阅读说明：本技术 一种硫酸锰溶液制备微纳米四氧化三锰的方法 (Method for preparing micro-nano manganous manganic oxide by manganese sulfate solution ) 是由 闫冠杰 李春流 农艳莉 万维华 杨茂峰 阮籍 廖伟峰 黎明 于 2021-08-11 设计创作，主要内容包括：本发明提供一种硫酸锰溶液制备微纳米四氧化三锰的方法,溶解电解金属锰片并进行除杂净化制备得到杂质含量低的硫酸锰溶液,再将硫酸锰溶液一步氧化制备四氧化三锰,通过对原材料杂质含量的控制,大大降低了产品的杂质含量；通过在碱性沉淀剂中添加分散剂抑制晶粒的生长,制备得到的微纳米四氧化三锰颗粒尺寸小,分散性好；该工艺操作简单,生产成本低,容易实现工业化生产；制备得到的微纳米四氧化三锰的粒度指标为：D50＜2μm,Mn≥70.5wt%,S≤1000ppm,Fe≤50ppm,Ca≤50ppm,Mg≤50ppm,Na≤50ppm,K≤50ppm,重金属≤10ppm。(The invention provides a method for preparing micro-nano manganous manganic oxide by manganese sulfate solution, which comprises the steps of dissolving electrolytic manganese metal sheets, removing impurities, purifying to obtain the manganese sulfate solution with low impurity content, oxidizing the manganese sulfate solution by one step to prepare the manganous manganic oxide, and greatly reducing the impurity content of a product by controlling the impurity content of raw materials; the dispersing agent is added into the alkaline precipitator to inhibit the growth of crystal grains, so that the prepared micro-nano manganous manganic oxide particles are small in size and good in dispersibility; the process is simple to operate, low in production cost and easy to realize industrial production; the particle size indexes of the prepared micro-nano manganous manganic oxide are as follows: d50 is less than 2 mu m, Mn is more than or equal to 70.5wt%, S is less than or equal to 1000ppm, Fe is less than or equal to 50ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, Na is less than or equal to 50ppm, K is less than or equal to 50ppm, and heavy metal is less than or equal to 10 ppm.)

1. The method for preparing micro-nano manganous manganic oxide by using manganese sulfate solution is characterized by comprising the following steps of:

(1) adding electrolytic manganese metal sheets and pure water into a dissolving tank, adding concentrated sulfuric acid for dissolving, adding an impurity removing agent for removing impurities and purifying after the electrolytic manganese metal sheets are completely dissolved, and filtering to obtain filtrate to obtain a manganese sulfate solution;

(2) adding pure water into a reaction kettle as a base solution, heating to 30-70 ℃, adding the manganese sulfate solution prepared in the step (1) and the aqueous solution of the alkaline precipitator into the reaction kettle in a parallel flow manner under the condition of stirring, and simultaneously adding an oxidant for oxidation; in the reaction process, controlling the pH value of a reaction system to be 4.0-5.0 by adjusting the flow rate of an aqueous solution of an alkaline precipitator, controlling the pH value to be unchanged after the manganese sulfate solution is added, and continuously stirring, preserving heat and aging to obtain a reaction solution;

(3) and (3) centrifuging the reaction liquid obtained in the step (2) to obtain a crude manganous-manganic oxide product, washing the crude manganous-manganic oxide product with pure water for several times, then putting the washed crude manganous-manganic oxide product into a drying oven, and drying the washed crude manganous-manganic oxide product for 6-15 hours at the temperature of 110-130 ℃ to obtain the micro-nano manganic oxide.

2. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the weight ratio of the electrolytic manganese metal sheet to pure water in the step (1) is 1: 5-30.

3. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the impurity removal and purification in the step (1) comprises two steps of removing iron and heavy metals; in the iron removal process, manganese powder is used for adjusting the pH value to 4.0-5.0, then hydrogen peroxide is added and stirred, and the amount of the hydrogen peroxide is 2-7 g per liter of solution to be treated; in the heavy metal removing process, the selected heavy metal removing reagent is one or two of sodium dimethyl dithiocarbamate and ammonium sulfide, and the dosage of the heavy metal removing reagent is 0.1-1 g of the heavy metal removing reagent added into each liter of solution to be treated.

4. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution as claimed in claim 1, wherein the stirring speed in the step (2) is 300-800 r/min.

5. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the alkaline precipitant in the aqueous solution of the alkaline precipitant in the step (2) is one or two of sodium hydroxide and ammonia water; the concentration of the alkaline precipitant is 1-10 mol/L; the aqueous solution of the alkaline precipitator contains a dispersant, and the dispersant is any one or two of ethanol, n-butanol, polyethylene glycol, polyvinyl alcohol, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, carboxymethyl cellulose, SP-80, polydimethylsiloxane, ammonium polyacrylate, ethyl acetate, glycerol, sodium acetate and stearic acid.

6. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution as claimed in claim 5, wherein the concentration of the dispersant in the aqueous solution of the alkaline precipitant is 1-20 g/L.

7. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the flow rate of the manganese sulfate solution in the step (2) is 50-600 ml/min.

8. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the manganese sulfate solution in the step (2) is fed for 6-20 hours and aged for 5-10 hours.

9. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 8, wherein the manganese sulfate solution in the step (2) is fed for 8-20 hours and aged for 6-10 hours.

10. The method for preparing micro-nano manganous manganic oxide from manganese sulfate solution according to claim 1, wherein the micro-nano manganous manganic oxide has the following granularity indexes: d50 is less than 2 mu m, Mn is more than or equal to 70.5wt%, S is less than or equal to 1000ppm, Fe is less than or equal to 50ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, Na is less than or equal to 50ppm, K is less than or equal to 50ppm, and heavy metal is less than or equal to 10 ppm.

Technical Field

The invention relates to the technical field of manganese oxide preparation, in particular to a method for preparing micro-nano manganous manganic oxide by a manganese sulfate solution.

Background

Mangano manganic oxide (Mn)₃O₄) Is an important novel functional material and is widely applied to the fields of new energy materials, magnetic materials, catalysts and the like. Wherein Mn₃O₄As the main raw material of the lithium manganate serving as the anode material of the lithium ion battery, the use effect of the lithium manganate is superior to that of manganese dioxide and Mn₃O₄The lithium manganate has the same spinel structure as lithium manganate, manganous-manganic oxide with low impurity content is used as a raw material, no violent structural change exists in the process of synthesizing the lithium manganate through solid-phase reaction, the caused internal stress is smaller, the material structure is more stable, and the prepared lithium manganate has more excellent performance. Mn₃O₄Is also the main raw material for producing a new generation of soft magnetic material, namely nano Mn₃O₄Particles exhibiting excellent properties in soft magnetic ferrite material due to quantum size effect, using high purity Mn₃O₄Can be used as raw material to prepare high-quality manganese-zinc ferrite which is widely used in electronic industry. Further, Mn₃O₄Can be used as a catalyst for various reactions in the chemical industry. Mn₃O₄The method has wide application and large demand in domestic and foreign markets, is a high and new technical material product encouraging development in China, and has high commercial value.

With the rapid development of nanotechnology, the preparation and application of trimanganese tetroxide nanomaterial with high dispersibility and uniform size are receiving wide attention of researchers. At present, Mn₃O₄The preparation method mainly comprises an oxidation method, a roasting method, a hydrothermal method, a solvent method and the like. At present, the domestic preparation of mangano-manganic oxide mostly adopts a metal manganese powder suspension oxidation method, and the process flow is as follows: adding metal manganese powder into deionized water to prepare suspension with a certain solid-to-liquid ratio, and adding ammonium salt as a catalystAnd introducing air for oxidation under the heating condition to prepare the trimanganese tetroxide. The process is mature and simple, but is greatly influenced by raw materials, the production cost is high, and the impurity content is high. Preparation of Mn by roasting method₃O₄Manganese oxide and manganese sulfate are mostly used as raw materials, roasting is needed under high temperature conditions, preparation conditions are harsh, and industrial production is difficult to realize. The manganese salt hydrothermal oxidation method is characterized in that manganese ions in a manganese salt solution are hydrolyzed and precipitated into manganese hydroxide, and then an oxidant is added to oxidize the manganese hydroxide to prepare mangano-manganic oxide. The process has low cost and easy operation, and can prepare high-specific surface area and high-purity Mn₃O₄Mn produced by hydrothermal oxidation system₃O₄The particles are easy to agglomerate, the particle size is large, and the problem of high sulfur content exists. Therefore, these methods have problems in purity, process, particle size, and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the method for preparing the micro-nano manganous manganic oxide by using the manganese sulfate solution, which has the advantages of simple process, low production cost, low impurity content of the prepared micro-nano manganous manganic oxide, good dispersity, small particle size and controllable particle size.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a method for preparing micro-nano manganous manganic oxide by a manganese sulfate solution comprises the following steps:

(1) adding electrolytic manganese metal sheets and pure water into a dissolving tank, adding concentrated sulfuric acid for dissolving, adding an impurity removing agent for removing impurities and purifying after the electrolytic manganese metal sheets are completely dissolved, and filtering to obtain filtrate to obtain a manganese sulfate solution;

(2) adding pure water into a reaction kettle as a base solution, heating to 30-70 ℃, adding the manganese sulfate solution prepared in the step (1) and the aqueous solution of the alkaline precipitator into the reaction kettle in a parallel flow manner under the condition of stirring, and simultaneously adding an oxidant for oxidation; in the reaction process, controlling the pH value of a reaction system to be 4.0-5.0 by adjusting the flow rate of an aqueous solution of an alkaline precipitator, controlling the pH value to be unchanged after the manganese sulfate solution is added, and continuously stirring, preserving heat and aging to obtain a reaction solution;

(3) and (3) centrifuging the reaction liquid obtained in the step (2) to obtain a crude manganous-manganic oxide product, washing the crude manganous-manganic oxide product with pure water for several times, then putting the washed crude manganous-manganic oxide product into a drying oven, and drying the washed crude manganous-manganic oxide product for 6-15 hours at the temperature of 110-130 ℃ to obtain the micro-nano manganic oxide.

Further, the weight ratio of the electrolytic manganese metal sheet in the step (1) to pure water is 1: 5-30.

Further, the impurity removal and purification in the step (1) comprises two steps of removing iron and heavy metals; in the iron removal process, manganese powder is used for adjusting the pH value to 4.0-5.0, then hydrogen peroxide is added and stirred, and the amount of the hydrogen peroxide is 2-7 g per liter of solution to be treated; in the heavy metal removing process, the selected heavy metal removing reagent is one or two of sodium dimethyl dithiocarbamate and ammonium sulfide, and the dosage of the heavy metal removing reagent is 0.1-1 g of the heavy metal removing reagent added into each liter of solution to be treated.

Further, the stirring speed in the step (2) is 300-800 r/min.

Further, the alkaline precipitant in the aqueous solution of the alkaline precipitant in the step (2) is one or two of sodium hydroxide and ammonia water; the concentration of the alkaline precipitant is 1-10 mol/L; the aqueous solution of the alkaline precipitator contains a dispersant, and the dispersant is any one or two of ethanol, n-butanol, polyethylene glycol, polyvinyl alcohol, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, carboxymethyl cellulose, SP-80, polydimethylsiloxane, ammonium polyacrylate, ethyl acetate, glycerol, sodium acetate and stearic acid.

Furthermore, the concentration of the dispersing agent in the aqueous solution of the alkaline precipitator is 1-20 g/L.

Further, the flow rate of the manganese sulfate solution in the step (2) is 50-600 ml/min.

Further, the charging time of the manganese sulfate solution in the step (2) is 6-20 hours, and the aging time is 5-10 hours.

Further, the charging time of the manganese sulfate solution in the step (2) is 8-20 hours, and the aging time is 6-10 hours.

Further, the micro-nano manganous-manganic oxide has the granularity indexes that: d50 is less than 2 mu m, Mn is more than or equal to 70.5wt%, S is less than or equal to 1000ppm, Fe is less than or equal to 50ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, Na is less than or equal to 50ppm, K is less than or equal to 50ppm, and heavy metal is less than or equal to 10 ppm.

According to the method for preparing the micro-nano manganous manganic oxide by the manganese sulfate solution, electrolytic metal manganese sheets are dissolved, impurities are removed, purification is carried out, the manganese sulfate solution with low impurity content is obtained, the manganous sulfate solution is oxidized in one step to prepare the manganous manganic oxide, and the impurity content of a product is greatly reduced by controlling the impurity content of raw materials; the dispersing agent is added into the alkaline precipitator to inhibit the growth of crystal grains, so that the prepared micro-nano manganous manganic oxide particles are small in size and good in dispersibility; the process is simple to operate, low in production cost and easy to realize industrial production; the particle size indexes of the prepared micro-nano manganous manganic oxide are as follows: d50 is less than 2 mu m, Mn is more than or equal to 70.5wt%, S is less than or equal to 1000ppm, Fe is less than or equal to 50ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, Na is less than or equal to 50ppm, K is less than or equal to 50ppm, and heavy metal is less than or equal to 10 ppm.

Drawings

Fig. 1 is an XRD chart of the micro-nano mangano-manganic oxide prepared in example 1 of the present invention.

Fig. 2 is an SEM image of the micro-nano mangano-manganic oxide prepared in example 1 of the present invention.

Fig. 3 is a particle size diagram of the micro-nano mangano-manganic oxide prepared in example 1 of the present invention.

Fig. 4 is an SEM image of the micro-nano mangano-manganic oxide prepared in example 2 of the present invention.

Fig. 5 is a particle size diagram of the micro-nano mangano-manganic oxide prepared in example 2 of the present invention.

Fig. 6 is an SEM image of the micro-nano mangano-manganic oxide prepared in example 3 of the present invention.

Fig. 7 is a particle size diagram of the micro-nano mangano-manganic oxide prepared in example 3 of the present invention.

Detailed Description

The following examples may help one skilled in the art to more fully understand the present invention, but are not intended to limit the invention in any way.

The invention relates to a method for preparing micro-nano manganous manganic oxide by a manganese sulfate solution, wherein concentrated sulfuric acid with the mass fraction of 98% is used in the step (1); the manganese content in the electrolytic manganese metal sheet is more than 99.5 wt%; the reagents used, such as hydrogen peroxide, sodium dimethyl dithiocarbamate, ammonium sulfide, dispersing agent and the like, are all chemically pure.

A method for preparing micro-nano manganous manganic oxide by a manganese sulfate solution comprises the following steps:

(1) adding electrolytic manganese metal sheets and pure water into a dissolving tank, wherein the weight ratio of the electrolytic manganese metal sheets to the pure water is 1: 5-30, adding concentrated sulfuric acid for dissolving, adding an impurity removing agent for removing impurities and purifying after the electrolytic manganese metal sheets are completely dissolved, and filtering to obtain filtrate to obtain a manganese sulfate solution;

the impurity removal and purification comprises two steps of removing iron and heavy metals; in the iron removal process, manganese powder is used for adjusting the pH value to 4.0-5.0, then hydrogen peroxide is added and stirred, and the amount of the hydrogen peroxide is 2-7 g per liter of solution to be treated; in the heavy metal removing process, the selected heavy metal removing reagent is one or two of sodium dimethyl dithiocarbamate and ammonium sulfide, and the dosage of the heavy metal removing reagent is 0.1-1 g of the heavy metal removing reagent added into each liter of solution to be treated;

(2) adding pure water into a reaction kettle as a base solution, heating to 30-70 ℃, adding the manganese sulfate solution prepared in the step (1) and an aqueous solution of an alkaline precipitator into the reaction kettle in a parallel flow manner under the stirring condition, wherein the flow rate of the manganese sulfate solution is 50-600 ml/min, and simultaneously adding an oxidant for oxidation, and the stirring speed is 300-800 r/min; in the reaction process, controlling the pH value of a reaction system to be 4.0-5.0 by adjusting the flow rate of an aqueous solution of an alkaline precipitator, controlling the pH value to be unchanged after the manganese sulfate solution is added, and continuously stirring, preserving heat and aging to obtain a reaction solution; the feeding time of the manganese sulfate solution is 6-20 hours, and the aging time is 5-10 hours;

the alkaline precipitant in the aqueous solution of the alkaline precipitant is one or two of sodium hydroxide and ammonia water; the concentration of the alkaline precipitant is 1-10 mol/L; the aqueous solution of the alkaline precipitator contains a dispersant, wherein the dispersant is any one or two of ethanol, n-butanol, polyethylene glycol, polyvinyl alcohol, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, carboxymethyl cellulose, SP-80, polydimethylsiloxane, ammonium polyacrylate, ethyl acetate, glycerol, sodium acetate and stearic acid; the concentration of the dispersing agent in the aqueous solution of the alkaline precipitator is 1-20 g/L;

