JP6820148B2 - Method for reducing the volume of used radioactive cesium-adsorbed fibers - Google Patents
Method for reducing the volume of used radioactive cesium-adsorbed fibers Download PDFInfo
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- 230000002285 radioactive effect Effects 0.000 title claims description 76
- 239000000835 fiber Substances 0.000 title claims description 47
- 238000000034 method Methods 0.000 title claims description 12
- 229910052792 caesium Inorganic materials 0.000 claims description 55
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims description 55
- 238000010438 heat treatment Methods 0.000 claims description 32
- 239000002861 polymer material Substances 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 229910021536 Zeolite Inorganic materials 0.000 claims description 17
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 17
- 239000010457 zeolite Substances 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 15
- 229920002492 poly(sulfone) Polymers 0.000 claims description 14
- 239000011148 porous material Substances 0.000 claims description 10
- 229920000642 polymer Polymers 0.000 claims description 9
- 239000000243 solution Substances 0.000 description 15
- 238000010828 elution Methods 0.000 description 10
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 6
- 238000011038 discontinuous diafiltration by volume reduction Methods 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 238000005979 thermal decomposition reaction Methods 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 239000008188 pellet Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 239000004677 Nylon Substances 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- DCYOBGZUOMKFPA-UHFFFAOYSA-N iron(2+);iron(3+);octadecacyanide Chemical compound [Fe+2].[Fe+2].[Fe+2].[Fe+3].[Fe+3].[Fe+3].[Fe+3].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-].N#[C-] DCYOBGZUOMKFPA-UHFFFAOYSA-N 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 229920001778 nylon Polymers 0.000 description 2
- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 229960003351 prussian blue Drugs 0.000 description 2
- 239000013225 prussian blue Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 150000008360 acrylonitriles Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- -1 for example Substances 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920000172 poly(styrenesulfonic acid) Polymers 0.000 description 1
- 229940005642 polystyrene sulfonic acid Drugs 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
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- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Artificial Filaments (AREA)
Description
本発明は、使用済み放射性セシウム吸着繊維の減容化方法に関する。 The present invention relates to a method for reducing the volume of used radioactive cesium-adsorbed fibers.
東日本大震災における原子力発電所の事故の影響で、大量の放射性セシウムが拡散した。しかし、水に溶解した放射性セシウムを水から除去するための放射性セシウム吸着繊維は、ほとんど知られていなかった。なお、特許文献１には、金属イオン吸着性の変性アクリロニトリルポリマーが開示されているが、セシウムは対象となっていない。また、特許文献２には、セシウムを吸着することができるとの記載があるが、実際にセシウムを吸着したデータはない。また、ゼオライト粉末は放射性セシウムを吸着することが知られているが、ゼオライト粉末の回収は極めて困難であり、また、ゼオライトは一旦吸着した放射性セシウムを放出する性質があるため、放射性セシウムの回収には向いていなかった。 Due to the impact of the nuclear power plant accident caused by the Great East Japan Earthquake, a large amount of radioactive cesium was diffused. However, little is known about radioactive cesium-adsorbing fibers for removing radioactive cesium dissolved in water from water. Although Patent Document 1 discloses a modified acrylonitrile polymer that adsorbs metal ions, it does not cover cesium. Further, although Patent Document 2 describes that cesium can be adsorbed, there is no data that actually adsorbs cesium. Zeolite powder is known to adsorb radioactive cesium, but it is extremely difficult to recover the zeolite powder, and since zeolite has the property of releasing the once adsorbed radioactive cesium, it can be used to recover radioactive cesium. Was not suitable.
このような背景から、本発明者らは、水に溶解した放射性セシウムを効率的に吸着、回収することのできる、放射性セシウム吸着繊維及びその製造方法を提案した（特許文献３）。 Against this background, the present inventors have proposed a radioactive cesium-adsorbing fiber capable of efficiently adsorbing and recovering radioactive cesium dissolved in water and a method for producing the same (Patent Document 3).
ところで、放射性セシウムを効率的に吸着、回収することも重要であるが、使用済みの放射性セシウム吸着繊維を減容化することも重要な課題となっている。なお、焼却によっても減容化は可能であるが、減容化後に雨水などに曝された場合に放射性セシウムが溶出する虞があった。 By the way, it is important to efficiently adsorb and recover radioactive cesium, but it is also an important issue to reduce the volume of used radioactive cesium adsorbed fibers. Although the volume can be reduced by incineration, there is a risk that radioactive cesium will elute when exposed to rainwater or the like after the volume reduction.
