Composite separation membranes, their preparation methods and applications

Abstract

This invention relates to the field of membrane separation technology, and discloses a composite separation membrane, its preparation method, and its application. The composite separation membrane includes: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; wherein, the crosslinked polymer forming the separation layer includes structural unit A provided by an amino compound and structural unit B provided by an epoxy compound; wherein, the epoxy compound is a compound containing 2-6 epoxy groups; the composite separation membrane is stable in acidic and alkaline solutions and organic solvents, and has the characteristics of high water flux and high organic solvent flux while having good retention performance.

Description

Technical Field

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

[0002] Membrane separation technology, as an advanced separation and purification technology, has become an effective means to solve problems such as resource shortages and environmental pollution due to its high efficiency, energy saving, and environmental friendliness. Composite separation membranes are composed of two or more membrane materials with different properties. They combine the advantages of different membrane materials, resulting in higher separation efficiency, better stability, and lower cost. Currently, commercially available nanofiltration and reverse osmosis membranes are thin-layer composite membranes formed by interfacial polymerization of a thin polyamide layer onto a porous support layer. Although they are widely used in chemical environmental protection, seawater desalination, biomedicine, and food industries, they still have drawbacks such as poor chlorine resistance, poor temperature resistance, poor acid and alkali resistance, and poor solvent resistance.

[0003] CN114272767A discloses a biphenol-based organic solvent composite nanofiltration membrane and its preparation method. Using a polyacrylonitrile or polyimide ultrafiltration membrane as the base membrane, after removing the surface pore-retaining agent, the membrane is first immersed in an aqueous solution containing a 2,2'-biphenol-based compound, and then immersed in an organic solution containing polyacrylamide chlorides for interfacial polymerization. Finally, the composite nanofiltration membrane is obtained by thermal crosslinking and drying. Although the composite nanofiltration membrane prepared by this method exhibits high stability in various polar organic solvents, its separation layer is a polyester structure, thus posing a risk of degradation and decreased separation performance when used in acidic or alkaline solvents. CN117427493A discloses a method for preparing a PPTA / polyelectrolyte composite nanofiltration membrane. First, a polycationic solution and a polyanionic solution are prepared. Then, a PPTA ultrafiltration membrane is immersed in one of the polycationic or polyanionic solutions, followed by immersion in the other, forming an in-situ polymerization cycle. This in-situ polymerization cycle is repeated n / 2 times, alternating the immersion of the PPTA ultrafiltration membrane in the polycationic and polyanionic solutions to obtain a nascent PPTA / polyelectrolyte composite nanofiltration membrane. This membrane is then immersed in a salt solution for salt treatment and heat treatment, and finally submerged in deionized water to obtain the final PPTA / polyelectrolyte composite nanofiltration membrane. Although the composite nanofiltration membrane prepared by this method has advantages such as high flux, high retention, temperature resistance, acid and alkali resistance, and solvent resistance, its preparation method is relatively cumbersome and complex.

[0004] In conclusion, how to prepare a composite separation membrane with good acid and alkali resistance as well as solvent resistance has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor acid and alkali resistance, poor solvent resistance, and low permeation rejection performance of existing composite separation membranes, and to provide a composite separation membrane, its preparation method, and its application. This composite separation membrane is stable in acidic and alkaline solutions and organic solvents, and has the characteristics of high water flux and high organic solvent flux while having good rejection performance.

[0006] To achieve the above objectives, the first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; The cross-linked polymer forming the separation layer includes structural unit A provided by an amino compound and structural unit B provided by an epoxy compound; The epoxy compound is a compound containing 2-6 epoxy groups.

[0007] A second aspect of the present invention provides a method for preparing a composite separation membrane, wherein the method includes: The material, including the reinforcing layer and the support layer, was immersed in an amino compound solution and an epoxy compound solution, respectively, and then dried to obtain a composite separation membrane. The epoxy compound in the epoxy compound solution contains 2-6 epoxy functional groups.

[0008] A third aspect of the present invention provides a composite separation membrane prepared by the above-described preparation method.

[0009] The fourth aspect of the present invention provides an application of the above-mentioned composite separation membrane in the fields of acidic water, alkaline water treatment, or organic solvent separation.

[0010] Through the above technical solutions, the composite separation membrane, its preparation method, and its application provided by the present invention have the following beneficial effects.

