Lithium recovery method and lithium recovery device

Abstract

Provided are a lithium recovery method and a lithium recovery device with which it is possible to improve the lithium recovery rate while reducing impurities when recovering lithium from a roasted spent lithium ion battery (black mass), said lithium recovery method having: a leaching step in which an acidic solution containing an inorganic acid is added to a lithium-containing starting material to cause lithium to leach into the acidic solution; a precipitating step in which a first slurry obtained in the leaching step is neutralized to obtain a precipitate; a solid-liquid separating step in which a second slurry obtained in the precipitating step is subjected to solid-liquid separation; a washing step in which a solid phase obtained in the solid-liquid separating step is washed with a washing liquid; and a recycling step in which a post-washing liquid obtained in the washing step is reused in one or both of the leaching step and the precipitating step.

Description

Lithium recovery method and lithium recovery device

[0001] The present invention relates to a method and an apparatus for recovering lithium. This application claims priority to Japanese Patent Application No. 2023-109269 filed on July 3, 2023, and Japanese Patent Application No. 2024-107349 filed on July 3, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, the growing demand for lithium-ion batteries has raised concerns about the scarcity of lithium resources. For this reason, efforts are being made to recover and reuse lithium from lithium-ion batteries that are discarded due to factors such as the end of their product life.

[0003] When recovering lithium from lithium-ion batteries, it is common to use a recycled raw material called black mass, which is obtained by firing and pulverizing lithium-ion batteries.

[0004] As a method for recovering lithium from a fired product of a lithium-ion battery, for example, Patent Document 1 discloses a method for recovering lithium by adding water and an inorganic acid to black mass to adjust the pH to a range of 3 to 10, and leaching water-soluble lithium in the black mass into water.

[0005] Patent Document 2 focuses on the lithium aluminate contained in black mass and discloses a method of recovering lithium by leaching black mass containing lithium aluminate in an acidic solution.

[0006] Japanese Patent No. 5791917 (B) Japanese Patent No. 6998241 (B)

[0007] To recover lithium from black mass, lithium is typically leached from the black mass using water or an acidic solution. In the lithium recovery method disclosed in Patent Document 1, water-soluble lithium is leached into water by selecting a pH that prevents manganese, nickel, and cobalt in the black mass from eluting with lithium. However, the method of Patent Document 1 has a problem in that the leaching rate of lithium into water is low for lithium compounds that are poorly soluble in water, such as lithium fluoride (LiF) in the black mass.

[0008] In Patent Document 1, in order to increase the lithium concentration in the leachate, it is considered to add black mass to the obtained leachate and repeat the lithium leaching process. However, such a method of Patent Document 1 has a problem in that it does not improve the recovery rate of lithium from the black mass.

[0009] The lithium aluminate discussed in Patent Document 2 is poorly soluble in water. In Patent Document 2, an acidic solution with a pH range of 1 to 6 is used to leach the lithium aluminate from the black mass. The method of Patent Document 2 has a problem in that the leachate contains not only lithium but also valuable metals such as cobalt and aluminum. Therefore, in Patent Document 2, the leachate is neutralized to precipitate valuable metals such as cobalt and aluminum. However, even with the method of Patent Document 2, there is a problem in that the recovery rate of lithium from the black mass is insufficient.

[0010] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a lithium recovery method and lithium recovery device that can improve the lithium recovery rate while reducing impurities when recovering lithium from a fired product (black mass) of a lithium ion battery.

[0011] In order to solve the above-mentioned problems, the present invention is characterized by having any one of the following aspects: (1) A method for recovering lithium, comprising: a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing raw material, a precipitation step of neutralizing a first slurry obtained in the leaching step to obtain a precipitate, a solid-liquid separation step of performing solid-liquid separation on the second slurry obtained in the precipitation step, a washing step of washing the solid phase obtained in the solid-liquid separation step with a washing liquid, and a recycling step of reusing the post-washing liquid obtained in the washing step in either or both of the leaching step and the precipitation step.

