A method for preparing superhydrophobic aerogels under ambient pressure based on framework regulation and its application

Abstract

This invention discloses a method for preparing superhydrophobic aerogels under ambient pressure based on framework regulation and its application. The invention involves a multi-component composite of carboxymethyl cellulose, aramid fiber, carboxylated nitrile rubber, melamine-formaldehyde resin, modified montmorillonite, hydrophobic silica, and an organosilicon waterproofing agent. A vertical pore template is constructed through directional freezing, followed by gradient solvent displacement and ambient pressure drying to finally solidify the superhydrophobic-superoleophilic aerogel. This invention successfully overcomes the core challenge of structural collapse caused by capillary forces during ambient pressure drying through the synergistic enhancement of the organic-inorganic hybrid framework and surface energy regulation, achieving a balance between low shrinkage, high porosity, and stable superwetting properties. The aerogel of this invention possesses excellent mechanical strength and elasticity, and its functionality can be expanded by introducing photothermal fillers. The process equipment is simple and energy-efficient, providing an economical and feasible technical path for the large-scale preparation of high-performance superhydrophobic aerogels.

Description

Technical Field

[0001] This invention relates to a method for preparing superhydrophobic aerogels under ambient pressure based on framework regulation and its application, belonging to the field of porous material preparation and application technology. Background Technology

[0002] Aerogels, as three-dimensional nanoporous materials with extremely high porosity, extremely low density, and extremely large specific surface area, have shown great application potential in fields such as thermal insulation, adsorption, catalysis, and energy storage and conversion. Among them, aerogels with superhydrophobic-superoleophilic properties are considered ideal materials for treating environmental problems such as marine oil spills and industrial oily wastewater because they can selectively adsorb oil phases and repel water phases.

[0003] The preparation of aerogels typically involves two key steps: the synthesis of wet gels and the drying of wet gels. The drying process is the most critical step in determining the final pore structure, physical properties, and scalability. Currently, industry and academia mainly employ the following three drying technologies: Supercritical drying: This technology completely eliminates the gas-liquid interface by removing the solvent from the gel in a supercritical state, thus avoiding capillary force damage and producing aerogels with intact structures and excellent properties. However, this process requires high temperature and pressure, the equipment is expensive, the operation is dangerous, energy consumption is huge, and continuous production is difficult, which seriously restricts its large-scale application.

[0004] Freeze-drying: This technology first freezes the solvent in the gel into a solid, then removes it by sublimation under vacuum, thus avoiding the influence of liquid capillary forces. Although its energy consumption and equipment cost are lower than supercritical drying, the long freezing and sublimation cycle leads to low production efficiency, and energy consumption is still considerable. In addition, ice crystal growth may cause mechanical damage to the gel network.

[0005] Atmospheric pressure drying: This technology directly evaporates the solvent at atmospheric pressure and relatively low temperature, offering significant advantages such as simple equipment, safe operation, extremely low energy consumption, and ease of continuous production, making it the most promising route for large-scale application. However, during solvent evaporation, the enormous capillary forces generated at the gas-liquid interface can cause severe shrinkage or even collapse of the gel network, with shrinkage rates typically exceeding 60%, making it difficult to obtain products with high porosity and structural integrity.

[0006] To overcome the shrinkage problem during atmospheric pressure drying, existing research mainly focuses on improving the material through a single or a few strategies, such as strengthening the gel network (e.g., adding crosslinking agents or reinforcing fibers) or reducing capillary forces (e.g., solvent displacement or surface hydrophobic modification). Although these methods can reduce the shrinkage rate to some extent, they often fail to simultaneously achieve the following key properties: (1) controlling the shrinkage rate at a low level; (2) accurately preserving fine structures such as "oriented pores" under atmospheric pressure; (3) stably endowing the material with special wetting functions such as "superhydrophobic-superoleophilic"; and (4) ensuring that the material has sufficient mechanical strength to meet the deformation and recycling requirements in practical applications.

[0007] Therefore, developing an integrated technology that can synergistically solve problems such as insufficient network strength, capillary force damage, and functional vulnerability under mild ambient pressure drying conditions, and prepare aerogels with high porosity, low shrinkage, directional pore structure, stable superwetting properties, and good mechanical properties in one step, has become a key technological bottleneck that urgently needs to be overcome to promote the practical application of such functional materials. Summary of the Invention

[0008] To address the series of technical challenges faced by existing atmospheric pressure drying methods for preparing aerogels, such as high shrinkage, difficulty in maintaining fine structures, easy damage to functional properties, and insufficient mechanical properties, as described in the background art, this invention aims to provide a new solution. Through synergistic material design and process, a multifunctional aerogel with high porosity, low shrinkage, regular oriented pore structure, stable superhydrophobic-superoleophilic properties, and excellent mechanical strength and elastic recovery ability can be prepared under mild atmospheric pressure drying conditions. Furthermore, the preparation process of this aerogel has the advantages of low cost, low energy consumption, and easy scalability.

[0009] The present invention provides a method for preparing aerogels that are superhydrophobic and superoleophilic and have a directional porous structure, comprising the following steps: S1. Provides a precursor suspension comprising organic reinforcing fibers, a polymer matrix, inorganic reinforcing materials, and a hydrophobic agent; S2. The precursor suspension is directionally frozen to form a wet gel with an oriented pore structure; S3. Replace the solvent in the wet gel with a low surface tension solvent to obtain an alcohol gel; S4. Dry the alcohol gel under normal pressure to obtain the aerogel.

[0010] In step S1, the organic reinforcing fiber may be aramid fiber, the polymer matrix comprises cellulose derivatives and rubber latex, the inorganic reinforcing material comprises layered silicate, and the hydrophobic agent comprises crosslinkable organosilicon compound; Preferably, the cellulose derivative is carboxymethyl cellulose, the rubber latex is carboxylated nitrile rubber latex, the layered silicate is modified montmorillonite, and the crosslinkable organosilicon compound is an organosilicon waterproofing agent.

[0011] In step S1, the precursor suspension further comprises a water-soluble resin for enhancing the rigidity of the skeleton, wherein the water-soluble resin is melamine-formaldehyde resin; and / or, The precursor suspension also contains hydrophobic nanoparticles for constructing surface micro-nano rough structures. The hydrophobic nanoparticles are hydrophobic silica nanoparticles.

[0012] The synergistic effects of the components in the precursor suspension are as follows: The polymer matrix and organic reinforcing fibers (such as carboxymethyl cellulose CMC and aramid fibers T-AFs) form a three-dimensional flexible skeleton matrix through hydrogen bonds and physical entanglement, providing initial network support; Inorganic reinforcing materials (such as modified montmorillonite MMT) intercalate into the skeleton with their layered structure, providing rigid reinforcement points and significantly improving the network modulus; Water-soluble resins (such as melamine-formaldehyde resin MF) form a rigid compensation network after curing, further strengthening the skeleton; Hydrophobic agents and hydrophobic nanoparticles (such as organosilicon waterproofing agent SWPA and hydrophobic silica SiO2) work together. The former enhances the interface and introduces low surface energy through cross-linking polymerization, while the latter constructs a surface micro-nano rough structure, which synergistically endows superhydrophobic properties and reduces capillary forces. The introduction of rubber latex (such as carboxylated nitrile rubber XNBR) increases the viscoelasticity and toughness of the network.

[0013] In step S1, the proportions of each component of the precursor suspension by weight of the total system are as follows: Carboxymethyl cellulose: 0.5%-2.0%; melamine-formaldehyde resin: 0.5%-3.0%; modified montmorillonite: 0.5%-2.0%; aramid fiber: 0.3%-1.0%; carboxylated acrylonitrile rubber: 15%-25%; hydrophobic silica: 2%-6%; organosilicon waterproofing agent: balance, its volume ratio with water is 1:4-1:8; The preferred formulation is as follows: carboxymethyl cellulose: 1%; melamine-formaldehyde resin: 1%; modified montmorillonite: 1%; aramid fiber: 0.5%; carboxylated nitrile rubber: 20%; hydrophobic silica: 4%; organosilicon waterproofing agent: balance, with a volume ratio of 1:6 to water.

[0014] In step S2, the directional freezing process is as follows: the precursor suspension is injected into a mold for bottom-up directional freezing. During this process, ice crystals grow directionally along the temperature gradient, displacing solid components, thereby replicating and forming a template structure with vertically oriented through-holes.

[0015] In step S3, a gradient solvent replacement method is used, with a total replacement time of 24-48 hours; The preferred method is step-by-step replacement, with a total replacement time of 36 hours; The displacement process is as follows: the frozen gel is immersed in a low surface tension solvent (such as anhydrous ethanol), and water or other high surface tension solvents in the gel pores are fully displaced through one or more gradient displacements. This step aims to minimize capillary forces during the subsequent drying process.

[0016] In step S4, the temperature for atmospheric pressure drying is 30℃-120℃; After drying, heat treatment is performed to achieve full cross-linking and curing of the hydrophobic agent, ultimately obtaining the target aerogel.

