Process development for the recovery of high-grade lanthanum by solvent extraction

The development of a solvent extraction process for the recovery of high-grade lanthanum oxide from a light rare earth (RE) (La, Pr, Nd) chloride solution is described. In a preliminary stage, process parameters and experimental conditions were explored in bench-scale experiments. The effect of variables such as nature and concentration of the extractants (di-2-ethylhexylphosphoric acid [DEHPA] and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester [HEH(EHP)]), contact time, acidity and rare earth concentration in the extraction stage as well as the effect of the hydrochloric acid concentration in the stripping stage were investigated. The continuous counter-current experiments were carried out in a mini-battery unit of mixer-settlers. The final set-up was comprised of 22 stages: 8 for extraction, 8 for scrubbing and 6 for stripping. A high-grade oxide (>99.9% La2O3) was obtained with a yield superior to 99.9%.