Method for preparing nickel sulfate aqueous solution from raw material containing nickel

Abstract

The present invention provides a method for preparing a nickel sulfate aqueous solution, the method comprising: (A-i) a reduction heat treatment step of heat-treating a first raw material containing nickel and lithium; (B) a first leaching step of leaching a heat treatment product generated through the reduction heat treatment step; (A-ii) a roasting step of heat-treating a second raw material containing nickel and sulfur; (C) a second leaching step of leaching first leaching residues generated through the first leaching step and roasted ore generated through the roasting step; (D) a neutralization step of neutralizing a second leachate generated through the second leaching step; and (E) a solvent extraction step of purifying nickel from a neutralized solution generated through the neutralization step.

Description

Method for producing an aqueous nickel sulfate solution from a raw material containing nickel

[0001] The present invention relates to a method for producing an aqueous nickel sulfate solution from a nickel-containing raw material. More specifically, the present invention relates to a method for producing a high-purity nickel sulfate aqueous solution from a nickel-containing raw material that can be used for various purposes (particularly as a precursor raw material for a positive electrode active material in a lithium secondary battery).

[0002] Nickel can be recovered from various raw materials such as nickel metal, nickel matte, nickel concentrate, and nickel-containing process byproducts. Among the various forms of nickel recovery, an aqueous nickel sulfate solution is known to have a nickel content of 110 g / L or more and an impurity content of several hundred mg / L or less.

[0003] In order to produce such a nickel sulfate aqueous solution, a high-purity nickel sulfate aqueous solution was produced through leaching at atmospheric pressure using an inorganic acid, neutralization using sodium hydroxide or sodium carbonate, and removal of impurities.

[0004] However, the conventional method has a limited number of raw materials that are soluble in specific inorganic acids, and a method of removing Na through sludge filtration and then washing to remove the material (e.g., Na) added as a neutralizing agent has been used, but this method has the disadvantage of increasing the amount of wastewater and requiring a lot of process time, which has led to problems such as a decrease in production volume and an increase in wastewater treatment costs.

[0005] The present invention aims to provide an all-in-one process capable of flexible response according to nickel-containing raw materials, by using a hybrid process combining dry refining and wet refining technologies to produce a high-purity nickel sulfate aqueous solution from nickel-containing composite raw materials.

[0006] The purpose of the present invention is to provide an economical and environmentally friendly process that enables recycling of process by-products.

[0007] The purpose of the present invention is to provide an environmentally friendly process capable of selectively separating lithium, converting complex compounds into single compounds, and recovering inorganic acids from hazardous gases through pretreatment using a dry smelting method.

[0008] The present invention aims to provide an economical and environmentally friendly process that can reduce additional wastewater treatment costs by minimizing the inflow of impurities from precipitants or raw materials by using a wet refining process including a solvent extraction process that can reduce the amount of raw materials used through recycling of process liquid.

[0009] One aspect of the present invention relates to a method for producing a nickel sulfate aqueous solution, comprising: (Ai) a reduction heat treatment process for heat treating a first raw material containing nickel and lithium; (B) a first leaching process for leaching a heat treatment product produced by the reduction heat treatment process; (A-ii) a roasting process for heat treating a second raw material containing nickel and sulfur; (C) a second leaching process for leaching a first leaching residue produced by the first leaching process and a roasting ore produced by the roasting process; (D) a neutralization process for neutralizing a second leaching solution produced by the second leaching process; and (E) a solvent extraction process for purifying nickel from the neutralized solution produced by the neutralization process.

[0010] One embodiment of the present invention can provide a method for producing an aqueous nickel sulfate solution, wherein the first raw material and the second raw material independently include at least one selected from the group consisting of oxides, hydroxides, sulfides, and sulfur oxides, and the oxides, hydroxides, sulfides, and sulfur oxides independently include ore, matte, black mass (BM), black powder (BP), mixed hydroxide precipitate (MHP), mixed carbonate precipitate (MCP), mixed sulfide precipitate (MSP), or mixtures thereof.

[0011] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first raw material includes nickel in the form of nickel oxide or nickel metal composite oxide.

[0012] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the second raw material includes nickel in the form of nickel sulfide.

[0013] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the reduction heat treatment process is performed at a temperature of 650 to 950°C by introducing a first raw material into a heat treatment device and injecting nitrogen gas.

[0014] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first leaching process is performed using a first leaching agent including an inorganic acid, water, or a mixture thereof.

[0015] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first leaching liquid obtained by the first leaching process contains lithium, and the first leaching residue contains nickel.

[0016] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the firing process is performed at a temperature of 650 to 950°C by introducing a second raw material into a heat treatment device and injecting oxygen gas.

[0017] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein, in the second leaching process, the first leaching residue is leached in a normal pressure reactor, and the slag is leached in a high temperature and high pressure reactor.

[0018] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the second leaching process is performed using a second leaching agent comprising an inorganic acid or a mixture of an inorganic acid and water.

[0019] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the second leaching process is performed at a temperature of 150 to 250°C and a pressure of 800 to 4300 kPa.

[0020] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the second leaching process is performed in an atmosphere having an acidity of 100 to 200 g / L.

[0021] One embodiment of the present invention can provide a method for producing an aqueous nickel sulfate solution, wherein the neutralization process is performed using a neutralizing agent including MHP, MCP, nickel hydroxide (Ni(OH)2), nickel carbonate (NiCO3), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), or a mixture thereof.

[0022] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the neutralization process is performed at 80°C under conditions of pH 2 to 4.5.

[0023] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the neutralization process is performed for 2 hours or more, and the residual acidity of the neutralized solution produced by the neutralization process is 10 g / L or less.

[0024] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the solvent extraction process includes: (Ei) a first solvent extraction process for purifying nickel from a neutralization solution produced by the neutralization process; and (E-ii) a second solvent extraction process for purifying nickel from a first extraction solution produced by the first solvent extraction process.

[0025] One embodiment of the present invention provides a method for producing a nickel sulfate aqueous solution, wherein the first solvent extraction process is performed by (i) a first loading process in which a first organic extractant is added to a nickel sulfate aqueous solution to load nickel into an organic phase; (ii) a first extraction process in which an organic extractant is added to a neutralized solution after the first loading process to extract nickel back into an aqueous phase; (iii) a first scrubbing process in which an inorganic extractant is added to the organic extractant after the first extraction to recover cobalt into an aqueous phase; (iv) a first stripping process in which an inorganic extractant is added to the organic extractant after the first scrubbing process to recover copper into an aqueous phase, or a combination thereof.