そこで、本発明は、使用済みの放射性セシウム吸着繊維を効率的に減容化することができ、かつ、減容化後に放射性セシウムが溶出することのない、使用済み放射性セシウム吸着繊維の減容化方法を提供することを目的とする。 Therefore, according to the present invention, the volume of used radioactive cesium-adsorbed fiber can be efficiently reduced, and the volume of used radioactive cesium-adsorbed fiber is reduced so that radioactive cesium does not elute after the volume reduction. The purpose is to provide a method.
本発明者らは鋭意検討した結果、Ｎ−メチルピロリドン（ＮＭＰ）にポリスルホンを溶解するとともにゼオライトを分散させ、これを水中にシリンジを用いて押し出すことにより得られた、ゼオライトを担持した多孔質のポリスルホンについて、放射性セシウムを吸着させた後に、所定の温度で加熱しながら加圧することで減容化した場合に、放射性セシウムの溶出を防止できることを見出し、本発明に想到した。 As a result of diligent studies, the present inventors have obtained a porous structure carrying zeolite, which is obtained by dissolving polysulfone in N-methylpyrrolidone (NMP), dispersing zeolite, and extruding it into water using a syringe. We have found that the elution of radioactive cesium can be prevented when the volume of polysulfone is reduced by adsorbing radioactive cesium and then pressurizing it while heating it at a predetermined temperature, and came up with the present invention.
すなわち、本発明の使用済み放射性セシウム吸着繊維の減容化方法は、多孔質粒子を担持した多孔質の高分子材料からなり放射性セシウムを吸着した放射性セシウム吸着繊維の減容化方法であって、前記放射性セシウム吸着繊維は前記高分子材料を溶解し前記多孔質粒子を分散させたポリマー溶液を水中に押し出すことによって得られたものであり、前記放射性セシウム吸着繊維を加熱しながら加圧する加熱加圧工程を備え、前記多孔質粒子はゼオライトであって、前記高分子材料はポリスルホンであり、前記加熱加圧工程は、２５０〜４５０℃で行われ、前記加熱加圧工程において、前記高分子材料が融解して放射性セシウムを細孔内に吸着した前記多孔質粒子の細孔を覆うことを特徴とする。 That is, the method for reducing the volume of the used radioactive cesium-adsorbed fiber of the present invention is a method for reducing the volume of the radioactive cesium-adsorbed fiber made of a porous polymer material carrying porous particles and adsorbing radioactive cesium. The radioactive cesium-adsorbed fiber is obtained by dissolving the polymer material and extruding a polymer solution in which the porous particles are dispersed into water, and pressurizes the radioactive cesium-adsorbed fiber while heating it. The porous particles are zeolite, the polymer material is polysulfone, and the heating and pressurizing step is performed at 250 to 450 ° C., and in the heating and pressurizing step, the polymer material is It is characterized by covering the pores of the porous particles that have been melted and adsorbed radioactive cesium into the pores.
本発明によれば、使用済みの放射性セシウム吸着繊維を効率的に減容化することができ、かつ、減容化後に放射性セシウムが溶出することのない、使用済み放射性セシウム吸着繊維の減容化方法が提供される。 According to the present invention, the volume of used radioactive cesium-adsorbed fiber can be efficiently reduced, and the volume of used radioactive cesium-adsorbed fiber is reduced so that radioactive cesium does not elute after the volume reduction. The method is provided.
本発明において用いられる放射性セシウム吸着繊維は、多孔質粒子を担持した多孔質の高分子材料からなる。 The radioactive cesium-adsorbing fiber used in the present invention is made of a porous polymer material supporting porous particles.
