Method for efficient comprehensive recovery of aluminum electrolysis solid waste

Abstract

The application discloses a kind of aluminum electrolysis solid waste efficient comprehensive recovery method, belong to solid waste resource recovery technical field, solve the following technical problems one: low aluminum lithium leaching rate in alkali process, fluoride is difficult to high-value recovery, HF pollution in acid process, long process flow.The method comprises the following steps: aluminum electrolysis solid waste powder and reaction accessories are mixed uniformly and then added to alkali solution for leaching;After leaching reaction is finished, the material is filtered, and the filter residue and filtrate are obtained respectively;The filter residue is acid-dissolved and purified, filtered, and the filter cake is dried to obtain high-grade CaF2;The filtrate is extracted to obtain loaded organic phase and raffinate;The loaded organic phase is stripped to obtain lithium-containing solution;The raffinate is concentrated to obtain alkali product.The method of the application has high recovery rate and high product quality.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource recycling technology, and in particular to a method for efficient and comprehensive recycling of solid waste from aluminum electrolysis. Background Technology

[0002] The continuous development of the aluminum electrolysis industry has generated a large amount of waste aluminum electrolyte. In 2020, global primary aluminum production reached 69.75 million tons. Based on the calculation that each ton of primary aluminum produced generates 15-25 kg of waste aluminum electrolyte, this amounts to 1.5 million tons of waste aluminum electrolyte annually. Since lithium is commonly found in bauxite, it accumulates in alumina during production and circulates in the electrolyte during electrolysis, resulting in approximately 2% lithium in the waste aluminum electrolyte. Waste aluminum electrolyte has a simple phase composition and contains multiple valuable components such as aluminum, fluorine, and lithium, possessing both hazardous waste and secondary resource attributes. The resource utilization of waste aluminum electrolyte can not only address the environmental hazards it causes but also effectively utilize its valuable components.

[0003] Currently, the main processing technologies for waste aluminum electrolytes include alkaline / acid leaching and leaching after roasting. CN112919507B provides a method for disposing of waste aluminum electrolytes, utilizing 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 the resource utilization of waste aluminum electrolytes, achieving lithium extraction and recovery by adding sodium salt to a medium-concentration acid solution. Existing technologies mainly employ alkaline leaching, acid leaching (or acid leaching under conditions of adding aluminum or sodium salts), and acid leaching after roasting, with most focusing primarily on lithium extraction and emphasizing the recovery of a single element, making it difficult to simultaneously recover multiple elements; furthermore, existing processes often suffer from long process flows and high costs. Summary of the Invention

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

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] This invention provides a method for efficient and comprehensive recycling of solid waste from aluminum electrolysis, comprising the following steps:

[0007] S1. After mixing the aluminum electrolysis solid waste powder with the reaction auxiliary materials evenly, add it to the 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. The filter residue obtained in step 2 is purified by acid dissolution, filtered, and the filter cake is dried to obtain high-grade CaF2.

[0010] S3b. Extract the filtrate obtained in step 2 to obtain a loaded organic phase and raffinate.

[0011] S4a. The supported organic phase is back-extracted to obtain a lithium-containing solution;

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

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

[0014] Furthermore, in S3a, the pH range of the solution during the acid dissolution purification process is 0–3.

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

[0016] Furthermore, in S3b, the phosphate ester organic reagent includes at least one of tributyl phosphate, trioctyl phosphate, trialkylphosphonate, and trioctylphosphine 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 phosphate ester organic reagents and ketone organic reagents is 0.5:0.1 to 0.1:0.5.

[0019] Furthermore, in S1, the reaction excipient is one that can provide Ca. 2+ Calcium-containing substances.

[0020] Furthermore, in S1, the lithium content in the aluminum electrolysis solid waste is <0.5wt%, S3b and S4a are omitted, and the filtrate obtained in S2 is directly concentrated to obtain the alkaline 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 20–80 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 the Ca provided by the reaction excipients. 2+ Under the influence of alkaline leaching, the solution chemical equilibrium among elements such as calcium, aluminum, fluorine, and lithium is controlled to achieve rapid decomposition of cryolite, the main component of aluminum electrolysis solid waste. This promotes the rapid conversion of aluminum, fluorine, and calcium ions entering the solution through alkaline leaching 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 resulting leachate is a relatively pure alkaline solution containing lithium, which is beneficial for subsequent lithium recovery through solvent extraction. The raffinate can be concentrated to obtain a qualified alkaline product, thus effectively removing sodium components from aluminum electrolysis solid waste. Compared to existing alkaline leaching processes, this invention utilizes auxiliary materials to dissolve aluminum electrolysis solid waste. The resulting fluoride / aluminate ions react with calcium ions to precipitate, and both processes occur simultaneously, effectively preventing the loss of leached Li components due to fluoride ion complexation and precipitation. Compared to existing alkaline roasting or calcium-added alkaline roasting-leaching processes, this invention avoids problems such as incomplete reaction during roasting, poorly soluble LiF, and the encapsulation of Li / Al components by CaF2 formed during roasting, which can lead to low lithium-aluminum conversion rates. Furthermore, unlike existing processes that do not focus on the recovery of sodium components in waste aluminum electrolytes, this invention can recover sodium components in waste aluminum electrolytes in the form of alkaline solution, thus achieving resource utilization of valuable components such as sodium, aluminum, fluorine, and lithium in waste aluminum electrolytes.

