Proposed cesium-free mineralization method for soil decontamination; Demonstration of cesium removal from weathered biotite

土壌除染へ向けたセシウムフリー鉱化法の提案; 福島風化黒雲母からのCs除去デモンストレーション

本田 充紀   ; 下山 巖   ; 小暮 敏博*; 馬場 祐治  ; 鈴木 伸一; 矢板 毅

Honda, Mitsunori; Shimoyama, Iwao; Kogure, Toshihiro*; Baba, Yuji; Suzuki, Shinichi; Yaita, Tsuyoshi

The possibility to remove sorbed cesium (Cs) from weathered biotite (WB), which is considered a major Cs-adsorbent in the soil of Fukushima, has been investigated by the addition of NaCl-CaCl mixed salt and subsequent heat treatment in a low pressure. X-ray fluorescence analysis was employed to determine the Cs removal rate with elevated temperature. The structural changes and new phases formed were determined using powder X-ray diffraction, as well as electron diffraction and X-ray microanalysis in a transmission electron microscope. We found that Cs was completely removed from the specimen heated at 700 C, when WB completely decomposed and augite with a pyroxene structure was formed. On the basis of this finding, we propose the cesium-free mineralization (CFM) method, a new soil decontamination process by means of transformation of Cs-sorbing minerals to those where Cs is impossible to be incorporated, by heating with certain additives.