Nanofiltration membrane with high selective permeability and scaling resistance and preparation method thereof

Abstract

The embodiment of the invention discloses a nanofiltration membrane with high selective permeability and scaling resistance and a preparation method thereof, and the preparation method comprises the following steps: sequentially dipping a porous ultrafiltration membrane support layer in a water phase solution containing polyamine and an organic phase solution containing polyacyl chloride, carrying out interfacial polymerization reaction on the polyamine and the polyacyl chloride to generate a polyamide separation layer of the nanofiltration membrane; the polyamide separation layer is soaked in a functionalized solution, the nanofiltration membrane with high selective permeability and scaling resistance is formed, and functionalized monomer molecules in the functionalized solution are connected to the surface of the polyamide separation layer through covalent bonds.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiltration membrane preparation, and in particular to a nanofiltration membrane with high selective permeability and anti-fouling properties and a preparation method thereof. Background Art

[0002] Nanofiltration technology is widely used in many fields. Nanofiltration membrane is the core material of nanofiltration technology, and its performance directly determines the stability and economy of system operation. The charge properties of the nanofiltration membrane surface have an important influence on the membrane performance. The mainstream nanofiltration membrane surface carries a large number of negatively charged carboxylic acid groups, which have a strong attraction to divalent cations during the separation process, which is not conducive to the retention of divalent cations and the separation of monovalent and divalent cations. At the same time, carboxyl groups easily attract calcium, magnesium and other ions to form inorganic scale on the surface, resulting in reduced membrane permeability and shortened service life. Calcium sulfate, in particular, is a major problem affecting membrane application. Calcium ions are widely present in water bodies and are easily enriched on the membrane surface. Calcium sulfate is insensitive to pH and is extremely difficult to remove once formed. Therefore, the chemical structure of the membrane surface should be modified to adjust the charge properties, so as to obtain a nanofiltration membrane with both high permeability and anti-scaling properties.

[0003] In the prior art, the methods for regulating the membrane surface structure include layer-by-layer self-assembly, coating, covalent grafting, etc., among which covalent grafting is a major membrane surface functionalization technology. This is because layer-by-layer self-assembly and coating combine the functional materials with the membrane surface through electrostatic force and van der Waals force respectively. During the use of the membrane, there is a problem of loss due to hydraulic scouring, so the application effect is not good. During the covalent grafting functionalization process, the chemical groups in the functional monomers react chemically with the membrane surface groups, and are connected by covalent bonds to obtain higher stability. For example, polyaminoamide dendrimers are grafted on the surface of nanofiltration membranes to increase the density of positively charged groups on the membrane surface and increase the retention rate of magnesium chloride. However, since the functional monomers are polymers, the resistance to water on the membrane surface is large, resulting in a decrease in the water flux of the membrane and a decrease in permeability. For another example, polyethyleneimine is grafted on the surface of a nanofiltration membrane, and amino hydrolysis is used to increase the number of positive charges on the membrane surface. However, there are also problems with polyethyleneimine grafting. On the one hand, polyethyleneimine is also a polymer. While improving the anti-scaling property, it reduces the permeability of the membrane. On the other hand, the amino group is easily oxidized, and the number and stability of positive charges cannot be guaranteed. Therefore, the prepared nanofiltration membrane has poor stability and a short service life.

[0004] Although the prior art provides some methods for improving the selective permeability and / or anti-fouling property of the membrane, which can improve the selective permeability and / or anti-fouling property of the membrane to a certain extent, while improving the anti-fouling property, the permeability of the membrane is reduced, and even the prepared nanofiltration membrane has poor stability and a short service life.

[0005] Based on this, a new nanofiltration membrane having both high selective permeability and anti-fouling properties and a preparation method thereof are needed. Summary of the invention

[0006] The embodiments of this specification provide a nanofiltration membrane with high selective permeability and anti-fouling properties and a preparation method thereof, which are used to solve the following technical problems: Although the prior art provides some methods for improving the selective permeability and / or anti-fouling performance of the membrane, to a certain extent, the selective permeability and / or anti-fouling properties of the membrane can be improved, but while improving the anti-fouling properties, the permeability of the membrane is reduced, and even the prepared nanofiltration membrane has poor stability and a short service life.

