Electrochemistry-assisted method for extracting lithium and sodium from overhaul slag

Abstract

The invention discloses a method for extracting lithium and sodium from overhaul slag through electrochemistry assistance, and belongs to the technical field of aluminum electrolysis lithium-containing solid waste cyclic economic utilization and environmental protection. A method for extracting lithium and sodium from overhaul slag through electrochemical assistance comprises the following steps that the overhaul slag and auxiliary materials are subjected to die-casting forming to prepare an electrode plate, and then lithium and sodium are extracted from the overhaul slag through an electrochemical method. According to the method, for the lithium-containing overhaul slag solid waste generated in the electrolytic aluminum industry, migration and dissolution of metal ions are enhanced through electrochemical assistance in a weak acid environment, so that comprehensive recycling of valuable elements of lithium and sodium is achieved, and meanwhile the recovery rate of lithium can be larger than 90%. In addition, the method can be carried out at low temperature, so that the energy consumption can be obviously reduced, and meanwhile, the equipment investment can be greatly reduced; meanwhile, solid waste resource utilization can be achieved, the risk of secondary pollution is reduced, and good economic and environmental benefits are achieved.

Description

Technical Field

[0001] This invention belongs to the field of circular economy utilization and environmental protection technology of lithium-containing solid waste from aluminum electrolysis, and particularly relates to an electrochemical-assisted method for extracting lithium and sodium from overhaul slag. Background Technology

[0002] Spent Pot Lining (SPL) is solid waste generated when aluminum electrolytic cells are replaced after 5-10 years of operation. It mainly originates from the cathode carbon blocks, refractory materials, and insulation layers of the electrolytic cell. Its composition is complex and can generally be divided into two categories: Category 1 (non-carbonaceous portion): mainly consists of waste refractory materials (such as Al2O3, SiO2, CaF2) and fluorides (Na3AlF6, CaF2). Category 2 (carbonaceous portion): mainly consists of waste cathode carbon blocks, containing fixed carbon (60%-80%), fluorides (5%-15%), lithium (0.1%-1.5%), sodium (2%-10%), and other valuable metals. Because SPL contains soluble fluorides and highly toxic cyanides, it is classified as hazardous waste. Direct landfilling or dumping would severely pollute the soil and groundwater. Therefore, its resource utilization is urgently needed.

[0003] With the continuous development of the new energy industry, the demand for lithium carbonate is increasing. The lithium content in overhaul slag has high economic value. Therefore, the comprehensive recovery and utilization of lithium and sodium contained in overhaul slag has great commercial prospects. At present, the main methods for recovering lithium and sodium from overhaul slag include pyrometallurgy, hydrometallurgy, and combined processes, but all of them have significant drawbacks.

[0004] Pyrometallurgy involves high-temperature calcination at 1000-1200℃ to volatilize fluorides (such as NaF and AlF3), while lithium and sodium accumulate in the residue as oxides. The disadvantages include a recovery rate of less than 50%, high energy consumption, and the generation of large amounts of fluorine-containing waste gas.

[0005] Hydrometallurgy employs acid leaching: H₂SO₄, HCl, or HNO₃ are used to leach the overhaul slag at low temperatures, allowing lithium and sodium to enter the solution, followed by separation through precipitation or extraction. The disadvantages of this method are high acid consumption (requiring excessive acid to dissolve impurities such as Al₂O₃ and SiO₂) and cumbersome subsequent purification steps, resulting in high costs.

[0006] The combined pyrometallurgical-hydrometallurgical process employs a roasting-water leaching method: first, low-temperature roasting (500℃) is used for activation, followed by acid leaching to extract lithium and sodium. The disadvantages are a long process and low lithium-sodium separation efficiency. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes an electrochemically assisted method for extracting lithium and sodium from overhaul slag. By utilizing electrochemical assistance to enhance the migration and dissolution of metal ions in a weakly acidic environment, energy consumption and environmental burden are significantly reduced, while simultaneously achieving comprehensive recovery of lithium and sodium metals, with a lithium recovery rate >90%.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] An electrochemically assisted method for extracting lithium and sodium from overhaul slag includes the following steps:

[0010] Electrode sheets were prepared by die casting of overhaul slag and auxiliary materials, and then lithium and sodium were extracted from the overhaul slag using an electrochemical method.

