Graphene oxide dispersion having high emulsification level and method for preparing the same

Abstract

The application discloses a graphene oxide dispersion liquid with high emulsification level and a preparation method thereof, and belongs to the technical field of two-dimensional interface materials. The graphene oxide material with different hydrophilic and hydrophobic properties is obtained on the basis of Hummers method, and the method for preparing the graphene oxide solid emulsifier with high emulsification level is as follows: for alkanes such as n-hexadecane and cyclohexane, the amount of oxidant and acid is increased, the oxidation time is prolonged, and the ball milling time is increased (the particle size of the exfoliated graphite is reduced); for solvents containing benzene rings such as benzene, the amount of oxidant is appropriately reduced, the amount of acid is controlled, the oxidation time is shortened, and the ball milling time is increased. The experimental results show that, through the control method, the appropriate graphene oxide solid emulsifier product can be prepared according to the organic phase of the emulsion more conveniently and quickly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional interface materials, and particularly relates to a graphene oxide dispersion liquid with high emulsification level and a preparation method thereof. BACKGROUND

[0002] Graphene material has great development potential in many fields such as electronic devices, energy industry and medical materials due to its flexibility, light weight and electrical conductivity caused by its unique two-dimensional conjugated structure. Graphene oxide, as a precursor material for preparing graphene material by chemical reduction method, also has a two-dimensional sheet structure. Meanwhile, the hydrophilic groups such as hydroxyl, carboxyl and epoxy groups on the surface of graphene oxide and the unoxidized SP 2 Hybrid region exists, so it has hydrophilic and lipophilic properties. The solid emulsifier prepared on the basis of graphene oxide has higher adsorption energy than traditional emulsifiers, so it can be more firmly adsorbed at the interface of two phases, and therefore the emulsion prepared by using graphene oxide as the basis has more excellent stability.

[0003] At present, the post-modification based on the surface functional groups of graphene oxide is the main means to regulate the amphiphilic properties of graphene oxide. The hydrophilic properties of graphene oxide prepared by thermal oxidation methods (such as Brodie method, Staudenmaie method and Hummers method) are much stronger than the hydrophobic properties. Hydrazine reduction, thermal reduction and organic amine modification reduction are common methods for regulating hydrophilic and hydrophobic properties. However, the post-modification method for regulating the amphiphilic properties of graphene oxide objectively prolongs the preparation process and increases the production cost, which is contrary to the current ecological concept of economy and environmental protection. Therefore, it is very urgent and necessary to accurately regulate various oxidation reaction conditions during the preparation of graphene oxide, shorten the preparation process of amphiphilic graphene oxide, reduce the production cost, and thus obtain graphene oxide materials with different amphiphilic properties.

[0004] The currently reported methods for preparing graphene oxide mainly include Brodie method, Staudenmaie method and Hummers method. Among them, Hummers is the most reliable in terms of safety, ease of operation and product stability. SUMMARY

[0005] The application aims to provide a graphene oxide dispersion liquid with high emulsification level and a preparation method thereof.

[0006] The application is improved on the basis of Hummers method to obtain two-dimensional graphene oxide materials with different hydrophilic and hydrophobic properties, and the prepared two-dimensional graphene oxide materials are applied to the emulsification of three organic solvents, namely n-hexadecane, cyclohexane and benzene, to obtain emulsion systems with high emulsification level. Specifically, for n-hexadecane, cyclohexane and other alkane solvents, the application adopts the method of increasing the amount of oxidant and acid, prolonging the oxidation time and increasing the ball milling time (reducing the particle size of exfoliated graphite) to prepare graphene oxide solid emulsifier with high emulsification level; for benzene and other solvents containing benzene ring, due to the influence of aromatic conjugation, the amount of oxidant should be appropriately reduced, the amount of acid should be controlled, the oxidation time should be shortened, and the ball milling time should be increased to prepare graphene oxide solid emulsifier with high emulsification level.

