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Journal Articles

Evaluation of physicochemical properties of radioactive cesium in municipal solid waste incineration fly ash by particle size classification and leaching tests

Fujii, Kengo*; Ochi, Kotaro; Obuchi, Atsushi*; Koike, Yuya*

Journal of Environmental Management, 217, p.157 - 163, 2018/07

 Times Cited Count:16 Percentile:14.22(Environmental Sciences)

After the Fukushima Daiichi-Nuclear Power Plant accident, environmental recovery was a major issue because a considerable amount of municipal solid waste incineration (MSWI) fly ash was highly contaminated with radioactive cesium. In this study, MSWI fly ash was sampled in Fukushima Prefecture, and the physicochemical properties of radioactive cesium in MSWI fly ash were evaluated by particle size classification and the Japanese leaching test No. 13 (JLT-13). The results obtained from the classification of fly ash indicated that the activity concentration of radioactive cesium and the content of the coexisting matter (i.e., chloride, potassium, and sylvite) temporarily change in response to the particle size of fly ash. X-ray diffraction results indicated that water-soluble radioactive cesium exists as CsCl because of the cooling process and that insoluble cesium is bound to the inner sphere of amorphous matter.

Journal Articles

Neutron diffraction of ice in hydrogels

Sekine, Yurina; Fukazawa, Tomoko*; Aizawa, Mamoru*; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Yamauchi, Hiroki; Fukazawa, Hiroshi

Journal of Physical Chemistry B, 118(47), p.13453 - 13457, 2014/08

 Times Cited Count:1 Percentile:97.66(Chemistry, Physical)

Neutron diffraction patterns for deuterated poly-$$N$$,$$N$$,-dimethylacrylamide (PDMAA) hydrogels were measured from 10 to 300 K to investigate the structure and properties of water in the gels. Diffraction peaks observed below 250 K indicate the existence of ice in the hydrogels. Some diffraction peaks from the ice are at lower diffraction angles than those in ordinary hexagonal ice (Ih). These shifts in peaks indicate that the lattice constants of the $$a$$ and $$c$$ axes in the ice are about 0.29% and 0.3% higher than those in ice Ih, respectively. The results show that bulk low-density ice can exist in PDMAA hydrogels. The distortions in the lattice structure of ice imply significant interactions between water molecules and the surrounding polymer chains, which play an important role in the chemical and mechanical properties of the hydrogel.

Journal Articles

Structural changes of water in poly(vinyl alcohol) hydrogel during dehydration

Kudo, Kushi*; Ishida, Junichi*; Syuu, G.*; Sekine, Yurina; Fukazawa, Tomoko*

Journal of Chemical Physics, 140(4), p.044909_1 - 044909_8, 2014/01

 Times Cited Count:29 Percentile:17.52(Chemistry, Physical)

To investigate the mechanism of structural changes of water and polymer networks with drying and swelling, we measured the Raman spectra of a physically cross-linked poly(vinyl alcohol) (PVA) hydrogel synthesized using the freezing thawing method. On the basis of the dependence of the frequency shifts on the PVA concentration of the original solution, it was found that the structure of the polymer network in the reswollen hydrogel becomes inhomogeneous due to shrinkage of the polymer network with drying. Furthermore, to investigate the effects of the cross-linking structure on the drying process, these results were compared with those of a chemically cross-linked PVA hydrogel synthesized using glutaraldehyde as a cross-linker. The results show that the structures of the polymer network and water change with the gel preparation process, cross-linking method, and drying and reswelling processes.

Journal Articles

Effects of crosslinker density on the polymer network structure in poly-$$N$$,$$N$$-dimethylacrylamide hydrogels

Fukazawa, Tomoko*; Ikeda, Naohiro*; Tabata, Mayu*; Hattori, Masataka*; Aizawa, Mamoru*; Yunoki, Shunji*; Sekine, Yurina

Journal of Polymer Science, Part B; Polymer Physics, 51(13), p.1017 - 1027, 2013/07

 Times Cited Count:21 Percentile:32.13(Polymer Science)

Oral presentation

Structure of water and ice in poly-N,N,-dimethylacrylamide hydrogel

Sekine, Yurina; Fukazawa, Tomoko*; Yamauchi, Hiroki; Songxue, C.*; Chakoumakos, B.*; Fernandez-Baca, J. A.*; Fukazawa, Hiroshi

no journal, , 

Neutron diffraction data of deuterated poly-N,N,-dimethylacrylamide (PDMAA) hydrogel were measured at temperatures of 10 - 290 K in order to investigate the structure and properties of water in the hydrogel. Diffraction peaks observed below 270 K indicate the existence of a solid ice in the hydrogel. The positions of some peaks from the ice are lower than those in ordinary hexagonal ice (Ih). The lower shifts of the peaks indicates that the lattice constants of the c-axis in the ice are about 0.3% higher than those in ice Ih, whereas those of the a-axis are almost consist. The results show that bulk of a low-density ice crystal exists in the PDMAA hydrogel. The water molecules, which have a significant interaction with the polymer chains, play an important role in the chemical and mechanical properties of the hydrogel.

Oral presentation

Characterization of radiocesium in core soil collected at Kawasaki

Ichihashi, Jun*; Kasari, Mitsuki*; Ochi, Kotaro; Koike, Yuya*

no journal, , 

In this study, we sampled a core soil using a core sampler (0-30 cm) at Kawasaki. A sequential extraction procedure was used to characterize radiocesium in each layer of soil. We selected six sampling points in cosideration of the vegetation. Four soils were collected at 900 cm$$^{2}$$ range area. Core sample (0-30 cm) was devided into 5 cm layer and put in U-8 container, respectively. From measurement results, the vertival distribuition of radiocesium in core soil was 2.5 Bq kg$$^{-1}$$ (0-5 cm), 22.3 Bq kg$$^{-1}$$ (5-10 cm), 3.4 Bq kg$$^{-1}$$ (10-15 cm), 0.3 Bq kg$$^{-1}$$ (15-20 cm), 0.8 Bq kg$$^{-1}$$ (20-25 cm), 1.0 Bq kg$$^{-1}$$ (25-30 cm). It is indicated that radiocesium penetrate to deeper layer at Kawasaki.

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