A hydrophobic nanocellulose / graphene / polyurea aerogel, and a preparation method and application thereof

Abstract

The application belongs to the technical field of environmental protection materials, and relates to an oil-water separation material, in particular to a hydrophobic nanocellulose / graphene / polyurea aerogel as well as a preparation method and application thereof. A nanocellulose suspension and a graphene solution are uniformly mixed to prepare a nanocellulose / graphene dispersion; poly-1,4-butanediol bis(4-aminobenzoate) and maleimide-modified diphenyl methane diisocyanate are added to the nanocellulose / graphene dispersion to spontaneously form a nanocellulose / graphene / polyurea aerogel; and a silane is used to form a hydrophobic layer on the surface of the nanocellulose / graphene / polyurea aerogel through chemical vapor deposition. The aerogel provided by the application has good oil-water separation performance; meanwhile, the unique internal structure and excellent mechanical stability can not only effectively separate simple oil-water mixtures, but also can deal with complex emulsified systems such as water-in-oil and oil-in-water, so as to realize multifunctional oil-water separation.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection materials technology, and relates to oil-water separation materials, specifically to a hydrophobic nanocellulose / graphene / polyurea aerogel, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the acceleration of global industrialization, the extraction, transportation, and use of oil have become increasingly frequent, resulting in oil spills that pose a serious threat to marine and terrestrial ecosystems. Effectively controlling oil pollution and protecting aquatic ecosystems and public health has become an urgent environmental issue.

[0004] Polyurea aerogel, a high-performance organic aerogel, is produced through the addition reaction of isocyanates and amino compounds and a self-foaming process. It possesses advantages such as high porosity, low thermal conductivity, hydrophobicity, and low degassing properties. However, pure polyurea aerogel has limitations such as insufficient mechanical strength, restricting its application in complex environments.

[0005] Therefore, developing a composite aerogel that combines good mechanical properties, hydrophobic and oleophilic characteristics, and additional functions (such as photothermal effect) is of great significance for efficient oil-water separation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a hydrophobic nanocellulose / graphene / polyurea aerogel, its preparation method, and its applications. The aerogel provided by the present invention exhibits excellent oil-water separation performance, including both filtration and absorption separation methods. Furthermore, its unique internal structure combined with superior mechanical stability enables it to effectively separate not only simple oil-water mixtures but also complex emulsion systems such as water-in-oil and oil-in-water emulsions, thereby achieving multifunctional oil-water separation.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, a method for preparing a hydrophobic nanocellulose / graphene / polyurea aerogel includes the following steps:

[0009] A nanocellulose / graphene dispersion was prepared by uniformly mixing a nanocellulose suspension with a graphene solution.

[0010] Poly(1,4-butanediol bis(4-aminobenzoate)) (PBBA) and maleimide-modified diphenylmethane diisocyanate (CDMDI) were added to a nanocellulose / graphene dispersion to form a nanocellulose / graphene / polyurea aerogel through self-foaming.

[0011] A hydrophobic layer is formed on the surface of the nanocellulose / graphene / polyurea aerogel by chemical vapor deposition using silane.

[0012] In PBBA, the poly(1,4-butanediol) chains act as "flexible spacer arms" or "soft segments," introduced into the polymer backbone. Under stress, these flexible segments can dissipate energy through rotation and extension, significantly improving the aerogel's flexibility and impact resistance while reducing brittleness. This allows the aerogel to maintain a certain strength while better recovering its deformation capacity. In traditional polyurea aerogels, the reactions of -NCO with -NH2 and -NCO with H2O occur almost simultaneously and are extremely rapid, making the reaction process difficult to control and prone to uneven bubble formation, structural collapse, or cracking. The carbon-carbon double bond (C=C) of maleimide in CDMDI has lower reactivity with amines at room temperature than the -NCO group. In the initial mixing stage, the rapid reaction between -NCO on CDMDI and -NH2 on PBBA forms the polyurea network gel. Simultaneously, the reaction heat generated when -NCO reacts with -NH2 triggers the C=C on maleimide to react with the remaining -NH2 in the system, undergoing additional, mild post-crosslinking and curing to further enhance the network. Finally, water is controllably introduced to react with the remaining small amount of -NCO. The mechanical strength of the polyurea aerogel is increased by adding nanocellulose; graphene is added to give the aerogel photothermal conversion properties; and finally, hydrophobic modification is performed using silane via chemical vapor deposition to reduce the surface energy of the polyurea aerogel, thereby giving it high oil-water separation performance. Furthermore, research has found that in the material system prepared in this invention, the addition of graphene not only gives the aerogel photothermal conversion properties but also further increases its hydrophobic and mechanical properties; simultaneously, nanocellulose also further enhances the hydrophobic properties of the aerogel.

