JP2020001996A - Method for producing nickel sulfate compound - Google Patents

Abstract

To provide a method for producing a nickel sulfate compound, which can produce a high purity nickel sulfate compound under a milder condition than before.SOLUTION: The method for producing a nickel sulfate compound comprises: a conversion step S1 of converting at least a part of a nickel-containing raw material 10 to a nickel sulfate compound by treating the nickel-containing raw material 10 together with an abrasive material with concentrated sulfuric acid; a solid-liquid separation step S2 of separating a mixture 11 obtained in the conversion step S1 into a solid phase 21 and a liquid phase 22; and a dissolution and separation step S3 of adding water to the solid phase 21 obtained in the solid-liquid separation step S2 and dissolving a nickel sulfate compound contained in the solid phase 21 to separate an impurity 32.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a nickel sulfate compound.

  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.

  Impurities that may be included in the low-purity nickel compound include other metal compounds such as iron, copper, cobalt, manganese, and magnesium. Conventionally, a method of obtaining a high-purity nickel compound includes a solvent extraction method. 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 a nickel compound for a sulfate group 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 of 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. In Patent Document 1, as the sulfuric acid used for the heat treatment, a sulfuric acid solution having a concentration of 30% to 60% (claims 1 to 5) and a concentrated sulfuric acid having a concentration of 95% (claims 6 to 7) are mentioned. 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 more is required.

US Patent No. 30021814

  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 at a higher conversion rate even under milder conditions than before.

  In a first aspect of the present invention, a nickel-containing raw material is treated with concentrated sulfuric acid together with an attrition material to convert at least a part of the nickel-containing raw material into a nickel sulfate compound. A solid-liquid separation step of separating the mixture into a solid phase and a liquid phase; adding water to the solid phase obtained in the solid-liquid separation step; dissolving the nickel sulfate compound contained in the solid phase in the water; And a dissolution / separation step of separating a nickel sulfate compound.

  In a second aspect of the present invention, the nickel-containing raw material in the conversion step is at least one selected from the group consisting of nickel oxide, nickel hydroxide, nickel sulfide, nickel chloride, nickel metal, ferronickel, and nickel ore. The method for producing a nickel sulfate compound according to the first aspect, comprising:

  A third aspect of the present invention is the nickel sulfate according to the first aspect, wherein in the conversion step, the nickel-containing raw material contains nickel sulfide, an oxidizing agent is added, and the oxidation-reduction potential is 300 mV or more. This is a method for producing a compound.

  A fourth aspect of the present invention is any of the first to third aspects, wherein concentrated sulfuric acid contained in the liquid phase obtained in the solid-liquid separation step is reused in the conversion step. This is a method for producing a nickel sulfate compound.

  A fifth aspect of the present invention is the nickel sulfate compound according to any one of the first to fourth aspects, wherein in the dissolution separation step, the temperature of water added to the solid phase is 15 to 60 ° C. It is a manufacturing method.

  According to a sixth aspect of the present invention, in the dissolving and separating step, impurities are separated by setting a pH of a solution in which the nickel sulfate compound is dissolved in the water to 4 to 5 and separating the impurities. The method for producing a nickel sulfate compound according to any one of the above.

  A seventh aspect of the present invention is a method for producing a nickel sulfate compound according to any one of the first to sixth aspects, further comprising a purification step of removing a cobalt compound contained in the solution obtained in the dissolution separation step. It is a manufacturing method.

  An eighth aspect of the present invention is any one of the first to seventh aspects, further comprising a crystallization step of adding an organic solvent to the solution obtained in the dissolution separation step to precipitate a nickel sulfate compound. This is a method for producing a nickel sulfate compound.

  A ninth aspect of the present invention is characterized in that the organic solvent in the crystallization step is at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol, butyl alcohol, ethylene glycol and acetone. The method for producing a nickel sulfate compound according to the eighth aspect described above.

  A tenth aspect of the present invention is the method for producing a nickel sulfate compound according to the eighth or ninth aspect, wherein the nickel sulfate compound obtained in the crystallization step is nickel sulfate hexahydrate. is there.

