Manganese dioxide and preparation method thereof

Abstract

The invention provides manganese dioxide and a preparation method thereof, and belongs to the field of manganese dioxide preparation.The preparation method of manganese dioxide comprises the following steps that alkali metal hydroxide, an oxidizing agent, a dispersing agent and an additive are mixed to obtain electrolyte, the electrolyte is added into an electrolytic bath, and electrolysis is conducted with manganese as an anode and graphite as a cathode; and carrying out solid-liquid separation on the electrolyzed electrolyte to obtain filter residues, and then washing and drying the filter residues to obtain manganese dioxide. According to the method, manganese dioxide with higher purity can be obtained, the raw materials used in the method are relatively cheap, part of the raw materials can be recycled in the electrolysis process, and the production cost is reduced; the particle size and purity of the manganese dioxide can be effectively controlled by controlling the electrolysis conditions and the types and proportions of the additives, the manganese dioxide with larger specific surface area is obtained, the production efficiency of the manganese dioxide is improved, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of manganese dioxide preparation, and in particular to manganese dioxide and a preparation method thereof. Background Art

[0002] With the continuous progress of new energy technology, especially the widespread application of lithium-rich manganese-based materials and lithium iron manganese phosphate materials in the field of lithium batteries, the demand for manganese dioxide has shown a significant growth trend. As an important industrial raw material, manganese dioxide is widely used in many fields such as lithium battery positive electrode materials, catalysts, pigments, dry batteries, etc. In particular, with the increasing demand for primary zinc-manganese dry batteries, the application of manganese dioxide in the field of dry batteries is becoming increasingly important.

[0003] However, the current preparation method of manganese dioxide has certain limitations. Although the chemical preparation method has high purity, it is costly and is not conducive to large-scale production. Although the traditional electrolytic method for preparing manganese dioxide is mature, it has problems such as high cell voltage, the need to heat the electrolyte to above 90°C, high energy consumption, and low purity, which limit its scope of application. At present, there is also technology that can electrolytically prepare manganese dioxide at a temperature of about 80°C, but the purity of its preparation is low. For example, the prior art discloses a method for electrochemically preparing manganese dioxide powder, which dissolves a soluble salt containing ammonium, sulfate, persulfate or halogen anion and a soluble salt containing permanganate or manganate in deionized water to form an electrolyte, puts a double graphite electrode in the electrolyte and connects to a DC voltage for electrochemical reaction, and the black-brown powder obtained by washing the electrolyte after the reaction is dried to obtain manganese dioxide. This method can be achieved at a temperature below 90°C, but the purity of the prepared manganese dioxide is not high.

[0004] According to theoretical calculations, 1.58 tons of manganese dioxide can be obtained from each ton of electrolytic manganese. Due to the increase in production capacity and the decrease in downstream demand, the price of electrolytic manganese has gradually decreased. If electrolytic manganese is used as a raw material to produce manganese dioxide, manganese dioxide with lower cost and higher purity can be obtained, which has good economic and environmental benefits. Therefore, the development of a low-cost, high-purity method for preparing manganese dioxide is of great significance for the promotion and application of lithium-rich manganese-based materials and lithium iron manganese phosphate materials. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a manganese dioxide and a preparation method thereof, aiming to solve the technical problems that the preparation method of manganese dioxide is high in cost and the purity of the obtained manganese dioxide is low.

[0006] In a first aspect, the present invention provides a method for preparing manganese dioxide, comprising the following steps:

[0007] An alkali metal hydroxide, an oxidant, a dispersant and an additive are mixed to obtain an electrolyte, and the electrolyte is added to an electrolytic cell to perform electrolysis using manganese as an anode and graphite as a cathode;

[0008] The electrolyzed electrolyte is subjected to solid-liquid separation to obtain a filter residue, and then the filter residue is washed and dried to obtain manganese dioxide.

[0009] In the technical scheme of the embodiment of the present application, an electrolyte is obtained by mixing raw materials, and then electrolysis, solid-liquid separation, washing and drying are performed. The operation process is relatively simple and easy to realize industrial production. In the electrolysis process, manganese directly participates in the reaction as an anode material, which helps to improve the purity of the final product, improve the utilization rate of manganese resources, and reduce resource waste; at the same time, by adjusting parameters such as current and voltage, manganese dioxide with specific specifications and performance can be obtained. This method is relatively environmentally friendly, and the substances used in the electrolysis process can be recycled to a certain extent to reduce waste emissions; and the manganese dioxide prepared by electrolysis under alkaline conditions has better performance in terms of particle size distribution, specific surface area, activity, etc., and is suitable for the needs of high-performance batteries and other fields.

[0010] In some embodiments, the alkali metal hydroxide is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or the concentration of the alkali metal hydroxide is 1.5 to 3 mol / L.

[0011] In this embodiment, by selecting a specific alkali metal hydroxide, a suitable electrolyte environment can be provided, which helps to improve the electrolysis efficiency and product purity. Specifically, when the concentration range of the alkaline metal hydroxide is 1.5 to 3 mol / L, the conductivity and reaction rate of the electrolyte can be optimized, and the ion concentration and current efficiency can be improved.

[0012] In some embodiments, the oxidant is persulfate; and / or the concentration of the oxidant is 0.2-0.5 mol / L; the persulfate is one or more of sodium persulfate, potassium persulfate, lithium persulfate and ammonium persulfate.

[0013] In this embodiment, the use of persulfate as an oxidant helps to control the oxidation process and improve the generation rate and purity of manganese dioxide. In the concentration range of 0.2 to 0.5 mol / L, the oxidizing ability of persulfate can be well controlled, the occurrence of side reactions can be reduced, and the selectivity of the reaction can be improved. At the same time, persulfate has high stability in this concentration range and is not easy to decompose, thereby ensuring the stability of the electrolysis process. In addition, by controlling the concentration of persulfate, excessive use can also be avoided, raw material costs can be reduced, and economic benefits can be improved. Selecting a suitable persulfate can improve oxidation efficiency and optimize product quality.

[0014] In some embodiments, the dispersant is a polymer or an anionic surfactant; and / or the concentration of the dispersant is 0.2-2 g / L. The polymer is one of polyethylene glycol, polyvinyl alcohol and polyacrylamide; and the anionic surfactant is sodium alkylbenzene sulfonate or sodium dodecyl sulfonate.

[0015] In this embodiment, a polymer (such as polyethylene glycol, polyvinyl alcohol, polyacrylamide) or an anionic surfactant (such as sodium alkylbenzene sulfonate, sodium dodecyl sulfate) is used as a dispersant with a concentration of 0.2 to 2 g / L, which can effectively disperse the electrolyzed manganese dioxide, prevent the generated manganese dioxide particles from agglomerating, and improve the dispersibility and specific surface area of ​​the product.

[0016] In some embodiments, the additive is a chloride ion salt; and / or the concentration of the additive is 0.1-0.5 g / L. The chloride ion salt is one or more of sodium chloride, potassium chloride and lithium chloride.

[0017] In this embodiment, adding chloride ion salt (such as sodium chloride, potassium chloride, lithium chloride) at a concentration of 0.1 to 0.5 g / L helps to improve the conductivity of the electrolyte or serve as an auxiliary catalyst in the electrolysis process, further improving the electrolysis efficiency and product quality, and can effectively reduce energy consumption and the primary particle size of manganese dioxide.

[0018] In some embodiments, the voltage of the electrolytic cell is 1.2-1.8V, and the current density is 30-60A / m 2 ; and / or, the distance between the plates of the electrolytic cell is 5 to 10 cm, and the electrolysis temperature is <90°C.

[0019] In this embodiment, the voltage is controlled at 1.2-1.8V, which helps to provide a suitable electrolysis potential, promotes the formation of manganese dioxide, and avoids excessive voltage causing energy waste or side reactions. Current density 30-60A / m 2 The setting of 5 to 10 cm between the plates helps optimize the electric field distribution in the electrolytic cell and improve the electrolysis efficiency. The electrolysis temperature is 25 to 40 ° C, which helps control the reaction rate and avoid side reactions or product decomposition that may be caused by high temperature, while ensuring safe operation.

[0020] In a second aspect, an embodiment of the present application provides a manganese dioxide having a particle size of 5 to 50 μm and a purity greater than or equal to 99.1%.

[0021] In the technical solution of the embodiment of the present application, precise control of particle size helps to meet the specific requirements of material performance in different application scenarios. Manganese dioxide with a purity greater than or equal to 99.1% means that the product contains very few impurities, which is crucial to improving the cycle stability and service life of the battery. The presence of impurities may cause unnecessary side reactions inside the battery and reduce the overall performance of the battery. High-purity manganese dioxide can also reduce quality problems that may occur during the battery manufacturing process and improve the safety and reliability of the battery.

[0022] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a process flow chart of the method for preparing manganese dioxide provided in this application.

[0025] Figure 2 This is a morphology image of the manganese dioxide obtained in Example 1 of the present application at a magnification of 10000X.

[0026] Figure 3 This is a morphology picture of the manganese dioxide obtained in Comparative Example 6 of the present application at a magnification of 10000X. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0029] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0030] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0032] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0033] Among the preparation methods of manganese dioxide, although the chemical preparation method has high purity, it is relatively costly and is not conducive to large-scale production; although the traditional electrolytic method for preparing manganese dioxide is mature, it has problems such as high cell voltage, high electrolyte heating temperature, high energy consumption, and low purity. These factors limit its scope of application.

[0034] In order to solve the technical problems that the preparation method of manganese dioxide is high in cost and the purity of the obtained manganese dioxide is low, the present application provides a manganese dioxide and a preparation method thereof. In the preparation method of manganese dioxide provided by the present application, electrolytic manganese is used as a raw material by electrolysis, and electrolysis is performed under alkaline conditions, so that the obtained manganese dioxide has higher purity, larger specific surface area and higher activity.

