Method for producing nickel sulfate

Abstract

To provide a novel method of producing nickel sulfate from nickel oxide.SOLUTION: The method of producing nickel sulfate comprises a step of feeding nickel oxide particles and an aqueous solution of an acid to a pressure-resistant container, a step of heating the pressure-resistant container in a sealed state to raise the temperature to a temperature exceeding 100°C to obtain a mixed solution in which nickel oxide is dissolved, and a step of producing nickel sulfate using the mixed solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing nickel sulfate.

Background Art

[0002] In recent years, the demand for lithium-ion secondary batteries has been increasing steadily. Many of the cathode active materials for lithium-ion secondary batteries contain nickel, such as lithium nickel cobalt manganese composite oxides and lithium nickel cobalt aluminum composite oxides. On the other hand, nickel is also used in stainless steel, special steel, etc., and the demand for these is also increasing.

[0003] Therefore, the demand for nickel has increased rapidly, and from the perspective of stable supply of nickel sources, the development of methods for securing new nickel sources is desired. As one method for securing a nickel source, a method for recovering nickel from nickel-containing oxide ores is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The method described in Patent Document 1 is intended to secure a nickel source for stainless steel, and therefore, nickel is finally obtained as ferronickel. On the other hand, nickel sulfate is generally used as the nickel source for cathode active materials containing nickel. Therefore, a method capable of producing nickel sulfate from a nickel-containing raw material (for example, nickel oxide) is very useful for securing a nickel source for cathode active materials of lithium-ion secondary batteries.

[0006] Therefore, an object of the present invention is to provide a novel method for producing nickel sulfate from nickel oxide.

Means for Solving the Problems

[0007] The method for producing nickel sulfate disclosed herein includes a step of charging nickel oxide particles and an aqueous acid solution into a pressure-resistant container, a step of heating the pressure-resistant container in a sealed state to a temperature exceeding 100 °C to obtain a mixed solution in which nickel oxide is dissolved, and a step of producing nickel sulfate using the mixed solution. According to such a configuration, a novel method for producing nickel sulfate from a raw material containing nickel oxide can be provided.

[0008] In a preferred embodiment of the method for producing nickel sulfate disclosed herein, the aqueous acid solution is hydrochloric acid. According to such a configuration, the dissolution rate of nickel oxide in the aqueous acid solution increases, and the production efficiency of nickel sulfate can be enhanced.

[0009] In a preferred embodiment of the method for producing nickel sulfate disclosed herein, the average particle diameter of the nickel oxide particles is 1.0 mm or less. According to such a configuration, the dissolution rate of nickel oxide in the aqueous acid solution increases, and the production efficiency of nickel sulfate can be enhanced. Further, when the average particle diameter of the nickel oxide particles is 0.5 μm or more and 100 μm or less, the dissolution rate of nickel oxide in the aqueous acid solution becomes even greater, and the production efficiency of nickel sulfate can be further enhanced.

[0010] In a preferred embodiment of the method for producing nickel sulfate disclosed herein, the concentration of the aqueous acid solution is 2 mol / L or more. In addition, the particles are charged into the pressure-resistant container such that the concentration of nickel oxide becomes 0.80 mol / L or less. According to such a configuration, the dissolution rate of nickel oxide in the aqueous acid solution increases, and the production efficiency of nickel sulfate can be enhanced. Furthermore, when nickel oxide is charged such that the concentration becomes 0.30 mol / L or more and 0.60 mol / L or less, the dissolution rate of nickel oxide in the aqueous acid solution becomes even greater, and the production efficiency of nickel sulfate can be further enhanced.

[0011] In a preferred embodiment of the method for producing nickel sulfate disclosed herein, the pressure-resistant container is heated to 150°C or higher and 270°C or lower in a sealed state. According to such a configuration, the dissolution rate of nickel oxide in the aqueous acid solution increases, and the production efficiency of nickel sulfate can be enhanced. Also, it is excellent in terms of cost.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Matters that are not mentioned in this specification but are necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field.

[0014] Figure 1 shows each step of the method for producing nickel sulfate according to this embodiment. The method for producing nickel sulfate according to this embodiment includes a step S101 of charging nickel oxide particles and an aqueous acid solution into a pressure-resistant container (hereinafter also referred to as the "charging step"), and a step S102 of heating the pressure-resistant container in a sealed state to a temperature exceeding 100°C to obtain a mixed solution in which nickel oxide is dissolved (hereinafter also referred to as the "mixed solution preparation step"), and a step S103 of producing nickel sulfate using the mixed solution (hereinafter also referred to as the "nickel sulfate production step"). Hereinafter, each step will be described in detail.

