Positively charged ceramic membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of filtering materials, in particular to a positively charged ceramic membrane and a preparation method and application thereof.The preparation method comprises the steps that two kinds of Al2O3 particles with different particle sizes are taken and dispersed in ZrO2 or TiO2 sol, two kinds of precursor solutions are obtained, a tubular supporting body is sequentially coated with the two kinds of precursor solutions, drying and sintering are conducted, and the positively charged ceramic membrane is obtained; repeatedly coating, drying and sintering to obtain a tubular ceramic membrane; nano MgO particles with the particle size of 0.03-0.1 [mu] m are uniformly dispersed in the second sol, the content of nano MgO is 1-5%, and a sol charging agent is obtained; and immersing the tubular ceramic membrane in the sol charging agent for 3-5 min, and then carrying out third drying and third sintering to obtain the positively charged ceramic membrane. The positively charged ceramic membrane disclosed by the invention has the advantages of good virus interception effect, high flux, low cost, simple preparation process and strong pollution resistance, and can be widely applied to a virus separation process in water treatment.

Description

Technical Field

[0001] This invention relates to the field of filtration materials technology, and in particular to a positively charged ceramic membrane, its preparation method, and its application. Background Technology

[0002] With rapid economic development, industrial pollution has become increasingly severe, leading to a growing number of environmental problems, such as declining air quality and freshwater resource crises. Among these, the pollution of drinking water sources is of particular concern to the public, as it is closely related to human life and safety. There are many types of pollutants in water, including inorganic, organic, biological, thermal, and radioactive pollutants. Pathogenic microorganisms (bacteria, viruses, etc.) are numerous and widely distributed, and some can multiply not only in living organisms but also in water. Some pathogenic microorganisms are also highly resistant to drugs, making general water treatment methods such as chlorination ineffective. Because viruses are extremely small, with most viruses around 100 nm in size, and there are many different types with vastly different properties, the isolation and removal of viruses is extremely complex. Currently, in the biological and pharmaceutical fields, methods for virus removal mainly include high temperature, physical adsorption, chemical inactivation, and ultraviolet radiation. These methods involve complex virus isolation processes and are costly.

[0003] Since viruses are charged colloidal particles, separating viruses through the electroadsorption of charged materials is characterized by its simplicity, safety, and excellent adsorption and separation effect. Therefore, charged materials, as a novel type of virus separation and removal material, have significant application value. Charged membranes refer to membranes with fixed charged groups on their surface or in their bulk. During the separation process, charged membranes can separate components through physical sieving and also utilize the electrostatic adsorption of their surface charges to separate smaller particles with opposite charges. Their unique separation performance gives them a significant technological advantage over electrically neutral membranes. Organic charged membranes suffer from poor stability, acid and alkali corrosion resistance, and high-temperature resistance. They are also prone to fouling, difficult to clean and regenerate, resulting in short membrane lifespan, low flux, and high maintenance and operating costs, all of which limit their application in real life. Inorganic charged ceramic membranes, on the other hand, possess a series of advantages of ordinary ceramic membranes, such as high mechanical strength, good stability, high temperature resistance, pressure resistance, and wear resistance. They also have the characteristic of being able to achieve specific separations due to their charged nature. They can be used for gas separation, liquid separation and purification, and membrane reactors, and have wide applications in the food industry, pharmaceutical and bioengineering, chemical and petrochemical industries, and environmental protection.

[0004] Existing technologies using neutral nanofiltration membranes to separate viruses from water suffer from problems such as low virus removal rate, low operating flux, severe membrane fouling, and short service life. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a positively charged ceramic membrane, its preparation method and application, so as to at least solve the problems of low virus removal rate, low operating flux, serious membrane fouling and short service life in the prior art of using neutral nanofiltration membranes to separate viruses in water.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] In a first aspect, the present invention provides a method for preparing a positively charged ceramic film, comprising the following steps:

[0008] Large-diameter Al2O3 particles are dispersed in a first sol to prepare a first precursor solution, and small-diameter Al2O3 particles are dispersed in the first sol to prepare a second precursor solution.