[0026] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the first organic extractant to the nickel sulfate aqueous solution in the first loading process is 3.5 to 6.5.

[0027] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, which comprises precipitating a first loading liquid produced by the first loading process and then using the precipitated nickel-containing byproduct as a neutralizing agent in the neutralization process.

[0028] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the organic extractant after the first loading to the neutralized solution in the first extraction process is 1.5 to 4.5.

[0029] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the organic extractant to the inorganic extractant in the first scrubbing process and the volume ratio of the organic extractant to the inorganic extractant in the first stripping process are each 9.5 to 12.5.

[0030] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first scrubbing process is performed under conditions of pH 2 to 3.

[0031] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first stripping process is performed under conditions of pH 0.5 to 1.5.

[0032] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the first post-stripping organic extractant is reused as a first organic extractant.

[0033] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, further comprising a first precipitation process for recovering cobalt by adding a first precipitant to a first scrubbing liquid produced by the first scrubbing process.

[0034] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, further comprising a second precipitation process for recovering copper by adding a second precipitant to a first stripping liquid produced by the first stripping process.

[0035] One embodiment of the present invention provides a method for producing a nickel sulfate aqueous solution, wherein the second solvent extraction process is performed by (i) a second loading process in which a second organic extractant is added to a nickel sulfate aqueous solution to load nickel into an organic phase; (ii) a second extraction process in which an organic extractant is added to a first post-extraction liquid after the second loading process to extract nickel back into an aqueous phase; (iii) a second stripping process in which an inorganic extractant is added to the organic extractant after the second extraction process to recover impurities into an aqueous phase, or a combination thereof.

[0036] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the second organic extractant to the nickel sulfate aqueous solution in the second loading process is 4.5 to 8.5.

[0037] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, which comprises precipitating a second loading liquid produced by the second loading process and then using the precipitated nickel-containing byproduct as a neutralizing agent in the neutralization process.

[0038] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the organic extractant after the second loading to the first extraction liquid in the second extraction process is 0.3 to 1.5.

[0039] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the volume ratio of the organic extractant to the inorganic extractant in the second stripping process is 3.5 to 7.5.

[0040] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the second stripping process is performed under conditions of pH 0.25 to 1.5.

[0041] One embodiment of the present invention can provide a method for producing a nickel sulfate aqueous solution, wherein the organic extractant after the second stripping is reused as a second organic extractant.

[0042] According to the present invention, a high-purity nickel sulfate aqueous solution can be produced from various nickel-containing raw materials.

[0043] According to the present invention, selective leaching and recovery of lithium can be achieved through heat treatment of a raw material containing lithium in a strong chemical bond using a reduction heat treatment process.

[0044] According to the present invention, nickel-containing raw materials having various chemical bonding forms are phase-changed into a single phase using a firing process, thereby ensuring uniformity in subsequent processes, thereby improving the usability of the entire process as a process capable of flexibly responding to the rapidly changing nickel raw material market.

[0045] According to the present invention, by utilizing a process by-product as a neutralizing agent in a neutralization process, the inflow of impurities introduced from a commonly used neutralizing agent or precipitant can be blocked, and the effect of improving the concentration of nickel, which is a target metal, can be exhibited.

[0046] According to the present invention, nickel sulfate can be suitably used as a precursor raw material among the raw materials for positive electrode active materials of lithium secondary batteries.

[0047] FIG. 1 is a drawing showing the overall process for producing a nickel sulfate aqueous solution according to one embodiment of the present invention.

[0048] FIG. 2 is a drawing showing a first solvent extraction process among processes for producing a nickel sulfate aqueous solution according to one embodiment of the present invention.

[0049] FIG. 3 is a drawing showing a second solvent extraction process among the processes for producing a nickel sulfate aqueous solution according to one embodiment of the present invention.

[0050] The embodiments of the present invention are provided for the purpose of illustrating the technical concept of the present invention. The scope of the rights of the present invention is not limited to the embodiments presented below or the specific descriptions of these embodiments.

[0051] The embodiments of the present invention are provided for the purpose of illustrating the technical concept of the present invention. The scope of the rights of the present invention is not limited to the embodiments presented below or the specific descriptions of these embodiments.

[0052] In this specification, “%” is understood to be measured based on weight (wt) unless otherwise specified.

[0053] Hereinafter, the present invention will be described with reference to the drawings.

[0054] FIG. 1 is a diagram illustrating an overall process for producing a nickel sulfate aqueous solution according to one embodiment of the present invention. FIG. 2 and FIG. 3 are diagrams illustrating a first solvent extraction process and a second solvent extraction process, respectively, among the processes for producing a nickel sulfate aqueous solution according to one embodiment of the present invention.

[0055] Referring to Figures 1 to 3, a method for refining nickel to a high purity through a series of processes and using this nickel to produce a nickel aqueous solution can be provided. This method can improve versatility for various raw materials and products, operational stability, and purity, and reduce manufacturing costs. Below, each process will be described in detail with reference to the respective drawings.

[0056] raw material

[0057] The first and second raw materials, which are the starting materials of the present invention, are raw materials mainly containing nickel, and may independently include at least one selected from the group consisting of oxides, hydroxides, sulfides, and sulfur oxides. For example, the oxides, hydroxides, sulfides, and sulfur oxides may independently include ore concentrate (ore), matte, black mass (BM), black powder (BP), mixed hydroxide precipitate (MHP), mixed carbonate precipitate (MCP), mixed sulfide precipitate (MSP), or mixtures thereof.

[0058] For example, the first raw material may include black mass (BM), black powder (BP), mixed hydroxide precipitate (MHP), mixed carbonate precipitate (MCP), or a mixture thereof. For example, the first raw material may include, in addition to nickel (Ni) and lithium (Li), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), sodium (Na), silicon (Si), or a combination thereof as impurities. For example, the composition of the first raw material may be as shown in Table 1 below. For example, the first raw material may include nickel in the form of nickel oxide (NiO), or a nickel metal composite oxide mixed with other metals.

[0059]

[0060] For example, the second raw material may include a concentrate, a matte, a mixed sulfide precipitate (MSP), or a mixture thereof. For example, the second raw material may include, in addition to nickel (Ni) and sulfur (S), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), sodium (Na), silicon (Si), or a combination thereof as impurities. For example, the composition of the second raw material may be as shown in Table 2 below. For example, the second raw material may include nickel in the form of nickel sulfide (NiS).

[0061]

[0062] Reduction heat treatment process (S10)

[0063] A reduction heat treatment process (S10) can be performed as a pretreatment process of the first raw material.

