Methods for processing alloys

Abstract

To provide a method of efficiently obtaining a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt, and copper of a waste lithium ion battery and the like.SOLUTION: A processing method of alloy for obtaining a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt, and copper includes a leach process of subjecting a slurry containing the alloy to leach processing by an acid solution in the presence of a sulfating agent to obtain a leachate and a leach residue. In the leach process, the leach processing is performed by adjusting an initial concentration of the slurry containing the alloy to 100 g / L or more and 250 g / L or less. Also in the leach process, the leach processing is performed preferably while controlling an oxidation reduction potential (a silver / silver chloride electrode as a reference electrode) to 200 mV or lower. Also in the leach process, the leach processing is performed preferably in the presence of the sulfating agent by an amount in a range of 1.05-1.25 equivalent (S mol / Cu mol) to an amount of copper contained in the alloy.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for treating an alloy to obtain a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt and copper.

Background Art

[0002] Vehicles such as electric vehicles and hybrid vehicles, and electronic devices such as mobile phones, smartphones, and personal computers are equipped with lithium-ion batteries (hereinafter also referred to as "LIBs") having the characteristics of being lightweight and having a large output.

[0003] An LIB has a structure in which a negative electrode material in which a negative electrode active material such as graphite is fixed on the surface using a copper foil as a negative electrode current collector and a positive electrode material in which a positive electrode active material such as lithium nickelate or lithium cobaltate is fixed on a positive electrode current collector made of an aluminum foil are loaded together with a separator made of a porous resin film of polypropylene or the like, and an organic solvent containing an electrolyte such as lithium hexafluorophosphate (LiPF6) is impregnated as an electrolytic solution.

[0004] When an LIB is incorporated and used in vehicles, electronic devices, etc. as described above, it will eventually become unusable due to deterioration of the vehicle, electronic device, etc. or the life of the LIB itself, and becomes a waste lithium-ion battery (waste LIB). Note that "waste LIB" includes those generated as defective products during the manufacturing process.

[0005] These waste LIBs contain valuable components such as nickel, cobalt, and copper, and it is desirable to recover and reuse these valuable components for effective utilization of resources.

[0006] Generally, when attempting to efficiently recover valuable components from metal-made devices, parts, or materials, dry processing, which utilizes the principle of dry smelting—where the metal is placed in a furnace and melted at high temperatures to separate the valuable metal from the slag—has been widely practiced. For example, Patent Document 1 discloses a method for recovering valuable metals using dry processing. By applying the method disclosed in Patent Document 1 to the recovery of valuable metals from waste lithium-ion batteries (LIBs), a copper alloy containing nickel and cobalt can be obtained.

[0007] While this type of dry treatment (hereinafter also referred to as the "dry method") has the disadvantage of requiring energy to heat to high temperatures using a furnace, it has the advantage of being able to separate various impurities all at once. Moreover, the slag obtained by dry treatment has chemically stable properties, poses little concern to the environment, and is easy to dispose of.

[0008] However, when waste lithium-ion batteries (LIBs) are processed using a dry process, there is a problem in that most of the valuable components, especially cobalt, are distributed into the slag, resulting in unavoidable cobalt recovery losses. Furthermore, the metal obtained through dry processing is an alloy containing the valuable components, and in order to reuse it, it is necessary to separate the components from this alloy and purify it by removing impurities.

[0009] A commonly used method for elemental separation in dry processing involves slowly cooling a molten material at high temperatures, for example, to separate copper from lead or lead from zinc. However, in cases where copper and nickel are the main components, such as in waste lithium-ion batteries (LIBs), copper and nickel have the property of melting uniformly across the entire composition range. Therefore, even with slow cooling, the copper and nickel only solidify in layers, and separation is not possible.

[0010] Furthermore, there is a purification method that uses carbon monoxide (CO) gas to disproportionate nickel, causing it to volatilize and separate from copper and cobalt. However, this method uses toxic CO gas, making it difficult to ensure safety.

[0011] Another industrially employed method for separating copper and nickel involves the rough separation of a mixed matte (sulfide). In this method, a matte containing copper and nickel is generated during the smelting process, and this is slowly cooled, similar to the method described above, to separate it into a sulfide rich in copper and a sulfide rich in nickel. However, even with this separation method, the separation of copper and nickel is only rough, and further processing such as electrolytic refining is required to obtain high-purity nickel and copper.

[0012] Other methods, such as utilizing the vapor pressure difference via chlorides, have also been considered. However, this process involves handling large quantities of toxic chlorine, requiring extensive measures to prevent corrosion and ensure safety, making it difficult to consider it an industrially suitable method.

[0013] Thus, dry processing for elemental separation and purification has the disadvantage of either remaining at a crude separation level or being highly costly.

[0014] On the other hand, wet smelting methods (hereinafter also referred to as "wet methods") that use acid treatment, neutralization treatment, solvent extraction treatment, etc., have the advantage of consuming less energy and being able to separate mixed valuable components individually and recover them with high purity.

