Method for preparing aqueous solution containing nickel or cobalt

Abstract

A method for preparing an aqueous solution containing nickel or cobalt comprises: (A) a leaching step, comprising a first atmospheric pressure heating leaching step and a second atmospheric pressure heating leaching step, wherein a raw material is heated and leached at atmospheric pressure to form a leaching solution containing nickel, cobalt and impurities; (B) a first extraction step, wherein a first solvent extractant is added to the leaching solution to separate the leaching solution into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities; (C-i) a precipitation removal step, wherein a precipitant is added to the first filtrate to precipitate and remove impurities including magnesium, calcium, or a mixture thereof; and (D-i) a target material precipitation step, wherein a neutralizing agent is added to the first filtrate to selectively precipitate a nickel cake containing nickel.

Description

Technical Field

[0001] The present invention relates to a method for preparing an aqueous solution containing nickel or cobalt. More specifically, the present invention relates to a method for preparing an aqueous solution containing nickel or cobalt, which is used to recover nickel and cobalt from a raw material and then prepare an aqueous solution containing nickel or cobalt that can be used to prepare a cathode active material for a lithium-ion secondary battery. Background Art

[0002] A one-stage atmospheric heating reaction leaching step or a two-stage leaching step consisting of atmospheric heating reaction and pressurized heating reaction has been mainly used to ionize nickel and cobalt in mixed hydroxide precipitate (MHP) filter cake feed containing nickel / cobalt mixed hydroxides.

[0003] However, in the case of a one-stage atmospheric pressure heating reaction leaching step, the recovery rate of nickel (Ni) and cobalt (Co) decreases. In the case of a two-stage leaching step consisting of atmospheric pressure heating reaction and pressurized heating reaction, there is a problem that the range of material selection is narrowed due to erosion, corrosion, and damage to pipeline and reactor materials, and there is a problem that competitiveness is reduced due to energy costs.

[0004] Alternatively, solvent extractants such as Ion Quest 801, Cyanex 272, Versatic Acid 10, and LIX 84I are used to selectively recover nickel and cobalt from ionized aqueous nickel / cobalt solutions. However, the use of organic solvents in the solvent extraction process poses a risk of fire and explosion. The high unit price of solvent extractants increases the production cost of high-purity nickel and cobalt sulfate, reducing price competitiveness. Summary of the Invention

[0005] Technical issues

[0006] An object of the present invention is to prepare a high-purity aqueous solution by recovering nickel and cobalt from a mixed hydroxide precipitate (MHP) filter cake feedstock containing nickel / cobalt mixed hydroxide.

[0007] Furthermore, an object of the present invention is to improve nickel / cobalt recovery and reduce energy consumption by ionizing nickel and cobalt using a two-stage atmospheric heating leaching step.

[0008] Furthermore, an object of the present invention is to use sodium fluoride (NaF) as a precipitant to separate magnesium and calcium in the step of preparing an aqueous solution containing high-purity nickel, to use sodium hydrosulfide (NaSH) to separate magnesium and manganese by solubility difference in the step of preparing an aqueous solution containing high-purity cobalt, and to additionally separate impurities such as copper, magnesium, and manganese by using sodium hydrosulfide (NaSH) and sodium fluoride (NaF), thereby reducing the number of solvent extraction steps.

[0009] Since the solvent extraction step carries the risk of fire and explosion due to the use of an organic solvent, an object of the present invention is to minimize the solvent extraction step, thereby improving the operating environment and reducing the preparation cost of the final product.

[0010] Technical Solution

[0011] According to one embodiment of the present invention, a method for preparing an aqueous solution containing nickel or cobalt is provided, comprising: (A) a leaching step, comprising a first atmospheric pressure heating leaching step and a second atmospheric pressure heating leaching step, wherein a raw material is heated and leached at atmospheric pressure to form a leaching solution containing nickel, cobalt and impurities; (B) a first extraction step, wherein a first solvent extractant is added to the leaching solution to separate the leaching solution into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities; (Ci) a precipitation removal step, wherein a precipitant is added to the first filtrate to precipitate and remove impurities including magnesium, calcium, or a mixture thereof; and (Di) a target material precipitation step, wherein a nickel filter cake containing nickel is selectively precipitated by adding a neutralizing agent to the first filtrate from which the impurities have been precipitated and removed.

[0012] According to another embodiment of the present invention, a method for preparing an aqueous solution containing nickel or cobalt is provided, comprising: (A) a leaching step, comprising a first atmospheric heating leaching step and a second atmospheric heating leaching step, wherein a raw material is heated and leached at atmospheric pressure to form a leaching solution containing nickel, cobalt, and impurities; (B) a first extraction step, wherein a first solvent extractant is added to the leaching solution to separate the leaching solution into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities; and (C-ii) a purification step, wherein a sulfuric acid solution is added to the first organic layer to prepare a second filtrate, and a sulfide is added to the second filtrate to precipitate and recover a cobalt precipitate to remove impurities including magnesium, manganese, zinc, copper, or a mixture thereof.

