Super-hydrophobic ordered porous aerogel film as well as preparation method and application thereof

Abstract

The invention relates to the field of oil-water separation materials, and discloses a super-hydrophobic ordered porous aerogel film as well as a preparation method and application thereof. The method comprises the following steps: dispersing Tempo oxidized nanocellulose in water to prepare a cellulose suspension; preparing an MXene suspension liquid; mixing the cellulose suspension and the MXene suspension to obtain a cellulose / MXene composite solution, performing temperature-controlled drying in a mold, then performing directional freezing, and finally performing freeze drying to obtain an aerogel film; soaking the aerogel film in a mixed solution prepared from hexadecyl trimethoxysilane, tetraethyl silicate, ammonia water and absolute ethyl alcohol for modification, and drying to obtain the hydrophobic aerogel film. The oil-water separation efficiency of the aerogel membrane can reach 99%, the single circulation flux is larger than 27000L m <-2 > h <-1 > bar <-1 >, and the aerogel membrane has excellent reusability and is a novel efficient oil-water separation membrane.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil-water separation materials, more particularly, to a super-hydrophobic ordered porous aerogel film and a preparation method and application thereof. BACKGROUND

[0002] In recent decades, water pollution caused by oil spill accidents, oil extraction activities and oily wastewater is a global problem. It not only causes waste of resources and energy, but also threatens the ecological system and human health. At present, researchers have developed various separation technologies, and membrane separation is considered to be a relatively effective separation technology for oily wastewater due to its simple operation, low energy consumption and high separation efficiency. However, the existing oil-water separation membranes have the disadvantages of unsustainable raw materials, high price, difficulty in biodegradation and secondary pollution.

[0003] Cellulose is the most widely distributed and abundant biomass material in nature, and has the characteristics of biodegradability. Nanocellulose is a rod, whisker, fiber or linear nanomaterial with a diameter of less than 100 nm, which has a high specific surface area and elastic modulus, and is an ideal separation membrane raw material, which has great application potential in the petroleum industry. However, there are a large number of -OH on the surface of nanocellulose, which is easy to adsorb water or oil, and a super-hydrophobic coating needs to be built to improve the oil-water separation efficiency. Importantly, the nanocellulose membranes obtained by filtration, casting and other processes are mostly tightly structured, and in the oil-water separation process, the pore channels are easily blocked by chemical agents, surfactants, impurities and the like, resulting in low oil-water separation efficiency.

[0004] The prior art CN110183722A realizes excellent hydrophobic performance by introducing DMSO and a directional freezing process combined with fluorosilane vapor deposition to prepare a super-amphiphobic nanocellulose aerogel, but the use of fluorine-containing modifiers poses an environmental pollution risk, which is not conducive to green and sustainable development; CN114805920A proposes a method for preparing a super-hydrophobic aerogel by using acid-induced gelation and organic silicon soaking modification, which improves the environmental friendliness and operability, but the structure of the aerogel is still loose, and the uniformity and stability of the hydrophobic layer are easily affected in a complex oil-water environment; CN118767882A proposes to use a multi-component nanocomposite strategy to improve the performance of the aerogel, but the pore channel order control is not effectively realized in the preparation process, and the drying process relies on freeze-drying technology, lacking a drying strategy that takes into account structure guidance and cost control. Although the above examples can achieve oil-water separation, compared with aerogel materials, aerogel film materials not only have the advantages of aerogel materials but also can be better applied in pipeline and other application scenarios.

[0005] Therefore, it is of important practical significance to design an aerogel film with pore order, green hydrophobic modification, structural stability and repeated use performance for efficient separation of oil-water mixtures. SUMMARY

[0006] The present invention aims to overcome the defects of the above-mentioned prior art oil-water separation materials, such as insufficient structural control ability, unstable hydrophobic performance, and unsatisfactory separation efficiency and reusability, and provides a method for preparing a hydrophobic ordered porous aerogel membrane.

[0007] Another object of the present invention is to provide a super-hydrophobic ordered porous aerogel membrane;

[0008] Another object of the present invention is to provide an application of a super-hydrophobic ordered porous aerogel membrane.

