JP2023150694A - Separation method for cobalt and nickel - Google Patents

Abstract

To provide a separation method for cobalt and nickel in which cobalt and nickel are collected from a lithium ion secondary battery at low cost.SOLUTION: A separation method for cobalt and nickel includes a crushing and classifying step of crushing and classifying a lithium ion secondary battery to yield an electrode material, a cleaning step of cleaning the electrode material with water and collecting alkaline cleaning waste liquid, a leaching step of immersing the electrode material cleaned in the cleaning step in a treatment liquid containing sulfuric acid to yield a leachate, a copper precipitation step of adding a hydrogen sulfide compound to the leachate and stirring, followed by solid-liquid separation to yield an eluate containing cobalt and nickel and a residue containing copper sulfide, a first treatment step or a second treatment step that includes a neutralization process and a filtration process, and a cobalt-nickel separation step of adding a hydrogen sulfide compound to the eluted liquid generated in the first treatment step or the neutralized liquid generated in the second treatment step, followed by stirring and solid-liquid separation to yield a precipitate containing cobalt sulfide and nickel sulfide, and a residual liquid containing lithium.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for separating cobalt and nickel that makes it possible to accurately separate and recover cobalt and nickel contained in a lithium ion secondary battery from other metals.

Lithium ion secondary batteries are used as power sources in a wide range of fields, from small devices such as various electronic devices to large devices such as electric vehicles. When such lithium ion secondary batteries are disposed of, there is a need to recover and reuse useful metals.

Lithium ion secondary batteries are made by separating the negative electrode material and the positive electrode material with a separator such as porous polypropylene and stacking them in layers, and using aluminum or stainless steel along with an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ) and an electrolytic solution. It is enclosed in a case such as

The negative electrode material of a lithium ion secondary battery is formed by applying a negative electrode active material such as graphite mixed with a binder to a negative electrode current collector made of copper foil or the like. Further, the positive electrode material is formed by applying a positive electrode active material such as lithium manganate, lithium cobalt oxide, lithium nickel oxide, etc. mixed with a binder to a positive electrode current collector made of aluminum foil or the like.

In this way, the positive electrode active material of lithium ion secondary batteries contains a large amount of cobalt and nickel, but in addition to cobalt and nickel, the positive electrode active material that has been crushed and separated in advance during the recycling process also contains manganese, copper, Contains aluminum and lithium. Therefore, in order to separate and recover cobalt and nickel from lithium ion secondary batteries with high yield, it is necessary to accurately remove metals other than these.

Conventionally, as a method for separating and recovering cobalt and nickel contained in a lithium ion secondary battery, for example, Patent Documents 1 and 2 describe a method for recovering valuable metals from a used lithium ion secondary battery. A recovery method is disclosed in which a positive electrode active material is taken out from a secondary battery, a leachate in which metal is leached from the positive electrode active material is obtained by acid leaching, and cobalt and nickel are separated from this leachate by solvent extraction.

Japanese Patent Application Publication No. 2015-183292 Japanese Patent Application Publication No. 2007-122885

Electrode active materials often contain compounds that exhibit alkalinity when dissolved in water or the like. For this reason, in the recovery methods disclosed in Patent Documents 1 and 2, a large amount of sulfuric acid is used to dissolve the electrode active material when acid leaching the electrode active material.

In addition, in the subsequent process of the leaching process, in order to neutralize such acidic leaching solution, a large amount of alkali metal hydroxide such as sodium hydroxide is used to adjust the pH. In this way, in the conventional recovery method, it is necessary to adjust the liquid property widely from strong acidity to strong alkalinity in each treatment process, so it is necessary to use a large amount of chemical solutions such as acids and alkaline compounds, and lithium ion secondary The problem was that the processing costs involved in separating and recovering the cobalt and nickel contained in batteries were high.

This invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a method for separating cobalt and nickel that can recover cobalt and nickel from lithium ion secondary batteries at low cost. .

In order to solve the above problems, the cobalt and nickel separation method of the present invention is a cobalt and nickel separation method that separates cobalt and nickel from a lithium ion secondary battery. A crushing and sorting step to obtain an electrode material containing at least cobalt, nickel, copper, and lithium by crushing and classifying, washing the electrode material with water, and collecting an alkaline washing waste liquid after washing the electrode material. a leaching step in which the electrode material cleaned in the cleaning step is immersed in a treatment solution containing sulfuric acid to obtain a leaching solution; a hydrogen sulfide compound is added to the leaching solution and stirred to precipitate copper as copper sulfide. a copper precipitation step, a first neutralization step in which the washing waste liquid and an alkali metal hydroxide are added to the mixed solution containing the precipitate obtained in the copper precipitation step to adjust the pH to obtain a first neutralized solution; A first treatment step comprising in order a first filtration step of performing solid-liquid separation of the first neutralized liquid to obtain a first eluate containing cobalt and nickel and a residue containing copper sulfide, or the copper precipitation step. A second filtration process in which the mixed solution containing the precipitate obtained is subjected to solid-liquid separation to obtain a second eluate containing cobalt and nickel and a residue containing copper sulfide; A second neutralization step in which a second neutralized solution is obtained by adjusting the pH by adding an alkali metal hydroxide; A hydrogen sulfide compound is added to the first eluate or the second neutralized solution obtained in the second treatment step, stirred, and solid-liquid separated to produce a precipitate containing cobalt sulfide and nickel sulfide and a residual solution containing lithium. A cobalt-nickel separation step for obtaining

According to the present invention, by washing the electrode material separated in the crushing and sorting process with water in the washing process, a part of the electrode material that dissolves in water and becomes alkaline, such as a lithium compound, is removed. is transferred to the cleaning waste liquid after cleaning the electrode material. This makes it possible to reduce the amount of sulfuric acid used when acid leaching the electrode material in the leaching step, which is a subsequent step, and to reduce the processing cost related to the separation of cobalt and nickel.