[0011] The crosslinked polymer forming the separation layer of the present invention comprises structural units provided by amino compounds and structural units provided by epoxy compounds containing a specific number of epoxy groups, so that the composite separation membrane has the characteristics of high throughput and good retention performance, while also having the advantages of acid and alkali resistance and / or solvent resistance.

[0012] This invention involves immersing and drying materials comprising a reinforcing layer and a support layer in solutions of amino compounds and epoxy compounds, respectively. This allows the epoxy compounds and amino compounds to undergo an epoxy ring-opening reaction, forming a cross-linked network. This results in a composite separation membrane with high flux and good retention performance, while also exhibiting resistance to acids, alkalis, and / or solvents. Furthermore, by controlling the concentrations of the amino compound solution and the epoxy compound solution, the flux and retention rate of the composite separation membrane can be adjusted.

[0013] The composite separation membrane provided by this invention has a simple preparation method, low production cost, and is easy to promote industrially. Detailed Implementation

[0014] 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.

[0015] The first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; The cross-linked polymer forming the separation layer includes structural unit A provided by an amino compound and structural unit B provided by an epoxy compound; The epoxy compound is a compound containing 2-6 epoxy groups.

[0016] In this invention, the crosslinked polymer forming the separation layer comprises structural units provided by an amino compound and structural units provided by an epoxy compound containing a specific number of epoxy groups, so that the composite separation membrane has the characteristics of high throughput and good retention performance, while also having the advantages of acid and alkali resistance and / or solvent resistance.

[0017] Furthermore, the epoxy compound is a compound containing 2-4 epoxy groups.

[0018] Furthermore, the epoxy compound is selected from at least one of 1,4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerythritol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether-terminated polydimethylsiloxane, glycerol triglycidyl ether, and glycerol diglycidyl ether.

[0019] In this invention, when the separation layer contains structural units from the aforementioned types of epoxy compounds, the composite separation membrane has the characteristics of high throughput and good retention performance.

[0020] According to the present invention, the amino compound is a compound containing at least two primary amine groups.

[0021] Further, the amino compound is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyethyleneimine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

[0022] In this invention, when the separation layer contains structural units from the aforementioned types of amino compounds, the composite separation membrane exhibits high throughput and good retention performance.

[0023] According to the present invention, the separation layer contains 7-28% nitrogen and 8-32% oxygen.

[0024] In this invention, when the content of nitrogen and oxygen elements in the separation layer meets the above-mentioned range, the separation layer has an appropriate degree of cross-linking and mechanical strength.

[0025] Furthermore, in the separation layer, the molar percentage of nitrogen is 9-18%, and the molar percentage of oxygen is 16-28%.

[0026] According to the present invention, the material of the support layer is selected from one of polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyethylene, polypropylene, cellulose acetate, polyetherketone, polyetheretherketone, polyaniline, and polyarylamide.

[0027] According to the present invention, the porosity of the support layer is 30-80%.

[0028] According to the present invention, the average pore size of the support layer is 5-50 nm.

[0029] In this invention, when the porosity and / or average pore size of the support layer meet the above-mentioned range, the composite separation membrane can have good permeation retention performance.

[0030] Furthermore, the porosity of the support layer is 40-70%.

[0031] Furthermore, the average pore size of the support layer is 10-30 nm.

[0032] In this invention, the reinforcing layer is a polyester nonwoven fabric or / or a polyolefin nonwoven fabric.

[0033] According to the present invention, the thickness of the reinforcing layer is 50-300 μm.

[0034] Furthermore, the thickness of the reinforcing layer is 80-120 μm.

[0035] According to the present invention, the thickness of the support layer is 20-80 μm.

[0036] Furthermore, the thickness of the support layer is 30-50 μm.

[0037] According to the present invention, the thickness of the separation layer is 50-1000 nm.

[0038] Furthermore, the thickness of the separation layer is 80-300 nm.

[0039] According to the present invention, the average pore size of the composite separation membrane is 0.15-0.5 nm.

[0040] In this invention, when the average pore size of the composite separation membrane meets the above-mentioned range, it has the characteristics of high flux and high rejection rate, resulting in a better permeation rejection effect.

[0041] Furthermore, the average pore size of the composite separation membrane is 0.2-0.3 nm.

