Method for preparing high-purity cobalt salt from neodymium iron boron waste cobalt concentrate

Abstract

The invention relates to the field of resource recovery, in particular to a method for preparing high-purity cobalt salt from neodymium iron boron waste cobalt enrichment. Comprising the steps of raw material liquid preparation, saponification difficult-to-extract impurity separation, easy-to-extract impurity separation, extraction agent regeneration, cobalt salt preparation and the like. Through the synergistic effect of two steps of extraction processes, in the first step, more than 80% of difficult-to-extract impurities such as calcium and magnesium are preferentially removed by adopting a hydrochloric acid eluent, and in the second step, deep separation of cobalt and easy-to-extract impurities is realized through sulfuric acid elution, so that a complete two-stage impurity separation system is formed; two key processes of separation of impurities difficult to extract and purification of impurities easy to extract are subjected to process linkage and linkage, a saponification organic phase circulation system is shared, equipment investment is reduced, process control operation is simpler, and the purity of a final product is stabilized at 99.3% or above. Through the design of removing a large number of difficult-to-extract impurity elements in advance, the treatment load of the subsequent cobalt purification process is remarkably reduced, the consumption of an extracting agent is reduced, the wastewater discharge amount is reduced, and the stepped reduction of the production cost is realized.

Description

Technical Field

[0001] The present invention relates to the field of resource recovery, and in particular to a method for preparing high-purity cobalt salts by utilizing cobalt concentrates from NdFeB waste. Background Art

[0002] As a key metallic element, cobalt plays a vital role in modern industry. In the battery sector, cobalt is a crucial component of lithium-ion battery cathode materials, playing a key role in improving the battery's energy density, charge-discharge performance, and cycle life. In the alloy manufacturing industry, the addition of cobalt can significantly improve the alloy's hardness, wear resistance, and high-temperature resistance. In catalyst preparation, cobalt-based catalysts, due to their unique catalytic activity, are widely used in various chemical reactions.

[0003] Neodymium iron boron (NdFeB) permanent magnets are widely used in the new energy and electronic information industries. In the drive motors of new energy vehicles and generators of wind turbines, NdFeB permanent magnets, with their excellent magnetic properties, provide a strong guarantee for efficient and stable operation. They also play an indispensable role in electronic information products such as hard disk drives and headphones. With the rapid development of these industries, market demand for NdFeB materials continues to rise, and the amount of waste generated during its processing and from device scrapping has also increased dramatically. This NdFeB waste has become a highly promising secondary cobalt resource.

[0004] Currently, cobalt is typically recovered as cobalt concentrate during the processing of NdFeB waste. However, this cobalt concentrate presents numerous challenges. Firstly, its relatively low cobalt content makes subsequent purification more difficult. Secondly, it contains significant amounts of impurities such as calcium and magnesium. These impurities make it difficult to effectively process using existing cobalt purification processes, making it incapable of producing high-purity cobalt carbonate and cobalt sulfate products.

[0005] Most existing cobalt purification processes are designed for primary cobalt ores or cobalt raw materials with low impurity content, and have poor adaptability to special raw materials such as cobalt concentrates recovered from NdFeB waste. If the existing process is directly used to treat the cobalt concentrate, it will not only significantly increase the purification cost and reduce production efficiency, but also produce a large amount of difficult-to-treat wastewater and waste residue, which will put great pressure on the environment. At the same time, due to incomplete removal of impurities, the quality of the prepared cobalt carbonate and cobalt sulfate products is unstable, making it difficult to meet the strict requirements of high-end application fields for product purity and performance. Therefore, developing an efficient purification process specifically for cobalt concentrates recovered from NdFeB waste, converting the cobalt therein into high-quality cobalt salt products such as cobalt carbonate or cobalt sulfate, realizing the recycling of cobalt resources and creating considerable economic benefits, has become a key issue that needs to be urgently addressed in this field. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the embodiments of the present invention is to provide a method for preparing high-purity cobalt salts using cobalt concentrates from NdFeB waste, which solves the problem that the cobalt concentrates recovered from NdFeB waste in the prior art cannot be effectively separated by traditional purification processes due to the high content of calcium and magnesium impurities, and the recovery process is complicated and costly. It realizes the efficient separation of cobalt and impurity elements through a graded extraction system, and the high-value recovery and utilization of cobalt resources.

