JP5951950B2 - Method for treating contaminated water containing radioactive substance and method for adjusting particle size of radioactive substance removing agent - Google Patents

Description

  The present invention relates to a radioactive substance removing agent capable of adsorbing and removing radioactive substances, a method for producing the same, and a method for treating radioactive contaminated water using the radioactive substance removing agent.

  The Great East Japan Earthquake that struck Japan on March 11, 2011 was accompanied by the occurrence of a large tsunami, and it was an unprecedented disaster that caused devastating damage to municipalities on the coast of the Tohoku region. The damage caused by the tsunami also affected TEPCO's Fukushima Nuclear Power Station, causing the reactor cooling facility to stop functioning, fuel rods melting down, steam explosions, etc. The alarming situation of a large amount of high-level radioactive material-contaminated wastewater emerged. Therefore, removal of radioactive materials from radioactive material contaminated effluent is one of the issues that Japan must solve as quickly as possible.

  As main radionuclides released from radioactive material handling facilities such as nuclear power plants, radioactive iodine such as iodine-131 (half-life 8.02 days) produced by fission reaction of uranium-235, and cesium-137 ( And radioactive cesium such as cesium-134 (half-life 2.06 years).

As a technique related to the removal of radioactive iodine, adsorption treatment with activated carbon has been conventionally known. Meeting document 2-3 “Investigation on removal of iodine by combined use of powdered activated carbon and pre-chlorination” in the “Ministry of Health, Labor and Welfare” According to the above, although iodide ion (I ⁻ ) and iodate ion (IO ₃ ⁻ ) can hardly be removed by powdered activated carbon, powdered activated carbon / pre-weak chlorine (injection rate 0.5 to 1) with respect to iodide ion 0.0 mg / L), it is reported that about 30% can be removed at a powdered activated carbon injection rate of 15 mg / L, and about 50% can be removed at 30 mg / L.

  As a technology related to the removal of radioactive cesium, ferrocyanic compound powders utilizing the steric properties of ferrocyanic compounds (iron, copper, nickel salts, etc.) that can selectively incorporate cesium ions into the crystal lattice. Is added to the radioactive cesium-containing wastewater and brought into contact with it, followed by solid-liquid separation to reduce the radioactive cesium content, and six oxygen atoms formed by the arrangement of the SiO tetrahedral layer on the clay crystal lattice plane. Add montmorillonite clay mineral powder to radioactive cesium-containing wastewater by utilizing the three-dimensional properties of montmorillonite clay mineral (see Fig. 1 and Fig. 2), which can selectively incorporate cesium ions into the square structure. And then radiate the powdered adsorbent with cesium adsorption ability, such as solid-liquid separation to reduce the radioactive cesium content. Contacting the cesium containing wastewater to adsorb and remove the cesium technique is known (see FIGS. 1 and 2).

However, in the method of solid-liquid separation after bringing radioactive substance-containing wastewater into contact with a powdery adsorbent that has the ability to adsorb radioactive substances, it is difficult to separate moisture from the powdery adsorbent. There was a problem that a large amount of sludge containing substances was generated, and that sludge volume reduction treatment was required.
As means for solving such a problem, a method using a granular adsorbent that is relatively easy to separate moisture, or a material having a radioactive substance adsorbing ability is attached to or supported on the surface or void of a porous material. For example, a method using a radioactive substance removing agent that has been removed can be considered.

  Regarding the former method, for example, in Patent Document 1 (Japanese Patent Laid-Open No. Sho 56-79999), an X-type zeolite having a diameter of 60 to 80 mesh is moistened, and then an aqueous copper sulfate solution is added to adsorb copper ions. Disclosed is an addition method for attaching a ferrocyanide metal compound by reacting with an aqueous potassium cyanide solution to form copper ferrocyanide in the voids and on each surface of the zeolite, and a treatment method using the adsorbed zeolite as an adsorbent. Has been.

  On the other hand, regarding the latter method, for example, in Patent Document 2 (Japanese Patent Laid-Open No. 9-173832), a porous resin is supported with a quaternary ammonium salt that is soluble in a low-boiling organic solvent and hardly soluble in water. After treatment with an aqueous solution containing hexacyanoferrate (II) (inventor's note: another name for ferrocyanide salt), the treated product is brought into contact with an aqueous solution containing copper salt to form hexacyanoiron (II) in the pores of the resin. A method for producing a hexacyanoferrate (II) -supported porous resin characterized by depositing copper acid and then extracting a quaternary ammonium salt in the resin with a low-boiling organic solvent is disclosed.

Patent Document 3 (Japanese Patent Publication No. 62-43519) discloses a radioactive substance removing agent obtained by adding copper ferrocyanide to zeolite, and Patent Document 4 (Japanese Patent Application Laid-Open No. 9-173832). In addition, a radioactive substance removing agent formed by supporting copper hexacyanoferrate (II) on a porous resin is disclosed.
Furthermore, Patent Document 5 (Japanese Examined Patent Publication No. 62-43519) discloses a radioactive substance removing agent obtained by adding copper ferrocyanide to granular activated carbon.

Meeting document 2-3 “Investigation on iodine removal by combined use of powdered activated carbon and pre-chlorination” of “2nd Committee on Countermeasures against Radioactive Substances in Tap Water” (Ministry of Health, Labor and Welfare, Date: May 26, 2011) "

JP-A-56-79999 Japanese Patent Laid-Open No. 9-173832 Japanese Examined Patent Publication No. 62-43519 Japanese Patent Laid-Open No. 9-173832 Japanese Examined Patent Publication No. 62-43519

As described above, the use of a radioactive substance removing agent in which a substance having a radioactive substance adsorbing ability is attached to or supported on the surface or voids of a porous material facilitates solid-liquid separation. Compared with the case where the agent is used, a large amount of sludge can be prevented from being generated.
However, if a radioactive material adsorbing material is attached or supported on porous resin or zeolite, the portion that can be attached or supported is limited to a very small part, so only a very small amount of radioactive material adsorbing material can be attached. There was a problem that it was difficult to increase the removal efficiency of substances.

