Method for leaching nickel from oxide ore, method for producing nickel sulfate, and nickel leaching agent

Abstract

A method is provided that enables selective leaching of Ni from oxide ores containing Ni and Si. [Solution] The disclosed method for leaching nickel from oxide ore comprises the steps of preparing a liquid leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds), and contacting an oxide ore containing nickel and silicon with the leaching agent.

Description

[Technical Field]

[0001] The present disclosure relates to a method for leaching nickel (Ni) from an oxide ore containing nickel (Ni) and silicon (Si) into a leaching agent. The present disclosure also relates to a method for producing nickel sulfate using the method. The present disclosure further relates to a leaching agent for leaching nickel from an oxide ore containing nickel (Ni) and silicon (Si). [Background technology]

[0002] In recent years, the demand for lithium-ion secondary batteries has been increasing. The positive electrode active materials used in lithium-ion secondary batteries are often materials containing Ni, such as lithium-nickel-cobalt-manganese composite oxides and lithium-nickel-cobalt-aluminum composite oxides. Meanwhile, Ni is also used in stainless steel, special steel, and other materials, and demand for these materials is also increasing. As a result, the demand for Ni is rapidly increasing, and methods for obtaining Ni sources (especially nickel sulfate) are becoming increasingly important.

[0003] One known method for obtaining a Ni source is a leaching method in which Ni is leached from a Ni-containing oxide ore using an acid-containing leaching agent. For example, Patent Document 1 proposes using a hydrophobic deep eutectic solvent containing an acidic hydrogen bond donor and a hydrogen bond acceptor, and an organic phase containing an organic acid, as a leaching agent. Nickel oxide ore is then brought into contact with the organic phase, and Ni is leached into the organic phase. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-119164 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the leaching method, metal components other than Ni can also be leached. In particular, there is a problem that Si is leached along with Ni in nickel oxide ores that contain a lot of Si. Therefore, there is a need to develop a method that can selectively leach Ni from oxide ores that contain Ni and Si.

[0006] Therefore, an object of the present disclosure is to provide a method capable of selectively leaching Ni from oxide ores containing Ni and Si. [Means for solving the problem]

[0007] The disclosed method for leaching nickel from oxide ore comprises the steps of preparing a liquid leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds), and contacting an oxide ore containing nickel and silicon with the leaching agent.

[0008] According to this configuration, Ni can be selectively leached from oxide ore containing Ni and Si.

[0009] In another aspect, the nickel leaching agent of the present disclosure is a liquid nickel leaching agent that contains a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound.

[0010] According to this configuration, Ni can be selectively leached from oxide ore containing Ni and Si.

[0011] From another aspect, a method for producing nickel sulfate according to the present disclosure includes the steps of obtaining a nickel leachate by the method for leaching nickel from an oxide ore described above, and performing back extraction on the nickel leachate with sulfuric acid to obtain an aqueous phase containing nickel sulfate.

[0012] According to this configuration, nickel can be selectively leached from oxide ore containing nickel and silicon, and nickel sulfate can ultimately be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a flow chart showing the steps of the disclosed method for leaching nickel from oxide ore. [Figure 2] 1 is a flowchart showing the steps of a method for producing nickel sulfate according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that matters not mentioned in this specification but necessary for carrying out the present invention can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. It should be noted that a numerical range expressed as "A to B" in this specification includes A and B.

[0015] As shown in FIG. 1 , the method for leaching nickel from oxide ore of the present disclosure includes a step S101 of preparing a liquid leaching agent containing a hydrogen bond acceptor and a hydrophobic organic compound (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds) in contact with hydrochloric acid (hereinafter also referred to as the "leaching agent preparation step"), and a step S102 of contacting an oxide ore containing nickel and silicon with the leaching agent (hereinafter also referred to as the "leaching agent contact step"). As shown in FIG. 2 , the method for producing nickel sulfate of the present disclosure utilizes the method for leaching nickel from oxide ore of the present disclosure. The method for producing nickel sulfate of the present disclosure includes a step S201 of obtaining a nickel leachate by the method for leaching nickel from oxide ore of the present disclosure (hereinafter also referred to as the "nickel leaching step"), and a step S202 of stripping the nickel leachate with sulfuric acid to obtain an aqueous phase containing nickel sulfate (hereinafter also referred to as the "stripping step"). Each step is described in detail below.

[0016] <Leaching agent preparation process S101> The leaching agent prepared in the leaching agent preparation step S101 is liquid. The leaching agent may be liquid at the temperature at which leaching is performed (i.e., the leaching temperature). The leaching agent is typically liquid at 25°C. The leaching agent contains a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound. However, the hydrophobic organic compound used in the leaching agent is a hydrophobic organic compound other than an unsubstituted alicyclic hydrocarbon compound and an unsubstituted aromatic hydrocarbon compound. The leaching agent preferably further contains a hydrogen bond donor.

