WO2014168048A1 - Magnetized zeolite, production method therefor, and method for selective and specific capture of cesium - Google Patents

Magnetized zeolite, production method therefor, and method for selective and specific capture of cesium Download PDF

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WO2014168048A1
WO2014168048A1 PCT/JP2014/059649 JP2014059649W WO2014168048A1 WO 2014168048 A1 WO2014168048 A1 WO 2014168048A1 JP 2014059649 W JP2014059649 W JP 2014059649W WO 2014168048 A1 WO2014168048 A1 WO 2014168048A1
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zeolite
magnetized
cesium
soil
magnetite nanoparticles
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French (fr)
Japanese (ja)
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宏通 青野
逸見　彰男
山本　徹
直人 松枝
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国立大学法人愛媛大学
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    • 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
    • G21F9/28—Treating solids
    • 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
    • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
    • 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
    • B01J20/16—Alumino-silicates
    • B01J20/18—Synthetic zeolitic molecular sieves
    • B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
    • 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
    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28009—Magnetic properties
    • 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
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • 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
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • B03C1/005—Pretreatment specially adapted for magnetic separation
    • B03C1/01—Pretreatment specially adapted for magnetic separation by addition of magnetic adjuvants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • B03C1/02—Magnetic separation acting directly on the substance being separated
    • B03C1/10—Magnetic separation acting directly on the substance being separated with cylindrical material carriers
    • B03C1/14—Magnetic separation acting directly on the substance being separated with cylindrical material carriers with non-movable magnets
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/026—After-treatment
    • 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
    • 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
    • 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
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4875—Sorbents characterised by the starting material used for their preparation the starting material being a waste, residue or of undefined composition
    • B01J2220/4887—Residues, wastes, e.g. garbage, municipal or industrial sludges, compost, animal manure; fly-ashes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Definitions

  • the present invention relates to a magnetized zeolite, a method for producing the same, and a method for selectively capturing cesium.
  • Zeolite is an aluminosilicate having an infinite number of pores in the crystal structure, and is a substance composed of M-Al-Si-O (M is an alkali metal or alkaline earth metal).
  • M is an alkali metal or alkaline earth metal.
  • Si / Al ratio the more negatively charged the zeolite skeleton is due to isomorphous substitution, and M plus ions are required to compensate for it.
  • CEC cation exchange capacity
  • a method for recovering zeolite mixed in a fluid a method is known in which an adsorbent containing zeolite and magnetic particles is used and the adsorbent is recovered by magnetic separation (see, for example, Patent Documents 4 to 6). ).
  • general zeolite such as natural zeolite is weak because the capture ability of cesium ions relies only on electric affinity. Moreover, since a general zeolite captures regardless of a kind if it is a cation, it cannot selectively capture a cesium ion. Moreover, general zeolite does not have the ability to attract cesium taken in between clay layers in soil until it is drawn out from the clay layers.
  • CEC value a standard for the capture capacity of zeolites
  • mordenite Si / Al ratio of about 5
  • SI unit is cmol (+) ⁇ kg ⁇ 1
  • the crystal pores are 5.5 to 8.0 mm and larger than the diameter of cesium ions (3.6 mm)
  • the capture and fixing ability of radioactive cesium is weak.
  • the soil in Fukushima where there is concern about contamination with radioactive cesium, is “masa soil” in which granite is weathered.
  • the CEC of the “masa soil” is about 20
  • the clay mineral kaolinite derived from feldspar weathered from the “masa soil” has a CEC of 3 to 15 meq / 100 g.
  • the clay mineral illite derived from mica has a CEC of 10 to 40 meq / 100 g.
  • clay mineral vermiculite with altered illite has a relatively large CEC value of 100-150 meq / 100 g, which is a measure of adsorption capacity. It has the property of easily incorporating cesium ions between layers. Therefore, it was difficult to capture cesium free from such soil.
  • An object of the present invention is to provide a magnetized zeolite capable of efficiently capturing radioactive cesium in soil or a liquid containing soil, a method for producing the same, and a method for capturing cesium.
  • Na-P1 type zeolite has countless crystal pores having the same size as cesium ions (diameter: 3.6 mm), so that cesium It was found that it has the ability to selectively capture and fix ions selectively.
  • Na-P1 type zeolite is disclosed in Non-Patent Document 1, for example.
  • the method for producing a magnetized zeolite according to the present invention includes a step of softening the surface of the incineration ash by adding an alkaline solution to a zeolite raw material containing incineration ash of coal or paper sludge, and the surface of the incineration ash is softened. And obtaining a magnetized zeolite which is a composite material of magnetite nanoparticles and Na—P1 type zeolite by mixing and heating the zeolite raw material and magnetite nanoparticles.
  • the zeolite raw material may be an example in which the Si / Al ratio is adjusted to 2 or less using one or more of sodium aluminate and an aluminum compound. .
  • the magnetized zeolite according to the present invention is a magnetized zeolite obtained by the method for producing a magnetized zeolite of the present invention, wherein magnetite nanoparticles are confined at the grain boundaries of the Na—P1 type zeolite polycrystal, or Na—
  • This is a composite material of a magnetite nanoparticle and Na—P1 type zeolite in which a nanocomposite is formed by partial substitution of magnetite nanoparticles in a P1 type zeolite crystal, or both of these structures.
  • the method for capturing cesium according to the present invention comprises a step of mixing the magnetized zeolite of the present invention in soil or a liquid containing soil, and recovering the magnetized zeolite by magnetic separation, so that the Selectively and specifically capturing radioactive cesium.
  • Examples of the method for capturing cesium according to the present invention include reusing the magnetized zeolite recovered by the magnetic separation.
  • the method for capturing cesium of the present invention is not limited to a configuration in which the recovered magnetized zeolite is reused.
  • the method for capturing cesium of the present invention can be exemplified by reusing the magnetized zeolite after elution of radioactive cesium from the magnetized zeolite recovered by the magnetic separation.
  • the magnetized zeolite may be reused without performing the process of eluting radioactive cesium from the magnetized zeolite recovered by magnetic separation.
  • the magnetized zeolite and the method for producing the same of the present invention can provide a magnetized zeolite which is a composite material of magnetite nanoparticles and Na—P1 type zeolite capable of efficiently capturing radioactive cesium in the soil or a liquid containing the soil.
  • the method for capturing cesium of the present invention can efficiently capture radioactive cesium in soil or in a liquid containing soil using the magnetized zeolite of the present invention. Furthermore, since the Na—P1 type zeolite mixed in the soil or the liquid containing the soil is recovered by magnetic separation, the method for capturing cesium of the present invention makes it easy to recover the zeolite capturing the cesium.
  • FIG. 3 is a view showing a framework structure model of Na—P1 type zeolite. It is a figure which shows the result of having investigated the capture ability of the cesium ion and the strontium ion of Na-P1 type
  • FIG. 1 is a schematic diagram for explaining one embodiment of a method for producing magnetized zeolite.
  • 2 mol / L (mol / liter) of sodium hydroxide solution 3 is added to iron salt solution 1 containing iron (II) chloride or iron (III) chloride or both, and mixed at 100 ° C.
  • a dispersion of magnetite nanoparticles was obtained by coprecipitation.
  • the average particle size of the obtained magnetite nanoparticles is about 30 nm (nanometers).
  • the zeolite incineration ash whose Si / Al ratio was previously examined by fluorescent X-ray analysis was mixed with aluminum hydroxide so that the Si / Al ratio was 2, to obtain a zeolite raw material 5.
  • a 2 mol / L sodium hydroxide solution 7 was added to the zeolite raw material 5 and allowed to stand at room temperature for 24 hours. Thereby, the zeolite raw material containing the incinerated ash whose surface was softened was obtained.
  • Magnetite nanoparticles were mixed with zeolite raw material containing incinerated ash whose surface was softened, and heated to reflux (heat treatment) at 100 ° C. for 24 hours. As a result, a magnetized zeolite 13 which is a composite material of the Na—P1 type zeolite 9 and the magnetite nanoparticles 11 was obtained.
  • the molar ratio of Na—P1 type zeolite 9 to magnetite nanoparticle 11 was about 7: 3.
  • the particle diameter of the Na—P1 type zeolite 9 was about several tens of ⁇ m (micrometer).
  • the particle size of the magnetite nanoparticle 11 was about several tens of nm.
  • the magnetite nanoparticles 11 are partially substituted in the crystals of the Na—P1 type zeolite 9 to form a nanocomposite.
  • magnetite nanoparticles 11 are confined at the grain boundaries of the polycrystalline Na—P1 zeolite 9.
  • the magnetized zeolite 13 has a different structure from that obtained by simply mixing the Na—P1 type zeolite particles and the magnetite nanoparticles.
  • a pretreatment is performed before mixing and heating the magnetite nanoparticles and the zeolite raw material 5.
  • a pretreatment is performed to soften the surface of the incinerated ash contained in the zeolite raw material 5.
  • FIG. 2 is a diagram showing a framework structure model of Na—P1 type zeolite.
  • the chemical formula of the Na-P1 type zeolite 9 is described as Na 6 Al 6 Si 10 O 32 ⁇ 12H 2 O in Non-Patent Document 1.
  • the basic unit of the structure of the Na—P1 type zeolite 9 is the same tetrahedral structure of SiO 4 or AlO 4 . Therefore, the Na—P1 type zeolite 9 can maintain the Na—P1 type zeolite structure even if the Si / Al ratio changes to some extent.
  • the crystal pores of the Na-P1 type zeolite 9 are about 3.6 cm, which is almost the same as the diameter of cesium ions. Therefore, the Na—P1 type zeolite 9 has particularly excellent selective capture characteristics for cesium ions.
  • the Si / Al ratio of the Na—P1 type zeolite 9 is smaller than 2. That is, the Na—P1 type zeolite 9 has a high CEC.
