Polyamide nanofiltration membrane based on resveratrol middle layer as well as preparation method and application of polyamide nanofiltration membrane

Abstract

The invention relates to the technical field of sewage and wastewater treatment. More specifically, the invention discloses a polyamide nanofiltration membrane based on a resveratrol middle layer for sewage and wastewater treatment and resource utilization as well as a preparation method and application of the polyamide nanofiltration membrane. The preparation method comprises the following steps: S1, contacting a resveratrol solution with the surface of a base membrane, standing, and preparing a resveratrol intermediate layer on the surface of the base membrane; s2, carrying out interfacial polymerization on a water-phase solution containing an amine monomer and an organic-phase solution containing an acyl chloride monomer on the resveratrol intermediate layer to prepare a polyamide nanofiltration membrane; the concentration of the resveratrol is 0.1 to 2.0 weight percent; and the concentration of the amine monomer is 0.3-2.0 wt%. The polyamide nanofiltration membrane has excellent water flux, bivalent salt rejection rate and anti-pollution performance, has wide application prospects, and can be applied to devices such as sewage treatment equipment, seawater desalination equipment, industrial wastewater treatment and recycling equipment and the like.

Description

Technical Field

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

[0002] Rational utilization and protection of water resources is an important and arduous task. The average molecular weight cut-off (MWCO) of nanofiltration membranes is 200 - 1000 Da, which is between reverse osmosis (RO) and ultrafiltration (UF) membranes, and the surface is usually negatively charged, capable of effectively separating divalent / monovalent inorganic salts, and has broad application prospects in the fields of seawater desalination, high-salt wastewater treatment and resource recovery, sewage treatment and drinking water purification. At present, existing commercial nanofiltration membranes are mainly thin-film composite membranes (TFCs) prepared by the interfacial polymerization method, that is, an aqueous amine monomer and an organic phase acyl chloride monomer generate a polyamide selective layer on the surface of an ultrafiltration or microfiltration substrate membrane through an interfacial polymerization process. Due to the rapid and difficult-to-control interfacial polymerization reaction, the prepared polyamide nanofiltration membranes often face the "trade-off" effect that permeability and selectivity cannot be improved simultaneously. In addition, the surface of polyamide nanofiltration membranes is easily affected by the deposition of composite pollutants such as proteins, polysaccharides, humic acids, and inorganic salts, leading to serious membrane fouling problems, which severely restrict their actual application performance and lifespan.

[0003] The literature "Polyphenol Coating as an Interlayer for Thin-Film Composite Membranes with Enhanced Nanofltration Performance, Xi Zhang, ACS Applied Materials & Interfaces, DOI: 10.1021 / acsami.6b10693" discloses that on a polysulfone ultrafiltration substrate, a polyphenol interlayer is formed by the co-deposition of tannic acid (TA) and diethylenetriamine (DETA), and then an interfacial polymerization reaction is carried out to construct a polyamide selective layer, thereby preparing a TFC nanofiltration membrane with enhanced nanofiltration performance. However, due to the ortho-phenolic hydroxyl groups of tannic acid being extremely easy to oxidize into benzoquinones, through Michael addition or Schiff base reaction and polymerization with amine monomers, when using it as an interlayer, it is easy to participate in the synthesis of the polyamide layer, resulting in the water flux of the finally obtained TFC nanofiltration membrane being much smaller than that of commercial membranes. The water permeation flux of the TFC nanofiltration membrane synthesized by the above method is 10.5 L·m -2 ·h -1 ·bar -1 , which is difficult to meet the requirements.

