Process for the recovery of lithium from aluminium-based scrap

Abstract

The application discloses a method for recovering lithium from aluminum-based impurity removal residues, and belongs to the technical field of waste recovery. The method comprises the following steps: mixing the aluminum-based impurity removal residues with a roasting aid and roasting to obtain roasting clinker; adding water to the roasting clinker for leaching, and obtaining a lithium salt solution after impurity removal; adding a precipitant to the lithium salt solution for lithium precipitation treatment, and obtaining a lithium-containing precipitate. The application solves the technical problem that the recovery rate of lithium from conventional aluminum-based impurity removal residues is low.

Description

Technical Field

[0001] This application relates to the field of waste recycling technology, and in particular to a method for recovering lithium from aluminum-based impurity removal slag. Background Technology

[0002] Spodumene and lepidolite are the main lithium-containing ore raw materials for producing lithium carbonate. Processing the lithium-containing ore through the sulfuric acid process, sulfate roasting, or sulfuric acid roasting yields a lithium-containing sulfate solution. Calcium hydroxide or calcium oxide can then be added to this solution to produce a solid slag, thereby removing aluminum from the solution. However, during this process, due to the adsorption properties of aluminum hydroxide, some lithium enters the solid slag and is difficult to recover through washing, resulting in lithium loss.

[0003] To extract lithium from aluminum-based impurity removal slag, acidic solutions are typically used for direct leaching. During this process, lithium, aluminum, and fluorine all react with the acidic solution, making it difficult to effectively separate lithium from aluminum and fluorine, resulting in a low lithium recovery rate from the aluminum-based impurity removal slag.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this application is to provide a method for recovering lithium from aluminum-based impurity removal slag, aiming to solve the technical problem of low lithium recovery rate in conventional aluminum-based impurity removal slag.

[0006] To achieve the above objectives, this application provides a method for recovering lithium from aluminum-based impurity removal slag, wherein the aluminum-based impurity removal slag is a solid slag generated after aluminum removal from lithium-containing materials during the lithium extraction process, and the method for recovering lithium from the aluminum-based impurity removal slag includes the following steps:

[0007] Aluminum-based impurity-removing slag is mixed with a roasting aid and roasted to obtain roasted clinker;

[0008] Water is added to the roasted clinker for leaching, and after removing impurities, a lithium salt solution is obtained.

[0009] A precipitant is added to the lithium salt solution to perform lithium precipitation treatment, resulting in a lithium-containing precipitate.

[0010] Optionally, the step of mixing and calcining the aluminum-based impurity removal slag with the calcination aid includes:

[0011] The aluminum-based impurity removal slag is mixed with a calcination aid and pelletized to obtain a mixture pellet, which is then calcined.

[0012] And / or, the mass ratio of the aluminum-based impurity removal slag to the calcination aid is 1:(0.02-0.2).

[0013] Optionally, the roasting temperature is 600-900℃ and the roasting time is 0.5-5h.

[0014] Optionally, the calcination aid includes at least one of sodium sulfate and potassium sulfate.

[0015] Optionally, the step of adding water to the roasted clinker for leaching to remove impurities and obtaining a lithium salt solution includes:

[0016] Water is added to the roasted clinker for leaching, and the leachate is obtained after solid-liquid separation.

[0017] The pH of the leachate was adjusted to 9-12, and a lithium salt solution was obtained after solid-liquid separation.

[0018] Optionally, the liquid-solid ratio of the water to the roasted clinker is (1-3):1;

[0019] And / or, the leaching temperature is 10-40℃ and the leaching time is 0.5-5h.

[0020] Optionally, before the step of adding the precipitant to the lithium salt solution for lithium precipitation, the method further includes:

[0021] The lithium salt solution is concentrated, and the resulting concentrate is mixed with the precipitant for lithium precipitation treatment, wherein the concentration of lithium oxide in the concentrate is greater than 15 g / L.

[0022] Optionally, the precipitant includes: sodium carbonate;

[0023] And / or, the reaction temperature of the lithium deposition treatment is 85-95°C.

[0024] Optionally, the aluminum-based impurity removal slag is a solid slag produced after adjusting the pH value to remove aluminum during the lithium extraction process of lithium-containing materials, and the aluminum-based impurity removal slag contains aluminum hydroxide.

[0025] Optionally, after the step of adding the precipitant to the lithium salt solution for lithium precipitation, the method further includes:

[0026] After lithium precipitation treatment, solid-liquid separation is performed to obtain the lithium-containing precipitate and the first mother liquor. The first mother liquor is acidified and evaporated to crystallize, resulting in calcination aid crystals and the second mother liquor.