In addition, by reusing the cleaning waste liquid collected in the cleaning process in the first neutralization process or the second neutralization process, the amount of expensive sodium hydroxide used can be reduced, and cobalt and nickel It is possible to reduce the processing cost related to the separation.

Further, in the present invention, it is preferable that the first treatment step is performed as a subsequent step of the copper precipitation step.

Further, in the present invention, the cleaning waste liquid may have a pH of 9 or more.

Further, in the present invention, the cleaning step may be a step of adding the electrode material to water and stirring for a period of 0.33 hours or more and 6 hours or less.

Further, in the present invention, an antifoaming agent containing a saturated linear alcohol having 8 or less carbon atoms may be further added to the treatment liquid used in the leaching step.

Further, in the present invention, the leaching step includes a kneading step of kneading the sulfuric acid and the electrode material cleaned in the cleaning step to form a leaching paste, and a dilution step of adding water to the leaching paste to dilute it. The process may include a process.

Further, in the present invention, after adding a redissolution solution containing sulfuric acid to the precipitate separated in the cobalt-nickel separation step and stirring, solid-liquid separation is performed to obtain a cobalt-nickel solution containing cobalt and nickel. The method may further include a dissolving step and a solvent extraction step of adding an extractant solution to the cobalt-nickel solution to obtain a cobalt extract and a nickel extract.

Further, the present invention may further include a heat treatment step of heating and heat-treating the lithium ion secondary battery as a pre-step of the pulverizing and sorting step.

According to the present invention, cobalt and nickel contained in lithium ion secondary batteries are separated from other metals at low cost and with high precision, and cobalt and nickel are recovered from lithium ion secondary batteries at low cost. A method for separating cobalt and nickel can be provided.

1 is a flowchart showing step-by-step a method for recycling an electrode material of a lithium ion secondary battery, including a method for separating cobalt and nickel according to a first embodiment of the present invention. It is a flowchart showing step-by-step a method for recycling an electrode material of a lithium ion secondary battery, including a method for separating cobalt and nickel according to a second embodiment of the present invention.

Hereinafter, a method for separating cobalt and nickel according to an embodiment of the present invention will be described with reference to the drawings. It should be noted that each of the embodiments shown below will be specifically described in order to better understand the gist of the invention, and unless otherwise specified, the embodiments are not intended to limit the invention.

(First embodiment)
FIG. 1 is a flowchart showing step-by-step a method for recycling an electrode material of a lithium ion secondary battery, including a method for separating cobalt and nickel according to a first embodiment of the present invention.

(Heat treatment step S1)
As a pre-treatment step for separating the electrode materials constituting discarded lithium ion secondary batteries (hereinafter referred to as waste LIBs), waste LIBs are heat-treated by heating them in a heating furnace, for example, with superheated steam to about 500°C. .

The heat treatment may be performed under vacuum or normal pressure, but heating in an inert atmosphere containing no oxygen is preferred. Due to the presence of the binder and electrolyte, waste LIB has a strong adhesion force between the positive electrode active material and the negative electrode active material and the current collector such as aluminum foil or copper foil. Therefore, by performing a heat treatment step at 400° C. or higher, the active material and the current collector can be easily separated. By setting the heating temperature of the waste LIB to 650° C. or lower, it is possible to prevent the aluminum from melting, enveloping the active material, cooling and solidifying, and making it difficult to take out only the active material.

(Crushing and sorting process S2)
Next, after the heat-treated waste LIB is pulverized, the electrode material is separated by sieving. The waste LIB is crushed using, for example, a twin-shaft shear crusher or a hammer mill.

Then, the crushed waste LIB is classified using a sieve with an appropriate opening, and the battery container, aluminum foil, copper foil, and nickel terminal are passed through the sieve, and the positive electrode active material (such as LiCoO ₂ ) and the negative electrode active material are separated. Electrode materials containing (graphite) are recovered as a sieve product. Such an electrode material may be one that has passed through a sieve with an opening of about 0.5 mm, for example.

The separated electrode material mainly contains cobalt, nickel, manganese, copper, iron, aluminum, lithium, calcium, etc., which are the constituent materials and impurities of the positive electrode active material, and carbon, etc., which is the constituent material of the negative electrode active material. There is.

(Cleaning step S3)
Next, the powdered electrode material containing the electrode active material separated in the crushing and sorting step S2 is washed with water. For example, distilled water can be used as water. In the cleaning step S3, for example, the electrode material may be placed in water with a liquid temperature of 0° C. or more and 100° C. or less, and stirred for 0.33 hours or more and 6 hours or less.

Thereafter, for example, by performing solid-liquid separation using a filter medium, the electrode material after washing and the washing waste liquid after washing the electrode material are respectively collected. In the cleaning step S3, the lithium compound (for example, lithium carbonate) contained in the electrode material dissolves in water, so that the pH of the cleaning drainage liquid obtained here becomes weakly alkaline, about 9 to 10. ing. Moreover, the electrode material after washing may be supplied to the next step, leaching step S4, in a wet state without particularly drying.