(3) and (3) centrifuging the reaction liquid obtained in the step (2) to obtain a crude manganous-manganic oxide product, washing the crude manganous-manganic oxide product with pure water for several times, then putting the washed crude manganous-manganic oxide product into a drying oven, and drying the washed crude manganous-manganic oxide product for 6-15 hours at the temperature of 110-130 ℃ to obtain the micro-nano manganic oxide.

Example 1:

(1) adding 11kg of electrolytic metal manganese pieces and 200L of pure water into a dissolving tank, adding 20kg of 98% concentrated sulfuric acid for reaction, adjusting the pH value to 4.0-5.0 after the manganese pieces are dissolved, adding 400g of hydrogen peroxide for iron removal, stirring for 30min, adding 40g of ammonium sulfide for removing heavy metals, continuing stirring for 30min, and finally filtering to obtain a manganese sulfate solution;

(2) preparing 200L of 2.5mol/L alkali liquor by using ammonia water as an alkaline precipitator, and adding 600g of polyethylene glycol;

(3) adding pure water into the reaction kettle to serve as a base solution, wherein the volume of the pure water just submerges the stirring paddle, and heating in a water bath to 40 ℃; under the condition of stirring, the stirring speed is 500r/min, the manganese sulfate solution obtained in the step (1) and the alkaline precipitator in the step (2) are added into a reaction kettle in a concurrent flow mode, the feeding speed of the manganese sulfate solution is 280mL/min, and air is introduced for oxidation; in the reaction process, the pH value of a reaction system is controlled to be 7.0-7.4 by adjusting the flow rate of an alkaline precipitator; after the manganese sulfate solution is added, controlling the pH value to be unchanged, continuously stirring, and preserving heat and aging for 6 hours;

(4) and (4) centrifuging the product obtained in the step (3), washing the product for 3 times by using pure water, putting the product into an oven, and standing the product at 120 ℃ for 10 hours to dry the product to obtain the trimanganese tetroxide.

The trimanganese tetroxide prepared in this example had a particle size D50 of 0.67 μm, a Mn content of 70.7%, a S content of 0.091%, a Ca content of 34.8ppm, a Mg content of 27.3ppm, a Na content of 14.5ppm, a K content of 6.9ppm, a Fe content of 26.7ppm, a Pb content of 2.3ppm, a Zn content of 8.5ppm, a Cu content of 1.5ppm, a Cd content of 3.1ppm, and a Cr content of 0.6 ppm. The crystal structure of the product is determined by an XRD diffractometer, and the result is shown in figure 1, and the product is truly manganous manganic oxide; the morphology was observed by Scanning Electron Microscopy (SEM) and the results are shown in FIG. 2.

Example 2:

(1) adding 16.5kg of electrolytic metal manganese pieces and 200L of pure water into a dissolving tank, adding 32kg of 98% concentrated sulfuric acid for reaction, adjusting the pH value to 4.0-5.0 after the manganese pieces are dissolved, adding 700g of hydrogen peroxide for iron removal, stirring for 30min, adding 70g of sodium ferbamate for removing heavy metals, continuing stirring for 30min, and finally filtering to obtain a manganese sulfate solution;

(2) preparing 200L of 5mol/L alkali liquor by using ammonia water and sodium hydroxide as an alkaline precipitator, wherein the molar ratio of the ammonia water to the sodium hydroxide is 1:1, and 400g of sodium dodecyl sulfate is added;

(3) adding pure water into the reaction kettle to serve as a base solution, wherein the volume of the pure water just submerges the stirring paddle, and heating in a water bath to 60 ℃; under the condition of stirring, the stirring speed is 500r/min, the manganese sulfate solution obtained in the step (1) and the alkaline precipitator obtained in the step (2) are added into a reaction kettle in a concurrent flow mode, the feeding speed of the manganese sulfate solution is 200mL/min, and oxygen is introduced for oxidation; in the reaction process, controlling the pH value of a reaction system to be 7.4-7.8 by adjusting the flow rate of an alkaline precipitator; after the manganese sulfate solution is added, controlling the pH value to be unchanged, continuously stirring, and preserving heat and aging for 8 hours;

(4) and (4) centrifuging the product obtained in the step (3), washing the product for 3 times by using pure water, putting the product into an oven, and standing the product at 120 ℃ for 10 hours to dry the product to obtain the trimanganese tetroxide.

