Hybrid matrix nanofiltration membrane, method for preparing the same and application thereof

Abstract

This invention relates to the field of membrane separation technology, and discloses a hybrid matrix nanofiltration membrane, its preparation method, and its applications. The hybrid matrix nanofiltration membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; the support layer is a polymer layer containing nano-manganese dioxide; and the separation layer is a polyamide layer. In the polymer support layer of this hybrid matrix nanofiltration membrane, the nano-manganese dioxide gives the support layer a rich pore structure, thus increasing the flux of the support layer. The abundant hydroxyl groups on the surface of the nano-manganese dioxide increase the hydrophilicity of the support layer surface, resulting in a thinner polyamide separation layer with lower permeation resistance. Simultaneously, the polyamide separation layer exhibits good solvent resistance, giving this hybrid matrix nanofiltration membrane excellent separation performance in the field of solvent-resistant nanofiltration.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a mixed matrix nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] Organic solvent nanofiltration is a green and energy-saving novel membrane technology for treating organic solvents, with broad application prospects in industries such as petrochemicals, food, and pharmaceuticals. Most existing commercial organic solvent nanofiltration membranes are monolithic asymmetric membranes prepared by phase inversion. Due to their thicker skin and higher filtration resistance, they have lower flux and require higher operating pressures. Hybrid matrix membranes prepared by filling a polymer continuous phase with inorganic materials as the dispersed phase typically exhibit higher flux than nanofiltration membranes prepared solely from organic polymers due to the combined effects of the pore and interface properties of the inorganic materials. This has become a research hotspot for many scholars both domestically and internationally.

[0003] CN105536575A discloses a solvent-resistant nanofiltration hybrid matrix membrane and its preparation method. The membrane is obtained by sequentially coating the surface of a fully water-absorbed polyacrylonitrile ultrafiltration membrane with solution A and solution B, followed by drying. Solution A is an aqueous solution of polydopamine nanoparticles dispersed in polyethyleneimine, and solution B is an organic solution of trimesoyl chloride. The prepared solvent-resistant nanofiltration hybrid matrix membrane exhibits suitable separation performance and superior solvent resistance compared to pure polymer membranes, enabling its application in solvents of varying polarities.

[0004] CN114288881A discloses a ZIFs mixed matrix composite nanofiltration membrane and its preparation method. The method includes the following steps: 1) preparation of a functionalized support membrane, 2) immersion in a metal salt solution, 3) surface reaction to generate a selective separation layer and ZIFs, and 4) post-treatment. The nanofiltration membrane prepared by this method exhibits high efficiency in retaining small molecule pollutants and high selective permeability to inorganic salts.

[0005] CN114100372A discloses a method for preparing a nanoparticle hybrid matrix nanofiltration membrane for drug separation. The method includes the following steps: first, using aldehyde monomers, ketone monomers, and amino-rich conjugated aromatic hydrocarbon monomers as raw materials, imine-type conjugated microporous nanoparticles are polymerized under mild conditions; then, an interfacial polymerization method is used to prepare the nanoparticle hybrid matrix nanofiltration membrane. The resulting nanoparticle hybrid matrix nanofiltration membrane has a stable structure and exhibits good hydrophilicity and antifouling properties.

[0006] In summary, most existing technologies for preparing hybrid matrix nanofiltration membranes involve adding inorganic materials to the separation layer of the composite membrane. However, due to the very thin separation layer and the poor compatibility between inorganic materials and organic polymers, the introduction of inorganic materials often introduces defects into the separation layer, leading to a decrease in retention capacity. Furthermore, the aforementioned introduced nanoparticles, such as polydopamine nanoparticles, ZIF nanoparticles, and imine-type conjugated microporous nanoparticles, still suffer from problems such as complex preparation methods and high production costs.

[0007] Therefore, the current problem is the urgent need to research and develop a mixed matrix organic solvent nanofiltration membrane with high throughput, good separation performance, simple preparation process, and low cost, as well as its preparation method. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of poor compatibility between inorganic materials and organic polymers in existing separation membranes, which easily lead to defects and reduced retention capacity, as well as the complexity and high cost of preparation methods. This invention provides a hybrid matrix nanofiltration membrane, its preparation method, and its applications. In the polymer support layer of this hybrid matrix nanofiltration membrane, the presence of nano-manganese dioxide gives the support layer a rich pore structure, thus increasing the flux of the support layer. Furthermore, the abundant hydroxyl groups on the surface of nano-manganese dioxide increase the hydrophilicity of the support layer surface, resulting in a thinner polyamide separation layer with lower permeation resistance. Simultaneously, the polyamide separation layer exhibits good solvent resistance, giving this hybrid matrix nanofiltration membrane excellent separation performance in the field of solvent-resistant nanofiltration.

[0009] To achieve the above objectives, the first aspect of the present invention provides a hybrid matrix nanofiltration membrane, wherein the hybrid matrix nanofiltration membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer;

[0010] The support layer is a polymer layer containing nano-manganese dioxide;

[0011] The separation layer is a polyamide layer.

