Preparation method of cation modified graphene oxide ceramic composite nanofiltration membrane

Abstract

The invention discloses a preparation method of a cation modified graphene oxide ceramic composite nanofiltration membrane, and belongs to the technical field of membrane separation, and the preparation method comprises the following steps: (1) preparing a graphene oxide aqueous solution; (2) soaking the porous ceramic membrane support body with a sodium hydroxide solution to obtain an activated ceramic membrane support body; (3) soaking the activated ceramic membrane support body in a 3-aminopropyldiethoxysilane ethanol solution, and reacting at room temperature to obtain a grafted ceramic membrane support body; (4) diluting a graphene oxide aqueous solution, and carrying out a cross-flow filtration reaction on the surface of the grafted ceramic membrane support body; (5) soaking the material obtained in the step (4) in a magnesium chloride solution, a potassium chloride solution or a calcium chloride solution; and (6) carrying out heat treatment on the material obtained in the step (5). The prepared product is high in durability, the ceramic supporting body provides mechanical and chemical stability, and the ceramic supporting body is suitable for complex environments such as dye wastewater and heavy metal separation and has good economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and in particular relates to a method for preparing a cation-modified graphene oxide ceramic composite nanofiltration membrane. Background Art

[0002] Membrane separation technology, as an efficient and energy-saving separation method, has been widely used in water treatment, ion separation and pollutant removal. Among them, nanofiltration membranes have become an important tool for industrial wastewater treatment, seawater desalination and fine chemical separation because of their pore size range between ultrafiltration and reverse osmosis (usually 0.5-2nm), which can achieve selective separation of small molecular organic matter, divalent ions and high-valent ions. In recent years, graphene and its derivatives, especially graphene oxide (GO), have been regarded as ideal materials for the preparation of high-performance nanofiltration membranes due to their unique two-dimensional layered structure, rich oxygen-containing functional groups (such as hydroxyl, epoxy and carboxyl groups) and good hydrophilicity. GO nanosheets can form ordered layered membranes through layer-by-layer assembly, and their interlayer channels can serve as transport paths for molecules or ions, achieving precise size screening and charge repulsion effects.

[0003] Currently, methods for preparing GO-based nanofiltration membranes primarily include vacuum filtration, spin coating, layer-by-layer self-assembly, and doping. Each of these methods has its own advantages. For example, vacuum filtration is simple to operate and can quickly form a dense membrane; spin coating facilitates control of membrane thickness; layer-by-layer self-assembly allows for functionalization; and doping enhances the mechanical strength and stability of the membrane by introducing other materials. For example, some studies have used vacuum filtration to deposit GO onto organic supports (such as polyethersulfone or polyamide) to form GO composite nanofiltration membranes for dye wastewater treatment or heavy metal ion removal. These membranes exhibit high water flux and anti-fouling properties, with some composite membranes achieving heavy metal ion rejection rates exceeding 90%. Furthermore, the combination of GO with inorganic materials has also been explored, such as combining GO with metal-organic frameworks (MOFs) or nanoparticles to enhance membrane durability and selectivity.

[0004] In order to further improve the mechanical stability and chemical tolerance of GO membranes, researchers began to combine GO with ceramic supports. Ceramic membranes (such as alumina, titanium oxide or zirconium oxide based membranes) have excellent thermal stability, mechanical strength and corrosion resistance, and are suitable for applications in high temperature, high pressure or acidic and alkaline environments. In the prior art, the preparation of GO-ceramic composite nanofiltration membranes usually involves surface modification, such as grafting the surface of the ceramic support with a silane coupling agent (such as γ-aminopropyltriethoxysilane) to improve the adhesion of GO. Subsequently, the GO dispersion is deposited on the modified ceramic by vacuum filtration or spin coating to form a composite membrane layer. This composite structure can utilize the porous support of the ceramic to provide a high-throughput channel, while achieving nanofiltration function with the help of the layered screening of GO. Relevant patents and literature reports show that such membranes show potential in oil-water separation, dye interception and seawater pretreatment. For example, some GO-ceramic hollow fiber membranes can achieve efficient separation of oil droplets with a flux of tens of L / m 2 ·h.

