A process for the production of battery grade cobalt sulfate by multistage extraction

Abstract

A method for preparing battery-grade cobalt sulfate by multistage extraction, comprising the following steps: (1) P204 extraction: uniformly mixing P204 extractant and diluent, saponification treatment, clarification, adding cobalt sulfate solution to be extracted, multistage extraction, oil removal, and obtaining raffinate; (2) Cyanex272 extraction: uniformly mixing Cyanex272 extractant and diluent, saponification treatment, clarification; A section: adding the obtained saponification cobalt extraction organic phase into the raffinate, multistage extraction, stripping; B section: adding the obtained saponification cobalt extraction organic phase into the stripping cobalt sulfate solution obtained in the A section, multistage extraction, stripping, oil removal, evaporation crystallization, and the battery-grade cobalt sulfate is obtained. The cobalt sulfate crystal obtained by the method meets the quality requirements of battery cobalt sulfate type II in the national standard, cobalt and calcium and magnesium are completely separated, the purity and yield of cobalt sulfate are high, the process is simple and short, other impurities are not introduced, it is green and environmental protection, the cost is low, and it is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing battery-grade cobalt sulfate, specifically a method for preparing battery-grade cobalt sulfate through multi-stage extraction. Background Technology

[0002] Cobalt is a very scarce metallic resource, often referred to as "industrial MSG" and "industrial teeth," and is a crucial strategic resource. Due to its high energy density, good electrical conductivity, excellent stability, high melting point, and low thermal conductivity, cobalt is widely used in aerospace, electrical appliances, machinery manufacturing, chemical, and ceramic industries. Especially in the new energy sector, with the booming development of the battery industry, global cobalt consumption has shown an upward trend, reaching 175,000 tons in 2023. Cobalt is an active material in battery electrodes to improve the energy density and stability of batteries, such as lithium-ion batteries and methanol fuel cells. In recent years, cobalt mineral resources have received increasing attention. With the rapid increase in global demand for cobalt, countries in Europe and the United States have elevated cobalt resources to national strategic mineral resources.

[0003] The smelting methods for cobalt vary depending on the ore composition. Furthermore, since cobalt mainly exists as a byproduct in other metal ores, its extraction, except for extraction from arsenic-cobalt ore and cobaltite, is based on the main metal production process. Cobalt is enriched in intermediate products and then recovered, making the process flow often quite complex. However, the methods for extracting cobalt from cobalt-containing raw materials are essentially pyrometallurgical and hydrometallurgical processes. Pyrometallurgical treatment alters the phase composition of cobalt in the material or enriches it in intermediate products, preparing for subsequent hydrometallurgical processing. The purpose of hydrometallurgical processing is to remove impurities and obtain high-purity metallic cobalt, or to directly produce various cobalt-containing compounds required for industrial applications. Therefore, the methods for extracting cobalt from cobalt-containing raw materials can be summarized into three types: a fully pyrometallurgical process, a fully hydrometallurgical process, and a combined pyrometallurgical and hydrometallurgical process. The complexity of cobalt-containing raw materials means that there are no traditional processes or standards to follow in cobalt metallurgy, but all processes ultimately require hydrometallurgical treatment, which is a characteristic of cobalt metallurgy. The cobalt sulfate solution to be processed by the method of the present invention is obtained by leaching, purification and other processes of arsenic cobalt ore, and has the characteristics of high content of impurity ions such as calcium, magnesium and arsenic in the solution.

[0004] In recent years, cobalt prices have continued to rise, leading to increasing attention being paid to the processing of complex cobalt-containing minerals and the recycling of cobalt-containing waste. However, these raw materials often have complex compositions, and battery-grade cobalt sulfate has very high requirements for impurity content, with the treatment of calcium and magnesium impurities being two major technical challenges. Therefore, there is an urgent need to find a new solution to these technical problems.

[0005] CN116171264A discloses a method for manufacturing cobalt sulfate. This method first removes copper using a sulfiding agent, then removes magnesium using a neutralizing agent or carbonizing agent, and finally extracts with alkyl phosphate-based extractant bis(2-ethylhexyl) hydrogen phosphate. However, this method is suitable for preparing cobalt sulfate solution from cobalt chloride solution and cannot meet the requirements for battery-grade cobalt sulfate. CN 118421959A discloses a method for separating and preparing cobalt sulfate from cobalt-containing pyrite, using a two-stage extraction technology of P204+P507. However, this method is suitable for cobalt pyrite and not for high-arsenic cobalt ore, nor for producing battery-grade cobalt sulfate. CN 113046573A discloses a cobalt sulfate production process using P204+P507 extraction. However, this method is suitable for cobalt concentrate and not for producing high-arsenic cobalt ore, especially cobalt-arsenic ore with high calcium and magnesium content, nor can it produce battery-grade cobalt sulfate. Therefore, none of the above three methods can guarantee the yield of battery-grade cobalt sulfate.

[0006] CN115353152A discloses a production process for battery-grade cobalt sulfate, employing copper removal agents, aluminum removal agents, nickel removal via resin, and cobalt extraction via resin. However, this method consumes a large amount of impurity removal agents, has limited resin adsorption capacity, poor resin regeneration performance, high operating costs, and is sensitive to resin operating conditions.

[0007] CN117843041A discloses a method for deep purification of cadmium ions during the production of battery-grade cobalt sulfate. However, this method is only applicable to cobalt sulfate solutions with high cadmium concentrations and is not applicable to cobalt sulfate solutions with high levels of impurities such as arsenic, calcium, and magnesium.

[0008] CN115108592A discloses a method for producing high-purity cobalt sulfate. This method uses solid cobalt to produce battery-grade cobalt sulfate, which has high production costs and generates hydrogen gas during the production process, posing a high risk.

[0009] CN117210700A discloses a method for producing battery-grade cobalt sulfate from a magnesium-containing cobalt sulfate solution, which involves first using Mextral® V10 nickel soap and then sodium soap. However, this saponification process is complex and has drawbacks such as high cost of nickel soap. In addition, this method first uses C272 nickel-cobalt separation and then uses Mextral® V10 to extract cobalt, resulting in high overall operating costs.