[0017] The aerogel prepared by the method of the present invention has the following characteristics; Structural characteristics: The aerogel has a vertically arranged through-pore structure with a porosity greater than 85% and a volume shrinkage rate of less than 20%. Surface properties: It exhibits stable superhydrophobic-superoleophilic properties. The aerogel has a contact angle of more than 150° with water, a roll-off angle of less than 10°, and a contact angle of 0° with oil, which can realize spontaneous and rapid penetration of the oil phase. Mechanical properties: It has both good strength and elasticity. The compression recovery rate of the aerogel is greater than 85%, and it can withstand at least 1000 cycles of compression with 30% strain.

[0018] Functionalized aerogels are obtained by incorporating functional fillers into the framework or surface of the aerogel. These aerogels can heat up rapidly under light irradiation, thereby significantly improving the adsorption rate of high-viscosity oils. The functional filler is a photothermal conversion material selected from at least one of carbon black, iron oxide nanoparticles, carbon nanotubes, and graphene.

[0019] Based on the aerogel, the present invention also provides an oil-water separation component comprising the aerogel as a separation medium.

[0020] The aerogel of this invention can be used to adsorb and recover floating oil on the water surface or to filter and separate oil from water.

[0021] Regarding the application of the aerogel of this invention in the adsorption and recovery of floating oil on the water surface: The aerogel of this invention possesses superhydrophobic (water contact angle > 150°) and superoleophilic (oil contact angle ≈ 0°) properties. When in contact with an oil-water mixture, its surface repels the aqueous phase while simultaneously adsorbing the oil phase spontaneously and rapidly through capillary forces in its vertical channels. Because the porosity of the aerogel of this invention is > 85%, it provides a large storage space for the oil phase. Furthermore, the directional pore structure remains stable during adsorption and will not clog the pores due to swelling or contraction. Based on these characteristics, the following advantages can be achieved: low-viscosity oils (such as diesel and gasoline) can reach adsorption saturation within seconds; physical adsorption, without introducing chemical reagents, avoiding secondary pollution; after adsorption, the oil can be recovered through methods such as extrusion and distillation; the aerogel can be reused after simple treatment (such as ethanol cleaning and drying).

[0022] Regarding the application of the aerogel of this invention in the filtration and separation of oil and water: The through-channels inside the aerogel of this invention can serve as filtration channels. When the oil-water mixture enters the separation device, the aqueous phase comes into contact with the material surface. Due to the low adhesion and superhydrophobicity of the filter layer, the interaction force between water molecules and the filter layer surface is extremely weak, preventing water molecules from adhering to or penetrating its surface. Conversely, oily substances, due to their strong affinity for the filter layer surface, can easily pass through the microporous structure of the filter layer and smoothly enter the lower collection area of ​​the separation device. Based on the above characteristics, the following advantages can be achieved: Under gravity drive, the throughput of heavy oil (such as tetrachloromethane) can reach 15000 L·m -2 ·h -1 The above features allow for operation under gravity or low pressure, resulting in energy savings and reduced consumption. The superhydrophobic surface reduces the adhesion of organic matter or particles in the aqueous phase, thus delaying filter media contamination.

[0023] Compared with the prior art, the present invention has the following significant advantages: Successfully overcame the bottleneck of atmospheric pressure drying: Through a unique combination of "multi-component synergistic reinforcement framework" and "gradient solvent replacement" processes, the core problem of structural collapse caused by capillary forces during atmospheric pressure drying was solved. The drying shrinkage rate was significantly reduced from 60-80% in traditional methods to below 15%, while perfectly preserving the precise directional pore structure.

[0024] Achieving an excellent balance of performance: The prepared aerogel simultaneously achieves high porosity (>88%), low density (<0.15 g / cm³), stable superhydrophobic-superoleophilic properties (water contact angle >154°), and significant mechanical strength and elasticity. This integration of multiple excellent properties is difficult to achieve with existing single strategies.

[0025] The drying process is greatly simplified and reduced in cost: it completely abandons the expensive and dangerous supercritical drying and the energy-intensive and time-consuming freeze drying process, and adopts atmospheric pressure drying with simple equipment and extremely low energy consumption (the drying energy consumption is estimated to be about 94% lower than freeze drying), paving the way for the large-scale and continuous industrial production of aerogel materials.

[0026] This aerogel imparts superior application performance to the material: thanks to its oriented pores and superwetting properties, it exhibits high flux in oil-water separation (e.g., a flux of up to 15391 L·m⁻¹ for tetrachloromethane). -2 ·h -1 It exhibits high selectivity. Its excellent mechanical elasticity ensures structural stability during extrusion recycling and reuse, and its performance retention rate remains above 88% after 50 adsorption-desorption cycles.

[0027] It has good functional scalability: The preparation system has good compatibility with functional fillers and can easily introduce functional components such as photothermal without significantly affecting the performance of the main structure, thereby deriving intelligent responsive aerogels and expanding their application capabilities in complex environments (such as low temperature and high viscosity oil).

[0028] In summary, this invention provides a novel aerogel preparation route that combines high performance, low cost, and easy scalability, making it particularly suitable for developing high-performance oil-water separation materials. It has significant scientific value and broad industrial application prospects. Attached Figure Description

[0029] Figure 1 This is a comparison of the performance of aerogels with different raw material contents. Figure a represents CMC, Figure b represents MF, and Figure c represents MMT.

[0030] Figure 2 These are images of alcohol gels with different displacement times and aerogels dried at normal pressure.

[0031] Figure 3 These are SEM images of aerogels at different replacement times.

[0032] Figure 4 These are the porosity, shrinkage, and density of aerogels at different replacement times.

[0033] Figure 5 These are images of alcohol gels dried at different temperatures and aerogels dried at normal pressure.

[0034] Figure 6 These are SEM images of aerogels dried at different temperatures.

[0035] Figure 7 These are the porosity, shrinkage, and density of aerogels dried at different temperatures.

[0036] Figure 8 These are SEM and mapping images from APDS-Aerogel. Image a shows the cross-section, and image b shows the longitudinal section.

[0037] Figure 9 These are SEM images of APDS-Aerogel and its raw materials. Image a shows the cross-section of APDS-Aerogel, image b shows CMC, image c shows T-AFs, image d shows MMT, image e shows the edges of APDS-Aerogel exposing MMT and SiO2, image f shows SWPA without CO2, image g shows SWPA with CO2, image h shows MF, and image i shows MF coating the surface of T-AFs and edges.

[0038] Figure 10 The rheological behavior of suspensions prepared from different raw materials is shown in Figures a and b: storage modulus (G′, hollow icon), loss modulus (G′′, solid icon), viscosity (Figures c and d), and photograph (Figure e).

[0039] Figure 11 These are the FT-IR spectra (Figure a), XPS spectra (Figure b), and high-resolution XPS spectra (Figure c) of APDS-Aerogel.

[0040] Figure 12 Figure 1 shows the wettability of water and oil droplets on the APDS-Aerogel surface (Figure 2), the water contact angle and roll-off angle of the APDS-Aerogel (Figure 3), and the dynamic contact angle of water droplets on the cross-section of the APDS-Aerogel (Figure 4).

[0041] Figure 13 The figures show the water droplets bouncing off the cross-section of APDS-Aerogel (Figure a), the low adhesion behavior of water droplets on APDS-Aerogel: no adhesion upon contact (Figure b), rolling off at a small angle (Figure c), and the rapid absorption of water droplets by the hydrophilic material (Figure d).

[0042] Figure 14 These are SEM images magnified from the APDS-Aerogel edges (Figure a) and SEM images of SiO2 exposed on the edges (Figure b).

[0043] Figure 15 Figure 1 shows the stress-strain curves of APDS-Aerogel under different strains (Figure 1a), the cyclic stress-strain curves under 30% constant strain (Figure 1b), the fatigue test curves (Figure 1c), the tensile curves (Figure 1d), and the stress-strain curves at different cross sections (Figure 1e).

[0044] Figure 16The images show the compression and recovery of APDS-Aerogel after 50 cycles in dodecane (Figure a), and the fact that APDS-Aerogel still retains mechanical elasticity after extreme compression (Figure b).

[0045] Figure 17 It is the cyclic adsorption and recovery of oil by APDS-Aerogel.

[0046] Figure 18 The images show photos of APDS-Aerogel completely removing the oil film floating on the water surface (Figure a) and the separation process of the heavy oil (tetrachloromethane)-water mixture (Figure b).

[0047] Figure 19 This describes the absorption behavior of APDS-Aerogel on different oil phases.

[0048] Figure 20 These are images of alcohol gels and aerogels dried at normal pressure using different functionalized fillers.

[0049] Figure 21 These are the porosity, shrinkage, and density of aerogels with different functionalized fillers.

[0050] Figure 22 The temperature change of aerogels with different functionalized fillers over time (1 kW·m) -2 (Figure a) and the corresponding infrared thermal image of the upper surface (Figure b).

[0051] Figure 23 It describes the absorption behavior of aerogels with different functionalized fillers on viscous engine oil under light irradiation. Detailed Implementation

[0052] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0053] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0054] To address the industrial bottlenecks of existing aerogel materials, which rely on high-energy-consuming drying technologies and struggle to simultaneously maintain the integrity of high-pore structures, specific wetting functions, and excellent mechanical properties, this invention provides the following technical solution: Through a multi-component synergistically enhanced gel framework design (utilizing carboxymethyl cellulose and aramid fibers to construct a flexible network, montmorillonite and melamine resin to provide rigid reinforcement, and organosilicon and hydrophobic silica to achieve surface functionalization), and combined with directional freezing and gradient solvent replacement processes, the large-scale preparation of superhydrophobic-superoleophilic aerogels with vertically oriented pore structures has been successfully achieved under mild ambient pressure drying conditions.

