SEPARATION OF NEODYMIUM FROM LIGHTER RARE-EARTHS USING ALKYL PHOSPHONIC ACID, PC-88A

Separation of Nd as a high grade product ( > 96% Nd2O3) from a mixture containing all the lighter rare earth elements (LREE), especially Pr, is a very difficult task. An attempt has been made in this paper to d evelop a solvent extraction process for the production of magnet grade Nd2O3 by using 20% saponified alkyl phosphonic acid, PC 88A, as an ex tractant. The basic experimental data on the distribution of rare eart h elements (REE) against initial aqueous acidity (D vs H(i)) at varyin g initial metal concentrations have been determined and utilised to de rive the mathematical models for the extraction behaviour of La, Ce, P r, Nd and Sm. A computer program has been developed in FORTRAN to calc ulate the individual rare earth concentrations in both aqueous and sol vent phases. These data are further utilised to evaluate the process p arameters such as the phase ratio, acidity of feed and scrub solution, etc., for a given number of extraction and scrubbing stages, to obtai n 97% pure Nd2O3 at an overall recovery exceeding 85%. The computed pa rameters have been utilised for running counter-current extraction tri als using mixer-settlers and over 5 kg of Nd2O3 (97%) have been produc ed at > 85% recovery. This paper summarises the basic approach and the experimental data for process optimisation.