High-flux ceramic membrane and preparation method thereof

Abstract

The invention relates to the field of ceramic membranes, and particularly discloses a high-flux ceramic membrane and a preparation method thereof. The membrane structure of the high-flux ceramic membrane comprises a separation layer, a transition layer and an aluminum oxide ceramic matrix, the transition layer is prepared from the following raw materials in parts by weight: 50 to 60 parts of nano titanium dioxide, 20 to 25 parts of mesoporous silicon dioxide microspheres, 5 to 10 parts of polyethylene glycol and 20 to 30 parts of water, and the transition layer is used for communicating the aluminum oxide ceramic matrix with the separation layer; the raw material of the separation layer comprises tetrabutyl titanate; the aperture of the ceramic matrix is 1-5 [mu] m, the aperture of the transition layer is 0.1-1 [mu] m, and the aperture of the separation layer is 0.05-0.1 [mu] m. The high-flux ceramic membrane has the advantages of high flux and high selectivity.

Description

Technical Field

[0001] This application relates to the field of ceramic membranes. More specifically, it relates to a high-flux ceramic membrane and a preparation method thereof. Background Art

[0002] Ceramic membranes originated in the early 20th century and were only capable of handling simple liquid filtration to remove large particulate impurities in water. Limited by materials and processes, their performance was poor and the application scope was narrow. With new ceramic materials, ceramic membranes with uniform pore size distribution, higher porosity and mechanical strength were prepared, enabling their initial application in fields with high separation precision requirements such as food sterilization and pharmaceutical purification. In recent years, with the popularization of environmental awareness and the concept of sustainable development, ceramic membranes have attracted much attention in fields such as sewage treatment, seawater desalination, and new energy development due to their advantages of good chemical stability, high temperature resistance, acid and alkali corrosion resistance, and easy cleaning and regeneration. The application scope has been continuously expanded, making them a research hotspot in separation technologies.

[0003] The separation principle of ceramic membranes is mainly based on the sieving effect and adsorption. When the mixture to be separated passes through the ceramic membrane, particles, molecules or ions larger than the membrane pore size are intercepted, while substances smaller than the membrane pore size pass through the membrane, thus achieving separation. At the same time, the chemical groups on the surface of the ceramic membrane have an adsorption effect on certain substances, further improving the separation selectivity.

[0004] Traditional ceramic membranes face many challenges in improving flux. To improve the separation precision of the membrane, the membrane pore size is often reduced, which inevitably leads to a decrease in the flux of the membrane. In actual application scenarios, such as in the sterilization of the food and beverage industry, the purification of drugs in the pharmaceutical industry, and sewage treatment, a lower flux means longer processing time and higher energy consumption. Summary of the Invention

[0005] In order to obtain a new type of ceramic membrane with high flux and strong filtration and separation ability, this application provides a high-flux ceramic membrane and a preparation method thereof.

[0006] The high-flux ceramic membrane and the preparation method thereof provided by this application adopt the following technical solutions: A high-flux ceramic membrane, the membrane structure of which includes a separation layer, a transition layer and an alumina ceramic matrix; the raw materials of the transition layer include 50 - 60 parts by weight of nano-titanium dioxide, 20 - 25 parts by weight of mesoporous silica microspheres, 5 - 10 parts by weight of polyethylene glycol and 20 - 30 parts by weight of water. The transition layer is used to connect the alumina ceramic matrix and the separation layer; the raw materials of the separation layer include tetrabutyl titanate; the pore size of the ceramic matrix is 1 - 5 μm, the pore size of the transition layer is 0.1 - 1 μm, and the pore size of the separation layer is 0.05 - 0.1 μm.

[0007] By adopting the above technical solution, the alumina ceramic matrix provides good mechanical strength and chemical stability, providing support for the entire membrane structure. The transition layer connects the ceramic matrix and the separation layer. Nano-titanium dioxide has good chemical stability and high mechanical strength. Mesoporous silica microspheres have a large specific surface area and regular mesoporous structure, which can increase the porosity of the membrane and improve the flux of the membrane; polyethylene glycol can improve the fluidity and dispersibility of the suspension, enabling the transition layer to be more evenly coated on the surface of the ceramic matrix during the preparation process. The separation layer with a specific pore size can effectively intercept the target substances. The different pore size designs of the ceramic matrix, transition layer, and separation layer enable the ceramic membrane to achieve hierarchical filtration of substances with different particle sizes, improving the filtration efficiency and accuracy.