[0013] Secondly, a hydrophobic nanocellulose / graphene / polyurea aerogel is obtained by the preparation method described in the first aspect of this invention.

[0014] Thirdly, the application of the hydrophobic nanocellulose / graphene / polyurea aerogel described in the second aspect of the present invention in oil-water separation.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) The hydrophobic nanocellulose / graphene / polyurea aerogel provided by the present invention has low density and specific surface area, high hydrophobicity (WCA>146°), high photothermal conversion efficiency (>89%) and excellent mechanical properties, and can therefore be used as an environmentally friendly oil-water separation material.

[0017] (2) The addition of nanocellulose in this invention greatly enhances the mechanical strength of the polyurea aerogel, provides it with more adsorption active sites and superior binding affinity; graphene enables the polyurea aerogel to possess photothermal conversion properties; the addition of methyltrimethoxysilane endows the polyurea aerogel with low surface energy, enabling it to separate oil and water. This aerogel can not only be used for conventional oil-water mixture separation, but its photothermal properties also allow it to actively reduce the viscosity of heavy oils such as crude oil under light irradiation, thereby improving adsorption efficiency and making it suitable for processing complex oil products.

[0018] (3) This invention uses renewable nanocellulose as one of the main raw materials, which reduces costs and conforms to the concept of sustainable development. The preparation process is simple, requires no complex equipment, and is easy to scale up. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a scanning electron microscope image of the nanocellulose / graphene / polyurea aerogel prepared in Example 3 of the present invention.

[0021] Figure 2 Thermogravimetric analysis (TGA) diagrams of the nanocellulose / graphene / polyurea aerogel, hydrophobic nanocellulose / graphene / polyurea aerogel, and nanocellulose / polyurea aerogel prepared in Example 3 and Comparative Example 1, respectively; (1) is the hydrophobic nanocellulose / graphene / polyurea aerogel prepared in Example 3, (2) is the nanocellulose / graphene / polyurea aerogel prepared in Example 3, and (3) is the nanocellulose / polyurea aerogel prepared in Comparative Example 1.

[0022] Figure 3 This is a graph showing the absorption capacity of the hydrophobic nanocellulose / graphene / polyurea aerogel prepared in Example 3 of the present invention for different organic solvents.

[0023] Figure 4Images shown are taken under an optical microscope before and after the adsorption of water-in-oil and oil-in-water emulsions by the hydrophobic nanocellulose / graphene / polyurea aerogel prepared in Example 3 of this invention; A is a photograph of the benzene-in-water (X / W) emulsion before (left) adsorption and after (right) adsorption; a is an electron microscope image of the benzene-in-water (X / W) emulsion before adsorption; a' is an electron microscope image of the benzene-in-water (X / W) emulsion after adsorption; B is a photograph of the emulsion before (left) adsorption and after (right) adsorption; b is an electron microscope image of the dichloromethane-in-water (T / W) emulsion before adsorption; b' Image 1 shows an electron microscope (EM) image of a water-in-water (T / W) emulsion after adsorption; image 2 shows an EEM image of a benzene-in-water (W / X) emulsion before adsorption (left) and after adsorption (right); image 3 shows an EEM image of a benzene-in-water (W / X) emulsion before adsorption; image 4 shows an EEM image of a benzene-in-water (W / X) emulsion after adsorption; image 5 shows an EEM image of a dichloromethane-in-water (W / T) emulsion before adsorption (left) and after adsorption (right); image 6 shows an EEM image of a dichloromethane-in-water (W / T) emulsion before adsorption; image 7 shows an EEM image of a dichloromethane-in-water (W / T) emulsion after adsorption. Figure 2 Chloromethane in water (T / W).

