Selective Bioprecipitation of Rare Earth Elements from Bioleachates: The Role of Biorefining

The selective recovery of Rare Earth Elements (REEs) from red mud leachates is a major challenge due to the presence of interfering metals such as Fe, Al, Ca, and Mg. This review examines microbial bioprecipitation as a promising strategy to improve selectivity in REE recovery. Microorganisms can produce metabolites, such as phosphates, carbonates, and oxalates, that help selectively precipitate REEs from solution, while sulfate-reducing bacteria can remove competing metals through sulfide precipitation. Although research on similar waste streams exists, studies specifically addressing red mud bioleachates are still limited. Key factors affecting selectivity are discussed, including pH, competing ions, metabolite specificity, and microbial strain selection. Integrating microbial bioprecipitation into broader biorefinery processes could enhance the sustainable and efficient recovery of REEs from red mud, contributing to circular economy goals. This review also identifies important research gaps and suggests future directions for scaling up this approach in metallurgical applications.