Production method and application of cobalt sulfate

Abstract

The invention discloses a production method and application of cobaltous sulfate. The production method comprises the following steps: (1) removing impurities with dilute acid; (2) acid leaching reduction; (3) separating out and removing impurities; (4) extracting and deeply removing impurities; (5) separating out and removing impurities again; and (6) recrystallizing and the like. The cobalt sulfate obtained by the production method provided by the invention meets the requirements of battery-grade cobalt sulfate and can be used for synthesizing a ternary precursor.

Description

Technical Field

[0001] The invention belongs to the technical field of battery-grade cobalt sulfate manufacturing, and particularly relates to a production method of cobalt sulfate and application thereof. Background Art

[0002] The battery-grade cobalt sulfate required for the positive electrode material of ternary lithium batteries is mostly produced by hydrometallurgical smelting of laterite nickel ore intermediate product nickel cobalt hydroxide or recycled crude cobalt hydroxide as raw materials. These raw materials mostly contain impurity elements such as Ni, Fe, Mg, Al, Cr, Mn, Cu, Ca, Si, Pb, Zn, As, Cd, etc. The production process method currently used is sulfuric acid reduction leaching-solution extraction purification and impurity removal-extraction separation and enrichment of cobalt-evaporation crystallization. Due to the use of extraction separation and impurity removal and extraction and enrichment of cobalt in the solution, the oil content of the obtained cobalt sulfate solution exceeds the standard, and in actual production, it is often difficult to meet the battery-grade index requirements due to the depth of impurities. In view of the current characteristics of long production process and high purification cost caused by the large variety and high content of impurity elements in the raw materials, how to break through the bottleneck of existing process technology and seek a more efficient and simple short-process process for producing battery-grade cobalt sulfate has become a top priority. Therefore, it is necessary to provide a new method for producing cobalt sulfate. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a production method and a preparation method of cobalt sulfate and application of the cobalt sulfate in medical packaging.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] On the one hand, the present application provides a method for producing cobalt sulfate, the production method comprising the following steps: step (1) dilute acid impurity removal; step (2) acid leaching reduction; step (3) precipitation impurity removal; step (4) deep extraction impurity removal; step (5) precipitation impurity removal again; step (6) recrystallization.

[0006] Furthermore, the specific steps of the step (1) of removing impurities with dilute acid are: taking crude cobalt hydroxide and adding it into dilute sulfuric acid for reaction, maintaining the pH value of the solution between 2.0 and 3.0 during the reaction, filtering after the reaction is complete to obtain refined cobalt hydroxide after impurities are removed;

[0007] Furthermore, the reaction temperature during the dilute acid impurity removal is 60-70°C, the reaction time is 0.5-1.5h, and the concentration of the dilute sulfuric acid is 3×10 -3 -7×10 -3 mol / L; preferably, the concentration of the dilute sulfuric acid is 4×10 -3 -6×10 -3 mol / L;

[0008] Furthermore, the specific steps of the acid leaching reduction in step (2) are: taking the refined cobalt hydroxide described in step (1) and adding it to a sulfuric acid solution of sodium sulfite to react, the pH value at the end of the reaction is 1.5±0.3, and after the reaction is completed, solid-liquid separation is performed to obtain a filtrate;

[0009] Furthermore, the reaction temperature during the dilute acid impurity removal is 60-70° C., the reaction time is 2-3 hours, and the molar ratio of the cobalt hydroxide to the sodium sulfite is 1:1.4-1.6; preferably, the molar ratio of the cobalt hydroxide to the sodium sulfite is 1:1.45-1.55;

[0010] Furthermore, the specific steps of precipitation and impurity removal in step (3) are as follows: the crude cobalt sulfate solution A obtained by concentrating the filtrate in step (2) is then cooled to 25±5° C., and a precipitation agent A is added. When the Co concentration in the crude cobalt sulfate solution A is 1-5 g / L, the precipitation agent A is stopped. After stirring and aging, solid-liquid separation is performed to obtain crude cobalt sulfate crystals. Preferably, the precipitation agent A is stopped when the Co concentration in the crude cobalt sulfate solution A is 1-3 g / L.

