Method for efficiently and comprehensively recycling aluminum electrolysis solid waste

Abstract

The invention discloses a method for efficiently and comprehensively recycling aluminum electrolysis solid waste, belongs to the technical field of solid waste resource recycling, and solves one of the following technical problems that in an alkaline process, the leaching rate of aluminum and lithium is low, high-value recycling of fluorine is difficult, and in an acid process, HF pollution is caused, and the technological process is long. The method comprises the following steps that aluminum electrolysis solid waste powder and reaction auxiliary materials are evenly mixed and then added into an alkaline solution to be leached; after the leaching reaction is finished, filtering the materials to respectively obtain filter residues and filtrate; carrying out acid dissolution purification on filter residues, filtering, and drying a filter cake to obtain high-grade CaF2; extracting the filtrate to obtain a loaded organic phase and raffinate; carrying out reverse extraction on the loaded organic phase to obtain a lithium-containing solution; and concentrating the raffinate to obtain an alkali liquor product. The method is high in recovery rate and high in product quality.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource recovery, and in particular to a method for efficient and comprehensive recovery of aluminum electrolysis solid waste. Background Art

[0002] The continuous development of the aluminum electrolysis industry has produced a large amount of waste aluminum electrolyte. In 2020, the global primary aluminum production reached 69.75 million tons. Based on the calculation that 15 to 25 kilograms of waste aluminum electrolyte is produced for every ton of primary aluminum produced by electrolysis, 1.5 million tons of waste aluminum electrolyte is produced each year. Since lithium is commonly associated with bauxite, lithium is enriched in alumina during the production of alumina, and circulates and accumulates in the electrolyte during the electrolysis process, resulting in about 2% lithium in the waste aluminum electrolyte. The waste aluminum electrolyte has a simple phase and contains multiple valuable components such as aluminum / fluorine / lithium, and has both hazardous waste and secondary resource attributes. The resource utilization of waste aluminum electrolyte can not only solve the environmental hazards caused by waste aluminum electrolyte, but also effectively utilize the valuable components therein.

[0003] At present, the treatment process of waste aluminum electrolyte mainly includes alkaline / acid leaching, leaching after roasting, etc. CN112919507B provides a method for disposing waste aluminum electrolyte, which uses 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 electrolyte, which realizes lithium extraction and recovery by adding sodium salt to medium-concentration acid solution. In the existing technical route, it is mainly treated by alkaline leaching, acid leaching (or acid leaching under the condition of adding aluminum salt and sodium salt), acid leaching after roasting, etc., and most of them are mainly for lithium extraction, focusing on the recovery of a single element, and it is difficult to take into account the recovery of multiple elements; and the existing processes mostly have the problems of long process flow and high cost. Summary of the invention

[0004] In view of the above situation, the present invention aims to provide a method for efficient and comprehensive recovery of aluminum electrolysis solid waste, which is used to solve one of the following technical problems: the existing processes mostly focus on the recovery of a single element and it is difficult to take into account the recovery of multiple elements. The aluminum and lithium leaching rate in the alkaline process is low, and fluorine is difficult to recover at a high value. The acid process causes HF pollution and fluorine resource loss, the process flow is long, and the energy consumption is high.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention provides a method for efficient and comprehensive recovery of aluminum electrolysis solid waste, comprising the following steps:

[0007] S1. Mixing aluminum electrolysis solid waste powder and reaction auxiliary materials uniformly and adding them into alkaline solution for leaching;

[0008] S2. After the leaching reaction is completed, the material is filtered to obtain filter residue and filtrate respectively;

[0009] S3a, acid-dissolve and purify the filter residue obtained in step 2, filter it, and dry the filter cake to obtain high-grade CaF2;

[0010] S3b, extracting the filtrate obtained in step 2 to obtain a loaded organic phase and a raffinate;

[0011] S4a, stripping the loaded organic phase to obtain a lithium-containing solution;

[0012] S4b, the raffinate is concentrated to obtain an alkaline solution product;

[0013] In S1, aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, the main component of which is cryolite, and the lithium content in the aluminum electrolysis solid waste is above 0.5wt%.

[0014] Furthermore, in S3a, the pH value of the solution during the acid dissolution purification process ranges from 0 to 3.

[0015] Furthermore, in S3b, the extractant is an organic solvent extractant, and the organic solvent extractant is a mixed solvent composed of a phosphate organic reagent, a ketone organic reagent and sulfonated kerosene.

[0016] Furthermore, in S3b, the phosphate organic reagent includes at least one of tributyl phosphate, trioctyl phosphate, trialkyl phosphonate and trioctyl phosphine oxide.

[0017] Furthermore, in S3b, the ketone organic reagent includes at least one of β-diketone and trifluorodimethylhexanedione.

[0018] Furthermore, in S3b, the molar concentration ratio of the phosphate organic reagent to the ketone organic reagent is 0.5:0.1 to 0.1:0.5.

[0019] Further, in S1, the reaction auxiliary material is capable of providing Ca 2+ of calcium-containing substances.

[0020] Furthermore, in S1, the lithium content in the aluminum electrolysis solid waste is less than 0.5wt%, S3b and S4a are omitted, and the filtrate obtained in S2 is directly concentrated to obtain the alkaline solution product.

