A polyamide nanofiltration membrane based on a resveratrol intermediate layer, and its preparation method and application

Abstract

The present invention relates to the technical field of sewage and wastewater treatment. More specifically, the present invention discloses a polyamide nanofiltration membrane based on a resveratrol intermediate layer for sewage and wastewater treatment and resource utilization, as well as its preparation method and application. The preparation method comprises the following steps: S1. a resveratrol solution is brought into contact with the surface of a basement membrane, allowed to stand, and a resveratrol intermediate layer is prepared on the surface of the basement membrane; S2. an aqueous phase solution containing an amine monomer and an organic phase solution containing an acyl chloride monomer are interfacially polymerized on the resveratrol intermediate layer to prepare a polyamide nanofiltration membrane; the concentration of resveratrol is 0.1-2.0wt%; the concentration of amine monomer is 0.3-2.0wt%. The polyamide nanofiltration membrane has excellent water flux, divalent salt retention rate and anti-pollution performance, has broad application prospects, and can be used in sewage treatment equipment, seawater desalination equipment, industrial wastewater treatment and reuse equipment and other devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater and sewage treatment, and more specifically, relates to a polyamide nanofiltration membrane based on a resveratrol intermediate layer, a preparation method and an application thereof. Background Art

[0002] The rational utilization and protection of water resources is a crucial and arduous task. Nanofiltration membranes have an average molecular weight cutoff (MWCO) of 200-1000 Da, intermediate between reverse osmosis (RO) and ultrafiltration (UF) membranes. Their surface is typically negatively charged, effectively separating divalent and monovalent inorganic salts. They hold broad application prospects in desalination, high-salinity wastewater treatment and resource recovery, sewage treatment, and drinking water purification. Currently, commercial nanofiltration membranes are primarily thin-film composite (TFC) membranes prepared via interfacial polymerization. This involves forming a polyamide selective layer on the surface of an ultrafiltration or microfiltration membrane by interfacial polymerization of aqueous amine monomers and organic acyl chloride monomers. Due to the rapid and difficult-to-control interfacial polymerization reaction, these polyamide nanofiltration membranes often suffer from a "trade-off" effect, where both permeability and selectivity cannot be simultaneously improved. Furthermore, the surface of polyamide nanofiltration membranes is susceptible to the deposition of complex pollutants such as proteins, polysaccharides, humic acid, and inorganic salts, leading to severe membrane fouling and severely limiting their practical performance and lifespan.

[0003] The paper "Polyphenol Coating as an Interlayer for Thin-Film Composite Membranes with Enhanced Nanofiltration Performance, Xi Zhang, ACS Applied Materials & Interfaces, DOI: 10.1021 / acsami.6b10693" discloses the preparation of a TFC nanofiltration membrane with enhanced nanofiltration performance by co-depositing tannic acid (TA) and diethylenetriamine (DETA) on a polysulfone ultrafiltration substrate, followed by interfacial polymerization to construct a polyamide selective layer. However, because the ortho-phenolic hydroxyl groups of tannic acid are easily oxidized to benzoquinone, they are easily involved in the synthesis of the polyamide layer when used as an interlayer through Michael addition or Schiff base reaction and polymerization of amine monomers, resulting in the final water flux being much lower than that of commercial membranes. The water permeation flux of the TFC nanofiltration membrane synthesized by this method is 10.5 L·m -2 ·h -1 bar -1 , it is difficult to meet the demand.

[0004] Therefore, the development of a polyamide nanofiltration membrane with high permeability, selectivity and anti-fouling properties has broad application prospects. Summary of the Invention

[0005] In response to the above-mentioned existing technical problems, the primary purpose of the present invention is to provide a method for preparing a polyamide nanofiltration membrane based on a resveratrol intermediate layer. The prepared polyamide nanofiltration membrane has excellent water flux, divalent salt (Na2SO4) retention rate and anti-pollution performance, and has broad application prospects.

[0006] The second object of the present invention is to provide a polyamide nanofiltration membrane based on a resveratrol intermediate layer obtained by the above preparation method.

