Composite separation membrane and preparation method and application thereof

Abstract

The application belongs to the technical field of composite membrane materials, and discloses a composite separation membrane and a preparation method and application thereof. The preparation method of the composite separation membrane comprises the following steps: combining a crosslinking agent with graphene oxide to prepare a selective separation layer of the composite separation membrane, combining UIO-66-(COOH)2 with graphene oxide to prepare an intermediate transition layer of the composite separation membrane, and selecting PA6 superfine fiber cloth as a support layer to obtain a negatively charged graphene oxide / PA6 superfine fiber composite separation membrane. The composite separation membrane prepared by the application can significantly improve the permeation flux of the graphene oxide composite separation membrane, and ensure high retention rate of dyes while maintaining high permeation flux. The application can be used for removing anionic dyes in dye wastewater.

Description

Technical Field

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

[0002] The production of dyes and pesticides generates numerous intermediates and pollutants in wastewater. Dyes and their intermediates have complex molecular structures, often containing reactive groups such as benzene rings, naphthalene, quinones, sulfonic acid groups, amodiphenyl groups, hydroxyl groups, carbonyl groups, carboxyl groups, nitro groups, and amine groups. Dye wastewater is characterized by high organic matter and salt content, high toxicity, and poor biodegradability. Treatment methods mainly fall into two categories: biological and physicochemical methods. Biological methods are currently one of the most widely used, with the main advantage of low treatment costs. However, they require diluting the wastewater tens to hundreds of times, and the treatment effect is still not ideal. Physicochemical methods mainly include adsorption, solvent extraction, micro-electrolysis, and catalytic oxidation. These methods are costly, have generally poor results, and are difficult to implement in engineering applications.

[0003] Membrane separation technologies, including microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO), nanofiltration (NF), electrodialysis (ED), and liquid membrane (LM), offer advantages such as strong adaptability, high treatment efficiency, simple operation, no phase change, and material recyclability, making them promising for future applications. Different membrane technologies have varying separation sizes and treatment ranges; a rational combination of these technologies can leverage their respective strengths and optimize treatment efficiency. While research and applications of combined membrane technologies for treating dye and pesticide wastewater have made some progress, reports of their engineering applications are still limited. Developing energy-saving, environmentally friendly, and low-emission water treatment technologies has become a key development area. Membrane separation is gaining importance in water treatment due to its high separation efficiency, lack of phase change and chemical reaction, small size, low energy consumption, and ease of operation.

[0004] Nanofiltration membrane separation technology has wide applications in seawater desalination, drinking water treatment, and industrial wastewater treatment due to its advantages such as high separation efficiency, low energy consumption, environmental friendliness, and ease of coupling with other technologies. The commonly used and relatively mature method for preparing nanofiltration membranes is interfacial polymerization, which utilizes two highly reactive monomers to react at the interface of two immiscible phases, polymerizing to form a nanoscale thin film. Interfacial polymerization is simple and efficient, and the resulting nanofiltration membranes exhibit excellent retention performance. However, the "trade-off" effect between retention rate and flux makes it difficult to simultaneously improve both solute retention rate and flux, becoming a key issue in nanofiltration membrane modification.

[0005] UIO-66 is a metal-organic framework (MOF) material composed of an organic framework of terephthalic acid linked to zirconium nodes. It exhibits a regular structure with flexible and diverse designability, persistent porosity, and an extremely high specific surface area. UIO-66-(COOH)2 is a product obtained by carboxylating the functional groups of UIO-66.