[0008] Optionally, the pore size of the transition layer on the side close to the ceramic matrix is 0.9 - 1 μm, and the pore size on the side close to the separation layer is 0.1 - 0.2 μm. The pore size of the transition layer decreases along the direction from the ceramic matrix to the separation layer.

[0009] By adopting the above technical solution, the progressive pore size transition can reduce the interfacial stress between layers, avoid membrane structure cracking, and at the same time form a "flow guiding gradient", reducing the fluid flow resistance and improving the permeation flux.

[0010] Optionally, the thickness ratio of the alumina ceramic matrix, transition layer, and separation layer is (8 - 10):(1 - 4):1.

[0011] By adopting the above technical solution, the relatively thick alumina ceramic matrix can provide sufficient mechanical support to ensure that the membrane will not rupture or deform due to factors such as pressure during use, guaranteeing the structural stability of the membrane; the thickness of the transition layer is moderate, which can not only achieve good connection with the ceramic matrix and separation layer, but also give full play to its hierarchical filtration and buffering effects on substances; the relatively thin separation layer can reduce the resistance to fluid while ensuring the separation accuracy, improving the flux of the membrane. The thickness ratio of this application enables the layers to work together synergistically, optimizing the filtration performance and flux of the membrane while ensuring the mechanical properties and chemical stability of the membrane, improving the comprehensive performance and service life of the membrane.

[0012] In the second aspect, the present application provides a method for preparing a high-flux ceramic membrane, adopting the following technical solution: A method for preparing a high-flux ceramic membrane includes the following steps: Sinter alumina to obtain an alumina ceramic matrix; Mix nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol, and water and ultrasonically disperse them for 20 - 30 min to obtain a suspension. Centrifugally spray the suspension onto one side of the surface of the ceramic matrix and heat it to 400 - 500 °C for heat preservation for 1 - 1.5 h to obtain a transition layer; At a temperature of 260 - 300 °C, tetrabutyl titanate is deposited on the surface of the transition layer by atomic deposition to obtain a separation layer, and then sintered at 950 - 1050 °C for 1 - 2 h to obtain a high-flux ceramic membrane.

[0013] By adopting the above technical solution, ultrasonic dispersion can evenly disperse raw materials such as nano-titanium dioxide and mesoporous silica microspheres in the suspension, and centrifugal spraying can make the suspension adhere to the surface of the ceramic matrix more evenly, and heat treatment forms a stable transition layer structure. Tetrabutyl titanate is deposited on the surface of the transition layer by atomic deposition, and then a separation layer is obtained through high-temperature sintering. Atomic deposition can precisely control the thickness and pore size of the separation layer, and high-temperature sintering further improves the crystallinity and stability of the separation layer.

[0014] Optionally, the preparation method of the alumina ceramic matrix is as follows: Dissolve aluminum nitrate nonahydrate and urea in water at a molar ratio of 1:(2.5 - 3.5), add 0.5 wt% polyvinylpyrrolidone, and perform hydrothermal reaction at 175 - 185 °C for 12 - 14 h to obtain nano-γ-alumina, and perform surface modification on it with 3-aminopropyltrimethoxysilane; Disperse 60 - 65 wt% of the modified nano-γ-alumina, 3 - 5 wt% of carbon nanotubes, and 30 - 35 wt% of sodium chloride with a particle size of 200 - 400 μm in water to obtain a suspension. The suspension is cooled to -80 - -60 °C at a rate of 5 - 6 °C / min for directional freezing, and after freezing, it is heated to 500 - 550 °C to remove sodium chloride, and sintered at 1500 - 1600 °C for 1.5 - 2 h to form an alumina ceramic matrix.

