Method for recovering metals from lithium-ion battery waste

Abstract

This invention provides a method for efficiently recovering metals from lithium-ion battery waste while reducing the use of sodium hydroxide as a pH adjuster. [Solution] A method for recovering metal from lithium-ion battery waste, comprising a wet treatment in which lithium-containing metal in lithium-ion battery waste is leached with acid, and the metal is extracted from the metal-containing solution in which the metal has dissolved, and the lithium extracted in the wet treatment is used as a pH adjuster in the wet treatment.

Description

Technical Field

[0001] This specification discloses a method for recovering metals from lithium-ion battery waste.

Background Art

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

[0003] To recover valuable metals from lithium-ion battery waste, for example, wet treatment is performed on battery powder obtained through roasting or other predetermined dry treatments of lithium-ion battery waste. In 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 metal is dissolved. Then, as described in Patent Document 1 for example, aluminum, iron, manganese, etc. among the elements dissolved in the metal-containing solution are sequentially or simultaneously removed by neutralization or solvent extraction. After that, cobalt and nickel in the metal-containing solution are separated and concentrated by solvent extraction. After nickel is separated by extraction, a lithium-containing solution in which lithium is dissolved and remains is obtained. For the lithium-containing solution thus obtained, lithium ions are concentrated by repeating solvent extraction or the like, and then carbonation is performed by adding carbonate or blowing carbon dioxide gas, etc., to recover the lithium ions contained in the lithium-containing solution as lithium carbonate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when recovering valuable metals from lithium-ion battery waste, sodium hydroxide is mainly used as a pH adjuster, for example, during solvent extraction, and a relatively large amount of sodium may be dissolved in the lithium-containing solution. Although sodium is separated and removed from lithium in the process of purifying lithium carbonate, removal is difficult if the sodium content is high, and it may be necessary to repeat the lithium washing process, for example. In this case, it may lead to a decrease in the lithium recovery rate and an increase in recovery costs.

[0006] This specification discloses a method for efficiently recovering metals from lithium-ion battery waste while reducing the use of sodium hydroxide as a pH adjuster. [Means for solving the problem]

[0007] The method for recovering metals from lithium-ion battery waste disclosed in this specification is a method for recovering metals from lithium-ion battery waste, comprising a wet treatment in which lithium-containing metals in the lithium-ion battery waste are leached with acid, and the metals are extracted from the metal-containing solution in which the metals have dissolved, and the lithium extracted in the wet treatment is used as a pH adjuster in the wet treatment. [Effects of the Invention]

[0008] According to the above-described method for recovering metals from lithium-ion battery waste, the use of sodium hydroxide as a pH adjuster can be reduced, and metals can be efficiently recovered from lithium-ion battery waste. [Brief explanation of the drawing]

[0009] [Figure 1] This is a flowchart illustrating the wet treatment included in a metal recovery method for lithium-ion battery waste according to one embodiment. [Figure 2]Figure 1 is a flowchart showing an example of a dry treatment process that can be used to obtain battery powder from lithium-ion battery waste. [Modes for carrying out the invention]

[0010] The following describes in detail an embodiment of the metal recovery method for lithium-ion battery waste described above. One embodiment of the metal recovery method for recovering metal from lithium-ion battery waste includes a wet treatment in which lithium-containing metals in the lithium-ion battery waste are leached with acid, and the metals are extracted from the metal-containing solution in which the metals have been dissolved. The wet treatment may include the steps illustrated in Figure 1.

[0011] In this process, lithium is extracted from the metal-containing solution using a wet treatment method, and this extracted lithium is then used as a pH adjuster in the wet treatment process. This reduces the amount of sodium hydroxide used as a pH adjuster, or eliminates its use altogether. As a result, the inclusion of sodium, which is an impurity, is suppressed, and the metal can be recovered efficiently. Furthermore, by using lithium extracted through the wet treatment method as a pH adjuster, processing costs can be reduced compared to when sodium hydroxide is used separately as a pH adjuster.

