WO2017170785A1 - Metal ion adsorption agent - Google Patents

Metal ion adsorption agent Download PDF

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Publication number
WO2017170785A1
WO2017170785A1 PCT/JP2017/013090 JP2017013090W WO2017170785A1 WO 2017170785 A1 WO2017170785 A1 WO 2017170785A1 JP 2017013090 W JP2017013090 W JP 2017013090W WO 2017170785 A1 WO2017170785 A1 WO 2017170785A1
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Prior art keywords
adsorbent
crystalline silicotitanate
sodium
potassium
mixed gel
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PCT/JP2017/013090
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French (fr)
Japanese (ja)
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慎介 宮部
木ノ瀬　豊
坂本　剛
英治 野口
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日本化学工業株式会社
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Priority to JP2018509391A priority Critical patent/JP6812415B2/en
Publication of WO2017170785A1 publication Critical patent/WO2017170785A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/12—Processing by absorption; by adsorption; by ion-exchange

Definitions

  • the present invention relates to an adsorbent for metal ions, particularly an adsorbent containing crystalline silicotitanate that can be suitably used for selectively and efficiently separating and recovering cesium or strontium in seawater.
  • coprecipitation treatment is known as a treatment technique for wastewater containing radioactive substances (see Patent Document 1 below).
  • the coprecipitation treatment is not effective, and at present, adsorption removal by an inorganic adsorbent such as zeolite is performed (see Patent Document 2 below).
  • Non-Patent Document 1 When radioactive cesium and radioactive strontium flow into seawater, an increase in the sodium concentration of seawater components 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 studied so far for the adsorption of cesium and / or strontium. Crystalline silicotitanates are known to have a plurality of types of compositions such as those with a Ti / Si ratio of 1: 1, 5:12, and 2: 1. It is known that there is crystalline silicotitanate in which is 4: 3.
  • 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 are three-dimensional from the X-ray diffraction pattern.
  • Non-Patent Document 3 discloses a hydrothermal treatment of a crystalline silicotitanate having a Ti / Si ratio of 4: 3, titanium tetrachloride as a Ti source, and a highly dispersed SiO 2 powder as a Si source. The fact that it was manufactured by applying is described. This document describes that the synthesized crystalline silicotitanate has strontium ion exchange capacity.
  • the inventors previously obtained a mixed gel by adding a silicic acid source, a sodium compound and / or potassium compound, titanium tetrachloride, and water in Patent Document 3 below, and then obtaining the mixed gel.
  • the adsorbent useful for adsorption removal of cesium and strontium from seawater containing crystalline silicotitanate having a Ti / Si molar ratio of 4/3 was proposed by hydrothermal reaction of the resulting mixed gel.
  • an object of the present invention is to provide an adsorbent comprising a crystalline silicotitanate having a Ti / Si ratio of 4: 3, which is effective for adsorption of metal ions, particularly cesium even in seawater, and even strontium. There is to do.
  • an adsorbent containing crystalline silicotitanate having excellent cesium and strontium adsorption / removal characteristics, particularly in seawater.
  • FIG. 1 is an X-ray diffraction chart of an 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.
  • the adsorbent according to the present invention is an adsorbent that adsorbs metal ions.
  • the metal ions to be adsorbed by the adsorbent of the present invention include metal ions such as cesium, strontium, antimony, lead, zinc, mercury, copper, cadmium, and mercury, and in particular, adsorption of cesium in seawater, Has excellent adsorption capacity for strontium adsorption.
  • 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 (wherein A represents an alkali metal selected from Na and K. In the formula, , N represents 0 to 8).
  • A represents an alkali metal selected from Na and K
  • the detailed composition of crystalline silicotitanate 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 or containing 2 O, or (Na x K (1-x )) in 4 Ti 4 Si 3 O 16 ⁇ nH 2 O ( wherein, x is less than 0 ultra 1
  • a in the formula of crystalline silicotitanate is an alkali metal selected from Na and K.
  • a contains both Na and K and the K content is a molar ratio (K 2 O / K) in terms of A 2 O (Na 2 O + K 2 O) and K 2 O.
  • a 2 O) is preferably more 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 obtained by measuring X-ray diffraction using Cu-K ⁇ rays with the crystalline silicotitanate as a radiation source.
  • the half-value width of a diffraction peak (main peak (B1)) of not more than 1.0 ° is 1.0 ° or less, preferably 0.2 to 0.9 °, particularly preferably 0.2 to 0.5 °, and more preferably 0.00.
  • One characteristic is that the angle is 3 to 0.50 °.
  • the adsorbent according to the present invention has a BET specific surface area of 100 m 2 / g or more, preferably 100 to 200 m 2 / g, particularly preferably 100 to 180 m 2 / g. Is another feature. The reason for this is that when 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.
  • the granular material include a powder, a granule, a molded body other than a granule (spherical, cylindrical), and the like, and a powder or a granule is preferable.
  • the adsorbent of the present invention is a granular material, it preferably has a particle size of 200 ⁇ m or more and 1000 ⁇ m or less. Since the adsorbent of the present invention composed of granules of this particle size does not have particles finer than 200 ⁇ m or is extremely small even if present, the adsorbent of the present invention is packed in an adsorption tower and passed through. In this case, it is possible to prevent the problem that particles are clogged in the adsorption tower. Moreover, when the particle size is 1000 ⁇ m or less, it is easy to improve the adsorption performance of the adsorbent.
  • the adsorbent of the present invention is a granular material
  • the sieve according to JIS Z8801 standard has a sieve having an opening of 212 ⁇ m and the sieve having an aperture of 1 mm
  • the adsorbent of the present invention It is preferable that 98% by mass or more, particularly 99% by mass or more pass through a sieve having an opening of 1 mm, and 98% by mass or more, particularly 99% by mass or more should not pass through a sieve having an opening of 212 ⁇ m.
  • the adsorbent of the present invention is preferably composed of a granular material having a particle size of 300 ⁇ m or more and 600 ⁇ m or less.
  • adsorbent of the present invention when a sieve having an opening of 300 ⁇ m according to JIS Z8801 standard and a sieve having an opening of 600 ⁇ m are used, 98 mass% or more, particularly 99 mass% or more of the adsorbent of the present invention is the above-mentioned 600 ⁇ m. It is preferable that 98% by mass or more, particularly 99% by mass or more, does not pass through the 300 ⁇ m sieve.
  • the adsorbent of the present invention in the form of a powder having a particle size of less than 200 ⁇ m can be used in a form fixed to a nonwoven fabric or the like.
  • the adsorbent of the present invention is obtained by, for example, a first step of mixing a silicate source, a sodium compound and / or potassium compound, titanium tetrachloride, and water to obtain a mixed gel, and the first step.
  • the manufacturing method of the adsorbent of this invention is demonstrated.
  • the silicic acid source in the first step include sodium silicate and potassium silicate.
  • the active silicic acid obtained by carrying out cation exchange of the alkali silicate namely, alkali metal salt of silicic acid is also mentioned.
  • Active silicic acid is obtained by cation exchange by bringing an aqueous alkali silicate solution into contact with, for example, a cation exchange resin.
  • a sodium silicate aqueous solution usually called water glass (water glass No. 1 to No. 4 etc.) is preferably used. This is relatively inexpensive and can be easily obtained.
  • an aqueous potassium silicate solution is suitable as a raw material.
  • the aqueous alkali silicate solution is diluted 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.
  • the alkali silicate aqueous solution is diluted with water so that the silica has a concentration of 3% by mass or more and 10% by mass or less.
  • a strong acidic or weakly acidic cation exchange resin to dealkalize. Further, if necessary, it can be deanioned by contacting with an OH type strongly basic anion exchange resin.
  • an active silicic acid aqueous solution is prepared.
  • various proposals have already been made, 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 and sodium carbonate.
  • sodium hydroxide when sodium carbonate is used, carbon dioxide gas is generated. Therefore, it is preferable to use sodium hydroxide that does not generate such gas from the viewpoint of smoothly promoting the neutralization reaction.
  • Examples of the potassium compound include potassium hydroxide and potassium carbonate.
  • potassium hydroxide when potassium carbonate is used, carbon dioxide gas is generated. Therefore, it is preferable to use potassium hydroxide that does not generate such gas from the viewpoint of smoothly promoting the neutralization reaction.
  • 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) in terms of Na 2 O and K 2 O. Is preferably 0.5 or less, more preferably 0.05 or more and 0.4 or less.
  • the addition amount of the silicic acid source and titanium tetrachloride 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, has a specific ratio.
  • 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.
  • 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.
  • the total amount of the SiO 2 equivalent silicic acid source concentration and the TiO 2 equivalent titanium tetrachloride concentration in the mixed gel is 2.0 mass% or more and 40 mass% or less, 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 is 0.5 to 2.5.
  • A represents Na and K.
  • the number of moles of A 2 O is the number of ions of sodium and potassium in the mixed gel expressed in terms of oxide, in other words, used by the neutralization reaction between alkali such as sodium or potassium and titanium tetrachloride. 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.
  • the silicic acid source, sodium compound, potassium compound, and titanium tetrachloride can be added to the reaction system in the form of an aqueous solution, respectively. In some cases, it can be added in solid form. Further, in the first step, the concentration of the mixed gel can be adjusted using pure water if necessary for the obtained mixed gel.
  • the silicate source, sodium compound, potassium compound, and titanium tetrachloride can be added in various addition orders.
  • a mixed gel can be obtained by adding titanium tetrachloride to a mixture of a silicate source, a sodium compound and / or a potassium compound, and water (this addition order is simply referred to as “additional order” hereinafter). (It may be called “Implementation of (1)”.)
  • the implementation of (1) is preferable in that the generation of chlorine from titanium tetrachloride is suppressed.
  • an aqueous solution of activated silicic acid obtained by cation exchange of alkali silicate, titanium tetrachloride and water, A mode in which a sodium compound and / or a potassium compound is added to a mixture of these can be employed. Even if this order of addition is adopted, a mixed gel can be obtained in the same manner as in the embodiment of (1) (this order of addition may hereinafter be simply referred to as “execution of (2)”). Titanium tetrachloride can be added in the form of an aqueous solution or solid form. Similarly, sodium compounds and potassium compounds can also be added in the form of their aqueous solutions or solid forms.
