A method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud

Abstract

The application provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud, and relates to the field of hydrometallurgy.The application realizes manganese leaching of the anode mud by stirring and mixing the zinc electrodeposition anode mud after water washing, drying and ball milling with a sulfuric acid solution and continuously introducing SO2 reducing gas, and performs pressure filtration treatment on the slurry after reaction, then adjusts the pH value of the filtrate to neutral and filters, finally transfers the obtained filtrate to a double-membrane three-chamber electrolytic cell, under the action of electric current and anion exchange membrane, Mn 2+ and the like cations enter the cathode chamber, and S2O6 2‑ and the like anions enter the anode chamber, so that the separation of Mn 2+ and S2O6 2‑ is realized, thereby improving the generation rate of subsequent manganese sulfate.The preparation method greatly improves the generation rate of manganese sulfate and optimizes the purification process flow of the battery-grade manganese sulfate.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for preparing battery-grade manganese sulfate from electrolytic zinc electrowinning anode mud. Background Technology

[0002] Zinc, due to its excellent electrical conductivity and ductility, and its ability to form alloys with other metals, is widely used in fields such as machinery and electronics, defense industry, aerospace, and new energy materials. Currently, zinc smelting mainly relies on the hydrometallurgical process, which includes four steps: roasting, leaching, purification, and electrodeposition. During the electrodeposition process, a large amount of anode mud, mainly composed of manganese and lead, is inevitably generated, which seriously harms the zinc electrodeposition process and the quality of zinc.

[0003] Most zinc smelting companies treat zinc electrowinning anode slime by returning it as an oxidant to the zinc leaching process for iron removal. However, this method has low manganese utilization rate in the anode slime and introduces impurities such as lead and silver into the leaching residue, increasing the difficulty of smelting slag recovery. In contrast, using anode slime as the main raw material to prepare battery-grade manganese sulfate for resource utilization is a feasible solution. Most research focuses on adding various reducing agents to dissolve manganese in the anode slime, thereby separating manganese from other insoluble substances. However, this method greatly increases production costs. Using sulfur dioxide from smelting flue gas as a reducing agent to treat anode slime is a low-cost technology that can achieve resource utilization of hazardous waste. However, sulfur dioxide generates manganese dithionate as a byproduct during the manganese leaching process of anode slime, reducing the manganese sulfate formation rate. Subsequent purification requires further oxidation treatment, increasing processing costs. For example, existing patent CN 108031255 A discloses a method for removing sulfur dioxide from flue gas and preparing manganese sulfate solution using manganese oxide ore. This method involves introducing sulfur dioxide-containing flue gas into an absorption device containing manganese oxide ore slurry to react and obtain slurry and discharged flue gas, with the sulfur dioxide concentration in the flue gas meeting environmental emission requirements. Then, an oxidizing gas is introduced for further reaction and filtration, and the filtrate is purified to obtain manganese sulfate solution. However, this method also produces manganese dithionate as a side reaction during the desulfurization of the manganese oxide ore slurry flue gas, which negatively impacts the purity of manganese sulfate and its subsequent utilization. Patent application number 2019108092343 discloses a highly efficient decomposition method for manganese dithionate based on the catalytic oxidation of manganese dioxide, but this method is a post-processing method and requires relatively harsh operating conditions, resulting in high processing costs. Furthermore, the subsequent purification of the manganese sulfate solution to prepare battery-grade manganese sulfate requires the introduction of various purification agents, making the process complex and costly.

[0004] Therefore, it is necessary to develop a new process technology that can improve the manganese sulfate production rate and simplify the purification process of battery-grade manganese sulfate. Summary of the Invention

[0005] This invention provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud, the purpose of which is to solve the aforementioned problems existing in the background art.

[0006] To achieve the above objectives, embodiments of the present invention provide a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud. The present invention involves mixing washed, dried, and ball-milled zinc electrodeposition anode mud with a sulfuric acid solution and continuously introducing SO2 reducing gas to leach manganese from the anode mud. The resulting slurry is then pressure-filtered, the pH of the filtrate is adjusted to neutral, and the filtrate is filtered again. Finally, the filtrate is transferred to a double-membrane three-chamber electrolytic cell for manganese resource separation and extraction at a certain current density, followed by further concentration and crystallization to prepare battery-grade manganese sulfate. This invention significantly improves the manganese sulfate production rate and optimizes the purification process of battery-grade manganese sulfate.

