Uranium (U) deposits and U mine wastes may contain Rare Earth Elements (REEs). There were 15,000 abandoned uranium mines throughout 14 western states (75% on tribal and federal lands) identified in 2013. REEs are valuable raw materials, used extensively in modern technologies. Low concentration per location, expensive mining operations, and high demand of global market make them politically and industrially important for countries. The development of green technologies for REE recovery from abandoned mine wastes will provide less negative impacts than conventional approaches, while remediating the existed abandoned mines and reducing the health issues of the radioactive exposed nearby communities. In this study, we used samples of St. Anthony mine, New Mexico to enhance microbial activity responsible for cerium (Ce) reduction from Ce(IV) to Ce(III) by adding Ce(IV) oxide nanoparticles and ethanol as an external electron donor under anaerobic conditions. Preliminary results show that ore samples were rich in U and REE and there were available microorganisms capable of reducing these elements. In addition, bioleaching experiment showed that Ce mobilization was successful with the highest efficiency in ore, ethanol and CeO<sub>2 </sub>treatments in comparison with the controls. Other REEs were not bioleached into the liquid phase which supports the idea of selective REE extraction. High initial U concentration quickly decreased in all of bottles contained ore samples due to the chemical precipitation or microbial reduction of U(VI) to U(IV). Increasing concentrations of vanadium and arsenic in all ore containing treatments were observed, which need to be more investigated in this research and future work. The expected outcome of this project will generate a comprehensive base for understanding the bio-interaction of REEs and U in mine wastes and the design of an environmentally-friendly process to selectively extract them by the isolation of U and REE utilizing microorganisms.

Cerium bioleaching from abandoned uranium mine wastes

2019 Spring National Meeting

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