JP5849880B2 - Method for leaching metal and method for recovering metal from battery - Google Patents

Description

  The present invention relates to a metal leaching method and a method for recovering metal from a battery, and more particularly, a metal leaching method for reducing and leaching metal contained in a positive electrode active material constituting a battery such as a lithium ion battery, and the like The present invention relates to a metal recovery method to which a leaching method is applied.

  As a method of recovering valuable metals such as nickel, cobalt, manganese, etc. from used lithium-ion batteries (hereinafter collectively referred to as “waste batteries”), etc. A method called dry processing for incineration has been used in many cases. In dry processing, plastics used in parts of waste batteries are decomposed at high temperatures, so valuable metals can be easily separated, and the recovered valuable metals can be further purified to recycle them as, for example, magnet materials. Can be used.

  On the other hand, there is also a method for recovering valuable metals by using a method called wet processing of a waste battery. In the wet treatment, one of the main chemical treatments is to take out a positive electrode active material containing valuable metals from a waste battery and leaching the positive electrode active material from a solid state to a liquid state, that is, a metal ion state.

  Conventionally, in the leaching treatment, a method of mixing the positive electrode active material with an acidic solution has been used. However, in the solution leached with an acid, in addition to valuable metals such as nickel and cobalt to be collected, aluminum or the like is used. In addition, elements that are not targeted for recovery are also contained, and it has been desired to leach at a higher leaching rate.

  Therefore, in order to selectively leach valuable metals and improve the leach rate, for example, Patent Document 1 proposes a method of adding ascorbic acid, sodium sulfite or the like as a reducing agent.

  However, for example, a reducing agent as disclosed in Patent Document 1 is a very expensive agent, which is accompanied by an increase in processing cost, and is capable of leaching metal efficiently and sufficiently efficiently. Can not.

  Patent Document 2 proposes a reprocessing method of a positive electrode active material for the purpose of suppressing the chemical cost and energy cost of an expensive reducing agent. However, the method described in Patent Document 2 is to inject the sulfuric acid gas of the reducing agent into the sulfuric acid aqueous solution until it is saturated and dissolve the positive electrode active material. The reducing agent is used in an amount more than necessary for the reaction. It is considered that the economy is not improved sufficiently.

Japanese Patent Laid-Open No. 11-293357 JP 2012-64557 A

  Therefore, the present invention has been proposed in view of such a situation, and in a method of reducing and leaching a metal from a positive electrode active material constituting a battery using a reducing agent, the present invention is efficient and efficient. It is an object of the present invention to provide a metal leaching method capable of effectively leaching metal at a high leaching rate and a method for recovering metal from a battery to which the leaching method is applied.

  As a result of intensive investigations to achieve the above-described object, the present inventors reduced the oxidation-reduction potential according to fluctuations in the oxidation-reduction potential of the slurry while maintaining the slurry containing the positive electrode active material in a predetermined pH range. By controlling the supply of the agent, it was found that the metal can be leached efficiently and effectively, and the present invention has been completed.

That is, the metal leaching method according to the present invention is a metal leaching method in which a reducing agent is added to a slurry containing a positive electrode active material constituting a battery, and the metal contained in the positive electrode active material is reduced and leached. In a state where an acidic solution is added to the slurry containing the positive electrode active material of the battery and the pH of the slurry is maintained within a predetermined range, the supply of the reducing agent is controlled according to the fluctuation of the oxidation-reduction potential of the slurry, and the metal is added. When reducing and leaching , the supply of the reducing agent lowers the oxidation-reduction potential of the slurry, and when the oxidation-reduction potential stops decreasing, the supply of the reducing agent is temporarily stopped and the oxidation-reduction potential is increased again. In this case, the operation of restarting the supply of the reducing agent is repeated, and the point at which the oxidation-reduction potential does not increase even if the supply of the reducing agent is stopped is determined as the end of leaching. Agent supply Characterized in that it completely stopped.