[0027] The second mother liquor, together with the precipitant and the lithium salt solution, is subjected to lithium precipitation treatment and subsequent processing.

[0028] This application discloses a method for recovering lithium from aluminum-based impurity removal slag. The method involves mixing the solid slag (aluminum-based impurity removal slag) generated after aluminum removal during lithium extraction with a roasting aid and then roasting it to obtain roasted clinker. By adding the roasting aid, the lithium in the aluminum-based impurity removal slag is converted into soluble lithium salts during roasting, while aluminum and fluorine in the slag are insoluble. Water is then added to the roasted clinker for leaching. After leaching, impurities are removed, separating lithium from aluminum and fluorine to obtain a lithium salt solution. A precipitant is then added to the lithium salt solution for lithium precipitation, resulting in a high-purity lithium precipitate. This method effectively recovers lithium from the aluminum-based impurity removal slag and improves the lithium recovery rate. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart of a method for recovering lithium from aluminum-based impurity removal slag according to an embodiment of this application.

[0030] Figure 2 This is a process flow diagram of the lithium recovery method from aluminum-based impurity removal slag involved in the embodiments of this application.

[0031] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional finished products that can be purchased commercially.

[0033] Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0034] To extract lithium from aluminum-based impurity slag, direct leaching with sulfuric acid is typically used, or the aluminum-based impurity slag is mixed with sulfuric acid, roasted, and then leached. However, because aluminum-based impurity slag has a high aluminum content, adding sulfuric acid to it causes the aluminum in the slag to enter the leaching solution along with the slag. This necessitates further removal of impurities from the aluminum in the leaching solution, which generates new aluminum-based impurity slag and may adsorb some lithium, resulting in a low lithium recovery rate.

[0035] In view of this, this application proposes a method for recovering lithium from aluminum-based impurity removal slag. The method involves mixing the solid slag (aluminum-based impurity removal slag) generated after aluminum removal during the lithium extraction process with a roasting aid and then roasting it to obtain roasted clinker. By adding the roasting aid, the lithium in the aluminum-based impurity removal slag is converted into soluble lithium salts during roasting, while the aluminum and fluorine in the slag are insoluble. Water is then added to the roasted clinker for leaching. After leaching, impurities are removed, separating lithium from aluminum and fluorine to obtain a lithium salt solution. A precipitant is then added to the lithium salt solution for lithium precipitation, resulting in a high-purity lithium precipitate. This method effectively recovers lithium from the aluminum-based impurity removal slag and improves the lithium recovery rate.

[0036] The first aspect of this application provides a method for recovering lithium from aluminum-based impurity removal slag, referring to... Figure 1 Methods for recovering lithium from aluminum-based impurity removal slag include:

[0037] Step S10: Mix the aluminum-based impurity removal slag with the roasting aid and roast to obtain roasted clinker;

[0038] During the lithium extraction process, aluminum removal from lithium-containing materials produces solid slag, namely aluminum-based impurity removal slag. Due to the adsorption properties of aluminum hydroxide in the aluminum-based impurity removal slag, some lithium enters the slag, resulting in lithium loss. In order to recover lithium from the aluminum-based impurity removal slag, the slag is mixed with a roasting aid and roasted at high temperature. High-temperature roasting promotes the displacement reaction between the roasting aid and the lithium in the slag, converting the lithium into soluble lithium salts to obtain roasted clinker.

[0039] In one feasible embodiment, the aluminum-based impurity removal slag is a solid slag produced after adjusting the pH value to remove aluminum during the lithium extraction process of lithium-containing materials, and the aluminum-based impurity removal slag contains aluminum hydroxide.

[0040] Optionally, the aluminum-based impurity removal slag is a solid slag produced after adding calcium hydroxide and / or calcium oxide to lithium-containing materials during the lithium extraction process to adjust the pH value and remove aluminum. The solid slag contains aluminum hydroxide. The lithium-containing materials can be lithium-containing ores, such as spodumene and lepidolite, or one or more of waste lithium battery cathode materials, waste electrolytes, and waste polishing powder.

[0041] In this embodiment, during the lithium extraction process, the aluminum in the lithium-containing material can be converted into aluminum hydroxide precipitate by adjusting the pH, thereby removing aluminum through solid-liquid separation. However, due to the adsorption properties of aluminum hydroxide, some lithium enters the solid slag, resulting in lithium loss. Therefore, lithium is recovered from the solid slag generated after adjusting the pH value to remove aluminum during the lithium extraction process of the lithium-containing material, so as to achieve efficient use of mineral resources.

[0042] In one feasible embodiment, the lithium oxide content in the aluminum-based impurity removal slag is higher than 0.2 wt.%.

