JP5962487B2 - Method for separating rare earth elements contained in nickel metal hydride battery and method for recovering valuable metals from nickel metal hydride battery - Google Patents

Description

  The present invention relates to a method for separating rare earth elements contained in a nickel metal hydride battery, and a method for recovering valuable metals from a nickel metal hydride battery to which the method for separating rare earth elements is applied.

  In recent years, environmental problems such as global warming due to acid rain and carbon dioxide gas caused by acid gases such as nitrogen oxides and sulfur oxides released into the atmosphere have been highlighted as global issues. One of the causes is automobile exhaust gas. In order to reduce pollution caused by the exhaust gas, a hybrid vehicle equipped with a secondary battery such as a nickel metal hydride battery has attracted attention.

  The nickel-metal hydride battery has a positive electrode, a negative electrode, an electrode terminal, and an electrolyte as functional members, and further, as a structural member, a separator provided between the electrodes of the positive electrode and the negative electrode, and a case for housing these Etc.

  A large-capacity nickel-metal hydride battery mounted on a hybrid vehicle is replaced with a new one when it deteriorates with use, or is removed when the car is scrapped and discharged as a used nickel-metal hydride battery. In addition, defective products generated in the manufacturing process of the nickel-metal hydride battery, members such as active materials and positive / negative electrodes that are no longer assembled without being assembled into the battery, and prototypes are also generated. Since these used nickel metal hydride batteries, defective products, members, prototypes, etc. (hereinafter collectively referred to as “waste batteries”) contain many kinds of rare valuable metals such as nickel and rare earth elements, It has been studied to recover these valuable metals and reuse them.

  As a method of recovering nickel or cobalt from used nickel metal hydride batteries, for example, the used nickel metal hydride battery is melted by putting it in a furnace, and the synthetic resin constituting the battery is burned and removed. There is a dry processing method in which the iron is removed by slag and the nickel is reduced and recovered as ferronickel alloyed with part of the iron.

  However, in the case of this dry processing method, although there is an advantage that existing smelter equipment can be used as it is and the processing is not troublesome, it is difficult to separate impurities from the recovered ferronickel. Not suitable for uses other than raw materials. In particular, since most of cobalt and rare earth elements are distributed in slag and discarded, it is not a desirable method in terms of effective utilization of rare cobalt and rare earth elements.

  As another method, for example, as described in Patent Document 1, a method of recovering valuable metals by wet processing has been proposed.

  The method described in Patent Document 1 is a method for recovering valuable metals from a used nickel-metal hydride battery. After dissolving in sulfuric acid and leaching into a metal ion state, a rare earth metal is separated from the aqueous phase as a bisulfate. It is to do. Specifically, the leachate obtained by the leaching treatment contains rare earth elements such as lanthanum, cerium, and neodymium in addition to nickel and cobalt. In order to efficiently separate the rare earth elements, the leachate is desorbed. An alkali sulfate such as sodium sulfate is added as a rare earth agent to generate a precipitate.

  However, rare earth elements have low solubility in sulfuric acid, and when leached in accordance with the low solubility of rare earth elements, a leachate with a low nickel concentration is generated, which is an undesirable concentration from the viewpoint of sulfidation in the subsequent sulfidation process. It becomes. Further, in this method, the amount of a rare earth agent such as a sulfiding agent used for rare earth separation is increased, and the cost of chemicals is increased.

Japanese Patent No. 3918041

  Therefore, the present invention has been proposed in view of such circumstances, and when recovering nickel and rare earth elements, which are valuable metals, from the negative electrode parts of nickel metal hydride batteries, the efficiency is improved while leaching nickel at a high leaching rate. It is an object of the present invention to provide a method for separating rare earth elements contained in a nickel-metal hydride battery capable of separating rare earth elements and a method for recovering valuable metals from nickel-metal hydride batteries using this method.

As a result of intensive studies to achieve the above-described object, the present inventors have found that the amount of nickel and rare earth contained in the negative electrode component can form a sulfate with respect to the negative electrode component at the start of leaching. It was added sulfuric acid solution, with nickel to total amount dissolved as sulfate solution, by subjecting the leach process for negative electrode part using a sulfuric acid solution with an adjusted concentration so rare earth is partially dissolved, high nickel It was found that rare earth elements can be efficiently separated while leaching at a leaching rate.

That is, the method for separating a rare earth element contained in a nickel metal hydride battery according to the present invention separates the rare earth element contained in the negative electrode component when recovering nickel and rare earth elements as valuable metals from the negative electrode component of the nickel hydrogen battery. In the method, at the start of leaching, to the negative electrode component, an amount of sulfuric acid solution in which both the nickel and the rare earth contained in the negative electrode component can form a sulfate is added, and the nickel is sulfate as well as the total amount dissolved in solution, the rare earth by adjusting the concentration of the sulfuric acid solution to partially dissolve, leach valuable metals from the negative electrode parts, resulting leach slurry is separated into a leach residue and leachate The rare earth element dissolved in the leachate is separated by adding a rare earth agent to the leachate.

