JP6673841B2 - Adsorbent - Google Patents

Description

  The present invention relates to an adsorbent containing crystalline silicotitanate that can be suitably used for selectively and efficiently separating and recovering cesium or strontium in seawater.

  2. Description of the Related Art Conventionally, co-precipitation treatment is known as a treatment technique for wastewater containing radioactive substances (see Patent Document 1 below). However, for water-soluble radioactive cesium and radioactive strontium, the above-mentioned coprecipitation treatment is not effective, and adsorption removal with an inorganic adsorbent such as zeolite is currently performed (see Patent Document 2 below).

  However, when radioactive cesium and radioactive strontium flow out into seawater, an increase in the sodium concentration of the seawater component acts to suppress the ion exchange reaction between cesium and the adsorbent (see Non-Patent Document 1 below). The problem is known.

One of the inorganic adsorbents that have been studied for the adsorbability of cesium and / or strontium is crystalline silicotitanate. As the crystalline silicotitanate, there are known a plurality of kinds of compositions such as a Ti / Si ratio of 1: 1, 5:12, and 2: 1. It is known that there is a crystalline silicotitanate having a ratio of 4: 3. According to Non-Patent Document 2, products 3B and 3C produced by hydrothermal treatment using an alkoxide of Ti (OET) ₄ as a Ti source and colloidal silica as a Si source have three-dimensional structures based on their X-ray diffraction patterns. That the crystalline silicotitanate of this structure ideally has a composition represented by M ₄ Ti ₄ Si ₃ O ₁₆ (M is Na, K, etc.) And named the crystalline silicotitanate of this structure Grace titanium silicate (GTS-1). Non-Patent Document 3 discloses that a crystalline silicotitanate having a Ti / Si ratio of 4: 3 is hydrothermally treated with a mixed solution containing titanium tetrachloride as a Ti source and highly dispersed SiO ₂ powder as a Si source. Is described as being produced. The document describes that the synthesized crystalline silicotitanate has strontium ion exchange ability.

JP-A-62-266499 JP 2013-57599 A

JAEA-Research 2011-037 ZEOLITES, 1990, Vol 10, November / December Keiko Fujiwara, "Modification and Evaluation of Microporous Crystal as Heat Pump Adsorbent", [online], [Search March 3, 2014], Internet <URL: http://kaken.nii.ac.jp/pdf /2011/seika/C-19/15501/21560846seika.pdf>

However, although it is reported that crystalline silicotitanate having a Ti / Si ratio of 4: 3 has strontium exchange ability as described above, further improvement in cesium adsorption performance is desired, and strontium is desired. Adsorption performance is also required.
Therefore, an object of the present invention is to provide an adsorbent containing crystalline silicotitanate which is effective for cesium adsorption and also for strontium adsorption in seawater.

The present inventor has conducted intensive studies in view of the above-mentioned circumstances, and as a result, a general formula in which the crystallite diameter and the half-width of the diffraction peak on the lattice plane (100 plane) are in a specific range; A ₄ Ti ₄ Si ₃ O ₁₆ .nH _The crystalline silicotitanate represented by ₂ O (where A represents one or two kinds of alkali metals selected from Na and K. In the formula, n represents 0 to 8), particularly, cesium and The inventors have found that the strontium adsorption ability is excellent, and have completed the present invention.

That is, the adsorbent provided by the present invention is a cesium and / or strontium adsorbent,
In crystallite size 60 Å or more, and the general formula the half-width of the diffraction peak is 0.9 ° or less in the lattice plane (100 _{plane); A 4 Ti 4 Si 3} O 16 · nH 2 O ( in the formula, A Represents one or two kinds of alkali metals selected from Na and K. In the formula, n represents 0 to 8), and is characterized by containing a crystalline silicotitanate represented by the following formula:

  ADVANTAGE OF THE INVENTION According to this invention, the crystalline silico titanate excellent in the adsorption removal characteristic of cesium and strontium also in seawater can be provided.

FIG. 1 is an X-ray diffraction chart of the adsorbent containing the crystalline silicotitanate obtained in Examples 1 to 3. FIG. 2 is an X-ray diffraction chart of the adsorbent containing the crystalline silicotitanate obtained in Comparative Example 1. FIG. 3 is an X-ray diffraction chart of the crystalline silicotitanate-containing adsorbent obtained in Example 4. FIG. 4 is an X-ray diffraction chart of the adsorbent containing the crystalline silicotitanate obtained in Example 5.

Hereinafter, the present invention will be described based on preferred embodiments.
The adsorbent according to the present invention is an adsorbent that adsorbs cesium and / or strontium. The crystalline silicotitanate contained in the adsorbent according to the present invention has a general formula: A ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O (where A is one or two alkali metals selected from Na and K) In the formula, n represents 0 to 8.)

