Method for treating black powder of waste power battery

Abstract

The application discloses a method for treating black powder of waste power battery. Lithium is preferentially extracted from the black powder through high-pressure leaching, and lithium sulfate solution and lithium extraction residue are generated. The lithium extraction residue is subjected to acid leaching to obtain leaching solution. The leaching solution is subjected to organic extraction containing carboxylic acid extractant, and iron, aluminum and copper are sequentially separated and recovered. The raffinate after copper separation is subjected to P204 manganese extraction, P507 cobalt extraction and C272 magnesium extraction in sequence, and manganese sulfate solution, cobalt sulfate solution, magnesium sulfate solution and nickel sulfate solution are obtained. Compared with the prior art, lithium is extracted through high-pressure leaching, SO2 tail gas is eliminated from the source, high-temperature roasting is not needed, and the method is clean and efficient. Meanwhile, iron, aluminum, copper and magnesium removed as hazardous waste in the traditional process are converted into by-products such as iron sulfate, aluminum sulfate, electrodeposited copper and magnesium sulfate through carboxylic acid extraction, and high-value resourceization of impurity elements is realized. The method has the advantages of high valuable metal yield, low cost, green environmental protection and the like, and realizes efficient resource utilization of nickel, cobalt, lithium, iron, aluminum and copper in the black powder of the waste power battery.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery recycling technology, and in particular to a method for treating black powder from waste power batteries. Background Technology

[0002] With the rapid development of the new energy industry, the amount of waste power batteries generated is increasing year by year. Their recycling can not only alleviate the supply and demand imbalance of key mineral resources such as lithium, nickel, and cobalt, but also reduce environmental pollution, thus having significant economic and strategic importance. In the field of lithium battery recycling, traditional back-end lithium extraction processes have inherent defects: lithium elements need to undergo multiple complex processes such as high-temperature roasting, leaching, and impurity removal, which easily lead to entrainment losses (in silicon slag, iron-aluminum slag), co-precipitation losses, high-temperature volatilization losses, and solution residue losses, thus limiting the overall recovery rate and economic benefits.

[0003] To overcome the inherent defects of downstream lithium extraction, the concept of priority lithium extraction has emerged. Current mainstream priority lithium extraction processes, such as carbon reduction roasting, hydrogen reduction roasting, and sulfation roasting, although they have achieved priority extraction or activation of lithium to a certain extent, all have insurmountable drawbacks that limit their efficiency, economy, and environmental friendliness.

[0004] Specifically: carbon reduction roasting has extremely high energy consumption and carbon emissions, and produces complex flue gas containing CO, fluorides, etc., resulting in high treatment costs and safety risks; hydrogen reduction roasting relies on expensive and risky hydrogen gas, has stringent equipment and operational requirements, and is costly; sulfation roasting produces a highly corrosive SO2 / SO3 atmosphere and molten salt, causing severe equipment corrosion and incurring huge costs for tail gas desulfurization. In addition, all of the above traditional processes suffer from problems such as nickel and cobalt loss (5%~8%) due to the subsequent iron-aluminum precipitation step, and the need to add a high-cost nickel extraction process, resulting in poor resource recovery efficiency and economic viability.

[0005] Therefore, developing a new technology for treating battery black powder that has a high recycling rate, low cost, and is environmentally friendly has become an urgent need for the industry. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for processing waste power battery black powder. This method has advantages such as high yield of valuable metals, low cost, and environmental friendliness, achieving efficient resource utilization of nickel, cobalt, lithium, iron, aluminum, and copper in waste power battery black powder.

[0007] To achieve this technical objective, the present invention adopts the following solution: A method for treating black powder from waste power batteries includes the following steps: S1. Lithium is preferentially extracted from black powder by high-pressure leaching, producing lithium sulfate solution and lithium extraction residue; S2. The lithium extraction residue is acid-leached to obtain leachate; S3. The leachate is subjected to organic extraction with a carboxylic acid extractant to sequentially separate and recover iron, aluminum, and copper. S4. The raffinate after copper separation is then subjected to P204 for manganese extraction, P507 for cobalt extraction, and C272 for magnesium extraction to obtain manganese sulfate solution, cobalt sulfate solution, magnesium sulfate solution, and nickel sulfate solution.

