Method for efficiently leaching lithium and aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2

Abstract

The invention discloses a method for efficiently leaching lithium and aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2, belongs to the technical field of solid waste resource recovery, and solves one of the problems of low aluminum and lithium leaching rate in an alkaline process, HF pollution and fluorine resource loss in an acid process, long process flow and high cost in the prior art. The method comprises the following steps that aluminum electrolysis solid waste blocks are crushed, ground and screened, and aluminum electrolysis solid waste powder A is obtained; uniformly mixing the aluminum electrolysis solid waste powder A with a reaction auxiliary material to obtain a material B; preparing an alkali solution, adding the material B into the alkali solution, uniformly stirring, and adding into an alkali-resistant reaction device for reaction; after the reaction is finished, materials are filtered, filter residues and filtrate are obtained respectively, and the filtrate can be used for recycling aluminum and lithium; and 4, carrying out acid pickling and impurity removal on the filter residues obtained in the step 4 by adopting a low-concentration inorganic acid solution, filtering, and drying a filter cake to obtain high-grade CaF2. The method is high in aluminum and lithium leaching rate and high in calcium fluoride purity.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource recovery, and in particular to a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. Background Art

[0002] Lithium has important applications in modern industry and technology, especially as an electrode material for high-energy-density batteries, and is increasingly used in portable electronic devices, electric vehicles, and grid energy storage systems. China is the world's largest lithium consumer, accounting for more than 70% of the global total in 2022. China is also the world's largest lithium battery producer, accounting for more than 80% of the global total. Although China has abundant lithium resources, the supply and demand situation remains tight. China's self-sufficiency rate of lithium resources is relatively low, and it relies heavily on imports, which to some extent limits the stable supply of lithium resources.

[0003] Fluorite is a scarce non-renewable resource with a wide range of applications. In addition to traditional fields such as steel, electrolytic aluminum, and cement, fluorite consumption in the fluorine chemical industry accounts for as much as 52%. Since 2018, global fluorite production has been on an upward trend. Among them, acid-grade fluorite concentrate and high-grade fluorite are in high demand and in short supply. In March 2022, the Ministry of Industry and Information Technology and six other departments jointly issued the "Guiding Opinions on Promoting the High-quality Development of the Petrochemical Industry during the 14th Five-Year Plan Period", encouraging the development and utilization of associated fluorine resources.

[0004] Lithium-containing alumina is used as a raw material in the production of electrolytic aluminum. Lithium accumulates continuously in the electrolyte, causing great changes in the electrolyte composition and physical and chemical properties. When the lithium content exceeds the standard, a part of the new electrolyte needs to be replaced, which will produce a certain amount of waste aluminum electrolyte containing more than 2% lithium. Waste aluminum electrolyte has a simple phase and high fluorine content, and is also an important secondary fluorine resource.

[0005] At present, the treatment process of waste aluminum electrolyte mainly includes alkaline / acid leaching, leaching after roasting, etc. CN112919507B provides a method for extracting lithium salts from electrolytes, using multiple alkaline leaching, acid leaching, and lithium carbonate precipitation to obtain high-grade cryolite and lithium carbonate; CN117430144A provides a green acid leaching method for resource utilization of waste aluminum electrolytes, by adding sodium salt to medium-concentration acid solution for leaching, to achieve lithium extraction and recovery; CN114890447B provides a method for directly preparing aluminum fluoride without roasting using aluminum electrolyte as raw material, by adding aluminum salt for high-energy ball milling, and washing and filtering to obtain aluminum fluoride. In the existing technical route, the treatment is mainly carried out through alkaline leaching, acid leaching (or acid leaching under the condition of adding aluminum salt and sodium salt), acid leaching after roasting, etc., but most of them are mainly for lithium extraction. The recovery of fluorine is prone to overflow of harmful and highly corrosive HF gas during the acid leaching process, which is an environmental pollution problem and also causes waste of fluorine resources; in the alkaline extraction process, due to the dissolution of cryolite and the slightly soluble nature of LiF, the aluminum-lithium leaching rate is generally not high, and cryolite phase and aluminum fluoride coexist in the leached residue, which is difficult to recycle. In addition, the existing processes are mostly long process flow and high cost. Summary of the invention

[0006] In view of the above situation, the present invention aims to provide a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2, which is used to solve one of the following technical problems: low aluminum-lithium leaching rate in the alkaline process, HF pollution and fluorine resource loss in the acid process, long process flow and high cost.

[0007] The purpose of the present invention is mainly achieved through the following technical solutions:

[0008] The present invention provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2, comprising the following steps:

[0009] Step 1, crushing, grinding and screening aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A;

[0010] Step 2: Evenly mix the aluminum electrolysis solid waste powder A and the reaction auxiliary materials to obtain material B;

[0011] Step 3, prepare an alkaline solution, add material B to the alkaline solution, stir evenly, and add it to an alkali-resistant reaction device for reaction;

[0012] Step 4: After the reaction is completed, the material is filtered to obtain filter residue and filtrate, respectively, and the filtrate can be used for aluminum and lithium recovery;

[0013] Step 5: Use a low-concentration inorganic acid solution to pickle the filter residue obtained in step 4 to remove impurities, filter it, and dry the filter cake to obtain high-grade CaF2.

[0014] Furthermore, in step 1, aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, and its main component is cryolite.

[0015] Furthermore, the aluminum electrolysis solid waste includes at least one of the solid wastes generated in the aluminum electrolysis process, such as waste aluminum electrolyte, aluminum electrolysis overhaul slag, and carbon powder.

[0016] Further, in step 2, the reaction auxiliary material is capable of providing Ca 2+ of calcium-containing substances.

[0017] Furthermore, in step 2, the reaction auxiliary material is at least one of CaO, CaCl2, CaF2, Ca(OH)2, Ca(NO3)2 and their hydrates.

[0018] Furthermore, in step 2, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder A is 0.7 to 0.9:1.

[0019] Furthermore, in step 3, the concentration of the alkaline solution is 20 to 160 g / L.

[0020] Furthermore, in step 3, the liquid-to-solid ratio of the alkaline solution to material B is in the range of (4-15 mL): 1 g.

[0021] Furthermore, in step 3, the reaction temperature of the reaction between material B and the alkaline solution is 120-200°C.

[0022] Furthermore, in step 3, the stirring speed is 200 to 500 rpm.