  According to the first aspect, by treating the nickel-containing raw material with concentrated sulfuric acid together with the attrition material, it is possible to generate a nickel sulfate compound at a higher conversion even under milder conditions than before. When a mixture containing the produced nickel sulfate compound and unreacted concentrated sulfuric acid is subjected to solid-liquid separation, the nickel sulfate compound can be easily separated as a solid phase, and the unreacted concentrated sulfuric acid can be easily separated as a liquid phase. In addition, the treatment can be easily performed without bringing unreacted concentrated sulfuric acid into contact with water.

  According to the second 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 third aspect, when a nickel-containing raw material containing nickel sulfide such as nickel matte is used, the oxidation-reduction potential at the time of the conversion reaction is set to an oxidation region of 300 mV or more to prevent precipitation of sulfur and generation of hydrogen sulfide gas. By maintaining the conditions for generating ionic sulfur, for example, HSO ₄ ⁻ ions, the conversion efficiency from nickel sulfide to nickel sulfate compound can be improved.

  According to the fourth aspect, unreacted concentrated sulfuric acid can be effectively used, and the cost required for the disposal of concentrated sulfuric acid can be reduced.

  According to the fifth aspect, the nickel sulfate compound can be selectively extracted into the aqueous phase while suppressing dissolution of impurities such as iron salts.

  According to the sixth aspect, the nickel sulfate compound can be selectively extracted into the aqueous phase while suppressing dissolution of impurities such as iron salts.

  According to the seventh aspect, a cobalt compound which is likely to coexist with the nickel sulfate compound can be removed to produce a higher quality nickel sulfate compound.

  According to the eighth aspect, the impurities are removed by dissolving the nickel sulfate compound contained in the solid phase in water and then crystallization using an organic solvent. Since it is removed as a part remaining in the aqueous phase during the precipitation, a high-purity nickel sulfate compound can be produced more efficiently.

  According to the ninth aspect, effective purification can be achieved by crystallization using an organic solvent that is easily miscible with water. Further, the organic solvent can be efficiently recovered from the liquid phase containing water and the organic solvent obtained by crystallization by distillation.

  According to the tenth aspect, by precipitating nickel sulfate hexahydrate from a solution, a high-purity product is easily obtained at the time of crystallization, and its usefulness as an industrial product is high.

It is a flow chart which shows the outline of the manufacturing method of the nickel sulfate compound of a 1st embodiment. It is a flowchart which shows the outline of the manufacturing method of the nickel sulfate compound of 2nd Embodiment.

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

  In the method for producing a nickel sulfate compound according to the present embodiment, as shown in FIG. 1, a nickel-containing raw material 10 is treated with concentrated sulfuric acid together with an abrasive to convert at least a part of the nickel-containing raw material 10 into a nickel sulfate compound. Conversion step S1, solid-liquid separation step S2 for separating mixture 11 obtained in conversion step S1 into solid phase 21 and liquid phase 22, and water added to solid phase 21 obtained in solid-liquid separation step S2, A dissolution separation step S3 of dissolving the nickel sulfate compound contained in the solid phase 21 in water to separate the impurities 32. The solution 31 containing the nickel sulfate compound is obtained by the dissolution separation step S3.

  In the conversion step of this embodiment, the nickel-containing raw material is treated with concentrated sulfuric acid together with the abrasive.

  The nickel-containing raw material may be a nickel compound or metallic nickel as long as it contains a nickel element. Examples of the nickel compound include, but are not particularly limited to, nickel salts such as nickel oxide, nickel hydroxide, nickel sulfide, and nickel chloride. The nickel compound may be a hydrate. The metallic nickel may be a nickel alloy such as ferronickel. When metallic nickel (simple or alloy) is used as a nickel-containing raw material, a shot or the like in which molten metal is fragmented may be used. Nickel ore can also be used as a nickel-containing raw material. As the nickel ore, at least one kind of oxide ore, sulfide ore and the like can be mentioned. Nickel mat or the like containing nickel sulfide as a main component can also be used as a nickel-containing raw material.

  In the conversion step, the nickel-containing raw material is not limited to one type, and two or more types may be used. The two or more nickel-containing raw materials may be supplied in a mixed state, or may be supplied separately. Before supplying the nickel-containing raw material to the conversion step, it is preferable to reduce the particle diameter by operations such as shredding, pulverization, and attrition. The pulverizing 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.

