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Journal Articles

Microscopic structural changes during the freeze cross-linking reaction in carboxymethyl cellulose nanofiber hydrogels

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.

Journal Articles

Ion-selective adsorption of lead by a two-dimensional terbium oxalate framework

Nankawa, Takuya; Sekine, Yurina; Yamada, Teppei*

Bulletin of the Chemical Society of Japan, 95(5), p.825 - 829, 2022/05

 Times Cited Count:0 Percentile:0(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$$^{2+}$$, Cd$$^{2+}$$, Mn$$^{2+}$$, Co$$^{2+}$$, Ni$$^{2+}$$, Cu$$^{2+}$$, Na$$^{+}$$, K$$^{+}$$, Mg$$^{2+}$$, and Ca$$^{2+}$$ showed that the TOF has high selectivity for Pb$$^{2+}$$ among other metal ions. The saturated adsorption capacity of the TOF for Pb$$^{2+}$$ was 276 mg g$$^{-1}$$, which is higher than that of conventional adsorbents. Furthermore, the TOF exhibited reversible Pb$$^{2+}$$ 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$$^{2+}$$, and because of its reusability, it is also a promising material for wastewater clean-up.

Journal Articles

Super adsorbent for removing harmful metals using pig bone waste

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.

Journal Articles

Carbonated nanohydroxyapatite from bone waste and its potential as a super adsorbent for removal of toxic ions

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:6 Percentile:53.12(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$$_{3}$$ solution produced a carbonated nanohydroxyapatites (C-NHAP). The C-NHAP exhibited high adsorptivity for Sr$$^{2+}$$, Cd$$^{2+}$$, Pb$$^{2+}$$, and Cu$$^{2+}$$. 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.

Journal Articles

Development of a high-performance toxic metal adsorbent using waste bones

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.

Journal Articles

Eco-friendly carboxymethyl cellulose nanofiber hydrogels prepared via freeze cross-linking and their applications

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:17 Percentile:79.32(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.

Journal Articles

High spectral resolution of diode laser absorption spectroscopy for isotope analysis using a supersonic plasma jet

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:6 Percentile:48.54(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.

Journal Articles

Development of an isotope analysis method based on diode laser absorption spectroscopy using an arc-jet plasma wind tunnel

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:48.54(Chemistry, Analytical)

no abstracts in English

Journal Articles

Proton-exchange mechanism of specific Cs$$^{+}$$ adsorption $$via$$ lattice defect sites of Prussian blue filled with coordination and crystallization water molecules

Ishizaki, 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:161 Percentile:99.53(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$$^{III}$$$$_{4}$$[Fe$$^{II}$$(CN)$$_{6}$$]3$$cdot$$xH$$_{2}$$O (x = 10-15) (PB-1) and (NH$$_{4}$$)0.70Fe$$^{III}$$1.10[Fe$$^{II}$$(CN)$$_{6}$$]$$cdot$$1.7H$$_{2}$$O (PB-2) with respect to the Cs$$^{+}$$ adsorption ability. The synthesised PB-1, by a common stoichiometric aqueous reaction between 4Fe$$^{3+}$$ and 3[Fe$$^{II}$$(CN)$$_{6}$$]$$^{4-}$$, showed much more efficient Cs$$^{+}$$ adsorption ability than did the commercially available PB-2.

Journal Articles

Redox behavior of uranium(VI) adsorbed onto a phosphate-modified indium tin oxide electrode

Suzuki, Yoshinori*; Nankawa, Takuya; Onuki, Toshihiko

Chemistry Letters, 42(8), p.888 - 890, 2013/08

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Selective removal of cesium ions from wastewater using copper hexacyanoferrate nanofilms in an electrochemical system

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:104 Percentile:95.3(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 ($$K$$$$_{d}$$ $$>$$ 5$$times$$10$$^{5}$$ 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.

Journal Articles

Preparation of a film of copper hexacyanoferrate nanoparticles for electrochemical removal of cesium from radioactive wastewater

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:48 Percentile:80.29(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.

