Metal leaching methods

Abstract

The present invention provides a method for leaching out a metal contained in a battery powder of lithium ion battery waste into an acidic leaching liquid 21 by bringing the battery powder into contact with the acidic leaching liquid 21 within a leaching container 1. With respect to this method for leaching out a metal, the leaching container 1 has a movable member which is positioned and movable on the liquid level 22 of the acidic leaching liquid 21 retained within the leaching container 1; and when the metal is leached out within the leaching container 1, air bubbles Ba generated in the acidic leaching liquid 21 are broken by the action of the movable member.

Description

[Technical Field]

[0001] This specification discloses technology relating to metal leaching methods. [Background technology]

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

[0003] To recover valuable metals from lithium-ion battery waste, for example, battery powder obtained through heat treatment or other treatments is brought into contact with an acidic leachate to leach metals such as nickel, cobalt, manganese, aluminum, and iron contained in the battery powder into the acidic leachate, thereby obtaining a leachate in which the metals have been dissolved.

[0004] Next, among the metals dissolved in the post-leaching solution, aluminum, iron, manganese, etc. are sequentially or simultaneously removed by solvent extraction or neutralization, as described in Patent Documents 1 to 3. Thereafter, valuable metals such as nickel and cobalt are separated by solvent extraction and then concentrated and recovered. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-180439 [Patent Document 2] US Patent Application Publication No. 2011 / 0135547 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-162982 Summary of the Invention [Problem to be solved by the invention]

[0006] In the treatment of lithium-ion battery waste as described above, when battery powder is brought into contact with the acidic leaching solution, a relatively large amount of bubbles may be generated in the acidic leaching solution, which may hinder the smooth operation of the process of leaching metals in the battery powder into the acidic leaching solution.

[0007] This specification discloses a metal leaching method that can effectively suppress foaming of the acidic leaching solution when leaching metals in battery powder into the acidic leaching solution. [Means for solving the problem]

[0008] The metal leaching method disclosed in this specification is a method for bringing battery powder from lithium-ion battery waste into contact with an acidic leachate inside a leaching vessel to leach metals contained in the battery powder into the acidic leachate, wherein the leaching vessel has a movable member that is positioned above the liquid surface of the acidic leachate stored inside, and includes breaking up bubbles that are generated in the acidic leachate when the metals are leached inside the leaching vessel by the operation of the movable member. The sulfuric acid concentration of the acidic leaching solution is 50 g / L to 400 g / L, and the area ratio of the peak located on the smallest diameter side in a particle size distribution graph of the battery powder is 15% or more. . [Effects of the Invention]

[0009] According to the above metal leaching method, foaming of the acidic leaching solution can be effectively suppressed when the metals in the battery powder are leached into the acidic leaching solution. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram illustrating an example of a metal recovery process to which the metal leaching method of one embodiment can be applied. [Figure 2] FIG. 2 is a cross-sectional view along the depth direction schematically showing an example of an infusion container. [Figure 3] A cross-sectional view along the depth direction schematically showing another example of an infusion container. [Figure 4] A cross-sectional view along the depth direction schematically showing yet another example of an infusion container, and a cross-sectional view along line bb thereof. [Figure 5]1A and 1B are graphs, schematic diagrams, and photographs showing the results of Example 1 of the invention in confirming the effectiveness of the rotating member in the examples. [Figure 6] 10A and 10B are graphs, schematic diagrams, and photographs showing the results of Example 2 of the invention in confirming the effectiveness of the rotating member in the examples. [Figure 7] 10A and 10B are graphs, schematic diagrams, and photographs showing the results of Example 3 of the invention in confirming the effectiveness of the rotating member in the examples. [Figure 8] 10 is a graph showing the results of confirming the influence of the proportion of small particles in the battery powder on foaming in an example. [Figure 9] 10 is a graph showing the results of confirming the influence of the carbon content of the battery powder on foaming in an example. [Figure 10] 1 is a graph schematically showing an example of a particle size distribution graph of battery powder. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes in detail an embodiment of the above-mentioned metal leaching method. In one embodiment, the metal leaching method is a method in which battery powder of lithium ion battery waste is brought into contact with an acidic leachate inside a leaching vessel, and metals contained in the battery powder are leached into the acidic leachate.

