JPS62187118A - Production of manganese dioxide - Google Patents

Abstract

PURPOSE:To produce manganese dioxide which is suitable for a dry cell and has activity and high bulk density in excellent yield by performing the acid treatment of slurried manganese suboxide in the presence of an oxidizing agent. CONSTITUTION:Manganese suboxide such as Mn2O3 obtained by roasting manga nese ore is crushed in >= about 60 mesh particle size and slurried. Both an oxidizing agent such as sodium chlorate and acid such as sulfuric acid are added to this slurry and acid-treated. The oxidizing agent and acid which respec tively have the amount of about 1.0-2.0 times for the amount stoichiometrically necessary to obtain manganese dioxide from a raw material are used and prefer ably acid-treated at >= about 60 deg.C temp. The solid content wherein manganese dioxide obtained in this treatment is made to an essential component is fully washed with water and dried and thereby recovered as a final product. By this method, high-activity manganese dioxide having the electric discharge characteristics comparing with electrolytic manganese dioxide is obtained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for producing manganese dioxide.

More specifically, the present invention relates to a method capable of obtaining manganese dioxide having high activity and high bulk density in good yield.

BACKGROUND OF THE INVENTION Manganese dioxide is used as a depolarizer in the main material of dry batteries, and its properties have a very large effect on the performance of dry batteries, so it is very important in battery design.

Among various battery systems, manganese dioxide dry batteries are particularly widely used, probably because manganese dioxide ore is naturally available at relatively low cost and in large quantities. However, in recent years, it has become increasingly difficult to select high-quality natural ores, and as a result, various attempts have been made to artificially produce minerals with good properties.

As an example, mention may be made, for example, of electrolytic manganese dioxide. This electrolytic manganese dioxide is usually obtained by anodic oxidation of manganese sulfate, has a crystal phase mainly consisting of r-MnO3, and is generally considered to be optimal as a depolarizing agent. However, in order to obtain electrolytic manganese dioxide, an electrolytic oxidation step is essential and requires a large amount of electric power, resulting in problems such as high cost and significant energy consumption.

In addition, as seen in the invention disclosed in JP-A No. 58-82697, manganese dioxide ore after roasting is acid-treated with nitric acid to activate it, and a solution containing the soluble substance obtained at that time, that is, manganese nitrate. A method has been developed in which manganese dioxide is recovered as manganese dioxide through electrolysis in order to improve the yield, but the manganese dioxide obtained by this method has a low bulk density, and because it uses an electrolytic process, it is expensive. The problem persists.

In this current situation, low cost and highly active MnO2
For example, manganese sulfate is roasted to obtain lower oxides of manganese, that is, Mn2O3 and/or Mn*CL, and this Mn3O3 and/or Method for obtaining manganese dioxide by acid treatment of Mn3O4 (Patent application No. 76334/1989)
) has been developed. According to this method, it is possible to prevent high costs and energy consumption due to the electrolytic process, and the obtained manganese dioxide is highly purified and has high activity mainly composed of r-MnO2. It is.

Problems to be Solved by the Invention As mentioned above, as a method of obtaining highly active manganese dioxide at low cost, a method of completely chemical synthesis was developed, which achieved considerable results in terms of cost and purity. It's coming. However, this method had the following problems.

That is, this method involves the production of divalent manganese in the acid treatment of the lower oxide of manganese, and therefore the yield of manganese dioxide is poor. For example, the yield of manganese dioxide obtained by one acid treatment is When Mn1CL was used as a raw material, it was 50%, and when Mn1CL was used as a raw material, it was only 33%, which caused the problem of poor productivity.

In addition, the manganese dioxide obtained by this acid treatment is
The bulk density was low, and when it was directly filled into a dry battery, the discharge characteristics were poor. Therefore, the manganese dioxide obtained by this acid treatment had to be made heavier by compression molding using a roll press or the like.

The heavy manganese dioxide is crushed to the desired particle size and then filled into dry batteries, but the necessity of the heavy weighting process and the crushing process complicates the entire work process and makes it difficult to use. The impact on costs is unavoidable.

As detailed above, conventional chemical production methods have had problems such as poor yield of manganese dioxide, low bulk density, and the need to make it heavier. Solving these problems is very important in obtaining low-cost, high-quality batteries. Therefore, the object of the present invention is to develop a highly active and high bulk density carbon dioxide suitable for use in dry batteries. An object of the present invention is to provide a method for obtaining manganese in good yield through chemical treatment.

Means for Solving the Problems As a result of various studies in order to solve the above-mentioned problems of the conventional chemical production method, the inventors of the present invention have found that the divalent manganese compound generated during acid treatment is oxidized at the same time as the acid treatment. Based on this finding, the present invention was developed based on the finding that manganese dioxide is very advantageous in achieving the above object of the present invention.