[0013] In one embodiment of the present invention, the pH of the filtrate obtained in the second atmospheric pressure heating leaching step may be lower than the pH of the filtrate obtained in the first atmospheric pressure heating leaching step.

[0014] In one embodiment of the present invention, the filtrate obtained in the second atmospheric pressure heating leaching step may be fed to the first atmospheric pressure heating leaching step.

[0015] In one embodiment of the present invention, the first solvent extractant may be bis(2,4,4-trimethylpentyl)phosphinic acid.

[0016] In one embodiment of the present invention, the first extraction step may be performed at a temperature of 40 degrees Celsius and a pH greater than 5.0 and less than 5.4.

[0017] In one embodiment of the present invention, the precipitant may be sodium fluoride.

[0018] In one embodiment of the present invention, the precipitant may be added in an amount greater than 2.0 equivalents and less than 2.4 equivalents of magnesium, calcium, or a mixture thereof.

[0019] In one embodiment of the present invention, the neutralizing agent may be a sodium-containing alkaline substance.

[0020] In one embodiment of the present invention, after adding the neutralizing agent, the pH of the first filtrate at a temperature of 85 degrees Celsius may be 8 or higher.

[0021] In one embodiment of the present invention, the method of the present invention may further include: (Ei) a washing step of washing the nickel filter cake with pure water.

[0022] In one embodiment of the present invention, the sulfide may be sodium hydrosulfide (NaSH).

[0023] In one embodiment of the present invention, sulfide having a content of cobalt and zinc greater than 1.0 equivalent and less than 1.6 equivalent may be added.

[0024] In one embodiment of the present invention, the method of the present invention may further include: (D-ii) a copper removal step of dissolving the cobalt precipitate in a sulfuric acid solution and then removing the copper.

[0025] In one embodiment of the present invention, the copper removal step may be performed by adding sodium hydrosulfide (NaSH) having a copper content greater than 4.5 equivalents and less than 5.5 equivalents.

[0026] In one embodiment of the present invention, the method of the present invention may further include: (E-ii) a second extraction step, wherein a second solvent extractant is added to the aqueous solution from which copper has been removed to separate the aqueous solution from which copper has been removed into a third filtrate containing cobalt and impurities and a second organic layer containing zinc and impurities.

[0027] In one embodiment of the present invention, the second solvent extractant may be di-(2-ethylhexyl)phosphoric acid (D2EHPA).

[0028] In one embodiment of the present invention, the second extraction step may be performed at a temperature of 40 degrees Celsius and a pH greater than 2.4 and less than 3.2.

[0029] In one embodiment of the present invention, the method of the present invention may further include: (F) a precipitation removal step of adding a precipitant to the third filtrate to precipitate and remove impurities including magnesium.

[0030] In one embodiment of the present invention, the method of the present invention may further include: (G) a target material precipitation step, wherein a neutralizing agent is added to the third filtrate after precipitation and removal of impurities to selectively precipitate a cobalt filter cake containing cobalt.

[0031] In one embodiment of the present invention, after adding the neutralizing agent, the pH of the third filtrate at a temperature of 85 degrees Celsius may be 8 or higher.

[0032] In one embodiment of the present invention, the method of the present invention may further include: (H) a washing step of washing the cobalt filter cake with pure water.

[0033] Effects of the Invention

[0034] According to the present invention, by using a two-stage atmospheric heating step, it is possible to improve nickel / cobalt recovery and reduce energy consumption.

[0035] Furthermore, by minimizing the solvent extraction step (which carries fire and explosion risks due to the use of organic solvents) in the impurity removal step, it is possible to improve the operating environment and reduce the production cost of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A diagram illustrating a two-stage leaching step and a first extraction step for preparing an aqueous solution containing nickel or cobalt according to one embodiment of the present invention.

[0037] Figure 2 FIG. 1 is a diagram illustrating a precipitate removal step and a target material precipitation step for preparing a nickel-containing aqueous solution according to an embodiment of the present invention.

[0038] Figure 3 A diagram illustrating an impurity removal step, a copper removal step, a second extraction step, a precipitate removal step, and a target material precipitation step for preparing a cobalt-containing aqueous solution according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described to illustrate the technical essence of the present invention. The scope of the invention is not limited to the embodiments described below or the specific description of these embodiments.

[0040] The present invention will now be described with reference to the accompanying drawings.

[0041] Figure 1 FIG. 1 is a diagram illustrating a two-stage leaching step S10 and a first extraction step S20 for preparing an aqueous solution containing nickel or cobalt according to an embodiment of the present invention. Figure 2 FIG. 1 is a diagram illustrating a precipitate removal step S31 and a target material precipitation step S41 for preparing a nickel-containing aqueous solution according to an embodiment of the present invention. Figure 3FIG. 1 is a diagram illustrating impurity removal steps S32 and S42 , copper removal step S62 , second extraction step S72 , precipitate removal step S82 , and target material precipitation step S92 for preparing a cobalt-containing aqueous solution according to an embodiment of the present invention.

