A New Method for Partitioning of Trivalent Actinides from High-Level Liquid Waste

Abstract

The extraction behavior of Am(III) and Eu(III) in a solution of tetra-bis(2-ethylhexyl)diglycolamide (TEHDGA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) in n-dodecane (n-DD) was studied from nitric acid medium. The distribution ratio of Am(III) and Eu(III) in TEHDGA-HDEHP/n-DD was measured as a function of various parameters such as concentrations of nitric acid, TEHDGA, HDEHP, and nitrate ion. The data were compared with those obtained in individual solvents namely 0.1 M TEHDGA/n-DD and 0.25 M HDEHP/n-DD. The synergistic extraction of Am(III) and Eu(III) observed in a solution of 0.1 M TEHDGA – 0.25 M HDEHP/n-DD was attributed to the involvement of both TEHDGA and HDEHP for extraction. Slope analysis of the extraction data indicated the predominant participation of HDEHP for extraction at low acidities and TEHDGA and nitrate ion at higher acidity. The stripping behavior of Am(III) and Eu(III) from the extracted organic phase was investigated using citric acid (CA) and diethylenetriaminepentaacetic acid (DTPA). A suitable aqueous formulation was developed to separate Am(III) alone from chemically similar Eu(III) present in loaded organic phase, to facilitate a single-step separation of trivalent actinides from the high-level liquid waste (HLLW).