JP5715591B2 - Composite containing bitumen and radioactive cesium adsorbent using the same - Google Patents

Description

  The present invention relates to a composite containing bitumen and an oxide, and a radioactive cesium adsorbent using the same.

  Practical use of bitumen includes various materials such as radioactive material adsorbents, electrochromic elements, sensors, secondary battery electrode materials, and pigments. In particular, as cesium adsorbents, radioactive cesium is separated from radioactive liquid waste discharged as a result of nuclear power generation (see Patent Document 1), and the transfer coefficient of radioactive cesium from soil to plants by soil application is reduced (see Non-Patent Document 1). It is used for administration to humans and livestock (see Use of Prussian blue for decorporation of radiocesium by HPA, Non-Patent Document 2). All of them are used for the purpose of adsorbing and separating radioactive cesium from the environment, the body, waste liquid, and the like, and reducing its influence. Examples of the utilization method include dispersion in liquid, granulation, utilization as an adsorbent such as a column, and dispersion in soil.

  There are several problems when implementing the above usage. One is a molding problem. Bitumen is considered to be obtained only as a fine powder and is difficult to mold (see Non-Patent Document 3).

Further, general molding includes a technique using a binder such as a polymer. However, for the purpose of radioactive cesium adsorption, generally, organic substances have low durability against radiation, and there remains a problem in durability of radioactive cesium adsorption.
In addition, it is desirable that the radioactive cesium adsorbent can be further added with a function due to the problem of post-processing. Since the radioactive cesium adsorbent contains a large amount of radioactive cesium after use, it emits strong radiation. Therefore, handling is difficult. One way to solve this problem is to add other functions that simplify handling. In addition, when recovering radioactive waste, when it is realized in a general space such as a house, design properties and the like are important, and these are considered as one of new functions added.

Japanese Patent No. 4168172

Vandenhove97JERa IAEA TECDOC-926 (1997/02) JAERI-Review 2001-027

  It is an object of the present invention to provide a bituminous composite that is easy to mold, has a robust molded body, and that can realize additional functions, and a radioactive cesium adsorbent using the composite.

The above problems have been achieved by the following means.
1. A bitumen-containing composite obtained by mixing and combining bitumen and an oxide containing metal atoms.
2. The bitumen-containing composite according to 1 above, wherein heat treatment is performed at 100 ° C. or more and 200 ° C. or less in the mixing and composite treatment.
3. The bitumen-containing composite according to 1 above, wherein a polymer material is added as a binder in the mixing and composite treatment.
4). 4. The bitumen-containing composite according to any one of 1 to 3, wherein the mixing and composite treatment are completed on the surface or inside of another structure.
5. The bitumen-containing composite according to any one of 1 to 4 above, wherein the main component of the oxide is titanium oxide.
6). The bitumen-containing composite according to any one of the above 1 to 4, which contains activated clay as an oxide.
7). The radioactive cesium adsorbent using the bitumen containing complex in any one of said 1-6.

ADVANTAGE OF THE INVENTION According to this invention, it can manufacture by the technique which is simple and can be mass-produced, and can obtain the robust bituminous composite and the radioactive cesium adsorption material using the same.
By using an oxide having various functions as a material to be combined, a composite having both the function of bitumen and the function of an oxide can be obtained.
The composite imparted with the desired physical properties exhibits its function to the maximum extent, particularly as a cesium adsorbent, enriches the variation of this kind of material, and contributes to the expansion of application modes and functions.

  In the present invention, the oxide is compounded with bitumen to fulfill two kinds of roles. One is that the oxide itself functions as a binder, and bitumen can be formed without using a binder containing an organic substance. As described above, organic substances have low durability against radioactivity, and there may be a problem in durability after adsorption of radioactive cesium. It is also possible to improve the amount of bitumen in the composite.

