Method for preparing high-purity manganese sulfate solution by electrochemical deep purification and magnesium removal

Abstract

The application provides a method for preparing high-purity manganese sulfate solution by electrochemical deep purification and magnesium removal, and belongs to the technical field of extraction metallurgy, and comprises the following steps: manganese-magnesium purification and separation are carried out in a double-chamber diaphragm electrolytic cell, a current collector loaded with magnesium-lean ion sieve is inserted into a purification chamber as a cathode and is discharged into a manganese sulfate solution containing magnesium, a current collector loaded with magnesium-rich ion sieve is inserted into an enrichment chamber as an anode and is discharged into a supporting electrolyte, and an anion exchange membrane is used for separation; direct current is input between the electrodes, under the driving of an external electric potential, Mg 2+ in the purification chamber is embedded into the magnesium-lean ion sieve, magnesium in the magnesium-rich ion sieve is removed in the form of ions and enters the supporting electrolyte; after one charging and discharging is completed, the relative positions of the electrodes are exchanged, direct current is input, and the next cycle is started, and finally, high-purity manganese sulfate solution is obtained. The application has the continuity and stability of a chemical method, no impurity elements are introduced in the preparation process, no waste residue is generated, and the application has the advantages of simple operation, stable operation, environmental friendliness, and economic feasibility.

Description

Technical Field

[0001] This invention relates to the field of metallurgical extraction technology, and in particular to a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification to remove magnesium. Background Technology

[0002] High-purity MnSO4, as an important trace chemical substance, is widely used as a precursor in the synthesis of ternary cathode materials, lithium manganese oxide, and lithium-rich manganese-based cathode materials. With the expansion of lithium battery applications and the rapid development of electric vehicles, the market demand for high-purity MnSO4 is experiencing explosive growth. Currently, China's annual production capacity of high-purity manganese sulfate exceeds 700,000 tons, and it is poised to become one of the main manganese products in competition among major producers in the future.

[0003] The production of high-purity manganese sulfate generally uses high-grade pyrolusite as the main source, which is reacted with sulfuric acid after high-temperature reduction roasting to produce sulfate; or a two-ore method is used, where pyrolusite, pyrite, and sulfuric acid are mixed in a certain proportion and reacted at a certain temperature to produce manganese sulfate; or electrolytic metallic manganese is used as raw material, dissolved in sulfuric acid, and then high-purity manganese sulfate is obtained through settling, sedimentation, filtration, and concentration. All of these processes suffer from high energy consumption, high raw material prices, high costs, and poor economic efficiency. To further reduce costs, most companies use rhodochrosite as the manganese source, which is acidically leached and impurity removed to produce an industrial-grade MnSO4 solution, which is then further purified to produce high-purity MnSO4·H2O. Due to different impurity removal processes, the quality of high-purity MnSO4 varies. Most commercially available products contain approximately 100 ppm of Ca and Mg. This is closely related to the mineralization environment and geological characteristics of manganese ore resources in my country. Rhodochrosite often coexists with carbonate minerals such as calcite, magnesite, and siderite. They have similar crystal structures, and Mn atoms in the crystal lattice often substitute for Ca and Mg, forming isomorphous structures. However, low-grade manganese ore contains up to 2000 μg / g of calcium and magnesium, and the content of impurities such as Ca and Mg in the prepared manganese sulfate solution generally exceeds the standard, failing to meet the requirements for preparing battery-grade high-purity manganese sulfate.

[0004] Currently, the deep purification process for manganese sulfate solution includes: 1) adding MnO2 to industrial-grade MnSO4 solution to remove iron; 2) adding a sulfiding agent to the filtrate to remove heavy metals; 3) adding a fluoridating agent to the solution to remove magnesium and calcium; and 4) using extraction to remove free fluoride from the solution to obtain a high-purity manganese sulfate solution. This process is cumbersome, requiring the addition of organic reagents during extraction. The fluorination method consumes a large amount of high-purity purifying agent, easily leading to excessive F- content. Residual F- in the solution affects the synthesis of cathode material precursors; the fluoride content in high-purity MnSO4·H2O needs to be below 100 ppm. Furthermore, the MgF2 generated in the solution easily forms colloids, making filtration difficult or even impossible. Simultaneously, excessively high F content can corrode equipment, causing numerous inconveniences to production.