[0035] Please refer to Figure 1 In a first aspect, the present invention provides a method for preparing manganese dioxide, comprising the following steps:

[0036] S1. Mixing an alkali metal hydroxide, an oxidant, a dispersant and an additive to obtain an electrolyte, adding the electrolyte to an electrolytic cell, and performing electrolysis with manganese as an anode and graphite as a cathode;

[0037] S2. The electrolyzed electrolyte is subjected to solid-liquid separation to obtain a filter residue, and then the filter residue is washed and dried to obtain manganese dioxide.

[0038] In this embodiment, the alkali metal hydroxide and the oxidant are the core components of the electrochemical reaction, and a redox reaction will occur during the electrolysis process, thereby reducing the manganese ions on the manganese anode to manganese dioxide. Among them, the addition of dispersants and additives can adjust the properties and flow characteristics of the electrolyte, increase the reaction rate, and promote the generation and separation of manganese dioxide, thereby improving the quality and yield of manganese dioxide.

[0039] Specifically, during the electrolysis process, the manganese anode provides atoms for the oxidation reaction, and the graphite cathode provides electrons for the reduction reaction, thereby realizing the transfer of manganese ions to the graphite cathode to generate manganese dioxide. The manganese dioxide in the electrolyte is obtained by solid-liquid separation, wherein the filter residue contains unreacted impurities and other ions and other substances, which need to be washed and dried to obtain manganese dioxide with higher purity; and the filtrate obtained by solid-liquid separation of the electrolyte after electrolysis can be added with sodium hydroxide and sodium persulfate to prepare a new electrolyte, and added to the electrolytic cell to maintain the concentration of sodium hydroxide and sodium persulfate in the electrolyte unchanged.

[0040] Furthermore, in some embodiments, the alkali metal hydroxide is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or the concentration of the alkali metal hydroxide is 1.5 to 3 mol / L.

[0041] In the technical solution of the embodiment of the present application, the alkali metal hydroxide will ionize into OH in water. - Ion, OH - Ions can react with Mn in solution 2+ The reaction generates MnO2. By selecting a specific alkali metal hydroxide and adjusting its concentration, the pH value of the electrolyte can be controlled. Within a certain pH range, the activity of the reactant molecules is the highest, which is conducive to the electrolytic reaction. At the same time, within the appropriate concentration range, the collision frequency between the reactant molecules increases, thereby increasing the reaction rate and facilitating the generation of the desired product.

[0042] Furthermore, in some embodiments, a diaphragm is placed on the anode plate during electrolysis, and the diaphragm is one of polypropylene, polyethylene and polytetrafluoroethylene.

[0043] In the technical solution of the embodiment of the present application, a diaphragm is put on the anode plate. The diaphragm can effectively prevent the gas generated in the anode area from diffusing to the cathode area, thereby avoiding the influence of the gas on the cathode area and ensuring the stability of the electrolysis process; at the same time, the diaphragm can also prevent the anions generated in the cathode area from diffusing to the anode area, thereby avoiding the influence of the anions on the anode area and ensuring the stability of the electrolysis process.

[0044] Furthermore, in some embodiments, the oxidant is persulfate; the concentration of the oxidant is 0.2-0.5 mol / L.

[0045] In the technical solution of the embodiment of the present application, persulfate is a strong oxidant that can effectively oxidize manganese ions. The concentration of the oxidant needs to be appropriate. Too high a concentration may lead to excessive oxidation and affect the purity of the product; too low a concentration may not effectively oxidize manganese ions. The concentration of the oxidant is 0.2-0.5 mol / L, that is, the concentration ratio of alkali metal hydroxide and persulfate is (1.5-3.0): (0.2-0.5). By adjusting the concentration ratio of sodium hydroxide and sodium persulfate, the power consumption, the consumption ratio of sodium hydroxide and sodium persulfate are regulated, the electrolysis process is optimized, the efficiency of manganese ion oxidation to manganese dioxide is improved, and the production cost is reduced.

[0046] Furthermore, in some embodiments, the persulfate is one or more of sodium persulfate, potassium persulfate, lithium persulfate and ammonium persulfate.

[0047] In the technical solution of the embodiment of the present application, selecting a suitable persulfate can better adapt to the chemical reaction during the electrolysis process and improve the electrolysis efficiency.

[0048] Furthermore, in some embodiments, the dispersant is a polymer or an anionic surfactant; and / or the concentration of the dispersant is 0.2 to 2 g / L.

[0049] Furthermore, in some embodiments, the polymer is one of polyethylene glycol, polyvinyl alcohol and polyacrylamide; and / or the anionic surfactant is sodium alkylbenzene sulfonate or sodium dodecyl sulfonate.

