Efficient Separation of Pr(III) and Nd(III) via Shear-Induced Dissociation Coupling with Ultrafiltration: Insights from Experiments and Theory

The separation of Pr(III) and Nd(III) poses a significant challenge due to their similar physicochemical properties, including comparable ionic radii and coordination chemistry. In this study, acidic phosphoric chitosan (aPCS) was employed as a complexing agent in the shear-induced dissociation coupling with ultrafiltration (SID-UF) technique for the sequential separation of Pr(III) and Nd(III). SID-UF uses shear stress to reduce membrane contamination and enables efficient metal ion separation while allowing complexing agent recovery without acid decomplexation, simplifying the process and lowering costs. The complexation kinetics of Pr(III) and Nd(III) with aPCS were investigated for the first time, following a pseudo-first-order model. The SID-UF technique achieved over 97% removal efficiency under optimized conditions, with a separation factor β_Pr/Nd of 12.01. DFT calculations showed greater electron transfer for Nd(III) (0.2218 e) compared to Pr(III) (0.2149 e), indicating stronger complexation with Nd(III). The interaction energies further confirmed this, with Nd(III) exhibiting a more favorable binding energy of −32.19 kcal mol^–1 compared to −31.09 kcal mol^–1 for Pr(III). These results highlight the high selectivity, efficiency, and environmental benefits of SID-UF, making it a promising alternative for industrial rare-earth separations.