Aluminum removal method and metal recovery method

Abstract

Provided is an aluminum removal method and a metal recovery method capable of effectively removing aluminum. The method for removing aluminum 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 containing at least aluminum ions and nickel ions and / or cobalt ions, and a neutralization step of using the leaching solution as a metal-containing solution, increasing the pH of the metal-containing solution, separating a neutralization residue and obtaining a neutralization solution, in which a molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more, and in the neutralization step, the metal-containing solution contains calcium and fluorine, and a molar ratio of calcium to aluminum ions in the metal-containing solution (Ca / Al molar ratio) is 0.2 or more, and aluminum ions in the metal-containing solution are precipitated and contained in the neutralization residue together with calcium and fluorine.

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 leaching solution to leach the battery powder and obtain a leaching solution containing at least aluminum ions and nickel ions and / or cobalt ions, and a neutralization step of treating the leaching solution as a metal-containing solution, increasing the pH of the metal-containing solution, separating a neutralization residue and obtaining a neutralization solution, wherein the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is set to 1.3 or more, and in the neutralization step, the metal-containing solution contains calcium and fluorine, the molar ratio of calcium to aluminum ions in the metal-containing solution (Ca / Al molar ratio) is set to 0.2 or more, and the aluminum ions in the metal-containing solution are precipitated and contained in the neutralization residue together with calcium and fluorine. The neutralization residue is LiCa(AlF 6 ) That is it.

[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] 1 is a graph showing an X-ray diffraction pattern of a neutralization residue obtained in a test in which calcium was added to increase the pH in the neutralization step, as determined by an X-ray diffraction method. [Diagram 3] 1 shows the results of the change in the form of aluminum in the neutralization residue depending on the F / Al molar ratio on a graph showing the relationship between the aluminum grade and the fluorine grade of the raw material in Test Example 2. [Figure 4]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 2. 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. The aluminum removal method of one embodiment includes a leaching step in which a raw material having battery powder obtained from lithium ion battery waste, the battery powder containing at least aluminum and nickel and / or cobalt, is contacted with an acidic leaching solution to leach the battery powder and obtain a leaching solution, and a neutralization step in which the leaching solution is used as a metal-containing solution to increase the pH of the metal-containing solution, and a neutralization residue is separated to obtain a neutralization solution. In the neutralization step, the metal-containing solution contains calcium and fluorine. Here, the molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more. In addition, in the neutralization step, the molar ratio of calcium to aluminum ions in the metal-containing solution (Ca / Al molar ratio) is 0.2 or more. Thereby, aluminum ions in the metal-containing solution are precipitated and contained in the neutralization residue together with calcium and fluorine.

[0014] It has been newly discovered that if calcium is contained in a metal-containing solution, aluminum will form a compound with calcium during neutralization, and will precipitate together with the calcium. 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 more, aluminum will combine with calcium and fluorine during the neutralization process to form LiCa(AlF 6 ) and other compounds such as LiCa(AlF 6 ) has low solubility in the acid leachate, so LiCa(AlF 6 By precipitating aluminum in the form of ammonium nitrate, more aluminum can be removed from the neutralized residue without increasing the pH significantly.

[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, the lithium ion battery waste is heated 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 an air atmosphere or an inert atmosphere such as nitrogen, or it can be performed in both an air atmosphere and an inert atmosphere in this order or in the reverse order. The roasting furnace may be of a batch type or a continuous type, and for example, a stationary furnace for a batch type and a rotary kiln furnace for a continuous type are available, and various other furnaces can also be used.

[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 also contain lithium, for example, 2% by mass to 8% 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. The battery powder may also contain 0.1% by mass to 10% by mass of fluorine.

