A ceramic membrane and its preparation method

Abstract

This invention discloses a ceramic membrane comprising a metal oxide particle stacked ceramic membrane body, with shellac adhering to the surface of the metal oxide particles. Using water-resistant, oil-resistant, and corrosion-resistant shellac as a raw material, this invention combines the shellac with the surface of the metal oxide particles via a hydrothermal method, solving the problem of poor oil-water separation and oil removal rate in blank membranes in vinegar-water mixtures, and is also environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of ceramic membrane preparation technology, and specifically relates to a method for preparing shellac-modified ceramic membranes. Background Technology

[0002] Ceramic membranes are a type of inorganic membrane. Due to their advantages such as high mechanical strength, resistance to high temperature and organic solvents, long life and large processing capacity, they are widely used in wastewater treatment, coal tar purification, oil-water separation, food processing and pharmaceutical manufacturing, metal smelting and textile dyeing industries. However, there is relatively little research on the oil-water separation of volatile oils from traditional Chinese medicine.

[0003] Shellac is a dried resin secreted by lac insects (lac insects, family Colleidae). It possesses properties such as clearing heat, cooling the blood, and detoxifying. It is a natural amphiphilic polymer material. Shellac is tough, has a good luster, is resistant to ultraviolet light and high-voltage electric arcs, and is resistant to oil and acids. It is soluble in alcohols and alkalis and is non-toxic and non-irritating to humans. Currently, it is widely used in defense, medicine, electrical, coatings, rubber, plastics, papermaking, printing, and food industries.

[0004] Volatile oils are an important material basis for the efficacy of traditional Chinese medicine (TCM). Currently, the extraction of volatile oils from TCM is generally carried out using steam distillation. In the laboratory, volatile oil extractors are commonly used. This method has high extraction efficiency and can directly collect the volatile oil, but the throughput is small and not suitable for large-scale production. Large-scale production commonly uses multi-functional extraction tanks. However, due to significant differences in heating methods and condensation and separation devices compared to the laboratory, in practical applications, a portion of the volatile oil and a large amount of oil-water mixture are usually collected. Traditional methods for treating oil-water mixtures in TCM involve extraction with organic solvents such as ethyl acetate, but this method has drawbacks such as organic solvent residue.

[0005] Membrane separation technology is widely used in pharmaceuticals, food, and water treatment, but its application in the separation and enrichment of volatile oils from traditional Chinese medicine is still relatively limited, especially the application of ceramic membranes in this field. This invention addresses the problem of low volatile oil yield in large-scale production. Using a large quantity of oil-water mixtures of traditional Chinese medicine collected in large-scale production as the research object, it employs membrane separation to replace methods such as ethyl acetate chemical extraction for enriching volatile oils.

[0006] Currently, membrane materials and membrane preparation technologies used in the extraction, separation, and enrichment of volatile oils from traditional Chinese medicine are diverse. Compared to polymer membranes, which are prone to pollution, hydrophilic ceramic membranes have advantages such as high efficiency in obtaining target products and regenerability in the separation and purification of volatile oil emulsions from traditional Chinese medicine. However, ensuring the efficient enrichment of volatile oils from traditional Chinese medicine while maintaining a green and environmentally friendly process remains an urgent issue to be addressed.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a ceramic membrane with high separation efficiency and environmental friendliness. This invention employs a hydrothermal method, utilizing high temperature and pressure to react shellac molecules with the ceramic membrane. This partially carbonizes the shellac molecules while firmly fixing them to the ceramic membrane surface, resulting in a high-roughness, irregular needle-like structure covering the ceramic membrane surface. Simultaneously, under high temperature and pressure conditions, shellac molecules may undergo lactone or etherification reactions, altering their structure and increasing the oleophobicity of the ceramic membrane surface. This enhances the oil-water separation effect, thereby improving the performance of the porous ceramic membrane in multiple ways.

[0009] To achieve the above objectives, the present invention provides a ceramic membrane for separating oil-water mixed solutions, comprising a metal oxide particle stacked ceramic membrane body, wherein a shellac molecular layer is attached to the surface of the metal oxide particles.

[0010] This invention uses shellac, a natural amphiphilic polymer, as a raw material to form a shellac molecular layer on the surface of metal oxide particles. This improves the enrichment efficiency of blank ceramic membranes in the oil-water separation of traditional Chinese medicine and forms a highly rough, irregular needle-like surface, which to some extent increases its surface oleophobicity and improves its performance.

[0011] Preferably, in the above technical solution, the metal oxide particles are alumina, zirconium oxide, titanium oxide, or other metal oxides suitable for preparing metal ceramic films.