[0010] CN114959302A discloses a method for preparing nickel / cobalt sulfate from lateritic nickel ore. The method involves first subjecting the lateritic nickel ore to sequential sulfuric acid leaching, pre-neutralization, and primary iron and aluminum removal to obtain a primary iron and aluminum removal solution. Subsequently, nickel and cobalt in the primary iron and aluminum removal solution are preferentially extracted using a mixed extractant of lix63 and Verzatic acid 10, lix64N, or any one of lix63 extractant. After back-extraction, a first aqueous phase is obtained. This first aqueous phase is then subjected to a secondary iron and aluminum removal process to obtain a nickel-cobalt-rich solution. This solution is then subjected to conventional extraction-cobalt extraction processes (such as P204 extraction-P507 cobalt extraction-C272 deep extraction) to obtain nickel sulfate and cobalt sulfate solutions. However, this method is designed for lateritic nickel ore and is not suitable for high-arsenic cobalt ores. Furthermore, the extraction process is complex and the overall operating cost is high. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing battery-grade cobalt sulfate by multi-stage extraction, which yields cobalt sulfate crystals that meet the quality requirements of cobalt sulfate type II for batteries according to industry standards, with complete separation of cobalt from calcium and magnesium, high purity and yield of cobalt sulfate, simple process, short process, strong operability, no introduction of other impurities, green and environmentally friendly, low cost, and suitable for industrial production.

[0012] The technical solution adopted by this invention to solve its technical problem is as follows: A method for preparing battery-grade cobalt sulfate by multi-stage extraction, comprising the following steps: (1) P204 extraction: First, P204 extractant and diluent are mixed evenly, then saponified and clarified to obtain saponified extracted organic phase; The obtained saponified and extracted organic phase was added to the cobalt sulfate solution to be extracted, and multi-stage extraction was performed to remove oil and obtain raffinate. (2) Cyanex272 extraction: First, Cyanex272 extractant and diluent are mixed evenly, then saponified and clarified to obtain saponified cobalt organic phase; Section A: First, add the obtained saponified cobalt organic phase to the raffinate obtained in step (1) and perform multi-stage extraction to obtain the Cyanex272 loaded organic phase. Then, back-extract with back-extracting acid to obtain the back-extracted cobalt sulfate solution. Section B: First, add the obtained saponified cobalt-extracted organic phase to the back-extracted cobalt sulfate solution obtained in Section A for multi-stage extraction to obtain a Cyanex 272-loaded organic phase. Then, back-extract with back-extraction acid to remove oil and obtain a purified cobalt sulfate solution. Evaporate and crystallize to obtain battery-grade cobalt sulfate crystals.

[0013] The inventive concept of this invention is as follows: This invention utilizes multi-stage P204 extraction for impurity removal and multi-stage Cyanex 272 cobalt extraction (divided into A and B stages); P204 extraction of Ca...2+ Mn 2+ Cu 2+ Zn 2+ Al 3+ The impurity concentration is reduced, and a cobalt sulfate solution that meets the requirements for cobalt-nickel separation by Cyanex 272 extraction is produced. Cyanex 272 extraction separates cobalt from nickel and magnesium, enriching cobalt and producing a qualified battery-grade cobalt sulfate solution. The method of this invention solves the technical problem of incomplete separation of cobalt from calcium and magnesium impurities in the prior art through two-step extraction.

[0014] Preferably, in step (1), the volume ratio of the P204 extractant to the diluent is 1:5 to 7. If too much P204 extractant is used, phase separation becomes difficult, entrainment is severe, a third phase is easily formed, the extractant utilization rate decreases, and costs increase, emulsification may occur, and back-extraction becomes difficult. If too much diluent is used, the extraction rate decreases, the recovery rate decreases, the number of extraction stages increases, production efficiency decreases, the loading capacity decreases, the selectivity may deteriorate, and the consumption of chemical reagents increases relatively.

[0015] Preferably, in step (1), the diluent includes kerosene or 260# solvent oil, etc.

[0016] Preferably, in step (1), the saponification treatment refers to: adding sodium hydroxide solution to the mixed phase of P204 extractant and diluent, and performing saponification treatment until the saponification rate is 10-20%. The saponification rate is a fixed value, determined according to the impurity content of the cobalt sulfate solution to be extracted, and by adjusting the flow rates of the organic phase and the aqueous phase.

[0017] Preferably, in step (1), the molar concentration of the sodium hydroxide solution is 8 to 12 mol / L.

[0018] Preferably, in step (1), the flow rate ratio of the saponified extraction organic phase to the cobalt sulfate solution to be extracted is 0.8–1.2:1. The O2 content is adjusted according to the different impurity levels in the aqueous cobalt sulfate solution to be extracted. 有机相 / A 水相 The size of the ratio.

[0019] Preferably, in step (1), the concentrations of the main components in the cobalt sulfate solution to be extracted are as follows: Co 17-25 g / L, Ni 1.2-3.0 g / L, Fe < 1 mg / L, As < 1 mg / L, Cu 6-25 mg / L, Mn 0.25-0.50 g / L, Zn 0.05-0.30 g / L, Ca 0.1-0.5 g / L, Mg 0.60-0.69 g / L, Al ≤ 6 mg / L, Cd < 0.01 mg / L, Cr ≤ 0.6 mg / L, and K ≤ 10 mg / L. The cobalt sulfate solution to be extracted processed by the method of the present invention is mainly derived from arsenic cobalt ore through leaching, purification, and impurity removal processes.

[0020] Preferably, in step (1), the flow rate of the saponified organic phase is 6–9 L / h. This is determined based on the equipment size and the impurity content of the cobalt sulfate solution.

[0021] Preferably, in step (1), the total number of stages of the P204 extraction process is 32 to 36.

[0022] Preferably, in step (1), the P204 extraction process includes a saponification stage 1 corresponding to the saponification treatment, a clarification stage 2 corresponding to the clarification, and a multi-stage extraction stage 29 to 33.

[0023] Preferably, the multi-stage extraction includes: 10 stages of extraction, 4 to 8 stages of cobalt washing, 2 stages of back-extraction clarification, 5 stages of back-extraction copper-manganese, 2 stages of clarification, 3 stages of iron washing, 2 stages of chlorine washing, and 1 stage of organic phase clarification.

[0024] Preferably, the cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.25 to 0.33 mol / L.

[0025] Preferably, the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3 to 4:1.

[0026] Preferably, the back-extraction acid in the copper-manganese back-extraction section is a sulfuric acid solution with a concentration of 0.5–0.7 mol / L. The back-extraction acid is recyclable, but its acidity needs to be monitored frequently, and sulfuric acid needs to be replenished to maintain a stable sulfuric acid concentration of 0.5–0.7 mol / L. When the impurity content of the back-extraction acid reaches 10 g / L, it is discharged and discarded. If the impurity content of the back-extraction acid is too high, it is detrimental to the back-extraction of impurities.

