CN120882890A

CN120882890A - Methods for recycling valuable elements

Info

Publication number: CN120882890A
Application number: CN202480019028.1A
Authority: CN
Inventors: 长冈谅介; 山口东洋司; 日野雄太; 井上阳太郎; 木岛秀夫
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2023-04-28
Filing date: 2024-04-10
Publication date: 2025-10-31
Also published as: WO2024225035A1; JP7670248B2; JPWO2024225035A1

Abstract

A reducing agent containing metallic iron and/or iron oxide is added to an oxide containing a valuable element, which is Ni and/or Co and Mn, and an impurity element, which is copper and iron, in an amount of 1.5 equivalents or less to obtain a mixed oxide. The mixed oxide is heated to reduce the oxide, thereby obtaining a metal. And (3) contacting the metal with acid liquor to obtain leaching liquid. Adding a sulfidizing agent to the leaching solution to precipitate copper, thereby obtaining the leaching solution from which copper is removed as a copper removal solution. And adding an oxidizing agent to the copper removal solution to precipitate iron, thereby obtaining the copper removal solution from which iron has been removed as a valuable element solution containing the valuable element. Thus, a recovery method capable of removing impurity elements and selectively recovering valuable elements of Ni and Co can be provided.

Description

Recovery method of valuable element

Technical Field

The present invention relates to a method for recovering valuable elements.

Background

In recent years, demand for lithium ion batteries has rapidly increased due to the popularization of electric vehicles.

In particular, from the viewpoint of recent reduction in the amount of CO ₂ generated, it is considered that the demand for electric vehicles not using fossil fuel will be further increased in the future, and it is expected that the demand for lithium ion batteries will be further increased in the future.

In general, a positive electrode material of a lithium ion battery includes an oxide (composite oxide) containing nickel (Ni), cobalt (Co), manganese (Mn), and the like. Specific examples of the complex oxide include LiNiO ₂、LiCoO₂、LiMnO₂.

The metal elements such as Ni, co, and Mn are not so called as being rich worldwide.

Therefore, it is very advantageous from the viewpoint of effective utilization of resources to recover these metal elements (valuable elements) from the positive electrode material of the waste lithium ion battery.

The term "waste lithium ion battery" refers to waste lithium ion batteries (used products), defective lithium ion batteries (defective products generated during manufacturing processes of lithium ion batteries, etc.), and the like.

The lithium ion battery is composed of a combination of components such as a positive electrode material, a negative electrode material, and a separator, and further includes an electrolyte solution.

Therefore, when valuable elements are recovered from the positive electrode material of the waste lithium ion battery, pretreatment such as removal, pulverization, and crushing of the electrolyte is performed before recovery.

After such pretreatment, the positive electrode material is separated from the waste lithium ion battery, and then valuable elements are recovered from the separated positive electrode material.

As a process for recovering valuable elements, there is a dry process in which a positive electrode material is heated together with a reducing agent and reduced to produce valuable elements (for example, patent document 1).

Prior art literature

Patent literature

Patent document 1 Japanese patent application laid-open No. 2021-95628

Disclosure of Invention

Problems to be solved by the invention

In the dry treatment, the composite oxide (LiNiO ₂、LiCoO₂、LiMnO₂) is reduced to produce slag in addition to metals containing valuable elements (Ni, co, mn).

In this case, it is sometimes required to recover the Mn without reducing it as much as possible (without converting Mn to metal and leaving it in slag), and selectively converting Ni and Co to metal.

The metal obtained by the dry treatment may contain an impurity element in addition to valuable elements such as Ni and Co. Examples of the impurity element include copper (Cu) and iron (Fe) from waste lithium ion batteries.

When the metal obtained by the dry treatment is reused as a positive electrode material of a lithium ion battery, if the metal contains impurity elements (Cu and Fe), there is a possibility that battery performance may be deteriorated. Therefore, it is desirable to remove the impurity element as much as possible.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a recovery method of valuable elements that can remove impurity elements and can selectively recover Ni and Co.

Means for solving the problems

As a result of intensive studies, the inventors of the present application have found that the above-mentioned object can be achieved by adopting the following constitution, and have accomplished the present application.

Namely, the present invention provides the following [1] to [12].

[1] A method for recovering valuable elements, wherein a mixed oxide is obtained by adding a reducing agent containing at least 1 kind selected from the group consisting of metallic iron and ferric oxide to an oxide containing valuable elements and impurity elements in an amount of 1.5 equivalent or less, wherein the valuable elements are at least 1 kind selected from the group consisting of nickel and cobalt and manganese, wherein the impurity elements are copper and iron, and wherein the mixed oxide is heated to reduce the oxide to obtain a metal, wherein the metal is brought into contact with an acid solution to obtain a leachate containing the valuable elements and the impurity elements, wherein a sulfidizing agent is added to the leachate to precipitate copper as a copper sulfide, wherein the leachate from which copper has been removed is obtained as a copper removal solution, wherein an oxidizing agent is added to the copper removal solution to precipitate iron as an iron hydroxide, and wherein the copper removal solution from which iron has been removed is obtained as a valuable element solution containing the valuable elements.

[2] The method for recovering a valuable element as recited in the above [1], wherein the oxide is obtained from a spent lithium ion battery.

[3] The method for recovering a valuable element as described in the above [1] or [2], wherein the metal is powdered and then brought into contact with the acid solution.

[4] The method for recovering a valuable element according to any one of the above [1] to [3], wherein the temperature at which the mixed oxide is heated is 1450 ℃ or higher.

[5] The method for recovering a valuable element according to any one of the above [1] to [4], wherein the iron oxide is ferrous oxide.

[6] The method for recovering a valuable element according to any one of [1] to [5], wherein the reducing agent is at least 1 selected from the group consisting of dust (dust), scale, sludge (slip) and crushed iron (scrap).

[7] The method for recovering a valuable element according to any one of the above [1] to [6], wherein the metal obtained by heating the mixed oxide contains the valuable element and the impurity element.

[8] The method for recovering a valuable element according to any one of [1] to [7], wherein the acid solution contains an acid and an oxidizing agent for the acid solution, and the content of the oxidizing agent for the acid solution is 0.5% by volume or more with respect to the acid.

[9] The method for recovering a valuable element according to item [8], wherein the oxidizing agent for an acid solution is hydrogen peroxide.

[10] The method for recovering a valuable element according to any one of [1] to [9], wherein the amount of the sulfidizing agent added is 1.0 equivalent or more to copper contained in the leachate, and the pH of the leachate to which the sulfidizing agent is added is 3.0 or less when precipitating the copper sulfide.

