Bioleaching is a process, whereby metals are leached from ore as a result of bacterial action. In nature, bioleaching is triggered spontaneously by micro-organisms in the presence of air and water. Commercially applied bioleaching technologies utilize the same phenomenon, but accelerate this natural process. Several physicochemical and microbiological process parameters are modified in order to enhance and speed up the metal recovery process.
Typically, primary and secondary sulphides are associated with pyrite which, when oxidised, has the potential to release sufficient quantities of heat. The biological oxidation of the sulphide components of minerals is an exothermic reaction which releases substantial amounts of energy. This process needs to be carefully managed to maximise effective metal recovery. To reach and maintain the temperatures required for enhanced sulphide mineral leaching, different microbial populations are required to be present over time and the microbial growth rates need to be optimum.
The bacteria used in the Talvivaara bioheapleaching process are naturally growing in the ore. The bacteria are thus endemic to the area and therefore well adjusted to the prevailing environmental conditions.