CN117105676A - Preparation method and product of flat ceramic membrane with high hardness and smooth film layer - Google Patents

Abstract

The application provides a preparation method and a product of a flat ceramic membrane with a high-hardness smooth membrane layer, which are used for solving the problems that the membrane layer of the conventional flat ceramic membrane is not high in hardness and rough, has poor pollution resistance and affects the qualification rate and the stable operation period of the flat ceramic membrane. The preparation method comprises the following steps: performing gelation treatment on the silica sol to obtain jelly-like silica sol; mixing jelly-like silica sol with alumina powder, water and the like to prepare film slurry; coating the membrane slurry on the surface of a flat ceramic membrane support, drying and sintering to obtain the flat ceramic membrane with the high-hardness smooth membrane layer. The Mohs hardness of the prepared flat ceramic membrane layer is 5-6, and the surface roughness of the membrane layer is 1-3. According to the application, the gelled silica sol is adopted to improve the stacking state of particles on the surface of the film, so that the film with high hardness and very smooth is obtained, the anti-pollution performance of the flat ceramic film is improved, and the qualification rate and the stable operation period of the flat ceramic film are ensured.

Description

Preparation method and product of flat ceramic membrane with high hardness and smooth film layer

Technical field

The present invention relates to the technical field of separation membrane products, and in particular to a preparation method and product of a flat ceramic membrane with a high hardness smooth film layer.

Background technique

At present, the warranty period of flat ceramic membranes on the product application side is required to be more than 5 years, or even 10 years. However, the Mohs hardness of the flat ceramic membranes on the market is around 2 to 3. The low hardness of the membranes leads to scratches during the loading and unloading process of the flat ceramic membranes, which reduces the qualification rate of the flat ceramic membranes. At the same time, flat ceramic membranes are prone to scratches and damage during transportation and transfer, causing the filtration function of flat ceramic membranes to be lost. In addition, long-term aeration and erosion of flat ceramic membranes during operation will also cause the membrane layer with a thickness of 10 to 50 μm to wear, resulting in leakage and substandard filtration.

On the other hand, the flat ceramic membranes on the market are relatively rough, and pollutants are easily adsorbed and bonded to the surface of the membrane to form dense and irreversible pollution, making it impossible to clean and recover through simple backwashing. This also causes the ceramic flat The membrane cannot operate stably for a long time.

Contents of the invention

In order to overcome the problems that the existing flat ceramic film layer is not very hard and rough, has poor stain resistance, and affects the qualification rate and stable operation cycle of the flat ceramic film, the present invention provides a flat plate with a high hardness and smooth film layer. Preparation methods and products of ceramic membranes. The present invention improves the accumulation state of particles on the surface of the film layer by using gelled silica sol, thereby obtaining a high hardness and very smooth film layer, improving the anti-pollution performance of the flat ceramic film layer, and ensuring the qualification rate and quality of the flat ceramic film. Stable operating cycle.

The technical solution adopted by the present invention is:

A method for preparing a flat ceramic membrane with a high hardness smooth film layer, the preparation method includes the following steps:

Step S1, gelling the silica sol to obtain jelly-like silica sol;

Step S2, mix the jelly-like silica sol with alumina powder, lubricating oil, dispersant, lubricant, thickener, defoaming agent and water to prepare film layer slurry;

Step S3: Apply the film layer slurry on the surface of the flat ceramic membrane support by spraying, brushing or dipping, drying and sintering to obtain a flat ceramic membrane with a high hardness and smooth film layer.

Further, in the step S1, the specific process of gelling the silica sol to obtain the jelly-like silica sol includes:

Step S11, mix the silica sol and phosphate or nitrate under stirring;

Step S12, maintain the stirring state, add or not add soda ash or water glass to the mixture in step S11, continue stirring for a preset time and then stop stirring, the mixture gradually gelates, and the jelly-like silica sol is obtained.

Further, the solid content of the silica sol is 10~30%;

And/or, the phosphate is sodium hexametaphosphate or sodium tripolyphosphate;

And/or, the nitrate is sodium nitrate or potassium nitrate;

And/or, the weight ratio of the silica sol, the phosphate or the nitrate and the soda ash or the water glass is 5~15:0.1~1:0~1.

Further, the preset duration of continuing stirring in step S12 is 1 to 30 minutes.

