WO2020044849A1 - Method for producing nickel sulfate compound - Google Patents

Abstract

A method for producing a nickel sulfate compound, said method comprising a roasting step for heating a nickel-containing starting material which also contains iron under such conditions, wherein an oxygen partial pressure p(O₂) and a sulfur dioxide partial pressure p(SO₂) are controlled so that nickel sulfate becomes thermodynamically more stable than nickel oxide in an Ni-S-O system and iron oxide becomes thermodynamically more stable than iron sulfate in an Fe-S-O system, to thereby form the nickel sulfate compound.

Description

Method for producing nickel sulfate compound

The present invention relates to a method for producing a nickel sulfate compound.
Priority is claimed on Japanese Patent Application No. 2018-161837 filed on August 30, 2018, the content of which is incorporated herein by reference.

Conventionally, nickel sulfate compounds have been used as raw materials for various nickel compounds or metallic nickel for applications such as electrolytic nickel plating, electroless nickel plating, and catalyst materials. 2. Description of the Related Art In recent years, demand for secondary batteries using a nickel compound or metallic nickel as a positive electrode material is expected to be increased as a power source for transportation equipment such as electric vehicles and electronic equipment. In order to obtain a high-performance secondary battery, stable supply of a high-purity nickel sulfate compound is desired.

不純 物 Examples of impurities that may be contained in the low-purity nickel compound include other metal compounds such as iron, copper, cobalt, manganese, and magnesium. Conventionally, a solvent extraction method has been used as a method for obtaining a high-purity nickel compound. In the solvent extraction method, a step of selectively extracting and removing other metal compounds or selectively extracting and extracting nickel compounds is performed. In any case, in order to selectively extract a specific metal ion, a special agent is required, and the cost is high.

As a method for producing nickel sulfate, a method of exchanging anions of nickel compounds for sulfate groups by an ion exchange method and a method of dissolving nickel metal powder in a sulfuric acid solution while generating hydrogen gas are also known. Patent Document 1 describes a method for obtaining water-soluble nickel sulfate by subjecting green nickel oxide powder having a specific gravity of more than 6.30 to heat treatment in sulfuric acid and then leaching with hot water. ing. Patent Document 1 describes sulfuric acid solutions having a concentration of 30% to 60% (claims 1 to 5) and concentrated sulfuric acid having a concentration of 95% (claims 6 to 7) as the sulfuric acid used for the heat treatment. In the case of using concentrated sulfuric acid having a concentration of 95% in Patent Document 1 (Examples 7 to 9), a high temperature of 275 ° C. or higher is required.

US Patent No. 300002814

In the method of obtaining nickel sulfate using liquid-phase sulfuric acid, the iron content coexisting with nickel in the raw material is dissolved in sulfuric acid, so that the consumption of sulfuric acid increases, and hydrogen gas may be generated during the reaction. And so on.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a nickel sulfate compound capable of producing a nickel sulfate compound even in a gas phase atmosphere.

The first aspect of the present invention is to reduce the oxygen partial pressure and the sulfur dioxide partial pressure by making nickel sulfate thermodynamically more stable than nickel oxide in the Ni—SO system and oxidizing in the Fe—SO system. A method for producing a nickel sulfate compound, characterized by having a roasting step of heating a nickel-containing raw material containing iron and producing a nickel sulfate compound under conditions where iron is thermodynamically more stable than iron sulfate. is there.

第 A second aspect of the present invention is the method for producing a nickel sulfate compound according to the first aspect, wherein the roasting temperature is in a range of 400 to 750 ° C. in the roasting step.

In a third aspect of the present invention, in the roasting step, a common logarithm log p (O ₂ ) of oxygen partial pressure in units of atmospheric pressure (atm) is in a range of −4 to −6, The method for producing a nickel sulfate compound according to the first or second aspect, wherein a common logarithm log p (SO ₂ ) of sulfur dioxide partial pressure is in a range of −1 to +1. The common logarithm is a logarithm (log ₁₀ ) with the base being 10.

