Complete nickel recovery method for recovering nickel oxide from nickel-containing raw materials

Description

1 / 29 COMPLETE NICKEL RECOVERY METHOD FOR RECOVERING NICKEL OXIDE FROM NICKEL-CONTAINING RAW MATERIALS TECHNICAL FIELD

[0001] This disclosure relates to a method for recovering nickel and a method for producing a nickel solution using the same. More specifically, this disclosure relates to a method for recovering nickel from feedstocks to recover high-purity nickel in the form of nickel oxide. BACKGROUND

[0002] Nickel can be recovered from various raw materials, such as nickel metal, nickel matte, nickel concentrate, and nickel-containing process by-products. It is known that, among various forms of recovered nickel, nickel sulfate is preferably contained in an amount of 99% or greater, with impurities amounting to a few hundred ppm or less, for common cases.

[0003] Conventionally, this nickel sulfate was produced by preparing a high-purity nickel sulfate solution through atmospheric pressure leaching with inorganic acids, neutralization with sodium hydroxide or sodium carbonate, and removal of impurities, and then crystallizing the solution into nickel sulfate hexahydrate.

[0004] However, such conventional methods are disadvantageous in that there is a limited number of raw materials soluble in specific inorganic acids. In conventional methods, substances used as neutralizing agents (e.g., Na) are removed by washing with water after sludge filtration. This method of removing Na increases the volume of wastewater and requires significant processing time, resulting in decreased productivity and increased wastewater treatment costs. SUMMARY Petition 870260065682, dated 03 / 07 / 2026, page 15 / 85 2 / 29

[0005] One embodiment of the present disclosure is to provide a complete process for recovering highly pure nickel from complex nickel-containing feedstocks, which is a hybrid process combining pyrometallurgical and hydrometallurgical technologies, whereby even when various nickel-containing feedstocks are applied, appropriate responses can be made, followed by appropriate subsequent processes to acquire nickel in desired forms.

[0006] Another aspect of this disclosure is to provide an environmentally friendly process that allows for the recycling of process by-products.

[0007] Furthermore, this disclosure aims to provide an economical and environmentally friendly nickel recovery process that allows for the selective isolation of lithium, the conversion of composite compounds into single compounds, and the recovery of inorganic acids from noxious gas through a pyrometallurgical pretreatment, which is combined with a hydrometallurgical recycling process minimizing the influx of Na impurities, thus enabling application to complex feedstocks even in a single process.

[0008] Several embodiments of the present disclosure relate to a nickel recovery method comprising: (A) a reduction heat treatment process for thermally treating a first feedstock containing nickel and lithium; (B) a first leaching process for leaching the thermally treated product produced by the reduction heat treatment process; (A-ii) a first roasting process for thermally treating a second feedstock containing nickel and sulfur; (C) a second leaching process for leaching the first leaching residue produced by the first leaching process and the calcined material produced by the first roasting process; (D) a neutralization process for neutralizing the second leachate (solution Petition 870260065682, dated 03 / 07 / 2026, page 16 / 85 3 / 29 leached) produced by the second leaching process; (E) a purification process to remove impurities contained in the neutralized solution produced by the neutralization process; (F) a precipitation process to perform precipitation on the purified solution produced by the purification process; and (G) a second roasting process to roast the precipitated residue produced by the precipitation process to recover nickel.

[0009] In the nickel recovery method, according to an embodiment of the present disclosure, the first and second feedstocks may each independently include at least one selected from the group of an oxide, a hydroxide, a sulfide and a sulfur oxide, the oxide, hydroxide, sulfide and sulfur oxide containing, each 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.

[0010] In the nickel recovery method, according to one embodiment of the present disclosure, the first feedstock may comprise nickel in the form of nickel oxide or nickel oxide metal composite.

[0011] In the nickel recovery method, according to one embodiment of the present disclosure, the second feedstock may comprise nickel in the form of nickel sulfide.

[0012] In the nickel recovery method, according to an embodiment of the present disclosure, the reduction heat treatment process can be carried out at 650 to 950°C in a manner of introducing the first raw material into a heat treatment equipment and injecting nitrogen gas.

[0013] In the nickel recovery method, according to an embodiment of the present disclosure, the first leaching process can be carried out using a first agent of Petition 870260065682, dated 03 / 07 / 2026, page 17 / 85 4 / 29 Leaching including an inorganic acid, water or a mixture thereof.

[0014] In the nickel recovery method, according to one embodiment of the present disclosure, the first leachate obtained by the first leaching process may contain lithium and the first leaching residue may contain nickel.

[0015] In the nickel recovery method, according to an embodiment of the present disclosure, the first roasting process can be carried out at 650 to 950°C in a manner of introducing the second raw material into a heat treatment equipment and injecting oxygen gas.

[0016] In the nickel recovery method, according to one embodiment of the present disclosure, the first leaching residue and the calcined material can be leached in an atmospheric reactor and a high-temperature, high-pressure reactor, respectively, in the second leaching process.

[0017] In the nickel recovery method, according to one embodiment of the present disclosure, the second leaching process can be carried out using a second leaching agent including an inorganic acid, water or a mixture thereof.

[0018] In the nickel recovery method, according to one embodiment of the present disclosure, the second leaching process can be carried out at a temperature of 150 to 250°C under a pressure of 800 to 4,300 kPa.

[0019] In the nickel recovery method, according to one embodiment of the present disclosure, the second leaching process can be carried out in an environment with an acidity of 100 to 200 g / L.

[0020] In the nickel recovery method, according to one embodiment of the present disclosure, the neutralization process can be carried out using a neutralizing agent including MHP, MCP, nickel hydroxide (Ni(OH)2), carbonate Petition 870260065682, dated 03 / 07 / 2026, p. 18 / 85 5 / 29 nickel (NiCO3), sodium hydroxide (NaOH), sodium carbonate (Na2COs), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), magnesium oxide (MgO), or a mixture thereof.

[0021] In the nickel recovery method, according to an embodiment of the present disclosure, the neutralization process can be carried out at 80°C under pH conditions of 2 to 4.5.

