Method for recovering metals

Abstract

To provide a method for recovering metals, which can produce a lithium hydroxide solution from a metal-containing solution and appropriately process the impurities separated at that time.SOLUTION: Provided is a method for recovering metals from battery powder of lithium ion battery waste, the method including: an acid leaching step of leaching the metals in the battery powder into an acidic 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, following the metal separation step, an electrodialysis step of subjecting the metal-containing solution containing lithium ions and fluoride ions as impurities to electrodialysis using a bipolar membrane to obtain a lithium hydroxide solution and an acidic solution comprising the fluoride ions, wherein the acidic solution obtained in the electrodialysis step is mixed with the acidic leaching solution, ensuring that the acidic leaching solution contains calcium in the acid leaching step, and the calcium induces precipitation of the fluoride ions.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

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

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

[0004] In the wet process, 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 metal is dissolved. Next, as described in Patent Document 1, for example, aluminum ions, iron ions, manganese ions, etc. 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 separating nickel ions by extraction, a metal-containing solution in which lithium ions remain is obtained. For the metal-containing solution thus obtained, lithium ions are concentrated, for example, by repeating solvent extraction.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, the above 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 an impurity can be separated from such a metal-containing solution to obtain a lithium hydroxide solution, it is desirable to appropriately treat the solution containing the separated impurity and effectively utilize it.

[0008] This specification provides a metal recovery method capable of producing a lithium hydroxide solution from a metal-containing solution and appropriately treating the impurities separated therein.

Means for Solving the Problems

[0009] One metal recovery method disclosed in this specification is a method for recovering metals from battery powder of lithium ion battery waste. The method includes an acid leaching step of leaching the metals in the battery powder into an acidic 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 after the metal separation step, performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions as impurities to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. 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 contains calcium so that the fluoride ions are precipitated by the calcium.

[0010] Other metal recovery methods disclosed in this specification are methods for recovering metals from battery powder of lithium-ion battery waste. An acid leaching step of leaching metals in the battery powder into an acidic leaching solution to obtain a metal-containing solution containing lithium ions and other metal ions, and a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including neutralization of raising the pH of the metal-containing solution to precipitate at least a part of the other metal ions, and after the metal separation step, performing electrodialysis using a bipolar membrane on a metal-containing solution containing lithium ions and fluoride ions as impurities to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. The acidic solution obtained in the electrodialysis step is mixed with the metal-containing solution obtained in the acid leaching step, and at the time of the neutralization, the metal-containing solution contains iron and / or calcium, and the fluoride ions are precipitated by the iron and / or calcium.

Advantages 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 the impurities separated at that time can be appropriately treated.

Brief Description of the Drawings

[0012]

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Mode for Carrying Out the Invention

[0013] Hereinafter, the embodiments of the above-described metal recovery method will be described in detail. The 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 metals in the battery powder into an acidic 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 after the metal separation step, performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions as impurities 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 leaching solution used in the acid leaching step. Thus, when the acidic solution obtained in the electrodialysis step is used in the acid leaching step, the acidic solution can be effectively utilized. On the other hand, when the acidic solution obtained in the electrodialysis step contains fluoride ions, if the acidic solution is returned to the acid leaching step, fluoride ions will circulate within the series of steps from acid leaching to electrodialysis, and fluoride ions will accumulate within the steps. Therefore, in the acid leaching step, calcium is added or the like to make the acidic leaching solution contain calcium. In this case, the fluoride ions contained in the acidic leaching solution due to mixing with the acidic solution containing fluoride ions will precipitate during the acid leaching step, and thus can be removed by solid-liquid separation or the like.

[0015] In another embodiment, the metal separation step includes neutralization to raise the pH of the metal-containing solution and 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. Also in this case, the acidic solution can be effectively utilized, while fluoride ions contained in the acidic solution circulate and accumulate within the series of steps. Therefore, in the metal separation step, iron and / or calcium is added or the like to make the metal-containing solution contain iron and / or calcium during neutralization. In this case, the fluoride ions contained in the metal-containing solution due to mixing with the acidic solution containing fluoride ions will precipitate during neutralization, and thus can be removed by solid-liquid separation or the like.

[0016] If the fluoride ions are precipitated and removed as described above, the accumulation and concentration of fluoride ions due to mixing the acidic solution with the acidic leaching solution or the metal-containing solution can be suppressed. Therefore, according to this, the fluoride ions of the impurities separated from the lithium hydroxide solution in the electrodialysis step are appropriately treated, and the acidic solution obtained together with the lithium hydroxide solution can be effectively utilized.

[0017] In the metal recovery method of the embodiment described herein, as illustrated in FIG. 1, as a wet treatment, an acid leaching step of leaching battery powder of lithium-ion battery waste with an acid to obtain a metal-containing solution, and the above-described metal separation step and electrodialysis step are performed. 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, depending on the types of metal ions other than lithium ions contained in the metal-containing solution, at least one of neutralization and multiple solvent extractions may be omitted.

[0018] (Lithium-ion battery waste) The lithium-ion battery waste targeted is a lithium-ion secondary battery that can be used in mobile phones and various other electronic devices, etc., and is discarded due to the life of the battery product, manufacturing defects, or other reasons. Recovering valuable metals from such lithium-ion battery waste is preferable from the viewpoint of effective utilization of resources.

[0019] The lithium-ion battery waste has a housing containing aluminum as an exterior that wraps around it. Examples of this housing include those made of only aluminum, those containing aluminum and iron, aluminum laminates, etc.

[0020] In addition, the lithium-ion battery waste includes a cathode active material made of a single metal oxide containing lithium and one type selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more types, etc. The cathode active material may include, for example, an aluminum foil (cathode substrate) coated and fixed with polyvinylidene fluoride (PVDF) or other organic binders. 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. As the organic solvent, for example, ethylene carbonate, diethyl carbonate, etc. may be used.

[0022] (Pretreatment process) In many cases, a pretreatment process of dry treatment is performed on lithium-ion battery waste. The pretreatment process may include at least one of roasting, crushing, and sieving. Lithium-ion battery waste becomes battery powder through the pretreatment process. Roasting, crushing, and sieving in the pretreatment process may be performed separately as needed or in any order. In the example shown in FIG. 2, roasting, crushing, and sieving are performed in this order.

[0023] Note that battery powder means powder in which the positive electrode material component is separated and concentrated by subjecting lithium-ion battery waste to some treatment. Battery powder may be obtained as a powdery substance in which the positive electrode material component is concentrated by performing crushing and sieving on lithium-ion battery waste with or without heat treatment.

[0024] In roasting, the above-mentioned 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 into a form that is easy to melt. During roasting, it is preferable to perform heating by holding the lithium-ion battery waste in a temperature range of, for example, 450°C to 1000°C, and further 600°C to 800°C for 0.5 hours to 4 hours. Roasting can be performed in an air atmosphere or an inert atmosphere such as nitrogen, or both the air atmosphere and the inert atmosphere may be performed in this sequential order or in the reverse order. The roasting furnace may be a batch type or a continuous type. For example, in the batch type, there is a stationary furnace, and in the continuous type, there is a rotary kiln furnace, etc., and various other furnaces can also be used.

[0025] During roasting, at least a part of the electrolytic solution is removed from the lithium-ion battery waste due to evaporation of the electrolytic solution or the like. In many cases, when the lithium-ion battery waste is heated during roasting, the low-boiling components in the electrolytic solution inside evaporate sequentially. Also, when the lithium-ion battery waste reaches a higher temperature, resins such as organic binders decompose or vaporize. Even if a part of the electrolytic solution and the organic binder are removed in this way, predetermined components such as fluorine contained in the electrolytic solution and the organic binder remain and may be contained in the battery powder obtained after the pretreatment step. When roasting is performed, the electrolytic solution is removed and rendered harmless, and the organic binder is decomposed, promoting the separation of the aluminum foil and the positive electrode active material during the subsequent crushing and sieving. Note that although the composition of the positive electrode active material changes due to roasting, here it will be referred to as the positive electrode active material even if it has undergone roasting.

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

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

[0028] After crushing the lithium-ion battery waste, sieving is performed using a sieve with an appropriate mesh size. Thereby, aluminum and copper remain on the sieve, and battery powder with aluminum and copper removed to a certain extent can be 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% to 8% by mass, the cobalt content is 1% to 30% by mass, the nickel content is 1% to 30% by mass, the manganese content is 1% to 30% by mass, the aluminum content is 1% to 10% by mass, the iron content is 1% to 5% by mass, and the copper content is 1% to 10% by mass. Further, the battery powder may contain fluorine at 0.1% 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. Thereby, lithium in the battery powder leaches into the water. In this case, the battery powder as the water leaching residue is subjected to the acid leaching step. However, when performing water leaching, equipment is required, and the treatment time increases by performing both the water leaching and the acid leaching in the acid leaching step. In addition, it may be necessary to control conditions such as roasting for effectively leaching lithium with water. Also, even with such control, the leaching rate of lithium by water may not be increased so much. Therefore, the battery powder obtained as described above may be subjected to acid leaching in the acid leaching step without performing water leaching. When water leaching is not performed, it becomes easier to maintain a high lithium ion concentration in the liquid in the wet treatment after the acid leaching step.

[0031] (Acid Leaching Step) In the acid leaching step, the above-mentioned battery powder is added to an acidic leaching solution of sulfuric acid, nitric acid, hydrochloric acid, or other inorganic acids, etc., to leach lithium and other metals contained in the lithium ion battery waste with acid.

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

[0033] Calcium may be contained in lithium-ion battery waste and the battery powder obtained by performing a pretreatment step thereon. Calcium may be contained in lithium-ion battery waste (such as the glass fiber of a battery cell), and this calcium may remain in and be contained in the battery powder. In this case, due to the contact between the battery powder and the acidic leachate, the acidic leachate becomes one containing calcium.

[0034] However, when the calcium contained in the battery powder is insufficient, calcium may be added to the acidic leachate 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 when solid-liquid separation is performed). For example, calcium can be included in the battery powder and brought into contact with the acidic leachate, or calcium can be added to the acidic leachate before or after bringing the acidic leachate into contact with the battery powder. Also, for example, when the battery powder is mixed with water such as distilled water to form a slurry and then an acid such as sulfuric acid is added to the slurry to obtain an acidic leachate, calcium can be added to the slurry before the acid addition, or calcium can be added to the slurry together with the acid.

