Treatment method of aluminum electrolysis waste cathode

Abstract

The invention provides a treatment method of an aluminum electrolysis waste cathode. The treatment method comprises the steps that in inert gas, the aluminum electrolysis waste cathode and anode are subjected to first electrolysis in fused salt, and the graphitized cathode material is obtained. According to the method, aluminum electrolysis waste cathodes and anodes are subjected to first electrolysis in molten salt, the first electrolysis is carried out at a relatively mild temperature, and an amorphous carbon material is graphitized in the molten salt through electrochemical reforming. According to the treatment method disclosed by the invention, the energy consumption required by traditional high-temperature graphitization is remarkably reduced, the harsh requirement of equipment on high temperature is avoided, meanwhile, impurities such as fluoride and sulfur are effectively removed, and the graphitization degree of the waste cathode is improved. In addition, the method is simple in technological process and low in cost, and the prepared graphitized cathode material can be applied to the fields of structural materials, energy storage and the like.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis solid waste treatment technology, and more specifically, to a method for treating waste cathodes from aluminum electrolysis. Background Technology

[0002] With the advancement of high-performance technologies in industrial materials, lightweight aluminum and aluminum alloys have been widely used in key fields such as aviation, aerospace, and shipbuilding. However, the amount of solid hazardous waste from waste cathode carbon produced during current industrial electrolytic aluminum production processes is increasing year by year. Because it contains fluorides, long-term stockpiling will cause significant harm to human life and the environment. Currently, researchers have developed a series of processes, including aqueous chemical methods, physical methods, and high-temperature methods, to treat the fluorides in waste cathodes. High-temperature heat treatment is the most commonly used graphitization method, typically carried out at temperatures above 2000℃. The calcined waste cathode is then subjected to prolonged treatment at high temperatures (usually between 2000℃ and 3000℃) and in a specific atmosphere (such as inert gas or vacuum). During this process, carbon atoms rearrange to form an ordered graphite crystal structure. This process can take several hours to several days, requiring equipment capable of withstanding high temperatures and presenting a high energy consumption problem.

[0003] For processes like chemical leaching of waste cathodes to remove fluorides, aqueous solutions can remove them, but the resulting fluoride-containing wastewater generates large amounts of secondary hazardous waste and increases equipment corrosion. High-temperature combustion involves heating the waste cathode to approximately 1000°C and adding chemical reagents to induce a chemical reaction that removes impurities. However, in the presence of oxygen, carbon combustion inhibits the fluoride reaction. Physical flotation involves adding a capturing agent and flotation, recovering carbon at the top while fluorides settle at the bottom. This method suffers from low conversion efficiency and generates significant secondary hazards from the wastewater.

[0004] Graphitization is an effective way to alter the structure of carbonaceous materials, giving them excellent properties such as high-temperature resistance, electrical conductivity, lubricity, and chemical stability, thereby achieving high-value-added and efficient utilization of carbonaceous resources. Currently, methods for improving graphitization mainly include catalytic graphitization, chemical vapor deposition (CVD), microwave heating, and high-temperature, high-pressure (HTHP). However, catalytic graphitization results in graphite heavily coated with catalysts, which are difficult to remove completely. CVD has low production efficiency and is difficult to achieve low-cost industrial production. Microwave heating produces graphite with low crystallinity, and subsequent catalyst removal is difficult. HTHP cannot achieve graphitization of porous, disordered-layer carbonaceous materials even at temperatures above 2000℃. Therefore, these graphitization methods all have drawbacks to varying degrees, including high energy consumption, significant pollution, and high requirements for the purity of the carbon materials. Summary of the Invention

[0005] The main objective of this invention is to provide a method for processing waste cathodes from aluminum electrolysis, thereby solving the problems of high energy consumption and pollution in existing methods for processing waste cathodes from aluminum electrolysis.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for processing waste aluminum electrolysis cathodes is provided, the method comprising: performing a first electrolysis of the waste aluminum electrolysis cathode and anode in molten salt in an inert gas to obtain a graphitized cathode material.

[0007] Furthermore, the temperature of the molten salt is 500–1000°C.

[0008] Furthermore, the voltage of the first electrolysis is 2.5V to 3.0V; and / or the time of the first electrolysis is 2 to 6 hours.

[0009] Furthermore, the mass ratio of the aforementioned aluminum electrolysis waste cathode to the molten salt is 1:200 to 500.

