JP6812415B2 - Metal ion adsorbent - Google Patents

Description

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

Conventionally, coprecipitation treatment is known as a treatment technique for wastewater containing radioactive substances (see Patent Document 1 below). However, the coprecipitation treatment is not effective for water-soluble radioactive cesium and radioactive strontium, and adsorption and removal with an inorganic adsorbent such as zeolite is currently being carried out (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.

Crystalline silicotitanate is one of the inorganic adsorbents that have been studied for the adsorptivity of cesium and / or strontium. Crystalline silicon titanates are known to have a plurality of types of compositions such as those having a Ti / Si ratio of 1: 1 and those having a Ti / Si ratio of 5:12 and 2: 1. It is known that there is a crystalline silicon titanate with a ratio of 4: 3. In Non-Patent Document 2, the products 3B and 3C produced by hydrothermal treatment using an alkoxide called Ti (OET) ₄ as a Ti source and colloidal silica as a Si source are three-dimensional from the X-ray diffraction pattern. It has a typical 8-membered ring structure, and the crystalline silicon silicate having 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 silicon silicate of this structure Grace titanium silica (GTS-1). Further, Non-Patent Document 3 describes hydrothermal treatment of a mixed solution containing crystalline silicon titanate having a Ti / Si ratio of 4: 3, titanium tetrachloride as a Ti source, and highly dispersed SiO ₂ powder as a Si source. It is stated that it was manufactured by applying. The document describes that the synthesized crystalline silicotitanate has a strontium ion exchange ability.
Further, the present inventors first obtain a mixed gel by adding a silicic acid source, a sodium compound and / or a potassium compound, titanium tetrachloride, and water in Patent Document 3 below. By hydrothermally reacting the resulting mixed gel, we proposed an adsorbent useful for adsorbing and removing cesium and strontium from seawater containing crystalline silicotitanate having a Ti / Si molar ratio of 4/3.

Japanese Unexamined Patent Publication No. 62-266499 Japanese Unexamined Patent Publication No. 2013-57599 JP 2015-188782

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

In Patent Document 3, a silicic acid source, a sodium compound and / or a potassium compound, titanium tetrachloride, and water are added to obtain a mixed gel, and then the obtained mixed gel is subjected to a hydrothermal reaction. A mixture of crystalline silicotitanate and titanate having a Ti / Si molar ratio of 4/3 is produced at once, and this is used as an adsorbent. Therefore, there is a problem that it is difficult to control the mixing ratio of crystalline silicotitanate and titanate.
Further, when crystalline silicon titanate having a Ti / Si ratio of 4: 3 is used alone, the adsorption ability of strontium is particularly inferior, and further improvement of the adsorption performance of strontium is required.

Therefore, an object of the present invention is to provide an adsorbent made of crystalline silicotitanate having a Ti / Si ratio of 4: 3, which is effective for adsorbing metal ions, particularly cesium even in seawater, and further adsorbing strontium. To do.

The present inventor has conducted extensive research in view of the above circumstances, the X-ray diffraction analysis, the general formula half width and a BET specific surface area of 2 [Theta] = 10 ° or 13 ° or less of the main peak is in a specific range; A ₄ The crystalline silicotitanate represented by Ti ₄ Si ₃ O ₁₆ · nH ₂ O (in the formula, A represents an alkali metal selected from Na and K; in the formula, n represents 0 to 8) is In particular, they have found that the adsorption ability of cesium and strontium is excellent, and have completed the present invention.

That is, the adsorbent to be provided by the present invention is a metal ion adsorbent, and in X-ray diffraction analysis, the half width of the main peak of 2θ = 10 ° or more and 13 ° or less is 1.0 ° or less. There is a general formula in which the BET specific surface area is 100 m ² / g or more; A ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (in the formula, A represents an alkali metal selected from Na and K. In the formula, n. Indicates 0 to 8), which is characterized by being composed of crystalline silicotitanate.

According to the present invention, it is possible to provide an adsorbent containing crystalline silicotitanate having excellent adsorption and removal characteristics of cesium and strontium, particularly even in seawater.

FIG. 1 is an X-ray diffraction chart of the adsorbent containing crystalline silicotitanate obtained in Example 2. FIG. 2 is an X-ray diffraction chart of the adsorbent containing crystalline silicotitanate obtained in Reference Example 2.

