Composite separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the field of organic solvent-resistant nanofiltration membrane separation, and discloses a composite separation membrane as well as a preparation method and application thereof. The composite separation membrane comprises a supporting layer and a coating layer coated on the surface of the supporting layer, wherein the coating layer is obtained by coating the surface of the supporting layer with a membrane casting solution and then performing post-treatment; the membrane casting solution contains graphene oxide, rubber latex, a water-soluble high-molecular polymer and deionized water. According to the composite separation membrane, the problem of organic solvent pollution in the traditional membrane preparation process can be reduced, the modification effect of the graphene oxide is greatly improved, the composite separation membrane has relatively good stability in an organic solvent, and the membrane with relatively high permeation flux and retention rate can be prepared.

Description

Technical Field

[0001] The present invention relates to the field of organic solvent-resistant nanofiltration membrane separation, and in particular to a composite separation membrane, a preparation method thereof, and applications thereof. Background Art

[0002] The concept of organic solvent-resistant nanofiltration membranes (OSN membranes) was first proposed by Sourirajan in 1964, using cellulose acetate membranes to separate liquid hydrocarbon mixtures. Due to the low level of membrane material development and demand for OSN membranes at the time, interest in them has only garnered interest in the past two decades. Currently, industry uses millions of tons of solvents to manufacture pharmaceuticals, oils, and chemicals, requiring multiple separation and purification steps to purify products from the solvents. As a result, OSN membrane separation has gradually become an energy-efficient alternative to existing processes. Consequently, employing membrane technology for organic solvent separation presents one of the greatest challenges currently faced.

[0003] The core of OSN technology is the OSN membrane, which must not only have high permeability and high rejection rate, but also chemical stability. In recent years, scientists have conducted a lot of membrane research in the field of OSN membranes, making outstanding contributions to the development of OSN membranes.

[0004] Among them, the research groups of Andrew G. Livingston at Imperial College London and Tai-Shung Chung at the National University of Singapore has been at the forefront of scientific research and industry, providing guidance for the commercialization of OSN membranes. Since 2008, they have continuously reported innovative OSN membranes and preparation methods, using membrane materials such as polyimide, polyaniline, polyetheretherketone, polybenzimidazole, and polydimethylsiloxane.

[0005] Researchers in related fields around the world have conducted research on organic solvent-resistant nanofiltration membranes.

[0006] CN113491960A uses a super-hydrophobic micro / nano binary rough structure and a continuous three-dimensional network structure composed of polyimide nanofibers and polyimide micro-nanospheres to prepare a high-temperature resistant oil-water separation membrane. The disclosed membrane material, polyimide nanofibers, is tightly wrapped on the surface of polyimide micro-nanospheres, and has good mechanical properties and super-hydrophobic stability.

[0007] Most of the preparation processes of OSN membranes disclosed in the prior art involve dissolving the membrane material in a polar organic solvent to form a casting solution and then performing phase change to form the membrane. This preparation method is very environmentally unfriendly, and the volatilized organic solvents are also very harmful to the researchers' health. In addition, the membranes prepared by the general phase change method require further cross-linking to have strong solvent resistance, and the preparation process is complicated.

[0008] In addition, also have a part to report and adopt the method for interfacial polymerization, this method film-making time is long, and organic phase also uses organic solvent.Along with the progress of mankind, environmentally friendly film-making method is more and more paid attention to, and CN1640534A adopts the method for concentrated emulsion polymerization to prepare a kind of preferential dealcoholization film, and this film-making method avoids the use of a large amount of organic solvents.But the film thickness prepared by high concentration emulsion is often thicker, and permeation flux can be greatly restricted.

[0009] Currently, there are few reports on rubber materials. Most of the reported organic solvent-resistant membrane materials are plastic or fiber-based. Only cross-linked polydimethylsiloxane (silicone rubber) has been reported, and no other rubber materials have been reported. This is partly because rubber has high viscosity, making it difficult to coat into a thin film. Furthermore, rubber has poor resistance to organic solvents and tends to dissolve in them. These two factors limit the potential of rubber as an OSN membrane material.

[0010] Graphene oxide is a nanomaterial with rich oxygen-containing functional groups such as carbonyl, hydroxyl, and carboxyl groups on the basal plane of infinite extension in a two-dimensional space. It has excellent hydrophilicity and will swell after being added to water. It will be further dispersed into a stable mixture under the action of mechanical force. The preparation of polymer graphene oxide composite membranes is mostly to add graphene oxide to a polymer and an organic solvent casting solution for blending preparation. Due to the large viscosity and low density of the polymer solution, graphene oxide is mostly embedded in the matrix of the membrane and can not give full play to the hydrophilic effect of graphene oxide. CN104096488A introduces graphene oxide into a coagulation bath, and the graphene oxide in the coagulation bath is assembled to the surface of the membrane by a phase inversion process, which significantly increases the hydrophilicity of the membrane. However, this method may only allow a very small amount of graphene to adhere to the surface of the membrane, and may gradually fall off during use, causing the membrane to lose its hydrophilicity.

[0011] Therefore, it is of great significance to research and develop an organic solvent-resistant composite membrane and a green and environmentally friendly preparation method. Summary of the Invention

[0012] The purpose of the present invention is to overcome the defects in the prior art of complex preparation process of organic solvent-resistant nanofiltration membranes and environmental pollution caused by the use of organic solvents in the preparation process, as well as the defect of poor surface modification effect of graphene oxide and polymer composite membranes. A composite separation membrane and its preparation method and application are provided. The composite separation membrane can reduce the organic solvent pollution problem in the traditional membrane preparation process, greatly improve the modification effect of graphene oxide, and the composite separation membrane has good stability in organic solvents, and can prepare membranes with high permeation flux and retention rate.