[0012] A second aspect of the present invention provides a method for preparing a hybrid matrix nanofiltration membrane, wherein the method includes the following steps:

[0013] S1. The dispersion containing nano-manganese dioxide is mixed and dissolved with the polymer to obtain the casting solution;

[0014] S2. Load the casting liquid onto a nonwoven fabric and perform a phase transformation to obtain a support layer substrate;

[0015] S3. The support layer substrate is first immersed in a polyamine composite solution to obtain the initial nanofiltration membrane-I;

[0016] S4. The initial nanofiltration membrane-I is immersed in a solution containing polyacrylamide chloride to obtain the initial nanofiltration membrane-II, and then subjected to heat treatment to obtain the mixed matrix nanofiltration membrane.

[0017] The polyamine composite solution contains polyethylene polyamine compounds and branched polyethyleneimine.

[0018] A third aspect of the present invention provides a mixed matrix nanofiltration membrane prepared by the preparation method described in the second aspect of the present invention.

[0019] The fourth aspect of the present invention provides an application of the hybrid matrix nanofiltration membrane described in the first or third aspect of the present invention in the fields of organic solvent nanofiltration and solvent-resistant nanofiltration.

[0020] Through the above technical solutions, the hybrid matrix nanofiltration membrane, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0021] (1) In the polymer support layer of the hybrid matrix nanofiltration membrane, the presence of nano-manganese dioxide gives the support layer a rich pore structure, thus increasing the flux of the support layer. In addition, the abundant hydroxyl groups on the surface of nano-manganese dioxide increase the hydrophilicity of the support layer surface, resulting in a thinner polyamide separation layer with lower permeation resistance. At the same time, the polyamide separation layer has good solvent resistance, giving the hybrid matrix nanofiltration membrane excellent separation performance in the field of solvent-resistant nanofiltration.

[0022] (2) The addition of nano-manganese dioxide to the support layer can improve the stability of the mixed matrix nanofiltration membrane; in addition, by adjusting the content of nano-manganese dioxide, the separation performance of the mixed matrix nanofiltration membrane can be controlled, making the performance of the mixed matrix nanofiltration membrane easy to adjust according to actual needs and with a wide range of applications.

[0023] (3) The method for preparing the mixed matrix nanofiltration membrane is simple, and the operating pressure is low and the flux is high, making it suitable for separation in alcohol, ester, benzene and alkane organic solvents. Attached Figure Description

[0024] Figure 1 This is a 4μm scanning electron microscope image of the surface of the mixed matrix nanofiltration membrane A1 prepared in Example 1.

[0025] Figure 2 This is a 200nm scanning electron microscope image of the surface of the mixed matrix nanofiltration membrane A1 prepared in Example 1.

[0026] Figure 3 This is the infrared spectrum of the mixed matrix nanofiltration membrane A1 prepared in Example 1.

[0027] Figure 4The surface XPS oxygen element fine spectrum and multi-peak fitting curve of the composite separation membrane A2 prepared in Example 2 of this invention are shown. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] The first aspect of the present invention provides a hybrid matrix nanofiltration membrane, wherein the hybrid matrix nanofiltration membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer;

[0030] The support layer is a polymer layer containing nano-manganese dioxide;

[0031] The separation layer is a polyamide layer.

[0032] In this invention, the presence of nano-manganese dioxide in the polymer support layer of the hybrid matrix nanofiltration membrane gives the support layer a rich pore structure, thereby increasing the flux of the support layer. Furthermore, the abundant hydroxyl groups on the surface of the nano-manganese dioxide enhance the hydrophilicity of the support layer surface, resulting in a thinner polyamide separation layer with lower permeation resistance. Simultaneously, the polyamide separation layer exhibits better solvent resistance, further improving the flux for ethanol. Therefore, this hybrid matrix nanofiltration membrane demonstrates excellent separation performance in the field of solvent-resistant nanofiltration.

[0033] According to the present invention, in the support layer, the mass ratio of nano-manganese dioxide to polymer is 1-50:100.

[0034] In this invention, the mass ratio of nano-manganese dioxide to polymer satisfies the above-mentioned range, which can obtain a support layer with specific pore structure and porosity, thereby improving membrane separation performance.

[0035] Furthermore, the mass ratio of the nano-manganese dioxide to the polymer is 10-30:100.

[0036] According to the present invention, the average particle size of the nano-manganese dioxide is 20-80 nm.

[0037] In this invention, the average particle size of the nano-manganese dioxide meets the above-mentioned range, which enables the formation of a polymer support layer with well-dispersed nano-manganese dioxide.

[0038] Furthermore, the average particle size of the nano-manganese dioxide is 30-60 nm.

[0039] According to the present invention, the polymer is selected from at least one of polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyacrylonitrile, and polyarylamide.

[0040] According to the present invention, the material constituting the reinforcing layer is selected from polyolefin nonwoven fabric and / or polyester nonwoven fabric.

[0041] According to the present invention, the thickness of the support layer is 20-100 μm, preferably 30-60 μm.

[0042] According to the present invention, the support layer has a porous structure, wherein the porosity of the support layer is 30-80% and the average pore size of the support layer is 10-50 nm.

[0043] In this invention, the porosity and average pore size of the support layer meet the above-mentioned range, which enables the support layer to have a specific pore structure, thereby improving the separation performance of the mixed matrix nanofiltration membrane.

[0044] Furthermore, the support layer has a porous structure, wherein the porosity of the support layer is 50-70%, and the average pore size of the support layer is 15-30 nm.

