A method for preparing a flexible ceramic membrane using a manganese oxide combined with a layer-by-layer assembly technique

Abstract

The application relates to a method for preparing a flexible ceramic membrane by combining a manganese oxide with a layer-by-layer assembly technique, and belongs to the field of drinking water purification and wastewater pollution treatment. The application aims to solve the problems of poor hydrophilicity of existing organic membranes and high cost of ceramic membranes prepared by using the organic membranes. The application utilizes the chlorine resistance of polyelectrolyte layers to make the modified membranes have the advantages of flexible ceramics, solves the problems of poor hydrophilicity of existing organic membranes and high cost of ceramic membranes, and improves the problem of easy pollution in the membrane operation process by retaining colloidal substances in water according to the combination force of positive and negative electricities, thereby laying a foundation for the research of the application in the field of drinking water purification and wastewater pollution treatment. The method comprises the following steps: one, pretreatment of the organic membrane; two, preparation of a pre-preparation liquid; three, introduction of a polar group; four, preparation of a polycation coating liquid; five, preparation of A coating liquid and B coating liquid; six, in-situ layer-by-layer assembly; seven, repetition of step six; and eight, air drying and storage in deionized water. The application can obtain a flexible ceramic membrane.

Description

Technical Field

[0001] This invention belongs to the field of drinking water purification and wastewater pollution control, specifically relating to a method for preparing flexible ceramic membranes using manganese oxide combined with layer-by-layer assembly technology. Background Technology

[0002] Inorganic ceramic membranes possess excellent mechanical, chemical, and thermal stability and are resistant to chemical damage caused by the catalytic environment and physical damage during operation. However, the brittleness of ceramic membranes complicates their modification, increasing the cost and energy consumption of the corresponding separation devices. Currently, organic polymer membranes are the most widely used substrate in catalytic membrane manufacturing due to their excellent flexibility and plasticity. However, the active species generated during these catalytic reactions can not only degrade adsorbed fouling but also attack the polymer chains themselves, leading to membrane structure damage and changes in membrane surface properties. Flexible ceramic nanomembranes, made by uniformly dispersing nanoscale ceramic particles in a polymer matrix, are a novel composite material combining ceramic and elastic properties, opening up new avenues for creating material miracles. The challenge lies in the complexity of the flexible ceramic membrane preparation process, involving interdisciplinary technologies such as sol chemistry, interface control, and sintering processes. Currently, the stability and repeatability of large-scale production still need improvement.

[0003] Compared to the limitations of blending and surface coating methods in membrane preparation, which suffer from poor uniformity and stability, the bottom-up approach is a novel method for membrane preparation. Different catalyst precursors react with each other under specific conditions, forming active components in situ on the membrane matrix surface, thus improving membrane filtration performance. Several bottom-up synthesis methods have been developed, including chemical grafting, chemical vapor deposition (CVD), and layer-by-layer assembly. In chemical grafting, the active groups on the membrane surface react with the catalyst precursor, and the polymer chains of the precursor are covalently bonded to the membrane surface. However, this method consumes a large amount of catalyst and often involves multiple complex reaction steps. CVD is complex to operate, and uneven deposition can lead to membrane surfaces with impurities or defects, posing a risk of residual gas toxicity. Layer-by-layer assembly offers advantages such as easy control of layer thickness and simple operation. It utilizes different polyelectrolytes to cover the membrane, alternately exposing the membrane to positively and negatively charged polyelectrolytes, thereby forming a thin polyelectrolyte multilayer membrane. This membrane exhibits some resistance to chlorination, but this method relies on manual operation in multiple stages, requires large amounts of polymer solution, and can cause equipment corrosion and secondary pollution. Therefore, layer-by-layer assembly technology still needs further improvement.

[0004] Overall, bottom-up synthesis is the most promising technology for large-scale production of catalytic membranes due to its precise control over the thickness and density of catalyst coatings. Therefore, it is necessary to improve the dispersibility of organic framework-supported catalysts and the chlorination resistance of organic membranes through mild and stable modification methods, and to rationally combine different preparation methods such as impregnation coatings to improve catalyst uniformity on the membrane surface, in order to develop new technologies for the simpler and more efficient preparation of flexible ceramic membranes. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of poor hydrophilicity of existing organic membranes and high cost of ceramic membranes prepared using organic membranes, and to provide a method for preparing flexible ceramic membranes by combining manganese oxide with layer-by-layer assembly technology.

