JPH0687970B2 - Lithium adsorbent and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel lithium adsorbent and a method for producing the same. More specifically, the present invention provides an inexpensive lithium adsorbent which is excellent in selective adsorption to lithium, has a large adsorption capacity and adsorption rate, is extremely stable in a solution, and has low toxicity, and an efficient production method thereof. It is about how to do it.

[0002]

2. Description of the Related Art In recent years, lithium metal and its compounds have been
In many fields such as ceramics, batteries, refrigerant adsorbents,
It is used for medicines, etc.
Since it can be used as an aluminum alloy material, a fusion fuel, etc., the demand for lithium is expected to increase significantly (“Journal of the Japan Mining Industry” vol. 97, p. 221).

The lithium metal and its compound are currently produced mainly from lithium-containing ores such as spodumene, ambriconite, betterlite and lepidrite, and salt lakes and ground brines having a high lithium concentration.

However, in Japan, the above-mentioned lithium ore resources are scarce, and the current situation is that lithium metal and its compounds are entirely imported. On the other hand, some of Japan's geothermal water and hot spring water contain a considerable amount of lithium, and the surrounding ocean also contains a small amount of lithium. Therefore, it is strongly desired to establish a technique for efficiently recovering these lithium.

By the way, various crystal forms of manganese oxide are known, and they exist naturally as soft manganese ore and nastite. Recently, a manganese compound prepared from a lithium-containing manganese oxide has been found to be excellent as a lithium adsorbent ["Chemistry and Industry", page 686 (1985)], and is an adsorption material for extracting lithium from a dilute solution. Application as a drug is expected.

For example, LiMn ₂ O ₄ and Li _1.33
The manganese compound obtained by treating Mn _1.67 O ₄ with an acid has a spinel structure substantially equivalent to that of LiMn ₂ O ₄ , has excellent selective adsorption of lithium in seawater, and its lithium equilibrium adsorption amount is 8.5 mg / g and 20 mg / g, respectively
It is g. However, these adsorbents have a drawback that manganese is dissolved by the acid treatment in the preparation process, which is a barrier to practical use.

In order to practically adsorb and recover the lithium from a dilute solution such as seawater, geothermal water, ground brackish water, salt lake brackish water containing lithium, the lithium has excellent selective adsorption to lithium and has an excellent adsorption rate and adsorption capacity. In addition, it is required to be stable in a dilute solution, less toxic, and capable of repeated adsorption and desorption.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, the amount of manganese dissolved in the acid treatment in the preparation step is small, the selective adsorption to lithium is excellent, the adsorption capacity and the adsorption rate are large, and it is extremely stable in a solution. In addition, the purpose of the invention is to provide an inexpensive lithium adsorbent having low toxicity.

[0009]

The inventors of the present invention firstly proposed spinel type LiMnO ₄ and Li _1.33 Mn as raw materials.
It was found that by using _1.67 O ₄ and Mg ₂ MnO ₄ and treating them with these acids, a manganese oxide excellent in lithium selective adsorption can be obtained. However, these manganese oxides have a problem that a large amount of manganese is dissolved in the acid treatment in the preparation process, and are not always sufficiently satisfactory.

The present inventors have further researched on a composite oxide containing a third component in addition to lithium and manganese as a raw material, and as a result, using a composite oxide having a specific composition having a spinel structure as a raw material. By using this, by acid treatment to elute the lithium and metals other than manganese therein, an adsorbent excellent in chemical stability and lithium adsorption performance can be obtained, and the amount of dissolved manganese during the acid treatment is It was found that the number was small, and the present invention was completed based on this finding.

That is, according to the present invention, the general formula LixMyMnzO ₄ (I) (M in the formula is Mg, Zn, Cu, Ni or Co, x, y)
And z are 1 ≦ x <1.33 and 0 <y ≦ 0.5, respectively.
And a number satisfying the relationship of 1.5 ≦ z ≦ 1.67), which is an acid-treated product of a compound having a spinel structure.

According to the present invention, the lithium adsorbent is obtained by treating the compound having the spinel structure represented by the general formula (I) with an acidic solution having a pH of 3 or less to obtain lithium and M in the general formula (I). It can be produced by eluting the metal represented by.