[0006] Compared to traditional separation membranes, graphene oxide-based separation membranes have attracted significant attention in the field of membrane separation due to their unique stacked interlayer mass transfer channels. In particular, the abundant oxygen-containing functional groups on the surface of graphene oxide nanosheets provide active sites for the diversity of interlayer structures. Graphene oxide (GO) exhibits excellent permeability due to the large in-plane porosity and tunability within the stacked layers, and the flexible interlayer nanochannels for rapid water molecule transport. These oxygen-containing groups endow the separation membrane with outstanding hydrophilicity and electronegativity. The hydrophilic surface can significantly improve the antifouling performance of the separation membrane, while the presence of a strong negative charge can provide electrostatic repulsion, thereby contributing to improved separation performance. Therefore, separation membranes constructed using graphene oxide stacked layers have potential advantages compared to similar structures (e.g., molybdenum disulfide MoS2, MXene). However, the stability of the interlayer structure of graphene oxide-based separation membranes cannot address the swelling phenomenon caused by prolonged exposure to aqueous environments. It has been reported that reduction, chemical crosslinking, and metal ion coordination can improve the separation stability of graphene oxide. Post-heat treatment can improve separation stability, but excessive reduction treatment severely reduces permeability. Therefore, stringent preparation conditions remain a major obstacle to large-scale production. Furthermore, in practical applications, the long-term stability of the membrane structure under high-pressure operation and its flexural strength to meet application requirements remain key issues to be addressed. Simultaneously, most stacked separation membranes rely excessively on commonly used microporous membrane substrates, and the adhesion between the graphene selective layer and the microporous membrane substrate exhibits instability. Therefore, the mechanical stability required for the production and practical application of large-size membranes are crucial scientific problems that need to be solved. Summary of the Invention

[0007] To overcome the shortcomings of existing graphene oxide membranes, such as poor stability, low water flux, low separation selectivity, and poor mechanical stability, this invention provides a composite separation membrane, its preparation method, and its application. Research has found that by arranging carboxyl-modified materials, polyamide-6, and graphene oxide in a layered manner, a graphene oxide composite separation membrane is obtained, which significantly improves the efficiency of pollutant separation in wastewater and is easy to operate.

[0008] On one hand, the present invention relates to a method for preparing a composite separation membrane, comprising: adding sulfonated cellulose fiber (S-CNF) to a graphene oxide dispersion, reacting fully, and then ultrasonically dispersing to obtain a cross-linked graphene oxide casting solution as a selective separation layer;

[0009] UIO-66-(COOH)2 was added to the graphene oxide dispersion and ultrasonically dispersed to obtain a graphene oxide / UIO-66-(COOH)2 composite casting solution, which served as an intermediate transition layer.

[0010] PA6 microfiber cloth was immersed in a polyethyleneimine solution and, after treatment, a PA6 microfiber support substrate was obtained as a support layer.

[0011] The graphene oxide / UIO-66-(COOH)2 composite casting solution was deposited on the surface of the PA6 ultrafine fiber support substrate by vacuum filtration to obtain a smooth composite separation membrane support substrate.

[0012] The graphene oxide casting solution was deposited layer by layer on the surface of the composite separation membrane support substrate, and after vacuum drying, a negatively charged graphene oxide / PA6 ultrafine fiber composite separation membrane was obtained.

[0013] Furthermore, in the preparation method provided by the present invention, the concentration of the graphene oxide dispersion is 0.01–0.05 mg / mL; in the graphene oxide casting solution, the mass ratio of sulfonated cellulose fiber to graphene oxide is 1:10–100; in the full reaction, the reaction temperature is 25–30°C, and the reaction time is 30–60 min; the ultrasonic dispersion time is 20–30 min.

[0014] Furthermore, in the preparation method provided by the present invention, the concentration of the graphene oxide dispersion is 0.01-0.05 mg / mL; in the graphene oxide / UIO-66-(COOH)2 composite casting solution, the mass ratio of UIO-66-(COOH)2 to graphene oxide is 1:1-5; and the ultrasonic dispersion time is 20-30 min.

[0015] Furthermore, in the preparation method provided by the present invention, the concentration of the polyethyleneimine solution is 50-100 mg / mL;

[0016] Furthermore, in the preparation method provided by the present invention, the treatment includes pretreatment, vacuum drying and hot pressing; the pretreatment time is 1 to 3 hours, the vacuum drying temperature is 30 to 80°C and the drying time is 8 to 24 hours; the vacuum filtration time is 30 to 120 minutes.

[0017] Furthermore, in the preparation method provided by the present invention, the layer-by-layer deposition time is 30-120 min, the pressure is 2-4 bar; the vacuum drying temperature is 60-120℃, and the drying time is 5-20 min.

[0018] Furthermore, in the preparation method provided by the present invention, the thickness ratio of the selective separation layer, the intermediate transition layer and the support layer is 0.5-1:1-50:50-100.

