Graphene purification methods and equipment

Abstract

This application relates to the field of carbon materials technology, and particularly to a graphene purification method and apparatus. The method includes uniformly mixing graphene powder containing metallic impurities with a pre-prepared electrolyte to obtain a graphene electrolyte mixture; placing the graphene electrolyte mixture in a material chamber within an electrolytic cell, and electrolyzing the mixture to remove metallic impurities from the graphene powder; during electrolysis, placing the anode in the center of the material chamber and the cathode inside the electrolytic cell but outside the material chamber, while stirring the graphene electrolyte mixture; collecting the electrolyzed graphene powder, washing and drying it to obtain purified graphene powder. This application can effectively improve the efficiency and effect of electrolytic purification.

Description

Technical Field

[0001] This application relates to the field of carbon materials technology, and in particular to a graphene purification method and a graphene purification apparatus. Background Technology

[0002] Graphene powder grown using CVD methods in vapor deposition furnaces or by blowing bubbles in liquid metal inevitably contains attached metal catalyst powder. Graphene powder containing metal impurities can severely negatively impact subsequent applications, thus requiring purification. Chemical etching is a common technique for removing metal impurities; however, this process consumes large amounts of etching solution, resulting in high costs and significant wastewater discharge. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this application provides a graphene purification method and a graphene purification apparatus, the specific technical solution of which is as follows:

[0004] On one hand, a method for purifying graphene, the method comprising:

[0005] Graphene powder containing metallic impurities is mixed evenly with a pre-prepared electrolyte to obtain a graphene electrolyte mixture. The graphene electrolyte mixture is placed in the material chamber of an electrolytic cell and electrolyzed to remove metallic impurities from the graphene powder. During the electrolysis process, the anode is placed in the middle of the material chamber, and the cathode is placed in the inner cavity of the electrolytic cell but outside the material chamber. The graphene electrolyte mixture is also stirred.

[0006] The graphene powder after electrolytic treatment was collected, washed, and dried to obtain purified graphene powder.

[0007] In a possible implementation, during the electrolysis process, the graphene electrolyte mixture in the material cavity is stirred by a material stirring paddle, and the material stirring paddle moves up and down reciprocating in the material cavity, with a stirring speed of 350 to 450 rpm.

[0008] In a possible implementation, the pre-prepared electrolyte comprises sulfuric acid, metal sulfate, and water, wherein the mass fraction ratio of sulfuric acid, metal sulfate, and water is (10%–17%):(2%–5%):100%.

[0009] In a possible implementation, the distance between the anode and the inner wall of the material cavity is 35-50 mm, and the distance between the cathode and the outer wall of the material cavity is 35-50 mm.

[0010] In a possible implementation, the viscosity of the graphene electrolyte mixture is 3000–4500 mPa·s.

[0011] In a possible implementation, during the electrolysis process, the DC voltage applied to the anode and cathode in the electrolysis device is 3.5 to 5V.

[0012] In a possible implementation, the temperature of the pre-prepared electrolyte in the electrolysis device is 45–60°C during the electrolysis process.

[0013] In a possible implementation, the electrolytic cell is connected to an electrolyte storage device, and during the electrolysis process, the pre-prepared electrolyte in the electrolyte storage device is controlled to circulate between the pre-prepared electrolyte in the electrolytic cell.

[0014] In a possible implementation, during the preparation of the graphene electrolyte mixture, the stirring speed is 1000-1500 rpm and the stirring time is 30-45 min.

[0015] In a possible implementation, the material cavity has multiple through holes on its wall, and the material cavity communicates with the inner cavity of the electrolytic cell through these through holes. The aperture of the through holes is 800-2000 mesh. On the other hand, this application provides a graphene purification apparatus applied to the above-mentioned graphene purification method, comprising an electrolytic cell, a material cavity placed in the electrolytic cell, a mixing tank, and an electrolyte storage device. The material cavity communicates with the inner cavity of the electrolytic cell, and the inner cavity of the electrolytic cell is respectively connected to the mixing tank and the electrolyte storage device via pipelines.

[0016] An anode is provided in the middle of the material cavity, and a cathode is provided outside the material cavity in the electrolytic cell;

[0017] The material cavity is also equipped with a material stirring paddle for stirring the graphene electrolyte mixture; under external force, the graphene electrolyte mixture in the mixing tank can enter the material cavity and circulate with the pre-made electrolyte in the electrolytic cell, and the pre-made electrolyte in the electrolyte storage device and the pre-made electrolyte in the electrolytic cell can circulate.

[0018] In a possible implementation, one or more of the material chambers may be placed in the electrolytic cell, and each material chamber is equidistant from the cathode.

[0019] In a possible implementation, the material cavity includes a support grid and an inner liner. The support grid is located outside the inner liner, and the inner liner is attached to and fixed to the inner wall of the support grid of the material cavity. The inner liner is provided with a plurality of through holes, through which the inner liner can confine the graphene within the inner cavity of the inner liner.

[0020] In a possible implementation, the anode is an anode plate, and the cathode is a cathode plate;

[0021] The distance between the surface of the anode plate and the inner wall of the liner is 35-50 mm, and the distance between the surface of the cathode plate and the outer wall of the liner is 35-50 mm.

[0022] In a possible implementation, the material stirring paddle may also be connected to a reciprocating motion drive device, which can drive the material stirring paddle to reciprocate back and forth within the inner cavity of the material chamber.

[0023] In a possible implementation, the material stirring impeller has a plurality of randomly distributed stirring impeller through holes. Based on the above technical solution, this application has the following beneficial effects:

[0024] The graphene purification method provided in this application involves uniformly mixing graphene powder containing metal impurities with a pre-prepared electrolyte to obtain a graphene electrolyte mixture; placing the graphene electrolyte mixture in the material chamber of the electrolytic cell of an electrolytic device, and electrolyzing the graphene electrolyte mixture to remove metal impurities from the graphene powder; during the electrolysis process, placing the anode in the middle of the material chamber, placing the cathode in the inner cavity of the electrolytic cell and located outside the material chamber, and stirring the graphene electrolyte mixture; collecting the electrolyzed graphene powder, washing and drying it to obtain purified graphene powder. Thus, graphene purification via electrolysis removes metallic impurities, reduces costs, and improves the environmental friendliness of the purification process. The anode is positioned in the center of the material cavity, extending into the middle of the graphene electrolyte mixture, ensuring that all graphene particles are within the effective electrolysis zone, thus improving electrolysis efficiency and purification effect. Furthermore, stirring ensures a uniform concentration of the graphene electrolyte mixture within the material cavity, preventing sedimentation and improving the uniformity of contact between the graphene and the anode. Simultaneously, it promotes internal and external electrolyte exchange, further optimizing electrolysis efficiency and purification effect. The graphene powder purified using this method can achieve a specific surface area of ​​up to 240 m². 2 The particle size of graphene powder is above / g, and the oxygen content can reach below 0.0032%. 50 Above 70μm, D 99 Above 215 μm, the resistivity of the film material made from an acrylic resin emulsion containing 5 wt% of the graphene powder is below 1.37 Ω·cm. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0026] Figure 1 : A schematic diagram of the graphene purification device provided in the embodiments of this application;

[0027] Figure 2 : Figure 1 A magnified view of a portion of the image;

[0028] Figure 3 : Figure 1 Enlarged top view of the middle slide rail drive rod and reciprocating motion drive device;

[0029] Figure 4 A schematic flowchart of the graphene purification method provided in this application embodiment;

[0030] Figure 5 Raman spectra of graphene powder products provided in the embodiments of this application;

[0031] Figure 6 Infrared spectra of graphene powder products provided in the embodiments of this application;

[0032] Figure 7 : Figure 5 Raman spectra of the graphene powder product after acid washing;

[0033] Figure 8 : Figure 6 Infrared spectrum of the graphene powder product after acid washing;

[0034] Reference numerals: 1-Electrolytic cell, 2-Cavity limiting strip, 3-Cathode limiting strip, 4-Anode limiting column, 5-Material cavity, 6-Anode, 7-Cathode, 8-Diaphragm pump, 9-Filter cylinder, 10-Water circulation pump, 11-Filtrate storage tank, 12-Evaporation and concentration device, 13-Pure water outlet, 14-Electrolytic cell inlet, 15-Electrolytic cell outlet, 16-Mixing tank, 17-Drive device bracket, 18-Third drive motor, 19-Mixing agitator. 20-Mixing tank outlet, 21-Electrolyte storage device, 22-Fourth drive motor, 23-Electrolyte stirring paddle, 24-Storage device outlet, 25-Anode support plate, 26-Material stirring paddle, 27-First drive motor, 28-Slide rail device, 29-Reciprocating motion drive device, 30-Motor lead screw, 31-Second drive motor, 32-Slide rail drive rod, 33-Integrated cooling and heating device, 34-Contact terminal, 35-Rectified DC power supply. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application 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 can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0038] The following describes the graphene purification apparatus provided in the embodiments of this application. Please refer to it. Figure 1-3 , Figure 1-3 This is a schematic diagram of a graphene purification device. It is understood that the method structure shown in the figures is merely a technical solution of one specific embodiment of this application, and the method of this application may include fewer or more structural features, and is not limited to the purification device structure described in the figures.

