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Kot F.S.,Technion - Israel Institute of Technology | Farran R.,Technion - Israel Institute of Technology | Fujiwara K.,Chiba University | Kharitonova G.V.,Russian Academy of Sciences | And 3 more authors.
Geoderma | Year: 2016

Boron (B) is an indispensable constituent of plant lignin st\ructures inherited by soil humus compounds. However, little is known about plant litter as a factor of B turnover in the plant-soil system. Also, the sources of soil available B and the mechanism of its release and mobility are poorly understood. In a series of experiments, we considered (1) leachates from decomposing plant litter and leaves and (2) soil-water mobile phase ('soil solution') as the carriers and sources of potentially available B compounds. The obtained data showed that plant litter is the main source of available and water-mobile compounds of B to the soils; this is 1 to 3 orders of magnitude higher than the B income with rain and aerosol precipitation, and even more than the income from rock weathering. We can assume that the B turnover occurs in a semi-closed system 'plant-litter-soil' ('plant-litter-soil organic matter-soil water mobile compounds-available B'). Mobile colloids of particular size of 0.20 < d < 0.45 μm were found to be the main carrier of the soil available B. The character of B release from the colloids indicated at least two forms of B bonding: (1) easy-exchangeable, which is pH-dependent, and (2) firmly-bound B-organic complexes. © 2016 Elsevier B.V. Source


Okamura Y.,Chiba University | Fujiwara K.,Chiba University | Fujiwara K.,KJK Co. | Ishihara R.,Chiba University | And 4 more authors.
Radiation Physics and Chemistry | Year: 2014

Potassium cobalt hexacyanoferrate compounds (KCo-HCFe's) were impregnated onto a 6-nylon fiber by radiation-induced graft polymerization and subsequent chemical modifications. First, dimethylaminoethyl methacrylate was graft-polymerized onto the nylon fiber. Second, hexacyanoferrate ions were bound to graft chains via an anion-exchange interaction. Third, KCo-HCFe's were formed on the nylon fiber via the precipitation reaction of hexacyanoferrate ions with cobalt ions in the presence of potassium chloride. The resulting KCo-HCFe-impregnated fiber had an impregnation percentage of the fiber for KCo-HCFe's of 7%. The cesium concentration in 10. ppm cesium chloride solution with the immersion of this fiber decreased to 0.6. ppm within 60. min at a ratio of liquid volume (10. mL) to fiber mass (0.1. g). The fiber was fabricated into a braid with a length of 100. cm and a diameter of 8. cm for practical use at sites contaminated with cesium. © 2013 Elsevier Ltd. Source


Goto S.-I.,Chiba University | Kono M.,Chiba University | Kawai-Noma S.,Chiba University | Umeno D.,Chiba University | And 6 more authors.
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2015

The Great East Japan Earthquake and the tsunami that followed caused the meltdown of three reactors of the TEPCO Fukushima Daiichi nuclear power station (NPS), resulting in the emission of radionuclides such as cesium-137 and strontium-90 to the environment. Radioactive strontium was detected in seawater and groundwater at concentrations of 1.8 × 102 and 5.5 × 105 Bq/L, respectively, on October 7th 2014 [1]. Nonradioactive strontium dissolves at a concentration of 8 mg/L in seawater. No adsorbent can distinguish radioactive strontium from nonradioactive strontium; therefore, the adsorbent must collect both ions which coexist with other alkaline-earth metal ions such as magnesium and calcium ions. Inorganic compounds and chelate-forming resins are candidate adsorbents for strontium removal [2, 3]. However, It is difficult to use these adsorbents to process a large volume of water contaminated with radionuclides because of their granule and bead forms. We have prepared two kinds of adsorptive fiber by radiation-induced graft polymerization and subsequent chemical modifications: (1) sodium-titanate-impregnated fiber (ST fiber) [4-7] and (2) iminodiacetate-group-immobilized fiber (IDA fiber)[4]. The preparation scheme of the ST fiber consisted of four steps. First, a commercially available 6-nylon fiber was irradiated with γ-rays to produce radicals. Second, sodium styrene sulfate was graft-polymerized onto the irradiated fiber. Third, a titanium species [Ti(OH)2 2+]was bound to the sulfonic acid group of the grafted polymer chain. Finally, the titanium species was converted into sodium titanate with sodium hydroxide, and the resulting precipitate was impregnated onto the fiber. On the other hand, the IDA fiber was prepared as follows. An epoxy-group-containing vinyl monomer, glycidyl methacrylate, was graft-polymerized onto a previously γ-ray-irradiated 6-nylon fiber. Subsequently, the epoxy group was converted into an iminodiacetate group as a chelate-forming group by a reaction with disodium iminodiacetate. The former and latter fibers are applicable to strontium removal from seawater and groundwater, respectively. Copyright © 2015 by JSME. Source


