JP6959591B2 - Tritium absorbent and its manufacturing method and separation method of tritium from light water - Google Patents

Description

INDUSTRIAL APPLICABILITY According to the present invention, a tritium absorber for separating tritium from light water containing tritium and a method for producing the same, particularly, a production capable of precisely controlling the lattice constants of hydrogen ion and lithium ion-containing manganese oxide. It relates to a method and a method for separating tritium from light water.

Tritium (T) is an isotope of hydrogen (H) and is a radioactive element with a half-life of 12.3 years that emits β-rays (electron rays). Tritium (T) exists mainly as an isotopic isomer (HTO) of water in water in the environment and in the atmosphere. Further, since triple hydrogen (T) has similar physical and chemical properties to hydrogen (H) and deuterium (D), in the conventional separation method, isotopes of water molecules in a high temperature environment. Boiling point for isomers (T ₂ O, D ₂ O, H ₂ O, DTO, HTO, HDO, etc.) or isotope isomers of hydrogen gas (T ₂ , D ₂ , H ₂ , DT, HT, HD, etc.) It is separated by a distillation method that utilizes the difference in physical properties such as hydrogen and mass, and a method that utilizes the difference in chemical reactivity with a catalytic metal such as platinum.

For example, it is described in Non-Patent Document 1, Non-Patent Document 2, Non-Patent Document 3, etc. below. However, these conventional methods are costly because they require a high temperature condition and a noble metal catalyst for the separation of tritium.

_{In recent years, light water (H 2} O) containing tritium (T) and various manganese oxide containing ^{hydrogen ion (H +} ) or ^{dehydrogen ion (D +} ) in a spinel-type crystal structure as a powder or reaction film have been used. contacting heavy water (D 2 _O), it was reported that tritium contained in room light water or heavy water are collected in the solid phase of the various manganese oxide (non-Patent Document 4, Patent Document 1, See Patent Document 2).

In these methods, various manganese oxide absorbers ^{oxidatively decompose hydroxide ion isotope isomers (OT −} ) in water at room temperature, and the resulting tritium ions (T ⁺ ) are converted into various manganese oxide absorbers. This is a method for collecting tritium from light water or heavy water, which is taken into various crystals by exchanging ions with hydrogen ions (H ⁺ ) or heavy water ions (D ^{+) contained in various crystals, and is compared with the conventional method.} It has made it possible to inexpensively separate tritium (T) from water.

International release WO2015 / 037734 International release WO2017 / 0265333

Vasaru, G. Tritium Isotope Separation 1993, CRC Press, Chapter 4-5 Villani, S. Isotope Separation 1976, Am. Nuclear Soc., Chap. 9 Gold, RF Separation of Hydrogen Isotopes 1978, Am. Nuclear Soc., Chap. 9 Hideki Koyanaka and Hideo Miyatake, Extracting tritium from water using a protonic manganese oxide spinel ”, Separation Science 142

It is described in the above patent document that tritium (T) has a spinel-type crystal structure (space group: Fd3 m) as an absorbent capable of collecting tritium (T) in light water at room temperature, and acid-treated lithium-containing manganese oxide functions. And is clarified in non-patent literature.

Here, in order to put into practical use a technique for separating tritium (T) from light water using a tritium absorbent material having the spinel-type crystal structure and made of acid-treated lithium-containing manganese oxide, the absorption is performed. Improving the ability of materials to absorb tritium is an extremely important issue.

Therefore, an object of the present invention is to provide a tritium absorber composed of hydrogen ions and lithium ion-containing manganese oxide having a spinel-type crystal structure and having a high ability to absorb tritium from light water. To do.

As a result of diligent studies in view of the above problems, the present inventor has determined that the absorption of triple hydrogen (T) in light water by lithium-containing manganese having a spinel-type crystal structure is solid in the light water and in the manganese oxide crystal. It involves ion exchange of triple hydrogen ion (T ⁺ ) and hydrogen ion (H ⁺ ) between liquids, and therefore, the crystal lattice of manganese oxide is changed from triple hydrogen ion (T ⁺ ) to hydrogen ion (H ⁺ ). By controlling the crystal lattice size to facilitate ion exchange, the absorption capacity of triple hydrogen (T) is improved, and by doping hydrogen ions having a spinel-type crystal structure and lithium-containing manganese oxide with lithium, the crystal lattice It has been found that the size can be controlled, thereby improving the absorption capacity of triple hydrogen (T) from light water, and the present invention has been completed.

That is, the present invention (1) is composed of hydrogen ion-containing lithium ion-containing manganese oxide (3) having a spinel-type crystal structure.
The lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.0370 to 8.0395 Å.
It is intended to provide a tritium absorbent characterized by.

Further, in the present invention (2), the lattice constant determined by correcting and refining the X-ray diffraction pattern measured by the powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.1000 to 8.2600 Å. The acid-treated product (2) obtained by acid-treating lithium-ion-containing manganese oxide (1) having a spinel-type crystal structure is doped with lithium, and the lithium-ion-containing manganese oxide (1) is acid-treated and lithium-doped. It provides the triple hydrogen absorber of (1), which is characterized by being a treated product.

Further, the present invention (3) is characterized in that the doping amount of lithium is 0.001 to 0.5 mg per 1 g of the acid-treated product (2) of lithium ion-containing manganese oxide (1) (2). Provides a tritium absorber.

Further, in the present invention (4), the lattice constant determined by correcting and refining the X-ray diffraction pattern measured by the powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.1000 to 8.2600 Å. The present invention provides the tritium absorber (1), which is an acid-treated product obtained by acid-treating a lithium ion-containing manganese oxide (1) having a spinel-type crystal structure.

Further, the present invention ( 5 ) includes a mixing step of mixing a manganese compound and a lithium compound to obtain a calcination raw material mixture.
The calcined raw material mixture is calcined at 200 to 800 ° C. under atmospheric pressure, and the lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is obtained. A firing step for obtaining lithium ion-containing manganese oxide (1) having a spinel-type crystal structure and a thickness of 8.1000 to 8.2600 Å.
An acid treatment step (1) of contacting the lithium ion-containing manganese oxide (1) with an aqueous acid solution containing hydrogen ions to obtain an acid-treated product (2) of the lithium ion-containing manganese oxide (1).
The acid-treated product (2) of the lithium ion-containing manganese oxide (1) is brought into contact with an aqueous solution containing lithium ions having a pH of 5.5 to 6.5, and the acid-treated product of the lithium ion-containing manganese oxide (1) is treated. A lithium doping step of obtaining a lithium ion-containing manganese oxide (1) acid-treated and lithium-doped product by doping (2) with lithium.
A method for producing tritium absorber to have a,
The lattice constant determined by correcting and refining the X-ray diffraction pattern measured by the powder X-ray diffraction analysis of the tritium absorber by the WHOLE POWDER PATTERN FITTING method is 8.0370 to 8.0395 Å.
The present invention provides a method for producing a tritium absorbent, which is characterized by the above.

Further, in the present invention ( 6 ), in the lithium doping step, as the lithium ion-containing aqueous solution, the total amount of lithium ions in the aqueous solution is measured by powder X-ray diffraction analysis of hydrogen ions and lithium ion-containing manganese oxide. The amount of lithium ions required to correct and refine the X-ray diffraction pattern by the WHOLE POWDER PATTERN FITTING method to make the lattice constant determined to be 8.0370 to 8.0395 Å, and the same amount or slightly more than the same amount. The present invention provides a method for producing a triple hydrogen absorber according to (5 ), which is characterized by using an aqueous solution containing lithium ions adjusted in an amount.

Further, the present invention ( 7 ) is characterized in that the tritium absorbing material according to any one of (1) to (4 ) is brought into contact with light water containing tritium to separate the tritium in the water. It provides a method for separating tritium from light water.

According to the present invention, it is possible to provide a tritium absorber composed of hydrogen ion and lithium ion-containing manganese oxide having a spinel-type crystal structure and having a high ability to absorb tritium from light water. ..