[0015] However, when waste lithium-ion batteries (LIBs) are treated using wet processes, the electrolyte components contained in the waste LIBs, such as hexafluoride anions, are difficult to treat and cannot be completely decomposed even with high temperatures and high concentrations of sulfuric acid, and end up contaminating the acidic solution from which the valuable components have been leached. Since hexafluoride anions are water-soluble carbonate esters, it is also difficult to recover phosphorus and fluorine from the aqueous solution after the valuable components have been recovered, and various measures must be taken to suppress their release into public sea areas, etc., resulting in significant environmental constraints.

[0016] Furthermore, it is not easy to obtain a solution that can efficiently extract valuable components from waste lithium-ion batteries (LIBs) using only acid for purification. In particular, the waste LIB body itself is difficult to extract with acids, and it is not easy to completely extract the valuable components. Moreover, if extraction is forcibly carried out using strong oxidizing acids, impurities such as aluminum, iron, and manganese, which are not industrially targeted for recovery, will also be extracted along with the valuable components. This increases the cost of neutralizing agents used to treat the impurities, and leads to problems such as increased wastewater and sediment volume. In addition, waste LIBs may retain electrical charges, and attempting to process them as is may cause overheating or explosions, requiring extra effort to discharge the residual charges.

[0017] Thus, using only wet processing to treat waste lithium-ion batteries was not necessarily an advantageous method.

[0018] Therefore, attempts have been made to combine dry and wet treatments to address the difficulties in processing waste LIBs using either the dry or wet treatments described above. Specifically, these methods involve removing as many impurities as possible through dry treatment, such as roasting the waste LIBs, to obtain a homogeneous waste LIB treatment material, and then separating the resulting treatment material into valuable components and other components through wet treatment.

[0019] In this method, which combines dry and wet processing, fluorine and phosphorus in the electrolyte are removed by volatilization during the dry processing, and organic materials such as plastics and separators, which are structural components of waste lithium-ion batteries (LIBs), are decomposed by heat. Furthermore, since the waste LIB material obtained through dry processing has uniform properties, it is easy to handle as a uniform raw material during wet processing.

[0020] However, simply combining dry and wet processing methods still leaves the problem of recovery losses, where cobalt contained in waste lithium-ion batteries is distributed into the slag.

[0021] For example, by adjusting the processing conditions in dry processing, a method of reducing and melting to efficiently distribute cobalt into metal rather than slag and reduce the distribution into slag is also conceivable. However, the metal obtained by such a method becomes a poorly soluble corrosion-resistant alloy containing nickel and cobalt based on copper. Even if an attempt is made to separate and recover valuable components from this corrosion-resistant alloy by wet processing, acid dissolution becomes difficult and effective recovery cannot be achieved.

[0022] When using, for example, chlorine gas to leach the corrosion-resistant alloy, the resulting dissolution solution (leachate) comes to contain high-concentration copper and relatively low-concentration nickel and cobalt. Among them, although nickel and cobalt can be easily separated using known methods such as solvent extraction, it is particularly difficult to easily and at low cost separate copper from nickel and cobalt.

[0023] The recovery of valuable metals from waste LIBs has attracted attention as an effective utilization of urban mines, and in recent years, active development has been carried out. However, as described above, in existing wet processing methods, the concentrations of nickel and cobalt in a solution containing nickel and / or cobalt obtained from an alloy derived from waste LIBs or the like are low, and there is a problem that the concentration and purification of the resulting solution are costly.

[0024] In addition, the above-described problems similarly exist when separating nickel and / or cobalt and copper from waste batteries other than waste LIBs, and further similarly exist when separating nickel and / or cobalt and copper from alloys derived from sources other than waste batteries.

Prior Art Documents

Patent Documents

[0025]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0026] The present invention has been proposed in view of such circumstances, and an object thereof is to provide a method for efficiently obtaining a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt and copper, such as a used lithium-ion battery.

Means for Solving the Problems

[0027] As a result of intensive studies by the present inventors, it has been found that by adjusting the initial concentration of a slurry containing an alloy containing nickel and / or cobalt and copper to a specific range and performing leaching treatment, a solution containing nickel and / or cobalt at a high concentration can be obtained. Further, preferably, the leaching treatment is performed while controlling the redox potential (reference electrode: silver / silver chloride electrode) within a specific range, and preferably, by performing the leaching treatment with a sulfiding agent coexisting in an amount within a specific range with respect to the amount of copper contained in the alloy, it has been found that nickel and / or cobalt can be leached more efficiently and effectively. Specifically, the present invention provides the following.

[0028] (1) The first invention of the present invention is a method for treating an alloy to obtain a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt and copper, comprising a leaching step of subjecting a slurry containing the alloy to leaching treatment with an acid solution in a state where a sulfiding agent coexists to obtain a leachate and a leaching residue, wherein in the leaching step, the initial concentration of the slurry containing the alloy is adjusted to 100 g / L or more and 250 g / L or less and the leaching treatment is performed.

[0029] (2) The second invention of the present invention is a method for treating an alloy according to the first invention, wherein in the leaching step, the leaching treatment is performed while controlling the redox potential (with the reference electrode being a silver / silver chloride electrode) to 200 mV or less.

[0030] (3) The third invention of the present invention is a method for treating an alloy according to the first or second invention, wherein in the leaching step, the sulfiding agent coexists in an amount in the range of 1.05 to 1.25 equivalents (S-mol / Cu-mol) with respect to the amount of copper contained in the alloy and the leaching treatment is performed.

