JP2775412B2 - Lithium isotope separating agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lithium isotope separating agent. More specifically, the present invention relates to a layered titanium phosphate having excellent lithium isotope separation performance and a lithium isotope separating agent comprising a heat-treated product thereof.

[0002]

2. Description of the Related Art In recent years, lithium has been used as a raw material for, for example, ceramics, grease, refrigerants for air conditioning, pharmaceuticals, batteries, and the like. In the future, lithium is attracting attention as an important substance used for aluminum alloy materials and the like. . In each of these, a mixture of lithium isotopes having an atomic weight of 6 and 7 is used as a raw material. However, lithium separated into each having a single atomic weight is useful in the field of nuclear power. As a raw material for a nuclear fusion reactor, lithium having an atomic weight of 7 has attracted attention as a neutron scavenger in nuclear power generation. For this reason, there is a strong demand for establishing a technique for mutually separating lithium isotopes from a mixed solution.

Conventionally, as a method for separating lithium isotopes, for example, an amalgam method, a molten salt method, a distillation method, an adsorption method and the like are known. The amalgam method is a method in which isotopes are separated by electrolyzing lithium as mercury amalgam. However, since mercury is used, there is a major problem in environmental health. The molten salt method is a method of heating a lithium compound to a molten state and performing electrophoresis to separate isotopes.However, heating requires high energy and the equipment is complicated, so the separation cost is high. There is a drawback that you can not escape. The distillation method is a method of separating isotopes by evaporating lithium metal or a lithium compound, but has the disadvantage that the cost of separation is also high because the raw materials are expensive and high temperatures are required.

[0004] In contrast to these methods, the adsorption method is a method of separating isotopes by utilizing an adsorption reaction from a solution to a solid phase such as an ion exchange reaction, which can be operated at room temperature and has a simple apparatus. Although it is a suitable method as a separation method, an adsorbent having high separation performance must be used in order to perform isotope separation. As a lithium isotope separating agent, a strongly acidic ion exchange resin or zeolite is conventionally known. However, the strong acid ion exchange resin is ⁶ Li
^Since the separation coefficient with 7Li is as low as 1.002, there is a problem that it is necessary to use a large amount of resin and perform the separation treatment precisely in order to completely separate the lithium isotope. On the other hand, zeolite has a separation factor of 1.00.
Although relatively high at 4 to 1.006, it has the disadvantage of being unstable in aqueous solution.

A method for separating lithium isotopes using an organic cryptand resin has also been reported. However, this method has disadvantages in that the production cost of the resin is high and the separation efficiency is not sufficient.

[0006]

In the separation of lithium isotopes by a chemical exchange method, a separating agent having high separation efficiency and being stable in an aqueous solution is required. If this problem can be solved, an efficient and economical lithium isotope separation process can be constructed.

The object of the present invention is to provide a lithium isotope separating agent satisfying such requirements.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the layered titanium phosphate monohydrate or its heat-treated product has a high content of lithium isotope. The present inventors have found that the present invention exhibits a separation efficiency, and have completed the present invention based on this finding. That is, the present invention provides a separating agent for efficiently and economically separating lithium isotopes.

Layered titanium phosphate 1 as the separating agent of the present invention
Hydrates are synthesized by refluxing amorphous titanium phosphate in a 10 M or more phosphoric acid solution for 2-3 days. The chemical formula is Ti
It is represented by (HPO ₄ ) ₂ .H ₂ O, and the layer interval is 7.6 Å. The substance has an ion-exchange group between layers and can adsorb ions in a solution. Also,
Heat treatment of the material to 400 ° C. results in the loss of water of hydration, reducing the layer spacing to 7.4 angstroms. Further heating to a high temperature changes to α-type TiP ₂ O ₇ . These heated samples also exhibit ion adsorption performance, but selectivity for ions is different from unheated samples. In particular, the sample heated at 400 ° C. is characterized by having high selectivity for sodium ions.

[0010] Although the layered titanium phosphate monohydrate and heat treatment product is a lithium selective adsorptivity is not a different or adsorption energy is ⁶ Li energy of dehydration is at ⁶ Li and ⁷ Li when lithium is adsorbed by utilizing the fact that different ⁷ Li can be separated lithium isotopes with high efficiency. These samples are usually in the form of a powder, but may be used as it is as a lithium isotope separating agent, or may be granulated and used as a granular material, or may be used as a fibrous or film-like material. It may be molded.