As in this embodiment, by washing the electrode material separated in the crushing and sorting step S2 with water in the washing step S3, components of the electrode material that become alkaline when dissolved in water, such as a lithium compound, are removed. part is transferred to the cleaning waste liquid. Thereby, in the subsequent leaching step S4, when acid leaching the electrode material, the amount of sulfuric acid used can be reduced, and the processing cost related to the separation of cobalt and nickel can be reduced. For example, by performing the cleaning step S3, the amount of sulfuric acid used in the leaching step can be reduced by about 10 to 20% compared to the case where the cleaning step S3 is not performed.

(Leaching step S4)
Next, the electrode material cleaned in the cleaning step S3 is immersed in a treatment liquid to obtain a leachate. As the treatment liquid, a mixture of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) may be used. Since the Co and Ni contained in waste LIB also include trivalent and tetravalent states that are difficult to dissolve in sulfuric acid, by using hydrogen peroxide as a reducing agent, it is possible to convert the Co and Ni to divalent Co and Ni, which are more easily soluble in sulfuric acid. It can be returned.

An example of the treatment liquid is one in which 100 ml of dilute sulfuric acid with a concentration of 2 mol/L or more is mixed with 5 ml or more of hydrogen peroxide solution with a concentration of 30 wt%. By setting the concentration of dilute sulfuric acid to 2 mol/L or more and the amount of hydrogen peroxide added to 5 ml or more, the leaching rate of cobalt and nickel can be increased. Although there is no particular limit, the upper limit of the sulfuric acid concentration is 18 mol/L, and the upper limit of the amount of hydrogen peroxide added is 30 ml, since further improvement in the leaching rate cannot be expected even if the concentration is higher than that.

As a specific example of the leaching step S4, for example, the wet electrode material that has been washed with water in the washing step S3 is added to a treatment liquid heated to 60° C. or higher, and is immersed for 4 hours or more. At this time, it is preferable to further stir the mixture.

By setting the treatment liquid temperature to 60° C. or higher and the leaching (immersion) time to 4 hours or more, the leaching rate of cobalt and nickel can be increased. Although there is no particular limit, the upper limit of the treatment liquid temperature is 90° C. and the upper limit of the leaching time is 15 hours, since further improvement in the leaching rate cannot be expected even if the temperature is increased beyond that.

Through this leaching step S4, the metal components (cobalt, nickel, manganese, copper, iron, aluminum, lithium, calcium, etc.) derived from the positive electrode active material in the electrode material are dissolved in the treatment liquid, and the carbon derived from the negative electrode active material is dissolved. , remains as a carbon residue without dissolving.

In addition, in the leaching step S3, an antifoaming agent containing a saturated linear alcohol having 8 or less carbon atoms can be added together with sulfuric acid and hydrogen peroxide. When the electrode material is dissolved by sulfuric acid or when hydrogen peroxide acts as a reducing agent, gas is generated and the solution foams, but by adding an antifoaming agent containing alcohol such as 1-butanol, The generated bubbles are quickly reduced. This prevents part of the electrode material from becoming a hard foam and floating up. Therefore, it is possible to prevent the reaction between the electrode material and sulfuric acid from slowing down due to foaming, and to allow the reaction between the electrode material and sulfuric acid to proceed quickly without adding an excess of sulfuric acid equal to or more than the reaction amount. can.

The leaching process S3 includes a kneading process in which the electrode material is kneaded with a small amount of sulfuric acid (processing liquid) to form a leaching paste, and a dilution process in which the obtained leaching paste is diluted with water to form a leaching liquid. It can also be done in a two-step process. At this time, by supplying the cleaned electrode material that has undergone the cleaning step S3, which is the previous step, to the kneading process in a wet state without drying it, it becomes easy to knead it with sulfuric acid and form a leaching paste.

By kneading in a paste state in the leaching step S3, contact between the electrode material and the sulfuric acid becomes easier than in conventional stirring in a liquid state. In addition, air bubbles caused by leaching are crushed by kneading, making it easier for the electrode material and sulfuric acid to become compatible. Thereby, the electrode material can be efficiently leached with acid in a short time.

(Copper precipitation step S5)
Next, a hydrogen sulfide compound is added to the leaching solution obtained in the leaching step S4 and stirred to obtain a mixture of an eluate containing cobalt and nickel and a precipitate containing copper sulfide (CuS).
In the present embodiment, the hydrogen sulfide compound refers to a compound that contains sulfur, and when dissolved in water, the sulfur content takes the form of H ₂ S, HS ^- or S ^{2 -} .
As the hydrogen sulfide compound used in the copper precipitation step S5, a water-soluble alkali metal hydrogen sulfide, in this embodiment, an aqueous solution of sodium hydrogen sulfide (NaSH) is used. As a specific example of the copper precipitation step S5, the leachate is diluted with ion-exchanged water, and then an aqueous solution of sodium hydrogen sulfide is added to the diluted leachate and stirred.

The aqueous solution of sodium hydrogen sulfide may be added, for example, until the oxidation/reduction potential (vs Ag/AgCl) becomes 0 mV or less. By adding sodium hydrogen sulfide until the oxidation/reduction potential becomes 0 mV or less, almost all of the copper contained in the leachate can be precipitated.

