CN117963895A - Xanthan gum edge grafting modified graphene and aqueous dispersion thereof and preparation method - Google Patents
Xanthan gum edge grafting modified graphene and aqueous dispersion thereof and preparation method Download PDFInfo
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- HIFJUMGIHIZEPX-UHFFFAOYSA-N sulfuric acid;sulfur trioxide Chemical compound O=S(=O)=O.OS(O)(=O)=O HIFJUMGIHIZEPX-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
- C01B32/19—Preparation by exfoliation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2204/00—Structure or properties of graphene
- C01B2204/20—Graphene characterized by its properties
- C01B2204/32—Size or surface area
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- Chemical & Material Sciences (AREA)
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Nanotechnology (AREA)
- Inorganic Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention belongs to the technical field of graphene preparation, and relates to xanthan gum edge grafting modified graphene and an aqueous dispersion liquid and a preparation method thereof. The xanthan gum edge grafting modified graphene comprises graphene and xanthan gum grafted on the edge of the graphene, and the mass content of the xanthan gum grafted in the xanthan gum edge grafting modified graphene is 1-6% based on the total mass of the edge grafting modified graphene. The xanthan gum can improve the solution viscosity, indirectly transfer the shearing force between the millstone to the graphite flake, further reduce the damage to the graphite lattice and improve the stripping effect of the graphite flake.
Description
Technical Field
The invention belongs to the technical field of graphene preparation, and particularly relates to xanthan gum edge grafting modified graphene, an aqueous dispersion of xanthan gum edge grafting modified graphene and a preparation method thereof.
Background
Graphene is a monolayer of carbon atoms in a honeycomb structure formed by the bonding of one carbon atom to three immediately surrounding carbon atoms. Graphene is attracting attention as a novel material with high light transmittance, high electric conductivity, high heat conduction, high specific surface area and excellent mechanical properties. Currently, graphene is in the discovery phase of large-scale preparation and application. The preparation technology of the high-quality low-cost functionalized graphene is the basis of future scale application. The scientists have developed a series of preparation techniques: mechanical exfoliation, redox, chemical vapor deposition, epitaxial growth, thermal expansion, electrochemical, and the like. The mechanical stripping method and the oxidation-reduction method are both based on graphite raw materials and are prepared by a mechanical or chemical stripping technology, so that the raw materials are rich in sources, the cost is easy to control, and the method is more suitable for large-scale production of graphene. The oxidation-reduction method is characterized in that natural graphite is oxidized by a strong oxidant, rich polar groups are introduced into the surface of the natural graphite, graphene oxide is obtained through solvation or ultrasonic dispersion, and then the polar groups on the surface of the graphene oxide are removed through reduction, so that the graphene is obtained. However, a large amount of strong acid and strong oxidant, such as concentrated sulfuric acid, fuming nitric acid, potassium permanganate, perchloric acid, etc., are used in the production process, which causes serious waste liquid pollution. The prepared graphene has certain defects, such as topological defects of five-membered rings, seven-membered rings and the like left by polar groups removed by reduction or structural defects of hydroxyl groups, which can cause loss of partial performance of the graphene, so that the application of the graphene is limited. National standard GB/T30544.13-2018 section 13: graphene oxide and reduced graphene oxide are defined separately from graphene in graphene and related two-dimensional materials.
