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論文

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

吉越 章隆; 塩飽 秀啓; 小林 徹; 下山 巖; 松村 大樹; 辻 卓也; 西畑 保雄; 小暮 敏博*; 大河内 拓雄*; 保井 晃*; et al.

Applied Physics Letters, 112(2), p.021603_1 - 021603_5, 2018/01

放射光光電子顕微鏡(SR-PEEM)を人工的にCs吸着したミクロンサイズの風化黒雲母微粒子のピンポイント分析に適用した。絶縁物にもかかわらず、チャージアップの影響無しに構成元素(Si, Al, Cs, Mg, Fe)の空間分布を観察できた。Csが粒子全体に分布することが分かった。Cs M$$_{4,5}$$吸収端近傍のピンポイントX線吸収分光(XAS)から、1価の陽イオン状態(Cs$$^{+}$$)であることがわかった。さらに、Fe L$$_{2,3}$$吸収端の測定から、Feの価数状態を決定した。我々の結果は、サンプルの伝導性に左右されること無く、SR-PEEMがさまざまな環境試料に対するピンポイント化学分析法として利用可能であることを示すものである。

論文

Proposed cesium-free mineralization method for soil decontamination; Demonstration of cesium removal from weathered biotite

本田 充紀; 下山 巖; 小暮 敏博*; 馬場 祐治; 鈴木 伸一; 矢板 毅

ACS Omega (Internet), 2(12), p.8678 - 8681, 2017/12

The possibility to remove sorbed cesium (Cs) from weathered biotite (WB), which is considered a major Cs-adsorbent in the soil of Fukushima, has been investigated by the addition of NaCl-CaCl$$_{2}$$ mixed salt and subsequent heat treatment in a low pressure. X-ray fluorescence analysis was employed to determine the Cs removal rate with elevated temperature. The structural changes and new phases formed were determined using powder X-ray diffraction, as well as electron diffraction and X-ray microanalysis in a transmission electron microscope. We found that Cs was completely removed from the specimen heated at 700 $$^{circ}$$C, when WB completely decomposed and augite with a pyroxene structure was formed. On the basis of this finding, we propose the cesium-free mineralization (CFM) method, a new soil decontamination process by means of transformation of Cs-sorbing minerals to those where Cs is impossible to be incorporated, by heating with certain additives.

論文

Comparison of the extractabilities of tetrachloro- and tetrabromopalladate(II) ions with a thiodiglycolamide compound

成田 弘一*; 前田 泰生*; 所 千晴*; 鈴木 智也*; 田中 幹也*; 元川 竜平; 塩飽 秀啓; 矢板 毅

Analytical Sciences, 33(11), p.1305 - 1309, 2017/11

Using $$N,N,N',N'$$-tetra-2-ethylhexyl-thiodiglycolamide (TEHTDGA) in $$n$$-dodecane as the extractant, we compared the percentages of Pd(II) extracted from HCl and HBr solutions, and analyzed the structures of the Pd(II)-extractant complexes. TEHTDGA rapidly extracted Pd(II) from both HCl and HBr solutions, predominantly by formation of a 1:2 Pd(II)/TEHTDGA complex. The extractability of Pd(II) from HBr solution was inferior to that from HCl solution. FT-IR spectroscopy and EXAFS measurements indicated that two of the halide ions in the tetrachloro- or tetrabromopalladate(II) ions were replaced by the sulfur atoms of two TEHTDGA molecules. In the [PdBr$$_{2}$$(TEHTDGA)$$_{2}$$] complex, the Pd-S bond was shorter than the Pd-Br bond. We suggest that this bond length difference resulted in greater steric hindrance during coordination of TEHTDGA to the Pd(II) atom in the HBr system than in the HCl system, leading to the lower extractability in the HBr system.