Further, the method of recovering valuable metals from nickel-hydrogen battery according to the present invention is a method of recovering valuable metals to recover nickel and rare earth elements are valuable metal from the anode part of the nickel hydrogen battery, at the beginning the leaching, the to the negative electrode parts, it was added to the nickel and the rare earth and is capable of forming both sulfates amount of sulfuric acid solution contained in the negative electrode parts, with the nickel to total amount dissolved as sulfate solution, the rare earth A leaching step of leaching valuable metal from the negative electrode component to obtain a leaching slurry by adjusting the concentration of the sulfuric acid solution that partially dissolves, and a solid-liquid separation step of separating the leaching slurry into a leaching solution and a leaching residue And a rare earth element step of separating a rare earth element dissolved in the leachate by adding a rare earth agent to the leachate.

Here, at the start of the leaching , the concentration of the sulfuric acid solution is determined such that the nickel contained in the negative electrode component and the rare earth element having the highest solubility in the sulfuric acid solution among the rare earth elements can form a sulfate. the addition of sulfuric acid solution, with the nickel to total amount dissolved as the sulfate solution, the rare earth is preferably adjusted so as to partially dissolved.

In the present invention, at the start leaching, negative both nickel and rare earth contained in the in the part is added the amount of the sulfuric acid solution capable of forming a sulfate salt, with nickel to total amount dissolved as sulfate solution, the rare earth portion Nickel is leached using a sulfuric acid solution whose concentration is adjusted so as to dissolve it. Therefore, nickel can be leached at a high leaching rate, and a rare earth element sulfate can be partially deposited on the leaching residue obtained by the leaching treatment, which is used when separating the rare earth element from the leachate. Rare earth elements can be efficiently separated and recovered while reducing the amount of the rare earth agent used.

It is a flowchart which shows the flow of the separation method of the rare earth elements contained in the nickel metal hydride battery which concerns on this Embodiment. It is a graph which shows the solubility (25 degreeC theoretical value) with respect to the sulfuric acid concentration of La, Ce, and Nd of rare earth elements. It is a graph which shows the solubility (25 degreeC theoretical value) with respect to the sulfuric acid concentration of rare earth elements La, Ce, Nd, and Ni.

Specific embodiments of a method for separating rare earth elements contained in a nickel metal hydride battery according to the present invention and a method for recovering valuable metals from a nickel metal hydride battery to which this method is applied (hereinafter referred to as “the present embodiment”) Will be described in detail in the following order with reference to the drawings. 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. 1. Method for separating rare earth elements contained in nickel metal hydride battery 1-1. Leaching process 1-2. Solid-liquid separation process 1-3. 1. Rare earth removal process Method for recovering valuable metals from nickel metal hydride batteries

<1. Separation of rare earth elements contained in nickel metal hydride batteries>
The rare earth element separation method according to the present embodiment is a method of separating rare earth elements contained in a negative electrode component when recovering nickel and rare earth elements, which are valuable metals, from the negative electrode component of a nickel metal hydride battery. More specifically, when leaching and recovering a valuable metal using a sulfuric acid solution from, for example, a hydrogen storage alloy or the like constituting the negative electrode component, the leached valuable metal nickel and a rare earth element that is also a valuable metal are used. It is a separation method for separating and recovering each.

Specifically, this rare earth element separation method is obtained by a leaching step of leaching a valuable metal from a negative electrode part of a nickel-metal hydride battery, which is a raw material, using a sulfuric acid solution, as shown in a flow chart in FIG. A solid-liquid separation step of separating the leached slurry into a leaching solution and a leaching residue, and a rare earth element such as sodium sulfate (Na ₂ SO ₄ ) is added to the leaching solution to separate the rare earth elements dissolved in the leaching solution With a rare earth removal step.

In the rare earth element separation method according to the present embodiment, in the leaching step described above, at the start of leaching, an amount of sulfuric acid solution in which both nickel and rare earth contained in the negative electrode component can form a sulfate is formed. was added, together with nickel to total amount dissolved as sulfate solution, rare earth becomes important to leach nickel with sulfuric acid solution adjusted to a concentration of partially dissolved.

  Here, conventionally, for example, when recovering a valuable metal from a negative electrode part of a nickel metal hydride battery, after dissolving it in a sulfuric acid solution and leaching it into a metal ion state, the rare earth metal is converted into a bisulfate from the aqueous phase. The method of separating was taken. Specifically, the leachate (aqueous phase) obtained by the leaching treatment contains rare earth elements such as lanthanum, cerium, and neodymium in addition to nickel. In order to efficiently separate the rare earth elements. A rare earth agent was added to the leachate and fixed as a sulfate double salt. However, the rare earth elements as described above dissolved in the leachate have a low solubility in sulfuric acid. Therefore, when leaching is performed in accordance with the solubility of these rare earth elements, a leachate having a low nickel concentration is generated without sufficiently leaching nickel. Will be. Such a leachate having a low nickel concentration makes it difficult to effectively recover nickel in a subsequent recovery step, making it difficult to effectively recycle valuable metals. In addition, the amount of the rare earth agent used in the rare earth treatment for separating and recovering the rare earth element from the leachate is increased, leading to an increase in chemical cost.