[0021] Furthermore, in S1, the mass ratio of reaction auxiliary materials to aluminum electrolysis solid waste powder is 0.9 to 1.5:1.

[0022] Furthermore, in S1, the concentration of the alkaline solution is 20 to 80 g / L.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] a) In the method of the present invention, an alkaline solution is used to react with Ca provided by a reaction auxiliary material. 2+ Under the action of the alkali leaching agent, the chemical balance of the solution between elements such as calcium, aluminum, fluorine, and lithium is used to achieve the rapid decomposition of cryolite, the main component of aluminum electrolytic solid waste, and the aluminum, fluorine and calcium ions entering the solution through alkali leaching are quickly converted into CaF2 and mCaO·nAl2O3 (calcium aluminate), thereby achieving the separation of aluminum and fluorine components from sodium in cryolite and the efficient leaching of lithium. The obtained leachate is a relatively pure alkaline solution containing lithium, which is conducive to the subsequent recovery of lithium by solvent extraction. The raffinate can be concentrated to obtain a qualified alkaline solution product, thereby achieving the effective recovery of sodium components in aluminum electrolytic solid waste. Recycling; Compared with the existing alkaline leaching process technology, the present invention dissolves the aluminum electrolytic solid waste by adding auxiliary materials, and the fluoride ions / aluminate generated after the dissolution react with calcium ions to precipitate. The two processes occur simultaneously, effectively avoiding the loss of the leached Li component due to the complex precipitation of fluoride ions; Compared with the existing alkaline roasting or calcium-added alkaline roasting-leaching process, the present invention can avoid the low lithium aluminum conversion rate caused by incomplete reaction or difficult dissolution of the formed LiF during the roasting process and the encapsulation of the Li / Al components by the CaF2 formed during the roasting process. In addition, compared with the existing process that does not pay attention to the recovery of the sodium component in the waste aluminum electrolyte, the present invention can recover the sodium component in the waste aluminum electrolyte in the form of an alkaline solution product, taking into account the resource utilization of valuable components such as sodium, aluminum, fluorine, and lithium in the waste aluminum electrolyte;

[0025] b) In the method of the present invention, by leaching under an alkaline system and the calcification transformation of aluminum and fluorine, 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 converted into calcium fluoride, and the fluorine recovery rate is high; compared with the existing alkaline leaching and alkaline roasting-leaching process technology, by regulating the alkaline leaching process, the efficient dissolution of aluminum electrolytic solid waste can be achieved, and the regulation of the precipitation process of calcium aluminate and calcium fluoride can make aluminum and fluorine completely converted into precipitation. By utilizing the difference in stability of calcium aluminate and calcium fluoride in acid solution, hydrochloric acid or nitric acid can be used to achieve the selective dissolution of calcium aluminate in the precipitated slag, and the leachate can be used to further recover aluminum. The leached slag is high-grade calcium fluoride with few impurities, which has higher economic value. Through the method of the present invention, the aluminum, fluorine, sodium and a small amount of lithium contained in the aluminum electrolytic solid waste are comprehensively recovered in steps, with the advantages of high recovery rate, good separation effect and high product quality.

[0026] 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

[0027] 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.

[0028] Figure 1 This is the process flow chart of Example 1.

[0029] Figure 2 The XRD patterns of CaF2 obtained for the filter residue of step 4 and step 5 in Example 1;

[0030] Figure 3 It is the CaF2 product composition obtained in Example 3 under the condition of reaction auxiliary material mass ratio of 1.1:1. DETAILED DESCRIPTION

[0031] 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.

[0032] The present invention provides a method for efficient and comprehensive recovery of aluminum electrolysis solid waste, comprising the following steps:

[0033] S1. Mixing aluminum electrolysis solid waste powder and reaction auxiliary materials uniformly and adding them into alkaline solution for leaching;

[0034] S2. After the leaching reaction is completed, the material is filtered to obtain filter residue and filtrate respectively;

[0035] S3a, acid-dissolve and purify the filter residue obtained in step 2, filter it, and dry the filter cake to obtain high-grade CaF2;

[0036] S3b, extracting the filtrate obtained in step 2 to obtain a loaded organic phase and a raffinate;

[0037] S4a, stripping the loaded organic phase to obtain a lithium-containing solution;

[0038] S4b, the raffinate is concentrated to obtain an alkaline solution product.

[0039] Specifically, the above-mentioned method for efficient and comprehensive recycling of aluminum electrolysis solid waste comprises the following steps:

[0040] Step 1, crushing, grinding and screening aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A;

[0041] Step 2: Evenly mix the aluminum electrolysis solid waste powder A and the reaction auxiliary materials to obtain material B;

[0042] 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;

[0043] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0044] Step 5a, using an inorganic acid solution to acid-dissolve and purify the filter residue obtained in step 4, filtering, and drying the filter cake to obtain high-grade CaF2;

[0045] Step 5b, extracting the filtrate obtained in step 4 with an organic solvent extractant to obtain a loaded organic phase and a raffinate;

[0046] Step 6a, stripping the loaded organic phase obtained in step 5b to obtain a lithium-containing solution, which can be used to prepare industrial-grade lithium carbonate after concentration;

[0047] Step 6b: The raffinate is concentrated to obtain an alkali solution product of a certain concentration.

[0048] 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.

[0049] 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.

