JPH0357814B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a lithium adsorbent, a method for producing the same, and a method for recovering lithium from a dilute solution using the same. More specifically, an inexpensive lithium adsorbent that has excellent selective adsorption for lithium, has a large adsorption capacity and adsorption rate, is stable in the dilute solution, and has low toxicity, a method for producing the same, and the adsorbent. The present invention relates to a method for efficiently and easily recovering lithium from a dilute solution containing lithium. In recent years, lithium metal and its compounds have been used in many fields, such as ceramics, batteries, refrigerant adsorbents,
The demand for lithium is expected to increase significantly as it is used in pharmaceuticals and other products, and is expected to be used in large capacity batteries, aluminium alloy materials, nuclear fusion fuels, etc. [Japan Mining Association Journal] Volume 97, page 221]. At present, the lithium metal and its compounds are mainly lithium-containing ores such as sposiumene, ampliconite, betterite, and lepidolite;
It is also manufactured using raw materials such as salt lakes and underground brine that have high lithium concentrations. However, our country does not have the above-mentioned lithium ore resources, and currently relies entirely on imports for lithium metal and its compounds. On the other hand, some geothermal waters and hot spring waters in Japan contain a considerable amount of lithium, and the surrounding ocean also contains trace amounts of lithium. Therefore, it is strongly desired to establish a technique for efficiently recovering lithium from dilute solutions containing lithium. Conventional technology Conventionally, as a method for recovering lithium from a dilute solution containing lithium such as seawater, for example, aluminum hydroxide coprecipitation method ["Chemical Society of Japan 43rd Annual Meeting,
Collection of Lecture Abstracts, p. 1240 (1981)], or amorphous aluminum hydroxide [Seawater Journal, No. 32
Vol. 78 (1978), Journal of the Japan Mining Association, No. 99
Vol. 585, p. 1983 (1983)], metallic aluminum ["Rust Prevention Management", vol. 1982, p. 369], hydrous tin oxide ["Journal of the Japan Mining Association", vol. 99, p. 933 (1983)]. Adsorption methods to be used are known. However, these methods have the disadvantage that the adsorption capacity and adsorption rate for lithium are low, making it difficult to put them into practical use. Also, sodium arsenate ["J.Inorg.Nucl.Chem." Vol. 32, page 1719 (1970)], tin antimonate ["Solvent
Extraction & Ion-Exchange, Volume 1, Page 97 (1983)] have also been reported to exhibit lithium adsorption properties, but issues such as improving adsorption properties remain for practical use. In addition, it has been reported that various ion sheep-type adsorbents exhibit adsorption properties for lithium [``Neorgan.Mat.'', Vol. 9, p. 1041 (1973); Volume 12, page 1451 (1976)], the manufacturing conditions of the adsorbent and its lithium adsorption properties in natural water are not clear;
It has not yet been put into practical use. Problems to be Solved by the Invention In order to practically adsorb and recover lithium from dilute solutions such as seawater, geothermal water, and underground brine containing lithium, it is necessary to have excellent selective adsorption for lithium, and to improve the adsorption rate and adsorption rate. It is required to have a large capacity, be stable in the dilute solution, have low toxicity, and be able to be repeatedly used for adsorption and desorption. The purpose of the present invention is to provide an adsorbent that satisfies these requirements, a method for producing the adsorbent, and a practical lithium recovery method for extremely efficiently recovering lithium from a dilute solution containing lithium. will be provided. Means for Solving the Problems As a result of various studies, the present inventors found that a lithium eluate of magnesium manganese oxide (Mg ₆ MnO ₈ ) prepared by heating at a specific temperature satisfies the above requirements. The inventors have discovered that lithium can be easily and efficiently recovered from a dilute solution containing lithium by using this adsorbent, and based on this knowledge, they have completed the present invention. . Namely, the present invention provides a lithium adsorbent consisting of an acid-treated product of Mg ₆ MnO ₈ prepared by heating at 300-600°C, and a lithium adsorbent comprising a mixture of magnesium and manganese at a temperature of 300-600°C. A method of producing Mg ₆ MnO ₈ by heat treatment and then eluting the magnesium with acid;
The present invention provides a method for recovering lithium by adsorbing and separating lithium and lithium, and then eluting the lithium adsorbed on the adsorbent using a weak acid or a weakly acidic aqueous solution. In the present invention, the mixture of magnesium and manganese used for producing the adsorbent is prepared, for example, by adding an alkaline solution to a mixed solution of a magnesium salt solution and a manganese salt solution and separating the resulting precipitation product from the solution. However, it is of course not limited to this method. The adsorbent of the present invention is produced by heating the magnesium and manganese mixture thus obtained at a temperature of 300 to 600°C, preferably 300 to 500°C.
It is obtained by preparing Mg ₆ MnO ₈ and then eluting the magnesium with acid. Mg ₆ MnO ₈
is a cubic crystal that is prepared by heating a mixture of magnesium and manganese at temperatures above 300°C. Mg ₆ MnO ₈ obtained by heat treatment at a temperature of 700°C or higher is unstable, and its acid-treated product shows almost no adsorption performance for lithium. When prepared by heating at a temperature below 500°C, magnesium was easily eluted, and the magnesium eluted product had a stable structure and exhibited adsorption properties for lithium. In particular, those heat-treated at 400°C exhibit significantly high lithium adsorption properties. Further, the heat treatment time varies depending on the treatment temperature, but generally about 30 minutes to 5 hours is sufficient. The acids used to elute the magnesium from Mg ₆ MnO ₈ prepared by heating at 300 to 600°C include hydrochloric acid with a concentration of about 0.05 to 1N, sulfuric acid, nitric acid, etc. An aqueous solution of mineral acid is preferred, but is not limited thereto as long as the magnesium can be easily eluted and does not adversely affect lithium adsorption performance. The adsorbent thus obtained may be used in powder form, or may be formed into granules or fibers using a binder or the like. Examples of the dilute solution containing lithium used in the present invention include not only seawater but also geothermal water, hot spring water, mineral spring water, underground brine such as natural gas brine,
Examples include salt manufacturing brine and factory waste liquid. In the present invention, the adsorbent obtained as described above is added to a dilute solution containing lithium to sufficiently adsorb the lithium, and then the adsorbent is separated from the solution and Contact with an acidic aqueous solution to elute and recover the lithium, or
Alternatively, the lithium is adsorbed by passing a dilute solution containing lithium through a column filled with an adsorbent shaped into particles or fibers, and then a weak acid or weakly acidic aqueous solution is passed through the column to adsorb the lithium. Lithium can also be recovered by desorption. The weak acid or weakly acidic aqueous solution used to elute the adsorbed lithium is not particularly limited as long as it can easily elute the lithium and does not adversely affect the performance of the adsorbent, but it is usually 0.05 to 1N.
An aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, etc. having a concentration of . Effects of the Invention The lithium adsorbent of the present invention is composed of a magnesium eluate of Mg ₆ MnO ₈ prepared by heating at a specific temperature, and has excellent selectivity for lithium, and has a large adsorption amount and rate. Sucking,
It can be used repeatedly by desorption, is stable in aqueous solution, has low toxicity, and is inexpensive. By using this adsorbent, lithium can be recovered very efficiently and economically from a dilute solution containing lithium. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 While stirring a mixed solution of 600ml of 1M magnesium chloride aqueous solution and 100ml of 1M manganese chloride aqueous solution, add ammonia water (1:
1) was added. Further 100ml of 30% hydrogen peroxide solution
was added dropwise. 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 magnesium to manganese content in the product was 5.8:1. 1 at 200-800℃
Magnesium-manganese oxide was prepared by heat treatment for a period of time. As a result of an X-ray diffraction test, it was confirmed that all of the heat-treated products at 300° C. or higher were Mg ₆ MnO ₈ . 1 g of this heated product was added to 0.5N hydrochloric acid solution 1 and after stirring for 25 days, the product was filtered off, washed and dried at 70°C. 50 mg of each type of adsorbent thus obtained was added to each of the two natural seawaters (Li concentration 170 μg/g), stirred for 7 days, and then the lithium concentration in the supernatant was determined to determine the amount of lithium adsorbed. I asked for it. The result is the first
Shown in the table.

