JP2014041111A - Radioactive cesium adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent which collects radioactive cesium from liquid wastes having the radioactive cesium therein.SOLUTION: In the radioactive cesium adsorbent, complex particles having radioactive cesium adsorption ability represented by the general formula [1] defined by AM[Fe(CN)]are supported on glass wool surfaces subjected to at least one dry cleaning treatment selected from the group consisting of plasma irradiation, ozone exposure, UV irradiation, and corona discharge. (In the formula [1], A are each independently either a metal atom selected from the group consisting of Fe, Na, K, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au, W, Ru, Rh and Ag, or NH; x is an integer between 0 and 5, y is an integer between 1 and 3, and M is a metal atom selected from the group consisting of Fe, Na, K, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au, W, Ru, Rh and Ag. In addition, the compound of the formula [1] may further comprise hydration water.)

Description

  The present invention relates to a radioactive cesium adsorbent that adsorbs radioactive cesium.

The Tokyo Electric Power Fukushima Daiichi Nuclear Power Plant accident caused by the Tohoku-Pacific Ocean Earthquake that broke out on March 11, 2011 has damaged radioactive contamination throughout Fukushima Prefecture and other parts of eastern Japan. Major radioactive material has been confirmed, cesium 134, cesium 137, (each hereinafter ^"134 Cs", ^"137 Cs", may be referred to as ^"131 I") I-131 is ^a, the ¹³¹ I Since the half-life is relatively short as 8 days, ¹³⁴ Cs (half-life: 2 years) and ¹³⁷ Cs (half-life: 30 years) are highly likely to affect the environment in the long term. Therefore, there is a high social demand for practical decontamination techniques for these radioactive cesiums. When decontaminating concrete and gutters by high-pressure washing, cleaning and extracting contaminated soil, decontaminating incineration ash such as radioactively contaminated plants and rubble, or inside the nuclear power plant When the cooling water is decontaminated, since the radioactive cesium is contained in the waste liquid generated by washing, it is necessary to separate the radioactive cesium from the waste liquid and immobilize it safely.

  As a technique for separating radioactive cesium from waste liquid, a method of selectively removing radioactive cesium with a substance having cesium adsorption ability is known. For example, Patent Document 1 discloses a method for selectively extracting cesium from an aqueous effluent discharged from a spent nuclear fuel reprocessing facility or a spent fuel solution with a calix [4] arene crown ether compound. . In Patent Document 2, a nuclear power plant is obtained by an inorganic ion exchanger obtained by calcining a mixture of a crystalline phosphate compound and an alkoxysilane or a hydrolyzate thereof, or thereafter contacting with an acid. And a method of selectively adsorbing cesium ions from waste liquid containing cesium ions discharged from nuclear facilities such as nuclear fuel reprocessing plants. Further, in Patent Document 3, radioactive contaminants (such as cesium) are obtained from an aqueous solution by an adsorbent containing a transition metal ferrocyanide, particularly copper ferrocyanide and based on a fibrous chitin-containing substance obtained from fungi. A method of removing is disclosed.

  In Non-Patent Document 1, after irradiating an existing nylon fiber skeleton with an electron beam, vinylbenzyltrimethylammonium chloride is graft polymerized, and ferrocyanide ions are adsorbed on anion exchange groups in the graft polymer chain. A method is disclosed in which a nylon fiber carrying cobalt ferrocyanide is obtained by immersing in an aqueous cobalt chloride solution, and radioactive cesium is selectively adsorbed from contaminated water by the nylon fiber.

  Further, in Non-Patent Document 2, a cellulose-based cloth is dipped in a solution of potassium ferrocyanide and then dipped in an iron chloride solution to obtain a cloth soaked with Prussian blue having a cesium adsorption ability. Discloses a method for selectively removing radioactive cesium from contaminated water.

  Further, hexacyano iron-based substances having cesium adsorption ability are disclosed in Patent Documents 4 to 7 and Non-Patent Documents 3 and 4.