[0031] (4) The fourth invention of the present invention is a method for treating an alloy, further comprising a reduction step in any of the first to third inventions, in which a reducing agent is added to the leaching solution obtained through the leaching step to perform a reduction treatment to obtain a post-reduction solution and a reduction residue.

[0032] (5) The fifth invention of the present invention is an alloy treatment method that further includes an oxidation neutralization step, in any of the first to third inventions, in which a neutralizing agent and an oxidizing agent are added to the reducing solution obtained through the reduction step to perform an oxidation neutralization treatment to obtain an oxidation neutralized solution and an oxidation neutralization residue.

[0033] (6) The sixth invention of the present invention is a method for processing an alloy, wherein the alloy in any of the first to fifth inventions includes an alloy obtained by melting down a used lithium-ion battery. [Effects of the Invention]

[0034] According to the present invention, nickel and / or cobalt can be efficiently and selectively leached from alloys containing nickel and / or cobalt and copper, such as waste lithium-ion batteries, and a solution containing nickel and / or cobalt at a high concentration can be obtained. [Brief explanation of the drawing]

[0035] [Figure 1] This is a process diagram showing an example of a method for processing alloys. [Modes for carrying out the invention]

[0036] The following describes in detail specific embodiments of the present invention (hereinafter referred to as "these embodiments"). It should be noted that the present invention is not limited in any way to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In this specification, the notation "X~Y" (where X and Y are arbitrary numerical values) means "X or greater and Y or less".

[0037] The alloy processing method according to this embodiment is a method for obtaining a solution containing nickel and / or cobalt from an alloy containing nickel and / or cobalt and copper.

[0038] The alloy to be processed, which contains nickel and / or cobalt and copper, can be, for example, waste materials resulting from the deterioration of automobiles and electronic equipment, lithium-ion battery scrap generated at the end of the lithium-ion battery's lifespan, or defective batteries from the battery manufacturing process. Alternatively, an alloy obtained by reducing such waste batteries by heating and melting them in a dry process can be used.

[0039] The following section will explain in more detail the processing method for alloys (alloys containing nickel and / or cobalt and copper) obtained by melting down used lithium-ion batteries (hereinafter also referred to as "used lithium-ion batteries"), using this as an example.

[0040] Figure 1 is a process diagram showing an example of the flow of the alloy processing method according to this embodiment. This method comprises: a leaching step S1 in which an alloy containing nickel and / or cobalt and copper is subjected to a leaching treatment with an acid solution in the presence of a sulfidizing agent to obtain a leached liquid and a leached residue; a reduction step S2 in which a reducing agent is added to the obtained leached liquid to perform a reduction treatment to obtain a reduced liquid and a reduced residue; and an oxidation neutralization step S3 in which a neutralizing agent and an oxidizing agent are added to the obtained reduced liquid to perform an oxidation neutralization treatment to obtain an oxidation neutralized liquid and an oxidation neutralization residue.

[0041] In particular, the method according to this embodiment is characterized in that, in the leaching step S1, the initial concentration of the slurry containing the alloy is adjusted to a specific range, specifically between 100 g / L and 250 g / L, and the leaching treatment is performed. This allows for efficient leaching of nickel and / or cobalt, and a solution containing nickel and / or cobalt at a high concentration can be obtained.

[0042] Preferably, in the leaching step S1, the leaching treatment is performed while controlling the oxidation-reduction potential (ORP) to 200 mV or less using the silver / silver chloride electrode as the reference electrode. This suppresses the formation of an oxide film (passivation film) on the alloy surface, allowing for more selective leaching of nickel and / or cobalt.

[0043] Preferably, in the leaching step S1, the amount of sulfiding agent is added in a specific range, i.e., 1.05 to 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy, and the leaching treatment is carried out. This makes it possible to leach nickel and / or cobalt more efficiently, in a short time, and easily, and to obtain a solution containing nickel and / or cobalt at a high concentration.

[0044] (1) Leaching process [Regarding leaching treatment] In the leaching process S1, an alloy containing nickel and / or cobalt and copper (hereinafter also simply referred to as "alloy") is subjected to an acid leaching treatment. At this time, a sulfiding agent is added before contacting the alloy with the acid, or simultaneously with contacting the alloy with the acid, and the leaching treatment is carried out under conditions in which the sulfiding agent is present. Through this leaching treatment, a leaching solution containing dissolved nickel and / or cobalt and a leaching residue mainly containing copper sulfide are obtained.

[0045] The reactions that occur during the leaching process S1 are shown in the following reaction equations [1] to [5]. The following equations show the case where solid sulfur (S) is used as the sulfurizing agent and sulfuric acid is used as the acid. ·Cu+S → CuS ···[1] • Ni + H2SO4 + 1 / 2O2 → NiSO4 + H2O • [2] ·Co+H2SO4+1 / 2O2→ CoSO4+H2O ···[3] ·H2S+1 / 2O2→ S+H2O ···[4] CuS + 2O2 → CuSO4···[5]

[0046] By subjecting an alloy to a leaching treatment in the presence of both an acid and a sulfiding agent, the copper leached from the alloy reacts with the sulfiding agent and precipitates as copper sulfide (reaction equation [1]). The precipitated copper sulfide is recovered as a leaching residue. On the other hand, leaching treatment using acid also leaches nickel and / or cobalt, which constitute the alloy, into the solution, yielding a leaching solution in which nickel and cobalt exist as ions (reaction equations [2], [3]). In this way, copper and nickel and / or cobalt can be separated from the alloy.

