Lithium extraction method from aluminum electrolytic cell overhaul residue

Abstract

This application provides a method for lithium extraction from aluminum electrolytic cell overhaul slag. The method includes: grinding the aluminum electrolytic cell overhaul slag to form a powder; mixing the powder with sulfuric acid and calcining it at a temperature range of 300℃ to 450℃ to form a calcined material; adding the calcined material to water and stirring thoroughly, then filtering to obtain a filtrate; adjusting the pH of the filtrate to 7 to 12 to form a lithium-aluminum coprecipitate; and calcining, water leaching, and filtering the lithium-aluminum coprecipitate to obtain a lithium-rich solution and Al2O3 solid. This invention applies a sulfuric acid calcination-water leaching process to lithium extraction from overhaul slag. The calcination temperature is 300℃ to 450℃, which is relatively low and can improve the lithium leaching rate. Furthermore, utilizing the characteristic that the aluminum electrolytic cell overhaul slag is rich in both aluminum and lithium, the lithium-aluminum coprecipitate method is used to efficiently extract lithium from the leachate and simultaneously recover Al2O3 without adding an additional aluminum source, achieving efficient separation of lithium and aluminum, thereby reducing impurities in the lithium-containing solution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of comprehensive utilization of electrolytic aluminum industrial waste resources, and particularly relates to a method for extracting lithium from overhaul residue of an aluminum electrolysis cell. BACKGROUND

[0002] The overhaul residue contains toxic substances and heavy metals such as cyanide and lead. In addition, lithium, fluorine and aluminum are contained in the overhaul residue of the aluminum electrolysis cell because lithium fluoride is added as an electrolysis aid in the electrolytic aluminum process and a part of lithium is associated with aluminum ore.

[0003] In the prior art, the method for extracting lithium from the overhaul residue usually adopts the method of sulfating roasting and sulfuric acid leaching. However, the roasting temperature is high and the leaching is insufficient. SUMMARY

[0004] The present application provides a method for extracting lithium from overhaul residue of an aluminum electrolysis cell, which is beneficial to improving the lithium recovery rate.

[0005] In a first aspect, the present application provides a method for extracting lithium from overhaul residue of an aluminum electrolysis cell, which comprises the following steps:

[0006] Grinding the overhaul residue of the aluminum electrolysis cell to form a powder material;

[0007] Mixing the powder material with sulfuric acid uniformly and roasting the mixture at a temperature ranging from 300 DEG C to 450 DEG C to form a roasted material;

[0008] Adding the roasted material into water and stirring sufficiently to obtain a filtrate by filtration;

[0009] Adjusting the pH value of the filtrate to 7-12 to form a lithium-aluminum co-precipitate;

[0010] Roasting, water leaching and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid.

[0011] According to the first aspect, in a possible implementation manner, in the step of mixing the powder material with sulfuric acid uniformly and roasting the mixture at a temperature ranging from 300 DEG C to 450 DEG C to form a roasted material, the mass ratio of the powder material to the sulfuric acid is (0.8-1.6):1, and the roasting time is 1h to 3h.

[0012] According to the first aspect, in a possible implementation manner, after the step of roasting, water leaching and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid, the method further comprises the following steps:

[0013] Adding the Al2O3 solid into a NaOH solution to obtain a sodium tetrahydroxy aluminate solution;

[0014] Adding the sodium tetrahydroxy aluminate solution into a solution containing NaF to obtain Na3AlF6.

[0015] wherein the molar ratio of the Al2O3 solid to NaOH is 1:2.

[0016] According to the first aspect, in a possible implementation manner, the method further includes:

[0017] The waste gas generated in the step of mixing the powder material with sulfuric acid uniformly and roasting at a temperature ranging from 300 DEG C to 450 DEG C to form a roasted material is absorbed by pure water to generate hydrofluoric acid;

[0018] The hydrofluoric acid is mixed with the Al2O3 solid and reacts sufficiently to obtain aluminum fluoride.

[0019] According to the first aspect, in a possible implementation manner, the waste gas generated in the step of mixing the powder material with sulfuric acid uniformly and roasting at a temperature ranging from 300 DEG C to 450 DEG C to form a roasted material is absorbed by an alkali liquor, and the alkali liquor includes one or more of sodium carbonate, sodium hydroxide, calcium oxide, and calcium hydroxide.

