RU2841255C1 - Complex method of extracting nickel for extracting nickel oxide from raw materials containing nickel - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to extraction of high-purity nickel from complex raw materials. Method involves a process of reducing heat treatment of a first raw material containing nickel and lithium and a first leaching of the obtained treated product. Further, the first calcination process is carried out with thermal treatment of the second raw material containing nickel and sulphur. After that, the second leaching process is carried out with leaching of the first leaching residue obtained as a result of the first leaching process, and the roasting product obtained as a result of the first roasting process. Obtained second leaching product is neutralized to obtain a neutralized solution and purified with removal of impurities. From the purified solution, deposition and a second process of burning the precipitated residue obtained as a result of the deposition process are carried out, with extraction of nickel.

EFFECT: processing of secondary raw materials with obtaining of nickel of high purity by environmentally friendly method is provided.

23 cl, 9 tbl, 1 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[01] The present invention relates to a method for extracting nickel and a method for producing a nickel solution using the said. More specifically, the present invention relates to a method for extracting nickel from raw materials for extracting high-purity nickel in the form of nickel oxide.

BACKGROUND OF THE INVENTION

[02] Nickel can be recovered from various raw materials such as metallic nickel, nickel matte, nickel concentrate and nickel-containing by-products from processes. It is known that among the various forms of recovered nickel, nickel sulfate is preferably contained in an amount of 99% or more, with impurities being several hundred ppm or less in ordinary cases.

[03] Typically, such nickel sulfate was obtained by obtaining a high-purity nickel sulfate solution through atmospheric pressure leaching using inorganic acids, neutralizing with sodium hydroxide or sodium carbonate and removing impurities, and then crystallizing the solution into nickel sulfate hexahydrate.

[04] However, such conventional methods are disadvantageous because there are limited 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 route of Na removal increases the volume of wastewater and requires a long processing time, resulting in lower productivity and higher costs of wastewater treatment.

ESSENCE OF THE INVENTION

[05] In a first aspect of the present invention, there is provided a method for recovering nickel, comprising: (A-i) a reductive heat treatment process of heat treating a first raw material containing nickel and lithium; (B) a first leaching process of leaching a heat-treated product obtained by performing the reductive heat treatment process; (A-ii) a first roasting process of heat treating a second raw material containing nickel and sulfur; (C) a second leaching process of leaching a first leach residue obtained by performing the first leaching process and a roasting product obtained by performing the first roasting process; (D) a neutralization process of neutralizing a second leach product obtained by performing the second leaching process; (E) a purification process of removing impurities contained in the neutralized solution obtained by performing the neutralization process; (F) a precipitation process of performing precipitation in a purified solution obtained as a result of performing the purification process; and (G) a second roasting process of roasting the precipitated residue obtained as a result of performing the precipitation process to extract nickel.

[06] In one embodiment, each of the first feedstock and the second feedstock independently comprises at least one material selected from the group consisting of an oxide, a hydroxide, a sulfide, and a sulfur oxide, wherein each of the oxide, hydroxide, sulfide, and sulfur oxide independently comprises an ore, a matte, a black mass (BM), a black powder (BP), a mixed hydroxide precipitate (MHP), a mixed carbonate precipitate (MCP), a mixed sulfide precipitate (MSP), or a mixture thereof.

[07] In another embodiment, the first feedstock material comprises nickel in the form of nickel oxide or a complex oxide of metallic nickel.

[08] In another embodiment, the second feedstock material comprises nickel in the form of nickel sulfide.

[09] In another embodiment, the reduction heat treatment process is carried out at 650-950°C in such a way as to introduce the first raw material into the heat treatment equipment and pump nitrogen gas.

[010] In another embodiment, the first leaching process is carried out using a first leaching agent comprising an inorganic acid, water, or a mixture thereof.

[011] In another embodiment, the first leachate obtained from the first leaching process comprises lithium and the first leach residue comprises nickel.

[012] In another embodiment, the first calcination process is carried out at 650-950°C in such a way as to introduce the second raw material into the heat treatment equipment and pump oxygen gas.

[013] In another embodiment, the second leaching process is carried out using a second leaching agent comprising an inorganic acid, water, or a mixture thereof.

[014] In another embodiment, the second leaching process is carried out at a temperature of 150-250°C at a pressure of 800-4300 kPa.

[015] In another embodiment, the second leaching process is carried out at an acid concentration in the solution of 100-200 g/L.

[016] In another embodiment, the neutralization process is carried out using a neutralizing agent comprising MHP, MCP, nickel hydroxide (Ni(OH) ₂ ), nickel carbonate (NiCO ₃ ), sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), calcium oxide (CaO), magnesium oxide (MgO), or a mixture thereof.

[017] In another embodiment, the neutralization process is carried out at 80°C under pH conditions of 2-4.5.

[018] In another embodiment, the purification process comprises: (E-i) a first purification process of removing impurities contained in a neutralized solution obtained as a result of performing the neutralization process; (E-ii) a second purification process of removing impurities contained in a first purified solution obtained as a result of performing the first purification process; and (E-iii) a third purification process of removing impurities contained in a second purified solution obtained as a result of performing the second purification process.