  In addition, a radioactive substance removing agent in which a radioactive substance adsorbing substance is attached or supported on a porous resin or zeolite adsorbs the radioactive substance on the surface of the adsorbent, so that the radiation dose detected on the surface of the adsorbent can be reduced in a short period of time. Since it became high and it was judged that it was time to replace, the problem was that the service life of the adsorbent was short.

  Accordingly, the present invention provides a new radioactive substance removing agent that does not generate sludge slurry as a processing waste, can efficiently remove radioactive substances, and can further extend the service life, and its production. It is intended to provide a method.

As one aspect of the present invention, one or more radioactive substance removing materials selected from the group consisting of clay minerals, hardly soluble ferrocyan compounds, activated carbon and zeolite are added and dispersed in an aqueous solution of metal alginate. A porous agglomerated product obtained by preparing a metal alginate sol, adding the sol to an aqueous solution containing a gelling agent that is a calcium salt to prepare a calcium alginate gel, and drying the gel The radioactive substance removing agent is formed, and the radioactive substance removing agent increases or decreases the addition amount of the radioactive substance removing material dispersed in the metal alginate salt sol so that the particle diameter of the calcium alginate gel in a wet state is constant. Then, the particle size is adjusted by shrinking by the subsequent drying, and a packed layer containing the radioactive substance removing agent is formed in a predetermined filled container. The filling layer, and passing water treated to passed through contaminated water containing radioactive materials, proposes a method for treating a radioactive contaminated water with radioactive material removing agent and removing said radioactive material.

The present invention also adds one or more radioactive substance removing materials selected from the group consisting of clay minerals, sparingly soluble ferrocyan compounds, activated carbon, and zeolites in an aqueous solution of metal alginate and disperses the metal alginate. A sol production step for producing a sol, and a gel for producing a calcium alginate gel that uniformly includes the radioactive substance removing material by adding the produced sol to an aqueous solution containing a gelling agent that is a calcium salt. And a step of drying the prepared gel to obtain radioactive substance-removing agent particles made of a porous granule, and the amount of the radioactive substance-removing material added is increased or decreased to increase the alginic acid. Prepare multiple types of metal salts, dry them under the same conditions to obtain the radioactive substance remover particles, measure the average particle size of each, A power regression proportional relationship between the addition amount of the removal material and the average particle diameter of the radioactive substance removal agent particles is obtained, and the addition amount of the radioactive material removal material added to the aqueous solution in the sol preparation step is the power. The present invention proposes a method for adjusting the particle size of a radioactive substance removing agent, wherein the particle size of the radioactive substance removing agent particle after drying is adjusted based on a proportional relationship .

  The radioactive substance removing agent proposed by the present invention is formed by, for example, filling a radioactive substance removing agent in a container such as a filtration column to form a packed bed, and passing contaminated water containing the radioactive substance through the packed bed. Thus, radioactive materials can be removed.

Since the radioactive substance removing agent proposed by the present invention is a granular material and is easier to separate into solid and liquid than a powdery one, it may generate sludge slurry as processing waste like a powdery removing agent. Absent.
In addition, the radioactive substance removing agent proposed by the present invention has a structure in which the radioactive substance removing agent is scattered on the surface and inside of the base particle composed of a porous granule containing a metal alginate, so that the porous substance removing agent is porous. Radiation-contaminated water (treated water) easily penetrates into the inside of the particles through the voids of the granular particles, and also comes into contact with the radioactive substance removing agent scattered inside the particles, so that the radioactive substances can be efficiently removed. In addition, the radioactive substance can be adsorbed inside and on the surface in this way, and the radioactive substance is not adsorbed on the particle surface, so that the increase in radiation dose on the particle surface can be suppressed and the service life can be extended.
Furthermore, clay minerals and poorly soluble ferrocyan compounds can selectively remove radioactive cesium, activated carbon can remove radioactive iodine, and zeolite has a high cation exchange capacity. Because it is possible to remove radioactive cation nuclides, it is possible to select a radioactive substance removal agent according to the purpose and use it in combination as necessary, so it is also possible to remove multiple nuclides simultaneously And versatility can be improved.

  According to the method for producing a radioactive substance removing agent proposed by the present invention, a radioactive substance removing agent comprising porous granular particles and containing a radioactive substance removing material dispersed and contained on the surface and inside of the granular particles is provided. It can be manufactured easily. Moreover, the particle size of the porous granulated product after drying can be controlled by increasing or decreasing the amount of radioactive material removing material added to the aqueous metal alginate solution. The particle size of the agent can also be freely controlled.

It is the figure which showed typically the oxygen atom arrangement | sequence of the silicon oxide layer of a montmorillonite clay mineral. It is the figure which showed typically an example of the state which takes in a cesium ion in the hexagonal lattice of oxygen of a montmorillonite clay mineral. It is the graph which showed the relationship between bentonite powder addition amount and a dry spherical body average particle diameter. It is the graph which showed the relationship between a bentonite * activated carbon (mixing ratio 1: 1) powder addition amount and a dry spherical body average particle diameter.

  Next, an exemplary embodiment for carrying out the present invention (referred to as “this embodiment”) will be described, but the present invention is not limited to the embodiment described below.

<This radioactive substance remover>
The radioactive substance removing agent according to the present embodiment (hereinafter referred to as “the present radioactive substance removing agent”) is a porous granule containing an alginic acid metal salt as a base particle, clay mineral, sparingly soluble ferrocyan compound, activated carbon and Removal of radioactive substances containing particles (hereinafter referred to as “the present radioactive substance removing agent particles”) dispersed on the surface and inside of the base particles with one or more radioactive substance removing materials selected from the group consisting of zeolite It is an agent.

