J. Qiu
Texas A&M University,
United States
Keywords: rare earth elements (REEs), neodymium (Nd) and dysprosium (Dy), solid-phase extraction (SPE), REE-specific ligands
Summary:
Rare earth elements (REEs) comprise a collection of 17 chemically similar metallic elements, including 15 lanthanides, accounting for about 17% of all naturally occurring metal elements. Known as “industrial vitamins,” REEs have been extensively utilized across various fields such as solid-state drives, petroleum refining operations, electric vehicles, windmills, personal electronics, and military equipment. However, the high market demand and limited supply of REEs have resulted in fluctuating prices and significant price increases for elements like Neodymium (Nd), Praseodymium (Pr), and Dysprosium (Dy). Traditional techniques for REE recovery, including solvent extraction, chemical precipitation, ion exchange, adsorption, and eutectic freeze crystallization, are hampered by high energy consumption, environmental pollution, and the generation of toxic waste. Additionally, the high investment, operational, and maintenance costs render these methods labor-intensive and less economically viable. In contrast, solid-phase extraction (SPE) offers high selectivity, enabling efficient and precise recovery of specific REEs from electronic waste (E-waste) leaching solutions with minimal contamination. SPE circumvents the need for tedious solvent extraction systems, expensive high-temperature furnaces, or large ion exchange columns for REE extraction. In this project, REE-specific ligand-functionalized carbon foams were synthesized as solid-phase extractants. The large surface area, highly reactive functional groups, and hierarchical porous structure of the carbon-based extractants are integrated to achieve stronger affinity to Nd and Dy, over interfering ions. Through chelation and surface adsorption, REE metal ions are extracted onto solid adsorbents, minimizing the use of solvents and additives. Their REE extraction technique from industrial E-waste significantly reduces operation cycles and waste generation. The highly selective functionalized adsorbents not only demonstrate high adsorption capacity and extraction rate for REEs but also allow for easy and convenient regeneration/reuse. This research aims to foster sustainable recovery of critical materials from end-of-life E-waste and holds great promise for the next generation of REE recovery, with reduced energy consumption and waste generation to address the urgent REE market demand.