[0009] The pretreated tubular support was coated for the first time using a first precursor solution, followed by a first drying at 80–110°C for 10–20 min, and a first sintering at 400–600°C for 0.5–2 h. Then, a second coating was performed using a second precursor solution, followed by a second drying at 80–110°C for 10–20 min, and a second sintering at 400–600°C for 0.5–2 h, to obtain a tubular ceramic membrane.

[0010] Nano-MgO particles with a particle size of 0.03–0.1 μm are uniformly dispersed in the second sol, with a nano-MgO content of 1–5%, to obtain a sol-charged agent;

[0011] The tubular ceramic membrane was immersed in a sol-gel charging agent for 3-5 minutes, followed by a third drying and a third sintering to obtain a positively charged ceramic membrane.

[0012] In conjunction with the first aspect, in some embodiments, the particle size of the first Al2O3 particle is 0.3 μm, and the particle size of the second Al2O3 particle is 0.15 μm.

[0013] In conjunction with the first aspect, in some embodiments, the concentration of Al2O3 in the first precursor solution is 1-10%, and the concentration of Al2O3 in the second precursor solution is 1-10%.

[0014] In conjunction with the first aspect, in some embodiments, the first sol is a ZrO2 sol or a TiO2 sol, the solvent in the first sol is a methylcellulose solution with a concentration of 2-4%, and the content of ZrO2 or TiO2 in the first sol is 2-5%.

[0015] In conjunction with the first aspect, in some embodiments, the first coating, first drying, and first sintering are repeated 3 to 5 times in the order of coating, drying, and sintering, and the second coating, second drying, and second sintering are repeated 3 to 5 times in the order of coating, drying, and sintering.

[0016] In conjunction with the first aspect, in some embodiments, the second sol is a boehmite sol with a concentration of 1 to 2%.

[0017] In conjunction with the first aspect, in some embodiments, the temperature of the third drying is 80–110°C and the time is 10–20 min, and the temperature of the third sintering is 350–600°C and the time is 1–2 h.

[0018] In conjunction with the first aspect, in some embodiments, the third coating, third drying, and third sintering are repeated 2 to 3 times in the order of coating, drying, and sintering.

[0019] Secondly, the present invention provides a positively charged ceramic membrane, which is prepared by the preparation method described above.

[0020] Thirdly, the present invention provides the application of the above-mentioned positively charged ceramic membrane in the treatment of virus-containing water.

[0021] The positively charged ceramic membrane of this invention has nano-MgO on its surface. Nano-MgO has a high specific surface area and numerous lattice defects, resulting in a positive charge. The electrostatic adsorption effect of the positively charged membrane surface can separate viruses with small particle sizes. Furthermore, due to the repulsive effect of like charges, the membrane's antifouling performance is improved. It has advantages such as good virus retention, high flux, low cost, simple preparation process, and strong antifouling properties, and can be widely used in virus separation processes in water treatment. The positively charged ceramic membrane of this invention has a porous structure, with an average pore size of 0.11–0.12 μm as tested. The positively charged ceramic membrane of this invention has a high flux, with a pure water flux of 45.2–67.0 L / m³ as tested. 2 hbar.

[0022] Testing showed that the positively charged ceramic membrane of this invention achieved a removal rate of over 95% for Escherichia coli bacteriophage MS2, with a higher removal rate observed in smaller pore sizes. Furthermore, after 60 minutes of operation, the flux did not significantly decrease compared to the initial flux, indicating no fouling or clogging on the membrane surface. This positively charged ceramic membrane can be applied in water treatment to treat and retain viruses in water. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the connection device for pure water flux testing, which includes: 1. Pure water tank; 2. Water pump; 3. Pressure gauge; 4. Ceramic membrane and membrane module; 5. Back pressure valve; 6. Online balance.

[0024] Figure 2 The zeta potentials of the charged agent at different pH values ​​are given. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified in the following examples, the conditions are as per standard conditions or the manufacturer's recommendations. Raw materials, equipment, or instruments whose manufacturers are not specified are all commercially available products.