[0011] Optionally, the excipients include at least one of a carbon raiser and an adhesive.

[0012] Furthermore, the carbon raiser is any one of waste cathode powder, carbon powder, and graphite powder; its particle size is 80 mesh or larger; the amount of carbon raiser added is 0-15% of the mass of the overhaul slag.

[0013] Furthermore, the adhesive is any one of asphalt-based, phenolic resin, and phosphate-based adhesives; the amount of adhesive added is 5% to 25% of the mass of the overhaul slag.

[0014] Optionally, the thickness of the electrode sheet is 0.1~10cm.

[0015] Optionally, the electrochemical method includes the following steps:

[0016] (1) The electrode sheet is used as the anode, the inert electrode is used as the cathode, and a DC power supply is connected between the anode and the cathode; an acid solution containing sodium salt and / or aluminum salt is used as the conductive liquid;

[0017] (2) Adjust the power supply potential once and perform auxiliary stirring to dissolve lithium ions from the anode;

[0018] (3) Adjust the power supply potential a second time and add stirring to dissolve sodium ions from the anode;

[0019] (4) After the dissolution is completed, the lithium-rich sodium-rich solution is evaporated and concentrated to obtain sodium salt compound products and high lithium solution;

[0020] (5) Add a precipitant to the high-lithium solution, and after filtration, washing and drying, obtain a lithium carbonate compound product.

[0021] Beneficial effects: First, the present invention prepares electrode sheets by mixing overhaul slag with carbon raisers and binders and then die casting them. This step not only realizes the molding treatment of solid waste, giving it good conductivity and mechanical strength, but also controls the thickness of the electrode sheet within the range of 0.1~10 cm, taking into account both ion transport efficiency and structural stability, providing an efficient and stable anode material basis for subsequent electrochemical reactions.

[0022] Secondly, using this electrode sheet as the anode and an inert electrode (such as platinum or graphite) as the cathode, a weakly acidic solution containing sodium and / or aluminum salts was used as the conductive liquid and connected to a DC power supply to construct a complete electrochemical leaching system. This design abandons the high-energy-consuming and highly corrosive path of traditional high-temperature calcination or strong acid leaching, and achieves selective dissolution of valuable metals under mild conditions by driving the directional migration of metal ions through an external electric field. It also reduces equipment corrosion and acid consumption, significantly improving process safety and sustainability.

[0023] In the electrochemical leaching process, the orderly and efficient extraction of lithium and sodium was achieved by staged control of the power supply potential and supplemented by stirring. Stirring effectively enhanced the mass transfer process, prevented electrode surface passivation, ensured continuous renewal of the reaction interface, and improved the leaching rate and uniformity. In other words, this invention achieves gradient dissolution of lithium and sodium by precisely controlling the electrochemical driving force, avoiding cross-interference caused by the simultaneous large-scale dissolution of multiple metals, and providing favorable conditions for subsequent separation.

[0024] After leaching, the lithium-rich and sodium-rich solution is evaporated and concentrated. Taking advantage of the difference in solubility between lithium and sodium salts, sodium salt is preferentially precipitated and recovered as a by-product. At the same time, a high-lithium solution with a lithium concentration of >5 g / L is obtained, providing high-grade raw materials for subsequent lithium extraction and significantly improving the level of comprehensive resource utilization.

[0025] Finally, a precipitant is added to the high-lithium solution to selectively precipitate lithium as lithium carbonate. After solid-liquid separation, washing, and drying, the lithium carbonate compound product is obtained.