On the other hand, in the method for separating nickel and rare earth elements according to the present embodiment, the concentration of the sulfuric acid solution used in the leaching process is controlled within a predetermined range. More specifically, at the start of leaching, was added sulfuric acid solution of nickel amount and which is capable of forming both sulfates rare earth contained in the negative electrode parts, with nickel to total amount dissolved as sulfate solution, rare earth so that leaching of nickel with sulfuric acid solution adjusted to a concentration of partially dissolved. According to such a method, nickel can be leached at a high leaching rate to obtain a leaching solution having a high nickel concentration, and the rare earth element sulfate can be partially precipitated on the leaching residue produced by the leaching treatment. At this stage, some rare earth elements can be separated as leaching residues. And thereby, compared with the conventional method, the density | concentration of the rare earth element melt | dissolved in the obtained leachate can be reduced. Therefore, even when the rare earth element is fixed and separated from the leachate with the rare earth element, the amount of the rare earth element used can be effectively reduced, and the rare earth element separated as the leaching residue can be effectively combined with the rare earth element. Elements can be separated and recovered.

<1-1. Leaching process>
In the leaching step, a leaching treatment using a sulfuric acid solution is performed on the negative electrode part of the nickel metal hydride battery containing valuable metals such as nickel and rare earth elements. This leaching treatment proceeds until the reaction proceeds as shown in the following reaction formula (i), and the generation of hydrogen accompanying the reaction disappears.
Ni + 2RE + 4H ₂ SO ₄ → NiSO ₄ + RE ₂ (SO ₄ ) ₃ + 4H ₂
... (i)

  The negative electrode part of the nickel metal hydride battery is not particularly limited. For example, defective parts (manufacturing process scrap) generated in the manufacturing process of the negative electrode part or the negative electrode part taken out by disassembling the used nickel metal hydride battery Can be used. For this negative electrode component, a hydrogen storage alloy containing nickel or a rare earth element can be mainly used.

In the method for separating nickel and rare earth element in the present embodiment, as described above, in this leaching step, at the start of leaching , the amount of nickel and rare earth contained in the negative electrode component can each form sulfate. It was added sulfuric acid solution, with nickel to total amount dissolved as sulfate solution, rare earth leach nickel with sulfuric acid solution adjusted to a concentration of partially dissolved.

Here, the negative electrode component of the nickel metal hydride battery contains, for example, lanthanum, cerium, neodymium, etc. as rare earth elements. Moreover, depending on the kind of hydrogen storage alloy which comprises the negative electrode components, rare earth elements other than these may be contained. Thus, the negative electrode component includes a plurality of rare earth elements, and the solubility of each rare earth element in sulfuric acid is different. Therefore, as the concentration of the sulfuric acid solution used for leaching, at the start of leaching, an amount of sulfuric acid solution in which nickel contained in the negative electrode component and the rare earth having the highest solubility in sulfuric acid can form a sulfate salt is added. with nickel to total amount dissolved as sulfate solution, most rare earth solubility sulfate is more preferable to adjust the concentration to partially dissolve.

For example, FIG. 2 is a graph showing the solubility (theoretical value at 25 ° C.) of the rare earth elements lanthanum (La), cerium (Ce), and neodymium (Nd) in sulfuric acid. As shown in the graph of FIG. 1, it is understood that Ce is the rare earth element having the highest solubility in sulfuric acid among La, Ce, and Nd. Therefore, for example, when leaching is performed using a negative electrode component containing these three kinds of rare earth elements, nickel and Ce contained in the negative electrode component can both form sulfates at the start of leaching. an amount of added sulfuric acid solution, with nickel to total amount dissolved as sulfate solution, Ce adjusts the concentration to partially dissolve.

  That is, as shown in FIG. 3, the concentration fluctuation accompanying the leaching occurs in the shaded portion in the figure where the concentration of the sulfuric acid solution used for leaching is in the range above the solubility of rare earth elements and above the solubility of nickel. The leaching process is performed by adjusting as described above. In the experimental example shown in FIG. 3, the concentration of the sulfuric acid solution at the start of the leaching process is 300 g / L (open star), and the sulfuric acid concentration fluctuation due to leaching is two stars (open star, black star). It shows that it has changed as shown by the dotted line that connects.

As described above, when the concentration of the sulfuric acid solution used for leaching is adjusted so as to cause fluctuation due to the leaching within the range of the solubility of rare earth elements and the solubility of nickel, as shown in the above reaction formula (i). In addition, the rare earth element contained in the negative electrode component dissolves in the sulfuric acid solution as it leaches out, but since the sulfuric acid concentration is made higher than the solubility of the rare earth element, the saturated content becomes starch. To precipitate. This starch is a rare earth element sulfate (RE ₂ (SO ₄ ) ₃ ), and becomes a leaching residue produced by leaching treatment. On the other hand, since the concentration of the sulfuric acid solution is in the above-described range, nickel leaching can proceed efficiently, and nickel can be leached at a high leaching rate. Moreover, since the upper limit of the concentration of the sulfuric acid solution is in the range below the solubility of nickel, it prevents the nickel sulfate (NiSO ₄ ) produced by leaching from precipitating and forming a leaching residue, resulting in high leaching. Nickel can be leached at a high rate.

