Method for recovering metal

Abstract

A method for recovering metal from battery powder of lithium ion battery waste, the powder containing at least copper, aluminum, cobalt and / or nickel, the method comprising: an acid leaching step for leaching metal in the battery powder into an acidic leaching solution to obtain a metal-containing solution comprising at least aluminum ions, cobalt ions, and / or nickel ions; and a neutralization step for raising the pH of the metal-containing solution, and precipitating and removing the aluminum. In the acid leaching step, a plurality of leaching stages are repeated a plurality of times. The plurality of leaching stages comprises: a first leaching stage in which metal in the battery powder is leached into an acidic leaching solution, the leaching is completed before the elution of copper, the leaching residue is separated, and a post-leaching solution is obtained; and a second leaching stage in which the metal in the leaching residue is leached into an acidic leaching solution, the leaching is completed after the elution of copper, and a post-leaching solution is obtained. The post-leaching solution obtained in the first leaching stage is used as the metal-containing solution, and the post-leaching solution obtained in the final leaching stage among the plurality of leaching stages is used as the acidic leaching solution in the next first leaching stage. In the acid leaching step, a phosphate ion source and / or a calcium ion source is included in the acidic leaching solution to precipitate aluminum.

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, the metals are separated 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 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] The aluminum in the battery powder is leached by acid and exists as aluminum ions in the metal-containing solution. The aluminum ions in the metal-containing solution can be removed by precipitation through neutralization. However, if the aluminum ion concentration in the metal-containing solution is high, cobalt and nickel ions will also precipitate if neutralization is performed under conditions that precipitate many aluminum ions, resulting in losses of cobalt and nickel. Therefore, it is desirable to suppress the leaching of aluminum during acid leaching.

[0009] This specification provides a metal recovery method that can effectively leach cobalt and / or nickel while suppressing copper leaching during acid leaching, and can also suppress the aluminum leaching rate.

[0010] The metal recovery method disclosed in this specification is a method for recovering metals from battery powder containing at least copper, aluminum, cobalt, and / or nickel, which is a lithium-ion battery waste, and includes an acid leaching step of leaching the metals in the battery powder in an acidic leaching solution to obtain a metal-containing solution containing at least aluminum ions and cobalt ions and / or nickel ions, and a neutralization step of increasing the pH of the metal-containing solution to precipitate and remove aluminum ions, and in the acid leaching step, multiple leaching steps are repeated multiple times to recover the metals in the battery powder. in an acidic leach solution, leaching is terminated before copper is eluted, and the leach residue is separated to obtain a post-leach solution; and a second leach step is performed in which metals in the leach residue are leached in an acidic leach solution, leaching is terminated after copper is eluted, and a post-leach solution is obtained. The post-leach solution obtained in the first leach step is used as the metal-containing solution, and the post-leach solution obtained in the final leach step of the multiple leach steps is used as the acidic leach solution in the next first leach step. In the acid leaching step, the acidic leach solution is made to contain a phosphate ion source and / or a calcium ion source, and aluminum is precipitated.

[0011] According to the above-described metal recovery method, during acid leaching, cobalt and / or nickel can be effectively leached while suppressing copper leaching, and the leaching rate of aluminum can be suppressed.

[0012] 1 is a flow chart showing a metal recovery method according to one embodiment of the present invention, FIG. 2 is a flow chart showing an example of a pretreatment process for obtaining battery powder from lithium ion battery waste, and FIG. 3 is a flow chart showing details of an acid leaching process included in the metal recovery method of FIG.

[0013] The following describes in detail an embodiment of the metal recovery method described above. 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, aluminum, cobalt, and / or nickel. This metal recovery method includes an acid leaching step and a neutralization 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 aluminum 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. A second leaching stage in which the metals in the leach residue are leached in the 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 neutralization 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 and sufficiently leaches cobalt and / or nickel, resulting in a metal-containing solution that contains cobalt and / or nickel ions but is almost free of copper ions.

