl, MgCl2 and MgSO4. The permeate concentration was measured using a conductivity meter, and the salt retention rate R (%) was calculated using formula (2).

[0071] (2)

[0072] In formula (2), R is the retention rate of salt (%); C p —Concentration of filtrate in permeate (mg·L −1 );C f —Concentration of filtrate in feed solution (mg·L −1 ).

[0073] Figure 2-5The flux and retention rate of Na2SO4, NaCl, MgCl2 and MgSO4 of different membranes are shown. According to the experiment, the zwitterionic nanofiltration membrane (ZTFCM-0.2 membrane) prepared in Example 1 has the largest flux and the best performance. First, the branched molecular structure of TAEA is introduced into the polyamide separation layer through the interfacial polymerization process, and its unique spatial configuration effectively regulates the cross-linked network structure of the polymer. This significantly reduces the water transmission resistance. Secondly, through the quaternization reaction of 1,3-PS and the tertiary amine group of TAEA, zwitterionic sulfonic acid groups are constructed on the membrane surface. This is mainly attributed to the strong hydration layer formed by the zwitterionic structure, which enhances the salt retention performance and improves the flux.

[0074] 3. Anti-pollution performance test

[0075] The test was performed at an operating pressure of 5.0 bar. The membrane was first stabilized with deionized water and the initial water flux (J w0 ). Then, the deionized water was immediately replaced with a 500 ppm humic acid solution. Afterwards, the permeate flux (J w1 Then, the feed solution was replaced with deionized water, and the water flux (J) was recorded after one hour of rinsing. w2 ).

[0076] (3)

[0077] In formula (3), J w0 —pure water flux; J w2 —Flux after membrane fouling, FRR flux recovery rate.

[0078] Figure 6 The flux recovery ratios of different membranes are shown. According to the experiment, it was found that the zwitterionic nanofiltration membrane (ZTFCM-0.2 membrane) prepared in Example 1 had the best anti-fouling performance.

[0079] 4. Dye removal performance test

[0080] The removal efficiency of different membranes for various dyes was tested using 100 ppm solutions of Rhodamine B (RB), Congo Red (CR), and Basic Blue 24 (BB24) at an operating pressure of 5.0 bar. Feed and permeate concentrations were measured using a UV spectrophotometer to calculate dye retention.

[0081] (4)

[0082] In formula (4), R is the retention rate of dye (%); C is p —Concentration of filtrate in permeate (mg·L −1 );C f —Concentration of filtrate in feed solution (mg·L−1 ).

[0083] Figure 7-8 The dye rejection rates of different membranes are shown. According to the experiment, the zwitterionic nanofiltration membrane (ZTFCM-0.2 membrane) prepared in Example 1 has the best dye removal performance.

[0084] Through the quaternization reaction of 1,3PS and TAEA tertiary amine groups, zwitterionic sulfonic acid groups are formed on the membrane surface. These zwitterionic groups render the membrane surface electrically neutral, effectively reducing electrostatic interactions with charged organic molecules in the dye wastewater and preventing dye molecules from adsorbing on the membrane surface due to electrostatic attraction. Furthermore, the zwitterionic groups strongly interact with water molecules to form a strong hydration layer, acting as a barrier to separate the membrane surface from the dye molecules, further preventing dye molecules from contacting the membrane surface, reducing membrane fouling, and thus maintaining a high dye retention rate and improving dye removal performance.

[0085] By precisely controlling the interfacial polymerization reaction, a polyamide separation layer with excellent performance is formed. Factors such as the concentration of the reactants and the reaction time determine the degree of crosslinking and the pore size of the polyamide layer. The present invention, through reasonable process parameter settings, enables the polyamide separation layer to have a suitable pore size and selectivity, which can effectively intercept different types of dye molecules. Higher water flux means that more water flow can carry dye molecules through the membrane per unit time, while ensuring the interception rate, increasing the dye processing capacity, thereby improving the overall efficiency of dye removal.

[0086] 5. Humic acid removal performance test

[0087] The test was performed at an operating pressure of 5.0 bar. The membrane was first stabilized with deionized water and the initial water flux (J w0 ). Then, the deionized water was immediately replaced with a 500 ppm humic acid solution. Afterwards, the permeate flux (J w1 Then, the feed solution was replaced with deionized water, and the water flux (J) was recorded after one hour of rinsing. w2 ), and thus the flux recovery ratio of humic acid was calculated.