[0008] Further, step S1, high-pressure leaching for preferential lithium extraction, involves mixing black powder with ammonium sulfate or ammonium bisulfate to form a slurry, placing it in a high-pressure reactor, and reacting it for 2-5 hours at a temperature of 100°C to 200°C and a pressure of 1MPa to 3MPa under an inert gas atmosphere. After the reaction is completed, solid-liquid separation is performed to obtain lithium sulfate solution and lithium extraction residue, respectively.

[0009] Furthermore, the reaction temperature can be 100℃, 120℃, 150℃, 180℃, or 200℃; the reaction pressure can be 1 MPa, 2 MPa, or 3 MPa; and the reaction time can be 2h, 3h, 4h, or 5h.

[0010] Furthermore, the molar ratio of lithium ions to sulfate ions in the black powder is 2:1.1~1.3, and the inert gas is nitrogen or argon.

[0011] Further, step S2, acid leaching, involves subjecting the obtained lithium extraction residue to two-stage countercurrent acid leaching. The pH value of the final solution is adjusted and controlled between 1.5 and 1.8 using dilute sulfuric acid, with a concentration of 150-300 g / L, specifically 150 g / L, 200 g / L, 250 g / L, or 300 g / L.

[0012] Furthermore, the specific steps of the two-stage countercurrent acid leaching are as follows: First, dilute sulfuric acid is used for a first-stage leaching of the lithium extraction residue, controlling the pH value at 2.5-3.0, yielding a first-stage leaching residue and leachate. The leachate is then used in the subsequent extraction step. Second, the first-stage leaching residue is used for a second-stage leaching, controlling the pH value at 1.5-1.8, yielding a final residue and a second-stage leachate. The second-stage leachate is returned to the first-stage leaching process for recycling, while the final residue is centrally treated as solid waste. Using this two-stage countercurrent acid leaching method ensures that valuable metals in the leaching residue are fully extracted, and that the sulfuric acid can be recycled, saving costs.

[0013] Further, step S3, the carboxylic acid extraction process, includes the following steps: extracting iron with an empty organic phase containing a carboxylic acid extractant; washing and back-extracting the resulting iron-loaded organic phase to obtain a ferric sulfate solution; extracting aluminum with the raffinate after iron extraction; washing and back-extracting the resulting aluminum-loaded organic phase to obtain an aluminum sulfate solution; and performing a first-stage and second-stage copper extraction on the aqueous phase after aluminum extraction; washing and back-extracting the resulting copper-loaded organic phase to obtain a copper sulfate solution.

[0014] Furthermore, in the organic compound containing a carboxylic acid extractant, the volume concentration of the carboxylic acid extractant is 20% to 30%. The carboxylic acid extractant includes any one or a combination of at least two of Versatic 10, Versatic 911, oleic acid, or naphthenic acid. The diluent in the organic compound is kerosene or sulfonated kerosene, preferably kerosene.

[0015] Furthermore, the washing step is carried out using a 1N sulfuric acid solution, and the back-extraction step is carried out using a 200g / L sulfuric acid solution.

[0016] Furthermore, the obtained nickel sulfate solution is evaporated and concentrated, cooled and crystallized, and then centrifuged and dried to obtain nickel sulfate crystal products; the lithium sulfate, ferric sulfate, aluminum sulfate, copper sulfate, manganese sulfate, cobalt sulfate, and magnesium sulfate solutions generated in each stage are converted into corresponding solid products through conventional evaporation and crystallization.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Dual improvement in environmental protection and resource utilization: High-pressure leaching for lithium extraction eliminates SO2 tail gas generation at the source, eliminating the need for high-temperature roasting, making it clean and efficient; at the same time, through carboxylic acid extraction, iron, aluminum, copper, and magnesium, which are removed as hazardous waste in traditional processes, are converted into by-products such as ferric sulfate, aluminum sulfate, electrolytic copper, and magnesium sulfate, respectively, realizing the high-value resource utilization of impurity elements.

