Metal recovery method

Abstract

The present invention provides a metal recovery method capable of producing a lithium hydroxide solution from a metal-containing solution and appropriately treating impurities separated during the production process. The method for recovering metals from battery powder of lithium-ion battery waste includes an acid leaching step of leaching the metals in the battery powder with an acid to obtain a metal-containing solution containing lithium ions and other metal ions including manganese ions and / or aluminum ions, a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including extraction of manganese ions and / or aluminum ions from the metal-containing solution into a solvent and stripping the manganese ions and / or aluminum ions from the solvent into a stripping solution after the extraction, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions after the metal separation step, and the acidic solution obtained in the electrodialysis step is included in the stripping solution in the metal separation step.

Description

[Technical field]

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

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

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

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

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

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

[0007] However, the metal-containing solution contains impurities such as fluoride ions, etc. Even if it is possible to obtain a lithium hydroxide solution by separating the impurities from such a metal-containing solution, it is necessary to treat the solution containing the separated impurities.

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

[0009] One metal recovery method disclosed in this specification is a method for recovering metals from battery powder of lithium-ion battery waste, and includes an acid leaching step of leaching the metal in the battery powder with acid to obtain a metal-containing solution containing lithium ions and other metal ions including manganese ions and / or aluminum ions; a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including extraction of manganese ions and / or aluminum ions from the metal-containing solution into a solvent and, after the extraction, stripping of the manganese ions and / or aluminum ions from the solvent into a stripping solution; and an electrodialysis step of, after the metal separation step, subjecting the metal-containing solution containing lithium ions and fluoride ions to electrodialysis using a bipolar membrane to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions, and the acidic solution obtained in the electrodialysis step is included in the stripping solution in the metal separation step.

[0010] Another metal recovery method disclosed in this specification is a method for recovering metals from battery powder of lithium-ion battery waste, and includes an acid leaching step of leaching the metal in the battery powder with acid to obtain a metal-containing solution containing lithium ions and other metal ions including manganese ions and / or aluminum ions, and a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including extraction of manganese ions and / or aluminum ions from the metal-containing solution into a solvent, stripping of the manganese ions and / or aluminum ions from the solvent into a stripping solution after the extraction, and scavenging to remove residual components from the solvent with a scavenging solution after the stripping, and an electrodialysis step of performing electrodialysis using a bipolar membrane on the metal-containing solution containing lithium ions and fluoride ions after the metal separation step to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions, and the acidic solution obtained in the electrodialysis step is included in the scavenging solution in the metal separation step. Effect of the Invention

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

[0012] [Figure 1] FIG. 1 is a flow diagram showing an example of a metal recovery method including an impurity removal method according to one embodiment. [Diagram 2] FIG. 1 is a flow diagram showing an example of a pretreatment process for obtaining battery powder from lithium ion battery waste. [Diagram 3] FIG. 1 is a cross-sectional view illustrating an example of a bipolar membrane electrodialysis device that can be used in an electrodialysis step included in an impurity removal method according to one embodiment. [Figure 4] FIG. 2 is a diagram showing the components of each liquid before and after electrodialysis in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0014] In one embodiment, the acidic solution obtained in the electrodialysis step is included in the stripping solution in the metal separation step. In the extraction of manganese ions and / or aluminum ions, a relatively large amount of metal or substance tends to be extracted into the solvent, and the stripping solution obtained by performing stripping on the solvent similarly contains a large amount of substances, so it is desirable to discard it. Here, the above-mentioned acidic solution is effectively used for the stripping, and the fluoride ions, which are impurities contained in the acidic solution, are included in the stripping solution and can be appropriately disposed of.

[0015] In another embodiment, after the extraction and back-extraction of manganese ions and / or aluminum ions in the metal separation step, scavenging is further performed to remove residual components from the solvent using a scavenging solution. Then, the acidic solution obtained in the electrodialysis step is added to the scavenging solution in the metal separation step. The scavenging solution after scavenging may contain substances such as calcium that can combine with fluoride ions. Therefore, by adding an acidic solution containing fluoride ions to the scavenging solution, the fluoride ions can be precipitated and removed in the scavenging solution. The scavenging solution from which the fluoride ions have been removed can be used as an acid in the acid leaching step.

[0016] If the acid solution obtained in the electrodialysis step were used as the acid in the acid leaching step as is, there would be a concern that the fluoride ions in the acid solution would accumulate and concentrate in the wet treatment, which would affect the wet treatment. In contrast, in the above-mentioned embodiment, the acid solution is included in the stripping solution or the scavenging solution, so that the accumulation and concentration of fluoride ions is suppressed.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0032] The acid leaching step can be carried out by known methods or under known conditions, but the pH is preferably 0.0 to 2.0, and the oxidation-reduction potential (ORP value, based on silver / silver chloride potential) may be 0 mV or less.

[0033] The leaching residue that remains after the acid leaching can be separated from the metal-containing solution by solid-liquid separation such as filtration using known devices and methods such as a filter press or thickener. Most of the copper in the battery powder may be contained in the leaching residue. This solid-liquid separation can be omitted, and a metal separation step such as neutralization may be performed after leaching without solid-liquid separation.

[0034] The acid leaching step results in a metal-containing solution containing lithium ions and other metal ions, which may be at least one selected from the group consisting of cobalt ions, nickel ions, manganese ions, aluminum ions, iron ions and copper ions, typically including cobalt ions and / or nickel ions. The metal-containing solution may also contain fluoride ions.

[0035] The metal-containing solution obtained in the acid leaching step may have a cobalt ion concentration of 10 g / L to 50 g / L, a nickel ion concentration of 10 g / L to 50 g / L, a manganese ion concentration of 0 g / L to 50 g / L, an aluminum ion concentration of 1.0 g / L to 20 g / L, an iron ion concentration of 0.1 g / L to 5.0 g / L, a copper ion concentration of 0.005 g / L to 0.2 g / L, and a fluoride ion concentration of 0.01 g / L to 20 g / L. This metal-containing solution is subjected to the metal separation step described below.

[0036] (neutralization) When the metal-containing solution obtained in the acid leaching step contains aluminum ions and / or iron ions, the metal separation step can first involve neutralization, in which the pH of the metal-containing solution is increased and the neutralization residue is separated to obtain a neutralized solution. The neutralization step can include a dealumination step and a deironization step. However, in cases where the metal-containing solution does not contain aluminum ions and / or iron ions, the dealumination step and / or the deironization step may be omitted.

[0037] In the dealumination step, the pH of the metal-containing solution is increased to precipitate at least a portion of the aluminum ions, which are then removed by solid-liquid separation. At this time, for example, if the pH is increased to within a range of 4.0 to 5.0 using a pH adjuster at a liquid temperature of 50° C. to 90° C., the aluminum ions can be effectively separated while suppressing the precipitation of nickel ions and / or cobalt ions.

[0038] In the iron removal stage, an oxidizing agent is added, and a pH adjuster is further added to increase the pH. As a result, iron ions are oxidized from divalent to trivalent, and precipitate as a solid such as iron oxide or hydroxide (Fe(OH)3), which can be removed by solid-liquid separation. The ORP value during oxidation is preferably 300mV to 900mV. The oxidizing agent is not particularly limited as long as it can oxidize iron, but it is preferable to use manganese dioxide, a positive electrode active material, and / or a manganese-containing leaching residue obtained by leaching the positive electrode active material. The manganese-containing leaching residue obtained by leaching the positive electrode active material with an acid may contain manganese dioxide. When the above-mentioned positive electrode active material or the like is used as the oxidizing agent, a precipitation reaction occurs in which manganese dissolved in the liquid becomes manganese dioxide, and the precipitated manganese can be removed together with iron.

[0039] Examples of pH adjusters used in neutralization in the above-mentioned dealuminization and iron removal steps include lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia, among which it is preferable to use a lithium hydroxide solution obtained in the electrodialysis step described below. In this case, lithium ions circulate within the wet treatment.

[0040] (Manganese etc. extraction) The metal-containing solution may be neutralized as necessary, and then the manganese ions may be extracted and removed by solvent extraction. In this case, if the metal-containing solution contains aluminum ions, not only the manganese ions but also the aluminum ions are extracted and removed.

[0041] For the extraction of manganese ions, it is preferable to use an extractant containing a phosphate ester extractant. A specific example of the phosphate ester extractant is di-2-ethylhexyl phosphoric acid (abbreviation: D2EHPA or product name: DP-8R).

