Separation of Light and Middle-Heavy Rare Earths from Nitrate Medium by Liquid-Liquid Extraction

Abstract

Separation of light (LREEs) and middle-heavy (M-HREEs) rare earths from a nitrate medium was studied using a liquid-liquid extraction technique. Tri-n- butyl phosphate (TBP) in kerosene was used as the extractant. The effect of the TBP concentration (30–80% volume per volume; v/v), contact time (3–10 min) and shaking speed (100–200 rpm) on rare earth extraction were investigated. The distribution ratio and separation factor were determined to evaluate the extraction behavior and the separation possibilities of M-HREEs from LREEs. The results showed that the distribution ratio increased with increasing TBP concentration. The concentration of rare earth in the aqueous phase decreased as the contact time and shaking speed increased. The separation factor values for M-HREEs/LREEs markedly increased as the atomic number of the LREEs decreased. High separation factor values were observed for Y/Nd, Y/Pr, Y/La of 6.35, 11.15 and 13.95 respectively. The best conditions for the separation in this study were found to be: a TBP concentration of 50% v/v, a contact time of 5 min and a shaking speed of 200 rpm. Under these conditions, it was possible to separate M-HREEs (Sm, Gd, Y) from LREEs (La, Pr, Nd).