High-flux asymmetric aluminum oxide ceramic membrane and preparation method and application thereof

Abstract

The present application relates to a kind of high flux asymmetric aluminum oxide ceramic membrane and its preparation method and application.The ceramic membrane has three-layer asymmetric structure: support layer, transition layer, separation layer.Alumina support layer is prepared by support layer slurry film casting, drying, calcination, and the support layer slurry includes alumina, binder, sintering aid and water.Alumina in the alumina support layer is large particle size, alumina in the transition layer is medium particle size, and alumina in the separation layer is nanoscale.The membrane has high flux, stable performance, small thickness, and the preparation process is simple, easy to industrialization.Compared with traditional dry pressing method, the ceramic membrane support layer prepared by film casting method shows significant improvement in flux.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic membranes, and relates to a high-flux asymmetric alumina ceramic membrane and a preparation method and application thereof. BACKGROUND

[0002] In recent years, membrane separation technology research has developed rapidly. Due to the advantages of high separation efficiency, easy operation, no pollution, low energy consumption and the like, the technology has great potential in separation and has been applied to the separation research of various systems. Different from traditional ceramic membranes, an asymmetric ceramic membrane is generally composed of three layers of powders with different particle sizes, that is, a support layer with large particle size provides mechanical strength, a transition layer with medium particle size prevents the leakage of particles in the separation layer, and the separation layer is generally composed of nano-sized powders and mainly plays a role in separation and screening. Due to the thin thickness of the separation layer, the asymmetric ceramic membrane generally has a very high flux and has a wide application prospect in oil-water separation and industrial wastewater treatment. However, the support layer of the existing flat asymmetric alumina-based ceramic membrane is generally prepared by dry pressing. This method has a high requirement for equipment and may significantly affect the flux of the membrane. In addition, the dry pressing method is limited by the mold, resulting in that the shape and area of the membrane are generally fixed and it is difficult to realize large-scale production and the preparation of special-shaped membranes. During the scale-up of traditional alumina ceramic membrane materials, problems such as membrane material fracture, membrane layer peeling and uneven thickness often occur. Therefore, it is particularly important to explore a more flexible preparation method to improve the performance and adaptability of the membrane. SUMMARY

[0003] In view of the defects and deficiencies of the prior art, the purpose of the present application is to provide a high-flux asymmetric alumina ceramic membrane which has high flux, stable performance, thin thickness and simple preparation process and is easy to industrialize.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0005] An alumina ceramic membrane comprises an alumina support layer, an alumina transition layer and an alumina separation layer arranged in sequence; the alumina support layer is prepared by casting a support layer slurry, drying and calcining, the support layer slurry comprises alumina, a binder, a sintering aid and water; the sintering aid is selected from a combination of one or more of kaolin, fumed silica, titanium dioxide, zirconium oxide and yttrium oxide; the particle size of the alumina in the alumina support layer, the alumina in the alumina transition layer and the alumina in the alumina separation layer decreases in sequence.

[0006] In some embodiments, the sintering aid is a mixture of kaolin and fumed silica; preferably, the mass ratio of kaolin to fumed silica in the mixture is 1:8-1:10.

[0007] In some embodiments, the particle size of alumina in the alumina support layer is in the range of 4-20 pm; preferably 5-10 pm.

[0008] In some embodiments, the particle size of alumina in the alumina transition layer is in the range of 1-3 pm, preferably 1-2 pm.

[0009] In some embodiments, the particle size of alumina in the alumina separation layer is in the range of 200-800 nm, preferably 400-600 nm.

[0010] In some embodiments, the alumina support layer is a flat plate-shaped a- AI2O3 porous ceramic support layer.

[0011] In some embodiments, the thickness of the alumina support layer is in the range of 0.5-2 mm.

[0012] In some embodiments, the thickness of the alumina transition layer is in the range of 5-25 pm.

[0013] In some embodiments, the thickness of the alumina separation layer is in the range of 15-25 pm.

[0014] In some embodiments, the support layer slurry comprises 100-120 parts of alumina, 2-2.5 parts of a binder, 8-10 parts of a sintering aid, and 75-90 parts of water.