  As the abrasive, any material may be used as long as it has a function of abrading the particle surface of the nickel-containing raw material. Stainless steel, ceramics, and the like having corrosion resistance to concentrated sulfuric acid are preferable, and ceramic balls are particularly preferable. In the case of the present embodiment, as described later in detail, in the solid-liquid separation step after the conversion step, since concentrated sulfuric acid is separated as a liquid phase, even a substance that is soluble in dilute sulfuric acid such as steel. Any substance that is hardly soluble in concentrated sulfuric acid can be used. Even if iron or the like is slightly dissolved by bringing steel or the like into contact with concentrated sulfuric acid, it can be separated and removed in a step described later.

  Conventionally, when a nickel-containing raw material is dissolved in a sulfuric acid solution, the dissolution reaction is such that the sulfuric acid solution permeates into the particles of the nickel-containing raw material, and nickel reacts with sulfuric acid to be dissolved. In this case, the diffusion of the sulfuric acid solution on the particle surface determines the rate of the reaction. For example, if insoluble crystals or the like are generated on the particle surface due to the relationship between the oxidation-reduction region and the pH region, there is a problem that nickel inside may not be dissolved because the particle surface is covered with the insoluble matter. For this reason, in order to improve the conversion rate to nickel sulfate, it was necessary to lengthen the residence time or increase the reaction temperature.

  In the conversion step, it is preferable that the nickel-containing raw material and the abrasive are collided by stirring or the like in a state where the nickel-containing raw material, the abrasive and the concentrated sulfuric acid are mixed. As a result, the reaction between the nickel-containing raw material and the concentrated sulfuric acid becomes a mechanochemical reaction via the attrition material, insoluble matter is less likely to be deposited on the particle surface of the nickel-containing raw material, and sulfuric acid easily permeates into the inside of the particles. For this reason, the conversion rate to the nickel sulfate compound can be improved even under mild conditions.

  As for the temperature of the mixture in the conversion step, good conversion proceeds at, for example, 15 to 200 ° C., and the time required for conversion becomes shorter as the temperature increases to room temperature, 90 ° C., 120 ° C., and 150 ° C. As a mild reaction condition, 90 ° C. or less at which the sulfuric acid mist does not fly is preferable. Nickel and sulfuric acid react to give a nickel sulfate compound. When the conversion reaction is performed under heating conditions, the nickel-containing raw material, concentrated sulfuric acid, and the like may be heated before being supplied and mixed into the conversion reaction system.

  The nickel sulfate compound formed in the conversion step may be in a state of nickel sulfate anhydrous, monohydrate, dihydrate, pentahydrate, hexahydrate, heptahydrate and the like. . Examples of the concentrated sulfuric acid include a liquid containing 90% or more sulfuric acid. Examples of the concentration of concentrated sulfuric acid include 95%, 96%, 98%, and the like. At least a portion of the concentrated sulfuric acid used in the conversion step may be procured and used from other sources. As at least a part of the concentrated sulfuric acid used in the conversion step, the concentrated sulfuric acid recovered from the liquid phase in the solid-liquid separation step described below can be reused.

  The mixing ratio between the nickel-containing raw material and the concentrated sulfuric acid is preferably selected within a range where the viscosity of the slurry-like mixture is appropriate. For example, assuming that the total of the nickel-containing raw material and the concentrated sulfuric acid is 100 wt%, the ratio of the nickel-containing raw material is preferably 5 wt% to 50 wt%. 5 wt% to 15 wt% is desirable within the range having the properties of Newtonian fluid.

When the nickel-containing raw material contains nickel sulfide, the conversion reaction is performed by injecting oxygen (O ₂ ) gas or adding an oxidizing agent such as hydrogen peroxide (H ₂ O ₂ ) or ozone (O ₃ ). Is preferably promoted. Thus, when a nickel-containing raw material containing nickel sulfide such as nickel matte is used, the conversion efficiency from nickel sulfide to a nickel sulfate compound can be improved. Normally, HSO ₄ ^{− in} concentrated sulfuric acid is used for conversion from a nickel-containing raw material to a nickel sulfate compound. However, when nickel sulfide is included as a nickel-containing raw material, sulfur in nickel sulfide is present in an ionic state. And it does not escape as sulfur gas, so that the sulfur content is hardly reduced. Therefore, the amount of HSO ₄ ⁻ in the concentrated sulfuric acid is maintained at a predetermined amount, and it is not necessary to add concentrated sulfuric acid or the amount of addition can be reduced. In order to promote a reaction with an oxidizing agent such as oxygen, it is preferable to heat concentrated sulfuric acid to, for example, about 95 to 200 ° C., or about 100 to 150 ° C. Hot concentrated sulfuric acid may be used as the concentrated sulfuric acid.

