Study on the Performance and Mechanism of Separating La from Light Rare Earth Elements Using Single-Column Method with a New Type of Silica-Based Phosphate-Functionalized Resin

This work develops a novel phosphate-functionalized extraction resin (HEHEHP + Cyanex272)/SiO2-P via the vacuum impregnation method for efficient separation of light rare earth element impurities from lanthanum (La3+) in nitric medium through synergistic extraction. Batch experiments have demonstrated superior adsorption selectivity toward impurity ions over La3+ in a pH 4 nitric acid solution. Column studies confirmed exceptional performance under ambient conditions, achieving a lanthanum treatment capacity of 120.6 mg/g and over 98% impurity removal, which surpasses most reported values. Notably, this purification process enables direct production of purified La3+ solutions through a single-column system without desorption, significantly enhancing efficiency and reducing costs. Mechanistic insights revealed combined ion exchange and coordination interactions between metal ions and P-OH/P=O groups, corroborated by advanced characterization and density functional theory calculations. These findings indicate a higher binding affinity of light rare earth compared with La3+. This strategy provides a scalable approach for ultra-high-purity lanthanum compound production in advanced optical and electronic applications.