  Moreover, it is preferable to heat the slurry prior to supplying the reducing agent.

  Moreover, it is preferable to carry out reductive leaching in the state which maintained the pH of the said slurry at 0.5-1.5.

  The reducing agent is preferably sodium bisulfite or sodium sulfite.

The method for recovering a metal from a battery according to the present invention is a method for recovering a metal from a battery that recovers a metal from a positive electrode active material constituting the battery, wherein the reducing agent is added to the slurry containing the positive electrode active material of the battery. In the leaching step, an acidic solution is added to the slurry containing the positive electrode active material of the battery to adjust the pH of the slurry to a predetermined range. In this state, when the metal is reduced and leached by controlling the supply of the reducing agent according to the change in the oxidation-reduction potential of the slurry, the oxidation-reduction potential of the slurry is lowered by the supply of the reducing agent, The supply of the reducing agent is temporarily stopped when the oxidation-reduction potential stops decreasing, and the process of restarting the supply of the reducing agent is repeated when the oxidation-reduction potential rises again to stop the supply of the reducing agent. Even Reduction reduction potential is determined when the leaching time endpoint no longer increases, characterized in that it completely stopping the supply of the reducing agent at the end out該浸.

  According to the present invention, by controlling the supply of the reducing agent according to the fluctuation of the oxidation-reduction potential of the slurry, the reducing agent used when reducing and leaching the metal does not contribute to the leaching reaction and becomes a loss. The amount of the reducing agent used can be suppressed to the minimum necessary, and the metal can be efficiently leached efficiently and at a high leaching rate.

It is a trend graph of ORP and pH when a reductive leaching reaction is advanced, controlling supply of a reducing agent according to the fluctuation | variation of the oxidation reduction potential of a slurry.

Hereinafter, specific embodiments of a metal leaching method and a method for recovering metal from a battery according to the present invention (hereinafter referred to as “the present embodiment”) will be described in detail in the following order with reference to the drawings. To do. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.
1. Metal leaching method 2. Method for recovering metal from battery Example

<1. Metal leaching method>
The metal leaching method according to the present embodiment is a method of leaching valuable metals such as nickel, cobalt, and manganese contained in a positive electrode active material that constitutes a battery such as a lithium ion battery. A reducing agent is added to a slurry obtained by adding pure water or the like to a scrap material or the like, and these metals are reduced and leached.

  Specifically, the supply of the reducing agent is controlled in accordance with fluctuations in the oxidation-reduction potential of the slurry while adding an acidic solution to the slurry containing the positive electrode active material of the battery and maintaining the pH of the slurry within a predetermined range. And reducing leaching of the metal.

According to such a metal leaching method, it is possible to reduce the reducing agent that does not contribute to the reduction leaching reaction while maintaining a high leaching rate, so that the amount of reducing agent used is minimized. Therefore, it is possible to perform the leaching treatment with extremely high efficiency and high leaching rate. Further, since the loss of the reducing agent can be reduced, for example, when sodium sulfite or sodium hydrogen sulfite is used as the reducing agent, it is possible to effectively suppress the generation amount of sulfur dioxide (SO ₂ ) gas corresponding to the loss. This makes it possible to reduce the amount of chemicals used for the detoxification treatment, and to effectively reduce the burden on the environment.

  Although it does not specifically limit as a battery, For example, a lithium ion battery is mentioned. For example, the positive electrode active material of the lithium ion battery includes a compound constituting the positive electrode active material such as nickel (Ni) -cobalt (Co) -manganese (Mn) composite hydroxide. In the metal leaching method according to the present embodiment, valuable metals such as nickel, cobalt, and manganese contained in such a positive electrode active material are reduced and leached with a reducing agent.

  First, in this leaching method, pure water or the like is added to the positive electrode active material scraps constituting the battery to make a slurry, and an acidic solution is added to the slurry containing the positive electrode active material to adjust the pH to a predetermined value. Keep in range.

  The acidic solution to be added to the slurry is not particularly limited as long as it can be adjusted to a predetermined pH range, and a solution made of a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, an organic acid solution, or the like is used. be able to. Among these, it is preferable to use a sulfuric acid solution industrially from a viewpoint of cost, work environment, and recovery of metal obtained by leaching.

  Although it does not specifically limit as pH of the slurry adjusted and maintained by adding an acidic solution, It is preferable to set it as at least 2.0 or less, and when it considers the reactivity of a leaching reaction, it shall be about 0.5-1.5. It is more preferable. Among them, it is particularly preferable to adjust and maintain the pH at about 1.0.

  Next, in this leaching method, a reducing agent is supplied and the metal contained in the positive electrode active material is reduced and leached while maintaining the pH of the slurry in a predetermined range.

Here, for example, in the positive electrode active material constituting the lithium ion battery, nickel, cobalt, and manganese, which are valuable metals to be leached, are present in the form of, for example, Li (Ni—Co—Mn) O ₂ . . Therefore, these metals cannot be effectively leached only by adding an acidic solution such as sulfuric acid as described above. Therefore, for example, a reductive leaching reaction as shown in the following reaction formula (1) is advanced by supplying a reducing agent to the slurry in a state where the pH of the slurry is adjusted and maintained within a certain range with a sulfuric acid solution or the like.

4LiNiO ₂ + 5H ₂ SO ₄ + 2NaHSO ₃
→ 2Li ₂ SO ₄ + 4NiSO ₄ + Na ₂ SO ₄ + 6H ₂ O (1)
(In the reaction formula (1), Co and Mn are represented by Ni.)

The reducing agent used for reductive leaching is not particularly limited, and sulfites such as sodium bisulfite (NaHSO ₃ ) and sodium sulfite (Na ₂ SO ₃ ), sulfur dioxide, and the like can be used. Among these, it is preferable to use sodium bisulfite or sodium sulfite in that the metal can be leached more efficiently.

  In this reductive leaching reaction, as the reducing agent is supplied to the slurry, the oxidation-reduction potential (ORP) of the slurry changes. Specifically, for example, when a reducing agent such as sulfite is supplied to the slurry, the ORP rapidly decreases to about 400 to 500 mV (reference electrode: silver / silver chloride electrode), and the supply of the reducing agent is stopped. The ORP gradually rises.

  By the way, when a reducing agent such as sodium bisulfite is supplied and the reaction shown in the above reaction formula (1) is advanced, if the amount of the reducing agent supplied becomes excessive, a part of the reducing agent is reduced. It may be a loss without contributing to.

For example, when sodium bisulfite is used as the reducing agent, if the supply amount becomes excessive, a part of the hydrogen bisulfite does not contribute to the reduction reaction, and a part of the sodium bisulfite is lost by the reaction shown in the following reaction formula (2). And is discharged as sulfur dioxide (SO ₂ ) gas.

H ₂ SO ₄ + NaHSO ₃ → SO ₂ + NaHSO ₄ + H ₂ O (2)

If the reducing agent supplied in this way loses without contributing to the reduction reaction, the leaching efficiency with respect to the amount of reducing agent used is significantly reduced. In addition, reducing agents such as sodium hydrogen sulfite and sodium sulfite are very expensive chemicals, and if they are lost without contributing to the reaction, the processing efficiency from the viewpoint of economy is significantly reduced. Further, the SO ₂ gas corresponding to the loss is a harmful gas, and it is necessary to separately perform a detoxification process using a chemical when discharged. Therefore, the generation of SO ₂ gas leads to an increase in processing costs.

  Therefore, in the leaching method according to the present embodiment, the metal is reduced and leached while controlling the supply of the reducing agent in accordance with the fluctuation of the oxidation-reduction potential (ORP) of the slurry due to the supply of the reducing agent. Thus, by controlling the supply of the reducing agent according to the fluctuation of the oxidation-reduction potential of the slurry, it is possible to suppress the loss of the supplied reducing agent, and a minimum amount of reducing agent can be used. Thus, the leaching reaction can proceed efficiently and efficiently at a high leaching rate.