Further, in step S2, based on the weight of alumina powder based on 100%, the proportion of each raw material in the weight of alumina powder is:

Alumina powder, 100%;

Jelly-like silica sol, 5~20%;

Lubricating oil, 0.1~1%;

Dispersant, 0.1~1%;

Lubricant, 0.01~0.1%;

Thickening agent, 0.1~1%;

Defoaming agent, 0.1~1%;

Water, 100~200%.

Further, the D50 particle size of the alumina powder is 0.9~2.6 μm;

And/or, the lubricating oil is one or more of tung oil, white oil, palm oil, glycerin, oleic acid, and sodium stearate;

And/or, the dispersant is one or more of polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol;

And/or, the lubricant is one or more of polyethylene oxide, polyvinyl alcohol, and polyethylene glycol;

And/or, the thickener is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose;

And/or, the defoaming agent is a silane defoaming agent.

Further, the specific process of configuring the film layer slurry in step S2 includes:

Step S21, put alumina powder, jelly-like silica sol, lubricating oil, dispersant, lubricant, thickener and water into a ball mill and ball mill to disperse for a preset time;

Step S22: Filter the slurry dispersed by ball milling in step S21, add a defoaming agent, and then use a high-speed mixer to continue stirring at high speed for a preset time to obtain a film layer slurry.

Further, the preset duration of ball milling and dispersion in step S21 is 1.5~7h;

And/or, in step S21, a high-speed mixer is used to continue high-speed stirring for a preset duration of 5 to 30 minutes.

Further, in step S3, the sintering temperature is 1200~1300°C, and the sintering time is 2~2.5 hours.

Based on the same inventive concept, the flat ceramic membrane product is produced by the aforementioned preparation method of a flat ceramic membrane with a high hardness and smooth film layer;

The flat ceramic film layer has a Mohs hardness of 3 to 6 and a surface roughness of 1 to 3.

The beneficial effects of the present invention are:

In order to overcome the problems that the existing flat ceramic film layer is not very hard and rough, has poor stain resistance, and affects the qualification rate and stable operation cycle of the flat ceramic film, the present invention provides a flat plate with a high hardness and smooth film layer. Preparation methods and products of ceramic membranes. The preparation method of the flat ceramic membrane with a high hardness smooth film layer in the present invention first gelates the silica sol to obtain a jelly-like silica sol, and then mixes the jelly-like silica sol with alumina powder and other raw materials to form a The film layer slurry is finally sintered to obtain a flat ceramic film with a high hardness and smooth film layer. Due to the gelation process of silica sol, the nano-silica particles are transformed into large-sized branched or beaded silica aggregates, and then the branched or beaded silica aggregates react with the oxidized Aluminum powder and other materials are mixed with the support film slurry and coated on the surface of the flat ceramic support. During the drying and film forming process, they overlap each other to form a dense and uniform film layer. Finally, a high-hardness and very smooth film is prepared through high-temperature sintering. layer. The preparation method is simple to operate and the raw materials are easily available. At the same time, the flat ceramic membrane layer made by the preparation method of the present invention has high hardness, and can better avoid scratches and other phenomena during the production and transportation of the flat ceramic membrane, ensuring the qualification of the flat ceramic membrane. efficiency and filtration function, and can effectively cope with aeration and scouring, ensuring a stable operating state of the flat ceramic membrane and extending its service life. At the same time, the flat ceramic membrane layer supported by the preparation method of the present invention is very smooth and can delay Pollution and other adhesion to the surface of the flat ceramic membrane improves the pollution resistance of the flat ceramic membrane and can be recovered through backwashing, ensuring the stable operation of the flat ceramic membrane and extending its service life.

Description of drawings

In order to more clearly explain the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for this purpose. For some embodiments of the application, those of ordinary skill in the art can also obtain other drawings based on these drawings without exerting creative efforts.

Figure 1 is a schematic flow chart of the preparation of flat ceramic membranes.

Figure 2a is a diagram of the appearance of silica sol without any treatment.

Figure 2b is a diagram of the appearance of the silica sol after gelation in Example 3.

Figure 3a is a scanning electron microscope image of silica sol without any treatment.

Figure 3b is a scanning electron microscope image of the silica sol after gelation in Example 3.

Figure 4 is an appearance diagram of the film layer of the flat ceramic membrane in Example 12.