It is preferable to maintain the pH of the leachate at 2.0 or less from the start to the end of addition of the hydrogen sulfide compound. If the pH of the leachate exceeds 2.0, cobalt and nickel sulfides may be produced, which may reduce the recovery rate of these eluates.
In addition to the above-mentioned sodium hydrogen sulfide, the hydrogen sulfide compound may be, for example, sodium sulfide, sodium thiosulfate, or sodium dithionite.

By adding a hydrogen sulfide compound to the leachate, copper and sulfur among the metal components dissolved in the leachate react, and copper sulfide (CuS) is generated and precipitated. On the other hand, metal components other than copper (cobalt, nickel, manganese, iron, aluminum, lithium, calcium, etc.) remain in the liquid phase, and an eluate containing cobalt and nickel is obtained.

(First treatment step S6A)
Next, as a first treatment step S6A, a first neutralization step S6A-1 and a first filtration step S6A-2 are performed in order.
In the first neutralization step S6A-1, the pH of the mixed solution containing the precipitate obtained in the copper precipitation step S5 is adjusted by adding the washing waste liquid collected in the washing step S3 and an alkali metal hydroxide. , obtain a first neutralized solution.

In the copper precipitation step S5, which is the previous step, the pH of the leachate is maintained at 2.0 or less from the start to the end of addition of the hydrogen sulfide compound. However, as the hydrogen sulfide compound is added, the pH of the eluate decreases, although it may become difficult for the hydrogen sulfide compound to react with cobalt and nickel. After pH adjustment, if the pH at the start of addition of the hydrogen sulfide compound is less than 3.0, the pH will decrease excessively before the addition of the hydrogen sulfide compound is finished, making it necessary to adjust the pH again. For this reason, it is more efficient to adjust the pH to 3.0 or higher in the pre-step of the cobalt-nickel separation step S7.

Furthermore, if the pH is set to a value exceeding 4.0 during pH adjustment, it will take time to adjust the pH, but the pH will drop to 4.0 or less as soon as the hydrogen sulfide compound is added, which is inefficient. Therefore, the pH adjustment range is preferably 3.0 to 4.0.

In addition, in this first neutralization step S6A-1, using sodium hydroxide (NaOH), the pH of the mixed solution containing the precipitate obtained in the copper precipitation step S5 is adjusted to about 3.0 to 4.0. Then, the aluminum contained in this mixed solution can be converted into aluminum hydroxide (Al(OH) ₃ ) and precipitated.

In the first neutralization step S6A-1, which is the pretreatment pH adjustment for the cobalt-nickel separation step S7, a pH adjustment solution is used to adjust the eluate with a pH of about 1.0 to pH 3.0 to 4.0. As a result, the cleaning waste liquid having a pH of about 9 to 10, which is collected in the cleaning step S3, is reused. If the pH of the eluate cannot be adjusted to 3.0 to 4.0 with this washing waste alone, if the pH is less than 3.0, add an alkali metal hydroxide such as sodium hydroxide (NaOH), potassium hydroxide ( KOH), an acid such as sulfuric acid can be used if the pH exceeds 4.0. In this embodiment, the pH of the eluate is adjusted to within the range of 3.0 to 4.0 by using the washing waste liquid with a pH of 10 collected in the washing step S3 and an aqueous sodium hydroxide solution with a concentration of 25 wt%. For example, I adjusted it to 3.5.

In this way, in the first neutralization step S6A-1, by reusing the cleaning waste liquid collected in the cleaning step S3, the amount of expensive sodium hydroxide used can be reduced, and cobalt and nickel It is possible to reduce the processing cost related to the separation.

Next, in the first filtration process S6A-2, the first neutralized liquid obtained in the first neutralization process S6A-1 is subjected to solid-liquid separation, and the first eluate containing cobalt and nickel is separated from copper sulfide (CuS). ) and the residue containing them. As a result, the carbon residue produced in the leaching step S4, the precipitation residue containing copper sulfide (CuS) produced in the copper precipitation step S5, and the aluminum hydroxide (Al(OH) ₃ produced in the first neutralization step S6A-1) ) and the first eluate (liquid phase) are separated.

Note that in this embodiment, the carbon residue generated in the leaching step S4 is also filtered out by solid-liquid separation in the first filtration step S6A-2, but by performing solid-liquid separation also in the leaching step S4, the first It is also possible to separate the carbon residue in advance before performing the filtration step S6A-2.

The solid phase separated in the first filtration step S6A-2 is repulped (purified by adding water to the solid phase to resuspend it and then dehydrating it) or cake washed and then treated as waste. Bye.

(Cobalt/nickel separation process S7)
Next, a hydrogen sulfide compound is added to the first eluate obtained in the first treatment step S6A, followed by stirring and solid-liquid separation to separate a precipitate (solid phase) containing cobalt sulfide and nickel sulfide and lithium. A residual liquid (liquid phase) containing

In the cobalt-nickel separation step S7, a water-soluble hydrogen sulfide compound is added to the first eluate obtained in the first treatment step S6A, so that the cobalt and nickel contained in the first eluate are separated, respectively. It precipitates into water-insoluble cobalt sulfide (CoS) and nickel sulfide (NiS).

Examples of hydrogen sulfide compounds for sulfurizing cobalt-nickel include water-soluble alkali metal hydrogen sulfides. The hydrogen sulfide compound may be the same as that used in the copper precipitation step S5, or may be different. In this embodiment, an aqueous solution of sodium hydrogen sulfide having a concentration of 250 g/L was used.