[0019] On the other hand, the present invention relates to a composite separation membrane, which is prepared by the above-described method for preparing a composite separation membrane.

[0020] On the other hand, the present invention relates to the application of the above-mentioned method for preparing composite separation membranes in the removal of pollutants from wastewater.

[0021] Furthermore, in the application provided by this invention, the pollutant in the wastewater is anionic dye, and the concentration of the anionic dye is ≤100 mg / L; the initial pH value of the wastewater is 2-12; and the concentration of the pollutant is m. 2 The volume ratio of the composite separation membrane to the anionic dye is 1:250 to 4000, calculated per L.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects or advantages:

[0023] (1) Using sulfonated cellulose fibers as a crosslinking agent reduced and stabilized the channel size between the graphene oxide sheets in the surface selective layer, improving the retention rate of the composite separation membrane for dye molecules and its stability in different separation environments. Simultaneously, the sulfonated cellulose fibers and graphene oxide provided a negative charge to the surface of the composite separation membrane, which facilitated the charge repulsion effect of the composite separation membrane on negatively charged dye molecules, thus improving the retention rate of the composite separation membrane for negatively charged dyes. Regularly shaped UIO-66-(COOH)2 nanoparticles could fill the surface of PA6 microfiber cloth, providing a smooth supporting substrate for the gradual deposition of graphene oxide casting solution. Furthermore, the embedding of UIO-66-(COOH)2 nanoparticles could adjust the size and transport path of the fluid permeation channels, reducing the mass transfer resistance of water molecules and effectively improving the permeation flux of the composite separation membrane.

[0024] (2) The process of this invention is simple, low-cost, universal, and environmentally friendly. It can achieve good selective separation of different charged dyes. Furthermore, the composite separation membrane exhibits good operational stability, and its size can be scaled up for mass production. The composite separation membrane prepared by this invention is used in experiments separating solutions of different charged dyes, maintaining a high dye rejection rate even with high permeation flux. Under conditions of 25℃ and a dye concentration of 100 mg / mL, the permeation flux is 2.91–21.87 L / (m³).2 The retention rate of Congo red dye was as high as 99.32% (·h·bar). Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a cross-sectional scanning electron microscope image of the composite separation membrane prepared in Example 3 of the present invention.

[0027] Figure 2 This is a cross-sectional scanning electron microscope image of the composite separation membrane support substrate prepared in Example 3 of the present invention.

[0028] Figure 3 The image shows the zeta potential diagrams of the composite separation membranes prepared in Examples 1-3 of this invention. Detailed Implementation

[0029] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[0030] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0031] Example 1

[0032] This embodiment provides a composite separation membrane and its preparation method.

[0033] Step 1: Add sulfonated cellulose fibers to a graphene oxide dispersion with a mass ratio of 1:10, magnetically stir for 30 min, sonicate for 20 min to fully disperse the crosslinking agent, and react the mixed solution in a water bath at 25℃ for 30 min to obtain the crosslinked graphene oxide casting solution.

[0034] Step 2: Add graphene oxide to deionized water to prepare a graphene oxide dispersion with a concentration of 0.01 mg / mL. Add UIO-66-(COOH)2 to the graphene oxide dispersion to make the concentration of UIO-66-(COOH)2 0.01 mg / mL. Sonicate for 20 min to obtain graphene oxide / UIO-66-(COOH)2 composite casting solution.

[0035] Step 3: The PA6 microfiber cloth was pretreated by immersing it in a 50 mg / mL polyethyleneimine solution for 1 h, and then dried in a vacuum environment at 30 °C for 8 h. The thickness of the PA6 microfiber support substrate was 500 μm. The dried PA6 microfiber support substrate was then immersed in a graphene oxide / UIO-66-(COOH)2 composite casting solution and vacuum filtered for 30 min. The thickness of the intermediate transition layer deposited on the PA6 microfiber support substrate was 10 μm, resulting in a smooth composite separation membrane support substrate.

[0036] Step 4: Immerse the composite separation membrane support substrate in the cross-linked graphene oxide casting solution, and form a film for 30 minutes using a pre-pressure assisted film forming device with a pressure of 2 bar. The thickness of the selective separation layer deposited on the composite separation membrane support substrate is 0.05 μm. The vacuum drying temperature is 60℃ and the vacuum drying time is 5 minutes.