[0047] Furthermore, even if the leached nickel and / or cobalt react with the sulfidating agent to form sulfides, the presence of the acid solution decomposes these sulfides, leaving the nickel and cobalt as ions in the leachate. In addition, some copper that did not react with the sulfidating agent may remain in the leachate, but this remaining copper can be effectively and efficiently separated and removed in the reduction step S2 described later.

[0048] [Regarding the alloy to be processed] The alloys to be processed, i.e., alloys obtained by melting waste lithium-ion batteries, can be alloys cast in the form of plates, alloys drawn into wires and cut into rods, or powdered alloys (hereinafter, powdered alloys will also be referred to as "alloy powder"), and their shape is not particularly limited. Among these, using powdered alloy powder as the target of processing is preferable because it allows for more effective and efficient leaching treatment.

[0049] Furthermore, when using alloy powder, a particle size of approximately 300 μm or less allows for more effective leaching. On the other hand, if the particle size of the alloy powder is too fine, it becomes costly and can cause dust generation or ignition, so a particle size of approximately 10 μm or larger is preferable.

[0050] In the leaching process, it is preferable to pre-clean the alloy to be treated with a dilute acid. This allows the alloy surface to be activated, thereby promoting the leaching reaction.

[0051] Furthermore, in the leaching treatment, the alloy to be treated is mixed with pure water or the like to form a slurry, and then an acid solution is added to the slurry containing the alloy to perform the treatment. The sulfiding agent is added to the slurry containing the alloy and allowed to coexist with it.

[0052] [About acid solutions] The acid solution used for the leaching treatment is not particularly limited, and mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid can be used. A mixed solution of these mineral acids may also be used. Furthermore, an acid solution containing chloride in sulfuric acid, for example, may be used. In particular, when the alloy to be treated is derived from waste lithium-ion batteries, it is preferable to use an acid containing sulfuric acid in order to realize the so-called "battery-to-battery" method, which is an ideal recycling method in which the waste lithium-ion batteries are recycled and used again as raw materials for lithium-ion batteries. By using sulfuric acid, the leaching solution can be obtained in the form of sulfates that are easy to use as cathode materials for lithium-ion batteries.

[0053] Furthermore, the added acid solution leaches out nickel and / or cobalt contained in the alloy to produce nickel and cobalt salts. However, an excess of free acid (for example, "free sulfuric acid" if a sulfuric acid solution is used) is also needed to act as a driving force to rapidly advance the leaching reaction. Therefore, an amount greater than 1 equivalent and less than or equal to 1.2 equivalents is required.

[0054] In the leaching process, the acid solution and the alloy may be supplied to a device consisting of multiple stages of mixing sections, such as a thickener, and the acid and alloy may be brought into contact in a countercurrent manner in stages. For example, the alloy may be supplied to the uppermost mixing section of the device, and the acid to the lowermost mixing section, bringing the acid and alloy into contact in a countercurrent manner in stages.

[0055] [About sulfiding agents] Sodium hydrosulfide or elemental sulfur can be used as the sulfiding agent added along with the acid. When using elemental sulfur, it is preferable to pulverize it appropriately to facilitate the reaction.

[0056] In the method according to this embodiment, preferably, the sulfiding agent is added in an amount in the range of 1.05 to 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy, and the alloy is allowed to coexist with the sulfiding agent while undergoing leaching treatment. This makes it possible to further improve the leaching rate of nickel and / or cobalt.

[0057] Sulfidating agents are used to fix all the copper in the alloy as copper sulfide and to efficiently and selectively leach nickel and cobalt. Therefore, an amount of at least 1 equivalent (S-mol / Cu-mol) of sulfidating agent relative to the amount of copper in the alloy is required. Furthermore, since a larger amount of sulfidating agent is advantageous for efficiently promoting the sulfidation reaction, an amount of 1.05 equivalents or more is preferable. On the other hand, adding an excessive amount of sulfidating agent may generate hydrogen sulfide gas, which should be avoided, and may also increase the amount of residue, making handling more difficult. From these perspectives, the upper limit for the amount of sulfidating agent should be 1.25 equivalents or less.

[0058] Furthermore, it is more preferable that the amount of sulfiding agent added be in the range of 1.15 to 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy. More preferably, by adding such an amount of sulfiding agent and performing the leaching treatment in its presence, the leaching rate of nickel and / or cobalt can be further improved.

[0059] [Conditions for leaching treatment] (Slurry concentration) The method according to this embodiment is characterized by adjusting the initial concentration of a slurry containing an alloy containing nickel and / or cobalt to a specific range, and then adding an acid solution to the slurry to perform a leaching treatment. Specifically, the initial concentration of the alloy slurry is adjusted to 100 g / L or more, preferably 150 g / L or more, and more preferably 200 g / L or more, and then the leaching treatment is performed.

