Disc type hollow ceramic membrane as well as preparation method and application thereof

Abstract

The invention provides a disc type hollow ceramic membrane and a preparation method and application thereof, the preparation method comprises the following steps: S1, mixing alumina ceramic powder with different particle sizes, a dispersant, a binder, a sintering aid and a sodium carboxymethyl cellulose aqueous solution according to different mass proportions to prepare a support slurry and a membrane surface slurry; s2, adopting a 3D printer to print and form a first membrane surface by utilizing the membrane surface slurry, then printing and forming a support body on the first membrane surface by utilizing the support body slurry, and finally printing and forming a second membrane surface on the support body by utilizing the membrane surface slurry, so as to obtain a ceramic green body; s3, sequentially drying, curing and sintering the ceramic green body to obtain the disc type hollow ceramic membrane. The preparation method disclosed by the invention can be used for preparing various ceramic materials which are complex in shape, high in strength, good in pore connectivity, controllable in pore diameter and porosity and highly ordered, and the prepared product is excellent in performance and can be widely applied to preparation of filtering membranes.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printed ceramic membranes, and in particular relates to a disc-type hollow ceramic membrane and a preparation method and application thereof. Background Art

[0002] As a high-performance separation membrane material, inorganic ceramic membrane has the advantages of high mechanical strength, good chemical stability, strong cycle stability, and long service life. It has broad application prospects in the filtration and separation of high organic concentration wastewater such as food wastewater, molasses wastewater, landfill leachate and aquaculture wastewater. At present, the industrialized inorganic ceramic membrane material products are mainly tubular ceramic membranes and flat ceramic membranes. Although tubular ceramic membranes are cross-flow filtration, they have a long filtration path and low filtration efficiency. Flat membranes are very easy to clog, so their application areas are very limited. They are mainly used in the MBR stage of municipal sewage treatment.

[0003] The disc-type ceramic membrane adopts a ceramic disc design. During operation, the dynamic rotation filtration method generates high shear force and turbulence on the membrane surface, which can effectively remove pollution on the membrane disc surface and control the filter cake layer on the filter membrane surface to a very thin range, avoiding blockage and maintaining a stable operating flux.

[0004] Patents CN106512751A and CN208694725U have publicly reported methods for preparing rotatable disc-shaped ceramic membranes. These patents clearly report that a straight or curved water guide groove is opened in the middle of the disc-shaped ceramic membrane cake to reduce the membrane's permeation resistance and facilitate the circulation of the membrane permeate. However, the design of opening a flow channel inside the disc-shaped ceramic membrane cake greatly increases the difficulty and complexity of the process, and the preparation generally requires the development of a mold with a corresponding complex model. At present, two types of molds are often used in the prior art: one of the molds has a guide groove for forming a channel, and two blanks are pressed separately, and then the two blanks of different thicknesses are buckled into a complete round cake. The buckling part also needs a high-temperature binder to bond, which is easy to produce irregular products or there is a risk of leakage; the other is a metal mold cavity, the powder is loaded into the metal mold cavity, and the powder particles in the mold cavity are rearranged and compacted by applying pressure to form a ceramic blank with a certain strength and shape, but this process has large mold wear, complex processing, and high cost. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing disc-type hollow ceramic membranes with complex shapes, high strength, good pore connectivity, controllable pore size and porosity, and high order without a mold. The preparation is specifically carried out by a 3D printing method, and the preparation process is simple, the cost is low, and the printing accuracy is high.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A 3D printing preparation method for a disc-type hollow ceramic membrane comprises the following steps:

[0008] S1, alumina ceramic powder I, dispersant, binder, sintering aid and sodium carboxymethyl cellulose aqueous solution are mixed uniformly according to the mass ratio of (40-80): (0.5-5): (2-10): (5-10): (10-50), and vacuum degassing is performed after grinding to obtain support slurry A;

[0009] Alumina ceramic powder II, dispersant, binder, sintering aid and sodium carboxymethyl cellulose aqueous solution are uniformly mixed in a mass ratio of (50-80): (0.5-5): (5-15): (5-10): (20-50), and vacuum degassed after grinding to obtain membrane surface slurry B;