[0007] In order to prepare graphene oxide products with different amphiphilic properties, the application provides a preparation method of graphene oxide dispersion liquid with high emulsification level, and the steps are as follows:

[0008] (1) Select high-purity exfoliated graphite with a certain mesh number, and ball mill under the conditions of revolution of 150-300 rpm and rotation of 1000-1500 rpm for 2-9 h, and then screen and remove the ball milling beads;

[0009] (2) Mix a certain amount of exfoliated graphite and sodium nitrate after ball milling in step (1) into concentrated sulfuric acid and stir to mix uniformly;

[0010] (3) Slowly add potassium permanganate to the system obtained in step (2) in 2-5 times under ice bath, and keep for 20-40 minutes under ice bath for pre-oxidation;

[0011] (4) Oil-bath the system obtained in step (3) at 30-40℃ for a certain time for oxidation reaction;

[0012] (5) Slowly add a certain amount of deionized water to the system obtained in step (4) within 15-30 minutes, and control the temperature of the system to be not more than 75℃;

[0013] (6) Increase the temperature of the system obtained in step (5) to 95-98℃ within 10 minutes;

[0014] (7) Stir the system obtained in step (6) at 95-98℃ for 20-40 minutes to accelerate the oxidation reaction process;

[0015] (8) Add a certain amount of deionized water to the system obtained in step (7) to terminate the oxidation process, and naturally cool to room temperature;

[0016] (9) Add a certain amount of 30wt% hydrogen peroxide to the system obtained in step (8) until the system is brown red-gold yellow and no bubbles are generated;

[0017] (10) centrifuging the system obtained in step (9) at a speed of 10000-15000 rpm for 4-8 minutes, removing the supernatant after centrifugation, and retaining the precipitate;

[0018] (11) adding dilute hydrochloric acid of a certain concentration to the precipitate obtained in step (10), uniformly dispersing by ultrasonic, removing the supernatant after centrifugation, and retaining the precipitate;

[0019] (12) adding deionized water to the precipitate obtained in step (11), uniformly dispersing by ultrasonic, removing the supernatant after centrifugation, and retaining the precipitate; repeating the operation process of "adding deionized water, uniformly dispersing by ultrasonic, removing the supernatant after centrifugation, and retaining the precipitate" for multiple times, until the pH of the supernatant is 5-6, to obtain a brownish red paste precipitate;

[0020] (13) freezing and drying the paste graphene oxide obtained in step (12) by liquid nitrogen extraction, to obtain a brownish red-gold yellow porous graphene oxide aerogel;

[0021] (14) rapidly (8-15 minutes) ultrasonic dispersing the porous graphene oxide aerogel obtained in step (13) under ice water bath, to prepare the graphene oxide dispersion liquid with high emulsification level according to the present application.

[0022] Mixing and oscillating the graphene oxide dispersion liquid obtained in step (14) with n-hexadecane, cyclohexane or benzene according to a certain volume ratio, ultrasonic mixing and emulsifying at a certain power for 1 h, rapidly transferring to an elongated glass tube after oscillating again, and measuring the emulsification rate after standing for 24 h, to detect the amphiphilic emulsification performance;

[0023] Using cottonseed oil and turpentine oil, and span 20 and Tween 80 to prepare gradient HLB value oil phases respectively, mixing and emulsifying the graphene oxide dispersion liquid of a certain concentration with the two types of mixed oil phases at a certain power, to prepare emulsions, measuring the emulsification rate after standing for 24 h, and detecting the influence of oil phase HLB value on the emulsification performance of graphene oxide.

[0024] Preferably, the mesh number of the high-purity flake graphite in step (1) is 200-3500 mesh, and the ball milling time is 2-9 h;

[0025] Preferably, the mass-volume ratio of the flake graphite, sodium nitrate and concentrated sulfuric acid after ball milling in step (2) is 1 g: 1 g: 25-75 mL, and the mass fraction of the used concentrated sulfuric acid is 98%;

[0026] Preferably, the mass ratio of the total amount of potassium permanganate to graphite in step (3) is 2.25-4.50:1;

[0027] Preferably, the oxidation time in step (4) is 0.5-2 h;