[0015] In some embodiments, the binder is selected from the group consisting of one or a combination of hydroxymethyl cellulose, polyvinyl alcohol.

[0016] In some embodiments, the support layer slurry further comprises a dispersant, a leveling agent, a plasticizer, an antifoaming agent.

[0017] In some embodiments, the support layer slurry comprises 100-120 parts of alumina, 2-2.5 parts of a dispersant, 2-2.5 parts of a binder, 1-1.25 parts of a leveling agent, 4-5 parts of a plasticizer, 2-2.5 parts of an antifoaming agent, 8-10 parts of a sintering aid, and 75-90 parts of water, by weight.

[0018] In some embodiments, the dispersant is selected from the group consisting of one or more combinations of cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, and octadecyl trimethyl ammonium chloride.

[0019] In some embodiments, the leveling agent is selected from the group consisting of one or a combination of polydimethylsiloxane, polyacrylic acid.

[0020] In some embodiments, the plasticizer is selected from the group consisting of one or a combination of polyethylene glycol, dibutyl phthalate.

[0021] In some embodiments, the defoaming agent is one or a combination of the two of tributyl phosphate, isopropyl alcohol.

[0022] The present application also provides a preparation method of the aforementioned alumina ceramic membrane, comprising the following steps: 1) casting, drying and calcining the support layer slurry to obtain the alumina support layer; 2) dipping the transition layer modification liquid on the alumina support layer, and drying and calcining to obtain the alumina transition layer, wherein the transition layer modification liquid comprises alumina and water; 3) dipping the separation layer modification liquid on the alumina transition layer, and drying and calcining to obtain the alumina ceramic membrane, wherein the separation layer modification liquid comprises alumina and water. The present application uses the casting method to prepare the high-flux alumina ceramic membrane support layer, and uses the dip-coating method to prepare the asymmetric alumina ceramic membrane transition layer and separation layer.

[0023] In some embodiments, the casting is performed in a polytetrafluoroethylene mold; preferably, the polytetrafluoroethylene mold is coated with a release agent paraffin oil. The polytetrafluoroethylene mold can be of any size and any shape, and thus the shape of the alumina ceramic membrane of the present application is not limited.

[0024] In some embodiments, in step 1), the drying temperature is 30-40℃.

[0025] In some embodiments, in step 1), the drying time is 8-12h.

[0026] In some embodiments, in step 1), the calcining temperature is 1200-1600℃. By controlling the final sintering temperature, the performance of the membrane material can be adjusted. Alumina will undergo thermal shrinkage during cooling, and thus the higher the calcining temperature, the tighter the particle packing, and the mechanical strength increases, and the porosity and gas flux decrease accordingly.

[0027] In some embodiments, in step 1), the calcining time is 1-3h.

[0028] In some embodiments, the transition layer modification liquid further comprises a dispersant, a leveling agent and a pH adjuster.

[0029] In some embodiments, the transition layer modification liquid comprises 50-60 parts by weight of alumina, 1-1.2 parts by weight of a dispersant, 6-10 parts by weight of a leveling agent, 10-12 parts by weight of a pH adjuster and 500-600 parts by weight of water.

[0030] In some embodiments, the pH adjusting agent is selected from one or both of nitric acid and hydrochloric acid. The pH adjusting agent can change the amount of charge on the surface of the particles. After the pH adjusting agent is added, the alumina groups in the modification liquid simultaneously carry the same charge, enhancing the charge repulsion and reducing the possibility of agglomeration. This characteristic reduces the viscosity of the overall modification liquid and slows the settling speed, so that the modification liquid can be stored for a long time and reused.

[0031] The dispersant and the leveling agent in the transition layer modification liquid can be conventional types, such as the aforementioned types in the support layer slurry.

[0032] In some embodiments, the separation layer modification liquid further comprises a dispersant, a leveling agent, and a pH adjusting agent.

[0033] In some embodiments, the separation layer modification liquid comprises, by weight, 50-60 parts of alumina, 1-1.2 parts of a dispersant, 6-10 parts of a leveling agent, 12-14 parts of a pH adjusting agent, and 400-500 parts of water.

