Separation of Rare Earth Elements Using Aromatic Sulfonic Acid-Modified Silica Chromatographic Stationary Phase

Ion exchange chromatography (IEC) is one of the essential methods to separate rare earth elements (REEs), which relies on the stationary phase. In this study, a novel aromatic sulfonic acid-modified silica stationary phase (SCX-Tol) was synthesized by grafting aromatic sulfonic acid groups onto silica surfaces using 2-(4-chlorosulfonylphenyl)ethyl trichlorosilane as the functionalizing agent in toluene. The successful modification was confirmed by scanning electron microscopy (SEM), elemental analysis, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The chromatographic performance of SCX-Tol was systematically evaluated and compared with two commercial ion-exchange columns. The results demonstrated the superior separation efficiency of SCX-Tol, particularly in the challenging separation of dysprosium (Dy) and yttrium (Y), which are traditionally difficult to resolve using chromatographic methods. The separation efficiency improved with an increasing density of sulfonic acid groups on the stationary phase surface. These findings indicate that SCX-Tol is a promising stationary phase for both the separation and quantification of REEs, offering the potential applications in separating and detecting REEs.