[0017] The hydrogen bond acceptor used in the leaching agent is a component that forms a hydrophobic deep eutectic solvent together with the hydrogen bond donor. As used herein, "deep eutectic solvent" refers to a mixture containing a hydrogen bond donor and a hydrogen bond acceptor, at least one of which is solid at 25°C, and which is a liquid at 25°C. Specifically, despite containing a substance that is solid at 25°C, a deep eutectic solvent exhibits a eutectic melting point depression by mixing the hydrogen bond donor and hydrogen bond acceptor in a predetermined ratio, resulting in a liquid at 25°C. Strictly speaking, deep eutectic solvents differ from ionic liquids in that they contain hydrogen bond donors and are not composed solely of ions. Deep eutectic solvents have the advantage of being easier to construct from substances with lower environmental impact than ionic liquids.

[0018] As used herein, the term "hydrophobic deep eutectic solvent" refers to a deep eutectic solvent that undergoes phase separation into an aqueous phase and a hydrophobic deep eutectic solvent phase when brought into contact with water at 25° C. The solubility of the hydrophobic deep eutectic solvent in water at 25° C. is preferably 1 g / 100 mL or less, more preferably 0.1 g / 100 mL or less, and even more preferably 0.01 g / 100 mL or less.

[0019] Examples of hydrogen acceptors used in the leaching agent include halogen salts.

[0020] Examples of halogen salts include quaternary ammonium halides, quaternary phosphonium halides, tertiary ammonium halides, and primary ammonium halides.

[0021] Examples of quaternary ammonium halides include choline chloride, tetrabutylammonium chloride, tetramethylammonium chloride, methyltrioctylammonium chloride, tetraoctylammonium chloride, acetylcholine chloride, chlorocholine chloride, tetraethylammonium bromide, N-(2-hydroxyethyl)-N,N-dimethylbenzenemethanaminium chloride, fluorocholine bromide, and tetrabutylammonium bromide.

[0022] Examples of quaternary phosphonium halides include methyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, and the like.

[0023] An example of a tertiary ammonium halide is 2-(diethylamino)ethanol hydrochloride.

[0024] An example of a primary ammonium halide is ethylamine hydrochloride.

[0025] As the hydrogen bond acceptor, these can be used alone or in combination of two or more.

[0026] As the hydrogen bond acceptor, a quaternary ammonium halide is preferred, and tetrabutylammonium chloride is more preferred.

[0027] The hydrogen bond acceptor used in the leaching agent is contacted with hydrochloric acid. By contacting the hydrogen bond acceptor with hydrochloric acid, the leaching agent has high nickel leaching ability. This is thought to be because the hydrogen bond acceptor captures protons, chloride ions, or both, or hydrochloric acid, resulting in the leaching agent containing acid.

[0028] The hydrogen bond donor used in the leaching agent is an optional component. When the oxide ore further contains Mg, adding a hydrogen bond donor to the leaching agent allows Ni to be selectively leached from Ni, Si, and Mg. That is, Ni can be selectively leached into the leaching agent from an oxide ore containing Ni, Si, and Mg, while Si and Mg can remain in the oxide ore.

[0029] The hydrogen bond donor is preferably an acidic hydrogen bond donor. Acidic hydrogen bond donors have a strong ability to release protons, which is thought to contribute to improving the nickel leaching rate. In this specification, "the hydrogen bond donor is acidic" means that the acid dissociation constant (pKa) of the hydrogen bond donor is less than 7. The acid dissociation constant (pKa) of the hydrogen bond donor is preferably 6 or less, more preferably 5 or less. The acid dissociation constant (pKa) of the hydrogen bond donor may be 0 or more, 1 or more, or 2 or more. In this specification, the acid dissociation constant (pKa) is a value in water at 25°C, and can be determined by known methods (e.g., neutralization titration method, etc.).

[0030] Examples of acidic hydrogen bond donors include carboxy group-containing compounds. Examples of carboxy group-containing compounds include fatty acids such as formic acid, acetic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, and triacontanoic acid; polycarboxylic acid compounds such as oxalic acid, malonic acid, succinic acid, adipic acid, itaconic acid, suberic acid, and 1,2,3-propanetricarboxylic acid; aromatic carboxylic acid compounds such as benzoic acid; aromatic compounds having a carboxy group-containing substituent such as phenylacetic acid, 3-phenylpropionic acid, and trans-cinnamic acid; levulinic acid; and hydroxyl group-containing compounds such as lactic acid, tartaric acid, ascorbic acid, citric acid, 4-hydroxybenzoic acid, p-coumaric acid, caffeic acid, and gallic acid.

[0031] As the hydrogen bond donor, these can be used alone or in combination of two or more.