[0018] 2. Significantly improved recovery rate of key metals: The innovative extraction process directly separates iron, aluminum and copper, completely avoiding the 5% to 8% loss of nickel and cobalt caused by the traditional alkaline precipitation method. This allows the comprehensive recovery rate of valuable metals nickel and cobalt to reach a stable level of over 99%, greatly improving resource utilization efficiency.

[0019] 3. Simplified process and significant cost advantages: The "extracting impurities but not nickel" design enables efficient enrichment of nickel ions in solution, which not only eliminates the complex and expensive dedicated nickel extraction process, reducing reagent consumption and equipment investment, but also reduces the wastewater treatment load through solution circulation. The overall process is more compact and economically superior to traditional methods. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for treating black powder from waste power batteries according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0022] Please see Figure 1This invention provides a method for treating black powder from waste power batteries, specifically including the following steps: S1, High-pressure leaching preferentially extracts lithium. Mix the black powder with ammonium sulfate or ammonium bisulfate in a certain proportion, with the molar ratio of lithium ions to sulfate ions in the black powder being 2:1.1~1.3. Place the mixture in a corrosion-resistant autoclave, seal it, and then fill the autoclave with an inert gas (such as nitrogen or argon) to replace the air and pressurize it to the target pressure of 1MPa~3MPa.

[0023] Initiate heating and stirring, maintaining the reaction system at 100℃~200℃ for 2~5 hours. Under these conditions, lithium compounds in the black powder selectively react with sulfate ions to form soluble lithium sulfate, while metals such as nickel, cobalt, and manganese remain largely in the solid phase.

[0024] After the reaction, water is added directly for leaching. After the reaction is complete, solid-liquid separation is performed. The resulting liquid is a lithium sulfate solution rich in lithium, which can be directly used for subsequent purification to produce lithium salts; the resulting solid is lithium extraction slag, whose main components are compounds of nickel, cobalt, and manganese, as well as unreacted carbon powder.

[0025] S2, Acid leaching for decarbonization and enrichment The lithium extraction slag was subjected to a two-stage countercurrent acid leaching process. Dilute sulfuric acid was used to adjust and control the pH of the final solution to between 1.5 and 1.8, with a concentration of 150–300 g / L. Under these conditions, valuable metals such as nickel, cobalt, manganese, copper, aluminum, and iron in the lithium extraction slag were leached into the solution, while inert substances such as carbon residue were removed through solid-liquid separation because they did not react or were not leached. After solid-liquid separation, a purified leachate (rich in Ni, Co, Mn, Cu, Al, and Fe) and waste carbon residue were obtained.

[0026] The specific steps of the two-stage countercurrent acid leaching are as follows: First, dilute sulfuric acid is used to leach the lithium extraction residue, controlling the pH value at 2.5-3.0, yielding a first-stage leaching residue and leachate. The leachate is then used in the subsequent extraction step. Second, the first-stage leaching residue is used to leach the residue again, controlling the pH value at 1.5-1.8, yielding a final residue and a second-stage leachate. The second-stage leachate is returned to the first-stage leaching process for recycling, while the final residue is centrally treated as solid waste. Using this two-stage countercurrent acid leaching method ensures that valuable metals in the leaching residue are fully extracted, and the sulfuric acid can be recycled, saving costs.

[0027] S3, carboxylic acid extraction to separate iron, aluminum, and copper. An organic extractant containing carboxylic acid was used to perform multi-stage, sequential extraction and separation of the leachate.

[0028] Step 1: Iron extraction. Iron ions in the leachate are extracted using an unloaded carboxylic acid organic extractant. The iron-loaded organic phase is washed with 1N sulfuric acid solution and then back-extracted with 200g / L concentrated sulfuric acid solution to obtain a pure ferric sulfate solution.

[0029] Step 2: Aluminum extraction. The aqueous phase after iron extraction is brought into contact again with the unloaded organic phase to extract aluminum ions. The aluminum-loaded organic phase is then washed with 1N sulfuric acid solution and back-extracted with 200 g / L concentrated sulfuric acid solution to obtain an aluminum sulfate solution.