[0025] (b) In the method of this invention, the leaching under an alkaline system and the calcification transformation of aluminum and fluorine avoid the loss and dispersion of fluorine as HF gas compared to the acidic roasting / leaching system. Almost all the fluorine in the aluminum electrolysis solid waste is converted into calcium fluoride, resulting in a high fluorine recovery rate. Compared to existing alkaline leaching and alkaline roasting-leaching processes, the alkaline leaching process enables efficient dissolution of aluminum electrolysis solid waste, and the precipitation process of calcium aluminate and calcium fluoride can be controlled to completely convert aluminum and fluorine into precipitates. Utilizing the difference in stability between calcium aluminate and calcium fluoride in acidic solutions, hydrochloric acid or nitric acid can be used to selectively dissolve calcium aluminate in the precipitate residue. The leachate can be used for further aluminum recovery, and the leaching residue is high-grade calcium fluoride with few impurities, possessing higher economic value. Through the method of this invention, aluminum, fluorine, sodium, and a small amount of lithium contained in aluminum electrolysis solid waste are comprehensively recovered in stages, offering advantages such as high recovery rate, good separation effect, and high product quality.

[0026] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a process flow diagram for Example 1.

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

[0030] Figure 3 The CaF2 product composition obtained in Example 3 under the condition of a reaction excipient mass ratio of 1.1:1. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0032] This invention provides a method for efficient and comprehensive recycling of solid waste from aluminum electrolysis, comprising the following steps:

[0033] S1. After mixing the aluminum electrolysis solid waste powder with the reaction auxiliary materials evenly, add it to the 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. The filter residue obtained in step 2 is purified by acid dissolution, filtered, and the filter cake is dried to obtain high-grade CaF2.

[0036] S3b. Extract the filtrate obtained in step 2 to obtain a loaded organic phase and raffinate.

[0037] S4a. The supported organic phase is back-extracted to obtain a lithium-containing solution;

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

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

[0040] Step 1: Crush, grind, and screen the aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A;

[0041] Step 2: Mix aluminum electrolysis solid waste powder A with reaction auxiliary materials evenly to obtain material B;

[0042] Step 3: Prepare the alkaline solution. Add material B to the alkaline solution, stir evenly, and then add it to the alkali-resistant reaction device for reaction.

[0043] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0044] Step 5a: The filter residue obtained in step 4 is purified by acid dissolution with inorganic acid solution, filtered, and the filter cake is dried to obtain high-grade CaF2.

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

[0046] Step 6a: The supported organic phase obtained in step 5b is back-extracted to obtain a lithium-containing solution, which can be used to prepare industrial-grade lithium carbonate after concentration.

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

[0048] In one specific implementation, in step 1, the aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process, and its main component is cryolite.

[0049] For example, solid waste from aluminum electrolysis includes at least one of the solid wastes generated during the aluminum electrolysis process, such as waste aluminum electrolyte, aluminum electrolysis overhaul slag, and carbon powder.

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

[0051] In one specific implementation, in step 1, considering that if the particle size of aluminum electrolysis solid waste powder A is too large, the leaching process will be inefficient and will result in low lithium aluminum leaching; if the particle size is too small, the material will easily clump together during the leaching process; therefore, the aluminum electrolysis solid waste block is crushed, ground and screened to obtain aluminum electrolysis solid waste powder A with a particle size ≤74μm.

[0052] In one specific implementation, in step 2, the reaction excipient is a substance that can provide Ca. 2+ The calcium-containing substances, such as reaction excipients, are at least one of CaO, CaCl2, CaF2, Ca(OH)2, Ca(NO3)2 and their hydrates. For example, the reaction excipients are 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 excipients is to provide CaO that combines with aluminate and fluoride ions during the alkaline leaching process. 2+ This allows the aluminate and fluoride ions dissolved in the solution to be rapidly 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 electrolysis solid waste. All calcium salts that can achieve this purpose are within this protection range.

[0054] Compared with existing technologies, the method of this invention promotes the conversion of aluminate and fluoride ions generated from the dissolution of aluminum electrolysis solid waste into calcium salt precipitates by adding reaction excipients. This further promotes the dissolution of aluminum electrolysis solid waste and effectively avoids the formation of coordination precipitates between fluoride ions and dissolved lithium, which would affect the lithium leaching rate. Using the method of this invention, efficient recovery of fluorine resources can be achieved, avoiding problems such as fluorine dispersion and insufficient purity of the precipitate products. By utilizing the stability difference between calcium aluminate and calcium fluoride in the precipitate, selective acid dissolution can be used to separate calcium aluminate and calcium fluoride, obtaining high-grade CaF2 products.

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

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

[0057] In one specific embodiment, in step 3, the alkaline solution is prepared using NaOH, and the concentration of the alkaline solution is 20-80 g / L. For example, the concentrations of the alkaline solution are 30 g / L, 40 g / L, 60 g / L, and 70 g / L.