[0042] The extractant may be a mixture of a phosphoric acid ester extractant and an oxime extractant. In this case, the oxime extractant is preferably an aldoxime or an aldoxime-based extractant. Specific examples include 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecylsalicyaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), and 5-nonylsalicylaldoxime (trade name: ACORGAM5640).

[0043] 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.

[0044] During extraction, the equilibrium pH is preferably adjusted to 2.3 to 3.5, more preferably 2.5 to 3.0. As the pH adjuster used at this time, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis step described below.

[0045] It is desirable to perform the extraction by countercurrent multi-stage extraction in which the aqueous phase and the solvent used in each extraction flow in opposite directions. This makes it possible to suppress the extraction of cobalt ions, nickel ions, and lithium ions, and to increase the extraction rate of manganese ions. When performing countercurrent multi-stage extraction, it is effective to set the equilibrium pH during the first extraction stage within the above-mentioned range, and to lower the equilibrium pH during each extraction stage.

[0046] The solvent from which manganese ions and / or aluminum ions have been extracted is scrubbed as necessary, and then stripped. The stripping solution used for stripping is an inorganic acid such as sulfuric acid, nitric acid, or hydrochloric acid, but it is preferable that a part or all of it is an acidic solution obtained in the electrodialysis step described below. The stripping solution may contain various metals or substances in addition to manganese ions. By adding the above-mentioned acidic solution to the stripping solution, the fluoride ions in the acidic solution are included in the stripping solution, and the fluoride ions can be disposed of together with other metals or substances in the stripping solution. During stripping, for example, the pH may be 0.0 to 1.0 and the O / A ratio may be 0.5 to 2.0. The acid concentration in this case may be 10 g / L to 100 g / L.

[0047] The stripped liquid containing manganese ions and / or aluminum ions and fluoride ions can be subjected to wastewater treatment to make it dischargeable. Examples of wastewater treatment include mixing the liquid with other wastewater to reduce the fluoride ion concentration below the wastewater standard value. In addition, slaked lime or calcium chloride may be added to precipitate fluoride ions as calcium fluoride, and the precipitate may be removed or discarded. Note that the stripped liquid may be neutralized to precipitate manganese ions and the like other than fluoride ions as hydroxides, etc., as necessary.

[0048] The solvent that has undergone stripping is subjected to scavenging so that it can be reused. Scavenging is performed by mixing the scavenging liquid and the solvent while stirring them with a mixer or the like. This removes residual components that were not separated from the solvent by scrubbing or stripping. The acid concentration during scavenging may be 300g / L to 550g / L, and the O / A may be 0.5 to 2.0. In this way, the acid concentration during scavenging may be higher than the acid concentration during stripping described above.

[0049] It is preferable that a part or all of the scavenging solution of an inorganic acid such as sulfuric acid, nitric acid, or hydrochloric acid used in scavenging is an acidic solution obtained in the electrodialysis step described below. The scavenging solution may contain calcium and the like contained in the solvent, and the fluoride ions contained in the acidic solution may be removed by reacting with the calcium and the like in the scavenging solution. In one example, the calcium concentration may be 0.025 g / L in the stripping solution and 0.186 g / L in the scavenging solution. A part of the scavenging solution may be used in the acid leaching step, but the remainder is often used repeatedly in scavenging as the scavenging solution, which may cause calcium to accumulate in the scavenging solution. When the scavenging solution contains fluoride ions and calcium, it is considered that calcium fluoride (CaF2) is generated by their reaction. The precipitate formed by the reaction of fluoride ions with calcium can be removed by a back filter or a filter press.

[0050] The scavenging solution from which fluoride ions have been removed as described above can be used as at least a part of the acid in the acid leaching process. If the acid solution obtained in the electrodialysis process is directly used in the acid leaching, the fluoride ions in the acid solution will be returned to the wet treatment process and will be combined with the fluoride ions contained in the battery powder newly added to the acid leaching process, resulting in the accumulation of fluoride ions during the wet treatment process. In contrast, the acid solution is included in the scavenging solution, and the scavenging solution obtained thereafter is used in the acid leaching process, whereby the fluoride ions are removed during scavenging as described above, thereby suppressing the accumulation of fluoride ions during the wet treatment process.