[0007] Embodiments of the present invention provide a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud, comprising the following steps:

[0008] S1: Pre-treat the zinc electrowinning anode mud, add sulfuric acid, stir and mix, and continuously pass SO2 gas to carry out a reduction leaching reaction, and filter to obtain filtrate; first add sulfuric acid to the anode mud to dissolve the valuable metal, enhance the oxidizing property of manganese-containing substances in the system, and at the same time increase the reaction rate of anode mud particles with SO2 reducing gas.

[0009] S2: Adjust the pH value of the filtrate and filter it. Then transfer the secondary filtrate to the middle chamber of the double-membrane three-chamber electrolytic cell and add salt solution to the corresponding anode and cathode chambers. By adjusting the pH value, iron and aluminum impurities in the filtrate can be precipitated and removed. At the same time, adding salt solution to the corresponding anode and cathode chambers can increase the ionic conductivity of the solution and reduce the voltage of the electrolytic cell.

[0010] S3: Place the corresponding anode and cathode plates into a double-membrane three-chamber electrolytic cell for electrolysis;

[0011] The initial electrolysis uses a high current, followed by a low current when gas begins to be generated, while continuously monitoring the pH value of the solution in the cathode chamber. Electrolysis is stopped once the pH reaches a certain value. The initial high current electrolysis ensures that the deposition of heavy metal ions in the solution takes precedence over the hydrogen evolution reaction, while the subsequent use of a low current electrolysis increases the hydrogen evolution potential (as the solution pH increases, the hydrogen evolution potential decreases), ensuring that the hydrogen evolution reaction takes precedence over the manganese ion deposition reaction. Electrolysis is stopped once the pH value in the cathode chamber reaches a certain value, at which point manganese ions have precipitated completely, but calcium and magnesium ions have not yet begun to precipitate.

[0012] S4: After electrolysis, the solution in the cathode chamber is filtered and separated. The resulting filter residue is reacted with sulfuric acid solution, concentrated, crystallized, filtered and dried to obtain high-purity battery-grade manganese sulfate.

[0013] According to one aspect of an embodiment of the present invention, in step S1, the pretreatment process includes sequentially performing water washing, drying, and ball milling, wherein the drying temperature is 100-120°C; the pretreatment process also includes sieving of zinc electrowinning anode mud particles with a particle size between 100 and 300 mesh.

[0014] According to one aspect of an embodiment of the present invention, in step S1, the sulfuric acid concentration is 10-50 g / L; the liquid-to-solid ratio of sulfuric acid to zinc electrowinning anode mud is 5-50 mL / g; and the amount of SO2 gas introduced is 1.1-2.0 times the theoretical reaction amount.

[0015] According to one aspect of an embodiment of the present invention, in step S1, the reaction time is 6 to 12 hours and the reaction temperature is 15 to 60°C.

[0016] According to one aspect of an embodiment of the present invention, in step S2, the structure of the double-membrane three-chamber electrolyzer from left to right is: anode plate - anion exchange membrane - cation exchange membrane - cathode plate.

[0017] According to one aspect of an embodiment of the present invention, in step S2, the pH value of the filtrate is 7.0, and the substance added to adjust the pH value is any one of manganese hydroxide, sodium hydroxide, and potassium hydroxide; the salt solution is at least one of sodium sulfate and potassium sulfate.

[0018] According to one aspect of the present invention, in step S3, the anode plate is either a lead-based anode or a titanium-based anode; the cathode plate is either an aluminum plate or a stainless steel plate.

[0019] According to one aspect of an embodiment of the present invention, in step S3, the cathode current density is controlled at 8–12 mA / cm². 2 The cathode current density is controlled between 0.2 and 1.2 mA / cm². 2 Electrolysis is stopped when the pH value of the solution in the cathode chamber reaches 10.0 to 10.2.