[0015] In the acid leaching step, the acidic leachate contains a phosphate ion source and / or a calcium ion source. In this case, the phosphate ion source and / or the calcium ion source form a compound with aluminum ions, thereby precipitating aluminum. This reduces the leaching rate of aluminum during acid leaching. This lowers the aluminum ion concentration in the metal-containing solution to a certain extent, allowing most of the aluminum to precipitate and be removed in the neutralization step without significantly increasing the pH of the metal-containing solution. As a result, the loss of cobalt and nickel during the neutralization step can be effectively suppressed.

[0016] Furthermore, in the first leaching stage where a metal-containing solution is obtained, the leaching is terminated before copper is eluted, so the metal-containing solution tends to have a relatively low oxidation-reduction potential. Since such a metal-containing solution is subjected to the neutralization step, it is thought that, in combination with the action of the phosphate ion source and / or calcium ion source, aluminum can be effectively removed in the neutralization step even at a relatively low pH.

[0017] 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 neutralization step, a manganese extraction step, a cobalt extraction step, a nickel extraction 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 made 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.

[0018] (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.

[0019] 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.

[0020] (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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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. The battery powder may also contain 0.1% by mass to 10% by mass of fluorine.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] (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 have 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 neutralization process, is referred to as the metal-containing solution. The solution in the middle of the processes after the neutralization process may also be referred to as the metal-containing solution.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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).

[0039] 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.

[0040] 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.

[0041] 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 an increase in the redox potential may increase the copper ion concentration to a certain extent, which may result in copper ions being contained in the leaching solution.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In at least one of the multiple leaching stages in the acid leaching process, the acid leaching solution contains a phosphate ion source and / or a calcium ion source. The phosphate ion source and / or the calcium ion source may be contained in the battery powder, but if this is not sufficient, the phosphate ion source and / or the calcium ion source may be added to the acid leaching solution separately from the battery powder.

[0048] The timing of adding the phosphate ion source and / or calcium ion source is not particularly limited as long as it is before the end of leaching in the leaching step (or after the end of leaching but before solid-liquid separation, if solid-liquid separation is performed). The phosphate ion source and / or calcium ion source may be added to the acidic leachate together with the battery powder, or may be added to the acidic leachate before or after contacting the battery powder with the acidic leachate. The phosphate ion source and / or calcium ion source may also be added after the start of leaching in the leaching step. Furthermore, for example, when battery powder is mixed with water such as distilled water to form a slurry and then an acid such as sulfuric acid is added to the slurry to prepare the acidic leachate, the phosphate ion source and / or calcium ion source may be added to the slurry before the acid is added, or the phosphate ion source and / or calcium ion source may be added to the slurry together with the acid. When the lithium ion battery waste and the battery powder obtained by subjecting the lithium ion battery waste to a pretreatment process contain a phosphate ion source and / or a calcium ion source, the battery powder comes into contact with the acidic leachate, causing the acidic leachate to contain a phosphate ion source and / or a calcium ion source.

[0049] As a source of phosphate ions and calcium ions, phosphate ions (PO4 3- ) and calcium ions (Ca 2+ Various sources can be used as long as they produce a phosphate ion source. Specific examples of phosphate ion sources include phosphoric acid (H3PO4), calcium phosphate (e.g., Ca3(PO4)2), calcium hydrogen phosphate (CaHPO4), trisodium phosphate (Na3PO4), disodium hydrogen phosphate (Na2HPO4), sodium dihydrogen phosphate (NaH2PO4), and lithium phosphate (Li3PO4). Calcium phosphate and calcium hydrogen phosphate are preferred because they function as both phosphate ion sources and calcium ion sources. Examples of calcium ion sources include calcium sulfate (CaSO4), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), other calcium compounds, and elemental calcium. Of these, calcium sulfate is preferred because it does not increase the pH of the acidic leachate, as occurs when calcium carbonate or calcium hydroxide is used.

[0050] If the acidic leachate contains a source of phosphate ions, aluminum may precipitate by forming compounds such as aluminum orthophosphate (AlPO4), and if the acidic leachate contains a source of calcium ions, aluminum may precipitate as compounds such as LiCa(AlF6), Ca3Al2F8(OH)2(SO4).2H2O, and Ca2AlF7.

