JP6012536B2 - Water purification method - Google Patents

Description

The present invention relates to a method for purifying water using an adsorption sheet used for decontamination of radioactive substances, particularly treatment of contaminated water containing radioactive substances generated during decontamination work using water, or radioactive substances. The present invention relates to a method of using a water-based adsorption sheet for purification of water containing radioactive substances such as decontamination of contaminated seawater and river water.

  The Great East Japan Earthquake occurred on March 11, 2011, and due to the accident at the Fukushima Daiichi Nuclear Power Station, soil contamination by radioactive materials has been recognized in the surrounding area and the ocean. In addition, after the accident, many cases where high concentrations of radioactive substances were contained in crops and drinking water were discovered, and toxicity to human bodies and damage to reputation have been regarded as serious problems.

  Radioactive substances are generally decontaminated by washing with high-pressure water and cutting out contaminated civil engineering surfaces. However, radioactive materials are washed away, and contaminated soil and trees are removed and transported and stored. It is necessary to prevent leakage of radioactive pollutants after decontamination. Therefore, there is a need for simpler decontamination of contaminated soil and water quality.As a countermeasure, decontamination sheets with the ability to adsorb radioactive substances in the soil and water quality are installed for a long time. Attempts have been made to collect the sheets.

Known materials for adsorbing radioactive materials include zeolites, ion exchange resins, activated carbon and the like. In addition, as a sheet using these substances, there are many known air filters for gas adsorption, sheets pursuing deodorizing performance, and the like.

For example, Patent Document 1 proposes a method in which activated carbon and a thermal adhesive are mixed and thermally fixed to a nonwoven fabric sheet to obtain a deodorizing effect (an odor component is fixed). Patent Document 2 proposes a gas adsorption air filter in which zeolite or an ion exchange material is thermally fixed to a nonwoven fabric. Even with the sheets introduced in these, it is possible to fix and adsorb a certain amount of radioactive material, but when installed in the same system for a long time, it is possible to recover the sheet without dropping the adsorbed radioactive material. Has a problem. For example, when used as a filter in the air or soil, the sheet strength cannot be maintained due to aging or microbial corrosion, and the adsorbent falls off the sheet, causing the adsorbed radioactive material to leak. There is a risk that. Similarly, even when used as an aqueous filter in water, there is a problem that the strength of the sheet deteriorates when exposed to water pressure or water for a long period of time, and the adsorbent also falls off from the sheet.

In general, hydrophilic non-woven fabrics are used for water-based filter applications because water affinity and water absorption are required, but non-woven fabrics using hydrophilic fibers such as pulp and rayon fibers are exposed to water for a long time. As a result, there is a problem that the wet strength decreases. In particular, it is possible to efficiently decontaminate contaminated water by applying a high water pressure to the adsorbing sheet, but if the wet strength of the sheet is low, it cannot withstand the water pressure, and furthermore, the adsorption present in the adsorbing sheet due to the high water pressure. There is a problem that the material falls off.

JP 2005-349570 A JP 2003-334410 A

In view of the above-described problems, an object of the present invention is to provide a water purification method using an adsorption sheet that keeps the adsorption performance of radioactive substances even when used for decontamination in an aqueous system. Specifically, the absorbent sheet has good water absorption performance, does not cause deterioration in strength in water, and can maintain fixation of the adsorbed radioactive material without dropping the adsorbent even under high water pressure. It is providing the purification method of the water which uses .

As a result of intensive studies to solve the above problems, the present inventors have used two or more non-woven fabrics hydrophilized using hydrophobic fibers and adsorbed a thermal adhesive and a radioactive substance adsorbent between them. By obtaining a sheet, it was found that moderate water absorption and wet strength can be maintained, and further, the radioactive substance can be fixed for a long time even under high water pressure, and the present invention has been completed.

