WO2014178380A1 - Method for purifying water contaminated with radioactive cesium - Google Patents

Method for purifying water contaminated with radioactive cesium Download PDF

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WO2014178380A1
WO2014178380A1 PCT/JP2014/061888 JP2014061888W WO2014178380A1 WO 2014178380 A1 WO2014178380 A1 WO 2014178380A1 JP 2014061888 W JP2014061888 W JP 2014061888W WO 2014178380 A1 WO2014178380 A1 WO 2014178380A1
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surfactin
cesium
salt
ions
contaminated water
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PCT/JP2014/061888
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French (fr)
Japanese (ja)
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恵広 柳澤
将司 泉田
敏彰 平
井村　知弘
北本　大
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株式会社カネカ
独立行政法人産業技術総合研究所
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Publication of WO2014178380A1 publication Critical patent/WO2014178380A1/en

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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/12—Processing by absorption; by adsorption; by ion-exchange
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing

Definitions

  • the present invention relates to a method for purifying contaminated water containing radioactive cesium, which can selectively remove cesium from contaminated water containing potassium or sodium.
  • Nuclear power generation has a basic structure in which primary cooling water is heated by fission energy to generate steam directly or indirectly, and a turbine is rotated by steam to generate power. Therefore, when a nuclear reactor or the like is damaged due to an accident, primary cooling water containing a radioactive substance is released to the natural world.
  • radioactive substances contained in the primary cooling water include radioactive cesium ( 134 Cs and 137 Cs).
  • radioactive cesium is not only highly water-soluble and easily diffuses into nature, but is also replaced with potassium in the body, and may be taken into cells while circulating through the liver and intestine instead of potassium.
  • 137 Cs has a long half-life of about 30 years, which causes internal exposure.
  • the technology for purifying water contaminated with radioactive cesium is very important in addition to countermeasures against accidents at nuclear power plants.
  • adsorbents such as zeolite and activated carbon are used to purify contaminated water containing radioactive substances.
  • these adsorbents are miniaturized in order to increase the surface area in order to increase the adsorption capacity, and the pressure loss increases accordingly.
  • a fertilizer component such as potassium is also adsorbed due to a decrease in the adsorbing effect with time and lack of selectivity of adsorbing substances.
  • Patent Document 1 discloses decontamination in which a capturing compound that captures radioactive substances is bound to magnetic nanoparticles via a coating layer such as a surfactant. Magnetic composite particles for use are disclosed. Examples of such trapping compounds include metal ferrocyanides and ion exchangers in addition to zeolite and nanoporous materials.
  • Patent Document 2 discloses a contaminant adsorbent containing bitumen, a foaming agent and a polymer compound, and may contain a surfactant as a binder.
  • the adsorbent is said to effectively exhibit the ability of adsorbing bitumen to pollutants.
  • Bitumen is a blue pigment mainly composed of ferric ferrocyanide, and ferrocyanide ions are considered to have a selective binding ability to cesium.
  • ferrocyanide ions are said to have a selective binding ability to cesium, ferrocyanide ions and iron ions as counter anions themselves are regulated substances. Therefore, it is unsuitable as a treatment agent when a large amount of contaminated water is generated.
  • the present invention is a method for purifying contaminated water containing radioactive cesium, which can selectively remove cesium from contaminated water containing potassium, sodium, etc., and gives a large load to the natural environment. It aims to provide a method that can be safely implemented without any problems.
  • the surfactin salt which is a natural surfactant, has a selective binding ability to cesium, and since it is a peptide compound, it is easily decomposed in nature, so it has a low environmental impact and is safe. It has been found that the present invention is extremely suitable for purifying contaminated water containing radioactive cesium, and the present invention has been completed.
  • a method for purifying contaminated water containing radioactive cesium comprising a step of adding a surfactin salt represented by the following formula (I) to the contaminated water and combining it with radioactive cesium to form a cesium salt of surfactin.
  • cesium ions can be selectively adsorbed and removed from contaminated water containing radioactive cesium. Therefore, for example, cesium ions can be selectively removed from seawater contaminated with radioactive cesium, despite the presence of a large amount of sodium ions, and also from agricultural water, it affects the potassium ions important for plant growth. It is possible to remove cesium ions without imparting.
  • the surfactin salt used in the purification method according to the present invention is a natural peptide surfactant, even if it is released into the environment by use, it is rapidly degraded by microorganisms and the like. The applied load is small, and it can be used in large quantities outdoors. Therefore, the method of the present invention is very useful as a means for purifying contaminated water containing radioactive cesium, particularly in post-accident processing of a nuclear power plant where a large amount of radioactive cesium contaminated water is generated.
  • FIG. 1 is a MALDI-TOFMS spectrum of an aqueous solution of surfactin sodium (FIG. 1a) and an aqueous solution containing surfactin sodium and cesium chloride (FIG. 1b).
  • FIG. 2 is a MALDI-TOFMS spectrum of an aqueous solution of sodium dodecyl sulfate (FIG. 2a) and an aqueous solution containing sodium dodecyl sulfate and cesium chloride (FIG. 2b).
  • FIG. 3 is a MALDI-TOFMS spectrum of an aqueous solution of surfactin sodium (FIG.
  • FIG. 3a an aqueous solution containing surfactin sodium, sodium chloride, potassium chloride and cesium chloride
  • FIG. 4 is an IR spectrum of a concentrated dried product of an aqueous solution of surfactin sodium and an concentrated dried product of an aqueous solution containing surfactin sodium and cesium chloride.
  • FIG. 5 is an NMR spectrum of cesium ions gradually added to an aqueous solution of surfactin sodium.
  • FIG. 6 is an NMR spectrum of cesium ions gradually added to an aqueous solution of sodium dodecyl sulfate.
  • Step of adding surfactin salt The method of the present invention is a method for purifying contaminated water containing radioactive cesium.
  • the radioactive cesium to be removed from the contaminated water by the method of the present invention is not particularly limited as long as it is harmful and exhibits radioactivity and should be removed, and examples thereof include 134 Cs and 137 Cs.
  • the long 137 Cs is targeted for removal.
  • the contaminated water may contain cesium that does not exhibit radioactivity.
  • the contaminated water to be purified by the method of the present invention is not particularly limited as long as it contains radioactive cesium.
  • primary cooling water of a nuclear power plant fresh water, seawater, groundwater mixed with radioactive cesium in a leakage accident or nuclear test of the primary cooling water can be given.
  • a surfactin salt represented by the following formula (I) is added to contaminated water containing radioactive cesium.
  • the surfactin salt can selectively bind cesium even from contaminated water containing other metal ions such as sodium ions and potassium ions. Moreover, since it is a peptide compound, the load given to the natural environment is small and safe.
  • X represents an amino acid residue selected from leucine, isoleucine and valine; R represents a C 9-18 alkyl group; M represents a hydrogen atom, an alkali metal ion or an ammonium ion, and at least one M is an alkali metal ion or an ammonium ion]
  • the amino acid residue as X may be L-form or D-form, but L-form is preferred.
  • C 9-18 alkyl group refers to a linear or branched monovalent saturated hydrocarbon group having 9 to 18 carbon atoms.
  • Alkali metal ions are not particularly limited, but represent lithium ions, sodium ions, potassium ions, and the like. Further, the two alkali metal ions may be the same as or different from each other.
  • Examples of the substituent of the ammonium ion include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl, particularly C 1-6 alkyl groups; aralkyl such as benzyl, methylbenzyl, and phenylethyl Groups, especially (C 6-12 aryl)-(C 1-6 alkyl) groups; aryl groups such as phenyl, toluyl, xylyl, etc., and particularly organic groups such as C 6-12 aryl groups.
  • Examples of ammonium ions include tetramethylammonium ions, tetraethylammonium ions, pyridinium ions, and the like.
  • two Ms may be the same or different from each other.
  • One of the two —CO 2 M may be in the state of —COOH or —COO 2 — .
  • the surfactin salt (I) may be used alone or in combination of two or more.
  • a plurality of surfactin salts (I) having different C 9-18 alkyl groups of R may be included.
  • Surfactin salt (I) can be cultivated from a microorganism, for example, a strain belonging to Bacillus subtilis according to a known method, and separated from the culture solution. Can be used as is. Moreover, what is obtained by a chemical synthesis method can be used similarly.
  • the method for adding the surfactin salt (I) to the contaminated water is not particularly limited.
  • surfactin salt (I) may be added as it is, may be added after formulation, or a solution prepared in advance may be added.
  • the concentration of the surfactin salt (I) in the contaminated water may be appropriately adjusted depending on the concentration of cesium contained, and may be, for example, 0.003 mass% or more. If the concentration is 0.003% by mass or more, the surfactin salt (I) can sufficiently form micelles in the solution, and cesium can be taken in and removed more reliably.
  • the upper limit of the concentration is not particularly limited, but the concentration is preferably 50% by mass or less because the effect may be saturated or nonspecific adsorption may become a problem even if the concentration is too high. .
  • the means for separating the surfactin cesium salt is not particularly limited, and examples thereof include ultrafiltration, dialysis, and gel filtration chromatography.
  • Surfactin salt (I) forms micelles in an aqueous solution, where M and cesium ions are considered to be substituted. Therefore, it is conceivable to perform ultrafiltration using a filter having a pore size corresponding to the size of the micelle. For example, since the size of the micelle is considered to be about 100 nm or more and about 5 ⁇ m or less, it can be separated using an ultrafiltration membrane having a fractional molecular weight (MWCO) of 3000 and a pore diameter of 5 nm or less. Further, a centrifugal ultrafiltration system of about 500 g or more and about 20,000 g or less, about 5 minutes or more and about 5 hours or less may be used.
  • MWCO fractional molecular weight
  • the separated cesium salt of Surfactin is dispersed in as little water as possible, and an excess amount of alkaline earth metal ions such as calcium ions and magnesium ions is added.
  • alkaline earth metal salt of surfactin since the alkaline earth metal salt of surfactin is insoluble, it can be separated by solid-liquid separation means such as filtration or centrifugation.
  • surfactin can be easily recovered as a free form, to which alkali metal ions and ammonium ions are collected.
  • the surfactin salt (I) according to the present invention can be regenerated and reused. Further, the separated cesium ions are easier to treat because the smaller the amount of water added to the cesium salt of surfactin, the higher the concentration of the solution.
  • the method of the present invention can selectively and safely remove cesium contained in contaminated water. According to the experimental findings by the present inventors, it was confirmed that 97% of cesium contained in the contaminated water was captured by the surfactin salt (I). Therefore, the method of the present invention can be defined as an effective treatment means for contaminated water of the Fukushima nuclear power plant that is currently a problem.