[0010] Furthermore, the above-mentioned treatment method also includes: soaking the aluminum electrolysis waste cathode in the molten salt before performing the first electrolysis; wherein the soaking time is 1 to 5 hours.

[0011] Further, the above processing method includes: step S1, crushing the aluminum electrolysis waste cathode to obtain aluminum electrolysis waste cathode powder; step S2, wrapping the aluminum electrolysis waste cathode powder with a current collector, and then performing the first electrolysis with the anode in the molten salt to obtain the graphitized cathode material; wherein, the current collector is selected from any one or more of graphite mesh, graphite grid, graphite paper, metal foam and metal mesh, and more preferably the current collector is graphite paper and / or nickel foam.

[0012] Furthermore, the above-mentioned method for preparing molten salt includes: subjecting solid salt to dehydration and a second electrolysis in sequence to obtain the molten salt.

[0013] Further, the temperature for dehydration is 200–250°C; and / or the dehydration time is 24–28 h; preferably, the dehydration is performed by vacuum dehydration; and / or, the voltage of the second electrolysis is 2.0–3.0 V; and / or, the time of the second electrolysis is 8–24 h; and / or, the temperature of the second electrolysis is 500–1000°C.

[0014] Further, the molten salt is a water-soluble molten salt; preferably, the water-soluble molten salt is selected from any one or more of NaCl, KCl, CaCl2 and BaCl2; more preferably, the water-soluble molten salt is CaCl2; and / or, the inert gas is argon or helium; and / or, the anode is a graphite rod.

[0015] Furthermore, by mass percentage, the aforementioned aluminum electrolysis waste cathode comprises: 72.25% carbon, 5.95–6.80% fluorine, 4.46–5.05% sodium, 0.62–0.83% sulfur, and the balance being other impurity elements; and / or, the graphitization degree of the graphitized cathode material is 93.0–98.0%.

[0016] By applying the technical solution of this invention, the waste cathode and anode from aluminum electrolysis undergo a first electrolysis in molten salt at a relatively mild temperature, thereby graphitizing the amorphous carbon material through electrochemical reforming in the molten salt. Driven by electrochemistry, impurities such as fluorine and sulfur are removed from the carbon material, accompanied by a rearrangement of carbon atoms, thus converting the amorphous carbon into graphite. This method significantly reduces the energy consumption required for traditional high-temperature graphitization, avoids the stringent high-temperature requirements of the equipment, and effectively removes impurities such as fluorides and sulfur, improving the graphitization degree of the waste cathode. Furthermore, the method of this application has a simple process flow and low cost, and the resulting graphitized cathode material can be applied in structural materials, energy storage, and other fields. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 The XRD comparison diagrams of the original waste cathode and the soaked waste cathode in Embodiment 1 of this application are shown;

[0019] Figure 2 The XRD pattern of the waste cathode after the first electrolysis in Embodiment 1 of this application is shown;

[0020] Figure 3 A TEM image of the graphitized cathode material in Embodiment 1 of this application is shown. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] As analyzed in the background section of this application, the existing methods for treating waste cathodes from aluminum electrolysis have problems of high energy consumption and pollution. In order to solve this problem, this application provides a method for treating waste cathodes from aluminum electrolysis.

[0023] It should be noted that the aluminum electrolysis waste cathode in this application refers to the carbonaceous material that is dismantled and replaced in the aluminum electrolysis industry; it is usually collected from the bottom of the electrolytic cell.

[0024] In a typical embodiment of this application, a method for processing waste aluminum electrolysis cathodes is provided. The method includes: performing a first electrolysis of the waste aluminum electrolysis cathode and anode in molten salt in an inert gas to obtain graphitized cathode material.

[0025] This application involves a first electrolysis of waste aluminum electrolysis cathodes and anodes in molten salt at a relatively mild temperature. This first electrolysis electrochemically reforms amorphous carbon materials in the molten salt to achieve graphitization. Driven by electrochemistry, impurities such as fluorine and sulfur are removed from the carbon material, accompanied by a rearrangement of carbon atoms, thereby converting amorphous carbon into graphite. This method significantly reduces the energy consumption required for traditional high-temperature graphitization, avoids the stringent high-temperature requirements of equipment, and effectively removes impurities such as fluorides and sulfur, improving the graphitization degree of the waste cathodes. Furthermore, the method described in this application has a simple process flow and low cost, and the resulting graphitized cathode material can be applied in structural materials, energy storage, and other fields.

