Nanofiltration membrane, water treatment device, preparation method and application

Abstract

The invention discloses a nanofiltration membrane, a water treatment device, a preparation method and application. The preparation method of the nanofiltration membrane provided by the invention comprises the following steps: putting a polymer base membrane infiltrated with a water-phase monomer into an organic solution containing multi-acyl chloride, and carrying out interfacial polymerization reaction to prepare the nanofiltration membrane, wherein the water-phase monomer meets one of the following characteristics: (a1) a polyamine monomer containing a substituent group without reaction activity; and (a2) a polyamine monomer containing a substituent group without reaction activity and a polyamine monomer not containing a substituent group without reaction activity. Compared with a traditional polyamine monomer, after a substituent group without reaction activity is introduced, the diffusion rate and the reaction rate of the monomer are changed, and the introduced substituent group without reaction activity can increase the steric hindrance characteristic between polymer chains; the changes can realize regulation and control on the thickness and pore connectivity (or free volume connectivity) of the polyamide separation layer, and the water permeability coefficient of the prepared nanofiltration membrane is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and relates to a nanofiltration membrane, a water treatment device, a preparation method and application. BACKGROUND

[0002] Nanofiltration is a water treatment membrane technology that is gradually being popularized and applied. Generally, pressure-driven separation membranes with a molecular weight cut-off in the range of 200 Da to 2000 Da are collectively referred to as nanofiltration membranes. Nanofiltration membranes can selectively retain part of the solutes in water and allow another part of the solutes to pass through, exhibiting a variety of selectivity and being able to meet different water treatment needs. However, the current nanofiltration membranes have a low water permeability coefficient and an unsatisfactory selectivity, and there is a serious mutual restriction relationship between the selectivity and the permeability, which increases the investment and operating costs of the nanofiltration process in the water treatment process and limits its further large-scale application. Therefore, improving the water permeability of the nanofiltration membranes and preparing nanofiltration membranes with high permeability and selectivity are crucial for reducing the energy consumption of the nanofiltration process and promoting the wide application of the nanofiltration process.

[0003] At present, the prepared nanocomposite nanofiltration membranes, such as the construction of an intermediate layer between the separation layer and the base membrane to reduce the thickness of the separation layer and optimize the water permeation path, can significantly improve the water permeability coefficient of the nanofiltration membranes and to a certain extent, break the mutual restriction relationship between the permeability and the selectivity. However, due to the reasons such as the easy agglomeration of nanoparticles, the existence of defects at the interface between the particles and the polymer, and the poor compatibility of the intermediate layer with the base membrane and the separation layer, these methods often have great difficulty in large-scale production. Therefore, it is urgent to develop a new membrane preparation method that can significantly improve the water permeability coefficient of the nanofiltration membranes and be easy to scale up production, and promote the application of the nanofiltration membranes in the field of water treatment. SUMMARY

[0004] Therefore, it is necessary to provide a nanofiltration membrane with high permeability and selectivity, a water treatment device, a preparation method and application.

[0005] In some embodiments, a preparation method of a nanofiltration membrane is provided, comprising the following steps:

[0006] placing a polymer base membrane infiltrated with an aqueous phase monomer in an organic solution containing a polyacyl chloride to perform an interfacial polymerization reaction, to prepare the nanofiltration membrane;

[0007] wherein the aqueous phase monomer satisfies one of the following characteristics:

[0008] (a1) a polyamine monomer containing a non-reactive substituent;

[0009] (a2) a polyamine monomer containing a non-reactive substituent and a polyamine monomer not containing a non-reactive substituent.

[0010] In some embodiments, the preparation method of the nanofiltration membrane provided satisfies one or both of the following conditions:

[0011] (1) the non-reactive substituent in the polyamine monomer containing a non-reactive substituent includes at least one of methyl, ethyl, isopropyl, phenyl, trifluoromethyl and ketone;

[0012] (2) the polyamine monomer containing a non-reactive substituent includes at least one of 2-methylpiperazine, 2-phenylpiperazine, trans-2,5-dimethylpiperazine, 2-ethylpiperazine, trans-2,5-diethylpiperazine, 2-isopropylpiperazine, 2-piperazinone, 2-carboxypiperazine, 2,3-diphenylpiperazine, 2-phenyl-2-methylpiperazine, 3,5-diaminotoluene and 3,5-diaminotrifluorotoluene.

