Home – Home – Jornals – Chemistry for Sustainable Development 2003 number 4

In relation to the problem of recovery of fission palladium from highly active liquid wastes from spent nuclear fuel reprocessing, the efficiency of a flow sheet based on solvent extraction and electrochemical processes for palladium purification from a number of accompanying elements (Ag, Te, Se, Sb) was tested using model (in the absence of radiation) nitrate-nitrite solutions. The flow sheet is composed of two extraction cycles which involve solvent extraction of palladium with petroleum sulphides, washing of the extracts with acid solutions, and palladium stripping with aqueous ammonia. In the first cycle imitating recovery from HLW, ~99 % Pd and ~25 % Ag is recovered and separation from other accompanying elements is achieved. High efficiency of palladium separation from silver (10⁵) is achieved during the second cycle due to solvent extraction affining from hydrochloric solution. For passing from the ammonia strip liquor of palladium and silver, which is the final product of the first cycle, to the starting hydrochloric solution for the second cycle, electrochemical operations are applied, involving co-deposition of these metals on the cathode followed by their anodic dissolution in HCl solution. The efficiency of these operations was also not less than 99 %. At the final stage, purified palladium is recovered from the strip liquor of the second cycle as a difficultly soluble trans-dichlorodiammine ("palladozammine", PZA). End-to-end palladium fraction extracted with the help of this flow sheet is 97_98 %. No Te, Se or Sb admixtures were detected in the resulting PZA; Ag content is close to the level observed in the reference experiment (mass concentration 10^_5 %).