[0011] Further, the Co content in the crude cobalt sulfate solution A obtained after concentration is 100-140 g / L, the precipitating agent A includes one or more of methanol, ethanol, n-propanol and isopropanol, and the stirring aging time is 0.5-1.5 h; preferably, the Co content in the crude cobalt sulfate solution A obtained after concentration is 110-130 g / L; more preferably, the Co content in the crude cobalt sulfate solution A obtained after concentration is 115-125 g / L; even more preferably, the Co content in the crude cobalt sulfate solution A obtained after concentration is 120 g / L;

[0012] Furthermore, the specific steps of the extraction and deep impurity removal in step (4) are: re-dissolving the crude cobalt sulfate crystals in step (3) in sulfuric acid to obtain a solution B with a pH of 3±0.3, and then extracting the solution B with an extractant A to obtain a raffinate;

[0013] Further, the extractant A comprises diluent sulfonated kerosene, P204 and TBP, the saponification rate of the extractant A is 40%-50%, the ratio of the extractant A to the solution B is 1:0.8-1.2, the extraction is countercurrent extraction, the extraction level of the countercurrent extraction is 4-6, and the volume concentrations of P204 and TBP in the extractant A are 16%-20% and 8%-12%, respectively; preferably, the saponification rate of the extractant A is 43%-47%, the ratio of the extractant A to the solution B is 1:0.9-1.1, and the volume concentrations of P204 and TBP in the extractant A are 17%-19% and 9%-11%, respectively; more preferably, the saponification rate of the extractant A is 44%-46%, the ratio of the extractant A to the solution B is 1:1, and the volume concentrations of P204 and TBP in the extractant A are 18% and 10%, respectively;

[0014] Furthermore, the specific steps of precipitation and impurity removal in step (5) are as follows: the crude cobalt sulfate solution B obtained by concentrating the extract in step (4) is cooled to 25±5° C., and a precipitation agent B is added. When the Co concentration in the crude cobalt sulfate solution is 1-5 g / L, the precipitation agent B is stopped, and the mixture is stirred and aged to perform solid-liquid separation to obtain refined cobalt sulfate crystals. Preferably, the precipitation agent B is stopped when the Co concentration in the crude cobalt sulfate solution B is 1-3 g / L.

[0015] Furthermore, the Co content in the crude cobalt sulfate solution B obtained after the concentration is 100-140 g / L, the precipitation agent B includes one or more of methanol, ethanol, n-propanol and isopropanol, and the stirring and aging time is 0.5-1.5 h;

[0016] Furthermore, the specific steps of the recrystallization in step (6) are as follows: dissolving the refined cobalt sulfate crystals in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, adjusting the pH value of the cobalt sulfate solution to 1.0±0.1, then heating and concentrating the solution, adding seed crystals after cooling to perform recrystallization, and naturally cooling the solution to obtain high-purity cobalt sulfate crystals.

[0017] Furthermore, in the step (6), the temperature during heating and concentrating in the recrystallization is 110±5°C, and after the specific gravity of the solution reaches 1.20-1.40, the solution is cooled to 80±5°C and then seed crystals are added, and the temperature is maintained at 80±5°C. After the volume of the solution is reduced to 60% of the volume before the seed crystals are added, the recrystallization is completed, and then the solution is naturally cooled to 40±5°C, filtered and dried to obtain high-purity cobalt sulfate crystals; preferably, after the specific gravity of the solution reaches 1.25-1.35, the seed crystals are added after being cooled to 80±5°C; more preferably, after the specific gravity of the solution reaches 1.28-1.32, the seed crystals are added after being cooled to 80±5°C; it should be noted that the specific gravity of a liquid refers to the ratio of the weight of a unit volume of liquid to the weight of an equal volume of water.

[0018] Furthermore, the mass content of cobalt in the high-purity cobalt sulfate crystals is greater than 21.03%, and the mass content of each impurity is less than 0.001%, which meets the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors; preferably, the mass content of cobalt in the high-purity cobalt sulfate crystals is between 21.03% and 21.85%, and the mass content of each impurity is less than 0.001%.

