On the use of hexacyanocobaltates in the separation of caesium from radioactive waste solutions

Abstract

This paper reviews our work on the use ofhexacyanocobaltate salts in the chemical treatment of radioactive waste solutions. The divalent cations of the 3d-block elements together with the hexacyanocobaltate moiety form insoluble polymeric coordination compounds. These compounds have been used as chemical precipitants or ion exchangers for the separation ofradiocesium from various simulated and actual waste solutions. Precipitation in situ has been performed by using various hexacyanocobaltate salts of the divalent cations ofMn, Fe, Co and Ni. The results showed that Co 2 § and Ni 2 § salts have high selectivity for caesium. The presence of monovalent cations and detergent has significant effect on the precipitation process. On the other hand Cd 2 § salt has been found to be more stable than other salts in alkaline medium. As ion exchanger the sorption properties ofhexacyanocobaltate salts were studied. Adsorption of a cesium seems to proceed via an ion exchange mechanism. It has been used for the treatment of reprocessing medium active waste solution. A decontamination factor of about 103 has been achieved.