[0042] In this invention, the composite separation membrane has a water flux of greater than or equal to 25 L / (m³) at 25°C. 2 ·h 1 ), preferably greater than or equal to 65L / (m 2 ·h 1 ).

[0043] In this invention, the composite separation membrane has an ethyl acetate flux of greater than or equal to 0.5 L / (m³) at 25°C. 2 ·h 1 ), preferably greater than or equal to 3L / (m 2 ·h 1 ).

[0044] In this invention, the composite separation membrane has a rejection rate of polyethylene glycol with a log-average molecular weight of 600 g / mol greater than or equal to 60%, preferably greater than or equal to 75%.

[0045] In this invention, the composite separation membrane has a rejection rate of Acid Red 249 of greater than or equal to 85%, preferably greater than or equal to 97%.

[0046] A second aspect of the present invention provides a method for preparing a composite separation membrane, wherein the method includes: The material, including the reinforcing layer and the support layer, was immersed in an amino compound solution and an epoxy compound solution, respectively, and then dried to obtain a composite separation membrane. The epoxy compound in the epoxy compound solution contains 2-6 epoxy functional groups.

[0047] In this invention, the inventors discovered that when the material comprising the reinforcing layer and the support layer is immersed in an amino compound solution and then dried, the amino compound disperses and fixes itself on the surface of the pores in the support layer. Subsequent immersion in an epoxy compound solution forms a dense cross-linked polymer layer, resulting in a composite separation membrane with high throughput and good retention performance, while also exhibiting resistance to acids, alkalis, and / or solvents. In this invention, the order in which the material comprising the reinforcing layer and the support layer is immersed in the amino compound solution and the epoxy compound solution is not required.

[0048] Furthermore, by controlling the concentrations of the amino compound solution and the epoxy compound solution, the water flux and rejection rate of the composite separation membrane can be regulated.

[0049] The composite separation membrane provided by this invention has a simple preparation method, low production cost, and is easy to promote industrially.

[0050] In this invention, there is no particular limitation on the method for preparing the material including the reinforcing layer and the support layer. However, in order to obtain a composite separation membrane with both high water flux and high rejection rate, it is preferable to dissolve the polymer used to form the support layer to obtain a casting solution, and then load it on the reinforcing layer to undergo phase transformation to obtain the material including the reinforcing layer and the support layer.

[0051] In this invention, the polymer is selected from one of polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyethylene, polypropylene, cellulose acetate, polyetherketone, polyetheretherketone, polyaniline, and polyarylamide.

[0052] In this invention, the reinforcing layer is a polyester nonwoven fabric and / or a polyolefin nonwoven fabric.

[0053] In this invention, the solid content of the casting solution is 12-25 wt%, preferably 18-22 wt%.

[0054] In this invention, the ratio of the volume of the casting solution to the area of ​​the reinforcing layer is 0.004-0.02 mL / cm². 2 Preferably, it is 0.006-0.015 mL / cm 2 .

[0055] In this invention, the solvent used in the phase transformation process is a poor solvent for the polymer.

[0056] In this invention, the solvent of the casting solution is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, PolarClean, tetrahydrofuran, dioxane, acetonitrile, and acetone.

[0057] In this invention, the support layer can be crosslinked and modified using techniques known in the art to further improve solvent resistance, for example, by immersing the polyimide support layer in a hexamethylenediamine solution to crosslink it.

[0058] According to the present invention, the amino compound in the amino compound solution contains at least two primary amine groups.

[0059] Further, the amino compound is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyethyleneimine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

[0060] According to the present invention, the solvent of the amino compound solution is selected from at least one of water, methanol, ethanol, acetone and tetrahydrofuran.

[0061] According to the present invention, the concentration of the amino compound solution is 0.1-10 wt%.

[0062] In this invention, when the concentration of the amino compound solution meets the above-mentioned range, it is beneficial to obtain a composite separation membrane with higher throughput and higher retention performance.

[0063] Furthermore, the concentration of the amino compound solution is 0.5-2 wt%.

[0064] According to the present invention, the epoxy compound in the epoxy compound solution contains 2-4 epoxy functional groups.

[0065] Further, the epoxy compound is selected from at least one of 1,4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerythritol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether-terminated polydimethylsiloxane, glycerol triglycidyl ether, and glycerol diglycidyl ether.

[0066] According to the present invention, the solvent of the epoxy compound solution is selected from at least one of water, methanol, ethanol, acetone and tetrahydrofuran.

[0067] According to the present invention, the concentration of the epoxy compound solution is 0.1-30 wt%.

[0068] In this invention, when the concentration of the epoxy compound solution meets the above-mentioned range, it is beneficial to obtain a composite separation membrane with higher throughput and higher retention performance.

[0069] Furthermore, the concentration of the epoxy compound solution is 0.5-10 wt%.

[0070] According to the present invention, the soaking conditions include: a temperature of 20-40°C and a time of 0.5-5 min.

[0071] In this invention, when the soaking conditions meet the above-mentioned range, it is beneficial to obtain a composite separation membrane with higher throughput and higher retention performance.

[0072] According to the present invention, the volume ratio of the amino compound solution to the area of ​​the material is 0.01-0.3 mL / cm². 2 .

[0073] Furthermore, the volume ratio of the amino compound solution to the surface area of ​​the material is 0.1-0.2 mL / cm². 2 .

[0074] According to the present invention, the volume ratio of the epoxy compound solution to the area of ​​the material is 0.01-0.3 mL / cm². 2 .

[0075] Furthermore, the volume ratio of the epoxy compound solution to the area of ​​the material is 0.1-0.2 mL / cm². 2 .

[0076] According to the present invention, the material is immersed in an amino compound solution, then subjected to a first drying, then immersed in an epoxy compound solution, and then subjected to a second drying; Alternatively, the material may be soaked in an epoxy compound solution, subjected to a first drying, then soaked in an amino compound solution, and then subjected to a second drying.

[0077] According to a preferred embodiment of the present invention, the material is soaked in an amino compound solution, then subjected to a first drying, then soaked in an epoxy compound solution, and then subjected to a second drying.

[0078] According to the present invention, the conditions for the first drying include: a temperature of 40-80°C and a time of 1-10 min.

[0079] According to the present invention, the conditions for the second drying include: a temperature of 60-100°C and a time of 3-30 minutes.

[0080] In this invention, when the conditions for the first drying and / or the conditions for the second drying meet the above-mentioned range, it is advantageous to obtain a composite separation membrane with higher throughput and higher retention performance.

[0081] Furthermore, the conditions for the first drying include: a temperature of 50-70°C and a time of 3-6 minutes.

[0082] Furthermore, the conditions for the second drying include: a temperature of 70-90°C and a time of 5-20 minutes.

[0083] According to the present invention, the amino compound solution and the epoxy compound solution each independently contain a surfactant, a pore-retaining agent and a catalyst.

[0084] In this invention, surfactants, pore-retaining agents, and catalysts can be selectively added depending on the type of amino compound or epoxy compound used.

[0085] According to the present invention, in the amino compound solution and the epoxy compound solution, the concentration of the surfactant is independently 0-0.2 wt%.

[0086] Furthermore, in the amino compound solution and the epoxy compound solution, at least one solution contains a surfactant, wherein the concentration of the surfactant is 0.05wt%-0.2wt%.

[0087] In this invention, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and dodecyltrimethylammonium chloride.

[0088] According to the present invention, in the amino compound solution and the epoxy compound solution, the concentration of the pore-retaining agent is independently 0-5 wt%.

[0089] Furthermore, in the amino compound solution and the epoxy compound solution, at least one solution contains a pore-retaining agent, wherein the concentration of the pore-retaining agent is 1wt%-3wt%.

[0090] In this invention, the pore-retaining agent is selected from at least one of glycerol, glucose, sucrose and polyethylene glycol (e.g., PEG200, PEG300, PEG400, PEG600).

[0091] According to the present invention, in the amino compound solution and the epoxy compound solution, the concentration of the catalyst is independently 0-2 wt%.

[0092] Furthermore, in the amino compound solution and the epoxy compound solution, at least one solution contains a catalyst, wherein the concentration of the catalyst is 0.5wt%-1.5wt%.

[0093] In this invention, the catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, tetrabutylammonium bromide, 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, and 2-ethyl-4-methylimidazole.

[0094] A third aspect of the present invention provides a composite separation membrane prepared by the above-described preparation method.

[0095] The fourth aspect of the present invention provides an application of the above-mentioned composite separation membrane in the fields of acidic water, alkaline water treatment, or organic solvent separation.

[0096] The present invention will be described in detail below through embodiments.

