Preparation method and application of high-permeability and high-selectivity polyamide nanofiltration membrane

Abstract

The application belongs to the technical field of water treatment membranes, and relates to a preparation method and application of a high-permeability and high-selectivity polyamide nanofiltration membrane; during preparation, 3-aminopropyl triethoxysilane / tannic acid nanoparticles are first grown on the surface of a base film, then the treated base film is soaked in an amine solution containing keratin, taken out, dried, soaked in a uniform benzene triformyl chloride n-hexane solution, taken out again, and subjected to heat treatment to obtain the nanofiltration membrane; the water permeability of the nanofiltration membrane is 40.3-100.6 L / (m 2 ·h·bar), the rejection rate of sodium sulfate is 97.7-99.1%, the rejection rate of magnesium sulfate is 83.8-94.1%, the rejection rate of calcium sulfate is 80.5-91.3%, and the rejection rate of sodium chloride is 8.5-24.9%; the application is: used for desalination of seawater and brackish water, selective separation of monovalent anions and divalent anions in high-salt wastewater, and separation of a mixed system of antibiotic small-molecule organic matters and salts; the method is simple to operate, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment membrane technology, and relates to a method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane and its application. Background Technology

[0002] Developing efficient and durable water treatment technologies is crucial. Membrane separation technology, especially nanofiltration (NF) technology, has become an ideal choice for removing contaminants and purifying water due to its advantages of low energy consumption and high separation efficiency. Thin-layer composite polyamide membranes are widely used in the nanofiltration field due to their excellent separation selectivity and chemical stability. However, existing polyamide nanofiltration membranes often face a trade-off between permeability and selectivity in practical applications, and are also susceptible to membrane fouling, leading to performance degradation and shortened lifespan. Therefore, developing membrane materials that combine high permeability and high selectivity has become a current research hotspot in membrane technology.

[0003] Traditional interfacial polymerization membrane fabrication methods involve the rapid diffusion of polyamine monomers (such as piperazine) from the aqueous phase to the organic phase, followed by a vigorous polycondensation reaction with organic phase monomers (pyromellitic pyromellitic chloride). This rapid reaction kinetics easily leads to localized polymerization at the interface, forming a dense and non-uniform membrane structure, which in turn limits the membrane's water permeability.

[0004] Current research indicates that modification methods involving the addition of nanomaterials to the aqueous phase to modulate interfacial polymerization have attracted widespread attention due to their ease of operation and integration into production processes. These additives regulate the selective layer of polyamides by modulating the diffusion rate of amine monomers or influencing their reaction with acyl chloride monomers. However, the introduction of heterogeneous materials can lead to defects at the composite interface, and the relatively low amount of nanomaterials added limits their effectiveness in improving membrane separation performance. Furthermore, existing substrate modification studies often employ simple physical coating, resulting in weak adhesion between the modified layer and the supporting substrate membrane, which is prone to peeling under long-term high-pressure operation. More importantly, single interfacial polymerization control methods often struggle to precisely balance the thickness and crosslinking degree of the selective layer.

[0005] The literature (Interface-Facilitated Removal of Environmental Micropollutants by Nanofiltration Membranes Prepared from Amino Acid-Mediated Interfacial Polymerization: Mechanistic Insights into Micropollutant Interfacial Partitioning Regulation [J]. Environmental Science & Technology 59, 13085-13095 (2025)) utilizes the addition of amino acid monomers with surfactant properties to the aqueous phase of interfacial polymerization to regulate the diffusion rate of piperazine and perform in-situ modification. However, the water permeability of the membrane material prepared by this method is only 11.9 L / (m²). 2 Even at ·h·bar), it is still difficult to fully meet the industrial demand for high permeability.

[0006] Therefore, it is of great significance to study a polyamide nanofiltration membrane with high permeability, high selectivity and excellent stability in order to solve the problems existing in the current technology. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and to provide a method for preparing and applying a highly permeable and highly selective polyamide nanofiltration membrane.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane involves first growing 3-aminopropyltriethoxysilane / tannic acid (APTES / TA) nanoparticles on the surface of a base membrane, then immersing the treated base membrane in an amine solution containing keratin, removing and drying it, then immersing it in a hexane solution of trimesoyl chloride (TMC), and finally heat-treating it to obtain a high-permeability, high-selectivity polyamide nanofiltration membrane.

