A Highly Stable Ceramic-Based Subnanoporous Graphene Composite Membrane and Its Precision Separation Application

Abstract

A highly stable ceramic-based sub-nanoporous graphene composite membrane and its precision separation applications are disclosed, belonging to the field of environmental membrane separation technology. This composite membrane introduces an inorganic transition layer on the outer surface of an inorganic ceramic substrate with sheet-like, hollow fiber, or tubular configurations, increasing its bonding strength with the graphene separation layer. The thickness and pore structure of the composite membrane are precisely controlled by changing the filtration time, filtrate concentration, crosslinking agent content, and high-temperature reduction temperature and time. Through optimization of the preparation conditions, a highly stable ceramic-based sub-nanoporous graphene composite membrane was obtained. This composite membrane can achieve efficient and precise separation applications through pervaporation processes, such as seawater desalination, high-salinity wastewater desalination, boron removal from seawater and geothermal wastewater, and other wastewater (such as antibiotic wastewater and low-concentration volatile organic pollutant wastewater), exhibiting excellent separation performance and stability in extreme environments.

Description

Technical Field

[0001] This invention relates to a highly stable ceramic-based sub-nanoporous graphene composite membrane and its precision separation applications, belonging to the field of environmental membrane separation technology. Background Technology

[0002] With the growth of the Earth's population and industry, the demand for water resources is increasing. Seawater contains a vast amount of water, accounting for 97.3% of the Earth's total water resources; therefore, seawater desalination and boron removal are important research areas now and in the future. Meanwhile, geothermal energy is used for various purposes, such as power plants, heating, greenhouses, and other industrial and domestic applications. However, the unrestricted discharge of waste geothermal water into the environment leads to pollution of surface water and groundwater with various pollutants such as salt and boron, impacting existing freshwater resources. Conventional seawater desalination and boron removal technologies mainly include reverse osmosis (RO), nanofiltration (NF), forward osmosis (FO), membrane distillation (MD), multistage flash evaporation (MFS), and electrodialysis (ED). Conventional RO, forward osmosis, and nanofiltration technologies have low boron retention rates (approximately 40%) under neutral conditions, requiring increased alkalinity to achieve higher retention rates. Multistage flash evaporation and electrodialysis suffer from high operating costs, complex equipment, and susceptibility to corrosion.

[0003] Pervaporation (PV) is a technology suitable for seawater desalination and high-salinity water treatment, offering excellent retention and theoretically achieving 100% separation efficiency. However, current research has focused less on PV for boron removal in water. Existing membrane materials suffer from low flux, poor chemical and mechanical stability, and susceptibility to fouling. Furthermore, the membrane structure is prone to degradation during long-term operation under high salinity and extreme conditions. Therefore, it is necessary to develop a stable, high-performance PV membrane material suitable for boron removal in seawater desalination and for treating pollutants in water.

[0004] Graphene oxide is an inorganic two-dimensional nanosheet containing various functional groups that can combine with other materials. However, cross-linked membranes face key challenges: balancing membrane permeability and selectivity, and improving membrane stability. Graphene oxide nanosheets can be reduced to graphene using a high-temperature inert gas atmosphere, resulting in more stable graphene. Currently, graphene nanosheets stacked into membranes can be used in water treatment, with sub-nanopore graphene membranes exhibiting high permeability and selectivity. However, the poor bonding between graphene membranes and ceramic supports, along with the relatively large membrane thickness, leads to a decrease in separation performance. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a highly stable ceramic-based sub-nanoporous graphene composite membrane and its precision separation applications. This composite membrane is cross-linked with graphene oxide using cross-linking agents (such as chitosan, polyacrylic acid, and polyvinyl alcohol), thereby controlling the interlayer spacing of the graphene oxide nanosheets. Furthermore, a low-roughness inorganic transition layer is introduced on the surface of the ceramic carrier, increasing the bonding force between the support layer and the reduced graphene oxide. Finally, an ultrathin, stable sub-nanoporous graphene composite membrane is obtained through high-temperature carbonization and reduction. It can be used for seawater desalination, boron removal, high-salinity water treatment, geothermal wastewater treatment, and other water treatment processes via pervaporation. It achieves high separation performance (high rejection rate, high throughput) and long-term stability (mechanical and chemical stability).