  Note that the concentration of the sulfuric acid solution at the start of leaching can be appropriately adjusted depending on the composition of the negative electrode component as the raw material and the input amount. For example, the concentration can be set by calculating backward from the Ni concentration required after leaching.

  Although it does not specifically limit as pH of the sulfuric acid solution used for this leaching process, It is preferable to adjust to the range of pH 0-5, and it is more preferable to adjust to pH 0-1. When the pH of the sulfuric acid solution is less than 0, for example, when the neutralization treatment is performed in the subsequent step, the amount of neutralizing agent used increases. On the other hand, if the pH of the sulfuric acid solution exceeds 5, the leaching rate of nickel may decrease.

  The temperature (liquid temperature) of the sulfuric acid solution is not particularly limited, but is preferably about 20 to 95 ° C., more preferably about 50 to 90 ° C., and maintained at about 80 ° C. It is particularly preferable to carry out the treatment. In addition, it is preferable to perform the density | concentration adjustment of the sulfuric acid solution mentioned above based on the solubility of nickel and rare earth elements based on the liquid temperature of the sulfuric acid solution.

  Further, this leaching treatment is preferably performed while stirring the sulfuric acid solution. By stirring the solution in this manner, the leaching reaction can be efficiently advanced, and valuable metals to be leached can be leached at a higher leaching rate.

  Moreover, it is although it does not specifically limit as slurry density | concentration in a leaching process, It is preferable to adjust to about 50-300 g / L. When the slurry concentration is less than 50 g / L, the equipment for the leaching process is increased in size, and the amount of wastewater generated is also increased. On the other hand, when the slurry concentration exceeds 300 g / L, the stirring is uneven and tends to be non-uniform.

<1-2. Solid-liquid separation process>
Next, in the solid-liquid separation step, the leaching slurry obtained by the above leaching process is subjected to a solid-liquid separation process to separate the leaching liquid and the leaching residue.

As described above, in the leaching process, since the leaching process is performed using a sulfuric acid solution whose concentration is adjusted to be higher than the solubility of the rare earth element, the precipitate of rare earth element (sulfate) contained in the negative electrode component (RE ₂ (SO ₄ ) ₃ )) is formed and is a leaching residue. Therefore, in this solid-liquid separation step, by separating the leaching residue from the obtained leaching slurry, it is possible to effectively separate and recover a predetermined amount of the rare earth element before separation of the rare earth element in the subsequent derareening step. Can do. And by separating and recovering rare earth elements as leaching residues in this way, the amount of rare earth elements to be separated and recovered in the post-desorption rare earth step can be reduced, and the amount of derare earth agent used can be effectively reduced. Can be reduced.

  The method for the solid-liquid separation treatment is not particularly limited, and for example, separation can be performed using a method such as suction filtration, pressure filtration, or centrifugal separation.

<1-3. Rare earth removal process>
In the rare earth removal step, a rare earth element is added to the leachate and stirred, and the rare earth elements dissolved in the leachate are separated and recovered.

  The leaching solution in the leaching slurry obtained by the leaching treatment described above contains a high concentration of nickel leached from the negative electrode component, and a part of the rare earth elements that did not become leaching residue are similarly sulfuric acid solution. Leached and dissolved by Specifically, the rare earth element dissolved by the leaching reaction at the sulfuric acid concentration in the encircled portion X in the sulfuric acid concentration fluctuation line (dotted line) in FIG. 3 is contained in the leaching solution. Therefore, in this de-rare earth step, by separating and recovering the rare earth element dissolved in the leachate, nickel and the rare earth element can be separated, and each can be recovered with a high concentration.

Specifically, in this de-rare earth process, for example, a rare earth element is separated as a precipitate (sulfuric acid double salt) by causing a sulfate double salt formation reaction as shown in the following reaction formula (ii).
RE ₂ (SO ₄ ) ₃ + Na ₂ SO ₄ + xH ₂ O
→ RE · Na (SO ₄ ) ₂ · xH ₂ O (ii)

  As the rare earth removal agent used in the rare earth removal step, for example, alkali sulfates such as sodium sulfate and potassium sulfate can be used. By using these alkali sulfates, the sulfate complex as shown in the above reaction formula (ii) can be used. A salt formation reaction can occur. In addition, as the rare earth agent, for example, alkali hydroxides such as sodium hydroxide and potassium hydroxide can be used. By using these alkali hydroxides, hydroxide precipitates of rare earth elements can be formed. it can. Further, when such an alkali hydroxide is used, the leachate can be neutralized simultaneously with the separation of the rare earth elements, and for example, it can also serve as a preliminary treatment for subsequent nickel recovery.

