A method for preparing battery-grade manganese sulfate from manganese sulfate solution

Abstract

This invention discloses a method for preparing battery-grade manganese sulfate from manganese sulfate solution, belonging to the field of manganese sulfate preparation technology. The method includes the following steps: A first organic extractant undergoes a first saponification; after saponification, without oil-water separation, it is directly subjected to countercurrent extraction with the manganese sulfate raw material solution. After extraction separation, back-extraction is performed; the back-extracted aqueous phase is aged and filtered to obtain a calcium-removed back-extraction solution. A second organic extractant undergoes a second saponification; after saponification, without oil-water separation, it is directly subjected to countercurrent extraction of zinc with the above-mentioned calcium-removed back-extraction solution. After oil-water separation, an aqueous phase after zinc extraction is obtained. The aqueous phase after zinc extraction is neutralized to remove residual acid, and manganese powder is added for a weight removal reaction. The solution is filtered to obtain a weight-removed liquid. Finally, the pH of the weight-removed liquid is adjusted, followed by crystallization, filtration, and drying to obtain battery-grade manganese sulfate. This invention can directly prepare battery-grade manganese sulfate from complex raw materials such as MHP leachate. The process is simple, impurity removal is thorough, and the product purity is high, making it suitable for continuous industrial production.

Description

Technical Field

[0001] This invention belongs to the field of manganese sulfate preparation technology, and specifically relates to a method for preparing battery-grade manganese sulfate from a manganese sulfate solution. Background Technology

[0002] Manganese sulfate is an important raw material in battery manufacturing, chemical industry, agriculture, and other fields. Among them, battery-grade manganese sulfate is in increasing market demand due to its high purity requirements and extremely low impurity content. Currently, the industrial process mainly uses manganese ore leaching to obtain manganese sulfate solution, and then uses extraction to remove impurities, chemical precipitation to remove impurities, and crystallization to purify and prepare manganese sulfate products. However, for complex raw material solutions such as MHP (mixed nickel-cobalt hydroxide) leaching solutions, the existing processes have significant shortcomings, resulting in poor treatment effects and low raw material utilization.

[0003] Currently, the process for purifying and preparing manganese sulfate in this field typically employs a "manganese sulfate solution extraction for impurity removal - multiple crystallization process for preparing manganese sulfate." The specific flow is as follows: manganese sulfate feedstock solution - single extractant extraction for impurity removal - back-extraction to obtain a low-concentration manganese solution - chemical reagent removal for weight removal - multiple evaporation and crystallization - manganese sulfate product. This process uses a single extraction system, requires oil-water separation after saponification, the back-extraction acid concentration is not specifically optimized, impurity removal uses chemical reagents, and crystallization needs to be repeated 2-3 times to achieve the basic purity requirements. However, it is still difficult to obtain battery-grade products, and the calcium ion separation effect is poor, making it impossible to reduce its concentration to below 0.25 g / L during the extraction stage.

[0004] In summary, current extraction and impurity removal processes in manganese sulfate solutions mostly employ a single extraction system, making it difficult to achieve efficient separation of copper, manganese, zinc, and calcium. After back-extraction, the manganese concentration in the solution is low (unable to reach 150-190 g / L), and the calcium ion residue is high, difficult to reduce to below 0.25 g / L. The impurity removal process often uses chemical reagents, easily introducing additional impurities and affecting product purity. The crystallization process requires multiple repetitions, increasing production costs and leading to product loss, making it difficult to obtain battery-grade manganese sulfate in a single step, and the impurity (copper and zinc) content cannot be reduced to below 20 ppm. Furthermore, the parameters for extraction, saponification, back-extraction, impurity removal, and crystallization in existing processes lack proper matching. An additional oil-water separation step is required after saponification, making the process cumbersome and unstable, unable to meet the needs of large-scale industrial production. Summary of the Invention