[0060] As a result of our investigations, we found that the initial concentration of the alloy-containing slurry is an important factor that affects, for example, the stirring power of the reaction equipment, the rate of addition of the acid solution, and the leaching time when performing the leaching treatment. In the method according to this embodiment, by adjusting the initial concentration of the slurry to a specific range of 100 g / L or more and performing the leaching treatment, nickel and / or cobalt can be efficiently leached out, and a solution containing high concentrations of nickel and / or cobalt can be obtained quickly and easily.

[0061] While there is no particular upper limit to the initial slurry concentration, it is preferable that it be 250 g / L or less. If the slurry concentration exceeds 250 g / L, the time required for leaching will increase, necessitating measures such as strengthening the stirring capacity or increasing the amount of acid solution added to shorten the leaching time. Furthermore, if the acid concentration is too high, the acid may react violently in localized areas, potentially generating hydrogen gas or hydrogen sulfide gas. In addition, if the slurry concentration is too high, the alloy content will be too high, making it difficult to effectively stir during the leaching reaction, which may reduce the leaching rate. Moreover, wear and tear on stirring equipment and reaction vessels may occur during the reaction, leading to increased processing costs.

[0062] The method for slurrying the nickel and / or cobalt alloy to be processed, and the method for adjusting its concentration, are not particularly limited. For example, this can be done by adding pure water or the like to the alloy and adjusting the amount added.

[0063] (pH) Furthermore, during the leaching process, it is preferable to measure the pH of the resulting leached solution and monitor and control the measured pH. As nickel and cobalt metals dissolve in the acid during the leaching process, the pH increases as the acid is consumed. Therefore, it is preferable to perform the process while appropriately controlling the pH conditions within a range that promotes the leaching reaction of valuable metals.

[0064] Specifically, regarding pH conditions, it is preferable to control the treatment so that the pH of the resulting leachate is within the range of 0.8 to 1.6. By performing the leaching treatment within this range, leaching is promoted, and the situation in which the precipitated copper sulfide is excessively oxidized and redissolved can be more effectively suppressed.

[0065] pH can be controlled by adjusting the amount of acid added. A suitable guideline for the amount of acid added to reach the reaction endpoint is approximately 1.2 equivalents relative to the total amount of nickel and / or cobalt contained in the alloy.

[0066] (Redox potential) Furthermore, during the leaching process, it is preferable to measure the oxidation-reduction potential (ORP) of the resulting leachate and monitor and control the measured ORP.

[0067] Specifically, in the method according to this embodiment, preferably, the ORP is controlled to 200 mV or less using a silver / silver chloride electrode as the reference electrode while performing the leaching treatment.

[0068] In this process, the alloy being treated tends to form an oxide film in solutions containing oxidizing agents or dissolved oxygen, such as in acid-based leaching. When an oxide film forms on the alloy, even if nickel and / or cobalt, which are the target of recovery, remain in the alloy, leaching may not proceed sufficiently, and only the ORP value of the leaching solution increases, resulting in what is known as passivation. As the ORP increases, the leaching of copper is also promoted, and this becomes a significant factor.

[0069] Therefore, in the method according to this embodiment, it is preferable to perform the leaching treatment while controlling the ORP within a specific range, specifically controlling the ORP to 200 mV or less using a silver / silver chloride electrode as the reference electrode. For example, by reducing the supply amount of oxidizing agent, the ORP value can be kept low at 200 mV or less, thereby effectively suppressing the formation of an oxide film (passivation film) on the alloy being treated.

[0070] In this way, by preferably maintaining an ORP lower than conventionally and performing the leaching treatment, the formation of a passivation film on the alloy surface can be suppressed, and the leaching of nickel and / or cobalt can be carried out more efficiently and effectively. At the same time, the reaction between copper and the sulfiding agent proceeds more smoothly, copper can be efficiently immobilized as a sulfide, and it becomes possible to suppress the leaching of copper and more selectively leach nickel and / or cobalt.

[0071] While there are no particular limitations on the lower limit of ORP, it is preferably 50mV or higher, and more preferably 100mV or higher. If the ORP is too low, the rate of the nickel and / or cobalt leaching reaction may decrease. In addition, nickel and / or cobalt sulfides may begin to form, potentially resulting in recovery loss.

[0072] Specific means of controlling ORP include adding an oxidizing agent. In the method according to this embodiment, since the ORP is preferably controlled to 200 mV or less, if the ORP of the leachate rises too high, the ORP can be reduced by reducing or stopping the supply of the oxidizing agent.

[0073] Conventional known oxidizing agents such as oxygen, air, hydrogen peroxide, and ozone gas can be used. For example, when using a gaseous oxidizing agent, the ORP of the leachate can be controlled by bubbling it into the solution and adjusting the supply amount (aerosol volume).

[0074] Furthermore, since ORP fluctuates with pH and temperature, it is preferable to simultaneously measure ORP, pH, and liquid temperature during the leaching process and control them to maintain their respective appropriate ranges at the same time.

[0075] (Other conditions) Furthermore, it is preferable to determine appropriate ranges for conditions such as temperature and time during the leaching process by conducting preliminary tests. In addition, the leaching solution may be bubbling with air or the like during the leaching process to ensure a uniform reaction. Moreover, divalent copper ions may be added during the leaching process, as these ions act as a catalyst to accelerate the leaching reaction.

