JPH0626661B2 - Granular lithium adsorbent and lithium recovery method using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel particulate lithium adsorbent and a method for recovering lithium using the same. More specifically, the present invention provides a granular lithium adsorbent which is excellent in selective adsorption to lithium, has a large adsorption capacity and adsorption rate, is stable in an aqueous solution, has little toxicity, and is easy to handle, and The present invention relates to a method for efficiently recovering lithium in a dilute solution by using the same.

2. Description of the Related Art In recent years, lithium metal and its compounds have been used in various fields in various applications, such as ceramics, batteries, refrigerant absorbents, pharmaceuticals, etc., and in the future, large capacity batteries, aluminum alloy materials, nuclear fusion The demand for lithium is expected to increase remarkably because it is expected to be used as fuel, etc. [Journal of the Japan Mining Industry Association, No. 79].
Volume, page 221].

The lithium metal and the compound thereof are currently produced mainly from lithium-containing ores such as spodumene, ambrigonite, petalite, and lepidrite, and salt lakes and underground brackish water having a high lithium concentration.

However, in Japan, there is no such lithium ore resource as described above, and the total amount of lithium metal and its compounds depends on import. On the other hand, some of Japan's geothermal water and hot spring water contain a considerable amount of lithium, and the surrounding seawater also contains a small amount of lithium. Therefore, it is strongly desired to establish a technique for efficiently recovering the lithium from the dilute solution containing the lithium.

Conventionally, various adsorbents have been developed in order to recover the lithium from a solution containing lithium such as seawater or brackish water. For example, amorphous aluminum hydroxide (Japanese Patent Laid-Open No. 55-10
541), tin oxide hydroxide (JP-A-57-61623),
Tin antimonate (JP-A-58-167424), bismuth phosphate (JP-A-59-195525), heat-treated titanic acid (JP-A-61-72623), manganese oxide (JP-A-61-72623) Akira
61-171535 and 61-228334) are known.

Among these adsorbents, manganese oxide-based adsorbents exhibit high lithium selectivity, and their adsorbed amount has been increased to a level comparable to the lithium content of low-grade ores. Is expected. This adsorbent is produced by introducing lithium ions or magnesium ions into porous manganese hydroxide in advance to immobilize them, and then eluting the lithium ions or magnesium ions by acid treatment or the like. Therefore, it is characterized in that ultrafine pores suitable for lithium are formed in the adsorbent.

However, since the adsorbent is usually a powder, it has a drawback that separation and recovery from a solution is extremely difficult when adsorbing treatment by contacting with a large amount of seawater or brackish water, which is a lithium recovery process. Is a major impediment to the commercialization of.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention overcomes the drawbacks of such conventional lithium adsorbents, has excellent selective adsorption properties for lithium, and has a large adsorption rate and adsorption capacity, and separation from a dilute lithium solution. Practical granular lithium for recovering lithium from dilute solutions such as lithium-containing seawater, geothermal water, and ground brackish water, which are characterized by easy recovery, low toxicity, and stability in dilute solutions. The object of the present invention is to provide an adsorbent and a method for efficiently recovering lithium from a dilute solution using the adsorbent.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and after molding a lithium-containing manganese oxide into a granular body using an organic polymer substance as a binder, in an aqueous solution. By eluting the lithium, a granular lithium adsorbent having the above-mentioned preferable properties can be obtained, and this is packed in a column, and a dilute solution containing lithium is caused to flow into the column to adsorb lithium, and then lithium desorption is performed. It was found that lithium can be efficiently recovered from a dilute solution by eluting the lithium adsorbed on the adsorbent using an aqueous solution having the ability, and the present invention has been completed based on this finding.

That is, the present invention is characterized in that the lithium-containing manganese oxide particles formed by granulation using an organic polymer substance are treated with an aqueous solution having a lithium elution capacity to elute the lithium. After the adsorbent and the granular lithium adsorbent are packed in a column, a dilute solution containing lithium is flowed through the column to adsorb lithium, and then a dilute acid solution or an aqueous solution containing an oxidizing compound exhibiting acidity is used. The present invention provides a method for recovering lithium from a dilute solution, characterized in that the lithium adsorbed on the adsorbent is eluted.

