CN117963895A - Xanthan gum edge grafting modified graphene and aqueous dispersion thereof and preparation method - Google Patents

Abstract

The invention belongs to the technical field of graphene preparation, and relates to a xanthan gum edge-grafted modified graphene, an aqueous dispersion thereof, and a preparation method thereof. The xanthan gum edge-grafted modified graphene comprises graphene and xanthan gum grafted on its edge, and the mass content of the grafted xanthan gum in the xanthan gum edge-grafted modified graphene is 1-6% based on the total mass of the edge-grafted modified graphene. The xanthan gum can increase the viscosity of the solution, indirectly transmit the shear force between the grinding discs to the graphite sheet, further reduce the damage to the graphite lattice, and improve the peeling effect of the graphite sheet.

Description

Xanthan gum edge-grafted modified graphene and its aqueous dispersion and preparation method

Technical Field

The invention belongs to the technical field of graphene preparation, and specifically relates to xanthan gum edge-grafted modified graphene, an aqueous dispersion of xanthan gum edge-grafted modified graphene, and preparation methods thereof.

Background technique

Graphene is a single layer of carbon atoms with a honeycomb structure formed by a carbon atom and three adjacent carbon atoms. As a new type of material, graphene has attracted much attention for its high light transmittance, high electrical conductivity, high thermal conductivity, high specific surface area, and excellent mechanical properties. At present, graphene is in the exploratory stage of large-scale preparation and application. The preparation technology of high-quality and low-cost functionalized graphene is the basis for future large-scale application. Scientific and technological personnel have developed a series of preparation technologies: mechanical exfoliation, redox method, chemical vapor deposition method, epitaxial growth method, thermal expansion method and electrochemical method. Among them, mechanical exfoliation and redox method are both based on the preparation of graphite raw materials through mechanical or chemical exfoliation technology. The raw material source is abundant, the cost is easy to control, and it is more suitable for large-scale production of graphene. The redox method oxidizes natural graphite with a strong oxidant, introduces rich polar groups on the surface, obtains graphene oxide through solvation or ultrasonic dispersion, and then reduces and removes the polar groups on the surface of graphene oxide to obtain graphene. However, a large amount of strong acid and strong oxidant is used in the production process, such as concentrated sulfuric acid, fuming nitric acid, potassium permanganate, perchloric acid, etc., which brings serious waste liquid pollution. The prepared graphene has certain defects, such as topological defects such as five-membered rings and seven-membered rings left by the polar groups removed by reduction or structural defects of hydroxyl groups, which will lead to the loss of some properties of graphene and limit the application of graphene. In the national standard GB/T30544.13-2018: "Nanotechnology Terminology Part 13: Graphene and Related Two-Dimensional Materials", graphene oxide and reduced graphene oxide are separately defined to distinguish them from graphene.

The surface of graphene obtained by oxidation contains abundant oxygen-containing groups, such as epoxy, hydroxyl and carboxyl groups, which can be chemically modified by chemical reactions. Salavagione HJ et al. (Salavagione HJ, G Martínez, MA Gómez. Synthesis of poly(vinyl alcohol)/reduced graphite oxide nanocomposites with improved thermal and electrical properties [J]. Journal of Materials Chemistry, 2009, 19 (28): 5027-5032.) grafted PVA onto graphene oxide through esterification reaction between hydroxyl groups on PVA and carboxyl groups on graphene oxide to obtain PVA-grafted graphene oxide. Xu Guoqiang et al. (Xu Guoqiang, Xu Pengwu, Shi Dongjian, et al. Preparation and Cell Imaging of PEG-grafted Graphene Oxide [J]. Journal of Inorganic Chemistry, 2014, 30 (009): 1994-1999.) studied polyethylene oxide grafted graphene oxide. Li Shanrong et al. (Li Shanrong, Lu Shaorong, Qi Bo, et al. Synthesis and application of biphenyl-type thermotropic liquid crystal grafted graphene oxide [J]. Polymer Materials Science and Engineering, 2013, 29 (007): 17-20) studied biphenyl-type thermotropic liquid crystal grafted graphene oxide. They all used the rich active groups on the surface of graphene oxide prepared by oxidation to prepare grafted graphene oxide. Sun Shuang et al. (Sun Shuang, Ma Xiaofei, Wang Nan, et al. Preparation and performance test of GN-PVA/PVA composite film materials [J]. Chemistry and Bioengineering, 2016, 33 (9): 5.) prepared PVA grafted reduced graphene oxide by reacting PVA with graphene oxide and then reducing it. At present, polymer grafted graphene is mainly prepared based on the above methods. However, the topological defects such as five-membered rings and seven-membered rings and residual oxygen-containing groups on the surface of the polymer-grafted graphene prepared by the method of grafting and reducing graphene oxide still exist, which belongs to polymer-grafted graphene oxide or polymer-grafted reduced graphene oxide, and its structure is different from that of polymer-grafted graphene.

