Ceramic flat sheet membrane liquid, its preparation method and its application in ceramic flat sheet membranes

Abstract

The application belongs to the technical field of ceramic product preparation, and particularly relates to a ceramic flat plate membrane layer liquid, a preparation method thereof and application of the ceramic flat plate membrane layer liquid in a ceramic flat plate membrane. The preparation method of the ceramic flat plate membrane layer liquid comprises the following steps: adding glass powder, divalent oxide and tetravalent oxide into alumina, mixing, placing in a V-shaped mixer, mixing for 30-50 min to obtain a mixed material; preparing a methyl cellulose solution or a PVC solution, and standing for standby; putting the mixed material, the methyl cellulose solution or the PVC solution, water and a dispersing agent into a ball mill, ball-milling and dispersing, and standing to obtain the ceramic flat plate membrane layer liquid, and coating the ceramic flat plate membrane layer liquid on a support to obtain a ceramic flat plate membrane. The preparation method of the ceramic flat plate membrane layer liquid provided by the application can improve the hydrophilic property and oleophobic property of the ceramic flat plate membrane after the prepared membrane layer liquid is used in the ceramic flat plate membrane, and can greatly improve the problem of pollution and blockage.

Description

Technical Field

[0001] This invention belongs to the field of ceramic product preparation technology, specifically relating to ceramic flat sheet membrane liquid, its preparation method and its application in ceramic flat sheet membranes. Background Technology

[0002] Ceramic flat sheet membranes possess advantages such as good thermal stability, high chemical stability, and high permeation flux, making them particularly effective in wastewater filtration and thus widely used in the environmental industry. Ceramic flat sheet membranes consist of a support structure and membrane layers.

[0003] Currently, flat-sheet ceramic membranes are mainly composed of single materials such as alumina and silicon carbide. The flux of these single-component ceramic membranes is adjusted solely by the particle size and distribution range of the raw materials, aiming to achieve higher flux. High-flux membrane materials imply increased pore size. Since flat-sheet ceramic membranes are primarily used in aqueous systems, the hydrophilicity of the membrane material directly affects the permeate flux. Furthermore, in water-oil composite systems, oil can adhere to and even clog the membrane, leading to a rapid decline in flux. Routine backwashing and chemical flushing are ineffective at removing oil contaminants from the membrane layer, making it difficult to restore the flux of flat-sheet ceramic membranes to their original levels, resulting in short lifespans and low efficiency.

[0004] CN113385052A discloses an alumina-based ceramic flat sheet membrane. The preparation of the membrane slurry involves first adding a dispersant such as ammonium polyacrylate solution to water and stirring to disperse it; then adding alumina powder with an average particle size of 0.3–3 μm and sintering aids (two or more of silica sol, nano-titanium dioxide, nano-zirconia, nano-zinc oxide, washed kaolin, and calcined talc) and stirring to disperse it; next, adding a binder such as polyvinyl alcohol solution and a ceramic polyether defoamer and stirring to disperse it; finally, transferring the slurry to a ball mill jar and ball milling for 2 hours to obtain the coating slurry. The viscosity of the coating slurry is 50–100 mPa·s. It employs a one-step co-sintering process of "support + membrane layer," which saves significant time and energy consumption. While cost is a concern, in actual implementation, the membrane solution during the coating process permeates into the green support. Small-diameter particles in the membrane solution (such as alumina particles) randomly fill the loose green support. Simultaneously, due to the presence of sintering aids, random and uncontrollable dense regions are formed between the support and the separation layer during sintering, significantly affecting the pore size of the membrane and the final pore size distribution. The attached figures clearly indicate fatal defects such as excessively wide pore size distribution and multiple distribution peaks (low filtration accuracy, the membrane layer is easily and rapidly clogged by pollutants of various sizes, resulting in rapid flux decay and difficulty in flux recovery). On the other hand, a narrow and uniform pore size distribution is a key parameter for evaluating the performance of membrane materials, which will significantly affect the filtration accuracy, flux, and flux regeneration of the membrane material.