[0024] Figure 5 The change in crude oil viscosity on the surface of hydrophobic nanocellulose / graphene / polyurea aerogel as temperature increases. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] Given that polyurea aerogels have limitations such as limited mechanical strength and insufficient high-temperature stability, making them difficult to use for efficient oil-water separation, this invention proposes a hydrophobic nanocellulose / graphene / polyurea aerogel, its preparation method, and its applications.

[0028] A typical embodiment of the present invention provides a method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel, comprising the following steps:

[0029] A nanocellulose / graphene dispersion was prepared by uniformly mixing a nanocellulose suspension with a graphene solution.

[0030] Poly(1,4-butanediol bis(4-aminobenzoate)) and maleimide-modified diphenylmethane diisocyanate were added to a nanocellulose / graphene dispersion to form a nanocellulose / graphene / polyurea aerogel through self-foaming.

[0031] A hydrophobic layer is formed on the surface of the nanocellulose / graphene / polyurea aerogel by chemical vapor deposition using silane.

[0032] In some embodiments, the nanocellulose in the nanocellulose suspension is wheat straw-based nanocellulose. Specifically, the wheat straw-based nanocellulose is obtained by homogenizing wheat straw pulp through a high-pressure microfluidic jet.

[0033] In some embodiments, the nanocellulose suspension and graphene solution are mixed and then homogenized by ultrasonication and stirring to obtain a nanocellulose / graphene dispersion. The graphene solution mentioned in this invention refers to a stable suspension formed by uniformly dispersing graphene in water.

[0034] Specifically, the concentration of the nanocellulose suspension is 0.1–2 wt%. Studies have shown that the concentration of the nanocellulose suspension also affects the hydrophobic properties of the aerogel; when the concentration of the nanocellulose suspension is 0.8–1.2 wt% or 0.9–1.1 wt%, the prepared aerogel has better hydrophobic properties.

[0035] Specifically, the concentration of the graphene solution is 0.1~0.5wt%.

[0036] Specifically, the mass ratio of nanocellulose suspension to graphene solution is 2.7~3.3:0.9~1.1.

[0037] In some embodiments, the mass ratio of nanocellulose in the nanocellulose suspension to graphene in the graphene solution is 0.3~6:0.1~0.5. Studies have shown that the concentration of the nanocellulose suspension also affects the hydrophobic properties of the aerogel, and the concentration of the nanocellulose suspension affects the amount of nanocellulose added. When the mass ratio of nanocellulose to graphene is 2.4~3.6:0.1~0.5 or 2.7~3.3:0.1~0.5, the prepared aerogel has better hydrophobic properties.

[0038] In some embodiments, the mass ratio of poly(1,4-butanediol bis(4-aminobenzoate), maleimide-modified diphenylmethane diisocyanate, nanocellulose suspension and graphene solution is 7:2.7~3.3:2.7~3.3:0.9~1.1.

[0039] In some embodiments, the mass ratio of poly(1,4-butanediol bis(4-aminobenzoate), maleimide-modified diphenylmethane diisocyanate, nanocellulose in the nanocellulose suspension, and graphene in the graphene solution is 7:2.7~3.3:0.003~0.06:0.001~0.005. When the mass ratio is 7:2.7~3.3:0.024~0.036:0.001~0.005 or 7:2.7~3.3:0.027~0.033:0.001~0.005, the prepared aerogel exhibits better hydrophobic properties.