[0050] Exemplarily, the lithium content in the aluminum electrolysis solid waste is 0.0 to 7.0 wt %.

[0051] 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.

[0052] 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.

[0053] It should be noted that the main purpose of the added reaction auxiliary material is to provide Ca2+ to combine with aluminate and fluoride ions during the alkali leaching process. 2+ , so that the aluminate and fluoride ions dissolved into the solution are quickly converted into calcium aluminate and calcium fluoride precipitates, reducing the concentration of aluminate and fluoride ions in the solution, and further promoting the alkaline leaching and dissolution of aluminum electrolytic solid waste. Calcium salts that can achieve this purpose are within this protection range.

[0054] Compared with the prior art, the method of the present invention promotes the conversion of aluminate and fluoride ions produced by the dissolution of aluminum electrolytic solid waste into calcium salt precipitates by adding reaction auxiliary materials, which further promotes the dissolution of aluminum electrolytic solid waste on the one hand, and can effectively avoid the formation of coordination precipitates between fluoride ions and dissolved lithium, thereby affecting the lithium leaching rate; the method of the present invention can effectively achieve efficient recovery of fluorine resources, avoid the dispersion of fluorine and the problem of insufficient purity of the formed precipitate product; and utilize the difference in stability of calcium aluminate and calcium fluoride in the precipitate to achieve separation of calcium aluminate and calcium fluoride through selective acid dissolution, thereby obtaining a high-grade CaF2 product.

[0055] In a specific embodiment, in step 2, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder A is 0.9 to 1.5:1, and illustratively, the mass ratio is 1:1, 1.1:1, 1.2:1, 1.3:1, and 1.4:1.

[0056] It should be noted that when the quality of the reaction auxiliary materials and the aluminum electrolysis solid waste powder is relatively low, the aluminum fluoride in the aluminum electrolysis solid waste cannot be completely converted into calcium salt precipitates, which will reduce the aluminum fluoride conversion rate and recovery rate in cryolite; when the quality is relatively high, the reaction auxiliary materials will not react completely and enter the precipitate slag, affecting the subsequent purification of calcium fluoride; therefore, the mass ratio of the reaction auxiliary materials to the aluminum electrolysis solid waste powder A is controlled to be 0.9~1.5:1.

[0057] In a specific embodiment, in step 3, the alkaline solution is prepared using NaOH, and the concentration of the alkaline solution is 20-80 g / L. Exemplarily, the concentration of the alkaline solution is 30 g / L, 40 g / L, 60 g / L, or 70 g / L.

[0058] 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 low fluorine aluminum conversion rate and low lithium leaching rate; therefore, the concentration of the alkaline solution is controlled to be 20-80g / L. Preferably, the concentration of the alkaline solution is 40-60g / L.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 calcium aluminate and CaF2 precipitation to wrap the unreacted aluminum electrolytic solid waste, causing the leaching reaction to be blocked. If the stirring speed is too high, a vortex is easily formed, which cannot achieve the stirring and mixing effect. If the reaction time is lower than this range, the reaction is incomplete, and if it is higher than this range, the reaction efficiency is 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.

[0063] In a specific embodiment, in step 5a, the filter residue obtained in step 4 is acid-dissolved 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; the pH range of the solution during the acid-dissolving purification process is 0 to 3, and illustratively, the pH of the solution is 0, 1, 2, 3;

[0064] It should be noted that, considering the economic cost, the acid solution is preferably prepared with concentrated hydrochloric acid; the acid dissolution process mainly uses the acid solution to remove the auxiliary materials such as CaO / Ca(OH)2 and calcium aluminate that do not participate in the reaction in the filter residue. 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, calcium aluminate, etc., affecting the purity of CaF2. Therefore, the pH range of the solution is controlled to be 0 to 3 during the pickling process.

[0065] 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.

[0066] 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, trifluorodimethyl hexanedione, etc., and the molar concentration ratio of the phosphate organic reagent and the ketone organic reagent is 0.5:0.1 to 0.1:0.5. For example, tributyl phosphate: β-diketone = 0.3:0.4, tributyl phosphate: β-diketone = 0.2:0.4, trioctyl phosphine oxide: β-diketone = 0.1:0.3, tributyl phosphate: trifluorodimethyl hexanedione = 0.2:0.2.

[0067] In a specific embodiment, in step 5b, the pH value of the filtrate in step 4 is controlled to be 12.5-14, the volume ratio of the organic solvent extractant to the filtrate is 1:20-1:1, the oscillation time is 5-30 min, and the temperature is 10-40°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.

[0068] In a specific embodiment, in step 6a, the stripping reagent is one of inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, carbonic acid, etc., and the hydrogen ion concentration in the stripping reagent is 1 to 6 mol / L, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L.

[0069] In a specific embodiment, in step 6a, in the stripping step, the volume ratio of the loaded organic phase to the stripping reagent is 2:1 to 15:1, for example, 3:1, 5:1, 10:1, or 13:1.

