JPH0310578B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a manganese compound. MnOOH is an important compound as a raw material for magnetic ferride heads and catalysts. In particular, the development of magnetic head ferrite with excellent wear resistance has been progressing recently, and for this purpose, the manganese raw material for the ferrite must be highly purified and have a specific crystal shape.
MnOOH is required. In addition, from the perspective of environmental conservation, we will remove and utilize diluted manganese in wastewater discharged from various processes.
A method of obtaining MnOOH is also needed. JP-A-50-80297 describes a method said to be suitable for obtaining acicular γ-MnOOH useful as a manganese raw material for oriented ferrite. According to this method, by simultaneously adding aqueous ammonia and hydrogen peroxide to an aqueous solution of manganese sulfate, it is possible to achieve the above-mentioned results in a shorter aging time than conventional methods.
It is said that MnOOH can be obtained. However, in reality, this method requires aging in air for 50 hours after the reaction, and is still a time-consuming method. Furthermore, the method of JP-A-50-80297 is disadvantageous in that it uses expensive hydrogen peroxide. It is also unclear what manganese grade products can be obtained by such methods. JP-A-50-67817 suggests a method for producing plate-like or scale-like β-MnOOH, which is also said to be useful as a raw material for oriented ferrite. This method also involves adding aqueous ammonia and aqueous hydrogen peroxide to the manganese sulfate solution, and is disadvantageous in that hydrogen peroxide is used. Moreover, if the method is followed, the desired
To obtain MnOOH, the concentration of manganese sulfate solution must be below 1.0 normal (i.e., the concentration of manganese must be
55/2 = 27.5 g/or less), therefore, it is not suitable for industrial mass production of MnOOH. Also, in the method suggested in this Japanese Patent Application Laid-open No. 50-67817,
It is unclear how high the manganese quality of the product is being obtained. To obtain manganese compounds such as MnOOH,
Some studies have also been conducted on air oxidation of manganese sulfate aqueous solutions. For example, "Higuchi et al.: Journal of the Japan Mining Society, 98, 625-628 (1982)" reports a study on air oxidation of an aqueous solution of manganese sulfate in an alkaline region. In this paper,
It has been reported that β-MnOOH is produced by blowing an O ₂ -N ₂ mixed gas under normal pressure into a manganese sulfate aqueous solution in a high pH range to which NaOH has been added. However, as acknowledged by the authors of the article, such methods require control of the hydrodynamic conditions during gas injection to promote the desired reaction. Therefore, several problems remain to be solved before implementing such a method on an industrial scale. Furthermore, the method described in this paper involves air oxidation of an extremely dilute manganese-containing solution (0.01 mol/Mn(OH) ₂ ), and therefore cannot be applied to the simple treatment of manganese-containing wastewater. However, it is not suitable for use in producing ferrites and catalysts on a practical scale. Therefore, an object of the present invention is to provide an economical method for producing MnOOH in a short period of time, which has a wide range of application for a manganese-containing solution as a raw material. The object of the present invention is achieved by hydrothermally treating a slurry obtained by adding ammonia water to an aqueous manganese sulfate solution at high temperature and high pressure in the presence of oxygen gas. By such a method of the present invention, β-
MnOOH, γ-MnOOH, etc. are obtained. The conditions for the hydrothermal treatment depend on the purpose of carrying out the method of the present invention and the desired type and quality of MnOOH. The presence of oxygen gas can be obtained by introducing oxygen gas alone, but a mixture of oxygen gas and an inert gas (eg nitrogen) or air may also be used. The present inventors have also discovered conditions for obtaining highly pure MnOOH, mainly acicular γ-MnOOH, which is used as a raw material for ferrite for magnetic heads. Thus, according to a preferred embodiment of the present invention, a slurry prepared by adding aqueous ammonia to an aqueous manganese sulfate solution to adjust the pH to more than 9.1 and less than 9.6 is heated at a temperature of 80 to 200° C. to 5 to 30 kg/cm ^{2 .}
Provided is a method for producing MnOOH, which is characterized by hydrothermal treatment in an oxygen gas atmosphere at a pressure of . In other words, the PH of a slurry (containing Mg(OH) ₂ ) made by adding ammonia water to a manganese sulfate aqueous solution is
If hydrothermal treatment is performed at a temperature below 9.1, the yield of manganese in the resulting product will be poor. On the other hand, if the PH
If it is larger than 9.6, the inside of the raw material manganese sulfate
Impurities such as Ca and Mg remain in the product. Furthermore, even if the temperature of the hydrothermal treatment is lower than 80°C, the yield of manganese in the product will be poor and the amount of impurities will increase. However, the temperature of hydrothermal treatment is 300℃.
Setting it higher is not preferable because it wastes thermal energy. Furthermore, if the oxygen pressure in the hydrothermal treatment is too low, the manganese yield in the product will be poor and the amount of impurities will increase, so the pressure should be 8 Kg/cm ² or higher. On the other hand, the pressure during hydrothermal treatment was increased to 30
Even if the pressure is higher than Kg/cm ² , the cost of pressure-resistant equipment will be increased, but no particularly significant effect will be obtained. However, in the method of the present invention, there is no particular restriction on the concentration of the manganese sulfate aqueous solution used as a raw material. That is, the method for producing a manganese compound of the present invention can also use an extremely dilute aqueous manganese sulfate solution, for example, wastewater containing manganese sulfate with a manganese concentration of about 1000 ppm, and therefore, such wastewater can be treated. It also has a face. Of course, the method of the present invention can also be carried out to produce MnOOH, which is a raw material for ferrite and catalysts, on an industrial scale, and in such cases, even higher concentrations, for example 150 to 200 g/
An aqueous manganese sulfate solution with a manganese concentration of . According to the present invention, a manganese compound such as γ-MnOOH can be obtained in a very short time by the above-described hydrothermal treatment, and there is no need for long-term aging as in conventional methods. That is, in a typical hydrothermal treatment in the method of the present invention, the temperature is raised to a predetermined temperature in about 1 hour, and the temperature is raised to a predetermined temperature for about 1 to 1 hour.
This is carried out by holding for 2 hours and then cooling to room temperature in about 1 hour. As is clear from the above explanation, according to the present invention, MnOOH can be produced economically and in large quantities using manganese sulfate aqueous solutions of low to high concentrations without the need for particularly expensive raw materials. Become. Hereinafter, the present invention will be explained along with comparative examples and examples. Comparative Example As shown in Table 1, 2N NH ₄ OH was added to 200ml of an aqueous manganese sulfate solution with a manganese concentration of 184g/
A slurry with a pH of 9.6 was obtained. Filter this slurry,
After washing with water and drying, the obtained solid was analyzed and the results were as shown in Table 2. As can be seen from Table 2, the manganese yield is low at 58.2%, and Ca and
The amount of impurities such as Mg is also large.