[0009] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0010] A method for preparing a super-hydrophobic ordered porous aerogel film comprises the following steps:

[0011] S1, Tempo-oxidized nanocellulose is dispersed in water to prepare a cellulose suspension;

[0012] S2, preparing MXene suspension;

[0013] S3, mixing the cellulose suspension with the MXene suspension to obtain a cellulose / MXene composite solution, drying the solution under controlled temperature in a mold, performing directionally freezing, and finally freeze-drying to obtain an aerogel film;

[0014] S4. The aerogel film is modified by immersing it in a mixed solution of hexadecyltrimethoxysilane, tetraethyl silicate, ammonia water and anhydrous ethanol, and then dried to obtain a superhydrophobic aerogel film.

[0015] Furthermore, the mass concentration of the cellulose suspension is 0.6 wt% to 1.5 wt%.

[0016] Preferably, the weight percentage of the Tempo-oxidized nanocellulose is 1% to 2%.

[0017] Preferably, the length of the Tempo-oxidized nanocellulose is 400 to 1000 nm and the diameter is 5 to 10 nm.

[0018] Furthermore, the mass concentration of the MXene suspension is 3 to 5 mg / mL.

[0019] Furthermore, MXene accounts for 2.5 wt% to 10 wt% of the cellulose / MXene composite solution.

[0020] Furthermore, the temperature-controlled drying is performed at 45 to 55° C. for 0.5 to 1 hour.

[0021] Preferably, copper rods are used for directional freezing.

[0022] Preferably, the directional freezing is carried out at room temperature, and the mold is placed at one end of a copper rod immersed in liquid nitrogen, and the height of the liquid nitrogen is close to 90% of the copper rod.

[0023] Preferably, the temperature of the freeze-drying is -45℃ to -55℃, the pressure is 1 to 2.5 Pa, and the drying time is 24 to 48 h.

[0024] Further, the volume ratio of ammonia water to anhydrous ethanol is 1:10 to 20; the volume ratio of hexadecyl trimethoxysilane, tetraethyl silicate to anhydrous ethanol is 0.28 to 0.40:0.28 to 0.40:20 to 40.

[0025] Preferably, the mass concentration of ammonia water is 25% to 28%.

[0026] Preferably, the volume ratio of hexadecyl trimethoxysilane, tetraethyl silicate is 0.30 to 0.38:0.30 to 0.38.

[0027] The volume ratio of ammonia water to anhydrous ethanol is 1:10; the volume ratio of hexadecyl trimethoxysilane, tetraethyl silicate to anhydrous ethanol is 0.34:0.34:20.

[0028] Preferably, the soaking time is 12 to 24 h.

[0029] Preferably, the drying time is 12 to 24 h, and the oven temperature is 50 to 60℃.

[0030] Further, lithium fluoride and titanium aluminum carbide are sequentially added in hydrochloric acid, stirred and reacted, centrifuged, and the supernatant is collected; the MXene suspension is obtained by rotary evaporation.

[0031] Preferably, the addition amount of lithium fluoride and titanium aluminum carbide is 0.05 to 0.1 g / mL of hydrochloric acid.

[0032] Preferably, the stirring and reaction time is 24 to 48 h.

[0033] Preferably, the centrifugal speed is 3000 to 4000 rpm, the centrifugal time is 3 to 5 min, and the centrifugal frequency is 10 to 13 times. Further, the mass concentration of hydrochloric acid is 27% to 28.5%.

[0034] An ultrahydrophobic ordered porous aerogel film is prepared by a method for preparing the ultrahydrophobic ordered porous aerogel film.

[0035] An application of the ultrahydrophobic ordered porous aerogel film is used for oil-water separation.

[0036] Preferably, in the oil-water separation, the oil includes n-hexane, hexadecane, engine oil, soybean oil, and waste engine oil.

[0037] Through multi-dimensional collaborative design, the present invention successfully prepared a new aerogel membrane with a regular pore structure, excellent superhydrophobicity and efficient oil-water separation ability.

[0038] First, a two-dimensional transition metal carbide / carbonitride MXene was introduced using nanocellulose as the backbone material. Due to its large specific surface area and abundant surface functional groups, MXene can effectively form a stable network structure by hydrogen bonding and chemical bonding with cellulose. Furthermore, the hydroxyl groups (-OH) on the MXene surface can condense with the -Si-OH groups generated by silane hydrolysis during the hydrophobic modification process, thereby enhancing the hydrophobic properties of the aerogel membrane.