According to a fourth aspect of the present invention, there is provided the nickel sulfate compound according to any one of the first to third aspects, further comprising a water dissolving step of dissolving the nickel sulfate compound in water after the roasting step. It is a manufacturing method.

A fifth aspect of the present invention is characterized in that after the water dissolving step, there is provided a solid-liquid separation step of separating the liquid phase containing the nickel sulfate compound and the solid phase containing the iron component. Is a method for producing a nickel sulfate compound.

In a sixth aspect of the present invention, the nickel-containing raw material includes at least one selected from the group consisting of nickel sulfide ore, nickel sulfide, nickel matte, nickel oxide, and ferronickel. To a method for producing a nickel sulfate compound according to any one of the fifth to fifth aspects.

A seventh aspect of the present invention is characterized in that, before the roasting step, an oxidizing roasting step of oxidizing and roasting the nickel-containing raw material under conditions different from the roasting step is provided. A method for producing a nickel sulfate compound according to any one of the sixth aspects.

According to the first aspect, even when the nickel-containing raw material contains iron, the nickel is converted to a nickel sulfate compound, and the conversion of iron to iron sulfate is suppressed. Can be suppressed, and the production efficiency of the nickel sulfate compound can be improved.

According to the second aspect, the reduction of iron is suppressed, and iron can coexist with the nickel sulfate compound in the form of iron oxide, iron sulfide, and the like. Can be easily processed.

According to the third aspect, the formation of the nickel sulfate compound can be promoted under the condition where the oxygen partial pressure is low and the sulfur dioxide partial pressure is high.

According to the fourth aspect, iron can be easily removed by preferentially dissolving the nickel sulfate compound.

According to the fifth aspect, the removal of impurities containing iron from the nickel sulfate compound is facilitated through the solid-liquid separation step.

According to the sixth aspect, it is possible to use a nickel-containing raw material that is relatively easy to procure, so that productivity can be improved.

According to the seventh aspect, before the roasting step, the iron content, the sulfur content, and the like contained in the nickel-containing raw material can be oxidized, so that the efficiency of impurity separation after the roasting step can be improved. .

It is a conceptual phase diagram of a Ni-SO system and a Fe-SO system. It is a flow chart showing an outline of a manufacturing method of a nickel sulfate compound of an embodiment. FIG. 2 is a configuration diagram illustrating a device used in an embodiment.

Hereinafter, the present invention will be described based on preferred embodiments.

As shown in FIG. 1, in the method for producing a nickel sulfate compound of the present embodiment, the nickel sulfate is thermodynamically more stable than the nickel oxide in the Ni—SO system, as shown in FIG. In addition, a roasting step of heating a nickel-containing raw material to generate a nickel sulfate compound is performed under a condition in which iron oxide is more thermodynamically stable than iron sulfate in the Fe—SO system.

FIG. 1 is an example of a conceptual phase diagram of a Ni—SO system and an Fe—SO system. The boundary of each phase in the Ni-SO system is indicated by a dashed line (-----), and the boundary of each phase in the Fe-SO system is indicated by a dashed line (----). . The chemical formula attached to the arrow indicates a thermodynamically stable phase on the side from each boundary line toward the arrow. The horizontal axis in the state diagram shown in FIG. 1 shows the logarithm of the partial pressure of O _2, the right side as the O ₂ partial pressure is high, the left as O ₂ partial pressure is low. The vertical axis in the state diagram shown in FIG. 1 shows the logarithm of the SO ₂ partial pressure, the upper as SO ₂ partial pressure is high, the lower the lower SO ₂ partial pressure. The unit of the partial pressure is, for example, the atmospheric pressure (atm = 101325 Pa).