[0012] Preferably, in the above technical solution, the shellac layer is a surface coating composed of irregular needle-like structures with high roughness formed on the surface of a ceramic film after shellac has undergone high temperature and high pressure treatment.

[0013] A method for preparing a ceramic membrane as described above involves placing a metal oxide particle-stacking type ceramic membrane substrate in a shellac solution for full immersion, followed by a hydrothermal reaction of the immersion ceramic membrane substrate to obtain a ceramic membrane with shellac adhering to its surface.

[0014] Hydrothermal reaction processes refer to the general term for chemical reactions that occur in fluids such as water, aqueous solutions, or steam under certain temperature and pressure conditions.

[0015] Preferably, in the above technical solution, the shellac solution is an aqueous solution of shellac, and the concentration of the shellac solution is not higher than 2.0 mg / mL. The shellac solution is initially prepared as a concentrated solution in ethanol, and then diluted with water.

[0016] Preferably, in the above technical solution, the hydrothermal reaction time is no more than 6 hours and the reaction temperature is no less than 180°C.

[0017] Preferably, in the above technical solution, the reaction point of the hydrothermal reaction is: the ceramic film changes from white to grayish-brown or brownish, the reaction stops, and a ceramic film with shellac molecules attached is obtained.

[0018] Preferably, in the above technical solution, the ceramic membrane is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0019] Preferably, in the above technical solution, the ceramic film to which the shellac molecules are attached has an irregular needle-like structure, and the irregular needle-like structure is a high-roughness surface layer formed by the attachment of shellac molecules to the surface of ceramic film matrix particles under high temperature and high pressure conditions.

[0020] Preferably, in the above technical solution, the shellac hydrothermally heated ceramic membrane is washed with water until the washing liquid is colorless, and then dried to obtain the final product.

[0021] Compared with existing technologies, this invention has the following beneficial effects: The oil-water mixture of vinegar and Cyperus rotundus is milky white and shows no significant change after prolonged standing under sealed conditions at room temperature and away from light, indicating that the oil-water mixture is relatively stable and contains a large amount of emulsified oil. Separating it using existing membrane technologies still presents certain difficulties. This invention utilizes an aqueous solution of shellac as a raw material for a hydrothermal reaction. The molecular structure of shellac changes during the reaction, possibly undergoing etherification or lactone formation, which can increase the oleophobicity of the membrane surface to a certain extent. Simultaneously, the microstructure of the membrane surface significantly increases the roughness, and nanoscale irregular columnar and needle-like structures grow on the membrane surface, reducing the average pore size of the ceramic membrane to a certain extent, thereby significantly improving the oil rejection rate of the vinegar-Cyperus rotundus aqueous solution. The characteristics of this invention are: 1. Improved surface roughness of the ceramic membrane; 2. Increased oleophobicity of the ceramic membrane surface. Attached Figure Description

[0022] Figure 1 The appearance morphology of the ceramic membrane before shellac modification.

[0023] Figure 2 The appearance morphology of the shellac-modified ceramic membrane is shown.

[0024] Figure 3 Infrared contrast spectra of shellac flakes and hydrothermally modified membrane surfaces.

[0025] Figure 4 For comparative experimental data statistics. Detailed Implementation

[0026] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0027] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components. Example 1

[0028] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0029] 2. Experimental steps:

[0030] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0031] S2. Dilute the 50 mg / mL shellac solution with water to 0.1 mg / mL;

[0032] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0033] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 1 hour. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0034] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 2

[0035] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0036] 2. Experimental steps:

[0037] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0038] S2. Dilute the 50 mg / mL shellac solution with water to 0.1 mg / mL;

[0039] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0040] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 2 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0041] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 3

[0042] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0043] 2. Experimental steps:

[0044] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0045] S2. Dilute the 50 mg / mL shellac solution with water to 0.1 mg / mL;

[0046] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0047] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 6 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0048] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 4

[0049] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0050] 2. Experimental steps:

[0051] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0052] S2. Dilute the 50 mg / mL shellac solution with water to 1.0 mg / mL;

[0053] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0054] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 1 hour. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0055] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 5

[0056] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0057] 2. Experimental steps:

[0058] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0059] S2. Dilute the 50 mg / mL shellac solution with water to 1.0 mg / mL;

[0060] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0061] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 2 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0062] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 6

[0063] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0064] 2. Experimental steps:

[0065] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0066] S2. Dilute the 50 mg / mL shellac solution with water to 1.0 mg / mL;

[0067] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0068] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 6 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0069] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 7

