Rare Earth Element Recovery Using Monoethanolamine
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JMEPEG https://doi.org/10.1007/s11665-020-04887-7
Rare Earth Element Recovery Using Monoethanolamine Paul Kim, Gaurav Das, Malgorzata M. Lencka, Andre Anderko, and Richard E. Riman (Submitted December 3, 2019; in revised form April 24, 2020) Current methods of rare earth element (REE) recovery from industrial solutions are environmentally untenable and have significant waste management challenges. Increasing global REE consumption necessitates the development of new, sustainable means of production. Herein, we report a means of recovering aqueous REEs using monoethanolamine and carbon dioxide as predicted using the Mixed-Solvent Electrolyte thermodynamic model. Validation experiments have demonstrated the > 99% recovery of Nd3+ as its normal carbonate, with the filtrate containing monoethanolamine hydrogen chloride. Additional experimentation also demonstrated the > 99% recovery of aqueous La3+ and Y3+ as their respective normal carbonates. These findings demonstrate that a thermodynamic simulation engine may be used to decrease the number of empirically driven experiments required to develop a new, high yield REE recovery unit operation that is applicable to concentrated and dilute aqueous solutions typical of industrial streams. Keywords
modeling and simulation, monoethanolamine, rare earth carbonates, rare earths
1. Introduction Rare earth elements (REE) are integral to modern society and standards of living. They have made renewable energy, optics, lasers, metallic alloys, and high temperature applications possible due to their unique properties and will be crucial to technological development (Ref 1-3). Geological surveys have determined that there are more than adequate reserves to meet current and future REE demand. Thus, the real question is where and how they will be produced. In 2018, China accounted for ‡ 70% of global rare earth oxide (REO) production (Ref 4) due to significant investments made in the 1980s (Ref 5,6). However, REO production is a chemically and energy intensive process that will require significantly more investment to improve its sustainability. REO production has been associated with acidified wastewater, concentrated radioactive waste, acid rain, and ammonialaden water among others. For example, every metric ton of REO produced at Bayan Obo results in an estimated 8.5 kg of fluorine, 13 kg of dust, 9600-12,000 m3 of waste gas that contains hydrogen fluoride and sulfur dioxide, 75 m3 of acidic wastewater, 1 ton of radioactive residue (usually thorium), and 2000 tons of radioactive tailings (Ref 6). These figures do not This article is an invited paper selected from presentations at the ‘‘11th International Symposium on Green and Sustainable Technologies for Materials Manufacturing and Processing,’’ held during Materials Science & Technology (MS&T19), September 29-October 3, 2019, in Portland, OR, and has been expanded from the original presentation. Paul Kim and Richard E. Riman, Department of Materials Science and Engineering, Rutgers – The State University of New Jersey, 607 Taylor Road,
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