[0051] When the acidic leachate contains a calcium ion source, it is preferable to add fluorine to the acidic leachate in addition to the calcium ion source so that aluminum can more easily form the above-mentioned compound containing fluorine. Fluorine may also be contained in the battery powder. For example, lithium-ion battery waste (glass fiber, electrolyte, organic binder, etc. of battery cells) may contain calcium and fluorine, and these calcium and fluorine may remain in the battery powder. On the other hand, fluorine may be added to the acidic leachate separately from the battery powder, as needed. A calcium ion source and / or fluorine may be added to the acidic leachate separately from the battery powder. Furthermore, multiple types of battery powders with different calcium and / or fluorine contents may be mixed.

[0052] When fluorine is added to the acidic leachate, the form of fluorine may be, for example, a fluoride salt, specifically, at least one selected from the group consisting of lithium fluoride (LiF), sodium fluoride (NaF), and potassium fluoride (KF). Alternatively, hydrofluoric acid (HF) may be used as at least a part of the acid to include fluorine in the acidic leachate.

[0053] The amounts of calcium and phosphoric acid to be added to the acid leaching solution can be determined appropriately, taking into account the aluminum content of the battery powder and other factors. Specifically, the battery powder added in each of the multiple leaching steps of the acid leaching process may be subjected to a preliminary component analysis to determine the aluminum content of the battery powder, and the amounts of calcium and phosphoric acid may be determined based on this. In at least one of the multiple leaching steps, and preferably in each step, the molar ratio of calcium to aluminum (Ca / Al molar ratio) is preferably 0.20 or greater, or greater than 0.20, and even more preferably 0.5 to 2.0. The amount of calcium here refers to the total amount of calcium in the acid leaching solution (including the amount of calcium added to the acid leaching solution, if any), regardless of whether at least a portion of the calcium in the acid leaching solution is dissolved. Furthermore, for example, the molar ratio of phosphorus in phosphoric acid to aluminum (P / Al molar ratio) is preferably 0.5 or greater, and more preferably 1.0 or greater. In each repetition of the leaching step, calcium is contained in the battery powder, and if the calcium content or phosphorus content of the battery powder is insufficient, the required amount of calcium or phosphorus can be added separately.

[0054] By having the battery powder-containing material (including a calcium ion source, if added separately) contacted with the acidic leaching solution contain a relatively high fluorine content relative to aluminum, a large amount of aluminum can be precipitated in the form of LiCa(AlF6) or the like. Specifically, the fluorine-to-aluminum molar ratio (F / Al molar ratio) of the material contacted with the acidic leaching solution is preferably 1.3 or greater at least once, preferably each time, of the repeated leaching steps. If the F / Al molar ratio is less than 1.3, much of the aluminum in the precipitate precipitated in the acid leaching step will not combine with calcium but will instead form Li-Al composite hydroxide. Because Li-Al composite hydroxide has a higher solubility in the acidic leaching solution than LiCa(AlF6), if the precipitate forms Li-Al composite hydroxide, the amount of aluminum precipitated will be reduced, resulting in insufficient aluminum removal. Therefore, when the F / Al molar ratio of the above substance is less than 1.3, the F / Al molar ratio can be adjusted by adding fluorine to the substance so that the F / Al molar ratio is 1.3 or more. When the F / Al molar ratio is 2.0 or more, or even 3.0 or more, almost all of the aluminum in the precipitate may become LiCa(AlF), thereby achieving even more effective removal of aluminum.

[0055] If the battery powder contains a certain amount of fluorine, the F / Al molar ratio of the battery powder may be 1.3 or more. Alternatively, fluorine may be added separately from the battery powder to adjust the F / Al molar ratio so that the F / Al molar ratio is 1.3 or more. When fluorine is added to the acidic leachate after the start of leaching of the battery powder, the total amount of fluorine contained in the acidic leachate and precipitate after the addition of fluorine is theoretically equal to the amount of fluorine in the material brought into contact with the acidic leachate. Therefore, the above F / Al molar ratio can be calculated from the total amount of fluorine contained in the acidic leachate and precipitate after the addition of fluorine.