[0070] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0071] 2. Experimental steps:

[0072] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0073] S2. Dilute the 50 mg / mL shellac solution with water to 2.0 mg / mL;

[0074] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0075] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 1 hour. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0076] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 8

[0077] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0078] 2. Experimental steps:

[0079] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0080] S2. Dilute the 50 mg / mL shellac solution to 2.0 mg / mL;

[0081] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0082] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 2 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0083] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it. Example 9

[0084] 1. Experimental reagents: Shellac (batch number: Y03N11D129408, Yuanye Biotechnology);

[0085] 2. Experimental steps:

[0086] S1. Weigh an appropriate amount of shellac flakes, dissolve them in an appropriate amount of ethanol, and sonicate them in an ultrasonic cleaner for 10 min to prepare a 50 mg / mL shellac solution. After the shellac is completely dissolved in ethanol, place it in a centrifuge and centrifuge at 8000 r / min for 10 min. Take the supernatant, which is the 50 mg / mL shellac solution.

[0087] S2. Dilute the 50 mg / mL shellac solution to 2.0 mg / mL;

[0088] S3. The alumina ceramic membrane (pore size approximately 800 nm) is fully immersed in the shellac solution by immersion or hydraulic pressure.

[0089] S4. Perform a hydrothermal reaction at a temperature of 180℃ for 6 hours. The surface of the ceramic film changes from white to grayish-brown. Stop the reaction to obtain an alumina ceramic film with shellac molecules attached.

[0090] S5. Clean the alumina ceramic film to which shellac molecules adhere until the washing solution is colorless, and then dry it.

[0091] Comparative Example 1: This comparative example provides an alumina ceramic membrane, which is cleaned with deionized water and dried.

[0092] Experimental Example 1

[0093] 1. Scanning electron microscopy morphology

[0094] The morphology of the ceramic films was observed using field emission scanning electron microscopy and transmission electron microscopy, respectively. Before use, the scanning electron microscope samples were sputtered with gold. The appearance morphology of the ceramic films in Example 5 and Comparative Example 1 was characterized.

[0095] 2. Experimental apparatus: Hitachi SU8010 scanning electron microscope;

[0096] 3. Experimental Results:

[0097] Depend on Figure 1 It can be seen that the blank membrane is composed of alumina particles, and the membrane surface is smooth and porous; the shellac-modified membrane has a rough surface, and nanoscale irregular columnar and needle-like structures grow on the membrane surface, which reduces the average pore size of the ceramic membrane to a certain extent; the SEM image of the modified membrane cross section also shows that the shellac layer is relatively thin, and some shellac molecules enter the pores to form a similar structure.

[0098] Experimental Example 2

[0099] 1. Infrared comparison of the surfaces of shellac flakes and shellac hydrothermally modified films.

[0100] 2. Experimental apparatus: Thermo Nicolet iS5 Fourier transform infrared spectroscopy microscope;

[0101] 3. Experimental Results:

[0102] The infrared spectrum of the shellac-modified membrane shows significant absorption only around 545 cm⁻¹, primarily related to the stretching vibrations of Al-O-Al and the bending vibrations of Al-O hexahedrons, exhibiting typical characteristics of alumina and indicating that the main component of the modified membrane is alumina. However, after normalizing the organic structural characteristic region (1000 cm⁻¹~1300 cm⁻¹), the characteristics of shellac molecules remain evident. For example, absorption peaks for -OH and CH stretching vibrations appear at 3319 cm⁻¹, 2921 cm⁻¹, and 2850 cm⁻¹, a C=O stretching vibration absorption peak appears at 1717 cm⁻¹, and a CO stretching vibration absorption peak appears at 1258 cm⁻¹. Notably, a strong peak appears around 1575 cm⁻¹, mainly originating from the C=C structure, indicating that a large number of olefin / benzene ring structures appeared after hydrothermal treatment. Furthermore, the absorption peaks at 1717 cm⁻¹, 1194 cm⁻¹, and 1258 cm⁻¹ broadened and shifted significantly, indicating that the hydrothermal process may have led to lactone formation or etherification of the shellac. Influenced by changes in alumina and polar groups, the absorption peak of the -OH stretching vibration at 3319 cm⁻¹ also shifted significantly.

