Date of Award

Spring 2015

Degree Type



Metallurgical Engineering

Committee Chair

William Gleason

First Advisor

Courtney Young

Second Advisor

Jerome Downey

Third Advisor

Larry Twidwell

Fourth Advisor

Michael Webb


The use of applied chemistry in the production and optimization of leach solutions from Rare Earth Element (REE) ores and concentrates was investigated. Ore and concentrate samples were characterized using scanning electron microscopy/mineral liberation analysis (SEM/MLA), X-ray Diffraction (XRD), and Inductively-coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Multiple leach tests were performed to analyze the effects of temperature, residence time, and reagent concentration on the leaching of REEs. Analysis of leach solutions was carried out using ICP-AES. Modeling and statistical analysis of extraction behavior was carried out using DesignExpert 9. Modeling data for multiple REEs indicate that extraction is strongly influenced by temperature and reagent concentration, while leaching time plays a much less important role. Experimental design techniques were able to optimize REE recovery while minimizing the extraction of gangue elements, such as iron, and a series of series of parameters were determined that were optimal for REE extraction. Differences in extraction between some of the REEs indicate that a multistage, direct leaching, operation could be implemented to effectively extract REEs from both ores and concentrates.


A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Metallurgical/Mineral Processing Engineering.

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