[0012] Preferably, the lithium extracted by the wet treatment is used in all alkaline pH adjusting agents used in the wet treatment. Furthermore, it is preferable that all alkaline pH adjusting agents used in the wet treatment do not contain sodium. To achieve this, it is desirable to minimize lithium loss during the wet treatment and maintain a relatively high lithium ion concentration in the solution. A high lithium ion concentration in the solution can increase the yield when extracting lithium in processes such as the crystallization process described later.

[0013] In many cases, prior to wet processing, lithium-ion battery waste is subjected to a dry processing method as shown in Figure 2 to obtain battery powder. This battery powder is then subjected to wet processing.

[0014] (Lithium-ion battery waste) Lithium-ion battery waste refers to lithium-ion secondary batteries that can be used in mobile phones and various other electronic devices, and which are discarded due to the battery product's lifespan, manufacturing defects, or other reasons. Recovering valuable metals such as cobalt and nickel from such lithium-ion battery waste is desirable from the perspective of effective resource utilization.

[0015] Lithium-ion battery waste has an outer casing that includes aluminum. This casing may be made solely of aluminum, or it may contain aluminum and iron, aluminum laminate, etc.

[0016] Furthermore, lithium-ion battery waste may contain, within the casing, a positive electrode active material consisting of one single metal oxide or two or more composite metal oxides selected from the group consisting of lithium, nickel, cobalt, and manganese, or aluminum foil (positive electrode substrate) to which the positive electrode active material is coated and fixed with, for example, polyvinylidene fluoride (PVDF) or other organic binders. In addition, lithium-ion battery waste may also contain copper, iron, and other materials.

[0017] Furthermore, lithium-ion battery waste typically contains electrolyte within its casing. Examples of electrolytes used include ethylene carbonate and diethyl carbonate.

[0018] (Dry treatment) For the lithium-ion battery waste mentioned above, dry processing may be carried out, including roasting, crushing, and sieving. In the roasting process, the lithium-ion battery waste is heated using a rotary kiln or other heating equipment. In the roasting process, it is preferable to heat the lithium-ion battery waste by holding it at a temperature range of, for example, 450°C to 1000°C, preferably 600°C to 800°C, for 0.5 hours to 4 hours.

[0019] After the roasting process, a crushing process can be performed using a crusher such as an impact crusher to break the casing of the lithium-ion battery waste and extract the positive electrode material and the negative electrode material therefrom.

[0020] After the crushing process, a sieving process is performed to sieve the lithium-ion battery waste using a sieve with an appropriate mesh size, for example, for the purpose of removing aluminum powder. By the above-described dry treatment, powdery battery powder can be obtained from the lithium-ion battery waste. Such battery powder is then subjected to a wet treatment as described below to recover the metals contained in the battery powder.

[0021] (Acid leaching process) In the acid leaching process, metals containing lithium contained in the lithium-ion battery waste are leached with an acid by adding the above battery powder to an acidic leaching solution such as sulfuric acid. Thereby, a metal-containing solution in which the metal is dissolved is obtained.

[0022] In addition, in order to extract only lithium from the battery powder in advance, it is also possible to bring the battery powder into contact with water before leaching with an acid, leach the lithium in the battery powder into the water, and then subject the water leaching residue to acid leaching. However, in this case, facilities for water leaching and acid leaching are both required, and the processing time increases by performing both. In addition, roasting conditions and the like for effectively leaching lithium with water must be managed. Also, even if managed in this way, the leaching rate of lithium with water may not be increased so much. Therefore, it is preferable that the battery powder obtained by the dry treatment is subjected to acid leaching in the acid leaching process without performing water leaching, thereby obtaining a metal-containing solution containing lithium ions. When water leaching is not performed, it becomes easier to maintain a high lithium ion concentration in the liquid in the wet treatment.

[0023] The acid leaching process can be carried out using known methods or 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. Here, as a diluent to adjust the pH of the acid leaching solution, the extraction residue from the nickel extraction process (such as an aqueous lithium sulfate solution) can be used, as described later. In this way, lithium ions can be circulated within the series of steps in the wet treatment, and the lithium ions in the solution can be concentrated within these steps.