[0097] Flux of the composite separation membrane: The solvent permeation rate of the composite separation membrane was measured by loading the composite membrane into the membrane cell; the specific test conditions were a temperature of 25℃ and a pressure of 0.5MPa, and the flux was calculated using the following formula 1: flux Formula 1; In the formula, V is the volume of permeate, in liters (L); A is the effective area of ​​the membrane, in m². 2 t represents time in hours (h); P represents test pressure in bars.

[0098] Retention rate of polyethylene glycol 600: The separation performance of the composite membrane in aqueous solution was measured using cross-flow filtration. Specific test conditions were: temperature 25℃, pressure 0.5 MPa. The original solution used for the retention rate test was a 100 ppm polyethylene glycol 600 aqueous solution. The polyethylene glycol concentration in the original solution and permeate was measured and calculated using a total organic carbon analyzer; the retention rate was calculated according to Formula 2.

[0099] Retention rate of Acid Red 249: The separation performance of the composite membrane in organic solvents was measured using dead-end filtration. Specific test conditions were: temperature 25℃, pressure 1.0 MPa, and stirring speed 500 rpm. The flux test was conducted with ethyl acetate, and the initial solution used for retention rate was an ethyl acetate solution of Acid Red 249 (molecular weight 748) with a concentration of 200 ppm. The concentration of the ethyl acetate solution of Acid Red 249 was calculated using an absorbance-concentration curve at a wavelength of 524 nm using a UV-Vis spectrophotometer; the retention rate was calculated according to Formula 2.

[0100] Retention rate Formula 2; c1 is the concentration of polyethylene glycol or acid red in the permeate (i.e., the solution after passing through the composite separation membrane); c0 is the concentration of polyethylene glycol or acid red in the retention solution (i.e., the concentration of polyethylene glycol or acid red after being retained by the composite separation membrane).

[0101] Porosity of the support layer: The porosity (ɛ) of the support layer is calculated by gravimetric method. First, the material including the reinforcing layer and the support layer is immersed in deionized water, then removed and dried, and weighed w. The area and thickness of the support layer are measured. Then, it is vacuum dried at 60°C to constant weight, and the weight w1 after drying is recorded. The porosity is calculated using the following formula 3: Formula 3 Where w and w1 are the weights (g) of the support layer before and after drying, respectively, and A is the area (cm²) of the support layer. 2 h is the thickness of the support layer (cm), and ρ is the density of water under the test conditions (g / cm³). 3 ).

[0102] Average pore size of the support layer: measured using an ultrafiltration membrane pore size analyzer (PSMA-10, Nanjing Gaoqian Functional Materials Technology Co., Ltd.).

[0103] The thickness of the support layer is measured by a thickness gauge.

[0104] The thickness of the separation layer was observed using a scanning electron microscope.

[0105] The nitrogen and oxygen content in the separation layer: The nitrogen and oxygen content in the composite membrane separation layer was tested by X-ray photoelectron spectroscopy (XPS). Specifically, it was obtained by Al-Kα X-ray irradiation on an ESCALAB250 X-ray photoelectron spectrometer.

[0106] The average pore size of the composite separation membrane was measured using the PEG solute transfer method, the detailed steps of which are as follows: (1) Test the retention rate of the composite separation membrane for PEG of different molecular sizes; (2) Linear fitting of PEG size and retention rate in log-probability coordinate system, the PEG size corresponding to 50% retention rate is the average pore size of composite separation membrane.

[0107] Acid resistance of composite separation membrane: The percentage change in the PEG600 rejection rate of the composite separation membrane after immersion in 10wt% hydrochloric acid for 10 days compared with the rejection rate of PEG600 before immersion was calculated according to Formula 4. Formula 4 Alkali resistance of composite separation membrane: The percentage change in the PEG600 rejection rate of the composite separation membrane after immersion in 10wt% sodium hydroxide aqueous solution for 10 days was calculated according to Formula 4.

[0108] Solvent resistance of composite separation membrane: The percentage change in the PEG600 rejection rate of the composite separation membrane after immersion in ethyl acetate for 10 days compared with the rejection rate of Acid Red 249 before immersion was calculated according to Formula 4.

[0109] Polysulfone, purchased from Solvay, grade P-3500.

[0110] Polyimide, purchased from Evonik, brand name P84.