Commonly used mechanical exfoliation methods include ball milling, sand milling, and ultrasonic methods. Although these methods can produce graphene on a large scale, due to the large destructive effect of mechanical force, the structure of graphene is severely damaged and the size is often small, even less than 100 nanometers. Therefore, the technical key to mechanical exfoliation is to reduce destructiveness and prepare graphene with a larger area.

Summary of the invention

The invention aims to provide a xanthan gum edge-grafted modified graphene, a stable aqueous dispersion of the xanthan gum edge-grafted modified graphene and a preparation method thereof.

The first aspect of the present invention provides a xanthan gum edge-grafted modified graphene, wherein the xanthan gum edge-grafted modified graphene comprises graphene and xanthan gum grafted on its edge, and the mass content of the grafted xanthan gum in the xanthan gum edge-grafted modified graphene is 1-6%, preferably 1-5%, based on the total mass of the edge-grafted modified graphene.

The second aspect of the present invention provides an aqueous dispersion of xanthan gum edge-grafted modified graphene, the aqueous dispersion comprising water and xanthan gum edge-grafted modified graphene stably dispersed therein, and the xanthan gum edge-grafted modified graphene is the above-mentioned xanthan gum edge-grafted modified graphene.

The third aspect of the present invention provides a method for preparing the aqueous dispersion of the above-mentioned xanthan gum edge-grafted modified graphene, comprising the following steps:

The xanthan gum, water and graphite are uniformly mixed and ground in a grinding wheel kettle. After the grinding, the mixture is allowed to stand and the precipitate is removed to obtain an aqueous dispersion of the xanthan gum edge-grafted modified graphene.

The fourth aspect of the present invention provides a method for preparing the above-mentioned xanthan gum edge-grafted modified graphene, comprising the following steps:

(1) preparing an aqueous dispersion of xanthan gum edge-grafted modified graphene according to the above method;

(2) filtering and drying the aqueous dispersion of the xanthan gum edge-grafted modified graphene obtained in step (1) to obtain the xanthan gum edge-grafted modified graphene.

The aqueous dispersion of xanthan gum grafted graphene prepared by the above technical invention has the following advantages:

1. Compared with ultrasonic, ball milling, sand milling and other grinding processes, the grinding disc has a weaker destructive effect on the graphite crystal structure, and it is easy to prepare larger sheets of xanthan gum edge-grafted graphene.

2. Xanthan gum can increase the viscosity of the solution and indirectly transfer the shear force between the grinding discs to the graphite flakes, further reducing the damage to the graphite lattice and improving the peeling effect of the graphite flakes.

3. During the stripping process, xanthan gum is grafted to the edge of graphene, and the xanthan gum edge-grafted graphene is stably dispersed in water.

4. During the preparation process, xanthan gum edge-grafted graphene can be stably dispersed in water, while graphite sheets will precipitate out, so it is easy to separate.