[0019] On the other hand, the present application also provides the use of cobalt sulfate prepared by the above-mentioned cobalt sulfate production method in the synthesis of ternary precursors.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses a production method and application of cobalt sulfate. The dilute acid impurity removal step in the production method can remove a large amount of metal impurities, shorten and simplify the process of preparing high-purity cobalt sulfate, reduce the consumption of raw materials in the subsequent impurity removal process, thereby reducing production costs, etc. The precipitation impurity removal step in the production method can effectively reduce the free acid, oil, water-insoluble matter concentration and metal impurity element content in the crystal slurry, and significantly reduce the acid, oil, water-insoluble matter and the like entrained in the crystal product. Combining the dilute acid impurity removal step, the precipitation impurity removal step and the extraction impurity removal step together can omit the chemical precipitation step, reduce the consumption of related raw materials, etc., and use P204 and TBP as composite extractants to selectively extract and separate other trace metal impurity elements from the cobalt sulfate solution, thereby improving the purity of the final product. The precipitation agent used in the precipitation impurity removal step of the present application can be recovered by vacuum distillation, and recycled, thereby reducing costs. In addition, the high-purity cobalt sulfate crystals obtained by the production method described in the present application meet the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors, etc. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention, and the terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In the description of the present application, it should be understood that "and / or" describes the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single (individual) or plural (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b, c can be single or multiple, respectively.

[0024] The present application is described in detail below through specific embodiments. The following embodiments are only partial embodiments of the present application and cannot be used as a limitation of the present application.

[0025] The chemical element composition (wt / %) of the crude cobalt hydroxide used in the present application includes: Co 46%, Ni 0.1%, Cu 0.09%, Mn 0.98%, Zn 1.58%, Fe 0.68%, Cd 0.86%, As 0.03%, Pb 0.25%, Si 0.05%, Ca 0.28%, Mg 0.53%, etc.

[0026] Example 1

[0027] This embodiment provides a production process for battery-grade cobalt sulfate, the production process comprising the following steps:

[0028] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500 g of crude cobalt hydroxide and add dilute sulfuric acid (5×10 -3 mol / L) and stirred for 1 hour, and during the stirring and washing process, sulfuric acid with a slightly higher concentration was slowly added to maintain the pH value of the solution between 2.0 and 3.0. After the reaction was complete, the solution was filtered to obtain the refined cobalt hydroxide after impurities were removed;

[0029] (2) Acid leaching reduction: at a temperature of 65° C., add refined cobalt hydroxide to a sulfuric acid solution of sodium sulfite for a reaction time of 2-3 hours. The pH value at the end of the reaction is 1.5±0.3. Filter to obtain a filtrate, wherein the molar ratio of cobalt hydroxide to sodium sulfite is 1:1.5;

[0030] (3) Precipitation and impurity removal: The filtrate is concentrated to obtain a crude cobalt sulfate solution A having a Co content of 120 g / L. After cooling to 25±5° C., ethanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A reaches 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain crude cobalt sulfate crystals.

[0031] (4) Extraction depth removal: The crude cobalt sulfate crystals are redissolved in dilute sulfuric acid to obtain a solution A with a pH of 3±0.3, and then the organic phase P204 and TBP are diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase is diluted, it is saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate is 45%. After saponification, the solution A is subjected to 5 levels of countercurrent extraction and phase separation at a phase ratio of 1:1 to obtain a raffinate;

[0032] (5) Precipitation and impurity removal again: After the extract is concentrated, the crude cobalt sulfate solution with a Co content of 120 g / L is cooled to 25±5° C., and ethanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reaches 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain refined cobalt sulfate crystals;

[0033] (6) Recrystallization: Dissolve the refined cobalt sulfate crystals in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, adjust the pH value thereof to 1.0±0.1, and then heat the solution to 110±5°C. After the specific gravity of the solution reaches 1.30, cool the solution to 80±5°C, add seed crystals, and maintain the temperature at 80±5°C. After the volume of the solution is reduced to 60% of the volume before adding the seed crystals, the recrystallization is completed. Then, cool the solution naturally to 40±5°C, filter, and dry to obtain high-purity cobalt sulfate crystals. The mass content of cobalt in the high-purity cobalt sulfate crystals is 21.85%, and the mass content of each impurity is less than 0.001%, which meets the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors.

