Methods for processing alloys

Abstract

The present invention provides a method that is capable of selectively obtaining nickel and / or cobalt from an alloy, which contains copper as well as nickel and / or cobalt, in a waste lithium ion battery or the like.　A method for processing an alloy according to the present invention comprises: a leaching step S1 in which an alloy that contains copper as well as nickel and / or cobalt is subjected to a leaching treatment by means of an acid solution in the coexistence of a sulfurizing agent, thereby obtaining a leachate and a leaching residue; and a reduction step S2 in which a reducing agent is added to the thus-obtained leachate so as to reduce the leachate, thereby obtaining a post-reduction solution and a reduction residue. This method for processing an alloy is characterized in that the reduction is carried out in the reduction step S2, while controlling the addition amount of the reducing agent so that the redox potential of the leachate is 0 mV or less as determined where a silver / silver chloride electrode is the reference electrode.

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 obtained by using a copper foil as a negative electrode current collector and fixing a negative electrode active material such as graphite on the surface inside an exterior can made of a metal such as aluminum or iron or a plastic such as vinyl chloride, and a positive electrode current collector made of an aluminum foil are filled 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 automobiles, electronic devices, etc. or the life of the LIB itself, etc., and become 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 melting can be considered, in which cobalt is efficiently distributed into metal rather than slag, thereby reducing its distribution into slag. 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 is difficult and effective recovery cannot be achieved.

[0022] When chlorine gas is used, for example, to leach the corrosion-resistant alloy, the resulting dissolution solution (leachate) contains high concentrations of copper and relatively low concentrations of 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 separate copper from nickel and cobalt easily and at low cost.

[0023] As described above, it has been difficult to efficiently separate nickel and / or cobalt from copper from alloys derived from waste LIBs and the like, which contain various components in addition to the valuable components nickel, cobalt, and copper.

[0024] In addition, the above-described problems similarly exist when separating nickel and / or cobalt from copper in waste batteries other than waste LIBs, and further similarly exist when separating nickel and / or cobalt from copper in 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 selectively obtaining nickel and / or cobalt from an alloy containing nickel and / or cobalt, copper, such as a used lithium-ion battery.

Means for Solving the Problems

[0027] As a result of intensive studies by the present inventors, after acid leaching the alloy to be treated in the coexistence of a sulfiding agent, a reducing agent is added to the obtained leachate so that its oxidation-reduction potential becomes a predetermined value or less, and reduction treatment is performed. It has been found that copper can be separated and nickel and / or cobalt can be selectively obtained, and the present invention has been completed.

[0028] (1) A first invention of the present invention is an leaching step of subjecting an alloy containing nickel and / or cobalt and copper to leaching treatment with an acid solution in a state where a sulfiding agent coexists to obtain a leachate and a leaching residue, and adding a reducing agent to the obtained leachate. A reduction step of performing a reduction treatment to obtain a post-reduction liquid and a reduction residue, and in the reduction step, the reduction treatment is performed by controlling the addition amount of the reducing agent so that the oxidation-reduction potential of the leachate becomes 0 mV or less with a silver / silver chloride electrode as a reference electrode. It is a method for treating an alloy.

[0029] (2) A second invention of the present invention is a method for treating an alloy according to the first invention, wherein in the reduction step, at least a part of the alloy used for the leaching treatment in the leaching step is used as the reducing agent to be added.

[0030] (3) A third invention of the present invention is a method for leaching and treating an alloy according to the first or second invention, wherein the reduction residue obtained by the treatment in the reduction step is subjected to the leaching treatment in the leaching step.

[0031] (4) A fourth invention of the present invention is a method for treating an alloy according to any one of the first to third inventions, wherein the alloy includes an alloy obtained by melting a used battery of a lithium-ion battery.

[0032] (5) The fifth invention of the present invention is a method for treating an alloy, wherein in the leaching step, an amount of the sulfurizing agent is present in the alloy in an amount of 1 equivalent or more and 1.25 equivalents or less relative to the copper contained in the alloy, and the leaching treatment is performed.

[0033] (6) The sixth invention of the present invention is a method for treating an alloy, wherein in the leaching step of any of the first to fifth inventions, the leaching treatment is performed so that the pH of the resulting leached liquid is in the range of 0.8 or more and 1.6 or less. [Effects of the Invention]

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

[0035] [Figure 1] This graph shows the change in oxidation-reduction potential (ORP, silver / silver chloride reference electrode) over time during the reduction treatment performed in the example. [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 the processing method for alloys in more detail, using the example of processing alloys obtained by melting down used lithium-ion batteries (hereinafter also referred to as "used lithium-ion batteries").

[0040] The method according to this embodiment comprises a leaching step S1 in which an alloy containing nickel and / or cobalt and copper is subjected to leaching treatment with an acid solution in the presence of sulfur to obtain a leaching solution and a leaching residue, and a reduction step S2 in which a reducing agent is added to the obtained leaching solution to perform a reduction treatment to obtain a post-reduction solution and a reduction residue.