Goto S.,Chiba University | Kawai-Noma S.,Chiba University | Umeno D.,Chiba University | Saito K.,Chiba University | And 4 more authors.
International Conference on Nuclear Engineering, Proceedings, ICONE | Year: 2015

The meltdown of three reactors of the TEPCO Fukushima Daiichi nuclear power station (NPS) caused by the Great East Japan Earthquake on March 11th 2011 resulted in the emission of radionuclides such as cesium-137 and strontium-90 to the environment. For example, radioactive cesium exceeding the legal discharge limit (90 Bq/L, 2×1013 M) was detected in the seawater of the seawater-intake area of the NPS at the end of September 2014. Adsorbents with a high selectivity for cesium ions over other alkali metal ions such as sodium and potassium ions are required for cesium removal from seawater because sodium and potassium ions dissolve respectively at much higher concentrations of 5×10-1 and 1×10-2 M than cesium ions (2×109 M). In addition, the simple operations of the immersion in seawater and the recovery of the adsorbents from seawater are desirable at decontamination sites. We prepared a cobalt-ferrocyanide-impregnated fiber capable of specifically capturing cesium ions in seawater by radiation-induced graft polymerization and chemical modifications. First, a commercially available 6-nylon fiber was irradiated with γ-rays. Second, an epoxy-group-containing vinyl monomer, glycidyl methacrylate, was graft-polymerized onto the γ-ray-irradiated nylon fiber. Third, the epoxy ring of the grafted polymer chain was reacted with triethylenediamine to obtain an anion-exchange fiber. Fourth, ferrocyanide ions, [Fe(CN)6]4-, were bound to the anion-exchange group of the polymer chains. Finally, the ferrocyanide-ion-bound-fiber was placed in contact with cobalt chloride to precipitate insoluble cobalt ferrocyanide onto the polymer chains. Insoluble cobalt ferrocyanide was immobilized at the periphery of the fiber. However, the impregnation structure remains unclear. Here, we clarified the structure of insoluble cobalt ferrocyanide impregnated onto the polymer chain grafted onto the fiber to ensure the chemical and physical stability of the adsorptive fiber in various contaminated waters. The adsorption rate and capacity of the fiber for cesium ions were compared with those of a zeolite as a conventional adsorbent. Copyright © 2015 by JSME. Source


Nakamura Y.,Chiba University | Fujiwara K.,KJK Co. | Sugo T.,KJK Co. | Kawai-Noma S.,Chiba University | And 2 more authors.
Kagaku Kogaku Ronbunshu | Year: 2016

For recovery of palladium (Pd) from a hydrochloric acid medium, dioctyl sulfide (DOS), a neutral extractant capable of specifically capturing Pd anionic species, was impregnated onto a hydrophobic ligand-containing polymer chain grafted onto 6-nylon fiber, using radiation-induced graft polymerization. The hydrophobic ligand was the dode canethiol(C12S) moiety, which functions both in the impregnation of DOS via hydrophobic interaction and in the direct uptake of Pd species by a similar mechanism as DOS. The C12S group was immobilized at a density of 2.0 mmol/g through its reaction of C12S with the epoxy group of the poly-glycidyl methacrylate (GMA) chain grafted onto the nylon fiber, and DOS was impregnated onto the resulting fiber at a density of 0.40-1.1 mmol/g. For example, fiber impregnated with DOS at a density of 0.40 mmol/g possessed a saturation capacity of 0.70 mmol-Pd/g in 1 mol/L HCl. The molar binding ratios of Pd to impregnated DOS and immobilized C12S were calculated as 0.50 and 0.27, respectively. In addition, the DOS-impregnated fiber specifically captured Pd species from a mixture solution of Pd and platinum (Pt) species in 1-4 mol/L HCl. © 2016 The Society of Chemical Engineers, Japan. Source

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