JP2016003353A - Method of recovering valuable metal from waste nickel hydrogen battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering valuable metals from waste nickel hydrogen batteries which achieves cost reduction of the whole process by establishing a process bypassing a nickel refining process and is improved in safety.SOLUTION: In a neutralization step S13, an oxidizer is added to and then a neutralizer is added to a liquid with a rare earth element removed, which is obtained in a rare earth crystallization step S12, to keep the pH of the liquid with a rare earth element removed to 4.5-6.0 so as to obtain a mixed aqueous solution with an impurity removed and containing nickel sulfate and cobalt sulfate, and recover them as valuable metals.

Description

  The present invention relates to a method for separating and recovering valuable metals such as nickel, cobalt, and rare earth elements from used nickel-metal hydride batteries and waste nickel-metal hydride batteries such as defective products produced during production.

  In recent years, environmental problems such as global warming due to wide-area air pollution caused by sulfur oxides and dusts released into the atmosphere and carbon dioxide have been highlighted as global issues.

  One of the causes of air pollution and global warming is automobile exhaust gas. To reduce pollution caused by exhaust gas, the production and demand of hybrid vehicles and electric vehicles equipped with secondary batteries such as nickel metal hydride batteries are increasing. It is increasing at an accelerating rate.

  A nickel-metal hydride battery, which is a type of secondary battery, has a structural member such as a functional member such as a positive electrode, a negative electrode, an electrode terminal, and an electrolyte, a separator provided between an electrode substrate, a positive electrode and a negative electrode, and a case for housing them It is comprised from the member.

  Various materials are contained in the functional member and the structural member constituting the nickel metal hydride battery. For example, the positive electrode contains a positive electrode active material, and the positive electrode active material is made of nickel hydroxide containing a trace amount of added elements. Further, the negative electrode contains a negative electrode active material, and the negative electrode active material is composed of a hydrogen storage alloy containing nickel, cobalt, a rare earth element (Misch metal), or the like.

  The positive substrate is made of a nickel plate, a foamed nickel plate, or the like, and the negative substrate is made of a nickel-plated iron plate or the like. Furthermore, the separator is made of a synthetic resin or the like, the electrolyte is made of a potassium hydroxide aqueous solution or the like, the electrode terminal material is made of copper, an iron-based metal, or the like, and the case is made of a synthetic resin, steel, or the like.

  Nickel metal hydride batteries mounted on hybrid vehicles and electric vehicles are expected to be eventually discarded. To recover valuable metals contained in the above-mentioned components from used nickel metal hydride batteries and recycle them as resources. Technical development is also underway.

  As a method for recovering valuable metals such as nickel and cobalt from used nickel metal hydride batteries, for example, waste nickel metal hydride batteries are melted in a furnace and the synthetic resin constituting the used nickel hydride batteries is burned. There is a dry processing method in which a large part of iron is removed by slag removal and nickel is reduced and recovered as ferronickel alloyed with a part of iron.

  The dry processing method has an advantage that mass processing is possible at low cost, and the facilities of the existing smelter can be used as they are, so that the processing is not troublesome. However, the dry processing method is difficult to separate impurities from the recovered ferronickel, and is not suitable for applications other than stainless steel raw materials.

  In addition, the dry processing method is particularly undesirable in terms of effective utilization of rare cobalt and rare earth elements because most of cobalt and rare earth elements are distributed in the slag and discarded as slag.

  That is, in the dry processing method, valuable metals with low purity may be recovered, or valuable metals may not be recovered and may be discarded. Therefore, the dry processing method has a problem that valuable metals contained in used nickel-metal hydride batteries cannot be recovered as high-purity metals that can be recycled for batteries.

  Therefore, in order to solve the above problem, for example, a wet processing method as disclosed in Patent Document 1 has been proposed. The valuable metal recovery method described in Patent Document 1 includes the following steps (1) to (6).

