Microbial Leaching Strategies for Extraction of Rare Earth Elements from Primary and Secondary Resources

Rare Earth elements (REEs) are a group of 17 elements, including 15 lanthanides, coupled with chemically similar yttrium and scandium. Due to their unique physical and electrochemical characteristics, they are applied in a wide variety of sectors of the global economy, standing as elements of strategic importance. The rapid increase in the demand, together with the limitations of their availability, have addressed the study of alternative, secondary sources of REEs as well as the development of eco-friendly processes to pursue their sustainable recovery. The need to set environmentally sound treatments has thus driven the scientific and technical interest towards bio-metallurgy, as a promising alternative to conventional methods. This chapter focuses on the application of biotechnological strategies to leach REEs from both primary and secondary sources. Biological-mediated leaching processes are discussed to point out the main mechanisms driving the extraction of REEs as well as the factors influencing their yields. The current state-of-the-art of REE bioleaching processes is figured out in order to highlight the potential for scale up as well as to address future research perspectives.