[019] In another embodiment, the first purification process removes impurities including copper, iron, aluminum, silicon, zinc, cobalt, magnesium, or a combination thereof using a precipitation method.

[020] In another embodiment, the first purification process is carried out using (i) a sulfide precipitation process by adding a sulfide precipitating agent to the neutralized solution at a content of 1.0-2.5 equivalents of copper in the neutralized solution, (ii) a hydroxide precipitation process by adding a hydroxide precipitating agent to the neutralized solution at a content of 0.8-1.5 equivalents of impurities in the neutralized solution, or a combination of (i) and (ii).

[021] In another embodiment, the second purification process removes impurities, including zinc, magnesium, manganese, or a combination thereof, using a solvent extraction method.

[022] In another embodiment, the second purification process is carried out using (i) a loading process of adding a first extractive agent in the form of a solvent to the first purified solution to extract impurities, including zinc, magnesium, manganese or a combination thereof, into an organic phase and (ii) a separation process of adding an inorganic acid to the organic phase to extract impurities, including zinc, magnesium, manganese or a combination thereof, contained in the organic phase into an aqueous phase.

[023] In another embodiment, the third purification process removes impurities, including cobalt, using a solvent extraction method.

[024] In another embodiment, the third purification process comprises (i) a loading process by adding a second extracting agent in the form of a solvent to the second purified solution to extract impurities, including cobalt, into the organic phase and (ii) a separation process by adding an inorganic acid to the organic phase to extract impurities, including cobalt, contained in the organic phase into an aqueous phase.

[025] In another embodiment, the precipitation process is carried out using a precipitating agent comprising sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), calcium oxide (CaO), magnesium oxide (MgO) or a mixture thereof.

[026] In another embodiment, the precipitation process is carried out at 85°C under conditions of pH 6.5-10.0.

[027] In another embodiment, the second calcination process is carried out at 350-800°C in such a way as to introduce the precipitated residue into the heat treatment equipment and pump oxygen gas.

[028] According to the present invention, the reductive heat treatment process provides, through heat treatment, selective leaching and extraction of lithium from raw materials containing lithium that forms strong chemical bonds.

[029] According to the present invention, the first roasting process is used to convert various nickel-containing raw materials with different forms of chemical bonds into one phase, ensuring uniformity in subsequent processes, and the process can be flexibly adapted to the rapidly changing market of nickel raw materials, promoting the applicability of the entire process.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[030] Fig. 1 is a schematic diagram showing the entire process of nickel extraction and nickel oxide production according to an embodiment of the present invention.

DETAILED DESCRIPTION

[031] Embodiments of the present invention are shown for the purpose of explaining the technical idea of the present invention. The scope of rights according to the present invention is not limited to the embodiments shown below or the detailed descriptions of such embodiments.

[032] In this document, unless otherwise specified, “%” is understood on a weight basis.

[033] The present invention will be described below with reference to the accompanying drawings.

[034] Fig. 1 is a graphical representation showing the entire process of extracting nickel and producing nickel oxide according to an embodiment of the present invention.

[035] As shown in Fig. 1, a method for extracting high-purity nickel by performing a series of processes and for producing nickel oxide using such smelted nickel can be provided. This method can provide increased operational flexibility for various raw materials and products, stable operation and purity while reducing the production cost. Hereinafter, each process will be described in detail with reference to the corresponding figures.

[036] Raw Materials

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

[038] For example, the first raw material may include a black mass (BM), a black powder (BP), a mixed hydroxide precipitate (MHP), a 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 can be given as shown in Table 1. The first raw material may contain nickel in the form of nickel oxide (NiO) or a complex oxide of metallic nickel mixed with other metals.

[039] TABLE 1

[040] (Unit: wt.%)

[041] The second raw material may comprise an ore, a matte, a precipitate of mixed sulfides, or a mixture thereof. For example, the second raw material may comprise 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). As an example, the composition of the second raw material may be as shown in Table 2. The second raw material may comprise nickel in the form of nickel sulfide (NiS).

[042] TABLE 2

[043] (Unit: wt.%)

[044] Process (S10) of reductive heat treatment

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

[046] In the process (S10) of the reducing heat treatment, the heat treatment in a reducing atmosphere can be carried out for the first raw material 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 with the conversion of lithium-containing compounds into substances with high solubility in water or inorganic acids.

[047] Thus, by converting the form of the compound of the first raw material containing lithium by carrying out the reduction heat treatment process (S10) before proceeding to the first lithium leaching/extraction leaching process (S20) described later, it is possible to improve the leaching efficiency in the first lithium leaching/extraction leaching process (S20).

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

[049] According to an embodiment of the present invention, the reductive heat treatment process (S10) can be carried out by introducing a first raw material into a heat treatment equipment and pumping nitrogen gas at a temperature of 650-950°C. For example, a certain amount of the first raw material can be charged into the heat treatment equipment, and by pumping a sufficient amount of nitrogen gas (N ₂ gas) to maintain a reducing atmosphere, the reductive heat treatment can be carried out at 650-950°C. In this process, not only lithium but also other metals can react by undergoing a phase transition in reactions according to [Reaction Formula 1]. In addition, additional reactions can occur according to [Reaction Formula 2] and [Reaction Formula 3].

