A method for preparing a high water flux organic / inorganic composite membrane with hierarchical pore structure

Abstract

The application discloses a preparation method of a high-water-flux organic / inorganic composite membrane with hierarchical pore structures, and comprises the following steps: preparing a carboxyl siloxane polymer solid; preparing a primary low-surface-energy silicone sol; preparing a secondary low-surface-energy silicone sol; sequentially depositing the primary low-surface-energy silicone sol and the secondary low-surface-energy silicone sol onto an anodic aluminum oxide support by using ultrasonic atomization and a pore structure grading method; and performing high-temperature post-processing to obtain the high-water-flux organic / inorganic composite membrane with hierarchical pore structures. The composite membrane has the advantages of solvent resistance, high-temperature resistance, ultra-thin thickness, uniform membrane thickness, good membrane surface anti-pollution performance and separation performance, and can be industrialized and applied to a high-temperature wastewater treatment process.

Description

Technical Field

[0001] This invention belongs to the field of composite membrane preparation, specifically relating to a method for preparing a high water flux organic / inorganic composite membrane with a hierarchical pore structure. Background Technology

[0002] Bridged organosilicon materials possess excellent hydrothermal stability, chemical stability, and superior molecular sieving properties, and have attracted widespread attention as potential solvent-resistant and high-temperature resistant nanofiltration membrane materials.

[0003] The sol-gel method is one of the most studied and mature membrane fabrication methods. The principle involves the precursor undergoing hydrolysis or alcoholysis in a solvent, followed by condensation and aggregation to form a sol, and then the solvent evaporates to form a gel. The sol has a certain viscosity and surface tension. If the sol concentration is too high or the support surface temperature is too high, the solvent will evaporate completely before the sol can spread evenly, forming a coffee-ring-shaped gel separation layer. This results in uneven separation layer thickness and poor membrane antifouling performance, affecting the membrane's separation performance.

[0004] Currently, separation membranes prepared using anodic aluminum oxide as a support have a relatively simple pore structure in the separation layer, which can only retain dyes with larger molecular weights. If α-Al₂O₃ is used as a support, its large pore size and rough surface cause pore leakage when the separation layer sol is directly coated, preventing the formation of a complete separation layer. Therefore, multiple coatings of inorganic particle sol are required between the support and the separation layer to form a transition layer, resulting in a cumbersome and unrepeatable preparation process. Furthermore, separation membranes prepared using traditional α-Al₂O₃ supports suffer from excessive mass transfer resistance due to their high thickness, leading to higher energy consumption and operating costs in practical applications. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a high water flux organic / inorganic composite membrane with a hierarchical pore structure.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a high water flux organic / inorganic composite membrane with a hierarchical pore structure, comprising,

[0009] Chlorinated silane monomers, sodium hydroxide and water were stirred in a constant temperature water bath, and the reaction was followed by heating and evaporation to obtain carboxysiloxane polymer solids.

[0010] 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids were dissolved in an alcohol solvent, and then water and hydrochloric acid were added and stirred in a constant temperature water bath. After stirring in a constant temperature water bath, an alkaline catalyst was added and stirred. After the reaction, a surfactant was added to obtain a primary low surface energy organosilicon sol.

[0011] 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids were dissolved in an alcohol solvent, and then water and hydrochloric acid were added and stirred in a constant temperature water bath. After the reaction, a surfactant was added to prepare a secondary low surface energy organosilicon sol.

[0012] A high-water-flux organic / inorganic composite membrane with a hierarchical pore structure was prepared by sequentially depositing a primary low-surface-energy organosilicon sol and a secondary low-surface-energy organosilicon sol onto a preheated anodic alumina support using a pore structure hierarchical method and then performing high-temperature post-treatment.

[0013] In a preferred embodiment of the preparation method described in this invention, the method for preparing the carboxysiloxane polymer solid includes:

[0014] Chlorinated silane monomers and sodium hydroxide were added to deionized water and stirred continuously in a constant temperature water bath at 20–40°C for 12–15 hours. Then, the mixture was heated and evaporated in an oven at 50–60°C to obtain a solid carboxysiloxane polymer.

[0015] The molar ratio of chlorosilane monomer, sodium hydroxide, and deionized water is 1:3 to 6:80 to 100.

[0016] As a preferred embodiment of the preparation method described in this invention, the chloro-containing silane monomer includes 2-cyanoethyltriethoxysilane, trimethylchlorosilane, and tert-butyldimethylchlorosilane.

