Bamboo-based gradient aerogels and hydrophobic bamboo-based gradient aerogels, methods of making and applications

Abstract

The present application relates to the technical field of gradient aerogel, and particularly relates to a bamboo-based gradient aerogel, a hydrophobic bamboo-based gradient aerogel, a preparation method and application. The preparation method of the bamboo-based gradient aerogel comprises the following steps: (1) contacting bamboo with an acetic acid buffer solution containing 0.1-2wt% NaClO2, and the contacting conditions include a temperature of 50-90 DEG C; (2) freeze-drying the bamboo obtained in step (1) to obtain a gradient aerogel. The gradient aerogel is prepared by partially removing lignin and hemicellulose in the bamboo and then freeze-drying; the gradient aerogel retains a natural anisotropic structure and has high mechanical strength, efficient heat insulation, noise reduction and other performances.

Description

Technical Field

[0001] The present invention relates to the technical field of gradient aerogels, and in particular to a bamboo-based gradient aerogel and a hydrophobic bamboo-based gradient aerogel, as well as a preparation method and application thereof. Background Art

[0002] Aerogels have the characteristics of low density and high porosity, and have broad application prospects in the fields of energy storage, sensing, catalysis, thermal insulation, wastewater treatment, etc. Among them, compared with traditional homogeneous structure aerogels, gradient structure aerogels show obvious advantages in air filtration, sound absorption and other fields. Cellulose aerogel materials not only have the above basic characteristics of aerogels, but are also renewable and biodegradable, making them widely concerned. However, due to the cumbersome process and low reproducibility of traditional sedimentation or layer-by-layer methods, the preparation of cellulose gradient aerogels still faces challenges. Bamboo has the advantages of fast growth rate and natural gradient structure. Therefore, the preparation of natural gradient aerogels from bamboo can not only promote the "replacing plastic with bamboo", but also realize the application of cheap biomass in industries such as construction, thermal insulation, and oil absorption. Summary of the Invention

[0003] The present invention provides a bamboo-based gradient aerogel, a preparation method thereof, and an application thereof. The gradient aerogel is prepared by partially removing lignin and hemicellulose from bamboo material and then freeze-drying the material. The aerogel retains a natural anisotropic structure and has properties such as high mechanical strength, high-efficiency heat insulation, and noise reduction.

[0004] In order to achieve the above object, the first aspect of the present invention provides a bamboo-based gradient aerogel, which comprises a high-density layer, a medium-density layer and a low-density layer;

[0005] The density of the high-density layer is 0.075-0.1g / cm 3 ;

[0006] The density of the medium density layer is 0.06-0.075g / cm 3 ;

[0007] The density of the low-density layer is 0.04-0.06g / cm 3 .

[0008] A second aspect of the present invention provides a method for preparing a bamboo-based gradient aerogel, the method comprising the following steps:

[0009] (1) contacting the bamboo material with an acetic acid buffer solution containing 0.1-10 wt% NaClO2;

[0010] (2) freeze-drying the bamboo material obtained in step (1) to obtain a gradient aerogel.

[0011] A third aspect of the present invention provides a hydrophobic bamboo-based gradient aerogel, which comprises the bamboo-based gradient aerogel of the present invention and a hydrophobic substance loaded on the bamboo-based gradient aerogel.

[0012] A fourth aspect of the present invention provides a method for preparing the hydrophobic bamboo-based gradient aerogel, the method comprising the following steps:

[0013] The hydrophobic material is loaded onto the bamboo-based gradient aerogel according to any one of claims 1 to 3 by chemical vapor deposition.

[0014] A fifth aspect of the present invention provides an application of the bamboo-based gradient aerogel of the present invention or the hydrophobic bamboo-based gradient aerogel of the present invention in the fields of thermal insulation, noise reduction and oil absorption.

[0015] Through the above technical solution, the preparation method provided by the present invention maintains the natural gradient structure of bamboo to produce bamboo-based gradient aerogel. The bamboo-based aerogel of the present invention retains the natural anisotropic structure of bamboo and has high mechanical strength, efficient thermal insulation, noise reduction and other properties, and is elastic. The bamboo-based gradient aerogel has broad application prospects in thermal insulation, noise reduction, construction and other fields.