[0020] According to one aspect of an embodiment of the present invention, in step S4, the concentration and crystallization temperature is 90-95°C, and the drying temperature is 100-120°C.

[0021] According to one aspect of an embodiment of the present invention, the battery-grade manganese sulfate has a purity of up to 99.5%. The above-described solution of the present invention has the following beneficial effects:

[0022] (1) This invention employs a dual-membrane, three-chamber electrolytic treatment of the solution after SO2 leaching of zinc electrowinning anode mud. Under the action of current and anion / cation exchange membranes, the Mn in the middle chamber... 2+ When cations enter the cathode chamber, S2O6... 2- When anions enter the anode chamber, Mn is realized. 2+ and S2O62- The separation of manganese sulfate can improve the subsequent production rate of manganese sulfate.

[0023] (2) During high-current electrolysis, due to the large hydrogen evolution overpotential, the Pb in the cathode chamber solution... 2+ Ag + Zn 2+ The deposition reaction of heavy metal ions on the cathode plate preferentially occurs over the hydrogen evolution reaction and the manganese ion deposition reaction, thereby achieving Mn deposition. 2+ Separation from other heavy metal ions; During low-current electrolysis, because the hydrogen evolution potential is higher than the manganese ion deposition potential, a hydrogen evolution reaction begins in the cathode chamber. However, due to the cation exchange membrane, the OH- in the cathode chamber... - The manganese ions cannot migrate to the anode chamber, causing the pH value in the cathode chamber to rise continuously. Manganese ions begin to form precipitate Mn(OH)2. Since calcium and magnesium have not yet started to precipitate after manganese precipitation is completed, manganese can be effectively separated from impurities such as sodium, potassium, calcium, and magnesium.

[0024] (3) The method of the present invention can separate manganese from other impurity elements in one step, optimize the purification process of battery-grade manganese sulfate, and is simple to operate, economical and environmentally friendly, with significant economic and social benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the apparatus in a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a double-membrane three-chamber electrolytic cell in an embodiment of the present invention for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud;

[0028] Figure 3 This is a schematic diagram of the process flow in an embodiment of the present invention for preparing battery-grade manganese sulfate from electrolytic zinc electrowinning anode mud. Detailed Implementation

[0029] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] To address the aforementioned problems in the prior art, this invention provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud, as illustrated in the schematic diagram of the process flow. Figure 1 As shown, it includes the following steps:

[0033] S1: Pre-treat the zinc electrowinning anode mud, add sulfuric acid, stir and mix, and continuously pass SO2 gas to carry out a reduction leaching reaction, and filter to obtain filtrate; first add sulfuric acid to the anode mud to dissolve the valuable metal, enhance the oxidizing property of manganese-containing substances in the system, and at the same time increase the reaction rate of anode mud particles with SO2 reducing gas.

[0034] S2: Adjust the pH value of the filtrate and filter it. Then transfer the secondary filtrate to the middle chamber of the double-membrane three-chamber electrolytic cell and add salt solution to the corresponding anode and cathode chambers. By adjusting the pH value, iron and aluminum impurities in the filtrate can be precipitated and removed. At the same time, adding salt solution to the corresponding anode and cathode chambers can increase the ionic conductivity of the solution and reduce the voltage of the electrolytic cell.

[0035] S3: Place the corresponding anode and cathode plates into a double-membrane three-chamber electrolytic cell for electrolysis;

[0036] The initial electrolysis uses a high current, followed by a low current when gas begins to be generated, while continuously monitoring the pH value of the solution in the cathode chamber. Electrolysis is stopped once the pH reaches a certain value. The initial high current electrolysis ensures that the deposition of heavy metal ions in the solution takes precedence over the hydrogen evolution reaction, while the subsequent use of a low current electrolysis increases the hydrogen evolution potential (as the solution pH increases, the hydrogen evolution potential decreases), ensuring that the hydrogen evolution reaction takes precedence over the manganese ion deposition reaction. Electrolysis is stopped once the pH value in the cathode chamber reaches a certain value, at which point manganese ions have precipitated completely, but calcium and magnesium ions have not yet begun to precipitate.