本発明において用いられる放射性セシウム吸着繊維は、高分子材料を溶解し多孔質粒子を分散させたポリマー溶液を調製する溶液調製工程と、前記溶液調製工程で調製されたポリマー溶液を水中に押し出して繊維状に成形する繊維成形工程とによって得ることができる。なお、溶液調製工程において、必要に応じてプルシアンブルーなどの放射性セシウム吸着成分を添加してもよい。このようにして製造された放射性セシウム吸着繊維は、繊維に微細孔が形成された構造となっていて通水性が良好であるとともに、繊維中の多孔質粒子の分散性が良好であることから、水に溶解した放射性セシウムを極めて効率的に吸着することができ、水中の放射性セシウムの濃度が検出限界外のごく薄い濃度であっても、放射性セシウムを効率的に吸着して濃縮することができる。また、繊維状に形成されたものであるため、河川などに設置した際に水を堰き止めるようなことがなく、放射性セシウムの吸着に用いられた後の回収が簡単である。 The radioactive cesium-adsorbed fiber used in the present invention is a fiber in which a solution preparation step of dissolving a polymer material and preparing a polymer solution in which porous particles are dispersed and a polymer solution prepared in the solution preparation step are extruded into water. It can be obtained by a fiber molding step of molding into a shape. In the solution preparation step, a radioactive cesium adsorbing component such as Prussian blue may be added if necessary. The radioactive cesium-adsorbing fiber produced in this manner has a structure in which fine pores are formed in the fiber and has good water permeability, and also has good dispersibility of the porous particles in the fiber. Radioactive cesium dissolved in water can be adsorbed extremely efficiently, and even if the concentration of radioactive cesium in water is extremely thin, which is outside the detection limit, radioactive cesium can be efficiently adsorbed and concentrated. .. Further, since it is formed in a fibrous form, it does not block water when it is installed in a river or the like, and it is easy to recover it after it is used for adsorbing radioactive cesium.
ここで、高分子材料としては、ポリスルホン、６，６−ナイロン、６−ナイロン、ポリアクリロニトリル、ポリスチレンスルホン酸が好ましい。また、高分子材料を溶解する有機溶媒としては、Ｎ−メチルピロリドン（ＮＭＰ）、蟻酸、ｎ−ブタノール、Ｎ，Ｎ−ジメチルホルムアミド、テトラヒドロフランが好ましい。 Here, as the polymer material, polysulfone, 6,6-nylon, 6-nylon, polyacrylonitrile, and polystyrene sulfonic acid are preferable. Further, as the organic solvent for dissolving the polymer material, N-methylpyrrolidone (NMP), formic acid, n-butanol, N, N-dimethylformamide and tetrahydrofuran are preferable.
また、多孔質粒子としては、例えば、ゼオライトを好適に用いることができ、ゼオライトを用いる場合は、１５０メッシュ以下のものが好ましい。 Further, as the porous particles, for example, zeolite can be preferably used, and when zeolite is used, those having a mesh of 150 mesh or less are preferable.
溶液調製工程において、高分子材料を溶かす際には、３０〜１００℃に有機溶媒を加温することにより高分子材料の溶解が早くなる。また、ポリマー溶液中の高分子材料含有量は、１０〜３０質量％が好ましい。 When melting the polymer material in the solution preparation step, the dissolution of the polymer material is accelerated by heating the organic solvent to 30 to 100 ° C. The content of the polymer material in the polymer solution is preferably 10 to 30% by mass.
また、ポリマー溶液中のゼオライトなどの多孔質材料の含有量は２０〜３０質量％が好ましく、プルシアンブルーなどの放射性セシウム吸着成分を添加する場合、放射性セシウム吸着成分は５〜１５質量％が好ましい。 The content of the porous material such as zeolite in the polymer solution is preferably 20 to 30% by mass, and when a radioactive cesium adsorbing component such as Prussian blue is added, the radioactive cesium adsorbing component is preferably 5 to 15% by mass.
繊維成形工程において、射出に用いられる水の温度を５０℃程度とすることにより、有機溶媒の溶けだしが早く、繊維が形成されやすい。 By setting the temperature of the water used for injection to about 50 ° C. in the fiber molding step, the organic solvent dissolves quickly and fibers are easily formed.
放射性セシウムを吸着させた後の使用済み放射性セシウム吸着繊維は、加熱加圧工程により、所定の温度で加熱しながら加圧することでペレット状に減容化される。 The used radioactive cesium-adsorbed fiber after adsorbing the radioactive cesium is reduced in volume into pellets by pressurizing while heating at a predetermined temperature by a heating and pressurizing step.