[0015] By adopting the above technical solution, aluminum nitrate nonahydrate and urea undergo hydrothermal reaction to generate nano-rod-shaped γ-alumina (diameter 50 - 80 nm, length 200 - 300 nm). The nano-rod-shaped structure constructs the matrix skeleton to provide a high specific surface area and mechanical support. Adding 0.5 wt% polyvinylpyrrolidone (PVP) inhibits agglomeration and avoids excessive grain growth during sintering. Through modification with 3-aminopropyltrimethoxysilane (APTES), amino (-NH 2 ) groups are introduced. The amino groups can form covalent bonds (Si-O-Al bonds) with the transition layer, enhancing the interfacial bonding force and relieving the interlayer thermal stress. Directional freezing can form vertically through pores, and carbon nanotubes penetrate the pore walls, enhancing the flexural strength and toughness of the matrix. Sodium chloride, as a pore-forming agent, has no harmful residues during the removal process. Its particle size controls the spherical pore size, and forms a dual-scale structure with the directional pores, further improving the flux. Sintering at 1500 - 1600 °C converts γ-Al 2 O 3 to α-Al 2 O 3 stable phase.

[0016] Optionally, the alumina ceramic substrate is further processed as follows: Etch the surface of the alumina ceramic substrate with an Ar / O 2 plasma at a power of 100 - 150 W. After the treatment, the surface roughness of the alumina ceramic substrate is Ra50 - 80 nm.

[0017] By adopting the above technical solution, plasma etching to make the surface roughness reach Ra50 - 80 nm can increase the contact area between the transition layer and the ceramic substrate, improve the bonding force between the transition layer and the ceramic substrate, make the transition layer not easy to fall off during use, and thus ensure the stability and service life of the entire membrane structure.

[0018] Optionally, the preparation method of the transition layer is as follows: Mix nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol and water and ultrasonically disperse to obtain a suspension; Place the alumina ceramic substrate in a centrifugal spraying device, and spray the suspension onto the surface of the alumina ceramic substrate at a rotation speed of 500 - 600 r / min and a spraying pressure of 0.1 - 0.15 MPa. After each layer is sprayed, the rotation speed is increased by 80 - 120 r / min, and the spraying pressure is increased by 0.02 - 0.05 MPa until the rotation speed reaches 1000 r / min and the spraying pressure reaches 0.3 MPa, and after each layer is sprayed, it is heated to 120 - 150 °C and kept warm for 5 - 10 min; After centrifugal spraying, heat the alumina ceramic substrate with the coating to 400 - 500 °C and keep it warm for 1.5 - 2 h to obtain the transition layer.

[0019] By adopting the above technical solution, through the gradient control of the rotation speed and pressure in centrifugal spraying, combined with the compounding of nano-titanium dioxide and mesoporous silica microspheres, a continuous gradient structure with pore sizes ranging from 0.9 - 1 μm (substrate side) to 0.1 - 0.2 μm (separation layer side) is constructed, realizing the coordination of high-throughput transmission and high-precision retention; step-by-step curing and low-temperature sintering form a Ti - O - Si covalent bond interface, enhancing the interfacial bonding force.

[0020] Optionally, the specific preparation method of the separation layer is as follows: Add 0.5 - 2 vol% of polysorbate to tetrabutyl titanate, and ultrasonically disperse to obtain a precursor; Under a nitrogen atmosphere, the precursor is subjected to atomic deposition at a deposition temperature of 260 - 280 °C and a pulse time of 0.15 - 0.2 s. After completion, oxygen plasma is injected with a pulse time of 0.2 - 0.3 s. Repeat the above steps for 20 - 30 cycles to obtain the separation layer.

[0021] By adopting the above technical solution, polysorbate is added to tetrabutyl titanate and ultrasonically dispersed. As a surfactant, polysorbate can reduce the surface tension, avoid the agglomeration of the precursor, and make the precursor evenly distributed during atomic deposition. At the same time, by controlling the temperature and pulse time of atomic deposition, and performing multiple cycles of deposition, the separation layer structure becomes denser and more uniform, forming a separation layer with regular structure and reducing film layer defects. After atomic deposition is completed, oxygen plasma is injected with a pulse time of 0.2 - 0.3 s. This process helps to improve the surface properties of the separation layer. Oxygen plasma can make the surface of the separation layer more hydrophilic, improve its compatibility with the aqueous phase, and thus facilitate the penetration of the aqueous phase during the separation process.