[0013] In some embodiments, the preparation method of the nanofiltration membrane provided, the molar ratio of the polyamine monomer containing a non-reactive substituent to the polyamine monomer not containing a non-reactive substituent is 1: (0-2).

[0014] In some embodiments, the preparation method of the nanofiltration membrane provided, the polyamine monomer not containing a non-reactive substituent includes at least one of piperazine, m-phenylenediamine, p-phenylenediamine, murexide and ethylenediamine.

[0015] In some embodiments, the preparation method of the nanofiltration membrane provided, the preparation method of the polymer-based membrane infiltrated with the aqueous phase monomer includes the following steps:

[0016] mixing the aqueous phase monomer with water to prepare an aqueous phase solution,

[0017] immersing the polymer-based membrane in the aqueous phase solution to obtain the polymer-based membrane infiltrated with the aqueous phase monomer;

[0018] wherein the mass concentration of the aqueous phase monomer in the aqueous phase solution is 0.1%-2.0%;

[0019] Optionally, the polymer-based membrane is immersed in the aqueous phase solution for 0.5 min-10 min in the immersion step.

[0020] In some embodiments, the preparation method of the nanofiltration membrane provided satisfies one or more of the following conditions:

[0021] (1) the solvent in the organic solution containing polyacyl chloride includes at least one of n-hexane, cyclohexane, n-heptane, petroleum ether and isomeric alkanes;

[0022] (2) the polyacyl chloride includes at least one of trimesoyl chloride, terephthaloyl chloride and isophthaloyl chloride.

[0023] (3) the polymer base film comprises at least one of a polysulfone base film, a polyethersulfone base film, a polyacrylonitrile base film, a polyvinylidene fluoride base film, a polytetrafluoroethylene base film and a polyethylene base film;

[0024] (4) in the organic solution containing the polybasic acid chloride, the mass concentration of the polybasic acid chloride is 0.05% to 1.0%;

[0025] (5) the time of the interfacial polymerization reaction is 0.5 min to 10 min.

[0026] In some embodiments, the preparation method of the nanofiltration membrane provided further comprises a solidification treatment after the interfacial polymerization reaction;

[0027] Optionally, the solidification treatment comprises heat solidification and / or air-drying solidification.

[0028] Optionally, the heat solidification is performed at 50°C to 70°C for 1 min to 10 min.

[0029] In some embodiments, a nanofiltration membrane is provided, which is prepared by the preparation method.

[0030] In some embodiments, the nanofiltration membrane is used in water treatment.

[0031] In some embodiments, a water treatment device is provided, wherein the filtration component of the water treatment device comprises the nanofiltration membrane.

[0032] The preparation method of the nanofiltration membrane provided in the foregoing embodiments adopts a water-phase monomer comprising a polyamine monomer with a non-reactive substituent, wherein the non-reactive substituent refers to a substituent that is non-reactive with the acyl chloride functional group, and can be a non-reactive side chain and / or a non-reactive functional group. Compared with traditional polyamine monomers, the diffusion and reaction rate of the monomer are changed after the introduction of the non-reactive side chain and / or the non-reactive functional group, and the non-reactive side chain and / or the non-reactive functional group introduced increases the steric hindrance characteristics between the polymer chains. These changes can realize the structure regulation of the polyamide separation layer, and the water permeability coefficient of the nanofiltration membrane prepared is significantly improved, which can significantly overcome the mutual restriction relationship between the water permeability coefficient and the pore size of the traditional nanofiltration membrane, and maintain a high Na2SO4 retention rate. In the field of water treatment, the water permeability can be significantly improved, and the solute removal efficiency can be maintained. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments and examples of the present application, and more completely understand the present application and its beneficial effects, the attached drawings needed to be used in the description of the embodiments or examples will be briefly introduced. Obviously, the attached drawings in the following description are only some embodiments of the present application, and other attached drawings can be obtained by those skilled in the art without any creative effort on the basis of these attached drawings.

[0034] Figure 1 Correlation diagram between water permeability coefficient and molecular weight cut-off for each example and comparative example;

[0035] Figure 2 Correlation diagram between water permeability coefficient and Na2SO4 rejection rate for each example and comparative example;

[0036] Figure 3 The graph shows the calculated porosity results of comparative example 2, example 2, example 6 and example 7.