[0024] The metal-containing solution obtained in the acid leaching process contains lithium ions, cobalt ions, nickel ions, and manganese ions as metals dissolved from the battery powder. The metal-containing solution may also contain aluminum ions and iron ions, but it is preferable that it contains almost none of these metal ions. If it contains some aluminum ions and iron ions, a neutralization step will be required before the manganese extraction step described later, and there is a concern that lithium will form a complex compound with aluminum and precipitate during this neutralization step, resulting in lithium loss. If aluminum ions and iron ions are almost absent from the metal-containing solution, the neutralization step described above can be omitted, as in this embodiment. Copper, which may be present in the battery powder, can be left in the acid leaching residue without being dissolved by acid leaching and removed by solid-liquid separation.

[0025] For example, the lithium ion concentration in the metal-containing solution obtained in the acid leaching process may be 3 g / L to 35 g / L, the cobalt ion concentration 5 g / L to 30 g / L, the nickel ion concentration 5 g / L to 30 g / L, the manganese ion concentration 1 g / L to 10 g / L, the aluminum ion concentration 0.3 g / L to 10 g / L, the iron ion concentration 0.1 g / L to 5 g / L, and the copper ion concentration 0.001 g / L to 0.05 g / L.

[0026] (Manganese extraction process) For the metal-containing solution obtained in the acid leaching process, a neutralization process described later may be performed as needed, followed by a manganese extraction process in which manganese ions are separated from the metal-containing solution by solvent extraction.

[0027] In the manganese extraction process, it is preferable to use a solvent containing a phosphate ester extractant. Examples of phosphate ester extractants include di-2-ethylhexyl phosphoric acid (trade names: D2EHPA or DP8R). The extractant may be diluted with a hydrocarbon organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% to 30% by volume, and this diluted solvent may be used.

[0028] In the solvent extraction process for manganese extraction, the equilibrium pH is preferably set to 2.3 to 3.5, more preferably 2.5 to 3.0. The pH adjusting agent used at this time is lithium, extracted as described later, or more specifically, an aqueous lithium hydroxide solution (see Figure 1). By using lithium extracted by wet treatment as the pH adjusting agent, it is possible to suppress the residue of sodium in the extraction residue after the nickel extraction process described later, and the inclusion of sodium as an impurity in the aqueous lithium hydroxide solution produced from the extraction residue, which occurs when sodium hydroxide is used as the pH adjusting agent. During extraction, it is desirable to perform the extraction using a counter-flow multi-stage extraction method in which the flow directions of the aqueous phase and solvent used in each extraction are reversed. By doing so, the extraction of cobalt ions, nickel ions, and lithium ions can be suppressed, and the extraction rate of manganese ions can be increased.

[0029] Since the solvent from which manganese ions have been extracted may contain cobalt ions, nickel ions, and lithium ions, these ions that may be present in the solvent are extracted into the aqueous phase by scrubbing, back-extraction, and scavenging. The scrubbing solution can be, for example, a sulfuric acid solution with a pH of 2.0 to 3.0. The back-extract solution can be, for example, a sulfuric acid solution with a pH of 0.0 to 1.0. It is desirable to use the scrubbing solution, back-extraction solution, and scavenging solution in the manganese extraction process (for example, mixing the scrubbing solution with a metal-containing solution and using it as a pre-extraction solution for solvent extraction in the manganese extraction process, using the back-extraction solution for scrubbing in the manganese extraction process, or using the scavenging solution as a back-extract solution in the manganese extraction process). This allows cobalt ions, nickel ions, and lithium ions to be circulated or retained within the process without loss. However, if the solvent from which manganese ions were extracted does not contain cobalt ions, nickel ions, or lithium ions, scrubbing, back extraction, or scavenging may not be necessary.

[0030] (Cobalt extraction process and crystallization process) In the cobalt extraction process, cobalt ions are separated from the metal-containing solution, which is the extraction residue obtained after the manganese ions have been extracted in the manganese extraction process, by solvent extraction.

