CN117776266A - Preparation method of high-purity manganese dioxide - Google Patents

Abstract

The application relates to a preparation method of high-purity manganese dioxide, which comprises the following steps: pretreating electrolytic manganese to remove sulfate impurities on the electrolytic manganese; then, adopting nitric acid to carry out material melting on electrolytic manganese to obtain manganese nitrate solution; filtering and concentrating the manganese nitrate solution, decomposing at 200-250 ℃, centrifugally drying, and screening to obtain high-purity manganese dioxide; the pretreatment comprises the following steps: adding pure water and nitric acid into electrolytic manganese, heating, boiling and washing, and repeating the treatment for 3-5 times; the mass ratio of electrolytic manganese to pure water to nitric acid is 1: (1-3): (0.001-0.02). The method can improve the purity of the manganese dioxide obtained by preparation.

Description

Preparation method of high-purity manganese dioxide

Technical Field

The application relates to the field of manganese dioxide preparation technology, in particular to a preparation method of high-purity manganese dioxide.

Background

Manganese dioxide has a changeable crystal structure and flexible electrochemical activity, so that the manganese dioxide is an important electrode material and is widely applied to chemical power sources such as alkaline manganese batteries, zinc manganese batteries, magnesium manganese batteries and the like; in addition, manganese dioxide is used as a multifunctional fine inorganic reagent, and has wide application prospect in the emerging fields of nano materials, advanced catalysts and the like.

The existing manganese dioxide preparation methods generally comprise an electrolytic method, a manganese carbonate thermal decomposition method and a manganese sulfate oxidation method, and the manganese dioxide prepared by the electrolytic method has high purity, but the electrolytic manganese dioxide has high cost and unstable product quality, and can not meet the requirements of the rapidly developed battery industry on high-quality manganese dioxide.

The higher the purity of the manganese dioxide is, the discharge performance of the product is enhanced, and the chemical methods such as a manganese carbonate thermal decomposition method, a manganese sulfate oxidation method and the like are used for preparing the manganese dioxide, so that the production cost is relatively low, but the prepared chemical manganese dioxide cannot reach high purity, and the application of the chemical manganese dioxide is restricted to a certain extent.

Disclosure of Invention

In order to improve the purity of manganese dioxide obtained by preparation, the application provides a preparation method of high-purity manganese dioxide.

In a first aspect, the preparation method of high-purity manganese dioxide provided by the application adopts the following technical scheme:

a preparation method of high-purity manganese dioxide comprises the following steps:

pretreating electrolytic manganese to remove sulfate impurities on the electrolytic manganese; then, adopting nitric acid to carry out material melting on electrolytic manganese to obtain manganese nitrate solution; filtering and concentrating the manganese nitrate solution, decomposing at 200-250 ℃, centrifugally drying, and screening to obtain high-purity manganese dioxide;

the pretreatment comprises the following steps: adding pure water and nitric acid into electrolytic manganese, heating, boiling and washing, and repeating the treatment for 3-5 times;

the mass ratio of the electrolytic manganese to the pure water to the nitric acid is 1: (1-3): (0.001-0.02).

By adopting the technical scheme, the electrolytic manganese is simple substance metal obtained by leaching manganese ore with acid and then delivering the manganese salt to an electrolytic tank for electrolytic precipitation, so that the cost of the electrolytic manganese is low, and the cost can be effectively reduced when the electrolytic manganese is used as a raw material for preparing manganese dioxide. The manganese nitrate solution is obtained by adopting nitric acid to electrolyze the manganese material, and then the manganese nitrate solution is subjected to thermal decomposition at high temperature to obtain a manganese dioxide product.