[0023] Furthermore, in step 5, the pH value of the solution during the pickling process is in the range of 3 to 6.

[0024] The present invention also provides a method for efficient and comprehensive recovery of aluminum electrolysis solid waste, which comprises steps 1 to 5 in the above method, and further comprises:

[0025] Step 5b, extracting the filtrate obtained in step 4 with an organic solvent extractant to obtain a loaded organic phase and a raffinate;

[0026] Step 6a, stripping the loaded organic phase obtained in step 5b to obtain a lithium-containing solution;

[0027] Step 6b, adding reaction auxiliary materials to the raffinate obtained in step 5b, stirring and reacting uniformly and standing for a period of time, filtering and separating to obtain calcium aluminate precipitate;

[0028] Step 7: Continue to add reaction auxiliary materials to the filtrate obtained in step 6b, stir evenly, let stand, and filter and separate.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0030] a) In the method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2 of the present invention, under the action of reaction auxiliary materials, the main cryolite phase in the aluminum electrolysis solid waste is rapidly decomposed in an alkaline solution, and the strong coordination precipitation effect between the calcium ions in the reaction auxiliary materials and the fluoride ions produced after the dissolution of cryolite is utilized to promote the rapid conversion of fluoride ions entering the solution through alkaline leaching into CaF2 and precipitate, thereby avoiding the coordination precipitation of fluoride ions with aluminum and lithium, thereby achieving efficient leaching of aluminum and lithium; compared with the existing alkaline leaching process technology, the present invention achieves aluminum leaching by adding auxiliary materials. While the electrolytic solid waste is dissolved in the alkaline solution, the fluoride ions generated after the dissolution directly react with the calcium ions to precipitate and remove, avoiding the loss of valuable components such as leached Li / Al due to the complex precipitation of fluoride ions; compared with the existing alkaline roasting or calcium-added alkaline roasting-leaching process, the method of the present invention realizes the reaction process of cryolite dissolution and CaF2 formation in aluminum electrolytic solid waste in one step, avoiding the problems of low lithium aluminum leaching rate caused by incomplete reaction or difficult dissolution of LiF formed during the roasting process and the wrapping of Li / Al components by CaF2 formed during the roasting process. The method of the present invention has a short process flow, low energy consumption, high aluminum-lithium leaching rate, and high calcium fluoride purity; the content of impurities such as fluorine / calcium in the solution is low, and the subsequent aluminum-lithium recovery process of the aluminum-lithium leaching solution is simple and easy to implement.

[0031] b) In the method for efficiently leaching lithium aluminum from aluminum electrolytic solid waste and preparing high-grade CaF2 of the present invention, by leaching in an alkaline system and calcification transformation of fluoride ions, compared with the acidic roasting / leaching system, the overflow loss and dispersion of fluorine in the form of HF gas are avoided, and the fluorine in the aluminum electrolytic solid waste is basically completely converted into calcium fluoride, with a high fluorine recovery rate; compared with the existing alkaline leaching and alkaline roasting-leaching process technologies, by regulating the alkaline leaching process, efficient dissolution of aluminum electrolytic solid waste can be achieved, and the regulation of the calcium fluoride precipitation process can make the output calcium fluoride slag have high grade and less impurities, and after acid washing and impurity removal, the grade can reach 98wt.%, which has higher value.

[0032] c) In the method for efficient comprehensive recovery of aluminum electrolysis solid waste of the present invention, the main process is carried out in an alkaline system, and the alkaline lithium-containing solution obtained is compatible with the lithium solution extraction system. Compared with leaching in an acidic system and extracting after the leachate is adjusted to alkaline, the method of the present invention does not require a large range of changes in the solution pH, and the extraction process is easy to implement and the lithium extraction recovery rate is high; the raffinate is added with reaction auxiliary materials again, which can achieve efficient removal and recovery of aluminum and preparation of high-purity calcium aluminate products through the coordination precipitation of calcium ions and aluminate ions, and is also beneficial to increase the alkalinity of the raffinate; the liquid after aluminum precipitation is treated by adding reaction auxiliary materials, which can realize the concentration of the alkali solution without evaporation, and obtain qualified alkali solution, with low energy consumption and easy operation, and the obtained Ca(OH)2 can be used as a reaction auxiliary material in step 2.

[0033] d) The method for efficient comprehensive recovery of aluminum electrolytic solid waste of the present invention has a short process flow and low energy consumption. Through the method of the present invention, various components such as fluorine, lithium, aluminum, sodium, etc. in aluminum electrolytic solid waste are recovered step by step and efficiently, and the comprehensive utilization rate is high.

[0034] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0036] Figure 1 This is the process flow chart of Example 1.

[0037] Figure 2 is the XRD diagram of the filter residue during the alkali leaching process in Example 1;

[0038] Figure 3 is the aluminum-lithium leaching rate in Example 1;

[0039] Figure 4 This is the XRD diagram of the filter residue in the alkaline leaching process in Comparative Example 2. DETAILED DESCRIPTION

[0040] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0041] The present invention provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2, comprising the following steps:

[0042] Step 1, crushing, grinding and screening aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A;

[0043] Step 2: Evenly mix the aluminum electrolysis solid waste powder A and the reaction auxiliary materials to obtain material B;

[0044] Step 3, prepare an alkaline solution, add material B to the alkaline solution, stir evenly, and add it to an alkali-resistant reaction device for reaction;

[0045] Step 4: After the reaction is completed, the material is filtered to obtain filter residue and filtrate, respectively, and the filtrate can be used for aluminum and lithium recovery;

[0046] Step 5: Use a low-concentration inorganic acid solution to pickle the filter residue obtained in step 4 to remove impurities, filter it, and dry the filter cake to obtain high-grade CaF2.

[0047] In a specific embodiment, in step 1, the aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, and its main component is cryolite.

[0048] Exemplarily, aluminum electrolysis solid waste includes at least one of the solid wastes generated in the aluminum electrolysis process, such as waste aluminum electrolyte, aluminum electrolysis overhaul slag, and carbon powder.

[0049] Exemplarily, the lithium content in the aluminum electrolysis solid waste is 0.5 to 7 wt.%.