Hereinafter, the present invention will be described in detail.

The manganese oxide used as a raw material of the lithium adsorbent of the present invention is not particularly limited as long as it contains lithium, but one containing LiMn ₂ O ₄ or Li ₂ MnO ₃ is preferably used. Such a lithium-containing manganese oxide is prepared by, for example, adsorbing lithium on a porous manganese-containing hydroxide and then heat-treating it at a temperature of 500 ° C. or higher (JP-A-61-171535). It can be produced by a method of heat-treating a mixture of manganese and lithium carbonate at a temperature of 200 ° C. or higher (JP-A-63-80844). The particle size of the lithium-containing manganese oxide thus obtained is usually 0.01 to 100 μm.
However, in the present invention, those having a particle size of 0.1 to 10 μm are preferably used.

The organic polymer substance used in the adsorbent of the present invention may be any one having a function as a binder, and is not particularly limited, and examples thereof include polyvinyl chloride, acrylonitrile copolymer, polysulfone, polyamide, polyimide, polyester. , Acetyl cellulose and the like.

In order to produce the granular adsorbent of the present invention, first, a lithium-containing manganese oxide as a raw material is granulated by using the organic polymer substance to prepare a granular body, which is prepared by using an appropriate organic solvent. Into a solution in which the polymer substance is dissolved, a lithium-containing manganese oxide is added and sufficiently kneaded, and the kneaded product has an affinity for the organic solvent and is a non-solvent for the polymer substance. It can be prepared by dropping through a thin tube. The particle size of the granular material can be adjusted by the diameter of the thin tube and the dropping rate. Examples of the non-solvent include water, acetone, alcohol and the like, and water is preferable from the viewpoint of easy handling. Also,
The organic solvent used to dissolve the polymer substance is appropriately selected according to the type of the non-solvent. For example, when water is used as the non-solvent, the organic solvent may be dimethylformamide, formamide or dimethylsulfone. Sid, dioxane, tetrahydrofuran, acetone and the like are preferably used.

The amount of the polymer substance used is usually selected in the range of 5 to 60% by weight based on the lithium-containing manganese oxide. If this amount is less than 5% by weight, the polymer substance is not uniformly dispersed in the granules, and the granules are likely to be crushed or powdered.
If it exceeds 60% by weight, it is difficult to elute lithium in the manganese oxide and the adsorption performance tends to be deteriorated.

The granular material thus obtained is thoroughly washed with water,
Immerse in an aqueous solution that has the ability to elute lithium and treat it.
The lithium contained in it is eluted. As the aqueous solution having the lithium elution ability, an aqueous solution containing an acid or an oxidizing substance exhibiting acidity and having a pH of 4 or less is preferably used. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and hydrochloric acid is particularly preferable. The concentration of the aqueous solution containing these acids is not particularly limited, but a concentration of 0.05 to 0.5 M is usually used. The treatment temperature is usually room temperature, and the treatment time is usually several hours or longer, although it depends on the acid concentration.

On the other hand, the oxidizing substance exhibiting acidity is not particularly limited as long as it is an oxidizing agent exhibiting weak acidity in an aqueous solution. Examples of such substances include peroxodisulfate and bromine. Ammonium peroxodisulfate is preferable in terms of economy, handleability, solubility and the like. The concentration of the oxidizing substance exhibiting acidity is not particularly limited, but a concentration of 0.1 to 1 M is usually used. The treatment temperature is usually selected in the range of 40 ° C to the boiling point. If this temperature is lower than 40 ° C., it takes a long time to elute lithium, which is not practical.

Thus, by treating the granular material with an aqueous solution having a lithium elution ability, about 90% or more of the lithium contained in the manganese oxide is eluted and a granular lithium adsorbent is obtained.

Using the thus obtained granular lithium adsorbent of the present invention, in order to recover lithium from a dilute lithium solution, the granular lithium adsorbent is packed in a column, and a dilute solution containing lithium is poured into the column. Adsorb lithium,
Then, the lithium adsorbed on the adsorbent may be eluted using a dilute acid solution or an aqueous solution containing an oxidizing substance exhibiting acidity. Further, since the granular adsorbent of the present invention has good stability against a dilute solution containing lithium and a lithium desorption solution, a column containing the granular adsorbent is provided with a diluted solution containing lithium and a lithium desorption solution. By alternating flow, adsorption-desorption can be repeated.

