A method for preparing a high-flux ceramic membrane

Abstract

The application provides a preparation method of a high-flux ceramic membrane to solve the problems of a large number of sintering times and high production cost of a flat ceramic membrane with a sandwich structure, and the method comprises the following steps: sintering a ceramic membrane support; using alpha-aluminum oxide B as a transition layer skeleton raw material, and adding a second adhesive, a second sintering aid, a second dispersing agent and a polyvinyl alcohol aqueous solution with a mass concentration of 2-5% to prepare a transition layer slurry; forming a water-resistant transition layer on the surface of the ceramic membrane support; preparing a separation layer slurry; drying and sintering to obtain a high-flux ceramic membrane. The water-resistant transition layer is formed on the porous ceramic membrane support, the separation layer slurry can be coated on the transition layer without sintering, then drying and sintering are performed to reduce the sintering times, improve the production efficiency and reduce the production cost, and the prepared flat ceramic membrane has a high filtration flux.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a method for preparing a high-flux ceramic membrane. Background Technology

[0002] In the field of membrane separation, porous inorganic ceramic membrane elements have been widely used and rapidly developed in recent years due to their advantages such as high temperature resistance, chemical corrosion resistance, high mechanical strength after sintering, recyclability and long service life.

[0003] Currently, there are two main structural forms of flat ceramic membranes on the market: a "sandwich" structure consisting of a porous ceramic substrate, a transition layer, and a separation layer, and a two-layer structure consisting of a porous ceramic substrate and a separation layer.

[0004] Most two-layer flat-plate ceramic membranes form the separation layer directly by sintering on a porous ceramic substrate. Therefore, the average pore size of the porous ceramic substrate is generally small. This results in the porous ceramic substrate having high permeation resistance during filtration, which in turn leads to a low pure water flux of general flat-plate ceramic membranes and a low membrane operating flux in commercial applications.

[0005] The "sandwich" structure of the flat-plate ceramic membrane allows for a large pore size in the porous ceramic substrate, unaffected by the particle size of the separation layer material, resulting in low permeation resistance and high pure water flux during filtration. However, the preparation method of the "sandwich" structure flat-plate ceramic membrane requires multiple sintering processes, leading to high production costs. Summary of the Invention

[0006] This invention addresses the problem of high production costs and numerous sintering steps in existing "sandwich" structure flat ceramic membranes by providing a method for preparing a high-flux ceramic membrane. In this method, a water-resistant transition layer is formed on a porous ceramic membrane support. This transition layer can be coated with a separation layer slurry without sintering, followed by drying and firing. This reduces the number of sintering steps required to manufacture the "sandwich" structure flat ceramic membrane, improving production efficiency and reducing production costs. Furthermore, the resulting flat ceramic membrane exhibits lower permeation resistance due to the larger pore size on the ceramic membrane support, thus demonstrating higher filtration flux.

[0007] The technical solution adopted in this invention is:

[0008] A method for preparing a high-flux ceramic membrane includes the following steps:

[0009] Step S1: Using α-alumina A as the support framework material, a ceramic film support is sintered; the average particle size of the α-alumina A is 3~50μm.

[0010] Step S2: Using α-alumina B as the transition layer skeleton material, supplemented with a second binder, a second sintering aid, a second dispersant, and a 2-5% (w / w) polyvinyl alcohol aqueous solution, a transition layer slurry with a solid concentration of 10-30% is prepared and passed through a 40-mesh sieve for later use; the average particle size of the α-alumina B is 2-10 μm; the second binder is one or more of polyester-based binder, vinyl acetate-based binder, vilan gum, and silica sol; the second sintering aid is one or more of glass powder and feldspar; the second dispersant is one or more of polycarboxylate and polyacrylate.

[0011] Step S3: Apply the transition layer slurry to the surface of the ceramic membrane support by spraying or brushing, and dry at 150~200℃ for 2~6 hours to form a water-resistant transition layer on the surface of the ceramic membrane support.

[0012] Step S4: Using α-alumina C as the framework material for the separation layer, prepare the separation layer slurry; the average particle size of the α-alumina C is 1 μm;

[0013] Step S5: Apply the separation layer slurry to the transition layer by spraying or brushing, dry, and sinter to obtain a high-throughput ceramic membrane.

[0014] Furthermore, in step S1, the specific process of firing the ceramic film support using α-alumina A as the support framework material includes:

[0015] Step S11: α-alumina A is the raw material for the support skeleton. The raw material for the support skeleton, as well as the pore-forming agent, the first binder, the lubricant and the first sintering aid are mixed in a high-speed mixer according to the formula to obtain the dry powder of the support.

[0016] In step S12, the dry powder of the support body and a polyvinyl alcohol aqueous solution with a mass concentration of 2-5% are kneaded evenly in a kneader, then vacuum-kneaded by a vacuum pumice machine, and finally aged in a sealed container under constant temperature and humidity conditions for 24-48 hours.

[0017] Step S13: The aged mud is extruded by an extruder to form a support blank;

[0018] Step S14: After the support blank is dried, it is sintered at 1400~1500℃ for 2~3 hours to obtain the ceramic film support.

