TECHNICAL FEASIBILITY OF SELECTIVELY SEPARATING RARE EARTH ELEMENTS BY VAPOR PHASE EXTRACTION AND CONDENSATION

Publication Year:
2017
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Repository URL:
https://digitalcommons.mtech.edu/grad_rsch/123
Author(s):
Lyons, Katie
Tags:
Rare Earth Extraction; Vapor Phase Extraction; Thermodynamics; Rare Earth; Separation; Volatilization; Other Chemical Engineering; Other Chemistry; Other Materials Science and Engineering
thesis / dissertation description
Experiments were performed to evaluate the technical feasibility of selectively separating selected rare earth halides (bromides and chlorides) using a volatilization and condensation technique. Initially, optimum chloridizing and bromidizing roast parameters were secured in studies performed on reagent grade rare earth oxide samples and subsequently confirmed in tests performed on mineral ore and concentrate samples. The volatilization and condensation experiments were performed by placing the subject rare earth halide samples in an argon-purged multiple-zone tube furnace wherein the temperature profile was controlled to establish separate vaporization and condensation regions. Following each experiment, condensate and solid residue samples were analyzed to determine their respective rare earth element contents. The analytical results indicate potential exists for separating the more volatile halide species from those with relatively low vapor pressures; separation of species with intermediate vapor pressures was inconclusive. In most experiments, the rare earth halide vaporization efficiencies were severely limited by the extremely hygroscopic nature of the rare earth halides coupled with their high affinities for oxygen. At elevated temperatures, the hydrates react with halides to produce rare earth oxyhalides and oxides, which are not volatile at the temperatures (up to 1400 °C) considered in this research.