Note that the crystallinity represented by the general formula: A ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O (where A represents an alkali metal of Na and K. In the formula, n represents 0 to 8). In silico titanate (hereinafter sometimes simply referred to as “crystalline silico titanate”), the detailed composition is not clear, but when A in the formula contains Na and K, a general formula: Na ₄ Ti Containing ₄ Si ₃ O ₁₆ .nH ₂ O and K ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O, or (Na _x K _(1-x) ) ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O (formula The present inventors speculate that x is more than 0 and less than 1).

The crystalline silicotitanate to be contained in the adsorbent according to the present invention is subjected to X-ray diffraction analysis using Cu-Kα radiation with the crystalline silicotitanate as a radiation source, and a diffraction peak of 2θ = 10 ° or more and 13 ° or less ( main peak (B1)) of crystallite size from the half width determined from the formula of Scherrer is 60 Å or more, preferably 60 to 250 Å, especially one of the features that it is preferably 80 to 230 Å.

  The adsorbent according to the present invention, in addition to having the above-mentioned features, has a characteristic that when the crystalline silicotitanate is subjected to X-ray diffraction measurement using Cu-Kα ray as a radiation source, 2θ = 10 ° of the crystalline silicotitanate is obtained. The half value width of the diffraction peak (main peak (B1)) of the lattice plane (100 plane) of 13 ° or less and 0.9 ° or less, preferably 0.3 to 0.9 °, particularly preferably 0.3 to 0 °. It is also one feature that the angle is 0.8 °.

In Non-Patent Document 3, titanium tetrachloride is used as a titanium source, and the silicic acid source and titanium tetrachloride have a crystallite diameter of 8 to 10 obtained by adding Ti / Si to the mixed solution in an amount of 0.32. A crystalline silicotitanate that is 13 nm is disclosed.
The present inventors have determined that the ability to adsorb cesium and / or strontium is based on the crystallites determined from the diffraction peak (main peak (B1)) of 2θ = 10 ° to 13 ° of the crystalline silicotitanate contained in the adsorbent. The diameter and the half width are related, and the crystallite diameter is in a specific range larger than that of the non-patent document, and the cesium adsorption ability is improved as compared with the non-patent document 3 by setting the half width to the above range. It has also been found that strontium has a high adsorbing ability.

Further, in the adsorption material of the present invention, crystalline Shirikochitaneto to be contained is in a content of potassium K ₂ O in terms of, 0 in a weight ratio to the _{A 2 O (K 2 O /} A 2 O) Ultra 40 Weight %, Preferably 5% by mass or more and 40% by mass or less from the viewpoint of further improving the cesium and / or strontium adsorption ability.

In the adsorbent according to the present invention, the crystalline silicotitanate may be used alone, but has the general formula: A ′ ₄ Ti ₉ O ₂₀ .mH ₂ O (where A ′ is selected from Na and K In the formula, m represents a number of 0 or more.) When used in combination with 9 titanates represented by the following formulas, the strontium adsorption performance can be further improved.

_{Incidentally, A '4 Ti 9 O 20} · mH 2 O ( wherein, A' is. In formula indicating one or two alkali metal selected from Na and K, m represents a number of 0 or more.) In the 9 titanate represented by (hereinafter sometimes simply referred to as “9 titanate”), the detailed composition is not clear, but when A in the formula contains Na and K, General formula; contains Na ₄ Ti ₉ O ₂₀ · mH ₂ O and K ₄ Ti ₉ O ₂₀ · mH ₂ O, or (Na _x K _(1-x) ) ₄ Ti ₉ O ₂₀ · mH ₂ O (formula The present inventors speculate that x is more than 0 and less than 1).

  In the adsorbent according to the present invention, the content of the 9 titanate is 2θ = 8 to 10 derived from 9 titanate when the adsorbent is measured using Cu-Kα radiation as an X-ray source. 5 to 40%, preferably 5 to 30%, in a height ratio (A1 / B1) between the main peak (A1) at 2 ° and the main peak (B1) at 2θ = 10 to 13 ° of the crystalline silicotitanate. Is preferred from the viewpoint that strontium adsorption performance can be improved while maintaining high cesium adsorption capability.

  Further, in the adsorbent of the present invention, the molar ratio of the 9 titanate to the crystalline silicotitanate obtained by composition analysis (the former: the latter) is preferably 1: 0.25 to 0.45, The ratio is more preferably 1: 0.30 to 0.40, and even more preferably 1: 0.35 to 0.38.