[050] [Reaction formula 1]

[051] 9LiNi _1/3 Co _1/3 Mn _1/3 O ₂ + 0.25C → 3NiO + 3MnO ₂ + Co ₃ O ₄ + 4.5Li ₂ O + 0.25CO ₂ (g)

[052] [Reaction formula 2]

[053] 4MnO ₂ + C → 2Mn ₂ O ₃ + CO ₂ (g)

[054] [Reaction formula 3]

[055] Li ₂ O + CO ₂ (g) → Li ₂ CO ₃

[056] First process (S20) leaching

[057] In the first leaching process (S20), raw materials containing nickel and lithium that have undergone a phase transition by carrying out the reductive heat treatment process (S10) can be leached.

[058] The first leaching process (S20) may be carried out after the reduction heat treatment process (S10) is carried out. For example, the first leaching process (S20) may be carried out in a wet milling device. The wet milling device may be a ball mill, a rod mill, a bead mill, a disc mill, etc. In the first leaching process, a first leaching agent (for example, an inorganic acid, water, or a mixture thereof) may be used to selectively leach the treated lithium.

[059] In one embodiment, the inorganic acid may be at least one acid selected from the group consisting of _sulfuric acid ( _H2SO4 ), hydrochloric acid (HCl), and nitric acid ( _HNO3 ). The inorganic acid may be diluted with water, and sulfuric acid obtained by capturing gaseous sulfur dioxide formed in the subsequent roasting process (S30) may be used.

[060] In one embodiment, water may be used as the first leaching agent. In such cases, lithium from the lithium-containing feedstock may be leached as lithium hydroxide (LiOH) according to [Reaction Formula 4] to form a first leachate. The first leachate may comprise lithium.

[061] [Reaction formula 4] Li ₂ CO ₃ + 2H ₂ O → 2LiOH + H ₂ O + CO ₂

[062] 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.

[063] The lithium concentration in the first leachate obtained in the first leaching process may be about 0.1-8.5 g/L. This leachate can be processed into lithium hydroxide monohydrate (LiOH H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium phosphate (Li ₃ PO ₄ ), etc. by carrying out well-known precipitation and crystallization methods for use as raw materials in cathodes of lithium-ion batteries.

[064] MHP and MCP generated in the recycling process of lithium-ion batteries, which may contain Li in addition to Ni, Co, Mn, can be used as the first raw material to perform the first leaching process.

[065] First process (S30) of firing

[066] The first firing process (S30) may be carried out as a pre-treatment step for the second raw material.

[067] In the first process (S30) of roasting, a phase transition of nickel-containing raw materials bound in various compounds occurs, together with the recirculation of sulfuric acid gas (SO ₂ gas) formed during the heat treatment process to obtain inorganic acids.

[068] Before the first roasting process (S30), the second raw material containing nickel may be in the form of a sulfide, which can be converted into an oxide by carrying out the first roasting process (S30). Leaching the second raw material containing nickel directly in its sulfide state may result in low leaching efficiency due to the formation of hydrogen sulfide gas ( _H2S gas) and metal precipitation reactions. Therefore, by converting the compound form of the second raw material containing nickel by carrying out the roasting process (S30) before carrying out the second leaching process (S40), it is possible to improve the leaching efficiency in the second leaching process (S40). In this case, the roasting process (S30) can be carried out using heat treatment equipment such as an electric furnace (box furnace) or a rotary kiln.

[069] According to one embodiment of the present invention, the first roasting process (S30) may include loading a certain amount of nickel-containing raw material into an electric furnace, injecting a sufficient amount of oxygen ( _O2 ) to convert into nickel oxide, and performing roasting at 650-950°C. During this process, not only nickel but also other impurities may react to undergo a phase transition according to the reaction described in [Reaction Formula 5] below. In addition, the sulfur dioxide gas generated during the first roasting process (S30) may be captured in a separate collection unit and converted into sulfuric acid ( _H2SO4 ) by mixing with water, which can then _be used in subsequent leaching processes.

[070] [Reaction formula 5] 2NiS + 3O ₂ → 2NiO + 2SO ₂

[071] Second process (S40) leaching

[072] In the second leaching process (S40), the roasting residue (roasting product) that has undergone a phase transition due to the first roasting process (S30) can be leached together with the first leaching residue remaining in the residue from the first leaching process (S20). 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 roasting residue can be leached in a reactor operating at high temperature and high pressure, while the first leaching residue can be leached in a reactor operating at atmospheric pressure. In the second leaching process (S40), a second leaching agent (for example, an inorganic acid, water, or a mixture thereof) can be used. In one embodiment, the second leaching process (S40) can be carried out using an inorganic acid. For example, it is possible to use at least one inorganic acid selected from the group consisting of _sulfuric acid ( _H2SO4 ), hydrochloric acid (HCl) and nitric acid ( _HNO3 ), an inorganic acid diluted with water or sulfuric acid obtained by capturing gaseous sulfur dioxide formed in the preceding first roasting process (S30).