[0022] In summary, the present application has the following beneficial effects: 1. Since the present application controls the pore size gradient of the alumina ceramic matrix, the transition layer, and the separation layer, and combines the advantages of different materials, it can achieve high-throughput transmission and high-precision retention. The transition layer adopts a composite material of nano-titanium dioxide and mesoporous silica microspheres to increase the porosity and flux of the membrane. At the same time, the separation layer precisely controls the pore size, effectively retains the target substance, and significantly improves the filtration efficiency and precision.

[0023] 2. In the present application, hydrothermal reaction, surface modification, directional freezing, sintering and other processes are preferably adopted to successfully prepare an alumina ceramic matrix with excellent performance. The structure of nano-rod-shaped γ-alumina provides the matrix with a high specific surface area and mechanical support. The amino groups introduced by surface modification enhance the interfacial bonding force between the matrix and the transition layer. The pores formed by directional freezing and the strengthening effect of carbon nanotubes improve the flexural strength and toughness of the matrix. The application of sodium chloride pore-forming agent and the dual-scale structure formed by directional pores further improve the flux of the membrane. At the same time, through plasma etching treatment, the surface roughness of the alumina ceramic matrix reaches Ra50 - 80 nm, significantly enhancing the bonding force between the transition layer and the matrix, and ensuring the long-term stability and efficient use of the membrane.

[0024] 3. The preparation method of the present application forms a transition layer with a gradually decreasing pore gradient through centrifugal spraying, and precisely controls the thickness and pore size of the separation layer through atomic deposition, thereby significantly improving the flux, selectivity and stability of the membrane. After high-temperature sintering, the crystallinity of the separation layer is enhanced, and finally high-efficiency and stable separation performance is achieved, which is applicable to multiple fields such as water treatment and gas separation. Specific Embodiments

[0025] The following further details the present application in conjunction with embodiments. It should be specifically noted that: for those not indicating specific conditions in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. All raw materials used in the following embodiments can be obtained from ordinary commercial sources unless otherwise specified. Embodiment

[0026] Example 1 A preparation method of a high-throughput ceramic membrane: Aluminum nitrate nonahydrate and urea are mixed according to a molar ratio of 1:3, and then deionized water and 0.5 wt% polyvinylpyrrolidone are added. The addition amount of deionized water is 100 mL / mol Al source. The raw materials are added to a reaction kettle and stirred at 180 °C and 500 rpm for 12 h to generate nanorod-shaped γ-Al 2 O 3 γ-Al 2 O 3 with a diameter of 50 - 80 nm and a length of 200 - 300 nm. It is centrifugally washed with an ethanol solution with a mass concentration of 25% and vacuum dried at 60 °C for 12 h. A modification solution is prepared according to a volume ratio of 3-aminopropyltrimethoxysilane:ethanol:water = 1:5:0.5. γ-Al 2 O 3 is added to the modification solution and stirred at room temperature of 25 °C for 2 h. After completion, it is centrifuged and dried to obtain modified γ-Al 2 O 3 ; 620 g of modified γ-Al 2 O 3 , 40 g of carbon nanotubes (diameter 10 - 20 nm, length 1 - 2 μm), and 340 g of NaCl (particle size 200 - 400 μm) are mixed. Deionized water is added to the mixed materials to adjust the solid content to 50 wt%, and then ultrasonic dispersion is carried out at 200 W for 30 min to obtain a suspension; the suspension is transferred to a mold and placed on a freezing table, cooled to -70 °C at a rate of 5 °C / min, and kept for 2 h to form vertical ice template pores. The frozen material is placed in a heating device, heated to 500 °C at a heating rate of 5 °C / min and kept for 2 h. NaCl is completely dissolved and removed to form spherical pores, and then heated to 1550 °C and sintered for 2 h, and cooled to room temperature with the furnace to obtain an alumina ceramic matrix with a thickness of 45 microns.