[0005] To date, methods for removing Ca and heavy metals from MnSO4 solutions are quite mature. However, the separation of manganese and magnesium has remained a technical challenge in the production of high-purity MnSO4·H2O. Conventional purification processes cannot meet the quality requirements of high-end lithium battery cathode material manufacturers abroad. Most methods are optimizations of existing processes, and original and disruptive research results are almost non-existent, seriously hindering the sustainable development of the high-purity MnSO4 industry. Therefore, developing a low-cost, pollution-free electrochemical separation technology to achieve deep purification of magnesium impurities in MnSO4 solutions is of significant practical importance. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for electrochemical deep purification and magnesium removal to prepare a high-purity sulfur-manganese solution, involving the application of anion exchange membranes to Mn. 2+ Mg 2+ Under the obstruction of MnO2, the magnesium in industrial-grade manganese sulfate solution is deeply purified by cyclic de-intercalation / intercalation of MnO2-based complex ion sieves. This method combines the continuity and stability of chemical methods, introduces no impurity elements and generates no waste residue during the preparation process, and has the technical advantages of simple operation, stable operation, environmental friendliness and economic feasibility. The high-purity manganese sulfate solution obtained meets the magnesium ion content requirements for battery-grade raw material production.

[0007] To achieve the above objectives, the present invention provides the following solution: a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal, wherein the manganese-magnesium purification and separation is carried out in a dual-chamber membrane electrolytic cell, comprising the following steps:

[0008] S1. Preliminary preparation: The dual-chamber membrane electrolyzer includes a purification chamber and an enrichment chamber. The industrial-grade MnSO4 solution to be purified and the supporting electrolyte are added to the purification chamber and the enrichment chamber respectively, and separated by anion exchange membrane.

[0009] S2. Electrode construction: The current collector loaded with magnesium-poor MnO2-based composite ion sieve is inserted into the purification chamber as the cathode, and the current collector loaded with magnesium-rich MnO2-based composite ion sieve is inserted into the enrichment chamber as the anode, and the cathode and anode are arranged in parallel.

[0010] S3. Electrolysis: Apply a stable direct current between the cathode and the anode, dynamically monitor the potential of the two electrodes, and complete the cathode discharge and anode charging.

[0011] S4. After completing step S3, remove the two electrodes simultaneously and swap their relative positions. Then, apply a stable direct current between the two electrodes and dynamically monitor the electrode potential until both the cathode and anode have completed one charge / discharge cycle.

[0012] S5. Repeat steps S2 to S4 to finally obtain a high-purity sulfur-manganese solution.

[0013] Furthermore, in step S1, the industrial-grade MnSO4 solution to be purified needs to undergo heavy metal removal treatment before being added to the purification chamber. 2+ The concentration is 50-150 g / L, Mg 2+ The concentration of sodium sulfate is 0–1000 mg / L, and the supporting electrolyte is sodium sulfate with a concentration of 5–30 g / L.

[0014] Furthermore, after adding the industrial-grade MnSO4 solution to be purified into the purification chamber, the pH of the solution is adjusted to 4.0–7.0, and then heated to 20°C–50°C.

[0015] Further, in step S2, MnO2-based composite and polyvinylidene fluoride are added to N-methylpyrrolidone in a mass ratio of 9:1 to form a slurry, which is then uniformly loaded onto the current collector and dried. After repeating the operation 3 to 10 times, a current collector loaded with magnesium-poor MnO2-based composite ion sieve is finally obtained.