[0050] In a specific embodiment, in step 1, it is considered that when the particle size of the aluminum electrolytic solid waste powder A is too large, the leaching process efficiency is low, which will cause problems such as low lithium aluminum leaching; when the particle size is too small, it is easy to cause agglomeration of materials in the leaching process; therefore, the aluminum electrolytic solid waste blocks are crushed, ground, and screened, and the powder particle size of the obtained aluminum electrolytic solid waste powder A is ≤74μm.

[0051] In a specific embodiment, in step 2, the reaction auxiliary material is capable of providing Ca 2+ Calcium-containing substances, for example, the reaction auxiliary material is at least one of CaO, CaCl2, CaF2, Ca(OH)2, Ca(NO3)2 and hydrates thereof. Exemplarily, the reaction auxiliary material is one of CaO, Ca(OH)2, CaCl2, CaF2, or CaO+Ca(OH)2, CaO+CaCl2, CaO+CaF2, or CaO+CaCl2+CaF2.

[0052] It should be noted that the main purpose of the added reaction auxiliary material is to provide Ca2+ to combine with fluoride ions during the alkaline leaching process. 2+ , so that the fluoride ions dissolved into the solution are quickly converted into calcium fluoride precipitates, reducing the fluoride ion concentration in the solution, and further promoting the alkaline leaching and dissolution of waste aluminum electrolyte. Calcium salts that can achieve this purpose are all within this protection range.

[0053] Compared with the prior art, the method of the present invention promotes the conversion of fluoride ions produced by the dissolution of aluminum electrolytic solid waste into CaF2 by adding reaction auxiliary materials. On the one hand, it further promotes the dissolution of aluminum electrolytic solid waste, and on the other hand, it can effectively avoid the formation of coordination precipitation between fluoride ions and dissolved aluminum, lithium, etc., which affects the aluminum and lithium leaching rate. The method of the present invention can effectively achieve efficient recovery of fluorine resources and avoid problems such as fluorine dispersion and insufficient purity of the formed precipitate.

[0054] In a specific embodiment, in step 2, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder A is 0.7 to 0.9:1, and illustratively, the mass ratio is 0.7:1, 0.8:1, or 0.9:1.

[0055] It should be noted that when the quality of the reaction auxiliary materials and the aluminum electrolysis solid waste powder is relatively low, the fluorine in the aluminum electrolysis solid waste cannot be completely converted into CaF2, which will reduce the lithium aluminum leaching rate and the fluorine recovery rate; when the quality is relatively high, the reaction auxiliary materials will not react completely and enter the calcium fluoride slag, affecting its grade; therefore, the mass ratio of the reaction auxiliary materials to the aluminum electrolysis solid waste powder A is controlled to be 0.7~0.9:1.

[0056] In a specific embodiment, in step 3, the alkaline solution is prepared using at least one of NaOH and KOH, preferably, NaOH is used, and the concentration of the alkaline solution is 20-160 g / L. Exemplarily, the concentration of the alkaline solution is 30 g / L, 40 g / L, 60 g / L, 80 g / L, 100 g / L, 120 g / L, and 140 g / L.

[0057] It should be noted that when the concentration of the alkaline solution is low, the aluminum electrolysis solid waste is not completely dissolved; when the concentration of the alkaline solution is high, it is easy to cause the added calcium salt to be difficult to enter the solution; both will cause a low lithium aluminum leaching rate; therefore, the concentration of the alkaline solution is controlled to be 20 to 160 g / L. Preferably, the concentration of the alkaline solution is 40 to 100 g / L.

[0058] In a specific embodiment, in step 3, the liquid-to-solid ratio of the alkaline solution to material B is in the range of (4-15 mL):1 g; illustratively, the liquid-to-solid ratio is 5 mL:1 g, 10 mL:1 g, 13 mL:1 g.

[0059] It should be noted that if the liquid-to-solid ratio is too large, the single processing capacity of the reaction vessel of the same volume will be reduced; if the liquid-to-solid ratio is too small, it will cause problems such as high density of the mixed slurry, slow solid-liquid reaction, and insufficient alkaline solution reactants; therefore, the liquid-to-solid ratio of the alkaline solution to material B is controlled in the range of (4-15mL):1g.

[0060] In a specific embodiment, in step 3, material B reacts with an alkaline solution, the reaction temperature is 120-200°C, the reaction time is 0.5-2 hours, and the stirring speed is 200-500rpm; illustratively, the reaction temperature is 130°C, 150°C, 170°C, 190°C; the reaction time is 0.6 hour, 1.0 hour, 1.5 hours, 1.8 hours; the stirring speed is 250rpm, 300rpm, 350rpm, 400rpm, 450rpm.

[0061] It should be noted that if the reaction temperature is lower than this range, the aluminum electrolytic solid waste is difficult to dissolve in the alkaline solution and the reaction kinetics are limited. If the temperature is too high, the energy consumption and pressure of the reaction vessel will be large. If the stirring speed is lower than this range, the solution will cause CaF2 precipitation to wrap the unreacted aluminum electrolytic solid waste, resulting in the leaching reaction being blocked. If the stirring speed is too high, a vortex will easily form, which will not play a stirring and mixing role. If the reaction time is lower than this range, the reaction will be incomplete, and if it is higher than this range, the reaction efficiency will be limited. Therefore, the reaction temperature is controlled to be 120-200°C, the reaction time is 0.5-2 hours, and the stirring speed is 200-500rpm.

[0062] In a specific embodiment, in step 5, the filter residue obtained in step 4 is pickled with an inorganic acid solution, and the inorganic acid solution is prepared by at least one of hydrochloric acid and nitric acid, preferably, hydrochloric acid is used; the pH range of the solution during the pickling process is 3 to 6, and illustratively, the solution pH is 3, 4, 4.5, 5, 5.5.

[0063] It should be noted that, considering the economic cost, the acid solution is preferably prepared with concentrated hydrochloric acid; the acid washing process mainly uses the acid solution to remove the auxiliary materials such as CaO / Ca(OH)2 in the filter residue that do not participate in the reaction. If the pH of the solution is too low, it may cause the dissolution loss of CaF2. If the pH of the solution is too high, it will cause incomplete removal of CaO / Ca(OH)2 and affect the purity of CaF2. Therefore, the pH range of the solution is controlled to be 3-6 during the acid washing process.