[0035] The form of calcium to be included in the acidic leachate is not particularly limited, and examples include calcium sulfate (CaSO4), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), other calcium compounds, and calcium in its elemental form. Among them, calcium sulfate is suitable in that it does not cause an increase in the pH of the acidic leachate as in the case of using calcium carbonate or calcium hydroxide. At least a part of the calcium can be dissolved in the liquid by contact with the acidic leachate.

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

[0037] When calcium is included in the acidic leachate, a precipitate formed by the combination of calcium and fluoride ions may be generated.

[0038] When the acidic leachate after mixing the acidic solution and the battery powder contains a certain amount of fluorine with respect to aluminum, fluorine may precipitate in the form of LiCa(AlF6). Therefore, fluorine can be effectively removed by separating this precipitate by solid-liquid separation or the like. To obtain a precipitate of LiCa(AlF6), the molar ratio of fluorine to aluminum (F / Al molar ratio) in the raw material containing battery powder is preferably 1.3 or more. Further, when the F / Al molar ratio is 2.0 or more, and further 3.0 or more, much of the precipitate may be LiCa(AlF6).

[0039] On the other hand, when the F / Al molar ratio is less than 1.3, much of the precipitate that precipitates in the acid leaching step becomes a Li-Al composite hydroxide. In this case as well, the precipitate contains fluorine, but fluorine is removed more effectively when the precipitate contains more LiCa(AlF6). However, as a result of intensive studies by the present inventors, it has been found that even when the F / Al molar ratio is less than 1.3, 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] Since both LiCa(AlF6) and Li-Al composite hydroxide contain Al in their compositions, aluminum can be removed together with fluorine by separating these precipitates. However, the Li-Al composite hydroxide has a higher solubility in the acidic leachate compared to LiCa(AlF6). Therefore, when the precipitate contains more LiCa(AlF6), more aluminum precipitates, 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 form 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 material containing the battery powder that is contacted or mixed with the acidic leachate. When the acidic solution obtained in the electrodialysis step is mixed with the acidic leachate, the fluoride ions in the acidic solution are also included in the raw material. In addition, when a substance containing fluorine or the like other than the battery powder is contacted with the acidic leachate by adding it to the acidic leachate or the like, the substance is also regarded as part of the raw material.

[0042] Since the acidic solution obtained in the electrodialysis step contains fluoride ions, by mixing the acidic solution with the acidic leachate, the amount of fluoride ions in the acidic leachate increases, and the F / Al molar ratio tends to be 1.3 or more.

[0043] In addition, when iron is used instead of calcium for the precipitation and removal of fluoride ions, iron is added at the time of neutralization as described later, not during the acid leaching step. This is because if iron is added during the acid leaching step, the iron will dissolve.

[0044] Incidentally, in the acid leaching step, although it may be a plurality of leaching stages as described later, it can be only a single-stage leaching. The amount of acid used in the acid leaching step can be determined based on the amount of acid such as sulfuric acid necessary 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 necessary for leaching all of the above metals contained in the battery powder. In the case of only single-stage leaching, in that single-stage leaching, an acid such as sulfuric acid corresponding to the above usage amount can be used. In this case, the pH of the leachate after the single-stage leaching may be less than 2.0.

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

[0046] Also, in the acid leaching step, as shown in FIG. 3, a plurality of leaching stages may be repeated a plurality of times. Each leaching stage includes a first leaching stage in which the battery powder is leached with an acidic leaching solution and the leaching residue is separated to obtain a leachate after leaching, and a second leaching stage in which the leaching residue of the first leaching stage is leached with an acidic leaching solution to obtain a leachate after leaching. Among these leaching stages, the leachate obtained in the final leaching stage (the second leaching stage in the case of the first and second leaching stages) is included and used in the acidic leaching solution of the next first leaching stage.

[0047] By repeating a plurality of leaching stages in this way, while increasing the leaching rate of the metal to be leached (such as cobalt and / or nickel, etc.) in the battery powder, most of the metals (such as copper, etc.) for which leaching suppression is desired can be separated as a leaching residue without being leached.

[0048] As an example of repeatedly performing a plurality of leaching steps, in the first leaching step of the first time, leaching is terminated before copper dissolves (while the copper ion concentration in the acidic leaching solution is 0.01 g / L or less), and the leaching residue is taken out by solid-liquid separation. Then, a leaching post-liquid containing no copper ions but containing cobalt ions and nickel ions is obtained. This leaching post-liquid is sent to subsequent processes such as the neutralization process described later. On the other hand, the leaching residue will contain cobalt and nickel that remained undissolved and copper. In order to further leach cobalt and nickel from this leaching residue, a second leaching step is performed.

[0049] In the second leaching step of the first time, the leaching residue obtained in the first leaching step is brought into contact with the acidic leaching solution to leach cobalt and nickel in the leaching residue. In the second leaching step, leaching is continued even after copper has dissolved (after the copper ion concentration in the acidic leaching solution has become higher than 0.01 g / L). Thereby, almost all of the cobalt and nickel in the leaching residue can be leached. After copper has dissolved and after cobalt and nickel have been sufficiently leached, leaching is terminated and the leaching residue is taken out by solid-liquid separation. Then, the leaching residue will contain copper but will substantially contain no cobalt and nickel. The leaching post-liquid after the leaching residue has been taken out contains cobalt ions, nickel ions, and copper ions. Note that in the second leaching step, new battery powder may be added, and not only the metals in the leaching residue of the first leaching step but also the metals in the new battery powder may be leached. Since leaching is continued even after copper has dissolved in the second leaching step, cobalt and nickel in the new battery powder can also be sufficiently leached.

[0050] Next, in the second first leaching stage, the post-leaching solution obtained in the first second leaching stage is used as the acidic leaching solution. At this time, if necessary, a new acidic leaching solution may be added. In the second first leaching stage, copper ions in the above-mentioned post-leaching solution are reduced by a metal less noble than copper in the newly introduced battery powder through a substitution reaction and precipitated as copper, which is contained in the leaching residue. Also, in the second first leaching stage, cobalt and nickel dissolve out from the new battery powder, but it ends before copper dissolves out. Therefore, the leaching residue will also contain copper derived from the new battery powder, as well as cobalt and nickel that remained undissolved. This leaching residue is taken out by solid-liquid separation and subjected to leaching in the second second leaching stage. The post-leaching solution from which the leaching residue has been taken out contains not only cobalt ions and nickel ions dissolved out from the new battery powder, but also cobalt ions and nickel ions brought in from the first leaching process, and is sent to the subsequent process.

[0051] The second second leaching stage is carried out in the same manner as the first second leaching stage, so a repeated description thereof will be omitted. Solid-liquid separation in the second leaching stage does not need to be carried out every time. If solid-liquid separation is not carried out in the second leaching stage, the post-leaching solution containing the leaching residue will be sent to the next time, and copper will accumulate in the leaching residue. If solid-liquid separation is carried out in the second leaching stage at least once among multiple times, the leaching residue containing copper can be separated and removed in the second leaching stage of that time. 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, an acid amount of 70% or less, typically 50% - 70% by mass, may be used with respect to the total amount of acid used in a plurality of leaching stages for each batch (total acid usage; when each batch consists of two leaching stages, the total amount of acid used in the first and second leaching stages). The total acid usage in a plurality of leaching stages can be determined based on the amount of acid required to leach all 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 process, the total usage amount of the sulfuric acid can be set to 1.0 - 1.8 times the molar equivalent of the amount of sulfuric acid required for leaching all of the above metals contained in the battery powder.

[0053] When performing a plurality of leaching stages as described above, since the amount of acid used in the first leaching stage is less than that in the case of performing only one-stage leaching, the pH of the post-leaching solution obtained after solid-liquid separation at the end of the first leaching stage may be somewhat higher, typically 3.1 - 3.5, typically 3.1 - 3.3. When the pH is somewhat high in this way, many fluoride ions are removed together with calcium.

[0054] When adding calcium to the acidic leaching solution in a plurality of leaching stages, the addition timing is not particularly limited, but it is preferably the first leaching stage. In this case, in the first leaching stage, since the pH tends to be somewhat high as described above, many fluoride ions can be precipitated.

[0055] Regardless of whether only one-stage leaching is performed or a plurality of leaching stages are repeated, in the leaching process, the pH of the acidic leaching solution or the post-leaching solution may be less than 3.5. Also, the oxidation-reduction potential (ORP value, silver / silver chloride electrode reference) may be 100 mV or less.

[0056] As described above, in the acid leaching step, a metal-containing solution is obtained as a leachate 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 contain 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 step contains aluminum ions and / or iron ions, in the metal separation step, first, the pH of the metal-containing solution can be raised, and neutralization can be performed to separate the neutralization residue by solid-liquid separation to obtain a post-neutralization solution.

[0059] Neutralization may include an aluminum removal stage and an iron removal stage. However, in cases where the metal-containing solution does not contain aluminum ions and / or iron ions, etc., the aluminum removal stage and / or the iron removal stage may be omitted.

[0060] In the aluminum removal stage, by raising the pH of the metal-containing solution, at least a part of the aluminum ions is precipitated and removed by solid-liquid separation. At this time, for example, when the liquid temperature is 50°C to 90°C and the pH is raised to the range of 2.5 to 5.0, particularly 3.0 to 4.5, with a pH adjuster, 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 solids such as oxides or iron hydroxide (Fe(OH)3), which can be removed by solid-liquid separation. The ORP value (silver / silver chloride electrode reference) 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 preferably 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 using the above positive electrode active material or the like 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 obtained in the electrodialysis step described later is mixed with the metal-containing solution obtained in the acid leaching step. Then, during neutralization, the metal-containing solution is made to contain iron and / or calcium. In this way, typically in the de-aluminum stage, when the pH is increased, fluoride ions in the metal-containing solution precipitate due to the iron and / or calcium contained in the metal-containing solution.

[0063] If the metal-containing solution already contains iron and / or calcium in the required amounts before neutralization, it may not be necessary to add further iron and / or calcium. 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 raising the pH of the metal-containing solution to a predetermined value.

[0064] The form of calcium added to the metal-containing solution is not particularly limited, and examples include calcium sulfate, calcium carbonate, calcium hydroxide, and other calcium compounds, as well as elemental calcium. Among them, calcium carbonate is preferred because it is relatively inexpensive. Also, the form of iron added to the metal-containing solution is not particularly limited, and it can be in the form of metal powder, metal pieces, metal lumps, etc. Either only one of iron and calcium can be added to the metal-containing solution, or both of them can be added.

[0065] The amounts of calcium and iron in the metal-containing solution may be determined based on, for example, the fluoride ion concentration in the metal-containing solution (when adding calcium or iron, 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 (in one example, 0.43), 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 (in one example, 0.36). However, the amounts of calcium and iron may be determined according to other metal ion concentrations, etc.

[0066] Also, as described above, by increasing the F / Al molar ratio of the raw material containing battery powder to a certain extent, a large amount of aluminum can be precipitated in the form of LiCa(AlF6) etc. in the neutralization step. When mixing the acidic solution obtained in the electrodialysis step with the metal-containing solution, that 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 in the calculation of the F / Al molar ratio.

[0067] Examples of the pH adjuster used in the neutralization such as the above-described de-aluminum stage and de-iron stage include lithium hydroxide, sodium hydroxide, sodium carbonate, ammonia, etc., but it is preferable to use the lithium hydroxide solution obtained in the electrodialysis step described later. In this case, lithium ions circulate within the wet treatment.

[0068] (Extraction of manganese, etc.) The metal-containing solution can extract and remove manganese ions by solvent extraction after the above neutralization if necessary. Here, when the metal-containing solution contains aluminum ions, not only manganese ions but also aluminum ions are extracted and removed.

[0069] For the extraction of manganese ions, it is preferable to use an extractant containing a phosphoric acid ester-based extractant. Specific examples of the phosphoric acid ester-based extractant include di-2-ethylhexyl phosphoric acid (abbreviation: D2EHPA or trade name: DP-8R).

[0070] In addition, the extractant may be a mixture of an oxime-based extractant and a phosphoric acid ester-based extractant. In this case, the oxime-based extractant is preferably an aldoxime or one mainly composed of aldoxime. Specifically, for example, 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecylsalicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), 5-nonylsalicylaldoxime (trade name: ACORGAM5640), etc. Among them, 5-nonylsalicylaldoxime is preferable in terms of price and the like.

[0071] The extractant may be diluted to a concentration of 10% to 30% by volume using a hydrocarbon-based organic solvent such as an aromatic-based, paraffin-based, or naphthene-based solvent, and used as the solvent.

[0072] During extraction, the equilibrium pH is preferably 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 later.

[0073] Upon extraction, it is desirable to perform extraction by countercurrent multi-stage extraction in which the flow directions of the aqueous phase and the solvent used for each extraction are opposite. By doing so, the extraction of cobalt ions, nickel ions, and lithium ions can be suppressed, and the extraction rate of manganese ions can be increased. In the case of countercurrent multi-stage extraction, for example, it is effective to set the equilibrium pH at the time of the first-stage extraction to a value within the above range and lower the equilibrium pH at the time of extraction for each successive stage.

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

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

[0076] When extracting cobalt ions, the equilibrium pH at the time of extraction is preferably 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is less than 5.0, there is a possibility that cobalt ions may not be sufficiently extracted into the solvent. As the pH adjuster in this case, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis step described later.

[0077] Also in the extraction of cobalt ions, it is desirable to perform extraction by countercurrent multi-stage extraction in which the flow directions of the aqueous phase and the solvent used for each extraction are opposite. By doing so, the extraction rate of cobalt ions can be increased while suppressing the extraction of nickel ions and lithium ions.

[0078] During the above extraction, not only cobalt ions but also some nickel ions and lithium ions may be extracted into the solvent. In this case, if necessary, the solvent from which 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 can be, for example, a sulfuric acid solution, and the pH can be set to 3.5 to 5.5. The scrubbed solution may contain nickel ions and lithium ions. Therefore, it is desirable to mix part or all of the scrubbed solution with the solution after manganese extraction and use it as the solution before extraction to extract cobalt ions. This allows nickel ions and lithium ions to be circulated or retained within the wet treatment without loss. However, if the solvent from which cobalt ions have been extracted does not contain nickel ions or lithium ions, the scrubbing step may not be necessary.

[0079] Thereafter, back extraction is performed on the solvent from which cobalt ions have been extracted. The back extraction solution used for back extraction may be any of inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, but sulfuric acid is desirable when obtaining sulfate by crystallization in the next step. Here, the back extraction is performed under pH conditions such that as much cobalt ions as possible transfer from the solvent to the back extraction 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 post-back extraction liquid can be crystallized. Here, the post-back extraction liquid is heated to, for example, 40°C to 120°C and concentrated. Thereby, cobalt ions are crystallized, and cobalt salts such as cobalt sulfate are obtained. The cobalt salt thus obtained has a nickel content of preferably 5 mass ppm or less, and since nickel is sufficiently removed, it can be effectively used as a raw material for manufacturing lithium-ion secondary batteries and other batteries. Here, the post-crystallization liquid may contain cobalt ions and lithium ions that did not crystallize. Therefore, the post-crystallization liquid can be mixed with the post-back extraction liquid before crystallization and subjected to crystallization again, used to adjust the cobalt ion concentration of the scrubbing liquid used in the solvent for extracting cobalt ions, or mixed with the post-manganese extraction liquid and subjected to cobalt ion extraction. In this way, cobalt ions and lithium ions can be circulated or retained within the wet treatment without loss and concentrated.

[0081] (Nickel extraction and crystallization) For the post-cobalt extraction liquid (metal-containing solution) after extracting cobalt ions, solvent extraction can be performed to extract nickel ions.