[0016] Furthermore, the MnO2-based composite ion sieve is an MnO2-based composite grown in situ on the surface of a ternary MAX phase layered compound. The structural characteristics of the MnO2 are one of layered, tunnel-pore, and spinel structures. The ternary MAX phase layered compound is one of Ti2AlC, Ti3AlC2, Ti3SiC2, Ti2SiC, and Mo3AlC2.

[0017] Furthermore, the current collector is one of the following: a flat plate, foil, mesh, porous foam, or hydrophilic carbon cloth made of carbon, aluminum, nickel, platinum, stainless steel, titanium and titanium-based coatings, lead and lead alloys.

[0018] Furthermore, in step S3, after applying a stable direct current between the two electrodes, the cathode begins to discharge under the drive of the external potential, and the Mg in the purification chamber... 2+ The cathode is embedded, and the cathode is transformed from a magnesium-poor ion sieve to a magnesium-rich ion sieve.

[0019] As the anode begins to charge, magnesium in the enrichment chamber is released from the anode in ionic form, and the anode changes from a magnesium-rich ion sieve to a magnesium-poor ion sieve.

[0020] Furthermore, the cathode discharge current density is 0.05 to 0.15 A / g, discharging to -0.4V to -1.0V; the anode charging current density is 0.05 to 0.15 A / g, charging to 0.6V to 1.2V.

[0021] Furthermore, in step S4, after swapping the relative positions of the two electrodes, the current density of the cathode discharge is 0.05 to 0.15 A / g, discharging to -0.4V to -1.0V; the current density of the anode charge is 0.05 to 0.15 A / g, charging to 0.6V to 1.2V.

[0022] Furthermore, in step S5, if Mg in the cleanroom... 2+ The concentration of the solution is no more than 50 ppm. The solution in the purification chamber is drained and replaced with industrial-grade MnSO4 solution to be purified. At the same time, an equal volume of solution in the enrichment chamber is drained and replaced with the same volume of supporting electrolyte, and finally a high-purity sulfur-manganese solution is obtained.

[0023] According to the specific technical solution provided by the present invention, compared with the prior art, the present invention discloses the following technical effects:

[0024] (1) The method provided by the present invention achieves the separation of manganese and magnesium in magnesium-containing solutions without adding any reagents, effectively preventing the loss of manganese sulfate; and achieves deep purification of impurity magnesium in manganese sulfate solutions without adding fluorinating agents, without generating secondary pollution.

[0025] (2) The MnO2-based composite ion sieve provided by this invention has the advantages of simple preparation and environmental friendliness; the synergistic effect of the ternary MAX phase and MnO2 can ensure rapid electron transport and Mg 2+ Rapid deintercalation / intercalation; the pseudocapacitive properties of the MnO2-based composite ion sieve can adsorb residual heavy metal impurities in the solution while discharging, reducing the pressure of purification and impurity removal and improving production efficiency.

[0026] (3) The high-purity sulfur-manganese solution prepared by the present invention can be directly sent to the concentration stage to prepare high-purity MnSO4·H2O products, which omits the extraction and defluorination step in the traditional process and avoids organic matter from entering the system.

[0027] (4) The high-purity manganese sulfate solution obtained by this invention meets the magnesium content requirements for battery-grade raw material production, and can also be adjusted according to the magnesium content requirements of the end product. 2+ The concentration requirement further reduces the Mg content in the purification solution. 2+ This concentration lays the foundation for the further development and utilization of magnesium resources in ores. Attached Figure Description

[0028] 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.

[0029] Figure 1 This invention provides a method flow chart for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal.

[0030] Figure 2 This is a high-magnification transmission image of the composite-doped manganese oxide coating provided in Embodiment 1 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0032] like Figure 1 As shown, this invention provides a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal. The manganese-magnesium purification and separation is carried out in a dual-chamber membrane electrolytic cell, and includes the following steps:

[0033] S1. Preliminary preparation: The dual-chamber membrane electrolyzer includes a purification chamber and an enrichment chamber. The industrial-grade MnSO4 solution to be purified and the supporting electrolyte are added to the purification chamber and the enrichment chamber respectively, and separated by anion exchange membrane.