That is, the present invention is an adsorption sheet in which a thermal adhesive and an adsorbent are fixed between two or more non-woven fabrics, wherein the non-woven fabric is a non-woven fabric composed of hydrophobic fibers, and the sheet surface and water The contact angle is 100 ° or less after 0.05 seconds after water dripping and 80 ° or less after 1 second after water dripping, the wet tensile strength remaining rate of the sheet is 80% or more, and the adsorbent is adsorbed with radioactive material. It is related with the purification | cleaning method of the water using the adsorption sheet for water systems which is a material and the ratio whose particle diameter of the radioactive substance adsorbent is less than the average pore size of the said nonwoven fabric is 40 to 70%.

The average pore size of the nonwoven fabric is preferably 10 μm to 50 μm.

It is preferable that the wet tensile strength of the water-based adsorbent sheet is 1.0 kN / m or more.

The radioactive substance content of the adsorbent is ^{50g / m 2 ~200g / m 2} , and, the thermal bonds relative to the total weight of the thermal bonds radioactive material adsorbent is contained in a range of 10 to 30 mass% Is preferred.

It is preferable that the radioactive material adsorbent is zeolite.

By using the adsorbing sheet of the present invention, it is possible to easily fix radioactive substances particularly in an aqueous system, and it is possible to efficiently collect and store radioactive substances.

Schematic sectional view of the sheet of the present invention Simplified water pressure test

As shown in FIG. 1, the adsorbing sheet of the present invention includes a thermal adhesive and a radioactive substance adsorbing material sandwiched between one or more non-woven fabrics arbitrarily selected from two or more specific non-woven fabrics by hot pressure or the like. It is an adsorption sheet obtained by adhering between non-woven fabrics, and is particularly applied in aqueous systems such as water decontamination and filtration.

Adsorption sheets applied in water systems are required to have the ability to absorb water into the interior. In the adsorbing sheet of the present invention, the contact angle between the sheet surface and water must be 100 ° or less immediately after dropping water (referring to 0.05 seconds after dropping) and 80 ° or less 1 second after dropping water. I must. A sheet having a contact angle of more than 100 ° immediately after dripping water is too high in water repellency to absorb water into the sheet and is not suitable for aqueous systems. Furthermore, if the contact angle does not decrease to 80 ° or less after 1 second from the dropping of water, the water absorption speed becomes slow and water cannot be absorbed efficiently. In addition, it is preferably 50 ° or less after 1 second from the dropping of water, and more preferably 40 ° or less, allowing more efficient water absorption.

As the sheet having the above contact angle, a nonwoven fabric made of hydrophilic fibers can be considered. However, the nonwoven fabric made of hydrophobic fibers is used as the nonwoven fabric used in the present invention. This is because a non-woven fabric made of hydrophilic fibers is not suitable because it causes a decrease in tensile strength, which will be described later, when used in an aqueous system as an adsorption sheet. For example, nonwoven fabrics mainly using hydrophilic fibers such as rayon, cotton, silk, various celluloses, hemp, and vinylon cannot be used. However, since the contact angle with water as the adsorbing sheet needs to be within a predetermined range as described above, moderate hydrophilicity is required as the nonwoven fabric. Therefore, the non-woven fabric used in the present invention must be hydrophilic while the fiber material itself is hydrophobic. As the hydrophobic fiber, one kind selected from polyolefin fibers such as polyethylene fibers and polypropylene fibers, polyester fibers such as polyethylene terephthalate fibers, polyethylene naphthalate fibers and polytrimethylene terephthalate fibers, nylon, polyamide fibers, acrylic fibers, etc. Two or more kinds of fibers can be mentioned, and examples thereof include a nonwoven fabric hydrophilized using these. As a method of hydrophilizing the hydrophobic fiber, for example, a method of preparing a nonwoven fabric by a spunbond method in which a hydrophilic agent is mixed with a hydrophobic fiber, or a spunbond nonwoven fabric is prepared by using a hydrophobic fiber. Examples of the method include a method in which a hydrophilizing agent is accompanied, and a method in which a spunbonded nonwoven fabric is prepared with hydrophobic fibers and then impregnated with the hydrophilizing agent.

