JP2013226494A - Granular adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a granular adsorbent excellent in adsorption characteristic for radioactive substances.SOLUTION: For a granular adsorbent, by mixing 100 pts.wt. of glassy material powder, 200-300 pts.wt. of a particulate mixture for which two or more different groups are selected from four kinds of groups of tuff particulates, pumice particulates, brick particulates and secondary concrete product particulates and materials are selected from the groups and combined, and 0.6-15 pts.wt. of foaming material powder, heating the mixture in the range of 700-900°C to accelerate foaming and heat denaturation, cooling it, and then crushing it, the granular adsorbent is obtained.

Description

  The present invention relates to a granular adsorbent excellent in radioactive material adsorption characteristics, and more specifically, tuffstone granule, pumice granule, brick granule, concrete secondary product granule 4 A granular adsorbent obtained by heating a mixture composed of seed powder, vitreous material powder and foam powder to promote melting and foaming of the vitreous material powder and heat-denaturing the four mixed powder particles About.

  Conventionally, in order to recycle glassy or coal ash, which is a kind of inorganic waste material, several types of inorganic waste material are mixed and heated, forming closed cells in a matrix such as glassy material, Glassy foams that are excellent in heat insulation and sound insulation, lightweight artificial aggregates, and the like have been developed.

Recently, an inorganic foam composition that forms a vitreous foam having a desired specific gravity has been provided, which has been proposed as a plate-like long foam for practical use in improving water quality (Patent Document 1).
The outline is that inorganic foam composition powder such as glassy waste, combustion ash, brick waste and shell powder are mixed, and the thickness is 7 mm, the width is 0.4 m, and the length is 1. on the mesh belt. The inorganic foam composition powder is 15 mm thick, 0.4 m wide, and 1.2 m long, with a volume approximately doubled. To obtain a plate-like long inorganic foam. By this stepwise heating method, the foam can be integrated with a low specific gravity foam layer and a high specific gravity foam layer having different specific gravity. And can be placed with the high specific gravity foam layer facing down. By such an installation method, water purification such as decomposition of organic substances in water can be performed efficiently, fishing reefs formed by elution of metal ions are formed, and algae attach to biofilms.
However, in the above technique, carbon dioxide generated by the thermal decomposition of the shell cannot continuously escape from the glass layer due to the viscosity of molten glass, etc., and closed cells can be formed. The continuous pore which has is not able to be formed. Therefore, there are limits to various improvements such as water quality improvement and air quality improvement, and the actual situation is limited to heat insulation and sound insulation.

On the other hand, there is a proposal of a radioactive waste burying material having a water stopping action and an adsorption action corresponding to the artificial geothermal environment of a disposal site where the radioactive waste is buried (Patent Document 2).
This proposal is a radioactive material made by mixing bentonite and volcanic glass with fine cracks, or further mixing fly ash with a buffer material or backfill material used when burying radioactive waste drugs underground. It is used as a filling material for burial.
However, this technology uses volcanic glass as an alternative material for bentonite in view of the fact that bentonite is subjected to geothermal heat and deteriorates its performance, and does not improve the adsorption properties of radioactive substances.

JP 2004-123425 A Patent 4096328

  The present inventor conducted research on radioactive material adsorbents. As a result, four types of powders, tuff granule, pumice granule, brick granule, and concrete secondary product granule, were obtained. By performing heat treatment at 700-900 ° C on the granule, it is found that the ability improvement excellent in the adsorption characteristic of the radioactive substance can be seen, and the vitreous material powder and the foam material powder are utilized to combine these granular materials. A granular adsorbent is proposed.

  In order to achieve the above object, the granular adsorbent according to claim 1 includes: a) 100 parts by weight of vitreous material powder, tuffite granule obtained by crushing Otani stone, Wakakusa stone, deep rock stone and the like; Crushing pumice powder granules made by crushing lightweight cellular concrete or natural pumice, brick granules made by crushing at least one of the group consisting of bricks, tiles and tiles, and concrete secondary products Mixed granular material in which two or more different groups are selected from the four types of concrete secondary product granular materials, and at least one material is selected from the selected group and combined. 200 to 300 parts by weight and 0.6 to 15 parts by weight of foaming material powder are mixed. B) The mixture is heated in the range of 700 to 900 ° C. to promote thermal denaturation and continuously with foaming. A lump containing bubbles; c) the lump The ones crushed after cooling, characterized in that to obtain granules.