[0019] Further, the α-alumina A includes α-alumina A1 with an average particle size of 10~50 μm and α-alumina A2 with an average particle size of 3~10 μm;

[0020] And / or, the pore-forming agent is one or more of starch and graphite powder, with an average particle size of 0.5~3μm;

[0021] And / or, the first adhesive is one or more of cellulose, xanthodextrin, polyvinyl alcohol, and gum arabic;

[0022] And / or, the lubricant is one or more of tung oil, oleic acid, glycerin, and polyethylene glycol;

[0023] And / or, the first sintering aid is one or more of kaolin, clay, feldspar, and glass powder.

[0024] Further, in step S11, the weight ratio of α-alumina Al to α-alumina A2 in the support skeleton material is 2.5~3:1;

[0025] And / or, the weight of the pore-forming agent is 1 to 10% of the weight of the support skeleton material;

[0026] And / or, the weight of the first adhesive is 1 to 5% of the weight of the support skeleton material;

[0027] And / or, the weight of the lubricant is 2-6% of the weight of the support skeleton material;

[0028] And / or, the weight of the first sintering aid is 1 to 4% of the weight of the support skeleton material.

[0029] Furthermore, in step S11, the raw material of the support skeleton also includes calcined kaolin with an average particle size of 2~3μm; the weight of the calcined kaolin is 4~6% of the sum of the weights of α-alumina A1 and α-alumina A2.

[0030] Furthermore, in step S2, the transition layer framework material further includes titanium dioxide and clay or kaolin; the weight ratio of titanium dioxide to clay or kaolin is 1:1~5; the total weight of titanium dioxide and clay or kaolin is 5~17% of the weight of α-alumina B;

[0031] And / or, the weight of the second adhesive is 5-15% of the weight of the transition layer skeleton material;

[0032] And / or, the weight of the second sintering aid is 1 to 5% of the weight of the transition layer skeleton material;

[0033] And / or, the weight of the second dispersant is 0.1 to 0.3% of the weight of the transition layer skeleton material.

[0034] Furthermore, in step S4, the specific process of preparing the separation layer slurry using α-alumina C as the framework material for the separation layer includes:

[0035] Step S41: Using α-alumina C as the separation layer skeleton material, the separation layer skeleton material, the third binder, the third sintering aid, the third dispersant and water are mixed in a ball mill according to the formula to prepare a slurry with a solid concentration of 10~12%.

[0036] Step S42: Filter the mixture through a 40-mesh sieve to obtain the separation layer slurry.

[0037] Further, in step S41, the third adhesive is a polyvinyl alcohol aqueous solution with a mass concentration of 2-5%;

[0038] And / or, the third sintering aid is talc;

[0039] And / or, the third dispersant is a water-soluble acrylic resin.

[0040] Further, in step S41, the weight of the third adhesive is 0.3~0.5% of the weight of the separation layer skeleton material;

[0041] And / or, the weight of the third sintering aid is 0.1~0.2% of the weight of the separation layer skeleton raw material;

[0042] And / or, the weight of the third dispersant is 0.3 to 0.5% of the weight of the separation layer skeleton material.

[0043] Furthermore, in step S5, the drying process involves drying at 110~120℃ for 1~3 hours;

[0044] And / or, during sintering, hold at 1100~1300℃ for 2~3 hours.

[0045] The beneficial effects of this invention are:

[0046] This invention provides a method for preparing a high-throughput ceramic membrane, comprising the following steps: Step S1, using α-alumina A as the support skeleton material, a ceramic membrane support is sintered; Step S2, using α-alumina B as the transition layer skeleton material, supplemented with a second binder, a second sintering aid, a second dispersant, and a 2-5% (w / w) polyvinyl alcohol aqueous solution, a transition layer slurry with a solid concentration of 10-30% is prepared, and then passed through a 40-mesh sieve for later use; Step S3, the transition layer slurry is coated onto the surface of the ceramic membrane support by spraying or brushing, and dried at 150-200℃ for 2-6 hours to form a water-resistant transition layer on the surface of the ceramic membrane support; Step S4, using α-alumina C as the separation layer skeleton material, a separation layer slurry is prepared; Step S5, the separation layer slurry is coated onto the transition layer by spraying or brushing, dried, and sintered to obtain a high-throughput ceramic membrane. The preparation method of this invention, by redesigning the composition of the transition layer, uses α-alumina B as the framework material for the transition layer, along with a second binder, a second sintering aid, and a second dispersant. The resulting transition layer exhibits water resistance; when an aqueous separation layer slurry is coated onto the transition layer, it will not absorb water and be damaged, nor will it separate from the ceramic membrane support after absorbing water, thus ensuring the overall structural stability of the ceramic membrane. Furthermore, the preparation method of this invention eliminates the need for separate firing of the transition layer, reducing the sintering process from three stages to two, effectively simplifying the preparation process, lowering the cost of ceramic membrane production, significantly improving production efficiency, and resulting in a clear competitive advantage. Finally, in existing two-layer flat ceramic membranes, because the raw materials used in the membrane layers have very small particle sizes, the substrate pore size cannot be too large, otherwise, permeation blockage will occur, leading to very low flux. However, if the substrate pore size is too small, the filtration pressure will be too high. In this invention, a three-layer structure consisting of a separation layer, a transition layer, and a ceramic membrane support is still used. The water-resistant transition layer plays a crucial role in connecting the two layers. The ceramic membrane support can be designed with a large pore size to achieve low permeation resistance, thereby enabling the ceramic membrane to exhibit high filtration flux. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a SEM image of the cross-section of the ceramic membrane in Example 1.