Examples of the hydrophilizing agent include surfactants, for example, cationic surfactants such as quaternary ammonium salts, anionic surfactants such as aliphatic sulfonates and higher alcohol sulfates, polyethylene Stains composed of nonionic surfactants such as glycol fatty acid esters, polyglycerin fatty acid esters and sorbitan fatty acid esters, silicone surfactants such as polyoxyalkylene-modified silicones, and polyester, polyamide, acrylic and urethane resins -Release agents are used.

Moreover, it is preferable to use the hydrophobic fiber which does not biodegrade for the said nonwoven fabric. For example, the nonwoven fabric sheet of fiber structures, such as a polyester fiber, a nylon fiber, an aramid fiber, a polyphenylene sulfide fiber, a polyethylene terephthalate fiber, a polyalkylene arylate fiber, an acrylic fiber, is mentioned. Moreover, it is more preferable that the nonwoven fabric is composed of fibers having a melting point of 250 ° C. or higher. In particular, a non-woven sheet using thermoplastic fibers such as polypropylene fiber, polyethylene fiber, polyester fiber, nylon fiber, aramid fiber, polyphenylene sulfide fiber, etc., when the layer structure is a structure of two non-woven fabrics sandwiching a thermal adhesive and an adsorbent It is preferable to use a single-sided heat-seal type nonwoven fabric in which the melting and softening temperatures on both sides differ by 10 ° C. or more.

As described above, in the present invention, a non-woven fabric using hydrophobic fibers is used. However, a hydrophilic fiber mixed or mixed is used as long as the performance such as the residual wet tensile strength of the present invention is not impaired. May be used. By including hydrophilic fibers, there is an effect of reducing the contact angle. The ratio of hydrophobic fibers to hydrophilic fibers in the fibers used for the whole nonwoven fabric is preferably 100: 0 to 60:40, more preferably 100: 0 to 75:25, and still more preferably 100: 0 to 90: 10.

The nonwoven fabric used in the present invention preferably has an average pore size of 50 μm or less, more preferably 10 μm to 50 μm. If the average pore size exceeds 50 μm, it will be difficult to suppress the removal of the adsorbent.

In the present invention, the above-described nonwoven fabric is used on both sides of the sheet. However, in the embodiment in which three or more nonwoven fabrics are used, the nonwoven fabric used in the middle is not particularly limited, and a known nonwoven fabric is used as long as the performance of the present invention is not impaired. Used. Here, it is preferable to select a non-woven fabric that can prevent the thermal adhesive / radioactive material adsorbent to be thermally fixed. For example, if the non-woven fabric of the intermediate layer is in direct contact with the radioactive material adsorbent, fibers that partially melt and soften when hot pressed in the process of forming the adsorbent sheet are preferable. For example, it is preferable to use a nonwoven fabric composed of thermoplastic fibers such as polypropylene fiber, polyethylene fiber, polyester fiber, nylon fiber, aramid fiber, polyphenylene sulfide fiber, and the nonwoven fabric is composed of fibers having a melting point of 210 ° C. or lower. More preferably.

Nonwoven having a mass per unit area of the present invention, but is not particularly limited in thickness, weight per unit area is preferably 5 to 70 g / ^{m 2,} more preferably 10 to 50 g / ^{m 2.}

The absorbent sheet of the present invention has a wet tensile strength residual ratio measured according to JIS-P8135 of 80% or more. When the wet tensile strength residual ratio is less than 80%, the strength of the sheet deteriorates rapidly when used in an aqueous system and cannot be used for a long time. The absorbent sheet preferably has a wet tensile strength of 1.0 kN / m or more in both the vertical and horizontal directions. If it is less than 1.0 kN / m, the strength required for use as a water-based adsorbing sheet is insufficient, and there is a concern that the sheet may be damaged. The wet tensile strength is more preferably 1.5 kN / m or more.