[0039] Secondly, an innovative dual drying process of "controlled temperature drying + directional freezing + freeze drying" was employed. Controlled temperature drying regulates the physical entanglement, hydrogen bonding, and capillary action between cellulose fibers and the solvent, thereby affecting the material's porosity and pore structure. Directed freezing creates a vertical temperature gradient in a liquid nitrogen environment, promoting the directional growth of ice crystals from bottom to top, which in turn forms an orderly arranged pore structure during the subsequent freeze drying process. The synergistic effect of these two drying methods enables precise control of the aerogel membrane's pore structure, resulting in the production of a porous membrane with high porosity, small pore size, and an orderly structure.

[0040] Finally, in an anhydrous ethanol system, concentrated ammonia provided alkaline catalysis to promote the synergistic grafting of tetraethyl silicate (TEOS) and hexadecyltrimethoxysilane (HDTMS) onto the nanocellulose surface. The silica formed by TEOS creates a micro-nanoscale rough structure on the membrane surface, while HDTMS provides long-chain alkyl groups with low surface energy, thus imparting superhydrophobic properties to the aerogel membrane.

[0041] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0042] The hydrophobic ordered porous aerogel membrane prepared by the present invention has a highly ordered through-hole porous structure, which significantly improves the mass transfer efficiency of liquids within the membrane and the stability of the separation path. The hydrophobic contact angle of the membrane surface is as high as 157°, and the static contact angle remains at 149.9° after 10 minutes, showing excellent superhydrophobic properties. It can effectively block water penetration and selectively pass through the oil phase, achieving 99% efficient separation of various oil-water mixtures. The membrane has a separation flux of up to 27520 L·m under normal pressure conditions. -2 ·h-1·bar -1 , far higher than traditional membrane materials, and maintained high separation efficiency and flux during 15 reuses, showing good stability and durability. In addition, this material is mainly made of renewable nanocellulose, the preparation process is green and environmentally friendly, and its comprehensive performance is excellent, which has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The preparation process of the super-hydrophobic ordered porous aerogel membrane of the present invention is as follows;

[0044] Figure 2 SEM images of aerogel membrane cross sections, a is a cross-sectional view of Example 1, b is a cross-sectional view of Comparative Example 1, c is a cross-sectional view of Comparative Example 2, and d is a longitudinal cross-sectional view of Example 1;

[0045] Figure 3 This is the hydrophobicity test of the aerogel film in Example 1. a is a schematic diagram of the aerogel film surface contacting a water droplet, b is the wettability change of the aerogel film after being soaked in hexadecyltrimethylsilane / tetraethyl silicate, and c is the change in the contact angle of the aerogel film at different times;

[0046] Figure 4 This is a reusability test of Example 1, a is the oil-water separation flux and separation efficiency of n-hexane / water, hexadecane / water, engine oil / water, soybean oil / water, and waste engine oil / water in the first cycle of Example 1, b is the oil-water separation flux and separation efficiency of n-hexane / water in 15 cycles of Example 1, c is the oil-water separation flux and separation efficiency of hexadecane / water in 15 cycles of Example 1, d is the oil-water separation flux and separation efficiency of engine oil / water in 15 cycles of Example 1, e is the oil-water separation flux and separation efficiency of soybean oil / water in 15 cycles of Example 1, and f is the oil-water separation flux and separation efficiency of waste engine oil / water in 15 cycles of Example 1; g and h are oil-water separation effect diagrams of aerogel membrane, g is before separation and h is after separation.

[0047] Figure 5 This is the separation of the water-in-oil emulsion in Example 1, a is a photograph and an optical microscope image of the water-in-oil emulsion separation before and after soybean oil filtration, and b is a photograph and an optical microscope image of the water-in-oil emulsion separation before and after hexadecane filtration. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0049] Unless otherwise specified, all reagents and materials used in the following examples were commercially available.

[0050] The Tempo-oxidized nanocellulose used in the following embodiments has a length of 400 to 1000 nm and a diameter of 5 to 10 nm.