[0040] In some embodiments, poly(1,4-butanediol bis(4-aminobenzoate)) is first added to the nanocellulose / graphene dispersion and stirred for a set time, followed by the addition of maleimide-modified diphenylmethane diisocyanate and stirring. The mixture is then poured into a mold and allowed to stand for self-foaming. Specifically, the stirring time for adding poly(1,4-butanediol bis(4-aminobenzoate)) is 0.9–1.1 min. Specifically, the stirring time for adding maleimide-modified diphenylmethane diisocyanate is 1.8–2.2 min.

[0041] In some embodiments, the chemical vapor deposition process is carried out at a temperature of 70-90 °C for 5.5-6.5 h.

[0042] In some embodiments, the silane is methyltrimethoxysilane, dichlorosilane, or monomethylsilane. Studies have shown that when the silane is methyltrimethoxysilane, the prepared aerogel exhibits better hydrophobic properties.

[0043] Another embodiment of the present invention provides a hydrophobic nanocellulose / graphene / polyurea aerogel, which is obtained by the above preparation method.

[0044] A third embodiment of the present invention provides an application of the above-mentioned hydrophobic nanocellulose / graphene / polyurea aerogel in oil-water separation.

[0045] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0046] The method for preparing the nanocellulose suspension used in the following examples is as follows:

[0047] Take 50 g of oven-dried wheat straw and place it in a polyethylene bag. Add 300 ml of alkaline solution (the total alkalinity of the solution is 22% of the oven-dried wheat straw, and the alkali is formed by mixing sodium carbonate and sodium hydroxide in a molar ratio of 4:6). Knead repeatedly to ensure the wheat straw is evenly soaked in the alkaline solution. Transfer the pre-soaked wheat straw to a small cooking tank, tighten the lid, and expel the air from the tank by repeatedly filling and venting it three times. Finally, introduce O2 and maintain the initial oxygen pressure at 0.8 MPa. Fix the small cooking tank in an electric cooking pot and keep it at 130℃ for 3 hours. After the heat treatment, collect the pulp in the tank, wash the pulp several times until the washing liquid is neutral, and sieve the fine pulp through a flat plate pulping machine. This is the desired wheat straw pulp.

[0048] The obtained wheat straw slurry was processed by a high-pressure microfluidic homogenizer. First, it was passed through a tube with a pore size of 200 μm 10 times, and then through a tube with a pore size of 87 μm 5 times to obtain the nanocellulose suspension. It was then stored in a medical freezer (YC-260L) for later use at a storage temperature of about 4 ℃.

[0049] Example 1

[0050] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel, comprising the following steps:

[0051] (1) Take 3 g of nanocellulose suspension with a concentration of 1 wt% and mix it with 1 g of graphene solution with a concentration of 0.1 wt%. Obtain a uniform nanocellulose / graphene dispersion by ultrasound and vigorous stirring.

[0052] (2) 7 g of PBBA and 3 g of CDMDI (WANNATE® CDMDI-100L Shanghai Zhenzhi Chemical Technology Co., Ltd.) were added sequentially to the nanocellulose / graphene dispersion obtained in step (1), and nanocellulose / graphene / polyurea aerogel was formed by self-foaming under stirring.

[0053] (3) The nanocellulose / graphene / polyurea aerogel obtained in step (2) and methyltrimethoxysilane were subjected to chemical vapor deposition at 70 °C for 6 h, and then placed in a vacuum drying oven for further processing to obtain hydrophobic nanocellulose / graphene / polyurea aerogel.

[0054] Example 2

[0055] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, which differs from Example 1 in that: the concentration of graphene solution added in step (1) is 0.2wt%, and other experimental parameters and conditions are the same as in Example 1.

[0056] Example 3

[0057] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, differs in that: the concentration of graphene solution added in step (1) is 0.3 wt%, while other experimental parameters and conditions are the same as in Example 1. The aerogel prepared in this example is as follows: Figure 1 As shown, its thermogravimetric analysis results are as follows: Figure 2 As shown.

[0058] Example 4

[0059] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, which differs from Example 1 in that: the concentration of graphene solution added in step (1) is 0.5wt%, and other experimental parameters and conditions are the same as in Example 1.