  However, if most of the particles constituting the present radioactive substance removing agent are the present radioactive substance removing agent particles, the same effect as when only the present radioactive substance removing agent particles are contained, even if other particles are mixed somewhat. Therefore, the present radioactive substance removing agent contains particles other than the present radioactive substance removing agent particles if the present radioactive substance removing agent particles occupy 80% by mass or more, preferably 90% by mass or more. May be.

(This radioactive substance remover particle)
If the radioactive substance removing agent particles are fine particles, it is difficult to separate moisture from the radioactive substance removing agent even after solid-liquid separation after contacting the radioactive substance-containing wastewater as described above. Later, a large amount of sludge containing radioactive substances will be generated. Therefore, it is preferable that the present radioactive substance removing agent particles have a size that facilitates solid-liquid separation. From this viewpoint, it is important that the average particle diameter of the present radioactive substance removing agent particles is 1 mm or more. On the other hand, when the present radioactive substance removing agent particles are too large, the surface area becomes small, and the removal efficiency of the radioactive substance is lowered, so that it is preferably 5 mm or less.
From this point of view, it is important that the average particle diameter of the present radioactive substance removing agent particles is 1 mm or more, and considering contact efficiency and pressure loss, 1.2 mm or more or 3 mm or less, especially 1.5 mm or more. Or it is preferable that it is 2.5 mm or less.

  The shape of the present radioactive substance removing agent particles, in other words, the shape of the porous granular material (substrate) is arbitrary such as a spherical shape, an elliptical spherical shape, and a flat plate shape. Among them, the spherical shape is preferable in terms of dispersibility.

The present radioactive substance removing agent particles are preferably a porous body containing a large number of voids communicating from the particle surface to the inside in that the water to be treated can penetrate into the inside of the particle.
The porosity is preferably 10 v / v% to 70 v / v% from the viewpoint of the adsorption efficiency of the radioactive substance, and more preferably 30 v / v% or more or 60 v / v% or less.
Similarly, from the viewpoint of the adsorption efficiency of the radioactive substance, the pore diameter is preferably 0.1 μm to 50 μm, and more preferably 0.5 μm or more or 20 μm or less.

  The packing density of the present radioactive substance removing agent particles is preferably 0.3 to 1.5 g / mL in terms of fluidity when passing through the column and backwashing, among which 0.4 g / mL or more or 1 It is preferably 2 g / mL or less.

(Metal alginate)
The radioactive substance removing agent particles contain a metal alginate.
It is known that a metal salt of alginic acid instantly causes a gelling reaction to form a spherical granulated product when dropped into water containing divalent or higher metal ions such as barium ions and calcium ions. For example, when a sodium alginate aqueous solution is dropped into a calcium chloride aqueous solution, sodium alginate and calcium chloride react to form a calcium alginate film on the surface of the sodium alginate aqueous solution, and the sodium alginate aqueous solution becomes spherical, so-called artificial seeds (Ikura) Is known to form.

  Examples of the metal alginate constituting the present radioactive substance removing agent particles include sodium alginate, lithium alginate, potassium alginate, etc., among which sodium alginate, lithium alginate, and potassium alginate are preferable. Sodium alginate is particularly preferred.

  It should be noted that natural or synthetic organic substances such as polyvinyl alcohol, methyl cellulose acetate, carrageenan and agar also have the property of forming a gel in the same manner as the metal alginate in constituting the radioactive substance removing agent gel particles. It is believed that these can be used in place of the metal alginate. Examples of gelation techniques for substances other than these alginate include, for example, “Bioreactor technology” (CMC editorial department, CMC Publishing, published December 10, 2001), “Wastewater treatment by microbial immobilization method” (Ryuichi Sudo, Industrial Water Research Committee, issued on June 10, 1988), "Water Treatment by Microbial Immobilization Method" (NTS, Inc., issued July 30, 2000), "Immobilization Encapsulation methods and microencapsulation methods such as those disclosed in books such as “Enzyme” (edited by Ichiro Chibata, Kodansha Co., Ltd., published on October 1, 1982) can be used.

(Radioactive material removal material)
The radioactive substance removing material contained in the present radioactive substance removing agent particles can be arbitrarily adopted as long as it has a function capable of capturing the radioactive substance by some means. Among these, it is preferable to select and use one type of radioactive substance removing material or a combination of two or more types of radioactive substance removing material from the group consisting of clay minerals, poorly soluble ferrocyan compounds, activated carbon and zeolite.

The clay mineral is not particularly limited as long as it has a three-dimensional structure of an oxygen sequence capable of selectively adsorbing cesium ions. Those having a hexagonal structure (FIG. 1) of six oxygen atoms formed by the arrangement of SiO tetrahedral layers on the clay crystal lattice plane, such as genus montmorillonite or kaolinite, are preferable. A montmorillonite genus clay mineral having a three-layer structure in which both sides of an ALO octahedral layer are sandwiched by SiO tetrahedral layers is particularly suitable.
Examples of the clay mineral belonging to the genus montmorillonite include bentonite, which is Na-type montmorillonite, acidic clay, which is H-type montmorillonite, and activated clay in which these are acid-treated to elute soluble cations to increase surface activity.
As described above, since the clay mineral can selectively remove radioactive cesium and the selective adsorption based on the crystal structure is effective, montmorillonite clay mineral, bitumen, and natural zeolite are effective. Among them, bentonite which is a montmorillonite clay mineral is particularly preferable.

Examples of the hardly soluble ferrocyan compound include poorly soluble ferrocyan compounds such as Fe salt, Ni salt and Cu salt. Among them, Fe salt (bitumen) is preferable in consideration of price.
This kind of poorly soluble ferrocyanide compound can selectively remove radioactive cesium.