[0013] In order to achieve the above-mentioned object, the first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises a support layer and a coating layer coated on the surface of the support layer, wherein the coating layer is obtained by coating a casting liquid on the surface of the support layer and then post-processing;

[0014] The casting solution contains graphene oxide, rubber latex, water-soluble high molecular polymer and deionized water.

[0015] A second aspect of the present invention provides a method for preparing the aforementioned composite separation membrane, wherein the preparation method comprises:

[0016] (1) mixing graphene oxide with deionized water and then subjecting the mixture to a first ultrasonic treatment to obtain a graphene oxide aqueous solution;

[0017] (2) performing a second mixing of the water-soluble polymer and deionized water to prepare a polymer aqueous solution;

[0018] (3) mixing the graphene oxide aqueous solution, the polymer aqueous solution and the rubber latex for a third time and then subjecting the mixture to a second ultrasonic treatment to obtain a mixed solution; and diluting the mixed solution with deionized water to obtain a casting solution;

[0019] (4) The casting solution is coated on the surface of the support layer and subjected to post-processing to obtain a composite separation membrane.

[0020] The third aspect of the present invention provides an application of the aforementioned composite separation membrane in removing impurities from a weakly polar organic solvent.

[0021] Through the above technical solution, the technical solution of the present invention has the following beneficial effects:

[0022] (1) No organic solvent is used in the preparation process of the composite separation membrane of the present invention, thereby avoiding the harm to human health and environmental pollution caused by the use of organic solvents;

[0023] (2) During the preparation of the composite separation membrane of the present invention, no additional cross-linking of the membrane material is required, making the membrane preparation process simpler; it is a green, environmentally friendly and simple membrane preparation method;

[0024] (3) The composite separation membrane prepared by the present invention has good stability in organic solvents. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] As mentioned above, the first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises a support layer and a coating layer coated on the surface of the support layer, wherein the coating layer is obtained by coating a casting liquid on the surface of the support layer and then post-processing;

[0027] The casting solution contains graphene oxide, rubber latex, water-soluble high molecular polymer and deionized water.

[0028] The inventors of the present invention have discovered through research that the present invention uses highly cross-linked rubber latex as the membrane material, which, on the one hand, can overcome the problem of high viscosity of rubber solution making it difficult to apply the film, and on the other hand, the rubber is highly cross-linked and can remain stable in organic solvents; in addition, the present invention uses rubber material to prepare OSN membranes, which greatly reduces the cost of membrane production.

[0029] Furthermore, the inventors of the present invention took into account the defect problem of low utilization rate of graphene encapsulated by polymers in the prior art, and dispersed graphene oxide in a water emulsion in the casting liquid used by the inventors of the present invention. Since the density of graphene oxide is slightly lower than that of water, after the scraping is completed, the water evaporates on the surface of the membrane, and the graphene oxide will migrate to the surface of the membrane along with the water molecules, making the membrane hydrophilic. In addition, a certain amount of graphene oxide will also be distributed inside the membrane, which increases the flux when the polar organic solvent penetrates through the membrane.

[0030] In the present invention, it should be noted that “dry rubber” and “dry rubber” refer to the remaining rubber after water and a part of the emulsifier are removed from the rubber latex composed of rubber, water and an emulsifier.

[0031] According to the present invention, preferably, the casting solution consists of graphene oxide, rubber latex, water-soluble high molecular polymer and deionized water.

[0032] According to the present invention, in the casting solution, the weight ratio of the graphene oxide to the dry rubber in the rubber latex is (0.1-100):100, preferably (0.5-10):100, and more preferably (1-5):100.

[0033] According to the present invention, the weight ratio of the water-soluble high molecular weight polymer in the casting solution to the dry rubber in the rubber latex is (0.01-2):100, preferably (0.2-1):100, and more preferably (0.3-0.6):100. In the present invention, selecting a weight ratio within the above range allows the water-soluble polymer to stabilize and uniformly disperse the latex particles while preventing the adhesion between the rubber and the support film from being affected by excessively high concentrations.

[0034] According to the present invention, in the process of preparing polar organic solvent-resistant nanofiltration membrane, the main material used is emulsified rubber material, preferably, the rubber latex is styrene-butadiene latex and / or acrylonitrile-butadiene latex; in the present invention, the rubber latex material used has a high degree of crosslinking, and the level of crosslinking is characterized by the gel content of the dry rubber after latex coagulation in a polar organic solvent (such as tetrahydrofuran). Preferably, the gel content in the rubber latex is 50-99%, preferably 70-95%, and more preferably 80-90%. In the present invention, a rubber with a high gel content (high crosslinking degree) is selected. On the one hand, the rubber is not 100% crosslinked, has a certain flexibility, can maintain the mobility of the rubber molecular chain, and is conducive to the flux of the membrane. On the other hand, such a high degree of crosslinking can ensure that the membrane material can tolerate common mild organic solvents.

[0035] In addition, it should be noted that in the present invention, the gel content test is to test the gel content of the dried membrane material in tetrahydrofuran.

[0036] According to the present invention, the particle size of the rubber in the rubber latex is 10-1000nm, preferably 50-200nm, preferably 80-120nm, and most preferably 90-115nm. In the present invention, the selection of the particle size of the rubber latex takes into account the pore size of the supporting layer ultrafiltration membrane, ensuring that the latex particles are not too small to prevent the rubber particles from entering the ultrafiltration layer pores during the coating process, blocking the channels and reducing the flux of the membrane. On the other hand, it is considered that too large a particle size will make it difficult to control the membrane thickness, resulting in poor membrane surface uniformity.

[0037] According to the present invention, the mass concentration of rubber in the rubber latex is 10-80%, preferably 20-60%, and more preferably 30-50%. In the present invention, the rubber in the rubber latex satisfies the above mass concentration, and such rubber latex has good stability and reduces the demulsification ratio during the process of blending with the water-soluble polymer solution.