The adsorbent used in the present invention is one that adsorbs a radioactive substance. The radioactive substance adsorbent is selected from porous particles such as ion exchange resin, activated carbon, and zeolite. The radioactive material adsorbent may be appropriately selected for its particle size and pores. For example, for the purpose of radioactive cesium ^{(137 Cs)} adsorption can be efficiently adsorbed With zeolite. The type of zeolite is not particularly limited, but a method of preparing natural zeolite or synthetic zeolite by a dealumination treatment using a mineral acid or the like as a starting material, a silica source, an alumina source, an alkali source and an organic mineralizer. What was obtained by the direct synthesis method etc. which mix and crystallize can be used. In particular, crystalline aluminophosphates (ALPO-based zeolite) containing at least Al and P in the skeleton structure are preferable because the three-dimensional structure and adsorption characteristics can be easily controlled. Examples of such zeolite include SAPO-34 and FAPO-5. Said adsorbent can be used 1 type or in combination of 2 or more types.

In water-based filter applications and the like, water pressure is often applied in a direction perpendicular to or close to the adsorbing sheet, and the adsorbent held inside the sheet may flow out from the holes of the nonwoven fabric due to water pressure. Therefore, in the present invention, the ratio that the particle size of the adsorbent is lower than the average pore size of the nonwoven fabric that forms the outside of the adsorbent sheet needs to be 40 to 70%. Inside the adsorbent sheet, the adsorbent with a particle diameter exceeding the average pore size of the nonwoven fabric used on both sides of the sheet can block the adsorbent by closing the pores of the non-woven fabric, but when the ratio exceeds 70% Since there are few adsorbents that block the holes in the nonwoven fabric, the adsorbents cannot be prevented from falling off. On the other hand, when the ratio is less than 40%, the adsorbent can be easily prevented from falling off, but the specific surface area of the adsorbent is reduced, so that the effect of adsorbing the radioactive substance is inferior. The proportion is preferably 40 to 65%.

It is preferable to select a radioactive material adsorbent having mesopores. The mesopores referred to herein are those having a pore diameter of 2 to 50 nm. For example, carbon or zeolite having mesopores is known. In particular, the proportion of the mesopores in the radioactive material adsorbent is preferably 70% or more. If it is less than 70%, the adsorption of the radioactive substance cannot be maintained and it may be released into the environment again.

In order to uniformly distribute the above-mentioned radioactive substance adsorbing material on the nonwoven fabric sheet, it is preferable that the radioactive substance adsorbing material is present in the sheet at 90 g / m ² or more, so that the radioactive substance adsorbing material is stably fixed in the sheet. And, since the radioactive substance adsorbing material itself does not inhibit the adhesive strength between the nonwoven fabrics, it is preferable to be less than 150 g / m ² .

In the present invention, a thermal adhesive is used to fix the radioactive substance adsorbent distributed between the nonwoven fabrics in the sheet. It is possible to firmly fix the radioactive substance to the sheet by melting the thermal adhesive with heat in the manufacturing process of the suction sheet.

The thermal adhesive is mixed at a ratio of 10 to 30% by mass with respect to the total mass of the radioactive substance adsorbent and the thermal adhesive. For example, this mixture may be introduced when two or more non-woven fabrics are made together and heated and pressed. When the mixing ratio is less than 10% by mass, the radioactive material adsorbent is hardly fixed, and when it exceeds 30% by mass, the thermal adhesive is melted and softened in a large amount, and the non-woven sheet to be used has good air permeability and water permeability. There is a risk of obstruction. The mixing ratio is particularly preferably in the range of 20 to 30% by mass. By adjusting to this range, the fixation of the radioactive material adsorbent can be strengthened without impairing the performance, and the possibility of dropping off can be reduced.