[0088] like Figure 9As shown, the flux recovery ratio of different modified membranes to humic acid is shown. The zwitterionic structure forms a dense and stable strong hydration layer. When the solution containing humic acid contacts the membrane surface, this strong hydration layer acts as a physical barrier, effectively hindering the direct contact and adsorption of humic acid molecules with the membrane surface, reducing the deposition of humic acid on the membrane surface, and slowing down the flux decline of the membrane during the filtration process. The surface of the zwitterionic nanofiltration membrane of the present invention is electrically neutral, effectively eliminating the electrostatic attraction between the membrane and the humic acid molecules. At the same time, the zwitterionic structure will ionize in the solution, so that the membrane surface carries both positive and negative charges, and can also produce an electrostatic repulsion effect to a certain extent, further preventing humic acid molecules from approaching the membrane surface, reducing the probability of humic acid adhering to the membrane surface, reducing the occurrence of membrane fouling, maintaining the stability of the membrane flux, and improving the flux recovery ratio and anti-pollution performance.

[0089] 6. Fourier transform infrared spectroscopy characterization

[0090] like Figure 10 The FTIR spectra of the ZTFCM-0.2 membrane after 1,3-PS was grafted onto the membrane were shown in Figure 2. −1 A main peak was found at 1039 cm −1 A new characteristic peak appeared at 3- In summary, FTIR analysis provides clear evidence that 1,3-PS was successfully grafted onto the TFCM-0.2 membrane and cross-linked on the membrane surface. This process ultimately resulted in the successful preparation and grafting of zwitterionic groups onto the membrane surface.

[0091] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane, characterized in that: The following steps are involved: S1. Immerse the supporting base film in deionized water, and then stick the supporting base film to the bottom of the glass plate; S2, immersing the supporting base membrane in an inorganic phase solution, and then drying until no obvious water droplets are present on the surface, wherein the inorganic phase solution comprises a compound having a polyamine structure and an aqueous phase monomer; S3, immersing the supporting base membrane in an organic phase solution to form a thin polyamide layer on the surface, and then performing a heat treatment, wherein the organic phase solution includes a polyacyl chloride monomer and a solvent; S4, soaking the membrane obtained in step S3 in a grafting solution for surface grafting, and then performing heat treatment to obtain the high-performance anti-pollution zwitterionic nanofiltration membrane.

2. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, wherein: In step S1, the supporting base membrane is immersed in deionized water for more than 30 minutes; the supporting base membrane is one of polyethersulfone ultrafiltration membrane, polyvinylidene fluoride membrane, polyacrylonitrile membrane, and polysulfone membrane.

3. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, wherein: In the inorganic phase solution in step S2, the compound having a polyamine structure is one of tetraethylenepentamine, polyethyleneimine, and tri(2-aminoethyl)amine; the aqueous phase monomer is one of piperazine, m-phenylenediamine, and p-phenylenediamine; the mass ratio of the compound having a polyamine structure, the aqueous phase monomer, and anhydrous sodium phosphate is (0.1-1.0):(0.5-2):(0.3-0.8); the inorganic phase solution also includes a pH adjuster, which is one of anhydrous sodium phosphate, sodium carbonate, sodium bicarbonate, and disodium hydrogen phosphate.

4. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, wherein: In step S2, the supporting base film is immersed in the inorganic phase solution for 2-10 minutes; and the drying temperature is 20-30°C.

5. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, characterized in that: In the organic phase solution in step S3, the polyacyl chloride monomer is a mixture of one or more of 1,3,5-benzenetricarbonyl trichloride, isophthaloyl chloride, terephthaloyl chloride, trimesoyl chloride, and biphenyltetracarboxylic acid chloride, and the solvent is a mixture of one or more of n-hexane, cyclohexane, n-heptane, toluene, and chloroform.

6. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, characterized in that: In step S3, the supporting base membrane is immersed in the organic phase solution for 1-3 minutes; the heat treatment is carried out in a blast drying oven at a temperature of 40-60° C. for 5-15 minutes.

7. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, characterized in that: In step S4, the grafting solution is an anhydrous ethanol solution containing 1,3-propane sultone.

8. The method for preparing a high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 1, characterized in that: In step S4, the membrane obtained in step S3 is immersed in the grafting solution for 10-40 minutes; the heat treatment temperature is 40-60° C., and the heat treatment time is 5-15 minutes.

9. A high-performance anti-fouling zwitterionic nanofiltration membrane prepared by the method for preparing the high-performance anti-fouling zwitterionic nanofiltration membrane according to claims 1-8.

10. The use of the high-performance anti-pollution zwitterionic nanofiltration membrane according to claim 9, characterized in that: The high-performance anti-pollution zwitterion nanofiltration membrane is used for removing dyes or treating wastewater.

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