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

[0005] In view of the above-mentioned existing technical problems, the primary object 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) rejection rate, and anti-fouling 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 prepared by the above-mentioned 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 objects, the present invention is realized by the following technical solutions: A method for preparing a polyamide nanofiltration membrane based on a resveratrol intermediate layer, comprising the following steps: S1. The resveratrol solution is brought into contact with the surface of the substrate membrane and allowed to stand to prepare a resveratrol intermediate layer on the surface of the substrate membrane; S2. An aqueous solution containing an amine monomer and an organic solution containing an acyl chloride monomer are subjected to interfacial polymerization on the resveratrol intermediate layer and cured to prepare a polyamide nanofiltration membrane; In the resveratrol solution, the concentration of resveratrol is 0.1-2.0 wt%; In the aqueous solution containing an amine monomer, the concentration of the amine monomer is 0.3-2.0 wt%.

[0009] The present invention innovatively proposes to regulate the interfacial polymerization reaction by introducing resveratrol as a functional intermediate layer. Resveratrol molecules bind to the substrate membrane through their unique molecular configuration (rich in phenolic hydroxyl groups and benzene rings), and effectively delay the diffusion rate of amine monomers through hydrogen bonding and π-π interactions, thereby precisely controlling the formation of the polyamide active layer, and finally obtaining an ultrathin and low cross-linking degree polyamide active layer. In addition, the resveratrol intermediate layer endows the polyamide nanofiltration membrane with excellent organic-inorganic composite anti-fouling ability by synergistically enhancing the hydrophilicity of the membrane surface, strengthening the negative charge of the membrane surface, and improving the calcium ion permeability.

[0010] The inventors have found through research that the concentration of resveratrol and the concentration of amine monomers in the aqueous solution have a great influence on the water flux and divalent salt rejection rate of the polyamide nanofiltration membrane. Only when resveratrol and amine monomers are within the above ranges, the prepared polyamide nanofiltration membrane has excellent water flux, divalent salt rejection rate, and anti-fouling performance. The preparation method provided by the present invention has mild conditions, and the raw material resveratrol is a natural plant extract, which is green and environmentally friendly. The method can prepare an ultrathin, highly hydrophilic and strongly negatively charged polyamide nanofiltration membrane under mild conditions.

[0011] Specifically, in the resveratrol solution, the concentration of resveratrol can be 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, etc., or an interval range formed by any of the above values, such as 0.2 - 0.5 wt%, 0.3 - 0.6 wt%, 0.3 - 0.4 wt%, etc. The present invention is not limited thereto.

[0012] Specifically, in the aqueous solution containing the amine monomer, the concentration of the amine monomer can be 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, etc., or an interval range formed by any of the above values, such as 0.2 - 0.5 wt%, 0.3 - 0.6 wt%, 0.3 - 0.7 wt%, etc. The present invention is not limited thereto.

[0013] Preferably, in the resveratrol solution, the concentration of resveratrol is 0.3 - 1.0 wt%. Under this preferred condition, the prepared polyamide nanofiltration membrane has more excellent water flux.

[0014] Preferably, 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%. Under this preferred condition, the prepared polyamide nanofiltration membrane has more excellent water flux and divalent salt rejection rate; in addition, it also has more excellent selectivity for monovalent and divalent ion salts.

[0015] Preferably, in the organic phase solution, the concentration of the acyl chloride monomer is 0.01 - 0.1 wt%. More specifically, in the organic phase solution, the concentration of the acyl chloride monomer can 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%, etc., or an interval range 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. The present invention is not limited thereto.

[0016] 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.

[0017] Specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600 - 750,000 Da. Specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600 - 10,000 Da; specifically, in some embodiments, the molecular weight of the polyethyleneimine is 600 - 1,000 Da.

[0018] Preferably, the acyl chloride monomer is selected from at least one of trimesoyl chloride, terephthaloyl chloride, and isophthaloyl chloride. More preferably, the acyl chloride monomer is selected from trimesoyl chloride.

[0019] Preferably, the base membrane is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polyvinyl chloride, or polytetrafluoroethylene. More preferably, the base membrane is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, or polyacrylonitrile. Under this preference, resveratrol has a better hydrogen bond or hydrophobic interaction with the base membrane, and thus can be better adsorbed on the base membrane.