加熱加圧工程における加熱温度は、放射性セシウム吸着繊維を構成する高分子材料の融点以上であって、熱分解温度未満の範囲とするのが好ましい。加熱加圧工程における加熱温度をこの範囲とすることにより、高分子材料が融解して放射性セシウムを細孔内に吸着した多孔質粒子の細孔を覆うため、減容化後の放射性セシウムの溶出が確実に防止される。なお、熱分解温度以上で加熱すると、高分子材料が熱分解により消失して多孔質粒子の細孔が露出してしまい、多孔質粒子に吸着された放射性セシウムが溶出しやすくなる。放射性セシウム吸着繊維を構成する高分子材料がポリスルホンの場合、加熱加圧工程は、２５０〜４５０℃で行われるのが好ましい。 The heating temperature in the heating and pressurizing step is preferably in the range of not more than the melting point of the polymer material constituting the radioactive cesium adsorbing fiber and less than the thermal decomposition temperature. By setting the heating temperature in the heating and pressurizing step within this range, the polymer material melts and covers the pores of the porous particles adsorbing radioactive cesium in the pores, so that the radioactive cesium elutes after volume reduction. Is definitely prevented. When heated at a temperature higher than the thermal decomposition temperature, the polymer material disappears due to thermal decomposition and the pores of the porous particles are exposed, so that the radioactive cesium adsorbed on the porous particles is easily eluted. When the polymer material constituting the radioactive cesium-adsorbing fiber is polysulfone, the heating and pressurizing step is preferably performed at 250 to 450 ° C.
加熱加圧工程において使用済み放射性セシウム吸着繊維を加圧する圧力の範囲は、加熱加圧工程の後に減容化が図れる値であればよく、特に限定されるものではないが、例えば、２０〜２００ｋｇｆ／ｃｍ２とすることができる。 The range of the pressure for pressurizing the used radioactive cesium adsorbed fiber in the heating and pressurizing step is not particularly limited as long as the volume can be reduced after the heating and pressurizing step, but is not particularly limited, for example, 20 to 200 kgf. It can be / cm 2 .
以下、本発明の使用済み放射性セシウム吸着繊維の減容化方法について具体的に説明する。 Hereinafter, the method for reducing the volume of the used radioactive cesium-adsorbed fiber of the present invention will be specifically described.
なお、本発明は以下の実施例に限定されるものではなく、種々の変形実施が可能である。 The present invention is not limited to the following examples, and various modifications can be made.
（１）放射性セシウム吸着繊維の作製
原料として、ポリスルホン（BASF社製、分子量不明、グレードE2010）、ゼオライト（日東粉化商事株式会社製、粒径１５０メッシュ）、ＮＭＰ（米山科学工業社製）を用いた。
(1) Preparation of radioactive cesium-adsorbed fiber Polysulfone (manufactured by BASF, molecular weight unknown, grade E2010), zeolite (manufactured by Nitto Flour Chemical Co., Ltd., particle size 150 mesh), NMP (manufactured by Yoneyama Kagaku Kogyo Co., Ltd.) are used as raw materials. Using.
室温にて、ポリスルホン３０質量％、ゼオライト３０質量％、ＮＭＰ４０質量％となるように原料を混合し、ゼオライトが分散したポリスルホンのポリマー溶液を作製した。このポリマー溶液をシリンジに入れ、シリンジの先を水中に入れた状態でシリンジの先からポリマー溶液を水中に押し出すと、水中に繊維が成形された。得られた繊維は、多孔質のポリスルホン中にゼオライトが取り込まれている構造を有していた。 At room temperature, the raw materials were mixed so as to have 30% by mass of polysulfone, 30% by mass of zeolite, and 40% by mass of NMP to prepare a polymer solution of polysulfone in which zeolite was dispersed. When this polymer solution was put into a syringe and the polymer solution was extruded into water from the tip of the syringe with the tip of the syringe in water, fibers were formed in the water. The obtained fiber had a structure in which zeolite was incorporated into porous polysulfone.
（２）加熱加圧工程における温度条件の検討
加熱加圧工程における最適な温度を検討するため、上記で作製した使用前の放射性セシウム吸着繊維を大気下の常圧で各温度にて２時間加熱して、外観、質量、ＢＥＴ比表面積の変化を測定した。
(2) Examination of temperature conditions in the heating and pressurizing process In order to examine the optimum temperature in the heating and pressurizing process, the pre-use radioactive cesium-adsorbed fibers prepared above are heated at normal pressure in the atmosphere for 2 hours at each temperature. Then, changes in appearance, mass, and BET specific surface area were measured.