[0010] S2, using a 3D printer to first use the membrane surface slurry B to continuously print layer by layer to form a first membrane surface, then use the support body slurry A to continuously print layer by layer on the first membrane surface to form a support body, and finally use the membrane surface slurry B to continuously print layer by layer on the support body to form a second membrane surface, that is, to obtain a ceramic green body;

[0011] S3, drying, solidifying and sintering the ceramic green body in sequence to obtain a disc-type hollow ceramic membrane.

[0012] Wherein, the particle size of the aluminum ceramic powder I is 10-100 μm, and the particle size of the alumina ceramic powder II is 0.5-10 μm.

[0013] Furthermore, the sintering aid is prepared by mixing aluminum sol, magnesium carbonate, aluminum dihydrogen phosphate and kaolin in a mass ratio of (45-85):(10-25):(5-20):(5-20).

[0014] Furthermore, the concentration of the sodium carboxymethyl cellulose aqueous solution is 30% to 50%.

[0015] Furthermore, the dispersant is at least one of ammonium polyacrylate, ammonium citrate and triethanolamine.

[0016] Furthermore, the adhesive is at least one of methyl cellulose, hydroxypropyl methyl cellulose, polymethyl methacrylate, polyethylene glycol or polyacrylamide.

[0017] Furthermore, the vacuum degassing treatment time in step S1 is 30 to 60 minutes.

[0018] Furthermore, the conditions for 3D printing in step S2 are: nozzle diameter 400-600 μm, extrusion pressure 0.2-0.4 MPa.

[0019] Furthermore, the drying and curing conditions in step S3 are: temperature 100-120° C., heat preservation 12-24 hours;

[0020] The sintering conditions are as follows: a heating rate of 5 to 10° C. / min, a temperature of 1200 to 1600° C., and a sintering time of 1 to 5 hours.

[0021] The disc-type hollow ceramic membrane prepared by the above preparation method.

[0022] Application of the disc-type hollow ceramic membrane prepared by the above preparation method in filtration membrane materials.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adopts 3D printing to prepare disc-type hollow ceramic membranes. Ceramic materials with complex shapes, high strength, good pore connectivity, controllable pore size and porosity, and high order can be prepared without molds. The preparation process is simple, the cost is low, and the printing accuracy is high. The prepared slurry has good uniformity, can be continuously extruded, and has fast molding, which is suitable for the industrial production of high-performance multi-level porous ceramics with various complex shapes. The molding conditions are mild, the operation is simple and easy, the cost is low, the efficiency is high, the design modification is convenient, and it has great market promotion value.

[0025] (2) The disc-type hollow ceramic membrane prepared by the present invention is printed and bonded at room temperature. The support body and the membrane surface are integrated to reduce the risk of falling off. The porosity can reach 39% and the flexural strength is 37MPa. The support skeleton is evenly distributed, the pores are abundant, the water production rate is high, and the energy consumption is low. At the same time, this disc-type flat ceramic membrane adopts dynamic cross-flow filtration, which makes the membrane highly resistant to pollution, has low backwashing frequency, and has a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a plan view of the disc-type hollow ceramic membrane prepared in the present invention.

[0027] Figure 2 This is a cross-sectional view of the disc-type hollow ceramic membrane prepared in the present invention.

[0028] Figure 3 This is a schematic diagram of a slice of a disc-type hollow ceramic membrane prepared in the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0030] Example 1

[0031] This embodiment provides a 3D printing preparation method for a disc-type hollow ceramic membrane, comprising the following steps:

[0032] S1. Take alumina ceramic powder I with an average particle size of 50 μm, ammonium polyacrylate, methyl cellulose, a sintering aid and a 50% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 50:2:8:10:30, mix them evenly, grind them and vacuum degas for 30 minutes to obtain a support slurry A.