[0042] Reference Figures 1 to 3 A method for preparing an aqueous solution containing nickel or cobalt can be provided. This method can be used to prepare a cathode active material for lithium secondary batteries from a mixed hydroxide precipitate (MHP filter cake) in a single step. This method can improve operational stability and purity, while reducing production costs. The individual steps will be described in detail below.

[0043] First, refer to Figure 1 , a leaching step S10 of forming a leachate by performing a two-stage atmospheric pressure heating leaching step on the mixed hydroxide precipitate (MHP) filter cake, and a first extraction step S20 of separating the leachate into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities can be performed.

[0044] Leaching step S10

[0045] Leaching step S10 involves dissolving the mixed hydroxide precipitate (MHP) filter cake in the hydroxide form in an acid solution (e.g., sulfuric acid) to ionize the MHP filter cake and form a leachate. Leaching step S10 includes a first atmospheric pressure heating leaching step S11 and a second atmospheric pressure heating leaching step S12. The atmospheric pressure heating leaching step involves preparing an acid solution at a temperature of 100 degrees Celsius or less in an open reactor, introducing a raw material into the reactor, and leaching valuable metals through the reaction represented by the following reaction formula 1. The raw material introduced here can be a mixed hydroxide precipitate (MHP) filter cake in the hydroxide form containing 40% nickel by weight.

[0046] Reaction 1

[0047]

[0048] (M is a metal, such as nickel (Ni), cobalt (Co), magnesium (Mg), etc.)

[0049] The first atmospheric pressure heating leaching step S11 and the second atmospheric pressure heating leaching step S12 can be performed in two-stage equipment, or can be performed in one pressurized equipment by simply changing the process conditions (eg, temperature, pressure, or acidity).

[0050] Valuable metals can be leached from the raw material through the first atmospheric pressure heating leaching step S11. For example, valuable metals such as nickel, cobalt, and manganese can be leached from the raw material. Elements such as iron, copper, aluminum, zinc, and magnesium can also be leached from the raw material. The first atmospheric pressure heating leaching step S11 can be performed at a temperature between 50°C and 70°C and a pH between 2.7 and 3.3 for approximately 2 hours. By achieving optimal temperature and pH, high leaching efficiency can be achieved under optimal conditions.

[0051] In the first atmospheric pressure heating leaching step S11, the solid density of the raw material introduced into the reactor may be 100 g / L or higher. For example, the solid density of the raw material may be in the range of 100 g / L to 200 g / L. As used herein, the term "solid density" is defined as the ratio of the mass of the raw material introduced into the pressurizing device to the volume of the acid solution previously introduced into the reactor. In other words, the solid density may be the ratio of the mass of the raw material introduced per unit of solvent (and may be the mass of the raw material per 1 L of solvent).

[0052] The filtrate obtained in the first atmospheric heating leaching step S11 may be introduced into the first extraction step S20 , and the residue may be subsequently processed in the second atmospheric heating leaching step S12 .

[0053] In the second normal-pressure heating leaching step S12, the leached residue obtained in the first normal-pressure heating leaching step S11 may be leached at a temperature ranging from 80°C to 100°C for approximately 3 hours. Other conditions in the second normal-pressure heating leaching step S12 may be the same as those in the first normal-pressure heating leaching step S11.

[0054] The pH of the filtrate obtained in the second atmospheric-pressure heating leaching step S12 can be lower than the pH of the filtrate obtained in the first atmospheric-pressure heating leaching step S11. By controlling the pH, the leaching rate in each atmospheric-pressure heating leaching step can be increased. As a result, the entire content of the valuable metals contained in the raw material can be leached. For example, the entire content of nickel, cobalt, manganese, iron, copper, aluminum, zinc, and magnesium contained in the raw material can be leached.

[0055] In one embodiment, the filtrate formed in the second atmospheric pressure heating leaching step S12 can be fed to the first atmospheric pressure heating leaching step S11, as shown in FIG. Figure 1 shown.

[0056] In the commonly used atmospheric pressure leaching method, the reaction time must be 18 hours or longer to increase the leaching rate of valuable metals. This results in additional costs due to the increased fuel and steam usage. The low daily volume of raw material processed results in low productivity. However, according to one embodiment of the present invention, a two-stage atmospheric pressure heating leaching method can improve nickel and cobalt recovery rates and reduce energy consumption. This reduces production costs and improves productivity.

[0057] The residue produced in the second atmospheric pressure heating leaching step S12 can be discarded, such as Figure 1 shown.

[0058] First extraction step S20

[0059] The first extraction step S20 is a step of selectively separating or extracting nickel from the aqueous solution (leaching solution) containing nickel / cobalt ionized by the two-stage atmospheric pressure heating leaching step by using a first solvent extractant.

[0060] The first solvent extractant is not particularly limited as long as the nickel loading rate is low, and may be, for example, bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272).