[0045] According to the present invention, the thickness of the separation layer is 20-150 nm.

[0046] In this invention, the thickness of the separation layer meets the above-mentioned range, which enables a high membrane flux.

[0047] Furthermore, the thickness of the separation layer is 50-100 nm.

[0048] According to the present invention, the average pore size of the separation layer is 0.15-0.5 nm.

[0049] In this invention, the porosity and average pore size of the separation layer meet the above-mentioned range, which can ensure high throughput and high retention rate, and ensure excellent separation performance.

[0050] Furthermore, the average pore size of the separation layer is 0.2-0.3 nm.

[0051] According to the present invention, the polymer forming the polyamide layer comprises structural unit A provided by polyethylene polyamine, segment B provided by branched polyethyleneimine, and structural unit C provided by polyacrylamide compound.

[0052] According to the present invention, based on the total weight of the polymer forming the polyamide layer, the content of structural unit A is 15-45 wt%, preferably 20-35 wt%; the content of segment B is 5-35 wt%, preferably 5-20 wt%; and the content of structural unit C is 50-80 wt%, preferably 60-70 wt%.

[0053] According to the present invention, the degree of crosslinking of the polyamide layer is 40-80%.

[0054] In this invention, the content of carboxyl and amide groups in the crosslinked polymer is measured by XPS method, and the degree of crosslinking of the separation layer polymer is calculated accordingly.

[0055] Furthermore, the degree of crosslinking of the polyamide layer is 60-80%.

[0056] According to the present invention, the polyethylene polyamine has the structure shown in Formula I;

[0057] Where n≥5.

[0058] According to the present invention, the polyethylene polyamine is selected from at least one of hexaethylene heptaamine, heptaethylene octaamine, and octaethylene nonaamine.

[0059] In this invention, the polyethylene polyamine can be any one selected from hexaethylene heptaamine, heptaethylene octaamine, and octaethylene nonaamine, or a mixture of any two or more of them.

[0060] Furthermore, n is preferably 5-7.

[0061] According to the present invention, the branched polyethyleneimine has a weight-average molecular weight of 1800-70000 g / mol.

[0062] In this invention, the weight-average molecular weight of the branched polyethyleneimine meets the above-mentioned range, and the resulting separation layer is thinner and has a higher retention rate.

[0063] According to the present invention, the polyacrylamide chloride compound is selected from at least one of pyromellitic chloride, isophthaloyl chloride and terephthaloyl chloride.

[0064] According to the present invention, the toluene flux of the hybrid matrix nanofiltration membrane is ≥5 Lm. -2 h -1 bar -1 Ethanol flux ≥ 2.5 Lm - 2 h -1 bar -1 Sudan III interception rate ≥90%.

[0065] According to the present invention, the inventors further discovered that the hybrid matrix nanofiltration membrane prepared by further crosslinking the support layer can achieve high flux for ethanol and toluene solvents, while also exhibiting high flux for DMF solvent; specifically, the flux for DMF is ≥5 L / m³. -2 h -1 .

[0066] A second aspect of the present invention provides a method for preparing a hybrid matrix nanofiltration membrane, wherein the method includes the following steps:

[0067] S1. The dispersion containing nano-manganese dioxide is mixed and dissolved with the polymer to obtain the casting solution;

[0068] S2. Load the casting liquid onto a nonwoven fabric and perform a phase transformation to obtain a support layer substrate;

[0069] S3. The support layer substrate is first immersed in a polyamine composite solution to obtain the initial nanofiltration membrane-I;

[0070] S4. The initial nanofiltration membrane-I is immersed in a solution containing polyacrylamide chloride to obtain the initial nanofiltration membrane-II, and then subjected to heat treatment to obtain the mixed matrix nanofiltration membrane.

[0071] The polyamine composite solution contains polyethylene polyamine compounds and branched polyethyleneimine.

[0072] In this invention, a casting solution is prepared by combining nano-manganese dioxide with a polymer. This increases the interfacial effect between the manganese dioxide and the polymer, resulting in a support layer with abundant pores and improved separation efficiency. Furthermore, the support layer substrate is immersed in a polyamine composite solution and a solution containing polyacrylamide compounds, respectively, for a first and a second immersion. This allows the polyamine and polyacrylamide compounds to undergo interfacial polymerization on the support layer surface, forming a polyamide separation layer. The inventors discovered that the abundant hydroxyl groups on the surface of nano-manganese dioxide promote a thinner polyamide separation layer with lower permeation resistance, thereby further improving the separation efficiency of the mixed matrix nanofiltration membrane.

[0073] In this invention, the dispersion containing nano-manganese dioxide can be prepared in accordance with conventional methods in the art. In this invention, the dispersion containing nano-manganese dioxide is obtained by ultrasonically dispersing nano-manganese dioxide in a solvent.

[0074] In this invention, the solvent is not particularly limited. For the sake of subsequent processes, the solvent can be any solvent capable of dissolving the polymer, such as N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, dioxane, acetonitrile, acetone, chloroform, etc.

[0075] In this invention, there are no particular limitations on the conditions for ultrasonic dispersion. For example, ultrasonic dispersion can be performed at 10-60℃ and 20kHz-200kHz for 30-120 minutes.

[0076] According to the present invention, in step S1, the mass ratio of the nano-manganese dioxide to the polymer is 1-50:100.