[0007] In order to solve the above technical problems, the embodiment of the present invention provides a method for preparing high-purity cobalt salt using cobalt enriched material of NdFeB waste, comprising the following steps: S1. Preparation of raw material solution: mixing the cobalt-enriched solid of NdFeB waste with an inorganic acid solution for acid leaching reaction, and preparing a raw material solution with a pH value of 3.5 to 4.5 after solid-liquid separation, or preparing a raw material solution with a pH value of 3.5 to 4.5 by preparing the cobalt-enriched solution obtained in the NdFeB waste recovery process; S2. Saponification: Cyanex 272 is mixed with 260# solvent oil or kerosene to form an organic phase, which is then saponified with aqueous ammonia to obtain a saponified organic phase; S3. Separation of Difficult-to-Extract Impurities: The saponified organic phase, raw material liquid, and hydrochloric acid eluent are introduced into the first stage, intermediate feed stage, and final stage of the first extraction tank via flow meters. After extraction and washing, the difficult-to-extract impurity elements are discharged from the first stage aqueous phase, while the remaining elements are loaded in the organic phase to form a loaded organic phase and discharged from the final stage. S4. Separation of easily extractable impurities: The saponified organic phase, the loaded organic phase, and the sulfuric acid eluent are introduced into the first stage, the intermediate feed stage, and the last stage of the washing section of the second extraction tank via flow meters. After extraction and washing, cobalt is discharged with the first-stage aqueous phase to obtain a cobalt sulfate solution, while the remaining easily extractable impurities are carried in the organic phase and discharged from the last stage. S5, extractant regeneration: the organic phase loaded with easily extractable impurity elements then enters the stripping extraction tank, and after stripping to form a blank organic phase, returns to step S2 for recycling; S6. Preparation of cobalt salt: slowly adding a precipitant to the cobalt sulfate solution obtained in step S4 to generate a cobalt salt precipitate, which is then filtered, washed, and dried to obtain a high-purity cobalt salt; or The cobalt sulfate solution obtained in step S4 is concentrated under reduced pressure to obtain high-purity cobalt sulfate.

[0008] In some embodiments of the present invention, in step S1, the inorganic acid is at least one of hydrochloric acid, sulfuric acid or nitric acid.

[0009] As a preference in some embodiments of the present invention, in step S1, the inorganic acid is industrial hydrochloric acid.

[0010] As a preference in some embodiments of the present invention, in step S1, at this time, the cobalt content in the raw material solution is 10 g / L to 30 g / L.

[0011] As some embodiments of the present invention, in step S2, Cyanex 272 and 260# solvent oil or kerosene are mixed in a volume ratio of 1:4 to 1:1 to form an organic phase.

[0012] As a preference in some embodiments of the present invention, in step S2, Cyanex 272 and 260# solvent oil or kerosene are mixed in a volume ratio of 1:1 to form an organic phase.

[0013] As preferred in some embodiments of the present invention, in step S2, the saponification degree is 0.2 mol / L to 0.5 mol / L.

[0014] As a preference in some embodiments of the present invention, in step S2, the saponification degree is 0.45 mol / L.

[0015] As some embodiments of the present invention, in step S3, the concentration of hydrochloric acid used as the eluent is 2 mol / L to 6 mol / L.

[0016] As a preference in some embodiments of the present invention, in step S3, the concentration of hydrochloric acid used as the eluent is 4 mol / L.

[0017] As some embodiments of the present invention, in step S3, 80% of the difficult-to-extract impurity elements in the raw material liquid are discharged from the first-stage aqueous phase.

[0018] As some embodiments of the present invention, in step S3, the molar ratio of the saponified organic phase, the raw material liquid and the hydrochloric acid eluent introduced into the first extraction tank is: (0.2-0.5):1:(0.02-0.05).

[0019] As some embodiments of the present invention, in step S4, the concentration of sulfuric acid used as the eluent is 1 mol / L to 2 mol / L.

[0020] As preferred in some embodiments of the present invention, in step S4, the concentration of sulfuric acid used as the eluent is 2 mol / L.

[0021] As some embodiments of the present invention, in step S4, the molar ratio of the saponified organic phase, the loaded organic phase and the hydrochloric acid eluent introduced into the second extraction tank is: (0.8-1.2):1:(1.0-2.0).

[0022] As some embodiments of the present invention, in step S5, the concentration of hydrochloric acid used for stripping is 2 mol / L to 6 mol / L.

[0023] As a preference in some embodiments of the present invention, in step S5, the concentration of hydrochloric acid used for stripping is 6 mol / L.

[0024] As some embodiments of the present invention, in step S6, the precipitant is one of ammonium bicarbonate, sodium carbonate, oxalic acid, and oxalate.