Examples of nickel sulfate contained in the Ni—SO system include NiSO ₄ , and examples of nickel oxide include NiO. In the state diagram shown in FIG. 1, the boundary line _LNi indicates a boundary line between a region where nickel sulfate is thermodynamically stable and a region where nickel oxide is thermodynamically stable. In borderline L _Ni than SO ₂ partial pressure and the partial pressure of O ₂ is high region, nickel sulfate is the thermodynamically stable phase. In a region where the SO ₂ partial pressure and the O ₂ partial pressure are lower than the boundary line _LNi , nickel oxide becomes a thermodynamically stable phase.

Examples of the iron sulfate contained in the Fe—SO system include FeSO ₄ and Fe ₂ (SO ₄ ) ₃ , and examples of the iron oxide include Fe ₂ O ₃ . In the state diagram shown in FIG. 1, a boundary line L _Fe indicates a boundary line between a region where iron sulfate is thermodynamically stable and a region where iron oxide is thermodynamically stable. In a region where the SO ₂ partial pressure and the O ₂ partial pressure are higher than the boundary line L _Fe , iron sulfate becomes a thermodynamically stable phase. In a region where the SO ₂ partial pressure and the O ₂ partial pressure are lower than the boundary line L _Fe , the iron oxide becomes a thermodynamically stable phase.

According to the state diagram shown in FIG. 1, SO ₂ partial pressure and the partial pressure of _{O 2} is lower than the boundary line _{L Fe,} and, SO ₂ partial pressure and the partial pressure of _{O 2} is in the higher region A than the boundary line _{L Ni,} Ni Nickel sulfate is a thermodynamically stable phase in the -SO system and iron oxide in the Fe-SO system. Therefore, by roasting a system containing nickel (Ni), oxygen (O), and sulfur (S) under the conditions of the overlapping region A, the formation of iron sulfate can be performed even when iron is present in the system. It is possible to convert the nickel content to nickel sulfate while suppressing it.

The roasting temperature is preferably in the range of 400 to 750 ° C, more preferably in the range of 550 to 750 ° C. With such a roasting temperature, reduction of iron is suppressed, and iron can coexist with a nickel sulfate compound in a state of iron oxide, iron sulfide, etc. Post-processing can be facilitated. Further, at these temperatures, the carbonate is decomposed, so that it is possible to prevent the carbonate from dissolving in water and remaining as an impurity even in the case where the carbonate is mixed, so that the post-process can be performed. Can be easily processed.

As the O ₂ partial pressure in the roasting step, the logarithmic log p (O ₂ ) of the O ₂ partial pressure in units of atmospheric pressure (atm) is preferably in the range of −4 to −6, and log p (O ₂ ) is −5. The range of from to -6 is more preferable. By lowering the O ₂ partial pressure, the SO ₂ partial pressure tends to increase even in the overlapping region A in FIG. 1, so that the production of nickel sulfate can be promoted while suppressing the production of iron sulfate.

The partial pressure of SO ₂ in the roasting step is preferably such that the logarithm log p (SO ₂ ) of the partial pressure of SO _{2 in the} unit of atmospheric pressure (atm) is in the range of −1 to +1 and the log p (SO ₂ ) is in the range of −1 to A range of 0 is more preferred. In the overlapping region A in FIG. 1, by further increasing the partial pressure of SO ₂ , the production of sulfate can be promoted. Furthermore, the total pressure of the roasting atmosphere is not excessively increased by setting the partial pressure of SO ₂ to about the normal pressure or lower (the common logarithm of the partial pressure is substantially 0 or less), thereby facilitating the handling of the equipment. be able to.

The nickel-containing raw material may be a nickel compound or metallic nickel as long as it contains a nickel element. The nickel-containing raw material in the roasting step preferably contains at least one selected from the group consisting of nickel sulfide ore, nickel sulfide, nickel matte, nickel oxide, and ferronickel. The nickel-containing raw material may contain iron or may not contain iron. The iron content is separated from the nickel sulfate compound in a later step, but from the viewpoint of energy consumption, the lower the iron content in the raw material, the more desirable. The nickel-containing raw material is not limited to one kind, and two or more kinds may be used. When two or more nickel-containing raw materials are used, these raw materials may be supplied in a mixed state, or may be supplied separately.

The nickel matte includes, for example, a composition (weight ratio) of 45 to 55% Ni, about 20% Fe, 20 to 25% S, and about 1% or less Co. Further, as a nickel mat whose nickel concentration is increased in a converter, for example, a composition (weight ratio) of about 78% of Ni, about 1% of Co, about 1% of Fe, and about 20% of S can be cited. Ferronickel includes, for example, a composition (weight ratio) of 18 to 23% of Ni, about 1% of Co, and 76 to 81% of Fe.

Prior to the roasting step, it is preferable to reduce the particle diameter of the nickel-containing raw material by operations such as shredding, pulverization, and attrition. Since the reaction starts from the surface of the raw material in the roasting step, the smaller the particle diameter of the raw material, the shorter the reaction time, which is preferable. The crushing means is not particularly limited, but one or more of a ball mill, a rod mill, a hammer mill, a fluid energy mill, a vibration mill and the like can be used. The particle size after the pulverization is not particularly limited, but is, for example, about 1 to 1000 μm, or about 10 to 100 μm. In the case of a raw material that can be obtained in the form of fine particles, such as limonite ore, it may be supplied to the roasting step as it is.

The roasting device for performing the roasting step is not particularly limited, and examples thereof include a rotary kiln, a fluidized bed heating furnace, and an electric furnace. In order to maintain the condition in which the O ₂ partial pressure is low in the roasting device, an inert gas such as nitrogen (N ₂ ) or argon (Ar) may be supplied to the roasting device. These inert gases can also be used as carriers when supplying volatile components such as gas and vapor to the roasting apparatus. If the nickel-containing raw material has a low sulfur content, the sulfur content may be supplied to the roasting step. The source of the sulfur content is not particularly limited, but includes elemental sulfur, sulfur oxide, sulfuric acid, sulfate, sulfide and the like.

Before performing the roasting process under the conditions of the overlap region A, preliminary oxidation roasting is performed under conditions different from the roasting process for the purpose of oxidizing iron, sulfur, and the like contained in the raw materials. A step may be provided. In the preliminary oxidation roasting step, O ₂ gas or the like may be supplied as an oxidizing agent.

FIG. 2 schematically illustrates a method for producing a nickel sulfate compound according to the present embodiment. By the above-described roasting step S1 of the nickel-containing raw material 10, a roasted product 11 containing a nickel sulfate compound is obtained. A solution 21 containing a nickel sulfate compound is obtained in a water dissolving step S2 in which water 20 is supplied to the roasted product 11 and the nickel sulfate compound is dissolved in water. As described above, since the iron component contained in the roasted product 11 is in a state of being hardly soluble in water such as iron oxide and iron sulfide, it is separated into a solid phase and a liquid phase in the solid-liquid separation step S3. Then, a crude nickel sulfate compound 31 is obtained as a liquid phase, and impurities 32 containing iron and the like are separated as a solid phase. Further, if necessary, for example, a purifying agent 40 is added to the crude nickel sulfate compound 31 to remove coexisting substances such as cobalt, and the purification step S4 is performed to remove impurities 42 such as cobalt. A nickel compound 41 can be obtained.

(4) The water added to the roasted product in the water dissolving step is preferably pure water treated so as not to contain impurities. The water treatment method is not particularly limited, but includes one or more of filtration, membrane separation, ion exchange, distillation, disinfection, chemical treatment, adsorption and the like. As the water for dissolution, tap water obtained from a water source, industrial water, or the like may be used, or water obtained by treating wastewater generated in another process may be used. Two or more types of water may be used.