[0077] In this invention, the mass ratio of the nano-manganese dioxide and the polymer satisfies the above range, which can obtain a support layer with specific pore structure and porosity, thereby improving membrane separation performance.

[0078] Furthermore, the mass ratio of the nano-manganese dioxide to the polymer is 10-30:100.

[0079] According to the present invention, the polymer is selected from at least one of polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyacrylonitrile, and polyarylamide.

[0080] According to the present invention, in step S2, the casting solution is scraped onto a nonwoven fabric and immersed in a coagulation bath to carry out the phase transformation, wherein the solvent used in the coagulation bath is a poor solvent for the polymer.

[0081] In this invention, the unsuitable solvent for the polymer can be at least one of water, methanol, ethanol, and isopropanol.

[0082] In this invention, when the polymer in step S1 is selected from polyimide and / or polyetherimide, in order to further improve the solvent resistance of the prepared mixed matrix nanofiltration membrane, the support layer substrate can be crosslinked by immersing it in an alcohol solution of hexamethylenediamine.

[0083] In this invention, there are no particular limitations on the immersion conditions of the support layer substrate in the alcoholic solution of hexamethylenediamine. For example, it can be immersed at 20-60°C for 0.5-48 hours.

[0084] According to the present invention, in step S3, the total mass concentration of the polyethylene polyamine compound and the branched polyethyleneimine in the polyamine composite solution is 0.1-5 wt%, preferably 0.2-2 wt%.

[0085] Preferably, the content of the polyethylene polyamine compound is 10-99 wt%, based on the total mass of the polyethylene polyamine compound and the branched polyethyleneimine.

[0086] In this invention, based on the total mass of the polyethylene polyamine compound and the branched polyethyleneimine, the content of the polyethylene polyamine compound within the above-mentioned range can yield a separation layer with smaller pore size and thinner thickness.

[0087] Furthermore, based on the total mass of the polyethylene polyamine compound and the branched polyethyleneimine, the content of the polyethylene polyamine compound is 50-95 wt%.

[0088] According to the present invention, the polyethylene polyamine has the structure shown in Formula II;

[0089] Where n≥5.

[0090] In this invention, the types of polyethylene polyamines are the same as those described in the first aspect of this invention, and will not be repeated here.

[0091] In this invention, each polyethylenepolyamine compound molecule contains two primary amines and multiple secondary amines. The polyacrylamide chloride can react with both primary and secondary amines to form a cross-linked polyamide structure. Compared to commonly used amine monomers such as piperazine and m-phenylenediamine, polyethylenepolyamine has a suitable molecular weight and a longer chain structure, resulting in a slower diffusion rate. This allows it to better perform interfacial polymerization with polyacrylamide chloride to prepare thinner mixed-matrix nanofiltration membranes.

[0092] According to the present invention, the branched polyethyleneimine has a weight-average molecular weight of 1800-70000 g / mol.

[0093] According to the present invention, in step S4, the concentration of the polyacryl chloride compound in the solution containing the polyacryl chloride compound is 0.05-2.5 wt%, preferably 0.08-0.5 wt%.

[0094] According to the present invention, the polyacrylamide chloride compound is selected from at least one of pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride.

[0095] According to the present invention, the solvent in the solution containing the polyacrylamide chloride compound is selected from at least one of n-hexane, n-heptane, and isoalkanes.

[0096] According to the present invention, the conditions for the first immersion and the second immersion each independently include: a temperature of 20-30°C and a time of 10-300s.

[0097] According to the present invention, the conditions for the heat treatment include: a temperature of 50-80°C and a time of 1-10 min.

[0098] In some embodiments of the present invention, the heat treatment can further increase the crosslinking degree of the separation layer polymer and improve the stability of the composite membrane.

[0099] According to the present invention, based on the total amount of the polyamine composite solution, the polyamine composite solution further contains 0.1-2 wt% of catalyst and 0.03-0.2 wt% of surfactant.

[0100] In this invention, the inventors discovered that when the polyamine composite solution contains a catalyst, the flux of the mixed matrix nanofiltration membrane can be further improved. When the polyamine composite solution contains a surfactant, the retention performance of the mixed matrix nanofiltration membrane can be further improved.

[0101] According to the present invention, the catalyst is selected from at least one of sodium bicarbonate, ammonium bicarbonate, sodium hydroxide, and triethylamine.

[0102] According to the present invention, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and dodecyltrimethylammonium chloride.

[0103] A third aspect of the present invention provides a mixed matrix nanofiltration membrane prepared by the preparation method described in the second aspect of the present invention.

[0104] In this invention, the hybrid matrix nanofiltration membrane has the same structure and performance as the hybrid matrix nanofiltration membrane described in the first aspect of this invention, and will not be described again here.

[0105] The fourth aspect of the present invention provides an application of the hybrid matrix nanofiltration membrane described in the first or third aspect of the present invention in the fields of organic solvent nanofiltration and solvent-resistant nanofiltration.

[0106] The present invention will be described in detail below through embodiments.