[0032] As the hydrogen bond donor, a fatty acid is preferable, a fatty acid having 8 to 12 carbon atoms is more preferable, and decanoic acid is even more preferable.

[0033] The hydrogen bond donor and hydrogen bond acceptor typically form a deep eutectic solvent at a molar ratio of 2:1. Furthermore, the hydrogen bond acceptor alone, when contacted with hydrochloric acid, has the ability to extract nickel. Therefore, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor (hydrogen bond donor:hydrogen bond acceptor) is preferably 3:1 to 1:3, more preferably 2.5:1 to 1:1, and even more preferably 2.1:1 to 2:1.1.

[0034] The hydrophobic organic compound used in the leaching agent may be liquid or solid at, for example, 25°C. The hydrogen bond donor and hydrogen bond acceptor form a liquid deep eutectic solvent, so even if the hydrophobic organic compound is solid, it can be dissolved in the deep eutectic solvent to obtain a liquid leaching agent. When the leaching agent does not contain a hydrogen bond donor, the hydrophobic compound is preferably liquid.

[0035] In this specification, the term "hydrophobic organic compound" refers to an organic compound having a solubility in water of 1.0 g / L or less at 20° C. The solubility of the hydrophobic organic compound in water at 20° C. is preferably 0.3 g / L or less, and more preferably 0.1 g / L or less.

[0036] The hydrophobic organic compound may be a saturated organic compound or an unsaturated organic compound. The hydrophobic organic compound may be a linear or branched one. Examples of the hydrophobic organic compound include hydrocarbon compounds (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds), ether compounds, ester compounds, etc.

[0037] Examples of the hydrocarbon compound that can be used include saturated aliphatic hydrocarbon compounds, unsaturated aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds having a substituent, and aromatic hydrocarbon compounds having a substituent.

[0038] Examples of saturated aliphatic hydrocarbon compounds include n-paraffin hydrocarbons such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane, n-hexadecane, n-octadecane, and n-eicosane; and isoparaffin hydrocarbons such as isoheptane, isooctane, isononane, isodecane, isoundecane, isododecane, isotridecane, isotetradecane, isopentadecane, isohexadecane, isooctadecane, and isoeicosane. The saturated aliphatic hydrocarbon compound preferably has 6 to 20 carbon atoms, and more preferably has 8 to 18 carbon atoms.

[0039] Examples of unsaturated aliphatic hydrocarbon compounds include hexene, heptene, octene, nonene, decene, undecene, dodecene, decadiene, undecadiene, dodecadiene, etc. The unsaturated aliphatic hydrocarbon compound preferably has 6 to 20 carbon atoms, more preferably 8 to 18 carbon atoms.

[0040] The number of substituents that the alicyclic hydrocarbon compound has is not particularly limited, and is preferably 1 to 4. The substituent is preferably a hydrocarbon group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. Examples of alicyclic hydrocarbon compounds having a substituent include methylcyclohexane and 4-methyl-1-isopropylcyclohexane.

[0041] The number of substituents that the aromatic hydrocarbon compound has is not particularly limited, and is preferably 1 to 4. As the substituent, a hydrocarbon group having 1 to 4 carbon atoms is preferred, and an alkyl group having 1 to 4 carbon atoms is more preferred. Examples of aromatic hydrocarbon compounds having a substituent include toluene, xylene (e.g., o-xylene, m-xylene, p-xylene), ethyltoluene (e.g., 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene), propylbenzene (e.g., n-propylbenzene, cumene, etc.), butylbenzene (e.g., n-butylbenzene, sec-butylbenzene, isobutylbenzene, tert-butylbenzene), propyltoluene (e.g., 4-propyltoluene, etc.), butyltoluene (e.g., 4-sec-butyltoluene, 4-tert-butyltoluene, 2-tert-butyltoluene, etc.), amylbenzene, diethylbenzene, ethylpropylbenzene, trimethylbenzene (e.g., 1,2,3 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene), tetramethylbenzene (e.g., 1,2,3,4-tetramethylbenzene, 1,2,4,5-tetramethylbenzene), ethylxylene (e.g., 2-ethyl-p-xylene, 4-ethyl-o-xylene, 5-ethyl-m-xylene, etc.), dimethylpropylbenzene (e.g., 2,5-dimethylcumene, 5-isopropyl-m-xylene, etc.), butyldimethylbenzene, diethylmethylbenzene, triethylbenzene, diethylpropylbenzene, allylmethylbenzene (e.g., 1-allyl-2-methylbenzene, etc.), methylnaphthalene (e.g., 1-methylnaphthalene, 2-methylnaphthalene, etc.).

[0042] From the viewpoint of hydrophobicity, the ether compound is preferably an ether having an alkyl group having 4 or more carbon atoms (preferably 6 to 12 carbon atoms). Examples of the ether compound include dibutyl ether, dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, etc. As the ether compound, a dialkyl ether having 8 to 24 carbon atoms is preferred, and a dialkyl ether having 12 to 20 carbon atoms is more preferred.

