A nanofiltration membrane with high permselectivity and anti-fouling property and a preparation method thereof

Abstract

The embodiment of the specification discloses a nanofiltration membrane with high selective permeability and anti-fouling property and a preparation method thereof, the preparation method comprising: sequentially immersing a porous ultrafiltration membrane support layer in an aqueous phase solution containing a polyamine and an organic phase 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; and immersing the polyamide separation layer in a functionalized solution to form the nanofiltration membrane with high selective permeability and anti-fouling property, wherein functionalized monomer molecules in the functionalized solution are covalently connected to the surface of the polyamide separation layer.

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-scaling properties and a preparation method thereof. Background Art

[0002] Nanofiltration technology is widely used in numerous fields, and nanofiltration membranes are the core material of nanofiltration technology. Their performance directly determines the stability and economic efficiency of system operation. The charge properties of the nanofiltration membrane surface have a significant impact on membrane performance. Mainstream nanofiltration membranes carry a large number of negatively charged carboxylic acid groups on their surface, which strongly attract divalent cations during the separation process, hindering the retention of divalent cations and the separation of monovalent and divalent cations. At the same time, carboxyl groups easily attract ions such as calcium and magnesium, forming inorganic scale on the surface, which reduces the membrane's permselectivity and shortens its service life. Calcium sulfate, in particular, is a major problem affecting membrane applications. Calcium ions are widely present in water and easily accumulate on the membrane surface. Furthermore, calcium sulfate is insensitive to pH and, once formed, is extremely difficult to remove. Therefore, the chemical structure of the membrane surface should be modified to adjust the charge properties to obtain a nanofiltration membrane with both high permselectivity and anti-fouling properties.

[0003] In the prior art, 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 respectively bind the functional material to the membrane surface through electrostatic force and van der Waals force. During the use of the membrane, there is a problem of loss due to hydraulic scouring, so the application effect is poor. During the covalent grafting functionalization process, the chemical groups in the functional monomer react chemically with the membrane surface groups and are connected through covalent bonds, which can achieve higher stability. For example, polyaminoamide dendrimers are grafted onto the surface of a nanofiltration membrane to increase the density of positively charged groups on the membrane surface and increase the retention rate of magnesium chloride. However, since the functional monomer is a polymer, 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 onto 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 the positive charge 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-scaling properties of membranes, which can improve the selective permeability and / or anti-scaling properties of membranes to a certain extent, while improving the anti-scaling properties, 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 with 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 both 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 permselectivity 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 with 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 embodiments of this specification provide a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein 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 via covalent bonds.

[0015] The embodiments of this specification provide a nanofiltration membrane with both high permselectivity 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 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the method for preparing a nanofiltration membrane with 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 will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended 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 examples 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 permselectivity and anti-fouling properties provided in the embodiments of this specification. Figure 1 As shown, the preparation method includes:

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

[0022] In the embodiment of this specification, the polyamine is piperazine, and the composition of the aqueous solution containing the polyamine includes: 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;

[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 embodiment of the present 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 non-uniform, 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 30-50 nm.

[0026] In the embodiment of this 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 form a polyamide separation layer of the nanofiltration membrane, which specifically includes:

[0027] After contacting the porous ultrafiltration membrane support layer with the aqueous solution containing the polyamine according to first contact conditions, contacting the porous ultrafiltration membrane support layer with the organic solution containing the polyacyl chloride according to second contact conditions, and performing heat treatment according to heat treatment conditions, so that the polyamine and the polyacyl chloride undergo interfacial polymerization reaction to form the polyamide separation layer of the nanofiltration membrane;

[0028] in,

[0029] The first contact conditions are: contact time of 20-120s, contact temperature of 15-30°C;

[0030] The second contact conditions are: contact time of 20-120s, contact temperature of 15-30°C;

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

[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 the 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 functionalization solution to form a nanofiltration membrane with high selectivity and anti-fouling, wherein the functional monomer molecules in the functionalization solution are covalently connected to the surface of the polyamide separation layer.

[0034] In the embodiments of the present application, the functionalization solution is an aqueous solution containing a functional monomer and an acid acceptor.

[0035] The functional monomer refers to a compound containing one or more specific functional groups in the molecular structure in addition to the reactive sites (such as double bonds, epoxy groups, etc.) required for polymerization. These functional groups can introduce special chemical or physical properties on the polymer chain, thereby endowing the final material with unique properties or functions. In the present embodiment, the introduction of the functional monomer improves the anti-fouling property on the one hand and ensures the high selectivity of the nanofiltration membrane on the other hand.