Journal Articles

Yeast genes involved in uranium tolerance and uranium accumulation; A Functional screening using the nonessential gene deletion collection

Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*

Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05

 Times Cited Count:6 Percentile:18.43(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.

Journal Articles

Redox behavior of Ce(IV)/Ce(III) in the presence of nitrilotriacetic acid; A Surrogate study for An(IV)/An(III) redox behavior

Suzuki, Yoshinori*; Nankawa, Takuya; Francis, A. J.*; Onuki, Toshihiko

Radiochimica Acta, 98(7), p.397 - 402, 2010/07

 Times Cited Count:17 Percentile:75.72(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Association of actinides with microorganisms and clay; Implications for radionuclide migration from waste-repository sites

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:16 Percentile:21.33(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.

Journal Articles

In situ observation of reductive deposition of uranium on an electrode/electrolyte interface by optical waveguide spectroscopy

Nankawa, Takuya; Suzuki, Yoshinori; Onuki, Toshihiko

Chemistry Letters, 38(11), p.1090 - 1091, 2009/11

 Times Cited Count:1 Percentile:7.2(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.

Journal Articles

Modeling of the interaction of Pu(VI) with the mixture of microorganism and clay

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:50.57(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 ${it B. subtilis}$ 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.

Journal Articles

Concurrent transformation of Ce(III) and formation of biogenic manganese oxides

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:25 Percentile:53.2(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.

Journal Articles

Sorption of U(VI) on the 4-mercaptopyridine self-assembled monolayer

Nankawa, Takuya; Suzuki, Yoshinori; Ozaki, Takuo; Francis, A. J.; Onuki, Toshihiko

Journal of Nuclear Science and Technology, 45(3), p.251 - 256, 2008/03

 Times Cited Count:3 Percentile:24.16(Nuclear Science & Technology)

Sorption of U(VI) on the 4-mercaptopyridine self-assembled-monolayer (4-PyS-SAM) on Au(111) was studied by cyclic voltammetry. Cyclic voltammograms (CV) of the 4-PyS-SAM working electrode was obtained by contact with 1 mM UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$ solution, 1 mM UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$ and 50 mM acetic acid solution, or 1 mM UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$ and 50 mM oxalic acid solution for 6 h at pH 4. Reduction current of uranium(VI) to U(V) was detected in the CV. The CV of the U(VI) associated 4-PyS-SAM after transporting to U(VI) free 0.1 M NaClO4 solution showed that the reduction current was detected in the cases of UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$ and U(VI)-acetate, but not in the case of U(VI)-oxalate solutions, indicating that U(VI) was adsorbed on the 4-PyS-SAM from the UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$ and U(VI)-acetate solutions, but not from U(VI)-oxalate solution. These results suggests that stability of U(VI)-4-PyS-SAM is not so high that U(VI)-4-PyS-SAM cannot be formed in the presence of 50 mM oxalate.

Journal Articles

Protein expression of ${it Saccharomyces cerevisiae}$ in response to uranium exposure

Sakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.; Onuki, Toshihiko

Journal of Nuclear and Radiochemical Sciences, 8(2), p.133 - 136, 2007/10

Protein expression of ${it Saccharomyces cerevisiae}$ grown in the medium containing $$^{238}$$U(VI) and $$^{233}$$U(VI) was examined by two-dimensional gel electrophoresis. ${it S. cerevisiae}$ of BY4743 was grown in medium containing $$^{238}$$U of 0, 2.0, and 5.0 $$times$$ 10$$^{-4}$$ M or $$^{233}$$U of 2.5 $$times$$ 10$$^{-6}$$ (radioactivity was higher by 350 times than 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U) and 5.0 $$times$$ 10$$^{-6}$$ M for 112 h at 30$$^{circ}$$C. The growths of the yeast grown in the above media were in the following order: control $$>$$ 2.5 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 2.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U $$>$$ 5.0 $$times$$ 10$$^{-6}$$ M $$^{233}$$U $$>$$ 5.0 $$times$$ 10$$^{-4}$$ M $$^{238}$$U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing $$^{238}$$U or $$^{233}$$U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to $$^{238}$$U or to $$^{233}$$U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins.

102 (Records 1-20 displayed on this page)