[0010] The water permeability of highly permeable and selective polyamide nanofiltration membranes is 40.3~100.6 L / (m²). 2The high-permeability, high-selectivity polyamide nanofiltration membrane prepared by this invention has the following characteristics: ·h·bar), a rejection rate of 97.7-99.1% for sodium sulfate, 83.8-94.1% for magnesium sulfate, 80.5-91.3% for calcium sulfate, and 8.5-24.9% for sodium chloride. While maintaining high water permeability, it can efficiently retain divalent sulfates, while exhibiting extremely low rejection rates for monovalent chlorides.

[0011] High-permeability, high-selectivity polyamide nanofiltration membranes exhibit separation factors of 40–212 for sodium chloride and sodium sulfate, and 31–853 for sodium chloride and tetracycline (an antibiotic model molecule). The separation factor is a core indicator for evaluating the selective sieving efficiency of nanofiltration membranes for different components; a higher value indicates a stronger ability to distinguish solutes. Taking the antibiotic / sodium chloride system as an example, a high separation factor means that the membrane efficiently intercepts antibiotic molecules while allowing the vast majority of sodium chloride salts to permeate. This selective characteristic, combining high salt permeability and high drug rejection, is significant for the desalination and purification of antibiotic fermentation broths. It enables high recovery rates of the target product and simultaneous removal of inorganic salts, thereby significantly reducing energy consumption in subsequent crystallization and drying processes and improving the overall economic efficiency of the process.

[0012] As a preferred technical solution:

[0013] The preparation method of a high-permeability, high-selectivity polyamide nanofiltration membrane as described above involves growing 3-aminopropyltriethoxysilane / tannic acid nanoparticles on the surface of a base membrane. The specific process is as follows: the base membrane is immersed in a mixed solution of 3-aminopropyltriethoxysilane ethanol solution and tannic acid solution for 3-10 h, and 3-aminopropyltriethoxysilane / tannic acid nanoparticles are grown on the surface of the base membrane through Michael addition and Schiff base reaction. After removal, the membrane is washed and dried.

[0014] The preparation method of a high-permeability, high-selectivity polyamide nanofiltration membrane as described above, wherein the base membrane is an ultrafiltration membrane with a porous structure, and the material is polyethersulfone, polyvinylidene fluoride or polytetrafluoroethylene.

[0015] In the preparation method of the high-permeability and high-selectivity polyamide nanofiltration membrane described above, the concentration of the 3-aminopropyltriethoxysilane ethanol solution is 0.5~2.5 mg / mL, and the concentration of the tannic acid solution is 1.6~3.2 mg / mL; in the mixed solution of the 3-aminopropyltriethoxysilane ethanol solution and the tannic acid solution, the volume ratio of 3-aminopropyltriethoxysilane to tannic acid is 1~5:1, preferably 4:1.

[0016] The method for preparing a highly permeable and highly selective polyamide nanofiltration membrane as described above uses a keratin-containing amine solution that is a keratin-containing piperazine (PIP) solution, wherein the concentration of piperazine is 0.01~0.05 wt%, preferably 0.015~0.02 wt%; and the concentration of keratin is 0.01~0.05 wt%, preferably 0.015~0.02 wt%.

[0017] The method for preparing a highly permeable and highly selective polyamide nanofiltration membrane as described above involves keratin being prepared from raw wool fibers, which may be wool, chicken feathers, human hair, rabbit hair, or cow hair.

[0018] The specific preparation process of keratin is as follows: raw wool fibers are degreased in 0.2M sodium bicarbonate solution for 2 hours, rinsed thoroughly with deionized water, and dried at 60℃ to constant weight to obtain degreased raw wool fibers; 6g sodium sulfide, 24g urea and 1.44g sodium dodecyl sulfate (SDS) are dissolved in 50mL deionized water, dissolved with ultrasonic assistance, and 5g of degreased raw wool fibers are added, and reacted at 60℃ for 8 hours; the reaction product is centrifuged three times at 9000r / min to remove insoluble matter, the supernatant is collected and placed in a dialysis bag with a molecular weight cutoff of 3500Da, dialyzed in deionized water for 3 days, and finally freeze-dried to obtain keratin powder.