In the present invention, the general formula LixMyMnzO ₄ (I) used as a raw material (M, x, y, and z in the formula have the same meanings as described above)
The compound having a spinel structure represented by is, for example, lithium carbonate, manganese carbonate, and a carbonate of magnesium, zinc, nickel, copper, or cobalt mixed at a constant ratio, and then usually heated at a temperature of 300 ° C. or higher for several hours. By treatment, or lithium hydroxide, oxides, hydrogen carbonates, nitrates, halides and manganese hydroxides, hydrous oxides, oxides, hydrogen carbonates, nitrates, halides and magnesium, After appropriately combining and mixing zinc, nickel, copper or cobalt hydroxide, oxide, hydrogen carbonate, nitrate, halide, etc.,
It can be usually produced by heat treatment at a temperature of 300 ° C. or higher.

The above-mentioned general formula (I) thus obtained
The compound having a spinel structure represented by is added to an acidic solution containing at least one mineral acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or an organic acid such as formic acid or acetic acid and adjusted to pH 3 or less. After immersing and stirring at room temperature for at least 1 hour, preferably for several days to elute and remove lithium and the metal represented by M in the general formula (I), the solid matter is washed with water, preferably at 70 ° C or lower. By drying at a temperature, a lithium adsorbent composed of the desired manganese compound is obtained.

The lithium adsorbent composed of the manganese compound thus obtained is the above-mentioned general formula (I) as a raw material.
10 shows an X-ray diffraction pattern of a spinel structure similar to the compound represented by. The difference in the X-ray diffraction characteristics of the adsorbent and the compound represented by the general formula (I) is that a slight change in the peak position and a change in the peak intensity are observed in the formation of a new form of manganese. is there.

In the acid treatment of the present invention, LiMn ₂ O ₄ , Li _1.33 Mn _1.67 O ₄ and M are used as raw materials.
The solubility of manganese is extremely low as compared with the case of using g ₂ MnO ₄ .

[0017]

INDUSTRIAL APPLICABILITY The adsorbent of the present invention has an extremely small amount of manganese dissolved during the acid treatment in its preparation step, is chemically stable, and has fine pores suitable for lithium adsorption. It has excellent selective adsorption to lithium, and has an extremely high adsorption rate and adsorption capacity. Further, the adsorbent is non-toxic and stable in acidic and alkaline solutions, and the adsorbed lithium concentration in the adsorbent is similar to that of lithium-containing ore, and dilute solutions such as seawater, geothermal water and salt lake brine are used. Thus, lithium can be efficiently and economically recovered. Further, the manganese compound used as the adsorbent of the present invention can also be used as a battery active electrode material or the like.

[0018]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 While stirring a mixed solution of 100 ml of 1M magnesium nitrate aqueous solution and 300 ml of 1M manganese nitrate aqueous solution, p
About 1M lithium hydroxide solution was added until H10.5 to pH 11.5 range. The product was filtered off and washed several times with water. 200 ml of 1M lithium hydroxide solution was added thereto, and the mixture was boiled for 3 hours and then dried at 80 ° C. overnight. This is heat-treated at 600 ° C. for 8 hours to obtain LiMg _0.5.
Mn _1.5 O ₄ was prepared. 10 g of this heated product was
The mixture was added to 1 liter of a 5M nitric acid solution, and the mixture was stirred for 2 days, then the product was separated by filtration, washed, and dried at 70 ° C. to prepare a manganese compound. Table 1 shows the X-ray diffraction characteristics of the obtained heating product and manganese compound.

[0020]

[Table 1]

LiMg _0.5 Mn prepared in the examples
The X-ray diffraction characteristics of _1.5 O ₄ matched very well with those described in the ASTM card. In addition, LiMg _0.5 Mn of the present invention
Manganese compound prepared by acid treatment of _1.5 O ₄ is LiM
Although the interplanar spacing is slightly smaller than that of g _0.5 Mn _1.5 O ₄ , it is clear that the original structure is maintained. Table 2 shows the chemical analysis values of these manganese compounds.

[0022]

[Table 2]

LiMg _0.5 Mn _1.5 O prepared in this example
The chemical analysis values of ₄ were almost theoretically in agreement. The manganese compound of the present invention is a novel compound having a significantly lower lithium and magnesium content than LiMg _0.5 Mn _1.5 O ₄ and different compositions.