[0031] Here, it is preferable to use a solvent containing a phosphonic acid ester extractant. Among these, 2-ethylhexyl 2-ethylhexylphosphonate (trade names: PC-88A, Ionquest801) is particularly preferred from the viewpoint of nickel and cobalt separation efficiency, etc. The extractant may be diluted with a hydrocarbon organic solvent such as aromatic, paraffinic, or naphthenic solvent to a concentration of 10% to 30% by volume and used as the solvent.

[0032] When extracting cobalt ions, the pH can be adjusted using a pH adjusting agent such as an aqueous lithium hydroxide solution containing lithium extracted by wet processing, thereby setting the equilibrium pH during extraction to preferably 5.0 to 6.0, more preferably 5.0 to 5.5. If the pH is lower than 5.0, there is a risk that cobalt ions may not be sufficiently extracted into the solvent. This allows for the extraction of cobalt ions from the cobalt-containing solution into the solvent, but as will be described later, some impurity ions such as nickel ions and lithium ions may also be extracted in this process. Furthermore, when extracting cobalt ions, it is desirable to perform the extraction using a counter-flow multi-stage extraction method in which the flow direction of the aqueous phase and the solvent used in each extraction is reversed. By doing so, it is possible to increase the extraction rate of cobalt ions while suppressing the extraction of nickel ions and lithium ions.

[0033] Next, if necessary, the solvent from which the cobalt ions were extracted may be scrubbed once or more times using a scrubbing solution to remove impurities such as nickel ions that may be present in the solvent. The scrubbing solution can be, for example, a sulfuric acid solution, and its pH can be 3.5 to 5.5. Here, the post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to use part or all of the post-scrubbing solution for solvent extraction in the cobalt extraction step (i.e., to mix part or all of the post-scrubbing solution with a metal-containing solution and use this as the pre-extraction solution for solvent extraction in the cobalt extraction step). This allows nickel ions and lithium ions to be circulated or retained within the process without loss. However, if the solvent from which the cobalt ions were extracted does not contain nickel ions or lithium ions, the scrubbing step may not be performed.

[0034] Subsequently, back-extraction is performed on the solvent from which the cobalt ions were extracted. The back-extract solution used can be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, but sulfuric acid is preferable if sulfate is to be obtained in the crystallization step described later. Here, the pH is set so that as many cobalt ions as possible are extracted from the organic phase (solvent) into the aqueous phase. 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 determined as appropriate. The liquid temperature may be room temperature, but is preferably 0°C to 40°C.

[0035] A crystallization step is performed on the back-extraction solution obtained in the cobalt extraction step. In the crystallization step after the cobalt extraction step, cobalt ions crystallize, and cobalt sulfate is obtained. In the crystallization step, the back-extraction solution is heated to a temperature of, for example, 40°C to 120°C to concentrate it. This causes the cobalt ions to crystallize as cobalt sulfate. The cobalt sulfate produced in this way has a nickel content of preferably 5 ppm by mass or less, and since nickel has been sufficiently removed, it can be effectively used as a raw material for the manufacture of lithium-ion secondary batteries and other batteries. However, the crystallized solution may contain cobalt ions and lithium ions that did not crystallize. Therefore, it is desirable to use the crystallized solution by mixing it with the back-extraction solution in the crystallization step for further crystallization, or by using it to adjust the cobalt concentration of the scrubbing solution in the cobalt extraction step, or by using it for solvent extraction in the cobalt extraction step. By using it repeatedly within the process in this way, cobalt ions and lithium ions can be circulated or retained within the process and concentrated without loss.

[0036] (Nickel extraction process and crystallization process) After separating cobalt ions from the metal-containing solution in the cobalt extraction process, a nickel extraction process is performed on the metal-containing solution remaining from the cobalt extraction process.

[0037] In the nickel extraction process, a carboxylic acid-based extractant is preferably used to separate nickel ions from the metal-containing solution. Examples of carboxylic acid-based extractants include neodecanoic acid and naphthenic acid, but neodecanoic acid is preferred due to its ability to extract nickel ions. The extractant may be diluted with a hydrocarbon-based organic solvent such as an aromatic, paraffinic, or naphthenic solvent to a concentration of 10% to 30% by volume, and this may be used as the solvent.