  • the sodium compound and / or potassium compound has a total concentration of sodium and potassium (A 2 O concentration) in the mixed gel of 0.5% by mass or more in terms of Na 2 O. It is preferable to add so that it may become 0 mass% or less, especially 0.7 mass% or more and 13 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 referred to as “total concentration of sodium and potassium (the potassium compound is used in the first step) If not, it is referred to as “sodium concentration”).
  • sodium silicate When sodium silicate is used as the silicate source, the sodium component in the sodium silicate simultaneously becomes the sodium source in the mixed gel. Therefore, the “Na 2 O equivalent mass (g) of sodium in the mixed gel” mentioned here is counted as the sum of all sodium components in the mixed gel. Similarly, “Na 2 O equivalent mass (g) of potassium in the mixed gel” is also counted as the sum of all potassium components in the mixed gel.
  • titanium tetrachloride stepwise or continuously as an aqueous titanium tetrachloride solution over a certain period of time in order to obtain a uniform gel.
  • a peristaltic pump etc. can be used suitably for addition of 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 period of 0.1 hour or longer and 5 hours or shorter before performing a hydrothermal reaction which is the second step described later. From the viewpoint of obtaining a uniform product.
  • 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.
  • the mixed gel obtained in the first step is subjected to a hydrothermal reaction as the second step to obtain crystalline silicotitanate.
  • the hydrothermal reaction is not particularly limited as long as the crystalline silicotitanate can be synthesized.
  • the temperature is 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 longer and 90 hours or shorter, more preferably 12 hours or longer and 80 hours or shorter.
  • React under pressure The reaction time can be selected according to the scale of the synthesizer.
  • the water-containing product containing the crystalline silicotitanate obtained in the second step can be dried, and the obtained dried product can be pulverized or pulverized as necessary to form a powder (including granules).
  • a hydrous material containing crystalline silicotitanate may be extruded from an aperture member in which a plurality of apertures are formed to obtain a rod-shaped molded body, and the obtained rod-shaped molded body may be dried to form a columnar shape.
  • the dried rod-shaped molded body may be formed into a spherical shape, or may be pulverized or pulverized into particles.
  • the true circle equivalent diameter of the opening 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 true circle equivalent diameter here is a diameter of a circle calculated from the area when the area of one hole is a circle area.
  • the drying temperature after extrusion molding can be, for example, 50 ° C. or more and 200 ° C. or less.
  • the drying time can be 1 hour or more and 120 hours or less.
  • the dried rod-shaped molded body can be used as an adsorbent as it is, or it can be used after lightly loosening. Moreover, you may grind
  • 2 ⁇ 10 ° to 13 ° of the crystalline silicotitanate obtained by appropriately selecting the mixing ratio of the sodium compound and potassium compound in the first step and the reaction temperature and reaction time in the second step.
  • the value of the half width of the diffraction peak (main peak (B1)) and the range of the BET specific surface area can be controlled within the range according to the present invention. That is, in the first step, the compounding 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.
  • the characteristic adsorbent comprising the crystalline silicotitanate according to the present invention may be molded according to a conventional method if necessary, and the resulting molded product may be used as an adsorbent for metal ions.
  • a powdery adsorbent composed of crystalline silicotitanate is granulated to form a granule or a powdered adsorbent composed of crystalline silicotitanate is slurried to obtain calcium chloride or the like.
  • a method of encapsulating a powdery adsorbent composed of crystalline silicotitanate by dripping into a liquid containing a curing agent, and a method of applying a powder adsorbent composed of crystalline silicotitanate to the surface of a resin core examples thereof include a method of adhering a powdery adsorbent made of crystalline silicotitanate to the surface and / or inside of a nonwoven fabric formed of natural fibers or synthetic fibers and fixing it to form a sheet.
  • Examples of the granulation 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. A grain etc. can be mentioned.
  • a binder and a solvent may be added and mixed as necessary.
  • binder known ones such as polyvinyl alcohol, polyethylene oxide, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, starch, cornstarch, molasses, lactose, gelatin , Dextrin, gum arabic, alginic acid, polyacrylic acid, glycerin, polyethylene glycol, polyvinylpyrrolidone and the like.
  • solvent various solvents such as an aqueous solvent and an organic solvent can be used.
  • 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 material adsorbent. I can do it.
  • the shape and size of the granular material obtained by granulating the water-containing material containing crystalline silicotitanate is filled in an adsorption vessel or a packed tower, and treated water containing metal ions is passed through. It is preferable to appropriately adjust the shape and size so as to adapt to watering.
  • the granular material obtained by granulating the water-containing material containing crystalline silicotitanate is used as an adsorbent that can be recovered by magnetic separation from water containing metal ions by further containing magnetic particles.
  • magnetic particles include metals such as iron, nickel, and cobalt, or powders of magnetic alloys based on these metals, metal oxides such as iron trioxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite, and strontium ferrite. Examples thereof include powders of magnetic system.
  • the above-described granulation processing operation may be performed in a state where magnetic particles are contained.
  • the adsorbent of the present invention is used in combination with other adsorbents such as zeolite, titanate, barium silicate, crystalline silicotitanate having a Ti / Si ratio of 2: 1, apatite, activated carbon and the like. I can do it.
  • the adsorbent according to the present invention can also be used as, for example, a metal ion adsorbent for tap water.
  • X-ray diffraction Bruker D8 AdvanceS was used. Cu-K ⁇ 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 Cs and Sr adsorption tests were performed with a Cs measurement wavelength of 697.327 nm and a Sr measurement wavelength of 216.596 nm.
  • Standard samples used were Cs: 100 ppm, 50 ppm and 10 ppm aqueous solutions containing 0.3% NaCl, and Sr: 100 ppm, 10 ppm and 1 ppm aqueous solutions containing 0.3% NaCl.
  • XRF fluorescent X-ray apparatus (device name: ZSX100e, tube: Rh (4 kW), atmosphere: vacuum, analysis window: Be (30 ⁇ m), measurement mode: SQX analysis (EZ scan), measurement diameter: 30 mm ⁇ , (stock) ) All elements were measured with Rigaku. The sample for measurement was obtained by putting in a suitable container (aluminum ring or the like), sandwiching with a die, and pelletizing by applying a pressure of 10 MPa with a press.
  • -BET specific surface area Determined by the BET one-point method using Flowsorb II 2300 manufactured by Shimadzu Corporation as a measuring device.
  • Simulated seawater is composed of NaCl (99.5%): 3.0151 g, SrCl ⁇ 6H 2 O (99%): 0.3074 g, CsNO 3 (99%): 0.1481 g, 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% caustic potash 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 titanium tetrachloride aqueous solution was continuously added over 30 minutes with a peristaltic 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.
  • Example 2 (1) First Step 3 No. 3 sodium silicate 60 g, caustic soda aqueous solution 224.3 g, 85% caustic potassium 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 titanium tetrachloride aqueous solution was continuously added over 0.5 hour with a peristaltic pump to produce a mixed gel. The mixed gel was aged by standing at room temperature (25 ° C.) for 1 hour after the addition of the aqueous titanium tetrachloride solution.
  • Example 3 In Example 2, the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 150 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 ⁇ m, dried, and classified to obtain a granular material having a particle size of 300 ⁇ m to 600 ⁇ m.
  • Example 4 In Example 2, the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 160 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 ⁇ m, dried, and classified to obtain a granular material having a particle size of 300 ⁇ m to 600 ⁇ m.
  • Example 2 the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 170 ° C. for 96 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 ⁇ m, dried, and classified to obtain a granular material having a particle size of 300 ⁇ m to 600 ⁇ m.
  • 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: The molar ratio was 7.30, A 2 O / SiO 2 molar ratio: 1.56, Na 2 O equivalent concentration: 3.22%.
  • the obtained granular material is the main phase Na 4 Ti 4 Si 3 O 16 .nH 2 O, and Na 4 Ti 9 O 20 .mH 2 O is detected. It was confirmed to be a mixture of crystalline silicotitanate and the titanate.
  • the ratio of the height of MP derived from Na 4 Ti 9 O 20 ⁇ 5 to 7H 2 O observed in the range was 38.5%.
  • 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.

Abstract

The present invention provides an adsorption agent that comprises crystalline silicotitanate, has a Ti/Si ratio of 4:3, and is useful for adsorbing metal ions, particularly for adsorbing cesium in seawater, as well as for adsorbing strontium. The present invention is a metal ion adsorption agent, comprising crystalline silicotitanate represented by the general formula A4Ti4Si3O16∙nH2O (where A is an alkali metal selected from Na and K, and n is a number from 0 to 8), in which the X-ray diffraction analysis half-width value of the main peak at which 2θ is 10° to 13° is 1.0° or less, and the BET specific surface area is 100 m2/g.

Description

金属イオン吸着剤Metal ion adsorbent
　本発明は、金属イオンの吸着剤、特に海水中のセシウム又はストロンチウムを選択的にかつ効率的に分離・回収することに好適に用い得る結晶性シリコチタネートを含有する吸着剤に関する。 The present invention relates to an adsorbent for metal ions, particularly an adsorbent containing crystalline silicotitanate that can be suitably used for selectively and efficiently separating and recovering cesium or strontium in seawater.
　従来、放射性物質を含む排水の処理技術としては共沈処理が知られている（下記特許文献１参照）。しかし、水溶性である放射性セシウム及び放射性ストロンチウムについては、前記共沈処理は有効ではなく、現在、ゼオライトなどの無機系吸着剤による吸着除去が行われている（下記特許文献２参照）。 Conventionally, coprecipitation treatment is known as a treatment technique for wastewater containing radioactive substances (see Patent Document 1 below). However, for radioactive cesium and radioactive strontium that are water-soluble, the coprecipitation treatment is not effective, and at present, adsorption removal by an inorganic adsorbent such as zeolite is performed (see Patent Document 2 below).
　しかしながら、海水中に放射性セシウム及び放射性ストロンチウムが流出した場合においては、海水成分のナトリウム濃度の増加はセシウムと吸着剤とのイオン交換反応を抑制する方向に作用する（下記非特許文献１参照）といった問題が知られている。 However, when radioactive cesium and radioactive strontium flow into seawater, an increase in the sodium concentration of seawater components acts to suppress the ion exchange reaction between cesium and the adsorbent (see Non-Patent Document 1 below). The problem is known.