[0026] The battery powder can be brought into contact with water before the leaching step using the acid leaching solution described later in order to extract substantially only lithium therefrom. As a result, the lithium in the battery powder is leached into water. In this case, the battery powder as the water leaching residue is subjected to the leaching step. When the water leaching is performed, at least a part of the electrolyte and other electrolytes in the lithium ion battery waste is removed by flowing into the water, etc. As an example, when the lithium in the battery powder that has been roasted in an inert atmosphere switched from the air atmosphere is leached with water, the fluorine content of the water leaching residue may be reduced to about 10% of the fluorine content of the battery powder by mass, and the fluorine concentration in the solution after the water leaching may be about 0.5 g / L.

[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, it is preferable to subject the battery powder obtained as described above 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 process, 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 process.

[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 produces a leaching 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] The raw material that is brought into contact with the acid leachate contains a relatively large amount of fluorine relative to aluminum, so that LiCa(AlF 6 ), etc. 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 that precipitates in the neutralization step becomes Li-Al composite hydroxide without combining with calcium. Li-Al composite hydroxide is LiCa(AlF 6), so when the precipitate is in the form of Li-Al composite hydroxide, the amount of aluminum precipitated is small and aluminum removal is insufficient. For this reason, when 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 is converted to LiCa(AlF) in the neutralization step. 6 ), which can provide more effective removal of aluminum.

[0031] In order to adjust the F / Al molar ratio as described above, if necessary, fluorine can be added to the raw material as described above. In this case, the raw material can contain fluorine in addition to the battery powder. There is no particular limit to the timing of adding fluorine, and it can be added at any time until the dealumination stage of the neutralization step described below is completed.

[0032] For example, fluorine may be included in the raw material together with the battery powder and then brought into contact with the acid leaching solution, or fluorine may be added as the remaining raw material to the acid leaching solution before or after the battery powder is brought into contact with the acid leaching solution, or fluorine may be added as the remaining raw material to the post-leaching solution obtained in the leaching step or to the metal-containing solution during the dealumination stage of the neutralization step. The timing of adding fluorine is not limited to before the start of leaching of the battery powder in the leaching step, but may be after the start of leaching, after the leaching step, or even in the neutralization step. When fluorine is added during the leaching step, after the leaching step, or in the neutralization step, the F / Al molar ratio is calculated assuming that the amount of fluorine added is contained in the raw material before the leaching step. Alternatively, when fluorine is contained in the lithium ion battery waste and the battery powder obtained by carrying out the pretreatment step thereon, it may not be necessary to add fluorine, but fluorine may be added to the raw material separately from the battery powder.

[0033] Lithium-ion battery waste (such as glass fibers, electrolyte, and organic binders in battery cells) may contain calcium and fluorine, which may remain in the battery powder.

[0034] In addition, multiple types of battery powders with different fluorine contents can be mixed. Regardless of whether the battery powder contains fluorine or not, the fluorine added to the acid leaching solution in the leaching process until the end of leaching (or until just before solid-liquid separation if solid-liquid separation is performed) is considered to be part of the raw material. The raw material may be added to the acid leaching solution all at once, but it can also be added in multiple portions between the start and end of leaching.

[0035] When fluorine is added to the raw material separately from the battery powder, 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).

[0036] 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.

[0037] 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.

[0038] In the leaching process, the pH of the acidic leaching solution or the post-leaching solution may be less than 3.5, and the oxidation-reduction potential (ORP value, based on silver / silver chloride potential) may be less than 100 mV.

[0039] 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.

[0040] 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.

[0041] (neutralization process) The post-leaching solution obtained in the leaching step contains at least aluminum ions and nickel and / or cobalt ions. The leaching step is followed by a neutralization step. Here, the solution obtained after the leaching step and containing the metal ions as a result of the metal being dissolved in the leaching step is referred to as a metal-containing solution. This metal-containing solution includes both the post-leaching solution obtained in the leaching step and the solution during the neutralization step during which the pH of the post-leaching solution is increased as described below.

[0042] 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.

[0043] 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.

[0044] In the dealumination stage of the neutralization process, the metal-containing solution 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.