[0033] Alumina ceramic powder II with an average particle size of 5 μm, ammonium polyacrylate, polyacrylamide, a sintering aid and sodium carboxymethyl cellulose aqueous solution were mixed evenly in a mass ratio of 50:3:7:10:20, and vacuum degassed for 30 minutes after grinding to obtain membrane surface slurry B.

[0034] The sintering aid is a mixture of aluminum sol, magnesium carbonate, aluminum dihydrogen phosphate and kaolin in a mass ratio of 50:10:20:20.

[0035] S2. Use a 3D printer to continuously print the slurry layer by layer, set the nozzle diameter to 600μm, and the extrusion pressure to 0.3MPa; first use membrane surface slurry B to continuously print layer by layer to form a first membrane surface, then use support body slurry A to continuously print layer by layer on the first membrane surface to form a support body, and finally use membrane surface slurry B to continuously print layer by layer on the support body to form a second membrane surface, so as to obtain a ceramic green body.

[0036] S3. The ceramic green body is dried and cured at 120°C for 12 hours, and then placed in a sintering furnace, with a heating rate of 5°C / min, and sintered at an ambient temperature of 1350°C for 2 hours to obtain a disc-type hollow ceramic membrane, the specific structure of which is as follows Figure 1-3 shown.

[0037] Example 2

[0038] This embodiment provides a 3D printing preparation method for a disc-type hollow ceramic membrane, comprising the following steps:

[0039] S1. Take alumina ceramic powder I with an average particle size of 100 μm, triethanolamine, polyacrylamide, a sintering aid and a 30% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 60:1:9:10:20, mix them evenly, grind them and degas them in vacuum for 60 minutes to obtain a support slurry A.

[0040] Alumina ceramic powder II with an average particle size of 10 μm, ammonium polyacrylate, hydroxypropyl methylcellulose, a sintering aid and a 30% sodium carboxymethyl cellulose aqueous solution were mixed evenly in a mass ratio of 50:2:8:5:35, and vacuum degassed for 60 minutes after grinding to obtain membrane surface slurry B.

[0041] The sintering aid is a mixture of aluminum sol, magnesium carbonate, aluminum dihydrogen phosphate and kaolin in a mass ratio of 50:15:15:20.

[0042] S2. Use a 3D printer to continuously print the slurry layer by layer, set the nozzle diameter to 400μm, and the extrusion pressure to 0.4MPa; first use membrane surface slurry B to continuously print layer by layer to form a first membrane surface, then use support body slurry A to continuously print layer by layer on the first membrane surface to form a support body, and finally use membrane surface slurry B to continuously print layer by layer on the support body to form a second membrane surface, so as to obtain a ceramic green body.

[0043] S3. The ceramic green body is dried and cured at 100°C for 24 hours, and then placed in a sintering furnace, the heating rate is set to 3°C / min, and sintered at an ambient temperature of 1400°C for 2 hours to obtain a disc-type hollow ceramic membrane.

[0044] Example 3

[0045] This embodiment provides a 3D printing preparation method for a disc-type hollow ceramic membrane, comprising the following steps:

[0046] S1. Take alumina ceramic powder I with an average particle size of 40 μm, ammonium citrate, polymethyl methacrylate, a sintering aid and a 40% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 40:5:10:10:35, mix them evenly, grind them and degas them in vacuum for 60 minutes to obtain a support slurry A.

[0047] Alumina ceramic powder II with an average particle size of 2 μm, ammonium polyacrylate, polyethylene glycol, a sintering aid and a 40% sodium carboxymethyl cellulose aqueous solution were mixed evenly in a mass ratio of 65:3:5:7:20, and vacuum degassed for 60 minutes after grinding to obtain membrane surface slurry B.

[0048] The sintering aid is a mixture of aluminum sol, magnesium carbonate, aluminum dihydrogen phosphate and kaolin in a mass ratio of 45:20:15:20.