  That is, in the method described in Patent Document 1, (1) a positive electrode active material and a negative electrode active material are subjected to a cleaning treatment using an acidic aqueous solution, and an electrolyte component adhering to the positive electrode active material and the negative electrode active material is removed. (2) The leachate is subjected to a reduction treatment by mixing the residue after washing and the leachate obtained in the leaching step, and the iron in the leachate is divalent. Holding step to obtain a reduction solution and reduction residue containing nickel, cobalt, rare earth elements and other coexisting metal elements, and (3) leaching treatment with addition of sulfuric acid aqueous solution to the reduction residue and oxidation A leaching step for obtaining a leaching solution containing nickel and a rare earth element and a leaching residue; (4) mixing an alkaline sulfate or alkali hydroxide with the reducing solution; Nickel with salt deposits And a rare earth recovery step for obtaining a filtrate containing cobalt, and (5) adding an oxidizing agent and a neutralizing agent to the filtrate obtained in the rare earth recovery step and subjecting it to an oxidation neutralization treatment, containing nickel and cobalt An oxidation neutralization step for obtaining an oxidized neutralized solution and an oxidized neutralized starch containing iron and aluminum; and (6) subjecting the oxidized neutralized solution to a solvent extraction treatment using a phosphate-based extractant. And a solvent extraction step of obtaining a back extract containing cobalt, manganese, zinc and yttrium and an extraction residual solution containing nickel.

  However, the method described in Patent Document 1 has a large number of steps and is complicated, so it requires a great deal of processing cost and is not a commercially viable process.

  On the other hand, as another wet processing method for recovering valuable metals contained in used nickel-metal hydride batteries as high-purity metals, for example, a method as disclosed in Patent Document 2 has been proposed. The valuable metal recovery method described in Patent Document 2 includes the following steps (1) to (3).

  That is, in the method described in Patent Document 2, as shown in FIG. 2, (1) a leaching step S21 in which a positive / negative active material-containing material is mixed and dissolved in a sulfuric acid solution and then separated into a leaching solution and a leaching residue. (2) A rare earth crystallization step S22 in which an alkali metal sulfate is added to the leachate obtained in the leaching step S21 to obtain a rare earth element sulfate double salt mixed precipitate and a derare earth element solution, and (3) a rare earth element. It comprises a sulfide raw material recovery step S23 in which a sulfiding agent is added to the rare earth element liquid obtained in the crystallization step S22 to separate it into a nickel / cobalt sulfide raw material and a residual liquid.

  According to the method described in Patent Document 2, the number of steps and the complexity that have been problems in the method described in Patent Document 1 are eliminated.

  However, in the method described in Patent Document 2, the sulfide raw material recovery step S23 is indispensable in order to selectively separate nickel and cobalt as recovery targets. Therefore, in the sulfide raw material recovery step S23, a large amount of nickel is precipitated instead of a very small amount of impurities, so that the amount of the sulfiding agent used is enormous, which causes a cost increase.

  In addition, some impurities such as zinc have a property of forming a sulfide precipitate more easily than nickel and cannot be completely separated. Therefore, in the method described in Patent Document 2, when nickel and cobalt are separated from zinc and the like, a two-stage sulfidation operation is required.

  That is, in the method described in Patent Document 2, first, a sulfide is added to the rare earth element liquid to generate a sulfide precipitate containing zinc or the like, and then the sulfide precipitate and the filtrate are solid-liquid separated. . Next, a sulfurizing agent is again added to the obtained filtrate to obtain a sulfide precipitate of nickel and cobalt.

  Therefore, when using the sulfide precipitation method, when separating zinc and the like, it is necessary to increase the two-stage sulfidation process and the equipment used therefor, and recovery of valuable metals from used nickel-metal hydride batteries. The number of steps in the whole process is large and complicated.

  Since the nickel / cobalt sulfide raw material can be used as a raw material for the nickel smelting process S24, the method described in Patent Document 2 can recycle valuable metals contained in used nickel-metal hydride batteries for batteries. The purpose of recovering as a high purity metal is achieved.

  However, in the method described in Patent Document 2, the nickel / cobalt sulfide raw material obtained in the sulfide raw material recovery step S23 is processed in the nickel smelting process S24 to become high-purity nickel sulfate (raw material for battery materials). The battery material manufacturing process S25 is commercialized into battery materials such as nickel hydroxide and lithium nickelate.

  Therefore, from the viewpoint of the manufacturing cost of the raw material for battery materials, since the processing cost in the nickel smelting process S24 is added to the wet processing cost, it is difficult to reduce the processing cost with the method described in Patent Document 2. It is.

JP 2010-174366 A JP 2012-025992 A

  As described in Patent Document 1 and Patent Document 2, as a method for recovering valuable metals from used nickel metal hydride batteries, it is obtained by performing pretreatment such as firing, crushing, and sorting on used nickel metal hydride batteries. High-purity nickel, cobalt, etc. that can be recycled for batteries by subjecting valuable metal-containing materials to leaching treatment, de-rare earth treatment using precipitation of sodium double salt, solvent extraction treatment, sulfidation treatment, etc. A wet processing method for recovering valuable metals is technically established.

  However, these wet processing methods consume a large amount of reagents such as acid for leaching treatment, sulfidizing agent for sulfidizing treatment, alkali for wastewater neutralization, etc. with respect to nickel which is the main component of the raw material. The cost is high.

  In particular, in the method described in Patent Document 2, a large amount of a sulfiding agent having a relatively high unit price is used, which occupies most of the cost of the drug and causes a cost increase. In addition, by using a sulfiding agent, hydrogen sulfide gas is expected to be generated during the process, so it is essential to install an exhaust gas treatment facility such as a detoxification tower, which increases equipment costs and operating costs. .

  The sulfide raw material recovery step S23 in the method described in Patent Document 2 is for removing impurities, but this is also not universal and zinc or the like that easily forms a sulfide precipitate cannot be separated from nickel. Therefore, as it is, it cannot be used as a nickel raw material for battery material production as it is, and it is necessary to obtain high-purity nickel by treating again in the nickel smelting process S24.

  If the entire process of recovering valuable metals contained in used nickel metal hydride batteries and recycling them as battery material raw materials is considered, if some impurities are allowed as battery material raw materials, wet processing There is no need to recover as a high purity metal by the method. Thereby, it is possible to omit the sulfurization step (sulfide raw material recovery step S23) and bypass the nickel refining process S24.

  In other words, instead of collecting valuable metals contained in used nickel metal hydride batteries as high-purity metals and recycling them as raw materials for batteries (battery materials), valuable metals contained in used nickel metal hydride batteries are If it can be recovered in a state containing a small amount of impurities and recycled as a raw material for a battery, it is considered that facility costs and operation costs can be reduced by simplifying the manufacturing process.

  Further, if valuable metals contained in a used nickel metal hydride battery can be recovered without using a relatively expensive unit of sulfiding agent, the cost of the drug can be reduced. Furthermore, it is not necessary to install an exhaust gas treatment facility associated with the generation of hydrogen sulfide gas, and it is possible to reduce facility costs and operation costs.

  Therefore, the present invention has been devised in view of the above problems of the prior art, and a valuable metal-containing material obtained by pretreating a used nickel-metal hydride battery is mixed with a sulfuric acid solution and dissolved. After obtaining the leaching solution, the rare earth element which is a useful element is separated from the leaching solution containing nickel, cobalt, rare earth elements and other impurities. Next, the present invention separates a trace amount of impurities from nickel and cobalt without using a sulfurizing agent, and supplies nickel and cobalt to the battery material manufacturing process.

  That is, in the prior art, as shown in FIG. 2, in the sulfide raw material recovery step S23, a nickel / cobalt sulfide raw material is manufactured by sulfidation, and the nickel / cobalt sulfide raw material is processed in a nickel smelting process S24. .

  On the other hand, in the present invention, a process for recovering valuable metals from waste nickel metal hydride batteries has been established by establishing a process for bypassing the nickel smelting process and reducing the cost of the entire process while further improving safety. The purpose is to provide.

  In order to achieve the above-mentioned object, the present inventors supply a neutralizing agent after adding an oxidizing agent to the de-rare earth element liquid obtained in the rare earth crystallization process, in particular, to separate impurities as precipitates, In the neutralization step of obtaining a mixed aqueous solution containing nickel sulfate and cobalt sulfate from which impurities have been removed, research was repeated focusing on the pH and heavy metal concentration of the mixed solution.

  As a result, the present inventors manufactured a mixed aqueous solution containing nickel sulfate and cobalt sulfate that can be used as a raw material for battery materials by maintaining the pH of the aqueous solution in the neutralization step at 4.5 or more and 6.0 or less. As a result, the present invention has been completed.

  That is, the method for recovering valuable metals from waste nickel metal hydride batteries according to the present invention for achieving the above object is a method for separating and recovering nickel, cobalt and rare earth elements from valuable metal-containing materials obtained from waste nickel metal hydride batteries. In addition, a valuable metal-containing material obtained from a waste nickel metal hydride battery is dissolved in a sulfuric acid solution and then separated into a leaching solution and a leaching residue, and the leaching solution obtained in the leaching step contains alkali metal. After adding an oxidizing agent to the rare earth element crystallization process obtained by adding sulfate and obtaining a rare earth element sulfate mixed precipitate and a rare earth element liquid, and the rare earth element liquid obtained in the rare earth element crystallization process By adding a summing agent and maintaining the pH of the rare earth element liquid at 4.5 or more and 6.0 or less, impurities in the rare earth element liquid are separated as precipitates, and nickel sulfate and And having a neutralization step to obtain a mixed aqueous solution containing cobalt sulfate.

  According to the method for recovering valuable metals from waste nickel metal hydride batteries of the present invention, unlike the conventional method for recovering valuable metals from waste nickel metal hydride batteries, valuable metals can be recovered without undergoing a sulfiding step. Therefore, the processing cost can be reduced in the entire valuable metal recovery process.

  Furthermore, according to the method for recovering valuable metals from the waste nickel metal hydride battery of the present invention, nickel and cobalt as battery materials can be obtained without going through a nickel smelting process. Therefore, the processing cost can be halved in the entire battery material manufacturing process including the valuable metal recovery process described above.

  According to the method for recovering valuable metals from the waste nickel metal hydride battery of the present invention, the mixed aqueous solution containing nickel sulfate and cobalt sulfate obtained in the neutralization step can be used as a raw material for battery materials. Thereby, it is possible to establish a process in which recovering valuable metals contained in waste nickel metal hydride batteries as recyclable metals for batteries can be established economically.

  According to the method for recovering valuable metals from the waste nickel metal hydride battery of the present invention, since no sulfiding agent is used, the risk of hydrogen sulfide gas generation is eliminated, so that an effect in terms of safety environment can be expected.

It is process drawing which shows the outline of the collection process of a valuable metal in the recovery method of the valuable metal from the waste nickel metal hydride battery which concerns on this invention. It is process drawing which shows the outline of the collection process of the valuable metal in the recovery method of the valuable metal from the conventional waste nickel metal hydride battery.

  A specific embodiment to which the present invention is applied (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings in the following order. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

1. Leaching process 2. Rare earth crystallization process 3. Neutralization process Battery material manufacturing process

  As shown in FIG. 1, the method for recovering valuable metals from waste nickel metal hydride batteries according to the present embodiment (hereinafter sometimes simply referred to as “valuable metal recovery method”) A leaching step S11 for obtaining a leaching solution containing a valuable metal and a leaching residue by performing a leaching treatment, and performing a rare earth crystallization treatment on the leaching solution obtained in the leaching step S11 to obtain a mixed rare earth element sulfate precipitation and a rare earth element solution Rare earth crystallization step S12 to be obtained, and a neutralized starch and valuable metal mixed solution (nickel sulfate / cobalt mixed solution) after oxidation treatment is performed on the rare earth element liquid obtained in the rare earth crystallization step S12 And a neutralization step S13 to obtain

  In the valuable metal recovery method, the valuable metal mixed solution is obtained in the neutralization step S13 using the derare earth element liquid obtained in the rare earth crystallization step S12, thereby recovering the valuable metal from the waste nickel metal hydride battery. Can do. Moreover, by supplying the valuable metal mixed solution obtained in the neutralization step S13 to the battery material manufacturing process S14, the battery material is produced from the valuable metal mixed solution, and various batteries are produced using the obtained battery material. be able to.

[1. Leaching process]
In the leaching step S11, as shown in FIG. 1, a valuable metal-containing material obtained by pre-treating a waste nickel metal hydride battery and a sulfuric acid solution are mixed, heated and dissolved to obtain a leachate containing valuable metals. And leaching residue.

Of the valuable metals contained in the valuable metal-containing material, for example, lanthanum, which is one of nickel and rare earth elements, is dissolved according to the following formula.
Ni + H ₂ SO ₄ → NiSO ₄ + H ₂ (Formula 1)
2La + 3H ₂ SO ₄ → La ₂ (SO ₄ ) ₃ + 3H ₂ (Formula 2)

  The pH of the leachate is not particularly limited, but is preferably maintained at 0 or more and 5 or less, more preferably 0 or more and 1 or less. When the pH of the leachate is less than 0, the neutralizing agent used in the subsequent process increases. On the other hand, when the pH of the leaching solution exceeds 5, the leaching rate of valuable metals such as nickel and cobalt decreases.

