Solvent extraction of La(III) and Nd(III) from nitrate solutions with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester

Equilibrium and kinetic studies on solvent extraction of single and binary La(III) and Nd(III) from nitrate solutions with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A) in kerosene at 298 K were studied. Experiments were performed at different initial pH (2–6), metal concentrations (2.5–35 mol/m3), and dimeric extractant concentrations (1.7–100 mol/m3). The strip phase consisted of 500–1500 mol/m3 of HNO3 (mostly, 500 mol/m3). The stoichiometry and equilibrium constant for the extraction reactions were determined. The extractant PC88A exhibited higher extractability for Nd(III) than La(III) under comparable conditions. Rate equations for the extraction and stripping of La(III) and Nd(III), as well as the related rate constants, were obtained at 298 K. It was shown that the extraction rates of La(III) and Nd(III) were comparable but the stripping rate of Nd(III) was near two order of magnitude larger than that of La(III). The present results had demonstrated extraction separation of Nd(III) over La(III) from nitrate solutions with PC88A to be kinetically and thermodynamically favorable.