Feed phase salting agent prevails the absence of organic phase Ligand: A sustainable extraction process for Eu(III)/Am(III) in an undiluted phosphonium ionic liquid

Abstract

• Europium(III)/Americium(III) extraction by undiluted Cyphos nitrate ionic liquid. • Appreciable extraction factors with the use of low cost and readily available salting agent in the feed phase. • Avoidance of any extra ligand in the ionic liquid phase for the extraction process. • Straightforward extraction mechanism rendering the complexation of M(III) in the ionic liquid phase. • Quantitative stripping within 2–3 stages using Millipore water. Long chain quarternary alkyl phosphonium based ionic liquids have several fascinating merits over conventional imidazolium based ionic liquids. In this context, trihexyl(tetradecyl)phosphonium nitrate ([P 66614 ][NO 3 ]) ionic liquid (commonly known as cyphos nitrate) was chosen as the extractant in its undiluted status for the extraction and separation of trivalent Ln(III)/An(III) from the nitric acid phase. Experimental parameters such as the concentration of initial nitric acid, initial nitrate ion in the feed phase, initial feed metal concentration, equilibration time, etc. were varied precisely to furnish the extraction process. The major highlights in the study is the fascinating salting effect of the feed phase NO 3 – ion in the efficient extraction of Eu(III)/Am(III). This methodology avoids the use of additional extractant in the ionic liquid phase for extracting the metal ion leading to an economical process. The use of [P 66614 ][NO 3 ] avoids the loss of any ionic liquid component to the aqueous phase during the extraction. The proposed ionic liquid was found to be radiation stable which enhances its reliability as solvent for the separation of Ln(III)/An(III) in the context of spent nuclear fuel reprocessing. The present ionic liquid was found to be superior in metal loading in comparison to other ionic liquids with similar type of structure. Another underscore of the present study is the use of only Millipore water as the stripping agent without adding any aqueous phase complexing agent which certainly offer economic and environmental benefit.