When a nickel mat is used as a nickel-containing raw material, it is preferable that the nickel mat be pulverized to, for example, about 20 μm and then supplied to the conversion step. The iron content in the nickel mat is preferably reduced in advance by a converter or the like. For example, there is a nickel mat having Fe of 1 wt% or less. The oxidation-reduction potential in the reaction system is preferably 300 mV or more so that elemental sulfur (S ⁰ ) does not precipitate and ionic HSO ₄ ⁻ is generated. That is, by setting the oxidation-reduction potential in the reaction system to 300 mV or more, sulfur generated from nickel sulfide is used in an ion state. For example, elementary sulfur (S) precipitates on the surface of nickel sulfide, and Conversion efficiency can be improved without hindering the conversion from methane to a nickel sulfate compound. Further, by setting the oxidation-reduction potential in the reaction system to 300 mV or more, generation of hydrogen sulfide (H ₂ S) is suppressed.

  When oxygen gas is injected, a mixed gas containing oxygen, for example, air may be used. The conversion step of the present embodiment can be effectively performed at normal pressure, but may be performed under pressurized conditions to increase the solubility of oxygen gas in concentrated sulfuric acid. The partial pressure of the oxygen gas may be about 0.02 MPa as in air, or may be a higher pressure.

  In the solid-liquid separation step of the present embodiment, the mixture obtained in the conversion step is separated into a solid phase and a liquid phase.

  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 to use a device that has high separation performance of fine particles contained in the solid phase and has excellent corrosion resistance to sulfuric acid in a portion that can come into contact with concentrated sulfuric acid contained in the liquid phase. For example, in a filtration method, a sulfuric acid-resistant material can be used as a filter medium or the like. The method 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 press-filtration.

  The concentrated sulfuric acid contained in the liquid phase obtained in the solid-liquid separation step can be reused as the concentrated sulfuric acid added to the nickel-containing raw material in the conversion step. As a result, unreacted concentrated sulfuric acid can be used effectively, and the cost required for disposal of concentrated sulfuric acid can be reduced. When the metal compound is dissolved in the collected concentrated sulfuric acid, it is preferable to remove the metal compound from the concentrated sulfuric acid by treating with a purification device.

  A small amount of concentrated sulfuric acid may remain in the solid phase obtained in the solid-liquid separation step in order to obtain a solution having a preferable pH range in the dissolution separation step described later. When the residual concentrated sulfuric acid is excessive, air blow or the like may be performed on the solid phase cake to reduce the amount of the concentrated sulfuric acid from the solid phase. When removing concentrated sulfuric acid from the solid phase, it is economical to use air as a fluid that does not react with sulfates and concentrated sulfuric acid in the solid phase, but other fluids or methods may be used.

  In the dissolution separation step of the present embodiment, water is added to the solid phase obtained in the solid-liquid separation step, and the nickel sulfate compound contained in the solid phase is dissolved in water to separate impurities.

  The water added to the solid phase in the dissolution separation step is preferably pure water that has been treated so as not to contain impurities. The water treatment method is not particularly limited, and 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 waste water generated in a crystallization step or another process described later may be used. Two or more types of water may be used.

  By leaching the solid phase with water, the components in the solid phase dissolve in water to obtain a solution. The pH of the resulting solution is made acidic in order to dissolve the nickel sulfate compound in the solid phase in water. In order to selectively extract the nickel sulfate compound into the aqueous phase while suppressing the dissolution of impurities such as iron sulfate, the pH of the solution is about 4 to 5, and the oxidation range is preferably determined by measuring the oxidation-reduction potential. 8 to 5.5.

The method of adjusting the pH of the solution is not limited to the adjustment of the residual amount of concentrated sulfuric acid in the solid-liquid separation step described above, but may be performed by adding an acid or an alkali. The acid is not limited to concentrated sulfuric acid, but may be dilute sulfuric acid or the like. As the alkali, a hydroxide of an alkaline earth metal (for example, calcium hydroxide) which can be easily removed from the aqueous phase by forming a precipitate in the presence of sulfate ions is preferable. Further, an oxidizing agent such as H ₂ O ₂ may be added as needed to maintain the solution in the oxidized region. When the oxidizing agent used in the conversion step can remain until the dissolution separation step, the residual amount of the oxidizing agent may be adjusted.