[0070] It should be noted that in step 5b, the extraction system is a synergistic extraction system composed of phosphate and ketone, in which the ketone organic reagent has a key selectivity for lithium in the solution, and the neutral phosphate organic reagent as a strong electron donor can further improve the lithium coordination selectivity, and is easy to chelate with Li in water to form a stable hexavalent structure, resulting in the extraction order Li>Na>K; the ketone organic matter in the extraction organic phase as a hydrogen ion donor shows a certain dependence on the pH value of the solution. When the pH value of the solution is too low, the ketone organic matter has a certain dependence on H +The attraction ability is relatively large, and the extraction ability of Li is weak. If the alkalinity of the solution is too high, the structure of the organic phase is easily destroyed, resulting in emulsification. Therefore, the pH value of the filtrate in step 4 is controlled to be 12.5-14, preferably 13, 13.5. The selection of the molar ratio of the organic solvent extractant and the volume ratio of the filtrate is related to the lithium content of the filtrate. When the molar concentration of the organic solvent extractant is too high, it is easy to cause problems such as waste of the extractant and difficulty in extraction phase separation. When the lithium concentration of the solution is high, the molar concentration of the organic solvent extractant is too low, which is easy to cause unclean lithium extraction and waste of lithium resources. Therefore, the molar ratio of the phosphate ester to the ketone organic phase is controlled to be 0.5:0.1-0.1:0.5, and the volume ratio of the organic solvent extractant to the filtrate is 1:1-1:20. Preferably, the molar ratio of the phosphate ester to the ketone organic phase is 0.4:0.1-0.1:0.1, and the volume ratio of the organic solvent extractant to the filtrate is 1:10-1:20. Contact time and temperature are also important factors affecting the extraction efficiency. A shorter contact time means a faster mass transfer rate. If the contact time is too short, the reaction is not sufficient, resulting in a low lithium extraction rate. If the contact time is too long, the lithium extraction rate does not change significantly, the entrainment of impurities such as sodium and potassium increases, and the extraction efficiency decreases. Increasing the temperature is conducive to improving the ion migration rate, but it will destroy the structure of the extractant to a certain extent, which is not conducive to the extraction of lithium. Therefore, the oscillation time is 5 to 30 minutes, the temperature range is 10 to 40°C, and the preferred time is 10 to 20 minutes and the temperature is 20 to 30°C.

[0071] In step 6a, considering the economic cost of the acid used for the stripping reagent and the damage to the organic phase, it is preferred to use concentrated hydrochloric acid for preparation; if the acid concentration of the stripping reagent is too low, Li in the organic phase cannot be stripped down; if the acid concentration is too high, it will cause reagent waste and affect the subsequent organic phase regeneration cycle efficiency. Therefore, the hydrogen ion concentration in the stripping reagent is controlled to be 1-6 mol / L, preferably 2-4 mol / L; in addition, the amount of the stripping reagent must also take into account the lithium concentration and the stripping efficiency. If the A / O volume ratio is too large and the lithium concentration is too low, the burden of subsequent lithium carbonate product preparation will be increased. If the A / O volume ratio is too small, phase separation will be difficult, affecting manual and industrial equipment operations. Therefore, in the stripping, the volume ratio O / A of the loaded organic phase to the stripping reagent is 2:1-15:1, preferably O / A is 5:1-10:1.

[0072] In a specific embodiment, in step 6b, the raffinate can be concentrated by heating and evaporation, or by adding CaO and stirring evenly, standing for 1 to 3 hours, and filtering. The filtrate obtained is an alkaline solution with a certain concentration; the filter residue can be used as a reaction auxiliary material in step 2; considering the energy consumption cost, in a specific embodiment, CaO is preferably added to achieve the concentration of the alkaline solution.

[0073] In the method of the present invention, under the action of reaction auxiliary materials, the main cryolite phase in the aluminum electrolytic 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 cryolite produced after the dissolution is utilized to promote the rapid conversion of the aluminate and fluoride ions entering the solution through alkaline leaching into CaF2 and precipitate, thereby avoiding the coordination precipitation of fluoride ions and lithium, thereby achieving efficient leaching of lithium and efficient conversion of fluorine-aluminum components, and obtaining an alkaline solution with low impurity content that is easy to recover lithium through solvent extraction; compared with the existing alkaline leaching process technology, the present invention realizes the aluminum electrolytic solid waste in alkaline by adding auxiliary materials. While dissolving in the solution, aluminate and fluoride ions generated after the dissolution directly react with calcium ions to be precipitated and removed, which not only avoids the loss of leached Li valuable components due to complex precipitation of fluoride ions, but also can further promote the rapid dissolution of cryolite. Compared with the existing alkali roasting or calcium-added alkali roasting-leaching process, the method of the present invention realizes the reaction process of cryolite dissolution and calcium aluminate and CaF2 formation in aluminum electrolysis solid waste in one step, avoiding the problems of low lithium leaching rate and high impurity content in CaF2 caused by incomplete reaction or difficult dissolution of LiF formed during the roasting process and the encapsulation of Li components by CaF2 formed during the roasting process.

[0074] The method of the present invention has a short process flow, low energy consumption, high lithium leaching rate, high fluorine-aluminum conversion rate, low content of impurities such as fluorine / calcium in the solution, and a simple and easy-to-implement process for subsequent lithium recovery from the lithium-containing leaching solution. Valuable components such as sodium, aluminum, and fluorine in cryolite are all utilized as resources with high added value.

[0075] In the method of the present invention, through leaching in an alkaline system and calcification transformation of aluminate and fluoride ions, compared with an 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 electrolysis 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 technology, by regulating the alkaline leaching process, efficient dissolution of aluminum electrolysis solid waste can be achieved, and the regulation of the calcium fluoride precipitation process can make the output calcium fluoride slag high in grade and less in impurities, and the grade can reach 98wt% after acid dissolution purification, which has higher value.