[0022] In the nickel recovery method, according to one embodiment of the present disclosure, the purification process may comprise: (Ei) a first purification process to remove impurities contained in the neutralized solution produced by the neutralization process; (E-ii) a second purification process to remove impurities contained in a first purified solution produced by the first purification process; and (E-iii) a third purification process to remove impurities contained in a second purified solution produced by the second purification process.

[0023] In the nickel recovery method, according to one embodiment of the present disclosure, the first purification process can remove impurities including copper, iron, aluminum, silicon, zinc, cobalt, magnesium or a combination thereof, using a precipitation method.

[0024] In the nickel recovery method, according to one embodiment of the present disclosure, the first purification process can be carried out using (i) a sulfide precipitation process to add a sulfide precipitating agent to the neutralized solution at a level of 1.0 to 2.5 equivalents of a copper content in the neutralized solution, (ii) a hydroxide precipitation process to add a hydroxide precipitating agent to the neutralized solution at a level of 0.8 to 1.5 equivalents of an impurity content in the neutralized solution, or a combination of (i) and (ii). Petition 870260065682, dated 03 / 07 / 2026, page 19 / 85 6 / 29

[0025] In the nickel recovery method, according to one embodiment of the present disclosure, the second purification process can remove impurities including zinc, magnesium, manganese or a combination thereof, using a solvent extraction method.

[0026] In the nickel recovery method, according to one embodiment of the present disclosure, the second purification process can be carried out using (i) a loading process to add a first solvent extractor to the first purified solution to extract impurities including zinc, magnesium or a combination thereof in an organic phase, and (ii) a desorption process to add an inorganic acid to the organic phase to extract impurities including zinc, manganese or a combination thereof, contained in the organic phase, in an aqueous phase.

[0027] In the nickel recovery method, according to one embodiment of the present disclosure, the third purification process can remove impurities including cobalt, using a solvent extraction method.

[0028] In the nickel recovery method, according to one embodiment of the present disclosure, the third purification process may comprise (i) a loading process to add a second solvent extractor to the second purified solution to extract impurities including cobalt in an organic phase, and (ii) a desorption process to add an inorganic acid to the organic phase to extract impurities including cobalt, contained in the organic phase, in an aqueous phase.

[0029] In the nickel recovery method, according to one embodiment of the present disclosure, the precipitation process can be carried out using a precipitating agent including 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. Petition 870260065682, dated 03 / 07 / 2026, p. 20 / 85 7 / 29

[0030] In the nickel recovery method, according to an embodiment of the present disclosure, the precipitation process can be carried out at 85°C under pH conditions of 6.5 to 10.0.

[0031] In the nickel recovery method, according to one embodiment of the present disclosure, the second roasting process can be carried out at 350 to 800°C in a manner of introducing the precipitated residue into a heat treatment equipment and injecting oxygen gas.

[0032] According to the present disclosure, the reduction heat treatment process enables selective leaching and recovery of lithium from lithium-containing feedstocks, which forms strong chemical bonds, through heat treatment.

[0033] According to the present disclosure, a first roasting process is used to transform various nickel-containing raw materials with various forms of chemical bonding into a single phase, ensuring uniformity in subsequent processes, where the process can be flexibly adapted to the constantly changing nickel raw material market, contributing to the applicability of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a diagram illustrating all processes for recovering nickel and manufacturing nickel oxide according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] The modalities of this disclosure are illustrated for the purpose of explaining the technical idea of ​​this disclosure. The scope of the prerogatives, according to this disclosure, is not limited to the modalities presented below or to the detailed descriptions of such modalities.

[0036] In the present invention, unless otherwise specified, % is understood to be based on weight. Petition 870260065682, dated 03 / 07 / 2026, p. 21 / 85 8 / 29

[0037] Below, a description of the present disclosure will be given with reference to the drawing.

[0038] Figure 1 is a diagram showing the entire process for recovering nickel and manufacturing nickel oxide according to an embodiment of the present disclosure.

[0039] Referring to Figure 1, a method for recovering high-purity nickel through a series of processes, and for manufacturing nickel oxide using such refined nickel, can be provided. This method can enhance the versatility of various raw materials and products, operational stability and purity, while reducing manufacturing costs. Hereafter, each process will be described in detail with reference to the respective figures. Raw materials

[0040] As starting materials, first and second raw materials each consist essentially of nickel-containing complex raw materials. The starting materials may each independently include at least one selected from the group of oxides, hydroxides, sulfides, and sulfates. For example, these oxides, hydroxides, sulfides, and sulfates may independently include ore, matte, black mass (BM), black powder (BP), mixed hydroxide precipitate (MHP), mixed carbonate precipitate (MCP), mixed sulfide precipitate (MSP), or a mixture thereof.

[0041] 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. The first raw material may contain impurities such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), sodium (Na), silicon (Si), or a combination thereof, in addition to nickel (Ni) and lithium (Li). As an example, the composition of the first raw material may be given as shown in Table 1. The first raw material may Petition 870260065682, dated 03 / 07 / 2026, p. 22 / 85 9 / 29 contain nickel in the form of nickel oxide (NiO) or a nickel oxide metal composite mixed with other metals. TABLE 1 (% by unit weight) Ni Li Fe Co Cu Zn Mg Al Si Mn Content 5- 35 0.001 -5 0.001- 1.5 0.1- 10 0.1- 7 0.01- 2.0 0.01- 18 0.01- 2.0 0.01- 35 0.01- 5.5

[0042] The second raw material may include ore, matte, mixed sulfide precipitates, or a mixture thereof. For example, the second raw material may contain impurities such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), magnesium (Mg), sodium (Na), silicon (Si), or a combination thereof, in addition to nickel (Ni) and sulfide (S). By way of example, the composition of the second raw material may be given as shown in Table 2. The second raw material may contain nickel in the form of nickel sulfide (NiS). TABLE 2 (% by unit weight) Ni Fe Co Cu Zn Mn Mg Al Si Content 6-30 5-45 0.1- 1.0 0.1- 5.0 0.01- 1.0 0.01- 1.0 0.3- 15 0.1- 1.0 10- 30 Reduction Heat Treatment Process (S10)

[0043] As a pre-processing step for the first raw material, a reduction heat treatment process (S10) can be carried out.