[0028] Preferably, the volume ratio of the deionized water added in step (5) to the concentrated sulfuric acid in step (2) is 1-3:1;

[0029] Preferably, the volume ratio of the deionized water added in step (8) to the concentrated sulfuric acid in step (2) is 1:0.5-2.0;

[0030] Preferably, the volume-mass ratio of the hydrogen peroxide added in step (9) to the ball-milled flake graphite is 20-30 mL:1 g;

[0031] Preferably, the molar concentration of the dilute hydrochloric acid added in step (11) is 2 mol / L;

[0032] Preferably, the centrifugal speed in steps (10), (11) and (12) is 10,000-15,000 rpm, and the centrifugal time each time is 8-15 minutes;

[0033] The embodiment of the present application provides a preparation method of a graphene oxide dispersion liquid with high emulsification level, which shortens the preparation process and is more economical and environmentally friendly compared to a post-modification method for preparing a graphene oxide product with amphiphilic properties.

[0034] According to an embodiment of the present application, the HLB value of the graphene oxide measured by the emulsification method is between 11 and 12, and the corresponding oil phase meeting the range shows better emulsification effect.

[0035] According to other embodiments of the present application, the graphene oxide with regulated amphiphilic properties shows different emulsification properties in n-hexadecane, benzene and cyclohexane, and shows a fixed trend. It is illustrated that the preparation conditions of the graphene oxide have different effects on the amphiphilic properties in different oil phases. According to the regulation means of the present application, the appropriate graphene oxide solid emulsifier product can be prepared according to the organic phase of the emulsion more conveniently and quickly. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The appearance photo of the graphene oxide aerogel prepared for Example 1;

[0037] Figure 2 : XRD variation diagram of different graphene oxide aerogels under the regulation of potassium permanganate / concentrated sulfuric acid / oxidation time / milling time, for Examples 1-9;

[0038] Figure 3 : Infrared curve of the graphene oxide aerogel under the regulation of potassium permanganate / concentrated sulfuric acid / oxidation time / milling time, for Examples 1-9;

[0039] Figure 4a : This is a graph showing the changes in emulsification rate and emulsion bubble particle size of different types of graphene oxide in the hexadecane / water emulsion systems of Examples 1 to 9;

[0040] Figure 4b : Particle size distribution of emulsion bubbles in the hexadecane / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0041] Figure 4c : Microscopic images of emulsion bubbles in hexadecane / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0042] Figure 5a : This is a graph showing the changes in emulsification rate and emulsion bubble particle size of cyclohexane / water emulsion systems for different types of graphene oxide in Examples 1 to 9;

[0043] Figure 5b : Particle size distribution of emulsion bubbles in cyclohexane / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0044] Figure 5c : Microscopic images of emulsion bubbles in cyclohexane / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0045] Figure 6a : This is a graph showing the changes in emulsification rate and emulsion bubble particle size of benzene / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0046] Figure 6b : Particle size distribution of emulsion bubbles in benzene / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0047] Figure 6c : Microscopic images of emulsion bubbles in benzene / water emulsion systems of different types of graphene oxide in Examples 1 to 9;

[0048] Figure 7 : Emulsification rate curve of graphene oxide in cottonseed oil / turpentine oil-water system and state diagram of emulsion system;

[0049] Figure 8 : Emulsification rate curve and emulsion state diagram of graphene oxide in the span20 / Tween80-water system;

[0050] Figure 9 Scanning electron microscope image and structural model of graphene oxide dispersion. Detailed Implementation

[0051] In order to make the purposes, technical solutions, effects and advantages of the embodiments of the present application more clear, the embodiments will be described in more details and completeness below. It should be noted that the following described embodiments are not all the embodiments, but only the embodiments of the preferred inventive conditions of the present application. The reagents and instruments used in the embodiments can be purchased through normal market channels. Based on the embodiments of the present application, the ordinary skilled in the art can directly obtain the embodiments without creative activities, which belongs to the protection scope of the present application.

