Ore column leaching with thermophiles: II, polymetallic sulfide ore

A polymetallic sulfide ore from which several metals are commercially extracted has a high pyrrhotite content that results in elevated temperatures in the ore leaching heaps. Laboratory ore columns were inoculated with moderately thermophilic bacteria and thermophilic archaea to assess the influence of microbial activity on leaching of metals from the ore at 47 °C and 68 °C. The populations of moderately thermophilic bacteria that became established on the ore were dominated by acidophilic Actinobacteria. Excessive precipitation of oxidized iron compounds in the presence of microbial activity hindered extensive leaching from small-scale ore columns (0.7 kg ore). Copper extraction was generally delayed in comparison to that of the other target metals (principally nickel and zinc) when ore column effluent solutions remained above about pH 2.5.