The granular adsorbent according to claim 2 is a mixed granular material having a particle diameter of 1 to 1000 μm.

  The granular adsorbent according to claim 3 is made of a vitreous material powder as window glass and / or a cup and / or a bottle and having a particle diameter of 1 to 1000 μm.

In the granular adsorbent according to claim 4, the foam powder is calcium carbonate derived from shells such as akoya shells, scallop shells, oyster shells, and the like, and the particle size is a granular material having a particle diameter of 1-1000 μm.

Four types of groups, tuff granule, pumice granule, brick granule, and concrete secondary product granule, adsorb excellent radioactive materials which are different after thermal denaturation. Has characteristics. For example, tuff granulates have excellent adsorbability in all dose values (CPM values), cesium values (Cs values), and strontium (Sr values), and pumice powder granules have CPM values, Cs Adhesive capacity excellent in value, brick powder particles show CPM value, Cs value, Sr value, especially adsorbability excellent in Sr value, concrete secondary product powder particles show CPM value, Cs Excellent adsorption capacity in value. Each group has different tissue component ratios and different characteristics in the void form.
The above group is most suitable for adsorbing the target radioactive substance by combining the powder particles together with the glassy material powder softened by heat as the core, and the combination becomes a combination of two or more. The adsorption characteristics and form of radioactive materials can be realized.
In the above-mentioned adsorption characteristics of radioactive substances, the powders belonging to the above group are Al ₂ O ₃ —SiO ₂ system, such as CaO, Fe ₂ O ₃ , Na ₂ O, K ₂ O, TiO ₂ etc. Formed amorphous, heat denaturation that causes some structural change is promoted by heating in the range of 700-900 ° C, and improved characteristics such as CPM value, Cs value, Sr value, etc. compared to before heating Is planned.
Also, a foam material powder and its heating yielded a light-weight carme-like foam containing open cells, and by granulating it, a radioactive material having a large surface area on both the outer and inner surfaces Granules having excellent adsorption characteristics can be obtained.

It is an electron micrograph before heat denaturation of Otani stone among tuff powder granular materials. It is an electron micrograph before heat denaturation of artificial lightweight cellular concrete (ALC) among pumice granular fluid. It is an electron micrograph before heat denaturation of natural pumice among pumice powder fluids. It is an electron micrograph before heat denaturation of a brick among brick type granular materials. It is an electron micrograph before heat denaturation of a tile among brick granular materials. It is an electron micrograph before heat denaturation of a tile among brick granular materials. It is an electron micrograph before heat denaturation of a side groove among concrete secondary product granular materials. It is a graph showing the adsorption and removal status of radioactive materials with respect to contaminated water of Otani stone belonging to the tuff granule of the present invention, comparing with zeolite, (A) is CPM before heat denaturation (radiation dose per minute) (B) is a graph showing CPM after heat denaturation, (C) is a graph comparing Se values after heat denaturation, and (D) is a graph showing Sr values after heat denaturation. The graph which shows the adsorption removal condition with respect to the contaminated water of the artificial lightweight aerated concrete (ALC) which belongs to the pumice granular material of this invention, comparing with a zeolite, (A) is a graph which shows CPM before heat denaturation, (B ) Is a graph showing CPM after heat denaturation, (C) is a graph comparing Se values after heat denaturation, and (D) is a graph showing Sr values after heat denaturation. The graph which shows the adsorption removal condition with respect to the contaminated water of the brick which belongs to the brick granular material of this invention comparing with a zeolite, (A) is a graph which shows CPM before heat denaturation, (B) is after heat denaturation. A graph showing CPM, (C) is a graph comparing Se values after heat denaturation, and (D) is a graph showing Sr values after heat denaturation. The graph which shows the adsorption removal condition with respect to the contaminated water of the side groove | channel which belongs to the concrete secondary product granular material of this invention, comparing with a zeolite, (A) is a graph which shows CPM before heat denaturation, (B) is heat The graph which shows CPM after modification | denaturation, (C) is the graph which compared Se value after heat denaturation, (D) is a graph which shows Sr value after heat denaturation.

Accordingly, an embodiment of the present invention will be described with reference to FIGS.
The present invention comprises four types of granular materials, tuff powder, foam material powder and foam material powder of tuff powder powder, pumice powder granular material, brick powder, concrete secondary product granular material. The function of each material will be described.

