Sorption of Scandium from Acidic Chloride Solutions on Strong-Acid Cation-Exchange Resins: Comparative Assessment and Isotherm Modeling

Recovery of scandium from chloride-bearing process liquors formed during titanium–magnesium production remains constrained by trace-level metal content and chemically aggressive solution matrices. Within the present study, the retention behaviour of Sc3+ species in strongly acidic chloride media was examined through batch-mode interaction with gel-type sulfonated cation exchangers, namely KU-2-8, Lewatit SP112H, Purosorb SAC140H, and Purolite C-150H. Quantitative evaluation of sorption efficiency was performed by calculating equilibrium uptake (qe), phase distribution factor (Kd), and percentage recovery (R). Under identical liquid–solid ratios, the Lewatit SP112H matrix exhibited superior affinity toward dissolved scandium, achieving qe = 179.82 mg/g and Kd = 172.41 mL/g. Equilibrium fitting procedures revealed that scandium uptake by Purosorb SAC140H conforms to monolayer-type retention described by the Langmuir formalism (R2 = 0.9786), whereas sorption on Lewatit SP112H proceeds over energetically non-uniform sites and is more adequately represented by Freundlich and Dubinin–Radushkevich approximations. The observed retention characteristics establish a selection framework for ion-exchange media applicable to scandium concentration from acidic chloride hydrometallurgical streams.