The graphene surface obtained through oxidation contains rich oxygen-containing groups, such as epoxy groups, hydroxyl groups, carboxyl groups and the like, and can be chemically modified through chemical reaction. Salavagione H J et al (Salavagione H J,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.) graft PVA to graphene oxide by esterification between hydroxyl groups on polyvinyl alcohol (PVA) and carboxyl groups on graphene oxide to obtain PVA grafted graphene oxide. Xu Guojiang et al (Xu Guojiang, xu Pengwu, shi Dongjian, et al, preparation of PEG grafted graphene oxide and cell imaging [ J ]. Inorganic chemistry theory, 2014,30 (009): 1994-1999.) studied polyethylene oxide grafted graphene oxide. Li Shanrong et al (Li Shanrong, liu Shaorong, qi Bo, et al) synthesized and applied biphenyl thermotropic liquid crystal grafted graphene oxide [ J ]. Polymer science and engineering, 2013,29 (007): 17-20) studied biphenyl thermotropic liquid crystal grafted graphene oxide. The method is to prepare the grafted graphene oxide by using abundant active groups on the surface of the graphene oxide prepared by an oxidation method. Sun Shuang et al (Sun Shuang, ma Xiaofei, wang Nan, et al. Preparation of GN-PVA/PVA composite film materials and Performance test [ J ]. Chemical and biological engineering, 2016,33 (9): 5.) PVA graft reduced graphene oxide was prepared by reacting PVA with graphene oxide and then reducing. At present, polymer grafted graphene is mainly prepared based on the above method. However, topological defects such as five-membered rings, seven-membered rings and the like on the surface of the polymer grafted graphene prepared by a graphene oxide-based grafting and re-reduction method and residual oxygen-containing groups still exist, and the polymer grafted graphene belongs to polymer grafted graphene oxide or polymer grafted reduced graphene oxide, and the structure of the polymer grafted graphene is different from that of polymer grafted graphene.
Common mechanical stripping methods are ball milling, sanding, ultrasonic, and the like. Although the methods can be used for mass production of graphene, the structural damage of the graphene is serious because of the large damage effect of mechanical force, and the size of the graphene is also often smaller than 100 nanometers. Therefore, the technical key of the mechanical stripping method is to reduce the destructiveness and prepare the graphene with larger area.
Disclosure of Invention
The invention aims to provide xanthan gum edge grafted modified graphene, stable aqueous dispersion of the xanthan gum edge grafted modified graphene and a preparation method thereof.
The first aspect of the invention provides xanthan gum edge grafting modified graphene, which comprises graphene and xanthan gum grafted on the edge of the graphene, wherein the mass content of the xanthan gum grafted in the xanthan gum edge grafting modified graphene is 1-6%, preferably 1-5%, based on the total mass of the edge grafting modified graphene.
The second aspect of the 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, the xanthan gum edge-grafted modified graphene being the xanthan gum edge-grafted modified graphene described above.
The third aspect of the present invention provides a method for preparing the aqueous dispersion of xanthan gum edge grafting modified graphene, comprising the following steps:
and uniformly mixing xanthan gum, water and graphite, grinding in a millstone kettle, standing after finishing grinding, and removing precipitation to obtain the xanthan gum edge grafted modified graphene aqueous dispersion.
The fourth aspect of the present invention provides a method for preparing the xanthan gum edge grafting modified graphene, comprising the following steps:
(1) According to the method, the aqueous dispersion of the xanthan gum edge grafting modified graphene is prepared;
(2) And (3) filtering and drying the aqueous dispersion of the xanthan gum edge grafting modified graphene obtained in the step (1) to obtain the xanthan gum edge grafting modified graphene.
The aqueous dispersion of the xanthan gum grafted graphene prepared by the technical invention has the following advantages:
1. Compared with the grinding processes such as ultrasonic, ball milling, sand milling and the like, the grinding disc has weak damage to the graphite crystal structure, and the xanthan gum edge grafted graphene with a larger sheet layer is easy to prepare.
2. The xanthan gum can improve the solution viscosity, indirectly transfer the shearing force between the millstone to the graphite flake, further reduce the damage to the graphite lattice and improve the stripping effect of the graphite flake.
3. In the stripping process, the xanthan gum is grafted to the edge of the graphene, and the graphene grafted on the edge of the xanthan gum is stably dispersed in water.
4. In the preparation process, the xanthan gum edge grafted graphene can be stably dispersed in water, and the graphite flakes can be precipitated, so that the separation is easy.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.
FIG. 1 is a schematic view of an apparatus for preparing an aqueous dispersion of grafted graphene according to an embodiment of the present invention;
FIG. 2 is a photograph of a stable aqueous dispersion of edge-grafted graphene of xanthan gum prepared in examples 1-5;
FIG. 3 is a scanning electron micrograph of edge grafted graphene of xanthan gum prepared in example 1;
FIG. 4 is a transmission electron micrograph of edge grafted graphene of xanthan gum prepared in example 1;
FIG. 5 is an infrared absorption spectrum of the xanthan gum edge-grafted graphene prepared in example 1;
FIG. 6 is a graph of the infrared absorption spectrum of FIG. 5 after baseline flattening treatment;
Fig. 7 is a thermogravimetric analysis diagram of the xanthan gum edge grafted graphene prepared in example 1, the upper curve represents crystalline flake graphite, and the lower curve represents xanthan gum edge grafted graphene.
