JPS6114137A - Manufacture of manganese dioxide - Google Patents

Abstract

PURPOSE:To manufacture inexpensively MnO2 for a manganese dry cell having high performance by treating a manganese compd. with a low-concn. acid and thereafter treated with a high-concn. acid. CONSTITUTION:After a manganese compd. such as Mn2O3, Mn3O4 and MnOOH is immersed into nitric acid of >=0.1 equivalent for the manganese compd. or an acid (for example, surfuric acid) other than nitric acid and treated at 70-100 deg.C for 30min-2hr, it is filtered and rinsed. Then, after manganese compd. is immersed into comparatively concentrated acid (for example, nitric acid) of 2-6N concn. of >=1 equivalent for the manganese compd. and treated at 70-100 deg.C for 30min-2hr, it is filtered, rinsed and dried.

Description

[Detailed description of the invention] Shy 1yo p encounter! The present invention relates to a method for producing manganese dioxide.

More specifically, the present invention relates to a chemical method for producing T-type manganese dioxide suitable for use in manganese dry batteries by stepwise treating a manganese compound with an acid.

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 crystalline phase mainly consisting of r-MnOa, 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.

Furthermore, many chemical treatment methods are known in which highly active MnO2 is formed by acid treatment of lower manganese oxides such as Mn+03, Mn30a, and Mn0OH.

Many conventional chemical treatment methods use nitric acid, but nitric acid is expensive and processing costs are high.

Furthermore, when an acid other than nitric acid is used, if the acid concentration is increased, the produced manganese dioxide becomes α-type and cannot be used as manganese dioxide for dry batteries. After all, α-Mno2 is electrolytic manganese dioxide, or r-
This is because, unlike MnO7, during heavy discharge (load of 2 to 4 Ω), the reduction reaction rate of Mn4+-Mn3+ is slow, resulting in a significant voltage drop.
On the other hand, if a low concentration of acid is used, it is possible to obtain T-type manganese dioxide suitable for dry batteries;
At such a low concentration, the amount of liquid required for acid treatment becomes extremely large, which not only increases the size of the treatment equipment, but also requires a large amount of post-treatment processes such as filtration and waste liquid treatment. A large scale device is required, resulting in extremely high equipment costs and processing costs.

Problems to be Solved by the Invention As mentioned above, in conventional methods for producing artificial manganese dioxide, for example, high-performance T-type manganese dioxide can be obtained using the electrolytic method, but the energy cost is high. ,
As a result, the manufacturing cost of manganese dry batteries is high, and even in force-ratio acid treatment, α-type MnO2, which is unsatisfactory as a depolarizer for dry batteries, is the main product, and the amount of treatment liquid is low. There are various problems that need to be improved, such as the large amount of water and the need to increase the size of treatment equipment, waste liquid treatment equipment, etc.

Therefore, in view of the situation of conventional methods, the present invention makes it possible to produce high-performance manganese dioxide for use in manganese dry batteries using as little processing liquid as possible.As a result, processing equipment can be made smaller and manufacturing costs can be reduced. The purpose of this project is to develop a method for producing manganese poxide that can save money and, in turn, reduce the unit price of dry batteries.

Means for Solving the Problems Therefore, the inventors of the present invention have conducted various studies and researches to achieve the above-mentioned object, and have found that the main cause of the α-type crystal structure in the method of obtaining manganese dioxide by acid treatment. However, it is thought that this is because cations such as ``('', Na+, etc.) in the manganese compound before acid treatment and anions such as 8042- in the acid invade into the crystal lattice. It has been found that pre-treatment with a small amount of acid to elute ions such as K", Na+, etc. and convert it into a state in which ions such as 8- and '- are difficult to enter is extremely effective in achieving the above purpose. The present invention has been completed based on this new finding.

That is, the method for producing manganese dioxide of the present invention is characterized in that a manganese compound is first treated with nitric acid or an acid other than nitric acid of 2N or less, and then subjected to a second treatment with a relatively concentrated acid.

Manganese compounds that can be used in the method of the present invention include MnzO++, 1lln+o*, Mn0OH, and other compounds obtained by roasting manganese ore, and these can be used alone or in a mixture of two or more. Is possible.

The manganese ore generally contains about 45% or more of Mn (Mn
O, about 70% or more), 5102 about 4% or less, A1. O8
A material containing about 5% or less, about 2% or less of Fe2r3, and other unavoidable elements can be used.

The ore is usually roasted at 600 to 950°C for 30 minutes or more in the atmosphere. In this roasting, the main component of the roasted product is Mn2O.
It is advantageous to do so so that 3. This is because Mn20a generally provides a higher manganese dioxide yield in the subsequent acid treatment than other manganese oxides such as Mn301.

Mn20v! To obtain the J Petucci roasted product,
It is desirable that the raw ore be roasted at a relatively low temperature within the above temperature range, or even at a higher temperature under oxygen-rich conditions.

Examples of acids other than nitric acid used in the primary treatment include mineral acids such as hydrochloric acid and sulfuric acid.

In this primary treatment, when an acid other than nitric acid is used, what is important is that the concentration is 2N or less, regardless of the type of acid. It is therefore also possible to use mixed acid systems.

Furthermore, examples of acids used in the secondary treatment include mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid. In this case too, the acids can be used alone or in mixtures. The acid concentration in this secondary treatment is not particularly limited, but the amount of treated liquid is reduced, and the equipment for post-treatment processes such as treatment string ends, filtration, and waste liquid treatment is downsized to reduce equipment costs and treatment costs. For the purpose, it is desirable that the concentration be higher than that in the primary treatment, and it is generally advantageous to carry out the concentration within a range of about 2 to 6N.

That is, if it is less than 2N, the acid becomes tingly and requires a large amount of processing liquid. On the other hand, when the concentration exceeds 6N, the amount of treatment liquid is small, the slurry concentration becomes too high, acid treatment becomes difficult, and the gelatinization rate tends to increase.

In the method of the present invention, the treatment conditions other than the acid and its concentration in the primary treatment and secondary treatment, such as temperature, treatment time, etc., are not particularly limited. Since it is disadvantageous industrially, from an economic point of view, the temperature is within the range of 70 to 100°C.
Sufficient effects can be expected with a treatment time of about 2 hours.

Preparation In the method for producing manganese dioxide of the present invention, in the primary treatment, treatment is performed with nitric acid or other acids of low concentration, that is, 2N or less, to remove α that is unsuitable for use as a depolarizer for manganese dry batteries. In order to promote the formation of a - type crystal structure, cations such as +, Na+, and Ba2+ are eluted from the manganese compound to be treated, thereby preventing the crystal form of MnO2 produced from becoming an α-type. The amount of acid required for this treatment is at least about 0.1 equivalent relative to the manganese compound to be treated, which is sufficient to achieve the purpose. Also, with this process,
During the subsequent secondary acid treatment, it is possible to prevent so, ions, etc. (which are also thought to promote α-form formation) from penetrating into the crystals and forming α-form formation. It seems that

Next, in the secondary acid treatment step, the material is treated with any acid of any concentration, and this treatment is for producing Mn0z by a so-called disproportionation reaction. The amount of acid required for this treatment is at least 1 equivalent relative to the amount of manganese compound to be treated.

In this secondary treatment, the factors that cause α-ization have already been eliminated in the previous stage, that is, the primary treatment, so even if the acid concentration is increased as in the past, the formation of an α-type crystal structure is avoided. High-grade manganese dioxide, which is advantageous for producing manganese dry batteries, can be obtained.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on comparative examples and examples, but the scope of the present invention is not limited by these examples.

Comparative example S i'o a about 3wt%, KrJo, 6wt%, Na
Manganese ore containing about 0.1 wt% and Mn0z content of about 77 wt% is crushed into 200 mesh or less, and this is roasted at 800 tons for 5 hours to produce manganese lower oxides (MniOa, Mn5 (L etc.) were created.

The lower manganese oxide was acid-treated with 3N sulfuric acid (obtained by diluting commercially available sulfuric acid) using a '91) C4 trowel for 1 hour.

Then, it was filtered, washed with water, and dried (at 1 °C) to obtain manganese dioxide.

When the thus obtained crab manganese oxide was analyzed using an xa diffraction device, its crystal structure was found to be α-type.

