A high-flux ceramic membrane and its preparation method

Abstract

This application relates to the field of ceramic membranes, specifically disclosing a high-throughput ceramic membrane and its preparation method. The high-throughput ceramic membrane comprises a separation layer, a transition layer, and an alumina ceramic substrate. The transition layer, by weight, comprises 50-60 parts of nano-titanium dioxide, 20-25 parts of mesoporous silica microspheres, 5-10 parts of polyethylene glycol, and 20-30 parts of water, serving to connect the alumina ceramic substrate and the separation layer. The separation layer comprises tetrabutyl titanate. The pore size of the ceramic substrate 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. The high-throughput ceramic membrane of this application has the advantages of achieving high throughput and high selectivity.

Description

Technical Field

[0001] This application relates to the field of ceramic membranes, and more specifically, to a high-throughput ceramic membrane and a method for preparing the same. Background Technology

[0002] Originating in the early 20th century, ceramic membranes were initially limited to simple liquid filtration, removing large particles from water. However, their performance was suboptimal due to material and manufacturing limitations, resulting in a narrow range of applications. New ceramic materials have led to the development of membranes with more uniform pore size distribution, higher porosity, and greater mechanical strength, enabling their initial applications in fields requiring high separation precision, such as food sterilization and pharmaceutical purification. In recent years, with the increasing awareness of environmental protection and sustainable development, ceramic membranes have gained significant attention in wastewater treatment, seawater desalination, and new energy development due to their advantages such as good chemical stability, high temperature resistance, acid and alkali corrosion resistance, and ease of cleaning and regeneration. Their application scope continues to expand, making them a research hotspot in separation technology.

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

[0004] Traditional ceramic membranes face numerous challenges in increasing flux. To improve membrane separation accuracy, the pore size is often reduced, inevitably leading to a decrease in membrane flux. In practical applications, such as sterilization in the food and beverage industry, drug purification in the pharmaceutical industry, and wastewater treatment, lower flux translates to longer processing times and higher energy consumption. Summary of the Invention

[0005] In order to obtain a novel ceramic membrane with high flux and strong filtration and separation capabilities, this application provides a high-flux ceramic membrane and its preparation method.

[0006] This application provides a high-throughput ceramic membrane and its preparation method, which adopts the following technical solution:

[0007] A high-flux ceramic membrane has a membrane structure comprising a separation layer, a transition layer, and an alumina ceramic substrate. The transition layer comprises, by weight, 50-60 parts of nano-titanium dioxide, 20-25 parts of mesoporous silica microspheres, 5-10 parts of polyethylene glycol, and 20-30 parts of water. The transition layer serves to connect the alumina ceramic substrate and the separation layer. The separation layer comprises tetrabutyl titanate. The pore size of the ceramic substrate 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.

[0008] By employing the above technical solutions, the alumina ceramic matrix provides excellent mechanical strength and chemical stability, supporting the entire membrane structure. The transition layer connects the ceramic matrix and the separation layer. Nano-titanium dioxide possesses good chemical stability and high mechanical strength, while mesoporous silica microspheres, with their large specific surface area and regular mesoporous structure, increase the membrane's porosity and flux. Polyethylene glycol improves the fluidity and dispersibility of the suspension, allowing the transition layer to be coated more uniformly onto the ceramic matrix surface during preparation. The separation layer with specific pore sizes effectively traps target substances. The different pore sizes of the ceramic matrix, transition layer, and separation layer enable this ceramic membrane to achieve graded filtration of substances with different particle sizes, improving filtration efficiency and precision.

[0009] Optionally, the pore size of the transition layer is 0.9-1 μm on the side near the ceramic substrate and 0.1-0.2 μm on the side near the separation layer, and the pore size of the transition layer decreases from the ceramic substrate to the separation layer.

[0010] By adopting the above technical solution, the progressive pore size transition can reduce interlayer interface stress, avoid membrane structure cracking, and at the same time form a "flow gradient" to reduce fluid flow resistance and increase permeation flux.

