(633c) Selectivity and Recovery of Rare Earth Elements from Coal Ash Leachates Using Liquid Membrane-Based Separations

This research investigated the recovery of rare earth elements (REEs) from leachates of coal fly ash, a large volume waste material that is enriched in REEs. Here, we investigated two types of liquid membrane separation methods, liquid emulsion membrane (LEM) and a supported liquid membrane (SLM), for their potential to effectively concentrate REEs from fly ash leachates. This work focused on the selective of these processes for REEs relative to other major metal ions in leachates and the mechanism controlling REE selectivity. Both SLM and LEM processes demonstrated 3-5 orders of magnitude greater selectivity of individual REEs compared to major ions (e.g. Al, Si, Na). The LEM-based separation and conventional solvent extraction were most efficient for the light REEs (e.g. La, Ce, Pr, Nd, Sm, Eu, Gd) while the SLM approach was most efficient for the heavy REEs (e.g. Y, Dy, Ho, Er, Tm, Yb, Lu), suggesting different rate limiting steps for REE recovery. Future work will explore the alternative solvents and extractants for the process as a means to improve recovery efficiency of high value REEs.