JP7198081B2 - Valuable metal recovery method - Google Patents

Description

This specification describes that valuable metals such as cobalt and nickel are extracted from an acidic solution containing cobalt ions, nickel ions and impurities obtained by wet treatment of waste containing positive electrode materials of lithium ion secondary batteries. It relates to a method of recovery.

In recent years, effective utilization of resources has been achieved by recovering valuable metals such as cobalt and nickel from waste containing cathode materials of lithium-ion batteries that have been discarded due to product life, manufacturing defects, or other reasons by wet processing. has been widely considered from the perspective of

For example, in order to recover valuable metals from waste containing positive electrode materials for lithium ion secondary batteries, battery powder obtained through roasting or other predetermined processes is usually added to acid to leach out and It is an acidic solution in which lithium, nickel, cobalt, manganese, iron, copper, aluminum, etc., which can be dissolved, are dissolved.

After that, iron, copper and aluminum among the metal elements dissolved in the acidic solution are sequentially or simultaneously removed by multiple steps of solvent extraction or neutralization, and nickel, cobalt, manganese and lithium are removed. Valuable metals are separated and concentrated by solvent extraction to obtain a solution in which each metal is dissolved. Nickel and cobalt are recovered from each solution by electrolysis or the like (see Patent Documents 1 to 3, for example).

JP 2010-180439 A U.S. Patent Application Publication No. 2011/0135547 Japanese Patent No. 5706457

By the way, in the recovery process as described above, it is possible to recover high-purity cobalt or nickel in the form of a compound with a predetermined inorganic acid such as sulfate from the waste containing the positive electrode material of the lithium ion secondary battery. If possible, these compounds can be used in the manufacture of lithium ion secondary batteries, which is desirable in aiming for a recycling-oriented society that efficiently reuses limited resources.

Here, an acidic solution obtained by dissolving battery powder or the like in an acid and then subjecting it to predetermined neutralization or solvent extraction may contain impurities such as sodium, aluminum, manganese, and the like. Since such impurities lower the purity of the finally obtained compounds of cobalt and nickel with inorganic acids, it is required to remove them as much as possible when recovering cobalt and nickel.

This specification proposes a method for recovering valuable metals that can effectively remove predetermined impurities.

The method for recovering valuable metals disclosed in this specification is obtained by subjecting waste containing positive electrode materials of lithium ion secondary batteries to wet treatment, and from an acidic solution containing cobalt ions, nickel ions and impurities, A method for recovering at least cobalt among valuable metals cobalt and nickel, wherein a phosphonate ester-based extractant is used to extract cobalt ions from the acidic solution by solvent extraction and back extraction for Co recovery. and a phosphinic acid-based extractant is used to extract cobalt ions by solvent extraction from the back-extracted liquid obtained in the first extraction step for Co recovery, and back-extract. It includes a second extraction step and a precipitation step for recovering Co in which oxalic acid is added to the post-reverse extraction liquid obtained in the second extraction step for recovering Co to obtain a precipitate containing oxalate.

According to the method for recovering valuable metals described above, in particular, the precipitation step for recovering Co in which oxalic acid is added to the post-reverse extraction liquid obtained in the second extraction step for recovering Co to obtain a precipitate containing oxalate. By containing, the predetermined impurities can be effectively removed.

1 is a flow diagram showing a method for recovering valuable metals according to one embodiment; FIG. FIG. 2 is a flow diagram showing an example of a process for obtaining the acidic solution of FIG. 1;

Hereinafter, embodiments disclosed in this specification will be described in detail.
A method for recovering valuable metals according to one embodiment is obtained by subjecting waste containing positive electrode materials of lithium ion secondary batteries to wet treatment, and an acidic solution containing cobalt ions, nickel ions and impurities. , each step illustrated in FIG. 1 is performed, and at least cobalt of cobalt and nickel, which are valuable metals, is recovered therefrom. Specifically, this embodiment includes a first extraction step for recovering Co in which cobalt ions are extracted and back-extracted from the acidic solution by solvent extraction, and a back-extraction obtained in the first extraction step for recovering Co. A second extraction step for recovering Co in which cobalt ions are extracted and back-extracted from the post-liquid by solvent extraction; and a precipitation step for Co recovery to obtain a salt-containing precipitate. After the Co recovery precipitation step, if necessary, after a Co recovery cleaning step of washing the precipitate, the precipitate obtained in the Co recovery precipitation step is roasted in a reducing atmosphere. It can further include a roasting step for recovering Co to be burned, and a dissolving step for recovering Co for dissolving the roasted product obtained in the roasting step for recovering Co.

