Extraction of Some Rare Earth Elements (La, Pr and Er) from Citrate Medium Using D2EHPA in kerosene.

Abstract

Extraction and possible separation of the rare earth elements, REEs, lanthanum (III), praseodymium (III) and erbium (III) from citric acid solution using Di(2-ethylhexyl) phosphoric acid, D2EHPA, in kerosene were studied. The parameters affecting the extraction process were separately studied in order to achieve the maximum possible separation between the different REEs under investigation. It was found that from 1.0 mol/L citric acid solution at pH = 4.0, the extraction is dependent mainly on the citric acid and D2EHPA concentration as well as temperature. From the experimental results and the main species in the aqueous phase, a proposed extraction equilibrium of the different metal ions was given. Conditional extraction constants for the proposed extraction equilibrium were calculated for the different elements, and found to verify the experimental results. The order of the conditional extraction constants follows the sequence, Er (III) >> La (III) ≥ Pr (III). The thermodynamic functions associated with the extraction reaction were evaluated and discussed. Feasibility of separation of Er(III) from La (III), and Pr (III) obtained was given in terms of the separation factors between different elements at different extraction conditions. Keywords: