Metal recovery method

Abstract

Provided is a method for recovering a metal from a battery powder of lithium ion battery waste containing at least copper, lithium, and cobalt and / or nickel, said method comprising an acid leaching step for causing a metal in the battery powder to leach into an acidic leachate to obtain a metal-containing solution containing at least lithium ions and cobalt ions and / or nickel ions and a metal separation step for separating at least cobalt ions and / or nickel ions from the metal-containing solution, wherein: in the acid leaching step, a plurality of leaching stages are repeated a plurality of times; the plurality of leaching stages have a first leaching stage in which a metal in the battery powder is caused to leach into an acidic leachate, leaching is ended before elution of copper, and a leaching residue is separated to obtain a post-leaching liquid and a second leaching stage in which a metal in the leaching residue is caused to leach into an acidic leachate, leaching is ended after elution of copper, and a post-leaching liquid is obtained; the post-leaching liquid obtained in the first leaching stage is used as the metal-containing solution; a post-leaching liquid obtained in the final leaching stage among the plurality of leaching stages is used as an acidic leachate in the next first leaching stage; an acidic or neutral post-separation liquid containing at least one type of ion selected from the group consisting of cobalt ions, nickel ions, lithium ions, copper ions, and inorganic acid anions having been separated from the metal-containing solution is obtained after the metal separation step; and at least part of the post-separation liquid is mixed with the acidic leachate for use in the acid leaching step.

Description

Metal recovery method

[0001] This specification describes a metal recovery method.

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

[0003] For example, to recover metals from lithium-ion battery waste, battery powder obtained through heat treatment or other processes is brought into contact with an acidic leachate to leach metals such as nickel, cobalt, manganese, aluminum, and iron from the battery powder into the acidic leachate, thereby obtaining a metal-containing solution in which the metals are dissolved.

[0004] Next, a metal separation step is carried out to separate each metal from the metal-containing solution. Specifically, as described in Patent Documents 1 to 3, aluminum, iron, and manganese are sequentially or simultaneously removed from the metals dissolved in the metal-containing solution by neutralization or solvent extraction. Thereafter, nickel and cobalt are separated by solvent extraction and then concentrated and recovered.

[0005] Regarding this metal recovery method, in which metals in battery powder are leached with an acidic leaching solution, Patent Document 4 proposes a "lithium ion battery treatment method including a leaching step in which battery powder is leached with a leaching solution containing 0.9 to 1.5 molar equivalents of sulfuric acid required to dissolve all metal components contained in the battery powder, and the leaching is terminated before the oxidation-reduction potential ORP value (based on silver / silver chloride potential) of the leaching solution exceeds 0 mV." According to this method, "valuable metals added to the leaching solution are sufficiently dissolved, while most copper remains in a solid state at the end of leaching." "As a result, solid copper can be easily separated and removed from the leaching solution, and the process required to remove copper dissolved in the solution after leaching can be simplified or omitted, resulting in improved processing efficiency and reduced costs."

[0006] JP 2010-180439 A U.S. Patent Application Publication No. 2011 / 0135547 JP 2014-162982 A JP 2017-36489 A

[0007] As described in Patent Document 4, if copper is left in a solid state at the end of leaching, copper can be easily removed by solid-liquid separation after leaching. However, in this case, since leaching is terminated before copper dissolves, cobalt and nickel cannot be sufficiently leached. On the other hand, if the leaching time is extended with the aim of improving the leaching rate of cobalt and nickel, copper dissolves, making it impossible to easily separate and remove copper. The method described in Patent Document 4 has room for further improvement from the perspective of leaching as much cobalt and nickel as possible while suppressing copper leaching.

[0008] On the other hand, various post-separation solutions obtained by separation from the metal-containing solution after the subsequent metal separation step may contain trace amounts of cobalt ions and / or nickel ions, as well as metal ions such as lithium ions and copper ions, and inorganic acid anions such as sulfate ions. It is desirable to effectively recover, utilize, or remove such metal ions and inorganic acid anions.

[0009] This specification provides a metal recovery method that effectively leaches cobalt and / or nickel while suppressing copper leaching during acid leaching, and that effectively recovers, utilizes, or removes metal ions and inorganic acid anions in the solution following the metal separation step.

[0010] The metal recovery method disclosed in this specification is a method for recovering metals from battery powder containing at least copper, lithium, cobalt, and / or nickel, which is a lithium-ion battery waste, and includes an acid leaching step in which the metals in the battery powder are leached in an acidic leaching solution to obtain a metal-containing solution containing at least lithium ions, cobalt ions, and / or nickel ions, and a metal separation step in which at least cobalt ions and / or nickel ions are separated from the metal-containing solution, and the acid leaching step repeats a plurality of leaching steps multiple times, and the plurality of leaching steps include a first leaching step in which the metals in the battery powder are leached in an acidic leaching solution, the leaching is terminated before copper is eluted, and a leaching residue is separated to obtain a leached solution. and a second leaching step in which metals in the leaching residue are leached in an acidic leach solution, the leaching is terminated after the copper is leached, and a post-leach solution is obtained. The post-leach solution obtained in the first leaching step is used as the metal-containing solution, and the post-leach solution obtained in the final leaching step of the plurality of leaching steps is used as the acidic leach solution in the next first leaching step. After the metal separation step, an acidic or neutral post-separation solution containing at least one ion selected from the group consisting of cobalt ions, nickel ions, lithium ions, copper ions, and anions of inorganic acids is obtained, and at least a part of the post-separation solution is mixed with the acidic leach solution in the acid leaching step.

[0011] According to the above-described metal recovery method, cobalt and / or nickel can be effectively leached while suppressing copper leaching during acid leaching, and metal ions and inorganic acid anions in the solution following the metal separation step can be effectively recovered, utilized, or removed.

[0012] FIG. 1 is a flow chart showing a metal recovery method of one embodiment. FIG. 2 is a flow chart showing an example of a pretreatment step for obtaining battery powder from lithium ion battery waste. FIG. 3 is a flow chart showing details of an acid leaching step included in the metal recovery method of FIG. 1. FIG. 4 is a graph showing changes in pH, ORP, and each metal concentration over time in a first first leaching stage of Example 1. FIG. 5 is a graph showing changes in pH, ORP, and each metal concentration over time in a first second leaching stage of Example 1. FIG. 6 is a graph showing changes in pH, ORP, and each metal concentration over time in a second first leaching stage of Example 1. FIG. 7 is a graph showing changes in pH, ORP, and each metal concentration over time in a second second leaching stage of Example 1. FIG. 8 is a graph showing changes in pH, ORP, and each metal concentration over time in a third first leaching stage of Example 1. FIG. 9 is a graph showing changes in pH, ORP, and each metal concentration over time in a third second leaching stage of Example 1. FIG. 10 is a flow chart showing a leaching step of a comparative example. FIG. 11 is a graph showing changes in pH, ORP, and each metal concentration over time in a leaching step of a comparative example.

[0013] The following describes in detail an embodiment of the metal recovery method. One embodiment of the metal recovery method is a method for recovering metals from battery powder obtained from lithium-ion battery waste and containing at least copper, lithium, cobalt, and / or nickel. This metal recovery method includes an acid leaching step and a metal separation step.