[0017] As a preferred embodiment of the preparation method described in this invention, the method for preparing the primary low surface energy organosilicon sol includes,

[0018] Dissolve the 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids in an alcohol solvent and stir for 1-2 minutes. Then add water and hydrochloric acid and immediately transfer to a constant temperature water bath at 25-60°C and continue stirring for 4-6 hours.

[0019] The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1~2:120~360:0.2~0.4.

[0020] Add an alkaline catalyst and stir continuously in a constant temperature water bath at 25-60℃ for 30-120 min. Add a surfactant and stir for 10-20 min to obtain a primary low surface energy organosilicon sol.

[0021] The molar ratio of the alkaline catalyst to the inorganic acid is 2:1 to 2; the mass ratio of the surfactant to the total sol is 0.1% to 1%.

[0022] In a preferred embodiment of the preparation method described in this invention, the alcohol solvent includes ethanol, n-propanol, and isopropanol; the alkaline catalyst includes ammonia, sodium hydroxide, and potassium hydroxide; and the surfactant includes sodium dodecylbenzenesulfonate, dodecyltrimethylammonium chloride, dodecyl betaine, and fatty alcohol polyoxyethylene ether.

[0023] As a preferred embodiment of the preparation method described in this invention, the method for preparing the secondary low surface energy organosilicon sol includes,

[0024] Dissolve 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids in an alcohol solvent and stir for 1-2 min. Then add water and hydrochloric acid, immediately transfer to a constant temperature water bath at 25-60°C and stir continuously for 4-6 h. Add surfactant and stir for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0025] The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1–2:120–360:0.2–0.4; the mass ratio of surfactant to total sol is 0.1%–1%.

[0026] In a preferred embodiment of the preparation method described in this invention, the alcohol solvent includes ethanol, n-propanol and isopropanol, the inorganic acid includes H2SO4, and the surfactant includes sodium dodecylbenzenesulfonate, dodecyltrimethylammonium chloride, dodecyl betaine and fatty alcohol polyoxyethylene ether.

[0027] In a preferred embodiment of the preparation method described in this invention, the anodic aluminum oxide support has a pore size of 20–50 nm and a thickness of 50 μm.

[0028] As a preferred embodiment of the preparation method described in this invention, the pore structure hierarchical method involves depositing a primary low surface energy organosilicon sol onto an anodic aluminum oxide support using ultrasonic atomization, followed by depositing a secondary low surface energy organosilicon sol onto the primary low surface energy organosilicon sol. The ultrasonic power of the ultrasonic atomization device is 0.5–2.5 Hz, the distance between the nozzle and the support is 20–40 mm, the preheating temperature of the anodic aluminum oxide support during deposition is 30–60 °C, and the deposition is performed 2–4 times.

[0029] In a preferred embodiment of the preparation method described in this invention, the high-temperature post-treatment is performed at a temperature of 100–300°C for a duration of 10–30 min.

[0030] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a high water flux organic / inorganic composite membrane with a hierarchical pore structure.

[0031] Beneficial effects of this invention:

[0032] (1) This invention introduces a carboxyl-functionalized siloxane polymer, which, in synergy with 1,2-bis(triethoxysilyl)ethane, increases the water flux of the membrane and improves the membrane's separation performance.

[0033] (2) The present invention uses a pore structure hierarchical method to deposit a primary low surface energy organosilicon sol onto an anodic aluminum oxide support, and then deposits a secondary low surface energy organosilicon sol onto the primary low surface energy organosilicon sol to form a separation layer with structural hierarchy. The film preparation method that combines ultrasonic atomization and pore structure hierarchical method has a simplified process, good repeatability, and excellent dye rejection rate and surface antifouling performance of the film.

[0034] (3) In this invention, anodic aluminum oxide is selected as the separation membrane support. Anodic aluminum oxide has the advantages of being ultra-thin, solvent-resistant, high-temperature resistant and high-throughput. It also has a regular porous nanostructure with controllable pore size, which can be adjusted from 5nm to 10μm. By selecting an anodic aluminum oxide support with a pore size of 20nm, the step of coating the transition layer is eliminated, and the separation layer is directly coated, which is simple and efficient. Due to its ultra-thin advantage, the energy consumption is lower in actual application, reducing operating costs. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 This is a schematic diagram of the deposition method of a high water flux organic / inorganic composite membrane with a hierarchical pore structure in Embodiment 1 of the present invention.