[0044] In the reduction heat treatment process (S10), heat treatment in a reduction atmosphere can be conducted on the first feedstock containing nickel and lithium in the form of complex oxides that can bind to various metals. This treatment can cause a phase transition to oxides and / or carbonates, transforming lithium-containing compounds into substances with high solubility in water or inorganic acids.

[0045] As such, when converting the compound form of Petition 870260065682, dated 03 / 07 / 2026, page 23 / 85 10 / 29 first raw material containing lithium through the reduction heat treatment process (S10) before proceeding to the first leaching process (S20) for lithium leaching / extraction described later, the leaching efficiency in the first leaching process (S20) for lithium leaching / extraction can be improved.

[0046] For example, the reduction heat treatment process (S10) can be carried out using heat treatment equipment such as an electric furnace (e.g., box furnace) or a rotary kiln.

[0047] According to one embodiment of this disclosure, the reduction heat treatment process (S10) can be carried out by introducing the first raw material into the heat treatment equipment and injecting nitrogen gas at a temperature of 650 to 950°C. For example, a certain quantity of the first raw material can be loaded into the heat treatment equipment and, by injecting sufficient nitrogen gas (N2 gas) to maintain a reduction atmosphere, reduction heat treatment can proceed at 650 to 950°C. In this process, not only lithium but also other metals can react, undergoing a phase transition through reactions according to [Reaction Formula 1]. Additionally, further reactions can occur through [Reaction Formula 2] and [Reaction Formula 3]. [Reaction Formula 1] 9LiNi1 / 3Co1 / 3Mn1 / 3O2 + 0.25C ^ 3NiO + 3MnO2 + Co3O4 + 4.5Li2O + 0.25CO2(g) [Reaction Formula 2] 4MnO2 + C ^ 2Mn2O3 + CO2(g) [Reaction Formula 3] Li2O + CO2 (g) ^ Li2CO3 First Leaching Process (S20) Petition 870260065682, dated 03 / 07 / 2026, page 24 / 85 11 / 29

[0048] In the first leaching process (S20), raw materials containing nickel and lithium, which have undergone phase transition by the reduction heat treatment process (S10), can be leached.

[0049] The first leaching process (S20) can be performed after the reduction heat treatment process (S10). For example, the first leaching process (S20) can be carried out in a wet grinding mill. The wet grinding mill can be a ball mill, rod mill, sphere mill, attrition mill, etc. The first leaching process can use a first leaching agent (e.g., inorganic acid, water, or a mixture thereof) to selectively leach the treated lithium.

[0050] In one embodiment, the inorganic acid may be at least one selected from the group of sulfuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3). Inorganic acid diluted with water may be used, and sulfuric acid produced by capturing sulfur dioxide gas generated in the subsequent roasting process (S30) may be used.

[0051] In one embodiment, water can be used as the first leaching agent. In such cases, lithium from lithium-containing feedstock can be leached in the form of lithium hydroxide (LiOH) via [Reaction Formula 4], producing a first leachate. The first leachate may contain lithium.

[0052] [Reaction Formula 4] Li2CO3 + 2H2O ^ 2LiOH + H2O + CO2

[0053] 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 leaching residue.

[0054] The lithium concentration in the first leachate obtained from the first leaching process can be Petition 870260065682, dated 03 / 07 / 2026, page 25 / 85 12 / 29 approximately 0.1 to 8.5 g / L. This leachate can be processed into lithium hydroxide monohydrate (LiOH-ftO), lithium carbonate (Li2CO3), lithium phosphate (Li3PO4), etc., through well-known precipitation and crystallization methods for use as raw materials in lithium-ion battery cathodes.

[0055] MHP and MCP generated in the lithium-ion battery recycling process, which may contain Li in addition to Ni, Co, Mn, can be used as the first raw material to perform the first leaching process. First Roasting Process (S30)

[0056] A first roasting process (S30) can be carried out as a pre-processing step for the second raw material.

[0057] In the first roasting process (S30), the phase transition of nickel-containing raw materials bonded in various compounds occurs, along with the recycling of sulfuric gas (SO2 gas) generated during the heat treatment process for the production of inorganic acids.

[0058] Before the first roasting process (S30) is carried out, the second nickel-containing feedstock may be in the form of a sulfide, which can be converted into an oxide by the first roasting process (S30). Leaching the second nickel-containing feedstock directly in its sulfide state can result in low leaching efficiency due to the generation of hydrogen sulfide gas (H2S gas) and metal reprecipitation reactions. Therefore, by converting the compound form of the second nickel-containing feedstock through the roasting process (S30) before conducting the second leaching process (S40), the leaching efficiency in the second leaching process (S40) can be improved. For this purpose, the roasting process (S30) can be carried out using heat treatment equipment, such as an electric furnace (Box Furnace) or a rotary kiln. Petition 870260065682, dated 03 / 07 / 2026, page 26 / 85 13 / 29

[0059] According to one embodiment of the present disclosure, the first roasting process (S30) may involve loading a certain amount of nickel-containing feedstock into an electric furnace, injecting sufficient oxygen (O2) for conversion to nickel oxide, and conducting roasting at 650 to 950°C. During this process, not only nickel but also other impurities may react, undergoing a phase transition through the reaction described in [Reaction Formula 5] below. Furthermore, the sulfur dioxide gas generated during the first roasting process (S30) may be captured by a separate collection facility and converted to sulfuric acid (H2SO4) by mixing with water, which may then be used in subsequent leaching processes. [Reaction Formula 5] 2NiS + 3O2 → 2NiO + 2SO2 Second Leaching Process (S40)

[0060] In the second leaching process (S40), the post-roasting residue (calcined material) that underwent phase transition by the first roasting process (S30), together with the first leaching residue remaining in the residue from the first leaching process (S20), can be leached. The second leaching process (S40) can be carried out after the first roasting process (S30) and the first leaching process. In the second leaching process, the post-roasting residue can be leached in a high-temperature, high-pressure reactor, while the first leaching residue can be leached in an atmospheric pressure reactor. The second leaching process (S40) can utilize a second leaching agent (e.g., inorganic acid, water, or a mixture thereof). In one embodiment, the second leaching process (S40) can be conducted using inorganic acid.For example, at least one inorganic acid selected from the group of sulfuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3), diluted inorganic acid. Petition 870260065682, dated 03 / 07 / 2026, page 27 / 85 14 / 29 with water or sulfuric acid produced by capturing sulfur dioxide gas generated in the first preceding roasting process (S30) can be used.