[0039] refer to Figure 1-2The graphene purification apparatus of this application includes an electrolytic cell 1, a material cavity 5 placed in the electrolytic cell 1, a mixing tank 16, and an electrolyte storage device 21. The material cavity 5 is connected to the inner cavity of the electrolytic cell 1, and the inner cavity of the electrolytic cell 1 is connected to the mixing tank 16 and the electrolyte storage device 21 by pipelines. An anode 6 is provided in the middle of the material cavity 5, and a cathode 7 is provided outside the material cavity 5 in the electrolytic cell 1. A material stirring paddle 26 is also provided in the material cavity 5 for stirring the graphene electrolyte mixture. Under the drive of external force, the graphene electrolyte mixture in the mixing tank 16 can enter the material cavity 5 and circulate with the pre-made electrolyte in the electrolytic cell 1. The pre-made electrolyte in the electrolyte storage device 21 and the pre-made electrolyte in the electrolytic cell 1 can circulate. By setting an anode 6 in the middle of the material chamber 5 and combining it with a material stirring paddle 26, the contact and distance uniformity between graphene and anode 6 are improved, preventing material sedimentation and improving electrolysis efficiency and effect. In addition, an automatic replenishment system is set up for the graphene electrolyte mixture in the mixing tank 16 to the material chamber 5, and a circulation system is set up for the pre-prepared electrolyte in the electrolytic cell 1 and the replenished pre-prepared electrolyte. This achieves automation of graphene electrolysis while ensuring a constant concentration of ions in the electrolyte and promoting the flow and exchange of electrolyte between the material chamber 5 and the electrolytic cell 1, further improving electrolysis efficiency and purification effect.

[0040] Specifically, one or more material cavities 5 can be placed in the electrolytic cell 1. The distance between each material cavity 5 and the cathode 7 is the same to ensure the voltage stability and uniformity of the material cavity 5 in which the graphene electrolyte mixture is located. Specifically, the material cavity 5 includes a supporting grid and an inner liner. The supporting grid is located outside the inner liner, and the inner liner is attached to and fixed to the inner wall of the supporting grid of the material cavity 5. The inner liner is provided with multiple through holes. Through the multiple through holes, the inner liner can confine the graphene in the inner cavity of the inner liner, and the exchange between the pre-made electrolyte in the inner cavity and the pre-made electrolyte in the electrolytic cell 1 can be realized through the through holes.

[0041] The supporting grid and liner can be made of one or more of the following materials: corrosion-resistant polytetrafluoroethylene, PPR, PPA, and titanium. The aperture of the through holes in the liner can be 800–2000 mesh to limit the outflow of graphene.

[0042] Specifically, the electrolytic cell 1 is equipped with a cavity limiting strip 2 for fixing the material cavity 5, which is located on the outer wall of the supporting grid to prevent the material cavity 5 from drifting during electrolyte flow. A cavity support plate is provided at the lower part of the material cavity 5, with a gap between the cavity support plate and the bottom wall of the electrolytic cell 1 to support the material cavity 5 while avoiding obstructing electrolyte flow. The gap between the cavity support plate and the bottom of the electrolytic cell 1 is 15–40 mm to form a circulating flow channel below the cavity support plate.

[0043] Specifically, the anode 6 is an anode plate located in the middle of the inner cavity of the liner, preferably at the center. Anode limit posts 4 are provided on both sides of the anode plate, and an anode support plate 25 is also provided at the bottom of the anode 6 to prevent the anode 6 from drifting. Compared with the anode 6 being placed outside the material cavity 5 or close to the inner wall of the material cavity 5, this application enables the graphene to be effectively contacted on both sides of the anode plate by setting the position of the anode 6, thereby improving the power utilization rate and thus improving the purification efficiency and purification effect.

[0044] Specifically, the cathode 7 is a cathode plate located inside the electrolytic cell 1 and outside the material chamber 5, with the cathode plate and anode plate facing each other. Cathode limit strips 3 are provided on both sides of the cathode plate, and a cathode 7 support plate is provided at the bottom of the cathode plate to fix the position of the cathode 7 and form a stable electric field. The horizontal width of the cathode 7 support plate can be 30–50 mm.

[0045] In some embodiments, the distance between the anode plate surface and the inner wall of the liner is 35-50 mm, and the distance between the cathode plate surface and the outer wall of the liner is 35-50 mm. By controlling the distance between the anode plate and the inner wall to control the range of the electrolysis region, and controlling the distance between the cathode plate surface and the outer wall of the liner, the resistance of the circuit consisting of the anode plate-graphene electrolyte mixture-electrolyte-cathode plate can be reduced. This allows for electrolytic purification at lower voltages, avoiding the large number of bubbles generated by side reactions during high-voltage electrolysis. This prevents the shearing effect caused by bubble bursts from reducing the graphene sheet diameter, thus preserving the graphene sheet size, improving the electrical and mechanical properties of the graphene material, and accelerating the purification efficiency. Furthermore, controlling the distance to the above range ensures that the graphene material in the cavity is in a highly efficient electrolysis region, improving purification efficiency and facilitating the electrochemical reaction of metal impurities before deposition on the cathode plate, which is beneficial for the recovery and reuse of the metal catalyst.

[0046] The anode 6 can be made of graphite plate, titanium plate with iridium-tantalum coating, titanium plate with iridium coating, titanium plate with ruthenium-iridium coating, etc.; the cathode 7 can be made of copper foil, copper plate, titanium plate or 316L stainless steel plate, etc.

[0047] Both the cathode plate and the anode plate are electrically connected to the rectified DC power supply 35 via contact terminals 34 for power supply.

[0048] The material stirring paddle 26 is connected to the first drive motor 27, which rotates during the electrolysis process. The rotation speed of the first drive motor 27 can be 350 to 450 rpm, thus ensuring that the graphene is evenly dispersed and does not settle, and avoiding excessive disturbance that could interfere with the electrolysis reaction.

[0049] The material stirring paddle 26 can also be connected to a reciprocating motion drive device 29. The reciprocating motion drive device 29 can drive the material stirring paddle 26 to reciprocate back and forth in the inner cavity of the material chamber 5. The reciprocating frequency can be 200 to 350 times / min. Combined with the stirring setting, it further prevents graphene from settling and forms an instantaneous pressure difference inside the material chamber 5, allowing the pre-prepared electrolyte outside the material chamber 5 to enter its interior, and then allowing the ions in it to enter the interior of the chamber to compensate for the reaction loss of the electrolyte, balance the concentration of the internal and external electrolytes, and thus accelerate the electrolytic purification efficiency.