[0038] In the nickel extraction process, the equilibrium pH is preferably set to 6.0 to 8.0, more preferably to 6.8 to 7.2. The pH adjusting agent used at this time is also an aqueous lithium hydroxide solution obtained as described later. In the nickel extraction process, as in the cobalt extraction process described above, it is desirable to perform the extraction using a countercurrent multi-stage extraction method. By doing so, the extraction of lithium ions can be suppressed and the extraction rate of nickel ions can be increased.

[0039] Furthermore, it is preferable that all alkaline pH adjusting agents used in the wet treatment process, including the manganese extraction process, cobalt extraction process, and nickel extraction process, contain lithium extracted in the wet treatment process but do not contain sodium. This eliminates the need for sodium hydroxide as an alkaline pH adjusting agent, and allows for a sufficient reduction in sodium ions, which are impurities, in the lithium hydroxide aqueous solution obtained in the hydroxide process described later.

[0040] Next, if necessary, the solvent from which nickel ions were extracted may be scrubbed once or more times using a scrubbing solution to remove impurities such as lithium ions and sodium ions that may be present in the solvent. The scrubbing solution can be, for example, a sulfuric acid solution, and its pH can be 5.0 to 6.0. Here, the post-scrubbing solution may contain lithium ions. Therefore, it is desirable to use part or all of the post-scrubbing solution for solvent extraction in the nickel extraction step (i.e., mix part or all of the post-scrubbing solution with a metal-containing solution and use this as the pre-extraction solution for solvent extraction in the nickel extraction step). This allows lithium ions to be circulated or retained within the process and concentrated without loss. However, if the solvent from which nickel ions were extracted does not contain lithium ions, the scrubbing step may not be performed.

[0041] Next, back-extraction is performed using a back-extracting solution such as sulfuric acid, hydrochloric acid, or nitric acid in the solvent. If a crystallization step is performed afterward, sulfuric acid is preferred. The pH is preferably in the range of 1.0 to 3.0, and more preferably 1.5 to 2.5. The O / A ratio and the number of times can be determined as appropriate, but the O / A ratio is 5 to 1, more preferably 4 to 2.

[0042] When a nickel sulfate solution is obtained by back extraction, electrolysis and dissolution can be performed as needed, and then the solution can be heated to 40°C to 120°C in the crystallization step to crystallize the nickel ions as nickel sulfate. This yields nickel sulfate. However, the crystallized solution may contain uncrystallized nickel ions and lithium ions. Therefore, it is desirable to use the crystallized solution by mixing it with the back-extracted solution in the crystallization step for further crystallization, or to use it to adjust the nickel ion concentration of the scrubbing solution in the nickel extraction step, or to use it for solvent extraction in the nickel extraction step. By repeatedly using it in this way within the process, nickel ions and lithium ions can be circulated or retained within the process and concentrated without loss.

[0043] (Hydroxylation process) The extraction residue obtained after the nickel extraction process contains virtually only lithium ions, as a result of the separation of manganese ions, cobalt ions, and nickel ions in each of the extraction processes described above. From this extraction residue, lithium for use as a pH adjuster in wet processing can be extracted. More specifically, if the extraction residue after the nickel extraction process is an aqueous lithium sulfate solution, a hydroxide process can be performed to prepare an aqueous lithium hydroxide solution from that aqueous lithium sulfate solution.

[0044] Various methods can be used to obtain an aqueous lithium hydroxide solution from an aqueous lithium sulfate solution. For example, a lithium carbonate aqueous solution is first obtained by adding a carbonate to a lithium sulfate aqueous solution or by blowing in carbon dioxide. Then, in the so-called chemical conversion method, calcium hydroxide is added to the lithium carbonate aqueous solution, and a lithium hydroxide aqueous solution can be produced according to the reaction equation Li2CO3 + Ca(OH)2 → 2LiOH + CaCO3. Calcium ions that may remain in the solution can be removed using cation exchange resins or chelating resins. Alternatively, an aqueous lithium hydroxide solution can be obtained by adding barium hydroxide to an aqueous lithium sulfate solution and following the reaction Li2SO4 + Ba(OH)2 → 2LiOH + BaSO4. The barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin or chelating resin. Alternatively, when employing the so-called electrolytic method, a lithium hydroxide aqueous solution can be generated on the cathode side by supplying an aqueous lithium sulfate solution to the anode side and performing electrolysis in an electrolytic cell equipped with a cation exchange membrane that separates the anode side and the cathode side.