[0012] (2) The method for recovering lithium according to (1), wherein the lithium-containing raw material is a fired lithium-ion battery product having a particle size of 1 mm or less, obtained by classifying a pyrolyzed product obtained by firing a lithium-ion battery at 400°C to 600°C.

[0013] (3) The method for recovering lithium according to (1) or (2), wherein the precipitate contains at least one metal selected from cobalt, nickel, and manganese.

[0014] (4) The method for recovering lithium according to any one of (1) to (3), wherein in the leaching step, a solid-liquid ratio (solid:liquid) of the lithium-containing raw material as a solid component to the acidic solution as a liquid component is 1:3 to 1:7 by mass.

[0015] (5) The method for recovering lithium according to any one of (1) to (4), wherein in the washing step, a solid-liquid ratio between the solid phase and the washing solution (solid phase:washing solution) is 1:2 to 1:9 in mass ratio.

[0016] (6) The method for recovering lithium according to any one of (1) to (5), wherein the liquid phase obtained in the solid-liquid separation step is supplied to the leaching step.

[0017] (7) A lithium recovery apparatus comprising: a reaction tank including a lithium-containing raw material supply device, an acidic solution supply device, and a neutralizing agent supply device; a solid-liquid separation tank for performing solid-liquid separation of a slurry; a washing tank for washing a solid phase recovered from the solid-liquid separation tank; and a recycling device for supplying a post-washing liquid recovered from the washing tank to the reaction tank.

[0018] (8) The lithium recovery apparatus according to (7), wherein the reaction tank includes a leaching tank including the lithium-containing raw material supply device and the acidic solution supply device, and a neutralization tank including the neutralizing agent supply device.

[0019] According to the present invention, it is possible to provide a lithium recovery method and a lithium recovery device that can improve the lithium recovery rate while reducing impurities.

[0020] 1 is a flowchart showing a lithium recovery method according to an embodiment of the present invention in a stepwise manner. 2 is a schematic diagram showing the configuration of a lithium recovery device according to an embodiment of the present invention.

[0021] Hereinafter, a lithium recovery method and a lithium recovery apparatus according to an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiments are specifically described to provide a better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified.

[0022] (Method for recovering lithium) As shown in FIG. 1 , the method for recovering lithium of the present embodiment includes at least a leaching step S1 of adding an acidic solution containing an inorganic acid to a lithium-containing raw material to cause lithium to be leached into the acidic solution, a precipitation step S2 of neutralizing a first slurry obtained in the leaching step S1 to obtain a precipitate, a solid-liquid separation step S3 of performing solid-liquid separation on the second slurry obtained in the precipitation step S2, a washing step S4 of washing the solid phase obtained in the solid-liquid separation step S3 with a washing liquid, and a recycling step S5 of reusing the post-wash liquid obtained in the washing step S4 in either or both of the leaching step S1 and the precipitation step S2.

[0023] The lithium recovery method of this embodiment is preferably carried out by a lithium recovery apparatus 100 shown in Fig. 2. The lithium recovery apparatus 100 used in this embodiment includes at least a reaction tank 10 equipped with a lithium-containing raw material supply device 40, an acidic solution supply device 50, and a neutralizing agent supply device 60, a solid-liquid separation tank 20, a washing tank 30, and a recycling device 70. In this embodiment, the reaction tank 10 may be a single tank, or a tank equipped with two tanks, a leaching tank 11 and a neutralization tank 12.

[0024] (Leaching step: S1) In the leaching step S1 of the present embodiment, an acidic solution containing an inorganic acid is added to the lithium-containing raw material, and lithium is leached into the acidic solution, thereby obtaining a first slurry containing a leachate and insoluble matter.

[0025] More specifically, the lithium-containing raw material may be a fired lithium-ion battery (black mass) formed using lithium-ion batteries recovered as recycled raw materials.

[0026] The black mass used in this embodiment can be obtained, for example, by the following method. The positive electrode active material of the lithium ion battery is lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium manganese oxide (LiMn ２ O ４ The negative electrode active material may contain a lithium compound such as lithium titanate. The electrolyte may contain lithium hexafluorophosphate (LiPF ６ ) and lithium tetrafluoroborate (LiBF ４ ) and other lithium compounds.