[0037] Example 2

[0038] This embodiment provides a composite separation membrane and its preparation method.

[0039] Step 1: Add sulfonated cellulose fibers to a graphene oxide dispersion with a mass ratio of 1:50 (graphene oxide to sulfonated cellulose fibers). Stir magnetically for 30 minutes and sonicate for 25 minutes to fully disperse the crosslinking agent. React the mixed solution in a water bath at 25°C for 50 minutes to obtain a crosslinked graphene oxide casting solution.

[0040] Step 2: Add graphene oxide to deionized water to prepare a graphene oxide dispersion with a concentration of 0.03 mg / mL. Add UIO-66-(COOH)2 to the graphene oxide dispersion to make the concentration of UIO-66-(COOH)2 0.09 mg / mL. Sonicate for 30 min to obtain graphene oxide / UIO-66-(COOH)2 composite casting solution.

[0041] Step 3: The PA6 microfiber cloth was pretreated by immersing it in a 70 mg / mL polyethyleneimine solution for 2 h, and then dried in a vacuum environment at 50 °C for 15 h. The thickness of the PA6 microfiber support substrate was 800 μm. The dried PA6 microfiber support substrate was then immersed in a graphene oxide / UIO-66-(COOH)2 composite casting solution and vacuum filtered for 70 min. The thickness of the separation layer deposited on the PA6 microfiber support substrate was 30 μm, resulting in a smooth composite separation membrane support substrate.

[0042] Step 4: Immerse the composite separation membrane support substrate in the cross-linked graphene oxide casting solution, and form a film for 80 minutes using a pre-pressure assisted film forming device with a pressure of 3 bar. The thickness of the separation layer deposited on the composite separation membrane support substrate is 0.8 μm. The vacuum drying temperature is 90℃ and the vacuum drying time is 18 minutes.

[0043] Example 3

[0044] This embodiment provides a composite separation membrane and its preparation method.

[0045] Step 1: Add sulfonated cellulose fibers to a graphene oxide dispersion with a mass ratio of 1:100, magnetically stir for 30 min, sonicate for 30 min to fully disperse the crosslinking agent, and react the mixed solution in a 30℃ water bath for 60 min to obtain the crosslinked graphene oxide casting solution.

[0046] Step 2: Add graphene oxide to deionized water to prepare a graphene oxide dispersion with a concentration of 0.05 mg / mL. Add UIO-66-(COOH)2 to the graphene oxide dispersion to make the concentration of UIO-66-(COOH)2 0.25 mg / mL. Sonicate for 30 min to obtain graphene oxide / UIO-66-(COOH)2 composite casting solution.

[0047] Step 3: The PA6 microfiber cloth was pretreated by immersing it in a 100 mg / mL polyethyleneimine solution for 3 h, and then dried in a vacuum environment at 80 °C for 24 h. The thickness of the PA6 microfiber support substrate was 1000 μm. The dried PA6 microfiber support substrate was then immersed in a graphene oxide / UIO-66-(COOH)2 composite casting solution and vacuum filtered for 120 min. The thickness of the separation layer deposited on the PA6 microfiber support substrate was 50 μm, resulting in a smooth composite separation membrane support substrate.

[0048] Step 4: Immerse the composite separation membrane support substrate in the cross-linked graphene oxide casting solution, and form a membrane for 120 min using a pre-pressure assisted film forming device with a pressure of 4 bar. The thickness of the separation layer deposited on the composite separation membrane support substrate is 1 μm. The vacuum drying temperature is 120℃ and the vacuum drying time is 20 min.

[0049] Figure 1 This is a cross-sectional scanning electron microscope image of the composite separation membrane prepared in this embodiment. Figure 2 This is a cross-sectional scanning electron microscope image of the composite separation membrane support substrate prepared in this embodiment.

[0050] Example 4

[0051] Step 1: Add sulfonated cellulose fibers to a graphene oxide dispersion with a mass ratio of 1:10, magnetically stir for 30 min, sonicate for 20 min to fully disperse the crosslinking agent, and react the mixed solution in a water bath at 25℃ for 30 min to obtain the crosslinked graphene oxide casting solution.