[0007] The third object of the present invention is to provide an application of a polyamide nanofiltration membrane based on a resveratrol intermediate layer in wastewater and sewage treatment.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A method for preparing a polyamide nanofiltration membrane based on a resveratrol intermediate layer comprises the following steps:

[0010] S1. The resveratrol solution is brought into contact with the surface of the basement membrane and allowed to stand to form a resveratrol intermediate layer on the surface of the basement membrane;

[0011] S2. Interfacial polymerization of an aqueous solution containing an amine monomer and an organic solution containing an acyl chloride monomer on the resveratrol intermediate layer and curing to prepare a polyamide nanofiltration membrane;

[0012] In the resveratrol solution, the concentration of resveratrol is 0.1-2.0wt%;

[0013] In the aqueous solution containing the amine monomer, the concentration of the amine monomer is 0.3-2.0 wt %.

[0014] This invention innovatively proposes to regulate the interfacial polymerization reaction by introducing resveratrol as a functional interlayer. Resveratrol molecules, through their unique molecular configuration (rich in phenolic hydroxyl groups and benzene rings), bind to the basement membrane, effectively slowing the diffusion rate of amine monomers through hydrogen bonding and π-π interactions, thereby precisely controlling the formation of the polyamide active layer and ultimately achieving an ultrathin, low-crosslinked polyamide active layer. Furthermore, the resveratrol interlayer synergistically enhances the membrane's surface hydrophilicity, strengthens its surface negative charge, and improves calcium ion permeability, endowing the polyamide nanofiltration membrane with excellent resistance to organic-inorganic composite contamination.

[0015] Through research, the inventors have discovered that the concentration of resveratrol and the concentration of amine monomers in the aqueous solution have a significant impact on the water flux and divalent salt retention rate of polyamide nanofiltration membranes. Only when the resveratrol and amine monomer concentrations are within the above ranges can the prepared polyamide nanofiltration membranes have excellent water flux, divalent salt retention rate, and anti-fouling properties. The preparation method provided by the present invention is mild and the raw material resveratrol is a natural plant extract, which is environmentally friendly. The method can prepare ultrathin, highly hydrophilic, and strongly negatively charged polyamide nanofiltration membranes under mild conditions.

[0016] Specifically, in the resveratrol solution, the concentration of resveratrol can be 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, etc., or an interval range formed by any of the above values, such as 0.2-0.5wt%, 0.3-0.6wt%, 0.3-0.4wt%, etc., but the present invention is not limited thereto.

[0017] Specifically, in the aqueous solution containing the amine monomer, the concentration of the amine monomer may be 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, etc., or an interval range formed by any of the above values, such as 0.2-0.5wt%, 0.3-0.6wt%, 0.3-0.7wt%, etc., but the present invention is not limited thereto.

[0018] Preferably, the resveratrol solution has a resveratrol concentration of 0.3-1.0 wt %. Under these preferred conditions, the prepared polyamide nanofiltration membrane has a better water flux.

[0019] Preferably, the resveratrol solution has a resveratrol concentration of 0.3-0.5 wt %, and the aqueous solution containing the amine monomer has an amine monomer concentration of 0.5-0.7 wt %. Under these preferred conditions, the resulting polyamide nanofiltration membrane exhibits superior water flux and divalent salt rejection, as well as superior selectivity for monovalent and divalent ion salts.

[0020] Preferably, the concentration of the acyl chloride monomer in the organic phase solution is 0.01-0.1 wt %. More specifically, the concentration of the acyl chloride monomer in the organic phase solution may be 0.02 wt %, 0.03 wt %, 0.04 wt %, 0.05 wt %, 0.06 wt %, 0.07 wt %, 0.08 wt %, 0.09 wt %, or an interval formed by any of the above values, such as 0.02-0.05 wt %, 0.03-0.06 wt %, 0.03-0.08 wt %, etc., but the present invention is not limited thereto.

[0021] Preferably, the amine monomer is selected from at least one of piperazine, m-phenylenediamine, ethylenediamine, and polyethyleneimine. Further preferably, the amine monomer is selected from piperazine.

[0022] Specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600-750000 Da. Specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600-10000 Da; Specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600-1000 Da.