[0020] Preferably, in step S1, the standing time is 1 - 10 min. More preferably, the standing time is 3 - 6 min.

[0021] Preferably, the specific operation of step S2 is as follows: the base membrane treated in step S1 is mixed with an aqueous solution containing an amine monomer, left standing, and the excess aqueous solution is removed; the base membrane from which the excess aqueous solution has been removed is mixed with an organic solution containing an acyl chloride monomer, left standing, and heating is carried out to promote crosslinking to prepare a polyamide nanofiltration membrane.

[0022] Preferably, the standing time after the base membrane is mixed with the aqueous solution containing the amine monomer is 1 - 10 min. More preferably, the standing time after the base membrane is mixed with the aqueous solution containing the amine monomer is 3 - 6 min.

[0023] Preferably, the standing time after the base membrane is mixed with the organic solution containing the acyl chloride monomer is 30 - 60 s.

[0024] Specifically, in some embodiments, the heating to promote crosslinking is carried out at 50 - 60 °C. More specifically, the heating time is 5 - 15 min.

[0025] Specifically, the membrane pore size of the base membrane is 15 - 25 kDa.

[0026] Furthermore, the present invention claims the polyamide nanofiltration membrane based on the resveratrol intermediate layer prepared by the above preparation method.

[0027] The polyamide nanofiltration membrane provided by the present invention includes a three - layer structure, namely a base membrane, a resveratrol intermediate layer, and a polyamide active layer.

[0028] Preferably, the water contact angle of the polyamide nanofiltration membrane is 30 - 45°.

[0029] Preferably, the thickness of the polyamide active layer is 30 - 50 nm.

[0030] Furthermore, the present invention claims the application of a polyamide nanofiltration membrane based on a resveratrol interlayer in wastewater and sewage treatment.

[0031] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a preparation method of a polyamide nanofiltration membrane based on a resveratrol interlayer. Resveratrol effectively delays the diffusion rate of amine monomers through hydrogen bonding and π-π interactions, thereby precisely controlling the formation of the polyamide active layer. Finally, the prepared polyamide nanofiltration membrane has excellent water flux, divalent salt rejection rate, and anti-fouling performance. Description of the Drawings

[0032] Figure 1 Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of the traditional polyamide control nanofiltration (C-TFC) membranes and resveratrol interlayer-based nanofiltration (Res-TFC) membranes prepared in Comparative Example 1 and Example 1. Among them, Figure 1 (a) and (b) in are the AFM and TEM images of the C-TFC membrane prepared in Comparative Example 1; Figure 1 (c) and (d) in are the AFM and TEM images of the C-TFC membrane prepared in Example 1.

[0033] Figure 2 Water contact angles of the C-TFC membranes and Res-TFC membranes prepared in Comparative Example 1 and Example 1.

[0034] Figure 3 Surface Zeta potentials of the C-TFC membranes and Res-TFC membranes prepared in Comparative Example 1 and Example 1.

[0035] Figure 4 Schematic diagrams of the pure water fluxes and sodium sulfate rejection rates of the C-TFC membranes and Res-TFC membranes prepared in Comparative Example 1 and Example 1.

[0036] Figure 5 Test results of the C-TFC membranes, Res-TFC membranes, and commercial NF270 membrane for treating simulated organic pollutant wastewater prepared in Comparative Example 1 and Example 1. Among them, Figure 5 In (a) are the normalized flux test results of the C-TFC membrane, Res-TFC membrane, and commercial NF270 membrane for treating simulated bovine serum albumin sewage; Figure 5Among them, (b) shows the normalized flux test results of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane for treating simulated sodium alginate sewage; Figure 5 Among them, (c) shows the normalized flux test results of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane for treating simulated humic acid sewage; Figure 5 Among them, (d) shows the comparative analysis of flux decay rate (FDR) and flux recovery rate (FRR) in the test of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane for treating simulated bovine serum albumin sewage; Figure 5 Among them, (e) shows the comparative analysis of flux decay rate (FDR) and flux recovery rate (FRR) in the test of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane for treating simulated sodium alginate sewage; Figure 5 Among them, (f) shows the comparative analysis of flux decay rate (FDR) and flux recovery rate (FRR) in the test of C-TFC membrane, Res-TFC membrane and commercial NF270 membrane for treating simulated humic acid sewage.