Detailed Description
The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The invention provides xanthan gum edge grafting modified graphene, which comprises graphene and xanthan gum grafted on the edge of the graphene, wherein the mass content of the xanthan gum grafted in the xanthan gum edge grafting modified graphene is 1-6%, preferably 1-5%, such as 1%, 2%, 3%, 4% and 5% based on the total mass of the edge grafting modified graphene.
In the invention, the mass content of the grafted xanthan gum part in the edge grafting modified graphene can be measured by a thermogravimetric analysis method. For example, the mass loss of the xanthan gum edge grafted graphene sample is measured from 50.00 ℃ to 800.00 ℃ at a temperature rising speed of 20.00 ℃/min under the condition that the nitrogen flow rate of the sample is 20.0ml/min and the balance nitrogen flow rate is 40.0ml/min, namely the mass content of the xanthan gum polymer grafted to graphene.
In the present invention, "xanthan gum" may refer to both the compound form and the group form, for example, xanthan gum in "xanthan gum edge grafting modified graphene" is the group form, and in the preparation method, xanthan gum is the compound form. Those skilled in the art will be able to distinguish between the meaning explicitly according to the context.
The inventors found in the research process of preparing graphene by millstone peeling graphite/water slurry that adding xanthan gum to a system to increase the viscosity of the system can improve the graphite peeling effect, and unexpectedly, even in an aqueous solution, xanthan gum can be grafted to the edge of peeled graphene, so that a stable aqueous dispersion of xanthan gum grafted modified graphene is formed.
The structure and properties of the xanthan gum edge grafted graphene are obviously different from those of the prior grafted graphene oxide or the prior grafted reduced graphene oxide.
From the structural point of view, the national standard GB/T30544.13-2018 independently defines graphene oxide and reduced graphene oxide, wherein the graphene oxide is chemically modified graphene obtained by oxidizing and stripping graphite, and the surface of the graphene oxide is subjected to strong oxidation modification, so that the oxygen content is high; the reduced graphene oxide is the graphene oxide with reduced oxygen content, part of oxygen-containing functional groups still remain in practice, and the SP 3 chemical bond cannot be completely reduced to the SP 2 chemical bond, so that a plurality of topological defects are left. Therefore, the structure of graphene oxide and reduced graphene oxide is greatly different from that of graphene. The invention adopts graphene, but not graphene oxide and reduced graphene oxide. From the aspect of properties, the xanthan gum modified graphene reported in the literature is mostly based on the grafting reaction of an oxygen-containing group of graphene oxide and xanthan gum, and then the xanthan gum grafted graphene is prepared by reduction.
The xanthan gum selected for use in the present invention may be any of various types of water-soluble xanthan gum available in the prior art, such as transparent, instant or plain type.
According to the invention, the grinding disc shearing stripping action is that the xanthan gum aqueous solution acts on graphite, so that the damage action on graphene is small compared with methods such as ball milling and sand milling, therefore, the edge grafted graphene sheet is relatively large, and specifically, the average sheet diameter of the edge grafted modified graphene is 1-5 mu m.
The average sheet diameter of the edge grafting modified graphene can be obtained by randomly measuring the size of more than 10 pieces of graphene to calculate the average value after imaging by a Scanning Electron Microscope (SEM) or an atomic force microscope. The measurement method of the single-chip graphene size comprises the following steps: and (3) drawing three lines on the surface of the graphene sheet as far as possible through the center of the sheet, forming an included angle of about 60 degrees between the lines, measuring the lengths of the graphene on the three lines, and calculating an average value as the size of the graphene sheet.
The invention also provides an aqueous dispersion of the xanthan gum edge grafting modified graphene, which comprises water and the xanthan gum edge grafting modified graphene stably dispersed in the aqueous dispersion, wherein the xanthan gum edge grafting modified graphene is the xanthan gum edge grafting modified graphene.