[0041] [Leaching process] In leaching step S1, an alloy containing nickel and / or cobalt and copper is subjected to acid leaching. 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. This leaching treatment yields a leaching solution containing dissolved nickel and / or cobalt, and a leaching residue mainly containing copper sulfide.

[0042] 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]

[0043] Specifically, in the leaching process S1, the alloy is subjected to a leaching treatment in the presence of both acid and sulfiding agent. This allows the copper leached from the alloy to react with the sulfiding agent and precipitate as copper sulfide (reaction equation [1]). The precipitated copper sulfide is recovered as leaching residue. On the other hand, the leaching treatment using acid 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.

[0044] Furthermore, even if the leached nickel and / or cobalt react with the sulfidating agent to form sulfides, the presence of the acid solution causes these sulfides to decompose, 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. This remaining copper in the leachate can be effectively and efficiently separated and removed in the reduction step S2 described later.

[0045] The alloy to be processed, i.e., the alloy obtained by melting waste lithium-ion batteries, can be an alloy cast in the form of a plate, an alloy drawn into wires and cut as needed to form rods, etc., and its shape is not particularly limited. In particular, using powdered alloy (powdered material) as the target of processing is preferable because it allows for more effective and efficient leaching treatment.

[0046] When alloys are in powder form, a particle size of approximately 300 μm or less allows for more effective leaching. On the other hand, if the particle size 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 for alloy powders.

[0047] 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.

[0048] As the acid, hydrochloric acid, sulfuric acid, nitric acid, etc., can be used individually or in mixtures. Alternatively, sulfuric acid may be mixed with chlorides and used as the acid. When realizing the so-called "battery-to-battery" cycle, which is an ideal recycling method for reusing waste lithium-ion batteries as raw materials for lithium-ion batteries, it is preferable to use an acid containing sulfuric acid. By using sulfuric acid as the acid, the leachate can be obtained in the form of sulfates that are easily usable as positive electrode materials for lithium-ion batteries.

[0049] Furthermore, the amount of acid used should be at least 1 equivalent, preferably at least 1.2 equivalents, and more preferably between 1.2 and 5 equivalents, relative to the total amount of nickel and / or cobalt contained in the alloy. Increasing the acid concentration can increase the leaching reaction rate.

[0050] Furthermore, in the leaching process, the acid and alloy may be supplied to a device that has multiple stages of mixing sections connected together, 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 may be supplied to the lowermost mixing section of the device, bringing the acid and alloy into contact in a countercurrent manner in stages.

[0051] 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.

[0052] The amount of sulfiding agent added (coexisting amount) is preferably 1 equivalent or more relative to the amount of copper contained in the alloy. Furthermore, the amount of sulfiding agent added is preferably 1.5 equivalents or less, and more preferably 1.25 equivalents or less, relative to the amount of copper contained in the alloy. If too much sulfiding agent is added, it may not contribute to accelerating the reaction, but rather increase the amount of residue, making handling more difficult, and may also increase the possibility of hydrogen sulfide gas generation.

[0053] It is preferable to determine appropriate conditions such as temperature, time, and slurry concentration obtained by adding acid and sulfiding agents to the alloy through preliminary testing. Furthermore, the leaching solution may be bubbling with air or other means during the leaching process to ensure a uniform reaction. Additionally, divalent copper ions may be added during the leaching process, as these ions act as a catalyst to accelerate the leaching reaction.

[0054] In particular, during the leaching process, it is preferable to measure and control the oxidation-reduction potential (ORP) and pH of the resulting leached solution. Specifically, it is preferable to control the ORP so that it is in the range of 240mV to 280mV, based on the silver / silver chloride electrode. Furthermore, it is preferable to control the pH of the resulting leached solution so that it is in the range of 0.8 to 1.6. By performing the leaching process within these ranges, leaching is promoted, and the situation in which the precipitated copper sulfide is excessively oxidized and redissolved can be suppressed.

[0055] The endpoint of the leaching reaction can be determined based on the ORP of the leached liquid. For example, the endpoint of the nickel and / or cobalt leaching reaction can be determined when the ORP value stops decreasing without adding any new alloy to the reaction vessel.

[0056] Furthermore, after the leaching treatment of the alloy is completed, copper may re-leach out if the precipitated copper sulfide is oxidized. Therefore, it is preferable to maintain the ORP of the obtained leaching solution in the range of 240mV to 280mV until the leaching solution and copper sulfide are separated.

[0057] [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.

[0058] During leaching, copper, which constitutes the alloy along with nickel and / or cobalt, leaches out with the acid and dissolves in the solution, and some of it may remain in the solution without reacting with the sulfidating agent. For example, if the leaching process is carried out while controlling the ORP of the resulting leached solution to exceed 280mV, the leaching rate of nickel and / or cobalt will be high, but copper will also be leached out at the same time, making the leached solution more likely to contain copper. Similarly, if the leaching process is carried out while controlling the pH of the leached solution to be less than 0.8, the leaching rate of nickel and / or cobalt will be high, but copper will also be leached out at the same time, making the leached solution more likely to contain copper.