Hereinafter, the present invention will be described based on a preferred embodiment.
The adsorbent according to the present invention is an adsorbent that adsorbs metal ions. Examples of the metal ion to be adsorbed by the adsorbent of the present invention include metal ions such as cesium, strontium, antimony, lead, zinc, mercury, copper, cadonium, and mercury, and in particular, adsorption of cesium in seawater, and further. Has an excellent adsorption capacity for the adsorption of cesium.

The crystalline silicon titanate contained in the adsorbent according to the present invention has a general formula; A ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (in the formula, A represents an alkali metal selected from Na and K. , N represents 0 to 8).

In addition, the general formula; A ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (in the formula, A represents an alkali metal selected from Na and K) is represented by crystalline silicon titanate (hereinafter, simply “crystal”). The detailed composition of crystalline silicon titanate when A contains Na and K in "sex silicon titanate") is not clear, but the general formula; Na ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O and K ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O is included or (Na _x K _(1-x) ) ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (in the formula, x is greater than 0 and less than 1) ), The present inventors speculate.

In the present invention, A in the formula of crystalline silicotitanate is an alkali metal selected from Na and K. In the adsorbent of the present invention, A preferably contains both Na and K, and the content of K is the molar ratio (K ₂ O /) of A ₂ O (Na ₂ O + K ₂ O) conversion and K ₂ O conversion. A ₂ O) is preferably larger than 0 and 0.5 or less, more preferably 0.05 or more and 0.4 or less, particularly from the viewpoint of improving the adsorption performance of cesium and strontium.

The crystalline silicotitanate contained in the adsorbent according to the present invention is 2θ = 10 ° or more of 2θ = 10 ° or more of the crystalline silicotitanate when X-ray diffraction measurement is performed using Cu—Kα ray using the crystalline silicotitanate as a radiation source. The half-value width of the diffraction peak (main peak (B1)) of ° or less is 1.0 ° or less, preferably 0.2 to 0.9 °, particularly preferably 0.2 to 0.5 °, and further preferably 0. One feature is that it is 3 to 0.50 °.

The present inventors have related to the adsorption capacity of metal ions by the half-value width of the diffraction peak (main peak (B1)) of 2θ = 10 ° or more and 13 ° or less of the crystalline silicotitanate contained in the adsorbent. It has been found that the adsorption ability of cesium and strontium is particularly improved as compared with Non-Patent Document 3 by setting the half-value width of the diffraction peak to a specific range smaller than that of Non-Patent Document 3.

It adsorbent according to the present invention, in addition to having the above characteristics, BET specific surface area of 100 m ² / g or more, preferably 100 to 200 m ² / g, particularly preferably 100~180m ² / g Is also one of the features.
The reason for this is that if the BET specific surface area is less than 100 m ² / g, the adsorption performance of strontium is particularly poor, which is not preferable.

The form of the adsorbent of the present invention is preferably a granular material. Examples of the granules include powders, granules, molded bodies other than granules (spherical and columnar), and are preferably powdery or granular.

When the adsorbent of the present invention is a granular material, it preferably has a particle size of 200 μm or more and 1000 μm or less. Since the adsorbent of the present invention composed of particles having this particle size does not have particles finer than 200 μm, or even if they are present, the amount is extremely small, the adsorbent of the present invention is filled in the adsorption tower and water is passed through. In some cases, the problem of particles clogging in the adsorption tower can be prevented. Further, when the particle size is 1000 μm or less, the adsorption performance of the adsorbent can be easily improved.

Specifically, when the adsorbent of the present invention is a granular material, when a sieve having a mesh size of 212 μm according to the JIS Z8801 standard and a sieve having a mesh size of 1 mm are used, the adsorbent of the present invention can be used. It is preferable that 98% by mass or more, particularly 99% by mass or more, passes through a sieve having an opening of 1 mm, and 98% by mass or more, particularly 99% by mass or more, does not pass through a sieve having a mesh opening of 212 μm. In particular, the adsorbent of the present invention preferably comprises a granular material having a particle size of 300 μm or more and 600 μm or less. Specifically, when a sieve having a mesh size of 300 μm and a sieve having a mesh size of 600 μm according to the JIS Z8801 standard are used, 98% by mass or more, particularly 99% by mass or more of the adsorbent of the present invention is 600 μm. It is preferable that 98% by mass or more, particularly 99% by mass or more, does not pass through the above-mentioned 300 μm sieve.
The adsorbent of the present invention in the form of a powder having a particle size of less than 200 μm can also be used in the form of being fixed to a non-woven fabric.