[073] In one embodiment, sulfuric acid can be used as the second leaching agent. In this case, nickel can be leached from the first leaching residue and the roasting residue containing nickel in the form of nickel sulfate (NiSO ₄ ) to form a second leach product according to [Reaction Formula 6].

[074] [Reaction formula 6] NiO + H ₂ SO ₄ → NiSO ₄ + H ₂ O

[075] The second leaching process (S40) can be carried out at a temperature of about 150-250°C and at a pressure of 800-4300 kPa. The saturated steam pressure due to the high reaction temperature can lead to maintaining a certain pressure level, and additional pressure can be applied to complete the reaction.

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

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

[078] The nickel concentration in the second leach product obtained from the second (S40) leaching process may be approximately 45-105 g/L, and the residual acidity may be 10-80 g/L.

[079] Neutralization process (S50)

[080] In the neutralization process (S50), the second leaching product obtained as a result of the second leaching process (S40) may be neutralized. The neutralization process (S50) may be carried out after the second leaching process (S40) has been carried out.

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

[082] In an embodiment, after providing a sufficient amount of the second leachate by performing the second leaching process (S40) in a low acidic pH environment, the neutralization process (S50) may be performed.

[083] In the neutralization process (S50), a neutralizing agent may be added to increase the pH of the second leachate formed as a result of the second leaching process (S40). The addition of a neutralizing agent may also be carried out for a subsequent cleaning process.

[084] In one embodiment, the neutralizing agent may be at least one agent selected from the group consisting of nickel-containing _by -products (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).

[085] The reason for using MHP and MCP as raw materials as well as neutralizing agents may be that hydroxides and carbonates are generally characterized by high solubility in acids even without roasting, which eliminates the need for treatment under expensive high temperature and high pressure leaching conditions, and also ensures that the acid ( _H2SO4 ) remaining from the second (S40) leaching process _is consumed, thus pre-prepared for the (S60) purification process, which occurs in the high pH range.

[086] In an embodiment, nickel-containing by-products in the form of a wet sludge layer can be used in the neutralization process (S50). By using nickel-containing by-products, the amount of separately added neutralizing agent can be reduced, resulting in savings. In addition, the introduction of additional impurities can be prevented and the concentration of nickel in the neutralized solution can be increased.

[087] In an embodiment, the neutralization process (S50) can be carried out at 80°C under pH conditions of about 2-4.5. During this process, impurities including iron (Fe) and aluminum (Al) can be precipitated and removed.

[088] Cleaning process (S60)

[089] In the purification process (S60), impurities contained in the neutralized solution obtained as a result of performing the neutralization process (S50) can be removed such that the neutralized solution can be purified. The purification process (S60) can be performed after the neutralization process (S50).

[090] In an embodiment, the cleaning process (S60) may include a first cleaning process (S61) that can remove impurities contained in a neutralized solution obtained by performing the neutralization process (S50); a second cleaning process (S62) that can remove impurities contained in a first purified solution obtained by performing the first cleaning process (S61); and a third cleaning process (S63) that can remove impurities contained in a second purified solution obtained by performing the second cleaning process (S62).

[091] First cleaning process (S61)

[092] In the first purification process (S61), a neutralized solution obtained as a result of the neutralization process (S50) may be purified. The neutralized solution may be a leachate that has been neutralized. The first purification process (S61) may be a process for removing impurities from the neutralized solution after the neutralization process (S50) has been performed.

[093] The first purification process (S61) may be a process in which impurities are removed using a precipitation method. In the first purification process (S61), impurities can be removed by a sulfide precipitation method using at least one selected from the group consisting of sodium sulfide (Na ₂ S), sodium hydrosulfide (NaSH), ammonium hydrosulfide (NH ₄ HS) and hydrogen sulfide (H ₂ S) as a precipitant. During this process, precipitates consisting predominantly of copper sulfide (CuS) and containing impurities such as zinc, lead and cadmium can be recovered. The precipitates can then be processed into metallic copper by extraction and solvent exchange or other purification processes.

[094] Furthermore, in the first purification process (S61), impurities can be removed by a method of precipitating hydroxides using at least one selected from the group consisting of sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), calcium oxide (CaO) and magnesium oxide (MgO). This process can precipitate and remove impurities such as aluminum (Al), iron (Fe), chromium (Cr), silicon (Si), etc. The reaction can be as shown below in [reaction formula 7] when using sodium hydrosulfide as a precipitant and in [reaction formula 8] when using sodium hydroxide.

[095] [Reaction formula 7] 2CuSO ₄ + 2NaSH → Na ₂ SO ₄ + H ₂ SO ₄ + 2CuS↓

[096] [Reaction formula 8] MSO ₄ + 2NaOH → Na ₂ SO ₄ +M(OH) ₂ ↓ (M=Al, Fe, Cr, Si)

[097] During the process for precipitating sulfides from the first purification process (S61), the precipitant can be introduced in an equivalent proportion of approximately 1.0 to 2.5 relative to the copper contained in the neutralized solution. If the precipitant for sulfides is introduced in an equivalent proportion of less than 1.0 relative to copper, the degree of copper precipitation can be 83% or less, indicating an incomplete reaction. After introducing the precipitant for sulfides in an equivalent proportion greater than 2.5, impurities contained in the precipitant can excessively enter and adversely affect the process, thereby potentially reducing the degree of recovery due to co-precipitation of nickel. The pH at which the reaction can be carried out is in the range of from 0.8 to 2.5 at 70 °C.