[0043] Examples of the ester compound include saturated fatty acid esters such as isopropyl myristate, isopropyl palmitate, octyl palmitate, butyl stearate, etc. As the ester compound, saturated fatty acid esters having 15 to 25 carbon atoms are preferred.

[0044] These hydrophobic organic compounds can be used alone or in combination of two or more. Mixtures containing two or more of the above compounds are also commercially available. Examples include Swazol 1000 (containing 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, cumene, xylene, etc.) manufactured by Maruzen Petrochemical Co., Ltd., Swazol 1500 (containing 1,2,4-trimethylbenzene, naphthalene, etc.), and Swazol 1800 (containing methylnaphthalene, 4-tert-butyltoluene, etc.) manufactured by ENEOS Corporation, Techlean (containing naphthene, etc.) manufactured by Tobu Chemical Co., Ltd., and MC531 (containing isoparaffin, etc.) manufactured by Tobu Chemical Co., Ltd.

[0045] The hydrophobic organic compound preferably contains at least one hydrocarbon compound selected from the group consisting of saturated aliphatic hydrocarbon compounds having 6 to 20 carbon atoms, unsaturated aliphatic hydrocarbon compounds having 6 to 20 carbon atoms, alicyclic hydrocarbon compounds having a substituent, aromatic hydrocarbon compounds having a substituent, dialkyl ethers having 8 to 24 carbon atoms, and saturated fatty acid esters having 15 to 25 carbon atoms. When the oxide ore further contains Mg, it is possible to selectively leach Ni from among Ni, Si, and Mg, so it is more preferable that the hydrophobic organic compound contains an aromatic hydrocarbon compound having at least one alkyl group having 1 to 4 carbon atoms.

[0046] The amount of hydrophobic organic compound in the leaching agent is not particularly limited. If the amount of hydrophobic organic compound is too small, the effect of selectively leaching Ni will be reduced. If the amount of hydrophobic organic compound is too large, the leaching rate may decrease. Furthermore, a relatively large amount of hydrophobic organic compound improves the Ni leaching rate. Therefore, the volume fraction of the hydrophobic organic compound in the leaching agent is, for example, 5% to 95% by volume, preferably 40% to 95% by volume, more preferably 60% to 90% by volume, even more preferably 70% to 90% by volume, and particularly preferably 80% to 90% by volume.

[0047] Ni can be selectively leached from oxide ores containing Ni and Si by using a hydrophobic organic compound as a leaching agent in addition to a hydrogen bond donor and a hydrogen bond acceptor in contact with hydrochloric acid.

[0048] This phenomenon is thought to occur through the interaction of the hydrophobic organic compound with at least one of the hydrogen bond donor, the hydrogen bond acceptor contacted with hydrochloric acid, and Si (e.g., the hydrophobic organic solvent interacts with Si to suppress leaching; the hydrophobic organic solvent interacts with at least one of the hydrogen bond donor and hydrogen bond acceptor to inhibit the leaching of Si).

[0049] The water content in the infusion agent is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. The water content of the infusion agent can be determined by the Karl Fischer method.

[0050] The leaching agent may consist solely of a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound.The leaching agent may consist solely of a hydrogen bond donor, a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound.

[0051] Alternatively, the leaching agent may contain at least one of an unsubstituted alicyclic hydrocarbon compound and an unsubstituted aromatic hydrocarbon compound, as long as the effects of the present disclosure are not significantly impaired. When the leaching agent contains at least one of an unsubstituted alicyclic hydrocarbon compound and an unsubstituted aromatic hydrocarbon compound, the total mass of these hydrocarbon compounds is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 15% by mass or less, relative to the mass of the hydrophobic organic compound.

[0052] Alternatively, the leaching agent may contain components other than those described above within a range that does not significantly impair the effects of the present disclosure (for example, less than 10% by mass, less than 5% by mass, or less than 1% by mass of the leaching agent). Examples of other components include reducing agents, oxidizing agents, and various additives.

[0053] The leaching agent can be prepared, for example, as follows: If no hydrogen bond donor is used in the leaching agent, a hydrogen bond acceptor is dissolved in a hydrophobic organic compound. The resulting solution of the hydrogen bond acceptor is contacted with hydrochloric acid, thereby contacting the hydrogen bond acceptor with the acid. The organic phase is then recovered as the leaching agent.

[0054] When a hydrogen bond donor is used as the leaching agent, a deep eutectic solvent is first prepared by mixing a hydrogen bond donor and a hydrogen bond acceptor according to known methods. The hydrogen bond donor and the hydrogen bond acceptor are dry-blended and then stirred or kneaded above the eutectic point of the deep eutectic solvent to prepare the deep eutectic solvent. Alternatively, the hydrogen bond donor and the hydrogen bond acceptor are dissolved in a solvent, and the solvent is then removed to prepare the deep eutectic solvent.