[0016] Bamboo-based gradient aerogel was modified by chemical vapor deposition to prepare hydrophobic bamboo-based gradient aerogel. The hydrophobic bamboo-based gradient aerogel has obvious hydrophobicity and strong adsorption capacity for oils such as chloroform. The oil absorption performance of the hydrophobic bamboo-based gradient aerogel is reversible. After 10 adsorption-desorption cycles, it still maintains a strong oil absorption capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a tensile performance test diagram of the gradient aerogel prepared in Example 1;

[0018] Figure 2 is a scanning electron microscope (SEM) image of the cross section of the gradient aerogel prepared in Example 1;

[0019] Figure 3 is a scanning electron microscope (SEM) image of the medium density layer of the gradient aerogel prepared in Example 1;

[0020] Figure 4 is a scanning electron microscope (SEM) image of the medium density layer of the gradient aerogel prepared in Example 1;

[0021] Figure 5 This is a contact angle test diagram of the hydrophobic gradient aerogel prepared in Example 1. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] In the present invention, the high-density layer density refers to the aerogel density range of 0.075-0.1g / cm 3 The average density of the high-density layer;

[0024] The density of the medium density layer refers to the aerogel density range of 0.06-0.075g / cm 3 The average density of the medium-density layer;

[0025] Low density layer density refers to the aerogel density range of 0.04-0.06g / cm 3 The average density of the low-density layer.

[0026] In the present invention, the method for testing each density layer of the bamboo-based gradient aerogel is as follows: the gradient aerogel is evenly divided into at least 3 layers, preferably 3-6 layers, and the density of each layer is tested separately. The mass of the aerogel is weighed by an analytical balance and recorded as m. The length, width and height are respectively measured with a vernier caliper to calculate the volume V. The density is calculated according to the formula ρ = m / V.

[0027] A first aspect of the present invention provides a bamboo-based gradient aerogel, which comprises a high-density layer, a medium-density layer and a low-density layer;

[0028] The density of the high-density layer is 0.075-0.1g / cm 3 ;

[0029] The density of the medium density layer is 0.06-0.075g / cm 3 ;

[0030] The density of the low-density layer is 0.04-0.06g / cm 3 .

[0031] The bamboo-based gradient aerogel of the present invention retains the natural anisotropic structure of bamboo, has high mechanical strength, high-efficiency heat insulation, noise reduction and other properties, and is elastic.

[0032] According to a preferred embodiment of the present invention, the density of the high-density layer is 0.083-0.094 g / cm 3 .

[0033] According to a preferred embodiment of the present invention, the density of the medium density layer is 0.065-0.068 g / cm3 .

[0034] According to a preferred embodiment of the present invention, the density of the low-density layer is 0.049-0.055 g / cm 3 .

[0035] According to a preferred embodiment of the present invention, in terms of mass percentage, the cellulose content of the bamboo-based gradient aerogel is 65wt%-75wt%, the hemicellulose content is 11wt%-16wt%, the lignin content is 1wt%-7wt%, and the content of other substances is 10-20wt%.

[0036] In the present invention, the other substances include at least one of starch, pectin, ash and amino acids.

[0037] According to a preferred embodiment of the present invention, the radial thermal conductivity of the bamboo-based gradient aerogel is 0.03-0.055 W·m -1 ·K -1 .

[0038] According to a preferred embodiment of the present invention, the axial thermal conductivity of the bamboo-based gradient aerogel is 0.035-0.05 W·m -1 ·K -1 .

[0039] According to a preferred embodiment of the present invention, the bamboo-based gradient aerogel has an axial mechanical strength of 0.15-0.28 MPa and a radial mechanical strength of 0.15-0.25 MPa.

[0040] A second aspect of the present invention provides a method for preparing a bamboo-based gradient aerogel, the method comprising the following steps:

[0041] (1) contacting the bamboo material with an acetic acid buffer solution containing 0.1-10 wt% NaClO2;

[0042] (2) freeze-drying the bamboo material obtained in step (1) to obtain a gradient aerogel.

[0043] The present invention performs delignification and hemicellulose removal on block bamboo by the aforementioned method, removes most of the hemicellulose and lignin in the bamboo, retains the natural gradient structure of the bamboo, and then freeze-dries the delignified bamboo to obtain gradient aerogel.