EFFECTS OF THE INVENTION The granular lithium adsorbent of the present invention has excellent selective adsorption properties for lithium, and has a large adsorption capacity and adsorption rate,
It is easy to separate and recover from dilute lithium solution, has less toxicity, and is stable in dilute lithium solution or lithium desorption solution. Dilute lithium-containing seawater, geothermal water, underground brine, etc. It is preferably used as a practical lithium adsorbent for recovering lithium from a solution.

Further, the granular lithium adsorbent of the present invention has the excellent characteristics as described above, so that the adsorbent is packed in a column, and a dilute solution containing lithium and a lithium desorption solution are allowed to flow alternately. By repeating adsorption-desorption,
Lithium can be recovered very efficiently from a dilute solution.

The powdery lithium adsorbent obtained by previously treating the lithium-containing manganese oxide with an acid can be granulated as described above by using a polymer substance as a binder. Since the agent is unstable with respect to the organic solvent, the active sites are destroyed during granulation, and the obtained granule exhibits almost no lithium adsorption property.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

Example 1 500 g of manganese hydroxide oxide and 103 g of lithium carbonate were pulverized and mixed, and then heat-treated at 400 ° C. for 5 hours to prepare a lithium-containing manganese oxide. As a result of X-ray analysis, it was confirmed that a LiMn ₂ O ₄ phase was formed.

Then, 4 g of polyvinyl chloride (polymerization degree 2000) is added to 40 ml of tetrahydrofuran and 40 ml of N, N-dimethylformamide.
Then, 10 g of the above-mentioned lithium-containing manganese oxide was added to this solution and kneaded sufficiently, and then this suspension was dropped into water through a narrow tube having a diameter of 1.5 mm to prepare granules.

Next, 5 g of this granular material was immersed in 0.25M hydrochloric acid solution 2 at room temperature to elute lithium. FIG. 1 is a graph showing the change over time in the lithium elution rate of the granular material.

From FIG. 1, it can be seen that most of the lithium in the granular material was eluted after the treatment time of 4 hours, and the elution rate became almost constant after 24 hours.

Five kinds of granular adsorbents having different hydrochloric acid treatment times were produced, 1 g of each was packed in a column having a diameter of 3.5 cm, and natural seawater was allowed to flow at a rate of 50 ml / min for 7 days to carry out a lithium adsorption experiment from seawater. Table 1 shows the lithium adsorption amount at that time.

As can be seen from Table 1, the amount of lithium adsorbed is 2.3 to 2.5 mg.
/ G was shown and good results were obtained.

Example 2 A lithium-containing manganese oxide granular material was prepared in the same manner as in Example 1, and 5 g of this was placed in 300 ml of a 0.5 M ammonium peroxodisulfate aqueous solution and treated at 70 ° C. FIG. 2 is a graph showing the relationship between the treatment time and the lithium elution rate.
From FIG. 2, it can be seen that in the case of ammonium peroxodisulfate [(NH ₄ ) ₂ S ₂ O ₈ ] which is acidic and oxidative, the elution rate becomes 97% or more in 1 hour, and the treatment for an extremely short time is sufficient. I found out.

Next, 0.5 g of four kinds of granular adsorbents having different treatment times were prepared and immediately charged in a column having a diameter of 3.5 cm, and the adsorbent experiment was conducted by flowing natural seawater at a flow rate of 50 ml / min for 7 days. In addition, 0.5 g of each of the same granular adsorbents was stored in water for one month, and then subjected to an adsorption experiment under the same conditions. The results are shown in Table 2.

As can be seen from Table 2, the amount of lithium adsorbed is 2.1 to 2.6 mg.
/ G, and the highest adsorption amount (2.4-2.6 mg /) when the treatment time with ammonium peroxodisulfate was 0.5 hours.
g) was obtained. Also, the prepared adsorbent is stable,
There was no effect due to aging. Thus, the granular adsorbent of the present invention showed excellent performance.