  More specifically, the supply control of the reducing agent includes reducing the ORP of the slurry by supplying the reducing agent to the slurry whose pH is kept constant, and temporarily supplying the reducing agent when the ORP cannot be lowered. Stop. Then, since ORP will rise again, supply of a reducing agent is restarted. The operation of supplying the reducing agent and temporarily stopping the supply according to the fluctuation of the ORP is repeated.

Here, FIG. 1 shows a trend graph of ORP and pH when the reductive leaching reaction is advanced while controlling the supply of the reducing agent according to the fluctuation of the oxidation-reduction potential of the slurry. 1B is a graph when FIG. 1A is enlarged, and is after the start of supply of sodium hydrogen sulfite (NaHSO ₃ ) as a reducing agent. In the leaching method according to the present embodiment, as shown in this graph, the reducing agent is supplied to reduce the ORP in accordance with the fluctuation of the ORP of the slurry, and the reducing agent is supplied when the ORP no longer decreases. The operation of pausing and restarting the supply of the reducing agent when the ORP rises again is repeated.

  Then, when the supply of the reducing agent according to the ORP is repeatedly performed and the ORP does not increase even if the supply of the reducing agent is stopped, the time point is determined as the brewing end time, and the reducing agent is determined. Stop supplying completely.

  In the leaching method according to the present embodiment, the supply amount of the reducing agent is adjusted according to the variation of the ORP of the slurry as described above, and the end point of the reduction leaching reaction is determined to completely stop the supply of the reducing agent. By performing the supply control, it is possible to suppress loss of the supplied reducing agent without contributing to the reaction, and metal can be effectively leached with a minimum necessary amount of use.

Further, since the loss of the reducing agent can be suppressed, the amount of SO ₂ gas discharged out of the system can be reduced as shown in the above reaction formula (2), and the SO ₂ gas is removed. The amount of medicine used for processing can be reduced, and the load on the environment can be reduced more effectively.

  In this leaching reaction, if the composition of the raw material to be treated (positive electrode active material) is known, the behavior of the ORP during the reductive leaching reaction and the ORP value at the reaction end point can be estimated, so the target ORP value And reducing agent loss can be more effectively reduced.

  In addition, since the ratio of the reducing agent that is lost also varies depending on the shape of the reaction vessel used for the leaching reaction, stirring, and the like, even if the raw material composition is known, the ORP behavior or It is preferable to appropriately adjust the estimated value of the end point ORP value. Also by this, the loss of a reducing agent can be reduced more effectively.

Furthermore, from the viewpoint of more effectively suppressing the loss of the reducing agent, the reducing agent may be supplied while measuring and monitoring the SO ₂ gas concentration in the apparatus internal space.

  Further, for example, when valuable metals to be leached exist in the form of oxides, reduction leaching at room temperature takes a long time. Therefore, in the leaching method according to the present embodiment, it is preferable that the slurry is heated and leached in a state where the temperature is increased prior to supplying the reducing agent to the slurry whose pH is adjusted to a predetermined range. By doing so, not only can the reduction of the reaction rate of the reductive leaching reaction be prevented, but also the reaction rate can be further increased and the time required for leaching can be shortened.

  Although it does not specifically limit as temperature at the time of heating a slurry, It is preferable to set it as 60-80 degreeC. If it is less than 60 degreeC, the improvement effect of reaction rate cannot fully be acquired and there exists a possibility that required time cannot fully be shortened. On the other hand, when the temperature is higher than 80 ° C., the effect of improving the reaction rate can be sufficiently obtained, but the cost for heating increases, which is not economically preferable.

Here, a slurry (concentration 100 g / L) of nickel-cobalt-manganese composite oxide [Li (Ni—Co—Mn) O ₂ ], which is a positive electrode active material of a lithium ion battery, is shown in Table 1 below at room temperature (15 The results of the leaching time and the amount of residue in the case of reduction leaching treatment at ˜28 ° C. and in the case of reduction leaching treatment after heating to 60 ° C. are shown. In the reductive leaching process, 35% sodium hydrogen sulfite was used as the reducing agent, and the amount of reducing agent supplied was adjusted according to the change in the ORP of the slurry as described above.

  As shown in Table 1, it can be seen that the leaching time is greatly shortened and the amount of residue is reduced when the treatment is performed at a temperature of 60 ° C. or higher compared to the treatment at room temperature. Thus, by reducing and leaching in a state where the temperature of the slurry is increased by heating, the reduction reaction rate can be increased and more efficient treatment can be performed.

<2. Method for recovering metal from batteries>
Next, a method for recovering metal from a battery to which the above-described metal leaching method is applied will be described. This method for recovering metal from a battery is a method for recovering valuable metals such as nickel, cobalt, manganese, etc. from a positive electrode active material of a battery such as a lithium ion battery, and a reducing agent is added to the slurry containing the positive electrode active material of the battery. And a leaching step of reducing and leaching the metal contained in the positive electrode active material. In the leaching step, the reducing agent is supplied in accordance with fluctuations in the oxidation-reduction potential of the slurry while an acidic solution is added to the slurry containing the positive electrode active material of the battery and the pH of the slurry is maintained within a predetermined range. It is characterized by controlling and leaching metal.

  Specifically, the method for recovering the metal from the battery includes, for example, a discharge process, a crushing / crushing process, a cleaning process, a positive electrode active material peeling process, and a leaching process.

[Discharge process]
In the discharging step, the battery is discharged prior to disassembling the used battery (scrap product or the like) when recovering valuable metals from the used lithium ion battery or the like. When the battery is disassembled by crushing and crushing in a crushing and crushing process, which will be described later, since the battery is dangerous in a charged state, it is discharged and rendered harmless.

  In this discharge step, a discharge solution such as an aqueous solution of sodium sulfate or an aqueous solution of sodium chloride is used, and the used battery is discharged by immersing it in the aqueous solution.

[Crushing and crushing process]
In the crushing / disintegrating step, the used lithium ion battery, which has been made harmless by discharge, is disassembled by crushing / disintegrating.

  In this crushing and crushing process, the harmless battery is disassembled into an appropriate size using a normal crusher or crusher. In addition, the outer can can be cut to separate and disassemble the internal positive electrode active material, the negative electrode material, and the like, but in this case, it is preferable to further cut each separated portion into an appropriate size.

[Washing process]
In the cleaning step, the battery disassembled product obtained through the crushing / disintegrating step is washed with water or alcohol to remove the electrolytic solution and the electrolyte. The lithium ion battery includes an organic solvent such as ethylene carbonate, propylene carbonate, diethyl carbonate, and dimethyl carbonate, and an electrolyte such as lithium hexafluorophosphate (LiPF ₆ ). Therefore, by removing these in advance, organic components, phosphorus (P), fluorine (F), and the like are prevented from being mixed as impurities in the leachate in the leaching process described later.

  To clean the battery disassembly, water or alcohol is used, and the organic components and the electrolyte are removed by shaking or stirring. As the alcohol, ethanol, methanol, isopropyl alcohol, or a mixture thereof is used. Carbonates are generally insoluble in water, but the electrolyte component, ethylene carbonate, is arbitrarily soluble in water, and other organic components have some solubility in water, so they can be washed with water. is there.

  The battery disassembled product is preferably washed a plurality of times. This washing step removes organic components, phosphorus, fluorine, and the like derived from the electrolyte to such an extent that they do not affect the subsequent steps.

[Positive electrode active material peeling process]
In the positive electrode active material peeling step, the positive electrode active material is peeled off by immersing the disassembled battery obtained through the washing step in an acidic solution such as a sulfuric acid solution, an alkaline solution, or an aqueous solution containing a surfactant. Separate. In this step, the battery disassembled product is charged into an acidic solution such as a sulfuric acid solution or a surfactant solution and stirred, whereby the positive electrode active material and the aluminum foil can be separated as they are in a solid state. In this step, all of the battery disassembled material may be immersed in an aqueous sulfuric acid solution or a surfactant solution, but only the positive electrode material portion may be selected and immersed from the battery disassembled material.

  For example, when a sulfuric acid solution is used as the acidic solution, the pH of the solution is controlled in the range of pH 0-3. The input amount of the battery disassembled product with respect to the sulfuric acid solution is 10 to 100 g / l. Moreover, a sodium hydroxide solution etc. can be used as an alkaline solution, and it is set as 0.3-1.0N as the addition amount. Moreover, when using a surfactant containing solution, it does not specifically limit as a kind of surfactant to be used, Nonionic surfactant, anionic surfactant, etc. can be used. The addition amount of the surfactant is preferably 1.5 to 10% by weight, and the pH of the surfactant solution is preferably in the range of 5 to 9.

  The disassembled battery obtained through the positive electrode active material peeling step is sieved and separated from the positive electrode substrate, such as nickel-cobalt-manganese hydroxide, positive electrode active material such as lithium nickelate, lithium cobaltate, and the like. Collect the incidental items.

  In this positive electrode active material peeling step, the positive electrode active material and aluminum foil and other solids are separated by peeling the positive electrode active material from the battery disassembled product using the above-described acidic solution or surfactant-containing solution. Then, other than the solid content, treatment solutions such as an acidic solution, an alkali solution, and a surfactant solution used for the peeling treatment are discharged as a filtrate.

[Leaching process]
In the leaching step, for example, pure water is added to the positive electrode active material peeled and recovered in the positive electrode active material peeling step to form a slurry, and a reducing agent is added to the slurry containing the positive electrode active material, and the positive electrode active material is removed. Reduces and leaches out metals contained in substances.

  In this leaching step, as described above, a reducing agent is added according to fluctuations in the oxidation-reduction potential of the slurry while adding an acidic solution to the slurry containing the positive electrode active material of the battery and maintaining the pH of the slurry within a predetermined range. The metal is reduced and leached by controlling the supply.

  More specifically, as the supply control of the reducing agent, the supply of the reducing agent reduces the oxidation-reduction potential of the slurry, and when the oxidation-reduction potential stops decreasing, the supply of the reducing agent is temporarily stopped and the oxidation-reduction is again performed. The operation of restarting the supply of the reducing agent when the potential rises is repeated. Then, the point in time when the oxidation-reduction potential does not increase even if the supply of the reducing agent is stopped is determined as the brewing end point, and the supply of the reducing agent is completely stopped.

  In the leaching step, the reducing agent is leached by reducing and leaching the metal while controlling the supply of the reducing agent according to the fluctuation of the oxidation-reduction potential of the slurry while keeping the pH of the slurry constant in this way. It is possible to suppress the loss without contributing to the reaction, and to efficiently and effectively reduce and leach metals.

  In addition, since the reductive leaching reaction in the leaching step is the same as described above, a description thereof is omitted here.

  As described above, a leaching solution in which valuable metals such as nickel, cobalt, and manganese are leached and a leaching residue made of impurities are obtained by the reduction leaching process in the leaching step. And a leachate can be isolate | separated by performing solid-liquid separation processes, such as filtration, with respect to this.

  Here, when the recovered valuable metal is recycled to, for example, a ternary positive electrode material (NCM) of nickel, cobalt, and manganese, the positive electrode active material made of, for example, nickel-cobalt-manganese composite hydroxide is reduced. The leachate obtained by leaching is collected, and the positive electrode active material is produced using the leachate as a raw material, so that it can be recycled. That is, if impurities can be removed by the leaching process or the above-described cleaning process, it is not necessary to separate nickel, cobalt, and manganese contained in the leaching solution.