[0059] Therefore, in the reduction step S2, a copper-containing precipitate can be generated by reducing the trace amount of copper remaining in the obtained leachate. By separating the reduction residue containing the generated precipitate by solid-liquid separation, a reducing 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.

[0060] Furthermore, in this embodiment, the method is characterized by controlling the amount of reducing agent added so that the ORP (reference electrode: silver / silver chloride electrode) of the leachate becomes 0 mV or less, and then performing the reduction treatment. This makes it possible to more effectively reduce the copper remaining in the leachate, and to further reduce the copper concentration in the resulting reduced solution.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Furthermore, the alloy being 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 or cobalt equal to or greater than the equivalent amount necessary to reduce the copper in the leaching solution.

[0065] Regarding the conditions for the reduction treatment, it is preferable to control the pH of the resulting reduced solution to 1.6 or less, similar to the leachate. Furthermore, it is preferable to maintain the liquid temperature at 50°C or higher, the same as for the leachate treatment. The endpoint (reaction endpoint) where copper has been removed can be determined by the point when the ORP becomes 0 mV or less.

[0066] This reduction treatment yields a reducing solution containing nickel and / or cobalt, as well as a reduction residue. The resulting slurry can be separated and recovered by solid-liquid separation. The recovered reduction residue is mainly a copper-containing precipitate, but it may also contain some nickel and / or cobalt precipitated together with the copper. Therefore, the reduction residue obtained and recovered by the reduction treatment can be repeatedly subjected to the leaching treatment in leaching step S1. This allows the leaching treatment to be performed together with the newly treated alloy raw material, thereby suppressing the recovery loss of nickel and / or cobalt. [Examples]

[0067] 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.

[0068] [Example 1] (Leaching process) The alloy to be treated was a powdered alloy (powdered material) with a particle size of 300 μm or less, obtained by reducing and melting waste lithium-ion batteries (waste LIBs) in a dry process. The composition of the alloy is shown in Table 1 below.

[0069] [Table 1]

[0070] Specifically, 300 g / L of powdered alloy with the composition shown in Table 1 was used, and a sulfuric acid solution was added. In addition, sulfur (sulfidating agent) in an amount equivalent to 1.25 equivalents of copper in the powder was added, and a leaching treatment was performed. The liquid temperature was 60°C.

[0071] After the leaching treatment, the material was filtered to separate the filtrate (leachate) from the leaching residue. The resulting leached material was then analyzed using an ICP analyzer to determine the concentrations of each element. The analysis results are shown in Table 2 below. The leaching rates for both nickel and cobalt were 99%.

[0072] [Table 2]

[0073] (Reduction process) One liter of the obtained leachate was prepared, and 100 g of powder having a particle size of 1 μm to 300 μm and the composition shown in Table 1 above was added as a reducing agent. Furthermore, an amount of sulfur equal to 1.25 equivalents relative to the amount of copper in the powder and copper ions in the liquid was added, and the leachate was subjected to a reduction treatment.

[0074] Specifically, during the reduction treatment, the liquid temperature was maintained at 60°C, and the amount of reducing agent added was controlled to lower and maintain the oxidation-reduction potential (ORP, vs Ag / AgCl) until it reached 0mV. The reduced product obtained from this reduction treatment was separated into solid and liquid by filtration, and the reduced liquid and reduction residue were recovered. Figure 1 is a graph showing the change in ORP over time during the reduction treatment.

[0075] The concentrations of each element in the obtained reduced solution were measured using an ICP analyzer.

[0076] [Table 3]

[0077] As shown in Table 3, copper could be removed until the copper concentration was less than 0.01 g / L.

Claims

1. A leaching process in which an alloy containing nickel and / or cobalt and copper is subjected to leaching treatment with an acid solution in the presence of a sulfidizing agent to obtain a leaching solution and a leaching residue, The process includes a reduction step in which a reducing agent is added to the obtained leachate to perform a reduction treatment, thereby obtaining a post-reduction solution and a reduction residue. In the reduction step, the amount of reducing agent added is controlled so that the oxidation-reduction potential of the leachate is 0 mV or less, using a silver / silver chloride electrode as the reference electrode, and the reduction treatment is performed. Methods for processing alloys.

2. In the reduction step, at least a portion of the alloy subjected to the leaching treatment in the leaching step is used as the reducing agent to be added. A method for treating the alloy according to claim 1.

3. The reduction residue obtained by the processing in the reduction step, to be subjected to the leaching treatment in the leaching step, A method for treating the alloy according to claim 1.

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

5. In the leaching process, the sulfidizing agent is added in an amount equal to or greater than 1 equivalent and less than 1.25 equivalents relative to the copper contained in the alloy, and the leaching treatment is carried out in this manner. A method for treating the alloy according to claim 1.

6. In the aforementioned leaching process, the leaching treatment is performed so that the pH of the resulting leachate is in the range of 0.8 to 1.

6. A method for treating the alloy according to claim 1.

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