[0055] Next, the deep eutectic solvent and the hydrophobic organic compound are mixed to dissolve or mix the hydrophobic organic compound in the deep eutectic solvent. The resulting hydrophobic mixture is contacted with hydrochloric acid, thereby contacting the acid with the hydrogen bond acceptor. The organic phase is then recovered. Alternatively, the deep eutectic solvent is contacted with hydrochloric acid, thereby contacting the acid with the hydrogen bond acceptor. The organic phase (i.e., the deep eutectic solvent) is then recovered and mixed with the hydrophobic organic compound. The contacting procedure with hydrochloric acid is specifically described below.

[0056] The concentration of hydrochloric acid is not particularly limited. From the viewpoint of efficiency, a higher concentration of hydrochloric acid is preferable. The concentration of hydrochloric acid is, for example, 0.1 mol / L to 12 mol / L, preferably 3 mol / L to 12 mol / L, more preferably 5 mol / L to 11 mol / L, and even more preferably 8 mol / L to 11 mol / L.

[0057] When a solution of a hydrogen bond acceptor, a hydrophobic mixture, or a deep eutectic solvent is contacted with hydrochloric acid, the hydrochloric acid undergoes phase separation from the solution of the hydrogen bond acceptor, the hydrophobic mixture, or the deep eutectic solvent. Shaking, stirring, or the like is preferably performed during this contact, as this increases efficiency, and shaking is more preferred. Known tools and devices can be used for shaking, stirring, or the like. Therefore, for example, the contact with hydrochloric acid can be effectively achieved by adding the solution of a hydrogen bond acceptor, a hydrophobic mixture, or a deep eutectic solvent, and hydrochloric acid to an acid-resistant container and shaking using a known shaker or the like.

[0058] The contact time between the hydrogen bond acceptor solution, hydrophobic mixture, or deep eutectic solvent and hydrochloric acid is not particularly limited as long as it can impart nickel leaching ability to the leaching agent, and may be determined appropriately depending on the contact conditions. The contact time is, for example, 5 minutes to 48 hours, and preferably 30 minutes to 24 hours.

[0059] Here, the hydrogen bond acceptor solution or the hydrophobic mixture, which is a mixture of a deep eutectic solvent and a hydrophobic organic compound, may be a used leaching agent. The used leaching agent is a leaching agent that has been used at least once to leach nickel from an oxide ore, such as the organic phase recovered after performing the stripping step S202 described below. By contacting the used leaching agent with hydrochloric acid, the leaching agent can be replenished with protons and halogens, restoring the nickel leaching ability of the leaching agent. This prevents the leaching agent from becoming waste. Therefore, the method for leaching nickel from an oxide ore disclosed herein has the advantage that the leaching agent can be reused.

[0060] In this manner, the infusion agent can be prepared.

[0061] <Leaching agent contact step S102> In the leaching agent contact step S102, the oxide ore containing Ni and Si is brought into contact with the leaching agent prepared in the leaching agent preparation step S101. This allows Ni to be preferentially transferred from the oxide ore to the organic phase of the leaching agent. Therefore, solid-liquid extraction is performed using a special organic phase, allowing nickel (Ni) to be preferentially transferred from the oxide ore containing Ni and Si to the organic phase. Therefore, from another aspect, the leaching agent of the present disclosure is the above-mentioned leaching agent.

[0062] The oxide ore used in the leaching agent contact step S102 is not particularly limited as long as it contains Ni and Si. Suitable examples of the oxide ore include nickel oxide ores such as limonite and saprolite. Saprolite also contains a relatively large amount of Mg.

[0063] The oxide ore may be one that has been subjected to pulverization, classification, etc. By subjecting the oxide ore to pulverization, classification, etc., the particle size of the oxide ore can be adjusted to a predetermined range (for example, a median diameter D50 determined by a laser diffraction scattering method of 0.01 to 1000 μm, preferably 1 to 100 μm), thereby improving the leaching efficiency. The pulverization, classification, etc. can be performed according to known methods.

[0064] The amount of leaching agent used relative to the oxide ore is not particularly limited, and is, for example, 10 to 100,000 parts by mass, and preferably 100 to 10,000 parts by mass, relative to 100 parts by mass of the oxide ore.

[0065] The contact of the oxide ore with the leaching agent can be carried out by a known method. For example, the oxide ore can be placed in a vessel, and then the leaching agent can be added thereto. For example, the contact can be carried out by placing an acid leaching agent in a vessel, and then the oxide ore can be added thereto. Alternatively, the leaching agent can be prepared in the vessel containing the oxide ore, and the preparation of the leaching agent and the contact of the oxide ore with the leaching agent can be carried out simultaneously.