[11] The method for recovering a valuable element according to any one of [1] to [10], wherein the oxidizing agent is an oxidizing agent A of at least 1 selected from the group consisting of air and ozone, or an oxidizing agent B of at least 1 selected from the group consisting of hydrogen peroxide, hypochlorous acid and potassium permanganate, the amount of the oxidizing agent A added to the copper removal solution is 0.1vvm or more, the amount of the oxidizing agent B added to the copper removal solution is 0.005 vol.% or more, and the pH of the copper removal solution to which the oxidizing agent is added is 3.0 to 7.0 when the iron hydroxide is precipitated.

[12] The method for recovering a valuable element according to item [11], wherein the temperature of the copper removal solution to which the oxidizing agent is added is10 ℃ or higher.

Effects of the invention

According to the present invention, a recovery method capable of removing impurity elements and selectively recovering valuable elements of Ni and Co can be provided.

Drawings

FIG. 1 is a flowchart showing an example of a valuable element collection method.

FIG. 2 is an Eilelmer plot (standard free energy change versus temperature plot).

FIG. 3 shows the potential-pH diagram of Cu and Ni (S-H ₂ O system).

FIG. 4 shows the potential-pH diagram of Fe and Ni (O ₂-H₂ O system).

Detailed Description

[ Method for recovering valuable element ]

In the method for recovering valuable elements of the present embodiment (also referred to as "the present recovery method" for convenience), the positive electrode material (oxide) of the waste lithium ion battery is subjected to dry treatment and wet treatment.

Fig. 1 is a flowchart showing an example of a valuable element recovery method.

The present recovery method is schematically described with reference to fig. 1.

In the dry treatment, a reducing agent described later is first added to the oxide (Ni, co, mn, cu, fe) to obtain a mixed oxide. In this case, a slag former to be described later may be added.

Next, the obtained mixed oxide is heated to reduce the oxide, thereby obtaining metal (Ni, co, cu, fe) and slag (Mn). The two are suitably separated.

The resulting metal is preferably powdered prior to wet treatment to yield a metal powder (Ni, co, cu, fe).

In the wet treatment, first, a metal (metal powder) is brought into contact with an acid solution to obtain a leachate (Ni, co, cu, fe) and a leaching residue. The two are suitably separated.

Next, a sulfidizing agent was added to the obtained leachate to precipitate copper sulfide (Cu) and obtain a copper removal solution (Ni, co, fe). The two are suitably separated.

Then, an oxidizing agent is added to the copper removal solution to precipitate iron hydroxide (Fe) to obtain a valuable element solution (Ni, co).

Thus, the impurity elements (Cu, fe) can be removed from the oxide, and Ni and Co, which are valuable elements, can be selectively recovered, separately from Mn, which is also a valuable element.

According to the recovery method, valuable elements can be easily recovered from the positive electrode material (oxide) of the waste lithium ion battery with high purity to such an extent that the valuable elements can be reused as a raw material of the lithium ion battery.

Next, the present recovery method will be described in more detail.

< Object of reduction (oxide) >

The object of reduction in the present recovery method is an oxide containing valuable elements, which are at least 1 kind selected from the group consisting of nickel (Ni) and cobalt (Co) and manganese (Mn), and impurity elements, which are copper (Cu) and iron (Fe), specifically, for example, a positive electrode material of a spent lithium ion battery. The positive electrode material (oxide) may further contain a quasi-valuable element as lithium (Li).

The waste lithium ion batteries are subjected to pretreatment such as removal of electrolyte, crushing, pulverizing, and sorting, thereby obtaining a positive electrode material (oxide).

< Addition of reducing agent (Mixed oxide acquisition) >)

First, a reducing agent is added to an oxide to be reduced, to obtain a mixed oxide as a mixture of the oxide and the reducing agent.

Findings obtained by the inventors of the present application

The positive electrode material of the lithium ion battery generally contains an oxide (composite oxide) such as LiNiO ₂、LiCoO₂、LiMnO₂.

In the case of dry treatment in terms of thermodynamics, for example, liNiO ₂ and LiCoO ₂ undergo the following decomposition at high temperatures to produce NiO and CoO, respectively.

2LiNiO₂→Li₂O+2NiO+1/2O₂

2LiCoO₂→Li₂O+2CoO+1/2O₂

The standard free energy changes (Δg ⁰) in the decomposition reactions of NiO and CoO are shown below, respectively.

NiO→Ni+1/2O₂：ΔG⁰=234900-84.68T[J]

CoO→Co+1/2O₂：ΔG⁰=235480-71.55T[J]

At any temperature of high temperature, a substance having a free energy change value lower than the value of these standard free energy changes can be used as the reducing agent.

In the case of recovering valuable elements as metals from a composite oxide by dry treatment, in general, mn is inevitably reduced to convert into metals.

However, mn converted into metal is difficult to separate by wet treatment in the latter stage. Therefore, it is desirable to minimize Mn reduction (leaving Mn in slag).

However, conventionally, a substance having a strong reducing power such as an Al-containing substance or an Si-containing substance has been used as a reducing agent. This has the purpose of avoiding reduction defects, among others. If the reducing agent is insufficient in reducing power and a reduction failure occurs, a part of the positive electrode material is separated directly as slag in the form of oxide, and the content of valuable elements in the metal obtained by reducing the positive electrode material is reduced.

However, in the einlum diagram (fig. 2) described later, the upper element is more easily metallized, so when Si or Al is used as the reducing agent, mn is also easily metallized, and the requirement of reducing Mn as little as possible cannot be satisfied.

Therefore, the inventors of the present application studied substances that are not as strong as Al-containing substances, si-containing substances, and the like as possible as novel reducing agents. As a result, metallic iron (Fe) or iron oxide was found to be effective.

The standard free energy change (Δg ⁰) of the decomposition reaction of iron oxide is as follows.

FeO→Fe+1/2O₂：ΔG⁰=264430-64.73T[J]

Fe₃O₄→3FeO+1/2O₂：ΔG⁰=302370-108.15T[J]

Fig. 2 is an erlenmehm chart (standard free energy change versus temperature diagram).

With reference to the standard free energy changes and the Elmer diagram (FIG. 2) described above, the Fe/FeO equilibrium is lower than the Ni/NiO equilibrium and Co/CoO equilibrium, and it is believed that there is a possibility of Fe-based reduction.

In addition, feO/Fe ₃O₄ balance is lower than Ni/NiO balance but higher than Co/CoO balance.

Therefore, it is also expected to recover Ni as a metal and to leave Co in slag. Specifically, the following reaction is expected.

NiO+Fe→Ni+FeO:ΔG⁰=-29530-19.95T[J]

CoO+Fe→Co+FeO:ΔG⁰=-28950-6.82T[J]

Further, as described above, in the einlum diagram (fig. 2), the upper element is more easily metallized, and therefore, by using Fe (or FeO) as a reducing agent, it is possible to expect that only Ni and Co are metallized without metallizing Mn.