[0050] refer to Figure 3 The reciprocating motion drive device 29 is connected to the material stirring paddle 26 via a slide rail device 28. The reciprocating motion drive device 29 may include a second drive motor 31, a motor lead screw 30, and a slide rail drive rod 32. The second drive motor 31 is connected to the slide rail drive rod 32 via the motor lead screw 30. The slide rail drive rod 32 is connected to the slide rail device 28. The slide rail device 28 is connected to a first drive motor 27, and the first drive motor 27 is connected to the material stirring paddle 26. The second drive motor 31 can drive the motor lead screw 30 to move and drive the slide rail drive rod 32 to reciprocate. Furthermore, under the sliding connection of the slide rail device 28, the first drive motor 27 coordinates with the material stirring paddle 26 to reciprocate back and forth, so that the material stirring paddle 26 moves back and forth in the graphene electrolyte mixture within the material cavity 5.

[0051] Specifically, the material stirring paddle 26 has multiple randomly distributed stirring paddle through holes to allow liquid to pass through during the stirring process, thereby reducing the resistance during the stirring process.

[0052] Specifically, the mixing tank 16 is used to mix graphene powder and electrolyte. A mixing agitator 19 is provided in the mixing tank 16. The mixing agitator 19 is connected to the third drive motor 18. Under the drive of the third drive motor 18, the mixing agitator 19 rotates to achieve mixing. The third drive motor 18 is mounted on the drive device bracket 17 for fixation.

[0053] The mixing tank outlet 20 of the mixing tank 16 is connected to the material cavity 5 via a pipeline. A diaphragm pump 8 is installed in the connected pipeline to provide the power for conveying the graphene electrolyte mixture in the mixing tank 16 into the material cavity 5.

[0054] Specifically, the electrolyte storage device 21 is used to prepare and store the pre-made electrolyte. It includes an electrolyte stirring paddle 23 extending into the inner cavity of the storage device 21 and connected to a fourth drive motor 22 for stirring during electrolyte preparation. The electrolyte storage device 21 has a storage outlet 24, which is connected to the pipeline of the electrolytic cell 1 and receives electrolyte circulation power from a diaphragm pump 8.

[0055] Specifically, the electrolytic cell 1 is provided with an electrolytic cell inlet 14 and an electrolytic cell outlet 15. The electrolytic cell inlet 14 and the electrolytic cell outlet 15 are connected by a circulation pipeline. The storage device outlet 24 and the storage device inlet are respectively connected to the circulation pipeline, thereby realizing the connection between the storage device outlet 24 and the electrolytic cell inlet 14, and the connection between the storage device inlet and the electrolytic cell outlet 15. The pre-made electrolyte in the electrolytic cell 1 can achieve liquid circulation through the circulation pipeline. At the same time, the pre-made electrolyte is transported and replenished into the electrolytic cell 1 through the electrolytic cell inlet 14. The pre-made electrolyte flowing out of the electrolytic cell outlet 15 can be returned to the electrolyte storage device 21 for recycling.

[0056] In some embodiments, a cooling and heating integrated device 33 is provided in the circulation pipeline to heat or cool the pre-made electrolyte in the pipeline so that it is within a preset temperature range, thereby ensuring that the electrolyte temperature flowing back to the electrolytic cell 1 is stable.

[0057] In some embodiments, the graphene purification apparatus may further include a graphene filtration system, specifically comprising a filtration cylinder 9, a filtrate storage tank 11, and an evaporation and concentration device 12. The material chamber 5, the inlet and outlet of the filtration cylinder 9, the filtrate storage tank 11, and the inlet of the evaporation and concentration device 12 are sequentially connected by pipelines. Under the action of a diaphragm pump 8 in the pipeline, the purified graphene electrolyte mixture in the material chamber 5 can enter the filtration cylinder 9 for solid-liquid separation, and then the filtrate enters the filtrate storage tank 11. The filtration cylinder 9 is also connected to a water circulation pump 10 for water cleaning, and the cleaning solution used to clean the graphene in the filtration cylinder 9 also enters the filtrate storage tank 11. Through another diaphragm pump 8, the liquid in the filtrate storage tank 11 is input into the evaporation and concentration device 12 for concentration. The outlet of the evaporation and concentration device 12 can be connected to the electrolyte storage device 21, so that the concentrated liquid can be pumped into the electrolyte storage device 21 by the diaphragm pump 8 to readjust the concentration and realize the recycling of the electrolyte. The evaporation and concentration device 12 is also provided with a pure water outlet 13 to facilitate the outflow and storage of evaporated water for later use.

[0058] Understandably, the diaphragm pumps 8 and water circulation pumps 10 mentioned above can be implemented using other pump types that can achieve this application scenario, without limitation.

[0059] The following describes the graphene purification method provided in the embodiments of this application, in conjunction with the above-described method. Please refer to the following: Figure 4 , Figure 4This is a schematic flowchart of the preparation method. This specification provides method operation steps as shown in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many steps and does not represent the only execution order. In actual execution of the preparation method, it can be performed in the order shown in the embodiments or drawings or in parallel. The method includes:

[0060] S1: Mix graphene powder containing metal impurities with a pre-prepared electrolyte to obtain a graphene electrolyte mixture.

[0061] In some embodiments, the pre-prepared electrolyte comprises sulfuric acid, metal sulfate, and water, with a mass fraction ratio of (10%–17%):(2%–5%):100%. Preferably, when the mass fraction of water is 100%, the mass fraction of sulfuric acid is 10–15%, and more preferably, when the mass fraction of water is 100%, the mass fraction of metal sulfate is 4–5%. By controlling the concentrations of H₂SO₄ and metal sulfate in the electrolyte within the above ranges, the electrolyte possesses good conductivity and ensures that graphene has a good crystal structure. This avoids graphene oxidation caused by excessively high sulfuric acid concentrations (e.g., exceeding 20%) and crystallization caused by excessively high sulfate concentrations, thereby preventing damage to the graphene structure and agglomeration of graphene and sulfate crystals, and improving the electrolytic purification effect.

[0062] Understandably, the current methods for growing high-quality graphene powder using molten metal all employ elemental copper or copper alloys. The alloys contain very little of other metals (such as iron, nickel, cobalt, etc.), for example, less than 1%. Furthermore, due to differences in electronegativity, simultaneous recovery is challenging. This application uses H2SO4... 4、 The electrolyte is composed of CuSO4 and H2O in a mass fraction ratio of (10%–17%):(2%–5%):100%, ensuring efficient electrolytic purification. During the electrolysis process, other metals in the alloy dissolve in the electrolyte, which can be purified through periodic cleaning.

[0063] Prepare an aqueous solution containing H2SO4 and metal sulfate in an electrolyte storage tank, and stir it at 600-800 rpm for 20-30 minutes to ensure uniform mixing.

[0064] In some embodiments, the viscosity of the graphene electrolyte mixture is 3000–4500 mPa·s, preferably 3500–4000 mPa·s. Understandably, the viscosity can be any value within the above range, and will not be enumerated here. By controlling the viscosity to the above range, the concentration stability of the graphene electrolyte mixture is improved, the risk of sedimentation and graphene agglomeration is reduced, and the graphite powder content in the mixture is effectively controlled to the preferred range, thereby improving the electrolytic purification effect.

[0065] In some embodiments, during the preparation of the graphene electrolyte mixture, the stirring speed is 1000–1500 rpm, and the stirring time is 30–45 min. Vigorous stirring ensures that the graphene powder is completely wetted by the aqueous electrolyte without the need to add organic solvents such as ethanol, methanol, or acetone, thereby further improving the conductivity of the electrolyte.

[0066] Specifically, graphene powder containing metal impurities is added to the mixing tank 16, the valve between the electrolyte storage device 21 and the mixing tank 16 is opened, and an appropriate amount of electrolyte is delivered to the mixing tank 16 by the pumping force of the diaphragm pump 8 to stir and prepare the graphene electrolyte mixture.

[0067] S2: Place the graphene electrolyte mixture in the material chamber 5 inside the electrolytic cell 1 and electrolyze the graphene electrolyte mixture to remove metal impurities from the graphene powder.

[0068] Specifically, the graphene electrolyte mixture in the mixing tank 16 can be transported to the material chamber 5 by the diaphragm pump 8. The depth of the graphene electrolyte mixture added to the material chamber 5 shall not exceed 75% of the internal depth of the material chamber 5.

