Method for processing high-value repair slag after lithium extraction

Abstract

The present application belongs to the technical field of comprehensive utilization of aluminum industrial waste resources, and particularly relates to a method for high-value treatment of post-lithium-extraction slag of overhaul slag, which realizes a method for recovering valuable elements such as fluorine, aluminum and sodium in post-lithium-extraction slag of overhaul slag through fluorosilicic acid treatment. The post-lithium-extraction slag is treated by the method, so that the final product is converted into high-molecular poly cryolite and aluminum fluoride products with high quality; efficient recycling of valuable elements such as fluorine, aluminum and sodium is realized, and the resource utilization efficiency of related elements is improved.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of waste resources in the aluminum industry, and in particular relates to a method for high-value treatment of lithium extraction residue from overhaul slag, specifically separating and recovering valuable elements such as fluorine, aluminum, and sodium from the lithium extraction residue from overhaul slag. Background Technology

[0002] Overhaul slag is a hazardous solid waste generated during the overhaul of aluminum electrolytic cells. It has a complex composition, containing harmful substances such as soluble fluorides and cyanides, while also being rich in valuable elements such as lithium, aluminum, sodium, and fluorine. With the development of the new energy industry, lithium extraction from overhaul slag has become an important direction for resource utilization, and related technologies such as wet leaching and alkali roasting-water leaching have made some progress. However, existing technologies almost entirely focus on improving lithium leaching and recovery rates, lacking targeted solutions for the treatment of secondary solid residues generated during the lithium extraction process (i.e., "post-lithium extraction slag"), resulting in a serious shortcoming in the resource utilization chain.

[0003] Currently, patented technologies involving lithium extraction from overhaul slag typically stop at obtaining lithium products in their claims and process endpoints, often glossing over or employing crude methods for the subsequent treatment of the slag. For example, patent CN119735227A, after achieving comprehensive recovery of lithium, sodium, aluminum, and fluorine, explicitly states that the final filter residue will be "sent to a cement plant as a raw material for cement production." This is merely a low-value, large-scale disposal method, failing to deeply extract other potentially valuable components remaining in the slag, nor completely addressing the environmental risks of long-term stockpiling. Patent CN202311349102.X details a complex process of co-processing and separating lithium from overhaul slag and electrolyte, but all its technical effects revolve around obtaining "battery-grade lithium carbonate." The specification makes no mention of the properties, destinations, or subsequent treatment plans for secondary solid wastes such as "first residue" and "third residue" generated during the process. This "lithium extraction and slag disposal" model is the current prevalent state of technology.

[0004] Due to a lack of specialized technology, lithium extraction slag from overhaul slag currently faces similar industry challenges as ordinary lithium smelting slag: difficulty in large-scale utilization, difficulty in high-value utilization, and high storage costs. Specifically: Environmental risk transfer: Simply sending the slag to cement plants for mixing or landfilling may result in harmful components such as fluorine and cyanide remaining in the slag or undergoing transformation, causing secondary pollution. Severe resource waste: The slag usually still contains incompletely recovered elements such as aluminum, fluorine, and sodium; direct disposal results in resource waste. Poor economic viability: Low-value utilization cannot offset the transportation and processing costs of the slag, while paid stockpiling imposes a long-term burden on enterprises, affecting the economic viability of the entire lithium extraction process.

[0005] In summary, current technologies focus on the initial lithium extraction from overhaul slag, while severely neglecting the deep harmlessness and high-value utilization of the downstream slag. Therefore, there is an urgent need to invent a method specifically for treating the slag after lithium extraction from overhaul slag, in order to address its environmental hazards and resource waste, and fill the technological gap in the last mile of the industrial chain. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for recovering valuable elements such as fluorine, aluminum, and sodium from lithium extraction slag after overhaul slag through fluorosilicic acid treatment. Using this method to treat the lithium extraction slag allows the final products to be converted into high-quality cryolite and aluminum fluoride products; it achieves efficient recovery and utilization of valuable elements such as fluorine, aluminum, and sodium, thereby improving the resource utilization efficiency of these elements.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for high-value processing of lithium-extracting slag from overhaul slag involves first mixing and reacting the lithium-extracting slag with fluorosilicic acid, followed by solid-liquid separation to obtain solid A and liquid A; then mixing and reacting solid A with ammonia water at high temperature, followed by solid-liquid separation to obtain a fluorine-containing solution B and silicon-containing slag C; finally, reacting the fluorine-containing solution B with sodium aluminate yields cryolite.