The particle size D50 of the trimanganese tetroxide prepared in this example was 1.17 μm, the Mn content was 71.5%, the S content was 0.085%, the Ca content was 39.4ppm, the Mg content was 22.9ppm, the Na content was 45.1ppm, the K content was 9.4ppm, the Fe content was 36.6ppm, the Pb content was 1.7ppm, the Zn content was 9.1ppm, the Cu content was 0.3ppm, the Cd content was 2.4ppm, and the Cr content was 0.2 ppm. The morphology was observed by Scanning Electron Microscopy (SEM) and the results are shown in FIG. 3.

Example 3:

(1) adding 27.5kg of electrolytic metal manganese pieces and 200L of pure water into a dissolving tank, adding 56kg of 98% concentrated sulfuric acid for reaction, adjusting the pH value to 4.0-5.0 after the manganese pieces are dissolved, adding 1000g of hydrogen peroxide for iron removal, stirring for 30min, adding 40g of ammonium sulfide and 40g of sodium dimethyl dithiocarbamate for removing heavy metals, continuously stirring for 30min, and finally filtering to obtain a manganese sulfate solution;

(2) preparing 200L of 10mol/L alkali liquor with sodium hydroxide as an alkaline precipitator, wherein 300g of ethanol and 200g of carboxymethyl cellulose are added;

(3) adding pure water into the reaction kettle to serve as a base solution, wherein the volume of the pure water just submerges the stirring paddle, and heating in a water bath to 70 ℃; under the condition of stirring, the stirring speed is 700r/min, the manganese sulfate solution obtained in the step (1) and the alkaline precipitator obtained in the step (2) are added into a reaction kettle in a concurrent flow mode, the feeding speed of the manganese sulfate solution is 200mL/min, and air is introduced for oxidation; in the reaction process, the pH value of a reaction system is controlled to be 8.0-8.5 by adjusting the flow rate of an alkaline precipitator; after the manganese sulfate solution is added, controlling the pH value to be unchanged, continuously stirring, and preserving heat and aging for 8 hours;

(4) and (4) centrifuging the product obtained in the step (3), washing the product for 3 times by using pure water, putting the product into an oven, and standing the product at 120 ℃ for 10 hours to dry the product to obtain the trimanganese tetroxide.

The particle size D50 of the manganous-manganic oxide prepared in the embodiment is 1.54 mu m, the Mn content is 70.6 percent, the S content is 0.068 percent, the Ca content is 42.4ppm, the Mg content is 7.2ppm, the Na content is less than or equal to 48.4ppm, the K content is less than or equal to 4.3ppm, the Fe content is less than or equal to 21.4ppm, the Pb content is 1.7ppm, the Zn content is 7.9ppm, the Cu content is 0.7ppm, the Cd content is 1.6ppm, and the Cr content is 0.4 ppm. The morphology was observed by Scanning Electron Microscopy (SEM) and the results are shown in FIG. 4.

Comparative example 1:

(1) adding 27.5kg of electrolytic metal manganese pieces and 200L of pure water into a dissolving tank, adding 56kg of 98% concentrated sulfuric acid for reaction, adjusting the pH value to 4.0-5.0 after the manganese pieces are dissolved, adding 1000g of hydrogen peroxide for iron removal, stirring for 30min, adding 40g of ammonium sulfide, continuing stirring for 30min, and finally filtering to obtain a manganese sulfate solution;

(2) preparing 200L of 10mol/L alkali liquor with sodium hydroxide as an alkaline precipitator, wherein 300g of ethanol and 200g of carboxymethyl cellulose are added;

