JP5971790B2 - Radioactive Cs + ion adsorbent and method for producing the same - Google Patents

Description

The present invention relates to a radioactive Cs ⁺ ion adsorbent and a method for producing the same.

At present, in the industrial use of nuclear energy, how to capture and treat the radioactive Cs ⁺ ions discharged is an important issue.

As a method for capturing radioactive Cs ⁺ ions, for example, there is a method of removing radionuclides from a solution characterized by using Euglena (Patent Document 1). There is also a cesium adsorbent comprising denitrifying bacteria (Patent Document 2). With these methods and cesium adsorbents, radionuclides can be concentrated by microorganisms.
However, microorganisms must be isolated in the facility, handling is troublesome, and there is a risk that the microorganisms will mutate due to radiation or the like. There is also a risk of scattering.

In addition, as a method for capturing radioactive Cs ⁺ ions, there is a method for adsorbing Cs ⁺ ions to soil (Non-patent Document 1).
However, as shown in the relationship between the pH or ionic strength and the distribution coefficient (Kd) of Cs ⁺ ion adsorption (Fig. 1), when soil is used as it is, the amount of Cs ⁺ ion adsorption strongly depends on the pH and ionic strength. In addition, the amount of adsorption of Cs ⁺ ions is very small.

Further, as a method for capturing radioactive Cs ⁺ ions, there is a method of using a smectite clay mineral containing montmorillonite as a Cs ⁺ ion adsorbent (Non-patent Document 2).
However, as can be seen from the adsorption isotherm (Fig. 2) and conclusion of bentonite and montmorillonite, when a cation having a large ionic radius such as Cs ⁺ ion intercalates between layers of the layered compound such as clay mineral, Cs ⁺ Ions cannot be easily desorbed from the interlayer, and the clay mineral itself becomes a low-level radioactive waste.

Furthermore, there is a method using zeolite as a Cs ⁺ ion adsorbent (Non-patent Document 3). This method is most commonly used.
However, in zeolite, Cs ⁺ ions cannot be easily desorbed from the interlayer, and a large amount of low-level radioactive waste is generated.

JP 2005-315701 A JP 2007-271306 A

G. Lujanien, S.M. Motiejunas, J.M. Sapolite, Journal of Radiotactical and Nuclear Chemistry, 274, 345, (2006. 9.18) M.M. Galambos, V.M. Paucova, J .; Kufkakova, O .; Rosskopfova, P.M. Rajec, R.A. Adamcova, Journal of Radioanalytical and Nuclear Chemistry, 284, 55, (2011.19.19). B. Yidiz, N .; Erten, M.M. Kis, Journal of Radioanalytical and Nuclear Chemistry, 288, 475, (2011.12.12) T.A. Watanabe, T.A. Sato. Cray Science, 7, 129, (1988, 3.7) H. J. et al. Ploehn, C.I. Liu. Industrial and Engineering Chemistry Research. 45. 7025. (2006.3.1) Edited by Japan Clay Society, Clay Handbook, pp147, Table 3.5.1 (2009.4.30) The Chemical Society of Japan, Chemical Handbook II, Gibbs energy of hydration ppII-316, Table 10.15 (1993.9.30)

The present invention is to readily adsorb radioactive Cs ⁺ ions, and to provide a removable radioactive Cs ⁺ ion adsorbent and a manufacturing method thereof.

In view of the above circumstances, as a result of trial and error, the present inventor ion-exchanges part or all of Na ⁺ ions, Li ⁺ ions, and H ⁺ ions contained in a normal layered clay mineral with Rb ⁺ ions. When used as a pre-Cs ⁺ ions and ionic radius close Rb ⁺ ions intercalated between layers of the layered compound as a radioactive Cs ⁺ ion adsorbent, since only slightly less than the magnitude of Cs ⁺ ions, by ion exchange It was found that Cs ⁺ ions can be easily adsorbed between layers and surfaces, and adsorbed Cs ⁺ ions can be desorbed with water or a weakly acidic solution. It was also found that after desorption, it could be used again as a radioactive Cs ⁺ ion adsorbent, and the present invention was completed.
The present invention has the following configuration.

(1) It has a layered clay mineral and a cation intercalated between the layers of the layered clay mineral, the layered clay mineral belongs to smectites, and the cation has an ionic radius of 1.1 mm or more. A radioactive Cs ⁺ ion adsorbent characterized by being.