[0034] In some embodiments, the pH adjusting agent is selected from one or both of nitric acid and hydrochloric acid.

[0035] The dispersant and the leveling agent in the separation layer modification liquid can be conventional types, such as the aforementioned types in the support layer slurry.

[0036] In some embodiments, the preparation method further comprises, before the film casting, the steps of mechanically stirring the support layer slurry and allowing the slurry to stand for defoaming.

[0037] In some embodiments, in steps 1), 2), and 3), the calcination is all performed using programmed temperature increase, and the rate of the temperature increase is 8-12℃ / min.

[0038] In some embodiments, in step 2), the two alumina support layers are stacked on each other, and the gap between them is sealed before the impregnation.

[0039] The present application also provides the use of the aforementioned alumina ceramic membrane for oil-water separation or industrial wastewater treatment.

[0040] Thanks to the above technical solutions, the present application has the following advantages compared with the prior art:

[0041] The application realizes excellent balance between membrane material flux and separation capacity by adopting a three-layer asymmetric support structure. The three-layer structure is clearly visible in the scanning electron microscope image. Since the bottom support layer is prepared by the casting method, and the thickness of the bottom support layer is significantly reduced compared with traditional materials, this design ensures the high flux characteristics of the membrane material; the transition layer effectively prevents the leakage of the top layer, ensuring the overall stability of the membrane; the separation layer maintains an intact and smooth surface, greatly improving the separation effect, thereby enhancing the application performance of the membrane material.

[0042] The application innovatively adopts the casting method, forms bridging adhesion between aluminum oxide particles by using a sintering aid such as fumed silica, thereby enhancing the mechanical strength of the overall membrane material, and successfully prevents the undesirable phenomena such as membrane layer cracking and bending that easily occur during the shaping of the ceramic membrane slurry into a support layer. This method not only improves the structural integrity of the membrane, but also optimizes its physical properties, and also improves the separation performance of the final overall aluminum oxide ceramic membrane. Compared with the traditional dry pressing method, the ceramic membrane support layer prepared by the casting method of the application shows a significant improvement in flux.

[0043] The high-flux asymmetric aluminum oxide ceramic membrane of the application can be prepared into a heterogeneous membrane material by wire cutting or laser cutting. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 Surface electron microscope image of 400 nm particle size aluminum oxide;

[0045] Figure 2 Surface electron microscope image of 1 μm particle size aluminum oxide;

[0046] Figure 3 Surface electron microscope image of 10 μm particle size aluminum oxide;

[0047] Figure 4 Cross-sectional scanning electron microscope image of the three-layer asymmetric aluminum oxide ceramic membrane prepared by the support layer particle size of 10 μm aluminum oxide powder, the transition layer particle size of 1 μm aluminum oxide powder, and the separation layer particle size of 400 nm aluminum oxide powder of Example 1;

[0048] Figure 5 Flat plate-shaped aluminum oxide ceramic membrane and cut heterogeneous membrane finally obtained by Example 1;

[0049] Figure 6 Disc-shaped aluminum oxide ceramic membrane finally obtained by Comparative Example 1;

[0050] Figure 7 N2 flux comparison chart of the aluminum oxide ceramic membranes of Example 1, 2 and Comparative Example 1;

[0051] Figure 8The pure water flux comparison chart of the alumina ceramic membrane of examples 1, 2 and comparative example 1;

[0052] Figure 9 The surface electron microscope chart of comparative example 2;

[0053] Figure 10 The surface electron microscope chart of comparative example 3. DETAILED DESCRIPTION

[0054] When the support layer is prepared by the traditional dry pressing method, the membrane flux is not large enough, and the dry pressing method is limited by the mold, so that the shape and area of the membrane are generally fixed, and it is difficult to realize large-scale production and preparation of special-shaped membranes. The casting method is rarely used for the preparation of ceramic materials, and is usually used for the preparation of polymer polymer membranes. However, the casting method may cause cracking, bending and other problems during the preparation process. The application adds a sintering aid to bridge and bond the alumina particles, effectively avoiding the cracking phenomenon and increasing the mechanical strength of the ceramic membrane material.

