Bioleaching of a Marine Hydrothermal Sulfide Ore with Mesophiles, Moderate Thermophiles and Thermophiles

Abstract

Marine hydrothermal polymetallic sulfide ores contain high amounts of valuable metals such as Cu, Pb, Zn, Au, Ag, as well as In, Ge, Bi, and Se. Samples from a site in the Indian Ocean were taken during a BGR ship cruise, crushed and sieved for bioleaching experiments to reveal the extraction of the various metals. Chalcopyrite was the main mineral, the total copper content was 38.5 %wt. Comparative bioleaching with mesophilic, moderate thermophilic and thermophilic acidophilic iron- and sulfur-oxidizing bacteria and archaea was investigated. Batch culture experiments were conducted at 2% (w/v) pulp density in shake flasks in the presence of Acidithiobacillus ferrooxidans, Acidiphilium sp. and Acidithiobacillus thiooxidans as mesophiles (30°C), a mixed culture of moderate thermopilic iron- and sulfur oxidizing bacteria (50°C) and the thermophile Acidianus brierleyi (70°C). The results after four weeks showed most effective dissolution of copper in the presence of A. brierleyi (up to 4.3 g/l), compared with moderate thermophiles and mesophiles (3.3 g/l and 2.5 g/l, respectively). Furthermore, the bioleaching performance was approved with dissolved iron concentrations. Conclusively, an increase in temperature from 30 °C to 70 °C had a major impact on bioleaching efficiency. Copper and iron extraction efficiency occurred in the order thermophiles, moderate thermophiles, mesophiles.