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Hydrometallurgy 84 (2006) 81 – 108 www.elsevier.com/locate/hydromet

The bioleaching of sulphide minerals with emphasis on copper sulphides — A review
H.R. Watling
Parker Centre for Integrated Hydrometallurgy Solutions, CSIRO Minerals, PO Box 90, Bentley, WA 6982 Australia Received 16 January 2006; received in revised form 8 May 2006; accepted 12 May 2006 Available online 23 June 2006Abstract This review outlines current research in heap bioleaching, particularly in respect of the bioleaching of chalcopyrite, assesses the status of the bioprocessing of copper sulphides and evaluates promising developments. The bioleaching of sulphide minerals is reviewed with emphasis on the contribution from the microbial community, especially attachment and biofilm formation, bioleachingmechanisms and the potential benefits to be gained by a greater understanding of the molecular genetics of the relevant microbial strains. The leaching and bioleaching of copper sulphides is examined. The main focus is on heap bioleaching of whole ores, and the development of models to describe heap and dump processes that can be applied in the design phase as well as to optimise metal extraction. Thecharacteristics of chalcopyrite leaching are discussed in respect of those conditions and controls that might be needed to make a heap bioleach commercially productive. © 2006 Elsevier B.V. All rights reserved.
Keywords: Bioleaching; Heap leaching; Dump leaching; Copper sulphides; Chalcopyrite; Mechanism; Modeling

1. Introduction World copper production has increased steadily in the period1984–2005, from 9 Mt to 16 Mt per annum, and is predicted by the Australian Bureau of Agricultural and Resource Economics (ABARE) to reach close to 18 Mt in 2006. More than 20% of that copper is now produced via hydrometallurgy. An indirect indicator of the notable increase in hydrometallurgical copper production over recent years is the increased overall capacity of solvent extraction-electrowinning(SX-EW) plants producing cathode copper. Copper production from SX-EW rose from 0.8 to 2.0 Mt in the period 1993 to 1997 (Arbiter and Fletcher, 1994; Readett and Townson, 1997). In
E-mail address: helen.watling@csiro.au. 0304-386X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2006.05.001

2001, the combined copper production of Chile and the USA using SX-EWwas about 2.1 Mt (Bartos, 2002) with additional production of about 0.16 Mt from other countries. While world demand for copper is growing, the minerals industry is increasingly faced with the need to process low grade ores, overburden and waste from current mining operations. The economic extraction of copper from low-grade ores requires low-cost processing methods such as in situ, dump and heapleaching. Bacterially-assisted heap leaching of low-grade copper sulphides is a developing technology that has been applied successfully to the extraction of copper from secondary sulphide minerals such as chalcocite at a number of operations worldwide. However, heap bioleaching of the refractory primary copper sulphide,

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chalcopyrite,has yet to be implemented at commercial scale. Traditionally, the advantages of bacterial leaching technology are compatible with these requirements: • Moderate capital investment with low operating costs, • Appropriate recovery of metals from low-grade ores and waste materials, • Basic equipment and simple operating procedures. The most successful copper heap leaching operations have been thoseprocessing copper oxides and secondary copper sulphides (Table 1). Chalcocite (Cu2S) is the main copper sulphide mineral mined at bioleaching operations. Some of the chalcocite heap operations began as oxide (chemical) leach operations and were converted to bioleach (oxidative) operations by heap aeration and/or inoculation, when the oxidised ore was depleted. However, even if bacterial activity...