It is a graph which shows the relationship between the doping amount of lithium ion of Example 1 and the lattice constant of manganese oxide. It is an X-ray diffraction pattern of the hydrogen ion and lithium ion-containing manganese oxide before and after the acid treatment obtained in Example 1 and lithium-doped. It is a graph which shows the time-dependent change of the radioactivity concentration of tritium in the tritium absorption experiment of Example 2. It is a graph which shows the relationship between the lattice constant of manganese oxide and the reduction rate of the radioactivity concentration derived from tritium in the tritium absorption experiment of Example 2.

The tritium absorber of the present invention comprises hydrogen ion-containing lithium ion-containing manganese oxide (3) having a spinel-type crystal structure.
The lattice constant is 8.0370 to 8.0395 Å,
It is a tritium absorbent characterized by.

The tritium absorber of the present invention has a spinel-type crystal structure (space group: Fd3 m) and has a lattice constant of 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å. It is a lithium ion-containing manganese oxide (3). When the lattice constant of the tritium absorber is 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å, the ability to absorb tritium from water containing tritium is increased. In the present invention, the lattice constant is determined by correcting and refining the X-ray diffraction pattern measured by the powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method.

Examples of the tritium absorbing material of the present invention include the tritium absorbing material of the first form of the present invention and the tritium absorbing material of the second form of the present invention shown below.

The triple hydrogen absorber of the first embodiment of the present invention acid-treats lithium ion-containing manganese oxide (1) having a lattice constant of 8.1000 to 8.2600 Å and having a spinel-type crystal structure, and then lithium ions. Hydrogen ion and lithium ion-containing oxidation in which the lattice constant was adjusted to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å by doping the acid-treated product of the contained manganese oxide (1) with lithium. Manganese (3).

That is, the triple hydrogen absorber of the first embodiment of the present invention is acid-treated with lithium ion-containing manganese oxide (1) having a lattice constant of 8.1000 to 8.2600 Å and having a spinel-type crystal structure. The product (2) is a lithium ion-containing manganese oxide (1) acid-treated and lithium-doped product in which lithium is doped.

The acid-treated product (2) of lithium ion-containing manganese oxide (1) refers to hydrogen ions and lithium ions that are acid-treated and are subject to lithium doping in the triple hydrogen absorber of the first embodiment of the present invention. Hydrogen ions and lithium to be lithium-doped in the lithium doping step obtained by performing the acid treatment step (1) in the manganese oxide contained and the method for producing the triple hydrogen absorber of the first embodiment of the present invention. Refers to manganese oxide containing ions.

In the present invention, the lithium ion-containing manganese oxide (1) is obtained by firing a mixture of a manganese compound and a lithium compound at 200 to 800 ° C. under atmospheric pressure, and has a lattice constant of 8.1000 to 8. Refers to lithium ion-containing manganese oxide having a spinel-type crystal structure and 2600 Å, preferably 8.1549 to 8.1557 Å.

In the triple hydrogen absorber of the first embodiment of the present invention, the object to be subjected to the lithium doping treatment (the acid-treated product (2) of the lithium ion-containing manganese oxide (1)) is the lithium ion-containing manganese oxide (1). A part (50% to 95%) of lithium ions in the crystal is hydrogen ions exchanged for hydrogen ions and lithium ion-containing manganese oxide. In the tritium absorber of the first embodiment of the present invention, the object to be subjected to the lithium doping treatment (the acid-treated product (2) of lithium ion-containing manganese oxide (1)) has a spinel-type crystal structure. In the tritium absorber of the first embodiment of the present invention, the lattice constant of the object to be doped with lithium (the acid-treated product (2) of lithium ion-containing manganese oxide (1)) is 8.0300 to 8. It is 0395 Å, preferably 8.0371 to 8.0395 Å, and particularly preferably 8.0375 to 8.0390 Å. The lithium ion-containing manganese oxide (1) acid-treated product (2) has a lithium content of 1 to 19 mg per gram.

In the tritium absorber of the first embodiment of the present invention, the amount of lithium doped into the acid-treated product (2) of lithium ion-containing manganese oxide (1) is determined by the acid-treated product (2) of lithium ion-containing manganese oxide. It is 0.001 to 0.5 mg, preferably 0.05 to 0.4 mg per gram. When the amount of lithium doping in the tritium absorber is within the above range, the ability to absorb tritium from light water containing tritium is increased.

The triple hydrogen absorber of the second embodiment of the present invention has a lattice constant of 8.1000 to 8.2600 Å and has a spinel-type crystal structure by acid-treating lithium ion-containing manganese oxide (1). Is a hydrogen ion and lithium ion-containing manganese oxide (3) adjusted to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

That is, the tritium absorber of the second embodiment of the present invention is acid-treated with lithium ion-containing manganese oxide (1) having a lattice constant of 8.1000 to 8.2600 Å and having a spinel-type crystal structure. It is a thing.

The tritium absorbent material of the first embodiment of the present invention is suitably produced by the method for producing a tritium absorbent material of the first embodiment of the present invention described below.

The method for producing a tritium absorbent according to the first embodiment of the present invention includes a mixing step of mixing a manganese compound and a lithium compound to obtain a firing raw material mixture.
A firing step of calcining the calcining raw material mixture at 200 to 800 ° C. under atmospheric pressure to obtain a lithium ion-containing manganese oxide (1) having a lattice constant of 8.1000 to 8.2600 Å and a spinel-type crystal structure. When,
An acid treatment step (1) of contacting the lithium ion-containing manganese oxide (1) with an aqueous acid solution containing hydrogen ions to obtain an acid-treated product (2) of the lithium ion-containing manganese oxide (1).
The acid-treated product (2) of the lithium ion-containing manganese oxide (1) is brought into contact with an aqueous solution containing lithium ions having a pH of 5.5 to 6.5, and the acid-treated product of the lithium ion-containing manganese oxide (1) is treated. A lithium doping step of obtaining a lithium ion-containing manganese oxide (1) acid-treated and lithium-doped product by doping (2) with lithium.
It is a method for producing a tritium absorbent, which is characterized by having.

The mixing step according to the method for producing a tritium absorbent according to the first aspect of the present invention is a step of mixing a manganese compound and a lithium compound to obtain a firing raw material mixture. The manganese compound is a compound having manganese atoms such as manganese carbonate, manganese chloride, manganese oxide, manganese nitrate, manganese hydroxide, manganese sulfate, manganese phosphate, manganese bromide, and manganese oxalate. Manganese carbonate may be a hydrate. The lithium compound is a compound having a lithium atom such as lithium carbonate, lithium chloride, lithium hydroxide, lithium nitrate, lithium sulfate, lithium bromide, lithium phosphate, lithium oxalate and the like. Examples of the combination of the manganese compound and the lithium compound include "manganese carbonate and lithium carbonate" and "manganese carbonate and lithium hydroxide". In the mixing step, the powder raw materials of manganese carbonate and lithium hydroxide are mixed at room temperature until the mixture of manganese carbonate and lithium hydroxide turns black. As a result, in the mixing step, crystal nuclei of lithium ion-containing manganese oxide having a spinel-type crystal structure are generated to obtain a calcination raw material mixture.

In the firing step according to the method for producing a tritium absorber according to the first aspect of the present invention, the firing raw material mixture is calcined under atmospheric pressure, for example, in the air at 200 to 800 ° C. to form a powder. This is a step of obtaining a lithium ion-containing manganese oxide (1) having a spinel-type crystal structure.

Regarding the firing conditions in the firing step, the firing temperature is 200 to 800 ° C., preferably 300 to 500 ° C., more preferably 380 to 400 ° C., and the firing time is preferably 3 to 10 hours. The firing conditions in the firing step are within the above range, taking into consideration the acid treatment conditions in the acid treatment step and the doping amount of lithium ions in the lithium ion doping step, and finally obtained hydrogen ion and lithium-containing manganese oxide ( The lattice constant of 3) is adjusted to be 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

In the firing step, after firing, a powder containing lithium ion-containing manganese oxide (1) having a spinel-type crystal structure and unreacted residual manganese carbonate is suspended in distilled water and allowed to stand for a certain period of time. Place and collect the precipitate. This precipitate is lithium ion-containing manganese oxide (1) having a spinel-type crystal structure.