[0019] In the preparation method of the high-permeability and high-selectivity polyamide nanofiltration membrane described above, the soaking time in the amine solution containing keratin is 0.5~5 min, preferably 1 min.

[0020] In the preparation method of the high-permeability, high-selectivity polyamide nanofiltration membrane described above, the concentration of the n-hexane solution of trimesoyl chloride is 0.05~0.3 wt%, preferably 0.1 wt%.

[0021] The soaking time in the hexane solution of trimesoyl chloride is 0.5 to 5 minutes, preferably 1 minute.

[0022] The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane as described above involves a heat treatment temperature of 50-70°C, preferably 60°C, and a time of 10-30 min, preferably 20 min.

[0023] The present invention also provides the application of a highly permeable and highly selective polyamide nanofiltration membrane prepared by the method described in any of the preceding claims, for use in seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salt wastewater, and separation of mixed systems of antibiotic small molecule organics and salts.

[0024] Invention principle:

[0025] This invention grows APTES / TA nanoparticles in situ on the surface of a base film. These nanoparticles serve as a "structural template" to induce and regulate the subsequent interfacial polymerization process, effectively solving the problems of difficulty in film formation or numerous film defects when directly performing interfacial polymerization on the base film surface. Furthermore, natural macromolecular keratin, rich in amino, hydroxyl, and carboxyl groups, is introduced as a functional additive into the aqueous solution. During interfacial polymerization, it not only regulates the reaction process but also participates in the construction of the polyamide network as a comonomer. Through the dual regulation of the grown APTES / TA nanoparticles and keratin, the structure and properties of the polyamide separation layer are effectively improved. On the one hand, APTES / TA nanoparticles, rich in phenolic hydroxyl and amino groups, can adsorb and anchor amine monomers (such as PIP) in the aqueous phase through hydrogen bonding and π-π stacking interactions, forming a uniform monomer pre-enriched layer. Simultaneously, the polyphenolic structure of TA can slow down the diffusion rate of PIP into the organic phase, making the interfacial polymerization reaction more mild and controllable, thereby forming a thinner, more complete, and less defective polyamide selective layer. On the other hand, keratin, a natural macromolecule rich in amino, carboxyl, and hydroxyl groups, is embedded in the polyamide network as a comonomer, forming multi-point crosslinks with the traditional PIP-TMC system and increasing the network crosslink density. Its macromolecular properties increase the viscosity of the aqueous phase, regulate reaction kinetics, and suppress defects caused by excessively rapid polymerization. Simultaneously, the carboxyl groups introduced by keratin enhance the negative charge on the membrane surface. These two regulatory mechanisms work synergistically to give the polyamide separation layer a unique asymmetric structure of "dense surface, loose bottom," rather than the traditional uniform crosslinked bulk phase characteristics. In this structure, the highly crosslinked, dense surface layer ensures excellent selectivity, while the significantly reduced crosslinking degree along the depth direction constructs a highly loose bottom region. This asymmetry greatly reduces the resistance to water molecule transport, achieving high water permeability.