[0055] The preparation method of this invention eliminates the need for expensive and complex supercritical drying or time-consuming freeze-drying, significantly reducing energy consumption and greatly overcoming the cost and technical barriers to large-scale production of aerogels. The resulting aerogel product simultaneously achieves several properties: high porosity (>85%), low drying shrinkage (<15%), stable superhydrophobic-superoleophilic properties (water contact angle >154°), and good mechanical strength and elastic recovery. Based on these properties, the aerogel of this invention exhibits great application value in the field of oil-water separation, and can be used for efficient adsorption and recovery of floating oil on the water surface and filtration and separation of oil-water mixtures, with the material possessing good stability for recycling.

[0056] Furthermore, the system of this invention has good functional scalability, and can be easily combined with functional fillers such as photothermal fillers to generate intelligent responsive products, further expanding its application potential in complex environments.

[0057] In summary, this invention provides a new pathway for the preparation of aerogel materials that combines high performance, low cost, and easy scalability, which is of great significance for promoting the practical application of functionalized aerogels in environmental protection, energy and chemical industries.

[0058] The reagents and materials used in the following examples are as follows: Carboxymethyl cellulose (CMC), Hebei Qingjun Cellulose Factory; Sudan III, reagent grade, Shanghai Maclean Biochemical Technology Co., Ltd.; Methylene blue, indicator grade, Shanghai Maclean Biochemical Technology Co., Ltd.; Anhydrous ethanol (CH3CH2OH), 99%, Shanghai Maclean Biochemical Technology Co., Ltd.; Dodecane (C 12 H 26 ), 98%, Shanghai Maclean Biochemical Technology Co., Ltd.; Liquid paraffin, >99%, Shanghai Maclean Biochemical Technology Co., Ltd.; Engine oil, 145.5 mPa·s, 30 ℃, China Petroleum & Chemical Corporation; Carboxylated acrylonitrile butadiene rubber (XNBR), 45 wt%, Jinan Meiwang Chemical Co., Ltd.; Silica nanoparticles (SiO2), >99.8%, 2.2 g / cm³ 3 Wacker Chemie GmbH, Germany; Carbon black (CB), Guangzhou Meidan Titanium Dioxide Pigment Co., Ltd.; Magnetic nanosheets (Fe3O4), 30~200 nm, laboratory-made; Low viscosity crude oil (Crude Oil I), 31.6 mPa·s, 30 ℃, an oilfield in China; Modified montmorillonite (MMT), LD-5A, Shijiazhuang Runchuan Mineral Powder Processing Plant; Melamine-formaldehyde resin (MF), type 650, Zhongcheng Plastics Co., Ltd.; Aramid fiber (AFs), 3 mm, Teijin Corporation, Japan; Organosilicon waterproofing agent (SWPA), 30%, Shanxi Jinjingchen Building Materials Co., Ltd.

[0059] The instruments and equipment used in the following embodiments are as follows: Contact angle measuring instrument, Tracker, TECLIS, France; Scanning electron microscope (SEM), SU8010, Hitachi, Japan; Fourier transform infrared spectrometer (FT-IR), TENSOR II, Bruker, Germany; X-ray energy dispersive spectrometer (EDS), XFLASH 6130, Bruker, Germany; Texture analyzer, TA.XT PLUS, Stable Micro Systems, UK; Surface tensiometer, DCAT21, DataPhysics, Germany; Rotational rheometer, RS6000, HAAKE, Germany; X-ray photoelectron spectroscopy (XPS), Al-K-Alpha, Thermo Fisher Scientific, USA. Fisher Scientific; Sunlight Simulator, BBZM-Ⅲ, Bobai Optics Co., Ltd. (China); Infrared Imager, K20, Hikvision Co., Ltd. (China); Sunlight Detector, TES-1333R, Taishi Electronics Co., Ltd. (Taiwan, China); Cantilever Stirrer, EUROSTAR40, IKA GmbH (Germany); Electric Heating Drying Oven, DHG-9070A, Shanghai Yiheng Scientific Instruments Co., Ltd.

[0060] The sample characterization and evaluation methods in the following examples are as follows: (1) Surface wettability Contact angle measurement: The wettability of the aerogel surface was measured using a contact angle measuring instrument (Tracker, TECLIS). 5–6 μL droplets were precisely dropped onto the aerogel surface, and the angle formed by the droplet contact with the sample surface was determined using the droplet profile analysis system equipped with the instrument. To ensure the accuracy and reliability of the measurement data, five different locations were randomly selected on the sample surface for each measurement. The mean and standard deviation were calculated to evaluate the repeatability and accuracy of the measurement results. Simultaneously, image analysis software was used to extract the contact angle data between the droplet and the sample surface at different times, and the change of the contact angle over 1 minute was investigated.

[0061] Roll-off angle measurement: The aerogel sample to be tested is fixed flat on a horizontal adjustment platform, ensuring the platform is level and without tilt. A 5-6 μL droplet is placed on the surface of the aerogel sample. One end of the platform is slowly and uniformly raised, gradually tilting the sample surface. The movement of the droplet is recorded in real time using a camera. When the droplet begins to roll noticeably on the sample surface, the tilt angle of the platform at this point is recorded; this is the sample roll-off angle. Each sample is measured five times. The roll-off angles obtained from multiple measurements are statistically analyzed, and the average value is calculated.

[0062] The low adhesion properties of APDS-Aerogel: ① Use a microsyringe to squeeze out 5~6 μL of water droplets, allowing the droplets to gently contact the APDS-Aerogel surface. Then, slowly pull up the microsyringe at a constant speed, and record the separation of the water droplet from the aerogel surface using a high-definition camera; ② Place the APDS-Aerogel sample on an adjustable-angle experimental platform, and slowly release a water droplet onto the aerogel surface using a microsyringe, recording the rolling process of the water droplet using a high-definition camera; ③ Place a water droplet on the APDS-Aerogel surface, and then slowly bring a hydrophilic material close to the water droplet, observing the process of the water droplet being absorbed by the hydrophilic material using a high-definition camera.

[0063] (2) Microscopic morphology Scanning Electron Microscopy (SEM): The microstructure of the samples was characterized using a scanning electron microscope (SU8010, HITACHI). The samples were fixed to the stage using conductive adhesive, and the stage was sputter-coated with gold. For aerogel samples, gold sputtering was performed on both the top and side surfaces to ensure good conductivity throughout the sample. The prepared samples were then placed onto the stage inside the microscope tube, and the microstructure was observed. The microstructure was recorded using an image acquisition system.

[0064] (3) Porosity, density, and shrinkage Porosity testing (liquid saturation method): The porosity of APDS-Aerogel was calculated using the ethanol saturation method. The completely dried aerogel sample was vacuum-treated and then weighed on an electronic balance; the mass was recorded. m dry The sample was then immersed in anhydrous ethanol and placed in a vacuum apparatus to evacuate for 1 hour, ensuring that all air was expelled from the pores and that the ethanol fully wetted the pores. The sample was then removed, and any residual ethanol on the surface was quickly absorbed with filter paper. The total mass of the sample after saturation with ethanol was immediately weighed. m wet For regularly shaped samples, the length, width, and height are measured using vernier calipers. Measurements are taken at three different locations on each side, and the average value is calculated to determine the total volume. For irregularly shaped samples, the volume is calculated using the displacement method, with three measurements taken to minimize error. Porosity ( P The result is determined by formula (1): (1) in m dry (g) represents the dry weight of the aerogel. m wet (g) represents the wet weight of the aerogel. ρ (g·cm) -3 () represents the density of anhydrous ethanol.V dry (cm) 3 () indicates the volume of the dry aerogel.

[0065] Density: The apparent density of aerogels is calculated directly by the ratio of mass to volume. A completely dried aerogel sample is weighed on an electronic balance, and the mass is recorded. m dry The sample volume was determined using the same geometric or displacement method as the porosity test. Density ( ρ The result is determined by formula (2): (2) in m dry (g) represents the dry weight of the aerogel. V dry (cm) 3 () indicates the volume of the dry aerogel.

[0066] Shrinkage: The degree of shrinkage during atmospheric pressure drying was assessed by the change in aerogel volume before and after drying. The volume of the wet gel before and after drying, as well as the volume of the dry gel, was calculated using the method described in the porosity test above. For irregularly shaped wet gel samples, the ethanol displacement method was used to calculate the sample volume, and the measurement was repeated three times to minimize error. Shrinkage ( S The result is determined by formula (3): (3) in V dry (cm) 3 () indicates the volume of the dry aerogel. V wet (cm) 3 () indicates the volume of the wet gel.

[0067] (5) Chemical composition X-ray energy dispersive spectroscopy (EDS): Following the fixation method used in SEM measurements, conductive adhesive is used to fix the aerogel sample onto the sample stage. An X-ray energy dispersive spectrometer (JSM7500, JEOL) bombards the aerogel sample with electrons, acquiring the X-ray energy spectrum of that region to obtain information on the types and relative abundance of elements contained in the sample. After completing the EDS measurement, the area to be analyzed for elemental distribution is selected. Scanning begins, and the detector collects X-ray signals from different locations, generating an elemental distribution mapping map that visually displays the distribution of each element in the sample.