[0043] In this embodiment, in actual production processes, if the lithium content in the aluminum-based impurity removal slag is too low, the amount of lithium that can be recovered will also be small, resulting in production costs being lower than input costs; therefore, it is determined that the lithium oxide content in the aluminum-based impurity removal slag is higher than 0.2 wt.%, which has a higher return on investment.

[0044] In one feasible embodiment, step S10, the step of mixing and calcining the aluminum-based impurity removal slag with the calcination aid, includes:

[0045] Step S11: Mix the aluminum-based impurity removal slag with the calcination aid and pelletize the mixture to obtain mixed pellets, and then calcin the mixed pellets.

[0046] And / or, the mass ratio of the aluminum-based impurity removal slag to the calcination aid is 1:(0.02-0.2).

[0047] Aluminum-based impurity removal slag is mixed with a calcination aid and an appropriate amount of water, and then pelletized to obtain mixed pellets. Pelletizing ensures sufficient porosity between the resulting pellets, which are then calcined to allow for rapid heat transfer and more uniform heating. Furthermore, pelletizing allows for more thorough contact between the aluminum-based impurity removal slag and the calcination aid, facilitating the reaction and reducing the risk of melting at high temperatures, thus improving production continuity. The pellets are then calcined, with the mass ratio of aluminum-based impurity removal slag to calcination aid being 1:(0.02-0.2).

[0048] Optionally, the mass ratio of aluminum-based impurity removal slag to calcination aid can be 1:0.02, 1:0.04, 1:0.06, 1:0.08, 1:0.1, 1:0.12, 1:0.14, 1:0.16, 1:0.18, 1:0.2, etc.

[0049] In this embodiment, the roasting aid can replace lithium in the aluminum-based impurity slag with soluble lithium salts through a displacement reaction, thereby achieving lithium extraction. However, if the quality of the roasting aid is low, the lithium in the aluminum-based impurity slag will not undergo a sufficient displacement reaction, resulting in some lithium not being replaced with soluble lithium salts, thus reducing the lithium recovery rate. Furthermore, since the aluminum-based impurity slag is a solid slag produced after aluminum removal from lithium-containing materials during lithium extraction, the lithium content in the aluminum-based impurity slag is not high. A large amount of roasting aid cannot undergo a sufficient displacement reaction, which may introduce new impurities, leading to a decrease in the purity of the recovered lithium. Therefore, the mass ratio of aluminum-based impurity slag to the roasting aid is determined to be 1:(0.02-0.2), within which the lithium leaching rate is relatively high.

[0050] Optionally, aluminum-based impurity removal slag and calcination aids are placed in a cylindrical, disc, vibrating, or stirring pelletizing machine to form pellets.

[0051] In this embodiment, since there are no gaps between the powdered substances, it is difficult to heat them evenly during the calcination process. Therefore, this application uses pelletizing to create sufficient gaps between the formed mixture pellets before calcining them, allowing heat to be transferred to the interior quickly and the heating to be more uniform. Furthermore, pelletizing allows for more thorough contact between the aluminum-based impurity removal slag and the calcination aid, which is beneficial for the reaction and reduces the melting of materials at high temperatures, thus improving the continuity of production.

[0052] In one feasible embodiment, the calcination temperature is 600-900°C.

[0053] Optionally, the roasting temperature can be: 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, etc.

[0054] In this embodiment, if the calcination temperature is too high, the aluminum-based impurity removal slag and calcination aid may sinter and melt, and further increasing the calcination temperature will not significantly improve the lithium leaching rate, but will instead consume more energy; if the temperature is too low, the reaction between the aluminum-based impurity removal slag and the calcination aid is difficult to occur; therefore, the calcination temperature is determined to be 600-900℃.

[0055] In one feasible embodiment, the calcination time is 0.5-5 hours.

[0056] Optionally, the roasting time can be: 0.5h, 1h, 2h, 3h, 4h, 5h, etc.

[0057] In this embodiment, if the roasting time is too short, the aluminum-based impurity removal slag and roasting aid will not react fully, resulting in some lithium not being able to be replaced into soluble lithium salt, thus reducing the lithium recovery rate. If the roasting time is further extended, the lithium leaching rate will not be significantly improved, but more energy will be consumed instead. Therefore, the roasting time is determined to be 0.5-5h.

[0058] In one feasible embodiment, the calcination aid includes at least one of sodium sulfate and potassium sulfate.

[0059] In this embodiment, lithium, sodium, and potassium are elements in the same group. Therefore, it was determined that using sodium sulfate and / or potassium sulfate as calcination aids can displace lithium from aluminum-based impurity removal slag to obtain soluble lithium sulfate.