  • the CEC of Na—P1 type zeolite 9 is 250 meq / 100 g or more. If the Si / Al ratio is further lowered in the Na—P1 type zeolite, the CEC of the Na—P1 type zeolite can be 400 to 500 meq / 100 g.
  • FIG. 3 is a diagram showing the results of examining the capture ability of cesium ions (Cs + ) and strontium ions (Sr 2+ ) of Na—P1 type zeolite in a solution.
  • the horizontal axis indicates the amount of zeolite charged (g) in 50 ml (milliliter) of the solution.
  • the vertical axis represents the removal rate (%) of cesium ions or strontium ions.
  • 0.1 g or 0.2 g of Na—P1 type zeolite was put into 50 ml of a solution containing cesium ions or strontium ions at a concentration of 10 mmol / L, and cesium ions or strontium ions were adsorbed on the Na—P1 type zeolite. Thereafter, the concentration of cesium ions or strontium ions in the supernatant from which Na-P1 type zeolite was removed by centrifugation was measured by atomic absorption analysis.
  • Each cesium ion removal rate was 99%.
  • the removal rate of strontium ions when 0.1 g of Na-P1 type zeolite was added to 50 ml of the solution was 95%, and the removal rate of strontium ions when 0.2 g of Na-P1 type zeolite was added was 96%. Met.
  • Na-P1 type zeolite showed a high capturing ability for cesium ions. It was also found that Na-P1 type zeolite showed a high capturing ability for strontium ions.
  • FIG. 4 is a diagram showing the results of examining the capture ability of Na—P1 type zeolite for cesium in soil.
  • the horizontal axis indicates the amount of zeolite mixed with the soil (% by weight).
  • the vertical axis represents the cesium ion elution amount (mmol ⁇ kg ⁇ 1 ).
  • cesium-fixed soil granitic soil mixed with vermiculite (CEC: 3 to 15 meq / 100 g) at 10% by weight was used.
  • the cesium capture ability was determined by measuring the amount of cesium ions eluted from the cesium-fixed soil mixed with a predetermined amount of Na-P1-type zeolite after water mixing for 2 hours.
  • the mixing amount of the Na-P1 type zeolite is 0% (Cs saturated soil)
  • the mixing amount of the Na-P1 type zeolite is 0.1%, 23%, the case of 1% is 74%, 10%.
  • 85% of cesium could be captured. This means that Na-P1 type zeolite can capture cesium from soil with a large CEC.
  • the magnetized zeolite of the present invention contains Na—P1 type zeolite crystals, it has the same trapping ability with respect to cesium and stronium as non-magnetized Na—P1 type zeolite.
  • FIG. 5 is a conceptual diagram for explaining a method for recovering magnetized zeolite capturing cesium.
  • Granular magnetized zeolite 13 is mixed with cesium-contaminated soil containing cesium (Cs) 21 captured by the soil particles 19, and a water-containing shake is added by adding a release agent such as potassium chloride. To capture.
  • Cs cesium-contaminated soil containing cesium
  • the magnetized zeolite 13 capturing the cesium 21 and the soil particles 19 from which the cesium has been removed are separated. Thereby, the purified soil particle 19 is obtained.
  • the magnetic separator is not limited to the one provided with the magnet pulley 23 and the drum separator 25, and may have any structure.
  • FIG. 6 is a diagram showing changes in the concentration of radioactive cesium in the soil when magnetic separation using the magnetized zeolite of the present invention is performed a plurality of times.
  • the horizontal axis indicates the number of magnetic separations.
  • the vertical axis represents the radioactive cesium concentration (%).
  • a soil having a radioactivity concentration of 12000 to 16000 Bq / kg (becquerel / kilogram) was used as the soil.
  • the four types of samples A, B, C, and D show the difference in the types of release agents such as an aqueous potassium salt solution and an aqueous ammonium salt solution that are necessary for once releasing radioactive cesium from the soil.
  • Sample A release agent is a solution containing 0.1% potassium chloride and 4% oxalic acid.
  • Sample B release agent is a solution containing 0.1% potassium chloride, 4% oxalic acid and 4% ammonium oxalate.
  • Sample C release agent is a solution containing 0.1% potassium chloride, 2% oxalic acid and 2% ammonium oxalate.
  • the release agent for Sample D is a solution containing 0.1% potassium chloride and 4% ammonium oxalate.
  • Each sample is obtained by mixing 200 g of magnetized zeolite and 2 L (liter) of release agent in 2 kg of soil and stirring for 10 minutes.
  • Each magnetic sample was magnetically selected three times.
  • the addition of magnetized zeolite and release agent is only the first time, and the second and subsequent times are only magnetic separation operations.
  • the concentration of radioactive cesium decreased as the number of magnetic separations increased.
  • About 80% of the radioactive cesium was successfully removed by three magnetic separation operations.
  • the release agent is not limited to those used in the samples A, B, C, and D.
  • FIG. 7 is a conceptual diagram for explaining a soil decontamination method using magnetized zeolite.
  • Radioactive Cs elution step A soil containing cesium 21 (Cs + ) captured by the soil particles 19 is mixed with a free agent such as potassium chloride and shaken with water. The cesium 21 captured in the soil particles 19 is replaced with potassium ions 27 (K + ) and is eluted from the soil particles 19.
  • the release agent is not limited to potassium chloride, and other release agents such as other potassium salts and ammonium salts may be used.
  • Magnetized zeolite transfer step Magnetized zeolite 13 is further mixed. Cesium 21 is captured by the magnetized zeolite 13. In addition to cesium 21, potassium ions 27 are captured in the magnetized zeolite 13.
  • Magnetized zeolite magnetic separation step (weight reduction 1): Magnetized zeolite 13 is taken out by magnetic separation using a magnet 29. Cesium 21 is captured in the recovered magnetized zeolite 13.
  • the number of magnetic selection steps in this step may be one, but magnetic selection is preferably performed a plurality of times, for example, 2 to 3 times. The steps so far are the same as the magnetized zeolite recovery method described with reference to FIG.
  • Magnetized zeolite reuse step (weight loss 2): The magnetized zeolite 13 recovered by magnetic separation in the step (3) is reused. Specifically, the magnetized zeolite 13 recovered in the step (3) is used in the step (2).
  • the number of times that the magnetized zeolite 13 can be reused varies depending on the concentration of cesium 21 in the soil, but is, for example, five times. However, the number of reuses of the magnetized zeolite 13 is not particularly limited.
  • Elution step from magnetized zeolite The magnetized zeolite 13 whose number of reuses reaches an arbitrary specified number of times, for example, 5 times, is not reused (the above step (4)), and the captured cesium 21 Elution treatment is performed.
  • a high concentration potassium salt is mixed with the magnetized zeolite 13 as a release agent.
  • the cesium 21 captured in the magnetized zeolite 13 is replaced with potassium ions 27.
  • the concentration of the potassium salt used here is not particularly limited as long as cesium 21 can be eluted from the magnetized zeolite 13.
  • the releasing agent is not limited to the potassium salt.
  • the release agent is not particularly limited as long as it can release cesium 21, and may be, for example, an ammonium salt.
  • Elution Cs concentration step (weight loss 3): The magnetized zeolite 13 is recovered from the solution containing cesium 21 eluted from the magnetized zeolite 13 in the step (5) using, for example, a magnet.
  • the cesium 21 contained in the solution from which the magnetized zeolite 13 is recovered is solidified by, for example, heat drying.
  • the magnetized zeolite 13 collected here can be reused.
  • the amount is reduced by 1/10 (weight reduction 1). Furthermore, if the used magnetized zeolite containing radioactive Cs recovered by magnetic separation is used for the same decontamination and can be reused in a state where the radioactive Cs is captured by the magnetized zeolite, the amount of soil is doubled. Decontamination has been completed. In this case, the total weight reduction is 1/20 (weight loss 2). For example, if the used magnetized zeolite in which radioactive Cs is captured can be reused four times and the same magnetized zeolite can be used five times in total, a reduction of 1/50 can be realized.
  • the amount of radioactive Cs contained in the soil is extremely small, so that it is possible to repeatedly use magnetized zeolite recovered by magnetic separation.
  • recycling of used magnetized zeolite improves decontamination efficiency.
  • the radioactive Cs concentrated in the magnetized zeolite is eluted with a release agent for the magnetized zeolite, and the liquid is dried and solidified, thereby enabling a significant reduction in weight (weight reduction 3).
  • FIG. 8 is a diagram showing the relationship between the number of magnetic separation stages (times) and the radioactive concentration (%) of soil when magnetized zeolite is reused.
  • the spent magnetized zeolite mixed with the soil containing radioactive Cs and capturing the radioactive Cs collected by magnetic separation is left to dry at room temperature, and again as described in the above step (4), the above step Used in place of unused magnetized zeolite in (2).
  • the used magnetized zeolite captures about 2 to 5 times as much radioactive Cs as the soil.
  • soil from Kawamata Town, Date-gun, Fukushima Prefecture was used.
  • the magnetic separation process is performed in contrast to the process in which the magnetized zeolite and the release agent are mixed and mixed for 10 minutes (the above step (2)) and then the magnetic separation process (the above step (3)) is performed 2-3 times. Each time it was performed, 10% of the above used magnetized zeolite and 2% ammonium oxalate solution as a release agent were added and mixed for 10 minutes. This is for confirming the performance of the used magnetized zeolite capturing radioactive Cs.
  • the used magnetized zeolite captures about 2 to 5 times as much radioactive Cs as the soil, but about 10 to 20% in the first magnetic separation process and about 50% in the second magnetic separation process. It was possible to confirm the decay of the radioactive Cs concentration.
  • the used magnetized zeolite is a magnetized zeolite that is easily recovered by magnetic separation. This is also considered to be one of the factors that the used magnetized zeolite can be reused.
  • the magnetized zeolite recovered by magnetic separation is reused without being subjected to the elution treatment of the captured radioactive Cs (the above step (5)) (the above step). (4)), but the method of selective and specific capture of cesium of the present invention is not limited to this.