[0056] In the multiple leaching stages, the timing of adding or incorporating a phosphate ion source and / or calcium ion source to the acidic leachate to precipitate aluminum is not particularly limited, but it is preferable to do so in the first leach stage. In this case, the aluminum ion concentration of the post-leaching solution sent to the neutralization step as a metal-containing solution is likely to be reduced in the first leach stage, and the concentrations of the phosphate ion source and / or calcium ion source in the acidic leachate can be increased. If a phosphate ion source and / or calcium ion source is added or incorporated into the acidic leachate to precipitate aluminum in the second leach stage, the phosphate ion source and / or calcium ion source will be consumed in the second leach stage. In this case, if the post-leaching solution obtained in the second leach stage is used as the acidic leachate for the next first leach stage, there is a risk that the phosphate ion source and / or calcium ion source will not be sufficient to precipitate aluminum in the new battery powder. Even if a phosphate ion source and / or calcium ion source is added or incorporated in the first leach stage, aluminum may precipitate in the second leach stage.

[0057] 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.

[0058] (Neutralization Step) As described above, in the acid leaching step, a metal-containing solution in which the leaching rate of aluminum is suppressed is obtained by the action of the phosphate ion source and / or the calcium ion source. A neutralization step is carried out to remove mainly aluminum ions from this metal-containing solution.

[0059] In the neutralization step, 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 then an alkali is added to increase the pH, thereby removing the iron ions. This results in a neutralized solution, such as a de-ironized solution. However, if the metal-containing solution contains almost no iron ions, the de-ironization step may be omitted.

[0060] 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.

[0061] The metal-containing solution does not contain a large amount of aluminum ions because aluminum leaching is suppressed by the action of the phosphate ion source and / or calcium ion source in the acid leaching step. Furthermore, in the first leaching stage of the acid leaching step, the oxidation-reduction potential of the resulting metal-containing solution may be somewhat low because leaching is terminated before copper is eluted. For this reason, in the dealumination stage, it is sometimes possible to effectively remove almost all of the remaining aluminum ions without significantly increasing the pH of the metal-containing solution. If the pH of the metal-containing solution in the dealumination stage is not too high, precipitation of cobalt and / or nickel in the metal-containing solution and the resulting loss of cobalt and / or nickel can be suppressed. From this perspective, it is preferable to set the pH of the metal-containing solution to 4.5 or less in the dealumination stage of the neutralization step.

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

[0063] Next, in the iron removal 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.

[0064] 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.

[0065] The oxidizing agent is not particularly limited as long as it can oxidize iron, but is preferably manganese dioxide, a positive electrode active material, and / or a manganese-containing leaching residue obtained by leaching 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.

[0066] Specific examples of alkaline pH adjusters used in the neutralization step 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.

[0067] In the dealumination stage of the neutralization step, it is preferable to add a phosphate ion source and / or a calcium ion source to the metal-containing solution, since the aluminum ions in the metal-containing solution are more likely to precipitate due to the phosphate ion source and / or calcium ion source, thereby enabling effective removal of aluminum.

[0068] Regarding the inclusion of a phosphate ion source and / or a calcium ion source in the metal-containing solution, if the metal-containing solution already contains the necessary amount of a phosphate ion source and / or a calcium ion source, it may not be necessary to further add a phosphate ion source and / or a calcium ion source to the metal-containing solution. Alternatively, if the metal-containing solution does not contain a phosphate ion source and / or a calcium ion source, or if the phosphate ion source and / or the calcium ion source in the metal-containing solution is insufficient, a phosphate ion source and / or a calcium ion source may be added to the metal-containing solution before, during, and / or after increasing the pH of the metal-containing solution to a predetermined value. The form of the phosphate ion source and / or calcium ion source to be added to the metal-containing solution is not particularly limited, and examples thereof include phosphoric acid (H3PO4), calcium phosphate (Ca3(PO4)2, etc.), calcium hydrogen phosphate (CaHPO4), trisodium phosphate (Na3PO4), disodium hydrogen phosphate (Na2HPO4), sodium dihydrogen phosphate (NaH2PO4), lithium phosphate (Li3PO4), calcium sulfate (CaSO4), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), and elemental calcium.

[0069] When the metal-containing solution contains a calcium ion source, in order to sufficiently remove aluminum, the amount of calcium contained in the metal-containing solution in the dealumination stage of the neutralization step is preferably such that the molar ratio of calcium to aluminum (Ca / Al molar ratio) is 0.20 or greater, or greater than 0.20, and more preferably 0.5 to 3.0, and particularly preferably 0.5 to 1.5. The amount of calcium referred to here includes the amount of undissolved calcium, if any, present in the metal-containing solution.