[0049] Figure 2 This is a SEM image of the cross-section of the ceramic membrane in Example 6.

[0050] Figure 3 This is a SEM image of the cross-section of the ceramic membrane in Example 7. Detailed Implementation

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0052] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0053] The embodiments of the invention will now be described in detail with reference to the accompanying drawings.

[0054] This embodiment provides a method for preparing a high-flux ceramic membrane, including the following steps:

[0055] Step S1: Using α-alumina A as the support skeleton material, a ceramic film support is sintered.

[0056] The specific process includes:

[0057] Step S11: α-alumina A is the raw material for the support skeleton. The raw material for the support skeleton, as well as the pore-forming agent, the first binder, the lubricant and the first sintering aid are mixed in a high-speed mixer according to the formula to obtain the dry powder of the support.

[0058] The support skeleton material comprises α-alumina A1 with an average particle size of 10-50 μm and α-alumina A2 with an average particle size of 3-10 μm; the weight ratio of α-alumina A1 to α-alumina A2 in the support skeleton material is 2.5-3:1. Further, the support skeleton material also includes calcined kaolin with an average particle size of 2-3 μm; the weight of the calcined kaolin is 4-6% of the sum of the weights of α-alumina A1 and α-alumina A2.

[0059] The pore-forming agent is one or more of starch and graphite powder, with an average particle size of 0.5~3μm; the weight of the pore-forming agent is 1~10% of the weight of the support skeleton material.

[0060] The first adhesive is one or more of cellulose, dextrin, polyvinyl alcohol or gum arabic; the weight of the first adhesive is 1 to 5% of the weight of the support skeleton material.

[0061] The lubricant is one or more of tung oil, oleic acid, glycerin, and polyethylene glycol; the weight of the lubricant is 2 to 6% of the weight of the support skeleton material.

[0062] The first sintering aid is one or more of kaolin, clay, feldspar, and glass powder; the weight of the first sintering aid is 1 to 4% of the weight of the raw material of the support skeleton.

[0063] In step S12, the dry powder of the support body and an appropriate amount of polyvinyl alcohol aqueous solution with a mass concentration of 2-5% are placed in a kneader and kneaded evenly. Then, the mixture is vacuum-kneaded by a vacuum pumice machine and finally aged in a sealed container under constant temperature and humidity conditions for 24-48 hours.

[0064] In step S13, the aged mud is extruded by an extruder to form a support blank.

[0065] Step S14: After the support blank is dried, it is sintered at 1400~1500℃ for 2~3 hours to obtain the ceramic film support.

[0066] Step S2: Using α-alumina B as the transition layer skeleton material, supplemented with a second binder, a second sintering aid, a second dispersant and a polyvinyl alcohol aqueous solution with a mass concentration of 2-5%, a transition layer slurry with a solid concentration of 10-30% is prepared and passed through a 40-mesh sieve for later use.

[0067] The average particle size of α-alumina B in the transition layer framework material is 2~10 μm. Further, the transition layer framework material also includes titanium dioxide and clay or kaolin; the weight ratio of titanium dioxide to clay or kaolin is 1:1~5; the total weight of titanium dioxide and clay or kaolin is 5~17% of the weight of α-alumina B.

[0068] The second adhesive is one or more of polyester-based adhesive, vinyl acetate-based adhesive, vilan gum, and silica sol; the weight of the second adhesive is 5 to 15% of the weight of the transition layer skeleton material.

[0069] The second sintering aid is one or more of glass powder and feldspar; the weight of the second sintering aid is 1 to 5% of the weight of the transition layer skeleton material.

[0070] The second dispersant is one or more of polycarboxylate and polyacrylate; the weight of the second dispersant is 0.1 to 0.3% of the weight of the transition layer skeleton material.

[0071] Step S3: Apply the transition layer slurry to the surface of the ceramic membrane support by spraying or brushing, and dry it at 150~200℃ for 2~6 hours to form a water-resistant transition layer on the surface of the ceramic membrane support.

[0072] Step S4: Prepare the separation layer slurry using α-alumina C as the skeleton material of the separation layer.

[0073] The specific process includes:

[0074] Step S41: Using α-alumina C as the separation layer skeleton material, the separation layer skeleton material, the third binder, the third sintering aid, the third dispersant and water are mixed in a ball mill according to the formula to prepare a slurry with a solid concentration of 10~12%.

[0075] The average particle size of α-alumina C in the separation layer skeleton material is 1 μm.

[0076] The third adhesive is a polyvinyl alcohol aqueous solution with a mass concentration of 2-5%; the weight of the third adhesive is 0.3-0.5% of the weight of the separation layer skeleton raw material.

[0077] The third sintering aid is talc powder; the weight of the third sintering aid is 0.1~0.2% of the weight of the separation layer skeleton raw material.

[0078] The third dispersant is a water-soluble acrylic resin; the weight of the third dispersant is 0.3 to 0.5% of the weight of the separation layer skeleton raw material.

[0079] Step S42: Filter the mixture through a 40-mesh sieve to obtain the separation layer slurry.

[0080] Step S5: Apply the separation layer slurry to the transition layer by spraying or brushing, dry at 110~120℃ for 1~3 hours, and then calcine at 1100~1300℃ for 2~3 hours to obtain a high-flux ceramic membrane.

[0081] It should be noted that the high-throughput ceramic membrane preparation method provided in this embodiment can be used for flat ceramic membrane processing and is also applicable to ceramic tube membrane processing.