[0050] In the technical solution of the embodiment of the present application, the polymer can be adsorbed on the surface of the solid particles to form a protective layer to prevent the agglomeration between the particles. The anionic surfactant can reduce the surface tension of the solid particles, making them easier to disperse in the electrolyte. The appropriate concentration can provide sufficient dispersibility and avoid over-dispersion.

[0051] Furthermore, in some embodiments, the additive is a chloride ion salt; and / or the concentration of the additive is 0.1-0.5 g / L.

[0052] Furthermore, in some embodiments, the chloride ion salt is one or more of sodium chloride, potassium chloride and lithium chloride.

[0053] In the technical solution of the embodiment of the present application, the additives are added and their concentrations are adjusted in order to adjust the ionic strength of the electrolyte, affect the electrochemical kinetics of the electrolysis process, and improve the conductivity and stability of the electrolyte.

[0054] Furthermore, in some embodiments, the voltage of the electrolytic cell is 1.2 to 1.8 V, and the current density is 30 to 60 A / m 2 ; and / or, the distance between the plates of the electrolytic cell is 5 to 10 cm, and the electrolysis temperature is 25 to 40°C.

[0055] In the technical scheme of the embodiment of the present application, the voltage, current density, plate spacing and electrolysis temperature of the electrolytic cell are key operating parameters, which jointly affect the efficiency of the electrolysis process and the quality of the product. Suitable voltage can ensure that the electrolysis reaction proceeds smoothly without causing excessive energy waste or side reactions. The current density can ensure the rate of the electrolysis reaction while avoiding electrode overheating and local overheating of the electrolyte due to excessive current. The plate spacing can ensure that the electrolyte flows fully between the electrodes, reduce concentration polarization, and improve the electrolysis efficiency. In the temperature range of 25 to 40 ° C, the stability and conductivity of the electrolyte can be maintained, the electrolysis efficiency can be improved, and energy consumption can be reduced. Excessive temperature may cause the electrolyte to volatilize or decompose, while too low temperature may reduce the reaction rate. The circulation volume of the electrolyte per hour is 0.1 to 0.15 times the total volume of the electrolytic cell, which can maintain the uniformity of the ion concentration in the electrolytic cell, reduce concentration polarization, and thus improve the electrolysis efficiency.

[0056] Further, in some embodiments, when the concentration of sulfate in the electrolyte reaches 250-400 g / L after the electrolysis cycle, the electrolyte is taken out, the sodium sulfate crystals therein are precipitated, the remaining mother liquor is returned to continue preparing the electrolyte, the filtered residue is washed with pure water, and then dried, crushed, sieved and vacuum packaged to obtain manganese dioxide. The residue is washed until the conductivity of the washing water is ≤200 μS / cm, and the washing water produced by the washing is returned to prepare the electrolyte.

[0057] In the technical solution of the embodiment of the present application, the stability and efficiency of the electrolysis process can be maintained by controlling the concentration of sulfate in the electrolyte. The cooling crystallization and filtration steps realize the recovery of sodium sulfate and the purification of the electrolyte. The washing and post-treatment steps of the filter residue ensure the purity and quality of the final product manganese dioxide.

[0058] In a second aspect, an embodiment of the present application provides a manganese dioxide, which is obtained by the preparation method of manganese dioxide provided in the first aspect of the present application, and the particle size of the manganese dioxide is 5 to 50 μm, and the purity is greater than or equal to 99.1%.

[0059] The manganese dioxide of the present application uses electrolytic manganese as a raw material, so the manganese dioxide has a higher purity, and is electrolyzed under alkaline conditions, has a large BET specific surface area and high activity, and can be used to prepare high-performance lithium-rich manganese-based materials and lithium iron manganese phosphate materials.

[0060] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0061] 1. Preparation method

[0062] Example 1

[0063] Embodiment 1 provides a method for preparing manganese dioxide, comprising the following steps:

[0064] The electrolytic manganese sheet is used as the anode and graphite is used as the cathode. The electrolyte is added and the cell voltage is 1.6V and the current density is 45A / m 2 , electrolysis was carried out under the condition that the distance between the plates was 8 cm. A polyethylene diaphragm was put on the anode plate during electrolysis. The formula of the electrolyte was: sodium hydroxide concentration was 2.2 mol / L, sodium persulfate concentration was 0.35 mol / L, polyethylene glycol 2000 concentration was 1 g / L, sodium chloride concentration was 0.3 g / L, and the electrolysis temperature was 33±2°C. At the same time, the electrolyte was continuously extracted from the bottom of the electrolytic cell for filtration, and the circulating volume of the electrolyte per hour was 0.12 times the total volume of the electrolytic cell.