[0026] In summary, this invention achieves efficient, clean, and synergistic recovery of lithium and sodium from overhaul slag through a complete process chain of "electrode construction—weak acid electrochemical leaching—stepwise potential control—evaporation and salt separation—precipitation and lithium extraction." Compared to traditional methods, this invention operates at low temperature and normal pressure, significantly reducing energy consumption and equipment investment; it reduces acid usage, lowering the difficulty of wastewater treatment and the risk of secondary pollution; and it achieves a lithium recovery rate of >90%, more than 10% higher than traditional wet processes, resulting in significant economic benefits. The entire process combines resource recovery, volume reduction, and harmlessness, providing a green and efficient new path for the high-value utilization of lithium-containing solid waste such as overhaul slag.

[0027] Furthermore, the inert electrode material is selected from either platinum or graphite.

[0028] Furthermore, the sodium salt is one of sodium chloride, sodium sulfate, and sodium nitrate, or a mixture thereof; and / or,

[0029] The aluminum salt is one of aluminum chloride, aluminum sulfate, aluminum nitrate, or a mixture thereof; and / or,

[0030] The acid solution is one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, or a mixture thereof, and / or,

[0031] The aluminum salt has a mass concentration of 5% to 30% in the conductive liquid; and / or

[0032] The sodium salt has a mass concentration of 5% to 30% in the conductive liquid.

[0033] Furthermore, the initial adjustment of the power supply potential is 0.2~0.9V, and the stirring speed is 15~100r / min.

[0034] Furthermore, the secondary adjustment power supply potential is 0.9~1.5V, and the stirring speed is 15~100r / min.

[0035] Furthermore, the lithium concentration in the high-lithium solution is >5 g / L.

[0036] Furthermore, the precipitant is solid sodium carbonate or solid potassium carbonate.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] 1) This invention applies an electric current to a relatively weak acid solution, causing the valuable metal ions in the electrode prepared from lithium-containing overhaul slag to rapidly dissolve and transfer into the solution under electrochemical action. Compared with traditional high-temperature roasting or strong acid leaching methods, this invention can be carried out at low temperatures, which can significantly reduce energy consumption and greatly reduce equipment investment.

[0039] 2) The method disclosed in this invention significantly reduces the amount of acid used in the leaching process compared with other wet leaching processes. Therefore, it can significantly reduce the generation of acidic waste liquid throughout the process. At the same time, the waste liquid in this invention has a low acidity and is easy to treat, which can realize the resource utilization of waste liquid, reduce the risk of secondary pollution, significantly reduce costs, and has good economic and environmental benefits.

[0040] 3) The method disclosed in this invention can significantly improve the recovery rate of lithium metal, while reducing the entry of impurity elements. The overall recovery rate of lithium element is greater than 90%, which is more than 10% higher than the traditional wet leaching process, and can significantly increase the profitability of enterprises. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] This invention provides an electrochemically assisted method for extracting lithium and sodium from overhaul slag, comprising the following steps:

[0047] (1) Pretreatment: The overhaul slag is crushed and ground into powder to obtain overhaul slag powder;

[0048] (2) Electrode preparation: The overhaul slag is mixed evenly with carbon raiser and binder, and then die-cast to obtain the electrode.

[0049] (3) Preparation of conductive solution: Sodium salt, aluminum salt or a mixture of both are added to an acid solution of a specific concentration to prepare a conductive solution.

[0050] (4) Electrode installation and external electric field: The electrode is installed at the designated position in the reaction vessel as the anode, and the inert electrode is used as the cathode. An external DC power supply is connected between the anode and the cathode.

[0051] (5) Lithium ion dissolution: Adjust the power supply potential to dissolve lithium ions from the anode and enrich them in the solution. During the dissolution process, stirring is used to accelerate the dissolution.

[0052] (6) Sodium ion dissolution: Adjust the power supply potential to dissolve sodium ions from the anode and enrich them in the solution. During the dissolution process, stirring is used to accelerate the dissolution.

[0053] (7) Evaporation and concentration to extract sodium: When the concentration of sodium and lithium ions in the solution no longer increases, the dissolution is considered to be complete. The lithium-rich and sodium-rich solution is evaporated and concentrated to precipitate sodium ions in the form of sodium salt. After filtration, a high-lithium solution is obtained.

