JPH0232217B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel manganese compound and a method for producing the same. More specifically, the present invention provides a novel manganese compound that has excellent selective adsorption properties for lithium, has an extremely high adsorption rate and adsorption capacity, is suitable as a lithium adsorption material, and is also useful as a battery active electrode material. The present invention relates to a manufacturing method thereof. BACKGROUND OF THE INVENTION Manganese oxides are known to have various crystal forms, and exist naturally as manganese ore, nastite, and the like. This manganese oxide is generally used as an active cathode material in electrochemical cells such as dry batteries and batteries.A typical battery includes, for example, a manganese oxide cathode, a zinc anode, and an aqueous electrolyte solution (ammonium chloride and zinc chloride). An aqueous solution containing Conventionally, such manganese oxide for batteries has generally been prepared by an electrolytic method, but recently a method of preparing it from LiMn ₂ O ₄ has been proposed (Japanese Patent Publication No. 1983-
Publication No. 34414). Manganese oxide prepared from this LiMn ₂ O ₄ has electrochemical activity and is said to be effective not only in aqueous electrolytes but also in non-aqueous electrolytes. The LiMn ₂ O ₄ has a spinel structure, and is made by mixing lithium carbonate and manganese oxide in a ratio such that the atomic ratio of manganese and lithium is 2:1,
By heat treatment at a temperature in the range of 800 to 900°C, or a mixture of an appropriate combination of lithium salts/oxides such as lithium hydroxide and manganese carbonate and manganese salts/oxides to a temperature in the range of 500 to 900°C. It can be obtained by heat treatment at a temperature of . By the way, a manganese compound prepared from lithium-containing manganese oxide has recently been recognized as an excellent lithium adsorbent [Kagaku Kogyo, p. 686 (1985)], and has been used as an adsorbent for extracting lithium from dilute solutions. It is currently being used as an application. For example, the manganese compound obtained by acid-treating LiMn ₂ O ₄ exhibits almost the same X-ray diffraction characteristics as LiMn ₂ O ₄ and has excellent selective adsorption of lithium in seawater.
The equilibrium adsorption amount of lithium is 8.5 mg/g, which is 1.8% when converted to Li ₂ O content, which is about half that of lithium ore. As described above, manganese compounds prepared from manganese oxide containing lithium are useful as lithium adsorption materials and battery active electrode materials, but they are expensive because they use expensive lithium as a raw material. There is a problem that cannot be avoided. Problems to be Solved by the Invention An object of the present invention is to provide a novel manganese compound that is useful as a lithium adsorption material, a battery active electrode material, etc., and is inexpensive to produce. Means for Solving the Problems The present inventors have conducted intensive research to develop such a manganese compound, and as a result, we have developed MgMn ₂ O ₄ prepared using magnesium, which has an ionic radius slightly smaller than that of lithium, in an acid solution. The manganese compound obtained by the treatment shows clearly different X-ray diffraction characteristics from the manganese compound obtained from LiMn ₂ O ₄ ,
Although they are different materials, they have found that they have similar layer spacing and exhibit similar physical properties, and based on this knowledge, they have completed the present invention. That is, the present invention consists of an acid-treated product of MgMn ₂ O ₄ , and the relative intensity of the main X-ray diffraction peak is as follows: Interplanar spacing (Å) Relative intensity (CuKα irradiation) 4.63±0.03 strong 2.71±0.03 strong 2.42±0.03 It provides a manganese compound with a strength of 2.33±0.03, a weak 2.00±0.03, a medium of 1.54±0.03, which can be obtained by treating MgMn ₂ O ₄ with an acidic solution with a pH of 5 or lower and eluting the magnesium therein. It can be manufactured by. Used as a raw material in the present invention
MgMn ₂ O ₄ can be produced by, for example, mixing MgO and Mn ₃ O ₄ at a molar ratio of 3:2 and heating the mixture at a temperature of 1100°C for several hours [NBS Monograph]. ”Volume 25,,No.
No. 10, p. 35 (1972)] or hydroxides, oxides, carbonates, bicarbonates, nitrates, halides, etc. of magnesium and hydrated oxides, oxides, carbonates, bicarbonates of manganese. After mixing salts, nitrates, halides, etc. in appropriate combinations,
It can be produced by heat treatment at a temperature of 400°C or higher. This MgMn ₂ O ₄ is prepared by adding one or more mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and one or more organic acids such as formic acid and acetic acid, and adjusting the pH to 5 or less, preferably in the range of 1 to 3. The target manganese is obtained by immersing it in an acidic solution and stirring it at room temperature for usually at least 1 hour, preferably for several days to elute and remove the magnesium. A compound is obtained. The X-ray diffraction characteristics of this manganese compound are shown below. ASTM card MgMn ₂ O ₄ and
Manganese compound prepared from LiMn ₂ O ₄ (Tokuko Sho
58-34414) is also shown.

