Highly efficient selective separation of scandium and zirconium by 331 resin

Abstract

In the defense industry and high-tech fields, scandium (Sc) has become one of the most commercially valuable strategic resources due to its unparalleled performance and diverse applications. However, the effective separation of Sc(III) and Zr(IV) remains a significant challenge owing to their nearly identical ionic radii and chemical properties. This study introduces a novel approach for Sc-Zr separation using a commercially available weakly basic epoxy-based anion exchange resin (331 resin) in HCl medium. Unlike conventional adsorbents, the 331 resin exhibits significantly higher affinity for Sc(III) over Zr(IV), achieving a remarkable separation factor (SF_Sc/Zr) of 756.2 under weakly acidic conditions (pH 2), with excellent repeatability demonstrated over 5 cycles. The adsorption process follows the pseudo-second-order kinetic model and Langmuir isotherm model, with a saturated adsorption capacity of 63.99 mg_Sc/g at 318 K. Column experiments demonstrate practical applicability, achieving Sc(III) purity exceeding 99.99% using 1 mol/L NaCl eluent. The Thomas model perfectly predicts column behavior under the studied conditions, validating its inherent Langmuir-type adsorption kinetics and equilibrium assumptions (R² = 1 and low χ²). Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) analyses and density functional theory (DFT) calculations demonstrate that Sc(III) adsorption occurs through coordination with amine groups (–NH) on the resin, where these groups act as electron-donating ligands. This study provides a commercially viable, high-efficiency solution for strategic metal purification with significant implications for advanced material production.