A method for preparing super-hydrophobic ceramic membrane by pyrolysis and gasification of polytetrafluoroethylene film

Abstract

The present invention discloses a method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film, comprising the following steps: 1) pretreatment of the ceramic membrane element: treating the ceramic membrane element with a strong alkaline solution under ultrasonic conditions, then ultrasonically cleaning it with deionized water until it is neutral, and drying it; 2) heat treatment of the ceramic membrane element: wrapping the pretreated ceramic membrane with a polytetrafluoroethylene sheet, placing it in a high-temperature furnace, introducing a nitrogen source, heating it to 350-450°C at a rate of less than 10°C / min, holding it for 3-10 hours, and then cooling it naturally to obtain a super-hydrophobic ceramic membrane. The present invention transports the low surface energy substances vaporized and decomposed by the polytetrafluoroethylene film at high temperature to all levels of the modified ceramic membrane through a nitrogen source, thereby achieving the purpose of fully hydrophobizing the ceramic membrane. Not only is the super-hydrophobicity of the product high, but the hydrophobically modified ceramic membrane is also resistant to acid and alkali corrosion and high temperatures of 350°C, greatly expanding its scope of application.

Description

Technical Field

[0001] The present invention relates to a method for preparing a super-hydrophobic ceramic membrane, in particular to a method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film, and belongs to the field of ceramic membrane materials. Background Art

[0002] Ceramic membranes are widely used in food and medicine, biological fermentation, petrochemical industry, metallurgical water treatment and other industries due to their high strength, good chemical stability, high temperature resistance and high separation accuracy. However, their application is based on the fact that ceramic membranes are hydrophilic materials, so they are mostly used in water-soluble systems with water as the separation medium.

[0003] However, with the rapid development of industries such as petrochemicals and edible oils, the market has put forward a great demand for the hydrophobicity of ceramic membranes. Especially in the membrane distillation and membrane absorption processes that have developed rapidly in recent years, hydrophobic ceramic membranes have once again been brought to the forefront of membrane material development.

[0004] Currently, the preparation of hydrophobic ceramic membranes usually adopts ceramic membrane material modification, that is, on the basis of existing ceramic membrane materials, by chemically modifying or depositing the membrane surface, the hydrophilic surface of the ceramic membrane is converted into a hydrophobic surface, thereby facilitating the permeation of oil-soluble organic matter or gas, achieving the purpose of intercepting water and its soluble substances. Patent CN102423641B discloses a method for hydrophobic modification of ceramic membranes, its application, and apparatus. This is a typical method of using silane coupling agents to graft organic silicon materials onto ceramic membranes to achieve the purpose of modifying the hydrophobicity of the membrane surface. This method is simple, but the modified ceramic membrane has poor resistance to acid, alkali and oxidant corrosion, and its operating temperature is limited to below 200-250°C. Patent application CN114028948A discloses a highly stable hydrophobic ceramic membrane, its preparation method, and its application. This method uses vapor deposition to deposit a hydrophobic boron nitride film layer on the surface of the ceramic membrane. This film layer is resistant to acid, alkali and oxidants, and is resistant to high temperatures, which largely makes up for the shortcomings of coupling agent-modified membranes. However, this method has a relatively complex preparation process, involves high temperatures, has high processing costs, and only forms a hydrophobic layer on the membrane layer, which has limitations. Patent application CN112934012A discloses a method for modifying the surface of a polytetrafluoroethylene tubular ceramic membrane to be super-hydrophobic. This method uses a sol-gel method to coat a polytetrafluoroethylene film on the surface of the ceramic membrane, and then performs low-temperature sintering to make the ceramic membrane surface super-hydrophobic. Although this method reduces the sintering temperature, it has many modification steps, a complex process, and high costs, making it unfavorable for industrialization.