[0082] In the extraction of nickel ions, preferably a carboxylic acid-based extractant is used to separate nickel ions from the post-cobalt extraction liquid. Examples of the carboxylic acid-based extractant include neodecanoic acid, naphthenic acid, etc. Among them, neodecanoic acid is preferred due to its nickel ion extraction ability. The extractant may be diluted to a concentration of 10 vol% to 30 vol% using a hydrocarbon-based organic solvent such as an aromatic-based, paraffin-based, or naphthene-based solvent, 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. As the pH adjuster used for pH adjustment at this time, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis process described later. When extracting nickel ions, it is desirable to perform countercurrent multi-stage extraction. By doing so, the extraction of lithium ions is suppressed and the extraction rate of nickel ions can be increased.

[0084] For the solvent from which nickel ions have been extracted, if necessary, one or more scrubbings may be performed to remove lithium ions that may be contained in the solvent using a scrubbing solution. The scrubbing solution can be, for example, a sulfuric acid solution, and the pH can be 5.0 to 6.0. Here, the scrubbed solution may contain lithium ions. Therefore, it is desirable to mix part or all of the scrubbed solution with the solution after cobalt extraction and use it as the solution before extraction to extract nickel ions. Thereby, it is possible to circulate or retain and concentrate within the wet treatment without losing lithium ions. However, if the solvent from which nickel ions have been extracted does not contain lithium ions, scrubbing may not be necessary.

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

[0086] When a stripping post-liquid such as a nickel sulfate solution is obtained by reverse extraction, after electrolysis and dissolution are performed as necessary, it is heated to 40°C to 120°C for crystallization, and nickel ions can be crystallized as a nickel salt such as nickel sulfate. As a result, a nickel salt is obtained. Here, the post-crystallization liquid may contain nickel ions and lithium ions that did not crystallize. Therefore, the post-crystallization liquid may be mixed with the post-stripping liquid before crystallization and subjected to re-crystallization, used to adjust the nickel ion concentration of the scrubbing liquid with respect to the solvent from which nickel ions have been extracted, or mixed with the post-cobalt extraction liquid and subjected to nickel ion extraction. By repeatedly using it within the process in this way, nickel ions and lithium ions can be circulated or retained within the wet treatment for concentration without loss.

[0087] The post-nickel extraction liquid after nickel ions are extracted mainly contains lithium ions and may be added to the acidic leaching liquid in the acid leaching step. Thereby, the lithium ions contained in the post-nickel extraction liquid can be circulated within 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 of the post-nickel extraction liquid has increased to a certain extent, the electrodialysis step described below can be performed.

[0088] (Electrodialysis step) The metal-containing solution such as the post-nickel extraction liquid obtained in the above-described metal separation step has had metals other than lithium ions and impurities sufficiently separated and mainly contains lithium ions. The metal-containing solution contains, as impurities, for example, fluoride ions (F - ) derived from, for example, the electrolytic solution contained in the battery powder.

[0089] Incidentally, the metal-containing solution may contain trace amounts of cations such as nickel ions and magnesium ions that could not be completely separated in the metal separation step. Nickel ions and magnesium ions are cations like lithium ions and exhibit the same behavior as lithium ions during electrodialysis, making it difficult to separate them from lithium ions. Also, when electrodialysis is performed on a metal-containing solution containing nickel ions and magnesium ions, hydroxides of nickel and magnesium may be generated in the resulting lithium hydroxide solution, raising concerns that electrodialysis may not be able to continue due to process troubles. For this reason, in such cases, it is desirable to perform a cleaning to remove cations such as nickel ions and magnesium ions from the metal-containing solution prior to the electrodialysis described below. For this cleaning, for example, an ion exchange resin or a chelating resin can be used.

[0090] The metal-containing solution before the electrodialysis step may, for example, have 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 obtaining a lithium hydroxide solution from the above metal-containing solution, if methods such as carbonation and conversion are applied, impurities may remain in the lithium hydroxide solution without being removed. Using a lithium hydroxide solution containing a large amount of impurities as a pH adjuster in the metal separation step is not desirable because not only lithium ions but also impurities will circulate or accumulate within the wet process.

[0092] Therefore, in this embodiment, an electrodialysis step is performed on the metal-containing solution to obtain a lithium hydroxide solution and an acidic solution from the metal-containing solution. As a result, since most of the impurities are contained in the acidic solution, a lithium hydroxide solution with sufficiently removed impurities can be obtained.

[0093] The electrodialysis process can be carried out, for example, using a commercially available bipolar membrane electrodialysis device. As an example, the bipolar membrane electrodialysis device 1 shown in Fig. 4 (hereinafter, also simply referred to as "electrodialysis device 1") has an anode 2 and a cathode 3 in the cell, and between these anodes 2 and 3, a bipolar membrane 4, an anion exchange membrane 5, a cation exchange membrane 6, and a bipolar membrane 7 are sequentially arranged from the anode 2 side to the cathode 3 side. Thereby, 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 alkali chamber R3 between the cation exchange membrane 6 and the bipolar membrane 7. The bipolar membranes 4 and 7 are each composed of a superposed cation exchange layer and anion exchange layer.