[0037] Figure 6 It is the anti-fouling test results of the Res-TFC membrane prepared in Example 1 and the commercial NF270 membrane when treating actual wastewater. Figure 6 Among them, (a) shows the normalized flux test results of anti-fouling of the Res-TFC membrane and the commercial NF270 membrane when treating actual wastewater; Figure 6 Among them, (b) shows the comparative analysis of flux decay rate (FDR) and flux recovery rate (FRR) of the Res-TFC membrane and the commercial NF270 membrane when treating actual wastewater. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0039] Atomic force microscope (AFM, Dimension Fastscan, Bruker Corporation, USA) was used to observe the surface roughness of the membrane. Transmission electron microscope (TEM, JEOL JEM2100, Japan) was used to observe the cross-sectional morphology of the membrane and the thickness of the polyamide active layer. Contact angle goniometer (DSA25E, KRÜSS, Germany) was used to evaluate the hydrophilicity and wettability of different membranes. Electrokinetic solid surface analyzer (SurPASSTM 3, Anton Paar, Austria) was used to measure the zeta potential value of the membrane surface.

[0040] Example 1 Preparation of polyamide nanofiltration membrane based on resveratrol interlayer Step (1): Preparation of resveratrol (Res) intermediate layer composite substrate 1. Prepare Res aqueous solution: Dissolve Res in deionized water to prepare a Res aqueous solution with a concentration of 0.5 wt%, and adjust the pH of the solution to 11 using 10 wt% NaOH to ensure complete dissolution of Res.

[0041] 2. Substrate treatment: The polysulfone (PSF) ultrafiltration membrane (membrane pore size is 20 kDa, Zhongke Ruiyang Membrane Technology (Beijing) Co., Ltd.) needs to be pretreated before the experiment. Take out the PSF ultrafiltration membrane stored in a 1.0 wt% sodium bisulfite solution from the 4°C refrigerator, rinse the residual sodium bisulfite on the membrane surface with deionized water, then rinse the surface of the PSF ultrafiltration membrane with absolute ethanol to remove the pore-forming agent on the membrane, and rinse with deionized water to remove the residual ethanol. Finally, soak the membrane in deionized water for subsequent use.

[0042] 3. Preparation of Res intermediate layer composite substrate: Fix the prepared PSF ultrafiltration substrate to ensure that only the top surface of the substrate is exposed. Pour 20 mL of the Res aqueous solution evenly onto the surface of the PSF substrate and let it stand for 5 min to allow Res to fully adsorb on the substrate surface.

[0043] 4. Drainage and air knife treatment: After draining the Res solution, use an air knife to blow the surface of the substrate to further remove the residual solution, obtaining a composite substrate with a Res intermediate layer.

[0044] Step (2): In-situ interfacial polymerization (IP) to prepare a polyamide (PA) active layer 1. Aqueous phase monomer treatment: Prepare a 0.5 wt% aqueous solution of piperazine (PIP). Pour 20 mL of the PIP aqueous solution evenly onto the surface of the Res intermediate layer composite substrate prepared in step (1) and let it stand for 3 min to allow PIP to fully adsorb on the surface of the Res intermediate layer. After draining the PIP solution, use an air knife to blow to remove the residual solution.