[0037] Figure 2 This is a schematic diagram of the pore structure hierarchical method for a high water flux organic / inorganic composite membrane with a hierarchical pore structure in Embodiment 1 of the present invention.

[0038] Figure 3The images show SEM images of the cross-section and surface of the high water flux organic / inorganic composite membrane with hierarchical pore structure in Embodiment 1 of the present invention.

[0039] Figure 4 This is a SEM image of the surface of the high water flux organic / inorganic composite membrane with hierarchical pore structure in Comparative Example 1 of the present invention.

[0040] Figure 5 This is a side view showing the long-term stability of the high water flux organic / inorganic composite membrane with a hierarchical pore structure in Embodiment 1 of the present invention.

[0041] Figure 6 This is a schematic diagram of ultrasonic atomization deposition of a high water flux organic / inorganic composite membrane with a hierarchical pore structure in Embodiment 1 of the present invention.

[0042] Figure 7 The particle size distribution of the organosilicon sol in Example 1 and Comparative Example 1 of this invention is shown in the diagram. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0045] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0046] The ultrasonic atomizing device used in this invention was purchased from Beijing Dongfang Jinrong Ultrasonic Electric Co., Ltd.

[0047] In this embodiment of the invention, the pore spacing of the anodic aluminum oxide support is 65nm; the sheet diameter is 13mm; the pore size is 30nm; and the thickness is 50μm. Purchased from Shenzhen Topology Precision Film Technology Co., Ltd.

[0048] The specific experimental conditions for the composite membrane in this invention for separation in a 100ppm methyl orange / water solution are as follows: feed temperature: 25℃; nanofiltration operating pressure: 0.8MPa; methyl orange / water solution concentration: 100ppm; reaction time: 3h.

[0049] In this invention, the flux is L / (m2 The calculation method for h bar is as follows:

[0050] Flux L / (m 2 h bar) = volume of permeate / (membrane area × nanofiltration time × nanofiltration operating pressure);

[0051] The method for calculating the dye retention rate (%) is as follows:

[0052] Dye rejection rate (%) = (concentration of dye in raw material solution - concentration of dye in permeate) / concentration of dye in raw material solution × 100%.

[0053] Example 1

[0054] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0055] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0056] (3) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0057] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0058] (5) The secondary low surface energy organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120°C for 15 min.

[0059] (6) The prepared composite membrane was applied to a 100ppm methyl orange / water solution for separation. A schematic diagram of the process for preparing the high-flux organic / inorganic composite membrane with a hierarchical pore structure is provided. Figure 1 ;

[0060] SEM images of the cross-section and surface of the high water flux organic / inorganic composite membrane with hierarchical pore structure are shown below. Figure 3 As can be seen, the sol can be stacked on the anodic aluminum oxide support to form a separation layer gel, and the thickness is 196.7 nm (the thickness of the separation layer gel, with the thickness ratio of the first layer to the second layer being 1:1).

[0061] Long-term stability testing of high water flux organic / inorganic composite membranes with hierarchical pore structure, see [link to relevant documentation]. Figure 5 As can be seen, the composite membrane has good stability, and the flux change is very small during the test, indicating that the membrane has good antifouling performance. This also indicates that the separation layer surface is smooth, further demonstrating that the addition of surfactant can reduce the surface energy of the sol, allowing the sol to spread more evenly and fully on the support during the deposition process.

[0062] The test conditions were as follows: feed temperature: 25℃; nanofiltration operating pressure: 0.8MPa; methyl orange / water solution concentration: 100ppm.

[0063] A schematic diagram of the pore structure hierarchy method for the high water flux organic / inorganic composite membrane with hierarchical pore structure in Example 1 is shown below. Figure 2 ; Schematic diagram of ultrasonic atomization deposition of high water flux organic / inorganic composite membrane with hierarchical pore structure, see [reference] Figure 6 .

[0064] Example 2

[0065] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0066] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, then add 0.556g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.4. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.2g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0067] (3) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.556g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.4. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.2g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0068] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 0.5 Hz and the nozzle height to 40 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 60 ℃, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 300 ℃ for 15 min.

[0069] (5) The secondary low surface energy organosilicon sol prepared in step (3) is injected into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 0.5 Hz and the nozzle height to 40 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 60°C, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 300°C for 15 min.