[0026] The amino and carboxyl groups abundant in keratin molecules interact strongly with PIP monomers through hydrogen bonds, electrostatic induction, and dispersion forces, constructing a "capture network" in the aqueous phase. This interaction significantly limits the migration rate of monomers to the reaction interface, laying the foundation for constructing a heterogeneously cross-linked polyamide network by regulating monomer transport kinetics. Keratin, as a comonomer, participates in the reaction, significantly increasing the degree of cross-linking on the membrane surface, precisely shrinking the effective pore size from 0.52 nm to 0.48 nm. Utilizing the small difference between the critical pore size of 0.48 nm and the ion hydration radius (SO4⁻), the network is further refined. 2- 0.379nm, Cl -The nanofiltration membrane, with a diameter of 0.332 nm, significantly enhances size exclusion efficiency. Simultaneously, the abundant polar groups carried by keratin significantly enhance the Donnan effect during membrane separation, resulting in a substantial increase in divalent sulfate rejection through strong electrostatic repulsion. The nanofiltration membrane prepared in this invention exhibits significant separation selectivity for different salts, and its rejection characteristics conform to the typical rules of negatively charged nanofiltration membranes, enabling efficient rejection of divalent sulfate. Due to the smaller hydration radius and lower dielectric repulsion barrier of monovalent chloride ions in the membrane channels, they permeate through the membrane layer more easily than the larger, higher charge-density divalent sulfate ions, resulting in a much lower rejection rate for monovalent chloride than for divalent sulfate. The prepared nanofiltration membrane combines high permeability, high salt rejection rate, and good stability, successfully overcoming the traditional trade-off between permeability and selectivity in nanofiltration membranes, and showing great application potential in complex salt ion environments and antibiotic molecule separation.

[0027] Beneficial effects:

[0028] (1) The present invention provides a method for preparing a high-permeability and high-selectivity polyamide nanofiltration membrane. Compared with the traditional polyamide nanofiltration membrane preparation process, the present invention combines "base membrane modification" with "interfacial polymerization layer regulation" for the first time. First, hydrophilic nanoparticles are grown on the substrate surface by APTES / TA, which can not only optimize the pore structure of the substrate and reduce defects, but also enhance the anchoring and adsorption capacity of aqueous monomers through its rich functional groups, providing an ideal reaction platform for subsequent interfacial polymerization. On this basis, keratin is introduced into the reaction system. Its macromolecular chain can not only physically regulate the diffusion rate of piperazine, but also react with acyl chloride as a multifunctional monomer, thereby achieving synergistic optimization of the chemical structure and micromorphology of the polyamide layer. Through the above dual regulation, the prepared polyamide separation layer structure is more dense and uniform, with fewer defects and a reduced effective thickness, thereby significantly improving water permeability while maintaining high selectivity, successfully breaking the traditional trade-off between permeability and selectivity of nanofiltration membranes.

[0029] (2) The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane of the present invention, through the introduction of keratin, induces the polyamide layer to form a unique asymmetric structure of "dense surface and loose bottom", breaking the bulk phase characteristics of uniform cross-linking of traditional polyamide membranes; in this structure, the extremely thin and highly cross-linked dense surface layer ensures excellent selectivity, while the significantly reduced cross-linking degree along the depth direction constructs a highly loose bottom region, greatly reducing the resistance to water molecule transport. At the same time, the participation of keratin precisely regulates the surface charge properties and pore size distribution of the membrane, enhances the Donnan effect in the membrane separation process, and strengthens the size sieving effect caused by the difference in hydration radius, so that the membrane exhibits highly efficient retention characteristics for divalent sulfate.

[0030] (3) A method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to the present invention, wherein the prepared polyamide nanofiltration membrane has high permeability, high salt rejection rate and good stability; experimental results show that its water permeability is as high as 40.3~100.6 L / (m 2 The membrane exhibits a rejection rate of 97.7–99.1% for sodium sulfate, 83.8–94.1% for magnesium sulfate, and 80.5–91.2% for calcium sulfate. Furthermore, the membrane has a separation factor of 212 for sodium chloride and sodium sulfate, and a separation factor of 853 for sodium chloride and tetracycline (an antibiotic model molecule).

[0031] (4) The preparation method of the high-permeability and high-selectivity polyamide nanofiltration membrane of the present invention is simple, requires no harsh conditions, and the reaction process is mild, stable and controllable.

[0032] (5) The application of a high-permeability, high-selectivity polyamide nanofiltration membrane of the present invention has shown great application potential in complex salt ion environments and antibiotic molecule separation, and has extremely high practical application value. Attached Figure Description

[0033] Figure 1 The images shown are scanning electron microscope (SEM) images of the surface and cross-section of the polyamide nanofiltration membrane prepared in Example 1 of the present invention, wherein (a) is a surface morphology image and (b) is a cross-sectional morphology image.

