Preparation method of silicon carbide ceramic microfiltration membrane with high permeation flux

Abstract

The invention belongs to the technical field of inorganic ceramic membranes, and relates to a preparation method of a high-permeation-flux silicon carbide ceramic microfiltration membrane. Coating a silicon carbide ceramic support with the coating liquid, drying to obtain a silicon carbide ceramic microfiltration membrane blank, and sintering the blank to obtain the silicon carbide ceramic microfiltration membrane with high permeation flux. According to the invention, the silane coupling agent is used as a bonding auxiliary agent of the coating liquid to couple the methyl cellulose and the silicon carbide, so that the viscosity of the methyl cellulose can be enhanced, the dispersity and the film-forming property of the coating liquid can be improved, the coating liquid is stable, only one-time coating is needed, an intermediate transition layer is not needed, and the cost is low. The silicon carbide ceramic microfiltration membrane with high pure water permeation flux can be prepared at a low sintering temperature, and the production time and cost of the silicon carbide ceramic microfiltration membrane are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic ceramic membranes, and in particular to a method for preparing a high permeability flux ceramic microfiltration membrane, which comprises the preparation of a microfiltration ceramic coating liquid and a silicon carbide ceramic microfiltration membrane without an intermediate layer. Background Art

[0002] Ceramic microfiltration membrane is a porous membrane mainly made of inorganic materials such as Al2O3, ZrO2, TiO2, SiO2, etc. It is mostly used in water treatment, food and beverage processing, biomedicine and other fields. In recent years, SiC materials have also been used to produce ceramic membranes for gas separation, water separation and other fields. Silicon carbide ceramic membranes also have good performance in antibacterial properties. Compared with similar organic membranes, silicon carbide ceramic membranes have the advantages of high temperature resistance, bacteria resistance, good chemical stability and high mechanical strength, but the high cost has hindered its industrial development.

[0003] The preparation of traditional silicon carbide ceramic microfiltration membranes is mainly achieved through multiple steps. First, a support body is prepared to provide mechanical strength to the membrane layer. Secondly, one or more intermediate transition layers are coated on the support body, and finally a microporous separation layer is formed. Each step includes a high-temperature sintering process, which makes the preparation cost of the ceramic microfiltration membrane relatively high. Recently, the preparation technology of silicon carbide ceramic microfiltration membranes that omit the intermediate layer has emerged to reduce production time and cost. For example, CN113121241A discloses a high-throughput silicon carbide ceramic filter membrane and a preparation method thereof, which adopts a single direct coating separation layer process on the basis of a carrier, that is, after the carrier is sintered, the separation layer is directly coated, and then decarbonization is performed after sintering. However, the membrane slurry in this method requires silicon carbide powder and additives with different particle size mismatch ratios, and requires that the particles of the membrane slurry and the surface of the carrier carry the same charge. The composition of the membrane slurry is complex and the sintering temperature is as high as 1600-2000°C, which has high energy consumption. In order to solve the problem of high sintering temperature of silicon carbide ceramic microfiltration membrane, low temperature sintering technology has emerged. For example, CN117820007A discloses a method and application of ultra-low temperature co-sintering preparation of high flux silicon carbide ceramic membrane, and CN119186275A discloses a low temperature sintered asymmetric porous silicon carbide ceramic membrane separation layer and its preparation method, respectively reducing the sintering temperature to 600℃ and 800~1100℃. However, the pure water flux of silicon carbide ceramic membrane obtained by these two methods is between 2000 and 2461℃. , the pure water flux is low.

[0004] In view of the above characteristics of the prior art, in order to obtain a silicon carbide ceramic membrane with high pure water flux and reduce the preparation of the intermediate transition layer, the coating liquid is the key to obtain a silicon carbide ceramic membrane with high pure water flux under the condition of a lower sintering temperature. The existing silicon carbide ceramic coating liquid either has complex ingredients and high requirements for the coating liquid particles, or the high number of coatings leads to complex preparation procedures and prolongs the production time.