[0082] The following explanation uses the preparation of flat ceramic membranes as an example.

[0083] Example 1

[0084] Preparation of ceramic membrane support:

[0085] α-alumina A1 (average particle size 30μm, dosage 70kg), α-alumina A2 (average particle size 5μm, dosage 25kg), and calcined kaolin (average particle size 5000 mesh, dosage 5kg) were mixed together. Then, starch (dosage 2kg), tung oil (2.5kg), gum arabic (dosage 2.5kg), and clay (dosage 3kg) were added and mixed evenly using a high-speed mixer. The mixture was then placed in a kneader, and an appropriate amount of PVA aqueous solution with a solid content of 5% was added for kneading. The kneaded mud was then vacuum-kneaded. The clay was machine-mixed; after mixing, it was placed in a sealed container and aged for 48 hours under constant temperature and humidity conditions (temperature 25℃, humidity 80%); after aging, the support body blank was prepared by extrusion molding process, with an extrusion temperature of 25℃ and an extrusion pressure of 8 MPa; after molding, it was placed in a 110℃ oven for drying for 4 hours; after drying, the ceramic membrane blank was sintered at 1500℃ for 3 hours with a heating rate of 5℃ / min, to obtain a flat ceramic membrane support with an average pore size of 3.5μm and a porosity of 37%, and the three-point flexural strength of the ceramic membrane support was >50 MPa.

[0086] Transition layer preparation:

[0087] α-alumina particles B (average particle size 5 μm, dosage 93 kg), titanium dioxide (dosage 2 kg), and kaolin (dosage 5 kg) were mixed evenly. Then, polyester-based binder (dosage 5 kg), silica sol (dosage 2 kg), glass powder (dosage 2 kg), sodium polycarboxylate (dosage 0.2 kg), and an appropriate amount of 5% PVA aqueous solution were added and mixed evenly. The solid content of the slurry system was 25%. After passing through a 40-mesh sieve, a transition layer slurry was obtained. This slurry was then coated onto the prepared ceramic membrane support and dried at 160℃ for 6 hours to obtain a water-resistant transition layer, resulting in a ceramic membrane support-transition layer bilayer structure.

[0088] Separation layer preparation:

[0089] α-alumina C (average particle size 1 μm, 100 kg), water-soluble acrylic resin (0.5 kg), talc powder (0.1 kg), 5% PVA aqueous solution (0.5 kg), and an appropriate amount of water were ground and dispersed in a ball mill to prepare a slurry solution with a solid content of 10%. After passing through a 40-mesh sieve, a separation layer slurry was obtained. The separation layer slurry was then coated onto the prepared ceramic membrane support-transition layer double-layer structure by spraying, dried at 110℃ for 2 h, and then sintered at 1300℃ for 3 h to obtain a three-layer flat ceramic membrane.

[0090] Example 2

[0091] Preparation of ceramic membrane support:

[0092] α-alumina A1 (average particle size 30μm, dosage 70kg), α-alumina A2 (average particle size 5μm, dosage 25kg), and calcined kaolin (average particle size 5000 mesh, dosage 5kg) were mixed together. Then, starch (dosage 2kg), tung oil (2.5kg), gum arabic (dosage 2.5kg), and clay (dosage 3kg) were added and mixed evenly using a high-speed mixer. The mixture was then placed in a kneader, and an appropriate amount of PVA aqueous solution with a solid content of 5% was added for kneading. The kneaded mud was then vacuum-kneaded. The clay was machine-mixed; after mixing, it was placed in a sealed container and aged for 48 hours under constant temperature and humidity conditions (temperature 25℃, humidity 80%); after aging, the support body blank was prepared by extrusion molding process, with an extrusion temperature of 25℃ and an extrusion pressure of 8 MPa. After molding, it was placed in a 110℃ oven for drying for 4 hours; after drying, the ceramic membrane blank was sintered at 1500℃ for 3 hours with a heating rate of 5℃ / min, to obtain a flat ceramic membrane support with an average pore size of 3.5μm and a porosity of 37%. The three-point flexural strength of the ceramic membrane support was >50 MPa.

[0093] Transition layer preparation:

[0094] α-alumina particles B (average particle size 5 μm, dosage 93 kg), titanium dioxide (dosage 2 kg), and kaolin (dosage 5 kg) were mixed evenly. Then, vinyl acetate-based binder (dosage 5 kg), silica sol (dosage 1.5 kg), vilan gum (dosage 0.5 kg), glass powder (dosage 2 kg), sodium polycarboxylate (dosage 0.2 kg), and an appropriate amount of 5% PVA aqueous solution were added and mixed evenly. The solid content of the slurry system was 25%. After passing through a 40-mesh sieve, a transition layer slurry was obtained. This slurry was then coated onto the prepared ceramic membrane support and dried at 160℃ for 6 hours to obtain a water-resistant transition layer, resulting in a ceramic membrane support-transition layer bilayer structure.

[0095] Separation layer preparation:

[0096] α-alumina C (average particle size 1 μm, 100 kg), water-soluble acrylic resin (0.5 kg), talc powder (0.1 kg), 5% PVA aqueous solution (0.5 kg), and an appropriate amount of water were ground and dispersed in a ball mill to prepare a slurry solution with a solid content of 10%. After passing through a 40-mesh sieve, a separation layer slurry was obtained. The separation layer slurry was then coated onto the prepared ceramic membrane support-transition layer double-layer structure by spraying, dried at 110℃ for 2 h, and then sintered at 1300℃ for 3 h to obtain a three-layer flat ceramic membrane.

