A method and device for repairing macroporous defects of ceramic membranes based on cross-flow filtration

Abstract

The application relates to a ceramic membrane macropore defect repairing method and device based on cross-flow filtration, which comprises the following steps: S1, selecting alumina or zirconia ceramic material as raw material, adding 0.5-2 wt% pH-sensitive polymer as response regulator to prepare ceramic sol, wherein the ceramic sol particle size is greater than the average pore size of the ceramic membrane but smaller than the size of the macropore defect; S2, introducing the ceramic sol prepared in the step S1 into a cross-flow filtration equipment as a permeate, and making the ceramic sol flow parallel to the surface of the ceramic membrane under the action of the cross-flow filtration equipment, and the flow speed is 1-5 m / s; S3, after the penetration is completed, the ceramic membrane is taken out from the cross-flow filtration equipment, and the membrane surface is washed with pure water for 3-5 min; and S4, after the washing is completed, the ceramic membrane is placed into a high-temperature furnace with a temperature of 500-1200 DEG C for high-temperature sintering, wherein the temperature rising speed is 5-10 DEG C / min, and the holding time is 2-4 h; the application has the advantages of improving the service performance and the service life of the ceramic membrane.

Description

Technical Field

[0001] This invention belongs to the field of ceramic membrane technology, specifically relating to a method and apparatus for repairing macroporous defects in ceramic membranes based on cross-flow filtration. Background Technology

[0002] Macropore defects are a common problem in the preparation and use of ceramic membranes, which can seriously affect their performance. Existing technologies for repairing macropore defects in ceramic membranes mainly include physical filling and chemical deposition.

[0003] Physical filling methods involve directly filling macropores with filler material, but this method easily clogs the small pores of ceramic membranes, leading to a significant reduction in membrane flux and consequently affecting the filtration efficiency of the ceramic membrane. Chemical deposition methods form a deposition layer on the surface of macropores through chemical reactions; however, this method makes it difficult to precisely position the repair material in the macropores, often resulting in changes in the average pore size of the membrane and low repair efficiency.

[0004] Traditional direct coating methods result in the indiscriminate covering of the repair material onto the membrane surface, clogging both macropores and micropores and severely impacting the membrane's filtration performance. While high-temperature sintering can ensure a strong bond between the repair material and the membrane substrate, the high temperatures may alter the membrane's microstructure, leading to performance degradation. Furthermore, this method is energy-intensive and unsuitable for large-scale applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of easy pore clogging, uneven repair, and impact on membrane flux and average pore size in existing repair methods. Instead, it provides a method and apparatus for repairing macropore defects in ceramic membranes that ensures that macropores are effectively filled after repair, while maintaining the average pore size and flux of the membrane, avoiding pore clogging, and improving the performance and lifespan of the ceramic membrane.

[0006] The technical solution of the present invention is as follows:

[0007] A method for repairing macroporous defects in ceramic membranes based on cross-flow filtration includes the following steps:

[0008] S1: Select alumina or zirconia ceramic materials as raw materials, add 0.5-2wt% of pH-sensitive polymer as a response regulator, and prepare ceramic sol, wherein the particle size of ceramic sol is larger than the average pore size of ceramic film but smaller than the size of macropore defects.

[0009] S2: The ceramic sol prepared in step S1 is used as the permeate and introduced into the cross-flow filtration device. The ceramic sol flows parallel to the surface of the ceramic membrane under the action of the cross-flow filtration device, and the flow rate is 1-5 m / s.

[0010] S3: After the permeation is complete, remove the ceramic membrane from the cross-flow filtration device and rinse the membrane surface with pure water for 3-5 minutes;

[0011] S4: After rinsing, place the ceramic membrane in a high-temperature furnace at 500-1200℃ for high-temperature sintering, with a heating rate of 5-10℃ / min and a holding time of 2-4h.

[0012] Furthermore, the pH-sensitive polymer is specifically polyacrylic acid or polymethacrylic acid.