[0061] When the first solvent extractant is added to the leachate, nickel may not be carried by the first solvent extractant and may be distributed to the first filtrate (raffinate). Cobalt and other impurities (Mg, Mn, Zn, etc.) can be separated or extracted by distributing them along with the first solvent extractant to the organic layer. This separation or extraction can occur according to the reactions represented by the following equations 2 and 3. The reaction in equation 3 neutralizes the H2SO4 formed in the reaction in equation 2, thereby maintaining the pH.

[0062] Reaction 2

[0063]

[0064] (R is nickel (Ni) or the like, and M is cobalt (Co), magnesium (Mg), manganese (Mn) or the like)

[0065] Reaction 3

[0066]

[0067] The first extraction step can be performed at a temperature of 40 degrees Celsius and a pH greater than 5.0 and less than 5.4. By satisfying the temperature and pH, it is possible to increase the loading rate of cobalt and impurities and efficiently separate nickel into the filtrate.

[0068] In one embodiment, the ratio of the first solvent extractant (O) to the aqueous solution (A) can be controlled based on the concentration of the component to be extracted from the solution. For example, the ratio (O:A) of the first solvent extractant (O) to the aqueous solution (A) can be in the range of 0.5:1 to 2:1. For example, the O:A ratio can be 1.5:1.

[0069] Then refer to Figure 2, a precipitation removal step S31 of precipitating and removing impurities from the first filtrate that has passed the first extraction step S11, a target material precipitation step S41 of selectively precipitating a nickel filter cake containing high-purity nickel, and a final leaching step of preparing an aqueous solution containing high-purity nickel can be performed.

[0070] Sediment removal step S31

[0071] A precipitation removal step S31 may be performed to remove impurities such as magnesium, calcium, or a mixture thereof remaining in the first filtrate. After the precipitation removal step S31, the first filtrate may be fed to a target material precipitation step S41.

[0072] For example, in the precipitate removal step S31 , a remover may be introduced into the solution. The remover is not particularly limited as long as it can react with magnesium or calcium to form a precipitate. The remover may be, for example, sodium fluoride (NaF).

[0073] For example, magnesium and calcium can be precipitated as magnesium fluoride or calcium fluoride through the reaction represented by the following reaction formula 4.

[0074] For example, by performing the precipitation removal step S31 at a reaction temperature in the range of 50° C. to 70° C. for about 2 hours or longer, only magnesium and calcium can be separated by selective precipitation while reducing nickel precipitation in the filtrate.

[0075] Reaction 4

[0076] (M is magnesium (Mg) or calcium (Ca))

[0077] In one embodiment, more than 2.0 equivalents (eq) of magnesium, calcium, or a mixture thereof of sodium fluoride may be added. In another embodiment, less than 2.4 equivalents (eq) of magnesium, calcium, or a mixture thereof of sodium fluoride may be added.

[0078] Target material precipitation step S41

[0079] In the target material precipitation step S41 , after the precipitate removal step S31 , a neutralizing agent may be added to the first filtrate.

[0080] For example, the neutralizing agent may be a sodium-containing alkaline substance. For example, the neutralizing agent may be sodium carbonate (Na2CO3).

[0081] After removing impurities such as magnesium and calcium in the target material precipitation step S41 , nickel may be precipitated in the form of a filter cake through the reaction shown in the following Reaction Formula 5.

[0082] Reaction 5

[0083]

[0084] The target material precipitation step S41 may be performed at pH 8 or higher and at a temperature ranging from 80 degrees Celsius to 90 degrees Celsius for 4 hours or more.

[0085] Since nickel can be recovered through the target material precipitation step S41, it is possible to reduce the use of expensive organic solvents that have the risk of explosion and fire, thereby improving operational stability and productivity and reducing production costs.

[0086] Although not specifically shown in the accompanying figures, some sodium may be present in the precipitated nickel filter cake. Therefore, water-soluble sodium can be removed by using pure water in a later stage of washing. In this case, production costs can be reduced by reusing the removed sodium in the production of sodium carbonate (Na2CO3), a neutralizing agent.

[0087] Final leaching step S51

[0088] The final leaching step S51 is a step of preparing an aqueous solution containing high-purity nickel by washing and dissolving the nickel filter cake in a sulfuric acid solution to remove components (such as sodium, etc.).

[0089] In the final leaching step S51, the nickel filter cake can be added to a solution obtained by mixing pure water and sulfuric acid with an acidity of 150 g / L to 200 g / L. The nickel, cobalt, and trace impurities contained in the nickel filter cake can be dissolved in the sulfuric acid solution. The sulfuric acid solution and the nickel filter cake react until the pH reaches 2.0. According to one embodiment, in the final leaching step S51, the reaction can be carried out at a pH range of 1.0 to 3.0 and a temperature range of 50°C to 70°C for 4 hours or longer.