[0005] To address the aforementioned problems, the main objective of this invention is to provide a method for preparing battery-grade manganese sulfate from a manganese sulfate solution. This method employs a segmented extraction process using a saponified organic extractant. After saponification, oil-water separation is unnecessary, improving process stability and production efficiency. The first stage of extraction removes calcium, while the second stage purifies zinc, achieving stepwise separation of multiple impurities. Furthermore, manganese powder is used for weight removal to avoid introducing new impurities. Combined with a low-temperature primary crystallization process, manganese sulfate meeting battery-grade standards can be directly prepared from complex raw materials such as MHP leachate. Copper and zinc impurities can be reduced to below 20 ppm, and calcium ion concentration can be reduced to approximately 0.25 g / L. The process is simple, removes impurities thoroughly, and produces a high-purity product, making it suitable for continuous industrial production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing battery-grade manganese sulfate from a manganese sulfate solution, comprising the following steps: S1, the first organic extractant containing P204 and solvent oil is first saponified. After saponification, there is no need for oil-water separation. It is directly extracted with manganese sulfate feed solution in a countercurrent manner. After extraction and separation, sulfuric acid is used to back-extract the loaded organic phase. After back-extraction, the aqueous phase is aged and filtered to obtain calcium-removed back-extraction solution. S2, the second organic extractant containing P204 and solvent oil is subjected to a second saponification. After saponification, no oil-water separation is required. It is directly subjected to countercurrent zinc extraction with the calcium-removing back-extraction solution obtained in step S1. Oil-water separation is performed to obtain the aqueous phase after zinc extraction. S3, after neutralizing the residual acid in the zinc-extracted aqueous phase obtained in step S2, add manganese powder to carry out a weight removal reaction, and filter to obtain the weight-removed liquid; S4. After adjusting the pH of the deweighted liquid obtained in step S3, crystallize, filter, and dry to obtain battery-grade manganese sulfate.

[0007] Further, in step S1, the volume ratio of P204 to solvent oil in the first organic extractant is 20-30%:70-80%; the saponification rate of the first saponification is controlled at 55-65%.

[0008] Further, in step S1, the oil-to-water volume ratio of the countercurrent extraction is 1:1-2, the number of extraction stages is 10-15, and the temperature of the countercurrent extraction is 20-40℃; the oil-to-water volume ratio of the back-extraction is 25-32:1, the amount of sulfuric acid used in the back-extraction is 5-8N; the aging time of the aqueous phase after back-extraction is 4-8h, and the aging temperature is 20-40℃.

[0009] Further, in step S2, the volume ratio of P2O4 to solvent oil in the second organic extractant is 20-30%:70-80%; the saponification rate of the second saponification is controlled at 20-30%.

[0010] Furthermore, in step S2, the oil-to-water volume ratio of the countercurrent zinc extraction is 1:20-25, and the number of extraction stages is 5-10.

[0011] Furthermore, in step S2, the oil phase after the countercurrent zinc oil-water separation is subjected to sulfuric acid back-extraction to obtain the zinc back-extraction liquid, wherein the amount of sulfuric acid used is 3-5N, the number of back-extraction stages is 2-4, and the back-extraction oil-water volume ratio is 1-2:1.

[0012] Furthermore, in step S3, the excess coefficient of manganese powder added relative to the theoretical requirement in the degravation reaction is 3-7 times; the degravation reaction time is 25-35 minutes.

[0013] Furthermore, in step S4, the crystallization temperature is 100-120℃ and the time is 2-5h.

[0014] Furthermore, in steps S1 and S2, the extraction and back-extraction mixing time is 3-7 min, and the standing time is 5-8 min.

[0015] Furthermore, the manganese sulfate feed solution contains the following elements: Mn 5-7 g / L, Ca 0.25 g / L (saturation concentration), Cu 0.02-0.05 g / L, and Zn 0.4-0.8 g / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Excellent extraction and impurity removal effect and optimized parameters: Through two-stage extraction operations with different parameters, copper, manganese, zinc and calcium are separated efficiently. After back-extraction, the concentration of manganese solution can reach about 190 g / L and the concentration of calcium ions is reduced to below 0.2 g / L. The separation effect is better than the existing single extraction system.

[0017] 2. No additional impurities introduced: Excess manganese powder is used for weight removal, replacing existing chemical reagents for impurity removal, avoiding the introduction of new impurity ions, effectively improving product purity, and ensuring that the product meets battery-grade standards.

