Method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag

Abstract

The invention relates to a method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, and belongs to the technical field of recycling of electrolysis overhaul slag. The aluminum electrolysis overhaul slag contains fluorine and lithium, and the method comprises the steps that the aluminum electrolysis overhaul slag and a fluorine extracting agent are subjected to a fluorine extracting reaction, and first slurry is obtained; carrying out solid-liquid separation on the first slurry to obtain a fluorine-containing solution and fluorine-extracted filter residues; performing lithium extraction reaction on the fluorine extraction filter residue and a lithium extraction agent to obtain a first lithium-containing solution; performing an impurity removal reaction on the first lithium-containing solution and an impurity removal agent to obtain a second lithium-containing solution; and carrying out precipitation reaction on the fluorine-containing solution and the second lithium-containing solution to obtain lithium fluoride. According to the embodiment of the invention, the fluorine-containing solution and the lithium-containing solution are extracted step by step, so that the purity of a lithium fluoride product is high, and the comprehensive recovery rate of lithium is high. The implementation process of the whole method can be realized only by adding the fluorine extracting agent, the lithium extracting agent and the impurity removing agent, the flow is short, the efficiency is high, and the lithium loss is low.

Description

Technical Field

[0001] The present application relates to the technical field of recycling aluminum electrolysis overhaul slag, and in particular to a method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag. Background Art

[0002] Aluminum electrolysis overhaul slag is a hazardous waste generated in the production process of aluminum electrolysis. It mainly includes two parts: waste cathode and waste refractory. The waste cathode is mainly composed of carbon and electrolyte; the waste refractory is mainly composed of aluminum silicon and electrolyte; the electrolyte is mainly composed of sodium fluoride, sodium hexafluoroaluminate, etc. The electrolyte of northern aluminum electrolysis enterprises contains lithium salt. Electrolyte is the main toxic substance in overhaul slag, and it is also a valuable resource with a high content. The recovery of electrolyte and lithium salt is the focus of aluminum electrolysis overhaul slag.

[0003] The existing utilization of lithium components in aluminum electrolysis overhaul slag mostly adopts acid leaching or alkaline leaching or roasting. The impurities in the leaching solution during the extraction process are of many types and high content, the impurity removal process is long, the lithium loss rate in the impurity removal process is large, and the comprehensive recovery rate of lithium is low. In addition, roasting or acid leaching will also increase the content of sodium, potassium and other ions in the lithium extraction solution, resulting in a large amount of salt precipitation during the concentration process of the lithium extraction solution, which affects the concentration effect on the one hand, and on the other hand, the precipitated salt will carry lithium, causing lithium loss. Moreover, the products prepared after lithium salt extraction are mostly lithium carbonate products, and the products prepared after electrolyte extraction are mostly cryolite or aluminum fluoride products. There are many types of additives in the extraction process, a long process flow, and many control points. Summary of the invention

[0004] The present application provides a method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag to solve the following technical problem: how to simplify the existing process of recycling aluminum electrolysis overhaul slag.

[0005] In a first aspect, an embodiment of the present application provides a method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, wherein the aluminum electrolysis overhaul slag contains fluorine and lithium, and the method comprises:

[0006] The aluminum electrolysis overhaul slag and the fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry;

[0007] Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0008] The fluorine extraction filter residue and the lithium extraction agent are subjected to a lithium extraction reaction to obtain a first lithium-containing solution;

[0009] The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction to obtain a second lithium-containing solution;

[0010] The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride.

[0011] Optionally, the fluorine-extracting agent includes at least one of the following: water and sodium hydroxide.

[0012] Optionally, the solid-liquid ratio of the fluorine extraction reaction system is 1:(3-5).

[0013] Optionally, the process parameters of the fluorine extraction reaction include: temperature is room temperature, and time is 30min to 50min.

[0014] Optionally, the lithium extraction agent includes at least one of the following: sulfate and chloride.

[0015] Optionally, the amount of the lithium extraction agent added is 1.5 to 2 times the theoretical amount of the lithium extraction agent added, and the theoretical amount of the lithium extraction agent added is the mass of the lithium extraction agent required for the lithium extraction agent to react completely with the lithium in the fluorine extraction residue.

[0016] Optionally, the process parameters of the lithium extraction reaction include: temperature of 90°C to 100°C, and time of 40min to 80min.