[0005] In order to solve the above problems, the present invention proposes a modification method of directly vaporizing and depositing a polytetrafluoroethylene film onto the entire pre-treated film body. Summary of the Invention

[0006] The present invention provides a method for preparing a super-hydrophobic ceramic membrane by utilizing pyrolysis and gasification of a polytetrafluoroethylene film. The method comprises the following steps: increasing the surface roughness of the ceramic membrane by ultrasonic treatment in a strong alkaline solution; utilizing low-surface-energy substances generated by pyrolysis and gasification of the polytetrafluoroethylene film; and then transporting the low-surface-energy substances along with nitrogen under a certain nitrogen pressure to penetrate into various layers of the ceramic membrane, thereby achieving the purpose of hydrophobic modification of the entire ceramic membrane. The present invention can modify the entire ceramic membrane, and the modified ceramic membrane is acid-, alkali-, and high-temperature resistant; the manufacturing process is simple, the operation is convenient, and the method is suitable for ceramic membranes of all shapes, thus being very suitable for industrial production.

[0007] The technical solutions adopted in the present invention are as follows:

[0008] A method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film comprises the following steps:

[0009] 1) Pretreatment of ceramic membrane elements: Treat the ceramic membrane elements with a strong alkaline solution under ultrasonic conditions, then ultrasonically clean them with deionized water until they are neutral, and dry them;

[0010] 2) Heat treatment of the ceramic membrane element: Wrap the pretreated ceramic membrane element with a polytetrafluoroethylene film, place it in a high-temperature furnace, introduce a nitrogen source, heat it to 350-450°C at a rate of less than 10°C / min, keep it at this temperature for 3-8 hours, and then cool it naturally to obtain a superhydrophobic ceramic membrane.

[0011] The above method is simple and easy to operate, has good repeatability and good modification effect.

[0012] The heating rate in the above step 2) should not exceed 10°C / min, otherwise problems such as insufficient gasification and pyrolysis of the polytetrafluoroethylene film and cracks in the ceramic membrane tube may occur.

[0013] To further improve hydrophobicity, in step 1), the ceramic membrane element is placed in a 5-15% sodium hydroxide or potassium hydroxide solution and ultrasonically treated for 30-120 minutes. This treatment removes dust and other organic matter from the surface and roughens the surface of the ceramic membrane to make it more hydrophobic.

[0014] The concentration of the above sodium hydroxide or potassium hydroxide cannot exceed 20%, otherwise it will affect the strength of the ceramic membrane.

[0015] In the above step 1), the drying temperature is 100-150° C. and the drying time is more than 4 hours.

[0016] The material used for the ceramic membrane element in the above step 1) is aluminum oxide, titanium oxide, zirconium oxide, silicon dioxide or silicon carbide.

[0017] In order to achieve the purpose of modifying the entire super-hydrophobic ceramic membrane, in step 2), the thickness of the polytetrafluoroethylene film is 0.03 to 0.1 mm.

[0018] In the above step 2), the amount of polytetrafluoroethylene film used is 5-25% of the mass of the ceramic membrane element.

[0019] In order to achieve the purpose of modifying the entire ceramic membrane, nitrogen must be introduced during the heat treatment process. In step 2), the flow rate of nitrogen is preferably such that the pressure in the high-temperature furnace is maintained at a positive pressure of more than 0.15 MPa.

[0020] In the above step 2), the heating rate of the high temperature furnace is below 6°C / min.

[0021] The technologies not mentioned in this invention are all referred to the prior art.

[0022] The present invention provides a method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film. Based on increasing the surface roughness of the ceramic membrane through ultrasonic treatment in a strong alkaline solution, the polytetrafluoroethylene film is gasified at high temperature to form a substance with low surface energy. This low surface energy substance is then infiltrated into all layers of the ceramic membrane through positive gas pressure transport, and then cooled and deposited, thereby achieving the purpose of systemic modification of the ceramic membrane. The hydrophobic ceramic membrane obtained by the present invention not only continues to exhibit the characteristics of high temperature, high pressure and corrosion resistance of the ceramic membrane, but also has a simple process and low cost, is applicable to ceramic membranes of all shapes, and is easy to industrialize. Compared with existing methods, it has the following advantages:

[0023] 1) Super hydrophobicity of ceramic membrane: Due to the deposition of low surface energy hydrophobic substances on the surface of the ceramic membrane, the water contact angle on the surface of the ceramic membrane reaches above 165°. What is even more gratifying is that not only the part of the ceramic membrane in contact with tetrafluoroethylene is hydrophobic, but the entire ceramic membrane is hydrophobic, which greatly enhances the hydrophobicity and lipophilicity of the ceramic membrane and greatly facilitates the use of the hydrophobic ceramic membrane.