[0027] First, the lithium-ion battery is placed in a pyrolysis furnace and baked, preferably in a non-oxidizing atmosphere such as a superheated steam atmosphere or a nitrogen gas atmosphere, at a temperature in the range of about 400°C to 600°C for about 30 minutes to 5 hours to pyrolyze the lithium-ion battery. Through this pyrolysis, the organic fluorine compounds, which are the fluorine components contained in the lithium-ion battery, are pyrolyzed to produce hydrogen fluoride. Furthermore, the electrolytes, such as lithium hexafluorophosphate and lithium tetrafluoroborate, are pyrolyzed to produce hydrogen fluoride and phosphoric acid.

[0028] Then, metal oxides such as manganese oxide, nickel oxide, and cobalt oxide, and lithium fluoride (LiF) are produced from the produced hydrogen fluoride and a lithium compound contained in the electrode active material, such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, respectively.

[0029] In addition, phosphoric acid produced by thermal decomposition also reacts with lithium compounds to form lithium phosphate (Li ３ P.O. ４ ) is produced. In addition, the carbon dioxide produced during the thermal decomposition reacts with the lithium compound to produce lithium carbonate (Li ２ CO ３ ) and so on are also generated.

[0030] In this way, thermal decomposition of the electrode active materials and electrolyte contained in the lithium ion battery produces thermal decomposition products containing lithium compounds such as lithium fluoride, lithium phosphate, and lithium carbonate.

[0031] Next, the resulting pyrolyzed material containing the lithium compound is crushed. The crushed electrode active material after pyrolysis is broken into fine particles having a particle size of approximately less than 1 mm. For example, a shear crusher such as a biaxial shear crusher or an impact crusher such as a hammer mill can be used alone or in combination.

[0032] Next, the crushed pyrolyzate containing the lithium compound is classified using a sieve with an appropriate mesh size, for example, into fine particles of less than 1 mm, preferably 0.5 mm or less, and coarse particles larger than this. For classification, for example, a vibrating sieve with a mesh size of 0.1 mm to 1.0 mm, preferably 0.1 mm to 0.5 mm, may be used. By such classification, the metal chunks of the exterior case and the metal foil derived from the current collector contained in the coarse particles can be separated from the pyrolyzate of the electrode active material contained in the fine particles.

[0033] By the above steps, a lithium-ion battery fired product (black mass) containing the lithium compound of this embodiment and having a particle size of 1 mm or less can be obtained. In the leaching step S1 of this embodiment, the lithium-ion battery fired product (black mass) containing the lithium compound as described above is used as the lithium-containing raw material.

[0034] In this embodiment, the black mass described above is placed in a resin reactor 10, and an acidic solution containing water and an inorganic acid is then added to the reactor 10, followed by stirring and shaking the reactor 10. Note that the black mass may be finely pulverized or attrition-pulverized in the reactor 10 to improve the reaction efficiency.

[0035] The inorganic acid is preferably one or more selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. In a reaction tank 10, black mass, which is a lithium-containing raw material, is mixed with an acidic solution containing an inorganic acid, and lithium is leached into the acidic solution. In the first leaching step S1, the acidic solution may further contain water.

[0036] The pH condition of the acidic solution for leaching lithium into the acidic solution is preferably pH 6 or less, more preferably in the range of pH 1 to pH 3. When the pH of the acidic solution is 6 or less, lithium compounds that are poorly soluble in water, such as lithium carbonate, lithium fluoride, and lithium aluminate, dissolve as shown in the following formulas (1) to (3), and lithium can be leached into the acidic solution. Li ２ CO ３ +H ２ SO ４ →Li ２ SO ４ (liquid phase)+H ２ O (liquid phase) + CO ２ (Gas) (1) 2LiF + H ２ SO ４ →Li ２ SO ４ (liquid phase) + 2HF (liquid phase) (2) 2LiAlO ２ +4H ２ SO ４ →Li ２ SO ４ (liquid phase)+Al ２ (SO ４ ) ３ +4H ２ O (3)

