Molecular Mechanism of Heavily Adhesive Cs: Why Radioactive Cs is not Decontaminated from Soil

• Published in: Journal of physical chemistry. C Vol. 117; no. 27; pp. 14075 - 14080
• Main Authors: Sato, K, Fujimoto, K, Dai, W, Hunger, M
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 11-07-2013
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Physics; Solid surfaces and solid-solid interfaces; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Interfacial layer; Interlayers; Cesium 137; Nanoplate; pH value; Nanosheet; Molecular structure; Adsorption site; Minerals; Surface structure; Clays; Local structure; Adsorption; Adsorption structure; Crystal structure
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp403899w

Two years having passed since the nuclear crisis at Fukushima, radioactive 137Cs with a half-life of ∼30 years has come to the forefront of our largest concern. To gain an insight into current unsuccessful 137Cs decontamination from soil, heavily adhesive Cs adsorption, referred to as specific Cs adsorption here, is highlighted for layered clay minerals. Besides the interlayer Cs+ cations, a population of Cs is able to adsorb on the surfaces of open nanospaces with their sizes of ∼0.3 and ∼0.9 nm, which are formed by one- and two-clay nanosheet insertion into interlayer spaces. They are adsorbed on the surfaces of the open nanospaces so strongly that they cannot be removed even by a hydrochloric acid solution of pH 1.0; these open nanospaces thus act as the specific Cs adsorption sites. The characteristic local molecular structures as a clay-nanosheet edge and a wedge-shaped frayed part available in the open nanospaces are responsible for the specific Cs adsorption. Radioactive 137Cs that is not cleaned up after the decontamination work would originate from the specific Cs adsorption clarified in the present work.