[0005] However, the existing GO-ceramic composite nanofiltration membrane still has several technical defects that restrict its industrial application. First, the interlayer spacing of the GO membrane is uneven, and it is easily expanded in aqueous solution due to the insertion of water molecules, resulting in the expansion of the interlayer channels and a significant decrease in the ion retention rate. For example, for small ions such as Na + The retention rate of SO₄⁻ is often less than 80%, making it difficult to meet the requirements of fine separation. Secondly, the interaction between GO nanosheets is weak, and the membrane is prone to shrinkage, delamination, or cracking during drying or recycling. This is especially true on ceramic supports. Drying-related shrinkage can lead to microstructural instability, compromising the long-term durability of the membrane. Literature reports indicate that the instability of GO membranes in the dry state is primarily due to the disruption of van der Waals forces and hydrogen bonds, resulting in membrane shedding or performance degradation. Furthermore, existing preparation methods are time-consuming and costly. For example, layer-by-layer self-assembly requires multiple cycles, spin coating methods are equipment-intensive, and the degree of GO oxidation and sheet size are difficult to precisely control, resulting in large batch-to-batch variability in membrane performance. While conventional polyamide- or polydopamine-based GO composite membranes achieve improved compactness through interfacial polymerization, they suffer from random functional group distribution, pH sensitivity, and the risk of secondary contamination, such as the release of polymerization residues. For specific applications, such as magnesium and lithium separation in salt lakes or the removal of heavy metal complex ions, existing mechanisms rely on high pressure or chemical additives, resulting in high energy consumption, low economic efficiency, and environmental impact.

[0006] In addition, although some GO modification strategies such as the introduction of metal cations or nanoparticles can regulate the interlayer spacing, they are mostly limited to organic supports and do not fully combine the durability advantages of ceramics. Existing anion and cation regulation of GO membranes can improve stability, but the preparation is complex and it is easy to introduce interface defects in the ceramic composite, affecting the overall separation efficiency. In the patent literature, some GO-ceramic membranes achieve defect-free ultra-thin films through sacrificial layers (such as graphene oxide interlayers) or chemical grafting, but still face the challenges of interlayer expansion and low retention rate. These defects not only reduce the separation accuracy and life of the membrane, but also limit its application in high-concentration salt solutions or complex wastewater. Therefore, there is an urgent need to develop a GO-ceramic composite nanofiltration membrane that can effectively regulate the GO interlayer spacing, enhance membrane stability and improve ion retention rate, so as to overcome the limitations of existing technologies and promote the advancement of membrane separation technology. Summary of the Invention

[0007] The present invention aims to overcome the defects of the prior art and provide a method for preparing a cation-modified graphene oxide ceramic composite nanofiltration membrane.

[0008] The technical solutions of the present invention are as follows:

[0009] A method for preparing a cationic modified graphene oxide ceramic composite nanofiltration membrane comprises the following steps:

[0010] (1) preparing a graphene oxide aqueous solution with a concentration of 2-4 mg / mL;

[0011] (2) soaking the porous ceramic membrane support in a sodium hydroxide solution to obtain an activated ceramic membrane support;

[0012] (3) immersing the activated ceramic membrane support obtained in step (2) in a 3-aminopropyldiethoxysilane ethanol solution and reacting at room temperature to obtain a grafted ceramic membrane support;

[0013] (4) diluting the graphene oxide aqueous solution obtained in step (1) at room temperature, and performing a cross-flow filtration reaction on the surface of the grafted ceramic membrane support obtained in step (3) for 4-6 minutes, with a cross-flow pressure of 0.2-0.4 MPa and a surface cross-flow rate of 0.2-0.4 m / s; after the reaction, rinsing with RO water to remove unreacted graphene oxide dispersion;

[0014] (5) Soaking the material obtained in step (4) in 0.2-0.3M magnesium chloride solution, potassium chloride solution or calcium chloride solution for 2-4 hours, then taking it out and washing it with RO water;

[0015] (6) The material obtained in step (5) is subjected to heat treatment to obtain the cationic modified graphene oxide ceramic composite nanofiltration membrane.

[0016] Graphene oxide membranes can provide ultrathin, high-throughput, and energy-efficient membranes for precise ion and molecular screening in aqueous solutions. This method utilizes the strong interaction between cations and the π bonds of graphene oxide. Different cations can be used to regulate the interlayer spacing of graphene oxide, increasing the interaction between the membrane layers. Using a cross-flow filtration method, graphene oxide sheets are orderly arranged on a grafted ceramic membrane support to prepare a stable GO-ceramic composite nanofiltration membrane. The cation-regulated graphene oxide structure effectively reduces interlayer spacing and increases membrane strength, achieving efficient ion retention.

