Method for purifying high-purity manganese sulfate electrode material and application

Abstract

The invention provides a method for purifying an electrode material of high-purity manganese sulfate and application, and belongs to the technical field of extraction metallurgy. Comprising the following steps: depositing manganese dioxide on a carbon fiber substrate through constant current deposition at different temperatures by using a solution containing 40g / L Mn < 2 + > and 40g / L sulfuric acid. The deposited manganese dioxide and carbon fiber substrate composite material is applied to a manganese sulfate solution, and magnesium ions are selectively removed through an electrochemical deintercalation method. In a double-chamber diaphragm electrolytic cell, the impurity magnesium is adsorbed and extracted by taking electro-deposited manganese dioxide as a cathode, an inert conductive counter electrode as an anode and a manganese sulfate solution as an electrolyte. And after the magnesium is adsorbed to be saturated, electrolyzing by taking the electro-deposited manganese dioxide as an anode, an inert conductive counter electrode as a cathode and sodium sulfate as a recovery solution to desorb and recover the magnesium, and finally purifying the manganese sulfate solution through the adsorption and desorption processes of the electro-deposited manganese dioxide.

Description

Technical Field

[0001] The invention belongs to the technical field of extractive metallurgy, and in particular relates to a method for purifying electrode materials of high-purity manganese sulfate and its application. Background Art

[0002] In recent years, with the rapid development of the new energy and battery industries, demand for battery-grade manganese sulfate has continued to increase. While the technology for removing impurities such as potassium, sodium, and heavy metals during the production process is highly mature and efficient, the removal of calcium and magnesium still faces multiple challenges, including limited experimental conditions, high energy consumption, and the presence of fluorine. Rhodochrosite is the primary manganese ore type in my country, and the impurity content of its MnSO4 determines its application range. During the acid leaching process of rhodochrosite, a large number of soluble impurity ions such as potassium, sodium, calcium, magnesium, cobalt, nickel, and iron enter the MnSO4 solution. Therefore, current processes use a multi-step combined purification and impurity removal process, treating the impurity ions according to their different properties to ultimately produce a high-purity MnSO4 solution. Therefore, it is of great significance to strengthen research on the direct acid leaching process of rhodochrosite, impurity removal of the leachate, and preparation of manganese sulfate, and to develop an efficient, green, and economically viable method for removing calcium and magnesium ions. This will not only fully utilize my country's abundant low-grade manganese ore resources but also promote the development of the lithium battery industry.

[0003] There have been many studies and reports on the removal of calcium and magnesium at home and abroad, mainly including recrystallization, electrolysis, extraction, chemical precipitation, etc. The recrystallization method mainly uses the different solubility of MnSO4 and MgSO4 to achieve the purpose of purification. The recrystallization method is effective at a crystallization rate of 25%, a heating temperature of 130℃, and a stirring speed of 700r∙min. -1 Under the process conditions, the impurity removal rate of manganese sulfate reaches more than 77.95%. This method is simple to operate and has few steps, but it consumes a lot of energy and has high requirements on equipment. The extraction method is to use an extractant to extract Mg 2+ Extraction separation, but the extractant has an adverse effect on the properties of the solution, requires multi-stage extraction, low utilization rate of the extract, and complex stripping process. Chemical precipitation method uses the different solubility products of different ionic compounds to make chemical reagents and Mg 2+ The reaction generates an insoluble precipitate, achieving the purpose of impurity removal. Commonly used reagents include fluoride, carbonate, etc. The carbonate precipitation method can achieve the advantages of separating magnesium more than 98% under the best conditions, without introducing impurities other than other impurity ions, and can effectively precipitate manganese from sulfate solution. The carbonization manganese precipitation method is used to remove magnesium ions from manganese sulfate solution. Using CO2 as a carbonizing agent, Mn in manganese sulfate solution is 2+It is separated from the original solution in the form of manganese carbonate precipitate, and then the precipitate is dissolved with sulfuric acid to achieve the goal of impurity removal. However, the obtained manganese carbonate is solid, and the obtained manganese carbonate solid must be re-dissolved with sulfuric acid later, which consumes a lot of acid. Although the fluoride precipitation method has a good separation effect, the fluoride precipitate is colloidal and has extremely poor filterability. It also requires the addition of 2-3 times the theoretical amount of fluoride, and a defluorination process is required later. Using carbonate as a precipitant not only has a low calcium and magnesium removal rate, but also causes some manganese loss.