[0018] 3. Simple process and high efficiency: By optimizing process parameters such as extractant ratio, two-stage differentiated saponification rate, and feed acidity, this invention ensures that the organic phase after saponification remains uniform and stable, with no free alkali, no water separation, no emulsification, and no third phase formation. Therefore, after saponification, there is no need for settling, centrifugation, or oil-water separation before directly entering countercurrent extraction, which significantly shortens the process and improves process stability and production efficiency. Moreover, battery-grade products can be obtained with only one crystallization, eliminating the need for repeated crystallization, shortening the production cycle, reducing manganese sulfate product loss, and improving production efficiency and product recovery rate.

[0019] 4. Good process stability and controllable parameters: The process parameters of each step (extractant ratio, saponification rate, crystallization temperature, etc.) are clear and optimized, the process has good repeatability, the product quality fluctuates little, and it is suitable for large-scale industrial production.

[0020] 5. Wide compatibility with raw materials: It can be used with various manganese sulfate raw material solutions such as MHP leaching solution, which can improve the utilization rate of raw materials, reduce production costs, and solve the problem of poor raw material compatibility in existing processes.

[0021] 6. High product quality: The final product contains less than 20 ppm of copper and zinc impurities, meets the battery-grade manganese sulfate standard, and can be directly used in battery manufacturing, meeting the needs of high-end applications and outperforming the quality of products from existing processes.

[0022] Other features and effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic flowchart of the method for preparing battery-grade manganese sulfate from manganese sulfate solution according to the present invention is shown. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To achieve the above objectives, embodiments of the present invention provide a method for preparing battery-grade manganese sulfate from a manganese sulfate solution, such as... Figure 1 As shown, it includes the following steps: S1, the first organic extractant containing P204 and solvent oil is first saponified. After saponification, there is no need for oil-water separation. It is directly extracted with manganese sulfate feed solution in a countercurrent manner. After extraction and separation, sulfuric acid is used to back-extract the loaded organic phase. After back-extraction, the aqueous phase is aged and filtered to obtain calcium-removed back-extraction solution. S2, the second organic extractant containing P204 and solvent oil is subjected to a second saponification. After saponification, no oil-water separation is required. It is directly subjected to countercurrent zinc extraction with the calcium-removing back-extraction solution obtained in step S1. Oil-water separation is performed to obtain the aqueous phase after zinc extraction. S3, after neutralizing the residual acid in the zinc-extracted aqueous phase obtained in step S2, add manganese powder to carry out a weight removal reaction, and filter to obtain the weight-removed liquid; S4. After adjusting the pH of the deweighted liquid obtained in step S3, crystallize, filter, and dry to obtain battery-grade manganese sulfate.

[0027] This invention discloses a method for preparing battery-grade manganese sulfate from a manganese sulfate solution. Using a manganese sulfate feed solution (which can be derived from various manganese-containing feed solutions such as MHP leaching solution and low-manganese ore leaching solution, as long as the feed solution contains elements such as manganese, copper, zinc, and calcium) as raw material, the method involves sequential steps including P204 extraction and back-extraction to remove calcium, secondary P204 extraction for zinc purification, removal of manganese powder to remove impurities and weight, and crystallization to prepare battery-grade manganese sulfate. The method achieves step-by-step separation of multiple impurities through segmented extraction, removes manganese powder to remove weight without introducing additional impurities, and obtains battery-grade manganese sulfate through low-temperature single-stage crystallization. Copper and zinc impurities can be reduced to below 20 ppm, and calcium ion concentration can be reduced to approximately 0.25 g / L. This method is suitable for purifying complex manganese sulfate feed solutions such as MHP leaching solution, completing the preparation of battery-grade manganese sulfate. The process is simple, efficient, thoroughly removes impurities, and produces a high-purity product, making it suitable for continuous industrial production.