[0037] Figure 4 The graph shows the free volume fraction results of comparative example 4, example 4 and example 7. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the attached drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application can be more thoroughly and completely understood.

[0039] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be intervening elements. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can be present.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] Unless otherwise defined, or the context dictates otherwise, the terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Unless otherwise noted, or the context dictates otherwise, the terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Unless otherwise noted, or the context dictates otherwise, the terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0042] The selection range of the terms "and / or", "or / and", "and / or" used in the present application includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, which includes any two related listed items, any more related listed items, or all related listed items. It should be noted that when at least two conjunctions selected from "and / or", "or / and", "and / or" are combined to connect at least three items, it should be understood that in the present application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B, and "combination of A and B".

[0043] In the present application, "multiple", "various", "multiple times", "multiple" and the like are used without special limitation, which means more than two or equal to two in quantity. For example, "one or more" means one or more than two.

[0044] In the present application, "combination thereof", "any combination thereof", "any combination thereof" and the like include all suitable combinations of any two or more listed items.

[0045] In the present application, "suitable combination", "suitable manner", "any suitable manner" and the like are "suitable" as the implementation of the technical solution of the present application, the solution of the technical problem of the present application, and the realization of the expected technical effect of the present application.

[0046] In the present application, "preferably", "better", "better", "as appropriate" only describe the better implementation or embodiment, and it should be understood that it does not constitute a limitation on the protection scope of the present application.

[0047] In the present application, "further", "further", "especially" and the like are used to describe the purpose, indicating the difference in content, but should not be understood as a limitation on the protection scope of the present application.

[0048] In the present application, "optionally", "optional", "optional" means optional, that is, selected from two parallel solutions of "yes" or "no". If there are multiple "optional" in a technical solution, if there is no special description, and no contradiction or mutual restriction relationship, each "optional" is independent.

[0049] In the present application, the terms "first", "second", "third", "fourth" and the like in the "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the technical features indicated. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description and should be understood as not constituting a closed limitation on the quantity.

[0050] In the present application, the technical features described in an open manner include both closed technical solutions consisting of the listed features and open technical solutions containing the listed features.

[0051] In the present application, with respect to a numerical interval (i.e. a numerical range), if no special instructions are given, the optional numerical distribution within the above numerical interval is considered to be continuous, and includes the two numerical end points (i.e. the minimum value and the maximum value) of the numerical range and every numerical value between the two numerical end points. If no special instructions are given, when a numerical interval only points to integers within the numerical interval, including the two end point integers of the numerical range and every integer between the two end points, in this document, it is equivalent to directly listing every integer, for example, t is an integer selected from 1 to 10, which means that t is any one integer selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe a feature or a characteristic, these ranges can be combined. In other words, unless otherwise indicated, the ranges disclosed herein should be understood to include any and all sub-ranges encompassed therein.

[0052] In the present application, the temperature parameters, if not specifically limited, allow both constant temperature treatment and fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0053] In the present application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0054] In the present application, "room temperature" generally refers to 5°C to 30°C, preferably 25±5°C.

[0055] In some embodiments, a method for preparing a nanofiltration membrane is provided, comprising the following steps:

[0056] The polymer-based membrane infiltrated with the aqueous phase monomer is placed in an organic solution containing a polybasic acid chloride to perform an interfacial polymerization reaction to prepare a nanofiltration membrane.

[0057] The water-phase monomer satisfies one of the following characteristics:

[0058] (a1) a polyamine monomer containing a non-reactive substituent;

[0059] (a2) a polyamine monomer containing a non-reactive substituent and a polyamine monomer not containing a non-reactive substituent.

[0060] The preparation method of the nanofiltration membrane is based on the interfacial polymerization technology. The polymer base film is immersed into a water phase containing a water-phase monomer of polyamine and an oil phase containing a polyacyl chloride monomer, respectively, to form a separation layer on the surface of the polymer base film and prepare a composite nanofiltration membrane. The structure of the water-phase reaction monomer is designed to increase the number and connectivity of free volumes of the prepared membrane separation layer, construct more water permeation channels in the separation layer, and significantly improve the water permeability of the nanofiltration membrane without affecting the solute retention selectivity of the nanofiltration membrane.