[0027] This invention proposes a positively charged ceramic membrane, its preparation method, and its application. The surface of the positively charged ceramic membrane has nano-MgO, which has a high specific surface area and many lattice defects, resulting in a positive charge. The electrostatic adsorption effect of the positively charged membrane surface can separate viruses with small particle sizes. Furthermore, due to the repulsive effect of like charges, the membrane's antifouling performance is improved. It has the advantages of good virus interception effect, high flux, low cost, simple preparation process, and strong antifouling properties, and can be widely used in the virus separation process in current water treatment.

[0028] The method for preparing a positively charged ceramic membrane according to the present invention includes the following steps:

[0029] Large-diameter Al₂O₃ particles are dispersed in a first sol to prepare a first precursor solution. Small-diameter Al₂O₃ particles are dispersed in the first sol to prepare a second precursor solution. The particle size of the first Al₂O₃ particles is 0.3 μm, and the particle size of the second Al₂O₃ particles is 0.15 μm. The concentration of Al₂O₃ in both the first and second precursor solutions is 1–10%. The first sol is a ZrO₂ sol or a TiO₂ sol, and the solvent in the first sol is a 2–4% methylcellulose solution. The content of ZrO₂ or TiO₂ in the first sol is 2–5%.

[0030] The pretreated tubular support is first coated with a first precursor solution, followed by a first drying at 80–110°C for 10–20 min, and a first sintering at 400–600°C for 0.5–2 h. Then, a second coating is performed using a second precursor solution, followed by a second drying at 80–110°C for 10–20 min, and a second sintering at 400–600°C for 0.5–2 h, yielding a tubular ceramic film. The first coating, first drying, and first sintering process is repeated 3–5 times, and the second coating, second drying, and second sintering process is repeated 3–5 times. The tubular support described above is an alumina tubular support.

[0031] Nano-MgO particles with a particle size of 0.03–0.1 μm are uniformly dispersed in a second sol, with a nano-MgO content of 1–5%, to obtain a sol-charged agent. The second sol is a boehmite sol with a concentration of 1–2%.

[0032] The tubular ceramic membrane was immersed in a sol-gel charging agent for 3–5 minutes, followed by a third drying and a third sintering process to obtain a positively charged ceramic membrane. The third drying was performed at 80–110°C for 10–20 minutes, and the third sintering was performed at 350–450°C for 1–2 hours. This process of coating, drying, and sintering was repeated 3–5 times.

[0033] The positively charged ceramic membrane and its preparation method of the present invention will be described in detail below through Examples 1-4.

[0034] Example 1

[0035] The method for preparing the positively charged ceramic film in this embodiment is as follows:

[0036] (1) Preparation of transition layer

[0037] Weigh 2.1g of methylcellulose and dissolve it in 100g of distilled water. Use magnetic stirring to accelerate the dissolution of methylcellulose. Set the temperature to 80℃ and the speed to 300rpm to obtain a 2% methylcellulose solution.

[0038] Weigh 10.2g of TiO2 sol with a concentration of 20% (purchased from Shanghai Yingcheng New Materials Co., Ltd.), and dilute the TiO2 sol with 90g of 2% methylcellulose solution. Sonicate for 30min and let stand for 6h to obtain TiO2 sol, i.e., the first sol.

[0039] Weigh 6.0g of Al2O3 particles with a particle size of 0.3μm and disperse them in 94g of diluted and settled TiO2 sol. Sonicate for 30min to obtain a first precursor solution containing uniformly dispersed 0.3μm Al2O3 particles. Weigh 6.0g of Al2O3 particles with a particle size of 0.15μm and disperse them in 94g of diluted and settled TiO2 sol. Sonicate for 30min to obtain a second precursor solution containing uniformly dispersed 0.15μm Al2O3 particles. The tubular support was polished, boiled, and dried. The boiling temperature was 80℃, and the drying temperature was 110℃, with each boiling and drying time being 30 minutes. After drying, the tubular support was sealed at both ends and then completely immersed in the first precursor solution for 20 seconds. The tubular support was then slowly pulled out of the first precursor solution, ensuring that the first precursor solution was evenly coated on the surface of the tubular support. The immersed tubular support was then dried at 110℃ for 15 minutes, and then sintered in a tubular furnace at 550℃ for [duration missing]. For 40 minutes, the process of impregnation-lifting, drying, and sintering with the first precursor solution was repeated 5 times. Then, the tubular support was impregnated in the second precursor solution for 20 seconds. The tubular support was then slowly lifted out of the second precursor solution, ensuring that the second precursor solution was evenly coated on the surface of the tubular support. The impregnated tubular support was dried at 110°C for 15 minutes. After drying, it was sintered in a tube furnace at 550°C for 40 minutes. The process of impregnation-lifting, drying, and sintering with the second precursor solution was repeated 5 times to obtain the tubular ceramic film.