[0017] Optionally, the impurity remover includes at least one of the following: aqueous ammonia, sodium hydroxide, calcium hydroxide; and / or,

[0018] The pH of the impurity removal reaction system is 10-12.

[0019] Optionally, the process parameters of the precipitation reaction include: temperature of 40°C to 50°C, and time of 60min to 120min.

[0020] Optionally, the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.1 to 1.4 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution is the volume ratio of the fluorine-containing solution to the second lithium-containing solution required for the complete reaction of fluoride ions and lithium ions calculated based on the concentrations of fluoride ions and lithium ions in the precipitation reaction system.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The method for extracting and preparing lithium fluoride from the aluminum electrolysis overhaul slag provided in the embodiment of the present application, the aluminum electrolysis overhaul slag contains fluorine and lithium, and the method comprises: subjecting the aluminum electrolysis overhaul slag to a fluorine extraction reaction with a fluorine extraction agent to obtain a first slurry; subjecting the first slurry to solid-liquid separation to obtain a fluorine-containing solution and a fluorine extraction residue; subjecting the fluorine extraction residue to a lithium extraction reaction with a lithium extraction agent to obtain a first lithium-containing solution; subjecting the first lithium-containing solution to an impurity removal reaction with an impurity removal agent to obtain a second lithium-containing solution; subjecting the fluorine-containing solution to a precipitation reaction with the second lithium-containing solution to obtain lithium fluoride. The fluorine extraction and lithium extraction of the overhaul slag are carried out step by step to prepare a fluorine-containing solution and a first lithium-containing solution, respectively, and then the first lithium-containing solution is subjected to impurity removal to obtain a second lithium-containing solution, and the two solutions are mixed to undergo a precipitation reaction to obtain lithium fluoride. The extraction of fluorine-containing solution and lithium-containing solution is carried out step by step. On the one hand, it can ensure that the impurity ion content in the two solutions is low, the solutions are pure, and the final prepared lithium fluoride product has high purity; on the other hand, it can effectively avoid fluorine and lithium from being impurities to each other, increase the impurity removal process and reduce the comprehensive recovery rate of fluorine and lithium. The overall process only needs to add fluorine extraction agent, lithium extraction agent and impurity removal agent to achieve, with a short process, high efficiency, less lithium loss, and a comprehensive lithium recovery rate of more than 95%; the fluorine source for lithium fluoride preparation is provided by the fluorine element contained in the overhaul slag itself, without the need for external purchase, and low cost; the purity of lithium fluoride products reaches more than 99%, which can be returned to the electrolytic cell for recycling, and can also be used in the enamel industry and optical glass fields to realize resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic diagram of a process for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of an actual process for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] In a first aspect, the present application provides a method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, wherein the aluminum electrolysis overhaul slag contains fluorine and lithium. Figure 1 A schematic diagram of a process for extracting lithium fluoride from aluminum electrolysis overhaul slag provided in an embodiment of the present application; see Figure 1 , the method comprising:

[0032] S1, subjecting aluminum electrolysis overhaul slag and a fluorine extracting agent to a fluorine extracting reaction to obtain a first slurry;

[0033] After a long period of operation, the aluminum electrolytic cell needs to be overhauled due to erosion and damage of the lining material. During the overhaul process, the cathode and lining of the electrolytic cell will be removed, and various debris and sediments in the cleaning tank will be removed. These removed and cleaned materials form the aluminum electrolysis overhaul slag. In the embodiment of the present application, the aluminum electrolysis overhaul slag includes two parts: waste cathode and waste refractory material, wherein the waste cathode is mainly composed of carbon and electrolyte; the waste refractory material is mainly composed of aluminum silicon and electrolyte; the electrolyte is mainly composed of sodium fluoride, sodium hexafluoroaluminate, etc. The electrolyte of the northern electrolytic aluminum enterprise contains lithium salts. The embodiment of the present application uses the electrolyte of the northern electrolytic aluminum enterprise as raw material.

[0034] The aluminum electrolysis overhaul slag and the fluorine extraction agent are reacted to convert the fluorine element in the overhaul slag into the solution to form a fluorine-containing solution, which provides a fluorine source for the subsequent preparation of lithium fluoride. This step is the basis of the entire process. The efficiency and effect of the fluorine extraction reaction directly affect the fluorine content and purity in the final product.