[0103] Experimental Example 3

[0104] Comparison of retention rates between blank alumina ceramic membrane and shellac hydrothermally modified membrane:

[0105] 1. Experimental reagents: COD oxidant, COD reducing agent (Qingdao Lvyu Environmental Protection Technology Co., Ltd.); concentrated sulfuric acid (batch number B2204257, Xilong Scientific Co., Ltd.); vinegar-processed Cyperus rotundus slices (Shaanxi Xingshengde Pharmaceutical Co., Ltd.);

[0106] 2. Experimental instruments: PTHW type 2 L temperature-controlled electric heating mantle, Shanghai Kesheng Instrument Co., Ltd. LY-3D type multi-functional water quality analyzer, Qingdao Lvyu Environmental Protection Technology Co., Ltd.; laboratory-made 150 mL stainless steel membrane cup (dead-end filtration method);

[0107] 3. Experimental Procedure:

[0108] S1. Based on the SD method and the actual extraction conditions, take 1.0 kg of vinegar-processed Cyperus rotundus, add 10 times the amount of water and soak for 2 hours, then extract for 8 hours to obtain an oil-water mixture.

[0109] S2. The prepared vinegar-cured Cyperus rotundus oil-water mixture and the permeate collected using the membrane in Examples 1-9 were subjected to the classical potassium dichromate method for determination. Take 3 mL of sample, add 1 mL of COD oxidant, then quickly add 5 mL of reducing agent, digest for 10 min, cool, add 3 mL of distilled water, and then cool to room temperature. The chemical oxygen demand (COD) of organic matter in the sample can then be determined. The volatile oil rejection rate was calculated using the formula.

[0110] R = (COD undiluted - COD permeated) / COD undiluted

[0111] R represents the volatile oil rejection rate, CODoriginal is the COD value of the vinegar-fragrant oil-water mixture before separation, and CODpermeable is the COD value of the permeate.

[0112] 4. Experimental Results:

[0113] A blank alumina ceramic membrane was used to separate a mixture of vinegar-processed Cyperus rotundus oil and water under a pressure of 0.01 MPa, and the COD rejection rate of the volatile oil of Cyperus rotundus was approximately 64.81%. Figure 4 The COD rejection rates of shellac-modified membranes prepared under different conditions did not differ significantly, but were all above 80.00%, indicating that the shellac-modified alumina ceramic membrane significantly improved the separation effect of vinegar-Cyperus rotundus oil-water mixtures, with more volatile oil molecules being retained on the membrane surface. The shellac-modified alumina ceramic membrane has a significant effect in the separation of aromatic water from vinegar-Cyperus rotundus.

[0114] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A ceramic membrane for separating oil-water mixtures, comprising a metal oxide particle-stacking ceramic membrane substrate, characterized in that: The shellac layer is attached to the surface of the metal oxide particles of the ceramic membrane. Specifically, the main body of the ceramic membrane, which is a metal oxide particle stacked type, is fully immersed in the shellac solution. After immersion, the main body of the ceramic membrane undergoes a hydrothermal reaction to obtain a ceramic membrane with shellac attached to its surface. The shellac layer is a surface coating composed of irregular needle-like structures with high roughness formed on the surface of the ceramic membrane after the shellac undergoes a hydrothermal reaction.

2. The ceramic membrane according to claim 1, characterized in that, The metal oxide particles are alumina, zirconium oxide, titanium oxide, or other metal oxides suitable for preparing metal-ceramic films.

3. A method for preparing the ceramic membrane as described in claim 1, characterized in that: A metal oxide particle-stacking ceramic membrane substrate is fully immersed in a shellac solution. After immersion, the ceramic membrane substrate undergoes a hydrothermal reaction to obtain a ceramic membrane with shellac adhering to its surface. The ceramic membrane with shellac molecules adhering to it has an irregular needle-like structure. The irregular needle-like structure is a high-roughness surface layer formed by shellac molecules adhering to the surface of the ceramic membrane matrix particles under certain temperature and pressure conditions. The reaction point of the hydrothermal reaction is when the ceramic membrane changes from white to brownish-white, at which point the reaction stops, and a ceramic membrane with shellac molecules adhering to it is obtained. The hydrothermal reaction process refers to the general term for relevant reactions carried out in a sealed reaction vessel at a certain temperature in water, aqueous solution, or steam.

4. The preparation method according to claim 3, characterized in that, Shellac solution is an aqueous solution of shellac, and the concentration of shellac solution is not higher than 2.0 mg / mL.

5. The preparation method according to claim 3, characterized in that, The hydrothermal reaction time shall not exceed 6 hours, and the reaction temperature shall not exceed 180℃.

6. The preparation method according to claim 3, characterized in that, The ceramic membrane is fully immersed in the shellac solution by immersion or hydraulic pressure.

7. The preparation method according to claim 3, characterized in that, The shellac-coated ceramic membrane is washed with water until the washing liquid is colorless, and then dried.

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