[0034] The industrial-grade MnSO4 solution to be purified needs to undergo heavy metal removal treatment before being added to the purification chamber. 2+ The concentration is 50-150 g / L, Mg 2+ The concentration of Mn is 0–1000 mg / L, and the supporting electrolyte is sodium sulfate with a concentration of 5–30 g / L. 2+ The concentration is 100 g / L, Mg 2+ The concentration is 300 mg / L.

[0035] After the industrial-grade MnSO4 solution to be purified is added to the purification chamber, the pH of the solution is adjusted to 4.0–7.0, and then heated to 20°C–50°C. The pH of the solution in the purification chamber is preferably 7.0. The purification chamber and the enrichment chamber are separated by any one of the following anion exchange membranes: CMI-7001, AMI-7001S, and AMX. The membrane's surface groups impede the shuttle movement of Mn²⁺ and Mg²⁺ between the two chambers. The AMX anion exchange membrane is preferred.

[0036] S2. Electrode construction: The current collector loaded with magnesium-poor MnO2-based composite ion sieve is inserted into the purification chamber as the cathode, and the current collector loaded with magnesium-rich MnO2-based composite ion sieve is inserted into the enrichment chamber as the anode, and the cathode and anode are arranged in parallel.

[0037] In this process, MnO2-based composite and polyvinylidene fluoride are added to N-methylpyrrolidone at a mass ratio of 9:1 to form a slurry, which is then uniformly loaded onto the current collector and dried. After repeating this process 3 to 10 times, a current collector loaded with magnesium-poor MnO2-based composite ion sieve is finally obtained.

[0038] The MnO2-based composite ion sieve is a MnO2-based composite grown in situ on the surface of a ternary MAX phase layered compound. The MnO2 has a structural characteristic of one of the following: layered, tunneled, or spinel structure, preferably a 2×2 α-type tunnel structure. The ternary MAX phase layered compound is one of Ti2AlC, Ti3AlC2, Ti3SiC2, Ti2SiC, or Mo3AlC2, preferably Ti3AlC2.

[0039] The current collector is one of the following: a flat plate, foil, mesh, porous foam, or hydrophilic carbon cloth made of carbon, aluminum, nickel, platinum, stainless steel, titanium and titanium-based coatings, lead and lead alloys, with hydrophilic carbon cloth being preferred.

[0040] S3. Electrolysis: Apply a stable direct current between the cathode and the anode, dynamically monitor the potential of the two electrodes, and complete the cathode discharge and anode charging.

[0041] In this process, after a stable direct current is applied between the two electrodes, the cathode begins to discharge under the drive of the external potential, and the Mg in the cleanroom... 2+ The cathode is embedded, and the cathode is transformed from a magnesium-poor ion sieve to a magnesium-rich ion sieve.

[0042] As the anode begins to charge, magnesium in the enrichment chamber is released from the anode in ionic form, and the anode changes from a magnesium-rich ion sieve to a magnesium-poor ion sieve.

[0043] The cathode discharge current density is 0.05 to 0.15 A / g, discharging to -0.4V to -1.0V; the anode charging current density is 0.05 to 0.15 A / g, preferably 0.1 A / g, charging to 0.6V to 1.2V.

[0044] S4. After completing step S3, remove the two electrodes simultaneously and swap their relative positions. Then, apply a stable direct current between the two electrodes and dynamically monitor the electrode potential until both the cathode and anode have completed one charge / discharge cycle.

[0045] In this process, after swapping the relative positions of the two electrodes, the current density of the cathode discharge is 0.05 to 0.15 A / g, discharging to -0.4 V to -1.0 V; the current density of the anode charge is 0.05 to 0.15 A / g, charging to 0.6 V to 1.2 V.