[0005] CN115591411A discloses a process flow and application method for a ceramic flat sheet membrane. The process involves mixing 0.3-0.5μm alumina powder with a pore-forming agent (composed of starch and graphite), then mixing this mixture with a mixture of 0.1-0.2μm alumina powder, water, titanium dioxide, a dispersant, and an auxiliary adsorbent. This mixture is then sprayed onto a flat sheet carrier to obtain a ceramic flat sheet membrane, which enhances the filtration and adsorption effects and provides strong corrosion resistance. However, the production process used is a conventional flow, selecting 0.3-0.5μm and 0.1-0.2μm alumina powder. In practice, this particle size of raw material is expensive and prone to agglomeration, making it difficult to store. Furthermore, the pore-forming agent, composed of starch and graphite, is not easily dispersed uniformly, resulting in uneven pore formation and the random appearance of large-sized pores, which is detrimental to obtaining continuous, uniform, and complete micropores. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a ceramic flat sheet membrane liquid. When the prepared membrane liquid is used on a ceramic flat sheet membrane, it improves the hydrophilicity and oleophobicity of the ceramic flat sheet membrane and greatly improves the problem of fouling.

[0007] The method for preparing the ceramic flat-plate membrane liquid according to the present invention includes the following steps:

[0008] (1) Add glass powder, divalent oxide, and tetravalent oxide to alumina and mix.

[0009] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 30-50 minutes to obtain a mixture;

[0010] (3) Prepare a methylcellulose solution or PVC solution and let it stand for later use;

[0011] (4) Add the mixture from step (2), the methylcellulose solution or PVC solution from step (3), water, and dispersant to a ball mill and disperse for 4-6 hours. Let it stand to obtain a ceramic flat sheet membrane liquid with a solid content of 15%-20%. The solid content refers to the mass of solids.

[0012] The alumina particle size in step (1) is 1-2 μm; the glass powder particle size is 1 μm-3 μm.

[0013] The divalent oxide is one or more of MgO, CaO, BaO, CuO, and ZnO.

[0014] The tetravalent oxide is one or more of TiO2, MnO2, ZrO2, SiO2, and CeO2.

[0015] The proportions of each substance in step (1) are as follows, by weight: 80-90 parts of aluminum oxide, 1-10 parts of divalent oxide, 1-10 parts of tetravalent oxide, and 1-5 parts of glass powder.

[0016] In step (3), the concentration of the methylcellulose solution or PVC solution is 5 wt.%-10 wt.%; the standing time is 24 h-48 h.

[0017] In step (4), the mass ratio of the mixture in step (2), the methylcellulose solution or PVC solution in step (3), water, and dispersant is (5:30:55:0.4)-(20:30:50:0.5).

[0018] The dispersant is polyacrylate, specifically ammonium polyacrylate or sodium polyacrylate.

[0019] A ceramic flat sheet membrane layer liquid is prepared by the method described above.

[0020] The application of the ceramic flat sheet membrane layer liquid, used in the preparation of ceramic flat sheet membranes, includes the following steps:

[0021] (1) The ceramic flat plate membrane liquid is coated on the support. The coating can be carried out by spraying or dipping. The membrane thickness is 10-50μm.

[0022] (2) The support for coating liquid is dried at 120℃-180℃ for 8-12h to obtain the product;

[0023] (3) The product is fired at 1300℃-1350℃ to obtain a ceramic flat film.

[0024] Specifically, the method for using the ceramic flat sheet membrane layer solution to prepare a ceramic flat sheet membrane includes the following steps:

[0025] (1) Add 1-5 parts of glass powder with a particle size of 1-3 μm, 1-10 parts of divalent oxide and 1-10 parts of tetravalent oxide to 80-90 parts of alumina with a particle size of 1-2 μm, and mix.

[0026] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 30-50 minutes to obtain the mixture.

[0027] (3) Prepare a 5wt.%-10wt.% methylcellulose solution or PVC solution and let it stand for 24h-48h.

[0028] (4) The mixture from step (2), the methylcellulose solution or PVC solution from step (3), water, and dispersant are fed into a ball mill at a mass ratio of (5:30:55:0.4)-(20:30:50:0.5). After ball milling and dispersion for 4-6 hours, the mixture is discharged from the mill and allowed to stand for 24-48 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 15%-20%.

[0029] (5) Apply the ceramic flat plate membrane liquid onto the clean support after it has been cleaned and dried. The coating can be done by spraying or immersion. By controlling the spraying or immersion time, a membrane of a certain thickness can be obtained. The membrane thickness is 10-50μm.