[0020] According to the first aspect, in a possible implementation manner, the step of adjusting the pH value of the filtrate to 7-12 to form lithium-aluminum co-precipitate includes:

[0021] The pH value of the filtrate is adjusted to 7-12 by adding one of sodium hydroxide, ammonia water, ammonia gas, sodium carbonate, calcium oxide, potassium hydroxide, and calcium hydroxide to form lithium-aluminum co-precipitate.

[0022] According to the first aspect, in a possible implementation manner, in the step of roasting, water leaching, and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and an Al2O3 solid, the roasting temperature is 300 DEG C-700 DEG C, and the roasting time is 20 min-60 min.

[0023] According to the first aspect, in a possible implementation manner, the particle size of the powder material is less than 200 mesh.

[0024] The method for extracting lithium from an aluminum electrolysis cell overhaul residue provided in the application applies the sulfuric acid roasting-water leaching process to the extraction of lithium from an aluminum electrolysis cell overhaul residue, the roasting temperature is 300 DEG C-450 DEG C, the roasting temperature is relatively low, and the leaching rate of lithium can be improved. In addition, the aluminum electrolysis cell overhaul residue is rich in both aluminum and lithium, and the lithium-aluminum co-precipitation method is used to efficiently extract lithium from the leaching solution without adding an aluminum source and to recover Al2O3 at the same time, thereby realizing efficient separation of lithium and aluminum and reducing impurities in the lithium-containing solution. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and all of the embodiments of the present application can be obtained by those skilled in the art without any creative effort based on these drawings.

[0026] Figure 1 is a flowchart of a method for extracting lithium from the aluminum electrolysis cell overhaul slag in an embodiment;

[0027] Figure 2 is a flowchart of a method for extracting lithium from the aluminum electrolysis cell overhaul slag in another embodiment;

[0028] Figure 3 is a flowchart of a method for extracting lithium from the aluminum electrolysis cell overhaul slag in an embodiment.

[0029] Reference signs: DETAILED DESCRIPTION

[0030] The words "preferably", "more preferably", and the like in the present application refer to the embodiments of the present application which can provide certain beneficial effects in certain cases. However, other embodiments can also be preferred in the same or other cases. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not usable, nor is it intended to exclude other embodiments from the scope of the present application.

[0031] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum value and the maximum value of the range, and each value between the minimum value and the maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present application.

[0033] The reagents, methods and devices used in the present application are conventional reagents, methods and devices in the technical field unless otherwise specified.

[0034] The present application provides a method for extracting lithium from aluminum electrolysis cell overhaul slag, such asFigure 1 As shown, the method comprises the following steps:

[0035] Step S10, grinding the aluminum electrolysis cell overhaul slag to form a powder material;

[0036] The aluminum electrolysis cell overhaul slag is refined into powder by grinding, so that subsequent chemical reactions and physical treatment can be more fully and efficiently carried out.

[0037] The aluminum electrolysis cell overhaul slag can be ground using grinding equipment such as a ball mill, a vibration mill, etc. The particle size of the ground powder material needs to be less than 200 mesh. After grinding, sieving operation needs to be carried out to remove possible coarse particles, ensuring that the particle size of all powder materials meets the requirement of less than 200 mesh. Sieving can be carried out using a screen or a vibrating screen, etc.

[0038] Step S20, uniformly mixing the powder material with sulfuric acid and calcining at a temperature range of 300-450°C to form a calcined material;

[0039] The powder material and sulfuric acid are mixed in a certain mass ratio (0.8-1.6):1. The purpose is to ensure that the sulfuric acid can fully react, while avoiding waste and environmental pollution caused by excessive use.

[0040] Uniform mixing of the powder material and sulfuric acid needs to be ensured during the mixing process, which can be achieved by stirring, ball milling, etc. Uniform mixing helps the full chemical reaction in the subsequent calcination process.