[0051] Example 1

[0052] The preparation of a superhydrophobic ordered porous aerogel membrane is mainly divided into the following steps:

[0053] (1) 3.0 g of Tempo-oxidized CNF (1.0 wt%) was dispersed in 1 mL of water and stirred for 30 min to obtain a cellulose suspension.

[0054] (2) 1 g of lithium fluoride and 1 g of titanium aluminum carbide powder were added sequentially to a 27% hydrochloric acid solution (20 mL) and vigorously stirred at room temperature for 48 h. After the reaction, the mixture was centrifuged in a high-speed centrifuge (4000 rpm, 5 min; 10 centrifuges). The supernatant was collected and subjected to rotary evaporation to obtain a MXene suspension (3-5 mg / mL).

[0055] (3) Preparation of cellulose / MXene composite solution: The MXene suspension was mixed with the cellulose suspension and stirred for 30 min to obtain a cellulose / MXene composite solution (MXene accounted for 10 wt% of the cellulose / MXene composite solution).

[0056] (4) The obtained composite solution was poured into a mold, dried in an oven at 55°C for 0.5 h, and then directionally frozen at room temperature (the mold was placed at one end of a copper rod immersed in liquid nitrogen, with the height of the liquid nitrogen close to 90% of the copper rod), and then freeze-dried for 48 h (-45°C, 2.5 Pa) to obtain an ordered porous aerogel film.

[0057] (5) 0.28 mL, 0.30 mL, 0.34 mL, 0.36 mL, 0.38 mL, and 0.40 mL of hexadecyltrimethylsilane and tetraethyl silicate were added to 2 mL of concentrated ammonia and 20 mL of anhydrous ethanol, respectively, to prepare a mixed solution.

[0058] (6) The obtained ordered porous aerogel film was immersed in the prepared mixed solution for 12 h, and the reacted sample was gently rinsed with anhydrous ethanol to remove the residual unreacted solution. Finally, the modified sample was placed in an oven for drying (50°C, 24 h) to obtain the product.

[0059] Example 2

[0060] The preparation of a superhydrophobic ordered porous aerogel membrane is mainly divided into the following steps:

[0061] (1) 3.0 g of Tempo-oxidized CNF (1 wt%) was dispersed in 2 mL of water and stirred for 30 min to obtain a cellulose suspension.

[0062] (2) 2 g of lithium fluoride and 2 g of titanium aluminum carbide powder were added sequentially to a 28.5% hydrochloric acid solution (20 mL) and vigorously stirred at room temperature for 48 h. After the reaction, the mixture was centrifuged in a high-speed centrifuge (4000 rpm, 5 min; 13 times). The supernatant was collected and subjected to rotary evaporation to obtain a MXene suspension (3-5 mg / mL).

[0063] (3) Preparation of cellulose / MXene composite solution: The MXene suspension was mixed with the cellulose suspension and stirred for 30 min to obtain a cellulose / MXene composite solution (MXene accounted for 5 wt% of the cellulose / MXene composite solution).

[0064] (4) The obtained composite solution was poured into a mold, dried in an oven at 50°C for 0.75 h, and then directionally frozen at room temperature (the mold was placed at one end of a copper rod immersed in liquid nitrogen, with the height of the liquid nitrogen close to 90% of the copper rod), and then freeze-dried for 24 h (-55°C, 1 Pa) to obtain an ordered porous aerogel film.

[0065] (5) Hexadecyltrimethylsilane (0.34 mL), tetraethyl silicate (0.34 mL) and 2 mL of concentrated aqueous ammonia were added to 30 mL of anhydrous ethanol to prepare a mixed solution.

[0066] (6) The obtained ordered porous aerogel film was immersed in the prepared mixed solution for 24 h, and the reacted sample was gently rinsed with anhydrous ethanol to remove the residual unreacted solution. Finally, the modified sample was placed in an oven for drying (60°C, 12 h) to obtain the product.

[0067] Example 3

[0068] The preparation of a superhydrophobic ordered porous aerogel membrane is mainly divided into the following steps:

[0069] (1) 3.0 g of Tempo-oxidized CNF (2.0 wt%) was dispersed in 1.0 mL of water and stirred for 30 min to obtain a cellulose suspension.

[0070] (2) 1.5 g of lithium fluoride and 1.5 g of titanium aluminum carbide powder were added to a 27% hydrochloric acid solution (20 mL) and stirred vigorously at room temperature for 24 h. After the reaction, the mixture was centrifuged in a high-speed centrifuge (3000 rpm, 3 min; 13 times). The supernatant was collected and subjected to rotary evaporation to obtain a MXene suspension (3-5 mg / mL).

[0071] (3) Preparation of cellulose / MXene composite solution: The MXene suspension was mixed with the cellulose suspension and stirred for 30 min to obtain a cellulose / MXene composite solution (MXene accounted for 2.5 wt% of the cellulose / MXene composite solution).

[0072] (4) The obtained composite solution was poured into a mold, dried in an oven at 45°C for 1 h, and then directionally frozen at room temperature (the mold was placed at one end of a copper rod immersed in liquid nitrogen, with the height of the liquid nitrogen close to 90% of the copper rod), and then freeze-dried for 24 h (-55°C, 1 Pa) to obtain an ordered porous aerogel film.

[0073] (5) Hexadecyltrimethylsilane (0.40 mL), tetraethyl silicate (0.40 mL) and 2 mL of concentrated aqueous ammonia were added to 40 mL of anhydrous ethanol to prepare a mixed solution.

[0074] (6) The obtained ordered porous aerogel film was immersed in the prepared mixed solution for 24 hours, and the reacted sample was gently rinsed with anhydrous ethanol to remove the residual unreacted solution. Finally, the modified sample was placed in an oven for drying to obtain the product.

[0075] Comparative Example 1

[0076] The technical solution is similar to that of Example 1, except that:

[0077] (4) The obtained composite solution was poured into a mold and dried in an oven at 45°C for 24 h to obtain an aerogel film.

[0078] Comparative Example 2

[0079] The technical solution is similar to that of Example 1, except that:

[0080] (4) The obtained composite solution is poured into a mold and directly freeze-dried to obtain an aerogel film.

[0081] Comparative Example 3

[0082] The technical solution is similar to that of Example 1, except that:

[0083] (4) The obtained composite solution was poured into a mold and dried in an oven at 60°C for 3 h to obtain an aerogel film.

[0084] Comparative Example 4

[0085] The technical solution is similar to that of Example 1, except that:

[0086] (2) 1 g of lithium fluoride and 1 g of titanium aluminum carbide powder were added to 25% hydrochloric acid solution (20 mL) in sequence and stirred vigorously at room temperature for 48 h.

[0087] Detection method

[0088] Oil-water separation performance test:

[0089] (1) Oil-water mixture

[0090] The effective cross-sectional area of ​​the aerogel membrane material was measured, and a continuous oil-water separation device was designed using a peristaltic pump to investigate the continuous oil-water separation performance of the aerogel material. One end of the rubber tube was connected to a plastic nozzle, which was then connected to the superhydrophobic ordered porous aerogel membrane. The other end of the rubber tube was connected to a filter bottle. Next, the filter bottle was connected to a vacuum pump (1 bar) to assemble a continuous oil-water separation device. This self-built device was used to study the continuous oil-water separation performance of the superhydrophobic ordered porous aerogel membrane.

[0091] Deionized water was dyed blue with methylene blue. A 1:1 volume ratio of oil and water was then added to a beaker. The aerogel membrane was used to absorb the oil phase per unit volume, and the time required for the oil and water to separate was recorded.

[0092] The calculation formula of oil-water separation flux (J) is as follows:

[0093]

[0094] Where ΔV is the volume of the filtered oil phase; S is the effective filtration area of ​​the membrane, t is the time for oil-water separation; and p is the transmembrane pressure.

[0095] (2) Water-in-oil emulsion

[0096] The prepared soybean oil / water emulsion system (soybean oil:water=49:1) and hexadecane / water emulsion system (hexadecane:water=49:1) were poured onto the aerogel membrane, allowing the water-in-oil emulsions to separate under gravity conditions only.

[0097] Analysis

[0098] Figure 1 The preparation process of the super-hydrophobic ordered porous aerogel membrane of the present invention is as follows:

[0099] 1. Preparation of cellulose / MXene suspension

[0100] First, the Tempo-oxidized nanocellulose is placed in water and stirred; then the prepared MXene solution is added and stirred to obtain a cellulose / MXene composite solution for use.

[0101] 2. Preparation of ordered porous aerogel membrane

[0102] First, the prepared cellulose / MXene composite solution is poured into the prepared mold and placed in an oven for temperature control and drying. Then, the mold is placed at one end of a copper rod immersed in liquid nitrogen. The height of the liquid nitrogen is close to 90% of the copper rod. Then, it is immediately placed in a freeze dryer for freeze drying to obtain an aerogel film.

[0103] 3. Modification of aerogel membrane

[0104] Hexadecyltrimethylsilane and tetraethyl silicate were added to anhydrous ethanol, followed by concentrated ammonia. The mixture was allowed to soak at room temperature, and then the remaining solution on the aerogel cornea surface was gently rinsed with anhydrous ethanol. Finally, the modified sample was placed in an oven and dried to obtain a superhydrophobic, ordered porous aerogel membrane.

[0105] When the temperature-controlled drying time is too long or the temperature is too high (Comparative Examples 1 and 3), the surface of the aerogel membrane loses water to form a dense structure, which hinders the diffusion of the internal solvent. At the same time, the capillary effect aggravates the collapse of the pore structure, and eventually the aerogel composite membrane gradually becomes non-porous from the outside to the inside. Figure 2 b It can be seen that the surface of the composite membrane formed by temperature-controlled drying in Comparative Example 1 shows a dense structure and no pore structure. In Comparative Example 2, direct freeze drying is performed. Although the aerogel membrane has a porous structure, the disordered ice crystal growth makes its pores irregular and collapsed ( Figure 2 c). However, after double drying, the aerogel membrane prepared in Example 1 exhibited a highly porous structural feature, with a rough surface and an obvious open-pore macroporous structure inside ( Figure 2 a), showing good porosity and regularity. Figure 2 In d, the cellulose / Mxene suspension on the surface of Example 1 is directionally frozen at ultra-low temperature supplied by liquid nitrogen. The single vertical temperature gradient causes ice crystals to grow vertically from the bottom to the top in an orderly manner, forming ordered pores of the aerogel membrane.

[0106] Figure 3a shows the effect of different contents of hexadecyltrimethylsilane (Hdtms) / tetraethyl silicate (Teos) on the hydrophobicity of the aerogel film in Example 1. When the contents of Hdtms and Teos are within a certain range, the -OH on the surface of the SiO2 nanoparticles formed by the hydrolysis of Teos will be masked by the silane formed by the hydrolysis of Hdtms, and can be evenly covered on the cellulose surface to provide low surface energy and high roughness, thereby meeting the conditions required for super hydrophobicity. When the contents of Hdtms and Teos are both 0.28mL and 0.40mL, the contact angle is slightly reduced, which are 117.1° and 125° respectively; when the contents are both 0.30mL and 0.38mL, the contact angles are respectively 123.4° and 130°; when the contents are both 0.32mL and 0.36mL, the contact angles are respectively 139.1° and 135°; when the contents of Hdtms and Teos are both 0.34mL, the sample surface reaches super hydrophobicity, with a hydrophobic angle of 157° ( Figure 3 b). Figure 3 c shows the contact angle stability of the superhydrophobic ordered porous aerogel membrane. The initial contact angle is as high as 157.0°, the static contact angle is still greater than 150.0° within 5 minutes, and the static contact angle remains at 149.9° after 10 minutes, indicating that the superhydrophobic ordered porous aerogel membrane has good hydrophobic stability.

