Improving the selective extraction of lanthanides by using functionalised ionic liquids

Four ionic liquids, tetraoctylammonium oleate - [N-8888] [OL], 1-butyl-3-methylimidazolium-di(2-ethylhexyp-oxamate - [C(4)mim] [DEHOX], tetraoctylammonium dioctyl-diglycolamate - [N-8888] [DODGA] and tetraoctylammonium di(2-ethylhexyl)-oxamate - [N-8888] [DEHOX]), were studied concerning the extraction and selective separation of lanthanides from aqueous solutions. The influence of several factors (pH, time of contact between phases, ionic strength, ionic liquid to metal ratio) were analysed. Also, back-extraction and re-use of the ionic liquids were addressed. From all the obtained results, it should be stressed that the separation achieved along the lanthanide series by the use of [N-8888] [DEHOX] was significant, with an increasing separation factor along the series and close to 80 for Yb/Ce.