Example 2 While stirring a mixed solution of 100 ml of 1M zinc nitrate aqueous solution and 300 ml of 1M manganese nitrate aqueous solution, the pH was adjusted to 10.
About 1M lithium hydroxide solution was added until it was in the range of 5 to pH 11.5. The product was filtered off and washed several times with water. 200 ml of 1M lithium hydroxide solution was added thereto, and the mixture was boiled for 3 hours and then dried at 80 ° C. overnight. This was heat-treated at 400 ° C. for 8 hours to obtain LiZn _0.5 Mn _1.5.
O ₄ was prepared. 10 g of this heated product was added to 1 liter of a 2M nitric acid solution, and the mixture was stirred for 2 days, then the product was separated by filtration, washed, and dried at 70 ° C. to prepare a manganese compound. Table 3 shows the X-ray diffraction characteristics of the obtained heating product and manganese compound.

[0025]

[Table 3]

LiZn _0.5 Mn prepared in the examples
The X-ray diffraction characteristics of _1.5 O ₄ were almost the same as those described in the ASTM card. In addition, LiZn _0.5 Mn _1.5 O _{4 of the} present invention
Manganese compound prepared by acid treatment is LiZn _0.5 M
Although the interplanar spacing is slightly smaller than that of n _1.5 O ₄ , it is clear that the original structure is maintained. Table 4 shows the chemical analysis values of these manganese compounds.

[0027]

[Table 4]

LiZn _0.5 Mn _1.5 O prepared in this example
The chemical analysis values of ₄ were almost theoretically in agreement. The manganese compound of the present invention has a significantly lower lithium and zinc content than LiZn _0.5 Mn _1.5 O ₄ and is a novel compound having a different composition.

Example 3 When the heat-treated products were treated with an acid in Examples 1 and 2, the dissolution rate of manganese was examined. That is, the acid-treated product and the acid-treated solution were separated by filtration, and the manganese concentration in the filtrate was quantified by the atomic absorption method. The dissolution rate of manganese was obtained from the quantitative value and the chemical analysis value of the heat-treated product. The results are shown in Table 5.

[0030]

[Table 5] Note 1) A mixture of lithium carbonate and manganese carbonate (Li
/ Mn atomic ratio = 0.8) prepared by heating at 400 ° C. for 4 hours.

As can be seen from this table, Examples 1 and 2
Compared with the conventional lithium manganese oxide, the heat-treated product of 5 was lower than the dissolution rate of manganese at the time of acid treatment by 5 times or more, and it is understood that the obtained adsorbent is chemically extremely stable.

Example 4 With respect to the manganese compounds prepared in Examples 1 and 2, lithium adsorption in seawater was examined. That is,
50 mg of a manganese compound was added to 5 liters of seawater (lithium concentration 0.17 ppm), and the mixture was stirred for 7 days. The lithium concentration in seawater before and after adsorption was quantified by atomic absorption spectrometry to determine the amount of lithium adsorbed. The results are shown in Table 6.

[0033]

[Table 6]

From these results, it is clear that the manganese compound of the present invention concentrated lithium in seawater about 40,000 times, and was excellent in lithium adsorption.

Example 5 The manganese compounds prepared in Examples 1 and 2 were examined for lithium adsorption in salt lake brine. That is, 100 mg of manganese compound is added to 20 ml of salt lake brine.
(Lithium concentration 200 ppm) and stirred for 1 day. The lithium concentration in seawater before and after adsorption was quantified by atomic absorption spectrometry to determine the amount of lithium adsorbed. The results are shown in Table 7.

[0036]

[Table 7]

From these results, it is clear that the manganese compound of the present invention exhibits a high adsorptivity for lithium in salt lake brine and is an excellent lithium adsorbent.

Front Page Continuation (72) Inventor Hirofumi Kano 2-3-3 Hananomiya-cho, Takamatsu City, Kagawa Prefecture Shikoku Industrial Technology Laboratory, Institute of Industrial Technology (56) Reference JP 62-83035 (JP, A) JP Flat 3-57814 (JP, B2)

Claims (2)

[Claims] 1. The general formula LixMyMnzO ₄ (where M is Mg, Zn, Cu, Ni or Co, x, y).
And z are 1 ≦ x <1.33 and 0 <y ≦ 0.5, respectively.
And a number satisfying the relationship of 1.5 ≦ z ≦ 1.67), which is a spinel type structure. 2. The general formula LixMyMnzO ₄ (where M is Mg, Zn, Cu, Ni or Co, x, y).
And z are 1 ≦ x <1.33 and 0 <y ≦ 0.5, respectively.
And a compound satisfying the relationship of 1.5 ≦ z ≦ 1.67) having a spinel structure is treated with an acidic solution having a pH of 3 or less to elute lithium and the metal represented by M in the general formula. A method for producing a lithium adsorbent, comprising: