A production method of cobalt sulfate and its application

Abstract

The present invention discloses a method for producing cobalt sulfate and its application. The 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) further precipitation impurity removal; and step (6) recrystallization. The cobalt sulfate obtained by the production method of the present application meets the requirements of battery-grade cobalt sulfate and can be used for the synthesis of ternary precursors.

Description

Technical Field

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

[0002] The battery-grade cobalt sulfate required for ternary lithium-ion battery cathodes is often produced using nickel-cobalt hydroxide, an intermediate product produced by hydrometallurgical smelting of laterite nickel ore, or recycled crude cobalt hydroxide. These raw materials often contain impurities such as Ni, Fe, Mg, Al, Cr, Mn, Cu, Ca, Si, Pb, Zn, As, and Cd. The currently used production process involves sulfuric acid reduction leaching, followed by solution extraction purification and impurity removal, extraction separation and enrichment of cobalt, and evaporation and crystallization. Due to the extraction separation and impurity removal and extraction of cobalt from the solution, the resulting cobalt sulfate solution contains excessive oil content, and in actual production, the concentration of impurities often makes it difficult to meet battery-grade specifications. Given the long production process and high purification costs resulting from the high variety and content of impurity elements in the raw materials, it is imperative to overcome the bottlenecks of existing processes and develop a more efficient, simple, and short-process process for producing battery-grade cobalt sulfate. 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 its application 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, which 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.

[0006] Furthermore, the specific steps of the dilute acid impurity removal in step (1) are as follows: taking crude cobalt hydroxide and adding it into 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;

[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, wherein the pH value at the end of the reaction is 1.5±0.3, and after the reaction is completed, performing solid-liquid separation 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 reaches 1-5 g / L, the addition of the precipitation agent A is stopped. After stirring and aging, solid-liquid separation is performed to obtain crude cobalt sulfate crystals. Preferably, the addition of the precipitation agent A is stopped when the Co concentration in the crude cobalt sulfate solution A reaches 1-3 g / L.

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

[0012] Furthermore, 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;

[0013] Further, the extractant A comprises a 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 a countercurrent extraction, the number of extraction stages 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 reaches 1-5 g / L, the addition of the precipitation agent B is stopped, and the mixture is stirred and aged, and solid-liquid separation is performed to obtain refined cobalt sulfate crystals. Preferably, the addition of the precipitation agent B is stopped when the Co concentration in the crude cobalt sulfate solution B reaches 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 precipitating 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. 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 adding the seed crystals, the recrystallization is completed. The solution is then 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 cooling to 80±5°C. More preferably, after the specific gravity of the solution reaches 1.28-1.32, the seed crystals are added after cooling 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 method for producing cobalt sulfate and its application. The dilute acid impurity removal step in the production method can remove a large amount of metallic impurities, shorten and simplify the process for preparing high-purity cobalt sulfate, reduce raw material consumption in the subsequent impurity removal process, and thus reduce production costs. The precipitation impurity removal step in the production method can effectively reduce the concentration of free acid, oil, water-insoluble matter, and metallic impurity elements in the crystal slurry, and significantly reduce the acid, oil, and water-insoluble matter entrained in the crystal product. Combining the dilute acid impurity removal step, the precipitation impurity removal step, and the extraction impurity removal step can omit the chemical precipitation step, reduce the consumption of related raw materials, etc., and use P204 and TBP as a composite extractant to selectively extract and separate other trace metallic 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, enabling recycling, 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 in the synthesis of ternary precursors. 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 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 those skilled in the art of the present invention. 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 and indicates that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In the present application, "at least one" refers to one or more, and "a plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0024] The present application will be described in detail below through specific examples. The following examples are only some examples of the present application and cannot be used to limit the present application.

[0025] The chemical element composition (wt / %) of the crude cobalt hydroxide used in this 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, which comprises the following steps:

[0028] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500g 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 purified 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 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 was concentrated to obtain a crude cobalt sulfate solution A with a Co content of 120 g / L. After cooling to 25±5°C, ethanol was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was performed to obtain crude cobalt sulfate crystals.

[0031] (4) Extraction and impurity removal: The crude cobalt sulfate crystals were 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 were diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase was diluted, it was saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate was 45%. After saponification, the solution A was subjected to 5-stage countercurrent extraction and phase separation at a phase ratio of 1:1 to obtain a raffinate;

[0032] (5) Precipitation and impurity removal again: The crude cobalt sulfate solution with a Co content of 120 g / L obtained after concentrating the extract was cooled to 25±5°C, and ethanol was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was 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 and add seed crystals. 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, which comprises the following steps:

[0036] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500g 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 purified 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 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 was concentrated to obtain a crude cobalt sulfate solution A with a Co content of 120 g / L. After cooling to 25±5°C, methanol was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was performed to obtain crude cobalt sulfate crystals.