[0037] In this embodiment, it is particularly preferable to use an acidic solution containing sulfuric acid as the acidic solution, and it is more preferable to carry out the leaching step S1 under conditions of a temperature of 20°C to 80°C and a pH of 1 to 3. Under such conditions, lithium fluoride and lithium aluminate, which are poorly soluble in water, are dissolved, and an acidic solution containing leached lithium can be obtained. Under the above conditions, other lithium compounds that are poorly soluble in water also easily dissolve, making it possible to improve the recovery rate of lithium from the black mass.

[0038] In the leaching step S1, the solid-liquid ratio (solid:liquid) between the black mass (solid component) and the acidic solution containing an inorganic acid (liquid component) is not particularly limited, but can be set to a mass ratio of 1:3 to 1:7. A mass ratio of 1:4 to 1:5 is more preferable. If the solid-liquid ratio is less than 1:3, there is a concern that the fluidity will decrease and the lithium recovery rate will decrease. On the other hand, even if the solid-liquid ratio exceeds 1:7, the lithium recovery rate will not change, and from the perspective of cost reduction, the upper limit may be 1:7.

[0039] The shaking time of the reaction tank 10 may be, for example, in the range of 30 minutes to 20 hours. If the shaking time is less than 30 minutes, there is a concern that the poorly water-soluble lithium compound contained in the black mass will not react sufficiently with the inorganic acid. Furthermore, if the shaking time exceeds 20 hours, there is a concern that the reaction will not proceed any further, resulting in a decrease in treatment efficiency.

[0040] In the leaching step S1 of this embodiment, not only does the leaching of lithium contained in the black mass into the acidic solution proceed, but metal components such as cobalt, manganese, and nickel also dissolve in the acidic solution.

[0041] (Precipitation Step: S2) Next, in the precipitation step S2, the first slurry obtained in the leaching step S1 is neutralized to obtain a precipitate. In this embodiment, it is preferable to add a neutralizing agent from a neutralizing agent supply device 60 to the reaction tank 10 in which the first slurry consisting of the leaching solution and the insoluble matter is held. In this embodiment, it is more preferable to perform the leaching step S1 and the precipitation step S2 in the same reaction tank 10 to avoid loss of lithium contained in the first slurry.

[0042] Examples of the neutralizing agent include alkaline compounds such as calcium hydroxide and sodium hydroxide. Of these, calcium hydroxide is preferred because it is inexpensive and reduces the sodium load in subsequent steps.

[0043] In the precipitation step S2, a neutralizing agent is preferably added to the first slurry to adjust the pH of the first slurry to 9 to 11. By adjusting the pH of the first slurry to the above range, metal components such as cobalt, manganese, and nickel contained in the leachate of the first slurry are precipitated and precipitated. Note that if the pH is less than 9, there is a concern that the metal components may not be sufficiently extracted. According to the precipitation step S2 of this embodiment, metal components such as cobalt, manganese, and nickel are precipitated as precipitates, and a precipitated second slurry is obtained.

[0044] (Solid-Liquid Separation Step: S3) In the solid-liquid separation step S3 (first solid-liquid separation) of this embodiment, the second slurry obtained in the precipitation step S2 is separated into a liquid phase and a solid phase in the solid-liquid separation tank 20. The solid-liquid separation tank 20 is preferably equipped with a filtration device, and the second slurry obtained in the precipitation step S2 may be filtered using the filtration device to separate the solid phase from the liquid phase. The solid-liquid separation step S3 can obtain a solid phase containing precipitates including cobalt, manganese, nickel, etc. and the insoluble matter from the leaching step S1, and a liquid phase in which lithium is dissolved in the form of lithium sulfate, lithium chloride, or lithium nitrate. The liquid phase may be a solution containing lithium and cobalt, nickel, and manganese that were not completely precipitated in the precipitation step S2.