[0051] In addition, the acidic solution obtained in the electrodialysis step is added to the scavenging liquid, and calcium in the scavenging liquid is removed as described above. As a result, clogging of piping due to calcium in the manganese extraction step can be suppressed. This clogging of piping is considered to occur due to the precipitation of calcium in the scavenging liquid as calcium sulfate. In particular, the scavenging liquid often has a relatively high sulfuric acid concentration, and the higher the sulfuric acid concentration, the lower the solubility of calcium sulfate, so calcium sulfate is more likely to precipitate.

[0052] (Cobalt Extraction and Crystallization) For example, after manganese ions are extracted, cobalt ions can be extracted and separated from the post-manganese extraction solution (metal-containing solution) by solvent extraction.

[0053] For the extraction of cobalt ions, it is preferable to use a solvent containing a phosphonate ester extractant. In particular, 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest801) is suitable from the viewpoint of the efficiency of separating nickel and cobalt. The extractant can be used as a solvent by diluting it with a hydrocarbon organic solvent so that the concentration is 10% by volume to 30% by volume.

[0054] When cobalt ions are extracted, the equilibrium pH during extraction is preferably 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is lower than 5.0, the cobalt ions may not be sufficiently extracted into the solvent. As a pH adjuster in this case, it is preferable to use an aqueous lithium hydroxide solution obtained in the electrodialysis step described below.

[0055] It is also preferable to perform the extraction of cobalt ions by countercurrent multi-stage extraction in which the aqueous phase and the solvent flow in opposite directions in each extraction, thereby increasing the extraction rate of cobalt ions while suppressing the extraction of nickel ions and lithium ions.

[0056] During the above extraction, not only cobalt ions but also nickel ions and lithium ions may be extracted to a small extent into the solvent. In this case, if necessary, the solvent from which the cobalt ions have been extracted may be scrubbed one or more times using a scrubbing solution to remove nickel ions and lithium ions that may be contained in the solvent. The scrubbing solution may be, for example, a sulfuric acid solution, and may have a pH of 3.5 to 5.5. The post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to mix a part or all of the post-scrubbing solution with a post-manganese extraction solution, and use the resulting solution as a pre-extraction solution to extract cobalt ions. This allows nickel ions and lithium ions to be circulated or retained in the wet treatment without loss. However, if the solvent from which the cobalt ions have been extracted does not contain nickel ions or lithium ions, the scrubbing step may not be performed.

[0057] Then, stripping is performed on the solvent from which the cobalt ions have been extracted. The stripping solution used for stripping may be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, but sulfuric acid is preferable when a sulfate salt is to be obtained by the subsequent crystallization. Here, the stripping is performed under pH conditions such that as much of the cobalt ions as possible are transferred from the solvent to the stripping solution. Specifically, the pH is preferably in the range of 2.0 to 4.0, and more preferably in the range of 2.5 to 3.5.

[0058] The liquid after stripping can be crystallized. Here, the liquid after stripping is heated to, for example, 40°C to 120°C and concentrated. As a result, cobalt ions are crystallized to obtain a cobalt salt such as cobalt sulfate. The cobalt salt thus obtained preferably has a nickel content of 5 mass ppm or less, and nickel is sufficiently removed, so that it can be effectively used as a raw material for manufacturing lithium-ion secondary batteries and other batteries. Here, the liquid after crystallization may contain cobalt ions and lithium ions that have not crystallized. Therefore, it is desirable to mix the liquid after crystallization with the liquid after stripping before crystallization and use it for recrystallization, to use it to adjust the cobalt ion concentration of the scrubbing liquid used in the solvent that extracted the cobalt ions, or to mix it with the liquid after manganese extraction and use it for extracting the cobalt ions. In this way, the cobalt ions and lithium ions can be circulated or retained in the wet treatment and concentrated without loss.

[0059] (Nickel Extraction and Crystallization) After the cobalt ions have been extracted, the post-cobalt extraction solution (metal-containing solution) can be subjected to solvent extraction to extract nickel ions.

[0060] In the extraction of nickel ions, a carboxylic acid extractant is preferably used to separate nickel ions from the solution after cobalt extraction. Examples of carboxylic acid extractants include neodecanoic acid and naphthenic acid, and among them, neodecanoic acid is preferred due to its ability to extract nickel ions. The extractant may be diluted with a hydrocarbon organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% by volume to 30% by volume, and this may be used as the solvent.