[0014] In the acid leaching process, metals in the battery powder are leached in an acidic leach solution to obtain a metal-containing solution containing at least lithium ions and cobalt and / or nickel ions. More specifically, the acid leaching process involves multiple repeated leaching stages. The multiple leaching stages include a first leaching stage in which the metals in the battery powder are leached in an acidic leach solution, the leaching is terminated before copper is eluted, and the leach residue is separated to obtain a post-leach solution; and a second leaching stage in which the metals in the leach residue are leached in an acidic leach solution, the leaching is terminated after copper is eluted, and the post-leach solution is obtained. The post-leach solution obtained in the first leaching stage is then sent to the next metal separation stage as a metal-containing solution. Meanwhile, the post-leach solution obtained in the final leaching stage is used as the acidic leach solution for the next first leaching stage. This suppresses copper leaching while allowing cobalt and / or nickel to leach sufficiently, resulting in a metal-containing solution that contains almost no copper ions but contains cobalt ions and / or nickel ions.

[0015] In the metal separation step, at least cobalt ions and / or nickel ions are separated from the metal-containing solution. After the metal separation step, an acidic or neutral post-separation solution containing at least one ion selected from the group consisting of cobalt ions, nickel ions, lithium ions, copper ions, and inorganic acid anions is obtained by separation from the metal-containing solution. To recover, utilize, or remove the metal ions and / or inorganic acid anions in the post-separation solution, at least a portion of the post-separation solution is mixed with an acidic leach solution in the acid leaching step. In this way, the cobalt ions and / or nickel ions in the post-separation solution are contained in the metal-containing solution after the acid leaching step and can be effectively recovered. Lithium ions in the post-separation solution are also contained in the metal-containing solution after the acid leaching step and can be circulated into the solution in the acid leaching step and metal separation step, allowing for effective utilization. Copper ions in the post-separation solution are precipitated in the first leaching stage of the acid leaching step and can be removed by being contained in the leach residue. The inorganic acid anions in the separated solution are utilized to contribute to reducing the amount of acid required in the acid leaching step, thereby enabling the metal ions and inorganic acid anions to be effectively recovered, utilized, or removed.

[0016] The metal recovery method of this embodiment may include, as an example, the steps shown in Figure 1. In Figure 1, battery powder from lithium-ion battery waste is subjected to an acid leaching step, a metal separation step, a hydroxide step, and a crystallization step in this order. The battery powder can be obtained by subjecting lithium-ion battery waste to a pretreatment step, as shown in Figure 2. Here, the description will be given according to Figures 1 and 2, but Figures 1 and 2 are merely examples and the present invention is not limited to such specific flows.

[0017] (Lithium-ion battery waste) The target lithium-ion battery waste is lithium-ion secondary batteries that can be used in mobile phones and various other electronic devices, etc., that have been discarded due to the end of the battery product's life, manufacturing defects, or other reasons. Recovering valuable metals from such lithium-ion battery waste is preferable from the perspective of effective resource utilization.

[0018] Lithium-ion battery waste has an aluminum-containing casing as an exterior that encases the battery. This casing can be made of aluminum alone, aluminum and iron, or aluminum laminate. Lithium-ion battery waste may also contain a cathode active material, such as a single metal oxide containing lithium and one or more selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more selected metals. The cathode active material may also be coated and fixed to an aluminum foil (cathode substrate) with an organic binder, such as polyvinylidene fluoride (PVDF). Lithium-ion battery waste may also contain copper, iron, etc. Furthermore, the casing of lithium-ion battery waste typically contains an electrolyte solution, such as lithium hexafluorophosphate, dissolved in an organic solvent. Examples of organic solvents that may be used include ethylene carbonate and diethyl carbonate.

[0019] (Pretreatment Process) A pretreatment process is often performed on lithium-ion battery waste. The pretreatment process may include at least one of roasting, crushing, and sieving. Lithium-ion battery waste is converted into battery powder through the pretreatment process. The roasting, crushing, and sieving processes of the pretreatment process may be performed individually as needed, or may be performed in any order. Battery powder refers to powder obtained by separating and concentrating positive electrode material components from lithium-ion battery waste through some kind of pretreatment. Battery powder may also be obtained as a powder by concentrating positive electrode material components by crushing and sieving lithium-ion battery waste with or without heat treatment.

[0020] In the roasting process, the lithium-ion battery waste is heated. For example, roasting can convert metals such as lithium and cobalt contained in the lithium-ion battery waste into a form that is easily soluble in the acid leaching solution during the acid leaching process. During roasting, the lithium-ion battery waste is preferably heated at a temperature ranging from 450°C to 1000°C, preferably from 600°C to 800°C, for 0.5 to 6 hours. Roasting can be performed either in air or in an inert atmosphere such as nitrogen. Roasting can also be performed in both air and inert atmospheres, in this order, or in the reverse order. The roasting furnace can be either a batch or continuous furnace. For example, a stationary furnace can be used for the batch process, and a rotary kiln can be used for the continuous process. Various other furnaces can also be used.

[0021] During roasting, at least a portion of the electrolyte is removed from the lithium-ion battery waste, for example, by evaporation of the electrolyte solution. In many cases, when lithium-ion battery waste is heated during roasting, the components of the internal electrolyte evaporate sequentially, starting with those with low boiling points. Furthermore, when the lithium-ion battery waste reaches a higher temperature, resins such as organic binders decompose or vaporize. Even if a portion of the electrolyte solution and organic binder is removed in this way, certain components, such as fluorine, contained in the electrolyte solution and organic binder may remain and be included in the battery powder obtained after the pretreatment process. When roasting is performed, the electrolyte is removed and rendered harmless, and the organic binder is decomposed, facilitating the separation of the aluminum foil and the positive electrode active material during the crushing and sieving processes described below. Although the composition of the positive electrode active material changes upon roasting, the term "positive electrode active material" will be used here even if the material has undergone roasting.

[0022] After roasting, the lithium-ion battery waste can be crushed to remove the positive electrode active material and other materials from the casings. In the crushing, the casings of the lithium-ion battery waste are destroyed and the positive electrode active material is selectively separated from the aluminum foil on which the positive electrode active material is applied.

[0023] For crushing, various known devices or equipment can be used, but it is particularly preferable to use an impact crusher that can crush lithium-ion battery waste by applying impact while cutting the waste. Examples of this impact crusher include a sample mill, hammer mill, pin mill, wing mill, tornado mill, and hammer crusher. A screen can be installed at the outlet of the crusher, and the lithium-ion battery waste is discharged from the crusher through the screen once it has been crushed to a size that can pass through the screen.

[0024] After crushing the lithium-ion battery waste, 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 some extent is obtained below the sieve.

[0025] If the battery powder obtained in the pretreatment step contains nickel, the nickel content is, for example, 1% by mass to 30% by mass, typically 5% by mass to 20% by mass. If the battery powder contains cobalt, 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, for example, 2% by mass to 8% by mass of lithium, 1% by mass to 30% by mass of manganese, 1% by mass to 10% by mass of aluminum, 1% by mass to 5% by mass of iron, and 1% by mass to 10% by mass of copper.

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

[0027] However, water leaching requires special equipment, and performing both water leaching and acid leaching in the acid leaching step increases the processing time. Furthermore, it may be necessary to control roasting conditions, etc., to effectively leach lithium with water. Even with such control, the leaching rate of lithium with water may not be significantly increased. Therefore, the battery powder obtained as described above may be subjected to the acid leaching step without water leaching. If water leaching is not performed, it becomes easier to maintain a high lithium ion concentration in the solution during wet processing after the acid leaching step.

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

[0029] (Acid Leaching Process) In the acid leaching process, the metals in the battery powder are leached with an acidic leaching solution containing sulfuric acid, nitric acid, hydrochloric acid, or other inorganic or mineral acids. This results in a post-leaching solution (metal-containing solution) in which the metals in the battery powder are dissolved. Here, the solution that contains the metal ions resulting from the dissolution of the metals in the acid leaching process and is sent to the next process, the metal separation process, is called the metal-containing solution. The solution in the middle of the metal separation process may also be called the metal-containing solution.