[0007] To solve the above technical problems, the embodiments of this specification are implemented as follows:

[0008] The present invention provides a method for preparing a nanofiltration membrane having both high selective permeability and anti-fouling properties, the method comprising:

[0009] The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane;

[0010] The polyamide separation layer is immersed in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein the functionalized monomer molecules in the functionalized solution are covalently bonded to the surface of the polyamide separation layer.

[0011] The embodiment of this specification provides a nanofiltration membrane with both high permselectivity and anti-fouling properties, the nanofiltration membrane is prepared by the preparation method described in the claims of this application, and the nanofiltration membrane is formed by immersing the polyamide separation layer of the nanofiltration membrane in a functionalized solution;

[0012] in,

[0013] The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane;

[0014] The functionalized monomer molecules in the functionalized solution are connected to the surface of the polyamide separation layer by covalent bonds.

[0015] The embodiments of the present specification provide a nanofiltration membrane with both high selective permeability and anti-fouling properties and a preparation method thereof. The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane; the polyamide separation layer is immersed in a functionalized solution to form a nanofiltration membrane with both high selective permeability and anti-fouling properties, wherein the functionalized monomer molecules in the functionalized solution are covalently bonded to the surface of the polyamide separation layer, which can improve the high selective permeability and anti-fouling properties of the nanofiltration membrane, and has the advantages of good stability and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a method for preparing a nanofiltration membrane having both high permselectivity and anti-fouling properties provided in an embodiment of this specification. DETAILED DESCRIPTION

[0017] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0018] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Materials used in the present invention: There is no particular limitation on the sources of all raw materials in the present invention and the following embodiments and comparative examples, and any raw materials may be commercially available.

[0020] Figure 1 Schematic diagram of the method for preparing a nanofiltration membrane with high selective permeability and anti-fouling properties provided in the embodiments of this specification. Figure 1 As shown, the preparation method comprises:

[0021] Step 101: immersing the porous ultrafiltration membrane support layer in an aqueous solution containing polyamine and an organic solution containing polyacyl chloride in sequence, so that the polyamine and the polyacyl chloride undergo interfacial polymerization reaction to generate a polyamide separation layer of the nanofiltration membrane.

[0022] In the embodiment of the present specification, the polyamine is piperazine, and the composition of the aqueous phase solution containing the polyamine includes: an aqueous solution of 0.5-5.0wt% piperazine, 0.3-2.0wt% triethylamine, and 0.01-0.5wt% sodium dodecyl sulfate;

[0023] The polybasic acid chloride is trimesoyl chloride, and the composition of the organic phase solution containing the polybasic acid chloride includes: an Isopar G solution containing 0.05-0.5 wt % of trimesoyl chloride.

[0024] In the examples of this specification, the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution of the porous ultrafiltration membrane support layer is 30-100 nm.

[0025] It should be noted that in the embodiments of this specification, the pore size distribution of the porous ultrafiltration membrane support layer can be uniform or inconsistent, and whether the pore size is uniform does not limit the manufacturing method of this application. In a specific embodiment, the pore size distribution of the porous ultrafiltration membrane support layer is preferably 30-50nm.

[0026] In the embodiment of the present specification, the porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to generate a polyamide separation layer of the nanofiltration membrane, specifically comprising:

[0027] After the porous ultrafiltration membrane support layer is contacted with the aqueous phase solution containing the polyamine according to a first contact condition, the porous ultrafiltration membrane support layer is contacted with the organic phase solution containing the polyacid chloride according to a second contact condition, and heat-treated according to a heat treatment condition, so that the polyamine and the polyacid chloride undergo an interfacial polymerization reaction to generate a polyamide separation layer of the nanofiltration membrane;

[0028] in,

[0029] The first contact condition is: contact time is 20-120s, contact temperature is 15-30°C;

[0030] The second contact condition is: contact time is 20-120s, contact temperature is 15-30°C;

[0031] The heat treatment conditions are: treatment temperature is 40-80°C, and treatment time is 2-10min.

[0032] The purpose of sequentially immersing in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride to cause an interfacial polymerization reaction between the polyamine and the polyacyl chloride is to obtain a polyamide separation layer of the nanofiltration membrane. In this embodiment of the present application, the first contact condition is preferably 25°C, 60s, the second contact condition is preferably 25°C, 60s, and the heat treatment condition is preferably 50°C, 5min.

