| Summary: | Includes bibliographies. === Bioleaching is a biohydrometallurgical process whereby mineral sulphides are metabolically oxidised by microorganisms, releasing precious metals encapsulated in them. This pre-treatment is based on the action of microorganisms affecting oxidation of reduced sulphur species and ferrous iron to sulphate and ferric iron respectively. Conventionally Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans are implemented in this process in the region of 40-45°C and pH 1.8. A high temperature (65- 800C) process, utiltising thermophilic archaea such as Sulfolobus spp. can be considered as an alternative to current bioleaching practice. Literature indicates that there is an overall increase, 6 fold on average, in the rate of leaching due to the use thermophilic organisms. Bioleaching. involves nutrient transfer to microorganisms and interactions between several ionic species, including iron and sulphate. Thus, it is necessary to investigate the effect of the increased temperature on the gas-liquid mass transfer as well as ionic speciation of the system. Hence, the objectives of the present research were established as follows: to elucidate the effect of temperature on mass transfer from a theoretical point of view to establish whether ionic speciation is a contributing factor in thermophilic bioleaching to develop a generic and flexible means of representing ionic species
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