[0068] Fourier Transform Infrared Spectroscopy (FT-IR): An appropriate amount of sample was weighed, ground into a uniform fine powder, and then mixed with potassium bromide powder. The mixture was pressed into a transparent sheet using a tablet press, and the analysis was performed using a Fourier Transform Infrared Spectrometer (TENSOR II, Bruker). The resolution was set to 4 cm⁻¹. -1 The scanning range was selected as 400~4000 cm. -1 After removing background interference, the sample is scanned to obtain an infrared spectrum.

[0069] X-ray photoelectron spectroscopy (XPS): This method uses an X-ray photoelectron spectrometer (Al-K-Alpha, ThermoFisher) to characterize the chemical bonding state and elemental composition of aerogel samples. The fixed sample is placed in the analysis chamber, and X-rays are irradiated perpendicularly onto the target area of ​​the sample surface. A full-spectrum scan is first performed to obtain general information about all elements present in the aerogel. For specific elements, a high-resolution scan is then performed to accurately determine their binding energy, chemical state, and other information.

[0070] (6) Mechanical properties The mechanical properties of APDS-Aerogel were tested in compression mode using a texture analyzer (TA.XT PLUS, Stable Micro Systems). A 20×20×20 mm cube was used for compression at a rate of 0.5 mm·s. -1 Velocity measurement. The stress-strain curves of PT-Aerogel under different strains (10%~70%) and 30% strain were tested after 1000 cycles.

[0071] (7) Absorption properties of aerogel samples Determination of the relationship between absorbed mass and time: The liquid absorption behavior of APDS-Aerogel was precisely measured using a surface tensiometer (DCAT21, DataPhysics) with a balance detector (accuracy 0.00001 g). First, a cylindrical APDS-Aerogel sample (Ф20×15 mm) was fixed by a coil and suspended below the sensor of a high-sensitivity microbalance. The test liquid was placed on an electrically driven displacement platform, and the platform movement was automated through an intelligent control system. At the start of the experiment, the system performed sensor zero-point calibration, and then the platform moved at a speed of 0.1 mm. s -1A constant-rate rise was observed. The platform displacement ceased immediately upon contact between the lower surface of the APDS-Aerogel and the liquid surface, and the mass monitoring module recorded the adsorption dynamics at a sampling frequency of 50 Hz. The experiment continued until the absorbed mass remained constant, at which point adsorption equilibrium was determined. The entire process was completed at room temperature. The absorption volume of the APDS-Aerogel was obtained by the ratio of the absorbed mass to the density of the absorbed liquid, while the absorption height was determined by the ratio of the absorption volume to the sample bottom area.

[0072] Determination of absorption rate: The average absorption rate of APDS-Aerogel is calculated by the volumetric absorption efficiency of the aerogel during the process from initial wetting to adsorption equilibrium, i.e., the ratio of saturated absorption volume to absorption time. The instantaneous absorption rate is obtained by differentiating the absorption volume versus time curve.

[0073] (8) Photothermal conversion performance Photothermal Performance: Before testing the photothermal performance of aerogels, the experimental equipment must be fully debugged and calibrated. First, the aerogel sample (20×20×20 mm) is placed on an insulating substrate, and the light intensity stability of the simulated solar source (BBZM-Ⅲ) is calibrated using a solar radiation detector (TES-1333R). The solar radiation simulator is then turned on to vertically irradiate the sample surface, with the irradiance set to 1.0 kW·m². -2 Simultaneously, an infrared imager (K20) was used to record the surface temperature distribution of the samples in real time, and the illumination time-temperature curve was correlated using software. Ambient thermal radiation was shielded during the test using a blackbody cavity for isolation. The effects of different illumination intensities and cycle numbers on the photothermal conversion performance of the aerogel were further investigated by varying the illumination intensity and the number of cycles.

[0074] (9) Viscosity measurement Isothermal viscosity of crude oil: The viscosity of crude oil was determined using a rotational rheometer (RS6000, HAAKE). 11.5–12.0 mL of crude oil was added to the sample cup of the rheometer, ensuring the rotor was fully submerged. A constant shear rate of 7.34 s⁻¹ was set at 30 °C. -1 The measurement time is 300 seconds. The program is started, and the instrument automatically collects data on viscosity changes over time. The viscosity after the curve stabilizes is the viscosity of the crude oil at room temperature.

[0075] Viscoelasticity Measurement of Suspensions: The viscoelasticity of suspensions prepared from different raw materials was measured using a rotational rheometer (RS6000, HAAKE). 11.5–12.0 mL of suspension was added to the sample cup of the rheometer, ensuring the rotor was submerged. At room temperature, the linear viscoelastic region was first determined by strain scanning, and then the dynamic rheological properties of the liquid were tested within the frequency range of 0.1–100 Hz to obtain the storage modulus (G') and loss modulus (G'') data. A Z41Ti module was used for solution samples, and a PP20Ti module was used for gel samples.

[0076] Example 1: Preparation of APDS-Aerogel (1) Preparation of precursor suspension: 1.0 g carboxymethyl cellulose (CMC) was dispersed in 100.0 g silicone waterproofing agent (SWPA) solution (SWPA to water volume ratio of 1:6) and stirred until completely dissolved. The mixture was transferred to a 70°C water bath and kept at a constant temperature. Under high-speed stirring (500 rpm), 1.0 g water-soluble melamine-formaldehyde resin (MF) and 0.5 g aramid fiber (T-AFs) were added in sequence and stirred for 10 min to ensure uniform dispersion.

[0077] (2) Formation of viscoelastic matrix: After the above system is naturally cooled to room temperature (about 25°C), 20.0 g of carboxylated acrylonitrile butadiene rubber (XNBR) emulsion is added and stirred for 20 min to form a uniform viscoelastic matrix.

[0078] (3) Introduction of reinforcing and functional phases: Under continuous stirring, 1.0 g of modified montmorillonite (MMT) and 4.0 g of hydrophobic silica (SiO2) nanoparticles were added to the matrix in steps. After the addition was completed, the high-speed stirring was continued for 3 h to obtain a uniform and stable suspension.

[0079] (4) Gelation and aging: Dry carbon dioxide gas was introduced into the suspension for 5 min to induce gelation of the system. The gel was then placed in a constant temperature environment of 30℃ and allowed to stand for aging for 12 h.

[0080] (5) Directional freezing: The aged gel is injected into a specific mold and placed in a programmed freezing device. Directional freezing is performed from bottom to top along the mold axis at a freezing rate of 5℃ / min until the sample center temperature reaches -18℃ and is maintained for 1 h.

[0081] (6) Solvent replacement: The completely frozen sample was immersed in sufficient anhydrous ethanol and solvent replacement was performed at room temperature. A stepwise gradient replacement strategy was adopted: first, replacement was performed for 12 h, then fresh ethanol was replaced and replacement was continued for 24 h, for a total replacement time of 36 h. After the replacement was completed, an alcohol gel was obtained.

[0082] (7) Drying and curing at atmospheric pressure: The alcohol gel was removed from the ethanol and placed in a forced-air drying oven at 60°C for 2 h at atmospheric pressure. The dried sample was then transferred to an oven at 135°C and heat-treated for 1 h to allow SWPA and MF to fully crosslink and cure. Finally, a superhydrophobic-superoleophilic aerogel with a vertical pore structure was obtained, denoted as APDS-Aerogel.

[0083] Example 2: Study on the effect of raw material ratio on aerogel properties To determine the optimal formulation, the amounts of SWPA solution (100.0 g, SWPA:water = 1:6), T-AFs (0.5 g), SiO2 (4.0 g), and XNBR (20.0 g) were fixed, while the amounts of CMC, MF, and MMT were systematically varied. The specific experimental groups and ratios were carried out according to Table 1. The preparation steps for each group of experiments were the same as in Example 1.

[0084] Table 1 Experimental conditions for different CMC, MF and MMT contents

[0085] This invention investigated the effects of different conditions on the porosity, volume shrinkage, apparent density, wettability, and mechanical properties of aerogels, and determined the optimal raw material formulation for overall performance. A comparison of key parameters such as porosity, shrinkage, density, contact angle, and mechanical properties of aerogels prepared with different raw material ratios is summarized in [the following text is missing from the original] Figure 1 This study visually demonstrates the impact of different component contents on the overall performance of the material. The results show that, in a 1:6 solvent ratio of SWPA / water, the optimal formulation is characterized by 1 wt% CMC, 0.5 wt% T-AFs, 1 wt% MF, 20 wt% XNBR, 1 wt% MMT, and 4 wt% SiO2. The prepared aerogel exhibits a porosity of 88.7%, a shrinkage rate of 14.9%, and a density of 0.141 g·cm³. -3 It has a contact angle of 154.1° and a mechanical strength of 0.16 MPa.

[0086] Meanwhile, by optimizing the parameters of solvent replacement time and drying temperature, an effective atmospheric pressure drying process system was established.

[0087] Example 3: Solvent displacement process optimization Based on the optimal formulation (CMC 1 wt%, MF 1 wt%, MMT 1 wt%), with other steps fixed, the effect of solvent replacement time on aerogel structure was systematically studied.