Other features and advantages of the present invention will be described in detail in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

FIG1 is a schematic diagram of a device for preparing a grafted graphene aqueous dispersion in one embodiment of the present invention;

FIG2 is a photograph of a stable aqueous dispersion of xanthan gum edge-grafted graphene prepared in Examples 1-5;

FIG3 is a scanning electron microscope photograph of xanthan gum edge-grafted graphene prepared in Example 1;

FIG4 is a transmission electron microscope photograph of xanthan gum edge-grafted graphene prepared in Example 1;

FIG5 is an infrared absorption spectrum of xanthan gum edge-grafted graphene prepared in Example 1;

FIG6 is a spectrum diagram of the infrared absorption spectrum diagram of FIG5 after baseline flattening;

Figure 7 is a thermogravimetric analysis graph of xanthan gum edge-grafted graphene prepared in Example 1, the upper curve represents flake graphite, and the lower curve represents xanthan gum edge-grafted graphene.

Detailed ways

The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

The invention provides a xanthan gum edge-grafted modified graphene, which comprises graphene and xanthan gum grafted on the edge thereof. Based on the total mass of the edge-grafted modified graphene, the mass content of the grafted xanthan gum in the xanthan gum edge-grafted modified graphene is 1-6%, preferably 1-5%, for example 1%, 2%, 3%, 4%, 5%.

In the present invention, the mass content of the grafted xanthan gum portion in the edge-grafted modified graphene can be measured by thermogravimetric analysis. For example, under the conditions of a sample nitrogen flow rate of 20.0 ml/min and a balance nitrogen flow rate of 40.0 ml/min, the mass loss of the xanthan gum edge-grafted graphene sample is measured from 50.00°C to 800.00°C at a heating rate of 20.00°C/min, which is the mass content of the xanthan gum polymer grafted to the graphene.

In the present invention, "xanthan gum" can refer to either a compound form or a group form. For example, the xanthan gum in "xanthan gum edge-grafted modified graphene" is a group form, and the xanthan gum in the preparation method is a compound form. Those skilled in the art can clearly distinguish the meaning according to different contexts.

The inventors discovered during their research on preparing graphene by disc exfoliating graphite/water slurry that adding xanthan gum to the system to increase the viscosity of the system can improve the graphite exfoliation effect, and surprisingly, even in aqueous solution, xanthan gum can be grafted onto the edges of exfoliated graphene, thereby forming a stable aqueous dispersion of xanthan gum-grafted modified graphene.

The structure and properties of the xanthan gum edge-grafted graphene of the present invention are significantly different from those of the existing grafted graphene oxide or grafted reduced graphene oxide.

Structurally, graphene oxide and reduced graphene oxide are separately defined in the national standard GB/T30544.13-2018. Graphene oxide is a chemically modified graphene obtained by oxidizing and peeling graphite, and its surface has been strongly oxidized and modified, with a high oxygen content; reduced graphene oxide is graphene oxide after the oxygen content is reduced, and some oxygen-containing functional groups will actually remain, and the sp ³ chemical bonds cannot be completely reduced to sp ² chemical bonds, leaving many topological defects. Therefore, the structures of graphene oxide and reduced graphene oxide are quite different from those of graphene. The present invention uses graphene, not graphene oxide and reduced graphene oxide. In terms of properties, the xanthan gum modified graphene reported in the literature is mostly based on the grafting reaction of oxygen-containing groups of graphene oxide with xanthan gum, and then reduced to prepare xanthan gum grafted graphene.

The xanthan gum used in the present invention can be various types of water-soluble xanthan gum available in the prior art, such as transparent type, instant type or ordinary type.

According to the present invention, the shearing and peeling effect of the grinding disc is achieved by the xanthan gum aqueous solution acting on graphite, and the destructive effect on graphene is relatively small compared with methods such as ball milling and sand milling. Therefore, the edge-grafted graphene flakes are relatively large. Specifically, the average flake diameter of the edge-grafted modified graphene is 1-5 μm.

The average sheet diameter of the edge-grafted modified graphene can be obtained by randomly measuring the sizes of more than 10 graphene sheets after imaging by scanning electron microscope (SEM) or atomic force microscope and calculating the average value. The method for measuring the size of a single graphene sheet is as follows: draw three lines on the surface of the graphene sheet through the center of the sheet as much as possible, with the angle between the lines being about 60°, measure the length of the graphene on the three lines, and calculate the average value as the size of the graphene sheet.