[0107] In the following examples, the average particle size of nano-manganese dioxide was measured using a particle size analyzer;

[0108] The porosity of the substrate layer was determined by gravimetric method;

[0109] The average pore size of the substrate layer was measured using an ultrafiltration membrane pore size analyzer (PSMA-10, Nanjing Gaoqian Functional Materials Technology Co., Ltd.);

[0110] The thickness of the separation layer was observed using a scanning electron microscope;

[0111] The degree of crosslinking reaction (DC) of the composite membrane separation layer is characterized by testing the fine oxygen spectrum of the membrane surface using X-ray photoelectron spectroscopy (XPS). This is obtained by calculating the content of O=C-N and O=C-O groups, as shown in Equation III. By fitting the multiple peaks of the fine spectrum into a single peak, the peak area of ​​each peak is calculated, representing the content of that group. In Equation III, C... –CON< For the peak area of ​​O = C - N, C –COO– This represents the peak area of ​​O = C - O.

[0112]

[0113] The content of each structural unit in the separated layer was calculated by subtracting the amount of residual monomer in the solution after the reaction from the amount of the corresponding monomer added before the reaction. The amount of residual monomer in the solution after the reaction was determined by gas chromatography.

[0114] Membrane separation performance was measured using dead-end filtration, under the following conditions: temperature 25℃, pressure 2MPa, and stirring speed 500rpm. The concentration of Sudan III ethanol solution was calculated using an ultraviolet-visible spectrophotometer at a wavelength of 505nm via absorbance versus concentration curves.

[0115] Polyimide, purchased from Evonik, brand name P84.

[0116] Polyetherimide, purchased from SABIC Innovative Plastics (China) Co., Ltd., brand name Ultem 1000.

[0117] Nano-manganese dioxide, purchased from Shanghai Naio Nanotechnology Co., Ltd., with average particle sizes of 50nm and 80nm.

[0118] Nano-silica, purchased from Shenzhen Jingcai Chemical Co., Ltd., with an average particle size of 50nm.

[0119] Branched polyethyleneimine (weight average molecular weight 25,000), trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride were purchased from Bailingwei Technology Co., Ltd.; polyethylene polyamine (n=5) reagent was purchased from Beijing Innocare Technology Co., Ltd.

[0120] Isoparaffin: Isopar E, purchased from ExxonMobil.

[0121] The cross-linked polyimide support layer and the cross-linked polyetherimide support layer were prepared in the laboratory using the following method:

[0122] The polyimide support layer and the polyetherimide support layer were immersed in a methanol solution containing 4 wt% hexamethylenediamine for 4 hours at room temperature, and then rinsed with deionized water for later use.

[0123] Example 1

[0124] S1. Add 2.5g of nano-manganese dioxide to 37.5g of N,N-dimethylacetamide, ultrasonically disperse for 60min, then add 10g of polyetherimide, heat and stir to dissolve the polymer, and obtain the casting solution.

[0125] S2. The casting solution is scraped onto a polypropylene nonwoven fabric and immersed in deionized water for phase transformation to obtain the support layer substrate.

[0126] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.4g polyethylene polyamine, 0.1g branched polyethyleneimine and 100g water for 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0127] S4. The initial nanofiltration membrane-I is immersed for 30 seconds in a solution of 0.08 g pyromellitic acid chloride, 0.02 g isophthaloyl chloride and 100 g Isopar E solvent (25°C). The membrane is then removed to remove the residual Isopar E solvent on the surface, thus obtaining the initial nanofiltration membrane-II.

[0128] S5. Heat the initial nanofiltration membrane-II in a 60°C oven for 3 minutes to obtain the mixed matrix nanofiltration membrane A1.

[0129] The mixed matrix nanofiltration membrane A1 was subjected to scanning electron microscopy (SEM) analysis. Figure 1 and Figure 2 It can be observed that the surface of the hybrid matrix nanofiltration membrane exhibits a uniform and dense structure at both 4μm and 200nm. Figure 3 The presence of characteristic absorption peaks of amide structures in the infrared spectrum indicates that polyamines react with polyacryl chlorides to form polyamides.

[0130] Example 2

[0131] S1. Add 2.5g of nano-manganese dioxide to 37.5g of N,N-dimethylacetamide, ultrasonically disperse for 60min, then add 10g of polyetherimide, heat and stir to dissolve the polymer, and obtain the casting solution.

[0132] S2. The casting solution is scraped onto a polypropylene nonwoven fabric, immersed in deionized water for phase inversion, and then soaked in a 4 wt% hexamethylenediamine methanol solution for 12 h to obtain the support layer substrate.

[0133] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.4g polyethylene polyamine, 0.1g branched polyethyleneimine and 100g water for 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0134] S4. The initial nanofiltration membrane-I is immersed for 30 seconds in a solution of 0.08 g pyromellitic acid chloride, 0.02 g isophthaloyl chloride and 100 g Isopar E solvent (25°C). The membrane is then removed to remove the residual Isopar E solvent on the surface, thus obtaining the initial nanofiltration membrane-II.

[0135] S5. Heat the initial nanofiltration membrane-II in a 60°C oven for 3 minutes to obtain the mixed matrix nanofiltration membrane A2.

[0136] Figure 4 The XPS oxygen element fine curve of the surface of the mixed matrix nanofiltration membrane A2 was obtained by fitting the peaks to obtain the O=C-N group peak and the O=C-O group peak. The degree of crosslinking DC was calculated by comparing their peak areas using Equation III.

