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Sekine, Yurina; Nankawa, Takuya; Hiroi, Kosuke; Oba, Yojiro*; Nagakawa, Yoshiyasu*; Sugita, Tsuyoshi; Shibayama, Yuki; Ikeda-Fukazawa, Tomoko*
Carbohydrate Polymers, 327, p.121538_1 - 121538_11, 2024/03
Times Cited Count：0 Percentile：0.01(Chemistry, Applied)We describe non-toxic, tough nanocellulose (NC) hydrogels formed from chemically unmodified NC by cellulose crystalline transformation and subsequent freeze cross-linking reaction. Using low-concentration NaOH and freezing together induced the crystalline transformation of NC from cellulose I to II via freeze concentration. After the crystalline transformation, cross-linking between the NC and CA in the freeze concentration layer (FCL) provided a strong NC network structure, forming NC hydrogels with high mechanical strength. The freeze-cross-linked NC hydrogel easily retained powder adsorbents in its inner space by mixing the NC-NaOH sol and the powder, and the hydrogel showed high removal efficiency for heavy metals. The results highlight the versatility of chemically unmodified celluloses in developing functional materials, suggest possible practical applications.
Sekine, Yurina; Nankawa, Takuya
Bulletin of the Chemical Society of Japan, 96(10), p.1150 - 1155, 2023/10
Times Cited Count：0 Percentile：0.01(Chemistry, Multidisciplinary)The phase separation of ice crystals and solutes and bound water that occurs during freezing can be used as a reaction field to control a hierarchical structure of hydrogels. Here, we present a study of carboxymethyl cellulose nanofiber (CMCF) hydrogels formed using the solid-quasi liquid phase separation. CMCF hydrogels were formed simply by adding citric acid to frozen CMCF and thawing the mixture. It was found that rearrangement of CMCF structures via hydrogen bonding proceeds in the freeze concentration layer before the ice crystals melt. Under freeze concentration, CMCF and bound water are confined at high concentrations. The crosslinking reaction in such a unique space contributed to the formation of CMCF hydrogel with high mechanical strength. We discuss the gelation behavior and properties of freeze crosslinked CMCF hydrogels and their applications.
Miura, Daisuke*; Sekine, Yurina; Nankawa, Takuya; Sugita, Tsuyoshi; Oba, Yojiro; Hiroi, Kosuke; Ozawa, Tatsuhiko
Carbohydrate Polymer Technologies and Applications (Internet), 4, p.100251_1 - 100251_9, 2022/12
The reaction mechanism of carboxymethyl cellulose nanofiber (CMCF) hydrogel formed by freeze-crosslinking was investigated. We succeeded in observing the hierarchical structural changes during the freeze-crosslinking reaction. Freeze-crosslinked CMCF hydrogels exhibited a characteristic hierarchical alignment structure from the angstrom to micrometer scale that differed from normal cross-linked CMCF hydrogels produced by a conventional method without freezing. It was shown that the characteristic hierarchical structure contributes the excellent mechanical properties of freeze-crosslinked CMCF hydrogels.
Nankawa, Takuya; Sekine, Yurina; Yamada, Teppei*
Bulletin of the Chemical Society of Japan, 95(5), p.825 - 829, 2022/05
Times Cited Count：2 Percentile：14.86(Chemistry, Multidisciplinary)Advances in hazardous metal ion removal are essential for wastewater clean-up to tackle the global water shortage crisis. Here, we report a Pb-selective adsorbent using a Tb oxalate framework (TOF) synthesized by a one-pot hydrothermal method. The TOF has a two-dimensional sheet structure, in which the interlayer space functions as an ion exchangeable site. Sorption tests using a mixed-ion solution containing Pb
, Cd, Mn, Co, Ni, Cu, Na
, K, Mg, and Ca showed that the TOF has high selectivity for Pb among other metal ions. The saturated adsorption capacity of the TOF for Pb was 276 mg g
, which is higher than that of conventional adsorbents. Furthermore, the TOF exhibited reversible Pb adsorption/desorption and could be used for at least three cycles. The results showed that TOF has excellent potential as an adsorbent for removing Pb, and because of its reusability, it is also a promising material for wastewater clean-up.