[0065] During filtration, a filter press is used, and the filtered residue is washed with pure water. The washing is stopped after the residue is washed until the conductivity of the washing water is 180μS / cm. The washing water produced by washing is returned to prepare the electrolyte. At the same time, sodium hydroxide and sodium persulfate are added to the filtered filtrate to maintain the concentration of the electrolyte. The newly configured electrolyte is added from the top of the electrolytic cell. When the sulfate concentration in the electrolyte is 300g / L after circulation, the electrolyte is taken out, cooled to the electrolyte temperature of -5°C, and the sodium sulfate crystals therein are precipitated, and then dried by a horizontal screw centrifuge. The remaining mother liquor is returned to continue to prepare the electrolyte and then returned to electrolysis. After the electrolytic manganese sheet is completely dissolved, a new manganese sheet is replaced to continue electrolysis.

[0066] The filter residue is dried, crushed, sieved and vacuum packed to obtain manganese dioxide, wherein the primary particle size of the manganese dioxide is 250 nm.

[0067] Specifically, the obtained manganese dioxide detection data are as follows:

[0068] Table 1 Performance test results of manganese dioxide provided in Example 1

[0069]

[0070]

[0071] Example 2

[0072] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the electrolysis temperature is 27±2°C.

[0073] Specifically, the obtained manganese dioxide detection data are as follows:

[0074] Table 2 Performance test results of manganese dioxide provided in Example 2

[0075] index <![CDATA[MnO2]]> BET Ca Mg Al data 99.1％ <![CDATA[31.3m 2 / g]]> 35.1ppm 2.0ppm 1.6ppm Cu Zn Fe Na K Moisture 0.1ppm 2.1ppm 0.1ppm 106ppm 10.4ppm 0.16％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 12ppm 47ppm 0.1ppm 0.1ppm 0.1ppm 0.1ppm Sb As Cr V Ti pH 0.1ppm 0.1ppm 1.0ppm 0.1ppm 1.2ppm 7.21 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 347mV 16.8mL / 100g 0.23％ 89.2％ 74.9％ 1.71g / mL

[0076] Example 3

[0077] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the electrolysis temperature is 38±2°C.

[0078] Specifically, the obtained manganese dioxide detection data are as follows:

[0079] Table 3 Performance test results of manganese dioxide provided in Example 3

[0080]

[0081]

[0082] Example 4

[0083] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the cell voltage is 1.2V.

[0084] Specifically, the obtained manganese dioxide detection data are as follows:

[0085] Table 4 Performance test results of manganese dioxide provided by Example 4

[0086] index <![CDATA[MnO2]]> BET Ca Mg Al data 99.3％ <![CDATA[27.8m 2 / g]]> 27.8ppm 1.2ppm 2.1ppm Cu Zn Fe Na K Moisture 0.1ppm 1.9ppm 0.2ppm 89.4ppm 7.9ppm 0.15％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 10ppm 37ppm 0.1ppm 0.1ppm 0.1ppm 0.1ppm Sb As Cr V Ti pH 0.1ppm 0.1ppm 0.4ppm 0.2ppm 3.7ppm 7.35 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 390mV 18.2mL / 100g 0.21％ 89.6％ 75.1％ 1.79g / mL

[0087] Example 5

[0088] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the cell voltage is 1.8V.

[0089] Specifically, the obtained manganese dioxide detection data are as follows:

[0090] Table 5 Performance test results of manganese dioxide provided in Example 5

[0091]

[0092]

[0093] Example 6

[0094] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the concentration ratio of sodium hydroxide to sodium persulfate is 2.2:0.2.

[0095] Specifically, the obtained manganese dioxide detection data are as follows:

[0096] Table 6 Performance test results of manganese dioxide provided by Example 6

[0097] index <![CDATA[MnO2]]> BET Ca Mg Al data 99.5％ <![CDATA[33.2m 2 / g]]> 30.5ppm 2.2ppm 3.1ppm Cu Zn Fe Na K Moisture 0.1ppm 3.1ppm 0.1ppm 156ppm 16.1ppm 0.24％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 12ppm 31ppm 0.1ppm 0.1ppm 0.1ppm 0.1ppm Sb As Cr V Ti pH 0.1ppm 0.1ppm 1.1ppm 0.2ppm 1.5ppm 7.56 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 378mV 16.8mL / 100g 0.22％ 89.5％ 76.4％ 1.75g / mL

[0098] Example 7

[0099] This embodiment provides a method for preparing manganese dioxide, which is different from Embodiment 1 only in that the concentration ratio of sodium hydroxide to sodium persulfate is 2.2:0.5.

[0100] Specifically, the obtained manganese dioxide detection data are as follows:

[0101] Table 7 Performance test results of manganese dioxide provided in Example 7

[0102]

[0103] Example 8

[0104] This embodiment provides a method for preparing manganese dioxide, which is different from the embodiment 1 only in that the concentration of sodium chloride is 0.1 g / L. The primary particle size of the prepared manganese dioxide is 320 nm.