[0039] (4) Extraction and impurity removal: The crude cobalt sulfate crystals were 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 were diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase was diluted, it was saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate was 45%. After saponification, the solution A was subjected to 5-stage countercurrent extraction and phase separation at a phase ratio of 1:1 to obtain a raffinate;

[0040] (5) Precipitation and impurity removal again: The crude cobalt sulfate solution with a Co content of 120 g / L obtained after concentrating the extract was cooled to 25±5°C, and methanol was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was 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 and add seed crystals. 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, which comprises the following steps:

[0044] (1) Dilute acid impurity removal: At a temperature of 65°C, take 500g 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 purified 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 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 was 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 was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution A reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was performed to obtain crude cobalt sulfate crystals.

[0047] (4) Extraction and impurity removal: The crude cobalt sulfate crystals were 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 were diluted with a diluent sulfonated kerosene to a volume concentration of 18% and 10%, respectively. After the organic phase was diluted, it was saponified with a 2 mol / L sodium hydroxide solution, and the saponification rate was 45%. After saponification, the solution A was subjected to 5-stage 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 concentrating the extract was cooled to 25±5°C, and n-propanol was added as a precipitating agent. When the Co concentration in the crude cobalt sulfate solution reached 2 g / L, the addition of ethanol was stopped. After stirring and aging for 1 hour, solid-liquid separation was 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 and add seed crystals. 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, and step (2) acid leaching reduction is directly performed using crude cobalt hydroxide. The mass content of cobalt in the finally obtained high-purity cobalt sulfate crystals 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 deep extraction and impurity removal is performed. The mass content of cobalt in the finally obtained high-purity cobalt sulfate crystals 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 finally obtained high-purity cobalt sulfate crystals 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] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method of this application and its core ideas. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting this application, and the scope of protection of the present invention should be based on the scope defined by the claims. For those skilled in the art in this field, without departing from the spirit and scope of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the scope of protection of the present invention. Those skilled in the art should understand that they can still modify the technical solutions described 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 this 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: crude cobalt hydroxide is added to dilute sulfuric acid for reaction, and the pH value of the solution is maintained between 2.0 and 3.0 during the reaction. After the reaction is complete, the solution is filtered to obtain refined cobalt hydroxide; Step (2) acid leaching reduction: taking the refined cobalt hydroxide and adding it to a sulfuric acid solution of sodium sulfite to react, wherein the pH value at the end of the reaction is 1.5±0.3, and after the reaction is completed, performing solid-liquid separation to obtain a filtrate; Step (3) precipitation and impurity removal: the filtrate is concentrated to obtain a crude cobalt sulfate solution A, which is then cooled to 25±5° C., and ethanol is added. When the Co concentration in the crude cobalt sulfate solution A reaches 1-5 g / L, the addition of ethanol is stopped. After stirring and aging, solid-liquid separation is performed to obtain crude cobalt sulfate crystals; Step (4) extraction depth removal: the crude cobalt sulfate crystals are redissolved in sulfuric acid to obtain a solution B with a pH of 3±0.3, and then the solution B is extracted with an extractant A to obtain a raffinate; the extractant A is composed of a 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 a countercurrent extraction, the extraction stage 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; Step (5) precipitation and impurity removal again: the crude cobalt sulfate solution B obtained by concentrating the raffinate is cooled to 25±5° C., and ethanol is added. When the Co concentration in the crude cobalt sulfate solution reaches 1-5 g / L, the addition of ethanol is stopped, and the mixture is stirred and aged, and solid-liquid separation is performed to obtain refined cobalt sulfate crystals; Step (6) Recrystallization: The refined cobalt sulfate crystals are dissolved in a dilute sulfuric acid solution to obtain a cobalt sulfate solution, the pH value of which is adjusted to 1.0±0.1, and then the solution is heated and concentrated. After cooling, seed crystals are added to perform recrystallization. After the recrystallization is completed, the solution is cooled naturally, solid-liquid separation is performed, and drying is performed to obtain high-purity cobalt sulfate crystals.

2. The method for producing cobalt sulfate according to claim 1, wherein The reaction temperature during 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.

3. The method for producing cobalt sulfate according to claim 1, wherein 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.

4. The method for producing cobalt sulfate according to claim 1, wherein The crude cobalt sulfate solution A obtained after concentration in the step (3) of precipitation and impurity removal has a Co content of 100-140 g / L, and the stirring and aging time is 0.5-1.5 h.

5. The method for producing cobalt sulfate according to claim 1, wherein The crude cobalt sulfate solution B obtained after the concentration has a Co content of 100-140 g / L, and the stirring and aging time is 0.5-1.5 h.

6. The method for producing cobalt sulfate according to claim 1, wherein: The temperature during heating and concentrating in the recrystallization in step (6) is 110±5°C. After the specific gravity of the solution reaches 1.20-1.40, it 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.