The solubility of nickel sulfate in water is highest at 150 ° C., where 100 g of solution contains 55 g of NiSO _4, but even at 0 ° C., 100 g of solution contains 22 g of NiSO ₄ . For this reason, it is desirable to carry out the dissolving operation at a temperature lower than the boiling point of water. Further, the solution obtained in the water dissolving step preferably has a concentration at which NiSO ₄ does not precipitate even at room temperature, and it is preferable to maintain a heated state with a solution having a higher concentration than that.

In the solid-liquid separation step, the method of solid-liquid separation is not particularly limited, and examples thereof include a filtration method, a centrifugal separation method, and a sedimentation separation method. Desirably, it is preferable that the apparatus has a high performance of separating fine particles contained in the solid phase. For example, in the filtration method, the type of filtration is not particularly limited, and examples thereof include gravity filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, filtration with a filter aid, and compression squeezing.
Pressure filtration is preferred because it allows easy adjustment of the differential pressure and enables rapid separation.

Examples of impurities that can coexist with the nickel sulfate compound include iron (Fe), cobalt (Co), and aluminum (Al). When these metal salts are sulfates in the roasting step, iron sulfate, cobalt sulfate, and the like also dissolve when the nickel sulfate compound is dissolved in water. Further, in water, for example, iron precipitates as an oxide such as FeOOH, Fe ₂ O ₃ , Fe ₃ O _4, etc., and it becomes easy to remove impurities from the nickel sulfate compound. In the roasting step of the present embodiment, conditions are set such that iron does not easily turn into iron sulfate. Therefore, by passing through the solid-liquid separation step, a crude nickel sulfate compound containing less iron can be obtained.

Among the impurities, metals having a lower ionization tendency than hydrogen (H), such as copper (Cu), gold (Au), silver (Ag), and platinum group metals (PGM), remain as solids in the water dissolving step. It can be removed by a liquid separation step. The solid removed by the solid-liquid separation step may include compounds such as arsenic (As), lead (Pb), and zinc (Zn), in addition to the impurities described above. Solids containing these impurities can be recycled as valuables.

Since the solution obtained in the water dissolving step and the solid-liquid separation step contains a nickel sulfate compound as a main component, it can be transported and used as a solution of the nickel sulfate compound or as a solid of the nickel sulfate compound by drying or the like. it can. Depending on the application, when it is desired to reduce, for example, cobalt sulfate as an impurity in the solution, techniques such as solvent extraction, electrodialysis (Electrowinning), electrorefining (Electrorefining), ion exchange, and crystallization are used. Can be used.

(4) In the case of solvent extraction, it is preferable to use an extractant that can extract cobalt into a solvent preferentially or selectively over nickel. This allows the nickel sulfate compound to remain in the aqueous solution to allow for efficient purification. Examples of the extractant include organic compounds having a functional group capable of binding to a metal ion, such as a phosphinic acid group and a thiophosphinic acid group. In the solvent extraction, an organic solvent capable of separating the extractant from water may be used as a diluent. By dissolving the extractant combined with metal ions such as cobalt in the diluent, separation from the aqueous solution containing the nickel sulfate compound becomes easy without using a large amount of the extractant. The diluent is preferably an organic solvent that is hardly miscible with water.