[0011] Optionally, the thickness ratio of the alumina ceramic matrix, the transition layer, and the separation layer is (8-10):(1-4):1.

[0012] By adopting the above technical solution, the thicker alumina ceramic matrix provides sufficient mechanical support, ensuring that the membrane will not rupture or deform due to pressure or other factors during use, thus guaranteeing the membrane's structural stability. The transition layer has a moderate thickness, achieving good connection with the ceramic matrix and separation layer while fully utilizing its role in graded filtration and buffering. The thinner separation layer reduces fluid resistance and increases membrane flux while maintaining separation accuracy. The thickness ratio of this application enables the layers to work synergistically, optimizing membrane filtration performance and flux while ensuring the membrane's mechanical properties and chemical stability, thereby improving the membrane's overall performance and service life.

[0013] Secondly, this application provides a method for preparing a high-throughput ceramic membrane, employing the following technical solution:

[0014] A method for preparing a high-flux ceramic membrane includes the following steps:

[0015] Alumina ceramic matrix is ​​obtained by sintering alumina.

[0016] 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 a ceramic substrate and heated to 400-500℃ for 1-1.5 hours to obtain a transition layer.

[0017] Tetrabutyl titanate is atomically deposited onto the surface of the transition layer at a temperature of 260-300℃ to obtain a separation layer, which is then sintered at 950-1050℃ for 1-2 hours to obtain a high-throughput ceramic membrane.

[0018] By employing the above-mentioned technical solutions, ultrasonic dispersion enables the uniform dispersion of raw materials such as nano-titanium dioxide and mesoporous silica microspheres in a suspension, while centrifugal spraying allows the suspension to adhere more uniformly to the ceramic substrate surface. Heat treatment then forms a stable transition layer structure. Tetrabutyl titanate is atomically deposited onto the transition layer surface, followed by high-temperature sintering to obtain the separation layer. Atomic deposition allows for precise control of the thickness and pore size of the separation layer, while high-temperature sintering further enhances its crystallinity and stability.

[0019] Optionally, the alumina ceramic matrix is ​​prepared by:

[0020] Aluminum nitrate nonahydrate and urea were dissolved in water at a molar ratio of 1:(2.5-3.5), and 0.5wt% polyvinylpyrrolidone was added. The mixture was then subjected to a hydrothermal reaction at 175-185℃ for 12-14 hours to obtain nano-γ-alumina. The surface of the nano-alumina was then modified with 3-aminopropyltrimethoxysilane.

[0021] 60-65 wt% of 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 are dispersed in water to obtain a suspension. The suspension is cooled to -80 to -60 °C at a rate of 5-6 °C / min for directional freezing. After freezing, it is heated to 500-550 °C to remove sodium chloride. The suspension is then sintered at 1500-1600 °C for 1.5-2 h to form an alumina ceramic matrix.

[0022] By employing the above-mentioned technical solution, aluminum nitrate nonahydrate undergoes a hydrothermal reaction with urea to generate nanorod-shaped γ-alumina (50-80 nm in diameter, 200-300 nm in length). The nanorod-shaped structure forms the matrix framework, providing high specific surface area and mechanical support. Adding 0.5 wt% polyvinylpyrrolidone (PVP) inhibits agglomeration and prevents excessive grain growth during sintering. Modification with 3-aminopropyltrimethoxysilane (APTES) introduces amino (-NH2) groups. These amino groups can form covalent bonds (Si-O-Al bonds) with the transition layer, enhancing interfacial bonding and alleviating interlayer thermal stress. Directional freezing creates vertically penetrating pores, with carbon nanotubes interpenetrating the pore walls, enhancing the matrix's flexural strength and toughness. Sodium chloride, used as a pore-forming agent, leaves no harmful residues during the removal process. Its particle size controls the spherical pore size, forming a dual-scale structure with the directional pores, further improving flux. Sintering at 1500-1600℃ transforms γ-Al2O3 into the stable α-Al2O3 phase.

