Selective Adsorption Separation of Sc(III) and Zr(IV) from Acidic Solutions via Zr-SBA-15 with Rich Oxygen-Vacancy...

Aiming at the challenging selective separation of zirconium (Zr) and scandium (Sc) in hydrochloric acid systems, this study designed a Zr-SBA-15-30 adsorbent featuring abundant surface oxygen vacancy defects. The as-synthesized material possesses an ordered mesoporous structure, a high specific surface area of 477.606 m²/g, and a high density of surface oxygen vacancies. In a strongly acidic binary HCl solution containing both Zr and Sc, Zr-SBA-15-30 exhibited exceptional separation performance, achieving an adsorption capacity of 128 mg/g for Zr and an outstanding separation factor (SF_Sc/Zr) as high as 3480. Fitting results from adsorption isotherms and kinetic models revealed that the adsorption process is predominantly governed by chemisorption and proceeds mainly via monolayer adsorption. The higher ionic character of the Zr-O bond relative to the Si-O bond, Zr doping induces a redistribution of the local electron cloud density on the framework surface, thereby forming electron-rich centers with higher polarizability and stronger coordination activity. Meanwhile, the oxygen vacancy defects introduced by plasma treatment create defect energy levels within the band gap. This synergistic effect of Zr doping and oxygen vacancies can significantly enhance the separation of Zr/Sc. This work provides a viable material design strategy for the efficient separation of Zr and Sc under strongly acidic conditions.