The lattice constant of lithium ion-containing manganese oxide (1) having a spinel-type crystal structure obtained by performing the firing step is 8.1000 to 8.2600 Å, preferably 8.1549 to 8.1557 Å.

After the firing step, if necessary, the lithium ion-containing manganese oxide (1) having a spinel-type crystal structure can be dried. The drying treatment is performed in the air at about 90 to 120 ° C.

In the acid treatment step (1) according to the method for producing a triple hydrogen absorber according to the first aspect of the present invention, lithium ion-containing manganese oxide (1) having a spinel-type crystal structure obtained by performing a firing step is converted into hydrogen ions (1). This ^{is a step of contacting with an acid aqueous solution containing H +} ) to obtain an acid-treated product (2) of lithium-containing manganese oxide (1).

Examples of the acid aqueous solution according to the acid treatment step (1) include a dilute hydrochloric acid aqueous solution, a dilute nitrate aqueous solution, a dilute sulfuric acid aqueous solution, etc. A dilute aqueous hydrochloric acid solution with a small amount of water is preferable. The molar concentration (mol / L, M) normality of the acid aqueous solution is preferably 0.1 to 1.0 M, particularly preferably 0.3 to 0.6 M.

As a method for performing the acid treatment step (1), for example, a powder of lithium ion-containing manganese oxide (1) is suspended in an acid aqueous solution containing ^{hydrogen ions (H +) such as a dilute hydrochloric acid aqueous solution and stirred.} , Lithium ion-containing manganese oxide (1) is ^{brought into contact with an acid aqueous solution containing hydrogen ions (H +} ), then solid-liquid separated by filtration or the like to separate the solid component from the acid aqueous solution, and lithium-containing oxidation. An acid-treated product (2) of manganese (1) is obtained.

The acid treatment conditions in the acid treatment step (1) are the molar concentration of the aqueous acid solution, the stirring speed, the stirring time, the solid-liquid ratio, etc., but the acid treatment conditions in the acid treatment step are the firing conditions in the firing step and the lithium doping step. The lattice constant of the hydrogen ion and the lithium ion-containing manganese oxide (3) finally obtained is 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å, taking into consideration the amount of lithium doping in the above. Is adjusted so that. Further, in the acid treatment step (1), the acid treatment can be performed a plurality of times. That is, the lithium ion-containing manganese oxide (1) is acid-treated to obtain an acid-treated intermediate, and then the acid-treated intermediate is further acid-treated to obtain a lithium-ion-containing manganese oxide (1). ), The acid-treated product (2) can be obtained.

The acid-treated product (2) powder of lithium ion-containing manganese oxide (1) obtained by performing the acid treatment step (1) must not be heat-dried. The reason for this is that the heat-drying treatment promotes the reaction in which hydrogen ions in the crystal structure of manganese oxide evaporate from the crystals as water molecules, and as a result, the absorbability of triple hydrogen ions decreases. be. This phenomenon is described in Ref. B: Hideki Koyanaka and Hideo Miyatake, Extracting tritium from water using a protonic oxide spinel ", Separation 142 Science.

The lattice constant of the acid-treated product (2) of the lithium ion-containing manganese oxide (1) obtained by performing the acid treatment step (1) is 8.0300 or more and less than 8.0395 Å, preferably 8.0300 to 8.0375 Å, particularly. It is preferably 8.0366 to 8.0370 Å.

The lithium doping step according to the method for producing a triple hydrogen absorber according to the first aspect of the present invention is an acid-treated product (2) of a wet lithium-containing manganese oxide (1) obtained by performing the acid treatment step (1). Is brought into contact with an aqueous solution containing lithium ions having a pH of 5.5 to 6.5 according to the amount of doping, and the specified amount of lithium is contained in the crystal of the acid-treated product (2) of the lithium ion-containing manganese oxide (1). Is the process of doping.

Examples of the lithium source of the lithium ion-containing aqueous solution according to the lithium doping step include lithium salts having high water solubility such as lithium chloride, lithium nitrate and lithium sulfate. The lithium ion concentration in the aqueous solution containing lithium ions is preferably 0.5 to 30 mg / L, particularly preferably 1 to 15 mg / L. The reason for this is that when doping is carried out using an aqueous solution having a lithium concentration of more than 50 mg / L, manganese is eluted from the acid-treated product of lithium ion-containing manganese oxide (1) due to supersaturation of the amount of lithium absorbed.

In the lithium ion doping step, the acid-treated product (2) of lithium ion-containing manganese oxide (1) is suspended in an aqueous solution containing lithium ions, and an aqueous sodium hydroxide solution is added dropwise with stirring to generate lithium ions. Lithium is doped while maintaining the pH of the contained aqueous solution at 5.5 to 6.5. The reason for keeping the pH at 5.5 to 6.5 is that when the pH is made alkaline of 8 or more, manganese elutes from the acid-treated product (2) of the lithium ion-containing manganese oxide (1). The concentration of sodium hydroxide used for adjusting the pH of the lithium ion-containing aqueous solution is appropriately selected according to the amount of the lithium ion-containing aqueous solution and the amount of the acid-treated product of lithium ion-containing manganese oxide (1). .. In the lithium doping step, the amount of lithium doped into the acid-treated product (2) of the lithium ion-containing manganese oxide (1) is finally determined in consideration of the firing conditions in the firing step and the acid treatment conditions in the acid treatment step. The lattice constants of the hydrogen ion and lithium ion-containing manganese oxide (3) obtained in the above are adjusted to be 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

In the lithium doping step, the amount of lithium doped into the acid-treated product (2) of the lithium ion-containing manganese oxide (1) is preferably 0, per 1 g of the acid-treated product (2) of the lithium ion-containing manganese oxide (1). It is 001 to 0.5 mg, particularly preferably 0.05 to 0.4 mg. When the amount of lithium doped into the acid-treated product (2) of the lithium ion-containing manganese oxide (1) is in the above range, the lattice constant is 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å. Hydrogen ion and lithium ion-containing manganese oxide can be easily obtained.

In the lithium doping step, as an aqueous solution containing lithium ions, the total amount of lithium ions in the aqueous solution and the lattice constants of hydrogen ions and lithium-containing manganese oxide (3) are set to 8.0370 to 8.0395 Å, preferably 8.0375 to 8. It is possible to use an aqueous solution containing the amount of lithium ions required to obtain 8.0390 Å and the same amount or a slightly excess amount of the same amount, preferably the same amount or 1.01 times the amount of the lithium ions. , Hydrogen ion and lithium ion-containing manganese oxide (3) is preferable because it is easy to adjust the lattice constant to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

By simply acid-treating lithium-containing manganese oxide (1) to elute lithium ions (ie, without performing a lithium doping step), the lattice constants of hydrogen ions and lithium-containing manganese oxide are set to 8.0370 to 8.0395 Å. Preferably, it can be 8.0375 to 8.0390 Å. However, when the lattice constant is changed only by acid treatment, the lithium-containing manganese oxide (1) in the acid treatment step may be changed depending on the firing temperature and firing time in the firing step, the acid treatment time in the acid treatment, the stirring strength, and the like. The ability of lithium ions to exchange ions with hydrogen ions tends to vary. Therefore, the selection of conditions for realizing the lattice constant obtained only by acid treatment tends to be complicated, or the reproducibility of the lattice constant in industrial manufacturing tends to vary.
Further, the conventional manganese oxide containing hydrogen ions and lithium ions is obtained through some drying treatment step following the production step of lithium-containing manganese oxide and the acid treatment step, and the lithium-containing oxidation is carried out by this drying step. The drying treatment of the acid-treated product (2) of manganese greatly reduces the capacity at which lithium ions can be doped (H. Koyanaka, O. Matsubaya, Y. Koyanaka, N. Hatta, J. Electrical Chemistry 559). 77-81.). Therefore, even if lithium doping is attempted on manganese oxide containing hydrogen ions and lithium ions obtained by a conventional method, the lattice constant of hydrogen ions and lithium ion-containing manganese oxide is preferably 8.0370 to 8.0395 Å. It was difficult to adjust to 8.0375 to 8.0390 Å.

