A method for recovering lithium from lithium-containing aluminum electrolyte waste

Abstract

This invention provides a method for recovering lithium from lithium-containing aluminum electrolyte waste, relating to the field of lithium-containing waste resource utilization. The lithium-containing aluminum electrolyte waste is mixed with a calcium-containing substance and roasted. The calcium-containing substance includes a first calcium-containing substance and a second calcium-containing substance. The first calcium-containing substance is at least one selected from calcium sulfate, calcium bisulfate, calcium carbonate, or calcium bicarbonate. The second calcium-containing substance is at least one selected from calcium carbonate, bicarbonate, sulfate, bisulfate, hydroxide, oxide, or chloride. The molar ratio of calcium in the calcium-containing substance to aluminum in the lithium-containing aluminum electrolyte is controlled at 1-4:1. The molar amount of calcium in the carbonate, bicarbonate, sulfate, and bisulfate is 40%-80% of the total molar amount of calcium in the calcium-containing substance. After roasting, the roasted clinker is mixed with an acidic leachate for lithium extraction. This method significantly improves the lithium leaching rate and effectively and selectively recovers high-value lithium from lithium-containing aluminum electrolytes.

Description

Technical Field

[0001] This invention relates to a method for recovering lithium from lithium-containing aluminum electrolyte waste, belonging to the field of lithium-containing waste resource utilization. Background Technology

[0002] With the rapid development of the new energy industry, the demand for lithium-ion power batteries is increasing day by day, while the existing lithium mineral resources are decreasing. Therefore, the contradiction between the demand and reserves of lithium resources is becoming increasingly serious. How to rationally develop and recycle the developed lithium resources is a key issue that the new energy and resource recycling fields need to face in the future.

[0003] As a major producer of electrolytic aluminum, my country has a large and continuously increasing stockpile of lithium-containing aluminum electrolytes. Because these electrolytes contain toxic and harmful substances such as fluorides and cyanides, they are classified as hazardous waste and require harmless treatment. However, lithium-containing aluminum electrolytes are also a lithium resource. Although the lithium content in low-grade bauxite, converted to Li₂O, is only about 0.58%, it accumulates in the electrolytic cell as alumina feedstock accumulates, resulting in a Li content as high as 1-3%, equivalent to 2-6.5% Li₂O, approaching the 1.5-7% in spodumene ore, indicating a very high potential value for lithium extraction. How to simply and efficiently recover valuable lithium from lithium-containing aluminum electrolytes, solve the problem of low lithium leaching and recovery efficiency, and achieve the harmless treatment of lithium-containing aluminum electrolytes are urgent issues that need to be addressed.

[0004] To address this problem, existing technologies offer several solutions, such as direct leaching with sulfuric acid alone or leaching after sulfation and roasting. For example, CN105293536A reacts lithium-containing electrolytic aluminum waste with concentrated sulfuric acid at 200–400°C, followed by water leaching. This patent does not disclose the lithium leaching rate during the leaching stage. Based on data provided in Example 1, the leaching rate is estimated to be around 80%. This process has a low lithium leaching rate, making it unable to effectively extract and recover valuable lithium. Furthermore, the roasting stage generates a large amount of toxic, harmful, and highly corrosive hydrogen fluoride gas, placing extremely high demands on the equipment's corrosion resistance and sealing. The leaching stage involves high temperature and high acidity, creating a harsh working environment and posing significant safety hazards.

[0005] For example, CN105349786A uses inorganic acid to directly leach lithium-containing aluminum electrolyte at 75-95℃. According to its Example 1, the lithium leaching rate is estimated to be around 82%. However, when the inventors implemented weak acid leaching, the lithium leaching rate in the lithium-containing aluminum electrolyte was only 7.23%, which is difficult to reach the leaching level of CN105349786A.

[0006] In addition, high-temperature roasting is used to convert lithium-containing phases, but the overall lithium leaching rate is generally low, only about 70%-80%, and the leaching time is long and the efficiency is low. The leaching acid concentration is high, which requires high equipment corrosion resistance. Moreover, most of the aluminum and iron enter the acid leaching liquid phase with the lithium, making it difficult to avoid the common problems of difficult lithium and aluminum separation and large lithium loss in the lithium extraction industry. Secondly, the high-temperature roasting time is long, the process efficiency is low, the energy consumption is high, and the amount of additives is too large. Summary of the Invention

[0007] This application provides a method for recovering lithium from lithium-containing aluminum electrolyte waste to solve at least one of the technical problems in the prior art.

[0008] The technical solution of the present invention is as follows:

[0009] A method for recovering lithium from lithium-containing aluminum electrolyte waste includes the following steps:

[0010] Calcination involves mixing lithium-aluminum electrolyte waste with calcium-containing substances and calcining them to obtain calcined material.