[0012] The leaching vessel has a movable member that is positioned above the surface of the acid leachate stored therein. When the metals in the battery powder are leached inside the leaching vessel, the movable member is moved to break up any bubbles that form in the acid leachate. This effectively eliminates any bubbles that form in the acid leachate during the leaching of the metals.

[0013] Such a metal leaching method can be used in a process for recovering predetermined metals, such as valuable metals, from lithium-ion battery waste. Here, the metal leaching method will be described as being applied to a metal leaching step in a metal recovery process for lithium-ion battery waste, as illustrated in Figure 1. However, the metal leaching method is not limited to this, and can be used in various processes including a step of leaching metals in battery powder from lithium-ion battery waste into an acidic leachate.

[0014] (Lithium-ion battery waste) The targeted lithium-ion battery waste is lithium-ion secondary batteries for automotive or consumer use that have been discarded due to the end of the battery product's life, manufacturing defects, or other reasons. Examples of automotive lithium-ion secondary batteries include those contained in automotive battery packs installed in vehicles such as hybrid vehicles and electric vehicles. Examples of consumer lithium-ion secondary batteries include those used in mobile phones and various other electronic devices. From the perspective of effective resource utilization, recovery of valuable metals such as cobalt, nickel, and other metals from such lithium-ion battery waste is desirable.

[0015] An automotive battery pack containing an automotive lithium-ion secondary battery generally comprises a metal case that forms the surrounding housing, a battery such as a lithium-ion secondary battery having multiple battery cells housed inside the case, and other components. Automotive battery packs come in a variety of shapes depending on the space constraints of the vehicle in which they are installed, and some have an external shape that is elongated in one direction, such as a rectangular parallelepiped that is approximately rectangular in plan view.

[0016] Lithium-ion battery waste typically contains a positive electrode material, which is made of a positive electrode active material consisting of one or more single metal oxides of lithium, nickel, cobalt, and manganese, or a composite metal oxide of two or more metals, coated and fixed onto an aluminum foil (positive electrode substrate) with an organic binder such as polyvinylidene fluoride (PVDF), a negative electrode material made of a carbon-based material, and an organic electrolyte solution such as ethylene carbonate or diethyl carbonate, or other electrolytes. Lithium-ion battery waste may also contain copper, iron, etc.

[0017] (Pretreatment process) The pretreatment process may include heat treatment, crushing, and sieving, in this order or in any order, but at least one of these processes may be omitted. Battery powder is obtained by subjecting lithium-ion battery waste to a pretreatment process. Battery powder refers to a powder in which the positive electrode material components are separated and concentrated by subjecting lithium-ion battery waste to some pretreatment process. Battery powder may also be obtained as a powder in which the positive electrode material components are concentrated by subjecting lithium-ion battery waste to crushing and sieving, with or without heat treatment.

[0018] An example of a case where heat treatment is performed will be described in detail below. However, an example of a case where heat treatment is not performed includes a method in which residual electricity in lithium ion battery waste is first discharged, followed by crushing and sieving, and then the resulting cathode material with aluminum foil is treated with a solvent to dissolve the binder, and the cathode material components are separated and recovered from the aluminum foil.

[0019] When heat treatment is carried out, the lithium-ion battery waste is heated. In the case of lithium-ion battery waste from vehicle battery packs, these have a rigid structure protected by a metal case or the like, making them difficult to dismantle, and dismantling them poses a risk of electric shock due to residual voltage. Therefore, the lithium-ion battery waste is sometimes not dismantled, but rather subjected to heat treatment while maintaining the structure in which the battery, etc. is surrounded by the case.

[0020] The heat treatment of lithium-ion battery waste may be performed in an inert atmosphere or in the air. Alternatively, a portion of the heat treatment may be performed in either the inert atmosphere or the air, and the remaining portion of the heat treatment may be performed in either the inert atmosphere or the air. For example, the heat treatment may be performed first in an inert atmosphere, and then the atmosphere may be switched to the air atmosphere. The heat treatment atmosphere may be appropriately selected in consideration of various factors, such as the characteristics of each atmosphere and the working efficiency, which will be described later.