[0034] Figure 2 X-ray photoelectron spectra of the surface, the surface and bottom of the polyamide nanofiltration membrane prepared in Example 1 of the present invention after etching 5 nm.

[0035] Figure 3 This is a zeta potential diagram of the surface of the polyamide nanofiltration membrane prepared in Example 1 of the present invention;

[0036] Figure 4 The figure shows the test results of the separation performance of the polyamide nanofiltration membrane prepared in Example 1 of the present invention on sodium sulfate solution. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The test methods involved in the performance indicators in the embodiments and comparative examples of this invention are as follows:

[0039] (1) Water permeability:

[0040] The formula for calculating water permeability (J) is: J = V / (A × T × P), where V is the volume (L) of pure water permeating from the nanofiltration membrane within time T (h), and A is the effective area of ​​the membrane (m²). 2 P is 3 (bar);

[0041] (2) Salt rejection rate: The formula for calculating the salt rejection rate (r) is: In the formula, C0 is the concentration of the salt solution before filtration, and C t The concentration of the filtered salt solution is both measured using a FE38-Standard conductivity meter.

[0042] (3) Separation factor: In the formula, r1 is the salt rejection rate in the antibiotic salt mixture aqueous solution, measured using an FE38-Standard conductivity meter; r2 is the antibiotic rejection rate in the antibiotic salt mixture aqueous solution, measured using a Thermo Fisher Evolution... TM Measured using a One UV-Vis spectrophotometer;

[0043] The antibiotic concentration in the mixed aqueous solution of antibiotic salts is 10 ppm; the sodium sulfate / sodium chloride concentration is 1000 ppm; and the mass ratio of antibiotic to sodium sulfate / sodium chloride is 1:100.

[0044] (5) Scanning electron microscopy (SEM) test: The surface and cross-section of the polyamide nanofiltration membrane were observed using a field emission scanning electron microscope (SU8010, Hitachi, Japan).

[0045] (6) X-ray diffraction (XRD) test: The polyamide nanofiltration membrane was analyzed using an X-ray diffractometer (Bruker D8, Germany).

[0046] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0047] Example 1

[0048] A method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane, comprising the following specific steps:

[0049] (1) 3-aminopropyltriethoxysilane / tannic acid nanoparticles were grown on the surface of an ultrafiltration membrane;

[0050] A PVDF ultrafiltration membrane with a porous structure (manufacturer: Tianjin Jinteng Experimental Equipment Co., Ltd., pore size: 220nm) was immersed in a mixed solution of 3-aminopropyltriethoxysilane ethanol solution and tannic acid solution for 4 h. 3-aminopropyltriethoxysilane / tannic acid nanoparticles were grown on the surface of the ultrafiltration membrane through Michael addition and Schiff base reaction. The membrane was then removed, washed and dried.

[0051] The concentration of the 3-aminopropyltriethoxysilane ethanol solution was 2.5 mg / mL, and the concentration of the tannic acid solution was 2.5 mg / mL; in the mixed solution of the 3-aminopropyltriethoxysilane ethanol solution and the tannic acid solution, the volume ratio of 3-aminopropyltriethoxysilane to tannic acid was 4:1.

[0052] (2) Preparation of wool keratin:

[0053] (2.1) The wool was placed in a 0.2 M sodium bicarbonate solution for 2 h to degrease it. After being thoroughly rinsed with deionized water, it was dried at 60 °C to constant weight to obtain degreased wool.

[0054] (2.2) Dissolve 6 g sodium sulfide, 24 g urea and 1.44 g sodium dodecyl sulfate in 50 mL deionized water, add 5 g defatted wool after ultrasonic-assisted dissolution, and react at 60 °C for 8 h.

[0055] (2.3) The reaction product was centrifuged three times at 9000 r / min to remove unreacted substances. The supernatant was collected and placed in a dialysis bag with a molecular weight cutoff of 3500 Da. The product was dialyzed in deionized water for 3 days and finally freeze-dried to obtain wool keratin.