[0060] Example 5

[0061] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, is as follows: in step (1), the concentration of nanocellulose suspension is changed from 1 wt% to 0.5 wt%, and other experimental parameters and conditions are the same as in Example 1.

[0062] Example 6

[0063] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, is that in step (1), the concentration of nanocellulose suspension is changed from 1 wt% to 1.5 wt%, and other experimental parameters and conditions are the same as in Example 1.

[0064] Example 7

[0065] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, is that in step (1), the concentration of nanocellulose suspension is changed from 1 wt% to 2 wt%, and other experimental parameters and conditions are the same as in Example 1.

[0066] Example 8

[0067] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, is that in step (3), silane is replaced with dichlorosilane, and other experimental parameters and conditions are the same as in Example 1.

[0068] Example 9

[0069] A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel for oil-water separation, compared with Example 1, is that in step (3), silane is replaced with monomethylsilane, and other experimental parameters and conditions are the same as in Example 1.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that in step (1), 1 g of graphene solution was replaced with 1 g of deionized water, and other experimental parameters and conditions were the same as in Example 1.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that: in step (1), no nanocellulose suspension and graphene solution are added, and deionized water is used instead of nanocellulose and graphene solution to keep the total liquid volume consistent. Other experimental parameters and conditions are the same as in Example 1.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that in step (1), the nanocellulose suspension was replaced with 3 g of deionized water, the mass remained unchanged, and other experimental parameters and conditions were the same as in Example 1.

[0076] The performance of the prepared hydrophobic nanocellulose / graphene / polyurea aerogel was tested, and the results are shown in the table below.

[0077] Table 1 Performance Test Results

[0078] Contact Angle (WCA) Photothermal conversion efficiency (%) High recovery rate after one compression (%, compressed to 40%) High recovery rate (%) after 60 compressions, each compression to 40% Example 1 148° 89 99.115 96.143 Example 2 147° 90 99.394 95.634 Example 3 148° 93 98.994 95.838 Example 4 146° 97 99.024 96.025 Example 5 138° 93 99.115 94.08 Example 6 125° 91 98.994 93.838 Example 7 119° 90 98.055 93.753 Example 8 132° 93 97.263 91.928 Example 9 128° 91 97.359 92.045 Comparative Example 1 133° 11 97.365 92.945 Comparative Example 2 143° 13 98.541 94.086 Comparative Example 3 128° 93 97.134 92.512

[0079] As shown in Table 1, the hydrophobic nanocellulose / graphene / polyurea aerogels prepared in Examples 1-4 exhibit excellent hydrophobicity (WCA>146°), high photothermal conversion efficiency (>89%), and outstanding mechanical properties, significantly superior to the comparative samples without graphene. The content of the nanocellulose suspension has a certain impact on the hydrophobicity of the samples. Different silanes result in different contact angles. The hydrophobic cellulose / graphene / polyurea aerogels in Examples 1-4 successfully achieve a balance between high hydrophobicity, excellent photothermal performance, and superior mechanical strength and elasticity.

[0080] Oil absorption rate test experiment

[0081] To verify the oil absorption efficiency of hydrophobic cellulose / graphene / polyurea aerogel for different oils or organic substances, the specific method is as follows: A series of oils and organic solvents were selected and allowed to fully contact for 3 minutes. The samples were then removed, placed vertically, and allowed to stand for 10 seconds to allow residual droplets to drain. The mass change before and after adsorption was measured using a precision electronic balance with an accuracy of 0.1 g. The adsorption capacity (Q) was calculated according to the following formula:

[0082] Q = (m t -m i ) / m i ;

[0083] Where Q represents the adsorption capacity (g / g), that is, the amount of oil adsorbed per unit mass of adsorbent; m t It is the mass (g) of the wet sample after adsorption, m i It is the mass (g) of the dry sample before adsorption.