[0005] Therefore, it is an urgent problem to reduce the preparation and coating times of the intermediate transition layer and to prepare a silicon carbide ceramic membrane with a higher pure water flux at a lower sintering temperature. To this end, the present invention is proposed. Summary of the invention

[0006] In view of the above-mentioned state of the prior art, the present invention has conducted in-depth and extensive research in the field of silicon carbide ceramic microfiltration membranes and found that the use of silane coupling agents as adhesive aids for coating liquids to couple methyl cellulose and silicon carbide can not only enhance the viscosity of methyl cellulose, but also improve the dispersibility and film-forming properties of the coating liquid. The coating liquid is stable, only one coating is required, no intermediate transition layer is required, and a silicon carbide ceramic microfiltration membrane with a higher pure water permeation flux can be prepared at a lower sintering temperature. The present invention is completed based on the above-mentioned findings.

[0007] Therefore, the purpose of the present invention is to provide a method for preparing a silicon carbide ceramic microfiltration membrane with a high permeation flux, which only requires one coating and does not require an intermediate transition layer, and a silicon carbide ceramic microfiltration membrane with a high pure water permeation flux can be prepared at a lower sintering temperature.

[0008] The technical solution for achieving the above-mentioned invention object can be summarized as follows:

[0009] A method for preparing a silicon carbide ceramic microfiltration membrane with high permeation flux comprises the following steps:

[0010] The coating liquid is coated on a silicon carbide ceramic support, and after drying, a silicon carbide ceramic microfiltration membrane blank is obtained, and the blank is sintered at 1100-1300°C to obtain a silicon carbide ceramic microfiltration membrane with a high permeation flux;

[0011] The coating liquid comprises: silicon carbide powder, a binder, a bonding aid, a dispersant and water, wherein the binder is methyl cellulose, the bonding aid is a silane coupling agent, and the dispersant is polyacrylic acid; the mass ratio of silicon carbide powder, the binder and the dispersant is (10-15): (0.2-0.5): (0.2-1), the volume ratio of the bonding aid and water is (0.5-1): (82.5-89.1), and the mass ratio of silicon carbide powder to water is (10-15) g: (82.5-89.1) mL.

[0012] According to the present invention, preferably, the silane coupling agent is KH-550 (γ-aminopropyltriethoxysilane), and the purity of KH-550 is 99.8%.

[0013] According to the present invention, preferably, the particle size of the silicon carbide powder is 0.8-2.6 μm.

[0014] According to the present invention, preferably, the coating liquid is prepared by the following method: adding a binder and a dispersant to water, and adding a bonding aid after dissolution to obtain a suspension; adding silicon carbide powder to the suspension, stirring evenly, and standing to remove bubbles to obtain a coating liquid.

[0015] According to the present invention, preferably, the water temperature is heated to 50-80°C, more preferably 65-75°C before adding the binder and the dispersant.

[0016] According to the present invention, preferably, the coating liquid is applied by dipping and pulling, and the silicon carbide ceramic support is dipped into the coating liquid and then pulled and separated from the coating liquid, thus completing the coating liquid coating.

[0017] According to the present invention, preferably, the silicon carbide ceramic support is immersed in the coating liquid at a descending speed of 1-2 cm / s, a pulling speed of 2-3 cm / s, and an immersion time of 30-60 s. The coating liquid coating is completed after one immersion and pulling operation.

[0018] According to the present invention, preferably, the silicon carbide ceramic support body is a porous tubular silicon carbide ceramic support body.

[0019] According to the present invention, preferably, the sintering time is 1 to 3 h.

[0020] According to the present invention, preferably, the sintering process is to heat up from room temperature to the sintering temperature and then sinter at a temperature-maintaining rate of 2-5° C. / min.

[0021] According to the present invention, preferably, the drying temperature is 50-120° C. and the drying time is 1-5 hours.