According to a preferred embodiment of the 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 is stable for more than 10 months at room temperature and normal pressure. The stable time means that no macroscopic precipitation occurs during this period, and specifically, the precipitation amount is less than 1%.
The invention also provides a preparation method of the aqueous dispersion liquid of the xanthan gum edge grafting modified graphene, which comprises the following steps:
and uniformly mixing xanthan gum, water and graphite, grinding in a millstone kettle, standing after finishing grinding, and removing precipitation to obtain the xanthan gum edge grafted modified graphene aqueous dispersion.
The invention relates to a grinding disc graphite stripping and in-situ grafting technology based on the assistance of a xanthan gum aqueous solution, and 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 invention, the grinding is performed in a cyclic operation, and the mechanical stripping equipment used consists of a grinding disc and a cyclic part, and the structural schematic diagram of the mechanical stripping equipment is shown in fig. 1. The millstone part comprises a movable millstone, a fixed millstone and a rotating device, and the circulating part comprises a circulating pump, a slurry storage tank and a stirring device. Wherein the grinding disc is made of metal, ceramic, glass, plastic, etc., preferably metal.
During the millstone stripping process, the moving/stationary millstone imparts shear forces to the graphite sheets between the millstones through an aqueous solution of xanthan gum. The graphite flakes are first oriented in the rotational direction of the millstone under the action of shear stress, then slowly exfoliated into thinner graphite flakes, and finally exfoliated into graphene. In the stripping process, a plurality of new edges are generated, the activity of carbon atoms of the new edges is higher, and the new edges react with xanthan gum in an aqueous solution to generate xanthan gum edge grafted graphene. The method of the invention significantly reduces damage to the graphite lattice. The viscosity increasing effect of the xanthan gum on the dispersion system is achieved, and the shearing force between the fixed millstone and the movable millstone is more effectively applied to the graphite flake in the slurry, so that the stripping preparation of graphene is achieved. In the exfoliation process, xanthan gum is grafted to the edges of graphene, thereby stably dispersing the prepared graphene in water.
The grinding of the 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 no specific requirement is imposed on the atmosphere of the system.
The grinding conditions selected in the invention are as follows: the rotation speed is 10-300 rpm, preferably 50-200 rpm; the cycle stripping time is 5 to 200 hours, preferably 10 to 150 hours, more preferably 30 to 120 hours.
Xanthan gum in the system of the invention has two functions: (1) The viscosity of the dispersion system is increased, the stripping effect of the grinding disc on the graphite sheet is improved, and (2) the graphene is grafted to the graphene, so that the graphene is stably dispersed in the aqueous solution.
The aqueous dispersion of the xanthan gum edge grafted graphene is prepared by mechanically stripping graphite through a millstone, and optional graphite can be natural graphite and/or artificial graphite, wherein the natural graphite is selected from one or more of flake graphite, block graphite and aphanitic graphite, and the artificial graphite is selected from one or more of thermal cracking graphite and high-orientation thermal cracking graphite; the graphite is preferably flake graphite; the particle size of the graphite may be from 5 to 8000 mesh, preferably from 35 to 3000 mesh, more preferably from 50 to 1600 mesh, and even more preferably from 50 to 300 mesh.
According to a preferred embodiment of the present invention, xanthan gum and water are mixed first, and then graphite is added, the mass fraction of the xanthan gum being 0.1 to 5%, preferably 0.2 to 3%, based on the total mass of the xanthan gum and water.
The invention also provides a preparation method of the xanthan gum edge grafting modified graphene, which comprises the following steps:
(1) The method comprises the steps of preparing an aqueous dispersion of xanthan gum edge grafting modified graphene;
(2) And (3) filtering and drying the aqueous dispersion of the xanthan gum edge grafting modified graphene obtained in the step (1) to obtain the xanthan gum edge grafting modified graphene.
The filtration may be carried out by a variety of conventional methods, preferably by filtration using a microfiltration membrane under reduced pressure, with a pore size of 100-1000nm, preferably 200-800nm.
According to a preferred embodiment of the invention, the filtration step further comprises diluting the aqueous dispersion of xanthan edge grafted modified graphene prior to filtration.
According to a preferred embodiment of the present invention, the filtration step further comprises filtering free xanthan dissolved in water with (deionized) water after filtration to further purify the xanthan edge grafted modified graphene.
