Salt-tolerant bioleaching microbes for mining operations where fresh water is scarce

摘要

Anions and cations can accumulate in process waters due to the source water, to evaporation and because of gangue mineral dissolution. Common salts that can accumulate from mineral gangues are the anions, chloride and sulfate, both of which impact on microorganisms used in bioleaching processes. The search for salt-tolerant acidophilic microorganisms able to tolerate high concentrations of tese salts as well as high concentrations of metals has been underway for at least 20 years because their application would considerably improve bioleaching process efficiency in areas where fresh water is scarce. A thorough search of known saline and acidic drains, lakes and sediments in the South West of Western Australia and a CSIRO culture collection was undertaken to bio-prospect for salt-tolerant bioleaching microorganisms. Enrichment cultures of acidophilic microorganisms that could tolerate up to 70 g/L sea salts were established. Salt tolerant iron and sulfur oxidisers were obtained in mesophilic, moderately thermophilic and thermophilic temperature ranges. Sulfate was tolerated to a greater extent than chloride as was expected. The addition of pyrite to the salt tolerant iron oxidisers aided the microorganisms to tolerate higher concentration of salts. The salt tolerant cultures will be used for determining their efficiency in bioleaching a chalcopyrite ore.