A method for preparing a metal ion-modified graphene oxide film

Abstract

This method discloses a method for preparing metal ion-modified graphene oxide membranes. The method involves washing a prepared graphene oxide filter cake with a solution containing lanthanides and iron group elements to obtain a metal ion-modified graphene oxide filter cake. The graphene oxide membrane prepared from this metal ion-modified filter cake has fewer defects, a smoother surface, and fewer wrinkles under microscopic observation. Furthermore, it exhibits a higher degree of graphitization and larger grain size, resulting in a thermal diffusivity increase of 50–150 mm. 2 / s, the results show that lanthanides have a significant effect on improving the thermal diffusivity of graphene films.

Description

Technical Field

[0001] This invention relates to the field of graphene oxide preparation and its assembled film technology, and particularly to a method for preparing a metal ion modified graphene oxide film. Background Technology

[0002] Currently, the main industrial method for mass production of graphene oxide is the Hummers process. This method involves mixing graphite and an oxidant in a specific ratio under controlled solvent conditions, undergoing a series of rigorous temperature control processes, hydration, and purification steps to ultimately produce graphene oxide cake (GO filter cake). The GO filter cake then undergoes dispersion, homogenization, coating, and drying to obtain a GO membrane. After further low-temperature, high-temperature, graphitization, and densification treatments, the GO membrane yields a powerful and widely applicable graphene thermal conductive film. Summary of the Invention

[0003] One objective of this method is to provide a method for preparing metal-modified graphene oxide films. The graphene oxide films prepared by this method have fewer defects, a smoother surface with fewer wrinkles under microscopic observation, a higher degree of graphitization, and larger grain size, resulting in a thermal diffusivity increase of 50–150 mm. 2 / s, the results show that lanthanides have a significant effect on improving the thermal diffusivity of graphene films.

[0004] To achieve the above objectives, the following plan is proposed:

[0005] A method for preparing a metal ion-modified graphene oxide membrane, wherein the prepared graphene oxide filter cake is washed with a solution containing lanthanide and iron group elements to obtain a metal ion-modified graphene oxide filter cake, and then a metal ion-modified graphene oxide membrane is prepared from the metal ion-modified graphene oxide filter cake.

[0006] Preferably, the method specifically includes the following steps:

[0007] Step 1: Mix graphite with concentrated sulfuric acid and stir to obtain a graphite intercalation compound solution;

[0008] Step 2: At the first temperature, add an oxidizing agent to the graphite intercalation compound solution;

[0009] Step 3: Heat the mixture from Step 2 to the second temperature and stir continuously to complete the oxidation reaction;

[0010] Step 4: Add water to the system treated in Step 3 to carry out a hydration reaction, thereby exfoliating the graphene oxide;

[0011] Step 5: Wash and filter to obtain graphene oxide filter cake;

[0012] Step 6: Dry the graphene oxide filter cake from Step 5 and calculate the solid content. Wash it again with a mixed solution containing lanthanides and iron group elements. After filtration, obtain a metal ion modified graphene oxide filter cake. Then, prepare a metal ion modified graphene oxide membrane from the metal ion modified graphene oxide filter cake.

[0013] Preferably, in step 1, the graphite is natural graphite with a purity ≥90wt% and a particle size of 100-500 mesh.

[0014] Preferably, the weight ratio of graphite to concentrated sulfuric acid is 1:37 to 55, and more preferably, the mass ratio of graphite to concentrated sulfuric acid is 1:42 to 48.

[0015] Preferably, in step 2, the first temperature is 0-5°C; the oxidant is potassium permanganate (KMnO4); and the mass ratio of graphite to oxidant is 1:2-5, preferably 1:3-4.

[0016] Preferably, in step 3, the second temperature is 25-40°C higher than the first temperature; the second temperature is 30-40°C.

[0017] Preferably, in the hydration reaction in step 4, the volume of water added is 1 to 2 times the volume of concentrated sulfuric acid, and the system temperature of the hydration reaction is 70 to 80°C.

[0018] Preferably, the washing solution in step 5 is a dilute sulfuric acid solution with a mass percentage concentration of 1%.

