Separation of Tb(III) and Dy(III) from Chloride Solution by Extraction and Scrubbing with Ionic Liquid Prepared with Cyanex 272 and Aliquat 336

Abstract

Terbium and dysprosium are rare earth elements which are employed in the manufacture of advanced materials. Separating Tb(III) and Dy(III) is very complicated because their chemical properties are similar. In order to develop a separation process based on solvent extraction, extraction and scrubbing experiments were conducted using weak hydrochloric solutions containing Tb(III) and Dy(III). In this work, three kinds of Cyanex 272, namely, single Cyanex 272, a mixture with Alamine 336 and an ionic liquid prepared with Aliquat 336 were employed. In the initial pH range between 1.5 and 5, the extraction behavior of both Tb(III) and Dy(III) was very similar using these extractants, resulting in low separation factor. In terms of extraction percentage and separation factor, the ionic liquid showed better performance than both single Cyanex 272 and the mixture. Scrubbing experiments were conducted using the loaded ionic liquid, employing a Dy(III) scrubbing solution. The optimum concentration of Dy(III) in the scrubbing solution was determined. A McCabe-Thiele diagram for the scrubbing of Tb(III) in the loaded ionic liquid with Dy(III) solution was constructed. In order to verify the separation of both metal ions, batch simulation cross-current scrubbing experiments were performed. After 6 cross-current scrubbing stages, the purity of Dy(III) in the loaded ionic liquid increased from 50% to 99%. By utilizing the data reported in this work, a process can be developed for the separation of Tb(III) and Dy(III) by solvent extraction. Key words: terbium(III), dysprosium(III), solvent extraction, scrubbing, separation