Nankawa, Takuya; Sekine, Yurina
Isotope News, (778), p.34 - 35, 2021/12
A high-performance adsorbent was synthesized by reaction of waste bone and sodium hydrogen carbonate. Since waste bones are inexpensive and well-supplied materials, it has the potential to be used for a wide range of decontamination and removal of harmful metals.
Sekine, Yurina; Nankawa, Takuya; Yamada, Teppei*; Matsumura, Daiju; Nemoto, Yoshihiro*; Takeguchi, Masaki*; Sugita, Tsuyoshi; Shimoyama, Iwao; Kozai, Naofumi; Morooka, Satoshi
Journal of Environmental Chemical Engineering, 9(2), p.105114_1 - 105114_12, 2021/04
Times Cited Count：10 Percentile：49.28(Engineering, Environmental)Remediating toxic ion contamination is crucial for protecting human health and the environment. This study aimed to provide a powerful strategy for effectively utilizing bone waste from the food production and preparation industries for removal of toxic ions. Here, we show that immersing pig bone in NaHCO
solution produced a carbonated nanohydroxyapatites (C-NHAP). The C-NHAP exhibited high adsorptivity for Sr, Cd, Pb, and Cu. The strontium adsorptivity was about 250 and 4,500 times higher than that of normal bone and synthetic HAP, respectively. The C-NHAP is an eco-friendly, high-performance material that is simple to prepare and should be useful for tackling problems of food waste disposal and environmental pollution.
Sekine, Yurina; Nankawa, Takuya
Chem-Station (Internet), 1 Pages, 2021/03
We will explain the experimental results and the background of the research that developed a highly efficient toxic metal adsorbent using wastebone as a raw material.
Sekine, Yurina; Nankawa, Takuya; Yunoki, Shunji*; Sugita, Tsuyoshi; Nakagawa, Hiroshi; Yamada, Teppei*
ACS Applied Polymer Materials (Internet), 2(12), p.5482 - 5491, 2020/12
Times Cited Count：34 Percentile：86.51(Materials Science, Multidisciplinary)We developed a cross-linking method using freeze concentration and used it to synthesize a new type of carboxymethyl cellulose nanofiber (CMCF) hydrogel with high compressive strength (
80 MPa) and high compressive recoverability. The hydrogels were prepared by adding an aqueous solution of citric acid (CA) to a frozen CMCF sol and then thawing the sol. The reaction between the freeze-concentrated CMCF and CA created a rigid porous structure that reflected the ice crystal structure. Their cross-linked structure has a high stability to compressive stress. Bentonite was immobilized on a CMCF hydrogel by adding bentonite to the CMCF sol before freeze cross-linking. The CMCF-bentonite hydrogel showed high adsorptivity for chemical dyes. The physically cross-linked CMCF hydrogels are non-toxic, metal-free, and simple to prepare, and thus they may be useful as sustainable materials in various fields.
Kuwahara, Akira; Aiba, Yasuaki*; Yamasaki, Shinya*; Nankawa, Takuya; Matsui, Makoto*
Journal of Analytical Atomic Spectrometry, 33(7), p.1150 - 1153, 2018/07
Times Cited Count：7 Percentile：49(Chemistry, Analytical)Although high-temperature plasma sources have been used for direct isotope analysis of solid samples, the spectral resolution of diode laser absorption spectroscopy in high-temperature plasma is limited by the Doppler broadening of atomic absorption lines. Thus, a decrease in translational temperature is necessary to enhance the spectral resolution and distinguish isotope shifts due to mass number. In this study, a supersonic plasma wind tunnel, also called an arc-jet plasma wind tunnel, was used to enhance spectral resolution drastically, and a demonstration was carried out using natural stable xenon isotopes. As a result, the temperature was found to be about 180 K and the spectral resolution was about one order of magnitude higher than that of the conventional high-temperature source. Additionally, the method proposed herein was verified by using two xenon isotopes.