  In the leaching step S11, in order to obtain a practical and satisfactory reaction rate, leaching is preferably performed while maintaining a liquid temperature of 80 ° C. or higher under a strong acid. In the leaching step S11, for example, leaching processing can be performed using sulfuric acid having a concentration of 64%.

  Further, in the leaching step S11, the valuable metal-containing material and the sulfuric acid solution are mixed, heated and dissolved, and then a valuable metal-containing material can be further added to neutralize the excess sulfuric acid. Next, the slurry made of the obtained leachate and leach residue is allowed to cool, and then solid-liquid separation is performed to obtain the leachate. Although it does not specifically limit as a slurry density | concentration, It is preferable to adjust to 50 g / L or more and 300 g / L or less.

  As described above, in the leaching step S11, a leaching solution in which valuable metals such as nickel, cobalt, and rare earth elements are leached into the sulfuric acid solution can be obtained.

[2. Rare earth crystallization process]
Next, in the rare earth crystallization step S12, as shown in FIG. 1, an alkali metal sulfate is added to the leachate obtained in the leaching step S11, and the sulfate double salt mixed precipitate in which the rare earth element is combined with the alkali metal Then, the rare earth element is recovered by separating the rare earth element liquid, which is a mixed aqueous solution of nickel sulfate and cobalt sulfate from which the rare earth element has been separated.

In the rare earth crystallization step S12, for example, lanthanum, which is one of the rare earth elements in the leachate, generates a lanthanum and sodium double salt (sulfate double salt mixed precipitate) according to the following formula 3.
La ₂ (SO ₄ ) ₃ + Na ₂ SO ₄ → 2LaNa (SO ₄ ) ₂ (Formula 3)

  In the rare earth crystallization step S12, it is more preferable to use an alkali sulfate (alkali metal sulfate) such as sodium sulfate or potassium sulfate.

  Although it does not specifically limit as pH at the time of reaction, It is preferable to maintain at 1-5, and it is more preferable to maintain at 1-3. That is, in the rare earth crystallization step S12, when the pH during the reaction is 1 or more and 5 or less, the rare earth element can be separated as a precipitate.

  However, when the pH during the reaction exceeds 3, since metal elements such as nickel, cobalt, iron, and aluminum may precipitate together with the sulfate double salt mixed precipitation, the pH is maintained in the range of 1 to 3, It is more preferable that these metal elements remain in the rare-earth element liquid.

  In the rare earth crystallization step S12, the liquid temperature is not particularly limited, but is preferably 50 ° C. or higher and 70 ° C. or lower. When the liquid temperature is less than 50 ° C., a practical and satisfactory reaction rate cannot be obtained. On the other hand, the upper limit of the liquid temperature is not particularly limited, but is preferably 70 ° C. or lower in consideration of the amount of water evaporation and energy efficiency.

[3. Neutralization process]
Next, in the neutralization step S13, as shown in FIG. 1, an oxidizing agent is added to the rare earth element liquid obtained in the rare earth crystallization step S12 to perform oxidation treatment, and then a neutralizing agent is added. Neutralization treatment is performed to obtain a neutralized starch and a valuable metal mixed solution (nickel sulfate / cobalt mixed solution), and the valuable metal is recovered as the valuable metal mixed solution.

  In the neutralization step S13, air, hydrogen peroxide, lithium nickelate powder, sodium persulfate, or the like can be used as the oxidizing agent. Moreover, sodium hydroxide, sodium carbonate, calcium hydroxide, calcium carbonate, etc. can be used as a neutralizing agent. In these, it is preferable to use sodium hydroxide or sodium carbonate which does not have a fear of mixing of calcium.

  When air or hydrogen peroxide is used as the oxidant, the redox potential of the rare earth element liquid rises to about 400 mV (Ag / AgCl electrode standard), and then a neutralizer is added to adjust the pH to 4. 5 to 6.0, more preferably 5.4 to 5.6, and still more preferably 5.5. In this case, in the neutralization step S13, impurities such as aluminum, iron, and manganese are precipitated to form a neutralized starch, and the impurities can be removed.

  On the other hand, when lithium nickelate powder or sodium persulfate is used as the oxidant, the redox potential of the rare earth element liquid rises to 800 mV (Ag / AgCl electrode standard) or higher, and then a neutralizer is added. Then, the pH is 4.5 or more and 6.0 or less, more preferably 5.4 or more and 5.6 or less. In this case, in the neutralization step S13, particularly more manganese is precipitated to form a neutralized starch, and impurities can be efficiently removed.

