Bioliberation of gold

Abstract

In order to satisfy the high demand for gold, lower and complex grade resources must be treated in ever increasing amounts. This requires the development of new processing technologies, which are capable of recovering gold economically from these offgrade, difficult to process (refractory) ores, while safeguarding the environment. Within the novel processes, the biohydrometallurgical approach is continuously gaining importance. The microorganisms involved in these processes are numerous and the reaction mechanisms of leaching are not always understood. Some heterotrophic microorganisms may yield directly gold dissolution from the lateritic ores, while the chemolithotrophic bacteria are capable of liberating submicrometre size gold particles enclosed in the pyrite and arsenopyrite minerals. In this latter process gold remains in the bioleach residue from which it is dissolved by cyanide leaching. The present article systematically summarises the available information on bioleaching possibilities, and where appropriate, provides data on industrial applications.