The present invention also provides an aqueous dispersion of xanthan gum edge-grafted modified graphene, which comprises water and xanthan gum edge-grafted modified graphene stably dispersed therein, and the xanthan gum edge-grafted modified graphene is the above-mentioned xanthan gum edge-grafted modified graphene.

According to a preferred embodiment of the present invention, the mass fraction of edge-grafted modified graphene in the dispersion is 1-20%, preferably 1-15%, for example 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%.

The aqueous dispersion of the present invention can be stable for more than 10 months at room temperature and pressure. The stable time means that no visible precipitation occurs during this period of time, specifically, the amount of precipitation is less than 1%.

The present invention also provides a method for preparing the aqueous dispersion of the xanthan gum edge-grafted modified graphene, comprising the following steps:

The xanthan gum, water and graphite are uniformly mixed and ground in a grinding wheel kettle. After the grinding, the mixture is allowed to stand and the precipitate is removed to obtain an aqueous dispersion of the xanthan gum edge-grafted modified graphene.

The invention is based on a xanthan gum aqueous solution-assisted grinding disc graphite exfoliation and simultaneous in-situ grafting technology, wherein the prepared xanthan gum is grafted on the edge of graphene and stably dispersed in the aqueous solution.

According to a preferred embodiment of the present invention, the grinding adopts a cyclic operation, and the mechanical stripping equipment used is composed of a grinding disc and a circulation part, and its structural schematic diagram is shown in Figure 1. The grinding disc part includes a moving grinding disc, a fixed grinding disc and a rotating device, and the circulation part includes a circulation pump, a slurry storage tank and a stirring device. The grinding disc material can be selected from metal, ceramic, glass, plastic, etc., preferably metal.

During the disc stripping process, the moving disc/stationary disc transfers the shear force to the graphite flakes between the discs through the aqueous solution of xanthan gum. Under the action of shear stress, the graphite flakes are first oriented along the rotation direction of the disc, and then slowly stripped into thinner graphite flakes, and finally stripped into graphene. During the stripping process, many new edges are generated, and the carbon atoms at the new edges are highly active, which react with the xanthan gum in the aqueous solution to generate xanthan gum edge-grafted graphene. The method of the present invention significantly reduces the damage to the graphite lattice. The viscosity-increasing effect of xanthan gum on the dispersed system and the shear force between the fixed disc and the moving disc more effectively act on the graphite flakes in the slurry, thereby realizing the stripping preparation of graphene. During the stripping process, xanthan gum is grafted to the edge of graphene, so that the prepared graphene is stably dispersed in water.

The grinding of the present invention can be carried out in a closed or open system. The preparation process can be cyclic grinding at room temperature and normal pressure, and there is no specific requirement for the atmosphere of the system.

The grinding conditions selected in the present invention are: a rotation speed of 10-300 rpm, preferably 50-200 rpm; a cycle stripping time of 5-200 hours, preferably 10-150 hours, and more preferably 30-120 hours.

The xanthan gum in the system of the present invention has two functions: (1) increasing the viscosity of the dispersion system to improve the peeling effect of the grinding disc on the graphite sheet, and (2) grafting to the graphene to make the graphene stably dispersed in the aqueous solution.

The aqueous dispersion of xanthan gum edge-grafted graphene in the present invention is prepared by mechanically exfoliating graphite with a grinding disc, and the graphite that can be selected can be natural graphite and/or artificial graphite, the natural graphite is selected from one or more of flake graphite, block graphite, and cryptocrystalline graphite, and the artificial graphite is selected from one or more of thermal cracking graphite and highly oriented thermal cracking graphite; the graphite is preferably flake graphite; the particle size of the graphite can be 5-8000 mesh, preferably 35-3000 mesh, further preferably 50-1600 mesh, and more preferably 50-300 mesh.

According to a preferred embodiment of the present invention, xanthan gum and water are first mixed, and then graphite is added. The mass fraction of the xanthan gum is 0.1-5%, preferably 0.2-3%, based on the total mass of the xanthan gum and water.