[0023] Preferably, the acyl chloride monomer is selected from at least one of trimesoyl chloride, terephthaloyl chloride, and isophthaloyl chloride. Further preferably, the acyl chloride monomer is selected from trimesoyl chloride.

[0024] Preferably, the basement membrane is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polyvinyl chloride, or polytetrafluoroethylene. Further preferably, the basement membrane is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, or polyacrylonitrile. In this preferred embodiment, resveratrol has better hydrogen bonding or hydrophobic interaction with the basement membrane, thereby enabling better adsorption on the basement membrane.

[0025] Preferably, in step S1, the standing time is 1-10 minutes, and further preferably, the standing time is 3-6 minutes.

[0026] Preferably, the specific operation of step S2 is: mixing the base membrane treated in step S1 with an aqueous solution containing an amine monomer, allowing it to stand, and removing excess aqueous solution; mixing the base membrane from which the excess aqueous solution has been removed with an organic solution containing an acyl chloride monomer, allowing it to stand, and heating to promote cross-linking to prepare a polyamide nanofiltration membrane.

[0027] Preferably, the base film and the aqueous solution containing amine monomers are allowed to stand for 1-10 minutes after being mixed. Further preferably, the base film and the aqueous solution containing amine monomers are allowed to stand for 3-6 minutes after being mixed.

[0028] Preferably, the base film and the organic phase solution containing the acyl chloride monomer are allowed to stand for 30-60 seconds after being mixed.

[0029] Specifically, in some embodiments, the heating to promote cross-linking is heating at 50-60° C. More specifically, the heating time is 5-15 minutes.

[0030] Specifically, the basement membrane has a pore size of 15-25 kDa.

[0031] Furthermore, the present invention seeks to protect the polyamide nanofiltration membrane based on the resveratrol intermediate layer obtained by the above preparation method.

[0032] The polyamide nanofiltration membrane provided by the present invention comprises a three-layer structure, namely a base membrane, a resveratrol intermediate layer and a polyamide active layer.

[0033] Preferably, the water contact angle of the polyamide nanofiltration membrane is 30-45°.

[0034] Preferably, the thickness of the polyamide active layer is 30-50 nm.

[0035] Furthermore, the present invention seeks to protect the use of a polyamide nanofiltration membrane based on a resveratrol intermediate layer in wastewater and sewage treatment.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention provides a method for preparing a polyamide nanofiltration membrane based on a resveratrol intermediate layer. Resveratrol effectively slows down the diffusion rate of amine monomers through hydrogen bonds and π-π interactions, thereby precisely controlling the formation of a polyamide active layer. The resulting polyamide nanofiltration membrane has excellent water flux, divalent salt rejection rate, and anti-fouling properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The atomic force microscope (AFM) and transmission electron microscope (TEM) images of the conventional polyamide control nanofiltration membrane (C-TFC) and the resveratrol intermediate layer nanofiltration membrane (Res-TFC) prepared in Comparative Example 1 and Example 1 are shown. Figure 1 (a) and (b) are AFM and TEM images of the C-TFC membrane prepared in Comparative Example 1, respectively; Figure 1 (c) and (d) are AFM and TEM images of the C-TFC membrane prepared in Example 1, respectively.

[0039] Figure 2 The water contact angles of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1.

[0040] Figure 3 Surface Zeta potential of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1.

[0041] Figure 4 Schematic diagram of pure water flux and sodium sulfate rejection of the C-TFC membrane and Res-TFC prepared in Comparative Example 1 and Example 1.

[0042] Figure 5 The test results of the C-TFC membrane, Res-TFC membrane and commercial NF270 membrane prepared in Comparative Example 1 and Example 1 for treating simulated organic pollutant wastewater are shown. Figure 5 (a) shows the normalized flux test results of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane in treating simulated bovine serum albumin wastewater; Figure 5 (b) shows the normalized flux test results of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane in treating simulated sodium alginate wastewater; Figure 5 (c) shows the normalized flux test results of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane in treating simulated humic acid wastewater; Figure 5 (d) is a comparative analysis of the flux decay rate (FDR) and flux recovery rate (FRR) of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane in the treatment of simulated bovine serum albumin wastewater test; Figure 5 (e) is a comparative analysis of the flux decay rate (FDR) and flux recovery rate (FRR) of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane in the treatment of simulated sodium alginate wastewater; Figure 5 (f) is a comparative analysis of the flux decay rate (FDR) and flux recovery rate (FRR) in the treatment of simulated humic acid wastewater by C-TFC membrane, Res-TFC membrane and commercial NF270 membrane.