Examples of impurities that can coexist with the nickel sulfate compound include iron (Fe), cobalt (Co), and aluminum (Al). When these metal salts are converted into sulfates in the conversion step, iron sulfate, cobalt sulfate, and the like also dissolve when the nickel sulfate compound is dissolved in water. Furthermore, in water, for example, it precipitates as an oxide such as FeOOH, Fe ₂ O ₃ , and Fe ₃ O _4, which facilitates removal of impurities from the nickel sulfate compound. The higher the temperature of nickel sulfate, the higher the solubility in water. However, the temperature of water is preferably about 15 to 60 ° C. in order to suppress the dissolution of impurities. In order to adjust the temperature of the water, the temperature of the water added to the nickel sulfate compound or the temperature around the container used for dissolving the nickel sulfate compound may be controlled.

  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, and are thus solid-liquid such as by filtration. It can be removed by separation. The method for solid-liquid separation is not particularly limited, and examples thereof include a filtration method, a centrifugation method, and a sedimentation method. The solid removed by the solid-liquid separation may include compounds such as As, Pb, and Zn in addition to the above impurities. Solids containing these impurities can be recycled as valuables.

  When concentrated sulfuric acid is contained in the solid phase, the temperature rises due to the heat generated by the dissolution of sulfuric acid and water. However, the temperature is preferably adjusted to a temperature range suitable for use in a purification step such as a crystallization step described below. Examples of the temperature control method include adjustment of the temperature or amount of water added in the dissolution / separation step, heat exchange, heat release, cooling, and the like. From the viewpoint of the solubility of the nickel sulfate compound, the temperature of the solution is preferably room temperature or higher. When performing the crystallization step, the temperature of the solution obtained in the dissolution separation step is lower than the boiling point of the organic solvent used in the crystallization step, and lower than the azeotropic point of the mixture of the organic solvent and water. Is preferred.

  Since the solution obtained by the dissolution / 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. Depending on the application, if it is desired to reduce, for example, cobalt sulfate, as an impurity in the solution, techniques such as solvent extraction, electrodialysis (Electrowinning), electrorefining (Electro refining), ion exchange, and crystallization are used. Can be used.

  In the case of solvent extraction, it is preferable to use an extractant that can extract cobalt preferentially or selectively into a solvent over nickel. This allows the nickel sulfate compound to remain in the aqueous solution and allows 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.

  FIG. 2 shows an embodiment having a crystallization step S4 in which an organic solvent is added to the solution 31 obtained in the dissolution separation step S3 to precipitate a nickel sulfate compound 41. The conversion step S1, the solid-liquid separation step S2, and the dissolution separation step S3 are the same as described above, and thus redundant description will be omitted.

  In the crystallization step of the present embodiment, an organic solvent is added to the solution obtained in the dissolution separation step to precipitate a nickel sulfate compound. In the case where the dissolution / separation step and the crystallization step are performed by a batch method (batch method), the container used for obtaining the solution in the dissolution / separation step can be subsequently used for the crystallization step. In the case of a continuous method or the like, the solution obtained in the dissolution / separation step may be transferred from the vessel used in the dissolution / separation step to the vessel used in the crystallization step.

  The organic solvent used for crystallization is preferably an organic solvent miscible with water, and includes, for example, 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 that the organic solvent is mixed at a concentration to which the nickel sulfate compound is precipitated, and it is more preferable that the organic solvent is freely mixed at an arbitrary ratio. 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.

  The nickel sulfate compound precipitated in the crystallization step may be in a state of nickel sulfate hexahydrate or the like. The precipitated nickel sulfate compound can be separated from the solution by solid-liquid separation. The method for 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.

  As shown in FIG. 2, the organic solvent 45 separated from the solution 42 after the crystallization step S4 by distillation 43 or the like is added to the solution 31 obtained in the dissolution separation step S3 in the crystallization step S4. It may be reused. Further, the water 44 separated from the solution 42 after the crystallization step S4 may be reused in the step of being added to the solid phase 21 obtained in the solid-liquid separation step S2 in the dissolution separation step S3.

  When water or an organic solvent is reused, a purification step may be performed if necessary. The step of removing impurities such as metals may be performed not only before distillation but also after distillation. For example, when the amount of impurities is small, a step of removing impurities from the solution remaining after distilling the solution may be provided.