On the other hand, in the method for producing a triple hydrogen absorber according to the first aspect of the present invention, a lithium ion-containing manganese oxide containing lithium ion can be obtained by performing an acid treatment step without selecting complicated conditions in the firing step and the acid treatment step. Necessary for adjusting the lattice constant of hydrogen ion and lithium ion-containing manganese oxide to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å from the lattice constant of the acid-treated product (2) of (1). If the total amount of lithium ions is calculated and an aqueous solution containing lithium ions containing the same amount or a slightly excess amount of lithium ions is used in the lithium doping step, almost all of the lithium in the aqueous solution is hydrogen. Since it is doped with ion- and lithium-ion-containing manganese oxide, the lattice constant is precisely adjusted in units of 1 / 10,000 to 1/1000 angstrom (Å) to fine-tune the hydrogen ion- and lithium-ion-containing manganese oxide. The lattice constant of is adjusted to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

Regarding the grasp of the amount of lithium doped into the acid-treated product (2) of lithium ion-containing manganese oxide (1) in the lithium doping step, lithium before contacting with the acid-treated product of lithium ion-containing manganese oxide (1). ICP emission is the initial lithium concentration in an aqueous solution containing ions and the residual lithium concentration in an aqueous solution containing lithium ions obtained by performing solid-liquid separation with a vacuum filter or the like after doping lithium ions. It is possible to grasp the amount of lithium doping in the acid-treated product (2) of lithium ion-containing manganese oxide (1) from the measurement using an analytical method and the difference in their concentrations. In addition, the fact that lithium ions are not simply surface-adsorbed to the acid-treated product (2) of lithium ion-containing manganese oxide (1) but are doped inside the crystal is mainly due to the powder X-ray diffraction analysis method. It can be grasped from the fact that the diffraction peak group shifts. That is, when lithium ions having an ionic radius larger than hydrogen ions are doped in the crystal, the crystal expands and the lattice constant increases, so that the main diffraction peak group shifts to the low angle side. Since such a size change of the crystal itself does not occur by mere surface adsorption of lithium ions, the doping effect of lithium ions can be accurately measured through the change of the lattice constant.

In the lithium doping method in the method for producing a triple hydrogen absorber of the present invention, lithium ion-containing manganese oxide (1) is produced at a relatively low temperature in the process of producing hydrogen ion having a spinel-type crystal structure and lithium ion-containing manganese oxide (3). The hydrogen ion and lithium ion-containing manganese oxide (2) obtained after low-temperature synthesis at preferably 390 to 400 ° C. and subjected to a predetermined acid treatment is not subjected to a drying treatment step, whereby immediately after the acid treatment. The lattice constant is 1 / 10,000 of that of hydrogen ion and lithium ion-containing manganese oxide (2) in a state where the hydrogen ion content in the obtained spinel-type crystal structure is maintained, that is, in a state where lithium ions are most easily doped. It enables the doping of lithium ions, which can be finely tuned in units of 1/1000 angstrom (Å).
On the other hand, when the acid-treated product of lithium ion-containing manganese oxide (1) is dried, hydrogen ions are released into the atmosphere as water from the surface of the crystal, so that hydrogen in the spinel-type crystal structure is simply obtained. Not only does it reduce the ion content, but it also reduces the uniform reactivity with lithium ions on the crystal surface. Therefore, the lithium ion-containing manganese oxide (1) is subjected to a drying step after the acid treatment step, and the hydrogen ion and the lithium ion-containing manganese oxide obtained in the conventional manufacturing step are subjected to a lithium ion doping step. In the case of the above, it is extremely difficult to precisely control the lattice constant by doping the crystal with lithium ions from the lithium-containing water in a small amount.
The precise control of the lattice constant by doping lithium ions in the lithium doping step according to the method for producing a tritium absorber of the present invention is a final product as shown in FIGS. 1, 3 and 4 in Examples. It makes it possible to precisely fine-tune the lattice constants of lithium-ion-doped hydrogen ions and lithium-ion-containing manganese oxide (3) in units of 1 / 10,000 to 1/1000 angstrom (Å).

In the lithium doping step, after contacting the acid-treated product of lithium ion-containing manganese oxide (1) with an aqueous solution containing lithium ions, solid-liquid separation is performed by filtration or the like, and distilled water or ultrapure water is used as necessary. Rinse with water or store in a wet cake state after solid-liquid separation to obtain hydrogen ion- and lithium ion-containing manganese oxide (3) as final products.

In the lithium doping step, approximately 99% or more of lithium contained in the lithium ion-containing aqueous solution is doped into the crystals of the acid-treated product of lithium ion-containing manganese oxide (1). Therefore, it is possible to make the doping amount accurate by accurately preparing the amount of lithium in the aqueous solution containing lithium ions in advance. As a result, specifically, the lattice constant of the finally obtained hydrogen ion and lithium ion-containing manganese oxide (3) can be controlled in units of 1 / 10,000 to 1/1000 angstrom (Å). can. Such accurate lithium doping is preferably carried out by acid-treating lithium ion-containing manganese oxide (1) obtained by firing at a temperature of 380 to 400 ° C. and then performing doping in a wet state. , Easy to achieve. Then, in the lithium doping step, the lattice constant of the crystal of the acid-treated product of lithium ion-containing manganese oxide (1) changes regularly according to the amount of lithium ions to be doped. Then, by performing a lithium doping step using an aqueous solution containing a required amount of lithium in advance, the lattice constant was precisely controlled to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å. Hydrogen ion- and lithium-ion-containing manganese oxide (3) (final product) having a spinel-type crystal structure can be obtained.

In the method for producing a triple hydrogen absorber according to the first aspect of the present invention, the firing conditions in the firing step, the acid treatment conditions in the acid treatment step, and the doping amount of lithium ions in the lithium doping step are adjusted. The lattice constant of the finally obtained hydrogen ion-containing lithium ion-containing manganese oxide (3) having a spinel-type crystal structure is precisely controlled to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å. Can be done.

The tritium absorbent material of the second embodiment of the present invention is suitably produced by the method for producing a tritium absorbent material of the second embodiment of the present invention described below.

The method for producing a tritium absorbent according to the second embodiment of the present invention includes a mixing step of mixing a manganese compound and a lithium compound to obtain a firing raw material mixture.
A firing step of calcining the calcining raw material mixture at 200 to 800 ° C. under atmospheric pressure to obtain a lithium ion-containing manganese oxide (1) having a lattice constant of 8.1000 to 8.2600 Å and a spinel-type crystal structure. When,
The acid treatment step (2) of contacting the lithium ion-containing manganese oxide (1) with an aqueous acid solution containing hydrogen ions to obtain an acid-treated product of the lithium ion-containing manganese oxide (1).
It is a method for producing a tritium absorbent, which is characterized by having.

The mixing step according to the method for producing a tritium absorber according to the second aspect of the present invention is the same as the mixing step according to the method for producing a tritium absorber according to the first aspect of the present invention.

In the firing step according to the method for producing a tritium absorbent according to the second aspect of the present invention, the firing raw material mixture is calcined under atmospheric pressure, for example, in the air at 200 to 800 ° C. to form a powder. This is a step of obtaining a lithium ion-containing manganese oxide (1) having a spinel-type crystal structure.

Regarding the firing conditions in the firing step, the firing temperature is 200 to 800 ° C., preferably 300 to 500 ° C., more preferably 380 to 400 ° C., and the firing time is preferably 3 to 10 hours. The firing conditions in the firing step are within the above range, and the lattice constant of the lithium ion-containing manganese oxide (3) finally obtained is 8.0370 to 8. It is adjusted to 0395 Å, preferably 8.0375 to 8.0390 Å.

