Extraction of uranium from sulfuric acid media using amino-diamide extractants

Two extractants, N,N′-((octylazanediyl)bis(ethane-2,1-diyl))dioctanamide (LI) and N,N′-((octylazanediyl)bis(ethane-2,1-diyl))di-2-methylheptanamide (LII), have been synthesised in two steps starting from diethylenetriamine and involving a peptide coupling step. The efficiency and selectivity of the extractants in dodecane/octanol (95/5 v/v) toward the extraction of uranium from sulfate media have been investigated showing that the uranium extraction from sulfuric acid is more efficient at a low H2SO4 concentrations. Slope analysis method revealed 2:1 extractant/metal ratio, which is in accordance with NMR titration as well as DFT calculations. The extractants are found to be selective toward uranium over competitive cations present in a simulated leach solution. Finally, a stripping step has been performed and given rise to a successful quantitative recovery of uranium. •Extraction of uranium(VI) from sulfuric acidic solutions using amino-diamide as extracting system.•Detailed study of the extraction highlight a 2:1 stoichiometric ratio for the ligand:UO22+ complex.•A quantitative recovery of U(VI) is achieved by ammonium or sodium carbonate.