[0035] In some embodiments, the fluorine extracting agent includes at least one of the following: water and sodium hydroxide.

[0036] The fluorine extracting agent can be one or both of water and sodium hydroxide. Some fluorine-containing compounds in the aluminum electrolysis overhaul slag, such as sodium fluoride, have a certain solubility in water. By mixing water and overhaul slag, these fluorine-containing compounds can be dissolved in water, realizing the transfer of fluorine from the solid phase to the liquid phase, thereby achieving the purpose of fluorine extraction. Using water as a fluorine extracting agent can, on the one hand, ensure the efficient dissolution of soluble fluorine in the overhaul slag, and on the other hand, ensure that the impurity content in the obtained fluorine-containing solution is the lowest, without the need for impurity removal reaction, and water has the advantages of low cost and environmental friendliness. Sodium hydroxide will react chemically with the fluorine-containing compounds in the overhaul slag, and the generated fluorides such as sodium fluoride will enter the solution phase, thereby achieving fluorine extraction.

[0037] In some embodiments, the solid-liquid ratio of the fluorine extraction reaction system is 1:(3-5).

[0038] The solid-liquid ratio of the fluorine extraction reaction system can be 1: (3-5), which can increase the reaction rate of the overhaul slag and the fluorine extraction agent and achieve the full extraction of fluorine in the overhaul slag, and the appropriate solid-liquid ratio is conducive to the subsequent solid-liquid separation process. Exemplarily, the solid-liquid ratio of the fluorine extraction reaction system can be 1: 3, 1: 4, 1: 5, etc.

[0039] In some embodiments, the process parameters of the fluorine extraction reaction include: the temperature is room temperature, and the time is 30min to 50min. No additional heating or refrigeration equipment is required to adjust the reaction temperature, and the reaction is carried out directly at room temperature, which greatly reduces energy consumption and helps to reduce production costs. The time can be 30min to 50min, so that most fluorine-containing compounds have more time to contact and react with the fluorine extraction agent, which can allow more fluorine elements to enter the solution phase and improve the fluorine recovery rate. Exemplarily, the time of the fluorine extraction reaction can be 30min, 35min, 40min, 45min, 50min, etc.

[0040] S2, performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0041] Through the solid-liquid separation operation, the fluorine-containing solution and the fluorine extraction residue are separated, providing conditions for the subsequent treatment of the fluorine-containing solution and the fluorine extraction residue. This step ensures the purity of the fluorine-containing solution and prevents impurities in the fluorine extraction residue from entering the subsequent reaction and affecting the product quality.

[0042] S3, subjecting the fluorine extraction residue and the lithium extraction agent to a lithium extraction reaction to obtain a first lithium-containing solution;

[0043] A lithium extraction agent is added to the fluorine extraction residue to react, and the lithium element therein is extracted into the solution to obtain a first lithium-containing solution. This step realizes the effective extraction of lithium elements and provides a lithium source for the subsequent preparation of lithium fluoride. After the lithium extraction reaction, solid-liquid separation is required to obtain the first lithium-containing solution.

[0044] In some embodiments, the lithium extracting agent includes at least one of the following: sulfate and chloride.

[0045] The lithium extraction agent can be one or both of sulfate and chloride, which can undergo double decomposition reaction with the lithium-containing compound in the fluorine extraction filter residue to achieve lithium extraction; the sulfate can be a combination of one or more of calcium sulfate, sodium sulfate, and aluminum sulfate, and the chloride can be a combination of one or more of calcium chloride, sodium chloride, and aluminum chloride.

[0046] In some embodiments, the amount of the lithium extraction agent added is 1.5 to 2 times the theoretical amount of the lithium extraction agent added, and the theoretical amount of the lithium extraction agent added is the mass of the lithium extraction agent required for the lithium extraction agent to react completely with the lithium in the fluorine extraction residue.