(3) adding pure water into the reaction kettle to serve as a base solution, wherein the volume of the pure water just submerges the stirring paddle, and heating in a water bath to 70 ℃; under the condition of stirring, the stirring speed is 700r/min, the manganese sulfate solution obtained in the step (1) and the alkaline precipitator obtained in the step (2) are added into a reaction kettle in a concurrent flow mode, the feeding speed of the manganese sulfate solution is 200mL/min, and air is introduced for oxidation; in the reaction process, the pH value of a reaction system is controlled to be 8.0-8.5 by adjusting the flow rate of an alkaline precipitator; after the manganese sulfate solution is added, controlling the pH value to be unchanged, continuously stirring, and preserving heat and aging for 8 hours;

(4) and (4) centrifuging the product obtained in the step (3), washing the product for 3 times by using pure water, putting the product into an oven, and standing the product at 120 ℃ for 10 hours to dry the product to obtain the trimanganese tetroxide.

The particle size D50 of the manganous-manganic oxide prepared by the embodiment is 18.76 mu m, the Mn content is 63.6 percent, S is more than 1000ppm, Fe is more than 50ppm, Ca is more than 50ppm, Mg is more than 50ppm, Na is more than 50ppm, K is more than 50ppm, and heavy metal is more than 10 ppm; the prepared micro-nano manganous manganic oxide particles have large sizes and poor dispersibility.

Comparative example 2:

(1) adding 27.5kg of electrolytic metal manganese pieces and 200L of pure water into a dissolving tank, adding 56kg of 98% concentrated sulfuric acid for reaction, adjusting the pH value to 4.0-5.0 after the manganese pieces are dissolved, adding 1000g of hydrogen peroxide for iron removal, stirring for 30min, adding 40g of sodium dimethyl dithiocarbamate for removing heavy metals, continuing stirring for 30min, and finally filtering to obtain a manganese sulfate solution;

(2) preparing 200L of 10mol/L alkali liquor with sodium hydroxide as an alkaline precipitator, wherein 300g of ethanol and 200g of carboxymethyl cellulose are added;

(3) adding pure water into the reaction kettle to serve as a base solution, wherein the volume of the pure water just submerges the stirring paddle, and heating in a water bath to 70 ℃; under the condition of stirring, the stirring speed is 700r/min, the manganese sulfate solution obtained in the step (1) and the alkaline precipitator obtained in the step (2) are added into a reaction kettle in a concurrent flow mode, the feeding speed of the manganese sulfate solution is 200mL/min, and air is introduced for oxidation; in the reaction process, the pH value of a reaction system is controlled to be 8.0-8.5 by adjusting the flow rate of an alkaline precipitator; after the manganese sulfate solution is added, controlling the pH value to be unchanged, continuously stirring, and preserving heat and aging for 8 hours;

(4) and (4) centrifuging the product obtained in the step (3), washing the product for 3 times by using pure water, putting the product into an oven, and standing the product at 120 ℃ for 10 hours to dry the product to obtain the trimanganese tetroxide.

The particle size D50 of the manganous-manganic oxide prepared in the embodiment is 11.76 mu m, the Mn content is 64.3 percent, S is more than 1000ppm, Fe is more than 50ppm, Ca is more than 50ppm, Mg is more than 50ppm, Na is more than 50ppm, K is more than 50ppm, and heavy metal is more than 10 ppm; the prepared micro-nano manganous manganic oxide particles have large sizes and poor dispersibility.

According to the performance parameter measurement result of the micro-nano manganous oxide prepared by the embodiment, the method for preparing the micro-nano manganous oxide by using the manganese sulfate solution has the advantages that electrolytic manganese metal sheets are dissolved, impurities are removed, purification is carried out, the manganese sulfate solution with low impurity content is obtained, the manganese sulfate solution is oxidized by one step to prepare the manganous oxide, and the impurity content of a product is greatly reduced by controlling the impurity content of raw materials; the dispersing agent is added into the alkaline precipitator to inhibit the growth of crystal grains, so that the prepared micro-nano manganous manganic oxide particles are small in size and good in dispersibility; the process is simple to operate, low in production cost and easy to realize industrial production; the particle size indexes of the prepared micro-nano manganous manganic oxide are as follows: d50 is less than 2 mu m, Mn is more than or equal to 70.5wt%, S is less than or equal to 1000ppm, Fe is less than or equal to 50ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, Na is less than or equal to 50ppm, K is less than or equal to 50ppm, and heavy metal is less than or equal to 10 ppm.

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.