Separation and purification of heavy rare earth elements by a silica/ polymer-based β-aminophosphonic acid resin from chloride media

High-purity heavy rare earths (HREs) are important for promoting the development of cutting-edge materials, but their efficient separation and purification still face significant challenges. Here, a silica/polymer-based beta-aminophosphonic acid resin (HEHAEP/SiO2-P) was prepared by vacuum impregnation for the separation of HREs from chloride media. At pH = 2.0, the separation factors (SF) for Er/Ho, Tm/Er, Yb/Tm and Lu/Yb were 2.35, 3.62, 3.14 and 1.23, respectively, surpassing those of some other reported impregnating resins. The maximum adsorption capacity of HEHAEP/SiO2-P for Ho, Er, Tm, Yb and Lu were 33.5, 34.6, 37.0, 38.3 and 43.2 mg/g, respectively. The adsorption process was characterized as homogeneous monolayer chemisorption, driven by entropy in a spontaneous endothermic reaction. Complete desorption of the adsorbed HREs was achieved using 4.0 mol/L HNO3. Employing our strategy, as exemplified by Tm, high-purity Tm2O3 (99.997 %) was obtained by HEHAEP/SiO2-P resin in the column chromatography separation system. FT-IR and XPS analysis demonstrated that both P-OH and PO groups participated in the coordination reaction during the HREs adsorption.