[0033] Step 103: Immersing the polyamide separation layer in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein the functionalized monomer molecules in the functionalized solution are covalently bonded to the surface of the polyamide separation layer.

[0034] In the examples of this specification, the functionalization solution is an aqueous solution containing a functionalization monomer and an acid acceptor.

[0035] Functionalized monomers refer to compounds that contain one or more specific functional groups in addition to the reactive sites required for polymerization (such as double bonds, epoxy groups, etc.) in the molecular structure. These functional groups can introduce special chemical or physical properties into the polymer chain, thereby giving the final material unique properties or functions. In this embodiment, the introduction of functionalized monomers improves the anti-fouling property on the one hand, and ensures the high selective permeability of the nanofiltration membrane on the other hand.

[0036] In the examples of this specification, the functionalized monomer is betaine hydrazide chloride, and the concentration of the functionalized monomer is 2-10 wt %;

[0037] The acid acceptor is any one of triethylamine and sodium hydroxide.

[0038] Betaine chlorinated hydrazide (also known as hydrazine carbonylmethyl, also known as acetylhydrazide trimethylammonium chloride, also known as Girardt's reagent T) is composed of a positively charged quaternary ammonium salt part and a hydrazide functional group. It has nucleophilicity in structure and can react with compounds such as aldehydes and acyl halides to form corresponding amide derivatives. At present, betaine chlorinated hydrazide is commonly used in organic synthesis, mainly including the following aspects: selective protection of aldehydes, through the reaction of betaine chlorinated hydrazide with aldehydes to form a stable water-soluble addition product, to achieve selective protection of aldehydes; differentiation of aldehydes from other functional groups, betaine chlorinated hydrazide can react with aldehydes but not with ketones, so it can be used to distinguish aldehydes from ketones; purification of aldehydes, betaine chlorinated hydrazide forms an addition product with aldehydes, and then the addition product is treated with acid to release the original aldehyde, which provides an effective method for purifying aldehydes; detection of aldehydes, betaine chlorinated hydrazide is used as an analytical reagent for qualitative and quantitative analysis of the aldehyde content in samples. There are no reports on the application of betaine chlorinated hydrazide in membranes.

[0039] Betaine chlorinated hydrazide contains both amino groups and quaternary amine groups. Through the small molecule functional monomer containing betaine chlorinated hydrazide for surface grafting, the amino group reacts with the amide group remaining on the membrane surface after interfacial polymerization to form a covalent bond between the functional monomer and the membrane surface. The quaternary amine group increases the number of positive charges on the membrane surface, thereby improving the selective permeability and magnesium sulfate scaling performance of the nanofiltration membrane.

[0040] In the examples of this specification, the acid acceptor is triethylamine, and the concentration of triethylamine is 0.2-1.0 wt %.

[0041] Acid acceptors, also known as acid traps or acid neutralizers, are a class of chemical substances that can react with acids to reduce acidic substances in the system. In the embodiments of this specification, betaine chlorhydrazide reacts with acyl chloride groups on the membrane surface to produce HCl. The presence of the acid acceptor can neutralize HCl, promote the grafting reaction, and increase the grafting amount.

[0042] In the embodiments of the present specification, the polyamide separation layer is immersed in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties, specifically comprising:

[0043] The polyamide separation layer is immersed in the functionalization solution according to the third contact condition, and is dried to form the nanofiltration membrane having both high permselectivity and anti-fouling properties.

[0044] In the examples of this specification, the third contact condition is: contact time is 2-5 minutes, and temperature is 25-35°C.

[0045] The preparation method provided in the embodiments of the present specification comprises the following steps: sequentially immersing a porous ultrafiltration membrane support layer in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to generate a polyamide separation layer of a nanofiltration membrane; immersing the polyamide separation layer in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein the functionalized monomer molecules in the functionalized solution are covalently bonded to the surface of the polyamide separation layer, which can improve the high permselectivity and anti-fouling properties of the nanofiltration membrane, and has the advantages of good stability and long service life.