[0034] Example 2

[0035] This embodiment provides a production process for battery-grade cobalt sulfate, the production process comprising the following steps:

[0036] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500 g of crude cobalt hydroxide and add dilute sulfuric acid (5×10 -3 mol / L) and stirred for 1 hour, and during the stirring and washing process, sulfuric acid with a slightly higher concentration was slowly added to maintain the pH value of the solution between 2.0 and 3.0. After the reaction was complete, the solution was filtered to obtain the refined cobalt hydroxide after impurities were removed;

[0037] (2) Acid leaching reduction: at a temperature of 65° C., add refined cobalt hydroxide to a sulfuric acid solution of sodium sulfite for a reaction time of 2-3 hours. The pH value at the end of the reaction is 1.5±0.3. Filter to obtain a filtrate, wherein the molar ratio of cobalt hydroxide to sodium sulfite is 1:1.5;

[0038] (3) Precipitation and impurity removal: The filtrate is concentrated to obtain a crude cobalt sulfate solution A with a Co content of 120 g / L. After cooling to 25±5° C., methanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A is 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain crude cobalt sulfate crystals.

[0039] (4) Extraction depth removal: The crude cobalt sulfate crystals are redissolved in dilute sulfuric acid to obtain a solution A with a pH of 3±0.3, and then the organic phase P204 and TBP are diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase is diluted, it is saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate is 45%. After saponification, the solution A is subjected to 5 levels of countercurrent extraction and phase separation at a phase ratio of 1:1 to obtain a raffinate;

[0040] (5) Precipitation and impurity removal again: After the extract is concentrated, the crude cobalt sulfate solution with a Co content of 120 g / L is cooled to 25±5° C., and methanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reaches 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain refined cobalt sulfate crystals;

[0041] (6) Recrystallization: Dissolve the refined cobalt sulfate crystals in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, adjust the pH value thereof to 1.0±0.1, and then heat the solution to 110±5°C. After the specific gravity of the solution reaches 1.30, cool the solution to 80±5°C, add seed crystals, and maintain the temperature at 80±5°C. After the volume of the solution is reduced to 60% of the volume before adding the seed crystals, the recrystallization is completed. Then, cool the solution naturally to 40±5°C, filter, and dry to obtain high-purity cobalt sulfate crystals. The mass content of cobalt in the high-purity cobalt sulfate crystals is 21.03%, and the mass content of each impurity is less than 0.001%, which meets the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors.

[0042] Example 3

[0043] This embodiment provides a production process for battery-grade cobalt sulfate, the production process comprising the following steps:

[0044] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500 g of crude cobalt hydroxide and add dilute sulfuric acid (5×10 -3mol / L) and stirred for 1 hour, and during the stirring and washing process, sulfuric acid with a slightly higher concentration was slowly added to maintain the pH value of the solution between 2.0 and 3.0. After the reaction was complete, the solution was filtered to obtain the refined cobalt hydroxide after impurities were removed;

[0045] (2) Acid leaching reduction: at a temperature of 65° C., add refined cobalt hydroxide to a sulfuric acid solution of sodium sulfite for a reaction time of 2-3 hours. The pH value at the end of the reaction is 1.5±0.3. Filter to obtain a filtrate, wherein the molar ratio of cobalt hydroxide to sodium sulfite is 1:1.5;

[0046] (3) Precipitation and impurity removal: The filtrate is concentrated to obtain a crude cobalt sulfate solution A with a Co content of 120 g / L. After cooling to 25±5° C., n-propanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A is 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain crude cobalt sulfate crystals.