[0045] (Washing step: S4) In the washing step S4 of this embodiment, the solid phase separated in the solid-liquid separation step S3 is washed with a washing liquid in the washing tank 30, and a post-wash slurry can be obtained. The solid phase separated in the solid-liquid separation step S3 has lithium attached to its surface. In this embodiment, the solid phase is washed to transfer the lithium attached to the surface of the solid phase to the washing liquid.

[0046] The cleaning liquid may be water, dilute sulfuric acid, lime water, etc. Preferably, the concentration of the dilute sulfuric acid is 0.1 mol / L or less, and the concentration of the lime water is 0.1 mass% or less. In the cleaning tank 30, the solid phase separated in the solid-liquid separation step S3 is immersed in the cleaning liquid and washed.

[0047] The solid-liquid ratio (solid phase:cleaning liquid) in the cleaning tank 30 is preferably 1:2 to 1:9 by mass. A solid-liquid ratio of 1:2 to 1:4 by mass is more preferable. When the solid-liquid ratio is within the above range, lithium adhering to the solid phase surface can be removed and the lithium remaining in the solid phase can be recovered. When the solid-liquid ratio is less than 1:2, the fluidity of the slurry consisting of the solid phase and the cleaning liquid tends to be low, making it difficult to transfer lithium adhering to the solid phase surface to the cleaning liquid. On the other hand, even if the solid-liquid ratio exceeds 1:9, the amount of lithium that can be recovered remains unchanged. Therefore, from the perspective of cost reduction, an upper limit of 1:9 is preferable. The cleaning step S4 may be performed in the solid-liquid separation tank 20 used in the solid-liquid separation step S3, rather than in the cleaning tank 30.

[0048] (Recycling Step: S5) In the recycling step S5 of this embodiment, the post-washing liquid obtained in the washing step S4 is reused in either or both of the leaching step S1 and the precipitation step S2.

[0049] First, the post-washing slurry obtained in the washing step S4 is subjected to solid-liquid separation into a post-washing liquid and a washing residue (second solid-liquid separation). The solid-liquid separation may be performed by filtering the post-washing slurry using a filtering device to separate the post-washing liquid from the washing residue.

[0050] Next, the post-washing liquid is supplied to the reaction tank 10 using the recycling device 70. When the post-washing liquid is supplied to the reaction tank 10 and reused in the leaching step S1, the post-washing liquid can be used in place of the water used in the acidic solution containing an inorganic acid. When the post-washing liquid is supplied to the reaction tank 10 and reused in the precipitation step S2, the post-washing liquid can be added to the first slurry together with a neutralizing agent via the neutralizing agent supply device 60. In this case, an amount of liquid necessary for the first slurry obtained in the leaching step S1 may be taken from the post-washing liquid and reused in the leaching step S1, and then the remaining liquid of the post-washing liquid may be reused in the precipitation step S2.

[0051] That is, in the lithium recovery method including the recycling step S5 of this embodiment, the lithium-containing washing solution recovered in the washing step S4 can be used in either or both of the leaching step S1 and the precipitation step S2 from the second time onwards. The recycling step S5 of this embodiment prevents the lithium contained in the black mass from being discharged outside the system of the lithium recovery apparatus 100 in a form other than being recovered as a lithium leaching solution, thereby improving the lithium recovery rate. Furthermore, the recycling step of this embodiment ensures that the only liquid discharged outside the system of the lithium recovery apparatus 100 is the lithium-containing liquid phase, thereby reducing the cost of treating the wastewater.

[0052] Furthermore, in this embodiment, the liquid phase obtained in the solid-liquid separation step S3 (first solid-liquid separation) may be supplied to the leaching step S1 via a liquid phase supply device 80. When the liquid phase obtained in the solid-liquid separation step S3 is supplied to the leaching step S1 to perform the second or subsequent leaching steps S1, the lithium concentration in the liquid phase from the second or subsequent leaching steps can be increased.