各温度のおける加熱処理後の外観写真と質量を図１に、質量のグラフを図２に示す。３００℃、４００℃では変色が認められたものの質量の減少はわずかであった。一方、５００℃、６００℃、８００℃では形状が崩れるとともに著しく質量が減少した。これにより、４００℃と５００℃の間で熱分解が起こることが確認された。 The appearance photograph and mass after the heat treatment at each temperature are shown in FIG. 1, and the mass graph is shown in FIG. Although discoloration was observed at 300 ° C and 400 ° C, the decrease in mass was slight. On the other hand, at 500 ° C., 600 ° C., and 800 ° C., the shape collapsed and the mass decreased remarkably. As a result, it was confirmed that thermal decomposition occurred between 400 ° C and 500 ° C.
ＢＥＴ比表面積は、図３に示すように、３００℃、４００℃において、極めて低い値になった。これは、ポリスルホンが融解してゼオライトの細孔を覆ったためと考えられた。５００℃、６００℃ではＢＥＴ比表面積が大きい値になったが、これは、ポリスルホンが熱分解したことによると考えられた。 As shown in FIG. 3, the BET specific surface area became an extremely low value at 300 ° C. and 400 ° C. It was considered that this was because the polysulfone melted and covered the pores of the zeolite. The BET specific surface area became a large value at 500 ° C. and 600 ° C., which was considered to be due to the thermal decomposition of polysulfone.
以上の結果より、高分子材料がポリスルホンの場合は、２５０〜４５０℃が最適温度であり、さらにＢＥＴ比表面積が最小値になる４００℃前後がより最適であることが確認された。 From the above results, it was confirmed that when the polymer material is polysulfone, the optimum temperature is 250 to 450 ° C., and the optimum temperature is around 400 ° C., which is the minimum value of the BET specific surface area.
（３）加熱加圧工程によるペレット状試料の作製
内径４０ｍｍのステンレス製の円筒内に上記で作製した使用前の放射性セシウム吸着繊維を入れ、一定温度に温度を制御しながら油圧プレス機を用いて１００ｋｇｆ／ｃｍ２の圧力で加圧し、ペレット状試料を作製した。そして、加熱加圧工程前後の体積変化から、減容化率を求めた。その結果を下表に示す。
(3) Preparation of pellet-shaped sample by heating and pressurizing process The pre-use radioactive cesium adsorbing fiber prepared above is placed in a stainless steel cylinder with an inner diameter of 40 mm, and a hydraulic press is used while controlling the temperature to a constant temperature. A pellet-shaped sample was prepared by pressurizing with a pressure of 100 kgf / cm 2 . Then, the volume reduction rate was determined from the volume change before and after the heating and pressurizing step. The results are shown in the table below.
加熱をせず室温で加圧のみで成型した試料の減容化率は４０％であったのに対し、４００℃での加熱加圧工程を経ると１５％まで体積を減少させることが可能であった。 The volume reduction rate of the sample molded only by pressurization at room temperature without heating was 40%, but it is possible to reduce the volume to 15% through the heating and pressurizing step at 400 ° C. there were.
（４）ペレット状試料による溶出試験
（４−１）非放射性セシウムを用いた試験
セシウム濃度５，０００ｐｐｍの溶液１Ｌに５０ｇの上記で作製した放射性セシウム吸着繊維を入れ、４８時間震盪してセシウムを吸着させた。吸着後のセシウム濃度を測定したところ平衡濃度６９５ｐｐｍであり、放射性セシウム吸着繊維のセシウム吸着量は８６．１ｍｇ／ｇであった。この放射性セシウム吸着繊維に真空乾燥を行い、繊維状試料とした。また、同じ放射性セシウム吸着繊維を４００℃で加熱加圧工程を施し、ペレット状試料とした。そして、それぞれの試料について溶出試験を行い、溶液中に含まれる非放射性セシウム濃度を原子吸光光度計で測定し、溶出率を算出した。その結果を下表に示す。
(4) Elution test using pellet-shaped sample (4-1) Test using non-radioactive cesium Put 50 g of the radioactive cesium-adsorbing fiber prepared above in 1 L of a solution with a cesium concentration of 5,000 ppm, and shake for 48 hours to remove cesium. It was adsorbed. When the cesium concentration after adsorption was measured, the equilibrium concentration was 695 ppm, and the cesium adsorption amount of the radioactive cesium adsorption fiber was 86.1 mg / g. The radioactive cesium-adsorbed fibers were vacuum-dried to prepare a fibrous sample. Further, the same radioactive cesium-adsorbed fiber was subjected to a heating and pressurizing step at 400 ° C. to prepare a pellet-shaped sample. Then, an elution test was performed on each sample, the concentration of non-radioactive cesium contained in the solution was measured with an atomic absorption spectrophotometer, and the elution rate was calculated. The results are shown in the table below.