[0056] (3) Dissolve piperazine and wool keratin in deionized water and stir thoroughly until completely dissolved to obtain a piperazine solution containing keratin;

[0057] In the piperazine solution containing keratin, the concentration of piperazine was 0.02 wt%, and the concentration of keratin was 0.02 wt%.

[0058] (4) The ultrafiltration membrane after step (1) is immersed in a piperazine solution containing keratin for 1 min, then dried and immersed in a hexane solution of 0.1 wt% pyromellitic chloride for 1 min, then heat-treated at 60 °C for 20 min to obtain a high-permeability, high-selectivity polyamide nanofiltration membrane.

[0059] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts; such as Figure 4 As shown, the water permeability of the highly permeable and selective polyamide nanofiltration membrane is 81.1 L / (m²). 2(·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 99% for sodium sulfate, 93.8% for magnesium sulfate, 88.8% for calcium sulfate, and 12% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 174.2. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10 h·bar). (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 146.2.

[0060] like Figure 1 As shown, the polyamide nanofiltration membrane of Example 1 has a dense and defect-free surface, and APTES-TA nanoparticles on the substrate can be observed. The membrane cross-section shows an ultrathin polyamide layer with a thickness of 20.2 nm.

[0061] like Figure 2 As shown, X-ray photoelectron spectroscopy analysis of the surface, the surface of the polyamide nanofiltration membrane after 5 nm etching, and the bottom (bottom surface) quantitatively confirmed the existence of an asymmetric structure characterized by a dense surface and a porous bottom. The surface is highly dense: the crosslinking degree on the polyamide nanofiltration membrane surface reaches 55.1%. This dense surface layer reduces the effective pore size to 0.48 nm, ensuring high salt rejection through size exclusion and a stronger Donnan potential. The bottom is extremely porous: after deep etching, the crosslinking degree of the polyamide nanofiltration membrane is 13.3%, while the crosslinking degree at the bottom drops sharply to 12.5%. This asymmetry of "dense surface and porous bottom" exhibits a significant drag reduction effect. The extremely thin dense layer is responsible for accurately identifying differences in hydration radius, while the highly porous bottom region provides numerous low-resistance transport channels, greatly reducing the transport resistance of water molecules.

[0062] like Figure 3 As shown, within the normal operating pH range, the polyamide nanofiltration membrane of Example 1 maintains a strong negative charge, which is beneficial for achieving the removal of multivalent anions (such as SO42-) through electrostatic repulsion. 2- It also enables the efficient interception of negatively charged organic micro-pollutants.

[0063] Example 2

[0064] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of the n-hexane solution of trimesoyl chloride in step (4) is 0.3 wt%.

[0065] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 40.3 L / (m²). 2 (·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a retention rate of 98.4% for sodium sulfate, 90.8% for magnesium sulfate, 86.2% for calcium sulfate, and 9.3% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 44.3. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10 h·bar). (ppm), the separation factor of the highly permeable and selective polyamide nanofiltration membrane for sodium chloride and tetracycline is 45.9.

[0066] Example 3

[0067] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of the n-hexane solution of trimesoyl chloride in step (4) is 0.05 wt%.

[0068] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of mixed systems of antibiotic-like small-molecule organic matter and salt. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 88.6 L / (m²). 2(·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 97.7% for sodium sulfate, 89.8% for magnesium sulfate, 85.6% for calcium sulfate, and 8.9% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 40. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10... (ppm), the separation factor of the highly permeable and selective polyamide nanofiltration membrane for sodium chloride and tetracycline is 45.

[0069] Example 4

[0070] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of keratin in the piperazine solution containing keratin in step (3) is 0.05 wt%.

[0071] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 68.8 L / (m²). 2 (·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a retention rate of 98.5% for sodium sulfate, 91.3% for magnesium sulfate, 86.9% for calcium sulfate, and 10.2% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 50. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10... (ppm), the separation factor of the highly permeable and selective polyamide nanofiltration membrane for sodium chloride and tetracycline is 56.2.

[0072] Example 5

[0073] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of piperazine in the keratin-containing piperazine solution in step (3) is 0.015 wt%.