The adsorbent of the present invention is obtained by, 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 first step. It has a second step of hydrothermally reacting the mixed gel, and in the first step, the molar ratio of Ti and Si contained in the mixed gel is Ti / Si = 1.2 or more and 1.5 or less. , Silicic acid source and titanium tetrachloride can be added.

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 and potassium silicate. In addition, active silicic acid obtained by cation exchange of alkali silicate (that is, alkali metal salt of silicic acid) can also be mentioned.

Active silicic acid is obtained by bringing an alkaline aqueous solution of silicic acid into contact with, for example, a cation exchange resin and cation exchange. As a raw material for the alkaline silicate aqueous solution, a sodium silicate aqueous solution usually called water glass (water glasses Nos. 1 to 4 and the like) is preferably used. This is relatively inexpensive and easily available. Further, in semiconductor applications where Na ions are disliked, an aqueous potassium silicate solution is suitable as a raw material. There is also a method of preparing an aqueous alkali silicate solution by dissolving a solid alkali metasilicate in water. Since the alkali metasilicate is produced through a crystallization process, some of them have few impurities. The alkaline silicate aqueous solution is used after being diluted with water if necessary.

The cation exchange resin used when preparing the active silicic acid can be appropriately selected and used, and is not particularly limited. In the step of contacting the alkaline silicate aqueous solution and the cation exchange resin, for example, the alkaline silicate aqueous solution is diluted with water so that the silica concentration is 3% by mass or more and 10% by mass or less, and then the diluted alkaline silicate aqueous solution is H. Mold Dealkalinated by contact with strongly acidic or weakly acidic cation exchange resin. Further, if necessary, it can be contacted with an OH-type strong basic anion exchange resin to deanionize it. By this step, an aqueous solution of active silicic acid is prepared. Various proposals have already been made regarding the details of the contact conditions between the alkaline silicate aqueous solution and the cation exchange resin, and any known contact conditions can be adopted in the present invention.

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

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

When sodium compounds and potassium compounds are used in the first step, the molar ratio of K ₂ O / A ₂ O is greater than 0 and 0 with respect to the total number of moles (A ₂ O) converted to Na ₂ O and K ₂ O. It is preferably 5.5 or less, and more preferably 0.05 or more and 0.4 or less.

The amount of the silicic acid source and titanium tetrachloride added is such that Ti / Si, which is the molar ratio of Ti derived from titanium tetrachloride and Si derived from the silicic acid source, in the mixed gel becomes 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 an amount such that the Ti / Si ratio is 0.32. On the other hand, in this production method, the silicic acid source and titanium tetrachloride are added in an amount such that the Ti / Si ratio is 1.2 or more and 1.5 or less. As a result of the examination by the present inventors, by setting the Ti / Si ratio in the mixed gel to the above-mentioned molar ratio range, the crystallinity is high as the crystalline silicotitanate, and the half width and the BET specific surface area are in the above range. It becomes easier to obtain things.

Further, the total amount of the silicic acid source concentration in terms of SiO ₂ and the titanium tetrachloride concentration in terms of TiO ₂ in the mixed gel is 2.0% by mass or more and 40% by mass or less, and A ₂ O / SiO _{2 in the} mixed gel. It is desirable to add a silicic acid source and titanium tetrachloride so that the molar ratio of is 0.5 or more and 2.5 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 desired crystalline silicotitanate can be increased to a satisfactory level.

A 2 _O molar number of, what the number of ions of sodium and potassium in the mixed gel was expressed in terms of oxide, in other words, have been used by the neutralization reaction between the alkali and titanium tetrachloride, such as sodium or potassium It is obtained excluding the amount of sodium and potassium.