[0045] Regarding the inclusion of calcium and fluorine in the metal-containing solution, if the metal-containing solution already contains the necessary amounts of calcium and fluorine, there may be cases where it is not necessary to further add calcium and fluorine to the metal-containing solution. Alternatively, if the metal-containing solution does not contain calcium and / or fluorine, or if the calcium and / or fluorine in the metal-containing solution is insufficient, calcium and / or fluorine may be added to the metal-containing solution before, during, and / or after the pH of the metal-containing solution is increased to a predetermined value. The form of calcium to be added to the metal-containing solution is not particularly limited, but examples thereof include calcium sulfate, calcium carbonate (CaCO 3 ), calcium hydroxide (Ca(OH) 2 ) other calcium compounds, calcium itself, etc. Among them, calcium carbonate is preferable because it is relatively inexpensive. When fluorine is added to the metal-containing solution, 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).

[0046] In order to sufficiently remove aluminum, the amount of calcium contained in the metal-containing solution is such that the molar ratio of calcium to aluminum ions (Ca / Al molar ratio) is 0.2 or more or more, 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.

[0047] When the metal-containing solution contains calcium, aluminum ions in the metal-containing solution are precipitated, and the neutralization residue contains, for example, Ca(SO 4 )(H 2 O) 0.5 , LiCa(AlF 6 ), Ca 3 Al 2 F 8 (OH) 2 (SO 4 )·2H 2 O and Ca 2AlF 7 For reference, Figure 2 shows the X-ray diffraction pattern of the neutralization residue obtained in a test in which calcium was added to increase the pH in the neutralization process. 6 ) is included.

[0048] In addition, as mentioned above, since the raw material contains a relatively large amount of fluorine relative to aluminum, the neutralization process produces LiCa(AlF 6 ) and the like. In order to adjust the F / Al molar ratio in this way, fluorine can be added, if necessary, as described above.

[0049] When lithium hydroxide is used as a pH adjuster, the neutralization residue is LiCa(AlF 6 ) is included, and when sodium hydroxide is used, Na is included in the neutralization residue. 3 Li 3 (AlF 6 ) 2 May contain LiCa(AlF 6 The composition of the above-mentioned Ca / Al molar ratio can be made larger than 1.0, taking into consideration that calcium may be consumed by other compounds.

[0050] In the dealumination step, it is preferable to increase the pH of the metal-containing solution to within a range of 2.5 to 5.0, particularly 3.0 to 4.5, using a pH adjuster. This makes it possible to effectively separate aluminum ions 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 below 50°C, there is a concern that the reactivity may deteriorate, and if it is set above 90°C, a device that can withstand high heat is required, and it is also undesirable from the standpoint of safety.

[0051] 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.

[0052] In the iron removal step, an oxidizing agent can be added to the dealumination solution to remove iron ions from the dealumination solution. The addition of an oxidizing agent oxidizes the iron in the solution from divalent to trivalent, which precipitates as an oxide or hydroxide at a lower pH than divalent iron. In most cases, the iron is converted to iron hydroxide (Fe(OH) 3 The precipitated iron can be removed as a neutralization residue by solid-liquid separation.

[0053] 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.

[0054] 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.

[0055] After the addition of the oxidizing agent, the pH can be adjusted to a predetermined range by adding an alkali such as sodium hydroxide, sodium carbonate, ammonia, etc. For example, iron can be precipitated by adjusting the pH to a range of 3.0 to 4.5.

[0056] (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.

[0057] 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).

[0058] 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.

[0059] The solvent after the extraction and back extraction of manganese ions may be scavenged using a scavenging liquid such as sulfuric acid. In many cases, calcium contained in the manganese pre-extraction liquid (neutralized liquid) is extracted into the solvent and transferred to the scavenging liquid by this scavenging. For example, when the sulfuric acid concentration of the scavenging liquid is relatively high, the solubility of calcium sulfate decreases as the sulfuric acid concentration increases. Therefore, when the calcium concentration in the manganese pre-extraction liquid (neutralized liquid) is high, calcium in the scavenging liquid may precipitate as calcium sulfate, which may cause clogging of the piping in the manganese extraction process. In order to prevent such clogging of the piping, it is preferable not to add too much calcium in the neutralization process described above. From this viewpoint, the Ca / Al molar ratio may be 1.5 or less.