[0058] It should be noted that when the concentration of the alkaline solution is too low, the solid waste from aluminum electrolysis will not dissolve completely; when the concentration of the alkaline solution is too high, the added calcium salt may have difficulty entering the solution; both of these will result in low fluorine-aluminum conversion rate and low lithium leaching rate. Therefore, the concentration of the alkaline solution should be controlled at 20–80 g / L. Preferably, the concentration of the alkaline solution is 40–60 g / L.

[0059] In one specific embodiment, in step 3, the liquid-to-solid ratio of the alkaline solution to material B ranges from (4 to 15 mL): 1 g; for example, the liquid-to-solid ratios are 5 mL: 1 g, 10 mL: 1 g, and 13 mL: 1 g.

[0060] It should be noted that if the liquid-to-solid ratio is too high, the single-batch processing capacity of the same volume reaction vessel will be reduced; if the liquid-to-solid ratio is too low, it will result in a high density of mixed slurry, slow solid-liquid reaction, and insufficient reactants in the alkaline solution. Therefore, the liquid-to-solid ratio of the alkaline solution to material B should be controlled within the range of (4-15 mL):1 g.

[0061] In one specific embodiment, in step 3, material B reacts with an alkaline solution at a reaction temperature of 120–200°C, a reaction time of 0.5–2 hours, and a stirring speed of 200–500 rpm; for example, the reaction temperatures are 130°C, 150°C, 170°C, and 190°C; the reaction times are 0.6 hours, 1.0 hours, 1.5 hours, and 1.8 hours; and the stirring speeds are 250 rpm, 300 rpm, 350 rpm, 400 rpm, and 450 rpm.

[0062] It should be noted that if the reaction temperature is below this range, the aluminum electrolysis solid waste is difficult to dissolve in the alkaline solution, and the reaction kinetics are limited. If the temperature is too high, energy consumption and reaction vessel pressure will be high. If the stirring speed is below this range, the solution will cause calcium aluminate and CaF2 to precipitate and encapsulate the unreacted aluminum electrolysis solid waste, hindering the leaching reaction. If the stirring speed is too high, vortices will easily form, failing to achieve the desired mixing effect. If the reaction time is below this range, the reaction will be incomplete. If it is above this range, the reaction efficiency will be limited. Therefore, the reaction temperature should be controlled at 120–200℃, the reaction time at 0.5–2 hours, and the stirring speed at 200–500 rpm.

[0063] In one specific embodiment, in step 5a, the filter residue obtained in step 4 is acid-dissolved using an inorganic acid solution. The inorganic acid solution is prepared from at least one of hydrochloric acid and nitric acid, preferably hydrochloric acid. The pH range of the solution during the acid dissolution purification process is 0 to 3. For example, the pH of the solution is 0, 1, 2, or 3.

[0064] It should be noted that, considering economic costs, concentrated hydrochloric acid is preferred for preparing the acid solution. The acid dissolution process mainly uses the acid solution to remove unreacted auxiliary materials such as CaO / Ca(OH)2 and calcium aluminate from the filter residue. If the solution pH is too low, it may cause CaF2 dissolution loss. If the solution pH is too high, it will cause incomplete removal of CaO / Ca(OH)2 and calcium aluminate, affecting the purity of CaF2. Therefore, the pH range of the solution during the acid washing process should be controlled between 0 and 3.

[0065] In one specific embodiment, in step 5b, the organic solvent extractant is mainly a mixed solvent composed of phosphate ester organic reagents, ketone organic reagents and sulfonated kerosene.

[0066] In one specific embodiment, in step 5b, the phosphate ester organic reagent includes at least one of tributyl phosphate, trioctyl phosphate, trialkylphosphonate, and trioctylphosphine oxide; the ketone organic reagent includes at least one of β-diketone and trifluorodimethylhexanedione. The molar ratio of the phosphate ester organic reagent to the ketone organic reagent is 0.5:0.1 to 0.1:0.5. For example, the ratio of tributyl phosphate to β-diketone is 0.3:0.4, the ratio of tributyl phosphate to β-diketone is 0.2:0.4, the ratio of trioctylphosphine oxide to β-diketone is 0.1:0.3, and the ratio of tributyl phosphate to trifluorodimethylhexanedione is 0.2:0.2.

[0067] In one specific embodiment, in step 5b, the pH of the filtrate from 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 shaking time is 5–30 min, and the temperature is 10–40°C. For example, the pH is 12.5, 13, 13.5, or 14, the volume ratio of the organic solvent extractant to the filtrate is 1:15, 1:10, 1:5, or 1:2, the shaking time is 10 min, 15 min, 20 min, or 25 min, and the temperature is 15°C, 20°C, 25°C, 30°C, or 35°C.