[0061] The equilibrium pH during extraction is preferably 6.0 to 8.0, more preferably 6.8 to 7.2. The pH adjuster used to adjust the pH at this time is preferably an aqueous lithium hydroxide solution obtained in the electrodialysis step described below. When extracting nickel ions, it is desirable to carry out countercurrent multi-stage extraction. In this way, the extraction of lithium ions is suppressed, and the extraction rate of nickel ions can be increased.

[0062] The solvent from which nickel ions have been extracted may be scrubbed one or more times using a scrubbing solution to remove lithium ions that may be contained in the solvent, if necessary. The scrubbing solution may be, for example, a sulfuric acid solution, and may have a pH of 5.0 to 6.0. Here, the post-scrubbing solution may contain lithium ions. Therefore, it is desirable to mix a part or all of the post-scrubbing solution with a post-cobalt extraction solution, and use the resulting solution as a pre-extraction solution to extract nickel ions. This allows lithium ions to be circulated or retained in the wet treatment and concentrated without loss. However, if the solvent from which nickel ions have been extracted does not contain lithium ions, scrubbing may not be performed.

[0063] Then, the solvent is back-extracted using a back-extraction solution such as sulfuric acid, hydrochloric acid, or nitric acid. When crystallization is then performed, sulfuric acid is preferable. The pH is preferably in the range of 1.0 to 3.0, more preferably 1.5 to 2.5. The O / A ratio and the number of times can be appropriately determined, but the O / A ratio is 5 to 1, more preferably 4 to 2.

[0064] When a stripping solution such as a nickel sulfate solution is obtained by stripping, it can be heated to 40°C to 120°C as crystallization after electrolysis and dissolution as necessary, and nickel ions can be crystallized as nickel salts such as nickel sulfate. This results in a nickel salt. Here, the crystallization solution may contain nickel ions and lithium ions that have not crystallized. Therefore, it is desirable to mix the crystallization solution with the stripping solution before crystallization and use it for recrystallization, to use it to adjust the nickel ion concentration of the scrubbing solution with respect to the solvent from which the nickel ions were extracted, or to mix it with the cobalt extraction solution and use it for extracting nickel ions. By repeatedly using it in this way within the process, nickel ions and lithium ions can be circulated or retained in the wet processing and concentrated without loss.

[0065] The nickel-extracted solution after the nickel ions are extracted mainly contains lithium ions, and may be added to the acid leaching solution in the acid leaching step. This allows the lithium ions contained in the nickel-extracted solution to be circulated in a series of steps from acid leaching to nickel extraction. Preferably, after the lithium ions are circulated in this way and the lithium ion concentration in the nickel-extracted solution becomes relatively high, the electrodialysis step described below can be carried out.

[0066] (Electrodialysis process) The metal-containing solution such as the nickel-extracted solution obtained in the above-mentioned metal separation step is a solution in which metals other than lithium ions and impurities have been sufficiently separated, and mainly contains lithium ions. The metal-containing solution may contain, as impurities, fluoride ions (F - ) are included.

[0067] The metal-containing solution may contain a small amount of cations such as nickel ions and magnesium ions that could not be completely separated in the metal separation process. Nickel ions and magnesium ions are cations like lithium ions, and behave similarly to lithium ions during electrodialysis, making it difficult to separate them from lithium ions. In addition, when electrodialysis is performed on a metal-containing solution containing nickel ions and magnesium ions, nickel and magnesium hydroxides may be generated in the lithium hydroxide solution obtained, and there is a concern that electrodialysis may not be able to be continued due to process troubles. For this reason, in such a case, it is desirable to perform washing to remove cations such as nickel ions and magnesium ions from the metal-containing solution prior to the electrodialysis described below. For example, an ion exchange resin or a chelating resin can be used for this washing.

[0068] The metal-containing solution before the electrodialysis step may have, for example, a lithium ion concentration of 1.0 g / L to 30.0 g / L and a fluoride ion concentration of 0.01 g / L to 5.0 g / L.

[0069] When a lithium hydroxide solution is obtained from the above-mentioned metal-containing solution by carbonation, chemical conversion, etc., impurities may not be removed and may remain in the lithium hydroxide solution. It is not desirable to use a lithium hydroxide solution containing a large amount of impurities as a pH adjuster in the metal separation process, because not only lithium ions but also impurities are circulated or accumulated in the wet treatment.