[0028] In some preferred embodiments of the present invention, in step S1, the volume ratio of P204 to solvent oil in the first organic extractant is 20-30%:70-80%, more preferably 25%:75%; the saponification rate of the first saponification is controlled at 55-65%, more preferably 60%. In step S2, the volume ratio of P204 to solvent oil in the second organic extractant is 20-30%:70-80%, more preferably 25%:75%; the saponification rate of the second saponification is controlled at 20-30%, more preferably 25%.

[0029] This invention achieves precise stepwise separation by employing two-stage extraction with different saponification rates: first, efficient manganese loading for calcium removal, and then selective zinc extraction. This is the key to the invention's ability to obtain battery-grade manganese sulfate through a single crystallization.

[0030] In some preferred embodiments of the present invention, in step S1, the oil-to-water volume ratio of the countercurrent extraction is 1:1-2, and the number of extraction stages is 10-15. The temperature of the countercurrent extraction is 20-40°C, and the oil-to-water volume ratio of the back-extraction is 25-32:1.

[0031] This invention achieves efficient manganese extraction and deep calcium separation by limiting the oil-to-water volume ratio of extraction to 1:1-2, with the advantages of rapid phase separation and no emulsification. Furthermore, limiting the oil-to-water volume ratio of back-extraction to 25-32:1 can enrich the manganese concentration to 150-190 g / L in one step, while further suppressing the back-extraction of impurities, achieving unexpected technical effects of both high concentration and high purity.

[0032] In some preferred embodiments of the present invention, in step S1, the amount of sulfuric acid used for back-extraction is 5-8N (N refers to the equivalent concentration). The aqueous phase aging time after back-extraction is 4-8 hours, the aging temperature is 20-40℃, and the filtered solution is used to obtain calcium-removed back-extraction solution, so that the Mn content reaches 150-190 g / L and the Ca concentration is reduced to below 0.25 g / L.

[0033] In some preferred embodiments of the present invention, in step S2, the oil-to-water volume ratio of the countercurrent zinc extraction is 1:20-25. This oil-to-water volume ratio enables deep selective removal of zinc at high manganese concentrations, with almost no manganese extraction and a higher manganese recovery rate. The number of extraction stages is 5-10. This number of extraction stages ensures that zinc is deeply removed to below 20 ppm without impurities or emulsification, resulting in faster and more stable phase separation. Step S2 also includes sulfuric acid back-extraction on the oil phase after oil-water separation in the countercurrent zinc extraction to obtain a back-extracted zinc liquid. The amount of sulfuric acid used is 3-5N, the number of back-extraction stages is 2-4, and the oil-to-water volume ratio is 1-2:1. The organic phase after oil-water separation can be used to recover back-extracted zinc resources.

[0034] In step S1, by utilizing countercurrent extraction and the characteristic of high solubility of manganese sulfate and low solubility of calcium ions during the aqueous phase aging process after back-extraction at a relatively low temperature (20-40℃), calcium ions can be concentrated and crystallized at low temperature. Relying on the common ion effect (referring to the effect of adding a strong electrolyte containing the same ion to a saturated solution of a sparingly soluble electrolyte, which reduces the solubility of the sparingly soluble electrolyte; in this process, it is used to reduce the solubility of calcium ions and promote calcium crystal precipitation), the concentration of manganese ions is increased by back-extraction, the solubility of calcium ions is reduced, and the concentration of calcium ions in the back-extraction solution is further reduced. Using the precipitated calcium crystals as seed crystals, the characteristic of calcium ions easily crystallizing and growing on the seed crystals and precipitating more thoroughly is utilized to promote further precipitation of calcium ions in the solution and reduce the concentration of calcium ions in the back-extraction solution.

[0035] In some preferred embodiments of the present invention, in step S3, the excess coefficient of manganese powder added relative to the theoretical requirement in the degrafting reaction is 3-7 times, preferably 5; the degrafting reaction time is 25-35 minutes, and continuous low-speed stirring is carried out during the reaction to ensure complete reaction. The manganese powder is industrial manganese powder with a purity ≥99.5% (high purity, few impurities introduced). In the neutralization of residual acid, manganese oxide (such as manganese oxide) can be used instead of sodium hydroxide, which can also achieve the neutralization of residual acid without introducing new impurity ions.