[0023] Optionally, the alumina ceramic matrix may also undergo the following treatment:

[0024] The surface of the alumina ceramic substrate was etched with Ar / O2 plasma with a power of 100-150W, and the surface roughness of the alumina ceramic substrate after treatment was Ra50-80nm.

[0025] By adopting the above technical solution, plasma etching can achieve a surface roughness of Ra50-80nm, which 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, and make the transition layer less likely to fall off during use, thereby ensuring the stability and service life of the entire film structure.

[0026] Optionally, the transition layer is prepared by:

[0027] A suspension was obtained by mixing nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol and water and then ultrasonically dispersing them.

[0028] 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 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. After each layer is sprayed, the temperature is heated to 120-150℃ and held for 5-10 minutes.

[0029] After centrifugal spraying, the coated alumina ceramic substrate is heated to 400-500℃ and held for 1.5-2 hours to obtain a transition layer.

[0030] By adopting the above technical solution, through gradient control of rotation speed and pressure in centrifugal spraying, and combining nano-titanium dioxide and mesoporous silica microspheres, a continuous gradient structure with pore size from 0.9-1μm (substrate side) to 0.1-0.2μm (separation layer side) is constructed, realizing the synergy of high-throughput transport and high-precision retention; stepwise curing and low-temperature sintering form Ti-O-Si covalent bond interface, enhancing the interfacial bonding force.

[0031] Optionally, the specific preparation method of the separation layer is as follows:

[0032] The precursor is obtained by adding 0.5-2 vol% of polysorbate to tetrabutyl titanate and then dispersing it ultrasonically.

[0033] In a nitrogen atmosphere, the precursor is atomically deposited at a deposition temperature of 260-280℃ and a pulse time of 0.15-0.2s. After the deposition is completed, oxygen plasma is injected with a pulse time of 0.2-0.3s. The above steps are repeated for 20-30 cycles to obtain the separation layer.

[0034] By employing the above technical solution, polysorbate is added to tetrabutyl titanate and ultrasonically dispersed. Polysorbate, acting as a surfactant, reduces surface tension, prevents precursor aggregation, and ensures uniform distribution of the precursor during atomic deposition. Simultaneously, controlling the atomic deposition temperature and pulse duration, and performing multiple deposition cycles, results in a denser and more uniform separation layer structure, forming a well-structured separation layer and reducing film defects. After atomic deposition, oxygen plasma is injected with a pulse duration of 0.2-0.3 s. This process helps improve the surface properties of the separation layer. Oxygen plasma makes the separation layer surface more hydrophilic, improving its compatibility with the aqueous phase, thus facilitating the penetration of the aqueous phase during the separation process.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. By controlling the pore size gradient of the alumina ceramic matrix, transition layer, and separation layer, and combining the advantages of different materials, this application can achieve high-flux transport and high-precision retention. The transition layer uses a composite material of nano-titanium dioxide and mesoporous silica microspheres to increase the membrane porosity and flux, while the separation layer precisely controls the pore size to effectively retain target substances, significantly improving filtration efficiency and precision.

[0037] 2. This application utilizes hydrothermal reaction, surface modification, directional freezing, and sintering processes to successfully prepare an alumina ceramic matrix with excellent properties. The nanorod-like γ-alumina structure provides the matrix with a high specific surface area and mechanical support. The amino groups introduced by surface modification enhance the interfacial bonding between the matrix and the transition layer. The pores formed by directional freezing and the reinforcing 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 membrane flux. Simultaneously, through plasma etching, the surface roughness of the alumina ceramic matrix reaches Ra50-80 nm, significantly enhancing the bonding between the transition layer and the matrix, ensuring the long-term stability and efficient use of the membrane.