[0066] When the oxide ore and the leaching agent are brought into contact with each other, the mixture of the oxide ore and the leaching agent may be stirred. Stirring can be performed by a known method (for example, a method using a stirring device equipped with a stirring bar, stirring blades, etc.). When the oxide ore and the leaching agent are brought into contact with each other, ultrasonic waves may be irradiated.

[0067] The contact between the oxide ore and the leaching agent can be carried out at room temperature (specifically, 25°C). From the viewpoint of increasing the leaching rate, heating may be carried out when the oxide ore and the leaching agent are brought into contact with each other. Heating can be carried out using known means, such as an oil bath, a mantle heater, a strip heater (such as a ribbon heater), or a surface heater (e.g., a film heater or a silicone rubber heater). The heating temperature is not particularly limited, but is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. On the other hand, from the viewpoint of energy efficiency, the heating temperature is preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower.

[0068] When the oxidized ore is brought into contact with the leaching agent, pressure may be applied. Pressure application can be carried out according to a known method.

[0069] The time for which the oxide ore is brought into contact with the leaching agent is not particularly limited and can be determined appropriately depending on the components of the leaching agent used, the particle size of the oxide ore, the temperature, etc. The time for which the oxide ore is brought into contact with the leaching agent is, for example, 1 minute to 100 hours, and preferably 1 hour to 50 hours.

[0070] After contact, the organic phase containing the leached nickel (i.e., nickel leachate) can be recovered by a known solid-liquid separation method (e.g., filtration, etc.).

[0071] In this manner, the method for leaching nickel from oxide ore of the present disclosure can be carried out. According to the method for leaching nickel from oxide ore of the present disclosure, Ni can be selectively leached from oxide ore containing Ni and Si. Therefore, Ni is selectively leached into the nickel leach solution, and the nickel leach solution contains little or no Si. Nickel can be recovered from the nickel leach solution according to known methods. In the method for producing nickel sulfate of the present disclosure, nickel is recovered as nickel sulfate in the stripping step S202.

[0072] <Reverse extraction process S202> In the back-extraction step S202, back-extraction is performed using sulfuric acid as the extraction solvent (i.e., aqueous phase). That is, nickel that has migrated from the oxide ore to the leaching agent (i.e., organic phase) is transferred to the aqueous phase. The sulfuric acid converts the anions of nickel sulfate (SO4 2- ) is also a source of

[0073] The sulfuric acid concentration is not particularly limited as long as nickel can be transferred to the aqueous phase, and is, for example, 1 mol / L (1M) or higher. Here, oxide ores containing Ni and Si may contain iron oxide (Fe2O3). Therefore, Fe may be contaminated in the nickel leachate. By using high-concentration sulfuric acid in the stripping step S202, the transfer of Fe to the aqueous phase can be suppressed. In other words, nickel sulfate with little iron contamination can be obtained. From this perspective, the sulfuric acid concentration is preferably 1.5 mol / L or higher, more preferably 2 mol / L or higher, even more preferably 2.5 mol / L or higher, and most preferably 3 mol / L or higher. The upper limit of the sulfuric acid concentration is not particularly limited and is determined by technical limitations. The sulfuric acid concentration may be 15 mol / L or lower, 10 mol / L or lower, 7.5 mol / L or lower, or 5 mol / L or lower.

[0074] The extraction solvent (i.e., the aqueous phase) may contain components other than sulfuric acid within a range that does not significantly impair the effects of the present invention (e.g., less than 10% by mass, less than 5% by mass, or less than 1% by mass).

[0075] The amount of sulfuric acid used relative to the nickel leaching solution is not particularly limited, and is, for example, 1:0.05-20, preferably 1:0.2-5, in terms of leaching solution:sulfuric acid (volume ratio).

[0076] Stripping can be carried out according to a known method. After stripping, the aqueous phase can be recovered to obtain a solution containing nickel sulfate. Nickel sulfate can be obtained by crystallizing and recovering nickel sulfate from the solution containing nickel sulfate according to a known method.

[0077] Depending on the intended use of nickel sulfate, nickel sulfate may be recovered in the form of an aqueous solution without precipitating nickel sulfate from the solution containing nickel sulfate. In this case, the solution containing nickel sulfate may be used for the desired purpose as is, or may be used after being subjected to a treatment such as neutralization.

[0078] As described above, nickel sulfate can be produced by selectively leaching Ni from an oxide ore containing Ni and Si. In the above-described production method, nickel sulfate can be produced simply by performing the nickel leaching step S201 and the stripping step S202. Therefore, the above-described production method has a small number of steps and is easy to operate. Furthermore, the organic phase recovered after the stripping step S202 can be reused in the method for leaching nickel from an oxide ore and the method for producing nickel sulfate disclosed herein by contacting the organic phase with hydrochloric acid to perform the leaching agent preparation step S101, thereby reducing the amount of waste generated. Therefore, the method for producing nickel sulfate produces little waste and is easy to implement.