[0017] In a preferred embodiment of the present invention, step (2) comprises: selecting a porous ceramic membrane support with a pore size of 95-105 nm and a length of 45-55 cm, ultrasonically treating it for 4-6 hours, soaking it in a 1.8-2.2 mol / L sodium hydroxide solution for 20-25 hours, drying it at 95-100°C for 8-12 hours, then rinsing it with ethanol and deionized water several times in sequence, drying it at 95-100°C for 10-14 hours, and then cooling it in the furnace to obtain an activated ceramic membrane support.

[0018] In a preferred embodiment of the present invention, step (3) comprises: immersing the activated ceramic membrane support obtained in step (2) in a 3-aminopropyldiethoxysilane ethanol solution with a concentration of 4-6 mmol / L, reacting at room temperature for 10-12 hours, then rinsing with ethanol and deionized water several times, drying at 145-150°C for 10-14 hours and then cooling with the furnace to obtain a grafted ceramic membrane support.

[0019] In a preferred embodiment of the present invention, step (4) comprises: diluting the graphene oxide aqueous solution obtained in step (1) at room temperature, and then performing a cross-flow filtration reaction on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, with a cross-flow pressure of 0.3 MPa and a surface cross-flow rate of 0.3 m / s; after the reaction, rinsing with RO water to remove unreacted graphene oxide dispersion.

[0020] Further preferably, the step (4) comprises: diluting the graphene oxide aqueous solution obtained in step (1) to 20-40 mg / L at room temperature.

[0021] In a preferred embodiment of the present invention, step (6) comprises: placing the material obtained in step (5) in a cool place to air-dry, heat-treating it at 80-120° C. for 2-4 hours, and then cooling it in the furnace to obtain the cationic modified graphene oxide ceramic composite nanofiltration membrane.

[0022] In a preferred embodiment of the present invention, the porous ceramic membrane support is made of alumina, titanium oxide or zirconium oxide.

[0023] More preferably, the porous ceramic membrane support is made of alumina.

[0024] The beneficial effects of the present invention are:

[0025] 1. The present invention prepares a cationic modified graphene oxide-ceramic composite nanofiltration membrane by grafting an organic silane coupling agent on the surface of a ceramic membrane support, depositing a graphene oxide film layer using cross-flow filtration, then regulating the interlayer spacing using the cation-π interaction formed by soaking in a cationic salt solution, and finally curing it through heat treatment.

[0026] 2. The present invention significantly improves the stability and anti-swelling properties of the membrane. Specific cationic modification enhances the interaction between GO sheets, avoiding performance degradation caused by the expansion of interlayer spacing in aqueous solution.

[0027] 3. The cationic modified graphene oxide ceramic composite nanofiltration membrane prepared by the present invention has excellent separation performance for sodium sulfate solution. At room temperature and 0.6 MPa pressure, the pure water flux of 0.2 wt% Na2SO4 solution reaches 33-46 L / m 2 h, the rejection rate is 97.4%-99.2%, which is better than that of the unmodified membrane (flux 21L / m 2 h, 70% rejection) increased the flux by 57%-119% and the rejection by about 38%-41%.

[0028] 4. The present invention is simple and efficient, uses cross-flow filtration to ensure orderly assembly of GO layers, and is suitable for industrial-scale production.

[0029] 5. The cationic modified graphene oxide ceramic composite nanofiltration membrane prepared by the present invention has strong durability, and the ceramic support provides mechanical and chemical stability. It is suitable for complex environments such as dye wastewater and heavy metal separation, and has good economic and environmental benefits. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0031] The method for preparing graphene oxide by the above-mentioned improved Hummers method in the following examples and comparative examples specifically includes:

[0032] (1) Wash and dry a 1000 mL beaker, add 3 g of flake graphite, and slowly add 360 mL of concentrated sulfuric acid (98% H2SO4) and 40 mL of concentrated phosphoric acid (95% H3PO4) under magnetic stirring. Then slowly add 18 g of potassium permanganate (KMnO4) in batches. Move the beaker to a 50°C oil bath and stir for 12 hours. Remove the beaker and allow it to cool naturally to room temperature. Slowly pour the reaction solution onto ice cubes in 400 mL of dilute hydrogen peroxide (containing 18 ml of 30% H2O2). The solution turns bright yellow.