In the preparation process of electrolytic manganese, sulfuric acid is added to manganese ore for leaching reaction, so that sulfate impurities are usually contained in the surface layer and near-surface layer of the obtained electrolytic manganese, so that sulfate radicals are contained in the subsequently obtained manganese nitrate solution, and the purity of manganese dioxide is reduced. And adding a trace amount of nitric acid to slightly react with the surface of the electrolytic manganese, and then heating, boiling and washing to remove sulfate impurities on the surface layer and the near surface layer of the electrolytic manganese. And nitric acid is added for reaction and boiling and washing for a plurality of times in trace quantity, so that sulfate impurities of electrolytic manganese and a subsequent manganese nitrate solution can be effectively removed, and the purity of manganese dioxide obtained by thermal decomposition is obviously improved. The impurity removal and purification method is simple in operation and low in cost, has remarkable impurity removal and purification effects, and can be used for preparing high-purity manganese dioxide at low cost.

The pure water and the nitric acid are added according to the proportion, so that the reaction degree of the nitric acid and the surface of the electrolytic manganese can be better controlled, sulfate impurities on the surface layer and the near-surface layer of the electrolytic manganese are removed as much as possible, and excessive reaction and more loss of the electrolytic manganese in pretreatment are avoided.

And simultaneously, the manganese dioxide product obtained by thermal decomposition of the manganese nitrate solution can also obtain nitrogen dioxide waste gas, and the nitrogen dioxide waste gas is introduced into water or dilute nitric acid to be recycled to obtain nitric acid, so that the nitric acid is recycled for preparing the manganese nitrate solution, and the cost can be further saved.

Optionally, the heating and boiling temperature is 90-110 ℃ and the time is 3-5min.

Optionally, the sulfate content of the electrolytic manganese is less than or equal to 0.01 percent and is qualified in treatment.

By adopting the technical scheme, after the sulfate content on the electrolytic manganese is detected to be less than or equal to 0.01%, the pretreatment can be stopped, so that the purity of the manganese dioxide product obtained later reaches the standard.

Optionally, during material melting, the mass ratio of the electrolytic manganese to the nitric acid is 1: (0.1-0.3).

Optionally, when the nitric acid and the electrolytic manganese react, the pH value of the reaction end point is controlled to be 4-5.

By adopting the technical scheme, the electrolytic manganese prepared from manganese ore usually contains some iron ions, the reaction end point is controlled at pH 4-5, so that the iron ions in the manganese nitrate are completely precipitated, iron ion impurities are effectively removed, and the purity of manganese dioxide obtained by thermal decomposition is further improved.

Optionally, the concentration of the manganese nitrate solution is 50-60%.

By adopting the technical scheme, the manganese nitrate solution is concentrated to 50-60% and then subjected to pyrolysis, so that the pyrolysis efficiency is increased, and the situation that the manganese nitrate component is lost and the manganese dioxide yield is influenced due to splashing of the solution when the concentrated solution is too thick and boiling is caused can be reduced.

Optionally, before filtering and concentrating the manganese nitrate solution, heavy metal is removed from the manganese nitrate solution.

By adopting the technical scheme, some heavy metals are usually solidified in electrolytic manganese prepared from manganese ores, so that heavy metals also exist in manganese nitrate solution obtained after material melting, and the purity of manganese dioxide can be further improved only by removing the heavy metals before filtering and concentrating the manganese nitrate solution.

Optionally, the heavy metal removal treatment includes the following steps:

and adding an ammonium sulfide solution into the manganese nitrate solution, wherein the concentration of the ammonium sulfide solution is 10-14%, and the adding mass of the ammonium sulfide solution is 0.001-0.005% of that of electrolytic manganese.

In a first aspect, the present application provides a high purity manganese dioxide, which adopts the following technical scheme:

a high purity manganese dioxide is prepared by the preparation method.

High-purity manganese dioxide with purity more than or equal to 99.9%.