JP-A-8-508989 JP-A-10-202117 JP 2002-506979 gazette JP-A-5-254828 JP 7-308590 A Japanese Patent Laid-Open No. 9-173832 JP 2011-200856 A

Edited by Nikkei Printing Co., Ltd., “Measures against contamination of radioactive materials after the Great East Japan Earthquake: Environmental impact assessment, decontamination technology and its efforts from the basis of radiation” published by NTS Co., Ltd. (2012) pp. 162-163 The Chemical Industry Daily 10th page (May 29, 2012) nano tech 2011 presentation (2011.2.17) Chemistry Vol.67 No.11 (2012)

  In the conventional methods described in the prior literature, a complicated process for separating and recovering the extract containing cesium from the liquid phase is necessary, or there is a problem that the waste liquid increases due to the additionally used solvent. When high concentration radioactive cesium is recovered, there is a possibility that the adsorbent may ignite due to heat generation or decompose by radiation, and there is a possibility that it cannot be recovered safely, or after recovering radioactive cesium In order to fix safely, for example, when trying to vitrify commonly performed, there is a possibility that the adsorbent may be ignited by the heat during the solidification treatment, and there is a possibility that it can not be solidified safely was there. In addition, depending on the adsorbent, there is a problem that the adsorption efficiency of cesium ions is low, and a substance having a cesium adsorption ability is likely to fall out of the adsorbent, so that radioactive cesium cannot be efficiently recovered.

  Therefore, the present invention can recover the radioactive cesium from the waste liquid containing radioactive cesium by a simple operation, and particles having the ability to adsorb the radioactive cesium from the adsorbent even if the waste liquid contacts the adsorbent in the recovery operation The radioactive cesium can be efficiently recovered from the waste liquid because it is difficult to fall off, and even if high-concentration radioactive cesium is adsorbed, there is no risk of decomposition or ignition due to its heat generation or radiation. It is an object to provide a radioactive cesium adsorbent that can be vitrified without ignition later.

In the present invention, radioactive cesium adsorption represented by the following general formula [1] is applied to a glass wool surface subjected to at least one dry cleaning treatment selected from the group consisting of plasma irradiation, ozone exposure, UV irradiation, and corona discharge. It is a radioactive cesium adsorbent characterized in that complex particles having a function are supported.
A _x M [Fe (CN) ₆ ] _y
(In Formula [1], A is independently of each other, Fe, Na, K, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au. , W, Ru, Rh, and Ag, or NH ₄ , x is an integer of 0 to 5, y is an integer of 1 to 3, M is Fe, Na, K A metal atom selected from the group consisting of Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au, W, Ru, Rh, and Ag. The compound of the formula [1] may further contain water of hydration)

  The “dry cleaning process” means a process of decomposing and removing organic substances on the surface of the substrate in a dry process. Further, the dry cleaning treatment may have an effect that a part of the siloxane bond on the surface of the glass wool is broken by the treatment and a silanol group is generated. It is not clear why the complex particles having the radioactive cesium adsorption ability are easily carried on the glass wool surface that has been subjected to the dry washing treatment, but the complex particles having the hydroxyl group on the glass wool surface and the radioactive cesium adsorption ability by the dry washing treatment. It is conceivable that an interaction acts between the two and they can be easily adsorbed, and a bond is formed. In order to increase the amount of the complex particles supported, it is effective to increase the active points on the surface of glass wool (that is, hydroxyl groups on the surface of glass wool). Since the surface area of glass wool is large, the active points increase accordingly. The shape is more preferable as the specific surface area is larger. The above effect can be obtained even if the surface of the glass wool is subjected to a wet cleaning process, but it is necessary to dry the glass wool after the cleaning process, resulting in a problem that the process becomes complicated.

In addition, the above-mentioned “having radiocesium adsorption ability” means that radioactive cesium water is present in a gap between the crystal structures of A _x M [Fe (CN) ₆ ] _y constituting the complex particles represented by the general formula [1]. Meaning that it has the ability to easily take in a radioactive cesium hydrate that has been taken in without being desorbed, and x in the general formula [1] is an integer of 1 to 5 In this case, since the cation or ammonium ion of the metal atom represented by A has a high affinity with the radioactive cesium ion, the ion exchange between the A and the cesium ion causes the cesium ion to be taken into the complex particle and desorbed as it is. It means having the ability to be easily held without being separated.

Moreover, it is preferable that both M and A in the general formula [1] are Fe, or that A is NH ₄ and M is Fe, because the radiocesium adsorption ability of the complex particles becomes high.

  The water contact angle of the glass wool surface after the dry cleaning treatment is preferably 13 ° or less. When the water contact angle is 13 ° or less, it is preferable because more complex particles having the radioactive cesium adsorption ability can be easily supported, and the supported complex particles can be more difficult to be detached. When the angle is 10 ° or less, it is more preferable because more complex particles can be easily supported and the supported complex particles can be more easily detached. In addition, since the water contact angle on the surface of glass wool cannot be directly measured, the water contact angle is measured on the surface of a plate glass having the same composition as glass wool, and the contact angle is regarded as the water contact angle on the surface of glass wool. The surface water contact angle can be indirectly evaluated. The water contact angle of the glass wool surface subjected to the dry cleaning treatment can be obtained by measuring the water contact angle of the plate glass surface subjected to the dry cleaning treatment under the same conditions. The water contact angle on the surface of the plate glass can be measured according to JIS Z8830.