[0043] Figure 6 Anti-fouling test results of the Res-TFC membrane prepared in Example 1 and the commercial NF270 membrane when treating actual wastewater. Figure 6 (a) shows the normalized anti-fouling flux test results of Res-TFC membrane and commercial NF270 membrane when treating actual wastewater; Figure 6 (b) is a comparative analysis of the flux decay rate (FDR) and flux recovery rate (FRR) of Res-TFC membrane and commercial NF270 membrane when treating actual wastewater. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0045] Atomic force microscopy (AFM, Dimension Fastscan, Bruker, USA) was used to observe membrane surface roughness. Transmission electron microscopy (TEM, JEOL JEM2100, Japan) was used to examine the cross-sectional morphology of the membranes and the thickness of the polyamide active layer. A contact angle goniometer (DSA25E, KRÜSS, Germany) was used to evaluate the hydrophilicity and wettability of the various membranes. A motorized solid surface analyzer (SurPASS™ 3, Anton Paar, Austria) was used to measure the zeta potential of the membrane surfaces.

[0046] Example 1 Preparation of polyamide nanofiltration membrane based on resveratrol intermediate layer

[0047] Step (1): Preparation of resveratrol (Res) intermediate layer composite substrate

[0048] 1. Prepare Res aqueous solution: Dissolve Res in deionized water to prepare a 0.5 wt% Res aqueous solution, and adjust the pH of the solution to 11 with 10 wt% NaOH to ensure that Res is completely dissolved.

[0049] 2. Substrate Treatment: Before the experiment, a polysulfone (PSF) ultrafiltration membrane (pore size 20 kDa, produced by Zhongke Ruiyang Membrane Technology (Beijing) Co., Ltd.) was pretreated. The PSF ultrafiltration membrane, which had been stored in a 1.0 wt% sodium bisulfite solution at 4°C, was removed from a refrigerator. Residual sodium bisulfite on the membrane surface was rinsed with deionized water. The membrane surface was then rinsed with anhydrous ethanol to remove the pore-retaining agent. The membrane was then rinsed with deionized water to remove residual ethanol. Finally, the membrane was immersed in deionized water for subsequent use.

[0050] 3. Preparation of Res intermediate layer composite substrate: Fix the prepared PSF ultrafiltration substrate to ensure that the top surface of the substrate is exposed. Pour 20 mL of Res aqueous solution evenly on the surface of the PSF substrate and let it stand for 5 minutes to allow Res to be fully adsorbed on the substrate surface.

[0051] 4. Draining and air knife treatment: After draining the Res solution, use an air knife to blow the substrate surface to further remove the residual solution to obtain a composite substrate with a Res intermediate layer.

[0052] Step (2): Preparation of polyamide (PA) active layer by in situ interfacial polymerization (IP)

[0053] 1. Aqueous Monomer Treatment: Prepare a 0.5 wt% piperazine (PIP) aqueous solution. Pour 20 mL of the PIP solution evenly onto the surface of the Res interlayer composite substrate prepared in step (1). Allow to stand for 3 minutes to allow the PIP to fully adsorb onto the Res interlayer surface. Drain the PIP solution and remove any remaining solution using an air knife.

[0054] 2. Organic Monomer Reaction: Pour 20 mL of a 0.05 wt% solution of trimesoyl chloride (TMC) in n-hexane evenly onto the membrane surface for 30 seconds to allow interfacial polymerization between the PIP and TMC, forming a polyamide (PA) active layer on the Res intermediate layer. Subsequently, rinse the membrane surface with n-hexane for 5 seconds to remove unreacted TMC.