[Table] The manganese compound of the present invention is a new substance that has not been described in any literature, exhibits X-ray diffraction characteristics similar to those of the starting material MgMn ₂ O ₄ , and has a spinel structure. The difference between the X-ray diffraction characteristics of this manganese compound and the raw material MgMn ₂ O ₄ is that the lattice shrinks when a new form of manganese is formed, and a slight change in the peak position is observed. In addition, the manganese compound of the present invention has a lattice spacing of 2.71 Å.
It shows a strong diffraction peak in , and has a different microstructure from manganese oxide prepared from LiMn ₂ O ₄ . Furthermore, as a result of chemical analysis, the manganese compound of the present invention has a magnesium content of 1% by weight or less, and the theoretical magnesium content of the raw material MgMn ₂ O ₄
Since it differs from MgMn 2 O 4 by 12.3% by weight, it is recognized as a completely new substance with a different composition from MgMn ₂ O ₄ . Effects of the Invention The manganese compound of the present invention has a layer spacing suitable for lithium adsorption, has excellent selective adsorption for lithium, has an extremely high adsorption rate and adsorption capacity, is non-toxic, and is stable in an aqueous solution. The lithium concentration in the adsorbent is comparable to that of lithium-containing ores, and the lithium can be efficiently and economically recovered from dilute solutions, such as seawater or geothermal water. The manganese compounds are also useful as battery active electrode materials. Examples Next, the present invention will be explained in detail by examples. Example 1 Magnesium hydroxide 1.17g and manganese hydroxide
3.52g was pulverized and mixed, and heat treated in air at 950°C for 1 hour. 1 g of this heated product was added to 0.1 M aqueous hydrochloric acid solution 1 and stirred for 10 days, and then the solid matter was filtered off, washed with water, and dried at 70° C. to prepare a manganese compound. Table 1 shows the X-ray diffraction characteristics of the heated product and manganese compound obtained. In addition,
For comparison, ASTM card 23-392
The X-ray diffraction characteristics of MgMn ₂ O ₄ are shown.

[Table] The X-ray diffraction characteristics of MgMn ₂ O ₄ prepared in the examples were in excellent agreement with those described in the ASTM card. In addition, the manganese compound prepared by acid treatment of MgMn ₂ O ₄ of the present invention has a slightly smaller interplanar spacing compared to MgMn ₂ O ₄ ;
It is clear that the spinel structure is maintained. Table 2 shows the chemical analysis values of these manganese compounds.

[Table] The chemical analysis values of MgMn ₂ O ₄ prepared in this experiment were almost in agreement with the theory. The manganese compound of the present invention is
It is a new compound with a significantly lower magnesium content than MgMn ₂ O ₄ and a different composition. Example 2 While stirring a mixed solution of 150 ml of 1M aqueous magnesium chloride solution and 200 ml of 1M aqueous manganese chloride solution, aqueous ammonia (1:1) was added until the pH reached 10.5. After aging the product in the mother liquor for 3 days,
It was filtered and washed several times with aqueous ammonia at pH 10.5.
The atomic ratio of manganese and magnesium content in the product was 2:0.8. This was heat-treated at 700° C. for 1 hour to prepare MgMn ₂ O ₄ . This heat treated product 1
g was added to 0.1M nitric acid solution 1, and after stirring for 5 days, the product was filtered, washed, and dried. The X-ray diffraction properties of the product are shown in Table 3. Although slight shrinkage was observed in the obtained manganese compound as in Example 1, it was clear that it had the same structure as MgMn ₂ O ₄ . The chemical analysis results of these compounds are shown in Table 4.

【table】

[Table] It is clear that the magnesium compound of the present invention is a novel compound with a composition different from MgMn ₂ O ₄ . Example 3 The lithium adsorption properties of the manganese compounds prepared in Examples 1 and 2 in seawater were investigated. That is, 50 mg of the manganese compound was added to seawater 2, stirred for 7 days, and then the lithium concentration in the seawater before and after adsorption was determined by atomic absorption spectrometry to determine the amount of lithium adsorbed. The results are shown in Table 5. From these results, it is clear that the manganese compound of the present invention concentrates lithium in seawater approximately 40,000 times, and has excellent lithium adsorption properties.

【table】

Claims (1)

[Scope of Claims] 1. A manganese compound which is an acid-treated product of MgMn ₂ O ₄ and has the following relative intensity of the X-ray diffraction peak. Plane spacing (Å) Relative intensity (CuKα irradiation) 4.63±0.03 Strong 2.71±0.03 Strong 2.42±0.03 Strong 2.33±0.03 Weak 2.00±0.03 Medium 1.54±0.03 Medium 2 MgMn ₂ O ₄ was treated with an acidic solution with a pH of 5 or less. ,
A method for producing a manganese compound having the following relative intensity of an X-ray diffraction peak, the method comprising eluting magnesium therein. Planar spacing (Å) Relative intensity (CuKα irradiation) 4.63±0.03 strong 2.71±0.03 strong 2.42±0.03 strong 2.33±0.03 weak 2.00±0.03 medium 1.54±0.03 medium 3 Acidic solutions with PH5 or less are present in mineral acids and organic acids. The method according to claim 2, which contains at least one selected from the following.