Preparation method of battery-grade cobaltous sulfate solution

Abstract

The invention provides a preparation method of a battery-grade cobalt sulfate solution, which comprises the following steps: mixing crude cobalt hydroxide with water to obtain crude cobalt hydroxide slurry, adding acid into the crude cobalt hydroxide slurry to adjust the pH value to be below 8, carrying out magnesium removal reaction, and carrying out solid-liquid separation to obtain a magnesium-removed solid product; mixing the magnesium-removed solid product with water, and adding acid and a reducing agent for acid dissolution to obtain an acid-soluble solution; the acid solution is subjected to iron removal, calcium and magnesium removal and fluorine removal, and fluorine-removed liquid is obtained; and extracting the fluorine-removed liquid by adopting a P204 extracting agent to obtain raffinate, and removing oil from the raffinate to obtain the battery-grade cobalt sulfate solution. According to the method, high-impurity raw materials with high Mg and Ca content can be treated through acid pickling magnesium removal, acid dissolution, iron removal, calcium and magnesium removal through fluorination, deep fluorine removal, P204 extraction refining and oil removal, the cost can be reduced, and the battery-grade cobalt sulfate solution with low impurity content is obtained.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology and relates to a method for preparing battery-grade cobalt sulfate solution. Background Technology

[0002] Battery-grade cobalt sulfate, required for the cathode material of ternary lithium batteries, is typically produced using nickel-cobalt hydroxide, an intermediate product from the hydrometallurgical process of laterite nickel ore, or recycled crude cobalt hydroxide as raw material. However, these raw materials often contain impurities such as Ni, Fe, Mg, Al, Cr, Mn, Cu, Ca, Si, Pb, Zn, As, and Cd. Currently, the preparation method for battery-grade cobalt sulfate involves acid leaching and reduction of crude cobalt hydroxide to obtain a crude cobalt sulfate solution. This solution is then extracted using P204 to remove iron, copper, zinc, manganese, and calcium, and P507 to separate cobalt and magnesium, yielding a battery-grade cobalt sulfate solution. This process easily forms calcium slag in the extraction section, affecting production efficiency, increasing production costs, and the extraction process is lengthy with high alkali consumption.

[0003] Based on the above research, there is a need to provide a method for preparing battery-grade cobalt sulfate solution to solve the problems of calcium slag formation in the extraction stage, high production costs, and long process. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing battery-grade cobalt sulfate solution. The preparation method involves acid washing to remove magnesium, acid dissolution, iron removal, fluorination to remove calcium and magnesium, deep fluorination, P2O4 extraction purification, and oil removal. This method can process high-impurity raw materials with high Mg and Ca content, reduce costs, and obtain battery-grade cobalt sulfate solution with low impurity content.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing battery-grade cobalt sulfate solution, the method comprising the following steps:

[0007] (1) Crude cobalt hydroxide is mixed with water to obtain crude cobalt hydroxide slurry. Acid is added to the crude cobalt hydroxide slurry to adjust the pH to below 8, for example, 8, 7.8, 7.5, 7.3 or 7.0, to carry out magnesium removal reaction. After solid-liquid separation, magnesium-removed solid product is obtained.

[0008] (2) After mixing the magnesium-removing solid product from step (1) with water, add acid and reducing agent to dissolve it in acid to obtain an acid solution;

[0009] (3) Remove iron, calcium and magnesium and fluoride from the acid solution in step (2) to obtain a defluorinated solution;

[0010] During the iron removal process, the pH of the solution is below 4.5, for example, it can be 4.5, 4.3, 4.1, 3.9, 3.7 or 3.5;

[0011] (4) The defluorinated liquid in step (3) is extracted with P204 extractant to obtain raffinate. The raffinate is then deoiled to obtain the battery-grade cobalt sulfate solution.