[0045] 2. Organic phase monomer reaction: Pour 20 mL of a 0.05 wt% hexane solution of trimesoyl chloride (TMC) evenly onto the membrane surface and react for 30 s to allow the interfacial polymerization reaction between PIP and TMC to form a polyamide (PA) active layer on the Res intermediate layer. Subsequently, rinse the membrane surface with hexane for 5 s to remove the unreacted TMC.

[0046] 3. Curing treatment: Place the prepared membrane in an oven at 60°C for 10 minutes to promote the cross-linking of the polyamide network, and prepare a polyamide nanofiltration membrane (labeled as Res-TFC membrane). The cured membrane is stored in deionized water at 4°C for later use.

[0047] Example 2-4 Preparation of Polyamide Nanofiltration Membrane Based on Resveratrol Intermediate Layer The differences between Example 2-4 and Example 1 are as follows: In step (1), prepare Res aqueous solutions with concentrations of 0.1 wt%, 0.3 wt%, and 0.7 wt%.

[0048] Example 5-6 Preparation of Polyamide Nanofiltration Membrane Based on Resveratrol Intermediate Layer The differences between Example 5-6 and Example 1 are as follows: In step (2), prepare piperazine aqueous solutions with concentrations of 0.3 wt% and 0.7 wt%.

[0049] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the preparation of the Res intermediate layer in step (1) is omitted. After treating the PSF ultrafiltration membrane substrate, in-situ interfacial polymerization in step (2) is carried out to prepare a polyamide nanofiltration membrane (labeled as C-TFC membrane).

[0050] Comparative Example 2 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.

[0051] Test Example 1 Characterization of Polyamide Nanofiltration Membrane Figure 1 Figures showing the atomic force microscope (AFM) and transmission electron microscope (TEM) characterizations of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1. By using AFM and TEM to characterize the roughness and cross-section of the membranes respectively, we can see that the roughness (Ra) of the C-TFC membrane is 4.90 ± 0.25 nm, and the thickness of the PA active layer is 48.0 ± 1.9 nm, while the roughness of the Res-TFC membrane is reduced to 3.92 ± 0.05 nm, and the thickness of the PA active layer is decreased to 31.3 ± 1.2 nm. These differences occur because the Res intermediate layer hinders the diffusion of PIP to the water / organic interface, reduces the local monomer concentration, slows down the PIP-TMC reaction, thus restricting the growth of the PA active layer and resulting in a thinner and more uniform PA active layer.

[0052] Figure 2Water contact angles of the C-TFC and Res-TFC membranes prepared in Comparative Example 1 and Example 1. The contact angle of the C-TFC membrane was 43.3°, and that of the Res-TFC membrane was 36.0°. During the IP reaction, hydrogen bonding and π-π stacking between Res and PIP reduce the aqueous-phase diffusion rate of PIP, resulting in insufficient supply of PIP at the interface. Therefore, relatively excessive TMC will lead to an increase in unreacted acyl chloride groups in the PA active layer, and subsequently these groups are hydrolyzed as capping moieties to form carboxylic acids. Therefore, excessive TMC terminates chain growth and reduces the degree of crosslinking, promoting the formation of hydrophilic soft segments and carboxylic acid groups, resulting in an increase in the hydrophilicity of the Res-TFC membrane.

[0053] Figure 3 Zeta potentials of the C-TFC and Res-TFC membranes prepared in Comparative Example 1 and Example 1. As Figure 3 can be seen, the membrane surface of the Res-TFC membrane exhibits stronger negative charge. The reason is that the addition of Res leads to a slowdown in the diffusion of PIP, further resulting in relative excess of TMC, thus 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.

[0054] Test Example 2 Separation performance test of polyamide nanofiltration membranes (1) Test method: The separation performance of the polyamide nanofiltration membranes prepared in the examples and comparative examples was evaluated by a crossflow filtration device (CF016D, Sterlitech Corporation, USA) with an effective filtration area of 16 square centimeters. To obtain stable membrane performance, the polyamide nanofiltration membrane was first compacted at a pressure of 5 bar for 30 minutes. Then, separation performance measurements were carried out at a pressure of 5 bar. Unless otherwise specified, the crossflow velocity and the feed solution temperature were maintained at 0.1 m / s and 25 °C, respectively. The pure water flux (PWP) was calculated according to formula (1).