  Moreover, it is preferable that the average particle diameter (primary particle diameter) of the complex particle | grains which have the said radioactive cesium adsorption ability is 0.1-500 nm by the dynamic light-scattering method using the frequency analysis by a heterodyne method. When the average particle size is 0.1 to 500 nm, the surface area of the complex particles having the radioactive cesium adsorption ability is large, and thus the radiocesium adsorption ability per unit weight of the complex particles having the radioactive cesium adsorption ability is high. Preferably, when the average particle diameter is 200 nm or less, the surface area of the complex particles having the radioactive cesium adsorption ability is large, and thus the radiocesium adsorption ability per unit weight of the complex particles having the radioactive cesium adsorption ability is high. Therefore, it is more preferable.

Moreover, it is preferable that the specific surface area of the said glass wool is 10-1000 m < ² > / g. When the specific surface area is 10 to 1000 m ² / g, it is preferable because a large amount of the complex particles having the radioactive cesium adsorption ability can be supported, and when the specific surface area is larger than 50 m ² / g, the radioactive cesium adsorption is further performed. This is more preferable because a large amount of complex particles having a function can be supported. The specific surface area can be measured by, for example, the BET method using nitrogen gas.

Further, the present invention is a dry cleaning treatment step, wherein the glass wool surface is subjected to at least one dry cleaning treatment selected from the group consisting of plasma irradiation, ozone exposure, UV irradiation, and corona discharge,
A coating step in which a coating solution in which complex particles having the radioactive cesium adsorption ability represented by the general formula [1] are dispersed in a dispersion is brought into contact with the glass wool surface after the dry cleaning treatment step;
It is a manufacturing method of said radioactive cesium adsorbent characterized by having a drying process which dries the glass wool after the said application | coating process.

  In the manufacturing method of the said radioactive cesium adsorbent, it is preferable that the content rate of the complex particle | grains which have the radioactive cesium adsorption capacity in the said coating liquid is 0.01-20 mass%. The content is preferably 0.01 to 20% by mass because the complex particles having the radioactive cesium adsorption ability are easily supported on the surface of the glass wool in a primary particle state, and the content is preferably 0.05 to 10% by mass. % Is more efficient and preferable because the complex particles can be supported on the surface of the glass wool in a sufficient amount with little excess or deficiency.

  Moreover, in the manufacturing method of the said radioactive cesium adsorbent, it is preferable that the said coating liquid disperse | distributes the complex particle | grains which have the said radiocesium adsorption capacity in the solvent whose relative dielectric constant is 20 or more. When the relative dielectric constant of the dispersion is 20 or more, it is preferable because the complex particles having the radioactive cesium adsorption ability can be easily dispersed in the state of primary particles. When the relative dielectric constant is 25 or more, the dispersion is further performed. It is more preferable because

  Moreover, in the manufacturing method of the said radioactive cesium adsorbent, it is preferable to heat the glass wool after an application | coating process at 50-180 degreeC as the said drying process. Since the dispersion in the coating liquid adhering to the glass wool surface in the application process of the previous process can be removed in a short time by heating at 50 to 180 ° C. as the drying process, the heating temperature is preferably 80 to 180 ° C. If it exists, since the time for removing a dispersion liquid may be further shortened, productivity is improved and it is more preferable. Moreover, since the complex particle | grains which have the said radioactive cesium adsorption ability may heat | generate the decomposition product by heat when heated at the temperature exceeding 180 degreeC, it is preferable that the upper limit temperature of the said drying process is 180 degrees C or less.

  Further, in the method for producing the radioactive cesium adsorbent, the glass wool obtained after the drying step, on which the complex particles having the radioactive cesium adsorption ability are supported, is further brought into contact with a washing liquid and washed, and then 80 ° C. or less. It is preferable to dry at the temperature.