[0070] In this embodiment, the metal-containing solution is subjected to an electrodialysis process to obtain a lithium hydroxide solution and an acidic solution from the metal-containing solution, and since most of the impurities are contained in the acidic solution, it is possible to obtain a lithium hydroxide solution from which the impurities have been sufficiently removed.

[0071] The electrodialysis step can be carried out, for example, by using a commercially available bipolar membrane electrodialysis device. As an example, the bipolar membrane electrodialysis device 1 (hereinafter also simply referred to as "electrodialysis device 1") shown in FIG. 3 has an anode 2 and a cathode 3 in a cell, and a bipolar membrane 4, an anion exchange membrane 5, a cation exchange membrane 6, and a bipolar membrane 7 arranged in sequence from the anode 2 side to the cathode 3 side between the anodes 2 and 3. As a result, the inside of the cell is partitioned into a desalting chamber R1 between the anion exchange membrane 5 and the cation exchange membrane 6, an acid chamber R2 between the bipolar membrane 4 and the anion exchange membrane 5, and an alkaline chamber R3 between the cation exchange membrane 6 and the bipolar membrane 7. The bipolar membranes 4 and 7 are each formed by stacking a cation exchange layer and an anion exchange layer.

[0072] To perform electrodialysis using the electrodialysis device 1 shown in the figure, a metal-containing solution is placed in the deionization compartment R1, and pure water is placed in each of the acid compartment R2 and alkaline compartment R3. A predetermined voltage is then applied between the anode 2 and the cathode 3. Then, the lithium ions (Li + ) passes through the cation exchange membrane 6 and moves to the alkaline chamber R3. In the alkaline chamber R3, water (H2O) is decomposed by the bipolar membrane 7 to produce hydroxide ions (OH - ) is present, resulting in a lithium hydroxide solution.

[0073] On the other hand, the anions of the inorganic acid in the metal-containing solution in the deionization compartment R1 pass through the anion exchange membrane 5 and move to the acid compartment R2. In the acid compartment R2, the anions and hydrogen ions (H + ) produces an acidic solution such as a sulfuric acid solution. In the example shown, the anion of the inorganic acid is the sulfate ion (SO4 2- ), but depending on the type of acid used in the acid leaching process, nitrate ions (NO3 - ) or chloride ion (Cl - ) may be the case.

[0074] In the desalting compartment R1, the lithium salt is separated from the metal-containing solution as described above, and the desalted solution remains. The anion concentration of the inorganic acid tends to be higher in the acidic solution than in the lithium hydroxide solution, and also tends to be higher in the desalted solution than in the lithium hydroxide solution.

[0075] In this electrodialysis, most of the fluoride ions, which are impurities in the metal-containing solution, move from the desalting compartment R1 to the acid compartment R2 through the anion exchange membrane 5 and are included in the acidic solution. As a result, a lithium hydroxide solution containing almost no fluoride ions is obtained in the alkaline compartment R3. Therefore, the fluoride ion concentration in the lithium hydroxide solution is lower than that in the acidic solution.

[0076] The lithium hydroxide solution from which impurities have been removed by electrodialysis as described above can be effectively used as a pH adjuster in the metal separation step. After electrodialysis, the lithium ion concentration of the lithium hydroxide solution may be increased by heating and concentration, if necessary, and then the resulting solution may be used as a pH adjuster.

[0077] The acidic solution obtained by electrodialysis contains fluoride ions. This acidic solution can be discarded as it is, but as described above, it is preferable to use it by adding it to the stripping solution or scavenging solution for extracting manganese and the like in the metal separation process.

[0078] (Crystallization process) A part of the lithium hydroxide solution obtained in the electrodialysis step can be used for the crystallization step. For example, when the lithium hydroxide solution is returned to the wet treatment as a pH adjuster as described above, the lithium ion concentration in the solution may gradually increase due to the lithium in the battery powder newly added to the wet treatment. Depending on the lithium ion concentration, a crystallization step may be performed to recover lithium hydroxide.

[0079] In the crystallization step, a crystallization operation such as heating concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heating concentration, the higher the temperature during crystallization, the faster the process proceeds, so this is preferable. However, after crystallization, the temperature during drying of the crystallized product is preferably less than 60°C, at which water of crystallization does not desorb. This is because anhydrous lithium hydroxide from which water of crystallization has been desorbed is difficult to handle due to its deliquescent nature.