[0060] (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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] (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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] (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.

[0074] Various methods can be used to obtain an aqueous lithium hydroxide solution from an aqueous lithium sulfate solution. For example, first, a lithium carbonate solution is obtained by adding carbonate or blowing carbon dioxide into a lithium sulfate solution. Then, in the so-called chemical conversion method, calcium hydroxide is added to the lithium carbonate solution to obtain Li 2 CO 3 +Ca(OH) 2 →2LiOH+CaCO 3 A lithium hydroxide aqueous solution can be produced according to the following reaction formula: Calcium ions that may remain in the solution can be removed using a cation exchange resin or a chelating resin. Alternatively, barium hydroxide is added to the lithium sulfate solution, and Li 2 SO 4 +Ba(OH) 2 →2LiOH+BaSO 4 It is also possible to obtain an aqueous solution of lithium hydroxide based on the reaction of the above. In this case, barium that can dissolve in the liquid can be separated and removed using a cation exchange resin, a chelating resin, or the like. 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.

[0075] 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.

[0076] 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.

[0077] (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.

[0078] 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.

[0079] Thereafter, the lithium hydroxide may be subjected to a pulverization process or the like in order to adjust the lithium hydroxide to the required physical properties. EXAMPLES

[0080] The aluminum removal method described above was experimentally carried out, and its effectiveness was confirmed. The following description is given, however, for illustrative purposes only and is not intended to be limiting.

[0081] (Test Example 1) Lithium-ion battery waste was roasted, crushed, and sieved to obtain battery powder, which was then leached with sulfuric acid, and the leaching residue was separated by solid-liquid separation to produce a leaching solution. In this way, leaching solutions with at least different aluminum ion concentrations were prepared as metal-containing solutions, and tests were conducted on each of these metal-containing solutions by increasing the pH to 4.0 to neutralize them under conditions with and without calcium addition and in different amounts, as shown in Table 1.

[0082] Here, a 4M LiOH aqueous solution was used as the pH adjuster. In Examples 1 to 4 in which calcium was added, calcium sulfate was added as calcium to the pre-neutralization liquid before the pH was increased. The calcium was dissolved until the calcium ion concentration reached 0.6 g / L, and the remainder was present in the liquid as a solid. In Example 4, after adding 6 g / L of calcium in Example 3 and increasing the pH to 4.0 to perform solid-liquid separation, 6 g / L of calcium was further added to the post-neutralization liquid to precipitate aluminum ions, and neutralization residue was removed by solid-liquid separation.

[0083] After the neutralization, the neutralization residue was separated by solid-liquid separation to obtain a neutralized liquid. Thereafter, the concentration of each metal ion in the neutralized liquid was measured. The results are shown in Table 1. In Table 1, "Ca / Al molar ratio (liquid before neutralization)" in Examples 1 to 4 means the molar ratio after calcium addition.

[0084] [Table 1]

[0085] From Table 1, it can be seen that in Examples 1, 3, and 4, the aluminum ion concentration of the post-neutralization liquid was reduced by adding calcium compared to Comparative Examples 1 to 3. In Example 2, the aluminum ion concentration of the pre-neutralization liquid was relatively high, so that the aluminum ion concentration of the post-neutralization liquid at a pH of 4 was not so low, but since the difference in aluminum ion concentration (Al concentration difference Δ) between the pre-neutralization liquid and the post-neutralization liquid was large, it can be said that aluminum was sufficiently removed.

