Selective Separation of Zr(IV) from Simulated High-Level Liquid Wastes by Zeolites

Effectively separating Zr(IV) from strong acidic and radioactive solutions is crucial for spent fuel reprocessing plants, but it remains a challenging task. This study investigated the adsorption of Zr(IV) in HNO3 solutions using zeolites as adsorbents. The zeolites were characterized by X-ray diffraction (XRD)?scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The effects of adsorption time, HNO3 concentration, the initial concentration of Zr(IV), zeolites dosage, and temperature on the Zr(IV) adsorption behaviors were investigated. The results demonstrated that HY zeolite had a higher adsorption capacity for Zr(IV) than H-SSZ-13 zeolite. The adsorption capacity of HY zeolite was influenced by its Si/Al ratio, which determined the density of adsorption sites. The optimal HY zeolite (HY-25) exhibited a maximum adsorption capacity of 30.438 mg/g in 3 M HNO3 solution. Furthermore, the adsorption isotherms and kinetics of Zr(IV) adsorption were investigated. The adsorption of Zr(IV) on zeolites was endothermic and spontaneous, in accordance with the Freundlich's isotherm model and pseudo-second-order kinetic model. In a simulated strong acidic solution of Zr(IV) and 10 co-existing cations (Ag+, Ba2+, Cs+, Ce3+, Eu3+, Fe3+, La3+, Nd3+, Sm3+, Sr2+), HY-25 exhibited good selective adsorption of Zr(IV), indicating its potential application in the treatment of high-level radioactive liquid waste.