  • Example 1 The ability of surfactin (SF) to remove cesium ions (Cs + ) was measured using a matrix-assisted laser desorption / ionization mass spectrometer (MALDI-TOFMS: manufactured by Bruker, product name “autoflex speed”).
  • MALDI-TOFMS matrix-assisted laser desorption / ionization mass spectrometer
  • surfactin sodium was dissolved in ultrapure water to prepare a 1 mM (about 0.1 wt%) solution. 20 times moles of cesium chloride was added to the solution and allowed to stand at room temperature.
  • sinapinic acid manufactured by Sigma Aldrich
  • acetonitrile: trifluoroacetic acid 99: 1: 0.1 to obtain a saturated solution.
  • the mixed solution (10 ⁇ L) and the matrix solution (10 ⁇ L) were mixed on a plate and dried to measure.
  • surfactin sodium alone solution was used without adding cesium chloride.
  • the measurement result in the case of surfactin sodium alone is shown in FIG. 1a, and the measurement result in the case of adding surfactin sodium and cesium chloride is shown in FIG. 1b.
  • Example 1 Comparative Example 1 In Example 1, the experiment was conducted in the same manner except that a 10 mM (2.9 wt%) aqueous solution of sodium dodecyl sulfate (SDS), which is a general-purpose surfactant, was used instead of the 1 mM aqueous solution of surfactin sodium. .
  • SDS sodium dodecyl sulfate
  • FIG. 2a The measurement result in the case of SDS alone is shown in FIG. 2a, and the measurement result in the case of adding SDS and cesium chloride is shown in FIG. 2b.
  • Example 2 Next, the selectivity of surfactin for cesium ions in the presence of various alkali metal salts (NaCl, KCl, CsCl) was examined.
  • Surfactin sodium was dissolved in ultrapure water to prepare a 1 mM (about 0.1 wt%) solution.
  • Sodium chloride (20-fold mol), potassium chloride (20-fold mol) and cesium chloride (20-fold mol) were added to the solution, and the mixture was allowed to stand at room temperature.
  • sinapinic acid manufactured by Sigma Aldrich
  • acetonitrile: trifluoroacetic acid 99: 1: 0.1 to obtain a saturated solution.
  • the mixed solution (10 ⁇ L) and the matrix solution (10 ⁇ L) were mixed on a plate and dried to measure.
  • FIG. 3a shows the measurement results in the case of surfactin sodium alone
  • FIG. 3b shows the measurement results in the case of adding sodium chloride, potassium chloride and cesium chloride in addition to surfactin sodium.
  • Example 3 Changes in the molecular structure associated with surfactin capturing cesium ions were examined using a Fourier transform infrared spectrophotometer (IR Shimadzu Corporation).
  • a solid sample was prepared by lyophilizing an aqueous solution of surfactin sodium alone (1 mM) and an aqueous solution of surfactin sodium (1 mM) added with 20-fold molar cesium chloride, and total reflection of these samples. It measured by the measuring method (ATR method). The results are shown in FIG.
  • Example 4 The interaction between surfactin and cesium ions in an aqueous solution was verified by a nuclear magnetic resonance absorption spectrum measurement method (manufactured by Bruker, 400 MHz).
  • Example 5 The ratio (removal rate) of cesium ions in water actually removed by surfactin was verified.
  • Surfactin (1 mM) and cesium chloride (1 mM) were dissolved in 2 mL of ultrapure water and allowed to stand at room temperature. Thereafter, only water was removed from the mixture by lyophilization to obtain a solid. When 20 mL of chloroform was added to this solid, a mixture of a dissolved component and an insoluble solid was obtained.
  • the component dissolved in chloroform is a mixture of surfactin sodium salt and cesium salt (surfactin salt).
  • the insoluble solid component is a mixture (inorganic salt) of sodium chloride and cesium chloride. These were separated by a glass filter.
  • the filtrate component (surfactin salt) that passed through the pores of the glass filter was further dried under reduced pressure using a rotary evaporator to obtain a solid.
  • the insoluble solid component (inorganic salt) remaining on the glass filter was recovered by washing with ultrapure water (50 mL).
  • Cesium ions contained in both components thus obtained were quantified by inductively coupled plasma mass spectrometry (manufactured by Agilent, product name “7700x”). The results are shown in Table 1.
  • the concentrated components concentrated by centrifugal filtration and the filtrate components that passed through the ultrafiltration membrane were fractionated, and UV-visible absorption spectrum measurement (manufactured by JASCO Corporation, product name “V-560”) was used to determine the surfactin salt in each.
  • V-560 UV-visible absorption spectrum measurement
  • the concentrated component and the filtrate component were each transferred to a 100 mL volumetric flask and measured by dilution with ultrapure water, and the content of surfactin salt was calculated by creating a calibration curve based on the absorbance value at 230 nm. .
  • the results are shown in Table 2.
  • Example 7 We verified the removal of cesium ions in water by combining a surfactin salt with an ultrafiltration membrane.
  • Surfactin sodium (SFNa) and cesium chloride were mixed with ultrapure water so that the ratio of surfactin sodium and cesium ions was as shown in Table 3.
  • the obtained aqueous solution (0.5 mL) was put into a 1.5 mL tube in which an ultrafiltration membrane having a molecular weight cut-off of 3000 (Millipore, product name “Amicon Ultra”, pore size: 5 nm or less) was set, Centrifugal ultrafiltration was performed at 25 ° C. and 4000 G for 30 minutes using a centrifuge (product name “MX-301” manufactured by Tommy Seiko Co., Ltd.).
  • the concentrated solution concentrated by centrifugal ultrafiltration and the filtrate that has passed through the ultrafiltration membrane are fractionated, and the concentration of cesium ions contained in both is determined by an inductively coupled plasma mass spectrometer (ICP-MS) (Agilent). Quantitatively according to the product name “7700x”). The results are shown in Table 3.
  • acquisition rate was computed as a ratio of the cesium content contained in the concentrate component with respect to the whole cesium content.
  • the ratio of surfactin sodium to cesium ions is a mass ratio.
  • Example 7 Comparative Example 3 In Example 7, the experiment was conducted in the same manner except that 1 mM (0.03 wt%) aqueous solution of sodium dodecyl sulfate (SDS), which is a general-purpose surfactant, was used instead of Surfactin sodium.
  • SDS sodium dodecyl sulfate
  • the results are shown in Table 4.
  • acquisition rate was computed as a ratio of the cesium content contained in the concentrate component with respect to the whole cesium content.
  • Example 8 The ratio (capture rate) of cesium ions in water removed by an ultrafiltration membrane in the presence of various alkali metal salts (NaCl, KCl, CsCl) was examined.
  • Surfactin sodium is dissolved in ultrapure water, and aqueous solutions of 1.0 mM (about 0.1 wt%), 2.5 mM (about 0.25 wt%) and 5.0 mM (about 0.50 wt%) are prepared. did. Sodium chloride (1 mM), potassium chloride (1 mM), and cesium chloride (1 mM) were added to each aqueous solution. Each solution (0.5 mL) was placed in a 1.5 mL tube set with an ultrafiltration membrane (Millipore, product name “Amicon Ultra”, pore size: 5 nm or less) with a molecular weight cut-off of 3000, and centrifuged. Centrifugal ultrafiltration was performed at 25 ° C.

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Abstract

The purpose of the present invention is to provide a method for purifying contaminated water containing radioactive cesium that makes it possible to selectively remove cesium from contaminated water that contains potassium, sodium, or the like and that can be safely performed without imposing a large burden on the natural environment. The method for purifying water containing radioactive cesium according to the present invention is characterized by comprising a step in which a salt of surfactin is added to contaminated water and caused to bond with radioactive cesium in order to obtain a cesium salt of surfactin.

Description

放射性セシウム汚染水の浄化方法Purification method of radioactive cesium contaminated water
　本発明は、放射性セシウムを含む汚染水を浄化するための方法であって、カリウムやナトリウムなどを含む汚染水からもセシウムを選択的に除去できる方法に関するものである。 The present invention relates to a method for purifying contaminated water containing radioactive cesium, which can selectively remove cesium from contaminated water containing potassium or sodium.
　原子力発電は、一次冷却水を核分裂エネルギーにより加熱して直接的または間接的に蒸気を発生させ、蒸気によりタービンを回転させて発電するという基本構造を有する。よって、事故により原子炉などが破損すると、放射性物質を含む一次冷却水が自然界に放出されることになる。 Nuclear power generation has a basic structure in which primary cooling water is heated by fission energy to generate steam directly or indirectly, and a turbine is rotated by steam to generate power. Therefore, when a nuclear reactor or the like is damaged due to an accident, primary cooling water containing a radioactive substance is released to the natural world.
　一次冷却水に含まれる放射性物質としては、放射性セシウム（134Ｃｓや137Ｃｓ）などがある。放射性物質の中でも放射性セシウムは、水溶性が高く自然界に拡散し易いのみでなく、生体中でカリウムと置換され、カリウムの代わりに肝臓と腸を循環しつつ細胞内に取り込まれるおそれがある。また、特に137Ｃｓの半減期は約３０年と長いことから、内部被爆を引き起こす。さらに、生体中における放射性セシウムの蓄積量は食物連鎖に従って増大するため、ヒトなどの動物の癌発症率を高めるという問題がある。従って、原子力発電所の事故への対策にとどまらず、放射性セシウムに汚染された水を浄化する技術は非常に重要である。 Examples of radioactive substances contained in the primary cooling water include radioactive cesium ( 134 Cs and 137 Cs). Among radioactive substances, radioactive cesium is not only highly water-soluble and easily diffuses into nature, but is also replaced with potassium in the body, and may be taken into cells while circulating through the liver and intestine instead of potassium. In particular, 137 Cs has a long half-life of about 30 years, which causes internal exposure. Furthermore, since the amount of radioactive cesium accumulated in the body increases according to the food chain, there is a problem of increasing the cancer incidence of animals such as humans. Therefore, the technology for purifying water contaminated with radioactive cesium is very important in addition to countermeasures against accidents at nuclear power plants.
　放射線物質を含む汚染水の浄化には、一般的に、ゼオライトや活性炭などの吸着材が用いられている。しかし、これら吸着材は、吸着能を高めるために表面積を増大させるべく微細化されており、それに伴って圧力損失も高くなってしまう。また、吸着効果の経時的な低下や、吸着物質の選択性が無いために、例えばカリウムなどの肥料成分も吸着してしまうという問題がある。 In general, adsorbents such as zeolite and activated carbon are used to purify contaminated water containing radioactive substances. However, these adsorbents are miniaturized in order to increase the surface area in order to increase the adsorption capacity, and the pressure loss increases accordingly. In addition, there is a problem that a fertilizer component such as potassium is also adsorbed due to a decrease in the adsorbing effect with time and lack of selectivity of adsorbing substances.