[0046] The present specification embodiment provides a nanofiltration membrane having both high permselectivity and anti-fouling properties, the nanofiltration membrane is prepared by the preparation method provided by the present specification embodiment, the nanofiltration membrane is formed by immersing the polyamide separation layer of the nanofiltration membrane in a functionalized solution;

[0047] in,

[0048] The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane;

[0049] The functionalized monomer molecules in the functionalized solution are connected to the surface of the polyamide separation layer by covalent bonds.

[0050] The nanofiltration membrane with both high selective permeability and anti-scaling properties provided in the embodiments of this specification can be applied to water treatment nanofiltration membranes and components.

[0051] In order to further understand the method provided in this embodiment, it will be described in conjunction with specific embodiments below. In the embodiments of this specification, the evaluation of the permeation selectivity of the nanofiltration membrane is mainly to detect the water flux and the retention rate, and the evaluation of the anti-scaling performance is mainly to detect the anti-CaSO4 scaling performance.

[0052] The water flux and retention rate test method is as follows: using a cross-flow membrane detection device, the salt concentration on the raw material side is 2000±20ppm, the operating pressure is 0.69±0.02MPa, the temperature is 25.0±0.2℃, the inlet water pH is 7.5±0.5, and the water flux and retention rate of the membrane are tested after pre-pressure for 0.5h.

[0053] The water flux calculation formula is F = V / (A·Δt), where J is the water flux of the membrane (L·m -2 ·h -1 ), V is the volume of water permeating the membrane (L), A is the effective area of ​​the membrane (m 2 ), Δt is the penetration time (h).

[0054] The calculation formula of the interception rate is: R = (1-C p / C f )×100%, where R is the retention rate of salt, C p is the salt concentration in the permeate (ppm), C f is the salt concentration in the raw material solution (ppm).

[0055] The calculation formula for the monovalent / divalent salt selectivity is: α = (1-R1) / (1-R2), where α is the monovalent / divalent salt separation factor, and R1 and R2 are the retention rates of monovalent and divalent salts, respectively.

[0056] The present invention tests the anti-CaSO4 scaling performance (flux reduction rate) of the nanofiltration membrane, using Ca 2+ 、SO4 2- The scaling test calculates the flux attenuation rate of the membrane and characterizes the anti-CaSO4 scaling performance of the nanofiltration membrane. The main steps are: operate the membrane in cross-flow mode for 0.5h, the raw material is 2000ppm NaCl solution, the pressure is 0.69MPa, and the initial water flux J0 of the membrane is tested. CaCl2 is added to the raw material solution to make its concentration 20mmol·L -1 , and continue to run for 12 hours to allow the membrane surface to fully interact with the ions. Then add Na2SO4 to the raw material solution at a concentration of 20mmol·L -1 The water flux of the nanofiltration membrane was tested by continuing to run for 96 hours. 1，And calculate the flux decay rate.

[0057] Flux decay rate (FDR) of the membrane: FDR = (J0-J1) / J0×100%

[0058] Comparative Example 1

[0059] A non-functional modified nanofiltration membrane is used as comparative example 1, and its preparation method is as follows: preparing an aqueous phase solution with a piperazine content of 1.5wt%, a triethylamine content of 1.0wt% and a sodium dodecyl sulfate content of 0.1wt%; preparing an Isopar G organic phase solution with a trimesoyl chloride content of 0.1wt%; soaking a porous ultrafiltration support membrane with deionized water, and blowing the membrane surface with nitrogen until there are no droplets; immersing the surface of the porous ultrafiltration support membrane in the aqueous phase solution, contacting for 60s, and blowing the membrane surface with nitrogen until there are no droplets; immersing the surface of the support membrane containing an aqueous phase monomer in the organic phase solution, contacting for 60s, to obtain a nanofiltration membrane; placing the nanofiltration membrane in a 50°C oven for heat treatment for 5min to further crosslink the separation layer polyamide; washing the surface with deionized water, and storing it in deionized water for standby use.

[0060] The nanofiltration membrane obtained in Comparative Example 1 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0061] In this specification, Comparative Example 1 is a nanofiltration membrane prepared without using a functionalized solution. Subsequent Examples 1-6 are nanofiltration membranes prepared using a functionalized solution, but the components of the functionalized solution in Examples 1-6 are different. In Example 1, the functionalized solution contains only functional monomers and no acid acceptor; in Examples 2-6, the functionalized solutions contain both functional monomers and acid acceptors, but their contents are different.