[0070] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 198.3 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0071] Comparative Example 1

[0072] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0073] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Stir continuously in a constant temperature water bath at 40℃ for 2 h to obtain a primary organosilicon sol.

[0074] (3) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h to obtain a secondary organosilicon sol.

[0075] (4) The primary organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0076] (5) The secondary organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0077] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 202.7 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation;

[0078] SEM images of the surface of the high water flux organic / inorganic composite membrane with hierarchical pore structure in Comparative Example 1 are shown below. Figure 4 Without the addition of surfactants, the sol will spread unevenly on the support surface, forming coffee rings, resulting in uneven film thickness and poor separation performance of the composite membrane.

[0079] The particle size distributions of the organosilicon sols in Example 1 and Comparative Example 1 were obtained using a dynamic light scattering instrument (DLS, Malvern Zetasizer Nano-ZS ZEN3600). See [link to relevant documentation]. Figure 7 It can be seen that the addition of surfactant has little effect on the particle size of the sol. The particle size of the primary low surface energy sol with added surfactant is more uniform and concentrated than that of the primary sol without surfactant, which is more conducive to improving the separation performance of the membrane.

[0080] Comparative Example 2

[0081] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0082] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0083] (3) The secondary low surface energy organosilicon sol prepared in step (2) is injected into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30 ℃, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120 ℃ for 15 min.

[0084] (4) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 93.2 nm, and it is only a secondary low surface energy organosilicon gel) was applied to a 100 ppm methyl orange / water solution for separation.

[0085] Comparative Example 3

[0086] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0087] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:120:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0088] (3) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0089] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 103.2 nm, and it is only a first-order low surface energy organosilicon gel) was applied to a 100 ppm methyl orange / water solution for separation.

[0090] Comparative Example 4

[0091] The specific operations of steps (1), (2), and (3) are the same as those in Example 1;

[0092] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the α-Al2O3 support. The substrate temperature is set to 30℃, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120℃ for 15 min.

[0093] (5) The secondary low surface energy organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the α-Al2O3 support. The substrate temperature is set to 30℃, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120℃ for 15 min.

[0094] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 196.7 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0095] Comparative Example 5

[0096] The specific operations of steps (1), (2), and (3) are the same as those in Example 1;

[0097] (4) The primary low surface energy organosilicon sol prepared in step (1) is coated onto the anodic aluminum oxide support by wiping (using degreased cotton to soak the diluted sol and wiping it on the anodic aluminum oxide support, a common conventional method). The coating is applied twice. After the wiping is completed, the support is treated at 120°C for 15 min.

[0098] (5) The secondary low surface energy organosilicon sol prepared in step (2) is coated onto the anodic aluminum oxide support by wiping method. The coating is applied twice. After wiping, the support is treated at 120℃ for 15 min.

[0099] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 278.1 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0100] Comparative Example 6

[0101] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0102] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 1.39g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:60:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0103] (3) Add 1g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 1.39g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:60:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0104] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0105] (5) The secondary low surface energy organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120°C for 15 min.

[0106] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 201.2 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0107] Comparative Example 7

[0108] (1) Add 1g of 1,2-bis(triethoxysilyl)ethane to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, deionized water, and inorganic acid is 1:60:0.1. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0109] (2) Add 1g of 1,2-bis(triethoxysilyl)ethane to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:60:0.1. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0110] (3) The primary low surface energy organosilicon sol prepared in step (1) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0111] (4) The secondary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30 ℃, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120 ℃ for 15 min.

[0112] (5) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 198.2 nm, and the thickness ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0113] Comparative Example 8

[0114] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0115] (2) Add 1g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:60:0.1. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0116] (3) Add 1g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 2.78g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:60:0.1. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0117] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0118] (5) The secondary low surface energy organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120°C for 15 min.

[0119] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 199.6 nm; the ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0120] Comparative Example 9

[0121] (1) Add 0.625g of 2-cyanoethyltriethoxysilane to 4.5ml of 2mol / L NaOH aqueous solution, stir in a constant temperature water bath at 40℃ for 15h, the molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide and deionized water is 1:3:83, and then heat and evaporate to dryness in an oven at 50℃ to obtain carboxysiloxane polymer solid;

[0122] (2) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 4.17g of deionized water, continue stirring for 1-2 min, then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:180:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Then add ammonia water. The molar ratio of ammonia water to sulfuric acid is 2:1. Continue stirring in a constant temperature water bath at 40℃ for 2 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a first-grade low surface energy organosilicon sol.