[0024] 2) Maintaining the high strength, chemical stability, and temperature resistance of the ceramic membrane: The hydrophobic material deposited on the membrane surface is formed by the high-temperature vaporization and pyrolysis of the polytetrafluoroethylene film. This membrane combines the advantages of polytetrafluoroethylene—chemical corrosion resistance and high-temperature performance—with the high strength of the ceramic membrane itself, which gives it high-pressure resistance. These advantages greatly expand the range of applications for this type of ceramic membrane. Compared to existing ceramic membranes modified with silicone coupling agents, this membrane offers a significant performance improvement.

[0025] 3) Simple preparation method: This method does not involve complicated multiple grafting chemical reactions, nor does it require post-coating sintering on the ceramic membrane. It also does not interfere with the pore size of the ceramic membrane by soaking it in a polytetrafluoroethylene particle suspension. Instead, it simply utilizes the easy gasification and pyrolysis properties of the thin polytetrafluoroethylene film based on ultrasonic treatment with a strong alkaline solution, and uses nitrogen under a certain pressure to infiltrate the gasification and pyrolysis products into all layers of the ceramic membrane.

[0026] 4) This method is applicable to ceramic membranes of all shapes and pore sizes. Ultrasonic pretreatment with an alkali concentration of 5-15% provides roughness for the deposition of low surface energy substances. The 0.03-0.1 mm thick polytetrafluoroethylene film's easy pyrolysis and gasification properties produce a reliable source of low surface energy substances. A nitrogen source above 0.15 MPa becomes the driving force for the low surface energy substances to penetrate into all layers of the ceramic membrane. Therefore, whether it is a flat membrane or a tubular membrane, low surface energy substances will be evenly infiltrated from the support to the transition layer and then the membrane layer, thus ensuring that the entire ceramic membrane is hydrophobic and oleophilic. In addition, the good fluidity of the gas phase components under high temperature conditions makes this method suitable for ceramic membranes of all pore sizes, without the defect of uneven modification of the ceramic membrane due to the pore size being smaller than the polytetrafluoroethylene particles.

[0027] 5) Economical and environmentally friendly: As described in 3), this method does not use large amounts of organic solvents and silane coupling agents, especially expensive perfluorosilane coupling agents, and does not require sintering at high temperatures of 1000°C. Therefore, compared with both silane coupling agent modification methods and high-temperature sintering methods, this method has the lowest cost. Furthermore, since this method operates under positive pressure and in a closed environment, no harmful substances leak out, and alkali solution and the like can be recycled, which not only reduces manufacturing costs but also eliminates hazardous waste emissions, thus benefiting the environment. Furthermore, the method is wrapped with a polytetrafluoroethylene film, making it easy to operate, without dust pollution or material loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The microstructure characterization diagram of the ceramic membrane element before and after hydrophobic modification. In the figure, (a) is the surface of the membrane before modification, (b) is the surface of the membrane after modification, (c) is the cross-sectional view of the membrane after modification, and (d) is the support body after membrane modification;

[0029] Figure 2 The water contact angles of the ceramic membrane before and after hydrophobic modification; (1) is before modification, (2) is after modification;

[0030] Figure 3 The water contact angle of the hydrophobically modified ceramic membrane after being corroded by 5% sodium hydroxide and nitric acid at 80°C for 48 hours;

[0031] Figure 4 This is the water contact angle of the hydrophobically modified ceramic membrane after calcination at 350°C for 8 hours. DETAILED DESCRIPTION

[0032] For a better understanding of the present invention, the following examples further illustrate the present invention, but the present invention is not limited to the following examples. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the field (e.g., "Inorganic Membrane Separation Technology and Applications" by Xu Nanping et al., Chemical Industry Press, 2003) or the product instructions are used.

[0033] In each case, if the temperature is not specifically stated, the operation is carried out at room temperature (15-25°C); the temperature of ultrasonic treatment is 60°C; the ceramic membrane in each case is a tubular ceramic membrane;

[0034] Example 1

[0035] The method of preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film comprises the following steps:

[0036] Step 1) Pretreatment of the ceramic membrane element: The alumina ceramic membrane element was placed in a sodium hydroxide solution with a mass concentration of 15% and ultrasonically treated for 60 minutes; then ultrasonically cleaned with deionized water until neutral, and dried at 120° C. for 4 hours.