In order to separate a lithium isotope using a lithium isotope separating agent comprising such a layered titanium phosphate or a heat-treated product thereof, the separating agent is added to a mixed solution containing the lithium isotope. And the step of performing the lithium adsorption treatment may be repeated. Naturally stable
^{Of 6} Li and ⁷ Li, strongly adsorbed by the separating agent
⁶ Li gradually migrates into the solid phase, while ⁷ Li in solution
Is gradually increased, and the mutual separation is completed.

In general, there is used a method of preparing a chromatography column filled with the separating agent formed into a granular form and performing separation. That is, a lithium adsorption band is formed by flowing a fixed amount of a mixed solution containing a lithium isotope into the column, and then the lithium adsorption band is moved by continuously flowing an eluent from the upper portion of the column to move the lithium adsorption band, thereby forming an isotope. Perform separation. At this time, a neutral or acidic aqueous solution is usually used as the eluent. In this way,
The ⁷ Li to adsorb weakly by rear side ⁶ Li to strongly adsorbed by the separating agent can be concentrated on the front end side. Such an isotope separation treatment by adsorption-elution can also be performed using a fibrous or membrane-like separating agent.

[0013]

By using the lithium isotope separating agent of the present invention, a mixed solution containing a lithium isotope can be obtained.
⁶ Li and ⁷ Li can be separated efficiently and economically.

[0014]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0015] Example 1 layer spacing 7.64 Å layered titanium phosphate 1
0.14 g of hydrate is mixed with lithium hydroxide and lithium chloride (concentrations are 0.07M and 0.03M, respectively).
L and shaken at 25 ° C. for 1 week. The lithium adsorption after shaking was 25.7 mg / g, and 62% of the lithium in the solution was adsorbed. It was the stock solution and ⁷ Li ^/ 6 Li isotopic molar ratio in the supernatant after the adsorption was measured by thermal ionization mass spectrometer, respectively 12.53 and 12.
63.

From the above, it is clear that the separating agent of the present invention has higher isotope separation performance than ion exchange resins and zeolites.

Example 2 Layered titanium phosphate monohydrate was heated at 400 ° C. for 4 hours to prepare a sample having a layer interval of 7.43 Å. 0.14 g of this sample was mixed with a mixed solution of lithium hydroxide and lithium chloride (concentrations of 0.07 M and 0.03 M, respectively).
M) Immersion in 8 mL and shaking at 25 ° C. for 1 week. The lithium adsorption after shaking was 25.0 mg / g, and 59% of the lithium in the solution was adsorbed. Was the stock solution and ⁷ Li ^/ 6 Li isotopic molar ratio in the supernatant after the adsorption was measured by thermal ionization mass spectrometer, it was respectively 12.53 and 12.65.

From the above, it is apparent that the separating agent of the present invention has higher isotope separation performance than ion exchange resins and zeolites.

Comparative Example 1 0.14 g of layered zirconium phosphate having a layer spacing of 7.53 Å was mixed with 8 mL of a mixed solution of lithium hydroxide and lithium chloride (concentrations of 0.07 M and 0.03 M, respectively).
And shaken at 25 ° C. for 1 week. The lithium adsorption after shaking was 28.5 mg / g, and 68% of the lithium in the solution was adsorbed. It was the stock solution and ⁷ Li ^/ 6 Li isotopic molar ratio in the supernatant after the adsorption was measured by thermal ionization mass spectrometer, respectively 12.53 and 12.5
It was 5. Separation coefficient S is calculated by the formula

Where isotope ratio in the solution after the adsorption experiment,
α ₀ is the isotope ratio in the stock solution, C is the lithium concentration of the solution after the adsorption experiment, and C ₀ is the lithium concentration of the stock solution].

From the above, it is apparent that the separating agent of the present invention has almost the same isotope separation performance as the layered titanium phosphate or its heat-treated product while having the same layered structure.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Akinari Sonoda 2217-14 Hayashi-cho, Takamatsu-shi, Kagawa Pref. Institute of Industrial Technology, Shikoku Institute of Industrial Technology (56) References Patent Publication of the People's Republic of China Patent Application Publication 1090217 (CN, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01D 59/26-59 / 30 WPI (DIALOG)

Claims (1)

(57) [Claims] 1. A lithium isotope separating agent comprising lamellar titanium phosphate monohydrate or a heat-treated product thereof.