[0025] As preferred in some embodiments of the present invention, in step S6, the precipitant is ammonium bicarbonate or sodium carbonate, the reaction temperature of the cobalt salt precipitation process is 60° C. to 80° C., and the pH value is between 6 and 10.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1. High separation efficiency: Through the synergistic effect of the two-step extraction process and the selectivity of the Cyanex272 extractant, hydrochloric acid is used as the eluent in the first step to preferentially remove more than 80% of difficult-to-extract impurities such as calcium and magnesium. In the second step, sulfuric acid is used to achieve deep separation of cobalt and easily extractable impurities, forming a complete two-stage impurity separation system.

[0027] 2. Excellent process economy: Through the design of pre-removal of a large number of difficult-to-extract impurity elements, the processing load of the subsequent cobalt purification process is significantly reduced, the consumption of extraction agents and the amount of wastewater discharged are reduced, and a step-by-step reduction in production costs is achieved.

[0028] 3. Strong process linkage: The two key processes of separation of difficult-to-extract impurities and purification of easily extractable impurities are linked and connected, sharing the saponification organic phase circulation system, reducing equipment investment and making process control operations simpler.

[0029] 4. Good product stability: Through the two-stage impurity separation system, the purity of the final product is ensured to be stable at more than 99.3%, meeting industrial-grade application standards.

[0030] 5. High resource utilization: In view of the characteristics of low-cobalt NdFeB waste, the synergy of enrichment dissolution and preparation, multi-stage extraction and extractant recycling and regeneration processes can significantly improve the cobalt element recovery efficiency, reduce the extraction agent consumption, and achieve low-cost and high-purity recovery of metallic cobalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the drawings required for describing the specific implementation or the prior art will be briefly introduced below. Obviously, the drawings described below are only one implementation of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the process flow of Example 1 of the present invention; Figure 2 This is a schematic diagram of the extraction tank layout of Example 1 of the present invention; Figure 3This is a schematic diagram of the process flow of Example 2 of the present invention; Figure 4 This is a schematic diagram of the process flow of Example 3 of the present invention; Figure 5 This is a schematic diagram of the extraction tank layout of Example 3 of the present invention; Figure 6 This is a schematic diagram of the process flow of Example 4 of the present invention; Figure 7 This is a schematic diagram of the process flow of Example 5 of the present invention; Figure 8 This is a schematic diagram of the process flow of Example 6 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the technical solutions in the specific implementation methods of the present invention are clearly and completely described below to further illustrate the present invention. Obviously, the specific implementation methods described are only part of the implementation methods of the present invention, rather than all styles.

[0034] The embodiments of the present application provide a method for preparing high-purity cobalt salts using cobalt concentrates from NdFeB waste, thereby solving the technical problems of low cobalt recovery and high production costs caused by incomplete separation of impurities during the extraction and purification of cobalt concentrates from NdFeB waste in existing processes. The innovative use of a hydrochloric acid-sulfuric acid gradient elution process in a direct-down two-stage extraction system, combined with the selectivity of the Cyanex272 extractant, achieves a step-by-step and efficient separation of cobalt from impurities such as calcium and magnesium.

[0035] The technical solution in the embodiment of the present application is to solve the above-mentioned problems of low cobalt recovery rate and high production cost. The overall idea is as follows: Using cobalt-enriched solids and cobalt-enriched liquid recovered from NdFeB waste as raw materials, solvent extraction and separation technology is used to separate and purify the cobalt element. Di(2,4,4-trimethylpentyl)phosphonic acid (Cyanex272) is used as the extractant. The first extraction and separation process separates the cobalt from the difficult-to-extract impurities, allowing the cobalt and easily extractable components to enter the organic phase. The organic phase, loaded with cobalt and easily extractable components, then serves as the feed liquid for the second extraction and separation process, separating the cobalt from the difficult-to-extract components. Sulfuric acid is then used as the eluent to produce a cobalt sulfate solution. Finally, a cobalt salt product is obtained by adding a precipitant to the cobalt sulfate solution or by concentrating the cobalt sulfate solution to obtain the cobalt sulfate product.

[0036] In order to better understand the above technical solution, the above technical solution is described in detail below with specific implementation methods.