[0069] During the electrolysis process, the anode 6 is placed in the middle of the material-containing cavity 5, and the cathode 7 is placed inside the electrolytic cell 1 and outside the material-containing cavity 5. The graphene electrolyte mixture is stirred. In some embodiments, during the electrolysis process, the graphene electrolyte mixture in the material cavity is stirred by a material stirring paddle 26. The stirring speed of the material stirring paddle can be 350-450 rpm. By controlling the speed within the above range, combined with the concentration setting of the graphene electrode liquid mixture, graphene sedimentation and agglomeration can be avoided, the uniformity and efficiency of contact between graphene and the anode 6 can be improved, thereby improving the electrolysis efficiency and purification effect. At the same time, excessively high speed can be avoided, which would cause excessive disturbance of the electrolyte and affect the electrolysis reaction.

[0070] In some embodiments, the material stirring paddle 26 can also reciprocate back and forth in the material cavity to ensure that the graphene electrolyte mixture in the material cavity 5 can be stirred at a uniform speed, avoid the local sedimentation of graphene in the solution, and ensure concentration uniformity.

[0071] Specifically, the second drive motor 31 can drive the reciprocating motion drive device 29 to move, thereby driving the slide rail drive rod 32 to work with the material stirring paddle 26 to reciprocate in the material cavity 5. The reciprocating motion frequency can be 200-350 times / min. The rotation speed setting of the material stirring paddle 26 further prevents graphene from settling to avoid a decrease in electrolysis efficiency, and forms an instantaneous pressure difference in each layer of the mixture in the cavity, so that metal ions outside the material cavity 5 can quickly enter the cavity, promote the exchange between the inside and outside of the electrolyte, make up for the difference in ion concentration between the inside and outside of the electrolyte caused by electrolysis, and thus accelerate the electrolysis purification efficiency.

[0072] In some embodiments, the distance between the anode 6 and the inner wall of the material cavity 5 is 35-50 mm, and the distance between the cathode 7 and the outer wall of the material cavity 5 is 35-50 mm. Preferably, the distance between the anode 6 and the inner wall of the material cavity 5 is 40-45 mm; preferably, the distance between the cathode 7 and the outer wall of the material cavity 5 is 40-45 mm. It can be understood that the distance between the cathode 7 and the outer wall of the material cavity 5 and the distance between the cathode 7 and the outer wall of the material cavity 5 can be any value within the above ranges, and will not be enumerated here. Thus, the anode 6 is positioned at the center of the material cavity 5, and the anode plate is equidistant from both sides, with the spacing controlled within the aforementioned range. Relative to the anode 6 being placed on the side wall or outside of the material cavity 5, both sides of the anode 6 in this application can fully contact the graphene electrolyte mixture within the area. This not only reduces the voltage but also improves purification efficiency and the purification effect of graphene at various locations. Furthermore, combined with the aforementioned spacing setting, the resistance of the circuit consisting of anode 6-graphene electrolyte mixture-electrolyte-cathode 7 is reduced. Electrolytic purification can be achieved at the aforementioned lower voltage, avoiding the shearing effect caused by gas bubbles generated during water electrolysis at high voltage. This not only preserves the graphene sheet size and ensures efficient electrolysis within the voltage range of the graphene, but also prevents the graphene sheet size from decreasing and its conductivity from deteriorating.

[0073] In some embodiments, during the electrolysis process, the DC voltage applied to the anode plate 6 and the cathode plate 7 in the electrolysis device is 3.5–5V. Controlling the applied DC voltage to 3.5–5V via an external rectified power supply ensures efficient electrolysis, avoids low efficiency due to excessively low voltage, and allows other metallic impurities besides copper to be electrolyzed and enter the electrolyte for subsequent cleaning and purification. Combined with controlling the sulfuric acid concentration in the electrolyte, this ensures that graphene is not oxidized during the electrolysis reaction. Furthermore, it avoids excessively high voltage causing the formation of large amounts of oxygen bubbles generated by water electrolysis near the anode 6. Understandably, when these bubbles burst, they exert a shearing effect on the graphene, reducing the graphene sheet diameter and deteriorating its electrical and mechanical properties. The generated hydrogen and other bubbles also affect the deposition of metal powder on the cathode plate during the electrolysis reaction. Sulfuric acid is also carried away by the bubbles during electrolysis, affecting the electrolyte concentration. Using the aforementioned voltage range effectively avoids these problems caused by excessively high voltage. Furthermore, the graphene containing metal powder is in a slurry state in the solution and is not in close contact with the anode plate. When a voltage is applied, the anode plate first conducts the electrolyte medium to the graphene, and then the graphene conducts the electrolyte medium to the metal powder. The metal powder then undergoes an electrolytic reaction, detaches from the graphene, and is deposited on the cathode plate surface through the electrolyte transport. Therefore, there is a large contact resistance between the anode plate and the metal powder in the material cavity. The actual voltage applied to the metal powder is lower than the DC voltage applied to the anode and cathode plates. By controlling the DC voltage to the above range, the electrolytic purification effect can be ensured.

[0074] In some embodiments, the current intensity is 80–115 A during the electrolysis process. By controlling the composition of the electrolyte, temperature, cathode-anode distance, and material viscosity, the DC voltage applied to the electrolytic cell is 3.5–5 V, and the current intensity can reach 80–115 A, thereby accelerating the purification efficiency.

[0075] In some embodiments, during the electrolysis process, the temperature of the pre-prepared electrolyte in the electrolysis device is 45–60°C. Controlling the temperature within this range can accelerate the ion diffusion rate, thereby improving the conductivity of the electrolyte and achieving a higher current intensity at a lower electrolysis operating voltage, thus improving the purification efficiency.

[0076] In some embodiments, the electrolytic cell 1 is connected to the electrolyte storage device 21. During the electrolysis process, the pre-prepared electrolyte in the electrolyte storage device 21 and the pre-prepared electrolyte in the electrolytic cell 1 are circulated. Specifically, the valve connecting to the material chamber 5 is opened, and the graphene electrolyte mixture is added to the material chamber 5 using the diaphragm pump 8. Then, the prepared pre-prepared electrolyte is pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 and the liquid level of the graphene electrolyte mixture in the material chamber 5 are at the same level. Then, the pre-prepared electrolyte flows out from the electrolytic cell outlet 15 and flows back from the electrolytic cell inlet 14 to keep the ion concentration in the electrolyte consistent. Before the pre-prepared electrolyte flows back into the electrolytic cell 1, it passes through the integrated cooling and heating device 33 to ensure that the electrolyte temperature is stable at 45-60°C.

[0077] In some embodiments, the material cavity 5 has multiple through holes on its cavity wall. The material cavity 5 is connected to the inner cavity of the electrolytic cell 1 through the multiple through holes. The aperture of the through holes is 800 to 2000 mesh. The aperture setting achieves communication while preventing graphene from overflowing into the electrolyte of the electrolytic cell 1.

[0078] S3: Collect the electrolyzed graphene powder, wash and dry it to obtain purified graphene powder. Continue the electrolysis reaction for 3-5 hours, then stop the electrolysis reaction. Use diaphragm pump 8 to pump the pre-prepared electrolyte in electrolytic cell 1 from electrolytic cell outlet 15 back to electrolyte storage device 21. Use diaphragm pump 8 to pump the electrolyzed purified graphene material in material chamber 5 into filter cylinder 9. With the assistance of water circulation pump 10, filter and wash repeatedly with water 3-5 times. Place the obtained graphene filter cake in an oven and dry it at 80-150℃ to obtain purified clean graphene.

[0079] After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is then pumped into the evaporation and concentration device 12 by the diaphragm pump 8. The condensed pure water is discharged and stored for later use. The concentrated liquid is pumped back into the electrolyte storage tank by the diaphragm pump 8. After the required concentration of pre-made electrolyte is prepared, it is recycled back into the electrolytic purification system.