[0061] The preparation method of the nanofiltration membrane is based on the interfacial polymerization technology. The polymer base film is immersed into a water phase containing a water-phase monomer of polyamine and an oil phase containing a polyacyl chloride monomer, respectively, to form a separation layer on the surface of the polymer base film and prepare a composite nanofiltration membrane. The structure of the water-phase reaction monomer is designed to increase the number and connectivity of free volumes of the prepared membrane separation layer, construct more water permeation channels in the separation layer, and significantly improve the water permeability of the nanofiltration membrane without affecting the solute retention selectivity of the nanofiltration membrane.

[0062] The preparation method of the nanofiltration membrane is based on the interfacial polymerization technology. The polymer base film is immersed into a water phase containing a water-phase monomer of polyamine and an oil phase containing a polyacyl chloride monomer, respectively, to form a separation layer on the surface of the polymer base film and prepare a composite nanofiltration membrane. The structure of the water-phase reaction monomer is designed to increase the number and connectivity of free volumes of the prepared membrane separation layer, construct more water permeation channels in the separation layer, and significantly improve the water permeability of the nanofiltration membrane without affecting the solute retention selectivity of the nanofiltration membrane.

[0063] The preparation method of the nanofiltration membrane is based on the interfacial polymerization technology. The polymer base film is immersed into a water phase containing a water-phase monomer of polyamine and an oil phase containing a polyacyl chloride monomer, respectively, to form a separation layer on the surface of the polymer base film and prepare a composite nanofiltration membrane. The structure of the water-phase reaction monomer is designed to increase the number and connectivity of free volumes of the prepared membrane separation layer, construct more water permeation channels in the separation layer, and significantly improve the water permeability of the nanofiltration membrane without affecting the solute retention selectivity of the nanofiltration membrane.

[0064] The water permeability coefficient of the prepared nanofiltration membrane is significantly improved, which can significantly overcome the mutual restriction relationship between the water permeability coefficient and the pore size of the traditional nanofiltration membrane, maintain a high Na2SO4 retention rate, and be suitable for municipal water treatment and industrial water treatment.

[0065] In some embodiments, the polyamine monomer with non-reactive substituent includes at least one of methyl, ethyl, isopropyl, phenyl, trifluoromethyl, and ketone.

[0066] In some embodiments, the polyamine monomer with non-reactive substituent includes at least one of 2-methylpiperazine, 2-phenylpiperazine, trans-2,5-dimethylpiperazine, 2-ethylpiperazine, trans-2,5-diethylpiperazine, 2-isopropylpiperazine, 2-piperazinone, 2-carboxypiperazine, 2,3-diphenylpiperazine, 2-phenyl-2-methylpiperazine, 3,5-diaminotoluene, and 3,5-diaminotrifluorotoluene.

[0067] In some embodiments, the polyamine monomer with non-reactive substituent includes at least one of 2-methylpiperazine and 2,5-dimethylpiperazine.

[0068] In some embodiments, the polyamine monomer with non-reactive substituent and the polyamine monomer without non-reactive substituent have a molar ratio of 1:(0-2), for example, the polyamine monomer with non-reactive substituent and the polyamine monomer without non-reactive substituent can have a molar ratio of 1:0, 1:0.5, 1:1, 1:1.5, 1:2, or a range defined by any two of the foregoing.

[0069] In some embodiments, the polyamine monomer without non-reactive substituent includes at least one of piperazine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and ethylenediamine.

[0070] In some embodiments, the method for preparing the polymer matrix membrane infiltrated with the aqueous-phase monomer includes the following steps:

[0071] mixing the aqueous-phase monomer with water to prepare an aqueous-phase solution,

[0072] immersing the polymer matrix membrane in the aqueous-phase solution to obtain the polymer matrix membrane infiltrated with the aqueous-phase monomer.

[0073] In the aqueous-phase solution, the mass concentration of the aqueous-phase monomer is 0.1%-2.0%, for example, the mass concentration of the aqueous-phase monomer can be 0.1%, 0.5%, 1%, 1.5%, 2.0%, or a range defined by any two of the foregoing.