[0011] The calcium-containing substance includes a first calcium-containing substance and a second calcium-containing substance;

[0012] The first calcium-containing substance is at least one of calcium sulfate, calcium bisulfate, calcium carbonate, or calcium bicarbonate, for example, one, two, three, or four of them;

[0013] The second calcium-containing substance is at least one of calcium carbonate, bicarbonate, sulfate, hydrogen sulfate, hydroxide, oxide, and chloride, for example, one, two, three, four, five, or six of them. The second calcium-containing substance contains anions that are different or dissimilar to the first calcium-containing substance.

[0014] Among them, similar anions, such as carbonate and bicarbonate ions, sulfate and bisulfate ions, are used. For example, when the first calcium-containing substance is calcium sulfate and / or calcium bisulfate, the second calcium-containing substance is not only calcium sulfate and / or calcium bisulfate; when the first calcium-containing substance is calcium carbonate and / or calcium bicarbonate, the second calcium-containing substance is not only calcium bicarbonate and / or calcium carbonate. By combining different calcium salts, the guiding and promoting effect of the additives on the calcination reaction is ensured.

[0015] Furthermore, the first calcium-containing substance contains at least calcium sulfate and / or calcium bisulfate.

[0016] Furthermore, the second calcium-containing substance is calcium hydroxide and / or calcium oxide, or the second calcium-containing substance is calcium carbonate and calcium chloride, or the second calcium-containing substance is a combination of at least one of calcium hydroxide and calcium oxide with at least one of calcium chloride and calcium carbonate.

[0017] By optimizing the first and second calcium-containing substances, the transformation of lithium aluminum fluoride compounds into an easily soluble phase and an aluminum fluoride anion-stabilized phase can be further promoted, thereby further ensuring the leaching of lithium and inhibiting the leaching of fluorine and aluminum.

[0018] Furthermore, the molar amount of calcium in the first calcium-containing substance is 40%-80% of the total molar amount of calcium in the calcium-containing substance, for example, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, preferably 50%-80%, more preferably 60%-75%.

[0019] The ratio of the molar amount of calcium in the calcium-containing substance to the molar amount of aluminum in the lithium-aluminum electrolyte is 1-4:1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4:1, preferably 1.5-3.5:1, more preferably 2-3:1.

[0020] The existence of lithium in lithium-containing aluminum electrolytes is highly complex. Besides existing as LiF, lithium also exists to varying degrees as Li₂NaAlF₆, LiNa₂AlF₆, and other forms. Through long-term research, the inventors discovered that by controlling specific calcium salt mixtures, the total calcium addition, and different calcium salt ratios, the lithium-containing phase transformation in lithium-containing aluminum electrolytes can be achieved through short-time calcination. This transforms lithium into easily soluble lithium aluminum fluoride compounds, and ensures that most of the fluorine and aluminum exist as calcium aluminum fluorides such as Ca₂AlF₇ and CaAlF₅, which are difficult to dissolve through acid leaching. Furthermore, calcium will further solidify... The formation of insoluble CaF2 from the sulfur (F) element in the raw materials significantly improves both lithium conversion efficiency and lithium leaching rate, drastically reducing roasting energy consumption. Furthermore, during acid leaching, only a portion of the aluminum enters the liquid phase. Particularly when a specific calcium salt (calcium sulfate + calcium hydroxide) is used, the aluminum dissolved in the solution by the specific lithium aluminum fluoride compound can be converted into more stable aluminum-containing compounds by other components in the leaching slurry system and re-enter the slag phase. This results in an aluminum leaching rate in the high-aluminum lithium-containing aluminum electrolyte as low as below 0.1%, greatly reducing the subsequent aluminum removal burden and lithium loss in the leaching solution. In addition, the precise addition of calcium-containing substances avoids the adverse effects of excessive additives on additive costs, process materials, and slag volume.

[0021] The firing temperature is 750-1100℃, for example, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, preferably 780-1050℃, and more preferably 800-900℃.

[0022] The calcination time is 0.75h-5h, for example 45min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min, 150min, 160min, 170min, 180min, 190min, 200min, 210min, 220min, 230min, 240min, 250min, 260min, 270min, 280min, 290min, 300min, preferably 1-3h, more preferably 1-2h.

[0023] By combining, adding, and proportioning calcium-containing substances, the efficiency of the roasting stage is greatly improved, the roasting time is shortened to less than one hour, roasting energy consumption is significantly reduced, and roasting efficiency is improved.

[0024] Acid leaching involves mixing the roasted raw material with an acidic leachate to leach the roasted material.

[0025] The acid leaching pH is not higher than 6, for example, -2, -1.5, -1, -1.5, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3. 0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, preferably not higher than 5.5, more preferably 1.5-5, and even more preferably 2-4.

[0026] The acid leaching temperature is above 20°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 200°C, 250°C, 300°C, etc., preferably 25°C-99°C, more preferably 30°C-80°C.

[0027] The acid leaching time is 30 minutes or more, for example, 45 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, 130 minutes, 140 minutes, 150 minutes, 160 minutes, 170 minutes, 180 minutes, 190 minutes, 200 minutes, 210 minutes, 220 minutes, 230 minutes, 240 minutes, 250 minutes, 260 minutes, 270 minutes, 280 minutes, 290 minutes, 300 minutes, 360 minutes, 420 minutes, 480 minutes, 540 minutes, 600 minutes, etc., preferably 30-180 minutes, more preferably 45-120 minutes.

[0028] The initial solid volume ratio (L / Kg) of the acidic leaching solution is not less than 2:1, for example 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 13:1, 14:1, 15:1, 20:1, etc., preferably 2-10:1, more preferably 3-6:1.

[0029] By rationally controlling acid leaching parameters, including temperature and acidity, lithium leaching can be further optimized while suppressing the leaching of impurities such as aluminum and fluorine. This lays a good foundation for the subsequent separation and purification of lithium in the leaching solution. Furthermore, the weak acid leaching conditions are mild, have low equipment requirements, and are easy to operate.

[0030] Neutral leaching, wherein the pH of the neutral leachate is 7.5 ± 1, for example 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, is performed prior to the acidic leaching.

[0031] Before acid leaching, the roasted material is subjected to neutral leaching, which can leach easily soluble lithium and better suppress the leaching of fluorine and aluminum impurities, resulting in a low-fluorine aluminum lithium leachate. This reduces the burden and difficulty of subsequent impurity removal and effectively reduces the subsequent lithium separation loss.

[0032] Solid-liquid separation is performed after acid leaching to obtain lithium-containing acid leaching solution and acid leaching residue. The lithium-containing acid leaching solution can be partially or completely returned to acid leaching to enrich lithium before subsequent separation and purification operations.

[0033] Returning some or all of the lithium-containing acid leaching solution to the leaching process can not only further increase the lithium concentration in the leaching solution, but also make full use of the residual acid, which helps to achieve low-cost lithium recovery.

[0034] Compared with the prior art, the beneficial effects of the present invention include:

[0035] 1. Calcium-containing substances are precisely added based on the key components of the raw materials, which effectively avoids the increase in time and investment caused by repeated experiments to adjust the formulation of additives due to the fluctuation of raw material composition in batches, or the insufficient or excessive addition of additives due to blind adjustment of additive use, resulting in incomplete phase transformation, low lithium leaching rate in the subsequent leaching stage, or waste of additives, low effective batch processing capacity and large slag volume caused by blindly adding too much.

[0036] 2. By combining specific calcium-containing substances in a precise and synergistic manner, the reaction thermodynamic conditions of a single additive are altered. This reduces the activation energy for the conversion of lithium-containing phases into fluorinated aluminum lithium phases, promotes the conversion of lithium-containing phases into easily leached phases and drives the conversion process, and converts aluminum, calcium, and fluorine into more stable compound phases. This significantly shortens the duration of the high-temperature, high-energy-consumption roasting process. The overall roasting process time and roasting energy consumption can be reduced by more than 60-90%, significantly improving production efficiency and reducing operational difficulty and investment.

[0037] 3. The lithium leaching rate is significantly improved, reaching a maximum of 99.75%, which is more than 40% higher than existing technologies. Simultaneously, the leaching of fluorine and aluminum impurities is suppressed to varying degrees. Based on the efficient conversion of lithium-containing phases during the roasting stage, approximately 80% of lithium selectively leaches through neutral leaching. The aluminum leaching rate during neutral leaching is only about 0.001%, and the fluorine leaching rate is only about 0.005%, laying a solid foundation for the subsequent separation and purification of most lithium in lithium-containing aluminum electrolytes. The Li content in the acid leaching residue is basically <0.1wt.%, with a minimum of only 0.002wt.%, and the lithium leaching rate is above 85%, reaching a maximum of 99.75%. The fluorine leaching rate is controlled below 2.5%, mostly below 1%, and the aluminum leaching rate during acid leaching is as low as 0.003%. Most of the fluorine and aluminum elements remain in the slag phase, which not only greatly reduces the burden of subsequent wet lithium extraction and impurity removal, and simplifies the impurity removal process, but also effectively avoids the entrainment loss of lithium caused by aluminum removal and defluorination in the solution. In particular, for low-fluorine and low-aluminum neutral leaching solutions, there is no need for aluminum removal and defluorination stages, which not only effectively improves lithium recovery efficiency, but also has significant benefits for energy conservation, emission reduction and emission reduction.

[0038] 4. The acid leaching conditions are relaxed, the acid leaching process is efficient and simple to operate. The efficient leaching of lithium can be achieved under low acid conditions. The equipment requirements are low, the operating conditions are friendly, and it is conducive to the return and circulation of acid leaching solution.

[0039] 5. No harmful volatile substances such as HF and sulfur dioxide are generated during the roasting process. It is a neutral roasting process, with friendly operating conditions and low equipment requirements.