[0012] This invention targets crude cobalt hydroxide with high magnesium and calcium content. First, magnesium is removed by acid washing at a pH below 8 in the crude cobalt hydroxide slurry, significantly reducing the magnesium content in the sample. If acid is added to adjust the pH to >8 in the crude cobalt hydroxide slurry, the residual Mg content will be too high, and co-precipitation during iron removal will lead to excessively high residual magnesium and iron in the final product. After acid washing to remove magnesium, acid dissolution is performed, followed by iron removal at a pH below 4.5. This ensures that cobalt is not significantly lost while guaranteeing iron removal. Then, fluorination is used to remove calcium and magnesium, and fluorine is removed. Finally, P204 extractant is used for extraction and oil removal to obtain a battery-grade cobalt sulfate solution.

[0013] Preferably, the solid-liquid ratio of crude cobalt hydroxide to water in step (1) is 1g:(3-5)mL, for example, it can be 1g:3mL, 1g:4mL or 1g:5mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, in step (1), acid is added to the crude cobalt hydroxide slurry to adjust the pH to 7.0-7.5, for example, it can be 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the stirring speed of the magnesium removal reaction in step (1) is 200-400 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the temperature of the magnesium removal reaction in step (1) is 40-60℃, for example, it can be 40℃, 45℃, 50℃, 55℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the magnesium removal reaction time in step (1) is 25-35 min, for example, it can be 25 min, 27 min, 29 min, 31 min, 33 min or 35 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, in the crude cobalt hydroxide of step (1), the magnesium content is ≤8.5%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 8.5%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, in the magnesium-removed solid product of step (1), the magnesium content is ≤1.5%, for example, it can be 0.5%, 1% or 1.5%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the solid-liquid ratio of the magnesium-removing solid product to water in step (1) is 1g:(5-8)mL, for example, it can be 1g:5mL, 1g:6mL, 1g:7mL or 1g:8mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the amount of acid added in step (2) is 1.2-1.5 times the molar amount of cobalt, for example, it can be 1.2 times, 1.3 times, 1.4 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the amount of reducing agent added in step (2) is 0.1-0.3 times the molar amount of cobalt, for example, it can be 0.1 times, 0.15 times, 0.2 times, 0.25 times or 0.3 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the reducing agent in step (2) includes hydrogen peroxide.

[0024] Preferably, the acid dissolution temperature in step (2) is 60-80℃, for example, 60℃, 65℃, 70℃, 75℃ or 80℃, and the reaction time is 1-2h, for example, 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, hydrogen peroxide is added to the acid solution in step (2) to remove iron in step (3).

[0026] Preferably, the amount of hydrogen peroxide added to the acid solution in step (2) is 1.2-1.5 times the molar amount of iron, for example, it can be 1.2 times, 1.3 times, 1.4 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the iron removal temperature in step (3) is 60-80℃, for example, 60℃, 65℃, 70℃, 75℃ or 80℃, and the time is 0.5-1h, for example, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, during iron removal in step (3), the pH of the solution is 3.8-4.2, for example, it can be 3.8, 3.9, 4.0, 4.1 or 4.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the impurity removal agent used in step (3) for removing calcium and magnesium includes sodium fluoride.

[0030] Preferably, the amount of the impurity removal agent used in step (3) to remove calcium and magnesium is 1.2-1.5 times the total molar amount of calcium and magnesium, for example, it can be 1.2 times, 1.3 times, 1.4 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, when removing calcium and magnesium in step (3), the pH of the solution is 3.5-4.0, for example, it can be 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the time for removing calcium and magnesium in step (3) is 30-60 min, for example, it can be 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, in step (3), the removal of calcium and magnesium is carried out by adding the removal agent in two separate steps.

[0034] This invention removes calcium and magnesium through stepwise fluorination, which improves the removal efficiency and reduces the residue of calcium and magnesium compared to adding all the removal agents at once. In the process of removing calcium and magnesium, the amount of removal agent added in the first step accounts for 60-80% of the total removal agent, and the amount of removal agent added in the second step accounts for 20-40% of the total removal agent.

[0035] Preferably, the defluorinating agent used in step (3) includes a zirconium-titanium-based defluorinating agent.

[0036] Preferably, the zirconium-titanium-based defluorinating agent comprises zirconium-titanium composite oxide (the molar ratio of Ti to Zr can be, for example, 4:1).