<How to determine the molar ratio of crystalline silico titanate: 9 titanate>
(A) The sample for measurement is obtained by placing the adsorbent in an appropriate container (such as an aluminum ring), sandwiching the adsorbent with a die, and applying a pressure of 10 MPa with a press machine to form pellets. An X-ray fluorescence apparatus (apparatus name: ZSX100e, bulb: Rh (4 kW), atmosphere: vacuum, analysis window: Be (30 μm), measurement mode: SQX analysis (EZ scan), measurement diameter: 30 mmφ, ) All elements are measured by Rigaku). The content (% by mass) of SiO ₂ and TiO ₂ in the adsorbent is calculated by the SQX method which is a semi-quantitative analysis method.
(B) the obtained content of SiO ₂ and TiO ₂ (mass%) divided by the respective molecular weight, obtaining the number of moles of SiO ₂ and TiO ₂ in the adsorbent 100 g.
(C) One-third of the number of moles of SiO _{2 in} the adsorbent obtained as described above is used as the crystalline silicon titanate (Na ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O, (Na _x K _{( 1-x)} ) The number of moles is assumed to be at least one selected from ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O and K ₄ Ti ₄ Si ₃ O ₁₆ .nH ₂ O). Further, since the number of moles of Ti atoms in 1 mole of the crystalline silicotitanate is 4, the number of moles of the titanate in the adsorbent is determined by the following formula (1).
(D) The above ratio is obtained from the number of moles of the obtained crystalline silicotitanate and the number of moles of the titanate.

The adsorbent of the present invention, for example,
A first step of mixing a silicic acid source, a sodium compound and / or a potassium compound, titanium tetrachloride, and water to obtain a mixed gel, and a second step of hydrothermally reacting the mixed gel obtained in the first step. A silica source and titanium tetrachloride in the first step so that the molar ratio between Ti and Si contained in the mixed gel is Ti / Si = 0.5 or more and 3.0 or less. Can be produced by adding

  According to the method for producing an adsorbent, an adsorbent containing only crystalline silicotitanate and an adsorbent containing both crystalline silicotitanate and 9 titanate can be produced.

Hereinafter, the method for producing the adsorbent of the present invention will be described.
Examples of the silicic acid source according to the first step include sodium silicate. Further, active silicic acid obtained by cation exchange of alkali silicate (that is, alkali metal salt of silicic acid) is also included.

  The activated silicic acid is obtained by cation exchange by bringing an aqueous solution of an alkali silicate into contact with, for example, a cation exchange resin. As a raw material of the alkali silicate aqueous solution, a sodium silicate aqueous solution usually called water glass (water glass No. 1 to 4 or the like) is preferably used. It is relatively inexpensive and can be easily obtained. For semiconductor applications that dislike Na ions, an aqueous solution of potassium silicate is suitable as a raw material. There is also a method of dissolving a solid alkali metasilicate in water to prepare an alkali silicate aqueous solution. Alkali metasilicate is produced through a crystallization process, and therefore has some impurities. The aqueous alkali silicate solution is used by diluting with water as necessary.

  The cation exchange resin used when preparing the active silicic acid can be appropriately selected from known ones, and is not particularly limited. In the contacting step between the aqueous alkali silicate solution and the cation exchange resin, for example, the aqueous alkali silicate solution is diluted with water so that the concentration of silica is 3% by mass or more and 10% by mass or less. The substrate is contacted with a strongly acidic or weakly acidic cation exchange resin to remove alkali. Further, if necessary, it can be deionized by contacting with an OH type strongly basic anion exchange resin. Through this step, an active silicic acid aqueous solution is prepared. Various proposals have already been made on the details of the contact conditions between the aqueous alkali silicate solution and the cation exchange resin, and any known contact conditions can be employed in the present invention.

  Examples of the sodium compound used in the first step include sodium hydroxide, sodium carbonate and the like. When sodium carbonate is used among these sodium compounds, carbon dioxide gas is generated. Therefore, it is preferable to use sodium hydroxide which does not generate such a gas from the viewpoint of facilitating the neutralization reaction.

  Examples of the potassium compound include potassium hydroxide and potassium carbonate. When potassium carbonate is used among these potassium compounds, carbon dioxide gas is generated. Therefore, it is preferable to use potassium hydroxide which does not generate such a gas from the viewpoint of facilitating the neutralization reaction.

  When a sodium compound and a potassium compound are used in the first step, the ratio of the number of moles of the potassium compound to the total number of moles of the sodium compound and the potassium compound is preferably more than 0% and 50% or less, preferably 5% or more. More preferably, it is 30% or less.