[0088] Set the following replacement scheme: Group A: 12 h displacement (single); Group B: 24 h displacement (single); Group C: 12 h displacement + 12 h displacement (stepwise, total 24 h); Group D: 12 h displacement + 24 h displacement (stepwise, total 36 h, i.e., Example 1 scheme).

[0089] This embodiment employs a gradient replacement strategy, first replacing the aqueous solvent with ethanol, and then performing a second replacement with ethanol, effectively eliminating the risk of damage to the pore walls caused by residual high-tension solvent. Figure 2 As shown, both the replacement time and the number of replacements affect the quality of the final product. While a single replacement can reduce the shrinkage rate, uneven local distribution of residual solvent can still lead to structural defects. Two gradient replacements (12+24 h) achieve optimal shrinkage suppression through sufficient solvent replacement while ensuring efficiency. It is worth noting that excessively extending the replacement time, while potentially ensuring structural integrity, will significantly reduce preparation efficiency. Furthermore, long-term solvent penetration may cause potential changes in the surface chemical properties of the material.

[0090] SEM results of aerogels with different replacement times are shown in the figure. Figure 3 By comparing SEM images of aerogels at different replacement times, the influence of solvent replacement process on the microstructure of the material was revealed. Figure 3 As shown, in samples that have not undergone sufficient replacement, the pore structure exhibits significant heterogeneity, with a morphological feature of large-sized pores coexisting with micron-sized collapsed pores in localized areas. This is attributed to the capillary stress concentration effect of residual high-surface-tension solvent, leading to irreversible collapse of some weak pore walls during the drying process. When the replacement time is extended to two gradient replacements (12+24 h), the microstructure is significantly optimized, the pore size distribution is relatively uniform, the pore wall surface is smooth, and the long-term replacement ensures the integrity of the pore structure.

[0091] The effect of different replacement times on the structure of aerogels dried at ambient pressure is shown in the figure. Figure 4 .like Figure 4As shown, the porosity of the material exhibits a gradient increase as the replacement time increases from 12 h to 36 h with gradient replacement. A single 12-h replacement yields a porosity of 62.2%, which increases to 78.2% when extended to 24 h. Using a stepwise replacement strategy (12+12 h), the pore structure is further optimized to 82.0%, while the 12+24 h composite replacement process further increases the porosity to 88.7%, demonstrating a stepwise enhancement effect. The shrinkage behavior of the aerogel structure is negatively correlated with the replacement time. The volume shrinkage rate of the sample after a single 12-h replacement reaches 33.1%, which decreases to 28.4% when the replacement time is doubled to 24 h. The stepwise replacement process shows a more significant structural stability effect; the shrinkage rates of the samples after 12+12 h and 12+24 h replacement decrease to 19.5% and 14.9%, respectively, indicating that stepwise replacement can effectively alleviate drying stress concentration. The material density evolution trend corroborates this, starting from an initial density of 0.179 g·cm³. -3 Gradually reduced to 0.141 g·cm³ -3 A significant gradient change is formed. Experiments show that extending the displacement time promotes sufficient diffusion of solvent molecules, and in particular, the stepwise displacement strategy, through gradient concentration design, significantly enhances the degree of solvent displacement. This process effectively alleviates the compressive effect of capillary stress on the pore structure by reducing the solvent surface tension in stages, which is beneficial for constructing a more complete three-dimensional network framework during the atmospheric pressure drying stage. Experimental data confirm that the 12+24 h stepwise displacement process can achieve the preparation of high-porosity, low-shrinkage, and low-density aerogels, providing an optimized path for the preparation of high-performance aerogels by atmospheric pressure drying.

[0092] Example 4: Optimization of drying temperature and verification of process tolerance Based on the optimal formulation and displacement process, the effect of ambient pressure drying temperature was studied. The drying temperatures were set at 30℃, 60℃, 90℃, and 120℃. Other steps were the same as in Example 1.

[0093] Figure 5 Images show alcohol gels dried at different temperatures and aerogels dried at normal pressure. Figure 5As shown, the prepared aerogels exhibit excellent skeletal stability within a wide temperature range of 30–120 °C, maintaining a high degree of consistency in their macroscopic structure. This overcomes the stringent temperature requirements of traditional atmospheric pressure drying processes. This is attributed to the synergistic strengthening effect of the components in the composite system, effectively enhancing the mechanical strength of the gel network and significantly reducing the material's sensitivity to drying temperature. This temperature insensitivity provides greater operability to the preparation process, allowing for flexible selection of drying parameters within a wider temperature range based on actual needs. Considering both drying efficiency and industrial production costs, 60 °C was selected as the optimal drying temperature. Under this condition, a moderate solvent evaporation rate is ensured while avoiding additional energy consumption caused by high temperatures, resulting in an energy consumption reduction of approximately 94% compared to freeze-drying. This study achieves multi-selectivity of drying process parameters through innovative material design, providing crucial technical support for the low-cost, large-scale preparation of aerogels.

[0094] like Figure 6 As shown, by comparing SEM images of aerogels at different drying temperatures, from Figure 6 The microstructure showed no significant differences within the temperature range of 30–120 °C, confirming the synergistic effect of the multi-component combination on its structural stability. All samples exhibited a highly coherent three-dimensional network structure with smooth pore wall surfaces. No obvious pore wall collapse or densification regions were observed in the samples prepared under high-temperature drying (120 °C), and their pore size distribution was not significantly different from the low-temperature group, all exhibiting interconnected macroporous hierarchical channel characteristics. Even under extreme temperature conditions with significant differences in solvent evaporation rates, the gel network formed stable spatial support through chemical cross-linking and physical entanglement between the multi-components, effectively suppressing structural distortion induced by capillary stress. This microstructural stability, insensitive to drying temperature, provides the possibility for flexible control of the drying process in industrial production.

[0095] Figure 7 The results show the porosity, shrinkage, and density of aerogels at different drying temperatures, such as... Figure 7 As shown, within a wide temperature range of 30–120 °C, the porosity (88.0%–88.7%), volume shrinkage (14.9%–15.1%), and apparent density (0.136–0.142 g·cm³) of the aerogel are as follows: -3All values ​​remained within a stable range. This reveals the strong adaptability of the composite system to drying temperature, indicating that drying temperature does not significantly affect the performance of the aerogel, avoiding the temperature sensitivity limitations of traditional atmospheric pressure drying processes. The multi-component synergistic reinforcement mechanism of the framework structure offsets the capillary stress differences caused by temperature fluctuations. Although moderate heating may accelerate solvent molecule diffusion, excessively high temperature gradients did not induce significant network structure reconstruction. Under this system, even under high-temperature drying conditions of 120 ℃, the material can still maintain a high porosity of approximately 88% and a low shrinkage rate of approximately 15%, demonstrating the dynamic adaptability of the composite network to the solvent evaporation rate during drying. While ensuring solvent replacement efficiency, the drying temperature can be flexibly selected within a wide range without significantly altering product performance, providing an important basis for energy consumption optimization and process simplification in industrial production.

[0096] Example 5: Study on the mechanism of aerogel structure stabilization during atmospheric pressure drying During atmospheric pressure drying, the evaporation of solvent within the wet gel induces significant capillary stress, stemming from the surface tension at the gas-liquid interface acting on the micron-sized pore structure. When the solvent surface tension is high, the pore radius is small, or the contact angle approaches 0°, the capillary pressure can reach the MPa level, far exceeding the mechanical strength threshold of the gel skeleton, leading to irreversible collapse of the three-dimensional network structure. To suppress this phenomenon, a multi-dimensional synergistic control strategy is needed to eliminate the destructive effect of capillary forces and maintain the integrity of the gel skeleton during solvent removal. For example, chemical cross-linking can strengthen the gel skeleton or introduce rigid materials to enhance the compressive strength of the network skeleton; improving the uniformity of pore size distribution can reduce the risk of local stress concentration; hydrophobic surface modification can increase the contact angle and weaken the intensity of capillary forces; a gradient solvent replacement strategy can gradually reduce the surface tension of the system; and in-situ polymerization technology can simultaneously improve the stability of the skeleton structure. The synergistic effect of these methods promises to achieve efficient solvent removal and preservation of the microstructure, providing a possibility for the preparation of aerogels through atmospheric pressure drying.

[0097] As shown in Example 2, changes in the proportions of the components in the system significantly alter the macroscopic and microscopic structures of the dried aerogel. During atmospheric pressure drying, the integrity of the aerogel structure is controlled by multiple factors, and a single variable cannot completely eliminate the risk of framework collapse caused by capillary forces. By employing a multi-component synergistic enhancement strategy, the stable existence of the three-dimensional network structure was successfully achieved during solvent removal. To verify the synergistic effect of the multi-components, SEM and mapping images of APDS-Aerogel were characterized, and the results are shown in [Figure 2]. Figure 8 .like Figure 8As shown, the vertical channel characteristics of APDS-Aerogel indicate that it has a distinct oriented channel structure. EDS elemental scanning further verifies the coexistence of multiple elements, including C, N, O, Si, Al, Mg, and K, in the framework. These elements, derived from different precursors, construct a composite network with a certain strength through the synergistic effect of chemical bonding and physical entanglement, thereby effectively dispersing local stress and resisting capillary force damage.

