Aluminum removal method and metal recovery method

Abstract

Provided is an aluminum removal method and metal recovery method capable of effectively removing aluminum. The method for removing aluminum includes a leaching step of contacting a raw material obtained from lithium ion battery waste and having battery powder containing at least aluminum and nickel and / or cobalt with an acidic leachate to leach the battery powder and obtain a leaching solution, in which the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more, and in the leaching step, the acidic leachate contains calcium and fluorine, and aluminum is precipitated together with calcium and fluorine, and the precipitate is contained in a leach residue.

Description

[Technical field]

[0001] This specification discloses a method for removing aluminum and a method for recovering the metal. [Background technology]

[0002] In recent years, from the perspective of effective resource utilization, recovery of valuable metals such as cobalt and nickel by wet processing from waste lithium-ion secondary batteries that have been discarded due to product life, manufacturing defects, or other reasons has been widely considered.

[0003] In the process of recovering valuable metals from lithium-ion battery waste, for example, the lithium-ion battery waste is subjected to a pretreatment such as roasting, and then the resulting battery powder is added to an acidic leaching solution to leach cobalt, nickel, etc. that may be contained in the battery powder, thereby obtaining a leaching solution. Thereafter, the metal ions in the liquid are separated and the valuable metals are recovered by multiple solvent extractions, etc. In multiple solvent extractions, cobalt ions and nickel ions may be sequentially extracted and back-extracted (see, for example, Patent Document 1).

[0004] Incidentally, aluminum is used in lithium ion secondary batteries due to its excellent electrical and thermal conductivity, and therefore is also included in lithium ion battery waste. Aluminum in lithium ion battery waste is difficult to completely remove by the above pretreatment, and may remain in the battery powder and dissolve together with cobalt during leaching, and may be included in the leaching solution as aluminum ions. When recovering valuable metals from lithium ion battery waste, it is necessary to remove aluminum ions prior to separating valuable metals from the leaching solution.

[0005] In relation to this, Patent Document 2 describes "a method for removing aluminum from an acidic solution in which at least cobalt and aluminum are dissolved, comprising neutralizing the acidic solution in a state in which the oxidation-reduction potential (ORP vs Ag / AgCl) of the acidic solution is -600 mV or more and 100 mV or less to remove the aluminum." Patent Document 2 also states that "it is more preferable that the pH of the post-leaching solution in the dealumination step is 4.0 to 6.0, and particularly preferably 4.5 to 5.0," and "in the dealumination step, an alkali such as sodium hydroxide, sodium carbonate, or ammonia can be added to the acidic solution to raise the pH to within the above-mentioned range." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-162982 A [Patent Document 2] JP 2017-166028 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the "aluminum removal method" and "dealuminization process" described in Patent Documents 1 and 2, when the pH is increased to a certain level for neutralization, not only aluminum but also nickel and / or cobalt precipitate, resulting in a loss of nickel and / or cobalt. On the other hand, if the increase in pH during neutralization is limited to a level at which nickel and / or cobalt do not precipitate, aluminum cannot be sufficiently removed.

[0008] This specification provides an aluminum removal method capable of effectively removing aluminum and a metal recovery method. [Means for solving the problem]

[0009] The aluminum removal method disclosed in this specification includes a leaching step of contacting a raw material having battery powder obtained from lithium ion battery waste and containing at least aluminum and nickel and / or cobalt with an acidic leachate to leach the battery powder and obtain a leaching solution, the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) being 1.3 or more, the acidic leachate containing calcium and fluorine in the leaching step, and precipitating aluminum together with calcium and fluorine, LiCa(AlF 6 ) The precipitate is included in the leaching residue.

[0010] The metal recovery method disclosed in this specification involves recovering metals from lithium ion battery waste using the aluminum removal method described above. Effect of the Invention

[0011] According to the above-mentioned aluminum removal method and metal recovery method, aluminum can be effectively removed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram showing a metal recovery method including an aluminum removal method according to one embodiment. [Diagram 2] FIG. 1 is a flow diagram of a leaching process included in an aluminum removal method according to one embodiment. [Diagram 3] FIG. 2 is a flow chart showing the leaching process of Test Example 1. [Figure 4] 1 is a graph showing the X-ray diffraction pattern of the leaching residue obtained in the leaching step of Test Example 1. [Diagram 5] 1 is a graph showing the relationship between pH and aluminum ion concentration in the neutralization step of Test Example 1. [Figure 6] FIG. 6 is a graph showing the X-ray diffraction pattern of the neutralization residue obtained in the test of “Ca addition to the solution before neutralization” in FIG. 5. [Figure 7] 1 is a graph showing the relationship between pH and aluminum ion concentration in Test Example 2 with and without the addition of calcium and in different amounts. [Figure 8] 1 is a graph showing the relationship between the aluminum grade and the fluorine grade of the raw material in Test Example 3, showing the results of the change in the form of aluminum in the neutralization residue depending on the F / Al molar ratio. [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 content and the fluorine content of the raw material in Test Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the above-mentioned aluminum removal method and metal recovery method will be described in detail. In one embodiment, the aluminum removal method includes a leaching step of contacting a raw material having battery powder obtained from lithium ion battery waste, the battery powder including at least aluminum and nickel and / or cobalt, with an acidic leachate to leach the battery powder and to separate a leach residue therefrom to obtain a leachate. In this leaching step, the acidic leachate includes calcium and fluorine, thereby precipitating aluminum together with calcium and fluorine, and the precipitate is included in the leach residue.

