Extraction of micro- and macroconcentrations of rare earth ions with the mixture of D2EHPA and TBP in n-hexane and cyclohexane

The synergistic solvent extraction of Eu(III) and some other rare earth elements from nitrate solutions (HNO₃+LiNO₃) by a mixture of (TBP+D2EHPA) in n-hexane and cyclohexane has been investigated at 22 °C. Antagonism found in europium extraction from 0.1M HNO₃ transforms into a synergistic effect. The synergistic effects existing for all investigated metals in extraction from 0.1M HNO₃+3M LiNO₃ were caused by formation of mixed complexes of the type Ln(D2EHPA)_2nH_2n–3+1(NO₃)₁TBP_m, where 1=1 or 2. The selectivity of the extraction in a synergistic system is lower for the La–Yb pair than in the case of D2EHPA extraction under the same conditions. On the other hand, the application of the synergistic mixture is more suitable for Eu–Ho separation. Thus the synergistic effect can be used for the separation or refining of some lanthanides.