Lithium recovery method and lithium recovery device

Abstract

To provide a lithium recovery method and lithium recovery device capable of improving the lithium recovery rate while reducing impurities when recovering lithium from a fired product of a lithium ion battery (black mass).SOLUTION: The lithium recovery method of the present invention includes: a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing raw material to leach lithium into the acidic solution; a precipitation step of neutralizing a first slurry obtained in the leaching step to obtain a precipitate; a solid-liquid separation step of solid-liquid separating a second slurry obtained in the precipitation step; a washing step of washing a solid phase obtained in the solid-liquid separation step with a washing liquid; and a recycling step of reusing a post-washing liquid obtained in the washing step in either or both of the leaching step and the precipitation step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for recovering lithium. [Background technology]

[0002] In recent years, the growing demand for lithium-ion batteries has raised concerns about the scarcity of lithium resources. For this reason, there have been studies on recovering and reusing lithium from lithium-ion batteries that are discarded due to 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 leaching black mass containing lithium aluminate in an acidic solution to recover lithium. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5791917 [Patent Document 2] Patent No. 6998241 Summary of the Invention [Problem to be solved by the invention]

[0007] To recover lithium from black mass, it is usually 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 value that prevents manganese, nickel, and cobalt in the black mass from eluting together 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, the method of Patent Document 1 has a problem that the recovery rate of lithium from the black mass is not improved.

[0009] The lithium aluminate described 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 lithium aluminate from 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 the method of Patent Document 2 has a problem in that the recovery rate of lithium from black mass is not sufficient.

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

[0011] In order to solve the above problems, the present invention is characterized by having any one of the following aspects. (1) a leaching step of adding an acidic solution containing an inorganic acid to a lithium-containing raw material; a pre-precipitation step of neutralizing the first slurry obtained in the leaching step to obtain a precipitate; A solid-liquid separation step of separating the second slurry obtained in the precipitation step into solid and liquid; 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 solution 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, which is obtained by classifying a pyrolyzate 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 the group consisting of 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 in terms of mass ratio.

[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 terms of 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 reaction vessel 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 the slurry into solid and liquid; a washing tank for washing the solid phase recovered from the solid-liquid separation tank; and a recycling device that supplies the post-cleaning liquid recovered from the cleaning tank to the reaction tank.

[0018] (8) The lithium recovery apparatus according to (7), wherein the reaction tank comprises: 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. Effect of the Invention

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

[0020] [Figure 1] 1 is a flow chart showing a step-by-step lithium recovery method according to one embodiment of the present invention. [Diagram 2] 1 is a schematic configuration diagram of a lithium recovery device according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a lithium recovery method and lithium recovery device according to an embodiment of the present invention will be described with reference to the drawings. Note that each embodiment shown below is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0022] (How to recover lithium) As shown in FIG. 1 , the lithium recovery method of the present embodiment at least includes a leaching step S1 of adding an acidic solution containing an inorganic acid to a lithium-containing raw material to leach lithium 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 of 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 including 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 including two tanks, a leaching tank 11 and a neutralization tank 12.

[0024] (Leaching process: 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 to cause lithium to be leached into the acidic solution, thereby obtaining a first slurry consisting of a leachate and insoluble matters.

[0025] More specifically, the lithium-containing raw material may be a lithium-ion battery fired product (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 a lithium-ion battery contains lithium compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium manganese oxide (LiMn2O4). The negative electrode active material may contain lithium compounds such as lithium titanate. Furthermore, the electrolyte may contain lithium compounds such as lithium hexafluorophosphate (LiPF6) and lithium tetrafluoroborate (LiBF4).

[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 range of about 400°C to 600°C for about 30 minutes to 5 hours to pyrolyze the lithium ion battery. This thermal decomposition causes the organic fluorine compounds, which are the fluorine components contained in lithium-ion batteries, to decompose into hydrogen fluoride, while the electrolytes, such as lithium hexafluorophosphate and lithium tetrafluoroborate, decompose into 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, the phosphoric acid produced by the thermal decomposition also reacts with lithium compounds to produce lithium phosphate (Li3PO4), and the carbon dioxide produced during the thermal decomposition reacts with lithium compounds to produce lithium carbonate (Li2CO3) and other substances.

[0030] In this way, the 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 obtained pyrolyzate containing the lithium compound is crushed. By crushing, the electrode active material after pyrolysis is made into fine crushed material with a particle size of approximately less than 1 mm. For crushing, 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 pyrolysate containing the lithium compound is classified using a sieve with an appropriate mesh size, for example, into fine particles less than 1 mm, preferably 0.5 mm or less, and coarse particles larger than the fine particles. 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 mass of the exterior case and the metal foil derived from the current collector contained in the coarse particles can be separated from the pyrolysate 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, a lithium ion battery fired product (black mass) containing the above-mentioned lithium compound is used as the lithium-containing raw material.

[0034] In this embodiment, the black mass is placed in a resin reaction vessel 10, and an acidic solution containing water and an inorganic acid is then added to the reaction vessel 10, after which the reaction vessel 10 is stirred and shaken. Note that the black mass may be finely pulverized or ground by attrition in order to improve the reaction efficiency in the reaction vessel 10.

[0035] As the inorganic acid, it is preferable to use one or more acids selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. In the 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, and more preferably in the range of pH 1 to pH 3. If 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. Li2CO3+H2SO4→Li2SO4(liquid phase)+H2O(liquid phase)+CO2(gas) (1) 2LiF+H2SO4→Li2SO4(liquid phase)+2HF(liquid phase) (2) 2LiAlO2+4H2SO4→Li2SO4(liquid phase)+Al2(SO4)3+4H2O (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, can be dissolved to obtain an acidic solution in which lithium has been leached. Under the above conditions, other lithium compounds that are poorly soluble in water also become easily soluble, 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 (liquid component) containing an inorganic acid is not particularly limited, but may be 1:3 to 1:7 by mass. The solid-liquid ratio is more preferably 1:4 to 1:5 by mass. 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 the upper limit may be 1:7 from the viewpoint of cost reduction.

[0039] The shaking time of the reaction tank 10 may be, for example, in the range of 30 minutes or more and 20 hours or less. 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. Also, if the shaking time is more than 20 hours, there is a concern that the reaction will not proceed any further and the treatment efficiency will decrease.

[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 vessel 10 in which the first slurry consisting of the leachate and the insoluble matter is held. In this embodiment, it is more preferable to carry out the leaching step S1 and the precipitation step S2 in the same reaction tank 10 in order to avoid loss of lithium contained in the first slurry.

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

[0043] In the precipitation step S2, it is preferable to adjust the pH of the first slurry to 9 to 11 by adding a neutralizing agent to the first slurry. By setting the pH of the first slurry within the above range, metal components such as cobalt, manganese, and nickel contained in the leachate of the first slurry are precipitated and precipitated. If the pH is less than 9, there is a concern that the metal components may not be sufficiently precipitated. According to the precipitation step S2 of the present embodiment, metal components such as cobalt, manganese, and nickel are separated out as precipitates, and a precipitated second slurry is obtained.

[0044] (Solid-liquid separation process: S3) In the solid-liquid separation step S3 (first solid-liquid separation) of this embodiment, in a solid-liquid separation tank 20, the second slurry obtained in the precipitation step S2 is separated into a liquid phase and a solid phase. 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. By such a solid-liquid separation step S3, it is possible to obtain a solid phase containing precipitates containing cobalt, manganese, nickel, etc. and the insoluble matter of 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 are not precipitated in the precipitation step S2.

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

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

[0047] In the cleaning tank 30, the solid-liquid ratio (solid phase:cleaning liquid) with respect to the cleaning liquid is preferably 1:2 to 1:9 in mass ratio, and more preferably 1:2 to 1:4 in mass ratio. If the solid-liquid ratio is within the above range, the lithium attached to the solid phase surface can be removed and the lithium remaining in the solid phase can be recovered. If the solid-liquid ratio is less than 1:2, the fluidity of the slurry consisting of the solid phase and the cleaning solution is low, and it tends to be difficult to transfer the lithium attached to the solid phase surface to the cleaning solution. On the other hand, even if the solid-liquid ratio exceeds 1:9, there is no change in the amount of lithium that can be recovered, and from the viewpoint of cost reduction, the upper limit value is preferably 1:9. The washing step S4 may be carried out not in the washing tank 30 but in the solid-liquid separation tank 20 used in the solid-liquid separation step S3.

[0048] (Recycling process: 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] The post-wash liquid is then supplied to the reaction vessel 10 using a 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 inorganic acid. When the post-wash liquid is supplied to the reaction tank 10 and reused in the precipitation step S2, the post-wash liquid can be added to the first slurry together with the neutralizing agent via the neutralizing agent supply device 60. At this time, a liquid amount required 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 having the recycling step S5 of the present embodiment, the post-wash solution containing lithium 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. According to the recycling step S5 of the present embodiment, the lithium contained in the black mass is prevented from being discharged outside the system of the lithium recovery apparatus 100 in a form other than that of being recovered as a lithium leachate, and the lithium recovery rate can be improved. Furthermore, according to the recycling process of this embodiment, the liquid discharged outside the system of the lithium recovery apparatus 100 is only the liquid phase containing lithium, so that the cost of treating the discharged liquid can be reduced.

[0052] Furthermore, in this embodiment, the liquid phase obtained in the solid-liquid separation step S3 (first solid-liquid separation) may be supplied via a liquid phase supply device 80 to the leaching step S1. 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 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. As 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. Then, the first slurry produced in the leaching tank 11 in the leaching step S1 is moved to the neutralization tank 12, and then a neutralizing agent is added to the first slurry from the neutralizing agent supply device 60, and the precipitation step S2 is carried out. When the reaction tank 10 is equipped with a leaching tank 11 and a neutralization tank 12, it is preferable to use a recycling device 70 to supply the post-cleaning liquid to either or both of the leaching tank 11 and the neutralization tank 12, thereby recycling the post-cleaning liquid.

[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, so that the loss of lithium remaining in the solid residue of the solid-liquid separation can be prevented and the recovery rate of lithium from the black mass can be improved.

[0055] (Lithium recovery equipment) As shown in FIG. 2 , the lithium recovery apparatus 100 of the present embodiment at least includes 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 be a tank including two tanks, leaching tank 11 and 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, for example, a filtration device, which separates the second slurry after neutralization into solid and liquid. The cleaning tank 30 may be configured to clean the surface of the solid phase having lithium attached thereto and transfer the lithium to the cleaning solution. The recycling device 70 may be any device having a post-cleaning liquid delivery device that supplies the post-cleaning liquid containing lithium to the reaction tank. EXAMPLES

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

[0057] (Lithium-containing raw materials) The lithium-ion battery cells were heated to 500°C and pyrolyzed. The fired material was crushed and classified to recover the lithium-ion battery fired material (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 dissolving the black mass in acid and then using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0058] [Table 1]

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

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

[0061] Next, the second slurry was filtered by a vacuum filtration device (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 device where the solid phase remained so that the solid-liquid ratio (solid phase:washing liquid) was 1:3 by mass, and the mixture was filtered again under reduced pressure to obtain a washed slurry in which lithium attached 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 liquid obtained by solid-liquid separation of the post-washing slurry was 7 g / L. The lithium concentration in the cleaning residue was determined by washing the cleaning residue with water and then measuring the lithium concentration in the cleaning solution using an ICP (iCAP7600Duo manufactured by Thermo Fisher Scientific). The lithium concentration in the solution after cleaning was measured using an ICP (iCAP7600Duo manufactured by Thermo Fisher Scientific).

[0063] Example 1 The black mass and an acidic solution containing sulfuric acid and a lithium-containing liquid were supplied to a reaction tank 10, and the 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 to obtain a first slurry (leaching step S1). At this time, the solid-liquid ratio (solid:liquid) of the black mass (solid) and the acidic solution (liquid) was 1:7. The lithium concentration in the lithium-containing solution was set to 7 g / L, which is the same as the lithium concentration in the first post-cleaning solution obtained in Test Example 1. By using such a lithium-containing solution as the acidic solution instead of the water used in Test Example 1, the recycling process of the present invention was simulated.

