A method for preparing high-flux ceramic microfiltration membranes based on high-activity piezoelectric powder synthesized at low temperature

Abstract

The application discloses a preparation method of high-flux ceramic microfiltration membrane based on high-activity piezoelectric powder low-temperature synthesis, which comprises the following steps: step one: bismuth titanate, tetrabutyl titanate, sodium dodecyl sulfonate, barium hydroxide octahydrate and potassium hydroxide are dissolved in anhydrous ethanol and deionized water, mixed and stirred, and then hydrothermal reaction is carried out at 160 DEG C for 30 hours; after reaction, the obtained wet powder is washed and dried to obtain high-activity BaTiO3 / Bi4Ti3O 12 powder; step two: the powder is granulated after being sprayed with water mist, and is aged for 24 hours, and then is pressed into shape under a steel mold to obtain dry green sheets; step three: the dry green sheets are calcined in a muffle furnace, and the ceramic microfiltration membrane is obtained after furnace cooling. The application has the advantages of energy saving and low consumption, and the high-permeation-flux ceramic membrane prepared at a lower calcination temperature can be applied to solid-gas and solid-liquid separation fields, and therefore has good application value.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders. Background Technology

[0002] Membrane separation technology is a phase-change-free physical separation technology based on selectively permeable membranes. It boasts advantages such as mild separation conditions, high separation efficiency, and low carbon footprint, making it a crucial technology relied upon by modern process industries. However, concentration polarization inevitably occurs during membrane separation due to transmembrane pressure differences, leading to filter cake formation on the membrane surface and membrane fouling. Currently, membrane fouling is a common problem encountered in membrane separation and its applications, and it has become a bottleneck limiting the further high efficiency of membrane separation technology in process industries. Although some methods exist to mitigate the side effects of membrane fouling, such as physical flushing, chemical cleaning, and surface modification, these undoubtedly increase the time and economic costs of additional treatments. Furthermore, these additional processes corrode / damage the membrane itself, reducing its lifespan. Therefore, improving membrane fouling without compromising membrane performance is of great significance for promoting the development of membrane separation technology.

[0003] Based on the characteristic that piezoelectric materials can convert alternating current into mechanical vibration, separation membranes prepared using piezoelectric materials as substrates can mitigate or even prevent membrane fouling due to the mechanical vibrations generated during the separation process. Therefore, constructing separation membranes based on piezoelectric materials can avoid membrane fouling and achieve efficient separation. Non-toxicity, simple synthesis process, low preparation cost, and good piezoelectric response are considered essential conditions for selecting optimal membrane separation substrates. To this end, Gao Guandao's research group prepared a piezoelectric separation membrane using the typical perovskite piezoelectric material BaTiO3. Simultaneously, based on the mechanical vibrations generated during the separation process, membrane fouling was avoided, and a self-cleaning effect was achieved on the membrane surface. This work was published in Nature (Nature 608, 69-73 (2022)) and a patent application was filed (application number: CN202210546270.7). However, although the report shows good anti-fouling properties, the membrane product requires continuous high-temperature calcination at 1200℃ for 4 hours to sinter the separation membrane, significantly increasing the application cost. Furthermore, the high sintering temperature and holding time resulted in the formation of numerous neck connections between particles, leading to a significant decrease in permeation flux despite the high mechanical strength of the sample. This is primarily due to the reduction in pore size with increasing temperature. Although an effective solution to this paradox remains elusive, numerous researchers continue their tireless efforts to address this "seesaw" problem. Therefore, synthesizing piezoelectric separation membranes with both high permeability and high strength under low-temperature conditions is crucial for further reducing the cost of membrane preparation and promoting the application and development of membrane separation technology. Summary of the Invention

[0004] This invention addresses the technical problem of the contradiction between high sintering temperature and low permeability and high strength in the preparation of piezoelectric separation membranes in existing technologies. It provides a low-cost, simple, and mass-production-friendly method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders.

