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

This paper reviews our work on the use of hexacyanocobaltate salts in the c hemical treatment of radioactive waste solutions. The divalent cations of t he Ed-block. elements together with the hexacyanocobaltate moiety form inso luble polymeric coordination compounds. These compounds have been used as c hemical precipitants or ion exchangers for the separation of radiocesium fr om various simulated and actual waste solutions. Precipitation in situ has been performed by using various hexacyanocobaltate salts of the divalent ca tions of Mn, Fe, Co and Ni. The results showed that Co2+ and Ni2+ salts hav e high selectivity for caesium. The presence of monovalent cations and dete rgent has significant effect on the precipitation process. On the other han d Cd2+ salt has been found to be more stable than other salts in alkaline m edium. As ion exchanger the sorption properties of hexacyanocobaltate 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 10(3) has been achieved.