[0074] In some embodiments, the polymer-based membrane is placed in the water phase solution for a soaking time of 0.5 min to 10 min, for example, the soaking time can be 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., and can also be a range consisting of any two of the foregoing values.

[0075] In some embodiments, the organic solution containing the polybasic acid chloride in the preparation method of the nanofiltration membrane provided comprises at least one of n-hexane, cyclohexane, n-heptane, petroleum ether, and isomeric alkanes.

[0076] In some embodiments, the polybasic acid chloride in the preparation method of the nanofiltration membrane provided comprises at least one of trimesoyl chloride, terephthaloyl chloride, and isophthaloyl chloride.

[0077] In some embodiments, the polymer-based membrane in the preparation method of the nanofiltration membrane provided comprises at least one of a polysulfone-based membrane, a polyethersulfone-based membrane, a polyacrylonitrile-based membrane, a polyvinylidene fluoride-based membrane, a polytetrafluoroethylene-based membrane, and a polyethylene-based membrane.

[0078] In some embodiments, the organic solution containing the polybasic acid chloride in the preparation method of the nanofiltration membrane provided has a mass concentration of the polybasic acid chloride of 0.05% to 1.0%, for example, the mass concentration of the polybasic acid chloride can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc., and can also be a range consisting of any two of the foregoing values.

[0079] In some embodiments, the preparation method of the nanofiltration membrane provided has an interfacial polymerization time of 0.5 min to 10 min.

[0080] In some embodiments, the preparation method of the nanofiltration membrane provided further comprises a solidification treatment after the interfacial polymerization reaction.

[0081] In some embodiments, the solidification treatment comprises thermal solidification and / or ventilation drying solidification.

[0082] In some embodiments, the thermal solidification has a condition of thermal treatment at 50°C to 70°C for 1 min to 10 min.

[0083] In some embodiments, a nanofiltration membrane is provided, which is prepared by the preparation method described above.

[0084] The nanofiltration membrane provided has high pore connectivity or high free volume connectivity.

[0085] In some embodiments, the nanofiltration membrane is applied in water treatment.

[0086] In some embodiments, the nanofiltration membrane is used for municipal water treatment and / or industrial water treatment.

[0087] In some embodiments, a water treatment device is provided, and the filtration component of the water treatment device comprises the aforementioned nanofiltration membrane.

[0088] The following are specific examples. The purpose is to make further detailed description of the present application, to help the skilled and researchers further understand the present application, and the relevant technical conditions do not constitute any limitation on the present application. Any form of modification made within the scope of the claims of the present application is within the protection scope of the claims of the present application.

[0089] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. The experimental methods not specified in the examples are carried out according to the conventional conditions, such as the conditions described in the literature, books or the methods recommended by the manufacturer.

[0090] Example 1

[0091] The polysulfone-based membrane was immersed in a 2-methylpiperazine aqueous solution with a concentration of 0.1 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60°C for 5 min, washed with deionized water, and then tested for filtration performance.

[0092] Example 2

[0093] The polysulfone-based membrane was immersed in a 2-methylpiperazine aqueous solution with a concentration of 0.2 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60°C for 5 min, washed with deionized water, and then tested for filtration performance.

[0094] Example 3

[0095] The polysulfone-based membrane was immersed in a 2-methylpiperazine aqueous solution with a concentration of 0.6 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60°C for 5 min, washed with deionized water, and then tested for filtration performance.

[0096] Example 4

[0097] The polysulfone-based membrane was immersed in a 2-methylpiperazine aqueous solution with a concentration of 1.0 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0098] Example 5

[0099] The polysulfone-based membrane was immersed in a 2,5-dimethylpiperazine aqueous solution with a concentration of 0.2 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0100] Example 6

[0101] The polysulfone-based membrane was immersed in a 2,5-dimethylpiperazine aqueous solution with a concentration of 0.6 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0102] Example 7

[0103] The polysulfone-based membrane was immersed in a 2,5-dimethylpiperazine aqueous solution with a concentration of 1.0 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0104] Comparative Example 1

[0105] The polysulfone-based membrane was immersed in a piperazine aqueous solution with a concentration of 0.1 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0106] Comparative Example 2

[0107] The polysulfone-based membrane was immersed in a piperazine aqueous solution with a concentration of 0.2 wt% for 2 min, and then the excess aqueous solution on the surface was removed. Subsequently, the membrane was reacted in a trimesoyl chloride n-hexane solution with a concentration of 0.1 wt% for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, rinsed with deionized water, and then tested for filtration performance.