[0026] In one embodiment of this application, the temperature of the molten salt is 500–1000°C.

[0027] Preferably controlling the temperature of the molten salt within the above range helps to improve the efficiency of the first electrolysis while saving energy, thereby obtaining a graphitized cathode material with a high degree of graphitization.

[0028] In one embodiment of this application, the voltage of the first electrolysis is 2.5V to 3.0V; and / or the time of the first electrolysis is 2 to 6 hours.

[0029] Excessively high voltage during the first electrolysis is detrimental to improving the stability of the aluminum electrolysis waste cathode, while excessively low voltage is detrimental to reducing the impurity content in the cathode. Preferably, controlling the voltage of the first electrolysis within the aforementioned range helps improve the efficiency of impurity removal and promotes the rearrangement of carbon atoms, thereby increasing the graphitization degree of the cathode. Similarly, preferably controlling the duration of the first electrolysis within the aforementioned range helps improve the efficiency of impurity removal.

[0030] In one embodiment of this application, the mass ratio of the above-mentioned aluminum electrolysis waste cathode to molten salt is 1:200-500.

[0031] Excessive molten salt concentration is detrimental to reducing side reactions, while insufficient molten salt concentration is detrimental to impurity removal. It is preferable to control the mass ratio of waste aluminum electrolysis cathode to molten salt within the above-mentioned range. This helps to control the ion concentration and conductivity of the reaction system within a suitable range, thereby improving the stability of electrolysis voltage and current, and further improving the degree of graphitization of the cathode.

[0032] In one embodiment of this application, the above-mentioned processing method further includes: soaking the waste aluminum electrolysis cathode in molten salt and then performing a first electrolysis; wherein the soaking time is 1 to 5 hours.

[0033] Immersing spent aluminum electrolysis cathodes in molten salt serves two purposes: firstly, it helps to remove some impurities through etching; secondly, during immersion, the microporous structure of the spent aluminum electrolysis cathodes softens and expands to a certain extent, providing favorable conditions for the migration and recombination of carbon atoms during the electrolysis stage. This facilitates the smoother rearrangement of carbon atoms under electrochemical drive during subsequent electrolysis, forming an ordered graphite structure and thus improving the graphitization degree of the graphitized cathode material. Preferably, controlling the immersion time within the above-mentioned range further enhances the graphitization degree of the graphitized cathode material.

[0034] In one embodiment of this application, the above processing method includes: step S1, crushing the waste aluminum electrolysis cathode to obtain waste aluminum electrolysis cathode powder; step S2, wrapping the waste aluminum electrolysis cathode powder with a current collector, and then performing a first electrolysis with the anode in molten salt to obtain graphitized cathode material; wherein, the current collector is selected from any one or more of graphite mesh, graphite grid, graphite paper, metal foam and metal mesh, and more preferably the current collector is graphite paper and / or nickel foam.

[0035] Crushing spent aluminum electrolysis cathodes into powder increases the contact area between the spent cathode and the molten salt, thereby improving the dissolution rate of impurity elements and the efficiency of the electrochemical reaction. Powdered spent cathodes are more easily penetrated by the molten salt system, promoting the migration and recombination of carbon atoms, which in turn helps increase the graphitization degree of the graphitized cathode material. Preferably controlling the type of current collector within the above-mentioned range helps reduce the probability of introducing new impurities.

[0036] In one embodiment of this application, the method for preparing the molten salt includes: sequentially dehydrating and electrolyzing a solid salt to obtain molten salt.

[0037] Pre-melting dehydration of the solid salt helps remove moisture and reduces the probability of water decomposition in the high-temperature molten salt, producing gases such as hydrogen and oxygen. Hydrogen and oxygen can interfere with the electrochemical process and may also cause corrosion or safety risks to equipment. The second electrolysis process helps further optimize the molten salt system, removing any residual impurities, such as metal ions or other conductive impurities. These impurities may act as catalysts for side reactions during electrolysis, affecting the efficiency of the main reaction and the performance of the products. Through the second electrolysis, the molten salt system is purified, providing a purer and more stable electrolytic environment for the electrochemical purification and graphitization of waste cathodes.

[0038] In one embodiment of this application, the temperature for dehydration is 200–250°C; and / or the dehydration time is 24–28 h; preferably, the dehydration is performed by vacuum dehydration; and / or the voltage of the second electrolysis is 2.0–3.0 V; and / or the time of the second electrolysis is 8–24 h; and / or the temperature of the second electrolysis is 500–1000°C.