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 having high added value can be produced from various nickel-containing raw materials, production is possible even near a demand area, and transportation costs can be reduced.
2) A high-purity nickel sulfate compound can be produced.
3) The operating cost can be reduced by reusing concentrated sulfuric acid.
4) The reaction rate can be promoted in the conversion step. Further, generation of hydrogen (H ₂ ) gas can be reduced.
5) By reducing the residence time in the conversion step, productivity can be increased even if the apparatus is downsized.
6) By using concentrated sulfuric acid, a low-cost material can be applied.
7) Uses fewer drugs, making management easier.
8) Since an organic solvent is used for the nickel sulfate compound in the crystallization step, the use of evaporation energy is smaller than in conventional evaporation crystallization. Further, the time required for the precipitation is shortened, and the equipment can be downsized.
9) Equipment cost can be reduced as compared with the conventional method.
10) When nickel sulfide is reacted while being oxidized in the conversion step, a sulfate group is generated from the sulfide, and a high yield can be obtained in a short time even under normal pressure.

  As described above, the present invention has been described based on the preferred embodiments. However, 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.

  The conversion step of the above embodiment can be applied to a step in which a raw material containing a metal or a metal compound is treated with concentrated sulfuric acid together with an abrasive to convert at least a part of the raw material into a metal sulfate compound. The raw material in this case is not limited to the nickel mat, but may be a copper mat, a Ni / Cu mixed mat, or the like, and these mats may contain a platinum group metal (PGM). In the conversion from the mat, it is preferable to use an oxidizing agent such as oxygen as in the case of the nickel mat. After the conversion step, by passing through the solid-liquid separation step and the dissolution separation step, not only the nickel sulfate compound but also a water-soluble metal sulfate such as a copper sulfate compound can be efficiently obtained.

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

<Example 1-1>
100 mL of concentrated sulfuric acid (reagent having a purity of 98% as H ₂ SO ₄ ) and 5 g of nickel oxide (reagent of green NiO) are put in a 300 mL glass container, and stirred with a stirrer coated with a fluororesin. Heated with an electric heater. When the temperature exceeded 100 ° C., steam and white smoke-like sulfuric acid mist were generated on the gas side. After heating to 120 ° C., the electric heater was turned off and stirring continued for 72 hours. While continuing to stir, the mixture in the glass vessel cooled down naturally. In the mixture, some very hard crystals different from the nickel oxide added were generated. As a result of X-ray analysis, it was found that NiSO ₄ .H ₂ O was generated.

<Example 1-2>
A 6 mm diameter ceramic ball crushing media was added to a glass container having a capacity of 300 mL to a height of about 15 mm. A stirring blade made of fluororesin was inserted therein, and the inside of the glass container was heated with a water bath from the outside so that the temperature of the inside became 90 ° C. The rotation speed of the stirring blade was 60 rpm. Further, 5 g of nickel oxide (green NiO reagent) powder and 100 mL of concentrated sulfuric acid (98% pure reagent as H ₂ SO ₄ ) were added to the glass container. After about 30 minutes, the temperature inside the glass container reached 90 ° C, and thereafter, the temperature was maintained at 90 ° C. In this state, stirring was continued for up to 6 hours. Samples of the mixture containing the powder and concentrated sulfuric acid were taken from the inside of the glass container at the time when 3 hours and 6 hours had passed during the process. The sample was collected in a centrifuge tube, and separated into a solid phase and a liquid phase by centrifugation. The liquid phase had a nickel concentration of 1154 mg / L, but the solid phase had, as a result of X-ray analysis, 97.3% of the nickel oxide added to the glass container converted to nickel sulfate. From this result, it was confirmed that the conversion reaction to nickel sulfate can be directly performed with concentrated sulfuric acid while the nickel oxide is being worn away.

<Example 1-3>
Nickel sulfate hexahydrate reagent (NiSO ₄ · _6H 2 O blue) was 10g collected and placed in a glass container having a capacity of 300 mL. A mixed solution of 6.3 g of reagent sulfuric acid and 83.7 g of pure water was added thereto to prepare a solution in which nickel sulfate hexahydrate was dissolved in an aqueous sulfuric acid solution. After dispensing 10 mL of this solution into each centrifuge tube, 15 mL of each organic solvent was added to each centrifuge tube. There are four types of organic solvents: isopropanol, acetone, tributyl phosphate (TBP), and toluene. Further, a test in which the centrifuge tube was rapidly cooled from the outside without adding an organic solvent to the solution was also performed. Table 1 shows the results.