[0008] Liquid A and aluminum hydroxide are mixed and reacted at high temperature. After solid-liquid separation, aluminum fluoride liquid B and silicon slag C are obtained. The aluminum fluoride liquid B can be crystallized at high temperature and calcined to obtain high-quality aluminum fluoride products. The silicon slag C and C' produced in this process can be used to manufacture artificial stone or building fillers.

[0009] The specific steps of this method are as follows: S1. After lithium extraction from the overhaul slag, mix it with fluorosilicic acid and heat it in a microwave chemical reactor to 70-90℃ for 2-4 hours. After the reaction, separate the solid and liquid components to obtain solid A and liquid A. Wash solid A with water until the pH of the wash water reaches 4-5. The wash water can be reused in the next batch of experiments to dilute the fluorosilicic acid solution. The main components of solid A are sodium fluorosilicate generated in the reaction and other unreacted impurities in the original slag, such as carbon, alumina, and calcium fluoride. The main components of liquid A are aluminum fluorosilicate generated in the reaction and some fluorosilicic acid. The main reaction equations involved in this step are as follows: 2NaF+H2SiF6=Na2SiF6+2HF (1-1) 2AlF3+3H2SiF6=Al2(SiF6)3+6HF (1-2) 6HF+SiO2=H2SiF6+2H2O (1-3) S2. Mix solid A with an ammonia solution and react at room temperature for 1.5-2 hours. Separate the solid and liquid to obtain liquid B containing sodium fluoride and ammonium fluoride, and silicon-containing slag. The main components of the silicon-containing slag C are silicon dioxide and other unreacted impurities from the original slag, such as carbon, alumina, and calcium fluoride. The main reaction equations involved in this step are as follows: Na2SiF6+4NH3·H2O=2NaF+4NH4F+SiO2↓+2H2O (1-4) S3. Mix the fluorine-containing liquid B with the sodium aluminate solution and react at 90-100℃ for 2-4 hours. After solid-liquid separation, wash the filter cake with water and then dry it to obtain the cryolite product. The wash water is reused 4-5 times and then mixed with the cryolite mother liquor for reuse in ammonia absorption. The main reaction equations involved in this step are as follows: 2NaF+4NH4F+NaAlO2=Na3AlF6↓+4NH3↑+2H2O (1-5) S4. Preheat liquid A to 60-70℃, then add aluminum hydroxide in batches, followed by heating to 80-90℃ and reacting for 30 min-1 h. Separate the solid and liquid phases while hot to obtain aluminum fluoride-containing liquid B' and silicon-containing slag C'. The main component of silicon-containing slag C' is amorphous silicon dioxide. The main reaction equations involved in this step are as follows: Al2(SiF6)3+4Al(OH)3=6AlF3+3SiO2↓+6H2O (1-6) H2SiF6+2Al(OH)3=2AlF3+SiO2↓+4H2O (1-7) S5. Add a certain amount of seed crystals to the aluminum fluoride liquid B' and crystallize at high temperature. After crystallization, separate the solid and liquid to obtain aluminum fluoride trihydrate crystals and aluminum fluoride mother liquor. The aluminum fluoride trihydrate crystals can be calcined at high temperature to obtain high-quality anhydrous aluminum fluoride. The aluminum fluoride mother liquor can be further processed to obtain other fluoride salt products.

[0010] Specifically, in step S1, the solid-liquid ratio of the slag to fluorosilicic acid is 1:6-8; the concentration of fluorosilicic acid can be any integer between 15% and 25% (mass fraction); and the fluorosilicic acid used must ensure SO4 levels are low. 2- ≤0.030%, PO3 3- ≤0.0020% to avoid the introduction of sulfate and phosphate ions, which would affect the quality of aluminum fluoride products.

[0011] Furthermore, in step S1, a microwave chemical reactor is used for heating and stirring reaction. Compared with conventional solid-liquid mixing and stirring reaction, it can achieve endogenous heating under microwave intervention, better promote the occurrence of solid-liquid reaction, and make the reaction more thorough.

[0012] Specifically, the amount of ammonia used in step S2 is determined by the sodium content in the slag after lithium extraction from the overhaul slag in step S1. The molar ratio of sodium to ammonia in the slag is Na : NH3 = 1 : 2.1-2.2, meaning that the amount of ammonia used is 10-20% in excess of the theoretical molar ratio, ensuring that sodium fluorosilicate is completely consumed; the concentration of ammonia is 8-10 mol / L.