[0027] 550 g of nano-TiO 2 (anatase, 20 - 50 nm), 220 g of mesoporous SiO 2 microspheres (particle size 200 - 300 nm, specific surface area 800 m 2 / g), 80 g of polyethylene glycol (analytical pure, molecular weight 2000), and 150 g of deionized water are mixed in a clean container, and ultrasonic dispersion is carried out at 300 W for 30 min, and the temperature is controlled below 30 °C in an ice-water bath to form a uniform suspension; the suspension is sprayed onto the surface of the alumina ceramic matrix by a centrifugal spraying machine, and the spraying process is shown in the following table: Number of spray coating layers Rotation speed (r / min) Spray gun pressure (MPa) Spraying time (s) 1 500 0.10 60 2 600 0.14 60 3 700 0.18 60 4 800 0.22 60 5 900 0.26 60 6 1000 0.30 60 After spraying each layer, it is heated to 140 °C and kept warm for 8 min. After the spraying operation is completed, it is heated to 450 °C and kept warm for 2 h. PEG decomposes to form mesopores, and then it is naturally cooled to room temperature to obtain a transition layer with a gradually decreasing pore gradient. The pore diameter on the side of the transition layer close to the ceramic matrix is 0.9 - 1 μm, the pore diameter on the side close to the separation layer is 0.1 - 0.2 μm, and the total thickness of the transition layer is 20 μm.

[0028] 1 vol% of polysorbate (Tween - 80) is added to tetrabutyl titanate, and after ultrasonic dispersion for 30 min with 150 W, a precursor is formed; using a thermal ALD system (nitrogen flow rate 500 sccm, vacuum degree 10 -3 Pa), with a temperature control accuracy of ±1 °C, the alumina ceramic matrix containing the transition layer is placed in the deposition chamber. Under a nitrogen atmosphere, the precursor performs atomic deposition on the surface of the transition layer at a deposition temperature of 270 °C and a pulse time of 0.18 s. After completion, oxygen plasma is injected with a pulse time of 0.25 s. The above steps are repeated for 25 cycles to obtain a separation layer with a thickness of 5 μm.

[0029] The alumina ceramic matrix containing the separation layer and the transition layer after deposition is kept warm at 1000 °C for 1.5 h and then cooled to room temperature to obtain a high - flux ceramic membrane.

[0030] Example 2 A preparation method of a high - flux ceramic membrane: The difference from Example 1 is that the spraying process of the transition layer is as shown in the following table: Number of spray coating layers Rotation speed (r / min) Spray gun pressure (MPa) Spraying time (s) 1 800 0.10 60 2 800 0.14 60 3 800 0.18 60 4 800 0.22 60 5 800 0.26 60 6 800 0.30 60 Example 3 A preparation method of a high - flux ceramic membrane: The difference from Example 1 is that the spraying process of the transition layer is as shown in the following table: Number of spray coating layers Rotation speed (r / min) Spray gun pressure (MPa) Spraying time (s) 1 500 0.22 60 2 600 0.22 60 3 700 0.22 60 4 800 0.22 60 5 900 0.22 60 6 1000 0.22 60 Example 4 A preparation method of a high - flux ceramic membrane: The difference from Example 1 is that the alumina ceramic matrix is also subjected to the following treatment: Ar / O 2 plasma with a power of 120 W is used to etch the surface of the alumina ceramic matrix for 5 min, and the surface roughness of the alumina ceramic matrix after treatment is Ra 65 nm.

[0031] Example 5 A preparation method of a high - flux ceramic membrane: The difference from Example 1 is that polysorbate is not added to tetrabutyl titanate.

[0032] Example 6 A preparation method of a high - flux ceramic membrane: The difference from Example 1 is that 620 g of α - Al 2 O 3The powder is mixed with 40 g of SiO 2 a sintering aid and an aqueous solution containing 340 g of sodium chloride to obtain a mixture; the mixture is placed in a mold, heated to 500 - 550 °C to remove sodium chloride, and sintered at 1550 °C for 2 h to form an alumina ceramic matrix.

[0033] Example 7 A method for preparing a high - flux ceramic membrane: different from Example 1 in that no carbon nanotubes are added in the preparation of the alumina ceramic matrix.

[0034] Example 8 A method for preparing a high - flux ceramic membrane: different from Example 1 in that the nano - γ - alumina is not modified in the preparation of the alumina ceramic matrix.