[0055] 3. Curing: The prepared membrane was placed in a 60°C oven for 10 minutes to promote cross-linking of the polyamide network to obtain a polyamide nanofiltration membrane (labeled as Res-TFC membrane). The cured membrane was stored in deionized water at 4°C until use.

[0056] Example 2-4 Preparation of polyamide nanofiltration membrane based on resveratrol intermediate layer

[0057] The difference between Examples 2-4 and Example 1 is that in step (1), Res aqueous solutions with concentrations of 0.1 wt%, 0.3 wt%, and 0.7 wt% are prepared.

[0058] Example 5-6 Preparation of polyamide nanofiltration membrane based on resveratrol intermediate layer

[0059] The difference between Examples 5-6 and Example 1 is that in step (2), piperazine aqueous solutions with concentrations of 0.3 wt% and 0.7 wt% are prepared.

[0060] Comparative Example 1

[0061] The difference between Comparative Example 1 and Example 1 is that the preparation of the Res intermediate layer in step (1) is omitted, and after the PSF ultrafiltration membrane substrate is treated, the in-situ interfacial polymerization in step (2) is performed to prepare a polyamide nanofiltration membrane (labeled as C-TFC membrane).

[0062] Comparative Example 2

[0063] The difference between Comparative Example 2 and Example 1 is that in step (2), a piperazine aqueous solution with a concentration of 0.1 wt % is prepared.

[0064] Test Example 1 Characterization of polyamide nanofiltration membrane

[0065] Figure 1Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1, respectively, were obtained. Membrane roughness and cross-sectional characterization using AFM and TEM, respectively, revealed that the C-TFC membrane had a roughness (Ra) of 4.90±0.25 nm and a PA active layer thickness of 48.0±1.9 nm, while the Res-TFC membrane had a reduced roughness of 3.92±0.05 nm and a PA active layer thickness of 31.3±1.2 nm. These differences arise because the Res interlayer hinders the diffusion of PIP to the water / organic interface, reducing the local monomer concentration and slowing the PIP-TMC reaction, thereby limiting the growth of the PA active layer and resulting in a thinner and more uniform PA active layer.

[0066] Figure 2 The water contact angles of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1 are shown. The contact angle of the C-TFC membrane is 43.3°, and the contact angle of the Res-TFC membrane is 36.0°. During the IP reaction, hydrogen bonding and π-π stacking between Res and PIP reduce the aqueous diffusion rate of PIP, resulting in insufficient PIP supply at the interface. Consequently, a relatively excessive amount of TMC increases the number of unreacted acyl chloride groups in the PA active layer. These groups are then hydrolyzed to form carboxylic acids as end-capping moieties. Consequently, excess TMC terminates chain growth and reduces crosslinking, promoting the formation of hydrophilic soft segments and carboxylic acid groups, resulting in increased hydrophilicity of the Res-TFC membrane.

[0067] Figure 3 is the Zeta potential of the C-TFC and Res-TFC membranes prepared in Comparative Example 1 and Example 1. Figure 3 It can be seen that the surface of the Res-TFC membrane exhibits a stronger negative charge. The reason is that the addition of Res slows down the diffusion of PIP, which further leads to a relative excess of TMC, thereby increasing the carboxylic acid groups on the surface of the Res-TFC membrane and enhancing the negative charge on the surface of the Res-TFC membrane.

[0068] Test Example 2 Separation Performance Test of Polyamide Nanofiltration Membrane

[0069] (1) Test method:

[0070] The separation performance of the polyamide nanofiltration membranes prepared in the Examples and Comparative Examples was evaluated using a cross-flow filtration device (CF016D, Sterlitech, USA) with an effective filtration area of ​​16 square centimeters. To achieve stable membrane performance, the polyamide nanofiltration membranes were first compacted at a pressure of 5 bar for 30 minutes. Separation performance measurements were then performed at a pressure of 5 bar. Unless otherwise specified, the cross-flow velocity and feed solution temperature were maintained at 0.1 m / s and 25°C, respectively. Pure water flux (PWP) was calculated according to formula (1).

[0071] (1)

[0072] Where V (L) is the volume of the permeate, A (m 2 ) is the effective filtration area of ​​the membrane, Δt (h) is the permeate collection interval, and Δp (bar) represents the applied pressure.