[0030] Step 3: Copper Extraction. The aqueous phase after aluminum extraction undergoes a two-stage extraction to ensure copper recovery. The copper-loaded organic phase is washed with 1N sulfuric acid solution and back-extracted with 200g / L concentrated sulfuric acid solution to obtain a high-concentration copper sulfate solution, which can be directly used for electrodeposition to produce cathode copper.

[0031] The carboxylic acid extraction process specifically includes: 3-stage iron extraction, 3-stage washing, 3-stage iron removal, 6-stage aluminum extraction, 3-stage washing, 3-stage aluminum removal, 1-stage copper extraction, 2-stage copper extraction, 3-stage washing, and 3-stage copper removal.

[0032] The aqueous phase (raffinate) produced after copper extraction in this stage, whose main metal components are manganese, cobalt, nickel and magnesium, will be transported to the next process.

[0033] The carboxylic acid extractant has a volume concentration of 20% to 30%. The carboxylic acid extractant includes any one or a combination of at least two of Versatic 10, Versatic 911, oleic acid, or naphthenic acids. The diluent in the organic component is kerosene or sulfonated kerosene, preferably kerosene.

[0034] S4. Sequential extraction to separate manganese, cobalt, and magnesium, and recover nickel. The raffinate obtained in the previous step is then subjected to further separation using specific extractants: First, manganese is extracted using extractant P204 to obtain a manganese sulfate solution. Then, cobalt is extracted from the raffinate using extractant P507 to obtain a cobalt sulfate solution. Finally, magnesium is extracted using extractant C272 to obtain a magnesium sulfate solution. After these three extraction steps, the final aqueous phase is a high-purity nickel sulfate solution.

[0035] S5, Crystallization and Product Output The obtained nickel sulfate solution is evaporated and concentrated, cooled and crystallized, and then centrifuged and dried to obtain the final nickel sulfate crystal product. Similarly, the lithium sulfate, ferric sulfate, aluminum sulfate, copper sulfate, manganese sulfate, cobalt sulfate, and magnesium sulfate solutions produced at each stage can all be converted into corresponding solid products through conventional evaporation and crystallization or further purification methods.

[0036] Unless otherwise specified, all experimental methods used in this application are conventional methods. All materials and reagents used are commercially available unless otherwise specified.

[0037] Raw materials: Black powder from waste ternary lithium batteries (Li 3.9wt%, Ni 18.1wt%, Co 8.3wt%, Mn 11.4wt%, Fe 1.5wt%, Al 2.8wt%, Magnesium 1.8wt%, Cu 0.9wt%). Example 1

[0038] S1. High-pressure leaching for lithium extraction: 1.0 kg of waste ternary battery black powder was added to 410 g of ammonium sulfate (the molar ratio of lithium to sulfate was 2:1.1), mixed, and placed in a high-pressure reactor. Nitrogen gas was purged to a pressure of 2.0 MPa, and the mixture was heated to 180°C for 4 hours. After the reaction, water was added directly for leaching. After leaching, solid-liquid separation was performed to obtain a lithium sulfate solution and lithium extraction residue. The lithium leaching rate was 93.5%.

[0039] S2, Acid Leaching: The lithium residue is leached in two countercurrent stages with 200g / L dilute sulfuric acid, and the final pH is controlled to be 1.6 to obtain leachate and carbon residue.

[0040] S3, Carboxylic acid extraction and separation: Iron extraction: The leachate was subjected to three-stage countercurrent extraction of iron using a 25% Versatic 10 organic phase. The supported organic phase was washed with 1N sulfuric acid and back-extracted with 200g / L sulfuric acid to obtain pure ferric sulfate.

[0041] Aluminum extraction: The residue from iron extraction is subjected to six-stage countercurrent extraction of aluminum. The loaded organic phase is washed with 1N sulfuric acid and back-extracted with 200g / L sulfuric acid to obtain a pure aluminum sulfate solution.

[0042] Copper extraction: The aluminum extraction residue undergoes two-stage copper extraction, followed by back-extraction to obtain a copper sulfate solution. The nickel loss rate in the copper extraction residue is 0.1%, the cobalt loss rate is 0.1%, and the direct copper recovery rate is 99.2%.

[0043] S4. Sequential extraction and separation of Mn, Co, and Mg: The copper extraction residue is sequentially extracted with P204 for manganese, P507 for cobalt, and C272 for magnesium to obtain the corresponding sulfate solutions.