[0055] The application innovatively uses the casting method to prepare the support layer of the high-flux alumina ceramic membrane. In order to improve the permeation flux of the membrane material, alumina powder with a large particle size is selected as the alumina of the support layer, and the thickness of the alumina ceramic membrane is greatly reduced. During the casting process of the support layer, considering the difference between the particle size of the separation layer and the support layer, a transition layer is prepared by using alumina powder with a medium particle size. The introduction of this layer effectively prevents the downward penetration of the alumina particles of the top separation layer. While ensuring high flux of the membrane material, in order to improve the separation performance, alumina powder with a particle size of nanometer is used to prepare the separation layer, forming a structure with close packing and small pore size.

[0056] The application provides a new idea for the scale-up preparation of asymmetric alumina ceramic membranes. The traditional alumina ceramic membrane material is easily limited by the size of the mold and experimental equipment during the scale-up process, and problems such as membrane material fracture, membrane layer peeling and uneven thickness often occur. The alumina ceramic membrane prepared by the application has high flux, stable performance and simple membrane preparation process, and the membrane preparation time is significantly shortened, which has significant advantages and is beneficial to industrial application and large-scale production.

[0057] In addition, the application also innovatively first prepares an alumina plate by the casting method, and then forms a transition layer and a separation layer by the dip-coating method. The final membrane material can be in the form of a flat plate, which is convenient for further processing, such as being prepared into diversified special-shaped membrane materials by laser cutting and other technologies, to meet the needs of different industrial applications.

[0058] The application first prepares a large alumina support layer substrate by the casting method, and then successfully grows a three-layer asymmetric ceramic membrane by the twice dip-coating method. This method significantly improves the flux of the membrane material compared with the traditional solid particle sintering method.

[0059] This invention involves stacking two alumina plates during the dip-coating of the alumina support layer and using PTFE tape to seal the gaps between them, effectively preventing the back side from contacting the alumina modification solution. This design ensures that the transition and separation layers grow only on the front side of the support layer, avoiding back-side growth. By precisely controlling the dip-coating process, the structural integrity and functional properties of the membrane are guaranteed, further enhancing the membrane material's adaptability to various applications. This method not only simplifies the production process but also improves membrane production efficiency, giving it broader application potential in industrial fields.

[0060] The present invention will be further described in detail below through specific embodiments. However, those skilled in the art should understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Specific techniques and conditions not specified in the embodiments should be based on the techniques or conditions described in the literature in the art. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0061] Example 1

[0062] This embodiment provides a method for preparing a three-layer asymmetric alumina film, the preparation method of which is as follows:

[0063] Take 120g of alumina powder with a particle size of 10μm ( Figure 3 Add 90ml of deionized water and stir for 2 minutes. During stirring, add the following ingredients sequentially: dispersant 2.4g hexadecyltrimethylammonium chloride, binder 2.4g hydroxymethyl cellulose, leveling agent 1.2g polyacrylic acid, plasticizer 4.8g polyethylene glycol, defoamer 2.4g isopropanol, sintering aid 8.64g kaolin, and fumed silica 0.96g. Then, transfer the casting solution to a high-speed mixer, set the speed to 8000rpm, stir at high speed for 5 hours, and sonicate for 30 minutes to eliminate foam. Let it stand for 2 hours. Next, apply the release agent paraffin oil evenly to the adjusted temperature control plate, setting the temperature of the temperature control plate to 30℃. Use a polytetrafluoroethylene flat frame for casting, with a PET plastic film underneath, and dry for 12 hours. Subsequently, place the cast film in a muffle furnace, set the calcination temperature to 1400℃, the calcination time to 3 hours, and both the heating and cooling rates to 10℃ / min. A support layer (a single-layer symmetrical ceramic film) with a thickness of 1 mm was obtained.

