Lightweight graphene-based aerogel material with high specific surface area as well as preparation method and application of graphene-based aerogel material

Abstract

The invention provides a light graphene-based aerogel material with a high specific surface area as well as a preparation method and application of the graphene-based aerogel material. The light graphene-based aerogel material with the high specific surface area is prepared by the preparation method. The preparation method comprises the following steps: preparing a graphene oxide aqueous dispersion solution with the concentration of 1-10 mg / mL from graphene oxide; adding siloxane and a reducing agent into the dispersion solution, and carrying out hydrothermal reaction to obtain a graphene-based hydrogel precursor; and pre-freezing the precursor, and then freeze-drying to obtain the product. The light graphene-based aerogel material with the high specific surface area is used for adsorbing pollutants in water. The raw materials used in the method are low in cost, the light graphene-based aerogel with the high specific surface area is prepared through the hydrothermal reaction and freeze drying, operation is easy, secondary pollution is avoided, and large-scale production is easy; the prepared aerogel has a layered porous network structure, has the advantages of hydrophobicity, rapid adsorption, light weight and the like, and has a better effect of adsorbing organic matters and heavy metal ions in wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer composite materials, and particularly relates to a lightweight high specific surface area graphene-based aerogel material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, oil spills and chemical leakage accidents that seriously endanger the environment and ecology have occurred frequently. Moreover, a large amount of oily wastewater is also generated during oil extraction and processing, which not only wastes a large amount of resources but also causes great damage to the ecology. In addition to waste oil and organic solvents, the current heavy metal pollution in water environment has also become a global environmental problem. Industrial wastewater discharge has led to the continuous exceeding of the concentration of toxic heavy metal ions such as lead, cadmium, and mercury in water bodies. The continuous accumulation and enrichment of these pollutants in the biological chain have posed a serious threat to the natural environment and human health.

[0003] Currently, the most commonly used water pollution cleaning technologies include chemical methods, bioremediation, mechanical methods, adsorption, etc. Among them, adsorbents can remove pollutants without causing environmental damage, so they stand out among these conventional methods for cleaning wastewater and pollutants. Graphene aerogel shows significant advantages in the field of physical adsorption of pollutants due to its low density, high specific surface area, and three-dimensional porous network structure characteristics. However, the layered structure of graphene aerogel formed by traditional preparation processes is prone to stacking and collapse phenomena, which limits the performance of this material in actual adsorption applications. This is one of the hot issues that need to be solved urgently at present.

[0004] Current research has disclosed composite materials obtained by modifying graphene, which can be used for the purification of pollutants in some wastewater. However, the active functional groups are limited and it is difficult to recycle, which may cause secondary pollution. In addition, existing materials generally have disadvantages such as relatively high price, long preparation cycle, and complex process, which directly affect the efficiency and cost of pollution treatment. For example, patent CN114368746A discloses a composite process based on silane hydrolysis solution and graphene. This technology prepares a three-dimensional porous material with superhydrophobic characteristics through interfacial modification, which can achieve efficient adsorption of organic solvents. However, this preparation process requires multi-step dialysis treatment and high-speed centrifugation separation technology, significantly increasing the time cost and equipment energy consumption in the production process. Another technical solution CN108745290A proposes a carbon-based nanomaterial composite strategy, which effectively improves the mechanical properties and adsorption capacity of the aerogel by constructing a carbon nanotube-graphene heterostructure. Its elastic modulus and compressive strength reach 1.5 times and 2.3 times of the industry standard values respectively. However, limited by the relatively high raw material cost of carbon nanotubes, this solution faces economic feasibility challenges in large-scale production. Therefore, it is of great significance to develop an ideal adsorbent with light weight, high absorption capacity, low cost, and simple process.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The object of the present invention is to provide a lightweight graphene-based aerogel material with a high specific surface area, its preparation method and application, so as to solve the above problems.