[0137] Example 3

[0138] S1. Add 3g of nano-manganese dioxide to 37g of N,N-dimethylacetamide, ultrasonically disperse for 60min, then add 10g of polyetherimide, heat and stir to dissolve the polymer, and obtain the casting solution.

[0139] S2. The casting solution is scraped onto the polyolefin nonwoven fabric, immersed in deionized water for phase inversion, and then soaked in a 4 wt% hexamethylenediamine methanol solution for 12 h to obtain the support layer substrate.

[0140] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.4g polyethylene polyamine, 0.1g branched polyethyleneimine and 100g water for 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0141] S4. The initial nanofiltration membrane-I is immersed for a second time in a solution of 0.02g pyromellitic acid chloride, 0.08g isophthaloyl chloride and 100g Isopar E solvent (25°C) for 30s. The membrane is then removed to remove the residual Isopar E solvent on the surface, thus obtaining the initial nanofiltration membrane-II.

[0142] S5. Heat the initial nanofiltration membrane-II in a 60°C oven for 3 minutes to obtain the mixed matrix nanofiltration membrane A3.

[0143] Example 4

[0144] S1. Add 5g of nano manganese dioxide to 35g of N,N-dimethylacetamide, ultrasonically disperse for 60min, then add 10g of polyimide, heat and stir to dissolve the polymer, and obtain the casting solution.

[0145] S2. The casting solution is scraped onto a polyolefin nonwoven fabric and immersed in deionized water for phase transformation to obtain the support layer substrate.

[0146] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.3g polyethylene polyamine, 0.2g branched polyethyleneimine, 0.03g sodium dodecyl sulfate and 100g water for a first immersion of 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0147] S4. The initial nanofiltration membrane-I is immersed for 30 seconds in a solution of 0.08 g pyromellitic acid chloride, 0.02 g isophthaloyl chloride and 100 g Isopar E solvent (25°C). The membrane is then removed to remove the residual Isopar E solvent on the surface, thus obtaining the initial nanofiltration membrane-II.

[0148] S5. Heat the initial nanofiltration membrane-II in a 60°C oven for 3 minutes to obtain the mixed matrix nanofiltration membrane A4.

[0149] Example 5

[0150] S1, Same as Example 4;

[0151] S2, Same as Example 4;

[0152] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.3g polyethylene polyamine, 0.2g branched polyethyleneimine, 0.03g sodium dodecyl sulfate, 0.5g ammonium bicarbonate and 100g water for a first immersion of 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0153] S4, Same as Example 4;

[0154] S5. Same as in Example 4, to obtain a mixed matrix nanofiltration membrane A5.

[0155] Example 6

[0156] S1. Add 2g of nano-manganese dioxide to 38g of N,N-dimethylacetamide, disperse ultrasonically for 60min, then add 10g of polyetherimide, heat and stir to dissolve the polymer, and obtain the casting solution.

[0157] S2. The casting solution is scraped onto the polyolefin nonwoven fabric, immersed in deionized water for phase inversion, and then soaked in a 4 wt% hexamethylenediamine methanol solution for 12 h to obtain the support layer substrate.

[0158] S3. The support layer substrate is immersed in a polyamine composite solution (25°C) consisting of 0.3g polyethylene polyamine, 0.2g branched polyethyleneimine, 0.03g sodium dodecyl sulfate, 0.5g ammonium bicarbonate and 100g water for a first immersion of 30s. After removal, the residual water on the surface is removed to obtain the initial nanofiltration membrane-I.

[0159] S4. The initial nanofiltration membrane-I is immersed for 30 seconds in a solution of 0.08 g pyromellitic acid chloride, 0.02 g isophthaloyl chloride and 100 g Isopar E solvent (25°C). The membrane is then removed to remove the residual Isopar E solvent on the surface, thus obtaining the initial nanofiltration membrane-II.

[0160] S5. Heat the initial nanofiltration membrane-II in a 60°C oven for 3 minutes to obtain the mixed matrix nanofiltration membrane A6.

[0161] Example 7

[0162] Following the method of Example 6, except that the polyamine composite solution does not contain sodium dodecyl sulfate, a mixed matrix nanofiltration membrane A7 is obtained.

[0163] Example 8

[0164] Following the method of Example 6, except that the polyamine composite solution does not contain ammonium bicarbonate, a mixed matrix nanofiltration membrane A8 is obtained.

[0165] Example 9

[0166] The method of Example 6 was followed, except that the average particle size of the nano-manganese dioxide was 80 nm. A mixed matrix nanofiltration membrane A9 was obtained.

[0167] Example 10

[0168] The method of Example 6 is followed, except that in step S3, the polyamine composite solution consists of 0.2 g polyethylene polyamine, 0.3 g branched polyethyleneimine, 0.03 g sodium dodecyl sulfate, 0.5 g ammonium bicarbonate, and 100 g water. A mixed matrix nanofiltration membrane A10 is obtained.

[0169] Example 11

[0170] The method of Example 6 was followed, except that in step S4, 0.08 g of trimesoyl chloride and 0.02 g of isophthaloyl chloride were replaced with 0.1 g of trimesoyl chloride. A mixed matrix nanofiltration membrane A11 was obtained.

[0171] Example 12

[0172] The method of Example 6 was followed, except that in step S3, sodium dodecyl sulfate was 0.1 g and ammonium bicarbonate was 1 g; and in step S4, pyromellitic methyl chloride was 0.3 g and isophthaloyl chloride was replaced with 0.2 g. A mixed matrix nanofiltration membrane A12 was obtained.