[0076] [Reduction Process] In the reduction step S2, a reducing agent is added to the leachate obtained in the leaching step S1 to perform a reduction treatment, thereby obtaining a reduced solution (post-reduction solution) containing nickel and / or cobalt and a reduction residue.

[0077] In the leaching process, copper, which constitutes the alloy along with nickel and / or cobalt, leaches out with the acid and dissolves in the solution, but some of it may remain in the solution without reacting with the sulfidating agent. Therefore, in the reduction step S2, a precipitate containing copper can be generated by reducing the trace amount of copper remaining in the obtained leaching solution. By separating the reduced residue containing the generated precipitate by solid-liquid separation, a reduced solution containing nickel and / or cobalt from which copper has been separated can be obtained. This allows for the selective separation of copper while maintaining a high leaching rate of nickel and / or cobalt.

[0078] The reducing agent is not particularly limited, but for example, a metal less noble than copper can be used. Among these, it is preferable to use a metal containing nickel and / or cobalt and reduce the copper by bringing the leaching solution into contact with the metal. More specifically, as the metal containing nickel and / or cobalt, an alloy containing nickel and / or cobalt and copper, which is the target of the treatment in the method according to this embodiment, i.e., the target of the leaching treatment in leaching step S1, can be used. Note that the reducing agent is not limited to one component, but may be a mixture of multiple components.

[0079] In the method according to this embodiment, since a solution containing nickel and / or cobalt is obtained, using the nickel and / or cobalt-containing metal, which is the target of recovery, as a reducing agent eliminates the need to separately recover the reducing agent in a later step, which is industrially advantageous. Furthermore, the nickel and / or cobalt-containing metal used as a reducing agent is oxidized and dissolves in the reduced solution, thus increasing the amount of nickel and / or cobalt recovered.

[0080] In addition to the metals mentioned above, sulfides can also be used as reducing agents. The sulfides may be in solid, liquid, or gaseous form. Alternatively, a mixture of sulfur and the powdered alloy being treated in the leaching process described above may be used. When using sulfur as a reducing agent, an amount equivalent to the amount of copper contained in the treatment solution or the powdered alloy should be added.

[0081] Alternatively, atomized powder obtained by rapidly cooling the molten alloy to be treated may be used as a reducing agent. When using the powdered alloy itself as a reducing agent, it is sufficient to use a powder containing an amount of nickel and cobalt equal to or greater than the equivalent amount necessary to reduce the copper in the leaching solution.

[0082] Regarding the conditions for the reduction treatment, it is preferable to control the pH of the resulting reduced solution to 1.6 or less. Furthermore, it is preferable to maintain the solution temperature at 50°C or higher, similar to that of the leaching treatment. The endpoint (reaction endpoint) where copper is removed can be determined by the point when the ORP becomes 0 mV or less.

[0083] [Oxidation neutralization process] In the method according to this embodiment, an oxidation neutralization step S3 can be provided. In the oxidation neutralization step S3, a neutralizing agent and an oxidizing agent are added to the reducing solution obtained through the reduction step S2 to perform an oxidation neutralization treatment, thereby obtaining an oxidation neutralization solution and an oxidation neutralization residue.

[0084] In this way, by performing an oxidation-neutralization treatment, impurities such as iron and phosphorus contained in the reducing solution are precipitated and separated, and a purified solution containing high concentrations of nickel and / or cobalt can be obtained.

[0085] It is preferable to use an oxidizing agent such as hydrogen peroxide or hypochlorous acid. When adding the oxidizing agent, it is preferable to monitor the oxidation-reduction potential (ORP) of the solution and control it to a predetermined range. Specifically, the oxidizing agent is added to the solution and controlled, for example, so that the ORP (using silver / silver chloride as the reference electrode) is in the range of 380mV to 430mV.

[0086] Furthermore, after adding an oxidizing agent to induce an oxidation reaction, a neutralizing agent is added to control the pH of the solution, preferably within the range of 3.8 to 4.5. By controlling the pH within this range and performing neutralization treatment, impurities such as iron and / or phosphorus can be effectively precipitated.

[0087] While not particularly limited, it is preferable to use an alkali such as sodium hydroxide or potassium hydroxide as a neutralizing agent.

[0088] In oxidation-neutralization treatment, the oxidizing agent may be added to the reducing solution after the neutralizing agent has been added, or the oxidizing agent and neutralizing agent may be added to the reducing solution simultaneously. In particular, it is preferable to add the neutralizing agent after the oxidizing agent has been added to the reducing solution. For example, if the oxidizing agent is added to a reducing solution whose pH has become high due to the addition of the neutralizing agent, the iron may not be sufficiently oxidized if it contains iron as an impurity, and a precipitate of Fe(OH)3 (iron precipitate) may not be formed, resulting in insufficient separation of impurities.