[0086] In Example 4, the amount of calcium added is doubled compared to Example 3, but there is no significant difference in the aluminum ion concentration. This shows that adding too much calcium does not further increase the effect of reducing the aluminum ion concentration. On the other hand, if calcium is added in excess, there is a risk of causing a problem such as clogging of the piping in the subsequent manganese extraction process as described above. For this reason, it is preferable that the Ca / Al molar ratio is 1.5 or less.

[0087] In addition, the neutralization residue was analyzed by SEM-EDS, and aluminum was found to have combined with calcium and fluorine. From the conversion of the F / Al, Ca / Al, and F / Ca molar ratios, it was found that the main component was LiCa(AlF 6 ) compound was identified.

[0088] (Test Example 2) By changing the type of lithium-ion battery waste, the roasting atmosphere (air or inert), and other conditions, raw materials M1 to M6 consisting of six types of battery powders P1 to P6 were obtained. In addition, raw materials M7 and M8 were prepared by adding LiF to battery powder P3. The F / Al molar ratio and Al and F grades of raw materials M1 to M8 are shown in Table 2.

[0089] [Table 2]

[0090] The metals contained in each of the above raw materials M1 to M8 were leached using sulfuric acid, with calcium sulfate being added so that the Ca / Al molar ratio of the acidic leachate became 1.0.

[0091] After that, a neutralization step was carried out on the metal-containing solution, which was the post-leaching liquid of the above-mentioned leaching step, by adding 4M LiOH to adjust the pH to 4.0. The neutralization residue obtained was analyzed by X-ray diffraction. As a result, aluminum was found to be LiCa(AlF 6 ) and / or Li-Al composite hydroxides.

[0092] Based on these results, the form of aluminum in the neutralization residue is plotted on a graph showing the relationship between the Al and F contents of the raw materials, as shown in Figure 3. As shown in Figure 3, when the F / Al molar ratio of the raw materials 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 materials was 1.3 or more, the aluminum in the neutralization residue was in the form of Li-Al composite hydroxide and LiCa(AlF 6 Furthermore, if the F / Al molar ratio of the raw material is 2.0 or more, the aluminum in the neutralization residue is almost entirely LiCa(AlF 6 )

[0093] 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 4. From Figure 4, it can be seen 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.

[0094] 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: 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 containing at least aluminum ions and nickel ions and / or cobalt ions; a neutralization step of increasing the pH of the metal-containing solution as a metal-containing solution after the leaching and separating a neutralization residue to obtain a neutralized solution; Including, The molar ratio of fluorine to aluminum in the raw material (F / Al molar ratio) is 1.3 or more, The method for removing aluminum, wherein in the neutralization step, the metal-containing solution contains calcium and fluorine, the molar ratio of calcium to aluminum ions in the metal-containing solution (Ca / Al molar ratio) is 0.2 or more, the aluminum ions in the metal-containing solution are precipitated and contained in the neutralization residue together with calcium and fluorine, and the neutralization residue contains LiCa(AlF6).

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 pH of the metal-containing solution is increased to 3.0 to 4.5 when precipitating aluminum ions in the neutralization step.

7. The method for removing aluminum according to any one of claims 1 to 3, wherein calcium is added to the metal-containing solution in the neutralization step.

8. The aluminum removal method according to claim 7 , wherein calcium carbonate or calcium sulfate is added as the calcium to the metal-containing solution in the neutralization step.

9. The aluminum removal method according to any one of claims 1 to 3, wherein in the neutralization step, a molar ratio of calcium to aluminum ions (Ca / Al molar ratio) in the metal-containing solution is adjusted to 0.5 to 3.

0.

10. 10. The aluminum removal method according to claim 9, wherein in the neutralization step, a molar ratio of calcium to aluminum ions (Ca / Al molar ratio) in the metal-containing solution is adjusted to 0.5 to 1.

5.

11. 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.

12. the battery powder contains lithium and the neutralization solution contains lithium ions, The method for removing aluminum according to any one of claims 1 to 3, wherein after the neutralization step, lithium contained in the neutralized solution is recovered.

13. 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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