[0035] Example 9 A method for preparing a high - flux ceramic membrane: different from Example 1 in that the separation layer is obtained by evaporation coating with titanium metal having a purity ≥ 99% as the evaporation source, at 300 °C, an oxygen flow rate of 50 sccm, and a vacuum degree of 10 -3 Pa, and the evaporation rate is 1 Å / s.

[0036] Comparative example Comparative example 1 A method for preparing a high - flux ceramic membrane: different from Example 1 in that the spraying process of the transition layer is as shown in the following table: Number of spray coating layers Rotation speed (r / min) Spray gun pressure (MPa) Spraying time (s) 1 800 0.22 60 2 800 0.22 60 3 800 0.22 60 4 800 0.22 60 5 800 0.22 60 6 800 0.22 60 Comparative example 2 A method for preparing a high - flux ceramic membrane: different from Example 1 in that no mesoporous silica microspheres are added to the composition of the transition layer.

[0037] Comparative example 3 A method for preparing a high - flux ceramic membrane: different from Example 1 in that the thickness ratio of the alumina ceramic matrix, the transition layer, and the separation layer is 11:2:1.

[0038] Comparative example 4 A method for preparing a high - flux ceramic membrane: different from Example 1 in that the thickness ratio of the alumina ceramic matrix, the transition layer, and the separation layer is 7:6:1.

[0039] Performance detection test Detection method The pure water flux is tested using a flat - membrane permeator (effective membrane area 100 cm 2 ), with an operating pressure of 0.1 MPa, a temperature of 25 ± 2 °C, a circulation flow rate of 500 mL / min. Record the volume of the permeate every 30 minutes, and take the average value after continuous testing for 2 h. Flux calculation formula: J = V / (A*t) (L / (m 2 ·h)).

[0040] Retention rate test standard substances: titanium dioxide microparticles (particle size 50 - 100 nm), bovine serum albumin (BSA, molecular weight 67 kDa). Prepare a standard solution with a concentration of 500 mg / L. After filtering through the ceramic membrane, take the filtrate and use a dynamic light scattering instrument (DLS) to detect the concentration.

[0041] Retention rate: R = (1 - Cp / Cf) * 100%.

[0042] Table 1 Detection results <![CDATA[Pure water flux (L / (m 2 ·h))]]> Retention rate (50nm microspheres) Retention rate (BSA) Example 1 1100 99.8％ 99.2％ Example 2 1050 99.5％ 99.0％ Example 3 1020 99.3％ 98.8％ Example 4 1150 99.9％ 99.4％ Example 5 1080 99.6％ 99.1％ Example 6 950 99.0％ 98.5％ Example 7 900 98.8％ 98.2％ Example 8 920 98.9％ 98.3％ Example 9 1000 99.2％ 98.6％ Comparative Example 1 980 99.1％ 98.7％ Comparative Example 2 930 98.7％ 98.1％ Comparative Example 3 850 98.5％ 97.8％ Combining Example 1 and Comparative Example 1 and referring to Table 1, it can be seen that in Example 1, double-gradient spraying was used with a rotation speed of (500 - 1000 r / min) and a pressure of (0.1 - 0.3 MPa), forming a continuous pore size gradient from 0.9 - 1 μm (substrate side) to 0.1 - 0.2 μm (separation layer side). This design reduces the interfacial stress between layers, reduces the risk of membrane structure cracking, and at the same time constructs a "diversion gradient" to reduce fluid resistance. Compared with the fixed-parameter spraying (800 r / min, 0.22 MPa) in Comparative Example 1, the pure water flux in Example 1 is higher and the retention accuracy is better, proving that the gradient process significantly improves the mass transfer efficiency and separation accuracy of the membrane.

[0043] Combining Example 1 and Comparative Example 2 and referring to Table 1, it can be seen that in Example 1, mesoporous silica microspheres (20 - 25 parts) were added to the transition layer. Utilizing its high specific surface area (800 m 2 / g) and regular mesoporous structure, the porosity of the membrane was increased and a gradient pore distribution (60% → 40%) was formed. Compared with Comparative Example 2 (without mesoporous SiO 2 ), the pure water flux in Example 1 is higher and the retention rate for bovine serum albumin (BSA) is better, indicating that the mesoporous microspheres effectively improve the permeation flux and sieving selectivity of the membrane.

