Efficient Separation\nof Pr(III) and Nd(III) via Shear-Induced\nDissociation Coupling with Ultrafiltration: Insights from Experiments\nand Theory

The separation of Pr(III) and Nd(III)\nposes a significant\nchallenge\ndue to their similar physicochemical properties, including comparable\nionic radii and coordination chemistry. In this study, acidic phosphoric\nchitosan (aPCS) was employed as a complexing agent in the shear-induced\ndissociation coupling with ultrafiltration (SID-UF) technique for\nthe sequential separation of Pr(III) and Nd(III). SID-UF uses shear\nstress to reduce membrane contamination and enables efficient metal\nion separation while allowing complexing agent recovery without acid\ndecomplexation, simplifying the process and lowering costs. The complexation\nkinetics of Pr(III) and Nd(III) with aPCS were investigated for the\nfirst time, following a pseudo-first-order model. The SID-UF technique\nachieved over 97% removal efficiency under optimized conditions, with\na separation factor β<sub>Pr/Nd</sub> of 12.01. DFT calculations\nshowed greater electron transfer for Nd(III) (0.2218 e) compared to\nPr(III) (0.2149 e), indicating stronger complexation with Nd(III).\nThe interaction energies further confirmed this, with Nd(III) exhibiting\na more favorable binding energy of −32.19 kcal mol<sup>–1</sup> compared to −31.09 kcal mol<sup>–1</sup> for Pr(III).\nThese results highlight the high selectivity, efficiency, and environmental\nbenefits of SID-UF, making it a promising alternative for industrial\nrare-earth separations.