Model experimental study on Cs removal from clay minerals by ion exchange under microwave irradiation

In this study, attempts were made to remove Cesium (Cs) from clay minerals using an ion exchange reaction, the rate of which is enhanced by microwave irradiation. This article reports fundamental studies performed, using vermiculite as a model of clay minerals, doped with non radioactive Cs and heated under irradiation of microwave with addition of various salts in powder state. Among various kinds of chemicals added for exchange reaction, CaCl₂ and KCl are shown to be effective for Cs removal, and further mixing of CaCO₃ has additional effects. Heating to temperature above 670 °C is shown to be effective for their removal, however, the heated features of the specimens differed between the microwave and the electric furnace heating. Microwave absorbability or heating characteristics of vermiculite with and/or without additives are also studied. It was shown that mixing of vermiculite with CaCl₂ and KCl can enhance microwave heating better than heating of each (vermiculite, KCl, CaCl₂) alone, this tendency was consistent with the results of the permittivity and conductivity measurement. Further addition of CaCO₃ enhanced thereaction kinetics, however, deteriorates the microwave heating ability.