　セシウム及び／又はストロンチウムの吸着性についてこれまでに研究されている無機系吸着剤の一つとして、結晶性シリコチタネートが挙げられる。結晶性シリコチタネートは、Ｔｉ／Ｓｉ比が１：１のもの、５：１２のもの、２：１のもの等、複数種類の組成のものが知られているが、その他に、Ｔｉ／Ｓｉ比が４：３である結晶性シリコチタネートが存在することが知られている。非特許文献２には、Ｔｉ源としてＴｉ（ＯＥＴ）4というアルコキシドを用い、Ｓｉ源としてコロイダルシリカを用いて水熱処理により製造される製造物３Ｂ及び３Ｃは、そのＸ線回折パターンから、３次元的な８員環構造を有していること、この構造の結晶性シリコチタネートは、理想的にはＭ4Ｔｉ4Ｓｉ3Ｏ16（ＭはＮａ、Ｋ等）で表される組成を有することを報告し、この構造の結晶性シリコチタネートにＧｒａｃｅ　ｔｉｔａｎｉｕｍ　ｓｉｌｉｃａｔｅ（ＧＴＳ－１）と名付けている。また、非特許文献３にはＴｉ／Ｓｉ比が４：３である結晶性シリコチタネートを、Ｔｉ源として四塩化チタンを含有し、Ｓｉ源として高分散ＳｉＯ2粉末を含有する混合溶液に水熱処理を施すことにより製造した旨が記載されている。同文献には、合成した結晶性シリコチタネートが、ストロンチウムイオン交換能を有する旨が記載されている。
　また、本発明者らは、先に、下記特許文献３で、ケイ酸源と、ナトリウム化合物及び／又はカリウム化合物と、四塩化チタンと、水とを添加して混合ゲルを得た後、得られた混合ゲルを水熱反応させることで、Ｔｉ／Ｓｉのモル比が４／３である結晶性シリコチタネートを含む海水からのセシウム及びストロンチウムの吸着除去に有用な吸着剤を提案した。 Crystalline silicotitanate is one of the inorganic adsorbents studied so far for the adsorption of cesium and / or strontium. Crystalline silicotitanates are known to have a plurality of types of compositions such as those with a Ti / Si ratio of 1: 1, 5:12, and 2: 1. It is known that there is crystalline silicotitanate in which is 4: 3. In 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 are three-dimensional from the X-ray diffraction pattern. It has a typical 8-membered ring structure, and the crystalline silicotitanate having this structure ideally has a composition represented by M 4 Ti 4 Si 3 O 16 (M is Na, K, etc.). The crystalline silicotitanate having this structure is named Grace titanium silicate (GTS-1). Non-Patent Document 3 discloses a hydrothermal treatment of a crystalline silicotitanate having a Ti / Si ratio of 4: 3, titanium tetrachloride as a Ti source, and a highly dispersed SiO 2 powder as a Si source. The fact that it was manufactured by applying is described. This document describes that the synthesized crystalline silicotitanate has strontium ion exchange capacity.
In addition, the inventors previously obtained a mixed gel by adding a silicic acid source, a sodium compound and / or potassium compound, titanium tetrachloride, and water in Patent Document 3 below, and then obtaining the mixed gel. The adsorbent useful for adsorption removal of cesium and strontium from seawater containing crystalline silicotitanate having a Ti / Si molar ratio of 4/3 was proposed by hydrothermal reaction of the resulting mixed gel.
特開昭６２－２６６４９９号公報Japanese Patent Laid-Open No. Sho 62-266499 特開２０１３－５７５９９号公報JP 2013-57599 A 特開２０１５－１８８７８２号公報Japanese Patent Laying-Open No. 2015-188782
　特許文献３では、ケイ酸源と、ナトリウム化合物及び／又はカリウム化合物と、四塩化チタンと、水とを添加して混合ゲルを得た後、得られた混合ゲルを水熱反応させることで、一気にＴｉ／Ｓｉのモル比が４／３である結晶性シリコチタネートとチタン酸塩との混合物を製造し、これを吸着剤として用いている。このため、結晶性シリコチタネートとチタン酸塩の配合割合を管理することが難しいと言う問題がある。
　また、Ｔｉ/Ｓｉ比が４：３である結晶性シリコチタネートを単独で用いた場合には、特にストロンチウムの吸着能が劣り、更なるストロンチウムの吸着性能の向上が求められている。 In patent document 3, after adding a silicic acid source, a sodium compound and / or potassium compound, titanium tetrachloride, and water to obtain a mixed gel, the resulting 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. For this reason, there exists a problem that it is difficult to manage the compounding ratio of crystalline silicotitanate and titanate.
Further, when a crystalline silicotitanate 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 demanded.
　したがって本発明の課題は、金属イオンの吸着、特に海水中においてもセシウムの吸着、更にはストロンチウムの吸着にも有効なＴｉ/Ｓｉ比が４：３である結晶性シリコチタネートからなる吸着剤を提供することにある。 Therefore, an object of the present invention is to provide an adsorbent comprising a crystalline silicotitanate having a Ti / Si ratio of 4: 3, which is effective for adsorption of metal ions, particularly cesium even in seawater, and even strontium. There is to do.
　本発明者は、上記実情に鑑み鋭意研究を重ねた結果、Ｘ線回折分析において、２θ＝１０°以上１３°以下のメーンピークの半値幅及びＢＥＴ比表面積が特定範囲にある一般式；Ａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、Ａは、Ｎａ及びＫから選ばれるアルカリ金属を示す。式中、ｎは０～８を示す。）で表される結晶性シリコチタネートは、特にセシウムとストロンチウムの吸着能が優れたものになることを見出し、本発明を完成するに到った。 As a result of intensive studies in view of the above circumstances, the present inventor, as a result of X-ray diffraction analysis, a general formula in which the half width of the main peak and the BET specific surface area of 2θ = 10 ° to 13 ° are in a specific range; A 4 The crystalline silicotitanate represented by Ti 4 Si 3 O 16 .nH 2 O (wherein A represents an alkali metal selected from Na and K. In the formula, n represents 0 to 8). In particular, the inventors have found that the adsorption ability of cesium and strontium is excellent, and have completed the present invention.
　即ち、本発明が提供しよとする吸着剤は、金属イオンの吸着剤であって、Ｘ線回折分析において、２θ＝１０°以上１３°以下のメーンピークの半値幅が１．０°以下であり、ＢＥＴ比表面積が１００ｍ2／ｇ以上である一般式；Ａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、Ａは、Ｎａ及びＫから選ばれるアルカリ金属を示す。式中、ｎは０～８を示す。）で表される結晶性シリコチタネートからなることを特徴とするものである。 That is, the adsorbent to be provided by the present invention is an adsorbent for metal ions, and in X-ray diffraction analysis, the half width of the main peak of 2θ = 10 ° to 13 ° is 1.0 ° or less. And a general formula having a BET specific surface area of 100 m 2 / g or more; A 4 Ti 4 Si 3 O 16 .nH 2 O (wherein A represents an alkali metal selected from Na and K. In the formula, n Is a crystalline silicotitanate represented by the following formula: 0-8.
　本発明によれば、特に海水においてもセシウム及びストロンチウムの吸着除去特性に優れた結晶性シリコチタネートを含有する吸着剤を提供することが出来る。 According to the present invention, it is possible to provide an adsorbent containing crystalline silicotitanate having excellent cesium and strontium adsorption / removal characteristics, particularly in seawater.
図１は、実施例２で得られた結晶性シリコチタネートを含む吸着剤のＸ線回折チャートである。1 is an X-ray diffraction chart of an adsorbent containing crystalline silicotitanate obtained in Example 2. FIG. 図２は、参考例２で得られた結晶性シリコチタネートを含む吸着剤のＸ線回折チャートである。FIG. 2 is an X-ray diffraction chart of the adsorbent containing crystalline silicotitanate obtained in Reference Example 2.
　以下、本発明を好ましい実施形態に基づき説明する。
　本発明に係る吸着剤は金属イオンを吸着する吸着剤である。本発明の吸着剤が吸着対象する金属イオンとしては、例えば、セシウム、ストロンチウム、アンチモン、鉛、亜鉛、水銀、銅、カドニウム、水銀等の金属イオンが挙げられ、特に海水中のセシウムの吸着、更にはストロンチウムの吸着に対して優れた吸着能を有する。 Hereinafter, the present invention will be described based on preferred embodiments.
The adsorbent according to the present invention is an adsorbent that adsorbs metal ions. Examples of the metal ions to be adsorbed by the adsorbent of the present invention include metal ions such as cesium, strontium, antimony, lead, zinc, mercury, copper, cadmium, and mercury, and in particular, adsorption of cesium in seawater, Has excellent adsorption capacity for strontium adsorption.
　本発明に係る吸着剤に含有させる結晶性シリコチタネートは、一般式；Ａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、Ａは、Ｎａ及びＫから選ばれるアルカリ金属を示す。式中、ｎは０～８を示す。）で表される。 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 (wherein A represents an alkali metal selected from Na and K. In the formula, , N represents 0 to 8).
　なお、一般式；Ａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、Ａは、Ｎａ及びＫから選ばれるアルカリ金属を示す。）で表される結晶性シリコチタネート（以下、単に「結晶性シリコチタネート」と呼ぶことがある）において、ＡがＮａ及びＫを含む場合の詳細な結晶性シリコチタネートの組成については定かではないが、一般式；Ｎａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ及びＫ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏを含むか、或いは（ＮａxＫ(1-x)）4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、ｘは０超１未満）であると本発明者らは推測している。 The crystalline silicotitanate represented by the general formula: A 4 Ti 4 Si 3 O 16 .nH 2 O (wherein A represents an alkali metal selected from Na and K) (hereinafter simply referred to as “crystal”). In the case where A contains Na and K, the detailed composition of crystalline silicotitanate 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 or containing 2 O, or (Na x K (1-x )) in 4 Ti 4 Si 3 O 16 · nH 2 O ( wherein, x is less than 0 ultra 1 The present inventors presume that.
　本発明において、結晶性シリコチタネートの式中のＡは、Ｎａ及びＫから選ばれるアルカリ金属である。本発明の吸着剤においてＡは、Ｎａ及びＫの両方を含むものが好ましく、Ｋの含有量は、Ａ2Ｏ（Ｎａ2Ｏ＋Ｋ2Ｏ）換算とＫ2Ｏ換算のモル比（Ｋ2Ｏ／Ａ2Ｏ）で好ましくは０より大きく０．５以下、より好ましくは０．０５以上０．４以下であることが、特にセシウム及びストロンチウムの吸着性能が高くなる観点から好ましい。 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, it is preferable that A contains both Na and K, and the K content is a molar ratio (K 2 O / K) in terms of A 2 O (Na 2 O + K 2 O) and K 2 O. A 2 O) is preferably more 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.