[0064] The present invention also provides a method for efficient and comprehensive recovery of aluminum electrolysis solid waste, which comprises steps 1 to 5 in the above method, and further comprises:

[0065] Step 5b, extracting the filtrate obtained in step 4 with an organic solvent extractant to obtain a loaded organic phase and a raffinate;

[0066] Step 6a, stripping the loaded organic phase obtained in step 5b to obtain a lithium-containing solution;

[0067] Step 6b, adding reaction auxiliary materials to the raffinate obtained in step 5b, stirring and reacting uniformly and standing for a period of time, filtering and separating to obtain calcium aluminate precipitate;

[0068] Step 7: Continue to add reaction auxiliary materials to the filtrate obtained in step 6b, stir evenly, let stand, and filter and separate.

[0069] In a specific embodiment, in step 5b, the organic solvent extractant is mainly a mixed solvent consisting of a phosphate organic reagent, a ketone organic reagent and sulfonated kerosene.

[0070] In a specific embodiment, in step 5b, the phosphate organic reagent includes at least one of tributyl phosphate, trioctyl phosphate, trialkyl phosphonate, trioctyl phosphine oxide, etc.; the ketone organic reagent includes at least one of β-diketone, trifluorodimethylhexanedione, etc., and the molar concentration ratio of the phosphate organic reagent to the ketone organic reagent is 0.5:0.1 to 0.1:0.5.

[0071] In a specific embodiment, in step 5b, the pH value of the filtrate in step 4 is controlled to be 12.5 < pH < 14, the volume ratio of the organic solvent extractant to the filtrate is 1:20 to 1:1, the oscillation time is 5 to 30 min, and the temperature is 10 to 40 °C. Exemplarily, the pH is 12.5, 13, 13.5, 14, the volume ratio of the organic solvent extractant to the filtrate is 1:15, 1:10, 1:5, 1:2, the oscillation time is 10 min, 15 min, 20 min, 25 min, and the temperature is 15 °C, 20 °C, 25 °C, 30 °C, 35 °C.

[0072] It should be noted that the ketone organic reagent has a selective chelating effect on lithium in the solution, and the neutral phosphorus organic reagent, as a strong electron donor, can enhance the selective stability of the extract. At the same time, the extraction process is also affected by the organic phase concentration, the solution pH value, the organic phase / water phase volume ratio O / A, the oscillation time, and the temperature. To ensure the complete extraction of lithium in the solution and avoid waste of organic reagents, the molar ratio of the phosphate ester to the ketone organic phase is controlled to be 0.5:0.1 to 0.1:0.5.

[0073] In a specific embodiment, in step 6a, the stripping reagent is one of inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, and carbonic acid, and the hydrogen ion concentration in the stripping reagent is controlled to be 1 to 6 mol / L.

[0074] In a specific embodiment, in step 6a, in the stripping process, the volume ratio of the loaded organic phase to the stripping reagent is 2:1 to 15:1, preferably 5:1 to 10:1.

[0075] It should be noted that considering the comprehensive utilization efficiency and cost of the acid used for stripping, as well as subsequent organic phase regeneration and other issues, hydrochloric acid is preferably used as the stripping reagent, and the hydrogen ion is controlled at 1 to 6 mol / L. Preferably, the hydrogen ion concentration of the hydrochloric acid solution is 4 mol / L. In addition, to ensure normal phase separation and operation during the stripping process, the volume ratio of the stripping organic phase to the aqueous phase is 2:1 to 15:1, preferably, the volume ratio of the stripping organic phase to the aqueous phase is 10:1.

[0076] In a specific embodiment, in step 6a, after the lithium-containing solution is concentrated and the lithium ion concentration reaches more than 20 g / L, sodium carbonate is added for lithium precipitation to obtain lithium carbonate.

[0077] In a specific embodiment, in step 6b, the reaction auxiliary material is at least one of CaO and Ca(OH)2, and preferably, Ca(OH)2 is used.

[0078] In a specific embodiment, in step 6b, the theoretical amount is the mass of the reaction auxiliary material calculated according to the aluminum concentration in the solution and the molecular formula of calcium aluminate precipitation.

[0079] In a specific embodiment, in step 6b, the added amount is 1 to 1.5 times the theoretical amount, and illustratively, the added amount is 1, 1.3, and 1.5 times; it should be noted that although the use of CaO can achieve the precipitation of the aluminum component in the raffinate, the addition of CaO will increase the alkalinity of the solution, which is not conducive to the reaction process. Therefore, Ca(OH)2 is preferably used as a reaction auxiliary material; the reaction temperature is 20 to 80°C, the stirring speed is 200 to 500 rpm, the reaction time is 0.5 to 2 hours, and the standing time is 0.5 to 1 hour. Schematically, the reaction temperature is 20°C, 40°C, 60°C, and 80°C; the reaction time is 1 hour and 1.5 hours; the stirring speed is 250rpm, 300rpm, 350rpm, 400rpm, and 450rpm.

[0080] In a specific embodiment, in step 6b, HCl and HNO3 solutions are used for pickling, and the pH value of the solution is 2 to 5; preferably, HCl solution is used; it should be noted that the acid solution is preferably prepared with concentrated hydrochloric acid in consideration of economic cost; the pickling process mainly uses an acid solution to remove the Ca(OH)2 auxiliary material that does not participate in the reaction in the filter residue. If the pH value of the solution is too low, it may cause the dissolution loss of calcium aluminate, and if the pH value of the solution is too high, it will cause incomplete removal of Ca(OH)2, affecting the purity of calcium aluminate; therefore, the pH value of the solution is controlled to be in the range of 2 to 5 during the pickling process.

[0081] In a specific embodiment, in step 7, the reaction auxiliary material is CaO.