[0105] Specifically, the obtained manganese dioxide detection data are as follows:

[0106] Table 8 Performance test results of manganese dioxide provided in Example 8

[0107] index <![CDATA[MnO2]]> BET Ca Mg Al data 99.0％ <![CDATA[41.5m 2 / g]]> 46.7ppm 4.2ppm 3.3ppm Cu Zn Fe Na K Moisture 0.3ppm 3.9ppm 0.9ppm 167ppm 15.2ppm 0.27％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 22ppm 67ppm 0.1ppm 0.3ppm 0.2ppm 0.2ppm Sb As Cr V Ti pH 0.1ppm 0.3ppm 1.9ppm 0.3ppm 11.3ppm 7.98 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 385mV 20.1mL / 100g 0.21％ 89.2％ 75.1％ 1.68g / mL

[0108] Example 9

[0109] This embodiment provides a method for preparing manganese dioxide, which is different from the embodiment 1 only in that the concentration of sodium chloride is 0.5 g / L. The primary particle size of the prepared manganese dioxide is 190 nm.

[0110] Specifically, the obtained manganese dioxide detection data are as follows:

[0111] Table 9 Performance test results of manganese dioxide provided in Example 9

[0112] index <![CDATA[MnO2]]> BET Ca Mg Al data 99.0％ <![CDATA[37.6m 2 / g]]> 40.1ppm 3.1ppm 2.2ppm Cu Zn Fe Na K Moisture 0.1ppm 3.2ppm 0.5ppm 176ppm 12.1ppm 0.20％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 13ppm 69ppm 0.1ppm 0.2ppm 0.2ppm 0.1ppm Sb As Cr V Ti pH 0.1ppm 0.1ppm 1.1ppm 0.3ppm 14.7ppm 7.57 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 382mV 20.1mL / 100g 0.21％ 89.0％ 75.1％ 1.70g / mL

[0113] Comparative Example 1

[0114] This comparative example provides a method for preparing manganese dioxide, which is different from Example 1 only in that the electrolysis temperature is 45±2°C.

[0115] Specifically, the obtained manganese dioxide detection data are as follows:

[0116] Table 10 Performance test results of manganese dioxide provided by comparative example 1

[0117]

[0118]

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing manganese dioxide, which is different from Example 1 only in that the cell voltage is 2V.

[0121] Specifically, the obtained manganese dioxide detection data are as follows:

[0122] Table 11 Performance test results of manganese dioxide provided by comparative example 2

[0123] index <![CDATA[MnO2]]> BET Ca Mg Al data 97.5％ <![CDATA[62.6m 2 / g]]> 44.6ppm 7.1ppm 7.9ppm Cu Zn Fe Na K Moisture 0.7ppm 4.6ppm 12.5ppm 189ppm 17.8ppm 0.29％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 27ppm 87ppm 0.2ppm 0.1ppm 0.3ppm 0.3ppm Sb As Cr V Ti pH 0.2ppm 0.4ppm 4.8ppm 0.8ppm 2.8ppm 7.79 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 376mV 20.7mL / 100g 0.21％ 89.1％ 73.2％ 1.67g / mL

[0124] Comparative Example 3

[0125] This comparative example provides a method for preparing manganese dioxide, which is different from Example 1 only in that the concentration ratio of sodium hydroxide to sodium persulfate is 2.2:0.1.

[0126] Specifically, the obtained manganese dioxide detection data are as follows:

[0127] Table 12 Performance test results of manganese dioxide provided by comparative example 3

[0128]

[0129]

[0130] Comparative Example 4

[0131] This comparative example provides a method for preparing manganese dioxide, which differs from Example 1 only in that sodium chloride is not added. The primary particle size of the prepared manganese dioxide is 415 nm.

[0132] Specifically, the obtained manganese dioxide detection data are as follows:

[0133] Table 13 Performance test results of manganese dioxide provided by comparative example 4

[0134] index <![CDATA[MnO2]]> BET Ca Mg Al data 98.7％ <![CDATA[16.7m 2 / g]]> 30.3ppm 1.4ppm 1.6ppm Cu Zn Fe Na K Moisture 0.1ppm 2.1ppm 0.2ppm 147ppm 12.9ppm 0.17％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 18ppm 43ppm 0.1ppm 0.1ppm 0.1ppm 0.1ppm Sb As Cr V Ti pH 0.1ppm 0.1ppm 0.5ppm 0.2ppm 1.1ppm 7.28 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 359mV 10.2mL / 100g 0.29％ 89.9％ 74.1％ 1.79g / mL

[0135] Comparative Example 5

[0136] This comparative example provides a method for preparing manganese dioxide, which is different from Example 1 only in that the concentration of sodium chloride is 1 g / L. The primary particle size of the prepared manganese dioxide is 176 nm.

[0137] Specifically, the obtained manganese dioxide detection data are as follows:

[0138] Table 14 Performance test results of manganese dioxide provided by comparative example 5

[0139]

[0140]

[0141] Comparative Example 6

[0142] The present comparative example provides a method for preparing manganese dioxide, which is prepared under acidic conditions, comprising the following steps: electrolyzing a manganese electrolyte (manganese concentration is 35 g / L, sulfuric acid concentration is 80 g / L) at a temperature of 95°C, a cell voltage of 2.5 V, and a current density of 150 A / m 2 The electrolysis was stopped after the manganese concentration reached 25 g / L. The anode plate was a titanium plate and the cathode plate was a graphite plate. The manganese dioxide was taken out and crushed to obtain electrolytic manganese dioxide.