[0030] The pH of the acidic leachate during leaching is preferably -0.5 to 3.0, and the pH of the post-leaching solution after leaching may be 0.5 to 2.0. During leaching, for example, the acidic leachate may be stirred at 100 rpm to 400 rpm using a stirrer as needed, and the solution temperature may be set to 65°C to 70°C.

[0031] In the acid leaching process, as shown in Figure 3, multiple leaching stages are repeated multiple times. Each leaching stage includes a first leaching stage in which the metals in the battery powder are leached in an acid leaching solution, the leaching is stopped before copper is eluted, and the leaching residue is separated to obtain a post-leaching solution. Another leaching stage involves leaching the leaching residue from the first leaching stage in an acid leaching solution, the leaching is stopped after copper is eluted, and a post-leaching solution is obtained. The post-leaching solution obtained in the first leaching stage is used as a metal-containing solution to be sent to subsequent processes such as neutralization, as described below. Meanwhile, the post-leaching solution obtained in the final leaching stage (the second leaching stage if there are two leaching stages) is used by incorporating it into the acid leaching solution for the next first leaching stage.

[0032] By repeating multiple leaching steps in this manner, it is possible to increase the leaching rate of the metals to be leached (such as cobalt and / or nickel) in the battery powder, while leaving much of the copper, the leaching of which should be suppressed, unleached and separating it as a leaching residue. More detailed information is provided below. Here, as an example, a battery powder containing cobalt, nickel, and copper will be described. However, the battery powder may contain neither cobalt nor nickel, or may further contain other metals.

[0033] As an example of repeating multiple leaching steps, in the first leaching step, leaching is terminated before copper dissolves (e.g., while the copper ion concentration in the acidic leaching solution is 0.01 g / L or less), and the leaching residue is extracted by solid-liquid separation. This results in a leaching solution that has a lower copper ion concentration than the leaching solution obtained in the second leaching step described below and contains cobalt ions and nickel ions. This leaching solution is sent to a subsequent process as a metal-containing solution. Meanwhile, the leaching residue contains copper as well as the remaining undissolved cobalt and nickel. A second leaching step is performed to further leach cobalt and nickel from this leaching residue.

[0034] In the first second leaching step, the leaching residue obtained in the first leaching step is contacted with an acidic leaching solution to leach cobalt and nickel from the leaching residue. In the second leaching step, leaching is continued even after copper has been dissolved (e.g., after the copper ion concentration in the acidic leaching solution becomes higher than 0.01 g / L). This allows almost all of the cobalt and nickel in the leaching residue to be leached. After copper has been dissolved and cobalt and nickel have been sufficiently leached, leaching is terminated and the leaching residue is extracted by solid-liquid separation. The leaching residue contains reduced cobalt and nickel and contains copper. The post-leaching solution after the leaching residue is extracted contains cobalt ions, nickel ions, and copper ions. In the second leaching step, new battery powder may be added to leach not only the metals in the leaching residue from the first leaching step, but also the metals in the new battery powder. In the second leaching stage, leaching is continued even after the copper has been dissolved, so that the cobalt and nickel in the new battery powder can also be sufficiently leached.

[0035] Next, in the second first leaching step, the post-leaching solution obtained in the first second leaching step is used as the acidic leaching solution. If necessary, new acidic leaching solution may be added. In the second first leaching step, copper ions in the post-leaching solution are reduced by a substitution reaction with a metal less noble than copper contained in new battery powder, resulting in copper precipitation and in the leaching residue. Furthermore, the second first leaching step, while intended to dissolve cobalt and nickel from the new battery powder, ends before copper dissolution. Therefore, the leaching residue contains copper derived from the new battery powder as well as undissolved cobalt and nickel. This leaching residue is separated by solid-liquid separation and then subjected to leaching in the second second leaching step. The post-leaching solution from which the leaching residue is removed contains not only the cobalt and nickel ions dissolved from the new battery powder but also the cobalt and nickel ions carried over from the first leaching step, and is sent to a downstream process.

[0036] The second second leaching stage is carried out in the same manner as the first second leaching stage, and therefore a detailed description thereof will be omitted. Solid-liquid separation in the second leaching stage does not need to be carried out every time. If solid-liquid separation is not carried out in the second leaching stage, the post-leaching solution containing the leaching residue will be sent to the next first leaching stage, and copper will accumulate in the leaching residue. If solid-liquid separation is carried out in at least one of multiple second leaching stages, the copper-containing leaching residue can be separated and removed in that second leaching stage. Preferably, solid-liquid separation is carried out in each second leaching stage, and the copper-containing leaching residue is removed each time.

[0037] Here, "before copper leaching" in the first leaching stage refers to a state in which the copper ion concentration in the acidic leaching solution is lower than that of the post-leaching solution obtained in the second leaching stage of that cycle. For example, a state in which the copper ion concentration in the acidic leaching solution is 0.01 g / L or less may be considered "before copper leaching." However, this copper ion concentration does not include the copper ion concentration in the post-leaching solution obtained in the previous second leaching stage and used as the acidic leaching solution in the current first leaching stage. When the post-leaching solution obtained in the previous second leaching stage is used as the acidic leaching solution in the first leaching stage, the period in which the relatively high copper ion concentration before leaching tends to decrease due to copper precipitation through a substitution reaction can be considered "before copper leaching" after the copper ion concentration once drops to 0.01 g / L or less and then remains at 0.01 g / L or less. In this case, leaching may be terminated while the copper ion concentration remains at 0.01 g / L or less (before the copper ion concentration exceeds 0.01 g / L).

[0038] Furthermore, "after copper leaching" in the second leaching stage refers to a state in which the copper ion concentration in the acidic leaching solution is higher than that of the post-leaching solution obtained in the first leaching stage of that cycle. Therefore, in each cycle, the copper ion concentration in the post-leaching solution obtained in the second leaching stage will be higher than that of the post-leaching solution obtained in the first leaching stage. For example, the state may be considered "after copper leaching" when the copper ion concentration in the acidic leaching solution is higher than 0.01 g / L. In the second leaching stage, leaching may be terminated, for example, after the copper ion concentration in the acidic leaching solution becomes higher than 0.01 g / L.

[0039] In the first and second leaching stages, the oxidation-reduction potential (based on silver / silver chloride potential) of the acidic leaching solution may be well below 0 mV before leaching and may gradually increase as leaching progresses. Hereinafter, "oxidation-reduction potential (based on silver / silver chloride potential)" will be simply referred to as "oxidation-reduction potential." This oxidation-reduction potential may also be referred to as ORP.

[0040] In the first leaching stage, leaching is preferably terminated before the redox potential of the acidic leaching solution becomes equal to or higher than 0 mV, more preferably before it becomes higher than −300 mV. This is because if the redox potential becomes high, the copper ion concentration may increase to a certain extent, and copper ions may be contained in the leaching solution.

[0041] On the other hand, in the second leaching stage, it is preferable to terminate leaching after the redox potential of the acidic leachate reaches 0 mV or higher. This allows most of the cobalt and nickel to be leached, thereby suppressing loss of cobalt and nickel. However, in the second leaching stage, it is preferable to terminate leaching before the redox potential of the acidic leachate reaches 60 mV or higher in order to prevent excessive copper leaching.

[0042] Furthermore, in the first and second leaching stages, the rate of increase in the redox potential of the acidic leachate tends to accelerate once metal leaching has progressed to a certain extent. In the first leaching stage, in order to suppress copper leaching, it is preferable to terminate the leaching before the hourly increase in the redox potential of the acidic leachate reaches 233 mV or more. On the other hand, in the second leaching stage, from the viewpoint of leaching as much cobalt and nickel as possible, it is preferable to terminate the leaching after the hourly increase in the redox potential of the acidic leachate reaches 233 mV or more. Here, the hourly increase in redox potential refers to the value obtained by subtracting the redox potential value one hour prior to a given time from the redox potential value at that time.