[0094] To perform electrodialysis with the illustrated electrodialysis device 1, a metal-containing solution is placed in the desalting chamber R1, pure water is placed in each of the acid chamber R2 and the alkali chamber R3, and a predetermined voltage is applied between the anode 2 and the cathode 3. Then, lithium ions (Li + ) in the metal-containing solution in the desalting chamber R1 pass through the cation exchange membrane 6 and move to the alkali chamber R3. In the alkali chamber R3, water (H2O) is decomposed by the bipolar membrane 7, and since hydroxide ions (OH - ) exist, a lithium hydroxide solution can be obtained.

[0095] On the other hand, the anions of the inorganic acid in the metal-containing solution in the desalting chamber R1 pass through the anion exchange membrane 5 and move to the acid chamber R2. In the acid chamber R2, an acidic solution such as a sulfuric acid solution is generated by the anions and hydrogen ions (H + ) generated from water (H2O) by the bipolar membrane 4. The anions of the inorganic acid are sulfate ions (SO4 2- ) in the illustrated example, but depending on the type of acid used in the acid leaching process, etc., they may be nitrate ions (NO3 - ) or chloride ions (Cl - ).

[0096] In the desalting chamber R1, as described above, lithium salts are separated from the metal-containing solution, and the post-desalting solution remains. The concentration of anions of the inorganic acid tends to be higher in the acidic solution than in the lithium hydroxide solution, and also higher in the post-desalting solution than in the lithium hydroxide solution.

[0097] In this electrodialysis, most of the fluoride ions of the impurities in the metal-containing solution move from the desalting chamber R1 to the acid chamber R2 through the anion exchange membrane 5 and are contained in the acidic solution. As a result, in the alkali chamber R3, a lithium hydroxide solution substantially free of fluoride ions can be obtained. Therefore, the fluoride ion concentration of the lithium hydroxide solution is lower than that of the acidic solution.

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

[0099] The acidic solution obtained by electrodialysis contains fluoride ions. Although this acidic solution can be discarded as it is, here, as described above, it is mixed with the acidic leaching solution in the acid leaching step or the metal-containing solution before neutralization and circulated.

[0100] (Crystallization step) A part of the lithium hydroxide solution obtained in the electrodialysis step can be used in 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 introduced into the wet treatment. Depending on the lithium ion concentration, a crystallization step may be performed to recover lithium hydroxide.

[0101] In the crystallization process, crystallization operations such as heating and concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heating and concentration, a higher temperature during crystallization is preferred because the treatment progresses faster. However, after crystallization, the temperature during drying of the crystallized product is preferably less than 60°C so that the water of crystallization does not desorb. This is because anhydrous lithium hydroxide from which the water of crystallization has desorbed is deliquescent and difficult to handle.

[0102] Subsequently, the above lithium hydroxide can be subjected to a grinding treatment or the like to adjust it to the required physical properties.

Example

[0103] Next, a test regarding the above-described metal recovery method was conducted and its effect was confirmed, which will be described below. However, this description is for illustrative purposes only and is not intended to be limited thereto.

[0104] (Test Example 1) Neutralization, manganese extraction, cobalt extraction, and nickel extraction were performed on the metal-containing solution obtained by leaching battery powder with sulfuric acid to separate each metal.

[0105] Next, electrodialysis was performed on the separated metal-containing solution using a bipolar membrane electrodialysis device (manufactured by Asahi Kasei Corporation) having a structure as shown in FIG. 4. Here, a metal-containing solution, pure water, and electrode solution having the compositions shown in FIG. 5 were respectively placed in the desalting chamber, alkali chamber, acid chamber, and electrode chamber. The conditions for electrodialysis were set to a low voltage of 32V.

[0106] The results are also shown in FIG. 5. In FIG. 5, the reason why the sum of the distribution ratios of each ion in the desalted solution, lithium hydroxide solution, acidic solution, and electrode solution after electrodialysis does not reach 100% is considered to be due to variations in the analytical values (including the portion that could not be quantified due to the lower limit of quantification in the analysis).

[0107] As can be seen 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. From this, it can be seen that an electrodialysis process can obtain a lithium hydroxide solution with most of the impurities removed. Also, as can be seen from FIG. 5, phosphorus contained in the metal-containing solution remains in the demineralized solution and tends not to be distributed in the acidic solution. Therefore, even if the acidic solution is mixed with the acidic leachate in the acid leaching step and used, it is considered that phosphorus accumulation or an increase in phosphorus concentration does not occur during the series of processes from acid leaching to extraction.

[0108] From the above tests, it was found that a lithium hydroxide solution can be prepared from a metal-containing solution, and that the acidic solution obtained by electrodialysis contains a large amount of the impurity fluoride ion.

[0109] (Test Example 2) For the battery powder, two-stage water leaching and filtration, and acid leaching using 95% by mass sulfuric acid were performed to obtain a metal-containing solution. Then, without filtration, aluminum ions were precipitated by neutralization while still containing the leaching residue. The pH at the end of acid leaching was 1.12, and the ORP value (silver / silver chloride electrode reference) was 30 mV. In neutralization, 250 g / L of sodium hydroxide was used to raise the pH of the metal-containing solution to 4.02 (ORP value (silver / silver chloride electrode reference): 86 mV), and then iron powder (Fe powder) was added to raise the pH to 4.27 (ORP value (silver / silver chloride electrode reference): 94 mV).