[0090] Then refer to Figure 3 , the following steps may be performed: a second filtrate preparation step S32 of adding sulfuric acid solution to the first organic layer that has passed the first extraction step S11, a purification step S42 of precipitating and recovering cobalt precipitate from the second filtrate and purifying impurities, a step S52 of re-dissolving the cobalt precipitate in sulfuric acid solution, a copper removal step S62 of removing copper by adding sodium hydrosulfide, a second extraction step S72 of separating the aqueous solution from which copper has been removed into a third filtrate containing cobalt and impurities and a second organic layer containing zinc and impurities, a precipitate removal step S82 of precipitating and removing impurities from the third filtrate, a target material precipitation step S92 of selectively precipitating a cobalt filter cake containing high-purity cobalt, and a final leaching step S102 of preparing an aqueous solution containing high-purity cobalt.

[0091] Second filtrate preparation step S32

[0092] The second filtrate preparation step S32 is a step of stripping cobalt into the sulfuric acid solution by adding the sulfuric acid solution to the first organic layer containing cobalt and impurities.

[0093] Stripping is a method in which sulfuric acid reacts with loaded cobalt to produce a cobalt-containing stripping filtrate, and the loaded impurities are recovered with an aqueous solution.

[0094] Purification step S42

[0095] The purification step S42 is a step of selectively recovering only cobalt from the stripped second filtrate. The difference between the purification step S42 and the precipitate removal step 31 is that cobalt (which is the target material) can be recovered as a precipitate in the purification step S42.

[0096] For example, in purification step S42, a cobalt precipitate can be generated by adding a sulfide to the solution. For example, the sulfide can be sodium hydrosulfide (NaSH). Cobalt in the form of the sulfide can be precipitated and recovered via the reactions shown in the following reaction formulas 6 and 7.

[0097] Reaction 6

[0098]

[0099] Reaction 7

[0100]

[0101] For example, the purification step S42 may be performed for about 3 hours or longer while maintaining a pH of 4.5 to 5.0 at a reaction temperature in the range of 70 degrees Celsius to 90 degrees Celsius.

[0102] In this pH range, the solubility of cobalt sulfide (CoS) and zinc sulfide (ZnS) is extremely low, as low as 0.1 mg / L or less, while the solubility of magnesium sulfide (MgS) and manganese sulfide (MnS) is high. Therefore, by controlling the pH range, it is possible to purify magnesium and manganese by selectively separating only cobalt and zinc through precipitation.

[0103] In one embodiment, the sulfide may be added in an amount greater than 1.0 equivalent and less than 1.6 equivalent of cobalt and zinc.

[0104] Sulfuric acid solution preparation step S52

[0105] In the sulfuric acid solution preparation step S52 , an aqueous solution is prepared by dissolving the cobalt-containing precipitate in a sulfuric acid solution.

[0106] For example, the sulfuric acid solution preparation step S52 can be performed by the reaction represented by the following reaction formula 8.

[0107] Reaction 8

[0108]

[0109] For example, in the sulfuric acid solution preparation step S52 , the solid density (S / D) of the precipitate in the sulfuric acid solution when preparing the aqueous solution may be 100 g / L or higher.

[0110] For example, the sulfuric acid solution preparation step S52 may be performed at a reaction temperature ranging from 80 degrees Celsius to 100 degrees Celsius for about 20 hours or more.

[0111] Copper removal step S62

[0112] The copper removal step S62 is a step of removing copper (Cu) from the solution by adding sodium hydrosulfide (NaSH) to the solution. Copper can be precipitated as a copper sulfide (CuS) compound through the reaction shown in the following reaction formula 9.

[0113] Reaction 9

[0114]

[0115] Copper sulfide (CuS) can precipitate at a pH of 1.0 or higher. Therefore, during the copper removal step ( S62 ), the solution pH can be maintained between 1.0 and 2.5. In one embodiment, the solution pH during the copper removal step ( S62 ) can be maintained between 1.0 and 1.5. When the solution pH is less than 1.0, copper removal from solutions of 20 mg / L or less is difficult. When the pH is greater than 2.5, the solubility of cobalt in sulfuric acid decreases, potentially leading to cobalt loss.

[0116] Alternatively, sodium hydrosulfide (NaSH) can be added slowly so that the pH of the solution does not change rapidly. For example, NaSH can be added over approximately three hours while the leachate is stirred. This can prevent an increase in cobalt loss due to a rapid rise in pH in certain areas of the solution.

[0117] In one embodiment, sodium hydrosulfide (NaSH) may be added at a copper content greater than 4.5 equivalents (eq) and less than 5.5 equivalents (eq). When the amount of sodium hydrosulfide (NaSH) added is 4.5 eq or less, copper removal rates of 95% or less may be difficult to adequately remove from the solution. When the amount of sodium hydrosulfide (NaSH) added is 5.5 eq or more, cobalt recovery may be reduced due to a cobalt removal rate of 0.05% or more.

[0118] By performing the copper removal step S62 for 3 hours or longer at a reaction temperature in the range of 50°C to 70°C, it is possible to reduce cobalt precipitation in the filtrate and separate only copper by selective precipitation. Sodium hydrosulfide may be a product having a concentration of 30 wt% to 70 wt%.

[0119] Second extraction step S72

[0120] The second extraction step S72 is a step of adding a second solvent extractant to the solution and separating the solution into a third filtrate containing cobalt and impurities and a second organic layer containing zinc and impurities.