[0089] Furthermore, any trace impurities that could not be removed by the oxidation-neutralization treatment may be removed by a step after the oxidation-neutralization step S3 using known techniques such as solvent extraction or ion exchange. [Examples]

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0091] [Example 1] (Leaching process) Waste lithium-ion batteries (waste LIBs) were subjected to oxidative roasting by heating them in an oxidizing atmosphere. Subsequently, a reducing agent was added to the resulting oxidative roasted material, and the material was heated and melted in a dry process to reduce it. The molten alloy obtained by reduction and melting was solidified to obtain a powdered alloy with a particle size of less than 300 μm. This alloy powder was used as the target alloy (an alloy containing nickel, cobalt, and copper). Table 1 below shows the composition of the alloy powder as analyzed using an ICP analyzer.

[0092] [Table 1]

[0093] Next, using the alloy powders with the composition shown in Table 1 above, leaching with a sulfuric acid solution was performed under the conditions shown in Table 2 below.

[0094] Specifically, a slurry containing the alloy was prepared by charging pure water and alloy powder into a 500 mL baffled separable flask. At this time, the concentration (initial concentration) of the slurry was set to 200 g / L.

[0095] To the alloy slurry, elemental sulfur was added as a sulfidating agent in an amount of 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy powder. The mixture was then heated in a water bath to a set temperature of 60°C while being stirred at a rotational speed of 1000 rpm.

[0096] Then, a 70% sulfuric acid solution was added at a rate of 14 mL / hr, and the alloy was leached while controlling the pH to maintain 1.6.

[0097] The oxidation-reduction potential (ORP) value (reference electrode: silver / silver chloride electrode) was adjusted by air bubbling at a flow rate of 0.5 L / min. The reaction endpoint was defined as the point when the ORP value reached 250 mV.

[0098] The slurry after leaching was collected, and solid-liquid separation was performed by filtration using a vacuum pump. The quality of the filtrate (leachate) and leaching residue after leaching was analyzed using an ICP analyzer.

[0099] [Example 2] In Example 2, the process was carried out in the same manner as in Example 1, except that the slurry concentration (initial concentration) was set to 100 g / L.

[0100] [Conditions and Results] Table 2 below summarizes the leaching conditions for Example 1 and Example 2. Table 3 below shows the analysis results of the leached liquid and leached residue for Example 1 and Example 2.

[0101] [Table 2]

[0102] [Table 3]

[0103] As shown in the results in Table 3, nickel and cobalt were leached with high leaching rates in both Example 1 and Example 2. Furthermore, from the results of Example 2 compared to Example 1, it was found that the concentration of nickel and cobalt in the resulting leached solution could be increased by increasing the concentration of the slurry used in the leaching treatment.

[0104] [Example 3] (Leaching process) Waste lithium-ion batteries (waste LIBs) were subjected to oxidative roasting by heating them in an oxidizing atmosphere. Subsequently, a reducing agent was added to the resulting oxidative roasted product, and it was heated and melted to perform a dry reduction process. The molten alloy obtained by reduction melting was solidified to obtain a powdered alloy with a particle size of less than 300 μm. The obtained alloy powder was used as the alloy to be treated (an alloy containing nickel, cobalt, and copper). Table 4 below shows the composition of the alloy powder as analyzed using an ICP analyzer.

[0105] [Table 4]

[0106] Next, using the alloy powders with the compositions shown in Table 4 above, leaching with a sulfuric acid solution was performed under the conditions shown in Table 5 below.

[0107] Specifically, a slurry containing the alloy was prepared by charging pure water and alloy powder into a 500 mL baffled separable flask. At this time, the concentration (initial concentration) of the slurry was set to 200 g / L.

[0108] To the alloy slurry, elemental sulfur was added as a sulfidating agent in an amount of 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy powder. The mixture was then heated in a water bath to a set temperature of 60°C while being stirred at a rotational speed of 1000 rpm.

[0109] The oxidation-reduction potential (ORP) value (reference electrode: silver / silver chloride electrode) was adjusted by air bubbling at a flow rate of 0.5 L / min using a cylindrical gas nozzle. In addition, the leaching of the alloy powder and pH adjustment were controlled by adding a 70% sulfuric acid solution at a rate of 14 mL / min to maintain a pH of 1.0.

[0110] In Example 3, the leaching reaction was carried out while controlling the airflow rate to maintain the ORP value below 200mV. Even after stopping the airflow when the predetermined reaction was deemed complete, the ORP value rose slightly, but the reaction was terminated when it reached 250mV.

[0111] The slurry after leaching was collected, and solid-liquid separation was performed by filtration using a vacuum pump. The quality of the filtrate (leachate) and leaching residue after leaching was analyzed using an ICP analyzer.

[0112] [Comparative Example 1] In Comparative Example 1, air was supplied in the same manner as in Example 3, but no specific control was made regarding the ORP value; it was left to chance. Even after the air supply was stopped, the ORP value remained at approximately 250 mV. Other than this, the procedure was the same as in Example 3.

[0113] [Conditions and Results] Table 5 below summarizes the leaching treatment conditions for Example 3 and Comparative Example 1. Table 6 below shows the analysis results of the leached liquid and leached residue.

[0114] [Table 5]

[0115] [Table 6]

[0116] As shown in the results in Table 6, in Example 3, where the leaching treatment was performed while controlling the ORP value to remain below 200 mV, copper leaching was suppressed, and nickel and cobalt leaching was selectively promoted. In contrast, in Comparative Example 1, the copper concentration in the leaching solution was high at 16 g / L, and nickel and cobalt could not be selectively leached.

