Recovery of rare earth elements from uranium leach liquors by adsorption with diglycolamic acid ligands and ionic liquids

Abstract

A series of extraction chromatographic resins containing various phosphorus-containing and DGA-based extractants and ionic liquids was synthesized and their sorption characteristics for rare earth elements (REE) in sulfate solutions were studied. The effects of the type and content of ionic liquid in the stationary phase as well as solid support type on the sorption capacity of the resins for La, Nd and Dy were evaluated. It was shown that the quantity of the stationary organic phase in the resins was 30–35% independent of the matrix type. In the case of the DODGAA: TODGA: [C4mim][Tf2N] system, the matrix type did not affect the resin capacity for REE in sulfuric acid solutions. Acidity of the aqueous phase was one of the most important factors affecting lanthanides sorption from sulfate solutions. The capacity of the sorbents for lanthanides decreased sharply with the increase of acidity of the solution, this decrease was stronger for light REE. The process of REE separation from uranium leach liquors was studied using real leach liquors after separation of uranium. It was shown that a resin based on hydrophobic silica gel impregnated by DODGAA:TODGA:[C4mim][Tf2N] mixture can be recommended for concentration and primary separation of lanthanides from multicomponent industrial solutions. The advantage of this sorbent is a high selectivity for REE over macro amounts of Al and Fe as compared with strong acid cation exchange resins and phosphorus-containing organic extractants, which are widely used for preconcentration. Using this sorbent for selective recovery of REE from uranium leach liquors provided concentration factors of 10–15 for light REE group and 150–300 for heavy REE group.