[0027] Preferably, the flow rate ratio of the organic phase to the back-extraction acid in the copper-manganese stripping section is 3 to 4:1.

[0028] Preferably, the iron washing acid in the iron washing section is a hydrochloric acid solution with a concentration of 5-6 mol / L. The iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 5-6 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped.

[0029] Preferably, the flow rate ratio of the organic phase to the iron washing acid in the iron washing section is 5-6:1.

[0030] Preferably, in step (2), the volume ratio of the Cyanex272 extractant to the diluent is 1:2 to 4.

[0031] Preferably, in step (2), the diluent includes kerosene or 260# solvent oil, etc.

[0032] Preferably, in step (2), the saponification treatment refers to adding sodium hydroxide solution to the mixed phase of Cyanex272 extractant and diluent, and performing saponification treatment until the saponification rate is 35-37%. The saponification rate is a fixed value, which is determined by adjusting the flow rates of the organic phase and the aqueous phase.

[0033] Preferably, in step (2), the molar concentration of the sodium hydroxide solution is 8 to 12 mol / L.

[0034] Preferably, in step (2) section A, the flow ratio of the saponified cobalt organic phase to the raffinate is 1:1 to 2.

[0035] Preferably, in step (2) A, the concentration of cobalt in the raffinate is 15-22 g / L (more preferably 18-21 g / L).

[0036] Preferably, in step (2)A, the flow rate of the saponified cobalt organic phase is 9-14 L / h.

[0037] Preferably, in step (2) A, the total number of stages in the Cyanex 272 extraction A stage process is 20 to 25.

[0038] Preferably, in step (2) A, the Cyanex272 extraction A process includes a saponification stage 1 corresponding to the saponification treatment, a clarification stage 1 corresponding to the clarification, and multi-stage extraction stages 18 to 23.

[0039] Preferably, the multi-stage extraction includes: extraction stage 4-5, clarification stage 1, acid washing stage 3-5, clarification stage 1, cobalt washing stage 5-6, iron washing stage 3-4, and clarification stage 1.

[0040] Preferably, the inlet pH of the extraction section in the multi-stage extraction is 3.5 to 6.0 (more preferably 3.5 to 5.0), the outlet pH of the raffinate is 3.0 to 6.0 (more preferably 3.0 to 4.5), and the Co concentration in the raffinate is ≤0.2 g / L.

[0041] Preferably, the acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05–0.15 mol / L.

[0042] Preferably, the flow rate ratio of the organic phase to the washing acid in the pickling section is 5 to 8:1.

[0043] Preferably, the cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.30 to 0.45 mol / L.

[0044] Preferably, the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 2.0 to 3.5:1.

[0045] Preferably, the iron washing acid in the iron washing section is a hydrochloric acid solution with a concentration of 4.0–7.5 mol / L. The iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 4.0–7.5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and discarded.

[0046] Preferably, the flow rate ratio of the organic phase to the iron washing acid in the iron washing section is 3.5 to 5.0:1.

[0047] Preferably, in step (2) B, the flow rate ratio of the saponified cobalt extraction organic phase to the back-extraction cobalt sulfate solution is 2-3:1.

[0048] Preferably, in step (2) B, the concentration of cobalt in the back-extracted cobalt sulfate solution is 30-126 g / L (more preferably 32-60 g / L).

[0049] Preferably, in step (2) B, the flow rate of the saponified cobalt organic phase is 12-16 L / h.

[0050] Preferably, in step (2) B, the total number of stages in the Cyanex 272 extraction B stage process is 20 to 25.

[0051] Preferably, in step (2) section B, the Cyanex272 extraction section B process includes saponification stage 1 corresponding to saponification treatment, clarification stage 1 corresponding to clarification, and multi-stage extraction stages 18 to 23.

[0052] Preferably, the multi-stage extraction includes: extraction stage 3-4, clarification stage 1, acid washing stage 3-5, clarification stage 2, back-extraction stage 5-6, iron washing stage 3-4, and clarification stage 1.

[0053] Preferably, the inlet pH of the extraction section in the multi-stage extraction is 3.5 to 6.0 (more preferably 4.0 to 5.5), the outlet pH of the raffinate is 3.0 to 6.0 (more preferably 3.5 to 5.0), and the Co concentration in the raffinate is ≤0.2 g / L.

[0054] Preferably, the acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05–0.15 mol / L.

[0055] Preferably, the flow rate ratio of the organic phase to the washing acid in the pickling section is 3 to 4:1.

[0056] Preferably, the back-extraction acid in the back-extraction section is a sulfuric acid solution with a concentration of 0.7 to 0.8 mol / L.

[0057] Preferably, the flow rate ratio of the organic phase to the back-extraction acid in the back-extraction section is 8 to 12:1.

[0058] Preferably, the iron washing acid in the iron washing section is a hydrochloric acid solution with a concentration of 4.0–7.5 mol / L. The iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 4.0–7.5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and discarded.

[0059] Preferably, the flow rate ratio of the organic phase to the iron washing acid in the iron washing section is 3 to 6:1.

[0060] Preferably, in steps (1) and (2)B, the oil removal is performed using activated carbon and oil-removing fiber balls for filtration. The purpose of oil removal is to remove the organic phase of P2O4 or Cyanex 272 and suspended solids from the solution. The used activated carbon and oil-removing fiber balls are washed clean, and finally washed with pure water and dilute acid solution respectively, and dried for later use.

[0061] Preferably, in step (2) section A, the back-extraction acid is a sulfuric acid solution with a concentration of 0.30 to 0.45 mol / L.

[0062] Preferably, in step (2) section A, the flow ratio of the back-extracting acid to the Cyanex272 supported organic phase is 1:2.0 to 3.5.

[0063] Preferably, in step (2) B, the back-extraction acid is a sulfuric acid solution with a concentration of 0.7 to 0.8 mol / L.

[0064] Preferably, in step (2) B, the flow ratio of the back-extracting acid to the Cyanex272 supported organic phase is 1:8 to 12.

[0065] Preferably, in step (2)B, the evaporation crystallization refers to evaporating and crystallizing the purified cobalt sulfate solution obtained in step (2)B until the specific gravity is 1.50-1.54 g / cm³. 3 Then cool it down to 30-40℃, centrifuge and dry it to obtain the final product.

[0066] In the method of this invention, P204 is scientifically known as di(2-ethylhexyl) phosphate, and Cyanex272 is scientifically known as di(2,4,4-trimethylpentyl)phosphonic acid; for operations in multi-stage extraction that are not specifically limited, existing conventional operations can be referred to.