[0004] Lean rhodochrosite differs from imported pyrolusite in its high magnesium content, making it a key component of the purification and impurity removal process in rhodochrosite leachates. Magnesium removal accounts for over 70% of the total impurity removal cost. Currently, rhodochrosite leachates are purified and impurity-removed using a multi-step process. This process involves potassium removal using jarosite, iron removal using sodium oxidation neutralization, heavy metal removal using aluminum sulfide, calcium removal using fluoride salts, and fluoride removal using magnesium extraction. However, this process suffers from lengthy processes, complex operations, and time-consuming operations. Therefore, developing efficient, low-cost, and short-term purification and impurity removal processes is a key development direction for high-purity MnSO₄ in Traditional Chinese Medicine. Summary of the Invention

[0005] The present invention aims to address the shortcomings of the aforementioned prior art by providing a method and application for purifying high-purity manganese sulfate electrode materials. The present invention utilizes electrodeposition to prepare a composite material of manganese dioxide and a conductive substrate, addressing the common difficulty in separating magnesium and manganese in manganese sulfate solutions. This reduces the loss of valuable manganese resources and avoids secondary pollution.

[0006] The present invention adopts the following technical solutions: A method for purifying high-purity manganese sulfate electrode material comprises the following steps: Step (1). Hydrophilic treatment of carbon cloth: Vapor phase heat treatment oxidation is one of the common methods to activate the reactivity of raw carbon cloth and improve its hydrophilicity. Calcination of raw carbon cloth in air atmosphere not only increases the surface area, but also produces oxygen-containing functional groups on the surface of the carbon cloth, improving the surface wettability and facilitating the deposition of manganese dioxide.

[0007] Step (2). Carbon cloth pretreatment: Place the calcined carbon cloth in a beaker containing a certain amount of acetone and perform ultrasonic treatment to remove surface impurities and oil stains. Then, place it in anhydrous ethanol for ultrasonic cleaning to remove the acetone. Finally, place it in deionized water for cleaning. After cleaning, dry it and cut it into suitable sizes to obtain the pretreated carbon cloth.

[0008] Step (3). Electrodeposition of carbon dioxide: containing 40g / L Mn 2+and 40g / L sulfuric acid solution as the electrolyte; a three-electrode system is used for constant current deposition, and after the deposition is completed, deionized water is used to rinse to remove residual ions on the surface, and finally the film is dried.

[0009] Preferably, the carbon cloth is calcined at a temperature of 450°C in step (1).

[0010] Preferably, the carbon cloth is calcined for 2 hours in step (1).

[0011] Preferably, the immersion in acetone and ultrasonic treatment in step (2) is performed for 15 minutes and three times.

[0012] Preferably, the ultrasonic treatment time of immersing in anhydrous ethanol in step (2) is 15 minutes and the number of times is 3 times.

[0013] Preferably, the ultrasonic cleaning time of immersing in deionized water in step (2) is 25 minutes and the number of times is 5 times.

[0014] Preferably, the drying condition in step (2) is vacuum drying at 80° C. for 12 hours.

[0015] Preferably, the size of the carbon cloth in step (2) is 2×8 cm.

[0016] Preferably, in the three-electrode system in step (3), the graphite electrode is the counter electrode and the saturated calomel electrode is the reference electrode.

[0017] Preferably, the constant current deposition time in step (3) is 1 hour.

