Waste aluminum electrolyte resource utilization method

Abstract

The invention relates to the technical field of aluminum electrolyte recovery, in particular to a waste aluminum electrolyte resource utilization method. The waste aluminum electrolyte resource utilization method comprises the following steps that waste aluminum electrolyte and a reactant are subjected to a reaction in a closed container, a product obtained after the reaction is completed is washed in water, then first solid-liquid separation is carried out to obtain a solid, aluminum fluoride is obtained after drying, and aluminum fluoride is obtained after second solid-liquid separation is carried out. The reactant is selected from one or two of anhydrous aluminum chloride and polyaluminum chloride, and the reaction temperature is not lower than 200 DEG C. By utilizing the physical characteristic that the melting point of the reactant is higher than the boiling point, the reactant forms a solid phase-liquid phase-gas phase three-phase coexistence system in a closed space at the temperature higher than the melting point and the boiling point, so that the reactant can more efficiently perform molecular collision and mutual diffusion at an interface, thereby accelerating the reaction rate and improving the conversion rate.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum electrolyte recovery, and in particular to a method for resource utilization of waste aluminum electrolyte. Background Art

[0002] Aluminum electrolysis is an important basic raw material industry in my country. my country's primary aluminum production has ranked first in the world for many consecutive years. In 2023, my country's electrolytic aluminum production was 41.5344 million tons, accounting for about 60% of the global electrolytic aluminum production. In the process of electrolytic aluminum production, a large amount of solid / hazardous wastes such as electrolyte blocks and carbon slag are inevitably produced. Among them, the main component of the waste electrolyte is sodium cryolite, and it also contains additives such as alumina, potassium fluoride, calcium fluoride, and lithium fluoride. In addition to the main electrolyte components, the carbon slag also contains carbonaceous materials. The two can be separated by flotation and other methods to obtain electrolyte powder. At present, my country produces about 800,000 to 1.2 million tons of waste electrolyte and 350,000 tons of carbon slag each year. These solid and hazardous wastes contain soluble fluoride salts that exceed national standards. If they are not handled properly, they will pose a threat to soil and groundwater; at the same time, aluminum electrolytes are rich in fluorine and aluminum elements, and the electrolytes of some enterprises are rich in lithium elements. If they are not used, it will cause a waste of resources. Therefore, developing resource utilization technology for aluminum electrolytes can not only eliminate environmental risks, but also realize the resource recovery of valuable elements. It has significant economic and social benefits and is of great significance.

[0003] At present, the resource utilization method of waste aluminum electrolyte mainly uses inorganic acid or aluminum salt solution as a leaching agent to treat the electrolyte, converts the fluorine, aluminum and other elements in the electrolyte into soluble fluorine-aluminum complex ions and transfers them into the liquid phase, and then adjusts the solution composition, pH value, temperature and other parameters to induce the precipitation of fluorine-aluminum complex ions in the form of basic aluminum fluoride or hydroxyaluminum fluoride. However, the basic aluminum fluoride or hydroxyaluminum fluoride obtained in the above manner cannot be directly reused in the aluminum electrolytic cell, and further fluorination and roasting treatment is required to obtain aluminum fluoride. The process flow is complicated and the processing cost is high.

[0004] The Chinese patent application with application publication number CN114853042A, which was applied for and published on August 5, 2022, discloses a method for preparing aluminum fluoride using waste aluminum electrolyte, wherein an additive (aluminum nitrate or its crystalline hydrate) is evenly mixed with the screened waste aluminum electrolyte in a ratio of 0.5 to 5:1, and a low-temperature heat treatment is performed at 50 to 135°C to obtain a heat-treated product, which is dissolved in water, and the filter residue obtained by filtration is dried to obtain aluminum fluoride. The heat treatment is performed at a temperature below the boiling point of aluminum nitrate, and the molten aluminum nitrate penetrates into the aluminum electrolyte powder to fully contact and transfer mass with the components therein, forming a solid-liquid reaction system. The obtained product aluminum fluoride can be directly reused and added to the electrolytic cell, effectively realizing the recycling of resources, and the operation is simple, the energy consumption is low, no harmful gases are generated throughout the process, and the process steps are few and the cycle is short.

[0005] However, the above-mentioned aluminum fluoride preparation method still has the problems of slow reaction rate and low conversion rate of electrolyte into aluminum fluoride, which reduces the resource utilization rate of waste aluminum electrolyte and causes resource waste. Summary of the invention

[0006] The invention provides a method for resource utilization of waste aluminum electrolyte, which solves the problems of slow reaction rate and low aluminum fluoride conversion efficiency in the existing process of resource utilization of waste aluminum electrolyte.