[0067] In the method of this invention, the concentration or content of each element in the solution or battery-grade cobalt sulfate crystals is detected directly or after dissolution by methods such as potentiometric titration, ICP, and flame atomic absorption.

[0068] The beneficial effects of the method of the present invention are as follows: (1) The method of the present invention processes the cobalt sulfate purification solution, whose content of impurities such as calcium and magnesium still does not meet the quality requirements after purification and impurity removal, and produces cobalt sulfate crystals that meet the quality requirements of the industry standard for battery-grade cobalt sulfate (HG / T 5918-2021) Type II, with the contents of each element being: Co≥21%, Ni≤3*10 -6 Fe < 1*10 -6 Cu≤1*10 -6 Mn≤4*10 -6 Zn≤0.5*10 -6 Ca≤2.6*10 -6 Mg≤0.8*10 -6 Cobalt is completely separated from calcium and magnesium, with a cobalt sulfate purity of ≥99.90% and a yield as high as 98.5%. (2) The present invention has a simple process, short process, strong operability, and does not introduce other impurities. It is green and environmentally friendly, low in cost, has good economic value, and is suitable for industrial production. Detailed Implementation

[0069] The present invention will be further described below with reference to the embodiments.

[0070] The cobalt sulfate solution to be extracted in this embodiment of the invention is obtained from arsenic cobalt ore through leaching, purification, and other processes. The concentrations of the main components are as follows: Co 20.1 g / L, Ni 1.56 g / L, Fe < 0.0001 g / L, As 0.0005 g / L, Cu 0.025 g / L, Mn 0.32 g / L, Zn 0.087 g / L, Ca 0.126 g / L, Mg 0.618 g / L, Al 6 mg / L, Cd < 0.01 mg / L, Cr 0.6 mg / L, K 3 mg / L; In the embodiments and comparative examples of this invention, the operations in the multi-stage extraction that are not specifically limited can refer to existing conventional operations; In the embodiments and comparative examples of this invention, the concentration or content of each element in the solution or battery-grade cobalt sulfate crystals is detected directly or after dissolution by methods such as potentiometric titration, ICP, and flame atomic absorption; Unless otherwise specified, the raw materials or chemical reagents used in the embodiments of this invention are obtained through conventional commercial channels.

[0071] Example 1 (1) P204 extraction: First, P204 extractant and kerosene are mixed evenly at a volume ratio of 3:17. Then, 8 mol / L sodium hydroxide solution is added and saponification is carried out until the saponification rate is 15%. After clarification, the saponified extracted organic phase is obtained. The obtained saponified organic phase was added to the cobalt sulfate solution to be extracted at a flow rate of 1:1. Multi-stage extraction was carried out at a flow rate of 6 L / h for the saponified organic phase. The oil was removed by filtration with activated carbon and oil-removing fiber balls to obtain the raffinate (cobalt concentration of 19.49 g / L). Specifically, the P204 extraction process has a total of 34 stages: 1 stage of saponification, 2 stages of clarification, 10 stages of extraction, 6 stages of cobalt washing, 2 stages of back-extraction clarification, 5 stages of back-extraction copper and manganese, 2 stages of clarification, 3 stages of iron washing, 2 stages of chlorine washing, and 1 stage of organic phase clarification. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.25 mol / L; the flow rate of the cobalt washing acid is 1.5 L / h; and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 4:1. The back-extraction acid in the copper-manganese back-extraction section is a 0.6 mol / L sulfuric acid solution; the flow rate of the back-extraction acid is 1.7 L / h, and the flow ratio of the organic phase to the back-extraction acid in the copper-manganese back-extraction section is 3.5:1; the back-extraction acid can be recycled, but its acidity needs to be monitored frequently and sulfuric acid needs to be added to maintain the sulfuric acid concentration in the back-extraction acid at 0.6 mol / L; when the impurity content of the back-extraction acid reaches 10 g / L, it is discharged and discarded. The iron washing acid in the iron washing section is a 6 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 1 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 6:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 6 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped. (2) Cyanex272 extraction: First, Cyanex272 extractant and kerosene are mixed evenly at a volume ratio of 27:73. Then, 8 mol / L sodium hydroxide solution is added and the mixture is saponified until the saponification rate is 36%. After clarification, the saponified cobalt organic phase is obtained. Section A: First, add the obtained saponified cobalt organic phase to the raffinate obtained in step (1) at a flow ratio of 1:1 (cobalt concentration is 19.49 g / L). Perform multi-stage extraction at a flow rate of 10.8 L / h to obtain the Cyanex272-loaded organic phase. Then, back-extract with 0.3 mol / L sulfuric acid solution at a flow ratio of 1:2 to the Cyanex272-loaded organic phase to obtain the back-extracted cobalt sulfate solution (cobalt content is 38.9 g / L). Specifically, the total number of stages in the Cyanex 272 extraction A stage process is 21: saponification stage 1 stage, clarification stage 1 stage, extraction stage 5 stages, clarification stage 1 stage, acid washing stage 3 stages, clarification stage 1 stage, cobalt washing stage 5 stages, iron washing stage 3 stages, and clarification stage 1 stage. In the multi-stage extraction, the inlet pH of the extraction section is 4, the outlet pH of the raffinate is 3.5, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05 mol / L; the flow rate of the acid is 2.15 L / h; and the flow rate ratio of the organic phase to the acid in the pickling section is 5:1. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.375 mol / L; the flow rate of the cobalt washing acid is 4 L / h, and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 2.7:1. The iron washing acid in the iron washing section is a 4 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 2.7 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 4:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 4 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; Section B: First, the obtained saponified cobalt-extracting organic phase is added to the back-extraction cobalt sulfate solution (cobalt content 38.9 g / L) obtained in Section A at a flow rate ratio of 3:1. Multi-stage extraction is performed at a flow rate of 12 L / h to obtain a Cyanex 272-loaded organic phase. Then, back-extraction is performed using a 0.7 mol / L sulfuric acid solution at a flow rate ratio of 1:12 to the Cyanex 272-loaded organic phase. Oil is removed by filtration with activated carbon and oil-removing fiber balls to obtain a purified cobalt sulfate solution. This solution is then evaporated and crystallized to a specific gravity of 1.54 g / cm³. 3 Then cool to 30°C, centrifuge and dry to obtain battery-grade cobalt sulfate crystals; Specifically, the total number of stages in the Cyanex 272 extraction process B section is 21: saponification stage 1, clarification stage 1, extraction stage 4, clarification stage 1, acid washing stage 3, clarification stage 2, back-extraction stage 5, iron washing stage 3, and clarification stage 1. In the multi-stage extraction, the inlet pH value of the extraction section is 4.5, the outlet pH value of the raffinate is 4, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.1 mol / L; the flow rate of the acid is 3 L / h; and the flow rate ratio of the organic phase to the acid in the pickling section is 4:1. The back-extraction acid in the back-extraction section is a sulfuric acid solution with a concentration of 0.75 mol / L; the flow rate of the back-extraction acid is 1 L / h, and the flow rate ratio of the organic phase to the back-extraction acid in the back-extraction section is 12:1. The iron washing acid in the iron washing section is a 4 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 2 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 6:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 4 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; In step (2), in the 5-stage extraction stage of section A, the aqueous phase of stages 1 to 3 is green, stage 4 is dark green or coffee-colored, and stage 5 is red; in the 5-stage cobalt washing stage of section A, the last 2 stages of cobalt washing aqueous phase are colorless. In step (2), in the 4-stage extraction stage of section B, the aqueous phase of stages 1-2 is green, stage 3 is dark green or coffee-colored, and stage 4 is red; in the 5-stage back-extraction stage of section B, the aqueous phase of the last 2 stages of back-extraction is colorless.