In summary, the present application includes at least one of the following beneficial technical effects:

1. and adding a trace amount of nitric acid to slightly react with the surface of the electrolytic manganese, and then heating, boiling and washing to remove sulfate impurities on the surface layer and the near surface layer of the electrolytic manganese. And nitric acid is added for reaction and boiling and washing for a plurality of times in trace quantity, so that sulfate impurities of electrolytic manganese and a subsequent manganese nitrate solution can be effectively removed, and the purity of manganese dioxide obtained by thermal decomposition is obviously improved. The operation of impurity removal and purification is simple, the cost is low, the impurity removal and purification effects are obvious, and the high-purity manganese dioxide can be prepared at low cost; 2. pure water and nitric acid are added according to the proportion, so that the reaction degree of the nitric acid and the surface of electrolytic manganese can be better controlled, sulfate impurities on the surface layer and near-surface layer of the electrolytic manganese are removed as much as possible, and excessive reaction and more loss of the electrolytic manganese in pretreatment are avoided;

3. the pH value of the reaction end point is controlled at 4-5, so that iron ions in manganese nitrate are completely precipitated, iron ion impurities are effectively removed, and the purity of manganese dioxide obtained by thermal decomposition is further improved.

Drawings

Fig. 1 is a process flow diagram of an embodiment of the present application.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the following examples, which are to be construed as merely illustrative and not limitative of the scope of the invention, but are not intended to limit the scope of the invention to the specific conditions set forth in the examples, either as conventional or manufacturer-suggested, nor are reagents or apparatus employed to identify manufacturers as conventional products available for commercial purchase.

1. Examples

Example 1:

a preparation method of high-purity manganese dioxide comprises the following steps:

firstly, pre-treating the electrolytic manganese slices, wherein the pre-treating comprises the following steps:

100g of electrolytic manganese tablets are put into a reaction pot, 100g of pure water and 0.1g of analytically pure nitric acid (the mass ratio of the electrolytic manganese tablets to the pure water to the nitric acid is 1:1:0.001) are added, and heating, boiling and washing are carried out, wherein the heating, boiling and washing temperature is 100 ℃, and the time is 4min. The same method is repeated for 3 to 5 times, and the sulfate content on the electrolytic manganese is detected to be less than or equal to 0.01 percent and is qualified.

After the pretreatment is completed, material melting is carried out: 20g of analytically pure nitric acid (the mass ratio of electrolytic manganese tablets to nitric acid is 1:0.2) is gradually and slowly added into the reaction pot, meanwhile, the feed liquid in the reaction pot is heated to gradually raise the temperature to 80 ℃, manganese nitrate solution is obtained after the reaction, and the pH value is controlled to be 4 at the end point of the reaction.

And then carrying out heavy metal removal treatment, wherein the heavy metal removal treatment comprises the following steps: 0.0003g of an ammonium sulfide solution was added to the reaction vessel and stirred, and the concentration of the ammonium sulfide solution was 12%.

Filtering the feed liquid in the reaction kettle to remove iron-containing precipitate and heavy metal precipitate, heating and concentrating the obtained filtrate to obtain manganese nitrate concentrate, decomposing the manganese nitrate concentrate at 230 ℃ to obtain high-purity manganese dioxide after centrifugal drying and screening.

Example 2:

a method for preparing high purity manganese dioxide, which is different from example 1 in that: the mass ratio of electrolytic manganese to pure water to nitric acid is 1:2:0.01.

example 3:

a method for preparing high purity manganese dioxide, which is different from example 1 in that: the mass ratio of electrolytic manganese to pure water to nitric acid is 1:3:0.02.

example 4:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: when the material is melted, the mass ratio of electrolytic manganese to nitric acid is 1:0.1.

example 5:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: when the material is melted, the mass ratio of electrolytic manganese to nitric acid is 1:0.3.

example 6:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: the temperature of heating and boiling is 90 ℃ and the time is 3min.

Example 7:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: the temperature of heating and boiling is 110 ℃ and the time is 5min.

Example 8:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: the concentration of the manganese nitrate solution was 50%.

Example 9:

a method for preparing high purity manganese dioxide, which is different from example 2 in that: the concentration of the manganese nitrate solution is 60%.

2. Comparative example

Comparative example 1:

the difference from example 2 is that: the electrolytic manganese is not pretreated, and nitric acid is directly added for material conversion.