[0076] Example 1

[0077] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0078] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0079] Step 2, mixing the reaction auxiliary material CaO and the waste aluminum electrolyte powder in a mass ratio of 1.1:1;

[0080] Step 3, prepare 20g / L, 40g / L, 60g / L, 80g / 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 180°C and 300rpm for 1.0 hour;

[0081] Step 4: After the reaction is completed, the material is filtered to obtain filter residue (also called leaching residue) and filtrate (also called leaching liquid);

[0082] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, keeping the pH of the solution at 0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0083] Step 5b, using a mixture of tributyl phosphate-containing organic matter: β-diketone organic reagent (molar concentration ratio of 0.3:0.4) and sulfonated kerosene as an organic solvent extractant, and performing three-stage countercurrent extraction with the organic solvent extractant and the filtrate obtained in step 4 at a volume ratio of 1:10;

[0084] Step 6a, using 4 mol / L HCl solution to perform two-stage stripping on the obtained balanced load organic phase, the stripping ratio O / A=5 / 1, the extraction-stripping process, the oscillation time is controlled at 10 min, the temperature is 25° C., the lithium extraction rate in the extraction process is 99.0%, and the lithium stripping rate in the stripping process is 99.5%. The raffinate is concentrated with CaO, and 30% alkali solution is obtained after filtration.

[0085] The results of the lithium leaching rate, the aluminum content in the filtrate during the leaching process of this embodiment, the fluorine recovery rate, the lithium recovery rate, the alkali recovery rate during the whole process, and the purity of the final product calcium fluoride are shown in Table 1. Figure 2 The XRD diagram of the filter residue and the final CaF2 in the alkaline leaching process in the embodiment. 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 obvious effect on the fluorine recovery rate and the purity of calcium fluoride in the final calcium fluoride product. As the alkali concentration increases, the lithium leaching rate gradually increases, and the fluorine recovery rate and calcium fluoride content also have this trend; the reason is that the alkali concentration affects the solubility of the reaction auxiliary materials in water, thereby affecting the dissolution of cryolite in the waste aluminum electrolyte, thereby having a corresponding effect on the above indicators. The aluminum content in the filtrate is relatively low, indicating that the calcium salt conversion of aluminum and fluorine can be achieved during the leaching process, thereby obtaining a relatively pure lithium-containing alkaline leachate, which is beneficial to the subsequent extraction and recovery of lithium and the recovery of alkali solution.

[0086] In this embodiment, the lithium leaching rate is 74% or more (e.g., 74.3% to 95.2%), the aluminum content in the filtrate is 33 to 37 ppm, the fluorine recovery rate is 92% or more (e.g., 92.1% to 98.4%), the CaF2 purity is 87% or more (e.g., 87.2% to 99%), the lithium recovery rate is 87% or more (e.g., 87.2% to 99%), and the alkali recovery rate is 95% or more (e.g., 95.3% to 96%).

[0087] Table 1 Results of each process under different alkali concentration conditions

[0088]

[0089] Example 2

[0090] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0091] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0092] Step 2, mixing the reaction auxiliary materials CaO, Ca(OH)2, CaCl2, CaO+Ca(OH)2, CaO+CaCl2, CaO+CaF2, CaO+CaCl2+CaF2 and the waste aluminum electrolyte powder in a mass ratio of 1.1:1;

[0093] Step 3, prepare 60g / 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 200°C and 500rpm for 2.0 hours;

[0094] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0095] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, maintaining the pH of the solution at 1.0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0096] Step 5b, the filtrate obtained in step 4 is subjected to three-stage countercurrent extraction using a mixture of trialkylphosphonate organic matter: β-diketone organic reagent (molar concentration ratio of 0.4:0.4) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate obtained in step 4 are in a volume ratio of 1:10;

[0097] Step 6a, using 4 mol / L HCl solution to perform two-stage stripping on the obtained balanced load organic phase, the stripping ratio O / A=5 / 1, the oscillation time of the entire extraction-stripping process is controlled at 10 min, the temperature is 25° C., the lithium extraction rate in the extraction process is 98.9%, and the lithium stripping rate in the stripping process is 99.2%. The raffinate is concentrated with CaO, and 30% alkali solution is obtained after filtration.

[0098] The results of the lithium leaching rate during the leaching process of this embodiment, the fluorine recovery rate, lithium recovery rate, alkali recovery rate during the whole process, and the purity of the final product calcium fluoride 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.

[0099] In this embodiment, the lithium leaching rate is more than 93% (e.g., 93.1% to 96%), the aluminum content in the filtrate is 33 to 37 ppm, the fluorine recovery rate is more than 97% (e.g., 97.8% to 99.2%), the CaF2 purity is more than 97% (e.g., 97.6% to 98.8%), the lithium recovery rate is more than 97% (e.g., 97.9% to 98.6%), and the alkali recovery rate is more than 95% (e.g., 95.3% to 96%).