Figures 5a, 5b, 5c and 5d are respectively scanning electron microscopy images of four positions on the surface of the flat ceramic film in Example 12.

Figures 5e, 5f, 5g and 5h are scanning electron microscopy images of four positions on the surface of the flat ceramic film in Comparative Example 5.

Figure 6a is a scanning electron microscope image of the cross section of the flat ceramic membrane in Example 12 with a magnification of 1000 times.

Figure 6b is a scanning electron microscope image of the cross section of the flat ceramic membrane in Example 12 with a magnification of 5000 times.

Detailed ways

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inside", "Outside", "Clockwise", "Counterclockwise", "Axis" The orientations or positional relationships indicated by "radial direction", "circumferential direction", etc. are based on the orientations or positional relationships shown in the figures. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply the devices or components referred to. Must have a specific orientation, be constructed and operate in a specific orientation and are therefore not to be construed as limitations of the invention.

The following disclosure provides many different embodiments or examples of various structures for implementing the invention. In order to simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the invention.

The embodiments of the invention will be described in detail below with reference to the drawings.

A method for preparing a flat ceramic membrane with a high hardness smooth film layer, the process of which is shown in Figure 1. The preparation method includes the following steps:

In step S1, the silica sol is gelled to obtain a jelly-like silica sol. Specifically: under stirring, mix silica sol with phosphate or nitrate; maintain stirring, add or not add soda ash or water glass to the mixture, continue stirring for a preset time and then stop stirring (for example, 1~30 minutes) , the mixture gradually gelled to obtain jelly-like silica sol.

Step S2: Mix the jelly-like silica sol with alumina powder, lubricating oil, dispersant, lubricant, thickener, defoaming agent and water to form a film layer slurry. Specifically: put alumina powder, jelly-like silica sol, lubricating oil, dispersant, lubricant, thickener and water into a ball mill and ball mill to disperse. The ball milling time is preset (such as 1.5~7h); for ball milling The dispersed slurry is filtered, a defoaming agent is added, and then a high-speed mixer is used to continue stirring at high speed for a preset time (such as 5 to 30 minutes) to obtain a film layer slurry.

Step S3: Apply the film slurry on the surface of the flat ceramic membrane support by spraying, brushing or dipping, drying and then sintering at a sintering temperature of 1200~1300°C and a sintering time of 2~2.5h to obtain a high-performance Flat ceramic membrane with smooth hardness.

Among them, the solid content of silica sol is 10~30%; phosphate is sodium hexametaphosphate or sodium tripolyphosphate; nitrate is sodium nitrate or potassium nitrate; the weight of silica sol, phosphate or nitrate and soda ash or water glass The ratio is 5~15:0.1~1:0~1.

Based on 100% of the weight of alumina powder, the proportion of each raw material in the weight of alumina powder is: alumina powder, 100%; jelly-like silica sol, 5~20%; lubricating oil, 0.1~1%; Dispersant, 0.1~1%; lubricant, 0.01~0.1%; thickener, 0.1~1%; defoaming agent, 0.1~1%; water, 100~200%.

The D50 particle size of alumina powder is 0.9~2.6μm; the lubricating oil is one or more of tung oil, white oil, palm oil, glycerin, oleic acid, and sodium stearate; the dispersing agent is polyacrylamide, poly One or more of vinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol; the lubricant is one or more of polyethylene oxide, polyvinyl alcohol, and polyethylene glycol; the thickener is carboxymethyl One or more of hydroxyethyl cellulose, hydroxypropyl methylcellulose, and hydroxypropyl methylcellulose; the defoaming agent is a silane defoaming agent.

The following further illustrates through more specific examples.

(1) Preparation of jelly-like silica sol

Examples 1 to 9 are for the preparation of jelly-like silica sol. The process is as follows: under stirring, mix silica sol (solid content: 20%) with phosphate or nitrate; maintain stirring, add or not to the mixture. Add soda ash or water glass, continue stirring for 10 minutes and then stop stirring. The mixture will gradually gel and obtain a jelly-like silica sol. The composition and appearance observation results of the jelly-like silica sol in Examples 1 to 9 are shown in Table 1.

From the observation results of the appearance state of the silica sol after gelation in Table 1, it can be seen that after adding phosphate or nitrate to the silica sol, or after adding phosphate or nitrate and soda ash or water glass to the silica sol, the silica sol It will gradually flocculate and clump, eventually forming a jelly-like gel.

