Studies of the Anaerobic Leaching of Iron and Copper Containing Dump Material and Comparison to Chemical Leaching

The objective of this study was to investigate the leaching of a non-sulfide copper ore by a new bioleaching process, the Ferredox process. In the Ferredox process, Acidithiobacillus ferrooxidans reduces ferric ions and oxidizes sulfur at low pH under anaerobic conditions. In this study, a bacterial culture (mainly A. ferrooxidans) was initially grown aerobically. Bacterial dissolution of iron sludge under anaerobic conditions versus sulfuric acid was compared. An iron slurry sample from the West Rand Ditch near Hoyerswerda, Germany and from the Golestan Mine in Iran was investigated. Two shake flasks each containing an iron slurry and non-sulfidic Fe/Cu ore were used. One shake flask each was subjected to an anaerobic process by A. ferrooxidans, while the other sample was leached with dilute sulfuric acid. In the chemical leaching, the amount of dissolved copper was 2.5 %, only slightly higher than in the bioleaching. In a subsequent anaerobic column leaching with A. ferrooxidans, 35 % of the contained copper was mobilized from 1366 g ore.