[0064] Take 56.8 g of alumina powder with a particle size of 1 μm, add 600 ml of deionized water, and stir for 5 min. During stirring, add dispersant cetyltrimethylammonium chloride 1.12 g, nitric acid 10.46 g, and leveling agent polyacrylic acid 6.67 g in sequence, and ultrasonic treatment for 30 min to remove foam, to prepare 1 μm alumina modification liquid (transition layer modification liquid). The prepared alumina support layer is subjected to dip coating for 30 s using a pulling instrument, and dip coating is performed twice. After dip coating, dry at room temperature for 12 h, set the calcination temperature to 1200 °C, and calcine at high temperature for 3 h, with the heating rate and cooling rate both set to 10 °C / min, to prepare a double-layer asymmetric alumina ceramic membrane. The transition layer has a thickness of 10 μm.

[0065] Take 51.12 g of alumina powder with a particle size of 400 nm Figure 1 ), add 500 ml of deionized water, and stir for 5 min. During stirring, add dispersant cetyltrimethylammonium chloride 1.12 g, nitric acid 12.5 g, and leveling agent polyacrylic acid 6.67 g in sequence, and ultrasonic treatment for 30 min to remove foam, to prepare 400 nm alumina modification liquid (separation layer modification liquid). The prepared double-layer asymmetric alumina ceramic membrane is subjected to dip coating for 30 s using a pulling instrument, and dip coating is performed twice. After dip coating, dry at room temperature for 12 h, set the calcination temperature to 1200 °C, and calcine at high temperature for 3 h, with the heating rate and cooling rate both set to 10 °C / min, to obtain a three-layer asymmetric alumina ceramic membrane, which is in the form of a flat plate. The separation layer has a thickness of 18 μm.

[0066] Example 2

[0067] This example provides a method for preparing a three-layer asymmetric alumina membrane, which is prepared as follows:

[0068] Take 120 g of alumina powder with a particle size of 5 μm, add 90 ml of deionized water, and stir for 2 min. During stirring, add dispersant cetyltrimethylammonium chloride 2.4 g, binder hydroxymethyl cellulose 2.4 g, leveling agent polyacrylic acid 1.2 g, plasticizer polyethylene glycol 4.8 g, defoaming agent isopropyl alcohol 2.4 g, sintering aid kaolin 8.64 g, and fumed silica 0.96 g in sequence. Then, transfer the casting solution into a high-speed beater, set the speed to 8000 rpm, and stir for 5 hours. Perform ultrasonic treatment for 30 min to eliminate foam, and stand for 2 hours. Next, evenly apply release agent paraffin oil on the temperature-controlled plate that has been adjusted to a horizontal position, and set the temperature of the temperature-controlled plate to 30℃. Use a polytetrafluoroethylene flat frame for the casting instrument, and place a PET plastic film under the flat frame. Dry for 12 hours. Then, place the cast film in a muffle furnace, set the sintering temperature to 1400℃, and sinter for 3 hours. Set the heating rate and the cooling rate to 10℃ / min. A support layer (single-layer symmetric ceramic membrane) with a thickness of 1 mm is obtained.

[0069] Take 56.8 g of alumina powder with a particle size of 1 μm, add 600 ml of deionized water, and stir for 5 min. During stirring, add dispersant cetyltrimethylammonium chloride 1.12 g, nitric acid 10.46 g, and leveling agent polyacrylic acid 6.67 g in sequence. Perform ultrasonic treatment for 30 min to remove foam, and prepare a 1 μm alumina modification solution (transition layer modification solution). Use a puller to perform dip coating on the prepared alumina support layer for 30 seconds, and perform dip coating twice. After dip coating, dry at room temperature for 12 hours, set the sintering temperature to 1200℃, and sinter at high temperature for 3 hours. Set the heating rate and the cooling rate to 10℃ / min. A double-layer asymmetric alumina ceramic membrane is obtained. The thickness of the transition layer is 10 μm.