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

[0069] In one specific embodiment, in step 6a, during the back-extraction step, the volume ratio of the supported organic phase to the back-extraction 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 co-extraction system composed of phosphate esters and ketones. The ketone organic reagents exhibit key selectivity for lithium in the solution, while neutral phosphate ester organic reagents, as strong electron donors, can further enhance lithium coordination selectivity and readily chelate with Li in water to form a stable six-membered structure, resulting in an extraction order of Li>Na>K. The ketone organic compounds in the extracted organic phase, acting as hydrogen ion donors, show a certain dependence on the solution pH. When the solution pH is too low, the ketone organic compounds' influence on H+ ions decreases. +The attraction of the solvent is relatively strong, but the extraction ability for Li is weak. If the solution alkalinity is too high, the organic phase structure is easily destroyed, causing emulsification. Therefore, the pH of the filtrate in step 4 is controlled at 12.5–14, preferably 13 or 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. If the molar concentration of the organic solvent extractant is too high, it can easily lead to waste of extractant and difficulty in extraction and phase separation. Conversely, if the lithium concentration in the solution is high and the molar concentration of the organic solvent extractant is too low, it can easily lead to incomplete lithium extraction and waste of lithium resources. Therefore, the molar ratio of phosphate esters to ketones in the organic phase is controlled at 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 phosphate esters to ketones in the 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 extraction efficiency. Shorter contact time means a faster mass transfer rate is required. If the contact time is too short, the reaction is incomplete, resulting in a low lithium extraction rate. If the contact time is too long, the lithium extraction rate does not change significantly, and more impurities such as sodium and potassium are entrained, leading to a decrease in extraction efficiency. Higher temperatures are beneficial for increasing ion migration rates, but they can also damage the structure of the extract to some extent, which is not conducive to lithium extraction. Therefore, the oscillation time is 5–30 min, and the temperature range is 10–40 °C. The preferred time is 10–20 min, and the preferred temperature is 20–30 °C.

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

[0072] In one specific embodiment, in step 6b, the concentration of the raffinate can be achieved by heating and evaporation, or by adding CaO, stirring evenly, letting it stand for 1 to 3 hours, and then filtering. The resulting filtrate is an alkaline solution with a certain concentration. The filter residue can be used as a reaction auxiliary material in step 2. Considering energy consumption costs, in one specific embodiment, it is preferable to add CaO to achieve the concentration of the alkaline solution.

[0073] In the method of this invention, under the action of reaction excipients, the main cryolite phase in aluminum electrolysis solid waste is rapidly decomposed in an alkaline solution. The strong coordination precipitation between aluminate and fluoride ions generated after the calcium ions in the reaction excipients dissolve with cryolite promotes the rapid conversion of aluminate and fluoride ions entering the solution through alkaline leaching into CaF2 and their precipitation. This avoids the coordination precipitation of fluoride ions with lithium, thereby achieving efficient lithium leaching and efficient conversion of fluoride and aluminum components. The resulting alkaline solution, with low impurity content and easily recoverable lithium through solvent extraction, is obtained. Compared with existing alkaline leaching processes, this invention, through the addition of excipients, achieves rapid decomposition of the main cryolite phase in aluminum electrolysis solid waste in an alkaline solution. While dissolving in the solution, the aluminate and fluoride ions generated after dissolution react directly with calcium ions to precipitate and remove the cryolite. This not only avoids the loss of valuable Li components due to the complexation and precipitation of fluoride ions, but also further promotes the rapid dissolution of cryolite. Compared with existing alkaline roasting or calcium-added alkaline roasting-leaching processes, the method of this invention realizes the reaction process of cryolite dissolution and the formation of calcium aluminate and CaF2 in aluminum electrolysis solid waste in one step. This avoids problems such as low lithium leaching rate and high impurity content in CaF2 caused by incomplete reaction or the difficulty in dissolving the formed LiF during roasting, as well as the encapsulation of Li components by the CaF2 formed during roasting.

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

[0075] In the method of this invention, the leaching under an alkaline system and the calcification transformation of aluminate and fluoride ions avoid the loss and dispersion of fluoride as HF gas compared to the acidic roasting / leaching system. Almost all the fluoride in the aluminum electrolysis solid waste is converted into calcium fluoride, resulting in a high fluoride recovery rate. Compared with existing alkaline leaching and alkaline roasting-leaching processes, by controlling the alkaline leaching process, efficient dissolution of aluminum electrolysis solid waste can be achieved, and the control of the calcium fluoride precipitation process can produce calcium fluoride slag with high grade and few impurities. After acid dissolution and purification, it can reach a grade of 98 wt%, which has higher value.

[0076] Example 1

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

[0078] Step 1: Crush, grind, and screen the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size ≤74μm;

[0079] Step 2: Mix the reaction auxiliary material CaO and waste aluminum electrolyte powder evenly at a mass ratio of 1.1:1;

[0080] Step 3: Prepare NaOH solutions of 20 g / L, 40 g / L, 60 g / L, and 80 g / L. Mix the well-mixed material with the NaOH solution at a liquid-solid ratio of 10 mL: 1 g, stir well, and put it into an alkali-resistant reaction vessel. React at 180°C and 300 rpm for 1.0 hour.

[0081] Step 4: After the reaction is complete, the material is filtered to obtain filter residue (also known as leaching residue) and filtrate (also known as leachate);

[0082] Step 5a: Use hydrochloric acid solution to acid dissolve and purify the filter residue, keeping the pH of the solution at 0, filter, and dry the filter cake to obtain high-grade calcium fluoride.