[0108] Comparative Example 3

[0109] The polysulfone-based membrane was immersed in a 0.6 wt% aqueous piperazine solution for 2 min, and then the excess surface water solution was removed. Subsequently, the membrane was reacted in a 0.1 wt% benzene tricarboxamidyl chloride solution in n-hexane for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, washed with deionized water, and then tested for filtration performance.

[0110] Comparative Example 4

[0111] The polysulfone-based membrane was immersed in a 1.0 wt% aqueous piperazine solution for 2 min, and then the excess surface water solution was removed. Subsequently, the membrane was reacted in a 0.1 wt% benzene tricarboxamidyl chloride solution in n-hexane for 1 min. Then, the membrane was taken out and heat treated at 60 °C for 5 min, washed with deionized water, and then tested for filtration performance.

[0112] The separation performance of the above examples and comparative examples was tested under the cross-flow filtration conditions of an operating pressure of 0.2-0.6 MPa and a water temperature of 25 °C. The test solution was a 100 mg / L single solute solution of xylose, glucose, sucrose, and raffinose (the rejection rate of which was used to calculate the molecular weight cut-off of the prepared membrane), and a 10 mmol / L Na2SO4 solution with an ionic strength.

[0113] The separation layer thickness of the prepared nanofiltration membrane was tested by atomic force microscopy (Bruker, USA), and the results are shown in Table 1.

[0114] The porosity of the separation layer was calculated by the Hagen-Poisseuille formula, and the results are shown in Table 1. Figure 3

[0115] The polymer internal free volume connectivity was obtained by molecular dynamics simulation (GROMACS 2019.6) tools. The results are shown in Table 1. Figure 4

[0116] The water permeability coefficient, molecular weight cut-off, and Na2SO4 rejection rate of the examples and comparative examples under an operating pressure of 0.2-0.6 MPa are shown in Table 1.

[0117] Table 1

[0118]

[0119] ​​From the comparison of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, it can be seen that under the condition of the same concentration of the reaction monomer, after the reaction monomer is introduced with a methyl group, the water permeability coefficient of the prepared membrane is obviously improved, and the pore size of the membrane is reduced (or changes little), and the rejection rate of Na2SO4 changes little. From the comparison of Example 5 and Example 2, Example 6 and Example 3, Example 7 and Example 4, it can be seen that when two methyl groups are introduced into the reaction monomer, the water permeability coefficient of the prepared membrane is further improved, although the membrane pore size is larger, but the rejection rate of Na2SO4 still maintains at a high level. After introducing the side chain functional group, the prepared nanofiltration membrane can maintain more than 95% rejection rate of Na2SO4, among which the water permeability coefficient of Example 5 reaches 57 LMH / bar, indicating that the example has superior permeation selectivity. Correspondingly, under the condition of the same concentration of the reaction monomer, after the reaction monomer is introduced with a methyl group, the thickness of the separation layer of the prepared membrane is reduced, and the more the number of methyl groups introduced, the more obvious the thickness reduction of the membrane.

[0120] From Figure 1 As can be seen from the mutual relationship diagram between the water permeability coefficient and the cut-off molecular weight of each example and comparative example shown in the table, except for Example 1, the mutual relationship between the water permeability coefficient and the cut-off molecular weight of the membrane of each example is beyond the mutual restriction relationship. As can be seen from the mutual relationship diagram between the water permeability coefficient and the cut-off molecular weight of each example and comparative example shown in the table, Figure 2 As can be seen from the mutual relationship diagram between the water permeability coefficient and the Na2SO4 rejection rate of each example and comparative example shown in the table, under the premise of maintaining a high Na2SO4 rejection rate, the water permeability coefficient of the membrane of Example 1, Example 5, Example 6, Example 7 and the like is greatly improved.