[098] In the method for purification by precipitation of hydroxides, the precipitant can be introduced in an equivalent proportion of approximately 0.8 to 1.5 relative to the impurities contained in the neutralized solution. If the precipitant for hydroxides is introduced in an equivalent proportion of less than 0.8 relative to the impurities, the degree of removal of impurities can be 85% or less, which indicates an incomplete reaction. After the introduction of the precipitant in an equivalent proportion exceeding 1.5, impurities contained in the precipitant can enter excessively and adversely affect the process, potentially reducing the degree of recovery due to co-precipitation of nickel. In this case, the pH at which the reaction can be carried out is in the range of from 2.5 to 4.5 at 60 °C.

[099] After the first purification process (S61) is carried out, the content of each of copper, iron, aluminum and silicon in the first purified solution may be reduced to 5 mg/L or less, and the content of each of zinc, cobalt and magnesium may be reduced to 20 mg/L or less.

[0100] Second cleaning process (S62)

[0101] The second purification process (S62) may further purify the first purified solution obtained as a result of the first purification process (S61). The second purification process (S62) may be performed after the first purification process (S61), and may be a process that uses solvent extraction to remove impurities.

[0102] In the second purification process (S62), an organic extracting agent can be used to remove impurities such as zinc (Zn), magnesium (Mg), and manganese (Mn).

[0103] In one embodiment, the second purification process (S62) may include a loading process and a separation process. Available as an organic extracting agent may be at least one agent 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.

[0104] The loading process may be a process of extracting impurities such as zinc, magnesium, manganese or a combination thereof contained in the first purified solution into an organic phase. The loading process may be a process of extracting zinc, magnesium and manganese contained in the first purified solution into an organic phase after performing the first purification process (S61), using an organic extracting agent.

[0105] The ratio of the organic phase to the aqueous phase in the loading process can be approximately 1 to 3 by volume. When the volume fraction of the organic phase relative to the 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 extracting agent. A volume fraction of the organic phase relative to the aqueous phase exceeding 3 can increase the cost of the process due to excessive use of the organic extracting agent. The pH range for the loading process can be controlled at 2.0-4.0 using at least one selected from the group consisting of sodium hydroxide (NaOH) or sodium carbonate (Na ₂ CO ₃ ). In addition, the reaction temperature can be set at 30-40 °C.

[0106] After extraction of zinc, magnesium and manganese into the organic phase, phase separation due to the difference in densities of the organic and aqueous phases may provide for the formation of a second purified solution. The second purified solution may be an aqueous solution containing nickel that is now free of zinc and magnesium and may contain nickel at concentrations of 50-100 g/L.

[0107] The organic phase containing zinc and magnesium can be subjected to a separation process. In the separation process, an inorganic acid can be added to the organic phase after the loading process has been carried out to remove impurities. This separation process can be a back extraction process to extract the zinc, magnesium and manganese contained in the organic phase back into the aqueous phase.

[0108] The volume fraction of the organic phase relative to the aqueous phase in the separation process may be approximately 5-10. When the volume fraction of the organic phase relative to the aqueous phase in the separation process is below 5, the use of water may be increased, and complete extraction of impurities is possible. When the volume fraction of the organic phase relative to the aqueous phase in the separation process is above 10, the efficiency of back extraction of impurities may be reduced. When carrying out the separation process, the pH range can be adjusted to approximately 0.5-1.5 using sulfuric acid (H ₂ SO ₄ ). In addition, the reaction temperature can be set to 30-40°C.

[0109] Third cleaning process (S63)

[0110] The third purification process (S63) may further refine the second purified solution obtained as a result of the second purification process (S62). The third purification process (S63) may be performed after the second purification process (S62). The third purification process (S63) may be a process for removing impurities using a solvent extraction technique. In the third purification process (S63), an organic extractive agent may be used to remove impurities, including cobalt. In one embodiment, the third purification process (S63) may include a loading process and a separation process. 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 as the organic extractive agent.

[0111] In the loading process, impurities containing cobalt can be extracted into an organic phase from the second purified solution. The loading process can be a process in which an organic extracting agent is used to extract cobalt into an organic phase from the second purified solution after the second purification process (S62) is performed.

[0112] The amount of organic phase introduced into the loading process may be a volume fraction of about 1-3 relative to the aqueous phase. When the volume fraction of the organic phase relative to the aqueous phase is less than 1, the target metal is not completely bound to the organic extracting agent, with the subsequent extraction rate of 90% or less. A weight fraction of the organic phase relative to the aqueous phase exceeding 3 may result in excessive use of the organic extracting agent, increasing the cost of the process. The pH range for the loading process can be controlled at 4-5 using sodium hydroxide (NaOH) or sodium carbonate (Na ₂ CO ₃ ), and the reaction temperature is maintained at 30 to 40 °C.