[0006] This invention utilizes the chlorination resistance of the polyelectrolyte layer to give the modified membrane the advantages of flexible ceramics, solving the problems of poor hydrophilicity of existing organic membranes and high cost of ceramic membranes. It improves the problem of membrane fouling during operation by trapping colloidal substances in water based on the binding force of positive and negative charges, laying the foundation for its research in the fields of drinking water purification and wastewater pollution treatment.

[0007] A method for preparing flexible ceramic membranes using manganese oxide combined with layer-by-layer assembly technology is carried out according to the following steps:

[0008] I. Pretreatment of organic membranes:

[0009] The organic membrane was immersed in anhydrous ethanol, then removed, and the anhydrous ethanol on the surface of the membrane was rinsed off with deionized water before being immersed in deionized water to obtain a pretreated organic membrane.

[0010] II. Preparation of pre-formulated solution:

[0011] Add potassium hydroxide and potassium permanganate to deionized water and stir to obtain the pre-prepared solution;

[0012] III. Introducing polar groups onto the surface of organic films:

[0013] After the pretreated organic membrane is placed in the pre-prepared solution and deposited for a period of time, the excess pre-prepared solution is washed with deionized water to obtain an organic membrane with polar groups.

[0014] IV. Preparation of polycationic coating solution:

[0015] Add polydimethyldiallylammonium chloride to deionized water and stir until homogeneous to obtain a polycationic coating solution;

[0016] V. Prepare coating solution A and coating solution B:

[0017] ① Add potassium permanganate to deionized water, stir well and react for a period of time to obtain potassium permanganate solution, which is coating solution A;

[0018] ② Add manganese chloride to deionized water, stir well, and react for a period of time to obtain manganese chloride solution, which is coating solution B;

[0019] VI. Perform in-situ layer-by-layer assembly:

[0020] ① Immerse the organic membrane with polar groups in the polycation coating solution. After soaking for a period of time, wash the organic membrane with deionized water to remove excess polycations from the surface of the organic membrane.

[0021] ② Immerse the organic membrane in coating solution A and react it in a shaker for a period of time. Then, immerse the organic membrane in coating solution B and react it in a shaker for a period of time to ensure that coating solution A and coating solution B are in full contact. Finally, use deionized water to clean the organic membrane to remove excess manganese oxide particles from the surface of the organic membrane.

[0022] 7. Repeat step 6 2 to 6 times to obtain the modified organic membrane;

[0023] 8. The modified organic membrane is air-dried naturally and then stored in deionized water to obtain a flexible ceramic membrane prepared by in-situ generation of manganese oxide combined with layer-by-layer assembly technology.

[0024] The principle of this invention:

[0025] Layer-by-layer assembly technology offers advantages such as easy control of layer thickness and simple operation. The bonding between the catalyst precursor and the membrane is based on interactions between them, such as hydrogen bonding, electrostatic attraction, and coordination bonds. This technology utilizes different polyelectrolytes to cover the membrane, alternately exposing the membrane to positively and negatively charged polyelectrolytes, thereby forming a thin polyelectrolyte multilayer membrane. The prepared nano-manganese oxide carries a negative charge, while polydimethyldiallylammonium chloride carries a positive charge; therefore, the driving force of this invention is the electrostatic interaction between molecules. On one hand, layer-by-layer assembly technology is considered to withstand chlorination environments, and the organic membrane impregnated with the polyelectrolyte layer exhibits a certain degree of chlorination resistance. On the other hand, nano-manganese oxide has excellent hydrophilicity, which can improve the hydrophobicity of the organic membrane and the defects of the functional layer on the membrane surface, making the modified membrane combine the advantages of both ceramic and organic membranes. When charged colloidal particles enter the membrane pores and cause irreversible fouling, the modified layer can form a barrier between the membrane and the pollutants through the electrostatic attraction between the positive and negative charges, hindering the permeation of pollutants and improving the membrane's pollutant retention performance. Meanwhile, the ability to achieve tight bonding between manganese oxides without solid-state sintering provides a new approach for manganese-based modified membranes. In summary, modification using manganese oxides combined with layer-by-layer assembly technology can improve the membrane's resistance to chlorination, hydrophilicity, and antifouling properties, showing great promise for application.

[0026] The advantages of this invention are:

[0027] 1. The manganese oxide prepared by this invention is modified by a layer-by-layer assembly technique, which is mild and produces a tightly bonded manganese oxide layer. The modified layer on the film surface is relatively stable after modification.