論文

1F事故による環境回復に伴う廃棄物の管理と除去土壌の減容・再生利用の取り組み,2; 再生利用を目指した粘土鉱物へのCs吸脱着機構解明

矢板 毅

日本原子力学会誌, 59(8), p.441 - 443, 2017/08

減容化に関する技術としては、これまで環境浄化などで用いられてきた処理法である分級、化学処理、熱処理などいくつかの方法論が考えられるが、それぞれに一長一短が有り、放射性Csの処理という視点で再度見直し、最適化する必要があると考えられる。本特集では、特に対象となる粘土鉱物への吸着機構について最新の知見について紹介すると共に、これらの情報を参考に開発を試みている除染および土壌の再生利用などについて解説する。

論文

福島の環境回復に向けた取り組み,4; 汚染土壌の除染、減容化および再生利用を目指した物理処理及び新しい熱処理法開発への試み

矢板 毅; 本田 充紀; 下山 巖; 伊藤 健一*; 万福 裕蔵*; 辻 卓也; 松村 大樹

日本原子力学会誌, 59(8), p.483 - 487, 2017/08

福島第一原子力発電所事故後に伴う環境汚染に対して事故からの復興に向けて取り組んだ減容化除染と再生利用に関する研究の取り組みについて、日本原子力研究開発機構と国立環境研究所が取り組んできた吸着機構の基礎から物理的除染および減容化と熱処理に関する研究を紹介した内容である。一般的な物理処理、熱処理に関する紹介に加え、粘土鉱物へのセシウムの取り込みメカニズムや溶融処理のその場観察を放射光X線分光を利用した研究により詳細に解説している。

論文

Local structure and distribution of remaining elements inside extraction chromatography adsorbents

渡部 創; 佐野 雄一; 塩飽 秀啓; 矢板 毅; 大野 真平*; 新井 剛*; 松浦 治明*; 江夏 昌志*; 佐藤 隆博*

Nuclear Instruments and Methods in Physics Research B, 404, p.202 - 206, 2017/08

Extraction chromatography is one of the most promising technology for minor actinide (MA(III): Am and Cm) recovery from high level liquid waste generated in the reprocessing. A brand-new adsorbent proposed by our group are expected to achieve more efficient MA(III) recovery than usual procedure. Fundamental MA(III) adsorption/elution performances of the adsorbents have been demonstrated. An appropriate washing process of lanthanides (Ln(III)) is necessary to be established to design a process flow. In this study, chemical state and distribution of Eu inside the adsorbent before and after contacting with candidate eluents for MA(III) or Ln(III) were evaluated by EXAFS measurements and micro-PIXE analysis, respectively. Two-dimensional PIXE images showed that adsorbed Eu and residual Eu after contacting with the eluents for MA(III) were uniformly distributed on the particle. However, EXAFS oscillation revealed that local structure around Eu drastically changes by the contact. Those results suggest that the Eu remained inside the particle without distinct shift and that they form various complexes with extractants in the particle.

論文

A Chemiluminescence sensor with signal amplification based on a self-immolative reaction for the detection of fluoride ion at low concentrations

久松 秀悟; 鈴木 伸一; 幸本 重男*; 岸川 圭希*; 山本 雄介*; 元川 竜平; 矢板 毅

Tetrahedron, 73(27-28), p.3993 - 3998, 2017/07

 被引用回数:3

A sensory system incorporated with an amplification function was developed for detection of trace-level fluoride ions. This sensory system comprises two steps, namely, amplification, and chemiluminescence. These steps were linked with chemical reactions and were induced continuously. The process from amplification to chemiluminescence was accomplished in the system by using fluoride ions. The amplification was based on a self-immolative system, which permitted the detection of emissions even at low fluoride ion concentration for system in which chemiluminescence cannot be induced in the absence of fluoride ions. An optical ratio of the chemiluminescent compound and the amplifier was calculated for achieving efficient amplification.