[0113] After the extraction of cobalt into the organic phase is complete, when the aqueous phase and the organic phase are mixed, the difference in specific gravity between the organic phase and the aqueous phase can provide for phase separation. This phase separation can provide for a third purified solution, which is a cobalt-depleted, nickel-containing aqueous solution with a nickel content of 65-125 g/L.

[0114] The cobalt-containing organic phase may be subjected to a separation process.

[0115] In a separation process following the loading process, an inorganic acid may be added to the organic phase to remove cobalt contained in the organic phase. The separation process may be a back extraction process to extract cobalt back into the aqueous phase from the organic phase.

[0116] The volume fraction of the organic phase relative to the aqueous phase in the separation process may be approximately 3-10. When the volume fraction of the organic phase relative to the aqueous phase in the separation process is below 3, the use of water may be increased, and complete extraction of impurities is possible. When the volume fraction of the organic phase relative to the aqueous phase in the separation process is above 10, the efficiency of back extraction of impurities may be reduced. When carrying out the separation process, the pH range can be adjusted to approximately 0.5-1.5 using sulfuric acid (H ₂ SO ₄ ). In addition, the reaction temperature can be set to 30-40°C.

[0117] After the extraction of cobalt into the organic phase is completed, when the aqueous phase and the organic phase are mixed, the difference in specific gravity between the organic phase and the aqueous phase can provide phase separation. This phase separation can provide a cobalt-containing solution, which can be further purified by precipitation and crystallization to obtain high-purity cobalt sulfate.

[0118] Precipitation process (S70)

[0119] The precipitation process (S70) may provide precipitation of the purified solution obtained as a result of performing the purification process (S60) (for example, the third purification process (S63)). The precipitation process (S70) may be performed after the third purification process (S63).

[0120] The precipitation process (S70) may be a process in which nickel is precipitated using a precipitation method with removal of impurities. In the precipitation process (S70), at least one selected from the group consisting of sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), calcium hydroxide (Ca(OH) ₂ ), magnesium hydroxide (Mg(OH) ₂ ), calcium oxide (CaO) and magnesium oxide (MgO) may be used as a precipitant for precipitating nickel.

[0121] When sodium carbonate is used as a precipitating agent, the reaction can be represented by the following reaction formula 9.

[0122] [Reaction formula 9] NiSO ₄ + 2NaOH + xH ₂ O → Ni(OH) ₂ + Na ₂ SO ₄ + xH ₂ O (x≥0)

[0123] The precipitation process (S70) can be carried out at a temperature of 75-85°C and a pH of 6.5-10.0. A pH below 6.5 can result in a nickel recovery rate of less than 80%. When the pH is above 10.0, impurities associated with the precipitant can be present in large quantities and enter the process, which adversely affects the process and reduces economic efficiency due to excessive use of precipitant.

[0124] Impurities, including sodium (Na) and potassium (K), can be partially removed during the precipitation process (S70). For example, after the precipitation reaction, a process of recovering nickel-containing precipitates by separating solid and liquid and washing them with dilute acid and water can ensure the removal of at least a portion of these impurities.

[0125] Second process (S80) of firing

[0126] In the second calcining process (S80), the residue obtained as a result of performing the precipitation process (S70) may be calcined. The second calcining process (S80) may be performed after performing the precipitation process (S70).

[0127] Before the second calcination process (S80) is performed, the nickel-containing residue may be in the form of a hydroxide or carbonate and may be converted into an oxide by performing the second calcination process (S80). The second calcination process (S80) may be performed using heat treatment equipment such as a chamber furnace or a rotary kiln.

[0128] According to an embodiment of the present invention, in the second calcination process (S80), a certain amount of nickel-containing raw material can be charged into an electric furnace and a sufficient amount of oxygen (O2) can be injected to convert into nickel oxide, and the calcination occurs at 350-800°C. During this process, the phase transformation can occur through the reaction formula 10 shown below.

[0129] [Reaction formula 10] 2NiCO ₃ ·3Ni(OH) ₂ ·4H ₂ O + O ₂ → 5NiO + 7H ₂ O(g) + 2CO ₂ (g)

[0130] The nickel-containing oxide obtained by the embodiment of the present invention can be used as a nickel compound in powder form and, through further processing, can be suitably used as a precursor of a nickel raw material for a cathode active material in lithium batteries.

[0131] EXPERIMENTAL EXAMPLES

[0132] Raw Materials

[0133] As shown in Table 3 below, the elements were mixed in predetermined ratios to obtain the first raw materials A-C.

[0134] TABLE 3

[0135] (Unit: wt.%)

[0136] * Each of the first raw materials contained sulfur (S), oxygen (O), and hydrogen (H) ions, in addition to metal ions, to provide 100 wt.%.

[0137] The second raw material was prepared to contain elements as indicated in Table 4 below.

[0138] TABLE 4

[0139] (Unit: wt.%)

[0140] * The second raw material contained oxygen (O) and hydrogen (H) ions, in addition to metal ions, to provide 100 wt%.

[0141] Reductive Heat Treatment Process

[0142] Reductive heat treatment was carried out on a first raw material containing nickel, lithium, etc. Specifically, 2.0 kg of the raw material was charged into a rotary kiln and then subjected to reductive heat treatment at 850°C for 3 hours, while maintaining a reducing atmosphere using N ₂ gas to obtain a reductive heat treatment residue that was converted from lithium oxide (Li ₂ O) to lithium carbonate (Li ₂ CO ₃ ).