[0044] In the present invention, a NaClO2 acetic acid buffer solution is used to perform delignification and hemicellulose treatment on bamboo, so that the cellulose content of the delignified and hemicellulose-treated bamboo is 65-75wt%, the hemicellulose content is 11-16wt%, and the lignin content is 1-7wt%, thereby ensuring that the natural gradient structure of the bamboo is retained.

[0045] In the present invention, as long as the cellulose content of the bamboo material after delignification and hemicellulose is ensured to be 65-75wt%, the hemicellulose content is 11-16wt%, and the lignin content is 1-7wt%, there is no particular limitation on the content of other substances, as long as the total content of other substances is within the range of 10-20wt%.

[0046] In the present invention, other substances refer to substances other than cellulose, lignin and hemicellulose that are not removed after the bamboo is treated by the method described in the present invention, such as starch, pectin, ash and amino acids.

[0047] In the present invention, there is no particular limitation on the bamboo raw material. Preferably, the bamboo raw material used has a cellulose content of 42-48 wt%, a lignin content of 7-12 wt%, a hemicellulose content of 26-33 wt%, and a content of other substances of 13-22 wt%.

[0048] According to a preferred embodiment of the present invention, for safety reasons, in step (1), the concentration of NaClO2 in the solution is 0.1-2 wt%.

[0049] According to a preferred embodiment of the present invention, the contact conditions include: a temperature of 50-90°C.

[0050] According to a preferred embodiment of the present invention, in step (1), the solid-liquid mass ratio is 1:5-20.

[0051] The acetate buffer solution refers to a buffer solution containing acetic acid and sodium acetate. According to a preferred embodiment of the present invention, in step (1), the pH value of the acetate buffer solution is 4-5.

[0052] According to a preferred embodiment of the present invention, in step (1), the contact conditions include: temperature of 50-90° C. and time of 0.5-3 h.

[0053] According to a preferred embodiment of the present invention, after the contact reaction, deionized water is used for washing until the conductivity is 0.

[0054] According to a preferred embodiment of the present invention, in step (2), the freeze-drying conditions include: a temperature of -60--90°C and a pressure of 0.0001-0.01Pa.

[0055] A third aspect of the present invention provides a hydrophobic bamboo-based gradient aerogel, which comprises the bamboo-based gradient aerogel of the present invention and a hydrophobic substance loaded on the bamboo-based gradient aerogel.

[0056] According to a preferred embodiment of the present invention, in the hydrophobic bamboo-based gradient aerogel, the hydrophobic substance accounts for 6.00-7.10 wt % of the hydrophobic bamboo-based gradient aerogel.

[0057] According to a preferred embodiment of the present invention, the hydrophobic substance is selected from one or more methoxysilane compounds.

[0058] According to a preferred embodiment of the present invention, the hydrophobic substance is selected from one or more methoxysilane compounds, preferably methyltrimethoxysilane.

[0059] According to a preferred embodiment of the present invention, the contact angle of the hydrophobic bamboo-based gradient aerogel is 153-156°.

[0060] According to a preferred embodiment of the present invention, the hydrophobic bamboo-based gradient aerogel has an adsorption capacity of chloroform of 49-57 g / g aerogel.

[0061] A fourth aspect of the present invention provides a method for preparing a hydrophobic bamboo-based gradient aerogel, the method comprising the following steps:

[0062] The hydrophobic material is loaded onto the bamboo-based gradient aerogel according to any one of claims 1 to 3 by chemical vapor deposition.

[0063] According to a preferred embodiment of the present invention, the chemical vapor deposition conditions include: temperature of 70-100° C., time of 5-10 h, and pressure of 0.07-0.09 Pa.

[0064] A fifth aspect of the present invention provides an application of the bamboo-based gradient aerogel or the hydrophobic bamboo-based gradient aerogel in the fields of thermal insulation, noise reduction and oil absorption.

[0065] In the present invention, the contact angle test method includes the following: water contact angle parameters are measured using a drop shape analyzer (Kruss DSA10, Kruss, Germany) in static contact angle measurement mode. A fixed volume of 4 μL of water droplet is dropped onto the sample surface, photographed, and the contact angle is calculated using software. Seven parallel measurements are performed, and the average value is calculated.

[0066] The thermal conductivity test method includes: In the following examples, the thermal conductivity is tested using a thermal conductivity meter (Hot Disk TPS2500S, Hot Disk, Sweden). Hot Disk measures the thermal conductivity of a block gradient aerogel sample at 25°C in accordance with the international standard ISO 22007-2. Two pieces of aerogel of the same size (20*20*5mm) are clamped around the thermal conductivity probe.