[0038] According to the present invention, deionized water is added to adjust the dry rubber concentration in the mixture. The dry rubber concentration in the casting solution is 0.1-10%, preferably 0.3-5%, and more preferably 0.5-1%. Controlling the dry rubber concentration is important, firstly, to obtain a thinner functional layer at the thickness of the scraper, thereby improving adhesion between the functional layer and the support layer and increasing membrane flux. Secondly, it facilitates the migration of graphene oxide to the membrane surface.

[0039] According to the present invention, a water-soluble polymer is added before mixing the highly cross-linked rubber latex and the graphene oxide aqueous solution to improve their mechanical stability. The water-soluble polymer is any water-soluble polymer. In the present invention, the water-soluble polymer preferably includes one or more of sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate, sodium polymethacrylate, and sodium polyphosphate.

[0040] According to the present invention, the graphene oxide is of J&K brand, purchased from J&K.

[0041] According to the present invention, the support layer is an ultrafiltration support layer, and the ultrafiltration support membrane is any polymer or polymer-modified membrane with suitable pore size and resistance to organic solvents. In the present invention, preferably, the support layer is selected from one or more of polyacrylonitrile, polyetherimide and polyimide ultrafiltration membranes.

[0042] According to the present invention, the average pore size of the support layer is 5-50 nm, preferably 10-40 nm, and more preferably 15-25 nm. This pore size can prevent latex particles from entering the pores and clogging the channels during the membrane preparation process.

[0043] According to the present invention, the thickness of the support layer membrane is 1-500 μm, preferably 10-200 μm, more preferably 50-150 μm. The support layer of this thickness can provide the membrane with a suitable flux.

[0044] In the present invention, it should be noted that the thickness of the coating layer refers to the thickness after the final drying process. Preferably, the thickness of the coating layer (ie, the final thickness of the coating layer) is 0.1-0.3 μm, preferably 0.11-0.21 μm.

[0045] A second aspect of the present invention provides a method for preparing the aforementioned composite separation membrane, wherein the preparation method comprises:

[0046] (1) mixing graphene oxide with deionized water and then subjecting the mixture to a first ultrasonic treatment to obtain a graphene oxide aqueous solution;

[0047] (2) performing a second mixing of the water-soluble polymer and deionized water to prepare a polymer aqueous solution;

[0048] (3) mixing the graphene oxide aqueous solution, the polymer aqueous solution and the rubber latex for a third time and then subjecting the mixture to a second ultrasonic treatment to obtain a mixed solution; and diluting the mixed solution with deionized water to obtain a casting solution;

[0049] (4) The casting solution is coated on the surface of the support layer and subjected to post-processing to obtain a composite separation membrane.

[0050] According to the present invention, in step (1), a highly dispersed aqueous solution of graphene oxide is prepared, and graphene oxide is added to deionized water under stirring conditions for a first mixing, so that the graphene oxide can be quickly dispersed in water. Wherein, the conditions for the first mixing include: a stirring speed of 100-10000 rpm, preferably 500-5000 rpm, more preferably 1000-3000 rpm; a first mixing time of 1-100 min, preferably 10-60 min, more preferably 20-50 min; ultrasonic mixing is continued after high-speed stirring, so that the graphene oxide can be dispersed more evenly, and the first ultrasonic time is 1-200 min, preferably 10-100 min, more preferably 20-50 min; in addition, in a more preferred case, the ultrasonic intensity of the first ultrasound is 28-100 Hz, preferably 30-60 Hz, more preferably 35-50 Hz.

[0051] According to the present invention, the mass concentration of the graphene oxide aqueous solution is 1-20%, preferably 2-10%, and more preferably 3-6%.

[0052] According to the present invention, in step (2), the mass concentration of the high molecular weight polymer aqueous solution is 0.1-5%, preferably 0.3-2%, and more preferably 0.5-1%. In the present invention, the above mass concentration is selected so that the water-soluble polymer can be more evenly dissolved in deionized water, and the moderate viscosity can be better mixed with the rubber latex.

[0053] According to the present invention, in step (3), during the preparation of the casting solution, the aqueous solution of graphene oxide is slowly added to the mixed solution of highly cross-linked rubber latex and water-soluble high molecular polymer, and the mixture is stirred while being added to perform a third mixing, wherein the conditions for the third mixing include: a stirring rate of 10-1000 rpm, preferably 100-600 rpm, more preferably 200-500 rpm; a time for the third mixing of 1-100 min, preferably 5-60 min, more preferably 10-30 min; a time for the second ultrasound of 10-600 min, preferably 20-200 min, more preferably 30-100 min; and, more preferably, an ultrasonic intensity of the second ultrasound of 28-100 Hz, preferably 30-60 Hz, more preferably 35-50 Hz.

[0054] According to the present invention, the preparation method further comprises filtering the uniformly mixed casting solution to remove demulsified rubber. In the present invention, the filtration is preferably performed using a mesh screen having a mesh size of 20-1000 mesh, preferably 40-500 mesh, and more preferably 50-150 mesh, so as to better remove demulsified rubber particles in the casting solution.

[0055] According to the present invention, in step (3), in order to improve the stability of the rubber latex, the rubber latex is first mixed with a water-soluble high molecular polymer solution before being mixed with the graphene oxide aqueous solution.

[0056] According to the present invention, in step (4), the casting solution is coated on the surface of the support layer. The casting solution can be scraped onto the ultrafiltration support membrane using a scraper having a thickness of 10-50 μm. In the present invention, the scraper scrapes the casting solution onto the ultrafiltration support membrane, thereby forming a coating layer having an initial thickness on the ultrafiltration support membrane. In the present invention, the initial thickness of the coating layer is 10-50 μm, preferably 15-45 μm, and more preferably 20-40 μm.