Reducing Agents

For the above reasons, in the present recovery method, a reducing agent containing at least 1 selected from the group consisting of metallic iron (Fe) and iron oxide is used.

As the metallic iron (Fe), for example, crushed iron, granulated iron, or the like used in a foundry or the like can be used.

In general, iron oxide is classified into 3 kinds of ferrous oxide (FeO) also called wustite, ferroferric oxide (Fe ₃O₄) also called magnetite, and ferric oxide (Fe ₂O₃) also called hematite.

Among them, magnetite and hematite have a higher standard free energy change than iron ore at the same temperature, and it is sometimes difficult to cause a reduction reaction.

Therefore, ferrous oxide (wustite) is preferable as the iron oxide from the viewpoint of easily causing a reduction reaction.

The iron oxide may be at least 1 kind of dust, scale, or sludge (hereinafter, referred to as "dust-like" for convenience) that is incidentally generated in the iron-making process.

The use of dust as iron oxide is preferable from the viewpoint of effectively utilizing the by-products of the iron-making process and the viewpoint of utilizing an inexpensive iron source.

Addition amount of reducing agent

The amount of the reducing agent required for reducing the oxide to be reduced is referred to as 1.0 equivalent.

For example, in the case where the reducing agent is metallic iron (Fe) or ferrous oxide (FeO), the reduction using 1 equivalent of the reducing agent is as follows, respectively.

Fe+(NiO,CoO,MnO)→(Ni,Co,Mn)+FeO

3FeO+(NiO,CoO,MnO)→(Ni,Co,Mn)+Fe₃O₄

When determining the amount of the reducing agent to be added, first, the contents of NiO, coO, and MnO in the oxide to be reduced are determined.

Specifically, the contents of Ni, co, and Mn in the object to be reduced (oxide) were measured and considered as the contents of NiO, coO, and MnO in the object to be reduced (oxide), respectively.

The contents of Ni, co and Mn were measured using an energy dispersive X-ray analyzer (EDX).

The smaller the amount of the reducing agent added, the larger the proportion of the valuable element (the smaller the proportion of Fe) metal can be obtained. This can prevent excessive Fe from remaining in the metal without being used as a reducing agent.

In addition, as the amount of the reducing agent added is smaller, a metal having a larger proportion of Ni, particularly Ni, among Ni and Co can be obtained. This is presumably because Ni is more easily metallized than Co because Ni is located above Co in the einlum diagram (fig. 2), and Ni is reduced by Fe (or iron oxide) first.

For these reasons, the amount of the reducing agent to be added is 1.5 equivalents or less, preferably 1.4 equivalents or less, more preferably 1.3 equivalents or less, further preferably 1.2 equivalents or less, particularly preferably 1.1 equivalents or less, and most preferably 1.0 equivalents or less.

The lower limit of the amount of the reducing agent to be added is not particularly limited from the viewpoint of further reducing the proportion of Fe.

However, from the viewpoint of suppressing reduction failure, the amount of the reducing agent to be added is preferably 0.1 equivalent or more, more preferably 0.3 equivalent or more, and still more preferably 0.5 equivalent or more.

In order to avoid reduction failure, if a large amount of reducing agent is added to the oxide, the amount of an element (e.g., fe) other than the valuable element contained in the produced metal tends to be large.

However, in the present recovery method, since Fe can be removed by wet treatment, the amount of the reducing agent to be added can be increased, and reduction failure can be easily suppressed.

< Heating of Mixed oxide (Metal acquisition) >)

Next, the mixed oxide (mixture of oxide and reducing agent) is heated. Thereby, the oxide is reduced.

In addition to the reducing agent, a flux such as CaO or SiO ₂ may be added during heating. That is, the mixed oxide may further contain a flux.

The equipment for heating the mixed oxide is not particularly limited, and examples thereof include conventionally known equipment such as an electric furnace, a resistance furnace, a high-frequency melting furnace, a low-frequency melting furnace, a rotary kiln, a vertical furnace, and a steel-making furnace.

Heating temperature

The temperature (heating temperature) at which the mixed oxide is heated is preferably 1300 ℃ or higher, more preferably 1350 ℃ or higher, still more preferably 1400 ℃ or higher, particularly preferably 1450 ℃ or higher, from the viewpoint of easily suppressing reduction defects.

The upper limit is not particularly limited, and the heating temperature is preferably 1800 ℃ or less, more preferably 1700 ℃ or less.

Heating atmosphere

The atmosphere (heating atmosphere) in heating the mixed oxide is preferably, for example, an inert atmosphere such as a nitrogen (N ₂) atmosphere or an argon (Ar) atmosphere, a reducing atmosphere such as a carbon monoxide (CO) atmosphere, or the like.

Heating time

The time for heating the mixed oxide (heating time) is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, from the viewpoint of easily suppressing reduction failure.

The upper limit is not particularly limited, and the heating time is preferably 6 hours or less, more preferably 5 hours or less.

Product (Metal)

The metal is produced by reducing an oxide (positive electrode material) to be reduced. Namely, ni and Co as valuable elements contained in the oxide are recovered as metals.

The metal obtained by reduction of the oxide (also referred to as "product metal") is an alloy containing valuable elements (Ni, co) and impurity elements (Cu, fe).

The metal to be produced may contain only 1 of the valuable elements (Ni, co).

The metal may be a metal in which the proportion of 1 valuable element is larger than the proportion of other valuable elements.

Product (slag)

By reducing the oxide (positive electrode material), slag (also referred to as "produced slag") is obtained in addition to the metal. The produced slag contains FeO and the like.

The produced slag contains, as an oxide (MnO), mn, a valuable element not contained in the produced metal.

When an oxide containing Mn (positive electrode material) is reduced, the Mn/MnO balance is lower than the Fe/FeO balance and the FeO/Fe ₃O₄ balance, and thus, the incorporation of Mn into the metal produced by the reduction can be suppressed.

The separation of Mn from the produced metal by wet treatment is heavy. It is advantageous to suppress the mixing of Mn into the produced metal and to retain Mn in the produced slag in advance, because such a load can be reduced.

< Separation of metals from slag >

The metal product and slag product obtained by reduction of the oxide are preferably separated before powdering the metal product (described later). The method of separation is not particularly limited, and known methods can be used.

< Powdering of Metal (acquisition of Metal powder) >)

The resulting metal product is then preferably powdered to obtain a metal powder.

In the wet treatment, as described later, first, leaching using an acid solution is performed on the produced metal. In this case, the leaching efficiency of the produced metal may be insufficient while the metal remains as it is obtained by reduction of the oxide. Therefore, it is preferable to pulverize the produced metal before leaching with an acid solution is performed.