  The addition amount of the silicic acid source and titanium tetrachloride is such that Ti / Si, which is a molar ratio of Ti derived from titanium tetrachloride and Si derived from the silicic acid source, in the mixed gel has a specific ratio. For example, in Non-Patent Document 3, titanium tetrachloride is used as the titanium source, but the silicic acid source and titanium tetrachloride are added to the mixed solution in such an amount that the Ti / Si ratio becomes 0.32. On the other hand, in the present production method, the silicic acid source and titanium tetrachloride are added in such amounts that the Ti / Si ratio becomes 0.5 or more and 3.0 or less. As a result of investigations by the present inventors, by setting the Ti / Si ratio in the mixed gel to the above molar ratio range, as a crystalline silico titanate, the crystallinity is high, and the crystallite diameter and half width are in the above ranges. Is easier to obtain. Further, the Ti / Si ratio in the mixed gel is preferably 1.0 or more and 3.0 or less.

  When obtaining an adsorbent containing only crystalline silicotitanate, the molar ratio of Ti / Si is 1.2 or more and 1.5 or less, and an adsorbent containing crystalline silicotitanate and 9 titanate is used. When it is obtained, the molar ratio of Ti / Si is preferably 1.8 or more and 2.2 or less.

Further, the total amount of the SiO ₂ -converted silicic acid source concentration and the TiO ₂ -converted titanium tetrachloride concentration in the mixed gel is from 2.0% by mass to 40% by mass, and A ₂ O / SiO _{2 in the} mixed gel. It is desirable to add the silicic acid source and titanium tetrachloride so that the molar ratio of the mixture becomes 0.5 or more and 3.0 or less. Here, A represents Na and K. By adjusting the addition amount of the silicic acid source and titanium tetrachloride within the above range, the yield of the target crystalline silicotitanate can be increased to a satisfactory level.

When an adsorbent containing only crystalline silicotitanate is obtained, the adsorbent containing crystalline silicotitanate and 9 titanate in a molar ratio of A ₂ O / SiO ₂ = 0.5 or more and 2.5 or less is used. When it is obtained, it is desirable to add a silicic acid source and titanium tetrachloride so as to be 1.0 or more and 1.8 or less.

  The titanium tetrachloride used in the first step can be used without any particular limitation as long as it is industrially available.

  In the first step, the silicic acid source, the sodium compound, the potassium compound, and the titanium tetrachloride can each be added to the reaction system in the form of an aqueous solution. In some cases, it can be added in solid form. Further, in the first step, the concentration of the obtained mixed gel can be adjusted using pure water, if necessary, with respect to the obtained mixed gel.

  In the first step, the silicic acid source, the sodium compound, the potassium compound, and the titanium tetrachloride can be added in various addition orders. For example, (1) a mixed gel can be obtained by adding titanium tetrachloride to a mixture of a silicic acid source, a sodium compound and / or a potassium compound, and water. "It may be referred to as" (1) implementation. ") Implementation of this (1) is preferable in that generation of chlorine from titanium tetrachloride is suppressed.

  As another order of addition in the first step, (2) an aqueous solution of active silicic acid (hereinafter, sometimes simply referred to as “active silicic acid”) obtained by cation exchange of alkali silicate, titanium tetrachloride, water and , A sodium compound and / or a potassium compound may be added to the mixture. Even if this addition order is adopted, a mixed gel can be obtained in the same manner as in the embodiment (1) (this addition order may be simply referred to as “(2) execution” hereinafter). Titanium tetrachloride can be added in the form of its aqueous solution or in the form of a solid. Similarly, sodium and potassium compounds can be added in the form of their aqueous solutions or in solid form.

In the implementation of (1) and (2), the sodium compound and / or potassium compound have a total concentration of sodium and potassium (A ₂ O concentration) in the mixed gel of not less than 0.5% by mass in terms of Na ₂ O. It is preferably added so as to be 0% by mass or less, particularly 0.7% by mass or more and 13% by mass or less. The concentration of the terms of Na ₂ O of the total of sodium and potassium in the mixed terms of Na ₂ O by weight, and mixed gels total of sodium and potassium in the gel (hereinafter "the total concentration of sodium and potassium," an (potassium compound in the first step If not used, referred to as "sodium concentration") is calculated by the following formula:

The total mass of sodium and potassium in the mixed gel in terms of Na ₂ O (g) = (the number of moles of A—the number of moles of chloride ions derived from titanium tetrachloride) × 0.5 × Na ₂ O molecular weight

Concentration (mass%) of the total of sodium and potassium in the mixed gel in terms of Na ₂ O = (the total mass of sodium and potassium in the mixed gel in terms of Na ₂ O / (the amount of water in the mixed gel + the amount in the mixed gel) The total mass of sodium and potassium in terms of Na ₂ O)) × 100

