JP2025002589A - Method for producing leachate from hydroxide containing nickel and cobalt - Google Patents

Abstract

To provide a method for producing a leachate containing a nickel ion and a cobalt ion, by using a material containing nickel and cobalt less expensive than metal nickel powder.SOLUTION: A hydroxide particle containing nickel and cobalt is mixed with ammonia water preferably containing ammonium sulfate prepared such that an ammonium sulfate concentration is within a range of 0.5 to 4.1 mol/L, to obtain a slurry. A leach treatment is applied to the obtained slurry under a prescribed temperature condition to obtain a leachate containing a nickel ion and a cobalt ion leached from the hydroxide particle.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a leachate containing nickel ions and cobalt ions from a hydroxide containing nickel and cobalt.

Lithium-ion secondary batteries, which charge and discharge by the movement of lithium ions between the positive and negative electrodes, have a high energy density and do not deteriorate easily even when repeatedly charged and discharged, so in recent years demand has been increasing for them as batteries for electronic devices such as mobile phones and laptops, as power sources for electric vehicles and smart grid storage batteries. Lithium-ion secondary batteries have a structure in which a positive electrode and a negative electrode face each other with a separator in between, and an electrolyte is filled between them. Lithium nickel oxide is used as the active material for the positive electrode, which is the main component. Lithium nickel oxide can be produced by mixing lithium hydroxide with nickel hydroxide as a precursor and firing the mixture.

The above-mentioned nickel hydroxide as a precursor can be produced by a neutralization reaction caused by adding an aqueous sodium hydroxide solution to an aqueous nickel sulfate solution as a raw material. In this neutralization reaction of the nickel sulfate raw material, as shown in the following formula 1, an equimolar amount of sodium sulfate (mirabilite) is produced as a by-product, which can cause problems. In other words, sodium sulfate cannot be easily disposed of because total wastewater volume restrictions are set in some areas, and it has sometimes been necessary to install separate facilities for its treatment or to limit the production volume of nickel hydroxide in order to suppress the discharge of sodium sulfate.
[Formula 1]
NiSO ₄ +2NaOH→Ni(OH) ₂ +Na ₂ SO ₄

Therefore, a method for producing nickel hydroxide that does not produce sodium sulfate as a by-product has been proposed. For example, Patent Document 1 proposes a technology in which oxygen is introduced into an aqueous ammonia solution containing powder of metallic nickel to leach the metallic nickel into the aqueous ammonia solution, and then seed crystals are added as necessary to the aqueous ammonia solution containing nickel and hydroxyl ions, and the aqueous ammonia solution is evaporated under atmospheric pressure or reduced pressure to precipitate and recover nickel hydroxide.

Japanese Patent Application Publication No. 10-324524

By using the technology of Patent Document 1, nickel hydroxide can be produced without producing sodium sulfate as a by-product, but this technology uses metallic nickel as the precursor raw material, and therefore is not economically advantageous. In other words, metallic nickel is generally produced by leaching nickel from intermediate raw materials such as matte, sulfide, or hydroxide obtained by processing nickel ore using acid or chlorine, and then separating impurities leached together with the nickel through a refining process before electrowinning, so that the metallic nickel finally obtained is in the form of a plate or a lump. Therefore, a process of processing metallic nickel into powder is required in order to efficiently leach it with an aqueous ammonia solution.

Also, as can be seen from the fact that cobalt is added to the precursor in the above-mentioned manufacturing stage of lithium nickel oxide, it is not a problem if the nickel used as the raw material for the precursor contains cobalt, and it is rather preferable for it to contain a certain amount of cobalt. However, although many of the intermediate raw materials used in the above-mentioned manufacturing of metallic nickel contain cobalt, a process is carried out to separate and remove cobalt from nickel by a refining process such as a solvent extraction process prior to electrowinning, which results in unnecessary separation costs. As such, the method of manufacturing nickel hydroxide using metallic nickel as the raw material requires many processes that increase costs, so there is a demand for an alternative method of manufacturing nickel hydroxide using unrefined intermediate raw materials containing a wide variety of impurities obtained, for example, by processing nickel oxide ore or scrap.

The present invention was made in consideration of the above circumstances, and aims to provide a method for producing a leachate containing nickel ions and cobalt ions using raw materials containing nickel and cobalt, which are cheaper than metallic nickel.

In order to achieve the above object, the method for producing a leachate according to the present invention is characterized in that a slurry obtained by mixing hydroxide particles containing nickel and cobalt with ammonia water containing ammonium sulfate is subjected to a leaching treatment under a specified temperature condition to obtain a leachate containing nickel ions and cobalt ions leached from the hydroxide particles.

According to the present invention, it is possible to produce a leachate containing nickel ions and cobalt ions using raw materials containing nickel and cobalt, which are cheaper than metallic nickel, without producing sodium sulfate as a by-product.

FIG. 1 is a block flow diagram of a method for producing nickel hydroxide containing cobalt, which preferably includes the method for producing a leachate of the present invention.

Hereinafter, an embodiment of the method for producing a leachate containing nickel ions and cobalt ions according to the present invention will be described. The method for producing a leachate according to the embodiment of the present invention is included in the method for producing nickel hydroxide containing cobalt as a precursor, as shown in FIG. That is, the manufacturing method of nickel hydroxide containing cobalt in FIG. 1 includes a water washing process in which nickel-cobalt mixed hydroxide particles (MHP) are washed with water at room temperature to mainly remove calcium and magnesium, an alkali washing reduction process in which the nickel-cobalt mixed hydroxide particles washed in the water washing process are washed and reduced with an alkali washing solution consisting of a room temperature caustic soda aqueous solution containing a reducing agent such as sodium sulfite and preferably having a concentration of about 8 mol/L to mainly remove zinc, sulfur, and silicon, a leaching process in which the alkali washed and reduced nickel-cobalt mixed hydroxide particles are leached with ammonia water containing ammonium sulfate, a thermal decomposition precipitation process in which the leachate obtained by the leaching process is heated to thermally decompose ammonium sulfate into ammonia and sulfur trioxide and precipitate nickel hydroxide and cobalt hydroxide as precursors, and an alkali washing process in which the precipitated nickel hydroxide and cobalt hydroxide are washed with an alkali washing solution consisting of a room temperature caustic soda aqueous solution having a concentration of about 4 mol/L to mainly remove carbon.

In addition, the washing effluent discharged after washing in the above-mentioned alkaline washing reduction process is used repeatedly as an alkaline washing effluent after impurities such as zinc, sulfur, and silicon are removed from the washing effluent by a precipitation method or the like. Here, the precipitation method refers to a method of extracting solutes dissolved in a solution as precipitate particles. For example, the above-mentioned solution is changed from an unsaturated state to a supersaturated state, and the above-mentioned precipitate particles can be obtained by promoting the generation and growth of crystal nuclei. In addition, manganese, iron, and aluminum that are not leached in the above-mentioned leaching process remain as leaching residue, and are separated and removed from the leaching effluent by solid-liquid separation means such as filtration. Furthermore, ammonia and sulfur trioxide generated by thermal decomposition in the thermal decomposition precipitation means are recovered and reused as ammonia water containing ammonium sulfate in the previous leaching process, and the carbon content in the washing effluent discharged after washing in the alkaline washing process can be precipitated as sodium carbonate by using the precipitation method in the same way as above, since the solubility of the carbon content decreases when the liquid temperature of the washing effluent decreases. After removing the sodium carbonate in this way, the washing effluent is used repeatedly as an alkaline washing effluent.

In the leaching process among the above series of steps, first, water is charged into a container equipped with a stirrer, and ammonia (NH ₃ ) water and ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) are added thereto to prepare an ammonium sulfate aqueous solution. Next, nickel-cobalt mixed hydroxide particles are charged into the container containing the prepared ammonium sulfate solution, and a slurry having a homogeneous concentration is prepared by stirring and mixing with the stirrer. In this state, the temperature of the slurry is preferably maintained under a temperature condition of 20°C or more and 60°C or less to perform the leaching process. In this way, nickel ions and cobalt ions can be leached from the nickel-cobalt mixed hydroxide particles. If the slurry temperature is less than 20°C, the reaction rate is too slow and the production efficiency is reduced, and conversely, if it exceeds 60°C, ammonium sulfate is easily thermally decomposed, making it impossible to leach it well. In addition, if the slurry temperature is less than 0°C, water freezes, making it difficult to prepare an ammonium sulfate solution.

In this leaching treatment, the ammonium sulfate concentration in the ammonium sulfate aqueous solution is preferably adjusted to a range of 0.5 mol/L to 4.1 mol/L, more preferably 1.5 mol/L to 3.5 mol/L, and most preferably 2.0 mol/L to 3.0 mol/L. If the ammonium sulfate concentration is less than 1.5 mol/L, the leaching rate may decrease, and especially if it is less than 0.5 mol/L, the effect of the present invention may not be exhibited well. On the other hand, even if the ammonium sulfate concentration is increased beyond about 3.5 mol/L, the leaching rate does not change much, but the cost required for neutralization increases, which is not preferable, and if it exceeds 4.1 mol/L, ammonium sulfate becomes supersaturated and precipitates, which may have a negative effect on the leaching treatment. The ammonium sulfate concentration can be measured by absorptiometry, ion chromatography, etc. If the ammonium sulfate concentration is outside the above range, it can be adjusted by the amount of ammonium sulfate added.

In addition, during the above leaching treatment, it is preferable to adjust the free ammonia concentration in the slurry to within the range of 0.1 to 1.3 mol/L. If the free ammonia concentration is within this range, nickel and cobalt can be leached stably in the form of ammine complexes. Even if the free ammonia concentration exceeds 1.3 mol/L, it has almost no effect on the stable leaching in the form of the above amine complexes, and it is not preferable because it increases costs and increases the load on wastewater treatment. Note that free ammonia refers to molecular ammonia (NH ₃ ), and its concentration can be measured by absorptiometry after separating it by distillation and converting it to NH ₄ ⁺ . If the free ammonia concentration is outside the above range, it can be adjusted by adding an amount of ammonia water.

As described above, the method for producing a leachate according to an embodiment of the present invention makes it possible to produce a leachate containing nickel and cobalt from the raw material nickel-cobalt mixed hydroxide particles without by-producing sodium sulfate, and also makes it possible to easily separate and remove impurities such as manganese, iron, and aluminum contained in the raw material, so that the leachate can be produced more inexpensively than when expensive metallic nickel is used as the raw material. The present invention will now be described in more detail with reference to examples, but the present invention is not limited in any way to the following examples.

(Example)
39.64 g of ammonium sulfate (( _NH4 ) _{2SO4 )} was added to 185 mL of pure water and 15 mL of 25% ammonia water placed in a container to prepare an ammonium sulfate aqueous solution with an ammonium sulfate concentration of 1.5 mol/L. 20 g of powdered nickel-cobalt mixed hydroxide (MHP) having the composition shown in Table 1 below was mixed with the resulting ammonium sulfate aqueous solution to prepare a slurry, which was stirred with a stirrer while maintaining the liquid temperature at 50°C for 2 hours to carry out a leaching treatment.

After the above leaching treatment, solid-liquid separation was performed by filtration to obtain a leaching residue with a dry mass of 12.5 g and a leaching solution of 204 mL. The element concentrations of the leaching residue and the leaching solution were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the leaching rate of each element was calculated by the following formula 2.
[Formula 2]
Leaching rate of element α=mass of element α in leaching solution/(mass of element α in leaching solution+mass of element α in leaching residue)×100

As a result, the nickel leaching rate was 45.6% and the cobalt leaching rate was 15.4%, and a leachate consisting of an aqueous ammonia solution containing a large amount of nickel ions and cobalt ions was produced.

Comparative Example
200 mL of 25% ammonia water was placed in a container, and 20 g of powdered nickel-cobalt mixed hydroxide (MHP) having the composition shown in Table 1 was mixed to form a slurry, which was stirred with a stirrer and held for 2 hours while adjusting the liquid temperature to 50° C., to carry out a leaching treatment. Thereafter, solid-liquid separation was carried out in the same manner as in the examples, and 200 mL of leachate was obtained. The element concentrations of this leachate were measured in the same manner as in the examples, and the leaching rate of each element was determined.

As a result, the leaching rate of nickel was 14.6%, and that of cobalt was 0.2%, which means that about 1/3 of the nickel was leached compared to the example in which the leaching treatment was performed at the same temperature, but almost no cobalt was leached. In this comparative example, the leaching rate of each element was calculated using the following formula 3. The measurement results of the above example and comparative example are summarized in Table 2 below.
[Formula 3]
Leaching rate of element α=mass of element α in leaching solution/mass of element α in MHP×100

Claims (2)

A method for producing a leachate from a hydroxide containing nickel and cobalt, comprising: mixing hydroxide particles containing nickel and cobalt with aqueous ammonia containing ammonium sulfate to obtain a slurry; and subjecting the slurry to a leaching treatment under a specified temperature condition to obtain a leachate containing nickel ions and cobalt ions leached from the hydroxide particles. 2. The method for producing a leachate from a hydroxide containing nickel and cobalt according to claim 1, wherein the ammonium sulfate concentration in the ammonia water containing ammonium sulfate is adjusted to be within the range of 0.5 to 4.1 mol/L.

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