[0018] Preferably, the drying condition in step (3) is 50° C. under vacuum conditions for 12 hours.

[0019] Also included is an electrode made by the above method for purifying electrode materials of high-purity manganese sulfate.

[0020] The method for purifying manganese sulfate solution comprises placing a binder-free manganese dioxide electrode prepared by any of the above methods for purifying electrode materials of high-purity manganese sulfate as a cathode in a separation chamber, injecting a manganese sulfate solution purified of heavy metal ions, placing an inert electrode as an anode in an enrichment chamber, injecting Na2SO4 as a supporting electrolyte, and performing cyclic iterative deintercalation / intercalation until the Mg in the separation chamber is reduced to Mg. 2+ Meet the usage standards of high-purity manganese sulfate for electrodes.

[0021] Due to the inherently poor conductivity of manganese dioxide, aged electrodes prepared using traditional slurry coating processes still suffer from poor rate performance and short life in aqueous electrolytes. However, a binder-free manganese dioxide prepared by electrodeposition exhibits significantly high specific capacity, excellent rate performance, and a long service life. This invention provides a new electrode material option for the electrochemical deintercalation method to purify high-purity manganese sulfate.

[0022] Beneficial effects of the present invention: (1) One-step preparation of binder-free manganese dioxide and conductive substrate composite materials.

[0023] (2) Overcome the problems of poor rate performance and short life of aged electrodes prepared by traditional slurry coating process in aqueous electrolytes.

[0024] (3) The binder-free manganese dioxide material prepared by the present invention exhibits excellent electrochemical properties: -1 The specific capacity is 259.5 mAh g -1 . And when the current density reaches 1Ag -1 , it exhibits good rate performance.

[0025] (4) The composite material of deposited manganese dioxide and carbon fiber substrate is applied to manganese sulfate solution, and magnesium ions are selectively removed by electrochemical deintercalation. In a double-chamber diaphragm electrolytic cell, the electrodeposited manganese dioxide is used as the cathode, the inert conductive counter electrode is used as the anode, and the manganese sulfate solution is used as the electrolyte to adsorb and extract the impurity magnesium. When the magnesium adsorption is saturated, the electrodeposited manganese dioxide is used as the anode, the inert conductive counter electrode is used as the cathode, and sodium sulfate is used as the recovery liquid for electrolysis to desorb and recover magnesium. Through the adsorption and desorption process of the electrodeposited manganese dioxide, the manganese sulfate solution is finally purified. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the steps of the present invention; Figure 2 is the XRD pattern of ε-MnO2; Figure 3 This is the XRD pattern of γ-MnO2. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Example 1 (ε-MnO2) like Figure 1 、 Figure 2 As shown, the present invention provides a method for purifying high-purity manganese sulfate electrode materials, comprising the following steps: Step (1). Hydrophilic treatment of carbon cloth Vapor-phase heat treatment oxidation is a common method for activating the reactivity of raw carbon cloth and improving its hydrophilicity. Calcining the raw carbon cloth at 450°C for 2 hours in air increases its surface area and creates oxygen-containing functional groups on the surface, improving surface wettability and facilitating the deposition of manganese dioxide.

[0029] Step (2). Carbon cloth pretreatment The calcined carbon obtained in step (1) was placed in a beaker containing a certain amount of acetone and subjected to repeated ultrasonic treatment for 3 times, each time for 15 minutes, to remove impurities and oil stains on the surface. Then, it was placed in anhydrous ethanol and ultrasonically cleaned 3 times, each time for 15 minutes to remove acetone. Finally, it was placed in deionized water and ultrasonically cleaned 5 times, each time for 25 minutes. After cleaning, it was dried and cut into a size of 2×8 cm to obtain a pretreated carbon cloth.