[0064] In the reduction heat treatment process (S10), a heat treatment can be performed on a first raw material containing nickel and lithium in the form of a complex oxide that can be combined with various metals, to cause a phase change into an oxide and / or carbonate through heat treatment in a reducing atmosphere, thereby converting the lithium-containing compound into a substance having high solubility in water or an inorganic acid.

[0065] In this way, by converting the compound form of the first raw material containing lithium through a reduction heat treatment process (S10) before performing the first leaching process (S20) for leaching / extracting lithium described below, the leaching efficiency in the first leaching process (S20) for leaching / extracting lithium can be increased.

[0066] For example, the reduction heat treatment process (S10) can be performed using a heat treatment device such as an electric furnace (e.g., a box furnace), a rotary kiln, etc.

[0067] According to one embodiment of the present invention, the reduction heat treatment process (S10) may be performed at a temperature of 650 to 950°C by charging a first raw material into a heat treatment device and injecting nitrogen gas. For example, a predetermined amount of the first raw material may be charged into the heat treatment device, and a reduction heat treatment may be performed at 650 to 950°C while sufficiently injecting nitrogen gas (N2gas) to maintain a reducing atmosphere. In this process, not only lithium but also other metals may react together, and a phase change may occur through a reaction according to [Reaction Scheme 1] below. In addition, additional reactions may occur through the reaction schemes of [Reaction Scheme 2] and [Reaction Scheme 3] below.

[0068] [Reaction Formula 1]

[0069] 9LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2+ 0.25C → 3NiO + 3MnO2+ Co3O4+ 4.5Li2O + 0.25CO2(g)

[0070] [Reaction Formula 2]

[0071] 4MnO2+ C → 2Mn2O3+ CO2(g)

[0072] [Reaction Formula 3]

[0073] Li2O + CO2(g) → Li2CO3

[0074] First leaching process (S20)

[0075] In the first leaching process (S20), nickel and lithium-containing raw materials that have undergone a phase change through the reduction heat treatment process (S10) can be leached.

[0076] The first leaching process (S20) may be performed after the reduction heat treatment process (S10). For example, the first leaching process (S20) may be performed in a wet mill. The wet mill may be a ball mill, a rod mill, a bead mill, an attrition mill, etc. The first leaching process may selectively leach the heat-treated lithium using a first leaching agent (e.g., an inorganic acid, water, or a mixture thereof).

[0077] In one embodiment, the inorganic acid may be at least one selected from the group consisting of sulfuric acid (H2SO4), hydrochloric acid (HCl), and nitric acid (HNO3), an inorganic acid diluted with water may be used, and sulfuric acid produced through capturing sulfurous acid gas generated in a subsequent roasting process (S30) may be used.

[0078] In one embodiment, water may be used as the first leaching agent. In this case, lithium may be leached from the lithium-containing raw material in the form of lithium hydroxide (LiOH) through the following reaction scheme 4, thereby producing a first leaching solution. The first leaching solution may contain lithium.

[0079] [Reaction Formula 4] Li2CO3+2H2O → 2LiOH + H2O + CO2

[0080] In one embodiment, metals other than lithium may remain in the residue. For example, metals such as nickel (Ni), cobalt (Co), manganese (Mn), etc. may remain in the residue and be included in the first leach residue.

[0081] The lithium concentration of the first leaching solution obtained in the first leaching process may be approximately 0.1 to 8.5 g / L. In order to use this as a raw material for a lithium-ion battery cathode material, it can be manufactured into lithium hydroxide (LiOH·H2O), lithium carbonate (Li2CO3), lithium phosphate (Li3PO4), etc. through generally known precipitation and crystallization processes.

[0082] In the case of MHP and MCP generated in the lithium-ion battery recycling process, they can contain Li in addition to Ni, Co, and Mn, and can be used as the first raw material for performing the first leaching process.

[0083] Distribution process (S30)

[0084] As a pretreatment process of the above second raw material, a roasting process (S30) can be performed.

[0085] In the firing process (S30), inorganic acid production can be performed through recycling of sulfur dioxide gas (SO2gas) generated during the heat treatment process, along with a phase change of nickel-containing raw materials combined with various compounds.

[0086] Before the roasting process (S30) is performed, the second raw material containing nickel may be in the form of sulfide, and may be converted into an oxide by the roasting process (S30). If the second raw material containing nickel is leached as it is in the form of sulfide, the leaching rate may be lowered due to a re-precipitation reaction of the metal caused by the generation of hydrogen sulfide gas (H2S gas). Accordingly, by converting the compound form of the second raw material containing nickel through the roasting process (S30) before performing the second leaching process (S40), the leaching efficiency in the second leaching process (S40) can be improved. Here, the roasting process (S30) may be performed using a heat treatment device such as an electric furnace (Box Furnace) or a tube furnace (Rotary Kiln).

[0087] According to one embodiment of the present invention, the roasting process (S30) may be performed by charging a certain amount of nickel-containing raw material into an electric furnace, sufficiently injecting oxygen (O2) for conversion into nickel oxide, and performing roasting at 650 to 950°C. During this process, not only nickel but also other impurities may react, causing a phase change through the reaction formula of [Reaction Formula 5] below. In addition, the sulfur dioxide gas generated in the roasting process (S30) may be produced into sulfuric acid (H2SO4) by mixing with water through a separate capture facility, and used for subsequent leaching.

[0088] [Reaction Formula 5] 2NiS + 3O2 → 2NiO + 2SO2

[0089] Second leaching process (S40)

[0090] In the second leaching process (S40), the first leaching residue remaining in the residue from the first leaching process (S20) can be leached together with the post-roasting residue (roasting light) that has undergone a phase change through the roasting process (S30). The second leaching process (S40) can be performed after the roasting process (S30) and the first leaching process. In the second leaching process, the post-roasting residue can be leached in a high-temperature and high-pressure reactor, and the first leaching residue can be leached in an atmospheric pressure reactor. In the second leaching process (S40), leaching can be performed using a second leaching agent (for example, an inorganic acid, or a mixture of an inorganic acid and water). In one embodiment, the second leaching process (S40) can be performed using an inorganic acid. For example, the inorganic acid may be at least one selected from the group consisting of sulfuric acid (H2SO4), hydrochloric acid (HCl), and nitric acid (HNO3), an inorganic acid diluted with water may be used, and sulfuric acid produced by capturing sulfurous acid gas generated in the preceding roasting process (S30) may be used.

[0091] In one embodiment, sulfuric acid may be used as a second leaching agent. In this case, nickel may be leached from the first leaching residue and the post-smelting residue containing nickel in the form of nickel sulfate (NiSO4) through the following reaction scheme 6, thereby generating a second leaching solution.