【table】

[Table] Example 2N NH ₄ OH (ammonia water) was added to 200 ml of an aqueous manganese sulfate solution having the quality shown in Table 1 above to prepare slurries having various pH values shown in Table 3. Each slurry was placed in an autoclave with an internal volume of 2, and oxygen was sealed at each pressure shown in Table 3. The temperature was raised to 150° C. in about 1 hour, maintained at this temperature for 1 hour, and then cooled to room temperature. The slurry thus hydrothermally treated was analyzed after filtration, washing with water, and drying, and the results were as shown in Table 3. As shown in Table 3, the product obtained by hydrothermal treatment according to the present invention has a significantly reduced amount of impurities, and furthermore, when slurry with a pH greater than 9.1 is hydrothermally treated, the manganese yield is extremely high. Furthermore, when the obtained product (Example 9) was observed under a microscope, it was as shown in Figures 1 and 2, and γ-
The presence of acicular MnOOH mainly composed of MnOOH is observed. In addition, Example Nos. 1 to 3 in the table are comparative examples.

【table】

【table】 [Brief explanation of the drawing]

Figures 1 and 2 show the manganese compound obtained by the present invention at 3000 times and 6000 times, respectively.
This is a magnified electron micrograph.

Claims (1)

[Claims] 1 A slurry with a pH greater than 9.1 and 9.6 or less obtained by adding ammonia water to an aqueous manganese sulfate solution is heated in an oxygen gas atmosphere at a pressure of 5 to 30 kg/cm ² .
A method for producing MnOOH, characterized by hydrothermal treatment at a temperature of 80 to 200°C.