[0072] The concentrations of each element in the cobalt sulfate solution to be extracted in step (1), the raffinate obtained, the purified cobalt sulfate solution obtained in step (2), and the content of each element in the battery-grade cobalt sulfate crystals are shown in Table 1.

[0073] Table 1. Comparison of the concentrations of each element in the cobalt sulfate solution to be extracted, the raffinate, the purified cobalt sulfate solution, and the content of each element in battery-grade cobalt sulfate crystals.

[0074] Note: In the table, " / " indicates not detected, "-" indicates not found, and "10" indicates not detected. -6 =0.0001%.

[0075] As shown in Table 1, the cobalt sulfate solution to be extracted was purified by P204, which greatly reduced the concentration of impurity ions such as Cu, Mn, Zn, and Ca. The raffinate was purified by Cyanex 272 A and B stages, which further reduced the concentration of impurity ions such as Mg and Na and enriched Co. The battery-grade cobalt sulfate crystals obtained by evaporation, crystallization, and centrifugation of the purified cobalt sulfate solution met the industry standard for battery-grade cobalt sulfate type II quality requirements. Cobalt was completely separated from calcium and magnesium, and the purity of cobalt sulfate reached 99.94%, with a yield of 98.5%.

[0076] Example 2 (1) P204 extraction: First, P204 extractant and kerosene are mixed evenly at a volume ratio of 1:5. Then, 10 mol / L sodium hydroxide solution is added and the mixture is saponified until the saponification rate is 10%. After clarification, the saponified extracted organic phase is obtained. The obtained saponified organic phase was added to the cobalt sulfate solution to be extracted at a flow rate of 0.8:1. Multi-stage extraction was carried out at a flow rate of 8 L / h for the saponified organic phase. The oil was removed by filtration with activated carbon and oil-removing fiber balls to obtain the raffinate (cobalt concentration of 19.38 g / L). Specifically, the P204 extraction process has a total of 34 stages: 1 stage of saponification, 2 stages of clarification, 10 stages of extraction, 6 stages of cobalt washing, 2 stages of back-extraction clarification, 5 stages of back-extraction copper and manganese, 2 stages of clarification, 3 stages of iron washing, 2 stages of chlorine washing, and 1 stage of organic phase clarification. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.3 mol / L; the flow rate of the cobalt washing acid is 2.66 L / h, and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3:1. The back-extraction acid in the copper-manganese back-extraction section is a 0.5 mol / L sulfuric acid solution; the flow rate of the back-extraction acid is 2.66 L / h, and the flow ratio of the organic phase to the back-extraction acid in the copper-manganese back-extraction section is 3:1; the back-extraction acid can be recycled, but its acidity needs to be monitored frequently and sulfuric acid needs to be added to maintain the sulfuric acid concentration in the back-extraction acid at 0.5 mol / L; when the impurity content of the back-extraction acid reaches 10 g / L, it is discharged and discarded. The iron washing acid in the iron washing section is a 5 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 1.6 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 5:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; (2) Cyanex272 extraction: First, Cyanex272 extractant and kerosene are mixed evenly at a volume ratio of 1:2. Then, 10 mol / L sodium hydroxide solution is added and the mixture is saponified until the saponification rate is 35%. After clarification, the saponified cobalt organic phase is obtained. Section A: First, add the obtained saponified cobalt organic phase to the raffinate obtained in step (1) at a flow ratio of 1:1.5 (cobalt concentration is 19.38 g / L). Perform multi-stage extraction at a flow rate of 9 L / h to obtain the Cyanex272-loaded organic phase. Then, back-extract with 0.4 mol / L sulfuric acid solution at a flow ratio of 1:3 to the Cyanex272-loaded organic phase to obtain the back-extracted cobalt sulfate solution (cobalt content is 38.8 g / L). Specifically, the total number of stages in the Cyanex 272 extraction A stage process is 21: saponification stage 1 stage, clarification stage 1 stage, extraction stage 5 stages, clarification stage 1 stage, acid washing stage 3 stages, clarification stage 1 stage, cobalt washing stage 5 stages, iron washing stage 3 stages, and clarification stage 1 stage. The inlet pH of the extraction section in the multi-stage extraction is 4, the outlet pH of the raffinate is 3.5, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.1 mol / L; the flow rate of the acid is 1.5 L / h; and the flow ratio of the organic phase to the acid in the pickling section is 6:1. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.4 mol / L; the flow rate of the cobalt washing acid is 3 L / h, and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3:1. The iron washing acid in the iron washing section is a 6 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 1.8 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 5:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 6 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; Section B: First, the obtained saponified cobalt-extracting organic phase is added to the back-extraction cobalt sulfate solution (cobalt content 38.8 g / L) obtained in Section A at a flow rate ratio of 2:1. Multi-stage extraction is performed at a flow rate of 14 L / h to obtain the Cyanex 272-loaded organic phase. Then, back-extraction is performed using 0.7 mol / L sulfuric acid solution at a flow rate ratio of 1:8 to the Cyanex 272-loaded organic phase. Oil is removed by filtration with activated carbon and oil-removing fiber balls to obtain a purified cobalt sulfate solution. This solution is then evaporated and crystallized to a specific gravity of 1.54 g / cm³. 3 Then cool to 30°C, centrifuge and dry to obtain battery-grade cobalt sulfate crystals; Specifically, the total number of stages in the Cyanex 272 extraction process B section is 21: saponification stage 1, clarification stage 1, extraction stage 4, clarification stage 1, acid washing stage 3, clarification stage 2, back-extraction stage 5, iron washing stage 3, and clarification stage 1. In the multi-stage extraction, the inlet pH of the extraction section is 4.5, the outlet pH of the raffinate is 4, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05 mol / L; the flow rate of the acid is 4.66 L / h; and the flow rate ratio of the organic phase to the acid in the pickling section is 3:1. The back-extraction acid in the back-extraction section is a sulfuric acid solution with a concentration of 0.70 mol / L; the flow rate of the back-extraction acid is 1.75 L / h, and the flow rate ratio of the organic phase to the back-extraction acid in the back-extraction section is 8:1. The iron washing acid in the iron washing section is a 5 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 4.66 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 3:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; In step (2), in the 5-stage extraction stage of section A, the aqueous phase of stages 1 to 3 is green, stage 4 is dark green or coffee-colored, and stage 5 is red; in the 5-stage cobalt washing stage of section A, the last 2 stages of cobalt washing aqueous phase are colorless. In step (2), in the 4-stage extraction stage of section B, the aqueous phase of stages 1-2 is green, stage 3 is dark green or coffee-colored, and stage 4 is red; in the 5-stage back-extraction stage of section B, the aqueous phase of the last 2 stages of back-extraction is colorless.

