Optical analysis and separation of trivalent lanthanides in deep eutectic solvents

Deep eutectic solvents(DESs) were used for luminescence measurements in quantitative analysis of trivalent lanthanide ions and as solvents for light rare earth elements(LREE) in solid-liquid separation.The spectroscopic characteristics of lanthanide chlorides LnCl3(Ln=Eu,Tb),respectively their aquo complexes,are described in a comprehensive study that demonstrates the significant enhancement of the phosphorescence emission intensity in DESs as polar and weakly coordinating solvent.Several DESs stabilize the lanthanide ion luminescence against changes in temperature and moisture,which is advantageous compared with the use of ionic liquids.Small amounts of water lead in certain eutectic systems even to a further increase in phosphorescence emission intensity.By investigating the solubility of lanthanide sesquioxides Ln2 O3(Ln=La,Nd,Sm,Eu,Gd,Tb,Dy) in DESs,selectivities are identified that may be of use for the separation of LREE.