The aqueous solution of sodium hydrogen sulfide is added, for example, until the oxidation/reduction potential (vs Ag/AgCl) becomes −400 mV or less. By adding sodium hydrogen sulfide until the oxidation/reduction potential becomes -400 mV or less, almost all of the cobalt and nickel contained in the first eluate can be precipitated.

The pH of the leachate from the start to the end of addition of the hydrogen sulfide compound is preferably maintained within the range of 2.0 to 5.0, preferably 2.0 to 3.5. When the pH of the leachate becomes less than 2.0, a reaction between sodium hydrogen sulfide and sulfuric acid (NaSH + H ₂ SO ₄ → H ₂ S + Na ₂ SO ₄ ) occurs, sodium hydrogen sulfide is consumed, and cobalt and nickel sulfidation occurs. It becomes difficult to proceed. On the other hand, if the pH of the leachate exceeds 5.0, hydroxides of other metals may be generated, which may reduce the purity of the precipitate. Furthermore, it is difficult to control pH in a high range.

Note that the cobalt sulfide mentioned here may include cobalt sulfide compounds of various compositions, such as cobalt (II) sulfide, cobalt disulfide (CoS ₂ ), and nine cobalt octasulfide (Co ₉ S ₈ ). Similarly, nickel sulfide (NiS) has various compositions such as nickel (II) sulfide, nickel disulfide (NiS ₂ ), trinickel tetrasulfide (Ni ₃ S ₄ ), and trinickel disulfide (Ni ₃ S ₂ ). may contain a nickel sulfide compound.

On the other hand, metal components (manganese, iron, aluminum, lithium, calcium, etc.) other than cobalt and nickel remain in the liquid phase (residual liquid) after adding the hydrogen sulfide compound. The liquid phase obtained here can then be subjected to solvent extraction through pH adjustment, etc. to separate and recover the manganese, iron, aluminum, lithium, calcium, etc. contained therein.

(Remelting step S8)
Next, a redissolution solution containing sulfuric acid is added to the precipitate obtained in the cobalt-nickel separation step S7 and stirred, followed by solid-liquid separation to obtain a cobalt-nickel solution containing cobalt and nickel.

As the re-dissolving liquid used in the re-dissolving step S8, for example, a mixture of sulfuric acid and hydrogen peroxide as an oxidizing agent is used. An example of the re-dissolving solution is a mixture of 100 ml of dilute sulfuric acid with a concentration of 1.5 mol/L and 20 ml of hydrogen peroxide solution with a concentration of 30 wt%.

As a specific example of the re-dissolving step S8, the precipitate is added to a re-dissolving solution heated to 60° C. or higher, for example, and immersed for 4 hours or more. At this time, it is preferable to further stir the mixture. Moreover, air bubbling can also be performed when immersing the precipitate without adding hydrogen peroxide solution to the redissolution solution.
At this time, the dissolution rate of cobalt and nickel can be increased by setting the treatment liquid temperature to 60° C. or higher and the leaching time to 1 hour or longer. Although there is no particular limit, the upper limit of the treatment liquid temperature is 90° C. and the upper limit of the leaching time is 15 hours, since further improvement in the dissolution rate cannot be expected even if the temperature is increased beyond that.

By treating the precipitate with such a redissolution solution, cobalt and nickel are dissolved in the redissolution solution. In addition, impurities that do not dissolve in the redissolution solution, elemental sulfur generated in the cobalt-nickel separation step S7, and the like remain as a solid phase. Thereafter, by performing solid-liquid separation using a filter or the like, a cobalt-nickel solution with increased (purified) cobalt and nickel purity is obtained.

The cobalt-nickel solution obtained in this way contains almost no other components of the electrode material other than cobalt and nickel (copper, iron, aluminum, lithium, calcium, etc.), and is a highly purified cobalt and nickel recovery solution. Suitable as a raw material.

Note that it is also preferable to remove impurities other than cobalt sulfide and nickel sulfide by repulping the precipitate as a pre-process of the remelting step S8.
In addition, although the procedure for removing dissolved aluminum by precipitating it as aluminum hydroxide in the first neutralization step S6A-1 has been described above, if such a procedure is not carried out, in the cobalt-nickel separation step S7 The obtained precipitate may contain aluminum compounds. In this case, the aluminum compound can be removed by repulping the precipitate.

(Solvent extraction step S9)
Next, an extractant solution is added to the cobalt-nickel solution obtained in the redissolution step S8 to obtain a cobalt extract and a nickel extract.
As the extractant solution, a mixed solution of a metal extractant and a diluent can be used. For example, a mixed solution containing 20 vol% of 2-ethylhexyl 2-ethylhexylphosphonate (PC88A: manufactured by Daihachi Chemical Co., Ltd.) and 80 vol% of kerosene (diluent) can be used.

Using the above extractant solution, the cobalt-nickel solution is separated and recovered as a cobalt sulfate (CoSO ₄ ) solution and a nickel sulfate (NiSO ₄ ) solution using a mixer settler.

Through the above steps, cobalt and nickel can be recovered from waste LIB at a high yield. For example, assuming that the amounts of cobalt and nickel in the electrode material taken out from waste LIB are each 100%, by the cobalt and nickel separation method of this embodiment, cobalt and nickel are each recovered at a high yield of 90% or more. can do.

