One-Step Strategy to Synthesize Sulfonic Acid-Functionalized Silica Chromatographic Stationary Phases for Separation of Rare-Earth Elements

Separation and analysis of rare-earth elements (REEs) with impurities are challenging processes. Ion-exchange chromatography has emerged as a valuable technology for rare-earth separation, and developing a simple and efficient preparation method for stationary ion-exchange chromatography remains a hot topic. In this study, a sulfonic acid-modified silica stationary phase was synthesized through a facile one-step strategy, where 1,3-propanesultone reacted with the silanol group. The stationary phase demonstrated effective cation-exchange chromatographic performance, achieving baseline separation of 15 REEs with resolution (R_S) ranging from 1.9 to 6.8 for adjacent lanthanides. Excellent separation capability was also observed for impurity ions, including Fe, U, and Th, from the REEs. The stationary phase demonstrated an enhanced separation performance for REEs compared to conventional bonded phases. In addition, the columns exhibited excellent repeatability and stability. The separation performance was systematically evaluated across particle sizes of 3, 5, and 10 μm (with surface coverages of 0.89, 0.70, and 0.58 μmol/m², respectively), demonstrating the universality of the preparation method. These findings support its potential application for preparative-scale stationary phases to separate REEs.