[0041] Through calcination, the lithium element in the powder material reacts with sulfuric acid to form a soluble lithium salt, while removing impurities and organic matter. The process of sulfuric acid calcination mainly occurs as follows:

[0042] 2Na3AlF66+6H2SO4=3Na2SO+Al2(SO4)3+12HF↑

[0043] 2AlF3+3H2SO4=Al2(SO4)3+6HF↑

[0044] 2LiF+H2SO4=Li2SO4+2HF↑

[0045] Li2O+H2SO4=Li2SO4+H2O

[0046] Al2O3+3H2SO4=Al2(SO4)3+H2O

[0047] Li2SO4+H2SO4+2NaF=2NaLi(SO4)+2HF↑

[0048] The calcination process needs to be carried out at a temperature range of 300℃ to 450℃. This temperature range is determined based on the kinetic and thermodynamic properties of the chemical reaction, aiming to ensure that the reaction can be fully carried out while avoiding equipment damage and energy consumption increase caused by high temperature.

[0049] The calcination time is usually 1 hour to 3 hours. The length of the calcination time depends on factors such as the properties of the powder material, the concentration of sulfuric acid, and the reaction temperature. Reasonable calcination time helps to ensure the completeness of the reaction and the quality of the product.

[0050] During the calcination process, waste gas containing harmful substances such as sulfur dioxide will be generated. In order to protect the environment, these waste gases need to be treated. The main components of the waste gas are HF and a small amount of SO2 and SO3, which can be treated by alkali absorption device. The alkali solution includes one or more of sodium carbonate, sodium hydroxide, calcium oxide, and calcium hydroxide. These alkalis can chemically react with harmful substances such as sulfur dioxide in the waste gas to convert them into harmless substances.

[0051] For example, using sodium carbonate solution to absorb waste gas, the main reaction is as follows:

[0052] 2HF + Na2CO3 = 2NaF + CO2↑ + H2O

[0053] Step S30, adding the calcined material to water and stirring thoroughly, and filtering to obtain the filtrate;

[0054] The calcined material is added to water at a solid-liquid ratio of 1:(2-6) to ensure that the soluble components in the calcined material can be fully dissolved in water, while avoiding excessive water causing difficulties in subsequent processing.

[0055] The stirring process is carried out at a temperature range of 50℃ to 90℃. The selection of this temperature range helps to accelerate the dissolution rate of the soluble components in the calcined material, while avoiding equipment damage or energy consumption increase caused by high temperature.

[0056] The stirring time is 0.5 hours to 2 hours. The length of the stirring time depends on factors such as the properties of the calcined material, the solid-liquid ratio, and the stirring temperature. Adequate stirring time helps to ensure that the soluble components in the calcined material can be completely dissolved in water.

[0057] An appropriate stirring device (such as a stirring tank, stirring paddle, etc.) can be used for stirring to ensure sufficient contact and mixing between the calcined material and water.

[0058] Through the filtering operation, the aqueous solution (filtrate) in which the soluble components are dissolved is separated from the undissolved solid residue (filtrate).

[0059] Step S40, adjust the pH value of the filtrate to 7-12 to form a lithium-aluminum co-precipitate;

[0060] By precisely regulating the pH value of the filtrate, aluminum ions are induced to precipitate in the form of amorphous aluminum hydroxide (Al(OH)3). Aluminum hydroxide has selective adsorption capacity for lithium ions, thereby forming lithium-aluminum co-precipitate, laying the foundation for subsequent separation and purification of lithium and aluminum.

[0061] Sodium hydroxide (NaOH) is added to the filtrate as a pH regulator to adjust the pH of the solution to a range of 7 to 12. It should be noted that if the pH exceeds 12, aluminum may be converted to sodium metaaluminate (NaAlO2), which will adversely affect the recovery of aluminum. The specific reaction equation is shown below:

[0062] Li2SO4 + Al2(SO4)3 + NaOH + nH2O = Li2SO4 · 2Al(OH)3 · nH2O↓ + 3Na2SO4

[0063] In addition to NaOH, ammonia, ammonia gas, sodium carbonate, calcium oxide, potassium hydroxide, or calcium hydroxide can also be used as a pH regulator to achieve the purpose of adjusting the pH and forming lithium-aluminum co-precipitate.

[0064] After the formation of lithium-aluminum co-precipitate, it is separated from the solution by methods such as standing, centrifugation, or filtration.

[0065] Step S50, roasting, water immersion, and filtration of the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid.

[0066] Through roasting treatment, the aim is to change the phase structure of the lithium-aluminum co-precipitate, convert the aluminum element into aluminum oxide form which is easier to separate, and promote the release of lithium elements, creating favorable conditions for subsequent water immersion operations.