[0030] Step (3). Electrodeposition of manganese dioxide The pretreated carbon cloth obtained in step (2) was used as the working electrode. 2+ A solution of 40 g / L sulfuric acid was used as the electrolyte, and a three-electrode system was used at room temperature with a flow rate of 3 mA cm -2 The constant current deposition was carried out under the condition of a current density of 100 nm and a deposition time of 1 h. After the deposition, the film was rinsed with deionized water to remove the residual ions on the surface, and finally dried.

[0031] Step (4) Electrochemical deintercalation to remove calcium and magnesium The purification and separation of manganese and magnesium is carried out in a double-chamber diaphragm electrolytic cell. The binder-free manganese dioxide electrode prepared in step (3) is placed in the separation chamber as the cathode, and the manganese sulfate solution that has been purified of heavy metal ions is injected. The inert electrode is placed in the enrichment chamber as the anode, and 0.5M Na2SO4 is injected as the supporting electrolyte. Through the cyclic iterative deintercalation / intercalation of the electrode, the magnesium in the manganese sulfate solution is achieved. 2+ Repeat this process until mg in the separation chamber 2+ Meet the usage standards of battery-grade high-purity manganese sulfate.

[0032] Example 2 Preparation of Electrodeposited Electrode γ-MnO2 like Figure 1 、 Figure 3 As shown, the electrode material for purifying high-purity manganese sulfate of the present invention comprises the following steps: Step (1). Hydrophilic treatment of carbon cloth: Vapor-phase heat treatment oxidation is a commonly used method to activate the reactivity of raw carbon cloth and improve its hydrophilicity. Calcination of the raw carbon cloth at 450°C for 2 hours in an air atmosphere increases the surface area and generates oxygen-containing functional groups on the carbon cloth surface, thereby improving surface wettability and making it more susceptible to the deposition of manganese dioxide.

[0033] Step (2). Carbon cloth pretreatment: Place the carbon cloth calcined in step 1 in a beaker containing a certain amount of acetone and ultrasonically treat it three times for 15 minutes each time to remove surface impurities and oil stains. Then, place the carbon cloth in anhydrous ethanol and ultrasonically clean it three times for 15 minutes each time to remove any acetone residue. Finally, place the carbon cloth in deionized water and ultrasonically clean it five times for 25 minutes each time until it is completely clean. After cleaning, dry the carbon cloth and cut it into pieces of 2 x 8 cm to obtain the pretreated carbon cloth.

[0034] Step (3) Electrodeposition of manganese dioxide: The carbon cloth pretreated in step (2) was used as the working electrode and placed in a 2+ and 40g / L sulfuric acid electrolyte. Using a three-electrode system, at 90℃ with 3mA / cm 2 The deposition was carried out at a constant current density of 100 nm for 1 hour. After the deposition, the carbon cloth was rinsed with deionized water to remove residual ions on the surface and then dried to obtain an electrodeposited manganese dioxide electrode.

[0035] Step (4) electrochemical deintercalation to remove calcium and magnesium: The purification and separation of manganese and magnesium was carried out in a double-chamber diaphragm electrolytic cell. The binder-free manganese dioxide electrode prepared in step (3) was placed as the cathode in the separation chamber, and 0.5M Na2SO4 was injected as the supporting electrolyte. The current density was set to 0.1A / g, and the electrochemical reaction was carried out by constant current discharge. The potential was dynamically detected and discharged to -0.6V to make mg 2+ After the discharge is completed, the electrode positions are exchanged and the electrochemical reaction is carried out by constant current charging to 1V, so that the mg in the manganese dioxide structure 2+ Driven by external potential, it is released and enters the supporting electrolyte. Through the cyclic iterative deintercalation / intercalation of the electrode, the magnesium in manganese sulfate solution is achieved. 2+ Repeat this process until mg in the separation chamber 2+ Meet the usage standards of battery-grade high-purity manganese sulfate.

[0036] The effect of the present invention is explored in Example 1-Example 2. During the cycle, the impurities mg in industrial manganese sulfate are detected. 2+ Content, calculate the mg of ε-MnO2 and γ-MnO22+ The removal amount, wherein the results obtained in Example 1-Example 2 are shown in Table 1.

