Liquid–liquid extraction and pertraction behavior of Am(III) and Sr(II) with diglycolamide carrier extractants

Solvent extraction and supported liquid membrane transport properties of Am(III) and Sr(II) from nitric acid medium using several substituted diglycolamides (DGAs) were investigated in detail. The DGAs studied were N,N,N′N′-tetraamyl diglycolamide (TPDGA), N,N,N′N′-tetrahexyl diglycolamide (THDGA), N,N,N′N′-tetraoctyl diglycolamide (TODGA), N,N,N′N′-tetra(2-ethyl hexyl)diglycolamide (T2EHDGA) and N,N,N′N′-tetradecyl diglycolamide (TDDGA). Effects of feed acidity, phase modifier composition, nature of species were investigated for the solvent extraction of the radionuclides using the DGAs. The trend of Am(III) extraction was TPDGA ≫ THDGA ≫ TODGA > TDDGA ≫ T2EHDGA. The slope analysis method for Am(III) extraction has indicated extracted species containing 4 and 3 molecules of the extractant for TODGA and T2EHDGA, respectively and about two molecules of extractant were found to be associated with the other DGAs. When simulated high level waste was used as the feed, the distribution ratio values decreased significantly. Supported liquid membrane transport of the radionuclides was evaluated to understand the effects of feed acidity, membrane pore size and phase modifier concentration for the DGAs. While the trends for Am(III) transport rate were TPDGA ∼ THDGA ∼ TDDGA > TODGA > T2EHDGA and usually 2–5 h were needed for quantitative transport (>99%), Sr(II) transport was found to be significant in this time scale. The trend for activation energies of transport of Am(III) was found to be TDDGA > THDGA > TPDGA (with 30% iso-decanol) > T2EHDGA > TODGA.