[0036] In some preferred embodiments of the present invention, in step S4, the pH of the deweighted liquid is adjusted to 1.5-2.5. The crystallization temperature is 100-120°C, and the time is 2-5 hours. During this crystallization process, no additional pressure is required besides the saturated vapor pressure; the reaction temperature is low, heat consumption is low, and cost is low; battery-grade manganese sulfate can be obtained through a single low-temperature crystallization without repeated crystallization, simplifying the process and avoiding the loss of manganese sulfate caused by multiple crystallizations.

[0037] In some preferred embodiments of the present invention, filtration is performed using a vacuum filtration device or centrifugation. The moisture content of the wet manganese sulfate crystals obtained by the vacuum filtration device is 20%-20.5%, while the moisture content of the wet manganese sulfate crystals obtained by centrifugation is 8%-10%.

[0038] In some preferred embodiments of the present invention, in steps S1 and S2, the extraction and back-extraction mixing time is 3-7 min and the standing time is 5-8 min.

[0039] In some preferred embodiments of the present invention, the manganese sulfate feed solution contains the following elements: Mn 5-7 g / L, Ca 0.25 g / L (saturation concentration), Cu 0.02-0.05 g / L, and Zn 0.4-0.8 g / L.

[0040] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0041] Detection method description: (1) The concentration of elements such as manganese, calcium, copper, and zinc in the solution is detected by conventional spectrophotometry or EDTA titration. The specific method can be selected according to the routine operation of the laboratory. (2) The moisture content of wet manganese sulfate crystals is detected by drying and weighing method, that is, drying the wet crystals to constant weight and calculating the ratio of the mass difference before and after drying to the mass of the wet crystals. (3) The purity of battery-grade manganese sulfate is detected in accordance with the industry's conventional standards, focusing on detecting the manganese content and the content of impurities such as copper, zinc, and calcium.

[0042] Example 1 A method for preparing battery-grade manganese sulfate from a manganese sulfate solution includes the following steps: (1) Preparation of raw material solution: Select MHP leachate and test its elemental content as Mn 6g / L, Ca 0.2g / L, Cu 0.03g / L, Zn 0.5g / L, and keep it at room temperature for later use; (2) P204 extraction and back-extraction for calcium removal: Prepare an organic extractant with a volume ratio of 25% P204 + 75% solvent oil, introduce 32% liquid alkali to saponify to 60%, mix at room temperature for 4 min with an oil-water volume ratio of 1:1.5, let stand for 7 min, and perform countercurrent extraction with 12 extraction stages. After oil-water separation, back-extract with 7.4N sulfuric acid at an oil-water volume ratio of 30:1, mix for 4 min, let stand for 7 min, and perform countercurrent extraction with 3 stages. Separate the back-extracted aqueous phase and age at room temperature for 6 h. Filter to obtain calcium-removed back-extract, and analyze its components: Mn 189.27 g / L, Ca 224.51 mg / L, Zn 32.96 g / L, Cu 829.19 mg / L; (3) Zinc extraction and purification using P204: Take the back-extraction liquid obtained from the P204 extraction and back-extraction calcium removal step, prepare an organic extractant at a volume ratio of 25% P204 + 75% solvent oil, and saponify it to 25% by introducing 32% liquid alkali. After saponification, directly extract with a simulated liquid at a flow rate of 0.045 L / h and 1 L / h in a shake flask. Separate the oil and water to obtain the aqueous phase after zinc extraction. Perform countercurrent zinc extraction at an oil-to-water volume ratio of 1:22, mix for 4 min, let stand for 7 min, and the extraction stage is 8. Separate the oil and water to obtain the aqueous phase after zinc extraction. Use 4N sulfuric acid to back-extract the oil phase after oil-water separation. The back-extraction stage is 3, and the back-extraction oil-to-water volume ratio is 1:1. Obtain the zinc-recovered liquid and recover zinc resources.