In the case of crystallization, the target nickel sulfate compound may be crystallized from the solution by at least one factor such as a change in temperature, a decrease in the solvent, and the addition of another substance. At this time, purification is enabled by leaving at least a part of the impurities in the liquid phase. Specific examples include an evaporation crystallization method and a poor solvent crystallization method. In the evaporative crystallization method, a solution is concentrated by boiling or evaporating under reduced pressure to crystallize a nickel sulfate compound. The poor solvent crystallization method is a crystallization method used in the production of pharmaceuticals and the like. For example, an organic solvent is added to a solution containing a nickel sulfate compound to precipitate a nickel sulfate compound. As the organic solvent used for crystallization, an organic solvent miscible with water is preferable, and examples thereof include one or more selected from the group consisting of methanol, ethanol, propanol, isopropanol, butyl alcohol, ethylene glycol, and acetone. Two or more organic solvents may be used. As for the concentration range in which the organic solvent is miscible with water, it is preferable to mix the organic solvent at a concentration to which the organic solvent is added to such an extent that the nickel sulfate compound is precipitated. The organic solvent can be mixed with water at an arbitrary ratio as long as the concentration allows precipitation of the nickel sulfate compound. The organic solvent added in the crystallization step is not limited to an anhydrous organic solvent, and may be a water-containing organic solvent to such an extent that crystallization is not hindered. The ratio of water to the organic solvent is not particularly limited, but may be set, for example, in the range of 1:20 to 20: 1, but is preferably about 1: 1, for example, 1: 2 to 2: 1.

When a solid nickel sulfate compound is obtained through crystallization or the like, the nickel sulfate is in a state of anhydrous, monohydrate, dihydrate, pentahydrate, hexahydrate, heptahydrate and the like. You may. The nickel sulfate compound precipitated by crystallization can be separated from the solution by solid-liquid separation. The method of solid-liquid separation is not particularly limited, and examples thereof include a filtration method, a centrifugation method, and a sedimentation method. The metal dissolved in the solution is preferably neutralized and removed from the solution by a method such as precipitation. When the purified solution is mainly composed of a mixture of water and an organic solvent, the water and the organic solvent can be separated by a method such as distillation.

According to the method for producing a nickel sulfate compound of the present embodiment, the following effects can be obtained.
(1) Since a nickel sulfate compound with high added value can be produced from various nickel-containing raw materials, production can be performed even near a place of demand, and transportation costs can be reduced.
(2) A highly pure nickel sulfate compound can be produced.
(3) The production of iron sulfate can be suppressed in the roasting step. Further, generation of hydrogen (H ₂ ) gas can also be suppressed.
(4) The roasted product is a chemical species in which iron is hardly dissolved in water, and nickel is easily dissolved in water as a nickel sulfate compound, so that iron is easily removed.
(5) It is possible to easily remove impurities including iron.
(6) Equipment cost can be reduced as compared with the conventional method, and existing equipment can be used as a roasting furnace.
(7) Before the roasting step, iron contained in the nickel-containing raw material can be oxidized, and the efficiency of iron removal can be improved.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

Hereinafter, the present invention will be described specifically with reference to examples.

(Example-1: Roasting test)
A test of sulfuric acid roasting was performed using the test apparatus 100 shown in FIG. After weighing 5 g of a nickel compound as a sample on the pan 101, the pan 101 was set inside a glass container 102 installed in an electric furnace 103. The glass container 102 was provided with a thermometer 104 such as a thermocouple capable of measuring an ambient temperature, an injection pipe 105 capable of injecting various gases, and an outlet 106 for exhaust gas generated inside. The temperature was raised to a specified temperature in the electric furnace 103, and the sample was steamed. In the injection tube 105, dry air or SO ₂ gas containing nitrogen gas can be supplied periodically while always injecting argon gas. The exhaust gas discharged from the outlet 106 passes through the gas analyzer 107 and can be treated by the exhaust gas treatment device 108. Data on various gas volumes and analytical values were collected on a computer.

The composition of the nickel compound used in the test was a nickel sulfide alloy in which the content of iron was reduced by converter treatment of a nickel mat, and the composition was as follows.
Ni: 78%, Co: 1%, Fe: 1%, S: 20%

Sulfuric acid roasting was performed at 680 ° C. on a 5 g sample. Argon gas was purged for 20 minutes until the sample rose to the specified temperature, and after reaching the specified 680 ° C., air was supplied for 20 minutes to burn iron and oxidized to oxidize iron. At the same time as air was injected, the weight of the sample was reduced and the evolution of SO ₂ gas was observed. Thereafter, the gas to be injected was switched to SO ₂ , and sulfuric acid roasting was performed for 40 minutes while adjusting the O ₂ partial pressure and the SO ₂ partial pressure. During the sulfuric acid roasting, a certain amount of SO ₂ consumption was confirmed. As a result of analyzing the roasted product by X-ray diffraction (XRD), it was confirmed that the iron content was changed to Fe ₂ O ₃ and the Ni content was changed to NiSO ₄ .