  In the radioactive cesium adsorbent of the present invention, when water is brought into contact with the adsorbent at room temperature, the concentration of total cyanide derived from the thermal decomposition product of the complex particles in the water is 1 mg / L or less. It is preferable. This is because when a radioactive cesium adsorbent is used to selectively remove radioactive cesium from contaminated water, harmful cyanide compounds derived from the thermal decomposition product of the compound represented by the general formula [1] are eluted in the water. This is because it is desirable to be difficult. For example, the total cyan concentration in the water after passing water at a flow rate of 12 ml / min on an adsorbent carrying 24 mg of complex particles having radioactive cesium adsorption capacity is 1 mg which is a regulation value of the Water Pollution Control Law. / L or less is desired. From the viewpoint of safety, the total cyan density is preferably as low as possible. When the radioactive cesium adsorbent obtained after the drying step of the present invention is used, the total cyan concentration in the water after passing through the water can be made not more than the regulation value of the Water Pollution Control Law. Further, when the adsorbent obtained by further bringing the radioactive cesium adsorbent obtained after the drying step into contact with a washing liquid and then drying at a temperature of 80 ° C. or less is used, The concentration can be made lower than or equal to the regulation value of the Water Pollution Control Law. In addition, the total cyan density | concentration in the water after the said water flow can be measured by the method based on JISK0102 38.3, for example.

  Further, the present invention is a method for selectively recovering the radioactive cesium from the waste liquid having radioactive cesium, comprising the step of bringing the waste liquid into contact with the radioactive cesium adsorbent described above. The radioactive cesium is recovered from

  In the method for recovering radioactive cesium from the waste liquid, the step of bringing the radioactive cesium into contact with the radioactive cesium adsorbent preferably circulates the waste liquid through a column packed with the adsorbent.

  The radioactive cesium adsorbent of the present invention can recover the radioactive cesium from waste liquid containing radioactive cesium by a simple operation, and even if the waste liquid comes into contact with the adsorbent in the recovery operation, the radioactive cesium adsorption capacity The complex cesium-containing particles are difficult to drop off, so that the radioactive cesium can be efficiently recovered from the waste liquid, and even if high-concentration radioactive cesium is adsorbed, the heat and radiation may cause decomposition and ignition. Because it is possible to solidify without igniting after adsorption, it has succeeded in decontaminating radioactive cesium safely and efficiently, and the adsorbent after adsorbing radioactive cesium It is effective to fix the battery safely and securely.

  As the glass wool used for the radioactive cesium adsorbent of the present invention, any glass wool that has been subjected to the above-mentioned dry cleaning treatment can be used. For example, commercially available glass wool or E glass of A glass type can be used. It is possible to use a glass wool made of a glass, S glass, C glass, AR glass, or D glass that has been subjected to the dry cleaning treatment. Glass wool generally includes phenolic resin, epoxy resin, glass wool that has been surface-treated with acrylic resin, and no-binder glass wool that has not been surface-treated as described above, but organic resins are heat resistant. Further, no binder glass wool is preferred because of its low radiation resistance. The fiber diameter is not particularly limited, but when the adsorbent of the present invention is used as a column filler, for example, in the case of processing into a cylindrical shape, a roll shape, or the like in accordance with the internal shape of the column, from the viewpoint of ease of processing. 1-20 μmφ is preferred.

  The dry cleaning treatment is a treatment necessary to carry more, more difficult to drop off, the complex particles having the radioactive cesium adsorption ability on the glass wool surface. As the plasma irradiation, for example, there is a method of irradiating plasma using a gas species such as argon, helium, nitrogen, air, oxygen, carbon dioxide under atmospheric pressure or low pressure. As ozone exposure, for example, there is a method of ozone exposure in the presence of oxygen. As the UV irradiation, for example, there is a method of irradiating UV light having energy larger than the binding energy between atoms of the organic substance constituting the dirt. As corona discharge, for example, there is a method of corona discharge in the atmosphere. The plasma irradiation, ozone exposure, UV irradiation, and corona discharge may be appropriately combined. In particular, dry cleaning combining plasma irradiation or UV irradiation with ozone exposure, which has a large cleaning power and enables uniform dry cleaning, is preferable.