[0037] Step 2) Heat treatment of ceramic membrane elements: Wrap the pretreated ceramic membrane element with a 5%wt, 0.03mm thick polytetrafluoroethylene film, place it in a high-temperature furnace, introduce nitrogen, and start heating at a rate of 3°C / min. When the heat treatment temperature reaches 350°C, keep it warm for 7 hours, then turn off the heater and let the ceramic membrane cool naturally to room temperature in the furnace. The modification is complete, the ceramic membrane is intact, and there is no residue of polytetrafluoroethylene film. The structure and performance of the inside and outside of the ceramic membrane and the transition layer are uniform. Nitrogen needs to be introduced throughout the heat treatment process (including the natural cooling process). The flow rate of nitrogen is required to ensure that the pressure in the furnace is maintained at a positive pressure of 0.2MPa.

[0038] The microstructure SEM of the ceramic membrane element obtained from this embodiment is as follows: Figure 1 As shown by Figure 1 It can be seen that after modification (b), the ceramic membrane surface is significantly more heavily deposited with low-surface-energy particles than before modification (a). Furthermore, Figures c and d show that these low-surface-energy particles are deposited on both the cross-section of the ceramic membrane (c) and the support (d). This indicates that the entire ceramic membrane has been hydrophobicized.

[0039] like Figure 2As shown in the figure, the water contact angle of the ceramic membrane before modification is 42°, and the water contact angle of the ceramic membrane after modification is 165°. The water contact angles of the parts of the ceramic membrane in contact with and not in contact with the polytetrafluoroethylene film are uniform, and the water contact angles of the inside and outside of the ceramic membrane and the transition layer are uniform, all of which are 165°.

[0040] In order to verify the acid and alkali corrosion resistance and high temperature performance of this ceramic membrane, the following verification methods and results were adopted in the experiment:

[0041] Acid and alkali corrosion resistance test: The ceramic membrane element modified in Example 1 was first placed in a 5% NaOH solution at 80°C for 48 hours, ultrasonically cleaned to neutrality, and then dried at 120°C for 4 hours. Then, it was placed in a 5% nitric acid solution at 80°C for 48 hours, ultrasonically cleaned to neutrality, and then dried at 120°C for 4 hours. Then, samples were taken to test the water contact angle. The results are as follows: Figure 3 As shown, the water contact angle is 155°.

[0042] High temperature performance test: After the ceramic membrane element sample modified in Example 1 was kept at 100°C for 20 hours, the water contact angle was still above 160°. It was then placed in a high-temperature furnace at 350°C and isolated from oxygen for calcination for 3 hours. After cooling in the furnace, the ceramic membrane was sampled and its water contact angle was tested. The results are as follows: Figure 4 As shown, the water contact angle is 153°.

[0043] Example 2

[0044] The method of preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film comprises the following steps:

[0045] Step 1) Pretreatment of the ceramic membrane element: The alumina ceramic membrane element was placed in a potassium hydroxide solution with a mass concentration of 10% and ultrasonically treated for 60 minutes. The element was then ultrasonically cleaned with deionized water until neutral and dried at 150° C. for 4 hours.

[0046] Step 2) Heat treatment of ceramic membrane elements: Wrap the pretreated ceramic membrane element with a polytetrafluoroethylene film with a weight of 10% wt and a thickness of 0.03 mm, and place it in a high-temperature furnace. After nitrogen is introduced, the temperature begins to rise. The heating rate is 5°C / min. When the heat treatment temperature reaches 400°C, the insulation time is 5 hours. Then turn off the heater and let the ceramic membrane cool naturally to room temperature with the furnace to complete the modification. The ceramic membrane is intact, and there is no residue of the polytetrafluoroethylene film. The structure and performance of the inside and outside of the ceramic membrane and the transition layer are uniform. Nitrogen needs to be introduced continuously during the heat treatment process (including the natural cooling process), and the flow rate of nitrogen should be adjusted to ensure that the air pressure in the furnace is maintained at a positive pressure of 0.25MPa.

