Metal recovery method

Abstract

A metal recovery method is provided that can prepare a lithium hydroxide solution from a metal-containing solution and properly treat impurities separated during the process. The method recovers metals from battery powder that is waste lithium-ion batteries, and includes an acid leaching step of leaching the metal in the battery powder into an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions, a metal separation step of separating the other metal ions from the metal-containing solution, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions as impurities after the metal separation step to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions, in which the acidic solution obtained in the electrodialysis step is mixed with the acidic leaching solution, and in the acid leaching step, the acidic leaching solution is made to contain calcium, and the fluoride ions are precipitated by the calcium.

Description

[Technical field]

[0001] This specification discloses a method for recovering metals. [Background technology]

[0002] In recent years, from the perspective of effective resource utilization, recovery of valuable metals such as cobalt and nickel contained in lithium-ion battery waste, which has been discarded due to product life, manufacturing defects, or other reasons, has been widely considered.

[0003] The process of recovering valuable metals from lithium ion battery waste may include, for example, roasting the lithium ion battery waste or other specified dry processing, and wet processing the battery powder obtained after the dry processing.

[0004] In the wet treatment, specifically, metals such as cobalt, nickel, manganese, lithium, aluminum, and iron in the battery powder are leached with an acid to obtain a metal-containing solution in which the metals are dissolved. Next, as described in Patent Document 1, for example, aluminum ions, iron ions, manganese ions, and the like are sequentially or simultaneously removed from the metal-containing solution by neutralization or solvent extraction. Thereafter, cobalt ions and nickel ions in the metal-containing solution are separated by solvent extraction. After nickel ions are separated by extraction, a metal-containing solution in which lithium ions remain is obtained. The metal-containing solution thus obtained is subjected to repeated solvent extraction to concentrate lithium ions, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 181816 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the above-mentioned metal-containing solution obtained after separating cobalt ions and / or nickel ions and other metals by solvent extraction or the like contains lithium ions. If a lithium hydroxide solution can be prepared therefrom, it can be effectively used as a pH adjuster or the like.

[0007] However, the metal-containing solution contains impurities such as fluoride ions. When the impurities are separated from such a metal-containing solution to obtain a lithium hydroxide solution, it is desirable to appropriately treat the solution containing the separated impurities and to utilize it effectively.

[0008] This specification provides a metal recovery method that can produce a lithium hydroxide solution from a metal-containing solution and properly treat the impurities separated during the process. [Means for solving the problem]

[0009] One metal recovery method disclosed in this specification is a method for recovering metals from battery powder that is lithium-ion battery waste, and includes an acid leaching step of leaching the metal in the battery powder into an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions, a metal separation step of separating the other metal ions from the metal-containing solution, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and impurity fluoride ions after the metal separation step to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions, in which the acidic solution obtained in the electrodialysis step is mixed with the acidic leaching solution, and in the acid leaching step, the acidic leaching solution is made to contain calcium, and the fluoride ions are precipitated by the calcium.

[0010] Another metal recovery method disclosed in this specification is a method for recovering metals from battery powder of lithium ion battery waste, and includes an acid leaching step of leaching the metal in the battery powder into an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions, a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including neutralization to increase the pH of the metal-containing solution to precipitate at least a portion of the other metal ions, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and impurity fluoride ions after the metal separation step to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions, and the acidic solution obtained in the electrodialysis step is Acid leachate and mixing the metal-containing solution with iron and / or calcium during the neutralization, thereby precipitating the fluoride ions by the iron and / or calcium. Effect of the Invention

[0011] According to the above-described metal recovery method, a lithium hydroxide solution can be produced from a metal-containing solution, and impurities separated during the production process can be appropriately treated. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram showing an example of a metal recovery method including an impurity removal method according to one embodiment. [Diagram 2] FIG. 1 is a flow diagram showing an example of a pretreatment process for obtaining battery powder from lithium ion battery waste. [Diagram 3] FIG. 1 is a flow diagram showing an example of an acid leaching process. [Figure 4] FIG. 1 is a cross-sectional view illustrating an example of a bipolar membrane electrodialysis device that can be used in an electrodialysis step included in an impurity removal method according to one embodiment. [Diagram 5] FIG. 2 is a diagram showing the components of each liquid before and after electrodialysis in Test Example 1 of the Examples. [Figure 6]FIG. 1 is a diagram showing the composition, quality, and distribution rate of battery powder, each solution, and residue in Test Example 2 of the embodiment. [Figure 7] FIG. 13 is a diagram showing the F concentration of battery powder and each solution, and the F grade and distribution rate of the residue in Test Example 3 of the embodiment. [Figure 8] 1 shows the results of the change in the form of aluminum in the neutralization residue depending on the F / Al molar ratio on a graph showing the relationship between the aluminum grade and the fluorine grade of the raw material in Test Example 4. [Figure 9] 1 shows the results of whether or not a predetermined low aluminum ion concentration was achieved in the leaching step and neutralization step on a graph showing the relationship between the aluminum grade and the fluorine grade of the raw material in Test Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the above-mentioned metal recovery method will be described in detail. An embodiment of the metal recovery method is a method for recovering metals from battery powder of lithium-ion battery waste. This method includes an acid leaching step of leaching the metals in the battery powder into an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions, a metal separation step of separating other metal ions from the metal-containing solution, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and impurity fluoride ions after the metal separation step to obtain a lithium hydroxide solution and an acidic solution containing fluoride ions.

[0014] In one embodiment, the acidic solution obtained in the electrodialysis step is mixed with the acidic leachate used in the acid leaching step. In this way, the acidic solution obtained in the electrodialysis step is used in the acid leaching step, whereby the acidic solution can be effectively utilized. On the other hand, when the acidic solution obtained in the electrodialysis step contains fluoride ions, when the acidic solution is returned to the acid leaching step, the fluoride ions circulate in a series of steps from acid leaching to electrodialysis, and accumulate in the steps. For this reason, in the acid leaching step, calcium is added or the like so that the acidic leachate contains calcium. In this case, the fluoride ions contained in the acidic leachate due to the mixing with the acidic solution containing fluoride ions are precipitated during the acid leaching step, and can be removed by solid-liquid separation or the like.

[0015] In another embodiment, the metal separation step includes neutralization to increase the pH of the metal-containing solution to precipitate at least a part of other metal ions, and the acidic solution obtained in the electrodialysis step is mixed with the metal-containing solution obtained in the acid leaching step. In this case, the acidic solution can be effectively utilized, while the fluoride ions contained in the acidic solution circulate and accumulate within a series of steps. For this reason, in the metal separation step, iron and / or calcium are added, etc., so that the metal-containing solution contains iron and / or calcium at the time of neutralization. In this case, the fluoride ions contained in the metal-containing solution due to mixing with the acidic solution containing fluoride ions precipitate at the time of neutralization, and can be removed by solid-liquid separation, etc.

[0016] By removing fluoride ions by precipitating them as described above, it is possible to suppress the accumulation and concentration of fluoride ions caused by mixing an acidic solution with an acidic leachate or a metal-containing solution, and therefore, it is possible to appropriately treat the impurity fluoride ions separated from the lithium hydroxide solution in the electrodialysis process, and to effectively utilize the acidic solution obtained together with the lithium hydroxide solution.

[0017] In the metal recovery method of the embodiment described here, as illustrated in Fig. 1, the wet treatment includes an acid leaching step in which battery powder of lithium ion battery waste is leached with acid to obtain a metal-containing solution, and the above-mentioned metal separation step and electrodialysis step. The lithium hydroxide solution obtained in the electrodialysis step is concentrated as necessary and then used as a pH adjuster in the metal separation step. In Fig. 1, the metal separation step includes neutralization, solvent extraction of manganese ions and / or aluminum ions (extraction of Mn, etc.), solvent extraction of cobalt ions, and solvent extraction of nickel ions. However, at least one of the neutralization and multiple solvent extractions may be omitted depending on the type of metal ions other than lithium ions contained in the metal-containing solution.

[0018] (Lithium ion battery waste) The lithium-ion battery waste targeted here is lithium-ion secondary batteries that can be used in mobile phones and various other electronic devices, and which have been discarded due to the end of the battery product's life, manufacturing defects, or other reasons. From the perspective of effective utilization of resources, it is preferable to recover valuable metals from such lithium-ion battery waste.

[0019] Lithium ion battery waste has a housing containing aluminum as an exterior that encases the periphery of the battery. For example, the housing may be made of only aluminum, or may contain aluminum and iron, aluminum laminate, etc.

[0020] In addition, the lithium ion battery waste may contain, in the above-mentioned casing, a positive electrode active material made of a single metal oxide containing lithium and one selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more kinds, or an aluminum foil (positive electrode substrate) to which the positive electrode active material is applied and fixed with, for example, polyvinylidene fluoride (PVDF) or other organic binders, etc. In addition, the lithium ion battery waste may contain copper, iron, etc.

[0021] Furthermore, the casing of lithium-ion battery waste usually contains an electrolyte solution in which an electrolyte such as lithium hexafluorophosphate is dissolved in an organic solvent, such as ethylene carbonate or diethyl carbonate.

[0022] (Pretreatment process) Lithium-ion battery waste is often subjected to a pretreatment process prior to dry processing. The pretreatment process may include at least one of roasting, crushing, and sieving. Lithium-ion battery waste is turned into battery powder through the pretreatment process. The roasting, crushing, and sieving processes in the pretreatment process may be performed individually as necessary, or may be performed in any order. In the example shown in FIG. 2, roasting, crushing, and sieving are performed in this order.

[0023] The battery powder means a powder in which the positive electrode material components are separated and concentrated by performing some kind of processing on lithium-ion battery waste. The battery powder may be obtained as a powder in which the positive electrode material components are concentrated by crushing and sieving the lithium-ion battery waste with or without performing heat treatment.

[0024] In the roasting, the lithium ion battery waste is heated. When roasting is performed, for example, metals such as lithium and cobalt contained in the lithium ion battery waste can be changed to a form that is easily soluble. In the roasting, it is preferable to heat the lithium ion battery waste at a temperature range of, for example, 450°C to 1000°C, and further 600°C to 800°C for 0.5 to 4 hours. The roasting can be performed in an air atmosphere or an inert atmosphere such as nitrogen, or it can be performed in both an air atmosphere and an inert atmosphere in this order or in the reverse order. The roasting furnace may be of a batch type or a continuous type, and for example, a stationary furnace for a batch type and a rotary kiln furnace for a continuous type are available, and various other furnaces can also be used.

[0025] During roasting, at least a part of the electrolyte is removed from the lithium ion battery waste by evaporating the electrolyte. In many cases, when the lithium ion battery waste is heated during roasting, the components of the electrolyte inside are evaporated in order starting from those with low boiling points. In addition, when the lithium ion battery waste reaches a higher temperature, the resin such as the organic binder is decomposed or vaporized. Even if a part of the electrolyte or the organic binder is removed in this way, certain components such as fluorine contained in the electrolyte or the organic binder may remain and may be contained in the battery powder obtained after the pretreatment process. When roasting is performed, the electrolyte is removed and made harmless, and the organic binder is decomposed, which promotes separation of the aluminum foil and the positive electrode active material during crushing and sieving, which will be described later. Note that the composition of the positive electrode active material changes due to roasting, but here, even if it has been roasted, it will be called the positive electrode active material.

[0026] After roasting, the lithium ion battery waste can be crushed to remove the positive electrode active material and the like from the casing of the lithium ion battery waste. In the crushing, the casing of the lithium ion battery waste is destroyed, and the positive electrode active material is selectively separated from the aluminum foil on which the positive electrode active material is applied.

[0027] For the crushing, various known devices or equipment can be used, but it is particularly preferable to use an impact crusher that can crush the lithium ion battery waste by applying an impact while cutting it. Examples of this impact crusher include a sample mill, a hammer mill, a pin mill, a wing mill, a tornado mill, and a hammer crusher. A screen can be installed at the outlet of the crusher, so that the lithium ion battery waste is discharged from the crusher through the screen when it is crushed to a size that can pass through the screen.

[0028] After the lithium-ion battery waste is crushed, it is sieved using a sieve with appropriate openings, whereby aluminum and copper remain on the sieve and battery powder from which aluminum and copper have been removed to a certain extent is obtained below the sieve.

[0029] The battery powder obtained in the pretreatment step contains lithium and, in addition to lithium, at least one other metal selected from the group consisting of cobalt, nickel, manganese, aluminum, iron, and copper. Typically, the battery powder contains lithium and at least one of nickel and cobalt. For example, the lithium content of the battery powder is 2% by mass to 8% by mass, the cobalt content is 1% by mass to 30% by mass, the nickel content is 1% by mass to 30% by mass, the manganese content is 1% by mass to 30% by mass, the aluminum content is 1% by mass to 10% by mass, the iron content is 1% by mass to 5% by mass, and the copper content is 1% by mass to 10% by mass. The battery powder may also contain fluorine at 0.1% by mass to 10% by mass.

[0030] The battery powder can be brought into contact with water before the acid leaching step described below in order to extract substantially only lithium therefrom. As a result, the lithium in the battery powder is leached into water. In this case, the battery powder as the water leaching residue is provided to the acid leaching step. However, when performing water leaching, the equipment is required, and the processing time increases by performing both the water leaching and the acid leaching in the acid leaching step, and it may be necessary to control the conditions of roasting and the like to effectively leach lithium with water. Even if such control is performed, the leaching rate of lithium with water may not be increased significantly. Therefore, the battery powder obtained as described above may be provided to the acid leaching in the acid leaching step without performing water leaching. When water leaching is not performed, it is easier to maintain a high lithium ion concentration in the liquid in the wet processing after the acid leaching step.

[0031] (Acid leaching process) In the acid leaching process, the battery powder is added to an acidic leaching solution such as sulfuric acid, nitric acid, hydrochloric acid, or other inorganic acid, to leach lithium and other metals contained in the lithium ion battery waste with the acid.

[0032] As described above, in one embodiment, the acidic leaching solution is mixed with the acidic solution obtained in the electrodialysis step described below before or after the addition of the battery powder (before or after contact with the battery powder). Then, the acidic leaching solution is made to contain calcium in order to precipitate the fluoride ions contained in the acidic solution.

[0033] Calcium may be contained in lithium-ion battery waste and in the battery powder obtained by pre-treatment of lithium-ion battery waste. Calcium may be contained in lithium-ion battery waste (such as glass fiber of battery cells), and this calcium may remain in the battery powder. In this case, the contact between the battery powder and the acid leachate causes the acid leachate to contain calcium.

[0034] However, when the calcium contained in the battery powder is insufficient, calcium may be added to the acid leaching solution separately from the battery powder. The timing of adding calcium is not particularly limited as long as it is before the end of leaching in the acid leaching step (after the end of leaching and before solid-liquid separation in the case of solid-liquid separation). For example, calcium may be contained in the battery powder and brought into contact with the acid leaching solution, or calcium may be added to the acid leaching solution before or after the battery powder is brought into contact with the acid leaching solution. In addition, for example, when the battery powder is mixed with water such as distilled water to prepare a slurry, and then an acid such as sulfuric acid is added to the slurry to prepare an acid leaching solution, calcium may be added to the slurry before the addition of the acid, or calcium may be added to the slurry together with the acid.

[0035] The form of calcium contained in the acidic leachate is not particularly limited, but examples include calcium sulfate (CaSO4), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), other calcium compounds, and elemental calcium. Among these, calcium sulfate is preferable because it does not increase the pH of the acidic leachate, as occurs when calcium carbonate or calcium hydroxide is used. At least a portion of calcium can dissolve in the acidic leachate upon contact with the solution.

[0036] The amount of calcium to be contained in the acidic leachate may be appropriately determined in consideration of the fluoride ion concentration in the acidic leachate after mixing with the acidic solution and other conditions. Specifically, the fluoride ion concentration may be analyzed and the amount of calcium may be determined based on this. For example, the amount of calcium may be adjusted so that the molar ratio of calcium to fluoride ions (Ca / F molar ratio) is 0.1 to 0.5 (0.43 in one example). However, the amount of calcium may be determined depending on the concentration of other metal ions, etc.

[0037] If calcium is contained in the acidic leachate, a precipitate may form that combines calcium with fluoride ions.

[0038] When the acid leachate obtained by mixing the acid solution with the battery powder contains a certain amount of fluorine relative to aluminum, fluorine may precipitate in the form of LiCa(AlF6). Therefore, the fluorine can be effectively removed by separating the precipitate by solid-liquid separation or the like. To obtain a precipitate of LiCa(AlF6), it is preferable that the molar ratio of fluorine to aluminum (F / Al molar ratio) of the raw material containing the battery powder is 1.3 or more. Furthermore, when the F / Al molar ratio is 2.0 or more, or even 3.0 or more, most of the precipitate may be LiCa(AlF6).

[0039] On the other hand, when the F / Al molar ratio is less than 1.3, most of the precipitate precipitated in the acid leaching step becomes Li-Al composite hydroxide. In this case, the precipitate also contains fluorine, but the more the precipitate contains LiCa(AlF6), the more effectively the fluorine is removed. However, after extensive research, the present inventors have found that even when the F / Al molar ratio is less than 1.3, the more fluorine is contained in the precipitate by adding calcium. Therefore, even when the F / Al molar ratio is less than 1.3, the accumulation and concentration of fluoride ions in the wet treatment by using the acidic solution obtained in the electrodialysis step can be suppressed.

[0040] In addition, since both LiCa(AlF6) and Li-Al composite hydroxide contain Al in their compositions, it is possible to remove aluminum together with fluorine by separating these precipitates. However, Li-Al composite hydroxide has a higher solubility in acidic leachate than LiCa(AlF6). Therefore, if the precipitate contains more LiCa(AlF6), more aluminum will precipitate, and aluminum can be removed more effectively. Thus, from the viewpoint of removing aluminum, it is preferable to set the F / Al molar ratio to 1.3 or more and generate the precipitate in the form of LiCa(AlF6).

[0041] The F / Al molar ratio is calculated from the total amount of fluorine and the total amount of aluminum in the raw materials, including the battery powder, which are to be brought into contact with or mixed with the acid leaching solution. When the acidic solution obtained in the electrodialysis process is mixed with the acidic leaching solution, the fluoride ions of the acidic solution are also included in the raw materials. In addition, when a substance containing fluorine, etc., other than the battery powder, is added to the acidic leaching solution and brought into contact with it, the substance is also considered to be part of the raw materials.

[0042] The acidic solution obtained in the electrodialysis step contains fluoride ions, so by mixing the acidic leaching solution with the acidic solution, the amount of fluoride ions in the acidic leaching solution increases, making it easier for the F / Al molar ratio to become 1.3 or more.

[0043] If iron is used instead of calcium to precipitate and remove fluoride ions, it should be added at the time of neutralization, as described below, rather than during the acid leaching process, because adding iron during the acid leaching process would result in the iron being dissolved.

[0044] Incidentally, the acid leaching step may have multiple leaching stages as described below, but may have only one leaching stage. The amount of acid used in the acid leaching step may be determined based on the amount of acid such as sulfuric acid required to leach all of the metals contained in the battery powder, among nickel, cobalt, lithium, manganese, aluminum, and iron. The amount of acid used may be 1.0 to 1.8 times the molar equivalent of the amount of acid required to leach all of the metals contained in the battery powder. When only one leaching stage is used, an amount of acid such as sulfuric acid equivalent to the above-mentioned amount may be used in the one leaching stage. In this case, the pH of the leaching solution after the one leaching stage is completed may be less than 2.0.

[0045] The leaching residue that remains after the acid leaching can be separated from the metal-containing solution by solid-liquid separation such as filtration using known devices and methods such as a filter press or thickener. Most of the copper in the battery powder may be contained in the leaching residue. This solid-liquid separation can be omitted, and a metal separation step such as neutralization may be performed after leaching without solid-liquid separation.

[0046] In addition, in the acid leaching process, a plurality of leaching steps may be repeated a plurality of times as shown in Fig. 3. Each leaching step includes a first leaching step in which the battery powder is leached with an acid leaching solution and the leaching residue is separated to obtain a leaching solution, and a second leaching step in which the leaching residue of the first leaching step is leached with an acid leaching solution to obtain a leaching solution. The leaching solution obtained in the final leaching step (the second leaching step in the case where there are two leaching steps, the first leaching step and the second leaching step) is used by being included in the acid leaching solution of the next first leaching step.

[0047] By repeating multiple leaching steps in this manner, it is possible to increase the leaching rate of the metals to be leached in the battery powder (such as cobalt and / or nickel), while separating many of the metals whose leaching is desired to be suppressed (such as copper) as leaching residue without leaching them.

[0048] As an example of repeating a plurality of leaching steps, in the first leaching step, leaching is terminated before copper is dissolved (while the copper ion concentration in the acidic leaching solution is 0.01 g / L or less), and the leaching residue is extracted by solid-liquid separation. This results in a post-leaching solution that does not contain copper ions but contains cobalt ions and nickel ions. This post-leaching solution is sent to a subsequent step such as a neutralization step described below. Meanwhile, the leaching residue contains the undissolved cobalt and nickel as well as copper. A second leaching step is performed to further leach cobalt and nickel from this leaching residue.

[0049] In the first second leaching stage, the leaching residue obtained in the first leaching stage is brought into contact with an acid leaching solution to leach cobalt and nickel in the leaching residue. In the second leaching stage, leaching is continued even after copper has been dissolved (after the copper ion concentration in the acid leaching solution becomes higher than 0.01 g / L). This allows almost all of the cobalt and nickel in the leaching residue to be leached. After copper has been dissolved and cobalt and nickel have been sufficiently leached, the leaching is terminated and the leaching residue is taken out by solid-liquid separation, so that the leaching residue contains copper but does not substantially contain cobalt or nickel. The post-leaching solution after the leaching residue is taken out contains cobalt ions, nickel ions and copper ions. In the second leaching stage, new battery powder may be added to leach not only the metals in the leaching residue in the first leaching stage but also the metals in the new battery powder. In the second leaching stage, leaching is continued even after the copper has been dissolved, so that the cobalt and nickel in the new battery powder can also be sufficiently leached.

[0050] Next, in the second first leaching stage, the leaching solution obtained in the first second leaching stage is used as the acid leaching solution. At this time, new acid leaching solution may be added if necessary. In the second first leaching stage, the copper ions in the leaching solution are reduced by a substitution reaction with a metal less noble than copper in the new battery powder added thereto, and are precipitated as copper, which is included in the leaching residue. In addition, in the second first leaching stage, cobalt and nickel are dissolved from the new battery powder, but the process ends before copper is dissolved, so that the leaching residue contains copper derived from the new battery powder as well as cobalt and nickel that remain undissolved. This leaching residue is extracted by solid-liquid separation and is used for leaching in the second second leaching stage. The leaching solution from which the leaching residue is extracted contains not only cobalt ions and nickel ions dissolved from the new battery powder, but also cobalt ions and nickel ions brought in from the first leaching process, and is sent to a subsequent process.

[0051] The second second leaching stage is carried out in the same manner as the first second leaching stage, and therefore a repeated description thereof will be omitted. It is not necessary to carry out solid-liquid separation in the second leaching stage every time. If solid-liquid separation is not carried out in the second leaching stage, the post-leaching liquid containing the leaching residue is sent to the next leaching stage, and copper accumulates in the leaching residue. If solid-liquid separation is carried out in at least one of the multiple leaching stages, the leaching residue containing copper can be separated and removed in the second leaching stage of that leaching stage. Preferably, solid-liquid separation is carried out in each second leaching stage, and the leaching residue containing copper is removed each time.

[0052] In the first leaching stage, the acid may be used in an amount of 70% or less, typically 50% to 70%, by mass, based on the total amount of acid used in each of the multiple leaching stages (total amount of acid used in the first and second leaching stages when each leaching stage consists of two leaching stages. The total amount of acid used in the multiple leaching stages can be determined based on the amount of acid required to leach all of the metals contained in the battery powder, among nickel, cobalt, lithium, manganese, aluminum, and iron. For example, when sulfuric acid is used as the acid in the acid leaching step, the total amount of sulfuric acid used can be 1.0 to 1.8 times the molar equivalent of the amount of sulfuric acid required to leach all of the above metals contained in the battery powder.

[0053] As described above, when multiple leaching stages are performed, the amount of acid used in the first leaching stage is smaller than that in the case of performing only one leaching stage, so that the pH of the leached solution obtained after the first leaching stage and solid-liquid separation may be somewhat high, such as 3.1 to 3.5, typically 3.1 to 3.3. When the pH is somewhat high, many fluoride ions are removed together with calcium.

[0054] When calcium is added to the acidic leachate in multiple leaching stages, the timing of addition is not particularly important, but it is preferable to add calcium in the first leaching stage, in which case the pH tends to be relatively high as described above, and most of the fluoride ions can be precipitated.

[0055] The leaching process, whether a single leaching step or multiple repeated leaching steps, may result in an acidic or post-leaching solution with a pH below 3.5 and an oxidation-reduction potential (ORP, silver / silver chloride potential) below 100 mV.

[0056] As described above, the acid leaching step produces a metal-containing solution as a post-leaching solution containing lithium ions and other metal ions. The other metal ions may be at least one selected from the group consisting of cobalt ions, nickel ions, manganese ions, aluminum ions, iron ions and copper ions, and typically include cobalt ions and / or nickel ions. The metal-containing solution may further contain fluoride ions.

[0057] The metal-containing solution obtained in the acid leaching step may have a cobalt ion concentration of 10 g / L to 50 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a manganese ion concentration of 0 g / L to 50 g / L, an aluminum ion concentration of 1.0 g / L to 20 g / L, an iron ion concentration of 0.1 g / L to 5.0 g / L, a copper ion concentration of 0.005 g / L to 0.2 g / L, and a fluoride ion concentration of 0.01 g / L to 20 g / L. This metal-containing solution is subjected to the metal separation step described below.

[0058] (neutralization) When the metal-containing solution obtained in the acid leaching process contains aluminum ions and / or iron ions, the metal separation process can first perform neutralization by increasing the pH of the metal-containing solution and separating the neutralization residue by solid-liquid separation to obtain a neutralized solution.

[0059] The neutralization may include a dealumination step and a deironization step, but the dealumination step and / or the deironization step may be omitted if the metal-containing solution does not contain aluminum ions and / or iron ions.

[0060] In the dealumination step, the pH of the metal-containing solution is increased to precipitate at least a portion of the aluminum ions, which are then removed by solid-liquid separation. At this time, for example, by increasing the pH to within a range of 2.5 to 5.0, particularly 3.0 to 4.5, using a pH adjuster at a liquid temperature of 50° C. to 90° C., the aluminum ions can be effectively separated while suppressing the precipitation of nickel ions and / or cobalt ions.

[0061] In the iron removal stage, an oxidizing agent is added, and a pH adjuster is further added to increase the pH. As a result, iron ions are oxidized from divalent to trivalent, and precipitate as a solid such as iron oxide or hydroxide (Fe(OH)3), which can be removed by solid-liquid separation. The ORP value (based on silver / silver chloride potential) during oxidation is preferably 300 mV to 900 mV. The oxidizing agent is not particularly limited as long as it can oxidize iron, but it is preferable to use manganese dioxide, a positive electrode active material, and / or a manganese-containing leaching residue obtained by leaching the positive electrode active material. The manganese-containing leaching residue obtained by leaching the positive electrode active material with an acid may contain manganese dioxide. When the above-mentioned positive electrode active material or the like is used as the oxidizing agent, a precipitation reaction occurs in which manganese dissolved in the liquid becomes manganese dioxide, so that the precipitated manganese can be removed together with iron.

[0062] In another embodiment, the acidic solution from the electrodialysis step described below is mixed with the metal-containing solution from the acid leaching step, and upon neutralization, the metal-containing solution contains iron and / or calcium, so that when the pH is increased, typically during the dealumination step, the iron and / or calcium contained in the metal-containing solution precipitates fluoride ions in the metal-containing solution.

[0063] If the metal-containing solution already contains the necessary amount of iron and / or calcium before neutralization, it may not be necessary to further add iron and / or calcium to it. Alternatively, if the metal-containing solution does not contain iron and / or calcium, or if the iron and / or calcium in the metal-containing solution is insufficient, iron and / or calcium may be added to the metal-containing solution before, during, and / or after the pH of the metal-containing solution is increased to a predetermined value.

[0064] The form of calcium to be added to the metal-containing solution is not particularly limited, but examples thereof include calcium sulfate, calcium carbonate, calcium hydroxide, other calcium compounds, and elemental calcium. Among these, calcium carbonate is preferable because it is relatively inexpensive. The form of iron to be added to the metal-containing solution is also not particularly limited, but it can be metal powder, metal pieces, metal lumps, etc. Either iron or calcium can be added to the metal-containing solution, or both of them can be added.

[0065] The amount of calcium or iron in the metal-containing solution may be determined based on the fluoride ion concentration contained in the metal-containing solution (for example, when calcium or iron is added, the fluoride ion concentration at the time of addition). Specifically, the amount of calcium may be adjusted so that the molar ratio of calcium to fluoride ions (Ca / F molar ratio) is 0.1 to 0.5 (0.43 as an example), and the amount of iron may be adjusted so that the molar ratio of iron to fluoride ions (Fe / F molar ratio) is 0.1 to 0.5 (0.36 as an example). However, the amount of calcium or iron may be determined depending on the concentration of other metal ions, etc.

[0066] As mentioned above, by increasing the F / Al molar ratio of the raw material containing the battery powder to a certain extent, a large amount of aluminum can be precipitated in the form of LiCa(AlF6) or the like in the neutralization process. When the acidic solution obtained in the electrodialysis process is mixed with the metal-containing solution, the acidic solution also corresponds to a part of the raw material. In this case, when the acidic solution contains fluorine, the amount of fluorine in the acidic solution is also added to the calculation of the F / Al molar ratio.

[0067] Examples of pH adjusters used in neutralization in the above-mentioned dealuminization and iron removal steps include lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia, among which it is preferable to use a lithium hydroxide solution obtained in the electrodialysis step described below. In this case, lithium ions circulate within the wet treatment.

[0068] (Manganese etc. extraction) The metal-containing solution may be neutralized as necessary, and then the manganese ions may be extracted and removed by solvent extraction. In this case, if the metal-containing solution contains aluminum ions, not only the manganese ions but also the aluminum ions are extracted and removed.

[0069] For the extraction of manganese ions, it is preferable to use an extractant containing a phosphate ester extractant. A specific example of the phosphate ester extractant is di-2-ethylhexyl phosphoric acid (abbreviation: D2EHPA or product name: DP-8R).

[0070] The extractant may be a mixture of a phosphoric acid ester extractant and an oxime extractant. In this case, the oxime extractant is preferably an aldoxime or an aldoxime-based extractant. Specifically, for example, there are 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecyl salicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), 5-nonyl salicylaldoxime (trade name: ACORGAM5640), etc., and among them, 5-nonyl salicylaldoxime is preferred from the viewpoint of price, etc.

[0071] The extractant may be diluted with a hydrocarbon organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% by volume to 30% by volume, and this may be used as the solvent.

[0072] During extraction, the equilibrium pH is preferably adjusted to 2.3 to 3.5, more preferably 2.5 to 3.0. As the pH adjuster used at this time, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis step described below.

[0073] It is desirable to perform the extraction by countercurrent multi-stage extraction in which the aqueous phase and the solvent used in each extraction flow in opposite directions. This makes it possible to suppress the extraction of cobalt ions, nickel ions, and lithium ions, and to increase the extraction rate of manganese ions. When performing countercurrent multi-stage extraction, it is effective to set the equilibrium pH during the first extraction stage within the above-mentioned range, and to lower the equilibrium pH during each extraction stage.

[0074] (Cobalt Extraction and Crystallization) For example, after manganese ions are extracted, cobalt ions can be extracted and separated from the post-manganese extraction solution (metal-containing solution) by solvent extraction.

[0075] For the extraction of cobalt ions, it is preferable to use a solvent containing a phosphonate ester extractant. In particular, 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest801) is suitable from the viewpoint of the efficiency of separating nickel and cobalt. The extractant can be used as a solvent by diluting it with a hydrocarbon organic solvent so that the concentration is 10% by volume to 30% by volume.

[0076] When cobalt ions are extracted, the equilibrium pH during extraction is preferably 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is lower than 5.0, the cobalt ions may not be sufficiently extracted into the solvent. As a pH adjuster in this case, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis step described below.

[0077] It is also preferable to perform the extraction of cobalt ions by countercurrent multi-stage extraction in which the aqueous phase and the solvent flow in opposite directions in each extraction, thereby increasing the extraction rate of cobalt ions while suppressing the extraction of nickel ions and lithium ions.

[0078] During the above extraction, not only cobalt ions but also nickel ions and lithium ions may be extracted to a small extent into the solvent. In this case, if necessary, the solvent from which the cobalt ions have been extracted may be scrubbed one or more times using a scrubbing solution to remove nickel ions and lithium ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid solution, and may have a pH of 3.5 to 5.5. The post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to mix a part or all of the post-scrubbing solution with a post-manganese extraction solution, and use the resulting solution as a pre-extraction solution to extract cobalt ions. This allows nickel ions and lithium ions to be circulated or retained in the wet treatment without loss. However, if the solvent from which the cobalt ions have been extracted does not contain nickel ions or lithium ions, the scrubbing step may not be performed.

[0079] Then, stripping is performed on the solvent from which the cobalt ions have been extracted. The stripping solution used for stripping may be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, but sulfuric acid is preferable when a sulfate salt is to be obtained by the subsequent crystallization. Here, the stripping is performed under pH conditions such that as much of the cobalt ions as possible are transferred from the solvent to the stripping solution. Specifically, the pH is preferably in the range of 2.0 to 4.0, and more preferably in the range of 2.5 to 3.5.

[0080] The liquid after stripping can be crystallized. Here, the liquid after stripping is heated to, for example, 40°C to 120°C and concentrated. As a result, cobalt ions are crystallized to obtain a cobalt salt such as cobalt sulfate. The cobalt salt thus obtained preferably has a nickel content of 5 mass ppm or less, and nickel is sufficiently removed, so that it can be effectively used as a raw material for manufacturing lithium-ion secondary batteries and other batteries. Here, the liquid after crystallization may contain cobalt ions and lithium ions that have not crystallized. Therefore, it is desirable to mix the liquid after crystallization with the liquid after stripping before crystallization and use it for recrystallization, to use it to adjust the cobalt ion concentration of the scrubbing liquid used in the solvent that extracted the cobalt ions, or to mix it with the liquid after manganese extraction and use it for extracting the cobalt ions. In this way, the cobalt ions and lithium ions can be circulated or retained in the wet treatment and concentrated without loss.

[0081] (Nickel Extraction and Crystallization) After the cobalt ions have been extracted, the post-cobalt extraction solution (metal-containing solution) can be subjected to solvent extraction to extract nickel ions.

[0082] In the extraction of nickel ions, a carboxylic acid extractant is preferably used to separate nickel ions from the solution after cobalt extraction. Examples of carboxylic acid extractants include neodecanoic acid and naphthenic acid, and among them, neodecanoic acid is preferred due to its ability to extract nickel ions. The extractant may be diluted with a hydrocarbon organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% by volume to 30% by volume, and this may be used as the solvent.

[0083] The equilibrium pH during extraction is preferably 6.0 to 8.0, more preferably 6.8 to 7.2. The pH adjuster used to adjust the pH at this time is preferably an aqueous lithium hydroxide solution obtained in the electrodialysis step described below. When extracting nickel ions, it is desirable to carry out countercurrent multi-stage extraction. In this way, the extraction of lithium ions is suppressed, and the extraction rate of nickel ions can be increased.

[0084] The solvent from which nickel ions have been extracted may be scrubbed one or more times using a scrubbing solution to remove lithium ions that may be contained in the solvent, if necessary. The scrubbing solution may be, for example, a sulfuric acid solution, and may have a pH of 5.0 to 6.0. Here, the post-scrubbing solution may contain lithium ions. Therefore, it is desirable to mix a part or all of the post-scrubbing solution with a post-cobalt extraction solution, and use the resulting solution as a pre-extraction solution to extract nickel ions. This allows lithium ions to be circulated or retained in the wet treatment and concentrated without loss. However, if the solvent from which nickel ions have been extracted does not contain lithium ions, scrubbing may not be performed.

[0085] Then, the solvent is back-extracted using a back-extraction solution such as sulfuric acid, hydrochloric acid, or nitric acid. When crystallization is then performed, sulfuric acid is preferable. The pH is preferably in the range of 1.0 to 3.0, more preferably 1.5 to 2.5. The O / A ratio and the number of times can be appropriately determined, but the O / A ratio is 5 to 1, more preferably 4 to 2.

[0086] When a stripping solution such as a nickel sulfate solution is obtained by stripping, it can be heated to 40°C to 120°C as crystallization after electrolysis and dissolution as necessary, and nickel ions can be crystallized as nickel salts such as nickel sulfate. This results in a nickel salt. Here, the crystallization solution may contain nickel ions and lithium ions that have not crystallized. Therefore, it is desirable to mix the crystallization solution with the stripping solution before crystallization and use it for recrystallization, to use it to adjust the nickel ion concentration of the scrubbing solution with respect to the solvent from which the nickel ions were extracted, or to mix it with the cobalt extraction solution and use it for extracting nickel ions. By repeatedly using it in this way within the process, nickel ions and lithium ions can be circulated or retained in the wet processing and concentrated without loss.

[0087] The nickel-extracted solution after the nickel ions are extracted mainly contains lithium ions, and may be added to the acid leaching solution in the acid leaching step. This allows the lithium ions contained in the nickel-extracted solution to be circulated in a series of steps from acid leaching to nickel extraction. Preferably, after the lithium ions are circulated in this way and the lithium ion concentration in the nickel-extracted solution becomes relatively high, the electrodialysis step described below can be carried out.

[0088] (Electrodialysis process) The metal-containing solution such as the nickel-extracted solution obtained in the above-mentioned metal separation step is a solution in which metals other than lithium ions and impurities have been sufficiently separated, and mainly contains lithium ions. The metal-containing solution may contain, as impurities, fluoride ions (F - ) are included.

[0089] The metal-containing solution may contain a small amount of cations such as nickel ions and magnesium ions that could not be completely separated in the metal separation process. Nickel ions and magnesium ions are cations like lithium ions, and behave similarly to lithium ions during electrodialysis, making it difficult to separate them from lithium ions. In addition, when electrodialysis is performed on a metal-containing solution containing nickel ions and magnesium ions, nickel and magnesium hydroxides may be generated in the lithium hydroxide solution obtained, and there is a concern that electrodialysis may not be able to be continued due to process troubles. For this reason, in such a case, it is desirable to perform washing to remove cations such as nickel ions and magnesium ions from the metal-containing solution prior to the electrodialysis described below. For example, an ion exchange resin or a chelating resin can be used for this washing.

[0090] The metal-containing solution before the electrodialysis step may have, for example, a lithium ion concentration of 1.0 g / L to 30.0 g / L and a fluoride ion concentration of 0.01 g / L to 5.0 g / L.

[0091] When a lithium hydroxide solution is obtained from the above-mentioned metal-containing solution by carbonation or chemical conversion, impurities may not be removed and may remain in the lithium hydroxide solution. The use of a lithium hydroxide solution containing a large amount of impurities as a pH adjuster in the metal separation process is undesirable because not only lithium ions but also impurities are circulated or accumulated in the wet treatment.

[0092] In this embodiment, the metal-containing solution is subjected to an electrodialysis process to obtain a lithium hydroxide solution and an acidic solution from the metal-containing solution, and since most of the impurities are contained in the acidic solution, it is possible to obtain a lithium hydroxide solution from which the impurities have been sufficiently removed.

[0093] The electrodialysis step can be carried out, for example, by using a commercially available bipolar membrane electrodialysis device. As an example, the bipolar membrane electrodialysis device 1 shown in FIG. 4 (hereinafter, simply referred to as "electrodialysis device 1") has an anode 2 and a cathode 3 in a cell, and a bipolar membrane 4, an anion exchange membrane 5, a cation exchange membrane 6, and a bipolar membrane 7 arranged in this order from the anode 2 side to the cathode 3 side between the anodes 2 and 3. As a result, the inside of the cell is partitioned into a desalting chamber R1 between the anion exchange membrane 5 and the cation exchange membrane 6, an acid chamber R2 between the bipolar membrane 4 and the anion exchange membrane 5, and an alkaline chamber R3 between the cation exchange membrane 6 and the bipolar membrane 7. Each of the bipolar membranes 4 and 7 is formed by stacking a cation exchange layer and an anion exchange layer.