As complex particles having the radioactive cesium adsorption ability represented by the general formula [1], generally available, for example, Fe ₄ [Fe (CN) ₆ ] ₃ (manufactured by Acros, Prussian blue (Prussian blue) ), Part number: 21521-0250), NH ₄ Fe [Fe (CN ₆ )] (manufactured by Dainichi Seika, bitumen, part number: MF-4905 blue), K ₄ Fe (CN) ₆ (manufactured by Wako Pure Chemical Industries, Hexacyano) Iron (III) potassium, product number: 93-1920), KFe [Fe (CN ₆ )], NaFe [Fe (CN ₆ )], Na ₄ Fe (CN) ₆ , Co [Fe (CN) ₆ ] Cu ₂ [Fe (CN) ₆ ], Ni ₂ [Fe (CN) ₆ ], K ₂ Co [Fe (CN ₆ )], Ca ₂ [Fe (CN) ₆ ], V ₂ [Fe (CN) ₆ ], Mn ₂ [Fe (CN) ₆ ], Sr ₂ [Fe (CN) ₆ ], Nb ₂ [Fe (CN) ₆ ], Nb [Fe (CN) ₆ ], Mo [Fe (CN) ₆ ], Mo ₂ [Fe (CN _{) 6], Cd 2 [Fe} (CN) 6], Pt 2 [Fe (CN) 6], Pt [Fe (CN) 6], Au 4 [Fe (CN) 6], Au 2 [Fe (CN) ₆ ], Au [Fe (CN) ₆ ], W ₂ [Fe (CN) ₆ ], W [Fe (CN) ₆ ], Ru ₂ [Fe (CN) ₆ ], Ru [Fe (CN) ₆ ], _{Rh 2 [Fe (CN) 6} ], Rh [Fe (CN) 6], Cr 4 [Fe (CN) 6] 3, Nb 4 [Fe (CN) 6] 3, Mo 4 [Fe (CN) 6] ₃ , Mo ₂ [Fe (CN) ₆ ] ₃ , Pt ₄ [Fe (CN) ₆ ] ₃ , W ₂ [Fe (CN) ₆ ] ₃ , Ru ₄ [ Fe (CN) ₆ ] ₃ , Ru ₂ [Fe (CN) ₆ ] ₃ , Rh ₄ [Fe (CN) ₆ ] ₃ , Rh ₂ [Fe (CN) ₆ ] ₃ , Cr ₄ [Fe (CN) ₆ ] ₃ , Cr ₂ [Fe (CN) ₆ ] ₃ , V ₄ [Fe (CN) ₆ ] _{3 and the} like. The compound represented by the above general formula may be a hydrate. In addition, the shape of the complex particle | grains which have the radioactive cesium adsorption ability represented by the said General formula [1] is not specifically limited, The thing of shapes, such as spherical shape and an ellipsoidal shape, can be used.

In addition, the loading amount of the complex particles having the radioactive cesium adsorption capacity per unit surface area of the glass wool as the base material (hereinafter sometimes simply referred to as “loading rate”) is the liquid after the coating step and described later. In any case after the contact test of (water), if it is 0.15 mg / m ² or more, the adsorbent obtained can be provided with sufficient radioactive cesium adsorption capacity and adsorbed by contact with a liquid during use. It is preferable because the complex particles hardly fall off from the material. The carrying rate is more preferably 0.25 mg / m ² or more.

  In the method for producing a radioactive cesium adsorbent of the present invention, the complex particles having the radioactive cesium adsorbing ability are provided on the surface of glass wool after the dry cleaning treatment step as a coating liquid dispersed in a dispersion. The dispersion is not particularly limited as long as it can disperse the complex particles having the radioactive cesium adsorption ability without agglomeration. For example, alcohols such as water, methanol, ethanol, etc. Examples thereof include solvents, ketone solvents such as acetone and MEK, mixed liquids thereof, and those containing a dispersion aid such as a surfactant. Among the above, the dispersion is preferably a solvent having a relative dielectric constant of 20 or more, and examples of the solvent include water and methanol.

  In addition, the method for providing the coating solution to the glass wool surface after the dry cleaning treatment step is not particularly limited, but the method of dropping the coating solution onto the glass wool, the method of spray-coating the coating solution onto the glass wool, A method of immersing the glass wool in the coating solution is exemplified.

  In the drying step of the method for producing the radioactive cesium adsorbent of the present invention, the drying method is not particularly limited, but a method of maintaining a high temperature atmosphere, a method of blowing warm air or hot air, a method of maintaining under reduced pressure, barrel drying, Examples of the drying method include spin drying and infrared drying.

  In the case where the radioactive cesium adsorbent obtained after the drying step is further brought into contact with a washing liquid and washed, and then dried at a temperature of 80 ° C. or lower to obtain a radioactive cesium adsorbent, the washing liquid includes water, methanol, ethanol, etc. Alcohol solvents, ketone solvents such as acetone and MEK, and mixtures thereof, water is preferred from the viewpoint of solubility of ionic compounds. The method for bringing the adsorbent into contact with the cleaning liquid is not particularly limited. For example, the adsorbent may be immersed in the cleaning liquid, the cleaning liquid may be dropped on the adsorbent, or the cleaning liquid in a distributed state. The adsorbent may be held therein. Moreover, the drying method at the time of drying at a temperature of 80 ° C. or lower is not particularly limited, but at a temperature of 80 ° C. or lower, a method of holding in a heating atmosphere, a method of blowing warm air or hot air, or a method of holding under reduced pressure , Barrel drying, spin drying, infrared drying, and the like, and drying is preferably performed at 10 to 80 ° C. from the viewpoint of work efficiency.