[0006] Furthermore, membrane materials with different structures can be designed according to the characteristics of pollutants in water treatment applications, and their application can be extended to the treatment of other polluted water bodies, such as wastewater containing antibiotics or low concentrations of volatile organic pollutants.

[0007] The technical solution of the present invention:

[0008] A zirconia ceramic support was modified with a γ-alumina interlayer, and then a ceramic-based sub-nanoporous graphene composite membrane was prepared by vacuum filtration and high-temperature reduction. The steps are as follows:

[0009] (1) Preparation of γ-alumina interlayer

[0010] (1.1) Immerse the zirconia ceramic support with a pore size of 100-200 nm in an ethanol solution for 30 min, take it out and rinse it with a large amount of deionized water, and finally put it in a 60℃ oven for 12 h to dry it thoroughly.

[0011] (1.2) Preparation of γ-alumina intermediate layer on zirconia hollow fiber ceramic: First, aluminum isopropoxide sol was prepared, and a uniform γ-alumina intermediate layer was coated by impregnation-coating process; the impregnation time was 5-10s, and the coating speed was controlled at 1.0cm / s. The successfully impregnated carrier was placed in a constant temperature and humidity drying oven for more than 24 hours, and then the carrier was placed in an air high temperature furnace at 750℃ for sintering to obtain a γ-alumina intermediate layer with a thickness of about 5.0 µm.

[0012] (2) Preparation of ceramic-based sub-nanoporous graphene composite membranes

[0013] (2.1) Preparation of graphene oxide suspension: 20 mg of graphene oxide powder was added to 100 mL of deionized water, and then the graphene powder was peeled off by an ultrasonic instrument for 2-3 h to obtain a graphene oxide nanosheet dispersion. The dispersion was then centrifuged at 10000 rpm for 30 minutes, and the unpeeled graphene oxide powder in the lower layer was removed to obtain a completely dispersed graphene oxide suspension.

[0014] (2.2) Preparation of graphene oxide-crosslinking agent suspension: A crosslinking agent solution with a mass fraction of 0.4 wt.% was prepared. The graphene oxide suspension was mixed with the 0.4 wt.% crosslinking agent solution at a volume ratio of 1:2, and the mixture was magnetically stirred for at least 16 h to ensure the crosslinking agent was fully dissolved and reacted with the graphene oxide nanosheets, ultimately obtaining a graphene oxide-crosslinking agent suspension for the preparation of sub-nanoporous graphene composite membranes.

[0015] (2.3) Preparation of ceramic-based sub-nanoporous graphene composite membranes

[0016] In this study, vacuum filtration and inert atmosphere reduction methods were used for preparation. The graphene oxide-crosslinking agent suspension was vacuum filtered for 10-60 min using a vacuum device, resulting in a stacked continuous film layer on the carrier surface. Subsequently, it was thoroughly dried in a 60℃ oven for 12 h, then removed and placed in a tube furnace. Argon gas was introduced at a flow rate of 20-40 mL / min, and the temperature was increased to 900℃ at a rate of 1-5℃ / min. After high-temperature carbonization and reduction for 3 h, the functional groups in the graphene oxide and crosslinking agent structure reacted fully, yielding a ceramic-based sub-nanoporous graphene composite film with a thickness between 20-80 nm.