The smaller the particle size of the metal powder, the better the leaching efficiency.

However, if the particle size of the metal powder is too small, there is a possibility that the operability is deteriorated and the risk of an explosive reaction is increased, and therefore, the particle size of the metal powder is controlled to be in an appropriate range in consideration of these points.

Specifically, for example, the particle diameter of the metal powder is preferably 250 to 6000 μm, more preferably 300 to 5000 μm.

The particle size is the median particle size (particle size at 50% cumulative value) based on the volume in the particle size distribution obtained by the laser diffraction/scattering method (the same applies hereinafter).

The method for producing the metal powder is not particularly limited as long as the particle diameter of the metal powder to be obtained can be controlled within an appropriate range, and examples thereof include a method using a pulverizing device such as a jaw crusher or a vibration mill, an atomization method, and the like.

< Contact of Metal with acid solution (extraction of leachate) >)

Next, the metal (metal powder) is brought into contact with an acid solution to leach out valuable elements (Ni, co) and impurity elements (Cu, fe). That is, a leachate containing valuable elements and impurity elements is obtained.

The metal from which the valuable element and the impurity element are leached becomes a residue (leaching residue).

The method of bringing the metal into contact with the acid solution is not particularly limited, and examples thereof include a method of immersing the metal in the acid solution, a method of spraying the acid solution onto the metal, and the like.

Solid-to-liquid ratio (metal/acid liquor)

If the amount of the acid solution in contact with the metal is too small (the amount of the metal is too large relative to the amount of the acid solution), a part of the metal elements such as valuable elements of the acid solution is temporarily eluted to reach a saturated solubility and is precipitated, and the leaching rate becomes insufficient.

Therefore, the ratio of the mass (unit: g) of the metal as a solid to the volume (unit: mL) of the acid solution as a liquid (also referred to as "solid-to-liquid ratio (metal/acid solution)") is preferably 1/5 or less, more preferably 1/7 or less, and still more preferably 1/10 or less.

When the solid-to-liquid ratio (metal/acid solution) is 1/10, for example, 1g of metal is immersed in 10mL of acid solution.

On the other hand, the solid-to-liquid ratio (metal/acid solution) is preferably 1/50 or more, more preferably 1/35 or more, and still more preferably 1/20 or more.

Acid liquor

The acid solution in contact with the metal contains at least an acid.

(Acid)

Examples of the acid used for the acid solution include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and 1 kind of acid may be used alone or 2 or more kinds of acid may be used in combination.

From the viewpoint of realizing "battery-to-battery (Battery to Battery)" in which waste lithium ion batteries are recycled and used again as raw materials for lithium ion batteries, sulfuric acid is preferably used as the acid. This is because valuable elements can be obtained in the form of sulfate, which is easily used as a positive electrode material for lithium ion batteries.

The sulfuric acid may contain a chloride, and may be used as an acid.

((Acid concentration))

The concentration (acid concentration) of the acid (for example, sulfuric acid) used in the acid solution is preferably 0.1mol/L or more, more preferably 0.5mol/L or more, and even more preferably 1.0mol/L or more, from the viewpoint of improving the leaching rate.

The upper limit is not particularly limited, and the acid concentration is preferably 8.0mol/L or less, more preferably 6.0mol/L or less, still more preferably 4.0mol/L or less, and particularly preferably 3.0mol/L or less.

(Oxidizing agent for acid solution)

The inventors of the present application have found that leaching is insufficient even when the solid-to-liquid ratio (metal/acid solution) and the acid concentration are within the above-described ranges.

Therefore, as the leaching accelerator, an oxidizing agent (oxidizing agent for acid liquor) is preferably added to the acid liquor. Examples of the oxidizing agent for acid solution include hydrogen peroxide, hypochlorous acid, potassium permanganate, and ozone. Among them, when hypochlorous acid and potassium permanganate are used, complex post-treatment of chlorine, potassium, manganese and the like may be required, and hydrogen peroxide and ozone are preferable.

((Content of oxidant for acid liquor))

From the viewpoint of sufficiently conducting leaching, the content of the oxidizing agent (e.g., hydrogen peroxide) for an acid in an acid solution is preferably 0.5% by volume or more, more preferably 1.0% by volume or more, still more preferably 3.0% by volume or more, still more preferably 5.0% by volume or more, particularly preferably 6.0% by volume or more, and most preferably 6.9% by volume or more, relative to an acid (e.g., sulfuric acid).

On the other hand, the content of the oxidizing agent (e.g., hydrogen peroxide) for an acid in the acid solution is preferably 15.0% by volume or less, more preferably 13.0% by volume or less, and still more preferably 10.0% by volume or less, relative to the acid (e.g., sulfuric acid).

Contact time

In order to sufficiently carry out leaching, the time (contact time) for bringing the metal into contact with the acid solution is preferably 0.5 hours or more, more preferably 0.8 hours or more, and still more preferably 1.0 hour or more.

On the other hand, from the viewpoint of productivity, the contact time is preferably 3.0 hours or less, more preferably 1.5 hours or less.

< Separation of leachate from leaching residue >

The leachate and the leaching residue are preferably separated before adding the sulfidizing agent (described later). The separation method is not particularly limited, and a known solid-liquid separation method can be used.

< Addition of vulcanizing agent (acquisition of copper removal solution) >)

Next, a sulfidizing agent is added to the leachate containing valuable elements (Ni, co) and impurity elements (Cu, fe), and copper (Cu) as an impurity element is precipitated as copper sulfide. Thus, a leaching solution from which copper (Cu) was selectively removed was obtained as a copper removal solution.

FIG. 3 is a potential-pH diagram (S-H ₂ O system) of copper (Cu) and nickel (Ni). In fig. 3, the potential-pH diagram of the copper (Cu) -sulfur (S) -water (H ₂ O) system shows the region of the formation of the precipitate of oxides (hydroxides) or sulfides of copper (Cu) and nickel (Ni) taking into account the solubility.

Since cobalt is precipitated in the same manner as nickel, the illustration of cobalt is omitted in fig. 3.

As shown in fig. 3, copper (Cu) was selectively precipitated in a region where pH was 3.0 or less and the oxidation-reduction potential was low. Although not shown in fig. 3, copper precipitates as copper (II) sulfide (CuS) in this region. By utilizing this, copper (Cu) contained in the leachate is selectively removed as copper (II) sulfide by making the leachate low in pH and reducing. Namely, a copper (Cu) -removed leaching solution was obtained as a leaching solution from which copper (Cu) was removed.

Vulcanizing Agents

Examples of the sulfidizing agent to be added to the leachate include sulfur (S), hydrogen sulfide (H ₂ S), sodium hydrosulfide (NaSH), sodium sulfide (Na ₂ S), etc., and 1 kind of these agents may be used alone or 2 or more kinds of them may be used in combination.