[0040] (2) Preparation of charged ultrafiltration layer

[0041] 3.1 g of 0.05 μm nano-MgO particles (purchased from West Asia Reagent) were weighed and dispersed in a 2% boehmite sol. The mixture was sonicated for 30 min to prepare a sol-charged agent with a nano-MgO solid content of 1%. A tubular ceramic membrane was sealed at both ends and completely immersed in the sol-charged agent for 4 min. The membrane was then slowly pulled out of the sol-charged agent, ensuring a uniform coating. The membrane was dried at 110℃ for 15 min and then sintered in a tube furnace at 600℃ for 1 h. This process of sol-charged agent immersion-pulling, drying, and sintering was repeated three times to obtain a positively charged ceramic membrane.

[0042] Example 2

[0043] The method for preparing the positively charged ceramic film in this embodiment is as follows:

[0044] (1) Preparation of transition layer

[0045] Weigh 3.1g of methylcellulose and dissolve it in 100g of distilled water. Use magnetic stirring to accelerate the dissolution of methylcellulose. Set the temperature to 80℃ and the speed to 300rpm to obtain a 3% methylcellulose solution.

[0046] Weigh 25.2g of TiO2 sol with a concentration of 20% (purchased from Shanghai Yingcheng New Materials Co., Ltd.), and dilute the TiO2 sol with 75g of 2% methylcellulose solution. Sonicate for 30min and let stand for 6h to obtain TiO2 sol, i.e., the first sol.

[0047] Weigh 1.0 g of Al2O3 particles with a particle size of 0.3 μm, disperse them in 99 g of diluted and settled TiO2 sol, and sonicate for 30 min to obtain a first precursor solution containing uniformly dispersed 0.3 μm Al2O3 particles; weigh 1.0 g of Al2O3 particles with a particle size of 0.15 μm, disperse them in 99 g of diluted and settled TiO2 sol, and sonicate for 30 min to obtain a second precursor solution containing uniformly dispersed 0.15 μm Al2O3 particles. The tubular support was polished, boiled, and dried. The boiling temperature was 80℃, and the drying temperature was 110℃, with each boiling and drying time being 30 minutes. After drying, the tubular support was sealed at both ends and then completely immersed in the first precursor solution for 30 seconds. The tubular support was then slowly pulled out of the first precursor solution, ensuring that the first precursor solution was evenly coated on the surface of the tubular support. The immersed tubular support was then dried at 80℃ for 20 minutes, and then sintered in a tubular furnace at 400℃. The process of impregnation-pulling, drying, and sintering with the first precursor solution was repeated three times over a 1-hour period. Subsequently, the tubular support was impregnated in the second precursor solution for 30 seconds. The tubular support was then slowly pulled out of the second precursor solution, ensuring that the second precursor solution was evenly coated onto the surface of the tubular support. The impregnated tubular support was dried at 80°C for 20 minutes and then sintered in a tube furnace at 400°C for 1 hour. The process of impregnation-pulling, drying, and sintering with the second precursor solution was repeated three times to obtain the tubular ceramic membrane.

[0048] (2) Preparation of charged ultrafiltration layer

[0049] 1.0 g of 0.05 μm nano-MgO particles (purchased from West Asia Reagent) were weighed and dispersed in a 2% boehmite sol. The mixture was sonicated for 30 min to prepare a sol-charged agent with a nano-MgO solid content of 2%. A tubular ceramic membrane was sealed at both ends and completely immersed in the sol-charged agent for 5 min. The membrane was then slowly pulled out of the sol-charged agent, ensuring a uniform coating. The membrane was dried at 80℃ for 20 min and then sintered in a tube furnace at 350℃ for 2 h. This process of sol-charged agent immersion-pulling, drying, and sintering was repeated three times to obtain a positively charged ceramic membrane.