[0040] 6. The overall process is simple to operate, with a high lithium leaching rate. The lithium in the leachate is easy to separate and purify, resulting in low overall operating costs and energy consumption, which significantly enhances the value of the lithium-containing aluminum electrolyte recycling industry. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0042] Figure 1The image shows the XRD pattern of lithium-aluminum electrolyte waste 1.

[0043] Figure 2 The XRD patterns of the roasted clinker before and after leaching in Example 1 of the present invention are shown.

[0044] Figure 3 The XRD patterns of the roasted clinker before and after leaching in Comparative Example 2 of this invention are shown. Detailed Implementation

[0045] As used in this article:

[0046] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0047] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0048] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0049] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0050] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0051] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0052] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. Unless otherwise specified, the relevant percentages refer to mass percentages.

[0053] The lithium content in lithium-containing aluminum electrolyte waste is generally greater than 0.5 wt.%, the aluminum content is generally greater than 5 wt.%, and the fluorine content fluctuates greatly.

[0054] In the following examples and comparative examples, the main components of lithium-aluminum electrolyte waste 1 used in Examples 1-10 and the comparative examples are as follows: 15.85 wt.% Al, 2.06 wt.% Li, 13.82 wt.% F. The XRD pattern of this lithium-aluminum electrolyte waste 1 is shown below. Figure 1 As shown.

[0055] The main components of the lithium-aluminum electrolyte waste 2 used in Examples 11-18 are as follows: 13.45 wt.% Al, 1.38 wt.% Li, and 11.68 wt.% F.

[0056] Example 1

[0057] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium carbonate and calcium sulfate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium carbonate to calcium sulfate in the calcium-containing material is 1:1.

[0058] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 800℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.3 at a liquid-to-solid volume ratio of 3:1 (L / Kg, the same below), and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled between 2.3 and 0.2 during the reaction. After the reaction, the mixture was filtered to obtain a lithium-containing leaching solution and leaching residue. The XRD patterns of the roasted clinker before and after leaching are shown in the figure. Figure 2 As shown.

[0059] In this embodiment, the lithium leaching rate of the lithium-aluminum electrolyte is 96.48%, the fluorine leaching rate is 0.49%, and the aluminum leaching rate is 36.36%.

[0060] Example 2

[0061] The calcium-containing material that has passed through an 80-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium carbonate and calcium hydroxide, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 1:1, and the molar ratio of calcium carbonate to calcium hydroxide is 1:1.

[0062] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 750℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.0 at a liquid-to-solid ratio of 3:1 and reacted at 65℃ for 90 minutes. The pH of the slurry was controlled between 2±0.2 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0063] In this embodiment, the lithium leaching rate is 86.16%, the fluorine leaching rate is 0.15%, and the aluminum leaching rate is 44.37%.

[0064] Example 3

[0065] Calcium-containing material passing through a 100-mesh sieve is mixed with lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium chloride, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2:1, and the molar ratio of calcium sulfate to calcium chloride is 1:1. The mixture is placed in a roasting furnace, the furnace door is closed, and roasting is carried out at 780°C for 120 minutes to obtain roasted clinker. The roasted clinker is ground to pass through an 80-mesh sieve to obtain roasted powder. The roasted powder is then mixed with an acid leaching solution with a pH of 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 40°C for 120 minutes. The pH of the slurry is controlled between 2.5 and 0.5 during the reaction. After the reaction is completed, the solid and liquid are separated to obtain leachate and leachate residue.

[0066] In this embodiment, the lithium leaching rate was 87.19%, the fluorine leaching rate was 0.48%, and the aluminum leaching rate was 29.34%.

[0067] Example 4

[0068] The calcium-containing material that has passed through a 70-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium hydroxide, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium hydroxide is 1:1.

[0069] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1, and the pH of the slurry was controlled between 2.5 and 0.5 during the reaction. The mixture was reacted at 60℃ for 120 minutes. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0070] In this embodiment, the lithium leaching rate is 92.15%, the fluorine leaching rate is 0.04%, and the aluminum leaching rate is 0.04%.

[0071] Example 5

[0072] The calcium-containing material that has passed through a 50-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium carbonate and calcium chloride, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 1.5:1, and the molar ratio of calcium carbonate to calcium chloride is 1:1.

[0073] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 875℃ for 60 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 120-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 50℃ for 60 minutes. The pH of the slurry was controlled between 2.5 and 0.5 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0074] In this embodiment, the lithium leaching rate was 87.53%, the fluorine leaching rate was 0.37%, and the aluminum leaching rate was 45.13%.

[0075] Example 6

[0076] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium carbonate and calcium sulfate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 4:1, and the molar ratio of calcium carbonate to calcium sulfate is 1:1.

[0077] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 75 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 70-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 3.5 at a liquid-to-solid ratio of 3:1 and reacted at 95℃ for 30 minutes. The pH of the slurry was controlled between 3.5 and 0.5 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0078] In this embodiment, the lithium leaching rate was 89.80%, the fluorine leaching rate was 2.82%, and the aluminum leaching rate was 22.49%.

