Collective structural changes in vermiculite clay suspensions induced by cesium ions

Motokawa, Ryuhei   ; Endo, Hitoshi*; Yokoyama, Shingo*; Nishitsuji, Shotaro*; Kobayashi, Toru ; Suzuki, Shinichi; Yaita, Tsuyoshi

Following the Fukushima Daiichi nuclear disaster in 2011, Cs radioisotopes have been dispersed over a wide area. Most of the Cs has remained on the surface of the soil because Cs is strongly adsorbed in the interlayer spaces of soil clays, particularly vermiculite. We have investigated the microscopic structure of an aqueous suspension of vermiculite clay over a wide length scale (0.1-100 nm) by small-angle X-ray scattering. We determined the effect of the adsorption behavior of Cs on the structural changes in the clay. It was found that the abruption of the clay sheets was induced by the localization of Cs at the interlayer. This work provides important information for predicting the environmental fate of radioactive Cs in polluted areas, and for developing methods to extract Cs from the soil and reduce radioactivity.