[0061] In one embodiment, sulfuric acid can be used as a second leaching agent. For this purpose, nickel can be leached from the first leaching residue and post-roasting residue containing nickel in the form of nickel sulfate (NiSO4), generating a second leachate, as per [Reaction Formula 6].

[0062] [Reaction Formula 6] NiO + H2SO4 ^ NiSO4 + H2O

[0063] The second leaching process (S40) can be carried out at a temperature of approximately 150 to 250°C and a pressure of 800 to 4,300 kPa. The saturation vapor pressure, due to the high reaction temperature, may lead to the maintenance of a certain pressure level, and additional pressure may be applied for a complete reaction.

[0064] For example, the second leaching process (S40) can be carried out in an environment with an acidity of 100 to 200 g / L. The second leaching process (S40) can be carried out in a low pH acidic environment to ensure sufficient second leachate, followed by conducting a subsequent neutralization process (S50).

[0065] In one embodiment, not only nickel but also other impurities can be leached together. For example, impurities such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), etc., can be leached together with nickel and included in the second leachate.

[0066] The concentration of nickel in the second leachate obtained from the second leaching process (S40) can be approximately 45 to 105 g / L, and the residual acidity can be 10 to 80 g / L. Neutralization Process (S50) Petition 870260065682, dated 03 / 07 / 2026, page 28 / 85 15 / 29

[0067] In the neutralization process (S50), the second leachate produced by the second leaching process (S40) can be neutralized. The neutralization process (S50) can be carried out after the second leaching process (S40).

[0068] If the second leachate is produced in a high pH environment, the volume of the second leachate produced may be reduced.

[0069] In one embodiment, after securing sufficient second leachate by conducting the second leaching process (S40) in a low pH acidic environment, the neutralization process (S50) can be carried out.

[0070] In the neutralization process (S50), a neutralizing agent may be introduced to increase the pH of the second leachate generated in the second leaching process (S40). The addition of the neutralizing agent may also prepare for a subsequent purification process.

[0071] In one embodiment, the neutralizing agent may be at least one selected from the group of by-products containing nickel (MHP, MCP), nickel hydroxide (Ni(OH)2), nickel carbonate (N1CO3), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO) and magnesium oxide (MgO).

[0072] The reason for using MHP and MCP as raw materials and also as neutralizing agents may be that hydroxides and carbonates generally have high solubility in acids even without roasting, which eliminates the need for processing under expensive high temperature and high pressure leaching conditions, and also consumes the acid (H2SO4) remaining after the second leaching process (S40), thus preparing in advance for the purification process (S60) which occurs in a high pH range. Petition 870260065682, dated 03 / 07 / 2026, page 29 / 85 16 / 29

[0073] In one embodiment, the neutralization process (S50) can use nickel-containing byproducts in the form of a wet cake. By using nickel-containing byproducts, the amount of neutralizing agent added separately can be reduced, leading to cost reduction. Additionally, the introduction of additional impurities can be avoided, and the concentration of nickel in the neutralized solution can be increased.

[0074] In one embodiment, the neutralization process (S50) can be carried out at 80°C under conditions of approximately pH 2 to 4.5. During this process, impurities including iron (Fe) and aluminum (Al) can precipitate and be removed. Purification Process (S60)

[0075] In the purification process (S60), impurities contained in the neutralized solution produced by the neutralization process (S50) can be removed so that the neutralized solution can be purified. The purification process (S60) can be carried out after the neutralization process (S50).

[0076] In one embodiment, the purification process (S60) may include a first purification process (S61) that may remove impurities contained in the neutralized solution produced by the neutralization process (S50); a second purification process (S62) that may remove impurities contained in the first purified solution produced by the first purification process (S61); and a third purification process (S63) that may remove impurities contained in the second purified solution produced by the second purification process (S62). First Purification Process (S61)

[0077] In the first purification process (S61), the neutralized solution produced by the neutralization process (S50) can be purified. The neutralized solution can be the leachate that has been neutralized. The first purification process (S61) can be a process to remove impurities from the neutralized solution after the neutralization process (S50). Petition 870260065682, dated 03 / 07 / 2026, page 30 / 85 17 / 29

[0078] The first purification process (S61) may be a process that removes impurities using the precipitation method. In the first purification process (S61), impurities may be removed by a sulfide precipitation method using at least one selected from the group of sodium sulfide (Na2S), sodium hydrosulfide (NaSH), ammonium hydrosulfide (NH4HS), and hydrogen sulfide (H2S) as a precipitant. Through this process, precipitates consisting essentially of copper sulfide (CuS) and containing impurities such as zinc, lead, and cadmium may be recovered. The precipitates may then be processed into metallic copper through extraction and solvent replacement or other purification processes.

[0079] Furthermore, in the first purification process (S61), impurities can be removed by a hydroxide precipitation method using at least one selected from the group of sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO) and magnesium oxide (MgO). This process can allow the precipitation and removal of impurities such as aluminum (Al), iron (Fe), chromium (Cr), silicon (Si), etc. The reaction can be as follows in [Reaction Formula 7] when using sodium hydrosulfide as the precipitant, and in [Reaction Formula 8] when using sodium hydroxide.