[0047] The amount of lithium extraction agent added can be 1.5 to 2 times the theoretical amount of lithium extraction agent added. The existence form of lithium in the fluorine extraction filter residue may be more complicated, and not all lithium can react quickly and completely with the lithium extraction agent. Increasing the amount of lithium extraction agent can make the lithium-containing compound react with the lithium extraction agent as much as possible, so that the lithium is fully converted into a water-soluble lithium salt, enters the solution phase, and realizes efficient extraction of lithium and improves the comprehensive recovery rate of lithium. The lithium extraction reaction is usually a reversible reaction. According to the principle of chemical equilibrium, increasing the concentration of the reactant lithium extraction agent is conducive to the reaction moving in the direction of generating the product (the first lithium-containing solution), which promotes the reaction to proceed more thoroughly, thereby improving the extraction rate of lithium. At the same time, avoid impurities consuming the lithium extraction agent. Exemplarily, the amount of lithium extraction agent added is 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, and 2 times the theoretical amount of lithium extraction agent added.

[0048] In some embodiments, the process parameters of the lithium extraction reaction include: temperature of 90° C. to 100° C., and time of 40 min to 80 min.

[0049] The temperature of the lithium extraction reaction can be 90°C to 100°C, which can make the lithium extraction agent fully contact and react with the lithium-containing compounds in the fluorine extraction filter residue, thereby ensuring the efficient dissolution of lithium in the overhaul slag. The time of the lithium extraction reaction can be 40min to 80min, achieving a good reaction degree and realizing efficient extraction of lithium. Exemplarily, the temperature of the lithium extraction reaction can be 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, etc.

[0050] S4, subjecting the first lithium-containing solution and the impurity remover to an impurity removal reaction to obtain a second lithium-containing solution;

[0051] An impurity remover is added to the first lithium-containing solution to remove impurities and remove impurity ions in the solution to obtain a pure second lithium-containing solution. After the impurity removal reaction, solid-liquid separation is required to obtain the second lithium-containing solution.

[0052] In some embodiments, the impurity remover includes at least one of the following: aqueous ammonia, sodium hydroxide, calcium hydroxide; and / or,

[0053] The pH of the impurity removal reaction system is 10-12.

[0054] The impurity remover can be a combination of one or more of ammonia water, sodium hydroxide, and calcium hydroxide. Ammonia water, sodium hydroxide, and calcium hydroxide ionize hydroxide ions in the solution to remove impurities such as aluminum, calcium, iron, silicon, calcium, and magnesium in the first lithium-containing solution. Using ammonia water as an impurity remover, on the one hand, the impurities such as aluminum, calcium, iron, silicon, calcium, and magnesium in the first lithium-containing solution can be removed by adjusting the pH of the solution. On the other hand, ammonia water does not introduce other impurity ions, and ammonium ions do not affect the quality of aluminum fluoride products. The pH of the impurity removal reaction system can be 10 to 12, and the impurities such as aluminum, calcium, iron, silicon, calcium, and magnesium in the first lithium-containing solution are fully removed to form a stable impurity precipitate, while lithium ions are stably present in the solution, thereby achieving effective separation of lithium ions and impurity ions and improving the purity of lithium products. And the pH is 10 to 12, which can also inhibit the occurrence of some side reactions. Exemplarily, the pH of the impurity removal reaction system can be 10, 10.5, 11.0, 11.5, 12, etc.

[0055] S5. Performing a precipitation reaction on the fluorine-containing solution and the second lithium-containing solution to obtain lithium fluoride.

[0056] The fluorine-containing solution and the second lithium-containing solution are mixed to perform a precipitation reaction, so that the fluorine ions and lithium ions are combined to generate high-purity lithium fluoride.

[0057] In some embodiments, the process parameters of the precipitation reaction include: temperature of 40°C to 50°C, and time of 60min to 120min.

[0058] The temperature of the precipitation reaction can be 40°C to 50°C, which is conducive to the reaction to form lithium fluoride. The fluorine in the fluorine-containing solution and the lithium in the second lithium-containing solution are fully precipitated, thereby improving the conversion rate of the precipitation reaction. The reaction time of 60min to 120min can ensure that the precipitation reaction is fully carried out. Exemplarily, the temperature of the precipitation reaction can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, etc.; the time can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc.

[0059] In some embodiments, the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.1 to 1.4 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution is the volume ratio of the fluorine-containing solution to the second lithium-containing solution required for the complete reaction of fluorine ions and lithium ions calculated based on the concentrations of fluorine ions and lithium ions in the precipitation reaction system.