[0080] 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

[0081] Next, tests were carried out on the above-mentioned metal recovery method, and the effectiveness of the method was confirmed. The following description is given, however, for illustrative purposes only and is not intended to be limiting.

[0082] The battery powder was leached with sulfuric acid to obtain a metal-containing solution, which was then neutralized and subjected to manganese extraction, cobalt extraction, and nickel extraction to separate the individual metals.

[0083] Next, the metal-containing solution after the separation was subjected to electrodialysis using a bipolar membrane electrodialysis device (manufactured by Astom Corporation) having a structure as shown in Fig. 3. Here, the desalting compartment, alkaline compartment, acid compartment and electrode compartment were respectively filled with a metal-containing solution having the composition shown in Fig. 4, pure water and an electrode solution. The electrodialysis was performed at a constant voltage of 32 V.

[0084] The results are also shown in Figure 4. In Figure 4, the reason why the distribution ratios of each ion in the desalted liquid after electrodialysis, the lithium hydroxide solution, the acidic solution, and the electrode solution do not add up to 100% is thought to be due to the variability in the analytical values ​​(not including the amount that could not be quantified due to the lower limit of quantification in the analysis, etc.).

[0085] From Figure 4, it can be seen that the fluoride ion concentration, phosphorus concentration, and silicon concentration in the lithium hydroxide solution obtained after electrodialysis are all sufficiently low. This shows that the lithium hydroxide solution obtained by electrodialysis has almost all of the impurities removed.

[0086] The above tests demonstrated that a lithium hydroxide solution can be produced from a metal-containing solution, and that the acidic solution obtained by electrodialysis contains a large amount of fluoride ions as an impurity. [Explanation of symbols]

[0087] 1. Bipolar membrane electrodialysis device 2 Anode 3 cathode 4, 7 Bipolar membrane 5 Anion exchange membrane 6 Cation exchange membrane R1 Desalination room R2 acid chamber R3 Alkaline chamber

Claims

1. A method for recovering metals from battery powder of lithium-ion battery waste, an acid leaching step of leaching the metals in the battery powder with an acid to obtain a metal-containing solution containing lithium ions and other metal ions including manganese ions and / or aluminum ions; a metal separation step for separating the other metal ions from the metal-containing solution, the metal separation step comprising: extraction of manganese ions and / or aluminum ions from the metal-containing solution into a solvent; and stripping, after the extraction, of the manganese ions and / or aluminum ions from the solvent into a stripping solution; After the metal separation step, an electrodialysis step is performed on the metal-containing solution containing lithium ions and fluoride ions using a bipolar membrane to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. Including, the acidic solution obtained in the electrodialysis step is included in the stripping solution in the metal separation step.

2. 2. The method for recovering metals according to claim 1, wherein in the metal separation step, a stripped liquid obtained after the stripping contains fluoride ions, and the stripped liquid is subjected to a wastewater treatment.

3. A method for recovering metals from battery powder of lithium-ion battery waste, an acid leaching step of leaching the metals in the battery powder with an acid to obtain a metal-containing solution containing lithium ions and other metal ions including manganese ions and / or aluminum ions; a metal separation step of separating the other metal ions from the metal-containing solution, the metal separation step including: extraction of manganese ions and / or aluminum ions from the metal-containing solution into a solvent; stripping the manganese ions and / or aluminum ions from the solvent into a stripping liquid after the extraction; and scavenging of removing residual components from the solvent with a scavenging liquid after the stripping; After the metal separation step, an electrodialysis step is performed on the metal-containing solution containing lithium ions and fluoride ions using a bipolar membrane to obtain a lithium hydroxide solution and an acidic solution containing the fluoride ions. Including, The metal recovery method comprises adding the acidic solution obtained in the electrodialysis step to the scavenging solution in the metal separation step.

4. The metal recovery method according to claim 3 , wherein in the metal separation step, a post-scavenging solution obtained after the scavenging contains fluoride ions and calcium, and calcium fluoride is produced.

5. 5. The method of claim 4, wherein the scavenging solution is used as the acid in the acid leaching step after separation of the calcium fluoride.

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

7. the other metal ions include cobalt ions and / or nickel ions; The metal recovery method according to any one of claims 1 to 5, wherein in the metal separation step, cobalt ions and / or nickel ions are separated from the metal-containing solution by solvent extraction.

Images