[0067] The method for testing the chloroform adsorption capacity of the hydrophobic bamboo-based gradient aerogel includes the following: The saturated oil phase adsorption capacity and the saturated oil phase adsorption capacity after 10 cycles are tested in the following examples: the gradient aerogel is placed in a 40°C oven for 1 hour, the mass of the aerogel to be tested, m1, is weighed, and placed in a covered glass bottle containing 10 mL of chloroform. The mass of the sponge after saturation is weighed, m2, and the saturated oil phase adsorption capacity (Φ) is: Φ = m1 / m2. The saturated oil phase adsorption capacity after 10 cycles is tested by first saturating the gradient aerogel with chloroform, mechanically squeezing until no oil phase drips naturally, and then placing it in a 40°C oven for 1 hour. This process is repeated 10 times, and the subsequent testing steps are consistent with the saturated oil phase adsorption capacity.

[0068] Strength testing methods include: In the following examples, the gradient aerogel strength test utilizes a dual-column universal material testing system (Instron 5966, Instron, USA) to measure mechanical compression properties.

[0069] The cellulose content was determined using the nitroethanol method; the lignin content was determined according to GB / T 2677.8-1994; and the hemicellulose content was determined according to GB / T 2677.9-1994.

[0070] The present invention will be described in detail below through examples.

[0071] In the following examples, the acetate buffer solution consists of HaC, NaAc and water, with a pH of 4.6.

[0072] In the following examples, the bamboo material has a cellulose content of 44.57 wt%, a hemicellulose content of 28.62 wt%, a lignin content of 9.12 wt%, and a content of other substances of 17.69 wt%. The bamboo material is cut into 20×20×5 mm 3 (tangential × radial × axial) dimensions as bamboo raw material.

[0073] Example 1

[0074] (1) Bamboo was added with an acetic acid buffer solution containing 1 wt% NaClO2 and pH = 4.6 at a solid-liquid mass ratio of 1:10, maintained at 80 ° C for 2 h, and then washed with deionized water until the conductivity was zero; the cellulose content of the delignified bamboo was 69.78 wt%, the lignin content was 2.38 wt%, the hemicellulose content was 13.22 wt%, and the content of other substances was 14.62 wt%.

[0075] (2) freezing the bamboo obtained in step (1) in a refrigerator at -20°C for 2 h, and then freeze-drying it in a freeze dryer at -80°C and 0.001-0.01 Pa for 24 h to obtain a bamboo-based gradient aerogel;

[0076] (3) 640 μL MTMS (methyltrimethoxysilane) was added to 0.1 g of bamboo-based gradient aerogel, and the bamboo aerogel was placed in a vacuum dryer, evacuated to 0.1 MPa, and finally placed in the dryer at 80°C for 7 h to obtain hydrophobic bamboo-based gradient aerogel, wherein methyltrimethoxysilane accounted for 6.5 wt% of the hydrophobic bamboo-based gradient aerogel.

[0077] The strength, radial thermal conductivity, and axial thermal conductivity of the bamboo-based gradient aerogel were tested, and the contact angle and saturated chloroform adsorption capacity of the hydrophobic bamboo-based gradient aerogel were tested. The test results are shown in Table 1.

[0078] The mechanical properties of bamboo-based gradient aerogel were tested using a tensile testing machine. The test results are as follows: Figure 1 As shown, the bamboo-based gradient aerogel exhibits anisotropic mechanical properties in the growth direction and perpendicular to the growth direction, with compressive strengths of 0.23 MPa and 0.02 MPa, respectively. Furthermore, five cycles of compression perpendicular to the bamboo growth direction demonstrated the bamboo-based gradient aerogel's elasticity, allowing it to recover to its original state after cyclic compression.

[0079] SEM images of bamboo-based gradient aerogels are shown in Figure 2. Figure 2-4 As shown, Figure 2 Cross-sectional scanning electron microscopy (SEM) image of gradient aerogel; Figure 3 is a scanning electron microscope (SEM) image of the medium density layer of the gradient aerogel (500X); Figure 4 This is a scanning electron microscope (SEM) image (2000X) of the medium density layer of the gradient aerogel, indicating that the aerogel has a gradient structure.