[0092] [Reaction Formula 6] NiO + H2SO4 → NiSO4 + H2O

[0093] The second leaching process (S40) can be performed at a temperature of approximately 150 to 250°C and a pressure of 800 to 4300 kPa. As the reaction temperature increases, a certain level of pressure is maintained by the saturated vapor pressure, and additional pressure can be applied to ensure complete reaction.

[0094] For example, the second leaching process (S40) may be performed in an atmosphere with an acidity of 100 to 200 g / L. After performing the second leaching process (S40) in an acidic atmosphere with a low pH to secure a sufficient second leaching solution, the subsequent neutralization process (S50) may be performed.

[0095] In one embodiment, not only nickel, but also other impurities may be leached together. For example, impurities such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), etc. may be leached together with nickel and included in the second leaching solution.

[0096] The nickel concentration of the second leaching liquid obtained in the second leaching process (S40) may be about 45 to 105 g / L, and the residual acidity may be 10 to 80 g / L.

[0097] Neutralization process (S50)

[0098] In the neutralization process (S50), the second leaching liquid produced by the second leaching process (S40) can be neutralized. The neutralization process (S50) can be performed after the second leaching process (S40).

[0099] When the second leaching solution is produced in an atmosphere with high pH, ​​less of the second leaching solution may be produced.

[0100] In one embodiment, a second leaching process (S40) may be performed in an acidic atmosphere with low pH to secure sufficient second leaching liquid, and then a neutralization process (S50) may be performed.

[0101] In the neutralization process (S50), a neutralizing agent may be added to increase the pH of the second leaching solution generated in the second leaching process (S40). Additionally, the addition of the neutralizing agent may be for a solvent extraction process to be performed in the future.

[0102] In one embodiment, the neutralizing agent may be at least one selected from the group consisting of nickel-containing byproducts (MHP, MCP), nickel hydroxide (Ni(OH)2), nickel carbonate (NiCO3), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), and magnesium oxide (MgO).

[0103] The reason why MHP and MCP are used as raw materials and neutralizers is that hydroxides and carbonates generally have high solubility in acids even without roasting, so there is no need to process them under high temperature and high pressure leaching conditions with high processing costs, and there is an effect of preparing in advance the purification process (S60) that is carried out in a high pH range by consuming the acid (H2SO4) remaining after the second leaching process (S40).

[0104] In one embodiment, the neutralization process (S50) may be performed using a nickel-containing byproduct in the form of a moist cake as the neutralizing agent. Using a nickel-containing byproduct can reduce the amount of neutralizing agent separately injected by utilizing the byproduct generated during the process, thereby reducing costs. Furthermore, the inflow of additional impurities can be prevented, and the nickel concentration in the neutralized solution can be increased.

[0105] In one embodiment, the neutralization process (S50) may be performed at a temperature of 80°C and a pH of about 2 to 4.5. During this process, some impurities, including iron (Fe) and aluminum (Al), may be precipitated and removed.

[0106] In one embodiment, the neutralization process (S50) is performed for 2 hours or more, and the residual acidity of the neutralized solution produced by the neutralization process may be 10 g / L or less. For example, the neutralization process (S50) may be performed for 10 hours or less.

[0107] Solvent extraction process (S60)

[0108] In the solvent extraction process (S60), nickel can be purified from the neutralized solution generated by the neutralization process (S50). The solvent extraction process (S60) can be performed after the neutralization process (S50).

[0109] In one embodiment, the solvent extraction process (S60) may include a first solvent extraction process (S70) for purifying nickel from the neutralization liquid produced by the neutralization process (S50); and a second solvent extraction process for purifying nickel from the first extraction liquid produced by the first solvent extraction process.

[0110] First solvent extraction process (S70)

[0111] Nickel can be purified from the neutralization liquid produced by the neutralization process (S50) in the first solvent extraction process (S70). The neutralization liquid may be a neutralized leaching liquid. The first solvent extraction process (S70) is a process for purifying nickel by removing impurities from the neutralization liquid after the neutralization process (S50), and an organic extractant (first organic extractant) may be used.

[0112] The first solvent extraction process (S70) may include a first loading process (S71), a first extraction process (S72), a first scrubbing process (S73), and a first stripping process (S74). As the organic extractant, at least one selected from the group consisting of Di-2-Ethylhexyl phosphoric acid, Mono-2-ethylhexyl (2-ethylhexyl)phosphonate, and Bis (2,4,4-trimethylpentyl) phosphinic acid may be used.

[0113] First loading process (S71)

[0114] The first loading process (S71) may be a process for increasing the nickel concentration in the organic phase. The first loading process (S71) may be a process for loading nickel contained in the nickel sulfate aqueous solution into the first organic extractant using a nickel sulfate (NiSO4) aqueous solution and a first organic extractant, thereby moving the nickel to the organic phase.

[0115] The volume ratio of the first organic extractant (organic phase) to the nickel sulfate aqueous solution (aqueous phase) in the first loading process (S71) may be 3.5 to 6.5. If the volume ratio of the organic phase to the aqueous phase in the first loading process (S71) is less than 3.5, the binding of the target metal (nickel) and the organic extractant may be incomplete, resulting in a low extraction rate (e.g., 85% or less). If the volume ratio of the organic phase to the aqueous phase in the first loading process (S71) is greater than 6.5, the process cost may increase due to excessive use of the first organic extractant.

[0116] The first loading process (S71) can be performed in a pH range of 4.5 to 6.0, and to adjust to this pH range, at least one selected from the group consisting of sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) can be used.

[0117] When nickel extraction into the organic phase is completed by mixing the aqueous and aqueous phases, phase separation is possible based on the difference in specific gravity between the organic and aqueous phases. Phase separation can produce a first loading solution (aqueous phase). The first loading solution is a nickel-containing aqueous solution from which most of the nickel has been extracted, and the nickel content can range from 0.1 to 4.5 g / L.

[0118] After precipitating the above first loading liquid, the precipitated nickel-containing byproduct can be used as a neutralizing agent in the neutralization process (S50). For example, nickel-containing byproducts such as nickel hydroxide (Ni(OH)2) and nickel carbonate (NiCO3) can be precipitated using precipitants such as sodium hydroxide (NaOH) and sodium carbonate (Na2CO3).