[0017] (3) Application of ceramic-based sub-nanoporous graphene composite membranes in seawater desalination and boron removal

[0018] The prepared composite membrane was fixed on a pervaporation unit. The feed solution (32000 ppm NaCl, 5 ppm B solution) was kept at a temperature of 20-70°C. Liquid nitrogen or ice water was used to condense the vaporized water vapor at the condenser. The water flux of the composite membrane pervaporation ranged from 10-300 L∙m⁻¹. -2 ∙h -1 It has a salt rejection rate of over 99.9% and a boron rejection rate of over 99%. It can effectively retain boron in different pH environments, has good acid and alkali resistance, and its water flux and rejection rate can remain stable over a long period of time.

[0019] (4) Application of ceramic-based sub-nanoporous graphene composite membranes in high-salinity extreme environment treatment

[0020] The prepared composite membrane was fixed on a pervaporation unit. The feed solution was high-salt wastewater with a NaCl concentration of 100 g / L and a temperature of 20-70 °C. Water vapor was condensed in liquid nitrogen or ice water. The composite membrane maintained stable performance during long-term separation, achieving a salt rejection rate of over 99.9%. Membrane fouling was minimal, allowing for zero discharge of high-salt water through pervaporation. Furthermore, the composite membrane operated stably even under extreme conditions (acidic pH < 4 or alkaline pH > 9 or sodium hypochlorite concentration of 50-1000 mg / L), with no significant damage to the separation layer before and after operation. The ceramic-based sub-nanoporous graphene composite membrane exhibited excellent chemical stability.

[0021] (5) Application of ceramic-based sub-nanoporous graphene composite membrane in geothermal wastewater treatment

[0022] The prepared composite membrane was fixed onto a pervaporation unit. The feed liquid was geothermal wastewater containing pollutants, with a temperature of 20-70℃. Liquid nitrogen or ice water was added to the condenser to condense the water vapor from the vaporization process. The membrane flux during the composite membrane pervaporation process ranged from 10-300 L∙m⁻¹. -2 ∙h -1 The system retains over 99% of sodium (Na), calcium (Ca), magnesium (Mg), and boron (B) elements in the water, maintaining stable flux and retention rates throughout long-term operation. Furthermore, the thermal energy contained in the actual geothermal water can serve as a driving force for the pervaporation process, reducing geothermal water treatment costs.

[0023] (6) Application of ceramic-based sub-nanoporous graphene composite membrane in antibiotic wastewater treatment

[0024] The prepared composite membrane was fixed onto a pervaporation unit. The feed liquid was wastewater containing antibiotics, and the temperature was 20-70 °C. Liquid nitrogen or ice water was used to condense and vaporize the water vapor at the condenser. The composite membrane exhibited effective treatment performance for antibiotics of different properties. At an antibiotic concentration of 50 ppm, the water flux of the composite membrane pervaporation at different temperatures could be maintained at 15-90 L∙m⁻¹. -2 ∙h -1 Antibiotics in water can be completely removed, and reducing antibiotic concentration or increasing temperature can increase the pervaporation flux. Stable ceramic-based sub-nanoporous graphene composite membranes have demonstrated excellent performance in treating polluted wastewater.

[0025] (7) Application of ceramic-based sub-nanoporous graphene composite membranes in the treatment of wastewater with low concentrations of volatile organic pollutants

[0026] The prepared composite membrane was fixed on a pervaporation device assembly. The feed liquid was wastewater containing antibiotics, and the temperature was 20-70 °C. The condenser was placed in liquid nitrogen or ice water for condensation and vaporization of water vapor. The test temperature was 30 °C. Gas chromatography was used to detect the composition of the feed liquid on the feed side and the permeate side. This study is the first to investigate the separation of low-concentration volatile organic pollutants in water using graphene membranes.

[0027] The beneficial effects of this invention are:

[0028] This composite membrane introduces a low-roughness, fine-porous inorganic transition layer on the surface of a ceramic carrier, increasing the bonding force between the support layer and the reduced graphene oxide. The pore thickness structure of the composite membrane can be precisely controlled by varying the filtration time, filtrate concentration, crosslinking agent content, and high-temperature reduction temperature and time. Through optimization of the preparation conditions, a highly stable ceramic-based sub-nanoporous graphene composite membrane was successfully prepared.

