Exchange of Cs Ion in Clay Minerals by Microwave Application

It is known that many kinds of clay minerals consist of layered silicates, and some cations are tightly fixed in them. The cations exist in the inter-layer clearance and are bound due to the electrostatic force. Especially, Cs ion fits the size of the 'hole' in the layer crystal structure. Therefore, Cs ions, once contained in a clay, are not dissolved into water. One of the possible methods for the Cs removal is to exchange it with some other cations. In this study, vermiculite was selected as an example of clay mineral. In the experiment, the vermiculite water suspension was doped with non-radioactive Cs. After separating from the water and drying, we attempted microwave application with addition of KG in powder state (solid state) for examination of the ion exchange. It was observed that the KCI addition to vermiculite improved the microwave heating ability, although KCI itself is not heated well by microwave. Electric conductivity of the mixture was measured up to 5MHz and shown to be higher than that of vermiculite. Transition frequency to the dielectric conductivity is also higher in the mixture. However, the permittivity in GHz range was not influenced by KCI addition very much. It was speculated that the loss factor increased as the temperature increase more in the mixture. Dissolution of Cs was enhanced by the microwave treatment, indicating the promotion of the Cs ion exchange with K ion.