[0080] [Reaction Formula 7] 2CuSO4 + 2NaSH ^ Na2SO4 + H2SO4 + 2CuS;

[0081] [Reaction Formula 8] MSO4 + 2NaOH ^ Na2SO4 + M(OH)2l (M=Al, Fe, Cr, Si)

[0082] During the sulfide precipitation method of the first purification process (S61), the precipitant may be introduced at an equivalent ratio of about 1.0 to 2.5 relative to the copper contained in the neutralized solution. If the sulfide precipitant is introduced at an equivalent ratio less than 1.0 relative to the copper, the precipitation rate of Petition 870260065682, dated 03 / 07 / 2026, p. 31 / 85 18 / 29 copper may be 83% or less, indicating an incomplete reaction. By introducing the sulfide precipitant in an equivalent ratio exceeding 2.5, impurities originating from the precipitant may enter excessively and negatively affect the process, potentially reducing the recovery rate due to nickel coprecipitation. The pH at which the reaction can be carried out ranges from 0.8 to 2.5 at 70°C.

[0083] In the purification hydroxide precipitation method, the precipitant can be introduced in an equivalent ratio of about 0.8 to 1.5 relative to the impurities contained in the neutralized solution. If the hydroxide precipitant is introduced in an equivalent ratio less than 0.8 relative to impurities, the impurity removal rate may be 85% or less, indicating an incomplete reaction. By introducing the precipitant in an equivalent ratio exceeding 1.5, impurities originating from the precipitant may enter excessively and negatively affect the process, potentially reducing the recovery rate due to nickel coprecipitation. For this purpose, the pH at which the reaction can be carried out ranges from 2.5 to 4.5 at 60°C.

[0084] After the first purification process (S61), the content of copper, iron, aluminum and silicon, in the first purified solution, can be reduced to 5 mg / L or less each, and the content of zinc, cobalt and magnesium can be reduced to 20 mg / L or less each. Second Purification Process (S62)

[0085] The second purification process (S62) may allow further purification of the first purified solution produced by the first purification process (S61). The second purification process (S62) may be carried out after the first purification process (S61) and may be a process using solvent extraction to remove impurities. Petition 870260065682, dated 03 / 07 / 2026, page 32 / 85 19 / 29

[0086] In the second purification process (S62), an organic extractor can be used to remove impurities such as zinc (Zn), magnesium (Mg) and manganese (Mn).

[0087] In one embodiment, the second purification process (S62) may include a loading process and a desorption process. At least one selected from the group of di-2-ethylhexyl phosphoric acid, mono-2-ethylhexyl (2-ethylhexyl)phosphonate and bis (2,4,4-trimethylpentyl)phosphinic acid may be available as the organic extractant.

[0088] The loading process can be a process to extract impurities, such as zinc, magnesium, manganese, or a combination thereof, contained in the first purified solution in the organic phase. The loading process can be a process to extract zinc, magnesium, and manganese contained in the first purified solution after the first purification process (S61) in an organic phase using the organic extractor.

[0089] The organic-to-aqueous phase ratio in the loading process can be approximately 1 to 3 by volume. When the volume ratio between the organic-to-aqueous phase is below 1, the extraction efficiency can drop to 90% or less due to incomplete binding of the target metals to the organic extractant. A volume ratio between the organic-to-aqueous phase exceeding 3 can increase the process cost due to excessive use of the organic extractant. The pH range for the loading process can be controlled to 2.0 to 4.0 using at least one selected from the group of sodium hydroxide (NaOH) or sodium carbonate (Na2CO3). Furthermore, the reaction temperature can be set to 30 to 40°C.

[0090] After the extraction of zinc, magnesium, and manganese in the organic phase, phase separation, due to the density difference between the organic and aqueous phases, may allow the formation of a second purified solution. The second purified solution may be an aqueous solution containing nickel that now Petition 870260065682, dated 03 / 07 / 2026, page 33 / 85 20 / 29 is devoid of zinc and magnesium and may contain nickel in concentrations of 50 to 100 g / L.

[0091] The organic phase containing zinc and magnesium can be subjected to a desorption process. In the desorption process, inorganic acid can be added to the organic phase after the loading process to remove impurities. This desorption process can be a back-extraction process to pull the zinc, magnesium, and manganese contained in the organic phase back into the aqueous phase.

[0092] The volume ratio between the organic and aqueous phases in the desorption process can be approximately 5 to 10. When the volume ratio between the organic and aqueous phases in the desorption process is below 5, water usage can increase while complete impurity extraction is still possible. When the volume ratio between the organic and aqueous phases in the desorption process is above 10, the impurity back-extraction efficiency may decrease. In the desorption process, the pH range can be controlled from approximately 0.5 to 1.5 using sulfuric acid (H2SO4). Additionally, a reaction temperature can be set at 30 to 40°C. Third Purification Process (S63)

[0093] The third purification process (S63) may allow further refinement of the second purified solution produced by the second purification process (S62). The third purification process (S63) may be conducted after the second purification process (S62). The third purification process (S63) may be a process to remove impurities using a solvent extraction technique. In the third purification process (S63), an organic extractant may be employed to remove impurities including cobalt. In one embodiment, the third purification process (S63) may include a loading process and a desorption process. As the organic extractant, at least one selected from the acid group Petition 870260065682, dated 03 / 07 / 2026, page 34 / 85 21 / 29 di-2-ethylhexyl phosphoric, mono-2-ethylhexyl (2-ethylhexyl)phosphonate and bis (2,4,4-trimethylpentyl) phosphinic acid can be used.

[0094] In the loading process, cobalt-containing impurities can be extracted in an organic phase from the second purified solution. The loading process can be a process in which an organic extractor is used to extract cobalt in an organic phase from the second purified solution after the second purification process (S62).

[0095] The amount of organic phase incorporated into the loading process can be a volume ratio of approximately 1 to 3 relative to the aqueous phase. When the volume ratio between the organic and aqueous phases is less than 1, the target metal binds incompletely to the organic extractant, resulting in an extraction rate of 90% or less. A weight ratio between the organic and aqueous phases exceeding 3 can lead to excessive use of the organic extractant, increasing process costs. The pH range for the loading process can be controlled between 4 and 5 using sodium hydroxide (NaOH) or sodium carbonate (Na2CO3), with the reaction temperature maintained between 30°C and 40°C.