[0050] Example 3

[0051] The method for preparing the positively charged ceramic film in this embodiment is as follows:

[0052] (1) Preparation of transition layer

[0053] Weigh 4.1g of methylcellulose and dissolve it in 96g of distilled water. Use magnetic stirring to accelerate the dissolution of methylcellulose. Set the temperature to 80℃ and the rotation speed to 300rpm to obtain a 4% methylcellulose solution.

[0054] Weigh 10.2g of ZrO2 sol with a concentration of 20% (purchased from Shanghai Yingcheng New Materials Co., Ltd.), and dilute the ZrO2 sol with 90g of 2% methylcellulose solution. Sonicate for 30min and let stand for 6h to obtain ZrO2 sol, i.e., the first sol.

[0055] 10g of Al2O3 particles with a diameter of 0.3μm were weighed and dispersed into 90g of diluted and settled ZrO2 sol. The solution was sonicated for 30min to obtain a first precursor solution containing uniformly dispersed Al2O3 particles with a diameter of 0.3μm. 10g of Al2O3 particles with a diameter of 0.15μm were weighed and dispersed into 90g of diluted and settled ZrO2 sol. The solution was sonicated for 30min to obtain a second precursor solution containing uniformly dispersed Al2O3 particles with a diameter of 0.15μm. The tubular support was polished, boiled, and dried. The boiling temperature was 80℃, and the drying temperature was 110℃, with each boiling and drying time being 30 minutes. After drying, the tubular support was sealed at both ends and then completely immersed in the first precursor solution for 20 seconds. The tubular support was then slowly pulled out of the first precursor solution, ensuring that the first precursor solution was evenly coated on the surface of the tubular support. The immersed tubular support was then dried at 100℃ for 10 minutes, and then sintered in a tubular furnace at 600℃ for [duration missing]. For 30 minutes, the process of impregnation-lifting, drying, and sintering with the first precursor solution was repeated four times. Then, the tubular support was impregnated in the second precursor solution for 20 seconds. The tubular support was then slowly lifted out of the second precursor solution, ensuring that the second precursor solution was evenly coated on the surface of the tubular support. The impregnated tubular support was dried at 100°C for 10 minutes. After drying, it was sintered in a tube furnace at 600°C for 30 minutes. The process of impregnation-lifting, drying, and sintering with the second precursor solution was repeated four times to obtain the tubular ceramic membrane.

[0056] (2) Preparation of charged ultrafiltration layer

[0057] 2.1 g of 0.05 μm nano-MgO particles (purchased from West Asia Reagent) were weighed and dispersed in a 2% boehmite sol. The mixture was sonicated for 30 min to prepare a sol-charged agent with a nano-MgO solid content of 3%. A tubular ceramic membrane was sealed at both ends and completely immersed in the sol-charged agent for 3 min. The membrane was then slowly pulled out of the sol-charged agent, ensuring a uniform coating. The membrane was dried at 100℃ for 10 min and then sintered in a tube furnace at 550℃ for 1.5 h. This process of sol-charged agent immersion-pulling, drying, and sintering was repeated twice to obtain a positively charged ceramic membrane.

[0058] Example 4

[0059] The method for preparing the positively charged ceramic film in this embodiment is as follows:

[0060] (1) Preparation of transition layer

[0061] Weigh 3.1g of methylcellulose and dissolve it in 97g of distilled water. Use magnetic stirring to accelerate the dissolution of methylcellulose. Set the temperature to 80℃ and the rotation speed to 300rpm to obtain a 3% methylcellulose solution.

[0062] Weigh 10.2g of TiO2 sol with a concentration of 20% (purchased from Shanghai Yingcheng New Materials Co., Ltd.), and dilute the TiO2 sol with 90g of 2% methylcellulose solution. Sonicate for 30min and let stand for 6h to obtain TiO2 sol, i.e., the first sol.

