SELECTIVE REMOVAL OF CESIUM FROM RADIOACTIVE WASTE SOLUTIONS USING INSOLUBLE FERROCYANIDE-LOADED

Potassium nickel hexacyanoferrate(II)s (KNiFC) were incorporated in the porous matrix of mordenites by successive impregnation of Ni(NO3)2 and K4Fe(CN)6. The KNiFC crystals with fcc structure were uniformly dispersed throughout the granule, resulting in the lowering of specific surface area and pore volume. The ion-exchange equilibrium of Cs+ in KNiFC-loaded mordenite (NMFC) was reached within 2 days. Relatively large distribution coefficients of Cs+, Kd,Cs, above 104 cm3/g were obtained even in the presence of highly concentrated 5 M NaNO3 or 5 M HNO3. There was a large difference between the Kd value of 137Cs and those of other nuclides; separation factor of Cs/Sr (αCs/Sr = Kd,Cs/Kd,Sr) was estimated to be 104 in the presence of 2.5 M HNO3-0.981 M NaNO3. Favorable S-shaped breakthrough curves for Cs+ were obtained by passing the simulated high-level liquid wastes containing 29 components through the column packed with NMFC exchanger, and the breakthrough capacity of Cs+ was estimated to be 0.19 mmol/g. This exchanger proved to be effective for the selective removal of radioactive cesium from high-level liquid wastes