JPS6346009B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for recovering lithium from a dilute solution, and more specifically to a method for recovering lithium from a dilute solution containing lithium, using a heat-treated titanic acid having excellent selective adsorption properties for lithium as an adsorbent. The present invention relates to a method for efficiently and extremely easily recovering . In recent years, lithium metal and its compounds have been used in many fields, such as ceramics, batteries, refrigerant absorbers,
It is used in medicines, etc., and in the future, it is expected to be used in large-capacity batteries, aluminum alloy materials, nuclear fusion fuel, etc., so demand for these products is expected to increase significantly [Hisato Hayashi et al.; Japan Mining Journal, 97 , (1118)]. These lithium metals and their compounds are
Currently, it is mainly obtained from lithium-containing ores such as spodiumen, ambrigonite, petalite, and lepidolite, and underground brine such as geothermal water and natural gas brine. By the way, Japan does not have the above-mentioned lithium ore resources and is currently completely dependent on imports for lithium metal and its compounds. Establishing recovery technology has become an important issue. Conventional technology Conventionally, as a method for recovering lithium from a dilute solution containing lithium such as seawater, for example, a coprecipitation method using aluminum hydroxide [Toshikazu Matsuoka et al., 43rd Annual Meeting of the Chemical Society of Japan, abstracts of lectures, 1240] has been used.
(1981)], amorphous aluminum hydroxide [Takao Kitamura et al.; Seawater Journal, 32 , 78 (1978), Hideo Wada et al.; Japan Mining Association Journal, 99 , (1145), 585 (1983)], metal aluminum [Takeuchi Bunji; Rust Prevention Management, 1982, (2), 369], hydrated tin oxide [Kenta Oi et al.; Journal of the Japan Mining Association, 99 ;
(1148), 933 (1983)] are known. However, these methods have drawbacks such as low lithium adsorption capacity and low adsorption rate, and furthermore, lithium recovery is obstructed by coexisting silica, making it difficult to put them into practical use. On the other hand, some alkali titanates have a unique layered structure, and the titanic acid obtained from these alkali titanates is known to have ion exchange ability, and it is known that titanic acid obtained from these alkali titanates has an ion-exchange ability, and is suitable for alkali metals and alkaline earth metals. Ion exchange has been studied in detail [Yoshiki Fujiki et al.; Ceramics, 19 , 128
(1984)]. In previous studies, the acid fraction coefficient, or adsorption amount, of the layered titanic acid in the measured pH range was Cs>Rb>K>Na>Li> and Ba>Sr>Ca>
It is known that ions with a larger ionic radius have a larger exchange amount and are selectively adsorbed. As described above, conventional layered titanic acid has a drawback of having a small adsorption capacity for lithium. On the other hand, some titanic acids exhibit lithium selective adsorption properties for aqueous solutions containing high concentrations of lithium hydroxide (Japanese Unexamined Patent Publication No. 150543/1983); This is due to the special conditions of a lithium solution, which is weakly alkaline such as seawater or geothermal water, and contains sodium, potassium,
It has the disadvantage that it does not exhibit lithium adsorption properties in dilute lithium solutions where large amounts of magnesium ions and the like coexist. Problems to be Solved by the Invention In order to practically adsorb and recover lithium from a dilute solution containing lithium, it is necessary to have excellent selectivity for lithium, high adsorption capacity and high adsorption rate, and
Moreover, it is necessary to use an inexpensive adsorbent that is stable in the dilute solution and has low toxicity. Although the layered titanic acid obtained from the layered alkali titanate has the advantages of being safe in the dilute solution, having little toxicity, and being inexpensive, the conventional layered titanate has a high resistance to lithium as described above. It has the disadvantage of poor selective adsorption. The purpose of the present invention is to improve the drawbacks of conventional layered titanic acid as an adsorbent for lithium, and to efficiently remove lithium from a dilute solution containing lithium using a titanate-based adsorbent with excellent selective adsorption properties. The objective is to provide a practical method for extremely easy recovery. Means for Solving the Problems As a result of various studies, the present inventors have found that, by using a heat-treated product of titanic acid obtained by acid-treating alkali metal titanate, the titanate has a high resistance to lithium. It was discovered that the selective adsorption property was significantly improved and the objective could be achieved, and based on this knowledge, the present invention was completed. That is, in recovering lithium from a dilute solution containing lithium, the present invention uses the following as an adsorbent:
It is characterized by using a heat-treated titanic acid obtained by acid-treating an alkali metal titanate.
A method for recovering lithium from a dilute solution is provided. The alkali metal titanates used in the method of the present invention include, for example, titanium oxide, hydrated titanium oxide, etc., and alkali metal hydroxides, oxides, carbonates,
After mixing with hydrogen carbonate, etc., heat at 600 to 1300℃.
It can be obtained by heating in the temperature range of . The alkali metals are generally sodium and potassium, but other alkali metals such as lithium may also be used. Further, the titanium/alkali metal molar ratio is suitably in the range of 1/2 to 3/2. Titanic acid can be obtained by treating these alkali metal titanates with an acid or a solution containing 0.1 to 2 moles of acid based on the salt to remove alkali metal ions. As the acid, for example, mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid and formic acid are used. By heat-treating the titanic acid thus obtained, preferably at a temperature in the range of 80 to 300°C for 1 to 50 hours, an adsorbent with excellent selective adsorption for lithium can be obtained. It was found that with such heat treatment, the peak in X-ray diffraction shifted to the high angle side and the interlayer spacing became smaller. In this way, it is presumed that because the voids inside the adsorbent are reduced by the heat treatment, an ion sieving effect acts on lithium ions having the smallest ionic radius among alkali metal ions, increasing selectivity. At this time, if the heating temperature is 150°C or less, it is necessary to heat for 3 hours or more, but if the heating time is too long, the crystal form will change, so it is appropriate to heat it for 50 hours or less. Also, if the heating temperature exceeds 150℃,
The heating time is preferably within 5 hours. Examples of the dilute solution containing lithium used in the method of the present invention include natural gas brine, underground brine, seawater, and industrial wastewater. In the method of the present invention, the adsorbent obtained as described above is added to a dilute solution containing lithium and stirred to sufficiently adsorb the lithium, and then the adsorbent is separated from the solution to have a pH of 4 or less. By contacting the lithium with an acidic solution to elute and recover the lithium, or by passing a dilute solution containing lithium through a column filled with an adsorbent,
After adsorbing the lithium, the lithium can also be desorbed and recovered by passing an acidic solution with a pH of 4 or less. In addition, to increase collection efficiency,
It is desirable to condition the adsorbent in advance with an alkaline solution. Effects of the Invention The method for recovering lithium from a dilute solution of the present invention is as follows:
As an adsorbent, it has excellent selectivity for lithium,
This is a method of efficiently and economically recovering the lithium using a material that has a large adsorption capacity and adsorption rate, is stable in the dilute solution, has low toxicity, and is of extremely practical value. expensive. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples. Example 1 Potassium titanate obtained by mixing commercially available titanium oxide and potassium carbonate in a predetermined ratio and heating at 800°C for 5 hours was immersed in 0.5M hydrochloric acid for 3 days, and then the obtained titanium Acid 90, 160, 210, 290
The adsorbent was obtained by heat treatment at each temperature of .degree. C. for a predetermined period of time. 1 g of the adsorbent thus obtained is 1mMLi ⁺
The adsorbed amount of lithium was measured by adding it to 100 ml of the solution (pH 8.3 buffer solution), and the distribution ratio (lithium concentration in the adsorbent/lithium concentration in the solution) was determined. The results are shown in Table 1.

