Extraction of Erbium(III) from Nitrate Solutions Using Mixtures of Neodecanoic Acid and Diacylated Ethylene Amines

The article presents the novel binary mixtures of neodecanoic acid (HA) with diacylated ethylene amines (L), synthesized in our laboratory, for the recovery and separation of trivalent lanthanides. The extraction of Er(III), representing heavy lanthanides, from nitrate solutions has been studied using mixtures of HA with diacylated ethylenediamine, diacylated diethylenetriamine, and diacylated triethylenetetramine in tetrachloromethane. The FT-IR spectra for HA, L, and their mixtures have been analyzed to investigate the interaction in the binary mixtures. The effects of the nature of diluent, the aqueous phase acidity, and variation of one extractant at a fixed concentration of the other extractant have been investigated. The extracted species were determined to be [Er(OH)A(2)center dot L] by the slope analysis method, and the extraction mechanism was proposed. At pH values above 6.5, the [Er(OH)(2)A center dot L] species begin to prevail in the organic phase. Separation factors for Nd/Pr, Gd/Pr, Er/Pr, and Er/Gd pairs have been calculated to evaluate the possibility of the separation of lanthanides in the proposed mixed-extractant systems.