  Another role of the oxide is to newly impart the function of the oxide to the composite. For example, when a magnetic material is used as the oxide, it is possible to produce a composite that is attracted to a magnet. As a function of bitumen, when the purpose is adsorption of radioactive cesium, it is assumed that the bitumen after adsorption emits strong radiation, which makes it difficult for humans to handle it directly. However, by providing the magnetism by complexing, remote operation using magnetism and the like can be performed, so that the risk of exposure can be reduced. In addition, when radioactive cesium dispersed in soil is adsorbed and aimed at reducing migration to plants, recovery after adsorption is an issue, but by providing magnetism, recovery with a magnet or the like is possible. It becomes possible.

Furthermore, in order to prevent radioactive cesium floating in the atmosphere from adhering to the ground or houses due to rain, etc., a radioactive cesium adsorbent is provided on the protective sheet, etc., and covers what should be protected such as the ground and houses. However, in such a case, organic substances or the like may be attached at the same time, and the function of the adsorbent may be deteriorated. In this case, for example, by providing a photocatalytic function or a superhydrophilic function possessed by titanium oxide, tungsten oxide, or the like, it is possible to prevent functional degradation due to organic matter deposition. Furthermore, when it is used in a house or the like, not only the adsorption function but also the design properties are important functions. In this case, it is possible to control the color of the adsorbent by adding an inorganic material such as a pigment, which is effective in controlling the design.
In this way, combining bitumen and oxides not only contributes to the improvement of direct radioactive cesium adsorption performance such as durability and moldability, but also provides magnetic function, photocatalytic function, optical function, etc. It becomes possible to do.

  Hereinafter, the present invention will be described in detail based on preferred embodiments thereof.

Bitumen used in the present invention is a blue pigment mainly composed of ferric ferrocyanide, and the chemical formula thereof is represented by M _{1 / n} Fe [Fe (CN) ₆ ]. However, M in the chemical formula is any one of K, NH ₄ , Na, and Fe, and n represents the valence of M.
Bitumen is mass-produced industrially and is a very fine pigment, and is a highly safe compound widely used in inks, paints, cosmetics and the like. The compound has a cubic crystal structure, and is a compound that can easily take in monovalent cations, particularly cesium, into the lattice.
The bitumen used for the cesium-removing material of the present invention may be in the form of fine particles or wet including water.

The oxides in the present invention may be those containing a metal and oxygen as the main composition. For example, oxides such as alumina, titania and zirconia, magnetic materials such as barium ferrite, strontium ferrite and magnetite, activated clay, acidic clay Clay-derived substances such as white clay can be used. These can be selected depending on the function to be given. For example, titania and activated clay are desirable when fastness is important. Magnetite, barium ferrite, and strontium ferrite are particularly desirable for imparting a magnetic function, and titania corresponding to each is desirably utilized for imparting a photocatalytic function, a superhydrophilic function, and an optical function.
When titania is used as the main component of the oxide, the titania ratio in the oxide is preferably 50% by weight or more.

  As for the ratio of bitumen and oxide, the ratio of bitumen is preferably 20 to 95% by weight, and more preferably 30 to 90%.

  Further, the surface of the oxide can be subjected to additional treatment as necessary. For example, when titanium oxide is used, when the photocatalytic effect is not necessary, the deterioration of the composite may be accelerated by the photocatalytic effect. In this case, it is effective to cover the surface of titanium oxide with zirconia, silica, alumina or the like. It is also effective to perform a treatment for improving the dispersibility in a solvent in order to achieve more uniform mixing with bitumen.

  Further, the composite of the present invention does not necessarily need to be composed only of bitumen and oxide. When used in applications where radiation durability or the like does not become a problem, a binder such as a polymer may be used together. Furthermore, it is good also as a sheet-like composite by adsorb | sucking or apply | coating the obtained composite to a sheet | seat, a nonwoven fabric, etc. As described later, it is important to select the shape of the oxide in accordance with the manufacturing method.

In order to produce the bitumen and oxide composite according to the present invention, several approaches are possible:
Method 1. Bitumen and oxide fine particles are suspended or dispersed in a solvent such as water to form a slurry, and then heat-treated.
Method 2. The bitumen and oxide fine particles are suspended or dispersed in a solvent such as water to form a slurry, which is then applied or adsorbed to other structures such as sheets, and then subjected to heat treatment to obtain the surface of the structure or Complete compounding inside.
Method 3. A bitumen and a binder such as fine oxide particles and a polymer are suspended or dispersed in a solvent such as water, followed by drying treatment.

