Equilibrium analysis of neodymium - yttrium extraction in nitric acid media with D2EHPA as solvent

Abstract

This study aimed to develop the liquid-liquid equilibrium models to predict neodymium (Nd) and yttrium (Y) distribution in the extraction system. Feed solution (solution of Nd and Y in the 1 M nitric acid media) was mixed with solvent (di-2-ethyl-hexyl-phosphate (D2EHPA) diluted in kerosene) with volume ratio of 1:1 using a mechanical shaker for 25 min. The solution was settled to separate the aqueous and organic phase. Neodymium and yttrium concentrations in the aqueous phase were analyzed by using X-Ray Fluorescence - Ortec 7010 with Am 241. Meanwhile, the concentration of Nd and Y in the organic phase were evaluated by using mass balance. The results showed that the separation of Y from Nd was successfully carried out using 0.30 M D2EHPA diluted in kerosene. The Y extraction efficiency of 93% was obtained. To predict Nd and Y distributions, two mathematical equilibrium models were formulated: (i) the stoichiometric model derived from the reaction mechanism by considering the available reaction coefficients and (ii) the non-stoichiometric model is proposed to obtain approximate equilibrium data of Nd – Y extraction. The models were validated using experimental data. Neodymium and yttrium equilibrium distribution with D2EHPA as the solvent was better approximated using the non-stoichiometric than the stoichiometric equilibrium model as shown by the lower of mean relative errors.

Keywords

• Extraction
• Liquid-liquid equilibrium
• Neodymium
• Yttrium