The Effect of Solvent on the Liquid – Liquid Extraction of Lanthanides Using DODGAA as an Extractant

4-Methyl-1,3-dioxolan-2-one and 4-ethyl-1,3-dioxolan-2-one are well-known solvent in the name of propylene carbonate (PC) and butylene carbonate (BC), respectively, and PC is classified to level 1 in terms of combustibility and health hazard by National Fire –Protection Association. Therefore, PC is less toxic and environment-friendly solvent compared to the usual solvents, such as hexane and toluene. PC and BC are not only safe but also are having strong polarity, however, their application to solvent extraction of metal chelates as an extraction solvent were not carried out so much. Then, in this study, PC and BC were applied to N,N-dioctyldiglycolamic acid (DODGAA) extraction of lanthanides as the diluent and their extractabilities were compared with that of hexane. Lanthanum and scandium were found to be affected with solvent comparatively strongly to the other lanthanides. It was observed in the slope analysis of in the relationship between log D vs. pH plots that the some slopes of straight lines in DODGAA-PC and DODGAA-BC system deviated from theoretical value of 3. The possibilities of the change of metal ion concentration based on the volume change due to the mutual dissolution and the formation of different kind of complex other than LnR3 were considered as the causes for the deviations in a slope analysis and were examined experimentally.