[0082] Example 1

[0083] This embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in this embodiment is waste aluminum electrolyte. The process flow chart of this embodiment is as follows: Figure 1 As shown, the following steps are included:

[0084] The waste aluminum electrolyte block was crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and the reaction auxiliary material CaO was mixed with the waste aluminum electrolyte powder at a mass ratio of 0.8:1; 20g / L, 40g / L, 60g / L, 80g / L, 100g / L, and 160g / L NaOH solutions were prepared, and the mixed materials were stirred evenly with the NaOH solution at a liquid-solid ratio of 10mL:1g, and placed in an alkali-resistant reactor, and reacted at 180°C and 300rpm for 1.0 hour; after the reaction, the material was filtered to obtain filter residue and filtrate respectively; low-concentration hydrochloric acid was used to pickle the filter residue to remove impurities, the solution pH was maintained at 4.5, filtered, and the filter cake was dried to obtain high-grade calcium fluoride. The results of lithium aluminum leaching rate, final fluorine recovery rate and calcium fluoride content during the leaching process are shown in Table 1. Figure 2 is the XRD diagram of the filter residue during the alkali leaching process in Example 1, Figure 3 is the aluminum-lithium leaching rate in Example 1. It should be noted that the alkali concentration not only has a significant effect on the aluminum-lithium leaching rate, but also has a relatively significant effect on the fluorine recovery rate and the purity of calcium fluoride in the calcium fluoride product. As the alkali concentration increases, the aluminum-lithium leaching rate will first increase and then decrease, and the fluorine recovery rate and calcium fluoride content also have this trend; the reason is that the alkali concentration will affect the solubility of the reaction auxiliary materials in water, thereby affecting the dissolution of cryolite in the waste aluminum electrolyte, thereby having a corresponding impact on the above indicators.

[0085] In this embodiment, the aluminum and lithium leaching rates are relatively high, and the obtained calcium fluoride product has a relatively high purity. For example, the lithium leaching rate is above 74% (e.g., 74.3% to 95.2%), the aluminum leaching rate is above 76% (e.g., 76.4% to 96.2%), the fluorine recovery rate is above 78% (e.g., 78.3% to 98.4%), and the purity of the calcium fluoride product is above 85% (e.g., 85.4% to 98.8%). When the purity of calcium fluoride reaches above 80%, it has a relatively high economic value. When it reaches above 98%, it can be used as a raw material for the production of electronic-grade HF, and is a high-quality CaF2 product.

[0086] Table 1 Results of each process under different alkali concentration conditions

[0087] NaOH concentration / (g / L) Lithium leaching rate / % Aluminum leaching rate / % Fluorine recovery rate / % <![CDATA[CaF2 content / wt. %]]> 20 74.3 86.1 92.1 87.2 40 93.3 95.4 98.4 95.1 60 95.2 96.2 98.3 98.8 80 94.6 95.6 96.2 96.7 100 94.5 93.2 91.3 91.5 160 86.5 76.4 78.3 85.4

[0088] Example 2

[0089] This embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in this embodiment is waste aluminum electrolyte, comprising the following steps:

[0090] The waste aluminum electrolyte block is crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm. The reaction auxiliary materials CaO, Ca(OH)2, CaCl2, CaO+Ca(OH)2, CaO+CaCl2, CaO+CaF2, CaO+CaCl2+CaF2 and waste aluminum electrolyte powder are mixed evenly at a mass ratio of 0.8:1; 60g / L NaOH solution is prepared, and the mixed materials and NaOH solution are stirred evenly at a liquid-solid ratio of 10mL:1g, and put into an alkali-resistant reactor, and reacted at 200℃ and 500rpm for 2.0 hours; after the reaction, the material is filtered to obtain filter residue and filtrate respectively; low-concentration hydrochloric acid is used to pickle and remove impurities from the filter residue, the solution pH is maintained at 6.0, filtered, and the filter cake is dried to obtain high-grade calcium fluoride. The results of lithium aluminum leaching rate, final fluorine recovery rate and calcium fluoride content during the leaching process are shown in Table 2. It should be noted that different reaction auxiliary materials can provide Ca in the alkaline leaching system. 2+ , thereby promoting the leaching of aluminum and lithium, and achieving the effect of converting fluoride ions into CaF2. Therefore, various types of reaction auxiliary materials can achieve good reaction effects. In this embodiment, the aluminum and lithium leaching rate is high, and the purity of the obtained calcium fluoride product is high. For example, the purity of calcium fluoride reaches more than 97%, which is a high-quality CaF2 product.

[0091] In this embodiment, the lithium leaching rate is above 93% (e.g., 93.1% to 95.3%), the aluminum leaching rate is above 94% (e.g., 94.7% to 96.7%), the fluorine recovery rate is above 97% (e.g., 97.8% to 98.5%), and the purity of the calcium fluoride product is above 97% (e.g., 97.6% to 98.8%).

[0092] Table 2 Results of each process under different reaction auxiliary materials conditions

[0093] Reaction auxiliary type Lithium leaching rate / % Aluminum leaching rate / % Fluorine recovery rate / % <![CDATA[CaF2 content / wt.%]]> CaO 95.2 96.2 98.3 98.8 <![CDATA[Ca(OH)2]]> 94.2 96.0 98.1 98.5 <![CDATA[CaCl2]]> 93.1 94.7 99.2 97.8 <![CDATA[CaO+Ca(OH)2]]> 95.1 96.4 98.5 98.6 <![CDATA[CaO+CaCl2]]> 95.0 95.7 97.8 98.5 <![CDATA[CaO+CaF2]]> 95.3 96.7 98.4 97.9 <![CDATA[CaO+CaCl2+CaF2]]> 94.8 96.1 98.4 97.6

[0094] Example 3

[0095] This embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in this embodiment is waste aluminum electrolyte, comprising the following steps:

[0096] The waste aluminum electrolyte block was crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and the reaction auxiliary material CaO+Ca(OH)2+CaF2 was mixed with the waste aluminum electrolyte powder at a mass ratio of 0.7:1, 0.8:1, and 0.9:1; 60g / L KOH solution was prepared, and the mixed material and KOH solution were stirred at a liquid-solid ratio of 15mL:1g, and placed in an alkali-resistant reactor, and reacted at 180℃ and 200rpm for 0.5 hours; after the reaction, the material was filtered to obtain filter residue and filtrate respectively; low-concentration hydrochloric acid was used to pickle the filter residue to remove impurities, the solution pH was maintained at 3.0, filtered, and the filter cake was dried to obtain high-grade calcium fluoride. The results of lithium aluminum leaching rate, final fluorine recovery rate and calcium fluoride content during the leaching process are shown in Table 3. It should be noted that when the mass ratio is 0.7:1, the calcium ions that the reaction auxiliary materials can provide are slightly lower than the theoretical demand value, resulting in a slightly lower aluminum-lithium leaching rate, a slightly lower recovery rate due to the entry of some fluoride ions into the solution, and a slightly lower CaF2 content due to the undissolved cryolite during the alkali leaching process; when the amount of reaction auxiliary materials added reaches 0.8:1, the aluminum-lithium leaching rate is relatively high. In this embodiment, the aluminum-lithium leaching rate is relatively high, and the obtained calcium fluoride product has a relatively high purity, for example, 92.1% to 98.8%, which is a high-quality CaF2 product.