  • the selective and specific capture method of cesium of the present invention may be configured such that radioactive cesium is eluted and then reused without reusing the magnetized zeolite recovered by magnetic separation as it is. Since this configuration uses magnetized zeolite recovered by magnetic separation, that is, magnetized zeolite that is easily recovered by magnetic separation, decontamination efficiency can be improved.
  • the method of capturing cesium of the present invention is an innovative method that can recover only radioactive elements such as cesium in the current situation where there is no true decontamination technology against soil contamination by radionuclides caused by an accident at a nuclear power plant in Fukushima. Technology. Furthermore, the method for capturing cesium according to the present invention is a technology that can be readily adapted to the current decontamination around Fukushima as a technology that is suitable for widespread use with a large amount, low cost and ease of use. Furthermore, it can be expected to be useful even in areas where decontamination is not sufficiently advanced, such as Chernobyl.
  • coal incineration ash is used as a zeolite raw material for synthesizing magnetized zeolite.
  • a composite of magnetite nanoparticles and Na-P1 type zeolite is used. It is possible to synthesize magnetized zeolite as a material.
  • magnetized zeolite which is a composite material of magnetite nanoparticles and Na-P1 type zeolite, is synthesized using a mixture of water glass, sodium aluminate, and an aluminum compound that is adjusted to have a Si / Al ratio of 2 or less. You can also.
  • the Si / Al ratio of the zeolite raw material may be adjusted to a desired value.
  • the material for adjusting the Si / Al ratio is a compound containing silicon or aluminum, preferably water glass, sodium aluminate, or an aluminum compound.
  • the value of Si / Al ratio is 2 or less, for example, 2.
  • the value of the Si / Al ratio of the synthesis material is a value at which the composite material of magnetite nanoparticles and Na—P1 type zeolite is synthesized, and may be any number as long as it is 2 or less.
  • the particle size of the magnetite nanoparticles mixed with the zeolite raw material containing the incinerated ash having a softened surface is, for example, 5 to 200 nm, preferably 30 nm or less.
  • the magnetite nanoparticles may be commercially available.
  • the alkaline solution is not limited to sodium hydroxide, and may be another alkaline solution such as potassium hydroxide.

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Abstract

A magnetized zeolite being a composite material of magnetite nanoparticles and a Na-P1-type zeolite is obtained by: adding an alkaline solution to a zeolite raw material including incinerated coal ash or incinerated paper-making sludge ash and softening the surface of the incinerated ash; and mixing magnetite nanoparticles and the zeolite raw material having the incinerated ash surface thereof softened, and heat treating same. The magnetized zeolite has a structure whereby magnetite nanoparticles are locked in the particle boundary of a polycrystalline body of the Na-P1-type zeolite, a structure whereby some magnetite nanoparticles are substituted inside the Na-P1-type zeolite crystals and a nano complex is formed therein, or both of these structures.

Description

磁化ゼオライト及びその製造方法並びにセシウムの選択特異的捕獲方法Magnetized zeolite, method for producing the same, and selective specific capture method for cesium
　本発明は、磁化ゼオライト及びその製造方法並びにセシウムの選択特異的捕獲方法に関するものである。 The present invention relates to a magnetized zeolite, a method for producing the same, and a method for selectively capturing cesium.
　原子力発電所の事故等によって放射性核種で汚染された土壌から放射性核種の１つである放射性セシウムを除去するための除染方法が要求されている。放射性セシウムの除染方法の１つとしてゼオライトを利用することが考えられている。ゼオライトは、電気的親和力によりセシウムに対して吸着作用をもつことが知られている（例えば特許文献１から３を参照。）。 There is a need for a decontamination method for removing radiocesium, which is one of the radionuclides, from soil contaminated with radionuclides due to accidents at nuclear power plants. As one of the methods for decontaminating radioactive cesium, it is considered to use zeolite. It is known that zeolite has an adsorbing action on cesium due to electric affinity (see, for example, Patent Documents 1 to 3).
　ゼオライトは、結晶構造中に無数の孔隙をもつアルミノ珪酸塩であって、Ｍ－Ａｌ－Ｓｉ－Ｏ（Ｍはアルカリ金属又はアルカリ土類金属）から成る物質である。ゼオライトに関し、Ｓｉ／Ａｌ比が小さい程、同像置換によってゼオライト骨格が負に帯電し、それを補償するためにＭプラスイオンが必要となる。また、ゼオライトは、Ｓｉ／Ａｌ比が小さい程、陽イオン交換容量（ＣＥＣ；Cation Exchange Capacity）が向上する。 Zeolite is an aluminosilicate having an infinite number of pores in the crystal structure, and is a substance composed of M-Al-Si-O (M is an alkali metal or alkaline earth metal). With respect to zeolite, the smaller the Si / Al ratio, the more negatively charged the zeolite skeleton is due to isomorphous substitution, and M plus ions are required to compensate for it. In addition, the cation exchange capacity (CEC) of zeolite increases as the Si / Al ratio decreases.
　また、流体中に混合されたゼオライトを回収する方法として、ゼオライトと磁性粒子とを含む吸着剤を用い、磁選によって吸着剤を回収する方法が知られている（例えば特許文献４から６を参照。）。 Further, as a method for recovering zeolite mixed in a fluid, a method is known in which an adsorbent containing zeolite and magnetic particles is used and the adsorbent is recovered by magnetic separation (see, for example, Patent Documents 4 to 6). ).
特開平１０－１５４０１号公報Japanese Patent Laid-Open No. 10-15401 特開平８－２７１６９２号公報Japanese Patent Laid-Open No. 8-271699 特開平６－１８６３９６号公報JP-A-6-186396 特開２００５－１７７７０９号公報JP 2005-177709 A 特開２００５－１３７９７３号公報JP 2005-137773 A 特開２００７－２３４０９７号公報JP 2007-234097 A
　しかし、天然ゼオライト等の一般的なゼオライトは、セシウムイオンの捕獲能が電気的親和力のみに頼っているために弱い。また、一般的なゼオライトは、陽イオンならば種類を問わずに捕獲するので、セシウムイオンを選択的に捕獲することができない。また、一般的なゼオライトは、土壌中の粘土層間に取り込まれているセシウムを、粘土層間から引き出してまで、ゼオライトに引きつける能力はない。 However, general zeolite such as natural zeolite is weak because the capture ability of cesium ions relies only on electric affinity. Moreover, since a general zeolite captures regardless of a kind if it is a cation, it cannot selectively capture a cesium ion. Moreover, general zeolite does not have the ability to attract cesium taken in between clay layers in soil until it is drawn out from the clay layers.
　一般的なゼオライトのセシウムイオンの捕獲能が低い理由として、２つの理由が考えられる。
　１つは、一般的なゼオライトは陽イオンならば種類を問わずに捕獲するので、ゼオライトの捕獲容量の目安となる陽イオン交換容量（ＣＥＣ値）がすぐに容量値いっぱいとなるため、目的とするセシウムイオンに対して充分働けないことである。 There are two possible reasons why the cesium ion capture ability of a general zeolite is low.
One is that, since general zeolites can be captured regardless of the type if they are cations, the cation exchange capacity (CEC value), which is a standard for the capture capacity of zeolites, is quickly filled. It does not work well against cesium ions.
　もう１つは、一般的なゼオライトは、セシウムイオンの捕獲能が電気的親和力のみに頼っているために弱く、また、物理的形状のゼオライト孔隙がセシウムイオンの直径（３.６Å（オングストローム）程度）に対して大きすぎたり小さすぎたりするなど、捕獲条件に適合しているとは言いがたいことである。 The other is that general zeolite is weak because the trapping ability of cesium ions relies only on electric affinity, and the zeolite pores of physical shape are about the diameter of cesium ions (3.6 angstroms). ) Is too large or too small to meet the capture conditions.
　例えば、天然ゼオライトの１つであるモルデナイト（Ｓｉ／Ａｌ比は５程度）は、陽イオンの捕獲容量であるＣＥＣが１２０～１５０ｍｅｑ／１００ｇ（ＳＩ単位はｃｍｏｌ（＋）・ｋｇ-1)と大きいが、結晶孔隙が５.５～８.０Åであり、セシウムイオンの直径（３.６Å）よりも大きいために、放射性セシウムの捕獲固定能が弱い。 For example, mordenite (Si / Al ratio of about 5), which is one of natural zeolites, has a large cation capture capacity of CEC of 120 to 150 meq / 100 g (SI unit is cmol (+) · kg −1 ). However, since the crystal pores are 5.5 to 8.0 mm and larger than the diameter of cesium ions (3.6 mm), the capture and fixing ability of radioactive cesium is weak.
　また、放射性セシウムによる汚染が懸念されている福島の土壌は、主に花崗岩質が風化した「まさ土」土壌である。「まさ土」土壌のＣＥＣは２０程度であり、「まさ土」土壌が風化した長石起因の粘土鉱物カオリナイトは、ＣＥＣが３～１５ｍｅｑ／１００ｇである。また、雲母起因の粘土鉱物イライトは、ＣＥＣが１０～４０ｍｅｑ／１００ｇである。さらに、イライトが変質した粘土鉱物バーミキュライトは、吸着容量の目安であるＣＥＣ値が１００～１５０ｍｅｑ／１００ｇと比較的大きいのに加えて、２：１型粘土鉱物の特性である層間膨張をし、放射性セシウムイオンを容易に層間に取り込む性質がある。したがって、このような土壌からセシウムを遊離捕獲することは困難であった。 In addition, the soil in Fukushima, where there is concern about contamination with radioactive cesium, is “masa soil” in which granite is weathered. The CEC of the “masa soil” is about 20, and the clay mineral kaolinite derived from feldspar weathered from the “masa soil” has a CEC of 3 to 15 meq / 100 g. The clay mineral illite derived from mica has a CEC of 10 to 40 meq / 100 g. Furthermore, clay mineral vermiculite with altered illite has a relatively large CEC value of 100-150 meq / 100 g, which is a measure of adsorption capacity. It has the property of easily incorporating cesium ions between layers. Therefore, it was difficult to capture cesium free from such soil.