[0043] (4) Manganese powder deweighting: Manganese powder was added to the aqueous phase after zinc extraction to neutralize the residual acid to neutral. 99.5% manganese powder was added at an excess coefficient of 5 times. The mixture was stirred and reacted for 30 min. The deweighted liquid was obtained by filtration and its composition was tested: Mn 185.34 mg / L, Ca 221.65 mg / L, Zn 13.20 mg / L, Cu 17.72 mg / L. The copper and zinc were both below 20 ppm. (5) Low-temperature crystallization: Add dilute sulfuric acid to the liquid after removing the heavy weight to adjust the pH to 2, and crystallize at 120℃ for 4 hours. While hot, filter the liquid using a vacuum filter to obtain wet manganese sulfate crystals. The water content was measured to be 20.19%. After drying, the manganese content was measured to be 32.4%, the calcium content to be 0.012%, the zinc content to be 0.0015%, and the copper content to be 0.0006%. The impurity content met the industry standard for battery-grade manganese sulfate.

[0044] Example 2 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that: the aging time of the back-extraction aqueous phase in step (2) is 4 h, the crystallization temperature in step (5) is 100 °C, and the remaining steps and parameters are the same as in Example 1.

[0045] Test results: In the calcium-free stripping solution, Mn 188.31 g / L, Ca 235.27 mg / L, Zn 32.46 g / L, and Cu 802.37 mg / L; in the heavy-duty stripping solution, Mn 186.29 g / L, Ca 215.91 mg / L, Cu 17.5 ppm, and Zn 12.8 ppm; the moisture content of the wet manganese sulfate crystals was 20.5%; the measured manganese content was 32.2%, calcium content was 0.014%, zinc content was 0.0013%, and copper content was 0.0007%, and the impurity content met the battery-grade manganese sulfate standard.

[0046] Example 3 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the saponification rate of the organic extractant in steps (2) and (3) is controlled at 60%. The remaining steps and parameters are the same as in Example 1.

[0047] Test results: In the calcium-free stripping solution, Mn was 187.62 g / L, Ca was 241.38 mg / L, Zn was 31.85 g / L, and Cu was 815.64 mg / L; in the heavy-duty stripping solution, Mn was 154.17 g / L, Ca was 238.25 mg / L, Cu was 18.3 ppm, and Zn was 16.5 ppm; the moisture content of the wet manganese sulfate crystals was 20.32%; after drying, the manganese content was 32.3%, the calcium content was 0.013%, the zinc content was 0.0018%, and the copper content was 0.0007%. The impurity content met the industry standard for battery-grade manganese sulfate. The zinc removal effect decreased, with the final product having a zinc content close to 20 ppm, reduced purity and stability, and significant manganese loss.

[0048] Example 4 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the saponification rate of the organic extractant in steps (2) and (3) is controlled at 80%. The remaining steps and parameters are the same as in Example 1.

[0049] Test results: A third phase appeared during the extraction process, making oil-water separation difficult; the calcium-free back-extraction solution contained Mn 162.45 g / L, Ca 387.62 mg / L, Zn 28.74 g / L, and Cu 762.31 mg / L; the heavy-duty solution contained Mn 158.73 g / L, Ca 382.47 mg / L, Cu 26.8 ppm, and Zn 24.3 ppm; the final product had a manganese content of 31.8%, a calcium content of 0.021%, a zinc content of 0.0026%, and a copper content of 0.0011%, which could not stably meet the battery-grade manganese sulfate standard.

[0050] Example 5 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the saponification rate of the organic extractant in steps (2) and (3) is controlled at 30%. The remaining steps and parameters are the same as in Example 1.

[0051] Test results: In the calcium-free stripping solution, Mn 124.38 g / L, Ca 312.54 mg / L, Zn 22.63 g / L, and Cu 687.42 mg / L; in the heavy-duty stripping solution, Mn 121.76 g / L, Ca 308.69 mg / L, Cu 19.2 ppm, and Zn 17.8 ppm; the final product had a manganese content of 32.1%, a calcium content of 0.017%, a zinc content of 0.0019%, and a copper content of 0.0008%. The manganese enrichment effect was not optimal, and the production efficiency was lower than that of Example 1.