[0057] According to the present invention, in step (4), the post-treatment conditions include: allowing the support layer coated with the casting solution to stand, first drying the support layer, and then immersing the support layer in deionized water for ultrasonic cleaning to remove the water-soluble polymer and emulsifier in the membrane.

[0058] According to the present invention, the support layer coated with the casting solution is allowed to stand at room temperature for 1-30 minutes, preferably 5-25 minutes, and more preferably 10-20 minutes, to ensure that moisture on the membrane surface evaporates, the membrane is initially shaped, and the casting solution is prevented from flowing. The support layer is then placed in a vacuum oven for further drying to further remove water from the membrane interior.

[0059] According to the present invention, the conditions for the first drying treatment include: an oven absolute pressure of 0.01-0.08 MPa, preferably 0.02-0.07 MPa, more preferably 0.03-0.06 MPa; a temperature of 20-80°C, preferably 30-70°C, more preferably 40-60°C; a drying time of 10-1000 min, preferably 30-500 min, most preferably 60-200 min; the removal of water inside the membrane can bring some rubber emulsifier molecules to the surface of the membrane, forming microchannels inside the membrane.

[0060] According to the present invention, the dried membrane requires further post-treatment to remove water-soluble polymers from the membrane and emulsifiers from the rubber. This treatment involves ultrasonic cleaning in deionized water. Specifically, the membrane, after the first drying step, is placed in deionized water and ultrasonically cleaned to remove the water-soluble polymers and emulsifiers. The ultrasonic cleaning duration is 10-1000 minutes, preferably 20-500 minutes, and more preferably 30-200 minutes. The ultrasonic intensity is 28-100 Hz, preferably 30-60 Hz, and most preferably 35-50 Hz.

[0061] According to the present invention, the cleaned membrane is then placed in a vacuum oven for further drying. This not only removes water molecules that have entered the membrane during the cleaning process, but also allows the rubber molecules to further expand, enhancing their interaction with the graphene oxide. This also facilitates the diffusion of graphene oxide to the surface, compensating for the graphene oxide lost on the membrane surface during cleaning. Specifically, the membrane, which has been ultrasonically cleaned by immersion in deionized water, is then placed in a vacuum oven for a second drying process. The conditions for this second drying process include an absolute pressure of 0.01-0.08 MPa, preferably 0.02-0.07 MPa, and more preferably 0.03-0.06 MPa; a temperature of 40-120°C, preferably 50-100°C, and more preferably 60-90°C; and a drying time of 10-1000 min, preferably 20-200 min, and most preferably 30-100 min.

[0062] According to a particularly preferred embodiment of the present invention, in order to make the membrane preparation process of the organic solvent-resistant nanofiltration composite membrane green, environmentally friendly, efficient and simple, the preparation method of the organic solvent-resistant nanofiltration composite membrane provided by the present invention includes three steps:

[0063] First, a casting solution is prepared: a highly dispersed aqueous solution of graphene oxide, a highly cross-linked rubber latex, and an aqueous solution of a water-soluble polymer are mixed, and the resulting mixture is diluted to a certain concentration as the casting solution;

[0064] Then, the casting solution is applied to an ultrafiltration support membrane with a certain pore size by scraping at a certain thickness, and then dehydrated and dried;

[0065] Finally, the prepared membrane is washed to remove the water-soluble high molecular polymer and the emulsifier in the rubber latex.

[0066] In the present invention, this process not only loosens the membrane surface but also removes impurities, increasing the rubber's adhesion to the support layer. Furthermore, after washing, high-temperature dehydration and drying are performed again. This firstly removes moisture from the membrane pores; secondly, it stretches the functional layer polymer chains, increasing their binding strength with graphene oxide; and thirdly, it increases the migration of graphene molecules to the membrane surface, compensating for graphene loss from cleaning and ensuring a more uniform arrangement of graphene oxide on the membrane surface.

[0067] The third aspect of the present invention provides an application of the aforementioned composite separation membrane in removing trace impurities from a weakly polar organic solvent.

[0068] In the present invention, the weakly polar organic solvent may be an organic solvent with relatively low polarity, preferably an alcohol, more preferably one or more of methanol, ethanol and propanol.

[0069] Specifically, the present invention provides an application of the aforementioned composite separation membrane in removing trace impurities from weakly polar organic solvents, for example, for the separation of ethanol and the dye molecule rose bengal.

[0070] The present invention will be described in detail below through examples.

[0071] In the following examples and comparative examples:

[0072] The highly cross-linked emulsified rubber used was all styrene-butadiene latex purchased from Ruiong with a product brand of 430B. The latex particle size was 111 nm, the rubber content in the latex was 40% wt, and the gel content in tetrahydrofuran was 85%.

[0073] Sodium carboxymethyl cellulose, purchased from Innochem, brand name Innochem A05925, MW 250000 (DS = 0.9), 1500-3100 mPa.s.

[0074] The ultrafiltration support membrane used was cross-linked polyacrylonitrile, with an average pore size of 20 nm and a thickness of 120 μm.

[0075] All filter screens are 100-mesh stainless steel screens.

[0076] The cross-flow evaluation system is used to separate ethanol and dye molecules. The cross-flow evaluation system consists of two membrane cassettes connected in series, a flow pump, a solution tank, a temperature control system, and a pressure control system. The effective area of ​​the membrane in each cassette is 14.2 cm. 2The flow pump only provides flow, not pressure, and its flow rate is fixed at 60L / h. The feed tank holds 700ml. System pressure is provided by a high-pressure nitrogen cylinder, which is adjusted by controlling a pressure reducing valve. System temperature control is achieved by immersing the feed tank in an ethylene glycol bath and adjusting the bath's temperature. The entire device is constructed from 316 stainless steel and has a pressure resistance of 69 bar.