In addition, after the radioactive cesium adsorbent of the present invention adsorbs and collects the radioactive cesium, the recovered adsorbent can be safely fixed by general vitrification. As the glass used for the glass solidification, the temperature at which the melt viscosity becomes 10 ⁴ Pa · s is low (1400 ° C. or lower) from the viewpoint of moldability and the safe solidification treatment of the adsorbent, and long-term storage stability. In view of the above, a glass having high water resistance is preferable. For example, borosilicate glass is preferable, but silicate glass, soda lime glass, and lead glass may be used.

In addition, after the radioactive cesium adsorbent of the present invention adsorbs and collects radioactive cesium, the concentration of radioactive cesium contained in the adsorbent after the recovery does not cause heat generation or ignition, and vitrification is necessary. When long-term storage stability is not required (for example, less than about 10 ⁷ Bq / g), it can be safely fixed by, for example, cement solidification other than vitrification. Although the cement used for cement solidification is not specifically limited, For example, Portland cement etc. can be used.

  Hereinafter, the present invention will be described specifically by way of examples. The present invention is not limited to these examples.

[Example 1]
(Preparation of coating solution)
As complex particles having the ability to adsorb radioactive cesium (described as “Cs-adsorbed complex particles” in Table 1), Prussian blue (product number 21521-0250, average particle size D50: 40 nm manufactured by Acros Corporation, Nanotrac UPA- manufactured by Nikkiso Co., Ltd.) Measurement with EX250, measurement principle: dynamic light scattering method, frequency analysis, heterodyne method)) 0.06 g was dispersed in 6 g of ion-exchanged water (relative permittivity: 80) to prepare a 1% by mass coating solution.

(Dry cleaning process)
Glass wool with a surface area of 38 m ² (about 5 mm × about 20 mm and thickness about 5 mm) (manufactured by Central Glass Fiber, no binder glass wool, specific surface area: 253 m ² / g, borosilicate glass, wire diameter: By applying plasma irradiation to the surface of 5.5 ± 0.5 μmφ) at atmospheric pressure plasma irradiation surface modification device manufactured by Sink Engineering Co., Ltd. Model No .: PS-610C under conditions of irradiation distance: 20 mm, irradiation time: 10 seconds Dry-cleaned. When a plate glass surface having the same composition as the glass wool is subjected to a dry cleaning treatment under the same conditions as described above, the water contact angle of the surface is 6 °. The surface area is measured and calculated according to JIS Z8830.

(Coating process)
After the dry cleaning treatment step, 150.198 mg of glass wool was placed in a glass cup, and the Prussian blue coating solution was added dropwise to the glass wool.

(Drying process)
After the coating process, the glass cup was heated at 150 ° C. for 4 hours to dry the coating solution, thereby obtaining a radioactive cesium adsorbent. Since the mass of the adsorbent obtained after the drying step was 180.205 mg, the mass of Prussian blue supported in the adsorbent is 30.007 mg. Therefore, the loading rate of Prussian blue is 0.79 mg / m ² . The production conditions are shown in Table 1.

[Contact test with liquid (water)]
The adsorbent obtained after the drying step was put in a glass bottle containing ion-exchanged water, and shaken at 20 ° C. with MIX-ROTAR VMR-5 (manufactured by Inoue Seieido) at 20 rpm for 3 hours. Later, the adsorbent was removed and dried. Since the mass of the adsorbent after drying was 170.301 mg, the mass of Prussian blue supported in the adsorbent after the contact test was 20.103 mg.
The drop-out rate (mass%) of Prussian blue by the contact test with liquid (water) is (((Mass of Prussian blue supported on the adsorbent after the drying step))-(supported on the adsorbent after the contact test). Mass of Prussian blue)) × 100 / (mass of Prussian blue supported on the adsorbent after the drying step)), and the drop-off rate was 33.0 mass%.