[0007] In order to solve the above technical problems, the technical solution of the method for resource utilization of waste aluminum electrolyte of the present invention is: A method for resource utilization of waste aluminum electrolyte comprises the following steps: reacting the waste aluminum electrolyte and a reactant in a closed container, washing the product obtained after the reaction is completed in water, and then performing a first solid-liquid separation to obtain a solid, and obtaining aluminum fluoride after drying, wherein the reactant is selected from one or both of anhydrous aluminum chloride and polyaluminum chloride, and the reaction temperature is not less than 200°C.

[0008] The beneficial effect of the present invention is that: the present invention improves the existing technology and provides a method for resource utilization of waste aluminum electrolyte. The waste aluminum electrolyte and the reactant are reacted in a closed container. The reaction equation is: Na3AlF6+AlCl3=3NaCl+2AlF3. The fluorine and aluminum elements in the waste aluminum electrolyte are converted into aluminum fluoride products, which can be directly reused in aluminum electrolytic cells, thereby realizing the resource recycling of fluorine and aluminum resources.

[0009] The present invention utilizes the physical properties of the reactants anhydrous aluminum chloride and polyaluminum chloride, and the melting point is higher than the boiling point, so that under the temperature condition higher than the melting point and the boiling point, the reactants are first converted into gaseous state, and then the gas pressure is increased under the closed condition, and the reactants melt after reaching the saturated vapor pressure to obtain liquid reactants, and a three-phase coexistence system of solid phase (waste aluminum electrolyte), liquid phase (liquid reactant) and gas phase (gaseous reactant) is formed in the closed space, and the solid electrolyte and gaseous and liquid aluminum chloride can form a multiphase interface, which increases the surface contact area of ​​the reactants. This multiphase interface structure can make the reactants more efficiently collide and diffuse with each other at the interface, thereby accelerating the reaction rate and improving the conversion rate. At the same time, the dynamic gas-liquid mass transfer process in the reaction process can make the reactants quickly update on the solid phase surface, thereby avoiding the accumulation of reaction products on the surface of the solid phase reactants, and further improving the effective conversion rate of the reaction.

[0010] The method for resource utilization of waste aluminum electrolyte provided by the present invention has a short process flow and a high recovery rate of valuable elements. The prepared aluminum fluoride product has a high content of effective aluminum fluoride and can be directly reused in the aluminum electrolysis industry, thereby having good economic benefits.

[0011] In order to further improve the reaction efficiency, preferably, the reaction temperature is 200-600° C., and the reaction time is 0.5-5 h.

[0012] In order to further improve the utilization rate of raw materials, preferably, the theoretical addition amount of the reactant is calculated based on the content of fluorine and aluminum in the waste aluminum electrolyte and the additional aluminum required when the molar ratio of fluorine to aluminum in the reaction system reaches 3, and the actual addition amount of the reactant is 1 to 1.5 times the theoretical addition amount.

[0013] In order to further remove the residual Al element in the waste aluminum electrolyte and recover the organic salt, preferably, the filtrate obtained after the first solid-liquid separation is mixed with an alkaline compound and the system pH is adjusted to 5-8, and then a second solid-liquid separation is performed. The obtained filtrate is evaporated, concentrated and crystallized, subjected to a third solid-liquid separation, and dried to obtain an inorganic salt.

[0014] In order to further recover lithium elements in the waste aluminum electrolyte, preferably, when the waste aluminum electrolyte contains lithium elements, the concentrated liquid obtained after the third solid-liquid separation is reacted with a water-soluble carbonate to produce lithium carbonate precipitation.

[0015] In order to further improve the raw material utilization rate in the lithium recovery process, preferably, the amount of water-soluble carbonate added is calculated based on the molar ratio of lithium in the concentrate to carbonate ions in the water-soluble carbonate being 1:(0.5~2.5).

[0016] In order to further reduce the energy consumption when lithium carbonate precipitates are generated and reduce the waste of resources caused by volatilization, preferably, the temperature when the reaction produces lithium carbonate precipitates is 70-80° C. The solubility of lithium carbonate decreases with increasing temperature, and increasing the temperature can improve the recovery efficiency of lithium carbonate, but too high a temperature will increase energy consumption, increase volatility, and cause waste of resources.

