Radioactive cesium removal from seawater using adsorptive fibers prepared by radiation-induced graft polymerization

Shota Goto, Shigeko Kawai-Noma, Daisuke Umeno, Kyoichi Saito, Kunio Fujiwara, Takanobu Sugo, Takahiro Kikuchi, Yasutomi Morimoto

Research output: Contribution to conferencePaperpeer-review

Abstract

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.

Original languageEnglish
Publication statusPublished - 2015
Externally publishedYes
Event23rd International Conference on Nuclear Engineering: Nuclear Power - Reliable Global Energy, ICONE 2015 - Chiba, Japan
Duration: 2015 May 172015 May 21

Conference

Conference23rd International Conference on Nuclear Engineering: Nuclear Power - Reliable Global Energy, ICONE 2015
Country/TerritoryJapan
CityChiba
Period15/5/1715/5/21

Keywords

  • Adsorptive fiber
  • Cesium removal
  • Insoluble cobalt ferrocyanide
  • Radiation-induced graft polymerization
  • Seawater

ASJC Scopus subject areas

  • Nuclear Energy and Engineering

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