According to the invention, a millstone process is adopted, xanthan gum, graphite and water are circularly stripped among the millstones, and the shearing action between the fixed millstone and the movable millstone is transmitted to the graphite flake through the high-viscosity xanthan gum solution, so that the stripping preparation of graphene is realized. Compared with the methods of ball milling, sand milling, ultrasonic and the like, the millstone process effectively utilizes the peeling force between millstones, and reduces the breakage of graphite sheets. Especially after the xanthan gum is thickened, the shearing force between the millstone is more effectively transferred to the graphite sheet layer through the high-viscosity solution, so that the stripping efficiency is improved, and the damage effect is reduced. Therefore, the graphene sheet prepared by the millstone method is large, flat and difficult to agglomerate. Moreover, the xanthan edge grafted graphene can be more stably dispersed in water. Therefore, the xanthan gum edge modified graphene disclosed by the invention has wide application in the fields of polymer composite materials, adsorption materials, sewage treatment, thickening aids and the like.
The present invention will be further described with reference to examples, but the scope of the present invention is not limited to these examples.
The experimental reagents in the following examples were purchased commercially, except for labeling homemade.
The millstone used in the examples was self-made.
The infrared spectrum model used in the examples was the Siemens Feicolet IS5.
The scanning electron microscope used in the examples was of the type Japanese Hitachi S4800.
Example 1
6.0 G of xanthan gum (MHF-80R, inc. of plum blossom Biotechnology group Co., ltd.) was dissolved in 1000 ml of deionized water, and 150 g of 100 mesh flake graphite (Qingdao Sanzheng graphite Co., ltd.) was added thereto and stirred uniformly. The rotating speed of the grinding disc is set to be 100rpm, after the grinding disc is circularly ground for 72 hours, the graphene suspension processed by the grinding disc is poured into a beaker, after the grinding disc is kept stand for 10 hours, the sediment is removed through filtration, and the stable aqueous dispersion of the graphene grafted on the edge of the xanthan gum is obtained, wherein the mass fraction of the graphene grafted is 2.8%. The graphene yield was about 20% of the mass of the flake graphite added. Sample No.1 in fig. 2 is a stable aqueous dispersion of xanthan gum grafted graphene after standing for 10 months, and no precipitation is seen. This is mainly because xanthan grafted at the edges of graphene plays a role in stable dispersion.
Adding 10mL of xanthan gum grafted graphene aqueous dispersion into 200mL of deionized water for dilution, then adopting a microporous filter membrane with a pore diameter of 0.22 micrometer for reduced pressure filtration, finally using 2L of deionized water for filtering out free xanthan gum, and drying to obtain purified xanthan gum grafted graphene.
Fig. 3 is a scanning electron micrograph of the prepared xanthan gum grafted graphene, with the average size of the sheets of grafted graphene being about 2.9 microns.
Fig. 4 is a transmission electron micrograph of the prepared xanthan edge grafted graphene. From the pictures, only one layer of graphene is shown, indicating that graphene is prepared.
Fig. 5 is an infrared spectrum of the prepared xanthan gum edge grafted graphene, and the infrared absorption peak of the functional group is weaker due to the low grafting rate of the xanthan gum. FIG. 6 is a graph of the infrared spectrum of FIG. 5 after a baseline has been straightened, and the absorption peaks of the functional groups are magnified to improve resolution. From the figure, it can be seen that the absorption peak of various functional groups, the stretching vibration of the alcoholic hydroxyl group at 3458cm -1, the stretching vibration of the methylene group at 2922cm -1, the vibration absorption peak of the benzene ring skeleton at 1622cm -1, the bending vibration absorption peak of the methyl group in the pyruvic acid group and the acetyl group at 1406cm -1, and the stretching vibration of the ether bond between the D-glucose unit and the D-mannose unit and the ether bond generated by the etherification reaction at 1080cm -1. The infrared spectrum shows that xanthan gum is grafted to graphene.
Fig. 7 is a thermogravimetric analysis curve of pure crystalline flake graphite and xanthan edge grafted graphene. The flake graphite has almost no weight loss; the graphene grafted on the edge of the xanthan gum starts to decompose and lose weight at 280 ℃ until the graphene is almost no longer lost weight at 330 ℃, and the loss weight is 3.2%, which shows that the mass content of the graphene grafted xanthan gum is 3.2%.
