Separation of samarium, europium and gadolinium in high purity using photochemical reduction-extraction chromatography

An effective method was studied for the separation of high-purity individual rare earths from middle rare earth concentrate. The method combines photochemical reduction and extraction chromatography and consists of two steps: first, injecting a middle rare earth feed solution to a column packed with extraction resin while photo chemically reducing Eu3+ to Eu2+ in the feed solution, followed by separating the reduced Eu2+ which has not been adsorbed on the extraction resin by washing; and, second, separating Sm3+ and Gd3+ adsorbed on the extraction resin by elution. This study was carried out with a 193 nm ArF excimer laser source, a column packed with HEH[EHP] resin, isopropanol as scavenger of hydroxyl radical formed in the photolysis of water, deionized water as washing solution and HCl solution as eluent. With the aim of obtaining high yields of high-purity products, parameters such as concentrations of isopropanol and Eu2O3 in the feed solution, acidity and flow rate of the feed solution and acidity and flow rate of the eluent were evaluated with synthetic solutions. Based on the obtained results, the method was applied to separate individual rare earths from a commercial solution. Finally, the yields of Sm2O3, Eu2O3 and Gd2O3 products were 82.5%, 93.7% and 78.1% respectively, with purities of 99.99%.