[0015] <Charging step S101> In charging step S101, nickel oxide particles and an aqueous acid solution are charged into a pressure-resistant container. As the pressure-resistant container, a known pressure-resistant container used in chemical reactions can be used. Specific examples thereof include an autoclave, a pressure tank, a pressure chamber, etc. The pressure-resistant container preferably includes temperature measuring means such as a thermometer and a temperature sensor.

[0016] The nickel oxide particles are commercially available and may be reagent-grade products, industrial-grade products, etc.

[0017] The smaller the particle size of the nickel oxide particles, the greater the dissolution rate of the nickel oxide particles. In other words, when the particle size of the nickel oxide particles is large, the dissolution rate becomes small. Therefore, the average particle size of the nickel oxide particles is, for example, 2.5 mm or less, preferably 1.0 mm or less, more preferably 500 μm or less, still more preferably 200 μm or less, and most preferably 100 μm or less. On the other hand, if the average particle size of the nickel oxide particles is too small, it becomes difficult to finely pulverize them to the desired average particle size. Therefore, the particle size of the nickel oxide particles is, for example, 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more.

[0018] In this specification, the average particle diameter of nickel oxide particles means the median diameter D50. Therefore, the average particle diameter can be obtained, for example, by measuring the volume-based particle size distribution based on the laser diffraction / scattering method and taking the particle diameter corresponding to 50% by volume of the cumulative frequency from the side of fine particles with a small particle diameter.

[0019] The acid contained in the acid aqueous solution is not particularly limited, but an inorganic acid is preferable. Examples thereof include hydrogen chloride (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), phosphoric acid (H3PO4), etc. Among these, sulfuric acid has the advantage that sulfate ions (SO4 2- ) which are anions of nickel sulfate can be introduced into the system. On the other hand, hydrogen chloride is considered to be capable of forming a complex with nickel and has the advantage that the dissolution rate of nickel oxide particles is particularly large. Therefore, hydrochloric acid is preferably used as the acid aqueous solution.

[0020] The higher the acid concentration of the acid aqueous solution, the greater the dissolution rate of nickel oxide particles. Therefore, the acid concentration of the acid aqueous solution is preferably 1.8 mol / L (1.8 M) or more, more preferably 2.0 mol / L or more. On the other hand, if the acid concentration of the acid aqueous solution is too high, it is disadvantageous in terms of cost. Therefore, the acid concentration of the acid aqueous solution is preferably 20 mol / L or less, more preferably 5.0 mol / L or less.

[0021] Regarding the input amounts of nickel oxide particles and the acid aqueous solution, the smaller the amount of nickel oxide particles, the greater the tendency for the dissolution rate to be large. Therefore, it is preferable to input them so that the concentration of nickel oxide becomes 1.0 mol / L or less. This concentration of nickel oxide is more preferably 0.8 mol / L or less, and even more preferably 0.6 mol / L or less. On the other hand, if this concentration of nickel oxide is small, the yield of nickel sulfate per method is small, which is disadvantageous in terms of cost. Therefore, this concentration of nickel oxide is preferably 0.1 mol / L or more, more preferably 0.2 mol / L or more, and even more preferably 0.3 mol / L or more.

[0022] In a preferred embodiment, from the viewpoint of high solubility of nickel oxide, the concentration of the aqueous acid solution is 2 mol / L or more. Further, nickel oxide particles are put into a pressure-resistant container so that the concentration of nickel oxide becomes 0.80 mol / L or less.

[0023] The method of putting nickel oxide particles and the aqueous acid solution into the pressure-resistant container is not particularly limited, and a known method may be adopted. Either the nickel oxide particles or the aqueous acid solution may be put into the pressure-resistant container first, or they may be put in simultaneously.

[0024] <Mixed solution preparation step S102> In the mixed solution preparation step S102, the pressure-resistant container is sealed and heated to a temperature exceeding 100°C to obtain a mixed solution in which nickel oxide is dissolved.

[0025] Therefore, first, the sealed container into which nickel oxide particles and the aqueous acid solution are put is sealed. Then, it is heated to a temperature exceeding 100°C.

[0026] The heating can be performed according to a known method. For example, a method of immersing the pressure-resistant container in an oil bath for heating, a method of winding a strip heater such as a ribbon heater, a surface heater such as a film heater or a silicon rubber heater around the pressure-resistant container for heating, etc. may be mentioned.