[0013] Furthermore, the initial pH of the ceramic sol is adjusted to 7.0-8.0 using hydrochloric acid or ammonia, the viscosity of the ceramic sol is controlled at 8-15 mPa·s at a standard temperature of 25°C, and the pH response threshold is 5.0-6.0.

[0014] Furthermore, the pressure range of the cross-flow filtration device is 0.1-0.5 MPa.

[0015] Furthermore, the sintering temperature of the alumina ceramic film is 800-1000℃.

[0016] Furthermore, the sintering temperature of the zirconium oxide ceramic film is 1000-1200℃.

[0017] This invention also proposes an apparatus for a method of repairing macroporous defects in ceramic membranes based on cross-flow filtration:

[0018] The invention includes a cross-flow filtration device for directing ceramic sol to flow parallel to the surface of a ceramic membrane.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. Precisely repairs large pores without changing the average pore size of the ceramic membrane.

[0021] Because the particle size of the sol particles is strictly controlled, they can only penetrate into the macropores and not into the micropores. Therefore, macropore defects can be precisely repaired without changing the average pore size of the membrane, thus ensuring the filtration accuracy of the membrane.

[0022] 2. Cross-flow filtration avoids pore clogging and maintains membrane flux.

[0023] The shear force generated by cross-flow filtration effectively prevents the deposition of sol at the pores, avoiding pore blockage, thereby maintaining the membrane flux and ensuring the membrane's filtration efficiency.

[0024] 3. Enhanced mechanical strength of the film after sintering

[0025] High-temperature sintering firmly bonds the sol particles to the membrane substrate, forming a dense structure that enhances the membrane's mechanical strength, improves its impact resistance and abrasion resistance, and extends its service life.

[0026] 4. The process is simple and suitable for large-scale restoration.

[0027] The entire repair process is simple, easy to operate and control, requires no complex equipment or high costs, and is suitable for large-scale industrial production and application.

[0028] 5. Improve the efficiency of filling large holes

[0029] pH-responsive deposition increases the filling rate of macroporous defects (especially deep and corner areas) by 30%-50%, resulting in more thorough repair.

[0030] 6. Enhance process compatibility

[0031] The pH-responsive design is fully compatible with existing cross-flow equipment and parameters, requiring no additional modifications and reducing the cost of industrial applications. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope image of the ceramic film modified by the repair method of the present invention;

[0033] Figure 2 This is a scanning electron microscope image of the ceramic film after the repair method of this invention was not modified;

[0034] Figure 3 Comparison of pore size distribution before and after modification of the 8nm film;

[0035] Figure 4 This is a schematic diagram of a cross-flow filtration device. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figures 1 to 3 As shown, a method for repairing macroporous defects in ceramic membranes based on cross-flow filtration includes the following steps:

[0039] S1: Sol preparation: Select ceramic materials such as alumina and zirconium oxide as raw materials, and add 0.5-2wt% of pH-sensitive polymers (such as polyacrylic acid PAA and polymethacrylic acid PMAA) as response modifiers to prepare ceramic sol.

[0040] The prepared sol particles have a particle size larger than the average pore size of the ceramic membrane but smaller than the size of macropore defects. This ensures that the sol particles can penetrate into the macropores but not into the micropores, thereby achieving targeted repair of macropore defects. The particle size of the sol particles can be controlled by selecting powders with appropriate particle sizes when choosing ceramic materials, and by adding an appropriate amount of dispersant during sol preparation to prevent particle agglomeration.

[0041] For example, ceramic sol particles with a particle size of 0.3-0.8 μm can be prepared for ceramic membranes with an average pore size of 0.2 μm and macropore defect size of 1-5 μm. The initial pH of the ceramic sol is adjusted to 7.0-8.0 (neutral to weakly alkaline) by hydrochloric acid or ammonia. At this point, the pH-sensitive polymer chains formed by the pH-sensitive polymers are in an extended state, and the viscosity of the ceramic sol is controlled at 8-15 mPa·s (25℃), which meets the requirements for cross-flow fluidity. The designed pH response threshold is 5.0-6.0. When the ambient pH is lower than this value, the polymer chains shrink and aggregate, and the sol viscosity increases sharply to 50-100 mPa·s, triggering gelation deposition.

