A biological column leach testwork program was undertaken on a
chalcocite ore. Three tests were conducted in all, using 65 in x 100 mm
columns in three sections. The tests were started with varying acid
strengths and inoculated with bacterial solutions from previous column
testwork. The leaching of Cu was found to occur in three stages. These stages
consisted of direct acid leaching, bacterial oxidation and ferric iron
leaching. These leaching stages can most easily he described through the
examination of not only Cu dissolution but also Fe dissolution and its
subsequent oxidation and precipitation. The p11 of the system was found
to he critical in establishing and maintaining the bacterial leaching
system. The oxidation potential was seen to he influenced by the leaching
system as the oxidation states altered. Test variables such as, 02, COz,
and temperature were all found to influence the system. Final copper recoveries were in excess of 90 per cent in each column
test over a leach time ranging from 211 to 328 days. Given similar leach
conditions are applied, the application of this technology to site is
expected to give comparable results.