[0054] (8) Lithium precipitation: Add a precipitant to the high-lithium solution obtained in step (7) to produce lithium carbonate precipitate. After filtration, washing and drying, lithium carbonate compound product is obtained.

[0055] In some alternative embodiments, in step (1), the overhaul slag is crushed and ground to obtain overhaul slag powder, the particle size of which is required to be above 80 mesh.

[0056] In some optional embodiments, in step (2), the carbon raiser is a carbonaceous material such as waste cathode powder, carbon powder, or graphite powder, and its particle size is required to be above 80 mesh.

[0057] In some optional embodiments, in step (2), the adhesive is an asphalt-based, phenolic resin, or phosphate adhesive, and the amount of adhesive used is 5% to 25% of the mass of the overhaul slag.

[0058] In some optional embodiments, in step (2), after the overhaul slag is mixed evenly with the carbon raiser and binder, material A is obtained with a carbon content ≥8%.

[0059] In some alternative embodiments, in step (2), the die casting method is to press the die with a tablet press or to use a mold, and the thickness of the die casting is 0.1~10cm.

[0060] In some alternative embodiments, in step (3), the sodium salt is one of sodium chloride, sodium sulfate, sodium nitrate, or a mixture thereof.

[0061] In some alternative embodiments, in step (3), the mass fraction of sodium salt in the conductive liquid is 5% to 30%.

[0062] In some alternative embodiments, in step (3), the aluminum salt is one of aluminum chloride, aluminum sulfate, aluminum nitrate, or a mixture thereof.

[0063] In some alternative embodiments, in step (3), the mass fraction of aluminum salt in the conductive liquid is 5% to 30%.

[0064] In some alternative embodiments, in step (3), the acid solution is one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, or a mixture thereof.

[0065] In some alternative embodiments, in step (3), the concentration of the acid solution is 0.1~8 mol / L.

[0066] In some alternative embodiments, in step (4), the inert electrode material is selected from platinum and graphite.

[0067] In some alternative embodiments, during step (5), the power supply potential is 0.2~0.9V during the lithium ion dissolution process.

[0068] In some alternative embodiments, during step (5), the stirring speed is 15 to 100 revolutions during the lithium ion dissolution process.

[0069] In some alternative embodiments, during step (6), the power supply potential is 0.9~1.5V during the sodium ion dissolution process.

[0070] In some alternative embodiments, during step (6), the stirring speed is 15 to 100 revolutions during the sodium ion dissolution process.

[0071] In some alternative embodiments, in step (7), the lithium concentration in the high-lithium solution is >5 g / L.

[0072] In some optional embodiments, in step (8), the precipitant is solid sodium carbonate or solid potassium carbonate. After adding the precipitant, the concentration of sodium carbonate or potassium carbonate in the solution is 0.04 mol / L to 2.2 mol / L; the recovery rate of the obtained lithium is greater than 90%.

[0073] All raw materials used in this invention were purchased commercially. The asphalt-based binder used in the embodiments of this invention is SBS modified asphalt mortar, purchased from Shouguang Xinyi Waterproof Materials Co., Ltd.

[0074] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0075] The technical solution of the present invention will be further illustrated by the following embodiments.

[0076] Example 1

[0077] In this embodiment, the overhaul slag came from an electrolytic aluminum enterprise in Henan Province. The measured lithium content was 1.2%, and the carbon content was 12.7%. The specific steps for extracting lithium and sodium from the overhaul slag using an electrochemical-assisted method are as follows:

[0078] (1) Pretreatment: The overhaul slag is crushed and ground to obtain overhaul slag powder, and the powder particle size is 100% passing through a 100-mesh sieve.

[0079] (2) Electrode preparation: The overhaul slag powder and SBS modified asphalt mortar are mixed evenly at a mass ratio of 100:15, placed in a mold, and pressed to form the electrode.