A comparison of the appearance of the mid-silica sol in Example 3 after gelling is shown in Figure 2a and Figure 2b. Among them, Figure 2a shows the silica sol without any treatment, and Figure 2b shows the silica sol after gelling. As can be seen from the figure, silica sol is a colorless and transparent liquid before any treatment. When sodium tripolyphosphate and soda ash are added to the silica sol, the silica sol becomes milky white jelly-like.

The scanning electron microscope images of the mesosilica sol in Example 3 before and after gelation are shown in Figures 3a and 3b. Among them, Figure 3a shows the silica sol without any treatment, and Figure 3b shows the silica sol after gelling. It can be seen from the figure that the silica sol is uniformly dispersed small droplets before gelling. After sodium tripolyphosphate and soda ash are added to the silica sol, the small droplets in the silica sol gradually flocculate, forming aggregates with larger particle sizes, branched chains or beads.

(2) Preparation of flat ceramic membrane

Examples 10 to 17 are the preparation of flat ceramic membranes, and the preparation process refers to the aforementioned preparation method. The composition and performance test results of the flat ceramic membranes of Examples 10 to 17 are shown in Table 2.

Among them, the raw materials of the flat ceramic membrane support are: in parts by weight, the raw materials of the support body include 80 parts of ceramic aggregate, 15 parts of activated carbon (D50 particle size is 2 μm), 10 parts of polyvinyl alcohol, 5 parts of polyethylene glycol 20 parts of water and 90 parts of spherical alumina used to support the ceramic aggregate (D50 particle size is 20 μm), 5 parts of magnesium oxide, and 5 parts of kaolin.

The D50 particle size of the alumina powder in the film slurry is 1.1 μm. The ball mill dispersion time is 4.5 hours. The mixing time of the high-speed mixer is 5 minutes. Spray, 1 time. The sintering temperature is 1250℃ and the sintering time is 2h.

Comparative Examples 4 to 6 prepared flat ceramic membranes by referring to the aforementioned method. The differences are:

Comparative Example 4: Silica sol, sodium tripolyphosphate and soda ash are directly dispersed and configured with alumina powder through ball milling to form a film layer slurry. The composition and dosage are the same as in Example 12.

Comparative Example 5: The jelly-like silica sol was replaced with silica sol without any treatment, and the remaining composition and dosage were the same as in Example 12.

Comparative Example 6: After ball milling and dispersing the film layer slurry, the film layer slurry was directly sprayed without high-speed stirring using a high-speed mixer. The composition and dosage were the same as those in Example 12.

The performance test results of the flat ceramic membranes in Comparative Examples 4 to 6 are shown in Table 3.

It can be seen from the data in Table 3 that the Mohs hardness of the film layer of the flat ceramic film prepared in this embodiment is 3 to 6, and the film layer is smooth. The reason after analysis is that due to the gelation process of silica sol, the nano-silica particles are transformed into large-sized branched or beaded silica aggregates, and then the branched or beaded silica aggregates Silicon aggregates and alumina powder are mixed to support the film slurry and coated on the surface of the flat ceramic support. During the drying and film-forming process, they overlap each other to form a dense and uniform film layer. Finally, they are sintered at high temperature to prepare a high-hardness film. And very smooth film layer.

Because the flat ceramic membrane layer has a high hardness, it can better avoid scratches and other phenomena during the production and transportation of the flat ceramic membrane, ensuring the qualification rate and filtration function of the flat ceramic membrane, and can effectively deal with exposure. Air flushing ensures the stable operating state of the flat ceramic membrane and extends the service life. At the same time, the flat ceramic membrane layer supported by the preparation method of the present invention is very smooth, which can delay the adhesion of pollution and the like to the surface of the flat ceramic membrane and improve the performance of the flat ceramic membrane. The flat ceramic membrane is resistant to pollution and can be recovered through backwashing, ensuring the stable operation of the flat ceramic membrane and extending its service life.