[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 precipitating and precipitating the cobalt, manganese, nickel, and aluminum contained in the leachate to obtain a second slurry (precipitation step S2).

[0065] Next, the second slurry was filtered using a vacuum filtration device (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 device 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 attached 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 subjecting the post-washing slurry to solid-liquid separation after the washing step S4 was 0.8 mass %. The results are shown in Table 2. The lithium concentration in the second post-wash liquid obtained by subjecting the post-wash slurry to solid-liquid separation 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 carried out under the same conditions as in Example 1, except that the solid-liquid ratio (solid:liquid) of the black mass (solid) and 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 subjecting the post-washing slurry to solid-liquid separation after the washing step S4 was 0.8 mass %. The results are shown in Table 2. The lithium concentration in the second post-wash liquid obtained by subjecting the post-wash slurry to solid-liquid separation 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) and the acidic solution (liquid) in the leaching step S1 in Example 1 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 subjecting the post-washing slurry to solid-liquid separation after the washing step S4 was 0.4 mass %. The results are shown in Table 2. The lithium concentration in the second post-wash liquid obtained by subjecting the post-wash slurry to solid-liquid separation 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 subjecting the post-washing slurry to solid-liquid separation after the washing step S4 was 0.3 mass %. The results are shown in Table 2. The lithium concentration in the second post-wash liquid obtained by subjecting the post-wash slurry to solid-liquid separation after the washing step S4 was 1.6 g / L.

[0070] [Table 2]

[0071] Comparative Example 1 The leaching step S1, the precipitation step S2, and the solid-liquid separation step S3 were carried out 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. In other words, it was confirmed that if the washing step S4 of washing the solid phase obtained in the solid-liquid separation step S3 and the recycling step S5 of recycling the post-washing liquid are not performed, more lithium remains in the solid phase after the solid-liquid separation step, resulting in a constant loss of lithium and a decrease in the lithium recovery rate.

[0072] [Table 3]

[0073] From the above Examples 1 to 4, it was shown that by carrying out the washing step S4 and the 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 washing residue obtained by solid-liquid separation of the slurry after washing, was low, and the lithium recovery rate was improved. In Example 2, it was shown that if the solid-liquid ratio in the leaching step S1 is 1:3 or less, there is no problem with handling in the leaching step, and the post-wash liquid can 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 the cleaning solution in the cleaning step S4. That is, it was shown that by increasing the amount of the cleaning solution in the cleaning step S4, lithium attached to the surface of the solid phase can be more effectively transferred to the cleaning solution and used in the recycling step S5, and the concentration of lithium discharged outside the system of the lithium recovery device 100 of the present invention can be reduced. [Industrial Applicability]

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

[0075] 100: Lithium recovery device 10: Reactor 11: Leaching tank 12: Neutralization tank 20: Solid-liquid separation tank 30: Cleaning tank 40: Lithium-containing raw material supply device 50: Acid solution supply device 60: Neutralizer supply device 70: Recycled Devices

Claims

1. a leaching step of adding an acidic solution containing an inorganic acid to the lithium-containing raw material; a precipitation step of neutralizing the first slurry obtained in the leaching step to obtain a precipitate; A solid-liquid separation step of separating the second slurry obtained in the precipitation step into solid and liquid form; 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 solution obtained in the washing step in either or both of the leaching step and the precipitation step.

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

3. 2. The method of claim 1, wherein the precipitate comprises at least one metal selected from cobalt, nickel, and manganese.

4. 2. 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 mass ratio.

5. 2. The method for recovering lithium according to claim 1, wherein in the washing step, a solid-liquid ratio (solid phase:washing solution) between the solid phase and the 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 reaction vessel 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 the slurry into solid and liquid; a washing tank for washing the solid phase recovered from the solid-liquid separation tank; and a recycling device that supplies the post-cleaning liquid recovered from the cleaning tank to the reaction tank.

8. 8. The lithium recovery apparatus according to claim 7, wherein the reaction tank comprises 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.

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