[0047] (4) Extraction depth removal: The crude cobalt sulfate crystals are redissolved in dilute sulfuric acid to obtain a solution A with a pH of 3±0.3, and then the organic phase P204 and TBP are diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase is diluted, it is saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate is 45%. After saponification, the solution A is subjected to 5 levels of countercurrent extraction and phase separation at a phase ratio of 1:1 to obtain a raffinate;

[0048] (5) Precipitation and impurity removal again: The crude cobalt sulfate solution with a Co content of 120 g / L obtained after the extract is concentrated is cooled to 25±5° C., and n-propanol is added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reaches 2 g / L, the addition of ethanol is stopped. After stirring and aging for 1 hour, solid-liquid separation is performed to obtain refined cobalt sulfate crystals;

[0049] (6) Recrystallization: Dissolve the refined cobalt sulfate crystals in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, adjust the pH value thereof to 1.0±0.1, and then heat the solution to 110±5°C. After the specific gravity of the solution reaches 1.30, cool the solution to 80±5°C, add seed crystals, and maintain the temperature at 80±5°C. After the volume of the solution is reduced to 60% of the volume before adding the seed crystals, the recrystallization is completed. Then, cool the solution naturally to 40±5°C, filter, and dry to obtain high-purity cobalt sulfate crystals. The mass content of cobalt in the high-purity cobalt sulfate crystals is 21.45%, and the mass content of each impurity is less than 0.001%, which meets the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors.

[0050] Comparative Example 1

[0051] Compared with Example 1, the only difference is that step (1) is not performed, but the crude cobalt hydroxide is directly used for step (2) acid leaching reduction, and the mass content of cobalt in the high-purity cobalt sulfate crystals finally obtained is 19.28%, Ni is 0.008%, Cu is 0.003%, Mn is 0.0028%, Zn is 0.002%, Fe is 0.008%, Cd is 0.003%, As is 0.0001%, Pb is 0.00003%, Si is 0.005%, Ca is 0.008%, and Mg is 0.009%.

[0052] Comparative Example 2

[0053] Compared with Example 1, the only difference is that step (3) is not performed, but the pH value of the filtrate is directly adjusted to 3±0.3, and then step (4) of extraction depth impurity removal is performed. The mass content of cobalt in the high-purity cobalt sulfate crystals finally obtained is 19.63%, Ni is 0.006%, Cu is 0.002%, Mn is 0.0022%, Zn is 0.0015%, Fe is 0.005%, Cd is 0.002%, As is 0.00008%, Pb is 0.00002%, Si is 0.003%, Ca is 0.006%, and Mg is 0.007%.

[0054] Comparative Example 3

[0055] Compared with Example 1, the only difference is that step (5) is not performed, but the pH of the raffinate is adjusted to 3±0.3, and then step (6) recrystallization is directly performed. The mass content of cobalt in the high-purity cobalt sulfate crystals finally obtained is 20.08%, Ni is 0.003%, Cu is 0.0012%, Mn is 0.0018%, Zn is 0.0012%, Fe is 0.003%, Cd is 0.0014%, As is 0.00003%, Pb is 0.00001%, Si is 0.001%, Ca is 0.003%, and Mg is 0.0054%.

[0056] Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application, and the scope of protection of the present invention shall be based on the scope defined by the claims. For those of ordinary skill in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the scope of protection of the present invention. Those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing cobalt sulfate, characterized in that: The production method comprises the following steps: step (1) dilute acid impurity removal; step (2) acid leaching reduction; step (3) precipitation impurity removal; step (4) deep extraction impurity removal; step (5) precipitation impurity removal again; and step (6) recrystallization.

2. The method for producing cobalt sulfate according to claim 1, characterized in that: The specific steps of step (1) of removing impurities with dilute acid are as follows: taking crude cobalt hydroxide and adding dilute sulfuric acid to react, maintaining the pH value of the solution between 2.0 and 3.0 during the reaction, and filtering after the reaction is complete to obtain refined cobalt hydroxide after impurities are removed.

3. The method for producing cobalt sulfate according to claim 2, characterized in that: The specific steps of the acid leaching reduction in step (2) are: taking the refined cobalt hydroxide described in step (1) and adding it into a sulfuric acid solution of sodium sulfite to react, the pH value at the end of the reaction is 1.5±0.3, and after the reaction is completed, solid-liquid separation is performed to obtain a filtrate.