[0080] Based on the above technical solution, by controlling the voltage and electrolyte concentration applied between the anode 6 and the cathode 7, and using a reciprocating drive motor to drive the material stirring paddle 26 to stir the mixture in the material chamber 5, the metal impurities contained in the material chamber 5 are separated from the graphene powder through electrolysis. The impurity metals continue to deposit on the cathode plate. After the metal impurities are completely removed, the graphene in the material chamber 5 is transferred to a suction filter to achieve product collection and electrolyte recycling. This method can achieve efficient purification of graphene powder while ensuring structural integrity. There is no wastewater discharge containing heavy metal impurities, strong acids, or strong oxidants during the purification and preparation process, making it green and environmentally friendly.

[0081] The initial graphene powder containing metallic impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to corrode the metallic impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing metallic impurities was calculated to be 12% based on the ratio of the two. Raman spectroscopy was then performed on the purified and dried graphene powder. Figure 5 I was calculated D / I G =0.250, specific surface area test result is 250m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy. Reference Figure 6 This indicates that the graphene prepared by this method does not contain oxygen-containing groups. The O content was found to be 0.003% using a CHNSO elemental analyzer, and the powder D content was found to be... 50 =75um, D 99 =230um; 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.350Ω·cm.

[0082] The dried graphene powder obtained by the above technical solution was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining metal impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that the purification method in this case can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, referencing... Figure 7 I was calculated D / I G =0.249, specific surface area measured is 250.3 m². 2 / g, no characteristic peak signal was detected by infrared spectroscopy. Reference Figure 8 This indicates that the graphene surface of this technical solution has no suspended oxygen-containing groups, and the graphene is not oxidized. Furthermore, elemental analysis using a CHNSO analyzer revealed an O content of 0.0031%, further demonstrating that the graphene treated according to this application will not be oxidized. Powder D was measured using a laser particle size analyzer. 50 =75um, D 99=230um, indicating that the graphene powder sheet diameter has hardly decreased, maintaining the large sheet diameter characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying resulted in a film resistivity of 1.351Ω·cm, indicating that the graphene powder structure remains well-preserved after electrolytic purification using this process, with almost no structural damage. The resulting composite slurry also showed no significant reduction in conductivity of the dry film. The following describes specific embodiments of this application in conjunction with the above-described graphene purification methods. The specific surface area of ​​the graphene powder purified according to this application can reach 240m². 2 The particle size of graphene powder is above / g, and the oxygen content can reach below 0.0032%. 50 Above 70μm, D 99 At a thickness of 215 μm or more, the resistivity of the film prepared from an acrylic resin emulsion containing 5 wt% of the graphene powder is below 1.37 Ω·cm.

[0083] Example 1

[0084] 1. Prepare an aqueous solution containing H2SO4 and CuSO4 in an electrolyte storage device 21, wherein the mass fraction ratio of H2SO4:CuSO4:H2O is 10%:2%:100%, and stir at 600 rpm for 20 min to mix it evenly to obtain a pre-prepared electrolyte.

[0085] 2. Add graphene powder containing copper powder impurities to mixing tank 16, add an appropriate amount of pre-made electrolyte from electrolyte storage device 21, stir at 1000 rpm for 30 minutes to mix it evenly, and prepare a graphene electrolyte mixture with a viscosity of 3000 mPa·s.

[0086] 3. Using a diaphragm pump 8, the graphene electrolyte mixture containing copper impurities is added to the material chamber 5, which has an 800-mesh aperture. The pre-prepared electrolyte is then pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 is level with the liquid level of the graphene mixture containing copper impurities in the material chamber 5. The electrolyte is then allowed to flow out from the electrolytic cell outlet 15 and back into the electrolytic cell inlet 14 to maintain a consistent ion concentration. Before being returned to the electrolytic cell 1, the pre-prepared electrolyte passes through a cooling and heating integrated device 33 to ensure the electrolyte temperature is stabilized at 45°C.

[0087] During electrolysis, the anode plate is located at the center of the material chamber 5, and is equidistant from both sides with a spacing of 50 mm. The cathode plate is located outside the material chamber 5, with a spacing of 35 mm between the cathode plate and the outer wall of the material chamber 5. The applied DC voltage is 3.5 V, the corresponding current intensity is 80 A, the rotation speed of the material stirring paddle 26 is 350 rpm, the reciprocating frequency is 200 times / min, and the electrolysis reaction time is 5 h.

[0088] 4. After the electrolysis reaction stops, the pre-prepared electrolyte in the electrolytic cell 1 is pumped back to the electrolyte storage device 21 from the outlet 15 of the electrolytic cell using the diaphragm pump 8; the electrolyzed and purified graphene material in the material chamber 5 is pumped into the filter cylinder 9 by the diaphragm pump 8, and filtered and washed repeatedly 3 times under the synergistic action of the water circulation pump 10. The graphene filter cake is then placed in an oven and dried at 80°C to obtain purified graphene powder.

[0089] 5. After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is fed into the evaporation and concentration device 12 by the diaphragm pump 8. After treatment, the condensed pure water is discharged and stored for later use. The concentrated liquid enters the electrolyte storage device 21 again by the diaphragm pump 8. After being prepared into a pre-made electrolyte of the required concentration, it enters the electrolytic purification system again.

[0090] The initial graphene powder containing copper impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to erode the copper impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing copper impurities was calculated to be 12% based on the ratio of the two. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.250, specific surface area test result is 250m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the prepared graphene does not contain oxygen-containing groups. The O content was determined to be 0.003% by CHNSO elemental analyzer, and the powder D was determined by laser particle size analyzer. 50 =75um, D 99 =230um, 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.350Ω·cm.

[0091] The dried graphene powder was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two mixtures showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that this embodiment can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated.D / I G =0.249, specific surface area measured is 250.3 m². 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the graphene obtained in this embodiment has no suspended oxygen-containing groups on its surface and has not been oxidized. Furthermore, the O content was found to be 0.0031% using a CHNSO elemental analyzer, further demonstrating that the graphene treated in this embodiment will not be oxidized. The powder D was measured using a laser particle size analyzer. 50 =75um, D 99 =230um, indicating that the particle size of the powder in this embodiment has hardly decreased, maintaining the large particle size characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying, the resistivity of the film was measured to be 1.351Ω·cm, indicating that the graphene powder structure remained well maintained after the electrolytic purification treatment in this embodiment, with almost no structural damage. The resulting composite slurry also showed no significant decrease in conductivity of the dry film.

[0092] Example 2

[0093] 1. Prepare an aqueous solution containing H2SO4 and CuSO4 in an electrolyte storage device 21, wherein the mass fraction ratio of H2SO4:CuSO4:H2O is 17%:5%:100%, and stir at 800 rpm for 30 min to mix it evenly to obtain a pre-prepared electrolyte.

[0094] 2. Add graphene powder containing copper powder impurities to mixing tank 16, add an appropriate amount of pre-made electrolyte from electrolyte storage device 21, stir at 1500 rpm for 45 min to make it evenly mixed, and prepare a graphene electrolyte mixture with a viscosity of 4500 mPa·s.

[0095] 3. Using a diaphragm pump 8, the graphene electrolyte mixture containing copper impurities is added to the material chamber 5, which has a 2000-mesh aperture. The pre-prepared electrolyte is then pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 is level with the liquid level of the graphene mixture containing copper impurities in the material chamber 5. The electrolyte is then allowed to flow out from the electrolytic cell outlet 15 and back into the electrolytic cell inlet 14 to maintain a consistent ion concentration. Before being returned to the electrolytic cell 1, the pre-prepared electrolyte passes through a cooling and heating integrated device 33 to ensure the electrolyte temperature is stabilized at 60℃.

[0096] During electrolysis, the anode plate is located at the center of the material cavity 5, and is equidistant from both sides with a spacing of 35 mm. The cathode plate is located outside the material cavity 5, with a spacing of 50 mm between the cathode plate and the outer wall of the material cavity 5. The applied DC voltage is 5V, and the corresponding current intensity is 115A. The rotation speed of the material stirring paddle 26 is 450 rpm, the reciprocating frequency is 350 times / min, and the electrolysis reaction time is 3h.