[0047] The water contact angle of the ceramic membrane before modification is 42°, and the water contact angle of the ceramic membrane after modification is 169.1°. The water contact angles of the parts of the ceramic membrane in contact with and not in contact with the polytetrafluoroethylene film are uniform. The water contact angles of the inside and outside of the ceramic membrane and the transition layer are uniform, all 169.1°.

[0048] The test methods for acid and alkali corrosion resistance and high temperature performance are as follows: referring to Example 1, the water contact angle after acid and alkali corrosion resistance is 158.3°, and the water contact angle after high temperature resistance test is 156.9°.

[0049] Comparative Example 1

[0050] To verify the pretreatment effect of alkaline solution under ultrasonic conditions, the inventors conducted an experimental study without pretreatment of the ceramic membrane. The results are as follows:

[0051] The ceramic membrane in step 1) of Example 1 was not subjected to any pretreatment, and the rest was referred to Example 1. The water contact angle of the ceramic membrane before modification was 42°, and the water contact angle of the ceramic membrane after modification was 132°.

[0052] It can be seen from Comparative Example 1 that the pretreatment effect of the alkaline solution under ultrasonic conditions is obvious and has the effect of promoting surface hydrophobicity.

[0053] Comparative Example 2

[0054] To further verify the pretreatment effect of alkali concentration, the inventors replaced the sodium hydroxide solution with a mass concentration of 15% during pretreatment in step 1) of Example 1 with a sodium hydroxide solution with a mass concentration of 3%. The rest were referred to Example 1. The water contact angle of the ceramic membrane before modification was 42°, and the water contact angle of the ceramic membrane after modification was 143°.

[0055] Comparative Example 3

[0056] To verify the effect of nitrogen gas on the complete modification of the ceramic membrane, the inventors omitted nitrogen gas during the heat treatment in step 2) of Example 1, following the same principles as in Example 1. The water contact angle of the ceramic membrane before modification was 42°, while that after modification was 55°, indicating virtually no hydrophobic modification. This may be due to the fact that the PTFE film was burned by the air in the furnace during the heat treatment, without producing low-surface-energy species.

[0057] Based on this, the inventors conducted the experiment of Comparative Example 4.

[0058] Comparative Example 4

[0059] The inventors did not introduce nitrogen during the heat treatment process in step 2) of Example 1, but isolated the ceramic membrane wrapped in the polytetrafluoroethylene film from air and heated it. The rest of the treatment was similar to that in Example 1. The water contact angle of the ceramic membrane before modification was 42°, while the water contact angle of the surface of the ceramic membrane in contact with the polytetrafluoroethylene film after modification was 162°. The water contact angle of the portion of the ceramic membrane not in contact with the polytetrafluoroethylene film, such as the membrane layer (internal pressure tubular ceramic membrane), remained almost unchanged at only 57°.

[0060] From the above comparative examples 4 and 5, it can be seen that the introduction of nitrogen during the heat treatment process is important for the hydrophobic modification of the ceramic membrane, and more importantly, it is important for the hydrophobic modification of the entire ceramic membrane.

[0061] Comparative Example 5

[0062] To further verify the importance of the nitrogen source pressure in this patent application, the inventors replaced the pressure of the nitrogen source during the heat treatment process in step 2) of Example 1 with 0.1 MPa, and the rest were referred to Example 1. The water contact angle of the ceramic membrane before modification was 42°, and the water contact angle of the surface in contact with the polytetrafluoroethylene film after modification was 163°, while the water contact angle of the part of the ceramic membrane that was not in contact with the polytetrafluoroethylene film, such as the membrane layer (internal pressure tubular ceramic membrane), was only 105°.

[0063] From this comparative example, it can be seen that the pressure of the nitrogen source in the patent of the present invention needs to be above 0.15 MPa to ensure that the entire ceramic membrane is hydrophobic.

