Hokkaido University Research Profiles


Capturing and Insolubilization of Cesium by Aluminosilicates

Capturing of cesium contained in decontamination waste by aluminosilicate (alkali feldspar)

The insoluble form of cesium in incineration bottom ash was concentrated in the amorphous phase on the surface of a specific mineral, namely, alkali feldspar. This trapping phenomenon is applied to insolubilize cesium in soil and waste generated during decontamination, and we are developing a technology to control the leaching of cesium, even during long-term storage.

Content of research

The solubility of cesium (Cs) in incineration bottom ash is low due to strong trapping of Cs in the amorphous phase on the surface of microcline, which is a kind of alkali feldspar. When Cs salts such as Cs carbonate and Cs chloride are added to pure microcline and heated, Cs is trapped at an extremely high rate and becomes insoluble (Fig. 1). Since the Cs trapped by this process is fixed very tightly, it cannot be extracted unless hydrofluoric acid is used. Similar Cs trapping occurs when using a reagent to synthesize microcline (Fig. 2). In this study, we are applying this phenomenon of Cs capture by microcline (aluminosilicate) to Cs-enriched materials (e.g., fly ash with high Cs concentration) generated during volume reduction thermal treatment of removed soil and decontamination waste, aiming to establish a technology to reduce the mobility of Cs in the waste to be finally disposed of to the extent possible (Fig. 3).

Potential for social implementation

  • ・Decontamination waste disposal method
  • ・Insolubilization of radioactive Cs
  • ・Long-term Management of Radioactive Contaminated Incineration residue

Appealing points to industry and local governments

This study is part of the research conducted in our laboratory to assure the safety and security of final waste disposal sites. The main focus of our research is to clarify the behavior of chemical substances, such as radioactive Cs in landfill layers, which needs to be strictly controlled for a long period of time, and to propose a management strategy for such substances. Besides research for disposal sites, it is also possible to perform collaborative research on the behavior and management of hazardous materials in the environment, such as safety assessment of recycled materials.