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

Abstract

Abstract 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.