[0005] To solve the above technical problems, the technical solution of the present invention is: a method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders, characterized by comprising the following steps: Step 1: Bismuth titanate, tetrabutyl titanate, sodium dodecyl sulfonate, barium hydroxide octahydrate, and potassium hydroxide are dissolved in anhydrous ethanol and deionized water. After mixing and stirring, a hydrothermal reaction is carried out at 160℃ for 30 hours. The resulting wet powder is washed and dried to obtain highly active BaTiO3 / Bi4Ti3O 12 Powder; Step 2: The powder obtained in Step 1 is granulated after being sprayed with water mist and aged for 24 hours. It is then pressed into shape under a steel mold to obtain a dry blank. Step 3: Place the dry blank obtained in Step 2 into a muffle furnace for calcination, and obtain a ceramic microfiltration membrane after cooling in the furnace.

[0006] In step one, the mass ratio of bismuth titanate, tetrabutyl titanate, sodium dodecyl sulfonate, and anhydrous ethanol is 0.4~0.5:3.3~3.5:1~2:50~60.

[0007] In step one, the mass ratio of potassium hydroxide, barium hydroxide octahydrate, and deionized water is 3.36~6.72:3~3.3:10~20.

[0008] The washing process in step one involves first washing with dilute hydrochloric acid at pH=1, then washing with deionized water until neutral, and then drying at 70~90℃ for 5~9 hours.

[0009] In step two, the mass ratio of powder to sprayed water mist is 5~10:0.2~0.5.

[0010] In step two, the granulation process involves grinding for 1 to 1.5 hours until well-flowing particles are formed.

[0011] The pressing pressure in step two is 4 MPa.

[0012] The calcination temperature in step three is 950~1100℃, and the holding time is 1~2h.

[0013] The ceramic microfiltration membrane prepared in step three has a porosity of 37-44%, a mechanical strength of 18.6-31 MPa, and a pure water permeation flux of ~600 L / (m²).2 ·h·bar).

[0014] The present invention has the following beneficial effects: (1) The present invention intentionally introduces typical piezoelectric materials to ensure the piezoelectric effect during the separation process. The nanosheets rich in the separation membrane substrate have high activity characteristics, which effectively reduces the firing temperature of the separation membrane.

[0015] (2) The separation membrane substrate of the present invention is a large number of nanosheets and particle assemblies. After pressing, the sheets are interlocked to form a network structure with porous characteristics. After calcination, the interlocked sheets form a large number of neck connections, resulting in a high-strength separation membrane. The pore structure formed by the interlocking sheets is retained, providing favorable channels for water permeation and ensuring high permeability.

[0016] (3) The piezoelectric separation membrane provided by the present invention has a relatively smooth wavy surface after firing. According to the Hagen-Poiseuille equation, the smooth wavy structure is conducive to the rapid flow of the medium in the membrane pores, which further ensures permeability and prevents membrane fouling caused by concentration polarization.

[0017] (4) Compared with traditional methods of improving membrane fouling such as physical flushing, chemical cleaning, and surface modification, this technology uses highly active piezoelectric powder with a hierarchical structure formed by the assembly of nanosheets and particles as raw material, which effectively avoids the physical / chemical damage to the separation membrane caused by traditional methods of improving membrane fouling. In addition, its high strength increases the membrane life. Attached Figure Description

[0018] Figure 1 This is a SEM image of the powder obtained in Embodiment 1 of the present invention; Figure 2 This is a TEM image of the powder obtained in Embodiment 1 of the present invention; Figure 3 This is a surface SEM image of the separation membrane obtained in Embodiment 1 of the present invention; Figure 4 This is the X-ray diffraction pattern of the separation membrane obtained in Example 1 of the present invention; Figure 5 This is a permeation performance diagram of the separation membrane obtained in Example 1 of the present invention; Figure 6 This is a surface SEM image of the separation membrane obtained in Embodiment 2 of the present invention; Figure 7 This is a permeation performance diagram of the separation membrane obtained in Example 2 of the present invention; Figure 8 This is a cross-sectional SEM image of the separation membrane obtained in Embodiment 3 of the present invention; Figure 9This is a permeation performance diagram of the separation membrane obtained in Example 3 of the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0020] A method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders, characterized by comprising the following steps: Step 1: Dissolve 0.4g bismuth titanate, 3.3g tetrabutyl titanate, 1g sodium dodecyl sulfonate, 3.15g barium hydroxide octahydrate, and 3.36g potassium hydroxide in 50ml anhydrous ethanol and 20ml deionized water. After mixing and stirring, carry out a hydrothermal reaction at 160℃ for 30h. The resulting wet powder is washed and dried to obtain highly active BaTiO3 / Bi4Ti3O 12 Powder; Step 2: Spray 0.5g of water mist onto 10g of powder obtained in Step 1, granulate for 1 hour to obtain free-flowing granules, and age for 24 hours. Then, press the powder into shape under a steel mold at a pressure of 4MPa to obtain dry blanks. Step 3: Place the dry blank obtained in Step 2 into a muffle furnace and heat it to 950℃ for 2 hours. After cooling in the furnace, a ceramic microfiltration membrane is obtained.