[0039] Preferably controlling the dehydration conditions within the above-mentioned range helps to improve the dehydration efficiency and reduce the water content in the molten salt. Preferably controlling the second electrolysis conditions within the above-mentioned range helps to improve the efficiency of the second electrolysis and reduce the impurity content in the molten salt.

[0040] In one embodiment of this application, the molten salt is a water-soluble molten salt; preferably, the water-soluble molten salt is selected from any one or more of NaCl, KCl, CaCl2 and BaCl2; more preferably, the water-soluble molten salt is CaCl2; and / or, the inert gas is argon or helium; and / or, the anode material is a graphite rod.

[0041] Water-soluble molten salts can be removed after electrolysis through a simple water washing step, avoiding the complex post-processing procedures, such as high-temperature melting separation or chemical precipitation, required when using insoluble molten salts. This simplifies the post-processing flow, reduces costs, and improves the overall efficiency of the process. The aforementioned types of water-soluble molten salts exhibit good conductivity and stability in electrochemical reactions, effectively promoting the electrochemical removal of impurities from waste cathode materials.

[0042] In one embodiment of this application, the aforementioned aluminum electrolysis waste cathode, by mass percentage, comprises: 72.25% carbon, 5.95–6.80% fluorine, 4.46–5.05% sodium, 0.62–0.83% sulfur, and the balance being other impurity elements; and / or, the graphitization degree of the graphitized cathode material is 93.0–98.0%.

[0043] The processing method described in this application can remove the aforementioned types of aluminum electrolysis waste cathodes and achieve the aforementioned degree of graphitization in the graphitized cathode material. Other impurity elements include calcium, aluminum, silicon, and iron.

[0044] In one embodiment of this application, the above processing method further includes: removing the cathode product from the molten salt, washing it with water, applying dilute hydrochloric acid, and drying it to obtain a graphitized cathode material.

[0045] The first electrolysis of this application can realize continuous first electrolysis operation. The cathode is removed after the operation is completed, and then a new cathode is replaced to perform first electrolysis graphitization. Furthermore, the molten salt can be used continuously without the need to replace it with a new one each time, which helps to further reduce the cost of impurity removal.

[0046] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0047] Example 1

[0048] By mass percentage, the waste cathode blocks recycled from aluminum electrolysis contain 72.25% carbon, 6.80% fluorine, 5.05% sodium, and 0.83% sulfur, with the remainder being other impurities. The waste cathode blocks are crushed, and then 1g of waste cathode carbon powder is pressed into tablets using a powder press. The cathode was then wrapped with graphite paper. 200g of anhydrous CaCl2 was placed in a high-purity alumina crucible and vacuum-treated at 200℃ for 24 hours to remove moisture. Then, under argon atmosphere protection, the temperature was raised to 850℃ for a second electrolysis at 2.0V for 8 hours to remove impurities from the CaCl2. The graphite-paper-wrapped electrode was then immersed in the CaCl2 melt at 850℃ for 5 hours. Afterward, a graphite rod anode was inserted into the CaCl2, and a first electrolysis at a constant voltage of 2.8V was performed for 6 hours. After electrolysis, the cathode product was removed from the molten salt and washed sequentially with distilled water and dilute hydrochloric acid. Finally, it was dried in a vacuum oven at 80℃ to obtain the graphitized cathode material.

[0049] Example 2

[0050] The difference from Example 1 is that the waste cathode blocks recycled from aluminum electrolysis are crushed, and then 1g of waste cathode carbon powder is wrapped in graphite paper and placed in a self-made graphite frame. Then, it was connected to a 304 stainless steel rod to form a cathode. 200g of anhydrous CaCl2-NaCl (Molar ratio of CaCl2 to NaCl: 0.59:0.41) was placed in a high-purity alumina crucible and vacuumed at 200℃ for 24 hours to remove moisture from the eutectic molten salt. Then, under argon atmosphere protection, the temperature was raised to 900℃ for a second electrolysis at 2.0V for 8 hours to remove impurities from the CaCl2-NaCl. Next, a graphite frame electrode was immersed in the CaCl2-NaCl melt at 900℃ for 5 hours. Then, a graphite rod anode was inserted into the CaCl2-NaCl and a first electrolysis at a constant voltage of 3.0V was performed for 4 hours. After electrolysis, the cathode product was removed from the molten salt and washed sequentially with distilled water and dilute hydrochloric acid. Finally, it was dried in a vacuum oven at 80℃ to obtain the graphitized cathode material.