[0143] Specifically, the obtained manganese dioxide detection data are as follows:

[0144] Table 15 Performance test results of manganese dioxide provided by comparative example 6

[0145] index <![CDATA[MnO2]]> BET Ca Mg Al data 94.2％ <![CDATA[27.5m 2 / g]]> 56.9ppm 12.6ppm 4.8ppm Cu Zn Fe Na K Moisture 0.4ppm 2.9ppm 0.9ppm 201ppm 15.8ppm 0.23％ Sulfate Hydrochloric acid insoluble matter Pb Ni Co Mo 8356ppm 129ppm 0.9ppm 0.6ppm 0.8ppm 0.2ppm Sb As Cr V Ti pH 0.3ppm 0.1ppm 2.1ppm 0.9ppm 25.7ppm 6.5 Initial potential Liquid aspiration Fineness (+100 mesh) Fineness(-200 mesh) Fineness(-325mesh) Apparent Density 275mV 15.9mL / 100g 0.22％ 86.8％ 74.7％ 1.75g / mL

[0146] 2. Test Method

[0147] 1. SEM test

[0148] The morphology of the manganese dioxide prepared in the embodiment and the comparative example was detected by a scanning electron microscope.

[0149] 2. Particle size test

[0150] The particle sizes of the manganese dioxide prepared in the examples and comparative examples were measured using a laser particle size analyzer.

[0151] 3. BET test

[0152] The specific surface area of ​​the manganese dioxide prepared in the embodiment and the comparative example was tested by using a BET tester.

[0153] 4. Purity test

[0154] The purity of the manganese dioxide prepared in the examples and comparative examples was tested by titration method, and the results are shown in Tables 1 to 15.

[0155] 5. Apparent density test

[0156] The apparent density of the manganese dioxide prepared in the examples and comparative examples was tested using an apparent density tester. The results are shown in Tables 1 to 15.

[0157] 6. Element content analysis

[0158] The metal element contents in the manganese dioxide prepared in the examples and comparative examples were tested by inductively coupled plasma optical emission spectrometry (ICP-OES). The results are shown in Tables 1 to 15.

[0159] III. Analysis of test results of various embodiments and comparative examples

[0160] In this application, from Figure 2 It can be seen from the figure that the primary particles of manganese dioxide prepared in Example 1 are spherical and have uniform particle size distribution. Figure 3 It can be seen that the manganese dioxide particles prepared in Comparative Example 6 present irregular shapes such as flakes, and the particle size difference is significant. At the same time, combined with the contents in Tables 1 to 15 above, it can be seen that the purity of the manganese dioxide prepared in Examples 1 to 9 is above 99.0%, while the purity of the manganese dioxide prepared in Comparative Examples 1 to 6 ranges from 93.8% to 98.7%. Therefore, compared with the traditional process of synthesizing manganese dioxide under acidic conditions, the present application can obtain manganese dioxide with higher purity, regular particle morphology, and more uniform particle size distribution.

[0161] Further, it can be seen from the test data of Examples 1 to 3 shown in Tables 1 to 3 and the test data of Comparative Example 1 shown in Table 10 that when the electrolysis temperature is controlled within the range of 25 to 40°C, the side reactions caused by high temperature can be avoided, thereby improving the purity of the prepared manganese dioxide. At the same time, the lower electrolysis temperature helps to control the reaction energy consumption and save production costs. Specifically, in the preparation process of Comparative Example 1, due to the high electrolysis temperature, the energy consumption required for heating the electrolyte increases, and the probability of side reactions increases, resulting in a decrease in the purity of manganese dioxide. Among them, the energy consumption required for the preparation process of Comparative Example 1 is 7.5% higher than that required for the preparation process of Example 1.

[0162] Further, it can be seen from the test data of Examples 4 and 5 shown in Tables 4 and 5 and the test data of Comparative Example 2 shown in Table 11 that controlling the voltage of the electrolytic cell at 1.2 to 1.8 V helps to provide a suitable electrolytic potential and promote the formation of manganese dioxide, while avoiding excessive voltage leading to energy waste or side reactions. Among them, in the preparation process of Comparative Example 2, the cell voltage is increased to 2 V, and the energy consumption required for the preparation process of Comparative Example 2 is 8.6% higher than that required for the preparation process of Example 1, and there are side reactions, resulting in a significant increase in the corrosion of the cathode plate and the anode plate of the electrolytic cell, which in turn leads to the purity of the prepared manganese dioxide being only 97.5%.

