Separation of americium (III) and strontium (II) using TEHDGA and 18-crown-6

This work describes extraction of Am(III) and Sr(II) together with tetra(2-ethylhexyl) diglycolamide (TEHDGA) and selective back-extraction of strontium with a strontium complexant, 18-crown-6, leading to their separation from each other. 0.3 M TEHDGA+5% isodecyl alcohol/n-dodecane was used to extract Am(III) and Sr(II) from 4 M nitric acid into organic phase with very high D (D_Am=1000, D_Sr=22) and 0.1 M 18-crown-6 dissolved in 4 M nitric acid is used for selective stripping of Sr(II) from loaded extract phase. Am(III) left in the extract phase was then stripped with 0.01 M nitric acid. Stripping of Sr(II) was found to increase with increase in 18-crown-6 concentration, at 0.1 M 18-crown-6 dissolved in 4 M nitric acid, 83% of the loaded strontium (D_Sr=0.20) was back-extracted in a single contact while loss of Am(III) was 0.8% (D_Am=122.45). Stoichiometry limit of 1:1 was observed between strontium and 18-crown-6. Strontium was precipitated and separated from the complexant by Na₂SO₄ or Na₂CO₃. This process was tested with simulated solution of high level waste and found suitable for quantitative recovery of strontium with high purity.