[0173] Example 13

[0174] The method of Example 6 was followed, except that 0.3 g of polyethylene polyamine and 0.2 g of branched polyethyleneimine were replaced with 0.5 g of polyethylene polyamine. A mixed matrix nanofiltration membrane A13 was obtained.

[0175] Comparative Example 1

[0176] Following the method of Example 6, except that nanofiltration membrane D1 was obtained without nano-manganese dioxide.

[0177] Comparative Example 2

[0178] Following the method of Example 6, except that nano-manganese dioxide was replaced with nano-silica, a mixed matrix nanofiltration membrane D2 was obtained.

[0179] Comparative Example 3

[0180] The method of Example 6 was followed, except that 0.3 g of polyethylenepolyamine and 0.2 g of branched polyethyleneimine were replaced with 0.5 g of piperazine. A mixed matrix nanofiltration membrane D3 was obtained.

[0181] Test case

[0182] The separation performance of the mixed matrix nanofiltration membranes prepared in the examples and comparative examples was tested, and the results are shown in Table 1. The porosity, average pore size, and thickness of each layer of the mixed matrix nanofiltration membranes prepared in the examples and comparative examples were tested, and the results are shown in Table 2.

[0183] Table 1

[0184]

[0185] P.S.: The support layers in Examples 1, 4, and 5 were not cross-linked, and therefore dissolved in DMF.

[0186] Table 2

[0187]

[0188]

[0189] Table 3

[0190] serial number Structural unit A (wt%) Segment B (wt%) Structural unit C (wt%) Example 1 23 8 69 Example 2 22 8 70 Example 3 20 7 73 Example 4 21 10 69 Example 5 19 9 72 Example 6 22 10 68 Example 7 20 9 71 Example 8 23 12 65 Example 9 25 13 62 Example 10 18 12 70 Example 11 25 11 64 Example 12 16 9 75 Example 13 29 0 71 Comparative Example 1 23 10 67 Comparative Example 2 23 10 67 Comparative Example 3 / / /

[0191] As can be seen from Examples and Comparative Example 1, the mixed-matrix organic solvent nanofiltration membrane prepared by the present invention has higher flux and retention rate than the organic solvent nanofiltration membrane composed of pure polymer. As can be seen from Example 6 and Comparative Example 3, the polyethylenepolyamine separation layer unique to the mixed-matrix organic solvent nanofiltration membrane prepared by the present invention exhibits higher flux and retention rate than the traditional piperazine amide separation layer. As can be seen from Examples 3 and 6-7, the method provided by the present invention can further improve the retention performance of the nanofiltration membrane when the aqueous phase contains a surfactant; and can significantly improve the water flux of the nanofiltration membrane when the aqueous phase contains a catalyst.

[0192] Examples 1 and 2 demonstrate that the support layer, after being immersed in hexamethylenediamine alcohol solution, can resist the dissolution of DMF and has excellent flux for DMF.

[0193] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A hybrid matrix nanofiltration membrane, characterized in that, The hybrid matrix nanofiltration membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; The support layer is a polymer layer containing nano-manganese dioxide, and the polymer is selected from at least one of polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyacrylonitrile and polyarylamide; The separation layer is a polyamide layer.

2. The hybrid matrix nanofiltration membrane according to claim 1, wherein, In the support layer, the mass ratio of nano-manganese dioxide to polymer is 1-50:

100.

3. The hybrid matrix nanofiltration membrane according to claim 2, wherein, In the support layer, the mass ratio of nano-manganese dioxide to polymer is 10-30:

100.

4. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The average particle size of the nano-manganese dioxide is 20-80 nm.

5. The hybrid matrix nanofiltration membrane according to claim 4, wherein, The average particle size of the nano-manganese dioxide is 30-60 nm.

6. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The material constituting the reinforcing layer is selected from polyolefin nonwoven fabric and / or polyester nonwoven fabric.

7. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The thickness of the support layer is 20-100 μm.

8. The hybrid matrix nanofiltration membrane according to claim 7, wherein, The thickness of the support layer is 30-60 μm.

9. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The support layer has a porous structure, wherein the porosity of the support layer is 30-80%.

10. The hybrid matrix nanofiltration membrane according to claim 9, wherein, The porosity of the support layer is 50-70%.

11. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The average pore size of the support layer is 10-50 nm.

12. The hybrid matrix nanofiltration membrane according to claim 11, wherein, The average pore size of the support layer is 15-30 nm.

13. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The thickness of the separation layer is 20-150 nm.

14. The hybrid matrix nanofiltration membrane according to claim 13, wherein, The thickness of the separation layer is 50-100 nm.

15. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The average pore size of the separation layer is 0.15-0.5 nm.

16. The hybrid matrix nanofiltration membrane according to claim 15, wherein, The average pore size of the separation layer is 0.2-0.3 nm.

17. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The polymer forming the polyamide layer comprises structural unit A provided by polyethylene polyamine, segment B provided by branched polyethyleneimine, and structural unit C provided by polyacrylamide compound.

18. The hybrid matrix nanofiltration membrane according to claim 17, wherein, Based on the total weight of the polymer forming the polyamide layer, the content of structural unit A is 15-45 wt%, the content of segment B is 5-35 wt%, and the content of structural unit C is 50-80 wt%.