　放射性物質を含む汚染水のその他の浄化技術としては、例えば特許文献１には、磁性ナノ粒子に、界面活性剤などの被覆層を介して放射性物質類を捕捉する捕捉性化合物が結合した除染用磁性複合粒子が開示されている。かかる捕捉性化合物としては、ゼオライトやナノ多孔材料の他、金属フェロシアン化物やイオン交換体が挙げられている。 As another purification technique for contaminated water containing radioactive substances, for example, Patent Document 1 discloses decontamination in which a capturing compound that captures radioactive substances is bound to magnetic nanoparticles via a coating layer such as a surfactant. Magnetic composite particles for use are disclosed. Examples of such trapping compounds include metal ferrocyanides and ion exchangers in addition to zeolite and nanoporous materials.
　また、特許文献２には、紺青、発泡剤および高分子化合物を含む汚染物質の吸着剤であって、結着剤として界面活性剤を含んでもよいものが開示されている。当該吸着剤では、汚染物質に対する紺青の吸着能が有効に発揮されるとされている。紺青はフェロシアン化第二鉄を主成分とする青色顔料であり、また、フェロシアン化物イオンはセシウムに対する選択的な結合能を有するとされている。 Patent Document 2 discloses a contaminant adsorbent containing bitumen, a foaming agent and a polymer compound, and may contain a surfactant as a binder. The adsorbent is said to effectively exhibit the ability of adsorbing bitumen to pollutants. Bitumen is a blue pigment mainly composed of ferric ferrocyanide, and ferrocyanide ions are considered to have a selective binding ability to cesium.
特開２０１２－２３７７３５号公報JP 2012-237735 A 特開２０１３－１７４７号公報JP 2013-1747 A
　上述したように、放射性セシウムを含む汚染水の浄化方法としては様々なものが開発されているが、ゼオライト等には、表面積が大きく吸着能が高いものほど圧力損失が高いことや吸着能の低下、低選択性などの問題がある。 As described above, various methods for purifying contaminated water containing radioactive cesium have been developed. For zeolites and the like, the higher the surface area and the higher the adsorption capacity, the higher the pressure loss and the lower the adsorption capacity. There are problems such as low selectivity.
　また、フェロシアン化物イオンはセシウムに対する選択的結合能を有するとされているが、フェロシアン化物イオンやそのカウンターアニオンである鉄イオンなど自体が規制物質である。よって、汚染水が大量に生じた場合の処理剤としては不適である。 In addition, although ferrocyanide ions are said to have a selective binding ability to cesium, ferrocyanide ions and iron ions as counter anions themselves are regulated substances. Therefore, it is unsuitable as a treatment agent when a large amount of contaminated water is generated.
　そこで本発明は、放射性セシウムを含む汚染水を浄化するための方法であって、カリウムやナトリウムなどを含む汚染水からもセシウムを選択的に除去することができ、且つ自然環境に大きな負荷を与えることなく安全に実施できる方法を提供することを目的とする。 Therefore, the present invention is a method for purifying contaminated water containing radioactive cesium, which can selectively remove cesium from contaminated water containing potassium, sodium, etc., and gives a large load to the natural environment. It aims to provide a method that can be safely implemented without any problems.
　本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、天然の界面活性剤であるサーファクチン塩がセシウムに対する選択的な結合能を有する上に、ペプチド化合物であることから自然界で容易に分解されるため環境負荷が小さく安全であることから、放射性セシウムを含む汚染水を浄化するのに極めて適していることを見出して、本発明を完成させるに至った。 The inventors of the present invention have made extensive studies to solve the above problems. As a result, the surfactin salt, which is a natural surfactant, has a selective binding ability to cesium, and since it is a peptide compound, it is easily decomposed in nature, so it has a low environmental impact and is safe. It has been found that the present invention is extremely suitable for purifying contaminated water containing radioactive cesium, and the present invention has been completed.
　以下、本発明を示す。 Hereinafter, the present invention will be described.
　［１］　放射性セシウムを含む汚染水を浄化するための方法であって、
　当該汚染水に下記式（Ｉ）で表されるサーファクチンの塩を添加し、放射性セシウムと結合させ、サーファクチンのセシウム塩とする工程を含むことを特徴とする放射性セシウム汚染水の浄化方法。 [1] A method for purifying contaminated water containing radioactive cesium,
A method for purifying radioactive cesium-contaminated water, comprising a step of adding a surfactin salt represented by the following formula (I) to the contaminated water and combining it with radioactive cesium to form a cesium salt of surfactin.
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
［式中、
　Ｘは、ロイシン、イソロイシンおよびバリンから選択されるアミノ酸残基を示し；
　ＲはＣ9-18アルキル基を示し；
　Ｍは、水素原子、アルカリ金属イオンまたはアンモニウムイオンを示すが、少なくとも一方のＭはアルカリ金属イオンまたはアンモニウムイオンであるとする］
　［２］　上記汚染水に対して０．００３質量％以上のサーファクチン塩（Ｉ）を添加する上記［１］に記載の放射性セシウム汚染水の浄化方法。当該添加量が０．００３質量％以上であれば、汚染水中においてサーファクチン塩（Ｉ）のミセルがより確実に形成され、汚染水中に安定的に分散することによりセシウムに対する吸着能が飛躍的に向上すると考えられる。また、ミセルの形成により、汚染水中に油性成分が混入している場合には、これをミセル内部に取り込んで汚染水を浄化することが可能になる。 [Where:
X represents an amino acid residue selected from leucine, isoleucine and valine;
R represents a C 9-18 alkyl group;
M represents a hydrogen atom, an alkali metal ion or an ammonium ion, and at least one M is an alkali metal ion or an ammonium ion]
[2] The method for purifying radioactive cesium-contaminated water according to [1], wherein 0.003% by mass or more of Surfactin salt (I) is added to the contaminated water. If the amount added is 0.003 mass% or more, surfactin salt (I) micelles are more reliably formed in the contaminated water, and the ability to adsorb to cesium is dramatically improved by being stably dispersed in the contaminated water. It is thought to improve. In addition, when an oily component is mixed in the contaminated water due to the formation of the micelles, the contaminated water can be purified by taking it into the micelle.
　［３］　さらに、サーファクチンのセシウム塩を分離する工程を含む上記［１］または［２］に記載の放射性セシウム汚染水の浄化方法。サーファクチン塩（Ｉ）に結合させるのみでも放射性セシウムの挙動は制限され、汚染水は浄化されることになるが、かかる工程により、サーファクチンのセシウム塩が分離されて水の放射性セシウム濃度が顕著に低減され、また、有害な放射性セシウムを水から除外することができる。 [3] The method for purifying radioactive cesium-contaminated water according to the above [1] or [2], further comprising a step of separating the cesium salt of surfactin. Even if it is bound to Surfactin Salt (I), the behavior of radioactive cesium is limited, and contaminated water is purified. However, this process separates the cesium salt of Surfactin and the concentration of radioactive cesium in water is remarkable. And harmful radiocesium can be excluded from water.
　［４］　限外濾過によりサーファクチンのセシウム塩を分離する上記［３］に記載の放射性セシウム汚染水の浄化方法。限外濾過によれば、サーファクチンのセシウム塩から構成されるミセルを簡便な操作で水から分離することができ、非常に効率的である。 [4] The method for purifying radioactive cesium-contaminated water according to [3] above, wherein the cesium salt of surfactin is separated by ultrafiltration. According to ultrafiltration, micelles composed of the cesium salt of surfactin can be separated from water by a simple operation, which is very efficient.
　本発明方法によれば、放射性セシウムを含む汚染水からセシウムイオンを選択的に吸着除去できる。よって、例えば放射性セシウムが混入した海水からも、多量のナトリウムイオンの存在にもかかわらずセシウムイオンを選択的に除去可能であり、また、農業用水からも、植物の生育に重要なカリウムイオンに影響を与えることなくセシウムイオンを除去可能である。また、本発明に係る浄化方法で必須的に用いるサーファクチン塩は、天然のペプチド界面活性剤であることから、使用により環境中に放出されても微生物などにより速やかに分解されるため、環境へ与える負荷が小さく、屋外でも大量に使用することができる。よって、本発明方法は、放射性セシウムを含む汚染水の浄化手段として、特に放射性セシウム汚染水が大量に生じる原子力発電所の事故後処理などにおいて、非常に有用である。 According to the method of the present invention, cesium ions can be selectively adsorbed and removed from contaminated water containing radioactive cesium. Therefore, for example, cesium ions can be selectively removed from seawater contaminated with radioactive cesium, despite the presence of a large amount of sodium ions, and also from agricultural water, it affects the potassium ions important for plant growth. It is possible to remove cesium ions without imparting. In addition, since the surfactin salt used in the purification method according to the present invention is a natural peptide surfactant, even if it is released into the environment by use, it is rapidly degraded by microorganisms and the like. The applied load is small, and it can be used in large quantities outdoors. Therefore, the method of the present invention is very useful as a means for purifying contaminated water containing radioactive cesium, particularly in post-accident processing of a nuclear power plant where a large amount of radioactive cesium contaminated water is generated.
図１は、サーファクチンナトリウムの水溶液（図１ａ）と、サーファクチンナトリウムおよび塩化セシウムを含む水溶液（図１ｂ）のＭＡＬＤＩ－ＴＯＦＭＳスペクトルである。FIG. 1 is a MALDI-TOFMS spectrum of an aqueous solution of surfactin sodium (FIG. 1a) and an aqueous solution containing surfactin sodium and cesium chloride (FIG. 1b). 図２は、ドデシル硫酸ナトリウムの水溶液（図２ａ）と、ドデシル硫酸ナトリウムおよび塩化セシウムを含む水溶液（図２ｂ）のＭＡＬＤＩ－ＴＯＦＭＳスペクトルである。FIG. 2 is a MALDI-TOFMS spectrum of an aqueous solution of sodium dodecyl sulfate (FIG. 2a) and an aqueous solution containing sodium dodecyl sulfate and cesium chloride (FIG. 2b). 図３は、サーファクチンナトリウムの水溶液（図３ａ）と、サーファクチンナトリウム、塩化ナトリウム、塩化カリウムおよび塩化セシウムを含む水溶液（図３ｂ）のＭＡＬＤＩ－ＴＯＦＭＳスペクトルである。FIG. 3 is a MALDI-TOFMS spectrum of an aqueous solution of surfactin sodium (FIG. 3a) and an aqueous solution containing surfactin sodium, sodium chloride, potassium chloride and cesium chloride (FIG. 3b). 図４は、サーファクチンナトリウムの水溶液の濃縮乾固物と、サーファクチンナトリウムおよび塩化セシウムを含む水溶液の濃縮乾固物のＩＲスペクトルである。FIG. 4 is an IR spectrum of a concentrated dried product of an aqueous solution of surfactin sodium and an concentrated dried product of an aqueous solution containing surfactin sodium and cesium chloride. 図５は、サーファクチンナトリウムの水溶液にセシウムイオンを徐々に加えていったもののＮＭＲスペクトルである。FIG. 5 is an NMR spectrum of cesium ions gradually added to an aqueous solution of surfactin sodium. 図６は、ドデシル硫酸ナトリウムの水溶液にセシウムイオンを徐々に加えていったもののＮＭＲスペクトルである。FIG. 6 is an NMR spectrum of cesium ions gradually added to an aqueous solution of sodium dodecyl sulfate.