[0060] Step S20: Water is added to the roasted clinker for leaching to remove impurities and obtain a lithium salt solution;

[0061] After obtaining the roasted clinker, water is added to the roasted clinker for leaching, thereby dissolving the soluble lithium salt in the roasted clinker. The leaching residue is then removed by solid-liquid separation to obtain a lithium salt solution.

[0062] Optionally, after obtaining the roasted clinker, the roasted clinker is crushed and ball-milled, and water is added to the obtained powdered clinker for leaching, thereby improving the leaching efficiency of soluble lithium salts in the roasted clinker.

[0063] In one feasible embodiment, step S20, the step of adding water to the roasted clinker for leaching and removing impurities to obtain a lithium salt solution, includes:

[0064] Step S21: Water is added to the roasted clinker for leaching, and the leachate is obtained after solid-liquid separation;

[0065] After obtaining the roasted clinker, water is added to the roasted clinker for leaching, thereby dissolving the soluble lithium salts in the roasted clinker. The leaching residue is then removed by solid-liquid separation to obtain the leachate.

[0066] Optionally, after obtaining the roasted clinker, the roasted clinker is crushed and ball-milled, water is added to the obtained powdered clinker for leaching, and the leaching residue is removed by solid-liquid separation to obtain leachate.

[0067] Step S22: Adjust the pH of the leachate to 9-12, and obtain a lithium salt solution after solid-liquid separation.

[0068] The leachate obtained after the initial impurity removal may contain impurities such as iron and manganese, which may affect the purity of the recovered lithium product. Therefore, it is necessary to remove impurities again. Then, by adjusting the pH of the leachate to 9-12, the impurities in the leachate are converted into precipitates, and then the lithium salt solution is obtained after solid-liquid separation.

[0069] Optionally, the pH of the adjusted leachate can be 9, 10, 11 or 12.

[0070] Optionally, the pH of the leachate can be adjusted by adding substances such as calcium hydroxide, sodium hydroxide, and calcium oxide.

[0071] In this embodiment, the first impurity removal is achieved by leaching with water followed by solid-liquid separation. Since the pH is in the range of 9-12, impurities such as iron and manganese in the leachate can be converted into precipitates. Therefore, the pH of the obtained leachate is adjusted to 9-12, and a second impurity removal is achieved by solid-liquid separation to obtain a lithium salt solution.

[0072] In one feasible embodiment, the liquid-to-solid ratio of the water to the roasted clinker is (1-3):1.

[0073] Optionally, the liquid-solid ratio of water to calcined clinker can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc.

[0074] In this embodiment, if the liquid-to-solid ratio is too small, the mixture of calcined clinker and water may be too viscous, resulting in insufficient dissolution of the soluble lithium salt. Conversely, if the liquid-to-solid ratio is too large, a larger amount of water will be used, increasing the production cost and making the volume of the mixture too large, which increases the difficulty of subsequent processing.

[0075] In one feasible embodiment, the leaching temperature is 10-40°C.

[0076] Optionally, the leaching temperature can be 10℃, 20℃, 30℃, 40℃, etc.

[0077] In this embodiment, if the leaching temperature is too low, the lithium leaching rate will decrease; while if the leaching temperature is too high, impurity ions in the calcined clinker will be more easily leached out; therefore, the leaching temperature is determined to be 10-40°C.

[0078] In one feasible embodiment, the leaching time is 0.5-5 hours.

[0079] Optionally, the leaching time can be: 0.5h, 1h, 2h, 3h, 4h, 5h, etc.

[0080] In this embodiment, if the leaching time is too short, the soluble lithium salt in the calcined clinker will be difficult to leach out fully, resulting in a decrease in the lithium recovery rate; if the leaching time is too long, the lithium leaching rate will not be significantly improved, but the process time will be extended; therefore, the leaching time is determined to be 0.5-5h.

[0081] Step S30: Add the precipitant to the lithium salt solution to perform lithium precipitation treatment, and obtain lithium-containing precipitate.

[0082] A precipitant is added to a lithium salt solution to perform lithium precipitation, thereby generating a lithium-containing precipitate.

[0083] Optionally, after obtaining the lithium-containing precipitate, the lithium-containing precipitate is dried, pulverized, and packaged to produce a finished lithium salt product.

[0084] Optionally, sodium carbonate is used as the precipitant. Sodium carbonate is added to a lithium salt solution to precipitate lithium and generate lithium carbonate.