[0117] Thus, it was found that controlling the ORP to 200mV or less during leaching can promote the leaching of nickel and cobalt. This is thought to be because controlling the ORP suppressed the formation of an oxide film (passivation film) on the surface of the alloy being treated.

[0118] [Example 4] (Leaching process) Waste lithium-ion batteries (waste LIBs) were subjected to oxidative roasting by heating them in an oxidizing atmosphere. Subsequently, a reducing agent was added to the resulting oxidative roasted product, and it was heated and melted to perform a dry reduction process. The molten alloy obtained by reduction melting was solidified to obtain a powdered alloy with a particle size of less than 300 μm. The obtained alloy powder was used as the alloy to be treated (an alloy containing nickel, cobalt, and copper). Table 7 below shows the composition of the alloy powder as analyzed using an ICP analyzer.

[0119] [Table 7]

[0120] Next, using the alloy powders with the compositions shown in Table 7 above, leaching with a sulfuric acid solution was performed under the conditions shown in Table 8 below.

[0121] Specifically, a slurry containing the alloy was prepared by charging pure water and alloy powder into a 500 mL baffled separable flask. At this time, the concentration (initial concentration) of the slurry was set to 200 g / L.

[0122] To the alloy slurry, elemental sulfur particles several millimeters in diameter were added as a sulfidizing agent in an amount of 1.05 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy powder. The mixture was then heated in a water bath to a set temperature of approximately 60°C while being stirred at a rotational speed of 1000 rpm.

[0123] Furthermore, the oxidation-reduction potential (ORP) value (reference electrode: silver / silver chloride electrode) was adjusted by air bubbling at a flow rate of 0.5 L / min, and the alloy was leached while adding 70% sulfuric acid solution at a rate of 14 mL / h, while controlling the pH to maintain 1.2.

[0124] The reaction endpoint was defined as the point at which the ORP value reached 250 mV.

[0125] The slurry after leaching was collected, and solid-liquid separation was performed by filtration using a vacuum pump. The quality of the filtrate (leachate) and leaching residue after leaching was analyzed using an ICP analyzer.

[0126] [Example 5] In Example 5, the treatment was carried out in the same manner as in Example 4, except that the amount of elemental sulfur added was set to 1.15 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy powder.

[0127] [Example 6] In Example 6, the treatment was carried out in the same manner as in Example 4, except that the amount of elemental sulfur added was set to 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy powder.

[0128] [Conditions and Results] Table 8 below summarizes the leaching treatment conditions for Examples 4 to 6. Table 9 shows the analysis results of the leached liquid and leached residue for each of Examples 4 to 6.

[0129] [Table 8]

[0130] [Table 9]

[0131] As shown in the results in Table 9, by adding 1.05 to 1.25 equivalents of sulfiding agent relative to the amount of copper in the alloy powder, nickel and cobalt could be efficiently leached out with a high leaching rate. In particular, in Examples 5 and 6, where the amount of sulfiding agent added was 1.15 equivalents or more, it is presumed that a sufficient amount was supplied for the fixation (sulfidation) of copper contained in the alloy, resulting in the leaching of nickel and cobalt progressing to 99%.

[0132] Furthermore, in Examples 5 and 6, where the amount of sulfurizing agent added was 1.15 equivalents or more, it was confirmed that the time it took for the ORP of the leachate to reach 250 mV was shortened compared to Example 4 (amount of sulfurizing agent added: 1.05 equivalents), indicating that the processing could be performed more efficiently.

Claims

1. A method for processing an alloy to obtain a nickel and / or cobalt-containing solution from an alloy containing nickel and / or cobalt and copper, The process includes a leaching step in which a slurry containing the aforementioned alloy is subjected to leaching treatment with an acid solution in the presence of a sulfidizing agent to obtain a leaching liquid and a leaching residue. In the leaching process, the initial concentration of the slurry containing the alloy is adjusted to 100 g / L or more and 250 g / L or less, and the leaching treatment is performed. Methods for processing alloys.

2. In the aforementioned leaching process, the leaching treatment is performed while controlling the oxidation-reduction potential (using a silver / silver chloride electrode as the reference electrode) to 200 mV or less. A method for treating the alloy according to claim 1.

3. In the leaching process, the sulfidizing agent is added in an amount ranging from 1.05 to 1.25 equivalents (S-mol / Cu-mol) relative to the amount of copper contained in the alloy, and the leaching treatment is performed. A method for treating an alloy according to claim 1 or 2.

4. The process further includes a reduction step in which a reducing agent is added to the leachate obtained through the leaching step to perform a reduction treatment, thereby obtaining a reduced liquid and a reduced residue. A method for treating the alloy according to claim 1.

5. The process further includes an oxidation neutralization step in which a neutralizing agent and an oxidizing agent are added to the reduced solution obtained through the reduction step to perform an oxidation neutralization treatment, thereby obtaining an oxidation neutralized solution and an oxidation neutralization residue. A method for treating the alloy according to claim 4.

6. The aforementioned alloy includes an alloy obtained by melting down used lithium-ion batteries. A method for treating the alloy according to claim 1.

7. The alloy comprises nickel and / or cobalt and copper in metallic form. A method for treating the alloy according to claim 1.

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