[0046] S5. Repeat steps S2 to S4 to finally obtain a high-purity sulfur-manganese solution;

[0047] Among them, if Mg in the clean room 2+ The concentration of the solution is no more than 50 ppm. The solution in the purification chamber is drained and replaced with industrial-grade MnSO4 solution to be purified. At the same time, an equal volume of solution in the enrichment chamber is drained and replaced with the same volume of supporting electrolyte, and finally a high-purity sulfur-manganese solution is obtained.

[0048] In the above technical solution, Mg 2+ The amount of extraction and insertion in the ion sieve is related to the loading of the MnO2-based composite per unit area on the current collector and the crystal structure of MnO2. Loading more oxides can improve the magnesium storage capacity of the electrode material. Optimizing the efficient loading of MnO2 in ternary MAX phase layered compounds can also increase the specific capacity and cycle stability of the material.

[0049] To make the objectives, features, and advantages of this invention more apparent and understandable, the invention will be further described in detail below with reference to specific embodiments.

[0050] Example 1

[0051] In this embodiment, a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification to remove magnesium includes the following steps:

[0052] Step 1: Pretreatment of the current collector: Using a stainless steel mesh substrate, place the stainless steel mesh in a beaker containing a certain amount of acetone and sonicate for 30 minutes to wash away the residual oil on the surface of the stainless steel mesh. Then wash it with ethanol 2-3 times, and then repeatedly sonicate it with deionized water to remove excess acetone and ethanol. After thoroughly cleaning, place it in a vacuum drying oven at 60°C and dry overnight. After drying, weigh each piece of stainless steel mesh for later use.

[0053] Step 2: Prepare Mxene@MnO2 composite material using a hydrothermal method. Weigh 30 mg of monolayer Mxene and dissolve it in 20 ml of deionized water, then sonicate for 1 h to ensure uniform dispersion. Add 0.025 mol / L... -1 MnSO4 and 0.15 mol / L -1 KMnO4 was dissolved in 40 ml of deionized water and magnetically stirred for 10 min to ensure uniform dispersion. Then, the KMnO4 solution was slowly added dropwise to the MnSO4 solution under magnetic stirring. After thorough mixing, Mxene solution was added and stirred for 1 h. Finally, the mixture was transferred to a hydrothermal reactor and reacted at 160 °C for 12 h under hydrothermal conditions. After the reaction was complete, the mixture was cooled to room temperature and centrifuged to obtain the precipitate, which was then dried overnight at 60 °C to obtain the Mxene@MnO2 composite material.

[0054] Step 3: Mix and grind the Mxene@MnO2 composite material obtained in Step 2, acetylene black, and polyvinylidene fluoride in a mass ratio of 8:1:1. Add N-methylpyrrolidone solvent to form a slurry. Coat the slurry evenly with a scraper onto the stainless steel mesh obtained in Step 1. Place the slurry in a vacuum drying oven at 60°C for 24 hours to obtain the Mxene@MnO2 electrode sheet.

[0055] Step four, manganese-magnesium purification and separation, is carried out in a dual-chamber membrane electrolytic cell. The electrolytic cell is divided into a purification chamber and an enrichment chamber by an anion exchange membrane. The purification chamber contains an industrial-grade MnSO4 solution after heavy metal removal, and the supporting electrolyte is sodium sulfate with a concentration of 20 g / L. The electrode obtained in step three is inserted into the purification chamber as the cathode, and the current collector loaded with a magnesium-rich MnO2-based composite ion sieve is inserted into the enrichment chamber as the anode, with the cathode and anode arranged in parallel. A constant current power supply is then applied between the two electrodes. Driven by the external potential, Mg... 2+ The electrode material embedded in the cleanroom is eventually transformed into a magnesium-rich ion sieve. Magnesium in the anode material is desorbed in ionic form and eventually transformed into a magnesium-poor ion sieve. The dynamic potential is monitored in real time to ensure that magnesium ions can be embedded at the cathode and desorbed at the anode. After the reaction is completed, the electrodes are reversed, and the dynamic potential is monitored in real time until both the cathode and anode have completed one charge-discharge cycle.