[0043] In the first leaching stage or the second leaching stage, leaching can be considered to be completed, for example, when the stirring by the stirrer that was performed during leaching is stopped and the next operation, such as solid-liquid separation or the addition of new battery powder, is started. Solid-liquid separation for removing the leaching residue from the post-leaching solution can be performed using known devices and methods such as a filter press or a thickener.

[0044] The multiple leaching stages may include not only a first leaching stage and a second leaching stage, but also three or more leaching stages. For example, the first leaching stage and / or the second leaching stage may be divided into multiple stages. In this case, each of the multiple first leaching stages may be terminated while the copper ion concentration in the acidic leachate is lower than the copper ion concentration in the post-leaching solution obtained in the second leaching stage. For example, each of the multiple first leaching stages may be terminated while the copper ion concentration in the acidic leachate is 0.01 g / L or less. Furthermore, each of the multiple second leaching stages may be terminated after the copper ion concentration in the acidic leachate is higher than the copper ion concentration in the post-leaching solution obtained in the first leaching stage. For example, each of the multiple second leaching stages may be terminated after the copper ion concentration in the acidic leachate is higher than the copper ion concentration in the post-leaching solution obtained in the first leaching stage.

[0045] When the first leaching stage and the second leaching stage are repeated multiple times as described above, it is desirable to minimize the loss of cobalt and nickel if cobalt or nickel transfers to the leaching residue of the second leaching stage. Specifically, when the battery powder contains cobalt, it is preferable that, when the sum or total of the cobalt content of the battery powder subjected to the first leaching stage in a given leaching run and the cobalt ion content of the acidic leaching solution used in the first leaching stage in that run is taken as 100%, the sum of the cobalt ion content of the post-leaching solution obtained in the first leaching stage and the post-leaching solution obtained in the second leaching stage in each run is 95% or more, on a mass basis. Furthermore, when the battery powder contains nickel, the sum of the nickel ion content in the post-leaching solution obtained in the first leaching step and the nickel ion content in the post-leaching solution obtained in the second leaching step is preferably 95% or more in each leaching step, where the sum or total of the nickel content of the battery powder subjected to the first leaching step in a given cycle and the nickel ion content of the acid leaching solution used in the first leaching step in that cycle is 100% by mass. Here, in the first leaching step, the cobalt ion content and nickel ion content of the acid leaching solution used in the first leaching step are both zero. In the second and subsequent leaching steps, the cobalt ion content and nickel ion content of the acid leaching solution used in the first leaching step refer to the cobalt ion content and nickel ion content of the post-leaching solution obtained in the previous second leaching step and used as the acid leaching solution in the first leaching step.

[0046] The post-separation liquid obtained by separation from the metal-containing solution after the metal separation step described below may contain trace amounts of residual cobalt ions and / or nickel ions, metal ions such as lithium ions and copper ions, and inorganic acid anions. In this embodiment, in order to effectively recover, utilize, or remove such metal ions and inorganic acid anions in the post-separation liquid, at least a portion of the post-separation liquid is mixed with an acidic leaching liquid in the acid leaching step.

[0047] According to this, if the post-separation solution contains cobalt ions and / or nickel ions, the cobalt ions and / or nickel ions in the post-separation solution mixed with the acid leaching solution are transferred to the metal-containing solution after the acid leaching process and can be effectively recovered thereafter. If the post-separation solution contains copper ions, the copper ions in the post-separation solution mixed with the acid leaching solution are precipitated as described above in the acid leaching process and are then incorporated into the leaching residue and removed. If the post-separation solution contains lithium ions and is mixed with the acid leaching solution in the acid leaching process, the lithium ions are incorporated into the metal-containing solution after the acid leaching process, contributing to an increase in the lithium ion concentration throughout the entire wet treatment process (from the acid leaching process to the hydroxide process). Furthermore, the anions of the inorganic acid in the post-separation solution are effectively utilized as part of the acid used to leach the metals in the battery powder in the acid leaching process. That is, by using at least a part of the post-separation liquid in the acid leaching step, metal ions and inorganic acid anions to be recovered, removed or utilized in the post-separation liquid are appropriately treated.

[0048] Specific examples of post-separation solutions include, as shown in FIG. 1 , a lithium-containing solution (post-nickel extraction solution) obtained after nickel ion extraction in nickel extraction, a post-scrubbing solution obtained by scrubbing after manganese ion extraction in manganese extraction, and an acidic solution obtained together with a lithium hydroxide solution in electrodialysis in the hydroxide step. The lithium-containing solution mainly contains lithium ions. The post-scrubbing solution may contain copper ions that were eluted in trace amounts in the metal-containing solution in the acid leaching step and that can be separated from the solvent by scrubbing after being extracted together with manganese ions in manganese extraction. The acidic solution obtained by electrodialysis in the hydroxide step may contain trace amounts of lithium ions. To recover, remove, or utilize such metal ions, the post-separation solution to be mixed with the acidic leachate in the acid leaching step may contain at least one of the lithium-containing solution, the post-scrubbing solution, and the acidic solution. Furthermore, since the lithium-containing solution, post-scrubbing solution, and acidic solution contain inorganic acid anions such as sulfate ions, mixing them with the acidic leaching solution in the acid leaching step may reduce the amount of acid used in the acid leaching step. In particular, since the acidic solution obtained by electrodialysis in the hydroxide step contains many inorganic acid anions, reducing the amount of acid used is highly effective. However, the post-separation solution is not limited to these, and may be any solution containing some metal ions or inorganic acid anions.

[0049] At least a portion of the post-separation liquid may be mixed with the acid leaching liquid used in the second leaching stage of the first and second leaching stages of the acid leaching process, but it is preferable to mix it with the acid leaching liquid used in the first leaching stage. Typically, the amount of leaching residue supplied to the second leaching stage is smaller than the amount of battery powder supplied to the first leaching stage. In this case, if the post-separation liquid is mixed with the acid leaching liquid of the second leaching stage, the pulp concentration in the second leaching stage will decrease, and it may be difficult to maintain a balance in the liquid volume and other leaching conditions with the post-separation liquid to be sent to the next first leaching stage.

[0050] The metal-containing solution obtained in the acid leaching step may have, for example, 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, and a copper ion concentration of 0.005 g / L to 0.2 g / L. The metal-containing solution may contain at least one of nickel ions and cobalt ions, but may not contain the other.

[0051] (Metal Separation Step) When the post-leaching solution obtained in the acid leaching step contains aluminum ions and / or iron ions, the metal-containing solution obtained in the acid leaching step may be neutralized first in the metal separation step, although neutralization may be omitted.

[0052] In the neutralization, the pH of the metal-containing solution is increased, and the neutralization residue is separated to obtain a neutralized solution. The neutralization 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. If the metal-containing solution contains iron ions, the neutralization preferably also includes a de-ironization step after the dealumination step to remove the iron ions. 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 solution such as a de-ironization solution.

[0053] When removing aluminum ions in the dealumination step, the pH of the metal-containing solution can be increased to a range of 2.5 to 5.0, typically 3.0 to 4.5, by adding a pH adjuster. Furthermore, during the dealumination step, the redox potential may be 50 mV to 400 mV (250 mV to 350 mV at the end). This allows for effective separation of aluminum ions while suppressing the precipitation of nickel ions and / or cobalt ions. The temperature of the metal-containing solution can be set to 50°C to 90°C.

[0054] 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.