Example 2
10.0 G of xanthan gum (MHF-80R, inc. of plum blossom Biotechnology group Co., ltd.) was dissolved in 1000 ml of deionized water, and 150 g of 100 mesh flake graphite (Qingdao Sanzheng graphite Co., ltd.) was added thereto and stirred uniformly. The rotating speed of the grinding disc is set to be 100rpm, after the grinding disc is circularly ground for 100 hours, the graphene suspension processed by the grinding disc is poured into a beaker, after the grinding disc is kept stand for 10 hours, the sediment is removed through filtration, and the stable aqueous dispersion of the graphene grafted on the edge of the xanthan gum is obtained, wherein the mass fraction of the graphene grafted is 3.0%. Purifying according to the method of example 1 to obtain xanthan gum grafted graphene, wherein the average size of the prepared sheet layer of the grafted graphene is about 2.1 micrometers, and the mass content of the grafted xanthan gum in the grafted modified graphene is 4.7%. The yield of the grafted modified graphene is about 25% of the mass of the added crystalline flake graphite. Sample No. 2 in fig. 2 is a stable dispersion after 10 months of standing.
Example 3
10.0 G of xanthan gum (MHF-80R, inc. of plum blossom Biotechnology group Co., ltd.) was dissolved in 1000 ml of deionized water, and 150 g of 100 mesh flake graphite (Qingdao Sanzheng graphite Co., ltd.) was added thereto and stirred uniformly. The rotating speed of the grinding disc is set to be 60rpm, after the grinding disc is circularly ground for 100 hours, the graphene suspension processed by the grinding disc is poured into a beaker, after the grinding disc is kept stand for 10 hours, the sediment is removed through filtration, and the stable aqueous dispersion of the graphene grafted on the edge of the xanthan gum is obtained, wherein the mass fraction of the graphene grafted is 2.5%. Purifying according to the method of example 1 to obtain xanthan gum grafted graphene, wherein the average size of the prepared sheets of grafted graphene is about 2.1 microns, and the mass content of the grafted xanthan gum in the grafted modified graphene is 3.4%. The yield of the grafted modified graphene is about 18% of the mass of the added crystalline flake graphite. In fig. 2, no. 3 is a stable dispersion of the graft-modified graphene sample after standing for 10 months, and no precipitation was observed.
Example 4
8.0 G of xanthan gum (MHF-80R, inc. of plum blossom Biotechnology group Co., ltd.) was dissolved in 1000 ml of deionized water, and 150 g of 100 mesh flake graphite (Qingdao Sanzheng graphite Co., ltd.) was added thereto and stirred uniformly. The rotating speed of the grinding disc is set to be 100rpm, after the grinding disc is circularly ground for 48 hours, the graphene suspension processed by the grinding disc is poured into a beaker, after the grinding disc is kept stand for 10 hours, the sediment is removed by filtration, and the stable aqueous dispersion of the graphene grafted on the edge of the xanthan gum is obtained, wherein the mass fraction of the grafted graphene is 2.3%. Purifying according to the method of example 1 to obtain xanthan gum grafted graphene, wherein the average size of the prepared sheet layer of the grafted modified graphene is about 2.3 microns, and the mass content of the grafted xanthan gum in the grafted modified graphene is 2.8%. The graphene yield was about 15% of the mass of the flake graphite added. No. 4 in FIG. 2 is a stable aqueous dispersion of the grafted modified graphene sample after 10 months of standing, and no precipitation was observed.
Example 5
12.0 G of xanthan gum (MHF-80R, inc. of plum blossom Biotechnology group Co., ltd.) was dissolved in 1000 ml of deionized water, and 100 g of 100 mesh expanded graphite (Qingdao Sanzheng graphite Co., ltd.) was added thereto and stirred uniformly. The rotating speed of the grinding disc is set to be 70rpm, after the grinding disc is circularly ground for 72 hours, the graphene suspension processed by the grinding disc is poured into a beaker, after the grinding disc is kept stand for 10 hours, the sediment is removed through filtration, and the stable aqueous dispersion of the graphene grafted on the edge of the xanthan gum is obtained, wherein the mass fraction of the grafted graphene is 3.5%. And (3) purifying according to the method of the embodiment 1 to obtain xanthan gum edge grafted graphene, wherein the average size of the prepared sheet layers of the grafted graphene is more than 3.1 micrometers, and the mass content of the xanthan gum in the grafted graphene is 2.6%. The graphene yield was about 18% of the mass of the flake graphite added. In fig. 2, no. 5 is a stable dispersion of the grafted graphene sample after 10 months of standing, and no precipitation was observed.
