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 (q_m) 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 (β_Dy/Nd = 1.557 and β_Dy/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.

In this study, we investigated the selective sorption of neodymium ions from a mixture of solutions using interpolymer systems consisting of two industrial sorbents – Amberlite IR120(Н+) and AB-17-8(ОН-) ion exchange resins – in various molar ratios. Based on the obtained results, we found that maximum polymer activation occurs at an Amberlite IR120:AB-17-8 ratio of 5:1. These ratios yield the highest neodymium ion sorption. The sorption process was carried out in static mode. After 48 hours of remote polymer interaction, the maximum neodymium ion sorption was 56.2%, and the degree of polymer chain binding was 3.96%. The calculated values of the unactivated polymers demonstrated that the sorption activity of the interpolymer systems in the Amberlite IR120:AB-17-8 (5:1) and Amberlite IR120:AB-17-8 (3:3) ratios is significantly higher than that of the original unactivated polymers Amberlite IR120 (6:0) and AB-17-8 (0:6). The results demonstrate that the electrochemical and sorption properties of the original polymers are altered in the interpolymer systems, increasing the reactivity of the functional groups. This allows them to be used in the development of an effective sorption technology for the separation of neodymium ions. Thus, it is demonstrated that the interpolymer systems can be used in industry by varying the sorption conditions for the efficient extraction of neodymium from industrial solutions.