[0070] Take 51.12 g of alumina powder with a particle size of 400 nm, add 500 ml of deionized water, and stir for 5 min. During stirring, add dispersant cetyltrimethylammonium chloride 1.12 g, nitric acid 12.5 g, and leveling agent polyacrylic acid 6.67 g in sequence. Perform ultrasonic treatment for 30 min to remove foam, and prepare a 400 nm alumina modification solution (separation layer modification solution). Use a puller to perform dip coating on the previously prepared double-layer asymmetric alumina ceramic membrane for 30 seconds, and perform dip coating twice. After dip coating, dry at room temperature for 12 hours, set the sintering temperature to 1200℃, and sinter at high temperature for 3 hours. Set the heating rate and the cooling rate to 10℃ / min. A three-layer asymmetric alumina ceramic membrane is obtained, which is in the form of a flat plate. The thickness of the separation layer is 18 μm.

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing a three-layer asymmetric alumina membrane, which is prepared as follows:

[0073] 120g of alumina powder with a particle size of 10 μm was selected, 8.64g of kaolin and 0.96g of fumed silica were added as sintering aids, and 7.2g of hydroxymethyl cellulose was added as a binder. The alumina solid powder was made into a disc-shaped alumina with a diameter of 22mm and a thickness of 2mm by a hydraulic machine. Subsequently, the alumina support layer was prepared after calcination at a high temperature of 1200℃ for 4 hours.

[0074] The transition layer and the separation layer were prepared on the alumina support layer by dip-coating in the same way as in Example 1, and finally a three-layer asymmetric disc-shaped alumina ceramic membrane was obtained.

[0075] The flux test device was used to test the flux of the above examples and comparative examples, and the results showed that the N2 flux of Example 1 was 350000 GPU, the N2 flux of Example 2 was 160000 GPU, and the N2 flux of Comparative Example 1 was only 120000 GPU. The pure water flux test results are shown in Figure 8 It can be seen that the pure water flux of the alumina ceramic membranes of Examples 1 and 2 is higher than that of Comparative Example 1. This shows that the membrane material prepared by the casting method has been significantly improved in terms of flux. The 5 μm powder used in Example 2 as the support layer base material has a slightly smaller flux than the 10 μm powder in Example 1, because the pore size of the 5 μm powder is smaller, and the gas channel is limited to a certain extent, but it is still significantly higher than that of Comparative Example 1.

[0076] Figure 5 The shape of the membrane material of the flat plate-shaped alumina ceramic membrane finally obtained in Example 1 and the cut-off shaped membrane can be freely controlled. Figure 6 The shape of the membrane material of the disc-shaped alumina ceramic membrane finally obtained in Comparative Example 1 is fixedly controlled by the size of the mold. Figure 7 The N2 flux comparison chart of the alumina ceramic membranes of each example and comparative example is shown in Figure 2, and the flux of the support layer, two layers and three layers in the preparation process was also tested. It can be seen that with the growth of the transition layer and the separation layer, the flux of the membrane material gradually decreases, because the particle gap in the transition layer and the separation layer becomes smaller and smaller, the gas / liquid channel is reduced, and the transition layer and the separation layer also have a certain thickness, which slows down the time of gas / liquid passing through the membrane material.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing a two-layer asymmetric alumina membrane, and the preparation method is basically the same as that of Example 1, except that the transition layer is not prepared, and the separation layer is directly prepared on the support layer. The result is that the particles of the separation layer are too small to directly penetrate into the support layer, i.e. the pore penetration phenomenon occurs, at which time an effective asymmetric structure cannot be generated, and the SEM image is shown in Figure 9 .

[0079] Comparative Example 3

[0080] This comparative example provides a preparation method of a three-layer asymmetric aluminum oxide film, which is basically the same as that of Example 1, except that no kaolin and fumed silica are added in the casting solution (support layer slurry) when preparing the support layer. The result is that the film material is broken during high-temperature sintering, as shown in Figure 10 .