[0097] Example 3

[0098] Preparation of ceramic membrane support:

[0099] α-alumina A1 (average particle size 30μm, dosage 70kg), α-alumina A2 (average particle size 5μm, dosage 25kg), and calcined kaolin (average particle size 5000 mesh, dosage 5kg) were mixed together. Then, starch (dosage 2kg), tung oil (2.5kg), gum arabic (dosage 2.5kg), and clay (dosage 3kg) were added and mixed evenly using a high-speed mixer. The mixture was then placed in a kneader, and an appropriate amount of PVA aqueous solution with a solid content of 5% was added for kneading. The kneaded mud was then vacuum-kneaded. The clay was machine-mixed; after mixing, it was placed in a sealed container and aged for 48 hours under constant temperature and humidity conditions (temperature 25℃, humidity 80%); after aging, the support body blank was prepared by extrusion molding process, with an extrusion temperature of 25℃ and an extrusion pressure of 8 MPa. After molding, it was placed in a 110℃ oven for drying for 4 hours; after drying, the ceramic membrane blank was sintered at 1500℃ for 3 hours with a heating rate of 5℃ / min, to obtain a flat ceramic membrane support with an average pore size of 3.5μm and a porosity of 37%. The three-point flexural strength of the ceramic membrane support was >50 MPa.

[0100] Transition layer preparation:

[0101] α-alumina particles B (average particle size 5 μm, dosage 93 kg), titanium dioxide (dosage 2 kg), and kaolin (dosage 5 kg) were mixed evenly. Then, polyester-based adhesive (dosage 2.5 kg), vinyl acetate-based adhesive (dosage 2.5 kg), silica sol (dosage 1.5 kg), glass powder (dosage 2 kg), sodium polycarboxylate (dosage 0.2 kg), and an appropriate amount of 5% PVA aqueous solution were added and mixed evenly. The solid content of the slurry system was 25%. After passing through a 40-mesh sieve, a transition layer slurry was obtained. This slurry was then coated onto the prepared ceramic membrane support and dried at 160℃ for 6 hours to obtain a water-resistant transition layer, resulting in a ceramic membrane support-transition layer bilayer structure.

[0102] Separation layer preparation:

[0103] α-alumina C (average particle size 1 μm, 100 kg), water-soluble acrylic resin (0.5 kg), talc powder (0.1 kg), 5% PVA aqueous solution (0.5 kg), and an appropriate amount of water were ground and dispersed in a ball mill to prepare a slurry solution with a solid content of 10%. After passing through a 40-mesh sieve, a separation layer slurry was obtained. The separation layer slurry was then coated onto the prepared ceramic membrane support-transition layer double-layer structure by spraying, dried at 110℃ for 2 h, and then sintered at 1300℃ for 3 h to obtain a three-layer flat ceramic membrane.

[0104] Example 4

[0105] Preparation of ceramic membrane support:

[0106] α-Alumina A1 (average particle size 30μm, dosage 70kg) and α-Alumina A2 (average particle size 5μm, dosage 35kg) were mixed together. Then, starch (dosage 2kg), tung oil (2.5kg), gum arabic (dosage 2.5kg), and clay (dosage 3kg) were added and mixed thoroughly using a high-speed mixer. The mixture was then placed in a kneader, and an appropriate amount of 5% PVA aqueous solution was added for kneading. The kneaded mud was then kneaded using a vacuum plow. After kneading, the mixture was placed in a dense... The ceramic membrane was aged in a closed container under constant temperature and humidity conditions (temperature 25℃, humidity 80%) for 48 hours. After aging, the support body blank was prepared by extrusion molding at a temperature of 25℃ and a pressure of 8 MPa. After molding, it was placed in an oven at 110℃ and dried for 4 hours. After drying, the ceramic membrane blank was sintered at 1500℃ for 3 hours at a heating rate of 5℃ / min to obtain a flat ceramic membrane support with an average pore size of 3.5μm and a porosity of 35%. The three-point flexural strength of the ceramic membrane support was >50 MPa.

[0107] Transition layer preparation:

[0108] α-alumina particles B (average particle size 5 μm, dosage 100 kg) were mixed with polyester-based adhesive (dosage 5 kg), silica sol (dosage 2 kg), glass powder (dosage 2 kg), sodium polycarboxylate (dosage 0.2 kg), and an appropriate amount of 5% PVA aqueous solution. The solid content of the slurry system was 25%. After passing through a 40-mesh sieve, a transition layer slurry was obtained. This slurry was then coated onto the prepared ceramic membrane support and dried at 160℃ for 6 hours to obtain a water-resistant transition layer, resulting in a ceramic membrane support-transition layer bilayer structure.

[0109] Separation layer preparation:

[0110] α-alumina C (average particle size 1 μm, 100 kg), water-soluble acrylic resin (0.5 kg), talc powder (0.1 kg), 5% PVA aqueous solution (0.5 kg), and an appropriate amount of water were ground and dispersed in a ball mill to prepare a slurry solution with a solid content of 10%. After passing through a 40-mesh sieve, a separation layer slurry was obtained. The separation layer slurry was then coated onto the prepared ceramic membrane support-transition layer double-layer structure by spraying, dried at 110℃ for 2 h, and then sintered at 1300℃ for 3 h to obtain a three-layer flat ceramic membrane.

