Soil decontamination using cesium-free mineralization with alkaline chloride; Cs removal processes depending on valence of cations in reactants

Shimoyama, Iwao   ; Kogure, Toshihiro*; Okumura, Taiga*; Baba, Yuji  

We study decontamination ratio and structural change of soil after heat treatments with four kinds of alkaline chloride reagents in air and under low-pressure conditions to optimize soil decontamination method. Each reagent was added to contaminated soil with the weight ratio of 1/1, and we measured radioactivity and analyzed crystal phases of the samples after the heat treatments for 2 hours. In the case of CaCl, only small differences in decontamination ratio were observed in air and low-pressure conditions, and decontamination ratio reached to about 95% at 790C. After the processing, biotite in soil decomposed and products depended on in air and under low-pressure conditions. Whereas, in the case of MgCl, decontamination ratios were 40 and 90% after the heat treatments at 695C in air and under low-pressure conditions, respectively. We found that decomposition and phase transformation of biotite were more facilitated under low-pressure conditions than in air. Also, in the cases of NaCl and KCl, soil decontamination was more facilitated under low-pressure conditions; decontamination ratios were 15 and 94% after the heat treatments with NaCl at 790C in air and under low-pressure conditions, respectively. However, biotite remained after the heat treatments both in air and under low-pressure conditions. Based on this result, we conclude that ion exchange was the dominant Cs removal process for NaCl and KCl.