Insights Into the Extraction of Am(III) by Aliquat-336 Based Ionic Liquids

Abstract

The extraction behavior of Am(III) in a solution of tetra-(2-ethylhexyl)diglycolamide (TEHDGA) in n−dodecane (n−DD) or toluene was studied as a function of nitric acid concentration. The distribution ratio of Am(III) in 0.1 M TEHDGA/molecular diluent increased with increase in the concentration of nitric acid. Since the Aliquat-336 based ionic liquid namely, tri-n-octylmethylammonium di-(2-ethylhexyl)phosphate ([A336]+[DEHP]−) was miscible in molecular diluents such as n-DD and toluene, the extraction behavior of Am(III) in TEHDGA/molecular diluent was investigated in the presence of small concentrations of ionic liquid to understand the role of ionic liquid in extraction. The distribution ratio of Am(III) in 0.2 M [A336]+[DEHP]−/molecular diluent was negligible. Significant increase in distribution ratio of Am(III) was observed when [A336]+[DEHP]− was added to 0.1 M TEHDGA/molecular diluent. Since [A336]+[DEHP]− was converted into its components, namely tri-n-octylmethylammonium nitrate ([A336]+[NO3]−) and di-(2-ethylhexyl)phosphoric acid (HDEHP) when contacted with nitric acid, the extraction behavior of Am(III) in 0.1 M TEHDGA/molecular diluents was also studied in the presence of [A336]+[NO3]− and HDEHP to elucidate the mechanism of extraction. The study confirmed that the extraction of Am(III) in ionic liquid medium was controlled by constituents of ionic liquid and the distribution ratio of Am(III) obtained in organic phase was due to the resultant of contributions of ionic liquid constituents.