Role of indigenous microbial communities in the mobilization of potentially toxic elements and rare-earth elements from alkaline mine waste

This study aims to evaluate the role of indigenous microorganisms in the mobilization of potentially toxic elements (PTE) and rare-earth elements (REE), the influence of the bioavailability of carbon sources that might boost microbial leaching, and the generation of neutral/alkaline mine drainage from alkaline tailings. These tailings, with significant concentrations of total organic carbon (TOC), were mainly colonized by bacteria belonging to the genera Sphingomonas, Novosphingobium and Solirubrobacter, and fungi of the genera Alternaria, Sarocladium and Aspergillus. Functionality analysis suggests the capability of these microorganisms to leach PTE and REE. Bio-/leaching tests confirmed the generation of neutral mine drainage, the influence of organic substrate, and the leaching of higher concentrations of PTE and REE due to the production of organic acids and siderophores by indigenous microorganisms. In addition, this study offers some insights into a sustainable alternative for reprocessing PMC alkaline tailings to recover REE. This multidisciplinary study (i.e., environmental characterization, biogeochemical techniques, metagenomics sequencing and bioinformatics) uncovers the gap in the current environmental practice regarding landfill disposal by confirming the influence of microbial activity in the mobilization of potentially toxic elements (PTE) from alkaline mine tailings that use to be wrongly classified as inert wastes. In addition, this study offers the first insights into a sustainable recycling alternative to reprocessing alkaline mine tailings to recover REE via bioleaching.