Hereinafter, each method will be described in detail.
In the case of method 1, it is desirable that the bitumen and the oxide are sufficiently mixed, and it is desirable that each has a fine structure such as a fine particle or a colloid. As the bitumen, one synthesized in advance may be used, or it may be precipitated by a coprecipitation method or the like in a solvent to be suspended or dispersed. When synthesizing in advance, commercially available pigments can be used. Moreover, you may utilize what was synthesize | combined by the coprecipitation method, the electrolytic deposition method, etc. The particle size is desirably 100 μm or less, and particularly desirably 30 μm or less.

  There is no particular limitation on the oxide to be used, but it is necessary to have chemical stability that can be prevented from being oxidized by bitumen. Specifically, as described above, it is desirable to use properly depending on the intended application. For example, when importance is attached to fastness, alumina, titania, zirconia, activated clay and the like are desirable, and activated clay and titania are particularly desirable. For the purpose of imparting magnetic properties, barium ferrite, strontium ferrite, magnetite, hematite, or derivatives thereof can be used. In the case of imparting photocatalytic properties, titanium oxide, tungsten oxide or the like can be used. When controlling optical properties such as color, oxides used for pigments such as titanium oxide and magnetite can be used.

  These are suspended or dispersed in various solvents and slurried. The solvent to be used is not particularly limited as long as it can be suspended or dispersed, but water, ethanol, methanol, butanol, toluene, ethyl acetate, octane or a mixture thereof can be used. The ratio of mixing them is not particularly limited, but when the amount of the solvent is increased, the resulting composite becomes porous. For example, the cesium adsorption performance is improved, but the fastness is weakened. Increasing the amount of oxide increases the robustness, but reduces the amount of bitumen and reduces the amount of cesium that can be adsorbed. Therefore, it is necessary to adjust the mixing ratio according to the application. In addition, when providing a magnetic function, attention must be paid to the fact that the amount of oxide cannot be reduced so much. Specifically, the bitumen / oxide mixing ratio is preferably 20 to 95% by weight, and more preferably 30 to 90%.

  These are used to form a slurry, but before the heat treatment, a treatment for removing the solvent such as dehydration may be performed. For example, a centrifugal separation method, a suction filtration method, or the like can be used. In this case, the amount of the solvent in the slurry is remarkably reduced and the fluidity may be lost, but there is no problem as long as molding is possible. Moreover, when performing such a solvent removal process, it is also possible to increase the amount of the solvent at the time of slurrying. The mixing ratio of the solvent to the sum of bitumen and oxide is preferably 30% to 200%, particularly preferably 50 to 150%, when such a desolvation treatment is not performed.

  The obtained slurry is shaped as necessary, and then heat-treated. The heating temperature is preferably between 100 ° C. and 200 ° C., particularly preferably between 110 ° C. and 180 ° C. Since bitumen accelerates decomposition at about 200 ° C. to about 250 ° C., it is desirable that the temperature does not exceed the temperature. The heating time is not particularly problematic as long as it is sufficiently dried, but in general, the longer the heat treatment, the higher the fastness. Specifically, it is preferably 5 minutes or longer, particularly 15 minutes or longer. Necessary shaping can also be performed after heating. For example, when a fine powder is required, a desired product can be obtained by crushing after heating and drying.

In the case of the method 2, it is possible to proceed by the same method as the method 1 until the time of slurrying. However, since it is necessary to apply, it is desirable to increase the amount of solvent and increase the flow rate. Specifically, the mixing ratio of the solvent to the sum of bitumen and oxide is preferably 50% to 2000%, particularly preferably 100 to 1000%.
The structure for supporting the bitumen-oxide complex is not particularly limited as long as it can be adsorbed by applying slurry and has chemical stability such as not oxidized by bitumen. However, when durability is required, it is desirable that the bitumen-oxide composite is firmly adhered by drying after coating, such as a porous one. Specifically, stainless steel with improved surface roughness, such as ceramic, glass fiber, and a sheet made from the same, can be used.