　以下、本発明に係る放射性セシウム汚染水の浄化方法を、実施の順番に従って説明する。 Hereinafter, the method for purifying radioactive cesium-contaminated water according to the present invention will be described in the order of implementation.
　（１）　サーファクチン塩の添加工程
　本発明方法は、放射性セシウムを含む汚染水を浄化するための方法である。 (1) Step of adding surfactin salt The method of the present invention is a method for purifying contaminated water containing radioactive cesium.
　本発明方法により汚染水から除去すべき放射性セシウムは、放射性を示す有害なものであって除去すべきものであれば特に制限されないが、例えば134Ｃｓと137Ｃｓを挙げることができ、特に、半減期の長い137Ｃｓを除去対象とする。但し、汚染水には放射性を示さないセシウムが含まれていてもよいものとする。 The radioactive cesium to be removed from the contaminated water by the method of the present invention is not particularly limited as long as it is harmful and exhibits radioactivity and should be removed, and examples thereof include 134 Cs and 137 Cs. The long 137 Cs is targeted for removal. However, the contaminated water may contain cesium that does not exhibit radioactivity.
　本発明方法により浄化すべき汚染水は、放射性セシウムを含むものであれば特に制限されない。例えば、原子力発電所の一次冷却水や、当該一次冷却水の漏出事故や核実験により放射性セシウムが混入した淡水、海水、地下水などを挙げることができる。 The contaminated water to be purified by the method of the present invention is not particularly limited as long as it contains radioactive cesium. For example, primary cooling water of a nuclear power plant, fresh water, seawater, groundwater mixed with radioactive cesium in a leakage accident or nuclear test of the primary cooling water can be given.
　本発明方法では、放射性セシウムを含む汚染水に、下記式（Ｉ）で表されるサーファクチンの塩を添加する。サーファクチン塩は、ナトリウムイオンやカリウムイオンなど他の金属イオンを含む汚染水からでも、セシウムを選択的に結合することができる。また、ペプチド化合物であることから自然環境に与える負荷も小さく安全である。 In the method of the present invention, a surfactin salt represented by the following formula (I) is added to contaminated water containing radioactive cesium. The surfactin salt can selectively bind cesium even from contaminated water containing other metal ions such as sodium ions and potassium ions. Moreover, since it is a peptide compound, the load given to the natural environment is small and safe.
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
［式中、
　Ｘは、ロイシン、イソロイシンおよびバリンから選択されるアミノ酸残基を示し；
　ＲはＣ9-18アルキル基を示し；
　Ｍは、水素原子、アルカリ金属イオンまたはアンモニウムイオンを示すが、少なくとも一方のＭはアルカリ金属イオンまたはアンモニウムイオンであるとする］
　Ｘとしてのアミノ酸残基は、Ｌ体でもＤ体でもよいが、Ｌ体が好ましい。 [Where:
X represents an amino acid residue selected from leucine, isoleucine and valine;
R represents a C 9-18 alkyl group;
M represents a hydrogen atom, an alkali metal ion or an ammonium ion, and at least one M is an alkali metal ion or an ammonium ion]
The amino acid residue as X may be L-form or D-form, but L-form is preferred.
　「Ｃ9-18アルキル基」は、炭素数が９以上、１８以下の直鎖状または分枝鎖状の一価飽和炭化水素基をいう。例えば、ｎ－ノニル、６－メチルオクチル、７－メチルオクチル、ｎ－デシル、８－メチルノニル、ｎ－ウンデシル、９－メチルデシル、ｎ－ドデシル、１０－メチルウンデシル、ｎ－トリデシル、１１－メチルドデシル、ｎ－テトラデシル、ｎ－ペンタデシル、ｎ－ヘキサデシル、ｎ－ヘプタデシル、ｎ－オクタデシルなどが挙げられる。 The “C 9-18 alkyl group” refers to a linear or branched monovalent saturated hydrocarbon group having 9 to 18 carbon atoms. For example, n-nonyl, 6-methyloctyl, 7-methyloctyl, n-decyl, 8-methylnonyl, n-undecyl, 9-methyldecyl, n-dodecyl, 10-methylundecyl, n-tridecyl, 11-methyldodecyl N-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl and the like.
　アルカリ金属イオンは特に限定されないが、リチウムイオン、ナトリウムイオン、カリウムイオンなどを表す。また、２つのアルカリ金属イオンは、互いに同一であってもよいし、異なっていてもよい。 Alkali metal ions are not particularly limited, but represent lithium ions, sodium ions, potassium ions, and the like. Further, the two alkali metal ions may be the same as or different from each other.
　アンモニウムイオンの置換基としては、例えば、メチル、エチル、ｎ－プロピル、イソプロピル、ｎ－ブチル、ｔｅｒｔ－ブチル等のアルキル基、特にＣ1-6アルキル基；ベンジル、メチルベンジル、フェニルエチル等のアラルキル基、特に（Ｃ6-12アリール）－（Ｃ1-6アルキル）基；フェニル、トルイル、キシリル等のアリール基、特にＣ6-12アリール基等の有機基が挙げられる。アンモニウムイオンとしては、例えば、テトラメチルアンモニウムイオン、テトラエチルアンモニウムイオン、ピリジニウムイオン等が挙げられる。 Examples of the substituent of the ammonium ion include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl, particularly C 1-6 alkyl groups; aralkyl such as benzyl, methylbenzyl, and phenylethyl Groups, especially (C 6-12 aryl)-(C 1-6 alkyl) groups; aryl groups such as phenyl, toluyl, xylyl, etc., and particularly organic groups such as C 6-12 aryl groups. Examples of ammonium ions include tetramethylammonium ions, tetraethylammonium ions, pyridinium ions, and the like.
　なお、サーファクチン塩（Ｉ）中、２つのＭは互いに同一であってもよいし、異なっていてもよいものとする。また、２つの－ＣＯ2Ｍのうち一方は－ＣＯＯＨや－ＣＯＯ-の状態になっていてもよいものとする。 In the surfactin salt (I), two Ms may be the same or different from each other. One of the two —CO 2 M may be in the state of —COOH or —COO 2 — .
　上記サーファクチン塩（Ｉ）は１種、または２種以上使用してもよい。例えば、ＲのＣ9-18アルキル基が異なる複数のサーファクチン塩（Ｉ）を含むものであってもよい。 The surfactin salt (I) may be used alone or in combination of two or more. For example, a plurality of surfactin salts (I) having different C 9-18 alkyl groups of R may be included.
　サーファクチン塩（Ｉ）は、公知方法に従って、微生物、例えばバチルス・ズブチリスに属する菌株を培養し、その培養液から分離することができ、精製品であっても、未精製品、例えば培養液のまま使用することも出来る。また、化学合成法によって得られるものでも同様に使用できる。 Surfactin salt (I) can be cultivated from a microorganism, for example, a strain belonging to Bacillus subtilis according to a known method, and separated from the culture solution. Can be used as is. Moreover, what is obtained by a chemical synthesis method can be used similarly.
　汚染水へのサーファクチン塩（Ｉ）の添加方法は、特に制限されない。例えば、サーファクチン塩（Ｉ）をそのまま添加してもよいし、製剤化した上で添加してもよいし、事前調製した溶液を添加してもよい。 The method for adding the surfactin salt (I) to the contaminated water is not particularly limited. For example, surfactin salt (I) may be added as it is, may be added after formulation, or a solution prepared in advance may be added.
　汚染水におけるサーファクチン塩（Ｉ）の濃度は、含まれるセシウムの濃度などにより適宜調整すればよいが、例えば、０．００３質量％以上とすることができる。当該濃度が０．００３質量％以上であれば、サーファクチン塩（Ｉ）は溶液中で十分にミセルを形成することができ、セシウムをより確実に取り込んで除去することが可能になる。一方、当該濃度の上限は特に制限されないが、当該濃度が高過ぎても効果が飽和したり、非特異的吸着が問題になる可能性があり得るので、当該濃度としては５０質量％以下が好ましい。 The concentration of the surfactin salt (I) in the contaminated water may be appropriately adjusted depending on the concentration of cesium contained, and may be, for example, 0.003 mass% or more. If the concentration is 0.003% by mass or more, the surfactin salt (I) can sufficiently form micelles in the solution, and cesium can be taken in and removed more reliably. On the other hand, the upper limit of the concentration is not particularly limited, but the concentration is preferably 50% by mass or less because the effect may be saturated or nonspecific adsorption may become a problem even if the concentration is too high. .
　（２）　サーファクチンのセシウム塩の分離工程
　次に、セシウムイオンが結合したサーファクチンの塩を分離することにより、汚染水を浄化する。なお、放射性セシウムは、サーファクチン塩（Ｉ）に結合させるのみでも挙動は制限され、汚染水は浄化されることになるので、本工程の実施は任意である。 (2) Separation Step of Surfactin Cesium Salt Next, the contaminated water is purified by separating the surfactin salt bound with cesium ions. In addition, since the behavior of radioactive cesium is limited only by binding to surfactin salt (I) and contaminated water is purified, this step is optional.
　サーファクチンのセシウム塩を分離する手段は特に制限されないが、例えば、限外濾過、透析、ゲル濾過クロマトグラフィーを挙げることができる。 The means for separating the surfactin cesium salt is not particularly limited, and examples thereof include ultrafiltration, dialysis, and gel filtration chromatography.