[0013] Furthermore, the feeding method in step S2 is as follows: solid A is prepared into a slurry of 12% using water or recycled cryolite mother liquor, and ammonia water is added dropwise under continuous stirring at room temperature for 15-30 minutes. After the feeding is completed, the reaction is continuously stirred at room temperature for 1-1.5 hours, then filtered, the filter cake is rinsed with hot water, and the wash water is reused 4-5 times and then reused for subsequent steps to absorb ammonia.

[0014] Specifically, in step S3, the cryolite synthesis reaction is carried out at a temperature of 90-100℃. The raw materials are a fluorine-containing solution B and a sodium aluminate solution, with a feed ratio of F:Al = 6.0-6.6 (molar ratio). The fluorine-containing solution and the sodium aluminate solution are added to the reactor simultaneously, reacting while being added, to obtain a cryolite slurry. The synthesis reaction can be carried out intermittently or continuously. The slurry can be filtered by vacuum filtration, pressure filtration, centrifugal filtration, or other filtration methods. The filter cake is then washed and dried to obtain a high-quality cryolite product.

[0015] Furthermore, in step S3, sodium aluminate α k =0.8-1.1, meaning the molar ratio of caustic soda to alumina in sodium aluminate is 0.8-1.1:1; during the synthesis of cryolite, the α-coated sodium aluminate content is adjusted... k The value can be used to synthesize cryolite products with different molecular ratios.

[0016] Furthermore, the ammonia gas generated in step S3 can be collected from recycled cryolite mother liquor or water, reprocessed into ammonia water, and reused in step S2 to participate in the ammonolysis reaction of slag A, thereby realizing ammonia recycling.

[0017] Specifically, the amount of aluminum hydroxide added in step S4 is determined by the aluminum content in the slag after lithium extraction from the overhaul slag in step S1, and the molar ratio of aluminum to aluminum hydroxide in the slag is 1:3.0-3.2.

[0018] Furthermore, the silica slag materials C and C' in steps S2 and S4 can be sold as by-products, used as admixtures for asphalt or concrete, or as auxiliary materials for ceramics and tile products.

[0019] Specifically, the seed crystals added in step S5 are aluminum fluoride trihydrate, the amount of seed crystals added is 10%-20% of the theoretical amount of aluminum fluoride trihydrate to be precipitated, the crystallization temperature is 95-100℃, the stirring rate is 100rpm, and the crystallization time is 4-6h.

[0020] Furthermore, in step S5, the calcination of aluminum trihydrate is a stepped heating calcination, and the temperature and time are controlled as follows: the room temperature is raised to 200°C, held at 200°C for 1 hour, then the temperature is raised to 550°C; after holding at 550°C for 3 hours, the temperature is lowered to room temperature to obtain a high-quality anhydrous aluminum fluoride product.

[0021] Furthermore, in the above invention, room temperature refers to a temperature of 25±5℃.

[0022] The present invention has the following beneficial effects: 1) This invention uses fluorosilicic acid to treat lithium extraction slag, realizing the comprehensive utilization of aluminum and sodium-containing slag after lithium extraction from overhaul slag. The final products are high-quality cryolite with different molecular ratios and high-quality aluminum fluoride, realizing the efficient recovery and utilization of valuable elements such as fluorine, aluminum, and sodium, improving resource utilization efficiency and avoiding resource waste and environmental pollution caused by direct disposal. 2) By optimizing the processing parameters, this invention overcomes the limitations of single-target component extraction in the prior art, ensuring the high purity and quality of cryolite and aluminum fluoride products, improving the market competitiveness of the products. At the same time, all liquids and gases generated during the reaction are recycled and reused in the system, and the solids generated are sold as by-products, avoiding the discharge of waste gas, wastewater, and solid waste, and realizing low-carbon and green production. 3) The method of the present invention is simple in process and easy to operate. It does not require complicated equipment and technology and is easy to industrialize. At the same time, it can avoid direct high-temperature calcination in pyrometallurgy, reduce energy consumption, and has good economic benefits and practical value. 4) The cryolite product obtained after treatment by this invention meets the product index requirements in the GB / T 4291-2017 national standard for cryolite; the aluminum fluoride product obtained after treatment by this invention meets the product index requirements of AF-2 brand aluminum fluoride in the GB / T 4292-2017 national standard for aluminum fluoride; the product obtained after treatment by this invention can guarantee its quality and performance stability. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments.

