T.M. Dittrich, M. Dardona, C. Boxley, S.K. Mohanty, D. Kakaris Porter, C.M. Tummala, S. Praneeth
Wayne State University,
Keywords: solid-liquid separation, DTPA, packed-bed columns, rare earth elements, separation, unconventional sources
Summary:Commercial sources of rare earth elements (REEs) include ion exchange clays and bastnaesite, monazite, and xenotime minerals; however, the processing of these materials to extract and recover the rare earth elements is challenging and resource intensive. In addition to these traditional ores, waste materials such as coal fly ash, acid mine drainage solids, and mine tailings and waste have shown to be potentially viable alternative sources. There are several physical and chemical methods typically employed to separate the materials of interest from gangue material, which usually leads to the initial production of a mixed rare earth element concentrate. The mixed rare earth concentrate is then subjected to a separate process (usually organic solvent extraction) to isolate the individual rare earth elements into high purity materials for use in commercial applications. Wayne State University, along with partners at GlycoSurf LLC and the University of California-Los Angeles, have developed several new classes of ligand-associated separation media and designed a process to separate individual rare earth elements, ultimately resulting in individual separated high purity rare earth oxide (ISHP-REO) powders. We will present technical data to demonstrate the feasibility of using ligand-associated sorbent media in packed-bed columns with two promising ligand-associated media categories: 1) glycolipids and 2) DTPA-analogs, to concentrate REEs from leachates. Bench-scale testing has shown that our sorbent technology and sequential separation techniques can produce high purity Sc and Th in one pass through a packed-bed column, while producing significant separation among the remaining 15 naturally occurring REEs. Our process allows for the separation of mixed light REEs from the heavy REEs in a single pass through a column, with further separation of these concentrates into ISHP-REO REE materials occurring with subsequent passes through a sequential column separation scheme. Preliminary data suggest that our media and our novel process will result in the economic recovery of rare earth elements from REE-laden ores and waste materials, with a potential cost savings of over 20% relative to current solvent extraction approaches due to reduced energy consumption and waste disposal. This technology will result in an environmentally-friendly process having lower costs than are currently provided by state-of-the art liquid-liquid separations, and it will require significantly less hazardous waste disposal. Our commercialization strategy will enable this team to work with its industry partners to demonstrate the large scale deployment of this technology, which will help ensure a domestic and global supply of critical REOs for industrial applications. Our group is also developing similar technologies and processes to recover other critical elements (Ni, V, Co) from pregnant leach liquors derived from various sources.