[0052] The method for synthesizing graphene oxide aerogel with different amphiphilic properties is prepared by the following specific steps:

[0053] Embodiment 1

[0054] Select 325 purpose high-purity flake graphite, use high-speed ball mill, under the parameters of revolution 200 rpm, rotation 1200 rpm ball mill 2 h, separate the ball milling beads with a screen. Take 1 g of the flake graphite ball milled for 2 h, 1 g of sodium nitrate, 75 mL of concentrated sulfuric acid (mass fraction of 98%), stir and mix evenly and keep for 5 minutes. Under the condition of ice water bath stirring, slowly add a total of 4.50 g of potassium permanganate in three times, keep the ice water bath for 30 minutes, at this time the color of the system is dark green. Transfer the system to the oil bath at 35℃ and heat for 1 h, the color gradually changes to brown red. Slowly drop 75 mL of deionized water in 20 minutes, and control the temperature not to exceed 75℃. Increase the temperature to 98℃ in 10 minutes, and stir for 30 minutes. During this process, the color changes from brown red to golden yellow. Stop heating and add 45 mL of deionized water to terminate the reaction, and naturally cool down to room temperature. Add excess 25 mL of 30% wt. hydrogen peroxide to completely reduce the high valence manganese ions.

[0055] (1) Centrifuge the reaction solution of step (1) at 12000 rpm for 5 minutes, remove the supernatant, and retain the precipitate. Add 100 mL of 2 mol / L dilute hydrochloric acid solution to the precipitate, ultrasonic dispersion is uniform, centrifuge at 12000 rpm for 5 minutes, remove the supernatant, and retain the precipitate. Add 100 mL of deionized water to the precipitate, ultrasonic dispersion is uniform, centrifuge at 12000 rpm for 10 minutes, remove the supernatant, and retain the precipitate; repeat the operation process of “add 100 mL of deionized water, ultrasonic dispersion is uniform, centrifuge at 12000 rpm for 10 minutes, remove the supernatant, and retain the precipitate” for 5 times, finally the supernatant pH is 5-6, and the lower part of the graphene oxide precipitate exists in the form of paste.

[0056] (2) Freeze the paste-like graphene oxide with liquid nitrogen extraction, and then place it in a freeze dryer at -55℃ and a vacuum degree of >1000 Pa for freeze drying, finally obtain the graphene oxide aerogel product (the product mass is 0.898 g), as shown in Figure 1As shown, the graphene oxide aerogel product appears as a golden yellow foam with uniform pores, and is easy to ultrasonically disperse to prepare a graphene oxide dispersion liquid.

[0057] For convenience of statistical graphing, we respectively mark the product as K-4.50g, H-3 / 3V, O-1h, Q-2h according to the conditions in the drawings.

[0058] Example 2

[0059] The potassium permanganate is added in an amount of 3.00g, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as K-3.00g.

[0060] Example 3

[0061] The potassium permanganate is added in an amount of 2.25g, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as K-2.25g.

[0062] Example 4

[0063] The concentrated sulfuric acid is added in an amount of 50mL, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as H-2 / 3V.

[0064] Example 5

[0065] The concentrated sulfuric acid is added in an amount of 25mL, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as H-1 / 3V.

[0066] Example 6

[0067] The oil bath at 35℃ is maintained for 0.5h, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as O-0.5h.

[0068] Example 7

[0069] The oil bath at 35℃ is maintained for 2h, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as O-2h.

[0070] Example 8

[0071] The ball milling time is regulated to 4h, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as Q-4h.

[0072] Example 9

[0073] The ball milling time is regulated to 9h, and the rest of the implementation process is completely consistent with Example 1, and the obtained product is marked as Q-9h.

[0074] The graphene oxide aerogel prepared in Example 1-Example 9 is subjected to XRD determination in the range of 5°-30°, and the results are as follows Figure 2The XRD analysis results show that with the increase of the amount of KMn04, concentrated H2S04, the extension of oxidation time and ball milling time, the characteristic peak position in the XRD pattern gradually moves to small angle, which indicates that the interlayer spacing of the prepared graphene oxide two-dimensional material gradually expands. In the K-2.25g, H-1 / 3V example, there is an incomplete oxidation of graphite characteristic peak near 26°.