<Acid solution>
In order to obtain an acidic solution, for example, as shown in FIG. 2, after the roasting step of roasting the waste containing the positive electrode material of the lithium ion secondary battery, a sieving step is performed as necessary, and the sieving step is performed. A lithium dissolving step of dissolving lithium using water or the like and an acid leaching step of leaching the residue of the lithium dissolving step with an acid can be performed. This post-leaching solution can be used as an acid leaching solution. In some cases, after the acid leaching step, the post-leaching solution is subjected to only the neutralization step, only the Al.Mn extraction step, or both of the neutralization step and the Al.Mn extraction step in order, and The post-neutralization solution or the post-extraction solution can also be an acidic solution. Each is described in detail below. However, the acidic solution is not limited to those described here as long as it can be obtained by subjecting waste containing positive electrode materials of lithium ion secondary batteries to some kind of wet treatment.

(Waste containing positive electrode materials for lithium-ion secondary batteries)
The target lithium ion secondary battery waste containing positive electrode material (hereinafter also simply referred to as "battery waste") is a lithium ion secondary battery that can be used in mobile phones and other various electronic devices, This includes cathode materials discarded due to battery product lifespan, manufacturing defects, or other reasons. It is preferable from the viewpoint of effective utilization of resources to recover valuable metals from such battery waste. Another object of the present invention is to recover valuable metals such as cobalt and nickel with high purity so that they can be reused in the manufacture of lithium ion secondary batteries.

Here, in this embodiment, battery waste containing at least cobalt and nickel is targeted. In particular, battery waste may typically contain up to 30% by weight cobalt and up to 30% by weight nickel. Battery waste may contain, for example, 0.1 wt.% to 40.0 wt.% cobalt and 0.1 wt.% to 15.0 wt.% nickel.

A lithium-ion secondary battery has a housing containing aluminum as an exterior wrapping around it. Examples of this housing include those made only of aluminum, those containing aluminum and iron, aluminum laminates, and the like. In addition, the lithium ion secondary battery has a positive electrode active layer made of a single metal oxide selected from the group consisting of lithium, nickel, cobalt and manganese, or a composite metal oxide of two or more types, etc., in the housing. The material, or cathode active material, may include aluminum foil (cathode substrate) that is coated and adhered by, for example, polyvinylidene fluoride (PVDF) or other organic binder or the like. In addition, the lithium ion secondary battery may contain copper, iron, and the like. In addition, lithium ion secondary batteries typically contain an electrolyte within the housing. As the electrolytic solution, for example, ethylene carbonate, diethyl carbonate, etc. may be used.

The battery waste may be in the form of being wrapped in the housing, or it may have already been subjected to some processing such as crushing, decomposition, or separation and turned into powder. Such powdery battery waste may have a black color. On the other hand, when the target is battery waste in the form of being wrapped in a casing, a crushing step for taking out the positive electrode material and the negative electrode material from the casing can be performed after the roasting step.

(Roasting process)
In the roasting step, the battery waste is heated. This roasting step is performed for the purpose of, for example, changing metals such as lithium and cobalt contained in the battery waste into a form that is easy to dissolve.
In the roasting step, it is suitable to heat the battery waste, for example, at a temperature range of 450° C. to 1000° C., preferably 600° C. to 800° C., for 0.5 hour to 4 hours. This roasting step can be performed using various heating equipment such as a rotary kiln, various other furnaces, and a furnace that performs heating in an air atmosphere.

(Lithium dissolution process)
In the lithium dissolving step, the battery waste that has undergone the roasting step is brought into contact with water to dissolve the lithium contained therein. This allows the lithium contained in the battery waste to be separated at an early stage in the recovery process. The water used here can be tap water, industrial water, distilled water, purified water, ion-exchanged water, pure water, ultrapure water, or the like.

