(763c) Leaching Rare Earth Elements from Coal and Fly Ash through Biochemical Processes

To avoid using toxic chemicals that have been traditionally used in leaching of various metals, research and development on bioleaching or biomining have been on the rise. Bioleaching takes advantage of microbial activities to turn valuable but insoluble metal compounds into water soluble forms. Compared to chemical leaching, this technology has the advantages of being: 1) environmentally friendly, 2) low energy input and 3) low chemical cost. Specific to recovery of Rare Earth Elements (REEs), bioleaching has been shown to be technically feasible. Recovery rates ranging between 2.5% and 75% have been reported from use of different microorganisms under different leaching conditions. In this talk, we will present our recent studies on leaching REEs from Illinois coal and fly ash. Microbes including a fungus strain and two yeast strains were investigated on their capability in bioleaching REEs under different testing conditions. The raw materials together with those residues after leaching were characterized in terms of their REE content and composition. Our results have demonstrated that up to 86% of REEs can be extracted out of coal or fly ash through microbial activities. This bioleaching process, upon further optimization, has great potential in becoming an economically viable approach for recovering REEs from coal and coal byproducts.