[0044] S5. Crystallization: The final cobalt sulfate and nickel sulfate solution is evaporated and crystallized to obtain cobalt sulfate and nickel sulfate crystals. Ni recovery rate is 99.3%, and Co recovery rate is 99.4%. Example 2

[0045] The difference from Example 1 is that: S1. High-pressure leaching for lithium extraction: 1.0 kg of waste ternary battery black powder was added to 485 g of ammonium sulfate (the molar ratio of lithium to sulfate was 2:1.3), mixed, and placed in a high-pressure reactor. Nitrogen gas was purged to a pressure of 2.0 MPa, and the mixture was heated to 180°C for 4 hours. After the reaction, water was added directly for leaching. After leaching, solid-liquid separation was performed to obtain a lithium sulfate solution and lithium extraction residue. The lithium leaching rate was 93.3%.

[0046] In step S3, the nickel loss rate is 0.1%, the cobalt loss rate is 0.1%, and the direct copper recovery rate is 99.8%; in step S5, the nickel recovery rate is 99.2% and the cobalt recovery rate is 99.1%. Example 3

[0047] The difference from Example 1 is that: S1. High-pressure leaching for lithium extraction: 1.0 kg of waste ternary battery black powder was added to 360 g of ammonium bisulfate (the molar ratio of lithium to sulfate was 2:1.1), mixed, and placed in a high-pressure reactor. Nitrogen gas was purged to a pressure of 2.0 MPa, and the mixture was heated to 180°C for 4 hours. After the reaction, water was added directly for leaching. After leaching, solid-liquid separation was performed to obtain a lithium sulfate solution and lithium extraction residue. The lithium leaching rate was 94.2%.

[0048] In step S3, the nickel loss rate is 0.1%, the cobalt loss rate is 0.1%, and the direct copper recovery rate is 99.6%; in step S5, the nickel recovery rate is 99.4% and the cobalt recovery rate is 99.2%. Example 4

[0049] The difference from Example 1 is that: S1. High-pressure leaching for lithium extraction: 1.0 kg of waste ternary battery black powder was added to 410 g of ammonium sulfate (the molar ratio of lithium to sulfate was 2:1.1), mixed, and placed in a high-pressure reactor. Nitrogen gas was purged to a pressure of 2.0 MPa, and the mixture was heated to 120°C for 4 hours. After the reaction, water was added directly for leaching. After leaching, solid-liquid separation was performed to obtain a lithium sulfate solution and lithium extraction residue. The lithium leaching rate was 92.7%.

[0050] In step S3, the nickel loss rate is 0.1%, the cobalt loss rate is 0.1%, and the direct copper recovery rate is 99.3%; in step S5, the nickel recovery rate is 99.2% and the cobalt recovery rate is 99.3%. Comparative Example 1

[0051] The difference from Example 1 is that: S1. Lithium extraction by sulfation roasting: 1.0 kg of waste ternary battery black powder was added to 180 ml of 98% concentrated sulfuric acid and roasted at 650℃ for 2 hours. After the reaction, water was added directly for water leaching. After water leaching, solid and liquid were separated to obtain lithium sulfate solution and lithium extraction residue. The lithium leaching rate was 91.1%, but a large amount of SO2 / SO3 tail gas was generated. Comparative Example 2

[0052] The difference from Example 1 is that: S3, Iron and Aluminum Removal: Add sodium carbonate solution to the leachate to adjust the pH to 4.0. After the reaction is complete, separate the solid and liquid phases. Nickel loss rate: 6.2%, Cobalt loss rate: 5.8%.

[0053] Nickel sulfate crystals and cobalt sulfate crystals were obtained by crystallization. The overall recovery rate of nickel was only 92.5%, and the overall recovery rate of cobalt was only 93.1%.

