Separation and recovery of high grade Dy2O3 by solvent extraction process with DEHPA in kerosene

During the solvent extraction (SX) fractionation of rare earths chloride obtained from monazite, a heavy RE (HRE) fraction assaying 60% Y2O3 is produced. This is purified further to 93% Y2O3 by another SX cycle. During this step most of Dy and Tb get separated to yield a concentrate assaying >50% Dy2O3. An attempt has been made to process this Dy rich concentrate to obtain a high grade Dy2O3 by a SX route using DEHPA in kerosene. The distribution data (D vs Hi+) of Dy have been generated experimentally at various metal concentrations and similar data for other metals present (Gd, Tb, Y, Er and Ho) have been derived using a mathematical expression developed in our laboratory. Based on this information mathematical models for extraction behaviour of these HRE have been derived and used in a computer program developed for multicomponent system. This program has been utilised to optimise the process parameters to obtain 95-97% pure Dy2O3 at about 90% recovery. The parameters have been experimentally confirmed and Dy2O3 95.5% pure w.r.t. Tb was obtained at about 90% recovery, thus confirming the validity of the program. This paper presents data obtained during these investigations. (author). 6 refs., 5 tabs