THE EXTRACTION OF METALS FROM ORES USING BACTERIA

This chapter discusses the use of acidophilic, autotrophic bacteria in the extraction of metals. Microorganisms are responsible for the precipitation of a range of metal compounds out of solution, notably oxide, sulfide, and carbonate minerals. Two fundamentally different mechanisms may be envisaged for such mineral formation. The first involves the precipitation of metallic compounds by the action of anions produced by microorganisms. The second pathway is part of the subject of biomineralization that is currently attracting much attention. In this case, the microbial cell has precise control over the type of mineral that is formed. Also present in certain environments are acidophilic microorganisms whose normal metabolic processes result in the oxidation and solubilization of minerals, usually metal sulfides. This process is responsible for acid runoff from disused mines, spoilage tips, and ore bodies. Such acid runoff may contain substantial amounts of metal ions, such as Cu(II), which have been solubilized or leached out by the action of the acid. © 1991 Academic Press, Inc.