[0036] In the embodiments of the present application, the functional monomer is betaine hydrazide chloride, and the concentration of the functional monomer is 2-10 wt%.

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

[0038] Betaine hydrazide chloride (also known as hydrazinocarbonylmethyl, also known as acethydrazide trimethylammonium chloride, also known as Girard's reagent T) is composed of a positively charged quaternary ammonium salt part and a hydrazide functional group, and has nucleophilic structure, which can react with aldehydes, acyl halides and other compounds to form corresponding amide derivatives. At present, betaine hydrazide chloride is commonly used in organic synthesis, mainly including the following aspects: selective protection of aldehyde, by reacting betaine hydrazide chloride with aldehyde to form a stable water-soluble adduct, the selective protection of aldehyde is achieved; distinction of aldehyde and other functional groups, betaine hydrazide chloride can react with aldehyde but not with ketone, so it can be used to distinguish aldehyde and ketone; purification of aldehyde, betaine hydrazide chloride forms an adduct with aldehyde, and then the adduct is treated with acid to release the original aldehyde, which provides an effective method for purifying aldehyde; detection of aldehyde, betaine hydrazide chloride is used as an analytical reagent for qualitative and quantitative analysis of aldehyde content in samples. There is no report on the application of betaine hydrazide chloride in membranes.

[0039] Betaine hydrazide chloride contains both amino and quaternary amine groups. By surface grafting with this small molecule functional monomer containing betaine hydrazide chloride, 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, and the quaternary amine group increases the number of positive charges on the membrane surface, thereby improving the selectivity and magnesium sulfate fouling performance of the nanofiltration membrane.

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

[0041] Acid acceptors, also known as acid traps or neutralizers, are chemicals that react with acids, thereby reducing the amount of acid in a system. In the examples presented herein, betaine chlorohydrazide reacts with acyl chloride groups on the membrane surface to produce HCl. The presence of the acid acceptor neutralizes the HCl, promoting the grafting reaction and increasing the grafting yield.

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

[0043] The polyamide separation layer is immersed in the functionalized solution according to the third contact condition and dried to form the nanofiltration membrane with 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 this 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 form 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 linked to the surface of the polyamide separation layer, thereby improving the high permselectivity and anti-fouling properties of the nanofiltration membrane, and having the advantages of good stability and long service life.

[0046] The present embodiment provides a nanofiltration membrane having both high permselectivity and anti-fouling properties, wherein the nanofiltration membrane is prepared by the preparation method provided in the present embodiment, wherein 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 via covalent bonds.

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

[0051] To further understand the method provided in this embodiment, the following description will be provided with reference to specific examples. In the examples of this specification, the permeation selectivity of the nanofiltration membrane was evaluated by primarily testing water flux and rejection, while the anti-scaling performance was evaluated by primarily testing 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-pressing for 0.5h.

[0053] The calculation formula of water flux 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 rejection rate is: R = (1-C p / C f )×100%, where R is the salt retention rate, 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 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 CaSO4 2+ 、SO4 2- The scaling test calculates the flux decay 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, using 2000ppm NaCl solution as the raw material at a pressure of 0.69MPa, and test the initial water flux J0 of the membrane. CaCl2 is added to the raw material solution to make its concentration 20mmol·L -1 , 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 Continue to run for another 96 hours to test the water flux of the nanofiltration membrane J 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-functionalized modified nanofiltration membrane was used as comparative example 1, and its preparation method was as follows: preparing an aqueous solution with a piperazine content of 1.5 wt%, a triethylamine content of 1.0 wt% and a sodium lauryl sulfate content of 0.1 wt%; preparing an Isopar G organic solution with a trimesoyl chloride content of 0.1 wt%; soaking a porous ultrafiltration support membrane with deionized water, and blowing nitrogen gas on the membrane surface until no droplets were present; immersing the surface of the porous ultrafiltration support membrane in the aqueous solution for 60 seconds, and then blowing nitrogen gas on the membrane surface until no droplets were present; immersing the surface of the support membrane containing the aqueous monomer in the organic solution for 60 seconds to obtain a nanofiltration membrane; placing the nanofiltration membrane in an oven at 50° C. for heat treatment for 5 minutes to further crosslink the polyamide in the separation layer; washing the surface with deionized water, and storing it in deionized water for later 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.