　本発明に係る吸着剤に含有させる結晶性シリコチタネートは、該結晶性シリコチタネートを線源としてＣｕ－Ｋα線を用いてＸ線回折測定したときに、結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅が１．０°以下、好ましくは０．２～０．９°、特に好ましくは０．２～０．５°、更に好ましくは０．３～０．５０°であることを一つの特徴とする。 The crystalline silicotitanate contained in the adsorbent according to the present invention is obtained by measuring X-ray diffraction using Cu-Kα rays with the crystalline silicotitanate as a radiation source. The half-value width of a diffraction peak (main peak (B1)) of not more than 1.0 ° is 1.0 ° or less, preferably 0.2 to 0.9 °, particularly preferably 0.2 to 0.5 °, and more preferably 0.00. One characteristic is that the angle is 3 to 0.50 °.
　本発明者らは、金属イオンの吸着能には、吸着剤に含有させる結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅が関係し、該回折ピークの半値幅が、非特許文献３に比べて小さい特定の範囲とすることで非特許文献３に比べて、特にセシウム及びストロンチウムの吸着能が向上することを見出した。 The inventors of the present invention relate to the adsorption capacity of metal ions, and the half width of the diffraction peak (main peak (B1)) of 2θ = 10 ° to 13 ° of the crystalline silicotitanate contained in the adsorbent, It has been found that the adsorption capacity 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.
　また、本発明に係る吸着剤は、上記特性を有することに加えて、ＢＥＴ比表面積が１００ｍ2／ｇ以上、好ましくは１００～２００ｍ2／ｇ、特に好ましくは１００～１８０ｍ２／ｇであることも一つの特徴である。
　この理由は、ＢＥＴ比表面積が１００ｍ2／ｇ未満では、特にストロンチウムの吸着性能が劣り、好ましくないからである。 In addition to having the above properties, the adsorbent according to the present invention has a BET specific surface area of 100 m 2 / g or more, preferably 100 to 200 m 2 / g, particularly preferably 100 to 180 m 2 / g. Is another feature.
The reason for this is that when the BET specific surface area is less than 100 m 2 / g, the adsorption performance of strontium is particularly poor, which is not preferable.
　本発明の吸着剤の形態としては、粒状体であることが好ましい。粒状体としては、例えば粉末状、顆粒状、顆粒以外の成型体（球状、円柱状）等を挙げることができ、粉末状又は顆粒状であることが好ましい。 The form of the adsorbent of the present invention is preferably a granular material. Examples of the granular material include a powder, a granule, a molded body other than a granule (spherical, cylindrical), and the like, and a powder or a granule is preferable.
　本発明の吸着剤が粒状体である場合、２００μｍ以上１０００μｍ以下の粒度を有することが好ましい。この粒度の粒状体からなる本発明の吸着剤には、２００μｍよりも細かい粒子が存在しないか或いは存在しても極微量であるため、本発明の吸着剤を吸着塔に充填して通水した場合に、粒子が吸着塔内で詰まる問題を防止することができる。また、粒径が１０００μｍ以下である場合、吸着剤の吸着性能を向上しやすい。 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 granules of this particle size does not have particles finer than 200 μm or is extremely small even if present, the adsorbent of the present invention is packed in an adsorption tower and passed through. In this case, it is possible to prevent the problem that particles are clogged in the adsorption tower. Moreover, when the particle size is 1000 μm or less, it is easy to improve the adsorption performance of the adsorbent.
　具体的には、本発明の吸着剤が粒状体である場合、ＪＩＳ　Ｚ８８０１規格による目開きが２１２μｍの篩と、前記の目開きが１ｍｍの篩とを用いたときに、本発明の吸着剤の９８質量％以上、特に９９質量％以上が目開き１ｍｍの篩を通り且つ９８質量％以上、特に９９質量％以上が目開き２１２μｍの篩を通らないことが好ましい。特に、本発明の吸着剤は、３００μｍ以上６００μｍ以下の粒度を有する粒状体からなることが好ましい。具体的には、ＪＩＳ　Ｚ８８０１規格による目開きが３００μｍの篩と、目開きが６００μｍの篩とを用いたときに、本発明の吸着剤の９８質量％以上、特に９９質量％以上が前記の６００μｍの篩を通り且つ９８質量％以上、特に９９質量％以上が前記の３００μｍの篩を通らないことが好ましい。
　なお、本発明の吸着剤を粒径２００μｍ未満の粉末の形態のものは、不織布に固定された形態等で用いることもできる。 Specifically, when the adsorbent of the present invention is a granular material, when the sieve according to JIS Z8801 standard has a sieve having an opening of 212 μm and the sieve having an aperture of 1 mm, the adsorbent of the present invention It is preferable that 98% by mass or more, particularly 99% by mass or more pass through a sieve having an opening of 1 mm, and 98% by mass or more, particularly 99% by mass or more should not pass through a sieve having an opening of 212 μm. In particular, the adsorbent of the present invention is preferably composed of a granular material having a particle size of 300 μm or more and 600 μm or less. Specifically, when a sieve having an opening of 300 μm according to JIS Z8801 standard and a sieve having an opening of 600 μm are used, 98 mass% or more, particularly 99 mass% or more of the adsorbent of the present invention is the above-mentioned 600 μm. It is preferable that 98% by mass or more, particularly 99% by mass or more, does not pass through the 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 be used in a form fixed to a nonwoven fabric or the like.
　本発明の吸着剤は、例えば、ケイ酸源と、ナトリウム化合物及び／又はカリウム化合物と、四塩化チタンと、水とを混合して、混合ゲルを得る第一工程と、第一工程により得られた混合ゲルを水熱反応させる第二工程とを有し、第一工程において、混合ゲルに含まれるＴｉとＳｉとのモル比がＴｉ／Ｓｉ＝１．２以上１．５以下となるように、ケイ酸源及び四塩化チタンとを添加することにより製造することが出来る。 The adsorbent of the present invention is obtained by, for example, a first step of mixing a silicate source, a sodium compound and / or potassium compound, titanium tetrachloride, and water to obtain a mixed gel, and the first step. 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. It can be produced by adding a silicic acid source and titanium tetrachloride.
　以下、本発明の吸着剤の製造方法について説明する。
　第一工程に係るケイ酸源としては、例えば、ケイ酸ソーダ、ケイ酸カリが挙げられる。また、ケイ酸アルカリ（すなわちケイ酸のアルカリ金属塩）をカチオン交換することにより得られる活性ケイ酸も挙げられる。 Hereinafter, the manufacturing method of the adsorbent of this invention is demonstrated.
Examples of the silicic acid source in the first step include sodium silicate and potassium silicate. Moreover, the active silicic acid obtained by carrying out cation exchange of the alkali silicate (namely, alkali metal salt of silicic acid) is also mentioned.
　活性ケイ酸は、ケイ酸アルカリ水溶液を例えばカチオン交換樹脂に接触させてカチオン交換して得られるものである。ケイ酸アルカリ水溶液の原料としては、通常水ガラス（水ガラス１号～４号等）と呼ばれるケイ酸ナトリウム水溶液が好適に用いられる。このものは比較的安価であり、容易に手に入れることができる。また、Ｎａイオンを嫌う半導体用途では、ケイ酸カリウム水溶液が原料としてふさわしい。固体状のメタケイ酸アルカリを水に溶かしてケイ酸アルカリ水溶液を調製する方法もある。メタケイ酸アルカリは晶析工程を経て製造されるので、不純物の少ないものがある。ケイ酸アルカリ水溶液は、必要に応じて水で希釈して使用する。 Active silicic acid is obtained by cation exchange by bringing an aqueous alkali silicate solution into contact with, for example, a cation exchange resin. As a raw material for the alkali silicate aqueous solution, a sodium silicate aqueous solution usually called water glass (water glass No. 1 to No. 4 etc.) is preferably used. This is relatively inexpensive and can be easily obtained. For semiconductor applications that dislike Na ions, an aqueous potassium silicate solution is suitable as a raw material. There is also a method of preparing an alkali silicate aqueous solution by dissolving solid alkali silicate in water. Alkali metasilicates are produced through a crystallization process, so some of them have few impurities. The aqueous alkali silicate solution is diluted with water as necessary.
　活性ケイ酸を調製するときに使用するカチオン交換樹脂は、公知のものを適宜選択して使用することができ、特に制限されない。ケイ酸アルカリ水溶液とカチオン交換樹脂との接触工程では、例えばケイ酸アルカリ水溶液をシリカが濃度３質量％以上１０質量％以下となるように水に希釈し、次いで、希釈したケイ酸アルカリ水溶液をＨ型強酸性又は弱酸性カチオン交換樹脂に接触させて脱アルカリする。更に必要に応じてＯＨ型強塩基性アニオン交換樹脂に接触させて脱アニオンすることができる。この工程によって、活性ケイ酸水溶液が調製される。ケイ酸アルカリ水溶液とカチオン交換樹脂との接触条件の詳細については、従来、様々な提案が既にあり、本発明ではそれら公知のいかなる接触条件も採用することができる。 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 alkali silicate aqueous solution and the cation exchange resin, for example, the alkali silicate aqueous solution is diluted with water so that the silica has a concentration of 3% by mass or more and 10% by mass or less. Contact with a strong acidic or weakly acidic cation exchange resin to dealkalize. Further, if necessary, it can be deanioned by contacting with an OH type strongly basic anion exchange resin. By this step, an active silicic acid aqueous solution is prepared. Regarding the details of the contact conditions between the aqueous alkali silicate solution and the cation exchange resin, various proposals have already been made, and any known contact conditions can be adopted in the present invention.
　第一工程において用いられるナトリウム化合物としては、例えば、水酸化ナトリウム、炭酸ナトリウム等が挙げられる。これらのナトリウム化合物のうち、炭酸ナトリウムを用いると炭酸ガスが発生するため、そのようなガスの発生がない水酸ナトリウムを用いることが、中和反応を円滑に進める観点から好ましい。 Examples of the sodium compound used in the first step include sodium hydroxide and sodium carbonate. Among these sodium compounds, when sodium carbonate is used, carbon dioxide gas is generated. Therefore, it is preferable to use sodium hydroxide that does not generate such gas from the viewpoint of smoothly promoting the neutralization reaction.
　また、カリウム化合物としては、例えば、水酸化カリウム、炭酸カリウム等が挙げられる。これらのカリウム化合物のうち、炭酸カリウムを用いると炭酸ガスが発生するため、そのようなガスの発生がない水酸化カリウムを用いることが、中和反応を円滑に進める観点から好ましい。 Examples of the potassium compound include potassium hydroxide and potassium carbonate. Among these potassium compounds, when potassium carbonate is used, carbon dioxide gas is generated. Therefore, it is preferable to use potassium hydroxide that does not generate such gas from the viewpoint of smoothly promoting the neutralization reaction.
　第一工程においてナトリウム化合物及びカリウム化合物を用いる場合は、Ｎａ2ＯとＫ2Ｏ換算の合計モル数（Ａ2Ｏ）に対して、Ｋ2Ｏ／Ａ2Ｏのモル比が０より大きく０．５以下であることが好ましく、０．０５以上０．４以下であることがより好ましい。 When a sodium compound and a potassium compound 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) in terms of Na 2 O and K 2 O. Is preferably 0.5 or less, more preferably 0.05 or more and 0.4 or less.
　ケイ酸源及び四塩化チタンの添加量は、混合ゲル中の四塩化チタン由来のＴｉとケイ酸源由来のＳｉとのモル比であるＴｉ／Ｓｉが特定比となる量にする。例えば、非特許文献３においては、チタン源として四塩化チタンを用いているが、ケイ酸源及び四塩化チタンは、Ｔｉ／Ｓｉ比が０．３２となる量で混合溶液に添加されている。これに対し、本製造方法では、Ｔｉ／Ｓｉ比が１．２以上１．５以下となるような量でケイ酸源及び四塩化チタンを添加する。本発明者らが検討した結果、混合ゲル中のＴｉ／Ｓｉ比を前記のモル比範囲に設定することで、結晶性シリコチタネートとして、結晶化度が高く、半値幅及びＢＥＴ比表面積が上記範囲のものが得られやすくなる。 The addition amount of the silicic acid source and titanium tetrachloride 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, has a specific ratio. For example, in Non-Patent Document 3, titanium tetrachloride is used as the titanium source, but the silicate source and titanium tetrachloride are added to the mixed solution in such an amount that the Ti / Si ratio is 0.32. On the other hand, in this manufacturing method, a silicic acid source and titanium tetrachloride are added in such an amount that the Ti / Si ratio is 1.2 or more and 1.5 or less. As a result of the study by the present inventors, by setting the Ti / Si ratio in the mixed gel to the above molar ratio range, as a crystalline silicotitanate, the crystallinity is high, and the full width at half maximum and the BET specific surface area are in the above range. It becomes easy to obtain.
　また、混合ゲルに占めるＳｉＯ2換算のケイ酸源濃度とＴｉＯ2換算の四塩化チタン濃度の総量が２．０質量％以上４０質量％以下であり、かつ混合ゲルに占めるＡ2Ｏ／ＳｉＯ2のモル比＝０．５以上２．５以下となるようにケイ酸源及び四塩化チタンを添加することが望ましい。ここで、ＡはＮａ及びＫを示す。前記範囲内にケイ酸源および四塩化チタンの添加量を調整することで、目的とする結晶性シリコチタネートの収率を満足すべき程度に高めることができる。 Further, the total amount of the SiO 2 equivalent silicic acid source concentration and the TiO 2 equivalent titanium tetrachloride concentration in the mixed gel is 2.0 mass% or more and 40 mass% or less, 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 is 0.5 to 2.5. 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.
　Ａ２Ｏのモル数は、混合ゲル中のナトリウム及びカリウムのイオン数を酸化物換算で表したもの、換言すれば、ナトリウムやカリウム等のアルカリと四塩化チタンとの中和反応により使用されたナトリウムやカリウムの量を除いて求められるものである。 The number of moles of A 2 O is the number of ions of sodium and potassium in the mixed gel expressed in terms of oxide, in other words, used by the neutralization reaction between alkali such as sodium or potassium and titanium tetrachloride. It is obtained excluding the amount of sodium and potassium.
　第一工程において用いられる四塩化チタンは、工業的に入手可能なものであれば、特に制限なく用いることができる。 The titanium tetrachloride used in the first step can be used without particular limitation as long as it is industrially available.
　第一工程において、ケイ酸源、ナトリウム化合物、カリウム化合物、及び四塩化チタンは、それぞれ水溶液の形態で反応系に添加することができる。場合によっては固体の形態で添加することができる。更に第一工程では、得られた混合ゲルに対して、必要であれば純水を用いて該混合ゲルの濃度を調整することができる。 In the first step, the silicic acid source, sodium compound, potassium compound, and titanium tetrachloride can be added to the reaction system in the form of an aqueous solution, respectively. In some cases, it can be added in solid form. Further, in the first step, the concentration of the mixed gel can be adjusted using pure water if necessary for the obtained mixed gel.
　第一工程において、ケイ酸源、ナトリウム化合物、カリウム化合物、及び四塩化チタンは、種々の添加順序で添加することができる。例えば（１）ケイ酸源、ナトリウム化合物及び／又はカリウム化合物、並びに水を混合したものに、四塩化チタンを添加することにより混合ゲルを得ることができる（この添加順序のことを、以下、単に「（１）の実施」ということもある。）。この（１）の実施は、四塩化チタンから塩素の発生をおさえる点で好ましい。 In the first step, the silicate source, sodium compound, potassium compound, and 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 silicate source, a sodium compound and / or a potassium compound, and water (this addition order is simply referred to as “additional order” hereinafter). (It may be called “Implementation of (1)”.) The implementation of (1) is preferable in that the generation of chlorine from titanium tetrachloride is suppressed.
　第一工程において別の添加順序として、（２）ケイ酸アルカリをカチオン交換することによって得られる活性ケイ酸（以下、単に「活性ケイ酸」ということもある。）水溶液と四塩化チタンと水とを混合したものに、ナトリウム化合物及び／又はカリウム化合物を添加する、という態様を採用することができる。この添加順序を採用しても、（１）の実施形態と同様に混合ゲルを得ることができる（この添加順序のことを、以下、単に「（２）の実施」ということがある。）。四塩化チタンはその水溶液の形態又は固体の形態で添加することができる。同様に、ナトリウム化合物及びカリウム化合物も、その水溶液の形態又は固体の形態で添加することができる。 As another order of addition in the first step, (2) an aqueous solution of activated silicic acid (hereinafter sometimes simply referred to as “activated silicic acid”) obtained by cation exchange of alkali silicate, titanium tetrachloride and water, A mode in which a sodium compound and / or a potassium compound is added to a mixture of these can be employed. Even if this order of addition is adopted, a mixed gel can be obtained in the same manner as in the embodiment of (1) (this order of addition may hereinafter be simply referred to as “execution of (2)”). Titanium tetrachloride can be added in the form of an aqueous solution or solid form. Similarly, sodium compounds and potassium compounds can also be added in the form of their aqueous solutions or solid forms.
　（１）及び（２）の実施において、ナトリウム化合物及び／又はカリウム化合物は、混合ゲル中のナトリウム及びカリウムの合計濃度（Ａ2Ｏ濃度）がＮａ2Ｏ換算で０．５質量％以上１５．０質量％以下、特に０．７質量％以上１３質量％以下となるように添加されることが好ましい。混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算質量及び混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算の濃度（以下「ナトリウム及ぶカリウムの合計濃度（第一工程でカリウム化合物を用いない場合、ナトリウム濃度」と言う）は、以下の式で計算される。
　
混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算質量（ｇ）＝（前記のＡのモル数ー四塩化チタン由来の塩化物イオンのモル数）×０．５×Ｎａ2Ｏ分子量
 
混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算の濃度（質量％）＝混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算質量／｛混合ゲル中の水分量＋混合ゲル中におけるナトリウム及びカリウムの合計のＮａ2Ｏ換算質量｝×１００ In the implementation of (1) and (2), the sodium compound and / or potassium compound has a total concentration of sodium and potassium (A 2 O concentration) in the mixed gel of 0.5% by mass or more in terms of Na 2 O. It is preferable to add so that it may become 0 mass% or less, especially 0.7 mass% or more and 13 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 referred to as “total concentration of sodium and potassium (the potassium compound is used in the first step) If not, it is referred to as “sodium concentration”).

Total Na 2 O equivalent mass (g) of sodium and potassium in the mixed gel = (number of moles of A above−number of moles of chloride ions derived from titanium tetrachloride) × 0.5 × Na 2 O molecular weight
Concentration (mass%) of total sodium and potassium in mixed gel in terms of Na 2 O = total mass of sodium and potassium in mixed gel converted to Na 2 O / {water content in mixed gel + sodium in mixed gel And potassium total Na 2 O equivalent mass} × 100
　ケイ酸源の選択と混合ゲル中のナトリウム及びカリウムの合計濃度の調整を組み合わせることにより、Ｔｉ：Ｓｉのモル比が４：３の結晶性シリコチタネート以外の結晶性シリコチタネートの生成を抑制することができる。ケイ酸源としてケイ酸ソーダ又はケイ酸カリを用いた場合、混合ゲル中のナトリウム及びカリウムの合計濃度をＮａ2Ｏ換算で２．０質量％以上とすることで、Ｔｉ：Ｓｉのモル比が５：１２の結晶性シリコチタネートの生成を効果的に抑制することが可能となり、一方、混合ゲル中のナトリウム及びカリウムの合計濃度をＮａ2Ｏ換算で６．０質量％以下とすることで、Ｔｉ：Ｓｉのモル比が１：１の結晶性シリコチタネートの生成を効果的に抑制することが可能となる。また、ケイ酸源としてケイ酸アルカリをカチオン交換することにより得られる活性ケイ酸を用いた場合、Ｎａ2Ｏ換算で１．０質量％以上とすることで、Ｔｉ：Ｓｉのモル比が５：１２の結晶性シリコチタネートの生成を効果的に抑制することが可能となり、一方、混合ゲル中のナトリウム及びカリウムの合計濃度をＮａ2Ｏ換算で６．０質量％以下とすることで、Ｔｉ：Ｓｉのモル比が１：１の結晶性シリコチタネートの生成を効果的に抑制することが可能となる。 Suppressing the formation of crystalline silicotitanate other than crystalline silicotitanate with a molar ratio of Ti: Si of 4: 3 by combining the selection of the silicate source with the adjustment of the total concentration of sodium and potassium in the mixed gel Can do. When sodium silicate or potassium silicate is used as the silicic acid source, the molar ratio of Ti: Si is set to 2.0% by mass or more in terms of Na 2 O in terms of the total concentration of sodium and potassium in the mixed gel. It becomes possible to effectively suppress the formation 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 becomes possible to effectively suppress the formation of crystalline silicotitanate having a molar ratio of Ti: Si of 1: 1. Also, when using the active silicic acid obtained by the alkali silicate to cation exchange as silicic acid source, by setting more than 1.0 mass% in terms of Na 2 O, Ti: molar ratio of Si 5: It is possible to effectively suppress the formation of 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, so that Ti: Production of crystalline silicotitanate having a Si molar ratio of 1: 1 can be effectively suppressed.
　なお、ケイ酸源としてケイ酸ナトリウムを用いた場合は、ケイ酸ナトリウム中のナトリウム成分は、同時に混合ゲル中のナトリウム源となる。したがって、ここで言う「混合ゲル中におけるナトリウムのＮａ2Ｏ換算質量（ｇ）」とは混合ゲル中のすべてのナトリウム成分の和として計数される。同様に、「混合ゲル中におけるカリウムのＮａ2Ｏ換算質量（ｇ）」も混合ゲル中のすべてのカリウム成分の和として計数される。 When sodium silicate is used as the silicate source, the sodium component in the sodium silicate simultaneously becomes the sodium source in the mixed gel. Therefore, the “Na 2 O equivalent mass (g) of sodium in the mixed gel” mentioned here is counted as the sum of all sodium components in the mixed gel. Similarly, “Na 2 O equivalent mass (g) of potassium in the mixed gel” is also counted as the sum of all potassium components in the mixed gel.
　（１）及び（２）の実施において、四塩化チタンの添加は、均一なゲルを得るため一定の時間をかけて、四塩化チタン水溶液として段階的又は連続的に行うことが望ましい。このため、四塩化チタンの添加にはペリスタポンプ等を好適に用いることができる。 In the implementation of (1) and (2), it is desirable to add titanium tetrachloride stepwise or continuously as an aqueous titanium tetrachloride solution over a certain period of time in order to obtain a uniform gel. For this reason, a peristaltic pump etc. can be used suitably for addition of titanium tetrachloride.
　第一工程により得られた混合ゲルは、後述する第二工程である水熱反応を行う前に、０．１時間以上５時間以下の時間にわたり、１０℃以上１００℃以下で熟成を行うことが、均一な生成物を得る点で好ましい。熟成工程は、例えば静置状態で行ってもよく、あるいはラインミキサーなどを用いた撹拌状態で行ってもよい。 The mixed gel obtained in the first step may be aged at 10 ° C. or higher and 100 ° C. or lower for a time period of 0.1 hour or longer and 5 hours or shorter before performing a hydrothermal reaction which is the second step described later. From the viewpoint of obtaining a uniform product. 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.
　本発明においては第一工程において得られた前記混合ゲルを、第二工程である水熱反応に付して結晶性シリコチタネートを得る。水熱反応としては、結晶性シリコチタネートが合成できる条件であれば、いかなる条件であってもよく制限されない。通常、オートクレーブ中で好ましくは１００℃以上２００℃以下、更に好ましくは１２０℃以上１８０℃以下の温度において、好ましくは６時間以上９０時間以下、更に好ましくは１２時間以上８０時間以下の時間にわたって、加圧下に反応させる。反応時間は、合成装置のスケールに応じて選定できる。 In the present invention, the mixed gel obtained in the first step is subjected to a hydrothermal reaction as the second step to obtain crystalline silicotitanate. The hydrothermal reaction is not particularly limited as long as the crystalline silicotitanate can be synthesized. Usually, in an autoclave, the temperature is 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 longer and 90 hours or shorter, more preferably 12 hours or longer and 80 hours or shorter. React under pressure. The reaction time can be selected according to the scale of the synthesizer.
　前記第二工程で得られた結晶性シリコチタネートを含有する含水物は乾燥させ、得られた乾燥物を必要により解砕又は粉砕して粉末状（粒状を含む）とすることができる。また、結晶性シリコチタネートを含有する含水物を複数の開孔が形成された開孔部材から押出成形して棒状成形体を得、得られた該棒状成形体を乾燥させて柱状にしてもよいし、乾燥させた該棒状成形体を球状に成形したり、解砕又は粉砕して粒子状としてもよい。 The water-containing product containing the crystalline silicotitanate obtained in the second step can be dried, and the obtained dried product can be pulverized or pulverized as necessary to form a powder (including granules). Alternatively, a hydrous material containing crystalline silicotitanate may be extruded from an aperture member in which a plurality of apertures are formed to obtain a rod-shaped molded body, and the obtained rod-shaped molded body may be dried to form a columnar shape. The dried rod-shaped molded body may be formed into a spherical shape, or may be pulverized or pulverized into particles.
　開孔部材に形成された孔の形状としては、円形、三角形、多角形、環形等を挙げることができる。開孔の真円換算径は０．１ｍｍ以上１０ｍｍ以下が好ましく、０．３ｍｍ以上５ｍｍ以下がより好ましい。ここでいう真円換算径は、孔一つの面積を円面積とした場合の該面積から算出される円の直径である。押出成形後の乾燥温度は例えば例えば５０℃以上２００℃以下とすることができる。また乾燥時間は１時間以上１２０時間以下とすることができる。 As the shape of the hole formed in the opening member, a circle, a triangle, a polygon, an annulus, and the like can be given. The true circle equivalent diameter of the opening 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 true circle equivalent diameter here is a diameter of a circle calculated from the area when the area of one hole is a circle area. The drying temperature after extrusion molding can be, for example, 50 ° C. or more and 200 ° C. or less. The drying time can be 1 hour or more and 120 hours or less.
　乾燥させた棒状成形体は、そのままでも吸着剤として用いることができるし、軽くほぐして用いてもよい。また乾燥後の棒状成形体は粉砕して用いてもよい。これら各種の方法で得られた結晶性シリコチタネートを含有する粉末状のものは、更に分級してから吸着剤として用いることが、セシウム及び／又はストロンチウムの吸着効率を高める等の観点から好ましい。分級は、例えばＪＩＳＺ８８０１－１に規定する公称目開きが１０００μｍ以下、特に７１０μｍ以下の第１の篩を用いることが好ましい。また前記の公称目開きが１００μｍ以上、特に３００μｍ以上の第２の篩を用いて行うことも好ましい。更に、これら第１及び第２の篩を用いて行うことが好ましい。 The dried rod-shaped molded body can be used as an adsorbent as it is, or it can be used after lightly loosening. Moreover, you may grind | pulverize and use the rod-shaped molded object after drying. From the viewpoint of increasing the adsorption efficiency of cesium and / or strontium, it is preferable that the powdery material containing crystalline silicotitanate obtained by these various methods is further classified and then used as an adsorbent. For the classification, for example, it is preferable to use a first sieve having a nominal opening prescribed in JISZ8801-1 of 1000 μm or less, particularly 710 μm or less. Moreover, it is also preferable to carry out using the 2nd sieve whose said nominal opening is 100 micrometers or more, especially 300 micrometers or more. Furthermore, it is preferable to carry out using these first and second sieves.
　上記した製造方法において、第一工程のナトリウム化合物とカリウム化合物の配合割合や第二工程の反応温度及び反応時間を適宜選択することで、得られる結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅の値とＢＥＴ比表面積の範囲を本発明に係る範囲に制御することが出来る。
　即ち、第一工程においてナトリウム化合物及びカリウム化合物の配合割合が、Ｎａ2ＯとＫ2Ｏ換算の合計モル数（Ａ２Ｏ）に対して、Ｋ2Ｏ／Ａ２Ｏのモル比が０超０．５以下、好ましくは０．０５以上０．４以下では、得られる結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅の値が小さくなる傾向がある。
　また、第二工程の反応温度が低いほど、また、反応時間を短いほど得られる結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅の値が大きくなる一方で、ＢＥＴ比表面積も大きくなる傾向がある。 In the manufacturing method described above, 2θ = 10 ° to 13 ° of the crystalline silicotitanate obtained by appropriately selecting the mixing ratio of the sodium compound and potassium compound in the first step and the reaction temperature and reaction time in the second step. The value of the half width of the diffraction peak (main peak (B1)) and the range of the BET specific surface area can be controlled within the range according to the present invention.
That is, in the first step, the compounding 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. If it is 0.5 or less, preferably 0.05 or more and 0.4 or less, the half-width value of the diffraction peak (main peak (B1)) of 2θ = 10 ° or more and 13 ° or less of the crystalline silicon titanate obtained becomes small. Tend.
In addition, the lower the reaction temperature in the second step and the shorter the reaction time, the half-width value of the diffraction peak (main peak (B1)) of 2θ = 10 ° to 13 ° of the crystalline silicotitanate obtained. While increasing, the BET specific surface area tends to increase.
　本発明に係る結晶性シリコチタネートからなる特徴とする吸着剤は、必要に応じて常法に従い成形加工し、それによって得られた成形体を金属イオンの吸着剤として用いてもよい。 The characteristic adsorbent comprising the crystalline silicotitanate according to the present invention may be molded according to a conventional method if necessary, and the resulting molded product may be used as an adsorbent for metal ions.
　前記の成形加工としては、例えば結晶性シリコチタネートからなる粉末状の吸着剤を顆粒状に成型するための造粒加工や結晶性シリコチタネートからなる粉末状の吸着剤をスラリー化して塩化カルシウム等の硬化剤を含む液中に滴下して結晶性シリコチタネートからなる粉末状の吸着剤をカプセル化する方法、樹脂芯材の表面に結晶性シリコチタネートからなる粉末状の吸着剤を添着被覆処理する方法、天然繊維または合成繊維で形成された不織布の表面及び／又は内部に結晶性シリコチタネートからなる粉末状の吸着剤を付着させて固定化してシート状にする方法などを挙げることができる。造粒加工の方法としては、公知の方法が挙げられ、例えば攪拌混合造粒、転動造粒、押し出し造粒、破砕造粒、流動層造粒、噴霧乾燥造粒（スプレードライ）、圧縮造粒等を挙げることができる。造粒の過程において必要に応じバインダーや溶媒を添加、混合してもよい。バインダーとしては、公知のもの、例えばポリビニルアルコール、ポリエチレンオキサイド、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、ヒドロキシプロピルメチルセルロース、ヒドロキシエチルメチルセルロース、カルボキシメチルセルロース、ヒドロキシプロピルメチルセルロース、メチルセルロース、エチルセルロース、デンプン、コーンスターチ、糖蜜、乳糖、ゼラチン、デキストリン、アラビアゴム、アルギン酸、ポリアクリル酸、グリセリン、ポリエチレングリコール、ポリビニルピロリドン等を挙げることができる。溶媒としては水性溶媒や有機溶媒等各種のものを用いることができる。 As the molding process, for example, a powdery adsorbent composed of crystalline silicotitanate is granulated to form a granule or a powdered adsorbent composed of crystalline silicotitanate is slurried to obtain calcium chloride or the like. A method of encapsulating a powdery adsorbent composed of crystalline silicotitanate by dripping into a liquid containing a curing agent, and a method of applying a powder adsorbent composed of crystalline silicotitanate to the surface of a resin core Examples thereof include a method of adhering a powdery adsorbent made of crystalline silicotitanate to the surface and / or inside of a nonwoven fabric formed of natural fibers or synthetic fibers and fixing it to form a sheet. Examples of the granulation 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. A grain etc. can be mentioned. In the granulation process, a binder and a solvent may be added and mixed as necessary. As the binder, known ones such as polyvinyl alcohol, polyethylene oxide, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, starch, cornstarch, molasses, 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.
　また、結晶性シリコチタネートを含有する含水状態のものを造粒加工した顆粒状のものは、放射性物質吸着剤を充填してなる吸着容器及び吸着塔を有する水処理システムの吸着剤として好適に使用することが出来る。 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 material adsorbent. I can do it.
　この場合、結晶性シリコチタネートを含有する含水状態のものを造粒加工して得られる顆粒状のものの形状や大きさは、吸着容器や充填塔に充填して、金属イオンを含む処理水を通水するのに適応するようにその形状及び大きさを適宜調整することが好ましい。 In this case, the shape and size of the granular material obtained by granulating the water-containing material containing crystalline silicotitanate is filled in an adsorption vessel or a packed tower, and treated water containing metal ions is passed through. It is preferable to appropriately adjust the shape and size so as to adapt to watering.
　また、結晶性シリコチタネートを含有する含水状態のものを造粒加工した顆粒状のものは、更に磁性粒子を含有させることにより、金属イオンを含む水から磁気分離で回収可能な吸着剤として使用することが出来る。磁性粒子としては、例えば鉄、ニッケル、コバルト等の金属またはこれらを主成分とする磁性合金の粉末、四三酸化鉄、三二酸化鉄、コバルト添加酸化鉄、バリウムフェライト、ストロンチウムフェライト等の金属酸化物系磁性体の粉末が挙げられる。 In addition, the granular material obtained by granulating the water-containing material containing crystalline silicotitanate is used as an adsorbent that can be recovered by magnetic separation from water containing metal ions by further containing magnetic particles. I can do it. Examples of magnetic particles include metals such as iron, nickel, and cobalt, or powders of magnetic alloys based on these metals, metal oxides such as iron trioxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite, and strontium ferrite. Examples thereof include powders of magnetic system.
　結晶性シリコチタネートを含有する含水状態のものを造粒加工した顆粒状のものに磁性粒子を含有させる方法としては、例えば、前述した造粒加工操作を磁性粒子を含有させた状態で行えばよい。 As a method of adding magnetic particles to a granulated product obtained by granulating a water-containing material containing crystalline silicotitanate, for example, the above-described granulation processing operation may be performed in a state where magnetic particles are contained. .
　また、本発明の吸着剤は、例えば、ゼオライト、チタン酸塩、ケイ酸バリウム、Ｔｉ／Ｓｉ比が２：１である結晶性シリコチタネート、アパタイト、活性炭等の他の吸着剤と併用して用いることが出来る。
　また、本発明に係る吸着剤は、例えば、水道水の金属イオン吸着剤として用いることもできる。 Further, the adsorbent of the present invention is used in combination with other adsorbents such as zeolite, titanate, barium silicate, crystalline silicotitanate having a Ti / Si ratio of 2: 1, apatite, activated carbon and the like. I can do it.
The adsorbent according to the present invention can also be used as, for example, a metal ion adsorbent for tap water.
　以下、本発明を実施例により詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
　以下に、実施例及び比較例により本発明を具体的に説明するが、本発明はこれらに限定されるものではない。特に断らない限り「％」は「質量％」を表す。実施例及び比較例で使用した評価装置及び使用材料は以下のとおりである。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these. Unless otherwise specified, “%” represents “mass%”. Evaluation devices and materials used in Examples and Comparative Examples are as follows.
＜評価装置＞
・Ｘ線回折：Ｂｒｕｋｅｒ社　Ｄ８　ＡｄｖａｎｃｅＳを用いた。線源としてＣｕ－Ｋαを用いた。測定条件は、管電圧４０ｋＶ、管電流４０ｍＡ、走査速度０．１°／ｓｅｃとした。
・ＩＣＰ－ＡＥＳ：Ｖａｒｉａｎ社７２０－ＥＳを用いた。Ｃｓの測定波長は６９７．３２７ｎｍ、Ｓｒの測定波長は２１６．５９６ｎｍとしてＣｓ及びＳｒの吸着試験を行った。標準試料はＮａＣｌを０．３％含有したＣｓ：１００ｐｐｍ、５０ｐｐｍ及び１０ｐｐｍの水溶液、並びにＮａＣｌを０．３％含有したＳｒ：１００ｐｐｍ、１０ｐｐｍ及び１ｐｐｍの水溶液を使用した。
・ＸＲＦ：蛍光Ｘ線装置（装置名：ＺＳＸ１００ｅ、管球：Ｒｈ（４ｋＷ）、雰囲気：真空、分析窓：Ｂｅ（３０μｍ）、測定モード：ＳＱＸ分析（ＥＺスキャン）、測定径：３０ｍｍφ、（株）リガク製）で全元素測定した。測定用試料は、適当な容器（アルミリング等）に入れ、ダイスで挟みこんでからプレス機で１０ＭＰａの圧力をかけてペレット化することにより得た。
・ＢＥＴ比表面積：測定装置として島津製作所製　Ｆｌｏｗｓｏｒｂ　ＩＩ　２３００を用いて、ＢＥＴ１点法により求めた。 <Evaluation equipment>
X-ray diffraction: Bruker D8 AdvanceS 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 Cs and Sr adsorption tests were performed with a Cs measurement wavelength of 697.327 nm and a Sr measurement wavelength of 216.596 nm. Standard samples used were Cs: 100 ppm, 50 ppm and 10 ppm aqueous solutions containing 0.3% NaCl, and Sr: 100 ppm, 10 ppm and 1 ppm aqueous solutions containing 0.3% NaCl.
XRF: fluorescent X-ray apparatus (device name: ZSX100e, tube: Rh (4 kW), atmosphere: vacuum, analysis window: Be (30 μm), measurement mode: SQX analysis (EZ scan), measurement diameter: 30 mmφ, (stock) ) All elements were measured with Rigaku. The sample for measurement was obtained by putting in a suitable container (aluminum ring or the like), sandwiching with a die, and pelletizing by applying a pressure of 10 MPa with a press.
-BET specific surface area: Determined by the BET one-point method using Flowsorb II 2300 manufactured by Shimadzu Corporation as a measuring device.
＜使用材料＞
・ケイ酸カリウム：日本化学工業株式会社製（ＳｉＯ2：２６．５％、Ｋ2Ｏ：１３．５％、Ｈ2Ｏ：６０．００％、ＳｉＯ2／Ｋ2Ｏ＝３．０９）。
・ケイ酸ナトリウム：日本化学工業株式会社製（ＳｉＯ2：２８．９６％、Ｎａ2Ｏ：９．３７％、Ｈ2Ｏ：６１．６７％、ＳｉＯ2／Ｎａ2Ｏ＝３．１）。
・シリカゾル：日本化学工業株式会社製（ＳｉＯ2：３０％、粒子径１５ｎｍ）
・苛性カリ：固体試薬　水酸化カリウム（ＫＯＨ：８５％）
・苛性ソーダ水溶液；工業用２５％水酸化ナトリウム（ＮａＯＨ：２５％、Ｈ2Ｏ：７５％）
・四塩化チタン水溶液：株式会社大阪チタニウムテクノロジーズ社製３６．４８％水溶液・二酸化チタン：石原産業ＳＴ－０１
・模擬海水：Ｃｓ及びＳｒをそれぞれ１００ｐｐｍ含有した０．３％ＮａＣｌ水溶液を模擬海水とした。模擬海水はＮａＣｌ（９９．５％）：３．０１５１ｇ、ＳｒＣｌ・６Ｈ2Ｏ（９９％）：０．３０７４ｇ、ＣｓＮＯ3（９９％）：０．１４８１ｇ、Ｈ2Ｏ：９９６．５２９４ｇを混合して得た。 <Materials used>
Potassium silicate: manufactured by Nippon Chemical Industry 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 Industry 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%)
・ 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: 0.3% NaCl aqueous solution containing 100 ppm of Cs and Sr was used as simulated seawater. Simulated seawater is composed of NaCl (99.5%): 3.0151 g, SrCl · 6H 2 O (99%): 0.3074 g, CsNO 3 (99%): 0.1481 g, H 2 O: 996.5294 g. I got it.
　　〔実施例１〕
（１）第一工程
　ケイ酸カリ６４．５ｇ、８５％苛性カリ１２６．７ｇ及びイオン交換水２１０．２ｇを混合し撹拌して混合水溶液を得た。この混合水溶液に、四塩化チタン水溶液２０３．３ｇをペリスタポンプで３０分にわたって連続的に添加して混合ゲルを製造した。当該混合ゲルは、四塩化チタン水溶液の添加後、１時間にわたり７０℃で混合して熟成した。 [Example 1]
(1) First Step 64.5 g of potassium silicate, 126.7 g of 85% caustic potash 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 titanium tetrachloride aqueous solution was continuously added over 30 minutes with a peristaltic 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）第二工程
　第一工程で得られた混合ゲルをオートクレーブに入れ、１．５時間かけて１７０℃に昇温したのち、この温度を維持しながら静置下に７２時間反応を行った。反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。 (2) Second Step The mixed gel obtained in the first step was put 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 using a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm.