That is, the present invention is characterized in that the slurry-formed lower manganese oxide is acid-treated in the presence of an oxidizing agent.

The above-mentioned oxidizing agent may be any agent as long as it can efficiently oxidize the divalent manganese compound generated during the acid treatment and convert it into manganese dioxide. For example, sodium chlorate, lithium chlorate, and mixtures thereof are preferable. This can be cited as an example.

Furthermore, examples of the above-mentioned acids include sulfuric acid, nitric acid, and hydrochloric acid. Although these can be used alone or as a mixture, it is preferable to use sulfuric acid from the viewpoint of cost.

Further, the reaction rate can be increased by increasing the amount of the oxidizing agent and acid used in the acid treatment to a certain extent, but there is an upper limit from an economic viewpoint. Therefore, in the acid treatment, the amounts of the oxidizing agent and acid used are 1.0 to 2.0 times the stoichiometrically necessary amount to obtain manganese dioxide from the lower oxide, and generally 1.
About twice as much is preferable.

Further, the acid treatment is preferably performed at a temperature of 60° C. or higher. When carried out at a temperature below 60°C, it takes a long time to complete the reaction, which is economically unfavorable.

Furthermore, the particle size of the lower manganese oxide must be such that a sufficient contact area with the acid treatment solution can be obtained;
It is preferably 0 mesh or more, generally 120 mesh or more.

Furthermore, the manganese lower oxide may be one that can provide manganese dioxide in good yield through the acid treatment (
Examples include Mr+zO3, Mn5O- and Mn008, which can be used alone or as a mixture thereof.

In addition, the lower oxides of manganese dioxide include, for example, Mn2O3, which is produced by roasting manganese ore, Mn20a, which is obtained by roasting divalent manganese compounds, and Mn, O
,,MnO obtained by wet oxidation of divalent manganese compound
Examples include OH and Mn3O4.

In the present invention, the manganese dioxide raw material obtained by the above-mentioned known technique is pulverized to a particle size of 120 mesh or more, made into a slurry, and further acid-treated by adding the above-mentioned oxidizing agent and the above-mentioned acid.

As already mentioned, this acid treatment is preferably carried out at a temperature of 60°C or higher for several hours using about 1.2 times the amount of acid and oxidizing agent as required to obtain manganese dioxide from the above raw materials. . However, these processing conditions should be set to the most suitable conditions depending on the type and properties of the raw materials used.

The solid content mainly composed of manganese dioxide obtained by this acid treatment is thoroughly washed with water, dried, and recovered as a final product. It is also possible to neutralize with an alkali such as NHloH, which is free from contamination with potassium, and then wash with water and dry.

In order to obtain manganese dioxide having a high bulk density and high activity in a good yield by a chemical production method, it is preferable to use the method according to the present invention in which an oxidizing agent is added during acid treatment.

That is, the reaction of obtaining manganese dioxide by acid treatment of a lower oxide of manganese is a disproportionation reaction, and for example, M
When n2O3 or MnaO4 is acid-treated with sulfuric acid, a divalent manganese compound (here, manganese sulfate) is inevitably produced as shown in the following reaction formula: %Formula %. Therefore, the yield of manganese dioxide obtained by this acid treatment is Mn2O3
It cannot exceed 50% for Mn3CL and 33% for Mn3CL.

Therefore, according to the present invention, by adding an oxidizing agent such as sodium chlorate, lithium chlorate, or a mixture thereof during this acid treatment, for example, as shown in the following reaction formula: % formula % (:103) Thus, according to the method of the present invention, by adding the above-mentioned oxidizing agent, the yield of Mn0z becomes 90% or more, and the bulk density is also greatly improved, so it can be used as a battery as it is. High discharge characteristics can be obtained even when filled with

EXAMPLES The present invention will be explained in more detail based on Examples below.
This example does not limit the invention in any way.

Example 1 After crushing manganese ore having the chemical composition shown in Table 1 below to a particle size of 5 mm or less, it was roasted in the air at a temperature of 800°C for 1 hour to produce a manganese ore containing α-Mn20* as the main component. Manganese oxide was obtained.

Table 1: Chemical composition of original ore (%) After grinding this reduced roasted manganese oxide ore to a particle size of 120 mesh or more, each I
ON sulfuric acid and chloric acid (IJ) were added, and acid treatment was performed for 6 hours. The amounts of sulfuric acid and sodium chlorate used were 1 stoichiometrically necessary to obtain manganese dioxide.
．． It was twice as much.

Next, the solid matter generated during the sulfuric acid treatment was washed with pure water at a ratio of solid matter: water = 1:30, adjusted to pf 16.5 with a dilute NH4OH solution, and further dried at a temperature of 120°C. It had a chemical composition as shown in Table 2, and the MnOz contained therein was active manganese dioxide mainly composed of T-MnO2 and partially containing α-MnO□.