[0033] (2) The solution obtained in step (1) is subjected to cross-flow filtration with a tubular ceramic membrane having a pore size of 0.05 μm to remove impurities, thereby obtaining a graphene oxide solution after impurities removal; the basic principle is to utilize the pore screening effect of the tubular ceramic membrane, that is, the filtration pore size of the tubular ceramic membrane is smaller than the size of the GO sheet, so that the GO sheet cannot flow out through the tubular ceramic membrane, but flows back to the feed liquid barrel with the circulation of the liquid in the pipeline, which neither blocks the membrane pores nor ensures the smoothness of the membrane pores, and also crushes and peels off the larger GO sheets; the filtration pore size of the tubular ceramic membrane is larger than the impurity ion size of the GO solution, so that H + , K + 、Mn 2+ Acid radicals and metal ions can easily pass through the pores of the ceramic tubular membrane and be discharged. This cycle is repeated to achieve the separation of GO and waste acid, K + , and Mn 2+ The separation of metal ions and the collection of GO solution complete the washing and impurity removal of GO;

[0034] (3) Diluting or concentrating according to the required concentration to obtain graphene oxide aqueous solutions of different concentrations.

[0035] Example 1

[0036] (1) Using the modified Hummers method described above, a graphene oxide aqueous solution with a concentration of 3 mg / mL was prepared;

[0037] (2) After cutting the alumina ceramic membrane tube with a length of about 50 cm and a pore size of 100 nm, ultrasonically treat it for 5 hours, soak it in 2 mol / L sodium hydroxide for 24 hours, dry it at 100°C for 10 hours, and then rinse it with ethanol and deionized water several times in sequence. After drying it in an oven at a temperature setting of 100°C for 12 hours, it was cooled in the oven to obtain an activated ceramic membrane support body;

[0038] (3) Soaking the activated ceramic membrane support obtained in step (2) in a 5 mmol / L 3-aminopropyldiethoxysilane ethanol solution, reacting for 12 h at room temperature, then rinsing with ethanol and deionized water several times, placing in an oven at a temperature setting of 150° C. and drying for 12 h, and then cooling in the oven to obtain a grafted ceramic membrane support;

[0039] (4) At room temperature, the grafted ceramic membrane support obtained in step (3) is positioned, the graphene oxide aqueous solution is diluted to 20 mg / L, and a cross-flow filtration reaction is performed on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, the cross-flow pressure is 0.3 MPa, and the surface cross-flow rate is 0.3 m / s; after the cross-flow filtration reaction is completed, RO water is used to rinse to remove the unreacted graphene oxide aqueous solution;

[0040] (5) The material obtained in step (4) was soaked in 0.25 M potassium chloride solution for 3 h, then taken out and washed with RO water.

[0041] (6) The material obtained in step (5) was placed in a cool place to air-dry and then placed in an 80° C. oven for heat treatment for 3 h, and then cooled in the oven to obtain a cationic modified graphene oxide ceramic composite nanofiltration membrane.

[0042] Membrane tube performance test: The cationic modified graphene oxide ceramic composite nanofiltration membrane prepared in this example was tested at room temperature and a pressure of 0.6 MPa. Its pure water flux was 33 LHM, and its rejection rate for 0.2 wt % sodium sulfate solution was 99.2%.

[0043] Example 2

[0044] (1) Using the modified Hummers method described above, a graphene oxide aqueous solution with a concentration of 3 mg / mL was prepared;

[0045] (2) After cutting the alumina ceramic membrane tube with a length of about 50 cm and a pore size of 100 nm, ultrasonically treat it for 5 hours, soak it in 2 mol / L sodium hydroxide for 24 hours, dry it at 100°C for 10 hours, and then rinse it with ethanol and deionized water several times in sequence. After drying it in an oven at a temperature setting of 100°C for 12 hours, it was cooled in the oven to obtain an activated ceramic membrane support body;