As the material used for the thermal adhesive, a general material can be used as long as the material itself can be melted or softened by heat and the adsorbent can be fixed between the nonwoven fabrics, but has a particularly low melting point and a softening point. A fibrous or particulate material composed of a low substance is preferred. More preferably, the particulate material has a particle size smaller than that of the radioactive material adsorbent. When the particle size of the radioactive substance adsorbing material is larger than the particle size of the radioactive substance adsorbing material, it is not preferable because the heat adhering material covers the surface of the radioactive substance adsorbing material due to thermal melting, and the adsorption efficiency of the radioactive substance becomes extremely poor. As the fibrous thermal adhesive, for example, heat-sealable fibers can be used, and single fibers, core-sheath fibers, and parallel fibers such as parallel fibers, a combination of polypropylene and polyethylene, a combination of polypropylene and ethylene vinyl alcohol, Although the combination of polyester and polyester is mentioned, the single fiber (total melt type) comprised only by low melting-point resin, such as polyethylene, is more preferable. As the particulate thermal adhesive, known materials such as polyolefins such as polyethylene resins, polyester resins, polyamide resins, vinyl acetate resins, acrylic resins, urea resins, melamine resins, and phenol resins can be used.

In the present invention, embossing can be applied to all or part of the sheet. Embossing can be performed either on-machine or off-machine, but for production efficiency, it is preferable to perform embossing simultaneously when an adsorbent and a thermal adhesive are provided between the nonwoven fabrics and heated and pressed. Thereby, it is possible to further prevent the adsorbent from falling off.

EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, the scope of the present invention is not limited to an Example.

(1) Average pore size The pore size distribution was measured using a pore size distribution evaluation apparatus (trade name “Palm Porometer” manufactured by PMI) using a bubble point method, and the average value was defined as the average pore size.
(2) Adsorbent particle size and ratio Measured by laser diffraction scattering method. The ratio of the adsorbent particle diameter below the average pore size of the nonwoven fabric was calculated from the particle diameter distribution of the adsorbent by the laser diffraction scattering method.
(3) Evaluation of dropout 10 sheets of adsorbed sheets cut into 10 cm squares were stacked and sealed in a 100 mL plastic container, stirred for 10 minutes with vertical shaking, and then the amount of the dropped powder was visually evaluated. Was passed.
◎: Adsorbent does not fall off at all ○: Adsorbent hardly falls off △: Adsorbent falls off slightly, but there is no problem in actual use ×: Adsorbent has dropped out and there is a problem in actual use (4 ) Evaluation of radioactive material adsorption rate
^The chemical efficiency of ¹³³ Cs (non-radioactive material) was the same as that of ¹³⁴ Cs and ¹³⁷ Cs (radioactive material), and the adsorption efficiency of ¹³³ Cs was tested. Five sheets obtained by cutting the adsorbing sheet into 2 cm square were put into a 100 ppm cesium chloride solution, stirred for 30 minutes with shaking, and then the Cs concentration in the solution was measured. The adsorption rate was calculated according to the following formula.
Adsorption rate (%) = { ¹³³ Cs concentration before treatment (mg / L) ⁻¹³³ Cs concentration after treatment (mg / L)} / { ¹³³ Cs concentration (ppm) before treatment} × 100
◎: Adsorption rate is 98% or more ○: Adsorption rate is 90% or more and less than 98% ×: Adsorption rate is less than 90% (5) Residual rate of wet tensile strength The tensile strength of the absorbent sheet is JIS-P8113 (2006) Measured based on. Furthermore, the wet tensile strength measured based on JIS-P8135 (1998) was measured, and the residual rate was calculated according to the “calculation method of residual wet tensile strength” of the same standard.
(6) Using a dynamic surface contact angle measuring device (Dynamic Absorption Tester DAT1100, manufactured by Fibro) under a contact angle of 23 ° C. and 50% RH atmosphere, 0.05 seconds after dropping 3 mL of water and The surface contact angle after 00 seconds was measured.
(7) Submergence test An adsorbent sheet cut to 10 cm square was prepared, immersed in water at room temperature under an atmosphere of 23 ° C., allowed to stand for 3 minutes, and then the sheet was taken out. The state was observed visually. ○ was accepted.
◯: The sheet contains sufficient water.
X: The sheet surface is water-repellent or hardly contains water.
(8) Water pressure test 15 cm square adsorption sheet is prepared and used for the water pressure test apparatus 6 shown in FIG. The buffer material 5 is placed on the surface opposite to the surface in contact with water, and water at room temperature is kept flowing for 1 minute at a water pressure of 3.7 MPa. Then, the adsorption sheet 4 is taken out, and the visual evaluation and the above (3) The same dropout evaluation was performed. ○ was accepted.
○: The adsorbent does not fall off, or falls off slightly, but there is no problem in actual use. ×: The adsorbent falls off easily, or the sheet at the hydraulic pressure point is damaged.

