CROWN-ETHERS AS ACTINIDE EXTRACTANTS IN ACIDIC AQUEOUS BIPHASIC SYSTEMS - PARTITIONING BEHAVIOR IN SOLUTION AND CRYSTALLOGRAPHIC ANALYSES OF THE SOLID-STATE

The partitioning behavior of UO22+, Pu4+, Th4+, and Am3+ has been investigated in aqueous biphasic systems formed by the addition of polyethylene glycol of average molecular weight 2000 (PEG-2000) and (NH4)(2)SO4. Water-soluble crown ethers 18-crown-6 and 15-crown-5 have been utilized as extractants. A positive correlation has been observed between crown ether concentration and metal ion partitioning with D-An,, decreasing in the order UO22+ > Pu4+ > Th4+ > Am3+. A distribution ratio above unity, however, has only been observed for UO22+ at very high (1.25 M) concentrations of 18-crown-6. In general the distribution ratios for 15-crown-5 are all lower. Matrix ions introduced as NH4NO3, H2SO4, or HNO3 drastically reduce the observed distribution ratios and level the extractant dependencies.