[0014] It has been newly discovered that if calcium is contained in the acid leachate, aluminum will form a compound with calcium and precipitate together with the calcium during leaching of the battery powder. Furthermore, if the raw material containing the battery powder contains fluorine and the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or higher, aluminum will combine with calcium and fluorine during the leaching process and may precipitate in the form of LiCa(AlF6) or similar. Because LiCa(AlF6) has low solubility in the acid leachate, precipitating it in the form of LiCa(AlF6) allows more aluminum to be included in the leaching residue and removed.

[0015] The aluminum removal method of this embodiment may be used, as an example, in the metal recovery method shown in Figure 1. The metal recovery method of Figure 1 includes a pretreatment step, a leaching step, a neutralization step, a manganese extraction step, a cobalt extraction step, a nickel extraction step, a hydroxide step, and a crystallization step, which are carried out in this order, on lithium-ion battery waste. When a crystallization step is carried out on the stripped liquids obtained in each of the cobalt extraction step and the nickel extraction step, compounds such as sulfates of cobalt and nickel can be produced. Here, the description will be given according to Figure 1, but Figure 1 is an example and is not limited to such a specific flow.

[0016] (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.

[0017] Lithium ion battery waste has a housing containing aluminum as an exterior that envelops the periphery. For example, this housing may be made of only aluminum, or may contain aluminum and iron, aluminum laminate, etc. In addition, lithium ion battery waste may contain 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. In addition, lithium ion battery waste may contain copper, iron, etc. Furthermore, the housing of lithium ion battery waste usually contains an electrolyte solution in which an electrolyte such as lithium hexafluorophosphate is dissolved in an organic solvent. For example, ethylene carbonate, diethyl carbonate, etc. may be used as the organic solvent.

[0018] (Pretreatment process) A pretreatment process is often carried out on lithium ion battery waste. The pretreatment process may include at least one of roasting, crushing, and sieving. The lithium ion battery waste becomes battery powder through the pretreatment process. The roasting, crushing, and sieving processes in the pretreatment process may be carried out individually as necessary, or may be carried out in any order. The battery powder refers to a powder in which the positive electrode material components are separated and concentrated by carrying out some kind of pretreatment on the lithium ion battery waste. The battery powder may be obtained as a powder in which the positive electrode material components are concentrated by carrying out crushing and sieving on the lithium ion battery waste with or without carrying out heat treatment.

[0019] 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 converted into a form that is easily dissolved in the acid leachate in the leaching process. 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, preferably 600°C to 800°C for 0.5 hours to 6 hours. The roasting can be performed in either an air atmosphere or an inert atmosphere such as nitrogen, or 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.

[0020] During roasting, at least a part of the electrolyte is removed from the lithium ion battery waste by evaporating the electrolyte solution as an electrolyte. In many cases, when the lithium ion battery waste is heated during roasting, the components of the electrolyte solution 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 solution or the organic binder is removed in this way, certain components such as fluorine contained in the electrolyte solution 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The battery powder obtained in the pretreatment step contains at least aluminum and at least one of nickel and cobalt. The battery powder has an aluminum content of, for example, 1% by mass to 10% by mass, typically 3% by mass to 5% by mass. When nickel is contained, the nickel content is, for example, 1% by mass to 30% by mass, typically 5% by mass to 20% by mass. When cobalt is contained, the cobalt content in the battery powder is, for example, 1% by mass to 30% by mass, typically 5% by mass to 20% by mass. The battery powder may contain lithium, for example, 2% by mass to 8% by mass. The battery powder may contain fluorine, for example, 0.1% by mass to 10% by mass.

[0025] The battery powder may further contain manganese. When manganese is contained, the manganese content is, for example, 1% by mass to 30% by mass. In addition, the battery powder may contain 1% by mass to 5% by mass of iron and 1% by mass to 10% by mass of copper.

[0026] The battery powder can be brought into contact with water before the leaching step using an acid leaching solution described below in order to extract substantially only lithium therefrom. This causes the lithium in the battery powder to leach into the water. In this case, the battery powder as the water leaching residue is subjected to the leaching step using an acid leaching solution. When the water leaching is performed, at least a part of the electrolyte and other electrolytes in the lithium ion battery waste are removed by flowing into the water, for example.

[0027] However, when water leaching is performed, the equipment is required, and the processing time increases by performing both the water leaching and the acid leaching in the leaching step. In addition, it may be necessary to control the roasting conditions in order 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 subjected to the acid leaching in the leaching step without performing water leaching. When water leaching is not performed, it is easier to maintain a high lithium ion concentration in the solution in the wet treatment after the leaching step.

[0028] In addition, in order to remove the electrolyte from the lithium ion battery waste in the pretreatment step, in addition to the above-mentioned roasting and water leaching, the lithium ion battery waste may be washed with a washing liquid such as water at any time during the pretreatment step.

[0029] (Leaching process) In the leaching process, the raw material containing the battery powder is leached with an acidic leaching solution such as sulfuric acid. This results in a leached solution (metal-containing solution) in which the metals in the battery powder have been dissolved. If necessary, solid-liquid separation can be performed after the leaching is completed to separate the leaching residue.

[0030] In the leaching step, the acidic leaching solution contains calcium and fluorine. Calcium and fluorine may be contained in the battery powder, but if the calcium and / or fluorine is insufficient, calcium and / or fluorine may be added separately by being contained in the raw material. The raw material may contain calcium and / or fluorine in addition to the battery powder. There is no particular restriction on the timing of adding calcium and / or fluorine, so long as it is before the end of leaching (after the end of leaching and before solid-liquid separation, if solid-liquid separation is performed).