First, four types of granular materials, tuff granule, pumice granular material, brick granular material, and concrete secondary product granular material will be described.
The first group of tuff granulates is composed of tuff such as Otani stone, Wakakusa stone, and pebble stone, and mainly composed of SiO ₂ (66.96%) and Al ₂ O ₃ (12.55%). This contains Na ₂ O (2.87%), K ₂ O (2.35%), etc., and forms a porous structure inside (the parentheses indicate the component values of Oyaishi).
As shown in the electron micrograph according to FIG. 1, it can be confirmed that a porous material is formed inside.
Such tuff particles are excellent in the ability to adsorb radioactive substances, and after modification by thermal denaturation accompanying the heating of the present invention, which will be described later, for example, Oyaishi has a CPM (total dose) value modified by a scintillation LSC7400 counter. It shows a remarkable adsorption effect (over zeolite over) from the front 60 to 20 after reforming (FIGS. 8A and 8B).
That is, before the modification, the CPM of the zeolite was 25, whereas Otaniishi was 60, which was inferior to the zeolite, but after the modification, the CPM value was 20, which exceeded 25 of the zeolite. The value is shown.
When it was a radioactive substance and was measured separately for cesium (Cs) and strontium (Sr), the dose value after modification showed 0.002 for Cs, and 0.0075 for Sr. In both cases, excellent adsorption ability was confirmed (FIG. 8C).
In particular, in the case of Sr, Oyaishi after modification showed an extremely excellent value of 0.0075 compared to 0.36 of zeolite, and it was confirmed that the adsorption characteristics of Sr were excellent (FIG. 8 (D )).
In addition, with respect to the mixed granular material of the present application, a zeolite that exhibits an excellent adsorbing ability with respect to a radioactive substance is cited as a comparison object, and the performance comparison is performed by comparison with this zeolite.

The second group of pumice grains is composed of artificial lightweight cellular concrete (ALC) such as Hebel (trademark) or natural pumice, and is composed of SiO ₂ (47.9%), Al ₂ O ₃ (12. 47%) and CaO (32.8%) are added to show porosity as a feature of the cellular concrete (the values in parentheses indicate ALC component values).
In natural pumice, SiO ₂ (61.75%), Al ₂ O ₃ (11.88%), Fe ₂ O ₃ (5.99%), CaO (6.67%), etc. are shown. .
As shown in the electron micrographs shown in FIGS. 2 and 3, it can be confirmed that a porous material is formed inside.
Such a pumice powder granule exhibits an excellent ability to adsorb radioactive substances, although it does not reach the tuff.
That is, for example, in ALC, as shown in FIGS. 9A and 9B, CPM is inferior to 53 and 25 of zeolite before reforming, but after reforming, CPM31 and zeolite Excellent adsorption capacity approaching 25 was exhibited.
The Cs value was 0.0052, which was close to 0.003 of the zeolite after the modification, and even in Sr, the value was 0.58 relative to 0.36 of the zeolite after the modification. (FIGS. 8C and 8D).

The third group of powdered bricks is made by solidifying by heating clay at a temperature above a certain level. It consists of bricks, tiles or tiles. SiO ₂ (62.8%) , Al ₂ O ₃ (22.9%) as a main component, which includes Fe ₂ O ₃ (6.78%), CaO (0.95%), MgO (1.47%), and the like.
The roof tiles are SiO ₂ (50.08%), Al ₂ O ₃ (10.22%), Fe ₂ O ₃ (6.21%), CaO (11.15%), Na ₂ O (1.67%). ) And K ₂ O (4.53%).
The tile has a component composition such as SiO ₂ (71.36%), Al ₂ O ₃ (19.57%), Na ₂ O (0.94%), K ₂ O (1.39%).
As shown in the electron micrographs shown in FIGS. 4, 5, and 6, it can be confirmed that there are fine voids inside.
Such brick powder particles were confirmed to have excellent properties in that the CPM after modification was equivalent to zeolite, but Sr was superior to zeolite.
That is, for example, as shown in FIGS. 10 (A) and 10 (B), the CPM before reforming is 43, which is inferior to 25 zeolite, but after reforming, CPM values 28 and 25 are equivalent to zeolite. It was.
The Cs value shows the same value as 0.0015 and 0.0003 zeolite, but Sr has an excellent adsorption that greatly exceeds 0.035 for 0.36 zeolite. The characteristics were confirmed (FIGS. 10C and 10D).

The fourth group of concrete secondary product granular materials refers to concrete secondary products such as side grooves, drainage grooves, manholes, fume pipes, curbs, etc., SiO ₂ (76.83%), Al ₂ O ₃ (12.47%) as a main component, and CaO (12.3%), Fe ₂ O ₃ (1.0%), Na ₂ O (3.5%), K ₂ O (5.0 %) Etc.
As shown in the electron micrograph according to FIG. 7, it is confirmed that there are fine voids inside as with the brick.
Such a concrete secondary product granular material does not reach tuff, but exhibits an excellent radioactive substance adsorbing ability.
That is, for example, as shown in FIGS. 11 (A) and 11 (B), the side groove has an excellent adsorptive capacity close to 25 of zeolite, with CPM before modification being 32, and close to 25 of zeolite and CPM after modification. Indicated.
The Cs value was 0.0011, which was close to 0.003 of the zeolite after the modification, and even in Sr, the value was 0.6 relative to 0.36 of the zeolite after the modification. (FIGS. 11C and 11D).

Summarizing the characteristics of the above group, the first group (tuffstone granule) showed excellent adsorbing ability in all of the modified CPM value, Cs value, and Sr value. (Pumice granular material) shows the adsorbing ability excellent in CPM value and Cs value after modification, and the third group (brick granular material) is CPM value, Cs value after modification, Adsorption ability excellent in Sr value, especially Sr value is shown, and the fourth group (concrete secondary product powder) shows excellent adsorption ability in CPM value and Cs value after modification. Moreover, the difference of the ratio of a different structure | tissue component and a void | hole form is seen for every group.
Therefore, in consideration of the characteristics of these different groups, a combination of group selections determines how to implement the intended radioactive substance adsorption.
For example, when the objective is to reduce CPM as a whole, group 1 or group 2 is selected and its ratio is increased. In particular, when Cs is the target of adsorption, groups 2 and 4 are added to increase the ratio. A group can be selected. In particular, when targeting Sr adsorption, the use of group 1 and group 3 is effective. Further, in addition to the adsorption characteristics of the radioactive substance, a comprehensive determination is made by adding the tissue components of each group, hardness, porosity, lightness, and the like.
In the combination, two or more different groups are selected from the four groups, and at least one material is selected from the selected groups and combined. Therefore, it is possible to change the combination of 2, 3, and 4 according to the purpose, and to change the selection of the material belonging to the group.

Subsequently, although the said granular material mixes glass material powder and foaming material powder, glass material powder is demonstrated first.
The glassy material powder is made from window glass, cups, bottles and the like as raw materials, crushed by a crusher, and made into a granular material having a particle diameter of 1-1000 μm. The glassy material powder begins to soften and melt at a temperature as low as 700 ° C. prior to the powder and foam powder, and the mixed powder and foam powder adhere to the molten glass softened as the temperature rises. Then, they are connected to each other.
At this time, since the vitreous material powder has a relatively small content ratio of 100 parts by weight with respect to 200 to 300 parts by weight of the mixed granular material, the whole is not hardened and the glass is fused. When heated as described below, the vitreous material melts the individual particles, and the other parts with less fusion are pores and through holes. It becomes pores and appears three-dimensionally as a porous granular material.

Next, the foamed powder is, for example, calcium carbonate powder derived from shells such as coconut shells, scallop shells, oyster shells, and the blending ratio is 0.6 to 15 parts by weight, and the particle diameter is 1 to 1000 μm. Use powder and granules. In the case of shells, the salt content of seawater inhibits the foaming of the inorganic powder, so it is washed with water or left to stand to remove the salt content. The particle diameter was set to 1 to 1000 μm because the calcium carbonate was thermally decomposed to generate a large amount of carbon dioxide, which was once bound by the softened glassy material powder. The agglomerated material is swelled, and it is taken out of the furnace and cooled to obtain a calme-like expanded solid containing open cells and foamed voids.
This carme-like expanded body becomes an Al ₂ O ₃ —SiO ₂ -based amorphous granular material having a very large surface area and has relatively brittle properties. Therefore, as a final stage, this is pulverized with a pulverizer or the like to form a granular material, which is easily used as a granular adsorbent.

Table 1 shows the blending ratio of the materials to be mixed.