[0077] The oven was purchased from Tester, model DZ-IBCIV.

[0078] Example 1

[0079] This embodiment is intended to illustrate the composite separation membrane prepared by the method of the present invention.

[0080] (1) 4 g of graphene oxide was weighed using an electronic balance and added to 96 g of deionized water. The mixture was stirred at a high speed of 2000 rpm for 40 min. Ultrasonic mixing was then continued at an ultrasonic intensity of 40 Hz for 30 min to obtain an aqueous solution with a graphene oxide mass concentration of 4%.

[0081] (2) Weigh 0.8 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.2 g of deionized water, and stir until completely mixed to prepare an aqueous solution with a concentration of 0.8%.

[0082] (3) In another clean beaker, add 10 g of styrene-butadiene latex (the rubber content in the latex is 40% by weight, and the calculated dry styrene-butadiene rubber is 4 g). Use a dropper to add 2.5 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene latex, so that the mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is 0.5%. After stirring until uniformly mixed, slowly add 2 g of the graphene oxide solution while stirring, so that the mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is 2%.

[0083] Continue to add deionized water to the mixed solution to dilute it so that the total amount of the mixed solution is 652 g. After adding, continue stirring at a stirring rate of 2000 rpm for 15 minutes and a stirring speed of 400 rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40 Hz for 40 minutes to obtain a casting solution with a dry styrene-butadiene rubber concentration of 0.6%.

[0084] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh screen, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 15 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.03 MPa, the temperature was 40°C, and the drying time was 100 minutes.

[0085] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 60 min at an ultrasonic frequency of 40 Hz. After washing, it was placed in an oven and dried for 50 min at a pressure of 0.04 MPa and a temperature of 70°C.

[0086] Results The thickness of the coating layer of the prepared composite separation membrane was 0.13 μm.

[0087] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.8L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 1000ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then the experiment was repeated. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 4.0L / m 2 / bar / h, and the content of Rose Bengal in ethanol at the permeate end was 1050 ppm. This indicates that the composite separation membrane prepared by the method of the present invention has good stability in organic solvents.

[0088] Example 2

[0089] This embodiment is intended to illustrate the composite separation membrane prepared by the method of the present invention.

[0090] (1) 3 g of graphene oxide was weighed using an electronic balance and added to 97 g of deionized water. The mixture was stirred at 1000 rpm for 20 min. Ultrasonic mixing was then continued at 35 Hz for 50 min to obtain an aqueous solution with a graphene oxide mass concentration of 3%.

[0091] (2) Weigh 0.6 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.4 g of deionized water, and stir until completely mixed to prepare an aqueous solution with a concentration of 0.6%.

[0092] (3) In another clean beaker, add 10 g of styrene-butadiene latex (the rubber content in the latex is 40% by weight, and the calculated dry styrene-butadiene rubber is 4 g). Use a dropper to add 2.7 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene latex, so that the mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is 0.4%. After stirring until uniformly mixed, slowly add 4 g of the graphene oxide solution while stirring, so that the mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is 3%.

[0093] Continue to add 783g of deionized water to the mixture for dilution. After adding, continue stirring at a stirring rate of 1000rpm for 20min and a stirring speed of 200rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40Hz for 60min to obtain a casting solution with a dry styrene-butadiene rubber concentration of 0.5%.

[0094] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh screen, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 20 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.04 MPa, the temperature was 45°C, and the drying time was 150 minutes.

[0095] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 100 min at an ultrasonic frequency of 35 Hz. After washing, it was placed in an oven and dried again for 70 min at a pressure of 0.05 MPa and a temperature of 80°C.

[0096] Results The thickness of the coating layer of the prepared composite separation membrane was 0.11 μm.

[0097] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 4 L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 1050ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then tested again. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 4.2L / m 2 / bar / h, and the content of Rose Bengal in ethanol at the permeate end was 1100 ppm. This indicates that the membrane prepared by our method has good stability in organic solvents.

[0098] Example 3

[0099] This embodiment is intended to illustrate the composite separation membrane prepared by the method of the present invention.

[0100] (1) 5 g of graphene oxide was weighed using an electronic balance and added to 95 g of deionized water. The mixture was stirred at a high speed of 2500 rpm for 45 min. Ultrasonic mixing was then continued at an ultrasonic intensity of 50 Hz for 40 min to obtain an aqueous solution with a graphene oxide mass concentration of 5%.

[0101] (2) Weigh 0.5 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.5 g of deionized water, and stir until completely mixed to prepare a 0.5% aqueous solution.

[0102] (3) In another clean beaker, add 10 g of styrene-butadiene rubber latex. Using a dropper, add 2.4 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene rubber latex. The mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is now 0.3%. After stirring to mix thoroughly, slowly add 3.2 g of the graphene oxide solution while stirring. The mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is now 4%.

[0103] Continue to add 384g of deionized water to the mixture for dilution. After adding, continue stirring at a stirring rate of 2500rpm for 30min and a stirring speed of 300rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 50Hz for 100min to obtain a casting solution with a dry styrene-butadiene rubber concentration of 1%.

[0104] (4) The demulsified rubber was then filtered out using a 100-mesh stainless steel sieve, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, obtaining a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 10 minutes before forming, and then placed in an oven for further drying. The oven pressure was set to 0.05 MPa, the temperature was 50°C, and the drying time was 60 minutes.

[0105] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 30 min at an ultrasonic frequency of 50 Hz. After washing, it was placed in an oven and dried for 80 min at a pressure of 0.06 MPa and a temperature of 90°C.

[0106] Results The thickness of the coating layer of the prepared composite separation membrane was 0.21 μm.