[0121] From Figure 3 As can be seen from the calculated porosity of the examples and comparative examples shown in the table, the calculated porosities of Comparative Example 2, Example 2, Example 6, Example 7 are 1.83%, 2.69%, 2.87, 3.02% respectively, it can be seen that the porosity of the separation layer is significantly improved after the introduction of the methyl group, which indicates that the internal connectivity of the separation layer is obviously improved, it is necessary to note that the calculated porosity is greatly affected by the non-uniformity of the thickness of the separation layer, therefore, when calculating, the comparative examples and examples with similar thickness are selected for comparison. Figure 4 The data shows the internal free volume distribution of the polymer by molecular dynamics simulation, from the simulation results, it is not difficult to see that the introduction of the methyl group significantly improves the proportion of the internal free volume of the polymer, which further proves the synthesis of the high connectivity polymer.

[0122] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0123] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for preparing a nanofiltration membrane, characterized in that, Includes the following steps: The nanofiltration membrane is prepared by interfacial polymerization of a polymer-based membrane impregnated with an aqueous monomer in an organic solution containing polyacryl chlorides. The aqueous monomer satisfies one of the following characteristics: (a1) Polyamine monomers containing non-reactive substituents; (a2) Polyamine monomers containing non-reactive substituents and polyamine monomers without non-reactive substituents.

2. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, One or both of the following conditions must be met: (1) In the polyamine monomer containing a non-reactive substituent, the non-reactive substituent includes at least one of methyl, ethyl, isopropyl, phenyl, trifluoromethyl and ketone groups; (2) The polyamine monomer containing non-reactive substituents includes at least one of 2-methylpiperazine, 2-phenylpiperazine, trans-2,5-dimethylpiperazine, 2-ethylpiperazine, trans-2,5-diethylpiperazine, 2-isopropylpiperazine, 2-piperazinone, 2-carboxypiperazine, 2,3-diphenylpiperazine, 2-phenyl-2-methylpiperazine, 3,5-diaminotoluene, and 3,5-diaminotrifluorotoluene.

3. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The molar ratio of the polyamine monomer containing non-reactive substituents to the polyamine monomer without non-reactive substituents is 1:(0~2).

4. The method for preparing a nanofiltration membrane according to claim 1, characterized in that, The polyamine monomers that do not contain non-reactive substituents include at least one of piperazine, m-phenylenediamine, p-phenylenediamine, pyromellitic triamine, and ethylenediamine.

5. The method for preparing a nanofiltration membrane according to any one of claims 1 to 4, characterized in that, The method for preparing the polymer-based membrane impregnated with aqueous monomers includes the following steps: The aqueous monomer is mixed with water to prepare an aqueous solution; The polymer-based membrane is immersed in the aqueous solution to prepare the polymer-based membrane impregnated with the aqueous monomer. In the aqueous solution, the mass concentration of the aqueous monomer is 0.1% to 2.0%. Optionally, in the step of immersing the polymer-based membrane in the aqueous solution, the immersion time is 0.5 min to 10 min.

6. The method for preparing a nanofiltration membrane according to any one of claims 1 to 4, characterized in that, One or more of the following conditions must be met: (1) In the organic solution containing polyacryl chloride, the solvent includes at least one of n-hexane, cyclohexane, n-heptane, petroleum ether and isoparaffins; (2) The polyacryl chloride includes at least one of pyromellitic trichloroisocyanurate, terephthaloyl chloride and isophthaloyl chloride; (3) The polymer-based membrane includes at least one of polysulfone-based membrane, polyethersulfone-based membrane, polyacrylonitrile-based membrane, polyvinylidene fluoride-based membrane, polytetrafluoroethylene-based membrane, and polyethylene-based membrane; (4) In the organic solution containing polyacryl chloride, the mass concentration of polyacryl chloride is 0.05%~1.0%; (5) The time for the interfacial polymerization reaction is 0.5 min to 10 min.

7. The method for preparing a nanofiltration membrane according to any one of claims 1 to 4, characterized in that, After the interfacial polymerization reaction is completed, a curing process is also included; Optionally, the curing process may include heat curing and / or ventilation drying curing; Optionally, the heat curing conditions include heat treatment at 50°C to 70°C for 1 min to 10 min.

8. A nanofiltration membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the nanofiltration membrane according to claim 8 in water treatment.

10. A water treatment device, characterized in that, The filtration component of the water treatment device includes the nanofiltration membrane as described in claim 8.

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