[0123] (3) Add 0.5g of 1,2-bis(triethoxysilyl)ethane and 0.5g of carboxysiloxane polymer solid to 15.94g of n-propanol, stir for 1-2 min, then add 4.17g of deionized water, continue stirring for 1-2 min, and then add 0.278g of 3.7% sulfuric acid. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid is 1:1:180:0.2. Immediately transfer the beaker to a constant temperature water bath at 40℃ and stir continuously for 4 h. Finally, add 0.02g of sodium dodecylbenzenesulfonate and continue stirring for 10-20 min to obtain a secondary low surface energy organosilicon sol.

[0124] (4) The primary low surface energy organosilicon sol prepared in step (2) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 minutes. The coating is applied twice and treated at 120°C for 15 minutes.

[0125] (5) The secondary low surface energy organosilicon sol prepared in step (3) is drawn into a syringe and connected to an ultrasonic atomizing device. The ultrasonic controller recognizes the set parameter signal, sets the ultrasonic frequency to 2.5 Hz and the nozzle height to 20 mm. The sol is dispersed into uniform and tiny droplets by ultrasonic action, enters the deposition chamber with nitrogen gas, and is uniformly deposited on the anodic aluminum oxide support. The substrate temperature is set to 30°C, and the solvent is allowed to evaporate naturally for 1-2 min. The coating is applied twice and treated at 120°C for 15 min.

[0126] (6) The prepared composite membrane (the thickness of the composite membrane separation layer gel is 201.4 nm, and the ratio of the first layer to the second layer is 1:1) was applied to a 100 ppm methyl orange / water solution for separation.

[0127] The experimental results of the above embodiments and comparative examples are shown in Table 1.

[0128] Table 1

[0129] membrane <![CDATA[Flux L / (m 2 h bar)]]> Dye retention rate (%) Example 1 1.43 98.9 Example 2 1.43 99.2 Comparative Example 1 1.32 91.4 Comparative Example 2 2.32 36.8 Comparative Example 3 1.96 70.4 Comparative Example 4 1.63 42.5 Comparative Example 5 1.19 96.2 Comparative Example 6 1.84 66.8 Comparative Example 7 1.14 98.8 Comparative Example 8 1.81 92.2 Comparative Example 9 1.55 86.0

[0130] As can be seen from Table 1, compared with Example 1, the membrane prepared by the sol with added surfactant in Comparative Example 1 has a larger flux and dye rejection rate, indicating that the addition of surfactant reduces the membrane thickness and makes the membrane more uniform and complete.

[0131] Comparative Example 2 shows that if the first-stage low surface energy silicone sol is not sprayed, the second-stage low surface energy silicone sol will be sprayed directly, resulting in a porosity phenomenon, thus the throughput is large and the dye retention rate is very low.

[0132] Comparative Example 3 shows that if the secondary low surface energy organosilicon sol is not sprayed, the pore size of the separation layer gel is not small enough, so the flux is large and the dye rejection rate is low.

[0133] Comparative Example 4 shows that if a traditional α-Al2O3 support is used without coating with transition layers such as large and small particles, a porosity phenomenon will occur, resulting in a large flux and a very low dye rejection rate.

[0134] Comparative Example 5 shows that the separation layer coated by the wiping method is thicker and more uneven, resulting in lower throughput and lower dye rejection rate.

[0135] Comparative Example 6 illustrates that the ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and inorganic acid affects the uniformity of sol particle size, thereby affecting membrane flux and rejection rate.

[0136] Comparative Example 7 shows that if carboxysiloxane polymer solids are not added, the water flux of the composite membrane will be significantly reduced.

[0137] Comparative Example 8 shows that without the addition of 1,2-bis(triethoxysilyl)ethane, the separation layer gel is not dense enough, resulting in an increase in the flux of the composite membrane while the rejection rate decreases.

[0138] Comparative Example 9 illustrates that when preparing the sol, adding too much deionized water can affect the uniformity of the sol particle size, thereby affecting the membrane flux and rejection rate.