[0079] Example 7

[0080] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium carbonate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 3:1, and the molar ratio of calcium sulfate to calcium carbonate is 2:1.

[0081] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 900℃ for 150 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 1.5 at a liquid-to-solid ratio of 3:1 and reacted at 70℃ for 120 minutes. The pH of the slurry was controlled between 1.5 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leach residue.

[0082] In this embodiment, the lithium leaching rate is 87.76%, the fluorine leaching rate is 0.29%, and the aluminum leaching rate is 43.53%.

[0083] Example 8

[0084] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium carbonate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 3:1, and the molar ratio of calcium sulfate to calcium carbonate is 2:1.

[0085] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 900℃ for 150 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 5.0 at a liquid-to-solid ratio of 3:1 and reacted at 80℃ for 180 minutes. During the reaction, the pH of the slurry was controlled between 5.0 and 0.1. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0086] In this embodiment, the lithium leaching rate was 89.47%, the fluorine leaching rate was 0.71%, and the aluminum leaching rate was 6.98%.

[0087] Example 9

[0088] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium hydroxide, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium hydroxide is 1.5:1.

[0089] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 900℃ for 180 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 3.5 at a liquid-to-solid ratio of 5:1, and the pH of the slurry was controlled between 3.5 and 0.1 during the reaction. The mixture was reacted at 90℃ for 90 minutes. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0090] In this embodiment, the lithium leaching rate is 89.35%, the fluorine leaching rate is 0.37%, and the aluminum leaching rate is 5.19%.

[0091] Example 10

[0092] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium hydroxide, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium hydroxide is 1.5:1.

[0093] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 900℃ for 180 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 10:1 and reacted at 95℃ for 60 minutes. The pH of the slurry was controlled between 2.5 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0094] In this embodiment, the lithium leaching rate is 98.68%, the fluorine leaching rate is 1.27%, and the aluminum leaching rate is 0.03%.

[0095] Example 11

[0096] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium carbonate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium carbonate is 3:1.

[0097] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 1.0 at a liquid-to-solid ratio of 2:1 and reacted at 50℃ for 240 minutes. The pH of the slurry was controlled between 1 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0098] In this embodiment, the lithium leaching rate is 91.41%, the fluorine leaching rate is 0.47%, and the aluminum leaching rate is 64.35%.

[0099] Example 12

[0100] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium carbonate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium carbonate is 3:1.

[0101] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 4.0 at a liquid-to-solid ratio of 15:1 and reacted at 75℃ for 120 minutes. The pH of the slurry was controlled between 4 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0102] In this embodiment, the lithium leaching rate is 89.16%, the fluorine leaching rate is 1.66%, and the aluminum leaching rate is 1.70%.

[0103] Example 13

[0104] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate, calcium carbonate and calcium chloride. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 3:1, and the molar ratio of calcium sulfate, calcium carbonate and calcium chloride is 1:1:1.

[0105] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 6:1 and reacted at 65℃ for 120 minutes. During the reaction, the pH of the slurry was controlled between 2.5 and 0.1. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0106] In this embodiment, the lithium leaching rate is 93.72%, the fluorine leaching rate is 2.31%, and the aluminum leaching rate is 15.58%.

[0107] Example 14

[0108] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate, calcium carbonate and calcium chloride. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 3:1, and the molar ratio of calcium sulfate, calcium carbonate and calcium chloride is 1:1:1.

[0109] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.0 at a liquid-to-solid ratio of 8:1 and reacted at 25℃ for 120 minutes. The pH of the slurry was controlled between 2.0 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0110] In this embodiment, the lithium leaching rate is 99.75%, the fluorine leaching rate is 1.97%, and the aluminum leaching rate is 22.21%.

[0111] Example 15

[0112] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium carbonate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium carbonate is 1:1.

[0113] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 1100℃ for 45 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 4:1 and reacted at 60℃ for 75 minutes. The pH of the slurry was controlled between 2.5 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0114] In this embodiment, the lithium leaching rate is 86.17%, the fluorine leaching rate is 0.90%, and the aluminum leaching rate is 35.69%.

[0115] Example 16

[0116] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate, calcium chloride and calcium oxide. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate, calcium chloride and calcium oxide is 1:1:1.

[0117] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 800℃ for 90 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled between 2.5 and 0.1 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0118] In this embodiment, the lithium leaching rate is 93.98%, the fluorine leaching rate is 0.77%, and the aluminum leaching rate is 6.19%.

[0119] Example 17

[0120] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate and calcium hydroxide, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium sulfate to calcium oxide is 3:2.