In the firing step, after firing, a powder containing lithium ion-containing manganese oxide (1) having a spinel-type crystal structure and an unreacted product, which is a fired product, is suspended in distilled water and allowed to stand for a certain period of time to precipitate. Collect things. This precipitate is lithium ion-containing manganese oxide (1) having a spinel-type crystal structure.

The lattice constant of lithium ion-containing manganese oxide (1) having a spinel-type crystal structure obtained by performing the firing step is 8.1000 to 8.2600 Å, preferably 8.1549 to 8.1557 Å.

After the firing step, if necessary, the lithium ion-containing manganese oxide (1) having a spinel-type crystal structure can be dried. The drying treatment is performed in the air at about 90 to 120 ° C.

In the acid treatment step (2) according to the method for producing a triple hydrogen absorber according to the second aspect of the present invention, lithium ion-containing manganese oxide (1) having a spinel-type crystal structure obtained by performing a firing step is converted into hydrogen ions (1). This ^{is a step of contacting with an acid aqueous solution containing H +} ) to obtain an acid-treated product of lithium ion-containing manganese oxide (1).

Examples of the acid aqueous solution according to the acid treatment step (2) include a dilute hydrochloric acid aqueous solution, a dilute nitrate aqueous solution, a dilute sulfuric acid aqueous solution, etc. A dilute aqueous hydrochloric acid solution with a small amount of water is preferable. The molar concentration of the aqueous acid solution is preferably 0.1 to 1.0 M, particularly preferably 0.3 to 0.6 M.

As a method for performing the acid treatment step (2), for example, a powder of lithium ion-containing manganese oxide (1) is suspended in an acid aqueous solution containing ^{hydrogen ions (H +) such as a dilute hydrochloric acid aqueous solution and stirred.} , Lithium ion-containing manganese oxide (1) is ^{brought into contact with an acid aqueous solution containing hydrogen ions (H +} ), then solid-liquid separated by filtration or the like to separate the solid component from the acid aqueous solution, and contains lithium ions. A powder of an acid-treated product of manganese oxide (1) is obtained.

The acid treatment conditions in the acid treatment step (2) are the molar concentration of the aqueous acid solution, the stirring speed, the stirring time, the solid-liquid ratio, etc., but the acid treatment conditions in the acid treatment step also take into consideration the firing conditions in the firing step. The lattice constant of the finally obtained hydrogen ion and lithium ion-containing manganese oxide (3) is adjusted to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

The acid-treated powder of lithium ion-containing manganese oxide (1) obtained by performing the acid treatment step (2) must not be heat-dried. The reason for this is that the heat-drying treatment promotes the reaction in which hydrogen ions in the crystal structure of manganese oxide evaporate from the crystals as water molecules, and as a result, the absorbability of triple hydrogen ions decreases. be.

By performing the acid treatment step (2), the lithium ions in the crystal of the lithium ion-containing manganese oxide (1) are exchanged for hydrogen ions, and the lattice constant is 8.0370 to 8.0395 Å, preferably 8.0375 to 8. Hydrogen ion- and lithium-ion-containing manganese oxide (3) (final product) having a spinel-type crystal structure at .0390 Å is obtained.

The method for producing a triple hydrogen absorber according to the second aspect of the present invention has a spinel-type crystal structure finally obtained by adjusting the firing conditions in the firing step and the acid treatment conditions in the acid treatment step. The lattice constant of the hydrogen ion- and lithium ion-containing manganese oxide (3) can be set to 8.0370 to 8.0395 Å, preferably 8.0375 to 8.0390 Å.

The tritium absorber of the present invention has a crystal lattice constant of 8.0370 to 8.0395 Å, preferably 8.0375 to 8, in which ^{tritium ions (T +} ) are easily exchanged for hydrogen ions (H ^+). Since it is .0390 Å, the tritium absorber of the present invention has a high ability to absorb tritium from light water containing tritium.

Regarding the absorption capacity of tritium from light water containing tritium, a sample of tritium absorber is suspended in a certain amount of test water containing tritium at a constant radioactivity concentration, and is derived from tritium. By measuring the change in the radioactivity concentration by the liquid scintillation counter method, the ability of the tritium absorber to absorb tritium can be grasped.

The method for separating tritium from light water of the present invention is characterized in that the tritium absorber of the present invention is brought into contact with light water containing tritium to absorb tritium in the water. This is a method for separating tritium.

In the method for separating tritium from light water of the present invention, the tritium absorber of the present invention is added and suspended in light water containing tritium, and the mixture is stirred to obtain the tritium absorber of the present invention as tritium. By contacting with light water containing tritium, the tritium in the water containing tritium is absorbed by the tritium absorber of the present invention.

Then, in the method for separating tritium from light water of the present invention, the tritium absorber of the present invention is brought into contact with light water containing tritium, and the tritium absorber of the present invention absorbs tritium. After that, tritium is separated from light water containing tritium by solid-liquid separation by filtration or the like to separate and recover the tritium absorber that has absorbed tritium.

An example of a tritium separation test is shown below. Test water containing tritium was prepared by diluting a commercially available tritium standard solution with ultrapure water. The tritium absorber of the present invention was added and suspended in this test water, and the mixture was stirred for 1 hour using a magnetic stirrer. During the test, an alkaline reagent (eg, aqueous sodium hydroxide solution) was added to the test water to keep the pH of the suspension at a value suitable for absorption of tritium (eg, pH 5.5-6.5). .. Every time a predetermined time elapses, about 1.5 mL of a sample of test water is collected by filtration, 1.0 mL of which is precisely weighed, and light is emitted by beta rays emitted by tritium as a scintillator. A surfactant (10.0 mL) containing a fluorescent substance was added. The change in the radioactivity concentration of tritium contained in each test water sample (1.0 mL) to which this scintillator was added was measured using a liquid scintillation counter.

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention.

(Example 1)
<Synthesis of Lithium Ion-Containing Manganese Oxide (1) Powder with Spinel Crystal Structure>
<Mixing process>
Wako Pure Chemical Industries' special grade reagent manganese carbonate hydrate (MnCO ₃ · nH ₂ O) and special grade lithium hydroxide hydrate (LiOH · H ₂ O) powder are mixed at a weight ratio of 2: 1 and at room temperature. It was mixed well until it turned black to obtain a baking material mixture powder.
<Baking process>
Using an electric furnace (FO-410 manufactured by YAMATO), about 42 g of the baking material mixture powder obtained above is placed in an alumina crucible and heated in the air at 390 ° C. for 4 hours and 30 minutes, and then naturally reaches room temperature. Cooled.
<Recovery>
41 g of the powder after natural cooling was suspended in 2 L of distilled water in a glass beaker, and ultrasonic waves were irradiated for 15 minutes through the wall surface of the beaker to loosen the agglomeration of the powder. In the suspension allowed to stand in the beaker, unreacted manganese carbonate has a small specific density, so that it remains turbid in the supernatant of the suspension, and lithium ion-containing manganese oxide having a spinel-type crystal structure with a large specific density is at the bottom of the container. Settled in. The unreacted residual manganese carbonate that had floated in the supernatant after being allowed to stand for 1 hour was removed using an aspirator, and the precipitated lithium ion-containing manganese oxide powder having a spinel-type crystal structure was removed using a vacuum filter. It was collected on a glass fiber filter paper (GS-25 manufactured by ADVANTEC).
<Drying>
The lithium ion-containing manganese oxide powder having a spinel-type crystal structure recovered by filtration was dried in an air atmosphere at 105 ° C. for 62 hours to obtain 16.7 g of a lithium ion-containing manganese oxide powder having a spinel-type crystal structure.
A powder X-ray diffraction analyzer (Smart Lab X-RAY DIFFRACTIOMETER manufactured by Rigaku) was used for identification of the crystal structure. The analysis conditions are characteristic X-ray: Cu-Kα, X-ray output: 40 kV, 30 mA, scan speed: 0.5010 deg / min, step width: 0.0100 deg, scan angle (2θ): 15-70 °, and filter: Cu. -Set to Kβ. As a result of the analysis, the X-ray diffraction pattern of the lithium ion-containing manganese oxide obtained is described in Reference C: S.A. Bagci, H. et al. M. Tuetuencue, S.M. Duman, E.I. Blut, M.D. Oezacar, G.M. p. Srivastava, J. et al. Physics and Chemistry of Solids, 75 (2014) 463-469. (ICSD-192028) Similar to the X-ray diffraction pattern _{of lithium ion-containing manganese oxide (chemical composition: LiMn 2} O ₄ ) having a spinel-type crystal structure (space group: Fd3 m, crystal lattice constant: 8.1600 Å). I understood. Furthermore, as a result of analyzing the X-ray diffraction pattern by the WPPF method, it was found that the lattice constant of the obtained lithium ion-containing manganese oxide was 8.1553 ± 0.0004 Å.

