Extraction of lanthanides from nitric acid solution using isobutyl-BTP/ionic liquid system

Extraction behavior of lanthanides (La, Eu, Dy, Lu) from HNO₃ solution was studied using a novel extraction system with hydrophobic ionic liquid being diluent and isobutyl-BTP being extractant. Compared with that in isobutyl-BTP/cyclohexane extraction system, application of ionic liquid as the extracting phase provided unprecedented enhancement of the extraction performance of isobutyl-BTP for lanthanides. It was found that the isobutyl-BTP/[C_nmim][NTf₂] extraction system is favorable to get good extraction at low acidity condition (< 0.1 M). Of all the isobutyl-BTP/[C_nmim][NTf₂] (n = 2, 6, 8) systems, isobutyl-BTP/[C₂mim][NTf₂] extraction system provides the best extraction performance and fastest extraction kinetics within 5 min towards Dy³⁺. The extraction is spontaneous endothermic and temperature is good for extraction. The transfer of lanthanides, in isobutyl-BTP/[C₂mim][NTf₂] extraction system, proceeded via a cation exchange mechanism, in contrast to extraction of neutral complex in the cyclohexane system. (authors)