[0022] The present invention has the following beneficial effects:

[0023] 1. The present invention couples methyl cellulose and silicon carbide with a silane coupling agent such as KH-550, thereby enhancing the viscosity of the methyl cellulose and improving the dispersibility and film-forming properties of the coating liquid, thereby being able to prepare a silicon carbide ceramic microfiltration membrane without an intermediate transition layer in one step of coating, omitting the step of preparing the intermediate transition layer, shortening the production time, and reducing the production cost.

[0024] 2. The coating liquid used in the present invention is relatively uniform and stable, with almost no precipitation within 48 hours. Compared with the traditional multiple coating, the present invention only needs to coat once before sintering, which reduces the number of coatings and shortens the production time.

[0025] 3. The sintering temperature of the silicon carbide ceramic microfiltration membrane of the present invention is relatively low. It can be sintered at 1100-1300°C to obtain a silicon carbide ceramic microfiltration membrane without an intermediate transition layer and with good permeation flux. Compared with the prior art with a sintering temperature above 1400°C, the present invention reduces energy consumption and saves production costs.

[0026] 4. The membrane layer of the silicon carbide ceramic microfiltration membrane prepared by the present invention is complete. In a preferred embodiment, the SEM morphology images of the membrane surface and cross-section show that the membrane thickness is about 35 μm, the membrane layer is tightly combined with the silicon carbide ceramic support layer, the pores inside the silicon carbide ceramic support layer are much larger than the particle size of the silicon carbide particles in the membrane layer, but very few film-forming particles penetrate into the silicon carbide ceramic support layer to cause blockage.

[0027] 5. The silicon carbide ceramic microfiltration membrane prepared by the present invention has a high permeation flux, and the pure water permeation flux is as high as 3990 . BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 These are SEM photos of the support surface and the cross-section after coating in Experimental Example 1. DETAILED DESCRIPTION

[0029] The invention provides a method for preparing a silicon carbide ceramic microfiltration membrane with high permeation flux, which only requires one coating and does not require an intermediate transition layer, and can prepare a silicon carbide ceramic microfiltration membrane with high pure water permeation flux at a relatively low sintering temperature.

[0030] The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux of the present invention comprises the following steps:

[0031] The coating liquid is coated on a silicon carbide ceramic support, and after drying, a silicon carbide ceramic microfiltration membrane blank is obtained, and the blank is sintered at 1100-1300°C to obtain a silicon carbide ceramic microfiltration membrane with a high permeation flux;

[0032] The coating liquid comprises: silicon carbide powder, a binder, a bonding aid, a dispersant and water, wherein the binder is methyl cellulose, the bonding aid is a silane coupling agent, and the dispersant is polyacrylic acid; the mass ratio of silicon carbide powder, the binder and the dispersant is (10-15): (0.2-0.5): (0.2-1), the volume ratio of the bonding aid and water is (0.5-1): (82.5-89.1), and the mass ratio of silicon carbide powder to water is (10-15) g: (82.5-89.1) mL.

[0033] According to the present invention, a silane coupling agent is used as a bonding aid, and the silane coupling agent can couple methyl cellulose and silicon carbide, thereby enhancing the viscosity of methyl cellulose and improving the dispersibility and film-forming properties of the coating liquid.

[0034] In one or more preferred embodiments, the silane coupling agent is KH-550 (γ-aminopropyltriethoxysilane), and the purity of KH-550 is 99.8%.

[0035] According to the present invention, the pure water permeation capacity of the silicon carbide ceramic microfiltration membrane is related to the particle size of the silicon carbide powder in the coating solution. The larger the particle size of the silicon carbide powder, the larger the pore size of the silicon carbide ceramic microfiltration membrane, and the correspondingly larger the pure water permeation capacity. However, the larger the better, the larger the particle size of the silicon carbide powder will also cause the pores of the support to be blocked, thereby reducing the pure water permeation capacity.

