Method for producing leachate from mixed sulfide 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 mixed sulfide particle containing nickel and cobalt is mixed with ammonia water preferably containing ammonium carbonate or ammonium hydrogen carbonate prepared such that an ammonium carbonate concentration or an ammonium hydrogen carbonate concentration is within a range of 0.5 mol / L to 4.1 mol / L, to obtain a slurry. A leach treatment is applied to the obtained slurry preferably under an oxidation condition by blowing air or oxygen gas to obtain a leachate containing a nickel ion and a cobalt ion leached from the mixed sulfide particle.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a leach solution containing nickel ions and cobalt ions from a mixed sulfide 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 leachate containing nickel ions and cobalt ions is obtained by mixing mixed sulfide particles containing nickel and cobalt with ammonia water containing ammonium carbonate or ammonium hydrogen carbonate to obtain a slurry, and subjecting the slurry to a leaching treatment under oxidizing conditions. 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 showing a method for producing a leachate of the present invention together with a method for producing MS, which is a raw material thereof. 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 uses a mixed sulfide containing nickel and cobalt as a raw material. The mixed sulfide containing nickel and cobalt can be produced by a high-pressure acid leaching method called HPAL (High Pressure Acid Leach) method, in which sulfuric acid is added to nickel oxide ore under high temperature and high pressure to perform acid leaching.

[0013] The above-mentioned high-pressure acid leaching method includes, for example, as shown in FIG. 1, a pretreatment step of adding water to nickel oxide ore to prepare an ore slurry, a pressure acid leaching step of charging the obtained ore slurry together with sulfuric acid into a pressure leaching reactor called an autoclave, and further injecting high-pressure steam to perform a leaching treatment under high temperature and high pressure at a temperature of about 220 to 250°C and a pressure of about 3.5 to 4.5 MPaG to leach nickel and cobalt contained in the nickel oxide ore, a solid-liquid separation step of separating the acid leachate containing nickel and cobalt obtained in the pressure acid leaching step from the leach residue, a neutralization step of adding a neutralizing agent to the acid leachate to neutralize it at a pH of about 3 to 4 to separate and remove impurity elements such as iron contained in the acid leachate, and a sulfurization step of adding a sulfurizing agent such as hydrogen sulfide gas to the leachate from which the impurity elements have been removed to produce a nickel-cobalt mixed sulfide (also referred to as MS).

[0014] The method for producing a leachate according to an embodiment of the present invention comprises the steps of: mixing the nickel-cobalt mixed sulfide particles obtained by the high-pressure acid leaching method with ammonia water containing ammonium carbonate or ammonium hydrogen carbonate to obtain a slurry; and subjecting the slurry to a leaching treatment under oxidizing conditions to produce a nickel ion (Ni 2+ ) and cobalt ions (Co 2+) containing leachate (containing Ni 2+ Co 2+ The process produces a solution (infusion solution).

[0015] Specifically, water is first placed in a container equipped with a stirrer, and ammonia water (NH4OH) and ammonium carbonate ((NH4)2CO3) are added thereto to prepare an ammonia-containing aqueous solution. Alternatively, ammonium bicarbonate (NH4HCO3) may be added instead of ammonium carbonate to prepare an ammonia-containing aqueous solution. Next, nickel-cobalt mixed sulfide particles are placed in the container containing the ammonia-containing aqueous solution prepared above, and the mixture is stirred and mixed with the stirrer to prepare a slurry having a uniform concentration. In this state, air or oxygen gas is blown into the slurry to create an oxidizing condition, thereby performing a leaching process. This allows nickel ions and cobalt ions to be leached from the nickel-cobalt mixed sulfide particles.

[0016] In the leaching treatment, it is preferable to maintain the temperature of the slurry at a temperature between 20°C and 60°C, which can promote the leaching reaction. If the slurry temperature is less than 20°C, the reaction rate may slow down and the production efficiency may decrease, and conversely, if it exceeds 60°C, ammonium carbonate is easily thermally decomposed, which may also decrease the production efficiency. If the slurry temperature is less than 0°C, water will freeze, making it difficult to leach well in this case as well.

[0017] In the above-mentioned leaching treatment, when the ammonia-containing aqueous solution is prepared by adding ammonium carbonate, the ammonium carbonate concentration in the above-mentioned ammonia-containing aqueous solution is preferably prepared within the range of 0.5 mol / L to 4.1 mol / L, more preferably within the range of 1.5 mol / L to 3.5 mol / L, and most preferably within the range of 2.0 mol / L to 3.0 mol / L. If the ammonium carbonate 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 carbonate 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, the ammonium carbonate becomes supersaturated and precipitates, which may adversely affect the leaching treatment. The ammonium carbonate concentration can be measured by absorptiometry, ion chromatography, etc. If the ammonium carbonate concentration is out of the above range, it can be adjusted by the amount of ammonium carbonate added.

[0018] Alternatively, in the case where the ammonia-containing aqueous solution is prepared by adding ammonium hydrogen carbonate instead of ammonium carbonate in the above-mentioned leaching treatment, similarly to the above, the ammonium hydrogen carbonate concentration in the ammonia-containing aqueous solution is preferably adjusted to within a range of 0.5 mol / L or more and 4.1 mol / L or less, more preferably within a range of 1.5 mol / L or more and 3.5 mol / L or less, and most preferably within a range of 2.0 mol / L or more and 3.0 mol / L or less.

[0019] 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.

[0020] As described above, according to the method for producing a leachate of the embodiment of the present invention, a leachate containing nickel and cobalt can be produced from the raw material nickel-cobalt mixed sulfide particles without producing sodium sulfate as a by-product, and therefore 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

[0021] Example 1 An aqueous solution containing 28.82 g of ammonium carbonate ((NH4)2CO3) 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 aqueous solution containing ammonia with an ammonium carbonate concentration of 1.5 mol / L. 18 g of powdered nickel-cobalt mixed sulfide (MS) having the composition shown in Table 1 below was mixed with the resulting aqueous solution containing ammonia to prepare a slurry. While blowing oxygen gas from an oxygen cylinder into the slurry at a flow rate of 1 L / min, the mixture was stirred with a stirrer and held at a liquid temperature of 50°C for 2 hours to perform a leaching treatment.

[0022] [Table 1]

[0023] After the above leaching treatment, solid-liquid separation was performed by filtration, and a leaching residue with a dry mass of 15.2 g and a leaching solution of 205 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 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) x 100

[0024] As a result, the leaching rate of nickel was 18.3% and that of cobalt was 7.2%, and a leachate consisting of an aqueous ammonia solution containing a large amount of nickel ions and cobalt ions was produced.

[0025] Example 2 The leaching treatment of MS and the subsequent solid-liquid separation were carried out in the same manner as in Example 1, except that an ammonia-containing aqueous solution with an ammonium carbonate concentration of 3.0 mol / L was prepared by changing the amount of ammonium carbonate ((NH4)2CO3) added from 28.82 g to 57.65 g, and a leachate with a dry mass of 9.80 g and 238 mL of leachate were obtained. The element concentrations of the obtained leachate residue and leachate were measured in the same manner as in Example 1, and the leachate rate of nickel was 44.7%, and the leachate rate of cobalt was 24.5%, indicating that a leachate consisting of an aqueous ammonia solution containing a large amount of nickel ions and cobalt ions could be produced.

[0026] Example 3 The leaching treatment of MS and the subsequent solid-liquid separation were carried out in the same manner as in Example 1, except that the amount of ammonium carbonate ((NH4)2CO3) added was changed from 28.82 g to 115.30 g to prepare an ammonia-containing aqueous solution with an ammonium carbonate concentration of 4.1 mol / L. As a result, a leaching residue with a dry mass of 7.84 g and a leachate of 200 mL were obtained. The element concentrations of the obtained leachate residue and leachate were measured in the same manner as in Example 1, and the leachate rate of nickel was 45.1% and the leachate rate of cobalt was 39.4%, indicating that a leachate consisting of an aqueous ammonia solution containing a large amount of nickel ions and cobalt ions could be produced.

[0027] Example 4 Leaching of MS and the subsequent solid-liquid separation were carried out in the same manner as in Example 2, except that the liquid temperature during the leaching treatment was changed to 20°C instead of 50°C, and a leaching residue with a dry mass of 12.6 g and a leachate of 220 mL were obtained. The element concentrations of the obtained leachate residue and leachate were measured in the same manner as in Example 1, and the leaching rate of nickel was 27.7% and the leaching rate of cobalt was 21.6%, indicating that a leachate consisting of an aqueous ammonia solution containing large amounts of nickel ions and cobalt ions could be produced.

[0028] Example 5 In Example 1, ammonium carbonate was used in the leaching treatment, but this was replaced with ammonium hydrogen carbonate, and the same procedure was followed as in Example 1. As a result, it was confirmed that a leachate consisting of an aqueous ammonia solution containing large amounts of nickel ions and cobalt ions, almost equivalent to that in Example 1, was obtained.

[0029] Comparative Example 1 The leaching treatment of MS and the subsequent solid-liquid separation were carried out in the same manner as in Example 1, except that 200 mL of ammonia water with a concentration of 25% was used instead of the ammonia-containing aqueous solution containing ammonium carbonate as the leaching solution, and 200 mL of leaching solution was obtained. The element concentrations of this leaching solution were measured in the same manner as in Example 1 to determine the leaching rate of each element. As a result, the leaching rate of nickel was 14.6%, and the leaching rate of cobalt was 0.2%, which was insufficient for leaching nickel ions compared to Examples 1 to 3 in which the leaching treatment was carried out at the same temperature, and almost no cobalt ions were leached. In this Comparative Example 1, the leaching rate of each element was calculated using the following formula 3. [Formula 3] Leaching rate of element α = mass of element α in leaching solution / mass of element α in MS × 100

[0030] Comparative Example 2 The leaching of MS and the subsequent solid-liquid separation and concentration measurement were carried out in the same manner as in Comparative Example 1, except that the liquid temperature during the leaching treatment was changed from 50°C to 20°C. The nickel leaching rate was 14.6%, and the cobalt leaching rate was 0.2%, which was insufficient for nickel ions to be leached compared to Example 4, in which the leaching treatment was carried out at the same temperature, and almost no cobalt ions were leached. The leaching rates were calculated in the same manner as in Comparative Example 1. The measurement results of the above-mentioned Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Table 2 below.

[0031] [Table 2]

Claims

1. A method for producing a leachate from a mixed sulfide containing nickel and cobalt, comprising: mixing mixed sulfide particles containing nickel and cobalt with ammonia water containing ammonium carbonate or ammonium hydrogen carbonate to obtain a slurry, and subjecting the slurry to a leaching treatment under oxidizing conditions to obtain a leachate containing nickel ions and cobalt ions leached from the mixed sulfide particles.

2. 2. The method for producing a leachate from a mixed sulfide containing nickel and cobalt according to claim 1, wherein the leaching treatment is carried out by blowing air or oxygen gas into the slurry.

3. 2. The method for producing a leachate from a mixed sulfide containing nickel and cobalt according to claim 1, characterized in that the ammonium carbonate or ammonium hydrogen carbonate concentration in the ammonia water containing the ammonium carbonate or ammonium hydrogen carbonate is adjusted to be within a range of 0.5 mol / L or more and 4.1 mol / L or less.

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