[0053] In the embodiment described above, the leaching step S1 and the precipitation step S2 were performed in one reaction tank 10. In another embodiment, the leaching step S1 and the precipitation step S2 may be performed using a reaction tank 10 equipped with two tanks, a leaching tank 11 and a neutralization tank 12. In this case, the leaching tank 11 is equipped with a lithium-containing raw material supply device 40 and an acidic solution supply device 50, and the neutralization tank 12 is equipped with a neutralizing agent supply device 60. The first slurry produced in the leaching tank 11 in the leaching step S1 may then be transferred to the neutralization tank 12, and a neutralizing agent may be added to the first slurry from the neutralizing agent supply device 60, to perform the precipitation step S2. When the reaction tank 10 is equipped with the leaching tank 11 and the neutralization tank 12, it is preferable to recycle the post-cleaning solution by using a recycling device 70 to supply the post-cleaning solution to either or both of the leaching tank 11 and the neutralization tank 12.

[0054] In any of the embodiments of the present invention described above, solid-liquid separation is not performed between the leaching step S1 and the precipitation step S2, which prevents loss of lithium remaining in the solid residue of the solid-liquid separation and improves the recovery rate of lithium from the black mass.

[0055] (Lithium Recovery Apparatus) As shown in FIG. 2 , the lithium recovery apparatus 100 of this embodiment includes at least a reaction tank 10 equipped with a lithium-containing raw material supply device 40, an acidic solution supply device 50, and a neutralizing agent supply device 60, a solid-liquid separation tank 20, a washing tank 30, and a recycling device 70. The reaction tank 10 may be a single tank or may include two tanks, a leaching tank 11 and a neutralization tank 12. The reaction tank 10 (leaching tank 11) of this embodiment may be any reaction tank capable of leaching lithium from the lithium-containing raw material using one or more inorganic acids selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. The reaction tank 10 (neutralization tank 12) of this embodiment may be any reaction tank capable of neutralizing the first slurry containing the lithium leaching solution. The solid-liquid separation tank 20 may be a separation device, such as a filtration device, that separates the second slurry after neutralization into solid and liquid. The cleaning tank 30 may have a configuration capable of cleaning the surface of the solid phase having lithium attached thereto and transferring the lithium to a cleaning solution. The recycling device 70 may have a post-cleaning solution delivery device that supplies a post-cleaning solution containing lithium to the reaction tank.

[0056] The effectiveness of the lithium recovery method of the present invention was verified.

[0057] (Lithium-containing raw material) A lithium-ion battery cell was heated at 500°C for pyrolysis. The fired product was crushed and classified to recover a lithium-ion battery fired product (black mass) with a particle size of 0.5 mm or less. The composition of the obtained black mass is shown in Table 1. The composition of the black mass was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) after dissolving the black mass in acid.

[0058]

[0059] Test Example 1 Black mass and an acidic solution containing sulfuric acid and water were supplied to a reaction vessel 10, and the mixture was stirred in the reaction vessel 10 for 60 minutes under conditions of pH: 1.8 to 1.9 and temperature: 25°C, thereby leaching lithium from the black mass into the acidic solution and obtaining a first slurry (leaching step S1). At this time, the solid-liquid ratio (solid:liquid) of the black mass (solid) to the acidic solution (liquid) was 1:7. The pH was obtained by measuring the pH during lithium leaching using a pH meter (manufactured by DKK-TOA).

[0060] Next, calcium hydroxide was added to the reaction tank 10, and the first slurry was neutralized under conditions of pH: 9 or higher and temperature: 25°C, thereby causing the cobalt, manganese, nickel, and aluminum contained in the leachate to precipitate and deposit, thereby obtaining a second slurry (precipitation step S2).

[0061] Next, the second slurry was filtered using a vacuum filtration apparatus (solid-liquid separation tank 20) ​​to separate it into a solid phase and a liquid phase (solid-liquid separation step S3). Water (washing liquid) was added to the vacuum filtration apparatus where the solid phase remained, so that the solid-liquid ratio (solid phase:washing liquid) was 1:3 by mass, and the mixture was again filtered under reduced pressure to obtain a washed slurry in which lithium adhering to the surface of the solid phase was transferred to the washing liquid (washing step S4).