<Synthesis of acid-treated powder of lithium ion-containing manganese oxide (1)>
<Acid treatment process>
0.5 g of the lithium ion-containing manganese oxide (lattice constant: 8.1553 ± 0.0004 Å) having the spinel-type crystal structure obtained above is suspended in 100 mL of a dilute aqueous hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 0.5 M. After turbidity, stirring was continued for 30 minutes using a stirrer coated with Teflon® resin and a magnetic stirrer, and then allowed to stand for 30 minutes. An acid-treated powder of lithium-containing manganese oxide (1) having a wet spinel-type crystal structure was recovered from the suspension on a glass fiber filter paper (GS-25 manufactured by ADVANTEC) by a vacuum filter.
When analyzed using a powder X-ray diffraction analyzer, the X-ray diffraction pattern of the acid-treated product of the obtained lithium ion-containing manganese oxide (1) is described in Document D: A. Ibarra Palos, M. Anne, P. Strobel. , J. Solid State Chemistry 160 (2001) Acid treatment of lithium ion-containing manganese oxide (1) of spinel-type crystal (space group: Fd3 m, crystal lattice constant: 8.0916 Å) (ICSD-93743) according to 108-117. It was found to be similar to the X-ray diffraction pattern of the substance (chemical composition: Li _0.42 H _0.304 Mn _1.81 O _4). Furthermore, as a result of analyzing the X-ray diffraction pattern by the WPPF method, it was found that the lattice constant of the acid-treated product of lithium-containing manganese oxide (1) obtained by the above-mentioned acid treatment was 8.0368 ± 0.0002 Å. .. Since the lattice constant of the acid-treated product of the obtained lithium ion-containing manganese oxide (1) is considerably smaller than the value of 8.0916 Å, which is the value of the lattice constant of the above-mentioned literature value, the obtained lithium was obtained. The acid-treated product of ion-containing manganese oxide (1) has a lower lithium ion content than _{the chemical composition (Li 0.42} H _0.304 Mn _1.81 O _{4) described in Document D, and contains it.} It is considered to have a chemical composition with a high proportion of hydrogen ions.

<Synthesis of acid-treated and lithium-doped products>
<Lithium Doping (1)-(3)>
As described above, an acid-treated product of lithium-containing manganese oxide (1) obtained by acid-treating 0.5 g of lithium ion-containing manganese oxide (1) (lattice constant: 8.1553 ± 0.0004 Å). (Lithium constant: 8.0368 ± 0.0002 Å) is tested for the lithium concentrations of the following three types ((1) to (3)) in a wet state after filtration and recovery from a dilute hydrochloric acid aqueous solution having a concentration of 0.5 M. Suspended in water (100 mL). The test water (100 mL) used in the lithium doping process is 100 mL of ultrapure water (resistance value: 18.5 MΩ) and a lithium chloride aqueous solution (lithium concentration 10000 mg / L, special grade lithium chloride LiCl powder manufactured by Wako Pure Chemical Industries, Ltd.). Was diluted with ultrapure water to prepare the mixture). The suspension was stirred at room temperature for 2 hours in an air atmosphere using a stirrer coated with Teflon® resin and a magnetic stirrer. At this time, the pH of the suspension was maintained at 5.5 to 6.5 by dropping an aqueous solution of sodium hydroxide (aqueous solution of NaOH manufactured by Wako Pure Chemical Industries, Ltd., a concentration of 0.5 M or 0.1 M). Then, after stopping the stirring of the suspension, the suspension was allowed to stand for 30 minutes, and the suspension was subjected to a wet acid treatment and a lithium doping treatment on a glass fiber filter paper (GS-25 manufactured by ADVANTEC) using a vacuum filter. The product powder was collected by filtration.
-Test water for lithium doping (1): Add 15 μL of a lithium chloride aqueous solution having a lithium concentration of 10000 mg / L to 100 mL of ultrapure water (Li concentration: 1.5 mg / L, Li amount: 0.15 mg).
-Test water for lithium doping (2): 60 μL of a lithium chloride aqueous solution having a lithium concentration of 10000 mg / L was added to 100 mL of ultrapure water (Li concentration: 6 mg / L, Li amount: 0.6 mg).
-Test water for lithium doping (3): 150 μL of a lithium chloride aqueous solution having a lithium concentration of 10000 mg / L was added to 100 mL of ultrapure water (Li concentration: 15 mg / L, Li amount: 1.5 mg).

<Analysis method>
The wet lithium-doped product powder obtained above was subjected to X-ray diffraction analysis, and the obtained X-ray diffraction pattern was analyzed by the WPPF method to correct and refine the lattice constant of the crystal.
Further, from the suspension after the test, using a filter paper unit (ADVANTEC DISMIC GS-25AS020AN) and a disposable syringe (Terumo SS-02SZP), the lithium remaining in the solid-liquid separated test water sample. The concentration was quantified using an ICP luminescence analyzer (SSI Nanotechnology SPS3520UV-DD). From the difference between the quantified residual lithium concentration and the initial lithium concentration of the test water, the amount of lithium doped in the solid phase of the acid-treated product of lithium-containing manganese oxide (1) was examined from the liquid phase of the test water. Lithium Doping The amount of lithium doping in (1), (2), and (3) was 0.1475 mg, 0.5977 mg, and 1.4950 mg, respectively, per 0.5 g of lithium-containing manganese oxide. From these results, in each of the test waters (1) to (3), 98.4 to 99.7% of lithium previously dissolved in 100 mL of ultrapure water was doped into the solid phase of manganese oxide. I found out. When converted to the doping amount per 1.0 g of manganese oxide, it was 0.295 mg / g and 1.195 mg / g, 2.990 mg / g, respectively.

<Effect of Lithium Doping on Lattice Constant>
Next, as a result of analyzing the crystal structure of the acid-treated and lithium-doped products by the X-ray diffraction analysis method, all the lithium ion-containing manganese oxides obtained by lithium doping (1) to (3) are described in Document D. _{Similar to the lithium ion and hydrogen ion containing manganese oxide (chemical composition: Li 0.42} H _0.304 Mn _1.81 O ₄ ) of the spinel type crystal (space group: Fd3 m, crystal lattice constant: 8.0916 Å) described. The X-ray diffraction pattern is shown. Further, the X-ray diffraction pattern of each sample was analyzed by the WPPF method, and the lattice constant of each sample was corrected and refined to obtain the result. As a result, the hydrogen ion obtained from the lithium doping (1) and the lithium ion-containing manganese oxide have a lattice constant of 8.0381 ± 0.0002 Å of the spinel type crystal, and the hydrogen obtained from the lithium doping (2). The ion and lithium ion-containing manganese oxide has a lattice constant of 8.0401 ± 0.0005 Å, and the hydrogen ion and lithium ion-containing manganese oxide obtained from lithium doping (3) are spinnel-type crystals. It was analyzed that the lattice constant was 8.0453 ± 0.0002 Å. Lithium Doping In the order of (1), (2), and (3), the lattice constant increased as the amount of lithium doping increased. FIG. 1 shows these results as a change in the lattice constant with respect to the doping amount of lithium per 1 g of hydrogen ion-containing manganese oxide. From the above, it was found that by doping lithium, the lattice constants of hydrogen ions and lithium ion-containing manganese oxide can be precisely controlled and changed in units of 1/1000 to 1/10000 Å. The above precision control means that the size of manganese oxide crystals can be fine-tuned in units of ^{0.01 to 0.1 pm (1 pico meter: 10 to 12 meters).} The size of the lattice constant is controlled 10 to 100 times more precisely than in the conventional technique.