  As the activated carbon, any kind of activated carbon powder such as coal-based, coconut shell-based, and wood-based can be used, and this type of activated carbon can remove radioactive iodine.

The zeolite may be either natural zeolite or synthetic zeolite.
Since this type of zeolite has a high cation exchange capacity, radioactive cation nuclides can be removed. Therefore, radioactive strontium can be removed in addition to radioactive cesium.

  As described above, since the radioactive substance removing agent particles can be selected according to the purpose and used in combination as necessary, it is possible to simultaneously remove multiple nuclides. Therefore, it can be said that the versatility is extremely high.

(Content of radioactive material removal material)
From the viewpoint of radioactive substance removal efficiency, the present radioactive substance removing agent particles preferably contain a total of 60% by mass or more of the radioactive substance removing material on the surface and inside of the particles, and more preferably 70% by mass or more. preferable.
In this radioactive substance removing agent particle, from the viewpoint of radioactive substance removal efficiency, the radioactive substance removing material is dispersed at a uniform concentration on the surface and inside of the particle, or the surface concentration is higher than the internal concentration. Are preferably dispersed.

<Method for producing the present radioactive substance removing agent>
The present radioactive substance removing agent comprises a step of adding the above-mentioned radioactive substance removing material to an aqueous solution of metal alginate and dispersing it to prepare an alginate metal salt sol; and the alginate metal salt sol in an aqueous solution containing a gelling agent. The calcium alginate gel can be produced by dripping and the step of forming a porous granulated product by drying the calcium alginate gel to release moisture (hereinafter referred to as “the present production method”). Called).
However, the manufacturing method of this radioactive substance removal agent is not limited to this manufacturing method.

According to such a production method, it is possible to easily form a granular material at an arbitrary ratio by enveloping an arbitrary poorly water-soluble powder material with a calcium alginate gel.
In addition, powder molding methods include rolling granulation molding, compaction molding, extrusion molding, etc., but all of these methods bring the compact into a compacted state. However, according to the present production method, the calcium alginate gel is dried to release moisture to remove voids in the particles. Therefore, it is possible to create a porous body containing many voids that lead from the particle surface to the inside, so that the water to be treated can easily enter the inside of the particle, so the radioactive substance removing agent inside is also effective. Used.
In addition, as will be described later, the particle size of the radioactive substance removing agent can be controlled by adjusting the concentration of the radioactive substance removing material to be added.

(Alginic acid metal salt sol production process)
In this step, for example, a metal alginate salt sol is prepared by dissolving a metal alginate in water to prepare a viscous aqueous solution, and adding a radioactive substance removing material to the aqueous solution and uniformly dispersing and mixing the solution.

  The metal alginate is soluble in water and becomes a viscous aqueous solution. The concentration of the aqueous solution of metal alginate is preferably 0.5 to 5 w / v%, and particularly preferably 1 w / v% or more or 2 w / v% or less.

The amount of the radioactive substance removing material added to the aqueous solution of metal alginate is preferably 60% by mass or more, more preferably 70% by mass or more, based on the metal alginate, from the viewpoint of the efficiency of removing the radioactive substance.
As described above, it can be considered that the same effect can be obtained by using natural or synthetic organic substances such as polyvinyl alcohol, methyl cellulose acetate, carrageenan and agar instead of the metal alginate.

(Calcium alginate gel production process)
In this step, for example, an aqueous solution containing a gelling agent such as a calcium salt is prepared, and the sol-like liquid is dropped from a nozzle having an inner diameter of 2 mm to 3 mm into the gently stirred aqueous solution. Then, a calcium alginate gel uniformly containing the radioactive substance removing material is prepared.

As the gelling agent, a metal salt having a valence of 2 or more can be used, and examples thereof include salts of barium, calcium, copper and the like. Specifically, for example, barium chloride, calcium chloride, copper sulfate, ferric chloride and the like can be mentioned, among which calcium salts are particularly preferred for reasons of price and safety in handling.
The calcium salt is not particularly limited as long as it is a water-soluble calcium salt such as a chloride salt, a bromide salt, or a nitrate. In view of price and the like, calcium chloride is preferable.
Although it does not specifically limit as a density | concentration of calcium salt aqueous solution, About 2 to 6% is suitable.

(Porosification process)
The granulated product can be made porous in the process of desorbing moisture from the granulated product by drying the calcium alginate gel obtained as described above.

  Before the calcium alginate gel is dried, the calcium alginate gel may be washed with water or saline as necessary. Moreover, after freezing once at 0 degreeC--20 degreeC, you may add the process of performing the freezing and thawing | melting which makes this thaw. Excessive calcium ions can be removed by such washing, so that it can be expected to increase the removal rate of radioactive strontium similar to calcium, for example.

As the drying means, for example, known drying means such as natural drying, reduced pressure drying, and warm drying can be appropriately employed. Among these, heating drying is particularly preferable in terms of drying time.
The drying temperature is preferably 60 to 120 ° C., more preferably 105 ° C. or higher or 115 ° C. or lower, from the viewpoint of adjusting the size and ratio of voids inside the particles.

  You may add the process baked at 400-900 degreeC after a drying process. Since the excess gelled product can be removed by incineration by such firing, the porous formation can be further promoted.

(Method for adjusting the particle size of the radioactive substance remover particles)
The particle size of the radioactive substance removing agent particles affects the removal efficiency of the radioactive substance, the water passage resistance, etc., so it is effective if the particle size of the radioactive substance removing agent particles can be adjusted according to the application.
By the way, as in the present production method, a radioactive substance removing material is added to and dispersed in an aqueous solution of a metal alginate to prepare a metal alginate sol, and the metal alginate sol is added to an aqueous solution containing a gelling agent. In the manufacturing method to make calcium alginate gel by dripping to the porous body by drying this calcium alginate gel and releasing the moisture, the concentration of the alginate metal salt aqueous solution, the addition of radioactive substance removing material The particle size of this radioactive substance remover particle (dry state) is controlled by changing the nozzle diameter and drop height when dropping the amount of alginic acid metal salt sol and controlling the particle size of the wet calcium alginate gel. that control.
In this production method, when these parameters are set under conditions suitable for dropping spherical droplets, the particle size of the wet calcium alginate gel is substantially constant from 4 mm to 4 mm even when these parameters are changed. It turned out to be 5 mm, and it was found difficult to arbitrarily control the particle size of the wet calcium alginate gel.