  On the other hand, when recycle for manufacturing raw materials other than nickel, cobalt and manganese ternary cathode materials (NCM) such as magnet materials and other cathode active materials, Further processing for separating and recovering the metal is required. Specifically, for example, when nickel and cobalt contained in the leachate are separated and recovered, the following sulfurization step can be performed.

[Sulfurization process]
In the sulfidation step, the solution (leaching solution) obtained through the leaching step is introduced into a reaction vessel, and a sulfidation agent is added to cause a sulfidation reaction, thereby producing a nickel / cobalt mixed sulfide. Thereby, nickel and cobalt contained in the leachate are separated and recovered. As the sulfiding agent, sodium sulfide, sodium hydrosulfide, alkali sulfide such as hydrogen sulfide gas, or the like can be used.

Specifically, in this sulfidation step, nickel ions (or cobalt ions) contained in the solution obtained through the leaching step are sulfided by alkali sulfide according to the following reaction formula (3), (4) or (5). By reaction, it becomes sulfide.
Ni ² + + H ₂ S ⇒ NiS + 2H ⁺ (3)
Ni ²⁺ + NaHS ⇒ NiS + H ⁺ + Na ⁺ (4)
Ni ²⁺ + Na ₂ S ⇒ NiS + 2Na ⁺ (5)

  Addition of the sulfiding agent in the sulfiding step is performed until the ORP in the reaction solution does not fluctuate even if more sulfiding agent is added. The reaction is usually completed in the range of −200 to 400 mV (reference electrode: silver / silver chloride electrode). The pH of the solution used for the sulfurization reaction is about 2 to 4. The temperature of the sulfurization reaction is not particularly limited, but is 0 to 90 ° C, preferably about 25 ° C.

  In particular, in the above formulas (3) and (4), an acid is also generated when the reaction proceeds, and the reaction is delayed. For this reason, in order to accelerate and complete the reaction, it is preferable to neutralize the generated acid by adding an alkali such as sodium hydroxide together with the addition of the sulfurizing agent.

  Thus, by causing a sulfurization reaction in the sulfurization process, nickel and cobalt, which are valuable metals contained in the positive electrode active material of a battery such as a lithium ion battery, are converted into nickel / cobalt sulfide (sulfurized starch). It can be separated and recovered, and can be used as a raw material for producing a magnetic material or a positive electrode active material.

<3. Example>
Specific examples and comparative examples to which the present invention is applied will be described below, but the present invention is not limited to these examples and comparative examples.

[Example 1]
As a raw material, 50 g of a positive electrode scrap of a lithium ion battery (positive electrode active material: Ni—Co—Mn composite hydroxide) was used, and pure water was added thereto to obtain a slurry having a concentration of 100 g / L.

After adding 64% concentration H ₂ SO ₄ to the slurry and adjusting the pH of the slurry to 1.0, while controlling the concentration of 35% NaHSO ₃ as a reducing agent according to the variation of the ORP of the solution, A leaching treatment was performed to reduce and leach valuable metals such as nickel and cobalt. H ₂ SO ₄ was continuously added to maintain the pH of the slurry at 1.0.

The ORP of the solution decreased rapidly when the reducing agent was supplied, and the supply was temporarily stopped when it did not decrease. Then, since the ORP rose again, the supply of the reducing agent was resumed. When this operation was repeated and reduction leaching was performed, the ORP became difficult to increase even when the supply was stopped. At this time, it was determined that leaching was completed, and the supply of H ₂ SO ₄ and NaHSO ₃ was stopped.

When the obtained leachate was suction filtered, the leach residue was 0.85 g, and leaching was almost completed. The amount of reagent used was 51.9 ml of 64% H ₂ SO ₄ , 17 ml of 35% NaHSO ₃ and the leaching time was 1 hour 50 minutes.

[Example 2]
The method of leaching treatment is the same as that of Comparative Example 1, but a method of heating before leaching was adopted. That is, reductive leaching was performed at a slurry temperature of 60 ° C. during leaching.