[Table] As is clear from this table, those heat-treated at 300 to 600°C exhibit lithium adsorption properties. Example 2 Regarding sample No. 3 (heating temperature: 400° C.) in Example 1, the lithium adsorption properties were investigated when the acid treatment time was changed. As a result, as shown in Table 2, as the acid treatment time increased, the lithium adsorption increased, and the adsorbent obtained with the acid treatment time of 20 days showed the highest adsorption ability, and the It was observed that the adsorption performance tended to decrease as the length increased.

[Table] Example 3 In Example 2, 0.5 g of sample No. 10 (lithium adsorption amount 3.2 mg/g), which had the best adsorption performance, was
Lithium was desorbed by placing it in 50ml of 0.05N hydrochloric acid solution and keeping it at room temperature for 5 hours, and the desorption rate was 90%.
It was confirmed that the adsorbent could be easily desorbed from the adsorbent.

Claims (1)

[Claims] 1. A lithium adsorbent comprising an acid-treated product of Mg ₆ MnO ₈ prepared by heating at 300 to 600°C. 2 Molar ratio of magnesium and manganese is 12:2 ~
1. A method for producing a lithium adsorbent, which comprises heat-treating lithium adsorbent 1 at a temperature of 300 to 600°C to prepare Mg ₆ MnO ₈ , and then treating this with an acid to elute magnesium. 3. Add an adsorbent consisting of a magnesium eluate of Mg ₆ MnO ₈ prepared by heating at a temperature of 300 to 600°C to a dilute solution containing lithium, adsorb and separate lithium, and then add a weak acid or a weak acidic aqueous solution. A method for recovering lithium from a dilute solution, characterized in that lithium adsorbed on the adsorbent is eluted using a method of recovering lithium from a dilute solution.