[0100] Table 2 Results of each process under different reaction auxiliary materials conditions

[0101]

[0102] Example 3

[0103] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0104] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0105] Step 2, mixing the reaction auxiliary materials CaO + Ca (OH) 2 + CaF 2 and the waste aluminum electrolyte powder in a mass ratio of 0.9: 1, 1.1: 1, 1.3: 1, and 1.5: 1;

[0106] Step 3, prepare 60g / L NaOH solution, stir the mixed material and NaOH solution at a liquid-solid ratio of 15mL:1g, put into an alkali-resistant reactor, and react for 0.5 hours at 170°C and 200rpm;

[0107] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0108] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, maintaining the pH of the solution at 2.0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0109] Step 5b, the filtrate obtained in step 4 is subjected to three-stage countercurrent extraction using a mixture of trioctylphosphine oxide organic matter: β-diketone organic reagent (molar concentration ratio of 0.1:0.3) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate obtained in step 4 are in a volume ratio of 1:20;

[0110] Step 6a, using 4 mol / L HCl solution to perform two-stage stripping on the obtained balanced load organic phase, the stripping ratio O / A=10 / 1, the whole extraction-stripping process, the oscillation time is controlled at 10min, the temperature is 25°C, the lithium extraction rate in the extraction process is 98.8%, and the lithium stripping rate in the stripping process is 99.6%. The raffinate is concentrated with CaO, and 30% alkali solution is obtained after filtration.

[0111] The results of the lithium leaching rate, fluorine recovery rate, lithium recovery rate, alkali recovery rate, and purity of the final product calcium fluoride during the leaching process of this embodiment are shown in Table 3. It should be noted that when the mass ratio is 0.9:1, the calcium ions that can be provided by the reaction auxiliary materials are slightly lower than the theoretical demand value, resulting in a high aluminum content in the leachate and incomplete precipitation and conversion of aluminum calcium salts. When the mass ratio is increased to 1.1:1 or more, the precipitation and conversion effect of aluminum can be improved. And the lithium leachate also increases with the increase of the mass ratio.

[0112] In addition, by comparing Examples 1 to 3, it can be found that when the filter residue obtained in step 4 is acid-dissolved with an inorganic acid solution in step 5a, the pH of the solution increases, the dissolution effect of calcium aluminate and calcium hydroxide in the filter residue is weakened, and the purity of CaF2 is slightly reduced, but the purity of the obtained CaF2 still reaches more than 92%, which is a high-quality calcium fluoride product.

[0113] In this embodiment, the lithium leaching rate is more than 95% (e.g., 95.2% to 97.3%), the aluminum content in the filtrate is 18 to 1881 ppm, the fluorine recovery rate is more than 92% (e.g., 92.1% to 98.4%), the CaF2 purity is more than 92% (e.g., 92.7% to 93.8%), the lithium recovery rate is more than 87% (e.g., 87.2% to 98.8%), and the alkali recovery rate is more than 95% (e.g., 95.2% to 96%).

[0114] Table 3 Results of each process with different amounts of reaction auxiliary materials added

[0115]

[0116] Example 4

[0117] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0118] Step 1, crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm;

[0119] Step 2, mixing the reaction auxiliary materials CaO+Ca(OH)2+CaF2 and the waste aluminum electrolyte powder in a mass ratio of 1.3:1;

[0120] Step 3, prepare 60g / L NaOH solution, stir the mixed material and NaOH solution at a liquid-solid ratio of 15mL:1g, put it into an alkali-resistant reactor, and react for 0.5 hours at 130°C, 150°C, 170°C, and 190°C with stirring at 200rpm;

[0121] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0122] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, maintaining the pH of the solution at 1.0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0123] Step 5b, the filtrate obtained in step 4 is subjected to three-stage countercurrent extraction using a mixture of tributyl phosphate organic matter: trifluorodimethylhexanedione organic reagent (molar concentration ratio of 0.2:0.2) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate obtained in step 4 are in a volume ratio of 1:20;

[0124] Step 6a, using 2 mol / L HCl solution to perform two-stage stripping on the obtained balanced load organic phase, the stripping ratio O / A=5 / 1, the whole extraction-stripping process, the oscillation time is controlled at 10min, the temperature is 25°C, the lithium extraction rate in the extraction process is 98.2%, and the lithium stripping rate in the stripping process is 99.6%. The raffinate is concentrated with CaO, and 30% alkali solution is obtained after filtration.

[0125] The results of the lithium leaching rate during the leaching process of this embodiment, the fluorine recovery rate, lithium recovery rate, alkali recovery rate during the whole process, and the purity of the final product calcium fluoride are shown in Table 4.

[0126] 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 waste aluminum electrolyte can be achieved, and the calcification precipitation conversion effect of aluminum and fluorine is better, the recovery rate of each component is high, and high-quality CaF2 can be produced.

[0127] In this embodiment, the lithium leaching rate is 89% or more (e.g., 89.5% to 96.2%), the aluminum content in the filtrate is 22 to 26 ppm, the fluorine recovery rate is 94% or more (e.g., 94.8% to 99%), the CaF2 purity is 93% or more (e.g., 93.1% to 98.8%), the lithium recovery rate is 93% or more (e.g., 93.4% to 95.8%), and the alkali recovery rate is 95% or more (e.g., 95.1% to 96%).