[0075] The graphene oxide aerogels prepared in Examples 1-9 were ground and mixed uniformly according to the mass ratio of graphene oxide to KBr of 1mg:200mg, and then subjected to infrared measurement, and the results are shown in Figure 3 The infrared analysis shows that with the increase of the amount of KMn04, concentrated H2S04, the extension of oxidation time and ball milling time, the absorption intensity of graphene oxide at 3000cm -1 The above infrared absorption intensity is stronger, the oxidation degree is higher, and the number of oxygen-containing functional groups on the surface increases.

[0076] Example 10

[0077] The specific preparation process of the graphene oxide dispersion liquid is as follows:

[0078] Take 100mg of graphene oxide aerogel prepared in Examples 1-9, respectively, and add to 50mL of deionized water, and ultrasonic in the ultrasonic dispersing instrument for 10 minutes (instrument: SCIENTZ-1500F ultrasonic dispersing instrument of Ningbo Xinzhi Biological Technology Co., Ltd.; parameters: 10Min, 30%, 2.0Sed), and the whole process of ultrasonic dispersion is carried out in ice water bath, and finally 2mg / mL graphene oxide dispersion liquid is obtained. The color of the graphene oxide dispersion liquid prepared under different conditions presents regular change, and the results are consistent with the infrared results, and with the increase of the oxidation degree, the color of the dispersion liquid presents the change from brown red to light golden yellow. The dispersion liquid is sampled and subjected to scanning electron microscope shooting. As shown in Figure 9 The graphene oxide is distributed in the form of two-dimensional sheet, Figure 9 The lower left image in the structure model is the structure model, and a large number of oxygen-containing groups such as carboxyl and hydroxyl are distributed on the edge of the graphene oxide sheet material, and the inside is mainly epoxy and hydroxyl.

[0079] Example 11

[0080] Take 3.2mL, 2mg / mL graphene oxide dispersion liquid obtained in Example 10 and 3mL n-hexadecane, respectively, mix and ultrasonic for 30 minutes (frequency 40Khz), and then place in constant temperature incubation shaker for 1h (200rpm), transfer the obtained emulsion system to glass test tube (8*300mm) and seal for 24h, and use the scale to measure the height H 乳 of the emulsified layer and the total height H总 Emulsification rate = (H 乳 / H 总 )*100% was calculated; and the microstate of each sample was photographed by fluorescence inverted microscope, and the emulsion bubble particle size and its distribution range were statistically analyzed. The results are shown in Figure 4a and Figure 4b . Among them Figure 4c shows the real emulsion state of the dispersion / cyclohexane emulsion system corresponding to each example, which presents small particle size and basically normal distribution characteristics.

[0081] From the analysis of Figure 4, it can be seen that the oxidation degree can be increased by increasing the amount of KMnO4 and concentrated sulfuric acid, and prolonging the oxidation and ball milling time, so as to improve the ability of graphene oxide to emulsify cyclohexane / water system, and obtain an emulsion system with high emulsification rate and dense emulsion bubbles.

[0082] Example 12

[0083] 3.2 mL of 2 mg / mL graphene oxide dispersion obtained in Example 10 and 3 mL of cyclohexane were mixed, ultrasonicated for 30 minutes (frequency 40 kHz), and then placed in a constant temperature incubation shaker for 1 h (200 rpm). The obtained emulsion system was transferred to a glass test tube (8*300 mm) and sealed for 24 h. The emulsification rate was measured; and the microstate of each emulsion sample was photographed by fluorescence inverted microscope, and the emulsion bubble particle size was statistically analyzed. The results are shown in Figure 5a and Figure 5b . Among them Figure 5c shows the real emulsion state of the dispersion / cyclohexane emulsion system corresponding to each example, which presents small particle size and basically normal distribution characteristics. Compared with Example 11, cyclohexane belongs to carbon number less than n-hexadecane, and the system viscosity is low, and the intermolecular force between graphene oxide is smaller, so the emulsion bubble of the emulsion system is larger than that of Example 11.