(2) The radioactive Cs ⁺ ion adsorbent according to (1), wherein the layered clay mineral is montmorillonite or beidellite.
(3) The radioactive Cs ⁺ ion adsorbent according to (1) or (2), wherein the cation is any one cation selected from the group of Rb ⁺ , K ⁺ or Ba ²⁺ .
(4) The radioactive Cs ⁺ ion adsorbent according to any one of (1) to (3), wherein an X-ray diffraction peak value at 95% relative humidity is 3.85 ° to 8.46 ° .

(6) After dispersing a smectite layered clay mineral in an aqueous solution in which a cation having a concentration of 100 mmol / L or more and an ionic radius of 1.1 Å or more is dispersed, the layered clay mineral and the cation A method for producing a radioactive Cs ⁺ ion adsorbent, characterized by stirring an aqueous solution in which an aqueous solution is dispersed.

The radioactive Cs ⁺ ion adsorbent of the present invention has a layered clay mineral and a cation intercalated between layers of the layered clay mineral, the layered clay mineral belongs to smectites, and the cation of the cation Since the ionic radius is 1.1 mm or more, a sufficient bottom surface spacing (d value) can be secured in the aqueous solution, and the radioactive Cs ⁺ ions can be easily adsorbed and the radioactive Cs ⁺ ions can be easily desorbed. can do. Thereby, it can be used as a radioactive Cs ⁺ ion adsorbent that can be used repeatedly, and the problem of generating a large amount of low-level radioactive waste can be solved.

In the method for producing the radioactive Cs ⁺ ion adsorbent of the present invention, a smectite layered clay mineral is dispersed in an aqueous solution in which a cation having an ion radius of 1.1 mm or more is dispersed at a concentration of 100 mmol / L or more. Therefore, since the aqueous solution in which the layered clay mineral and the cation are dispersed is stirred, a radioactive Cs ⁺ ion adsorbent that can be used repeatedly can be easily manufactured.

It is a cross-sectional schematic diagram which shows an example of the radioactive Cs ⁺ ion adsorption agent of this invention. It is a schematic diagram of the A section of FIG. It is a figure which shows an example of a normal layered clay mineral, Comprising ^: It is a schematic diagram of the part corresponding to the A section of FIG. 1 of the layered clay mineral before intercalating Rb ⁺ . It is a schematic diagram which shows the state by which the Na ^<+> ion between the layers of the layered clay mineral was hydrated to the water molecule. It is a schematic diagram which shows the state which the layered clay mineral isolate | separated into many clay mineral layers. It is a schematic diagram of the part corresponding to the A section of FIG. 1 of the layered clay mineral intercalated with Rb ⁺ . FIG. 2 is a schematic diagram of a portion corresponding to part A of FIG. 1 of a layered clay mineral in which water molecules are hydrogen-bonded to Rb ⁺ intercalated between layers. It is a schematic diagram of the part corresponding to the A section of FIG. 1 of the layered clay mineral intercalated with Cs ⁺ . It is a flowchart which shows an example of the manufacturing method of radioactive Cs ⁺ ion adsorption agent of this invention. It is process drawing which shows an example of the manufacturing method of radioactive Cs ⁺ ion adsorbent of this invention. It is the bottom surface distance d value (Å) of the 001 plane of the diffraction peak of the sample of Example 1 at each relative humidity. It is process drawing of radioactive Cs ⁺ ion adsorption property evaluation of Example 1 sample. It is process drawing of radioactive Cs ⁺ ion adsorption property evaluation of Example 1 sample. It is process drawing of radioactive Cs ⁺ ion adsorption property evaluation of Example 1 sample. It is process drawing of radioactive Cs ⁺ ion adsorption property evaluation of Example 1 sample.

(Embodiment of the present invention)
Hereinafter, a radioactive Cs ⁺ ion adsorbent and a method for producing the same according to embodiments of the present invention will be described with reference to the accompanying drawings.