[0019] Preferably, in step 6, the mixed solution is a solution formed by adding lanthanide chlorides and iron group chlorides to a 1% (w / w) sulfuric acid solution; the lanthanides include any one of lanthanum, cerium, and praseodymium; the iron group elements include any one of iron, cobalt, and nickel.

[0020] Preferably, in step 6, the amount of lanthanide elements added is 0.1% to 2% of the dry weight of graphene oxide, and more preferably, the amount of lanthanide elements added is 0.5% to 1% of the dry weight of graphene oxide; the amount of iron group elements added is 0.1% to 2% of the dry weight of graphene oxide, and more preferably, the amount of iron group elements added is 0.2% to 0.5% of the dry weight of graphene oxide.

[0021] The beneficial effects of this plan are as follows:

[0022] This method is simple, quick, and adds almost no increase to production costs. It can be applied to all Hummers processes for preparing and synthesizing graphene oxide.

[0023] Graphene films prepared using the graphene oxide filter cake obtained by the modification method in this application, compared with graphene films prepared from graphene oxide synthesized by the conventional Hummers method, exhibit fewer defects, a smoother surface, and fewer wrinkles under microscopic observation. Furthermore, they possess a higher degree of graphitization and larger grain size, resulting in a thermal diffusivity increase of 50–150 mm. 2 / s, the results show that lanthanides have a significant effect on improving the thermal diffusivity of graphene films. Attached Figure Description

[0024] To more clearly illustrate the implementation of this solution, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this solution. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a SEM image of the unmodified blank graphene oxide film from Example 1;

[0026] Figure 2A Lanthanum-added (La) prepared in Example 2 3+ ) and iron (Fe 3+ Electron micrograph of the graphene oxide film after oxidation;

[0027] Figure 2B Lanthanum-added (La) prepared in Example 2 3+ ) and iron (Fe 3+ Energy spectrum of the graphene oxide film after oxidation;

[0028] Figure 3A Lanthanum-added (La) prepared in Example 3 3+ ) and nickel (Ni 3+ Electron micrograph of the graphene oxide film after oxidation;

[0029] Figure 3B Lanthanum-added (La) prepared in Example 3 3+ ) and nickel (Ni 3+ Energy spectrum of the graphene oxide film after oxidation;

[0030] Figure 4A The cerium-added (Ce) prepared in Example 4 3+ ) and iron (Fe 3+ Electron micrograph of the graphene oxide film after oxidation;

[0031] Figure 4B The cerium-added (Ce) prepared in Example 4 3+ ) and iron (Fe 3+ Energy spectrum of the graphene oxide film after oxidation;

[0032] Figure 5A The cerium-added (Ce) prepared in Example 5 3+ ) and cobalt (Co) 3+ Electron micrograph of the graphene oxide film after oxidation;

[0033] Figure 5B The cerium-added (Ce) prepared in Example 5 3+ ) and cobalt (Co) 3+ Energy spectrum of the graphene oxide film after oxidation;

[0034] Figure 6A Praseodymium (Pr) prepared in Example 6 3+ ) and nickel (Ni 3+ Electron micrograph of the graphene oxide film after oxidation;

[0035] Figure 6B Praseodymium (Pr) prepared in Example 6 3+ ) and nickel (Ni 3+ Energy spectrum of the graphene oxide film after oxidation;

[0036] Figure 7A Praseodymium (Pr) prepared in Example 7 3+ ) and cobalt (Co) 3+ Electron micrograph of the graphene oxide film after oxidation;

[0037] Figure 7B Praseodymium (Pr) prepared in Example 7 3+ ) and cobalt (Co) 3+ The energy spectrum of the graphene oxide film after oxidation. Detailed Implementation

[0038] The implementation methods of this solution will be described in further detail below. Obviously, the described embodiments are only a part of the embodiments of this solution, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this solution can be combined with each other.

[0039] The terms “first,” “second,” etc. (if applicable) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data used in this way can be interchanged where appropriate. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or apparatus that comprises a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0040] In the development of the Hummers process for preparing graphene oxide, research has primarily focused on the impact of factors such as the type and amount of oxidant used in the early stages of the reaction, as well as stirring time and temperature, on the performance of the resulting graphene oxide cake (GO filter cake). Changes to these factors mainly affect the carbon content and exfoliation degree of the GO filter cake, with the aim of improving the thermal, mechanical, or electrical properties of downstream graphene oxide (GO) products, such as graphene assembled films. However, these changes in experimental conditions often bring drawbacks, such as increased experimental steps, increased types and amounts of oxidant, increased hazardous waste generation, and more stringent experimental conditions.