[0111] Example 5

[0112] Preparation of ceramic membrane support:

[0113] α-alumina A1 (average particle size 30μm, dosage 70kg), α-alumina A2 (average particle size 5μm, dosage 25kg), and calcined kaolin (average particle size 5000 mesh, dosage 5kg) were mixed together. Then, starch (dosage 2kg), tung oil (2.5kg), gum arabic (dosage 2.5kg), and clay (dosage 3kg) were added and mixed evenly in a high-speed mixer. The mixture was then placed in a kneader, and an appropriate amount of PVA aqueous solution with a solid content of 5% was added for kneading. The kneaded mud was then vacuum-kneaded. The clay was machine-mixed and then placed in a sealed container for aging under constant temperature and humidity conditions (temperature 25℃, humidity 80%) for 48 hours. After aging, the support body blank was prepared by extrusion molding at a temperature of 25℃ and a pressure of 8 MPa. After molding, it was placed in a 110℃ oven for drying for 4 hours. After drying, the support body blank was sintered at 1500℃ for 3 hours at a heating rate of 5℃ / min to obtain a flat ceramic membrane support with an average pore size of 3.5μm and a porosity of 37%. The three-point flexural strength of the ceramic membrane support was >50 MPa.

[0114] Transition layer preparation:

[0115] α-alumina particles B (average particle size 5 μm, dosage 93 kg), titanium dioxide (dosage 2 kg), and kaolin (dosage 5 kg) were mixed evenly. Then, polyester-based binder (dosage 10 kg), silica sol (dosage 4 kg), glass powder (dosage 2 kg), sodium polycarboxylate (dosage 0.2 kg), and an appropriate amount of 5% PVA aqueous solution were added and mixed evenly. The solid content of the slurry system was 30%. After passing through a 40-mesh sieve, it was coated on the prepared ceramic membrane support and dried at 160℃ for 6 hours to obtain a water-resistant transition layer, thus obtaining a ceramic membrane support-transition layer bilayer structure.

[0116] Separation layer preparation:

[0117] α-alumina C (average particle size 1 μm, 100 kg), water-soluble acrylic resin (0.5 kg), talc powder (0.1 kg), 5% PVA aqueous solution (0.5 kg), and an appropriate amount of water were ground and dispersed in a ball mill to prepare a slurry solution with a solid content of 10%. After passing through a 40-mesh sieve, a separation layer slurry was obtained. The separation layer slurry was then coated onto the prepared ceramic membrane support-transition layer double-layer structure by spraying, dried at 110℃ for 2 h, and then sintered at 1300℃ for 3 h to obtain a three-layer flat ceramic membrane.

[0118] Compare with Example 1

[0119] Commercially available double-layer ceramic flat sheet membrane.

[0120] Compare with Example 2

[0121] The difference from Example 1 is that the transition layer is composed of: α-alumina particles (average particle size 5 μm, amount 100 kg), polyvinyl alcohol (amount 1 kg) and ammonium polyacrylate (0.9 kg).

[0122] In Examples 1-3 and Comparative Example 2, water resistance tests were conducted after the transition layer dried. The water resistance tests were performed using a oscillating tube water spray test apparatus.

[0123] Test equipment: Oscillating tube type water spray and splash test device.

[0124] Sample placement: Select a DN32 oscillating tube, and after drying, place the sample with the prepared transition layer on the sample stage below the diameter of the oscillating tube. The distance between the sample and the water spray nozzle of the oscillating tube should be 200mm, and the sample stage should not rotate.

[0125] Test conditions: The diameter of the water spray nozzle on the oscillating tube is 1 mm, the outlet flow velocity of each nozzle is 8 m / s, the oscillating tube swings back and forth during the water spraying process, the swing angle covers the entire sample, and the swing period is 5 s. The water resistance test is performed for 1 minute. After the test, the sample is dried and then proceeds to the separation membrane coating process.

[0126] The water resistance test results of the transition layer in Examples 1-5 are shown in Table 1 below.

[0127] Table 1. Water resistance test results in Examples 1-5

[0128] Example 1 The transition layer is basically intact, with no obvious swelling, and has not separated from the ceramic membrane support. Example 2 The transition layer is basically intact, with no obvious swelling, and has not separated from the ceramic membrane support. Example 3 The transition layer is basically intact, with no obvious swelling, and has not separated from the ceramic membrane support. Example 4 The transition layer is basically intact, with no obvious swelling, and has not separated from the ceramic membrane support. Example 5 The transition layer is basically intact, with no obvious swelling, and has not separated from the ceramic membrane support. Compare with Example 1 / Compare with Example 2 The transition layer was partially damaged, exposing the ceramic membrane support.

[0129] Visual observation shows that after 1 minute of water spraying, the transition layers in Examples 1-5 remained largely intact, without significant swelling or separation from the ceramic membrane support. This indicates that the transition layers in this example possess a certain degree of water resistance, preventing damage or separation from the ceramic membrane support during subsequent application of the water-containing separation layer slurry. In other words, even when the water content of the separation layer slurry is greater than that of the transition layer slurry, the transition layer in this example remains unaffected by the separation layer slurry, ensuring the integrity of the transition layer.