In the heating process at 700 ° C. to 900 ° C., it was confirmed that the following thermal denaturation is induced in the mixed powder particles forming the Al ₂ O ₃ —SiO ₂ structure.
That is, in the mixed granular material consisting of the above four groups, a significant improvement in the ability to adsorb radioactive substances can be seen by heating at 700 to 900 ° C.
For example, in Otani stone, the CPM value by the scintillation LSC7400 counter decreases from 60 before reforming to 20 after reforming, and in Cs, the dose value after reforming shows 0.002. In Sr, it shows 0.0075, and it has been confirmed that the adsorption capacity is improved. As described above, the same adsorptive capacity is improved even in other granular materials.
As described above, the heating at 700 to 900 ° C. shows a significant improvement in the ability to adsorb radioactive substances (this was called thermal denaturation or modification as described above). The cause of this thermal denaturation is as follows. The exact reason is not clear yet, but it is presumed as follows.
That is, as described above, the granular materials belonging to the four groups listed in the present invention have CaO, Fe ₂ O ₃ , Na ₂ O, K ₂ O in the main Al ₂ O ₃ —SiO ₂ structure. , TiO _{2 and} other components added, Na ₂ O-Al ₂ O ₃ -SiO ₂ system, CaO-K ₂ O-Al ₂ O ₃ -SiO ₂ system, Fe ₂ O ₃ -TiO _2-
Forms an amorphous body such as Na ₂ O-Al ₂ O ₃ -SiO _2, but this amorphous body does not depend on the crystalline body, but partly contains crystalline It is understood that when 700 ° C. to 900 ° C. heat is applied to such an amorphous body and cooled, an interaction is induced between the entire amorphous body and a part of the crystalline body, Some kind of change is urged. Due to the change in the binding form, performance changes occur in the adsorption characteristics etc. of radioactive substances. As a result, some of them approach the adsorption characteristics of zeolite radioactive substances, or some have characteristics that exceed those of zeolite. It is thought that

  Although it has been confirmed that the adsorbent of the present invention exhibits excellent characteristics mainly for the adsorption of radioactive substances, the above characteristics can also be applied to adsorption of heavy metals and the like.

The method for measuring the total radiation dose (CPM) of the radioactive material is to stir the powder before heat treatment and the powder after heat treatment for 30 minutes in contaminated water that radiates several 150 cpm of total radiation of radioactive material. Then, each was filtered and measured with scintillation LSC7400, and the measured value was cpm.
In addition, the method for measuring cesium and strontium adsorption is to add 4% mass powder after heat treatment to contaminated water with a cesium and strontium concentration of 1 ppm, and stir for 30 minutes to adsorb the radioactive material. The powder was filtered, and the concentration of radioactive material in the contaminated water after the treatment was measured with an ICP mass spectrometer (Agilent Technologies, Agilent 7500cx), and the measured value was ppm.

In the present invention, waste can be used for tuff granule, pumice granule, brick powder, concrete secondary product granule, and it is cheap and easy to mass produce using this. Can adsorb material.

Claims (4)

a) 100 parts by weight of vitreous material powder;
At least one of the group consisting of tuffstone granule made by crushing Otani stone, Wakakusa stone, deep rock stone, etc., pumice granule made by crushing artificial lightweight cellular concrete or natural pumice, and brick, tile, tile Two or more different groups were selected from the four groups of bricks and granules made by crushing two or more and concrete secondary products and granules made by crushing a secondary concrete product. 200 to 300 parts by weight of a mixed granular material obtained by selecting and combining at least one material from a group;
0.6 to 15 parts by weight of foam material powder,
Mix and
b) The above mixture is heated in the range of 700 to 900 ° C. to promote thermal denaturation, and into a lump containing open cells with foaming,
c) The agglomerated material is crushed after cooling to obtain a granular material,
A granular adsorbent characterized by that. The granular adsorbent according to claim 1, wherein the mixed granular material is a granular material having a particle diameter of 1 to 1000 µm.   The granular adsorbent according to claim 1 or 2, wherein the vitreous material powder is window glass and / or a cup and / or a bottle, and the particle diameter thereof is a granular material having a particle diameter of 1 to 1000 µm. The granular adsorbent according to any one of claims 1 to 3, wherein the foamed material powder is calcium carbonate derived from shells such as oyster shells, scallop shells, oyster shells, and the like, and the particle size is in the form of powder having a particle diameter of 1 to 1000 µm.