[0046] (3) Soaking the activated ceramic membrane support obtained in step (2) in a 5 mmol / L 3-aminopropyldiethoxysilane ethanol solution, reacting for 12 h at room temperature, then rinsing with ethanol and deionized water several times, placing in an oven at a temperature setting of 150° C. and drying for 12 h, and then cooling in the oven to obtain a grafted ceramic membrane support;

[0047] (4) At room temperature, the grafted ceramic membrane support obtained in step (3) is positioned, the graphene oxide aqueous solution is diluted to 20 mg / L, and a cross-flow filtration reaction is performed on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, the cross-flow pressure is 0.3 MPa, and the surface cross-flow rate is 0.3 m / s; after the cross-flow filtration reaction is completed, RO water is used to rinse to remove the unreacted graphene oxide aqueous solution;

[0048] (5) The material obtained in step (4) was soaked in 0.25M calcium chloride solution for 3 hours, then taken out and washed with RO water.

[0049] (6) The material obtained in step (5) was placed in a cool place to air-dry and then placed in an 80° C. oven for heat treatment for 3 h, and then cooled in the oven to obtain a cationic modified graphene oxide ceramic composite nanofiltration membrane.

[0050] Membrane tube performance test: The cationic modified graphene oxide ceramic composite nanofiltration membrane prepared in this example was tested at room temperature and a pressure of 0.6 MPa. Its pure water flux was 42 LHM, and its rejection rate for 0.2 wt % sodium sulfate solution was 98.1%.

[0051] Example 3

[0052] (1) Using the modified Hummers method described above, a graphene oxide aqueous solution with a concentration of 3 mg / mL was prepared;

[0053] (2) After cutting the alumina ceramic membrane tube with a length of about 50 cm and a pore size of 100 nm, ultrasonically treat it for 5 hours, soak it in 2 mol / L sodium hydroxide for 24 hours, dry it at 100°C for 10 hours, and then rinse it with ethanol and deionized water several times in sequence. After drying it in an oven at a temperature setting of 100°C for 12 hours, it was cooled in the oven to obtain an activated ceramic membrane support body;

[0054] (3) Soaking the activated ceramic membrane support obtained in step (2) in a 5 mmol / L 3-aminopropyldiethoxysilane ethanol solution, reacting for 12 h at room temperature, then rinsing with ethanol and deionized water several times, placing in an oven at a temperature setting of 150° C. and drying for 12 h, and then cooling in the oven to obtain a grafted ceramic membrane support;

[0055] (4) At room temperature, the grafted ceramic membrane support obtained in step (3) is positioned, the graphene oxide aqueous solution is diluted to 20 mg / L, and a cross-flow filtration reaction is performed on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, the cross-flow pressure is 0.3 MPa, and the surface cross-flow rate is 0.3 m / s; after the cross-flow filtration reaction is completed, RO water is used to rinse to remove the unreacted graphene oxide aqueous solution;

[0056] (5) The material obtained in step (4) was soaked in 0.25M magnesium chloride solution for 3 hours, then taken out and washed with RO water.

[0057] (6) The material obtained in step (5) was placed in a cool place to air-dry and then placed in an 80° C. oven for heat treatment for 3 h, and then cooled in the oven to obtain a cationic modified graphene oxide ceramic composite nanofiltration membrane.

[0058] Membrane tube performance test: The cationic modified graphene oxide ceramic composite nanofiltration membrane prepared in this example was tested at room temperature and a pressure of 0.6 MPa. Its pure water flux was 46 LHM, and its rejection rate for 0.2 wt % sodium sulfate solution was 97.4%.

[0059] Comparative Example 1

[0060] (1) Using the modified Hummers method described above, a graphene oxide aqueous solution with a concentration of 3 mg / mL was prepared;

[0061] (2) After cutting the alumina ceramic membrane tube with a length of about 50 cm and a pore size of 100 nm, ultrasonically treat it for 5 hours, soak it in 2 mol / L sodium hydroxide for 24 hours, dry it at 100°C for 10 hours, and then rinse it with ethanol and deionized water several times in sequence. After drying it in an oven at a temperature setting of 100°C for 12 hours, it was cooled in the oven to obtain an activated ceramic membrane support body;

[0062] (3) Soaking the activated ceramic membrane support obtained in step (2) in a 5 mmol / L 3-aminopropyldiethoxysilane ethanol solution, reacting for 12 h at room temperature, then rinsing with ethanol and deionized water several times, placing in an oven at a temperature setting of 150° C. and drying for 12 h, and then cooling in the oven to obtain a grafted ceramic membrane support;