  The addition amount of the rare earth remover is not particularly limited, but for example, when sodium sulfate is used, it is preferably added so as to be 90 g / L or more.

  In the present embodiment, as described above, a rare earth element precipitate (sulfate) is effectively generated in the leaching treatment to obtain a leaching residue, and the leaching residue is already separated and recovered from the obtained leaching slurry. Therefore, the amount of rare earth elements to be separated and recovered from the leachate in this derare earth step is effectively reduced. Therefore, the amount of the rare earth agent used in the derare earth process can be effectively suppressed, and the cost of the medicine can be reduced.

  In addition, as pH at the time of reaction in a rare earth removal process, although it does not specifically limit, It is preferable to set it as pH 1-5, and it is more preferable to set it as pH 1-3. By setting the pH during the reaction to 1 to 5, precipitation of rare earth elements can be more effectively generated and separated.

  The liquid temperature of the leachate to be treated is not particularly limited, but is preferably about 50 to 70 ° C. When the liquid temperature is less than 50 ° C., a practical and satisfactory reaction rate cannot be obtained. On the other hand, in consideration of the amount of water evaporation and energy efficiency, it is preferably set to 70 ° C. or lower.

  The slurry concentration is not particularly limited, but is preferably adjusted to about 50 to 300 g / L.

  In addition, the treatment time is not particularly limited, but if it is too long, the precipitated rare earth element may be redissolved, so in consideration of the concentration of the rare earth agent used, the liquid temperature, etc. It is preferable to adjust appropriately.

<2. Method for recovering valuable metals from nickel metal hydride batteries>
Next, a method for recovering valuable metals from a nickel metal hydride battery, to which the above-described method for separating rare earth elements contained in the nickel metal hydride battery is applied, will be described. This valuable metal recovery method is a method in which nickel and rare earth elements, which are valuable metals, are leached using a sulfuric acid solution from a negative electrode component constituting a nickel metal hydride battery.

  Specifically, the method for recovering valuable metals from the nickel metal hydride battery is a leaching method in which a sulfuric acid solution whose concentration is adjusted to a predetermined range is added to a negative electrode component to leach valuable metals from the negative electrode component to obtain a leach slurry. And a solid-liquid separation step of separating the leaching slurry into a leaching solution and a leaching residue, and a de-rare step of separating a rare earth element dissolved in the leaching solution by adding a rare earth agent to the leaching solution. In the following specific description, a case where valuable metal is recovered from a defective product (manufacturing process scrap) generated in the manufacturing process of the negative electrode component will be described as an example. Further, the description of the same contents as described above will be omitted as appropriate.

(1) Leaching step First, as a leaching step, a sulfuric acid solution is added to the negative electrode component that is a manufacturing process scrap, and a leaching process is performed to leach valuable metals contained in the negative electrode component. In the present embodiment, in this leaching treatment, a sulfuric acid solution whose concentration is adjusted so that a concentration fluctuation caused by the leaching occurs within the range of the solubility of the rare earth element contained in the negative electrode component and not more than the solubility of nickel. It is important to use it.

Thus, at the start leaching, the concentration of sulfuric acid solution used for leaching, both nickel and rare earth contained in the negative electrode component is added in an amount of sulfuric acid solution capable of forming a sulfate salt, nickel salt sulfuric acid solution as well as the total amount dissolved as, by adjusting to the rare earth is partially dissolved, while to effectively leach the nickel, for the rare earth element of valuable metals, saturated components exceed the solubility becomes the sediment was To precipitate. This starch is a rare earth element sulfate (RE ₂ (SO ₄ ) ₃ ) and becomes a leaching residue produced by the leaching process, so that the rare earth element is separated from the nickel and recovered at the stage of the leaching process. be able to.

  Although it does not specifically limit as pH of the sulfuric acid solution to be used, It is preferable to adjust to the range of pH 0-5, and it is more preferable to adjust to pH 0-1. The temperature of the sulfuric acid solution is not particularly limited, but is preferably about 20 to 95 ° C, more preferably about 50 to 90 ° C, and maintained at about 80 ° C. It is particularly preferred to carry out the treatment.

  Further, this leaching treatment is preferably performed while stirring the solution in order to allow the reaction to proceed efficiently and leaching nickel at a higher leaching rate. Moreover, you may be made to oxidize by adding oxidizers, such as blowing in air or hydrogen peroxide, as needed.

  The slurry concentration is not particularly limited, but is preferably adjusted to about 50 to 300 g / L. When the slurry concentration is less than 50 g / L, the equipment for the leaching process is increased in size, and the amount of wastewater generated is also increased. On the other hand, when the slurry concentration exceeds 300 g / L, the stirring is uneven and tends to be non-uniform.