[0096] Once the extraction of cobalt in the organic phase by mixing the aqueous and organic phases is complete, the difference in specific gravity between the organic and aqueous phases may allow for phase separation. This phase separation may yield a third purified solution, which is an aqueous solution containing nickel and depleted cobalt with a nickel content of 65 to 125 g / L.

[0097] The organic phase containing cobalt can be subjected to a desorption process.

[0098] In the desorption process subsequent to the loading process, an inorganic acid may be added to the organic phase to remove the cobalt contained in the organic phase. The Petition 870260065682, dated 03 / 07 / 2026, page 35 / 85 22 / 29 desorption process can be a back-extraction process to pull cobalt back into the aqueous phase from the organic phase.

[0099] The volume ratio between the organic and aqueous phases in the desorption process can be approximately 3 to 10. When the volume ratio between the organic and aqueous phases in the desorption process is below 3, water usage can increase while complete impurity extraction is still possible. When the volume ratio between the organic and aqueous phases in the desorption process is above 10, the impurity back-extraction efficiency may decrease. In the desorption process, the pH range can be controlled from approximately 0.5 to 1.5 using sulfuric acid (H2SO4). Additionally, a reaction temperature can be set at 30 to 40°C.

[0100] Once the extraction of cobalt from the organic phase by mixing the aqueous and organic phases is complete, the difference in specific gravity between the organic and aqueous phases can allow for phase separation. This phase separation can yield a cobalt-containing solution that can be further purified by precipitation and crystallization to generate high-purity cobalt sulfate. Precipitation Process (S70)

[0101] The precipitation process (S70) can allow the precipitation of the purified solution produced by the purification process (S60) (for example, the third purification process (S63)). The precipitation process (S70) can be carried out after the third purification process (S63).

[0102] The precipitation process (S70) may be a process in which nickel is precipitated using a precipitation method to remove impurities. In the precipitation process (S70), at least one selected from the group of sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO) and magnesium oxide (MgO) may be used as a precipitant to precipitate nickel. Petition 870260065682, dated 03 / 07 / 2026, page 36 / 85 23 / 29

[0103] When sodium carbonate is used as a precipitant, the reaction can be represented by Reaction Formula 9 below.

[0104] [Reaction Formula 9] NiSO4 + 2NaOH + XH2O ^ Ni(OH)2 + Na2SO4 + XH2O (x^Ü)

[0105] The precipitation process (S70) can be carried out at a temperature of 75 to 85°C and a pH of 6.5 to 10.0. A pH below 6.5 can result in a nickel recovery rate of less than 80%. When the pH is above 10.0, impurities attributed to the precipitant can be abundant and introduced, negatively affecting the process and thus reducing profitability due to excessive use of the precipitant.

[0106] Impurities including sodium (Na) and potassium (K) can be partially removed during the precipitation process (S70). For example, after the precipitation reaction, the process to recover nickel-containing precipitates through solid-liquid separation and washing them with dilute acid and water can remove at least some of these impurities. Second Roasting Process (S80)

[0107] In the second calcination process (S80), the precipitated residue produced by the precipitation process (S70) can be roasted. The second roasting process (S80) can be carried out after the precipitation process (S70).

[0108] Before the second roasting process (S80) is carried out, the precipitated residue containing nickel may be in the form of hydroxide or carbonate, and may be converted into oxide by the second roasting process (S80). The second roasting process (S80) may be carried out using heat treatment equipment, such as a box furnace or rotary kiln.

[0109] According to an embodiment of the present disclosure, in the second calcination process (S80), a certain Petition 870260065682, dated 03 / 07 / 2026, page 37 / 85 24 / 29 quantity of nickel-containing raw material can be loaded into an electric furnace, and sufficient oxygen (O2) can be injected for conversion to nickel oxide, with roasting proceeding at 350 to 800°C. During this process, a phase change can occur through Reaction Formula 10 below.

[0110] [Reaction Formula 10] 2NiCOa^3Ni(OH)2^4H2O + O2 ^ 5NiO + 7H2O(g) + 2CO2 (g)

[0111] The nickel-containing oxide produced by the present disclosure can be used as a nickel compound in powder form and, through further processing, can be suitablely used as a precursor to the nickel feedstock of the cathode active material in secondary lithium batteries. EXPERIMENTAL EXAMPLES [Raw materials]

[0112] As shown in Table 3 below, the elements were mixed in predetermined ratios to prepare first raw materials A to C. Table 3 (% by unit weight) Ni Li Co Cu Fe Zn Mg Al Mn A 26.0 4.5 5.0 0.7 0.01 0.005 0.004 0.5 4.5 B 12.0 0.001 0.3 2.7 34.0 0.02 2.0 0.4 0.02 C 35.0 0.1 3.0 0.01 0.05 0.5 3.0 0.06 6.0

[0113] * Each of the first raw materials contained sulfur (S), oxygen (O) and hydrogen (H) ions in addition to the metal ions to make up 100% by weight.

[0114] A second raw material was prepared to contain elements, as indicated in Table 4 below. TABLE 4 (% by unit weight) Petition 870260065682, dated 03 / 07 / 2026, page 38 / 85 25 / 29 Ni Fe Co Cu Zn Mn Mg Al S 13.6 32.8 0.3 2.0 0.02 0.02 2.5 0.4 25.7

[0115] * The second raw material contained oxygen (O) and hydrogen (H) ions in addition to the metal ions to make up 100% by weight. [Reduction Heat Treatment Process]

[0116] A reduction heat treatment was performed on the first raw material containing nickel, lithium, etc. Specifically, 2.0 kg of the raw material were loaded into a rotary furnace and then subjected to reduction heat treatment at 850°C for 3 hours while a reduction atmosphere was maintained using N2 gas, to generate a post-reduction heat treatment residue that was converted from lithium oxide (Li2O) to lithium carbonate (Li2CO3). [First Leaching Process]