[0083] Step 5b: Using a mixture of tributyl phosphate organic compounds, β-diketone organic reagents (molar concentration ratio of 0.3:0.4) and sulfonated kerosene as the organic solvent extractant, the organic solvent extractant and the filtrate obtained in step 4 are subjected to three-stage countercurrent extraction at a volume ratio of 1:10.

[0084] Step 6a: The obtained equilibrium loaded organic phase was subjected to two-stage back-extraction using a 4 mol / L HCl solution. The back-extraction ratio O / A = 5 / 1. The extraction-back-extraction process was controlled with a shaking time of 10 min and a temperature of 25℃. The lithium extraction rate was 99.0% during the extraction process and 99.5% during the back-extraction process. The raffinate was concentrated using CaO, and after filtration, a 30% alkaline solution was obtained.

[0085] The results of the leaching process in this embodiment, including lithium leaching rate, aluminum content in filtrate, fluorine recovery rate, lithium recovery rate, alkali recovery rate, and purity of the final product calcium fluoride, are shown in Table 1. Figure 2 The images show the XRD patterns of the filter residue and the final CaF2 from the alkaline leaching process in the examples. It should be noted that the alkali concentration not only significantly affects the aluminum-lithium leaching rate but also has a relatively significant impact 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 show this trend. This is because the alkali concentration affects the solubility of the reaction additives in water, thereby affecting the dissolution of cryolite in the waste aluminum electrolyte, thus impacting the above indicators. The low aluminum content in the filtrate indicates that the calcium salt conversion of aluminum and fluorine can be achieved during the leaching process, resulting in a relatively pure lithium-containing alkaline leachate, which is beneficial for subsequent lithium extraction and recovery, and alkali recovery.

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

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

[0088]

[0089] Example 2

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

[0091] Step 1: Crush, grind, and screen the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size ≤74μm;

[0092] Step 2: Mix the reaction excipients CaO, Ca(OH)2, CaCl2, CaO+Ca(OH)2, CaO+CaCl2, CaO+CaF2, CaO+CaCl2+CaF2 with waste aluminum electrolyte powder at a mass ratio of 1.1:1.

[0093] Step 3: Prepare a 60 g / L NaOH solution. Mix the well-mixed material with the NaOH solution at a liquid-solid ratio of 10 mL: 1 g, stir well, and put it into an alkali-resistant reaction vessel. React at 200°C and 500 rpm for 2.0 hours.

[0094] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0095] Step 5a: The filter cake is purified by acid dissolution with hydrochloric acid solution, the pH of the solution is maintained at 1.0, filtered, and dried to obtain high-grade calcium fluoride.

[0096] Step 5b: Using a mixture of trialkylphosphonic acid esters, β-diketone organic reagents (molar concentration ratio of 0.4:0.4), and sulfonated kerosene as organic solvent extractant, the organic solvent extractant and the filtrate obtained in step 4 are subjected to three-stage countercurrent extraction at a volume ratio of 1:10.

[0097] Step 6a: The obtained equilibrium loaded organic phase was subjected to two-stage back-extraction using a 4 mol / L HCl solution. The back-extraction ratio O / A = 5 / 1. The shaking time was controlled at 10 min and the temperature at 25℃ throughout the entire extraction-back-extraction process. The lithium extraction rate was 98.9% during the extraction process and 99.2% during the back-extraction process. The raffinate was concentrated using CaO and filtered to obtain a 30% alkaline solution.

[0098] Table 2 shows the results of lithium leaching rate, fluorine recovery rate, lithium recovery rate, alkali recovery rate, and purity of the final product, calcium fluoride, during the leaching process in this embodiment. It should be noted that different reaction excipients can provide Ca in the alkaline leaching system. 2+ This process promotes the leaching of lithium aluminum and achieves the conversion of fluoride ions into CaF2. Therefore, various types of reaction excipients can achieve good reaction results. In this embodiment, the lithium aluminum leaching rate is high, and the obtained calcium fluoride product has high purity, for example, the purity of calcium fluoride reaches over 97%, which is a high-quality CaF2 product.

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

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

[0101]

[0102] Example 3

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

[0104] Step 1: Crush, grind, and screen the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size ≤74μm;

[0105] Step 2: Mix the reaction excipients CaO+Ca(OH)2+CaF2 with waste aluminum electrolyte powder at mass ratios of 0.9:1, 1.1:1, 1.3:1, and 1.5:1 until homogeneous;

[0106] Step 3: Prepare a 60 g / L NaOH solution. Mix the well-mixed material with the NaOH solution at a liquid-to-solid ratio of 15 mL: 1 g, and place it in an alkali-resistant reactor. React at 170 °C and 200 rpm for 0.5 hours.

[0107] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0108] Step 5a: The filter cake is purified by acid dissolution with hydrochloric acid solution, the pH of the solution is maintained at 2.0, filtered, and dried to obtain high-grade calcium fluoride.