Comparative example 2:

the difference from example 2 is that: during pretreatment, the mass ratio of electrolytic manganese to pure water to nitric acid is 1:2:0.03.

comparative example 3:

the difference from example 2 is that: in pretreatment, pure water and nitric acid are added, and then the mixture is cleaned at normal temperature.

Comparative example 4:

the difference from example 2 is that: the pH is controlled between 4 and 5 at the end point of the reaction of nitric acid and electrolytic manganese when the material is not converted.

Comparative example 5:

the difference from example 2 is that: no ammonium sulfide solution was added to the manganese nitrate solution prior to concentration.

3. Performance testing

1) Yield determination:

examples 1 to 9 and comparative examples 1 to 5 were prepared according to the formula for yield calculation: yield = amount of raw material to form target product/amount of raw material to be fed x 100%, yield was calculated, and the results are shown in table 1;

2) Purity measurement:

taking manganese dioxide prepared in examples 1-9 and comparative examples 1-5, detecting the purity of the manganese dioxide by adopting a potassium permanganate titration method, wherein the purity detection result is shown in table 1;

a sample of 0.25g manganese dioxide was weighed and subjected to a blank test along with the sample in a 300mL Erlenmeyer flask. To a 0.25g manganese dioxide sample, 75mL of sulfuric acid was added, and a 35L oxalic acid standard solution was accurately added by a burette, and the mixture was heated in a hot water bath at 80℃until the black particle-disappeared sample was completely dissolved. When the sample is completely dissolved, taking down and titrating with a potassium permanganate standard solution while the sample is hot, slowly titrating when the sample approaches to the end point, and keeping the titration temperature between 75 ℃ until the last drop of the potassium permanganate standard solution turns the sample into reddish as the end point (V).

Table 1:

4. analysis and summary of results

As is evident from the combination of examples 1 to 3 and Table 2, the mass ratios of electrolytic manganese, pure water and nitric acid in the pretreatment processes of examples 1 to 3 were different. As can be seen from table 2, the yield of example 2 is significantly higher than that of example 3, and the yield of example 1 is slightly higher than that of example 2 but differs slightly from that of example 2; and example 2 had a significantly higher purity than example 1, while example 3 had a slightly higher purity than example 2 but was slightly different from example 2, i.e., example 2 was relatively excellent overall in both yield and purity.

And in combination with comparative examples 1-2, electrolytic manganese is not pretreated in comparative example 1, and nitric acid is directly added for material conversion; at the pretreatment in comparative example 2, the mass ratio of electrolytic manganese, pure water and nitric acid was 1:2:0.03, not within the scope of the present application. As can be seen from table 1, both the yield and purity of comparative example 1 and comparative example 2 are significantly lower than example 2.

Therefore, the method can be used for preprocessing electrolytic manganese by adopting nitric acid and pure water, and can obviously improve the yield and purity of manganese dioxide preparation; and in the pretreatment, the mass ratio of electrolytic manganese, pure water and nitric acid is 1:2: at 0.01, the yield of manganese dioxide can be increased, and the purity of the obtained manganese dioxide can be increased.

As can be seen from a combination of examples 2, examples 4 to 5 and Table 2, examples 4 to 5 were different from example 2 in terms of mass ratio of electrolytic manganese to nitric acid in the chemical feed, and it can be seen from Table 2 that example 2 was superior to examples 4 to 5 in terms of yield and purity. From the above, in the process of material melting, the mass ratio of electrolytic manganese to nitric acid is 1: and 0.2, the yield and purity of the prepared manganese dioxide are relatively better.

As can be seen from a combination of examples 2, examples 6 to 7 and Table 2, examples 6 to 7 were heated and boiled at different temperatures and times from example 2, and it can be seen from Table 2 that the yields and purities of examples 6 to 7 were significantly lower than those of example 2. In addition, in the pretreatment of comparative example 3, pure water and nitric acid were added thereto, followed by washing at room temperature in combination with comparative example 3. As can be seen from Table 1, the yield and purity of comparative example 3 were much lower than that of example 2.