(Second embodiment)
FIG. 2 is a flowchart showing step-by-step a method for recycling an electrode material of a lithium ion secondary battery, including a method for separating cobalt and nickel according to a second embodiment of the present invention.
Note that in the second embodiment described below, descriptions of steps similar to those in the first embodiment will be omitted.

In the second embodiment, a second treatment step S6B is performed between the copper precipitation step S5 and the cobalt/nickel separation step S7 instead of the first treatment step.
As the second treatment step S6B, a second filtration step S6B-1 and a second neutralization step S6B-2 are performed in order.

In the second filtration step S6B-1, solid-liquid separation is performed on the mixed liquid containing the precipitate obtained in the copper precipitation step S5, and the first eluate containing cobalt and nickel is separated from the residue containing copper sulfide (CuS). do. Thereby, the solid phase containing the carbon residue generated in the leaching step S4 and the precipitation residue containing copper sulfide (CuS) generated in the copper precipitation step S5 is separated from the second eluate (liquid phase).

The solid phase separated in the second filtration step S6B-1 is either repulped (purified by adding water to the solid phase to resuspend it and then dehydrated) or cake washed and then treated as waste. Bye.

In the second neutralization step S6B-2, the washing waste liquid and alkali metal hydroxide collected in the washing step S3 are added to the second eluate obtained in the second filtration step S6B-1 to adjust the pH. to obtain a second neutralized solution.

In the copper precipitation step S5, which is the previous step, the pH of the leachate is maintained at 2.0 or less from the start to the end of addition of the hydrogen sulfide compound. However, as the hydrogen sulfide compound is added, the pH of the eluate decreases, although it may become difficult for the hydrogen sulfide compound to react with cobalt and nickel. After pH adjustment, if the pH at the start of addition of the hydrogen sulfide compound is less than 3.0, the pH will decrease excessively before the addition of the hydrogen sulfide compound is finished, making it necessary to adjust the pH again. For this reason, it is more efficient to adjust the pH to 3.0 or higher in the pre-step of the cobalt-nickel separation step S7.

Furthermore, if the pH is set to a value exceeding 4.0 during pH adjustment, it will take time to adjust the pH, but the pH will drop to 4.0 or less as soon as the hydrogen sulfide compound is added, which is inefficient. Therefore, the pH adjustment range is preferably 3.0 to 4.0.

In addition, in this second neutralization step S6B-2, sodium hydroxide (NaOH) is used to adjust the pH of the second eluate obtained in the second filtration step S6B-1 to about 3.0 to 4.0. By doing so, aluminum contained in the second eluate can be converted into aluminum hydroxide (Al(OH) ₃ ) and precipitated.

In the second neutralization step S6B-2, which is the pretreatment pH adjustment for the cobalt-nickel separation step S7, a pH adjusting solution is As a result, the cleaning waste liquid having a pH of about 9 to 10, which is collected in the cleaning step S3, is reused. In addition, if the pH of the second eluate cannot be adjusted to 3.0 to 4.0 with this washing waste only, if the pH is less than 3.0, add an alkali metal hydroxide, such as sodium hydroxide (NaOH), hydroxide. Potassium (KOH) and an acid such as sulfuric acid can be used if the pH exceeds 4.0. In this embodiment, the pH of the second eluate is adjusted to a range of 3.0 to 4.0 using the washing waste liquid with a pH of 10 collected in the washing step S3 and an aqueous sodium hydroxide solution with a concentration of 25 wt%. For example, it was adjusted to 3.5.

In this way, in the second neutralization process S6B-2, by reusing the cleaning waste liquid collected in the cleaning process S3, the amount of expensive sodium hydroxide used can be reduced, and cobalt and nickel It is possible to reduce the processing cost related to the separation.

Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

The effects of the cobalt and nickel separation method of the present invention were verified.
(Procedure for invention example (present invention example))
72.5 g of the electrode material taken out from the waste LIB was placed in 200 mL of distilled water and stirred for 20 minutes (cleaning step). Thereafter, filtration was performed to obtain 95.7 g of electrode material (undried) and 162 mL of washing waste liquid. The pH of the washing waste liquid was 10.9, and the composition was as shown in Table 1.

Table 2 shows the test results in which the electrode material (undried) was leached (leaching step). The time (min) in Table 2 indicates the elapsed time from the start of addition of hydrogen peroxide. In addition, the pH, temperature, and ORP (oxidation-reduction potential) in the table are the values at each time point, and the cumulative addition amount (sulfuric acid, hydrogen peroxide, NaSH, NaOH) is the total addition amount and concentration at each time point. indicates the metal concentration value at each time point.

Each sample is as follows.
Example A1: 288 mL of a sulfuric acid solution containing 73 mL of sulfuric acid with a concentration of 47 wt% was added to the electrode material (undried) and stirred so that the pH was 2.0 or less.
Example A2: After the procedure of Example A1, changes over time from the start of addition of 30 wt% hydrogen peroxide were checked, and 25 mL of 30 wt% hydrogen peroxide and 10 mL of sulfuric acid with a concentration of 47 wt% were added over 71 minutes.
Example A3: After the procedure of Example A2, 200 g/L sodium bisulfide solution was added until the ORP was below 0 mV.
Example A4: After the procedure of Example A3, 162 mL of the washing waste liquid having a pH of 10.9 was added and stirred to effect neutralization.
Example A5: After the procedure of Example A4, a sodium hydroxide solution with a concentration of 25 wt% was added to the leachate to neutralize it and stabilize the pH at 3.0 to 4.0.
Thereafter, the carbon of the negative electrode material of the waste LIB that was insoluble during leaching with sulfuric acid and the generated residue (copper sulfide) were separated into solid and liquid by filtration to obtain 490 mL of eluate. The composition of 33.06 g of the residue (copper sulfide) is shown in Table 3.

