Preparation and Application of Photoelectric, Thermomagnetic, and Biomass Composite Materials with Easily Switchable Wettability Using a One-Pot Aqueous Method

Abstract

This invention relates to the field of composite material preparation technology, and particularly to the preparation and application of photoelectric, thermal, and magnetically controlled biomass composite materials with easily switchable wettability using an aqueous one-pot method. The material is an elastic aerogel with a three-dimensional porous structure, prepared from the following components via an aqueous one-pot method: nanocellulose, silica particles, polyvinyl alcohol, chitosan, citric acid, carbon nanotubes, iron(III) oxide, and methyltrimethoxysilane. The elastic aerogel is converted from hydrophobic to hydrophilic through alkali treatment. The composite material obtained by this invention can achieve easy switching of wettability and possesses multiple excellent properties, applicable to various fields such as photothermal and electrothermal conversion, flame retardancy, magnetically controlled windproofing and displacement manipulation, oil spill treatment, organic dye filtration, seawater desalination, and domestic sewage purification. The preparation method solves the problems of complex processes, environmental pollution, single function, difficulty in controlling wettability, and insufficient synergy among multiple components in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to the preparation and application of photoelectric, thermo-magnetic, and biomass composite materials with easily switchable wettability using an aqueous one-pot method. Background Technology

[0002] Oil spills and industrial oily wastewater discharges cause serious environmental problems. Traditional composite materials suffer from drawbacks such as limited adsorption capacity, poor selectivity, and difficulty in recycling, failing to meet the demands for efficient, green, and multifunctional environmental governance. Therefore, it is necessary to develop new composite materials. Traditional composite material preparation relies on organic solvents, resulting in pollution and high costs. Furthermore, processing methods face challenges such as cumbersome procedures, high energy consumption, difficulty in balancing mechanical and functional properties, difficulty in switching wettability, and uneven dispersion of functional components. Therefore, developing preparation methods based on green media is crucial.

[0003] Currently, some aqueous synthesis technologies are used for single-function materials, but there is a gap in the integrated design of "processing-mixing-functional integration". There is a lack of simple processes to achieve reversible control of wettability and adaptability to multiple scenarios. There is an urgent need to develop composite materials and preparation methods that are simple in process, environmentally friendly and can achieve synergistic multi-functionality. Summary of the Invention

[0004] The purpose of this invention is to provide a photoelectric, thermomagnetic, and magnetically controlled biomass composite material with easily switchable wettability prepared by a one-pot aqueous phase method and its application. The prepared composite material can achieve easy switching of wettability and has a variety of excellent properties, which can be applied to multiple fields. The preparation method solves the problems of complex process, environmental pollution, single function, difficulty in controlling wettability, and insufficient synergy of multiple components in the existing technology.

[0005] To achieve the above objectives, the present invention provides a photoelectric, thermomagnetic, and magnetically controlled biomass composite material with easily switchable wettability prepared by a one-pot aqueous phase method. The composite material is an elastic aerogel with a three-dimensional porous structure, and the elastic aerogel is wettable by alkali treatment or methyltrimethoxysilane treatment.

[0006] A one-pot aqueous method for preparing photoelectric, thermo-magnetic composite materials with easily switchable wettability includes the following steps:

[0007] S1. A nanocellulose (CNF) suspension was prepared by bleaching lignocellulosic biomass raw materials with sodium chlorite and then ultrasonically treating them.

[0008] S2. Mix anhydrous ethanol, deionized water, and ammonia, and sonicate to obtain solution A. Mix tetraethyl orthosilicate (TEOS) and anhydrous ethanol, and sonicate to obtain solution B. Add solution A to solution B. After the reaction is complete, centrifuge, wash, and dry to obtain silica particles (SiO2NPS).

[0009] S3. Add polyvinyl alcohol (PVA) to deionized water and heat and stir until completely dissolved to obtain a polyvinyl alcohol solution;

[0010] S4. Add chitosan (CS) and citric acid (CA) to deionized water in sequence, heat and stir until completely dissolved to obtain chitosan-citric acid mixture;

[0011] S5. Carbon nanotubes (CNTs) and surfactants are added to deionized water and ultrasonically treated to obtain a carbon nanotube suspension.

[0012] S6. After mixing the nanocellulose suspension of S1 with the silica particles of S2, add the nanocellulose suspension of S1 and methyltrimethoxysilane again, and stir to obtain the CSM precursor solution.

[0013] S7. Mix the polyvinyl alcohol solution of S3, the chitosan-citric acid mixture of S4, the carbon nanotube suspension of S5, and the precursor solution of S6 to prepare a mixture; weigh the iron oxide solid powder and add it to the mixture, stir evenly, and then transfer it into a mold for freezing.

[0014] S8. After freeze-drying the mixture frozen in S7 together with the mold, place it in an oven for heat treatment. The freeze-drying temperature is -70~-50℃, and the heat treatment temperature is 80-120℃ to obtain a hydrophobic elastic aerogel.

[0015] S9. Place the hydrophobic elastic aerogel of S8 into an alkaline solution for alkaline treatment to switch it to a hydrophilic elastic aerogel. Then, place the hydrophilic elastic aerogel into a methyltrimethoxysilane ethanol solution for treatment to switch it back to a hydrophobic elastic aerogel.

[0016] Preferably, the ultrasonic treatment in S1 and S5 is performed using an ultrasonic cell disruptor with a power of 800-1200W. More preferably, the ultrasonic treatment power is 900W and the ultrasonic treatment time is 30 minutes. More preferably, the concentration of the nanocellulose suspension in S1 is 0.95-1.05%.

[0017] Preferably, in step S2, the volume ratio of anhydrous ethanol, deionized water, and ammonia is 36~38:0.9~1.1:2.9~3.1, and the volume ratio of tetraethyl orthosilicate to anhydrous ethanol is 0.9~1.1:8.2~8.4. Under slow stirring at 45°C, solution A is added to solution B in two batches, with a volume ratio of 3:1 between the two additions, and the time interval between the two additions is 1 hour. More preferably, the cleaning in step S2 involves rinsing three times with anhydrous ethanol and deionized water.

[0018] Preferably, in S3, the solid-liquid ratio of polyvinyl alcohol to deionized water is 0.95~1.05:19.5~20.5 g / mL.

[0019] Preferably, in S4, the solid-liquid ratio (g / mL) of chitosan and citric acid to deionized water is 2.95~3.05:1.95~2.05:19.5~20.5. More preferably, in S3 and S4, heating and stirring are performed in a water bath at 60~80°C.

[0020] Preferably, in S5, the solid-liquid ratio (g / mL) of carbon nanotubes, surfactant, and deionized water is 1.20~1.88:0.35~0.45:59.5~60.5. More preferably, the surfactant includes one or more of sodium dodecyl sulfate (SDS), sodium alkylbenzene sulfonate, sodium lauryl polyoxyethylene ether sulfate, and fatty acid salts.

[0021] Preferably, in step S6, the solid-liquid ratio (g / mL) of the nanocellulose suspension, silica particles, and methyltrimethoxysilane is 49.5~50.5:0.32~0.36:3. More preferably, in step S6, stirring is performed continuously for 1 hour at a constant water bath temperature of 80°C.

[0022] Preferably, in step S7, the volume ratio of the polyvinyl alcohol solution, chitosan-citric acid mixture, carbon nanotube suspension, and precursor solution is 7.45~7.55:7.45~7.55:59.5~60.5:49.5~50.5; the mass ratio of iron(III) oxide solid powder to the mixture is 0.09~0.11:100. More preferably, in step S7, the stirring is performed at a speed of 1950~2050 rpm for 10 min.

[0023] In a more preferred embodiment, the freeze-drying time in S8 is 48 hours, and the heat treatment is performed at 100°C for 3 hours.

[0024] In a further preferred embodiment, in S9, the alkaline solution is a NaOH solution with a pH of 14, and the concentration of the methyltrimethoxysilane ethanol solution is 5-20 vol.

[0025] The above-mentioned aqueous one-pot method for preparing photoelectric, thermal, and magnetically controlled biomass composite materials with easily switchable wettability can be applied to high-efficiency, high-throughput oily wastewater separation, high-efficiency, high-throughput emulsion separation, photothermal and electrothermal conversion, flame retardancy and fire prevention, circulating oil adsorption-desorption, oil spill treatment, organic dye adsorption, seawater desalination, magnetically controlled windproofing and displacement manipulation, and domestic sewage purification.