[0037] S4: After electrolysis, the solution in the cathode chamber is filtered and separated. The resulting filter residue is reacted with sulfuric acid solution, concentrated, crystallized, filtered and dried to obtain high-purity battery-grade manganese sulfate.

[0038] This invention employs a dual-membrane, three-chamber electrolytic treatment of the solution following SO2 leaching of zinc electrowinning anode mud. Under the influence of current and the anion and cation exchange membranes, the Mn in the middle chamber... 2+ When cations enter the cathode chamber, S2O6... 2-When anions enter the anode chamber, Mn is realized. 2+ and S2O6 2- The separation of Pb in the cathode chamber solution improves the subsequent formation rate of manganese sulfate. In particular, during high-current electrolysis, due to the large hydrogen evolution overpotential, the Pb in the cathode chamber solution... 2+ Ag + Zn 2+ The deposition reaction of heavy metal ions on the cathode plate preferentially occurs over the hydrogen evolution reaction and the manganese ion deposition reaction, thereby achieving Mn deposition. 2+ Separation from other heavy metal ions; During low-current electrolysis, because the hydrogen evolution potential is higher than the manganese ion deposition potential, a hydrogen evolution reaction begins in the cathode chamber. However, due to the cation exchange membrane, the OH- in the cathode chamber... - The manganese ions cannot migrate to the anode chamber, causing the pH value in the cathode chamber to rise continuously. Manganese ions begin to form precipitate Mn(OH)2. Since calcium and magnesium have not yet started to precipitate after manganese precipitation is completed, manganese can be effectively separated from impurities such as sodium, potassium, calcium, and magnesium.

[0039] In the following embodiments of the present invention, the manganese sulfate formation rate and the battery-grade manganese sulfate purity are calculated according to formula (1-2).

[0040] Manganese sulfate formation rate = n 硫酸锰 / n 硫酸锰+连二硫酸锰 (1)

[0041] Battery-grade manganese sulfate purity = m 硫酸锰 / m 硫酸锰固体 (2)

[0042] Example 1

[0043] This embodiment provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud.

[0044] The method of this embodiment includes the following steps:

[0045] S1: Take 10 kg of anode mud from a zinc smelter and wash it with water to remove soluble substances attached to the anode mud. Then, dry and dehumidify it at 100℃, and then ball-mill it into anode mud particles with a particle size passing through a 200-mesh sieve. Mix the ball-milled anode mud particles with sulfuric acid solution and continuously bleed SO2 reducing gas to leach the anode mud. At this time, the liquid-to-solid ratio is 30 mL / g, the sulfuric acid concentration in the solution is 25 g / L, the SO2 flow rate is controlled at 1.2 times the theoretical reaction amount, the reaction temperature is controlled at 40℃, and the reaction time is 6 h.

[0046] S2: The slurry after the above reaction is filtered by pressure, and then sodium hydroxide is added to adjust the pH of the filtrate to 7.0. After further filtration, the filtrate is transferred to the middle chamber of the double membrane three-chamber electrolytic cell, and sodium sulfate solution is added to the corresponding anode and cathode chambers.

[0047] S3: After the above operations are completed, insert the Pb-Ag anode and Al plate cathode into the corresponding electrolysis chambers, and then initially use 8mA / cm 2 Electrolysis was performed using a high cathode current density. Once bubbles began to form, the current was switched to 0.8 mA / cm². 2 Electrolysis is performed using a low cathode current density, and electrolysis is stopped when the pH value of the solution in the cathode chamber reaches 10.2.

[0048] S4: The solution in the cathode chamber is filtered and separated. The resulting filter residue is dissolved in sulfuric acid solution, then concentrated and crystallized at 92°C. The solution is filtered while hot, and the resulting crystals are dried at 120°C to obtain qualified battery-grade manganese sulfate.

[0049] XRF and ICP-OES were used to test the main elements of the final manganese sulfate crystals. The corresponding manganese sulfate formation rate and battery-grade manganese sulfate purity were calculated according to equation (1-2), and the battery-grade manganese sulfate was determined to be qualified. The results are shown in Table 1 below:

[0050] Table 1. Calculation results of manganese sulfate formation rate and battery-grade manganese sulfate purity.