[0111] Branched polyethyleneimine (weight average molecular weight 25000 g / mol) and polyethylene glycol diglycidyl ether (degree of polymerization 22, containing 2 epoxy groups) were purchased from Bailingwei Technology Co., Ltd.; glycerol triglycidyl ether (containing 3 epoxy groups), pentaerythritol glycidyl ether (containing 4 epoxy groups), polyethylene polyamine (molecular weight 275) and other reagents were purchased from Beijing Innocare Technology Co., Ltd.

[0112] The thickness of the polypropylene nonwoven fabric is 120μm.

[0113] Example 1 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material, including the reinforcing layer and the support layer, in an aqueous solution of 1 wt% branched polyethyleneimine, 2 wt% glycerol, and 0.1 wt% sodium dodecyl sulfate at 25°C for 3 minutes. Then remove the material, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; S3. The product of S2 is immersed in an aqueous solution containing 1 wt% polyethylene glycol diglycidyl ether, 2 wt% glycerol, and 1 wt% 2,4,6-tris(dimethylaminomethyl)phenol (catalyst) at 25°C for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80°C for 8 min to obtain the composite separation membrane M1. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 .

[0114] Example 2 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material, including the reinforcing layer and the support layer, in an aqueous solution containing 0.1 wt% branched polyethyleneimine at 25°C for 3 minutes. Then remove the material, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; S3. The product of S2 is immersed in an ethanol solution containing 0.5 wt% pentaerythritol glycidyl ether at 25°C for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80°C for 8 min to obtain the composite separation membrane M2. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 .

[0115] Example 3 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material, including the reinforcing layer and the support layer, in an aqueous solution containing 0.5 wt% polyethylenepolyamine and 0.1 wt% sodium dodecyl sulfate at 25°C for 3 minutes. Then remove the material, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; S3. The product of S2 is immersed in an aqueous solution containing 1 wt% polyethylene glycol diglycidyl ether at 25°C for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80°C for 8 min to obtain the composite separation membrane M3. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 .

[0116] Example 4 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material, including the reinforcing layer and the support layer, in an aqueous solution containing 1% branched polyethyleneimine and 2wt% glycerol at 25°C for 3 minutes. Then remove the material, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; S3. The product of S2 is immersed in an aqueous solution containing 2 wt% polyethylene glycol diglycidyl ether and 2 wt% glycerol at 25°C for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80°C for 8 min to obtain the composite separation membrane M4. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 .

[0117] Example 5 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material, including the reinforcing layer and the support layer, in an aqueous solution containing 2% polyethylenepolyamine and 1 wt% glycerol at 25°C for 3 minutes. Then remove the material, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; The products of S3 and S2 were immersed in an ethanol solution containing 4 wt% pentaerythritol glycidyl ether and 2 wt% glycerol at 25°C for 3 min. Then, they were removed, excess solution was removed from the surface, and the membranes were dried in an oven at 80°C for 8 min to obtain the composite separation membrane M5. The volume ratio of the epoxy compound solution to the surface area of ​​the material was 0.15 mL / cm². 2 .

[0118] Example 6 S1. Dissolve 18g of polysulfone in 82g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.006 mL / cm². 2 ; S2. Immerse the material including the reinforcing layer and the support layer in an aqueous solution containing 2 wt% polyethylene glycol diglycidyl ether and 2 wt% glycerol at 25°C for 3 minutes. Then remove it, remove excess solution from the surface, and dry it in an oven at 50°C for 5 minutes. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 S3. The product of S2 is immersed in an aqueous solution containing 1% branched polyethyleneimine and 2wt% glycerol at 25℃ for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80℃ for 8 min to obtain the composite separation membrane M6. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 .

[0119] Example 7 The composite separation membrane was prepared according to the method of Example 1, except that the concentration of the amino compound solution was 3 wt% and the concentration of the epoxy compound solution was 3 wt%, resulting in composite separation membrane M7.

[0120] Example 8 The composite separation membrane was prepared according to the method of Example 1, except that the concentration of the amino compound solution was 0.3 wt% and the concentration of the epoxy compound solution was 0.3 wt%, resulting in composite separation membrane M8.

[0121] Example 9 The composite separation membrane was prepared according to the method of Example 1, except that in steps S2 and S3, the immersion temperature was 40°C and the time was 20s, resulting in composite separation membrane M9.