[0021] Heat treatment in an inert atmosphere suppresses explosive combustion of organic electrolytes and other substances that may be contained in lithium-ion battery waste, making it easier to control the temperature inside the heat treatment furnace. It also increases the recovery rate of valuable metals by suppressing the formation of nickel oxide and cobalt oxide and promoting the formation of metals such as cobalt and nickel, which are easily soluble in acid. If temperature control inside the heat treatment furnace becomes difficult, aluminum, such as aluminum foil, may melt, and valuable metals such as cobalt and nickel may be incorporated into the molten aluminum and solidify. In this case, there is a concern that the valuable metals may be removed along with the aluminum during the sieving process described below, resulting in a decrease in the recovery rate of valuable metals.

[0022] If the temperature in the heat treatment furnace can be controlled, the generation of powdery lithium aluminate due to the reaction between aluminum and lithium oxide can be suppressed. The generation of lithium aluminate, which is promoted under high temperatures and high oxygen partial pressures, leads to a decrease in the lithium leaching rate when lithium is leached in the metal leaching process described below, because lithium aluminate has a lower solubility in water than lithium carbonate. Furthermore, aluminum foil that has not reacted to lithium aluminate can be easily separated by sieving. However, if lithium aluminate is generated, the aluminum foil becomes brittle and is more likely to be mixed into the battery powder during sieving.

[0023] Specifically, the heat treatment in an inert atmosphere can be an atmosphere containing at least one selected from the group consisting of nitrogen, carbon dioxide, and water vapor. Among these, an atmosphere containing mainly nitrogen is preferable. The heat treatment can be performed while flowing such an inert gas. A small amount of oxygen may be contained, and the oxygen partial pressure during the heat treatment is 0 atm to 4×10 as measured by a zirconia oxygen analyzer. -2 When an inert gas is introduced into the heat treatment furnace, the oxygen concentration of the inert gas is set to 0.05% by volume to 4.00% by volume, and the flow rate in the heat treatment furnace is set to 6 m 3 / hr~60m 3 / hr. Here, the lithium ion battery waste can be heated to reach and maintain a temperature of 400°C to 800°C.

[0024] Heat treatment in an air atmosphere can suppress the foaming phenomenon that occurs during acid leaching in the metal leaching process. Substances produced by incomplete pyrolysis during heat treatment in an inert atmosphere can cause foaming during acid leaching.

[0025] Heat treatment in an air atmosphere is preferable because it is simple and does not require adjustment of the atmosphere. At this time, the lithium ion battery waste can be heated to a temperature of 400°C to 800°C and maintained at that temperature.

[0026] For the heat treatment, for example, an atmospheric electric furnace or atmospheric muffle furnace can be used for a batch type, or a roller hearth kiln, mesh belt kiln, pusher kiln, etc. can be used for a continuous type. Of these, the roller hearth kiln and pusher kiln are preferred because they are suitable for large-scale treatment.

[0027] The crushing process is carried out, for example, by removing the battery from the case of an automotive battery pack of lithium-ion battery waste, destroying the battery casing, and selectively separating the positive electrode active material from the aluminum foil to which the positive electrode active material is applied. Various known devices or equipment can be used here, and specific examples include impact crushers that can crush the case and battery by applying impact while cutting them, such as sample mills, hammer mills, pin mills, wing mills, tornado mills, and hammer crushers. A screen can be installed at the outlet of the crusher, and the batteries can be crushed to a size that can pass through the screen and then discharged through the screen.

[0028] After crushing, the crushed batteries are lightly crushed or pulverized as needed to obtain a powder, and then sieved using a sieve with appropriate openings, whereby aluminum, copper, etc. remain on the sieve, and battery powder containing lithium, cobalt, nickel, etc. from which aluminum, copper, etc. have been removed to some extent is obtained on the sieve.

[0029] As will be described later, when the battery powder contains carbon, for example, in the form of relatively fine carbon powder derived from the negative electrode material, foaming tends to become more pronounced during acid leaching in the metal leaching step. This tendency does not depend on the details of the pretreatment step, such as whether or not heat treatment is performed, as long as carbon is present in the battery powder. This embodiment can be used for either battery powder that does not contain carbon or battery powder that contains carbon, and foaming during acid leaching can be effectively suppressed in either case.

