JPH0423577B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a lithium adsorbent. More specifically, the present invention relates to a method for producing a lithium adsorbent that has excellent selective adsorption for lithium, has a large adsorption capacity and rate, is stable in a dilute lithium solution, has little toxicity, and is inexpensive. In recent years, lithium metal and its compounds have been used in many fields, such as ceramics, batteries, absorption refrigerants,
Lithium is used in pharmaceuticals, etc., and in the future, it is being considered for use in large-capacity batteries, aluminum alloy materials, fusion fuels, etc., and the demand for lithium is expected to increase significantly [Journal of the Japan Mining Association]
Volume 97, page 221]. The lithium metal and its compounds are currently mainly produced in lithium-containing ores (lithium content 2-6%) such as spodiumene, ambrigonite, betalite, and lepidolite, and in salt lakes and underground brine waters with high lithium concentrations (lithium concentration 50-200 ppm). )
It is manufactured using raw materials such as 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 water and hot spring water in Japan contain a considerable amount of lithium. The surrounding ocean also contains trace amounts of lithium (0.17ppm). 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,
A collection of lecture abstracts, p. 1240 (1981)], or amorphous aluminum hydroxide [Seawater magazine, No. 32
Vol. 78 (1978), Journal of the Japan Mining Association, No. 99
Vol., p. 585 (1983)], metal 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. In addition, methods are being considered to collect lithium salt by evaporating salt lake water or seawater using solar heat, precipitating out salt, etc. [Geological Survey
Professional Paper Volume 1005, Page 79 (1976)]. However, the adsorption method described above has the disadvantage that the adsorption capacity and adsorption rate for lithium is small, and the evaporation method using solar heat has the disadvantage that it requires a huge area and the same weather conditions.
Both are difficult to put into practical use. In addition, thorium arsenate ["J.lnorg.Nucl.Chem." Vol. 32, p. 1719 (1970)] and tin antimonate ["Hydrometallurgy" vol. 12, p. 83 (1984)] also adsorb lithium. However, there are still issues to be solved before it can be put into practical use, such as improving adsorption and desorption properties. It has also been reported that various ion sieve type adsorbents exhibit adsorption properties for lithium ["Neorgan. Mat.", Vol. 9, p. 1041 (1973); Page 1415 (1976)],
The manufacturing conditions and lithium adsorption properties of this adsorbent in natural water are not clear, and practical performance has not yet been achieved. 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. There is a need to develop an adsorbent that has a large capacity, is stable in the dilute solution, has low toxicity, and is capable of repeated adsorption and desorption. An object of the present invention is to provide a method for producing an adsorbent that can satisfy these requirements. Means for Solving the Problems As a result of repeated research on the synthesis of various adsorbents, the present inventors found that a manganese-aluminum composite compound containing magnesium was heated and then treated with an acid to elute the magnesium. It was recognized that the present invention is a lithium adsorbent that satisfies the above requirements, and the present invention was developed. In other words, the adsorbent prepared by heating a magnesium-containing manganese-aluminum composite compound at a temperature of 600°C or higher and then treating it with an acid solution of PH3 or lower to elute the magnesium showed excellent lithium selective adsorption. . The magnesium-containing manganese-aluminum composite compound used in the present invention is not prepared by a specific method, and compounds prepared by various methods can be used. For example, a coprecipitation method involves mixing a solution containing magnesium ions with a solution containing manganese ions and aluminum ions, adjusting the pH to 10 or higher and co-precipitating, and adding manganese oxide such as manganese oxide to a solution containing magnesium ions and hydroxide. An adsorption method in which an aluminum compound such as aluminum is added to adsorb magnesium, a mixing method in which a magnesium compound such as magnesium hydroxide, a manganese hydroxide oxide, and a compound such as aluminum hydroxide are mixed at a fixed ratio, etc. can be used. When the proportion of manganese in the aluminum-manganese composite compound is small, the lithium adsorption is low, but as the proportion of manganese increases, the lithium adsorption increases, reaching a maximum at 1:1, and conversely decreases as the proportion increases further. It was recognized that there were multiple effects. The heat treatment temperature of the magnesium-containing manganese-aluminum composite compound needs to be 600°C or higher, preferably 750°C or higher. The crystallization reaction rapidly progresses with heating, but it requires at least 10 minutes, preferably 1 hour or more. Elution of magnesium from the heat-treated product can be achieved by treating it with a weak acid solution with a pH of 3 or more for several hours or more, preferably for one day or more. The acid used for elution may be any acidic solution with a pH of 3 or less, but mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid are preferably used. The adsorbent produced by the method of the present invention selectively adsorbed lithium from dilute solutions such as seawater and geothermal water. The partition coefficient of lithium adsorption in dilute solution reached 8.5×10 ⁴ . Effects of the Invention The adsorbent produced from the magnesium-containing manganese oxide prepared by the method of the present invention has many micropores, has excellent selective adsorption for lithium, has an extremely high adsorption rate and adsorption capacity, is non-toxic, and can be used in aqueous solutions. The lithium concentration in the adsorbent is equivalent to that of ore, and by using the adsorbent produced by this method, the lithium can be recovered from a dilute solution extremely efficiently and economically. In these magnesium-doped adsorbents, although the ionic radii of magnesium ions and lithium ions are almost equal, hydration energy of magnesium is larger, and therefore lithium is thought to be selectively adsorbed. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 2.20 g of manganese hydroxide oxide, 1.96 g of aluminum hydroxide, and 1.46 g of magnesium hydroxide were pulverized and mixed, and then heat-treated at a predetermined temperature of 550 to 1150°C for 1 hour. Add 1 g of this heated product to 500 ml of 0.1N hydrochloric acid.
ml for 10 days to elute magnesium, then washed with water and air-dried to prepare an adsorbent. 30 mg of the adsorbent thus obtained was added to 25 ml of lithium chloride aqueous solution (lithium concentration 6.2 ppm, pH 8.5).
After stirring for 7 days, the lithium concentration in the supernatant was determined and the amount of lithium adsorbed was calculated.
Table 1 shows the results of measuring the amount of adsorption for adsorbents prepared at various temperatures from 550 to 1150°C. The amount of lithium adsorbed by these adsorbents increased as the heating temperature increased, and became almost constant between 850 and 1050°C, with a lithium adsorption rate of 99% and an acid fraction coefficient of 8.5×10 ⁴ . In contrast, adsorbents prepared by heating at a higher temperature of 1150°C tended to have lower adsorption performance. Note that the distribution coefficient here is the ratio of the equilibrium metal ion concentration in the solution to the metal ion concentration adsorbed on the adsorbent, and is expressed by the following equation. Partition coefficient = Equilibrium adsorption amount in adsorbent (mg/g)/Equilibrium metal ion concentration in solution (mg/mL)