  Therefore, when the method for adjusting the particle size of the radioactive substance remover particles was studied repeatedly, the content of the metal alginate per radioactive substance remover particle (dried product) was only a small amount. Since it hardly affects the particle size of the agent particles, it was found that the particle size of the radioactive material remover particles can be controlled by adjusting the amount of the radioactive material removing material dispersed in the metal alginate sol. That is, when the amount of radioactive material removing material dispersed in the metal alginate sol is increased or decreased, the particle size of the wet calcium alginate gel is almost constant, but the rate of shrinkage due to subsequent drying increases or decreases. It has been found that the particle size of the substance remover particles can be controlled.

More specifically, several types of metal alginate sols with the same conditions other than the addition amount of the radioactive material removal material, but only the addition amount of the radioactive material removal material were prepared, and dried under the same conditions. This radioactive substance remover particle (dry state) was prepared, the average particle size of each was measured, and the power regression relationship between the added amount of the radioactive substance remover and the average particle size of the radioactive substance remover particle was determined. (See FIGS. 3 and 4), it has been found that the average particle diameter of the radioactive substance removing agent particles increases and decreases in proportion to the amount of radioactive substance removing material added.
At this time, the average particle size of the present radioactive substance removing agent particles was subjected to a sieving test in accordance with the measurement method of particle size distribution in 6.4 of JIS K 1474 activated carbon test method, and the cumulative ratio (%) of passing weight was 50. % Was determined as the average particle size.
Moreover, FIG. 3 is a case where bentonite is added alone as a radioactive substance removing material, and FIG. 4 is a graph showing a case where a mixture of bentonite and powdered activated carbon is added at a mixing mass ratio of 1: 1. is there.
In this way, the amount of radioactive material removal material added and the average particle size of the present radioactive material removal agent particles are proportional to each other by power regression, so the desired average particle size can be controlled by adjusting the amount of radioactive material removal material addition. can do.

<Effluent treatment using this radioactive substance remover>
The radioactive substance removing agent is packed in a container such as a filtration column to form a packed bed, and contaminated water containing the radioactive substance is passed through the packed bed to remove the radioactive substance. Can be used.

  By treating the radioactive material contaminated water (treated water) in this way, it is possible not only to effectively remove the radioactive material from the treated water, but also to enjoy the advantage that no sludge slurry as treated waste is generated. Since many of the materials that can remove radioactive substances that have been used in the past are powdery, there is a problem that they must be separated into solid and liquid after contact with contaminated water containing radioactive substances. In addition, there was a problem that a large amount of sludge was generated as a result of solid-liquid separation. On the other hand, if this radioactive substance removing agent is used as described above, it is possible to pass the radioactive substance contaminated water (treated water) through, and the radioactive substance is directly adsorbed on the radioactive substance removing agent. Since it can be obtained by passing the treated water, large equipment such as a coagulation sedimentation treatment apparatus is not required, and since sludge is not generated, it is excellent in terms of concentration and volume reduction of radioactive substances. In addition, by combining various radioactive substance removing materials, it is possible to simultaneously remove a plurality of nuclides in one filling tank, which can be said to be a highly versatile treatment method.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X is preferably greater than X” or “preferably Y”. It also includes the meaning of “smaller”.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

  Hereinafter, the present invention will be described in more detail based on examples.

<Measurement of removal rate of radioactive material>
The treatment test conditions were that cesium chloride and potassium iodide were added to tap water so that the concentrations of cesium ions and iodine ions were 5 mg / L each, and the raw water thus prepared was dried in the examples. After adding 5000 mg / L of the pulverized product (average particle size of 45 μm or less) obtained by pulverizing the gel with a vibration mill, contact treatment was performed by continuous stirring at 100 rpm for 6 hours, and then filtered through a 0.45 μm GF filter. The concentration of cesium ions and iodine ions was measured by atomic absorption photometry, and the respective removal rates were measured.
Note that iodine ions were added to the raw water only in the case of the agent of the present invention containing activated carbon. In this case, sodium hypochlorite was added so that the free residual chlorine was 0.5 mg / L. It was.
In this test, the removal rate of cesium ions and iodine ions that did not emit radiation was measured, but considering the mechanism of removal, it can be considered that the removal rate of those emitting radiation is the same. it can.

<Measurement of particle size of wet gel>
The particle size of the wet gel was measured by a wet sieving method.

<Measurement of average particle size of dry gel>
A sieving test was performed in accordance with the particle size distribution measuring method in 6.4 of JIS K 1474 activated carbon test method, and the particle size at which the cumulative ratio (%) of passing weight was 50% was determined as the average particle size.

<Example>
The production conditions of Examples 1 to 34 are shown in Table 1, and the treatment test results are shown in Table 2.

Example 1
Bentonite was mixed with 1 w / v% sodium alginate aqueous solution to prepare a raw material sol solution (sodium alginate sol) having a weight composition ratio of 2.0 w / w% bentonite and 1.0 w / w sodium alginate. Separately, a 4 w / v% calcium chloride aqueous solution was prepared as a gelling solution. While gently stirring this gelled solution with a magnetic stirrer, the raw material sol solution is dropped at a rate of 25 mL / min from a nozzle having a height of 5 cm and an inner diameter of 3 mm, and held in the gelled solution for 30 minutes. A spherical wet gel (sodium alginate gel) having a diameter of 4 to 5 mm was obtained. The obtained wet gel was dried at 115 ° C. for 8 hours with a dryer to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 1.5 mm.
Then, the radioactive substance removal rate was measured as described above, and the results are shown in Table 2.