[0038] 3. The preparation method of this application forms a transition layer with 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, ultimately achieving efficient and stable separation performance, suitable for multiple fields such as water treatment and gas separation. Detailed Implementation

[0039] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0040] Example

[0041] Example 1

[0042] A method for preparing a high-flux ceramic membrane:

[0043] Aluminum nitrate nonahydrate and urea were mixed at a molar ratio of 1:3, and then deionized water and 0.5 wt% polyvinylpyrrolidone were added. The amount of deionized water added was 100 mL / mol Al source. The raw materials were added to a reaction vessel and stirred at 500 rpm for 12 h at 180 °C to generate γ-Al₂O₃ nanorods with a diameter of 50-80 nm and a length of 200-300 nm. The γ-Al₂O₃ was washed by centrifugation with a 25% ethanol solution and dried under vacuum at 60 °C for 12 h. A modification solution was prepared at a volume ratio of 3-aminopropyltrimethoxysilane:ethanol:water = 1:5:0.5. The γ-Al₂O₃ was added to the modification solution and stirred at room temperature at 25 °C for 2 h. After completion, the mixture was centrifuged and dried to obtain modified γ-Al₂O₃. 40g of modified γ-Al2O3, 40g of carbon nanotubes (diameter 10-20nm, length 1-2μm), and 340g of NaCl (particle size 200-400μm) were mixed. Deionized water was added to the mixture to adjust the solid content to 50wt%. The mixture was then ultrasonically dispersed at 200W for 30min to obtain a suspension. The suspension was transferred to a mold and placed on a freezing table. The temperature was lowered to -70℃ at 5℃ / min and held for 2h to form vertical ice template channels. The frozen material was then placed in a heating device and heated to 500℃ at a heating rate of 5℃ / min and held for 2h to completely dissolve and remove NaCl, forming spherical pores. The mixture was then heated to 1550℃ and sintered for 2h. After cooling to room temperature in the furnace, an alumina ceramic matrix with a thickness of 45 μm was obtained.

[0044] 550g of nano-TiO2 (anatase, 20-50nm) and 220g of mesoporous SiO2 microspheres (particle size 200-300nm, specific surface area 800m²) were combined. 2 80g of polyethylene glycol (analytical grade, molecular weight 2000) and 150g of deionized water were mixed in a clean container and dispersed by ultrasonication at 300W for 30 minutes, with the temperature controlled at <30℃ in an ice-water bath, to form a uniform suspension. The suspension was then sprayed onto the surface of an alumina ceramic substrate using a centrifugal sprayer. The spraying process is shown in the table below.

[0045] Number of coating layers Rotational 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

[0046] After each layer is sprayed, the temperature is raised to 140℃ and held for 8 minutes. After the spraying operation is completed, the temperature is raised to 450℃ and held for 2 hours. The PEG decomposes to form mesopores, and then the layer is naturally cooled to room temperature to obtain a transition layer with decreasing pore size. The pore size of the transition layer is 0.9-1 μm on the side near the ceramic substrate and 0.1-0.2 μm on the side near the separation layer. The total thickness of the transition layer is 20 μm.

[0047] 1 vol% polysorbate (Tween-80) was added to tetrabutyl titanate and ultrasonically dispersed at 150 W for 30 min to form a precursor; a thermal ALD system (nitrogen flow rate 500 sccm, vacuum degree 10) was used. -3 With a temperature control accuracy of ±1℃, an alumina ceramic substrate containing a transition layer is placed in a deposition chamber. Under a nitrogen atmosphere, the precursor is atomically deposited on the surface of the transition layer at a deposition temperature of 270℃ and a pulse time of 0.18s. After completion, oxygen plasma is injected with a pulse time of 0.25s. The above steps are repeated for 25 cycles to obtain a separation layer with a thickness of 5μm.

[0048] The alumina ceramic substrate containing the separation layer and transition layer after deposition was kept at 1000℃ for 1.5h and then cooled to room temperature to obtain a high-flux ceramic membrane.