[0085] In one feasible embodiment, before step S30, where a precipitant is added to the lithium salt solution for lithium precipitation to obtain a lithium-containing precipitate, the method further includes:

[0086] Step S31: The lithium salt solution is concentrated, and the resulting concentrate is mixed with the precipitant for lithium precipitation treatment, wherein the concentration of lithium oxide in the concentrate is greater than 15 g / L.

[0087] The lithium salt solution is concentrated to obtain a concentrated solution with a lithium oxide concentration greater than 15 g / L. The obtained concentrated solution is then mixed with a precipitant for lithium precipitation treatment.

[0088] In this embodiment, since lithium precipitates may have a certain solubility in water, if the lithium content in the lithium salt solution before lithium precipitation is low, the trace amount of lithium precipitate generated may dissolve directly, making it difficult for the lithium precipitation reaction to occur. Therefore, it is necessary to increase the lithium content in the lithium salt solution before lithium precipitation. Then, by concentrating the lithium salt solution, a concentrated solution with a lithium oxide concentration greater than 15 g / L is obtained, and the concentrated solution is subjected to lithium precipitation treatment to increase the yield of lithium precipitates.

[0089] In one feasible embodiment, the precipitant comprises sodium carbonate.

[0090] In this embodiment, sodium carbonate is added to react with the lithium salt solution to generate lithium carbonate precipitate.

[0091] In one feasible embodiment, the reaction temperature of the lithium deposition treatment is 85-95°C.

[0092] Optionally, the reaction temperature for lithium deposition treatment can be: 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, etc.

[0093] In this embodiment, if the reaction temperature of the lithium precipitation treatment is too low, it will not be conducive to the occurrence of the lithium precipitation reaction, resulting in a low lithium precipitation rate; if the reaction temperature of the lithium precipitation treatment is too high, too much water in the solution will evaporate, which will not be conducive to the lithium precipitation reaction. Therefore, the reaction temperature of the lithium precipitation treatment is determined to be 85-95℃.

[0094] In one feasible embodiment, after step S30, which involves adding the precipitant to the lithium salt solution for lithium precipitation, the method further includes:

[0095] Step S32: After lithium precipitation treatment, solid-liquid separation is performed to obtain the lithium-containing precipitate and the first mother liquor. The first mother liquor is acidified and evaporated to crystallize, resulting in calcination aid crystals and the second mother liquor.

[0096] After lithium precipitation, solid-liquid separation yields lithium-containing precipitate and a first mother liquor. Since the first mother liquor contains soluble lithium salts and dissolved lithium-containing precipitate, acidification is required to remove the dissolved lithium-containing precipitate to prevent it from precipitating along with the calcining aid crystals during the evaporation and crystallization process. After acidification and evaporation and crystallization, calcining aid crystals, pure water, and a second mother liquor are obtained. The second mother liquor can be a decarbonization mother liquor, enabling the recovery of the calcining aid.

[0097] Optionally, the precipitant is a carbonate, thus the first mother liquor contains dissolved lithium carbonate; that is, the first mother liquor can be a lithium carbonate mother liquor, and the lithium-containing precipitate can be a lithium carbonate precipitate. Furthermore, carbonate ions are removed by acidification to prevent lithium carbonate from precipitating out along with the calcination aid crystallization during the evaporation and crystallization process.

[0098] Alternatively, sulfuric acid can be added to the first mother liquor for acidification.

[0099] Optionally, when the calcination aid is sodium sulfate, the second mother liquor can be sodium sulfate mother liquor, and the calcination aid crystals can be sodium sulfate crystals. When the calcination aid is potassium sulfate, the second mother liquor can be decarburization mother liquor, and the calcination aid crystals can be a mixed crystallization of potassium sulfate and sodium sulfate.

[0100] Step S33: The second mother liquor is subjected to lithium precipitation treatment together with the precipitant and the lithium salt solution, as well as subsequent treatment.

[0101] Since the second mother liquor is a saturated solution, it does not need to be concentrated and can be directly subjected to lithium precipitation treatment and subsequent treatment together with the precipitant and the lithium salt solution, thereby further recovering lithium from the second mother liquor.

[0102] In this embodiment, after mixing the precipitant with the lithium salt solution for lithium precipitation, a first mother liquor is obtained. Since lithium still exists in the first mother liquor, it needs to be further recovered. Then, the dissolved lithium-containing precipitate in the first mother liquor is removed by acidification. Then, evaporation and crystallization are carried out to obtain calcination aid crystals and a second mother liquor. Then, the second mother liquor is subjected to lithium precipitation treatment together with the precipitant and the lithium salt solution, as well as subsequent treatment, to achieve the recovery of lithium in the second mother liquor and further improve the recovery rate of lithium in aluminum-based impurity removal slag.