  As a result, when isopropanol or acetone miscible with water was added to the solution, crystals of nickel sulfate hydrate were instantaneously formed upon the addition of the organic solvent. When isopropanol was added, sherbet-like crystals were obtained as a whole, and when acetone was added, needle-like fine crystals were obtained. Therefore, it was found that water, miscible with methanol, ethanol, propanol, isopropanol, butyl alcohol, ethylene glycol, acetone and the like can be applied to crystallization.

  When isopropanol was added, almost all of the dissolved nickel salt was instantaneously precipitated as a hydrate. For this reason, the crystallization method in which an organic solvent is added requires no evaporation energy and requires a batch operation (batch operation) as compared with a method in which an aqueous solution is concentrated beyond its saturation solubility as in continuous evaporation crystallization. Crystallization and solid-liquid separation became possible.

<Example 2-1>
A raw material slurry composed of nickel matte (Ni: 78%, Fe: 1%, Co: 1%, S: 20%) and 95% sulfuric acid was added to a glass container having a capacity of 300 mL together with ceramic balls having a diameter of 6 mm. While stirring the raw material slurry and the ceramic balls in an oil bath, the bath was heated. The rotation speed of the stirring was 60 rpm. After reaching the predetermined temperature, a small amount of sample was taken from the slurry being stirred at predetermined time intervals. The liquid phase was removed from the sample slurry by centrifugation. The solid phase was washed with water, and the amount of the nickel sulfate compound was determined as NiSO ₄ .H ₂ O by quantifying Ni ions contained in the washing water. Further, the ratio of S, Al, Ni, and Fe was quantified from the solid residue after washing by X-ray fluorescence elemental analysis (XRF) to determine the amount of nickel matte and the amount of aluminum oxide derived from ceramic balls. I asked.

  The total amount of Ni in the solid phase was determined from the amount of the nickel sulfate compound contained in the washing water and the amount of the nickel matte contained in the residue. From the ratio of this to the amount of the nickel sulfate compound contained in the washing water, the nickel sulfate compound The conversion rate was determined. Table 2 shows the results obtained when the predetermined temperature at which the conversion reaction was carried out was set at 90 ° C., 120 ° C., and 150 ° C., respectively.

  As a result, it was shown that the higher the temperature, the higher the efficiency was, and the higher the conversion rate to the nickel sulfate compound was. Since the amount of Al in the sample increased with the passage of time, it was found that the ceramic balls were worn and mixed into the slurry. Further, from the results in Table 2, when the velocity k was determined by Arrhenius plot, the following empirical formula was obtained.

y = −6322.727x + 11.693, R2 = 0.998
Here, it is assumed that x = 1 / T (k) and y = ln k.

  From the Arrhenius plot, conversion rates at 180 ° C. and 200 ° C. were calculated. At 180 ° C., the conversion rate was 91% in 15 minutes, and at 200 ° C., 98% in 15 minutes.

<Example 2-2>
90 mL of an aqueous solution containing FeSO ₄ at a concentration of 102 g / L and H ₂ SO ₄ at a concentration of 33 g / L was heated to 230 ° C. in an autoclave over 60 minutes, and oxygen gas having a partial pressure of 1.8 MPa was blown into the aqueous solution. It is. The pressure rose with the heat generation, and the pressure was confirmed when the temperature returned to equilibrium. Thus, while the amount of the oxygen gas blown was 63 mmol, the amount consumed for the oxidation of Fe (II) was 15 mmol, and the reduction amount of the oxygen gas in the gas phase calculated from the decrease in the partial pressure was 26 mmol. It was confirmed that oxygen dissolved in the high-temperature sulfuric acid aqueous solution and reacted. While maintaining the temperature at 230 ° C., a second injection was performed at a point 60 minutes after the first oxygen gas injection, and no pressure drop was observed as in the first injection. It was confirmed that the reaction was completely completed only by the first blowing.

From this test, it was confirmed that the oxidation reaction can be performed by dissolving oxygen in an aqueous solution under sulfuric acid. Here, an example in which FeSO ₄ is oxidized in dilute sulfuric acid is given as a reference. However, in the reaction of oxidizing NiS in concentrated sulfuric acid as in Example 2-1 above, oxygen may be supplied under pressure. , As well as possible.