[0041] The inventors of this application have proposed a new solution to address the above problems. Under unchanged experimental conditions (including intercalation, oxidation, and hydration processes, as well as the type and amount of oxidant), after obtaining graphene oxide filter cake through hydration and filtration, the washing process is modified. A combination of catalytically active metal elements, namely a combination of lanthanides (lanthanum, cerium, praseodymium) and iron group elements (iron, cobalt, nickel), is introduced into the GO filter cake. This influences the interlayer structure of graphene oxide, allowing for a higher degree of graphitization of the carbon material and affecting crystal orientation, thereby resulting in a final product with more significant thermal properties.

[0042] The method for modifying graphene oxide in this application is not only applicable to the preparation process mentioned in this application, but also to other synthesis processes (such as changing the type of graphite, the concentration and amount of concentrated sulfuric acid, the type and amount of oxidant, the amount of water added during the hydration process, and the synthesis temperature during the process). After obtaining the graphene oxide filter cake, the graphene oxide filter cake can be further processed by the method provided in this application, and the performance of the final modified graphene oxide filter cake can be further improved.

[0043] In this application, the applicant provides a method for preparing a metal ion-modified graphene oxide film, the method comprising the following steps:

[0044] Step 1: Mix graphite powder with concentrated sulfuric acid and stir to obtain a graphite intercalation compound solution;

[0045] Step 2: At the first temperature, add an oxidizing agent to the graphite intercalation compound solution;

[0046] Step 3: Heat the mixture from Step 2 to the second temperature and stir continuously to complete the oxidation reaction;

[0047] Step 4: Add water to the system treated in Step 3 to carry out a hydration reaction, thereby exfoliating the graphene oxide;

[0048] Step 5: Wash and filter to obtain graphene oxide filter cake;

[0049] Step 6: Dry the graphene oxide filter cake (GO filter cake) from Step 5 to calculate the solid content, wash it again with a mixed solution containing lanthanide and iron group elements, filter it to obtain the final product, which is a metal ion modified graphene oxide filter cake. Then, a metal ion modified graphene oxide membrane is made from the metal ion modified graphene oxide filter cake.

[0050] In one embodiment, the graphite is natural graphite with a purity ≥90wt% and a particle size of 100-500 mesh; the concentrated sulfuric acid concentration is ≥96%; and the weight ratio of graphite to concentrated sulfuric acid is 1:37-55, preferably 1:42-48.

[0051] The different graphite particle sizes affect the subsequent graphite exfoliation. If the size is too large, incomplete oxidation will occur, resulting in a large number of black particles in the material. If the size is too small, oxidation will be too complete, reducing the yield. In addition, small-sized graphene oxide is prone to agglomeration, forming thick sheets.

[0052] In the reaction system, concentrated sulfuric acid is used as a solvent. A mass ratio of concentrated sulfuric acid to graphite below 37 will result in a viscous reaction system, uneven heat exchange, and a tendency for local overheating. A ratio above 55 will cause the reaction system to become too dilute, resulting in waste of sulfuric acid. A ratio of 37 to 40 provides a suitable viscosity that neither affects the heat exchange of the reaction system nor causes waste of sulfuric acid.

[0053] In one embodiment, the first temperature is 0–5°C; the oxidant is potassium permanganate (KMnO4); and the mass ratio of graphite to oxidant is 1:2–5, preferably 1:3–4.

[0054] The addition of the oxidant during the reaction is exothermic. If the temperature exceeds 5°C, it can cause the temperature to rise rapidly and become uncontrollable during the addition of the oxidant. Temperature is easier to control within the range of 0–5°C. Using more than five times the amount of graphite will increase production costs, while using less than twice the amount will result in a low degree of oxidation and poor exfoliation of the graphene oxide. The oxidant should be added while stirring to prevent excessive localized exothermic reactions.

[0055] In one embodiment, the second temperature is 25 to 40°C higher than the first temperature, preferably 30 to 40°C.