[0051] Example 3

[0052] The difference from Example 1 is that the waste cathode blocks recycled from aluminum electrolysis are crushed, and then 1g of waste cathode carbon powder is wrapped in nickel foam and placed in a self-made graphite frame. Then, it was connected to a 304 stainless steel rod to form a cathode. 200g of anhydrous CaCl2-NaCl (Molar ratio of CaCl2 to NaCl: 0.59:0.41) was placed in a high-purity alumina crucible and vacuumed at 200℃ for 24 hours to remove moisture from the eutectic molten salt. Then, under argon atmosphere protection, the temperature was raised to 900℃ for a second electrolysis at 2.0V for 8 hours to remove impurities from the CaCl2-NaCl. Next, a graphite frame electrode was immersed in the CaCl2-NaCl melt at 900℃ for 3 hours. Then, a graphite rod anode was inserted into the CaCl2-NaCl melt and subjected to a first electrolysis at a constant voltage of 2.8V for 2 hours. After electrolysis, the cathode product was removed from the molten salt and washed sequentially with distilled water and dilute hydrochloric acid. Finally, it was dried in a vacuum oven at 80℃ to obtain the graphitized cathode material.

[0053] Example 4

[0054] The difference from Example 1 is that the temperature of CaCl2 is 500°C, and graphitized cathode material is finally obtained.

[0055] Example 5

[0056] The difference from Example 1 is that the temperature of CaCl2 is 1000℃, and graphitized cathode material is finally obtained.

[0057] Example 6

[0058] The difference from Example 1 is that the temperature of CaCl2 is 450°C, and graphitized cathode material is finally obtained.

[0059] Example 7

[0060] The difference from Example 1 is that the voltage of the first electrolysis is 2.5V and the time of the first electrolysis is 6h, and finally a graphitized cathode material is obtained.

[0061] Example 8

[0062] The difference from Example 1 is that the voltage of the first electrolysis is 3.0V and the time of the first electrolysis is 2h, and finally a graphitized cathode material is obtained.

[0063] Example 9

[0064] The difference from Example 1 is that the voltage of the first electrolysis is 3.5V and the time of the first electrolysis is 1h, and finally a graphitized cathode material is obtained.

[0065] Example 10

[0066] The difference from Example 1 is that the mass of CaCl2 is 500g, the mass ratio of aluminum electrolysis waste cathode to molten salt is 1:500, and graphitized cathode material is finally obtained.

[0067] Example 11

[0068] The difference from Example 1 is that the mass of CaCl2 is 150g, the mass ratio of the waste aluminum electrolysis cathode to the molten salt is 1:150, and the graphitized cathode material is finally obtained.

[0069] Example 12

[0070] The difference from Example 1 is that the soaking time is 1 hour, and the graphitized cathode material is finally obtained.

[0071] Example 13

[0072] The difference from Example 1 is that the soaking time is 0.5 hours, and the graphitized cathode material is finally obtained.

[0073] Example 14

[0074] The difference from Example 1 is that the water removal temperature is 250°C, the water removal time is 28h, the voltage of the second electrolysis is 3.0V, and the second electrolysis time is 24h, finally obtaining a graphitized cathode material.

[0075] Comparative Example 1

[0076] The difference from Example 1 is that 1g of waste cathode carbon powder was mixed with reduced iron powder to obtain a mixture, with the iron powder accounting for 20% of the total mass of the mixture. This mixture was thoroughly ground in a mortar to ensure uniform mixing, and then transferred to a crucible. Next, the crucible was placed in a high-temperature tube furnace, and argon gas was introduced as a protective atmosphere. If the temperature was below 1400°C, a heating rate of 10°C / min was maintained; if the temperature was above 1400°C, the heating rate was adjusted to 5°C / min. The temperature was raised to 1600°C and maintained for 60 minutes, after which the iron-containing graphite product was cooled to room temperature. The sample was collected and named SCC-CG-Fe. The sample was soaked in 1mol / L dilute sulfuric acid for 6 hours to separate the iron component from the graphite, obtaining the graphitized cathode material.

[0077] The graphitization degree of the graphitized cathode materials prepared in the examples and comparative examples was measured, and the measurement results are shown in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] Figure 1 This is a comparison XRD pattern of the original waste cathode and the soaked waste cathode in Example 1 of this application. Figure 1 In the diagram, A represents the diffraction peak of carbon, B represents the diffraction peak of NaF, C represents the diffraction peak of CaF2, and D represents the diffraction peak of Na3AlF6. Figure 1 It can be seen that after being soaked in CaCl2 molten salt, most of the original impurities in the waste cathode have been removed from the waste cathode.

