Crown ethers as actinide extractants in acidic aqueous biphasic systems: Partitioning behavior in solution and crystallographic analyses of the solid state

Article abstract of DOI:10.1016/0925-8388(94)90920-2

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)₂SO₄. 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.