For example, when lithium nickelate powder, which is a raw material for lithium ion battery materials, is used as the oxidizing agent, the oxidation-reduction potential is increased by adding the oxidizing agent to the rare earth element liquid. , Oxidized divalent iron ions to trivalent.
2Fe ²⁺ + 2H ⁺ + 2LiNiO ₂ + 3H ₂ SO ₄
→ 2Fe ³⁺ + 4H ₂ O + Li ₂ SO ₄ + 2NiSO ₄ (Formula 4)

  In the neutralization step S13, after that, a neutralizing agent is added, and the pH in the removed rare earth element liquid is set to 4.5 to 6.0, more preferably 5.4 to 5.6 to precipitate impurities. . In the metal recovery method of Patent Document 1, the pH at this time is 3.5 or more and 4.5 or less, but in the neutralization step S13 according to the present embodiment, in order to increase the separation efficiency of impurities, The pH in the liquid is set to 4.5 or more and 6.0 or less.

Aluminum, iron, and manganese in the rare-earth element liquid precipitate according to the following formulas 5 to 7, and become neutralized starch.
Al ³⁺ + 3NaOH → Al (OH) ₃ + 3Na ⁺ (Formula 5)
Fe ³⁺ + 3NaOH → Fe (OH) ₃ + 3Na ⁺ (Formula 6)
Mn ²⁺ + 2LiNiO ₂ + 3H ₂ SO ₄
→ MnO ₂ + Li ₂ SO ₄ + 2NiSO ₄ + 2H ₂ O + 2H ⁺ (formula 7)

  As explained above, in the neutralization step S13, valuable metals such as nickel and cobalt remain in the de-rare earth element liquid that has been subjected to oxidation treatment and neutralization treatment. A mixed aqueous solution of nickel and cobalt sulfate (nickel sulfate / cobalt mixed solution) can be used as a raw material for battery material production in the battery material production process S14 described later.

  The equipment for oxidizing iron (for example, an oxidation reaction tank) and the equipment for precipitating impurities (for example, a neutralization reaction tank) can be shared, and simultaneous treatment of oxidation and neutralization is also possible. Is possible.

[4. Battery material manufacturing process]
In the battery material manufacturing process S14, as shown in FIG. 1, the mixed aqueous solution (nickel sulfate / cobalt mixed solution) of nickel sulfate and cobalt sulfate obtained in the neutralization step S13 is used as a raw material. The sulfuric acid in the mixed aqueous solution of nickel sulfate and cobalt sulfate is finally discharged from the waste liquid treatment process in the form of sodium sulfate.

  If this sodium sulfate is a predetermined concentration or more, it can be used as a sodium salt used in the rare earth crystallization step S12, and the chemical cost required for the treatment can be reduced.

  As described above, the valuable metal recovery method can selectively separate and recover the rare earth element as the sulfate double salt mixed precipitate in the rare earth crystallization step S12. Further, in the neutralization step S13, nickel and cobalt can be selectively recovered as a mixed aqueous solution (nickel sulfate / cobalt mixed solution) containing nickel sulfate and cobalt sulfate.

  Thus, unlike the conventional method for recovering valuable metals from waste nickel metal hydride batteries, the valuable metal recovery method can recover valuable metals without undergoing a sulfiding step. Therefore, the processing cost can be reduced in the entire valuable metal recovery process.

  Furthermore, in the valuable metal recovery method, since the battery material can be produced without going through the nickel smelting process, the processing cost can be halved in the entire battery material manufacturing process including the valuable metal recovery process.

  In the valuable metal recovery method, a mixed aqueous solution containing nickel sulfate and cobalt sulfate obtained in the neutralization step can be used as a raw material for battery materials. Thereby, it is possible to establish a process for recovering valuable metals contained in the waste nickel metal hydride battery as recyclable metal for the battery. This process is economically effective and very useful.

  In the valuable metal recovery method, nickel and cobalt, which are valuable metals, can be recovered without using a sulfiding agent, so that the chemical cost associated with the use of the sulfiding agent can be reduced.