[0030] (Metal leaching process) To leach the metals in the battery powder, the battery powder may be brought into contact with a liquid such as water to leach lithium, and the residue may then be brought into contact with an acidic leach solution to leach other metals into the acidic leach solution. Lithium leaching produces a lithium solution, while acid leaching produces a leach solution containing dissolved metals such as cobalt, nickel, manganese, aluminum, copper, and iron.

[0031] When lithium is leached before leaching with an acidic leaching solution, the battery powder may be brought into contact with water, and specifically, tap water, industrial water, distilled water, purified water, ion-exchanged water, pure water, ultrapure water, etc. The temperature of the liquid when the battery powder comes into contact with the liquid may be 10°C to 60°C.

[0032] The lithium solution obtained by leaching lithium can be subjected to treatments such as solvent extraction, neutralization, carbonation, etc., to recover the lithium in the lithium solution as lithium carbonate. The lithium carbonate obtained in this manner may be purified as necessary to reduce the quality of impurities.

[0033] The battery powder, which is the residue after the lithium leaching, is brought into contact with an acidic leaching solution to leach metals such as cobalt and nickel contained therein. During acid leaching using an acidic leaching solution, bubbles may be generated from the acidic leaching solution, which can hinder the smooth execution of the acid leaching. In this example, a cylindrical leaching vessel 1 with a bottom, as shown in Figure 2, is used.

[0034] In the illustrated leaching container 1, a rotating member 2 having a plate-like shape such as a flat plate or other shape that can rotate above the liquid surface 22 is provided above the position where the liquid surface 22 would exist if the acid leaching solution 21 were stored inside. As a result, when the battery powder is brought into contact with the acid leaching solution 21, air bubbles Ba that are generated in the acid leaching solution 21 and rise to the liquid surface 22 as shown in the figure are destroyed by the rotation of the rotating member 2. As a result, the air bubbles Ba are prevented from leaking out from the opening 3 on the upper side of the leaching container 1, allowing for smooth acid leaching.

[0035] The specific structure and shape of the rotating member 2 are not particularly limited, as long as it can rotate on the liquid surface 22 and break up the bubbles Ba. In the illustrated example, the leaching vessel 1 further includes a rotating shaft 2a extending in the depth direction of the acidic leaching liquid 21 and receiving a rotational driving force from a driving source (not shown). The rotating member 2 is attached to the rotating shaft 2a so as to extend parallel to a direction perpendicular to the depth direction (horizontal direction). As the rotating shaft 2a rotates, the rotating member 2 can rotate around the rotating shaft 2a in a horizontal plane parallel to the liquid surface 22. The rotating shaft 2a may be positioned approximately at the center of a cross section perpendicular to the depth direction of the leaching vessel 1. In this example, a single plate-shaped rotating member 2 having a rectangular side view is provided around the rotating shaft 2a. However, two or more rotating members 2 may be provided, for example, at equal intervals in the circumferential direction.

[0036] The heightwise position of the rotating member 2 from the liquid surface 22 of the acidic leachate 21 (vertical direction in FIG. 2 ) can be anywhere above the liquid surface 22 of the acidic leachate 21, as long as it is in contact with the bubbles Ba on the liquid surface 22. For example, as shown in FIG. 2 , the heightwise position of the rotating member 2 can be determined so that VT, expressed by the equation VT = (VF + VL) / VL, is less than 2.0, or even less than 1.5, based on the volume VL of the acidic leachate 21 containing battery powder and the volume VF of the bubbles Ba on the liquid surface 22. The volume VF of the bubbles Ba on the liquid surface 22 can be calculated by multiplying the height from the liquid surface 22 to the top of the uppermost bubble Ba by the cross-sectional area perpendicular to the height direction at the location inside the leaching container 1 where the bubbles Ba are present. Note that if the cross-sectional area perpendicular to the height direction of the leaching container 1 is constant, the above equation can be used by replacing the volumes VL and VF with the height, respectively. The height direction here is the direction parallel to the depth direction of the leaching container 1, and corresponds to the up-down direction in FIG.

[0037] The leaching vessel 1 shown in Figure 3 is provided with an agitator blade 2b used to agitate the acidic leachate 21, for the purpose of increasing the leaching rate of the metals of the battery powder in the acidic leachate 21. The agitator blade 2b is positioned so as to be immersed in the acidic leachate 21 in order to effectively agitate the acidic leachate 21. The shape of the agitator blade 2b can be appropriately selected from those suitable for agitating the acidic leachate 21.