[0130] The performance test results of the ceramic membranes obtained by drying and coating the separation layer slurry after the transition layer in Examples 1-3 passed the water resistance test, and the ceramic membranes obtained by directly coating the separation layer slurry in Examples 1-5 without water resistance testing are shown in Table 2.

[0131] Table 2 Performance indicators of ceramic membranes in Examples 1-5

[0132] Example 1 3.5 0.82 25.89 0.1 20-40 4352 Example 1 (Water Resistance Test) 3.5 0.85 23.75 0.1 20-40 4378 Example 2 3.5 0.6 44 0.1 20-40 3800 Example 2 (Water Resistance Test) 3.5 0.6 42 0.1 20-40 3900 Example 3 3.5 0.7 32 0.1 20-40 4198 Example 3 (Water Resistance Test) 3.5 0.7 30 0.1 20-40 4385 Example 4 3.5 0.57 25 0.1 20-40 3700 Example 5 3.5 0.55 26 0.1 20-40 3600 Compare with Example 1 0.5 / / 0.1 20-40 2000

[0133] As can be seen from the test data in Table 2, after the transition layer prepared in this embodiment was subjected to a oscillating tube water spray test, dried, and then the separation layer was sprayed, the thickness of the transition layer did not change significantly after sintering, and the pore size of the transition layer was almost the same. After coating, the pore size of the separation layer was around 0.1 μm, and the pure water flux was similar. That is, in this embodiment, when the water-containing separation layer slurry was coated on the transition layer, it did not affect the transition layer, ensuring the stability of the overall structure of the ceramic membrane and maintaining a high filtration flux. In other words, the preparation method in this embodiment, by redesigning the composition of the transition layer, using α-alumina B as the transition layer skeleton material, as well as the second binder, the second sintering aid, and the second dispersant, etc., the prepared transition layer has water resistance. After the water-containing separation layer slurry is coated on the transition layer, it will not cause the transition layer to absorb water and be damaged, or the transition layer will separate from the ceramic membrane support after absorbing water, thereby ensuring the stability of the overall structure of the ceramic membrane. Meanwhile, in this embodiment, the transition layer does not need to be fired separately, reducing the sintering process from three times to two times. This effectively simplifies the manufacturing process, reduces the cost of ceramic membrane production, significantly improves production efficiency, and gives the product a clear competitive advantage. Finally, in existing two-layer flat ceramic membranes, the particle size of the raw materials used in the membrane layers is very small, so the substrate pore size cannot be too large, otherwise it will cause permeation blockage and result in very low flux. However, if the substrate pore size is too small, the pressure during filtration will be too high. This embodiment still uses a three-layer structure consisting of a separation layer, a transition layer, and a ceramic membrane support. The water-resistant transition layer plays a crucial role in connecting the layers, and the ceramic membrane support can be designed with a larger pore size to achieve lower permeation resistance, allowing the ceramic membrane to exhibit higher filtration flux.

[0134] Taking the ceramic membrane in Example 1 as an example (water resistance test was performed), its cross-sectional scanning electron microscope image is attached. Figure 1 As shown in the attached document. Figure 1 As shown, from top to bottom, the layers are a separation layer, a transition layer, and a ceramic membrane support. The separation layer has a thickness of 24.93 μm, and the transition layer has a thickness of 23.75 μm. The ceramic membrane support has relatively large internal porosity, resulting in low permeation resistance. The pore size of the transition layer falls between that of the separation layer and the ceramic membrane support, effectively bridging the gap between them and preventing the separation layer material from affecting the pores of the ceramic membrane support, thus ensuring a high filtration flux for the ceramic membrane.

[0135] Examples 6 and 7 use the same ceramic membrane composition as in Example 1, but differ in that the number of coats of the transition layer slurry and the separation layer slurry are changed, i.e., the thickness of the transition layer and the separation layer is altered to obtain the ceramic membrane. Scanning electron micrographs of their cross-sections are attached. Figure 2 and attached Figure 3 As shown in the figure. Among them, compared with Example 1, Example 6 increases the number of times the separation layer slurry is applied. Figure 2The thickness of the transition layer of the ceramic membrane is 27.39 μm, and the thickness of the separation layer is 38.02 μm. Compared with Example 1, Example 7 increases the number of coats of both the transition layer slurry and the separation layer slurry. Figure 3 The thickness of the transition layer in the ceramic membrane is 54.21 μm, and the thickness of the separation layer is 56.84 μm. From... Figure 2 and Figure 3 As can be seen, changing the number of coats of the transition layer slurry and the separation layer slurry can form transition layers and separation layers of different thicknesses, all with relatively complete structures and significant pore size variations, sufficient to maintain a high filtration flux. In other words, by using the preparation method in this embodiment and designing a water-resistant transition layer, ceramic membranes with transition and separation layers of arbitrary thickness can be prepared while maintaining a high filtration flux, demonstrating significant market value.