[0103] In this embodiment, the solid slag produced after aluminum removal during the lithium extraction process of lithium-containing materials, namely aluminum-based impurity removal slag, is mixed with a roasting aid and roasted to obtain roasted clinker. By adding the roasting aid, the lithium in the aluminum-based impurity removal slag is converted into soluble lithium salt during the roasting process, while the aluminum and fluorine in the aluminum-based impurity removal slag are insoluble substances. Then, water is added to the roasted clinker for leaching. After water leaching, impurities are removed and lithium, aluminum, and fluorine can be separated to obtain a lithium salt solution. Then, a precipitant is added to the lithium salt solution for lithium precipitation treatment to obtain a high-purity lithium-containing precipitate, thereby achieving effective recovery of lithium from the aluminum-based impurity removal slag and improving the lithium recovery rate.

[0104] Furthermore, based on the first embodiment described above, a more complete embodiment of the method for recovering lithium from aluminum-based impurity removal slag is proposed, referring to... Figure 2 Aluminum-based impurity removal slag is mixed with a calcination aid and pelletized to obtain mixed pellets, which are then calcined. Pelletizing ensures sufficient porosity between the pellets, allowing for rapid heat transfer and more uniform heating, which is beneficial for the reaction. This yields calcined clinker, which is then crushed and ball-milled. Water is added to the resulting powdered clinker for leaching, and the leaching residue is removed through solid-liquid separation to obtain a leachate. The pH of the leachate is adjusted to convert impurities such as iron and manganese into precipitates, which are then separated into a lithium salt solution. The lithium salt solution is concentrated, and the concentrate is mixed with a precipitant for lithium precipitation. After lithium precipitation, solid-liquid separation yields lithium carbonate (containing lithium precipitate) and lithium carbonate mother liquor (first mother liquor). Sulfuric acid is added to the lithium carbonate mother liquor for acidification to remove lithium carbonate precipitate. The liquor is then evaporated and crystallized to obtain calcination aid crystallization and decarbonization mother liquor (second mother liquor). The obtained decarbonization mother liquor can be used with a precipitant and lithium salt solution for lithium precipitation and subsequent processing to further recover lithium from the decarbonization mother liquor. The resulting lithium carbonate precipitate is dried, pulverized, and packaged to produce lithium carbonate products, achieving efficient recovery of lithium from aluminum-based impurity removal slag.

[0105] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of this application, and to demonstrate the significant improvement in the lithium recovery method from aluminum-based impurity slag in the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0106] Example 1

[0107] 1) Take 2000g of crushed aluminum-based impurity slag and 200g of sodium sulfate, mix them thoroughly, and add 200g of water to form the mixture into pellets.

[0108] 2) The mixture pellets were roasted at 700℃ for 2 hours to obtain 1800g of roasted clinker;

[0109] 3) The roasted clinker was crushed and ball-milled to obtain powdered roasted clinker. 1800g of water was added to the roasted clinker and leached at 20℃ for 2h. The solid and liquid were separated to obtain leachate and leach residue, of which the lithium leaching rate was 97.0%.

[0110] 4) Adjust the pH of the leachate to 10 with calcium hydroxide solution, separate the solid and liquid to remove impurities, and obtain a lithium sulfate solution (lithium salt solution); evaporate and concentrate the lithium sulfate solution to obtain a concentrated solution with a lithium oxide concentration of 40 g / L.

[0111] 5) Heat the concentrate to 85°C, add sodium carbonate, stir thoroughly, and let it stand at 85°C for 1.2 hours. Filter to separate wet crude lithium carbonate (containing lithium precipitate) and lithium carbonate mother liquor (first mother liquor). Wash, dry, crush, and package the wet crude lithium carbonate to obtain the finished lithium carbonate product. Add sulfuric acid to the lithium carbonate mother liquor for acidification, and then evaporate and crystallize to obtain sodium sulfate and sodium sulfate mother liquor (second mother liquor). Mix the sodium sulfate mother liquor with sodium carbonate and concentrate for further processing.

[0112] 6) After the above steps, lithium carbonate with a purity of 99.65% is obtained, and the lithium recovery rate is 92%. Sodium sulfate has a purity of 99%.

[0113] Example 2

[0114] 1) Take 2000g of crushed aluminum-based impurity slag and 200g of sodium sulfate, mix them thoroughly, and add 200g of water to form the mixture into pellets.

[0115] 2) The mixture pellets were roasted at 850℃ for 4 hours to obtain 1800g of roasted clinker;

[0116] 3) The roasted clinker was crushed and ball-milled to obtain powdered roasted clinker. 1800g of water was added to the roasted clinker and leached at 20℃ for 2h. The solid and liquid were separated to obtain leachate and leach residue, in which the lithium leaching rate was 99.0%.