[0051]

[0052] Tests and calculations show that the manganese sulfate production rate in this example is 100%, and the purity of battery-grade manganese sulfate reaches 99.5%, making it a qualified product.

[0053] Example 2

[0054] This embodiment provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud.

[0055] The method of this embodiment includes the following steps:

[0056] S1: Take 15 kg of anode mud from a zinc smelter and wash it with water to remove soluble substances attached to the anode mud. Then, dry and dehumidify it at 110℃, and then ball-mill it into anode mud particles with a particle size that passes through a 200-mesh sieve. Mix the ball-milled anode mud particles with sulfuric acid solution and continuously bleed SO2 reducing gas to leach the anode mud. At this time, the liquid-to-solid ratio is 40 mL / g, the sulfuric acid concentration in the solution is 30 g / L, the SO2 flow rate is controlled at 1.4 times the theoretical reaction amount, the reaction temperature is controlled at 35℃, and the reaction time is 10 h.

[0057] S2: The slurry after the above reaction is filtered by pressure, and then manganese hydroxide is added to adjust the pH of the filtrate to 7.0. After further filtration, the filtrate is transferred to the middle chamber of the double membrane three-chamber electrolytic cell, and sodium sulfate solution is added to the corresponding anode and cathode chambers.

[0058] S3: After the above operations are completed, insert the Pb-Ag anode and stainless steel cathode into the corresponding electrolysis chamber, and then initially use 12mA / cm 2 Electrolysis was performed using a high cathode current density. Once bubbles began to form, the current was switched to 0.8 mA / cm². 2 Electrolysis is performed using a low cathode current density, and electrolysis is stopped when the pH value of the solution in the cathode chamber reaches 10.1.

[0059] S4: The solution in the cathode chamber is filtered and separated. The resulting filter residue is dissolved in sulfuric acid solution, then concentrated and crystallized at 93°C. The solution is filtered while hot, and the resulting crystals are dried at 110°C to obtain qualified battery-grade manganese sulfate.

[0060] XRF and ICP-OES were used to test the main elements of the final manganese sulfate crystals. The corresponding manganese sulfate formation rate and battery-grade manganese sulfate purity were calculated according to equation (1-2), and the battery-grade manganese sulfate was determined to be qualified. The results are shown in Table 2 below:

[0061] Table 2. Calculation results of manganese sulfate formation rate and battery-grade manganese sulfate purity.

[0062]

[0063] Tests and calculations show that the manganese sulfate production rate in this example is 100%, and the purity of battery-grade manganese sulfate reaches 99.3%, making it a qualified product.

[0064] Example 3

[0065] This embodiment provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud.

[0066] The method of this embodiment includes the following steps:

[0067] S1: Take 20 kg of anode mud from a zinc smelter and wash it with water to remove soluble substances attached to the anode mud. Then, dry and dehumidify it at 100℃, and then ball-mill it into anode mud particles with a particle size passing through a 200-mesh sieve. Mix the ball-milled anode mud particles with sulfuric acid solution and continuously bleed SO2 reducing gas to leach the anode mud. At this time, the liquid-to-solid ratio is 45 mL / g, the sulfuric acid concentration in the solution is 25 g / L, the SO2 flow rate is controlled at 1.2 times the theoretical reaction amount, the reaction temperature is controlled at 40℃, and the reaction time is 6 h.

[0068] S2: The slurry after the above reaction is filtered by pressure, and then sodium hydroxide is added to adjust the pH of the filtrate to 7.0. After further filtration, the filtrate is transferred to the middle chamber of the double membrane three-chamber electrolytic cell, and sodium sulfate solution is added to the corresponding anode and cathode chambers.

[0069] S3: After the above operations are completed, insert the Pb-Ag anode and stainless steel cathode into the corresponding electrolysis chamber, and then initially use 12mA / cm 2 Electrolysis was performed using a high cathode current density. Once bubbles began to form, the current was switched to 0.6 mA / cm². 2 Electrolysis is performed using a low cathode current density, and electrolysis is stopped when the pH value of the solution in the cathode chamber reaches 10.0.