[0038] In this case, as shown in Figure 3, it is preferable to attach an agitator blade 2b to the rotating shaft 2a that rotates the rotating member 2, so that the rotating member 2 and the agitator blade 2b share the rotating shaft 2a. More specifically, in this leaching vessel 1, the rotating shaft 2a is made longer in the depth direction than that shown in Figure 2 so that it can be immersed in the acidic leachate 21, and the agitator blade 2b is provided around the extended tip of the rotating shaft 2a. As a result, when the rotating shaft 2a is rotated, the rotating member 2 rotates around the rotating shaft 2a above the liquid surface 22, and the agitator blade 2b rotates around the rotating shaft 2a in the acidic leachate 21. As a result, it is possible to simultaneously destroy the bubbles Ba with the rotating member 2 and agitate the acidic leachate 21 using a single driving source.

[0039] The rotation speed of the rotating element 2 during acid leaching is, for example, 50 rpm to 500 rpm. If the rotation speed is too slow, the rotation of the rotating element 2 cannot keep up with the generation of bubbles, resulting in insufficient suppression of foaming. On the other hand, a rotation speed that is too fast is not only unnecessary from the viewpoint of suppressing foaming, but also has the risk of causing the bubbles Ba to scatter. Furthermore, when the rotating element 2 and the stirring blade 2b share a rotating shaft 2a as shown in FIG. 3, if the rotation speed of the rotating element 2 is too fast, the stirring blade 2b will rotate at a higher speed, causing the acid leaching reaction to proceed excessively quickly and promoting foaming of the acid leaching solution 21.

[0040] In Figure 4, baffle plates 5 (baffle plates) protrude radially inward from the inner vessel surface 4 on the vessel inner surface 4, which faces inward in the radial direction (left-right direction in Figure 4) of the leaching vessel 1, to disrupt the flow caused by the stirring blades 2b and effectively stir the acidic leaching solution 21. One or more baffle plates 5 can be provided; in the illustrated example, four baffle plates 5 are arranged at equal intervals in the circumferential direction (see Figure 4(b)). The radial length Lb of the baffle plate 5 may be, for example, 0.03 to 0.15 as a ratio to the vessel inner diameter Dc.

[0041] In a leaching vessel 1 having a baffle plate 5, the radial length of the rotating member 2 (the distance from the rotating shaft 2a to the outer end of the rotating member 2) may not be very long due to considerations such as preventing interference between the rotating member 2 and the baffle plate 5. In the leaching vessel 1 shown in Figure 4, the rotating member 2 has a radial length that does not reach the position where the baffle plate 5 is installed. Even in such a case, the rotating member 2 rotating around the rotating shaft 2a can suppress the rise of bubbles Ba above the liquid surface 22 inside the leaching vessel 1, even in the vicinity of the baffle plate 5. The ratio of the radial length of the rotating member 2 to the vessel inner diameter Dc is, for example, 0.1 or more, preferably 0.2 or more. The width along the height direction of the rotating member 2 is not particularly limited as long as the rotating member 2 can rotate stably.

[0042] The above description has been given in detail with respect to a case where the rotating member 2 is used as an example of a movable member. However, the movable member is not limited to the rotating member 2, as long as it can move above the liquid surface 22 of the acidic leachate 21 and destroy the bubbles Ba. Other examples of movable members, although not shown, include a rod-shaped, plate-shaped, or other reciprocating member that is driven to repeatedly reciprocate above the liquid surface 22 of the acidic leachate 21 in a direction perpendicular to the height direction. Such a reciprocating member may contact the bubbles Ba generated above the liquid surface 22 of the acidic leachate 21 on its outward path to suppress the rise of the bubbles Ba, and then contact the bubbles Ba again on its return path until the bubbles Ba rise to an allowable height. This allows the reciprocating member to suppress the bubbles Ba below an allowable height.

[0043] Incidentally, the acidic leaching solution 21 may contain, for example, 50 g / L or more, typically 60 g / L to 400 g / L of sulfuric acid, although other acids may also be used. When the acidic leaching solution 21 containing sulfuric acid at a relatively high concentration, as described above, is brought into contact with the battery powder, the generation of bubbles Ba becomes significant, so it is effective to use a leaching vessel 1 having a movable member such as the rotating member 2 described above.