[0128] Table 4 Results of each process under different reaction temperature conditions

[0129]

[0130] Example 5

[0131] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0132] Step 1: crushing, grinding and screening the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size of ≤74 μm, wherein the lithium content in the powder is 0.3% and the recovery value is relatively small;

[0133] Step 2, mixing the reaction auxiliary materials CaO+Ca(OH)2+CaF2 and the waste aluminum electrolyte powder in a mass ratio of 1.3:1;

[0134] Step 3, prepare 60g / L NaOH solution, stir the mixed material and NaOH solution at a liquid-solid ratio of 15mL:1g, put into an alkali-resistant reactor, and react at 170°C and 200rpm for 1 hour;

[0135] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0136] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, maintaining the pH of the solution at 1.0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0137] The filtrate obtained in step 4 is directly concentrated using CaO, and 30% alkali solution is obtained after filtration.

[0138] In the leaching process of this embodiment, the lithium leaching rate is 96.3%, the aluminum content in the leaching solution is 22.7 ppm, the fluorine recovery rate is 99.2%, the purity of the obtained CaF2 is 98.7%, and the alkali recovery rate is 94.7%.

[0139] It should be noted that when the lithium content in the waste aluminum electrolyte is lower than 0.5wt% and the recovery value is low, steps 5b and 6a in the present invention can be skipped, and the filtrate obtained in step 4 can be directly concentrated to obtain an alkaline solution product of a certain concentration; this has little impact on other technical indicators in the present invention.

[0140] Example 6

[0141] This embodiment provides a method for efficient and comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0142] Step 1, crushing, grinding and screening the aluminum electrolysis overhaul slag to obtain waste aluminum electrolyte powder with a particle size of ≤74μm;

[0143] Step 2, mixing the reaction auxiliary material CaO+CaF2 and the overhaul slag powder in a mass ratio of 1.1:1;

[0144] Step 3, prepare 60g / 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 200°C and 500rpm for 2.0 hours;

[0145] Step 4: After the reaction is completed, the material is filtered to obtain a filter residue and a filtrate;

[0146] Step 5a, using hydrochloric acid solution to acid-dissolve and purify the filter residue, maintaining the pH of the solution at 1.0, filtering, and drying the filter cake to obtain high-grade calcium fluoride;

[0147] Step 5b, the filtrate obtained in step 4 is subjected to three-stage countercurrent extraction using a mixture of trialkylphosphonate organic matter: β-diketone organic reagent (molar concentration ratio of 0.4:0.4) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate obtained in step 4 are in a volume ratio of 1:10;

[0148] Step 6a, using 4 mol / L HCl solution to perform two-stage stripping on the obtained balanced load organic phase, the stripping ratio O / A=5 / 1, the oscillation time of the entire extraction-stripping process is controlled at 10 min, the temperature is 25°C, the lithium extraction rate in the extraction process is 98.9%, and the lithium stripping rate in the stripping process is 99.2%. The raffinate is concentrated with CaO, and 30% alkali solution is obtained after filtration;

[0149] In this embodiment, the lithium leaching rate is 93%, the aluminum content in the filtrate is 26ppm, the fluorine recovery rate is 95%, the CaF2 purity is 81.5%, the lithium recovery rate is 93.5%, and the alkali recovery rate is 96.1%. It should be noted that the impurity phases other than cryolite in the overhaul slag during the leaching process do not affect the lithium leaching rate, enter the leaching slag during the leaching process, and after pickling, the calcium fluoride product obtained has a high grade, which can meet the requirements of the slag-making agent of the steel smelting enterprise for the CaF2 grade.

[0150] Comparative Example 1

[0151] This comparative example provides a method for comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0152] The waste aluminum electrolyte blocks were crushed, ground and sieved to obtain waste aluminum electrolyte powder with a particle size of ≤74μm, and 20g / L, 40g / L, 60g / L and 80g / L NaOH solutions were prepared. The waste aluminum electrolyte powder was evenly stirred with the NaOH solution at a liquid-solid ratio of 10mL:1g without adding reaction auxiliary materials, and put into an alkali-resistant reactor, and reacted for 2.0 hours at 180°C and 300rpm. After the reaction, the material was filtered to obtain filter residue and filtrate respectively. The filter residue was pickled and impurities were removed with hydrochloric acid solution, and the pH of the solution was maintained at 1.0, filtered, and the filter cake was dried. The filtrate was subjected to three-stage countercurrent extraction using a mixture of tributyl phosphate organic matter: β-diketone organic reagent (molar concentration ratio of 0.2:0.4) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate were in a volume ratio of 1:20; a 4 mol / L HCl solution was used to perform two-stage stripping on the obtained balanced load organic phase, the stripping phase ratio O / A=10 / 1, and the oscillation time of the entire extraction-stripping process was controlled at 10 minutes and the temperature was 25°C. The lithium extraction rate in the extraction process was 78.4%, and the lithium stripping rate in the stripping process was 79.3%. The raffinate was concentrated with CaO to obtain an alkali solution.

[0153] The results of lithium leaching rate during the leaching process, fluorine recovery rate, lithium recovery rate, alkali recovery rate during the whole process, and purity of the final product calcium fluoride are shown in Table 5.

[0154] Table 5 Results of each process under different alkali concentration conditions without adding reaction auxiliary materials

[0155]

[0156] By comparing Example 1 and Comparative Example 1, it can be seen that in the absence of reaction auxiliary materials, the lithium leaching rate during the leaching process is low, the aluminum content is high, and it cannot be converted into a precipitate for removal from the filtrate; since the cryolite in the waste aluminum electrolyte is not completely dissolved, the filter residue obtained in step 4 is mainly a cryolite phase. Since no reaction auxiliary materials are added during 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.