[0055] (1) 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 time, and Δp (bar) represents the applied pressure.

[0056] An inorganic salt solution of Na2SO4 and NaCl with a concentration of 1000 mg / L was used as the feed solution to evaluate the single-salt rejection ability of the membrane. The rejection rate R of different salts was calculated according to formula (2).

[0057] (2) where C p and C frespectively represent the concentrations of salts or neutral solutes in the permeate and the feed solution.

[0058] Calculate the selectivity (αNaCl / Na2SO4) of different polyamide nanofiltration membranes for monovalent and divalent ions according to formula (3).

[0059] (3) where and represent the rejection rates of NaCl and Na2SO4 salt solutions respectively, and the test results are shown in Table 1.

[0060] Table 1

[0061] As can be seen from the data in Table 1 above, the polyamide nanofiltration membrane based on the resveratrol interlayer provided by the present invention has excellent water flux and divalent salt rejection rate. The water flux of the polyamide nanofiltration membrane ≥ 11.2 L m -2 h -1 bar -1 , and the Na2SO4 rejection rate ≥ 95.2%.

[0062] Further preferably, when the concentration of resveratrol is 0.3 - 1.0 wt%, the polyamide nanofiltration membrane has more excellent water flux and Na2SO4 rejection rate. Further preferably, when the concentration of resveratrol is 0.3 - 0.5 wt% and the concentration of amine monomer is 0.5 - 0.7 wt%, the polyamide nanofiltration membrane has more excellent water flux and Na2SO4 rejection rate; in addition, it also has excellent selectivity of monovalent salt / divalent salt, and the selectivity of monovalent salt / divalent salt ≥ 67.9.

[0063] Figure 4 are the pure water fluxes and sodium sulfate rejection rates of the C-TFC membrane and Res-TFC membrane prepared in Comparative Example 1 and Example 1. From Figure 4 the results, it can be seen that the water flux of the C-TFC membrane is 4.7 ± 0.7 L m -2 [[ID=...]]h -1 bar -1 . With the increase of the Res addition amount, the water flux of the modified Res-TFC membrane increases significantly, from 11.2 ± 0.8 L m -2 h -1 bar -1 increasing to 21.7 ± 0.7 L m -2 h - 1 bar -1, it is increased by about 4.6 times. In terms of sodium sulfate rejection, the rejection rate of the C-TFC membrane is 98.2%. After adding 0.1 wt% of Res, the sodium sulfate rejection rate is increased to 99.3%. However, when the Res addition amount is further increased to 0.7 wt%, the sodium sulfate rejection rate drops to 95.2%.

[0064] By adding Res, the membrane structure has undergone dual changes, which simultaneously affect the water flux and the sodium sulfate rejection performance. On the one hand, the addition of Res reduces the membrane thickness and crosslinking degree, which is beneficial to the rapid transmission of water molecules, thus significantly enhancing the water flux; on the other hand, although the reduction of crosslinking degree may lead to a decrease in the physical barrier ability of the membrane, the addition of Res significantly enhances the negative charge on the membrane surface. The salt rejection performance of the nanofiltration membrane mainly depends on the Donnan effect and the steric hindrance effect, and the enhanced negative surface charge can more effectively repel divalent anions (such as sulfate ions) with negative charges, thus offsetting the adverse effects brought about by the reduction of crosslinking degree. This negative charge effect ensures that even when the crosslinking degree is reduced, the Res-TFC membrane can still maintain a high sodium sulfate rejection rate. However, when the Res addition amount is too high, the excessive Res overly restricts the diffusion of PIP, significantly reduces the membrane crosslinking degree, and further enlarges the membrane pore size, resulting in the destruction of the membrane structure uniformity. Such structural defects weaken the steric hindrance effect of the membrane, and more sulfate ions can penetrate the membrane, leading to the sodium sulfate rejection rate dropping to 95.2%.