[0107] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.3 L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 800ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then tested again. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.5L / m 2 / bar / h, and the content of Rose Bengal in ethanol at the permeate end was 850 ppm. This indicates that the membrane prepared by our method has good stability in organic solvents.

[0108] Example 4

[0109] This embodiment is intended to illustrate the composite separation membrane prepared by the method of the present invention.

[0110] (1) 6 g of graphene oxide was weighed using an electronic balance and added to 94 g of deionized water. The mixture was stirred at a high speed of 1500 rpm for 50 min. Ultrasonic mixing was then continued at an ultrasonic intensity of 45 Hz for 20 min to obtain an aqueous solution with a graphene oxide mass concentration of 6%.

[0111] (2) Weigh 0.5 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.5 g of deionized water, and stir until completely mixed to prepare a 1% aqueous solution.

[0112] (3) In another clean beaker, add 10 g of styrene-butadiene rubber latex. Using a dropper, add 2.4 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene rubber latex. The mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is now 0.6%. After stirring to mix thoroughly, slowly add 3.3 g of the graphene oxide solution while stirring. The mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is now 5%.

[0113] Continue to add 484g of deionized water to the mixture for dilution. After adding, continue stirring at a stirring rate of 1500rpm for 10min and a stirring speed of 500rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 45Hz for 30min to obtain a casting solution with a dry styrene-butadiene rubber concentration of 0.8%.

[0114] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh screen, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 12 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.06 MPa, the temperature was 60°C, and the drying time was 200 minutes.

[0115] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 200 min at an ultrasonic frequency of 45 Hz. After washing, it was placed in an oven and dried for 30 min at a pressure of 0.03 MPa and a temperature of 60°C.

[0116] Results The thickness of the coating layer of the prepared composite separation membrane was 0.17 μm.

[0117] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.6L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 960ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then tested again. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.8L / m2 / bar / h, and the content of Rose Bengal in ethanol at the permeate end was 1000 ppm. This indicates that the membrane prepared by our method has good stability in organic solvents.

[0118] Example 5

[0119] This embodiment is intended to illustrate the composite separation membrane prepared by the method of the present invention.

[0120] (1) 4.5 g of graphene oxide was weighed using an electronic balance and added to 95.5 g of deionized water. The mixture was stirred at 3000 rpm for 30 min. Ultrasonic mixing was then continued at 40 Hz for 50 min to obtain an aqueous solution with a graphene oxide mass concentration of 4.5%.

[0121] (2) Weigh 0.35 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.65 g of deionized water, and stir until completely mixed to prepare an aqueous solution with a concentration of 0.7%.

[0122] (3) In another clean beaker, add 10 g of styrene-butadiene latex. Using a dropper, add 2.6 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene latex. The mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is now 0.45%. After stirring to mix thoroughly, slowly add 0.9 g of the graphene oxide solution while stirring. The mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is now 1%.

[0123] Continue to add 558g of deionized water to the mixture for dilution. After adding, continue stirring at a stirring rate of 3000rpm for 25min and a stirring speed of 250rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40Hz for 70min to obtain a casting liquid with a dry styrene-butadiene rubber concentration of 0.7%.

[0124] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 18 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.04 MPa, the temperature was 55°C, and the drying time was 120 minutes.

[0125] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 150 min at an ultrasonic frequency of 40 Hz. After washing, it was placed in an oven and dried for 100 min at a pressure of 0.04 MPa and a temperature of 75°C.

[0126] Results The thickness of the coating layer of the prepared composite separation membrane was 0.15 μm.

[0127] The prepared composite membrane, cut to appropriate size, was used to separate ethanol and the dye molecule Rose Bengal in a cross-flow evaluation system. The feed solution had a Rose Bengal concentration of 5%, an ethanol flux at the permeate end of 2.8 L / m² / bar / h, and a Rose Bengal content of 990 ppm in the ethanol at the permeate end. Following the experiment, the membrane was immersed in the ethanol system for one month before being retested. The feed solution had a Rose Bengal concentration of 5%, an ethanol flux at the permeate end of 2.9 L / m² / bar / h, and a Rose Bengal content of 1050 ppm in the ethanol at the permeate end. This demonstrates the excellent stability of the membrane prepared by our method in organic solvents.

[0128] Comparative Example 1

[0129] Compared with Example 1, no graphene oxide was added to the casting solution for modification.

[0130] (1) Weigh 0.8 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.2 g of deionized water, and stir until completely mixed to prepare an aqueous solution with a concentration of 0.8%.

[0131] (2) Take another clean beaker and add 10g of styrene-butadiene rubber latex. Use a dropper to take 2.5g of the prepared sodium carboxymethyl cellulose solution and add it to the styrene-butadiene rubber latex. At this time, the mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is 0.5%.

[0132] Continue to add 652g of deionized water to the mixed liquid for dilution. After adding, continue stirring at a stirring rate of 2000rpm for 15min and a stirring speed of 400rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40Hz for 40min to obtain a casting liquid with a dry styrene-butadiene rubber concentration of 0.6%.

[0133] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh screen, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 15 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.03 MPa, the temperature was 40°C, and the drying time was 100 minutes.

[0134] Finally, the membrane was post-treated by washing it in an ultrasonic deionized water bath for 60 min at an ultrasonic frequency of 40 Hz. After washing, it was placed in an oven and dried for 50 min at a pressure of 0.04 MPa and a temperature of 70°C.

[0135] Results The thickness of the coating layer of the prepared composite separation membrane was 0.12 μm.

[0136] The prepared membrane was cut into appropriate sizes and used to separate ethanol and the dye molecule Rose Bengal in a cross-flow evaluation system. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 0.6 L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 1000ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then the experiment was repeated. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 0.7L / m 2 / bar / h, the content of rose bengal in ethanol at the permeate end was 1050ppm.

