Indirect oxidative leaching of a polymetallic black schist sulfide ore: development of a protocol for in situ bioleaching of deep-buried ore bodies

摘要

Mining metals from ore bodies buried deep in Earth's crust could help meet the increasing global demands for base metals, though conventional mining of these deposits would be uneconomical and harmful to the environment. An alternative approach, where microorganisms are used to enhance the extraction and recovery of metals directly from ore deposits and mineral waste could provide a more sustainable method. An objective of the EU Horizon2020 "BioMOre" project is to develop "deep in situ biomining" technology where the oxidative dissolution of metal-bearing minerals would be mediated by ferric iron generated microbiologically in bioreactors located distant from the fractured ore body. A laboratory test was set up using a polymetallic black schist sulfide ore (from the Talvivaara mine, Finland). A biologically-generated ferric iron lixiviant (pH 1.8) was used to percolate a flooded column, following pre-leaching with 0.1 M sulfuric acid to remove most of the acid-labile minerals. While leaching of manganese and copper essentially came to a halt after about 60 days, other base metals (nickel, zinc and cobalt) continued to be extracted over the entire time-frame of the experiment, accounting for 30 to >99% extraction of these metals. Leptospirillum ferriphilum, iron-oxidizing Acidithiobacillus spp. and Ferroplasma acidiphilum dominated both the biologically-generated lixiviant and the ore leachate.