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

[0110] Step 6a: The obtained equilibrium-loaded organic phase was subjected to two-stage back-extraction using a 4 mol / L HCl solution. The back-extraction ratio O / A = 10 / 1. The entire extraction-back-extraction process was controlled with a shaking time of 10 min and a temperature of 25℃. The lithium extraction rate was 98.8% during extraction and 99.6% during back-extraction. The raffinate was concentrated using CaO, and after filtration, a 30% alkaline solution was obtained.

[0111] Table 3 shows the results of lithium leaching rate, fluorine recovery rate, lithium recovery rate, alkali recovery rate, and purity of the final product, calcium fluoride, during the leaching process in this embodiment. It should be noted that when the mass ratio is 0.9:1, the calcium ions provided by the reaction excipients are slightly lower than the theoretical requirement, resulting in a higher aluminum content in the leachate and incomplete calcium salt precipitation of aluminum. Increasing the mass ratio to above 1.1:1 improves the precipitation conversion effect of aluminum. Furthermore, the lithium content in the leachate also increases with the increase of the mass ratio.

[0112] Furthermore, 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 on calcium aluminate and calcium hydroxide in the filter residue weakens, and the purity of CaF2 decreases slightly. However, 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 above 95% (e.g., 95.2% to 97.3%), the aluminum content in the filtrate is 18 to 1881 ppm, the fluorine recovery rate is above 92% (e.g., 92.1% to 98.4%), the CaF2 purity is above 92% (e.g., 92.7% to 93.8%), the lithium recovery rate is above 87% (e.g., 87.2% to 98.8%), and the alkali recovery rate is above 95% (e.g., 95.2% to 96%).

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

[0115]

[0116] Example 4

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

[0118] Step 1: Crush, grind, and screen the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size ≤74μm;

[0119] Step 2: Mix the reaction excipients CaO+Ca(OH)2+CaF2 with the waste aluminum electrolyte powder at a mass ratio of 1.3:1 until homogeneous;

[0120] Step 3: Prepare a 60 g / L NaOH solution. Mix the well-mixed material with the NaOH solution at a liquid-solid ratio of 15 mL: 1 g, and place it in an alkali-resistant reactor. React at 130℃, 150℃, 170℃, and 190℃ with stirring at 200 rpm for 0.5 hours.

[0121] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0122] Step 5a: The filter cake is purified by acid dissolution with hydrochloric acid solution, the pH of the solution is maintained at 1.0, filtered, and dried to obtain high-grade calcium fluoride.

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

[0124] Step 6a: The obtained equilibrium-loaded organic phase was subjected to two-stage back-extraction using a 2 mol / L HCl solution. The back-extraction ratio O / A = 5 / 1. The shaking time was controlled at 10 min and the temperature at 25℃ throughout the entire extraction-back-extraction process. The lithium extraction rate was 98.2% during the extraction process and 99.6% during the back-extraction process. The raffinate was concentrated using CaO, and after filtration, a 30% alkaline solution was obtained.

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

[0126] It should be noted that within the range of 120 to 200°C, the reaction temperature has little impact on the results of each process. When the temperature is above 150°C, efficient leaching of waste aluminum electrolyte can be achieved, and the calcification and precipitation conversion 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 above 89% (e.g., 89.5% to 96.2%), the aluminum content in the filtrate is 22 to 26 ppm, the fluorine recovery rate is above 94% (e.g., 94.8% to 99%), the CaF2 purity is above 93% (e.g., 93.1% to 98.8%), the lithium recovery rate is above 93% (e.g., 93.4% to 95.8%), and the alkali recovery rate is above 95% (e.g., 95.1% to 96%).

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

[0129]

[0130] Example 5

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

[0132] Step 1: Crush, grind, and screen the waste aluminum electrolyte blocks to obtain waste aluminum electrolyte powder with a particle size ≤74μm. The lithium content in this powder is 0.3%, and its recycling value is relatively small.

[0133] Step 2: Mix the reaction excipients CaO+Ca(OH)2+CaF2 with the waste aluminum electrolyte powder at a mass ratio of 1.3:1 until homogeneous;

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

[0135] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0136] Step 5a: The filter cake is purified by acid dissolution with hydrochloric acid solution, the pH of the solution is maintained at 1.0, filtered, and dried to obtain high-grade calcium fluoride.

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

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

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

[0140] Example 6

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

[0142] Step 1: Crush, grind, and screen the aluminum electrolysis overhaul slag to obtain waste aluminum electrolyte powder with a particle size ≤74μm;

[0143] Step 2: Mix the reaction excipients CaO+CaF2 and the overhaul slag powder at a mass ratio of 1.1:1 until homogeneous;

[0144] Step 3: Prepare a 60 g / L NaOH solution. Mix the well-mixed material with the NaOH solution at a liquid-solid ratio of 10 mL: 1 g, stir well, and put it into an alkali-resistant reaction vessel. React at 200°C and 500 rpm for 2.0 hours.

[0145] Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively.

[0146] Step 5a: The filter cake is purified by acid dissolution with hydrochloric acid solution, the pH of the solution is maintained at 1.0, filtered, and dried to obtain high-grade calcium fluoride.