[0117] Lithium recovery was carried out by leaching water from the residue after thermal reduction treatment. Specifically, 100 g of the residue were loaded into a ball mill and then ground and leached with 2.5 L of water (H2O) for 2 hours. Subsequently, solid-liquid separation using vacuum filtration yielded a first leaching residue containing the elements shown in Table 5 and a first leachate containing the elements shown in Table 6 was ensured. TABLE 5 (% by unit weight) Ni Co Fe Mg Al Cu Mn Zn 36.0 7.0 0.02 0.001 0.6 0.9 6.5 0.007

[0118] In addition to metal ions, oxygen (O) and hydrogen (H) ions were contained to make up 100% by weight. TABLE 6 (g / L unit) Petition 870260065682, dated 03 / 07 / 2026, page 39 / 85 26 / 29 Li Na Co Fe Mg Al Cu Mn Zn 1.8 24.0 0.1 0.02 0.01 0.05 0.1 0.05 0.01 [First Roasting Process]

[0119] A roasting process was carried out on a second raw material containing nickel and sulfur. In summary, 2 kg of the raw material were loaded into a rotary kiln and roasted at 850°C for 3 hours by injecting sufficient oxygen (O2) to obtain roasted residue (calcined material) which was converted from nickel sulfide (NiS) to nickel oxide (NiO). [Second Leaching Process]

[0120] A raw material in which post-reduction heat treatment residue and post-roasting residue were mixed in a weight ratio of 2:8 was subjected to leaching at high temperature and high pressure.

[0121] In an autoclave, a mixture of 450 g of the mixed raw materials and 3 L of water was maintained at an initial acidity of 120 g / L and a temperature of 240°C under 3,500 kPa for 3 hours to generate a second leachate with a nickel leaching rate of 95% and a nickel concentration of 60 g / L. [Neutralization Process]

[0122] A neutralization process was carried out using nickel-containing byproducts in the second leachate.

[0123] By controlling the pH of 2L of the second leachate to 2.5 with the addition of nickel-containing byproducts and maintaining it at 80°C for 3 hours, a neutralized solution with a nickel concentration of 82 g / L was ensured. [First Purification Process]

[0124] A first purification process was conducted using a precipitation method to remove impurities contained in the neutralized solution. Petition 870260065682, dated 03 / 07 / 2026, page 40 / 85 27 / 29

[0125] By adding sodium hydrosulfide (NaSH) in an amount of 1.3 equivalents (eq) of the copper (Cu) content to the neutralized solution and maintaining a pH of 2.5 at 70°C for 2 hours, copper was removed by 99.8%. Furthermore, the neutralized solution was maintained at a pH of 4.5 for 2 hours with the byproducts containing nickel and sodium hydroxide (NaOH) to generate a first purified solution in which impurities including aluminum, iron, and silicon, contained therein, were removed by 99.5% or more. [Second Purification Process]

[0126] A second purification process was carried out using a solvent extraction method to remove impurities contained in the first purified solution.

[0127] Impurities including zinc and magnesium were removed by extraction. For this purpose, 500 mL of the first purified solution were mixed with 1000 mL of 25% diluted di-2-ethylhexyl phosphoric acid as an extractant, and the mixture was stirred at a pH of 3.5 at 40°C for 10 minutes. Phase separation by specific gravity difference allowed the extraction of zinc by 99% and magnesium by 43%. Complete extraction of impurities was possible using a countercurrent exchange method in a decanter mixer. [Third Purification Process]

[0128] The third purification process was carried out using a solvent extraction method to remove cobalt contained in the second purified solution.

[0129] A mixture of 500 mL of purified second solution containing cobalt and 1000 mL of bis(2,4,4-trimethylpentyl)phosphinic acid diluted to 25% as an extractant was stirred at a pH of 5.0 at 40°C for 10 minutes, and phase separation by specific gravity difference allowed the extraction of cobalt by approximately 55%. Complete extraction of impurities was possible using a countercurrent exchange method in a decanter mixer. Petition 870260065682, dated 03 / 07 / 2026, page 41 / 85 28 / 29

[0130] This process allowed the removal of cobalt to levels of 3 mg / L or less to generate a post-third purification solution containing the elements provided in Table 7 below. TABLE 7 (mg / L unit) Ni Co Fe Mg Al Cu Mn Zn 58 g / L 2.5 0.01 0.2 0.01 0.01 0.05 0.001 [Precipitation Process]

[0131] A precipitation process was conducted to recover nickel contained in the third purified solution in the form of a precipitate.

[0132] Using sodium carbonate (Na2CO3), the pH was maintained at 8.0 at 85°C for 2 hours for 1 L of the third refined solution containing 42 g / L of nickel. Solid-liquid separation using vacuum filtration was performed, followed by rinsing with 1 L of distilled water (DIW) to generate precipitated residue containing elements shown in Table 8. TABLE 8 (% by unit weight) Ni Co Fe Mg Al Cu Mn Zn 43 0.01 0.01 5.0 0.01 0.01 0.7 0.01 [Second Roasting Process]

[0133] To convert the nickel contained in the precipitated residue from hydroxide or carbonate form into oxide form, the second roasting process was carried out.

[0134] Specifically, 2 kg of raw material were loaded into a rotary kiln and, with sufficient oxygen (O2) injection, the material was roasted at 400°C for 3 hours to convert from nickel hydroxide (Ni(OH)2) or nickel carbonate (NiCO3) form to nickel oxide (NiO), and nickel oxide containing the elements listed in Table 9 below was obtained. TABLE 9 (% by unit weight) Petition 870260065682, dated 03 / 07 / 2026, page 42 / 85 29 / 29 Ni Co Fe Mg Al Cu Mn Zn 70 0.13 0.01 1.6 0.01 0.01 0.03 0.01

[0135] Although the embodiments of this disclosure have been described with reference to the accompanying drawings, those skilled in the art to whom this disclosure pertains will be able to understand that the embodiments can be implemented in other specific forms without changing the technical spirit or essential features of this disclosure.