[0037] Example 1: This example uses a cobalt-enriched solution (I) obtained from a certain NdFeB waste recovery process as a raw material, and adopts a method of preparing high-purity cobalt salt from NdFeB waste cobalt enriched solution according to the present invention. The process flow is as follows: Figure 1 As shown, the extraction tank used is divided into three sections, the first extraction tank (stage 1 to stage 18), the second extraction tank (stage 19 to stage 54), and the back extraction tank (stage 55 to stage 60). The layout is as follows Figure 2 As shown; Table 1 Element contents of cobalt-enriched solution (Ⅰ) recovered from NdFeB waste The specific steps are as follows: S1. Preparation of raw material solution: Add industrial hydrochloric acid to the cobalt-enriched solution (I) and adjust the pH to 3.5 to obtain a raw material solution. After testing, the cobalt content of the raw material solution is 19.5 g / L.

[0038] S2. Saponification: Cyanex 272 extractant and 260# solvent oil were mixed in a volume ratio of 1:1 to form an organic phase, which was then saponified with aqueous ammonia to obtain a saponified organic phase with a saponification degree of 0.45 mol / L.

[0039] S3. Separation of difficult-to-extract impurities: Prepare 4 mol / L hydrochloric acid as the eluent, and introduce the saponified organic phase, raw material liquid and hydrochloric acid eluent into the 1st, 8th and 18th stages of the first extraction tank at flow rates of 3.9 L / min, 3.1 L / min and 0.1 L / min, respectively. After extraction and washing, the difficult-to-extract impurity elements magnesium, calcium and nickel are discharged from the 1st stage aqueous phase at a flow rate of 3.2 L / min. Cobalt and the remaining elements (mainly Zn, Cu, Al, Mn, Fe) are loaded on the organic phase to form a loaded organic phase and discharged from the last stage, i.e., the 18th stage, at a flow rate of 3.9 L / min. At this time, cobalt and the difficult-to-extract components magnesium, calcium and nickel are separated.

[0040] S4. Separation of easily extractable impurities: The saponified organic phase, the loaded organic phase discharged from the 18th stage, and a 2 mol / L sulfuric acid eluent were introduced into the 19th, 38th, and 54th stages of the second extraction tank at flow rates of 3.0 L / min, 3.9 L / min, and 0.62 L / min, respectively. After extraction and washing, cobalt was discharged along with the 19th stage aqueous phase at a flow rate of 0.62 L / min to obtain a cobalt sulfate solution. The remaining easily extractable impurity elements (Zn, Cu, etc.) were loaded on the organic phase and discharged from the 55th stage at a flow rate of 0.13 L / min. The cobalt concentration in the obtained cobalt sulfate solution was tested to be 50 g / L.

[0041] S5, extractant regeneration: The organic phase loaded with easily extractable impurity elements then enters the 58th stage of the stripping extraction tank, is stripped with hydrochloric acid to form a blank organic phase, and then flows out from the 60th stage and returns to step S2 for recycling.

[0042] S6. Preparation of cobalt salt: The cobalt sulfate solution obtained in step S4 was transferred to a precipitation reaction tank and heated to 60° C., and then ammonium bicarbonate was slowly added until the pH value was 6.5. The mixture was stirred for 0.5 h and allowed to stand for 2 h. The mixture was then filtered and washed with water, and dried at 80° C. for 4 h to finally obtain a high-purity cobalt carbonate product.

[0043] After testing, the purity of the cobalt carbonate product obtained in this example was 99.5%, which met the requirements of the national chemical industry standard HG / T 4520-2023 for qualified products.

[0044] Example 2: This example uses the cobalt-enriched solution (II) obtained from a certain NdFeB waste recovery process as a raw material, and uses the method of the present invention for preparing high-purity cobalt salt using the cobalt-enriched solution from NdFeB waste. The process flow is as follows: Figure 3 As shown, the extraction tank layout is as follows Figure 2 shown.

[0045] Table 2 Element contents of cobalt-enriched solution (II) recovered from NdFeB waste The specific steps are as follows: S1. Preparation of raw material solution: Directly take the cobalt-enriched solution (II), add industrial ammonia water and accurately adjust the pH to 3.8 to obtain a raw material solution. After testing, the cobalt content of the raw material solution is 22.1 g / L.

[0046] S2. Saponification: Cyanex 272 extractant and kerosene were mixed in a volume ratio of 1:1 to form an organic phase, which was then saponified with aqueous ammonia to obtain a saponified organic phase with a saponification degree of 0.42 mol / L.