[0070] S4: The solution in the cathode chamber is filtered and separated. The resulting filter residue is dissolved in sulfuric acid solution, then concentrated and crystallized at 92°C. The solution is filtered while hot, and the resulting crystals are dried at 120°C to obtain qualified battery-grade manganese sulfate.

[0071] The main elements of the final manganese sulfate crystals were tested using XRF and ICP-OES techniques. The corresponding manganese sulfate formation rate and battery-grade manganese sulfate purity were calculated according to equation (1-2), and the battery-grade manganese sulfate was determined to be qualified. The results are shown in Table 3 below.

[0072] Table 3. Calculation results of manganese sulfate formation rate and battery-grade manganese sulfate purity.

[0073]

[0074] Tests and calculations show that the manganese sulfate production rate in this example is 100%, and the purity of battery-grade manganese sulfate reaches 99.2%, making it a qualified product.

[0075] The main chemical equations and the theoretical oxidation potential of the ions in the cathode chamber in the above embodiments of the present invention are as follows, wherein it is assumed that Mn in the cathode chamber 2+ Concentration of 10 -1 According to the standard for battery-grade manganese sulfate, the corresponding impurity concentration should be 10 mol / L. -6 The higher the concentration (mol / L), the higher the oxidation potential. The oxidation potentials of each ion are calculated based on the lowest concentrations mentioned above as follows:

[0076] Anode mud leaching reaction equation

[0077] (1) SO2 + MnO2 + H2O = MnSO4 + H2O

[0078] (2) SO2 + MnO2 + H2O = MnS2O6 + H2O

[0079] The oxidation potentials of ions in the cathode chamber, and their preferential deposition order, are arranged from top to bottom.

[0080] (1)Ag + +e=Ag(E=0.4450V, c=10 -6 mol / L)

[0081] (2)Cu 2+ +2e=Cu(E=0.1646V, c=10 -6 mol / L)

[0082] (3)Pb 2+ +2e=Pb (E=-0.3035V, c=10 -6 mol / L)

[0083] (4)Ni 2+ +2e=Ni(E=-0.4343V, c=10 -6 mol / L)

[0084] (5) Co 2+ +2e=Co(E=-0.4573V, c=10 -6 mol / L)

[0085] (6)Cd 2+ +2e=Cd(E=-0.5803V, c=10 -6 mol / L)

[0086] (7)Zn 2+ +2e=Zn(E=-9131V,c=10 -6 mol / L)

[0087] (8)2H + +e = H2 (E = -0.9737V to -1.0423V, pH = 7, high current density)

[0088] (9)2H + +e=H2 (E=-0.9087V~-1.0870V, pH=10.3, low current density)

[0089] (10)Mn 2+ +2e=Mn(E=-1.2348V, c=10 -1 mol / L)

[0090] (11)Mg 2+ +2e=Mg(E=-2.5493V, c=10 -6 mol / L)

[0091] (12)Ca 2+ +2e=Ca(E=-3.0453V, c=10 -6 mol / L)

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud. Except for step S1, where the amount of SO2 gas introduced is 0, the other steps are the same as in Example 1.

[0094] When sulfuric acid is added to the anode mud without the introduction of SO2 reducing gas, the system does not contain a reducing agent and cannot carry out the manganese reduction leaching reaction in the anode mud. At this time, the manganese leaching rate of the corresponding anode mud is extremely low, and the solution contains almost no manganese ions. Therefore, in the subsequent double-membrane three-chamber electrolysis process, no precipitation is generated in the cathode chamber when the pH reaches a certain value, thus making it impossible to prepare battery-grade manganese sulfate.

[0095] Comparative Example 2

[0096] This comparative example provides a method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud. Except for step S3, which initially uses 0.8 mA / cm... 2 Electrolysis was performed using a low cathode current density. Once bubbles began to form, the current was switched to 12 mA / cm². 2 Apart from electrolysis using a high cathode current density, the remaining steps are the same as in Example 1.