[0055] Next, 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 the oxidizing agent oxidizes the iron in the solution from divalent to trivalent, and the trivalent iron precipitates as an oxide or hydroxide at a lower pH than the divalent iron. In many cases, the iron precipitates as a solid such as iron hydroxide (Fe(OH)). The precipitated iron can be removed as a neutralization residue by solid-liquid separation.

[0056] To precipitate iron, the ORP value during oxidation is preferably 300 mV to 900 mV. After adding the oxidizing agent, an acid such as sulfuric acid, hydrochloric acid, or nitric acid can be added to lower the pH to, for example, less than 3. Thereafter, a pH adjuster can be added to adjust the pH to, for example, a range of 3.0 to 4.5, thereby precipitating iron.

[0057] 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 a positive electrode active material. The manganese-containing leaching residue obtained by leaching a 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 solution becomes manganese dioxide, and the precipitated manganese can be removed together with the iron.

[0058] Specific examples of alkaline pH adjusters used in neutralization include lithium hydroxide, sodium hydroxide, sodium carbonate, ammonia, etc. Among these, the lithium hydroxide solution 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.

[0059] The neutralized solution obtained after neutralization can be subjected to manganese extraction by solvent extraction to extract and remove manganese ions, and in some cases, residual aluminum ions as well. In this case, the residual manganese ions and aluminum ions are extracted, thereby obtaining a manganese-extracted solution from which they have been removed.

[0060] For manganese extraction, it is preferable to use an extractant containing a phosphate ester extractant. Examples of phosphate ester extractants include di-2-ethylhexyl phosphoric acid (abbreviated as D2EHPA or product name: DP-8R). The extractant may also be a mixture of a phosphate ester extractant and an oxime extractant. In this case, the oxime extractant is preferably an aldoxime or one containing aldoxime as the main component. Specific 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).

[0061] During extraction, the equilibrium pH is preferably adjusted to 2.3 to 3.5, more preferably 2.5 to 3.0. The alkaline or other pH adjuster used here is preferably the lithium hydroxide solution obtained in the hydroxide step described below, but separately prepared sodium hydroxide or the like may also be used. When the lithium hydroxide solution obtained in the hydroxide step is used as the pH adjuster, it is possible to prevent the sodium from remaining in the lithium-containing solution after nickel extraction described below, as well as to prevent the sodium from being mixed in as an impurity into the lithium hydroxide solution produced from the lithium-containing solution, as occurs when sodium hydroxide is used as the pH adjuster.

[0062] During extraction, it is desirable to perform extraction by countercurrent multistage extraction, in which the aqueous phase and solvent used in each extraction flow in opposite directions. This can suppress the extraction of cobalt ions, nickel ions, and lithium ions, and increase the extraction rate of manganese ions. When using countercurrent multistage extraction, it is effective to set the equilibrium pH during the first extraction stage within the above-mentioned range and then lower the equilibrium pH during each subsequent extraction stage.

[0063] Since the solvent used to extract manganese ions may contain cobalt ions, nickel ions, and lithium ions, it can be subjected to stripping after scrubbing. For example, the scrubbing solution can be a sulfuric acid solution with a pH of 2.0 to 3.0, and the stripping solution can be a sulfuric acid solution with a pH of 0.0 to 1.0. It is desirable to use the post-scrubbing solution or the post-stripping solution for manganese extraction (for example, by mixing the post-scrubbing solution with a metal-containing solution and using the resulting mixture as a pre-extraction solution for extracting manganese ions, or by using the post-stripping solution for scrubbing the solvent used to extract manganese ions, or by using the post-scrubbing solution as a stripping solution for the solvent used to extract manganese ions). This allows the cobalt ions, nickel ions, and lithium ions to be circulated or retained within the process and concentrated without loss. However, if the solvent used to extract manganese ions does not contain cobalt ions, nickel ions, or lithium ions, scrubbing or stripping may not be necessary.

[0064] As mentioned above, the post-scrubbing solution obtained by scrubbing the solvent that extracted the manganese ions may contain trace amounts of copper ions. In order to remove such copper ions, at least a portion of the post-scrubbing solution can be included in the post-separation solution and mixed with the acidic leaching solution in the acid leaching step.

[0065] Next, cobalt extraction can be carried out. In cobalt extraction, cobalt ions are separated by solvent extraction from the manganese extraction solution obtained after manganese extraction. In cobalt extraction, it is preferable to use a solvent containing a phosphonate ester extractant. Among them, 2-ethylhexyl 2-ethylhexyl phosphonate (trade names: PC-88A, Ionquest 801) is particularly suitable from the viewpoint of the 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.

[0066] When cobalt ions are extracted, the equilibrium pH during extraction can be preferably adjusted to 5.0 to 6.0, more preferably 5.0 to 5.5. In this case, it is preferable to use a lithium hydroxide solution obtained in the hydroxide oxidation step described below as a pH adjuster, but separately prepared sodium hydroxide or the like may also be used. If the pH is lower than 5.0, there is a risk that the cobalt ions may not be sufficiently extracted into the solvent. This allows the cobalt ions in the post-manganese extraction solution to be extracted into the solvent.

[0067] It is also desirable to perform the extraction of cobalt ions by countercurrent multistage extraction, in which the aqueous phase and the solvent flow in opposite directions in each extraction. This can increase the extraction rate of cobalt ions while suppressing the extraction of nickel ions and lithium ions.

[0068] During the extraction, not only cobalt ions but also small amounts of nickel ions and lithium ions, which become impurities during cobalt extraction, may be extracted into the solvent. In this case, if necessary, the solvent from which cobalt ions have been extracted may be subjected to one or more scrubbing steps using a scrubbing solution to remove impurities such as nickel ions that may be present in the solvent. The scrubbing solution may be, for example, a sulfuric acid solution with a pH of 3.5 to 5.5. The post-scrubbing solution may contain nickel ions and lithium ions. Therefore, it is desirable to use a portion or all of the post-scrubbing solution for cobalt extraction (i.e., mix a portion or all of the post-scrubbing solution with a manganese extraction solution and use this as a pre-extraction solution for cobalt extraction). This allows nickel ions and lithium ions to be circulated or retained within the process and concentrated without loss. However, if the solvent from which cobalt ions have been extracted does not contain nickel ions or lithium ions, scrubbing may not be necessary.

[0069] The solvent from which the cobalt ions have been extracted is then subjected to stripping. The stripping solution used for stripping may be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, but sulfuric acid is preferred when obtaining sulfate by crystallization, as described below. Here, the stripping is carried out 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 even 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 10°C to 50°C.

[0070] The strip-extracted solution, such as a cobalt sulfate solution obtained by strip-extraction of cobalt ions, can be crystallized. In this process, the strip-extracted solution is concentrated by heating, for example, to 40°C to 120°C, thereby crystallizing the cobalt ions as a cobalt salt. The cobalt salt thus produced preferably has a nickel content of 5 mass ppm or less, and since nickel has been sufficiently removed, it can be effectively used as a raw material for the production of lithium-ion secondary batteries and other batteries. The crystallized solution may contain uncrystallized cobalt ions and lithium ions. Therefore, it is desirable to mix the crystallized solution with the strip-extracted solution before crystallization and use it again for crystallization, to adjust the cobalt ion concentration of the scrubbing solution used as a solvent after cobalt ion extraction, or to use it for cobalt extraction. By repeatedly using the crystallized solution within the process in this way, the cobalt ions and lithium ions can be circulated or retained within the process and concentrated without loss.