[0017] In order to further increase the contact area between the waste aluminum electrolyte and the reactants, improve the reaction efficiency and the aluminum fluoride conversion rate, preferably, when the waste aluminum electrolyte includes electrolyte blocks taken out from the aluminum electrolytic cell, the electrolyte blocks are crushed, ground and sieved through a 100-mesh sieve before the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The XRD pattern of the anhydrous aluminum fluoride product obtained in Example 1 of the present invention; Figure 2 The XRD pattern of the lithium carbonate product obtained in Example 1 of the present invention; Figure 3 is a curve diagram of electrolyte conversion rate at different reaction times of Example 1 of the present invention; Figure 4 It is a curve chart of the electrolyte conversion rate of Comparative Example 1 at different reaction times. DETAILED DESCRIPTION

[0019] The technical concept of the method for resource utilization of waste aluminum electrolyte provided by the present invention is as follows: Since inorganic acid or aluminum salt solution is used as a leaching agent to treat the electrolyte, the obtained basic aluminum fluoride or hydroxyaluminum fluoride cannot be directly recycled into the aluminum electrolytic cell, and further fluorination and roasting treatment is required to obtain aluminum fluoride, which greatly increases the complexity and cost of the treatment process. Technicians have tried to use waste aluminum electrolyte to directly prepare aluminum fluoride products.

[0020] In terms of the technology for directly preparing aluminum fluoride from waste aluminum electrolytes, the Chinese patent application with application publication number CN114804171A, which was applied for and published on July 29, 2022, discloses a method for preparing aluminum fluoride and lithium carbonate using a lithium-aluminum electrolyte, wherein aluminum sulfate is used as an additive and mixed with the waste aluminum electrolyte, and the aluminum fluoride product is prepared by calcining at 500-700°C. Since the melting point of aluminum sulfate is as high as 770°C, aluminum sulfate and the electrolyte are subjected to a solid-phase reaction at high temperature to recover the valuable aluminum fluoride in the form of aluminum fluoride; however, the solid-phase reaction efficiency is low and the conversion rate is not high, resulting in low raw material utilization and a low content of effective aluminum fluoride in the product. In addition, the reaction of aluminum sulfate and cryolite will produce sub-cryolite, and high-purity aluminum fluoride cannot be directly prepared.

[0021] Technicians in this field use aluminum nitrate and aluminum chloride as additives for mixed heat treatment with waste aluminum electrolyte, but these additives will decompose quickly at high temperatures (200-500°C), resulting in raw material loss, failure to produce aluminum fluoride or extremely low aluminum fluoride yield.

[0022] At present, the existing technology uses aluminum nitrate as an additive and replaces high-temperature heat treatment with low-temperature heat treatment, and controls the temperature of low-temperature heat treatment (75~135℃) to be not lower than the melting point of aluminum nitrate (melting point 73℃, boiling point 135℃) and not higher than the boiling point of aluminum nitrate, so that it becomes a molten state at 75~135℃, forming a solid-liquid reaction system, improving the contact and mass transfer efficiency between the additive and the waste aluminum electrolyte, and greatly improving the recovery rate and purity of aluminum fluoride in the waste aluminum electrolyte. However, there are still problems of slow reaction rate and low conversion rate of electrolyte into aluminum fluoride.

[0023] The present invention utilizes the reactants anhydrous aluminum chloride and polyaluminum chloride, which have a moderate melting point (100-200°C) and good high-temperature stability, as an ideal aluminum electrolyte treatment agent, and utilizes their own physical property that the melting point is higher than the boiling point, so that under the temperature condition higher than the melting point and the boiling point, a solid-liquid-gas three-phase coexistence system is formed in a closed space, thereby accelerating the reaction rate and improving the conversion rate, and having the advantages of high efficiency and high purity.

[0024] When the aluminum electrolyte contains lithium, it forms a stable complex with fluorine-aluminum complex, and a strong chemical bond is formed between the ions, making the lithium ions in a relatively insoluble state. When the reactant described in the present invention is used to convert fluorine and aluminum into aluminum fluoride, the combination of fluorine ions and aluminum ions is converted into aluminum fluoride, thereby releasing lithium ions. This conversion process is equivalent to destroying the structural stability of the fluorine-aluminum complex, so that the lithium ions are liberated from the coordination structure and become free, soluble lithium ions. When the reactant is anhydrous aluminum chloride, the following reaction occurs: Na2LiAlF6+AlCl3=2AlF3+2Na + +Li + +3Cl - The method for resource utilization of electrolyte components in solid hazardous waste from aluminum electrolysis industry provided by the present invention realizes the comprehensive recovery and utilization of valuable elements such as fluorine, aluminum, and lithium in aluminum electrolyte. It is a thorough and efficient aluminum electrolyte treatment method with significant economic, social and environmental benefits.