[0079] Furthermore, nickel sulfate is mainly used as a nickel source for the positive electrode active material of lithium ion secondary batteries, and therefore the above-described method for producing nickel sulfate is of great industrial value as a new method for securing nickel sulfate as a nickel source for the positive electrode active material of lithium ion secondary batteries. [Example]

[0080] Examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples.

[0081] Comparative Example 1 A deep eutectic solvent was prepared by mixing decanoic acid (decA) as a hydrogen bond donor and trioctylmethylammonium chloride (TOMAC) as a hydrogen bond acceptor in a 2:1 volume ratio. 10 mol / L hydrochloric acid was added to this deep eutectic solvent in a 1:1 volume ratio and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain the leaching agent. 200 mg of nickel oxide ore (i.e., saprolite) was added per 20 mL of this leaching agent, and leaching was carried out at 60 °C for 24 hours while stirring at 400 rpm. The leachate was then collected and analyzed to determine the leaching rates of Ni and Si. The results are shown in Table 1.

[0082] Comparative Example 2 10 mol / L hydrochloric acid was added to Swasol 1800 (aromatic high-boiling point solvent) manufactured by Maruzen Petrochemical Co., Ltd. in a volume ratio of 1:1, and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain a leaching agent. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0083] Example 1 TOMAC and toluene were mixed in a 1:1 volume ratio. 10 mol / L hydrochloric acid was added to the resulting mixture in a 1:1 volume ratio, and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain a leaching agent. Leaching and analysis were performed using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0084] Example 2 TOMAC and Swazol 1800 were mixed in a 1:1 volume ratio. 10 mol / L hydrochloric acid was added to the resulting mixture in a 1:1 volume ratio, and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain a leaching agent. Leaching and analysis were performed using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0085] Example 3 A deep eutectic solvent was prepared by mixing decA as a hydrogen bond donor and TOMAC as a hydrogen bond acceptor in a 2:1 volume ratio. This deep eutectic solvent was mixed with toluene in a 1:1 volume ratio. 10 mol / L hydrochloric acid was added to the resulting mixture in a 1:1 volume ratio, and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain a leaching agent. Leaching and analysis were performed using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0086] Comparative Example 3 An extractant was obtained in the same manner as in Example 3, except that naphthalene was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0087] Example 4 An extractant was obtained in the same manner as in Example 3, except that methylnaphthalene was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0088] Example 5 An extractant was obtained in the same manner as in Example 3, except that 4-tert-butyltoluene was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0089] Example 6 An extractant was obtained in the same manner as in Example 3, except that Swazol 1800 was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0090] Comparative Example 4 An extractant was obtained in the same manner as in Example 3, except that Teclean (a naphthenic synthetic hydrocarbon) manufactured by ENEOS Corporation was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0091] Example 7 An extractant was obtained in the same manner as in Example 3, except that MC531 (main component: isoparaffin) manufactured by Tobu Chemical Co. was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0092] Example 8 A deep eutectic solvent was prepared by mixing decA as a hydrogen bond donor and TOMAC as a hydrogen bond acceptor in a 2:1 volume ratio. This deep eutectic solvent was mixed with Swazol 1800 in a 1:4 volume ratio. 10 mol / L hydrochloric acid was added to the resulting mixture in a 1:1 volume ratio, and the mixture was shaken for 1 hour. The organic phase was then extracted to obtain a leachant. This leachant was used for leaching and analysis in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0093] Example 9 An extractant was obtained in the same manner as in Example 8, except that the deep eutectic solvent and Swazol 1800 were mixed in a volume ratio of 1:3. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0094] Example 10 An extractant was obtained in the same manner as in Example 8, except that isopropyl myristate was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0095] Example 11 An extractant was obtained in the same manner as in Example 3, except that isopropyl myristate was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0096] Example 12 An extractant was obtained in the same manner as in Example 3, except that dioctyl ether was used instead of toluene. Using this leaching agent, leaching and analysis were carried out in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0097] Example 13 An extractant was obtained in the same manner as in Example 3, except that 1-dodecene was used instead of toluene. Leaching and analysis were carried out using this leaching agent in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0098] [Table 1]

[0099] In Comparative Example 1, leaching was performed using only a deep eutectic solvent. As a result, 5 mass% of Si was leached together with Ni. In Comparative Example 2, only a hydrophobic organic compound was used as the leaching agent. The results in Table 1 show that the hydrophobic organic compound itself does not have leaching ability.