[0027] Here, nickel oxide is a compound that is difficult to dissolve. Even when heated at 100°C under normal pressure, nickel oxide does not dissolve in the aqueous acid solution. Therefore, in this embodiment, heating is performed at a temperature exceeding 100°C. Since the pressure-resistant container is in a sealed state, the inside of the pressure-resistant container can be put into a pressurized state by this heating, and thereby, nickel oxide can be dissolved in the aqueous acid solution. Therefore, by this heating, a mixed solution in which nickel oxide is dissolved in the aqueous acid solution can be obtained.

[0028] Here, the higher the heating temperature, the greater the dissolution rate of nickel oxide. Therefore, the heating temperature is preferably 110°C or higher, more preferably 150°C or higher, still more preferably 180°C or higher, and most preferably 200°C or higher. However, in the region of high heating temperature, the effect of increasing the dissolution rate of nickel oxide becomes very small, and excessive heating leads to cost increase. Therefore, although the heating temperature is not particularly limited, it is preferably 270°C or lower, more preferably 250°C or lower.

[0029] The heating time greatly depends on the heating temperature and the type of acid. Therefore, the heating time may be appropriately selected according to the heating temperature and the type of acid to be sufficient for the nickel oxide particles to dissolve in the aqueous acid solution.

[0030] <Nickel Sulfate Generation Step S103> In the nickel sulfate generation step S103, nickel sulfate is generated using the mixed solution obtained above. This step can be carried out according to a known method.

[0031] When an aqueous sulfuric acid solution is used as the aqueous acid solution, nickel ions and sulfate ions exist in the mixed solution. In this case, for example, first, the pH of the mixed solution is adjusted using an aqueous alkali solution (e.g., an aqueous sodium hydroxide solution, etc.). The pH is preferably around 4. Then, solid-liquid separation is carried out according to a known method to separate into a solid phase and a liquid phase (i.e., an aqueous phase).

[0032] From the separated aqueous phase, nickel sulfate is crystallized according to a known method. Then, the precipitated nickel sulfate can be recovered and obtained according to a known method.

[0033] When an aqueous solution other than the sulfuric acid aqueous solution is used in the aqueous acid solution, nickel ions are present in the mixed solution, but sulfate ions are not present. In this case, for example, first, an extractant (e.g., alkyl phosphonate ester, etc.) is added to the mixed solution and stirred. Then, an alkali (e.g., sodium hydroxide) is added, and the pH is adjusted so that nickel ions move to the organic phase, and the organic phase is extracted. Then, an aqueous sulfuric acid solution is added to the extracted organic phase. As a result, nickel ions move to the aqueous phase containing sulfuric acid. This aqueous phase is extracted, nickel sulfate is crystallized according to a known method, and nickel sulfate can be recovered and obtained according to a known method.

[0034] Note that depending on the use of nickel sulfate, for example, nickel sulfate may be recovered in an aqueous solution state without precipitating nickel sulfate from the aqueous phase.

[0035] As described above, nickel sulfate can be produced from nickel oxide particles. The method for producing nickel sulfate according to the present embodiment is novel and is very useful as a new method for securing nickel sulfate used as a nickel source for the positive electrode active material of a lithium-ion secondary battery.

[0036] Hereinafter, examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples.

[0037] [Example 1] In Example 1, nickel oxide particles having an average particle diameter (D50) of 500 μm were used. As the nickel oxide particles, those having a Ni content of 75% by mass or more, an Fe content of 1% by mass or less, and an S content of 0.08% by mass or less were used.

[0038] Nickel oxide particles and sulfuric acid with a concentration of 2 mol / L were put into an autoclave so that the concentration of nickel oxide became 0.8 mol / L. The autoclave was sealed and heated to 110°C using a heater.

[0039] After heating for 30 minutes, undissolved nickel oxide particles were recovered from the mixed solution in the autoclave, and their weight was determined. The weight had decreased, confirming that the nickel oxide particles had dissolved in the aqueous acid solution. Furthermore, from the amount of weight decrease, the dissolution rate of nickel oxide per 30 minutes (% / 30 min) was calculated. This dissolution rate is shown in Table 1.

[0040] Also, the mixed solution in which nickel oxide was dissolved was adjusted to a pH of about 4 using sodium hydroxide. Then, the liquid phase was recovered by solid-liquid separation and introduced into a crystallization tank. The internal pressure was controlled to about 7.5 kPa using a vacuum pump, and crystallization was carried out while stirring the inside of the crystallization tank with a double propeller to produce nickel sulfate. This was recovered to obtain nickel sulfate.

[0041] 〔Examples 2 to 12〕 Nickel sulfate was obtained in the same manner as in Example 1, except that the average particle diameter (D50) of the nickel-containing particles, the concentration of nickel oxide, the concentration of the aqueous acid solution, and the heating temperature were changed to the values shown in Table 1. At this time, the dissolution rate of nickel oxide per 30 minutes was determined. The results are shown in Table 1.

[0042] 〔Examples 13 to 17〕 In Examples 13 to 17, nickel oxide particles with an average particle diameter (D50) shown in Table 1 were used. Nickel oxide particles and 2 mol / L hydrochloric acid were introduced into an autoclave so that the concentration of nickel oxide became 0.4 mol / L. The autoclave was sealed and heated to 180 °C using a heater.

[0043] After heating for 30 minutes, undissolved nickel oxide particles were recovered from the mixed solution in the autoclave, and their weight was determined. The weight had decreased, confirming that the nickel oxide particles had dissolved in the aqueous acid solution. Furthermore, from the amount of weight decrease, the dissolution rate of nickel oxide per 30 minutes was calculated. This dissolution rate is shown in Table 1.

[0044] Next, an alkyl phosphonate ester was added as an extractant to the mixed solution in which nickel oxide was dissolved, and the mixture was stirred. Thereafter, using sodium hydroxide, the pH was adjusted so that nickel ions would move to the organic phase, and the organic phase was extracted.

[0045] An aqueous sulfuric acid solution was added to the extracted organic phase, and the aqueous phase was extracted. The aqueous phase was put into a crystallization tank, the pressure inside the crystallization tank was controlled to about 7.5 kPa using a vacuum pump, and crystallization was carried out while stirring the inside of the crystallization tank with a double propeller to produce nickel sulfate. This was recovered to obtain nickel sulfate.

[0046] 〔Comparative Examples 1 and 2〕 Nickel oxide particles and sulfuric acid with a concentration of 2 mol / L were put into an autoclave such that the concentration of nickel oxide became 0.8 mol / L. The autoclave was sealed and heated to the temperature shown in Table 1. After heating for 30 minutes, the undissolved nickel oxide particles were recovered from the mixed solution in the autoclave, and their weight was determined. The weight had not decreased, indicating that the nickel oxide particles had not dissolved.

[0047] 〔Comparative Example 3〕 Nickel oxide particles and sulfuric acid with a concentration of 2 mol / L were put into an autoclave such that the concentration of nickel oxide became 0.8 mol / L. The autoclave was not sealed and was heated to 110°C using a heater. After heating for 30 minutes, the undissolved nickel oxide particles were recovered from the mixed solution in the autoclave, and their weight was determined. The weight had not decreased, indicating that the nickel oxide particles had not dissolved.

[0048]

Table 1

[0049] From the above, it can be seen that by heating nickel oxide particles and an aqueous acid solution in a sealed pressure-resistant container to a temperature exceeding 100°C, a mixed solution in which nickel oxide is dissolved can be prepared, and nickel sulfate can be produced using this. Therefore, according to the manufacturing method disclosed herein, it can be seen that nickel sulfate can be produced from nickel oxide.

[0050] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Claims

1. A step of introducing nickel oxide particles and an aqueous acid solution into a pressure-resistant container; A step of heating the pressure-resistant container in a sealed state to 150°C or higher and 270°C or lower to obtain a mixed solution in which nickel oxide is dissolved; A step of producing nickel sulfate using the mixed solution; comprising: The average particle diameter of the nickel oxide particles is 0.5 μm or more and 100 μm or less; The aqueous acid solution is hydrochloric acid; The particles are introduced into the pressure-resistant container such that the concentration of nickel oxide is 0.30 mol / L or more and 0.60 mol / L or less; A method for producing nickel sulfate.

2. In the step of producing nickel sulfate, an extractant is added to the mixed solution, and then an alkali is added to adjust the pH so that nickel ions move to the organic phase. After extracting the organic phase, an aqueous sulfuric acid solution is added to the extracted organic phase to move the nickel ions to the aqueous phase containing sulfuric acid, and the aqueous phase is extracted. The production method according to Claim 1.

3. The production method according to Claim 1 or 2, wherein the concentration of the aqueous acid solution is 2 mol / L or more.

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