Separation of Light and Heavy Rare Earth Elements via Electrospun Supported Liquid Membrane

Rare earth elements (REEs) are predominantly separated by using mixer-settler solvent extraction technology. While this method has been utilized in the industry, it does have a few setbacks, such as requirement of large module footprint to compensate for inefficient separation. Likewise, researchers have turned to membrane separation technology to address these challenges faced by mixer-settler solvent extraction. Supported liquid membranes (SLMs) are a viable alternative in membrane separation technology as they exhibit similar conceptual designs to that of solvent extraction, albeit requiring smaller amounts of organic carrier and lower module footprint compared to mixer settler solvent extraction. In this research, the application of an electrospun membrane was explored using SLMs for the separation between light REEs (LREEs) and heavy REEs (HREEs). To do this, the study initially employs the usage of neodymium (Nd) and dysprosium (Dy) as the baseline for LREEs and HREEs, and later using real REE leachate for the separation between LREEs and HREEs. This study also investigates the effects of different pH of feed solution, organic carrier loading, and stripping concentrations. Overall, to achieve higher selectivity of Nd/Dy, a higher pH of feed solution of 5, a low loading of organic carrier at 10 wt%, and a low stripping concentration of 1 M H₂SO₄ was recommended. For the separation of LREEs and HREEs, a separation factor of 2.38 was achieved with a recovery of 10.43% of LREEs in under 60 min by using a small-scale membrane of 4 cm² effective area. Long term operation indicates a stable LREE/HREE separation performance using the optimized condition.