[0080] The bamboo-based gradient aerogel consists of three density layers, of which the high-density layer has a density of 0.088 g / cm 3 The density of the medium density layer is 0.067g / cm 3 The density of the low-density layer is 0.052g / cm 3 .

[0081] Figure 5 This is a contact angle test diagram of hydrophobic gradient aerogel. The test shows that the contact angle of hydrophobic gradient aerogel is 156°.

[0082] Example 2

[0083] (1) Bamboo was added with an acetic acid buffer solution containing 2 wt% NaClO2 and pH = 4.6 at a solid-liquid mass ratio of 1:6, maintained at 60°C for 1.5 h, and then washed with deionized water until the conductivity was zero; the cellulose content of the delignified bamboo was 72.1 wt%, the lignin content was 1.55 wt%, the hemicellulose content was 11.6 wt%, and the content of other substances was 14.75 wt%.

[0084] (2) The bamboo material obtained in step (1) is frozen in a refrigerator at -20°C for 2h, and then freeze-dried in a freeze dryer at -80°C and 0.001-0.01 Pa for 24h to obtain a bamboo-based gradient aerogel;

[0085] (3) 0.1g of the bamboo-based gradient aerogel is added with 640μL of MTMS (methyltrimethoxysilane), and finally the bamboo material aerogel is placed in a vacuumable dryer, which is vacuumed to 0.1MPa, and finally the dryer is placed in a 80°C reaction for 7h to obtain a hydrophobic bamboo-based gradient aerogel, wherein the methyltrimethoxysilane accounts for 6.5wt% of the hydrophobic bamboo-based gradient aerogel.

[0086] The strength, radial thermal conductivity, axial thermal conductivity of the bamboo-based gradient aerogel are tested, the contact angle and saturated chloroform adsorption amount of the hydrophobic bamboo-based gradient aerogel are tested, and the test results are shown in Table 1.

[0087] The bamboo-based gradient aerogel comprises three density layers, wherein,

[0088] The density of the high-density layer is 0.083g / cm 3 ; the density of the medium-density layer is 0.066g / cm 3 ; and the density of the low-density layer is 0.054g / cm 3 .

[0089] Example 3

[0090] (1) The bamboo material is added to an acetic acid buffer solution containing 0.7wt% NaClO2 and pH=4.6 at a solid-liquid mass ratio of 1:20, and kept at 90°C for 3h, and then washed with deionized water until the conductivity is zero; the cellulose content in the delignified bamboo material is 65.8wt%, the lignin content is 5.3wt%, the hemicellulose content is 15.4wt%, and the content of other substances is 13.5wt%.

[0091] (2) The bamboo material obtained in step (1) is frozen in a refrigerator at -20°C for 2h, and then freeze-dried in a freeze dryer at -80°C and 0.001-0.01 Pa for 24h to obtain a bamboo-based gradient aerogel;

[0092] (3) 0.1g of the bamboo-based gradient aerogel is added with 640μL of MTMS (methyltrimethoxysilane), and finally the bamboo material aerogel is placed in a vacuumable dryer, which is vacuumed to 0.1MPa, and finally the dryer is placed in a 80°C reaction for 7h to obtain a hydrophobic bamboo-based gradient aerogel, wherein the methyltrimethoxysilane accounts for 6.5wt% of the hydrophobic bamboo-based gradient aerogel.

[0093] The strength, radial thermal conductivity, and axial thermal conductivity of the bamboo-based gradient aerogel were tested, and the contact angle and saturated chloroform adsorption capacity of the hydrophobic bamboo-based gradient aerogel were tested. The test results are shown in Table 1.

[0094] The bamboo-based gradient aerogel consists of three density layers, among which,

[0095] The density of the high-density layer is 0.092g / cm 3 The density of the medium density layer is 0.071g / cm 3 The density of the low-density layer is 0.051g / cm 3 .

[0096] Table 1

[0097]

[0098] From the results in Table 1, it can be seen that the bamboo-based gradient aerogel has a low thermal conductivity and hydrophobicity. This aerogel can not only be used in the fields of oil absorption and waterproofing, but also has potential application value in the direction of thermal insulation.