The method has the advantages that in the pretreatment, after pure water and nitric acid are added, the prepared manganese dioxide can be effectively improved in yield and purity by heating, boiling and washing; and when the temperature of heating and boiling is 100 ℃ and the time is 4min, the yield and purity of the prepared manganese dioxide are relatively better.

As can be seen from a combination of examples 2, examples 8 to 9 and Table 2, the concentration of the manganese nitrate solution in examples 8 to 9 was different from that in example 2, and it can be seen from Table 1 that the yields and purities of examples 8 to 9 were lower than those in example 2. From the above, when the manganese nitrate solution is concentrated to 55%, the yield and purity of the prepared manganese dioxide are relatively better.

As can be seen from a combination of example 2, comparative example 4 and Table 1, the reaction end point of nitric acid and electrolytic manganese in comparative example 4 was controlled to have a pH of 4-5 when not being converted, and it can be seen from Table 1 that the purity of comparative example 4 was much lower than that of example 2. The method can control the pH value between 4 and 5 at the reaction end point of nitric acid and electrolytic manganese in material melting, and can remarkably improve the purity of the prepared manganese dioxide.

As can be seen from a combination of example 2, comparative example 5 and table 1, the comparative example 5 was not added with an ammonium sulfide solution to a manganese nitrate solution before concentration, and as can be seen from table 1, the purity of comparative example 5 was much lower than that of example 2. From the above, the purity of the prepared manganese dioxide can be remarkably improved by adding the ammonium sulfide solution before concentrating the manganese nitrate solution.

The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.

Claims (10)

1. The preparation method of the high-purity manganese dioxide is characterized by comprising the following steps of:

pretreating electrolytic manganese to remove sulfate impurities on the electrolytic manganese; then, adopting nitric acid to carry out material melting on electrolytic manganese to obtain manganese nitrate solution; filtering and concentrating the manganese nitrate solution, decomposing at 200-250 ℃, centrifugally drying, and screening to obtain high-purity manganese dioxide;

the pretreatment comprises the following steps: adding pure water and nitric acid into electrolytic manganese, heating, boiling and washing, and repeating the treatment for 3-5 times;

the mass ratio of the electrolytic manganese to the pure water to the nitric acid is 1: (1-3): (0.001-0.02).

2. The method for preparing high purity manganese dioxide according to claim 1, wherein: the heating, boiling and washing temperature is 90-110 ℃ and the time is 3-5min.

3. The method for preparing high purity manganese dioxide according to claim 1, wherein: the sulfate content of the electrolytic manganese is less than or equal to 0.01 percent and is qualified in treatment.

4. The method for preparing high purity manganese dioxide according to claim 1, wherein: during material melting, the mass ratio of the electrolytic manganese to the nitric acid is 1: (0.1-0.3).

5. The method for preparing high purity manganese dioxide according to claim 1, wherein: when the nitric acid and the electrolytic manganese react, the pH value of the reaction end point is controlled to be 4-5.

6. The method for preparing high purity manganese dioxide according to claim 1, wherein: the concentration of the manganese nitrate solution is 50-60%.

7. The method for preparing high purity manganese dioxide according to claim 1, wherein: and before filtering and concentrating the manganese nitrate solution, carrying out heavy metal removal treatment on the manganese nitrate.

8. The method for preparing high purity manganese dioxide according to claim 1, wherein the heavy metal removal treatment comprises the steps of:

and adding an ammonium sulfide solution into the manganese nitrate solution, wherein the concentration of the ammonium sulfide solution is 10-14%, and the adding mass of the ammonium sulfide solution is 0.001-0.005% of that of electrolytic manganese.

9. A high purity manganese dioxide, characterized in that: a process according to any one of claims 1 to 8.

10. The high purity manganese dioxide according to claim 9, wherein: the purity is more than or equal to 99.9 percent.