[0031] For example, calcium and / or fluorine may be included in the raw material together with the battery powder, and the raw material may be brought into contact with the acid leaching solution, or calcium and / or fluorine may be added to the acid leaching solution as the remaining raw material before or after the battery powder is brought into contact with the acid leaching solution. The timing of adding calcium and / or fluorine is not limited to before the start of leaching of the battery powder in the leaching process, but may be after the start of leaching. In addition, for example, when the battery powder is mixed with water such as distilled water to make a slurry, and then an acid such as sulfuric acid is added to the slurry to make the acid leaching solution, calcium and / or fluorine may be added to the slurry before the acid is added, or calcium and / or fluorine may be added to the slurry together with the acid. Alternatively, when calcium and / or fluorine are contained in the lithium ion battery waste and the battery powder obtained by carrying out a pretreatment process thereon, the acid leaching solution becomes one containing calcium and / or fluorine by contacting the battery powder with the acid leaching solution, but calcium and / or fluorine may be added separately from the battery powder.

[0032] Lithium-ion battery waste (glass fiber, electrolyte, organic binder, etc. of battery cells) may contain calcium and fluorine, and this calcium and fluorine may remain in the battery powder. In addition, multiple types of battery powder with different calcium and / or fluorine contents may be mixed. Regardless of whether the battery powder contains calcium or fluorine, the calcium and fluorine added to the acid leachate in the leaching process until the end of leaching (or immediately before solid-liquid separation if solid-liquid separation is performed) are considered to be part of the raw material. The raw material may be added to the acid leachate all at once, or may be added in multiple portions between the start and end of leaching.

[0033] Alternatively, hydrofluoric acid (HF) may be used as at least a portion of the acid, in which case the fluorine in the hydrofluoric acid is considered to be part of the material that is contacted with the acidic leach solution.

[0034] The form of calcium contained in the acidic leachate is not particularly limited, and examples thereof include calcium sulfate (CaSO4), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), other calcium compounds, and calcium itself. Among them, calcium sulfate is preferable because it does not cause an increase in the pH of the acidic leachate, as occurs when calcium carbonate or calcium hydroxide is used. At least a part of the calcium can dissolve in the solution upon contact with the acidic leachate. When fluorine is added to the acidic leachate, the form of fluorine may be, for example, a fluoride salt, specifically, at least one selected from the group consisting of lithium fluoride (LiF), sodium fluoride (NaF), and potassium fluoride (KF).

[0035] The amount of calcium to be contained in the acid leaching solution can be appropriately determined in consideration of the aluminum content of the battery powder and other conditions. Specifically, the battery powder to be subjected to the leaching process may be subjected to a component analysis in advance to determine the aluminum content of the battery powder, and the amount of calcium may be determined based on this. The molar ratio of calcium to aluminum (Ca / Al molar ratio) is 0.20 or more or more than 0.20, and preferably 0.5 to 2.0. The amount of calcium referred to here means the total amount of calcium in the acid leaching solution (including the amount of calcium added to the acid leaching solution, if any) regardless of whether or not at least a part of the calcium in the acid leaching solution is dissolved. When calcium is contained in the battery powder and the calcium content of the battery powder is insufficient, a necessary amount of calcium may be added separately.

[0036] When calcium is present in the acid leachate, most of the aluminum in the battery powder is thought to combine with calcium and further with fluorine, forming a precipitate. The precipitate may be, for example, Ca(SO4)(H2O). 0.5 , LiCa(AlF6), Ca3Al2F8(OH)2(SO4)·2H2O, and at least one selected from the group consisting of Ca2AlF7, etc.

[0037] By making the raw material contacted with the acid leaching solution contain a certain amount of fluorine relative to aluminum, a large amount of aluminum can be precipitated in the form of LiCa(AlF6) or the like. Specifically, the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more. If the F / Al molar ratio is less than 1.3, most of the aluminum in the precipitate precipitated in the leaching process will not combine with calcium but will become Li-Al composite hydroxide. Since Li-Al composite hydroxide has a higher solubility in the acid leaching solution than LiCa(AlF6), when the precipitate is in the form of Li-Al composite hydroxide, the amount of aluminum precipitated will be small and the removal of aluminum will be insufficient. For this reason, if the F / Al molar ratio of the raw material is less than 1.3, fluorine is added to the raw material to adjust the F / Al molar ratio to 1.3 or more. When the F / Al molar ratio is 2.0 or more, or even 3.0 or more, almost all of the aluminum in the precipitate may become LiCa(AlF6), and further effective removal of aluminum can be achieved.

[0038] When the battery powder contains a certain amount of fluorine, the F / Al molar ratio of the battery powder may be 1.3 or more. Alternatively, fluorine may be added to the raw material separately from the battery powder, and the F / Al molar ratio of the raw material may be adjusted so that the F / Al molar ratio of the raw material is 1.3 or more. In addition, when fluorine is added to the acid leaching solution after starting the leaching of the battery powder, the total amount of fluorine contained in the acid leaching solution and the precipitate after the addition of fluorine is theoretically equal to the amount of fluorine in the raw material. Therefore, the above F / Al molar ratio can be obtained from the total amount of fluorine contained in the acid leaching solution and the precipitate after the addition of fluorine.

[0039] The leaching step may include multiple leaching steps as described below, but may include only one leaching step. The amount of acid used in the 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 step is performed, an amount of acid, such as sulfuric acid, equivalent to the amount used above may be used in the one leaching step. In this case, the pH of the post-leaching solution after the one-stage leaching may be less than 2.0. The pH of the post-leaching solution is preferably 1.0 or more and less than 2.0. This allows aluminum to be removed more effectively.