[0028] 2. The manganese oxide prepared by this invention, combined with the layer-by-layer assembly technology modification method, has a simple, controllable, short cycle, and low cost.

[0029] 3. The manganese oxide prepared in this invention, combined with the layer-by-layer assembly technology modification method, improves the chlorination resistance, hydrophilicity, and dynamic fouling resistance of the hydrophobic organic membrane;

[0030] 4. The modified organic membrane prepared in this invention does not require additional pressure or energy consumption during the filtration process; filtration is achieved by using gravity-driven water head. Attached Figure Description

[0031] Figure 1 The figures show the original membrane and the modified membrane. In the figure, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0032] Figure 2 The images show SEM images of the original membrane and the modified membrane. In the images, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0033] Figure 3 The table shows the elemental distribution of the original membrane and the modified membrane. In the figure, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0034] Figure 4 The figures show the dynamic contact angles of the original membrane and the modified membrane. In the figures, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0035] Figure 5 For Al 3+The diagram shows the retention of colloidal particles, where 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3. Detailed Implementation

[0036] Specific Implementation Method 1: This implementation method describes a method for preparing flexible ceramic membranes using manganese oxide combined with layer-by-layer assembly technology, which is completed according to the following steps:

[0037] I. Pretreatment of organic membranes:

[0038] The organic membrane was immersed in anhydrous ethanol, then removed, and the anhydrous ethanol on the surface of the membrane was rinsed off with deionized water before being immersed in deionized water to obtain a pretreated organic membrane.

[0039] II. Preparation of pre-formulated solution:

[0040] Add potassium hydroxide and potassium permanganate to deionized water and stir to obtain the pre-prepared solution;

[0041] III. Introducing polar groups onto the surface of organic films:

[0042] After the pretreated organic membrane is placed in the pre-prepared solution and deposited for a period of time, the excess pre-prepared solution is washed with deionized water to obtain an organic membrane with polar groups.

[0043] IV. Preparation of polycationic coating solution:

[0044] Add polydimethyldiallylammonium chloride to deionized water and stir until homogeneous to obtain a polycationic coating solution;

[0045] V. Prepare coating solution A and coating solution B:

[0046] ① Add potassium permanganate to deionized water, stir well and react for a period of time to obtain potassium permanganate solution, which is coating solution A;

[0047] ② Add manganese chloride to deionized water, stir well, and react for a period of time to obtain manganese chloride solution, which is coating solution B;

[0048] VI. Perform in-situ layer-by-layer assembly:

[0049] ① Immerse the organic membrane with polar groups in the polycation coating solution. After soaking for a period of time, wash the organic membrane with deionized water to remove excess polycations from the surface of the organic membrane.

[0050] ② Immerse the organic membrane in coating solution A and react it in a shaker for a period of time. Then, immerse the organic membrane in coating solution B and react it in a shaker for a period of time to ensure that coating solution A and coating solution B are in full contact. Finally, use deionized water to clean the organic membrane to remove excess manganese oxide particles from the surface of the organic membrane.

[0051] 7. Repeat step 6 2 to 6 times to obtain the modified organic membrane;

[0052] 8. The modified organic membrane is air-dried naturally and then stored in deionized water to obtain a flexible ceramic membrane prepared by in-situ generation of manganese oxide combined with layer-by-layer assembly technology.

[0053] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one, the organic membrane is immersed in anhydrous ethanol for 1-2 minutes, then removed, and the anhydrous ethanol on the membrane surface is rinsed off with deionized water before being immersed in deionized water for 24 hours to obtain a pretreated organic membrane. Other steps are the same as in Specific Implementation Method One.

[0054] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the organic membrane mentioned in step one is an ultrafiltration membrane or a microfiltration membrane, and its material is a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a polyvinylidene fluoride membrane, a cellulose acetate membrane, or a polyethersulfone membrane. The other steps are the same as in Specific Implementation Method One or Two.

[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the concentration of potassium hydroxide solution in the pre-prepared solution in step two is 2.0 mol / L to 2.5 mol / L; the concentration of potassium permanganate solution in the pre-prepared solution in step two is 0.15 mol / L to 0.20 mol / L. The other steps are the same as in Specific Implementation Methods One to Three.

[0056] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the volume ratio of potassium hydroxide solution to potassium permanganate solution in step two is (1-1.2):(1-1.2); the stirring speed in step two is 500 r / min to 700 r / min for 20-30 minutes. Other steps are the same as in Specific Implementation Methods One to Four.

[0057] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step three, the deposition time of the pretreated organic membrane in the pre-prepared solution is 10 to 15 minutes, and the deposition temperature is 50°C. The other steps are the same as in Specific Implementation Methods One to Five.

[0058] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the concentration of polydimethyldiallyl ammonium chloride in the polycationic coating solution described in step four is 0.5 g / L to 0.8 g / L. The other steps are the same as in Specific Implementation Methods One to Six.

[0059] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the concentration of the potassium permanganate solution mentioned in step five ① is 40 μmol / L to 80 μmol / L; and the reaction time after stirring is 10 min to 20 min. Other steps are the same as in Specific Implementation Methods One to Seven.

[0060] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the concentration of the manganese chloride solution mentioned in step five ② is 60 μmol / L to 120 μmol / L; and the reaction time after stirring is 10 min to 20 min. Other steps are the same as in Specific Implementation Methods One to Eight.

[0061] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: in step six①, the organic membrane with polar groups is immersed in the polycationic coating solution for 20 to 40 minutes; in step six②, the organic membrane is immersed in coating solution A and reacted in a shaker for 10 to 20 minutes, then removed and immersed in coating solution B, reacting in a shaker for 10 to 20 minutes. The other steps are the same as in Specific Implementation Methods One to Nine.

[0062] The beneficial effects of the present invention are verified using the following embodiments:

[0063] Example 1: A method for preparing flexible ceramic membranes using manganese oxide combined with layer-by-layer assembly technology, comprising the following steps:

[0064] I. Pretreatment of organic membranes:

[0065] The organic membrane was immersed in anhydrous ethanol for 1 minute, then removed and rinsed with deionized water to remove the anhydrous ethanol from the membrane surface. The membrane was then immersed in deionized water for 24 hours to obtain the pretreated organic membrane.

[0066] The organic membrane mentioned in step one is a polyvinylidene fluoride membrane (PVDF microfiltration membrane);

[0067] II. Preparation of pre-formulated solution:

[0068] Add potassium hydroxide and potassium permanganate to deionized water and stir at 700 r / min for 30 min to obtain the pre-prepared solution.

[0069] The concentration of potassium hydroxide solution in the pre-prepared solution mentioned in step two is 2.3 mol / L;

[0070] The concentration of potassium permanganate solution in the pre-prepared solution mentioned in step two is 0.19 mol / L;

[0071] III. Introducing polar groups onto the surface of organic films:

[0072] The pretreated organic membrane was placed in the pre-prepared solution and deposited for 10 minutes at a deposition temperature of 50°C. Excess pre-prepared solution was washed with deionized water to obtain an organic membrane with polar groups.

[0073] IV. Preparation of polycationic coating solution:

[0074] Add polydimethyldiallylammonium chloride to deionized water and stir until homogeneous to obtain a polycationic coating solution;

[0075] The concentration of polydimethyldiallyl ammonium chloride in the polycationic coating solution described in step four is 0.5 g / L;

[0076] V. Prepare coating solution A and coating solution B:

[0077] ① Add potassium permanganate to deionized water, stir well and react for 15 minutes to obtain potassium permanganate solution, which is coating solution A;

[0078] The concentration of the potassium permanganate solution mentioned in step 5① is 40 μmol / L;

[0079] ② Add manganese chloride to deionized water, stir well and react for 15 minutes to obtain manganese chloride solution, which is coating solution B;

[0080] The concentration of the manganese chloride solution mentioned in step 5② is 60 μmol / L;

[0081] VI. Perform in-situ layer-by-layer assembly:

[0082] ① Immerse the organic membrane with polar groups in the polycation coating solution and soak for 30 minutes. Then wash the organic membrane with deionized water to remove excess polycations from the surface of the organic membrane.

[0083] ② Immerse the organic membrane in coating solution A and react in a shaker for 15 minutes. Then, immerse the organic membrane in coating solution B and react in a shaker for 15 minutes to ensure that coating solutions A and B are in full contact. Finally, wash the organic membrane with deionized water to remove excess manganese oxide particles from the surface of the organic membrane.