[0110] The composition, grade, and distribution ratio of the battery powder, each solution, and the residue are shown in FIG. 6. In FIG. 6, “%” of the grade means mass%. As can be seen from FIG. 6, it can be seen that the fluoride ion concentration (0.29 g / L) after adding iron powder decreased significantly compared to that before adding iron powder during neutralization (2.21 g / L). From this, it can be said that by including iron in the metal-containing solution, the impurity fluoride ion can be effectively precipitated and removed.

[0111] (Test Example 3) For the battery powder, as acid leaching, after performing the first leaching stage (the first stage of leaching), the leaching residue obtained in the first leaching stage was leached again in the second leaching stage (the second stage of leaching). Then, neutralization (Al removal neutralization) for removing aluminum ions was performed on the post-leaching solution of the first leaching stage to obtain a post-neutralization solution and a neutralization residue. Here, the F / Al molar ratio of the battery powder as the raw material was 3.3.

[0112] Here, multiple tests were conducted by changing the conditions of whether calcium was added in the first leaching stage during leaching and whether calcium was added during neutralization. The results are shown in Fig. 7. In Fig. 7, “%” of the grade means mass%.

[0113] As can be seen from Fig. 7, when calcium is added either during leaching or during neutralization, the fluoride ion concentration (F concentration) and the distribution ratio of the post-leaching solution and / or the post-neutralization solution are lower than those when calcium is not added at any time. Thereby, it can be understood that fluoride ions can be effectively removed by making calcium contained during leaching or during neutralization.

[0114] In addition, except that the F / Al molar ratio of the raw material battery powder was set to 0.85, the conditions of whether calcium was added in the first leaching stage during leaching were changed, and the same test as above was conducted. The results are shown in Table 1. From Table 1, it can be seen that by adding calcium, the distribution ratio of fluorine decreases in both the post-acid-leaching solution and the post-neutralization solution, and the distribution ratio of fluorine in the acid leaching residue and the neutralization residue increases. From this result, it can be said that even if the F / Al molar ratio is somewhat small, calcium can effectively precipitate fluoride ions.

[0115]

Table 1

[0116] (Test Example 4) By changing the types of lithium-ion battery waste, the atmosphere of roasting (air or inert), and other conditions, raw materials M1 to M6 composed of six types of battery powders P1 to P6 were obtained. In addition, raw materials M7 and M8 with LiF added to battery powder P3 were prepared. The F / Al molar ratios and the 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 in one cycle of the first leaching stage and the second leaching stage shown in Figure 3 using sulfuric acid. At this time, calcium sulfate was added so that the Ca / Al molar ratio of the acidic leachate became 1.0 in the first leaching stage. 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-stage leaching was performed, calcium sulfate was added so that the Ca / Al molar ratio of the acidic leachate became 1.0, and the pH at the end of leaching was set to 1.0.

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

[0120] Based on those results, Figure 8 shows a graph representing the relationship between the Al grade and the F grade of the raw materials, with the forms in the neutralization residue entered. 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 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 a form in which Li-Al composite hydroxide and LiCa(AlF6) were mixed. Furthermore, when the F / Al molar ratio of the raw material was 2.0 or more, the aluminum in the neutralization residue was almost in the form of LiCa(AlF6).

[0121] Also, in the tests using each of the above raw materials M1 to M8, it was confirmed whether or not a low aluminum ion concentration of less than 0.5 g / L could be achieved in each solution of the post-leaching solution obtained in the acid leaching step or the post-neutralization solution obtained in the neutralization step. The results are shown in FIG. 9. From FIG. 9, it can be seen that when the F / Al molar ratio of the raw material is 3.0 or more, the aluminum ion concentration in each solution becomes even lower.

[0122] From the above, it was found that according to the metal recovery method described above, the acidic solution obtained by electrodialysis and containing fluoride ions can be appropriately treated.

Explanation of Reference Numerals

[0123] 1 Bipolar membrane electrodialysis device 2 Anode 3 Cathode 4, 7 Bipolar membranes 5 Anion exchange membrane 6 Cation exchange membrane R1 Desalination chamber R2 Acid chamber R3 Alkali 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 into an acidic 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 of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions as impurities to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions; including a metal recovery method 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 contains calcium, and the fluoride ions are precipitated by the calcium.

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

3. The metal recovery method according to claim 1, wherein the metal separation step includes neutralization of raising the pH of the metal-containing solution to precipitate at least a part 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 into an acidic 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 raising the pH of the metal-containing solution to precipitate at least a part of the other metal ions; after the metal separation step, an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions as impurities to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions; including a metal recovery method in which the acidic solution obtained in the electrodialysis step is mixed with the metal-containing solution obtained in the acid leaching step, and during the neutralization, the metal-containing solution contains iron and / or calcium, and the fluoride ions are precipitated by the iron and / or calcium.

5. The metal recovery method according to claim 4, wherein after the acid leaching step, iron and / or calcium is added to the metal-containing solution so that the metal-containing solution contains iron and / or calcium during the neutralization.

6. wherein the other metal ion contains aluminum ion, the neutralization includes a dealuminumization step of depositing at least a part of the aluminum ion by increasing the pH of the metal-containing solution within the range of 4.0 to 5.0, the metal recovery method according to any one of claims 3 to 5, wherein the fluoride ion is deposited in the dealuminumization 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) in the raw material containing the battery powder is 1.3 or more.

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