[0062] Example 1

[0063] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide was dissolved in deionized water at a concentration of 5 wt %, and stirred to dissolve it to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25° C. for 2 min, and excess solution was removed; the surface was washed with deionized water and stored in deionized water for later use.

[0064] The nanofiltration membrane obtained in Example 1 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0065] Example 2

[0066] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 5wt%, and the concentration of triethylamine was 0.2wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0067] The nanofiltration membrane obtained in Example 2 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0068] Example 3

[0069] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 2 wt %, and the concentration of triethylamine was 1.0 wt %, and the mixture was stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25° C. for 5 min, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0070] The nanofiltration membrane obtained in Example 3 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0071] Example 4

[0072] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 5wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 5 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0073] The nanofiltration membrane obtained in Example 4 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0074] Example 5

[0075] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, wherein the concentration of betaine chlorinated hydrazide was 8 wt % and the concentration of triethylamine was 1.0 wt %, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, kept in contact at 25° C. for 5 min, and excess solution was removed; the surface was washed with deionized water, and the mixture was stored in deionized water for later use.

[0076] The nanofiltration membrane obtained in Example 5 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0077] Example 6

[0078] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 10wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 5 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0079] The nanofiltration membrane obtained in Example 6 was evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 1 and 2 for details.

[0080] Table 1 Membrane permselectivity performance

[0081]

[0082] In the evaluation of the selective permeability of nanofiltration membranes, the water flux, NaCl retention rate, MgCl retention rate and Na + / Mg 2+ Evaluation of separation factor.

[0083] From the analysis results in Table 1, it can be seen that compared with Comparative Example 1, in the process of preparing nanofiltration membrane, the presence of functionalized solution can increase water flux, improve MgCl2 retention rate and Na + / Mg 2+ The separation factor has little effect on the NaCl retention rate. Therefore, the nanofiltration membrane provided in the embodiments of this specification can improve the selective permeability of the nanofiltration membrane.

[0084] Meanwhile, according to the analysis results in Table 1, when the concentration of betaine chlorhydrazide is 10 wt % and the concentration of triethylamine is 1.0 wt %, the selective permeability of the nanofiltration membrane is the best.

[0085] Table 2 Anti-fouling performance of nanofiltration membrane

[0086]

[0087] When evaluating the anti-scaling performance of the nanofiltration membrane, a solution containing scaling ions was used as the raw solution. After 96 hours of testing, the anti-scaling performance of the membrane was evaluated by the flux decline rate.

[0088] From the analysis results in Table 2, it can be seen that compared with Comparative Example 1, in the process of preparing nanofiltration membrane, surface functionalization can reduce the flux decline rate and improve the anti-fouling performance of the membrane.

[0089] Meanwhile, according to the analysis results in Table 2, when the concentration of betaine chlorhydrazide is 10 wt % and the concentration of triethylamine is 1.0 wt %, the anti-scaling performance of the nanofiltration membrane is the best.

[0090] In addition, in order to further verify the preparation method of the nanofiltration membrane with both high selective permeability and anti-fouling properties provided in the examples of this specification, the preparation method was verified as follows.

[0091] Example 7

[0092] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 20°C for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0093] Example 8

[0094] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0095] Example 9

[0096] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 30° C. for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0097] Example 10

[0098] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 35° C. for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0099] Embodiment 11

[0100] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 40°C for 2 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0101] The nanofiltration membranes obtained in Examples 7-11 were evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 3 and 4 for details.

[0102] Table 3 Membrane permselectivity performance

[0103]

[0104] Table 4 Anti-fouling performance of nanofiltration membrane

[0105]

[0106] According to the results in Table 3 and Table 4, in the method for preparing a nanofiltration membrane having both high permselectivity and anti-fouling properties, the contact temperature of the third contact condition is preferably 25-35°C.

[0107] At the same time, the contact time of the third contact condition was verified.

[0108] Example 12

[0109] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 1 min, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0110] Embodiment 13

[0111] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 3 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0112] Embodiment 14

[0113] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 4 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0114] Embodiment 15

[0115] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 6 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0116] Example 16

[0117] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 25°C for 8 minutes, and excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0118] Embodiment 17

[0119] A nanofiltration membrane was prepared by the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, the concentration of betaine chlorinated hydrazide was 8wt%, and the concentration of triethylamine was 1.0wt%, and the mixture was dissolved by stirring to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, kept in contact at 25°C for 10 minutes, and the excess solution was removed; the surface was washed with deionized water, and stored in deionized water for later use.