[0025] The method for recycling waste aluminum electrolyte provided by the present invention comprises the following steps: (1) When the waste aluminum electrolyte includes electrolyte blocks taken out from an aluminum electrolytic cell, the electrolyte blocks are crushed, ground, and sieved through a 100-mesh sieve, and the waste aluminum electrolyte and reactants are mixed in proportion and pressed into blocks or loosely packed in a closed container, and reacted at 200-600°C for 0.5-5h, wherein the reactants are selected from one or more of anhydrous aluminum chloride and polyaluminum chloride, and the actual amount of the reactants added is 1-1.5 times the theoretical amount of the reactants added, which is calculated based on the contents of fluorine and aluminum in the waste aluminum electrolyte and the additional aluminum required when the molar ratio of fluorine to aluminum in the reaction system reaches 3.

[0026] (2) The product A after the reaction in step (1) is dissolved in water at room temperature, and then subjected to a first solid-liquid separation to obtain a filter cake B and a filtrate C. The filter cake B is dried to obtain an anhydrous aluminum fluoride product.

[0027] (3) adding an alkaline substance to the filtrate C obtained in step (2), adjusting the pH value to 5-8, performing a second solid-liquid separation, evaporating and concentrating the obtained filtrate, and crystallizing the filtrate. After a third solid-liquid separation, a filter cake D and a concentrated solution E are obtained. The filter cake D is dried to obtain a sodium chloride product.

[0028] (4) When the waste aluminum electrolyte contains lithium, a water-soluble carbonate is added to the concentrated solution E obtained in step (3), and the solution is reacted at 70-80° C. to precipitate, which is filtered and dried to obtain a lithium carbonate product, wherein the amount of the water-soluble carbonate added is calculated based on a molar ratio of the lithium element in the concentrated solution to the carbonate ion in the water-soluble carbonate of 1:(0.5-2.5).

[0029] In a specific embodiment, the interior of the sealed container before the reaction in step (1) is evacuated, or an inert gas or dry air is introduced, in order to prevent the hydrolysis of aluminum chloride.

[0030] In a specific embodiment, the alkaline substance in step (3) is an alkaline hydroxide or its solution, specifically sodium hydroxide and its solution. The alkaline substance can, on the one hand, remove the residual Al element by forming aluminum hydroxide precipitation, and on the other hand, adjust the pH of the system to prevent corrosion of the distillation equipment in the subsequent inorganic salt concentration and crystallization process.

[0031] In a specific embodiment, the water-soluble carbonate in step (4) is sodium carbonate or potassium carbonate.

[0032] In a specific embodiment, the volume ratio of the total raw materials formed by the electrolyte raw materials and the reactants to the closed container is ( ).

[0033] It can be understood that the waste aluminum electrolyte is one or a mixture of electrolyte powders separated from electrolyte blocks and / or carbon slag taken out of aluminum electrolysis cells through pre-treatment methods such as flotation.

[0034] The present invention is described in detail below in conjunction with specific examples. The raw materials used in the following examples are all conventional commercial products and are well known to those skilled in the art.

[0035] 1. Specific embodiments of the method for recycling waste aluminum electrolyte of the present invention Example 1 The method for recycling waste aluminum electrolyte in this embodiment is as follows: (1) 50 g of waste aluminum electrolyte was crushed, ground, and passed through a 100-mesh sieve, and mixed with 50 g of electrolyte powder obtained after carbon slag flotation as an electrolyte raw material. The lithium content in the raw material was 1.9%, and the molecular ratio (molar ratio of sodium fluoride to aluminum fluoride) was 2.5; the electrolyte raw material and 88.2 g of anhydrous aluminum chloride were mixed in proportion (the actual addition amount of anhydrous aluminum chloride was 1.5 times the theoretical addition amount, and the theoretical addition amount of anhydrous aluminum chloride was based on the content of fluorine and aluminum elements in the waste aluminum electrolyte, and the additional aluminum element required to be added when the molar ratio of fluorine and aluminum elements in the reaction system reached 3) and placed in a stainless steel reactor equipped with a corrosion-resistant lining, evacuated and sealed, and reacted at 200°C for 2 hours to obtain product A.