[0026] The preparation method of this invention uses water as a dispersion medium, based on nanocellulose (CNF) and polyvinyl alcohol (PVA), and performs hydrophobic modification with methyltrimethoxysilane (MTMS). It utilizes silica particles (SiO2NPS) to modify the three-dimensional porous structure, adds carbon nanotubes (CNTs) to endow the material with photoelectric and thermal conversion functions, introduces iron(III) oxide (Fe3O4) to achieve magnetic field controllability, and after processing such as freeze drying, a biomass composite material that can realize the hydrophobic-hydrophilic property transformation and has multifunctional applications is successfully constructed.

[0027] Therefore, the present invention, using the above-mentioned aqueous one-pot method to prepare photoelectric, thermomagnetic, and biomass composite materials with easily switchable wettability and their applications, has the following beneficial effects:

[0028] (1) The present invention uses water as a dispersion medium, the preparation process is green and pollution-free, better avoids the traditional organic solvent system, and water resources are abundant and low cost. It is not easy to generate harmful volatile substances and wastes during the preparation process, which greatly reduces potential environmental risks and takes into account both environmental protection and cost control.

[0029] (2) In this invention, MTMS introduces hydrophobic genes on the surface and inside of nanocellulose through hydrolysis and condensation reaction, forming a covalently bonded siloxane network structure, reducing surface energy to increase water contact angle, and realizing the transformation of aerogel from hydrophilic to hydrophobic; PVA combines with the hydroxyl groups of nanocellulose to enhance elastic potential energy and structural stability; CA, as a polycarboxylic acid, can undergo esterification reaction with the amino groups of CS, CNF and the hydroxyl groups of PVA to form crosslinking points, further enhancing the network structure; SiO2NPS fills the gaps in the network formed by PVA and CNF, and inhibits drying shrinkage through a nanoscale rigid skeleton. The specific surface area is increased by using a mesoporous-macroporous hierarchical structure, and the interfacial bonding is enhanced by the formation of hydrogen bonds / covalent bonds between the surface hydroxyl groups and cellulose, thereby improving the overall mechanical strength, adsorption efficiency and structural stability. The CNT nanostructures are interspersed in the network skeleton to form conductive and thermally conductive pathways, which improves the conductivity and endows photothermal conversion performance. It can be rapidly heated under sunlight and at the same time improve the adsorption capacity for organic pollutants. Fe3O4 endows the aerogel with magnetism, which enables it to move and adsorb in a directional manner under the action of an external magnetic field, so as to achieve precise adsorption and recovery in oil-water separation, as well as magnetically controlled windproof self-repositioning effect.

[0030] (3) In this invention, wettability conversion can be achieved through simple alkaline treatment, giving the material multiple excellent properties. It is applicable to various fields such as photothermal and electrothermal conversion, flame retardancy and fire prevention, magnetic windproofing and displacement control, oil spill treatment, organic dye filtration, and seawater desalination. Among them, the -CH3 groups stably covered on the surface of the hydrophobic elastic aerogel form a hydrophobic layer, which shows excellent separation efficiency and high throughput in the separation of simple oil-water mixtures and water-in-oil emulsions. After wettability conversion, the surface of the hydrophilic elastic aerogel exposes more hydrophilic groups such as amino and hydroxyl groups, which can form hydrogen bonds or electrostatic attraction with organic dye molecules to enhance adsorption capacity. Moreover, it is easy to form a hydration layer after contact with water, achieving hydrophilicity and oil repellency, and showing excellent efficiency in the separation of simple oil-water mixtures and oil-in-water emulsions. When hydrophobic elastic aerogels are continuously exposed to high-temperature flames, the synergistic effect of the organic networks such as polyvinyl alcohol, chitosan, and nanocellulose (which are pyrolyzed and carbonized on the surface) and the inorganic networks such as SiO2NPs, CNTs, and Fe3O4 (which exhibit excellent thermal stability) effectively inhibits the combustion reaction, thus exhibiting excellent flame-retardant and fire-resistant properties. After alkali treatment, the aerogel contains more hydrophilic groups and retains a small number of hydrophobic groups, forming a unique hydrophilic-hydrophobic synergistic interface. The pores rich in hydrophilic groups rapidly transport moisture, while the areas with residual hydrophobic groups enhance heat retention and repel impurities such as seawater salt, synergistically improving seawater desalination efficiency. Simultaneously, it imparts better structural and chemical stability to the material, demonstrating excellent performance in low-energy operation and environmental friendliness.

[0031] (4) The preparation method and wettability switching method of the present invention effectively solve the problems of complex process, environmental pollution, single function, difficulty in controlling wettability and insufficient synergy of multiple components in the prior art.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 These are test images of the water contact angle and oil contact angle of the hydrophobic elastic aerogel in Embodiment 1 of the invention under different NaCl concentrations and pH conditions. Figure 1 In the figure, 'a' represents the test results for water contact angle and oil contact angle at different NaCl concentrations. Figure 1 In the figure, b represents the test diagrams of water contact angle and oil contact angle under different pH conditions;

[0034] Figure 2 These are contact angle test images of the hydrophobic elastic aerogel prepared in Example 1 of this invention at different pH values ​​and in 30% NaCl solution at different times. Figure 2 In the figure, 'a' represents the curve of the water contact angle of the hydrophobic elastic aerogel changing over time. Figure 2 b in the figure represents the morphological diagram of the water contact angle of the hydrophobic elastic aerogel changing over time.

[0035] Figure 3 This is a test image of the underwater oil contact angle of the hydrophilic elastic aerogel prepared in Example 4 of this invention. Figure 3 In the diagram, 'a' represents the oil-water interaction process of the hydrophilic elastic aerogel. Figure 3 Schematic diagram of underwater oil contact angle of b hydrophilic elastic aerogel at different times;

[0036] Figure 4 These are the stress-strain curves and cyclic compression performance test graphs of the hydrophobic elastic aerogel prepared in Example 1 of this invention under different compression ratios. Figure 4 In the figure, 'a' represents the stress-strain curves under different compression ratios. Figure 4 In the figure, b is the stress-strain curve after 100 cycles at 80% compression.

[0037] Figure 5 This is a graph showing the curve of the adsorption / loading capacity of the hydrophilic elastic aerogel of this invention as a function of alkali treatment time and the results of cyclic compression stress-strain tests. Figure 5 In the figure, 'a' represents the curve of adsorption / loading capacity changing with alkali treatment time. Figure 5 b in the figure is the stress-strain curve of the hydrophilic elastic aerogel treated with alkali for 3 hours under 100 cycles of compression at 80% strain.

[0038] Figure 6 These are stress-strain curves of hydrophilic elastic aerogels of the present invention under different compression ratios for different alkali treatment times. Figure 6 In the figure, 'a' represents the stress-strain curves of the hydrophilic elastic aerogel treated with alkali for 1 hour under different compression ratios. Figure 6 In the figure, b represents the stress-strain curves of the hydrophilic elastic aerogel treated with alkali for 2 hours under different compression ratios. Figure 6 In the figure, c represents the stress-strain curves of the hydrophilic elastic aerogel treated with alkali for 3 hours under different compression ratios.

[0039] Figure 7 These are SEM images of the hydrophobic elastic aerogel prepared in Example 1 of this invention at different magnifications. Figure 7 In the image, 'a' is the SEM image magnified to 100 μm. Figure 7 In the image, b is the SEM image magnified to 20 μm. Figure 7 In the image, 'c' represents the SEM image magnified to 2 μm. Figure 7 In the image, d represents the SEM image magnified to 500nm.

[0040] Figure 8 This is the elemental energy spectrum of the hydrophobic elastic aerogel prepared in Example 1 of this invention. Figure 8 In the image, 'a' represents a SEM image of the hydrophobic elastic aerogel. Figure 8 In the diagram, b represents the distribution of element C. Figure 8In the diagram, 'c' represents the distribution of element N. Figure 8 In the diagram, d represents the distribution of O elements. Figure 8 In the diagram, 'e' represents the distribution of Si elements. Figure 8 f in the figure represents the distribution of Fe element;

[0041] Figure 9 These are the elemental gravity diagram and total elemental energy spectrum of the hydrophobic elastic aerogel prepared in Example 1 of this invention. Figure 9 In the diagram, 'a' represents the proportion of each element. Figure 9 In this diagram, 'b' represents the total energy spectrum of the element.