[0024] In the following embodiments, all raw materials used are commercially available products or can be prepared using conventional methods in the art. The lithium extraction residue from overhaul slag used is a by-product of a lithium extraction plant in Yangquan, Shanxi Province. Its main elements are fluorine, aluminum, and sodium, and their proportions are shown in Table 1 below. The contents of other trace impurities are not listed.

[0025] Table 1 Example 1 A method for processing lithium extraction residue from overhaul slag, specifically including the following steps: 1) Select No. 1 slag as raw material. Mix 50g of No. 1 slag with 15% fluorosilicic acid solution at a solid-liquid ratio of 1:8. Place the reaction device in a microwave chemical reactor and heat it to 90℃ and stir for 2 hours. After the reaction is completed, cool it to room temperature. After solid-liquid separation and washing of the filter cake, a total of 39g of solid A and 405g of filtrate A are obtained.

[0026] 2) Solid A was prepared into a 12% slurry using pure water. With this slurry as a base, 89 mL of 8 mol / L ammonia water was added dropwise over 30 min while stirring at room temperature. The reaction was then stirred for 1 h. After the reaction was completed, the mixture was filtered to obtain 417.3 g of fluoride-containing solution B and 35.7 g of silicon-containing slag C. The slag C was washed with water and dried to obtain 25 g of dry weight.

[0027] 3) Using 100g of fluoride-containing solution B as a base, heat to 90℃, then add the remaining 317.3g of fluoride-containing liquid B and α dropwise. k 26.18 g of sodium aluminate solution with a concentration of 1 / 2 was added dropwise over 30 minutes. The slurry was then reacted at 90-100℃ for 2 hours. During the reaction, a negative pressure absorption device was activated, and circulating cryolite mother liquor or water was used to absorb the ammonia gas released from the reaction, forming ammonia water. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain cryolite ointment and cryolite mother liquor. The mother liquor was reused, and the ointment was washed and dried to obtain 37.48 g of high-quality cryolite, with a yield of 98.7%. Testing showed that the molecular weight ratio of the synthesized cryolite was 2.87, meeting the national standards for cryolite.

[0028] 4) Preheat liquid A from step 1) to 70°C, then add 47.8g of activated aluminum hydroxide particles in 3 portions, then raise the temperature to 90°C and react for 30 minutes. Separate the solid and liquid during the hot reaction to obtain 410g of aluminum fluoride liquid B' and 40g of silicon slag C'.

[0029] 5) Add 11.27g of aluminum fluoride trihydrate as seed crystals to the aluminum fluoride-containing liquid B' and crystallize at 95℃ for 6h. After crystallization, separate the solid and liquid to obtain aluminum fluoride trihydrate crystals and aluminum fluoride mother liquor. The aluminum fluoride trihydrate crystals can be calcined at high temperature to obtain 70g of high-quality anhydrous aluminum fluoride, whose indicators meet the national standards for aluminum fluoride. The aluminum fluoride mother liquor can be further processed to obtain other fluoride salt products.

[0030] Example 2 A method for processing lithium-extraction residue from overhaul slag / carbon slag, specifically including the following steps: 1) Select No. 2 slag as raw material. Mix 50g of No. 2 slag with 20% fluorosilicic acid solution at a solid-liquid ratio of 1:7. Place the reaction device in a microwave chemical reactor and heat it to 80℃ and stir for 3h. After the reaction is completed, cool it to room temperature. After solid-liquid separation and washing the filter cake, 37g of solid A and 360g of filtrate A are obtained.

[0031] 2) Solid A was prepared into a 12% slurry using pure water. Using this slurry as a base, 64.6 mL of 10 mol / L ammonia water was added dropwise over 30 minutes while stirring at room temperature. The reaction was then stirred for 1.5 hours. After the reaction was completed, the mixture was filtered to obtain 380.3 g of fluoride-containing solution B and 33.6 g of silicon-containing slag C. The slag C was washed with water and dried to obtain 23 g of dry weight.