<Radioactive Cs ⁺ ion adsorbent>
FIG. 1 is a schematic cross-sectional view showing an example of a radioactive Cs ⁺ ion adsorbent according to an embodiment of the present invention.
As shown in FIG. 1, a radioactive Cs ⁺ ion adsorbent 10 according to an embodiment of the present invention includes a layered clay mineral 11 and a cation 19 intercalated between the layers of the layered clay mineral 11. Have

The layered clay mineral 11 belongs to smectites.
Smectites are a general term for clay minerals such as montmorillonite, beidellite, nontronite, saponite, and hectorite. More preferably, montmorillonite or beidellite is used as the layered clay mineral 11.
As shown in FIG. 1, the layered clay mineral 11 has two or more clay mineral layers 12.
The clay mineral layer 12 has a SiO—OH layer 13a, an inorganic oxide layer 14, and a SiO—OH layer 13b. The inorganic oxide layer 14 is sandwiched between the SiO—OH layers 13a and 13b.

FIG. 2 is an enlarged schematic view of a part A in FIG.
The SiO—OH layers 13a and 13b are layers formed by connecting triangular pyramid-shaped structural units with Si at the center and O at the apex.
The inorganic oxide layer 14 is a layer formed by connecting octahedral structural units with a metal Me of Al, Mg, or Fe at the center and O at the top.

The clay mineral layer 12 is made of silicic acid (SiO ₂ , SiO ₂ .OH), aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), or iron hydroxide (Fe (OH) ₃ ). It is an inorganic substance having a crystal structure stacked in a sheet form.

The ionic radius (six coordination) of the cation 19 is 1.1 あ る or more. The value of the ion radius is based on Shannon, 1976 (hereinafter the same). Thereby, it is possible to easily exchange ions with radioactive Cs ⁺ ions having an ion radius (6-coordinate) of 1.67Å. Ion exchange means that ions bonded by ion bonding or the like are transferred to other ions.
When a cation of less than 1.1 kg is used, ion exchange becomes difficult. For example, the ion radius (6-coordinate) is 1.02 Ｎａ for Na ⁺ ions, 0.76 Ｌｉ for Li ⁺ ions, and -0.24 Å for H ⁺ ions, and cannot be ion-exchanged. Na ⁺ ions, Li ⁺ ions, and H ⁺ ions are contained in ordinary layered clay minerals.

The cation 19 is preferably any one cation selected from the group of Rb ⁺ ions, K ⁺ ions, or Ba ²⁺ ions. The ionic radii (6-coordinate) are 1.52Ｒ for Rb ⁺ ions, 1.52Ｋ for K ⁺ ions and 1.35 Ｂ for Ba ²⁺ ions. Rank) is 1.1 mm or more.

FIG. 3 is a diagram showing an example of a normal layered clay mineral, and is a schematic diagram of a portion corresponding to part A of FIG. 1 of the layered clay mineral before intercalating Rb ⁺ .
Ordinary layered clay minerals have cations with a small ionic radius, such as interlayer Na ⁺ ions and Li ⁺ ions. Since each layer has the same electric charge, the interlayer distance is determined by the balance of the coulomb repulsive force between the layers by the balance of cation attractive forces such as Na ⁺ ions and Li ⁺ ions between the layers.
FIG. 4 is a schematic diagram showing a state in which Na ⁺ ions between layers of the layered clay mineral are hydrated to water molecules.
As shown in FIG. 4, when water molecules are close to Na ⁺ ions between clay mineral layers, the Gibbs energy of hydration of Na ⁺ ions is large, so water molecules are not adsorbed on the surface of the clay mineral layers, and Na Adsorbed with ⁺ ions, water molecules are intercalated between layers. In water, since many water molecules are attracted around the layered clay mineral particles, the water molecules overlap with each other around the Na ⁺ ions, and the clay mineral layers cannot be connected with Na ⁺ ions. As a result, the clay mineral layer 12 cannot maintain the upper and lower interlayer spacing in water, but is separated into a single layer, and the layers are separated.
FIG. 5 is a schematic diagram showing a state in which the layered clay mineral is separated into a large number of clay mineral layers in water. In a layered clay mineral having Rb ⁺ ions between layers, the Gibbs energy of Rb ⁺ ion hydration is smaller than that of Na ⁺ ions, so even if clay mineral particles are present in the water, the upper and lower layers can be separated. Water molecules do not enter between the layers, and the interlayer distance is kept as long as possible to exchange ions with Cs ⁺ ions.
The interlayer distance (d value) is based on Non-Patent Document 4.
The layer thickness of the clay mineral is based on Non-Patent Document 5.
Further, the hydration number of ions between clay mineral layers is based on Non-Patent Document 6.
The Gibbs energy of hydration is based on Non-Patent Document 7.