論文

福島汚染土壌の除染と再利用のためのセシウムフリー鉱化法の開発

下山 巖; 本田 充紀; 小暮 敏博*; 馬場 祐治; 平尾 法恵*; 岡本 芳浩; 矢板 毅; 鈴木 伸一

Photon Factory News, 35(1), p.17 - 22, 2017/05

福島放射性汚染土壌のCs除染と再生利用に対して提案しているセシウムフリー鉱化法(CFM)について紹介すると共に、PFのJAEA放射光ビームラインで実施している研究について報告する。本研究では風化黒雲母(WB)からのCs脱離機構を調べるため、非放射性Csを収着させたWBにNaCl-CaCl$$_{2}$$混合塩を添加し、低圧加熱処理前後での組成と構造変化を調べた。蛍光X線分析により塩無添加の場合でも700$$^{circ}$$Cで約3割のCsが除去され、塩添加時はほぼ全てのCsとKが除去された。一方、Caは温度と共に増加し、700$$^{circ}$$CではSiよりも多い主成分となった。さらにX線回折法、透過型電子顕微鏡による分析によりWBが普通輝石などの異なるケイ酸塩鉱物に相変化することを明らかにした。これらの結果は相変化に伴ってイオン半径の大きい1価陽イオンが排出されるメカニズムを示唆しており、我々はこれに基づいてCFMの着想に至った。また、X線吸収分光法を用いたClの化学状態分析により、塩由来のClが反応の初期段階で粘土鉱物の酸素とCl-O結合を形成しながら生成物の鉱物中に取り込まれることを明らかにした。

論文

Selective extraction of Pt(IV) over Fe(III) from HCl with an amide-containing tertiary amine compound

前田 泰生*; 成田 弘一*; 所 千晴*; 田中 幹也*; 元川 竜平; 塩飽 秀啓; 矢板 毅

Separation and Purification Technology, 177, p.176 - 181, 2017/04

The separation properties of Pt(IV) over Fe(III) in HCl solutions using $$N$$-2-ethylhexyl-bis($$N$$-di-2-ethylhexyl-ethylamide)amine (EHBAA) were investigated and then compared with those using the conventional extractant tri-$$n$$-octylamine (TOA). Also, the structural analyses of Pt(IV) in both of the aqueous (HCl solution) and organic (EHBAA in $$n$$-dodecane-2-ethylhexanol solution) phases were performed with EXAFS spectroscopy. The extractability of Pt(IV) was much higher with EHBAA than with TOA in the studied HCl concentration range (0.2-0.8 M HCl); additionally, EHBAA selectively extracted Pt(IV) over Fe(III) under the condition of [EHBAA] $$leq$$ 0.1 M and [HCl] $$leq$$ 1 M. The Pt(IV) loading capacity of 0.1 M EHBAA was about 9.2 g/L (about 0.05 M). Most of the Pt(IV) extracted with 0.1 M EHBAA from 1 M HCl was stripped with 0.1 M NaOH; the co-extracted Fe(III) was selectively scrubbed with distilled water. The structural studies indicated that the Pt(IV) extracted with EHBAA from 1 M HCl formed an ion-pair complex, [PtCl$$_{6}$$]$$cdot$$(EHBAA$$cdot$$H)$$_{2}$$.

論文

Mechanism of Cs removal from Fukushima weathered biotite by heat treatment with a NaCl-CaCl$$_{2}$$ mixed salt

本田 充紀; 岡本 芳浩; 下山 巖; 塩飽 秀啓; 鈴木 伸一; 矢板 毅

ACS Omega (Internet), 2(2), p.721 - 727, 2017/02

 被引用回数:5

An in situ extended X-ray absorption fine structure (in situ EXAFS) spectroscopic analysis at high temperature was conducted to investigate the mechanism of Cs removal from weathered biotite (WB) from Fukushima, induced by heating with a mixed salt of NaCl and CaCl$$_{2}$$. This indicated that most Cs remained in WB during heating at 200-700$$^{circ}$$C. In addition, the in situ EXAFS spectra gradually changed on heating with the mixed salt and a completely different spectrum was observed for the sample after cooling from 700$$^{circ}$$C to room temperature. Ex situ EXAFS measurements and X-ray fluorescence analyses were also conducted on samples after heat treatment and removal of the mixed salt to clarify the temperature dependence of the Cs removal ratio. Based on the results of radial structure function analysis obtained from in situ EXAFS, we concluded that almost all Cs was removed from WB by heating at 700$$^{circ}$$C with the mixed salt, and that Cs formed CsCl bonds after cooling to room temperature from 700$$^{circ}$$C. In contrast, although more than half of the Cs present was removed from WB by heat treatment at 500$$^{circ}$$C, most Cs was surrounded by silica tetrahedrons, maintained by Cs-O bonds. On the basis of these results, different Cs removal processes are suggested for the high-temperature (600-700$$^{circ}$$C) and low-temperature (400-500$$^{circ}$$C) regions.