[0049] Example 2

[0050] A method for preparing a high-flux ceramic membrane: The difference from Example 1 lies in the spraying process of the transition layer, as shown in the table below:

[0051] Number of coating layers Rotational 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

[0052] Example 3

[0053] A method for preparing a high-flux ceramic membrane: The difference from Example 1 lies in the transition layer spraying process, as shown in the table below:

[0054] Number of coating layers Rotational 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

[0055] Example 4

[0056] A method for preparing a high-throughput ceramic film: The difference from Example 1 is that the alumina ceramic substrate is further treated as follows: the surface of the alumina ceramic substrate is etched with 120W Ar / O2 plasma for 5 minutes, and the surface roughness of the alumina ceramic substrate after treatment is Ra65nm.

[0057] Example 5

[0058] A method for preparing a high-flux ceramic membrane: The difference from Example 1 is that polysorbate is not added to tetrabutyl titanate.

[0059] Example 6

[0060] A method for preparing a high-throughput ceramic membrane: The difference from Example 1 is that 620g of α-Al2O3 powder is mixed with 40g of SiO2 sintering aid and an aqueous solution containing 340g of sodium chloride to obtain a mixture; the mixture is placed in a mold, heated to 500-550℃ to remove sodium chloride, and sintered at 1550℃ for 2h to form an alumina ceramic matrix.

[0061] Example 7

[0062] A method for preparing a high-throughput ceramic membrane: The difference from Example 1 is that carbon nanotubes are not added in the preparation of the alumina ceramic matrix.

[0063] Example 8

[0064] A method for preparing a high-throughput ceramic membrane: The difference from Example 1 is that the nano-γ-alumina is not modified in the preparation of the alumina ceramic matrix.

[0065] Example 9

[0066] A method for preparing a high-flux ceramic membrane: The difference from Example 1 is that the separation layer uses titanium metal with a purity ≥99% as the evaporation source, and the process is carried out at 300°C, with an oxygen flow rate of 50 sccm and a vacuum degree of 10... -3 The film was obtained by evaporation of Pa at an evaporation rate of 1 A / s.

[0067] Comparative Example

[0068] Comparative Example 1

[0069] A method for preparing a high-flux ceramic membrane: The difference from Example 1 lies in the spraying process of the transition layer, as shown in the table below:

[0070] Number of coating layers Rotational 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

[0071] Comparative Example 2

[0072] A method for preparing a high-throughput ceramic membrane: The difference from Example 1 is that mesoporous silica microspheres are not added to the transition layer component.

[0073] Comparative Example 3

[0074] A method for preparing a high-throughput ceramic membrane: The difference from Example 1 is that the thickness ratio of the alumina ceramic substrate, the transition layer and the separation layer is 11:2:1.

[0075] Comparative Example 4

[0076] A method for preparing a high-throughput ceramic membrane: the difference from Example 1 is that the thickness ratio of the alumina ceramic substrate, the transition layer and the separation layer is 7:6:1.

[0077] Performance testing

[0078] Detection methods

[0079] Pure water flux testing was performed using a flat sheet membrane permeameter (effective membrane area 100 cm²). 2 The operating pressure was 0.1 MPa, the temperature was 25 ± 2℃, and the circulation flow rate was 500 mL / min. The permeate volume was recorded every 30 minutes, and the average value was taken after 2 hours of continuous testing.

[0080] Flux calculation formula: J=V / (A*t)(L / (m 2 ·h)).

[0081] Retention rate test standards: titanium dioxide microparticles (particle size 50-100nm) and bovine serum albumin (BSA, molecular weight 67kDa). A standard solution with a concentration of 500mg / L was prepared, filtered through a ceramic membrane, and the filtrate was collected. The concentration was detected using a dynamic light scattering (DLS) instrument.

[0082] Retention rate: R = (1 - Cp / Cf) * 100%.

