Processing of halcopyrite low grade ore - enhancing gold recovery by leaching and bioleaching

摘要

The conventional flotation technologies cannot provide fair results when applaid to very low grade ores or to "refractory" ores. This class includes intimate and nonuniform mineral associations, with partialy oxidized minerals and high secondary mineral content and also high soluble salt content, pre-activated minerals because of the excessive permeability of the deposit and of the intense circulation of waters with heavy metal ions etc. Bacterial oxidation as a means to the recovery of metals from sulphidic deposits has been used for thousands of years. One of the major use of biooxidation is the leaching of copper or the liberation of refractory gold where this is encapsulated in pyrite. In the Bucim copper mine Macedonia, porphiritic type, the final product from flotation is the copper concentrate consisting 20% Cu, 21g/t gold and 25g/t silver, with recoveries: 88-90% for copper, 60% for gold and 40% for silver. The carried out investigations of the leaching in the agitated tank involve micro-organisms, thiobacillus ferro - oxidans and thiobacillus thio-oxidans. The achieved results are following: Copper recovery 95%, gold recovery from 70-85% and silver recovery from 70-80%.