[0036] (2) The product A obtained in step (1) was taken out, crushed and ground into powder, added into 500 mL of water and stirred for 1 hour to wash the product A, and then filtered to obtain a filter cake B and a filtrate C. After drying the filter cake B, 38.2 g of anhydrous aluminum fluoride product was obtained with a purity of 98.15%. The conversion rate of the electrolyte to aluminum fluoride was 95% calculated by the following formula: Conversion rate ω = (c1m1-c2m2) / c1m1 Wherein: c1 is the mass fraction of F in the electrolyte (%), m1 is the mass of the electrolyte (g), c2 is the mass fraction of F in the product aluminum fluoride (%), and m2 is the mass of aluminum fluoride in the product (g).

[0037] The XRD spectrum of the obtained anhydrous aluminum fluoride product is as follows: Figure 1 As shown, the horizontal axis is the diffraction angle (2 theta (degree), 2θ (°)), and the vertical axis is the diffraction intensity (intensity). Figure 1 It can be seen that the product obtained in this example is a pure phase AlF3 product with a single physical phase.

[0038] (3) Add 1 mol / L sodium hydroxide solution to the filtrate C obtained in step (2) to adjust the pH value to 7. After filtering the solid precipitate, evaporate and concentrate the filtrate to crystallize, and then filter to obtain filter cake D and concentrated solution E. After drying the filter cake D, sodium chloride product is obtained.

[0039] (4) The total lithium content in the concentrated solution E was 1.7 g. According to the molar ratio n(Li + ):n(CO3 2- )=2:1, sodium carbonate solid is added to the concentrated solution E obtained in step (3), and the mixture is stirred at 70°C to produce a precipitate, which is filtered and dried to obtain 8.6 g of lithium carbonate product. The XRD spectrum of the lithium carbonate product is shown in Figure 2 As shown, from Figure 2 It can be seen that the lithium carbonate product obtained in this embodiment has a single phase and a high purity.

[0040] Example 2 The method for recycling waste aluminum electrolyte in this embodiment is as follows: (1) 100 g of electrolyte powder obtained after carbon slag flotation is used as an electrolyte raw material (the raw material does not contain lithium and the molecular ratio is 2.5); the electrolyte raw material and 127.8 g of polyaluminium chloride are mixed in proportion (the actual addition amount of polyaluminium chloride is 1.2 times of the theoretical addition amount, and the theoretical addition amount of polyaluminium chloride is based on the content of fluorine and aluminium in the waste aluminium electrolyte, and the additional aluminium element required to be added when the molar ratio of fluorine to aluminium in the reaction system reaches 3 is calculated), and the mixture is placed in a stainless steel reactor equipped with a corrosion-resistant lining, and dry air is introduced into the reactor and then sealed. The mixture is reacted at 300°C for 5 h to obtain product A.

[0041] (2) The product A obtained in step (1) was taken out, crushed and ground into powder, added into 1000 mL of water and stirred for 1 h to wash the product A, and then filtered to obtain a filter cake B and a filtrate C. After drying the filter cake B, 76.3 g of anhydrous aluminum fluoride product was obtained with a purity of 98.7% and an electrolyte conversion rate of 95.5%.

[0042] (3) Add 1 mol / L sodium hydroxide solution to the filtrate C obtained in step (2) to adjust the pH value to 8. After filtering the solid precipitate, evaporate and concentrate the filtrate to crystallize, and then filter to obtain filter cake D and concentrated solution E. After drying the filter cake D, sodium chloride product is obtained.

[0043] Example 3 The method for recycling waste aluminum electrolyte in this embodiment is as follows: (1) 50 g of waste aluminum electrolyte powder was used as an electrolyte raw material (the raw material did not contain lithium and the molecular ratio was 2.5); the electrolyte raw material and anhydrous aluminum chloride were mixed in proportion (the amount of anhydrous aluminum chloride added was 1.2 times the theoretical amount, and the theoretical amount of anhydrous aluminum chloride added was based on the content of fluorine and aluminum in the waste aluminum electrolyte, and the additional aluminum required to be added when the molar ratio of fluorine to aluminum in the reaction system reached 3 was calculated), and the mixture was placed in a stainless steel reactor equipped with a corrosion-resistant lining, and dry air was introduced into the reactor and then sealed. The mixture was reacted at 600°C for 2 h to obtain product A.