　本発明は、土壌中又は土壌を含む液中の放射性セシウムを効率よく捕獲できる磁化ゼオライト及びその製造方法並びにセシウムの捕獲方法を提供することを目的とする。 An object of the present invention is to provide a magnetized zeolite capable of efficiently capturing radioactive cesium in soil or a liquid containing soil, a method for producing the same, and a method for capturing cesium.
　本願発明者らは、天然及び人工を含め多数の種類があるゼオライトのうち、Ｎａ－Ｐ１型ゼオライトがセシウムイオン（直径は３.６Å）と同じ大きさの結晶孔隙を無数に有することにより、セシウムイオンを選択特異的に捕獲固定する能力があることを見出した。Ｎａ－Ｐ１型ゼオライトは例えば非特許文献１に開示されている。 Among the various types of zeolites, including natural and artificial, the inventors of the present application have found that Na-P1 type zeolite has countless crystal pores having the same size as cesium ions (diameter: 3.6 mm), so that cesium It was found that it has the ability to selectively capture and fix ions selectively. Na-P1 type zeolite is disclosed in Non-Patent Document 1, for example.
　本発明に係る磁化ゼオライトの製造方法は、石炭の焼却灰又は製紙スラッジの焼却灰を含むゼオライト原料にアルカリ溶液を加えて上記焼却灰の表面を軟化させるステップと、上記焼却灰の表面が軟化された上記ゼオライト原料とマグネタイトナノ微粒子とを混合して加熱処理することによってマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライトを得るステップと、を含んでいる。 The method for producing a magnetized zeolite according to the present invention includes a step of softening the surface of the incineration ash by adding an alkaline solution to a zeolite raw material containing incineration ash of coal or paper sludge, and the surface of the incineration ash is softened. And obtaining a magnetized zeolite which is a composite material of magnetite nanoparticles and Na—P1 type zeolite by mixing and heating the zeolite raw material and magnetite nanoparticles.
　本発明の磁化ゼオライトの製造方法において、上記ゼオライト原料は、アルミン酸ナトリウム及びアルミニウム化合物のうち１つ又は複数を用いてＳｉ／Ａｌ比が２以下に調整されたものである例を挙げることができる。 In the method for producing a magnetized zeolite of the present invention, the zeolite raw material may be an example in which the Si / Al ratio is adjusted to 2 or less using one or more of sodium aluminate and an aluminum compound. .
　本発明に係る磁化ゼオライトは、本発明の磁化ゼオライトの製造方法によって得られた磁化ゼオライトであって、Ｎａ－Ｐ１型ゼオライト多結晶体の粒界にマグネタイトナノ微粒子が閉じ込められている、もしくはＮａ－Ｐ１型ゼオライト結晶内でマグネタイトナノ微粒子が一部置換してナノ複合体が形成されている、又はそれらの両方の構造をもつマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である。 The magnetized zeolite according to the present invention is a magnetized zeolite obtained by the method for producing a magnetized zeolite of the present invention, wherein magnetite nanoparticles are confined at the grain boundaries of the Na—P1 type zeolite polycrystal, or Na— This is a composite material of a magnetite nanoparticle and Na—P1 type zeolite in which a nanocomposite is formed by partial substitution of magnetite nanoparticles in a P1 type zeolite crystal, or both of these structures.
　本発明に係るセシウムの捕獲方法は、本発明の磁化ゼオライトを土壌中又は土壌を含む液中に混合するステップと、上記磁化ゼオライトを磁選によって回収することにより、土壌中又は土壌を含む液中の放射性セシウムを選択特異的に捕獲するステップと、を含んでいる。 The method for capturing cesium according to the present invention comprises a step of mixing the magnetized zeolite of the present invention in soil or a liquid containing soil, and recovering the magnetized zeolite by magnetic separation, so that the Selectively and specifically capturing radioactive cesium.
　本発明のセシウムの捕獲方法は、上記磁選によって回収された上記磁化ゼオライトを再利用する例を挙げることができる。ただし、本発明のセシウムの捕獲方法は、回収された磁化ゼオライトを再利用する構成に限定されない。 Examples of the method for capturing cesium according to the present invention include reusing the magnetized zeolite recovered by the magnetic separation. However, the method for capturing cesium of the present invention is not limited to a configuration in which the recovered magnetized zeolite is reused.
　また、本発明のセシウムの捕獲方法は、上記磁選によって回収された上記磁化ゼオライトから放射性セシウムを溶出させた後、上記磁化ゼオライトを再利用する例を挙げることができる。なお、本発明のセシウムの捕獲方法は、磁選によって回収された磁化ゼオライトから放射性セシウムを溶出させる処理を行うことなく、磁化ゼオライトを再利用してもよい。 In addition, the method for capturing cesium of the present invention can be exemplified by reusing the magnetized zeolite after elution of radioactive cesium from the magnetized zeolite recovered by the magnetic separation. In the cesium capturing method of the present invention, the magnetized zeolite may be reused without performing the process of eluting radioactive cesium from the magnetized zeolite recovered by magnetic separation.
　本発明の磁化ゼオライト及びその製造方法は、土壌中又は土壌を含む液中の放射性セシウムを効率よく捕獲できるマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライトを提供できる。 The magnetized zeolite and the method for producing the same of the present invention can provide a magnetized zeolite which is a composite material of magnetite nanoparticles and Na—P1 type zeolite capable of efficiently capturing radioactive cesium in the soil or a liquid containing the soil.
　本発明のセシウムの捕獲方法は、本発明の磁化ゼオライトを用いて、土壌中又は土壌を含む液中の放射性セシウムを効率よく捕獲できる。さらに、土壌中又は土壌を含む液中に混合されたＮａ－Ｐ１型ゼオライトは磁選によって回収されるので、本発明のセシウムの捕獲方法は、セシウムを捕獲したゼオライトの回収が容易になる。 The method for capturing cesium of the present invention can efficiently capture radioactive cesium in soil or in a liquid containing soil using the magnetized zeolite of the present invention. Furthermore, since the Na—P1 type zeolite mixed in the soil or the liquid containing the soil is recovered by magnetic separation, the method for capturing cesium of the present invention makes it easy to recover the zeolite capturing the cesium.
磁化ゼオライトの製造方法の一実施例を説明するための模式的な図である。It is a schematic diagram for demonstrating one Example of the manufacturing method of a magnetized zeolite. Ｎａ－Ｐ１型ゼオライトの骨格構造モデルを示す図である。FIG. 3 is a view showing a framework structure model of Na—P1 type zeolite. 溶液中でのＮａ－Ｐ１型ゼオライトのセシウムイオン及びストロンチウムイオンの捕獲能を調べた結果を示す図である。It is a figure which shows the result of having investigated the capture ability of the cesium ion and the strontium ion of Na-P1 type | mold zeolite in a solution. 土壌中のセシウムに対するＮａ－Ｐ１型ゼオライトの捕獲能を調べた結果を示す図である。It is a figure which shows the result of having investigated the capture ability of the Na-P1 type zeolite with respect to cesium in soil. セシウムを捕獲した磁化ゼオライトの回収方法を説明するための概念図である。It is a conceptual diagram for demonstrating the collection | recovery method of the magnetized zeolite which captured the cesium. 本発明の磁化ゼオライトを用いた磁選を複数回行なったときの、土壌中の放射性セシウム濃度の変化を示す図である。It is a figure which shows the change of the radioactive cesium density | concentration in soil when the magnetic separation using the magnetized zeolite of this invention is performed in multiple times. 磁化ゼオライトを用いた土壌の除染方法を説明するための概念図である。It is a conceptual diagram for demonstrating the decontamination method of the soil using a magnetized zeolite. 磁化ゼオライトを再利用したときの、磁選段数と土壌の放射能濃度の関係を示す図である。It is a figure which shows the relationship between the number of magnetic selection stages and the radioactivity density | concentration of soil when reusing a magnetized zeolite.
　図１は、磁化ゼオライトの製造方法の一実施例を説明するための模式的な図である。
　例えば、塩化（ＩＩ）鉄もしくは塩化（ＩＩＩ）鉄又はその両方を含む鉄塩溶液１に２ｍｏｌ／Ｌ（モル／リットル）の水酸化ナトリウム溶液３を添加し、１００℃の条件で混合して、共沈法によりマグネタイトナノ微粒子の分散液を得た。得られたマグネタイトナノ微粒子の平均粒径は約３０ｎｍ（ナノメートル）である。 FIG. 1 is a schematic diagram for explaining one embodiment of a method for producing magnetized zeolite.
For example, 2 mol / L (mol / liter) of sodium hydroxide solution 3 is added to iron salt solution 1 containing iron (II) chloride or iron (III) chloride or both, and mixed at 100 ° C. A dispersion of magnetite nanoparticles was obtained by coprecipitation. The average particle size of the obtained magnetite nanoparticles is about 30 nm (nanometers).
　例えば蛍光Ｘ線分析により予めＳｉ／Ａｌ比が調べられた石炭焼却灰に、Ｓｉ／Ａｌ比が２になるように水酸化アルミニウムを混合してゼオライト原料５を得た。ゼオライト原料５に２ｍｏｌ／Ｌの水酸化ナトリウム溶液７を添加し、室温で２４時間放置した。これにより、表面が軟化した焼却灰を含むゼオライト原料を得た。 For example, the zeolite incineration ash whose Si / Al ratio was previously examined by fluorescent X-ray analysis was mixed with aluminum hydroxide so that the Si / Al ratio was 2, to obtain a zeolite raw material 5. A 2 mol / L sodium hydroxide solution 7 was added to the zeolite raw material 5 and allowed to stand at room temperature for 24 hours. Thereby, the zeolite raw material containing the incinerated ash whose surface was softened was obtained.