Furthermore, the Na content in the manganese dioxide product is 0.03
Although the K content decreased to 1 wt%, it was quite high at 1 wt%.

Example 1 Using the same manganese ore as that used in the above comparative example, a manganese lower oxide obtained by roasting according to the same method was first treated with 041 equivalents of IN nitric acid (relative to the manganese lower oxide). The mixture was acid-treated at 90° C. for 1 hour, then filtered and washed with water.

Next, using 2 equivalents of 3N sulfuric acid, acid treatment was performed at 90°C for L hours, followed by filtration, washing with water, and drying (100°C).The resulting manganese dioxide was found to have T- It was found that it has a type crystal structure (slightly α-type is included). Furthermore, α゛-type Mn0z
The contents of Na and K, which are thought to promote the formation of O, were considerably reduced to 0.03 wt% and 0.171%, respectively, and clear suppression of gelatinization was observed.

Example 2 Manganese ore similar to that in the comparative example was used and roasted in the same manner to obtain lower manganese oxide. This was first acid-treated at 90°C for 1 hour using 0.1 equivalent of 0.5N sulfuric acid (for manganese lower oxide), and then 6N sulfuric acid was added to reduce the acid concentration in the treatment solution to 3N. Under these conditions, acid treatment was performed again at 90° C. for 1 hour. Then, it was filtered, washed with water, and dried to obtain the target manganese dioxide.

Analyzes using an X-ray diffraction apparatus similarly revealed that the manganese dioxide obtained in this manner had a γ-type crystal structure (including a slight α-type structure).Furthermore, Na
The content of K is 0.02wt% and 0.2w, respectively.
It can be seen that the gelatinization suppressing effect has been clearly achieved.

Example 3 Manganese dioxide was formed using the same manganese compound as in the above example, using the acids and concentrations shown in the table below, and under the same conditions as in the above example.

For each sample obtained in this way, the alpha conversion rate (%) and discharge characteristics (assembled into a single size ZnC11 type battery, with a load of 2Ω,
The continuous discharge life (continuous discharge life) was measured under the condition that the discharge end voltage was 0.9cm. The results are shown in the table below.

From the results in the above table, it is clear that Moerakana-2 is 2% in the primary acid treatment.
When an acid with a concentration of N or less is used, the gelatinization rate is considerably reduced, and the discharge characteristic is 250 minutes or more, which exceeds the minimum allowable limit of 240 minutes for this type of battery.

Therefore, according to the method for producing manganese dioxide of the present invention, a manganese compound as a starting material is subjected to two stepwise acid treatments, that is, a primary treatment and a secondary treatment, and the primary treatment first removes the cause of gelatinization. Based on the devised method to remove Mn0z and generate Mn0z in secondary treatment, it is not necessary to use large amounts of expensive acids such as nitric acid, and the amount of processing liquid can be significantly reduced. Larger acid treatment equipment, filtration, waste liquid treatment - larger post-processing equipment. This makes it possible to avoid oxidation, and in turn, it becomes possible to manufacture manganese dioxide for manganese dry batteries with excellent discharge characteristics at a low cost.

Therefore, the method of the present invention can be said to be extremely useful industrially as a method for producing manganese dioxide.

Claims (7)

[Claims] (1) A method for producing manganese dioxide, which comprises first treating a manganese compound with nitric acid or an acid other than nitric acid with a concentration of 2N or less, and then secondly treating a manganese compound with a relatively concentrated acid. (2) The manganese compound is Mn_2O_3, Mn_3O
_4, MnOOH and roasted manganese ore. (3) The method according to claim 1 or 2, wherein the acid other than nitric acid is sulfuric acid or hydrochloric acid. (4) The method according to any one of claims 1 to 3, characterized in that the amount of acid used in the primary treatment is at least 0.1 equivalent relative to the manganese compound. (5) The method according to any one of claims 1 to 3, wherein the acid used in the secondary treatment is at least one selected from the group consisting of nitric acid, hydrochloric acid, and sulfuric acid. (6) The method according to any one of claims 1 to 4, wherein the concentration of acid in the secondary treatment is within a range of 2 to 6N. (7) The method according to any one of claims 1 to 6, characterized in that the amount of acid used in the secondary treatment is at least 1 equivalent relative to the manganese compound.