〔実施例２〕
（１）第一工程
　３号ケイ酸ソーダ６０ｇ、苛性ソーダ水溶液２２４．３ｇ、８５％苛性カリ３４．６ｇ及びイオン交換水８２．５ｇを混合し撹拌して混合水溶液を得た。この混合水溶液に、四塩化チタン水溶液２０３．３ｇをペリスタポンプで０．５時間にわたって連続的に添加して混合ゲルを製造した。当該混合ゲルは、四塩化チタン水溶液の添加後、１時間にわたり室温（２５℃）で静置熟成した。 [Example 2]
(1) First Step 3 No. 3 sodium silicate 60 g, caustic soda aqueous solution 224.3 g, 85% caustic potassium 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 titanium tetrachloride aqueous solution was continuously added over 0.5 hour with a peristaltic pump to produce a mixed gel. The mixed gel was aged by standing at room temperature (25 ° C.) for 1 hour after the addition of the aqueous titanium tetrachloride solution.
（２）第二工程
　第一工程で得られた混合ゲルをオートクレーブに入れ、１時間かけて１４０℃に昇温したのち、この温度を維持しながら撹拌下に１８時間反応を行った。反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。 (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 for 18 hours with stirring while maintaining this temperature. The slurry after the reaction was filtered, and the obtained cake was extruded using a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm.
〔実施例３〕
　実施例２において、第二工程の反応温度を１５０℃で２４時間にした以外は、実施例２と同様に反応を行った。次いで、反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。 Example 3
In Example 2, the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 150 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm.
〔実施例４〕
　実施例２において、第二工程の反応温度を１６０℃で２４時間にした以外は、実施例２と同様に反応を行った。次いで、反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。 Example 4
In Example 2, the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 160 ° C. for 24 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm.
〔参考例１〕
　実施例２において、第二工程の反応温度を１７０℃で９６時間にした以外は、実施例２と同様に反応を行った。次いで、反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。 [Reference Example 1]
In Example 2, the reaction was performed in the same manner as in Example 2 except that the reaction temperature in the second step was changed to 170 ° C. for 96 hours. Next, the slurry after the reaction was filtered, and the obtained cake was extruded with a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm.
（物性評価）
　実施例及び参考例１で得られた粒状物について、ＢＥＴ比表面積を求めた。また、Ｘ線回折分析を行った。また、Ｘ線回折分析により結晶性シリコチタネートの２θ＝１０°以上１３°以下の回折ピーク（メーンピーク（Ｂ１））の半値幅を求めた。また、粒状物中のＫ2Ｏ、Ｎａ2Ｏ、ＳｉＯ2及びＴｉＯ2の含有量（質量％）を上記条件のＸＲＦにて測定した。その結果を表１に示す。
Figure JPOXMLDOC01-appb-T000001
 (Evaluation of the physical properties)
About the granular material obtained by the Example and the reference example 1, the BET specific surface area was calculated | required. Further, X-ray diffraction analysis was performed. Further, the half width of the diffraction peak (main peak (B1)) of the crystalline silicotitanate from 2θ = 10 ° to 13 ° was determined by X-ray diffraction analysis. Further, K 2 O in the granules, Na 2 O, SiO 2 content and TiO 2 (% by mass) was measured by XRF under the above conditions. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
〔参考例２〕
＜結晶性シリコチタネート及びチタン酸塩の混合物の合成＞
（１）第一工程
　３号ケイ酸ソーダ９０ｇ、苛性ソーダ水溶液６６７．４９ｇ及び純水８４．３８ｇを混合し撹拌して混合水溶液を得た。この混合水溶液に、四塩化チタン水溶液４４３．９０ｇをペリスタポンプで１時間２０分にわたって連続的に添加して混合ゲルを製造した。当該混合ゲルは、四塩化チタン水溶液の添加後、１時間にわたり室温で静置熟成した。混合ゲル中のＴｉ／Ｓｉモル比：２、Ｋ2Ｏ／Ｎａ2Ｏモル比：０／１００、ＳｉＯ2換算濃度ａ：２．００％、ＴｉＯ2換算濃度ｂ：５．３０％、ａ＋ｂ：７．３０、Ａ2Ｏ／ＳｉＯ2モル比：１．５６、Ｎａ2Ｏ換算濃度：３．２２％であった。 [Reference Example 2]
<Synthesis of crystalline silicotitanate and titanate mixture>
(1) First Step 90 g of sodium silicate No. 3, caustic soda aqueous solution 667.49 g and pure water 84.38 g were mixed and stirred to obtain a mixed aqueous solution. To this mixed aqueous solution, 443.90 g of titanium tetrachloride aqueous solution was continuously added over 1 hour and 20 minutes with 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 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: The molar ratio was 7.30, A 2 O / SiO 2 molar ratio: 1.56, Na 2 O equivalent concentration: 3.22%.
（３）第二工程
　第一工程で得られた混合ゲルをオートクレーブに入れ、１時間かけて１７０℃に昇温したのち、この温度を維持しながら撹拌下に２４時間反応を行った。反応後のスラリーを濾過し、得られたケーキを直径０．６μｍの円形の開孔部材で押出成形した後、乾燥し、分級して粒度が３００μｍ以上６００μｍ以下の粒状物を得た。得られた粒状物をＸ線回折測定した。その結果を図２に示す。図２に示すＸ線回折測定の結果より、得られた粒状物は主相Ｎａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏであり、Ｎａ4Ｔｉ9Ｏ20・ｍＨ2Ｏが検出され、前記結晶性シリコチタネート及び前記チタン酸塩の混合物であると確認した。また粒状物は２θ＝１０～１３°の範囲に観察されるＮａ4Ｔｉ4Ｓｉ3Ｏ16・６Ｈ2Ｏに由来するメーンピーク（M.P.）の高さに対して、２θ＝８～１０°に範囲に観察されるＮａ4Ｔｉ9Ｏ20・５～７Ｈ2Ｏに由来するM.P.の高さの比が３８．５％であった。また上記方法の組成分析によればＮａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ：Ｎａ4Ｔｉ9Ｏ20・ｍＨ2Ｏのモル比は１：０．３７であった。 (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 for 24 hours with stirring while maintaining this temperature. The slurry after the reaction was filtered, and the obtained cake was extruded using a circular aperture member having a diameter of 0.6 μm, dried, and classified to obtain a granular material having a particle size of 300 μm to 600 μm. The obtained granular material was subjected to X-ray diffraction measurement. The result is shown in FIG. From the result of the X-ray diffraction measurement shown in FIG. 2, the obtained granular material is the main phase Na 4 Ti 4 Si 3 O 16 .nH 2 O, and Na 4 Ti 9 O 20 .mH 2 O is detected. It was confirmed to be a mixture of crystalline silicotitanate and the titanate. The granular material is 2θ = 8 to 10 ° with respect to the height of the main peak (MP) derived from Na 4 Ti 4 Si 3 O 16 · 6H 2 O observed in the range of 2θ = 10 to 13 °. The ratio of the height of MP derived from Na 4 Ti 9 O 20 · 5 to 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.
　＜Ｃｓ及びＳｒの吸着試験＞
　粒状物を、１００ｍｌのポリ容器に０．５ｇ取り、上記模擬海水１（１００．００ｇ）を添加し、蓋をした後、内容物を振り混ぜた。内容物の振り混ぜは、ポリ容器の倒立を１０回行うことにより行った。その後、静置して１時間経過した後、再び内容物を振り混ぜ、約５０ｍｌを５Ｃのろ紙でろ過し、ろ過によって得られたろ液を採取した。また、残りの５０ｍｌはそのまま静置し、更に２３時間後（最初に振り混ぜてから２４時間後）に再び振り混ぜた。そして、５Ｃのろ紙でろ過し、ろ過によって得られたろ液を採取した。採取されたろ液を対象として、ＩＣＰ－ＡＥＳを用い、ろ液中のＣｓ及びＳｒの含有量を測定した。その結果を以下の表２に示す。 <Adsorption test of Cs and Sr>
0.5 g of the granular material was taken into a 100 ml plastic container, the simulated seawater 1 (100.00 g) was added, the lid was capped, and the contents were shaken and mixed. The contents were shaken by inverting the plastic container 10 times. Then, after standing for 1 hour, the contents were shaken and mixed again, about 50 ml was filtered with 5C filter paper, and the filtrate obtained by filtration was collected. Further, the remaining 50 ml was left as it was, and further shaken again after 23 hours (24 hours after first shaking). And it filtered with 5 C filter paper, and the filtrate obtained by filtration was extract | 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 2 below.
Figure JPOXMLDOC01-appb-T000002
  
Figure JPOXMLDOC01-appb-T000002
  

Claims (5)

  1. 　金属イオンの吸着剤であって、
    　Ｘ線回折分析において、２θ＝１０°以上１３°以下のメーンピークの半値幅が１．０°以下であり、ＢＥＴ比表面積が１００ｍ2／ｇ以上である一般式；Ａ4Ｔｉ4Ｓｉ3Ｏ16・ｎＨ2Ｏ（式中、Ａは、Ｎａ及びＫから選ばれるアルカリ金属を示す。式中、ｎは０～８を示す。）で表される結晶性シリコチタネートからなることを特徴とする吸着剤。     A metal ion adsorbent,
    In X-ray diffraction analysis, the general formula in which the half width of the main peak at 2θ = 10 ° to 13 ° is 1.0 ° or less and the BET specific surface area is 100 m 2 / g or more; A 4 Ti 4 Si 3 O It is characterized by comprising a crystalline silicotitanate represented by 16 · nH 2 O (wherein A represents an alkali metal selected from Na and K. In the formula, n represents 0 to 8). Adsorbent.
  2. 　結晶性シリコチタネートは、カリウム含有量がＫ2Ｏ換算で、Ａ2Ｏ（ＡはＮａ及びＫを示す）に対するモル比（Ｋ2Ｏ／Ａ2Ｏ）で、０超０．５以下であることを特徴とする請求項１項に記載の吸着剤。 The crystalline silicotitanate has a potassium content in terms of K 2 O and a molar ratio (K 2 O / A 2 O) to A 2 O (A represents Na and K) of more than 0 and 0.5 or less. The adsorbent according to claim 1.
  3. 　粉末状又は顆粒状であることを特徴とする請求項１又は２の何れか１項に記載の吸着剤。 The adsorbent according to any one of claims 1 and 2, wherein the adsorbent is powdery or granular.
  4. 　２００～１０００μｍの粒度を有することを特徴とする請求項３に記載の吸着剤。 The adsorbent according to claim 3, which has a particle size of 200 to 1000 µm.
  5. 　吸着する金属イオンが、セシウム及び／又はストロンチウムであることを特徴とする請求項１乃至４の何れか１項に記載の吸着剤。 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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