  Method 3 is an effective method for further improving the durability of the composite when a binder such as a polymer does not cause a problem regarding radiation durability. Molecular binders include polyethylene, polystyrene, polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylene-propene copolymer, ethylene-chlorotrifluoroethylene copolymer, perfluoroalkoxyalkane (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, Phenol resin, epoxy resin, melamine resin, acrylic resin, acrylic silicon resin, silicon resin, urethane resin, hydroxyethyl cellulose, CMC (carboxymethyl cellulose), PVA (polyvinyl alcohol), and the like can be used.

  Basically, it is realized by adding a polymer to the slurry prepared by Method 1 and Method 2 and performing a drying step such as heating. The polymer may be added with a monomer at the time of slurry preparation and may be polymerized by heating or light irradiation.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention should not be construed as being limited thereto.

Example 1
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 100 g, distilled water 200 g, alumina (manufactured by Wako Pure Chemicals, model number MP alumina A, particle size 50 μm) ~ 200μm) After mixing and slurrying 100g, forming by filling and extruding into a syringe, heat treatment at 150 ° C for 20 minutes, composite 1 (1-2mm, length 3-5mm) Columnar pellets).
Bituminous pigment (trade name: Milori Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 200 g, distilled water 210 g, titanium oxide (manufactured by Sakai Chemicals, model number GTR-100, particle size 260 nm ) After mixing and slurrying 100 g, forming by filling and extruding into a syringe, heat treatment was performed at 150 ° C. for 20 minutes, and composite 2 having the same shape as composite 1 was produced. .
Bituminous pigment (trade name: Milori Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 200 g, distilled water 180 g, titanium oxide (manufactured by Sakai Chemicals, model number GTR-100, particle size 260 nm) ) 100g and silica sol (Nissan Chemical Industry Model No. Snowtex 30) 5g were mixed and made into a slurry, and then molded by filling and extruding into a syringe, followed by heat treatment at 150 ° C for 20 minutes to obtain a composite. A composite 3 having the same shape as 1 was prepared.
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 200 g, distilled water 210 g, titanium oxide (Ishihara Sangyo Model No. CR-97, particle size 250 nm ) After mixing and slurrying 100 g, forming by filling and extruding into a syringe, heat treatment was performed at 150 ° C. for 20 minutes, and composite 4 having the same shape as composite 1 was produced. .
0.1M iron sulfate and 0.1M sodium ferrocyanide are mixed and iron-iron cyano complex (Berlin White) is precipitated by coprecipitation, then washed by centrifugation and dried, and 100g of dried sample and 120g of distilled water After mixing 50 g of titanium oxide (manufactured by Sakai Chemicals, model number GTR-100, particle size 260 nm) and making it into a slurry, it was molded by filling and extruding into a syringe, followed by heat treatment at 150 ° C. for 20 minutes, A composite 5 having the same shape as the composite 1 was produced.
For comparison, after mixing 200 g of bituminous pigment (trade name: Miloli Blue 905, chemical formula NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) and 220 g of distilled water, After molding by filling and extruding into a syringe, a composite 0 produced by heat treatment at 150 ° C. for 20 minutes was prepared. This complex 0 also had the same shape as the complex 1.

  About the comparison of the hardness of the composites 0-5 obtained above, it judged sensuously by breaking a pellet with the tip of a nail and crushing with the tip of a finger. Moreover, the ease of breakage in water was determined by putting in a screw tube bottle together with artificial salt water and shaking. As a result, the hardness was improved in all samples as compared with the composite 0. Among them, the composite 5 showed the highest hardness.

  Moreover, the composites 2-5 using a titania exhibited a light blue color as compared with the composite 1 showing a dark blue color. This is because titania uses what is sold as a white pigment, and its optical characteristics are considered to be light blue, which is a mixture of dark blue and white.