[0084] 7. Repeat step 6 twice to obtain the modified organic membrane;

[0085] 8. The modified organic membrane is air-dried naturally and then stored in deionized water to obtain a flexible ceramic membrane prepared by in-situ generation of manganese oxide combined with layer-by-layer assembly technology.

[0086] The flexible ceramic membrane prepared by combining manganese oxide with layer-by-layer assembly technology in Example 1 had an initial contact angle of 45.8° and a contact angle of 24.1° after 30s.

[0087] Example 2: The difference between this example and Example 1 is that step six is ​​repeated four times in step seven. All other steps and parameters are the same as in Example 1.

[0088] The flexible ceramic membrane prepared by combining manganese oxide with layer-by-layer assembly technology in Example 2 had an initial contact angle of 34.3° and a contact angle of 0.0° after 20s.

[0089] Example 3: The difference between this example and Example 1 is that step six is ​​repeated six times in step seven. All other steps and parameters are the same as in Example 1.

[0090] The flexible ceramic membrane prepared by combining manganese oxide with layer-by-layer assembly technology in Example 3 had an initial contact angle of 29.3° and a contact angle of 0.0° after 11 seconds.

[0091] Figure 1 The figures show the original membrane and the modified membrane. In the figure, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0092] from Figure 1 Visually, it can be seen that as the number of in-situ layer-by-layer assemblies increases, the color of the membrane gradually deepens.

[0093] Figure 2 The images show SEM images of the original membrane and the modified membrane. In the images, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0094] Depend on Figure 2 It can be seen that the original PVDF microfiltration membrane surface is relatively smooth. After in-situ layer-by-layer assembly of two layers, a layer of uniform spherical particles can be observed on the membrane surface at the nanoscale, which is presumably manganese oxide particles generated in situ. After in-situ layer-by-layer assembly of four and six layers of modified liquid, the membrane surface changed from the original granular structure to a sheet-like structure. With the increase of the number of assembled layers, the thickness of the modified layer increased.

[0095] Figure 3 The table shows the elemental distribution of the original membrane and the modified membrane. In the figure, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0096] Depend on Figure 3 It can be seen that there is no Mn element on the surface of the original PVDF microfiltration membrane. With the in-situ assembly of 2, 4 and 6 layers of modified liquid, the Mn element on the surface gradually increases. Combined with SEM images, it is further confirmed that manganese oxide particles were successfully coated on the surface of the original PVDF microfiltration membrane.

[0097] Figure 4 The figures show the dynamic contact angles of the original membrane and the modified membrane. In the figures, 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0098] Depend on Figure 4 It can be seen that the original PVDF microfiltration membrane exhibits strong hydrophobicity, with its water contact angle stabilizing at approximately 97.8°. In-situ layer-by-layer assembly of two layers significantly improved hydrophilicity; the initial water contact angle was 45.8°, decreasing to 24.1° after 30 seconds. At this point, it still maintains a certain degree of hydrophobicity, which is due to the MnO... x MnO has hydrophilic properties but adheres to the membrane surface x The limited quantity of these materials prevents a significant reduction in the surface energy of the hydrophobic membrane. The initial water contact angle of the in-situ, layer-by-layer assembly of four layers was 34.3°, decreasing to 0° at 20 s. The initial water contact angle of the in-situ, layer-by-layer assembly of six layers was 29.3°, decreasing to 0° at 11 s, indicating that the modified liquid containing manganese oxide particles of varying numbers of layers can significantly improve the wettability of the organic membrane.

[0099] Figure 5 For Al 3+ The diagram shows the retention of colloidal particles, where 1 is the original PVDF microfiltration membrane, 2 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 1, 3 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 2, and 4 is the flexible ceramic membrane prepared by manganese oxide combined with layer-by-layer assembly technology in Example 3.

[0100] The steps for preparing the pollutants are as follows: Add 5 mg of Al to 1000 mL of deionized water. 3+ / L and 20mg Al 3 + / L of polyaluminum chloride, adjusted to pH 7 and stirred until homogeneous, yields Al 3+ The colloidal particulate contaminated liquid was filtered using a dead-end filtration method, with a transmembrane pressure difference of 17 cm gravitational head. The effluent Al content was measured. 3+ It is known that when the raw water contains 5 mg / L of polyaluminum chloride, the PVDF microfiltration membrane can retain 90% of the Al. 3+ However, as the initial polyaluminum chloride concentration increased to 20 mg / L, the original membrane retention rate decreased to 65%. Comparative analysis revealed that the modified flexible ceramic membrane significantly improved the retention of Al. 3+ The retention is due to MnO x The surface carries a negative charge, while the polycationic surface carries a positive charge. Al is trapped through the electrostatic attraction between the positive and negative charges in the interlayer. 3+ Colloidal particles. This indicates that the flexible ceramic membrane modified with manganese oxide and layer-by-layer assembly technology exhibits enhanced antifouling properties.