[Table] As is clear from this table, when the heat treatment temperature of titanic acid is 90 to 160°C, the adsorption performance of lithium is particularly excellent. Example 2 Commercially available titanium oxide and sodium carbonate were mixed at a predetermined ratio, an adsorbent was prepared in the same manner as in Example 1, and the lithium distribution ratio was determined. The results are shown in Table 2.

[Table] As can be seen from this table, similarly to Example 1, titanic acid heated at 160°C showed excellent adsorption performance. Example 3 Commercially available titanium oxide and potassium carbonate were mixed so that the molar ratio of titanium and potassium was 1:1,
After melting at 1100°C, it was rapidly cooled to obtain potassium titanate fibers, which were then treated with 1M hydrochloric acid to obtain titanate fibers. 120% of this titanate fiber,
Heat treated at 250 and 300℃ for a specified period of time,
An adsorbent was obtained. 100 mg of the adsorbent obtained in this way was mixed with Li ⁺ ,
Add to 10 ml of a solution (pH 8.3 buffer) prepared so that Na ⁺ and Ca ²⁺ are 1 mM each, shake for 3 days, filter off the adsorbent, and measure the residual ion concentration. , the distribution ratio of each ion was determined. The results are shown in Table 3.

[Table] As is clear from this table, the distribution ratio of Li ⁺ is extremely large. In addition, this adsorbent has been found to adsorb a considerable amount of Ca ²⁺ .
Effective for recovering lithium from dilute solutions with low Ca ²⁺ concentration. Example 4 0.8 for each of the three adsorbents prepared in Example 3
g to 100ml of geothermal water (Li5.3ppm, PH8), 25
After shaking at ℃ for 3 days, the recovery rate of lithium was measured. The results are shown in Table 4.

[Table] As can be seen from this table, by using adsorbents No. 18 and No. 19, more than 90% of lithium (adsorption amount 0.6 mg/g) could be recovered. Furthermore, when the adsorbent adsorbing lithium was immersed in 0.1M hydrochloric acid for 8 hours, more than 95% of the lithium was eluted. These results show that the adsorbent of the present invention has excellent adsorption performance and is practical.

Claims (1)

[Claims] 1. When recovering lithium from a dilute solution containing lithium, titanic acid obtained by acid treatment of alkali metal titanate is heat-treated at 80 to 300°C for 1 to 50 hours and used as an adsorbent. Characteristic method for recovering lithium from dilute solution.