[0098] To further clarify the role of each component, the microstructure of the aerogel and each raw material was observed using SEM. The results are shown in [Figure number missing]. Figure 9 .like Figure 9 As shown in Figure a, APDS-Aerogel maintains the integrity and stability of its vertical pore structure during atmospheric pressure drying, primarily due to the synergistic strengthening mechanism of the multi-component system. Fully dried APDS-Aerogel exhibits a relatively regular pore structure without significant structural collapse, indicating the reliability of this method in maintaining the pore structure during atmospheric pressure drying. Specifically, CMC, as the main matrix material, forms a three-dimensional network structure through intramolecular hydrogen bonding and inter-polymer chain entanglement. Figure 9 (See Figure b). Its unique viscous properties effectively maintain the uniform dispersion of each component, providing a key guarantee for the stability of the aerogel precursor suspension and laying the foundation for subsequent structure assembly. Secondly, the introduction of T-AFs with high aspect ratio significantly improves the mechanical stability of the structure. For example... Figure 9 As shown in Figures c and g, T-AFs can form bridging support structures between pore walls through interfiber entanglement and steric hindrance. This cross-scale fiber reinforcement mechanism exists both within the skeleton and forms a three-dimensional interpenetrating network between adjacent pore walls, effectively improving the deformation resistance of the pore wall structure. MMT, through the intercalation effect of its sheet-like structure, is uniformly dispersed on the skeleton surface under the synergistic effect of CMC and XNBR. Its high modulus characteristics significantly improve the stiffness of the composite material. The sheet-like structure not only strengthens interfacial interactions but also significantly improves the overall mechanical properties of the skeleton through physical cross-linking effects. Figure 9 (See Figures d and e). Simultaneously, the thermosetting behavior of water-soluble MF provides a dual strengthening mechanism for the system. During the low-temperature stage, MF forms a rigid cured layer on the aerogel framework and T-AFs surface. This chemically cross-linked structure not only provides rigidity compensation at room temperature but also further enhances structural rigidity through increased cross-linking density during subsequent high-temperature curing. This staged curing strategy ensures structural integrity in the initial drying stage while also endowing the material with excellent resistance to deformation (…). Figure 9(See Figures f and g). Furthermore, SWPA undergoes hydrolysis in a carbon dioxide atmosphere to generate a methylsilicic acid intermediate. This intermediate undergoes a condensation reaction with hydroxyl groups in the aerogel backbone and simultaneously forms a polymethylsiloxane crosslinked network through intermolecular dehydration polymerization. This polymerization reaction not only reduces the surface energy of the material but, more importantly, enhances the connection strength of the backbone nodes through the siloxane crosslinked network (the crosslinking effect is confirmed by an inverted experiment), effectively suppressing capillary stress damage during the drying process. Figure 9 (h-plot and i-plot).

[0099] By systematically studying the rheological behavior of precursor suspensions with different raw material ratios, the influence of raw material components on the mechanical properties of the APDS-Aerogel framework structure was quantified, revealing the dynamic evolution mechanism of the multi-component synergistic network structure construction. The rheological behavior and viscosity results of suspensions prepared from different raw materials are shown in [reference needed]. Figure 10 ,like Figure 10 As shown, a stepwise addition method was used to systematically study the synergistic effect of each component. The results showed that the gradient introduction of the raw materials significantly altered the viscoelastic response of the system. Figure 10 As shown in Figures a, c, and e, when the system contains only MCC, SWPA, and MF, the loss modulus (G'') is greater than the storage modulus (G'), and the viscosity is below 400 mPa·s, indicating that viscosity dominates the system. After adding T-AFs, the increased entanglement of molecular chains leads to G'>G'', but the CMC (only 1 wt%) molecular chains only form a primary network through hydrogen bonding and entanglement; the intermolecular forces are insufficient to form a continuous network, resulting in no sol-gel transition. In this case, the viscosity increase is minimal (below 500 mPa·s). Figure 10 As shown in Figures b, d, and e, the introduction of 20 wt% XNBR under alkaline conditions promotes the dissociation of the carboxyl group into -COO. -The carboxyl groups form strong ion-dipole interactions with the MCC hydroxyl groups. Simultaneously, the dissociation of the carboxyl groups forms "ionic cross-linking points" with metal ions, increasing the intermolecular forces. This process causes the viscosity to jump to approximately 3200 mPa·s, with G'>G'', indicating that the system has transitioned from a liquid to a solid-like gel, forming a network structure with certain mechanical strength. Further addition of MMT enhances the strength of the network structure through the intercalation effect of the lamellar structure and interfacial interactions. Physical cross-linking and steric hindrance strengthen the entanglement between molecular chains, causing the system viscosity to further increase to approximately 10900 mPa·s. At the same time, G' and G'' show an order-of-magnitude increase, making the gel properties more pronounced. The hydrophobic SiO2 nanoparticles bring the system into a nanocomposite reinforcement stage. The physical filling effect between their hydrophobic surfaces and the matrix, along with weak chemical interactions, synergistically increases the solid content of the system, causing the viscosity to jump to approximately 15690 mPa·s. Upon further introduction of CO2, SWPA undergoes a hydrolytic polymerization reaction with CO2, generating a polymethylsiloxane crosslinked network. The viscosity further increases to 17510 mPa·s, and the chemical crosslinking further enhances the mechanical strength of the network structure. Furthermore, the freezing process promotes further aggregation and entanglement of polymer chains such as CMC, resulting in a significant increase in the sample's G', G'', and viscosity, revealing the strengthening mechanism of the network structure through low-temperature-induced physical crosslinking. The evolution of the above rheological behavior directly reflects the dynamic mechanism of multi-component synergistic network structure construction. This multi-mechanism synergistic enhancement provides the necessary mechanical support for APDS-Aerogel to resist capillary stress during atmospheric pressure drying, ensuring the complete formation of the vertical channel structure.

[0100] The chemical bond composition of APDS-Aerogel was analyzed by FT-IR spectroscopy and XPS energy dispersive spectroscopy. The results are shown in the figure. Figure 11 .like Figure 11 As shown in Figure a, at 3398 cm -1 The peak at 2931 cm⁻¹ corresponds to the stretching vibration of hydroxyl groups in the cellulose-MMT interlayer structure of CMC, indicating the formation of a complex network through hydrogen bonding. - ¹ and 2848 cm - The absorption peak at ¹ corresponds to the symmetric and asymmetric stretching vibrations of the CH3 groups in SWPA and hydrophobic SiO2 nanoparticles. The presence of methyl groups helps to improve the waterproof performance of the aerogel. 2237 cm⁻¹ -1 The sharp peak at 1560 cm⁻¹ represents the characteristic C≡N vibration of the acrylonitrile unit in XNBR. This shift in the group indicates that XNBR participates in network construction not only through physical entanglement but also through chemical crosslinking. -1 The peak value at 1450 cm is related to the bending vibration of CNH. -1 The peak value at 1350 cm⁻¹ is related to the bending vibration of the CH bond. -1The stretching vibrations at 1270 cm⁻¹ are attributed to the COC skeletal structure of the CMC and the CN vibrations of the MF triazine ring. -1 (Si-CH3 tensile vibration) and 780 cm -1 (Si-O-Si bending vibrations) collectively point to the siloxane condensation reaction of SWPA, while 1103 cm⁻¹ -1 The peak of the Si-O-Si asymmetric stretching vibration at 914 cm⁻¹ indicates interfacial coupling between the hydrophobic SiO₂ nanoparticles and the polymethylsiloxane network. -1 (Al-O deformation vibration) and 686 cm -1 (Al-O-Si tetrahedral vibrations) demonstrate that montmorillonite is embedded in the matrix, and its structural integrity provides rigid support for the aerogel. In summary, FT-IR spectroscopy results show that the characteristic functional groups of all raw materials can be detected in the aerogel's framework structure. These raw materials synergistically enhance the aerogel's framework structure through various interactions such as hydrogen bonding, intermolecular forces, and chemical bonds, effectively reducing the influence of capillary forces during atmospheric pressure drying.

[0101] XPS studies were conducted to investigate the chemical composition and state of the raw materials, further elucidating the synergistic enhancement mechanism. The results are shown in [Figure number missing]. Figure 11 Image b in the middle. (See image below.) Figure 11 As shown in Figure b, the XPS spectrum of APDS-Aerogel shows C 1s, N 1s, O 1s, Al 2p, and Si 2p peaks, indicating that the multi-component raw materials effectively participated in the framework construction of APDS-Aerogel, giving it good strength. Figure 11As shown in Figure c, the binding states of C 1s, O 1s, and Si 2p were further analyzed. The high-resolution XPS spectrum of C 1s showed five characteristic peaks at 283.1 eV, 284.8 eV, 286.2 eV, 288.1 eV, and 289.7 eV, corresponding to C-Si, CH / CC, CN / C≡N, CO, and C=O bonds from various raw materials, respectively. These different types of characteristic peaks reflect the diverse chemical environments of carbon elements in the raw materials, confirming the presence and interactions of multiple raw materials. The high-resolution XPS spectrum of O 1s showed peaks at 531.4 eV, 532.7 eV, 533.6 eV, and 536.1 eV, which are attributed to C=O, CO, O-Si, and OH bonds, respectively. After reacting with CO2, SWPA not only underwent self-polymerization but also chemically reacted with the hydroxyl groups on the CMC surface to form O-Si bonds. This chemical reaction enhanced the cross-linking structure of the aerogel, improving its stability and performance. The Si2p peak is attributed to Si-C, Si-OC, Si-O-Si, and SiO2, corresponding to binding energies of 101.4 eV, 102.8 eV, 103.7 eV, and 104.7 eV, respectively. Comparison revealed that the Si-O-Si peak area formed by APDS-Aerogel is larger than that of SHM-Aerogel, indicating that the polymerization reaction of SWPA occurs more completely in a CO2 environment. This multi-scale synergistic effect enables APDS-Aerogel to successfully resist capillary stress during atmospheric pressure drying, with a volume shrinkage rate controlled within 15%. This facilitates the successful preparation of superhydrophobic vertically porous aerogels under atmospheric pressure drying, providing a possibility for the large-scale production of this material.