[0044] Methods for contacting the battery powder with the acidic leaching solution 21 containing sulfuric acid include contacting the battery powder with an aqueous sulfuric acid solution containing concentrated or dilute sulfuric acid, or adding concentrated sulfuric acid to a slurry in which the battery powder is dispersed in water or other liquid. The generation of the bubbles Ba described above is thought to be mainly caused by hydrogen gas generated during the leaching reaction. Therefore, when the battery powder is contacted with an aqueous sulfuric acid solution containing dilute sulfuric acid, the rate of hydrogen gas generation is presumably relatively slow, and the degree of foaming is presumably low. On the other hand, a low sulfuric acid concentration slows the leaching rate and reduces the efficiency of the metal leaching process. Therefore, from the perspective of improving the efficiency of the metal leaching process, it is desirable to add the battery powder to an aqueous sulfuric acid solution containing concentrated sulfuric acid with a high concentration (e.g., a sulfuric acid concentration of 50 g / L or more) as described above, or to add concentrated sulfuric acid (a sulfuric acid concentration of 90 mass % or more (e.g., 98 mass %)) to a slurry containing the battery powder. In this embodiment, foaming can be suppressed by a movable member such as the rotating member 2, so the efficiency of the metal leaching process can be increased by adding battery powder to a concentrated sulfuric acid aqueous solution or adding sulfuric acid to a slurry containing battery powder.

[0045] Furthermore, it has been newly discovered that when the carbon content in the battery powder is high, such as 17% by mass or more, for example 17% by mass to 50% by mass, many bubbles Ba are generated when the battery powder comes into contact with the acidic leaching solution 21. Therefore, when battery powder with such a high carbon content is brought into contact with the acidic leaching solution 21, the defoaming effect of the movable member (rotating member 2, etc.) provided in the leaching container 1 works even more effectively.

[0046] We also discovered a new finding: the particle size distribution of battery powder affects the generation of Ba bubbles during acid leaching. Specifically, when the particle size of battery powder is measured using a laser diffraction / scattering particle size distribution analyzer (e.g., the MT3000II manufactured by Microtrac-Bell Corporation) and a volumetric particle size distribution graph is obtained, if multiple peaks appear on the particle size distribution graph, if the area ratio of the smallest peak is relatively high, such as 15% or more (e.g., 15% to 40%), the generation of Ba bubbles during acid leaching is high. Therefore, this embodiment is effective for battery powders with a high proportion of small particles. The area ratio of the smallest peak can be calculated as twice the cumulative frequency at the peak position on the particle size distribution graph. Here, the cumulative frequency at the peak position refers to the cumulative value of the frequency from the smallest peak to the peak on the particle size distribution graph, as shown in FIG. 10. The peak position is the particle size at which the cumulative frequency is 50% when the sum of the frequencies from the smallest particle size to the largest particle size of the peak for which the peak position is being determined is assumed to be 100% (i.e., when the peak is assumed to represent one particle size distribution). Multiple peaks each have multiple peaks and are separated by the valley bottom position where the frequency of the valley between them is lowest. In the example of Figure 10, the two peaks are separated by the valley bottom position indicated by the dashed line in the figure. The particle size intervals on the horizontal axis of a particle size distribution graph can be set based on the particle size classification of the Tyler standard sieve (mesh standard) in accordance with JIS Z8801-1.

[0047] The pH of the acid leaching solution is preferably 0.0 to 4.0 during acid leaching, and may be 0.5 to 2.0 after completion of acid leaching. The oxidation-reduction potential (ORP value, based on silver / silver chloride potential) is, for example, -250 mV to 0 mV immediately after acid leaching, and may be approximately 300 mV in the leaching solution after solid-liquid separation. During acid leaching, the acid leaching solution can be stirred at, for example, 50 rpm to 500 rpm using a stirrer having the stirring blades 2b as described above, as needed. The solution temperature during acid leaching may be, for example, 60°C to 80°C.