[0097] In this embodiment, the lithium leaching rate is above 89% (e.g., 89.3% to 96.2%), the aluminum leaching rate is above 91% (e.g., 91.4% to 97.9%), and the fluorine recovery rate is above 94% (e.g., 94.3% to 99.0%).

[0098] Table 3 Results of each process under different mass ratios of reaction auxiliary materials and waste aluminum electrolyte powder

[0099] Quality Ratio Lithium leaching rate / % Aluminum leaching rate / % Fluorine recovery rate / % <![CDATA[CaF2 content / wt.%]]> 0.7:1 89.3 91.4 94.3 92.1 0.8:1 95.7 95.9 98.6 98.6 0.9:1 96.9 90.4 98.5 98.2

[0100] Example 4

[0101] This embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in this embodiment is waste aluminum electrolyte, comprising the following steps:

[0102] The waste aluminum electrolyte blocks are crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and the reaction auxiliary materials CaO+Ca(OH)2 are mixed with the waste aluminum electrolyte powder at a mass ratio of 0.8:1; a mixed solution of 60g / L NaOH+KOH is prepared, and the mixed materials are stirred evenly with the alkaline solution at a liquid-solid ratio of 4mL:1g, and placed in an alkali-resistant reactor, and reacted at 180℃ and 300rpm for 1.0 hour; after the reaction, the materials are filtered to obtain filter residue and filtrate respectively; the filter residue is pickled and impurities are removed with low-concentration hydrochloric acid, the solution pH is maintained at 4.5, filtered, and the filter cake is dried to obtain high-grade calcium fluoride. The lithium aluminum leaching rates are 84.1% and 86.7% respectively, the fluorine recovery rate is 90.2%, and the CaF2 content is 84.6%. It should be noted that when the liquid-to-solid ratio is relatively low, the cryolite will not dissolve completely due to the small amount of alkali reactants, which will affect the aluminum-lithium leaching rate and fluorine recovery rate, and the calcium fluoride product content will reach more than 80%.

[0103] Example 5

[0104] This embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in this embodiment is waste aluminum electrolyte, comprising the following steps:

[0105] The waste aluminum electrolyte block was crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and the reaction auxiliary material CaO+Ca(OH)2+CaF2 was mixed with the waste aluminum electrolyte powder at a mass ratio of 0.8:1; 60g / L NaOH solution was prepared, and the mixed material was stirred evenly with the NaOH solution at a liquid-solid ratio of 10mL:1g, and placed in an alkali-resistant reactor, and reacted for 1.0 hour at 120℃, 150℃, 180℃, 200℃, and stirring at 200rpm; after the reaction, the material was filtered to obtain filter residue and filtrate respectively; low-concentration hydrochloric acid was used to pickle the filter residue to remove impurities, the solution pH was maintained at 4.5, filtered, and the filter cake was dried to obtain high-grade calcium fluoride. The results of lithium aluminum leaching rate, final fluorine recovery rate and calcium fluoride content during the leaching process are shown in Table 4. It should be noted that within the range of 120-200°C, the reaction temperature has little effect on the results of each process. When the temperature is higher than 150°C, efficient leaching of aluminum and lithium can be achieved and high-quality CaF2 can be produced.

[0106] In this embodiment, the lithium leaching rate is above 89% (e.g., 89.5% to 96.2%), the aluminum leaching rate is above 91% (e.g., 91.7% to 97.8%), the fluorine recovery rate is above 94% (e.g., 94.8% to 99.0%), and the purity of the calcium fluoride product is above 93% (e.g., 93.1% to 98.8%).

[0107] Table 4 Results of each process under different reaction temperature conditions

[0108]

[0109]

[0110] Example 6

[0111] The present embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2. The aluminum electrolysis solid waste in the present embodiment is aluminum electrolysis overhaul slag, and the method comprises the following steps: crushing, grinding and screening the aluminum electrolysis overhaul slag blocks to obtain overhaul slag powder with a particle size of ≤74μm, mixing reaction auxiliary materials CaO+Ca(OH)2+CaF2 and the overhaul slag powder at a mass ratio of 0.8:1; preparing 100g / L NaOH solution, stirring the evenly mixed materials and the NaOH solution at a liquid-solid ratio of 10mL:1g, putting them into an alkali-resistant reactor, and reacting them at 180°C and stirring at 200rpm for 1.0 hour; after the reaction is completed, filtering the materials to obtain filter residue and filtrate respectively; using low-concentration hydrochloric acid to pickle the filter residue and remove impurities, keeping the solution pH at 3.5, filtering, and drying the filter cake to obtain high-grade calcium fluoride. During the leaching process, the aluminum and lithium leaching rates were 93.8% and 95.1% respectively, the fluorine recovery rate was 98.4%, and the calcium fluoride grade reached 81.2%. It should be noted that the impurities other than cryolite and sodium fluoride in the overhaul slag during the leaching process do not affect the aluminum and lithium leaching rate. They enter the leaching slag during the leaching process. After pickling, the obtained calcium fluoride product has a high grade and can meet the requirements of the slag-making agent of the steel smelting enterprise for the CaF2 grade.

[0112] Example 7

[0113] The present embodiment provides a method for efficiently leaching lithium aluminum from aluminum electrolytic solid waste and preparing high-grade CaF2. The aluminum electrolytic solid waste in the present embodiment is carbon powder, comprising the following steps: crushing, grinding and screening the cathode carbon block to obtain carbon powder with a particle size of ≤74μm, mixing the reaction auxiliary material CaO+Ca(OH)2+CaF2 and the carbon powder at a mass ratio of 0.8:1; preparing 100g / L NaOH solution, stirring the mixed material with the NaOH solution at a liquid-solid ratio of 10mL:1g, putting it into an alkali-resistant reactor, and reacting it at 180°C and stirring at 200rpm for 1.0 hour; after the reaction is completed, filtering the material to obtain a filter residue and a filtrate respectively; using low-concentration hydrochloric acid to pickle the filter residue and remove impurities, keeping the solution pH at 3.5, filtering, and drying the filter cake to obtain high-grade calcium fluoride. During the leaching process, the aluminum and lithium leaching rates were 94.2% and 95.7% respectively, the fluorine recovery rate was 98.8%, and the calcium fluoride grade reached 82.5%. It should be noted that the impurity phases other than cryolite in the carbon powder during the leaching process do not affect the aluminum and lithium leaching rate, and enter the leaching slag during the leaching process. After pickling, the obtained calcium fluoride product has a high grade and can meet the requirements of the slag-making agent of the steel smelting enterprise for the CaF2 grade.