[0084] From the analysis of Figure 5, it can be seen that the oxidation degree can be increased by increasing the amount of KMnO4 and concentrated sulfuric acid, and prolonging the oxidation and ball milling time, so as to improve the ability of graphene oxide to emulsify cyclohexane / water system, and obtain an emulsion system with high emulsification rate and dense emulsion bubbles.

[0085] Example 13

[0086] Take 3.2 mL, 2 mg / mL graphene oxide dispersion solution obtained in Example 10 and 3 mL of benzene, respectively, mix them, and ultrasonic for 30 minutes (frequency 40 kHz), then place them in a constant temperature incubator for 1 h (200 rpm), transfer the obtained emulsion system to a glass test tube (8*300 mm) and seal it for 24 h, measure the emulsification rate; and take pictures of the microstate of the emulsified bubbles of each emulsified sample by fluorescence inverted microscope, and statistically analyze the particle size and distribution state of the emulsified bubbles. The results are shown in Figure 6a and Figure 6b . Figure 6c The real emulsion state of the dispersion / benzene emulsion system corresponding to each example is shown, which shows large particle size distribution as a whole, and the particle size distribution is uneven. The reason for the obvious emulsification difference from Examples 11 and 12 is the influence of the strong conjugation effect between the organic solvent benzene and graphene oxide.

[0087] As shown in Figure 6, the ability of graphene oxide dispersion to emulsify benzene / water system can be improved by appropriately reducing the amount of KMnO4 and concentrated sulfuric acid, selecting the peak value (i.e., graphite: concentrated H2SO4 = 1 g: 50 mL), appropriately shortening the oxidation time, and prolonging the ball milling time, so as to obtain a high emulsification rate dense emulsion bubble emulsion system. The benzene / water system has obvious regulation difference from Examples 11 and 12, which is affected by the conjugation effect between the aromatic group surface of graphene oxide and the organic phase of benzene.

[0088] Example 14

[0089] Cottonseed oil and turpentine are mixed according to the mass shown in Table 1 to prepare oil phases with gradient HLB values from 10.5 to 13. Take 2.5 mL of 2 mg / mL graphene oxide dispersion prepared in Example 10 and add 1.5 mL of water to dilute to obtain 4 mL of 1.25 mg / mL graphene oxide dispersion. Ultrasonic the graphene oxide dispersion mixed with the oil phase with gradient HLB values for 30 minutes (frequency 40 kHz), then place it in a constant temperature incubator for 1 h (200 rpm), transfer the obtained emulsion system to a glass test tube (8*300 mm) and seal it for 24 h, measure the emulsification rate. As shown in Figure 7 , it is known that the HLB value of graphene oxide is in the range of 11 to 12, indicating that the oil phase with HLB value in the range of 11 to 13 required for emulsification can also achieve good emulsification effect by using the graphene oxide aerogel solid emulsifier prepared by the present application.

[0090] Table 1: Proportion of mixed oil phase with gradient HLB value prepared by cottonseed oil and turpentine

[0091]

[0092] Example 15

[0093] Table 2: Span 20 and Tween 80 formulation gradient HLB value mixed oil phase ratio

[0094]

[0095] Span 20 and Tween 80 were mixed in the mass shown in Table 2 to prepare an oil phase with a gradient HLB value of 10.5-13. 2.5 mL of the graphene oxide dispersion prepared in Example 10 at 2 mg / mL was added to 1.5 mL of water to dilute to obtain 4 mL of a graphene oxide dispersion at 1.25 mg / mL. The graphene oxide dispersion was mixed with the oil phase with a gradient HLB value and then ultrasonicated for 30 minutes (frequency 40 kHz), and then placed in a constant temperature incubator for 1 h (200 rpm). The emulsion system was transferred to a centrifuge tube (10 mL size) and capped and allowed to stand for 24 h, and the emulsification rate was determined. As shown in Table 3, the HLB of the graphene oxide aerogel solid emulsifier prepared in the present application was between 11 and 13, and Example 14 confirmed the correctness of each other. Figure 8 Table 3: Emulsification rate of graphene oxide aerogel solid emulsifier

