Bioflotation and bioflocculation review: microorganisms relevant for mineral beneficiation

In a world of diminishing resources, current research efforts are often directed to extending the life of existing resources and developing technology to treat resources deemed uneconomic. To this end, biotechnology has been explored as a potential low cost, environmentally benign alternative to many of the current mineral processing techniques. Microorganisms and their metabolites have been successfully applied in the leaching of metals from medium and low grade sulphide minerals for many years. Recent fundamental studies have shown that selected bacteria may also assist in the beneficiation of these minerals through bioflotation and bioflocculation. The current published research demonstrates that several bacteria and their excreted proteins and polysaccharides have a significant effect on the surface chemical properties of some minerals. As such, the bacterial cells and their metabolites can be utilised as flotation collectors and modifiers enabling selective separation. To date, these studies have primarily focused on the sulphide minerals; however, there is considerable scope to expand this research for the beneficiation of oxide minerals such as those contained in iron ores. This paper provides a comprehensive review of current research on the use of microorganisms for mineral beneficiation and the potential use of genetically modified bacteria and, further, discusses the applicability of bioflotation and bioflocculation for the beneficiation of Australian iron ores.