　マグネタイトナノ微粒子と、表面が軟化した焼却灰を含むゼオライト原料とを混合し、１００℃、２４時間の条件で加熱還流（加熱処理）した。これにより、Ｎａ－Ｐ１型ゼオライト９とマグネタイトナノ微粒子１１の複合材料である磁化ゼオライト１３を得た。 Magnetite nanoparticles were mixed with zeolite raw material containing incinerated ash whose surface was softened, and heated to reflux (heat treatment) at 100 ° C. for 24 hours. As a result, a magnetized zeolite 13 which is a composite material of the Na—P1 type zeolite 9 and the magnetite nanoparticles 11 was obtained.
　磁化ゼオライト１３において、Ｎａ－Ｐ１型ゼオライト９とマグネタイトナノ微粒子１１のモル比（Ｎａ－Ｐ１型ゼオライト：マグネタイト）は約７：３であった。Ｎａ－Ｐ１型ゼオライト９の粒径は数十μｍ（マイクロメートル）程度であった。また、マグネタイトナノ微粒子１１の粒径は数十ｎｍ程度であった。 In the magnetized zeolite 13, the molar ratio of Na—P1 type zeolite 9 to magnetite nanoparticle 11 (Na—P1 type zeolite: magnetite) was about 7: 3. The particle diameter of the Na—P1 type zeolite 9 was about several tens of μm (micrometer). The particle size of the magnetite nanoparticle 11 was about several tens of nm.
　磁化ゼオライト１３において、Ｎａ－Ｐ１型ゼオライト９の結晶内にマグネタイトナノ微粒子１１が一部置換して、ナノ複合体が形成されている。また、Ｎａ－Ｐ１型ゼオライト９の多結晶体の粒界にマグネタイトナノ微粒子１１が閉じ込められている。
　このように、磁化ゼオライト１３は、Ｎａ－Ｐ１型ゼオライト粒子とマグネタイトナノ微粒子とが単に混合されたものとは構造が異なっている。 In the magnetized zeolite 13, the magnetite nanoparticles 11 are partially substituted in the crystals of the Na—P1 type zeolite 9 to form a nanocomposite. In addition, magnetite nanoparticles 11 are confined at the grain boundaries of the polycrystalline Na—P1 zeolite 9.
Thus, the magnetized zeolite 13 has a different structure from that obtained by simply mixing the Na—P1 type zeolite particles and the magnetite nanoparticles.
　この実施例では、マグネタイトナノ微粒子とゼオライト原料５とを混合して加熱処理する前に、ゼオライト原料５に含まれる焼却灰の表面を軟化させる前処理を行なっている。この前処理を行なうことにより、混合及び加熱処理によってＮａ－Ｐ１型ゼオライト９が合成される際に、上記前処理を行なわない場合に比べて、Ｎａ－Ｐ１型ゼオライト９の結晶にマグネタイトナノ微粒子１１の微粒子が取り込まれやすくなる。 In this embodiment, before mixing and heating the magnetite nanoparticles and the zeolite raw material 5, a pretreatment is performed to soften the surface of the incinerated ash contained in the zeolite raw material 5. By performing this pretreatment, when the Na—P1 type zeolite 9 is synthesized by mixing and heat treatment, the magnetite nanoparticles 11 are added to the crystals of the Na—P1 type zeolite 9 as compared with the case where the pretreatment is not performed. The fine particles are easily taken up.
　また、石炭焼却灰に対して水酸化アルミニウムを用いたＳｉ／Ａｌ比の調整をしない場合、マグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料のほかにムライトなどの不純物を多く含む磁化ゼオライトが得られた。ゼオライト原料に対するＳｉ／Ａｌ比の調整作業の省略は、製造方法の簡略化や、アルミニウム化合物の添加を行なわないことなどから、磁化ゼオライトの製造コストを下げることが可能である、などの利点がある。 In addition, when the Si / Al ratio using aluminum hydroxide is not adjusted for the coal incineration ash, a magnetized zeolite containing a large amount of impurities such as mullite in addition to the composite material of magnetite nanoparticles and Na-P1 type zeolite is obtained. It was. Omission of the Si / Al ratio adjustment work for the zeolite raw material has advantages such as simplification of the manufacturing method and the absence of the addition of an aluminum compound, which can reduce the manufacturing cost of the magnetized zeolite. .
　図２は、Ｎａ－Ｐ１型ゼオライトの骨格構造モデルを示す図である。
　Ｎａ－Ｐ１型ゼオライト９の化学式は、非特許文献１ではＮａ6Ａｌ6Ｓｉ10Ｏ32・１２Ｈ2Ｏとして述べられている。Ｎａ－Ｐ１型ゼオライト９の構造の基本的な単位はＳｉＯ4又はＡｌＯ4の同じ四面体構造である。したがって、Ｎａ－Ｐ１型ゼオライト９は、Ｓｉ／Ａｌ比がある程度変化しても、Ｎａ－Ｐ１型ゼオライト構造を維持することができる。 FIG. 2 is a diagram showing a framework structure model of Na—P1 type zeolite.
The chemical formula of the Na-P1 type zeolite 9 is described as Na 6 Al 6 Si 10 O 32 · 12H 2 O in Non-Patent Document 1. The basic unit of the structure of the Na—P1 type zeolite 9 is the same tetrahedral structure of SiO 4 or AlO 4 . Therefore, the Na—P1 type zeolite 9 can maintain the Na—P1 type zeolite structure even if the Si / Al ratio changes to some extent.
　Ｎａ－Ｐ１型ゼオライト９の結晶孔隙は、３．６Å程度であり、セシウムイオンの直径とほぼ同じである。したがって、Ｎａ－Ｐ１型ゼオライト９はセシウムイオンに対して特に優れた選択捕獲特性をもっている。 The crystal pores of the Na-P1 type zeolite 9 are about 3.6 cm, which is almost the same as the diameter of cesium ions. Therefore, the Na—P1 type zeolite 9 has particularly excellent selective capture characteristics for cesium ions.
　また、Ｎａ－Ｐ１型ゼオライト９のＳｉ／Ａｌ比は２よりも小さい。すなわち、Ｎａ－Ｐ１型ゼオライト９は高いＣＥＣをもつ。Ｎａ－Ｐ１型ゼオライト９のＣＥＣは２５０ｍｅｑ／１００ｇ以上である。なお、Ｎａ－Ｐ１型ゼオライトにおいてＳｉ／Ａｌ比がさらに下げられると、Ｎａ－Ｐ１型ゼオライトのＣＥＣは４００～５００ｍｅｑ／１００ｇになることも可能である。 Further, the Si / Al ratio of the Na—P1 type zeolite 9 is smaller than 2. That is, the Na—P1 type zeolite 9 has a high CEC. The CEC of Na—P1 type zeolite 9 is 250 meq / 100 g or more. If the Si / Al ratio is further lowered in the Na—P1 type zeolite, the CEC of the Na—P1 type zeolite can be 400 to 500 meq / 100 g.
　図３は、溶液中でのＮａ－Ｐ１型ゼオライトのセシウムイオン（Ｃｓ+）及びストロンチウムイオン（Ｓｒ2+）の捕獲能を調べた結果を示す図である。図３において、横軸は溶液５０ｍｌ（ミリリットル）中へのゼオライト投入量（ｇ）を示す。縦軸はセシウムイオン又はストロンチウムイオンの除去率（％）を示す。 FIG. 3 is a diagram showing the results of examining the capture ability of cesium ions (Cs + ) and strontium ions (Sr 2+ ) of Na—P1 type zeolite in a solution. In FIG. 3, the horizontal axis indicates the amount of zeolite charged (g) in 50 ml (milliliter) of the solution. The vertical axis represents the removal rate (%) of cesium ions or strontium ions.
　１０ｍｍｏｌ／Ｌの濃度のセシウムイオン又はストロンチウムイオンを含む溶液５０ｍｌ中にＮａ－Ｐ１型ゼオライトを０.１ｇ又は０.２ｇ投入し、Ｎａ－Ｐ１型ゼオライトにセシウムイオン又はストロンチウムイオンを吸着させた。その後、遠心分離によってＮａ－Ｐ１型ゼオライトを除去した上澄み液について、セシウムイオン又はストロンチウムイオンの濃度を原子吸光度分析で測定した。 0.1 g or 0.2 g of Na—P1 type zeolite was put into 50 ml of a solution containing cesium ions or strontium ions at a concentration of 10 mmol / L, and cesium ions or strontium ions were adsorbed on the Na—P1 type zeolite. Thereafter, the concentration of cesium ions or strontium ions in the supernatant from which Na-P1 type zeolite was removed by centrifugation was measured by atomic absorption analysis.
　セシウムイオンの除去率はそれぞれ９９％であった。また、溶液５０ｍｌ中に、Ｎａ－Ｐ１型ゼオライトを０.１ｇ投入したときのストロンチウムイオンの除去率は９５％、Ｎａ－Ｐ１型ゼオライトを０.２ｇ投入したときのストロンチウムイオンの除去率は９６％であった。 Each cesium ion removal rate was 99%. The removal rate of strontium ions when 0.1 g of Na-P1 type zeolite was added to 50 ml of the solution was 95%, and the removal rate of strontium ions when 0.2 g of Na-P1 type zeolite was added was 96%. Met.
　このように、Ｎａ－Ｐ１型ゼオライトはセシウムイオンに対して高い捕獲能を示した。また、Ｎａ－Ｐ１型ゼオライトはストロンチウムイオンに対しても高い捕獲能を示すことがわかった。 Thus, the Na-P1 type zeolite showed a high capturing ability for cesium ions. It was also found that Na-P1 type zeolite showed a high capturing ability for strontium ions.