[0049] S2. Use a 3D printer to continuously print the slurry layer by layer, set the nozzle diameter to 500μm, and the extrusion pressure to 0.4MPa; first use membrane surface slurry B to continuously print layer by layer to form a first membrane surface, then use support body slurry A to continuously print layer by layer on the first membrane surface to form a support body, and finally use membrane surface slurry B to continuously print layer by layer on the support body to form a second membrane surface, so as to obtain a ceramic green body.

[0050] S3. The ceramic green body is dried and cured at 110°C for 24 hours, and then placed in a sintering furnace, the heating rate is set to 2°C / min, and sintered at an ambient temperature of 1500°C for 4 hours to obtain a disc-type hollow ceramic membrane.

[0051] Comparative Example 1

[0052] This comparative example provides a 3D printing preparation method for a disc-type hollow ceramic membrane. The raw materials and method are basically the same as those in Example 1, except that the particle sizes of alumina ceramic powder I and alumina ceramic powder II are both 50 μm, and the rest remain unchanged.

[0053] Comparative Example 2

[0054] This comparative example provides a 3D printing preparation method for a disc-type hollow ceramic membrane. The raw materials and method are basically the same as those in Example 1, except that the particle sizes of alumina ceramic powder I and alumina ceramic powder II are both 5 μm, and the rest remain unchanged.

[0055] Comparative Example 3

[0056] This comparative example provides a 3D printing preparation method for a disc-type hollow ceramic membrane. The raw materials and method are basically the same as those in Example 1, except that the sintering aid is replaced by an equal mass of calcium oxide, and the rest remains unchanged.

[0057] Furthermore, in order to understand the specific performance of each disc-type hollow ceramic membrane prepared above, some tests were carried out. The specific test results are shown in Table 1.

[0058] Flexural strength (Mpa): three-point method, universal testing machine, loading speed 2mm / min, calculation formula: R f =3PL / 2bh 2 , where R f is the flexural strength value of the sample (MPa), P is the load when the sample breaks (N), L is the distance between the two supports of the bracket (mm), b is the width of the sample fracture (mm), and h is the height of the sample fracture (mm).

[0059] Porosity (%): ① Place the sample in an oven to a constant weight, and after cooling to room temperature, weigh the mass of the sample in the air m0; ② Place the sample in a beaker, place it in a porous ceramic porosity tester, evacuate it, and then immerse it in distilled water. Take out the samples one by one, and gently wipe off the excess liquid of the sample with a towel moistened with the immersion liquid. Be careful not to wash out the immersion liquid in the open pores, and immediately weigh the mass of the immersed sample in the air m1; ③ Use tweezers to carefully place the samples on the metal wire mesh of the liquid static balance in turn, and avoid spilling water on the weighing part of the balance when placing or taking out the sample, and ensure that the sample and the metal wire mesh are immersed in a certain depth below the water surface, and do not contact the wall or bottom of the beaker containing water, and weigh the mass of the immersed sample in water m2. The calculation formula of porosity is as follows: P = [(m1-m0) / (m1-m2)]×100%.

[0060] Table 1 Detailed performance of each disc-type hollow ceramic membrane

[0061] index Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Porosity (%) 32％ 33.5％ 39％ 52％ 26％ 34％ Flexural strength(Mpa) 37 35 34.8 33 35.5 31

[0062] It can be seen from Table 1 that the disc-type hollow ceramic membrane prepared by the present invention has better porosity and flexural strength. In Comparative Example 1, due to the large particle size of the powder in the membrane surface slurry B, local macropores are easily formed, resulting in membrane defects, resulting in an excessive overall porosity of 52%, and a decrease in flexural strength; in Comparative Example 2, the powder particle size in the support slurry A is small, and pores are accumulated to form, so that the support pore size is small and the porosity is 26%. It is easy to be blocked after long-term use, resulting in increased pollution; Comparative Example 3 uses a single sintering aid, and the flexural strength decreases significantly, only 31MPa, and its sintering driving force powder is insufficient, and the powder particles are not completely combined, resulting in low compressive strength and low density.