論文

Mineralogical characterization of radioactive particles from Fukushima soil using $$mu$$-XRD with synchrotron radiation

甕 聡子*; 向井 広樹*; 綿貫 徹; 大和田 謙二; 福田 竜生; 町田 晃彦; 倉又 千咲*; 菊池 亮佑*; 矢板 毅; 小暮 敏博*

Journal of Mineralogical and Petrological Sciences, 111(5), p.305 - 312, 2016/10

 被引用回数:7

福島土壌粒子から放射能をもつ粒子を選び出し、50ミクロン程度の粒子一粒ごとに鉱物種の同定を放射光X線回折によって行った。板状の風化雲母の粒については様々な度合のバーミキュライト化されたものが見出された。ごく微粒子の塊である土壌粒子からは、長石や石英に加えてスメクタイト状の粘土鉱物が検出された。

論文

Small-angle neutron scattering study of specific interaction and coordination structure formed by mono-acetyl-substituted dibenzo-20-crown-6-ether and cesium ions

元川 竜平; 小林 徹; 遠藤 仁*; 池田 隆司; 矢板 毅; 鈴木 伸一; 成田 弘一*; 阿久津 和宏*; Heller, W. T.*

Journal of Nuclear Science and Technology, 53(8), p.1205 - 1211, 2016/08

This study uses small-angle neutron scattering (SANS) to elucidate the coordination structure of the complex of mono-acetyl substituted dibenzo-20-crown-6-ether (ace-DB20C6) with Cs. SANS profiles obtained for the complex of ace-DB20C6 and Cs (ace-DB20C6/Cs) in deuterated dimethyl sulfoxide indicated that Cs coordination resulted in a more compact structure than the free ace-DB20C6. The data were fit well with SANS profiles calculated using Debye function for scattering on an absolute scattering intensity scale. For this theoretical calculation of the scattering profiles, the coordination structure proposed based on a density functional theory calculation. Consequently, we conclude that the SANS analysis experimentally supports the proposed coordination structure of ace-DB20C6/Cs and suggests the following: (1) the complex of ace-DB20C6 and Cs is formed with an ace-DB20C6/Cs molar ratio of 1/1; (2) the two benzene rings of ace-DB20C6 fold around Cs above the center of the crown ether ring of ace-DB20C6.

論文

真空加熱による粘土鉱物からのセシウム脱離挙動; 放射光を用いたX線光電子分光法及び昇温脱離法による分析

平尾 法恵; 下山 巖; 馬場 祐治; 和泉 寿範; 岡本 芳浩; 矢板 毅; 鈴木 伸一

分析化学, 65(5), p.259 - 266, 2016/05

 被引用回数:3

福島原子力発電所事故後の放射能汚染の主な原因であるCsは土壌中の粘土鉱物に強く固定されており、土壌除染のため様々なCs除去法が開発されている。本手法は、乾式法によるCs除去法として、乾式法における処理温度の低減を目的とし、真空溶融塩処理法を提案する。非放射性Csを飽和収着させたバーミキュライトを真空加熱し、X線光電子分光法を用いて加熱前後のCs含有量変化を分析した。バーミキュライトのみを用いた場合は、800$$^{circ}$$C 3分間の加熱で約4割のCsが除去された。NaCl/CaCl$$_{2}$$混合塩をバーミキュライトに添加した場合は、450$$^{circ}$$C 3分間の加熱で約7割のCsが除去されることを見いだした。これらの結果から真空溶融塩処理法による大幅な処理温度の低下と除去効率の向上が期待できる。