[0083] Table 1 Test Results

[0084] <![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％

[0085] Combining Example 1 and Comparative Example 1 with Table 1, it can be seen that Example 1 employs a dual-gradient spraying method with rotational speed (500-1000 r / min) and pressure (0.1-0.3 MPa) to form a continuous pore size gradient from 0.9-1 μm (substrate side) to 0.1-0.2 μm (separation layer side). This design reduces interlayer interface stress, decreases the risk of membrane structure cracking, and simultaneously constructs a "flow-guiding gradient" to reduce fluid resistance. Compared to the fixed-parameter spraying (800 r / min, 0.22 MPa) of Comparative Example 1, Example 1 exhibits higher pure water flux and better retention accuracy, demonstrating that the gradient process significantly improves the membrane's mass transfer efficiency and separation accuracy.

[0086] Combining Example 1 and Comparative Example 2 with Table 1, it can be seen that the transition layer of Example 1, with the addition of mesoporous silica microspheres (20-25 parts), utilizes their high specific surface area (800 m²) 2 The mesoporous microspheres (60%–40%) and their regular mesoporous structure increase the membrane porosity and create a gradient pore distribution. Compared to Comparative Example 2 (without mesoporous SiO2), Example 1 showed higher pure water flux and better retention of bovine serum albumin (BSA), indicating that the mesoporous microspheres effectively improved the membrane permeability and sieving selectivity.

[0087] Combining Example 1 and Comparative Examples 3-4 with Table 1, it can be seen that Example 1 optimizes the thickness ratio to 9:4:1 (matrix: transition layer: separation layer), ensuring that the matrix provides sufficient mechanical support (45 μm), the transition layer achieves pore size buffering (20 μm), and the separation layer remains ultra-thin and dense (5 μm). Compared to Comparative Example 3 (11:2:1, excessively thick matrix) and Comparative Example 4 (7:6:1, excessively thick transition layer), Example 1 exhibits superior flux and retention performance, demonstrating that the rational design of the thickness ratio balances support strength and mass transfer resistance.

[0088] Combining Examples 1, 2, and 3 with Table 1, it can be seen that the dual-gradient spraying (increasing rotation speed + increasing pressure) in Example 1, compared to the single-parameter gradient (fixed rotation speed in Example 2, fixed pressure in Example 3), produces a more uniform pore size gradient and a stronger interfacial bond. This results in Example 1 having better pure water flux and rejection rate than Examples 2-3, demonstrating that dual-parameter synergistic control is more beneficial for membrane structure optimization.

[0089] As can be seen from Examples 1 and 4 and Table 1, Example 4 involves Ar / O2 plasma etching (Ra 65nm) on the substrate surface, which increases surface roughness and expands the contact area between the transition layer and the substrate. Compared with Example 1, Example 4 shows further improvements in flux and rejection rate, indicating that the etching process enhances interlayer adhesion, reduces film defects, and improves overall performance.

[0090] As can be seen from Examples 1 and 5 and Table 1, the addition of 1 vol% polysorbate to the precursor of the separation layer in Example 1 serves as a surfactant to reduce the surface tension of the precursor and prevent aggregation. Compared to Example 5 (without polysorbate), the separation layer of Example 1 is more uniform and dense, with slightly better flux and rejection rate, demonstrating the effect of surfactant in improving membrane quality.

[0091] As can be seen from Examples 1 and 6 and Table 1, Example 1, employing a hydrothermal synthesis of nano-γ-Al₂O₃ and a directional freezing process, forms dual-scale channels (directional pores + spherical pores), resulting in higher porosity. Compared to Example 6 (conventional α-Al₂O₃ powder), the matrix of Example 1 provides superior mechanical support and permeability, demonstrating the advantages of nanostructure design and directional freezing technology.

[0092] As can be seen from Examples 1 and 7 and Table 1, the addition of 4 wt% carbon nanotubes to the matrix in Example 1 enhances toughness by penetrating the pore walls and reduces pore collapse. Compared to Example 7 (without carbon nanotubes), Example 1 shows a significant increase in flux and rejection rate, demonstrating that carbon nanotubes effectively enhance the mechanical properties and pore stability of the matrix.