[0119] First extraction process (S72)

[0120] In the first extraction process (S72), impurities contained in the neutralization solution can be removed while simultaneously increasing the concentration of nickel in the neutralization solution by mixing the neutralization solution and the first loading organic extractant containing nickel. The first extraction process (S72) can be performed after the first loading process (S71). The first loading organic extractant can be used to purify impurities in the first extraction process (S72).

[0121] In the first extraction process (S72), the volume ratio of the organic extractant (organic phase) after the first loading to the neutralized solution (aqueous phase) may be 1.5 to 4.5. If the volume ratio of the organic phase to the aqueous phase in the first extraction process (S72) is less than 1.5, the extraction efficiency of impurities may decrease (e.g., less than 75%). If the volume ratio of the organic phase to the aqueous phase in the first extraction process (S72) is greater than 4.5, the nickel remaining in the organic phase may increase, which may lower the process efficiency. The pH range of the first extraction process (S72) may be about 3.5 to 5.0.

[0122] When nickel extraction into the aqueous phase is completed by mixing the aqueous and organic phases, phase separation is possible due to the difference in specific gravity between the organic and aqueous phases. This phase separation can produce a first post-extraction solution (aqueous phase). The first post-extraction solution is an aqueous solution containing nickel as its main component, with a nickel content of 75 to 110 g / L.

[0123] First scrubbing process (S73)

[0124] In the first scrubbing process (S73), cobalt contained in the first extraction organic extractant can be recovered as an aqueous phase by mixing the first extraction organic extractant containing other impurities, such as cobalt (Co), magnesium (Mg), or manganese (Mn), with the inorganic extractant. The first scrubbing process (S73) can be performed after the first extraction process (S72).

[0125] The above inorganic extractant may be an inorganic acid, water or a mixture thereof.

[0126] The volume ratio of the organic extractant (organic phase) after the first extraction to the inorganic extractant (aqueous phase) in the first scrubbing process (S73) may be 9.5 to 12.5. If the volume ratio of the organic phase to the aqueous phase in the first scrubbing process (S73) exceeds 12.5, the cobalt recovery rate may decrease (e.g., less than 65%). If the volume ratio of the organic phase to the aqueous phase in the first scrubbing process (S73) is less than 9.5, the cobalt recovery rate may increase, but the process cost may increase due to the use of unnecessary inorganic extractant. The pH range of the first scrubbing process (S73) may be about 2.0 to 3.0.

[0127] Once the reverse extraction of impurities, including cobalt, into the aqueous phase is completed by mixing the aqueous and organic phases, phase separation is possible based on the difference in specific gravity between the organic and aqueous phases. This phase separation can produce a first post-scrubbing solution (aqueous phase). The first post-scrubbing solution is an aqueous solution containing cobalt as its main component, with a cobalt content of 3.5 to 8.5 g / L.

[0128] First stripping process (S74)

[0129] In the first stripping process (S74), the copper contained in the first extraction organic extractant is mixed with the inorganic extractant after the first extraction to recover the copper as an aqueous phase, and a pure organic extractant can be recovered. The first stripping process (S74) can be performed after the first scrubbing process (S73).

[0130] The above inorganic extractant may be an inorganic acid, water or a mixture thereof.

[0131] The volume ratio of the organic extractant (organic phase) after the first extraction to the inorganic extractant (aqueous phase) in the first stripping process (S74) may be 9.5 to 12.5. If the volume ratio of the organic phase to the aqueous phase in the first stripping process (S74) exceeds 12.5, the copper recovery rate may decrease (e.g., less than 90%). If the volume ratio of the organic phase to the aqueous phase in the first stripping process (S74) is less than 9.5, the copper recovery rate may increase, but the process cost may increase due to the use of unnecessary inorganic extractant. The pH range of the first stripping process (S74) may be about 0.5 to 1.5.

[0132] When the copper back-extraction into the aqueous phase is completed by mixing the aqueous and organic phases, phase separation is possible based on the difference in specific gravity between the organic and aqueous phases. Through phase separation, a first post-stripping solution (aqueous phase) and a first post-stripping organic extractant (organic phase) can be generated. The first post-stripping solution is an aqueous solution containing copper as a main component, and the copper content can be 40 to 50 g / L. The first post-stripping organic extractant can be reused as the first organic extractant in the first loading process (S71) (see Fig. 2).

[0133] Second solvent extraction process (S80)

[0134] In the second solvent extraction process (S80), nickel can be purified from the first extraction liquid produced by the first solvent extraction process (S70). The second solvent extraction process (S80) can be performed after the first solvent extraction process (S70). The second solvent extraction process (S80) is a process for purifying nickel by removing impurities from the first extraction liquid, and an organic extractant (second organic extractant) can be used.

[0135] The second solvent extraction process (S80) may include a second loading process (S81), a second extraction process (S82), and a second stripping process (S84). As the organic extractant, at least one selected from the group consisting of Di-2-Ethylhexyl phosphoric acid, Mono-2-ethylhexyl (2-ethylhexyl)phosphonate, and Bis (2,4,4-trimethylpentyl) phosphinic acid may be used.

[0136] Second loading process (S81)

[0137] The second loading process (S81) may be a process for increasing the nickel concentration in the organic phase. The second loading process (S81) may be a process for loading nickel contained in the nickel sulfate aqueous solution into the second organic extractant using a nickel sulfate (NiSO4) aqueous solution and a second organic extractant to move the nickel to the organic phase.

[0138] The volume ratio of the second organic extractant (organic phase) to the nickel sulfate aqueous solution (aqueous phase) in the second loading process (S81) may be 4.5 to 8.5. If the volume ratio of the organic phase to the aqueous phase in the second loading process (S81) is less than 4.5, the binding of the target metal (nickel) and the organic extractant may be incomplete, resulting in a low extraction rate (e.g., 90% or less). If the volume ratio of the organic phase to the aqueous phase in the second loading process (S81) is greater than 8.5, the process cost may increase due to excessive use of the second organic extractant.

[0139] The second loading process (S81) can be performed in a pH range of 5.5 to 6.5, and to adjust to this pH range, at least one selected from the group consisting of sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) can be used.

[0140] When nickel extraction into the organic phase is completed by mixing the aqueous and aqueous phases, phase separation is possible due to the difference in specific gravity between the organic and aqueous phases. Phase separation can produce a second loading solution (aqueous phase). The second loading solution is a nickel-containing aqueous solution from which most of the nickel has been extracted, and the nickel content can range from 0.1 to 9.5 g / L.

[0141] After precipitating the second loading liquid, the precipitated nickel-containing byproduct can be used as a neutralizing agent in the neutralization process (S50). For example, nickel-containing byproducts such as nickel hydroxide (Ni(OH)2) and nickel carbonate (NiCO3) can be precipitated using precipitants such as sodium hydroxide (NaOH) and sodium carbonate (Na2CO3).