[0122] Example 10 S1. Dissolve 22g of polyimide in 78g of N,N-dimethylformamide to obtain a casting solution. Then, use a doctor blade to apply the casting solution onto a polypropylene nonwoven fabric, which is then immersed in a deionized water coagulation bath to complete the phase inversion, yielding a material comprising a reinforcing layer and a support layer. The volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.008 mL / cm². 2 The material, including the reinforcing layer and the support layer, is immersed in a 5 wt% hexamethylenediamine methanol solution to obtain a material with a reinforcing layer and a cross-linked support layer. S2. Immerse the material, including the reinforcing layer and the cross-linking support layer, in a 25°C aqueous solution of 1 wt% branched polyethyleneimine and 2 wt% glycerol for 3 min. Then remove the material, remove excess solution from the surface, and dry it in a 50°C oven for 5 min. The volume ratio of the amino compound solution to the surface area of ​​the material is 0.15 mL / cm². 2 ; S3. The product of S2 is immersed in an aqueous solution containing 3 wt% glycerol triglycidyl ether and 1 wt% 2,4,6-tris(dimethylaminomethyl)phenol (catalyst) at 25°C for 3 min. Then, it is removed, excess solution is removed from the surface, and it is dried in an oven at 80°C for 8 min to obtain the composite separation membrane M10. The volume ratio of the epoxy compound solution to the area of ​​the material is 0.15 mL / cm². 2 .

[0123] Example 11 The composite separation membrane was prepared according to the method of Example 10, except that the amino compound solution was an aqueous solution of 3 wt% tetraethylenepentamine and 0.1 wt% sodium dodecyl sulfate (surfactant), and the epoxy compound solution was an aqueous solution of 5 wt% polyethylene glycol diglycidyl ether, to obtain the composite separation membrane M11.

[0124] Example 12 The composite separation membrane was prepared according to the method of Example 1, except that the amino compound solution in step S2 did not contain glycerol and sodium dodecyl sulfate; and the epoxy compound solution in step S3 did not contain glycerol and 2,4,6-tris(dimethylaminomethyl)phenol (catalyst). Composite separation membrane M12 was obtained.

[0125] Comparative Example 1 The composite separation membrane was prepared according to the method of Example 1, except that in step S3, 1 wt% epichlorohydrin ethanol solution was used to replace 1 wt% polyethylene glycol diglycidyl ether aqueous solution to obtain composite separation membrane D1.

[0126] The thickness of each layer of the composite separation membrane in the examples and comparative examples, the oxygen and nitrogen content in the separation layer, the porosity and average pore size of the support layer, and the average pore size of the composite separation membrane were tested, and the results are shown in Table 1.

[0127] Table 1

[0128] Test case The flux and rejection rate of the composite separation membrane prepared in the examples were tested, and the results are shown in Table 2.

[0129] Table 2

[0130] The results show that the composite separation membrane described in this invention exhibits high permeability in water and organic solvents while maintaining high retention performance. The examples show that the flux of the composite separation membrane decreases with increasing concentrations of amino and epoxide compounds, while the retention rate increases. This is because more reactive monomers remain on the support layer surface after soaking in a high-concentration amino compound solution, and the cross-linked network formed with the epoxide compound after a second soaking is denser, thus decreasing flux and increasing retention rate. This trend makes the separation performance of the composite membrane easier to control. Examples 6 and 4 show that while the composite membrane obtained by soaking the epoxide compound first followed by the amino compound has a slightly higher retention rate than the method of soaking the amino compound first followed by the epoxide compound, it suffers a greater flux loss.

[0131] 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 composite separation membrane, characterized in that, The composite separation membrane includes: a reinforcing layer and a support layer and a separation layer sequentially attached to the surface of the reinforcing layer; The cross-linked polymer forming the separation layer includes structural unit A provided by an amino compound and structural unit B provided by an epoxy compound; The epoxy compound is a compound containing 2-6 epoxy groups.

2. The composite separation membrane according to claim 1, wherein, The epoxy compound is a compound containing 2-4 epoxy groups; Preferably, the epoxy compound is selected from at least one of 1,4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerythritol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether-terminated polydimethylsiloxane, glycerol triglycidyl ether, and glyceryl diglycidyl ether. Preferably, the amino compound is a compound containing at least two primary amine groups; Preferably, the amino compound is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyethyleneimine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

3. The composite separation membrane according to claim 1 or 2, wherein, In the separation layer, the molar percentage of nitrogen is 7-28%, preferably 9-18%; and the molar percentage of oxygen is 8-32%, preferably 16-28%.