[0077] The concentrations of each element in the cobalt sulfate solution to be extracted in step (1), the raffinate obtained, the purified cobalt sulfate solution obtained in step (2), and the content of each element in the battery-grade cobalt sulfate crystals are shown in Table 2.

[0078] Table 2. Comparison of the concentrations of each element in the cobalt sulfate solution to be extracted, the raffinate, the purified cobalt sulfate solution, and the content of each element in battery-grade cobalt sulfate crystals.

[0079] Note: In the table, " / " indicates not detected, "-" indicates not found, and "10" indicates not detected. -6 =0.0001%.

[0080] As shown in Table 2, the cobalt sulfate solution to be extracted was purified by P204, which greatly reduced the concentration of impurity ions such as Cu, Mn, Zn, and Ca. The raffinate was purified by Cyanex 272 A and B stages, which further reduced the concentration of impurity ions such as Mg and Na and enriched Co. The battery-grade cobalt sulfate crystals obtained by evaporation, crystallization, and centrifugation of the purified cobalt sulfate solution met the industry standard for battery-grade cobalt sulfate type II quality requirements. Cobalt was completely separated from calcium and magnesium, and the purity of cobalt sulfate reached 99.92%, with a yield of 98.4%.

[0081] Example 3 (1) P204 extraction: First, P204 extractant and kerosene are mixed evenly at a volume ratio of 1:7. Then, 10 mol / L sodium hydroxide solution is added and saponification is carried out until the saponification rate is 20%. After clarification, the saponified extracted organic phase is obtained. The obtained saponified organic phase was added to the cobalt sulfate solution to be extracted at a flow rate of 1.2:1. Multi-stage extraction was carried out at a flow rate of 9 L / h for the saponified organic phase. The oil was removed by filtration with activated carbon and oil-removing fiber balls to obtain the raffinate (cobalt concentration of 19.3 g / L). Specifically, the P204 extraction process has a total of 34 stages: 1 stage of saponification, 2 stages of clarification, 10 stages of extraction, 6 stages of cobalt washing, 2 stages of back-extraction clarification, 5 stages of back-extraction copper and manganese, 2 stages of clarification, 3 stages of iron washing, 2 stages of chlorine washing, and 1 stage of organic phase clarification. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.33 mol / L; the flow rate of the cobalt washing acid is 2.57 L / h, and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3.5:1; The back-extraction acid in the copper-manganese back-extraction section is a 0.7 mol / L sulfuric acid solution; the flow rate of the back-extraction acid is 2.25 L / h, and the flow ratio of the organic phase to the back-extraction acid in the copper-manganese back-extraction section is 4:1; the back-extraction acid can be recycled, but its acidity needs to be monitored frequently and sulfuric acid needs to be added to maintain the sulfuric acid concentration in the back-extraction acid at 0.7 mol / L; when the impurity content of the back-extraction acid reaches 10 g / L, it is discharged and discarded. The iron washing acid in the iron washing section is a 5.5 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 1.64 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 5.5:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 5.5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped. (2) Cyanex272 extraction: First, Cyanex272 extractant and kerosene are mixed evenly at a volume ratio of 1:4. Then, 12 mol / L sodium hydroxide solution is added and saponification is carried out until the saponification rate is 37%. After clarification, the saponified cobalt organic phase is obtained. Section A: First, add the obtained saponified cobalt organic phase to the raffinate obtained in step (1) at a flow ratio of 1:2 (cobalt concentration is 19.3 g / L). Perform multi-stage extraction at a flow rate of 14 L / h to obtain the Cyanex272-loaded organic phase. Then, back-extract with 0.45 mol / L sulfuric acid solution at a flow ratio of 1:3.5 with the Cyanex272-loaded organic phase to obtain the back-extracted cobalt sulfate solution (cobalt content is 33.78 g / L). Specifically, the total number of stages in the Cyanex 272 extraction A stage process is 21: saponification stage 1 stage, clarification stage 1 stage, extraction stage 5 stages, clarification stage 1 stage, acid washing stage 3 stages, clarification stage 1 stage, cobalt washing stage 5 stages, iron washing stage 3 stages, and clarification stage 1 stage. The inlet pH of the extraction section in the multi-stage extraction is 4, the outlet pH of the raffinate is 3.5, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.15 mol / L; the flow rate of the acid is 1.75 L / h; and the flow rate ratio of the organic phase to the acid in the pickling section is 8:1. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.45 mol / L; the flow rate of the cobalt washing acid is 4 L / h; and the flow rate ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3.5:1. The iron washing acid in the iron washing section is a 7.5 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 4 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 3.5:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 7.5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; Section B: First, the obtained saponified cobalt-extracting organic phase is added to the back-extraction cobalt sulfate solution (cobalt content 33.78 g / L) obtained in Section A at a flow rate ratio of 2.5:1. Multi-stage extraction is performed at a flow rate of 16 L / h to obtain the Cyanex 272-loaded organic phase. Then, back-extraction is performed using 0.8 mol / L sulfuric acid solution at a flow rate ratio of 1:10 to the Cyanex 272-loaded organic phase. Oil is removed by filtration with activated carbon and oil-removing fiber balls to obtain a purified cobalt sulfate solution. This solution is then evaporated and crystallized to a specific gravity of 1.54 g / cm³. 3 Then cool to 30°C, centrifuge and dry to obtain battery-grade cobalt sulfate crystals; Specifically, the total number of stages in the Cyanex 272 extraction process B section is 21: saponification stage 1, clarification stage 1, extraction stage 4, clarification stage 1, acid washing stage 3, clarification stage 2, back-extraction stage 5, iron washing stage 3, and clarification stage 1. In the multi-stage extraction, the inlet pH of the extraction section is 4.5, the outlet pH of the raffinate is 4, and the Co concentration in the raffinate is ≤0.2g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.15 mol / L; the flow rate of the acid is 4.57 L / h; and the flow rate ratio of the organic phase to the acid in the pickling section is 3.5:1. The back-extraction acid in the back-extraction section is a sulfuric acid solution with a concentration of 0.80 mol / L; the flow rate of the back-extraction acid is 1.6 L / h, and the flow rate ratio of the organic phase to the back-extraction acid in the back-extraction section is 10:1. The iron washing acid in the iron washing section is a 7.5 mol / L hydrochloric acid solution; the flow rate of the iron washing acid is 3.2 L / h, and the flow ratio of the organic phase to the iron washing acid in the iron washing section is 5:1; the iron washing acid can be recycled, but its acidity needs to be monitored frequently and hydrochloric acid needs to be added to maintain the concentration of hydrochloric acid in the iron washing acid at 7.5 mol / L; when the impurity content of the iron washing acid reaches 10 g / L, it is discharged and scrapped; In step (2) A and B, the water phase of levels 3, 4 and 5 is green, level 6 is dark green or brown, and level 7 is red; In step (2) A and B, the last two stages of the aqueous phase in the back-extraction stage are colorless.