<Example 2-3>
A prescribed amount of powder of commercially available nickel sulfate reagent (99% purity) is weighed, put into 100 g of pure water, stirred for 10 minutes after reaching a prescribed temperature, sampled from the solution, and dissolved nickel sulfate. The amount was quantitatively analyzed. As a result, the following results were obtained as the solubility of nickel sulfate (value with respect to a 100 g solution).

0 ° C .: 22 g, 15 ° C .: 26.5 g, 35 ° C .: 32 g, 50 ° C .: 35 g, 60 ° C .: 37 g

  Further, in the same manner as in Example 2-1, the solid content generated by performing the conversion step at 150 ° C was subjected to solid-liquid separation with a pressure filter to obtain sludge having a temperature of 120 ° C. When 50 g of this sludge was collected and 100 g of pure water at 15 ° C. was added so that the sludge concentration became 30 wt%, a solution having a temperature of 22 ° C. was obtained. When Fe ions in the solution obtained by continuing stirring for 30 minutes were analyzed, it was several tens ppm. On the other hand, nickel sulfate had a value close to the saturation solubility at 22 ° C., that is, 28 g of nickel sulfate was dissolved in 100 g of the solution. From this result, it was found that nickel sulfate having high solubility has an effect of removing impurities by dissolving in cold water.

  INDUSTRIAL APPLICABILITY The present invention can be used for producing a high-purity nickel sulfate compound useful as a raw material for various nickel compounds or metallic nickel used in electric parts such as secondary batteries, chemical products, and the like.

S1: conversion step, S2: solid-liquid separation step, S3: dissolution separation step, S4: crystallization step, 10: nickel-containing raw material, 11: mixture, 21: solid phase, 22: liquid phase, 31: solution, 32 ... Impurities, 41: nickel sulfate compound, 42: solution, 43: distillation, 44: water, 45: organic solvent.

Claims (10)

A conversion step of treating the nickel-containing raw material with concentrated sulfuric acid together with the abrasive and converting at least a part of the nickel-containing raw material to a nickel sulfate compound;
A solid-liquid separation step of separating the mixture obtained in the conversion step into a solid phase and a liquid phase,
Water is added to the solid phase obtained in the solid-liquid separation step, a dissolution separation step of dissolving the nickel sulfate compound contained in the solid phase in the water and separating impurities,
A method for producing a nickel sulfate compound, comprising:   The said nickel-containing raw material in the said conversion process contains at least 1 sort (s) selected from the group consisting of nickel oxide, nickel hydroxide, nickel sulfide, nickel chloride, metallic nickel, ferronickel, and nickel ore. 2. The method for producing a nickel sulfate compound according to 1.   The method for producing a nickel sulfate compound according to claim 1, wherein in the conversion step, the nickel-containing raw material contains nickel sulfide, an oxidizing agent is added, and the oxidation-reduction potential is 300 mV or more.   The method for producing a nickel sulfate compound according to any one of claims 1 to 3, wherein concentrated sulfuric acid contained in the liquid phase obtained in the solid-liquid separation step is reused in the conversion step. .   The method for producing a nickel sulfate compound according to any one of claims 1 to 4, wherein the temperature of water added to the solid phase in the dissolution separation step is 15 to 60 ° C.   The nickel sulfate compound according to any one of claims 1 to 5, wherein in the dissolution separation step, impurities are separated by setting a pH of a solution obtained by dissolving the nickel sulfate compound in the water to 4 to 5. Manufacturing method.   The method for producing a nickel sulfate compound according to any one of claims 1 to 6, further comprising a purification step of removing a cobalt compound contained in the solution obtained in the dissolution separation step.   The method for producing a nickel sulfate compound according to any one of claims 1 to 7, further comprising a crystallization step of adding an organic solvent to the solution obtained in the dissolution separation step to precipitate a nickel sulfate compound. .   The nickel sulfate according to claim 8, wherein the organic solvent in the crystallization step is at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol, butyl alcohol, ethylene glycol, and acetone. A method for producing a compound.   The method for producing a nickel sulfate compound according to claim 8 or 9, wherein the nickel sulfate compound obtained in the crystallization step is nickel sulfate hexahydrate.

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