[0084] The oil absorption tests were performed on the samples from Example 3 for dichloromethane, ethanol, isopropanol, n-hexane, ethyl acetate, toluene, N,N-dimethylformamide, xylene, petroleum, diesel, and soybean oil, respectively. The results are shown in Table 2 below. Figure 3 As shown.

[0085] Table 2 Oil Absorption Test Results

[0086]

[0087] The oil absorption test results in Table 2 show that the hydrophobic cellulose / graphene / polyurea aerogel exhibits a high adsorption capacity (12.22-21.7 g / g) for various oils and organic solvents, and belongs to the category of high-performance oil-absorbing materials.

[0088] Four emulsions were prepared using benzene, dichloromethane, and water: benzene-in-water (X / W), dichloromethane-in-water (T / W), water-in-benzene (W / X), and water-in-dichloromethane (W / T), respectively. These four emulsions were then adsorbed onto the nanocellulose / graphene / polyurea aerogel prepared in Example 3. The results are as follows: Figure 4 As shown in A, a, a', B, b, b', C, c, c', D, d, and d', after the separation process, the dense oil droplets in the four emulsions completely disappeared, indicating that the nanocellulose / graphene / polyurea aerogel can handle complex emulsion systems such as water-in-oil and oil-in-water, and achieve multifunctional oil-water separation.

[0089] The viscosity of crude oil as temperature increases was measured using a viscometer, and the results are as follows: Figure 5As shown, the viscosity of crude oil decreases with increasing temperature. The data from the above embodiments demonstrate that the nanocellulose / graphene / polyurea aerogel provided by this invention has excellent photothermal conversion efficiency. Therefore, this nanocellulose / graphene / polyurea aerogel can actively reduce the viscosity of heavy oils such as crude oil under light irradiation, thereby improving adsorption efficiency.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing hydrophobic nanocellulose / graphene / polyurea aerogel, characterized in that, Includes the following steps: A nanocellulose / graphene dispersion was prepared by uniformly mixing a nanocellulose suspension with a graphene solution. Poly(1,4-butanediol bis(4-aminobenzoate)) and maleimide-modified diphenylmethane diisocyanate were added to a nanocellulose / graphene dispersion to form a nanocellulose / graphene / polyurea aerogel through self-foaming. A hydrophobic layer is formed on the surface of the nanocellulose / graphene / polyurea aerogel by chemical vapor deposition using silane; The concentration of the nanocellulose suspension is 0.1-2 wt%; the concentration of the graphene solution is 0.1-0.5 wt%; and the mass ratio of the nanocellulose suspension to the graphene solution is 2.7-3.3:0.9-1.

1.

2. The preparation method according to claim 1, characterized in that, The nanocellulose in the nanocellulose suspension is wheat straw-based nanocellulose.

3. The preparation method according to claim 1, characterized in that, The nanocellulose suspension was mixed with the graphene solution, and then ultrasonicated and stirred to obtain a nanocellulose / graphene dispersion.

4. The preparation method according to claim 1, characterized in that, The mass ratio of poly(1,4-butanediol bis(4-aminobenzoate), maleimide-modified diphenylmethane diisocyanate, nanocellulose suspension and graphene solution is 7:2.7~3.3:2.7~3.3:0.9~1.

1.

5. The preparation method according to claim 1, characterized in that, First, add poly(1,4-butanediol bis(4-aminobenzoate)) to the nanocellulose / graphene dispersion and stir for a set time. Then, add maleimide-modified diphenylmethane diisocyanate and stir. Finally, pour the mixture into a mold and let it stand to allow it to self-foam.

6. The preparation method according to claim 1, characterized in that, In chemical vapor deposition, the processing temperature is 70~90℃ and the processing time is 5.5~6.5 h.

7. The preparation method according to claim 1, characterized in that, The silane is methyltrimethoxysilane, dichlorosilane, or monomethylsilane.

8. A hydrophobic nanocellulose / graphene / polyurea aerogel, characterized in that, Obtained by any of the preparation methods described in claims 1 to 7.

9. The application of the hydrophobic nanocellulose / graphene / polyurea aerogel according to claim 8 in oil-water separation.

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