[0042] Figure 10 These are SEM images of the hydrophilic elastic aerogel prepared in Example 4 of this invention at different magnifications. Figure 10 In the image, 'a' is the SEM image magnified to 100 μm. Figure 10 In the image, b is the SEM image magnified to 20 μm. Figure 10 In the image, 'c' represents the SEM image magnified to 2 μm. Figure 10 In the image, d represents the SEM image magnified to 500nm.

[0043] Figure 11 This is the elemental energy spectrum of the hydrophilic elastic aerogel prepared in Example 4 of this invention. Figure 11 In the image, 'a' represents a SEM image of the hydrophilic elastic aerogel. Figure 11 In the diagram, b represents the distribution of element C. Figure 11 In the diagram, 'c' represents the distribution of element N. Figure 11 In the diagram, d represents the distribution of O elements. Figure 11 In the diagram, 'e' represents the distribution of Si elements. Figure 11 f in the figure represents the distribution of Fe element;

[0044] Figure 12 These are the elemental gravity diagram and total elemental energy spectrum of the hydrophilic elastic aerogel prepared in Example 4 of this invention. Figure 12 In the diagram, 'a' represents the proportion of each element. Figure 12 In this diagram, 'b' represents the total energy spectrum of the element.

[0045] Figure 13 This is a graph showing the test results of separating oil-water mixtures under gravity using the hydrophobic elastic aerogel prepared in Example 1 of this invention. Figure 13 In the diagram, 'a' represents a schematic diagram of oil-water separation driven by gravity using hydrophobic elastic aerogel. Figure 13 In the diagram, b represents the separation mass of different oil-water mixtures by the hydrophobic elastic aerogel in 10 cycles. Figure 13 In the figure, 'c' represents a comparison of the separation efficiency and separation flux of hydrophobic elastic aerogels for different oil-water mixtures. Figure 13In the figure, d represents the change curve of separation flux and separation efficiency of hydrophobic elastic aerogel for n-hexane-water mixture in 20 cycles;

[0046] Figure 14 The figure shows the test results of separating oil-water mixtures under gravity using the hydrophilic elastic aerogel prepared in Example 4 of this invention. Figure 14 In the diagram, 'a' represents a schematic diagram of oil-water separation driven by gravity in a hydrophilic elastic aerogel. Figure 14 In the figure, b is a schematic diagram of the separation mass of different oil-water mixtures by hydrophilic elastic aerogel in 10 cycles;

[0047] Figure 15 The figure shows the test results of separating water-in-oil emulsions under gravity using the hydrophobic elastic aerogel prepared in Example 1 of this invention. Figure 15 In the diagram, 'a' represents the separation of water-in-oil emulsions under gravity-driven conditions using hydrophobic elastic aerogels. Figure 15 In the figure, b is a comparison of the separation efficiency and separation flux of hydrophobic elastic aerogel for different water-in-oil emulsions. Figure 15 In the figure, c represents the change curve of separation flux and separation efficiency of hydrophobic elastic aerogel for dichloromethane water-in-oil emulsion in 20 cycles.

[0048] Figure 16 The figure shows the test results of separating the oil-in-water emulsion under gravity using the hydrophilic elastic aerogel prepared in Example 4 of this invention. Figure 16 In the diagram, 'a' represents the separation of oil-in-water emulsions under gravity-driven conditions using hydrophilic elastic aerogels. Figure 16 In the diagram, b represents the separation efficiency of hydrophilic elastic aerogel for different oil-in-water emulsions. Figure 16 In the figure, c represents the curve of separation flux and separation efficiency of hydrophilic elastic aerogel for different oil-in-water emulsions after 20 cycles.

[0049] Figure 17 These are schematic diagrams illustrating the photoelectric and thermal properties of hydrophobic elastic aerogels with different CNT contents at different voltages in Examples 1-3 of this invention. Figure 17 In the figure, 'a' represents the current variation of hydrophobic elastic aerogels with different CNT contents. Figure 17 In the figure, b represents the power variation of hydrophobic elastic aerogels with different CNT contents. Figure 17 In the figure, c represents the temperature change of hydrophobic elastic aerogels with different CNT contents;

[0050] Figure 18 The graphs show the temperature-time response characteristics of hydrophobic elastic aerogels with different CNT contents in Examples 1-3 of this invention under voltages of 1–6V. Figure 18 The graph shows the temperature-time response characteristics of a hydrophobic elastic aerogel with a CNT content of 1%. Figure 18In the figure, b represents the temperature-time response characteristics of a hydrophobic elastic aerogel with a CNT content of 1.25%. Figure 18 The temperature-time response characteristics of the hydrophobic elastic aerogel with 1.5% CNT content are shown in the figure.

[0051] Figure 19 The diagram shows the temperature rise curves, oil absorption diagram, and oil absorption volume diagram of the hydrophobic elastic aerogel with 1.5% CNT content of this invention under different voltages. Figure 19 In the figure, 'a' represents the temperature rise curves under different voltages. Figure 19 In the diagram, b represents the oil suction diagram under different voltages. Figure 19 In the diagram, 'c' represents the oil suction volume under different voltages.

[0052] Figure 20 These are test graphs showing the photothermal properties of hydrophobic elastic aerogels with different CNT contents in Examples 1-3 of this invention. Figure 20 The graph in Figure 'a' represents the photothermal properties of a 1% CNT hydrophobic elastic aerogel. Figure 20 Figure b shows the photothermal properties of a hydrophobic elastic aerogel containing 1.25% CNTs. Figure 20 The graph shows the photothermal properties of a hydrophobic elastic aerogel containing 1.5% CNTs (c).

[0053] Figure 21 This is a thermal imaging and temperature-time curve analysis diagram of the temperature change of the hydrophobic elastic aerogel under the photo-electric synergistic effect obtained in Example 1 of the present invention. Figure 21 In the image, 'a' represents a thermal image of temperature changes. Figure 21 In the figure, b represents the temperature-time curve analysis graph;

[0054] Figure 22 This is a schematic diagram illustrating the adsorption performance of the hydrophilic elastic aerogel prepared in Example 4 of the present invention on methylene blue. Figure 22 A schematic diagram showing the adsorption performance of α on different concentrations of methylene blue (100-600 mg / L). Figure 22 In the figure, b represents the performance of cyclic adsorption of the same concentration of methylene blue;

[0055] Figure 23 A flowchart illustrating the directional movement of an elastic aerogel floating on water, controlled by a magnet. Figure 23 In Example 1, 'a' is a flowchart illustrating the directional movement of the hydrophobic elastic aerogel. Figure 23 b in Example 4 is a flowchart of the directional movement of the hydrophilic elastic aerogel.

[0056] Figure 24 A flowchart for the directional and selective adsorption of floating oil stains by a hydrophobic elastic aerogel in a glass culture dish filled with deionized water using a magnet;

[0057] Figure 25 This diagram illustrates the traction and repositioning of aerogel by the non-uniform magnetic field generated by the electromagnet under different voltages. Figure 25 In Figure 'a', the hydrophobic elastic aerogel prepared in Example 1 is shown in the traction repositioning diagram under a 4V voltage. Figure 25 In Figure b, the hydrophobic elastic aerogel prepared in Example 1 is shown in the traction repositioning diagram under a voltage of 24V. Figure 25 c in the figure is the traction repositioning diagram of the hydrophilic elastic aerogel prepared in Example 4 under a voltage of 4V; Figure 25 In the figure, d represents the traction repositioning diagram of the hydrophilic elastic aerogel prepared in Example 4 under a voltage of 24V.

[0058] Figure 26 The diagram shows the effect of achieving self-repositioning of hydrophilic elastic aerogel floating in water using magnetic control under the measured maximum wind speed (10.3 m / s) and maximum output voltage (24 V).

[0059] Figure 27 The hydrophobic elastic aerogel prepared in Example 1 was subjected to four consecutive vertical combustion tests, each lasting 10 seconds.

[0060] Figure 28 This is a real-time data graph of outdoor simulated seawater desalination. Figure 28 In the graph, 'a' represents real-time data on wind speed, humidity, outdoor temperature, and the highest surface temperature of the hydrophobic elastic aerogel. Figure 28 In the graph, b represents real-time data on solar radiation intensity, water mass loss, and evaporation rate. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0062] The preparation of the nanocellulose suspension in all embodiments of this invention includes the following steps:

[0063] (1) Primary sodium chlorite bleaching treatment: Weigh 5g of corn stalks, wheat stalks, poplar powder, or pine powder, mix with 150mL of 1.5% sodium chlorite solution, and adjust the pH to 3 with 300μL of glacial acetic acid. Stir continuously in an 80℃ water bath for 6h, adding 300μL of glacial acetic acid and 0.2g of sodium chlorite solid every 1h. After the reaction, filter the residual solid, wash with deionized water until the filtrate is clear, and obtain the primary bleached solid powder.

