EXTRACTION OF NITROSORUTHENIUM BY TRIBUTYL-PHOSPHATE

A study has been made of distribution of highly extractable nitrosoruthenium complex RuNO(NO3)(3) (RuT) between aqueous solutions and tributyl phosphate (TBP) in n-dodecane. Short phase contact (similar to 30 s) was employed to minimize possible mutual conversion of nitrosoruthenium species, which takes place in the case of prolonged phase contact. The distribution coefficient alpha(RuT) is independent of hydrogen ion concentration and the presence of various salts in aqueous phase, i.e., RuT is extracted as nonelectrolyte. Experiments in which the TBP concentration was varied by dilution or binding TBP with nitric acid and uranyl nitrate indicates formation of trisolvate (as main complex characterized by extraction constant K-3 = 72) and disolvate (K-2 = 5). At high nitric acid and/or uranyl nitrate concentration, alpha(RuT) is insignificantly reduced, while solvate number decreases substantially. Probably, nitrosoruthenium tetranitrate, e.g., RuNO(NO3)(3) . HNO3 . TBP, and/or complex of RuT with uranyl nitrate is formed. The decontamination of valuable fuel components from ruthenium may be improved by a factor 10(3) by binding TBP with nitric acid and uranyl nitrate. Another way to reduce alpha(RuT) is to convert RuT into poorly extractable RuD form. The time of RuT half-conversion into RuD was found to be 15 min in the presence of HNO3, 9 min in the presence of uranyl nitrate, and 5 min at 50-60 degrees C(simultaneously alpha(RuT) decreases by an order of magnitude).