[0137] This demonstrates that the addition of graphene oxide to the membrane surface in Example 1 can modify the membrane surface, increasing its polarity and significantly improving the flux of polar solvents. In Comparative Example 1, the ethanol flux was relatively low because graphene oxide was not added to the casting solution for modification.

[0138] Comparative Example 2

[0139] Compared with Example 1, the water-soluble high molecular polymer sodium carboxymethyl cellulose is not added.

[0140] (1) 4 g of graphene oxide was weighed using an electronic balance and added to 96 g of deionized water. The mixture was stirred at a high speed of 2000 rpm for 40 min. Ultrasonic mixing was then continued at an ultrasonic intensity of 40 Hz for 30 min to obtain an aqueous solution with a graphene oxide mass concentration of 4%.

[0141] (2) Take another clean beaker and add 10g of styrene butadiene rubber latex, and slowly add 2g of graphene oxide solution while stirring. At this time, the mass ratio of graphene oxide to styrene butadiene rubber in the mixed solution is 2%.

[0142] Continue to add 650g of deionized water to the mixed liquid for dilution. After adding, continue stirring at a stirring rate of 2000rpm for 15min and a stirring speed of 400rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40Hz for 40min to obtain a casting solution with a polymer mass concentration of 0.6%.

[0143] (3) The demulsified rubber was then filtered out using a 100-mesh stainless steel sieve, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, obtaining a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 15 minutes to form, and then placed in an oven for further drying. The oven pressure was set to 0.03 MPa, the temperature was 40°C, and the drying time was 100 minutes.

[0144] Finally, the membrane was post-treated. Under the condition of ultrasonic frequency of 40 Hz, the membrane was placed in an ultrasonic deionized water bath for cleaning for 60 minutes. After cleaning, it was placed in an oven for drying for 50 minutes. The oven pressure was 0.04 MPa and the temperature was 70°C.

[0145] Results The thickness of the coating layer of the prepared composite separation membrane was 0.13 μm.

[0146] The prepared membrane was cut to appropriate size and used to separate ethanol and the dye molecule Rose Bengal in a cross-flow evaluation system. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 4.8 L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 1% ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then the experiment was repeated. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 5.0 L / m 2 / bar / h, the content of rose bengal in ethanol at the permeate end is 1% ppm.

[0147] Comparative Example 2 shows that without the addition of sodium carboxymethyl cellulose, the emulsified rubber is not evenly distributed, the prepared membrane has poor uniformity, many local defects, and a poor retention rate of the membrane.

[0148] Comparative Example 3

[0149] Compared with Example 1, the proportion of graphene oxide added is too large.

[0150] (1) 4 g of graphene oxide was weighed using an electronic balance and added to 96 g of deionized water. The mixture was stirred at a high speed of 2000 rpm for 40 min. Ultrasonic mixing was then continued at an ultrasonic intensity of 40 Hz for 30 min to obtain an aqueous solution with a graphene oxide mass concentration of 4%.

[0151] (2) Weigh 0.8 g of sodium carboxymethyl cellulose using an electronic balance, slowly add it to 99.2 g of deionized water, and stir until completely mixed to prepare an aqueous solution with a concentration of 0.8%.

[0152] (3) In another clean beaker, add 10 g of styrene-butadiene latex. Using a dropper, add 2.5 g of the prepared sodium carboxymethyl cellulose solution to the styrene-butadiene latex, so that the mass ratio of sodium carboxymethyl cellulose to dry styrene-butadiene rubber is 0.5%. After stirring until uniformly mixed, slowly add 20 g of the graphene oxide solution while stirring. At this point, the mass ratio of graphene oxide to dry styrene-butadiene rubber in the mixture is 20%.

[0153] Continue to add 630g of deionized water to the mixed liquid for dilution. After adding, continue stirring at a stirring rate of 2000rpm for 15min and a stirring speed of 400rpm. After stirring evenly, continue ultrasonic mixing at an ultrasonic intensity of 40Hz for 40min to obtain a casting liquid with a dry styrene-butadiene rubber concentration of 0.6%.

[0154] (4) Then, the demulsified rubber was filtered out with a 100-mesh stainless steel mesh screen, and a 20-μm-thick scraper was used to scrape the surface of the ultrafiltration support membrane to form a film, so as to obtain a membrane with an initial coating layer thickness of 20 μm. The membrane was allowed to stand in the air for 15 minutes and then formed, and then placed in an oven for further drying. The oven pressure was set to 0.03 MPa, the temperature was 40°C, and the drying time was 100 minutes.

[0155] Finally, the membrane was post-treated. Under the condition of ultrasonic frequency of 40 Hz, the membrane was placed in an ultrasonic deionized water bath for cleaning for 60 minutes. After cleaning, it was placed in an oven for drying for 50 minutes. The oven pressure was 0.04 MPa and the temperature was 70°C.

[0156] Results The thickness of the coating layer of the prepared composite separation membrane was 0.13 μm.

[0157] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 3.9 L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 1000ppm. After the experiment, the membrane was immersed in the ethanol system for one month and then tested again. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 4.1L / m 2 / bar / h, the content of rose bengal in ethanol at the permeate end was 1050ppm.

[0158] Compared with Example 1, the amount of graphene oxide increased by 9 times, but the performance of the membrane did not improve significantly, indicating that the ratio of graphene oxide to highly cross-linked rubber in Example 1 was appropriate. The additional graphene oxide not only increased the cost, but also added difficulties to the post-processing stage of the membrane.

[0159] Comparative Example 4

[0160] A composite separation membrane was prepared according to the same method as in Example 1, except that: instead of using the "styrene-butadiene latex" in Example 1, "10 g of styrene-butadiene latex with a low degree of cross-linking (the latex was homemade, with a latex particle size of 100 nm, a rubber content of 40 wt %, and a gel content of about 30% as measured by tetrahydrofuran)" was used.

