Microbial influence and dynamics of metallurgical waste dissolution in a landfill and recovery context: A multi-phase experimental approach and geochemical model.

The effects of abiotic and biotic dissolution on metallurgical wastes (slag and matte) were examined combining a multi-phase experimental approach with a solution renewal and geochemical model. The conditions studied included the exposure of solid wastes to water, a growth medium, and heterotrophic siderophore-producing bacterium Pseudomonas fluorescens. Quantification of the dissolution was performed by tracking the element release, whereas immobilization processes were predicted by applying a geochemical model and scanning electron microscopic observations. The results demonstrated that the phase composition of these wastes subjected to (bio)dissolution was linked to the behavior of Pseudomonas fluorescens, with the deteriorative dissolution effects varying between slag and matte. The contribution level of the bacteria to the mobilization of the elements exhibited the following order: Cu > Pb > Zn; however, the entrapment of these elements in biomass affected the amount of metals released. Copper-bearing sulfides and metallic lead-bearing phases were specifically found to be highly susceptible to (bio)dissolution. Moreover, the bacteria contribution to the Zn release from sphalerite played less of an important role compared to its abiotic mobilization. Overall, this study underlines the important role of bacteria at the interface where wastes are exposed to weathering, resulting in accelerated dissolution. The application of bacteria to Co and Mo recovery is an important approach to the detoxification of landfilled wastes.

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