[0117] 4) Adjust the pH of the leachate to 11 with calcium hydroxide solution, and perform solid-liquid separation to remove impurities, obtaining a lithium sulfate solution (lithium salt solution); evaporate and concentrate the lithium sulfate solution to obtain a concentrated solution with a lithium oxide concentration of 50 g / L;

[0118] 5) Heat the concentrate to 95°C, add sodium carbonate, stir thoroughly, and let stand at 95°C for 1 hour. Filter to separate wet crude lithium carbonate (containing lithium precipitate) and lithium carbonate mother liquor (first mother liquor). Wash, dry, pulverize, and package the wet crude lithium carbonate to obtain the finished lithium carbonate product. Add sulfuric acid to the lithium carbonate mother liquor for acidification, and then evaporate and crystallize to obtain sodium sulfate and sodium sulfate mother liquor (second mother liquor). Mix the sodium sulfate mother liquor with sodium carbonate and concentrate for further processing.

[0119] 6) After the above steps, lithium carbonate with a purity of 99.7% is obtained, and the lithium recovery rate is 94%. Sodium sulfate has a purity of 99%.

[0120] Example 3

[0121] 1) Take 2000g of crushed aluminum-based impurity slag and 400g of potassium sulfate, mix them thoroughly, and add 230g of water to form the mixture into pellets.

[0122] 2) The mixture pellets were roasted at 900℃ for 0.5h to obtain 2000g of roasted clinker;

[0123] 3) The roasted clinker was crushed and ball-milled to obtain powdered roasted clinker. 6000g of water was added to the roasted clinker and leached at 10℃ for 5h. The solid and liquid were separated to obtain leachate and leach residue, of which the lithium leaching rate was 98.1%.

[0124] 4) Adjust the pH of the leachate to 12 with calcium hydroxide solution, and remove impurities by solid-liquid separation to obtain lithium sulfate solution (lithium salt solution); evaporate and concentrate the lithium sulfate solution to obtain a concentrated solution with a lithium oxide concentration of 47 g / L.

[0125] 5) Heat the concentrate to 93°C, add sodium carbonate, stir thoroughly, and let it stand at 93°C for 1 hour. Filter to separate wet crude lithium carbonate (containing lithium precipitate) and lithium carbonate mother liquor (first mother liquor). Wash, dry, pulverize, and package the wet crude lithium carbonate to obtain the finished lithium carbonate product. Add sulfuric acid to the lithium carbonate mother liquor for acidification. After acidification, evaporate and crystallize to obtain a mixed salt of potassium sulfate and sodium sulfate (calcination aid) and decarbonization mother liquor (second mother liquor). Remix the decarbonization mother liquor with sodium carbonate and concentrate for subsequent processing.

[0126] 6) After the above steps, a lithium carbonate product with a purity of 99.68% is obtained, and the lithium recovery rate is 93.1%.

[0127] Example 4

[0128] 1) Take 2000g of crushed aluminum-based slag and 40g of sodium sulfate, mix them thoroughly, and add 170g of water to form the mixture into pellets.

[0129] 2) The mixture pellets were roasted at 600℃ for 5 hours to obtain 1600g of roasted clinker;

[0130] 3) The roasted clinker was crushed and ball-milled to obtain powdered roasted clinker. 3200g of water was added to the roasted clinker and leached at 40℃ for 0.5h. The solid and liquid were separated to obtain leachate and leach residue, of which the lithium leaching rate was 96.8%.

[0131] 4) Adjust the pH of the leachate to 9 with calcium hydroxide solution, and perform solid-liquid separation to remove impurities, obtaining a lithium sulfate solution (lithium salt solution); evaporate and concentrate the lithium sulfate solution to obtain a concentrated solution with a lithium oxide concentration of 38 g / L;

[0132] 5) Heat the concentrated solution to 90°C, add sodium carbonate, stir thoroughly, and let it stand at 90°C for 1.1 hours. Filter to separate wet crude lithium carbonate (containing lithium precipitate) and lithium carbonate mother liquor (first mother liquor). Wash, dry, crush, and package the wet crude lithium carbonate to obtain the finished lithium carbonate product. Add sulfuric acid to the lithium carbonate mother liquor for acidification, and then evaporate and crystallize to obtain sodium sulfate and sodium sulfate mother liquor (second mother liquor). Mix the sodium sulfate mother liquor with the sodium carbonate and lithium sulfate solution again for subsequent processing.

[0133] 6) After the above steps, a lithium carbonate product with a purity of 99.62% is obtained, and the lithium recovery rate is 91.5%. The sodium sulfate has a purity of 99%.