[0100] On the other hand, as shown by the results of Examples 1 to 13 in Table 1, it is clear that Ni can be selectively leached from saprolite containing Ni and Si by using a liquid leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound. However, the results of Comparative Examples 3 and 4 show that Si is also leached when the hydrophobic organic compound is an unsubstituted alicyclic hydrocarbon compound or an unsubstituted aromatic hydrocarbon compound.

[0101] Therefore, from the above results, it can be seen that the method for leaching nickel from oxide ore disclosed herein makes it possible to selectively leach Ni from oxide ore containing Ni and Si.

[0102] Although specific examples of the present disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0103] That is, the method for leaching nickel from oxide ore, the method for producing nickel sulfate, and the nickel leaching agent disclosed herein are as follows [1] to

[12] . [1] preparing a liquid leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds); contacting an oxide ore containing nickel and silicon with said leaching agent; A method for leaching nickel from oxide ore, comprising: [2] The method according to item [1], wherein the hydrophobic organic compound comprises a saturated aliphatic hydrocarbon compound having 6 to 20 carbon atoms, an unsaturated aliphatic hydrocarbon compound having 6 to 20 carbon atoms, an alicyclic hydrocarbon compound having a substituent, an aromatic hydrocarbon compound having a substituent, a dialkyl ether having 8 to 24 carbon atoms, or a saturated fatty acid ester having 15 to 25 carbon atoms. [3] The method according to item [1], wherein the hydrophobic organic compound comprises an aromatic hydrocarbon compound having at least one alkyl group having 1 to 4 carbon atoms. [4] The method according to any one of items [1] to [3], wherein the leaching agent further contains a hydrogen bond donor. [5] The method according to item [4], wherein the hydrogen bond donor is a carboxyl group-containing compound and the hydrogen bond acceptor is a halide salt. [6] The method according to item [4], wherein the hydrogen bond donor is a fatty acid and the hydrogen bond acceptor is a quaternary ammonium halide. [7] The method according to any one of items [1] to [6], wherein the volume ratio of the hydrophobic organic compound in the leaching agent is 5% by volume to 95% by volume. [8] The method according to any one of items [1] to [6], wherein the volume ratio of the hydrophobic organic compound in the leaching agent is 70% by volume to 90% by volume. [9] A liquid nickel leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound.

[10] A step of obtaining a nickel leachate by the method according to any one of items [1] to [8]; a step of back-extracting the nickel leachate with sulfuric acid to obtain an aqueous phase containing nickel sulfate; A method for producing nickel sulfate comprising the steps of:

[11] The method according to item

[10] , wherein the concentration of sulfuric acid in the step of obtaining the aqueous phase is 2 mol / L or more.

Claims

1. providing a liquid leaching agent containing a hydrogen bond acceptor and a hydrophobic organic compound (excluding unsubstituted alicyclic hydrocarbon compounds and unsubstituted aromatic hydrocarbon compounds) in contact with hydrochloric acid; contacting an oxide ore containing nickel and silicon with said leaching agent; A method for leaching nickel from oxide ore, comprising:

2. 2. The method according to claim 1, wherein the hydrophobic organic compound comprises at least one hydrocarbon compound selected from the group consisting of saturated aliphatic hydrocarbon compounds having 6 to 20 carbon atoms, unsaturated aliphatic hydrocarbon compounds having 6 to 20 carbon atoms, alicyclic hydrocarbon compounds having a substituent, aromatic hydrocarbon compounds having a substituent, dialkyl ethers having 8 to 24 carbon atoms, and saturated fatty acid esters having 15 to 25 carbon atoms.

3. 2. The method of claim 1, wherein the hydrophobic organic compound comprises an aromatic hydrocarbon compound having at least one alkyl group having 1 to 4 carbon atoms.

4. The method of claim 1 , wherein the leaching agent further comprises a hydrogen bond donor.

5. The method of claim 4, wherein the hydrogen bond donor is a carboxy group-containing compound and the hydrogen bond acceptor is a halide salt.

6. The method of claim 4, wherein the hydrogen bond donor is a fatty acid and the hydrogen bond acceptor is a quaternary ammonium halide.

7. 2. The method of claim 1, wherein the volume fraction of the hydrophobic organic compound in the leaching agent is 5% to 95% by volume.

8. 2. The method of claim 1, wherein the volume fraction of the hydrophobic organic compound in the leaching agent is 70% to 90% by volume.

9. A liquid nickel leaching agent containing a hydrogen bond acceptor in contact with hydrochloric acid and a hydrophobic organic compound.

10. Obtaining a nickel leach solution by the method according to any one of claims 1 to 8; a step of back-extracting the nickel leachate with sulfuric acid to obtain an aqueous phase containing nickel sulfate; A method for producing nickel sulfate comprising the steps of:

11. The method according to claim 10, wherein the concentration of sulfuric acid in the step of obtaining the aqueous phase is 2 mol / L or more.

Images