Claims

1. A method for preparing a graphene oxide dispersion with a high emulsification level, comprising the following steps: (1) Select high-purity flake graphite with a certain mesh size, and ball mill it for 2 to 9 hours under the parameters of 150 to 300 rpm revolution and 1000 to 1500 rpm rotation, and then remove the ball beads by sieving. (2) Add a certain mass of the flake graphite and sodium nitrate mixture after ball milling in step (1) into concentrated sulfuric acid and stir to mix well; (3) Under ice bath conditions, potassium permanganate is slowly added to the system obtained in step (2) in 2 to 5 portions, and pre-oxidation is carried out under ice bath conditions for 20 to 40 minutes; (4) The system obtained in step (3) is subjected to an oil bath oxidation reaction at 30-40℃ for a certain period of time; (5) Slowly add a certain amount of deionized water to the system obtained in step (4), and complete the addition within 15 to 30 minutes, while controlling the system temperature to not exceed 75°C; (6) Heat the system obtained in step (5) to 95-98°C within 10 minutes; (7) Stir the system obtained in step (6) at 95-98°C for 20-40 minutes to accelerate the oxidation reaction process; (8) Add a certain amount of deionized water to the system obtained in step (7) to terminate the oxidation process and allow it to cool naturally to room temperature; (9) Add a certain amount of 30% wt hydrogen peroxide to the system obtained in step (8) until the system is brownish-red to golden yellow and no bubbles are generated; (10) Centrifuge the system obtained in step (9) at 10,000 to 15,000 rpm for 4 to 8 minutes. After centrifugation, remove the supernatant and retain the precipitate. (11) Add a certain concentration of dilute hydrochloric acid to the precipitate obtained in step (10), disperse it evenly by ultrasonication, remove the supernatant after centrifugation, and retain the precipitate; (12) Add deionized water to the precipitate obtained in step (11), disperse it evenly by ultrasonication, remove the supernatant after centrifugation, and retain the precipitate; repeat the operation of "adding deionized water, dispersing it evenly by ultrasonication, removing the supernatant after centrifugation, and retaining the precipitate" multiple times until the pH of the supernatant is 5-6, and a brownish-red paste precipitate is obtained. (13) The paste-like graphene oxide obtained in step (12) was freeze-dried by liquid nitrogen extraction to obtain a brownish-red to golden-yellow porous graphene oxide aerogel. (14) The porous graphene oxide aerogel obtained in step (13) is rapidly ultrasonically dispersed in an ice-water bath to prepare the graphene oxide dispersion with a high level of emulsification.

2. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The high-purity flake graphite mentioned in step (1) has a mesh size of 200 to 3500 and a ball milling time of 2 to 9 hours.

3. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: In step (2), the mass-to-volume ratio of the ball-milled flake graphite, sodium nitrate, and concentrated sulfuric acid is 1 g: 1 g: 25-75 mL; the mass fraction of the concentrated sulfuric acid is 98%.

4. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The total amount of potassium permanganate in step (3) is in a mass ratio of 2.25 to 4.50:1 to graphite.

5. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The oxidation time in step (4) is 0.5 to 2 hours.

6. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The volume ratio of the deionized water added in step (5) to the concentrated sulfuric acid in step (2) is 1 to 3:1; the volume ratio of the deionized water added in step (8) to the concentrated sulfuric acid in step (2) is 1:0.5 to 2.

0.

7. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The volume-to-mass ratio of hydrogen peroxide added in step (9) to ball-milled graphite flakes is 20-30 mL: 1 g.

8. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The concentration of the dilute hydrochloric acid added in step (11) is 2 mol / L.

9. The method for preparing a graphene oxide dispersion with a high emulsification level as described in claim 1, characterized in that: The centrifugation speed in steps (10), (11) and (12) is 10,000 to 15,000 rpm, and the centrifugation time is 8 to 15 minutes each time.

10. A graphene oxide dispersion with a high emulsification level, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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