[0032] 3) Using 100g of fluoride-containing solution B as a base, heat to 95℃, then add the remaining 280.3g of fluoride-containing liquid B and α dropwise. k 22.71 g of sodium aluminate solution with a concentration of 1.1 was added dropwise over 30 minutes. The slurry was then reacted at 90-100°C for 2 hours. During the reaction, a negative pressure absorption device was activated, and the circulating cryolite mother liquor from Example 1 was used to absorb the ammonia gas released during the reaction, forming ammonia water. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain cryolite ointment and cryolite mother liquor. The ointment was rinsed and dried to obtain 32.27 g of high-quality cryolite, with a yield of 98%. Testing showed that the molecular weight ratio of the synthesized cryolite was 2.92, meeting the national standards for cryolite.

[0033] 4) Preheat liquid A from step 1) to 60°C, then add 58.7g of activated aluminum hydroxide particles in 4 portions, then raise the temperature to 95°C and react for 45min. Separate the solid and liquid during the hot reaction to obtain 374g of aluminum fluoride liquid B' and 44.6g of silicon slag C'.

[0034] 5) Add 13g of aluminum fluoride trihydrate as seed crystals to the aluminum fluoride-containing liquid B' and crystallize at 95℃ for 5h. After crystallization, separate the solid and liquid to obtain aluminum fluoride trihydrate crystals and aluminum fluoride mother liquor. The aluminum fluoride trihydrate crystals can be calcined at high temperature to obtain 86g of high-quality anhydrous aluminum fluoride, whose indicators meet the national standards for aluminum fluoride. The aluminum fluoride mother liquor can be further processed to obtain other fluoride salt products.

[0035] Example 3 A method for processing lithium-extraction residue from overhaul slag / carbon slag, specifically including the following steps: 1) Select No. 3 slag as raw material. Mix 50g of No. 3 slag with 25% fluorosilicic acid solution at a solid-liquid ratio of 1:6. Place the reaction device in a microwave chemical reactor and heat it to 70℃ and stir for 4h. After the reaction is completed, cool it to room temperature. After solid-liquid separation and washing the filter cake, a total of 43g of solid A and a total of 305g of filtrate A are obtained.

[0036] 2) Solid A was prepared into a 12% slurry using pure water. Using this slurry as a base, 69 mL of 8 mol / L ammonia water was added dropwise over 30 minutes while stirring at room temperature. The reaction was then stirred for 1.5 hours. After the reaction was completed, the mixture was filtered to obtain 430.9 g of fluoride-containing solution B and 35 g of silicon-containing slag C. The slag C was washed with water and dried to obtain 24.3 g on a dry basis.

[0037] 3) Using 100g of fluoride-containing solution B as a base, heat to 95℃, then add the remaining 330.9g of fluoride-containing liquid B and α dropwise. k 22.71 g of a 0.8% sodium aluminate solution was added dropwise over 30 minutes. The slurry was then reacted at 90-100°C for 1.5 hours. During the reaction, a negative pressure absorption device was activated, and the circulating cryolite mother liquor from Example 1 or 2 was used to absorb the ammonia gas released during the reaction, forming ammonia water. After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain cryolite ointment and cryolite mother liquor. The ointment was rinsed and dried to obtain 35 g of high-quality cryolite, with a yield of 98%. Testing showed that the synthesized cryolite had a molecular weight ratio of 2.83, which meets the national standards for cryolite.

[0038] 4) Preheat liquid A from step 1) to 65°C, then add 41.5g of activated aluminum hydroxide particles in 4 portions, then raise the temperature to 100°C and react for 30min. Separate the solid and liquid during the hot reaction to obtain 308g of aluminum fluoride liquid B' and 38.4g of silicon slag C'.

[0039] 5) Add 9g of aluminum fluoride trihydrate as seed crystals to the aluminum fluoride-containing liquid B' and crystallize at 100℃ for 4h. After crystallization, separate the solid and liquid to obtain aluminum fluoride trihydrate crystals and aluminum fluoride mother liquor. The aluminum fluoride trihydrate crystals can be calcined at high temperature to obtain 61.3g of high-quality anhydrous aluminum fluoride, whose indicators meet the national standards for aluminum fluoride. The aluminum fluoride mother liquor can be further processed to obtain other fluoride salt products.

[0040] II. Experimental Examples This experimental example illustrates the quality test results of cryolite and aluminum fluoride prepared in each embodiment. The various tests of cryolite were carried out in accordance with the provisions of "GB / T4291-2017 Cryolite", and the various tests of aluminum fluoride were carried out in accordance with the provisions of "GB / T4292-2017 Aluminum Fluoride", as shown in Tables 2 and 3.