[0029] 1. A highly stable ceramic-based sub-nanoporous graphene composite membrane structure was prepared by increasing the bonding force between the ceramic and graphene separation layers through an inorganic transition layer. Its thickness ranges from 10 to 500 nm, possessing highly efficient water molecule transport channels, and can be used in pervaporation processes for seawater deboron removal, geothermal wastewater treatment, and antibiotic wastewater treatment. Using zirconia ceramic as a carrier, the sub-nanoporous graphene composite membrane exhibits advantages such as acid, alkali, and chlorine resistance, and can operate stably in high-salt wastewater or extreme environments. The high stability of the composite membrane ensures its ability to treat extreme wastewater conditions.

[0030] 2. The ultrathin and stable composite membrane prepared by this method achieves high performance (high flux, high retention, high stability, and low pollution) in challenging seawater desalination and boron removal processes. It can achieve highly efficient boron retention under neutral and acidic conditions, saving the cost of adjusting solution pH to increase boron retention compared to reverse osmosis, forward osmosis, and nanofiltration processes. This provides promising industrial applications for large-scale seawater desalination and boron removal using pervaporation methods for drinking water resources. Simultaneously, its high stability at high temperatures and high boron retention and flux allow it to be used to treat geothermal wastewater (high-temperature, high-boron wastewater). The geothermal heat itself can serve as the driving force for the composite membrane pervaporation process, reducing the treatment cost of geothermal wastewater and mitigating current pollution of freshwater resources.

[0031] 3. The composite membrane prepared in this invention, used for boron removal technology, offers advantages over other membrane technologies, including high flux, high retention, and high stability. The composite membrane pervaporation technology achieves a water flux of 10-60 L∙m⁻¹ at room temperature (30°C). -2 ∙h -1 Between these parameters, the composite membrane surpasses most pervaporation membranes and membrane distillation membranes, thus allowing the invention to be extended to other water treatment fields, such as the separation and purification of pharmaceutical wastewater, antibiotic-containing wastewater, and wastewater with low concentrations of volatile organic pollutants. Attached Figure Description

[0032] Figure 1 This is a low-magnification scanning electron microscope image of the cross-section of the γ-alumina intermediate layer in Example 1.

[0033] Figure 2 This is a photograph of the highly stable ceramic-based sub-nanoporous graphene composite membrane from Example 2.

[0034] Figure 3 This is a scanning electron microscope image of the surface of the highly stable ceramic-based sub-nanoporous graphene composite film in Example 2.

[0035] Figure 4 This is a scanning electron microscope (SEM) image of the cross-section of the highly stable ceramic-based sub-nanoporous graphene composite membrane in Example 2.

[0036] Figure 5 This refers to the boron removal performance of the composite membrane pervaporation method for seawater desalination in Example 3.

[0037] Figure 6 The composite membrane pervaporation method for treating geothermal wastewater pollutants in Example 4 is shown.

[0038] Figure 7 The composite membrane pervaporation method for treating antibiotic wastewater pollutants in Example 5 is shown. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0040] Example 1: Preparation of γ-alumina transition layer on zirconia ceramic support

[0041] (1) Cleaning of the zirconia support: Seal both ends of the support with polytetrafluoroethylene tape to prevent impurities from entering the membrane pores. Then soak it in ethanol solution for 30 min. After taking it out, rinse it with a large amount of deionized water. Finally, put it in a 60 ℃ oven for 12 h to dry it thoroughly to obtain a cleaned support.