　サーファクチン塩（Ｉ）は、水溶液中でミセルを形成し、ここでＭとセシウムイオンが置換すると考えられる。よって、かかるミセルの大きさに応じた孔径を有するフィルターを用いて限外濾過することが考えられる。例えば、上記ミセルの大きさは１００ｎｍ以上、５μｍ以下程度と考えられるので、分画分子量（ＭＷＣＯ）が３０００で孔径が５ｎｍ以下の限外濾過膜を用いて分離することができる。また、５００ｇ以上、２０，０００ｇ以下程度、５分以上、５時間以下程度での遠心式限外濾過システムを用いてもよい。 Surfactin salt (I) forms micelles in an aqueous solution, where M and cesium ions are considered to be substituted. Therefore, it is conceivable to perform ultrafiltration using a filter having a pore size corresponding to the size of the micelle. For example, since the size of the micelle is considered to be about 100 nm or more and about 5 μm or less, it can be separated using an ultrafiltration membrane having a fractional molecular weight (MWCO) of 3000 and a pore diameter of 5 nm or less. Further, a centrifugal ultrafiltration system of about 500 g or more and about 20,000 g or less, about 5 minutes or more and about 5 hours or less may be used.
　（３）　サーファクチンと放射性セシウムの分離工程
　実施は任意であるが、上記工程（２）によりサーファクチンのセシウム塩を分離した場合には、さらに、サーファクチンを分離回収して再生および再利用し、また、セシウムも分離回収する工程を行ってもよい。 (3) Separation process of surfactin and radioactive cesium Although the implementation is optional, when the cesium salt of surfactin is separated by the above-mentioned process (2), the surfactin is further separated and recovered and regenerated and reused. In addition, a step of separating and collecting cesium may be performed.
　具体的には、分離したサーファクチンのセシウム塩をできるだけ少量の水に分散させ、カルシウムイオンやマグネシウムイオンなどのアルカリ土類金属イオンを過剰量加える。その結果、サーファクチンのアルカリ土類金属塩は不溶性であるので、濾過や遠心分離などの固液分離手段により分離することができる。得られたサーファクチンのアルカリ土類金属塩は、水に再分散させた上で酸性条件にすれば、サーファクチンは容易にフリー体となって回収可能となり、そこへアルカリ金属イオンやアンモニオウムイオンを添加することにより、本発明に係るサーファクチン塩（Ｉ）を再生でき、再利用することができる。また、分離されたセシウムイオンは、サーファクチンのセシウム塩に添加した水が少量であるほど高濃度の溶液になっているので、処理がより容易なものとなっている。 Specifically, the separated cesium salt of Surfactin is dispersed in as little water as possible, and an excess amount of alkaline earth metal ions such as calcium ions and magnesium ions is added. As a result, since the alkaline earth metal salt of surfactin is insoluble, it can be separated by solid-liquid separation means such as filtration or centrifugation. When the alkaline earth metal salt of surfactin obtained is redispersed in water and subjected to acidic conditions, surfactin can be easily recovered as a free form, to which alkali metal ions and ammonium ions are collected. The surfactin salt (I) according to the present invention can be regenerated and reused. Further, the separated cesium ions are easier to treat because the smaller the amount of water added to the cesium salt of surfactin, the higher the concentration of the solution.
　本発明方法により、汚染水に含まれるセシウムを選択的かつ安全に除去することができる。本発明者らによる実験的知見によれば、サーファクチン塩（Ｉ）により、汚染水に含まれるセシウムの実に９７％を捕捉することが確認できている。従って本発明方法は、現在、問題となっている福島原子力発電所の汚染水などに対する有効な処理手段として規定することができる。 The method of the present invention can selectively and safely remove cesium contained in contaminated water. According to the experimental findings by the present inventors, it was confirmed that 97% of cesium contained in the contaminated water was captured by the surfactin salt (I). Therefore, the method of the present invention can be defined as an effective treatment means for contaminated water of the Fukushima nuclear power plant that is currently a problem.
　本願は、２０１３年４月３０日に出願された日本国特許出願第２０１３－９５７３６号に基づく優先権の利益を主張するものである。２０１３年４月３０日に出願された日本国特許出願第２０１３－９５７３６号の明細書の全内容が、本願に参考のため援用される。 This application claims the benefit of priority based on Japanese Patent Application No. 2013-95736 filed on Apr. 30, 2013. The entire contents of the specification of Japanese Patent Application No. 2013-95736 filed on April 30, 2013 are incorporated herein by reference.
　以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
　実施例１
　サーファクチン（ＳＦ）のセシウムイオン（Ｃｓ+）の除去能を、マトリックス支援レーザー脱離イオン化質量分析装置（ＭＡＬＤＩ－ＴＯＦＭＳ：Ｂｒｕｋｅｒ社製，製品名「ａｕｔｏｆｌｅｘ　ｓｐｅｅｄ」）を用いて測定した。 Example 1
The ability of surfactin (SF) to remove cesium ions (Cs + ) was measured using a matrix-assisted laser desorption / ionization mass spectrometer (MALDI-TOFMS: manufactured by Bruker, product name “autoflex speed”).
　具体的には、サーファクチンナトリウムを超純水に溶解し、１ｍＭ（約０．１ｗｔ％）の溶液を調製した。当該溶液に２０倍モルの塩化セシウムを加え、室温で静置した。別途、ＴＯＦＭＳ用マトリックスであるシナピン酸（シグマアルドリッチ社製）を、水：アセトニトリル：トリフルオロ酢酸＝９９：１：０．１の混合溶液に溶解して飽和溶液を得た。上記混合液（１０μＬ）とマトリックス溶液（１０μＬ）をプレート上で混合し、乾燥させたものを測定した。対照実験として、塩化セシウムを加えずに、サーファクチンナトリウム単独溶液で測定した。サーファクチンナトリウム単独の場合の測定結果を図１ａに、サーファクチンナトリウムと塩化セシウムとを加えた場合の測定結果を図１ｂに示す。 Specifically, surfactin sodium was dissolved in ultrapure water to prepare a 1 mM (about 0.1 wt%) solution. 20 times moles of cesium chloride was added to the solution and allowed to stand at room temperature. Separately, sinapinic acid (manufactured by Sigma Aldrich), which is a matrix for TOFMS, was dissolved in a mixed solution of water: acetonitrile: trifluoroacetic acid = 99: 1: 0.1 to obtain a saturated solution. The mixed solution (10 μL) and the matrix solution (10 μL) were mixed on a plate and dried to measure. As a control experiment, surfactin sodium alone solution was used without adding cesium chloride. The measurement result in the case of surfactin sodium alone is shown in FIG. 1a, and the measurement result in the case of adding surfactin sodium and cesium chloride is shown in FIG. 1b.
　図１から明らかなように、サーファクチンナトリウム単独（図１ａ）では、主にアルキル鎖長の異なる３種類の分子イオンピークが検出された。それぞれのピークは、サーファクチンモノナトリウム塩（アルキル鎖炭素数：ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１０３０．６５）、サーファクチンモノナトリウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１０４４．６８）、およびサーファクチンモノナトリウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１０５８．７０）に帰属される。また、サーファクチンに含まれる不純物に由来する分子イオンピーク（１００８．７２，１０２２．７５，１０３６．７８）も検出された。 As is apparent from FIG. 1, surfactin sodium alone (FIG. 1a) mainly detected three types of molecular ion peaks having different alkyl chain lengths. Each peak is a molecular ion peak (1030.65) derived from a proton adduct of surfactin monosodium salt (alkyl chain carbon number: n = 13) and a proton adduct of surfactin monosodium salt (n = 14). Is attributed to the molecular ion peak derived from (104.68) and the molecular ion peak derived from the proton adduct of surfactin monosodium salt (n = 15) (1058.70). In addition, molecular ion peaks (1008.72, 1022.75, 1036.78) derived from impurities contained in surfactin were also detected.
　一方、サーファクチンナトリウムに２０倍モルのセシウムイオンを加えた場合（図１ｂ）、上述した３種類のサーファクチンモノナトリウム塩の分子イオンピークが消失し、９種類の新しい分子イオンピークが検出された。これらは、それぞれサーファクチンモノセシウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１１４０．６７）、サーファクチンモノセシウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１１５４．７０）、サーファクチンモノセシウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１１６８．７２）、サーファクチン二セシウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１２７２．６０）、サーファクチン二セシウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１２８６．６１）、サーファクチン二セシウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１３００．６３）、サーファクチン二セシウム塩（ｎ＝１３）のセシウムイオン付加体に由来する分子イオンピーク（１４０４．５０）、サーファクチン二セシウム塩（ｎ＝１４）のセシウムイオン付加体に由来する分子イオンピーク（１４１８．５２）、およびサーファクチン二セシウム塩（ｎ＝１５）のセシウムイオン付加体に由来する分子イオンピーク（１４３２．５４）に一致する。以上の結果より、サーファクチンナトリウムが、ナトリウムイオンとの交換反応によって、セシウムイオンを分子骨格内に取り込んでいることが明らかになった。 On the other hand, when 20 times mole of cesium ion was added to surfactin sodium (FIG. 1b), the molecular ion peaks of the three types of surfactin monosodium salts described above disappeared and nine new molecular ion peaks were detected. . These are the molecular ion peak (1140.67) derived from the proton adduct of surfactin monocesium salt (n = 13) and the molecular ion peak derived from the proton adduct of surfactin monocesium salt (n = 14), respectively. (1154.70), molecular ion peak (1168.72) derived from proton adduct of surfactin monocesium salt (n = 15), molecule derived from proton adduct of surfactin dicesium salt (n = 13) Ion peak (127.60), molecular ion peak derived from proton adduct of surfactin dicesium salt (n = 14) (1286.61), derived from proton adduct of surfactin dicesium salt (n = 15) Molecular ion peak (1300.63), surfactin dicesium salt (n = 13) Molecular ion peak (1414.50) derived from um ion adduct, molecular ion peak (1418.52) derived from cesium ion adduct of surfactin dicesium salt (n = 14), and surfactin dicesium salt (n This corresponds to the molecular ion peak (1432.54) derived from the cesium ion adduct of = 15). From the above results, it was clarified that surfactin sodium incorporated cesium ions into the molecular skeleton by exchange reaction with sodium ions.
　比較例１
　上記実施例１において、サーファクチンナトリウムの１ｍＭ水溶液の代わりに、汎用界面活性剤であるドデシル硫酸ナトリウム（ＳＤＳ）の１０ｍＭ（２．９ｗｔ％）水溶液を用いた以外は同様にして、実験を行った。結果を図２に示す。なお、ＳＤＳ単独の場合の測定結果を図２ａに、ＳＤＳと塩化セシウムとを加えた場合の測定結果を図２ｂに示す。 Comparative Example 1
In Example 1, the experiment was conducted in the same manner except that a 10 mM (2.9 wt%) aqueous solution of sodium dodecyl sulfate (SDS), which is a general-purpose surfactant, was used instead of the 1 mM aqueous solution of surfactin sodium. . The results are shown in FIG. The measurement result in the case of SDS alone is shown in FIG. 2a, and the measurement result in the case of adding SDS and cesium chloride is shown in FIG. 2b.
