Synchrotron X-ray photoemission spectroscopic analysis on chemical bonding states of Cs adsorbed in vermiculite

Teraoka, Yuden; Iwai, Yutaro*; Okada, Ryuta; Yoshigoe, Akitaka 

The decontamination of Cs is urgently necessary, especially in Fukushima prefecture, to make volume reduction of radioactive waste. In order to develop volume reduction techniques, chemical bonding states of Cs adsorbed in clay minerals, e.g. vermiculite, has been studied by using synchrotron radiation X-ray photoemission spectroscopy (SR-XPS). In this presentation, an interpretation of data obtained by surface charge modulation using an electron flood gun during SR-XPS and chemical bonding states of Cs in the vermiculite are discussed. SR-XPS experiments were conducted at the surface chemistry experimental station of BL23SU in SPring-8. The natural vermiculite was processed to adsorb Cs so that the Cs concentration was 2.1 wt%. The synchrotron radiation energy was 1486.6 eV, identical with the Al-K line. The Auger parameter of Cs of CsClO was closest to that of Cs-contained vermiculite, implying Cs in the vermiculite may interact with oxygen. In order to confirm it, chemical shift of Cs-3d core level was measured and four components were found. The highest binding energy component only shifted by using an electron flood gun may be originated from hydration in weathered wide crevices. The other three components not shifted as well as K atoms originally-contained between phyllosilicate layers are corresponding to covalent interaction with O and Si atoms in narrow phyllosilicate interlayers.