Effect of Diglycolamide Ligands Structure on Extraction Performance of Heavy Rare Earth Ions

The properties of four different extractants, TODGA ( N,N,N',N' -tetraoctyl-diglycolamide), T2EHDGA ( N,N,N',N' -tetraisooctyl-diglycolamide), DPDODGA ( N,N' -dipropyl- N,N' -dioctyl-diglycolamide) and DIPDODGA ( N,N' -diisopropyl- N,N' -dioctyl-diglycolamide), to extract heavy rare earth metal ions in hydrochloric acid were studied to understand the relationship between the chemical structure of the extractant and the extraction properties of rare earth metal ions. The extraction order of heavy rare earths in n -octane: n -octanol = 9:1 diluent was as follows: DIPDODGA > DPDODGA > TODGA > T2EHDGA. Alkyl chain shows great influence on extraction ability and the extractants with short chain can effectively extract heavy rare earth ions even at a concentration of less than 1.0 mol/L. The extraction mechanism was proposed with the results of slope methods, IR (Infrared) spectrometer and DFT (Density Functional Theory) theoretical study. T2EHDGA forms binuclear and the other three extractants form mononuclear extracted species with heavy rare earth ions.