  The raw sol solution was dropped from a nozzle with an inner diameter of 2 mm, and an attempt was made to obtain a spherical wet gel with a small particle diameter. The diameter was 4 mm to 5 mm, and the spherical wet gel diameter was the same even when the nozzle diameter was changed.

(Example 2)
Gelation was carried out in the same manner as in Example 1 except that a raw material sol solution of bentonite 7.4 w / w% and sodium alginate 0.9 w / w% was prepared in a weight composition ratio, and spherical wetness having a diameter of 4 to 5 mm. A gel was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“Dried Gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

Example 3
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of bentonite 21 w / w% and sodium alginate 0.8 w / w% was prepared in a weight composition ratio to obtain a spherical wet gel having a diameter of 4 to 5 mm. It was. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle diameter of 2.5 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Examples 1 to 3, by changing the amount of bentonite added to the raw sol solution, the average particle size of the spherical porous granulated product (“dry gel”) is changed to 1. It was possible to control accurately with 5 mm, 2.0 mm and 2.5 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

Example 4
The same method as in Example 1 except that the concentration of the sodium alginate aqueous solution was 0.5 w / v%, and the raw material sol solution was bentonite 7.4 w / w% and sodium alginate 0.5 w / w% in weight composition ratio. Gelation was performed to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 5)
Gelation was carried out in the same manner as in Example 1 except that the concentration of sodium alginate aqueous solution was 2 w / v%, and the raw material sol solution was 7.4 w / w% bentonite and 0.9 w / w% sodium alginate by weight composition ratio. To obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 6)
Gelation was carried out in the same manner as in Example 1, except that the concentration of sodium alginate aqueous solution was 3 w / v%, and the raw material sol solution was 7.4 w / w% bentonite and 1.8 w / w sodium alginate in weight composition ratio. To obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Examples 4 to 6, if the amount of bentonite added to the raw sol solution is the same, even if the concentration of the sodium alginate aqueous solution is changed in the range of 0.5 to 3 w / v%, the spherical porosity is increased. The particle size of the granular material (dry gel) could be accurately controlled to an average particle size of 2.0 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 7)
The same as in Example 1 except that the calcium chloride concentration of the gelled solution was 0.5 w / v%, and the raw material sol solution of bentonite 7.4 w / w% and sodium alginate 0.9 w / w% in weight composition ratio was prepared. Gelation was performed by the method described above to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 8)
The same method as in Example 1 except that the calcium chloride concentration of the gelled solution was 1 w / v%, and the raw material sol solution of bentonite 7.4 w / w% and sodium alginate 0.9 w / w% in weight composition ratio was prepared. Was gelled to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

Example 9
The same method as in Example 1 except that the calcium chloride concentration of the gelled solution was 2 w / v%, and the raw material sol solution was 7.4 w / w% bentonite and 0.9 w / w sodium alginate by weight composition ratio. Was gelled to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 10)
The same method as in Example 1 except that the calcium chloride concentration of the gelled solution was 3 w / v%, and the raw material sol solution was 7.4 w / w% bentonite and 0.9 w / w sodium alginate by weight composition ratio. Was gelled to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 11)
The same method as in Example 1 except that the calcium chloride concentration of the gelled solution was 5 w / v%, and the raw material sol solution of bentonite 7.4 w / w% and sodium alginate 0.9 w / w% in weight composition ratio was prepared. Then, the dripping solution was gelled to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Example 2 and Examples 7 to 11, if the bentonite addition amount of the raw material sol solution is the same, the concentration of the calcium chloride solution of the gelling solution is within the range of 0.5 to 5 w / v%. Even if it was changed, the particle size of the spherical porous granulated product (dry gel) could be accurately controlled to an average particle size of 2.0 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 12)
Example 1 except that a 1 w / v% aqueous solution of potassium alginate was used in place of the aqueous sodium alginate solution and a raw material sol solution containing 7.4 w / w% bentonite and 0.9 w / w potassium alginate was prepared. Gelation was performed in the same manner to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 13)
Example 1 except that a 1 w / v% aqueous solution of lithium alginate was used instead of the aqueous sodium alginate solution and a raw material sol solution containing 7.4 w / w% bentonite and 0.9 w / w potassium alginate was prepared by weight composition ratio. The dripping solution was gelled by the same method to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Example 2 and Examples 12 and 13, if the amount of bentonite added to the raw sol solution is the same, the alginate is replaced with a water-soluble alginate of any one of sodium salt, potassium salt and lithium salt. However, the particle diameter of the spherical porous body granulated product (dry gel) could be accurately controlled to an average particle diameter of 2.0 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 14)
Instead of the calcium chloride solution of the gelled solution, a 4 w / v% aqueous solution of calcium nitrate was prepared, and a raw material sol solution containing 7.4 w / w% bentonite and 0.9 w / w sodium alginate was prepared. Gelation was performed in the same manner as in Example 1 to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 15)
In place of the calcium chloride solution of gelling solution, a 4 w / v% aqueous solution of calcium bromide was used, and a raw material sol solution containing 7.4 w / w% bentonite and 0.9 w / w sodium alginate was prepared. Was gelled in the same manner as in Example 1 to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Example 2 and Examples 14 and 15, as long as the amount of bentonite added to the raw material sol solution is the same, the calcium salt of the gelled solution is changed to water-soluble calcium of chloride, nitrate or bromide. Even if it changed to salt, the particle size of the spherical porous body granulated material (dry gel) was able to be precisely controlled to the average particle size of 2.0 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 16)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution containing 0.7 w / w% bentonite, 0.7 w / w% activated carbon and 1.0 w / w% sodium alginate was prepared by weight composition ratio. A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 1.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 17)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of bentonite 2.4 w / w%, activated carbon 2.4 w / w%, and sodium alginate 0.9 w / w% was prepared by weight composition ratio, A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 18)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of bentonite 6.1 w / w%, activated carbon 6.1 w / w%, and sodium alginate 0.9 w / w% was prepared by weight composition ratio. A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle diameter of 2.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