FIG. 6 is a view showing an example of the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention, and is a view in the case of having Rb ⁺ ions between layers. As shown in FIG. 4, since the ionic radius of Rb ⁺ ions is large, the interlayer distance determined by the Coulomb repulsive force is further increased.
The interlayer distance (d value) is based on the peak value of 10% relative humidity in Table 1 of the examples.

FIG. 7 is a diagram showing an example of the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention in an aqueous solution, and is a diagram in the case of having Rb ⁺ ions between layers. As shown in FIG. 5, water molecules (H ₂ O) enter between the Rb ⁺ ions between the layers and the SiO—OH layer 13b to form hydrogen bonds. This further increases the interlayer distance.
The interlayer distance (d value) is based on the peak value of 95% relative humidity in Table 1 of the examples.

FIG. 8 is a diagram showing an example in which Cs ⁺ ions are adsorbed by the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention in an aqueous solution.
When the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention is immersed in an aqueous solution in which Cs ⁺ ions are dispersed at a high concentration, Rb ⁺ ions have a smaller ion radius (six coordination) than Cs ⁺ ions. Therefore, Rb ⁺ ions are easily ion-exchanged to Cs ⁺ ions as shown in FIG. 8 due to the concentration gradient.
On the other hand, in the case of a normal layered clay mineral, since the interlayer distance is narrow and it is difficult for water molecules to penetrate, cations existing between the layers are hardly exchanged with Cs ⁺ ions.

Radioactive Cs ⁺ ion adsorbent 10 that has adsorbed the Cs ⁺ ions, Rb ⁺ ions, by immersing in an aqueous solution prepared by dispersing the ^{K +} ions or ^{Ba 2+} ion, Cs ⁺ ions Rb ⁺ ions, ^{K +} ions or Ba ^It is ion-exchanged with ²⁺ ions and is easily desorbed from the layered clay mineral. Thereby, it can utilize again as radioactive Cs ⁺ ion adsorption agent.

In the adsorption / desorption step, it is preferable to make the aqueous solution weakly acidic by controlling the pH of the aqueous solution. For example, Cs ⁺ ions are ^{H +} ions Rb ⁺ ions, and ^{K +} ions or ^{Ba 2+} ion and ion-exchange from the ^{H +} ions and the ion-exchange, Cs ⁺ ions and Rb ⁺ ions, ^{K +} ions or ^{Ba 2+} An ion exchange reaction with ions can be made efficient.

The desorbed aqueous solution contains a large amount of desorbed radioactive Cs ⁺ ions. By drying this aqueous solution, only the radioactive substance can be concentrated. Thereby, the volume of low level radioactive waste can be made much smaller than before.

The radioactive Cs ⁺ ion adsorbent is preferably a material having an X-ray diffraction peak value at 95% relative humidity of 3.85 ° or more and 8.46 ° or less.
Thus, by inserting water molecules between layers in an aqueous solution and hydrogen bonding with a cation, the bottom surface distance (d value) of the radioactive Cs ⁺ ion adsorbent can be made 15.46 mm or more, and by ion exchange, Radioactive Cs ⁺ ions having an ionic radius of about 1.8 Å can be easily inserted between the layers and can be easily taken out from the layers.

Thus, by inserting water molecules between layers in an aqueous solution and hydrogen bonding with a cation, the bottom surface distance (d value) of the radioactive Cs ⁺ ion adsorbent can be made 15.46 mm or more, and by ion exchange, Radioactive Cs ⁺ ions having an ionic radius of about 1.8 Å can be easily inserted between the layers and can be easily taken out from the layers.

<Method for producing radioactive Cs ⁺ ion adsorbent>
A method for producing a radioactive Cs ⁺ ion adsorbent according to an embodiment of the present invention is a layered clay mineral of smectites in an aqueous solution in which a cation having an ionic radius of 1.1 mm or more is dispersed at a concentration of 100 mmol / L or more. And then stirring the aqueous solution in which the layered clay mineral and the cation are dispersed.