[0102] Example 6: Superhydrophobicity of APDS-Aerogel The wettability results of APDS-Aerogel are shown below. Figure 12 . Figure 12 Figure a illustrates the differentiated wetting behavior of APDS-Aerogel towards water and oil. When water droplets are placed on the APDS-Aerogel surface, they all exhibit a standard spherical shape and remain firmly on the aerogel surface, without any penetration during prolonged observation. In contrast, when oil droplets contact the APDS-Aerogel surface, the oil droplets are rapidly penetrated into the aerogel interior, with an oil contact angle of approximately 0°. The contact angle and roll-off angle of water droplets on the APDS-Aerogel surface were tested using a contact angle meter, and the results are shown below. Figure 12As shown in Figure b, the contact angle of the water droplet on the APDS-Aerogel surface is approximately 154.5°, and the roll-off angle is approximately 5°, consistent with the characteristics of a superhydrophobic material. Dynamic contact angle testing further reveals its persistent hydrophobic properties; after the water droplet remained on the surface for 300 seconds, the contact angle remained stably above 150°. Figure 12 (See Figure c). Experimental data confirm that the unique superhydrophobic-superoleophilic properties of the APDS-Aerogel surface enable it to achieve efficient and selective oil-water separation in complex liquid systems. At the same time, its superhydrophobic properties remain stable even after long-term exposure to aqueous environments, providing a reliable guarantee for oil-water separation applications under complex working conditions.

[0103] like Figure 13 As shown, the low adhesion behavior of APDS-Aerogel was characterized using a camera. Figure 13 As shown in Figure a, after a 5–6 μL water droplet falls freely from a height of 5 cm, it exhibits typical non-adhesive bouncing characteristics upon contact with the APDS-Aerogel cross-section. The droplet immediately bounces to another surface after contact, and similarly, it does not adhere to this new surface but bounces again, eventually being bounced back to the surface. The entire process takes approximately 20,000 μs, indicating that the APDS-Aerogel surface possesses ultra-low water adhesion. Further verification of other low-adhesion behaviors using a contact angle meter is shown in the results. Figure 13 As shown in the BD diagram, in multiple dynamic impact tests, the water droplets consistently bounced off as intact spheres, with no liquid film residue or contact angle decay observed on the surface. When the substrate was tilted to a critical angle of 5°, the water droplets spontaneously rolled off due to gravity, with a clear rolling trajectory. When a hydrophilic medium was introduced into contact with the water droplets on the surface, the droplets rapidly completed directional migration driven by the interfacial energy difference. These results demonstrate the stability of the material's surface microstructure and chemical modifications, highlighting the material's accurate identification ability of oil / water phases, and indicating that APDS-Aerogel possesses excellent superhydrophobic properties.

[0104] APDS-Aerogel achieves selective response to polar water and non-polar oil through the synergistic effect of surface chemical groups and micro / nano structures. The aqueous phase is effectively repelled, while the oil phase is rapidly penetrated after wetting. Figure 14 SEM images of the APDS-Aerogel edges and the SiO2 on those edges. (Example:) Figure 14As shown, the surface of the aerogel pore walls simultaneously contains micron-sized polymethylsiloxane clusters and nano-sized hydrophobic SiO2 particles. This hierarchical structure effectively reduces the actual contact area between the droplets and the solid interface by significantly enhancing the discontinuity of the gas-liquid-solid three-phase contact line. The Cassie wetting-state stabilization effect induced by structural regulation gives the material surface low adhesion properties, which constitutes the core mechanism of APDS-Aerogel's superhydrophobic properties. The cellulose skeleton is chemically bonded to the polymethylsiloxane matrix through Si-OC covalent bonds, while the hydrophobic SiO2 nanoparticles are embedded in the aerogel fiber network through physical interactions. This composite mechanism provides mechanical protection for the hierarchical rough structure. Based on the polymethylsiloxane system, a hierarchical composite rough structure is constructed through the synergistic effect of SWPA and hydrophobic SiO2 nanoparticles. Combined with the inherent low surface energy characteristics of the material, the synergistic effect of the multi-scale rough structure and surface chemistry can ultimately endow the APDS-Aerogel surface with ultra-low liquid adhesion and achieve an effective unification of superhydrophobic and superoleophilic properties.

[0105] Example 7: Mechanical Properties of APDS-Aerogel The mechanical properties of APDS-Aerogel were further quantified using a texture analyzer, and the results are shown in [Figure number missing]. Figure 15 .like Figure 15 As shown in Figure a, APDS-Aerogel exhibits a unique compressive response under different strains perpendicular to the pore direction. In the initial compression stage (below 10%), it displays linear characteristics similar to an elastomer, with reversible elastic deformation of the pore walls. When compressed to the 10-50% range, the material enters a stress-stabilized stage; this mechanical behavior stems from the ordered collapse of the porous structure and the progressive bending of the pore layers. Under extreme compression conditions (70% strain), the pore channels completely close, triggering a densification effect, at which point the compressive stress sharply increases to 0.72 MPa. Compared to SHM-Aerogel, the mechanical strength is increased by 2.48 times, mainly attributed to the introduction of MMT and MF, which significantly improve the skeletal strength of the aerogel. Simultaneously, this material exhibits excellent deformation recovery, maintaining a high recovery rate of 88.9% even after undergoing 70% ultimate compression. Figure 15As shown in Figures b and c, after 1000 cycles of 30% strain loading, the compressive stress of APDS-Aerogel gradually stabilizes after a brief, small-scale decrease, with the permanent deformation in the direction perpendicular to the pores being only 13.86%. This performance stems from the material's unique pore wall design; the rigid skeleton provides structural support, while the elastic network stores energy through reversible deformation, and the two work synergistically to achieve rapid shape recovery. Furthermore, different pore orientations significantly affect its mechanical response, and APDS-Aerogel exhibits marked anisotropy. Tensile tests show that the tensile strength parallel to the pore direction is 1.76 times that in the vertical direction. This mechanical difference originates from the vertically arranged pore channel system, whose special structure gives the material a stronger stress-bearing capacity in the axial direction. Figure 15 (See Figure d). Meanwhile, when the load direction is perpendicular to the channel, the layered structure is more prone to bending deformation, with a stress of 0.16 MPa. However, under parallel loading, the axial bearing mechanism of the cylindrical shell structure significantly improves energy dissipation efficiency, with a stress 1.43 times that of the structure perpendicular to the channel. Figure 15 (See Figure e). This orientation-dependent mechanical behavior further confirms the successful construction of the special vertical channel structure in APDS-Aerogel.

[0106] The cyclic stability of oil-water separation materials is a key indicator for evaluating their application potential. The structural stability test results of APDS-Aerogel are shown below. Figure 16 and Figure 17 .like Figure 16 As shown in Figure a, after 50 adsorption-desorption cycles, APDS-Aerogel did not exhibit significant structural collapse, with a volume shrinkage rate of approximately 10.9%. Figure 16 As shown in Figure b, the compression experiment further confirms that under extreme compression conditions ( Even with a concentration exceeding 70%, it maintains structural integrity and recovers its high-efficiency adsorption capacity after decompression, further verifying the mechanical reliability of APDS-Aerogel. Figure 17 As shown, the recovery rate of APDS-Aerogel slowly decreases with increasing usage. After 50 adsorption-desorption cycles, the retention rate of dodecane remains above 88.95%, with the residual oil phase accounting for approximately 21%. Efficient oil phase recovery and material performance regeneration can be achieved through simple mechanical extrusion, validating the material's advantages of both high-efficiency adsorption and low maintenance costs in dynamic oil-water separation from an engineering application perspective.

[0107] Example 8: Application of APDS-Aerogel in oil-water separation The oil-water separation performance of the APDS-Aerogel prepared in Example 1 is as follows: Figure 18 As shown. Figure 18As shown in Figure a, dynamic adsorption experiments demonstrate that this material can accurately identify the oil phase through its low-energy surface characteristics, combined with the capillary force of its internal vertical channels to drive rapid crude oil adsorption. In simulated marine oil spill cleanup processes, the material not only achieves efficient capture of floating crude oil but also completely removes diffused oil films, exhibiting excellent marine oil pollution treatment capabilities. Figure 18 As shown in Figure b, further designed filtration experiments revealed its engineering potential. By staining the oil-water system (water phase blue, oil phase red), the APDS-Aerogel filter layer was found to have significant selective permeability. In gravity-driven separation experiments, when the tetrachloromethane / water mixture flowed through the filter layer, the oil phase reacted at a rate of 15391.2 L·m⁻¹. -2 ·h -1 The high flux penetrates rapidly, while the aqueous phase is completely blocked by the superhydrophobic interface, achieving efficient separation under no-power conditions. These results demonstrate that, thanks to its superhydrophobic properties, vertical pore structure, and excellent mechanical stability, APDS-Aerogel shows promising multi-dimensional applications in oil-water separation.