[0052] Step 2: Add graphene oxide to deionized water to prepare a graphene oxide dispersion with a concentration of 0.01 mg / mL. Add UIO-66-(COOH)2 to the graphene oxide dispersion to make the concentration of UIO-66-(COOH)2 0.05 mg / mL. Sonicate for 30 min to obtain graphene oxide / UIO-66-(COOH)2 composite casting solution.

[0053] Step 3: The PA6 microfiber cloth was pretreated by immersing it in a 50 mg / mL polyethyleneimine solution for 1 h, and then dried in a vacuum environment at 50 °C for 12 h. The thickness of the PA6 microfiber support substrate was 800 μm. The dried PA6 microfiber support substrate was then immersed in a graphene oxide / UIO-66-(COOH)2 composite casting solution and vacuum filtered for 100 min. The thickness of the separation layer deposited on the PA6 microfiber support substrate was 40 μm, resulting in a smooth composite separation membrane support substrate.

[0054] Step 4: Immerse the composite separation membrane support substrate in the cross-linked graphene oxide casting solution, and form a film for 80 minutes using a pre-pressure assisted film forming device with a pressure of 3 bar. The thickness of the separation layer deposited on the composite separation membrane support substrate is 0.8 μm. The vacuum drying temperature is 100℃ and the vacuum drying time is 10 minutes.

[0055] Comparative Example 1

[0056] This comparative example provides a composite separation membrane and its preparation method.

[0057] The difference between this comparative example and Example 1 is that UIO-66-(COOH)2 and sulfonated cellulose fibers are not added. Instead, a graphene oxide dispersion with a concentration of 0.01 mg / mL is deposited layer by layer on a PA6 ultrafine fiber support substrate to obtain a composite separation membrane.

[0058] The composite separation membranes prepared in Examples 1-4 and Comparative Example 1 were tested for their permeability in pure water, as well as their permeability and rejection rates for Congo red dye, methylene blue dye, and bovine serum albumin (BSA). Specifically, the tests were conducted at 25°C using pure water, solutions of Congo red dye (CR), methylene blue dye (MB), and bovine serum albumin (BSA) at different concentrations and pH values. The results are shown in Table 1. Specifically, CR has a molecular weight of 696.68 Da and is negatively charged; MB has a molecular weight of 319.85 Da and is positively charged; and BSA has a molecular weight of 66.43 kDa and is electrically neutral.

[0059] The formula for calculating permeability is: J = V / (S × T × P0)

[0060] In the formula:

[0061] J—Pure water flux of the filtration membrane, L / (m²) 2 ·h·bar);

[0062] V – Water volume, m 3 ;

[0063] S – Area of ​​the filter membrane, m 2 ;

[0064] T—Time it takes for water to pass through the separation membrane, in hours;

[0065] P0 – Standard atmospheric pressure difference, bar.

[0066] The formula for calculating the rejection rate is: R = 100% × (C0 - C) t ) / C0

[0067] In the formula:

[0068] R—Dye degradation rate;

[0069] C0 — Average CR concentration before the reaction;

[0070] C t —Reaction time t (min) and average CR concentration.

[0071] Table 1. Separation performance of graphene oxide composite membranes for different charged target substances

[0072]

[0073]

[0074]

[0075] Table 1 shows that introducing UIO-66-(COOH)2 and sulfonated cellulose fibers into the graphene oxide composite separation membrane increases the dye permeability. The higher the content of the hydrophilic material UIO-66-(COOH)2, the higher the permeability. The composite separation membrane prepared by the method of this invention ensures a high dye rejection rate while increasing the permeation flux. When the dye pH is less than 2 and the solution concentration is greater than 100 mg / mL, the permeation flux and rejection rate of the composite separation membrane decrease.

[0076] Comparative Example 2

[0077] This comparative example describes the volume, permeability, and retention rate of the composite separation membrane prepared in Example 2 that effectively filters wastewater.

[0078] The graphene oxide composite separation membrane prepared in Example 2 was used to filter dye wastewater. The results, including the effectively filtered CR dye wastewater volume, permeability, and rejection rate, are shown in Table 2. The effective filtration area of ​​the membrane was 0.00096 m². 2 The concentration of CR dye was 100 mg / L, and the pH was 7.