[0099] Comparative Example 1

[0100] (1) Bamboo was added with 5 wt% NaOH solution at a solid-liquid mass ratio of 1:10, kept at 80°C for 10 h, and then washed with deionized water until the conductivity was zero;

[0101] (2) Freezing the bamboo obtained in step (1) in a refrigerator at -20°C for 2 hours, and then freeze-drying in a freeze dryer at -80°C and 0.001-0.01 Pa for 24 hours to obtain collapsed bamboo. The delignified bamboo has a cellulose content of 70 wt%, a lignin content of 2.2 wt%, a hemicellulose content of 13 wt%, and a content of other substances of 14.8 wt%.

[0102] In Comparative Example 1, when the delignified bamboo material maintained similar components to those in Example 1, the natural anisotropic structure of the bamboo material could not be maintained, the structure collapsed, and no gradient aerogel could be obtained.

[0103] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A bamboo-based gradient aerogel, characterized in that: The bamboo-based gradient aerogel comprises a high-density layer, a medium-density layer and a low-density layer; the high-density layer has a density of 0.075-0.1 g / cm 3 ; The density of the medium density layer is 0.06-0.075g / cm 3 ; The density of the low-density layer is 0.04-0.06 g / cm 3 ; In terms of mass percentage, the bamboo-based gradient aerogel has a cellulose content of 65wt%-75wt%, a hemicellulose content of 11wt%-16wt%, a lignin content of 1wt%-7wt%, and a content of other substances of 10-20wt%; The bamboo-based gradient aerogel has an axial mechanical strength of 0.15-0.28 MPa and a radial mechanical strength of 0.15-0.25 MPa; the radial thermal conductivity of the bamboo-based gradient aerogel is 0.03-0.055 W·m -1 ·K -1 The axial thermal conductivity of the bamboo-based gradient aerogel is 0.035-0.05 W·m -1 ·K -1 .

2. The method for preparing the bamboo-based gradient aerogel according to claim 1, characterized in that: The method comprises the following steps: (1) contacting the bamboo block with an acetic acid buffer solution containing 0.1-10 wt% NaClO2; (2) freeze-drying the bamboo obtained in step (1) to obtain a gradient aerogel; in the solution, the concentration of NaClO2 is 0.1-2wt%; the solid-liquid mass ratio is 1:5-20; the pH value of the acetic acid buffer solution is 4-5; the contact conditions include: temperature of 50-90°C; time of 0.5-3h; the bamboo raw material has a cellulose content of 42-48wt%, a lignin content of 7-12wt%, a hemicellulose content of 26-33wt%, and a content of other substances of 13-22wt%.

3. The preparation method according to claim 2, wherein In step (2), the freeze-drying conditions include: a temperature of -60°C to -90°C and a pressure of 0.001 to 0.01 Pa.

4. The preparation method according to claim 2, wherein In step (1), after the contact reaction, the sample is washed with deionized water until the conductivity is 0.

5. A hydrophobic bamboo-based gradient aerogel, characterized in that: The hydrophobic bamboo-based gradient aerogel comprises the bamboo-based gradient aerogel according to claim 1 and a hydrophobic substance loaded on the bamboo-based gradient aerogel; The hydrophobic substances accounted for 6.00–7.10 wt % of the hydrophobic bamboo-based gradient aerogels; The hydrophobic substance is selected from one or more methoxysilane compounds.

6. The hydrophobic bamboo-based gradient aerogel according to claim 5, wherein: The hydrophobic substance is methyltrimethoxysilane; and / or The contact angle of the hydrophobic bamboo-based gradient aerogel is 153-156°.

7. The hydrophobic bamboo-based gradient aerogel according to claim 5, wherein: The hydrophobic bamboo-based gradient aerogel has an adsorption capacity of 49-57 g / g aerogel for chloroform.

8. The method for preparing the hydrophobic bamboo-based gradient aerogel according to any one of claims 5 to 7, characterized in that: The method comprises the following steps: The hydrophobic substance is loaded onto the bamboo-based gradient aerogel according to claim 1 by chemical vapor deposition.

9. The preparation method according to claim 8, wherein The chemical vapor deposition conditions include: temperature of 70-100°C, time of 5-10 h, and pressure of 0.07-0.09 Pa.

10. Use of the bamboo-based gradient aerogel according to claim 1 or the hydrophobic bamboo-based gradient aerogel according to any one of claims 5 to 7 in the fields of thermal insulation, noise reduction or oil absorption.

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