[0108] The results of quantitative analysis of the absorption process of oils with different viscosities using APDS-Aerogel are shown below. Figure 19 .like Figure 19 As shown, the oil-phase adsorption process of APDS-Aerogel exhibits significant self-triggering characteristics, with spontaneous adsorption initiated upon contact with the liquid surface. The adsorption capacity of oils with different viscosities does not differ significantly, with dodecane showing an adsorption capacity of 0.815 mL / cm³. 3 The adsorption capacity of high-viscosity machine oil is 0.756 mL / cm³. 3 This confirms that the adsorption capacity is also affected by the viscosity of the absorbent liquid. The adsorption kinetics exhibit significant nonlinear characteristics, with its rate curve divided into two stages: an initial transient permeation stage dominated by capillary action and a later stage of gradual pore saturation, leading to a decreasing overall adsorption rate. Experimental data show that low-viscosity dodecane achieves adsorption saturation within seconds (average rate 2.853 kg·m³). -2 ·s -1 The adsorption efficiency of high-viscosity mechanical oil decreased to 0.575% of that of dodecane. This is attributed to the increased transport resistance of high-viscosity fluids in porous media. The fluid dynamics behavior within the pore channels has a significant impact on the actual adsorption performance of the material.

[0109] Example 9: Preparation and Properties of Functionalized Aerogels To demonstrate the functional scalability of this invention, four types of functionalized aerogels were prepared by adjusting the types and proportions of functional fillers based on the optimal formulation: F1: Control group (0 wt% CB + 4 wt% SiO2); F2: 2 wt% carbon black (CB) + 2 wt% SiO2; F3: 1 wt% CB + 1 wt% Fe3O4 + 2 wt% SiO2; F4: 2 wt% Fe3O4+ 2 wt% SiO2; Fe3O4 was a laboratory-made magnetic nanosheet. The preparation steps were the same as in Example 1.

[0110] Images of alcohol gels and aerogels dried at atmospheric pressure with different functionalized fillers are shown below. Figure 20 As shown. From Figure 20 It can be seen that during atmospheric pressure drying, all alcohol gels containing different functional fillers maintained structural integrity, and their drying shrinkage was similar to that of APDS-Aerogel, confirming the universality of this method. This controllable preparation of components, structure, and properties mainly stems from the multiphase synergistic effect of the composite system. The interfacial reinforcement between the functional components and the matrix effectively enhances the rigidity of the gel network, enabling the material to maintain structural stability during the drying process even when components are replaced. Based on this, this study avoids the stringent limitations of traditional aerogel preparation on the raw material system, not only achieving a wide range of drying process parameters but, more importantly, providing scalable possibilities for the development of customized functional aerogels, which has significant engineering value for promoting the low-cost, large-scale production of aerogel materials.

[0111] The influence of four different combinations of functionalized fillers on the structural properties of aerogel are as follows: Figure 21 .like Figure 21 As shown, the key parameters of the aerogel remained highly stable under different filler ratios, with porosity fluctuations ranging from ±1.5% (86.2% to 88.7%), volume shrinkage differences less than 1% (14.3% to 15.3%), and apparent density variations controlled within 8.3% (0.135 to 0.146 g·cm³). -3 This parameter stability confirms the strong compatibility of the composite system with different types and proportions of fillers. The multiphase synergistic effect effectively balances the stress distribution differences caused by component variations, and the three-dimensional network maintains structural integrity. This characteristic allows for the free combination and proportion control of functional fillers while maintaining a porosity >86% and a shrinkage rate <15.5% in the prepared aerogel. This unique advantage of functionalized and controllable design provides a reliable method for developing multifunctional composite aerogels, and significantly expands the application potential of this material in other fields.

[0112] The introduction of functional fillers improved the photothermal conversion performance of aerogels, as shown in the following figures. Figure 22 .like Figure 22 As shown in Figures a and b, at 1 kW m -2Under simulated solar irradiation, all aerogels containing photothermal components exhibited significant temperature rise effects. The 2wt% CB + 2wt% SiO2 composite system showed particularly outstanding performance, with its surface temperature increasing from 19.5℃ to 95.1℃ within 220 s, a temperature rise rate of 0.34℃ / s. Comparative experiments showed that the systems containing 1wt% CB + 1wt% Fe3O4 and 2wt% Fe3O4 reached equilibrium temperatures of 82.3℃ and 74.2℃, respectively, while the blank control group only showed a temperature rise of 13.2℃, confirming the crucial role of the photothermal filler in performance enhancement. This enhancement effect stems from the broadband light absorption characteristics and non-radiative relaxation effect of the photothermal nanomaterial (CB / Fe3O4), which can convert incident light energy into heat energy. Experiments observed that after the light irradiation stopped, the material surface temperature recovered to ambient temperature within 60 s, demonstrating its excellent thermal responsiveness. This property enables functionalized aerogels to reduce the viscosity of high-viscosity crude oil through in-situ heating, thereby significantly improving the efficiency of marine oil spill recovery.

[0113] At 1 kW m -2 Dynamic adsorption experiments under simulated solar irradiation conditions revealed the influence of photothermal effects on the adsorption of aerogel oil phases. For example... Figure 23 As shown, the adsorption rate of all functionalized aerogels is positively correlated with the photothermal conversion efficiency; that is, the better the photothermal conversion effect, the shorter the time required to reach saturation. Overall, their saturation adsorption capacities are similar, approximately 0.793 mL / cm³. 3 The adsorption rates varied significantly, with the sample containing 2 wt% CB exhibiting the most pronounced enhanced adsorption kinetics due to its optimal photothermal response characteristics. The time to adsorption saturation was 36.7% shorter than the control group, and its average adsorption rate reached 0.056 kg·m³. -2 ·s -1 The adsorption rate was 2.78 times higher than that of unmodified aerogel. This kinetic enhancement effect stems from the synergistic mechanism of photothermal conversion. CB nanoparticles convert incident light energy into heat energy, increasing the temperature at the aerogel-oil phase interface and reducing the flow resistance of high-viscosity engine oil. Experiments confirmed that the adsorption rate is positively correlated with the photothermal conversion efficiency, verifying the effectiveness of photothermally assisted adsorption materials in treating high-viscosity oil pollution.

Claims

1. A method for preparing a superhydrophobic-superoleophilic aerogel with a directional porous structure, comprising the following steps: S1. Provides a precursor suspension comprising organic reinforcing fibers, a polymer matrix, inorganic reinforcing materials, and a hydrophobic agent; S2. The precursor suspension is directionally frozen to form a wet gel with an oriented pore structure; S3. Replace the solvent in the wet gel with a low surface tension solvent to obtain an alcohol gel; S4. Dry the alcohol gel under normal pressure to obtain the aerogel.

2. The preparation method according to claim 1, characterized in that: In step S1, the polymer matrix comprises cellulose derivatives and rubber latex, the inorganic reinforcing material comprises layered silicates, and the hydrophobic agent comprises crosslinkable organosilicon compounds.

3. The preparation method according to claim 2, characterized in that: The cellulose derivative is carboxymethyl cellulose, the rubber latex is carboxylated nitrile rubber latex, the layered silicate is modified montmorillonite, and the crosslinkable organosilicon compound is an organosilicon waterproofing agent.

4. The preparation method according to claim 3, characterized in that: In step S1, the precursor suspension further comprises a water-soluble resin for enhancing the rigidity of the skeleton, wherein the water-soluble resin is melamine-formaldehyde resin; and / or, The precursor suspension also contains hydrophobic nanoparticles for constructing surface micro-nano rough structures. The hydrophobic nanoparticles are hydrophobic silica nanoparticles.

5. The preparation method according to claim 4, characterized in that: In step S1, the proportions of each component of the precursor suspension by weight of the total system are as follows: Carboxymethyl cellulose: 0.5%-2.0%; melamine-formaldehyde resin: 0.5%-3.0%; modified montmorillonite: 0.5%-2.0%; aramid fiber: 0.3%-1.0%; carboxylated acrylonitrile rubber: 15%-25%; hydrophobic silica: 2%-6%; organosilicon waterproofing agent: balance, its volume ratio with water is 1:4-1:

8.

6. The preparation method according to any one of claims 1-5, characterized in that: In step S3, a gradient solvent replacement method is used, with a total replacement time of 24-48 hours; In step S4, the temperature for atmospheric pressure drying is 30℃-120℃.

7. Aerogel prepared by the method according to any one of claims 1-6.

8. A functionalized aerogel, wherein a functional filler is composited in or on the surface of the aerogel of claim 7; The functional filler is a photothermal conversion material selected from at least one of carbon black, iron oxide nanoparticles, carbon nanotubes, and graphene.

9. An oil-water separation assembly comprising the aerogel of claim 7 as a separation medium.

10. The application of the aerogel according to claim 7 in adsorbing and recovering floating oil on the water surface or treating oily wastewater.

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