[0142] Second extraction process (S82)

[0143] In the second extraction process (S82), the impurities contained in the first extraction liquid can be removed while simultaneously increasing the concentration of nickel in the first extraction liquid by mixing the first extraction liquid from the first solvent extraction process (S70) with the second loading organic extractant containing nickel. The second extraction process (S82) can be performed after the second loading process (S81). The second loading organic extractant can be used to purify impurities in the second extraction process (S82).

[0144] In the second extraction process (S82), the volume ratio of the organic extractant (organic phase) after the second loading to the first post-extraction liquid (aqueous phase) may be 0.3 to 1.5. If the volume ratio of the organic phase to the aqueous phase in the second extraction process (S82) is less than 0.3, the extraction efficiency of impurities may decrease (e.g., less than 90%). If the volume ratio of the organic phase to the aqueous phase in the second extraction process (S82) is greater than 1.5, the nickel remaining in the organic phase may increase, which may lower the process efficiency. The pH range of the second extraction process (S82) may be about 4.5 to 5.5.

[0145] When the nickel back-extraction into the aqueous phase is completed by mixing the aqueous and organic phases, phase separation is possible due to the difference in specific gravity between the organic and aqueous phases. Through phase separation, a second post-extraction liquid (aqueous phase) can be generated. The second post-extraction liquid is an aqueous solution containing nickel as a main component, and the nickel content can be 85 to 125 g / L. The second post-extraction liquid can be used as a precursor raw material for the positive electrode active material of a lithium secondary battery.

[0146] Second stripping process (S84)

[0147] In the second stripping process (S84), the impurities contained in the organic extractant after the second extraction are recovered as an aqueous phase by mixing the organic extractant containing impurities with the inorganic extractant, and a pure organic extractant can be recovered. The second stripping process (S84) can be performed after the second extraction process (S82).

[0148] The above inorganic extractant may be an inorganic acid, water or a mixture thereof.

[0149] The volume ratio of the organic extractant (organic phase) after the second extraction to the inorganic extractant (aqueous phase) in the second stripping process (S84) may be 3.5 to 7.5. If the volume ratio of the organic phase to the aqueous phase in the second stripping process (S84) exceeds 7.5, the impurity removal rate may decrease (e.g., less than 85%). If the volume ratio of the organic phase to the aqueous phase in the second stripping process (S84) is less than 3.5, the impurity removal rate may increase, but the process cost may increase due to the use of unnecessary inorganic extractant. The pH range of the second stripping process (S84) may be about 0.25 to 1.5.

[0150] Once the reverse extraction of impurities into the aqueous phase is completed by mixing the aqueous and organic phases, phase separation is possible based on the difference in specific gravity between the organic and aqueous phases. Through phase separation, an organic extractant (organic phase) can be generated after the second stripping. The organic extractant after the second stripping can be reused as the second organic extractant in the second loading process (S81) (see Figure 3).

[0151] First sedimentation process (S90)

[0152] In the first precipitation process (S90), the first scrubbing liquid generated by the first scrubbing process (S73) within the first solvent extraction process (S70) can be purified. The first precipitation process (S90) can be performed after the first scrubbing process (S73). The first precipitation process (S90) is a process for removing magnesium and recovering cobalt within the first scrubbing liquid.

[0153] In one embodiment, a first precipitant may be used to remove magnesium in the first precipitation process (S90). The first precipitant may be at least one selected from the group consisting of sodium fluoride (NaF), oxalic acid (C2H2O4), sodium oxalate (Na2C2O4), sodium hydroxide (NaOH), and sodium carbonate (Na2CO3). For example, when sodium fluoride is used as the first precipitant, the reaction formula is as shown in [Reaction Formula 7] below.

[0154] [Reaction Scheme 7] MgSO4+2NaF → MgF2↓ + Na2SO4

[0155] In the first precipitation process (S90), the first precipitant may be added at an equivalent ratio of about 1.0 to 3.0 relative to the magnesium contained in the first scrubbing liquid. If the first precipitant is added at an equivalent ratio of less than 1.0 relative to the magnesium, the magnesium precipitation rate may be less than 80%, and complete reaction may not occur. If the first precipitant is added at an equivalent ratio of more than 3.0 relative to the magnesium, excessive impurities originating from the first precipitant may be introduced, which may negatively affect the overall process. The pH range of the first precipitation process (S90) may be about 4.5 to 5.5.

[0156] Once the precipitation reaction of the first precipitation process (S90) is completed, the solid and liquid phases can be separated through a commonly used solid-liquid separation process. A first precipitation liquid can be produced through the solid-liquid separation. The first precipitation liquid is a cobalt-containing aqueous solution with most impurities removed, and the cobalt content can be 20 to 45 g / L. The first precipitation liquid can be further purified to be used as a precursor raw material for the cathode active material of a lithium secondary battery.

[0157] Second sedimentation process (S100)

[0158] In the second precipitation process (S100), the first stripping liquid generated by the first stripping process (S74) within the first solvent extraction process (S70) can be purified. The second precipitation process (S100) can be performed after the first stripping process (S74). The second precipitation process (S100) is a process for recovering copper within the first stripping liquid.

[0159] In one embodiment, a second precipitant may be used to remove copper in the second precipitation process (S100). The second precipitant may be at least one selected from the group consisting of sodium sulfate (Na2S), sodium hydroxide (NaSH), ammonium hydrogen sulfide (NH4HS), hydrogen sulfide (H2S), and sodium sulfide (Na2S). For example, when sodium sulfate is used as the second precipitant, the reaction formula is as shown in [Reaction Formula 8] below.

[0160] [Reaction Formula 8] 2CuSO4+ 2NaSH → Na2SO4+ H2SO4+ 2CuS↓

[0161] In the second precipitation process (S100), the second precipitant may be added at an equivalent ratio of approximately 0.8 to 2.0 relative to the copper contained in the first stripping solution. If the second precipitant is added at an equivalent ratio of less than 0.8 relative to copper, the copper recovery rate may be less than 80%, and the reaction may not occur completely. If the second precipitant is added at an equivalent ratio of more than 2.0 relative to copper, impurities originating from the second precipitant may be excessively introduced, negatively affecting the overall process. The pH range of the second precipitation process (S100) may be approximately 2.0 to 3.0.