[0063] (4) At room temperature, the grafted ceramic membrane support obtained in step (3) is positioned, the graphene oxide aqueous solution is diluted to 20 mg / L, and a cross-flow filtration reaction is performed on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, the cross-flow pressure is 0.3 MPa, and the surface cross-flow rate is 0.3 m / s; after the cross-flow filtration reaction is completed, RO water is used to rinse to remove the unreacted graphene oxide aqueous solution;

[0064] (5) The material obtained in step (4) was placed in a cool place for air drying and then placed in an oven at 80°C for heat treatment for 3 hours, and then cooled in the oven to obtain a comparison film.

[0065] Membrane tube performance test: The comparative membrane prepared in this comparative example was tested at room temperature and a pressure of 0.6 MPa. The pure water flux was 21 LHM, and the rejection rate of 0.2 wt% sodium sulfate solution was 70%.

[0066] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made within the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a cationic modified graphene oxide ceramic composite nanofiltration membrane, characterized in that: The steps include: (1) preparing a graphene oxide aqueous solution with a concentration of 2-4 mg / mL; (2) soaking the porous ceramic membrane support in a sodium hydroxide solution to obtain an activated ceramic membrane support; (3) immersing the activated ceramic membrane support obtained in step (2) in a 3-aminopropyldiethoxysilane ethanol solution and reacting at room temperature to obtain a grafted ceramic membrane support; (4) diluting the graphene oxide aqueous solution obtained in step (1) at room temperature, and performing a cross-flow filtration reaction on the surface of the grafted ceramic membrane support obtained in step (3) for 4-6 minutes, with a cross-flow pressure of 0.2-0.4 MPa and a surface cross-flow rate of 0.2-0.4 m / s; after the reaction, rinsing with RO water to remove unreacted graphene oxide dispersion; (5) Soak the material obtained in step (4) in 0.2-0.3M magnesium chloride solution, potassium chloride solution or calcium chloride solution for 2-4 hours, then take it out and wash it with RO water; (6) The material obtained in step (5) is subjected to heat treatment to obtain the cationic modified graphene oxide ceramic composite nanofiltration membrane.

2. The preparation method according to claim 1, wherein: The step (2) comprises: selecting a porous ceramic membrane support with a pore size of 95-105 nm and a length of 45-55 cm, ultrasonically treating it for 4-6 hours, soaking it in a 1.8-2.2 mol / L sodium hydroxide solution for 20-25 hours, drying it at 95-100° C. for 8-12 hours, then rinsing it with ethanol and deionized water several times in sequence, drying it at 95-100° C. for 10-14 hours, and then cooling it in the furnace to obtain an activated ceramic membrane support.

3. The preparation method according to claim 1, wherein: The step (3) comprises: immersing the activated ceramic membrane support obtained in the step (2) in a 3-aminopropyldiethoxysilane ethanol solution having a concentration of 4-6 mmol / L, reacting at room temperature for 10-12 hours, then rinsing with ethanol and deionized water several times, drying at 145-150° C. for 10-14 hours, and then cooling in the furnace to obtain a grafted ceramic membrane support.

4. The preparation method according to claim 1, wherein: The step (4) comprises: diluting the graphene oxide aqueous solution obtained in step (1) at room temperature, and then performing a cross-flow filtration reaction on the surface of the grafted ceramic membrane support obtained in step (3) for 5 minutes, with a cross-flow pressure of 0.3 MPa and a surface cross-flow rate of 0.3 m / s; and rinsing with RO water after the reaction to remove unreacted graphene oxide dispersion.

5. The preparation method according to claim 4, wherein: The step (4) comprises: diluting the graphene oxide aqueous solution obtained in the step (1) to 20-40 mg / L at room temperature.

6. The preparation method according to claim 1, wherein: The step (6) comprises: placing the material obtained in step (5) in a cool place for air drying, heat treating at 80-120° C. for 2-4 hours, and then cooling with the furnace to obtain the cationic modified graphene oxide ceramic composite nanofiltration membrane.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The porous ceramic membrane support is made of aluminum oxide, titanium oxide or zirconium oxide.

8. The preparation method according to claim 7, wherein: The porous ceramic membrane support is made of alumina.