[0030] (6) Transfer the support of the coating liquid to an oven and dry it at 120℃-180℃ for 8-12 hours to obtain the product;

[0031] (7) The product is placed in a high-temperature kiln, stacked in 5-10 pieces, and fired at 1300℃-1350℃ to obtain a ceramic flat film.

[0032] The ceramic flat sheet membrane prepared by this invention involves applying a specially formulated membrane layer liquid onto its support to obtain a multiphase ceramic membrane layer. This invention employs a separate sintering process for the support and the membrane layer. The glass powder, divalent oxides, and tetravalent oxides added to the membrane layer do not interact with the pre-sintered support. During membrane sintering, they not only act as a flux to lower the sintering temperature, but more importantly, their optimized proportions form a continuous and uniform liquid phase coating between alumina particles, thereby significantly improving the hydrophilic and oleophobic properties and flux of the membrane material. This results in an excellent flux regeneration capability, and the ceramic membrane prepared by this invention has uniform pore size and a narrow distribution range. This invention selects alumina powder larger than 0.5 μm, which has a lower market price and is less prone to agglomeration. Furthermore, pore formation primarily utilizes particle packing to create pores, resulting in more uniform pores and a narrower pore size distribution, leading to a complete membrane layer without large pores. The pore size of the membrane formed by this invention is between 80 nm and 200 nm.

[0033] The introduction of glass powder and divalent and tetravalent oxides in this invention enables the formation of a continuous liquid phase during firing, increasing the film density and thus reducing film defects. Simultaneously, it increases the surface energy of the film, giving it strong hydrophilic and oleophobic properties, reducing oil-water interfacial tension, and preventing the deposition of grease and dirt on the film surface. During backwashing, water spreads more easily across the film surface, penetrating between the oil and the film layer, isolating the oil and making it easier to remove. The contact angle formed in the ceramic flat sheet film layer when water, oil, and solid phases coexist is as follows: Figure 7 As shown, under the action of external force, the condition for complete detachment of oil droplets, described by interfacial tension, is derived from Young's equation, namely: γ so -γsw =γ ow cosθ w ≥0, where γ so For solid / oil interfacial tension; γ sw For solid / water interfacial tension; γ ow Let γ be the oil / water interfacial tension. From the formula, we know that if γ... so >γ sw , then θ w <90°, θ o At >90°, oil droplets can detach from the film surface, and γ so -γ sw The larger the value, the easier it is to achieve; at this point, cosθ w =(γ so -γ sw ) / γ ow γ ow The lower the value, the better. w The larger θ is w The smaller γ is, the larger θo is, which is more conducive to the removal of oil stains. ow equal to γ so -γ sw , then θ w =0°, at which point water will automatically displace the oil film from the membrane surface. Adding divalent and tetravalent oxides in a certain proportion increases the surface free energy of the membrane. The larger the contact angle of the oil on the membrane, the easier it is for water to wet the membrane, thus increasing the flux. At the same time, water can more easily enter between the oil and the membrane. The oil will shrink and gather under the action of water, making it easier for the oil to detach from the membrane. Therefore, when the ceramic membrane is subjected to external force (i.e., during backwashing), the oil will more easily get off the membrane, thus restoring the membrane flux.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] (1) The ceramic flat sheet membrane prepared by the method of the present invention significantly reduces its water contact angle and greatly improves its hydrophilicity.

[0036] (2) The ceramic flat sheet membrane prepared by the method of the present invention has a flux increase of 10%-80% compared with the unmodified ceramic membrane.

[0037] (3) The method of using the ceramic flat sheet membrane liquid of the present invention to prepare ceramic flat sheet membranes has a low firing temperature and low firing energy consumption.

[0038] (4) The ceramic flat sheet membrane prepared by the method of the present invention has significantly reduced oil adhesion and thus has excellent oleophobic properties. In the water-oil composite system, the fouling can be easily removed by backwashing, thereby restoring the membrane flux. Attached Figure Description

[0039] Figure 1This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Example 1 of the present invention.

[0040] Figure 2 This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Example 2 of the present invention.

[0041] Figure 3 This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Example 3 of the present invention.

[0042] Figure 4 This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Example 4 of the present invention.

[0043] Figure 5 This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Comparative Example 1 of the present invention.

[0044] Figure 6 This is a pore size distribution diagram of the ceramic flat sheet membrane prepared in Comparative Example 2 of the present invention.