Claims

1. A method for preparing a high-flux ceramic membrane, characterized in that, Includes the following steps: Step S1: Using α-alumina A as the support framework material, a ceramic film support is sintered; the average particle size of the α-alumina A is 3~50μm. Step S2: Using α-alumina B as the transition layer skeleton material, supplemented with a second binder, a second sintering aid, a second dispersant, and a 2-5% (w / w) polyvinyl alcohol aqueous solution, a transition layer slurry with a solid concentration of 10-30% is prepared and passed through a 40-mesh sieve for later use; the average particle size of the α-alumina B is 2-10 μm; the second binder is one or more of polyester-based binder, vinyl acetate-based binder, vilan gum, and silica sol; the second sintering aid is one or more of glass powder and feldspar; the second dispersant is polycarboxylate or polypropylene. The transition layer framework material comprises one or more of the following: titanium dioxide and clay or kaolin; the weight ratio of titanium dioxide to clay or kaolin is 1:1 to 5; the total weight of titanium dioxide and clay or kaolin is 5 to 17% of the weight of the α-alumina B; the weight of the second binder is 5 to 15% of the weight of the transition layer framework material; the weight of the second sintering aid is 1 to 5% of the weight of the transition layer framework material; and the weight of the second dispersant is 0.1 to 0.3% of the weight of the transition layer framework material. Step S3: Apply the transition layer slurry to the surface of the ceramic membrane support by spraying or brushing, and dry at 150~200℃ for 2~6 hours to form a water-resistant transition layer on the surface of the ceramic membrane support. Step S4: Using α-alumina C as the framework material for the separation layer, prepare the separation layer slurry; the average particle size of the α-alumina C is 1 μm; Step S5: The separation layer slurry is coated onto the transition layer by spraying or brushing, dried, and sintered to obtain a high-throughput ceramic membrane. The transition layer prepared in step S3 is water-resistant. When the water-containing separation layer slurry is coated on the transition layer, it will not cause the transition layer to absorb water and be damaged, or the transition layer to separate from the ceramic membrane support after absorbing water, thereby ensuring the stability of the overall structure of the ceramic membrane.

2. The method for preparing a high-flux ceramic membrane according to claim 1, characterized in that, In step S1, the specific process of firing the ceramic film support using α-alumina A as the support skeleton material includes: Step S11: α-alumina A is the raw material for the support skeleton. The support skeleton raw material, pore-forming agent, first binder, lubricant and first sintering aid are mixed in a high-speed mixer according to the formula to obtain dry powder of the support. In step S12, the dry powder of the support body and a polyvinyl alcohol aqueous solution with a mass concentration of 2-5% are kneaded evenly in a kneader, then vacuum-kneaded by a vacuum pumice machine, and finally aged in a sealed container under constant temperature and humidity conditions for 24-48 hours. Step S13: The aged mud is extruded by an extruder to form a support blank; Step S14: After the support blank is dried, it is sintered at 1400~1500℃ for 2~3 hours to obtain the ceramic film support.

3. The method for preparing a high-flux ceramic membrane according to claim 2, characterized in that, The α-alumina A includes α-alumina A1 with an average particle size of 10~50μm and α-alumina A2 with an average particle size of 3~10μm; The pore-forming agent is one or more of starch and graphite powder, with an average particle size of 0.5~3μm; The first adhesive is one or more of cellulose, xanthodextrin, polyvinyl alcohol, and gum arabic; The lubricant is one or more of tung oil, oleic acid, glycerin, and polyethylene glycol; The first sintering aid is one or more of kaolin, clay, feldspar, and glass powder.

4. The method for preparing a high-flux ceramic membrane according to claim 3, characterized in that, In step S11, the weight ratio of α-alumina Al to α-alumina A2 in the raw material of the support skeleton is 2.5~3:1; And / or, the weight of the pore-forming agent is 1 to 10% of the weight of the support skeleton material; And / or, the weight of the first adhesive is 1 to 5% of the weight of the support skeleton material; And / or, the weight of the lubricant is 2-6% of the weight of the support skeleton material; And / or, the weight of the first sintering aid is 1 to 4% of the weight of the support skeleton material.

5. The method for preparing a high-flux ceramic membrane according to claim 4, characterized in that, In step S11, the raw material of the support skeleton also includes calcined kaolin with an average particle size of 2~3μm; the weight of the calcined kaolin is 4~6% of the sum of the weights of α-alumina A1 and α-alumina A2.

6. The method for preparing a high-flux ceramic membrane according to any one of claims 1 to 5, characterized in that, In step S4, the specific process of preparing the separation layer slurry using α-alumina C as the framework material for the separation layer includes: Step S41: Using α-alumina C as the separation layer skeleton material, the separation layer skeleton material, the third binder, the third sintering aid, the third dispersant and water are mixed in a ball mill according to the formula to prepare a slurry with a solid concentration of 10~12%. Step S42: Filter the mixture through a 40-mesh sieve to obtain the separation layer slurry.

7. The method for preparing a high-flux ceramic membrane according to claim 6, characterized in that, In step S41, the third adhesive is a polyvinyl alcohol aqueous solution with a mass concentration of 2-5%. And / or, the third sintering aid is talc; And / or, the third dispersant is a water-soluble acrylic resin.

8. The method for preparing a high-flux ceramic membrane according to claim 6, characterized in that, In step S41, the weight of the third adhesive is 0.3~0.5% of the weight of the separation layer skeleton material; And / or, the weight of the third sintering aid is 0.1~0.2% of the weight of the separation layer skeleton raw material; And / or, the weight of the third dispersant is 0.3 to 0.5% of the weight of the separation layer skeleton material.

9. The method for preparing a high-flux ceramic membrane according to any one of claims 1 to 5, characterized in that, In step S5, the drying process involves drying at 110-120°C for 1-3 hours. And / or, during sintering, hold at 1100~1300℃ for 2~3 hours.

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