[0007] To achieve the above object, the present invention specifically adopts the following technical solutions:

[0008] The first aspect of the present invention provides a preparation method of a lightweight graphene-based aerogel material with a high specific surface area. The preparation method includes the following steps:

[0009] S1: Prepare a graphene oxide aqueous dispersion solution with a concentration of 1-10 mg / mL using graphene oxide; preferably, the concentration of the graphene oxide aqueous dispersion solution is 2-5 mg / mL. There is a significant correlation between the concentration of the graphene oxide aqueous dispersion solution and the gelation process. Increasing the concentration can accelerate the formation of the gel network. Therefore, the control of the concentration is relatively important. Too low a concentration leads to too long a gelation time, which may cause insufficient curing. Too high a concentration leads to too fast a gelation process, which may affect the gel effect and cause problems such as uneven pore size distribution, which is not conducive to the smooth progress of subsequent operation steps;

[0010] Optionally, the graphene oxide can be graphene oxide prepared from natural high-purity graphite, flake graphite, dense crystalline graphite, artificial graphite or graphite paper as raw materials by the Hummers method, Modified Hummers method or Improved Hummers method; at the same time, the graphene oxide can be commercially available graphene powder;

[0011] S2: Add siloxane and a reducing agent to the graphene oxide aqueous dispersion solution obtained in S1, mix evenly, and carry out a hydrothermal reaction to obtain a graphene-based hydrogel precursor; the hydrophobic group and crosslinkable characteristics of the siloxane can effectively enhance the hydrophobicity of the aerogel and improve its structural stability through a chemical crosslinking network. During the gelation process, the siloxane forms Si-O-Si oligomers through hydrolysis and condensation, and at the same time constructs a three-dimensional network structure with the graphene sheets through crosslinking, and the Si-O-Si structure is interspersed between the graphene sheets. This synergistic effect effectively inhibits the π-π stacking phenomenon of the graphene sheets, resulting in a large increase in the porosity of the material.

[0012] The step S2 satisfies one or more of the following conditions:

[0013] a. The siloxane includes any one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane;

[0014] b. The reducing agent includes any one or more of ascorbic acid, sodium ascorbate, ethylenediamine, phenol, and hydroquinone;

[0015] c. The hydrothermal reaction is carried out in a pressurized closed device;

[0016] d. The volume ratio of the siloxane to the aqueous dispersion solution of graphene oxide is (0.005 - 0.02):1, preferably (0.01 - 0.02):1;

[0017] e. The mass ratio of the reducing agent to the graphene oxide is (0.5 - 5):1, preferably (0.5 - 2):1;

[0018] f. The temperature of the hydrothermal reaction is 100 - 250 °C, preferably 150 - 200 °C; the time is 10 - 48 h, preferably 10 - 36 h;

[0019] Preferably, in step S2, when adding the siloxane and the reducing agent to the aqueous dispersion solution of graphene oxide obtained in S1, water-soluble carbon black and / or carbon black derivatives are also added; the water-soluble carbon black and the carbon black derivatives are uniformly dispersed during the gelation process and stably attached to the surface of the three-dimensional network skeleton of the aerogel through cross-linking, providing more abundant active sites while regulating the structure of the aerogel. By hindering the stacking of graphene sheets, the network structure of the aerogel becomes more complete and regular, forming a uniform and abundant pore structure, and this effect greatly improves the adsorption performance of the material.

[0020] More preferably, the carbon black derivatives include chlorinated carbon black and / or sulfonated carbon black;

[0021] Even more preferably, the total amount of the water-soluble carbon black and / or the carbon black derivatives and the amount of the graphene oxide satisfy the condition that the mass ratio is (0.1 - 1):1, preferably (0.2 - 0.5):1;

[0022] S3: Pre-freeze the graphene-based hydrogel precursor obtained in S2, and then perform freeze-drying to obtain the lightweight high specific surface area graphene-based aerogel material.

[0023] The pre-freezing is carried out in a refrigerator, and the freeze-drying is carried out under vacuum conditions;

[0024] Step S3 satisfies one or more of the following conditions:

[0025] g. The temperature of the pre-freezing is -10 to -40 °C, preferably -20 to -30 °C;

[0026] h. The vacuum degree of the vacuum condition is 0 to 50 Pa, preferably 0 to 5 Pa;

[0027] i. The temperature of the lyophilization is -50 to -100 °C, preferably -70 to -90 °C; the drying time is 24 to 50 h, preferably 36 to 50 h.