[0114] Example 8

[0115] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0116] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0117] Step 2, mixing the reaction auxiliary materials CaO+Ca(OH)2+CaF2 and the waste aluminum electrolyte powder in a mass ratio of 0.8:1;

[0118] Step 3, prepare 100g / L NaOH solution, stir the mixed material and NaOH solution at a liquid-solid ratio of 10mL:1g, put into an alkali-resistant reactor, and react at 150°C and 300rpm for 1.5 hours;

[0119] Step 4: After the reaction is completed, the material is filtered to obtain filter residue (leaching residue) and filtrate (leaching liquid);

[0120] Step 5a, using low concentration hydrochloric acid to pickle the filter residue to remove impurities, the solution pH is maintained at 4, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0121] During the leaching process of step 4, the aluminum and lithium leaching rates were 95.34% and 94.27% respectively, the fluorine recovery rate was 99.87%, and the calcium fluoride grade reached 98.31%;

[0122] Step 5b, the leachate (pH = 13.1) of step 4 and an organic solvent extractant (tributyl phosphate organic matter and β-diketone organic reagent, molar concentration ratio of 0.3:0.4, and a mixed reagent configured with sulfonated kerosene) are placed in a separatory funnel at a volume ratio of 40mL:4mL for mixing, and three-stage countercurrent extraction is performed, and then the obtained balanced load organic phase is mixed with 4mol / L hydrochloric acid stripping reagent at a volume ratio of O / A = 20mL:2mL, and two-stage countercurrent stripping is performed. The entire extraction-stripping process, the oscillation time is 10min, the temperature is 25°C, and the stripping solution finally obtained has a lithium concentration of 20.6g / L and a lithium recovery rate of 98.6%.

[0123] The raffinate was treated with Ca(OH)2 in an amount of 1, 1.3, and 1.5 times the theoretical amount, respectively. The reaction was carried out at 60°C and a stirring speed of 300 rpm for 1 hour. After standing for 1 hour, the aluminum was filtered and separated. The aluminum precipitation rates were 86.7%, 96.7%, and 97.9%, respectively.

[0124] The filter residue is pickled with a hydrochloric acid solution at a pH of 4, and the purity of the obtained calcium aluminate product reaches 98.6%; the filtrate is concentrated with alkali solution by adding CaO to obtain 30% alkali solution, and the overall sodium recovery rate reaches 98.5%.

[0125] Example 9

[0126] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0127] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0128] Step 2, mixing the reaction auxiliary materials CaO+Ca(OH)2+CaF2 and the waste aluminum electrolyte powder in a mass ratio of 0.8:1;

[0129] Step 3, prepare 100g / L NaOH solution, stir the mixed material and NaOH solution at a liquid-solid ratio of 10mL:1g, put into an alkali-resistant reactor, and react at 150°C and 300rpm for 1.5 hours;

[0130] Step 4: After the reaction is completed, the material is filtered to obtain filter residue (leaching residue) and filtrate (leaching liquid);

[0131] Step 5a, using low concentration hydrochloric acid to pickle the filter residue to remove impurities, the solution pH is maintained at 4, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0132] During the leaching process of step 4, the aluminum and lithium leaching rates were 95.34% and 94.27% respectively, the fluorine recovery rate was 99.87%, and the calcium fluoride grade reached 98.31%;

[0133] Step 5b, the leachate (pH = 13.6) of step 4 and an organic solvent extractant (a mixed reagent prepared with tributyl phosphate organic matter and β-diketone organic reagent, with a molar concentration ratio of 0.1:0.4 and sulfonated kerosene) are placed in a separatory funnel at a volume ratio of 40mL:2mL for mixing, and two-stage countercurrent stripping is performed. The entire extraction-stripping process is oscillated for 10min at a temperature of 25°C. The stripping solution finally obtained has a lithium concentration of 25.1g / L and a lithium recovery rate of 98.7%.

[0134] The raffinate was treated with Ca(OH)2 in an amount of 1.3 times the theoretical amount, respectively, and reacted at 20°C, 40°C, 60°C, and 80°C, with a stirring speed of 300 rpm for 1 hour. After standing for 1 hour, the mixture was filtered and separated, and the aluminum precipitation rates were 67.2%, 93.9%, 96.7%, and 96.9%, respectively;

[0135] The filter residue is pickled with a hydrochloric acid solution at a pH of 4, and the purity of the obtained calcium aluminate product reaches more than 96%; the filtrate is concentrated with alkali solution by adding CaO to obtain 30% alkali solution, and the overall recovery rate of sodium reaches more than 98%.

[0136] Comparative Example 1

[0137] This comparative example provides a method for leaching lithium aluminum from aluminum electrolysis solid waste and preparing CaF2, comprising the following steps:

[0138] The waste aluminum electrolyte block was crushed, ground, and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and 20g / L, 40g / L, 60g / L, 80g / L, and 100g / L NaOH solutions were prepared. The waste aluminum electrolyte powder was mixed evenly with the NaOH solution at a liquid-solid ratio of 10mL:1g without adding reaction auxiliary materials, and placed in an alkali-resistant reactor. The reaction was carried out at 180°C and stirred at 300rpm for 2.0 hours; after the reaction, the material was filtered to obtain filter residue and filtrate respectively; the filter residue was pickled and impurities were removed with low-concentration hydrochloric acid, the solution pH was maintained at 4.5, filtered, and the filter cake was dried to obtain the final filter residue. The results of lithium aluminum leaching rate and final fluorine recovery rate during the leaching process are shown in Table 5.