[0067] The roasting temperature is controlled in the range of 300°C to 700°C, and the roasting time is 20 to 60 minutes. These conditions are based on the thermal stability of the lithium-aluminum co-precipitate and the temperature and time required for the conversion of aluminum to aluminum oxide.

[0068] The lithium-aluminum co-precipitate is placed in a roasting furnace and roasted at the set temperature and time. During the roasting process, the atmosphere inside the furnace should be kept stable to avoid adversely affecting the phase structure of the lithium-aluminum co-precipitate.

[0069] After roasting, the lithium element mainly exists in a soluble form, while the aluminum element is converted into aluminum oxide solid. The purpose of water immersion is to dissolve the soluble lithium element in the roasting product into water to form a lithium-rich solution.

[0070] The water leaching operation is usually carried out at room temperature, and the amount of water used should be sufficient to ensure that the soluble lithium elements in the calcined product can be fully dissolved.

[0071] The calcined product is added to an appropriate amount of water, and is subjected to sufficient stirring and soaking. Subsequently, the water solution (lithium-rich solution) in which the lithium elements are dissolved is separated from the undissolved alumina solids through a filtration operation.

[0072] The purpose of the filtration operation is to completely separate the lithium-rich solution from the alumina solids, so as to subsequently further purify the lithium-rich solution and recycle and utilize the alumina solids.

[0073] The method for extracting lithium from the aluminum electrolytic cell overhaul residue provided by the present application applies the sulfuric acid roasting- water leaching process to the extraction of lithium from the overhaul residue. The roasting temperature is 300-450°C, which is relatively low, and the leaching rate of lithium can be improved. Moreover, the aluminum electrolytic cell overhaul residue is rich in both aluminum and lithium, and the lithium-aluminum co-precipitation method is used to efficiently extract lithium from the leaching solution without adding additional aluminum source and simultaneously recycle Al2O3, so as to realize efficient separation of lithium and aluminum and reduce the impurities in the lithium-containing solution.

[0074] In some embodiments, as shown in Figure 2 and Figure 3 the step S50 is followed by:

[0075] Step S61, adding the Al2O3 solids to the NaOH solution to obtain a sodium tetrahydroxy aluminate solution;

[0076] The molar ratio of the Al2O3 solids to the NaOH is kept at 1:2, which is based on the stoichiometric relationship of the chemical reaction equation Al2O3+2NaOH+3H2O=2NaAl(OH)4.

[0077] The reaction is usually carried out under certain temperature and stirring conditions to ensure sufficient reaction of the Al2O3 solids with the NaOH solution.

[0078] Step S62, adding the sodium tetrahydroxy aluminate solution to a solution containing NaF to obtain Na3AlF6;

[0079] The sodium tetrahydroxy aluminate solution obtained in step S61 is converted into sodium aluminum fluoride (Na3AlF6). After the reaction is completed, Na3AlF6 is separated from the reaction mixture by evaporation, crystallization or other appropriate separation methods. It is a valuable fluoride and can be used for various industrial applications.

[0080] The solution containing NaF can be a solution of sodium carbonate or sodium hydroxide formed by absorbing the waste gas generated in step S20. Recycling Al2O3 and HF waste gas generated by calcination for the production of by-products has high economic benefits and cost advantages.

[0081] In some embodiments, step S50 is followed by:

[0082] Mixing the hydrofluoric acid with the Al2O3 solid and allowing them to react sufficiently to obtain aluminum fluoride.

[0083] Mixing Al2O3 solid with hydrofluoric acid solution in a certain molar ratio, and reacting under appropriate temperature and stirring conditions. The selection of molar ratio should be based on the stoichiometric relationship of the chemical reaction equation Al2O3 + 6HF = 2AlF3 + 3H2O, but in actual operation, it may need to be adjusted according to the specific circumstances. After the reaction is completed, aluminum fluoride is separated from the reaction mixture through steps such as filtration, washing and drying. Aluminum fluoride is widely used in aluminum industry, ceramic industry, glass industry, fluorine chemical industry and other fields, and plays an important role as fluxing agent, additive and raw material.

[0084] The hydrofluoric acid can be a solution formed by absorbing the waste gas generated in step S20 with pure water. Recycling Al2O3 and HF waste gas generated by calcination for the production of by-products has high economic benefits and cost advantages.