Comparative example
150 G of 100 mesh flake graphite (Qingdao Santong graphite Co., ltd.) was added to 1000 ml of deionized water and stirred well. The rotation speed of the grinding disc is set to be 100rpm, after the grinding disc is circularly ground for 100 hours, the graphene suspension processed by the grinding disc is poured into a beaker, and after standing for 10 hours, sediment is removed by filtration. Only a very small amount of graphene can be obtained, which is less than 0.5% of the mass of the added crystalline flake graphite. The graphene suspension can be stably stored for only a few days, obvious precipitation can be observed after a few days, and almost all precipitation is observed after one week.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
Claims (12)
1. The xanthan gum edge grafting modified graphene is characterized by comprising graphene and xanthan gum grafted on the edge of the graphene, wherein the mass content of the xanthan gum grafted in the xanthan gum edge grafting modified graphene is 1-6%, preferably 1-5%, based on the total mass of the edge grafting modified graphene.
2. The xanthan gum edge grafted modified graphene of claim 1, wherein the average sheet diameter of the xanthan gum edge grafted modified graphene is 1-5 μιη.
3. An aqueous dispersion of xanthan edge graft modified graphene, characterized in that the aqueous dispersion comprises water and xanthan edge graft modified graphene stably dispersed therein, wherein the xanthan edge graft modified graphene is the xanthan edge graft modified graphene according to any one of claims 1 to 2.
4. An aqueous dispersion according to claim 3, wherein the mass fraction of xanthan edge grafted modified graphene in the aqueous dispersion is 1-20%, preferably 1-15%.
5. An aqueous dispersion according to claim 3 or 4 wherein the aqueous dispersion is stable for a period of more than 10 months at ambient temperature and pressure.
6. A method for preparing the aqueous dispersion of xanthan gum edge-grafted modified graphene according to any of claims 3-5, comprising the steps of:
and uniformly mixing xanthan gum, water and graphite, grinding in a millstone kettle, standing after finishing grinding, and removing precipitation to obtain the xanthan gum edge grafted modified graphene aqueous dispersion.
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, block graphite and aphanitic graphite, and the artificial graphite is selected from one or more of thermally cracked graphite and highly oriented thermally cracked graphite; the graphite is preferably flake graphite; the particle size of the graphite is 5 to 8000 mesh, preferably 35 to 3000 mesh, further preferably 50 to 1600 mesh, more preferably 50 to 300 mesh.
8. The process according to claim 6, wherein the milling is carried out in a closed or open system, preferably by cyclic milling at room temperature and pressure; the grinding conditions are as follows: the rotation speed is 10-300 rpm, preferably 50-200 rpm; the time is 5 to 200 hours, preferably 10 to 150 hours, more preferably 30 to 120 hours.
9. The preparation method according to claim 6, wherein the mass fraction of xanthan gum is 0.1-5%, preferably 0.2-3% based on the total mass of xanthan gum and water.
10. The method for preparing the xanthan gum edge grafting modified graphene according to any one of claims 1-2, comprising the following steps:
(1) An aqueous dispersion of xanthan edge-grafted modified graphene prepared according to the method of any one of claims 6-9;
(2) And (3) filtering and drying the aqueous dispersion of the xanthan gum edge grafting modified graphene obtained in the step (1) to obtain the xanthan gum edge grafting modified graphene.
11. The production method according to claim 10, wherein the filtration is reduced-pressure filtration using a microporous filtration membrane.
12. The method of manufacturing of claim 10, wherein the filtering further comprises:
Diluting the aqueous dispersion of the edge grafting modified graphene before filtering; and/or the number of the groups of groups,
After filtration, the free xanthan gum dissolved in the water is filtered off with water.
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