[0064] (2) Hot solvent co-treatment: Take the solid powder that was initially bleached in step (1), mix it with 45 mL of anhydrous ethanol, 15 mL of deionized water and 190 μL of concentrated sulfuric acid, and transfer it into a reaction vessel. After heat treatment at 185℃ for 90 min, rinse the reaction vessel with a small stream of water until it reaches room temperature, take out the reactants and wash them with 65% ethanol until neutral, filter them and remove the ethanol with deionized water, and dry them in an oven at 60℃ for 2 h to obtain the solid powder after hot solvent treatment.

[0065] (3) Secondary hydrogen peroxide-alkali bleaching: Mix 10 mL of hydrogen peroxide with 45 mL of 1% NaOH solution, add the solid powder treated with hot solvent in step (2), and stir in a 50°C water bath for 90 min to deeply remove lignin and hemicellulose. After filtration, rinse with deionized water until the filtrate is clear to obtain high-purity cellulose solid powder.

[0066] (4) High-intensity ultrasonic dispersion: Weigh 1g of high-purity cellulose solid powder from step (3), disperse it in 99mL of deionized water, and treat it with a 900W ultrasonic cell disruptor for 30min to prepare a 1% nanocellulose suspension.

[0067] The preparation of silica particles in all embodiments of this invention includes the following steps:

[0068] (1) Preparation of A in solution: Measure 4 mL of deionized water, 12 mL of ammonia water and 150 mL of anhydrous ethanol and add them to a container. Use an ultrasonic cleaner to perform ultrasonic dispersion treatment for 15 min to obtain A in solution.

[0069] (2) Preparation of B in the solution: Take 6 mL of tetraethyl orthosilicate and 50 mL of anhydrous ethanol and mix them thoroughly. Then, use an ultrasonic cleaner to continuously oscillate the mixture for 25 min to obtain B in the solution.

[0070] (3) Synthesis of SiO2 nanoparticles (SiO2NPS): A water bath magnetic stirring device was set at 45℃. First, ¾ volume of solution A was slowly added dropwise to solution B, and the stirring reaction was maintained for 1 hour until the system gradually became turbid. Then, all the remaining solution A was added, and the reaction was continued for 1 hour. After the reaction was completed, the solid and liquid were separated by centrifugation at 10300 r / min for 15 min, and the mixture was washed three times alternately with deionized water and ethanol. Finally, it was dried at 60℃ for 6 hours to obtain SiO2 nanoparticles.

[0071] Example 1

[0072] The present invention provides a one-pot aqueous method for preparing photoelectric, thermo-magnetic, and biomass composite materials with easily switchable wettability, comprising the following steps:

[0073] S1. Preparation of nanocellulose suspension.

[0074] S2. Preparation of silica particles.

[0075] S3. Preparation of polyvinyl alcohol solution: Add 1g of solid polyvinyl alcohol to 20mL of deionized water and stir for 1h at a water bath temperature of 80℃ to obtain a polyvinyl alcohol solution.

[0076] S4. Preparation of chitosan-citric acid mixture: Add 3g of chitosan to 20mL of deionized water, stir in a water bath until completely dissolved, then add 2g of citric acid, and continue stirring at 80℃ in a water bath until completely dissolved to obtain chitosan-citric acid mixture.

[0077] S5. Preparation of carbon nanotube suspension: Add 1.25g of carbon nanotubes and 0.4g of sodium dodecyl sulfate to 60mL of deionized water, stir thoroughly, and then place in a cell disruptor for sonication for 15min to prepare a carbon nanotube suspension.

[0078] S6. Preparation of precursor solution: Take 45 mL of 1 wt% nanocellulose suspension of S1 and mix it with 0.34 g of silica particles of S2 and stir until uniform. Then add 5 mL of 1 wt% nanocellulose suspension of S1 and 3 mL of methyltrimethoxysilane. Stir continuously for 1 h at a constant temperature of 80℃ in a water bath to obtain CSM precursor solution.

[0079] S7. Take 7.45 mL of polyvinyl alcohol solution (S3), 7.45 mL of chitosan-citric acid mixture (S4), 49.5 mL of carbon nanotube suspension (S5), and 59.5 mL of precursor solution (S6), and mix them thoroughly to obtain a mixed solution. Add Fe3O4 solid powder to the mixed solution at a mass ratio of 100:0.1, and stir thoroughly until homogeneous to obtain the precursor mixed solution. Transfer the precursor mixed solution into a mold and freeze for 24 hours.

[0080] S8. Place the frozen mixture from S7, along with the mold, into a vacuum freeze dryer and freeze-dry at -60°C for 48 hours. After freeze-drying, remove the mixture and place it in an oven for thermal crosslinking at 100°C for 3 hours. This yields a hydrophobic elastic aerogel with a CNT content of 1 wt%.

[0081] Example 2

[0082] The present invention provides a one-pot aqueous method for preparing photoelectric, thermo-magnetic, and biomass composite materials with easily switchable wettability. The difference from Example 1 is that in step S5, the amount of carbon nanotubes is 1.56 g; in step S7, 7.5 mL of the polyvinyl alcohol solution from S3, 7.5 mL of the chitosan-citric acid mixture from S4, 50 mL of the carbon nanotube suspension from S5, and 60 mL of the precursor solution from S6 are mixed and stirred until homogeneous to obtain a mixed solution. The rest of the steps are the same as in Example 1, resulting in a hydrophobic elastic aerogel with a CNT content of 1.25 wt%.

[0083] Example 3

[0084] The present invention provides a one-pot aqueous method for preparing photoelectric, thermo-magnetic, and biomass composite materials with easily switchable wettability. The difference from Example 1 is that in step S5, the amount of carbon nanotubes is 1.87 g; in step S7, 7.55 mL of the polyvinyl alcohol solution from S3, 7.55 mL of the chitosan-citric acid mixture from S4, 50.5 mL of the carbon nanotube suspension from S5, and 60.5 mL of the precursor solution from S6 are mixed and stirred until homogeneous to obtain a mixed solution. The rest of the steps are the same as in Example 1, resulting in a hydrophobic elastic aerogel with a CNT content of 1.5 wt%.

[0085] Example 4

[0086] The difference from Example 1 is that the hydrophobic elastic aerogel with a CNT content of 1 wt% obtained in step S8 was subjected to alkali treatment to obtain a hydrophilic elastic aerogel. All other aspects were the same as in Example 1. Specifically, the alkali treatment involved mixing NaOH particles with 100 mL of deionized water and stirring until homogeneous. The pH of the solution was measured using pH paper and adjusted to 14, resulting in a strong alkaline solution with a pH of 14. The hydrophobic elastic aerogel prepared in S8 was then immersed in the strong alkaline solution for alkali etching treatment for 3 hours. Afterward, the aerogel was removed and washed with deionized water until neutral, resulting in a hydrophilic elastic aerogel with a CNT content of 1 wt% after 3 hours of alkali treatment.

[0087] Example 5

[0088] The difference from Example 4 is that the hydrophobic elastic aerogel prepared in S8 was immersed in a strong alkaline solution for 1 hour for alkaline treatment, while the rest was the same as in Example 4.

[0089] Example 6

[0090] The difference from Example 4 is that the hydrophobic elastic aerogel prepared in S8 is immersed in a strong alkaline solution for alkali treatment for 5 hours, while the rest is the same as in Example 4.

[0091] Example 7

[0092] The hydrophilic elastic aerogel treated with alkali in Example 4 was then immersed in a 6 vol% methyltrimethoxysilane ethanol solution for 1 hour, and then switched back to hydrophobic elastic aerogel.

[0093] Test

[0094] (1) Superhydrophobic-superoleophilic test of elastic aerogel

[0095] ① The water contact angle (WCA) and oil contact angle (OCA) of the hydrophobic elastic aerogel prepared in Example 1 were tested in different mass fractions of NaCl solution (salt water) and under different pH conditions. Figure 1 As shown in Figure a, the hydrophobic elastic aerogel exhibits significant hydrophobic properties, with water contact angles exceeding 155° at different NaCl concentrations; simultaneously, the oil contact angle is 0°, highlighting its superoleophilic properties. Figure 1 As shown in b, within a wide pH range (pH=1~14), the minimum water contact angle of the hydrophobic elastic aerogel remains above 157° (e.g., WCA reaches 161° at pH=1 and 159° at pH=14), exhibiting stable hydrophobic properties. Furthermore, the oil contact angle remains constant at 0° under all pH conditions, indicating that the oleophilic properties are unaffected by acidic or alkaline environments. This demonstrates that the hydrophobic elastic aerogel can stably maintain its hydrophobic and oleophilic binary wetting behavior in salt environments and in strong acidic or alkaline environments, possessing excellent resistance to salt interference.