[0063] Furthermore, in order to understand the filtration effect of each disc-type hollow ceramic membrane prepared above, a pure water flux test was also carried out:

[0064] Pure water flux (m 3 / m 2 h): Temperature 25°C, suction negative pressure 0.02Mpa, membrane surface rotation speed 200 rpm, pure water permeation flux value. The formula is: J0 = V0 / A t , where: J0 is the permeation flux (m 3 / m 2 ·h), V0 is the volume of permeated pure water L, A is the effective membrane area m 2 , t is the penetration time h.

[0065] Table 2 Comparison of filtration effects of various disc-type hollow ceramic membranes

[0066] index Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Pure water flux 1.6 1.65 1.68 3.2 1.22 1.55

[0067] It can be seen from Table 2 that the disc-type hollow ceramic membrane prepared by the present invention has good pure water flux. Among them, the pure water flux in Comparative Example 1 is the largest, but the selectivity of the membrane will decrease accordingly, while the pure water flux in Comparative Example 2 is the smallest, which will increase the risk of membrane clogging.

[0068] Based on the above data, it can be seen that the disc-type hollow ceramic membrane prepared in this application has good porosity, flexural strength, and pure water flow, and can be well used in the field of sewage treatment.

[0069] The specific raw materials not described in the present invention are all existing materials and can be directly purchased from the market.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A 3D printing preparation method for a disc-type hollow ceramic membrane, characterized in that: The following steps are involved: S1, alumina ceramic powder I, dispersant, binder, sintering aid and sodium carboxymethyl cellulose aqueous solution are mixed uniformly according to the mass ratio of (40-80): (0.5-5): (2-10): (5-10): (10-50), and vacuum degassing is performed after grinding to obtain support slurry A; Alumina ceramic powder II, dispersant, binder, sintering aid and sodium carboxymethyl cellulose aqueous solution are uniformly mixed in a mass ratio of (50-80): (0.5-5): (5-15): (5-10): (20-50), and vacuum degassed after grinding to obtain membrane surface slurry B; S2, using a 3D printer to first use the membrane surface slurry B to continuously print layer by layer to form a first membrane surface, then use the support body slurry A to continuously print layer by layer on the first membrane surface to form a support body, and finally use the membrane surface slurry B to continuously print layer by layer on the support body to form a second membrane surface, that is, to obtain a ceramic green body; S3, drying, solidifying and sintering the ceramic green body in sequence to obtain a disc-type hollow ceramic membrane. Wherein, the particle size of the alumina ceramic powder I is 10-100 μm, and the particle size of the alumina ceramic powder II is 0.5-10 μm.

2. The preparation method according to claim 1, characterized in that: The sintering aid is prepared by mixing aluminum sol, magnesium carbonate, aluminum dihydrogen phosphate and kaolin in a mass ratio of (45-85):(10-25):(5-20):(5-20).

3. The preparation method according to claim 1, characterized in that: The concentration of the sodium carboxymethyl cellulose aqueous solution is 30% to 50%.

4. The preparation method according to claim 1, characterized in that: The dispersant is at least one of ammonium polyacrylate, ammonium citrate and triethanolamine.

5. The preparation method according to claim 1, characterized in that: The adhesive is at least one of methyl cellulose, hydroxypropyl methyl cellulose, polymethyl methacrylate, polyethylene glycol or polyacrylamide.

6. The preparation method according to claim 1, characterized in that: The vacuum degassing treatment time in step S1 is 30 to 60 minutes.

7. The preparation method according to claim 1, characterized in that: The conditions for 3D printing in step S2 are: nozzle diameter 400-600 μm, extrusion pressure 0.2-0.4 MPa.

8. The preparation method according to claim 1, characterized in that: The drying and curing conditions in step S3 are as follows: temperature 100-120° C., heat preservation 12-24 hours; The sintering conditions are as follows: a heating rate of 5 to 10° C. / min, a temperature of 1200 to 1600° C., and a sintering time of 1 to 5 hours.

9. A disc-type hollow ceramic membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the disc-type hollow ceramic membrane prepared by the preparation method according to any one of claims 1 to 8 in filtration membrane materials.

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