[0045] The lithium hydroxide aqueous solution obtained in this way can be effectively used as an alkaline pH adjuster in the manganese extraction process, cobalt extraction process, and nickel extraction process, as well as in the neutralization process described later, as shown in Figure 1.

[0046] Incidentally, it is preferable to use a portion of the lithium sulfate aqueous solution in the hydroxide step, and the remaining portion (the remainder) as at least part of the acid in the acid leaching step, as shown in Figure 1. In this case, by using a portion of the lithium sulfate aqueous solution in the acid leaching step, the lithium concentration within the series of steps can be increased, and by obtaining only the amount of lithium hydroxide aqueous solution necessary for pH adjusters, etc., in the hydroxide step, the overall cost of the process, including the production of lithium hydroxide, can be reduced.

[0047] (Crystallization process) When a series of processes including acid leaching, manganese extraction, cobalt extraction, nickel extraction, and hydroxide extraction are repeated multiple times, as described above, when a portion of the lithium sulfate aqueous solution is sent to the acid leaching process, the lithium contained therein may be slightly separated in each extraction process. However, as the series of processes are repeated, new lithium-ion battery waste is introduced into the series of processes each time. As a result, the amount of lithium ions entering each process from the previous process and the amount of lithium ions moving from that process to the next process become almost equal, and the increase in lithium ions in each process saturates, causing a certain amount of lithium ions to accumulate. In this case, most of the lithium ions derived from the lithium hydroxide aqueous solution used as a pH adjuster in each process, and the lithium derived from the lithium sulfate aqueous solution used in the acid leaching process, are re-contained in the lithium sulfate aqueous solution after the nickel extraction process. In other words, at least a portion of the lithium circulates in the liquid during the series of processes.

[0048] Furthermore, as the series of processes are repeated, new lithium-ion battery waste is introduced into the process each time, which can gradually increase the lithium ion concentration in the lithium sulfate aqueous solution or other liquids.

[0049] In cases where the lithium ion concentration in the solution increases in this manner, a crystallization step can be further performed after the hydroxide step to precipitate lithium hydroxide from a portion of the lithium hydroxide aqueous solution, depending on the lithium ion concentration in the solution. This makes it possible to recover lithium hydroxide. Previously, because the lithium ion concentration in the residual extract solution containing lithium ions after the nickel extraction step was low, it was necessary to perform a lithium concentration step to increase the lithium ion concentration in the solution. However, in this embodiment, such a lithium concentration step is not necessary, and a high-concentration lithium aqueous solution can be obtained without performing complex steps, thus reducing lithium loss and manufacturing costs in this process.

[0050] In the crystallization process, crystallization operations such as heating and concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heating and concentration, a higher temperature during crystallization is preferable because it speeds up the process. However, after crystallization, it is preferable to dry the precipitate at a temperature below 60°C to prevent the desorption of crystal water. This is because if crystal water is desorbed, it becomes anhydrous lithium hydroxide, which is hygroscopic and difficult to handle.

[0051] Furthermore, the lithium hydroxide can subsequently be subjected to pulverization or other processes to adjust its physical properties to the required level.