[0157] Comparative Example 2

[0158] This comparative example provides a method for comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0159] 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+CaF2 are mixed with the waste aluminum electrolyte powder at a mass ratio of 0.8:1; 60g / L NaOH solution is prepared, and the mixed materials are stirred with the NaOH solution at a liquid-solid ratio of 15mL:1g, and put into an alkali-resistant reactor, and react at 170°C and 200rpm for 0.5 hours; after the reaction is completed, the material is filtered to obtain a filter residue and a filtrate respectively; the filter residue is pickled and impurities are removed with a hydrochloric acid solution, and the pH of the solution is maintained at 1.0, filtered, and the filter cake is dried to obtain high-grade calcium fluoride. The filtrate is subjected to three-stage countercurrent extraction using a mixture of trialkylphosphonic acid organic matter: β-diketone organic reagent (molar concentration ratio of 0.4:0.4) and sulfonated kerosene as an organic solvent extractant, and the organic solvent extractant and the filtrate are in a volume ratio of 1:10; a 4mol / L HCl solution is used to perform two-stage stripping of the obtained balanced load organic phase, the stripping phase ratio O / A=5 / 1, and the oscillation time of the entire extraction-stripping process is controlled at 10min and the temperature is 25°C. The lithium extraction rate in the extraction process is 95.5%, and the lithium stripping rate in the stripping process is 95.1%. The raffinate is concentrated with CaO and filtered to obtain a 30% alkali solution. The lithium leaching rate in the leaching process is 95.4%, the aluminum content in the leaching solution is 1.2g / L, the fluorine recovery rate is 98.5%, the purity of the obtained CaF2 is 98.4%, and the alkali recovery rate is 94.2%.

[0160] By comparing Example 3 and Comparative Example 2, it can be seen that when the amount of reaction auxiliary material added is low, the lithium leaching rate in the leaching process is slightly low, and the aluminum concentration in the leachate is relatively high. Although the effects on indicators such as fluorine recovery rate, CaF2 purity, alkali recovery rate, lithium extraction rate and stripping rate are relatively small, the aluminum concentration in the leachate entering the extraction system is relatively high, which will have a certain impact on the extraction system, and the aluminum will eventually enter the raffinate, which will also have a certain impact on the process of adding CaO to concentrate the alkali solution, which will cause problems such as a high aluminum content in the alkali solution.

[0161] Comparative Example 3

[0162] This comparative example provides a method for comprehensive recycling of aluminum electrolysis solid waste, comprising the following steps:

[0163] 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 130% 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 then 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 45%, and the lithium and aluminum leaching rates during the leaching process are 72% and 15%, respectively. Due to the low lithium content, the leachate is difficult to extract directly; 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.

[0164] 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 efficient and comprehensive recovery of aluminum electrolysis solid waste, characterized in that: The method comprises the following steps: S1. Mixing aluminum electrolysis solid waste powder and reaction auxiliary materials uniformly and adding them into alkaline solution for leaching; S2. After the leaching reaction is completed, the material is filtered to obtain filter residue and filtrate respectively; S3a, acid-dissolve and purify the filter residue obtained in step 2, filter it, and dry the filter cake to obtain high-grade CaF2; S3b, extracting the filtrate obtained in step 2 to obtain a loaded organic phase and a raffinate; S4a, stripping the loaded organic phase to obtain a lithium-containing solution; S4b, the raffinate is concentrated to obtain an alkaline solution product; In S1, the aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, the main component of which is cryolite, and the lithium content in the aluminum electrolysis solid waste is above 0.5wt%.

2. The method according to claim 1, characterized in that In S3a, the pH value of the solution during the acid-dissolving purification process is in the range of 0 to 3.

3. The method according to claim 1, characterized in that In the S3b, the extractant is an organic solvent extractant, and the organic solvent extractant is a mixed solvent composed of a phosphate organic reagent, a ketone organic reagent and sulfonated kerosene.

4. The method according to claim 3, characterized in that In S3b, the phosphate organic reagent includes at least one of tributyl phosphate, trioctyl phosphate, trialkyl phosphonate and trioctyl phosphine oxide.

5. The method according to claim 3, characterized in that: In S3b, the ketone organic reagent includes at least one of β-diketone and trifluorodimethylhexanedione.

6. The method according to claim 3, characterized in that In the S3b, the molar concentration ratio of the phosphate organic reagent to the ketone organic reagent is 0.5:0.1 to 0.1:0.

5.

7. The method according to claim 1, characterized in that In S1, the reaction auxiliary material is capable of providing Ca 2+ of calcium-containing substances.

8. The method according to claim 1, characterized in that In S1, the lithium content in the aluminum electrolysis solid waste is less than 0.5wt%, S3b and S4a are omitted, and the filtrate obtained in S2 is directly concentrated to obtain the alkaline solution product.

9. The method according to claim 1, characterized in that: In S1, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder is 0.9-1.5:

1.

10. The method according to any one of claims 1 to 9, characterized in that: In the S1, the concentration of the alkaline solution is 20 to 80 g / L.

Images