The present invention also provides a method for preparing the xanthan gum edge-grafted modified graphene, comprising the following steps:

(1) preparing an aqueous dispersion of xanthan gum edge-grafted modified graphene according to the aforementioned method;

(2) filtering and drying the aqueous dispersion of the xanthan gum edge-grafted modified graphene obtained in step (1) to obtain the xanthan gum edge-grafted modified graphene.

The filtration can be carried out by various conventional methods. Preferably, the filtration is carried out by reduced pressure filtration with a microporous filtration membrane, and the micropore size is 100-1000nm, preferably 200-800nm.

According to a preferred embodiment of the present invention, the filtering step further comprises diluting the aqueous dispersion of the xanthan gum edge-grafted modified graphene before filtering.

According to a preferred embodiment of the present invention, the filtration step further comprises filtering out free xanthan gum dissolved in water with (deionized) water after filtration to further purify the xanthan gum edge-grafted modified graphene.

The present invention adopts a grinding disc process, and xanthan gum, graphite and water are cyclically stripped between grinding discs. The shearing action between the fixed grinding disc and the movable grinding disc is transmitted to the graphite sheet through the high-viscosity xanthan gum solution, thereby realizing the stripping preparation of graphene. Compared with methods such as ball milling, sand milling and ultrasound, the grinding disc process effectively utilizes the stripping force between the grinding discs, and reduces the crushing of the graphite sheet. Especially after the xanthan gum is thickened, the shearing force between the grinding discs is more effectively transmitted to the graphite sheet through the high-viscosity solution, thereby improving the stripping efficiency and reducing the destructive effect. Therefore, the graphene sheet prepared by the grinding disc method is larger, smooth and not easy to agglomerate. Moreover, the xanthan gum edge-grafted graphene can be more stably dispersed in water. Therefore, the xanthan gum edge-modified graphene of the present invention has broad applications in the fields of polymer composite materials, adsorbent materials, sewage treatment and thickening aids.

The present invention will be further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

The experimental reagents in the following examples are all commercially available except those marked as homemade.

The grinding disc used in the examples was homemade.

The infrared spectrometer used in the examples is the American Thermo Fisher Nicolet IS5.

The scanning electron microscope used in the examples is a Hitachi S4800 from Japan.

Example 1

6.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) were dissolved in 1000 ml of deionized water, and then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding disc speed was set at 100 rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding disc was poured into a beaker. After standing for 10 hours, the precipitation was removed by filtering to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, wherein the mass fraction of grafted graphene was 2.8%. The graphene yield was about 20% of the mass of the added flake graphite. Sample No. 1 in Figure 2 is a stable aqueous dispersion of xanthan gum grafted graphene after standing for 10 months, and no precipitation was seen. This is mainly because the xanthan gum grafted on the graphene edge plays a stabilizing dispersion role.

10 mL of xanthan gum grafted graphene aqueous dispersion was added to 200 mL of deionized water for dilution, and then filtered under reduced pressure using a microporous filter membrane with a pore size of 0.22 μm. Finally, 2 L of deionized water was used to filter out free xanthan gum, and purified xanthan gum grafted graphene was obtained after drying.

FIG3 is a scanning electron microscope photograph of the prepared xanthan gum grafted graphene, and the average size of the grafted graphene flakes is about 2.9 microns.

Figure 4 is a transmission electron microscope photo of the prepared xanthan gum edge-grafted graphene. As can be seen from the picture, there is only one layer of graphene, indicating that graphene is prepared.

Fig. 5 is the infrared spectrum of the prepared xanthan gum edge grafted graphene. Due to the low grafting rate of xanthan gum, the infrared absorption peak of the functional group is weak. Fig. 6 is the spectrum after the baseline of the infrared spectrum of Fig. 5 is straightened, and the absorption peak of the functional group is amplified to improve the resolution. From the figure, it can be seen that the absorption peaks of various functional groups, the stretching vibration of alcoholic hydroxyl group is at 3458cm ^- 1, the stretching vibration of methylene is at 2922cm ^-1 , the vibration absorption peak of benzene ring skeleton is at 1622cm ^-1 , the bending vibration absorption peak of methyl in pyruvic acid group and acetyl group is at 1406cm ^-1 , and the stretching vibration of the ether bond between D-glucose unit and D-mannose unit and the ether bond produced by etherification reaction is at 1080cm ^-1 . The infrared spectrum shows that xanthan gum is grafted to graphene.