Calculating the leaching rate when the cobalt and nickel in the electrode material extracted from the waste LIB is taken as 100%, 92% of cobalt and 94% of nickel are leached, so cobalt and nickel are not sufficiently leached from the active material. There is. Furthermore, it was confirmed that by washing with water it was possible to reduce the amount of sulfuric acid required for leaching, and by adding washing waste liquid during neutralization, it was possible to reduce the amount of sodium hydroxide solution.

Next, 25 wt% sodium hydroxide solution and 200 g/L sodium hydrogen sulfide aqueous solution were added to the above eluate, and the ORP was -400 mV (vs Ag/AgCl) or less within the pH range of 2.0 to 3.5. The mixture was added and stirred until the mixture was mixed.

After confirming that a sufficient amount of black precipitate (cobalt sulfide, nickel sulfide) was generated, the precipitate was recovered by performing solid-liquid separation (cobalt-nickel separation step). On the other hand, the residual liquid contained impurities such as manganese, aluminum, iron, lithium, and calcium, and was disposed of as metal-containing waste liquid.

The precipitate was added to a re-dissolution solution of 100 mL of sulfuric acid with a concentration of 1.5 mol/L and 20 mL of hydrogen peroxide solution with a concentration of 30 wt%, and the mixture was heated and stirred at 60°C for 1 hour (re-dissolution step ). Thereafter, after cooling to room temperature, undissolved components and elemental sulfur produced in the reaction in the previous step were removed by filtration.

From the cobalt-nickel solution obtained in this way, a mixer-settler was used using an extractant solution containing 20 vol% of metal extractant PC88A (manufactured by Daihachi Kagaku Co., Ltd.) and 80 vol% of kerosene. The solution was separated and recovered as a cobalt sulfate solution and a nickel sulfate solution (solvent extraction step).

In the above procedure of the present invention example, when the cobalt and nickel in the electrode material taken out from the waste LIB are taken as 100%, the cobalt and nickel obtained in the back extraction solution by solvent extraction are 90% and 92%, respectively. Ta. Therefore, it was confirmed that according to the cobalt and nickel separation method of this embodiment, cobalt and nickel can be recovered from waste LIBs at a high yield.
Note that the metal concentration was measured by ICP-AES, the pH was measured by a pH meter, and the ORP was measured by an ORP meter. The percentage values are based on mass.

(Procedure 1 of comparative example)
Table 4 shows the leaching test results based on unwashed electrode material and with the amount of sulfuric acid being the same as in the above-mentioned example.
The time (min) in Table 4 indicates the elapsed time from the start of hydrogen peroxide addition. In addition, the pH, temperature, and ORP in Table 4 are the values at each time point, the cumulative addition amount (sulfuric acid, hydrogen peroxide, NaSH, NaOH) is the total addition amount at each time point, and the concentration is at each time point. shows the value of metal concentration at

Each sample is as follows.
Comparative Example B1: 500 mL of a sulfuric acid solution containing 85 mL of sulfuric acid with a concentration of 47 wt% was added to 72.5 g of the electrode material taken out from the waste LIB, and the mixture was stirred.
Comparative Example B2: After the procedure of Comparative Example B1, changes over time from the start of addition of 30 wt% hydrogen peroxide were confirmed, and 25 mL of 30 wt% hydrogen peroxide was added over 71 minutes.
Comparative Example B3: After the procedure of Comparative Example B2, 200 g/L sodium bisulfide solution was added until the ORP was 0 mV or less.
Comparative Example B4: After the procedure of Comparative Example B3, a sodium hydroxide solution with a concentration of 25 wt% was added to the leachate to stabilize the pH at 3.0-4.0.
After the procedure of Comparative Example B4, the carbon of the negative electrode material of the waste LIB that was insoluble during leaching with sulfuric acid and the generated residue (copper sulfide) were subjected to solid-liquid separation by filtration to obtain 410 mL of eluate.
The composition of 37.17 g of the residue (copper sulfide) is shown in Table 5.

In the comparative example (procedure 1), when the leaching rate is calculated when cobalt and nickel in the electrode material taken out from the waste LIB is taken as 100%, 86% of cobalt and 90% of nickel are leached.
Comparative Examples B1 and B2 show that by not performing the washing step, some of the sulfuric acid is consumed for neutralization, and the pH becomes 2.0 or higher after the addition of hydrogen peroxide. When the pH is 2.0 or higher, cobalt and nickel are not dissolved satisfactorily, resulting in a low leaching rate. It has been confirmed that the method of the present invention is effective in achieving sufficient leaching while reducing the amount of sulfuric acid and sodium hydroxide solution used.

(Procedure 2 of comparative example)
Table 6 shows the leaching test results based on unwashed electrode materials and with the pH during leaching set to 2.0 or less. The time (min) in Table 6 indicates the elapsed time from the start of hydrogen peroxide addition. In addition, the pH, temperature, and ORP in Table 6 are the values at each time point, the cumulative addition amount (sulfuric acid, hydrogen peroxide, NaSH, NaOH) is the total addition amount at each time point, and the concentration is at each time point. shows the value of metal concentration.