[0056] Using the preparation method provided in this embodiment, the obtained composite-doped manganese oxide coating was subjected to high-magnification transmission to obtain, as shown in the figure. Figure 2 The results are shown.

[0057] Example 2

[0058] In this embodiment, a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification to remove magnesium includes the following steps:

[0059] Step 1: Pretreatment of the current collector: Using carbon cloth as the substrate, immerse the carbon cloth in a beaker containing a certain amount of acetone for 30 minutes, then repeatedly ultrasonically clean it 3 times, 10 minutes each time, to remove the residual oil on the surface of the carbon cloth. Then, repeatedly ultrasonically clean it with deionized water to remove excess acetone. After thoroughly cleaning, place it in a vacuum drying oven at 80°C for 12 hours. After drying, weigh each piece of carbon cloth for later use.

[0060] Step 2: Synthesis of Mxene / MnO2 composite material via self-assembly. First, MnO2 samples were synthesized using a hydrothermal method. 36 mmol KMnO4 was dissolved in 100 mL of water, and 6 mmol MnSO4 was dissolved in 25 mL of water. Under continuous magnetic stirring, the KMnO4 solution was added dropwise to the MnSO4 solution for 30 min. The mixed solution was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and heated at 180 °C for 12 h. After the reaction was complete, the mixture was filtered and washed several times with ethanol and deionized water. Finally, it was dried overnight at 60 °C to obtain the MnO2 sample.

[0061] 0.03 g of Ti3C2Tx powder was dissolved in 40 ml of DMSO solution and sonicated for 30 min to homogenize it. Then, 0.03 g of the prepared MnO2 sample was slowly added, and the mixture was first stirred for 3 h to form a homogeneous solution, followed by sonication for 3 h. The precipitate was then obtained by centrifugation and washed several times alternately with ethanol and deionized water. Finally, it was dried overnight at 60 °C to obtain Mxene / MnO2.

[0062] Step 3: Mix and grind the Mxene / MnO2 composite material obtained in Step 2, acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, add N-methylpyrrolidone solvent to form a slurry, coat it evenly on the carbon cloth obtained in Step 1 with a scraper, and place it in a vacuum drying oven at 60°C for 24 hours to obtain the Mxene / MnO2 electrode sheet.

[0063] Step 4: Divide the electrolytic cell into a purification chamber and an enrichment chamber using an anion exchange membrane. The purification chamber contains an industrial-grade MnSO4 solution after heavy metal removal, and the supporting electrolyte is sodium sulfate with a concentration of 20 g / L. Insert the electrode obtained in Step 3 into the purification chamber as the cathode, and insert the current collector loaded with a magnesium-rich MnO2-based composite ion sieve into the enrichment chamber as the anode, with the cathode and anode arranged in parallel. Then, apply a constant current power supply between the two electrodes, and monitor the dynamic potential in real time under the drive of the external potential to ensure the Mg... 2+ The electrode material embedded in the cleanroom is eventually transformed into a magnesium-rich ion sieve, while the magnesium in the anode material is desorbed in ionic form and eventually transformed into a magnesium-poor ion sieve. After the reaction is complete, the electrodes are reversed, and the same method is used until both the cathode and anode have completed one charge-discharge cycle.

[0064] Example 3

[0065] In this embodiment, a method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification to remove magnesium includes the following steps:

[0066] Step 1: Pretreatment of the current collector: Using carbon cloth as the substrate, immerse the carbon cloth in a beaker containing a certain amount of acetone for 30 minutes, then repeatedly ultrasonically clean it 3 times, 10 minutes each time, to remove the residual oil on the surface of the carbon cloth. Then, repeatedly ultrasonically clean it with deionized water to remove excess acetone. After thoroughly cleaning, place it in a vacuum drying oven at 80℃ for 12 hours. After drying, weigh each piece of carbon cloth for later use.