  Furthermore, in the valuable metal recovery method, the equipment cost and the operating cost in the exhaust gas treatment facility associated with the generation of hydrogen sulfide gas can be eliminated due to the non-use of the sulfiding agent. As a result, the valuable metal recovery method eliminates the risk of hydrogen sulfide gas generation, and thus can be expected to be effective in terms of safety.

  The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

(Example 1)
In Example 1, a valuable metal-containing material obtained by pretreating a waste nickel metal hydride battery was used as a raw material. There are two types of raw materials, a metal piece that is difficult to leach and a powder that is easy to leach. In Example 1, these were treated and subjected to a leach treatment in the leach step described later. Moreover, in Example 1, in order to implement | achieve efficient leaching, the leaching of the raw material used as a process target was performed in two steps.

<Leaching process>
In the leaching step, 25 kg of metal flake raw material was put into the column tank, and 120 L of 59% sulfuric acid was supplied stepwise while circulating 300 L of water to obtain a leachate having a first stage acid concentration.

  Next, in the leaching step, 65 kg of the powdery raw material was put into a leaching tank equipped with a stirrer, 150 L of water was supplied, and 350 L of the first stage leachate was supplied stepwise while stirring. The powdery raw material was leached with excess sulfuric acid contained in the first stage leachate, and after leaching residue was filtered with a filter press, a leachate having a pH of 1.0 and a nickel concentration of 110 g / L was finally obtained.

<Rare earth crystallization process>
In the rare earth crystallization step, a 180 g / L sodium sulfate solution 140 L was put in a tank equipped with a stirrer in advance. Next, in the rare earth crystallization step, 140 L of the leachate obtained in the leaching step was charged into this tank, and stirring was continued for 3 hours while maintaining 60 ° C. Thereafter, the mixture was filtered with a filter press to obtain 280 L of a mixed aqueous solution of nickel sulfate and cobalt sulfate from which the precipitated rare earth sulfate double salt was separated. The nickel concentration at this time was 42 g / L.

<Neutralization process>
In the neutralization step, the mixed aqueous solution of nickel sulfate and cobalt sulfate obtained in the rare earth crystallization step has a nickel concentration of 41 g / L, a cobalt concentration of 6.3 g / L, an aluminum concentration of 1.1 g / L, and an iron concentration of 0.83 g. / L and a manganese concentration of 1.7 g / L were used as starting materials.

  In the neutralization step, 1.8 g of lithium nickelate powder for producing a lithium ion battery is added as an oxidizing agent to 0.25 L of a mixed aqueous solution of nickel sulfate and cobalt sulfate, and sulfuric acid is used so as to keep 60 ° C. and pH 2.4. The feed flow rate and water bath were controlled.

  Next, in the neutralization step, when the oxidation-reduction potential (Ag / AgCl electrode reference) reached 970 mV, the supernatant was sampled and allowed to cool to room temperature.

  Thereafter, in the neutralization step, caustic soda (neutralizing agent) is added to the obtained supernatant to pH 5.5, followed by filtration to mix impurities as starch (neutralized starch), a mixed aqueous solution of nickel sulfate and cobalt sulfate. Separated from.

  In the neutralization step, the recovered starch was 2.0 g, and the filtrate (nickel sulfate / cobalt mixed solution) was 0.27 L.

  Moreover, each analysis value analyzed about the obtained starch and filtrate using the ICP (Inductively Coupled Plasma) emission spectroscopic analysis method was as Table 1 and Table 2. Each analysis value of “neutralized pH 2.4 filtrate” in the lower part of Table 1 is a result of measuring the sampled supernatant before adding caustic soda.

  In Example 1, as shown in Tables 1 and 2, nickel and cobalt slightly moved to the starch side, which was a slight loss in terms of recovering valuable metals, but almost all of the aluminum and iron were added. As a result, it was possible to separate about 80% of manganese.

(Comparative Example 1)
In the method of recovering valuable metals from waste nickel metal hydride batteries, in the sense of separating impurities without using a sulfiding agent, a separation method in which the precipitate is formed in the form of nickel hydroxide in the neutralization step and the impurities are left on the filtrate side is also considered. It is done.

  Therefore, in Comparative Example 1, the value from the waste nickel metal hydride battery was the same as that in Example 1 except that the neutralizing agent was added beyond the upper limit of the predetermined pH value without adding the oxidizing agent in the neutralization step. An attempt was made to recover the metal.