[0052] Example 6 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that: in step (2), the oil-to-water volume ratio of countercurrent extraction is 1:3, and the oil-to-water volume ratio of back-extraction is 35:1; in step (3), the oil-to-water volume ratio of countercurrent zinc extraction is 1:28, and the oil-to-water volume ratio of back-extraction is 3:1. The remaining steps and parameters are the same as in Example 1.

[0053] Test results: In the calcium-free stripping solution, Mn 165.72 g / L, Ca 232.18 mg / L, Zn 30.25 g / L, and Cu 798.63 mg / L; in the heavy-duty stripping solution, Mn 162.47 g / L, Ca 229.35 mg / L, Cu 18.1 ppm, and Zn 14.2 ppm; the final product has a manganese content of 32.2%, a calcium content of 0.013%, a zinc content of 0.0016%, and a copper content of 0.0007%, which meets the battery-grade manganese sulfate standard, although the manganese enrichment concentration is slightly lower than in Example 1.

[0054] Comparative Example 1 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that: the excess coefficient of manganese powder added in step (4) is 2 times, while the remaining steps and parameters are the same as in Example 1.

[0055] Test results: After degrafting, the concentrations of Mn in the solution were 185.12 g / L, Ca 223.76 mg / L, Cu 29.45 ppm, and Zn 27.68 ppm; the moisture content of the wet manganese sulfate crystals was 20.21%; after drying, the manganese content was measured to be 32.1%, calcium content was 0.013%, zinc content was 0.0029%, and copper content was 0.0031%. The copper and zinc impurities were all higher than 20 ppm, which does not meet the industry standard for battery-grade manganese sulfate.

[0056] Comparative Example 2 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the reaction time for removing manganese powder in step (4) is 15 min, while the remaining steps and parameters are consistent with Example 1.

[0057] Test results: After degrafting, the concentrations of Mn in the solution were 184.92 g / L, Ca 224.11 mg / L, Cu 28.63 ppm, and Zn 25.74 ppm; the moisture content of the wet manganese sulfate crystals was 20.25%; after drying, the manganese content was measured to be 32.2%, calcium content was 0.013%, zinc content was 0.0027%, and copper content was 0.0030%. The copper and zinc impurities exceeded the standards and did not meet the industry standards for battery-grade manganese sulfate.

[0058] Comparative Example 3 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the aging temperature of the back-extraction aqueous phase in step (2) is 50°C, while the remaining steps and parameters are the same as in Example 1.

[0059] Test results: In the calcium removal stripping solution, Mn 188.43 g / L, Ca 356.72 mg / L, Zn 32.11 g / L, and Cu 818.36 mg / L; in the weight removal solution, Mn 184.25 g / L, Ca 352.14 mg / L, Cu 18.1 ppm, and Zn 16.3 ppm; the moisture content of wet manganese sulfate crystals was 20.28%; after drying, the manganese content was measured to be 32.2%, and the calcium content was 0.031%. The calcium removal effect was significantly worse, which does not meet the industry standard for battery-grade manganese sulfate.

[0060] Comparative Example 4 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that the crystallization temperature in step (5) is 130°C, while the remaining steps and parameters are the same as in Example 1.

[0061] Test results: After degrafting, the liquid contained 185.21 g / L Mn, 223.96 mg / L Ca, 17.5 ppm Cu, and 13.5 ppm Zn; the moisture content of the wet manganese sulfate crystals was 18.66%; after drying, the manganese content was 31.5%, calcium content was 0.022%, zinc content was 0.0028%, and copper content was 0.0012%. The crystals showed abnormal crystal form and severe agglomeration, resulting in a significant decrease in purity, which does not meet the industry standard for battery-grade manganese sulfate.

[0062] Comparative Example 5 A method for preparing battery-grade manganese sulfate from manganese sulfate solution differs from Example 1 in that: after the organic extractant in steps (2) and (3) is saponified, the saponified oil and water are separated. The remaining steps and parameters are the same as in Example 1.