[0139] It should be noted that 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 technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a high water flux organic / inorganic composite membrane with a hierarchical pore structure, characterized in that: include, 2-Cyanoethyltriethoxysilane, sodium hydroxide and water were stirred in a constant temperature water bath, and the reaction was followed by heating to dryness to obtain a solid carboxylsiloxane polymer. 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids were dissolved in an alcohol solvent, and then water and sulfuric acid were added and stirred in a constant temperature water bath. After stirring in a constant temperature water bath, an alkaline catalyst was added and stirred. After the reaction, a surfactant was added to obtain a primary low surface energy organosilicon sol. 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids were dissolved in an alcohol solvent, and then water and sulfuric acid were added and stirred in a constant temperature water bath. After the reaction, a surfactant was added to prepare a secondary low surface energy organosilicon sol. A high-water-flux organic / inorganic composite membrane with a hierarchical pore structure was prepared by sequentially depositing a primary low-surface-energy organosilicon sol and a secondary low-surface-energy organosilicon sol onto a preheated anodic alumina support using a pore structure hierarchical method and then performing high-temperature post-treatment.

2. The preparation method according to claim 1, characterized in that: The method for preparing the carboxysiloxane polymer solid includes, 2-Cyanoethyltriethoxysilane and sodium hydroxide were added to deionized water and stirred continuously in a constant temperature water bath at 20-40°C for 12-15 hours. Then, the mixture was heated and evaporated in an oven at 50-60°C to obtain a solid carboxylsiloxane polymer. The molar ratio of 2-cyanoethyltriethoxysilane, sodium hydroxide, and deionized water is 1:3~6:80~100.

3. The preparation method according to claim 1, characterized in that: The preparation method of the primary low surface energy organosilicon sol includes, Dissolve the 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids in an alcohol solvent and stir for 1-2 minutes. Then add water and sulfuric acid and immediately transfer to a constant temperature water bath at 25-60°C and stir continuously for 4-6 hours. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and sulfuric acid is 1:1~2:120~360:0.2~0.

4. Add an alkaline catalyst and stir continuously in a constant temperature water bath at 25~60℃ for 30~120min. Add a surfactant and stir for 10~20min to obtain a primary low surface energy organosilicon sol. The molar ratio of the alkaline catalyst to sulfuric acid is 2:1~2; the mass ratio of the surfactant to the total sol is 0.1%~1%.

4. The preparation method according to claim 3, characterized in that: The alcohol solvent includes ethanol, n-propanol, and isopropanol; the alkaline catalyst includes ammonia, sodium hydroxide, and potassium hydroxide; and the surfactant includes sodium dodecylbenzenesulfonate, dodecyltrimethylammonium chloride, dodecyl betaine, and fatty alcohol polyoxyethylene ether.

5. The preparation method according to claim 1, characterized in that: The preparation method of the secondary low surface energy organosilicon sol includes, Dissolve 1,2-bis(triethoxysilyl)ethane and carboxysiloxane polymer solids in an alcohol solvent and stir for 1-2 min. Then add water and sulfuric acid, immediately transfer to a constant temperature water bath at 25-60°C and stir continuously for 4-6 h. Add surfactant and stir for 10-20 min to obtain a secondary low surface energy organosilicon sol. The molar ratio of 1,2-bis(triethoxysilyl)ethane, carboxysiloxane polymer solid, deionized water, and sulfuric acid is 1:1~2:120~360:0.2~0.4; the mass ratio of surfactant to total sol is 0.1%~1%.

6. The preparation method according to claim 5, characterized in that: The alcohol solvent includes ethanol, n-propanol, and isopropanol, and the surfactant includes sodium dodecylbenzenesulfonate, dodecyltrimethylammonium chloride, dodecyl betaine, and fatty alcohol polyoxyethylene ether.

7. The preparation method according to claim 1, characterized in that: The anodic aluminum oxide support has a pore size of 20~50nm and a thickness of 50μm.

8. The preparation method according to claim 1, characterized in that: The pore structure grading method involves depositing a primary low surface energy organosilicon sol onto an anodic aluminum oxide support using ultrasonic atomization, followed by depositing a secondary low surface energy organosilicon sol onto the primary low surface energy organosilicon sol. The distance between the nozzle of the ultrasonic atomizing device and the support is 20-40 mm, and the preheating temperature of the anodic aluminum oxide support during deposition is 30-60°C. The deposition is repeated 2-4 times.

9. The preparation method according to claim 1, characterized in that: The high-temperature post-treatment includes a treatment temperature of 100~300℃ and a treatment time of 10~30min.

Images