[0047] S3, Separation of Difficult-to-Extract Impurities: Prepare 3.5 mol / L hydrochloric acid as the eluent. The saponified organic phase, feed solution, and hydrochloric acid eluent are introduced into the first, eighth, and 18th stages of the first extraction tank at flow rates of 4.2 L / min, 3.0 L / min, and 0.15 L / min, respectively. After extraction and washing, the difficult-to-extract impurities magnesium, calcium, and nickel are removed from the first-stage aqueous phase at a flow rate of 3.35 L / min. Cobalt and the remaining elements (primarily Zn, Cu, Al, Mn, and Fe) are loaded into the organic phase to form a loaded organic phase, which is discharged from the 18th stage at a flow rate of 4.2 L / min. At this point, the cobalt is separated from the difficult-to-extract components magnesium, calcium, and nickel.

[0048] S4, Separation of Easily Extractable Impurities: The saponified organic phase, the loaded organic phase discharged from stage 18, and a 2 mol / L sulfuric acid eluent were introduced into the second-stage extraction tank at flow rates of 3.5 L / min, 4.2 L / min, and 0.70 L / min, respectively, at stages 19, 38, and 54. After extraction and washing, cobalt was discharged with the aqueous phase from stage 19 at a flow rate of 0.70 L / min to produce a cobalt sulfate solution. The remaining easily extractable impurities (such as Zn and Cu) were carried in the organic phase and discharged from stage 55 at a flow rate of 0.18 L / min. Testing revealed a cobalt concentration of 48 g / L in the resulting cobalt sulfate solution.

[0049] S5, extractant regeneration: The organic phase loaded with easily extractable impurity elements then enters the 58th stage of the stripping extraction tank, is stripped with hydrochloric acid to form a blank organic phase, and then flows out from the 60th stage and returns to step S2 for recycling.

[0050] S6. Preparation of cobalt salt: The cobalt sulfate solution obtained in step S4 is transferred to a precipitation reaction tank and heated to 65°C. Then, oxalic acid solution is slowly added, and aqueous ammonia is added to control the end point pH to 2.0. Stirring is continued for 1.0 hour, and then allowed to stand for 3 hours. The solution is then filtered through a filter, washed with water, and dried at 80°C for 4 hours to obtain a high-purity cobalt oxalate product.

[0051] After testing, the purity of the cobalt oxalate product obtained in this example is 99.3%, which meets the requirements for the main content of cobalt oxalate used in battery materials.

[0052] Example 3: This example uses the cobalt-enriched solution (III) obtained from a certain NdFeB waste recovery process as a raw material, and is treated using the method of the present invention. The process flow is as follows: Figure 4 , the extraction tank layout used is reference Figure 5 The number of extraction tanks in the first stage was optimized to a total of 16 stages.

[0053] Table 3 Element contents of cobalt-enriched solution (III) recovered from NdFeB waste The specific steps are as follows: S1. Preparation of raw material solution: Take the cobalt-enriched solution (III), add ammonia water to accurately adjust the pH to 4.5, and filter to obtain a raw material solution. After testing, the cobalt content of the raw material solution is 15.8 g / L.

[0054] S2. Saponification: Same as in Example 1, the degree of saponification of the organic phase is 0.45 mol / L.

[0055] S3, Separation of Difficult-to-Extract Impurities: 4 mol / L hydrochloric acid was used as the eluent. The saponified organic phase, feed solution, and hydrochloric acid eluent were introduced into the first, sixth, and fourteenth stages of the optimized first-stage extraction tank (16 stages total) at flow rates of 3.5 L / min, 2.8 L / min, and 0.12 L / min, respectively. After extraction and washing, the difficult-to-extract impurities magnesium, calcium, and nickel were removed from the first-stage aqueous phase at a flow rate of 3.0 L / min. The loaded organic phase was removed from the 16th stage at a flow rate of 3.5 L / min. Cobalt was well separated from the difficult-to-extract components.

[0056] S4, Separation of Easily Extractable Impurities: The saponified organic phase, the loaded organic phase discharged from stage 16, and 1.8 mol / L sulfuric acid eluent were introduced into the second-stage extraction tank at flow rates of 2.8 L / min, 3.5 L / min, and 0.55 L / min, respectively, at stages 17, 36, and 52. Cobalt was discharged along with the aqueous phase from stage 17 at a flow rate of 0.55 L / min to produce a cobalt sulfate solution. The organic phase loaded with easily extractable impurities was discharged from stage 55 at a flow rate of 0.10 L / min. Testing revealed a cobalt concentration of 42 g / L in the cobalt sulfate solution.

[0057] S5. Extractant regeneration: As in Example 1, the loaded organic phase enters the stripping tank (stage 56) and is regenerated by stripping with hydrochloric acid.