　図４は、土壌中のセシウムに対するＮａ－Ｐ１型ゼオライトの捕獲能を調べた結果を示す図である。図４において、横軸は土壌に対するゼオライトの混合量（重量％）を示す。縦軸はセシウムイオンの溶出量（ｍｍｏｌ・ｋｇ-1）を示す。セシウム固定土壌として、花崗岩質土壌にバーミキュライト（ＣＥＣ：３～１５ｍｅｑ／１００ｇ）が１０重量％で混合されたものを用いた。セシウムの捕獲能は、所定量のＮａ－Ｐ１型ゼオライトが混合されたセシウム固定土壌を２時間含水ミキシングした後、その土壌からのセシウムイオンの溶出量を測定することにより求められた。 FIG. 4 is a diagram showing the results of examining the capture ability of Na—P1 type zeolite for cesium in soil. In FIG. 4, the horizontal axis indicates the amount of zeolite mixed with the soil (% by weight). The vertical axis represents the cesium ion elution amount (mmol · kg −1 ). As cesium-fixed soil, granitic soil mixed with vermiculite (CEC: 3 to 15 meq / 100 g) at 10% by weight was used. The cesium capture ability was determined by measuring the amount of cesium ions eluted from the cesium-fixed soil mixed with a predetermined amount of Na-P1-type zeolite after water mixing for 2 hours.
　Ｎａ－Ｐ１型ゼオライトの混合量が０％（Ｃｓ飽和土壌）の場合に比べ、Ｎａ－Ｐ１型ゼオライトの混合量が０.１％の場合は２３％、１％の場合は７４％、１０％の場合は８５％のセシウムを捕獲することができた。これは、Ｎａ－Ｐ１型ゼオライトがＣＥＣの大きい土壌中からのセシウムの捕獲が可能であることを意味する。 Compared to the case where the mixing amount of the Na-P1 type zeolite is 0% (Cs saturated soil), the mixing amount of the Na-P1 type zeolite is 0.1%, 23%, the case of 1% is 74%, 10%. In the case of, 85% of cesium could be captured. This means that Na-P1 type zeolite can capture cesium from soil with a large CEC.
　図３及び図４を参照して、磁化されていないＮａ－Ｐ１型ゼオライトのセシウム及びストロンチウムに対する捕獲能について説明した。本発明の磁化ゼオライトは、Ｎａ－Ｐ１型ゼオライト多結晶体の粒界にマグネタイトナノ微粒子が閉じ込められている、もしくはＮａ－Ｐ１型ゼオライト結晶内でマグネタイトナノ微粒子が一部置換してナノ複合体が形成されている、又はそれらの両方の構造をもつマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である。本発明の磁化ゼオライトは、Ｎａ－Ｐ１型ゼオライト結晶を含んでいるので、セシウム及びストロンウムに対して、磁化されていないＮａ－Ｐ１型ゼオライトと同様の捕獲能を有する。 Referring to FIGS. 3 and 4, the capturing ability of unmagnetized Na—P1 type zeolite for cesium and strontium was described. In the magnetized zeolite of the present invention, the magnetite nanoparticles are confined at the grain boundaries of the Na—P1 type zeolite polycrystal, or the magnetite nanoparticles are partially substituted in the Na—P1 type zeolite crystal to form a nanocomposite. It is a composite material of magnetite nanoparticles and Na—P1 type zeolite that are formed or have both structures. Since the magnetized zeolite of the present invention contains Na—P1 type zeolite crystals, it has the same trapping ability with respect to cesium and stronium as non-magnetized Na—P1 type zeolite.
　図５は、セシウムを捕獲した磁化ゼオライトの回収方法を説明するための概念図である。
　土壌粒子１９に捕獲されたセシウム（Ｃｓ）２１を含むセシウム汚染土壌に顆粒状の磁化ゼオライト１３を混合し、さらに塩化カリウム等の遊離剤を加えて含水振とうを行ない、セシウム２１を磁化ゼオライト１３に捕獲させる。 FIG. 5 is a conceptual diagram for explaining a method for recovering magnetized zeolite capturing cesium.
Granular magnetized zeolite 13 is mixed with cesium-contaminated soil containing cesium (Cs) 21 captured by the soil particles 19, and a water-containing shake is added by adding a release agent such as potassium chloride. To capture.
　例えば、マグネットプーリー２３とドラムセパレーター２５とを備えた磁選機を用いて、セシウム２１を捕獲した磁化ゼオライト１３と、セシウムが除去された土壌粒子１９とを分離する。これにより、浄化された土壌粒子１９が得られる。なお、磁選機はマグネットプーリー２３とドラムセパレーター２５とを備えたものに限定されず、どのような構造のものであってもよい。 For example, using a magnetic separator equipped with a magnet pulley 23 and a drum separator 25, the magnetized zeolite 13 capturing the cesium 21 and the soil particles 19 from which the cesium has been removed are separated. Thereby, the purified soil particle 19 is obtained. The magnetic separator is not limited to the one provided with the magnet pulley 23 and the drum separator 25, and may have any structure.
　図６は、本発明の磁化ゼオライトを用いた磁選を複数回行なったときの、土壌中の放射性セシウム濃度の変化を示す図である。図６において、横軸は磁選回数を示す。縦軸は放射性セシウム濃度（％）を示す。 FIG. 6 is a diagram showing changes in the concentration of radioactive cesium in the soil when magnetic separation using the magnetized zeolite of the present invention is performed a plurality of times. In FIG. 6, the horizontal axis indicates the number of magnetic separations. The vertical axis represents the radioactive cesium concentration (%).
　土壌として、放射能濃度が１２０００～１６０００Ｂｑ／ｋｇ（ベクレル／キログラム）の土壌を用いた。４種類のサンプルＡ，Ｂ，Ｃ，Ｄは、放射性セシウムを土壌から一旦遊離させるために必要なカリウム塩水溶液やアンモニウム塩水溶液などの遊離剤の種類の違いを示している。 As the soil, a soil having a radioactivity concentration of 12000 to 16000 Bq / kg (becquerel / kilogram) was used. The four types of samples A, B, C, and D show the difference in the types of release agents such as an aqueous potassium salt solution and an aqueous ammonium salt solution that are necessary for once releasing radioactive cesium from the soil.
　サンプルＡの遊離剤は０.１％塩化カリウムと４％シュウ酸を含んだ溶液である。サンプルＢの遊離剤は０.１％塩化カリウムと４％シュウ酸と４％シュウ酸アンモニウムを含んだ溶液である。サンプルＣの遊離剤は０.１％塩化カリウムと２％シュウ酸と２％シュウ酸アンモニウムを含んだ溶液である。サンプルＤの遊離剤は０.１％塩化カリウムと４％シュウ酸アンモニウムを含んだ溶液である。各サンプルは、土壌２ｋｇに、磁化ゼオライト２００ｇと遊離剤２Ｌ（リットル）を混合して１０分間攪拌したものである。 Sample A release agent is a solution containing 0.1% potassium chloride and 4% oxalic acid. Sample B release agent is a solution containing 0.1% potassium chloride, 4% oxalic acid and 4% ammonium oxalate. Sample C release agent is a solution containing 0.1% potassium chloride, 2% oxalic acid and 2% ammonium oxalate. The release agent for Sample D is a solution containing 0.1% potassium chloride and 4% ammonium oxalate. Each sample is obtained by mixing 200 g of magnetized zeolite and 2 L (liter) of release agent in 2 kg of soil and stirring for 10 minutes.
　各サンプルに対してそれぞれ３回の磁選を行なった。磁化ゼオライトと遊離剤の添加は初回のみで、２回目以降は磁選操作のみである。各サンプルとも、磁選回数が増すほど放射性セシウム濃度が小さくなった。３回の磁選操作により、約８０％の放射性セシウムの除去に成功した。 Each magnetic sample was magnetically selected three times. The addition of magnetized zeolite and release agent is only the first time, and the second and subsequent times are only magnetic separation operations. In each sample, the concentration of radioactive cesium decreased as the number of magnetic separations increased. About 80% of the radioactive cesium was successfully removed by three magnetic separation operations.
　なお、放射性セシウムを土壌から一旦遊離させるため遊離剤は、上記サンプルＡ，Ｂ，Ｃ，Ｄに用いられたものに限定されない。 In addition, since the radioactive cesium is once released from the soil, the release agent is not limited to those used in the samples A, B, C, and D.
　次に、除染に使用された磁化ゼオライトの再利用について説明する。
　図７は、磁化ゼオライトを用いた土壌の除染方法を説明するための概念図である。 Next, reuse of the magnetized zeolite used for decontamination will be described.
FIG. 7 is a conceptual diagram for explaining a soil decontamination method using magnetized zeolite.
（１）放射性Ｃｓ溶出工程：土壌粒子１９に捕獲されたセシウム２１（Ｃｓ+）を含む土壌に、例えば塩化カリウム等の遊離剤が混合され、含水振とうされる。土壌粒子１９に捕獲されているセシウム２１はカリウムイオン２７（Ｋ+）に置換されて土壌粒子１９から溶出する。なお、遊離剤は塩化カリウムに限定されず、他の遊離剤、例えば他のカリウム塩やアンモニウム塩であってもよい。 (1) Radioactive Cs elution step: A soil containing cesium 21 (Cs + ) captured by the soil particles 19 is mixed with a free agent such as potassium chloride and shaken with water. The cesium 21 captured in the soil particles 19 is replaced with potassium ions 27 (K + ) and is eluted from the soil particles 19. The release agent is not limited to potassium chloride, and other release agents such as other potassium salts and ammonium salts may be used.
（２）磁化ゼオライト移行工程：さらに磁化ゼオライト１３が混合される。セシウム２１が磁化ゼオライト１３に捕獲される。磁化ゼオライト１３には、セシウム２１の他に、カリウムイオン２７が捕獲されている。 (2) Magnetized zeolite transfer step: Magnetized zeolite 13 is further mixed. Cesium 21 is captured by the magnetized zeolite 13. In addition to cesium 21, potassium ions 27 are captured in the magnetized zeolite 13.