[0040] In addition, in the leaching process, a plurality of leaching stages may be repeated a plurality of times as shown in Fig. 2. Each leaching stage includes a first leaching stage 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 stage in which the leaching residue of the first leaching stage is leached with an acid leaching solution to obtain a leaching solution. The leaching solution obtained in the final leaching stage (the second leaching stage in the case where there are two leaching stages, the first leaching stage and the second leaching stage) is used by being included in the acid leaching solution of the next first leaching stage.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] In the case where a plurality of leaching stages are repeated in the leaching process as described above, if the acid leaching solution contains calcium and fluorine, even if some of the aluminum in the battery powder is dissolved and contained in the acid leaching solution, most of it will precipitate with calcium and fluorine and be removed as contained in the leaching residue in each of the first and second leaching stages. Aluminum ions that may be contained in the post-leaching solution can be removed in the subsequent neutralization step as described below.

[0047] 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 leaching process, 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.

[0048] 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 leaching solution obtained after the first leaching stage and solid-liquid separation may be somewhat higher, such as 2.5 to 3.5, or even 3.1 to 3.5, typically 3.1 to 3.3. When the pH is somewhat high, a large amount of aluminum is removed together with calcium and fluorine. When the pH is too low, the aluminum concentration in the acid leaching solution increases, and aluminum removal may be insufficient. On the other hand, when the pH is too high, there is a concern that cobalt and / or nickel, etc. may not be effectively leached.

[0049] When calcium and / or fluorine are added to the acidic leachate as part of the raw material in multiple leaching stages, the timing of addition is not particularly important, but it is preferable to add them in the first leaching stage, in which case the pH tends to be relatively high as described above, and most of the aluminum can be precipitated.

[0050] During the leaching process, whether a single leaching step or multiple repeated leaching steps are used, the acidic or post-leaching solution may have a pH of, for example, below 3.5, typically below 3.5, and an oxidation-reduction potential (ORP value, based on silver / silver chloride potential) of below 100 mV.

[0051] As a diluent for adjusting the pH of the acidic leaching solution in the leaching step, the nickel extraction solution (lithium sulfate aqueous solution, etc.) in the nickel extraction step can be used as described below. In this way, lithium ions are circulated in a series of steps in the wet treatment, and the lithium ions in the solution can be concentrated in the steps.

[0052] The post-leaching solution may have, for example, an aluminum ion concentration of 1.0 g / L to 20 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a cobalt ion concentration of 10 g / L to 50 g / L, a manganese ion concentration of 0 g / L to 50 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. The post-leaching solution may contain at least one of nickel ions and cobalt ions, and may not contain the other.

[0053] (neutralization process) When the post-leaching solution obtained in the leaching step contains aluminum ions, a neutralization step can be carried out after the leaching step. Here, the solution obtained after the leaching step and containing the metal ions due to the dissolution of the metal in the leaching step is called a metal-containing solution. This metal-containing solution includes both the post-leaching solution obtained in the leaching step and the solution in the middle of the neutralization step during which the pH of the post-leaching solution is increased as described below.

[0054] In the neutralization step, the pH of the metal-containing solution is increased, and the neutralization residue is separated to obtain a neutralized liquid. The neutralization step may include a dealumination step. In the dealumination step, the pH of the metal-containing solution is increased to precipitate and remove at least a portion of the aluminum ions. When the metal-containing solution contains iron ions, the neutralization step preferably also includes a de-ironization step for removing the iron ions after the dealumination step. In the de-ironization step, an oxidizing agent is added to the dealumination solution obtained in the dealumination step, and an alkali is further added to increase the pH, thereby removing the iron ions. This results in a neutralized liquid such as a de-ironization liquid.

[0055] When removing aluminum ions in the dealumination stage, an alkaline pH adjuster is first added to the metal-containing solution to quickly raise the pH. Specific examples of the alkaline pH adjuster include lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia. As the lithium hydroxide aqueous solution, the one obtained in the hydroxylation step described below can be used, and in this case, lithium ions circulate within the series of steps in the wet treatment.

[0056] In the dealumination stage of the neutralization step, the metal-containing solution preferably contains calcium and fluorine. In this case, the aluminum ions in the metal-containing solution are easily precipitated by calcium and fluorine. As a result, the neutralization residue contains a large amount of aluminum as well as calcium and fluorine, and aluminum can be effectively removed together with calcium and fluorine.

[0057] In this case, the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is set to 1.3 or more. The F / Al molar ratio of the raw material is preferably 2.0 or more, and more preferably 3.0 or more. When the F / Al molar ratio of the raw material is large like this, the aluminum in the precipitate that is deposited in the dealumination stage tends to be in the form of LiCa(AlF6) rather than Li-Al composite hydroxide, and aluminum ions in the metal-containing solution are removed more effectively.

[0058] Regarding the inclusion of calcium in a metal-containing solution, if the metal-containing solution already contains a necessary amount of calcium, there may be cases where it is not necessary to further add calcium to the metal-containing solution. Alternatively, if the metal-containing solution does not contain calcium or if the calcium in the metal-containing solution is insufficient, calcium may be added to the metal-containing solution before, during, and / or after increasing the pH of the metal-containing solution to a predetermined value. The form of calcium to be added to the metal-containing solution is not particularly limited, but examples include calcium sulfate, calcium carbonate, calcium hydroxide, other calcium compounds, and simple calcium. Among these, calcium carbonate is preferred because it is relatively inexpensive.

[0059] In order to sufficiently remove aluminum, the amount of calcium contained in the metal-containing solution in the dealumination stage of the neutralization step is preferably such that the molar ratio of calcium to aluminum ions (Ca / Al molar ratio) is 0.20 or more or greater than 0.20, more preferably 0.5 to 3.0, and particularly preferably 0.5 to 1.5. The amount of calcium referred to here includes the amount of undissolved calcium, if any, present in the metal-containing solution.