[0067] Step 2: In-situ oxidation method for synthesizing Mx / MnO2. 100 mg of prepared Ti3C2Tx nanosheets were dispersed in 50 mL of deionized water and sonicated for 1 h to form a uniform black suspension. Then, 250 mL of 5 mM KMnO4 solution was rapidly added. Subsequently, the mixture was stirred at room temperature for 54 h. During the reaction, the color of the mixture gradually changed from purple to brownish-yellow, indicating that KMnO4 was gradually reduced by carbon atoms. After the reaction, the mixture was washed alternately by centrifugation with deionized water and ethanol, and finally dried at 60 °C to obtain Mx / MnO2.

[0068] Step 3: Mix and grind the Mx / MnO2 composite material obtained in Step 2, acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, add N-methylpyrrolidone solvent to form a slurry, coat it evenly on the carbon cloth obtained in Step 1 with a scraper, and dry it overnight at 60°C in a vacuum drying oven to obtain the Mx / MnO2 electrode sheet.

[0069] Step 4: Divide the electrolytic cell into a purification chamber and an enrichment chamber using an anion exchange membrane. The purification chamber contains an industrial-grade MnSO4 solution after heavy metal removal, and the supporting electrolyte is sodium sulfate with a concentration of 20 g / L. Insert the electrode obtained in Step 3 into the purification chamber as the cathode, and insert the current collector loaded with a magnesium-rich MnO2-based composite ion sieve into the enrichment chamber as the anode, with the cathode and anode arranged in parallel. Then, apply a constant current power supply between the two electrodes, and monitor the dynamic potential in real time under the drive of the external potential to ensure the Mg... 2+ The electrode material embedded in the cleanroom is eventually transformed into a magnesium-rich ion sieve, while the magnesium in the anode material is desorbed in ionic form and eventually transformed into a magnesium-poor ion sieve. After the reaction is complete, the electrodes are reversed, and the same method is used until both the cathode and anode have completed one charge-discharge cycle.

[0070] By investigating the cyclic process of Examples 1-3, the Mg released in the enrichment chamber was detected. 2+ Content, calculation of the effect of MnO2 loaded on Mg in ternary MAX phase layered compounds. 2+ The amount of material removed is shown in Table 1.

[0071] Table 1 Mg in the supporting electrolyte 2+ Content and materials for Mg 2+ Removal amount

[0072]

[0073] By comparing the electrodes of Examples 1-3 in Table 1, it can be seen that as the number of cycles increases, the Mg content in the enrichment chamber decreases. 2+ The concentration was continuously increasing, and the addition of Mxene as a layered compound could improve the stability of the electrode. After each cycle in Examples 1-3, Mg 2+ The removal rates were relatively stable, therefore Mxene can extend the electrode's lifespan. Table 1 shows the effect of the electrode in Example 1 on Mg removal. 2+ The method achieves better removal efficiency, with the electrode unit of Example 1 exhibiting the highest removal rate. This method can effectively separate magnesium ions from industrial-grade MnSO4, improving the purity of MnSO4 and enabling its wider application.

[0074] Therefore, this invention employs the above-mentioned method for electrochemical deep purification and magnesium removal to prepare a high-purity sulfur-manganese solution, using an anion exchange membrane for Mn... 2+ Mg 2+ Under the obstruction of MnO2, the magnesium in industrial-grade manganese sulfate solution is deeply purified by cyclic de-intercalation / intercalation of MnO2-based complex ion sieves. This method combines the continuity and stability of chemical methods, introduces no impurity elements and generates no waste residue during the preparation process, and has the technical advantages of simple operation, stable operation, environmental friendliness and economic feasibility. The high-purity manganese sulfate solution obtained meets the magnesium ion content requirements for battery-grade raw material production.