(Acid leaching process)
In the acid leaching step, the residue obtained in the lithium dissolving step is added to an acid such as sulfuric acid for leaching. The acid leaching step can be performed by a known method or conditions, but the pH of the acidic solution should be 0 to 2.0, and the oxidation-reduction potential (ORP value, based on silver/silver chloride potential) of the acidic solution should be 0 mV or less. It is preferable that

(Neutralization process)
The post-leaching solution obtained in the acid leaching step can be subjected to a neutralization step in which an alkali such as sodium hydroxide, sodium carbonate, or ammonia is added to the post-leaching solution to raise the pH. As a result, the aluminum in the post-leaching solution can be precipitated and removed. However, this neutralization step can be omitted.

In the neutralization step, it is preferable to set the pH to 4.0 to 6.0, the ORP value (ORPvsAg/AgCl) to -500mV to 100mV, and the liquid temperature to 50°C to 90°C.
In the neutralization step, in order to suppress the loss of cobalt and nickel due to coprecipitation, conditions are generally set such that part of the aluminum contained in the post-leaching solution is removed. As a result, the remaining aluminum remains dissolved in the post-neutralization liquid. This aluminum residue can be removed in a subsequent extraction step. The aluminum concentration after the neutralization step is generally between 0.1 g/L and 1.0 g/L, typically between 0.3 g/L and 0.8 g/L.

(Al/Mn extraction step)
After the acid leaching step, or after the neutralization step when the neutralization step is performed, an Al/Mn extraction step is performed to extract the remaining aluminum and manganese from the post-leaching solution or the post-neutralization solution. And here, by extracting aluminum residues and manganese, an extraction residue (aqueous phase) from which they have been removed is obtained. This Al/Mn extraction step can be omitted.

In the Al/Mn extraction step, it is preferable to use a mixed extractant containing a phosphate ester-based extractant and an oxime-based extractant for the post-leaching solution or post-neutralization solution. Examples of the phosphate extractant include di-2-ethylhexyl phosphate (trade name: D2EHPA or DP8R). The oxime-based extractant is preferably aldoxime or one containing aldoxime as a main component. Specifically, for example, 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecyl salicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), 5- There are nonyl salicyl aldoxime (trade name: ACORGAM5640), etc. Among them, 5-nonyl salicyl aldoxime is preferable from the aspect of cost.
In this solvent extraction, the pH is preferably between 2.3 and 3.5, more preferably between 2.5 and 3.0.

The post-leaching solution obtained in the acid leaching step, the post-neutralization solution obtained in the neutralization step, or the residual extraction solution obtained in the Al/Mn extraction step is used as an acidic solution in the Co recovery step described later. can be

Such acidic solutions may contain cobalt ions, eg from 0 g/L to 15 g/L, typically from 5 g/L to 10 g/L, and nickel ions, eg from 0 g/L to 50 g/L. , typically from 5 g/L to 30 g/L.
Also, the acidic solution may contain, as impurities, at least one selected from the group consisting of sodium ions, aluminum ions, manganese ions, and lithium ions. Among them, sodium ions are impurities that may be mixed in various steps such as the neutralization step, and it is important to effectively remove them in the steps described later. When sodium ions are included, the sodium concentration is, for example, 0 g/L to 30 g/L, typically 10 g/L to 20 g/L. When aluminum ions are included, the aluminum concentration is, for example, 0.000 g/L to 0.050 g/L, typically 0.010 g/L to 0.020 g/L. When manganese ions are included, the manganese concentration is, for example, 0.000 g/L to 0.100 g/L, typically 0.010 g/L to 0.050 g/L. When containing lithium ions, the lithium concentration is, for example, 0.000 g/L to 2 g/L, typically 0.100 g/L to 1.5 g/L. In addition, the acidic solution may contain iron ions and/or copper ions, but the iron concentration is preferably 10 mg/L or less, more preferably 0.005 g/L or less, and the copper concentration is 10 mg/L or less. It is preferably 0.005 g/L or less.