[0161] Results The thickness of the coating layer of the prepared composite separation membrane was 0.13 μm.

[0162] The composite separation membrane prepared by cutting into appropriate size was used to separate ethanol and dye molecule rose bengal in a cross-flow evaluation system. The mass concentration of rose bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 18L / m 2 / bar / h, the Rose Bengal content in the ethanol at the permeate end was 3%. After the experiment, the membrane was immersed in the ethanol system for one month and then the experiment was repeated. The mass concentration of Rose Bengal in the raw liquid was 5%, and the ethanol flux at the permeate end was 28L / m 2 / bar / h, the content of rose bengal in ethanol at the permeation end was 4.5%.

[0163] Compared with Example 1, the membrane has no retention capacity.

[0164] In summary, the organic solvent-resistant nanofiltration composite membrane of the present invention does not use organic solvents in the preparation process, which can effectively avoid the harm of organic solvents to the human body and the environment. The membrane preparation process is simple, which greatly saves membrane preparation time; the preparation method is green, environmentally friendly, and efficient; and can prepare membranes with high permeation flux and retention rate.

[0165] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite separation membrane, characterized in that The composite separation membrane comprises a support layer and a coating layer coated on the surface of the support layer, wherein the coating layer is obtained by coating a casting liquid on the surface of the support layer and then performing post-processing; The casting solution contains graphene oxide, rubber latex, water-soluble high molecular polymer and deionized water.

2. The composite separation membrane according to claim 1, wherein The casting solution consists of graphene oxide, rubber latex, water-soluble high molecular polymer and deionized water; Preferably, in the casting solution, the weight ratio of the graphene oxide to the dry rubber in the rubber latex is (0.1-100):100, preferably (0.5-10):100; Preferably, in the casting solution, the weight ratio of the water-soluble high molecular polymer to the dry rubber in the rubber latex is (0.01-2):100, preferably (0.2-1):

100.

3. The composite separation membrane according to claim 1 or 2, wherein The rubber latex is styrene-butadiene latex and / or nitrile-butadiene latex; Preferably, the gel content of the rubber latex is 50-99%, preferably 70-95%; Preferably, the particle size of the rubber in the rubber latex is 10-1000 nm, preferably 50-200 nm; Preferably, the mass concentration of rubber in the rubber latex is 10-80%.

4. The composite separation membrane according to any one of claims 1 to 3, wherein The mass concentration of dry rubber in the casting solution is 0.1-10%, preferably 0.3-5%, more preferably 0.5-1%.

5. The composite separation membrane according to any one of claims 1 to 3, wherein The water-soluble high molecular polymer is selected from one or more of sodium carboxymethyl cellulose, sodium polyacrylate, sodium alginate, sodium polymethacrylate and sodium polyphosphate. The composite separation membrane according to claim 1 , wherein The support layer is an ultrafiltration support layer; Preferably, the support layer is selected from one or more of polyacrylonitrile, polyetherimide and polyimide ultrafiltration membranes; Preferably, the average pore size of the support layer is 5-50 nm, preferably 10-40 nm, more preferably 15-25 nm.

7. The composite separation membrane according to any one of claims 1 to 6, wherein: The thickness of the coating layer is 0.1-0.3 μm, preferably 0.11-0.21 μm; And / or, the thickness of the support layer membrane is 1-500 μm, preferably 10-200 μm, more preferably 50-150 μm.

8. A method for preparing the composite separation membrane according to any one of claims 1 to 7, characterized in that: The preparation method comprises: (1) mixing graphene oxide with deionized water and then subjecting the mixture to a first ultrasonic treatment to obtain a graphene oxide aqueous solution; (2) performing a second mixing of the water-soluble polymer and deionized water to prepare a polymer aqueous solution; (3) mixing the graphene oxide aqueous solution, the polymer aqueous solution and the rubber latex for a third time and then subjecting the mixture to a second ultrasonic treatment to obtain a mixed solution; and diluting the mixed solution with deionized water to obtain a casting solution; (4) The casting solution is coated on the surface of the support layer and subjected to post-processing to obtain a composite separation membrane.

9. The preparation method according to claim 8, wherein In step (1), the first mixing conditions include: a stirring speed of 100-10000 rpm, a first mixing time of 1-100 min, and a first ultrasonic time of 1-200 min; And / or, the mass concentration of the graphene oxide aqueous solution is 1-20%; And / or, in step (2), the mass concentration of the high molecular polymer aqueous solution is 0.1-5%; And / or, in step (3), the conditions of the third mixing include: a stirring rate of 10-1000 rpm, a time of the third mixing of 1-100 min, and a time of the second ultrasonication of 10-600 min; And / or, in step (4), the post-treatment conditions include: allowing the support layer coated with the casting solution to stand, first drying the support layer, and then immersing the support layer in deionized water for ultrasonic cleaning; Preferably, the standing time is 1-30 min; Preferably, the conditions of the first drying treatment include: an oven absolute pressure of 0.01-0.08 MPa, a temperature of 20-80° C., and a drying time of 10-1000 min; Preferably, the ultrasonic cleaning time is 10-1000 min.

10. The preparation method according to claim 9, wherein The preparation method further comprises: in step (4), subjecting the membrane after ultrasonic cleaning by immersion in deionized water to a second drying treatment; Preferably, the conditions of the second drying treatment include: absolute pressure of 0.01-0.08 MPa, temperature of 40-120° C., and drying time of 10-1000 min.

11. The preparation method according to any one of claims 8 to 10, wherein The preparation method further comprises: filtering the casting solution; Preferably, the filtration is performed using a mesh screen, the mesh size of which is 20-1000 mesh, preferably 40-500 mesh.

12. Use of the composite separation membrane according to any one of claims 1 to 7 in removing impurities from weakly polar organic solvents.