[0048] The acid leaching in the metal leaching process can be a single-stage leaching process, or multiple leaching stages can be repeated multiple times. When multiple leaching stages are used, each leaching stage includes a first leaching stage in which the battery powder is leached with an acid leaching solution and the leaching residue is separated to obtain a leaching solution, and a second leaching stage in which the leaching residue from the first leaching stage is leached with an acid leaching solution to obtain a leaching solution. The leaching solution obtained from the final leaching stage (the second leaching stage if there are two leaching stages, the first and second leaching stages) is used as the acid leaching solution for the next first leaching stage. In addition, the leaching solution obtained from the leaching stages other than the final one in each leaching stage (the first leaching stage if there are two leaching stages, the first leaching stage) is sent to the next process (impurity removal and metal recovery process). 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 separating many of the metals whose leaching should be suppressed (such as copper) as leaching residue without leaching them.

[0049] (Impurity removal and metal recovery process) The leaching solution can be subjected to a process for removing impurities and then recovering metals such as cobalt and nickel. For example, impurities can be removed by neutralizing to remove part of the aluminum and iron, or by solvent extraction to remove the remaining aluminum and manganese. Metal recovery can be achieved by sequentially extracting cobalt and nickel by solvent extraction and then stripping them. [Example]

[0050] The metal leaching method described above was experimentally carried out, and its effectiveness was confirmed. The following description is provided for illustrative purposes only and is not intended to be limiting.

[0051] (Verifying the effectiveness of rotating components) Lithium-ion battery waste was heat-treated to obtain battery powder. This battery powder was subjected to acid leaching using a leaching vessel (2 L beaker) equipped with a rotating element, stirring blades, and baffle plates as shown in Figure 4. The rotating element was positioned so that the edge on the liquid surface (lower side) was positioned in the height direction relative to the level of the acid leaching solution as shown in Table 1. The radial length Lb of each of the four baffle plates was 20 mm.

[0052] In the acid leaching, sulfuric acid was added while rotating the rotating element and stirring blade at the rotation speeds shown in Table 1. During this process, the foam height VT was measured using the volume of the acid leaching solution VL and the volume of bubbles above the liquid surface VF, as expressed by the formula: VT = (VF + VL) / VL. The results for Invention Examples 1 to 3 are shown in Figures 5 to 7, respectively.

[0053] [Table 1]

[0054] 5 to 7, it can be seen that in all of Examples 1 to 3, the bubbles were suppressed at a predetermined height without reaching the opening of the brewing container. In particular, in Examples 2 and 3, the foam height VT was suppressed to a sufficiently low position.

[0055] In Example 1, the foam height VT rose to 1.6 50 minutes after the start of sulfuric acid addition, but did not rise thereafter. In Example 1, the rotation speed of the rotating element was changed from 150 rpm at 70 to 75 minutes, to 360 rpm at 75 to 80 minutes, and to 300 rpm at other times. The foam height VT was suppressed to 1.6 or less at all rotation speeds. As shown in Figure 5, the bubbles on the liquid surface formed a mountain shape centered on the rotation axis when the foam height VT was in the range of 1.0 to 1.5. After that, the bubbles remained at the edge of the rotating element where the rotating element was in contact (VT = 1.5). In the area above the baffle plate around the rotating element, the bubbles rose to VT = 1.6, but did not rise any higher and were suppressed.

[0056] In Example 2, the foam height VT rose to 1.4 40 minutes after the start of sulfuric acid addition and did not rise thereafter. As shown in Figure 6, the bubbles on the liquid surface formed a mountain shape centered on the rotation axis when the foam height VT was in the range of 1.0 to 1.2. Thereafter, the bubbles remained at the edge of the rotating element where the rotating element was in contact (VT = 1.2), and rose to a position of VT = 1.4 in the area above the baffle plate around the rotating element, but did not rise any further and were suppressed.

[0057] In Example 3, the foam height VT rose to 1.4 50 minutes after the start of sulfuric acid addition and did not rise thereafter. As shown in Figure 7, the bubbles on the liquid surface formed a mountain shape centered on the rotation axis when the foam height VT was in the range of 1.0 to 1.2. Thereafter, the bubbles remained at the edge of the rotating element where the rotating element was in contact (VT = 1.2), and rose to a position of VT = 1.4 in the area above the baffle plate around the rotating element, but did not rise any further and were suppressed.