Table 2: Chemical composition (%) of active manganese dioxide Example 2 Manganese sulfate crystals were fired in a semi-closed furnace (atmospheric atmosphere) at a temperature of 1000°C for 60 minutes, and the main component was Mn+0.
Manganese oxide No. 4 was obtained. This manganese oxide containing Mn 30° as a main component was further roasted in a rotary kiln in the atmosphere at a temperature of 800° C. for 2 hours to obtain a manganese oxide containing Mn 20a as a main component.

This Mn20. Manganese oxide mainly composed of
At 0°C, 1ON sulfuric acid and sodium chlorate were added, and the reaction was carried out for 6 hours. The amounts of sulfuric acid and sodium chlorate used were each 1.2 times the stoichiometrically required amount to obtain manganese dioxide.

Next, the solid matter produced during the sulfuric acid treatment was washed with pure water at a ratio of solid matter: water = 1:30, and then dried, and the obtained product was shown in Table 3 below. The chemical composition is as follows, and the M n O2 contained therein is r
High purity active manganese dioxide containing -MnO2 as a main component and partially containing ρ-MnOz was obtained.

Table 3: Chemical composition (%) of high-purity active manganese dioxide The results of measuring the tap densities of the active manganese dioxide obtained in Example 1 and the high-purity active manganese dioxide obtained in Example 2 are shown in Table 4 below. Shown in the table.

Table 4 Example 3 A single zinc chloride battery was prepared using the manganese dioxide obtained in Example 1 and Example 2 as the anode active material, and a battery characteristic test (2Ω continuous discharge characteristic test) was conducted. Furthermore, the discharge time until the final discharge voltage of 0.9 .mu. was reached and the utilization rate of the active material were determined, and the results are shown in Table 5 below and the attached FIG. 1. For comparison, Table 5 and Figure 1 show electrolytic manganese dioxide (IC1No.
17. The results of a discharge test conducted under the same conditions on a single zinc chloride battery manufactured using Mitsui Mining & Co., Ltd.) as the anode active material are also shown. As understood from the results in Table 1 and Figure 1, activated manganese dioxide (Example 1)
and high-purity activated manganese dioxide (Example 2) both have excellent discharge characteristics.

Table 5 Effects of the Invention As explained in detail above, according to the method for producing manganese dioxide of the present invention, the lower oxide of manganese is treated with an acid in the presence of an oxidizing agent, so that it is comparable to electrolytic manganese dioxide. It has now become possible to obtain highly active manganese dioxide with discharge characteristics.

In addition, the manganese dioxide obtained by the production method of the present invention has a higher bulk density than that obtained by conventional chemical production, there is no need to make it heavier after acid treatment, and the yield is lower than that of conventional chemical production. We were able to raise it from 33% to 50% to around 90%.

As a result, manufacturing costs are low and high quality manganese dioxide can be obtained, making it possible to significantly reduce the unit price of dry batteries.

[Brief explanation of drawings]

Attached FIG. 1 is a diagram showing the battery life during discharge of a dry cell using manganese dioxide according to the method of the present invention and a dry cell using electrolytic manganese dioxide.

Claims (10)

[Claims] (1) A method for producing manganese dioxide, which comprises treating a lower oxide of manganese in the form of a slurry with an acid in the presence of an oxidizing agent. (2) The method for producing manganese dioxide according to claim 1, wherein the oxidizing agent contains at least one of sodium chlorate and lithium chlorate. (3) The method for producing manganese dioxide according to claim 1 or 2, wherein the acid contains at least one selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid. (4) The amounts of the acid and the oxidizing agent are each 1.0 to 2.0 times the amount stoichiometrically necessary to obtain manganese dioxide from the lower oxide. A method for producing manganese dioxide according to any one of claims 1 to 3. (5) The method for producing manganese dioxide according to any one of claims 1 to 4, wherein the acid treatment is performed at a temperature of 60°C or higher. (6) The method for producing manganese dioxide according to any one of claims 1 to 5, wherein the particle size of the lower manganese oxide is 60 mesh or more. (7) The lower oxide of manganese is Mn_2O_3,
The method for producing manganese dioxide according to any one of claims 1 to 6, characterized in that the method contains at least one selected from the group consisting of Mn_3O_4 and MnOOH. (8) The method for producing manganese dioxide according to claim 7, wherein the Mn_2O_3 is obtained by roasting manganese ore. (9) The method for producing manganese dioxide according to claim 7, wherein the Mn_2O_3 and Mn_3O_4 are obtained by roasting a divalent manganese compound. (10) The above Mn_3O_4 and the above MnOOH are
8. The method for producing manganese dioxide according to claim 7, which is obtained by wet oxidizing a divalent manganese compound.