[0121] The second solvent extractant is not particularly limited as long as it has a low cobalt loading rate. For example, the second solvent extractant may be di-(2-ethylhexyl)phosphoric acid (D2EHPA).

[0122] When the second solvent extractant is added to the solution, cobalt may not be carried by the second solvent extractant and may be distributed to the third filtrate (raffinate), while zinc, magnesium, manganese, and the like are distributed with the second solvent extractant and separated or extracted into the organic layer. This separation or extraction can occur via the reaction represented by the following reaction formula 10.

[0123] Reaction 10

[0124] (R is cobalt (Co), etc.)

[0125] The second extraction step S72 can be performed at a pH greater than 2.4 and less than 3.2 and a temperature of 40 degrees Celsius for approximately 10 minutes or longer. By maintaining the pH range at the aforementioned temperature, it is possible to increase the loading rate of impurities such as zinc, reduce the loading rate of cobalt, and efficiently separate the cobalt into the filtrate.

[0126] In one embodiment, the ratio of the second solvent extractant (O) to the aqueous solution (A) can be controlled based on the concentration of the component to be extracted in the solution. For example, the ratio (O:A) of the second solvent extractant (O) to the aqueous solution (A) can be in the range of 0.5:1 to 2:1. For example, the O:A ratio can be 1.5:1.

[0127] Sediment removal step S82

[0128] A precipitate removal step S82 may be performed to remove impurities remaining in the third filtrate, such as magnesium, etc. After the precipitate removal step S82, the third filtrate may be fed to a target material precipitation step S92.

[0129] The details of the sediment removal step S82 can be understood by referring to the description of the sediment removal step S31 .

[0130] Target material precipitation step S92

[0131] In the target material precipitation step S92 , after the precipitate removal step S82 , a neutralizing agent may be added to the third filtrate.

[0132] For example, the neutralizing agent may be a sodium-containing alkaline substance. For example, the neutralizing agent may be sodium carbonate (Na2CO3).

[0133] After removing impurities such as magnesium, etc., nickel may be precipitated in the form of a filter cake in the target material precipitation step S41 through a reaction represented by the following reaction formula 11.

[0134] Reaction 11

[0135]

[0136] The target material precipitation step S92 may be performed at a pH of 8 or higher and a temperature in a range of 80 degrees Celsius to 90 degrees Celsius for 4 hours or more.

[0137] Since cobalt can be recovered through the target material precipitation step S92, it is possible to reduce the use of expensive organic solvents that have the risk of explosion and fire, thereby improving operational stability and productivity and reducing production costs.

[0138] Although not specifically shown in the accompanying figures, some sodium may be present in the precipitated cobalt filter cake. Therefore, the water-soluble sodium can be removed in a later stage through a washing step using pure water. In this case, the removed sodium can be reused in the production of sodium carbonate (Na2CO3), a neutralizing agent, thereby reducing production costs.

[0139] Final leaching step S102

[0140] The final leaching step S102 is a step of preparing an aqueous solution containing high-purity cobalt by washing and dissolving the cobalt filter cake in a sulfuric acid solution to remove components such as sodium.

[0141] The details of the final leaching step S102 can be understood by referring to the above description of the final leaching step S51.

[0142] Experimental example

[0143] (1) The quality of the mixed hydroxide precipitate (MHP) filter cake raw material used in the experiment

[0144] Table 1

[0145]

[0146] The contents not shown in the table are impurities (mostly in the form of hydroxyl groups attached to them).

[0147] (2) Metal content in the leaching filtrate after the leaching step including the two-stage atmospheric pressure heating leaching step

[0148] Table 2

[0149]

[0150] Comparing Tables 1 and 2, it can be seen that the nickel and cobalt contents in the leaching filtrate increased after the two-stage atmospheric pressure heating leaching step.

[0151] (3) Comparison of cobalt content in the organic layer based on pH conditions during the extraction step

[0152] To determine the optimal pH conditions for loading cobalt and impurities (Mg, Mn, Zn, etc.) into the organic layer using 30% Cyanex 272 to separate nickel into the aqueous filtrate (raffinate), the loading rates of individual components in the organic layer at pH 5.0, 5.2, and 5.4 were compared. The reaction was performed at 40°C for 10 minutes, with an organic layer to aqueous solution ratio of 1.5:1. The loading rate is expressed as the relative ratio of the content of each component in the organic layer to the content of the component in the leachate.

[0153] Table 3

[0154]

[0155] Referring to Table 3, it can be seen that the difference between the contents of Co and Ni loaded in the organic layer is the largest at pH 5.2, and the separation of Co and Ni occurs best at pH 5.2.

[0156] At pH 5.0, the content of Ni loaded in the organic layer was small, but the loading of Co was relatively poor. At pH 5.4, the loading of Co was excellent, but the separation of Ni was relatively poor.