[0162] Once the precipitation reaction of the second precipitation process (S100) is completed, the solid and liquid phases can be separated through a commonly used solid-liquid separation process. A residue after the second precipitation can be generated through the solid-liquid separation. The residue after the second precipitation is a copper-containing precipitate, and the copper content can be 45 to 55 wt%. The first precipitation liquid can be further purified to be used as a precursor raw material for the positive electrode active material of a lithium secondary battery.

[0163] Experimental example

[0164] [raw material]

[0165] A first raw material was prepared by mixing A to C, each containing the elements in Table 3 below, in a predetermined ratio.

[0166]

[0167] * In addition to the above metal ions, the weight ratio becomes 100 through the sum of ions including sulfur (S), oxygen (O), and hydrogen (H).

[0168] A second raw material containing the elements in Table 4 below was prepared.

[0169]

[0170] * In addition to the above metal ions, the weight ratio becomes 100 through the sum of ions including oxygen (O) and hydrogen (H).

[0171] [Reduction heat treatment process]

[0172] A reduction heat treatment of the first raw material containing nickel, lithium, etc. was performed. Specifically, after charging 2.0 kg of the raw material in a tube furnace, a reduction heat treatment was performed at 850°C for 3 hours while maintaining a reduction atmosphere using nitrogen (N2) gas, thereby securing a residue after reduction heat treatment that was converted from a lithium oxide (Li2O) form to a lithium carbonate (Li2CO3) form.

[0173] [First leaching process]

[0174] Lithium recovery was performed through water leaching of the residue after reduction heat treatment. Specifically, 100 g of raw material was placed in a ball mill, crushed and water-leached with 2.5 L of water (H2O) for 2 hours, and then solid-liquid separation using reduced pressure filtration was performed to obtain a first leaching residue containing the elements listed in Table 5 below and a first leaching solution containing the elements listed in Table 6 below.

[0175]

[0176] * In addition to the above metal ions, the weight ratio becomes 100 through the sum of ions including oxygen (O) and hydrogen (H).

[0177]

[0178] [Batch Process]

[0179] A roasting process of a second raw material containing nickel, sulfur, etc. was performed. Specifically, after charging 2 kg of the raw material in a tube furnace, the raw material was roasted at 850°C for 3 hours while sufficiently injecting oxygen (O2), thereby obtaining a roasted residue (roasted ore) converted from nickel sulfide (NiS) to nickel oxide (NiO).

[0180] [Second Leaching Process]

[0181] The raw material, which was a mixture of the residue after the reduction heat treatment and the residue after the roasting at a weight ratio of 2:8, was subjected to high-temperature and high-pressure leaching.

[0182] In an autoclave, 450 g of mixed raw materials and 3 L of water were mixed and maintained at 240°C and 3500 kPa for 3 hours at an initial acidity of 120 g / L, resulting in a second leaching solution having a nickel concentration of 60 g / L and a nickel leaching rate of 95%.

[0183] [Neutralization process]

[0184] A neutralization process was performed using nickel-containing by-products from the second leaching solution.

[0185] As a result of maintaining the pH at 80℃ for 3 hours at pH 2.5 by adding 2 L of the second leaching liquid containing nickel by-product, a neutralized liquid with a nickel concentration of 82 g / L was obtained.

[0186] [First solvent extraction process]

[0187] A first solvent extraction process was performed to purify nickel contained in the neutralized solution.

[0188] The first loading process is a process of producing a nickel-containing organic extractant by extracting nickel contained in a nickel sulfate aqueous solution with a Di-2-Ethylhexyl phosphoric acid extractant. 500 mL of a nickel sulfate aqueous solution containing nickel at a concentration of 100 g / L and 2,000 mL of an organic extractant were mixed, stirred at pH 5.0 for 10 minutes, and 95% of nickel was extracted through phase separation due to the specific gravity difference.

[0189] Next, a first extraction process was performed to extract impurities contained in the neutralized liquid into an organic phase and simultaneously reversely extract nickel contained in the organic extractant after the first loading into an aqueous phase. 500 mL of the neutralized liquid and 1,500 mL of the organic extractant after the first loading were mixed and stirred at pH 4.0 for 10 minutes, and a first extracted liquid containing 105 g / L of nickel was secured through phase separation due to the specific gravity difference.

[0190] Next, a first scrubbing process was performed to extract cobalt contained in the organic extractant after the first extraction into the water phase. After the first extraction, 1,000 mL of the organic extractant and 100 mL of distilled water were mixed and stirred at pH 2.5 for 10 minutes, and 95% of the cobalt was reverse-extracted through phase separation due to the difference in specific gravity.

[0191] Next, a first stripping process was performed to extract copper contained in the organic extractant after the first scrubbing into the water phase. After the first scrubbing, 1,000 mL of the organic extractant and 100 mL of distilled water were mixed, stirred at pH 1.0 for 10 minutes, and 95% of the copper was reverse-extracted through phase separation due to the difference in specific gravity.

[0192] [Second solvent extraction process]

[0193] A second solvent extraction process was performed to further purify nickel contained in the first extraction liquid within the first solvent extraction.

[0194] The second loading process is a process of producing a nickel-containing organic extractant by extracting nickel contained in a nickel sulfate aqueous solution with a Bis (2,4,4-trimethylpentyl) phosphinic acid extractant. 1,000 mL of a nickel sulfate aqueous solution containing 110 g / L of nickel and 5,500 mL of an organic extractant were mixed, stirred at pH 6.5 for 10 minutes, and 95% of nickel was extracted through phase separation due to the specific gravity difference.

[0195] Next, a second extraction process was performed to extract impurities contained in the first extraction liquid into an organic phase and simultaneously reverse-extract nickel contained in the second loading organic extractant into an aqueous phase. 1,000 mL of the neutralized liquid and 500 mL of the first loading organic extractant were mixed and stirred at pH 5.0 for 10 minutes, and a second extraction liquid containing 115 g / L of nickel was secured through phase separation due to the specific gravity difference.

[0196] Next, a second stripping process was performed to extract impurities contained in the organic extractant after the second extraction into the water phase. After the second extraction, 500 mL of the organic extractant and 50 mL of distilled water were mixed and stirred at pH 1.0 for 10 minutes, and 95% of the impurities were reverse-extracted through phase separation by specific gravity difference.

[0197] [First Sedimentation Process]

[0198] A first precipitation process was performed to remove magnesium contained in the first scrubbing liquid in the first solvent extraction.

[0199] As a result of maintaining the pH at 5.5 for 2 hours by adding sodium fluoride and sodium carbonate to 1 L of the first scrubbing liquid, magnesium was removed and a first precipitation liquid with a cobalt concentration of 27 g / L was obtained.