Example 3 To 10 g of a lithium-containing manganese oxide prepared in the same manner as in Example 1, a solution prepared by dissolving polyvinyl chloride (polymerization degree: 700) in 50 ml of N, N-dimethylformamide was added and sufficiently kneaded. This was dropped into a mixed solution of water and alcohol through a thin tube having a diameter of 1.5 mm to obtain granular lithium manganese oxide.

Next, 5 g of this granular material was put into 0.25 M hydrochloric acid solution 2 and treated for 4 days while stirring to elute lithium. FIG. 3 is a graph showing the relationship between the treatment time and the lithium elution rate. As can be seen from FIG. 3, a lithium elution rate of 90% or more was obtained after a hydrochloric acid treatment time of 1 day, but there was almost no change in the elution rate at a time longer than that.

Next, an adsorption experiment was conducted under the same conditions as in Example 2 with 0.5 g of four types of granular adsorbents having different treatment times. The results are shown in Table 3.

The amount of lithium adsorbed was 2.1 to 3.0 mg / g, which was about the same as in Examples 1 and 2, and it was found that the degree of polymerization of the added polyvinyl chloride did not affect the lithium adsorbability.

Example 4 A repeated adsorption-desorption test was conducted using the granular adsorbent prepared under the same conditions as No. 11 of Example 3. The adsorption treatment conditions were the same as in Example 3, and the desorption treatment was carried out by immersing the granular adsorbent in 50 ml of a 0.25M hydrochloric acid solution for 8 hours.
The results are shown in Table 4.

As can be seen from Table 4, the adsorption performance did not decrease after repeated use three times, and the desorption rate was almost constant.
Good results have been obtained. Further, during this treatment process, the granular adsorbent was not finely divided and was stable.

It has been found that the use of the granular adsorbent of the present invention enables column treatment and enables efficient recovery of lithium from a dilute lithium solution.

Comparative Example 20 g of a lithium-containing manganese oxide powder prepared in the same manner as in Example 1 was put into a 0.25 M hydrochloric acid solution 2 and treated for 4 days while stirring to elute lithium to obtain a powdery lithium adsorbent.

Next, using this powdery adsorbent, a granule was prepared by granulating in the same manner as in Example 1, 0.5 g of this was packed in a column having a diameter of 3.5 cm, and 50 ml of natural seawater was added thereto. A lithium adsorption experiment from seawater was carried out by flowing the mixture at a speed of 7 minutes for 7 days. As a result, the lithium adsorption amount was 0.1 mg / g or less,
It was found that it showed almost no lithium adsorption.

[Brief description of drawings]

FIG. 1, FIG. 2 and FIG. 3 show the treatment time and the lithium when treating the lithium-containing manganese oxide particulates in the different production examples of the particulate lithium adsorbent of the present invention with the aqueous solution having the lithium elution ability. It is a graph which shows the relationship with an elution rate.

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Claims (5)

[Claims] 1. A granular lithium adsorbent characterized in that a lithium-containing manganese oxide granular material formed by granulation using an organic polymer substance is treated with an aqueous solution having a lithium elution ability to elute the lithium. Agent. 2. The granular lithium adsorbent according to claim 1, wherein the lithium-containing manganese oxide contains LiMn ₂ O ₄ or Li ₂ MnO ₃ . 3. The granular lithium adsorbent according to claim 1, wherein the organic polymer substance is soluble in an organic solvent miscible with water and insoluble in water or a mixed solvent of water and alcohol. 4. The granular lithium adsorbent according to claim 1, 2 or 3, wherein the aqueous solution having the ability to elute lithium has a pH of 4 or less containing an acid or an oxidizing substance exhibiting acidity. 5. A column is filled with the granular lithium adsorbent according to claim 1, and a dilute solution containing lithium is caused to flow through the column to adsorb lithium, and then a dilute acid solution or an oxidizing compound exhibiting acidity is contained. A method for recovering lithium from a dilute solution, characterized in that the lithium adsorbed on the adsorbent is eluted with an aqueous solution.