<Neutralization process>
In the neutralization step, the mixed aqueous solution of nickel sulfate and cobalt sulfate obtained in the rare earth crystallization step has a nickel concentration of 40 g / L, a cobalt concentration of 6.0 g / L, an aluminum concentration of 1.1 g / L, and an iron concentration of 0.85 g. / L and a manganese concentration of 1.7 g / L were used as starting materials.

  In the neutralization step, caustic soda was added as a neutralizing agent to 0.25 L of a mixed aqueous solution of nickel sulfate and cobalt sulfate to pH 8, and then filtered to separate the nickel hydroxide starch from the mixed aqueous solution of nickel sulfate and cobalt sulfate.

  In the neutralization step, the recovered starch was 45 g and the filtrate was 0.22 L.

Moreover, each analysis value analyzed about the obtained starch and filtrate using the ICP emission-spectral-analysis method like Example 1 was as Table 3 and Table 4.

  In Comparative Example 1, as shown in Tables 3 and 4, about half of the manganese content in the starting material could be separated while leaving the filtrate, but almost all of the aluminum and iron were on the nickel side ( The result was that it was transferred to the neutralized starch side). That is, in Comparative Example 1, separation of valuable metals nickel and cobalt and impurities manganese, aluminum and iron was not sufficient.

  Therefore, in Example 1, in the mixed aqueous solution of nickel sulfate and cobalt sulfate obtained in the rare earth crystallization step, the oxidation-reduction potential of the mixed aqueous solution of nickel sulfate and cobalt sulfate is 800 mV (Ag / AgCl electrode standard) or more. After adding the oxidizing agent, a neutralizing agent was added so that the pH of the mixed aqueous solution of nickel sulfate and cobalt sulfate was 4.5 or more and 6.0 or less.

  As a result, in Example 1, manganese, aluminum, and iron, which are impurities in the mixed aqueous solution of nickel sulfate and cobalt sulfate, were separated as neutralized starch, and the mixed solution containing nickel sulfate and cobalt sulfate as the filtrate from which the impurities were removed. An aqueous solution was obtained, and it was confirmed that valuable metals nickel and cobalt could be recovered.

  On the other hand, in Comparative Example 1, the pH of the mixed aqueous solution of nickel sulfate and cobalt sulfate exceeds 6.0 without adding an oxidizing agent to the mixed aqueous solution of nickel sulfate and cobalt sulfate obtained in the rare earth crystallization step. Neutralizing agent was added as follows.

  As a result, in Comparative Example 1, the impurities aluminum and iron migrate into the starch containing the valuable metal nickel, the impurities cannot be selectively separated, and the impurity separation performance is poor. It was found that there was a problem as a method for recovering valuable metals.

Claims (4)

A method for recovering valuable metals from waste nickel metal hydride batteries, which separates and recovers nickel, cobalt and rare earth elements from valuable metal-containing materials obtained from waste nickel metal hydride batteries,
A leaching step of separating a valuable metal-containing material obtained from the waste nickel metal hydride battery into a leaching solution and a leaching residue after being mixed and dissolved in a sulfuric acid solution;
A rare earth crystallization step of adding a sulfate of an alkali metal to the leachate obtained in the leaching step to obtain a rare earth element sulfate mixed salt precipitation and a rare earth element solution;
A neutralizing agent is added to the rare earth element liquid obtained in the rare earth crystallization step after adding an oxidizing agent, and the pH of the rare earth element liquid is maintained at 4.5 or more and 6.0 or less, And a neutralizing step of separating the impurities in the removed rare earth element liquid as a precipitate and obtaining a mixed aqueous solution containing nickel sulfate and cobalt sulfate from which the impurities have been removed. Metal recovery method.   2. The oxidizing agent is added to the rare earth element liquid so that the redox potential of the rare earth element liquid is 800 mV (Ag / AgCl electrode standard) or more in the neutralization step. A method for recovering valuable metals from waste nickel metal hydride batteries as described in 1.   In the neutralization step, an oxidant is added to the derare earth element liquid, and then a neutralizer is added to maintain the pH of the derare earth element liquid at 5.4 or more and 5.6 or less. A method for recovering valuable metals from a waste nickel metal hydride battery according to claim 1 or 2.   The method for recovering valuable metals from a waste nickel metal hydride battery according to any one of claims 1 to 3, wherein the alkali metal sulfate is sodium sulfate and / or potassium sulfate.

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