[0080] (3) Preparation of conductive solution: Add 15 parts of aluminum chloride, 15 parts of sodium sulfate and 10 parts of 8 mol / L hydrochloric acid to 100 parts of pure water and dissolve them completely to obtain a conductive solution;

[0081] (4) Electrode installation and external electric field: The electrode obtained in step (2) is installed in the designated position in the reaction vessel as the anode, and graphite is used as the cathode. An external DC power supply is connected between the anode and the cathode.

[0082] (5) Lithium ion dissolution: Turn on the power, adjust the power supply potential to 0.8V, and the stirring speed to 50r / min;

[0083] (6) Sodium ion dissolution: After 2 hours of reaction, the power supply potential is adjusted to 1.4V and the stirring speed is 50r / min. Electrochemical assisted leaching is continued. When the deviation of the lithium and sodium content in the solution is less than 2% after two tests at 30-minute intervals, the leaching is considered to be completed, and a lithium-rich and sodium-rich solution is obtained.

[0084] (7) Evaporation and concentration to extract sodium: The lithium-rich sodium-rich solution obtained in step (6) is evaporated and concentrated to precipitate sodium ions in the form of sodium salt. After filtration, a high lithium solution is obtained with a lithium concentration of 5.8 g / L.

[0085] (8) Lithium precipitation: Add the corresponding sodium carbonate solid precipitant to the high lithium solution obtained in step (7) so that the concentration of sodium carbonate in the solution is 2.0 mol / L to produce lithium carbonate precipitate. After filtration, washing and drying, lithium carbonate compound product is obtained with a lithium recovery rate of 92.3%.

[0086] Example 2

[0087] In this embodiment, the overhaul slag came from an electrolytic aluminum enterprise in Shaanxi Province. The measured lithium content was 1.7%, and the carbon content was 6.5%. The specific steps for extracting lithium and sodium from the overhaul slag using an electrochemical-assisted method are as follows:

[0088] (1) Pretreatment: The overhaul slag is crushed and ground into powder to obtain overhaul slag powder. The powder particle size is 100% passing through a 100-mesh sieve.

[0089] (2) Electrode preparation: The overhaul slag powder, graphite carbonizer and SBS modified asphalt mortar are mixed evenly in a mass ratio of 95:5:20, placed in a mold and pressed to form the electrode.

[0090] (3) Preparation of conductive solution: Add 20 parts of aluminum sulfate, 10 parts of sodium chloride and 16 parts of 4 mol / L hydrochloric acid to 100 parts of pure water and dissolve them completely to obtain a conductive solution;

[0091] (4) Electrode installation and external electric field: The electrode obtained in step 2) is installed in the designated position in the reaction vessel as the anode, and the graphite is used as the cathode. An external DC power supply is connected between the anode and the cathode.

[0092] (5) Lithium ion dissolution: Turn on the power, adjust the power supply potential to 0.6V, and the stirring speed to 40r / min;

[0093] (6) Sodium ion dissolution: After 2 hours of reaction, the power supply potential is adjusted to 1.2V and the stirring speed is 30r / min. Electrochemical assisted leaching is continued. When the deviation of the lithium and sodium content in the solution is less than 2% after two tests at 30-minute intervals, the leaching is considered to be completed, and a lithium-rich and sodium-rich solution is obtained.

[0094] (7) Evaporation and concentration to extract sodium: The lithium-rich sodium-rich solution obtained in step (6) is evaporated and concentrated to precipitate sodium ions in the form of sodium salt. After filtration, a high lithium solution is obtained with a lithium concentration of 6.9 g / L.

[0095] (8) Lithium precipitation: Add the corresponding sodium carbonate solid precipitant to the high lithium solution obtained in step (7) so that the concentration of sodium carbonate in the solution is 0.59 mol / L to produce lithium carbonate precipitate. After filtration, washing and drying, lithium carbonate compound product is obtained with a lithium recovery rate of 91.7%.