[0071] Thereafter, nickel extraction can be carried out on the cobalt-extracted solution after the cobalt ions have been extracted. In nickel extraction, a carboxylic acid extractant is preferably used to separate nickel ions from the cobalt-extracted solution. Examples of carboxylic acid extractants include neodecanoic acid and naphthenic acid, with neodecanoic acid being 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.

[0072] When extracting nickel ions, the equilibrium pH is preferably set to 6.0 to 8.0, more preferably 6.8 to 7.2. 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 solution obtained in the hydroxide oxidation step described below. Similarly to the cobalt extraction described above, it is desirable to perform nickel extraction using a countercurrent multistage extraction method. This suppresses the extraction of lithium ions, thereby increasing the extraction rate of nickel ions.

[0073] The solvent from which nickel ions have been extracted may be subjected to one or more scrubbing steps using a scrubbing solution, as needed, to remove impurities such as lithium ions and sodium ions that may be present in the solvent. The scrubbing solution may be, for example, a sulfuric acid solution with a pH of 5.0 to 6.0. The post-scrubbing solution may contain lithium ions. Therefore, it is desirable to use a portion or all of the post-scrubbing solution for nickel extraction (i.e., to mix a portion or all of the post-scrubbing solution with a post-cobalt extraction solution and use this as a pre-extraction solution for nickel extraction). This allows lithium ions to be circulated or retained within the process and concentrated without loss. However, if the solvent from which nickel ions have been extracted does not contain lithium ions, scrubbing may not be necessary.

[0074] The solvent from which nickel ions have been extracted is then back-extracted using a back-extraction solution such as sulfuric acid, hydrochloric acid, or nitric acid. If crystallization is to be performed afterwards, sulfuric acid is preferred. 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 number of times can be determined as appropriate, but the O / A ratio is preferably 5 to 1, more preferably 4 to 2.

[0075] When a stripping solution such as a nickel sulfate solution is obtained by stripping, it can be electrolyzed and dissolved as needed, and then heated to 40°C to 120°C to crystallize the nickel ions as nickel salts such as nickel sulfate. This process yields nickel salts. The crystallized solution may contain uncrystallized nickel ions and lithium ions. Therefore, it is desirable to mix the crystallized solution with the stripping solution before crystallization and use it for further crystallization, to adjust the nickel ion concentration in the scrubbing solution used as the solvent after nickel ion extraction, or to use it for nickel ion extraction. By repeatedly using the crystallized solution within the process in this way, nickel ions and lithium ions can be circulated or retained within the process and concentrated without loss.

[0076] As described above, at least a portion of the lithium-containing solution from which nickel ions have been extracted can be mixed with the acid leaching solution in the acid leaching step and used. This allows the lithium ions contained in the lithium-containing solution to be circulated through a series of steps including the acid leaching step, neutralization, and metal separation steps. Preferably, after the lithium ion concentration in the lithium-containing solution has increased to a certain extent by circulating the lithium ions in this way, the hydroxide step described below is carried out.

[0077] (Hydroxylation Step) The lithium-containing solution obtained after nickel extraction contains substantially only lithium ions as a result of the separation of manganese ions, cobalt ions, and nickel ions in the above-mentioned extractions. In the hydroxide step, a lithium hydroxide solution is prepared from the lithium-containing solution (lithium sulfate solution, etc.) by various methods described below.

[0078] For example, a lithium carbonate solution is first obtained by adding a carbonate or blowing carbon dioxide gas into a lithium sulfate solution. Then, as a so-called chemical conversion method, calcium hydroxide is added to the lithium carbonate solution to produce a lithium hydroxide solution according to the reaction formula Li2CO3 + Ca(OH)2 → 2LiOH + CaCO3. Calcium ions that may remain in the solution can be removed using a cation exchange resin, a chelating resin, or the like.

[0079] Alternatively, a lithium hydroxide solution can be obtained by adding barium hydroxide to a lithium sulfate solution and carrying out the reaction LiSO + Ba(OH) → 2LiOH + BaSO. Note that barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin, a chelating resin, or the like.

[0080] Alternatively, when a so-called electrolysis method is employed, a lithium sulfate solution is supplied to the anode side and electrolysis is performed in an electrolytic cell provided with a cation exchange membrane that separates the anode side from the cathode side, whereby a lithium hydroxide solution can be produced on the cathode side.

[0081] The lithium hydroxide solution thus obtained can be effectively used as a pH adjuster (neutralizing agent) in neutralization, as well as an alkaline pH adjuster in manganese extraction, cobalt extraction, and nickel extraction.

[0082] In the electrolysis method among the above-mentioned techniques, electrodialysis may be performed by supplying a lithium sulfate solution to a deionization compartment between an anion exchange membrane and a cation exchange membrane in a bipolar membrane electrodialysis apparatus. In this case, a lithium hydroxide solution may be obtained in the alkaline compartment between the cation exchange membrane and the bipolar membrane, while an acidic solution such as a sulfuric acid solution may be obtained in the acid compartment between the bipolar membrane and the anion exchange membrane. Such an acidic solution may be included in the post-separation liquid as described above and mixed with the acidic leaching solution in the acid leaching step.

[0083] The lithium-containing solution may contain trace amounts of cations, such as nickel ions and magnesium ions, that were not completely separated during the metal separation process. Nickel ions and magnesium ions, like lithium ions, are cations and behave similarly to lithium ions during electrodialysis, making them difficult to separate from lithium ions. Furthermore, electrodialysis of a lithium-containing solution containing nickel ions and magnesium ions can result in the generation of nickel and magnesium hydroxides in the resulting lithium hydroxide solution, potentially leading to process problems and the inability to continue the electrodialysis. Therefore, in such cases, it is desirable to perform washing to remove cations, such as nickel ions and magnesium ions, from the lithium-containing solution prior to electrodialysis. For example, an ion exchange resin or a chelating resin can be used for this washing. When the lithium-containing solution from which nickel ions have been extracted is mixed with the acidic leachate for use, the solution after washing can be used. This allows the magnesium ions to be removed before the lithium ions are circulated within the process. Alternatively, the solution before washing can be used. In this case, it is possible to effectively recover the nickel ions that were not completely separated during the metal separation process.

[0084] (Crystallization Step) After the hydroxide step, a crystallization step may be performed to precipitate lithium hydroxide from the lithium hydroxide solution. For example, when a series of steps including the acid leaching step and the metal separation step is repeated, the lithium ion concentration in a solution such as a lithium sulfate solution may gradually increase as new lithium ion battery waste is added to the series of steps. After the lithium ion concentration has increased to a certain extent, the crystallization step may be performed.

[0085] In the crystallization step, a crystallization procedure such as heat concentration or vacuum distillation can be performed to precipitate lithium hydroxide. In the case of heat concentration, a higher temperature during crystallization is preferable because the process proceeds more quickly. However, after crystallization, the crystallized product is preferably dried at a temperature of less than 60°C, at which water of crystallization does not detach. This is because, if water of crystallization detaches, anhydrous lithium hydroxide becomes deliquescent and becomes difficult to handle. The lithium hydroxide obtained in the crystallization step can be subjected to a pulverization process or the like to adjust the desired physical properties.

[0086] Next, tests were conducted to confirm the effectiveness of the above-described metal recovery method, which are described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0087] Example 1: Battery powder obtained by treating lithium-ion battery waste was subjected to the first and second leaching steps shown in Figure 3 three times to obtain a metal-containing solution. The changes in pH, ORP, and concentration in the solution during the first and second leaching steps were monitored for each leaching step. Specifically, the changes are as follows:

[0088] In the first first leaching stage and second leaching stage, a total of six elements, Ni, Co, Mn, Li, Al, and Fe, were selected as the metals to be leached. The molar equivalent of sulfuric acid required for leaching was calculated from the content of each metal in the battery powder calculated from the weight and grade, and 1.1 times this amount was set as the amount of sulfuric acid to be added as the acidic leaching solution.

