Extraction of uranium(VI) from nitric acid solutions using N,N-dihexyloctanamide in ionic liquids: Solvent extraction and spectroscopic studies

Abstract

ABSTRACTLiquid-liquid extraction studies of uranium(VI) were carried out from nitric acid medium using di-n-hexyloctanamide (DHOA) in several room-temperature ionic liquids (RTIL). The extraction of the metal ion as a function of nitric acid concentration showed different trends based on the alkyl substituents of the RTIL. While the DU values decreased with increasing HNO3 concentration (up to ca. 0.5 M) with [C4mim][NTf2] and [C6mim][NTf2], almost no change was seen with [C8mim][NTf2]. This suggested that while a cation-exchange mechanism is operative with the former diluents, which was to a much lower extent for the latter. The extracted species were found to contain about 2 molecules of DHOA from the feed solutions containing either 0.01 M and 4 M HNO3, which was arrived at from the ligand-concentration-variation experiments. Recycling studies were also performed by carrying out stripping and radiolytic stability studies. The nature of the extracted species as ascertained from the UV-visible spectrophotometry studies indicated similarity between the extracts obtained in RTIL medium, which were entirely different from that observed with n-dodecane as the diluent.