[Example 1]
Two nonwoven fabrics (average pore size of 32 μm) having a thickness of 0.115 mm made of polyester fiber and polypropylene fiber and subjected to a hydrophilic treatment were prepared. After mixing 40 parts of thermal adhesive (ethylene vinyl acetate copolymer) with a stirrer for 10 minutes or more to 100 parts of synthetic zeolite (average particle size 30 μm) as a radioactive material adsorbent, Then, the zeolite was sprayed on the nonwoven fabric so as to be 100 g / m ² . Furthermore, it laminated | stacked so that it might be pinched | interposed with the said nonwoven fabric from above, and it was set as the two-layer structure of the nonwoven fabric A, and thermocompression bonded with the roll temperature of 250 degreeC and the linear pressure of 6.0 kgf / cm < ² >. Thereby, an adsorption sheet was obtained.

[Example 2]
An adsorption sheet was obtained in the same manner as in Example 1 except that synthetic zeolite having an average particle diameter of 43 μm was used as the radioactive material adsorbent.

[Example 3]
An adsorption sheet was obtained in the same manner as in Example 1 except that synthetic zeolite having an average particle size of 16 μm was used as the radioactive material adsorbent.

[Example 4]
An adsorption sheet was obtained in the same manner as in Example 1 except that a nonwoven fabric (average pore size 50 μm) made of polypropylene fiber and subjected to a hydrophilic treatment was used as the nonwoven fabric.

[Example 5]
An adsorption sheet was obtained in the same manner as in Example 1 except that a nonwoven fabric (average pore size of 53 μm) made of polypropylene fiber and subjected to a hydrophilic treatment was used as the nonwoven fabric.

[Example 6]
As the non-woven fabric, an adsorbent sheet was obtained in the same manner as in Example 1 except that a non-woven fabric having a thickness of 30:70 of cellulose fiber and polyethylene terephthalate fiber and hydrophilized was used. It was.

[Example 7]
An adsorption sheet was obtained in the same manner as in Example 1 except that a 0.125 mm nonwoven fabric made of polyethylene terephthalate fiber and subjected to a hydrophilic treatment was used as the nonwoven fabric.

[Comparative Example 1]
An adsorption sheet was obtained in the same manner as in Example 1 except that synthetic zeolite having an average particle size of 57 μm was used as the radioactive material adsorbent.

[Comparative Example 2]
An adsorption sheet was obtained in the same manner as in Example 1 except that synthetic zeolite having an average particle size of 11 μm was used as the radioactive substance adsorbent.

[Comparative Example 3]
An adsorbent sheet was obtained in the same manner as in Example 1 except that a non-woven fabric having a thickness of 0.135 mm made of mixed fibers of rayon fiber: PET fiber = 70: 30 was used.

[Comparative Example 4]
An adsorption sheet was obtained in the same manner as in Example 1 except that a nonwoven fabric having a thickness of 0.143 mm made of 100% cotton fiber was used.