　図２から明らかなように、ＳＤＳの単独の場合（図２ａ）、ＳＤＳに起因する分子イオンピーク（２８８．２）が検出された。また、さらに塩化セシウムを２０倍モル加えた場合（図２ｂ）でも、引き続き、ＳＤＳに起因する分子イオンピーク（２８８．２）が検出された。しかし、ＳＤＳにセシウムイオンが付加した化学種の分子イオンピークは、いずれも検出されなかった。以上の結果から、サーファクチンナトリウムと異なり、ＳＤＳにはセシウムイオンを選択的に捕捉する能力は無いことがわかった。 As is clear from FIG. 2, in the case of SDS alone (FIG. 2a), a molecular ion peak (288.2) resulting from SDS was detected. Further, even when 20 times mole of cesium chloride was added (FIG. 2b), a molecular ion peak (288.2) attributed to SDS was continuously detected. However, none of the molecular ion peaks of chemical species in which cesium ions were added to SDS were detected. From the above results, it was found that unlike Surfactin sodium, SDS does not have the ability to selectively capture cesium ions.
　実施例２
　次に、種々のアルカリ金属塩（ＮａＣｌ、ＫＣｌ、ＣｓＣｌ）の共存下でのサーファクチンのセシウムイオンに対する選択性を調べた。 Example 2
Next, the selectivity of surfactin for cesium ions in the presence of various alkali metal salts (NaCl, KCl, CsCl) was examined.
　サーファクチンナトリウムを超純水に溶解し、１ｍＭ（約０．１ｗｔ％）の溶液を調製した。当該溶液に、塩化ナトリウム（２０倍モル）、塩化カリウム（２０倍モル）および塩化セシウム（２０倍モル）をそれぞれ加えて、室温で静置した。別途、ＴＯＦＭＳ用マトリックスであるシナピン酸（シグマアルドリッチ社製）を、水：アセトニトリル：トリフルオロ酢酸＝９９：１：０．１の混合溶液に溶解して飽和溶液を得た。上記混合液（１０μＬ）とマトリックス溶液（１０μＬ）をプレート上で混合し、乾燥させたものを測定した。対照実験として、サーファクチンナトリウム単独溶液で同様に測定した。サーファクチンナトリウム単独の場合の測定結果を図３ａに、サーファクチンナトリウムに加えて塩化ナトリウム、塩化カリウムおよび塩化セシウムを加えた場合の測定結果を図３ｂに示す。 Surfactin sodium was dissolved in ultrapure water to prepare a 1 mM (about 0.1 wt%) solution. Sodium chloride (20-fold mol), potassium chloride (20-fold mol) and cesium chloride (20-fold mol) were added to the solution, and the mixture was allowed to stand at room temperature. Separately, sinapinic acid (manufactured by Sigma Aldrich), which is a matrix for TOFMS, was dissolved in a mixed solution of water: acetonitrile: trifluoroacetic acid = 99: 1: 0.1 to obtain a saturated solution. The mixed solution (10 μL) and the matrix solution (10 μL) were mixed on a plate and dried to measure. As a control experiment, the same measurement was performed using a surfactin sodium single solution. FIG. 3a shows the measurement results in the case of surfactin sodium alone, and FIG. 3b shows the measurement results in the case of adding sodium chloride, potassium chloride and cesium chloride in addition to surfactin sodium.
　図３ｂに示す結果のとおり、サーファクチンナトリウムが３種類であったのに対して、９種類の新しい分子イオンピークを検出した。これらは、それぞれサーファクチンモノカリウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１０４６．７３）、サーファクチンモノカリウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１０６０．７４）、サーファクチンモノカリウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１０７４．７６）、サーファクチンモノセシウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１１４０．６３）、サーファクチンモノセシウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１１５４．７０）、サーファクチンモノセシウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１１６８．７１）、サーファクチン二セシウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１２７２．６１）、サーファクチン二セシウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１２８６．６１）、およびサーファクチン二セシウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１３００．６３）であった。このうち、最もピーク強度の強かったのは、サーファクチンモノセシウム塩（ｎ＝１３，１４，１５）のプロトン付加体に由来するものであった。したがって、サーファクチンナトリウムは、セシウムイオンに加えて過剰のナトリウムイオンとカリウムイオンが共存する場合においても、セシウムイオンを選択的に捕捉できることが分かった。 As shown in the results shown in FIG. 3b, nine types of new molecular ion peaks were detected while there were three types of surfactin sodium. These are the molecular ion peak (1046.73) derived from the proton adduct of surfactin monopotassium salt (n = 13) and the molecular ion peak derived from the proton adduct of surfactin monopotassium salt (n = 14), respectively. (1060.74), molecular ion peak (1074.76) derived from the proton adduct of surfactin monopotassium salt (n = 15), molecule derived from the proton adduct of surfactin monocesium salt (n = 13) Ion peak (1140.63), molecular ion peak derived from proton adduct of surfactin monocesium salt (n = 14), derived from proton adduct of surfactin monocesium salt (n = 15) Molecular ion peak (1168.71), surfactin dicesium salt (n = 13) Molecular ion peak (1272.61) derived from the proton adduct of, and molecular ion peak (1286.61) derived from the proton adduct of surfactin dicesium salt (n = 14), and surfactin dicesium salt (n = 15) was a molecular ion peak (1300.63) derived from the proton adduct. Among these, the strongest peak intensity was derived from the proton adduct of surfactin monocesium salt (n = 13, 14, 15). Therefore, it was found that surfactin sodium can selectively capture cesium ions even when excess sodium ions and potassium ions coexist in addition to cesium ions.
　実施例３
　サーファクチンがセシウムイオンを捕捉することに伴う分子構造の変化を、フーリエ変換赤外分光光度計（ＩＲ島津製作所）によって調べた。 Example 3
Changes in the molecular structure associated with surfactin capturing cesium ions were examined using a Fourier transform infrared spectrophotometer (IR Shimadzu Corporation).
　サーファクチンナトリウム単独の水溶液（１ｍＭ）、および、サーファクチンナトリウム（１ｍＭ）に２０倍モルの塩化セシウムを加えた水溶液を凍結乾燥によって溶媒を留去することで固体サンプルを調製し、これらを全反射測定法（ＡＴＲ法）によって測定した。結果を図４示す。 A solid sample was prepared by lyophilizing an aqueous solution of surfactin sodium alone (1 mM) and an aqueous solution of surfactin sodium (1 mM) added with 20-fold molar cesium chloride, and total reflection of these samples. It measured by the measuring method (ATR method). The results are shown in FIG.
　図４より、サーファクチンがセシウムイオンを捕捉すると、サーファクチンのラクトン環のカルボニル基の伸縮振動に由来する吸収（１７３７ｃｍ-1）と、サーファクチンの環状ペプチド骨格のカルボニル基の伸縮振動に由来する吸収（１６４４ｃｍ-1）が、サーファクチン単独の赤外吸収スペクトルと比べて低波数側にシフトすることがわかった。このことから、サーファクチンは、セシウムイオンをカルボニル基との水素結合によって強く認識していることが分かった。 From FIG. 4, when surfactin captures cesium ions, it is derived from absorption (1737 cm −1 ) derived from the stretching vibration of the carbonyl group of the lactone ring of surfactin and from the stretching vibration of the carbonyl group of the cyclic peptide skeleton of surfactin. It was found that the absorption (1644 cm −1 ) shifts to the lower wavenumber side compared to the infrared absorption spectrum of surfactin alone. This indicates that surfactin strongly recognizes cesium ions through hydrogen bonds with carbonyl groups.
　実施例４
　水溶液中でのサーファクチンとセシウムイオンとの相互作用を核磁気共鳴吸収スペクトル測定法（Ｂｒｕｋｅｒ社製，４００ＭＨｚ）によって検証した。 Example 4
The interaction between surfactin and cesium ions in an aqueous solution was verified by a nuclear magnetic resonance absorption spectrum measurement method (manufactured by Bruker, 400 MHz).
　まず、サーファクチンナトリウム（１ｍＭ）の重水溶液に対して炭酸セシウム（Ｃｓ2ＣＯ3）を徐々に添加することにより、サーファクチンナトリウムに対する炭酸セシウムの量を０．８倍モル、１．６倍モル、２．４倍モル、３．２倍モル、４．０倍モル、４．８倍モル、８．０倍モルとし、サーファクチンの水素原子核に由来する吸収スペクトルの変化を追跡した。結果を図５に示す。 First, by gradually adding cesium carbonate (Cs 2 CO 3 ) to a heavy aqueous solution of surfactin sodium (1 mM), the amount of cesium carbonate relative to surfactin sodium is 0.8 times mol and 1.6 times mol. Changes in absorption spectrum derived from hydrogen nuclei of surfactin were traced to 2.4-fold mole, 3.2-fold mole, 4.0-fold mole, 4.8-fold mole, and 8.0-fold mole. The results are shown in FIG.
　図５より、セシウムイオンを加えていくと、サーファクチンのカルボニル基に隣接するメチレンの水素原子核に由来する吸収ピーク（δ＝２．４８ｐｐｍ）は変化し、０．８倍モル以上では、２種類の異なるピークが新たに観察された。これらはそれぞれサーファクチンのナトリウム塩とサーファクチンのセシウム塩に由来するピークであり、これらが異なる化学シフト値を与えたことから、重水中でもサーファクチンセシウムが存在することが確認された。 As shown in FIG. 5, when cesium ions are added, the absorption peak (δ = 2.48 ppm) derived from the hydrogen nucleus of methylene adjacent to the carbonyl group of surfactin changes. Different peaks were observed. These were peaks derived from the sodium salt of surfactin and the cesium salt of surfactin, and these gave different chemical shift values, confirming the presence of surfactin cesium in heavy water.
　比較例２
　次に、ＳＤＳとセシウムイオンの水中における相互作用を核磁気共鳴吸収スペクトル測定によって検証した。 Comparative Example 2
Next, the interaction of SDS and cesium ions in water was verified by nuclear magnetic resonance absorption spectrum measurement.
　ＳＤＳ（１０ｍＭ）の重水溶液に対して炭酸セシウムを徐々に添加することにより、ＳＤＳに対する炭酸セシウムの量を０．５倍モル、１倍モル、１．５倍モル、２．６倍モルとし、ＳＤＳの水素原子核に由来する吸収スペクトルの変化を追跡した。結果を図６に示す。 By gradually adding cesium carbonate to a heavy aqueous solution of SDS (10 mM), the amount of cesium carbonate relative to SDS is 0.5 times mol, 1 time mol, 1.5 times mol, 2.6 times mol, Changes in absorption spectra derived from SDS hydrogen nuclei were followed. The results are shown in FIG.