論文

Encapsulation of cesium from contaminated water with highly selective facial organic-inorganic mesoporous hybrid adsorbent

Awual, M. R.; 宮崎 有史; 田口 富嗣; 塩飽 秀啓; 矢板 毅

Chemical Engineering Journal, 291, p.128 - 137, 2016/05

 被引用回数:36

A novel macrocyclic ligand of di-o-benzo-p-xylyl-28-crown-8-ether (DOBPX28C8) was prepared and successfully anchored onto the mesoporous silica for the fabrication of mesoporous hybrid adsorbent (MHA) using direct immobilization approach and serving as an efficient adsorbent for Cs removal. The high amount of K (7.69 mM) was slightly affected the Cs adsorption because the hydration radius of K is close to the Cs than that of the other cation of Na. Also the Cs adsorption efficiency was more higher even in the presence of 1,025 fold K and 1,739 fold Na, respectively. The functional group of DOBPX28C8 ligand embedded onto the mesoporous silica exhibited more conformational freedom, and the benzene ring in para position was consolidated for pai-electron orientation with expanding the ring size of DOBPX28C8 for easy capturing with high selectivity and adsorption ability towards the Cs.

論文

X-ray absorption fine structure at the cesium $$L$$3 absorption edge for cesium sorbed in clay minerals

本田 充紀; 下山 巖; 岡本 芳浩; 馬場 祐治; 鈴木 伸一; 矢板 毅

Journal of Physical Chemistry C, 120(10), p.5534 - 5538, 2016/03

 被引用回数:7

We present the use of near-edge X-ray absorption fine structure (NEXAFS) to investigate local electronic structures of cesium ions sorbed in two types of clay minerals (vermiculite and kaolinite) with a different capacity to fix Cs. NEXAFS is element specific because X-ray absorption edges of different elements have different energies. However, the energy of the Cs $$L$$3 absorption edge is close to that of the $$K$$-edge of titanium generally contained in clay minerals. Therefore, Cs $$L$$3-edge NEXAFS measurements of Cs in clay minerals have not yet succeeded. In this study, we successfully measured pure Cs $$L$$3-edge NEXAFS spectra for cesium sorbed in clay minerals by completely separating Ti $$K alpha$$ and Cs $$L alpha$$ fluorescence X-rays using a fluorescence method. We confirmed the peak intensity between vermiculite and kaolinite in the NEXAFS spectra. To clarify the identification of NEXAFS spectra, theoretical calculations were performed using the discrete variational X$$alpha$$ molecular orbital method (DV-X$$alpha$$), and peak identification was achieved. The difference in peak intensity was explained by the difference in the electron density of unoccupied molecular orbitals. We studied the influence of water molecules and found a change in the electron densities of unoccupied molecular orbitals caused by the coordination of water molecules.

論文

Cesium adsorption/desorption behavior of clay minerals considering actual contamination conditions in Fukushima

向井 広樹*; 廣瀬 農*; 甕 聡子*; 菊池 亮佑*; 田野井 慶太朗*; 中西 友子*; 矢板 毅; 小暮 敏博*

Scientific Reports (Internet), 6, p.21543_1 - 21543_7, 2016/02

 被引用回数:42

Cesium adsorption/desorption experiments for various clay minerals, considering actual contamination conditions in Fukushima, were conducted using the $$^{137}$$Cs radioisotope and an autoradiography using imaging plates (IPs). An aliquot containing 0.185 -1.85 Bq of $$^{137}$$Cs was dropped onto a substrate where various mineral particles were arranged. It was found that partially-vermiculitized biotite, which is termed "weathered biotite" (WB) in this study, from Fukushima sorbed $$^{137}$$Cs far more than the other clay minerals (fresh biotite, illite, smectite, kaolinite, halloysite, allophane, imogolite) on the same substrate. Cs-sorption to WB continued for about one day, whereas that to ferruginous smectite was completed within one hour. The sorbed $$^{137}$$Cs in WB was hardly leached with hydrochloric acid at pH 1, particularly in samples with a longer sorption time. The presence/absence of WB sorbing radiocesium is a key factor affecting the dynamics and fate of radiocesium in Fukushima.

論文

A Reliable hybrid adsorbent for efficient radioactive cesium accumulation from contaminated wastewater

Awual, M. R.; 矢板 毅; 宮崎 有史; 松村 大樹; 塩飽 秀啓; 田口 富嗣

Scientific Reports (Internet), 6, p.19937_1 - 19937_10, 2016/01

AA2015-0789.pdf:1.31MB

 被引用回数:37

A novel macrocyclic ligand of $$o$$-benzo-$$p$$-xylyl-22-crown-6-ether (OBPX22C6) was developed and successfully immobilized onto mesoporous silica for the preparation of hybrid adsorbent. The benzene ring $$pi$$ electron is the part of crown ether of OBPX22C6 for easy orientation of the macrocyclic compound for making the $$pi$$ electron donation with Cs complexation. The results clarified that the Cs removal process was rapid and reached saturation within a short time. Considering the effect of competitive ions, sodium did not markedly affect the Cs adsorption whereas potassium was slightly affected due to the similar ionic radii. Due to its high selectivity and reusability, significant volume reduction is expected as this promising hybrid adsorbent is used for Cs removal in Fukushima wastewater.

論文

分析化学における放射光の利用, 放射光分析の応用; 環境分析

岡本 芳浩; 矢板 毅

ぶんせき, 2015(11), p.478 - 485, 2015/11

放射光を利用した分析化学の中で、環境試料を対象とした放射光分析の応用を紹介した。環境試料を、(1)どのような元素から構成されているかが分からない、(2)どのような化学形で存在しているかが分からない、(3)どのように分布しているかが分からない、の3つの視点から、放射光を使い分析している現況を解説した。それらを実現する手法として、蛍光X線分析とそれを使用した蛍光XAFS、最近利用が広がりつつあるイメージングXAFSとその応用、実際に使用された例を題材として取り上げて説明した。

論文

Schiff based ligand containing nano-composite adsorbent for optical copper(II) ions removal from aqueous solutions

Awual, M. R.; Eldesoky, G. E.*; 矢板 毅; Naushad, M.*; 塩飽 秀啓; Alothman, Z. A.*; 鈴木 伸一

Chemical Engineering Journal, 279, p.639 - 647, 2015/11

 被引用回数:50

A novel Schiff base ligand based nano-composite adsorbent (NCA) was prepared for the detection and removal of copper (Cu(II)) ions in wastewater samples. Upon the addition of Cu(II) ions to NCA at optimum conditions, the clear color was visible to the naked-eye in the detection system. This NCA exhibited an obvious color change from yellowish to dark green in the presence of Cu(II) ions in aqueous solution. The NCA could detect the Cu(II) ions over other foreign ions with high sensitivity and selectivity. For adsorption behaviour, influences several factors such as solution pH, contact time, concentration for Cu(II) ion adsorption was investigated by batch experiment in detail. The results showed that neutral solution pH was suitable to get optimum Cu(II) ions adsorption.

論文

A Sensitive ligand embedded nano-conjugate adsorbent for effective cobalt(II) ions capturing from contaminated water

Awual, M. R.; 矢板 毅; 塩飽 秀啓; 鈴木 伸一

Chemical Engineering Journal, 276, p.1 - 10, 2015/09

 被引用回数:31

The organic ligand of N,N(octane-1,8-diylidene)di(2-hydroxyl-3,5-dimethylaniline) was synthesized and anchored onto inorganic mesoporous materials by direct immobilization method for Co(II) ions capturing from waste samples. The interaction of this material with various metal ions was evaluated, and it exhibited distinct color change from whitish to green in the presence of Co(II) ions, detectable even to the naked-eye. The effects of solution pH, contact time, competing ions and initial concentration on Co(II) sorption on NCA were investigated under optimum conditions. The data also clarified that the NCA adsorbent is an efficient and eco-friendly adsorbent for Co(II) treatment. Therefore, the proposed adsorbent can be considered as a potential candidate for Co(II) ions monitoring and removal from wastewater in large-scale operations.

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