[0070] Furthermore, when the metal-containing solution contains a calcium ion source, it is preferable that it further contains fluorine. In this case, the molar ratio of fluorine to aluminum (F / Al molar ratio) described above can be 1.3 or more. The F / Al molar ratio of the raw material is preferably 2.0 or more, and more preferably 3.0 or more. When the F / Al molar ratio is large in this way, the aluminum in the precipitate that is deposited in the dealumination stage tends to be in the form of LiCa(AlF6) rather than Li-Al composite hydroxide, and aluminum ions in the metal-containing solution are more effectively removed.

[0071] When the metal-containing solution contains a phosphate ion source, the neutralization residue may contain compounds such as aluminum orthophosphate (AlPO). When the metal-containing solution contains a calcium ion source, the neutralization residue may contain compounds such as Ca(SO)(HO). 0.5 It is believed that the neutralization residue contains at least one selected from the group consisting of LiCa(AlF), CaAlF(OH)(SO).2H0, and CaAlF. When lithium hydroxide is used as the pH adjuster, the neutralization residue may contain LiCa(AlF), and when sodium hydroxide is used, the neutralization residue may contain NaLi(AlF). The composition of LiCa(AlF) is Ca:Al = 1:1, but considering that calcium may be consumed by other compounds, the Ca / Al molar ratio in the neutralization step may be greater than 1.0.

[0072] If one of the phosphate ion source and the calcium ion source is added to the acidic leachate in the acid leaching step, it is preferable to add the other of the phosphate ion source and the calcium ion source to the metal-containing solution in the neutralization step (dealuminization step in this embodiment). When aluminum is precipitated by the action of the calcium ion source, fluorine may be consumed along with the precipitation. However, as described above, by using different phosphate ion sources in the acid leaching step and the neutralization step, aluminum can be effectively removed while avoiding a fluorine shortage. Furthermore, compared to using a phosphate ion source in both the acid leaching step and the neutralization step, the amount of expensive phosphoric acid used can be reduced, thereby suppressing increases in processing costs. More preferably, a calcium ion source is added to the acidic leachate in the acid leaching step, and a phosphate ion source is added to the metal-containing solution in the neutralization step. This allows for the addition of only the required amount of phosphate ion source after a certain amount of aluminum has been removed by the calcium ion source.

[0073] (Manganese Extraction Step) The neutralized solution obtained after the neutralization step can be subjected to 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.

[0074] In the manganese extraction step, 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-dodecylsalicyldoxime (product name: LIX860), a mixture of LIX84 and LIX860 (product name: LIX984), and 5-nonylsalicylaldoxime (product name: ACORGAM5640).

[0075] 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, although 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 the nickel extraction step described below, as well as to prevent the sodium from being mixed 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.

[0076] 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.

[0077] 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.

[0078] (Cobalt Extraction Step) Next, the cobalt extraction step can be carried out. In the cobalt extraction step, cobalt ions are separated by solvent extraction from the manganese extraction solution obtained after the manganese extraction step.

[0079] In the cobalt extraction step, it is preferable to use a solvent containing a phosphonate ester extractant. Among these, 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.

[0080] 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.

[0081] 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.

[0082] During the extraction, not only cobalt ions but also small amounts of nickel ions and lithium ions, which become impurities in the cobalt extraction process, 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 contained 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.

[0083] 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.

[0084] 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.

[0085] (Nickel Extraction Step) Thereafter, the cobalt-extracted solution after the cobalt ions have been extracted can be subjected to a nickel extraction step.

[0086] In the nickel extraction step, a carboxylic acid extractant is preferably used to separate nickel ions from the post-cobalt extraction 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% to 30% by volume, and this may be used as the solvent.

[0087] 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 a lithium hydroxide solution obtained in the hydroxide oxidation step described below. Similarly to the extraction of cobalt ions described above, the extraction of nickel ions is also preferably performed by countercurrent multistage extraction. This suppresses the extraction of lithium ions, thereby increasing the extraction rate of nickel ions.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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, the neutralization step, and various extraction 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.