[0060] The reaction ratio of the fluorine-containing solution to the second lithium-containing solution can be 1.1 to 1.4 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, which can make the actual reaction ratio of the fluorine-containing solution to the second lithium-containing solution slightly higher than the theoretical reaction ratio, and can ensure that the fluorine ions and lithium ions have enough opportunities to contact and react with each other, and ensure the complete precipitation of lithium. Since there may be other interfering factors in the reaction system or the reaction is not in an absolutely ideal state, the actual amount of fluorine-containing solution is high, which can compensate for the impact of these factors and ensure that the fluorine ions and lithium ions can fully combine to generate corresponding lithium fluoride. Exemplarily, the reaction ratio of the fluorine-containing solution to the second lithium-containing solution can be 1.1 times, 1.2 times, 1.3 times, 1.4 times, etc. of the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution.

[0061] The lithium fluoride is ultrasonically washed and then dried to obtain a lithium fluoride product. Ultrasonic washing of lithium fluoride can effectively remove impurity ions such as sodium and sulfate contained in lithium fluoride, thereby improving the purity of the lithium fluoride product. The lithium fluoride product can be returned to the aluminum electrolytic cell for recycling, and can also be used in the enamel industry, optical glass manufacturing, etc. to realize resource utilization.

[0062] The aluminum electrolysis overhaul slag extraction and preparation of lithium fluoride provided in the embodiment of the present application has the following advantages:

[0063] 1. By carrying out fluorine extraction and lithium extraction in steps, fluorine-containing solution and lithium-containing solution are prepared respectively. In the respective preparation processes, the introduction and removal of impurities can be more effectively controlled, thereby ensuring the purity of the two solutions. When the solution with low impurity content is subjected to precipitation reaction, the purity of the final lithium fluoride product is greatly improved to more than 99%, which makes the product widely used in fields with extremely high purity requirements, such as returning to the electrolytic cell for recycling, as well as in the enamel industry and optical glass fields;

[0064] 2. It effectively avoids the problem of fluorine and lithium being impurities to each other, reduces the loss of fluorine and lithium caused by impurity interference, makes the comprehensive recovery rate of lithium above 95%, improves the utilization efficiency of lithium resources in overhaul slag, and reduces the dependence on the mining of new lithium resources;

[0065] 3. The fluorine source required for the preparation of lithium fluoride comes directly from the overhaul slag itself, and there is no need to purchase additional fluorine sources, which greatly reduces the production cost. At the same time, the entire process only requires the addition of fluorine extracting agents, lithium extracting agents and impurity removers, which shortens the process, reduces equipment investment and energy consumption, and further reduces costs;

[0066] 4. The high-purity lithium fluoride obtained can be returned to the electrolytic cell for recycling, which not only reduces the discharge of waste, but also reduces the demand for new resources, which is in line with the concept of sustainable development. Its application in the enamel industry and optical glass fields has also further broadened the resource utilization of overhaul slag and achieved maximum utilization of resources.

[0067] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for the unrecorded specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, then carry out according to general international standards, normal conditions or according to the conditions recommended by the manufacturer.

[0068] Example 1

[0069] A method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, Figure 2 A schematic diagram of the actual process of extracting lithium fluoride from aluminum electrolysis overhaul slag provided in the embodiment of the present application; see Figure 2 ,include:

[0070] Aluminum electrolysis overhaul slag and a fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry; wherein the fluorine extracting agent is water, the fluorine extracting reaction is carried out at room temperature for 30 minutes, and the solid-liquid ratio of the fluorine extracting reaction system is 1:3;

[0071] Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0072] The fluorine extraction residue and the lithium extraction agent are subjected to a lithium extraction reaction, and solid-liquid separation is performed after the reaction to obtain a first lithium-containing solution; wherein the lithium extraction agent is calcium sulfate, the lithium extraction reaction is carried out at 90° C. for 80 minutes, and the amount of the lithium extraction agent added is 1.5 times the theoretical amount of the lithium extraction agent added;

[0073] The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction, and solid-liquid separation is performed after the reaction to obtain a second lithium-containing solution; wherein the impurity remover is aqueous ammonia, the impurity removal reaction is carried out at room temperature, and the pH of the impurity removal reaction system is 10.0;

[0074] The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride; wherein the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.1 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the precipitation reaction is carried out at 40° C. for 120 minutes;

[0075] The lithium fluoride is ultrasonically washed and then dried to obtain a lithium fluoride product.