[0042] The pH response threshold (5.0-6.0) serves to trigger the gelation and deposition of ceramic sol by changing the ambient pH, thereby achieving targeted repair of macroporous defects and preventing micropore blockage.

[0043] Directional deposition of macroporous defects: Due to fluid retention at macroporous defects, trace metal ions (such as Al³⁺, Zr) dissolve from the ceramic film substrate. 4 ⁺) It reacts with water to form a weakly acidic microenvironment (pH drops to 5.0-6.0, i.e. pH response threshold), triggering sol-gelation, which allows ceramic particles to be deposited rapidly in macropores, improving the filling rate of complex macropore defects such as deep layers and corners (by 30%-50%), and making the repair more thorough.

[0044] To prevent pore clogging: Due to the strong cross-flow shear force and rapid ceramic sol turnover at the pores, the initial pH (7.0-8.0, higher than the response threshold) is always maintained. The sol maintains a low viscosity (8-15 mPa·s) flow state and is carried away by the shear force, avoiding deposition and clogging at the pores, thereby maintaining the membrane flux and filtration efficiency.

[0045] S2: Cross-flow filtration permeation: The prepared ceramic sol is used as the permeate and introduced into the cross-flow filtration equipment. Under the action of the cross-flow filtration equipment, the ceramic sol flows parallel to the surface of the ceramic membrane. The flow rate of the feed liquid is controlled by adjusting the power of the circulation pump, and the flow rate is controlled at 1-5m / s.

[0046] During the flow of the liquid feed, the shear force generated by the flow prevents the sol from depositing at the pores. Simultaneously, due to hydrodynamic effects, sol particles are preferentially adsorbed at the macropores, achieving directional repair of macropore defects. Furthermore, due to fluid retention at macropore defects, trace metal ions (such as Al) dissolved from the ceramic membrane substrate... 3+ Zr 4+ The reaction with water forms a weakly acidic microenvironment (pH 5.0-6.0), triggering sol gelation and causing ceramic particles to rapidly deposit in the macropores. At the micropores, due to strong shear force and rapid material turnover, the initial pH (7.0-8.0) is maintained, and the sol remains in a low-viscosity flow state, being carried away by the shear force to avoid clogging. During this process, the pressure of the cross-flow filtration also needs to be controlled, typically within the range of 0.1-0.5 MPa.

[0047] S3: Rinsing: After permeation, remove the ceramic membrane from the cross-flow filtration device and rinse the membrane surface with pure water. Since undeposited pH-responsive sols have better fluidity in a neutral environment, the surface rinsing time can be shortened to 3-5 minutes to remove unadsorbed sols from the membrane surface, focusing on removing loose deposits at the macropore inlet to avoid residual sols affecting membrane performance.

[0048] S4: Sintering: After rinsing, the ceramic membrane is placed in a high-temperature furnace for high-temperature sintering. The sintering temperature is determined according to the materials of the ceramic membrane and the sol, and is between 500-1200℃.

[0049] For example, the sintering temperature for alumina ceramic membranes can be controlled at 800-1000℃; for zirconia ceramic membranes, the sintering temperature can be controlled at 1000-1200℃. During the sintering process, it is necessary to control the heating rate and holding time. The heating rate is generally 5-10℃ / min, and the holding time is 2-4 hours. At high temperatures (200-400℃), pH-sensitive polymers completely decompose, leaving no impurities. Only the strong bond between ceramic particles and the membrane substrate is preserved. Through high-temperature sintering, the sol particles solidify and firmly bond with the membrane substrate, thereby filling macroporous defects.

[0050] like Figure 1-2 As shown, where Figure 1 This is an electron micrograph of the ceramic film modified by the repair method of this embodiment. Figure 2 This is an electron micrograph of the ceramic film after it has not been modified by the repair method of this embodiment. Figure 1-2 It can be seen that the large pore images inside the ceramic membrane have been greatly reduced, indicating that the defects have been effectively filled.