Among them, sulfur, sodium hydrosulfide and sodium sulfide that can be handled as a solid or a solution are preferable from the viewpoint of operability as compared with hydrogen sulfide as a toxic gas. In either case, however, hydrogen sulfide gas is generated by the vulcanization reaction, and therefore, attention is required for implementation.

The temperature (sulfidation temperature) of the leachate to which the sulfidizing agent is added is not particularly limited, and may be, for example, room temperature.

(Amount of vulcanizing agent to be added)

The amount of the sulfidizing agent to be added is preferably 1.0 equivalent or more, more preferably 1.5 equivalent or more, and even more preferably 2.0 equivalent or more, to copper (Cu) contained in the leachate, from the viewpoint of sufficiently removing copper contained in the leachate.

On the other hand, if the sulfidizing agent is excessively added, the amount of sulfide (precipitate) of the valuable element (Ni, co, etc.) becomes large, and the amount of the valuable element to be left in the obtained copper removal solution may be reduced. From such a viewpoint, the amount of the sulfidizing agent to be added is preferably 3.0 equivalents or less, more preferably 2.5 equivalents or less, and even more preferably 2.0 equivalents or less, relative to copper (Cu) contained in the leachate.

For example, when 1.0 equivalent of sodium hydrosulfide (NaSH) is used as a sulfidizing agent to produce copper (II) sulfide (CuS), 1mol of sodium hydrosulfide (NaSH) is used with respect to 1mol of copper (Cu) contained in the leachate.

PH of vulcanization

When a sulfidizing agent is added to the leachate to precipitate copper sulfide, if the pH (sulfidizing pH) of the leachate to which the sulfidizing agent is added is high, the amount of sulfide (precipitate) of valuable elements that is desired to remain in the copper removal solution may increase. Therefore, the vulcanization pH is preferably 3.0 or less, more preferably 2.0 or less, further preferably 1.0 or less, and particularly preferably 0 (zero).

The sulfidation pH is adjusted, for example, by adding a pH adjuster to the leachate. The pH adjuster is not particularly limited, and sulfuric acid, sodium hydroxide, and the like are exemplified.

Vulcanization time

The time (sulfidation time) for sulfidizing the copper contained in the leachate by reacting with the sulfidizing agent is preferably 0.1 hours or more, more preferably 0.2 hours or more, and even more preferably 0.3 hours or more.

On the other hand, from the viewpoint of productivity, the vulcanizing time is preferably 3.0 hours or less, more preferably 2.0 hours or less, and still more preferably 1.0 hour or less.

< Separation of copper sulfide from copper removal solution >

The copper sulfide and the copper removal solution are preferably separated before the addition of the oxidizing agent (described later). The separation method is not particularly limited, and a known solid-liquid separation method can be used.

< Addition of oxidant (acquisition of valuable element solution) >)

Next, an oxidizing agent is added to a copper removal solution containing valuable elements (Ni, co) and iron (Fe), and iron (Fe) as an impurity element is precipitated as an iron hydroxide. Thus, a copper removal solution from which iron (Fe) is selectively removed is obtained as a valuable element solution containing valuable elements (Ni, co).

FIG. 4 is a potential-pH diagram (O ₂-H₂ O system) of iron (Fe) and nickel (Ni). In fig. 4, the potential-pH diagram of the iron (Fe) -acidulous (O ₂) -water (H ₂ O) system shows the region formed by precipitation of iron (Fe) and nickel (Ni) oxides (hydroxides) taking into account the solubility.

Since cobalt is precipitated in the same manner as nickel, the illustration of cobalt is omitted in fig. 4.

As shown in fig. 4, iron (Fe) is selectively precipitated in a region where pH is 3.0 to 7.0 and the oxidation-reduction potential is high. Although not shown in fig. 4, iron is precipitated as iron (III) hydroxide (FeO (OH)) in this region. By utilizing this, the copper removal solution is made acidic to neutral and oxidizing, whereby iron (Fe) contained in the copper removal solution is selectively removed as iron (III) hydroxide precipitate. Namely, a valuable element solution is obtained as a copper removal solution from which iron (Fe) is removed.

Oxidizing Agents

Examples of the oxidizing agent to be added to the copper removing solution include at least 1 oxidizing agent a selected from the group consisting of air and ozone, at least 1 oxidizing agent B selected from the group consisting of hydrogen peroxide, hypochlorous acid and potassium permanganate, and the like.

Among them, if hypochlorous acid and potassium permanganate are used, complicated post-treatment of chlorine, potassium, manganese and the like may be required, and thus air, hydrogen peroxide and ozone are preferable.

(Addition amount of oxidant)

The amount of the oxidizing agent a (air, ozone) to be added as a gas to the copper-removing solution is preferably 0.1vvm or more, more preferably 0.3vvm or more, and even more preferably 0.5vvm or more, from the viewpoint of sufficiently oxidizing iron contained in the copper-removing solution.

On the other hand, the amount of the oxidizing agent a to be added to the copper removal solution is preferably 5.0vvm or less, more preferably 4.0vvm or less, and even more preferably 3.0vvm or less.

The unit "vvm" is a unit that indicates that several times of gas is blown into the liquid per minute in terms of a volume ratio, and for example, when the addition amount of the oxidizing agent a is 2vvm, 2L of the oxidizing agent a is blown into 1L of the copper removal solution per minute.

For the same reason, the amount of the oxidizing agent B (hydrogen peroxide, hypochlorous acid, potassium permanganate) to be added to the copper removal solution is preferably 0.005% by volume or more, more preferably 0.015% by volume or more, still more preferably 0.050% by volume or more, and particularly preferably 0.100% by volume or more.

On the other hand, the amount of the oxidizing agent B to be added is preferably 1.500% by volume or less, more preferably 1.000% by volume or less, still more preferably 0.500% by volume or less, and particularly preferably 0.300% by volume or less, relative to the copper removal solution.

Oxidation temperature

The inventors of the present application have found that, when only the above-described oxidizing agent is used, the oxidation of iron contained in the copper removal solution may be insufficient.

Therefore, from the viewpoint of promoting oxidation, the temperature (oxidation temperature) of the copper removal solution to which the oxidizing agent is added is preferably high. Specifically, the oxidation temperature is preferably 10 ℃ or higher, more preferably 30 ℃ or higher, and still more preferably 50 ℃ or higher.

On the other hand, the oxidation temperature is preferably 90 ℃ or less, more preferably 80 ℃ or less.