[Table] Example 2 Add 50 mg of the adsorbent prepared in Example 1 to 2 L of natural seawater.
After stirring for 7 days, the lithium concentration in the supernatant was determined and the amount of lithium adsorbed was calculated.As shown in Table 2, the lithium adsorption rate was the highest.
65%, the adsorption amount is 4.4 mg/g, and this adsorbent is

[Table] It is clear that the adsorbent of the present invention is an excellent lithium adsorbent as it exhibits great adsorption for lithium in water. Example 3 Manganese hydroxide, aluminum hydroxide and magnesium hydroxide were mixed and ground in various proportions,
Heat treatment was performed at 950°C for 1 hour. 1 g of each product was immersed in 500 ml of 0.1N hydrochloric acid aqueous solution for 10 days to elute magnesium, then washed with water and air-dried to prepare various adsorbents. Add 30 mg of each of these adsorbents to lithium chloride solution (lithium concentration 6.2 ppm, PH 8.5)
After adding it to 25 ml and stirring for 7 days, the lithium concentration in the supernatant was measured and the amount of lithium adsorbed was calculated. As a result, as shown in Table 3, all adsorbents showed high lithium adsorption ability, especially No. 17.
It is clear that a mixture ratio (mole ratio) of 1:1:1 shows excellent lithium adsorption properties, and the adsorbent of the present invention has excellent lithium adsorption properties.

[Table] Example 4 50 mg of the adsorbent prepared in Example 3 was added to 2 L of seawater, and after stirring for 7 days, the lithium concentration in the supernatant was measured to determine the amount of lithium adsorbed. As shown in Table 4, it is clear that lithium is selectively adsorbed even from seawater. Especially Mn:Al is 1:1

[Table] showed the best adsorption properties. As described above, the adsorbent produced by the method of the present invention exhibits excellent lithium adsorption properties, and it is clear that the production method of the present invention is superior.

Claims (1)

[Scope of Claims] 1. A lithium adsorbent prepared by eluting magnesium from a heat-treated manganese-aluminum composite oxide containing magnesium with an acid. 2. A method for producing a lithium adsorbent, which comprises heating a manganese-aluminum composite oxide containing magnesium at a temperature of 600° C. or higher and then treating it with an acid to elute the magnesium. 3. The method for producing a lithium adsorbent according to claim 2, wherein the acid used to elute magnesium is a solution with a pH of 3 or less.