(2) Solid-liquid separation step Next, as the solid-liquid separation step, the leaching slurry obtained in the leaching step is separated into a leaching solution and a leaching residue. As described above, in the leaching step, a leaching process is performed using a sulfuric acid solution adjusted to a predetermined concentration range, whereby the rare earth element precipitate (sulfate (RE ₂ (SO 4) ₃ )). Since the formed rare earth element precipitate is included in the leaching residue, by separating the leaching residue from the obtained leaching slurry, before separation of the rare earth element in the subsequent derare earth step, A predetermined amount of rare earth elements can be effectively separated and recovered.

  The method for the solid-liquid separation treatment is not particularly limited, and for example, separation can be performed using a method such as suction filtration, pressure filtration, or centrifugal separation.

  As mentioned above, since the leaching residue obtained by solid-liquid separation contains rare earth elements in the form of sulfates, the leaching residue is subjected to metathesis treatment to remove the rare earth elements. The recovered metathesis process can be performed.

Specifically, in this metathesis step, an alkali solution is added to the leaching residue obtained through the solid-liquid separation step and subjected to a metathesis treatment to obtain a post-metathesis solution containing a rare earth element and a metathesis precipitate. For example, when lanthanum (La) is taken as an example of the rare earth element contained in the leaching residue, a metathesis reaction occurs according to the following reaction formula (iii), and a post-metathesis solution and a metathesis precipitate containing La are obtained. .
La ₂ (So ₄ ) ₃ · Na ₂ (SO ₄ ) +6 NaOH
→ 2La ₂ (OH) ₃ + 4Na ₂ SO ₄ (iii)

  Here, the alkali solution used for the metathesis treatment is not particularly limited, but is preferably an aqueous solution composed of at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like.

  In addition, the pH of the alkaline solution during the metathesis treatment is not particularly limited, but is preferably pH 7 to 10, and more preferably pH 9 to 10. If the pH is less than 7, metathesis precipitates cannot be obtained efficiently. On the other hand, even if the pH exceeds 10, no further effect is obtained. The slurry concentration is not particularly limited, but is preferably about 50 to 300 g / L.

(3) Rare earth step Subsequently, as a rare earth step, a rare earth element such as alkali sulfate is added to and mixed with the leachate obtained through the solid-liquid separation step described above, and a rare earth element precipitate generation treatment is performed. Do. The leachate obtained in the leaching step described above contains a high concentration of nickel leached from the negative electrode component, and part of the rare earth elements that did not become leaching residues were also leached with the sulfuric acid solution. Is dissolved. Therefore, the rare earth element dissolved in the leachate is separated and recovered in this derare earth step.

Specifically, in the de-rare earth step, the rare earth element dissolved in the leachate is reacted with a de-rare earth agent such as an alkali sulfate, for example, rare earth element double salt (La ₂ (So ₄ ) ₃ .Na ₂ (SO ₄ ) Etc.) and a filtrate containing nickel.

  Examples of the rare earth agent used in the derare earth step include alkali sulfates such as sodium sulfate and potassium sulfate. Moreover, alkali hydroxides, such as sodium hydroxide and potassium hydroxide, can also be used. Moreover, the addition amount of the rare earth agent is not particularly limited, but for example, when sodium sulfate is used, it is preferably added so as to be 90 g / L or more.

  As described above, in the leaching process in the leaching process, the rare earth element contained in the negative electrode component is separated and recovered as a precipitate (sulfate) as a leaching residue. The amount of elements is effectively reduced. Therefore, the amount of the rare earth agent used in the derare earth step can be effectively suppressed, the chemical cost can be reduced, and an efficient recovery process of valuable metals can be performed.

  Although it does not specifically limit as pH at the time of reaction in a rare earth removal process, It is preferable to set it as pH 1-5, and it is more preferable to set it as pH 1-3. The liquid temperature of the leachate to be treated is not particularly limited, but is preferably about 50 to 70 ° C. Furthermore, although it does not specifically limit as a slurry density | concentration, It is preferable to adjust to about 50-300 g / L.

(4) Nickel recovery process (example of recovery as nickel sulfide)
In the nickel recovery process, a sulfidizing agent is added to the solution after the rare earth elements have been separated and recovered through the above-described derare earth process (the filtrate after the derare earth treatment (removed RE solution)), and subjected to sulfidation treatment. Is recovered as sulfide. Here, as a method for recovering nickel contained in the filtrate, a recovery method by sulfidation will be described as an example. However, the present invention is not limited to this. For example, nickel is separated and recovered from the filtrate by a solvent extraction method or the like. You may make it do.

  Specifically, in this nickel recovery step, a neutralizer is added to a solution obtained after separating rare earth elements from double salt precipitates (de-RE solution) to a pH of about 2.5 to 4.5. While maintaining, a sulfiding agent is added to perform a sulfiding treatment to form a nickel sulfide precipitate. Then, the nickel sulfide precipitate and the solution after sulfurization treatment (poor solution) are subjected to solid-liquid separation to recover the precipitate.

  The sulfiding agent used for the sulfiding treatment is not particularly limited. For example, hydrogen sulfide gas, sodium hydrogen sulfide, sodium sulfide, or the like can be used. Moreover, it does not specifically limit about a neutralizing agent, For example, sodium hydrogencarbonate, sodium carbonate, sodium hydroxide etc. can be used.