<Step for recovering Co>
(First extraction step)
A first extraction step is performed to recover the cobalt of cobalt and/or nickel from the acidic solution described above. This first extraction step is also referred to as the first extraction step for recovering Co, since it mainly extracts and back-extracts cobalt ions in the acidic solution by solvent extraction.

Specifically, it is preferable to use a phosphonate ester-based extractant, and perform a solvent extraction process for extracting cobalt ions from an acidic solution into an extractant (organic phase) that is a solvent. As the phosphonate extractant, 2-ethylhexyl 2-ethylhexylphosphonate (trade name: PC-88A, Ionquest 801) is preferable from the viewpoint of separation efficiency between nickel and cobalt. The pH during extraction is preferably 5.0 to 6.0, more preferably 5.2 to 5.7.

Then, the extraction agent (organic phase) containing cobalt ions after extraction is back-extracted. The solution used for back extraction may be any of inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, but sulfuric acid is generally preferred. Here, the pH conditions are such that all cobalt ions are extracted from the organic phase into the solution (aqueous phase) as much as possible. Specifically, the pH is preferably in the range of 2 to 4, more preferably in the range of 2.5 to 3.5. Note that the O/A ratio and the number of times can be determined appropriately. The liquid temperature may be normal temperature, but preferably 0°C to 40°C.

The extractant from which cobalt ions have been extracted may be scrubbed one or more times with a scrubbing liquid to wash away any acidic solution that may be present in the extractant prior to being subjected to back extraction. As a result, nickel ions, sodium ions, and the like that may be contained in the extractant can be removed from the extractant. The scrubbing liquid can be, for example, a sulfuric acid acid solution and can have a pH of 3.5 to 5.5. Since the scrubbing liquid after being used for scrubbing may contain cobalt ions, in order to reduce the loss of cobalt, it may be mixed with an acidic solution from which cobalt ions are to be extracted in the first extraction step for Co recovery. can.

(Second extraction step)
In order to separate and selectively extract cobalt ions from nickel ions from the back-extracted liquid obtained in the first extraction step, a second extraction step (second extraction step for recovering Co) by solvent extraction is performed. In the Co recovery step, nickel ions can be treated as impurities.

Here, in order to selectively extract cobalt ions, it is preferable to use a masking agent that masks nickel ions and leaves them in the aqueous phase during extraction. Ammonia ions are particularly effective as this masking agent because they do not mask cobalt ions but do mask nickel ions. Ammonia ions also function as a pH adjuster during extraction.
Specifically, before or after contacting the post-reverse extraction solution obtained in the first extraction step with the extractant, ammonium ions are added to the cobalt solution to adjust the pH, and the cobalt ions are extracted. can be done. Ammonia ions can be added in the form of, for example, ammonia water or ammonium chloride (NH ₄ Cl). When ammonia water is added, the amount of ammonia water to be added is preferably 1% to 10% by volume relative to the back-extracted liquid obtained in the first extraction step.

The extractant to be brought into contact with the liquid after back extraction obtained in the first extraction step may be a phosphonic acid-based extractant or a phosphoric acid-based extractant. acid)-based extractant, and more preferably bis(2,4,4-trimethylpentyl)phosphinic acid. Specifically, ALBRITECT TH1 (trade name) or Cyanex 272 (trade name) manufactured by SOLVAY is particularly suitable, but the present invention is not limited to these. This results in extraction curves for cobalt and nickel that are well separated on the low and high pH sides compared to extractants such as 2-ethylhexyl 2-ethylhexylphosphonate (PC-88A, Ionquest 801), The range where cobalt ions are extracted but nickel ions are not extracted is expanded. That is, it becomes easier to selectively extract only cobalt ions. When the extractant comprises bis(2,4,4-trimethylpentyl)phosphinic acid, its purity can be, for example, 95% or higher.
The extractant can be diluted with an aromatic, paraffinic, naphthenic, or other hydrocarbon organic solvent to a concentration of 10 to 30% by volume.