[0037] Preferably, the amount of zirconium-titanium-based defluorinating agent added is 0.8-1.2 g / L, for example, it can be 0.8 g / L, 0.9 g / L, 1.0 g / L, 1.1 g / L or 1.2 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, during the defluorination process in step (3), the pH of the solution is adjusted to 4.5-5.5, for example, it can be 4.5, 4.7, 4.9, 5.1, 5.3 or 5.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the defluorination time in step (3) is 40-60 min, for example, it can be 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the saponification rate of the P204 extractant in step (4) is 60-80%, for example, it can be 60%, 65%, 70%, 75% or 80%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the extraction in step (4) is carried out at a pH of 2.5-3.5, such as 2.5, 2.7, 2.9, 3.1, 3.3 or 3.5, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, the O / A ratio extracted in step (4) is 1:(3-5), for example, it can be 1:3, 1:4 or 1:5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the degreasing agent used in step (4) includes activated carbon.

[0044] Preferably, the amount of activated carbon added is 0.5-1.5 g / L, for example, it can be 0.5 g / L, 1.0 g / L or 1.5 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the degreasing temperature in step (4) is 50-60℃, for example, 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃, and the time is 25-35min, for example, 25min, 27min, 29min, 31min, 33min or 35min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, in the battery-grade cobalt sulfate solution in step (4), the cobalt content is ≥20.5%, for example, it can be 20.5%, 21%, 21.5%, 22% or 22.5%, and the impurity content is ≤1ppm, for example, it can be 0.2ppm, 0.4ppm, 0.6ppm, 0.8ppm or 1ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention targets crude cobalt hydroxide with high magnesium and calcium content. First, magnesium is removed by acid washing at a pH below 8 in the crude cobalt hydroxide slurry, significantly reducing the magnesium content in the sample. If acid is added to adjust the pH to >8 in the crude cobalt hydroxide slurry, the residual Mg content will be too high, and co-precipitation during iron removal will lead to excessively high residual magnesium and iron in the final product. After acid washing to remove magnesium, acid dissolution is performed, followed by iron removal at a pH below 4.5. This ensures that cobalt is not significantly lost while guaranteeing iron removal. Then, fluorination is used to remove calcium and magnesium, and fluorine is removed. Finally, P204 extractant is used for extraction and oil removal to obtain a battery-grade cobalt sulfate solution. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0050] Example 1

[0051] This embodiment provides a method for preparing battery-grade cobalt sulfate solution, the preparation method comprising the following steps:

[0052] (1) Acid washing to remove magnesium: Crude cobalt hydroxide (Mg content of 8.5%) was mixed with water at a solid-liquid ratio of 1g:3mL and slurryed. Concentrated sulfuric acid of 98% was slowly added to adjust the pH to 7.0. The reaction was carried out for 30 minutes under the conditions of stirring speed of 300rpm and temperature of 40℃. Then, the mixture was separated by pressure filtration to obtain filter residue. The Mg content in the filter residue was reduced to 3.42%.

[0053] (2) Acid dissolution: Add the filter residue obtained in step (1) to water at a liquid-solid ratio of 5 mL: 1 g, then add concentrated sulfuric acid with a concentration of 98% (1.2 times the molar amount of cobalt) and hydrogen peroxide with a concentration of 30% (0.2 times the molar amount of cobalt), control the acid dissolution temperature at 60℃, and dissolve in acid for 1.5 h until completely dissolved;

[0054] (3) Iron removal: Add hydrogen peroxide at 1.2 times the molar amount of Fe in the acid solution obtained in step (2), control the iron removal temperature at 60℃, the iron removal pH at 3.8, and react for 45 minutes to remove iron;

[0055] (4) Fluorination to remove calcium and magnesium: Sodium fluoride is added to the iron-removed solution at a time at 1.2 times the total molar amount of Ca+Mg, the pH of calcium and magnesium removal is controlled at 3.5, the reaction is stirred for 60 min, and the CaF2 and MgF2 precipitates are removed by filtration.