[0062] The lithium concentration in the washing residue obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 0.2 mass%. The lithium concentration in the first post-washing solution obtained by solid-liquid separation of the post-washing slurry was 7 g / L. The lithium concentration in the washing residue was determined by washing the washing residue with water and then measuring the lithium concentration of the washing solution using an ICP (iCAP7600Duo manufactured by Thermo Fisher Scientific). The lithium concentration in the post-washing solution was measured using an ICP (iCAP7600Duo manufactured by Thermo Fisher Scientific).

[0063] Example 1 Black mass and an acidic solution containing sulfuric acid and a lithium-containing liquid were supplied to a reaction tank 10, and lithium in the black mass was leached into the acidic solution in the reaction tank 10 under conditions of pH: 1.8 to 1.9 and temperature: 25°C, thereby obtaining a first slurry (leaching step S1). At this time, the solid-liquid ratio (solid:liquid) of the black mass (solid) to the acidic solution (liquid) was 1:7. The lithium concentration in the lithium-containing liquid was 7 g / L. This was the same concentration as the lithium concentration in the first post-wash liquid obtained in Test Example 1. The recycling process of the present invention was simulated by using such a lithium-containing liquid in the acidic solution instead of the water used in Test Example 1.

[0064] Next, calcium hydroxide was added to the reaction tank 10, and the first slurry was neutralized in the reaction tank 10 under conditions of pH: 9 or higher and temperature: 25°C, thereby causing the cobalt, manganese, nickel, and aluminum contained in the leachate to precipitate and deposit, thereby obtaining a second slurry (precipitation step S2).

[0065] Next, the second slurry was filtered using a vacuum filtration apparatus (solid-liquid separation tank 20) ​​to separate it into a solid phase and a liquid phase (solid-liquid separation step S3). Then, water (washing liquid) was added to the vacuum filtration apparatus where the solid phase remained, so that the solid-liquid ratio (solid phase:washing liquid) was 1:2 by mass, and the solid phase was washed to transfer lithium adhering to the surface of the solid phase to the washing liquid, thereby obtaining a washed slurry (washing step S4).

[0066] The lithium concentration in the washing residue obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 0.8 mass %. The results are shown in Table 2. The lithium concentration in the second post-washing solution obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 7.0 g / L.

[0067] Example 2 The leaching step S1, precipitation step S2, solid-liquid separation step S3, and washing step S4 were performed under the same conditions as in Example 1, except that the solid-liquid ratio (solid:liquid) of the black mass (solid) to the acidic solution (liquid) in the leaching step S1 in Example 1 was changed to 1:3. The lithium concentration in the washing residue obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 0.8 mass%. The results are shown in Table 2. The lithium concentration in the second post-washing solution obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 4.7 g / L.

[0068] Example 3 The leaching step S1, precipitation step S2, solid-liquid separation step S3, and washing step S4 were performed under the same conditions as in Example 1, except that the solid-liquid ratio (solid:liquid) of the black mass (solid) to the acidic solution (liquid) in the leaching step S1 was changed to 1:3, and the solid-liquid ratio (solid phase:washing liquid) in the washing step S4 was changed to 1:5 by mass. The lithium concentration in the washing residue obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 0.4 mass%. The results are shown in Table 2. The lithium concentration in the second post-washing liquid obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 3.0 g / L.

[0069] Example 4 The leaching step S1, precipitation step S2, solid-liquid separation step S3, and washing step S4 were performed under the same conditions as in Example 1, except that the solid-liquid ratio (solid phase:washing liquid) in the washing step S4 in Example 1 was changed to 1:9 by mass. The lithium concentration in the washing residue obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 0.3 mass%. The results are shown in Table 2. The lithium concentration in the second post-washing liquid obtained by solid-liquid separation of the post-washing slurry after the washing step S4 was 1.6 g / L.