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

In the first step, the silicic acid source, the sodium compound, the potassium compound, and 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 mixed gel can be adjusted by 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 titanium tetrachloride can be added in various order of addition. 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 (the order of addition is simply referred to below. It may also be called "implementation of (1)"). The implementation of this (1) is preferable in that the 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, also simply referred to as "active silicic acid") obtained by cation exchange of alkali silicate, titanium tetrachloride, and water. An embodiment in which a sodium compound and / or a potassium compound is added to the mixture of the above can be adopted. Even if this addition order is adopted, a mixed gel can be obtained in the same manner as in the embodiment (1) (hereinafter, this addition order may be simply referred to as "implementation of (2)"). Titanium tetrachloride can be added in the form of an aqueous solution thereof or in the form of a solid. Similarly, sodium and potassium compounds can be added in the form of aqueous solutions or solids thereof.

In the implementation of (1) and (2), the total concentration (A ₂ O concentration) of sodium and potassium in the mixed gel of the sodium compound and / or the potassium compound is 0.5% by mass or more 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 total Na ₂ O-equivalent mass of sodium and potassium in the mixed gel and the total Na ₂ O-equivalent concentration of sodium and potassium in the mixed gel (hereinafter, "total concentration of sodium and potassium (potassium compound is used in the first step). If not, it is called "sodium concentration") is calculated by the following formula.

Total Na ₂ O reduced mass (g) of sodium and potassium in the mixed gel = (number of moles of A above-number of moles of chloride ion derived from titanium tetrachloride) x 0.5 x Na ₂ O molecular weight

Total Na ₂ O-equivalent concentration of sodium and potassium in the mixed gel (mass%) = Total Na ₂ O-equivalent mass of sodium and potassium in the mixed gel / {Water content in the mixed gel + Sodium in the mixed gel And potassium total Na ₂ O reduced mass} x 100

Combining the selection of a silicic acid source with the adjustment of the total concentration of sodium and potassium in the mixed gel suppresses the formation of crystalline silicotitanates other than crystalline silicotitanates with a Ti: Si molar ratio of 4: 3. Can be done. When sodium silicate or potassium silicate is used as the silicic acid source, the molar ratio of Ti: Si can be increased 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. It is possible to effectively suppress the production of 5:12 crystalline silicotitanate, while the total concentration of sodium and potassium in the mixed gel is 6.0% by mass or less in terms of Na ₂ O. It is possible to effectively suppress the formation of crystalline silicotitanate having a Ti: Si molar ratio of 1: 1. When active silicic acid obtained by cation exchange of alkali silicate is used as the silicic acid source, the molar ratio of Ti: Si is 5: by setting it to 1.0% by mass or more in terms of Na ₂ O. The formation of crystalline siliconitanate of 12 can be effectively suppressed, while the total concentration of sodium and potassium in the mixed gel is 6.0% by mass or less in terms of Na ₂ O, so that Ti: It is possible to effectively suppress the formation 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 becomes the sodium source in the mixed gel at the same time. Therefore, the "Na ₂ O reduced mass (g) of sodium in the mixed gel" referred to here is counted as the sum of all the sodium components in the mixed gel. Similarly, "Na ₂ O reduced mass (g) of potassium in a mixed gel" is also counted as the sum of all potassium components in the mixed gel.

In the implementation of (1) and (2), it is desirable that the addition of titanium tetrachloride is carried out 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 perista pump or the like can be preferably used for adding titanium tetrachloride.

The mixed gel obtained in the first step may be aged at 10 ° C. or higher and 100 ° C. or lower for a time of 0.1 hour or more and 5 hours or less before carrying out the hydrothermal reaction which is the second step described later. , Preferable in obtaining a uniform product. The aging step may be carried out, for example, in a stationary state or in a stirred 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 limited to any condition as long as the crystalline silicotitanate can be synthesized. Usually, it is added in an autoclave at a temperature of preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 120 ° C. or higher and 180 ° C. or lower, preferably 6 hours or more and 90 hours or less, further preferably 12 hours or more and 80 hours or less. React under pressure. The reaction time can be selected according to the scale of the synthesizer.

The water-containing material containing the crystalline silicotitanate obtained in the second step can be dried, and the obtained dried product can be crushed or pulverized as necessary to be in the form of powder (including granules). Further, a water-containing material containing crystalline silicotitanate may be extruded from a perforated member in which a plurality of pores are formed to obtain a rod-shaped molded product, and the obtained rod-shaped molded product may be dried to form a columnar shape. Then, the dried rod-shaped molded product may be formed into a spherical shape, or may be crushed or crushed into particles.

