Journal of Nuclear Fuel Cycle and Waste Technology

The applicability of room temperature ionic liquids (RTILs), 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim] [Tf2N]), was investigated for the extraction of Am(Ⅲ) and Eu(Ⅲ) from nitric acid using n-octyl(phenyl)-N,N-diisobutyl carbamoylmethyl phosphine oxide (CMPO) and tri-n-butylphosphate (TBP) as extractants. The distribution ratios of Am(Ⅲ) and Eu(Ⅲ) in CMPO-TBP/ [Cnmim][Tf2N] were measured as a function of various parameters such as the concentrations of nitric acid, CMPO, and TBP. The results were compared with those obtained in CMPO-TBP/n-dodecane (n-DD). With comparable concentrations of the extractants, the distribution ratios obtained with RTILs were much higher than those obtained with n-DD. It was observed that the extraction efficiency was less for Eu(Ⅲ) than for Am(Ⅲ). The extraction of Am(Ⅲ) and Eu(Ⅲ) decreased with increases in the feed acidity for all three RTILs. The results suggest that the extraction of Am(Ⅲ) and Eu(Ⅲ) by CMPO in RTILs from nitric acid proceeds through the cation-exchange mechanism. The distribution ratios of Am(Ⅲ) and Eu(Ⅲ) increased with increases in the concentration of CMPO for all three RTILs. A linear regression analysis of the extraction data resulted in a straight line with a slope of about 3, suggesting the involvement of 3 molecules of CMPO during the extraction process.

Keywords

Ionic liquid,Imidazolium,Solvent extraction,Distribution ratio,Molecular organic solvent,Complexing agent