[0058] (Confirmation of the effect of the proportion of small particles in battery powder on foaming) Lithium-ion battery waste was subjected to heat treatment under specified conditions, and several types of battery powder with different small particle ratios measured using the method described above were prepared. Each battery powder was subjected to acid leaching. VT was calculated using the formula VT = (VF + VL) / VL, where VL is the volume of the acid leachate and VF is the volume of bubbles generated in the acid leachate. The results are shown in Figure 8.

[0059] Figure 8 shows that there is a positive correlation between the volume of bubbles generated in the acid leaching solution and the proportion of small particles, and that when the proportion of small particles is 15% or more, the amount of bubbles increases and VT increases to 1.5 or more. Even when performing acid leaching on battery powder with a relatively high proportion of small particles, the use of a movable part as described above can suppress the generation of bubbles and effectively prevent an increase in VT.

[0060] (Confirming the effect of carbon content in battery powder on foaming) Several types of battery powder with different carbon contents were prepared from lithium-ion battery waste. Each battery powder was subjected to acid leaching. VT was calculated using the formula: VT = (VF + VL) / VL, where VL is the volume of the acid leachate and VF is the volume of bubbles generated in the acid leachate. The results are shown in Figure 9.

[0061] 9, it can be seen that the volume of bubbles generated in the acid leaching solution is roughly proportional to the carbon content of the battery powder. Furthermore, it can be seen that when the carbon content is 17% by mass or more, the amount of bubbles increases and the VT becomes large, reaching 1.5 or more. By using a movable member, it is possible to suppress the increase in bubbles and VT even when acid leaching is performed on battery powder with a relatively high carbon content.

[0062] From the above, it was found that the above-mentioned metal leaching method can effectively suppress foaming of the acidic leachate. [Explanation of symbols]

[0063] 1. Leaching vessel 2 Rotating members 2a Rotation axis 2b Stirring blade 3 Opening 4. Inner surface of container 5 Baffle plate 21 Acid leachate 22 Liquid level Ba bubbles VL Volume of acidic leachate VF bubble volume Ds Radial distance between the outer edge of the rotating member and the inner edge of the baffle plate Dc container inner diameter Lb Radial length of the baffle plate

Claims

1. A method for leaching metals contained in lithium ion battery waste into the acidic leachate by contacting battery powder of the waste with an acidic leachate inside a leaching vessel, comprising: the leaching vessel has a movable member that is arranged at a position above the liquid level of the acidic leaching solution stored therein and is operable; and breaking up bubbles generated in the acid leachate when the metal is leached in the leaching vessel by the operation of the movable member; The sulfuric acid concentration of the acidic leaching solution is 50 g / L to 400 g / L; the area ratio of the peak located on the smallest diameter side in a particle size distribution graph of the battery powder is 15% or more.

2. The infusion vessel has a baffle plate protruding inward from the inner surface of the vessel, The movable member is provided so as not to interfere with the baffle plate, the movable member is a rotating member that is rotatable on the liquid surface of the acidic leachate, The rotation of the rotating member breaks the bubbles; 2. The metal leaching method according to claim 1, wherein the rotating member has a length in the radial direction that does not reach the position where the baffle plate is provided.

3. 3. The metal leaching method according to claim 2, wherein the leaching vessel has a rotation shaft that extends in the depth direction of the acidic leach solution and rotates the rotating member.

4. 4. The metal leaching method according to claim 3, wherein the leaching vessel has an agitator blade that is immersed in the acidic leaching solution and is rotatable around the rotation axis.

5. 2. The metal leaching method according to claim 1, wherein the battery powder is added to an aqueous sulfuric acid solution, and the battery powder is contacted with the acidic leach solution.

6. The metal leaching method according to claim 1 , wherein 90% by mass or more of sulfuric acid is added to a slurry containing the battery powder, and the battery powder is brought into contact with the acidic leaching solution.

7. The metal leaching method according to any one of claims 1 to 6, wherein the battery powder contains 17% by mass or more of carbon.

8. The metal leaching method according to any one of claims 1 to 6, wherein the battery powder is a battery powder that has been at least partially heat-treated in an inert atmosphere.

9. 9. The metal leaching method according to claim 8, wherein the battery powder is subjected to heat treatment in an inert atmosphere and then heat treatment in an air atmosphere.

10. A metal leaching method described in any one of claims 1 to 6, wherein the lithium ion battery waste is obtained through a pretreatment process including a crushing treatment.

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