[0061] In this specification, Comparative Example 1 is a nanofiltration membrane prepared without a functionalizing solution. Subsequent Examples 1-6 are nanofiltration membranes prepared using functionalizing solutions, but the components of the functionalizing solutions differ between Examples 1-6. Specifically, in Example 1, the functionalizing solution contains only functional monomers and no acid acceptor; while in Examples 2-6, the functionalizing solutions all contain both functional monomers and an acid acceptor, but the amounts thereof vary.

[0062] Example 1

[0063] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine hydrazide chloride 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 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.

[0065] Example 2

[0066] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 5 wt % and the triethylamine concentration being 0.2 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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.

[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.

[0068] Example 3

[0069] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 2 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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.

[0071] Example 4

[0072] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 5 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution at 25° C. for 5 min, and the 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.

[0074] Example 5

[0075] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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.

[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.

[0077] Example 6

[0078] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 10 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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.

[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.

[0080] Table 1 Membrane permselectivity performance

[0081]

[0082] In the evaluation of the selective permeability of nanofiltration membrane, 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, the presence of the functionalized solution in the process of preparing the nanofiltration membrane can increase the water flux, the MgCl2 retention rate and the Na + / Mg 2+ The separation factor has little effect on the NaCl rejection 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 liquid. 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 permselectivity 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 according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution at 20° C. for 2 min, 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 according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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.

[0095] Example 9

[0096] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution at 30° C. for 2 min, 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 according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution at 35° C. for 2 min, and excess solution was removed; the surface was washed with deionized water and stored in deionized water for later use.

[0099] Example 11

[0100] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution, contacted at 40° C. for 2 min, 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.

[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 according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and 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 1 min, and excess solution was removed; the surface was washed with deionized water and stored in deionized water for later use.

[0110] Example 13

[0111] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution 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] Example 14

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

[0114] Example 15

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

[0118] Example 17

[0119] A nanofiltration membrane was prepared according to the method of Comparative Example 1; betaine chlorinated hydrazide and triethylamine were dissolved in deionized water, with the betaine chlorinated hydrazide concentration being 8 wt % and the triethylamine concentration being 1.0 wt %, and stirred to dissolve to form a functionalized solution; the surface of the nanofiltration membrane was immersed in the functionalized solution at 25° C. for 10 min, and 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, and 12-17 were evaluated for membrane permselectivity 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. Prolonging the contact time does not improve the performance of the nanofiltration membrane.

[0126] The above description is merely a preferred embodiment of the present invention and is not intended to limit the embodiments. It should be noted that those skilled in the art can make other variations or modifications without departing from the principles of the present invention, and such obvious variations or modifications are still within the scope of protection of the present invention.

Claims

1. A method for preparing a nanofiltration membrane having both high permselectivity 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 with 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. The functionalized solution is an aqueous solution containing a functionalized monomer and an acid acceptor, wherein 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.

2. The preparation method according to claim 1, wherein The polyamine is piperazine, and the aqueous 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, wherein 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, wherein 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, which specifically includes: After contacting the porous ultrafiltration membrane support layer with the aqueous solution containing the polyamine according to first contact conditions, contacting the porous ultrafiltration membrane support layer with the organic solution containing the polyacyl chloride according to second contact conditions, and performing heat treatment according to heat treatment conditions, so that the polyamine and the polyacyl chloride undergo interfacial polymerization reaction to form the polyamide separation layer of the nanofiltration membrane; in, The first contact conditions are: contact time of 20-120 s, contact temperature of 15-30°C; The second contact conditions are: contact time of 20-120 s, contact temperature of 15-30°C; The heat treatment conditions are: treatment temperature of 40-80° C., and treatment time of 2-10 min.

5. The preparation method according to claim 1, wherein The acid acceptor is triethylamine, and the concentration of the triethylamine is 0.2-1.0 wt %.

6. The preparation method according to claim 1, wherein 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 includes: The polyamide separation layer is immersed in the functionalized solution according to the third contact condition and dried to form the nanofiltration membrane with high permselectivity and anti-fouling properties.

7. The preparation method according to claim 6, wherein The third contact condition is: contact time is 2-5 minutes, and temperature is 25-35°C.

8. A nanofiltration membrane with both high permselectivity and anti-fouling properties, characterized in that: The nanofiltration membrane is prepared by the preparation method according to any one of claims 1 to 7, 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 via covalent bonds.

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