[0028] The second aspect of the present invention provides a lightweight high specific surface area graphene-based aerogel material, which is prepared by the above-mentioned preparation method.

[0029] The third aspect of the present invention provides an application of the lightweight high specific surface area graphene-based aerogel material, and the lightweight high specific surface area graphene-based aerogel material is used for adsorbing pollutants in water;

[0030] Preferably, the lightweight high specific surface area graphene-based aerogel material is used for adsorbing organic pollutants and heavy metal ions in water.

[0031] The present invention uses graphene oxide, siloxane, water-soluble carbon black and / or carbon black derivatives as raw materials. After mixing them, a hydrogel precursor is obtained through a cross-linking reaction under the assistance of a reducing agent and hydrothermal treatment, and then a lightweight high specific surface area graphene-based aerogel is obtained through lyophilization. It has a low density and has a high specific surface area and a porous network structure.

[0032] The present invention adopts a one-step hydrothermal method. First, a uniformly mixed precursor solution is prepared, and then a hydrothermal reaction is carried out for gelation and drying to obtain a finished aerogel. The process is simple and the preparation cycle is short. During this process, part of the graphene oxide is reduced, and a porous three-dimensional network is rapidly constructed through π-π stacking. The siloxane cross-links with graphene oxide through hydrolysis condensation and ring-opening reactions, etc., to jointly construct a three-dimensional network structure, hindering the excessive stacking of graphene sheets. The structure includes a polyorganosilane self-crosslinking network and a graphene oxide-polyorganosilane crosslinking network. The carbon black and carbon black derivatives are cross-linked and attached to the network skeleton, and the formation of larger mesopores and more regular pore structures is promoted through steric hindrance effects. This organic-inorganic hybridization improves the structural stability of the material. The optimization of the porous structure significantly improves the mass transfer performance of the material. The regular and perfect three-dimensional network pore structure constructed inside the material endows the aerogel with an ultra-high specific surface area. The granularly distributed carbon black and carbon black derivatives provide more active adsorption sites, and at the same time, the rich pore channels provide an effective channel for the rapid transmission of adsorbates.

[0033] The beneficial effects of the present invention:

[0034] The raw materials used in the present invention have low cost, are simple to prepare and do not produce secondary pollution; a lightweight high specific surface area graphene-based aerogel is prepared by a hydrothermal reaction and lyophilization method. The preparation process is simple and is easy to scale up production.

[0035] In the present invention, siloxane, water-soluble carbon black and / or carbon black derivatives are directly introduced into the graphene aerogel framework. The aerogel obtained through cross-linking and network construction has characteristics such as light weight, high specific surface area, and rich pore structure, and has a large number of adsorption sites, which enables it to have a good adsorption effect on oily wastewater and heavy metal ions, and is conducive to separation after adsorption, having good application prospects.

[0036] The light-weight and high-specific-surface-area graphene-based aerogel provided by the present invention has a hierarchical porous network structure, and has advantages such as hydrophobicity, rapid adsorption, and light weight. At the same time, it has rich adsorption and coordination active sites, and has wide applications in the treatment of organic solvents and the adsorption and purification of heavy metal ions in wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 It is the scanning electron microscope image of the light-weight and high-specific-surface-area graphene-based aerogel provided for Example 3;

[0039] Figure 2(a) is a comparison chart of the adsorption capacities of Example 3, Comparative Example 1, and Comparative Example 2 for organic solvents;

[0040] Figure 2(b) is the adsorption kinetic curve of Example 3;

[0041] Figure 2(c) is the adsorption kinetic curve of Comparative Example 1;

[0042] Figure 3(a) is the adsorption kinetic curve of Example 3 for Cu 2+ , Pb 2+ ;

[0043] Figure 3(b) is the adsorption isotherm of Example 3 for Cu 2+ , Pb 2+ . DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0045] Example 1

[0046] This example provides a lightweight graphene - based aerogel material with a high specific surface area and its preparation method. The specific steps are as follows:

[0047] S1: Take graphene oxide prepared by the Hummers method and prepare an aqueous dispersion solution with a concentration of 5 mg / mL;

[0048] S2: Place 30 mL of the graphene oxide aqueous dispersion solution obtained in S1 in a beaker. Under continuous stirring, add 0.6 mL of dimethyldimethoxysilane, 20 mg of water - soluble carbon black, and 100 mg of phenol to it. After fully stirring for 10 min, ultrasonicate for 30 min to make each component uniform. Transfer the uniformly mixed solution to a reaction kettle and carry out a hydrothermal reaction at 200 °C for 30 h to obtain a hydrogel precursor;

[0049] S3: Put the hydrogel precursor obtained in S2 above into a refrigerator and store it at - 30 °C for 10 h for pre - freezing. Then freeze - dry the pre - frozen product in a freeze - dryer under the conditions of a vacuum degree of 5 Pa and a temperature of - 85 °C for 30 h to obtain a graphene - based aerogel.

[0050] Example 2

[0051] This example provides a lightweight graphene - based aerogel material with a high specific surface area and its preparation method. The specific steps are as follows:

[0052] S1: Take graphene oxide prepared by the Hummers method and prepare an aqueous dispersion solution with a concentration of 3 mg / mL;

[0053] S2: Place 30 mL of the graphene oxide aqueous dispersion solution obtained in S1 in a beaker. Under continuous stirring, add 0.3 mL of dimethyldimethoxysilane, 10 mg of water - soluble carbon black, and 80 mg of ascorbic acid to it. After fully stirring for 10 min, ultrasonicate for 30 min to make each component uniform. Transfer the uniformly mixed solution to a reaction kettle and carry out a hydrothermal reaction at 200 °C for 24 h to obtain a hydrogel precursor;

[0054] S3: Put the hydrogel precursor obtained in S2 above into a refrigerator and store it at - 30 °C for 10 h for pre - freezing. Then freeze - dry the pre - frozen sample in a freeze - dryer under the conditions of a vacuum degree of 5 Pa and a temperature of - 85 °C for 36 h to obtain a graphene - based aerogel.

[0055] Example 3

[0056] This example provides a lightweight graphene - based aerogel material with a high specific surface area and its preparation method. The specific steps are as follows:

[0057] S1: Prepare a water-dispersed solution of graphene oxide prepared by the Hummers method with a concentration of 2 mg / mL;

[0058] S2: 30 mL of the graphene oxide aqueous dispersion obtained by S1 was placed in a beaker, and 0.45 mL of methyltrimethoxysilane, 15 mg of water-soluble carbon black, and 60 mg of sodium ascorbate were added thereto under continuous stirring. After being fully stirred for 10 min, ultrasonic treatment was performed for 30 min to make the components uniform. The uniform mixed solution was transferred to a reactor and subjected to hydrothermal reaction at 180 ° C for 24 h to obtain a hydrogel precursor;

[0059] S3: The hydrogel precursor obtained in the above S2 is placed in a refrigerator at -30°C for 10 hours for pre-freezing, and then the pre-frozen sample is freeze-dried in a freeze dryer (-85°C, 5Pa) for 48 hours to obtain a graphene-based aerogel.

[0060] The graphene-based aerogel prepared in this embodiment is the lightweight and high specific surface area graphene-based aerogel material, and its scanning electron microscope image is as follows: Figure 1 shown; Figure 1 (a) is a scanning electron microscope image with a magnification of 500 times. Figure 1 (b) is a scanning electron microscope image with a magnification of 1600 times; Figure 1 It can be seen that the aerogel has a layered porous structure, and the network structure in each layer is regular and uniform, providing the material with a large specific surface area. After measurement, its specific surface area is 358.55m 2 / g.

[0061] Example 4

[0062] This embodiment provides a lightweight and high specific surface area graphene-based aerogel material and a preparation method thereof, and the specific steps are as follows:

[0063] S1: Prepare a water-dispersed solution of graphene oxide prepared by the Hummers method with a concentration of 2 mg / mL;

[0064] S2: 30 mL of the graphene oxide aqueous dispersion obtained by S1 was placed in a beaker, and 0.3 mL of methyltrimethoxysilane, 5 mg of water-soluble carbon black, and 80 mg of phenol were added thereto under continuous stirring. After being fully stirred for 10 min, ultrasonic treatment was performed for 30 min to make the components uniform. The uniform mixed solution was transferred to a reactor and subjected to hydrothermal reaction at 200 ° C for 20 h to obtain a hydrogel precursor.