[0121] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 900℃ for 180 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with water at a liquid-to-solid ratio of 3:1 to form a slurry, and reacted at 60℃ for 120 minutes. After the reaction was completed, the mixture was filtered to obtain a neutral leachate and a neutral leachate residue. In this example, the lithium leaching rate was 77.72%, the fluorine leaching rate was 0.006%, and the aluminum leaching rate was 0.0015% during the neutral leaching stage.

[0122] Neutral leaching residue was mixed with acidic leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 60°C for 90 minutes. The pH of the slurry was controlled between 2.5 and 0.1 during the reaction. After the reaction, the solid and liquid phases were separated to obtain leaching solution and leaching residue. In this example, the total lithium leaching rate was 99.15%, the fluorine leaching rate was 1.31%, and the aluminum leaching rate was 0.04%.

[0123] Example 18

[0124] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this embodiment, the calcium-containing material is a mixture of calcium sulfate, calcium carbonate and calcium hydroxide. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 3:1, and the molar ratio of calcium sulfate, calcium carbonate and calcium hydroxide is 1:1:1.

[0125] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 850℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with water at a liquid-to-solid ratio of 4:1 to form a slurry, and reacted at 50℃ for 90 minutes. After the reaction was completed, the mixture was filtered to obtain a neutral leachate and a neutral leachate residue. In this example, the lithium leaching rate was 81.72%, the fluorine leaching rate was 0.005%, and the aluminum leaching rate was 0.0011% during the neutral leaching stage.

[0126] Neutral leaching residue was mixed with acidic leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 75°C for 90 minutes. The pH of the slurry was controlled between 2.3 and 0.1 during the reaction. After the reaction, the solid and liquid phases were separated to obtain leaching solution and leaching residue. In this example, the total lithium leaching rate was 99.35%, the fluorine leaching rate was 0.95%, and the aluminum leaching rate was 9.16%.

[0127] Comparative Example 1

[0128] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing material is a mixture of calcium chloride and calcium hydroxide. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium chloride to calcium hydroxide is 1:1.

[0129] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker was then ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.5 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 120 minutes. The pH of the slurry was controlled between 2.5 and 0.5 during the reaction. After the reaction was completed, the solid and liquid were separated to obtain leachate and leachate residue.

[0130] In this comparative example, the lithium leaching rate was 52.53%, the fluorine leaching rate was 0.48%, and the aluminum leaching rate was 24.18%.

[0131] As can be seen from this comparative example, not all combinations of different anionic calcium-containing compounds have excellent phase conversion effects of lithium-containing aluminum electrolytes. The calcium-containing composition in this comparative example not only fails to effectively promote the conversion of lithium-containing phases, but also, compared with the blank calcination of Comparative Example 8, inhibits lithium leaching to a certain extent, while promoting the leaching of the impurity element fluorine.

[0132] Comparative Example 2

[0133] Calcium carbonate that has passed through a 100-mesh sieve is mixed with lithium-aluminum electrolyte at a mass ratio of 1.5:1. The mixture is placed in a roasting furnace, the furnace door is closed, and it is roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker is ground until it passes through a 100-mesh sieve to obtain roasted powder. The roasted powder is then mixed with an acid leaching solution with a pH of 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry is controlled between 2.3 and 0.2 during the reaction. After the reaction is completed, the solid and liquid are separated to obtain leachate and leachate residue.

[0134] In this comparative example, the lithium leaching rate was 71.79%, the fluorine leaching rate was 1.38%, and the aluminum leaching rate was 15.30%.

[0135] The lithium leaching rate and Figure 3 (XRD patterns of the roasted clinker before and after leaching in this comparative example) It can be seen that although the addition of calcium carbonate alone can achieve lithium conversion and leaching promotion to a certain extent, the lithium is mainly converted into the Li3AlF6 phase, which is different from the main lithium-containing phase in Example 1. The weak acid leaching can only leach out part of the lithium in this comparative example. Compared with Example 1, the lithium leaching rate is reduced by about 25 percentage points.

[0136] Comparative Example 3

[0137] The calcium-containing material that has passed through a 100-mesh sieve is mixed with the lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing material is a mixture of calcium carbonate and calcium sulfate. The molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte is 2.5:1, and the molar ratio of calcium carbonate to calcium sulfate is 1:1.

[0138] The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 600℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with pH 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled within the range of 2.3±0.2 during the reaction. After the reaction was completed, the mixture was filtered to obtain lithium-containing leaching solution and leaching residue.

[0139] In this comparative example, the lithium leaching rate of the lithium-aluminum electrolyte was 67.60%, the fluorine leaching rate was 1.71%, and the aluminum leaching rate was 31.77%.

[0140] As can be seen from the lithium leaching rate in this comparative example, when the calcination aid is applied to the calcination of lithium-containing aluminum electrolyte, if the calcination temperature is too low, the lithium leaching rate will be low. Possible reasons include that the calcination temperature is too low, resulting in insufficient activation energy for the reaction of the lithium-containing phase, which makes the reaction unable to proceed effectively or unable to convert to the easily soluble phase.