[0056] (5) Deep defluorination: Add zirconium-titanium defluorination agent (zirconium-titanium composite oxide with a molar ratio of Ti to Zr of 4:1) to the filtrate of step (4). The amount of zirconium-titanium defluorination agent added to the filtrate of step (4) is 1.0 g / L. Adjust the defluorination pH to 4.0, stir the reaction for 40 min to remove fluoride, and then filter.

[0057] (6) P204 extraction and purification: Using P204 extractant (saponification rate of 65%) at pH=3.0, the filtrate obtained in step (5) was subjected to three-stage countercurrent extraction (O / A=1:3) to remove Fe, Cu, Zn, Mn and Ca;

[0058] (7) Activated carbon degreasing: Add activated carbon (addition amount is 0.8g / L) to the raffinate obtained in step (6), control the degreasing temperature at 50℃, stir to remove oil for 30min, and filter to obtain the battery-grade cobalt sulfate solution.

[0059] Examples 2-7

[0060] Examples 2-7 provide a method for preparing battery-grade cobalt sulfate solution. The difference between the preparation method and Example 1 is that, except for the changes in the conditions in Tables 1-7, the rest are the same as in Example 1.

[0061] In the preparation methods described in Examples 1-7, the reaction conditions, Mg removal rate, and Mg residue in step (1) for acid washing to remove magnesium are shown in Table 1:

[0062] Table 1

[0063]

[0064] In the preparation methods described in Examples 1-7, the reaction conditions for acid dissolution in step (2) and the solubility of acid dissolution are shown in Table 2:

[0065] Table 2

[0066]

[0067] In the preparation methods described in Examples 1-7, the reaction conditions for iron removal, Fe residue, and Co loss rate in step (3) are shown in Table 3:

[0068] Table 3

[0069]

[0070] In the preparation methods described in Examples 1-7, the reaction conditions, residual Ca content, and residual Mg content of fluorination for removing calcium and magnesium in step (4) are shown in Table 4:

[0071] Table 4

[0072]

[0073] In the preparation methods described in Examples 1-7, the reaction conditions, residual fluoride ions, and Co loss rate in step (5) of the deep defluorination process are shown in Table 5:

[0074] Table 5

[0075]

[0076] In the preparation methods described in Examples 1-7, the reaction conditions, residual Mn content, and residual Zn content of P204 extraction and purification in step (6) are shown in Table 6:

[0077] Table 6

[0078]

[0079] In the preparation methods described in Examples 1-7, the reaction conditions and TOC residue of activated carbon for oil removal in step (7) are shown in Table 7:

[0080] Table 7

[0081]

[0082] The Co content, total impurity content, and F content in the battery-grade cobalt sulfate solutions obtained by the preparation methods described in Examples 1-7 are as follows: - The content and conductivity of battery-grade cobalt sulfate solution are shown in Table 8:

[0083] Table 8

[0084]

[0085] Comparative Examples 1-3

[0086] Comparative Examples 1-3 provide a method for preparing a cobalt sulfate solution. The preparation method is the same as that of Example 1 except that the conditions in Table 9 are changed from those of Example 1.

[0087] Table 9

[0088]

[0089] Table 10 shows a comparison of the full-process data of Embodiment 3 and Comparative Example 3 of the present invention:

[0090] Table 10

[0091]

[0092] As can be seen from the table above, the raw material adaptability of the present invention is wide, and it can process high impurity raw materials with Mg>12% and Ca>1%, while reducing costs, reducing acid consumption by 18%, and achieving a cobalt recovery rate of >99%. In addition, stepwise fluorination (70% added in the first step + 30% added in the second step) can reduce cobalt loss by 2.1% (Example 3 compared to Comparative Example 2). At the same time, the zirconium-titanium defluorination agent (Ti:Zr=4:1) of the present invention can increase the fluorine adsorption capacity by 3 times compared with traditional aluminum salts.