[0065] S3: The hydrogel precursor was placed in a refrigerator at -30°C for 10 h for pre-freezing, and then the pre-frozen sample was freeze-dried in a freeze dryer (-85°C, 5 Pa) for 50 h to obtain a graphene-based aerogel.

[0066] Comparative Example 1

[0067] The difference from Example 3 is that water-soluble carbon black is not added in this comparative example S2.

[0068] The specific surface area of the obtained material is 156.64 m 2 / g.

[0069] Comparative Example 2

[0070] The difference from Example 3 is that siloxane is not added in this comparative example S2.

[0071] The specific surface area of the obtained material is 258.61 m 2 / g.

[0072] The materials obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to adsorption performance tests. The test methods are as follows:

[0073] Organic solvent adsorption experiment: Take a certain amount of the light high specific surface area graphene-based aerogel, record the weight as m0 after weighing, immerse it in the organic solvent for 1 min to reach saturation adsorption, quickly weigh the weight as m1 after taking it out for 10 s, and calculate the adsorption mass ratio as Q = (m1 - m0) / m0. Repeat the above operation 3 times to reduce errors. The adsorption kinetic process is determined by taking samples at regular intervals to measure the instantaneous mass mt, and when the mass fluctuation is <0.5% for five consecutive measurements, it is determined that the adsorption equilibrium is reached.

[0074] Heavy metal ion adsorption experiment: The usage ratio of the adsorption aerogel is 0.1 g / L. Use 0.1 mol / L nitric acid and sodium hydroxide solutions to adjust the pH value of the copper nitrate and lead nitrate working solutions to the optimal adsorption pH value. Add the adsorbent to the copper ion and lead ion solutions of 50 mg / L. After 3 h of adsorption to reach the saturation state, take an appropriate amount of the solution and dilute it by a certain multiple, and use ICP to measure the signal intensity at the specific wavelength of the target element. Calculate the pollutant concentration before and after adsorption according to the standard curve comparison. The calculation formula for the adsorption capacity is: Q = (C before -C after )V / m. In the formula, Q represents the adsorption capacity, with the unit of mg / g; C before represents the concentration before adsorption, with the unit of mg / L; C after represents the concentration after adsorption, with the unit of mg / L; V represents the solution volume; m is the mass of the adsorbent. The adsorption kinetic process is determined by taking samples at regular intervals to measure the instantaneous mass mt, and when the mass fluctuation is <0.5% for five consecutive measurements, it is determined that the adsorption equilibrium is reached.

[0075] The test results of the adsorption capacity are shown in Figures 2 and 3. Figure 2(a) is a comparison chart of the adsorption capacity of Example 3, Comparative Example 1, and Comparative Example 2 for organic solvents. It can be seen from Figure 2(a) that the adsorption capacity of Comparative Example 1 for various organic solvents is 87.47 - 288.63 g / g, that of Comparative Example 2 is 64.79 - 214.49 g / g, and that of Example 3 is 103.08 - 340.16 g / g, which is significantly higher than the adsorption capacity of the comparative examples.

[0076] Figure 2(b) is the adsorption kinetic curve of Example 3. It can be observed that the adsorption equilibrium state can be reached within 5 s for ethanol and n-hexane, and the adsorption can be basically completed at 10 s for pump oil with higher viscosity. Figure 2(c) is the adsorption kinetic curve of Comparative Example 1. Figures 2(b) and (c) show the adsorption kinetic images of Example 3 and Comparative Example 1 for specific organic solvents. By comparison, it can be seen that Example 3 has a higher adsorption capacity and faster adsorption efficiency than Comparative Example 1.