[0085] The following is one of the embodiments of the present application, which uses raw ore from the discarded cathode carbon block of a certain electrolytic aluminum enterprise in Guangxi for repair. The following is the composition content data of the carbon block after testing as follows:

[0086] Li Ca Mg Fe Na K Al SO4 2～ ]] F Cathode carbon block (raw ore) / wt% 0.371 1.639 0.161 1.209 16.846 0.583 9.426 0.692 9.519

[0087] The cathode carbon block is broken in a crusher and then put into a vibrating mill machine for 15 minutes. After grinding, it is sieved to 200 mesh. The sieved raw ore and sulfuric acid are mixed at a ratio of 1.2:1 and then moved into a crucible. Then, the mixture is calcined in a muffle furnace at 360°C for 2 hours. After calcination, the calcined material in the crucible is moved into a stirring device and then water leaching is performed. The solid-liquid ratio should be kept at 1:3. After stirring at 80°C for 1 hour, the first filter residue and the first filtrate are obtained by filtration. The pH of the first filtrate is adjusted to 12 with NaOH. After stirring until the reaction is complete, the second filter residue and the second filtrate are obtained by filtration. The second filter residue is calcined in a muffle furnace at 400°C for 30 minutes and then water leaching is performed. The solid-liquid ratio is kept at 1:3. After stirring for 10 minutes in a stirring device, the filtrate is obtained as a lithium-containing solution, and the filter residue is Al2O3. The obtained Al2O3 is added to NaOH to keep the molar ratio of Al2O3 and NaOH at 1:2. The mixture is added to the alkali solution containing fluorine-containing waste gas to obtain a Na3AlF6 solution. The calcination-water leaching-lithium-containing solution in this example is detected. The lithium recovery extraction rate in this example is 93.6%, which has a relatively high lithium extraction rate.

[0088] Example 2

[0089] The implementation of this example is basically the same as that of Example 1, except that the calcination conditions are changed. The raw ore used in this example is still the cathode carbon block of a certain electrolytic aluminum enterprise in Guangxi. The specific implementation is as follows:

[0090] The raw ore carbon block is broken in a crusher and then put into a vibrating mill machine for 15 minutes. After grinding, it is sieved to 200 mesh. The raw ore and sulfuric acid are mixed at a ratio of 1.2:1 and then moved into a crucible. Then, the mixture is calcined in a muffle furnace at 360°C for 2 hours. After calcination, the calcined material in the crucible is moved into a stirring device and then water leaching is performed. The solid-liquid ratio should be kept at 1:3. After stirring at 80°C for 1 hour, the first filter residue and the first filtrate are obtained by filtration. The pH of the first filtrate is adjusted to 12 with NaOH. After stirring until the reaction is complete, the second filter residue and the second filtrate are obtained by filtration. The second filter residue is calcined in a muffle furnace at 400°C for 30 minutes and then water leaching is performed. The solid-liquid ratio is kept at 1:3. After stirring for 10 minutes in a stirring device, the filtrate and the filter residue are obtained as a lithium-containing solution and Al2O3, respectively. The obtained Al2O3 is added to NaOH to keep the molar ratio of Al2O3 and NaOH at 1:2. The mixture is added to the alkali solution containing fluorine-containing waste gas to obtain a Na3AlF6 solution. The lithium-containing solution in this example is detected. The lithium extraction rate in this example is 90.0%.

[0091] Example 3

[0092] The embodiment is basically the same as embodiment 1, except that the conditions in step 4 and step 5 are changed, and the raw ore used in this embodiment is still the cathode carbon block of a certain electrolytic aluminum enterprise in Guangxi. The specific implementation is as follows:

[0093] After the raw ore is crushed in a crusher, it is put into a vibration mill for 15 minutes of grinding, and then sieved to 200 mesh. The raw ore and sulfuric acid are mixed at a ratio of 1.2:1 and then put into a crucible for roasting at 360°C in a muffle furnace, and the temperature is kept for 2 hours. After the roasting is completed, the roasted material in the crucible is moved into a stirring device together, and water is added for water immersion. The solid-liquid ratio during water immersion should be kept at 1:3, and after stirring at 80°C for 1 hour, the first filter residue and the first filtrate are obtained by filtration. The pH of the first filtrate is adjusted to 10 with NaOH, and after stirring until the reaction is complete, the second filter residue and the second filtrate are obtained by filtration. Different from embodiment 1, the second filter residue is roasted at 300°C in a muffle furnace for 20 minutes, and then water is added for water immersion, with a solid-liquid ratio of 1:3. After being moved into a stirring device and stirred for 10 minutes, the filtrate obtained is a lithium-containing solution, and the filter residue is Al2O3. The obtained Al2O3 is mixed with NaOH to keep the molar ratio of Al2O3 to NaOH at 1:2, and then added to the alkali solution containing fluorine-containing waste gas collected, to obtain a Na3AlF6 solution.