[0089] In the first leaching stage, 80% of 1.1 molar equivalents of sulfuric acid was added over 120 minutes, and leaching was terminated 300 minutes after the end of the sulfuric acid addition (before copper was dissolved). The pulp concentration was adjusted so that the Ni concentration after leaching was 20 g / L. The liquid temperature was 70°C. In the second leaching stage, 20% of 1.1 molar equivalents of sulfuric acid was added over 30 minutes, and leaching was terminated 300 minutes after the end of the sulfuric acid addition (after copper was dissolved). The pulp concentration was adjusted so that the Ni concentration after leaching was 10 g / L. The liquid temperature was 70°C.

[0090] Figures 4 and 5 show the changes in pH, ORP, and metal concentrations over time from the end of sulfuric acid addition for the first and second leaching stages, respectively. Here, the metal concentrations were measured by analyzing the leached solution using an ICP atomic emission spectrometer. During the first leaching stage, as shown in Figure 4, the pH varied from 1.14 to 1.61, and the ORP varied from -283 mV to -340 mV. Furthermore, during the first leaching stage, the concentrations of Ni and Co increased to 15.6 g / L and 16.4 g / L, respectively, while Cu was 0 g / L (less than 0.01 g / L). During the second leaching stage, as shown in Figure 5, the pH varied from -0.15 to 0.02, and the ORP varied from -293 mV to 123 mV. In the second leaching stage, as shown in the figure, the concentrations of Ni, Co, and Cu increased to 10.3 g / L, 8.0 g / L, and 8.0 g / L, respectively. In the second leaching stage, the increase in the oxidation-reduction potential of the acidic leaching solution per hour was 303 mV at its highest point (the point where the slope of the graph is steepest).

[0091] The second leaching run was conducted in a manner substantially similar to the first leaching run, except that the post-leaching solution obtained in the first second leaching stage was used as the acidic leaching solution in the first leaching stage, and the sulfuric acid addition ratio was changed accordingly. However, in the second leaching stage, leaching was terminated 180 minutes after the end of sulfuric acid addition (after copper had dissolved). The sulfuric acid addition ratio in the first leaching stage was 80% relative to 1.1 molar equivalents of sulfuric acid, and the amount of newly added sulfuric acid was calculated using the formula: (newly added amount, mol) = (1.1 equivalents) × 80 (%) - (amount of sulfuric acid in the post-leaching solution in the second leaching stage) - (amount of Cu in the post-leaching solution in the second leaching stage). In the second leaching stage, all newly added sulfuric acid was added in an amount of 20% relative to 1.1 molar equivalents of sulfuric acid.

[0092] Figures 6 and 7 show the changes in pH, ORP, and metal concentrations over time from the end of sulfuric acid addition for the first and second leaching stages of the second run. As shown in Figure 6, during the first leaching stage, the pH ranged from 1.27 to 1.7, and the ORP ranged from -250 mV to -336 mV. Also, as shown in Figure 6, the concentrations of Ni and Co in the leaching solution rose to 15.3 g / L and 16.2 g / L, respectively, while Cu was 0 g / L (less than 0.01 g / L). In the second run, the post-leaching solution obtained in the second leaching stage of the first run was used as the acidic leaching solution for the first leaching stage. Despite this, the Cu concentration remained at 0 g / L at the end of sulfuric acid addition. This indicates that the copper ions contained in the acidic leaching solution were reduced by a substitution reaction with a metal less noble than copper in the new battery powder added in the second run. During the second leaching stage, as shown in Figure 7, the pH during the reaction ranged from 0.17 to 0.21, and the ORP ranged from -312 mV to 34 mV. Furthermore, as shown in the figure, the concentrations of Ni, Co, and Cu in the leaching solution increased to 8.8 g / L, 7.6 g / L, and 0.38 g / L, respectively. During the second leaching stage, the maximum increase in the oxidation-reduction potential of the acidic leaching solution per hour was 306 mV.

[0093] In the third run, the post-leaching solution obtained in the second leaching stage of the previous run (the second run) was used as the acidic leaching solution in the first leaching stage, as in the second run. The proportion of sulfuric acid added was also the same as in the second run.

[0094] Figures 8 and 9 show the changes in pH, ORP, and metal concentrations over time from the end of sulfuric acid addition for the first and second leaching stages of the third run. As shown in Figure 8, during the first leaching stage, the pH ranged from 1.22 to 1.73, and the ORP ranged from -327 mV to -369 mV. Also, as shown in Figure 8, during the first leaching stage, the concentrations of Ni and Co in the leaching solution increased to 15.1 g / L and 15.6 g / L, respectively, while Cu was 0 g / L (less than 0.01 g / L). Similarly to the second leaching run, the concentration of Cu in the third leaching run was 0 g / L at the end of sulfuric acid addition. This indicates that the copper ions contained in the acidic leaching solution were reduced by a substitution reaction with a metal less noble than copper in the new battery powder added in the third run. As shown in Figure 9, during the second leaching stage, the pH varied between 0.27 and 0.46, and the ORP varied between -246 mV and 72 mV. Furthermore, as shown in the figure, the concentrations of Ni, Co, and Cu in the leaching solution increased to 8.0 g / L, 7.1 g / L, and 1.8 g / L, respectively. During the second leaching stage, the maximum increase in the oxidation-reduction potential of the acidic leaching solution per hour was 233 mV.

[0095] (Example 2) When metals in battery powder obtained by treating lithium ion battery waste were leached by repeating the first leaching stage and the second leaching stage as shown in Figure 3, it was confirmed to what extent each metal was distributed in the leaching solution and leaching residue.

[0096] Here, the battery powder was subjected to five cycles of the first and second leaching stages shown in Figure 3. In each run, 80% of the sulfuric acid (1.1 molar equivalents) was added over 120 minutes. The leaching was terminated 300 minutes after the end of the sulfuric acid addition (before copper dissolved). The pulp concentration was adjusted to a Ni concentration of 20 g / L after leaching. The solution temperature was 70°C. From the second run onward, the entire leaching solution from the previous second leaching stage was used as the acidic leaching solution for the first leaching stage. The sulfuric acid addition ratio was 80% relative to the 1.1 molar equivalents of sulfuric acid. The amount of newly added sulfuric acid was calculated using the formula: (newly added amount, mol) = (1.1 equivalents) × 80 (%) - (amount of sulfuric acid in the leaching solution from the second leaching stage) - (amount of Cu in the leaching solution from the second leaching stage). In the second leaching stage, 20% of 1.1 molar equivalents of sulfuric acid was added over 30 minutes, and the leaching was completed when the ORP was in the range of 0 mV to 100 mV. The ORP at the end was 123 mV. The pulp concentration was adjusted so that the Ni concentration after leaching was 10 g / L. The liquid temperature was 70°C.

