Method for producing leachate from hydroxide containing nickel and cobalt

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

[Technical field]

[0001] The present invention relates to a method for producing a leach solution containing nickel and cobalt ions from a hydroxide containing nickel and cobalt. [Background technology]

[0002] 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 driving power sources for electric vehicles, and as storage batteries for smart grids. 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. Of these, 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 baking the mixture.

[0003] Nickel hydroxide, the precursor mentioned above, can be produced by a neutralization reaction that occurs when an aqueous solution of sodium hydroxide is added to an aqueous solution of nickel sulfate, the raw material. This neutralization reaction of the nickel sulfate raw material can cause problems because it produces an equimolar amount of sodium sulfate (mirabilite) as a by-product, as shown in the following formula 1. 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 set up separate facilities for its treatment or to limit the production volume of nickel hydroxide in order to reduce the amount of sodium sulfate discharged. [Formula 1] NiSO4+2NaOH → Ni(OH)2+Na2SO4

[0004] 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 technique 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, 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-324524 Summary of the Invention [Problem to be solved by the invention]

[0006] By using the technology of the above-mentioned Patent Document 1, nickel hydroxide can be produced without producing sodium sulfate as a by-product, but this technology is not economically advantageous because it uses metallic nickel as a precursor raw material. That is, 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 by a refining process before electrowinning, so that the metallic nickel finally obtained has a plate or lump shape. Therefore, a process of processing metallic nickel into powder is required to efficiently leach it with an aqueous ammonia solution.

[0007] In addition, 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 that it contains 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 for separating and removing cobalt from nickel is performed by a refining process such as a solvent extraction process prior to electrowinning, which results in unnecessary separation costs. As described above, the method of manufacturing nickel hydroxide using metallic nickel as the raw material requires many processes that cause an increase in 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.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide a method for producing a leachate containing nickel ions and cobalt ions using a raw material containing nickel and cobalt, which are cheaper than metallic nickel. [Means for solving the problem]

[0009] 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 predetermined temperature condition to obtain a leachate containing nickel ions and cobalt ions leached from the hydroxide particles. Effect of the Invention

[0010] According to the present invention, a leachate containing nickel ions and cobalt ions can be produced using raw materials containing nickel and cobalt, which are cheaper than metallic nickel, without producing sodium sulfate as a by-product. [Brief description of the drawings]

[0011] [Figure 1]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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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 method for producing nickel hydroxide containing cobalt in FIG. 1 includes a water washing step 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 step in which the nickel-cobalt mixed hydroxide particles washed in the water washing step are washed and reduced with an alkali washing solution consisting of an aqueous caustic soda solution at room temperature, preferably having a concentration of about 8 mol / L, which contains a reducing agent such as sodium sulfite, to mainly remove zinc, sulfur, and silicon, a leaching step in which the nickel-cobalt mixed hydroxide particles that have been subjected to the alkali washing and reduction treatment are leached with ammonia water containing ammonium sulfate, a thermal decomposition precipitation step in which the leachate obtained by the leaching treatment is heated to thermally decompose ammonium sulfate into ammonia and sulfur trioxide, and nickel hydroxide and cobalt hydroxide are precipitated as precursors, and an alkali washing step in which the precipitated nickel hydroxide and cobalt hydroxide are washed with an alkali washing solution consisting of an aqueous caustic soda solution at room temperature, preferably having a concentration of about 4 mol / L, to mainly remove carbon.

[0013] In addition, the washing wastewater discharged after washing in the above-mentioned alkaline washing reduction step is repeatedly used as an alkaline washing liquid after impurities such as zinc, sulfur, and silicon are removed from the washing wastewater by a precipitation method or the like. Here, the precipitation method refers to a technique for extracting solutes dissolved in a solution as precipitate particles, and for example, the above-mentioned precipitate particles can be obtained by changing the above-mentioned solution from an unsaturated state to a supersaturated state and promoting the generation and growth of crystal nuclei. In addition, manganese, iron, and aluminum that are not leached in the above-mentioned leaching step remain as leaching residue, and are separated and removed from the leaching liquid by a 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 step, and the carbon content in the washing liquid discharged after washing in the alkaline washing step can be precipitated as sodium carbonate by using a precipitation method similar to the above in this case, since the solubility of the carbon content decreases when the liquid temperature of the washing wastewater decreases. After removing the sodium carbonate in this way, the washing wastewater is repeatedly used as an alkaline washing liquid.

[0014] Among the above series of steps, in the leaching step, water is first charged into a container equipped with a stirrer, and ammonia (NH3) water and ammonium sulfate ((NH4)2SO4) 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 treatment. 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 decreases, 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 the ammonium sulfate solution.

[0015] In this leaching treatment, the ammonium sulfate concentration in the ammonium sulfate aqueous solution is preferably adjusted to be in the range of 0.5 mol / L to 4.1 mol / L, more preferably in the range of 1.5 mol / L to 3.5 mol / L, and most preferably in the range of 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 adversely affect the leaching treatment. The ammonium sulfate concentration can be measured by absorptiometry, ion chromatography, etc. If the ammonium sulfate concentration is out of the above range, it can be adjusted by the amount of ammonium sulfate added.

[0016] 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 stably leached 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 (NH3), and its concentration can be determined by separating it by distillation and then changing the form to NH4. + and then measured by absorptiometry. If the free ammonia concentration is outside the above range, it can be adjusted by adjusting the amount of aqueous ammonia added.

[0017] As described above, the method for producing a leachate according to the 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 at a lower cost 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 to the following examples. EXAMPLES

[0018] (Example) 39.64 g of ammonium sulfate ((NH4)2SO4) was added to 185 mL of pure water and 15 mL of ammonia water with a concentration of 25% by mass 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 form a slurry, which was stirred with a stirrer and held at a liquid temperature of 50°C for 2 hours to carry out a leaching treatment.

[0019] [Table 1]

[0020] After the above leaching treatment, solid-liquid separation was performed by filtration, and a leaching residue with a dry mass of 12.5 g and a leaching solution of 204 mL were obtained. 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 using 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) x 100

[0021] As a result, the leaching rate of nickel was 45.6%, and that of cobalt was 15.4%, and a leachate consisting of an aqueous ammonia solution containing a large amount of nickel ions and cobalt ions was produced.

[0022] (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, for leaching treatment. Thereafter, solid-liquid separation was performed in the same manner as in the examples to obtain 200 mL of leachate. The element concentrations of this leachate were measured in the same manner as in the examples to determine the leaching rate of each element.

[0023] 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 examples and comparative examples 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

[0024] [Table 2]

Claims

1. A method for producing a leachate from a hydroxide containing nickel and cobalt, comprising: mixing hydroxide particles containing nickel and cobalt with ammonia water containing ammonium sulfate to obtain a slurry; and subjecting the slurry to a leaching treatment under a predetermined temperature condition to obtain a leachate containing nickel ions and cobalt ions leached from the hydroxide particles.

2. 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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