Extraction development for the separation of gadolinium from yttrium and dysprosium concentrate in nitric acid using cyanex 572

Abstract

Xenotime sand, a byproduct of the tin mining process of PT Timah, is one of the potential gadolinium (Gd) resources. Because of similarities in their physical and chemical properties, it is difficult to separate and purify Gd from rare earth elements (REEs) in xenotime sand (i.e., yttrium and dysprosium). In the present work, Gd was separated through an extraction process using Cyanex 572. The extraction feed solution was prepared by digesting the REE oxalate in NaOH to obtain REE(OH)3. The effects of the extraction parameters (i.e., stirring time and rate, feed pH and concentration, and Cyanex 572 concentration) were examined via a batch experiment. The optimum results of Gd separation from yttrium concentrate were achieved when the process conditions included a 250-rpm stirring rate for 30 minutes, a 150x103-ppm feed concentration at pH 3, and a 30% Cyanex 572 concentration. These conditions gave distribution coefficient results for Y, Gd, and Dy of about 0.031, 0.827, and 1.060, respectively; separation factors of Gd-Y and Gd-Dy of about 26.482 and 0.780, respectively; and extraction efficiencies for Y, Gd, and Dy of about 3.119%, 46.627%, and 53.007%, respectively.