FIG. 9 is a flowchart showing an example of a method for producing a radioactive Cs ⁺ ion adsorbent according to an embodiment of the present invention.

<1. Dispersion process>
First, an aqueous solution of a cation halide having a concentration of 100 mmol / L or more and an ionic radius of 1.1 mm or more is prepared. In order to reduce the influence of impurities, it is preferable to use ultrapure water.
Next, a layered clay mineral of smectites is dispersed in the aqueous solution. By using an aqueous solution having a concentration of 100 mM or more, some cations are intercalated between the layers of the layered clay mineral due to the concentration gradient.

<2. Stirring process>
Next, the aqueous solution in which the layered clay mineral is dispersed is stirred for a predetermined time. Stirring for 1 hour or more is preferable, and stirring for 3 hours or more is more preferable. Thereby, more cations can be intercalated between the layers of the layered clay mineral.

<3. Standing process>
Next, this aqueous solution is allowed to stand for a predetermined time. It is preferable to leave still for 1 day or more, and it is more preferable to leave still for 2 days or more. Thereby, more cations can be intercalated between the layers of the layered clay mineral.

<4. Container exchange process>
Next, the stationary aqueous solution is transferred into a centrifuge tube. When the steps 1 to 3 are performed using a centrifuge tube, this step is not performed.

<5. Centrifugation process>
Next, the centrifuge tube is set in a centrifuge, and the aqueous solution is centrifuged. The rotation speed is preferably 10,000 rpm or more, and more preferably 30000 rpm or more. Moreover, it is preferable to centrifuge for 1 minute or more, and it is more preferable to centrifuge for 30 minutes or more. Thereby, the solid phase which consists of the layered clay mineral which intercalated the cation between layers is isolate | separated from a liquid phase.
Note that the solid phase may be separated from the liquid phase by using a filtration step instead of the centrifugation step.

<6. Ultrasonic cleaning process>
Next, after removing the supernatant in the centrifuge tube, water is added.
Next, the tube for centrifugation is put into a beaker containing water, and ultrasonic waves are applied by an ultrasonic cleaner. It is preferable to apply ultrasonic waves for 1 minute or longer, and more preferable to apply ultrasonic waves for 60 minutes or longer.
Thereby, the impurity which exists in the interlayer or surface of a layered clay mineral can be removed from a layered clay mineral.

<7. Centrifugation process>
Next, the centrifuge tube is set in a centrifuge and centrifuged. The rotation speed is preferably 10,000 rpm or more, and more preferably 30000 rpm or more. Moreover, it is preferable to centrifuge for 1 minute or more, and it is more preferable to centrifuge for 30 minutes or more. Thereby, the solid phase which consists of the layered clay mineral which intercalated the cation between layers is isolate | separated from a liquid phase.
Note that the solid phase may be separated from the liquid phase by using a filtration step instead of the centrifugation step.

<8. Drying process>
Next, a centrifuge tube with a lid opened in the oven is placed and dried at a predetermined temperature to completely remove the liquid phase. Thereby, a lump solid substance can be obtained. The predetermined temperature is preferably 40 ° C. or higher, and more preferably 60 ° C. or higher.

<9. Grinding process>
Next, the solid is pulverized to obtain a radioactive cation adsorption / desorption agent powder according to an embodiment of the present invention. For example, lightly pulverize with an agate mortar.
It is preferable to obtain particles having a maximum diameter of 2 μm or less by pulverization. Thereby, a surface area can be raised and more radioactive Cs ⁺ ion adsorption agent can be adsorbed.

With the above manufacturing process, the radioactive Cs ⁺ ion adsorbent according to the embodiment of the present invention can be manufactured by intercalating cations between the layers of the layered clay mineral. Further, the radioactive Cs ⁺ ion adsorbent can be produced with high production efficiency. Furthermore, the purity of the radioactive Cs ⁺ ion adsorbent can be improved and the adsorption characteristics can be made more uniform.

The radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention includes a layered clay mineral 11 and a cation 19 intercalated between the layers of the layered clay mineral 11, and the layered clay mineral 11 is a smectite. Since the ionic radius of the cation 19 is 1.1 mm or more, a sufficient bottom surface distance (d value) can be secured in the aqueous solution, and radioactive Cs ⁺ ions can be easily adsorbed and radioactive Cs. ⁺ Ions can be easily desorbed. Thereby, it can be used as a radioactive Cs ⁺ ion adsorbent that can be used repeatedly, and the problem of generating a large amount of low-level radioactive waste can be solved.

The radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention has a configuration in which the layered clay mineral 11 is montmorillonite or beidellite, so that a sufficient bottom surface distance (d value) can be secured in the aqueous solution, and the radioactive Cs ⁺ Ions can be easily adsorbed and radioactive Cs ⁺ ions can be easily desorbed.

The radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention has a configuration in which the cation 19 is any one cation selected from the group of Rb ⁺ , K ^+, or Ba ^2+. A bottom surface distance (d value) can be secured, and radioactive Cs ⁺ ions can be easily adsorbed and radioactive Cs ⁺ ions can be easily desorbed.

Since the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention has a configuration in which the X-ray diffraction peak value at 95% relative humidity is 3.85 ° or more and 8.46 ° or less, a sufficient bottom surface separation ( d value) can be secured, and radioactive Cs ⁺ ions can be easily adsorbed and radioactive Cs ⁺ ions can be easily desorbed.

The method for producing the radioactive Cs ⁺ ion adsorbent 10 according to the embodiment of the present invention is a layered structure of smectites in an aqueous solution in which a cation 19 having an ion radius of 1.1 mm or more is dispersed at a concentration of 100 mmol / L or more. Since the clay mineral 11 is dispersed and then the aqueous solution in which the layered clay mineral 11 and the cation 19 are dispersed is stirred, a reusable radioactive Cs ⁺ ion adsorbent can be easily produced.

The radioactive Cs ⁺ ion adsorbent and the production method thereof according to the embodiment of the present invention are not limited to the above-described embodiment, and can be implemented with various modifications within the scope of the technical idea of the present invention. . Specific examples of this embodiment are shown in the following examples. However, the present invention is not limited to these examples.

Example 1
<1. Dispersion process>
As shown in FIG. 10A, first, 100 mmol / L of rubidium chloride was dissolved in 100 mL of ultrapure water to prepare a solution in which Rb ⁺ ions were dispersed.
Next, a clay mineral made of natural montmorillonite was dispersed in the solution.

<2. Stirring process>
Next, the solution in which the clay mineral was immersed was stirred for several hours using a stirrer. The rotor used was P70AT.

<3. Standing process>
Next, as shown in FIG.10 (b), it left still for 2 days.

<4. Container exchange process>
Next, the stationary solution was transferred to a centrifuge tube.

<5. Centrifugation process>
Next, as shown in FIG. 10 (c), the centrifuge tube was set in a centrifuge and centrifuged at 32000 rpm for 30 minutes. The centrifuge used was CP100α manufactured by Hitachi Koki.

<6. Ultrasonic cleaning process>
Next, after removing the supernatant in the centrifuge tube, water was added.
Next, the said tube for centrifugation was put in the beaker containing water, and the ultrasonic wave was applied for 1 hour with the ultrasonic cleaner.

<7. Centrifugation process>
Next, as shown in FIG. 10D, the centrifuge tube was set in a centrifuge and centrifuged at 32000 rpm for 30 minutes.

<8. Drying process>
Next, the centrifuge tube was placed in an oven, and the solution was dried at 60 ° C. to obtain a massive solid.

<9. Grinding process>
Next, the solid was lightly pulverized with an agate mortar to obtain a radioactive cation adsorption / desorption agent powder (Example 1 sample).

<X-ray diffraction analysis>
Next, an X-ray diffraction pattern of the sample powder was measured using CuK rays by a powder X-ray diffractometer capable of controlling the relative humidity and temperature in the sample chamber.
Specifically, the relative humidity was changed from 10% to 90% every 10% at a sample room temperature of 25 ° C., and further to 95%. After holding for 30 minutes at each relative humidity, the X-ray diffraction pattern of the sample was measured.
The results shown in Table 1 were obtained. The chemical composition of the sample of Example 1 was Rb _0.3 (Al _1.6 , Fe _0.2 , Mg _0.2 ) Si ₄ O ₁₀ (OH) ₂ .nH ₂ O.