[0096] Example 3

[0097] In this embodiment, the overhaul slag came from an electrolytic aluminum enterprise in Shanxi Province. The measured lithium content was 1.45%, and the carbon content was 16.5%. The specific steps for extracting lithium and sodium from the overhaul slag using an electrochemical-assisted method are as follows:

[0098] (1) Pretreatment: The overhaul slag is crushed and ground to obtain overhaul slag powder, and the powder particle size is 100% passing through a 100-mesh sieve.

[0099] (2) Electrode preparation: The overhaul slag powder and SBS modified asphalt mortar are mixed evenly at a mass ratio of 100:18, placed in a mold, and pressed to form the electrode.

[0100] (3) Preparation of conductive solution: Add 20 parts of aluminum chloride, 10 parts of sodium chloride and 5 parts of 15 mol / L sulfuric acid to 100 parts of pure water and dissolve them completely to obtain a conductive solution;

[0101] (4) Electrode installation and external electric field: The electrode obtained in step (2) is installed in the designated position in the reaction vessel as the anode, and graphite is used as the cathode. An external DC power supply is connected between the anode and the cathode.

[0102] (5) Lithium ion dissolution: Turn on the power, adjust the power supply potential to 0.9V, and the stirring speed to 70r / min;

[0103] (6) Sodium ion dissolution: After 2 hours of reaction, the power supply potential is adjusted to 1.5V and the stirring speed is 60r / min. Electrochemical assisted leaching is continued. When the deviation of the lithium and sodium content in the solution is less than 2% after two tests at 30-minute intervals, the leaching is considered to be completed, and a lithium-rich and sodium-rich solution is obtained.

[0104] (7) Evaporation and concentration to extract sodium: The lithium-rich sodium-rich solution obtained in step (6) is evaporated and concentrated to precipitate sodium ions in the form of sodium salt. After filtration, a high lithium solution is obtained with a lithium concentration of 6.25 g / L.

[0105] (8) Precipitation of lithium: Add the corresponding sodium carbonate solid precipitant to the high lithium solution obtained in step (7) so that the concentration of sodium carbonate in the solution is 0.54 mol / L to produce lithium carbonate precipitate. After filtration, washing and drying, lithium carbonate compound product is obtained with a lithium recovery rate of 96.8%.

[0106] Example 4

[0107] In this embodiment, the overhaul slag came from an electrolytic aluminum enterprise in Xinjiang. The measured lithium content was 0.85% and the carbon content was 4.65%. The specific steps for extracting lithium and sodium from the overhaul slag using an electrochemical-assisted method are as follows:

[0108] (1) Pretreatment: The overhaul slag is crushed and ground to obtain overhaul slag powder. 100% of the powder particles pass through an 80-mesh sieve and 78% pass through a 100-mesh sieve.

[0109] (2) Electrode preparation: The overhaul slag powder, carbon powder carbonizer, and SBS modified asphalt mortar are mixed evenly in a mass ratio of 90:10:15, placed in a mold, and pressed to form the electrode.

[0110] (3) Preparation of conductive solution: Add 15 parts of aluminum chloride, 15 parts of sodium chloride, and 8 parts of 10 mol / L sulfuric acid to 100 parts of pure water and dissolve them completely to obtain a conductive solution;

[0111] (4) Electrode installation and external electric field: The electrode obtained in step (2) is installed in the designated position in the reaction vessel as the anode, and graphite is used as the cathode. An external DC power supply is connected between the anode and the cathode.

[0112] (5) Lithium ion dissolution: Turn on the power, adjust the power supply potential to 0.8V, and the stirring speed to 50r / min;

[0113] (6) Sodium ion dissolution: After 2 hours of reaction, the power supply potential is adjusted to 1.3V and the stirring speed is 50r / min. Electrochemical assisted leaching is continued. When the deviation of the lithium and sodium content in the solution is less than 2% after two tests at 30-minute intervals, the leaching is considered to be completed, and a lithium-rich and sodium-rich solution is obtained.

[0114] (7) Evaporation and concentration to extract sodium: The lithium-rich sodium-rich solution obtained in step (6) is evaporated and concentrated to precipitate sodium ions in the form of sodium salt. After filtration, a high lithium solution is obtained with a lithium concentration of 5.05 g / L.