[0054] As can be seen from the above examples and comparative examples, the present invention uses high-pressure leaching to extract lithium, avoiding the SO2 / SO3 tail gas generated by the traditional roasting process, which is clean and efficient. At the same time, through a two-stage countercurrent acid leaching and carboxylic acid extraction process, the impurities iron, aluminum, copper and magnesium in the lithium extraction residue are fully leached out and extracted and separated in steps, and converted into by-products such as ferric sulfate and aluminum sulfate, realizing the resource utilization of impurity elements. In addition, the comprehensive recovery rate of nickel and cobalt using the process of the present invention can reach more than 99%.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should all be considered to be within the protection scope of the present invention.

Claims

1. A method for treating black powder from waste power batteries, characterized in that, Includes the following steps: S1. Lithium is preferentially extracted from black powder by high-pressure leaching, producing lithium sulfate solution and lithium extraction residue; S2. The lithium extraction residue is acid-leached to obtain leachate; S3. The leachate is subjected to organic extraction with a carboxylic acid extractant to sequentially separate and recover iron, aluminum, and copper. S4. The raffinate after copper separation is then subjected to P204 for manganese extraction, P507 for cobalt extraction, and C272 for magnesium extraction to obtain manganese sulfate solution, cobalt sulfate solution, magnesium sulfate solution, and nickel sulfate solution.

2. The method for treating waste power battery black powder according to claim 1, characterized in that, Step S1, high-pressure leaching for preferential lithium extraction, involves mixing black powder with ammonium sulfate or ammonium bisulfate to form a slurry, placing it in a high-pressure reactor, and reacting it for 2-5 hours at a temperature of 100℃~200℃ and a pressure of 1MPa~3MPa under an inert gas atmosphere. After the reaction is completed, solid-liquid separation is performed to obtain lithium sulfate solution and lithium extraction residue, respectively.

3. The method for treating waste power battery black powder according to claim 2, characterized in that, The molar ratio of lithium ions to sulfate ions in the black powder is 2:1.1~1.3, and the inert gas is nitrogen or argon.

4. The method for treating waste power battery black powder according to claim 1, characterized in that, The step S2 acid leaching is as follows: the obtained lithium extraction residue is subjected to two-stage countercurrent acid leaching, and the pH value of the final solution is adjusted and controlled between 1.5 and 1.8 using dilute sulfuric acid with a concentration of 150 to 300 g / L.

5. The method for treating waste power battery black powder according to claim 4, characterized in that, The specific steps of the two-stage countercurrent acid leaching are as follows: dilute sulfuric acid is used to perform a first-stage leaching of the lithium extraction residue to obtain a first-stage leaching residue and a leachate; the first-stage leaching residue is then subjected to a second-stage leaching to obtain a final residue and a second-stage leaching solution; the second-stage leaching solution is returned to the first-stage leaching for recycling.

6. The method for treating waste power battery black powder according to claim 1, characterized in that, Step S3, the carboxylic acid extraction process, includes the following steps: extracting iron with an empty organic phase containing a carboxylic acid extractant; washing and back-extracting the resulting iron-loaded organic phase to obtain a ferric sulfate solution; extracting aluminum with the raffinate after iron extraction; washing and back-extracting the resulting aluminum-loaded organic phase to obtain an aluminum sulfate solution; and performing a first-stage and second-stage copper extraction on the aqueous phase after aluminum extraction; washing and back-extracting the resulting copper-loaded organic phase to obtain a copper sulfate solution.

7. The method for treating waste power battery black powder according to claim 6, characterized in that, In organic compounds containing carboxylic acid extractants, the volume concentration of the carboxylic acid extractant is 20% to 30%. The carboxylic acid extractant includes any one or a combination of at least two of Versatic 10, Versatic 911, oleic acid, or naphthenic acid.

8. The method for treating waste power battery black powder according to claim 6, characterized in that, The washing step was carried out using a 1N sulfuric acid solution, and the back-extraction step was carried out using a 200g / L sulfuric acid solution.

9. The method for treating waste power battery black powder according to claim 1, characterized in that, The obtained nickel sulfate solution is evaporated and concentrated, cooled and crystallized, and then centrifuged and dried to obtain nickel sulfate crystal products. The lithium sulfate, ferric sulfate, aluminum sulfate, copper sulfate, manganese sulfate, cobalt sulfate, and magnesium sulfate solutions produced in each stage are converted into corresponding solid products through conventional evaporation and crystallization.

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