[0077] Figure 3(a) is the adsorption kinetic curve of Example 3 for Cu 2+ , Pb 2+ . It can be seen from Figure 3(a) that the adsorption saturation is basically reached in 2 h. Figure 3(b) is the adsorption isotherm of Example 3 for Cu 2+ , Pb 2+ . Figure 3(b) shows the fitting curve of the adsorption capacity for ionic solutions with different concentrations and the Langmuir model. It can be seen that the adsorption process of the material prepared in Example 3 mainly follows the monolayer adsorption mechanism. The theoretical maximum adsorption capacities of Example 3 for the two heavy metal ions are calculated, where Cu 2+ is 499.4 mg / g and Pb 2+ is 432.9 mg / g.

[0078] The doping of carbon black and carbon black derivatives effectively reduces the contact area between graphene layers, improves the network structure of the composite material, and forms a more regular hierarchical network structure. The specific surface area of the aerogel material obtained in Example 3 is as high as 358.55 m 2 / g, significantly increasing the number of surface active sites. The mesoporous structure inside the material simultaneously undertakes the dual functions of a mass transfer channel and an oil storage space. The excellent heavy metal adsorption performance is mainly attributed to the specific binding of the surface-modified active functional groups such as hydroxyl (-OH) and carboxyl (-COOH) to heavy metal ions through coordination complexation, ion exchange and other mechanisms.

[0079] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification. The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A preparation method of a lightweight graphene-based aerogel material with a high specific surface area, characterized in that, The preparation method includes the following steps: S1: Prepare a graphene oxide aqueous dispersion solution with a concentration of 1-10 mg / mL using graphene oxide. S2: Add siloxane and a reducing agent to the graphene oxide aqueous dispersion solution obtained in S1, mix evenly, and perform a hydrothermal reaction to obtain a graphene-based hydrogel precursor. S3: Pre-freeze the graphene-based hydrogel precursor obtained in S2, and then perform freeze-drying to obtain the lightweight high specific surface area graphene-based aerogel material.

2. The preparation method according to claim 1, characterized in that, The concentration of the graphene oxide aqueous dispersion solution is 2-5 mg / mL.

3. The preparation method according to claim 1, characterized in that, Step S2 satisfies one or more of the following conditions: a. The siloxane includes any one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane. b. The reducing agent includes any one or more of ascorbic acid, sodium ascorbate, ethylenediamine, phenol, hydroquinone. c. The hydrothermal reaction is carried out in a pressurized closed device.

4. The preparation method according to claim 3, wherein, Step S2 also satisfies one or more of the following conditions: d. The volume ratio of the siloxane to the graphene oxide aqueous dispersion solution is (0.005-0.02):

1. e. The mass ratio of the reducing agent to the graphene oxide is (0.5-5):

1. f. The temperature of the hydrothermal reaction is 100-250 °C, and the time is 10-48 h.

5. The preparation method according to claim 1, wherein The pre-freezing is carried out in a refrigerator, and the freeze-drying is carried out under vacuum conditions.

6. The preparation method according to claim 5, characterized in that, Step S3 satisfies one or more of the following conditions: g. The temperature of the pre-freezing is -10 to -40 °C. h. The vacuum degree of the vacuum condition is 0-50 Pa. i. The temperature of the freeze-drying is -50 to -100 °C, and the drying time is 24-50 h.

7. The preparation method according to claim 1, characterized in that, In step S2, when adding siloxane and a reducing agent to the graphene oxide aqueous dispersion solution obtained in S1, water-soluble carbon black and / or carbon black derivatives are also added. Preferably, the carbon black derivatives include chlorinated carbon black and / or sulfonated carbon black.

8. The preparation method according to claim 7, wherein, The total amount of the water-soluble carbon black and / or carbon black derivatives and the amount of the graphene oxide satisfy the condition of a mass ratio of (0.1-1):

1.

9. A lightweight graphene-based aerogel material with a high specific surface area, characterized in that, The lightweight high specific surface area graphene-based aerogel material is prepared by the preparation method according to any one of claims 1-8.

10. Use of the light high specific surface area graphene-based aerogel material according to claim 9, characterized in that, The lightweight high specific surface area graphene-based aerogel material is suitable for adsorbing pollutants in water.

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