[0045] Figure 7 This is a schematic diagram of the contact angle of the ceramic flat sheet membrane prepared in Example 1 of the present invention when it comes into contact with water, oil and solid phases. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. All reagents used in the present invention are commercially available products.

[0047] Example 1

[0048] The method for using the ceramic flat sheet membrane layer solution to prepare a ceramic flat sheet membrane includes the following steps:

[0049] (1) Add 1 part of glass powder with a particle size of 1 μm, 2 parts of divalent oxide MgO, 2 parts of CeO2, and 5 parts of tetravalent oxide TiO2 to 90 parts of alumina with a particle size of 0.5 μm, and mix.

[0050] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 30 minutes to obtain the mixture.

[0051] (3) Prepare a methylcellulose solution with a concentration of 5 wt.% and let it stand for 24 hours before use.

[0052] (4) The mixture from step (2), the methylcellulose solution from step (3), water, and polyacrylic acid in a mass ratio of 15:30:55:0.04 were fed into a ball mill. After ball milling and dispersion for 4 hours, the mixture was discharged from the mill and allowed to stand for 24 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 14.99%.

[0053] (5) Apply the ceramic flat plate membrane liquid onto the clean support after it has been cleaned and dried. The coating can be done by spraying. The spraying time is 20s and the membrane thickness is about 50μm.

[0054] (6) Transfer the support with the coating liquid to an oven and dry it at 120°C for 12 hours to obtain the product.

[0055] (7) The product is placed in a high-temperature kiln, stacked in 10 pieces, and fired at 1350℃ to obtain a ceramic flat film.

[0056] Example 2

[0057] The method for using the ceramic flat sheet membrane layer solution to prepare a ceramic flat sheet membrane includes the following steps:

[0058] (1) Add 3.5 parts of glass powder with a particle size of 1.8 μm, 2 parts of divalent oxide MgO, 2 parts of CaO, 1 part of CuO, 4 parts of tetravalent oxide MnO, and 2.5 parts of ZrO to 85 parts of alumina with a particle size of 0.9 μm, and mix.

[0059] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 40 minutes to obtain a mixture.

[0060] (3) Prepare a PVA solution with a concentration of 8 wt.% and let it stand for 36 hours before use.

[0061] (4) The mixture from step (2), the PVA solution from step (3), water, and polyacrylic acid were fed into a ball mill in a mass ratio of 18:30:52:0.05. After ball milling and dispersion for 5 hours, the mixture was discharged from the mill and allowed to stand for 36 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 17.99%.

[0062] (5) The ceramic flat plate membrane liquid is coated onto the clean support after being cleaned and dried. The coating is carried out by immersion, the immersion time is 8s, and the membrane thickness is about 10μm.

[0063] (6) Transfer the support with the coating liquid to an oven and dry it at 150°C for 10 hours to obtain the product.

[0064] (7) The product is placed in a high-temperature kiln, stacked in 10 pieces, and fired at 1330℃ to obtain a ceramic flat film.

[0065] Example 3

[0066] The method for using the ceramic flat sheet membrane layer solution to prepare a ceramic flat sheet membrane includes the following steps:

[0067] (1) Add 5 parts of glass powder with a particle size of 3μm, 1 part of divalent oxide MgO, 1 part of CaO, 0.5 parts of ZnO, 2 parts of tetravalent oxide SiO2, and 0.5 parts of CeO2 to 90 parts of alumina with a particle size of 2μm, and mix.

[0068] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 50 minutes to obtain the mixture.

[0069] (3) Prepare a PVA solution with a concentration of 10 wt. and let it stand for 48 hours before use.

[0070] (4) The mixture from step (2), the PVA solution from step (3), water, and sodium polyacrylate are fed into a ball mill in a mass ratio of 20:30:50:0.05. After ball milling and dispersion for 6 hours, the mixture is discharged from the mill and left to stand for 48 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 19.99%.

[0071] (5) The ceramic flat plate membrane liquid is coated onto the clean support after it has been cleaned and dried. The coating is carried out by spraying for 15 seconds, and the membrane thickness is about 40 μm.

[0072] (6) Transfer the support with the coating liquid to an oven and dry it at 180°C for 8 hours to obtain the product.