[0056] The rate of oxidation reactions is affected by temperature. Increased temperature causes an exponential increase in reaction rate and heat release, potentially leading to uncontrolled reactions or even explosions. Conversely, excessively low temperatures reduce the reaction rate and increase reaction time. Within a given temperature range, the reaction is easily controlled and relatively fast.

[0057] In one embodiment, the volume of water added in the hydration reaction is 1 to 2 times the volume of concentrated sulfuric acid, and the system temperature during the hydration reaction is controlled at 70 to 80°C.

[0058] Adding water initiates the hydration and exfoliation process. The amount of water added affects the final exfoliation of graphene oxide; too much or too little water can lead to the formation of thick flakes or black particles.

[0059] In one embodiment, the washing solution is a dilute sulfuric acid solution with a mass percentage concentration of 1%.

[0060] In one embodiment, the mixed solution is a solution formed by adding lanthanide chlorides and iron group chlorides to a 1% (w / w) sulfuric acid solution; the lanthanides include any one of lanthanum (La), cerium (Ce), and praseodymium (Pr); the iron group includes any one of iron (Fe), cobalt (Co), and nickel (Ni).

[0061] In the mixed solution, lanthanides are the primary catalysts, and iron group elements are the auxiliary catalysts. Both lanthanides and iron group elements are added in the form of water-soluble metal salts, and both are trivalent cations. Cl- is selected as the anion. - It should be noted that Cl - This only includes the most common anions; other types of anions, such as NO3-, are also mentioned. - Acetate ions, etc., can also be used, and their catalytic mechanism is similar to that of Cl. - same;

[0062] In one embodiment, the amount of lanthanides added is 0.1% to 2% of the dry weight of graphene oxide, preferably 0.5% to 1% of the dry weight of graphene oxide; the amount of iron group elements added is 0.1% to 2% of the dry weight of graphene oxide, preferably 0.2% to 0.5% of the dry weight of graphene oxide.

[0063] It should be noted that steps 1 to 5 are only a common method for synthesizing and preparing graphene oxide filter cake. This application is not only applicable to this method, but also to other synthesis methods (such as changing the type of graphite, the concentration and amount of concentrated sulfuric acid, the type and amount of oxidant, the amount of water added during the hydration process, and the synthesis temperature during the process). After obtaining the graphene oxide filter cake, step 6 can be used to further process the graphene oxide filter cake, and the performance of the final modified graphene oxide filter cake can be further improved.

[0064] In this application, without changing the synthesis method of graphene oxide filter cake, the post-processing can be modified to further introduce catalytically active lanthanides and iron group elements into the graphene oxide filter cake. Lanthanides can form covalent bonds with oxygen-containing functional groups in graphene oxide, thereby affecting the crystal orientation of graphene oxide, reducing defects inside the film, resulting in a smoother film surface and fewer micro-wrinkles. Furthermore, in the subsequent graphitization process, the graphene oxide film containing lanthanides exhibits a higher degree of graphitization and a larger grain size, significantly improving the thermal diffusivity of the graphene film compared to blank graphene oxide. Iron group elements are mainly used to suppress the "gas expansion" phenomenon caused by sulfur in the graphene oxide film during graphitization, while also playing a certain role in catalyzing graphitization.

[0065] Lanthanide elements such as lanthanum, cerium, and praseodymium react with carbon at high temperatures (>2000℃) to produce carbides (MC2). These carbides have a tetragonal crystal structure with a c value of approximately 0.59–0.65 nm, which is approximately twice the interlayer spacing of graphene (0.33 nm). Therefore, at high temperatures, lanthanide carbides can better promote the formation of graphitized carbon. During the graphitization process, the interlayer arrangement of graphene can be made more orderly, forming a directional arrangement, resulting in a higher degree of graphitization of the graphene film. This leads to a larger grain size (Lc value) of the graphene film, thereby improving the thermal properties and other related properties of the product.

[0066] The method of this application will be described below through specific embodiments.

[0067] Example 1

[0068] The steps for preparing graphene oxide in this embodiment are as follows:

[0069] 1. In a reactor, 200-mesh graphite was mixed with sulfuric acid (the mass percentage concentration of sulfuric acid was 98%, and the mass ratio of graphite to sulfuric acid was 1:35), and then stirred thoroughly at 15°C for 2 hours to obtain a pre-intercalated compound.