[0063] Weigh 5g of Al2O3 particles with a particle size of 0.3μm and disperse them in 95g of diluted and settled TiO2 sol. Sonicate for 30min to obtain a uniformly dispersed first precursor solution containing 0.3μm Al2O3 particles. Weigh 5g of Al2O3 particles with a particle size of 0.15μm and disperse them in 95g of diluted and settled TiO2 sol. Sonicate for 30min to obtain a uniformly dispersed first precursor solution containing 0.15μm Al2O3 particles. The tubular support was polished, boiled, and dried. The boiling temperature was 80℃, and the drying temperature was 110℃, with each boiling and drying time being 30 minutes. After drying, the tubular support was sealed at both ends and then completely immersed in the first precursor solution for 20 seconds. The tubular support was then slowly pulled out of the first precursor solution, ensuring that the first precursor solution was evenly coated on the surface of the tubular support. The immersed tubular support was then dried at 85℃ for 20 minutes, and then sintered in a tubular furnace at 550℃ for [duration missing]. The process of impregnation-lifting, drying, and sintering with the first precursor solution was repeated 5 times for 60 minutes. Then, the tubular support was impregnated in the second precursor solution for 20 seconds. The tubular support was then slowly lifted out of the second precursor solution, ensuring that the second precursor solution was evenly coated on the surface of the tubular support. The impregnated tubular support was dried at 85°C for 20 minutes. After drying, it was sintered in a tube furnace at 550°C for 60 minutes. The process of impregnation-lifting, drying, and sintering with the second precursor solution was repeated 5 times to obtain the tubular ceramic film.

[0064] (2) Preparation of charged ultrafiltration layer

[0065] 5.1 g of 0.05 μm nano-MgO particles (purchased from West Asia Reagent) were weighed and dispersed in a 2% boehmite sol. The mixture was sonicated for 30 min to prepare a sol-charged agent with a nano-MgO solid content of 5%. A tubular ceramic membrane was sealed at both ends and completely immersed in the sol-charged agent for 20 s. The membrane was then slowly pulled out of the sol-charged agent, ensuring a uniform coating. The membrane was dried at 110℃ for 20 min and then sintered in a tube furnace at 600℃ for 2 h. This process of sol-charged agent immersion-pulling, drying, and sintering was repeated three times to obtain a positively charged ceramic membrane.

[0066] The positively charged ceramic membranes prepared in Examples 1-4 were subjected to the following tests:

[0067] 1. Aperture testing

[0068] The pore size of the positively charged ceramic membranes prepared in Examples 1, 2, 3, and 4 was tested using the bubble pressing method. The test results are shown in Table 1 below.

[0069] Example 1 Example 2 Example 3 Example 4 Average pore size / μm 0.11 0.12 0.09 0.11

[0070] Table 1

[0071] 2. Water flux test

[0072] Please refer to Figure 1 The positively charged ceramic films prepared in Examples 1, 2, 3, and 4 were respectively assembled on... Figure 1 In the device, the positively charged ceramic membranes prepared in Examples 1, 2, 3, and 4 were tested for pure water flux. Figure 1 In the pure water flux testing connection device shown, the pure water tank 1 is connected to the water pump via a connecting water pipe. The water pump 2 is connected to the lower inlet of the ceramic membrane and membrane module 4 via a connecting water pipe. A pressure gauge 3 is installed on the connecting water pipe between the water pump 2 and the ceramic membrane and membrane module 4. The upper outlet of the ceramic membrane and membrane module 4 is connected to the pure water tank 1 via a connecting water pipe. A back pressure valve 5 is installed on the connecting water pipe between the upper outlet of the ceramic membrane and membrane module 4 and the pure water tank 1. An online balance 6 is installed below the ceramic membrane and membrane module 4. Pure water with a certain pressure is introduced into the membrane module by the water pump. Part of the pure water returns to the pure water tank through the back pressure valve, and the other part of the pure water passes through the membrane layer and the pure water flux is measured by the online balance. The test results are shown in Table 2 below.