[0147] Step 5b: Using a mixture of trialkylphosphonic acid esters, β-diketone organic reagents (molar concentration ratio of 0.4:0.4), and sulfonated kerosene as organic solvent extractant, the organic solvent extractant and the filtrate obtained in step 4 are subjected to three-stage countercurrent extraction at a volume ratio of 1:10.

[0148] Step 6a: The obtained equilibrium-loaded organic phase was subjected to two-stage back-extraction using a 4 mol / L HCl solution. The back-extraction ratio O / A = 5 / 1. The shaking time was controlled at 10 min and the temperature at 25℃ throughout the entire extraction-back-extraction process. The lithium extraction rate was 98.9% during extraction and 99.2% during back-extraction. The raffinate was concentrated using CaO, and after filtration, a 30% alkaline solution was obtained.

[0149] In this embodiment, the lithium leaching rate was 93%, the aluminum content in the filtrate was 26 ppm, the fluorine recovery rate was 95%, the CaF2 purity was 81.5%, the lithium recovery rate was 93.5%, and the alkali recovery rate was 96.1%. It should be noted that impurities other than cryolite in the leaching residue do not affect the lithium leaching rate. These impurities enter the leaching residue during the leaching process and, after acid washing, yield a high-grade calcium fluoride product that meets the CaF2 grade requirements of slag-forming agents in steel smelting enterprises.

[0150] Comparative Example 1

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

[0152] Waste aluminum electrolyte blocks were crushed, ground, and sieved to obtain waste aluminum electrolyte powder with a particle size ≤74μm. NaOH solutions of 20g / L, 40g / L, 60g / L, and 80g / L were prepared. The waste aluminum electrolyte powder was mixed with the NaOH solution at a liquid-to-solid ratio of 10mL:1g without the addition of reaction additives, and then placed in an alkali-resistant reactor. The reaction was carried out at 180℃ and 300rpm for 2.0 hours. After the reaction, the material was filtered to obtain filter residue and filtrate. The filter residue was acid washed with hydrochloric acid solution to remove impurities, with the pH of the solution maintained at 1.0. The filter cake was then dried. The filtrate was extracted using a mixture of tributyl phosphate, β-diketone organic reagents (molar ratio 0.2:0.4), and sulfonated kerosene as the organic solvent extractant. The organic solvent extractant and filtrate were subjected to a three-stage countercurrent extraction at a volume ratio of 1:20. The resulting equilibrium-loaded organic phase was then subjected to a two-stage back-extraction using a 4 mol / L HCl solution. The back-extraction ratio O / A = 10 / 1. Throughout the extraction-back-extraction process, the shaking time was controlled at 10 min, and the temperature was 25℃. The lithium extraction rate during extraction was 78.4%, and the lithium back-extraction rate during back-extraction was 79.3%. The raffinate was concentrated using CaO to obtain an alkaline solution.

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

[0154] Table 5 Results of each process under different alkali concentrations without the addition of reaction excipients.

[0155]

[0156] Comparing Example 1 and Comparative Example 1, it can be seen that without the addition of reaction excipients, the lithium leaching rate is low and the aluminum content is high during the leaching process, and it cannot be converted into precipitate to be removed from the filtrate. 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 excipients are added during the leaching process, fluorine cannot be converted into calcium fluoride and enter the filter residue, resulting in low fluorine recovery rate and no CaF2 product can be obtained.

[0157] Comparative Example 2

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

[0159] Waste aluminum electrolyte blocks were crushed, ground, and sieved to obtain waste aluminum electrolyte powder with a particle size ≤74μm. The reaction auxiliary material CaO+Ca(OH)2+CaF2 was mixed evenly with the waste aluminum electrolyte powder at a mass ratio of 0.8:1. A 60g / L NaOH solution was prepared, and the evenly mixed material was stirred with the NaOH solution at a liquid-to-solid ratio of 15mL:1g. The mixture was then placed in an alkali-resistant reactor and reacted at 170℃ with stirring at 200rpm for 0.5 hours. After the reaction, the material was filtered to obtain filter residue and filtrate. The filter residue was acid-washed with hydrochloric acid solution to remove impurities, maintaining the solution pH at 1.0. After filtration, the filter cake was dried to obtain high-grade calcium fluoride. The filtrate was extracted using a mixture of trialkylphosphonic acid esters, β-diketone organic reagents (molar ratio 0.4:0.4), and sulfonated kerosene as the organic solvent extractant. The organic solvent extractant and filtrate were subjected to a three-stage countercurrent extraction at a volume ratio of 1:10. The resulting equilibrium-loaded organic phase was then subjected to a two-stage back-extraction using a 4 mol / L HCl solution, with a back-extraction ratio of O / A = 5 / 1. The entire extraction-back-extraction process was controlled with a shaking time of 10 min and a temperature of 25℃. The lithium extraction rate was 95.5% during extraction, and the lithium back-extraction rate was 95.1% during back-extraction. The raffinate was concentrated using CaO, and after filtration, a 30% alkaline solution was obtained. During leaching, the lithium leaching rate was 95.4%, the aluminum content in the leachate was 1.2 g / L, the fluorine recovery rate was 98.5%, the purity of the obtained CaF2 was 98.4%, and the alkali recovery rate was 94.2%.