[0070] 2. Under ice-water bath conditions (with the reaction system temperature controlled at 0–5℃), KMnO4 (graphite and KMnO) is reacted... 4d The mixture (at a mass ratio of 1:2) is slowly added to the reactor and stirred.

[0071] 3. Heat the mixed solution formed in step 2 to 30°C and stir continuously;

[0072] 4. Add water to the reactor in an amount 1.5 times the volume of sulfuric acid, and control the temperature of the reaction system below 80℃ to exfoliate the graphene oxide.

[0073] 5. Washing and filtration were performed to obtain graphene oxide (GO) filter cake;

[0074] 6. Graphene oxide film was prepared;

[0075] 6.1 Graphene oxide filter cake was dispersed in an aqueous solution at a solid content of 4%, and then stirred and homogenized to obtain graphene oxide slurry;

[0076] 6.2 After defoaming the graphene oxide slurry, it is coated by a coating machine and dried in an oven to obtain a graphene oxide film with a smooth surface and no bubbles.

[0077] Furthermore, in this embodiment, the obtained graphene oxide film is used to prepare a graphene thermally conductive film, and the steps are as follows:

[0078] a. Graphene film can be obtained by subjecting graphene oxide film to low-temperature thermal reduction, high-temperature thermal reduction, graphitization and densification treatment;

[0079] b. Test the thermal diffusivity of the graphene thermally conductive film.

[0080] Example 2

[0081] The preparation method of graphene oxide (GO) in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing lanthanum chloride and ferric chloride. 3+ and Fe 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0082] The lanthanum-added (La) preparation in this embodiment 3+ ) and iron (Fe 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 2A As shown; Figure 2B To add lanthanum (La) 3+ ) and iron (Fe 3+ Energy spectrum of graphene oxide film after oxidation.

[0083] Figure 1 This is an electron microscope image of the graphene oxide film prepared in Example 1 (without added metal ions). Figure 2A To add (La) 3+ ) and iron (Fe 3+ Electron microscopy images of the modified graphene oxide film surface after addition show that the surface of the graphene oxide film is smoother and the wrinkles are significantly improved after the addition of lanthanide and iron group elements.

[0084] Example 3

[0085] The preparation method of graphene oxide in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing lanthanum chloride and nickel chloride. 3+ and Ni 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0086] The lanthanum-added (La) preparation in this embodiment 3+ ) and nickel (Ni 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 3A As shown; Figure 3B To add lanthanum (La) 3+ ) and nickel (Ni 3+ Energy spectrum of graphene oxide film after oxidation.

[0087] Example 4

[0088] The preparation method of graphene oxide in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing cerium chloride and ferric chloride. 3+ and Fe 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0089] The cerium-added (Ce) prepared in this embodiment 3+ ) and iron (Fe 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 4A As shown; Figure 4B To add cerium (Ce) 3+ ) and iron (Fe 3+ Energy spectrum of graphene oxide film after oxidation.

[0090] Example 5

[0091] The preparation method of graphene oxide in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing cerium chloride and cobalt chloride. 3+ and Co 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0092] The cerium-added (Ce) prepared in this embodiment 3+ ) and cobalt (Co) 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 5A As shown; Figure 5B To add cerium (Ce) 3+ ) and cobalt (Co) 3+ Energy spectrum of graphene oxide film after oxidation.

[0093] Example 6

[0094] The preparation method of graphene oxide in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing praseodymium chloride and nickel chloride. 3+ and Ni 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0095] The praseodymium (Pr) prepared in this embodiment 3+ ) and nickel (Ni 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 6A As shown; Figure 6B To add praseodymium (Pr 3+ ) and nickel (Ni 3+ Energy spectrum of graphene oxide film after oxidation.

[0096] Example 7

[0097] The preparation method of graphene oxide in this embodiment is the same as in Example 1. After obtaining the GO filter cake, it is washed with a dilute sulfuric acid solution containing praseodymium chloride and cobalt chloride. 3+ and Co 3+ The mass fractions were 1% and 0.5% of the weight of the GO filter cake, respectively, and the modified GO filter cake was obtained after vacuum filtration. The subsequent membrane fabrication process was the same as in Example 1.