[0094] To perform electrodialysis using the electrodialysis device 1 shown in the figure, a metal-containing solution is placed in the deionization compartment R1, and pure water is placed in each of the acid compartment R2 and alkaline compartment R3. A predetermined voltage is then applied between the anode 2 and the cathode 3. Then, the lithium ions (Li + ) passes through the cation exchange membrane 6 and moves to the alkaline chamber R3. In the alkaline chamber R3, water (H2O) is decomposed by the bipolar membrane 7 to produce hydroxide ions (OH - ) is present, resulting in a lithium hydroxide solution.

[0095] On the other hand, the anions of the inorganic acid in the metal-containing solution in the deionization compartment R1 pass through the anion exchange membrane 5 and move to the acid compartment R2. In the acid compartment R2, the anions and hydrogen ions (H + ) produces an acidic solution such as a sulfuric acid solution. In the example shown, the anion of the inorganic acid is the sulfate ion (SO4 2- ), but depending on the type of acid used in the acid leaching process, nitrate ions (NO3 - ) or chloride ion (Cl - ) may be the case.

[0096] In the desalting compartment R1, the lithium salt is separated from the metal-containing solution as described above, and the desalted solution remains. The anion concentration of the inorganic acid tends to be higher in the acidic solution than in the lithium hydroxide solution, and also tends to be higher in the desalted solution than in the lithium hydroxide solution.

[0097] In this electrodialysis, most of the fluoride ions, which are impurities in the metal-containing solution, move from the desalting compartment R1 to the acid compartment R2 through the anion exchange membrane 5 and are included in the acidic solution. As a result, a lithium hydroxide solution containing almost no fluoride ions is obtained in the alkaline compartment R3. Therefore, the fluoride ion concentration in the lithium hydroxide solution is lower than that in the acidic solution.

[0098] The lithium hydroxide solution from which impurities have been removed by electrodialysis as described above can be effectively used as a pH adjuster in the metal separation step. After electrodialysis, the lithium ion concentration of the lithium hydroxide solution may be increased by heating and concentration, if necessary, and then the resulting solution may be used as a pH adjuster.

[0099] The acidic solution obtained by electrodialysis contains fluoride ions. This acidic solution can be discarded as it is, but as described above, it is mixed with the acidic leaching solution from the acid leaching step and the metal-containing solution before neutralization and then circulated.

[0100] (Crystallization process) A part of the lithium hydroxide solution obtained in the electrodialysis step can be used for the crystallization step. For example, when the lithium hydroxide solution is returned to the wet treatment as a pH adjuster as described above, the lithium ion concentration in the solution may gradually increase due to the lithium in the battery powder newly added to the wet treatment. Depending on the lithium ion concentration, a crystallization step may be performed to recover lithium hydroxide.

[0101] In the crystallization step, a crystallization operation such as heating concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heating concentration, the higher the temperature during crystallization, the faster the process proceeds, so this is preferable. However, after crystallization, the temperature during drying of the crystallized product is preferably less than 60°C, at which water of crystallization does not desorb. This is because anhydrous lithium hydroxide from which water of crystallization has been desorbed is difficult to handle due to its deliquescent nature.

[0102] Thereafter, the lithium hydroxide may be subjected to a pulverization process or the like in order to adjust the physical properties to the required values. EXAMPLES

[0103] Next, tests were carried out on the above-mentioned metal recovery method, and the effectiveness of the method was confirmed. The following description is given, however, for illustrative purposes only and is not intended to be limiting.

[0104] (Test Example 1) The battery powder was leached with sulfuric acid to obtain a metal-containing solution, which was then neutralized and subjected to manganese extraction, cobalt extraction, and nickel extraction to separate the individual metals.

[0105] Next, the metal-containing solution after the separation was subjected to electrodialysis using a bipolar membrane electrodialysis device (manufactured by Astom Corporation) having a structure as shown in Fig. 4. Here, the desalting compartment, the alkaline compartment, the acid compartment and the electrode compartment were respectively filled with the metal-containing solution having the composition as shown in Fig. 5, pure water and an electrode solution. The electrodialysis condition was a low voltage of 32V.

[0106] The results are also shown in Figure 5. In Figure 5, the reason why the distribution ratios of each ion in the desalted liquid after electrodialysis, the lithium hydroxide solution, the acidic solution, and the electrode solution do not add up to 100% is thought to be due to the variability in the analytical values ​​(not including the amount that could not be quantified due to the lower limit of quantification in the analysis, etc.).

[0107] From FIG. 5, it can be seen that the fluoride ion concentration, phosphorus concentration, and silicon concentration in the lithium hydroxide solution obtained after electrodialysis are all sufficiently low. This shows that electrodialysis can obtain a lithium hydroxide solution from which most of the impurities have been removed. Also, as can be seen from FIG. 5, the phosphorus contained in the metal-containing solution tends to remain in the desalted solution and not to be distributed into the acidic solution. For this reason, even if an acidic solution is mixed with the acidic leaching solution in the acid leaching process, it is believed that there will be no accumulation of phosphorus or an increase in the phosphorus concentration in the series of processes from acid leaching to extraction.

[0108] The above tests demonstrated that a lithium hydroxide solution can be produced from a metal-containing solution, and that the acidic solution obtained by electrodialysis contains a large amount of fluoride ions as an impurity.

[0109] (Test Example 2) The battery powder was subjected to two stages of water leaching and filtration, and acid leaching using 95% by mass sulfuric acid to obtain a metal-containing solution, and then neutralized without filtration to precipitate aluminum ions while still containing the leaching residue. At the end of the acid leaching, the pH was 1.12, and the ORP value (based on silver / silver chloride potential) was 30 mV. In the neutralization, the pH of the metal-containing solution was increased to 4.02 (ORP value (based on silver / silver chloride potential): 86 mV) using 250 g / L sodium hydroxide, and then iron powder (Fe powder) was added to increase the pH to 4.27 (ORP value (based on silver / silver chloride potential): 94 mV).

[0110] The composition, quality, and distribution rate of the battery powder, each solution, and residue are shown in Figure 6. In Figure 6, "%" for quality means mass %. From Figure 6, it can be seen that the fluoride ion concentration after the addition of iron powder (0.29 g / L) is significantly lower than that before the addition of iron powder during neutralization (2.21 g / L). From this, it can be said that by adding iron to the metal-containing solution, the impurity fluoride ions can be effectively precipitated and removed.