Figure 7 shows the thermogravimetric analysis curves of pure flake graphite and xanthan gum edge-grafted graphene. Flake graphite has almost no weight loss; xanthan gum edge-grafted graphene begins to decompose and lose weight at 280°C, and almost stops losing weight at 330°C, with a weight loss of 3.2%, indicating that the mass content of graphene grafted xanthan gum is 3.2%.

Example 2

10.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) were dissolved in 1000 ml of deionized water, and then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding disc speed was set at 100 rpm. After 100 hours of circulation grinding, the graphene suspension processed by the grinding disc was poured into a beaker. After standing for 10 hours, the precipitation was filtered and removed to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, wherein the mass fraction of the grafted graphene was 3.0%. Purification according to the method of Example 1 obtained xanthan gum grafted graphene, the average size of the lamellae of the prepared grafted graphene was about 2.1 microns, and the xanthan gum mass content grafted in the grafted modified graphene was 4.7%. The grafted modified graphene yield was about 25% of the mass of the added flake graphite. Sample No. 2 in Figure 2 is a stable dispersion after standing for 10 months.

Example 3

10.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) were dissolved in 1000 ml of deionized water, and then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding disc speed was set at 60rpm. After 100 hours of circulation grinding, the graphene suspension processed by the grinding disc was poured into a beaker. After standing for 10 hours, the precipitation was removed by filtration to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, wherein the mass fraction of the grafted graphene was 2.5%. Purification according to the method of Example 1 was performed to obtain xanthan gum grafted graphene. Purification according to the method of Example 1 was performed to obtain xanthan gum grafted graphene. The average size of the lamellae of the grafted graphene prepared was about 2.1 microns, and the xanthan gum mass content grafted in the grafted modified graphene was 3.4%. The grafted modified graphene yield was about 18% of the mass of the added flake graphite. No. 3 in Figure 2 is a stable dispersion of the grafted modified graphene sample after standing for 10 months, with no precipitation observed.

Example 4

8.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) were dissolved in 1000 ml of deionized water, and then 150 grams of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding disc speed was set to 100rpm. After 48 hours of circulation grinding, the graphene suspension processed by the grinding disc was poured into a beaker. After standing for 10 hours, the precipitation was filtered and removed to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, and the grafted graphene mass fraction was 2.3%. Purification according to the method of Example 1 obtained xanthan gum grafted graphene, the average size of the lamellae of the prepared grafted modified graphene was about 2.3 microns, and the xanthan gum mass content grafted in the grafted modified graphene was 2.8%. The graphene yield was about 15% of the mass of the added flake graphite. No. 4 in Figure 2 is a stable aqueous dispersion of the grafted modified graphene sample after standing for 10 months, and no precipitation was seen.

Example 5

12.0 grams of xanthan gum (Meihua Biotechnology Group Co., Ltd., MHF-80R) were dissolved in 1000 ml of deionized water, and 100 grams of 100 mesh expanded graphite (Qingdao Santong Graphite Co., Ltd.) were added and stirred. The grinding disc speed was set at 70 rpm. After 72 hours of circulation grinding, the graphene suspension processed by the grinding disc was poured into a beaker. After standing for 10 hours, the precipitation was filtered and removed to obtain a stable aqueous dispersion of xanthan gum edge-grafted graphene, with a grafted graphene mass fraction of 3.5%. Purification according to the method of Example 1 obtained xanthan gum edge-grafted graphene, the average size of the lamellae of the prepared grafted graphene was greater than 3.1 microns, and the xanthan gum mass content in the grafted graphene was 2.6%. The graphene yield was about 18% of the mass of the added flake graphite. No. 5 in Figure 2 is a stable dispersion of the grafted graphene sample after standing for 10 months, with no precipitation.