FIG. 11 is a bottom surface distance d value (Å) of the 001 plane of the diffraction peak of the sample of Example 1 at each relative humidity. As a reference, the measurement results of montmorillonite alone are also shown.
With montmorillonite alone, the bottom face spacing changed greatly around 30% and around 90%. On the other hand, in the sample of Example 1, the bottom face interval changed greatly only in the vicinity of 90%. A large change in the bottom surface spacing indicates that the distance between the layers has increased.
In the case of montmorillonite alone, the bottom face spacing was about 18 mm at 95%, whereas in the sample of Example 1, it was about 16 mm.

<Radioactive Cs ⁺ Ion adsorption evaluation>
First, cesium hydroxide was dissolved in water to 5 mmol / L, and a cesium solution having a pH of 6.5 to 7 was prepared with 0.1 mol / L hydrochloric acid.
Next, as shown in FIG. 12A, 100 mg of the sample of Example 1 was dispersed in 5 mL of the cesium solution in a centrifuge tube and stirred for 2 hours with a rotary stirrer.
Next, as shown in FIG. 12 (b), the solid phase 1 and the supernatant were separated with a centrifuge.

Cs ⁺ ions in the supernatant were analyzed using a capillary electrophoresis apparatus 3DCE (HPCE: manufactured by HP (currently Agilent)) and a cation analysis kit (manufactured by Agilent).
A capillary electrophoresis apparatus (HPCE) is an apparatus that analyzes metal ions and organic substances. This is a device that detects a buffer solution in a tube having an inner diameter of 50 μm and applies a high voltage to move a sample in the tube and detect it by UV.

Next, as shown in FIG. 12 (c), 10 mL of water was added to the solid phase 1, dispersed using an ultrasonic cleaner, and then stirred for 2 hours using a rotary stirrer.
Next, as shown in FIG. 12 (d), the solid phase 2 and the supernatant were separated with a centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, as shown to Fig.13 (a), 10 mL of hydrochloric acid aqueous solution of pH 3.5 was added to the solid phase 2, and it disperse | distributed using the ultrasonic cleaner, and it stirred for 2 hours with the rotary stirrer.
Next, as shown in FIG.13 (b), it isolate | separated into the solid phase 3 and the supernatant liquid with the centrifuge.

Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, as shown in FIG.13 (c), 10 mL of water was added to the solid phase 3, and it disperse | distributed using the ultrasonic washing machine, Then, it stirred with the rotary stirring machine for 2 hours.
Next, as shown in FIG.13 (d), it isolate | separated into the solid-phase 4 and the supernatant liquid with the centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, the solid phase 4 was dried in an oven at 60 ° C.
Next, as shown to Fig.14 (a), 5 mL of cesium solutions were added to the solid phase 4, and it disperse | distributed using the ultrasonic washing machine, Then, it stirred with the rotary stirrer for 2 hours.
Next, as shown in FIG. 14 (b), the solid phase 5 and the supernatant were separated by a centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, as shown in FIG. 14 (c), an aqueous hydrochloric acid solution having a pH of 3.5 was added to the solid phase 4, dispersed using an ultrasonic cleaner, and then stirred with a rotary stirrer for 2 hours.
Next, as shown in FIG. 14 (d), the solid phase 5 and the supernatant were separated with a centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, as shown to Fig.15 (a), water was added to the solid-phase 5, and it disperse | distributed using the ultrasonic cleaning machine, Then, it stirred with the rotary stirrer for 2 hours.
Next, as shown in FIG. 15 (b), the solid phase 6 and the supernatant were separated with a centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPCE.

Next, the solid phase 6 was dried in an oven at 60 ° C.
Next, as shown in FIG.15 (c), 5 mL of cesium solutions were added to the solid-phase 6, and after dispersion | distribution using the ultrasonic cleaner, it stirred with the rotary stirrer for 2 hours.
Next, as shown in FIG. 15 (d), it was separated into the solid phase 7 and the supernatant with a centrifuge.
Cs ⁺ ions in the supernatant were analyzed in the same manner as described above using HPLE.
Table 2 shows the measurement results of Cs ⁺ ions in the supernatant obtained using HPCE.