[0134] Comparative Example 1

[0135] The experimental steps and raw material ratios were the same as in Example 1, except that sodium sulfate (calcination aid) was not added.

[0136] After the above steps, in step 3), the lithium leaching rate in the solid-liquid separation leachate is only 60.9%; the lithium recovery rate is only 58.2%; the purity of the lithium carbonate product is 99.50%, and the purity of sodium sulfate is 99%.

[0137] Comparative Example 2

[0138] The experimental steps and raw material ratios were the same as in Example 2, except that the calcination temperature was 500℃.

[0139] After the above steps, in step 3), the lithium leaching rate in the solid-liquid separation leachate is only 80.2%; the lithium recovery rate is only 76.8%; the purity of the lithium carbonate product is 99.50%, and the purity of sodium sulfate is 99%.

[0140] Comparative Example 3

[0141] The experimental steps and raw material ratios were the same as in Example 1. The difference was that the aluminum-based impurity slag was mixed evenly with sodium sulfate and then directly roasted without pelletizing.

[0142] After the above steps, in step 3), the lithium leaching rate in the solid-liquid separation leachate is only 80.4%; the lithium recovery rate is only 76.4%; the purity of the lithium carbonate product is 99.50%, and the purity of sodium sulfate is 99%.

[0143] As can be seen from Examples 1-4 and Comparative Examples 1-3 above, the lithium recovery method in aluminum-based impurity removal slag of this application can convert the lithium in the aluminum-based impurity removal slag into soluble lithium salts, while the aluminum and fluorine in the aluminum-based impurity removal slag are insoluble substances. Therefore, lithium can be separated from aluminum and fluorine by water leaching and impurity removal, achieving efficient lithium recovery. Compared with Comparative Examples 1-3, the lithium leaching rate and recovery rate are improved, and the lithium recovery rate is higher.

[0144] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A method for recovering lithium from aluminum-based impurity removal slag, characterized in that, The aluminum-based impurity removal slag is a solid slag produced after adjusting the pH value to remove aluminum during the lithium extraction process of lithium-containing materials. The aluminum-based impurity removal slag contains aluminum hydroxide, and the method for recovering lithium from the aluminum-based impurity removal slag includes the following steps: Aluminum-based impurity removal slag is mixed with a roasting aid and roasted to obtain roasted clinker, wherein the roasting aid includes at least one of sodium sulfate and potassium sulfate; Water is added to the roasted clinker for leaching, and after removing impurities, a lithium salt solution is obtained. A precipitant is added to the lithium salt solution to perform lithium precipitation treatment, resulting in a lithium-containing precipitate.

2. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1, characterized in that, The step of mixing and calcining the aluminum-based impurity removal slag with the calcination aid includes: The aluminum-based impurity removal slag is mixed with a calcination aid and pelletized to obtain a mixture pellet, which is then calcined. And / or, the mass ratio of the aluminum-based impurity removal slag to the calcination aid is 1:(0.02-0.2).

3. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1 or 2, characterized in that, The roasting temperature is 600-900 ℃, and the roasting time is 0.5-5 h.

4. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1, characterized in that, The step of adding water to the roasted clinker for leaching to remove impurities and obtaining a lithium salt solution includes: Water is added to the roasted clinker for leaching, and the leachate is obtained after solid-liquid separation. The pH of the leachate was adjusted to 9-12, and a lithium salt solution was obtained after solid-liquid separation.

5. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1 or 4, characterized in that, The liquid-to-solid ratio of the water to the roasted clinker is (1-3):1; And / or, the leaching temperature is 10-40 ℃ and the leaching time is 0.5-5 h.

6. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1, characterized in that, Prior to the step of adding the precipitant to the lithium salt solution for lithium precipitation, the method further includes: The lithium salt solution is concentrated, and the resulting concentrate is mixed with the precipitant for lithium precipitation treatment, wherein the concentration of lithium oxide in the concentrate is greater than 15 g / L.

7. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1 or 6, characterized in that, The precipitant includes: sodium carbonate; And / or, the reaction temperature of the lithium deposition treatment is 85-95 °C.

8. The method for recovering lithium from aluminum-based impurity removal slag as described in claim 1, characterized in that, After the step of adding the precipitant to the lithium salt solution for lithium precipitation, the method further includes: After lithium precipitation treatment, solid-liquid separation is performed to obtain the lithium-containing precipitate and the first mother liquor. The first mother liquor is acidified and evaporated to crystallize, resulting in calcination aid crystals and the second mother liquor. The second mother liquor, together with the precipitant and the lithium salt solution, is subjected to lithium precipitation treatment and subsequent processing.

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