As an example of the extraction procedure, while adding aqueous ammonia or the like, the back-extracted liquid (aqueous phase) obtained in the first extraction step and the extractant (organic phase) are brought into contact with each other, and then mixed with a mixer, for example, 200 to Stir and mix at 500 rpm for 5-60 minutes to allow the cobalt ions to react with the extractant. The liquid temperature at this time is 15°C to 60°C. After that, a settler separates the mixed organic phase and aqueous phase based on the difference in specific gravity.
The solvent extraction may be repeated, for example, in a multi-stage system in which the organic phase and the aqueous phase are in countercurrent contact. The O/A ratio (volume ratio of organic phase to aqueous phase) is generally 0.1-10.

The equilibrium pH at the time of extraction is preferably 4-7, more preferably 5-6. This allows the nickel ions to remain in the aqueous phase and the cobalt ions to be effectively extracted into the organic phase. However, since the appropriate pH range varies depending on the combination of cobalt concentration, volume fraction of the extractant, phase ratio of oil and water, temperature, etc., it may be outside the above range.

After extraction, back extraction is performed on the organic phase containing cobalt ions. The back extraction can be carried out by using a back extraction liquid such as an acidic aqueous solution of sulfuric acid or hydrochloric acid and stirring and mixing with a mixer or the like at 200 to 500 rpm for 5 to 60 minutes.
Considering the next step of crystallization of cobalt sulfate, it is preferable to use sulfuric acid as the back-extraction solution. The acid concentration of the reverse extract is preferably adjusted to pH 1.0 to 3.0, more preferably adjusted to pH 1.5 to 2.5.
Back extraction can be carried out at 15°C to 60°C or less.

By back extraction, cobalt ions move from the organic phase to the aqueous phase side, and a back extraction liquid (aqueous phase) containing cobalt ions can be obtained. Here, as described above, since many nickel ions were left in the aqueous phase during the extraction, almost no nickel ions were contained in the liquid after back extraction.
The cobalt concentration in the post-extraction liquid is, for example, 1 g/L to 200 g/L, typically 80 g/L to 100 g/L. Also, the nickel concentration in the post-extraction liquid can be, for example, 2 mg/L or less, typically 1 mg/L or less.

(Precipitation process)
After the second extraction step for recovering Co, a precipitation step for recovering Co is performed by adding oxalic acid to the resulting post-reverse extraction solution to precipitate oxalates such as cobalt ions. Here, cobalt and the like with low solubility as oxalates are included in the precipitate as oxalates, while sodium, manganese, magnesium and the like with high solubility remain dissolved in the liquid. Therefore, by performing solid-liquid separation such as filtration after the precipitation, a precipitate containing cobalt and the like and from which sodium, manganese, magnesium, and the like are removed can be obtained.

Oxalic acid can be added to the solution after back extraction in various forms. can.
The pH of the back-extracted solution before adding oxalic acid is preferably 1-4, more preferably 2-3. If the pH at this time is too low, there is concern that oxalic acid will decompose and become too small. The pH after adding oxalic acid is preferably 1 or less, and more preferably 0.5 or less. At this time, the liquid temperature is preferably maintained at 0° C. to 100° C., and the mixture is generally stirred.

(Washing process)
If necessary, the precipitate obtained in the precipitation step for Co recovery can be subjected to a washing step for Co recovery. This cleaning can use a cleaning liquid such as water, a cobalt sulfate solution, or a weak acid. As a result, impurities such as sodium can be washed away to further reduce impurities.

As described above, optionally after a washing step, the precipitate will contain primarily oxalates, such as cobalt oxalate, and will be substantially depleted in sodium, manganese and magnesium. The sodium content of the precipitate is, for example, 0.0015% by mass or less, preferably 0.0010% by mass or less, and the manganese content is, for example, 0.0005% by mass or less, preferably 0.0003% by mass or less. , the magnesium content is, for example, 0.0010% by mass or less, preferably 0.0005% by mass or less.

(Roasting process)
In the roasting step for recovering Co, a roasting step for recovering Co is performed in which the above-described precipitate containing oxalate is roasted at a predetermined temperature in a reducing atmosphere, a nitrogen atmosphere, or the like. As a result, cobalt oxalate or the like contained in the precipitate can be converted to metallic cobalt or the like.

In the roasting step, the precipitate is roasted at preferably 300°C to 500°C, more preferably 400°C to 450°C, in a reducing atmosphere such as hydrogen or carbon monoxide.