[0065] Test Example 3 Anti-fouling performance test of polyamide nanofiltration membrane (1) Test method: Use the above cross-flow device to study the anti-fouling performance of the prepared polyamide nanofiltration membrane and the commercial NF 270 nanofiltration membrane. The inorganic salts in the feed solution include 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). In addition, bovine serum albumin (BSA), sodium alginate (SA) and humic acid (HA) are selected as model organic pollutants to conduct anti-fouling tests on the membrane respectively, which represent protein, polysaccharide and humus model organic pollutants respectively. During the anti-fouling experiment, 100 mg / L of the model organic pollutant is added to the above inorganic salt solution to form an organic-inorganic composite pollutant.

[0066] The initial water flux of each anti-fouling experiment is maintained at 30 L·m -2 ·h -1Specifically, there are four steps in the test: compaction, adjustment, fouling, and cleaning. First, the polyamide nanofiltration membrane is compacted with deionized water at a pressure of 5 bar until the flux is stable (about 1 hour). Then, a sodium chloride solution with the same ionic strength as the simulated wastewater is used as the feed solution, and the operating pressure is adjusted so that the membrane permeation flux after the system stabilizes is 30 L·m -2 ·h -1 ⁻¹, and it is kept running stably for 1 hour. Record the permeation flux at this time as the baseline flux ( J J₀).

[0067] Next, 1 L of the above synthetic wastewater is used as the feed solution to evaluate the fouling resistance of the membrane at the same pressure. The membrane fouling experiment is carried out continuously for 10 hours, and the data recording system records the permeation flux ( J t J). The cross-flow velocity of the feed solution is kept at 0.1 m·s -1 ⁻¹, and the temperature of the feed solution is kept at 25.0 ± 2.0 °C using a circulating cooling system. After the membrane fouling test is completed, the fouled membrane is thoroughly rinsed with deionized water for 30 minutes, and the cross-flow velocity is increased to 0.24 m·s -1 ⁻¹. Finally, the baseline flux ( J l J₀) is detected again using a sodium chloride solution without contaminants. The membrane fouling test of the simulated wastewater is carried out for two cycles. The flux decline ratio (FDR) is calculated according to formula (4), and the flux recovery ratio (FRR) is calculated according to formula (5).

[0068] (4) (5) In addition, the fouling resistance experiments of the prepared polyamide nanofiltration membrane and the NF 270 nanofiltration membrane are carried out using actual industrial wastewater. Similar to the above process, before each experiment, the membrane is compacted with deionized water, and then a sodium chloride solution with the same ionic strength as the actual wastewater is used as the feed solution, and the operating pressure is adjusted until the flux is 50 ± 2 L·m -2 ·h -1 ⁻¹ after stabilization. Record the permeation flux at this time as the baseline flux ( J J₀). Then 1.5 L of actual wastewater is used as the feed solution to evaluate the fouling resistance of the membrane at the same pressure. The data recording system is used to record the permeation flux ( J t J) until 750 mL of permeated water is collected. The cleaning process, cross-flow velocity, and feed solution temperature are the same as above. The membrane fouling experiment of the actual wastewater is carried out for three cycles.

[0069] (2) Test results Figure 5Simulation wastewater test results of the C-TFC membrane, Res-TFC membrane, and commercial NF270 membrane prepared in Comparative Example 1 and Example 1. In all fouling experiments, the Res-TFC membrane showed the most gradual flux decline, with the lowest FDR and the highest FRR. For example, in the BSA fouling test, the FDR of the Res-TFC membrane was only 7.4% after two fouling cycles, which was 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 showed significantly better flux recovery compared to the other two membranes, indicating that its fouling layer was easily removed by physical cleaning. Under SA and HA fouling conditions, the FDR and FRR of the Res-TFC membrane were also much better than those of the C-TFC membrane and the NF270 membrane, further confirming its enhanced anti-fouling ability.

