Semester

Summer

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mining Engineering

Committee Chair

Qingqing Huang

Committee Member

Deniz talan

Committee Member

Deniz Tuncay

Abstract

Rare earth elements (REEs) are used in high-tech applications due to their electromagnetic and optical properties. As global demand for REEs surges, the limitation of primary mineral deposits has increased interest in alternative sources. One such source is acid mine drainage (AMD), which, although typically low in REE concentration, offers a promising avenue for recovery. Among the emerging recovery methods, ion exchange has shown promise due to its effectiveness at low concentrations and lower operational cost than conventional techniques such as acid leaching and solvent extraction.

This research focused on developing a recovery process by combining ion exchange with selective precipitation techniques. For this, 14 AMD samples were collected, and based on total REEs (TREEs) concentrations and other elemental compositions, one sample from Kanawha County, WV, was selected as the feedstock for process development.

The recovery process developed began with three sequential pH-dependent precipitation steps. Sodium hydroxide (NaOH) was added to the raw AMD to reach pH 4, removing 66% of iron and other impurities. A second adjustment to pH 5 facilitated the removal of 95% of aluminum and additional contaminants. After filtration, the pH increased from 5 to 9 to precipitate the majority of REEs. The resulting solids were redissolved in sulfuric acid (H₂SO₄), achieving a REE enrichment factor of 20 and producing a preconcentrated feedstock for ion exchange.

Ion exchange experiments employed 50WX8 cationic resin. Process parameters were optimized by evaluating REE recovery and selectivity at different flow velocities (1–10 L/h) and feedstock pH values (0.5–3). Optimal loading conditions were identified at pH 1.5 and 1 L/h flow rate, achieving 99% REE sorption. Elution studies used sulfuric acid at varying concentrations (1–3 M) and flow velocities (0.5–3 L/h). The best elution performance obtained 95% REE recovery and a REE enrichment factor of 148 with 2 M H₂SO₄ at 0.5 L/h.

The eluted solution was subjected to selective precipitation using oxalic acid. This step was optimized by varying the oxalate-to-REE molar ratio (1.5–17), precipitation pH (0.1–2), and reaction time (0–2 h). The highest REE precipitation recovery (98%) was achieved with a C₂O₄:REE ratio of 7, pH 1.5, and 1-hour reaction time. The resulting oxalates were washed with deionized water and calcined to produce REE oxides as the final product.

The overall process yielded REE oxides with a purity of 97% by weight, demonstrating the technical feasibility of recovering high-purity REEs AMD using an integrated ion exchange and selective precipitation approach.

Available for download on Saturday, August 01, 2026

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