4. The method for producing cobalt sulfate according to claim 3, characterized in that: The specific steps of precipitation and impurity removal in step (3) are as follows: the filtrate in step (2) is concentrated to obtain a crude cobalt sulfate solution A, which is then cooled to 25±5° C., and a precipitation agent A is added. When the Co concentration in the crude cobalt sulfate solution A is 1-5 g / L, the addition of the precipitation agent A is stopped, and after stirring and aging, solid-liquid separation is performed to obtain crude cobalt sulfate crystals.

5. The method for producing cobalt sulfate according to claim 4, characterized in that: The specific steps of deep extraction and impurity removal in step (4) are: re-dissolving the crude cobalt sulfate crystals described in step (3) in sulfuric acid to obtain a solution B with a pH of 3±0.3, and then extracting the solution B with an extractant A to obtain a raffinate.

6. The method for producing cobalt sulfate according to claim 5, characterized in that: The reaction temperature of the dilute acid impurity removal in step (1) is 60-70°C, the reaction time is 0.5-1.5h, and the concentration of the dilute sulfuric acid is 3×10 -3 -7×10 -3 mol / L; And / or, the reaction temperature during the acid leaching reduction in step (2) is 60-70° C., the reaction time is 2-3 hours, and the molar ratio of the cobalt hydroxide to the sodium sulfite is 1:1.4-1.6; And / or, the crude cobalt sulfate solution A obtained after concentration in the step (3) precipitation and impurity removal has a Co content of 100-140 g / L, the precipitation agent A comprises one or more of methanol, ethanol, n-propanol and isopropanol, and the stirring and aging time is 0.5-1.5 h; And / or, in the step (4) extraction depth impurity removal, the extractant A comprises diluent sulfonated kerosene, P204 and TBP, the saponification rate of the extractant A is 40%-50%, the ratio of the extractant A to the solution B is 1:0.8-1.2, the extraction is countercurrent extraction, the extraction level of the countercurrent extraction is 4-6, and the volume concentrations of P204 and TBP in the extractant A are 16%-20% and 8%-12%, respectively.

7. The method for producing cobalt sulfate according to any one of claims 5 to 6, characterized in that: The specific steps of the step (5) of precipitation and impurity removal again are as follows: the crude cobalt sulfate solution B obtained by concentrating the extract described in step (4) is cooled to 25±5° C., and a precipitation agent B is added. When the Co concentration in the crude cobalt sulfate solution is 1-5 g / L, the addition of the precipitation agent B is stopped, and the mixture is stirred and aged to perform solid-liquid separation to obtain refined cobalt sulfate crystals; Preferably, the Co content in the crude cobalt sulfate solution B obtained after concentration is 100-140 g / L, the precipitating agent B includes one or more of methanol, ethanol, n-propanol and isopropanol, and the stirring aging time is 0.5-1.5 h.

8. The method for producing cobalt sulfate according to claim 7, characterized in that: The specific steps of the recrystallization in step (6) are as follows: dissolving the refined cobalt sulfate crystals in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, adjusting the pH value of the cobalt sulfate solution to 1.0±0.1, then heating and concentrating the solution, adding seed crystals after cooling to perform recrystallization, and naturally cooling the solution to obtain high-purity cobalt sulfate crystals.

9. The method for producing cobalt sulfate according to claim 8, characterized in that: The temperature during heating and concentrating in the step (6) of recrystallization is 110±5°C. After the specific gravity of the solution reaches 1.20-1.40, the solution is cooled to 80±5°C and then seed crystals are added. The temperature is maintained at 80±5°C. After the volume of the solution is reduced to 60% of the volume before the seed crystals are added, the recrystallization is completed. The solution is then naturally cooled to 40±5°C, filtered, and dried to obtain high-purity cobalt sulfate crystals.

10. Use of the cobalt sulfate prepared by the method for producing cobalt sulfate according to any one of claims 1 to 9 in the synthesis of a ternary precursor.