[0060] When the metal-containing solution contains calcium, aluminum ions in the metal-containing solution are precipitated, and the neutralization residue contains, for example, Ca(SO4)(H2O). 0.5 It is believed that the neutralization residue contains at least one selected from the group consisting of LiCa(AlF6), Ca3Al2F8(OH)2(SO4)·2H2O, and Ca2AlF7. When lithium hydroxide is used as the pH adjuster, the neutralization residue may contain LiCa(AlF6), and when sodium hydroxide is used, the neutralization residue may contain Na3Li3(AlF6)2. The composition of LiCa(AlF6) is Ca:Al=1:1, but considering that calcium may be consumed by other compounds, the above-mentioned Ca / Al molar ratio in the neutralization step may be made larger than 1.0.

[0061] In the dealumination stage, the pH of the metal-containing solution can be increased to within a range of 2.5 to 5.0, typically 3.0 to 4.5, by using a pH adjuster. In addition, in the dealumination stage, the oxidation-reduction potential (ORP value, based on silver / silver chloride potential) may be 50 mV to 400 mV (250 mV to 350 mV at the end). This allows aluminum ions to be effectively separated while suppressing the precipitation of nickel ions and / or cobalt ions. In this case, the temperature of the metal-containing solution can be set to 50°C to 90°C. If the temperature of the metal-containing solution is set to less than 50°C, there is a concern that the reactivity may deteriorate, and if it is set to more than 90°C, a device that can withstand high heat is required, and it is also undesirable from the standpoint of safety.

[0062] After the aluminum has been precipitated, solid-liquid separation such as filtration is carried out using known devices and methods such as a filter press or a thickener to remove the neutralization residue and obtain a dealuminated liquid.

[0063] Next, in the iron removal stage, an oxidizing agent can be added to the dealumination solution to remove iron ions from the dealumination solution. The addition of the oxidizing agent oxidizes the iron in the solution from divalent to trivalent, and the trivalent iron precipitates as an oxide or hydroxide at a lower pH than the divalent iron. In many cases, the iron precipitates as a solid such as iron hydroxide (Fe(OH)3). The precipitated iron can be removed as a neutralization residue by solid-liquid separation.

[0064] In order to precipitate iron, the ORP value during oxidation is preferably 300 mV to 900 mV. After the addition of the oxidizing agent, the pH can be lowered by adding an acid such as sulfuric acid, hydrochloric acid, or nitric acid. For example, the pH is lowered to less than 3.

[0065] The oxidizing agent is not particularly limited as long as it can oxidize iron, but 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 or the like 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, and the precipitated manganese can be removed together with iron.

[0066] After the addition of the oxidizing agent, an alkali such as lithium hydroxide, sodium hydroxide, sodium carbonate, or ammonia can be added to adjust the pH to a predetermined range. For example, iron can be precipitated by adjusting the pH to a range of 3.0 to 4.5. The lithium hydroxide aqueous solution can be obtained in the hydroxide step described below.

[0067] (Manganese extraction process) The neutralized solution obtained after the neutralization step can be subjected to a manganese extraction step in which manganese ions, and possibly also the remaining aluminum ions, are extracted and removed by solvent extraction. In this case, a manganese-extracted solution from which the manganese ions and the remaining aluminum ions have been removed is obtained by extracting them.

[0068] In the manganese extraction step, it is preferable to use an extractant containing a phosphate ester extractant. Here, examples of the phosphate ester extractant include di-2-ethylhexyl phosphoric acid (abbreviation: D2EHPA or product name: DP-8R). The extractant may be a mixture of an oxime extractant and a phosphate ester extractant. In this case, the oxime extractant is preferably an aldoxime or one containing aldoxime as the main component. Specifically, examples include 2-hydroxy-5-nonylacetophenone oxime (product name: LIX84), 5-dodecylsalicyaldoxime (product name: LIX860), a mixture of LIX84 and LIX860 (product name: LIX984), and 5-nonylsalicylaldoxime (product name: ACORGAM5640).

[0069] During extraction, the equilibrium pH is preferably 2.3 to 3.5, more preferably 2.5 to 3.0. The alkaline pH adjuster used at this time is preferably an aqueous lithium hydroxide solution obtained in the hydroxide step described below, but sodium hydroxide or the like prepared separately may be used. When the aqueous lithium hydroxide solution obtained in the hydroxide step is used as the pH adjuster, it is possible to suppress the sodium remaining in the nickel extraction solution after the nickel extraction step described below, and the sodium being mixed as an impurity into the aqueous lithium hydroxide solution produced from the nickel extraction solution, as in the case of using sodium hydroxide as a pH adjuster. During extraction, it is desirable to perform extraction by a countercurrent multi-stage extraction in which the aqueous phase and the solvent used in each extraction flow in opposite directions. In this way, it is 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 also effective to set the equilibrium pH during the first extraction step to a value within the above range, and to lower the equilibrium pH during each extraction step.

[0070] (Cobalt extraction process and crystallization process) In the cobalt extraction step, cobalt ions are separated by solvent extraction from the manganese extraction liquid obtained after the extraction in the manganese extraction step.

[0071] Here, it is preferable to use a solvent containing a phosphonate ester extractant. Among them, 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest801) is particularly suitable from the viewpoint of separation efficiency of nickel and cobalt. 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] When extracting cobalt ions, the equilibrium pH during extraction can be preferably 5.0 to 6.0, more preferably 5.0 to 5.5. In this case, as the pH adjuster, it is preferable to use an aqueous lithium hydroxide solution obtained in the hydroxide oxidation step described below, but separately prepared sodium hydroxide or the like may also be used. If the pH is less than 5.0, there is a risk that the cobalt ions cannot be sufficiently extracted into the solvent. This allows the cobalt ions in the manganese extraction liquid to be extracted into the solvent. In addition, when extracting cobalt ions, it is desirable to perform extraction by a countercurrent multi-stage extraction in which the aqueous phase and the solvent used in each extraction flow in opposite directions. In this way, the extraction rate of cobalt ions can be increased while suppressing the extraction of nickel ions and lithium ions.

[0073] During the above extraction, not only cobalt ions but also nickel ions and lithium ions, which become impurities in the cobalt extraction process, may be extracted to a certain 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 impurities such as nickel ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid acid solution, and the pH may be 3.5 to 5.5. The post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to use a part or all of the post-scrubbing solution for the extraction in the cobalt extraction process (that is, 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 perform the extraction in the cobalt extraction process). This allows nickel ions and lithium ions to be circulated or retained in the process without loss. However, if the solvent from which the cobalt ions have been extracted does not contain nickel ions or lithium ions, the scrubbing process may not be performed.

[0074] Thereafter, 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 in the crystallization step described below. Here, the stripping is performed under pH conditions such that as much of the cobalt ions as possible are extracted from the organic phase (solvent) into the aqueous phase (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. The O / A ratio and the number of times can be appropriately determined. The liquid temperature may be room temperature, but is preferably 10°C to 50°C.

[0075] The liquid after stripping, such as the cobalt sulfate solution obtained in the cobalt extraction step, is subjected to a crystallization step. In the crystallization step after the cobalt extraction step, the cobalt ions are crystallized to obtain a cobalt salt, such as cobalt sulfate. In the crystallization step, the liquid after stripping is heated, for example, to 40°C to 120°C and concentrated. As a result, the cobalt ions are crystallized as a cobalt salt. The cobalt salt thus produced preferably has a nickel content of 5 mass ppm or less, and nickel has been sufficiently removed, so that it can be effectively used as a raw material for the production of 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 in the crystallization step and use it for recrystallization, or to use it for the purpose of adjusting the cobalt ion concentration of the scrubbing liquid in the cobalt extraction step, or to use it for extraction in the cobalt extraction step. By repeatedly using the cobalt ions and lithium ions in this manner within the process, the cobalt ions and lithium ions can be circulated or retained within the process and concentrated without loss.

[0076] (Nickel extraction process and crystallization process) The cobalt extraction liquid after the cobalt ions have been extracted in the cobalt extraction step can be subjected to a nickel extraction step.

[0077] In the nickel extraction step, 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.

[0078] In the nickel extraction step, the equilibrium pH is preferably 6.0 to 8.0, more preferably 6.8 to 7.2, when nickel ions are extracted. The pH adjuster used to adjust the pH at this time may be sodium hydroxide or the like, but it is preferable to use the lithium hydroxide aqueous solution obtained in the hydroxide step described below. In the nickel extraction step, it is desirable to perform extraction by countercurrent multi-stage extraction, as in the cobalt extraction step described above. In this way, it is possible to suppress the extraction of lithium ions and increase the extraction rate of nickel ions.

[0079] The solvent from which nickel ions have been extracted may be scrubbed one or more times using a scrubbing solution as necessary to remove impurities such as lithium ions and sodium ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid acid solution, and the pH may be 5.0 to 6.0. Here, the post-scrubbing solution may contain lithium ions. Therefore, it is desirable to use a part or all of the post-scrubbing solution for extraction in the nickel extraction step (that is, to mix a part or all of the post-scrubbing solution with a post-cobalt extraction solution, and use this as a pre-extraction solution to perform extraction in the nickel extraction step). This allows lithium ions to be circulated or retained in the process and concentrated without loss. However, if the solvent from which nickel ions have been extracted does not contain lithium ions, the scrubbing step may not be performed.

[0080] Then, the solvent is back-extracted using a back-extraction solution such as sulfuric acid, hydrochloric acid, or nitric acid. When a crystallization step 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.

[0081] When a stripping solution such as a nickel sulfate solution is obtained by stripping, it can be electrolyzed and dissolved as necessary, and then heated to 40°C to 120°C in a crystallization step to crystallize nickel ions 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 in the crystallization step and use it for recrystallization, or to use it for the purpose of adjusting the nickel ion concentration of the scrubbing solution in the nickel extraction step, or to use it for extraction in the nickel extraction step. By repeatedly using it in this way in the process, nickel ions and lithium ions can be circulated or retained in the process and concentrated without loss.

[0082] The nickel-extracted solution after nickel ions are extracted in the nickel extraction step can be added to the acidic leaching solution in the leaching step. This allows the lithium ions contained in the nickel-extracted solution to be circulated in a series of steps including the leaching step, neutralization step, manganese extraction step, cobalt step, and nickel extraction step. Preferably, after the lithium ions are circulated in this way and the lithium ion concentration of the nickel-extracted solution becomes somewhat high, the hydroxide step described below is carried out.

[0083] (Hydroxylation process) The nickel extraction solution obtained after the nickel extraction step contains substantially only lithium ions as a result of the separation of manganese ions, cobalt ions, and nickel ions in the above-mentioned extraction steps. These lithium ions are contained in the neutralization solution after the neutralization step. In the embodiment described here, after the neutralization step, the manganese extraction step, the cobalt step, and the nickel extraction step, a lithium hydroxide aqueous solution is obtained from the nickel extraction solution in order to recover lithium in the hydroxide step. More specifically, when the nickel extraction solution is a lithium sulfate aqueous solution, a lithium hydroxide aqueous solution is produced from the lithium sulfate aqueous solution in the hydroxide step.

[0084] Various methods can be used to obtain an aqueous lithium hydroxide solution from an aqueous lithium sulfate solution. For example, a lithium carbonate aqueous solution is first obtained by adding a carbonate or blowing carbon dioxide into a lithium sulfate aqueous solution. Then, in a so-called chemical conversion method, calcium hydroxide is added to the lithium carbonate aqueous solution to generate a lithium hydroxide aqueous solution according to the reaction formula Li2CO3+Ca(OH)2→2LiOH+CaCO3. Calcium ions that may remain in the solution can be removed by using a cation exchange resin, a chelating resin, or the like. Alternatively, barium hydroxide can be added to a lithium sulfate solution to obtain a lithium hydroxide solution based on the reaction Li2SO4+Ba(OH)2→2LiOH+BaSO4. Note that barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin or a chelating resin. Alternatively, in the case of employing a so-called electrolysis method, an aqueous lithium hydroxide solution can be produced on the cathode side by supplying an aqueous lithium sulfate solution to the anode side in an electrolytic cell provided with a cation exchange membrane that separates the anode side from the cathode side and performing electrolysis.

[0085] The lithium hydroxide aqueous solution thus obtained can be effectively used as a pH adjuster (neutralizing agent) in the neutralization step, as well as an alkaline pH adjuster in each of the manganese extraction step, cobalt extraction step, and nickel extraction step.

[0086] Incidentally, it is preferable to subject a part of the lithium sulfate aqueous solution to the hydroxide step, and use the remainder as at least a part of the acid in the leaching step. In this case, by using the remainder of the lithium sulfate aqueous solution in the leaching step, the lithium ion concentration in the series of steps can be increased, and by obtaining an amount of lithium hydroxide aqueous solution required for a pH adjuster, etc. in the hydroxide step, the cost of the entire process including the production of lithium hydroxide, etc. can be reduced.

[0087] (Crystallization process) After the hydroxide step, a crystallization step may be performed to precipitate lithium hydroxide from the lithium hydroxide aqueous solution. For example, when a series of steps including the leaching step, the manganese extraction step, the cobalt extraction step, and the nickel extraction step are repeated, the lithium ion concentration in the solution such as the lithium sulfate aqueous solution may gradually increase as new lithium ion battery waste is added to the series of steps. In such a case, a crystallization step may be performed.

[0088] 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 crystallized product is preferably dried at a temperature of less than 60°C at which water of crystallization does not desorb. If water of crystallization is desorbed, the product becomes anhydrous lithium hydroxide, which has deliquescent properties and is difficult to handle.

[0089] 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

[0090] Next, the above-mentioned aluminum removal method was experimentally carried out, and its effectiveness was confirmed, which will be described below. However, the description here is merely for illustrative purposes and is not intended to be limiting.

[0091] (Test Example 1) The lithium-ion battery waste was roasted in an inert atmosphere instead of air, crushed, and sieved to obtain battery powder with the quality shown in Table 1.

[0092] [Table 1]

[0093] The battery powder was subjected to a leaching process using sulfuric acid, in which the first leaching stage (first stage of leaching) and the second leaching stage (second stage of leaching) were repeated three times (three cycles) as shown in FIG. 3. Here, calcium (calcium sulfate) was added in each first leaching stage so that the Ca / Al molar ratio was 1.0. The total amount of sulfuric acid used in each first leaching stage and second leaching stage was 1.1 times the molar equivalent of the amount required to leach all of the nickel, cobalt, lithium, manganese, aluminum, and iron contained in the battery powder. In terms of the total amount used, 60% sulfuric acid was used in the first leaching stage, and 40% sulfuric acid was used in the second leaching stage, based on mass. The pH of the post-leaching solution obtained in the first leaching stage was 3.1 to 3.3. In FIG. 3, the distribution ratio is based on mass and represents the ratio when the content of each metal in the battery powder added in each stage is taken as 100%. In FIG. 3, the unit of grade, "%" means "mass%".

[0094] In addition, when the same leaching process was carried out except that calcium was not added, the aluminum concentration or grade and distribution ratio results shown in Table 2 were obtained.

[0095] [Table 2]

[0096] Comparing Figure 3 with Table 2, it can be seen that the distribution rate of aluminum in the post-leaching solution (first-stage leaching filtrate) obtained in the first leaching stage of the second run (second cycle) when calcium was added (Figure 3) was lower than the distribution rate of aluminum in the post-leaching solution (first-stage leaching filtrate) obtained in the first leaching stage of the second run (second cycle) when calcium was not added (Table 2). Specifically, in Figure 3, the distribution rate (leaching rate) of aluminum was 36% in the post-leaching solution after the second first leaching stage and 46% in the post-leaching solution after the third first leaching stage due to the addition of calcium. This shows that the aluminum ion concentration in the post-leaching solution sent to the subsequent process is reduced by the addition of calcium.

[0097] Furthermore, as can be seen from FIG. 3, the distribution rates (leaching rates) of nickel and cobalt both reached 99% or more.

[0098] The leaching residue was analyzed by X-ray diffraction, and the X-ray diffraction pattern graph shown in Figure 4 was obtained. Figure 4 shows that by adding calcium, aluminum reacted with calcium and fluorine and was removed as the leaching residue.

[0099] A neutralization step was carried out to raise the pH of the metal-containing solution, which is the post-leaching solution obtained in the first leaching stage of the above-mentioned leaching process, to remove aluminum ions. The results are shown in Figure 5 as "Ca added during leaching." For reference, Figure 5 also shows the results of a test in which calcium was added to the metal-containing solution (pre-neutralization solution), which is the post-leaching solution obtained by carrying out the leaching process without adding calcium, and then a neutralization step was carried out to raise the pH (Ca added to pre-neutralization solution).