Kuwahara, Akira; Aiba, Yasuaki*; Nankawa, Takuya; Matsui, Makoto*
Journal of Analytical Atomic Spectrometry, 33(5), p.893 - 896, 2018/05
Times Cited Count：6 Percentile：43.5(Chemistry, Analytical)no abstracts in English
adsorption 
lattice defect sites of Prussian blue filled with coordination and crystallization water moleculesIshizaki, Manabu*; Akiba, Sae*; Otani, Asako*; Hoshi, Yuji*; Ono, Kenta*; Matsuba, Mayu*; Togashi, Takanari*; Kanaizuka, Katsuhiko*; Sakamoto, Masatomi*; Takahashi, Akira*; et al.
Dalton Transactions, 42(45), p.16049 - 16055, 2013/12
Times Cited Count：178 Percentile：99.58(Chemistry, Inorganic & Nuclear)We have revealed the fundamental mechanism of specific Cs adsorption into Prussian blue (PB) in order to develop high-performance PB-based Cs adsorbents in the wake of the Fukushima nuclear accident. We compared two types of PB nanoparticles with formulae of Fe
[Fe
(CN)
]3
xH
O (x = 10-15) (PB-1) and (NH)0.70Fe1.10[Fe(CN)]1.7HO (PB-2) with respect to the Cs adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe
and 3[Fe(CN)]
, showed much more efficient Cs adsorption ability than did the commercially available PB-2.
Suzuki, Yoshinori*; Nankawa, Takuya; Onuki, Toshihiko
Chemistry Letters, 42(8), p.888 - 890, 2013/08
Times Cited Count：1 Percentile：6.98(Chemistry, Multidisciplinary)no abstracts in English
Chen, R.*; Tanaka, Hisashi*; Kawamoto, Toru*; Asai, Miyuki*; Fukushima, Chikako*; Na, H.*; Kurihara, Masato*; Watanabe, Masayuki; Arisaka, Makoto; Nankawa, Takuya
Electrochimica Acta, 87, p.119 - 125, 2013/01
Times Cited Count：108 Percentile：94.92(Electrochemistry)A novel electrochemical adsorption system using a nanoparticle film of copper (II) hexacyanoferrate (III) was proposed for selectively removing cesium from wastewater. This system can be used for cesium separation without extra chemical reagents or any filtration treatment. Cesium uptake and elution can be simply controlled by switching the applied potentials between anodes and cathodes. Data from batch kinetic studies well fitted the intraparticle diffusion equation, reflecting a two-step process: a steepest ascent portion followed by a plateau extending to the equilibrium. The effective cesium removal with a high distribution coefficient (
5
10
mL/g) can be adopted in a large pH range from 0.3 to 9.2, and in the presence of several diverse coexisting alkaline cations, suggesting it can be taken as a promising technology for actual nuclear wastewater treatment.
Chen, R.*; Tanaka, Hisashi*; Kawamoto, Toru*; Asai, Miyuki*; Fukushima, Chikako*; Kurihara, Masato*; Watanabe, Masayuki; Arisaka, Makoto; Nankawa, Takuya
Electrochemistry Communications, 25, p.23 - 25, 2012/11
Times Cited Count：50 Percentile：79.8(Electrochemistry)We first synthesized water-dispersed nanoparticle copper hexacyanoferrate (CuHCF) ink and then coated its nanoparticles on electrodes to electrochemically remove cesium from wastewater. Cesium uptake and elution can be controlled by switching the potentials between anodes and cathodes. Effective cesium removal can be adopted in a large pH range from 0.2 to 8.9, and in the presence of several diverse coexisting alkaline cations, suggesting that it can be taken as a promising technology for actual radioactive wastewater treatment. The prepared CuHCF nanoparticles can be simply and uniformly coated on electrodes by wet process like conventional printing methods, so any sizes or patterns are feasible at low cost, which indicated the potential as a promising sorption electrode of large size in the columns for sequential removal and recycle of Cs from wastewater.
Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*
Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05
Times Cited Count：6 Percentile：17.37(Environmental Sciences)We screened 4908 non-essential gene deletion mutant yeast strains for uranium sensitivity and low accumulation by growth in agar medium containing uranium. All mutant strains grew successfully on agar media containing 0 or 0.5 mM uranium for one week at 30 centigrade. Thirteen strains with single gene deletions showed reduced growth in the agar medium containing 0.5 mM uranium and were identified as uranium-sensitive mutant strains. The phosphate transporter genes of PHO86, PHO84, PHO2, and PHO87 were among the deleted genes in the uranium-sensitive mutant strains, suggesting that genes concerned with phosphate transport contribute to uranium tolerance. Seventeen single-deletion strains showed lower uranium accumulation than the wild-type after exposure to agar medium containing 0.5 mM uranium, and were identified as mutant strains with low uranium accumulation.
Suzuki, Yoshinori*; Nankawa, Takuya; Francis, A. J.*; Onuki, Toshihiko
Radiochimica Acta, 98(7), p.397 - 402, 2010/07
Times Cited Count：17 Percentile：74.1(Chemistry, Inorganic & Nuclear)no abstracts in English
Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*
Geomicrobiology Journal, 27(3), p.225 - 230, 2010/04
Times Cited Count：18 Percentile：21.61(Environmental Sciences)The recent research results on the interation of heavy-elements and microorganisms are shown. (1) Adsorption of Pu(IV), Th(IV) and Eu(III)-DFO complexes on bacteria, (2) Biodegradation of Eu(III) in the presence of malic acids.
Nankawa, Takuya; Suzuki, Yoshinori; Onuki, Toshihiko
Chemistry Letters, 38(11), p.1090 - 1091, 2009/11
Times Cited Count：1 Percentile：7.6(Chemistry, Multidisciplinary)We report the first in situ and real-time observation of UV-vis absorption spectra of uranium electrodeposited on indium-tin-oxide electrodes by slab optical waveguide spectroscopy. An absorption peak around 670 nm was distinguished after a 30-min holding period at -0.2 V (vs. Ag/AgCl). X-ray absorption near edge structure spectroscopy confirmed the presence of uranium(IV) in the uranium electrodeposited on the ITO electrode.
Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Kozai, Naofumi; Sakamoto, Fuminori; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.*
Journal of Nuclear Science and Technology, 46(1), p.55 - 59, 2009/01
Times Cited Count：8 Percentile：49.52(Nuclear Science & Technology)Model analysis of the transformation of Pu(VI) in a mixture of a common soil bacterium, Bacillus subtilis, and kaolinite clay was carried out. When we assumed in the model analysis that reduction rate of Pu(V) to Pu(IV) was higher on B. subtilis than on kaolinite, the estimated fractions of Pu in the solution and in the mixture, oxidation states of Pu in the solution and in the mixture were in good agreement with the measured ones. On the contrary, assumption that reduction rate of Pu(V) to Pu(IV) was the same on kaolinite as on 
gave wrong prediction of Pu association with the mixture. These results strongly suggested the electron transfer from the bacteria to Pu(V) on the bacterial cell to be reduced to Pu(IV) during the accumulation of Pu(VI) to the mixture.
Onuki, Toshihiko; Ozaki, Takuo; Kozai, Naofumi; Nankawa, Takuya; Sakamoto, Fuminori; Sakai, Takuro; Suzuki, Yoshinori; Francis, A. J.*
Chemical Geology, 253(1-2), p.23 - 29, 2008/07
Times Cited Count：28 Percentile：55.18(Geochemistry & Geophysics)We examined the changes in the chemical states of Ce(III) during the formation of manganese oxide occasioned by Mn(II)-oxidizing bacteria. The oxidation states of Ce and Mn then were measured by X-ray Absorption Near Edge Structure (XANES). We also determined the elemental distributions in the bacteria and precipitates by Scanning-Proton Induced X-ray Emission (S-PIXE). We found that the precipitation of Ce is preceded by its accumulation by the bacterium, followed by its oxidization to Ce(IV) by the Mn(III, IV)-containing precipitates that the bacteria generate.
