Selective Separation of Rare Earth Chlorides Utilizing Vapor Phase Extraction

Abstract

The Metallurgical and Materials Engineering Department at Montana Tech is investigating a new method of extracting and refining rare earth elements (REEs) from mineral ores and concentrates. The relative stabilities of various REE compounds at elevated temperatures were evaluated using thermogravimetric and differential thermal analyses (TGA/DTA). The results, in combination with thermodynamic analyses, revealed that vapor phase extraction and selective condensation is a potentially viable separation method for rare earth halides. Selective vaporization and condensation experiments were performed on selected rare earth chlorides. A series of close-coupled tube furnaces provided a temperature gradient ranging from 1150 to 400 °C. Within the condensation regions, a series of one-inch-diameter ceramic tube sections were packed with stainless steel (316L) wool to create high surface area for condensate collection. The ceramic tube sections and stainless steel wool were leached in 18 MΩ water. Analysis of the leachate samples revealed that selective separation had occurred but oxychlorides were detected in the non-volatile matter.