Comparing the data in Table 3 and Table 4, it can be seen that gelling the silica sol is beneficial to improving the film hardness and film smoothness of the flat ceramic membrane. At the same time, compared to the simultaneous gelation of silica sol, sodium tripolyphosphate, etc. and alumina powder during the ball milling dispersion process, the gelation process of silica sol before ball milling is more conducive to improving the film quality of flat ceramic membranes layer hardness and film smoothness properties. The reason after analysis is that when silica sol and alumina powder are gelled simultaneously during the ball milling and dispersion process, the small droplets of silica sol are violently impacted and are not easy to aggregate, which is not conducive to the transformation of nano-silica particles into large particle sizes. Branched or beaded silica aggregates.

On the other hand, the film slurry is continuously supplemented with high-speed stirring for a certain period of time after ball milling, which can further improve the dispersion effect of each raw material in the film slurry, which is conducive to further improving the film hardness and film smoothness of the flat ceramic membrane. .

The appearance photos of the flat ceramic membrane in Example 12 are shown in Figure 4. As can be seen from the picture, the surface of the flat ceramic membrane is smooth, with no obvious bulges and no cracks.

The scanning electron microscope images of the film surface of the flat ceramic membrane in Example 12 and the flat ceramic membrane in Comparative Example 5 are shown in Figure 5a, Figure 5b, Figure 5c and Figure 5d, as well as Figure 5e, Figure 5f, Figure 5g and Figure 5h. Show. 5a, 5b, 5c and 5d are respectively scanning electron microscopy images of multiple positions on the surface of the flat ceramic film in Example 12. Figures 5e, 5f, 5g and 5h are scanning electron microscopy images of multiple locations on the surface of the flat ceramic film in Comparative Example 5. It can be seen from the figure that the surface of the flat ceramic membrane made by adding jelly-like silica sol in a microscopic state and then sintering is relatively smooth. However, there are still protrusions, pits, etc. on the surface of the flat ceramic film made by adding silica sol and sintering in the microscopic state. The protrusions, pits, etc. can serve as anchor points for pollutants on the surface of the flat ceramic membrane, which increases the difficulty of backwash recovery of the flat ceramic membrane.

The scanning electron microscope images of the cross section of the flat ceramic membrane in Example 12 are shown in Figures 6a and 6b. Among them, the magnification of Figure 6a is 1000 times, and the magnification of Figure 6b is 5000 times. It can be seen from the figure that the thickness of the film layer at the cross section of the flat ceramic membrane is about 20 μm. At the same time, the remote pore diameter of the membrane layer is smaller than the pore diameter of the flat ceramic membrane support body.

During the preparation process of the flat ceramic membrane in Example 12, film layer slurries with different ball milling dispersion times were sprayed, and relevant tests were performed. The test results are shown in Table 4.

From the test data in Table 4, it can be seen that as the ball milling dispersion time increases, the spraying state of the film slurry remains unchanged, and the surface smoothness of the film layer increases slightly. Until 3 hours after ball milling and dispersion, the spraying state and surface smoothness suddenly change, resulting in obvious difference. Therefore, the film slurry ensures a certain ball milling dispersion time, which is conducive to improving the film hardness and film smoothness of the flat ceramic membrane. Moreover, as the ball milling dispersion time increases, the bubble point pore size of the membrane layer decreases and then tends to a stable value. The pore size concentration of the prepared membrane layer increases, which also improves the filtration accuracy and pollution resistance of the product.

Taking the flat ceramic membrane in Example 12, the flat ceramic membrane in Comparative Example 4, and the commercially available flat ceramic membrane as examples, a roughness measuring instrument using a stylus measurement method was used to detect the surface roughness of the flat ceramic membrane layer. The test results are shown in Table 5.

From the test data in Table 5, it can be seen that the flat ceramic film layer prepared in this example is very smooth.

Taking the flat ceramic membrane in Example 12, the flat ceramic membrane in Comparative Example 4 and the commercially available flat ceramic membrane as examples, first run for the same time (such as 3d) under the same concentration of sewage conditions, and then start the backwash operation to continue running. The same time (such as 3h). Calculate the ratio of the transmembrane pressure difference after backwashing to the initial transmembrane pressure difference under the same flux. This ratio is defined as the initial pressure difference recovery rate. After measurement, the initial pressure difference recovery rate of the flat ceramic membrane in Example 12 was calculated to be 98%, the initial pressure difference recovery rate of the flat ceramic membrane in Comparative Example 4 was 93%, and the initial pressure difference recovery rate of the commercially available flat ceramic membrane was 98%. 88%. Under the same backwash method, the flat ceramic membrane prepared in this example showed a more excellent initial pressure difference recovery rate, which also verified from the side that the flat ceramic membrane prepared in this example was very smooth and was not conducive to Impurities etc. are attached.