[Comparative Example 5]
An adsorption sheet was obtained in the same manner as in Example 1 except that a nonwoven fabric having a thickness of 0.137 mm made of 100% nylon fiber was used.

[Comparative Example 6]
An adsorbing sheet was obtained in the same manner as in Example 7 except that a non-woven fabric having a thickness of 0.125 mm produced without applying a hydrophilic treatment in the process of producing the nonwoven fabric of Example 7 was used.

Table 1 shows the results of dropout evaluation and radioactive material adsorption rate of the adsorption sheets prepared in Examples 1 to 5 and Comparative Examples 1 and 2.

Table 2 shows the results of wet tensile strength residual ratio, water immersion evaluation, and water pressure resistance evaluation of the adsorption sheets prepared in Examples 1, 4, 6, 7 and Comparative Examples 3-6.

Looking at the results in Table 1, in Examples 1 to 5, the ratio of the adsorbent particle diameter to be less than the average pore size of the nonwoven fabric is in the range of 40 to 70%, and there is no problem with the adsorbent falling off, and the radioactive substance adsorption The rate was also good. In Comparative Example 2 in which the ratio was 75%, the adsorbent was frequently dropped and it was difficult to actually use. Further, in Comparative Example 1 where the ratio was 35%, the adsorbent was not dropped at all, but the adsorption rate of the radioactive substance was inferior. In Example 5, the average pore size of the nonwoven fabric exceeded 50 μm, and the adsorbent was slightly removed. in this way,

Looking at the results in Table 2, each example was good in both water immersion evaluation and water pressure resistance evaluation. On the other hand, Comparative Example 3 and Comparative Example 4 using a nonwoven fabric made of hydrophilic fibers had a wet tensile strength residual ratio of less than 80%, and were unacceptable because the sheet strength could not be maintained as a result of the water pressure resistance test. . Further, Comparative Example 5 and Comparative Example 6 in which the contact angle between the sheet surface and water exceeded 100 ° after 0.05 seconds after water dripping were recognized as having water repellency and could not be used due to poor water absorption. In addition, Comparative Example 6 in which the contact angle between the sheet surface and water did not drop to 80 ° after 1 second from the dropping of water was not at a level where the water absorption was not improved and the actual use could be achieved even if the sheet was continuously used. .

As described above, the water purification method using the adsorbing sheet of the present invention can be suitably used for decontamination of radioactive substances in an aqueous system.

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric 2 Radioactive material adsorption material 3 Thermal adhesive material 4 Adsorption sheet for water systems 5 Buffer material (pressure-resistant porous material)
6 Water pressure test equipment

Claims (5)

An adsorption sheet in which a thermal adhesive and an adsorbent are fixed between two or more nonwoven fabrics,
The nonwoven fabric is composed of hydrophobic fibers,
The contact angle between the adsorbing sheet surface and water is 100 ° or less after 0.05 seconds after water dripping and 80 ° or less after 1 second after water dripping,
The wet tensile strength residual ratio of the adsorption sheet is 80% or more, and
The water purification method using the water- based adsorbent sheet , wherein the adsorbent is a radioactive substance adsorbent, and the proportion of the particle diameter being less than the average pore size of the nonwoven fabric is 40 to 70%. The water purification method according to claim 1, wherein the nonwoven fabric has an average pore size of 10 μm to 50 μm. The water purification method according to claim 1 or 2, wherein the adsorbent sheet has a wet tensile strength of 1.0 kN / m or more. The content of the radioactive substance adsorbing material with respect to the adsorbing sheet is 50 g / m ^{2 to} 200 g / m ² , and the thermal adhesive is within a range of 10 to 30% by mass with respect to the total mass of the thermal adhesive and the radioactive substance adsorbing material. The method for purifying water according to claims 1 to 3, which is contained. The water purification method according to claim 1, wherein the radioactive material adsorbent is zeolite.

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