As can be seen from the results of Examples 16 to 18, even in the case of a mixture of bentonite and activated carbon, a spherical porous granulated product (dry gel) can be obtained by changing the amount of bentonite and the amount of activated carbon added to the raw material sol solution. The particle size of each of the particles could be controlled to an average particle size of 1.5 mm, 2.0 mm, and 2.5 mm, respectively.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 19)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of zeolite 2.5 w / w% and sodium alginate 1.0 w / w% in weight composition ratio was prepared, and a spherical wet gel having a diameter of 4 mm to 5 mm. Got. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 1.5 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 20)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of zeolite 7.8 w / w% and sodium alginate 0.9 w / w% in weight composition ratio was prepared, and a spherical wet gel having a diameter of 4 mm to 5 mm. Got. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 21)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of zeolite 14 w / w% by weight composition ratio and sodium alginate 0.8 w / w% was prepared to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. It was. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle diameter of 2.5 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

As can be seen from the results of Examples 19 to 21, by changing the bentonite addition amount and the activated carbon addition amount of the raw material sol solution even in the case of zeolite, the particle size of the spherical porous granulated product (dry gel) is changed. The average particle diameters could be controlled to 1.5 mm, 2.0 mm, and 2.5 mm, respectively.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 22)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of zeolite 1.3 w / w%, activated carbon 1.3 w / w%, and sodium alginate 1.0 w / w% was prepared in a weight composition ratio. A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 1.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 23)
Gelation was performed in the same manner as in Example 1, except that a raw material sol solution of zeolite 5.0 w / w%, activated carbon 5.0 w / w%, and sodium alginate 0.9 w / w% was prepared in a weight composition ratio. A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 24)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution containing zeolite 8.0 w / w% by weight, activated carbon 8.0 w / w%, and sodium alginate 0.8 w / w% was prepared. A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle diameter of 2.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

As can be seen from the results of Examples 22 to 24, even in the case of a mixture of bentonite and activated carbon, a spherical porous body granulated product (dry gel) can be obtained by changing the amount of bentonite and activated carbon added to the raw sol solution. The particle size of each of the particles could be controlled to an average particle size of 1.5 mm, 2.0 mm, and 2.5 mm, respectively.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 25)
The same as in Example 1 except that a raw material sol solution containing 0.7 w / w% bentonite, 0.7 w / w% zeolite, 0.7 w / w% activated carbon, and 1.0 w / w% sodium alginate was prepared. Gelation was performed by the method described above to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 1.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 26)
Same as Example 1 except that a raw material sol solution of bentonite 2.6 w / w%, zeolite 2.6 w / w%, activated carbon 2.6 w / w%, sodium alginate 0.9 w / w% by weight composition ratio was prepared. Gelation was performed by the method described above to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 27)
Same as Example 1 except that a raw material sol solution of bentonite 5.0 w / w%, zeolite 5.0 w / w%, activated carbon 5.0 w / w%, sodium alginate 0.8 w / w% in weight composition ratio was prepared. Gelation was performed by the method described above to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle diameter of 2.5 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

As can be seen from the results of Examples 25 to 27, even in the case of three kinds of mixtures of bentonite, zeolite, and activated carbon, by changing the bentonite addition amount, zeolite addition amount, and activated carbon addition amount of the raw material sol solution, spherical porosity The particle size of the granulated product (dry gel) could be controlled to be an average particle size of 1.5 mm, 2.0 mm, and 2.5 mm, respectively.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Example 28)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution having a weight composition ratio of 8.0 w / w% bitumen and 0.9 w / w sodium alginate was prepared, and a spherical wet gel having a diameter of 4 to 5 mm. Got. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured similarly to Example 1, and the result was shown in Table 2.

(Example 29)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of bitumen 4.0 w / w%, activated carbon 4.0 w / w%, and sodium alginate 0.9 w / w% was prepared by weight composition ratio, A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be 0.5 mg / L, and the result was shown in Table 2.

(Example 30)
Gelation was performed in the same manner as in Example 1 except that a raw material sol solution of bitumen 4.0 w / w%, bentonite 4.0 w / w%, and sodium alginate 0.9 w / w% was prepared by weight composition ratio, A spherical wet gel having a diameter of 4 mm to 5 mm was obtained. The obtained wet gel was dried in the same manner as in Example 1 to obtain a spherical porous granulated product (“dry gel” in the table) having an average particle size of 2.0 mm.
And the processing test similar to Example 1 was done, the radioactive substance removal rate was measured as mentioned above, and the result was shown in Table 2.

(Example 31)
Except for preparing a raw material sol solution of bitumen 3.0 w / w%, bentonite 3.0 w / w%, activated carbon 3.0 w / w%, sodium alginate 0.9 w / w% by weight composition ratio, the same as in Example 1 The dropping solution was gelled by the above method to obtain a spherical wet gel having a diameter of 4 mm to 5 mm. The obtained wet gel was dried to obtain a dried sphere having an average particle size of 2.0 mm. Moreover, the radioactive substance removal rate was measured like Example 1 except having added sodium hypochlorite so that free residual chlorine might be set to 0.5 mg / L, and the result was shown in Table 2.