加熱加圧工程を施していないときの溶出率が０．９５％であったのに対し、４００℃で加熱加圧工程を施した後の溶出率は０．０３９％であり、約２５分の１となった。これは、加熱加工工程によりポリスルホンが融解してゼオライトの表面を覆い、セシウムを吸着したゼオライトと水の接触が阻害されたためと考えられた。 The elution rate was 0.95% when the heating and pressurizing step was not performed, whereas the elution rate after the heating and pressurizing step at 400 ° C. was 0.039%, which was about 25 minutes. It became 1. It is considered that this is because the polysulfone was melted by the heat processing step and covered the surface of the zeolite, and the contact between the zeolite adsorbing cesium and water was hindered.
（４−２）放射性セシウムを用いた試験
上記で作製した放射性セシウム吸着繊維２ｋｇをカラムに収容し、放射性セシウムを含む焼却灰を熱水抽出することにより得られた放射性セシウム濃度４８８Ｂｑ／ｋｇの抽出水７０Ｌを３００分間循環させ、放射性セシウム吸着繊維に放射性セシウムを吸着させた。抽出水の放射性セシウムの最終平衡濃度は８０Ｂｑ／ｋｇであった。カラムから放射性セシウム吸着繊維を取り出し、表面を簡単に水で洗浄した後、繊維状試料とした。また、同じ放射性セシウム吸着繊維を４００℃で加熱加圧工程を施し、ペレット状試料とした。そして、それぞれの試料について溶出試験を行い、溶液中に含まれる放射性セシウム濃度をＧｅ半導体検出器で測定し、溶出率を算出した。その結果を下表に示す。
(4-2) Test using radioactive cesium Extraction of radioactive cesium concentration 488 Bq / kg obtained by accommodating 2 kg of the radioactive cesium adsorbed fiber prepared above in a column and extracting incineration ash containing radioactive cesium with hot water. 70 L of water was circulated for 300 minutes to adsorb radioactive cesium on the radioactive cesium adsorbing fibers. The final equilibrium concentration of radioactive cesium in the extracted water was 80 Bq / kg. Radioactive cesium-adsorbed fibers were taken out from the column, and the surface was simply washed with water to prepare a fibrous sample. Further, the same radioactive cesium-adsorbed fiber was subjected to a heating and pressurizing step at 400 ° C. to prepare a pellet-shaped sample. Then, an elution test was performed on each sample, the concentration of radioactive cesium contained in the solution was measured with a Ge semiconductor detector, and the elution rate was calculated. The results are shown in the table below.
繊維状試料、ペレット状試料のいずについても、放射性セシウムの溶出は確認されなかった。検出限界値から算出すると、繊維状試料は１.４％以下、ペレット状試料は１％以下の溶出率であった。いずれも極めて強固に放射性セシウムを吸着していることが示された。 No elution of radioactive cesium was confirmed in either the fibrous sample or the pellet sample. Calculated from the detection limit, the elution rate of the fibrous sample was 1.4% or less and that of the pellet sample was 1% or less. It was shown that all of them adsorbed radioactive cesium extremely strongly.
Claims (1)
It is a method of reducing the volume of a radioactive cesium-adsorbed fiber made of a porous polymer material carrying porous particles and adsorbing radioactive cesium. The radioactive cesium-adsorbed fiber dissolves the polymer material to form the porous particles. It was obtained by extruding a dispersed polymer solution into water, and provided a heating and pressurizing step of pressurizing the radioactive cesium-adsorbed fibers while heating them. The porous particles were zeolite and the polymer material. Is a polysulfone, and the heating and pressurizing step is performed at 250 to 450 ° C., and in the heating and pressurizing step, the polymer material is melted and radioactive cesium is adsorbed in the pores. A method for reducing the volume of used radioactive cesium-adsorbed fibers, which comprises covering the pores.
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