<Comparative Example> Comparison of spinel-type lithium ion-containing manganese oxide (1) with the lattice constant of an acid-treated product in the literature Spinel-type lithium ion-containing manganese oxide and spinel-type lithium ion-containing manganese oxide (1) reported in Document B. It is described in Document B, Supplemental data, that the lattice constants of the acid-treated product of the above were 8.0154 Å and 8.011 Å, respectively. The lattice constant of the acid-treated product of spinel-type lithium ion-containing manganese oxide (1) described in Document B is a lithium-doped product having a spinel-type crystal structure obtained by lithium doping (1) of Example 1. It is smaller than the lattice constant value (8.0381 ± 0.0002 Å) of the lattice constant of lithium ion-containing manganese oxide.
In Example 1, lithium ion-containing manganese oxide (lattice constant: 8.16000 Å) was suspended in 100 mL of dilute hydrochloric acid having a concentration of 0.5 M, stirred for 30 minutes, allowed to stand for 30 minutes, and then collected by filtration. bottom. On the other hand, for example, in Document B above, when 0.5 g of a lithium ion-containing manganese oxide (lattice constant: 8.154 Å) powder was treated with acid, it was stirred with 1 L of dilute hydrochloric acid having a concentration of 0.5 M for 1 hour. After that, it is collected by filtration. Further, in WO2015-037734, 1 g of lithium ion-containing manganese oxide powder is stirred with 1 L of dilute hydrochloric acid having a concentration of 0.5 M for 1 hour, and then collected by filtration. Due to this difference in acid treatment time, the amount of lithium eluted from lithium-containing manganese oxide differs, and as a result, an acid-treated product (8.011 Å) of lithium-containing manganese oxide (1) having different lattice constants is obtained in the same document. It is thought that it was. Further, in this embodiment, the measurement result of the powder X-ray diffraction pattern is precisely corrected by the WPPF method, but in Document B, the diffraction peak in the measurement result of the powder X-ray diffraction pattern. Of these, since the lattice constant is calculated by considering only the three strong lines, it is considered that the accuracy of the numerical value of the lattice constant is inferior to that of this embodiment.

<Example 2>
<Tritium absorption experiment in water using tritium absorbent powder>
<Preparation of tritium-containing test water>
A test in which a standard reagent of tritium water (T, water manufactured by PerkinElmer) was diluted with 100 mL of ultrapure water (resistance value: 18.2 MΩ) at room temperature and contained tritium at a radioactivity concentration of 3176.6 Bq / mL. Water was mixed in a glass beaker. A liquid scintillation counter (Liquid Scintillation Analyzer TRI-CARB 2100TR PACKARD USA) was used to measure the radioactivity concentration of tritium. As a blank sample, 10.0 mL of a scintillator (Ultima Gold manufactured by PerkinElmer) was added to 1.0 mL of ultrapure water used in the experiment, and the radioactivity of tritium was measured, and 0.54 Bq / mL was detected. Therefore, in this method for measuring radioactivity, it was confirmed that 0.54 Bq / mL is the lower limit of detection of the radioactivity concentration of tritium.

<Tritium absorption experiment>
In the tritium absorption experiment, hydrogen ion and lithium ion-containing manganese oxide powder having a spinel-type crystal structure and being a lithium-doped product obtained by performing the above lithium doping (1) (lattice constant: 8.0381). ± 0.0002 Å) was collected under reduced pressure from a lithium chloride aqueous solution for doping, collected on a filter paper, and immediately washed with ultra-pure water (30 mL) in a wet cake state. It was suspended in 100 mL of test water having the above-mentioned radioactivity concentration of 3176.6 Bq / mL.
The suspension was then stirred for 60 minutes using a Teflon® resin coated stir bar and a magnetic stirrer. The initial pH of the suspension was adjusted to pH 6.22 by dropping an aqueous sodium hydroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a concentration of 0.1 M onto the suspension. 60 minutes after the start of the experiment, the pH of the suspension dropped to 5.41. The water temperature of the suspension was 19.3 to 20.8 ° C. After 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, and 60 minutes have passed since the start of suspension, a filter paper unit (ADVANTEC DISMIC GS-25AS020AN) and a disposable syringe (Terumo SS-02SZP) were used. , 1.3 mL of test water sample was collected from the suspension, and 1.0 mL of the sample was precisely weighed and separated from the 1.3 mL. Surfactant containing a fluorescent agent that emits β-rays as a scintillator. (Perkin Elmer ULtima Gold) was added in 10.0 mL. Finally, the radioactivity concentration derived from tritium contained in each sample of the test water was measured with a liquid scintillation counter (Liquid Scintillation Analyzer TRI-CARB 2100TR PACKARD USA). A pH meter (HORIBA pH / DO meter, D-55 glass electrode model 9678) was used to confirm the pH and water temperature.
A similar absorption test for triple hydrogen was carried out by subjecting hydrogen ion and lithium ion-containing manganese oxide powder having a spinel-type crystal structure and being a lithium ion-containing treated product obtained from lithium ion doping (2) and (3), and lithium doping. It was carried out using an acid-treated product of lithium ion-containing manganese oxide (1) which was not carried out.
In FIG. 2, the X-ray diffraction pattern of the manganese oxide sample subjected to the lithium doping (1) used in this experiment is shown in (3). In the figure, the X-ray diffraction pattern (1) is an X-ray diffraction pattern of lithium ion-containing manganese oxide before acid treatment, and the X-ray diffraction pattern (2) shows the X-ray diffraction pattern of (1). The X-ray diffraction pattern of the acid-treated product obtained by acid-treating the lithium ion-containing manganese oxide is shown. In the chemical formula of FIG. 2, x and y represent the molar ratio of the amounts of lithium ions and hydrogen ions contained in each manganese oxide. That is, in Li _1-x Mn ₂ O ₄ · H _x (2), x is the amount of lithium ions eluted by acid treatment of Li Mn ₂ O _{4 (1) and Li 1-x Mn by ion exchange.} for the amount of incorporated hydrogen ions _{2 O 4 · H x (2} ), it represents the molar ratio. Further, in Li _{1-x + y} Mn ₂ O ₄ · H _xy (3), y is _{doped against manganese oxide (Li 1-x} Mn ₂ O ₄ · H _x ) (2) after acid treatment. It represents the molar ratio of the amount of lithium ions and the amount of hydrogen ions eluted from manganese oxide into lithium ion-containing water by the doping treatment.

