Chelation Assisted Electrodialysis as a Practical Alternative to the SX-5 Stage for Separating (Tb, Dy) from (Sm, Eu, Gd)

This study demonstrates a chelation-assisted electrodialysis (CAED) process using DCTA as a potential solvent-free alternative to the SX-5 stage in rare earth element (REE) separation. The process was evaluated using synthetic feed solutions representative of the middle-to-heavy REE fraction, and its performance was compared with that of the conventional EDTA-assisted system. DCTA exhibited superior selectivity and faster precipitation kinetics, leading to improved separation performance under controlled laboratory conditions. A phenomenological model was developed, experimentally validated, and applied to identify an optimal operation window, providing insight into ion transport behavior and stage-wise selectivity trends. While DCTA offers clear chemical advantages, practical factors such as its higher cost, solubility limits, and recycling requirements remain important considerations for scale-up. The CAED approach demonstrated the potential to reproduce the SX-5 separation step while eliminating organic solvent use, offering a pathway toward more sustainable REE separation processes.