By combining the selection of the silicic acid source and the adjustment of the total concentration of sodium and potassium in the mixed gel, the production of crystalline silicotitanate other than the crystalline silicotitanate having a molar ratio of Ti: Si of 4: 3 is suppressed. Can be. When sodium silicate or potassium silicate is used as the silicic acid source, by setting the total concentration of sodium and potassium in the mixed gel to 2.0% by mass or more in terms of Na ₂ O, the molar ratio of Ti: Si is increased. The formation of 5:12 crystalline silicotitanate can be effectively suppressed. On the other hand, by setting the total concentration of sodium and potassium in the mixed gel to 6.0% by mass or less in terms of Na ₂ O, It is possible to effectively suppress the generation of crystalline silicotitanate having a molar ratio of Ti: Si of 1: 1. When an active silicic acid obtained by cation exchange of an alkali silicate is used as a silicic acid source, the molar ratio of Ti: Si is adjusted to 1.0% by mass or more in terms of Na ₂ O so that the molar ratio of Ti: Si is 5: 5. 12, the formation of crystalline silicotitanate can be effectively suppressed. On the other hand, by setting the total concentration of sodium and potassium in the mixed gel to 6.0% by mass or less in terms of Na ₂ O, Ti: It is possible to effectively suppress the production of crystalline silicon titanate having a molar ratio of Si of 1: 1.

When sodium silicate is used as the silicate source, the sodium component in the sodium silicate simultaneously serves as the sodium source in the mixed gel. Therefore, the “mass (g) of sodium in the mixed gel in terms of Na ₂ O” is counted as the sum of all sodium components in the mixed gel. Similarly, the “mass (g) of potassium in the mixed gel in terms of Na ₂ O” is also counted as the sum of all potassium components in the mixed gel.

  In the implementation of (1) and (2), the addition of titanium tetrachloride is preferably performed stepwise or continuously as an aqueous solution of titanium tetrachloride over a certain period of time in order to obtain a uniform gel. Therefore, a peristaltic pump or the like can be suitably used for the addition of titanium tetrachloride.

  The mixed gel obtained in the first step may be aged at 10 ° C. or more and 100 ° C. or less over a period of 0.1 hour or more and 5 hours or less before performing a hydrothermal reaction as a second step described below. This is preferable in that a uniform product is obtained. The aging step may be performed, for example, in a stationary state, or may be performed in a stirring state using a line mixer or the like.

  In the present invention, the mixed gel obtained in the first step is subjected to a hydrothermal reaction in the second step to obtain crystalline silicotitanate. The hydrothermal reaction is not particularly limited as long as it can synthesize crystalline silicotitanate. Usually, in an autoclave, preferably at a temperature of 120 ° C. to 200 ° C., more preferably 140 ° C. to 180 ° C., for 6 hours to 110 hours, more preferably 12 hours to 100 hours. React under pressure. The reaction time can be selected according to the scale of the synthesizer.

  The hydrous substance containing the crystalline silicotitanate obtained in the second step can be dried, and the obtained dried substance can be pulverized or pulverized, if necessary, to obtain a powder (including granules). Further, a hydrate containing crystalline silicotitanate may be extruded from an aperture member having a plurality of apertures to obtain a rod-shaped molded body, and the obtained rod-shaped molded body may be dried to have a columnar shape. Then, the dried rod-shaped compact may be formed into a spherical shape, or may be crushed or pulverized into a particulate shape.

  Examples of the shape of the hole formed in the aperture member include a circle, a triangle, a polygon, and a ring. The diameter of the opening is preferably from 0.1 mm to 10 mm, more preferably from 0.3 mm to 5 mm. The true circle-equivalent diameter here is the diameter of a circle calculated from the area of one hole when the area of the hole is a circle area. The drying temperature after the extrusion molding can be, for example, 50 ° C. or more and 200 ° C. or less. In addition, the drying time can be 1 hour or more and 120 hours or less.

  The dried rod-shaped compact can be used as it is as an adsorbent, or may be loosened lightly before use. The dried bar-shaped body may be used after being pulverized. It is preferable that the powdery material containing crystalline silicotitanate obtained by these various methods is further classified and then used as an adsorbent from the viewpoint of increasing the adsorption efficiency of cesium and / or strontium. For the classification, for example, it is preferable to use a first sieve having a nominal opening of 1000 μm or less, particularly 710 μm or less, as defined in JISZ8801-1. It is also preferable to use a second sieve having a nominal opening of 100 μm or more, particularly 300 μm or more. Further, it is preferable to carry out using these first and second sieves.

According to the above-mentioned production method, an industrial advantage that not only crystalline silicotitanate but also an adsorbent containing crystalline silicotitanate and 9 titanate can be produced at once by simply selecting reaction conditions is also provided. Have.
In the case of the adsorbent containing the crystalline silicotitanate and 9 titanate according to the present invention, a single-phase crystalline silicotitanate is produced by X-ray diffraction by the above-mentioned production method, and is separately sold or known. It goes without saying that the 9 titanate produced by the production method may be mixed later.

