Chapter 4 - Bioleaching Mechanisms

Abstract

Various mechanisms involved in bioleaching of sulfide minerals are illustrated with special focus on A. ferrooxidans, the most widely implicated and used bacteria. Through appropriate definitions and critical analyses of scientific research spread over 50 years, electrochemical and microbiological aspects of proposed mechanisms are analyzed in terms of direct, indirect, and contact leaching mechanisms. Bacterial attachment mechanisms on different sulfide minerals are illustrated with respect to surface chemical, electrochemical, and chemical forces. Role of galvanic interactions in selective biooxidation is discussed with respect to multimineral combinations. Metal toxicity in leaching bacteria and development of metal-tolerant strains are outlined in relation to improvement in bioleaching efficiency. Adaptation of leaching bacteria to leaching conditions in the presence of minerals is critically analyzed and the use of preadapted bacteria in bioleaching of various sulfide minerals is illustrated with examples.