[0107] from Figure 4 It can be seen that the super-hydrophobic ordered porous aerogel membrane has shown effective separation performance for oil-water mixtures such as n-hexane, hexadecane (low viscosity), motor oil, soybean oil, and waste motor oil (high viscosity), with separation efficiencies exceeding 95%. In the first cycle, the separation fluxes of n-hexane and waste motor oil on the super-hydrophobic ordered porous aerogel membrane were greater than 27520m –2 h –1 bar -1 , 8900m –2 h –1 bar -1 , the separation efficiency is higher than 99%. Figure 4 As can be seen from b and f, after 15 cycles, the separation flux of n-hexane waste oil on the superhydrophobic ordered porous aerogel membrane aerogel is greater than 26000m –2 h – 1 bar -1 and 5000m –2 h –1 bar -1 , and its separation efficiency is maintained above 95%. The super hydrophobic ordered porous aerogel membrane of Example 1 maintains a high oil-water separation efficiency and separation flux ( Figure 4b-f), demonstrating its excellent recycling performance and maintaining high oil-water separation flux and efficiency. Over 15 oil-water separation cycles, the oil-water separation flux for n-hexane and hexadecane decreased minimally, while the separation efficiency remained above 99%. This demonstrates its fine porosity and improved separation efficiency for less viscous oils, suggesting potential for practical application.

[0108] In contrast, Comparative Examples 1 and 3 cannot separate the oil-water mixture due to abnormal pore structures inside and outside the membrane and reduced porosity. In Comparative Example 2, the separation flux of n-hexane in the first cycle is only about 20,000 m –2 h –1 bar -1 In Comparative Example 4, the reduced hydrochloric acid concentration resulted in incomplete MXene etching, multi-layer block stacking, and the prepared aerogel membrane lacked a support network, with disordered pores and low liquid flow efficiency. In the first cycle, the separation flux of n-hexane was only about 18,000 m –2 h – 1 bar -1 , and the performance obviously decayed after 10 repetitions.

[0109] like Figure 5 As shown in the figure, the separation of the oil-in-water emulsion separation membrane simulated aerogel membrane in the pipeline, and the filtrate after separation changed from opaque to transparent. In addition, the optical microscope image shows that in the soybean oil / water emulsion system ( Figure 5 a) and hexadecane / water emulsion system ( Figure 5 In the initial emulsion image of b), randomly distributed crude oil droplets were observed, while almost no oil droplets were observed in the filtrate image, which indicates that the aerogel membrane of the present invention effectively separates the emulsion and has excellent separation performance.

[0110] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a super-hydrophobic ordered porous aerogel membrane, characterized in that: The following steps are involved: S1, Tempo-oxidized nanocellulose is dispersed in water to prepare a cellulose suspension; S2, preparing MXene suspension; S3, mixing the cellulose suspension with the MXene suspension to obtain a cellulose / MXene composite solution, drying the solution under controlled temperature in a mold, performing directionally freezing, and finally freeze-drying to obtain an aerogel film; S4. The aerogel film is modified by immersing it in a mixed solution of hexadecyltrimethoxysilane, tetraethyl silicate, ammonia water and anhydrous ethanol, and then dried to obtain a superhydrophobic aerogel film.

2. The method for preparing a super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: The mass concentration of the cellulose suspension is 0.6 wt% to 1.5 wt%.

3. The method for preparing the super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: The mass concentration of the MXene suspension is 3-5 mg / mL.

4. The method for preparing the super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: The MXene accounts for 2.5 wt% to 10 wt% of the cellulose / MXene composite solution.

5. The method for preparing the super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: The temperature-controlled drying is performed at 45 to 55° C. for 0.5 to 1 hour.

6. The method for preparing the super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: In the mixed solution, the volume ratio of ammonia water to anhydrous ethanol is 1:10-20; the volume ratio of hexadecyltrimethoxysilane, tetraethyl silicate and anhydrous ethanol is 0.28-0.40:0.28-0.40:20-40.

7. The method for preparing a super-hydrophobic ordered porous aerogel membrane according to claim 1, wherein: Lithium fluoride and titanium aluminum carbide are added to hydrochloric acid in sequence, stirred for reaction, centrifuged, and the supernatant is collected; and the MXene suspension is obtained by rotary evaporation.

8. The method for preparing the super-hydrophobic ordered porous aerogel membrane according to claim 7, characterized in that: The concentration of hydrochloric acid is 27% to 28.5%.

9. A super-hydrophobic ordered porous aerogel membrane, characterized in that: The super-hydrophobic ordered porous aerogel membrane is prepared by the preparation method of any one of claims 1 to 8.

10. An application of the super-hydrophobic ordered porous aerogel membrane according to claim 9, characterized in that: Used for oil-water separation.

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