[0141] Comparative Example 4

[0142] Calcium-containing material passing through a 100-mesh sieve was mixed with lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing material was a mixture of calcium carbonate and calcium sulfate, wherein the molar ratio of calcium in the calcium-containing material to aluminum in the lithium-aluminum electrolyte was 2.5:1, and the molar ratio of calcium carbonate to calcium sulfate was 1:1. The mixture was placed in a roasting furnace, the furnace door was closed, and roasted at 700℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with a pH of 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled within the range of 2.3±0.2 during the reaction. After the reaction was completed, the mixture was filtered to obtain lithium-containing leachate and leachate residue.

[0143] In this comparative example, the lithium leaching rate of the lithium-aluminum electrolyte was 77.56%, the fluorine leaching rate was 1.71%, and the aluminum leaching rate was 53.66%.

[0144] The lithium leaching rate in this comparative example shows that when the calcination aid is applied to the calcination of lithium-containing aluminum electrolytes, compared with Comparative Example 3, further increasing the calcination temperature can improve the lithium leaching rate to a certain extent, but the leaching of aluminum also increases accordingly. This indicates that the conversion of lithium-containing and aluminum-containing phases is a multi-parallel process, not a single conversion process.

[0145] Comparative Example 5

[0146] Calcium-containing material passing through a 100-mesh sieve was mixed with lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing material was calcium sulfate, and the molar ratio of calcium to aluminum in the lithium-aluminum electrolyte was 2.5:1. The mixture was placed in a roasting furnace, the furnace door was closed, and it was roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with a pH of 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled between 2.3 and 0.2 during the reaction. After the reaction, the solid and liquid were separated to obtain leachate and leachate residue.

[0147] In this comparative example, the lithium leaching rate was 79.13%, the fluorine leaching rate was 0.10%, and the aluminum leaching rate was 38.13%.

[0148] As can be seen from this comparative example, adding calcium sulfate alone is also insufficient to achieve effective lithium leaching.

[0149] Comparative Example 6

[0150] Calcium-containing materials passing through a 100-mesh sieve were mixed with lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing materials were calcium hydroxide and calcium oxide, with a molar ratio of calcium to aluminum in the lithium-aluminum electrolyte of 2.5:1 and a molar ratio of calcium oxide to calcium hydroxide of 1:1. The mixture was placed in a roasting furnace, the furnace door was closed, and it was roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with a pH of 2.5 at a liquid-to-solid ratio of 3:1. The pH of the slurry was controlled between 2.5 and 0.5 during the reaction, and the reaction was carried out at 60℃ for 90 minutes. After the reaction, the solid and liquid were separated to obtain leachate and leachate residue.

[0151] In this comparative example, the lithium leaching rate was 73.22%, the fluorine leaching rate was 0.87%, and the aluminum leaching rate was 27.55%.

[0152] As can also be seen from this comparative example, not all combinations of different anionic calcium-containing compounds have excellent lithium fluorine-aluminum compound conversion effects.

[0153] Comparative Example 7

[0154] Calcium-containing materials passing through a 100-mesh sieve were mixed with lithium-aluminum electrolyte powder. In this comparative example, the calcium-containing materials were calcium sulfate and calcium carbonate, with a molar ratio of calcium to aluminum in the lithium-aluminum electrolyte of 0.5:1 and a molar ratio of calcium sulfate to calcium carbonate of 1:1. The mixture was placed in a roasting furnace, the furnace door was closed, and it was roasted at 800℃ for 120 minutes to obtain roasted clinker. The roasted clinker was ground to pass through a 100-mesh sieve to obtain roasted powder. The roasted powder was then mixed with an acid leaching solution with a pH of 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 90 minutes. The pH of the slurry was controlled between 2.3 and 0.2 during the reaction. After the reaction, the solid and liquid were separated to obtain leachate and leachate residue.

[0155] In this comparative example, the lithium leaching rate was 67.38%, the fluorine leaching rate was 0.65%, and the aluminum leaching rate was 37.68%.

[0156] As can be seen from this comparative example, insufficient addition of calcium-containing additives cannot achieve efficient conversion promotion of lithium fluorine aluminum compounds.

[0157] Comparative Example 8

[0158] Lithium-aluminum electrolyte powder passing through a 100-mesh sieve was placed in a calcining furnace, the furnace door was closed, and calcined at 800℃ for 120 minutes to obtain calcined clinker. The calcined clinker was ground to pass through a 100-mesh sieve to obtain calcined powder. The calcined powder was then mixed with a leaching agent with pH 2.3 at a liquid-to-solid ratio of 3:1 and reacted at 60℃ for 120 minutes, controlling the pH of the leaching system between 2.3 and 0.1. After the reaction, the solid and liquid were separated to obtain leaching solution and leaching residue. In this comparative example, the lithium leaching rate was 55.88%, the fluorine leaching rate was 0.05%, and the aluminum leaching rate was 36.17%.

