Abstract
The lithium isotope separation in the liquid-liquid extraction system H2O/CHCl3 is investigated using benzo-15-crown-5 as complexing agent. The maximum single stage separation factor αmax for 6Li/7Li obtained in the present study was 1.044±0.003. For the chemical exchange reactions without valence change, this value is the second largest behind one obtained using cryptand (2B, 2, 1) polymer. The lithium salt was extracted into the organic phase with highly concentrated crown ether forming Li+[crown]2 complexes. The chemical and isotopic equilibria were attained rapidly. The separation factors were 1.026, 1.032 and 1.035 at 25°C for I-, SCN- and trifluoroacetate (TFA) as counter anions, respectively. In regard to the separation factor, the distribution coefficient and the stability to the change of temperature, lithium iodide would be most suitable for the industrial application. The isotope effects in Li+-crown complex are hindered by the hydration of the complex ion, but the obstraction can be avoided by using the organic solvent with highly concentrated crown ether.