[0044] Combining Example 1 and Comparative Examples 3 - 4 and referring to Table 1, it can be seen that in Example 1, the optimized thickness ratio is 9:4:1 (substrate: transition layer: separation layer), ensuring that the substrate provides sufficient mechanical support (45 μm), the transition layer realizes pore size buffering (20 μm), and the separation layer remains ultrathin and dense (5 μm). Compared with Comparative Example 3 (11:2:1, too thick substrate) and Comparative Example 4 (7:6:1, too thick transition layer), the flux and retention performance in Example 1 are better, proving that the reasonable design of the thickness ratio balances the support strength and mass transfer resistance.

[0045] Combined with Examples 1, 2, and 3 and Table 1, it can be seen that for the double-gradient spraying (increasing rotation speed + pressure) in Example 1, compared with the single-parameter gradient (fixed rotation speed in Example 2 and fixed pressure in Example 3), the formed pore size gradient is more uniform and the interfacial bonding is stronger. This makes the pure water flux and rejection rate of Example 1 better than those of Examples 2 - 3, proving that the dual-parameter collaborative control is more conducive to the optimization of the membrane structure.

[0046] Combined with Examples 1 and 4 and Table 1, it can be seen that in Example 4, the surface of the substrate was subjected to Ar / O 2 plasma etching (Ra 65 nm) to increase the surface roughness and expand the contact area between the transition layer and the substrate. Compared with Example 1, the flux and rejection rate of Example 4 were further improved, indicating that the etching treatment enhanced the interlayer adhesion, reduced the film layer defects, and improved the overall performance.

[0047] Combined with Examples 1 and 5 and Table 1, it can be seen that in Example 1, 1 vol% of polysorbate was added to the separation layer precursor as a surfactant to reduce the surface tension of the precursor and avoid agglomeration. Compared with Example 5 (without polysorbate), the separation layer of Example 1 was more uniform and dense, and the flux and rejection rate were slightly better, proving the promoting effect of the surfactant on the film layer quality.

[0048] Combined with Examples 1 and 6 and Table 1, it can be seen that in Example 1, the hydrothermal synthesis of nano-γ-Al 2 O 3 + directional freezing process was used to form a dual-scale pore structure (directional pores + spherical pores) with a higher porosity. Compared with Example 6 (conventional α-Al 2 O 3 powder), the substrate of Example 1 provided better mechanical support and permeability, proving the advantages of the nanostructure design and the directional freezing process.

[0049] Combined with Examples 1 and 7 and Table 1, it can be seen that in Example 1, 4 wt% of carbon nanotubes was added to the substrate, which penetrated the pore walls to enhance toughness and reduce pore channel collapse. Compared with Example 7 (without carbon nanotubes), the flux and rejection rate of Example 1 were significantly improved, proving that carbon nanotubes effectively enhanced the mechanical properties and pore stability of the substrate.

[0050] Combined with Examples 1 and 8 and Table 1, it can be seen that in Example 1, the substrate was silane-modified (-NH 2 group) to form a covalent bond (Si-O-Al) with the transition layer. Compared with Example 8 (unmodified), the interlayer bonding force of Example 1 was stronger, and the flux and rejection rate were better, proving that the surface modification significantly improved the interfacial stability.

[0051] Combined with Example 1 and Example 9 and in conjunction with Table 1, it can be seen that in Example 1, atomic layer deposition (ALD) was used to prepare the separation layer, achieving nanoscale pore size uniformity. Compared with Example 9 (evaporation coating), the separation layer in Example 1 is denser and more uniform, and the flux and rejection rate are better, demonstrating the advantage of ALD technology in the precision control of the film layer.

[0052] This specific embodiment is only an explanation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high flux ceramic membrane, characterized in that: Its membrane structure includes a separation layer, a transition layer and an alumina ceramic matrix; the transition layer raw materials include 50-60 parts by weight of nano titanium dioxide, 20-25 parts of mesoporous silica microspheres, 5-10 parts of polyethylene glycol and 20-30 parts of water, and the transition layer is used to connect the alumina ceramic matrix and the separation layer; the separation layer raw materials include tetrabutyl titanate; the pore size of the ceramic matrix is ​​1-5μm, the pore size of the transition layer is 0.1-1μm, and the pore size of the separation layer is 0.05-0.1μm.