[0097] When electrolysis is initially performed using a low current density, the hydrogen evolution overpotential is relatively small, while the hydrogen evolution potential is higher than that of some heavy metal ions (e.g., Zn). 2+ At this deposition potential, hydrogen evolution reaction preferentially occurs, leaving some heavy metal ion impurities in the solution. Switching to high current density electrolysis increases the hydrogen evolution overpotential, and the increased pH further increases the hydrogen evolution potential. This results in the hydrogen evolution potential falling below the manganese ion deposition potential when the pH reaches a certain value. Consequently, some manganese ions preferentially deposit on the cathode plate, reducing the amount of manganese hydroxide precipitated in the cathode chamber, leading to a lower battery-grade manganese sulfate production (only 1 / 2 of the example).

[0098] Comparative Example 3

[0099] This comparative example provides a conventional method for preparing battery-grade manganese sulfate using zinc electrowinning anode slime. Except for step S1, which is the same as in Example 1, subsequent steps use conventional methods for manganese sulfate purification, mainly including: (1) introducing Fe 3+ (1) Adjust the pH of the filtrate to 5.3 to remove iron, aluminum, sodium and potassium impurities; (2) Add manganese sulfide to remove heavy metal ion impurities in the filtrate; (3) Add manganese fluoride to remove calcium and magnesium impurities in the filtrate; (4) The filtrate is concentrated, crystallized, filtered and dried to obtain solid manganese sulfate.

[0100] The composition of solid manganese sulfate was analyzed using XRF and ICP-OES testing techniques. The results showed that the content of manganese dithionate in the prepared solid manganese sulfate was 20%, and the manganese sulfate formation rate was only 80%. The prepared solid manganese sulfate did not meet the standard of battery-grade manganese sulfate.

[0101] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud, characterized in that, Includes the following steps: S1: Pre-treat the zinc electrowinning anode mud, add sulfuric acid, stir and mix, and continuously pass SO2 gas to carry out a reduction leaching reaction, and filter to obtain the filtrate; S2: Adjust the pH value of the filtrate and filter it. Then transfer the secondary filtrate to the middle chamber of the double-membrane three-chamber electrolytic cell and add salt solution to the corresponding anode and cathode chambers. S3: Place the corresponding anode and cathode plates into a double-membrane three-chamber electrolytic cell for electrolysis; The initial electrolysis uses high current electrolysis, and when gas begins to be generated, low current electrolysis is used. The pH value of the solution in the cathode chamber is continuously monitored, and electrolysis is stopped when the pH reaches a certain value. S4: After electrolysis, the solution in the cathode chamber is filtered and separated. The resulting filter residue is reacted with sulfuric acid solution, concentrated, crystallized, filtered and dried to obtain high-purity battery-grade manganese sulfate.

2. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S1, the pretreatment process includes sequential washing, drying, and ball milling, wherein the drying temperature is 100-120℃; the pretreatment process also includes sieving of zinc electrowinning anode mud particles with a particle size between 100 and 300 mesh.

3. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S1, the sulfuric acid concentration is 10-50 g / L; the liquid-solid ratio of sulfuric acid to zinc electrowinning anode mud is 5-50 mL / g; and the amount of SO2 gas introduced is 1.1-2.0 times the theoretical reaction amount.

4. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S1, the reaction time is 6–12 h and the reaction temperature is 15–60 °C.

5. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S2, the structure of the double-membrane three-chamber electrolyzer from left to right is: anode plate - anion exchange membrane - cation exchange membrane - cathode plate.

6. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S2, the pH of the filtrate is 7.0, and the substance added to adjust the pH is any one of manganese hydroxide, sodium hydroxide, and potassium hydroxide; the salt solution is at least one of sodium sulfate and potassium sulfate.

7. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S3, the anode plate is either a lead-based anode or a titanium-based anode; the cathode plate is either an aluminum plate or a stainless steel plate.

8. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S3, the cathode current density is controlled at 8–12 mA / cm². 2 The cathode current density is controlled between 0.2 and 1.2 mA / cm². 2 Electrolysis is stopped when the pH value of the solution in the cathode chamber reaches 10.0 to 10.

2.

9. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, In step S4, the concentration and crystallization temperature is 90–95°C, and the drying temperature is 100–120°C.

10. The method for preparing battery-grade manganese sulfate from electrolytic zinc electrodeposition anode mud according to claim 1, characterized in that, The battery-grade manganese sulfate has a purity of up to 99.5%.

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