[0094] The lithium aluminum fluoride recovery rates of the various embodiments are shown in Table 1

[0095] Table 1: Lithium aluminum fluoride recovery rate table of various embodiments

[0096] Fluorine volatilisation rate % Lithium leaching rate % Aluminium leaching rate % Lithium recovery rate % Aluminium recovery rate % Example 1 94.5 96.2 77.4 93.6 75.9 Example 2 88.4 92.8 70.6 90.0 68.3 Example 3 93.7 95.8 76.5 91.2 72.1

[0097] The applicant declares that the above embodiments illustrate the detailed method of the present application, but the present application is not limited to the above detailed method, i.e. it does not mean that the present application must rely on the above detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the method of the present application, addition of auxiliary steps, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for extracting lithium from the slag of an aluminum electrolytic cell overhaul, characterized in that, The method comprises: grinding the overhaul residue of an aluminum electrolysis cell to form a powder material; mixing the powder material with sulfuric acid uniformly and calcining at a temperature range of 300-450 DEG C to form a calcined material; adding the calcined material into water and stirring thoroughly, and filtering to obtain a filtrate; adjusting the pH value of the filtrate to 7-12 to form a lithium-aluminum co-precipitate; calcining, water immersion and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid; in the step of mixing the powder material with sulfuric acid uniformly and calcining at a temperature range of 300-450 DEG C to form a calcined material, the mass ratio of the powder material to the sulfuric acid is (0.8-1.6):1, and the calcining time is 1-3 hours; the step of calcining, water immersion and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid further comprises: adding the Al2O3 solid into a NaOH solution to obtain a sodium tetrahydroxy aluminate solution; adding the sodium tetrahydroxy aluminate solution into a solution containing NaF to obtain Na3AlF6; wherein the molar ratio of the Al2O3 solid to NaOH is 1:2; in the step of calcining, water immersion and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid, the calcining temperature is 300-700 DEG C, and the calcining time is 20-60 minutes.

2. The aluminium reduction cell refurbishment slag lithium extraction process as claimed in claim 1, characterised in that, The method further comprises: absorbing the waste gas generated in the step of mixing the powder material with sulfuric acid uniformly and calcining at a temperature range of 300-450 DEG C to form a calcined material by pure water to generate hydrofluoric acid; mixing the hydrofluoric acid with the Al2O3 solid and reacting thoroughly to obtain aluminum fluoride.

3. The aluminium reduction cell refurbishment slag lithium extraction process as claimed in claim 1, characterised in that, absorbing the waste gas generated in the step of mixing the powder material with sulfuric acid uniformly and calcining at a temperature range of 300-450 DEG C to form a calcined material by an alkali liquor, wherein the alkali liquor comprises one or more of sodium carbonate, sodium hydroxide, calcium oxide and calcium hydroxide.

4. The aluminum electrolysis cell repair slag lithium extraction method of claim 1, characterized by, in the step of adjusting the pH value of the filtrate to 7-12 to form a lithium-aluminum co-precipitate: adding one of sodium hydroxide, ammonia water, ammonia gas, sodium carbonate, calcium oxide, potassium hydroxide and calcium hydroxide to the filtrate to adjust the pH value to 7-12 to form a lithium-aluminum co-precipitate.

5. The aluminum electrolysis cell repair slag lithium extraction method of claim 1, characterized by, in the step of calcining, water immersion and filtering the lithium-aluminum co-precipitate to obtain a lithium-rich solution and Al2O3 solid, the calcining temperature is 300-700 DEG C, and the calcining time is 20-60 minutes.

6. The aluminum electrolysis cell repair slag lithium extraction method of claim 1, characterized by, The particle size of the powder material is less than 200 mesh.

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