[0093] As can be seen from Examples 1 and 8 and Table 1, Example 1 modifies the matrix with silane (-NH2 group), forming covalent bonds (Si-O-Al) with the transition layer. Compared with Example 8 (unmodified), Example 1 has stronger interlayer bonding, better flux and retention rate, proving that surface modification significantly improves interfacial stability.

[0094] As can be seen from Examples 1 and 9 and Table 1, Example 1 uses atomic layer deposition (ALD) to prepare the separation layer, achieving nanoscale pore size uniformity. Compared with Example 9 (evaporation coating), the separation layer of Example 1 is denser and more uniform, with better flux and rejection rate, demonstrating the advantages of ALD technology in film precision control.

[0095] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-flux ceramic membrane, characterized in that, Its membrane structure includes a separation layer, a transition layer, and an alumina ceramic substrate; the transition layer raw materials, by weight, include 50-60 parts 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 substrate and the separation layer; the separation layer raw material includes tetrabutyl titanate; the pore size of the ceramic substrate 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; The method for preparing the alumina ceramic matrix is ​​as follows: Aluminum nitrate nonahydrate and urea were dissolved in water at a molar ratio of 1:(2.5-3.5), and 0.5wt% polyvinylpyrrolidone was added. The mixture was then subjected to a hydrothermal reaction at 175-185℃ for 12-14 hours to obtain nano-γ-alumina. The surface of the nano-alumina was then modified with 3-aminopropyltrimethoxysilane. 60-65 wt% modified nano-γ-alumina, 3-5 wt% carbon nanotubes, and 30-35 wt% sodium chloride with a particle size of 200-400 μm were dispersed in water to obtain a suspension. The suspension was cooled to -80 to -60℃ at a rate of 5-6℃ / min for directional freezing. After freezing, it was heated to 500-550℃ to remove sodium chloride. The suspension was then sintered at 1500-1600℃ for 1.5-2 hours to form an alumina ceramic matrix. The alumina ceramic matrix also undergoes the following treatment: The surface of the alumina ceramic substrate was etched with Ar / O2 plasma with a power of 100-150W, and the surface roughness of the alumina ceramic substrate after treatment was Ra50-80nm.

2. The high-flux ceramic membrane according to claim 1, characterized in that: The transition layer has a pore size of 0.9-1 μm on the side near the ceramic substrate and a pore size of 0.1-0.2 μm on the side near the separation layer. 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 1-3, characterized in that: Includes the following steps: Alumina ceramic matrix is ​​obtained by sintering alumina. 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 a ceramic substrate and heated to 400-500℃ for 1-1.5 hours to obtain a transition layer. Tetrabutyl titanate is atomically deposited onto the surface of the transition layer at a temperature of 260-300℃ to obtain a separation layer, which is then sintered at 950-1050℃ for 1-2 hours to obtain a high-throughput ceramic membrane.

5. The method for preparing a high-flux ceramic membrane according to claim 4, characterized in that: The method for preparing the transition layer is as follows: A suspension was obtained by mixing nano-titanium dioxide, mesoporous silica microspheres, polyethylene glycol and water and then ultrasonically dispersing them. 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 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. After each layer is sprayed, the temperature is heated to 120-150℃ and held for 5-10 minutes. After centrifugal spraying, the coated alumina ceramic substrate is heated to 400-500℃ and held for 1.5-2 hours to obtain a transition layer.

6. 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 as follows: The precursor is obtained by adding 0.5-2 vol% of polysorbate to tetrabutyl titanate and then dispersing it ultrasonically. In a nitrogen atmosphere, the precursor is atomically deposited at a deposition temperature of 260-280℃ and a pulse time of 0.15-0.2s. After the deposition is completed, oxygen plasma is injected with a pulse time of 0.2-0.3s. The above steps are repeated for 20-30 cycles to obtain the separation layer.