（３）磁化ゼオライト磁選工程（減量１）：磁石２９を用いた磁選によって磁化ゼオライト１３が取り出される。回収された磁化ゼオライト１３にはセシウム２１が捕獲されている。この工程での磁選段数は１回でもよいが、磁選は複数回、例えば２～３回行なわれることが好ましい。ここまでの工程は、図５を参照して説明した磁化ゼオライトの回収方法と同様である。 (3) Magnetized zeolite magnetic separation step (weight reduction 1): Magnetized zeolite 13 is taken out by magnetic separation using a magnet 29. Cesium 21 is captured in the recovered magnetized zeolite 13. The number of magnetic selection steps in this step may be one, but magnetic selection is preferably performed a plurality of times, for example, 2 to 3 times. The steps so far are the same as the magnetized zeolite recovery method described with reference to FIG.
（４）磁化ゼオライト再利用工程（減量２）：上記工程（３）で磁選によって回収された磁化ゼオライト１３は再利用される。具体的には、上記工程（３）で回収された磁化ゼオライト１３は上記工程（２）に使用される。磁化ゼオライト１３の再利用可能回数は、土壌中のセシウム２１の濃度などによって変化するが、例えば５回である。ただし、磁化ゼオライト１３の再利用回数は特に限定されない。 (4) Magnetized zeolite reuse step (weight loss 2): The magnetized zeolite 13 recovered by magnetic separation in the step (3) is reused. Specifically, the magnetized zeolite 13 recovered in the step (3) is used in the step (2). The number of times that the magnetized zeolite 13 can be reused varies depending on the concentration of cesium 21 in the soil, but is, for example, five times. However, the number of reuses of the magnetized zeolite 13 is not particularly limited.
（５）磁化ゼオライトからの溶出工程：再利用回数が任意の規定回数、例えば５回に達した磁化ゼオライト１３は、再利用（上記工程（４））されずに、捕獲されているセシウム２１の溶出処理が施される。例えば、濃度の高いカリウム塩が遊離剤として磁化ゼオライト１３に混合される。磁化ゼオライト１３に捕獲されているセシウム２１はカリウムイオン２７に置換される。ここで使用されるカリウム塩の濃度は磁化ゼオライト１３からセシウム２１を溶出させることができる濃度であれば特に限定されない。また、遊離剤はカリウム塩に限定されるものではない。遊離剤はセシウム２１を溶出させることができる遊離剤であれば特に限定されず、例えばアンモニウム塩であってもよい。 (5) Elution step from magnetized zeolite: The magnetized zeolite 13 whose number of reuses reaches an arbitrary specified number of times, for example, 5 times, is not reused (the above step (4)), and the captured cesium 21 Elution treatment is performed. For example, a high concentration potassium salt is mixed with the magnetized zeolite 13 as a release agent. The cesium 21 captured in the magnetized zeolite 13 is replaced with potassium ions 27. The concentration of the potassium salt used here is not particularly limited as long as cesium 21 can be eluted from the magnetized zeolite 13. Further, the releasing agent is not limited to the potassium salt. The release agent is not particularly limited as long as it can release cesium 21, and may be, for example, an ammonium salt.
（６）溶出Ｃｓ濃縮工程（減量３）：上記工程（５）で磁化ゼオライト１３から溶出したセシウム２１を含む溶液から磁化ゼオライト１３が例えば磁石を用いて回収される。磁化ゼオライト１３が回収された溶液に含まれるセシウム２１は、例えば加熱乾燥などによって固形化される。なお、ここで回収された磁化ゼオライト１３は再利用が可能である。 (6) Elution Cs concentration step (weight loss 3): The magnetized zeolite 13 is recovered from the solution containing cesium 21 eluted from the magnetized zeolite 13 in the step (5) using, for example, a magnet. The cesium 21 contained in the solution from which the magnetized zeolite 13 is recovered is solidified by, for example, heat drying. The magnetized zeolite 13 collected here can be reused.
　仮に、土壌重量に対して１０％の磁化ゼオライトが使用され、磁化ゼオライトに放射性Ｃｓが１００％移行したとすると、１／１０の減量化がされたことになる（減量１）。さらに、磁選によって回収された放射性Ｃｓを含む使用済み磁化ゼオライトが同様の除染に使用され、放射性Ｃｓが磁化ゼオライトに捕獲されている状態で再利用できたとすると、２倍の土壌量に対して除染ができたことになる。この場合、合計で１／２０の減量化がされたことになる（減量２）。例えば、放射性Ｃｓが捕獲されている使用済み磁化ゼオライトを４回再利用でき、同一の磁化ゼオライトを合計で５回使用することができれば、１／５０の減量化が実現されることになる。ゼオライトの吸着サイト数と比べ、土壌に含まれる放射性Ｃｓの量はきわめて微量であることから、磁選回収された磁化ゼオライトを繰り返して使用することが可能である。このように、使用済み磁化ゼオライトの再利用は除染効率を向上させる。 If 10% of the magnetized zeolite is used with respect to the soil weight, and the radioactive Cs is transferred to the magnetized zeolite by 100%, the amount is reduced by 1/10 (weight reduction 1). Furthermore, if the used magnetized zeolite containing radioactive Cs recovered by magnetic separation is used for the same decontamination and can be reused in a state where the radioactive Cs is captured by the magnetized zeolite, the amount of soil is doubled. Decontamination has been completed. In this case, the total weight reduction is 1/20 (weight loss 2). For example, if the used magnetized zeolite in which radioactive Cs is captured can be reused four times and the same magnetized zeolite can be used five times in total, a reduction of 1/50 can be realized. Compared to the number of zeolite adsorption sites, the amount of radioactive Cs contained in the soil is extremely small, so that it is possible to repeatedly use magnetized zeolite recovered by magnetic separation. Thus, recycling of used magnetized zeolite improves decontamination efficiency.
　さらに、磁化ゼオライトに濃縮された放射性Ｃｓを磁化ゼオライトに対する遊離剤にて溶出させ、その液を乾燥及び固化することにより、著しい減量化が可能となる（減量３）。 Further, the radioactive Cs concentrated in the magnetized zeolite is eluted with a release agent for the magnetized zeolite, and the liquid is dried and solidified, thereby enabling a significant reduction in weight (weight reduction 3).
　本願発明者らは、放射性Ｃｓが捕獲されている磁化ゼオライトの再利用の可否について実験によって検討した。
　図８は、磁化ゼオライトを再利用したときの、磁選段数（回）と土壌の放射能濃度（％）の関係を示す図である。 The inventors of the present application examined whether or not the magnetized zeolite in which radioactive Cs is captured can be reused by experiments.
FIG. 8 is a diagram showing the relationship between the number of magnetic separation stages (times) and the radioactive concentration (%) of soil when magnetized zeolite is reused.
　放射性Ｃｓを含む土壌に混合されて磁選によって回収された放射性Ｃｓを捕獲している使用済み磁化ゼオライトを、室温で放置して乾燥させ、上記工程（４）で説明したように、再度、上記工程（２）で未使用の磁化ゼオライトの代わりに使用した。使用済み磁化ゼオライトには土壌の２～５倍程度の放射性Ｃｓが捕獲されている。土壌のサンプルとして、福島県伊達郡川俣町の土壌が用いられた。 The spent magnetized zeolite mixed with the soil containing radioactive Cs and capturing the radioactive Cs collected by magnetic separation is left to dry at room temperature, and again as described in the above step (4), the above step Used in place of unused magnetized zeolite in (2). The used magnetized zeolite captures about 2 to 5 times as much radioactive Cs as the soil. As a soil sample, soil from Kawamata Town, Date-gun, Fukushima Prefecture was used.
　この実験では、磁化ゼオライトと遊離剤を混合して１０分間ミキシング（上記工程（２））を行なった後に磁選処理（上記工程（３））を２～３回行なう処理に対して、磁選処理を１回行なう毎に、上記使用済み磁化ゼオライト１０％と遊離剤として２％しゅう酸アンモニウム溶液を加えて１０分間ミキシングを行なった。放射性Ｃｓを捕獲している使用済み磁化ゼオライトの性能を確認するためのである。 In this experiment, the magnetic separation process is performed in contrast to the process in which the magnetized zeolite and the release agent are mixed and mixed for 10 minutes (the above step (2)) and then the magnetic separation process (the above step (3)) is performed 2-3 times. Each time it was performed, 10% of the above used magnetized zeolite and 2% ammonium oxalate solution as a release agent were added and mixed for 10 minutes. This is for confirming the performance of the used magnetized zeolite capturing radioactive Cs.
　その結果、使用済み磁化ゼオライトには土壌の２～５倍程度の放射性Ｃｓが捕獲されているにも関わらず、１回目の磁選処理で約１０～２０％、２回目の磁選処理で約５０％の放射性Ｃｓ濃度の減衰を確認することができた。 As a result, the used magnetized zeolite captures about 2 to 5 times as much radioactive Cs as the soil, but about 10 to 20% in the first magnetic separation process and about 50% in the second magnetic separation process. It was possible to confirm the decay of the radioactive Cs concentration.
　図８に示されるように、再現性を確認するため５回同じ実験を行なった。その結果、ほぼ同じような結果が得られた。これにより、使用済み磁化ゼオライトの再利用が可能であることが確認された。この理由としては、土壌中の放射性Ｃｓがきわめて少ないため、磁化ゼオライトは除染に使用された後でも十分なイオン吸着性能を有していることが要因の１つであると考えられる。 As shown in FIG. 8, the same experiment was performed five times to confirm reproducibility. As a result, almost the same result was obtained. Thereby, it was confirmed that the used magnetized zeolite can be reused. The reason for this is considered that one of the factors is that the magnetized zeolite has sufficient ion adsorption performance even after being used for decontamination because the radioactive Cs in the soil is extremely small.
　また、磁選によって回収された磁化ゼオライトを再度使用していることから、回収が困難な磁化ゼオライトは最初の使用で磁選回収されずに除去されたと考えられる。したがって、使用済み磁化ゼオライトは磁選によって回収されやすい磁化ゼオライトである。このことも、使用済み磁化ゼオライトの再利用が可能であることの要因の１つであると考えられる。 Also, since magnetized zeolite recovered by magnetic separation is used again, it is considered that magnetized zeolite, which is difficult to recover, was removed without being recovered by magnetic separation in the first use. Therefore, the used magnetized zeolite is a magnetized zeolite that is easily recovered by magnetic separation. This is also considered to be one of the factors that the used magnetized zeolite can be reused.