[0042] (2) Preparation of the γ-alumina interlayer on the zirconia ceramic support: A layer of aluminum isopropoxide sol was coated onto the zirconia ceramic using the dip-coating method to obtain the γ-alumina interlayer. First, 150 mL of deionized water was poured into a flask and heated to 90 °C. Then, 0.2 mol of aluminum isopropoxide was added in multiple portions. After reflux and stirring for 150 min, 15 mL of dilute nitric acid solution was added, and reflux was continued for 24 h. PVA solution was then added, and after reflux for 2 h, the mixture was cooled at room temperature to obtain the aluminum isopropoxide sol. The zirconia support obtained in the first step was dipped and coated in the sol for 5-10 s, with the coating speed controlled at 1.0 cm / s. The successfully dipped support was placed in a constant temperature and humidity drying oven for more than 24 h, and then sintered in an air furnace at 750 °C to obtain a γ-alumina interlayer with a thickness of approximately 5.0 µm. Scanning electron microscopy images of the γ-alumina cross-section are shown below. Figure 1 The bottom of the image shows a zirconia ceramic support, and the top shows a γ-alumina intermediate layer with a thickness of approximately 5.0 µm.

[0043] Example 2: Preparation of highly stable ceramic-based sub-nanoporous graphene composite membranes

[0044] (1) Preparation of graphene oxide suspension: 20 mg of graphene oxide powder was added to 100 mL of deionized water, and the graphene powder was exfoliated by ultrasonication for 3 h to obtain a graphene oxide nanosheet dispersion. The dispersion was centrifuged at 10000 rpm for 30 minutes, and the lower precipitate was removed to obtain a completely dispersed graphene oxide suspension.

[0045] (2) Preparation of graphene oxide-crosslinking agent suspension: Chitosan was selected as the crosslinking agent, and a chitosan solution with a mass fraction of 0.4 wt.% was prepared. The prepared graphene oxide suspension was mixed with the 0.4 wt.% chitosan solution at a certain volume ratio and stirred for more than 16 h to obtain the graphene oxide-chitosan suspension. The volume ratio of graphene oxide suspension to chitosan solution was 1:2.

[0046] (3) Preparation of highly stable ceramic-based sub-nanoporous graphene composite membrane: The membrane was prepared by vacuum filtration and inert atmosphere reduction. A zirconia support with a γ-alumina interlayer was connected to a filtration device and placed in a graphene oxide-chitosan suspension for 20 min to form a stacked continuous membrane layer on the support surface. The membrane was then dried in a 60℃ oven for 12 h. The dried composite membrane was placed in a tube furnace and high-purity argon gas at a flow rate of 30 mL / min was introduced. The temperature was increased to 900℃ at a rate of 5℃ / min. After high-temperature carbonization and reduction for 3 h, the highly stable ceramic-based sub-nanoporous graphene composite membrane was obtained. Figure 2 This is a photograph of the prepared composite membrane. Figure 3The image shows a scanning electron microscope (SEM) image of the surface of a composite membrane obtained by filtering a graphene oxide suspension and a chitosan solution at a volume ratio of 1:2 for 20 min and then carbonizing at 900 °C for 3 h. Figure 4 The cross-sectional scanning electron microscope image shows that the composite membrane surface is intact, without pinhole defects or obvious cracks; the cross-sectional results show that there is a distinct separation membrane layer above the γ-alumina intermediate layer, with a thickness of about 50 nm. The membrane layer is continuous and defect-free, proving that the composite membrane was successfully prepared.

[0047] Example 3: Application of composite membrane pervaporation method in seawater deboration and boron removal

[0048] The test used a reduced graphene oxide-chitosan ceramic-based composite membrane obtained from Example 2, with a volume ratio of graphene oxide suspension to chitosan solution of 1:2, filtered for 20 min, and carbonized at 900 °C for 3 h. Simulated seawater consisted of 32,000 ppm NaCl and 5 ppm B. The composite membrane was fixed on a pervaporation device assembly, and the test temperature was 30 °C. Water vapor was condensed and vaporized in liquid nitrogen or ice water. Figure 5 An 80-hour simulated desalination and boron removal test was conducted, demonstrating the stable desalination and boron removal capabilities of the composite membrane in simulated seawater. The membrane flux remained stable at 35 L∙m⁻¹. -2 ∙h -1 The membrane exhibits a salt rejection rate exceeding 99.9% and a boron rejection rate exceeding 99%, with low element concentrations detected by osmosis, resulting in high-quality effluent that meets drinking water standards. Therefore, this composite membrane demonstrates excellent application capability for boron removal in seawater desalination.