[0157] (4) Comparison of impurity (Mg and Ca) content in the filtrate based on the amount of sodium fluoride added in the precipitation removal step

[0158] To determine the optimal amount of sodium fluoride (NaF) for precipitating and removing impurities (Mg and Ca) from the filtrate, 2.0, 2.2, and 2.4 equivalents of NaF were added relative to the Mg and Ca concentrations in the filtrate. The resulting impurity (Mg and Ca) contents were compared. The reaction was carried out at 60°C for 2 hours.

[0159] Table 4

[0160]

[0161] Referring to Table 4, it can be seen that when 2.2 equivalents of sodium fluoride (NaF) are added, the sum of the contents of Mg and Ca in the filtrate is the smallest.

[0162] (5) Comparison of metal contents (Co, Cu, Zn, Mn, and Mg) in cobalt filter cakes based on the amount of sodium hydrosulfide (NaSH) added during the impurity removal step

[0163] To determine the optimal conditions for stripping cobalt loaded on Cyanex 272 from the organic layer using sulfuric acid solution, followed by precipitation and recovery of the cobalt as sulfide using sodium hydrosulfide (NaSH), 1.0, 1.3, and 1.6 equivalents of sodium hydrosulfide (NaSH) were added to the organic layer relative to the cobalt and zinc content, and the resulting filter cake contents were compared. The reaction was carried out at 85°C and a pH range of 4.5 to 5.0 for 3 hours.

[0164] Table 5.

[0165]

[0166] Referring to Table 5, it can be seen that when 1.3 equivalents of NaSH were added, the cobalt content in the filter cake was high, and even when more than 1.3 equivalents of NaSH were added, the cobalt content did not increase any more.

[0167] (6) Comparison of copper removal rates based on the amount of sodium hydrosulfide (NaSH) added in the copper removal step

[0168] To examine the optimal conditions for precipitating and removing copper in the form of CuS by adding NaSH to a cobalt-containing aqueous solution after dissolving the cobalt precipitate in sulfuric acid, 4.5, 5.0, and 5.5 equivalents of NaSH relative to the copper content were added, and the copper removal rates were compared. The reaction was carried out at 60°C and pH 1.0 for 3 hours. The removal rates were expressed by comparing the levels of individual components in the aqueous solution before and after the addition of NaSH.

[0169] Table 6.

[0170]

[0171] Referring to Table 6, it can be seen that when 5.0 equivalents of NaSH are added, the Cu removal rate is the highest.

[0172] (7) Comparison of cobalt content in the organic layer based on pH conditions in the extraction step

[0173] To examine the optimal pH conditions for loading zinc from aqueous solution into an organic layer and isolating the zinc using 30% di-(2-ethylhexyl)phosphoric acid (D2EHPA) as a solvent extractant from a cobalt-containing aqueous solution from which cobalt had been precipitated and removed, the loading ratios of individual components at pH 2.4, 2.8, and 3.2 were compared. The reaction was carried out at 40°C for 10 minutes. The organic layer to aqueous solution ratio was 1.5:1.

[0174] Table 7.

[0175]

[0176] Referring to Table 7, it can be seen that the difference between the contents of zinc (Zn) and cobalt (Co) loaded in the organic layer is the largest at pH 2.8, and the best separation of cobalt (Co) and zinc (Zn) occurs at pH 2.8.

[0177] At pH 2.4, the content of Co loaded in the organic layer was small, but the Zn loading was relatively poor. At pH 3.2, the Zn loading was excellent, but the separation of Co was relatively poor.

[0178] (8) Metal content in nickel / cobalt aqueous solutions (which have undergone a final washing step to remove impurities)

[0179] Table 8

[0180] After removing impurities, the metal content in the final nickel-containing aqueous solution is

[0181]

[0182] Table 9

[0183] After removing impurities, the metal content in the final aqueous solution containing cobalt is

[0184]

[0185] Comparing Table 2, Table 8 and Table 9 together, it can be confirmed that the purity of the nickel / cobalt-containing aqueous solution is increased after the steps of the present invention.

[0186] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art will appreciate that the embodiments may be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

[0187] Therefore, it should be understood that the above embodiments are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the specific embodiments. The scope of the present invention should be understood to include all variations and modifications derived from the meaning and scope of the claims and their equivalents.

Claims

1. A method for preparing an aqueous solution containing nickel or cobalt, characterized in that include: (A) a leaching step, comprising a first atmospheric pressure heating leaching step and a second atmospheric pressure heating leaching step, wherein a mixed hydroxide precipitate containing nickel and cobalt mixed hydroxide is heated and leached at atmospheric pressure to form a leaching solution containing nickel, cobalt and impurities; (B) a first extraction step of adding a first solvent extractant to the leach solution to separate the leach solution into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities; (Ci) a precipitation removal step, wherein a precipitant is added to the first filtrate to precipitate and remove impurities including magnesium, calcium, or a mixture thereof; and (Di) a target material precipitation step of selectively precipitating a nickel filter cake containing nickel by adding a neutralizing agent to the first filtrate after precipitation and removal of impurities including magnesium, calcium, or a mixture thereof, The first atmospheric pressure heating leaching step is carried out at a temperature in the range of 50 degrees Celsius to 70 degrees Celsius. The second atmospheric pressure heating leaching step is carried out at a temperature ranging from 80 degrees Celsius to 100 degrees Celsius.