[0097] 4. After the electrolysis reaction stops, the pre-prepared electrolyte in the electrolytic cell 1 is pumped back to the electrolyte storage device 21 from the outlet 15 of the electrolytic cell using the diaphragm pump 8; the electrolyzed and purified graphene material in the material chamber 5 is pumped into the filter cylinder 9 by the diaphragm pump 8, and filtered and repeatedly washed 4 times under the synergistic action of the water circulation pump 10. The graphene filter cake is then placed in an oven and dried at 120°C to obtain purified graphene powder.

[0098] 5. After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is fed into the evaporation and concentration device 12 by the diaphragm pump 8. After treatment, the condensed pure water is discharged and stored for later use. The concentrated liquid enters the electrolyte storage device 21 again by the diaphragm pump 8. After being prepared into a pre-made electrolyte of the required concentration, it enters the electrolytic purification system again.

[0099] The initial graphene powder containing copper impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to erode the copper impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing copper impurities was calculated to be 12% based on the ratio of the two. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.250, specific surface area test result is 250m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the prepared graphene does not contain oxygen-containing groups. The O content was determined to be 0.003% by CHNSO elemental analyzer, and the powder D was determined by laser particle size analyzer. 50 =72um, D 99 =224um, 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.350Ω·cm.

[0100] The dried graphene powder was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two mixtures showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that the purification method in this embodiment can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated.D / I G =0.251, specific surface area measured is 250.2 m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that there are no suspended oxygen-containing groups on the surface of the graphene in this embodiment, and the graphene has not been oxidized. Furthermore, the O content was found to be 0.0030% by CHNSO elemental analyzer, further demonstrating that the graphene will not be oxidized after treatment in this embodiment. The powder D was measured using a laser particle size analyzer. 50 =72um, D 99 =224um, indicating that the particle size of the powder in this embodiment has hardly decreased, maintaining the large particle size characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying, the resistivity of the film was measured to be 1.352 Ω·cm, indicating that the graphene powder structure remained well maintained after the electrolytic purification treatment in this embodiment, with almost no structural damage. The resulting composite slurry also showed no significant decrease in conductivity of the dry film.

[0101] Example 3

[0102] 1. Prepare an aqueous solution containing H2SO4 and CuSO4 in an electrolyte storage device 21, wherein the mass fraction ratio of H2SO4:CuSO4:H2O is 15%:4%:100%; stir at 750 rpm for 25 min to mix evenly to obtain a pre-prepared electrolyte.

[0103] 2. Add graphene powder containing copper metal impurities to mixing tank 16, add an appropriate amount of pre-made electrolyte from electrolyte storage device 21, stir at 1200 rpm for 35 min to make it evenly mixed, and prepare a graphene electrolyte mixture with a viscosity of 3500 mPa·s.

[0104] 3. Using a diaphragm pump 8, the graphene electrolyte mixture containing copper metal impurities is added to the material chamber 5, which has a 950-mesh aperture. Then, the pre-prepared electrolyte is pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 is at the same level as the liquid level of the graphene mixture containing copper metal impurities in the material chamber 5. The electrolyte is then allowed to flow out from the electrolytic cell outlet 15 and back into the electrolytic cell inlet 14 to maintain a consistent ion concentration. Before being returned to the electrolytic cell 1, the pre-prepared electrolyte passes through a cooling and heating integrated device 33 to ensure the electrolyte temperature is stabilized at 50℃.

[0105] During electrolysis, the anode plate is located at the center of the material chamber 5, and is equidistant from both sides with a spacing of 40 mm. The cathode plate is located outside the material chamber 5, and the distance between the cathode plate and the outer wall of the material chamber 5 is 45 mm. The applied DC voltage is 3.8 V, the corresponding current intensity is 88 A, the rotation speed of the material stirring paddle 26 is 380 rpm, the reciprocating frequency is 250 times / min, and the electrolysis reaction time is 4.7 h.

[0106] 4. After the electrolysis reaction stops, the pre-prepared electrolyte in the electrolytic cell 1 is pumped back to the electrolyte storage device 21 from the outlet 15 of the electrolytic cell using the diaphragm pump 8; the electrolyzed and purified graphene material in the material chamber 5 is pumped into the filter cylinder 9 by the diaphragm pump 8, and filtered and repeatedly washed 5 times under the synergistic action of the water circulation pump 10. The graphene filter cake is then placed in an oven and dried at 150°C to obtain purified graphene powder.

[0107] 5. After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is fed into the evaporation and concentration device 12 by the diaphragm pump 8. After treatment, the condensed pure water is discharged and stored for later use. The concentrated liquid enters the electrolyte storage device 21 again by the diaphragm pump 8. After being prepared into a pre-made electrolyte of the required concentration, it enters the electrolytic purification system again.

[0108] The initial graphene powder containing copper impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to erode the copper impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing copper impurities was calculated to be 13.5% based on the ratio of the two. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.257, specific surface area measured as 246 m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the prepared graphene does not contain oxygen-containing groups. The O content was determined to be 0.0029% by CHNSO elemental analyzer, and the powder D was determined by laser particle size analyzer. 50 =70um, D 99 =218um, 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.356Ω.cm.

[0109] The dried graphene powder was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two mixtures showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that this embodiment can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated.D / I G =0.257, specific surface area measured is 246.4 m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that there are no suspended oxygen-containing groups on the surface of the graphene in this embodiment, and the graphene has not been oxidized. Furthermore, the O content was found to be 0.0030% by CHNSO elemental analyzer, further demonstrating that the graphene will not be oxidized after treatment in this embodiment. The powder D was measured using a laser particle size analyzer. 50 =70um, D 99 =218um, indicating that the particle size of the powder in this embodiment has hardly decreased, maintaining the large particle size characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying, the resistivity of the film was measured to be 1.355 Ω·cm, indicating that the graphene powder structure remained well maintained after the electrolytic purification treatment in this embodiment, with almost no structural damage. The resulting composite slurry also showed no significant decrease in conductivity of the dry film.

[0110] Example 4

[0111] 1. Prepare an aqueous solution containing H2SO4 and CuSO4 in an electrolyte storage device 21, wherein the mass fraction ratio of H2SO4:CuSO4:H2O is 12%:4.2%:100%; stir at 700 rpm for 23 min to mix evenly to obtain a pre-prepared electrolyte.

[0112] 2. Add graphene powder containing copper powder impurities to mixing tank 16, add an appropriate amount of pre-made electrolyte from electrolyte storage device 21, stir at 1400 rpm for 43 minutes to make it evenly mixed, and prepare a graphene electrolyte mixture with a viscosity of 4000 mPa·s.

[0113] 3. Using a diaphragm pump 8, the graphene electrolyte mixture containing copper metal impurities is added to the material chamber 5, which has a 1200-mesh aperture. The pre-prepared electrolyte is then pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 is level with the liquid level of the graphene mixture containing copper impurities in the material chamber 5. The electrolyte is then discharged from the electrolytic cell outlet 15 and returned from the electrolytic cell inlet 14 to maintain a consistent ion concentration. Before being returned to the electrolytic cell 1, the pre-prepared electrolyte passes through a cooling and heating integrated device 33 to ensure the electrolyte temperature is stabilized at 57°C.

[0114] During electrolysis, the anode plate is located at the center of the material chamber 5, and is equidistant from both sides with a spacing of 42 mm. The cathode plate is located outside the material chamber 5, with a spacing of 40 mm between the cathode plate and the outer wall of the material chamber 5. The applied DC voltage is 4.8 V, the corresponding current intensity is 100 A, the rotation speed of the material stirring paddle 26 is 430 rpm, the reciprocating frequency is 320 times / min, and the electrolysis reaction time is 3.4 h.

[0115] 4. After the electrolysis reaction stops, the pre-prepared electrolyte in the electrolytic cell 1 is pumped back to the electrolyte storage device 21 from the outlet 15 of the electrolytic cell using the diaphragm pump 8; the electrolyzed and purified graphene material in the material chamber 5 is pumped into the filter cylinder 9 by the diaphragm pump 8, and filtered and washed repeatedly 3 times under the synergistic action of the water circulation pump 10. The graphene filter cake is then placed in an oven and dried at 100°C to obtain purified graphene powder.

[0116] 5. After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is fed into the evaporation and concentration device 12 by the diaphragm pump 8. After treatment, the condensed pure water is discharged and stored for later use. The concentrated liquid enters the electrolyte storage device 21 again by the diaphragm pump 8. After being prepared into a pre-made electrolyte of the required concentration, it enters the electrolytic purification system again.

[0117] The initial graphene powder containing copper impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to erode the copper impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing copper impurities was calculated to be 12.8% based on the ratio of the two. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.258, specific surface area measured as 245m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the prepared graphene does not contain oxygen-containing groups. The O content was found to be 0.0031% by CHNSO elemental analyzer, and the powder D was found to be... 50 =77um, D 99 =234um, 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.358Ω.cm.

[0118] The dried graphene powder was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two mixtures showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that this embodiment can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated.D / I G =0.257, specific surface area measured is 244.8 m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that there are no suspended oxygen-containing groups on the surface of the graphene in this embodiment, and the graphene has not been oxidized. Furthermore, the O content was found to be 0.0030% by CHNSO elemental analyzer, further demonstrating that the graphene will not be oxidized after treatment in this embodiment. The powder D was measured using a laser particle size analyzer. 50 =77um, D 99 =234um, indicating that the particle size of the powder in this embodiment has hardly decreased, maintaining the large particle size characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying, the resistivity of the film was measured to be 1.359Ω·cm, indicating that the graphene powder structure remained well maintained after electrolytic purification in this embodiment, with almost no structural damage. The resulting composite slurry also showed almost no change in the conductivity of the dry film.

[0119] Example 5

[0120] 1. Prepare an aqueous solution containing H2SO4 and CuSO4 in an electrolyte storage device 21, wherein the mass fraction ratio of H2SO4:CuSO4:H2O is 14%:4.5%:100%, and stir at 750 rpm for 28 min to mix it evenly to obtain a pre-prepared electrolyte.

[0121] 2. Add graphene powder containing copper powder impurities to mixing tank 16, add an appropriate amount of pre-made electrolyte from electrolyte storage device 21, stir at 1450 rpm for 40 min to make it evenly mixed, and prepare a graphene electrolyte mixture with a viscosity of 3700 mPa·s.

[0122] 3. Using a diaphragm pump 8, the graphene electrolyte mixture containing copper impurities is added to the material chamber 5, which has a 1500-mesh aperture. The pre-prepared electrolyte is then pumped into the electrolytic cell 1 using the diaphragm pump 8. The liquid level in the electrolytic cell 1 is level with the liquid level of the graphene mixture containing copper impurities in the material chamber 5. The electrolyte is then allowed to flow out from the electrolytic cell outlet 15 and back into the electrolytic cell inlet 14 to maintain a consistent ion concentration. Before being returned to the electrolytic cell 1, the pre-prepared electrolyte passes through a cooling and heating integrated device 33 to ensure the electrolyte temperature is stabilized at 58°C.

[0123] During electrolysis, the anode plate is located at the center of the material cavity 5, and is equidistant from both sides with a spacing of 44 mm. The cathode plate is located outside the material cavity 5, with a spacing of 42 mm between the cathode plate and the outer wall of the material cavity 5. The applied DC voltage is 4.5 V, the corresponding current intensity is 96 A, the rotation speed of the material stirring paddle 26 is 400 rpm, the reciprocating frequency is 300 times / min, and the electrolysis reaction time is 4 h.

[0124] 4. After the electrolysis reaction stops, the pre-prepared electrolyte in the electrolytic cell 1 is pumped back to the electrolyte storage device 21 from the outlet 15 of the electrolytic cell using the diaphragm pump 8; the electrolyzed and purified graphene material in the material chamber 5 is pumped into the filter cylinder 9 by the diaphragm pump 8, and filtered and washed repeatedly 3 times under the synergistic action of the water circulation pump 10. The graphene filter cake is then placed in an oven and dried at 85°C to obtain purified graphene powder.

[0125] 5. After filtration and cleaning, the waste liquid enters the filtrate storage tank. The waste liquid in the filtrate storage tank is fed into the evaporation and concentration device 12 by the diaphragm pump 8. After treatment, the condensed pure water is discharged and stored for later use. The concentrated liquid enters the electrolyte storage device 21 again by the diaphragm pump 8. After being prepared into a pre-made electrolyte of the required concentration, it enters the electrolytic purification system again.

[0126] The initial graphene powder containing copper impurities was weighed and recorded as m1. This mixture was then etched with excess dilute nitric acid to corrode the copper impurities. After washing and drying, the remaining powder was weighed and recorded as m2. The purity of the initial graphene powder containing copper impurities was calculated to be 11.5% based on the ratio of the two. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.263, specific surface area measured as 242 m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that the prepared graphene does not contain oxygen-containing groups. The O content was determined to be 0.0030% by CHNSO elemental analyzer, and the powder D was determined by laser particle size analyzer. 50 =73um, D 99 =232um, 5wt% purified graphene powder was added to acrylic resin emulsion, stirred evenly, coated, dried and the resistivity of the film was measured to be 1.364Ω.cm.

[0127] The dried graphene powder was weighed and recorded as m3. It was mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the powder was weighed again and recorded as m4. The ratio of the two mixtures showed that the purity of the electrolytically purified and dried graphene powder was almost 100%, indicating that this embodiment can completely and effectively remove metal impurities from the graphene powder. Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated.D / I G =0.263, specific surface area measured is 241.4 m². 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that there are no suspended oxygen-containing groups on the surface of the graphene in this embodiment, and the graphene has not been oxidized. Furthermore, the O content was found to be 0.0031% by CHNSO elemental analyzer, further demonstrating that the graphene will not be oxidized after treatment in this embodiment. The powder D was measured using a laser particle size analyzer. 50 =73um, D 99 =232um, indicating that the particle size of the powder in this embodiment has hardly decreased, maintaining the large particle size characteristic of graphene. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying, the resistivity of the film was measured to be 1.365Ω·cm, indicating that the graphene powder structure remained well maintained after electrolytic purification in this embodiment, with almost no structural damage. The resulting composite slurry also showed no significant decrease in conductivity of the dry film.

[0128] Comparative Example 1

[0129] The method differs from that in Example 1 above. In this case, the graphene electrolyte mixture in the material chamber 5 was not stirred. After 5 hours of electrolysis, the mixture was filtered, washed, and then the filter cake was dried in an oven. A certain amount of dried graphene powder was weighed and recorded as m4. It was mixed with excess dilute nitric acid to corrode and remove any residual copper metal impurities. After washing and drying, the mass was recorded as m5. The purity of the graphene powder after electrolysis and purification under these conditions was calculated to be 25% based on the ratio of the two. Due to the lack of stirring, the copper-containing graphene mixture solution in the material chamber 5 settled, aggregated, and densified. The copper powder inside the material could not fully contact the electrolyte, and ion transport was hindered during electrolysis, resulting in a significant decrease in electrolysis purification efficiency.

[0130] Comparative Example 2

[0131] The method differs from that in Example 1 above. In this example, the anode plate is placed closer to the material chamber 5. After 5 hours of electrolysis, the rectified DC power supply 35 is turned off, the filter cake is cleaned, and then dried in an oven. A certain amount of dried graphene powder, recorded as m4, is weighed and mixed with excess dilute nitric acid to corrode and remove any remaining copper impurities. After washing and drying, the mass is recorded as m5. The ratio of these two amounts yields a purity of 62% for the electrolyzed and dried graphene powder under these conditions. Only one side of the anode plate contacts the copper-containing graphene electrolyte mixture, reducing the contact area. Furthermore, the electrolysis purification speed is faster near the anode plate than further away. When voltage is applied, the anode plate first conducts the electrolyte medium to the graphene, which then conducts the electrolyte to the metal powder, leading to the electrolysis reaction. Therefore, placing the anode plate on one side of the material chamber reduces the electrolysis purification efficiency.