[0049] Example 4: Application of composite membrane pervaporation method for treating geothermal wastewater pollutants

[0050] The test used a reduced graphene oxide-chitosan ceramic-based composite membrane obtained in Example 2, with a volume ratio of graphene oxide suspension to chitosan solution of 1:2, filtered for 20 min, and carbonized at 900 °C for 3 h. The composite membrane was fixed on a pervaporation device assembly, and the test temperature was 30 °C. The simulated geothermal wastewater contained K... + Ca 2+ Na + Mg 2+ The composite membrane was composed of solutions with B concentrations of 380 ppm, 30 ppm, 3780 ppm, 10 ppm, and 60 ppm. The retention performance of the composite membrane was averaged by analyzing the changes in element concentrations before and after retention. Figure 6The results showed that all elements in the geothermal wastewater were removed after pervaporation treatment using the composite membrane. The element concentration in the treated water was below 0.2 ppm, and the water flux of the composite membrane was stable, thus achieving effective treatment of geothermal wastewater. Furthermore, the high temperature of geothermal water accelerates the transport of water molecules during pervaporation, increasing water flux and wastewater treatment capacity.

[0051] Example 5: Application of Composite Membrane Pervaporation Method for Treating Antibiotic Wastewater Pollutants

[0052] Unlike the saline wastewater mentioned above, antibiotic-contaminated wastewater contains complex pollutants, making it prone to membrane fouling during traditional membrane treatment. The reduced graphene oxide-chitosan ceramic-based composite membrane obtained in Example 2, with a volume ratio of graphene oxide suspension to chitosan solution of 1:2, filtered for 20 minutes, and carbonized at 900 °C for 3 hours, also showed promising application prospects for treating antibiotic-contaminated wastewater. Figure 7 To test the water flux of the composite membrane permeate evaporation at different temperatures, a tetracycline concentration of 50 ppm was used. The results showed that the water flux could reach 15-90 L∙m⁻¹ within the temperature range of 20-60 °C. -2 ∙h -1 The antibiotic rejection rate reached over 99%, meaning it could be completely removed.

[0053] Example 6: Application of composite membrane pervaporation method for treating wastewater with low concentration of volatile organic pollutants

[0054] A reduced graphene oxide-chitosan ceramic-based composite membrane was obtained by using the graphene oxide suspension and chitosan solution in Example 2 at a volume ratio of 1:2, filtration for 20 min, and high-temperature carbonization at 900℃ for 3 h. A saturated aqueous solution of methyl tert-butyl ether was used in the experiment, and the test temperature was 30℃. Gas chromatography was employed to detect the composition of the feed solution on both the raw material and permeate sides. This study is the first to investigate the application of sub-nanoporous graphene membranes for the separation of methyl tert-butyl ether in water.