Claims (10)

1. A method for preparing a flat ceramic membrane with a high hardness smooth film layer, characterized in that the preparation method includes the following steps: Step S1, gelling the silica sol to obtain jelly-like silica sol; Step S2, mix the jelly-like silica sol with alumina powder, lubricating oil, dispersant, lubricant, thickener, defoaming agent and water to prepare film layer slurry; Step S3: Apply the film slurry on the surface of the flat ceramic membrane support by spraying, brushing or dipping, drying and sintering to obtain a flat ceramic membrane with a high hardness and smooth film layer. 2. The method for preparing a flat ceramic film with a high hardness smooth film layer according to claim 1, characterized in that in step S1, the specific process of gelling the silica sol to obtain the jelly-like silica sol includes : Step S11, mix the silica sol and phosphate or nitrate under stirring; Step S12, maintain the stirring state, add or not add soda ash or water glass to the mixture in step S11, continue stirring for a preset time and then stop stirring, the mixture gradually gelates, and the jelly-like silica sol is obtained. 3. The method for preparing a flat ceramic film with a high hardness smooth film layer according to claim 2, characterized in that the solid content of the silica sol is 10 to 30%; And/or, the phosphate is sodium hexametaphosphate or sodium tripolyphosphate; And/or, the nitrate is sodium nitrate or potassium nitrate; And/or, the weight ratio of the silica sol, the phosphate or the nitrate and the soda ash or the water glass is 5~15:0.1~1:0~1. 4. The method for preparing a flat ceramic membrane with a high hardness smooth film layer according to claim 2 or 3, characterized in that the preset duration of continuing stirring in step S12 is 1 to 30 minutes. 5. The method for preparing a flat ceramic film with a high hardness smooth film layer according to claim 1, characterized in that in step S2, based on 100% of the weight of the alumina powder, each raw material accounts for the alumina powder. The proportion of body weight is: Alumina powder, 100%; Jelly-like silica sol, 5~20%; Lubricating oil, 0.1~1%; Dispersant, 0.1~1%; Lubricant, 0.01~0.1%; Thickening agent, 0.1~1%; Defoaming agent, 0.1~1%; Water, 100~200%. 6. The method for preparing a flat ceramic film with a high hardness smooth film layer according to any one of claims 1 to 3 and 5, characterized in that the D50 particle size of the alumina powder is 0.9 to 2.6 μm. ; And/or, the lubricating oil is one or more of tung oil, white oil, palm oil, glycerin, oleic acid, and sodium stearate; And/or, the dispersant is one or more of polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol; And/or, the lubricant is one or more of polyethylene oxide, polyvinyl alcohol, and polyethylene glycol; And/or, the thickener is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; And/or, the defoaming agent is a silane defoaming agent. 7. The method for preparing a flat ceramic membrane with a high hardness smooth film layer according to any one of claims 1, characterized in that the specific process of configuring the film layer slurry in step S2 includes: Step S21, put alumina powder, jelly-like silica sol, lubricating oil, dispersant, lubricant, thickener and water into a ball mill and ball mill to disperse for a preset time; Step S22: Filter the slurry dispersed by ball milling in step S21, add a defoaming agent, and then use a high-speed mixer to continue stirring at high speed for a preset time to obtain a film layer slurry. 8. The method for preparing a flat ceramic film with a high hardness smooth film layer according to any one of claims 1, characterized in that the preset duration of ball milling dispersion in step S21 is 1.5~7h; And/or, in step S21, a high-speed mixer is used to continue high-speed stirring for a preset duration of 5 to 30 minutes. 9. The method for preparing a flat ceramic film with a high hardness smooth film layer according to any one of claims 1 to 3, 5, 7 to 8, characterized in that the sintering temperature in step S3 is 1200 to 1300°C. , the sintering time is 2~2.5h. 10. Flat ceramic membrane product, characterized in that it is prepared by the preparation method of a flat ceramic membrane with a high hardness smooth film layer according to any one of claims 1 to 9; The flat ceramic film layer has a Mohs hardness of 3 to 6 and a surface roughness of 1 to 3.