[0120] The nanofiltration membranes obtained in Examples 5, 8, 12-17 were evaluated for membrane selective permeability and anti-fouling performance. The evaluation results are shown in Tables 5 and 6.

[0121] Table 5 Membrane permselectivity performance

[0122]

[0123] Table 6 Anti-fouling performance of nanofiltration membrane

[0124]

[0125] According to the results in Tables 5 and 6, in the third contact condition, the contact time is selected to be 2-5 min. Extending the contact time does not improve the performance of the nanofiltration membrane.

[0126] The above is only a preferred embodiment of the present invention, and is not intended to limit the embodiment. It should be noted that, for those skilled in the art, other different forms of changes or modifications can be made without departing from the principles of the present invention, and the obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a nanofiltration membrane having both high selective permeability and anti-fouling properties, characterized in that: The preparation method comprises: The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane; The polyamide separation layer is immersed in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein the functionalized monomer molecules in the functionalized solution are covalently bonded to the surface of the polyamide separation layer.

2. The preparation method according to claim 1, characterized in that The polyamine is piperazine, and the aqueous phase solution containing the polyamine comprises: an aqueous solution of 0.5-5.0 wt % piperazine, 0.3-2.0 wt % triethylamine, and 0.01-0.5 wt % sodium lauryl sulfate; The polybasic acid chloride is trimesoyl chloride, and the composition of the organic phase solution containing the polybasic acid chloride includes: an Isopar G solution containing 0.05-0.5 wt % of trimesoyl chloride.

3. The preparation method according to claim 1, characterized in that: The porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution of the porous ultrafiltration membrane support layer is 30-100 nm.

4. The preparation method according to claim 1, characterized in that: The method of sequentially immersing the porous ultrafiltration membrane support layer in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to generate a polyamide separation layer of the nanofiltration membrane specifically includes: After the porous ultrafiltration membrane support layer is contacted with the aqueous phase solution containing the polyamine according to a first contact condition, the porous ultrafiltration membrane support layer is contacted with the organic phase solution containing the polyacid chloride according to a second contact condition, and heat-treated according to a heat treatment condition, so that the polyamine and the polyacid chloride undergo an interfacial polymerization reaction to generate a polyamide separation layer of the nanofiltration membrane; in, The first contact condition is: contact time is 20-120s, contact temperature is 15-30°C; The second contact condition is: contact time is 20-120s, contact temperature is 15-30°C; The heat treatment conditions are: treatment temperature is 40-80°C, and treatment time is 2-10min.

5. The preparation method according to claim 1, characterized in that: The functionalization solution is an aqueous solution containing a functionalization monomer and an acid acceptor.

6. The preparation method according to claim 5, characterized in that: The functionalized monomer is betaine hydrazide chloride, and the concentration of the functionalized monomer is 2-10 wt %; The acid acceptor is any one of triethylamine and sodium hydroxide.

7. The preparation method according to claim 6, characterized in that: The acid acceptor is triethylamine, and the concentration of the triethylamine is 0.2-1.0 wt %.

8. The preparation method according to claim 1, characterized in that: The step of immersing the polyamide separation layer in a functionalized solution to form a nanofiltration membrane having both high permselectivity and anti-fouling properties specifically comprises: The polyamide separation layer is immersed in the functionalization solution according to the third contact condition, and is dried to form the nanofiltration membrane having both high permselectivity and anti-fouling properties.

9. The preparation method according to claim 8, characterized in that: The third contact condition is: contact time is 2-5 minutes, and temperature is 25-35°C.

10. A nanofiltration membrane having both high selective permeability and anti-fouling properties, characterized in that: The nanofiltration membrane is prepared by the preparation method according to any one of claims 1 to 9, and the nanofiltration membrane is formed by immersing the polyamide separation layer of the nanofiltration membrane in a functionalized solution; in, The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing a polyamine and an organic solution containing a polyacyl chloride, so that the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide separation layer of the nanofiltration membrane; The functionalized monomer molecules in the functionalized solution are connected to the surface of the polyamide separation layer by covalent bonds.

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