  The adsorbent characterized by containing the crystalline silicotitanate according to the present invention is molded and processed according to a conventional method if necessary, and the molded body obtained thereby is used as an adsorbent for cesium and / or strontium. Is also good.

  As the molding process, for example, a granulation process for molding a powdery adsorbent containing crystalline silicotitanate into granules or a slurry of a powdery adsorbent containing crystalline silicotitanate into calcium chloride A method of encapsulating a powdery adsorbent containing crystalline silicotitanate by dropping it into a liquid containing a curing agent such as, and attaching a powdery adsorbent containing crystalline silicotitanate to the surface of a resin core material A method of coating, a method of attaching a powdery adsorbent containing crystalline silicotitanate to the surface and / or inside of a sheet-like substrate formed of natural fibers or synthetic fibers, fixing the sheet-like material, and forming the sheet-like material. Can be mentioned. As a method of the granulation, known methods can be mentioned, for example, stirring and mixing granulation, tumbling granulation, extrusion granulation, crushing granulation, fluidized bed granulation, spray drying granulation (spray drying), compression molding. And the like. In the process of granulation, a binder or a solvent may be added and mixed as needed. Known binders include, for example, polyvinyl alcohol, polyethylene oxide, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, starch, corn starch, molasses, lactose, gelatin. Dextrin, gum arabic, alginic acid, polyacrylic acid, glycerin, polyethylene glycol, polyvinylpyrrolidone and the like. Various solvents such as an aqueous solvent and an organic solvent can be used as the solvent.

  In addition, a granulated product obtained by granulating a water-containing material containing crystalline silicotitanate is suitably used as an adsorbent for a water treatment system having an adsorption vessel and an adsorption tower filled with a radioactive substance adsorbent. You can do it.

  In this case, the shape and size of the granular product obtained by granulating the water-containing product containing crystalline silicotitanate may be filled in an adsorption vessel or a packed tower and treated with cesium and / or strontium. It is preferable to appropriately adjust the shape and size so as to adapt to the passage of water.

  In addition, the granular material obtained by granulating a water-containing material containing crystalline silicotitanate is further adsorbed by magnetic separation from water containing cesium and / or strontium by further containing magnetic particles. Can be used as Examples of the magnetic particles include metals such as iron, nickel, and cobalt, or powders of magnetic alloys containing these as main components, metal oxides such as iron tetroxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite, and strontium ferrite. Powder of a magnetic material.

  As a method of incorporating magnetic particles into granules obtained by granulating a water-containing material containing crystalline silicotitanate, for example, the above-described granulation operation may be performed in a state where the magnetic particles are contained. .

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” represents “% by mass”. The evaluation devices and materials used in the examples and comparative examples are as follows.

<Evaluation device>
X-ray diffraction: Bruker D8 AdvanceS was used. Cu-Kα was used as a radiation source. The measurement conditions were a tube voltage of 40 kV, a tube current of 40 mA, and a scanning speed of 0.1 ° / sec.
ICP-AES: Varian 720-ES was used. The adsorption test of Cs and Sr was performed with the measurement wavelength of Cs being 697.327 nm and the measurement wavelength of Sr being 216.596 nm. As standard samples, aqueous solutions of Cs containing 100%, 50 ppm and 10 ppm of Cs containing 0.3% of NaCl, and aqueous solutions of 100 ppm, 10 ppm and 1 ppm of Sr containing 0.3% of NaCl were used.

<Material used>
Potassium silicate: manufactured by Nippon Chemical Industrial Co., Ltd. _{(SiO 2: 26.5%, K} 2 O: 13.5%, H 2 O: 60.00%, SiO 2 / K 2 O = 3.09).
Sodium silicate: manufactured by Nippon Chemical Industrial Co., Ltd. _{(SiO 2: 28.96%, Na} 2 O: 9.37%, H 2 O: 61.67%, SiO 2 / Na 2 O = 3.1).
・ Silica sol: manufactured by Nippon Chemical Industry Co., Ltd. (SiO ₂ : 30%, particle size 15 nm)
・ Caustic potash: Solid reagent Potassium hydroxide (KOH: 85%)
· Sodium hydroxide aqueous solution: 25% sodium hydroxide for industrial _{(NaOH: 25%, H 2} O: 75%)
-Titanium tetrachloride aqueous solution: 36.48% aqueous solution manufactured by Osaka Titanium Technologies Inc.-Titanium dioxide: Ishihara Sangyo ST-01
Simulated seawater: Simulated seawater was a 0.3% NaCl aqueous solution containing 100 ppm of Cs and 100 ppm of Sr, respectively. Simulated seawater NaCl (99.5%): 3.0151g, SrCl · 6H 2 O (99%): 0.3074g, CsNO 3 (99%): 0.1481g, H 2 O: 996.5294g mixed I got it.