[0041] Table 2. Quality test results of cryolite products obtained in Examples 1-3 As can be seen from the results in Table 1, the cryolite products prepared in Examples 1-3 of this application are of high quality, with a molecular ratio of more than 2.8, which can meet the needs of cryolite manufacturers with high molecular ratios in the market.

[0042] Table 3. Quality test results of aluminum fluoride products obtained in Examples 1-3 As can be seen from the results in Table 2, the aluminum fluoride products prepared in Examples 1-3 of this application are of high quality, have high bulk density, and good flowability, which can meet the needs of electrolytic aluminum manufacturers in the market.

[0043] In summary, this invention not only enables the utilization of waste materials from lithium extraction from overhaul slag but also generates significant economic benefits for these enterprises. Calculations show that processing each ton of lithium-extracted overhaul slag using this technology yields 0.65 tons of high-molecular-weight cryolite and 1.5 tons of aluminum fluoride. The reagent cost is approximately 3,000 yuan / ton, and the revenue from cryolite and aluminum fluoride produced after processing is approximately 15,000 yuan / ton. Based on an annual processing capacity of 40,000 tons of lithium-extracted overhaul slag, the annual revenue could reach 600 million yuan, demonstrating substantial economic benefits.

[0044] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for high-value processing of lithium-extraction residue from overhaul slag, characterized in that, Includes the following steps: S1. After lithium extraction from the overhaul slag, the slag material is mixed with fluorosilicic acid and reacted, and solid-liquid separation is performed to obtain solid A and liquid A; S2. Mix the solid A obtained in step S1 with an ammonia solution, react at room temperature, and separate the solid and liquid to obtain a fluorine-containing liquid B and a silicon-containing slag material C. S3. Mix and react the fluorine-containing liquid B with sodium aluminate solution, separate the solid and liquid, rinse the filter cake with water and dry to obtain cryolite product; S4. After preheating the liquid A obtained in step S1, add aluminum hydroxide in batches. After heating and reacting, separate the solid and liquid to obtain aluminum fluoride liquid B' and silicon slag material C'. S5. Add seed crystals to liquid B' containing aluminum fluoride to crystallize, then separate the solid and liquid to obtain aluminum fluoride trihydrate crystals and aluminum fluoride mother liquor. The aluminum fluoride trihydrate crystals are calcined to obtain high-quality anhydrous aluminum fluoride, and the aluminum fluoride mother liquor is treated to obtain fluoride salt products.

2. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: In step S1, the mass ratio of slag to fluorosilicic acid is 1:6-8; the concentration of fluorosilicic acid is 15%-25%, and the SO4 content in the fluorosilicic acid is... 2- Concentration ≤0.030%, PO3 3- Concentration ≤ 0.0020%; reaction temperature 70-90℃, reaction time 2-4h.

3. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: In step S2, the concentration of ammonia water is 8-10 mol / L, and the molar ratio of sodium element to ammonia water in the slag is 1:2.1-2.

2. Before mixing solid A with ammonia water, it is necessary to add water to rinse until the pH value of the rinsing water is 4-5, and then add water to prepare a slurry.

4. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: In step S3, the molar ratio of fluorine-containing solution B to sodium aluminate solution is F:Al = 6.0-6.6, and the reaction conditions are 90-100℃ for 2-4 hours.

5. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: Sodium aluminate α in step S3 k =0.8-1.

1.

6. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: The amount of aluminum hydroxide added in step S4 is determined by the aluminum content in the slag after lithium extraction from the overhaul slag in step S1. The molar ratio of aluminum to aluminum hydroxide in the slag is 1:3.0-3.

2. The preheating temperature is 60-70℃, and the reaction conditions are: reaction at 80-90℃ for 30 min-1 h.

7. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: In steps S2 and S4, the silica-containing slag materials C and C' are sold as by-products, or used as admixtures for asphalt or concrete, or as auxiliary materials for ceramics and tile products.

8. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 1, characterized in that: In step S5, the calcination of aluminum trihydrate is carried out by step heating. The temperature and time are controlled as follows: the room temperature is raised to 200°C, and the temperature is held at 200°C for 1 hour. Then the temperature is raised to 550°C. After holding at 550°C for 3 hours, the temperature is lowered to room temperature to obtain anhydrous aluminum fluoride product.

9. The method for high-value processing of lithium-extraction residue from overhaul slag as described in claim 8, characterized in that: The room temperature is 25±5℃.

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