Separation of Heavy Rare Earths by Liquid- Liquid Extraction จารุณ ี ไกรแกว1 วรรณ ี ศรีนุตตระกูล1 ศุภกาญจน ชํานิ2 ศิริรัตน พานิช3 และเชาวเล ข ชยวัฒนางกูร1

Solvent extraction of heavy rare earths (Gd, Dy, Y, and Yb) has been investigated at 37+1oC. The equilibrium of heavy rare earths at various rare earth nitrate concentrations with isomolar mixtures of tributylphosphate(TBP) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene as the extractant was examined and compared with 50%TBP in kerosene. The distribution coefficients (Kd) of heavy rare earths tend to decrease with the increasing of their concentrations in feed solution. (Kd)Y and (Kd)Yb are high, approximately 20, when 1 M D2EHPA / kerosene is applied as the solvent. The separation factors of Y (αYb/Y, αY/Dy, and αY/Gd) increase with the increasing concentration of D2EHPA in isomolar (TBP-D2EHPA) / kerosene. When the solvent is 50%TBP / kerosene, αDy/Gd are around 1.1-1.2 at high feed concentration. It is possible to separate Y with isomolar (TBP-D2EHPA)