[0074] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-selectivity polyamide nanofiltration membrane was 96.9 L / (m²). 2 (·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 98.3% for sodium sulfate, 89.1% for magnesium sulfate, 86.6% for calcium sulfate, and 10.5% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 128. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10... (ppm), the separation factor of the highly permeable and selective polyamide nanofiltration membrane for sodium chloride and tetracycline is 55.9.

[0075] Example 6

[0076] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of piperazine in the keratin-containing piperazine solution in step (3) is 0.04 wt%.

[0077] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 66 L / (m³). 2(·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 99.1% for sodium sulfate, 94.1% for magnesium sulfate, 91.3% for calcium sulfate, and 24.9% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 185. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10 h·bar). (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 165.

[0078] Example 7

[0079] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that: in step (3), the concentration of piperazine in the keratin-containing piperazine solution is 0.015 wt%, and the concentration of keratin is 0.015 wt%.

[0080] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of mixed systems of antibiotic-like small-molecule organic matter and salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 100.6 L / (m²). 2 (·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 98.3% for sodium sulfate, 92% for magnesium sulfate, 86.4% for calcium sulfate, and 11.8% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 113. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10... (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 52.2.

[0081] Example 8

[0082] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that the concentration of piperazine in the keratin-containing piperazine solution in step (3) is 0.03 wt%.

[0083] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 77.7 L / (m²). 2 (·h·bar); Sodium sulfate solution, magnesium sulfate solution, calcium sulfate solution, and sodium chloride solution with a concentration of 1000 ppm were used as test systems. The prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a rejection rate of 99% for sodium sulfate, 91.1% for magnesium sulfate, 91.2% for calcium sulfate, and 17.3% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of sodium sulfate was 1000 ppm). The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 212. A mixed aqueous solution of sodium chloride and tetracycline was used as a test system (the concentration of sodium chloride in the mixed aqueous solution was 1000 ppm, and the concentration of tetracycline was 10... (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 853.

[0084] Example 9

[0085] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that: in step (1), the ultrafiltration membrane material is polyethersulfone (manufacturer: Tianjin Jinteng Experimental Equipment Co., Ltd., pore size: 220nm), which is immersed in a mixed solution of 3-aminopropyltriethoxysilane ethanol solution and tannic acid solution for 10 h. The concentration of 3-aminopropyltriethoxysilane ethanol solution is 0.5 mg / mL, the concentration of tannic acid solution is 1.6 mg / mL, and the volume ratio of 3-aminopropyltriethoxysilane to tannic acid is 4:1.

[0086] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 51.3 L / (m³). 2Using sodium sulfate, magnesium sulfate, calcium sulfate, and sodium chloride solutions with concentrations of 1000 ppm as test systems, the prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a retention rate of 98.6% for sodium sulfate, 92.1% for magnesium sulfate, 88.5% for calcium sulfate, and 10.5% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate (with a concentration of 1000 ppm sodium chloride and 1000 ppm sodium sulfate) was used as a test system. The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 125. A mixed aqueous solution of sodium chloride and tetracycline (with a concentration of 1000 ppm sodium chloride and 1000 ppm tetracycline) was also used as a test system. (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 65.

[0087] Example 10

[0088] A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane is basically the same as in Example 1, except that: in step (1), the ultrafiltration membrane material is polytetrafluoroethylene (manufacturer: Tianjin Jinteng Experimental Equipment Co., Ltd., pore size: 220nm), the concentration of tannic acid solution is 3.2 mg / mL, and the volume ratio of 3-aminopropyltriethoxysilane to tannic acid is 4:1.