19. The hybrid matrix nanofiltration membrane according to claim 18, wherein, Based on the total weight of the polymer forming the polyamide layer, the content of structural unit A is 20-35 wt%, the content of segment B is 5-20 wt%, and the content of structural unit C is 60-70 wt%.

20. The hybrid matrix nanofiltration membrane according to claim 1, wherein, The degree of crosslinking of the polyamide layer is 40-80%.

21. The hybrid matrix nanofiltration membrane according to claim 20, wherein, The degree of crosslinking of the polyamide layer is 60-80%.

22. The hybrid matrix nanofiltration membrane according to claim 17, wherein, The polyethylene polyamine has the structure shown in Formula I; Equation I, where n≥5.

23. The hybrid matrix nanofiltration membrane according to claim 22, wherein, The polyethylene polyamine is selected from at least one of hexaethylene heptaamine, heptaethylene octaamine, and octaethylene nonaamine.

24. The hybrid matrix nanofiltration membrane according to claim 17, wherein, The branched polyethyleneimine has a weight-average molecular weight of 1800-70000 g / mol.

25. The hybrid matrix nanofiltration membrane according to claim 17, wherein, The polyacryl chloride compound is selected from at least one of pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride.

26. A method for preparing a hybrid matrix nanofiltration membrane according to any one of claims 1-25, characterized in that, The method includes the following steps: S1. The dispersion containing nano-manganese dioxide is mixed and dissolved with the polymer to obtain the casting solution; S2. Load the casting liquid onto a nonwoven fabric and perform a phase transformation to obtain a support layer substrate; S3. The support layer substrate is first immersed in a polyamine composite solution to obtain the initial nanofiltration membrane-I; S4. The initial nanofiltration membrane-I is immersed in a solution containing polyacrylamide chloride to obtain the initial nanofiltration membrane-II, and then subjected to heat treatment to obtain the mixed matrix nanofiltration membrane; The polyamine composite solution contains polyethylene polyamine compounds and branched polyethyleneimine.

27. The preparation method according to claim 26, wherein, In step S1, the mass ratio of the nano-manganese dioxide to the polymer is 1-50:

100.

28. The preparation method according to claim 27, wherein, In step S1, the mass ratio of the nano-manganese dioxide to the polymer is 10-30:

100.

29. The preparation method according to claim 26, wherein, In step S2, the casting solution is scraped onto a nonwoven fabric and immersed in a coagulation bath to carry out the phase transformation, wherein the solvent used in the coagulation bath is a poor solvent for the polymer.

30. The preparation method according to claim 26, wherein, In step S3, the total mass concentration of the polyethylene polyamine compound and the branched polyethyleneimine in the polyamine composite solution is 0.1-5 wt%.

31. The preparation method according to claim 30, wherein, In step S3, the total mass concentration of the polyethylene polyamine compound and the branched polyethyleneimine in the polyamine composite solution is 0.2-2 wt%.

32. The preparation method according to claim 26, wherein, Based on the total mass of the polyethylene polyamine compound and the branched polyethyleneimine, the content of the polyethylene polyamine compound is 10-99 wt%.

33. The preparation method according to claim 32, wherein, Based on the total mass of the polyethylene polyamine compound and the branched polyethyleneimine, the content of the polyethylene polyamine compound is 50-95 wt%.

34. The preparation method according to claim 26, wherein, The polyethylene polyamine has the structure shown in Formula II; Equation II, where n≥5.

35. The preparation method according to claim 26, wherein, The branched polyethyleneimine has a weight-average molecular weight of 1800-70000 g / mol.

36. The preparation method according to claim 26, wherein, In step S4, the concentration of the polyacryl chloride compound in the solution containing the polyacryl chloride compound is 0.05-2.5 wt%.

37. The preparation method according to claim 36, wherein, In step S4, the concentration of the polyacryl chloride compound in the solution containing the polyacryl chloride compound is 0.08-0.5 wt%.

38. The preparation method according to claim 26, wherein, The polyacryl chloride compound is selected from at least one of pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride.

39. The preparation method according to claim 26, wherein, The solvent in the solution containing the polyacrylamide chloride compound is selected from at least one of n-hexane, n-heptane, and isoalkanes.

40. The preparation method according to claim 26, wherein, The conditions for the first and second soakings are each independent of the following: temperature of 20-30℃ and time of 10-300s.

41. The preparation method according to claim 26, wherein, The heat treatment conditions include: a temperature of 50-80℃ and a time of 1-10 min.

42. The preparation method according to claim 26, wherein, The polyamine composite solution also contains 0.1-2 wt% of a catalyst and 0.03-0.2 wt% of a surfactant.

43. The preparation method according to claim 42, wherein, The catalyst is selected from at least one of sodium bicarbonate, ammonium bicarbonate, sodium hydroxide, and triethylamine.

44. The preparation method according to claim 42, wherein, The surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and dodecyltrimethylammonium chloride.

45. A mixed matrix nanofiltration membrane prepared by the preparation method according to any one of claims 26-44.

46. ​​The application of the hybrid matrix nanofiltration membrane according to any one of claims 1-25 and 45 in the field of solvent-resistant nanofiltration.

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