[Evaluation of total cyan density in water in contact with adsorbent]
Of the adsorbent obtained after the drying step, 144.130 g (mass of Prussian blue supported on the adsorbent: 24 mg) was packed in a column and all water in the water after passing water at 12 ml / min. The cyan density was measured by a method based on JIS K 0102 38.3. In the first 50 ml of the water after the water flow, there is a possibility that a part of the adsorbent finely crushed at the time of filling may be mixed, and the total cyan density cannot be accurately evaluated due to the influence. As a result, it was discarded as drain, and then 100 ml was collected and measured. As a result, the first sample: 0.1 mg / L, the third sample: less than 0.1 mg / L (less than the lower limit of detection), sampled Fifth: Less than 0.1 mg / L (less than the lower limit of detection), and the total cyan concentration was less than the discharge standard for cyanide compounds in the Water Pollution Control Law. Further, the adsorbent obtained after the drying step is placed on the filter paper of a suction funnel provided with filter paper to obtain a suction state, and then the ion-exchanged water is 100 mass times the adsorbent in the adsorbent. In the same manner, the column was filled with the adsorbent obtained by holding the adsorbent for 18 hours in an electric furnace maintained at 60 ° C. and drying it. When the total cyan concentration in the water after passing water was measured, the first sample: less than 0.1 mg / L (lower than the lower limit of detection), the third sample: less than 0.1 mg / L (lower than the lower limit of detection), the sample collected Fifth: less than 0.1 mg / L (less than the lower limit of detection), and the total cyan concentration was less than the discharge standard for cyanide compounds in the water pollution control method, and was even lower. The operation from the cleaning using the ion-exchanged water as a cleaning liquid to the drying at 60 ° C. may be hereinafter referred to as “rinsing treatment”.

  Actually adsorbing radioactive cesium at a high concentration is difficult in terms of equipment and safety. Therefore, in the following, the radioactive cesium adsorbent obtained after the drying step is described as the state after adsorbing radioactive cesium. In view of this, the stability (heat resistance evaluation) of the radioactive cesium adsorbent when it is brought to a high temperature state by high-concentration radioactive cesium is evaluated, and the glass of the radioactive cesium adsorbent obtained after the above drying step Tried to solidify.

[Specific surface area measurement]
Adsorbed nitrogen gas on the surface of glass wool at liquid nitrogen temperature when (pressure of adsorbed gas at the boiling point of liquid nitrogen and in the equilibrium state with the sample surface) / (vapor pressure of nitrogen) is in the range of 0.05 to 0.35 The specific surface area was measured by the BET method.

[Measurement of water contact angle]
Based on JIS R 3257, the contact angle with water was measured.

[Heat resistance evaluation]
When the radioactive cesium adsorbent obtained after the drying step was heated at 400 ° C. for 10 hours, there was no change in the appearance of the adsorbent before and after heating.

[Vitrification test]
When the radioactive cesium adsorbent obtained after the drying step was melted at 1000 ° C. together with a borosilicate glass cullet and then cooled, it could be vitrified safely without ignition of the adsorbent. The evaluation results are shown in Table 2.

[Example 2]
The surface of the glass wool similar to that used in Example 1 was irradiated with UV light under the conditions of irradiation distance: 25 mm, irradiation time: 60 seconds with PHOTO LIGHT PROSECECOR manufactured by Sen Special Light Source Co., Ltd. Model number: PL2003N-10. A radioactive cesium adsorbent was prepared and evaluated in the same manner as in Example 1 except that the surface of the glass wool was exposed to ozone generated by UV light and subjected to a dry cleaning treatment. Production conditions and evaluation results are shown in Tables 1 and 2.

[Example 3]
A radioactive cesium adsorbent was prepared and evaluated in the same manner as in Example 2 except that the irradiation time in the dry cleaning treatment step of Example 2 was 45 seconds. Production conditions and evaluation results are shown in Tables 1 and 2.

[Example 4]
The radioactive cesium adsorbent was obtained in the same manner as in Example 1, except that NH ₄ Fe [Fe (CN ₆ )] (MF-4905 Blue manufactured by Dainichi Seika) was used as the complex particle having the radioactive cesium adsorption ability of Example 1. Were made and evaluated. Production conditions and evaluation results are shown in Tables 1 and 2.

[Comparative Example 1]
A radioactive cesium adsorbent was produced and evaluated in the same manner as in Example 1 except that the dry cleaning treatment step was not performed. The supporting rate after the drying step was 0.65 mg / m ² , which was lower than that in Example 1. Further, the loading rate after the contact test with the liquid (water) was 0.12 mg / m ² , and it was confirmed that Prussian blue was largely removed by the contact test with the liquid (water). Production conditions and evaluation results are shown in Tables 1 and 2.

