Date of Award

Fall 12-12-2025

Degree Type

Thesis

Degree Name

Master of Science in Metallurgical/Mineral Processing Engineering

Department

Metallurgy

Committee Chair

Richard LaDouceur

First Advisor

Blaine Berrington

Second Advisor

Grant Wallace

Abstract

Rare earth elements (REE) are crucial to the advancement of modern technologies. REE applications include electronics, defense systems, wind turbines, catalysts, magnets, and aircraft. Bastnasite, monazite, and xenotime are the primary resources, while the secondary resources, including coal ash, E-waste, and acid mine drainage, are for REE extraction. The primary processing techniques are chemical leaching, ion exchange, chemical precipitation, pyrometallurgy, solvent exchange, biosorption, and adsorption. Adsorption technique is simple, cost-effective, and environmentally friendly, with higher efficiency but at the cost of a longer mixing time. Therefore, there is a pressing need for an optimized mixing technique to improve the adsorption kinetics and efficiency. Hemp biochar produced through vacuum pyrolysis at 700 °C was evaluated for REE (La3+, Nd3+, Dy3+) adsorption using synthetic solutions. The maximum adsorption capacity of the hemp biochar was 77.56 mg/g for Dy3+, followed by 75.85 mg/g for La3+, and 72.65 mg/g for Nd3+ without using RVM (Resonant Vibratory Mixing) technology. For REE adsorption, hemp biochar was subjected to single-element solutions for single-element adsorption and to a multi-element solution for selectivity. This research study used a novel mixing technique for improving the kinetics of REE adsorption onto the hemp biochar using RVM factors such as time (5 – 30 min) and intensity (30 - 70%). RVM works by creating micro-mixing zones and by facilitating bulk movement of liquid in a mixing vessel. It uses a low-frequency (around 60 Hz) and high-intensity mixing. It is energy-efficient compared to conventional mixing methods due to the amplification of vibrational effects at resonance, reduced energy losses, rapid mixing, and minimal mechanical wear, reducing time and improving mixing efficiency. The recovery by adsorption (%) for all REE exceeded 98% in both single-element and multi-element adsorption processes, except for La3+ recovery (83.7%) in multi-element adsorption. It was determined that the hemp biochar has selectivity for Dy3+ and Nd3+ compared to La3+. This research study used synthetic solutions and batch RVM for the adsorption experiments. Therefore, future research must focus on natural aqueous solutions and continuous RVM for REE adsorption. The hemp biochar properties were examined via SEM, FTIR, BET Zeta-Potential, and CHN for surface morphology, functional groups, surface charge, surface textural properties, and carbon, hydrogen, and nitrogen %, respectively. The experimental data of this research study were consistent with the Langmuir adsorption isotherm model and the pseudo-second-order model. The adsorption mechanism in this study was determined to be an electrostatic attraction. Desorption tests were performed using oxalic acid and nitric acid using RVM to determine the economic and environmental feasibility. Nitric acid outperformed oxalic acid by a wide margin, recovering over 80% and over 70% of REE in single-element and multi-element desorption processes, respectively. Hemp biochar performance was excellent in the initial adsorption cycle using RVM, but the hemp biochar reusability needs further investigation.

Download

Included in

Metallurgy Commons

Share

COinS