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

The dried rod-shaped molded product can be used as it is as an adsorbent, or it may be lightly loosened and used. Further, the rod-shaped molded product after drying may be crushed and used. The powdery product containing crystalline silicotitanate obtained by these various methods is preferably further classified and then used as an adsorbent from the viewpoint of increasing the adsorption efficiency of cesium and / or strontium. For 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 use these first and second sieves.

In the above-mentioned production method, 2θ = 10 ° or more and 13 ° or less of the crystalline silicotitanate obtained by appropriately selecting the compounding ratio of the sodium compound and the potassium compound in the first step and the reaction temperature and reaction time in the second step. The range of the half-value width of the diffraction peak (main peak (B1)) and the BET specific surface area can be controlled to the range according to the present invention.
That is, in the first step, the mixing ratio of the sodium compound and the potassium compound is such that the molar ratio of K ₂ O / A ₂ O exceeds 0 with respect to the total number of moles (A ₂ O) converted to Na ₂ O and K ₂ O. When it is 0.5 or less, preferably 0.05 or more and 0.4 or less, the half-value width value of the diffraction peak (main peak (B1)) of 2θ = 10 ° or more and 13 ° or less of the obtained crystalline silicotitanate becomes small. Tend.
Further, the lower the reaction temperature in the second step and the shorter the reaction time, the more the half width of the diffraction peak (main peak (B1)) of the crystalline silicotitanate obtained at 2θ = 10 ° or more and 13 ° or less. While increasing, the BET specific surface area also tends to increase.

The characteristic adsorbent composed of crystalline silicotitanate according to the present invention may be molded according to a conventional method, if necessary, and the obtained molded product may be used as an adsorbent for metal ions.

Examples of the molding process include granulation processing for molding a powdery adsorbent made of crystalline silicotitanate into granules, and slurrying of a powdery adsorbent made of crystalline silicotitanate into a slurry such as calcium chloride. A method of encapsulating a powdery adsorbent made of crystalline silicotitanate by dropping it in a liquid containing a curing agent, and a method of adhering and coating a powdery adsorbent made of crystalline silicotitanate on the surface of a resin core material. , A method of adhering a powdery adsorbent made of crystalline silicotitanate to the surface and / or inside of a non-woven fabric formed of natural fibers or synthetic fibers and immobilizing the powder to form a sheet. Examples of the granulation processing method include known methods, such as stirring and mixing granulation, rolling granulation, extrusion granulation, crushing granulation, fluidized bed granulation, spray drying granulation (spray drying), and compression granulation. Grains and the like can be mentioned. Binders and solvents may be added and mixed as needed in the process of granulation. Known binders include, for example, polyvinyl alcohol, polyethylene oxide, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, starch, corn starch, sugar honey, lactose, gelatin. , Dextrin, gum arabic, alginic acid, polyacrylic acid, glycerin, polyethylene glycol, polyvinylpyrrolidone and the like. As the solvent, various solvents such as an aqueous solvent and an organic solvent can be used.

In addition, the granulated granules containing crystalline silicotitanate in a water-containing state are suitably used as an adsorbent for a water treatment system having an adsorption container and an adsorption tower filled with a radioactive substance adsorbent. Can be done.

In this case, the shape and size of the granular product obtained by granulating the water-containing product containing crystalline silico titanate is filled in an adsorption container or a filling tower, and treated water containing metal ions is passed therethrough. It is preferable to adjust the shape and size appropriately so as to be suitable for watering.

Further, the granules obtained by granulating the water-containing material containing crystalline silicotitanate are used as an adsorbent that can be recovered by magnetic separation from water containing metal ions by further containing magnetic particles. Can be done. Examples of the magnetic particles include metals such as iron, nickel and cobalt, or powders of magnetic alloys containing these as main components, and metal oxides such as iron trioxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite and strontium ferrite. Examples include powders of based magnetic materials.

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

The adsorbent of the present invention is used in combination with other adsorbents such as zeolite, titanate, barium silicate, crystalline silicon titanate having a Ti / Si ratio of 2: 1, apatite, and activated carbon. Can be done.
Further, the adsorbent according to the present invention can also be used as, for example, a metal ion adsorbent for tap water.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Unless otherwise specified, "%" represents "mass%". The evaluation devices and materials used in the examples and comparative examples are as follows.