[0097] Table 1 shows the distribution rates of Co, Ni, Mn, Li, and Cu to the post-leaching solution (liquid) and leaching residue (residue) in the first leaching stage (first stage of leaching) and the second leaching stage (second stage of leaching) for each leaching run, the total input and output amounts, the ratios thereof, and the reaction termination conditions. The distribution rates in Table 1 are shown by mass, with the content of each metal in the battery powder added in the first leaching run being set to 100%. Table 2 also shows the sum of the distribution rates of each metal in the first to fifth leaching runs. The distribution rates in Table 2 are shown by mass, with the content of each metal contained in the total amount of battery powder added in the first to fifth leaching runs (total amount added) being set to 100%. Furthermore, "Liquid: First-Stage Leaching" refers to the content of each metal contained in the total amount of post-leaching solution obtained in the first leaching stage (first stage leaching) from the first to fifth leaching runs. "Liquid: Second-Stage Leaching" refers to the content of each metal contained in the post-leaching solution obtained in the second leaching stage (second stage leaching) from the fifth leaching run. Furthermore, "Residue: Second-Stage Leaching" refers to the content of each metal contained in the total amount of residue obtained in the second leaching stage (second stage leaching) from the first to fifth leaching runs. Furthermore, Table 3 shows the amount of Cu contained in the acidic leaching solution obtained in the second leaching stage (previous cycle second-stage leaching filtrate) from the previous cycle, which was used in the second to fifth leaching runs. It also shows the amount of Cu contained in the battery powder newly added in the second to fifth leaching runs, the amount of Cu contained in the battery powder, which is less noble than Cu, and the amount of Cu (in terms of Cu amount) capable of undergoing a reduction-substitution reaction with all of these metals.

[0098]

[0099]

[0100]

[0101] Table 2 shows that 99.3% of Co was transferred to the post-leaching solution (97.5% in the first stage of leaching + 1.8% in the second stage of leaching) and 0.7% to the leaching residue, while 96.8% of Ni was transferred to the post-leaching solution (94.6% in the first stage of leaching + 2.2% in the second stage of leaching) and 3.2% to the leaching residue. Meanwhile, the distribution rate of Cu to the post-leaching solution in the first leaching stage was 0.0%. These results suggest that cobalt and / or nickel were leached at a high leaching rate while effectively suppressing Cu contamination in the final post-leaching solution.

[0102] Furthermore, as can be seen from Table 1, for both Co and Ni, the ratio (Output / Input) of the sum (Output) of the contents in the post-leaching solution obtained in the first leaching stage and the post-leaching solution obtained in the second leaching stage to the sum (Input) of the contents in the newly added battery powder and the post-leaching solution used as the acidic leaching solution (the post-leaching solution obtained in the previous leaching stage) was 95% or more.

[0103] Furthermore, in the second leaching stage of each run, the copper ion content of the acidic leachate during leaching was 16.6% by mass or less when the ORP was 57 mV (60 mV or less), but increased to a high value of 42.8% by mass when the ORP was 97 mV (more than 60 mV). This indicates that in the second leaching stage, it is preferable to terminate leaching before the oxidation-reduction potential of the acidic leachate becomes higher than 60 mV in order to prevent excessive copper leaching.

[0104] In each leaching step, the leached solution obtained in the second leaching stage also contains Mn and Li, although in trace amounts compared to Co and Ni. Therefore, it can be said that manganese and lithium are leached at high leaching rates while effectively suppressing Cu contamination in the final leaching solution.

[0105] Furthermore, as can be seen from Table 3, the amount of metals more noble than Cu contained in the battery powder newly added in each leaching step is greater than the amount of noble metals required to undergo a substitution reaction with all of the Cu ions in the post-leaching solution obtained in the previous second leaching step. This indicates that, in theory, all of the Cu ions in the post-leaching solution can be effectively reduced by the noble metals in the battery powder in each first leaching step.

[0106] Comparative Example: Metals in battery powder were leached in a single leaching step, as shown in Fig. 10. Here, a total of six elements, Ni, Co, Mn, Li, Al, and Fe, were selected as the target metals to be leached. The molar equivalent of sulfuric acid required for leaching was calculated from the content of each metal in the battery powder calculated from its weight and grade, and 1.1 times this amount was used as the amount of sulfuric acid to be added as the acidic leaching solution.

[0107] The test conditions were as follows: the total amount of sulfuric acid was added over 120 minutes, and the leaching was completed 320 minutes after the end of the sulfuric acid addition. The pulp concentration was adjusted so that the Ni concentration after leaching was 20 g / L. The reaction was completed when the ORP reached 0 mV. The liquid temperature was 70°C.

[0108] Figure 11 shows the changes in pH, ORP, and each metal concentration over time. Table 4 shows the distribution rates of Co, Ni, Mn, Li, and Cu to the post-leaching solution (liquid) and leaching residue (residue). The distribution rates in Table 4 are shown by mass, with the content of each metal in the battery powder added being 100%.

[0109]

[0110] Table 4 shows that 99.3% of Co was transferred to the post-leaching solution and 0.7% to the leaching residue, and 96.6% of Ni was transferred to the post-leaching solution and 3.4% to the leaching residue. On the other hand, 16.4% of Cu was transferred to the post-leaching solution and 83.6% to the leaching residue. This indicates that the post-leaching solution contained a large amount of copper.

[0111] From the above, it has been found that the acid leaching step of the metal recovery method described above can sufficiently leach cobalt and / or nickel while easily removing copper. It has also been found that, in such an acid leaching step, by mixing at least a portion of an acidic or neutral post-separation solution containing at least one ion selected from the group consisting of cobalt ions, nickel ions, lithium ions, copper ions, and inorganic acid anions with an acidic leach solution, the metal ions and inorganic acid anions can be effectively recovered, utilized, or removed.

Claims

1. A method for recovering metals from battery powder that is a lithium-ion battery waste and contains at least copper, lithium, and cobalt and / or nickel, the method comprising: an acid leaching step of leaching the metals in the battery powder into an acid leaching solution to obtain a metal-containing solution containing at least lithium ions, cobalt ions and / or nickel ions; and a metal separation step of separating at least cobalt ions and / or nickel ions from the metal-containing solution, the acid leaching step comprising repeating a plurality of leaching steps a plurality of times, the plurality of leaching steps including a first leaching step of leaching the metals in the battery powder into an acid leaching solution, terminating the leaching before copper is eluted, and separating the leaching residue to obtain a leaching solution, and a second leaching step of leaching the metals in the leaching residue into the acid leaching solution, terminating the leaching after copper is eluted, to obtain a leaching solution, a post-leaching solution obtained in the first leaching step is used as the metal-containing solution, and a post-leaching solution obtained in a final leaching step of the multiple leaching steps is used as an acidic leaching solution in a subsequent first leaching step; an acidic or neutral post-separation solution containing at least one ion selected from the group consisting of cobalt ions, nickel ions, lithium ions, copper ions and anions of inorganic acids is obtained after the metal separation step, and at least a portion of the post-separation solution is mixed with the acidic leaching solution and used in the acid leaching step.

2. The metal recovery method according to claim 1, wherein the post-separation liquid contains cobalt ions and / or nickel ions.

3. The method for recovering metals according to claim 1 or 2, wherein the metal separation step comprises extraction of nickel ions from the metal-containing solution into a solvent, and the post-separation liquid comprises a lithium-containing solution obtained after extraction of the nickel ions.

4. A method for recovering metals according to claim 1 or 2, wherein at least a portion of the post-separation liquid is mixed with the acid leaching liquid used in the first leaching stage of the acid leaching process.

5. A metal recovery method according to claim 1 or 2, wherein the post-separation liquid contains copper ions.

6. The metal recovery method according to claim 5, wherein the battery powder contains manganese and the metal-containing solution contains manganese ions, the metal separation step comprises extracting manganese ions from the metal-containing solution into a solvent and scrubbing the solvent from which the manganese ions have been extracted, a post-scrubbing liquid obtained after the scrubbing contains copper ions, and the post-separation liquid comprises the post-scrubbing liquid.

7. The metal recovery method according to claim 1 or 2, wherein the post-separation liquid contains lithium ions.

8. The metal recovery method according to claim 1 or 2, further comprising a hydroxide step of obtaining a lithium hydroxide solution and an acidic solution by electrodialysis from the lithium-containing solution obtained after the metal separation step, wherein the separated liquid contains the acidic solution.

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