[0051] Figure 3 This displays the results of the pore size distribution test, where the Y-axis represents the proportion of different pore sizes. Figure 3In the diagram, the 0.5 value corresponds to the average pore size of the membrane, which is 8 nm. As the pore size increases, its proportion gradually decreases, indicating that within a larger pore size range, the number of defects is relatively small. For example... Figure 3 As shown, the number of membrane defects repaired by the solution in this embodiment is significantly the lowest.

[0052] Example 2

[0053] like Figure 4 As shown, an apparatus for a method of repairing macroporous defects in ceramic membranes based on cross-flow filtration includes a cross-flow filtration device for flowing ceramic sol parallel to the surface of the ceramic membrane.

[0054] The cross-flow filtration device includes a high-pressure diaphragm pump, ball valve 1, membrane module, pressure gauge, and ball valve 2. The working principle of the cross-flow filtration device in this application is as follows: the high-pressure diaphragm pump drives the ceramic sol to flow parallel to the ceramic membrane surface through ball valve 1 and the membrane module at a certain flow rate, forming a cross-flow. Under system pressure, fluid retention at large pore defects causes Al³⁺ and Zr to dissolve from the ceramic membrane matrix. 4 ⁺Metal ions react with water to form a weakly acidic microenvironment (pH drops to 5.0-6.0, i.e., the pH response threshold), triggering the gelation and deposition of ceramic particles in the sol, thus improving the filling rate of complex macroporous defects. Meanwhile, at the micropores, due to the strong cross-flow shear force and rapid feed turnover, the initial pH (7.0-8.0) is maintained, and the sol remains in a low-viscosity flow state and is carried away by the shear force, avoiding micropore blockage. Undeposited sol is circulated through the return pipeline to achieve continuous permeation repair. Ultimately, through the synergistic effect of cross-flow and pH response, macroporous defects are repaired in a targeted manner and the membrane flux is maintained.

[0055] The pressure gauge is used to detect flow rate and pressure.

[0056] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for repairing macroporous defects in ceramic membranes based on cross-flow filtration, characterized in that: Includes the following steps: S1: Select alumina or zirconia ceramic materials as raw materials, add 0.5-2wt% polyacrylic acid or polymethacrylic acid as response modifiers to prepare ceramic sol, wherein the particle size of ceramic sol is larger than the average pore size of ceramic film but smaller than the size of macropore defects; S2: The ceramic sol prepared in step S1 is used as the permeate and introduced into the cross-flow filtration device. The ceramic sol flows parallel to the surface of the ceramic membrane under the action of the cross-flow filtration device, and the flow rate is 1-5 m / s. S3: After the permeation is complete, remove the ceramic membrane from the cross-flow filtration device and rinse the membrane surface with pure water for 3-5 minutes; S4: After rinsing, place the ceramic membrane in a high-temperature furnace at 500-1200℃ for high-temperature sintering, with a heating rate of 5-10℃ / min and a holding time of 2-4h.

2. The method for repairing macroporous defects in ceramic membranes based on cross-flow filtration according to claim 1, characterized in that: The initial pH of the ceramic sol is adjusted to 7.0-8.0 using hydrochloric acid or ammonia. The viscosity of the ceramic sol is controlled at 8-15 mPa·s at a standard temperature of 25°C, and the pH response threshold is 5.0-6.

0.

3. The method for repairing macroporous defects in ceramic membranes based on cross-flow filtration according to claim 1, characterized in that: The pressure range of the cross-flow filtration device is 0.1-0.5 MPa.

4. The method for repairing macroporous defects in ceramic membranes based on cross-flow filtration according to claim 1, characterized in that: Alumina ceramic material was selected as the raw material, and the sintering temperature of the ceramic film was 800-1000℃.

5. The method for repairing macroporous defects in ceramic membranes based on cross-flow filtration according to claim 1, characterized in that: Zirconia ceramic material was selected as the raw material, and the sintering temperature of the ceramic film was 1000-1200℃.

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