Bioleaching of rare earth elements challenges and opportunities: A critical review

Bioleaching has attracted more attention among researchers for Rare Earth Elements (REEs) extraction by using microorganisms as the means to initiate and advance mineral dissolution in aqueous media. Compared to other methods of mineral extraction such as pyrometallurgy and hydrometallurgy, bioleaching has the potential to be relatively eco-friendlier. The microorganisms used in bioleaching processes can be autotrophic or heterotrophic in nature. Studies showed that mixed culture bioleaching operations are preferred since they are relatively efficient in extracting REEs into solution as compared to the single culture bioleaching operation. Bioleaching of REEs encourages closed-loop recycling of REEs resources and reduces supply chain issues. Bioleaching technology could be an alternative approach to modernize the mining industry and encourage sustainable development. This literature review aims to provide an overview of challenges and opportunities associated with REEs extraction through bioleaching. It seeks to summarize the microorganisms employed in REEs bioleaching processes and the mechanisms by which these microorganisms extract REEs into solution. Various REEs bioleaching approaches and various parameters that influence bioleaching performance are reviewed. The techno-economic consideration of REEs bioleaching and future recommendations for advancements are briefly discussed.