[0089] The resulting high-permeability, high-selectivity polyamide nanofiltration membrane was used for seawater and brackish water desalination, selective separation of monovalent and divalent anions in high-salinity wastewater, and separation of antibiotic-like small-molecule organic compounds in mixed systems with salts. The water permeability of the high-permeability, high-selectivity polyamide nanofiltration membrane was 72.6 L / (m³). 2Using sodium sulfate, magnesium sulfate, calcium sulfate, and sodium chloride solutions with concentrations of 1000 ppm as test systems, the prepared polyamide nanofiltration membrane was installed in a cross-flow filtration device. Under an operating pressure of 0.3 MPa, the high-permeability, high-selectivity polyamide nanofiltration membrane showed a retention rate of 98.1% for sodium sulfate, 83.8% for magnesium sulfate, 80.5% for calcium sulfate, and 8.5% for sodium chloride. A mixed aqueous solution of sodium chloride and sodium sulfate (with a concentration of 1000 ppm sodium chloride and 1000 ppm sodium sulfate) was used as a test system. The separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and sodium sulfate was 43. A mixed aqueous solution of sodium chloride and tetracycline (with a concentration of 1000 ppm sodium chloride and 1000 ppm tetracycline) was also used as a test system. (ppm), the separation factor of the high-permeability, high-selectivity polyamide nanofiltration membrane for sodium chloride and tetracycline is 31.

Claims

1. A method for preparing a highly permeable and highly selective polyamide nanofiltration membrane, characterized in that: First, 3-aminopropyltriethoxysilane / tannic acid nanoparticles are grown on the surface of the base membrane. Then, the treated base membrane is immersed in an amine solution containing keratin, dried, and then immersed in a hexane solution of trimesoyl chloride. After being taken out and heat-treated, a high-permeability and high-selectivity polyamide nanofiltration membrane is obtained. The water permeability of highly permeable and selective polyamide nanofiltration membranes is 40.3~100.6 L / (m²). 2 The retention rates for sodium sulfate (·h·bar) were 97.7–99.1%, for magnesium sulfate 83.8–94.1%, for calcium sulfate 80.5–91.3%, and for sodium chloride 8.5–24.9%. The high-permeability, high-selectivity polyamide nanofiltration membrane has a separation factor of 40~212 for sodium chloride and sodium sulfate, and a separation factor of 31~853 for sodium chloride and tetracycline.

2. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The process of growing 3-aminopropyltriethoxysilane / tannic acid nanoparticles on the surface of a base film is as follows: the base film is immersed in a mixed solution of 3-aminopropyltriethoxysilane ethanol solution and tannic acid solution for 3-10 h, and 3-aminopropyltriethoxysilane / tannic acid nanoparticles are grown on the surface of the base film through Michael addition and Schiff base reaction. After removal, the nanoparticles are washed and dried.

3. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 2, characterized in that, The base membrane is an ultrafiltration membrane with a porous structure, and the material is polyethersulfone, polyvinylidene fluoride or polytetrafluoroethylene.

4. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 2, characterized in that, The concentration of the 3-aminopropyltriethoxysilane ethanol solution is 0.5~2.5 mg / mL, and the concentration of the tannic acid solution is 1.6~3.2 mg / mL; in the mixed solution of 3-aminopropyltriethoxysilane ethanol solution and tannic acid solution, the volume ratio of 3-aminopropyltriethoxysilane to tannic acid is 1~5:

1.

5. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The amine solution containing keratin is a piperazine solution containing keratin, with a piperazine concentration of 0.01~0.05 wt% and a keratin concentration of 0.01~0.05 wt%.

6. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, Keratin is prepared from raw wool fibers, which can be wool, chicken feathers, human hair, rabbit hair, or cow hair.

7. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The soaking time in an amine solution containing keratin is 0.5 to 5 minutes.

8. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The concentration of pyromellitic acid chloride in hexane solution is 0.05~0.3 wt%; The soaking time in the hexane solution of trimesoyl chloride is 0.5 to 5 minutes.

9. The method for preparing a high-permeability, high-selectivity polyamide nanofiltration membrane according to claim 1, characterized in that, The heat treatment temperature is 50~70℃, and the time is 10~30 min.

10. The application of a high-permeability, high-selectivity polyamide nanofiltration membrane prepared by the method according to any one of claims 1 to 9, characterized in that: It is used for the selective separation of monovalent and divalent anions in seawater and brackish water desalination, high-salt wastewater, and the separation of mixed systems of antibiotic small molecule organics and salts.

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