[0044] (2) The product A obtained in step (1) was taken out, crushed and ground into powder, added into 1000 mL of water and stirred for 1 h to wash the product A, and then filtered to obtain a filter cake B and a filtrate C. After drying the filter cake B, 39.4 g of anhydrous aluminum fluoride product was obtained with a purity of 98.9% and an electrolyte conversion rate of 95.7%.

[0045] (3) Add 1 mol / L sodium hydroxide solution to the filtrate C obtained in step (2) to adjust the pH value to 7. After filtering the solid precipitate, evaporate and concentrate the filtrate to crystallize, and then filter to obtain filter cake D and concentrated solution E. After drying the filter cake D, sodium chloride product is obtained.

[0046] 2. Comparison Comparative Example 1 The method for recycling waste aluminum electrolyte in this comparative example is basically the same as that in Example 1, except that: in step (1), the electrolyte raw material and aluminum nitrate (the actual amount of aluminum nitrate added is 1.5 times the theoretical amount of aluminum nitrate added, and the theoretical amount of aluminum nitrate added is based on the content of fluorine and aluminum in the waste aluminum electrolyte, and is calculated based on the additional aluminum element required when the molar ratio of fluorine to aluminum in the reaction system reaches 3) are mixed evenly, put into a stainless steel reactor equipped with a corrosion-resistant lining, and reacted at 115°C for 6 hours without sealing to obtain product A.

[0047] The curves of electrolyte conversion rates of Example 1 and Comparative Example 1 at different reaction times are shown as follows: Figure 3 and Figure 4 As shown, from Figure 3-4 It can be seen that the reaction speed of Example 1 is faster, and the reaction is basically completed within 2.5 hours of reaction time, and the electrolyte conversion rate reaches more than 95%, while the reaction of Comparative Example 1 is completed after 5 hours of reaction, and the electrolyte conversion rate is only about 85%. It can be explained that the use of the reactant of the present invention, at a higher reaction temperature, can achieve a faster electrolyte conversion rate and a faster reaction rate by synergizing the kinetic strengthening effect of the gas-liquid-solid three-phase reaction.

[0048] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling waste aluminum electrolyte, characterized in that: The method comprises the following steps: reacting waste aluminum electrolyte and reactant in a sealed container, washing the product obtained after the reaction is completed in water, and then performing a first solid-liquid separation to obtain a solid, and obtaining aluminum fluoride after drying, wherein the reactant is selected from one or both of anhydrous aluminum chloride and polyaluminum chloride, and the reaction temperature is not less than 200°C.

2. The method for recycling waste aluminum electrolyte according to claim 1, characterized in that: The reaction temperature is 200-600° C., and the reaction time is 0.5-5 h.

3. The method for recycling waste aluminum electrolyte according to claim 1, characterized in that: Based on the content of fluorine and aluminum in the waste aluminum electrolyte, the theoretical amount of reactant added is calculated based on the additional aluminum required when the molar ratio of fluorine to aluminum in the reaction system reaches 3. The actual amount of reactant added is 1 to 1.5 times the theoretical amount.

4. The method for recycling waste aluminum electrolyte according to claim 1, characterized in that: The filtrate obtained after the first solid-liquid separation is mixed with the alkaline compound and the system pH is adjusted to 5-8, and then the second solid-liquid separation is performed. The obtained filtrate is evaporated, concentrated, crystallized, subjected to the third solid-liquid separation, and dried to obtain an inorganic salt.

5. The method for recycling waste aluminum electrolyte according to claim 4, characterized in that: When the waste aluminum electrolyte contains lithium element, the concentrated liquid obtained after the third solid-liquid separation is reacted with a water-soluble carbonate to produce lithium carbonate precipitation.

6. The method for recycling waste aluminum electrolyte according to claim 5, characterized in that: The amount of water-soluble carbonate added is calculated based on a molar ratio of lithium element in the concentrate to carbonate ions in the water-soluble carbonate of 1:(0.5-2.5).

7. The method for recycling waste aluminum electrolyte according to claim 5, characterized in that: The temperature when the reaction produces lithium carbonate precipitation is 70~80℃.

8. The method for recycling waste aluminum electrolyte according to claim 1, characterized in that: When the waste aluminum electrolyte includes electrolyte blocks taken out from an aluminum electrolytic cell, the electrolyte blocks are crushed, ground, and passed through a 100-mesh sieve before the reaction.

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