Claims

1. A method for preparing a flexible ceramic membrane by layer-by-layer assembly using manganese oxides, characterized in that... This method is completed in the following steps: I. Pretreatment of organic membranes: The organic membrane was immersed in anhydrous ethanol, then removed, and the anhydrous ethanol on the surface of the membrane was rinsed off with deionized water before being immersed in deionized water to obtain a pretreated organic membrane. II. Preparation of pre-formulated solution: Add potassium hydroxide and potassium permanganate to deionized water and stir to obtain the pre-prepared solution; III. Introducing polar groups onto the surface of organic films: After the pretreated organic membrane is placed in the pre-prepared solution and deposited for a period of time, the excess pre-prepared solution is washed with deionized water to obtain an organic membrane with polar groups. IV. Preparation of polycationic coating solution: Add polydimethyldiallylammonium chloride to deionized water and stir until homogeneous to obtain a polycationic coating solution; V. Prepare coating solution A and coating solution B: ① Add potassium permanganate to deionized water, stir well and react for a period of time to obtain potassium permanganate solution, which is coating solution A; ② Add manganese chloride to deionized water, stir well, and react for a period of time to obtain manganese chloride solution, which is coating solution B; VI. Perform in-situ layer-by-layer assembly: ① Immerse the organic membrane with polar groups in the polycation coating solution. After soaking for a period of time, wash the organic membrane with deionized water to remove excess polycations from the surface of the organic membrane. ② Immerse the organic membrane in coating solution A and react it in a shaker for a period of time. Then, immerse the organic membrane in coating solution B and react it in a shaker for a period of time to ensure that coating solution A and coating solution B are in full contact. Finally, use deionized water to clean the organic membrane to remove excess manganese oxide particles from the surface of the organic membrane.

7. Repeat step 6 2 to 6 times to obtain the modified organic membrane; 8. The modified organic membrane is air-dried naturally and then stored in deionized water to obtain a flexible ceramic membrane prepared by in-situ generation of manganese oxide combined with layer-by-layer assembly modification.

2. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... In step one, the organic membrane is immersed in anhydrous ethanol for 1 to 2 minutes, then removed and rinsed with deionized water to remove the anhydrous ethanol from the membrane surface. After immersion in deionized water for 24 hours, a pretreated organic membrane is obtained.

3. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The organic membrane mentioned in step one is one of ultrafiltration membrane or microfiltration membrane, and its material is polytetrafluoroethylene membrane, polyvinylidene fluoride membrane, polyvinylidene fluoride membrane, cellulose acetate membrane or polyethersulfone membrane.

4. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The concentration of potassium hydroxide solution in the pre-prepared solution in step two is 2.0 mol / L to 2.5 mol / L; the concentration of potassium permanganate solution in the pre-prepared solution in step two is 0.15 mol / L to 0.20 mol / L.

5. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The stirring described in step two is carried out at a speed of 500 r / min to 700 r / min for 20 min to 30 min.

6. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... In step three, the pretreated organic membrane is placed in the pre-prepared solution for deposition for 10 to 15 minutes at a deposition temperature of 50°C.

7. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The concentration of polydimethyldiallylammonium chloride in the polycationic coating solution described in step four is 0.5 g / L to 0.8 g / L.

8. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The concentration of the potassium permanganate solution mentioned in step 5① is 40 μmol / L to 80 μmol / L; the reaction time after stirring is 10 min to 20 min.

9. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... The concentration of the manganese chloride solution mentioned in step 5② is 60 μmol / L to 120 μmol / L; the reaction time after stirring is 10 min to 20 min.

10. The method for preparing a flexible ceramic membrane by layer-by-layer assembly of manganese oxide according to claim 1, characterized in that... In step 6①, the organic membrane with polar groups is immersed in the polycationic coating solution for 20 min to 40 min; in step 6②, the organic membrane is immersed in coating solution A and reacted in a shaker for 10 min to 20 min, then removed and immersed in coating solution B and reacted in a shaker for 10 min to 20 min.

Images