When the obtained leachate was suction filtered, the leach residue was 0 g. As the reagent usage quantity, _64% H 2 SO ₄ is 65.8Ml, is 35% _Na 2 SO ₃ was 18.5 ml. The leaching time was 1 hour.

  Thus, by heating and performing the leaching treatment, the treatment time can be shortened and the amount of the leaching residue can be reduced. That is, the reduction leaching reaction can be advanced more efficiently and effectively.

[Comparative Example 1]
The leaching treatment method was the same as in Example 1, but after adjusting the pH of the slurry to 1.0, a method of supplying an excessive amount of 35% NaHSO ₃ as a reducing agent was adopted. That is, the supply of the reducing agent was not controlled, and an excessive amount of the reducing agent was supplied to the slurry.

The ORP of the solution gradually decreased with the progress of reductive leaching, but the decrease curve became steep near 300 to 400 mV (Ag / AgCl electrode). At this time, it was determined that the leaching was completed, and the supply of H ₂ SO _{4 and} NaHSO ₃ was stopped.

  When the obtained leachate was suction filtered, the leaching residue was 0.11 g, leaching was almost completed, and the leaching treatment could be performed effectively.

However, the amount of reagent used was 64% H ₂ SO ₄ was 61.3 ml, but 35% Na ₂ SO ₃ was 36 ml, which was more than double the amount used in Example 1. . This is thought to be because NaHSO ₃ that did not contribute to the reduction leaching reaction was lost as SO ₂ gas, and the generation of the loss led to an increase in the amount of reducing agent used. The leaching time was 1 hour 30 minutes.

Claims (5)

A metal leaching method for adding a reducing agent to a slurry containing a positive electrode active material constituting a battery and reducing and leaching a metal contained in the positive electrode active material,
In the state where the acidic solution is added to the slurry containing the positive electrode active material of the battery and the pH of the slurry is maintained within a predetermined range, the supply of the reducing agent is controlled according to the fluctuation of the oxidation-reduction potential of the slurry. When the reduction leaching is performed, the supply of the reducing agent lowers the oxidation-reduction potential of the slurry. When the oxidation-reduction potential no longer decreases, the supply of the reducing agent is temporarily stopped, and the oxidation-reduction potential is reduced again. The operation of resuming the supply of the reducing agent is repeated when it rises, and the point at which the oxidation-reduction potential does not rise even if the supply of the reducing agent is stopped is determined as the end of leaching. A metal leaching method characterized by completely stopping the supply of the reducing agent . The metal leaching method according to claim 1, wherein the slurry is heated prior to supplying the reducing agent. The metal leaching method according to claim 1 or 2 , wherein the reduction leaching is performed while maintaining the pH of the slurry at 0.5 to 1.5. The metal leaching method according to any one of claims 1 to 3 , wherein the reducing agent is sodium hydrogen sulfite or sodium sulfite. A method of recovering metal from a battery that recovers metal from a positive electrode active material constituting the battery,
A leaching step of reducing and leaching the metal contained in the positive electrode active material by adding a reducing agent to the slurry containing the positive electrode active material of the battery,
In the leaching process, an acidic solution is added to the slurry containing the positive electrode active material of the battery and the pH of the slurry is maintained within a predetermined range, and a reducing agent is supplied according to fluctuations in the oxidation-reduction potential of the slurry. When the metal is reduced and leached by controlling the reduction of the oxidation-reduction potential of the slurry by the supply of the reducing agent, the supply of the reducing agent is temporarily stopped when the oxidation-reduction potential no longer decreases. The process of restarting the supply of the reducing agent when the oxidation-reduction potential is increased is repeated, and the point in time when the oxidation-reduction potential does not increase even when the supply of the reducing agent is stopped is determined as the end of leaching, A method for recovering a metal from a battery , wherein the supply of the reducing agent is completely stopped at the end of leaching .

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