[0092] (Hydroxylation Step) The lithium-containing solution obtained after the nickel extraction step contains substantially only lithium ions as a result of the separation of manganese ions, cobalt ions, and nickel ions in the aforementioned extraction steps. In the hydroxide step, a lithium hydroxide solution is prepared from the lithium-containing solution (lithium sulfate solution, etc.) by various methods described below.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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 each of the manganese extraction step, cobalt extraction step, and nickel extraction step.

[0097] 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.

[0098] The lithium-containing solution may contain trace amounts of cations, such as nickel ions and magnesium ions, that were not completely separated during the nickel extraction process. Nickel ions and magnesium ions are cations, just like lithium ions, 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 that could prevent the electrodialysis from continuing. 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.

[0099] (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 to the nickel extraction step are 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 level, the crystallization step may be performed.

[0100] 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.

[0101] 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.

[0102] (Example 1) Battery powder obtained by treating lithium-ion battery waste was repeatedly subjected to the first leaching stage and the second leaching stage as shown in Figure 3, and the post-leaching solutions obtained in the first, second, and sixth first leaching stages were used as metal-containing solutions. Here, calcium phosphate (Ca3(PO4)2) was added to the acidic leaching solution in the first leaching stage (first stage) of each stage.

[0103] Table 1 shows the leaching conditions, the concentration of each substance in the post-leaching solution used as the metal-containing solution for neutralization, the leaching loss rate, and the aluminum leaching rate. In Table 1, "P / Al" refers to the ratio of the amount of phosphorus (mol) in the additive to the aluminum content (mol) in the battery powder newly added each time. Furthermore, "leaching loss" refers to the proportion of the amount of a given metal in the leaching residue obtained in the second leaching stage, based on the mass of the metal, when the content of the metal in the newly added battery powder each time is taken as 100%. Furthermore, "Al leaching rate" refers to the proportion of aluminum in the post-leaching solution obtained in the first leaching stage, based on the mass of the aluminum content in the newly added battery powder each time.

[0104] The pH of each metal-containing solution was then increased to neutralize it. Neither a phosphate ion source nor a calcium ion source was added during the neutralization. Table 2 shows the neutralization conditions, the concentration of each substance in the neutralized solution, the loss rate during neutralization, and the total loss rate from leaching and neutralization. The loss rate during neutralization is expressed as a percentage of the content of the specified metal in the leaching solution, taken as 100%.

[0105] As shown in Table 1, the leaching rate of aluminum in acid leaching was kept relatively low. Furthermore, Tables 1 and 2 show that the loss of cobalt and nickel was suppressed to a certain extent. In the treatment of the metal-containing solution obtained in the sixth first leaching stage, the loss of cobalt and nickel was slightly higher than in the first and second leaching runs, but this is presumably due to the reduced amount of calcium phosphate added.

[0106] Example 2 was essentially the same as Example 1, except that calcium sulfate was added in the first leaching stage of the acid leaching and phosphoric acid (H3PO4) was added in the neutralization. In this example, the metal-containing solution obtained in the second first leaching stage was subjected to neutralization.

[0107] As a result, as shown in Tables 1 and 2, the leaching rate of aluminum in acid leaching was sufficiently suppressed, and the loss of cobalt and nickel was also effectively suppressed.

[0108] Comparative Example 1: The same battery powder as in Examples 1 and 2 was subjected to a single acid leaching (single-stage leaching) without repeated leaching steps. Calcium phosphate (Ca3(PO4)2) was added during this acid leaching. In Table 1, "P / Al" refers to the ratio of the amount of phosphorus (mol) in the additive to the aluminum content (mol) in the battery powder added during single-stage leaching. Furthermore, "Leaching loss" refers to the mass ratio of a given metal in the leaching residue obtained by single-stage leaching, when the mass of the metal in the battery powder added during single-stage leaching is taken as 100%. Furthermore, "Al leaching rate" refers to the mass ratio of aluminum in the leached solution obtained by single-stage leaching, when the mass of the aluminum in the battery powder added during single-stage leaching is taken as 100%.