(Example 2)
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 30 g, distilled water 110 g, activated clay (model number Galeon Earth V2 manufactured by Mizusawa Chemical) 70 g Then, after forming a slurry, it was molded by filling and extruding into a syringe, followed by heat treatment at 150 ° C. for 1 hour, to produce a composite 6 having the same shape as composite 1.
Bituminous pigment (trade name: Miroli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 40 g, distilled water 100 g, activated clay (model number Galeon Earth V2 manufactured by Mizusawa Chemical) 60 g Then, after forming a slurry, it was molded by filling and extruding into a syringe, followed by heat treatment at 150 ° C. for 1 hour, and composite 7 having the same shape as composite 1 was produced. These hardness measurements were performed in the same manner as the method performed in Example 1. As a result, the hardness was improved as compared with composite 0 and composite 1.

(Example 3)
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 60 g, distilled water 50 g, titanium oxide (Ishihara Sangyo Co., Ltd., model number ST-21) After mixing and slurrying 40 g (particle diameter 20 nm), the syringe 8 was molded by filling and extruding, and then heat-treated at 150 ° C. for 1 hour to obtain the composite 8 having the same shape as the composite 1. Produced.
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) 60 g, distilled water 80 g, titanium oxide (Ishihara Sangyo Co., Ltd., model number ST-01, After mixing and slurrying 40 g (particle diameter 7 nm), filling into a syringe and extruding was performed, followed by heat treatment at 150 ° C. for 1 hour, and composite 9 having the same shape as composite 1 was obtained. Produced. These hardness measurements were performed in the same manner as the method performed in Example 1. As a result, the hardness was improved as compared with composite 0 and composite 1.
Bituminous pigment (trade name: Miloli Blue 905, chemical formula is NH ₄ Fe [Fe (CN) ₆ ], manufactured by Dainichi Seika Kogyo Co., Ltd.) )) After 40 g was mixed and slurried, it was molded by filling and extruding into a syringe, followed by heat treatment at 150 ° C. for 1 hour to produce a composite 10 having the same shape as composite 1 . These hardness measurements were performed in the same manner as the method performed in Example 1. As a result, the hardness was improved as compared with composite 0 and composite 1. Further, it was confirmed that the composite 10 was attached to a magnet and had magnetism.

Example 4
About the composite_body | complex obtained above, the cesium adsorption | suction characteristic in aqueous solution was measured. The cesium adsorption characteristics were determined by the following method.
10 g of each complex was added to an aqueous cesium nitrate solution having a concentration of 500 μg / liter, and sampling was performed after a certain period of time (4 hours, 24 hours) with stirring, and a polarized Zeeman atomic absorption photometer Z-2010 ((stock) ) The cesium concentration was measured by performing atomic absorption analysis at Hitachi High-Technologies), and the cesium adsorption capacity of each complex was calculated as the cesium removal rate. The measurement results are shown in Table 1.

  From the results of Table 1 above, it can be seen that the composite containing bitumen of the present invention is excellent in cesium removal rate.

  According to the present invention, the bitumen can be easily formed and can be formed without using a polymer binder as required. In particular, when radioactive cesium adsorption is used, various forms such as column beads and adsorption sheets can be formed. As a result, not only the separation and recovery of radioactive cesium in the treatment of radioactive waste discharged by nuclear power generation, but also various water (water, rainwater, drinking water, etc.), soil, houses, etc. of radioactive cesium released into the environment This makes it easy to separate and recover radioactive cesium from a wide range of objects.

Claims (4)

  A bitumen-containing composite obtained by mixing bitumen with an oxide containing at least one metal atom selected from aluminum, titanium, and iron and / or activated clay, and heat-treating at a temperature of 100 ° C. or higher and 200 ° C. or lower. .   When mixing bitumen with an oxide and / or activated clay containing at least one metal atom selected from aluminum, titanium and iron, the mixture is suspended or slurried in a solvent and obtained as a slurry. Or a bitumen-containing composite according to claim 1, wherein the slurry is applied or adsorbed on another structure and heat-treated.   The bitumen-containing composite according to claim 1 or 2, wherein a main component of the oxide is titanium oxide. The radioactive cesium adsorbent using the bitumen containing composite_body | complex in any one of Claims 1-3 .