(Melting process)
In the dissolution step for recovering Co, the roasted product obtained in the roasting step is dissolved in acid such as sulfuric acid or sulfuric acid and an oxidizing agent to obtain a cobalt solution.
The pH during dissolution can be, for example, 1-5, preferably 2-4. If the pH is too high, the leaching of cobalt may become slow.

(Crystallization step)
The cobalt solution is subjected to a Co recovery crystallization step for crystallizing the cobalt ions contained therein. Here, the back-extracted solution is heated to, for example, 40° C. to 120° C. to concentrate, and cobalt ions are crystallized as cobalt sulfate.

Cobalt sulfate produced in this manner preferably has a nickel content of 5 ppm by mass or less, and nickel is sufficiently removed. can be used.

<Ni recovery process>
(Extraction process)
In the extraction step for recovering Ni, a carboxylic acid-based extractant is preferably used for the residual extraction liquid obtained in the first extraction step for recovering Co described above, and nickel ions are separated from the extraction residual liquid. Carboxylic acid-based extractants include, for example, neodecanoic acid and naphthenic acid. Among them, neodecanoic acid is preferred because of its ability to extract nickel ions.
In the solvent extraction for Ni recovery, the pH is preferably 6.0-8.0, more preferably 6.8-7.2.

After the extraction, the organic phase containing nickel ions is back-extracted using a back-extraction liquid such as sulfuric acid, hydrochloric acid, or nitric acid. For general use, sulfuric acid is preferred. Here, pH conditions are such that 100% of nickel ions are extracted from the organic phase into the acidic solution (aqueous phase). Specifically, the pH is preferably in the range of 1.0 to 3.0, more preferably 1.5 to 2.5. Although the O/A ratio and the number of times can be determined as appropriate, the O/A ratio is 5-1, preferably 4-2. By increasing the number of times of back extraction, the concentration of the target metal can be increased, and the concentration can be made advantageous for the electrolysis step.

The extraction step for Ni recovery may also undergo one or more scrubbing steps to wash away any acidic solutions that may be contained in the extractant with a scrubbing liquid before being subjected to back extraction. As a result, nickel ions, sodium ions, and the like that may be contained in the extractant can be removed from the extractant. The scrubbing liquid can be, for example, a sulfuric acid acid solution and can have a pH of 4-5. The scrubbing liquid after being used for scrubbing can be mixed with an acidic solution to be subjected to an extraction step for recovering Ni.

(Precipitation process)
In the precipitation step for Ni recovery, oxalic acid is added to the post-extraction solution obtained in the extraction step for Ni recovery, and the difference in solubility is used to selectively precipitate nickel ions and the like as oxalates. A sedimentation step for recovery is performed.

Oxalic acid can be added to the liquid after back extraction in the form of, for example, solid oxalic acid crystals, solid salts such as sodium oxalate, or aqueous solutions thereof. The pH of the solution after the previous reverse extraction is preferably 1 to 4, more preferably 2 to 3, and the pH after addition of oxalic acid is preferably 1 or less, more preferably 0.5 or less. The liquid temperature is preferably maintained at 0°C to 100°C.

(Washing process)
The precipitate obtained in the precipitation step for Ni recovery may optionally be subjected to a cleaning step for Ni recovery in which the precipitate is washed with a cleaning liquid such as water, a cobalt sulfate solution, or a weak acid. preferable. This makes it possible to further reduce impurities such as sodium.

After the precipitation step, or if a washing step is performed, the precipitate after the washing step contains oxalates such as nickel oxalate. The sodium content of the precipitate is, for example, 0.0060% by mass or less, preferably 0.0050% by mass or less, and the manganese content is, for example, 0.0001% by mass or less, preferably 0.0001% by mass or less. , the magnesium content is, for example, 0.0010% by mass or less, preferably 0.0005% by mass or less.

(Roasting process)
In the roasting step for recovering Ni, the above-mentioned precipitate containing oxalate is roasted at a predetermined temperature in a reducing atmosphere, a nitrogen atmosphere, or the like, to perform a roasting step for recovering Ni. As a result, nickel oxalate or the like contained in the precipitate can be converted to metal nickel or the like.

