Hexavalent Actinide Extraction Using N,N-Dialkyl Amides

Recently, efforts toward closing the nuclear fuel cycle have considered oxidizing americium to a hexavalent, linear-dioxo cation for co-recovery with hexavalent U, Np, and Pu from molar nitric acid using solvating extraction ligands such as tributyl phosphate or diamyl amylphosphonate. This work assesses solvent extraction recovery of sodium bismuthate oxidized americium by N,N-di(2-ethylhexyl)butyramide (DEHBA), N,N-di(2-ethylhexyl)isobutyramide (DEHiBA), and N,N-dihexyloctanamide (DHOA). Extraction efficiency between the monoamides was found to increase in the order of DEHiBA < DHOA < DEHBA. For all monoamides, oxidized americium extraction was less than 50% from 4 M HNO3 and below. Extraction efficiency above 50% was obtained using concentrations of 5 M HNO3 or higher. The DEHBA extractant provided the highest distribution value of 5.4 at 7 M HNO3. Distribution values were found to be stable for up to 45 s aqueous/organic phase mixing times and indicated decreased reduction of hexavalent americium rela...