  As described above in detail, in the method for recovering valuable metals from the nickel-metal hydride battery according to the present embodiment, a sulfuric acid solution having a concentration adjusted to a predetermined range is added to the negative electrode parts to add valuable metal from the negative electrode parts. A leaching process for leaching the leaching slurry, a solid-liquid separation process for separating the leaching slurry into a leaching solution and a leaching residue, and a rare earth element for separating the rare earth element dissolved in the leaching solution by adding a rare earth agent to the leaching solution Process. In particular, in the leaching step, leaching is performed using a sulfuric acid solution whose concentration is adjusted so that concentration fluctuations accompanying the leaching occur within the range of the solubility of the rare earth element contained in the negative electrode component and below the solubility of nickel. It is characterized by that.

  According to such a valuable metal recovery method, nickel can be leached from the negative electrode component at a high leaching rate to obtain a leaching solution having a high nickel concentration, and a rare earth element sulfate can be added to the leaching residue produced by the leaching treatment. Part of the rare earth elements can be effectively separated as a leaching residue at this stage.

  Further, since the rare earth element dissolved in the leachate is also recovered by performing a rare earth treatment on the leachate, the rare earth element can be separated and recovered from the negative electrode component at a high recovery rate. . Furthermore, since a part of the rare earth element to be recovered has already been effectively recovered as a leaching residue, the amount of the rare earth element to be recovered by the derare earth treatment is reduced, and the The amount used can be reduced.

  In the above description, regarding the negative electrode component constituting the nickel metal hydride battery, the case of recovering valuable metals using defective products (manufacturing process scrap) of the negative electrode component generated in the manufacturing process is taken as an example. The negative electrode component is not limited to this. For example, a negative electrode part disassembled and recovered from a used nickel metal hydride battery may be used. In that case, prior to performing the above-described leaching step, it is possible to pass through a pretreatment step in which the nickel-metal hydride battery is deactivated and disassembled, and a cleaning step in which the positive electrode material obtained by disassembling is washed. .

  Specifically, as the pretreatment step, for example, the used nickel metal hydride battery is subjected to a baking treatment under an inert atmosphere, the used nickel metal hydride battery is deactivated, and then disassembled to remove the negative electrode component. Perform the removal process. As the roasting treatment, a method is used in which the used nickel metal hydride battery is placed in a furnace and roasted at a temperature of about 500 to 600 ° C. in an inert atmosphere.

  Next, as the cleaning process, the negative electrode component obtained by disassembling the used nickel metal hydride battery is subjected to a cleaning process using, for example, pure water or an acidic solution, and the electrolyte component adhered to the negative electrode component Etc. are removed. In this cleaning step, for example, an aqueous solution of sulfuric acid, hydrochloric acid, and nitric acid having a pH of about 5-8 is used.

  Examples of the present invention will be described below in comparison with comparative examples. In addition, this invention is not limited by these Examples.

[Example 1]
As a raw material, 564 g of a hydrogen storage alloy, which is a manufacturing process scrap of a negative electrode part of a nickel metal hydride battery, was used. In addition, 3.05 liters of sulfuric acid solution having a concentration of 300 g / L was used as the leaching start solution. The slurry concentration is 185 g / L. The amount of raw material added was set so that the Ni concentration in the leachate would be 100 g / L when the raw material was completely dissolved in the sulfuric acid solution having the above-mentioned concentration and amount. The leaching temperature was 80 ° C.

Using this raw material and the sulfuric acid solution, a leaching treatment was performed for leaching nickel from the negative electrode part. Specifically, the hydrogen storage alloy of the negative electrode component as a raw material was added to the H ₂ SO ₄ solution heated to 80 ° C. In this leaching treatment, the redox potential (ORP) of the solution was measured using a silver-silver chloride electrode as a reference electrode. In addition, ORP in process fell rapidly immediately after raw material addition, and became -150--200mV. Thereafter, as the leaching process proceeded, the ORP slightly decreased and shifted in the range of -200 to -300 mV.

  When the leaching ended, the amount of hydrogen generated decreased, and it was confirmed visually that hydrogen generation eventually disappeared. The ORP at this time rose to +100 to +200 mV. Then, it was determined that the leaching was completed when the generation of hydrogen disappeared, and the obtained leachate was lowered to a temperature of 60 ° C., and then suction filtered to separate the leachate and the leach residue.

  When the composition of 3.12 liters of the leachate obtained by filtration was analyzed by ICP emission analysis, a very high leachate with a Ni concentration of 100 g / L was obtained, and nickel was leached with a high leach rate of 99% or more. I was able to. Further, rare earth elements were dissolved in this leachate at a ratio of Nd: 3 g / L, Ce: 6.8 g / L, and La: 13 g / L. Note that the leaching rate of nickel described above is leaching rate (%) = (weight of Ni in the leaching solution [g] + weight of Ni in the leaching solution [g]) / (weight of Ni in the leaching solution [g] + Calculated by the weight [g] of Ni in the leaching cleaning solution + the weight of Ni in the leaching residue [g]) × 100.