[Examples 1 to 3]
<Synthesis of crystalline silico titanate>
(1) First step Using sodium silicate, 25% caustic soda, 85% caustic potash and pure water, mixing was carried out in the amounts shown in Table 1, followed by stirring to obtain a mixed aqueous solution. To this mixed aqueous solution, the titanium tetrachloride aqueous solution in the amount shown in Table 1 was continuously added over 0.5 hour by a peristaltic pump to produce a mixed gel. The mixed gel was aged at room temperature (25 ° C.) for 1 hour after the addition of the aqueous solution of titanium tetrachloride.

(2) Second Step The mixed gel obtained in the first step was put into an autoclave, and the temperature was raised to the temperature shown in Table 1 over 1 hour. Then, the reaction was carried out with stirring while maintaining this temperature. The slurry after the reaction was filtered, washed and dried to obtain massive crystalline silicotitanate.

The composition determined from the X-ray diffraction structure of the obtained crystalline silicotitanate is shown in Table 2 below. Further, the crystalline silicotitanate was subjected to elemental analysis by ICP, and the Na amount was expressed in terms of Na ₂ O. The results are also shown in Table 2. Further, X-ray diffraction charts of the crystalline silicotitanate obtained in Examples 1 to 3 are shown in the figure.
The half-width and the crystallite diameter of the crystalline silicotitanate samples obtained in Examples 1 to 3 were determined as described below, and the results are shown in Table 3.
The half-value width was obtained by X-ray diffraction measurement using Cu-Kα radiation as a radiation source, and the value of the main peak (B1) at 2θ = 10 ° to 13 ° on the lattice plane (100 plane) was determined.
The crystallite diameter was determined from Scherrer's equation based on the value obtained by determining the half width of the diffraction peak.

[Comparative Example 1]
An aqueous solution of NaOH was added to the silica sol in the amount shown in Table 1 and stirred, and then an aqueous solution of titanium tetrachloride was added and stirred at 25 ° C. for 40 minutes to prepare a mixed gel. Next, the obtained mixed gel was placed in an autoclave, and the temperature was raised to the temperature shown in Table 1 over 1 hour. Then, the reaction was carried out at 170 ° C. for 48 hours with stirring while maintaining this temperature. The slurry after the reaction was filtered, washed and dried to obtain massive crystalline silicotitanate. FIG. 2 shows an X-ray diffraction chart of the obtained crystalline silicotitanate. The composition determined from the X-ray diffraction structure is shown in Table 2 below. Further, the half width and the crystallite diameter were measured in the same manner as in Examples 1 to 3, and the results are shown in Table 3.

Example 4
(1) First step 90 g of sodium silicate No. 3, 667 and 49 g of aqueous sodium hydroxide solution and 84.38 g of pure water were mixed and stirred to obtain a mixed aqueous solution. To this mixed aqueous solution, 443.90 g of an aqueous titanium tetrachloride solution was continuously added over 1 hour and 20 minutes using a peristaltic pump to produce a mixed gel. The mixed gel was aged at room temperature for 1 hour after the addition of the aqueous solution of titanium tetrachloride. At this time, the molar ratio between Ti and Si in the mixed gel was Ti: Si = 2: 1. The concentration of SiO _{2 in} the mixed gel was 2%, the concentration of TiO ₂ was 5.3%, and the sodium concentration in terms of Na ₂ O was 3.22%.
(2) Second step The mixed gel obtained in the first step was put into an autoclave, and the temperature was raised to 170 ° C over 1 hour, and the reaction was carried out for 24 hours with stirring while maintaining this temperature. The slurry after the reaction was filtered, washed and dried to obtain an adsorbent. The composition of the resulting adsorbent determined from the X-ray diffraction structure is shown in Table 4 below. FIG. 3 shows an X-ray diffraction chart of the obtained adsorbent.
In X-ray diffraction chart in the range of 2 [Theta] = 10 to 13 °, with the main peak of the crystalline Shirikochitaneto (B1) (from _{Na 4 Ti 4 Si 3 O 16} · 6H 2 O) is detected, 2 [Theta] = 8-10 main peaks of sodium titanate is ° to 9 titanate (A1) (from _{Na 4 Ti 9 O 20 · 5~7H} 2 O) were detected.
The ratio of the height of the main peak of sodium titanate to the height of the main peak of crystalline silicotitanate was determined. The molar ratio between crystalline silicotitanate and sodium titanate was determined by the method described above. Further, the half width and the crystallite diameter were determined in the same manner as in Examples 1 to 3.

