|
内容記述 |
Please insert here a statement of the problem that motivated your study. Follow that statement with a statement of your objective in terms of what was measured or determined.] The Fukushima Daiichi Nuclear Power Plant accident caused severe soil contamination by radioactive cesium (Cs). The large volume of removed soil from decontamination must be disposed of by 2045, requiring volume reduction. However, Cs is strongly adsorbed onto clay minerals in the soil, making removal difficult. Thus, the desorption behavior of Cs adsorbed onto weathered biotite (WB), a clay mineral abundant in Fukushima soils, was investigated using a mechanochemical (MC) method which combines physical grinding by ball impact and friction with a wet process that promotes chemical reaction. The results, oxalic acid desorbed Cs to some extent without significantly affecting the layered structure of the clay minerals and ammonium chloride showed an exfoliation and an ion-exchange effect the layer structure, resulting in a similar level of desorption. The MC method using ammonium chloride solution desorbed ~73% of the stable Cs from WB samples and 80% of 137Cs from soil collected in Fukushima, and the desorption behavior was reliably reproduced in actual soil samples. In contrast, oxalic acid did not always result in high ¹³⁷Cs desorption. Based on these findings, the desorption behavior of Cs indicated that the MC method acts effectively promotes radioactive Cs desorption which has been adsorbed strongly on the interlayer due to the synergistic effect of the chemical effect of the ammonium chloride solution and the physical impact of exfoliation and pulverization of the layered structure. This method, therefore, should reduce the volume of remove soil requiring final disposal, thereby lowering associated management costs. |