[0115] (8) Precipitation of lithium: Add the corresponding sodium carbonate solid precipitant to the high lithium solution obtained in step (7) so that the concentration of sodium carbonate in the solution is 0.43 mol / L to produce lithium carbonate precipitate. After filtration, washing and drying, lithium carbonate compound product is obtained with a lithium recovery rate of 90.5%.

[0116] Comparative Example 1 (using traditional wet leaching)

[0117] Lithium was extracted from overhaul slag using the traditional sulfuric acid aging-water leaching method, with a maximum extraction rate of 87.48%. For specific steps, please refer to the literature "Xu Longlong, Ma Baozhong, Liu Yubo, et al. Efficient extraction of lithium and fluorine resources from aluminum electrolysis overhaul slag by sulfuric acid aging-water leaching method [J]. Mining and Metallurgy, 2025(3)".

[0118] Comparative Example 2

[0119] The patent, with publication number CN107974565A, is titled "A Method for Selective Nitric Acid Leaching of Lithium in Aluminum Electrolytes." This patent uses wet nitric acid leaching, achieving a lithium leaching rate of 88%.

[0120] In summary, compared with Comparative Examples 1 and 2, the lithium recovery rate of the method in Example 3 of the present invention is increased by more than 10%, and the problems of consuming a large amount of acid, complicated subsequent purification steps, and high cost are avoided.

[0121] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for extracting lithium and sodium from overhaul slag using electrochemical assistance, characterized in that, Includes the following steps: Electrode sheets were prepared by die casting of overhaul slag and auxiliary materials, and then lithium and sodium were extracted using electrochemical methods.

2. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 1, characterized in that, The auxiliary materials include at least one of carbon raisers and adhesives.

3. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 2, characterized in that, The carbon raiser is any one of waste cathode powder, carbon powder or graphite powder; and / or, the amount of carbon raiser added is 0 to 15% of the mass of the overhaul slag.

4. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 2, characterized in that, The adhesive is any one of asphalt-based adhesive, phenolic resin-based adhesive, or phosphate-based adhesive; and / or, the amount of adhesive added is 5% to 25% of the mass of the overhaul slag.

5. A method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to any one of claims 1-4, characterized in that, The electrochemical method includes the following steps: (1) The electrode sheet is used as the anode, the inert electrode is used as the cathode, and a DC power supply is connected between the anode and the cathode; an acid solution containing sodium salt and / or aluminum salt is used as the conductive liquid; (2) Adjust the power supply potential once and perform auxiliary stirring to dissolve lithium ions from the anode; (3) Adjust the power supply potential a second time and add stirring to dissolve sodium ions from the anode; (4) After the dissolution is completed, the lithium-rich sodium-rich solution is evaporated and concentrated to obtain sodium salt compound products and high lithium solution; (5) Add a precipitant to the high-lithium solution, and after filtration, washing and drying, obtain a lithium carbonate compound product.

6. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 5, characterized in that, The sodium salt is at least one of sodium chloride, sodium sulfate, or sodium nitrate; and / or, The aluminum salt is at least one of aluminum chloride, aluminum sulfate, or aluminum nitrate; and / or, The acid solution is at least one of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution; and / or, The aluminum salt has a mass concentration of 5% to 30% in the conductive liquid; and / or The sodium salt has a mass concentration of 5% to 30% in the conductive liquid.

7. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 5, characterized in that, The initial adjustment of the power supply potential is 0.2~0.9V, and the stirring speed is 15~100r / min.

8. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 5, characterized in that, The secondary adjustment power supply potential is 0.9~1.5V, and the stirring speed is 15~100r / min.

9. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 5, characterized in that, The lithium concentration in the high-lithium solution is >5 g / L.

10. The method for electrochemically assisted extraction of lithium and sodium from overhaul slag according to claim 5, characterized in that, The precipitant is solid sodium carbonate or solid potassium carbonate.