[0073] Example 1 Example 2 Example 3 Example 4 <![CDATA[Pure water flux / L / / m 2 hbar]]> 67.0 64.3 58.4 45.2

[0074] Table 2

[0075] 3. Zeta potential test

[0076] The zeta potentials of the nano-magnesium oxide charged agents prepared in Examples 1, 2, 3, and 4 were measured at different pH values ​​using a zeta potentiometer. The pH was adjusted using 0.1 mol / L HCl and 0.1 mol / L KOH solutions. The results are shown in the appendix. Figure 2 This indicates that when pH < 6.8, all the charging agents carry a positive charge, and the positive charge increases with the concentration of nano-magnesium oxide.

[0077] 4. E. coli MS2 filtration experiment

[0078] Escherichia coli bacteriophage MS2 was used to simulate the virus to be isolated in virus filtration and separation experiments on the positively charged ceramic membranes of Examples 1, 2, 3, and 4. The concentration of bacteriophage MS2 in the feed solution was approximately 10. 5 The removal rate of the positively charged ceramic membrane was calculated by detecting the phage content in the filtrate, and the change in operating flux after different operating times was measured. The experimental results are shown in Table 3 below.

[0079]

[0080]

[0081] Table 3

[0082] According to the data in Table 3, the positively charged ceramic membranes prepared in Examples 1, 2, 3, and 4 all had a removal rate of over 95% for Escherichia coli bacteriophage MS2, and the smaller the membrane pore size, the higher the removal rate. After running for 60 minutes, the flux of Examples 1, 2, 3, and 4 did not decrease significantly compared with the initial flux, indicating that there was no contamination or blockage on the membrane surface.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A method for producing a positively charged ceramic membrane, characterized by, Includes the following steps: Large-diameter Al2O3 particles are dispersed in a first sol to prepare a first precursor solution, and small-diameter Al2O3 particles are dispersed in the first sol to prepare a second precursor solution. The pretreated alumina tubular support was coated for the first time using a first precursor solution, followed by a first drying at 80–110°C for 10–20 min, and a first sintering at 400–600°C for 0.5–2 h. Then, a second coating was performed using a second precursor solution, followed by a second drying at 80–110°C for 10–20 min, and a second sintering at 400–600°C for 0.5–2 h, to obtain a tubular ceramic membrane. Nano-MgO particles with a particle size of 0.03–0.1 μm are uniformly dispersed in the second sol, with a nano-MgO content of 1–5%, to obtain a sol-charged agent; The tubular ceramic membrane was immersed in a sol-gel charging agent for 3-5 minutes, followed by a third drying and a third sintering to obtain a positively charged ceramic membrane.

2. The method for preparing a positively charged ceramic membrane according to claim 1, characterized in that, The first Al2O3 particle has a particle size of 0.3 μm, and the second Al2O3 particle has a particle size of 0.15 μm.

3. The method of claim 2, wherein the ceramic membrane is positively charged. The concentration of Al2O3 in the first precursor solution is 1-10%, and the concentration of Al2O3 in the second precursor solution is 1-10%.

4. The method of claim 1, wherein the ceramic membrane is positively charged. The first sol is a ZrO2 sol or a TiO2 sol, the solvent in the first sol is a methylcellulose solution with a concentration of 2-4%, and the content of ZrO2 or TiO2 in the first sol is 2-5%.

5. The method of claim 1, wherein the ceramic membrane is positively charged. Repeat the first coating, first drying, and first sintering process 3 to 5 times in the order of coating, drying, and sintering, and repeat the second coating, second drying, and second sintering process 3 to 5 times in the same order.

6. The method of claim 1, wherein the ceramic membrane is positively charged. The second sol is a boehmite sol with a concentration of 1-2%.

7. The method of claim 1, wherein the ceramic membrane is positively charged. The third drying temperature is 80-110℃ and the time is 10-20 min. The third sintering temperature is 350-600℃ and the time is 1-2 h.

8. The method of claim 7, wherein the method further comprises the step of: Repeat the third coating, third drying, and third sintering process 2 to 3 times in the order of coating, drying, and sintering.

9. A positively charged ceramic membrane, characterized in that, The positively charged ceramic membrane is prepared by the preparation method described in any one of claims 1-8.

10. The application of a positively charged ceramic membrane according to claim 9 in the treatment of virus-containing water.

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