[0021] The washing process in step one involves first washing with dilute hydrochloric acid at pH=1, then washing with deionized water until neutral, and finally drying at 80°C for 6 hours.

[0022] like Figure 1 As shown, the powder prepared in this embodiment exhibits a distinct hierarchical structure, with the overall structure consisting of a large number of one-dimensional sheets and nanoparticles assembled together. The individual structure is formed by the interlocking and staggered stacking of sheet-like bodies and nanoparticles.

[0023] like Figure 2 As shown, the TEM image and SEM image of the powder obtained in this embodiment are consistent, that is, the surface is rich in nanosheets that are interlaced, while a large number of nanoparticles are filled in the nanosheets, together forming a hierarchical structure.

[0024] like Figure 3 As shown, the separation membrane prepared in this embodiment exhibits a uniformly dispersed distribution of monomer particles and a uniform pore size distribution on its surface under a scanning electron microscope. The surface of the monomer particles shows obvious fusion marks and appears as smooth wavy patterns. The neck connections between monomer particles are good, and the interior of the monomer particles is accompanied by a pore structure of 20-40 nm.

[0025] like Figure 4As shown, the powder prepared in this embodiment was subjected to X-ray diffraction (XRD) analysis. The position and intensity of its characteristic peaks coincided with those of barium titanate (PDF 05-0626) and bismuth titanate (PDF35-0795), respectively. There were no other crystalline phase impurity peaks, indicating that the product is composed of barium titanate and bismuth titanate and has good crystallinity.

[0026] like Figure 5 As shown in the figure, the permeation performance of the separation membrane prepared in this embodiment is related to time when pure water is used as the separation medium, which shows that the material has good stability and permeation flux during separation. Example 2

[0027] A method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders, characterized by comprising the following steps: Step 1: Dissolve 0.5g bismuth titanate, 3.5g tetrabutyl titanate, 2g sodium dodecyl sulfonate, 3.3g barium hydroxide octahydrate, and 6.72g potassium hydroxide in 50ml anhydrous ethanol and 20ml deionized water. After mixing and stirring, carry out a hydrothermal reaction at 160℃ for 30h. The resulting wet powder is washed and dried to obtain highly active BaTiO3 / Bi4Ti3O 12 Powder; Step 2: Spray 0.2g of water mist onto the 5g powder obtained in Step 1, granulate for 1.5h until it becomes free-flowing granules, and age for 24h. Then press it into shape under a steel mold at a pressure of 4MPa to obtain a dry blank. Step 3: Place the dry blank obtained in Step 2 into a muffle furnace and heat it to 1000℃ for 1.5 hours. After cooling in the furnace, a ceramic microfiltration membrane is obtained.

[0028] The washing process in step one involves first washing with dilute hydrochloric acid at pH=1, then washing with deionized water until neutral, and finally drying at 70°C for 9 hours.

[0029] like Figure 6 As shown, the separation membrane prepared in this embodiment exhibits a porous structure formed by the accumulation of uniform particles under a scanning electron microscope. The monomer particles are uniformly distributed and overlap to form a uniform pore structure. There are neck connections between the monomer particles, and their surfaces are well fused and smooth. The monomer surface shows certain fish-scale-like ripples, and there are a certain number of 20-30 nm pore structures between the monomers.