2. A method for preparing an aqueous solution containing nickel or cobalt, characterized in that include: (A) a leaching step, comprising a first atmospheric pressure heating leaching step and a second atmospheric pressure heating leaching step, wherein a mixed hydroxide precipitate containing nickel and cobalt mixed hydroxide is heated and leached at atmospheric pressure to form a leaching solution containing nickel, cobalt and impurities; (B) a first extraction step of adding a first solvent extractant to the leach solution to separate the leach solution into a first filtrate containing nickel and impurities and a first organic layer containing cobalt and impurities; as well as (C-ii) a purification step of adding a sulfuric acid solution to the first organic layer to prepare a second filtrate, and adding a sulfide to the second filtrate to precipitate and recover a cobalt precipitate to remove impurities including magnesium, manganese, zinc, copper, or a mixture thereof, The first atmospheric pressure heating leaching step is carried out at a temperature in the range of 50 degrees Celsius to 70 degrees Celsius. The second atmospheric pressure heating leaching step is carried out at a temperature ranging from 80 degrees Celsius to 100 degrees Celsius.

3. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1 or 2, characterized in that The pH of the filtrate obtained in the second leaching step by heating at normal pressure is lower than the pH of the filtrate obtained in the first leaching step by heating at normal pressure.

4. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1 or 2, characterized in that The filtrate obtained in the second normal pressure heating leaching step is fed to the first normal pressure heating leaching step.

5. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1 or 2, characterized in that: The first solvent extractant is bis(2,4,4-trimethylpentyl) hypophosphorous acid.

6. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1 or 2, characterized in that: The first extraction step is performed at a temperature of 40 degrees Celsius and a pH greater than 5.0 and less than 5.

4.

7. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1, characterized in that The above-mentioned precipitant is sodium fluoride.

8. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1, characterized in that The precipitant is added in an amount greater than 2.0 equivalents and less than 2.4 equivalents of the magnesium, calcium, or a mixture thereof.

9. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1, characterized in that The above-mentioned neutralizing agent is a sodium-containing alkaline substance.

10. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1, characterized in that After the neutralizing agent is added, the pH of the first filtrate at a temperature of 85 degrees Celsius is 8 or higher.

11. The method for preparing an aqueous solution containing nickel or cobalt according to claim 1, characterized in that Also includes: (Ei) a washing step of washing the nickel filter cake with pure water.

12. The method for preparing an aqueous solution containing nickel or cobalt according to claim 2, characterized in that: The above-mentioned sulfide is sodium hydrosulfide.

13. The method for preparing an aqueous solution containing nickel or cobalt according to claim 2, characterized in that The sulfide is added in an amount greater than 1.0 equivalent and less than 1.6 equivalent of the cobalt and zinc.

14. The method for preparing an aqueous solution containing nickel or cobalt according to claim 2, characterized in that Also includes: (D-ii) A copper removal step, wherein the cobalt precipitate is dissolved in a sulfuric acid solution and the copper is subsequently removed.

15. The method for preparing an aqueous solution containing nickel or cobalt according to claim 14, characterized in that The copper removal step is performed by adding sodium hydrosulfide having a copper content greater than 4.5 equivalents and less than 5.5 equivalents.

16. The method for preparing an aqueous solution containing nickel or cobalt according to claim 14, characterized in that Also includes: (E-ii) a second extraction step of adding a second solvent extractant to the aqueous solution from which copper has been removed to separate the aqueous solution from which copper has been removed into a third filtrate containing cobalt and impurities and a second organic layer containing zinc and impurities.

17. The method for preparing an aqueous solution containing nickel or cobalt according to claim 16, characterized in that The second solvent extractant is di-(2-ethylhexyl)phosphoric acid.

18. The method for preparing an aqueous solution containing nickel or cobalt according to claim 16, characterized in that The second extraction step is performed at a temperature of 40 degrees Celsius and a pH greater than 2.4 and less than 3.

2.

19. The method for preparing an aqueous solution containing nickel or cobalt according to claim 16, characterized in that Also includes: (F) a precipitation removal step, wherein a precipitant is added to the third filtrate to precipitate and remove impurities including magnesium.

20. The method for preparing an aqueous solution containing nickel or cobalt according to claim 19, characterized in that Also includes: (G) A target material precipitation step of selectively precipitating a cobalt filter cake containing cobalt by adding a neutralizing agent to the third filtrate after precipitation and removal of the impurities including magnesium, calcium, or a mixture thereof.

21. The method for preparing an aqueous solution containing nickel or cobalt according to claim 20, characterized in that After the neutralizing agent is added, the pH of the third filtrate at a temperature of 85 degrees Celsius is 8 or higher.

22. The method for preparing an aqueous solution containing nickel or cobalt according to claim 20, characterized in that Also includes: (H) a washing step of washing the cobalt filter cake with pure water.

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