[Comparative Example 2]
The same method as in Example 1 except that a cellulose nonwoven fabric (BEMCOT M-1; manufactured by Asahi Kasei Fiber) having a surface area of 38 m ² (specific surface area: 162 m ² / g) was used instead of the glass wool used in Example 1. A radioactive cesium adsorbent was prepared and evaluated. The supporting rate after the drying step was 0.52 mg / m ² , which was lower than that in Example 1. Moreover, the carrying rate after the contact test with the liquid (water) was 0.11 mg / m ² , which was lower than that in Example 1. Further, when the heat resistance was evaluated in the same manner as in Example 1, the adsorbent was carbonized while generating decomposition components such as soot by heating. In addition, when the vitrification test was performed in the same manner as in Example 1, the adsorbent ignited, so that it could not be vitrified. Production conditions and evaluation results are shown in Tables 1 and 2.

Claims (14)

A complex having a radioactive cesium adsorption ability represented by the following general formula [1] on a glass wool surface subjected to at least one dry cleaning treatment selected from the group consisting of plasma irradiation, ozone exposure, UV irradiation, and corona discharge A radioactive cesium adsorbent characterized in that particles are supported.
A _x M [Fe (CN) ₆ ] _y
(In Formula [1], A is independently of each other, Fe, Na, K, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au. , W, Ru, Rh, and Ag, or NH ₄ , x is an integer of 0 to 5, y is an integer of 1 to 3, M is Fe, Na, K A metal atom selected from the group consisting of Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Nb, Mo, Cd, Pt, Au, W, Ru, Rh, and Ag. The compound of the formula [1] may further contain water of hydration) The radioactive cesium adsorbent according to claim 1, wherein M in the general formula [1] is Fe. The radioactive cesium adsorbent according to claim 1 or 2, wherein a water contact angle of the glass wool surface after the dry cleaning treatment is 13 ° or less. The average particle diameter of the complex particles having the radioactive cesium adsorption ability is 0.1 to 500 nm by a dynamic light scattering method using frequency analysis by a heterodyne method. The radioactive cesium adsorbent according to any one of the above. 5. The radioactive cesium adsorbent according to claim 1, wherein a specific surface area of the glass wool is 10 to 1000 m ² / g. A dry cleaning treatment step for subjecting the glass wool surface to at least one dry cleaning treatment selected from the group consisting of plasma irradiation, ozone exposure, UV irradiation, and corona discharge;
A coating step in which a coating solution in which complex particles having the radioactive cesium adsorption ability represented by the general formula [1] are dispersed in a dispersion is brought into contact with the glass wool surface after the dry cleaning treatment step;
The method for producing a radioactive cesium adsorbent according to any one of claims 1 to 5, further comprising a drying step of drying the glass wool after the coating step. 7. The method for producing a radioactive cesium adsorbent according to claim 6, wherein the content of the complex particles having radiocesium adsorption ability in the coating solution is 0.01 to 20% by mass. The radioactive cesium adsorption according to claim 6 or 7, wherein the coating liquid is obtained by dispersing the complex particles having the radioactive cesium adsorption ability in a solvent having a relative dielectric constant of 20 or more. A method of manufacturing the material. The method for producing a radioactive cesium adsorbent according to any one of claims 6 to 8, wherein the glass wool after the coating step is heated at 50 to 180 ° C as the drying step. The glass wool, which is obtained after the drying step and on which the surface of the complex particles having the radioactive cesium adsorption ability is supported, is further brought into contact with a washing solution and washed, and then dried at a temperature of 80 ° C. or less. 10. A method for producing a radioactive cesium adsorbent according to any one of 9 above. 11. The radioactive cesium adsorbent according to claim 10, wherein when contacted with water, the concentration of total cyanide derived from the thermal decomposition product of the complex particles in the water is 1 mg / L or less. Radioactive cesium adsorbent obtained by the manufacturing method. A method for selectively recovering radioactive cesium from a waste liquid containing radioactive cesium, wherein the waste liquid is brought into contact with the radioactive cesium adsorbent according to any one of claims 1 to 5 and claim 11. A method for recovering the radioactive cesium from the waste liquid. 13. The method for recovering radioactive cesium from waste liquid according to claim 12, wherein the step of contacting the radioactive cesium adsorbent is circulating the waste liquid through a column packed with the adsorbent. A method for immobilizing radioactive cesium, characterized in that the adsorbent adsorbed with radioactive cesium by the method according to claim 12 or 13 is vitrified or cement solidified.