[0100] As shown in Figure 5, when "Ca addition during leaching" was used, the aluminum ion concentration was reduced to 0.5g / L or less in the neutralization process. In the neutralization process, the cobalt loss was 0.9%, the nickel loss was 1.1%, and the lithium loss was 1.2% of the respective contents of cobalt, nickel, and lithium contained in the battery powder. The recovery rates through the leaching and neutralization processes were 98.9% for cobalt, 98.6% for nickel, and 95.7% for lithium. Therefore, it can be said that aluminum was sufficiently removed while minimizing the loss of cobalt, nickel, and lithium.

[0101] In addition, the neutralization residue obtained in the test of "Ca addition to the solution before neutralization" in Figure 5 was analyzed by X-ray diffraction. The X-ray diffraction pattern is shown in Figure 6. This revealed that adding calcium in the neutralization process causes the neutralization residue to contain LiCa(AlF6), which leads to lithium loss.

[0102] (Test Example 2) The same battery powder as in Test Example 1 was subjected to a leaching process, calcium was added so that the Ca / Al molar ratio became 1.0, and the relationship between the pH and the aluminum concentration at that time was examined.

[0103] The results are shown in Figure 7. Figure 7 shows that when the pH was higher than 1.0, the aluminum concentration was low and aluminum precipitated, so a higher pH means that more aluminum can be removed. This shows that it is particularly effective to carry out multiple leaching stages in the leaching process and remove aluminum with calcium in the first leaching stage, where the pH tends to be somewhat high.

[0104] (Test Example 3) 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 3.

[0105] [Table 3]

[0106] 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 2. 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.

[0107] 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.

[0108] 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).

[0109] In addition, in the tests using the above 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 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.

[0110] From the above, it was found that the aluminum removal method described above can effectively remove aluminum.

Claims

1. 1. A method for removing aluminum comprising the steps of: The method includes a leaching step of contacting a raw material having battery powder obtained from lithium ion battery waste and containing at least aluminum and nickel and / or cobalt with an acidic leaching solution to leach the battery powder and obtain a leaching solution, The molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more, A method for removing aluminum, wherein in the leaching step, the acidic leachate contains calcium and fluorine, aluminum is precipitated together with calcium and fluorine, and the precipitate containing LiCa(AlF 6 ) is included in a leaching residue.

2. The method for removing aluminum according to claim 1 , wherein the F / Al molar ratio of the battery powder is 1.3 or more.

3. The aluminum removal method according to claim 1 , further comprising the step of adding fluorine to the raw material separately from the battery powder to adjust the F / Al molar ratio of the raw material.

4. The aluminum removal method according to any one of claims 1 to 3, wherein the F / Al molar ratio of the raw material is 2.0 or more.

5. 5. The method for removing aluminum according to claim 4, wherein the F / Al molar ratio is 3.0 or more.

6. The method for removing aluminum according to any one of claims 1 to 3, wherein the battery powder contains calcium.

7. The aluminum removal method according to any one of claims 1 to 3, wherein calcium is added separately from the battery powder in the leaching step.

8. The method for removing aluminum according to any one of claims 1 to 3, wherein the acidic leachate in the leaching step contains calcium sulfate as the calcium.

9. A pretreatment step of obtaining the battery powder from the lithium ion battery waste, The aluminum removal method according to any one of claims 1 to 3, wherein the lithium ion battery waste contains an electrolyte, and at least a portion of the electrolyte is removed from the lithium ion battery waste in the pretreatment step.

10. The method for removing aluminum according to any one of claims 1 to 3, wherein only one stage of leaching is performed in the leaching step, and the pH of the leached solution obtained after the one stage of leaching is less than 2.

0.

11. The method for removing aluminum according to claim 10, wherein the pH of the leaching solution is 1.0 or higher.

12. The aluminum removal method according to claim 10, wherein the acid is used in the one-stage leaching in an amount of 1.0 to 1.8 times the molar equivalent of the amount of acid required for leaching all of the metals contained in the battery powder, selected from nickel, cobalt, lithium, manganese, aluminum, and iron.

13. the leaching step includes a first leaching stage in which the battery powder is leached with an acid leaching solution and a leaching residue is separated to obtain a leaching solution, and a second leaching stage in which the leaching residue is leached with an acid leaching solution to obtain a leaching solution, The method for removing aluminum according to any one of claims 1 to 3, wherein a post-leaching solution obtained in a final leaching step among the plurality of leaching steps is used as an acidic leaching solution in a next first leaching step, and the plurality of leaching steps are repeated a plurality of times.

14. The method for removing aluminum according to claim 13, wherein the pH of the leaching solution obtained in the first leaching step is 2.5 to 3.

5.

15. The method for removing aluminum according to claim 13, wherein an amount of acid used in the first leaching stage is 70% or less by mass of the total amount of acid used in the plurality of leaching stages in each leaching process.

16. The post-leaching solution contains aluminum ions, a neutralization step of increasing the pH of the leaching solution as a metal-containing solution and separating a neutralization residue to obtain a neutralized solution, The method for removing aluminum according to any one of claims 1 to 3, wherein in the neutralization step, the metal-containing solution contains calcium and fluorine, and aluminum ions in the metal-containing solution are precipitated and contained in the neutralization residue together with calcium and fluorine.

17. the battery powder contains lithium and the neutralization solution contains lithium ions, The aluminum removal method according to claim 16 , further comprising recovering lithium contained in the neutralized solution after the neutralization step.

18. A metal recovery method, comprising recovering metals from lithium ion battery waste using the aluminum removal method according to any one of claims 1 to 3.

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