[0075] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0076] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal, characterized in that, The purification and separation of manganese and magnesium is carried out in a dual-chamber membrane electrolyzer, including the following steps: S1. Preliminary preparation: The dual-chamber membrane electrolyzer includes a purification chamber and an enrichment chamber. The industrial-grade MnSO4 solution to be purified and the supporting electrolyte are added to the purification chamber and the enrichment chamber respectively, and separated by anion exchange membrane. S2. Electrode construction: The current collector loaded with magnesium-poor MnO2-based composite ion sieve is inserted into the purification chamber as the cathode, and the current collector loaded with magnesium-rich MnO2-based composite ion sieve is inserted into the enrichment chamber as the anode, and the cathode and anode are arranged in parallel. In this process, MnO2-based composite and polyvinylidene fluoride are mixed with N-methylpyrrolidone at a mass ratio of 9:1 to form a slurry, which is then uniformly loaded onto a current collector and dried. This process is repeated 3 to 10 times to finally obtain a current collector for a magnesium-poor MnO2-based composite ion sieve. The MnO2-based composite ion sieve is an MnO2-based composite grown in situ on the surface of a ternary MAX phase layered compound. The structural characteristics of the MnO2 are one of layered, tunnel-pore, or spinel structures. The ternary MAX phase layered compound is one of Ti2AlC, Ti3AlC2, Ti3SiC2, Ti2SiC, or Mo3AlC2. S3. Electrolysis: Apply a stable direct current between the cathode and the anode, dynamically monitor the potential of the two electrodes, and complete the cathode discharge and anode charging. S4. After completing step S3, remove the two electrodes simultaneously and swap their relative positions. Then, apply a stable direct current between the two electrodes and dynamically monitor the electrode potential until both the cathode and anode have completed one charge / discharge cycle. S5. Repeat steps S2 to S4 to finally obtain a high-purity sulfur-manganese solution.

2. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 1, characterized in that, In step S1, the industrial-grade MnSO4 solution to be purified needs to undergo heavy metal removal treatment before being added to the purification chamber. 2+ The concentration is 50~150g / L, Mg 2+ The concentration of the electrolyte is 0~1000mg / L, and the supporting electrolyte is sodium sulfate with a concentration of 5~30g / L.

3. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 2, characterized in that, After the industrial-grade MnSO4 solution to be purified is added to the purification chamber, the pH of the solution is adjusted to 4.0~7.0, and then heated to 20℃~50℃.

4. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 1, characterized in that, The current collector is one of the following: a flat plate, foil, mesh, porous foam, or hydrophilic carbon cloth made of carbon, aluminum, nickel, platinum, stainless steel, titanium and titanium-based coatings, lead and lead alloys.

5. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 1, characterized in that, In step S3, after a stable direct current is applied between the two electrodes, the cathode begins to discharge under the drive of the external potential, and the Mg in the purification chamber... 2+ The cathode is embedded, and the cathode is transformed from a magnesium-poor ion sieve to a magnesium-rich ion sieve. As the anode begins to charge, magnesium in the enrichment chamber is released from the anode in ionic form, and the anode changes from a magnesium-rich ion sieve to a magnesium-poor ion sieve.

6. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 5, characterized in that, The cathode discharge current density is 0.05~0.15A / g, discharging to -0.4V~-1.0V; the anode charging current density is 0.05~0.15A / g, charging to 0.6V~1.2V.

7. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 1, characterized in that, In step S4, after swapping the relative positions of the two electrodes, the cathode discharge current density is 0.05~0.15A / g, discharging to -0.4V~-1.0V; the anode charging current density is 0.05~0.15A / g, charging to 0.6V~1.2V.

8. The method for preparing a high-purity sulfur-manganese solution through electrochemical deep purification and magnesium removal according to claim 1, characterized in that, In step S5, if Mg in the cleanroom 2+ The concentration of the solution is no more than 50 ppm. The solution in the purification chamber is drained and replaced with industrial-grade MnSO4 solution to be purified. At the same time, an equal volume of solution in the enrichment chamber is drained and replaced with the same volume of supporting electrolyte, and finally a high-purity sulfur-manganese solution is obtained.

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