[0064] Comparative Example 6

[0065] The tubular alumina ceramic membrane in Example 1 was treated as follows:

[0066] Step 1) The tubular alumina ceramic membrane was placed in an ultrasonic cleaner for 10 minutes and then dried in an oven at 50° C. for 12 hours;

[0067] Step 2) spreading polytetrafluoroethylene powder as evenly as possible on the surface of the tubular alumina ceramic membrane obtained in step 1);

[0068] Step 3) The sample obtained in Step 2) was placed in a high-temperature furnace and treated at 300°C for 12 hours under a nitrogen atmosphere. Because the PTFE powder was difficult to spread evenly across the outer surface of the tubular ceramic membrane, the water contact angle reached 152° only at the very bottom and top portions of the membrane where the PTFE powder was in contact. The hydrophilicity of the remaining areas, including the transition layer and particularly the inner surface of the tubular membrane, remained around 42°, demonstrating no improvement in hydrophobicity. Furthermore, some PTFE particles remained unvaporized.

[0069] From this, it can be seen that the ceramic membrane obtained by the scheme of first ultrasonicating, cleaning and drying, and then spreading polytetrafluoroethylene powder not only has a significantly lower contact angle of the hydrophobic part than that of the present invention, but also has poor modification uniformity and cannot penetrate into the transition layer, and is not suitable for the tubular ceramic membrane in this patent.

[0070] Comparative Example 7

[0071] To further verify the pyrolysis and vaporization properties of the PTFE film thickness described in this patent, the inventors used a 1mm thick PTFE film for hydrophobic modification of the ceramic membrane, replacing the 0.03mm thick PTFE film used in step 2) of Example 1. All other conditions were similar to those of Example 1. The water contact angle of the ceramic membrane before modification was 42°, while the water contact angle of the modified ceramic membrane was 163°. However, a solid PTFE sheet approximately 1-2mm thick adhered to the surface of the ceramic membrane in contact with the PTFE film, while the inner surface of the tubular membrane remained hydrophilic and exhibited almost no hydrophobicity. This suggests that the 1mm thick PTFE film is poorly pyrolyzed. When multiple layers are stacked and wrapped around the ceramic membrane for pyrolysis, the PTFE film melts into a liquid state on the ceramic membrane surface, while the multiple layers condense and wrap around the outer surface of the ceramic membrane. This hinders the transport of low-surface-energy materials from the pyrolysis to the inner surface of the ceramic membrane under the pressure of the nitrogen flow, preventing the inner surface of the ceramic membrane from being hydrophobically modified.

[0072] From this comparative example, we can see the importance of the thickness of the polytetrafluoroethylene film to the modification of the ceramic membrane.

Claims

1. A method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film, characterized in that: The following steps are involved: 1) Pretreatment of ceramic membrane elements: treat the ceramic membrane elements with a strong alkaline solution under ultrasonic conditions, then ultrasonically clean them with deionized water until they are neutral, and dry them; 2) Heat treatment of the ceramic membrane element: Wrap the pretreated ceramic membrane element with a polytetrafluoroethylene film, place it in a high-temperature furnace, introduce a nitrogen source, and heat it to 350-450°C at a rate of less than 10°C / min. Hold it for 3-8 hours, then cool it naturally to obtain a super-hydrophobic ceramic membrane. In step 1), the ceramic membrane element is placed in a sodium hydroxide or potassium hydroxide solution with a mass concentration of 5-15%, and ultrasonically treated for 30-120 minutes; In step 2), the flow rate of nitrogen is maintained at a positive pressure of more than 0.15 MPa by the pressure in the high-temperature furnace; In step 2), the thickness of the polytetrafluoroethylene film is 0.03-0.1 mm.

2. The method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film according to claim 1, wherein: In step 1), the drying temperature is 100-150°C and the drying time is more than 4 hours.

3. The method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film according to claim 1 or 2, characterized in that: The material used for the ceramic membrane element in step 1) is alumina, titanium oxide, zirconium oxide, silicon dioxide or silicon carbide.

4. The method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film according to claim 1 or 2, characterized in that: In step 2), the amount of polytetrafluoroethylene film used is 5-25% of the mass of the ceramic membrane element.

5. The method for preparing a super-hydrophobic ceramic membrane by pyrolysis and gasification of a polytetrafluoroethylene film according to claim 1 or 2, characterized in that: In step 2), the heating rate of the high temperature furnace is below 6°C / min.

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