Claims

1. A method for preparing a highly stable ceramic-based sub-nanoporous graphene composite membrane, characterized in that: This composite membrane uses ceramic as a carrier, with a low-roughness, fine-porous inorganic transition layer introduced on the carrier surface, followed by a complete sub-nanoporous graphene separation layer. The thickness of the sub-nanoporous graphene separation layer is between 10-500 nm, and the pure water flux of the pervaporation process is 10-300 L∙m⁻¹ at 20-70 °C. -2 ∙h -1 ; The composite membrane preparation steps are as follows: (1) Preparation of inorganic transition layer on ceramic carrier: Inorganic transition layer is prepared on ceramic carrier by impregnation-pulling and high temperature sintering method; firstly, an inorganic transition layer sol with a concentration of 0.01%~0.5wt.% is prepared, and the ceramic carrier is impregnated and pulled in the inorganic transition layer sol. The impregnation time is 5-10 s, and the pulling speed is controlled at 0.5-1.5 cm / s; the successfully impregnated carrier is dried and sintered at high temperature to obtain an inorganic transition layer with a thickness of 1.0~10.0μm; (2) Preparation of graphene oxide suspension: Add graphene oxide powder to deionized water, and use an ultrasonic device to peel off the graphene powder for 2-3 hours to obtain a graphene oxide nanosheet dispersion. Centrifuge to remove the lower precipitate to obtain a completely dispersed graphene oxide suspension; the ratio of graphene oxide powder to deionized water is 5-50 mg: 100 mL. (3) Preparation of graphene oxide-crosslinking agent suspension: Prepare a crosslinking agent solution with a mass fraction of 0.1 ~ 1.0 wt.%; mix the graphene oxide suspension with the crosslinking agent solution and stir for more than 16 h to obtain graphene oxide-crosslinking agent suspension; the volume ratio of the graphene oxide suspension to the crosslinking agent solution is (1-10):(10-1). (4) Preparation of sub-nanoporous graphene composite membrane: The membrane was prepared by vacuum filtration and gas atmosphere reduction. A ceramic support with an inorganic transition layer was connected to the filtration device and placed in a graphene oxide-crosslinking agent suspension for 10-60 min to form a stacked continuous membrane layer on the surface of the support. The membrane was then dried in an oven at 40-100 ℃ for 6-12 h. The dried composite membrane was placed in a tube furnace and a gas with a flow rate of 10-100 mL / min was introduced. The temperature was increased to 300-1000 ℃ at a rate of 1-5 ℃ / min. After high-temperature carbonization and reduction for 0.5-10 h, a highly stable ceramic-based sub-nanoporous graphene composite membrane was obtained. The inorganic transition layer is γ-Al2O3, silicon oxide, zinc oxide, zirconium oxide, or titanium oxide; The crosslinking agent is chitosan, polyacrylic acid, polyvinyl alcohol, thiourea, m-phenylenediamine, ethylenediamine, acrylate, dopamine hydrochloride, or polyethyleneimine.

2. The preparation method according to claim 1, characterized in that: The ceramic carrier is a sheet or tubular material such as zirconium oxide, aluminum oxide, titanium oxide, silicon oxide, spinel, mullite, or copper oxide. The gas atmosphere is hydrogen, nitrogen, methane, argon, and ethylene.

3. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: This composite membrane is used for seawater desalination during the pervaporation process.

4. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: This composite membrane is used for zero discharge of high-salinity water in the pervaporation process, with a concentration of 70-300 g / L.

5. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: The composite membrane exhibits high stability under extreme environments, including acidic environments with pH < 4, alkaline environments with pH > 9, or sodium hypochlorite concentrations of 50-1000 mg / L.

6. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: This composite membrane is used to remove boron from water during pervaporation.

7. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: This composite membrane is used to remove antibiotic contaminants from water during pervaporation.

8. The application of the ceramic-based sub-nanoporous graphene composite membrane according to claim 7, characterized in that: The antibiotic contaminants are tetracycline, chloramphenicol, oxytetracycline, or levofloxacin.

9. The application of the ceramic-based sub-nanoporous graphene composite membrane obtained by the preparation method according to claim 1, characterized in that: This composite membrane is used in the pervaporation process for wastewater containing low concentrations of volatile organic pollutants.

10. The application of the ceramic-based sub-nanoporous graphene composite membrane according to claim 9, characterized in that: The low-concentration volatile organic pollutants are acetone, benzene, trichloroethane, ethyl acetate, n-butanol, and methyl tert-butyl ether.

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