Interaction between Ultra-Trace Amount of Cesium and Oxides Studied by Total-Reflection X-Ray Photoelectron Spectroscopy

Abstract

In order to clarify the chemical states of radioactive cesium sorbed in minerals such as clay, soil, sand and rock, X-ray photoelectron spectra (XPS) have been measured for cesium adsorbed on SiO2 and Al2O3 (sapphire), which are major components of these minerals. Since the number of atoms in radioactive cesium ( 134 Cs or 137 Cs) is extremely small, total reflection XPS (TR-XPS) using synchrotron radiation was applied in order to measure trace amount of cesium. For SiO2 surface, it was shown that ultra-trace amount of cesium down to 205 pg·cm −2 can be detected by TR-XPS. This amount corresponds to about 400 Bq of 137 Cs (t 1/2 =30.2 y). Thus it was demonstrated that the ultra-trace amount of cesium corresponding to the radioactive cesium level can be measured by TR-XPS. As to the chemical states of cesium, the binding energy of the Cs 3d 5/2 line for cesium adsorbed on SiO2 and Al2O3 ranges from 725.2 eV to 725.5 eV irrespective of the adsorption conditions, suggesting that the cesium is adsorbed through weak Van-der-Waals force. While after rinsing the cesium-adsorbed SiO2 in water, the binding energy of the Cs 3d 5/2 line shifted by 0.8 eV to higher energy side. The result indicates that the ultra-trace amount cesium remaining after rinsing is covalently bonded with the SiO2 surface rather than ionically bonded.

Vacancy Ordered Lead Free Double Perovskite Based Flexible Supercapacitor for Sustainable Energy Applications

“…From Figure , it can be observed that after charging in Li electrolyte, the Cs 3d 5/2 peak almost disappears and 3d 3/2 peak is much broader. The disappearance of the 3d 5/2 peak may be due to formation of the oxide phase, i.e., SnO 2 , in which cesium atoms are adsorbed on the SnO 2 surface which lowers and shifts the intensity of the 3d 5/2 peak . The broadening of the peak may be attributed to Li ion intercalation, which may shift the Cs atom from the A site position in perovskite octahedra, resulting in a diverse chemical environment of Cs atoms.…”

“…The disappearance of the 3d 5/2 peak may be due to formation of the oxide phase, i.e., SnO 2 , in which cesium atoms are adsorbed on the SnO 2 surface which lowers and shifts the intensity of the 3d 5/2 peak. 43 The broadening of the peak may be attributed to Li ion intercalation, which may shift the Cs atom from the A site position in perovskite octahedra, resulting in a diverse chemical environment of Cs atoms. After discharging, the 3d 5/2 peak again appears and peak shifts from 725.98 to 724.67 eV.…”

Chemical state analysis of trace-level alkali metals sorbed in micaceous oxide by total reflection X-ray photoelectron spectroscopy

“…So it is important to analyze the chemical states of ultra-trace amount of cesium in micaceous oxides in order to clarify the real adsorption states of radioactive cesium. In a previous paper, we have reported that XPS under total reflection (TR) shows enhanced surface sensitivity and detects trace amount of cesium adsorbed on oxides [18].…”