[0132] Comparative Example 3

[0133] The method differs from that in Example 1 above. The cathode plate is far from the material cavity 5, with a distance of 150 mm. After 5 hours of electrolysis, the rectified DC power supply 35 is turned off, the filter cake is cleaned, and then placed in an oven to dry. A certain amount of dried graphene powder is weighed and recorded as m4. It is mixed with excess dilute nitric acid to corrode and remove any residual copper metal impurities. After washing and drying, the mass is recorded as m5. The purity of the graphene powder after electrolysis and purification under these conditions is calculated to be 35% based on the ratio of the two. Since the cathode plate is far from the material cavity 5, the distance between the anode 6 and the cathode 7 increases, the resistance increases, and the electrolysis efficiency decreases.

[0134] Comparative Example 4

[0135] The difference from the method described in Example 1 is that the applied DC voltage is 7V. After the electrolytic reaction is completed, the obtained dried graphene powder is filtered, washed, and dried. Then, a certain amount of dried graphene powder is weighed and recorded as m4. It is mixed with excess dilute nitric acid to corrode and remove any possible residual copper metal impurities. After washing and drying, the mass is recorded as m5. The ratio of the two is used to calculate that the purity of the graphene powder after electrolytic purification and drying under these conditions is almost 100%, indicating that the purification method of Comparative Example 4 can remove metal impurities from the graphene powder.

[0136] Raman spectroscopy was performed on the purified and dried graphene powder, and I was calculated. D / I G =0.249, specific surface area measured at 250m² 2 / g, no characteristic peak signal was detected by infrared spectroscopy, indicating that there are no suspended oxygen-containing groups on the surface of graphene under this condition, and the graphene is not oxidized. In addition, the O content was found to be 0.0031% by CHNSO elemental analyzer, which further indicates that the graphene will not be oxidized after treatment.

[0137] Powder D was obtained by testing with a laser particle size analyzer. 50 =30um, D 99 =75um, indicating that the powder flake diameter in Comparative Example 4 is significantly smaller. Adding 5wt% purified graphene powder to an acrylic resin emulsion, stirring evenly, coating, and drying resulted in a film resistivity of 1.78Ω·cm. The smaller the flake diameter, the greater the contact resistance and the worse the conductivity.

[0138] Furthermore, under these conditions, the water electrolysis reaction is significant. When the oxygen and hydrogen produced evaporate, they carry away a large number of sulfuric acid molecules from the electrolyte. This not only causes sulfuric acid loss and poor conductivity of the electrolyte, reducing electrolysis efficiency, but also corrodes the power controller and copper busbar wires.

[0139] Comparative Example 5

[0140] The method differs from Embodiment 1 above in that the graphene containing copper metal impurities is mixed with water during the mixing process. After 5 hours of electrolysis, the rectified DC power supply is turned off, the mixture is filtered and washed, and then the filter cake is dried in an oven. A certain amount of dried graphene powder, recorded as m4, is then weighed and mixed with excess dilute nitric acid to corrode and remove any remaining copper metal impurities. After washing and drying, the mass of the mixed powder is recorded as m5. The purity of the graphene powder after electrolytic purification and drying under these conditions is calculated to be 75% based on the ratio of the two. Due to the viscosity of the graphene material located in the limited space of the material cavity and the special morphology of this molten metal-grown graphene, it takes a certain amount of time for the electrolyte outside the material cavity to diffuse into the material cavity and reach internal and external concentration equilibrium, thereby reducing the purification efficiency. The above description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims of this application. Accordingly, the scope of the claims of this application is not limited to the aforementioned specific embodiments.

Claims

1. A method for purifying graphene, characterized in that, The method includes: Graphene powder containing metal impurities is mixed evenly with a pre-prepared electrolyte to obtain a graphene electrolyte mixture. The graphene electrolyte mixture is placed in the material cavity (5) inside the electrolytic cell (1) and electrolyzed to remove metal impurities from the graphene powder. During the electrolysis process, the anode (6) is placed in the middle of the material cavity (5), and the cathode (7) is placed in the inner cavity of the electrolytic cell (1) and outside the material cavity (5). The graphene electrolyte mixture in the material cavity (5) is stirred at a speed of 350-450 rpm. Collect the electrolytically treated graphene powder, wash and dry it to obtain purified graphene powder. The pre-prepared electrolyte comprises sulfuric acid, metal sulfate and water, wherein, when the mass fraction of water is 100, the mass fraction of sulfuric acid is 10-15, and the mass fraction of metal sulfate is 4-5.

2. The method according to claim 1, characterized in that, During the electrolytic process, the graphene electrolyte mixture in the inner cavity of the material is stirred by the material stirring paddle (26), and the material stirring paddle (26) moves up and down in the inner cavity of the material. The stirring speed of the material stirring paddle (26) is 350 to 450 rpm.

3. The method according to claim 1, characterized in that, The distance between the anode (6) and the inner wall of the material cavity (5) is 35-50 mm, and the distance between the cathode (7) and the outer wall of the material cavity (5) is 35-50 mm.

4. The method according to claim 1, characterized in that, The viscosity of the graphene electrolyte mixture is 3000–4500 mPa·s.

5. The method according to any one of claims 1-4, characterized in that, During the electrolysis process, the DC voltage applied to the anode (6) and cathode (7) in the electrolysis device is 3.5 to 5V.

6. The method according to any one of claims 1-4, characterized in that, During the electrolysis process, the temperature of the pre-prepared electrolyte in the electrolysis device is 45–60°C.

7. The method according to any one of claims 1-4, characterized in that, The electrolytic cell (1) is connected to the electrolyte storage device (21). During the electrolysis process, the pre-prepared electrolyte in the electrolyte storage device (21) and the pre-prepared electrolyte in the electrolytic cell (1) are controlled to circulate.

8. The method according to any one of claims 1-4, characterized in that, During the preparation of the graphene electrolyte mixture, the stirring speed is 1000-1500 rpm and the stirring time is 30-45 min.

9. The method according to any one of claims 1-4, characterized in that, The material cavity (5) has multiple through holes on its cavity wall. The material cavity (5) is connected to the inner cavity of the electrolytic cell (1) through the multiple through holes. The aperture of the through holes is 800 to 2000 mesh.

10. A graphene purification apparatus, characterized in that, The graphene purification method applied to any one of claims 1-9 includes: an electrolytic cell (1), a material cavity (5) placed in the electrolytic cell, a mixing tank (16) and an electrolyte storage device (21), wherein the material cavity (5) is connected to the inner cavity of the electrolytic cell (1), and the inner cavity of the electrolytic cell (1) is connected to the mixing tank (16) and the electrolyte storage device (21) respectively via pipelines; An anode (6) is provided in the middle of the material cavity (5), and a cathode (7) is provided outside the material cavity (5) in the electrolytic cell (1). The material cavity (5) is also provided with a material stirring paddle (26) for stirring the graphene electrolyte mixture; Driven by external force, the graphene electrolyte mixture in the mixing tank (16) can enter the material cavity (5) and circulate with the pre-made electrolyte in the electrolytic cell (1). The pre-made electrolyte in the electrolyte storage device (21) and the pre-made electrolyte in the electrolytic cell (1) can circulate.

11. The apparatus according to claim 10, characterized in that, One or more material cavities (5) can be placed in the electrolytic cell (1), and the distance between each material cavity (5) and the cathode (7) is the same.

12. The apparatus according to claim 10, characterized in that, The material cavity (5) includes a support grid and an inner liner. The support grid is located outside the inner liner. The inner liner is attached to and fixed to the inner wall of the support grid of the material cavity (5). The inner liner is provided with multiple through holes. Through the multiple through holes of the inner liner, the inner liner can confine the graphene in the inner cavity of the inner liner.

13. The apparatus according to claim 10, characterized in that, The anode (6) is an anode plate, and the cathode (7) is a cathode plate; The distance between the surface of the anode plate and the inner wall of the liner is 35-50 mm, and the distance between the surface of the cathode plate and the outer wall of the liner is 35-50 mm.

14. The apparatus according to claim 10, characterized in that, The material stirring paddle (26) can also be connected to a reciprocating motion drive device (29), which can drive the material stirring paddle (26) to reciprocate back and forth in the inner cavity of the material cavity (5).

15. The apparatus according to claim 10, characterized in that, The material stirring paddle (26) has multiple randomly distributed stirring paddle through holes.

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