[0070] The excellent anti-fouling 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 denser hydration layer on the surface, effectively isolating the direct contact between the fouling and the membrane. In addition, its relatively smooth surface can reduce the adhesion and deposition of fouling, while a rougher surface tends to trap pollutants 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 blockage. (2) Strong negative charge on the surface: At neutral pH, BSA, SA, and HA are negatively charged. The increased negative charge intensity 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, the C-TFC membrane and the NF270 membrane have lower hydrophilicity and weaker negative charge intensity, which are prone to form local concentration regions, promoting the rapid aggregation of fouling and the formation of a thicker fouling layer. (3) Low calcium ion rejection: Compared with the C-TFC membrane and the NF270 membrane, the Res-TFC membrane shows lower calcium ion rejection, which can reduce the accumulation of calcium on the membrane surface and mitigate the "calcium bridge" effect, further slowing down the fouling layer formation rate.

[0071] Figure 6 Anti-fouling test results of the actual wastewater of the Res-TFC membrane prepared in Example 1 and the commercial NF270 membrane. From Figure 6During three consecutive fouling-cleaning cycles of the actual MBR effluent, the Res-TFC membrane outperformed the NF270 membrane in terms of both flux decline and permeate recovery. After three cycles, the Res-TFC membrane maintained a lower FDR of 42.7% while achieving a higher FRR of 86.4% through hydraulic cleaning. In contrast, the NF270 membrane exhibited an FDR of 69.5% and an FRR of only 46.1%, indicating more severe fouling and poorer flux recovery. These findings suggest that the Res-TFC membrane not only can maintain a high permeate flux during long-term operation but also can more effectively remove membrane surface fouling through conventional hydraulic cleaning. These findings confirm the strong competitiveness and broad application potential of the Res-TFC membrane in actual wastewater treatment scenarios.

[0072] The foregoing examples are illustrative only and are used to explain some of the features of the method of the present invention. The appended claims are intended to claim the broadest scope conceivable, and the embodiments presented herein are supported by the applicant's actual test results. Accordingly, it is the applicant's intention that the appended claims not be limited by the selection of examples that illustrate the features of the invention. Some of the numerical ranges used in the claims also include sub-ranges therewithin, and variations within these ranges should also be construed as being covered by the appended claims whenever possible.

Claims

1. A preparation method of a polyamide nanofiltration membrane based on a resveratrol intermediate layer, characterized in that, It includes the following steps: S1. The resveratrol solution is brought into contact with the surface of the base membrane and left standing to prepare a resveratrol intermediate layer on the surface of the base membrane; S2. An aqueous solution containing an amine monomer and an organic solution containing an acyl chloride monomer are subjected to interfacial polymerization on the resveratrol intermediate layer and cured to prepare a polyamide nanofiltration membrane; In the resveratrol solution, the concentration of resveratrol is 0.1-2.0 wt%; In the aqueous solution containing an 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 an 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 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, wherein The acyl chloride monomer is selected from at least one of trimesoyl chloride, terephthaloyl chloride, and isophthaloyl chloride.

7. According to the preparation method described in claim 1, characterized in that, The base membrane is selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polyacrylonitrile, polyethylene, polyvinyl chloride, or polytetrafluoroethylene.

8. According to the preparation method described in claim 1, wherein, The specific operation of step S2 is as follows: The base membrane after the treatment of step S1 is mixed with the aqueous solution containing an amine monomer and left standing to remove the excess aqueous solution; the base membrane from which the excess aqueous solution has been removed is mixed with the organic solution containing an acyl chloride monomer and left standing, and heating is carried out to promote crosslinking to prepare a polyamide nanofiltration membrane.

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

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

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