[0076] The purity of the lithium fluoride product of Example 1 is 99.2%, meeting the standard of GB / T22666-2008 "Lithium Fluoride", and the comprehensive recovery rate of lithium is 95.6%.

[0077] Example 2

[0078] A method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, comprising:

[0079] Aluminum electrolysis overhaul slag and a fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry; wherein the fluorine extracting agent is water, the fluorine extracting reaction is carried out at room temperature for 40 minutes, and the solid-liquid ratio of the fluorine extracting reaction system is 1:4;

[0080] Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0081] The fluorine extraction residue and the lithium extraction agent are subjected to a lithium extraction reaction, and solid-liquid separation is performed after the reaction to obtain a first lithium-containing solution; wherein the lithium extraction agent is aluminum sulfate, the lithium extraction reaction is carried out at 95° C. for 60 minutes, and the amount of the lithium extraction agent added is 1.6 times the theoretical amount of the lithium extraction agent added;

[0082] The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction, and solid-liquid separation is performed after the reaction to obtain a second lithium-containing solution; wherein the impurity remover is aqueous ammonia, the impurity removal reaction is carried out at room temperature, and the pH of the impurity removal reaction system is 10.5;

[0083] The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride; wherein the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.2 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the precipitation reaction is carried out at 45° C. for 100 minutes;

[0084] The lithium fluoride is ultrasonically washed and then dried to obtain a lithium fluoride product.

[0085] The purity of the lithium fluoride product of Example 2 is 99.5%, meeting the standard of GB / T22666-2008 "Lithium Fluoride", and the comprehensive recovery rate of lithium is 97.2%.

[0086] Example 3

[0087] A method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, comprising:

[0088] Aluminum electrolysis overhaul slag and a fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry; wherein the fluorine extracting agent is water, the fluorine extracting reaction is carried out at room temperature for 50 minutes, and the solid-liquid ratio of the fluorine extracting reaction system is 1:5;

[0089] Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0090] The fluorine extraction residue and the lithium extraction agent are subjected to a lithium extraction reaction, and solid-liquid separation is performed after the reaction to obtain a first lithium-containing solution; wherein the lithium extraction agent is calcium chloride, the lithium extraction reaction is carried out at 100° C. for 40 minutes, and the amount of the lithium extraction agent added is 1.8 times the theoretical amount of the lithium extraction agent added;

[0091] The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction, and solid-liquid separation is performed after the reaction to obtain a second lithium-containing solution; wherein the impurity remover is aqueous ammonia, the impurity removal reaction is carried out at room temperature, and the pH of the impurity removal reaction system is 11.0;

[0092] The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride; wherein the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.3 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the precipitation reaction is carried out at 50° C. for 80 minutes;

[0093] The lithium fluoride is ultrasonically washed and then dried to obtain a lithium fluoride product.

[0094] The purity of the lithium fluoride product of Example 3 is 99.35%, which meets the standard of GB / T22666-2008 "Lithium Fluoride", and the comprehensive recovery rate of lithium is 96.9%.

[0095] Example 4

[0096] A method for extracting and preparing lithium fluoride from aluminum electrolysis overhaul slag, comprising:

[0097] Aluminum electrolysis overhaul slag and a fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry; wherein the fluorine extracting agent is water, the fluorine extracting reaction is carried out at room temperature for 45 minutes, and the solid-liquid ratio of the fluorine extracting reaction system is 1:4.5;

[0098] Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue;

[0099] The fluorine extraction residue and the lithium extraction agent are subjected to a lithium extraction reaction, and solid-liquid separation is performed after the reaction to obtain a first lithium-containing solution; wherein the lithium extraction agent is aluminum chloride, the lithium extraction reaction is carried out at 100° C. for 40 minutes, and the amount of the lithium extraction agent added is 2.0 times the theoretical amount of the lithium extraction agent added;

[0100] The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction, and solid-liquid separation is performed after the reaction to obtain a second lithium-containing solution; wherein the impurity remover is aqueous ammonia, the impurity removal reaction is carried out at room temperature, and the pH of the impurity removal reaction system is 12.0;

[0101] The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride; wherein the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.4 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution, and the precipitation reaction is carried out at 40° C. for 60 minutes;

[0102] The lithium fluoride is ultrasonically washed and then dried to obtain a lithium fluoride product.