[0063] Test results: In the calcium-free stripping solution, Mn 188.53 g / L, Ca 228.76 mg / L, Zn 32.74 g / L, and Cu 824.35 mg / L; in the heavy-duty stripping solution, Mn 184.82 g / L, Ca 225.41 mg / L, Cu 17.9 ppm, and Zn 13.5 ppm; the final product quality was consistent with that of Example 1, but the production process was increased, the single-batch production cycle was extended by 20%, the organic phase loss increased by 15%, and the stability of continuous production decreased.

[0064] In summary, the method for preparing battery-grade manganese sulfate from manganese sulfate solution of the present invention achieves the following technical effects: Existing processes for preparing manganese sulfate generally require oil-water separation after saponification and multiple crystallizations. However, this application uses key steps such as differentiated two-stage extraction with a high saponification rate and a low saponification rate, eliminating the need for oil-water separation after saponification, and high oil-water volume ratio back-extraction to enrich manganese in the manganese sulfate solution to 150-190 g / L in one step and obtain battery-grade manganese sulfate after one crystallization. This results in unexpected technical effects such as more precise impurity removal, simplified process, higher yield, and more stable product.

[0065] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing battery-grade manganese sulfate from a manganese sulfate solution, characterized in that, Includes the following steps: S1, the first organic extractant containing P204 and solvent oil is first saponified. After saponification, there is no need for oil-water separation. It is directly extracted with manganese sulfate feed solution in a countercurrent manner. After extraction and separation, sulfuric acid is used to back-extract the loaded organic phase. After back-extraction, the aqueous phase is aged and filtered to obtain calcium-removed back-extraction solution. S2, the second organic extractant containing P204 and solvent oil is subjected to a second saponification. After saponification, no oil-water separation is required. It is directly subjected to countercurrent zinc extraction with the calcium-removing back-extraction solution obtained in step S1. Oil-water separation is performed to obtain the aqueous phase after zinc extraction. S3, after neutralizing the residual acid in the zinc-extracted aqueous phase obtained in step S2, add manganese powder to carry out a weight removal reaction, and filter to obtain the weight-removed liquid; S4. After adjusting the pH of the deweighted liquid obtained in step S3, crystallize, filter, and dry to obtain battery-grade manganese sulfate.

2. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S1, the volume ratio of P204 to solvent oil in the first organic extractant is 20-30%:70-80%; the saponification rate of the first saponification is controlled at 55-65%.

3. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S1, the oil-to-water volume ratio of the countercurrent extraction is 1:1-2, the number of extraction stages is 10-15, and the temperature of the countercurrent extraction is 20-40℃; the oil-to-water volume ratio of the back-extraction is 25-32:1, the amount of sulfuric acid used in the back-extraction is 5-8N; the aging time of the aqueous phase after back-extraction is 4-8h, and the aging temperature is 20-40℃.

4. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S2, the volume ratio of P204 to solvent oil in the second organic extractant is 20-30%:70-80%; the saponification rate of the second saponification is controlled at 20-30%.

5. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S2, the oil-to-water volume ratio of the countercurrent zinc extraction is 1:20-25, and the number of extraction stages is 5-10.

6. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S2, the oil phase after the countercurrent zinc oil-water separation is subjected to sulfuric acid back-extraction to obtain the zinc back-extraction liquid. The amount of sulfuric acid used is 3-5N, the number of back-extraction stages is 2-4, and the volume ratio of back-extraction oil to water is 1-2:

1.

7. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S3, the excess coefficient of manganese powder added relative to the theoretical requirement in the degravation reaction is 3-7 times; the degravation reaction time is 25-35 minutes.

8. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In step S4, the crystallization temperature is 100-120℃ and the time is 2-5h.

9. The method for preparing battery-grade manganese sulfate from manganese sulfate solution according to claim 1, characterized in that, In steps S1 and S2, the extraction and back-extraction mixing time is 3-7 min, and the standing time is 5-8 min.

10. The method for preparing battery-grade manganese sulfate from a manganese sulfate solution according to any one of claims 1 to 9, characterized in that, The manganese sulfate feed solution contains the following elements: Mn 5-7 g / L, Ca 0.25 g / L (saturation concentration), Cu 0.02-0.05 g / L, and Zn 0.4-0.8 g / L.

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