[0082] The concentrations of each element in the cobalt sulfate solution to be extracted in step (1), the raffinate obtained, the purified cobalt sulfate solution obtained in step (2), and the content of each element in the battery-grade cobalt sulfate crystals are shown in Table 3.

[0083] Table 3. Comparison of the concentrations of each element in the cobalt sulfate solution to be extracted, the raffinate, the purified cobalt sulfate solution, and the content of each element in battery-grade cobalt sulfate crystals.

[0084] Note: In the table, " / " indicates not detected, "-" indicates not found, and "10" indicates not detected. -6 =0.0001%.

[0085] As shown in Table 3, the cobalt sulfate solution to be extracted was purified by P204, which greatly reduced the concentration of impurity ions such as Cu, Mn, Zn, and Ca. The raffinate was purified by Cyanex 272 A and B stages, which further reduced the concentration of impurity ions such as Mg and Na and enriched Co. The battery-grade cobalt sulfate crystals obtained by evaporation, crystallization, and centrifugation of the purified cobalt sulfate solution met the industry standard for battery-grade cobalt sulfate type II quality requirements. Cobalt was completely separated from calcium and magnesium, and the purity of cobalt sulfate was as high as 99.91%, with a yield of 98.3%.

[0086] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step (2), the Cyanex272 extractant is replaced with P507; otherwise, it is the same as Example 1.

[0087] Testing revealed that the magnesium content in the purified cobalt sulfate solution obtained in this comparative example was >0.01 g / L. After evaporation and crystallization, the Mg content in the obtained cobalt sulfate crystals was 0.05%, thus failing to obtain qualified cobalt sulfate type II for batteries.

[0088] Comparative Example 2 The difference between this comparative example and Example 2 is that the multi-stage extraction and back-extraction process in step (2) of the Cyanex 272 extraction B section is omitted, and the cobalt sulfate solution obtained from the back-extraction in section A is directly evaporated and crystallized to a specific gravity of 1.54 g / cm³. 3 Then cool to 30°C, centrifuge and dry to obtain cobalt sulfate crystals; the rest is the same as in Example 2.

[0089] Upon testing, the concentrations of each element in the cobalt sulfate solution obtained from the Cyanex 272 extraction step A were as follows: Co 21.94 g / L, Cu 0.00073 g / L, Mn 0.0039 g / L, Zn 0.0001 g / L, Ca 0.0038 g / L, Mg 0.0003 g / L, Ni 0.00065 g / L; while the composition requirements of battery-grade cobalt sulfate solution (HGT5918-2021) have the following concentration limits for each element: Co≥8 g / L, Cu≤0.0005 g / L, Mn≤0.0005 g / L, Zn≤0.0005 g / L, Ca≤0.001 g / L, Mg≤0.01 g / L, Ni≤0.0005 g / L. This indicates that after canceling step (2) Cyanex272 extraction process B section in this comparative example, the impurity ions such as copper, manganese, calcium, and nickel exceed the standard and do not meet the requirements of battery-grade cobalt sulfate solution. Therefore, after evaporation and crystallization, qualified battery-grade cobalt sulfate type II cannot be obtained.

Claims

1. A method for preparing battery-grade cobalt sulfate through multi-stage extraction, characterized in that, Includes the following steps: (1) P204 extraction: First, P204 extractant and diluent are mixed evenly, then saponified and clarified to obtain saponified extracted organic phase; The obtained saponified and extracted organic phase was added to the cobalt sulfate solution to be extracted, and multi-stage extraction was performed to remove oil and obtain raffinate. (2) Cyanex272 extraction: First, Cyanex272 extractant and diluent are mixed evenly, then saponified and clarified to obtain saponified cobalt organic phase; Section A: First, add the obtained saponified cobalt organic phase to the raffinate obtained in step (1) and perform multi-stage extraction to obtain the Cyanex272 loaded organic phase. Then, back-extract with back-extracting acid to obtain the back-extracted cobalt sulfate solution. Section B: First, add the obtained saponified cobalt-extracted organic phase to the back-extracted cobalt sulfate solution obtained in Section A for multi-stage extraction to obtain a Cyanex 272-loaded organic phase. Then, back-extract with back-extraction acid to remove oil and obtain a purified cobalt sulfate solution. Evaporate and crystallize to obtain battery-grade cobalt sulfate crystals.

2. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to claim 1, characterized in that: In step (1), the volume ratio of the P204 extractant to the diluent is 1:5 to 7; the diluent includes kerosene or 260# solvent oil; the saponification treatment refers to adding sodium hydroxide solution to the mixed phase of P204 extractant and diluent, and performing saponification treatment until the saponification rate is 10 to 20%; the molar concentration of the sodium hydroxide solution is 8 to 12 mol / L.

3. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to claim 1 or 2, characterized in that: In step (1), the flow rate ratio of the saponified organic phase to the cobalt sulfate solution to be extracted is 0.8–1.2:1; the concentrations of the main components in the cobalt sulfate solution to be extracted are as follows: Co 17–25 g / L, Ni 1.2–3.0 g / L, Fe < 1 mg / L, As < 1 mg / L, Cu 6–25 mg / L, Mn 0.25–0.50 g / L, Zn 0.05–0.30 g / L, Ca 0.1–0.5 g / L, Mg 0.60–0.69 g / L, Al ≤ 6 mg / L, Cd < 0.01 mg / L, Cr ≤ 0.6 mg / L, K ≤ 10 mg / L; the flow rate of the saponification and extraction organic phase is 6–9 L / h; the total number of stages in the P204 extraction process is 32–36; the P204 extraction process includes one saponification stage corresponding to the saponification treatment, two clarification stages corresponding to the clarification, and 29–33 multi-stage extraction stages; the multi-stage extraction includes: 10 extraction stages, 4–8 cobalt washing stages, 2 back-extraction clarification stages, 5 copper-manganese back-extraction stages, and clarification stages. The process consists of a 2-stage cobalt washing section, a 3-stage iron washing section, a 2-stage chlorine washing section, and a 1-stage organic phase clarification section. The cobalt washing acid in the cobalt washing section is a sulfuric acid solution with a concentration of 0.25–0.33 mol / L. The flow ratio of the organic phase to the cobalt washing acid in the cobalt washing section is 3–4:

1. The copper-manganese back-extraction section uses a sulfuric acid solution with a concentration of 0.5–0.7 mol / L. The flow ratio of the organic phase to the back-extraction acid in the copper-manganese back-extraction section is 3–4:

1. The iron washing acid in the iron washing section is a hydrochloric acid solution with a concentration of 5–6 mol / L. The flow ratio of the organic phase to the iron washing acid in the iron washing section is 5–6:

1.

4. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to any one of claims 1 to 3, characterized in that: In step (2), the volume ratio of Cyanex272 extractant to diluent is 1:2 to 4; the diluent includes kerosene or 260# solvent oil; the saponification treatment refers to adding sodium hydroxide solution to the mixed phase of Cyanex272 extractant and diluent, and performing saponification treatment until the saponification rate is 35 to 37%; the molar concentration of the sodium hydroxide solution is 8 to 12 mol / L.

5. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to any one of claims 1 to 4, characterized in that: In step (2) section A, the flow rate ratio of the saponified cobalt extraction organic phase to the raffinate is 1:1 to 2; the cobalt concentration in the raffinate is 15 to 22 g / L; the flow rate of the saponified cobalt extraction organic phase is 9 to 14 L / h; the total number of stages in the Cyanex 272 extraction section A is 20 to 25; the Cyanex 272 extraction section A includes a saponification stage 1 corresponding to the saponification treatment, a clarification stage 1 corresponding to the clarification, and multi-stage extraction stages 18 to 23; the multi-stage extraction includes: extraction stages 4 to 5, clarification stage 1, acid washing stages 3 to 5, clarification stage 1, cobalt washing stages 5 to 6, iron washing stages 3 to 4, and clarification stage 1; the extraction in the multi-stage extraction... The inlet pH of the extraction section is 3.5–6.0, and the outlet pH of the raffinate is 3.0–6.0, with a Co concentration ≤0.2 g / L in the raffinate. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05–0.15 mol / L, and the flow ratio of the organic phase to the acid used in the pickling section is 5–8:

1. The cobalt washing section uses a cobalt washing acid solution with a concentration of 0.30–0.45 mol / L, and the flow ratio of the organic phase to the cobalt washing acid used in the cobalt washing section is 2.0–3.5:

1. The iron washing section uses a hydrochloric acid solution with a concentration of 4.0–7.5 mol / L, and the flow ratio of the organic phase to the iron washing acid used in the iron washing section is 3.5–5.0:

1.

6. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to any one of claims 1 to 5, characterized in that: In step (2) section B, the flow rate ratio of the saponification cobalt extraction organic phase to the back-extraction cobalt sulfate solution is 2-3:1; the concentration of cobalt in the back-extraction cobalt sulfate solution is 30-126 g / L; the flow rate of the saponification cobalt extraction organic phase is 12-16 L / h; the total number of stages in the Cyanex 272 extraction section B process is 20-25 stages; the Cyanex 272 extraction section B process includes a saponification stage 1 corresponding to the saponification treatment, a clarification stage 1 corresponding to the clarification, and a multi-stage extraction of 18-23 stages; the multi-stage extraction includes: extraction stages 3-4, clarification stage 1, acid washing stages 3-5, clarification stage 2, back-extraction stages 5-6, iron washing stages 3-4, and clarification stage 1; the inlet pH of the extraction stage in the multi-stage extraction is... The pH value of the raffinate at the extraction section is 3.5–6.0, and the Co concentration in the raffinate is ≤0.2 g / L. The acid used in the pickling section is a sulfuric acid solution with a concentration of 0.05–0.15 mol / L. The flow ratio of the organic phase to the acid used in the pickling section is 3–4:

1. The acid used in the back-extraction section is a sulfuric acid solution with a concentration of 0.7–0.8 mol / L. The flow ratio of the organic phase to the back-extraction acid used in the back-extraction section is 8–12:

1. The acid used in the iron washing section is a hydrochloric acid solution with a concentration of 4.0–7.5 mol / L. The flow ratio of the organic phase to the iron washing acid used in the iron washing section is 3–6:

1.

7. The method for preparing battery-grade cobalt sulfate by multi-stage extraction according to any one of claims 1 to 6, characterized in that: In steps (1) and (2)B, the oil removal is performed using activated carbon and oil-removing fiber balls for filtration; in step (2)A, the back-extraction acid is a sulfuric acid solution with a concentration of 0.30–0.45 mol / L; the flow rate ratio of the back-extraction acid to the Cyanex 272-supported organic phase is 1:2.0–3.5; in step (2)B, the back-extraction acid is a sulfuric acid solution with a concentration of 0.7–0.8 mol / L; the flow rate ratio of the back-extraction acid to the Cyanex 272-supported organic phase is 1:8–12; the evaporation crystallization refers to evaporating and crystallizing the purified cobalt sulfate solution obtained in step (2)B to a specific gravity of 1.50–1.54 g / cm³. 3 Then cool it down to 30-40℃, centrifuge and dry it to obtain the final product.

Images