[0052] (neutralization process) If the metal-containing solution obtained in the acid leaching process contains iron and aluminum, it is desirable to perform a neutralization step to separate at least some of the aluminum and / or iron. For example, if the aluminum ion concentration is 0.5 g / L or higher and the iron ion concentration is 0.001 g / L or higher, it is desirable to perform a neutralization step because there is a concern that the aluminum ions cannot be sufficiently removed in the manganese extraction step described above, and that the extraction capacity of the solvent will decrease due to the residual and accumulation of extracted iron ions in the solvent. In neutralization, first, the pH is set to 4.0 to 6.0 and the oxidation-reduction potential (ORP value, based on silver / silver chloride potential) to -500 mV to 100 mV by adding alkali, thereby precipitating the aluminum. Then, by adding an oxidizing agent and adjusting the pH to within the range of 3.0 to 4.0, the iron can be precipitated. The pH adjusting agent used at this time is lithium, extracted as described above, or more specifically, an aqueous lithium hydroxide solution.

[0053] As described above, by using lithium extracted through wet processing as a pH adjuster, the use of sodium hydroxide as a pH adjuster can be reduced, and metal can be efficiently recovered from lithium-ion battery waste.

Claims

1. A method for recovering metals from lithium-ion battery waste, This process includes a wet treatment in which lithium-containing metals in lithium-ion battery waste are leached with acid, and the metals are extracted from the metal-containing solution in which the metals have dissolved. A method for recovering metals from lithium-ion battery waste, wherein the lithium extracted by the aforementioned wet treatment is used as a pH adjusting agent in the said wet treatment.

2. The metal recovery method according to claim 1, wherein the lithium is extracted as an aqueous lithium hydroxide solution by the wet treatment, and the aqueous lithium hydroxide solution is used as the pH adjusting agent.

3. The metal recovery method according to claim 1 or 2, wherein the lithium extracted by the wet treatment is used in all alkaline pH adjusting agents used in the wet treatment.

4. The metal recovery method according to any one of claims 1 to 3, wherein all alkaline pH adjusting agents used in the wet treatment are sodium-free.

5. The wet treatment comprises an acid leaching step of leaching lithium-containing metals in lithium-ion battery waste with acid to obtain a metal-containing solution, and one or more extraction steps of separating the metals from the metal-containing solution by solvent extraction. The metal recovery method according to any one of claims 1 to 4, wherein lithium extracted by the wet treatment is used as the pH adjusting agent in at least one of the extraction steps.

6. The aforementioned metal includes cobalt, nickel, and manganese. The extraction process includes a manganese extraction process, a cobalt extraction process, and a nickel extraction process in this order. The metal recovery method according to claim 5, wherein lithium used as a pH adjusting agent in the wet treatment is extracted from the extraction residue obtained in the nickel extraction step.

7. The extraction residue is an aqueous lithium sulfate solution. The metal recovery method according to claim 6, further comprising a nickel extraction step followed by a hydroxide step to obtain a lithium hydroxide aqueous solution from the lithium sulfate aqueous solution.

8. The metal recovery method according to claim 7, wherein a portion of the lithium sulfate aqueous solution is subjected to the hydroxide step, and the remainder is used as at least a portion of the acid in the acid leaching step.

9. A metal recovery method according to claim 7 or 8, comprising repeatedly performing a series of steps including an acid leaching step, a manganese extraction step, a cobalt extraction step, a nickel extraction step, and a hydroxide step, thereby circulating at least a portion of the lithium in a liquid during the series of steps.

10. As the series of steps described above are repeated, the concentration of lithium ions in the liquid increases as metals from lithium-ion battery waste are added to the series of steps. The metal recovery method according to claim 9, further comprising, depending on the lithium ion concentration in the liquid, a crystallization step of precipitating lithium hydroxide from a portion of the lithium hydroxide aqueous solution after the hydroxide step.

11. The cobalt extraction step and the nickel extraction step each include extracting metal ions from the metal-containing solution into a solvent and back-extracting the metal ions from the solvent with a sulfuric acid solution, A metal recovery method according to any one of claims 6 to 10, further comprising a crystallization step after the cobalt extraction step and after the nickel extraction step, respectively, in which the metal ions in the back-extracted solution are crystallized to obtain sulfates.

12. Prior to the aforementioned wet treatment, a dry treatment is performed to obtain battery powder by a process that includes roasting of lithium-ion battery waste. A method for recovering metal according to any one of claims 1 to 11, comprising subjecting the battery powder to acid leaching in the wet treatment to obtain the metal-containing solution.

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