Example 5
(1) First Step No. 3 120 g of sodium silicate, 674 g of aqueous sodium hydroxide solution, 103 g of potassium hydroxide and 247.4 g of pure water were mixed and stirred to obtain a mixed aqueous solution. To this mixed aqueous solution, 610 g of an aqueous titanium tetrachloride solution was continuously added over 1 hour by a peristaltic pump to produce a mixed gel. The mixed gel was aged at room temperature for 1 hour after the addition of the aqueous solution of titanium tetrachloride. At this time, the molar ratio between Ti and Si in the mixed gel was Ti: Si = 2: 1. The concentration of SiO _{2 in} the mixed gel was 2.8%, the concentration of TiO ₂ was 7.4%, and the total concentration of sodium and potassium in terms of Na ₂ O was 3.5%.
(2) Second Step The mixed gel obtained in the first step was placed in an autoclave, and after raising the temperature to 140 ° C. over 3 hours, the reaction was carried out for 72 hours with stirring while maintaining this temperature. The slurry after the reaction was filtered, washed and dried to obtain an adsorbent. The composition of the obtained adsorbent determined from the X-ray diffraction structure is shown in Table 5 below. FIG. 4 shows an X-ray diffraction chart of the obtained adsorbent.
In X-ray diffraction chart in the range of 2 [Theta] = 10 to 13 °, with the main peak of the crystalline Shirikochitaneto (B1.) (From _{Na 4 Ti 4 Si 3 O 16} · 6H 2 O) is detected, 2 [Theta] = 8 to 10 main peaks of sodium titanate is ° to 9 titanate (A1) (from _{Na 4 Ti 9 O 20 · 5~7H} 2 O) were detected.
The ratio of the height of the main peak of sodium titanate to the height of the main peak of crystalline silicotitanate was determined. The molar ratio between crystalline silicotitanate and sodium titanate was determined by the method described above. Further, the half width and the crystallite diameter were determined in the same manner as in Examples 1 to 3.

<Adsorption test of Cs and Sr>
The obtained massive adsorbent was pulverized with a mortar and classified with a sieve of 600 μm and 300 μm into granules (300 to 600 μm). 0.5 g of this granular adsorbent was placed in a 100-ml plastic container, 100.00 g of simulated seawater was added, the contents were closed, and the contents were shaken. The contents were shaken by inverting the plastic container 10 times (the same applies hereinafter). Then, after 1 hour passed by standing still, the contents were shaken again, about 50 ml was filtered through 5C filter paper, and the filtrate obtained by filtration was collected. The remaining 50 ml was left as it was and shaken again after 23 hours (24 hours after the initial shaking). Then, the mixture was filtered with a 5C filter paper, and the filtrate obtained by the filtration was collected. Using the collected filtrate as a target, the contents of Cs and Sr in the filtrate were measured using ICP-AES. The results are shown in Table 6 below.

Claims (6)

A cesium and / or strontium adsorbent,
A general formula having a crystallite diameter of 60 ° or more and a half-width of a diffraction peak on a lattice plane (100 plane) of 0.9 ° or less; A ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (where A is in. formula exhibit more of an alkali metal Na and K, n is represented by showing a 0-8.), with potassium content of _{K 2} O in terms of the weight ratio _{a 2 O (K 2 O /} a adsorbent, characterized in that it contains the _{2 O)} in 5 wt% to 40 wt% or less der Ru crystalline Shirikochitaneto.   The adsorbent according to claim 1, wherein the crystalline silico titanate has a crystallite diameter of 60 to 250 °.   3. The adsorbent according to claim 1, wherein the crystalline silicotitanate has a half-width of a diffraction peak on a lattice plane (100 plane) of 0.3 to 0.9 °. 4. Further, a general formula: A ′ ₄ Ti ₉ O ₂₀ · mH ₂ O (where A ′ represents one or two kinds of alkali metals selected from Na and K. In the formula, m is a number of 0 or more. The adsorbent according to any one of claims 1 to 3 , further comprising a 9 titanate represented by the following formula: When the adsorbent was measured using Cu-Kα radiation as an X-ray source, the main peak (A1) of 2θ = 8 to 10 ° derived from 9 titanate and the 2θ = 10 of crystalline silicotitanate were obtained. The adsorbent according to claim 4, wherein the height ratio (A1 / B1) of the 13 ° main peak (B1) is 5 to 40%. By mixing a silicic acid source, a sodium compound, a potassium compound, titanium tetrachloride and water, a mixed gel having a Ti / Si molar ratio of Ti / Si = 0.5 or more and 3.0 or less was obtained. method for producing the adsorbent according to any one of claims 1 to 5 mixed gel, characterized in that to with the hydrothermal reaction.