[0200] [Second Sedimentation Process]

[0201] A second precipitation process was performed to recover copper contained in the first stripping solution in the first solvent extraction.

[0202] After maintaining the pH of 1 L of the first stripping solution at 2.5 with sodium hydroxide for 2 hours, solid-liquid separation was performed using reduced pressure filtration, and after washing with 1 L of distilled water (DIW), a second precipitate residue containing 51% copper was secured.

[0203] Although the embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features thereof.

[0204] Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims

1. (Ai) A reduction heat treatment process for heat-treating a first raw material containing nickel and lithium; (B) A first leaching process for leaching the heat treatment product generated by the above reduction heat treatment process; (A-ii) A roasting process for heat-treating a second raw material containing nickel and sulfur; (C) A second leaching process for leaching the first leaching residue generated by the first leaching process and the roasted ore generated by the roasting process; (D) a neutralization process for neutralizing the second leaching liquid generated by the second leaching process above; and (E) A method for preparing an aqueous nickel sulfate solution comprising a solvent extraction process for purifying nickel from the neutralization solution produced by the above neutralization process.

2. In Paragraph 1, The first raw material and the second raw material each independently comprise at least one selected from the group consisting of oxides, hydroxides, sulfides, and sulfur oxides, and A method for preparing an aqueous nickel sulfate solution, wherein the oxide, hydroxide, sulfide, and sulfate are independently ore, matte, black mass (BM), black powder (BP), mixed hydroxide precipitate (MHP), mixed carbonate precipitate (MCP), mixed sulfide precipitate (MSP), or a mixture thereof.

3. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the first raw material comprises nickel in the form of nickel oxide or a nickel metal complex oxide.

4. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the second raw material comprises nickel in the form of nickel sulfide.

5. In Paragraph 1, A method for producing an aqueous nickel sulfate solution, wherein the above reduction heat treatment process is performed at a temperature of 650 to 950°C by introducing a first raw material into a heat treatment apparatus and injecting nitrogen gas.

6. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the first leaching process is performed using a first leaching agent comprising an inorganic acid, water, or a mixture thereof.

7. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the first leaching solution obtained by the above first leaching process contains lithium, and the first leaching residue contains nickel.

8. In Paragraph 1, A method for producing an aqueous nickel sulfate solution, wherein the above-mentioned roasting process is performed at a temperature of 650 to 950°C by introducing a second raw material into a heat treatment device and injecting oxygen gas.

9. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein in the second leaching process above, the first leaching residue is leached in an atmospheric pressure reactor and the roasted ore is leached in a high-temperature, high-pressure reactor.

10. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the above neutralization process is performed using a neutralizing agent comprising MHP, MCP, nickel hydroxide (Ni(OH)2), nickel carbonate (NiCO3), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), or a mixture thereof.

11. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the above neutralization process is performed at 80°C under conditions of pH 2 to 4.

5.

12. In Paragraph 1, A method for preparing an aqueous nickel sulfate solution, wherein the above neutralization process is performed for 2 hours or more, and the residual acidity of the neutralized solution produced by the above neutralization process is 10 g / L or less.

13. In Paragraph 1, The above solvent extraction process is, (Ei) A first solvent extraction process for purifying nickel from the post-neutralization solution produced by the above neutralization process; and (E-ii) A method for preparing an aqueous nickel sulfate solution comprising a second solvent extraction process for purifying nickel from a first extraction solution produced by the first solvent extraction process.

14. In Paragraph 13, A method for preparing an aqueous nickel sulfate solution, wherein the first solvent extraction process is performed by (i) a first loading process in which a first organic extractant is added to an aqueous nickel sulfate solution to load nickel into the organic phase; (ii) a first extraction process in which an organic extractant is added to a neutralized solution after the first loading to back-extract nickel into the aqueous phase; (iii) a first scrubbing process in which an inorganic extractant is added to the organic extractant after the first extraction to recover cobalt into the aqueous phase; (iv) a first stripping process in which an inorganic extractant is added to the organic extractant after the first scrubbing process to recover copper into the aqueous phase, or a combination thereof.

15. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the volume ratio of the first organic extractant to the aqueous nickel sulfate solution in the above first loading process is 3.5 to 6.

5.

16. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the first loading liquid generated by the first loading process is precipitated, and the precipitated nickel-containing byproduct is used as a neutralizing agent in the neutralization process.

17. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the volume ratio of the organic extractant after the first loading to the liquid after neutralization in the first extraction process is 1.5 to 4.

5.

18. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the volume ratio of an organic extractant to an inorganic extractant in the first scrubbing process and the volume ratio of an organic extractant to an inorganic extractant in the first stripping process are each 9.5 to 12.

5.

19. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the first scrubbing process is performed under conditions of pH 2 to 3.

20. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, wherein the first stripping process is performed under conditions of pH 0.5 to 1.

5.

21. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution in which the organic extractant after the first stripping is reused as the first organic extractant.

22. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, further comprising a first precipitation process for recovering cobalt by adding a first precipitating agent to a first scrubbing liquid generated by the first scrubbing process.

23. In Paragraph 14, A method for preparing an aqueous nickel sulfate solution, further comprising a second precipitation process for recovering copper by adding a second precipitating agent to the first stripping liquid produced by the first stripping process.

24. In Paragraph 13, A method for preparing an aqueous nickel sulfate solution, wherein the second solvent extraction process is performed by (i) a second loading process in which a second organic extractant is added to an aqueous nickel sulfate solution to load nickel into the organic phase; (ii) a second extraction process in which a second organic extractant is added to the first extraction solution to back-extract nickel into the aqueous phase; (iii) a second stripping process in which an inorganic extractant is added to the organic extractant after the second extraction to recover impurities into the aqueous phase, or a combination thereof.

25. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution, wherein the volume ratio of the second organic extractant to the aqueous nickel sulfate solution in the above second loading process is 4.5 to 8.

5.

26. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution, wherein the second loading liquid generated by the second loading process is precipitated, and the precipitated nickel-containing byproduct is used as a neutralizing agent in the neutralization process.

27. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution, wherein the volume ratio of the organic extractant after the second loading to the liquid after the first extraction in the above second extraction process is 0.3 to 1.

5.

28. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution in which the volume ratio of an organic extractant to an inorganic extractant in the second stripping process is 3.5 to 7.

5.

29. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution, wherein the second stripping process is performed under conditions of pH 0.25 to 1.

5.

30. In Paragraph 24, A method for preparing an aqueous nickel sulfate solution in which the organic extractant after the second stripping is reused as a second organic extractant.

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