[0030] like Figure 7 As shown in the figure, the permeation performance of the separation membrane prepared in this embodiment is related to time when pure water is used as the separation medium, which shows that the material has good stability and permeation flux during separation. Example 3

[0031] A method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders, characterized by comprising the following steps: Step 1: Dissolve 0.45g bismuth titanate, 3.4g tetrabutyl titanate, 1.5g sodium dodecyl sulfonate, 3g barium hydroxide octahydrate, and 5.04g potassium hydroxide in 60ml anhydrous ethanol and 10ml deionized water. After mixing and stirring, carry out a hydrothermal reaction at 160℃ for 30h. The resulting wet powder is washed and dried to obtain highly active BaTiO3 / Bi4Ti3O 12 Powder; Step 2: Spray 0.4g of water mist onto the 7g powder obtained in Step 1, granulate for 1 hour until it becomes free-flowing granules, and age for 24 hours. Then, press it into shape under a steel mold at a pressure of 4MPa to obtain a dry blank. Step 3: Place the dry blank obtained in Step 2 into a muffle furnace and heat it to 1100℃ for 1 hour. After cooling in the furnace, a ceramic microfiltration membrane is obtained.

[0032] The washing process in step one involves first washing with dilute hydrochloric acid at pH=1, then washing with deionized water until neutral, and finally drying at 90°C for 5 hours.

[0033] like Figure 8 As shown, the separation membrane prepared in this embodiment exhibits a distinct pore structure in its cross-sectional morphology under a scanning electron microscope. The neck connections and fusions between particles are obvious, and the surface of the individual particles is highly smooth, with a distinct pore structure.

[0034] like Figure 9 As shown in the figure, the permeation performance of the separation membrane prepared in this embodiment is related to time when pure water is used as the separation medium, which shows that the material has good stability and permeation flux during separation.

[0035] As shown in Table 1, the porosity, mechanical strength and pure water permeation flux of the ceramic microfiltration membranes prepared in Examples 1-3 are shown.

[0036] Case 1 43.95% 18.6 MPa <![CDATA[~600 L / (m 2 ·h·bar)]]> Case 2 40.55% 24.2 MPa <![CDATA[~515 L / (m 2 ·h·bar)]]> Case 3 37.03% 30.4 MPa <![CDATA[~420 L / (m 2 ·h·bar)]]>

Claims

1. A method for preparing high-flux ceramic microfiltration membranes based on low-temperature synthesis of highly active piezoelectric powders, characterized in that... Includes the following steps: Step one: dissolve bismuth titanate, tetrabutyl titanate, sodium dodecyl sulfonate, barium hydroxide octahydrate, potassium hydroxide in anhydrous ethanol and deionized water, after mixing and stirring, carry out hydrothermal reaction at 160℃ for 30h, after reaction, the wet powder is washed and dried to obtain high-activity BaTiO3 / Bi4Ti3O 12 powder; Step 2: The powder obtained in Step 1 is granulated after being sprayed with water mist and aged for 24 hours. It is then pressed into shape under a steel mold to obtain a dry blank. Step 3: The dry blank obtained in Step 2 is placed in a muffle furnace for calcination and cooled with the furnace to obtain a ceramic microfiltration membrane. The membrane substrate is a large number of nanosheets and particle assemblies. After pressing, the sheets are stacked together to form a network structure with porous characteristics. The washing process in step one is to first wash with dilute hydrochloric acid with pH=1, then wash with deionized water until neutral, and then dry at 70-90℃ for 5-9 hours. The calcination temperature in step three is 950–1100℃, and the holding time is 1–2 hours. The ceramic microfiltration membrane prepared in step three has a porosity of 37–44%, a mechanical strength of 18.6–31 MPa, and a pure water permeation flux of ~600 L / (m²). 2 ·h·bar).

2. The preparation method according to claim 1, characterized in that: In step one, the mass ratio of bismuth titanate, tetrabutyl titanate, sodium dodecyl sulfonate, and anhydrous ethanol is 0.4–0.5: 3.3–3.5: 1–2: 50–60.

3. The preparation method according to claim 1, characterized in that: In step one, the mass ratio of potassium hydroxide, barium hydroxide octahydrate, and deionized water is 3.36–6.72:3–3.3:10–20.

4. The preparation method according to claim 1, characterized in that: In step two, the mass ratio of powder to sprayed water mist is 5-10:0.2-0.

5.

5. The preparation method according to claim 1, characterized in that: In step two, the granulation process involves grinding for 1 to 1.5 hours until well-flowing particles are formed.

6. The preparation method according to claim 1, characterized in that: The pressing pressure in step two is 4 MPa.

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