(Example-2: Water dissolution test)
The roasted product produced from 5 g of the nickel compound in Example-1 was put into 100 g of pure water and stirred at 90 ° C. to dissolve. A part of the solution was sampled, and the concentration in the solution was determined for each metal (Ni, Fe, Co) using an atomic absorption spectrometer. Further, from this concentration, the amount contained in the solution, that is, the total amount dissolved in pure water was determined for each metal, and the amount contained in the 5 g sample used for sulfuric acid roasting was set to 100% and dissolved in pure water. The ratio (dissolution rate) was determined. For example, the dissolution rate of Ni means the ratio of Ni dissolved in pure water to Ni contained in the roasted product. Table 1 shows the results of the determination of the dissolution rate.

From the results, it was confirmed that the iron content in the roasted product was hardly dissolved, and Ni and Co were easily dissolved. This indicates that the sulfuric acid roasting of Example 1 can produce a high-purity nickel sulfate compound having a low iron content.

The present invention can be used for the production of various types of nickel compounds or high-purity nickel sulfate compounds useful as raw materials for metallic nickel used in electric parts such as secondary batteries, chemical products, and the like.

S1: roasting step, S2: water dissolving step, S3: solid-liquid separation step, S4: refining step, 10: nickel-containing raw material, 11: roasted product, 20: water, 21: solution, 31: crude nickel sulfate Compound, 32: impurities separated in the solid-liquid separation step, 40: purification agent, 41: purified nickel sulfate compound, 42: impurities separated in the purification step.

Claims (7)

1. The oxygen partial pressure and the sulfur dioxide partial pressure were determined to be such that nickel sulfate is thermodynamically more stable than nickel oxide in the Ni—SO system, and iron oxide is more thermodynamic than iron sulfate in the Fe—SO system. A method for producing a nickel sulfate compound, comprising a roasting step of heating a nickel-containing raw material containing an iron component to generate a nickel sulfate compound as a condition to be stable.
2. 方法 The method for producing a nickel sulfate compound according to claim 1, wherein in the roasting step, the roasting temperature is in a range of 400 to 750 ° C.
3. In the roasting step, the common logarithm log p (O ₂ ) of the oxygen partial pressure in the unit of atmospheric pressure (atm) is in a range of −4 to −6, and the common logarithm log p of the sulfur dioxide partial pressure in the unit of the atmospheric pressure (atm). _{3. The} method for producing a nickel sulfate compound according to claim 1, wherein (SO ₂ ) is in the range of −1 to +1.
4. (4) The method for producing a nickel sulfate compound according to any one of (1) to (3), further comprising a water dissolving step of dissolving the nickel sulfate compound in water after the roasting step.
5. 5. The method for producing a nickel sulfate compound according to claim 4, further comprising a solid-liquid separation step of separating the liquid phase containing the nickel sulfate compound and the solid phase containing iron after the water dissolving step.
6. The method according to any one of claims 1 to 5, wherein the nickel-containing raw material includes at least one selected from the group consisting of nickel sulfide ore, nickel sulfide, nickel matte, nickel oxide, and ferronickel. A method for producing the nickel sulfate compound according to the above.
7. The method according to any one of claims 1 to 6, further comprising, before the roasting step, an oxidizing roasting step of oxidizing and roasting the nickel-containing raw material under conditions different from the roasting step. The method for producing a nickel sulfate compound of the present invention.

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