[0163] Further, it can be seen from the test data of Examples 6 and 7 shown in Tables 6 and 7 and the test data of Comparative Example 3 shown in Table 12 that the concentration ratio of sodium hydroxide and sodium persulfate is controlled within an appropriate range to improve the purity of the prepared manganese dioxide and reduce the process energy consumption. Among them, according to the actual calculation of the energy consumption per kilogram of electrolytic manganese dioxide, Example 6 is 4.5% higher than Example 1; Example 7 is 3.8% lower than Example 1, but the purity of the manganese dioxide prepared in Example 7 is slightly reduced, and the impurity content is slightly increased; Comparative Example 3 is 12.7% higher than Example 1, and because the amount of sodium persulfate added is relatively small, the content of Mn2O3 in manganese dioxide is relatively high, reaching 4.1%, and the MnO2 content is only 93.8%; while the content of Mn2O3 in Example 1 is less than 0.2%.

[0164] Further, it can be seen from the test data of Examples 8 and 9 shown in Tables 8 and 9 and the test data of Comparative Examples 4 and 5 shown in Tables 13 and 14 that adding an appropriate amount of sodium chloride can adjust the ionic strength of the electrolyte, improve the conductivity and stability of the electrolyte, and improve the quality of the prepared manganese dioxide. At the same time, it can also effectively reduce energy consumption, so that the primary particle size of the prepared manganese dioxide is smaller. Among them, according to the actual calculation, the energy consumption of electrolytic manganese dioxide per kilogram is 3.5% higher than that of Example 1, and Example 9 is 2.9% lower than that of Example 1; and the primary particle size of the manganese dioxide prepared in Example 8 is 320nm; the primary particle size of the manganese dioxide prepared in Example 9 is 190nm. Sodium chloride was not added in Comparative Example 4. According to the actual calculation, the energy consumption of electrolytic manganese dioxide per kilogram is obtained. The energy consumption of Comparative Example 4 increases by 7.5% compared with Example 1, and the primary particle size of the prepared manganese dioxide is 415nm.

[0165] Further, in Comparative Example 5, excessive chloride ions will cause the purity of the product to decrease, the impurity content to increase, and the corrosion degree and energy consumption of the anode plate and the cathode plate will increase significantly during the electrolysis process. Specifically, according to the actual calculation, the energy consumption of electrolytic manganese dioxide per kilogram is 15% higher than that of Example 1, and the side reactions are significantly increased. Therefore, by controlling the concentration of the chloride ion salt within the range of 0.1 to 0.5 g / L, the process energy consumption can be effectively reduced, the purity of the product can be improved, and at the same time, the corrosion of the anode plate and the cathode plate can be reduced, and the primary particle size of the prepared manganese dioxide can be regulated.

[0166] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing manganese dioxide, characterized in that: The following steps are involved: An alkali metal hydroxide, an oxidant, a dispersant and an additive are mixed to obtain an electrolyte, and the electrolyte is added to an electrolytic cell to perform electrolysis using manganese as an anode and graphite as a cathode; The electrolyzed electrolyte is subjected to solid-liquid separation to obtain a filter residue, and then the filter residue is washed and dried to obtain manganese dioxide.

2. The method for preparing manganese dioxide according to claim 1, characterized in that: The alkali metal hydroxide is one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; and / or The concentration of the alkali metal hydroxide is 1.5-3 mol / L.

3. The method for preparing manganese dioxide according to claim 1, characterized in that: The oxidant is a persulfate; and / or The concentration of the oxidant is 0.2-0.5 mol / L.

4. The method for preparing manganese dioxide according to claim 3, characterized in that: The persulfate is one or more of sodium persulfate, potassium persulfate, lithium persulfate and ammonium persulfate.

5. The method for preparing manganese dioxide according to claim 1, characterized in that: The dispersant is a polymer or an anionic surfactant; and / or The concentration of the dispersant is 0.2-2 g / L.

6. The method for preparing manganese dioxide according to claim 5, characterized in that: The polymer is one of polyethylene glycol, polyvinyl alcohol and polyacrylamide; and / or The anionic surfactant is sodium alkylbenzene sulfonate or sodium dodecyl sulfonate.

7. The method for preparing manganese dioxide according to claim 1, characterized in that: The additive is a chloride ion salt; and / or The concentration of the additive is 0.1-0.5 g / L.

8. The method for preparing manganese dioxide according to claim 7, characterized in that: The chloride ion salt is one or more of sodium chloride, potassium chloride and lithium chloride.

9. The method for preparing manganese dioxide according to claim 1, characterized in that: The voltage of the electrolytic cell is 1.2-1.8V, and the current density is 30-60A / m 2 ; and / or The distance between the pole plates of the electrolytic cell is 5 to 10 cm, and the electrolysis temperature is 25 to 40°C.

10. Manganese dioxide prepared according to the preparation method according to any one of claims 1 to 9, characterized in that: The manganese dioxide has a particle size of 5 to 50 μm and a purity greater than or equal to 99.1%.

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