[0109] As a result, as shown in Tables 1 and 2, in acid leaching, the addition of a phosphate ion source reduced the aluminum leaching rate to some extent, but the loss of cobalt and nickel, particularly during neutralization, increased, and the loss of cobalt and nickel overall could not be suppressed. The reason for the increased loss of cobalt and nickel is presumed to be due to the relatively high redox potential.

[0110] Comparative Example 2 Comparative Example 2 was substantially the same as Comparative Example 1, except that no phosphate ion source or calcium ion source was added during acid leaching and the pH during neutralization was changed.

[0111] As a result, by not adding a phosphate ion source or a calcium ion source during acid leaching, the aluminum leaching rate was increased, as shown in Table 1. Furthermore, as shown in Table 2, even though the pH during neutralization was increased to a certain extent, the post-neutralization solution still contained a large amount of aluminum ions.

[0112]

[0113]

[0114] From the above, it was found that the above-mentioned metal recovery method can effectively leach cobalt and / or nickel while suppressing copper leaching, and can also achieve a low aluminum leaching rate.

Claims

1. A method for recovering metals from battery powder containing at least copper, aluminum, cobalt and / or nickel, which is a lithium-ion battery waste, 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 aluminum ions, cobalt ions and / or nickel ions; and a neutralization step of increasing the pH of the metal-containing solution to precipitate and remove aluminum; in the acid leaching step, a plurality of leaching steps are repeated a plurality of times; the plurality of leaching steps include a first leaching step of leaching the metals in the battery powder into an acid leaching solution, leaching is terminated before copper is eluted, and a leaching residue is separated to obtain a leaching solution; and a second leaching step of leaching the metals in the leaching residue into an acid leaching solution, leaching is terminated after copper is eluted, and a leaching solution is obtained; the leaching solution obtained in the first leaching step is used as the metal-containing solution, and the leaching solution obtained in the final leaching step of the plurality of leaching steps is used as the acid leaching solution for the next first leaching step; The method for recovering metals, wherein in the acid leaching step, the acid leaching solution contains a phosphate ion source and / or a calcium ion source to precipitate aluminum.

2. A method for recovering metals according to claim 1, wherein the first leaching stage is terminated before the oxidation-reduction potential (based on silver / silver chloride potential) of the acidic leaching solution becomes 0 mV or higher, and the second leaching stage is terminated after the oxidation-reduction potential (based on silver / silver chloride potential) of the acidic leaching solution becomes 0 mV or higher.

3. The metal recovery method according to claim 1 or 2, wherein in the acid leaching step, the acid leaching solution contains a calcium ion source and fluorine.

4. The metal recovery method according to claim 3, wherein in the acid leaching step, a calcium ion source and / or fluorine is added to the acid leaching solution separately from the battery powder.

5. The metal recovery method according to claim 3, wherein the battery powder subjected to the acid leaching step contains a calcium ion source and / or fluorine.

6. The metal recovery method according to claim 1 or 2, wherein in the acid leaching step, a phosphate ion source is added to the acid leaching solution separately from the battery powder.

7. The metal recovery method according to claim 1 or 2, wherein the battery powder subjected to the acid leaching step contains a phosphate ion source.

8. The metal recovery method according to claim 7, wherein the phosphate ion source added in the acid leaching step is calcium phosphate.

9. The method for recovering metals according to claim 1 or 2, wherein in the first leaching stage, a source of phosphate ions and / or a source of calcium ions is added to the acidic leaching solution separately from the battery powder to precipitate the aluminum.

10. A metal recovery method as described in claim 1 or 2, wherein the pH of the metal-containing solution is adjusted to 4.5 or less in the neutralization step.

11. A metal recovery method according to claim 1 or 2, wherein in the neutralization step, the metal-containing solution contains a phosphate ion source and / or a calcium ion source.

12. The metal recovery method according to claim 11, wherein in the acid leaching step, one of a phosphate ion source and a calcium ion source is added to the acid leachate, and in the neutralization step, the other of a phosphate ion source and a calcium ion source is added to the metal-containing solution.

13. The method for recovering metals according to claim 12, wherein a source of calcium ions is added to the acid leachate in the acid leaching step, and a source of phosphate ions is added to the metal-containing solution in the neutralization step.

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