[0093] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing battery-grade cobalt sulfate solution, characterized in that, The preparation method includes the following steps: (1) Crude cobalt hydroxide is mixed with water to obtain crude cobalt hydroxide slurry. Acid is added to the crude cobalt hydroxide slurry to adjust the pH to below 8, and magnesium removal reaction is carried out. After solid-liquid separation, magnesium removal solid product is obtained. (2) After mixing the magnesium-removing solid product from step (1) with water, add acid and reducing agent to dissolve it in acid to obtain an acid solution; (3) Remove iron, calcium and magnesium and fluoride from the acid solution in step (2) to obtain a defluorinated solution; During the iron removal process, the pH of the solution is below 4.5; (4) The defluorinated liquid in step (3) is extracted with P204 extractant to obtain raffinate. The raffinate is then deoiled to obtain the battery-grade cobalt sulfate solution.

2. The preparation method according to claim 1, characterized in that, The solid-liquid ratio of crude cobalt hydroxide to water in step (1) is 1 g: (3-5) mL; Preferably, in step (1), acid is added to the crude cobalt hydroxide slurry to adjust the pH to 7.0-7.

5.

3. The preparation method according to claim 1 or 2, characterized in that, The stirring speed for the magnesium removal reaction in step (1) is 200-400 rpm; Preferably, the temperature of the magnesium removal reaction in step (1) is 40-60℃; Preferably, the magnesium removal reaction time in step (1) is 25-35 min.

4. The preparation method according to claim 1 or 2, characterized in that, In step (1), the content of magnesium in the crude cobalt hydroxide is ≤8.5%; Preferably, the magnesium content in the magnesium-removed solid product in step (1) is ≤1.5%.

5. The preparation method according to claim 1 or 2, characterized in that, The solid-liquid ratio of the magnesium removal solid product to water in step (1) is 1 g: (5-8) mL; Preferably, the amount of acid added in step (2) is 1.2-1.5 times the molar amount of cobalt; Preferably, the amount of reducing agent added in step (2) is 0.1-0.3 times the molar amount of cobalt; Preferably, the acid dissolution temperature in step (2) is 60-80℃ and the reaction time is 1-2h.

6. The preparation method according to claim 1 or 2, characterized in that, Hydrogen peroxide is added to the acid solution in step (2) to remove iron as described in step (3); Preferably, the amount of hydrogen peroxide added to the acid solution in step (2) is 1.2-1.5 times the molar amount of iron; Preferably, the iron removal temperature in step (3) is 60-80℃, and the time is 0.5-1h; Preferably, during iron removal in step (3), the pH of the solution is 3.8-4.

2.

7. The preparation method according to claim 1 or 2, characterized in that, The impurity removal agent used in step (3) to remove calcium and magnesium includes sodium fluoride; Preferably, the amount of the impurity removal agent used in step (3) to remove calcium and magnesium is 1.2-1.5 times the total molar amount of calcium and magnesium; Preferably, the calcium and magnesium removal time in step (3) is 30-60 min; Preferably, in step (3) when removing calcium and magnesium, the pH of the solution is 3.5-4.0; Preferably, in step (3), the removal of calcium and magnesium is carried out by adding the removal agent in two separate steps.

8. The preparation method according to claim 1 or 2, characterized in that, The defluorinating agent used in step (3) includes a zirconium-titanium-based defluorinating agent; Preferably, the zirconium-titanium-based defluorinating agent comprises zirconium-titanium composite oxide; Preferably, the amount of the zirconium-titanium-based defluorinating agent added is 0.8-1.2 g / L; Preferably, during the defluorination process in step (3), the pH of the solution is adjusted to 4.5-5.5; Preferably, the defluorination time in step (3) is 40-60 min.

9. The preparation method according to claim 1 or 2, characterized in that, The saponification rate of the P204 extractant in step (4) is 60-80%; Preferably, the extraction in step (4) is carried out under conditions of pH 2.5-3.5; Preferably, the O / A ratio extracted in step (4) is 1:(3-5).

10. The preparation method according to claim 1 or 2, characterized in that, The degreasing agent used in step (4) includes activated carbon; Preferably, the amount of activated carbon added is 0.5-1.5 g / L; Preferably, the oil removal temperature in step (4) is 50-60℃ and the time is 25-35 min; Preferably, in the battery-grade cobalt sulfate solution described in step (4), the cobalt content is ≥20.5% and the impurity content is ≤1ppm.

Images