　なお、図７を参照して説明した除染方法では、磁選によって回収された磁化ゼオライトは捕獲されている放射性Ｃｓの溶出処理（上記工程（５））が施されることなく再利用（上記工程（４））されているが、本発明のセシウムの選択特異的捕獲方法はこれに限定されない。本発明のセシウムの選択特異的捕獲方法は、磁選によって回収された磁化ゼオライトをそのまま再利用せずに、放射性セシウムを溶出させた後、再利用する構成であってもよい。この構成は、磁選によって回収された磁化ゼオライト、つまり磁選によって回収されやすい磁化ゼオライトを用いるので、除染効率を向上させることができる。 In the decontamination method described with reference to FIG. 7, the magnetized zeolite recovered by magnetic separation is reused without being subjected to the elution treatment of the captured radioactive Cs (the above step (5)) (the above step). (4)), but the method of selective and specific capture of cesium of the present invention is not limited to this. The selective and specific capture method of cesium of the present invention may be configured such that radioactive cesium is eluted and then reused without reusing the magnetized zeolite recovered by magnetic separation as it is. Since this configuration uses magnetized zeolite recovered by magnetic separation, that is, magnetized zeolite that is easily recovered by magnetic separation, decontamination efficiency can be improved.
　本発明のセシウムの捕獲方法は、福島の原子力発電所の事故に起因する放射性核種による土壌汚染に対して真の除染技術がない現状にあって、セシウム等の放射性元素のみを回収できる革新的な技術である。さらに、本発明のセシウムの捕獲方法は、大量、安価かつ使いやすさをもった普及適正のある技術として、現在の福島周辺の除染に即応する技術である。さらには、チェルノブイリなどの除染が十分には進んでいない地域でも役立つことが期待できる。 The method of capturing cesium of the present invention is an innovative method that can recover only radioactive elements such as cesium in the current situation where there is no true decontamination technology against soil contamination by radionuclides caused by an accident at a nuclear power plant in Fukushima. Technology. Furthermore, the method for capturing cesium according to the present invention is a technology that can be readily adapted to the current decontamination around Fukushima as a technology that is suitable for widespread use with a large amount, low cost and ease of use. Furthermore, it can be expected to be useful even in areas where decontamination is not sufficiently advanced, such as Chernobyl.
　上記実施例では、磁化ゼオライトを合成するためのゼオライト原料として石炭焼却灰を用いているが、石炭焼却灰に替えて製紙スラッジの焼却灰を用いてもマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライトを合成できる。また、水ガラス、アルミン酸ナトリウム及びアルミニウム化合物のうち複数を用いてＳｉ／Ａｌ比を２以下に調整した混合物を用いてマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライトを合成することもできる。 In the above embodiment, coal incineration ash is used as a zeolite raw material for synthesizing magnetized zeolite. However, even if paper incineration ash is used instead of coal incineration ash, a composite of magnetite nanoparticles and Na-P1 type zeolite is used. It is possible to synthesize magnetized zeolite as a material. In addition, magnetized zeolite, which is a composite material of magnetite nanoparticles and Na-P1 type zeolite, is synthesized using a mixture of water glass, sodium aluminate, and an aluminum compound that is adjusted to have a Si / Al ratio of 2 or less. You can also.
　また、本発明の磁化ゼオライトの製造方法おいて、ゼオライト原料のＳｉ／Ａｌ比を所望の値に調整するようにしてもよい。Ｓｉ／Ａｌ比を調整するための材料は、珪素又はアルミニウムを含む化合物であり、好ましくは水ガラス、アルミン酸ナトリウム、アルミニウム化合物である。また、Ｓｉ／Ａｌ比の値は、２以下であり、例えば２である。なお、合成用材料のＳｉ／Ａｌ比の値は、マグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料が合成される値であり、かつ２以下であれば、いくつであってもよい。 In the method for producing a magnetized zeolite of the present invention, the Si / Al ratio of the zeolite raw material may be adjusted to a desired value. The material for adjusting the Si / Al ratio is a compound containing silicon or aluminum, preferably water glass, sodium aluminate, or an aluminum compound. Moreover, the value of Si / Al ratio is 2 or less, for example, 2. The value of the Si / Al ratio of the synthesis material is a value at which the composite material of magnetite nanoparticles and Na—P1 type zeolite is synthesized, and may be any number as long as it is 2 or less.
　また、本発明の磁化ゼオライトの製造方法おいて、表面を軟化させた焼却灰を含むゼオライト原料に混合されるマグネタイトナノ微粒子の粒径は、例えば５～２００ｎｍ、好ましくは３０ｎｍ以下である。
　また、本発明の磁化ゼオライトの製造方法おいて、マグネタイトナノ微粒子は市販のものであってもよい。 In the method for producing a magnetized zeolite of the present invention, the particle size of the magnetite nanoparticles mixed with the zeolite raw material containing the incinerated ash having a softened surface is, for example, 5 to 200 nm, preferably 30 nm or less.
In the method for producing a magnetized zeolite of the present invention, the magnetite nanoparticles may be commercially available.
　また、本発明の磁化ゼオライトの製造方法おいて、アルカリ溶液は、水酸化ナトリウムに限定されず、他のアルカリ溶液、例えば水酸化カリウムであってもよい。 Further, in the method for producing a magnetized zeolite of the present invention, the alkaline solution is not limited to sodium hydroxide, and may be another alkaline solution such as potassium hydroxide.
　以上、本発明の実施例が説明されたが本発明はこれらに限定されるものではなく、特許請求の範囲に記載された本発明の範囲内で種々の変更が可能である。 As mentioned above, although the Example of this invention was described, this invention is not limited to these, A various change is possible within the range of this invention described in the claim.
５　ゼオライト原料
７　水酸化ナトリウム溶液（アルカリ溶液）
９　Ｎａ－Ｐ１型ゼオライト
１１　マグネタイトナノ微粒子
１３　磁化ゼオライト
１９　土壌粒子
２１　セシウム 5 Zeolite raw material 7 Sodium hydroxide solution (alkali solution)
9 Na-P1-type zeolite 11 Magnetite nanoparticles 13 Magnetized zeolite 19 Soil particles 21 Cesium

Claims (6)

  1. 　石炭の焼却灰又は製紙スラッジの焼却灰を含むゼオライト原料にアルカリ溶液を加えて前記焼却灰の表面を軟化させるステップと、
    　前記焼却灰の表面が軟化された前記ゼオライト原料とマグネタイトナノ微粒子とを混合して加熱処理することによってマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライトを得るステップと、を含んでいる磁化ゼオライトの製造方法。     Softening the surface of the incineration ash by adding an alkaline solution to the zeolite raw material containing the incineration ash of coal or the incineration ash of papermaking sludge;
    Obtaining a magnetized zeolite which is a composite material of magnetite nanoparticles and Na-P1 type zeolite by mixing and heating the zeolite raw material whose surface of the incinerated ash is softened and magnetite nanoparticles. A method for producing magnetized zeolite.
  2. 　前記ゼオライト原料は、アルミン酸ナトリウム及びアルミニウム化合物のうち１つ又は複数を用いてＳｉ／Ａｌ比が２以下に調整されたものである請求項１に記載の磁化ゼオライトの製造方法。 The method for producing a magnetized zeolite according to claim 1, wherein the zeolite raw material is adjusted to have a Si / Al ratio of 2 or less using one or more of sodium aluminate and an aluminum compound.
  3. 　請求項１又は２に記載された磁化ゼオライトの製造方法によって得られた磁化ゼオライトであって、Ｎａ－Ｐ１型ゼオライト多結晶体の粒界にマグネタイトナノ微粒子が閉じ込められている、もしくはＮａ－Ｐ１型ゼオライト結晶内でマグネタイトナノ微粒子が一部置換してナノ複合体が形成されている、又はそれらの両方の構造をもつマグネタイトナノ微粒子とＮａ－Ｐ１型ゼオライトの複合材料である磁化ゼオライト。 A magnetized zeolite obtained by the method for producing a magnetized zeolite according to claim 1 or 2, wherein magnetite nanoparticles are confined at the grain boundary of the Na-P1 type zeolite polycrystal, or the Na-P1 type Magnetized zeolite which is a composite material of a magnetite nanoparticle and Na-P1 type zeolite, in which a nanocomposite is formed by partial substitution of magnetite nanoparticles in a zeolite crystal, or both of these structures.
  4. 　請求項３に記載された磁化ゼオライトを土壌中又は土壌を含む液中に混合するステップと、
    　前記磁化ゼオライトを磁選によって回収することにより、土壌中又は土壌を含む液中の放射性セシウムを選択特異的に捕獲するステップと、を含んでいるセシウムの選択特異的捕獲方法。     Mixing the magnetized zeolite according to claim 3 in soil or a liquid containing soil;
    A step of selectively capturing radioactive cesium in soil or in a liquid containing soil by recovering the magnetized zeolite by magnetic separation, and a method for selectively capturing cesium, the method comprising:
  5. 　前記磁選によって回収された前記磁化ゼオライトを再利用する請求項４に記載のセシウムの選択特異的捕獲方法。 The method for selectively capturing cesium according to claim 4, wherein the magnetized zeolite recovered by the magnetic separation is reused.
  6. 　前記磁選によって回収された前記磁化ゼオライトから放射性セシウムを溶出させた後、前記磁化ゼオライトを再利用する請求項４又は５に記載のセシウムの選択特異的捕獲方法。 The method for selectively capturing cesium according to claim 4 or 5, wherein radioactive cesium is eluted from the magnetized zeolite recovered by the magnetic separation, and then the magnetized zeolite is reused.
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