Oxidation pH

When an oxidizing agent is added to the copper removal solution to precipitate the iron hydroxide, if the pH (oxidation pH) of the copper removal solution to which the oxidizing agent is added is too low, the precipitate may be difficult to produce. Accordingly, the oxidation pH is preferably 3.0 or more, more preferably 3.7 or more, further preferably 4.0 or more, and particularly preferably 4.5 or more.

On the other hand, if the oxidation pH is too high, the coprecipitation of the valuable elements (Ni, co, etc.) increases, and the amount of the valuable elements to be left in the obtained valuable element solution may decrease. Therefore, the oxidation pH is preferably 7.0 or less, more preferably 6.0 or less, and further preferably 5.0 or less.

The oxidation pH is adjusted, for example, by adding a pH adjuster to the copper removal solution. The pH adjuster is not particularly limited, and sulfuric acid, sodium hydroxide, and the like are exemplified.

Oxidation time

The time (oxidation time) for reacting the iron contained in the copper removal solution with the oxidizing agent is preferably 0.3 hours or more, more preferably 0.5 hours or more, and still more preferably 1.0 hour or more.

On the other hand, from the viewpoint of productivity, the oxidation time is preferably 3.0 hours or less, more preferably 2.0 hours or less, and still more preferably 1.5 hours or less.

Oxidation aids

From the viewpoint of increasing the reaction rate of forming the precipitate of the iron hydroxide, an oxidizing assistant may be used together with the oxidizing agent.

Examples of the oxidation aid include at least 1 selected from the group consisting of ferric oxide (Fe ₂O₃) and ferric (III) hydroxide (FeO (OH)), and the form of the oxidation aid is preferably a powder.

The principle of increasing the reaction rate by means of an oxidation aid is catalysis. Specifically, the oxidation assistant is easily negatively charged in an aqueous solution (copper removal solution), and thus adsorbs Fe ²⁺ ions, weakening the binding with e ^- inside Fe ²⁺. Thus, the activation energy of the reaction (Fe oxidation reaction) of Fe ²⁺→Fe³⁺+e^- is thought to be reduced, and the reaction is promoted.

(Addition amount of Oxidation aid)

It is considered that the larger the addition amount of the oxidation assistant, the larger the reaction surface area and the larger the Fe oxidation reaction rate. Therefore, the addition amount of the oxidation assistant to the copper removal solution is preferably 0.1g/L or more, more preferably 0.5g/L or more, and still more preferably 1.0g/L or more.

On the other hand, if the addition amount of the oxidation assistant is too large, there is a possibility that Co-precipitation of valuable elements (Ni, co, etc.) increases. Therefore, the addition amount of the oxidation assistant to the copper removal solution is preferably 40.0g/L or less, more preferably 10.0g/L or less, and even more preferably 5.0g/L or less.

(Particle size of Oxidation aid)

If the particle size of the oxidation assistant is too small, the reaction surface area becomes too large, and there is a possibility that Co-precipitation of valuable elements (Ni, co, etc.) increases. Therefore, the particle diameter of the oxidation assistant is preferably 0.1 μm or more, more preferably 0.3 μm or more, and still more preferably 0.5 μm or more.

On the other hand, if the particle diameter of the oxidation assistant is too large, the reaction surface area becomes too small, and the desired effect may not be obtained. Therefore, the particle diameter of the oxidation assistant is preferably 3.0 μm or less, more preferably 2.0 μm or less, and still more preferably 1.0 μm or less.

< Separation of iron hydroxide from valuable element solution >

For the iron hydroxide and the valuable element solution, it is preferable to separate the two. The separation method is not particularly limited, and a known solid-liquid separation method can be used.

In this way, the valuable element in the obtained valuable element solution can be used as a positive electrode material of a lithium ion battery, for example.

Examples

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below.

[ Test A ]

< Preparation of cathode Material test A >

And preparing a positive electrode material of the waste lithium ion battery.

Specifically, the waste lithium ion battery is subjected to pretreatment such as decomposition, discharge, and removal of an electrolyte, and the positive electrode material is separated. The composition ratios (molar ratios) of nickel (Ni), cobalt (Co) and manganese (Mn) in the positive electrode materials are shown in table 1 below. The positive electrode material further contains copper (Cu) and iron (Fe) as impurity elements.

TABLE 1

< Preparation of reducing agent test A >

As the reducing agent, powder of graphite (C), powder of metallic aluminum (Al), and powder of metallic silicon (Si) were prepared.

As other reducing agents, a powder of metallic iron (Fe) and a powder of ferrous oxide (FeO) obtained by atomization treatment were prepared.

In addition, as another reducing agent, powders of dust, scale and crushed iron generated in the iron making process were prepared, respectively.

The composition of the dust, scale and crushed iron is shown in table 2 below. In the following table 2, "m.fe" represents the amount of metallic Fe.

TABLE 2

< Addition of reducing agent and heating of Mixed oxide test A >

The prepared positive electrode material is charged into an electric furnace having a heating size of 50 to 80kg, and then, one of the above reducing agents and a flux (CaO, siO ₂) are added thereto, followed by heating. The heating time was 3 hours.

Thus, the positive electrode material is reduced to obtain a metal product and a slag product, and the metal product and the slag product are separated from each other.

The types and amounts (unit: equivalent) of the reducing agents used, the heating temperatures (unit: °c), and the heating atmospheres (Ar, N ₂, or CO) are shown in table 3 below.

The reduction ratio (unit: mass%) was determined for each metal element of Ni, co and Mn.

The reduction ratio is the ratio of the actually obtained metal amount relative to the theoretical metal amount produced by the reduction reaction. For example, when the reduction rate of Co is 20 mol%, it means that 20 mol% of Co contained in the positive electrode material is reduced to a metal, and the remainder remains as an oxide in the produced slag.

The results are shown in Table 3 below.

As shown in Table 3 below, the production metals of test examples 3-1 to 3-23 suppressed the reduction rate of Mn and gave high reduction rates for Ni and Co as compared with reference test examples 3-1 to 3-6 using C, al or Si as the reducing agent. Namely, ni and Co can be selectively recovered.

When the test examples (for example, test examples 3-1 to 3) in which only the addition amount of the reducing agent was different were compared, the decrease in the addition amount of the reducing agent showed a tendency that the ratio of Fe in the produced metal was decreased and the total ratio of Ni and Co was increased. Further, the smaller the addition amount of the reducing agent, the higher the Ni ratio in the produced metal (the lower the Co ratio).

The same applies to test cases 3-4 to 3-6, 3-7 to 3-9, 3-10 to 3-12, 3-13 to 3-15, 3-16 to 3-17, 3-18 to 3-19, 3-20 to 3-21, and 3-22 to 3-23.

TABLE 3

Table 3 (1/2)

Table 3 (2/2)

< Powdering of Metal test A >

The composition of the metal and slag produced by the reduction of the positive electrode material was determined.

The metal having the composition shown in table 4 below was pulverized into metal powder using a vibration mill from among metals produced by reduction of the cathode material.

The particle size of the obtained metal powder was 1100. Mu.m.

< Contact of Metal with acid solution test A >

To sulfuric acid (concentration: 2.0 mol/L), 7.0% by volume of hydrogen peroxide as an oxidizing agent for an acid solution was added to prepare an acid solution.

A metal (metal powder) having a composition shown in Table 4 below was brought into contact with the prepared acid solution at a solid-to-liquid ratio (metal/acid solution) of 1/10 (contact time: 1.0 hour). Specifically, the metal powder is immersed in an acid solution. Thus, a leachate and a leaching residue are obtained, and the leachate and the leaching residue are separated.

The concentration of each element contained in the leachate was determined by XRF (fluorescence X-ray) analysis, and the leaching rate (unit: mass%) of each element from the metal into the leachate was calculated. The results are shown in table 4 below.

As shown in table 4 below, the leaching rates of the respective elements were 100 mass%, and all the elements were leached from the metals into the leaching solution.

TABLE 4

TABLE 4 Table 4

< Addition of vulcanizing agent test A >

The contents (unit: g/L) of the respective elements in the obtained leachate are shown in Table 5 below.

Sodium hydrosulfide (NaSH) was added as a sulfidizing agent to the resulting leachate, and stirring was performed at room temperature (25 ℃). The amount of the sulfidizing agent (sodium hydrosulfide) added to Cu contained in the leachate was set to 2.0 equivalents.

The pH of the leachate added with the sulfidizing agent (sulfidizing pH) was adjusted to 0 (zero) using sulfuric acid and sodium hydroxide as pH adjusting agents.

Thus, copper (Cu) contained in the leachate is reacted with a sulfidizing agent to be sulfidized (sulfidized time: 20 minutes), and precipitated as copper sulfide (copper (II) sulfide). Then, copper sulfide is separated from the copper removal solution as a leaching solution from which copper is removed.

The content (unit: g/L) of each element in the copper-removing solution was determined by ICP-AES (inductively coupled plasma emission spectrometry). The results are shown in table 5 below.

Then, the ratio of the content in the copper removal solution to the content in the leachate was obtained as a residual ratio a (unit: mass%) for each element. The results are shown in table 5 below.

As shown in table 5 below, the Cu content in the copper removal solution is very low, and thus it is known that Cu can be removed from the leachate with very high efficiency.

< Addition of oxidant test A >

Next, first, the copper removal solution was diluted with water. The contents (unit: g/L) of the respective elements in the diluted copper removal solution are shown in Table 5 below. The reason why the dilution was performed is that, in the preliminary experiment, when the oxidizing agent was added to the model solution having the same composition as the copper removal solution shown in table 5 below, there was a case where the stirring was not performed due to excessive precipitation.

Hydrogen peroxide as an oxidizing agent was added to the copper removal solution (diluted) and stirred. The amount of the oxidizing agent (hydrogen peroxide) added was 0.020% by volume with respect to the copper-removing solution (diluted).

The pH (oxidation pH) of the copper removal solution to which the oxidizing agent was added was adjusted to 4.5 using sulfuric acid and sodium hydroxide as pH adjusters. The temperature (oxidation temperature) of the copper removal solution to which the oxidizing agent was added was set to 70 ℃ and maintained at that temperature.

Thus, iron (Fe) contained in the copper removal solution is oxidized by reacting with an oxidizing agent (oxidation time: 1.0 hour), and precipitated as iron hydroxide (iron (III) hydroxide). Then, the iron hydroxide is separated from the valuable element solution as the iron-removed copper removal solution.

The content (unit: g/L) of each element in the valuable element solution was determined by ICP-AES. The results are shown in table 5 below.

Then, the ratio of the content in the valuable element solution to the content in the copper-removed solution (diluted) was obtained as a residual ratio b (unit: mass%) for each element. The results are shown in table 5 below.

As shown in table 5 below, the content of Fe in the valuable element solution is very low, and thus it is known that Fe can be removed from the copper removal solution with very high efficiency.

Then, the final residual ratio in the valuable element solution was obtained as the total residual ratio (unit: mass%) from the residual ratio a and the residual ratio b for each element. The results are shown in table 5 below.

As is apparent from the results shown in table 5 below, valuable elements (Ni, co) can be recovered at a very high purity by performing a dry treatment, then powdering the metal obtained by the dry treatment, and then performing a wet treatment.

TABLE 5

[ Test B ]

< Preparation of cathode Material-powdering of Metal test B >

Since the preparation of the positive electrode material and the pulverization of the metal were the same as in test a, the explanation thereof was omitted.

< Contact of Metal with acid solution test B >

A plurality of acid solutions were prepared by adding an oxidizing agent (hydrogen peroxide) for an acid solution to sulfuric acid (concentration: 2.0 mol/L) in the amount (unit: vol%) shown in Table 6 below.

The same procedure as in test a above was repeated except that the amount of the oxidizing agent for acid solution was changed, and the metal (metal powder) was brought into contact with the acid solution to obtain a leachate.

Then, the leaching rate (unit: mass%) of each element from the metal into the leachate was calculated in the same manner as in the test a described above. The results are shown in Table 6 below.

As shown in table 6 below, as the amount of the acid solution oxidizing agent added increases, the leaching rate also increases. It is found that the addition amount of the oxidizing agent (hydrogen peroxide) for acid solution is preferably 6.9% by volume or more in order to sufficiently leach out the valuable metals (Ni, co).

However, if the addition amount exceeds 6.9% by volume, the leaching rate reaches the upper limit. Therefore, it is understood that the amount of the oxidizing agent (hydrogen peroxide) to be added as the acid liquid is preferably 6.9% by volume within the range of this example from the viewpoint of cost.

TABLE 6

< Addition of vulcanizing agent test B >

Sodium hydrosulfide (NaSH) as a vulcanizing agent was added to the leachate shown in Table 5 in the following amount (unit: equivalent) shown in Table 7, and the mixture was stirred. At this time, the sulfidation pH was adjusted to the values shown in Table 7 below.

Copper contained in the leachate was precipitated as copper sulfide to obtain a copper-removed solution, in the same manner as in test a described above, except that the addition amount of the sulfidizing agent and the sulfidizing pH were changed.

Then, the Cu content (unit: mg/L), ni residual rate (unit: mass%) and Co residual rate (unit: mass%) in the obtained copper removal solution were obtained in the same manner as in test A described above. The results are shown in Table 7 below.

As shown in table 7 below, it is understood that the amount of the vulcanizing agent added is preferably 2.0 equivalents or more relative to copper in order to sufficiently remove copper, but the Ni residual rate and Co residual rate decrease as the amount of the vulcanizing agent added increases.

As shown in table 7 below, copper removal was insufficient and the Ni residual rate and Co residual rate tended to decrease as the sulfidation pH increased.

From the above, the amount of the vulcanizing agent added is preferably 2.0 equivalents and the vulcanizing pH is preferably 0 (zero) within the range of this example.

TABLE 7

< Addition of oxidant test B >

First, the copper removal solution obtained in test examples 7 to 4 of Table 7 was diluted 5 times.

Next, hydrogen peroxide as an oxidizing agent was added to the copper removal solution (diluted) in the amount (unit: vol%) shown in table 8 below, and stirred. At this time, the oxidation pH and oxidation temperature (unit:. Degree.C.) were adjusted to the values shown in Table 8 below.

The same procedure as in test a above was repeated except that the amount of the oxidizing agent added, the oxidation pH and the oxidation temperature were changed, and iron contained in the copper removal solution was precipitated as iron hydroxide to obtain a valuable element solution.

In both test a and test B, no oxidizing assistant was used.

Then, the Fe content (unit: mg/L), ni residual rate (unit: mass%) and Co residual rate (unit: mass%) in the obtained valuable element solution were obtained in the same manner as in the above-described test A. The results are shown in Table 8 below.

As shown in table 8 below, it is known that in order to sufficiently remove iron, the oxidation pH is preferably set to 6.0, or the oxidation pH is preferably set to 4.5 or more and the oxidizing agent is added.

As shown in table 8 below, iron was efficiently removed as the oxidation pH increased, while the Ni residual rate and the Co residual rate tended to decrease.

From the above, in the range of this example, the addition amount of the oxidizing agent (hydrogen peroxide) is preferably 0.030 volume% and the oxidation pH is preferably 4.5 to 5.0.

TABLE 8

[ Test C ]

Dry and wet treatments (i.e., from preparation of the positive electrode material to addition of the oxidant) were performed according to test a to obtain a valuable element solution. As shown in table 9 below, the mass of the positive electrode material (oxide) used was set to 100kg for convenience.

In comparative test example 9-1, only the dry treatment was performed. In comparative test examples 9-2 and 9-1 to 9-2, the amounts of FeO used as the reducing agent were different from each other.

The Ni+Co recovery rate (unit: mass%) was determined from the Ni+Co reduction rate (unit: mass%) of the metal produced by the dry treatment and the Ni+Co residual rate (unit: mass%) of the valuable element solution obtained by the wet treatment. The results are shown in Table 9 below.

In the case of performing only the dry treatment, the ni+co reduction rate of the produced metal was expressed as the ni+co recovery rate, as shown in table 9 below.

The ni+co ratio in the metal element was obtained as the final ni+co purity (unit: mass%) for the valuable element solution obtained by wet treatment. The results are shown in Table 9 below.

However, in comparative test example 9-1 in which only the dry treatment was performed, the purity of ni+co of the metal product obtained by the dry treatment was described in table 9 below as the final purity of ni+co.

When comparative test example 9-1 was compared with test example 9-1, the conditions of the dry treatment were the same, but in comparison with comparative test example 9-1 in which wet treatment was not performed, in test example 9-1 in which wet treatment was performed, valuable element (ni+co) was finally obtained in high purity.

When comparing comparative test example 9-2 with test examples 9-1 to 9-2, the amount of Fe contained in the produced metal was small and the total mass of the reducing agent, vulcanizing agent and oxidizing agent was small in test examples 9-1 to 9-2 in which the amount of FeO added as the reducing agent was 1.5 equivalents or less, compared with comparative test example 9-2 in which the amount of FeO added as the reducing agent was 2.0 equivalents.

TABLE 9

Claims

1. A method for recovering valuable elements, wherein,

Adding a reducing agent containing at least 1 selected from the group consisting of metallic iron and iron oxide to an oxide containing a valuable element, which is at least 1 selected from the group consisting of nickel and cobalt, and manganese, and an impurity element, which is copper and iron, in an addition amount of 1.5 equivalents or less, to obtain a mixed oxide,

Heating the mixed oxide to reduce the oxide and obtain metal,

Contacting the metal with an acid solution to obtain a leachate containing the valuable element and the impurity element,

Adding a sulfidizing agent to the leachate to precipitate copper as copper sulfide, obtaining the leachate from which copper is removed as a copper removal solution,

Adding an oxidizing agent to the copper removal solution to precipitate iron as an iron hydroxide, thereby obtaining the copper removal solution from which iron has been removed as a valuable element solution containing the valuable element.

2. The method for recovering valuable elements according to claim 1, wherein the oxide is obtained from spent lithium ion batteries.

3. A method of recovering a valuable element as claimed in claim 1 or 2, wherein the metal is powdered and then contacted with the acid liquor.

4. The method for recovering valuable elements according to any one of claims 1 to 3, wherein the temperature at which the mixed oxide is heated is 1450 ℃ or higher.

5. The recovery method of valuable elements according to any one of claims 1 to 4, wherein the iron oxide is ferrous oxide.

6. The method for recovering valuable elements according to any one of claims 1 to 5, wherein the reducing agent is at least 1 selected from the group consisting of dust, scale, sludge and crushed iron.

7. The method for recovering a valuable element according to any one of claims 1 to 6, wherein the metal obtained by heating the mixed oxide contains the valuable element and the impurity element.

8. The method for recovering valuable elements according to any one of claim 1 to 7, wherein the acid solution contains an acid and an oxidizing agent for the acid solution,

The content of the oxidizing agent for acid is 0.5% by volume or more with respect to the acid.

9. The method for recovering valuable elements according to claim 8, wherein the oxidizing agent for acid solution is hydrogen peroxide.

10. The method for recovering valuable elements according to claim 1 to 9, wherein the sulfidizing agent is added in an amount of 1.0 equivalent or more to copper contained in the leachate,

When precipitating the copper sulfide, the pH of the leachate to which the sulfidizing agent is added is set to 3.0 or less.

11. The method for recovering valuable elements according to claim 1 to 10, wherein the oxidizing agent is at least 1 oxidizing agent A selected from the group consisting of air and ozone, or at least 1 oxidizing agent B selected from the group consisting of hydrogen peroxide, hypochlorous acid and potassium permanganate,

The addition amount of the oxidizing agent A is 0.1vvm or more with respect to the copper removal solution,

The amount of the oxidizing agent B added is 0.005% by volume or more based on the copper removal solution,

When the iron hydroxide is precipitated, the pH of the copper removal solution to which the oxidizing agent is added is set to 3.0 to 7.0.

12. The recovery method of valuable elements according to claim 11, wherein the temperature of the copper removal solution to which the oxidizing agent is added is 10 ℃ or higher.