[0143] First leaching process

[0144] The extraction of lithium was carried out by leaching the residue after the reduction heat treatment with water. Specifically, 100 g of the residue was loaded into a ball mill, and then ground and leached with 2.5 L of water ( _H2O ) for 2 hours. Then, solid-liquid separation using vacuum filtration provided a first leaching residue containing the elements shown in Table 5, and provided a first leaching product containing the elements shown in Table 6.

[0145] TABLE 5

[0146] (Unit: wt.%)

[0147] In addition to the metal ions, oxygen (O) and hydrogen (H) ions were present to provide 100 wt%.

[0148] TABLE 6

[0149] (Unit: g/l)

[0150] First firing process

[0151] The roasting process was carried out with a second raw material containing nickel and sulfur. Briefly, 2 kg of the raw material was loaded into a rotary kiln and roasted at 850°C for 3 hours while injecting sufficient oxygen ( _O2 ) to obtain a roasted residue (roasting product) that was converted from nickel sulfide (NiS) to nickel oxide (NiO).

[0152] Second leaching process

[0153] A raw material in which the residue after the reduction heat treatment and the residue after calcination were mixed in a weight ratio of 2:8 was subjected to leaching at high temperature and high pressure.

[0154] 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 at 3500 kPa for 3 hours to obtain a second leachate with a nickel leaching rate of 95% and a nickel concentration of 60 g/L.

[0155] Neutralization process

[0156] The neutralization process was carried out using nickel-containing by-products in the second leachate.

[0157] By adjusting the pH of 2 L of the second leach product to 2.5 by adding nickel-containing by-products and maintaining at 80°C for 3 hours, a neutralized solution with a nickel concentration of 82 g/L was provided.

[0158] First cleaning process

[0159] The first purification process was carried out using a precipitation method to remove impurities contained in the neutralized solution.

[0160] By adding sodium hydrosulfide (NaSH) in an amount of 1.3 equivalents (eq.) of copper (Cu) to the neutralized solution and maintaining the pH at 2.5 at 70°C for 2 hours, copper was removed by 99.8%. In addition, the pH of the neutralized solution was maintained at 4.5 for 2 hours using nickel-containing by-products and sodium hydroxide (NaOH) to obtain a first purified solution in which impurities including aluminum, iron, and silicon contained therein were removed by 99.5% or more.

[0161] Second cleaning process

[0162] The second purification process was carried out using a solvent extraction method to remove impurities contained in the first purified solution.

[0163] Impurities, including zinc and magnesium, were removed by extraction. In this case, 500 ml of the first purified solution was mixed with 1000 ml of 25% diluted di-2-ethylhexylphosphoric acid as an extracting agent and the mixture was shaken at pH 3.5 at 40°C for 10 minutes. Phase separation by difference in specific gravity ensured extraction of zinc by 99% and magnesium by 43%. Complete extraction of impurities was possible using the countercurrent exchange method in a mixer-settler.

[0164] Third Purification Process

[0165] The third purification process was carried out using a solvent extraction method to remove the cobalt contained in the second purified solution.

[0166] A mixture of 500 ml of the cobalt-containing second purified solution and 1000 ml of 25% diluted bis(2,4,4-trimethylphenyl)phosphinic acid as an extracting agent was shaken at pH 5.0 at 40°C for 10 minutes, and phase separation by specific gravity difference provided approximately 55% extraction of cobalt. Complete extraction of impurities was possible using the countercurrent exchange method in a mixer-settler.

[0167] This process provided cobalt removal at levels of 3 mg/L or less, producing a third cleaning solution containing the elements listed in Table 7 below.

[0168] TABLE 7

[0169] (Unit: mg/L)

[0170] Precipitation process

[0171] A precipitation process was carried out to recover the nickel contained in the third purified solution in the form of a precipitate.

[0172] Using sodium carbonate ( _Na2CO3 ), the pH was maintained at 8.0 at 85°C for 2 hours in the case of 1 L of the third purified solution containing 42 g/L nickel. Solid-liquid separation using vacuum filtration _was performed followed by washing with 1 L of distilled water (DIW) to obtain a residue-precipitate containing the elements shown in Table 8.

[0173] TABLE 8

[0174] (Unit: wt.%)

[0175] Second firing process

[0176] To convert the nickel contained in the residue-precipitate from the hydroxide or carbonate form to the oxide form, a second roasting process was carried out.

[0177] Specifically, 2 kg of the raw material was charged into a rotary kiln and, under sufficient oxygen ( _O2 ) injection, the material was calcined at 400°C for 3 hours to convert from the nickel hydroxide (Ni(OH) ₂ ) or nickel carbonate ( _NiCO3 ) form to the nickel oxide (NiO) form and obtain a nickel oxide containing the elements listed in Table 9 below.

[0178] TABLE 9

[0179] (Unit: wt.%)

[0180] Although embodiments of the present invention have been described with reference to the accompanying drawings, it will be understood by those skilled in the art to which the present invention pertains that the embodiments may be implemented in other specific forms without changing the technical essence or essential features of the present invention.