[0073] The single salt retention capacity of the membrane was evaluated using 1000 mg / L Na2SO4 and NaCl inorganic salt solutions as feed solutions. The retention rates R for different salts were calculated according to formula (2).

[0074] (2)

[0075] Among them, C p and C f Represents the concentration of salt or neutral solute in the permeate and feed solution, respectively.

[0076] The selectivity of different polyamide nanofiltration membranes for monovalent and divalent ions (αNaCl / Na2SO4) was calculated according to formula (3).

[0077] (3)

[0078] in, and They represent the retention rates of NaCl and Na2SO4 salt solutions respectively. The test results are shown in Table 1.

[0079] Table 1

[0080]

[0081] As can be seen from the data in Table 1 above, the polyamide nanofiltration membrane based on the resveratrol intermediate layer provided by the present invention has excellent water flux and divalent salt rejection rate. The water flux of the polyamide nanofiltration membrane is ≥11.2 L m -2 h -1 bar -1 , Na2SO4 retention rate ≥95.2%.

[0082] More preferably, when the resveratrol concentration is 0.3-1.0 wt%, the polyamide nanofiltration membrane has even better water flux and Na2SO4 rejection. More preferably, when the resveratrol concentration is 0.3-0.5 wt%, and the amine monomer concentration is 0.5-0.7 wt%, the polyamide nanofiltration membrane has even better water flux and Na2SO4 rejection. Furthermore, the membrane has excellent monovalent / divalent salt selectivity, with a monovalent / divalent salt selectivity of ≥67.9.

[0083] Figure 4 The pure water flux and sodium sulfate rejection of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1 are shown in FIG. Figure 4 The results show that the water flux of C-TFC membrane is 4.7±0.7 L m -2 h -1 bar -1 With the increase of Res addition, the water flux of the modified Res-TFC membrane increased significantly from 11.2 ± 0.8 L m -2 h -1 bar -1 Increased to 21.7 ± 0.7 L m -2 h - 1 bar -1 In terms of sodium sulfate rejection, the C-TFC membrane has a rejection rate of 98.2%. After adding 0.1 wt% Res, the sodium sulfate rejection rate increased to 99.3%. However, when the Res addition amount was further increased to 0.7 wt%, the sodium sulfate rejection rate dropped to 95.2%.

[0084] The addition of Res induces a dual change in the membrane structure, affecting both water flux and sodium sulfate retention. On the one hand, the addition of Res reduces membrane thickness and cross-linking, facilitating rapid water transport and significantly improving water flux. On the other hand, while reduced cross-linking may reduce the membrane's physical barrier capacity, the addition of Res significantly enhances the negative surface charge of the membrane. The salt retention performance of nanofiltration membranes primarily relies on the Donnan effect and steric hindrance. The enhanced negative surface charge more effectively repels negatively charged divalent ions (such as sulfate), offsetting the adverse effects of reduced cross-linking. This negative surface charge ensures that the Res-TFC membrane maintains a high sodium sulfate retention rate even with reduced cross-linking. However, when the Res addition level is too high, the excess Res excessively restricts the diffusion of PIP, significantly reducing the membrane's cross-linking degree and further expanding the membrane pore size, leading to a loss of membrane structural uniformity. Such structural defects weaken the steric hindrance effect of the membrane, allowing more sulfate ions to penetrate the membrane, resulting in a decrease in the sodium sulfate retention rate to 95.2%.

[0085] Test Example 3 Anti-fouling performance test of polyamide nanofiltration membrane

[0086] (1) Test method:

[0087] The antifouling properties of the prepared polyamide nanofiltration membrane and a commercial NF 270 nanofiltration membrane were investigated using the aforementioned cross-flow device. The feed solution contained inorganic salts consisting of 0.5 mM NaHCO₃, 0.93 mM NH₄Cl, 0.5 mM CaCl₂, 0.61 mM MgSO₄, 9.2 mM NaCl, and 0.45 mM KH₂PO₄ (pH = 7.40 ± 0.02). Furthermore, bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA) were selected as simulated organic pollutants for membrane antifouling testing. These represent model organic pollutants such as proteins, polysaccharides, and humic substances, respectively. During the antifouling experiments, 100 mg / L of the model organic pollutants was added to the inorganic salt solution to form an organic-inorganic composite pollutant.