<Results of tritium absorption experiment>
FIG. 3 shows a hydrogen ion-containing lithium ion-containing manganese oxide powder having a spinel-type crystal structure and a spinel-type crystal structure and a lithium-doped product obtained by performing the above lithium doping (1) (lithium ion doping amount: 3.0 mg / g, lattice constant: 8.0381 ± 0.0002 Å) is suspended and suspended in tritium-containing test water (capacity: 100 mL, tritium radioactivity concentration: 3716.6 Bq / mL) in a wet state. The time course of the tritium radioactivity concentration in the sample (1.0 mL) collected from the tritium-containing test water at the time of stirring at regular intervals is shown. In FIG. 3, after the start of the experiment, when the reaction time was 5 minutes, the radioactivity concentration of tritium decreased from the initial value of 3176.6 Bq / mL to 1714.4 Bq / mL, which corresponds to a concentration of about 54% of the initial value. bottom. In FIG. 3, the tritium concentration in the tritium-containing test water decreased after 5 minutes and then increased again to near the initial concentration. It has been pointed out in the literature that the cause of this re-elevation of the tritium concentration is caused by an insufficient amount of hydrogen ions contained in the manganese oxide powder which is a tritium absorbing material (Reference B). Further, in order to prevent such a re-rise in the tritium concentration, a film is processed with hydrogen ions and lithium ion-containing manganese oxide powder which have a spinel-type crystal structure as an absorbent and are lithium-doped products. It is effective to supply hydrogen ions from the outside (for example, WO2017 / 006973).
Similarly, a tritium-containing test was performed on hydrogen ions and lithium ion-containing manganese oxide having a spinel-type crystal structure and being lithium ion-containing treated products obtained by performing the above lithium doping (2) and (3) under the same experimental conditions. The maximum reduction rate of the radioactivity concentration when applied to water was about 5% and 12%, respectively, with respect to the initial value.
Further, when an acid-treated product (lattice constant: 3.0368 ± 0.0002 Å) of lithium ion-containing manganese oxide (1) not doped with lithium ions was subjected to a similar tritium absorption experiment, the maximum reduction rate was found. It was about 10% of the initial value.
In FIG. 4, these experimental results were compared as the rate of decrease (%) in the concentration of radioactivity derived from tritium with respect to the change in the lattice constant (Å) of hydrogen ion- and lithium-ion-containing manganese oxide crystals. From FIG. 4, it can be seen that a high reduction rate of the same radioactivity concentration can be obtained in the range of the lattice constant value of 8.0371 to 8.0395 Å.
From these facts, a tritium absorber that absorbs tritium in water with high efficiency can be obtained by doping lithium so that the lattice constant of lithium ion-containing manganese oxide falls within the range specified in the present invention. I understand.

<Comparative Example> Comparison with Tritium Absorption Capacity described in Document B and WO2015 / 037734 In Document B, lithium ion-containing manganese oxide having a lattice constant of 8.011 Å is wetted as a tritium absorber as in this example. As a result of applying it to tritium-containing test water (100 mL) in a dry state (dry weight: about 0.5 g), the initial radioactivity concentration derived from tritium in the tritium-containing test water corresponds to about 35% of the initial value. It has been reported that the concentration has decreased. On the other hand, in this example, hydrogen ions having a lattice constant of 8.0381 ± 0.0002 Å and lithium-containing manganese oxide containing lithium ions are wetted (dry weight: about 0.5 g) in the test water. When applied to tritium-containing test water (100 mL) under almost the same conditions except for the initial concentration of tritium, a concentration decrease corresponding to about 54% of the initial value was obtained. The initial concentration of tritium in Document B was 5607 Bq / mL, and the initial concentration of tritium in this example was 3176.6 Bq / mL. Generally, when the initial concentration is high, the pressure effect due to the concentration works, so that it is more advantageous to obtain a higher absorption effect than when the initial concentration is low. In this example, although the initial concentration of tritium in the test water is lower than the initial concentration of the experiment in Document B, the decrease in tritium concentration is remarkable, which is higher than the absorption effect of tritium in Document B. An absorption effect was obtained.
Therefore, it was found that the tritium absorption capacity was improved by increasing the lattice constants of hydrogen ion and lithium ion-containing manganese oxide to 8.0381 ± 0.0002 Å by doping with lithium ions.
Further, in WO2015 / 037734, lithium ion-containing manganese oxide (crystal lattice constant: 8.154 Å, dry weight: about 0.5 g) before acid treatment was used as a triple hydrogen absorber in triple hydrogen-containing test water (100 mL). After suspension, the pH of the suspension was adjusted to 3 to 4 by adding a dilute aqueous hydrochloric acid solution, and an alkaline reagent was added dropwise to the suspension to control the pH to converge to 5.75 to 5.98. It is stated that As a result, the concentration of tritium-derived radioactivity in the test water is reduced to a maximum of about 45% of the initial value.
However, the lithium-containing manganese oxide (crystal lattice constant: 8.154 Å) before acid treatment described in Document B and WO2015 / 037734 has a tritium-containing test water in which the initial pH is in a weakly acidic to neutral region (pH 5-7). In the case of), since it does not function as a tritium absorber, the initial pH of the suspension obtained by adding the tritium absorber to the tritium-containing test water as described above is adjusted to 3 to 4, and further pH 5. It is necessary to carry out complicated pH control so as to converge to 75 to 5.98. On the other hand, the hydrogen ion having a lattice constant of 8.0381 ± 0.0002 Å and the lithium ion-containing manganese oxide containing the lithium ion of this example were suspended as a tritium absorber in the tritium-containing test water. Just by maintaining the initial pH in the weakly acidic to neutral region (pH 5-6), the value of the initial concentration is used as the rate of decrease in the tritium concentration in the test water, as shown in FIGS. 3 and 4. It shows the absorption capacity of tritium corresponding to 54% of the above, and it is effective to dope the acid-treated product of lithium ion-containing manganese oxide (1) with an appropriate amount of lithium ions in order to improve the absorption performance of tritium. Is shown.

Claims (7)

It is composed of hydrogen ion and lithium ion-containing manganese oxide (3) having a spinel-type crystal structure.
The lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.0370 to 8.0395 Å.
A tritium absorbent characterized by. The lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.1000 to 8.2600 Å, and contains lithium ions having a spinel-type crystal structure. The acid-treated product (2) obtained by acid-treating manganese oxide (1) is lithium-doped, which is an acid-treated and lithium-doped product of lithium ion-containing manganese oxide (1). The triple hydrogen absorber according to claim 1. The tritium absorber according to claim 2, wherein the doping amount of lithium is 0.001 to 0.5 mg per 1 g of the acid-treated product (2) of lithium ion-containing manganese oxide (1). The lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is 8.1000 to 8.2600 Å, and contains lithium ions having a spinel-type crystal structure. The triple hydrogen absorber according to claim 1, wherein the triple hydrogen absorber is an acid-treated product obtained by acid-treating manganese oxide (1). A mixing step of mixing a manganese compound and a lithium compound to obtain a calcination raw material mixture,
The calcined raw material mixture is calcined at 200 to 800 ° C. under atmospheric pressure, and the lattice constant determined by correcting and refining the X-ray diffraction pattern measured by powder X-ray diffraction analysis by the WHOLE POWDER PATTERN FITTING method is obtained. A firing step for obtaining lithium ion-containing manganese oxide (1) having a spinel-type crystal structure and a thickness of 8.1000 to 8.2600 Å.
An acid treatment step (1) of contacting the lithium ion-containing manganese oxide (1) with an aqueous acid solution containing hydrogen ions to obtain an acid-treated product (2) of the lithium ion-containing manganese oxide (1).
The acid-treated product (2) of the lithium ion-containing manganese oxide (1) is brought into contact with an aqueous solution containing lithium ions having a pH of 5.5 to 6.5, and the acid-treated product of the lithium ion-containing manganese oxide (1) is treated. A lithium doping step of obtaining a lithium ion-containing manganese oxide (1) acid-treated and lithium-doped product by doping (2) with lithium.
A method for producing tritium absorber to have a,
The triple hydrogen absorber is a hydrogen ion- and lithium ion-containing manganese oxide having a spinel-type crystal structure, and the X-ray diffraction pattern measured by powder X-ray diffraction analysis is corrected and refined by the WHOLE POWDER PATTERN FITTING method. The lattice constant to be formed is 8.0370 to 8.0395 Å.
A method for producing a tritium absorbent, which is characterized by. In the lithium doping step, as the lithium ion-containing aqueous solution, the total amount of lithium ions in the aqueous solution is measured by powder X-ray diffraction analysis of hydrogen ions and lithium ion-containing manganese oxide. It contains the amount of lithium ions required to adjust the lattice constant determined by correction and refinement by the FITTING method to 8.0370 to 8.0395 Å, and lithium ions adjusted to the same amount or a slight excess amount from the same amount. The method for producing a triple hydrogen absorber according to claim 5 , wherein an aqueous solution is used. A method for separating tritium from light water, which comprises contacting the tritium absorbent according to any one of claims 1 to 4 with light water containing tritium to separate the tritium in the water. ..

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