[0073] (7) The product is placed in a high-temperature kiln, stacked in 5 pieces, and fired at 1300℃ to obtain a ceramic flat film.

[0074] Example 4

[0075] The method for using the ceramic flat sheet membrane layer solution to prepare a ceramic flat sheet membrane includes the following steps:

[0076] (1) Add 1 part of glass powder with a particle size of 1.2 μm, 5 parts of divalent oxide MgO, 5 parts of tetravalent oxide TiO2 and 2 parts of CeO2 to 87 parts of alumina with a particle size of 0.5 μm, and mix.

[0077] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 50 minutes to obtain a mixture;

[0078] (3) Prepare a PVA solution with a concentration of 10 wt. and let it stand for 48 hours before use;

[0079] (4) The mixture from step (2), the PVA solution from step (3), water, and sodium polyacrylate are fed into a ball mill in a mass ratio of 17:30:53:0.01. After ball milling and dispersion for 6 hours, the mixture is discharged from the mill and left to stand for 48 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 17%.

[0080] (5) The ceramic flat plate membrane liquid is coated onto the clean support after being cleaned and dried. The coating is carried out by spraying, the spraying time is 10s, and the membrane thickness is about 32μm.

[0081] (6) Transfer the support with the coating liquid to an oven and dry it at 150°C for 10 hours to obtain the product.

[0082] (7) The product is placed in a high-temperature kiln, stacked in 5 pieces, and fired at 1330℃ to obtain a ceramic flat film.

[0083] Comparative Example 1

[0084] A method for preparing a ceramic flat sheet membrane includes the following steps:

[0085] (1) Prepare a methylcellulose solution with a concentration of 10 wt. and let it stand for 48 hours before use.

[0086] (2) Add the methylcellulose solution from step (1), water, 1μm alumina, MgO, CaO and polyacrylic acid in sequence to the ball mill in a mass ratio of 30:50:18:1:1:0.04. After ball milling and dispersion for 7 hours, let stand for 36 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 19.99%.

[0087] (3) The ceramic flat plate membrane liquid is coated onto the clean support after it has been cleaned and dried. The coating is carried out by spraying for 15 seconds, and the membrane thickness is about 40 μm.

[0088] (4) Transfer the support with the coating liquid to an oven and dry it at 150°C for 10 hours to obtain the product.

[0089] (5) The product is placed in a high-temperature kiln, stacked in 10 pieces, and fired at 1450℃ to obtain a ceramic flat film.

[0090] Comparative Example 2

[0091] A method for preparing a ceramic flat sheet membrane includes the following steps:

[0092] (1) Add 2 parts of divalent oxide MgO, 2 parts of CaO, 1 part of ZnO, 4 parts of tetravalent oxide SiO, and 1 part of CeO to 90 parts of alumina with a particle size of 2 μm, and mix.

[0093] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 30 minutes to obtain the mixture.

[0094] (3) Prepare a PVA solution with a concentration of 10 wt. and let it stand for 48 hours before use.

[0095] (4) The mixture from step (2), the PVA solution from step (3), water, and sodium polyacrylate were fed into a ball mill in a mass ratio of 20:30:50:0.05. After ball milling and dispersion for 6 hours, the mixture was discharged from the mill and allowed to stand for 48 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 19.99%.

[0096] (5) The ceramic flat plate membrane liquid is coated onto the clean support after being cleaned and dried. The coating is carried out by spraying, the spraying time is 15s, and the membrane thickness is about 40μm.

[0097] (6) Transfer the support with the coating liquid to an oven and dry it at 180°C for 8 hours to obtain the product.

[0098] (7) The product is placed in a high-temperature kiln, stacked in 10 pieces, and fired at 1430℃ to obtain a ceramic flat film.

[0099] Comparative Example 3

[0100] A method for preparing a ceramic flat sheet membrane includes the following steps:

[0101] (1) Prepare a PVA solution with a concentration of 10 wt. and let it stand for 48 hours before use.

[0102] (2) PVA solution, water, 2μm alumina, 5 parts of 3μm glass powder, 1 part of divalent oxide MgO, 1 part of CaO, 0.5 parts of ZnO, 2 parts of tetravalent oxide SiO2, 0.5 parts of CeO2, and sodium polyacrylate were added to the ball mill in sequence with a mass ratio of 30:50:18:1:0.2:0.2:0.1:0.4:0.1:0.05. After ball milling and dispersion for 6 hours, the mixture was discharged from the mill and allowed to stand for 48 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 19.99%.

[0103] (3) The ceramic flat plate membrane liquid is coated onto the clean support after being cleaned and dried. The coating is carried out by immersion, the immersion time is 8s, and the membrane thickness is about 18μm.

[0104] (4) Transfer the support with the coating liquid to an oven and dry it at 180°C for 8 hours to obtain the product.

[0105] (5) The product is placed in a high-temperature kiln, stacked in 10 pieces, and fired at 1300℃ to obtain a ceramic flat film.

[0106] Comparative Example 4

[0107] A method for preparing a ceramic flat sheet membrane includes the following steps:

[0108] (1) Add 3.5 parts of glass powder with a particle size of 1.8 μm, 2 parts of divalent oxide MgO, 2 parts of CaO, 1 part of CuO, 4 parts of tetravalent oxide MnO, and 2.5 parts of ZrO to 85 parts of alumina with a particle size of 0.9 μm, and mix.

[0109] (2) Place the powder mixed in step (1) into a V-type mixer and mix for 40 minutes to obtain a mixture.

[0110] (3) Prepare a PVA solution with a concentration of 8 wt.% and let it stand for 36 hours before use.

[0111] (4) The mixture from step (2), the PVA solution from step (3), water, and polyacrylic acid were fed into a ball mill in a mass ratio of 24:27:49:0.05. After ball milling and dispersion for 5 hours, the mixture was discharged from the mill and allowed to stand for 36 hours to obtain a ceramic flat sheet membrane liquid with a solid content of 23.99%.

[0112] (5) The ceramic flat plate membrane liquid is coated onto the clean support after being cleaned and dried. The coating is carried out by spraying, the spraying time is 10s, and the membrane thickness is about 43μm.

[0113] (6) Transfer the support with the coating liquid to an oven and dry it at 150°C for 10 hours to obtain the product.

[0114] (7) The product is placed in a high-temperature kiln, stacked in 5-10 pieces, and fired at 1330℃ to obtain a ceramic flat film.

[0115] The ceramic flat sheet membranes prepared in the above examples and comparative examples were tested for their water flux at 25°C according to GB / T 39717-2020. Their water contact angle was tested according to the following steps: after drying the samples, the contact angle of the membrane was tested at 25°C using a DSA100 contact angle meter, with the droplet volume controlled at 5 μL. Each sample was tested three times, and the average value was taken. The test results are shown in Table 1.

[0116] Table 1 Test Results

[0117]

[0118]

[0119] As can be seen from the table above, the modified ceramic flat sheet membranes prepared in Examples 1-4 of this invention exhibit better water flux and water contact angle compared to the unmodified ceramic flat sheet membrane in Comparative Example 1. Compared to Example 3, Comparative Example 2 shows a decrease in both water flux and water contact angle after removing the 3μm glass powder. Compared to Example 3, Comparative Example 3 shows a decrease in both water flux and water contact angle after mixing the PVA solution with other dry materials. Compared to Example 2, Comparative Example 4, by changing the ratio of the mixture, PVA solution, water, and dispersant, achieves a solid content as high as 23.999%, but the prepared ceramic flat sheet membrane has a lower water flux and a larger water contact angle.

[0120] The ceramic flat sheet membranes prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to pore size analysis, and the results are shown in Table 2.

[0121] Table 2. Aperture distribution results

[0122] project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Average pore size / μm 0.0978 0.1227 0.1557 0.0996 0.2037 0.2375 Most probable pore size / μm 0.0953 0.1185 0.1493 0.0974 0.1219 0.1443