In Table 2, “remaining adsorption amount” is a value obtained by dividing the cesium peak area of the supernatant liquid analyzed by HPCE by the peak area in% when analyzing the cesium solution before adsorption. When the numerical value is large, it means that there is a lot of cesium in the supernatant, and it means that cesium is not adsorbed so much by the adsorbent. Conversely, when the numerical value is small, it means that a large amount of cesium was adsorbed on the adsorbent.
“Elution amount (water)” is expressed in% of the peak area of cesium in the supernatant after washing with the peak area of cesium before adsorption.
“Elution volume (pH 3.5)” is obtained by adding the aqueous solution adjusted to pH 3.5 with hydrochloric acid and washing the adsorbent, and dividing the peak area of cesium in the supernatant by dividing the peak area of initial cesium before adsorption. It is a percentage display.
“Elution volume (washed)” is expressed as a percentage of the peak area of cesium in the supernatant liquid washed to remove hydrochloric acid from the adsorbent treated at pH 3.5 divided by the peak area of initial cesium before adsorption. is there.

“Adsorption remaining amount (second time)” is a result of cesium adsorption using the washed adsorbent, and the meaning of the numerical value is the same as the adsorption remaining amount.
“Re-eluting amount (pH 3.5)” and “re-eluting amount (washing with water)” have the same meaning as the above-described required amount (HCl) and the required amount (washing with water).
“Adsorption remaining amount (third time)” is a result of cesium adsorption using the washed adsorbent, and the meaning of the numerical value is the same as the adsorption remaining amount.
In the case of washing with water or pH 3.5 aqueous solution, since the added water or aqueous solution is 10 mL, the numbers are small. N. d. This is because the presence of a peak could be confirmed by HPCE analysis, but the area could not be obtained. Although the number of the remaining amount of adsorption is not very small, the adsorption removal is performed three times, and almost the same amount is removed.

In addition, after adsorption by Cs solution, evaluation of the method of adding hydrochloric acid aqueous solution of pH 3.5, without wash | cleaning the solid-phase adsorbent with water was also performed. Values almost the same as the measurement results shown in Table 1 were obtained. Moreover, the ultrapure water was used as the water used at the said process.

(Comparative Example 1)
The radioactive Cs ⁺ ion adsorption property was evaluated in the same manner as in Example 1 except that montmorillonite alone (Comparative Example 1 sample) was used instead of the Example 1 sample.
Table 3 shows the measurement results.

As can be seen by comparing Tables 2 and 3, in the embodiment 1 sample can be eluted after adsorption Cs ⁺ ions, it was also able to adsorb Cs ⁺ ions in the adsorption second and third.
On the other hand, in the montmorillonite simple substance (Comparative Example 1 sample), Cs ⁺ ions cannot be eluted after adsorption, and the amount of adsorption of Cs ⁺ ions gradually decreases in the second and third adsorption.

Radioactive Cs ⁺ ion adsorbent and its manufacturing method of the present invention is to readily adsorb radioactive Cs ⁺ ions, relates removable radioactive Cs ⁺ ion adsorbent and a manufacturing method thereof, the nuclear industry use Can easily capture radioactive Cs ⁺ ions discharged in the nuclear power industry and the radioactive waste processing industry.

DESCRIPTION OF SYMBOLS 10 ... Radioactive Cs ⁺ ion adsorption agent, 11 ... Layered clay mineral, 12 ... Clay mineral layer, 13a, 13b ... SiO-OH layer, 19 ... Cation.

Claims (4)

A layered clay mineral, and a cation intercalated between the layers of the layered clay mineral,
The layered clay mineral is montmorillonite or beidellite,
The cation is an Rb ⁺ ion;
A radioactive Cs ⁺ ion adsorbent characterized in that it can be used repeatedly. The radioactive Cs ⁺ ion adsorbent according to claim 1, wherein the layered clay mineral is montmorillonite. The radioactive Cs ⁺ ion adsorbent according to claim 1 or 2, wherein an X-ray diffraction peak value at 95% relative humidity is 3.85 ° or more and 8.46 ° or less. The montmorillonite or beidellite is dispersed in an aqueous solution in which Rb ⁺ ions are dispersed at a concentration of 100 mmol / L or more, and then the aqueous solution in which the montmorillonite or beidellite and the Rb ⁺ ions are dispersed is stirred. A method for producing a reusable radioactive Cs ⁺ ion adsorbent.