[0096] ② The water contact angle of the hydrophobic elastic aerogel in 30% NaCl solution and droplets with pH=1, pH=7, and pH=14 was continuously monitored over time (10 minutes) using a contact angle meter. Figure 2 As shown in Figure a, the hydrophobic elastic aerogel maintained a water contact angle exceeding 155° in a 30% NaCl solution without significant decrease; the decrease in water contact angle was minimal at pH=1 and pH=7 (e.g., a droplet at pH=1 decreased only from 161° to 160° after 10 minutes); even in a strongly alkaline environment at pH=14, the initial water contact angle of the droplet was 156°, which remained at 110° after 10 minutes, and the aerogel morphology remained intact. Figure 2 As shown in b, the trend of droplet morphology on the surface of hydrophobic elastic aerogel over time highly coincides with the trend of water contact angle, indicating that hydrophobic elastic aerogel can maintain its morphological integrity and core wetting properties in high-salt and strong acid-base environments, thus possessing good environmental tolerance.

[0097] ③ The hydrophilic elastic aerogel prepared in Example 4 was placed in an underwater environment, and the contact state of oil droplets on the aerogel surface was observed. The underwater oil contact angle was measured. Figure 3As shown in a, the hydrophilic elastic aerogel is preferentially covered by water underwater, and the lipophilic groups are blocked by the water film. Furthermore, the bound water within the porous structure forms a physical barrier, preventing oil droplets from breaking through the water layer for adsorption. This demonstrates the superhydrophilic-oleophobic properties of the hydrophilic elastic aerogel prepared in Example 4, making it suitable for application in oil-in-water separation systems. Figure 3 As shown in b, the hydrophilic elastic aerogel can maintain an underwater oil contact angle of over 160° within 30 minutes of immersion in water, indicating that the hydrophilic elastic aerogel prepared in Example 4 can stably maintain superhydrophilic-oleophobic properties in water, has a continuous repulsion ability against the oil phase, is suitable for scenarios such as the separation of oil-in-water systems, and has stable performance within a certain period of time.

[0098] ④ The compressibility of the elastic aerogel was tested using a mechanical testing device. For example... Figure 4 As shown in Figure a, the hydrophobic elastic aerogel withstands a maximum pressure of 2 kPa at a strain of 20%, 3 kPa at a strain of 40%, 8 kPa at a strain of 60%, and 68 kPa at a strain of 80%. Figure 4 As shown in b, after 100 cycles of testing, the compressive strength did not decrease significantly, indicating that the internal structure of the hydrophobic elastic aerogel did not change much during this stage.

[0099] The hydrophobic elastic aerogel prepared in Example 1 was treated with NaOH solution at pH=14 for different times (0h, 1h, 3h, 5h) to prepare different hydrophilic elastic aerogels. The adsorption capacity and cyclic compressive stress-strain of these aerogels were tested. Figure 5 As shown in Figure a, the adsorption capacity of the hydrophilic elastic aerogel initially increases rapidly with prolonged alkali treatment time, then tends towards saturation. At 0 h of alkali treatment, the adsorption capacity is 0 g / g, indicating that the initial hydrophobic elastic aerogel has no adsorption capacity. After 1 h of alkali treatment, the adsorption capacity significantly increases to 19.4 g / g, indicating that short-term alkali treatment can endow the aerogel with strong adsorption capacity. After 3 h of alkali treatment, the adsorption capacity further increases to 34.87 g / g. After 5 h of alkali treatment, the adsorption capacity is 35.46 g / g, approaching saturation. This demonstrates that appropriately extending the alkali treatment time can enhance the adsorption performance of the hydrophilic elastic aerogel. Figure 5 As shown in b, after 100 cycles of compression at 80% strain, the stress change of the hydrophilic elastic aerogel is not significantly different from that of the first cycle. Although the hydrophilic elastic aerogel may undergo some structural changes due to alkali treatment, and its pressure resistance is lower than that of the hydrophobic elastic aerogel, it can still maintain stable mechanical properties during long-term cyclic compression. This indicates that the hydrophilic elastic aerogel prepared by alkali treatment for 3 hours has excellent fatigue resistance and structural recovery ability, which can meet the application requirements of repeated use.

[0100] The compressive properties of the hydrophilic elastic aerogels treated with alkali for 3 hours, 1 hour, and 5 hours in Examples 4, 5, and 6 were tested. Each aerogel was compressed to 20%, 40%, and 60% strain using a mechanical testing device to test the effect of alkali treatment time on the compressive strength of the hydrophilic aerogels. Figure 6 As shown, under the same compression ratio, the hydrophilic elastic aerogel treated with alkali for 1 hour exhibits relatively high stress. The hydrophilic elastic aerogel treated with alkali for 3 hours exhibits slightly lower stress. With the alkali treatment time increasing to 5 hours, although the stress of the hydrophilic elastic aerogel decreases, it still maintains good resilience. This indicates that appropriately extending the alkali treatment time may have a slight impact on the aerogel structure, but overall it still maintains good compressive strength. The hydrophilic elastic aerogels with all three alkali treatment times can generate effective stress response under 80% high strain, and the stress increases systematically with increasing compression ratio, indicating that regardless of the alkali treatment time, the hydrophilic elastic aerogel possesses mechanical stability to adapt to different degrees of deformation, meeting the stress requirements of practical applications.

[0101] (2) The microstructure of the aerogel from hydrophobic to hydrophilic was analyzed by SEM EDS elemental mapping.

[0102] ① The microstructure of the hydrophobic elastic aerogel prepared in Example 1 and the hydrophilic elastic aerogel prepared in Example 4 were observed using a scanning electron microscope. Figure 7 and Figure 10 As shown, the elastic aerogel has a three-dimensional porous network structure with abundant mesopores and macropores. SiO2NPS is uniformly attached to the surface of the framework composed of CNF and PVA. SiO2NPS forms crosslinks between CNF and PVA through physical action, and the bridging effect of the particles enhances the stability of the framework structure. Furthermore, the basic structure of the aerogel remains unchanged after alkali treatment.

[0103] ② Elemental analysis of the hydrophobic elastic aerogel and the hydrophilic elastic aerogel prepared in Example 4 was performed using energy-dispersive X-ray spectroscopy (EDS). Combined with scanning electron microscopy (SEM), the distribution of major elements (such as C, O, Si, and Fe) in the aerogel was determined using the EDS surface scanning function. The results are shown in [Figure number missing]. Figure 8 and Figure 11 .

[0104] like Figure 8As shown, the elements in the elastic aerogel are uniformly distributed. Carbon (C), nitrogen (N), and oxygen (O), as the main constituent elements of biomass substrates (CNF, PVA, etc.), exhibit a continuous and uniform distribution, forming the framework network of the aerogel. Silicon (Si) corresponds to SiO2NPS, which is uniformly dispersed in the framework, indicating that SiO2NPS did not agglomerate during the preparation process and effectively played a role in enhancing the three-dimensional structure. Iron (Fe) corresponds to Fe3O4 particles, which are also uniformly distributed, indicating that the magnetron functional components are well dispersed in the material. This shows that the aqueous one-pot method can achieve uniform composite of multiple components, providing structural guarantee for the multifunctional synergistic effect of the aerogel. Figure 11 and Figure 8 In contrast, most of the elements contained in the aerogel were removed, indicating that the aerogel was successfully changed from hydrophobic to hydrophilic.

[0105] ③ Elemental analysis of the hydrophobic elastic aerogel prepared in Example 1 and the hydrophilic elastic aerogel prepared in Example 4 was performed by energy-dispersive X-ray spectroscopy (EDS). The results are shown in [Figure number missing]. Figure 9 and Figure 12 .like Figure 9 a and Figure 12 As shown in Figure a, the highest proportion of carbon (C) is found in hydrophobic elastic aerogels (68.5%), while in hydrophilic elastic aerogels it is found in 76.58%. C, as the main element in the biomass substrate, forms the basic framework of the aerogel, followed by O, Si, Fe, and N. This indicates that the aerogel is predominantly C, containing small amounts of O, Si, Fe, and trace amounts of N, suggesting that the functional components exist in the expected proportions. Figure 9 b and Figure 12 As shown in b, each characteristic peak corresponds to the main elements in the material, and no extra impurity element peaks appear, indicating that the aerogel has high purity and no obvious impurities were introduced during the preparation process.

[0106] (3) Test of the adsorption capacity of elastic aerogel for various light oils, heavy oils and emulsions.

[0107] ① Performance test of separating oil-water mixtures using gravity-driven elastic aerogel. For example... Figure 13 As shown in Figure a, hydrophobic elastic aerogels can achieve rapid oil-water separation, with the oil phase preferentially passing through the aerogel while the aqueous phase is blocked, demonstrating good separation selectivity and making them suitable for the separation of water-in-oil systems. Figure 13 As shown in b, after 10 cycles, the separation quality of the aerogel for different heavy oil-water mixtures did not decrease significantly, indicating its stable recyclability. Figure 13 As shown in c, the separation efficiency for various oil-water mixtures all exceeded 99.5%, demonstrating extremely high separation selectivity; the separation fluxes for n-hexane, chloroform, dichloroethane, and dichloromethane were 6.32 × 10⁻⁶. 4 L•m-2 •h -1 5.61×10 4 L•m -2 •h -1 7.22×10 4 L•m -2 •h -1 7.58×10 4 L•m -2 •h -1 .like Figure 13 As shown in d, after 20 cycles of the dichloromethane-water mixture, the separation flux and efficiency remained at a high level, further demonstrating that the aerogel has excellent long-term cycling stability and practical value.

[0108] like Figure 14 As shown in 'a', hydrophilic elastic aerogels allow for preferential passage of the aqueous phase while effectively blocking the oil phase, demonstrating a separation selectivity complementary to that of hydrophobic elastic aerogels, making them suitable for the separation of oil-in-water systems. For example... Figure 14 As shown in b, the hydrophilic elastic aerogel can achieve a separation efficiency of over 99% for mixtures of hexane, dichloromethane, and water. After 10 cycles of separation, the separation efficiency did not decrease significantly, indicating that the hydrophilic elastic aerogel has good cycle stability and durability and can be used repeatedly.

[0109] ②Performance test of separating emulsions using gravity-driven elastic aerogels. For example... Figure 15 As shown, the hydrophobic elastic aerogel achieved a separation efficiency exceeding 99.5% for four water-in-oil emulsions: chloroform, dichloroethane, n-hexane, and dichloromethane. The dichloromethane system exhibited the highest separation flux, reaching 4.55 × 10⁻⁶. 4 L•m -2 •h -1 Furthermore, the separation flux and efficiency of the aerogel did not decrease significantly after 20 cycles, demonstrating that the hydrophobic aerogel possesses good cycle stability and durability, and has practical value in the field of water-in-oil emulsion separation.

[0110] like Figure 16 As shown, the hydrophilic elastic aerogel prepared in Example 4 achieved an efficiency exceeding 99.1% in a single separation of four oil-in-water emulsions: chloroform, dichloromethane, n-hexane, and dichloroethane, highlighting its high-efficiency separation capability for different oil phase systems. Furthermore, the aerogel showed no significant decrease in separation flux and efficiency after 20 cycles, demonstrating its good cycling stability and durability, and its practical value in the field of oil-in-water emulsion separation.

[0111] (4) Heating curve of elastic aerogel in photoelectric and thermal performance conversion and adsorption of high viscosity oil.

[0112] ① Curves of current, voltage, and temperature performance of elastic aerogel under energized conditions.

[0113] A test setup was constructed, comprising a simulated sunlight source, copper foil, a power supply, and an infrared thermal imager. The aerogel under test was used as the test object, secured by the copper foil for heat / electrical transfer. The power supply was connected to the copper foil via red and black wires to provide power. Simulated sunlight was used to irradiate the aerogel, and the infrared thermal imager was used to monitor the temperature changes of the aerogel in real time under the influence of light and electricity. Figure 17 As shown in the current-voltage curves in section a, the current of all CNT-containing hydrophobic elastic aerogels increases with increasing voltage. The hydrophobic elastic aerogel with a 1.5% CNT content shows the most significant current increase due to its more complete internal conductive network, while the current increase of the 1% CNT content is gradual and tends to stabilize at lower voltages. Figure 17 As shown in the power-voltage curve (b), its change is directly related to the current. The hydrophobic elastic aerogel with a 1.5% CNT ratio exhibits the fastest power increase with voltage due to its higher current, reflecting superior energy utilization efficiency and power output capability. Figure 17 As shown in the temperature-voltage curve in Figure c, the temperature of hydrophobic elastic aerogels of all proportions increases with increasing voltage due to the Joule heating effect. The hydrophobic elastic aerogel with a 1.5% CNT ratio has the highest temperature due to its large current, high Joule heating, and easy heat accumulation, while the 1% CNT ratio has the lowest temperature. The three figures present the material's electrical-thermal performance chain from "current transmission → power output → heat generation".

[0114] ② Temperature rise curve of elastic aerogel during electrothermal property conversion. (See figure) Figure 18 As shown in a, the hydrophobic elastic aerogel with 1% CNT content exhibits weak thermal response at low voltages but rapid heating at high voltages. Figure 18 As shown in b, the hydrophobic elastic aerogel with 1.25% CNT content exhibits better thermal stability in the medium-to-high voltage range, making it suitable for applications requiring stable medium-temperature heat output and temperature plateau compatibility. Figure 18 As shown in c, the hydrophobic elastic aerogel with 1.5% CNTs content exhibits high electrothermal conversion efficiency and strong heat accumulation capability across the entire voltage range. The peak temperature at 6V approaches 150℃ and remains at high temperature for a long time, which can meet the requirements of high temperature and long-term heat output.

[0115] ③ Temperature rise curve of elastic aerogel during electrothermal performance conversion and adsorption of high viscosity oil.

[0116] like Figure 19 As shown in the temperature-voltage curve, the maximum temperature of the hydrophobic elastic aerogel with a 1.5% CNT content increases significantly with increasing voltage, exhibiting a strong thermal response. This indicates that the hydrophobic elastic aerogel has good electrothermal conversion efficiency and heat accumulation capacity. Figure 19As shown in b, with no voltage and 2V, 4V, and 6V as variables, the pump oil volume was recorded over time. Under high voltage, the hydrophobic elastic aerogel surface quickly "dries" within 10 seconds, reflecting that the higher the voltage, the faster the thermal / functional triggering efficiency. Figure 19 As shown in c, the adsorption / desorption time of the hydrophobic elastic aerogel is significantly shortened with increasing voltage, while the adsorption capacity increases with increasing voltage and the adsorption time is even shorter.

[0117] ④ Temperature rise curve of multifunctional elastic aerogel during photothermal property conversion. (See figure.) Figure 20 As shown in Figure a, the heating rate of 1% CNTs hydrophobic elastic aerogel accelerated during the heating phase from 0 to 120 s under different light intensities. The curve slope was particularly steep at 2 sun sunlight irradiance, with the final equilibrium temperature rising to approximately 120 °C at 2 sun sunlight irradiance, compared to only about 40 °C at 0.5 sun sunlight irradiance. This indicates that the photothermal conversion efficiency of the aerogel increases with increasing light intensity, efficiently converting light energy into heat energy. After 120 s, upon removal of light, all curves showed rapid cooling, and the cooling trends under different light intensities largely overlapped. This demonstrates that the aerogel has a weak heat retention effect and can rapidly release heat through thermal conduction / radiation in the absence of light, exhibiting good temperature reversibility.

[0118] like Figure 20 As shown in b, the 1.25% CNTs hydrophobic elastic aerogel reaches thermal equilibrium at 45℃ after approximately 120 seconds under 0.5 sun sunlight irradiance; the equilibrium temperature rises to 70℃ under 1 sun sunlight irradiance; and it stabilizes at 100℃ under 1.5 sun sunlight irradiance. At 2 sun sunlight irradiance, the heating rate is the fastest, reaching 129℃ within 120 seconds. After the light is removed, the aerogel cools rapidly, and the overlapping curves demonstrate good temperature reversibility. Thermal imaging visually presents the temperature distribution, with the highest temperature reaching 129.5℃. Compared to the 1% CNTs hydrophobic elastic aerogel, under the same light intensity, the 1.25% CNTs hydrophobic elastic aerogel exhibits a slightly higher heating rate and equilibrium temperature, indicating that increasing the CNT concentration enhances the photothermal effect and clearly demonstrating the regulatory value of concentration variables on photothermal performance.

[0119] like Figure 20 As shown in Figure c, the heating pattern of the 1.5% CNTs hydrophobic elastic aerogel is consistent with that of the 1% and 1.25% CNTs hydrophobic elastic aerogels. With increased light intensity, the heating rate accelerates, and the equilibrium temperature reaches 138℃ in approximately 120 seconds when the solar irradiance reaches 2 sun. After the light is removed, the temperature drops rapidly, and the overlapping curves demonstrate temperature reversibility. The highest temperature in the thermal image on the right is 138.2℃, verifying uniform heat distribution. Compared to low-concentration solar irradiance, the photothermal effect of the 1.5% CNTs hydrophobic elastic aerogel is further enhanced, indicating that the thermal conversion capability of CNTs continuously increases with concentration, supporting applications of photothermal conversion regulation.

[0120] ⑤ Temperature rise curve of multifunctional elastic aerogel during photoelectric-thermal conversion. (See figure) Figure 21 As shown, the thermal image shows a temperature range of 31.7℃-33.2℃ at 0s, mostly appearing as a low-temperature blue. At 60s, the temperature stabilizes at 32.4℃-33.5℃, still appearing blue. After 120s, due to the interaction of light and electricity, the temperature transitions to a higher-temperature color. Different combinations exhibit different heating rates and peak values. For example, the 1.5sun + 2V combination shows significant initial heating and a high peak value. The 1sun + 3V combination shows a slightly slower heating, falling between the two. The 0.5sun + 4V combination shows a slow initial heating but a high temperature later. The temperature-time curves show that after illumination, the purple line with a light intensity of 1.5sun heats up rapidly, becoming significantly higher than other curves around 100s. The orange curve corresponding to a light intensity of 0.5sun heats up slowly, with a low initial temperature. After energization, voltage superposition demonstrates the interaction between light intensity and voltage affecting temperature; the weak light and high voltage (0.5sun + 4V) combination later surpasses the 1sun + 3V combination. After all lights were turned off, the temperature dropped, but residual heat remained, reflecting the characteristics of heat retention and dissipation. Thermal imaging dynamically presented the spatial distribution of temperature, and the curve quantified the temperature change over time. It can be seen that light intensity and voltage jointly regulate the heating rate, peak value, and thermal stability. Strong light and low voltage resulted in rapid heating in the early stage, while weak light and high voltage could achieve higher temperatures in the later stage. The photoelectric synergistic effect significantly affects thermal behavior.

[0121] The effects of different solar light intensities and voltage intensities on the pump oil transfer rate of the hydrophobic elastic aerogel prepared in Example 1 were observed, and the results are shown in Table 1.

[0122] Table 1. Pump oil adsorption completion time of the hydrophobic elastic aerogel prepared in Example 1 under different solar light intensities and voltage intensities.

[0123] ;

[0124] In Table 1, " / " represents no data.

[0125] As shown in Table 1, under the baseline conditions of no sunlight and no applied voltage, the hydrophobic elastic aerogel prepared in Example 1 required 720 s to complete the oil adsorption process. With only 1 sun of light and no voltage, the adsorption time was significantly shortened to 216 s, with an efficiency increase of approximately 2.3 times, confirming that light energy can effectively promote the adsorption process. With no sunlight but an applied 4V voltage, the adsorption time was 180 s, indicating that electrical energy also has the ability to drive adsorption. When 0.5 sun of light and 6V voltage worked synergistically, the adsorption process was significantly accelerated, completing in only 54 s, with an efficiency increase of 12.3 times compared to the baseline conditions. Under the optimized combination of 1 sun of light and 4V voltage, adsorption was achieved within 60 s. With 1.5 sun of light and 2V voltage, the adsorption completion time was 63 s. The time-adsorption height line graphs for each experimental group perfectly matched the adsorption process image data on the left, visually presenting the dynamic changes in the adsorption process. This figure confirms that multifunctional aerogels exhibit significant advantages in the field of high-viscosity oil adsorption. The mechanism of action is as follows: under the synergistic stimulation of light and electricity, the temperature of the aerogel increases, which intensifies the thermal motion of pump oil molecules, thereby reducing the pump oil density, reducing fluid resistance, and ultimately significantly improving the pump oil adsorption rate.

[0126] (5) Performance test of multifunctional elastic hydrophilic aerogel adsorption of water-soluble organic dyes.

[0127] An experiment was conducted to investigate the filtration effect of a multifunctional elastic aerogel on methylene blue organic dye. A syringe was vertically fixed using a stand as the supporting frame, with a graduated cylinder placed below it. First, a hydrophilic aerogel was placed at the bottom of the syringe. Then, an organic solvent containing methylene blue was poured into the syringe. The aerogel's filtration properties allowed the organic solvent to permeate and filter. The filtration process was observed, and the filtered liquid was collected to explore the filtration efficiency of the hydrophilic aerogel on this organic solvent.

[0128] like Figure 22 As shown in Figure a, with increasing initial concentration, the adsorption capacity of the hydrophilic elastic aerogel initially increases rapidly, then the rate of increase slows down, reaching a relatively high value at a high concentration of 600 mg / L. The removal rate, however, shows a trend of initially increasing slightly, then continuously decreasing after reaching 200 mg / L. This indicates that at low concentrations, there are sufficient adsorption sites, making it easy to increase the removal rate; at high concentrations, the adsorption sites become saturated, making it difficult to adsorb newly added dyes, thus reducing the removal rate. Figure 22 As shown in b, the adsorption capacity of the hydrophilic elastic aerogel remained relatively stable in the first three cycles, indicating good initial adsorption performance and regenerability. From the fourth cycle onwards, the adsorption capacity gradually decreased with increasing cycle number. This was due to the multiple adsorption-desorption processes, which clogged the pores of the hydrophilic elastic aerogel, reduced the number of active sites, and weakened its adsorption capacity. The removal rate showed a consistent trend, maintaining almost 100% high-efficiency removal in the first three cycles, and then continuously decreasing with increasing cycle number. This reflects the cycling stability of the hydrophilic elastic aerogel: initially, it exhibits stable and efficient adsorption, but its performance gradually declines after long-term cycling, although this decline is not significant.

[0129] (6) Test on the windproof, positioning and oil absorption performance of elastic aerogel magnetization.

[0130] ① An illustration showing the directional movement of aerogels on a water surface controlled by a magnet. Hydrophobic and hydrophilic elastic aerogels were placed in a 10cm diameter glass culture dish filled with deionized water. A controllable magnetic field was applied using an external permanent magnet, causing them to move in a quasi-two-dimensional circular motion along the inner wall of the dish. Figure 23 As shown, due to the low density and superhydrophobic surface properties of hydrophobic elastic aerogels, they float on water and experience only minimal viscous drag during movement, exhibiting extremely strong responsiveness to magnets. (And...) Figure 23 (b) The low density and superhydrophilic surface properties of hydrophilic elastic aerogels allow water to penetrate their interior, making them float in water and move more smoothly than ( Figure 23 a) Hydrophobic elastic aerogels exhibit high viscous resistance but also show strong responsiveness to magnets.

[0131] ② The selective adsorption effect of hydrophobic aerogel on oil on a water surface under the control of a magnet. A hydrophobic elastic aerogel was placed in a glass petri dish (10cm in diameter) filled with deionized water. A controllable magnetic field was applied using an external permanent magnet, which attracted the hydrophobic aerogel to rapidly move towards a 0.5mL oil stain in the water. Figure 24 As shown, when the hydrophobic elastic aerogel comes into contact with the oil stain, it quickly and completely adsorbs the oil stain within 0.5 seconds, achieving a precise selective oil stain removal function.

[0132] ③ Graph showing the wind resistance effect of aerogel under the attraction of electromagnets generated by different voltages on the water surface. (See diagram) Figure 25 And Table 2. (As shown in Table 2) Figure 25 As shown in Figure a, when the output voltage is 4V, the maximum distance between the hydrophobic aerogel and the magnet is 6cm. Figure 25 As shown in Figure c, the maximum distance between the hydrophilic aerogel and the magnet is 4 cm, and all of them return to their original positions in about 20 seconds. Figure 25 b and Figure 25 As shown in d, when the output voltage is 24V, the maximum distance between the hydrophobic aerogel and the magnet is 9cm, and the maximum distance between the aqueous aerogel and the magnet is 7cm, both of which complete their return to their original positions in about 26s.

[0133] Table 2. Resistance of elastic aerogel to maximum wind speed under the action of non-uniform magnetic field generated by electromagnet at different voltages.

[0134] ;

[0135] Table 2 shows that both hydrophobic and hydrophilic elastic aerogels maintain excellent magnetic response capabilities under strong fluid disturbance environments, providing a new research paradigm for the precise control of intelligent composite materials. It also provides key parameters for developing wave-resistant magnetically controlled surface equipment, indicating that optimizing the magnetic field gradient can further improve positioning accuracy and response speed in complex hydrodynamic environments.

[0136] ④ A diagram illustrating the effect of hydrophilic elastic aerogel achieving magnetic self-positioning in water under the control of a magnet. (See diagram for example.) Figure 26 As shown, when the wind speed was 10.3 m / s and lasted for 22 seconds, the wind field was shut off. Then, the hydrophilic elastic aerogel gradually moved to its maximum distance after 9 seconds. Under the influence of the magnetic field, the hydrophilic elastic aerogel slowly returned to its original position, completing the magnetically controlled repositioning test after 31 seconds. This result confirms that the hydrophilic elastic aerogel maintains excellent magnetic response capabilities under strong fluid disturbance environments, providing key parameters for the development of wind and wave resistant magnetically controlled surface equipment. It also indicates that optimizing the magnetic field gradient can further improve positioning accuracy and response speed in complex hydrodynamic environments.

[0137] (7) Flame retardant performance test of elastic aerogel.

[0138] The hydrophobic elastic aerogel prepared in Example 1, after undergoing a limiting oxygen index (LOI) test, showed a LIO of 27%, classifying it as a flame-retardant material. Figure 27 As shown, the hydrophobic elastic aerogel exhibited instantaneous self-extinguishing properties after four consecutive 10-second vertical burning tests. Furthermore, it met the UL94 standard for material flammability rating V0. This indicates that the material possesses good fire resistance in typical fire-risk environments.

[0139] (8) Outdoor seawater desalination performance test of elastic aerogel.

[0140] A simulated seawater desalination experimental device was constructed using the hydrophilic elastic aerogel prepared in Example 4 as the core material. The experiment employed simulated seawater with a salt concentration of 3.5 wt%. The entire device was placed outdoors (coordinates 43°50'17"N, 126°32'59"E) and mainly consisted of the following components: the hydrophilic elastic aerogel, serving as the photothermal conversion and evaporation unit, was placed in a transparent container; an electronic balance was connected below the container to monitor mass changes; an infrared thermal imager was fixed by a bracket to capture the real-time temperature distribution on the aerogel surface; a thermometer, hygrometer, and an anemometer were used to record environmental parameters (temperature, humidity, and wind speed); and a laptop computer was used for data acquisition and analysis. During the experiment, simulated seawater came into contact with the aerogel. Under natural sunlight, the aerogel absorbed solar energy and converted it into heat energy, causing water to evaporate and produce water vapor. Subsequent condensation and collection of this vapor enabled seawater desalination.

[0141] like Figure 28Figure 'a' shows real-time data for wind speed, humidity, outdoor temperature, and maximum surface temperature. Around 2 PM, the surface temperature of the hydrophilic elastic aerogel reached its highest point of the day, at 43.9℃. Figure 28 Figure b shows real-time data on solar radiation intensity, water mass loss, and evaporation rate. The evaporation rate reaches its highest point of the day, at 4.34 kg·m³, around 2 PM. -2 ·h -1 .

Claims

1. A method for one-pot aqueous preparation of a photoelectric, thermo-magnetic, and biomass composite material with easily switchable wettability, characterized in that, The composite material is an elastic aerogel with a three-dimensional porous structure, and the elastic aerogel is switched in wettability by alkali treatment or methyltrimethoxysilane treatment. A one-pot aqueous preparation method for photoelectric, thermo-magnetic, and biomass composite materials with easily switchable wettability includes the following steps: S1. A nanocellulose suspension is prepared by bleaching lignocellulose biomass raw materials with sodium chlorite and then ultrasonically treating them. S2. Mix anhydrous ethanol, deionized water, and ammonia, and sonicate to obtain solution A. Mix tetraethyl orthosilicate and anhydrous ethanol, and sonicate to obtain solution B. Add solution A to solution B. After the reaction is complete, centrifuge, wash, and dry to obtain silica particles. S3. Add polyvinyl alcohol to deionized water and heat and stir until completely dissolved to obtain a polyvinyl alcohol solution. S4. Add chitosan and citric acid to deionized water in sequence, heat and stir until completely dissolved to obtain chitosan-citric acid mixture; S5. Carbon nanotubes and surfactants are added to deionized water and ultrasonically treated to obtain a carbon nanotube suspension. S6. After mixing the nanocellulose suspension of S1 with the silica particles of S2, add the nanocellulose suspension of S1 and methyltrimethoxysilane again, and stir to obtain the precursor solution. S7. Mix the polyvinyl alcohol solution of S3, the chitosan-citric acid mixture of S4, the carbon nanotube suspension of S5, and the precursor solution of S6 to prepare a mixture; weigh the iron oxide solid powder and add it to the mixture, stir evenly, and then transfer it into a mold for freezing. S8. After freeze-drying the mixture frozen in S7 along with the mold, place it in an oven for heat treatment. The freeze-drying temperature is -70~-50℃, and the heat treatment temperature is 80~120℃ to obtain a hydrophobic elastic aerogel. S9. Place the elastic hydrophobic aerogel of S8 into an alkaline solution for alkaline treatment to switch it to a hydrophilic elastic aerogel. Then, place the hydrophilic elastic aerogel into a methyltrimethoxysilane ethanol solution for treatment to switch it back to a hydrophobic elastic aerogel.

2. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: Both S1 and S5 involve ultrasonic treatment using an ultrasonic cell disruptor with a power of 800-1200W.

3. The aqueous one-pot preparation method of a photoelectric, thermo-magnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S2, the volume ratio of anhydrous ethanol, deionized water, and ammonia is 36~38:0.9~1.1:2.9~3.1, and the volume ratio of tetraethyl orthosilicate to anhydrous ethanol is 0.9~1.1:8.2~8.

4. Under slow stirring at 45℃, solution A was added to solution B in two batches, with a volume ratio of 3:1 between the two additions and a time interval of 1 hour.

4. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S3, the solid-liquid ratio of polyvinyl alcohol to deionized water is 0.95~1.05:19.5~20.5 g / mL.

5. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S4, the solid-liquid ratio (g / mL) of chitosan and citric acid to deionized water is 2.95~3.05:1.95~2.05:19.5~20.

5.

6. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S5, the solid-liquid ratio (g / mL) of carbon nanotubes, surfactant, and deionized water is 1.20~1.88:0.35~0.45:59.5~60.

5. The surfactant includes one or more of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium lauryl polyoxyethylene ether sulfate, and fatty acid salts.

7. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S6, the solid-liquid ratio (g / mL) of the nanocellulose suspension, silica particles, and methyltrimethoxysilane is 49.5~50.5:0.32~0.36:

3.

8. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S7, the volume ratio of polyvinyl alcohol solution, chitosan-citric acid mixture, carbon nanotube suspension and precursor solution is 7.45~7.55:7.45~7.55:59.5~60.5:49.5~50.5; the mass ratio of iron oxide solid powder to mixture is 0.09~0.11:

100.

9. The aqueous one-pot preparation method of a photoelectric, thermomagnetic, and biomass composite material with easily switchable wettability according to claim 1, characterized in that: In S9, the alkaline solution is a NaOH solution with a pH of 14, and the concentration of the methyltrimethoxysilane ethanol solution is 5-20 vol.

10. The application of the photoelectric, thermomagnetic, and hydrodynamic biomass composite material with easily switchable wettability prepared by the aqueous one-pot preparation method of the photoelectric, thermomagnetic, and hydrodynamic biomass composite material with easily switchable wettability as described in any one of claims 1-9, characterized in that: It is applied to high-efficiency, high-throughput oily wastewater separation, high-efficiency, high-throughput emulsion separation, photothermal and electrothermal conversion, flame retardancy and fire prevention, circulating oil adsorption-desorption, oil spill treatment, organic dye adsorption, seawater desalination, magnetically controlled windproof and displacement manipulation, and domestic sewage purification.

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