[0079] Table 2. Effective filtration of CR dyes by graphene oxide composite separation membranes

[0080]

[0081]

[0082] As shown in Table 2, the composite separation membrane prepared under optimal conditions has an effective filtration volume of 250–4000 cubic meters per unit area for wastewater.

[0083] Comparative Example 3

[0084] This comparative example describes the Zeta potential diagrams of the composite separation membranes prepared in Examples 1-3.

[0085] Figure 3 The figure shows the Zeta potential diagrams of the composite separation membranes prepared in Examples 1-3. As can be seen from the figure, the graphene oxide composite separation membranes exhibit electronegativity, which gradually increases with the increase of UIO-66-(COOH)2 and sulfonated cellulose fiber content, thereby improving the repulsion performance of negatively charged particles in water. The composite separation membrane prepared by the method provided in this invention ensures a high rejection rate for dyes with the same charge while improving permeation flux and rejection rate.

[0086] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for producing a composite separation membrane, characterized by, The application relates to a preparation method of a composite separation membrane. Step 1: sulfonated cellulose fibers are added into a graphene oxide dispersion liquid, and after ultrasonic dispersion, a crosslinked graphene oxide casting solution is obtained through sufficient reaction, which is used as a selection separation layer; in the graphene oxide casting solution, the mass ratio of the sulfonated cellulose fibers to the graphene oxide is 1:10-100; Step 2: UIO-66-(COOH)2 is added into the graphene oxide dispersion liquid, the mass ratio of the UIO-66-(COOH)2 to the graphene oxide is 1:1-5, and after ultrasonic dispersion, a graphene oxide / UIO-66-(COOH)2 composite casting solution is obtained, which is used as an intermediate transition layer; Step 3: a PA6 superfine fiber cloth is immersed in a polyethyleneimine solution, and after treatment, a PA6 superfine fiber support substrate is obtained, which is used as a support layer; the graphene oxide / UIO-66-(COOH)2 composite casting solution is deposited on the surface of the PA6 superfine fiber support substrate through vacuum filtration, and a flat composite separation membrane support substrate is obtained; Step 4: the graphene oxide casting solution is deposited on the surface of the composite separation membrane support substrate layer by layer, and after vacuum drying, a negatively charged graphene oxide / PA6 superfine fiber composite separation membrane is obtained. The thickness ratio of the selection separation layer, the intermediate transition layer and the support layer is 0.5-1:1-50:50-100.

2. The production method according to claim 1, characterized by, In the sufficient reaction, the reaction temperature is 25-30 DEG C, and the reaction time is 30-60 min; the ultrasonic dispersion time in step 1 is 20-30 min.

3. The preparation method according to claim 1, characterized in that, The concentration of the graphene oxide dispersion liquid is 0.01-0.05 mg / mL; the ultrasonic dispersion time in step 2 is 20-30 min.

4. The method of claim 1, wherein, The concentration of the polyethyleneimine solution is 50-100 mg / mL.

5. The preparation method according to claim 1, characterized in that, The treatment includes pretreatment, vacuum drying and heat pressing treatment, wherein the pretreatment time is 1-3 h, the vacuum drying temperature is 30-80 DEG C, and the time is 8-24 h; The vacuum filtration time is 30-120 min.

6. The method of claim 1, wherein, The layer-by-layer deposition time is 30-120 min, and the pressure is 2-4 bar; in step 4, the vacuum drying temperature is 60-120 DEG C, and the time is 5-20 min.

7. A composite separation membrane, characterized by, The composite separation membrane is prepared by the preparation method in any one of claims 1-6.

8. The composite separation membrane in claim 7 is applied to removal of wastewater water body pollutants.

9. Use according to claim 8, characterized in that, The pollutant in the wastewater is anionic dye, and the concentration of the anionic dye is ≤100 mg / L; the initial pH value of the wastewater is 2~12; (The last part, "m", appears to be an unrelated fragment and is omitted from the translation.) 2 The ratio of the composite separation membrane to the anionic dye is 1:250~4000, calculated per L.

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