[0058] S6. Preparation of cobalt salt: The cobalt sulfate solution obtained in step S4 was transferred to a reactor and concentrated by evaporation at 70°C to a cobalt concentration of approximately 100 g / L. After cooling to room temperature, an appropriate amount of cobalt chloride seed crystals was added and stirred continuously for crystallization for 6 hours. Filter the solution, wash the crystals with a small amount of cold water, and dry them at 60°C for 3 hours to obtain high-purity cobalt chloride (CoCl2·6H2O) crystals.

[0059] After testing, the purity of the cobalt chloride (CoCl2·6H2O) product obtained in this example was 99.5%, which met the requirements of the national standard for industrial cobalt chloride (GB / T 26523-2022) for superior products.

[0060] Example 4: This example uses the cobalt-enriched solution (IV) obtained by recycling NdFeB waste as a raw material, and uses the method of the present invention for treatment. The process flow is as follows: Figure 6 , extraction tank layout reference Figure 2 (The first extraction tank has 18 stages, and the second extraction tank has 36 stages).

[0061] Table 4 Element contents of cobalt-enriched solution (IV) recovered from NdFeB waste The process is consistent with that of Example 1. The steps and specific process parameters of this example are as follows: S1. Preparation of raw material solution: Take the cobalt-enriched solution (IV), add industrial ammonia water and adjust the pH to 3.7 accurately to obtain a raw material solution. After testing, the cobalt content of the raw material solution is 25.6 g / L.

[0062] S2. Saponification: Cyanex 272 extractant and kerosene were mixed in a volume ratio of 1:1 to form an organic phase, which was saponified with aqueous ammonia to obtain a saponified organic phase. The saponification degree was controlled to be 0.48 mol / L.

[0063] S3, Separation of Difficult-to-Extract Impurities: Use 4.5 mol / L hydrochloric acid as the eluent. Saponified organic phase flow rate: 3.6 L / min (introduced into the first stage), feed liquid flow rate: 3.3 L / min (introduced into the eighth stage), hydrochloric acid eluent flow rate: 0.1 L / min (introduced into the eighteenth stage). Difficult-to-extract impurities (Ca, Mg, Ni) are discharged from the first stage aqueous phase at a rate of 3.5 L / min. The loaded organic phase (containing Co, Zn, Cu, Mn, and Fe) is discharged from the eighteenth stage at a rate of 3.6 L / min.

[0064] S4. Separation of easily extractable impurities: Saponified organic phase flow rate: 3.0 L / min (introduced into stage 19), loaded organic phase flow rate: 3.6 L / min (introduced into stage 38), eluent: 2.2 mol / L sulfuric acid, flow rate 0.65 L / min (introduced into stage 54). Cobalt product solution (cobalt sulfate solution) was discharged from the aqueous phase of stage 19 at a rate of 0.65 L / min. The organic phase loaded with easily extractable impurities (Zn, Cu, Mn, Fe) was discharged from stage 55 at a rate of 0.15 L / min.

[0065] After testing, the cobalt concentration of cobalt sulfate solution reached 62g / L, and the key impurity contents were: Ca<0.5mg / L, Mg<1mg / L, Zn<0.1mg / L, and Cu<0.05mg / L.

[0066] S5, extractant regeneration: the loaded organic phase (0.15 L / min) enters the 58th stage of the stripping tank and is stripped and regenerated with 4 mol / L hydrochloric acid, and the blank organic phase returns to S2 for circulation.

[0067] S6, cobalt sulfate crystallization: (1) Concentration and impurity removal: The cobalt sulfate solution obtained in S4 is pumped into a vacuum evaporator and concentrated to a density of 1.45 g / cm³ (corresponding to a cobalt concentration of approximately 120 g / L) at -0.08 MPa and 70°C. (2) Insulation filtration: Maintain 70°C and let it stand for 1 hour. Filter while hot to remove trace suspended matter. (3) Cooling crystallization: The filtrate is cooled to 25°C at a rate of 0.5°C / min. Cobalt sulfate seed crystals (particle size 100 mesh, dosage 0.5‰) are added. Crystallization is carried out by constant temperature stirring for 8 hours. (4) Centrifugal drying: The crystal slurry is separated by centrifuge and rinsed twice with 5°C cold pure water. The wet material is dried at 55°C with hot air for 4 hours to obtain rose-red cobalt sulfate (CoSO4·7H2O) crystals.

[0068] Example 5: This example uses the cobalt-enriched solution (V) obtained by recycling NdFeB waste as a raw material, and uses the method of the present invention to process it. The process flow is as follows: Figure 7 , extraction tank layout reference Figure 2 .