[0088] The initial water flow rate of each anti-pollution experiment was kept at 30 L·m -2 ·h -1 The specific test consists of four steps: compaction, adjustment, contamination, and cleaning. First, deionized water was used to compact the polyamide nanofiltration membrane at a pressure of 5 bar until the flux stabilized (about 1 hour). Then, a sodium chloride solution with the same ionic strength as the simulated wastewater was used as the feed solution, and the operating pressure was adjusted so that the membrane permeation flux after the system stabilized was 30 L·m -2 ·h -1, maintain stable operation for 1 hour, and record the permeation flux at this time as the baseline flux ( J 0).

[0089] Next, 1L of the above synthetic wastewater was used as the feed solution to evaluate the membrane's anti-fouling ability at the same pressure. The membrane fouling experiment was carried out continuously for 10 hours, and the data recording system recorded the permeate flux ( J t The cross flow velocity of the feed solution was maintained at 0.1 m·s -1 The feed solution temperature was maintained at 25.0±2.0℃ using a circulating cooling system. After the membrane fouling test, the fouled membrane was thoroughly rinsed with deionized water for 30 minutes, and the cross-flow velocity was increased to 0.24 m·s -1 Finally, the baseline flux was re-tested using a sodium chloride solution without contaminants ( J l The simulated wastewater membrane fouling test was conducted for two cycles. The flux decay rate (FDR) was calculated according to formula (4), and the flux recovery rate (FRR) was calculated according to formula (5).

[0090] (4)

[0091] (5)

[0092] In addition, anti-fouling experiments were conducted on the prepared polyamide nanofiltration membrane and NF 270 nanofiltration membrane using actual industrial wastewater. Similar to the above process, before each experiment, the membrane was compacted with deionized water. Then, a sodium chloride solution with the same ionic strength as the actual wastewater was used as the feed solution. The operating pressure was adjusted until the flux was stable at 50±2 L·m -2 ·h -1 , record the permeation flux at this time as the baseline flux ( J 0). Then, 1.5 L of actual wastewater was used as the feed solution to evaluate the membrane's anti-fouling ability at the same pressure. The permeate flux was recorded using a data recording system ( J t ) until 750 mL of permeate was collected. The cleaning process, cross-flow rate, and feed temperature remained the same as described above. The actual wastewater membrane fouling experiment was repeated three times.

[0093] (2) Test results

[0094] Figure 5Figure 1 shows the simulated wastewater test results for the C-TFC membrane, Res-TFC membrane, and commercial NF270 membrane prepared in Comparative Example 1 and Example 1. Across all fouling experiments, the Res-TFC membrane exhibited the most gradual flux decline, with the lowest FDR and highest FRR. For example, in the BSA fouling test, the Res-TFC membrane achieved an FDR of only 7.4% after two fouling cycles, significantly lower than that of the C-TFC membrane (51.1%) and the NF270 membrane (27.6%). After pure water cleaning, the Res-TFC membrane exhibited significantly better flux recovery than the other two membranes, indicating that its fouling layer is easily removed by physical cleaning. Under SA and HA fouling conditions, the Res-TFC membrane also achieved significantly better FDR and FRR than the C-TFC membrane and NF270 membrane, further demonstrating its enhanced anti-fouling capabilities.