[0081] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. An aluminum oxide ceramic membrane, characterized by: The alumina ceramic membrane comprises an alumina support layer, an alumina transition layer and an alumina separation layer arranged in sequence; the alumina support layer is prepared by casting, drying and calcining a support layer slurry, the support layer slurry comprises alumina, a binder, a sintering aid and water; the sintering aid is a mixture of kaolin and fumed silica; in the mixture, the mass ratio of kaolin to fumed silica is 1:8-1:10; the particle size of alumina in the alumina support layer, the alumina transition layer and the alumina separation layer decreases in sequence; The particle size of alumina in the alumina separation layer is 400-600 nm; The thickness of the alumina support layer is 0.5-2 mm; the thickness of the alumina transition layer is 5-25 μm; The thickness of the alumina separation layer is 15-25 μm; According to weight parts, the support layer slurry comprises 100-120 parts of alumina, 2-2.5 parts of a dispersant, 2-2.5 parts of a binder, 1-1.25 parts of a leveling agent, 4-5 parts of a plasticizer, 2-2.5 parts of an antifoaming agent, 8-10 parts of a sintering aid and 75-90 parts of water; According to weight parts, the raw materials of the alumina transition layer comprise 50-60 parts of alumina, 1-1.2 parts of a dispersant, 6-10 parts of a leveling agent, 10-12 parts of a pH regulator and 500-600 parts of water; The alumina support layer, the alumina transition layer and the alumina separation layer are all calcined during preparation.

2. The aluminum oxide ceramic membrane according to claim 1, characterized in that: The particle size of alumina in the alumina support layer is 4-20 μm; the particle size of alumina in the alumina transition layer is 1-3 μm; and / or, the alumina support layer is a flat α-Al2O3 porous ceramic support layer.

3. The aluminum oxide ceramic membrane of claim 1, wherein: The binder is selected from the group consisting of one or a combination of hydroxymethyl cellulose and polyvinyl alcohol; and / or, the support layer slurry further comprises a dispersant, a leveling agent, a plasticizer and an antifoaming agent.

4. The aluminum oxide ceramic membrane according to claim 3, characterized in that: The dispersant is selected from one or a combination of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride and octadecyltrimethylammonium chloride; and / or, the leveling agent is selected from one or a combination of polydimethylsiloxane and polyacrylic acid; and / or, the plasticizer is selected from one or a combination of polyethylene glycol and dibutyl phthalate; and / or, the antifoaming agent is one or a combination of tributyl phosphate and isopropyl alcohol.

5. A method for producing the alumina ceramic membrane according to any one of claims 1 to 4, characterized by: The preparation method comprises the following steps: 1) casting, drying and calcining the support layer slurry to prepare the alumina support layer; 2) immersing a transition layer modification liquid on the alumina support layer, and drying and calcining to obtain the alumina transition layer, wherein the transition layer modification liquid comprises alumina and water; 3) immersing a separation layer modification liquid on the alumina transition layer, and drying and calcining to obtain the alumina ceramic membrane, wherein the separation layer modification liquid comprises alumina and water.

6. The method for producing an alumina ceramic membrane according to claim 5, characterized by: The film is cast in a polytetrafluoroethylene mold; and / or, in step 1), the drying temperature is 30-40℃; and / or, in step 1), the drying time is 8-12h; and / or, in step 1), the calcination temperature is 1200-1600℃; and / or, in step 1), the calcination time is 1-3h.

7. The method of claim 5, wherein: The pH regulator is selected from one or both of nitric acid and hydrochloric acid.

8. The method of claim 5, wherein: The separation layer modifying solution further comprises a dispersant, a leveling agent and a pH regulator; the separation layer modifying solution comprises, by weight, 50-60 parts of alumina, 1-1.2 parts of a dispersant, 6-10 parts of a leveling agent, 12-14 parts of a pH regulator and 400-500 parts of water; and / or, the pH regulator is selected from one or both of nitric acid and hydrochloric acid.

9. The method of claim 5, wherein: The preparation method further comprises, before the film casting, a step of mechanically stirring and standing the support layer slurry to remove bubbles; and / or, in steps 1), 2) and 3), the calcination is performed by programmed temperature increase, and the temperature increase rate is 8-12℃ / min; and / or, in step 2), two alumina support layers are stacked on each other, and the gap therebetween is sealed before impregnation.

10. Use of the alumina ceramic membrane according to any one of claims 1-4 for oil-water separation or industrial wastewater treatment.

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