[0159] As can be seen from this comparative example, without the addition of calcium-containing additives, it is impossible to achieve efficient conversion promotion of lithium-containing phases.

[0160] Comparative Example 9

[0161] Lithium-aluminum electrolyte powder that has passed through a 100-mesh sieve was mixed with acid leaching solution at a liquid-to-solid ratio of 3:1 to form a slurry. The pH of the slurry was controlled within the range of 2.0 ± 0.1 during the reaction. The reaction was carried out at 60°C for 120 minutes. After the reaction was completed, the mixture was filtered to obtain a lithium-containing leaching solution and leaching residue. The lithium leaching rate in the lithium-aluminum electrolyte of this comparative example was 7.23%.

[0162] As can be seen from this comparative example, without roasting treatment, effective lithium leaching cannot be achieved under weak acid conditions.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0164] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method of recovering lithium from lithium-containing aluminum electrolyte waste material, characterized by, Includes the following steps: Calcination involves mixing lithium-aluminum electrolyte waste with calcium-containing substances and calcining them to obtain calcined material. Acid leaching involves mixing the roasted material with an acidic leachate and then leaching it. The ratio of the molar amount of calcium in the calcium-containing substance to the molar amount of aluminum in the lithium-aluminum electrolyte is 1-4:

1. The calcium-containing substance includes a first calcium-containing substance and a second calcium-containing substance; The first calcium-containing substance is at least one of calcium sulfate, calcium bisulfate, calcium carbonate, or calcium bicarbonate. The second calcium-containing substance is at least one of calcium carbonate, bicarbonate, sulfate, bisulfate, hydroxide, oxide, and chloride, and the second calcium-containing substance contains anions that are different or dissimilar to the first calcium-containing substance. Furthermore, the molar amount of calcium in the calcium sulfate, calcium bisulfate, calcium carbonate, or calcium bicarbonate is 40%-80% of the total molar amount of calcium in the calcium-containing substance.

2. The method of recovering lithium from lithium-containing aluminum electrolyte scrap according to claim 1, wherein The first calcium-containing substance contains at least calcium sulfate and / or calcium bisulfate; And / or, the second calcium-containing substance is calcium hydroxide and / or calcium oxide.

3. The method of recovering lithium from lithium-containing aluminum electrolyte scrap according to claim 1, wherein The second calcium-containing substance is calcium carbonate and calcium chloride; Alternatively, the second calcium-containing substance is a combination of at least one of calcium hydroxide and calcium oxide with at least one of calcium chloride and calcium carbonate.

4. The method of recovering lithium from lithium-containing aluminum electrolyte scrap of claim 1, wherein, The molar amount of calcium in the first calcium-containing substance is 50%-80% of the total molar amount of calcium in the calcium-containing substance, preferably 60%-75%.

5. The method of recovering lithium from lithium-containing aluminum electrolyte scrap of claim 1, wherein, The ratio of the molar amount of calcium in the calcium-containing material to the molar amount of aluminum in the lithium-aluminum electrolyte waste is 1.5-3.5:1, preferably 2-3:

1.

6. The method of recovering lithium from lithium-containing aluminum electrolyte scrap of claim 1, wherein, The roasting temperature is 750-1100℃, preferably 760-1050℃, more preferably 780-900℃, and / or the roasting time is 0.75-5h, preferably 1-3h, more preferably 1-2h.

7. The method of recovering lithium from lithium-containing aluminum electrolyte scrap of claim 1, wherein, The pH of the acid leaching is not higher than 6, preferably not higher than 5.5; and / or the acid leaching temperature is higher than 20°C, preferably 25-99°C; and / or the acid leaching time is more than 30 min, preferably 30-180 min; and / or the initial liquid-to-solid volume ratio of the acid leaching solution is not less than 2:1, preferably 2-10:

1.

8. The method for recovering lithium from lithium-containing aluminum electrolyte waste according to claim 7, characterized in that, The acidic pH is 1.5-5, preferably 2-4; and / or the acidic leaching temperature is 30℃-80℃; and / or the acidic leaching time is 45-120 min; and / or the initial liquid-to-solid ratio of the acidic leaching is 3-6:

1.

9. The method for recovering lithium from lithium-containing aluminum electrolyte waste according to claim 7 or 8, characterized in that, It also includes neutral leaching, wherein the pH of the neutral leachate obtained by the neutral leaching is 7.5 ± 1.0, and the neutral leaching is performed prior to the acidic leaching.

10. The method for recovering lithium from lithium-containing aluminum electrolyte waste according to claim 1, characterized in that, Also includes: After acid leaching, solid-liquid separation is performed to obtain lithium-containing acid leaching solution and acid leaching residue. Part or all of the lithium-containing acid leaching solution is returned to acid leaching, and lithium is enriched before subsequent separation and purification operations are carried out.

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