[0181] It should therefore be understood that the embodiments described above are illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the detailed description. It should be understood that all changes or modifications that come within the meaning and scope of the claims and their equivalent concepts are included within the scope of the present invention.

Claims (35)

1. A method for extracting nickel, comprising: (A-i) a reduction heat treatment process of heat treating a first raw material containing nickel and lithium; (B) a first leaching process involving leaching of the heat-treated product obtained as a result of the reductive heat treatment process; (A-ii) a first roasting process with heat treatment of a second raw material containing nickel and sulfur; (C) a second leaching process of leaching a first leaching residue obtained from the first leaching process and a roasting product obtained from the first roasting process; (D) a neutralization process for neutralizing the second leachate obtained as a result of the second leaching process; (E) a purification process to remove impurities contained in the neutralized solution obtained as a result of the neutralization process; (F) a precipitation process involving precipitation in a purified solution obtained as a result of the purification process; and (G) a second roasting process involving roasting the precipitated residue obtained as a result of the precipitation process to extract nickel. 2. The method of claim 1, wherein each of the first feedstock and the second feedstock independently comprises at least one material selected from the group consisting of an oxide, a hydroxide, a sulfide, and a sulfur oxide, wherein each of the oxide, hydroxide, sulfide and sulfur oxide independently provides an 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. The method according to claim 1, wherein the first raw material contains nickel in the form of nickel oxide or a complex oxide of metallic nickel. 4. The method according to claim 1, wherein the second raw material contains nickel in the form of nickel sulfide. 5. The method according to claim 1, wherein the process of reducing heat treatment is carried out at 650-950°C in such a way as to introduce the first raw material into the heat treatment equipment and pump in nitrogen gas. 6. The method according to claim 1, wherein the first leaching process is carried out using a first leaching agent comprising an inorganic acid, water or a mixture thereof. 7. The method of claim 1, wherein the first leach product obtained as a result of the first leaching process comprises lithium, and the first leach residue comprises nickel. 8. The method according to claim 1, wherein the first calcination process is carried out at 650-950°C in such a way as to introduce the second raw material into the heat treatment equipment and pump gaseous oxygen. 9. The method according to claim 1, wherein the second leaching process is carried out using a second leaching agent comprising an inorganic acid, water or a mixture thereof. 10. The method according to claim 1, wherein the second leaching process is carried out at a temperature of 150-250°C at a pressure of 800-4300 kPa. 11. The method according to claim 1, wherein the second leaching process is carried out at an acid concentration in the solution of 100-200 g/l. 12. The method according to claim 1, wherein the neutralization process is carried out 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. 13. The method according to claim 1, wherein the neutralization process is carried out at 80°C under pH conditions of 2-4.5. 14. The method according to claim 1, wherein the cleaning process comprises: (E-i) a first purification process for removing impurities contained in the neutralized solution obtained as a result of the neutralization process; (E-ii) a second purification process for removing impurities contained in the first purified solution obtained as a result of carrying out the first purification process; and (E-iii) a third purification process for removing impurities contained in the second purified solution obtained as a result of carrying out the second purification process. 15. The method of claim 14, wherein the first purification process removes impurities, including copper, iron, aluminum, silicon, zinc, cobalt, magnesium, or a combination thereof, using a precipitation method. 16. The method of claim 14, wherein the first purification process is carried out using (i) a sulphide precipitation process by adding a sulphide precipitation agent to the neutralised solution at a content of 1.0-2.5 equivalents of copper in the neutralised solution, (ii) a hydroxide precipitation process by adding a hydroxide precipitation agent to the neutralised solution at a content of 0.8-1.5 equivalents of impurities in the neutralised solution, or a combination of (i) and (ii). 17. The method of claim 14, wherein the second purification process removes impurities, including zinc, magnesium, manganese, or a combination thereof, using a solvent extraction method. 18. The method of claim 14, wherein the second purification process is carried out using (i) a loading process by adding a first extracting agent in the form of a solvent to the first purified solution with extraction of impurities, including zinc, magnesium, manganese or a combination thereof, into the organic phase and (ii) a separation process by adding an inorganic acid to the organic phase with extraction of impurities, including zinc, magnesium, manganese or a combination thereof, contained in the organic phase, into an aqueous phase. 19. The method according to claim 14, wherein in the third purification process, impurities, including cobalt, are removed using a solvent extraction method. 20. The method of claim 14, wherein the third purification process comprises (i) a loading process by adding a second extracting agent in the form of a solvent to the second purified solution with extraction of impurities, including cobalt, into the organic phase and (ii) a separation process by adding an inorganic acid to the organic phase with extraction of impurities, including cobalt, contained in the organic phase into an aqueous phase. 21. The method according to claim 1, wherein the precipitation process is carried out using a precipitating agent comprising 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. 22. The method according to claim 1, wherein the precipitation process is carried out at 85°C under the condition of pH 6.5-10.0. 23. The method according to claim 1, wherein the second calcination process is carried out at 350-800°C in such a way as to introduce the precipitated residue into the heat treatment equipment and pump in gaseous oxygen.

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