[0123] Depend on Figure 1 As can be seen from Table 2, the pore size distribution diagram of Example 1 has only one peak and an extremely narrow distribution on the horizontal axis. The pore size distribution of the prepared ceramic flat sheet membrane shows that approximately 83% of the pores have a diameter of 0.0953 μm, which is very close to the average pore size of 0.0978 μm. Figure 2 As can be seen from Table 2, the pore size distribution diagram of Example 2 has only one peak and a narrow distribution on the horizontal axis. The pore size distribution of the prepared ceramic flat sheet membrane shows that approximately 84% of the pores have a diameter of 0.1185 μm, which is very close to the average pore size of 0.1227 μm. Figure 3 As can be seen from Table 2, the pore size distribution diagram of Example 3 has only one peak and an extremely narrow abscissa distribution. The pore size distribution of the prepared ceramic flat sheet membrane shows that approximately 82% of the pores have a diameter of 0.1493 μm, which is very close to the average pore size of 0.1557 μm. Figure 4 As can be seen from Table 2, the pore size distribution diagram of Example 4 shows only a distinct peak and a narrow distribution on the horizontal axis. The pore size distribution of the prepared ceramic flat sheet membrane has approximately 87% of the pore size distribution in the range of 0.0875μm-0.0974μm, which is very close to the average pore size of 0.0996μm. Therefore, it can be seen that the sample prepared by this invention has a narrow and uniform pore size distribution, resulting in high filtration accuracy and stable and reliable flux in practical applications.

[0124] Depend on Figure 5 As shown in Table 2, the pore size distribution diagram of Comparative Example 1 exhibits a distinct bimodal distribution, with one peak corresponding to an extremely wide range of abscissa distribution. The pore size distribution of the prepared ceramic flat sheet membrane ranges from 0.0739 μm to 0.6957 μm, and the most probable pore size of 0.1219 μm differs significantly from the average pore size of 0.2037 μm. Figure 6As shown in Table 2, the pore size distribution diagram of Comparative Example 2 also exhibits a clear bimodal distribution, with one of the peaks corresponding to an extremely wide range of abscissa distribution. The pore size distribution of the prepared ceramic flat sheet membrane is between 0.0717 μm and 0.7653 μm, and the most probable pore size of 0.1443 μm differs greatly from the average pore size of 0.2375 μm. Therefore, the pore size distribution of the ceramic flat sheet membranes prepared in Comparative Example 1 and Comparative Example 2 is extremely uneven, making it difficult to guarantee filtration accuracy in practical applications. The membrane layer is easily and rapidly clogged by pollutants of various sizes, resulting in a rapid decline in flux, which is difficult to recover.

[0125] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. A method of preparing a ceramic flat sheet membrane layer solution, characterized by: The method comprises the following steps: (1) adding glass powder, divalent oxide and tetravalent oxide into alumina with a particle size of 1-2 μm and mixing; The ratio of each substance is calculated by weight fraction: 80-90 parts of alumina, 1-10 parts of divalent oxide, 1-10 parts of tetravalent oxide and 1-5 parts of glass powder; The divalent oxide is one or more of MgO, CaO, BaO, CuO and ZnO; The tetravalent oxide is one or more of TiO2, MnO2, ZrO2, SiO2 and CeO2; (2) placing the mixed powder in step (1) in a V-shaped mixer and mixing for 30-50 min to obtain a mixture; (3) preparing a methyl cellulose solution or a PVA solution and standing for use; (4) putting the mixture in step (2), the methyl cellulose solution or the PVA solution in step (3), water and a dispersant into a ball mill, ball-milling and dispersing for 4-6 h, standing to obtain a ceramic flat plate membrane layer liquid with a solid content of 15%-20%.

2. The method of claim 1, wherein: The particle size of the glass powder in step (1) is 1-3 μm.

3. The method of claim 1, wherein: The concentration of the methyl cellulose solution or the PVA solution in step (3) is 5wt.%-10wt.% and the standing time is 24-48 h.

4. The method of claim 1, wherein: The mass ratio of the mixture in step (2), the methyl cellulose solution or the PVA solution in step (3), water and the dispersant in step (4) is (5:30:55:0.4)-(20:30:50:0.5).

5. The method of claim 1, wherein: The dispersant is polyacrylate.

6. A ceramic flat sheet membrane layer solution characterized by: The ceramic flat plate membrane layer liquid is prepared by the method of any one of claims 1-5.

7. Use of the ceramic flat sheet membrane layer solution according to claim 6, characterized in that The ceramic flat plate membrane layer liquid is used for the preparation of a ceramic flat plate membrane, which comprises the following steps: (1) coating the ceramic flat plate membrane layer liquid on a support by spraying or dipping, and the thickness of the membrane layer is 10-50 μm; (2) drying the support coated with the membrane layer liquid at 120-180 ℃ for 8-12 h to obtain a product; (3) firing the product at 1300-1350 ℃ to obtain a ceramic flat plate membrane.

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