Desorption of cesium from Fukushima soils using a mechanochemical method

Le résumé fourni par la source

Abstract 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 stable Cs adsorbed onto weathered biotite (WB), a clay mineral abundant in Fukushima soils, was investigated using a mechanochemical (MC) method that combines physical grinding by ball impact and friction with a wet process promoting chemical reactions. The effectiveness of this method for desorbing radioactive Cs from Fukushima soil was also evaluated. The results are based on the scanning electron microscopy analysis and the results of the desorption experiment; oxalic acid desorbed Cs to some extent without affecting the layered structure of the clay minerals significantly, and ammonium chloride showed an exfoliation of the layer structure, resulting in a stable desorption of Cs independent of samples. Regarding the real soil samples collected in Fukushima, the MC method using ammonium chloride solution desorbed 80% of 137Cs, and the desorption behavior was reproduced reliably in actual soil samples. In contrast, oxalic acid did not always result in radioactive Cs made sufficiently desorbed for all the samples. Based on these findings, the MC method with ammonium chloride promotes radioactive Cs desorption effectively from interlayers due to synergistic effects from the layered structure’s exfoliation and chemical interaction. The MC method with ammonium chloride should reduce the volume of removed soil requiring final disposal, thereby reducing associated management costs.

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