2. The high flux ceramic membrane according to claim 1, characterized in that: The pore size of the transition layer on the side close to the ceramic substrate is 0.9-1 μm, and the pore size on the side close to the separation layer is 0.1-0.2 μm. The pore size of the transition layer decreases from the ceramic substrate to the separation layer.

3. The high flux ceramic membrane according to claim 1, characterized in that: The thickness ratio of the alumina ceramic matrix, the transition layer and the separation layer is (8-10):(3-5):

1.

4. A method for preparing a high-flux ceramic membrane according to any one of claims 1 to 3, characterized in that: The following steps are involved: The aluminum oxide is sintered to obtain an aluminum oxide ceramic matrix; Nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol and water are mixed and ultrasonically dispersed for 20-30 minutes to obtain a suspension, the suspension is centrifugally sprayed onto one side of the surface of the ceramic substrate, and heated to 400-500° C. for 1-1.5 hours to obtain a transition layer; At a temperature of 260-300°C, tetrabutyl titanate is atomically deposited on the surface of the transition layer to obtain a separation layer, which is then sintered at 950-1050°C for 1-2 hours to obtain a high-flux ceramic membrane.

5. The method for preparing a high-flux ceramic membrane according to claim 4, characterized in that: The preparation method of the alumina ceramic matrix is ​​as follows: Aluminum nitrate nonahydrate and urea are dissolved in water at a molar ratio of 1:(2.5-3.5), 0.5wt% polyvinyl pyrrolidone is added, and a hydrothermal reaction is carried out at 175-185°C for 12-14h to obtain nano-γ-alumina, and the surface of the nano-alumina is modified with 3-aminopropyltrimethoxysilane; 60-65wt% of modified nano-γ-alumina, 3-5wt% of carbon nanotubes, and 30-35wt% of sodium chloride with a particle size of 200-400μm are dispersed in water to obtain a suspension, and the suspension is cooled to -80--60℃ at a rate of 5-6℃ / min for directional freezing, and then heated to 500-550℃ after freezing to remove the sodium chloride, and sintered at 1500-1600℃ for 1.5-2h to form an alumina ceramic matrix.

6. The method for preparing a high-flux ceramic membrane according to claim 5, characterized in that: The alumina ceramic substrate is also subjected to the following treatments: The surface of the alumina ceramic substrate is etched with Ar / O2 plasma at a power of 100-150W, and the surface roughness of the alumina ceramic substrate after the treatment is Ra50-80nm.

7. The method for preparing a high-flux ceramic membrane according to claim 4, characterized in that: The preparation method of the transition layer is as follows: Nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol and water are mixed and ultrasonically dispersed to obtain a suspension; The alumina ceramic substrate is placed in a centrifugal spraying device, and the suspension is sprayed onto the surface of the alumina ceramic substrate at a speed of 500-600 r / min and a spraying pressure of 0.1-0.15 MPa. After each layer is sprayed, the speed is increased by 80-120 r / min, and the spraying pressure is increased by 0.02-0.05 MPa until the speed reaches 1000 r / min and the spraying pressure reaches 0.3 MPa, and after each layer is sprayed, it is heated to 120-150°C and kept warm for 5-10 minutes; After the centrifugal spraying is completed, the alumina ceramic substrate with the coating is heated to 400-500°C and kept warm for 1.5-2h to obtain a transition layer.

8. The method for preparing a high flux ceramic membrane according to claim 4, characterized in that: The specific preparation method of the separation layer is: Add 0.5-2 vol% of polysorbate to tetrabutyl titanate and obtain a precursor after ultrasonic dispersion; In a nitrogen atmosphere, the precursor is atomically deposited at a deposition temperature of 260-280°C and a pulse time of 0.15-0.2s. After completion, oxygen plasma is injected with a pulse time of 0.2-0.3s. The above steps are repeated for 20-30 cycles to obtain a separation layer.