[0036] In one or more preferred embodiments, the particle size of the silicon carbide powder is 0.8-2.6 μm.

[0037] In one or more preferred embodiments, the coating liquid is prepared as follows: a binder and a dispersant are added to water, and after dissolution, a bonding aid is added to obtain a suspension; silicon carbide powder is added to the suspension, stirred evenly, and allowed to stand to remove bubbles to obtain a coating liquid.

[0038] According to the present invention, the water temperature is heated before adding the binder and the dispersant, so as to increase the dissolution rate and the uniformity of the solution.

[0039] In one or more preferred embodiments, the water temperature is heated to 50-80°C, more preferably 65-75°C, before adding the binder and the dispersant.

[0040] In one or more preferred embodiments, the coating liquid is applied by dipping and pulling. After the silicon carbide ceramic support is dipped into the coating liquid, it is pulled and separated from the coating liquid, thus completing the coating liquid coating.

[0041] In one or more preferred embodiments, the silicon carbide ceramic support is immersed in the coating liquid at a descending speed of 1-2 cm / s, a pulling speed of 2-3 cm / s, and an immersion time of 30-60 s. The present invention completes the coating liquid coating after one immersion and pulling operation.

[0042] According to the present invention, there is no special requirement for the silicon carbide ceramic support, which reflects the universality of the coating solution of the present invention and is suitable for most types of silicon carbide ceramic supports in the field, thereby solving the problem of the prior art that the support needs to be prepared separately.

[0043] In one or more preferred embodiments, the silicon carbide ceramic support is a porous tubular silicon carbide ceramic support, in which the silicon carbide particle size is 10 to 15 μm and the pore size ranges from 1 to 3 μm.

[0044] In one or more preferred embodiments, the sintering time is 1 to 3 h.

[0045] In one or more preferred embodiments, the sintering process is to heat up from room temperature to the sintering temperature and then sinter at a temperature-maintaining rate of 2 to 5° C. / min.

[0046] In one or more preferred embodiments, the drying temperature is 50-120° C., and the drying time is 1-5 hours.

[0047] Unless otherwise specified in the present invention, all are based on the prior art in the art.

[0048] The technical solution of the present invention will be described clearly and completely below in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In the examples, the raw materials used are all conventional commercially available products unless otherwise specified. In particular, in the porous tubular silicon carbide ceramic support, the silicon carbide particle size is 10-15 μm, and the pore size ranges from 1-3 μm.

[0050] Example 1

[0051] The preparation of a high permeability flux silicon carbide ceramic microfiltration membrane without an intermediate transition layer comprises the following steps:

[0052] (1) At a constant temperature of 70 °C, dissolve 0.2 g of methyl cellulose and 0.5 g of polyacrylic acid in 88.8 mL of deionized water and stir to fully dissolve them to prepare a suspension;

[0053] (2) Stop heating, add weighed silicon carbide (particle size 0.8 μm) into the suspension, add 0.5 mL of silane coupling agent (KH-550) after it is evenly dispersed, stir for four hours, let it stand to remove bubbles, and obtain a uniform coating solution;

[0054] (3) The porous tubular silicon carbide ceramic support was cleaned with deionized water and dried in an oven at 100 °C for two hours for use; the silicon carbide ceramic support was coated by the immersion and pulling coating method, the silicon carbide ceramic support was immersed in the coating liquid at a descending speed of 1 cm / s, the pulling speed was 2 cm / s, the coating was carried out for 60 s, and after drying at room temperature for 1 hour, it was placed in an oven at 80 °C for 2 hours; then the temperature was increased to 1200 °C in a muffle furnace at a heating rate of 3 °C / min, sintered and kept at this temperature for 2 hours, and then naturally cooled to room temperature to obtain a silicon carbide ceramic microfiltration membrane.