In the roasting step, the precipitate is roasted at preferably 300°C to 500°C, more preferably 400°C to 450°C, in a reducing atmosphere such as hydrogen or carbon monoxide.

(Melting process)
Next, the roasted product obtained in the roasting step for Ni recovery is dissolved in an acid such as sulfuric acid or sulfuric acid and an oxidizing agent to perform a dissolving step for Ni recovery to obtain a nickel solution. The pH during this dissolution can be, for example, 1-5, preferably 2-4.

(Crystallization step)
In the crystallization step for recovering Ni, the nickel solution is heated to, for example, 40° C. to 120° C. to concentrate and crystallize nickel ions as nickel sulfate.
Cobalt sulfate obtained in this crystallization step contains almost no impurities and is suitable for use as a raw material for manufacturing lithium ion secondary batteries.

Claims (10)

At least cobalt of cobalt and nickel, which are valuable metals, is removed from an acidic solution containing cobalt ions, nickel ions and impurities obtained by subjecting waste containing positive electrode materials of lithium ion secondary batteries to wet treatment. A method of recovering comprising:
a first extraction step for recovering Co in which cobalt ions are extracted and back-extracted from the acidic solution by solvent extraction using a phosphonate ester-based extractant ;
a second extraction step for recovering Co , in which a phosphinic acid-based extractant is used to extract cobalt ions by solvent extraction and back extraction from the post-back-extraction liquid obtained in the first extraction step for recovering Co;
and a precipitation step for recovering Co, wherein oxalic acid is added to the liquid after back extraction obtained in the second extraction step for recovering Co to obtain a precipitate containing oxalate. 2. The method for recovering valuable metals according to claim 1, further comprising, after the precipitation step for recovering Co, a cleaning step for recovering Co for cleaning the precipitate obtained in the precipitation step for recovering Co. The impurities contained in the acidic solution include at least one selected from the group consisting of sodium ions, manganese ions and magnesium ions,
By washing in the washing step for Co recovery, the precipitate has a sodium content of 0.0015% by mass or less, a manganese content of 0.0005% by mass or less, and a magnesium content of 0.0010% by mass or less. The method for recovering valuable metals according to claim 2. After the precipitation step for recovering Co, further comprising a roasting step for recovering Co, in which the precipitate obtained in the precipitation step for recovering Co is roasted in a reducing atmosphere,
The method for recovering valuable metals according to any one of claims 1 to 3, wherein the precipitate is roasted at 300°C to 500°C in the roasting step for recovering Co. The method for recovering valuable metals according to any one of claims 1 to 4, wherein in the first extraction step for recovering Co, the solvent that has extracted the cobalt ions in the acidic solution is scrubbed prior to back extraction. An extraction step for recovering Ni, in which nickel ions are extracted by solvent extraction from the extraction residue obtained in the first extraction step for recovering Co, and back extraction is performed;
6. The method according to any one of claims 1 to 5, further comprising a precipitation step for recovering Ni, in which oxalic acid is added to the post-extraction liquid obtained in the extraction step for recovering Ni to obtain a precipitate containing oxalate. The method for recovering valuable metals described in . 7. The method for recovering valuable metals according to claim 6, further comprising a washing step for Ni recovery of washing the precipitate obtained in the precipitation step for Ni recovery after the precipitation step for Ni recovery. The impurities contained in the acidic solution include at least one selected from the group consisting of sodium ions, manganese ions and magnesium ions,
By washing in the washing step for recovering Ni, the precipitate has a sodium content of 0.0060% by mass or less, a manganese content of 0.0001% by mass or less, and a magnesium content of 0.0010% by mass or less. The method for recovering valuable metals according to claim 7. After the precipitation step for Ni recovery, further comprising a roasting step for Ni recovery, in which the precipitate obtained in the precipitation step for Ni recovery is roasted in a reducing atmosphere,
The method for recovering valuable metals according to any one of claims 6 to 8, wherein the precipitate is roasted at 300°C to 500°C in the roasting step for recovering Ni. The method for recovering valuable metals according to any one of claims 6 to 9, wherein in the first extraction step for recovering Ni, the solvent that has extracted the nickel ions in the acidic solution is scrubbed before back extraction.

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