PNNL

Abstract

Selective extraction of rare earth elements (REEs) from waste NdFeB mangets and natural mineral sources has been challenging due to the similar properties of neodymium (Nd) and dysprosium (Dy). Current separation methods mainly include solvent extraction and organic ligang-based selective precipitation, which are chemical- and energy-intensive in addition to long separation times required to reach the thermodynamic equilirbium. Here, we demonstrate a laminar co-flow method that relies on flow-induced non-equilibrium conditions to selectively precipitate Dy3+ from aqueous solutions containing mixed Nd3+ and Dy3+ at various ratios. The concentration of reactant sodium dibutly phosphate for selective precipitation was identified based on the differences in the spatiotemporal dynamics of the Nd3+ and Dy3+ precipitates. Under optimized conditions, our method showed increased Dy purity in the precipitate product at significantly shorter reaction times, compared to commonly used convective bulk mixing. We found nearly Dy-pure (99.9%) precipitate from starting mixtures of Nd:Dy in 50:50 and 30:70 ratios. Our single-step method is efficient, and enrivonmentally friendly and does not require harmful organic solvents or difficult to synthesize complex ligands.