[0055] Example 2

[0056] The preparation of a high permeability flux silicon carbide ceramic microfiltration membrane without an intermediate transition layer comprises the following steps:

[0057] (1) At a constant temperature of 70 °C, dissolve 0.3 g of methyl cellulose and 0.2 g of polyacrylic acid in 89.5 mL of deionized water and stir to fully dissolve them to prepare a suspension.

[0058] (2) Stop heating, add weighed silicon carbide (particle size 0.8 μm) into the suspension, add 0.5 mL of silane coupling agent (KH-550) after it is evenly dispersed, stir for four hours, let it stand to remove bubbles, and obtain a uniform coating solution;

[0059] (3) The porous tubular silicon carbide ceramic support was cleaned with deionized water and dried in a 100 °C oven for two hours for use; the silicon carbide ceramic support was coated by the dip-pull coating method, the silicon carbide ceramic support was immersed in the coating liquid at a descending speed of 2 cm / s, and the pulling speed was 3 cm / s. After coating for 40 seconds, it was dried at room temperature for 1 hour and placed in an 80 °C oven for 2 hours. Then, the temperature was raised to 1100 °C in a muffle furnace at a heating rate of 2 °C / min, sintered and kept at this temperature for 2 hours, and then naturally cooled to room temperature to obtain a silicon carbide ceramic microfiltration membrane.

[0060] Example 3

[0061] The preparation of a high permeability flux silicon carbide ceramic microfiltration membrane without an intermediate transition layer comprises the following steps:

[0062] (1) At a constant temperature of 70 °C, dissolve 0.4 g of methyl cellulose and 0.8 g of polyacrylic acid in 87.8 mL of deionized water and stir to fully dissolve them to prepare a suspension;

[0063] (2) Stop heating, add weighed silicon carbide (particle size 2.6 μm) into the suspension, add 1 mL of silane coupling agent (KH-550) after it is evenly dispersed, stir for four hours, let stand to remove bubbles, and obtain a uniform coating solution;

[0064] (3) The porous tubular silicon carbide ceramic support was cleaned with deionized water and dried in an oven at 100 °C for two hours for use; the silicon carbide ceramic support was coated by the dip coating method and the dip pulling coating method. The silicon carbide ceramic support was immersed in the coating liquid at a descending speed of 1 cm / s and a pulling speed of 2 cm / s. The coating was carried out for 30 s, dried at room temperature for 1 hour, and then dried in an oven at 80 °C for 2 hours; the temperature was then increased to 1300 °C in a muffle furnace at a heating rate of 5 °C / min, sintered and kept at this temperature for 1 hour, and then naturally cooled to room temperature to obtain a silicon carbide ceramic microfiltration membrane.

[0065] Comparative Example 1

[0066] As described in Example 1, except that:

[0067] No silane coupling agent KH-550 was added.

[0068] Comparative Example 2

[0069] As described in Example 1, except that:

[0070] The silane coupling agent KH-550 was replaced with polyethylene glycol.

[0071] Test Example 1

[0072] The surface and cross-section SEM morphology of the silicon carbide ceramic support and the silicon carbide ceramic microfiltration membrane prepared in Example 1 were observed respectively. The results are as follows: Figure 1 As shown. Among them, Figure 1 (a) is the microscopic morphology of the support, where the macroporous structure of the support and the silicon carbide particles can be clearly seen. The particle size is about 10 to 15 μm, and the pores between the silicon carbide particles are relatively large. Figure 1 (b) is a microscopic image of the surface morphology of a silicon carbide ceramic microfiltration membrane, in which the upper part is the film and the support is below the film. Figure 1 In (b), it can be clearly seen that there are a large number of micropores on the surface of the membrane, the silicon carbide particles are tightly combined together, the immersion and pulling coating is relatively successful, and the sintered silicon carbide ceramic microfiltration membrane layer is relatively complete.

[0073] Test Example 2

[0074] The stability and film-forming performance of the coating liquid of silicon carbide ceramic microfiltration membrane prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were tested. The stability of the coating liquid was measured by sedimentation method. The lower the sedimentation volume percentage of the coating liquid, the higher the stability. The film-forming performance was evaluated by apparent grade, and three evaluation grades were set: (1) with many pinholes and wrinkles, (2) with a small number of pinholes and wrinkles, and (3) without pinholes and wrinkles. The higher the grade, the better the film-forming performance of the coating liquid. The results are shown in Table 1.

[0075] Table 1 Stability and film-forming properties of coating solutions of Examples 1 to 3

[0076]

[0077] It can be seen from the results in Table 1 that the coating liquid of the present invention has good stability, is not easy to settle, has good film-forming performance, and has a smooth surface without pinholes and wrinkles.

[0078] In Comparative Examples 1 and 2, since no silane coupling agent is used in the coating liquid, the coating liquid has poor stability, is easy to settle, has poor film-forming properties, and has many pinholes and wrinkles on the surface.

[0079] Test Example 3

[0080] The pure water permeation flux data of the porous tubular silicon carbide ceramic support in Example 1, the silicon carbide ceramic microfiltration membrane prepared in Example 1, and the silicon carbide ceramic microfiltration membranes obtained in Comparative Examples 1 and 2 were tested, and the results are shown in Table 2.

[0081] Table 2 Pure water permeation flux of samples of Example 1-Example 3 and Comparative Example 1-Comparative Example 2

[0082]

[0083] As can be seen from Table 2, in Comparative Examples 1 and 2, since no silane coupling agent is used in the coating liquid, the film-forming performance of the coating liquid is poor, and the particles of the film-forming liquid block the macropores of the support body, causing the sample permeation flux to be significantly lower than that of the sample with the addition of silane coupling agent.

[0084] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux, characterized in that: The steps include: The coating liquid is coated on a silicon carbide ceramic support, and after drying, a silicon carbide ceramic microfiltration membrane blank is obtained, and the blank is sintered at 1100-1300°C to obtain a silicon carbide ceramic microfiltration membrane with a high permeation flux; The coating liquid comprises: silicon carbide powder, a binder, a bonding aid, a dispersant and water, wherein the binder is methyl cellulose, the bonding aid is a silane coupling agent, and the dispersant is polyacrylic acid; the mass ratio of silicon carbide powder, the binder and the dispersant is (10-15): (0.2-0.5): (0.2-1), the volume ratio of the bonding aid and water is (0.5-1): (82.5-89.1), and the mass ratio of silicon carbide powder to water is (10-15) g: (82.5-89.1) mL.

2. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 1, characterized in that: The silane coupling agent is KH-550.

3. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 1, characterized in that: The particle size of the silicon carbide powder is 0.8-2.6 μm.

4. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 1, characterized in that: The coating liquid is prepared by the following method: adding a binder and a dispersant into water, adding a bonding aid after dissolving to obtain a suspension; adding silicon carbide powder into the suspension, stirring evenly, standing to remove bubbles, and obtaining the coating liquid.

5. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 4, characterized in that: Before adding binder and dispersant, heat the water temperature to 50-80℃.

6. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 1, characterized in that: The coating liquid is applied by dipping and pulling. After the silicon carbide ceramic support is dipped into the coating liquid, it is pulled and separated from the coating liquid, thus completing the coating liquid coating.

7. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeation flux according to claim 6, characterized in that: The silicon carbide ceramic support is immersed in the coating liquid at a descending speed of 1 to 2 cm / s, a pulling speed of 2 to 3 cm / s, and an immersion time of 30 to 60 s.

8. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeability flux according to claim 1, characterized in that: The sintering time is 1 to 3 h.

9. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeation flux according to claim 1, characterized in that: The sintering process is to heat up from room temperature to the sintering temperature and then sinter at a temperature-keeping rate of 2 to 5 °C / min.

10. The method for preparing a silicon carbide ceramic microfiltration membrane with high permeation flux according to claim 1, characterized in that: The drying temperature is 50-120°C and the drying time is 1-5 hours.

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