4. The composite separation membrane according to any one of claims 1-3, wherein, The material of the support layer is selected from one of polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, cross-linked polyimide, cross-linked polyetherimide, polyethylene, polypropylene, cellulose acetate, polyetherketone, polyetheretherketone, polyaniline, and polyaramid. Preferably, the porosity of the support layer is 30-80%, more preferably 40-70%; Preferably, the average pore size of the support layer is 5-50 nm, and more preferably 10-30 nm.

5. The composite separation membrane according to any one of claims 1-4, wherein, The thickness of the reinforcing layer is 50-300 μm, preferably 80-120 μm; Preferably, the thickness of the support layer is 20-80 μm, and more preferably 30-50 μm; Preferably, the thickness of the separation layer is 50-1000 nm, and more preferably 80-300 nm; Preferably, the average pore size of the composite separation membrane is 0.15-0.5 nm, and more preferably 0.2-0.3 nm.

6. A method for preparing a composite separation membrane, characterized in that, The method includes: The material, including the reinforcing layer and the support layer, was immersed in an amino compound solution and an epoxy compound solution, respectively, and then dried to obtain a composite separation membrane. The epoxy compound in the epoxy compound solution contains 2-6 epoxy functional groups.

7. The preparation method according to claim 6, wherein, The amino compound in the amino compound solution contains at least two primary amine groups; Preferably, the amino compound is selected from at least one of ethylenediamine, propylenediamine, butanediamine, hexanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, polyethyleneimine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, and p-phenylenediamine; Preferably, the solvent for the amino compound solution is selected from at least one of water, methanol, ethanol, acetone, and tetrahydrofuran; Preferably, the concentration of the amino compound solution is 0.1-10 wt%, more preferably 0.5-2 wt%.

8. The preparation method according to claim 6 or 7, wherein the epoxy compound in the epoxy compound solution contains 2-4 epoxy functional groups; Preferably, the epoxy compound is selected from at least one of 1,4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, pentaerythritol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether-terminated polydimethylsiloxane, glycerol triglycidyl ether, and glyceryl diglycidyl ether. Preferably, the solvent of the epoxy compound solution is selected from at least one of water, methanol, ethanol, acetone and tetrahydrofuran; Preferably, the concentration of the epoxy compound solution is 0.1-30 wt%, more preferably 0.5-10 wt%.

9. The preparation method according to any one of claims 6-8, wherein, The soaking conditions include: a temperature of 20-40℃ and a time of 0.5-5 minutes; Preferably, the volume ratio of the amino compound solution to the surface area of ​​the material is 0.01-0.3 mL / cm². 2 Preferably, it is 0.1-0.2 mL / cm 2 ; Preferably, the volume ratio of the epoxy compound solution to the area of ​​the material is 0.01-0.3 mL / cm². 2 Preferably, it is 0.1-0.2 mL / cm 2 .

10. The preparation method according to any one of claims 6-9, wherein, The material is soaked in an amino compound solution, then dried for the first time, then soaked in an epoxy compound solution, and then dried for the second time. Alternatively, the material may be soaked in an epoxy compound solution, subjected to a first drying, then soaked in an amino compound solution, and then subjected to a second drying. Preferably, the conditions for the first drying include: a temperature of 40-80°C and a time of 1-10 minutes; Preferably, the conditions for the second drying include: a temperature of 60-100°C and a time of 3-30 minutes.

11. The preparation method according to any one of claims 6-10, wherein, The amino compound solution and the epoxy compound solution each independently contain a surfactant, a pore-retaining agent, and a catalyst; Preferably, in both the amino compound solution and the epoxy compound solution, the concentration of the surfactant is independently 0-0.2 wt%. Preferably, in the amino compound solution and the epoxy compound solution, the concentration of the pore-retaining agent is independently 0-5 wt%; Preferably, in the amino compound solution and the epoxy compound solution, the concentration of the catalyst is independently 0-2 wt%.

12. A composite separation membrane prepared by the preparation method according to any one of claims 6-11.

13. The application of the composite separation membrane according to any one of claims 1-5 and 12 in the field of acidic water, alkaline water treatment, or organic solvent separation.

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