[0136] Therefore, it should be understood that the embodiments described above are illustrative and not limiting in all respects. The scope of this disclosure is defined by the claims and not by the detailed description. It should be understood that all changes or modified forms derived from the meaning and scope of the claims and concepts equivalent to them are included in the scope of this disclosure. Petition 870260065682, dated 03 / 07 / 2026, p. 43 / 85

Claims

1 / 5 CLAIMS 1. Nickel recovery method, characterized in that it comprises: (A) a reduction heat treatment process for thermally treating a first feedstock containing nickel and lithium; (B) a first leaching process for leaching the thermally treated product produced by the reduction heat treatment process; (A-ii) a first roasting process for thermally treating a second feedstock containing nickel and sulfur; (C) a second leaching process for leaching the first leaching residue produced by the first leaching process and calcining produced by the roasting process; (D) a neutralization process for neutralizing the second leachate produced by the second leaching process; (E) a purification process for removing impurities contained in the neutralized solution produced by the neutralization process;(F) a precipitation process to perform precipitation on the purified solution produced by the purification process; and (G) a second roasting process to roast the precipitated residue produced by the precipitation process to recover nickel; wherein the first leaching residue and the calcined residue are leached together in the second leaching process.

2. Nickel recovery method according to claim 1, characterized in that the first raw material and the second raw material each independently comprise at least one selected from the group of an oxide, a hydroxide, a sulfide and a sulfur oxide, Petition 870260065682, dated 03 / 07 / 2026, page 73 / 85 2 / 5 the oxide, hydroxide, sulfide and sulfur oxide containing, each 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. A method for recovering nickel, according to claim 1, characterized in that the first feedstock comprises nickel in the form of nickel oxide or nickel-metal oxide composite.

4. Nickel recovery method according to claim 1, characterized in that the second feedstock comprises nickel in the form of nickel sulfide.

5. Nickel recovery method according to claim 1, characterized in that the reduction heat treatment process is carried out at 650 to 950°C in a manner of introducing the first raw material into a heat treatment equipment and injecting nitrogen gas.

6. Nickel recovery method according to claim 1, characterized in that the first leaching process is carried out using a first leaching agent including an inorganic acid, water or a mixture thereof.

7. Nickel recovery method according to claim 1, characterized in that the first leachate obtained by the first leaching process contains lithium and the first leaching residue contains nickel.

8. Nickel recovery method according to claim 1, characterized in that the first roasting process is carried out at 650 to 950°C in a manner that introduces the second raw material into a heat treatment equipment and injects oxygen gas. Petition 870260065682, dated 03 / 07 / 2026, pp. 74 / 85 3 / 5 9. Nickel recovery method according to claim 1, characterized in that, in the second leaching process, the first leaching residue and the calcined material are leached in an atmospheric reactor and a high-temperature, high-pressure reactor, respectively.

10. Nickel recovery method according to claim 1, characterized in that the second leaching process is carried out using a second leaching agent including an inorganic acid, water or a mixture thereof.

11. Nickel recovery method according to claim 1, characterized in that the second leaching process is carried out at a temperature of 150 to 250°C under a pressure of 800 to 4,300 kPa.

12. Nickel recovery method according to claim 1, characterized in that the second leaching process is carried out in an environment with an acidity of 100 to 200 g / L.

13. Nickel recovery method according to claim 1, characterized in that the neutralization process is carried out using a neutralizing agent including MHP, MCP, nickel hydroxide (Ni(OH)2), nickel carbonate (N1CO3), 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.

14. Nickel recovery method according to claim 1, characterized in that the neutralization process is carried out at 80°C under pH conditions of 2 to 4.

5.

15. Nickel recovery method according to claim 1, characterized in that the purification process comprises: Petition 870260065682, dated 03 / 07 / 2026, page 75 / 85 4 / 5 (Ei) a first purification process to remove impurities contained in the neutralized solution produced by the neutralization process; (E-ii) a second purification process to remove impurities contained in a first purified solution produced by the first purification process; and (E-iii) a third purification process to remove impurities contained in a second purified solution produced by the second purification process.

16. Nickel recovery method according to claim 15, characterized in that the first purification process removes impurities including copper, iron, aluminum, silicon, zinc, cobalt, magnesium or a combination thereof, using a precipitation method.

17. Nickel recovery method according to claim 15, characterized in that the first purification process is carried out using (i) a sulfide precipitation process to add a sulfide precipitating agent to the neutralized solution at a level of 1.0 to 2.5 equivalents of a copper content in the neutralized solution, (ii) a hydroxide precipitation process to add a hydroxide precipitating agent to the neutralized solution at a level of 0.8 to 1.5 equivalents of an impurity content in the neutralized solution, or a combination of (i) and (ii).

18. Nickel recovery method according to claim 15, characterized in that the second purification process removes impurities including zinc, magnesium, manganese or a combination thereof, using a solvent extraction method.

19. Nickel recovery method according to claim 15, characterized in that the second purification process is carried out using (i) a loading process to add a first solvent extractor to the first purified solution to extract impurities including zinc, magnesium, manganese or a combination thereof in an organic phase, and (ii) a desorption process to add an inorganic acid to the organic phase to extract impurities including zinc, magnesium, manganese or a combination thereof, contained in the organic phase, in an aqueous phase.

20. Nickel recovery method according to claim 15, characterized in that the third purification process removes impurities including cobalt, using a solvent extraction method.

21. Nickel recovery method according to claim 15, characterized in that the third purification process comprises (i) a loading process to add a second solvent extractor to the second purified solution to extract impurities including cobalt in an organic phase, and (ii) a desorption process to add an inorganic acid to the organic phase to extract impurities including cobalt, contained in the organic phase, in an aqueous phase.

22. Nickel recovery method according to claim 1, characterized in that the precipitation process is carried out using a precipitating agent including 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.

23. Nickel recovery method according to claim 1, characterized in that the precipitation process is carried out at 85°C under pH conditions of 6.5 to 10.

0.

24. Nickel recovery method according to claim 1, characterized in that the second roasting process is carried out at 350 to 800°C in a manner that introduces the precipitated residue into a heat treatment apparatus and injects oxygen gas. Petition 870260065682, dated 03 / 07 / 2026, pp. 77 / 85

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