[0103] The purity of the lithium fluoride product of Example 4 is 99.55%, which meets the standard of GB / T22666-2008 "Lithium Fluoride", and the comprehensive recovery rate of lithium is 96.6%.

[0104] Comparative Example 1

[0105] Based on the disclosure of Example 1, the following changes were made to Comparative Example 1: the impurity removal reaction was carried out at room temperature, and the pH of the impurity removal reaction system was 9.5.

[0106] Effect: The pH of the impurity removal reaction system is 9.5, and impurities such as aluminum and magnesium in the second lithium-containing solution are not completely removed, resulting in a lithium fluoride product purity of 98.6%.

[0107] Comparative Example 2

[0108] Based on the disclosure of Example 1, the following changes are made to Comparative Example 2: the reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 0.8 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution.

[0109] Effect: Since the fluorine-containing solution was not added in sufficient amount, the precipitation reaction was incomplete and the comprehensive recovery rate of lithium was reduced to 80.9%.

[0110] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0111] (1) The embodiment of the present application is effective in recycling aluminum electrolysis overhaul slag, with a short process and a small number of additives. The purity of the prepared lithium fluoride product is above 99%, and the comprehensive recovery rate of lithium is above 95%;

[0112] (2) By dissolving fluorine and lithium into lithium fluoride, it is only necessary to add fluorine extracting agent, lithium extracting agent and impurity removing agent. The fluorine source is the element of the overhaul slag itself and no external addition is required. Compared with the lithium carbonate preparation process, it can save the steps of concentration and lithium precipitation solution treatment. The process is short, less impurities are produced, and the efficiency is high.

[0113] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for extracting lithium fluoride from aluminum electrolysis overhaul slag, wherein the aluminum electrolysis overhaul slag contains fluorine and lithium, and the method comprises: The aluminum electrolysis overhaul slag and the fluorine extracting agent are subjected to a fluorine extracting reaction to obtain a first slurry; Performing solid-liquid separation on the first slurry to obtain a fluorine-containing solution and a fluorine extraction residue; The fluorine extraction filter residue and the lithium extraction agent are subjected to a lithium extraction reaction to obtain a first lithium-containing solution; The first lithium-containing solution and the impurity remover are subjected to an impurity removal reaction to obtain a second lithium-containing solution; The fluorine-containing solution and the second lithium-containing solution are subjected to a precipitation reaction to obtain lithium fluoride.

2. The method according to claim 1, characterized in that The fluorine extracting agent includes at least one of the following: water and sodium hydroxide.

3. The method according to claim 1, characterized in that The solid-liquid ratio of the fluorine extraction reaction system is 1:(3-5).

4. The method according to any one of claims 1 to 3, characterized in that: The process parameters of the fluorine extraction reaction include: temperature is room temperature, and time is 30min to 50min.

5. The method according to claim 1, characterized in that The lithium extracting agent includes at least one of the following: sulfate and chloride.

6. The method according to claim 1, characterized in that The amount of the lithium extracting agent added is 1.5 to 2 times the theoretical amount of the lithium extracting agent added, and the theoretical amount of the lithium extracting agent added is the mass of the lithium extracting agent required for the lithium extracting agent to react completely with the lithium in the fluorine extraction residue.

7. The method according to claim 1, 5 or 6, characterized in that: The process parameters of the lithium extraction reaction include: temperature of 90° C. to 100° C. and time of 40 min to 80 min.

8. The method according to claim 1, characterized in that The impurity remover comprises at least one of the following: aqueous ammonia, sodium hydroxide, calcium hydroxide; and / or, The pH of the impurity removal reaction system is 10-12.

9. The method according to claim 1, characterized in that: The process parameters of the precipitation reaction include: temperature of 40° C. to 50° C., and time of 60 min to 120 min.

10. The method according to claim 1 or 9, characterized in that: The reaction ratio of the fluorine-containing solution to the second lithium-containing solution is 1.1 to 1.4 times the theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution. The theoretical reaction ratio of the fluorine-containing solution to the second lithium-containing solution is the volume ratio of the fluorine-containing solution to the second lithium-containing solution required for the complete reaction of fluorine ions and lithium ions calculated based on the concentrations of fluorine ions and lithium ions in the precipitation reaction system.

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