[0069] Table 5 Element contents of cobalt-enriched solution (V) recovered from NdFeB waste The process is consistent with that of Example 1. The steps and specific process parameters of this example are as follows: S1. Preparation of raw material solution: pH adjusted to 3.9, cobalt concentration 18.2 g / L.

[0070] S2. Saponification: The saponification degree is increased to 0.50 mol / L.

[0071] S3. Separation of difficult-to-extract impurities: Eluent (HCl): 5.0 mol / L, flow rate: saponified organic phase 4.0 L / min into the first stage, raw liquid 3.2 L / min into the eighth stage, HCl eluent 0.12 L / min into the 18th stage, raffinate (containing Ca, Mg, Ni) flow rate: 4.0 L / min.

[0072] S4, separation of easily extractable impurities: loaded organic phase flow rate: 4.0 L / min into stage 38, sulfuric acid eluent: 2.5 mol / L H2SO4, flow rate 0.60 L / min into stage 54, cobalt product liquid flow rate: 0.60 L / min, cobalt concentration 52 g / L.

[0073] After testing, the key impurities are: Ca<1mg / L, Mg<2mg / L, Ni<0.5mg / L.

[0074] S5. Regenerating the extractant.

[0075] S6. Innovative process for cobalt carbonate precipitation: (1) Base solution preparation: Dilute the cobalt sulfate solution to 30 g / L Co, heat to 65°C, and add 0.5 g / L polyvinyl pyrrolidone (PVP) as a morphology control agent. (2) Coprecipitation reaction: Add in parallel: Solution A: 1.5 mol / L Na2CO3 solution, Solution B: 1.0 mol / L NH4OH solution, control the endpoint pH to 7.2, reaction temperature to 65°C, and feed rate to 10 mL / min. (3) Aging and washing: Maintain at 65°C, stir and age for 2 h, filter, and wash with 60°C deionized water until the conductivity is <100 μS / cm. (4) Drying: Dry in a vacuum oven at 80°C for 6 h.

[0076] Product performance: The Co content in the product is >46%, which meets the first-class requirements of the industrial cobalt carbonate industry standard (HG / T 4520-2023).

[0077] Example 6: This example uses the cobalt-enriched solution (VI) obtained by recycling NdFeB waste as a raw material, and uses the method of the present invention to treat it. The process flow is as follows: Figure 8 , extraction tank layout reference Figure 2 .

[0078] Table 6 Element contents of cobalt-enriched solution (VI) recovered from NdFeB waste The process is consistent with that of Example 1. The steps and specific process parameters of this example are as follows: S1. Preparation of raw material solution: pH adjusted to 3.5, cobalt concentration 12.5 g / L.

[0079] S2. Saponification: The saponification degree is reduced to 0.38 mol / L.

[0080] S3, separation of difficult-to-extract impurities: Eluent: 3.0 mol / L hydrochloric acid, flow rate: saponified organic phase 2.5 L / min into the first stage, raw liquid 3.5 L / min into the eighth stage, HCl eluent 0.08 L / min into the eighteenth stage.

[0081] S4, separation of easily extractable impurities: loaded organic phase flow rate: 2.5L / min into stage 38, sulfuric acid eluent: 3.0mol / LH2SO4, flow rate 0.45L / min into stage 54, cobalt product liquid flow rate: 0.45L / min, cobalt concentration 38g / L, key impurities detected: Zn <0.2mg / L, Cu <0.1mg / L.

[0082] S5. Regenerating the extractant.

[0083] S6. Nano-cobalt carbonate precipitation process: (1) Microreactor coprecipitation: Use a T-type microchannel reactor (channel diameter 1mm), channel A: cobalt sulfate solution (Co: 38g / L, 60℃), channel B: 1.0mol / L NH4HCO3 + 0.1mol / L NH4OH mixed solution (60℃), flow rate ratio A:B = 1:1.2, total flow rate 50mL / min, outlet pH 7.0, transient reaction time <2s. (2) Aging and surface treatment: Collect the slurry at 60℃, age for 30min, add 1wt% oleic acid ethanol solution, and stir for 1h to modify the surface. (3) Supercritical drying: After replacing the water with ethanol, dry in a CO2 supercritical device (40℃, 10MPa).

[0084] After testing, the nano-cobalt carbonate product obtained in this example has a purity of 99.4%, morphology of spherical nanoparticles, an average particle size of 50 nm, a specific surface area of ​​45 m² / g, and impurities of Zn < 20 ppm and Cu < 15 ppm.