[0139] Table 5 Results of each process under different alkali concentration conditions without adding reaction auxiliary materials

[0140] NaOH concentration / (g / L) Lithium leaching rate / % Aluminum leaching rate / % Fluorine recovery rate / % 20 16.2 60.9 41.0 40 16.5 73.6 46.7 60 16.6 78.4 36.6 80 23.5 92.3 41.9 100 24.7 84.2 42.8 160 25.8 85.7 33.7

[0141] By comparing Example 1 and Comparative Example 1, it can be seen that, in the absence of reaction auxiliary materials, the aluminum and lithium leaching rates and fluorine recovery rates in the leaching process are low, especially the lithium leaching rate; since the cryolite in the waste aluminum electrolyte is not completely dissolved, the filter residue obtained in step 4 is mainly cryolite phase; since no reaction auxiliary materials are added in the leaching process, fluorine cannot be converted into calcium fluoride and enter the filter residue, the fluorine recovery rate is low, and no CaF2 product can be obtained.

[0142] Comparative Example 2

[0143] This comparative example provides a method for leaching lithium aluminum from aluminum electrolysis solid waste and preparing CaF2, comprising the following steps:

[0144] The waste aluminum electrolyte block is crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and the waste aluminum electrolyte powder is mixed with the reaction auxiliary material CaO at a mass ratio of 0.8:1; 200g / L NaOH solution is prepared, and the mixed material and the NaOH solution are stirred at a liquid-solid ratio of 10mL:1g, and put into an alkali-resistant reactor, and reacted at 180℃ and 300rpm for 1.0 hour; after the reaction, the material is filtered to obtain filter residue and filtrate respectively; low-concentration hydrochloric acid is used to pickle and remove impurities from the filter residue, and the solution pH is maintained at 4.5, filtered, and the filter cake is dried to obtain high-grade calcium fluoride. The results of lithium aluminum leaching rate, final fluorine recovery rate and calcium fluoride content during the leaching process are 73.3%, 35.3%, 56.8% and 60.7wt.%, respectively.

[0145] Figure 4 The XRD diagram of the filter residue during the alkali leaching process in Comparative Example 2 shows that when the alkali concentration is too high, in the strong alkali solution system, it is more difficult for the added CaO auxiliary material to convert into Ca(OH)2 to release Ca 2+ The filter residue of the alkaline leaching process obviously contains the characteristic diffraction peak of unreacted Ca(OH)2 substances, which affects the dissolution process of cryolite and the conversion process of fluorine, thereby affecting the aluminum-lithium leaching rate and the purity of CaF2 in the final product.

[0146] Comparative Example 3

[0147] This comparative example provides a method for leaching lithium aluminum from aluminum electrolysis solid waste and preparing CaF2, comprising the following steps:

[0148] The waste aluminum electrolyte block is crushed, ground, and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, which is uniformly mixed with CaO and sodium carbonate, with CaO accounting for 80% of the mass of the waste aluminum electrolyte powder and sodium carbonate accounting for 80% of the mass of the waste aluminum electrolyte powder. Water and a small amount of binder are added to form pellets, and the pellets are placed in a high-temperature furnace and heated at 1000℃ for 1 hour; after the reaction is completed, the pellets are taken out, cooled to room temperature, and crushed to obtain powder B; powder B is added to a 5% mass fraction NaOH solution, and stirred and leached for 1 hour under a liquid-solid ratio of 5:1. After filtration, a filter residue and a leachate containing aluminum and lithium are obtained. The CaF2 content in the obtained filter residue is 67%, and the lithium and aluminum leaching rates during the leaching process are 72% and 69%, respectively. The obtained CaF2 slag contains a large amount of unreacted waste aluminum electrolyte (cryolite) components. The reason is that during the roasting process, the decomposition of cryolite in the waste aluminum electrolyte and the reaction with CaO are affected by the reaction product CaF2. The incomplete decomposition of cryolite will inevitably lead to problems such as low aluminum-lithium leaching rate and low CaF2 content in the filter residue.

[0149] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for efficiently leaching lithium aluminum from aluminum electrolysis solid waste and preparing high-grade CaF2, characterized in that: The method comprises the following steps: Step 1, crushing, grinding and screening aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A; Step 2: Evenly mix the aluminum electrolysis solid waste powder A and the reaction auxiliary materials to obtain material B; Step 3, prepare an alkaline solution, add material B to the alkaline solution, stir evenly, and add it to an alkali-resistant reaction device for reaction; Step 4: After the reaction is completed, the material is filtered to obtain filter residue and filtrate, respectively, and the filtrate can be used for aluminum and lithium recovery; Step 5: Use a low-concentration inorganic acid solution to pickle the filter residue obtained in step 4 to remove impurities, filter it, and dry the filter cake to obtain high-grade CaF2.

2. The method according to claim 1, characterized in that In step 1, the aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, and its main component is cryolite.

3. The method according to claim 1, characterized in that In step 2, the reaction auxiliary material is capable of providing Ca 2+ of calcium-containing substances.

4. The method according to claim 3, characterized in that In step 2, the reaction auxiliary material is at least one of CaO, CaCl2, CaF2, Ca(OH)2, Ca(NO3)2 and their hydrates.

5. The method according to claim 1, characterized in that In the step 2, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder A is 0.7 to 0.9:

1.

6. The method according to claim 1, characterized in that In step 3, the concentration of the alkaline solution is 20 to 160 g / L.

7. The method according to claim 1, characterized in that In the step 3, the liquid-to-solid ratio of the alkaline solution to the material B is in the range of (4-15 mL): 1 g.

8. The method according to claim 1, characterized in that In step 3, the reaction temperature of the material B and the alkaline solution is 120-200°C.

9. The method according to any one of claims 1 to 8, characterized in that: In step 5, the pH value of the solution during the pickling process is in the range of 3 to 6.

10. A method for efficient and comprehensive recovery of aluminum electrolysis solid waste, characterized in that: The method comprises steps 1 to 5 of the method according to any one of claims 1 to 9, and further comprises: Step 5b, extracting the filtrate obtained in step 4 with an organic solvent extractant to obtain a loaded organic phase and a raffinate; Step 6a, stripping the loaded organic phase obtained in step 5b to obtain a lithium-containing solution; Step 6b, adding reaction auxiliary materials to the raffinate obtained in step 5b, stirring and reacting uniformly and standing for a period of time, filtering and separating to obtain calcium aluminate precipitate; Step 7: Continue to add reaction auxiliary materials to the filtrate obtained in step 6b, stir evenly, let stand, and filter and separate.

Images