Document Type

Honors Thesis

Publication Date

Spring 5-6-2026

Abstract

Rare earth elements (REEs) are critical for modern technologies, but their extraction from minerals remains challenging due to various factors, and their impact on mineral bonding and resulting crystal structure. Fundamental studies have shown that the concentration of rare earth minerals (REMs), such as rare earth silicates (RES), depends on factors such as Lanthanide contraction (LC), Coordination Number (NC), and silicate polymerization (SP). These influence flotation responses pending silicate type (e.g., sorosilicates, phylosilicates, nesosilicates, inosilicates, orthosilicates, etc.). To better understand this behavior and optimize REE recovery, samples from Halleck Creek, an American Rare Earth property in Wyoming, were obtained. Characterization analysis using SEM/TIMA revealed that the sample contains about 37.82% K-felspar, 25.38 Albite, 13.68% ferrohornblende, 9.03% plagioclase, 7.24% quartz as the major components, 5.13% other minerals, and 1.72% allanite, a REE- bearing mineral, with cerium (Ce) being the most abundant REE at 0.20%, and therefore called allanite-(Ce). The samples were preconcentrated using wet high-intensity magnetic separation (WHIMS) at 1 Tesla, yielding 70.37% REE enrichment. Further tests included zeta potential measurements to determine and confirm the optimal pH of 9.0, while electrical resistivity tomography (ERT) assessed bubble formation and stability of the froth zone, yielding 5% mean gas holdup. A custom blend of collectors (mono, binary, and ternary) of salicyl hydroxamic acid (SHA), benzoic acid (BA), and phthalic acid (PA) was used in the flotation study. This approach is based on the hypothesis that matching collector headgroup ionic diameters with REE ionic diameters enhances adsorption and selectivity; therefore, SHA was selected as the primary collector due to its strong hydroxamate and phenolic binding, complemented by carboxylate coordination from PA and BA, creating a synergistic blend that broadens recovery across the REE spectrum. SHA and the ternary blend (SHA:PA:BA, 50:30:20) demonstrated selectivity for LREEs, achieving 39.3% Ce and 61% La recoveries. PA, BA, and Binary blends significantly improved selectivity and overall performance. Specifically, SHA+PA (60:40) and SHA+BA (60:40) optimized the recovery of MREEs and HREEs, yielding 76.5% Gd, 90% Dy, and 41% Y, respectively. These results, together with a tailored methodology, offer a promising selectivity and provide a strategy for the efficient flotation of REEs from silicate-bearing REM, thereby supporting the development of a robust domestic REE supply chain.

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