[0037] Table 1: mg of industrial manganese sulfate in Examples 1 and 2 2+ Content and different crystal forms of MnO2 on mg 2+ Removal amount

[0038] After the electrochemical deintercalation method was used to purify high-purity manganese sulfate using Example 1-Example 2, mg in industrial manganese sulfate 2+ The content gradually decreases. The results show that the electrochemical deintercalation method can purify the manganese sulfate solution by selectively intercalating the impurity magnesium, and achieve the effect of removing impurities without introducing impurities. As can be seen from Table 1, the electrode of Example 2 has a good effect on magnesium. 2+ The MnO2 polycrystalline cycle with high electrochemical reversibility is the key. 2+ / MnO2 electrode becomes increasingly important because new solid MnO2 is formed in each cycle. γ-MnO2 has the highest electronic conductivity compared to ε-MnO2, making it easy to undergo electrochemical reactions and thus having a higher electrochemical deintercalation and insertion capability of magnesium ions. Therefore, the unit removal amount of the γ-MnO2 electrode in Example 2 can reach up to 45.4 mg / g.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for purifying high-purity manganese sulfate electrode material, characterized in that: The steps include: Step 1. Hydrophilic treatment of carbon cloth: calcining the raw carbon cloth in an air atmosphere to increase the surface area and generate oxygen-containing functional groups on the surface of the carbon cloth, thereby improving the surface wettability and facilitating the deposition of manganese dioxide; Step 2. Carbon cloth pretreatment: The carbon cloth treated in step 1 is placed in a beaker containing a certain amount of acetone and ultrasonically treated to remove surface impurities and oil stains. The carbon cloth is then ultrasonically cleaned in anhydrous ethanol to remove the acetone. Finally, the carbon cloth is rinsed in deionized water. After cleaning, it is dried and cut into suitable sizes to obtain pretreated carbon cloth. Step 3. Electrodeposition of manganese dioxide: with a concentration of 40 g / L Mn 2+ A solution of 40 g / L sulfuric acid was used as the electrolyte, and a three-electrode system was used for constant current deposition. After the deposition, deionized water was used to rinse to remove residual ions on the surface, and the product was finally dried.

2. The method according to claim 1, characterized in that In the step 1, the calcination temperature is 400-600° C. and the calcination time is 1-6 hours.

3. The method according to claim 1, characterized in that In step 2, the ultrasonic treatment time in acetone is 10-20 minutes, and the number of times is 2-3 times. The ultrasonic treatment time in anhydrous ethanol is 10-20 minutes, and the number of times is 2-3 times. The ultrasonic cleaning time in deionized water is 20-30 minutes, and the number of times is 3-5 times.

4. The method according to claim 1, wherein The counter electrode is a graphite electrode.

5. The method according to claim 1, wherein The reference electrode is a saturated calomel electrode.

6. The method according to claim 1, wherein The constant current deposition in step 3 refers to a current density of 2-10 mA cm -2 , the deposition time is 0.5-3h.

7. The method according to claim 1, characterized in that In step 3, the drying temperature is 50-80° C. and the drying time is 1-3 hours.

8. An electrode produced by the method for purifying electrode materials of high-purity manganese sulfate according to any one of claims 1 to 7.

9. A method for purifying a manganese sulfate solution, characterized in that: The invention comprises placing a binder-free manganese dioxide electrode obtained by the method for purifying an electrode material of high-purity manganese sulfate according to any one of claims 1 to 7 as a cathode in a separation chamber, injecting a manganese sulfate solution purified of heavy metal ions, placing an inert electrode as an anode in an enrichment chamber, injecting Na2SO4 as a supporting electrolyte, and performing iterative deintercalation / intercalation until the Mg in the separation chamber is reduced to Mg. 2+ Meet the usage standards of high-purity manganese sulfate for electrodes.

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