[0160] Comparing Example 3 and Comparative Example 2, it can be seen that when the amount of reaction excipients added is low, the lithium leaching rate is slightly lower and the aluminum concentration in the leachate is higher. Although the impact on indicators such as fluorine recovery rate, CaF2 purity, alkali recovery rate, lithium extraction rate and back-extraction rate is small, the high aluminum concentration in the leachate entering the extraction system will have a certain impact on the extraction system. Furthermore, aluminum eventually enters the raffinate, which also has a certain impact on the process of adding CaO to concentrate the alkali solution, resulting in 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 solid waste from aluminum electrolysis, including the following steps:

[0163] Waste aluminum electrolyte blocks were crushed, ground, and sieved to obtain waste aluminum electrolyte powder with a particle size ≤74μm. This powder was then uniformly mixed with CaO and sodium carbonate, with CaO accounting for 130% of the powder's mass and sodium carbonate accounting for 80%. Water and a small amount of binder were added to form pellets, which were then heated in a high-temperature furnace at 1000℃ for 1 hour. After the reaction was complete, the pellets were removed, cooled to room temperature, and crushed to obtain powder B. Powder B was added to a 5% (w / w) NaOH solution and leached with stirring for 1 hour at a liquid-to-solid ratio of 5:1. After filtration, filter residue and a leachate containing aluminum and lithium were obtained. The obtained filter residue contained 45% CaF2, and the lithium and aluminum leaching rates during the leaching process were 72% and 15%, respectively. Due to the low lithium content, the leachate was difficult to extract directly. The resulting CaF2 residue contained a large amount of unreacted waste aluminum electrolyte (cryolite). 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. Incomplete decomposition of cryolite inevitably leads 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 embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for efficient and comprehensive recycling of solid waste from aluminum electrolysis, characterized in that, The method includes the following steps: Step 1: Crush, grind, and screen the aluminum electrolysis solid waste blocks to obtain aluminum electrolysis solid waste powder A; Step 2: Mix aluminum electrolysis solid waste powder A with reaction auxiliary materials evenly to obtain material B; Step 3: Prepare the alkaline solution. Add material B to the alkaline solution, stir evenly, and then add it to the alkali-resistant reaction device for reaction. Step 4: After the reaction is complete, the materials are filtered to obtain filter residue and filtrate respectively. Step 5a: The filter residue obtained in step 4 is purified by acid dissolution with inorganic acid solution, filtered, and the filter cake is dried to obtain high-grade CaF2. Step 5b: Extract the filtrate obtained in step 4 using an organic solvent extractant to obtain a loaded organic phase and raffinate; Step 6a: The supported organic phase obtained in step 5b is back-extracted to obtain a lithium-containing solution, which can be used to prepare industrial-grade lithium carbonate after concentration. Step 6b: The raffinate can be concentrated to obtain an alkaline solution product of a certain concentration; In step 1, the aluminum electrolysis solid waste is solid waste generated during the aluminum electrolysis process. Its main component is cryolite, and the lithium content in the aluminum electrolysis solid waste is above 0.5 wt%. In step 1, the particle size of aluminum electrolysis solid waste powder A is ≤74μm; The reaction auxiliary in step 2 is a calcium-containing substance capable of providing Ca 2+ ; the mass ratio of the reaction auxiliary to the aluminum electrolysis solid waste powder is 0.9-1.5:

1. In step 3, the alkaline solution is prepared using NaOH, and the concentration of the alkaline solution is 20~80g / L; the liquid-solid ratio of the alkaline solution to material B is 4~15 mL:1g; the reaction of material B with the alkaline solution is carried out at a reaction temperature of 120~200℃, a reaction time of 0.5~2 hours, and a stirring speed of 200~500rpm. In step 5b, the pH of the filtrate from step 4 is controlled to be 13-14, the volume ratio of organic solvent extractant to filtrate is 1:20-1:1, the shaking time is 5-30 min, and the temperature is 10-40℃. In step 6a, the hydrogen ion concentration in the back-extraction reagent is 1~6 mol / L.

2. The method according to claim 1, characterized in that, The pH range of the solution during acid dissolution purification is 0~3.

3. The method according to claim 1, characterized in that, The organic solvent extractant is a mixed solvent composed of phosphate ester organic reagents, ketone organic reagents and sulfonated kerosene.

4. The method according to claim 3, characterized in that, Phosphate ester organic reagents include at least one of tributyl phosphate, trioctyl phosphate, trialkylphosphonate, and trioctylphosphine oxide.

5. The method according to claim 3, characterized in that, Ketone organic reagents include at least one of β-diketone and trifluorodimethylhexanedione.

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

5.

7. The method according to claim 1, characterized in that, In step 2, the mass ratio of the reaction auxiliary material to the aluminum electrolysis solid waste powder is 1.1~1.5:

1.

8. The method according to any one of claims 1 to 7, characterized in that, In step 3, the concentration of the alkaline solution is 40~80g / L.

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