[0111] (Test Example 3) The battery powder was subjected to the first leaching stage (first stage of leaching) as an acid leaching, and the leaching residue obtained in the first leaching stage was leached again in the second leaching stage (second stage of leaching). After that, the leaching solution from the first leaching stage was neutralized to remove aluminum ions (de-Al neutralization), and a neutralized solution and a neutralized residue were obtained. Here, the F / Al molar ratio of the raw battery powder was 3.3.

[0112] Here, multiple tests were conducted by changing the conditions of adding or not adding calcium in the first leaching stage during leaching, and adding or not adding calcium during neutralization. The results are shown in Figure 7. In Figure 7, the "%" for the grade means mass %.

[0113] As can be seen from Fig. 7, when calcium was added either during leaching or neutralization, the fluoride ion concentration (F concentration) and distribution ratio of the post-leaching solution and / or post-neutralization solution were lower than when calcium was not added at either stage. This shows that by including calcium during leaching or neutralization, fluoride ions can be effectively removed.

[0114] In addition, the same test as above was conducted by changing the condition of adding or not adding calcium in the first leaching stage of leaching, except that the F / Al molar ratio of the raw battery powder was set to 0.85. The results are shown in Table 1. It can be seen from Table 1 that the addition of calcium reduces the fluorine distribution ratio in both the post-acid leaching solution and the post-neutralization solution, and increases the fluorine distribution ratio in the acid leaching residue and the neutralization residue. From this result, it can be said that even if the F / Al molar ratio is relatively small, fluoride ions can be effectively precipitated by calcium.

[0115] [Table 1]

[0116] (Test Example 4) By changing the type of lithium-ion battery waste, the roasting atmosphere (air or inert), and other conditions, raw materials M1 to M6 consisting of six types of battery powders P1 to P6 were obtained. In addition, raw materials M7 and M8 were prepared by adding LiF to battery powder P3. The F / Al molar ratio and Al and F grades of raw materials M1 to M8 are shown in Table 2.

[0117] [Table 2]

[0118] For each of the above raw materials M1 to M6, metals were leached using sulfuric acid in one cycle of the first leaching stage and the second leaching stage shown in Figure 3. At this time, calcium sulfate was added in the first leaching stage so that the Ca / Al molar ratio of the acid leaching solution was 1.0. In the first leaching stage, the pH was set to 3.0 or less, and in the second leaching stage, the pH was set to 1.5 or less. For raw materials M7 and M8, only one leaching stage was performed, calcium sulfate was added so that the Ca / Al molar ratio of the acid leaching solution was 1.0, and the pH at the end of leaching was 1.0.

[0119] After that, the metal-containing solution, which was the post-leaching liquid of the above leaching process, was subjected to a neutralization process in which 4M LiOH was added to adjust the pH to 4.0. The neutralization residue obtained was analyzed by X-ray diffraction. As a result, it was found that the neutralization residue contained aluminum in the form of LiCa(AlF6) and / or Li-Al composite hydroxide.

[0120] Based on these results, Figure 8 shows a graph showing the relationship between the Al grade and F grade of the raw material, along with the morphology of the aluminum in the neutralization residue. As shown in Figure 8, when the F / Al molar ratio of the raw material was less than 1.3, the aluminum in the neutralization residue was almost entirely in the form of Li-Al composite hydroxide. On the other hand, when the F / Al molar ratio of the raw material was 1.3 or more, the aluminum in the neutralization residue was in the form of a mixture of Li-Al composite hydroxide and LiCa(AlF6). Furthermore, when the F / Al molar ratio of the raw material was 2.0 or more, the aluminum in the neutralization residue was almost entirely in the form of LiCa(AlF6).

[0121] In addition, in the tests using the above-mentioned raw materials M1 to M8, it was confirmed whether a low aluminum ion concentration of less than 0.5 g / L could be achieved in each solution of the leaching solution obtained in the acid leaching step or the neutralization solution obtained in the neutralization step. The results are shown in Figure 9. It can be seen from Figure 9 that when the F / Al molar ratio of the raw materials is set to 3.0 or more, the aluminum ion concentration of each solution becomes even lower.

[0122] From the above, it was found that the above-mentioned metal recovery method can appropriately treat an acidic solution obtained by electrodialysis and containing fluoride ions. [Explanation of symbols]

[0123] 1. Bipolar membrane electrodialysis device 2 Anode 3 cathode 4, 7 Bipolar membrane 5 Anion exchange membrane 6 Cation exchange membrane R1 Desalination room R2 acid chamber R3 Alkaline chamber

Claims

1. A method for recovering metals from battery powder of lithium-ion battery waste, an acid leaching step of leaching the metals in the battery powder in an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions; a metal separation step of separating the other metal ions from the metal-containing solution; After the metal separation step, an electrodialysis step is performed using a bipolar membrane to the metal-containing solution containing lithium ions and impurity fluoride ions to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. Including, a step of mixing the acidic solution obtained in the electrodialysis step with the acidic leachate, and causing the acidic leachate to contain calcium in the acid leachate, thereby precipitating the fluoride ions by the calcium.

2. 2. The metal recovery method according to claim 1, wherein in the acid leaching step, calcium is added to the acid leaching solution so that the acid leaching solution contains calcium.

3. 2. The method of claim 1, wherein the metal separation step comprises neutralizing the metal-containing solution by increasing the pH to precipitate at least a portion of the other metal ions.

4. A method for recovering metals from battery powder of lithium-ion battery waste, an acid leaching step of leaching the metals in the battery powder in an acid leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions; a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including neutralization of the metal-containing solution by increasing the pH of the metal-containing solution to precipitate at least a portion of the other metal ions; After the metal separation step, an electrodialysis step is performed using a bipolar membrane to the metal-containing solution containing lithium ions and impurity fluoride ions to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. Including, a step of mixing the acidic solution obtained in the electrodialysis step with the acidic leachate, causing the metal-containing solution to contain iron and / or calcium during the neutralization step, and precipitating the fluoride ions by the iron and / or calcium.

5. 5. The method of claim 4, further comprising adding iron and / or calcium to the metal-containing solution after the acid leaching step so that the metal-containing solution contains iron and / or calcium upon neutralization.

6. the other metal ions include aluminum ions; said neutralization comprising a dealumination step of precipitating at least a portion of the aluminum ions by raising the pH of said metal-containing solution to within the range of 4.0 to 5.0; The method for recovering metals according to any one of claims 3 to 5, wherein the fluoride ions are precipitated in the dealumination step.

7. The metal recovery method according to any one of claims 3 to 5, wherein the lithium hydroxide solution is used as a pH adjuster for the neutralization.

8. The metal recovery method according to any one of claims 1 to 5, wherein the fluoride ion concentration of the lithium hydroxide solution is lower than the fluoride ion concentration of the acidic solution.

9. The metal recovery method according to any one of claims 1 to 5, wherein the molar ratio of fluorine to aluminum (F / Al molar ratio) of the raw material containing the battery powder is 1.3 or more.

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