[0085] The above describes the main technical features and basic principles of the present invention and the related advantages. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the concept or essential characteristics of the present invention. Therefore, from all perspectives, the above-mentioned specific embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all changes that come within the meaning and range of equivalents of the claims be included within the present invention.

[0086] In addition, it should be understood that although this specification is described according to various implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste, characterized in that: The steps include: S1. Preparation of raw material solution: Mix the cobalt-enriched solid of NdFeB waste with inorganic acid solution for acid leaching reaction, and prepare raw material solution with pH value of 3.5-4.5 after solid-liquid separation. or preparing the cobalt-enriched solution obtained from the NdFeB waste recovery process into a raw material solution with a pH value of 3.5 to 4.5; S2. Saponification: Cyanex 272 is mixed with 260# solvent oil or kerosene to form an organic phase, which is then saponified with aqueous ammonia to obtain a saponified organic phase; S3. Separation of Difficult-to-Extract Impurities: The saponified organic phase, raw material liquid, and hydrochloric acid eluent are introduced into the first stage, intermediate feed stage, and final stage of the first extraction tank via flow meters. After extraction and washing, the difficult-to-extract impurity elements are discharged from the first stage aqueous phase, while the remaining elements are loaded in the organic phase to form a loaded organic phase and discharged from the final stage. S4. Separation of easily extractable impurities: The saponified organic phase, the loaded organic phase, and the sulfuric acid eluent are introduced into the first stage, the intermediate feed stage, and the last stage of the washing section of the second extraction tank via flow meters. After extraction and washing, cobalt is discharged with the first-stage aqueous phase to obtain a cobalt sulfate solution, while the remaining easily extractable impurities are carried in the organic phase and discharged from the last stage. S5, extractant regeneration: the organic phase loaded with easily extractable impurity elements then enters the stripping extraction tank, and after stripping to form a blank organic phase, returns to step S2 for recycling; S6. Preparation of cobalt salt: slowly adding a precipitant to the cobalt sulfate solution obtained in step S4 to generate a cobalt salt precipitate, which is then filtered, washed, and dried to obtain a high-purity cobalt salt; or The cobalt sulfate solution obtained in step S4 is concentrated under reduced pressure to obtain high-purity cobalt sulfate.

2. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 1, wherein: In step S1, the inorganic acid is at least one of hydrochloric acid, sulfuric acid or nitric acid; The cobalt content in the raw material solution is 10g / L to 30g / L.

3. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 1, characterized in that: In step S2, Cyanex 272 and 260# solvent oil or kerosene are mixed in a volume ratio of 1:4 to 1:1 to form an organic phase; The saponification degree is 0.2mol / L~0.5mol / L.

4. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 3, wherein: Cyanex272 and 260# solvent oil or kerosene are mixed in a volume ratio of 1:1 to form an organic phase; The saponification degree is 0.45 mol / L.

5. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 1, characterized in that: In step S3, the concentration of hydrochloric acid used as an eluent is 2 mol / L to 6 mol / L; The molar ratio of the saponified organic phase, the raw material liquid and the hydrochloric acid eluent introduced into the first extraction tank is: (0.2-0.5):1:(0.02-0.05).

6. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 5, characterized in that: The concentration of hydrochloric acid used as eluent is 4 mol / L; 80% of the difficult-to-extract impurity elements in the raw liquid are discharged from the first-stage aqueous phase.

7. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 1, characterized in that: In step S4, the concentration of sulfuric acid used as an eluent is 1 mol / L to 2 mol / L; The molar ratio of the saponified organic phase, the loaded organic phase and the hydrochloric acid eluent introduced into the second extraction tank is: (0.8-1.2):1:(1.0-2.0).

8. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 7, characterized in that: In step S5, the concentration of hydrochloric acid for stripping is 2 mol / L to 6 mol / L.

9. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 8, characterized in that: The precipitant is one of ammonium bicarbonate, sodium carbonate, oxalic acid, and oxalate; The reaction temperature of the cobalt salt precipitation process is 60° C. to 80° C., and the pH value is between 6 and 10.

10. The method for preparing high-purity cobalt salt using cobalt concentrate from NdFeB waste according to claim 9, characterized in that: In step S4, the concentration of sulfuric acid used as the eluent is 2 mol / L; In step S5, the concentration of hydrochloric acid used for stripping is 6 mol / L; In step S6, the precipitant is ammonium bicarbonate or sodium carbonate.

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