<Evaluation device>
-X-ray diffraction: Bruker's D8 Advance S was used. Cu-Kα was used as the 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 carried out with the measurement wavelength of Cs being 679.327 nm and the measurement wavelength of Sr being 216.596 nm. As standard samples, aqueous solutions of Cs: 100 ppm, 50 ppm and 10 ppm containing 0.3% NaCl, and aqueous solutions of Sr: 100 ppm, 10 ppm and 1 ppm containing 0.3% NaCl were used.
XRF: Fluorescent X-ray device (device name: ZSX100e, tube: Rh (4 kW), atmosphere: vacuum, analysis window: Be (30 μm), measurement mode: SQX analysis (EZ scan), measurement diameter: 30 mmφ, Co., Ltd. ) All elements were measured with Rigaku). The measurement sample was obtained by placing it in an appropriate container (aluminum ring or the like), sandwiching it with a die, and then applying a pressure of 10 MPa with a press to pelletize it.
-BET specific surface area: Obtained by the BET 1-point method using a Flowsorb II 2300 manufactured by Shimadzu Corporation as a measuring device.

<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 Industrial Co., Ltd. (SiO _2: 30%, particle diameter 15nm)
・ Potassium hydroxide: Solid reagent Potassium hydroxide (KOH: 85%)
-Caustic soda aqueous solution; industrial 25% sodium hydroxide (NaOH: 25%, H ₂ O: 75%)
・ Titanium tetrachloride aqueous solution: 36.48% aqueous solution manufactured by Osaka Titanium Technologies Co., Ltd. ・ Titanium dioxide: Ishihara Sangyo ST-01
-Simulated seawater: A 0.3% NaCl aqueous solution containing 100 ppm each of Cs and Sr was used as simulated seawater. The simulated seawater is a mixture of NaCl (99.5%): 3.0151 g, SrCl · 6H ₂ O (99%): 0.3074 g, CsNO ₃ (99%): 0.1481 g, and H ₂ O: 996.5294 g. I got it.

[Example 1]
(1) First Step: 64.5 g of potassium silicate, 126.7 g of 85% potassium hydroxide and 210.2 g of ion-exchanged water were mixed and stirred to obtain a mixed aqueous solution. To this mixed aqueous solution, 203.3 g of a titanium tetrachloride aqueous solution was continuously added for 30 minutes with a perista pump to produce a mixed gel. The mixed gel was aged by mixing at 70 ° C. for 1 hour after the addition of the aqueous titanium tetrachloride solution.

(2) Second step The mixed gel obtained in the first step was placed in an autoclave, heated to 170 ° C. over 1.5 hours, and then reacted for 72 hours while maintaining this temperature. .. The slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less.

[Example 2]
(1) First Step No. 3 Sodium silicate (60 g), aqueous caustic solution (224.3 g), 85% potassium hydroxide (34.6 g) and ion-exchanged water (82.5 g) were mixed and stirred to obtain a mixed aqueous solution. To this mixed aqueous solution, 203.3 g of a titanium tetrachloride aqueous solution was continuously added over 0.5 hours with a perista 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 titanium tetrachloride solution.

(2) Second Step The mixed gel obtained in the first step was placed in an autoclave, heated to 140 ° C. over 1 hour, and then reacted under stirring for 18 hours while maintaining this temperature. The slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less.

[Example 3]
In Example 2, the reaction was carried out in the same manner as in Example 2 except that the reaction temperature in the second step was set to 150 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less.

[Example 4]
In Example 2, the reaction was carried out in the same manner as in Example 2 except that the reaction temperature in the second step was set to 160 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less.

[Reference Example 1]
In Example 2, the reaction was carried out in the same manner as in Example 2 except that the reaction temperature in the second step was set to 170 ° C. for 96 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less.

(Evaluation of the physical properties)
The BET specific surface area was determined for the granules obtained in Example and Reference Example 1. In addition, X-ray diffraction analysis was performed. In addition, the half width of the diffraction peak (main peak (B1)) of 2θ = 10 ° or more and 13 ° or less of crystalline silicotitanate was determined by X-ray diffraction analysis. Moreover, the content (mass%) of K ₂ O, Na ₂ O, SiO ₂ and TiO _{2 in} the granules was measured by XRF under the above conditions. The results are shown in Table 1.

