Study of a Sorption Activity of the Amberlite IR120:KU-2-8 Interpolymer Systems in Relation to Dysprosium, Neodymium and Samarium Ions

This study investigates the sorption, structural, and morphological properties of an interpolymer system (IPS) based on Amberlite IR120 (H+) and KU-2-8 (H+) cation exchangers with acidic sulfonic groups (−SO3H), applied for the selective sorption of dysprosium (Dy3+), neodymium (Nd3+), and samarium (Sm3+) ions from aqueous solutions. The sorption activity was evaluated for seven systems with molar ratios ranging from 6:0 to 0:6 over a contact time of up to 48 h within a pH range of 2.0 to 5.0. The interpolymer pair with a molar ratio of 5:1 demonstrated the highest sorption efficiency at pH 5.0, yielding extraction degrees of 61.8% for Dy3+, 62.0% for Nd3+, and 64.4% for Sm3+. Equilibrium data were accurately described by the Langmuir isotherm model (R2 > 0.974), indicating a dominant monolayer chemisorption mechanism. The maximum monolayer adsorption capacities (qm) followed the order Dy(III) (189.59 ± 31.52 mg/g) > Sm(III) (162.27 ± 52.38 mg/g) > Nd(III) (139.90 ± 35.40 mg/g). The selectivity toward dysprosium was supported by distribution coefficients (Kd) and separation coefficients (βDy/Nd = 1.557 and βDy/Sm = 1.757 for the 6:0 system). FTIR analysis confirmed the direct coordination of lanthanide ions by sulfonic groups, as evidenced by the shifts in the νas(S=O) bands. SEM-EDX characterization revealed distinct post-sorption morphological changes (surface cracking and flaking) and confirmed significant REE accumulation on the resins (up to 4.04 wt.%) coupled with a stoichiometric decrease in sulfur content, validating the ion-exchange mechanism. These findings provide a deeper insight into the remote conformational effects governing interpolymer interactions and offer a highly promising approach for the selective recovery of REEs in hydrometallurgy.