Comparative Example

In 1000 ml of deionized water, add 150 g of 100 mesh flake graphite (Qingdao Santong Graphite Co., Ltd.) and stir evenly. The grinding wheel speed is set to 100 rpm. After 100 hours of cyclic grinding, the graphene suspension processed by the grinding wheel is poured into a beaker, left to stand for 10 hours, and filtered to remove the precipitate. Only a very small amount of graphene can be obtained, which is less than 0.5% of the mass of the added flake graphite. The graphene suspension can only be stably stored for a few days, and obvious precipitation can be observed after a few days, and almost all precipitation after a week.

The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

The endpoints and any values of the ranges disclosed in this article 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 endpoint values of each range, the endpoint values of each range and the 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 regarded as specifically disclosed in this article.

Claims (12)

1. A xanthan gum edge-grafted modified graphene, characterized in that the xanthan gum edge-grafted modified graphene comprises graphene and xanthan gum grafted on its edge, and the mass content of the grafted xanthan gum in the xanthan gum edge-grafted modified graphene is 1-6%, preferably 1-5%, based on the total mass of the edge-grafted modified graphene. 2. The xanthan gum edge-grafted modified graphene according to claim 1, wherein the average sheet diameter of the xanthan gum edge-grafted modified graphene is 1-5 μm. 3. An aqueous dispersion of xanthan gum edge-grafted modified graphene, characterized in that the aqueous dispersion comprises water and xanthan gum edge-grafted modified graphene stably dispersed therein, and the xanthan gum edge-grafted modified graphene is the xanthan gum edge-grafted modified graphene described in any one of claims 1-2. 4. The aqueous dispersion according to claim 3, wherein the mass fraction of the xanthan gum edge-grafted modified graphene in the aqueous dispersion is 1-20%, preferably 1-15%. 5. The aqueous dispersion according to claim 3 or 4, wherein the aqueous dispersion is stable for more than 10 months at room temperature and pressure. 6. A method for preparing an aqueous dispersion of xanthan gum edge-grafted modified graphene according to any one of claims 3 to 5, comprising the following steps: The xanthan gum, water and graphite are uniformly mixed and ground in a grinding wheel kettle. After the grinding, the mixture is allowed to stand and the precipitate is removed to obtain an aqueous dispersion of the xanthan gum edge-grafted modified graphene. 7. The preparation method according to claim 6, wherein the graphite is natural graphite and/or artificial graphite, the natural graphite is selected from one or more of flake graphite, blocky graphite, and cryptocrystalline graphite, and the artificial graphite is selected from one or more of thermal cracking graphite and highly oriented thermal cracking graphite; the graphite is preferably flake graphite; the particle size of the graphite is 5-8000 mesh, preferably 35-3000 mesh, further preferably 50-1600 mesh, and more preferably 50-300 mesh. 8. The preparation method according to claim 6, wherein the grinding is carried out in a closed or open system, preferably in a cyclic grinding at room temperature and normal pressure; the grinding conditions are: a rotation speed of 10-300 rpm, preferably 50-200 rpm; a time of 5-200 hours, preferably 10-150 hours, and more preferably 30-120 hours. 9. The preparation method according to claim 6, wherein the mass fraction of the xanthan gum is 0.1-5%, preferably 0.2-3%, based on the total mass of the xanthan gum and water. 10. The method for preparing xanthan gum edge-grafted modified graphene according to any one of claims 1 to 2, comprising the following steps: (1) preparing an aqueous dispersion of xanthan gum edge-grafted modified graphene according to the method described in any one of claims 6 to 9; (2) filtering and drying the aqueous dispersion of the xanthan gum edge-grafted modified graphene obtained in step (1) to obtain the xanthan gum edge-grafted modified graphene. The preparation method according to claim 10 , wherein the filtration is carried out by vacuum filtration with a microporous filtration membrane. 12. The preparation method according to claim 10, wherein the filtering further comprises: diluting the aqueous dispersion of edge-grafted modified graphene before filtering; and/or, After filtering, use water to remove the free xanthan gum dissolved in water.