　図６に示すとおり、ＳＤＳのスルホン酸基に隣接するメチレンの水素原子核の吸収ピーク（δ＝３．９０ｐｐｍ）は、セシウムイオンを加えていくと、化学シフト値がわずかに変化（δ＝０．０１ｐｐｍ）するだけで、サーファクチンのように、異なる２種類の吸収ピークを与えることはなかった。このことから、ＳＤＳの場合は、セシウムイオンの捕捉能がほとんどなく、サーファクチンと異なり重水中でセシウムイオンとほとんど相互作用していないことが明らかにされた。 As shown in FIG. 6, the chemical shift value of the absorption peak (δ = 3.90 ppm) of the hydrogen nucleus of methylene adjacent to the sulfonic acid group of SDS slightly changes (δ = 0.0 ppm) as cesium ions are added. 01 ppm) did not give two different absorption peaks unlike surfactin. From this, in the case of SDS, it was clarified that there was almost no ability to capture cesium ions, and unlike surfactin, there was almost no interaction with cesium ions in heavy water.
　実施例５
　実際にサーファクチンにより除去される水中のセシウムイオンの割合（除去率）について検証した。 Example 5
The ratio (removal rate) of cesium ions in water actually removed by surfactin was verified.
　サーファクチン（１ｍＭ）と塩化セシウム（１ｍＭ）を超純水２ｍＬに溶解し、室温で静置した。その後、混合物から水だけを凍結乾燥によって取り除いて固体を得た。この固体にクロロホルム２０ｍＬを加えると、溶解成分と不溶固体との混合物が得られた。クロロホルムに溶解した成分は、サーファクチンのナトリウム塩とセシウム塩の混合物（サーファクチン塩）である。一方、不溶固体成分は、塩化ナトリウムと塩化セシウムの混合物（無機塩）である。これらをガラス濾過器によって濾別した。ガラス濾過器の細孔を通過した濾液成分（サーファクチン塩）について、ロータリーエバポレーターで減圧乾燥することによりさらに固体を得た。一方、ガラスフィルター上に残った不溶固体成分（無機塩）については、超純水（５０ｍＬ）で洗浄することで回収した。得られた両成分に含まれるセシウムイオンを、誘導結合プラズマ質量分析法（Ａｇｉｌｅｎｔ社製，製品名「７７００ｘ」）によって定量した。結果を表１に示す。 Surfactin (1 mM) and cesium chloride (1 mM) were dissolved in 2 mL of ultrapure water and allowed to stand at room temperature. Thereafter, only water was removed from the mixture by lyophilization to obtain a solid. When 20 mL of chloroform was added to this solid, a mixture of a dissolved component and an insoluble solid was obtained. The component dissolved in chloroform is a mixture of surfactin sodium salt and cesium salt (surfactin salt). On the other hand, the insoluble solid component is a mixture (inorganic salt) of sodium chloride and cesium chloride. These were separated by a glass filter. The filtrate component (surfactin salt) that passed through the pores of the glass filter was further dried under reduced pressure using a rotary evaporator to obtain a solid. On the other hand, the insoluble solid component (inorganic salt) remaining on the glass filter was recovered by washing with ultrapure water (50 mL). Cesium ions contained in both components thus obtained were quantified by inductively coupled plasma mass spectrometry (manufactured by Agilent, product name “7700x”). The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000004
 　表１に示す結果のとおり、サーファクチンのセシウムイオンの捕捉率は９７％に達した。一方、サーファクチンを加えずに同様の処理をした場合、セシウムイオンの捕捉率はわずか２％であった。このことから、サーファクチンによってセシウムイオンを極めて高い捕捉率で回収可能であることが分かった。
Figure JPOXMLDOC01-appb-T000004
 As shown in Table 1, the cesium ion capture rate of Surfactin reached 97%. On the other hand, when the same treatment was performed without adding surfactin, the capture rate of cesium ions was only 2%. From this, it was found that cesium ions can be recovered with an extremely high capture rate by surfactin.
　実施例６
　限外濾過膜によるサーファクチン塩の濃縮を検討した。 Example 6
Concentration of surfactin salt by ultrafiltration membrane was investigated.
　サーファクチンナトリウム（１ｍＭ）と塩化セシウム（１ｍＭ）を超純水１０ｍＬに溶解した。この溶液（０．５ｍＬ）を、分画分子量が３０００の限界濾過膜（ミリポア社製，製品名「アミコンウルトラ」，孔径：５ｎｍ以下）をセットした１．５ｍＬ用のチューブに入れ、遠心分離機（トミー精工社製，製品名「ＭＸ－３０１」）のアングルローターにセットし、２５℃、４０００ｇで３０分間遠心式限外濾過を行った。遠心濾過によって濃縮された濃縮成分と、限外濾過膜を通過した濾液成分を分画し、紫外可視吸収スペクトル測定（日本分光社製，製品名「Ｖ－５６０」）により、それぞれにおけるサーファクチン塩を定量した。濃縮成分と濾液成分は、それぞれ１００ｍＬのメスフラスコに移し、超純水で希釈したものを測定し、サーファクチン塩の含有量は、２３０ｎｍの吸光度の値を基に検量線を作成して算出した。結果を表２に示す。 Surfactin sodium (1 mM) and cesium chloride (1 mM) were dissolved in 10 mL of ultrapure water. This solution (0.5 mL) was put in a 1.5 mL tube set with a ultrafiltration membrane having a molecular weight cut-off of 3000 (manufactured by Millipore, product name “Amicon Ultra”, pore size: 5 nm or less), and centrifuged. (Tomy Seiko Co., Ltd., product name “MX-301”) was set on an angle rotor, and centrifugal ultrafiltration was performed at 25 ° C. and 4000 g for 30 minutes. The concentrated components concentrated by centrifugal filtration and the filtrate components that passed through the ultrafiltration membrane were fractionated, and UV-visible absorption spectrum measurement (manufactured by JASCO Corporation, product name “V-560”) was used to determine the surfactin salt in each. Was quantified. The concentrated component and the filtrate component were each transferred to a 100 mL volumetric flask and measured by dilution with ultrapure water, and the content of surfactin salt was calculated by creating a calibration curve based on the absorbance value at 230 nm. . The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000005
 　表２に示す結果のとおり、限外濾過により、溶液に含まれていたサーファクチン塩の９０％が濃縮成分中に残っており、濾別できたことが明らかとなった。
Figure JPOXMLDOC01-appb-T000005
 As shown in Table 2, it was revealed that 90% of the surfactin salt contained in the solution remained in the concentrated component by ultrafiltration and could be separated by filtration.
　また、実際に濃縮成分にサーファクチンセシウムが含まれていることを検証するため、マトリックス支援レーザー脱離イオン化質量分析装置（ＭＡＬＤＩ－ＴＯＦＭＳ：Ｂｒｕｋｅｒ社製，製品名「ａｕｔｏｆｌｅｘ　ｓｐｅｅｄ」）を使って分析した。遠心分離後の濃縮成分（２．５μＬ）とマトリックスであるシナピン酸（シグマアルドリッチ社製）の飽和溶液（水：アセトニトリル：トリフルオロ酢酸＝９９：１：０．１）２．５μＬをプレート上で混合し、乾燥させたものを測定した。なお、対照実験として、濾液成分も同様に測定した。その結果、濃縮成分からは、サーファクチンモノセシウム塩（ｎ＝１３）のプロトン付加体に由来する分子イオンピーク（１１４０．４０）、サーファクチンモノセシウム塩（ｎ＝１４）のプロトン付加体に由来する分子イオンピーク（１１５４．４２）、サーファクチンモノセシウム塩（ｎ＝１５）のプロトン付加体に由来する分子イオンピーク（１１６８．４３）が検出された。一方、濾液成分からは、サーファクチンセシウムに由来する分子イオンピークは検出されなかった。 In addition, in order to verify that surfactin cesium is actually contained in the concentrated component, analysis was performed using a matrix-assisted laser desorption / ionization mass spectrometer (MALDI-TOFMS: manufactured by Bruker, product name “autoflex speed”). did. 2.5 μL of a concentrated solution (2.5 μL) after centrifugation and a saturated solution of sinapic acid (manufactured by Sigma Aldrich) (water: acetonitrile: trifluoroacetic acid = 99: 1: 0.1) as a matrix on the plate What was mixed and dried was measured. As a control experiment, the filtrate components were also measured in the same manner. As a result, from the concentrated component, molecular ion peak (1140.40) derived from the proton adduct of surfactin monocesium salt (n = 13), derived from the proton adduct of surfactin monocesium salt (n = 14) Molecular ion peak (1164.43) derived from the proton adduct of surfactin monocesium salt (n = 15) was detected. On the other hand, no molecular ion peak derived from surfactin cesium was detected from the filtrate component.
　以上の結果より、サーファクチンセシウムは、限外濾過処理によって効率的に分離濃縮できることが分かった。 From the above results, it was found that surfactin cesium can be efficiently separated and concentrated by ultrafiltration treatment.
　実施例７
　サーファクチン塩に限外濾過膜を組み合わせた水中のセシウムイオン除去について検証した。 Example 7
We verified the removal of cesium ions in water by combining a surfactin salt with an ultrafiltration membrane.
　サーファクチンナトリウム（ＳＦＮａ）と塩化セシウムを、サーファクチンナトリウムとセシウムイオンとの割合が表３のとおりになるよう、超純水と混合した。得られた水溶液（０．５ｍＬ）を、分画分子量が３０００の限外濾過膜（ミリポア社製，製品名「アミコンウルトラ」，孔径：５ｎｍ以下）をセットした１．５ｍＬ用のチューブに入れ、遠心分離機（トミー精工社製，製品名「ＭＸ－３０１」）を用いて、２５℃、４０００Ｇで３０分間遠心式限外濾過を行った。遠心式限外濾過によって濃縮された濃縮液と、限外濾過膜を通過した濾液液を分画し、双方に含まれるセシウムイオンの濃度を、誘導結合プラズマ質量分析装置（ＩＣＰ－ＭＳ）（Ａｇｉｌｅｎｔ社製，製品名「７７００ｘ」）によって定量した。結果を表３に示す。なお、セシウム捕捉率は、全体のセシウム含有量に対する濃縮液成分に含まれるセシウム含有量の割合として計算した。また、サーファクチンナトリウムとセシウムイオンの比は質量比である。 Surfactin sodium (SFNa) and cesium chloride were mixed with ultrapure water so that the ratio of surfactin sodium and cesium ions was as shown in Table 3. The obtained aqueous solution (0.5 mL) was put into a 1.5 mL tube in which an ultrafiltration membrane having a molecular weight cut-off of 3000 (Millipore, product name “Amicon Ultra”, pore size: 5 nm or less) was set, Centrifugal ultrafiltration was performed at 25 ° C. and 4000 G for 30 minutes using a centrifuge (product name “MX-301” manufactured by Tommy Seiko Co., Ltd.). The concentrated solution concentrated by centrifugal ultrafiltration and the filtrate that has passed through the ultrafiltration membrane are fractionated, and the concentration of cesium ions contained in both is determined by an inductively coupled plasma mass spectrometer (ICP-MS) (Agilent). Quantitatively according to the product name “7700x”). The results are shown in Table 3. In addition, the cesium capture | acquisition rate was computed as a ratio of the cesium content contained in the concentrate component with respect to the whole cesium content. The ratio of surfactin sodium to cesium ions is a mass ratio.
Figure JPOXMLDOC01-appb-T000006
 　表３に示す結果のとおり、サーファクチン塩と限外濾過膜を組み合わせることにより水中のセシウムイオンを効率的に分離し、高い捕捉率で回収可能であることが実証された。特に、ＳＦＮａのセシウムイオンの捕捉率は、ＳＦＮａ／Ｃｓ+＝２．５／１の際に９０％にも達した。なお、サーファクチン塩の分子量は約１０００であるが、分画分子量が３０００の限外濾過膜でセシウムイオンを分離できた理由としては、サーファクチン塩が水中で巨大ミセルを形成し、その中にセシウムイオンを取り込んでいることが考えられる。
Figure JPOXMLDOC01-appb-T000006
 As shown in Table 3, it was demonstrated that cesium ions in water can be efficiently separated by combining a surfactin salt and an ultrafiltration membrane, and can be recovered with a high capture rate. In particular, the capture rate of cesium ions in SFNa reached 90% when SFNa / Cs + = 2.5 / 1. The molecular weight of the surfactin salt is about 1000, but the reason why the cesium ions could be separated with an ultrafiltration membrane with a molecular weight cut off of 3000 was that the surfactin salt formed huge micelles in water. It is possible that cesium ions are taken in.
　比較例３
　上記実施例７において、サーファクチンナトリウムの代わりに、汎用界面活性剤であるドデシル硫酸ナトリウム（ＳＤＳ）の１ｍＭ（０．０３ｗｔ％）水溶液を用いた以外は同様にして、実験を行った。結果を表４に示す。なお、セシウム捕捉率は、全体のセシウム含有量に対する濃縮液成分に含まれるセシウム含有量の割合として計算した。 Comparative Example 3
In Example 7, the experiment was conducted in the same manner except that 1 mM (0.03 wt%) aqueous solution of sodium dodecyl sulfate (SDS), which is a general-purpose surfactant, was used instead of Surfactin sodium. The results are shown in Table 4. In addition, the cesium capture | acquisition rate was computed as a ratio of the cesium content contained in the concentrate component with respect to the whole cesium content.
Figure JPOXMLDOC01-appb-T000007
 　表４に示す結果から明らかなように、ＳＤＳを用いた場合、セシウムイオンの捕捉率はわずかに２８％であった。これは、ＳＤＳがセシウムイオンと有意な相互作用を示さないことと、生成するＳＤＳのミセルの粒径が小さいためである。上記実施例７でＳＦＮａ／Ｃｓ+＝１／１の場合と比較しても、その効果の違いは明らかである。
Figure JPOXMLDOC01-appb-T000007
 As is clear from the results shown in Table 4, when SDS was used, the capture rate of cesium ions was only 28%. This is because SDS does not show a significant interaction with cesium ions, and the SDS micelles produced have a small particle size. Even when compared with the case of SFNa / Cs + = 1/1 in Example 7, the difference in the effect is clear.
　以上の結果から、ＳＤＳにはセシウムイオンを十分に捕捉する能力は無い一方で、ＳＦＮａと限外濾過膜との組み合わせによってセシウムイオンを極めて高い捕捉率で回収可能であることが分かった。 From the above results, it was found that while SDS does not have the ability to sufficiently capture cesium ions, cesium ions can be recovered with a very high capture rate by the combination of SFNa and an ultrafiltration membrane.
　実施例８
　種々のアルカリ金属塩（ＮａＣｌ、ＫＣｌ、ＣｓＣｌ）共存下での限外濾過膜により除去される水中のセシウムイオンの割合（捕捉率）について検証した。 Example 8
The ratio (capture rate) of cesium ions in water removed by an ultrafiltration membrane in the presence of various alkali metal salts (NaCl, KCl, CsCl) was examined.
　サーファクチンナトリウム（ＳＦＮａ）を超純水に溶解し、１．０ｍＭ（約０．１ｗｔ％）、２．５ｍＭ（約０．２５ｗｔ％）および５．０ｍＭ（約０．５０ｗｔ％）の水溶液を調製した。各水溶液に、塩化ナトリウム（１ｍＭ）、塩化カリウム（１ｍＭ）および塩化セシウム（１ｍＭ）をそれぞれ加えた。各溶液（０．５ｍＬ）を、分画分子量が３０００の限外濾過膜（ミリポア社製，製品名「アミコンウルトラ」，孔径：５ｎｍ以下）をセットした１．５ｍＬ用のチューブに入れ、遠心分離機（トミー精工社製，製品名「ＭＸ－３０１」）を用いて、２５℃、４０００Ｇで３０分間遠心式限外濾過を行った。遠心式限外濾過によって濃縮された濃縮液と、限外濾過膜を通過した濾液液を分画し、双方に含まれるセシウムイオンを、誘導結合プラズマ質量分析装置（Ａｇｉｌｅｎｔ社製，製品名「７７００ｘ」）によって定量した。結果を表５に示す。なお、セシウム捕捉率は、全体のセシウム含有量に対する濃縮液成分に含まれるセシウム含有量の割合として計算した。 Surfactin sodium (SFNa) is dissolved in ultrapure water, and aqueous solutions of 1.0 mM (about 0.1 wt%), 2.5 mM (about 0.25 wt%) and 5.0 mM (about 0.50 wt%) are prepared. did. Sodium chloride (1 mM), potassium chloride (1 mM), and cesium chloride (1 mM) were added to each aqueous solution. Each solution (0.5 mL) was placed in a 1.5 mL tube set with an ultrafiltration membrane (Millipore, product name “Amicon Ultra”, pore size: 5 nm or less) with a molecular weight cut-off of 3000, and centrifuged. Centrifugal ultrafiltration was performed at 25 ° C. and 4000 G for 30 minutes using a machine (manufactured by Tommy Seiko, product name “MX-301”). The concentrated solution concentrated by centrifugal ultrafiltration and the filtrate that has passed through the ultrafiltration membrane are fractionated, and cesium ions contained in both are separated by an inductively coupled plasma mass spectrometer (manufactured by Agilent, product name “7700 × )). The results are shown in Table 5. In addition, the cesium capture | acquisition rate was computed as a ratio of the cesium content contained in the concentrate component with respect to the whole cesium content.
Figure JPOXMLDOC01-appb-T000008
 　表５に示す結果から明らかなように、サーファクチンナトリウムは、セシウムイオンに加えてナトリウムイオンとカリウムイオンなど他のカチオンが共存する場合においても、限外濾過膜との組み合わせによってセシウムイオンを選択的に回収できることが分かった。
Figure JPOXMLDOC01-appb-T000008
 As is apparent from the results shown in Table 5, surfactin sodium is selective for cesium ions by combination with an ultrafiltration membrane even when sodium ions and other cations such as potassium ions coexist in addition to cesium ions. It was found that it can be recovered.

Claims (4)

  1. 　放射性セシウムを含む汚染水を浄化するための方法であって、
    　当該汚染水に下記式（Ｉ）で表されるサーファクチンの塩を添加し、放射性セシウムと結合させ、サーファクチンのセシウム塩とする工程を含むことを特徴とする放射性セシウム汚染水の浄化方法。
    Figure JPOXMLDOC01-appb-C000001
    ［式中、
    　Ｘは、ロイシン、イソロイシンおよびバリンから選択されるアミノ酸残基を示し；
    　ＲはＣ9-18アルキル基を示し；
    　Ｍは、水素原子、アルカリ金属イオンまたはアンモニウムイオンを示すが、少なくとも一方のＭはアルカリ金属イオンまたはアンモニウムイオンであるとする］     A method for purifying contaminated water containing radioactive cesium,
    A method for purifying radioactive cesium-contaminated water, comprising a step of adding a surfactin salt represented by the following formula (I) to the contaminated water and combining it with radioactive cesium to form a cesium salt of surfactin.
    Figure JPOXMLDOC01-appb-C000001
    [Where:
    X represents an amino acid residue selected from leucine, isoleucine and valine;
    R represents a C 9-18 alkyl group;
    M represents a hydrogen atom, an alkali metal ion or an ammonium ion, and at least one M is an alkali metal ion or an ammonium ion]
  2. 　上記汚染水に対して０．００３質量％以上のサーファクチン塩（Ｉ）を添加する請求項１に記載の放射性セシウム汚染水の浄化方法。 The method for purifying radioactive cesium-contaminated water according to claim 1, wherein 0.003% by mass or more of Surfactin salt (I) is added to the contaminated water.
  3. 　さらに、サーファクチンのセシウム塩を分離する工程を含む請求項１または２に記載の放射性セシウム汚染水の浄化方法。 The method for purifying radioactive cesium-contaminated water according to claim 1 or 2, further comprising a step of separating a cesium salt of surfactin.
  4. 　限外濾過によりサーファクチンのセシウム塩を分離する請求項３に記載の放射性セシウム汚染水の浄化方法。 The method for purifying radioactive cesium-contaminated water according to claim 3, wherein the cesium salt of surfactin is separated by ultrafiltration.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008512468A (en) * 2004-09-10 2008-04-24 ノボザイムス ノース アメリカ，インコーポレイティド Biofilm prevention, removal, reduction or destruction methods
WO2013065744A1 (en) * 2011-10-31 2013-05-10 株式会社カネカ Decontamination agent and decontamination method using same
JP2014016301A (en) * 2012-07-11 2014-01-30 Binos Corp Method and system for decontaminating object contaminated by radioactive material

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008512468A (en) * 2004-09-10 2008-04-24 ノボザイムス ノース アメリカ，インコーポレイティド Biofilm prevention, removal, reduction or destruction methods
WO2013065744A1 (en) * 2011-10-31 2013-05-10 株式会社カネカ Decontamination agent and decontamination method using same
JP2014016301A (en) * 2012-07-11 2014-01-30 Binos Corp Method and system for decontaminating object contaminated by radioactive material

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