[0082] Figure 2 This is the XRD pattern of the waste cathode after the first electrolysis in Embodiment 1 of this application. Figure 2 C represents the diffraction peak of CaF2, from Figure 2 The graphitization degree of the waste cathode after molten salt electrolytic graphitization can be calculated to be 97.8%.

[0083] Figure 3 This is a TEM image of the graphitized cathode material in Embodiment 1 of this application. Figure 3 It can be seen that the morphology of the waste cathode after molten salt electrolytic graphitization is mainly nanotube-shaped, accompanied by the formation of a small amount of graphene.

[0084] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0085] This application involves a first electrolysis of waste aluminum electrolysis cathodes and anodes in molten salt at a relatively mild temperature. This first electrolysis electrochemically reforms amorphous carbon materials in the molten salt to achieve graphitization. Driven by electrochemistry, impurities such as fluorine and sulfur are removed from the carbon material, accompanied by a rearrangement of carbon atoms, thereby converting amorphous carbon into graphite. This method significantly reduces the energy consumption required for traditional high-temperature graphitization, avoids the stringent high-temperature requirements of equipment, and effectively removes impurities such as fluorides and sulfur, improving the graphitization degree of the waste cathodes. Furthermore, the method described in this application has a simple process flow and low cost, and the resulting graphitized cathode material can be applied in structural materials, energy storage, and other fields.

[0086] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for processing waste cathodes from aluminum electrolysis, characterized in that, The processing method includes: In an inert gas atmosphere, the waste aluminum electrolysis cathode and anode are subjected to a first electrolysis in molten salt to obtain a graphitized cathode material.

2. The processing method according to claim 1, characterized in that, The temperature of the molten salt is 500–1000°C.

3. The processing method according to claim 1 or 2, characterized in that, The voltage of the first electrolysis is 2.5V to 3.0V; And / or, the first electrolysis time is 2 to 6 hours.

4. The processing method according to any one of claims 1 to 3, characterized in that, The mass ratio of the waste aluminum electrolysis cathode to the molten salt is 1:200-500.

5. The processing method according to any one of claims 1 to 4, characterized in that, The processing method further includes: The waste aluminum electrolysis cathode is soaked in the molten salt before the first electrolysis is performed; wherein the soaking time is 1 to 5 hours.

6. The processing method according to any one of claims 1 to 5, characterized in that, The processing method includes: Step S1: The waste aluminum electrolysis cathode is crushed to obtain waste aluminum electrolysis cathode powder; Step S2: The aluminum electrolysis waste cathode powder is wrapped with a current collector and then subjected to the first electrolysis with the anode in the molten salt to obtain the graphitized cathode material; wherein the current collector is selected from any one or more of graphite mesh, graphite grid, graphite paper, metal foam and metal mesh, and more preferably the current collector is graphite paper and / or nickel foam.

7. The processing method according to any one of claims 1 to 6, characterized in that, The method for preparing the molten salt includes: The solid salt is subjected to dehydration and a second electrolysis in sequence to obtain the molten salt.

8. The processing method according to claim 7, characterized in that, The dehydration temperature is 200–250°C; and / or the dehydration time is 24–28 hours; preferably, the dehydration is performed by vacuum dehydration. And / or, the voltage of the second electrolysis is 2.0 to 3.0 V; and / or, the time of the second electrolysis is 8 to 24 h; and / or, the temperature of the second electrolysis is 500 to 1000 °C.

9. The processing method according to any one of claims 1 to 8, characterized in that, The molten salt is a water-soluble molten salt; preferably, the water-soluble molten salt is selected from any one or more of NaCl, KCl, CaCl2 and BaCl2; more preferably, the water-soluble molten salt is CaCl2; And / or, the inert gas is argon or helium; And / or, the anode is a graphite rod.

10. The processing method according to any one of claims 1 to 9, characterized in that, By mass percentage, the aluminum electrolysis waste cathode comprises: 72.25% carbon, 5.95–6.80% fluorine, 4.46–5.05% sodium, 0.62–0.83% sulfur, and the balance being other impurity elements; and / or, the graphitization degree of the graphitized cathode material is 93.0–98.0%.

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