Each sample is as follows.
Comparative Example C1: 85 mL of sulfuric acid with a concentration of 47 wt% was added to 72.5 g of the electrode material taken out from the waste LIB, and kneaded for 15 minutes. 415 mL of distilled water was added and stirred.
Comparative Example C2: After the procedure of Comparative Example C1, the change over time from the start of addition of 30 wt% hydrogen peroxide was confirmed, and 30 wt% peroxide was added over 75 minutes while maintaining the pH below 2.0 using 47 wt% sulfuric acid. 25 mL of hydrogen was added.
Comparative Example C3: After the procedure of Comparative Example C2, 200 g/L sodium bisulfide solution was added until the ORP was below 0 mV.
Comparative Example C4: After the procedure of Comparative Example C3, a sodium hydroxide solution with a concentration of 25 wt% was added to the leachate to stabilize the pH at 3.0-4.0.
After the procedure of Comparative Example C4, solid-liquid separation was performed by filtration of the carbon of the negative electrode material of the waste LIB that was insoluble during leaching with sulfuric acid and the generated residue (copper sulfide), and 410 mL of eluate was obtained.
The composition of 37.17 g of the residue (copper sulfide) is shown in Table 7.

In the comparative example (procedure 2), when the leaching rate is calculated assuming that cobalt and nickel in the electrode material taken out from the waste LIB is 100%, 95% of cobalt and 95% of nickel are leached.
From Comparative Examples C1 and C2, some of the sulfuric acid is consumed for neutralization by not performing the washing step, and the sulfuric acid required to maintain the pH below 2.0 until the stage of adding hydrogen peroxide is not used in the example. It becomes excessive. From Comparative Example C4, since the pH is neutralized to 3.0 to 4.0 using only sodium hydroxide, more sodium hydroxide is required for neutralization than in the example. It has been confirmed that the method of the present invention is effective in achieving sufficient leaching while reducing the amount of sulfuric acid and sodium hydroxide solution used.

The method for separating cobalt and nickel of the present invention enables accurate separation and recovery of cobalt and nickel, especially cobalt and nickel, from other metals among valuable metals contained in used lithium ion secondary batteries at a low cost. This makes it possible to efficiently obtain highly purified recycled resources from lithium ion secondary batteries. Therefore, it has industrial applicability.

Claims (8)

A method for separating cobalt and nickel from a lithium ion secondary battery, comprising:
A crushing and sorting step of crushing and classifying the lithium ion secondary battery to obtain an electrode material containing at least cobalt, nickel, copper, and lithium;
a cleaning step of cleaning the electrode material with water and collecting an alkaline cleaning waste liquid after cleaning the electrode material;
a leaching step in which the electrode material cleaned in the cleaning step is immersed in a treatment solution containing sulfuric acid to obtain a leaching solution;
a copper precipitation step of adding a hydrogen sulfide compound to the leachate and stirring to precipitate copper as copper sulfide;
a first neutralization step in which a first neutralized solution is obtained by adding the washing waste liquid and an alkali metal hydroxide to the mixed solution containing the precipitate obtained in the copper precipitation step, and obtaining a first neutralized solution; A first treatment step that sequentially includes a first filtration step of performing solid-liquid separation of the Japanese liquid and obtaining a first eluate containing cobalt and nickel and a residue containing copper sulfide, or
A second filtration step in which the mixed solution containing the precipitate obtained in the copper precipitation step is subjected to solid-liquid separation to obtain a second eluate containing cobalt and nickel and a residue containing copper sulfide; A second neutralization process in which a second neutralization solution is obtained by adding a washing waste liquid and an alkali metal hydroxide to adjust the pH;
A hydrogen sulfide compound is added to the first eluate obtained in the first treatment step or the second neutralized solution obtained in the second treatment step, stirred, and solid-liquid separated to contain cobalt sulfide and nickel sulfide. A method for separating cobalt and nickel, comprising a cobalt-nickel separation step of obtaining a precipitate and a residual liquid containing lithium. The method for separating cobalt and nickel according to claim 1, wherein the first treatment step is performed as a subsequent step of the copper precipitation step. The method for separating cobalt and nickel according to claim 1 or 2, wherein the washing waste liquid has a pH of 9 or more. The cobalt according to any one of claims 1 to 3, wherein the washing step is a step of putting the electrode material in water and stirring for a period of 0.33 hours or more and 6 hours or less. and nickel separation methods. Cobalt according to any one of claims 1 to 4, characterized in that the treatment liquid used in the leaching step further contains an antifoaming agent containing a saturated linear alcohol having 8 or less carbon atoms. and nickel separation methods. The leaching step includes a kneading step of kneading the sulfuric acid and the electrode material cleaned in the cleaning step to form a leaching paste, and a diluting step of adding water to the leaching paste to dilute it. The method for separating cobalt and nickel according to any one of claims 1 to 5. A re-dissolving step of adding a re-dissolving solution containing sulfuric acid to the precipitate separated in the cobalt-nickel separation step and stirring, followed by solid-liquid separation to obtain a cobalt-nickel solution containing cobalt and nickel;
The cobalt according to any one of claims 1 to 6, further comprising a solvent extraction step of adding an extractant solution to the cobalt-nickel solution to obtain a cobalt extract and a nickel extract. and nickel separation methods. The method further comprises a heat treatment step of heating and heat-treating the lithium ion secondary battery as a pre-step of the pulverizing and sorting step. Separation method.

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