As a result of Examples 28-31, even in the case of bitumen, a mixture of bitumen and activated carbon, a mixture of bitumen and bentonite, and a mixture of bitumen, bentonite and activated carbon, the bentonite addition amount, the bitumen addition amount and the activated carbon addition amount of the raw material sol solution were changed. As a result, the particle diameter of the spherical porous body granulated product (dry gel) could be controlled to an average particle diameter of 2.0 mm.
In addition, when each of the examples was performed a plurality of times, it was possible to control with high accuracy so that the variation coefficient of the average particle diameter was within the range of less than 5%.

(Reference Example 32)
The dripping solution was gelled in the same manner as in Example 1 except that a raw material sol solution of kaolin 8.0 w / w% and sodium alginate 0.9 w / w% by weight composition ratio was prepared. A spherical wet gel was obtained. The obtained wet gel was dried to obtain a dried sphere having an average particle size of 2.0 mm. The radioactive substance removal rate was measured in the same manner as in Example 1, and the results are shown in Table 2.

(Reference Example 33)
The dripping solution was gelled in the same manner as in Example 1 except that a raw material sol solution having an acid clay of 8.0 w / w% and sodium alginate of 0.9 w / w% was prepared in a weight composition ratio. A spherical wet gel was obtained. The obtained wet gel was dried to obtain a dried sphere having an average particle size of 2.0 mm. The radioactive substance removal rate was measured in the same manner as in Example 1, and the results are shown in Table 2.

(Reference Example 34)
The dripping solution was gelled in the same manner as in Example 1 except that a raw material sol solution having an acid clay of 8.0 w / w% and sodium alginate of 0.9 w / w% was prepared in a weight composition ratio. A spherical wet gel was obtained. The obtained wet gel was dried to obtain a dried sphere having an average particle size of 2.0 mm. The radioactive substance removal rate was measured in the same manner as in Example 1, and the results are shown in Table 2.

  As can be seen from the results of Reference Examples 32-34, the particle size of the dried spheres can be changed by changing the amount of bentonite added, the amount of bitumen added, and the amount of activated carbon added to the raw sol solution even in the case of kaolin, acid clay, activated clay. The average particle size could be controlled to 2.0 mm.

(Example 35)
The spherical radioactive substance removing agent having an average particle diameter of 2.0 mm prepared in Example 2 was packed in a column having a diameter of 150 mm into a layer thickness of 300 mm, and cesium ions 5.0 mg / L and strontium ions 5.0 mg / L in tap water. When the raw water prepared so as to become a water flow treatment at a superficial velocity SV = 2 [m ³ -raw water / m ³ -filler / hour], cesium ions in a state 24 hours after the start of water flow, Both strontium ions were less than 0.01 mg / L.

(Example 36)
A spherical radioactive substance removing agent having an average particle diameter of 2.0 mm of bentonite and activated carbon prepared in Example 17 was packed in a column having a diameter of 150 mm and a layer thickness of 300 mm, and tap water was charged with cesium ions 5.0 mg / L and iodine ions 5.0 mg. / L and strontium ion 5.0 mg / L of raw water, sodium hypochlorite was added so that the free residual chlorine was 0.5 mg / L, and the superficial velocity SV = 2 [m ³ − When water flow treatment was performed using raw water / m ³ -filler / hour], cesium ions, iodine ions, and strontium ions were all less than 0.01 mg / L in a state 24 hours after the start of water flow.

(Example 37)
A spherical radioactive substance removing agent having an average particle diameter of 2.0 mm made of bentonite, zeolite and activated carbon prepared in Example 26 was packed in a column having an inner diameter of 150 mm and a layer thickness of 300 mm, and tap water was charged with cesium ions 5.0 mg / L, iodine ions 5 Sodium hypochlorite was added to the raw water prepared to 0.0 mg / L and strontium ion 5.0 mg / L so that the free residual chlorine was 0.5 mg / L, and the superficial velocity SV = 2 [m ³ -Raw water / m ³ -Filler / hour], the cesium ion, iodine ion, and strontium ion were all less than 0.01 mg / L in the state 24 hours after the start of water flow. .

Claims (2)

One or more radioactive substance removing materials selected from the group consisting of clay minerals, poorly soluble ferrocyan compounds, activated carbon and zeolite are added and dispersed in an aqueous solution of metal alginate to prepare a metal alginate sol, the sol was prepared calcium alginate gel was added to the aqueous solution containing the gelling agent is a calcium salt, the radioactive material removing agent ing a porous body obtained granules by drying the gel Forming ,
The radioactive substance removing agent increases or decreases the amount of the radioactive substance removing material dispersed in the metal alginate sol to make the particle size of the wet calcium alginate gel constant, and then shrinks by drying. The grain size is adjusted,
Forming a filling layer containing the radioactive substance removing agent in a predetermined filling container;
Water treatment for passing contaminated water containing radioactive substances to the packed bed,
A method for treating radioactive contaminated water using a radioactive substance removing agent, wherein the radioactive substance is removed. A sol for producing an alginate metal salt sol by adding and dispersing one or more radioactive substance removing materials selected from the group consisting of clay minerals, poorly soluble ferrocyan compounds, activated carbon and zeolite in an aqueous solution of metal alginate. Production process;
A gel preparation step of adding the prepared sol to an aqueous solution containing a gelling agent that is a calcium salt to prepare a calcium alginate gel uniformly including the radioactive substance removing material;
And a drying step to obtain a radioactive substance removal agent particles composed of Ri by the drying the produced gel multi porous material granules,
A plurality of kinds of the metal alginate are prepared by increasing / decreasing the amount of the radioactive substance removing material, obtaining the radioactive substance removing agent particles by drying them under the same conditions, measuring the average particle diameter of each, Obtain a power regression proportional relationship between the added amount of the radioactive substance removing material and the average particle diameter of the radioactive substance removing agent particles,
In the sol preparation step, the amount of the radioactive substance removing material added to the aqueous solution is increased / decreased based on the power proportional relationship to adjust the particle size of the radioactive substance removing agent particles after drying. Method for adjusting particle size of radioactive substance remover.

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