[Reference example 2]
<Synthesis of a mixture of crystalline silicotitanate and titanate>
(1) First Step No. 3 90 g of sodium silicate, 667.49 g of caustic soda aqueous solution and 84.38 g of pure water were mixed and stirred to obtain a mixed aqueous solution. A mixed gel was produced by continuously adding 443.90 g of a titanium tetrachloride aqueous solution to this mixed aqueous solution with a perista pump for 1 hour and 20 minutes. The mixed gel was aged at room temperature for 1 hour after the addition of the aqueous titanium tetrachloride solution. Ti / Si molar ratio in the mixed gel: 2, K ₂ O / Na ₂ O molar ratio: 0/100, SiO ₂ equivalent concentration a: 2.00%, TiO ₂ equivalent concentration b: 5.30%, a + b: It was 7.30, A ₂ O / SiO ₂ molar ratio: 1.56, and Na ₂ O conversion concentration: 3.22%.

(3) Second Step The mixed gel obtained in the first step was placed in an autoclave, heated to 170 ° C. over 1 hour, and then reacted under stirring for 24 hours while maintaining this temperature. The slurry after the reaction was filtered, and the obtained cake was extruded with a circular opening member having a diameter of 0.6 μm, dried, and classified to obtain granules having a particle size of 300 μm or more and 600 μm or less. The obtained granules were measured by X-ray diffraction. The result is shown in FIG. From the results of the X-ray diffraction measurement shown in FIG. 2, the obtained granules were the main phase Na ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O, and Na ₄ Ti ₉ O ₂₀ · mH ₂ O was detected. It was confirmed to be a mixture of crystalline silicotitanate and the titanate. Relative Further granulate main peak height (MP) derived from _{Na 4 Ti 4 Si 3 O 16} · 6H 2 O , which is observed in the range of 2 [Theta] = 10 to 13 °, in 2 [Theta] = 8 to 10 ° the ratio of the height of the MP originating from Na to _{4 Ti 9 O 20 · 5~7H 2} O observed in the range was 38.5%. According to the composition analysis of the above method, the molar ratio of Na ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O: Na ₄ Ti ₉ O ₂₀ · mH ₂ O was 1: 0.37.

<Adsorption test of Cs and Sr>
0.5 g of the granules was taken in a 100 ml plastic container, the simulated seawater 1 (100.00 g) was added, the lid was closed, and the contents were shaken. The contents were shaken by inverting the plastic container 10 times. Then, after allowing to stand for 1 hour, the contents were shaken again, about 50 ml was filtered through a 5C filter paper, and the filtrate obtained by filtration was collected. The remaining 50 ml was allowed to stand as it was, and was further shaken 23 hours later (24 hours after the first shaking). Then, it was filtered through a 5C filter paper, and the filtrate obtained by the filtration was collected. The contents of Cs and Sr in the filtrate were measured using ICP-AES for the collected filtrate. The results are shown in Table 2 below.

Claims (5)

It is an adsorbent for metal ions.
In X-ray diffraction analysis, the half width of the main peak of 2θ = 10 ° or more and 13 ° or less is 0.2 to 0.5 ° , and the BET specific surface area is 100 m ² / g or more. General formula; A ₄ Ti ₄ Si ₃ O ₁₆ · nH ₂ O (In the formula, A indicates an alkali metal selected from Na and K. However, A may not be K alone. In the formula, n indicates 0 to 8.) An adsorbent characterized by being composed of crystalline silicon titanate represented by. Crystalline silicotitanate has a potassium content of more than 0 and 0.5 or less in terms of K ₂ O, in terms of molar ratio (K ₂ O / A ₂ O) to A ₂ O (A indicates Na and K). The adsorbent according to claim 1, wherein the adsorbent is characterized by this. The adsorbent according to any one of claims 1 or 2, which is in the form of powder or granules. The adsorbent according to claim 3, which has a particle size of 200 to 1000 μm. The adsorbent according to any one of claims 1 to 4, wherein the metal ion to be adsorbed is cesium and / or strontium.

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