Moreover, the form of 240.78 g (dry) of the obtained leaching residue was analyzed using X-ray diffraction (XRD). As a result, the leach residue is in the form of _{RE 2 (SO 4) 3 ·} 9 (H 2 O), are formed sulfates of rare earth elements, it does not remain those of the form a single metal Was confirmed.

  Subsequently, 3.12 L of the obtained leachate was subjected to a treatment (de rare earth treatment) in which sodium sulfate having a concentration of 400 g / L was added as a rare earth agent to form a rare earth element sulfate double salt. Specifically, sodium sulfate having a concentration of 400 g / L was added to the leachate heated to 60 ° C. and mixed while heating, and the mixture was stirred for 3 hours after reaching 60 ° C. When 3 hours had passed, suction filtration was performed to separate the rare earth filtrate (the filtrate after the rare earth treatment) and the starch composed of a rare earth element sulfate double salt. In this de-rare earth treatment, the amount of sodium sulfate used per 100 g of raw material was calculated to be 0.58 L.

[Comparative Example 1]
Using the same equipment as in Example 1, except that 140 g of the same battery scrap as in Example 1 was used as a raw material, and 3.49 L of sulfuric acid solution having a concentration of 90 g / L was used as the leaching start solution. went. The balance between the amount of raw material added and the amount of leaching starting solution used was set so that the rare earth element was completely dissolved in the sulfuric acid solution having the above-mentioned concentration and amount and did not reprecipitate.

  As a result, 0.006 g of leaching residue and 2.54 L of leaching solution were obtained by this leaching treatment. Further, the leaching rates were Ni: 99% or more, Nd: 100%, Ce: 100%, and La: 100%. Thus, although the leaching rate of nickel was 99% or more, the nickel concentration in the leaching solution was as low as 34 g / L compared to Example 1, and Nd: 1.5 g / L, Ce: 4. It contained rare earth elements at a rate of 5 g / L and La: 11 g / L.

  Subsequently, in the same manner as in Example 1, 2.54 L of the obtained leachate was added with 400 g / L sodium sulfate as a rare earth agent to form a rare earth element sulfate (derare earth treatment). Went. In this de-rare earth treatment, the amount of sodium sulfate used per 100 g of raw material was calculated to be 1.45 L, which was twice the amount used in Example 1.

  Table 1 below summarizes the results regarding the amount of sodium sulfate used per 100 g of the raw material in the rare earth treatment for the leachate obtained in Example 1 and Comparative Example 1.

Claims (4)

When recovering valuable metals nickel and rare earth elements from negative electrode parts of a nickel metal hydride battery, a method for separating rare earth elements contained in the negative electrode parts,
During leaching the start, to the negative electrode parts, was added to the nickel and the rare earth and is capable of forming both sulfates amount of sulfuric acid solution contained in the negative electrode parts, the nickel is the total amount dissolved as sulfate solution In addition , the rare earth is adjusted to the concentration of the sulfuric acid solution that partially dissolves, thereby leaching valuable metals from the negative electrode component,
Separating the obtained leach slurry into leachate and leach residue;
A method for separating a rare earth element contained in a nickel metal hydride battery, wherein a rare earth element is added to the leachate to separate the rare earth element dissolved in the leachate. At the start of the leaching, the concentration of the sulfuric acid solution is adjusted so that the nickel contained in the negative electrode component and the rare earth element having the highest solubility in the sulfuric acid solution among the rare earth elements can form a sulfate. was added, together with the nickel to total amount dissolved as the sulfate solution, the rare earth separation of rare earth elements in the nickel-hydrogen battery according to adjust to claim 1, wherein to partially dissolve Method. In the method for recovering valuable metals, nickel and rare earth elements, which are valuable metals, from the negative electrode parts of nickel metal hydride batteries,
During leaching the start, to the negative electrode parts, was added to the nickel and the rare earth and is capable of forming both sulfates amount of sulfuric acid solution contained in the negative electrode parts, the nickel is the total amount dissolved as sulfate solution together, the rare earths by adjusting the concentration of the sulfuric acid solution to partially dissolve, and the leaching step to obtain a leach slurry by leaching a value metal from the negative electrode parts,
A solid-liquid separation step of separating the leaching slurry into a leaching solution and a leaching residue;
A method for recovering a valuable metal from a nickel metal hydride battery, comprising: adding a derare earth agent to the leachate and separating a rare earth element dissolved in the leachate. At the start of the leaching, the concentration of the sulfuric acid solution is adjusted so that the nickel contained in the negative electrode component and the rare earth element having the highest solubility in the sulfuric acid solution among the rare earth elements can form a sulfate. It was added, together with the nickel to total amount dissolved as the sulfate solution, a method of recovering valuable metals from nickel-hydrogen battery according to claim 3, wherein the rare earth is characterized by adjusting to partially dissolve .

Images