[0070]

[0071] Comparative Example 1 The leaching step S1, precipitation step S2, and solid-liquid separation step S3 were performed under the same conditions as in Example 1. The lithium content in the solid phase obtained in the solid-liquid separation step S3 was 2.0 mass%. The results are shown in Table 3. That is, it was confirmed that when the washing step S4 for washing the solid phase obtained in the solid-liquid separation step S3 and the recycling step S5 for recycling the post-washing liquid were not performed, more lithium remained in the solid phase after the solid-liquid separation step, resulting in a constant loss of lithium and a reduced lithium recovery rate.

[0072]

[0073] The above Examples 1 to 4 demonstrated that by performing the cleaning step S4 and recycling step S5 of the present invention, the lithium concentration discharged outside the system of the lithium recovery apparatus 100 of the present invention, i.e., the lithium concentration in the cleaning residue obtained by solid-liquid separation of the post-cleaning slurry, was low, and the lithium recovery rate was improved. In Example 2, it was demonstrated that, as long as the solid-liquid ratio in the leaching step S1 was 1:3 or less, there was no problem with handling the leaching step, and the post-cleaning solution could be repeatedly recycled. In Examples 1, 3, and 4, it was confirmed that the lithium concentration in the second post-cleaning solution was reduced by increasing the amount of cleaning solution in the cleaning step S4. That is, it was demonstrated that increasing the amount of cleaning solution in the cleaning step S4 more effectively transferred lithium adhering to the surface of the solid phase to the cleaning solution for use in the recycling step S5, and also reduced the lithium concentration discharged outside the system of the lithium recovery apparatus 100 of the present invention.

[0074] According to the method and apparatus for recovering lithium of the present invention, it is possible to reduce the loss of discharged lithium while reducing impurities such as cobalt, manganese, and nickel, thereby improving the recovery rate of lithium.

[0075] REFERENCE SIGNS LIST 100 Lithium recovery device 10 Reaction tank 11 Leaching tank 12 Neutralization tank 20 Solid-liquid separation tank 30 Washing tank 40 Lithium-containing raw material supply device 50 Acidic solution supply device 60 Neutralizing agent supply device 70 Recycling device

Claims

1. A method for recovering lithium, comprising: a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing raw material; a precipitation step of neutralizing a first slurry obtained in the leaching step to obtain a precipitate; a solid-liquid separation step of performing solid-liquid separation on the second slurry obtained in the precipitation step; a washing step of washing the solid phase obtained in the solid-liquid separation step with a washing liquid; and a recycling step of reusing the post-washing liquid obtained in the washing step in either or both of the leaching step and the precipitation step.

2. The method for recovering lithium according to claim 1, wherein the lithium-containing raw material is a fired lithium-ion battery product having a particle size of 1 mm or less, which is obtained by classifying a pyrolysate obtained by firing a lithium-ion battery at 400°C to 600°C.

3. The method for recovering lithium according to claim 1, wherein the precipitate contains at least one metal selected from cobalt, nickel, and manganese.

4. The method for recovering lithium according to claim 1, wherein in the leaching step, a solid-liquid ratio (solid:liquid) of the lithium-containing raw material as a solid component to the acidic solution as a liquid component is 1:3 to 1:7 in terms of mass ratio.

5. The method for recovering lithium according to claim 1, wherein in the washing step, a solid-liquid ratio between the solid phase and the washing solution (solid phase:washing solution) is 1:2 to 1:9 in mass ratio.

6. The method for recovering lithium according to claim 1, wherein the liquid phase obtained in the solid-liquid separation step is supplied to the leaching step.

7. A lithium recovery apparatus comprising: a reaction tank including a lithium-containing raw material supply device, an acidic solution supply device, and a neutralizing agent supply device; a solid-liquid separation tank for separating a slurry into solid and liquid; a washing tank for washing a solid phase recovered from the solid-liquid separation tank; and a recycling device for supplying a post-washing liquid recovered from the washing tank to the reaction tank.

8. The lithium recovery apparatus according to claim 7, wherein the reaction tank comprises a leaching tank having the lithium-containing raw material supply device and the acidic solution supply device, and a neutralization tank having the neutralizing agent supply device.

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