[0098] The praseodymium (Pr3) prepared in this embodiment + ) and cobalt (Co) 3+ The electron microscope image of the graphene oxide film after oxidation is shown below. Figure 7A As shown; Figure 7B To add praseodymium (Pr 3+ ) and cobalt (Co) 3+ Energy spectrum of graphene oxide film after oxidation.

[0099] The defect degree of the graphene oxide films prepared in the above embodiments was determined by Raman spectroscopy, and I was calculated. D / I G The thermal diffusivity (TDP) of the graphene film was measured, and the thermal diffusivity (In-Plane anisotropy), interlayer spacing, and grain size (X-ray diffractometer, XRD) of the reduced graphene film were measured. The results of the thermal diffusivity and grain size of the graphene film are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. The addition amounts of lanthanide elements and iron group elements in the embodiments are 1% and 0.5%, respectively, but are not limited to these amounts. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a metal ion-modified graphene oxide film, characterized in that, This method involves washing the prepared graphene oxide filter cake with a solution containing lanthanides and iron group elements to obtain a metal ion modified graphene oxide filter cake, and then using the metal ion modified graphene oxide filter cake to obtain a metal ion modified graphene oxide membrane. The method specifically includes the following steps: Step 1: Mix graphite with concentrated sulfuric acid and stir to obtain a graphite intercalation compound solution; Step 2: At the first temperature, add an oxidizing agent to the graphite intercalation compound solution; Step 3: Heat the mixture from Step 2 to the second temperature and stir continuously to complete the oxidation reaction; Step 4: Add water to the system treated in Step 3 to carry out a hydration reaction, thereby stripping away the oxidation. Graphene; Step 5: Wash and filter to obtain graphene oxide filter cake; Step 6: Dry the graphene oxide filter cake from Step 5, calculate the solid content, and use lanthanide-containing... The mixed solution of iron group elements and iron group elements was washed again and filtered to obtain a metal ion modified graphene oxide filter cake. Then, a metal ion modified graphene oxide membrane was prepared from the metal ion modified graphene oxide filter cake. In step 6, the mixed solution is a solution formed by adding lanthanide chlorides and iron group chlorides to a 1% (w / w) sulfuric acid solution; the lanthanides include any one of lanthanum, cerium, and praseodymium; the iron group elements include any one of iron, cobalt, and nickel. The amount of lanthanide elements added is 0.1% to 2% of the dry weight of graphene oxide; the amount of iron group elements added is 0.1% to 2% of the dry weight of graphene oxide.

2. The preparation method according to claim 1, characterized in that, The amount of lanthanide elements added is 0.5-1% of the dry weight of graphene oxide.

3. The preparation method according to claim 1, characterized in that, The amount of iron group elements added is 0.2~0.5% of the dry weight of graphene oxide.

4. The preparation method according to claim 1, characterized in that, In step 1, the graphite is natural graphite with a purity of ≥90wt% and a particle size of 100-500 mesh.

5. The preparation method according to claim 1, characterized in that, The weight ratio of graphite to concentrated sulfuric acid is 1:37~55.

6. The preparation method according to claim 5, characterized in that, The mass ratio of graphite to concentrated sulfuric acid is 1:42~48.

7. The preparation method according to claim 1, characterized in that, In step 2, the first temperature is 0~5℃; the oxidant is potassium permanganate KMnO4; and the mass ratio of graphite to oxidant is 1:2~5.

8. The preparation method according to claim 7, characterized in that, The mass ratio of graphite to oxidant is 1:3~4.

9. The preparation method according to claim 1, characterized in that, In step 3, the second temperature is 25-40°C higher than the first temperature; the second temperature is 30-40°C.

10. The preparation method according to claim 1, characterized in that, In the hydration reaction described in step 4, the volume of water added is 1 to 2 times the volume of concentrated sulfuric acid, and the system temperature of the hydration reaction is 70 to 80°C.

11. The preparation method according to claim 1, characterized in that, In step 5, the washing solution is a 1% (w / w) dilute sulfuric acid solution.

Images