[0095] The excellent antifouling performance of the Res-TFC membrane can be explained from the following aspects: (1) Strong hydrophilicity and relatively smooth surface: The more hydrophilic surface of the Res-TFC membrane promotes the formation of a more uniform and dense hydration layer on the surface, effectively isolating the foulants from direct contact with the membrane. In addition, its relatively smooth surface can reduce the adhesion and deposition of foulants, while the rougher surface tends to trap the foulants in its grooves. Therefore, the Res-TFC membrane with excellent hydrophilicity and relatively low root mean square roughness minimizes the formation of a dense fouling layer and protects the membrane from fouling deposition and clogging. (2) Strong surface negative charge: Under neutral pH conditions, BSA, SA and HA carry a negative charge. The increased negative charge strength on the surface of the Res-TFC membrane enhances the electrostatic repulsion between these negatively charged foulants and the membrane surface, reducing their adsorption and deposition, thereby delaying the flux decline. In contrast, C-TFC membrane and NF270 membrane have lower hydrophilicity and weaker negative charge strength, which easily form local concentration areas, which promotes the rapid accumulation of fouling and the formation of thicker fouling layers. (3) Low calcium ion retention: Compared with C-TFC membrane and NF270 membrane, Res-TFC membrane exhibits lower calcium ion retention, which can reduce the accumulation of calcium on the membrane surface and alleviate the "calcium bridge" effect, further slowing the formation rate of the fouling layer.

[0096] Figure 6 The actual wastewater anti-fouling test results of the Res-TFC membrane prepared in Example 1 and the commercial NF270 membrane. Figure 6During three consecutive fouling cleaning cycles of actual MBR effluent, the Res-TFC membrane outperformed the NF270 membrane in both flux decline and permeate recovery. After three cycles, the Res-TFC membrane maintained a low FDR of 42.7% while achieving a high FRR of 86.4% with hydraulic cleaning. In comparison, the NF270 membrane exhibited a FDR of 69.5% and a FRR of only 46.1%, indicating more severe fouling and poorer flux recovery. These findings demonstrate that the Res-TFC membrane not only maintains a high permeate flux during long-term operation but also more effectively removes membrane surface fouling with conventional hydraulic cleaning. These findings confirm the strong competitiveness and broad application potential of the Res-TFC membrane in real-world wastewater treatment scenarios.

[0097] The foregoing examples are merely illustrative, serving to illustrate some of the features of the method of the present invention. The appended claims are intended to claim the widest possible scope that can be envisioned, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the present invention. Some numerical ranges used in the claims also include subranges therein, and variations in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method for preparing a polyamide nanofiltration membrane based on a resveratrol intermediate layer, characterized in that: The steps include: S1. The resveratrol solution is brought into contact with the surface of the basement membrane and allowed to stand to form a resveratrol intermediate layer on the surface of the basement membrane; S2. Interfacial polymerization of an aqueous solution containing an amine monomer and an organic solution containing an acyl chloride monomer on the resveratrol intermediate layer and curing to prepare a polyamide nanofiltration membrane; In the resveratrol solution, the concentration of resveratrol is 0.1-2.0wt%; In the aqueous solution containing the amine monomer, the concentration of the amine monomer is 0.3-2.0 wt %.

2. The preparation method according to claim 1, characterized in that In the resveratrol solution, the concentration of resveratrol is 0.3-1.0 wt %.

3. The preparation method according to claim 2, characterized in that In the resveratrol solution, the concentration of resveratrol is 0.3-0.5 wt %; in the aqueous solution containing the amine monomer, the concentration of the amine monomer is 0.5-0.7 wt %.

4. The preparation method according to claim 1, characterized in that In the organic phase solution, the concentration of the acyl chloride monomer is 0.01-0.1 wt %.

5. The preparation method according to claim 1, characterized in that: The amine monomer is selected from at least one of piperazine, m-phenylenediamine, ethylenediamine, and polyethyleneimine.

6. The preparation method according to claim 1, characterized in that: The acyl chloride monomer is selected from at least one of trimesoyl chloride, terephthaloyl chloride and isophthaloyl chloride.

7. The preparation method according to claim 1, characterized in that: The base film is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polyvinyl chloride or polytetrafluoroethylene.

8. The preparation method according to claim 1, characterized in that: The specific operations of step S2 are: The base membrane treated in step S1 is mixed with an aqueous solution containing an amine monomer, allowed to stand, and excess aqueous solution is removed; the base membrane from which excess aqueous solution has been removed is mixed with an organic solution containing an acyl chloride monomer, allowed to stand, and heated to promote cross-linking to prepare a polyamide nanofiltration membrane.

9. A polyamide nanofiltration membrane based on a resveratrol intermediate layer obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the polyamide nanofiltration membrane based on the resveratrol intermediate layer according to claim 9 in wastewater and sewage treatment.

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