Abstract

The effect of silver ion, silver sulfide and silver-bearing concentrate (Ag–C) on the bioleaching of chalcopyrite has been investigated. It has been found that the addition of silver-bearing catalyst greatly enhanced copper dissolution from chalcopyrite and copper ores. The dissolved copper from chalcopyrite ore was increased from 25% to 75%, 65% and 67%, respectively, by addition of 0.32 g Ag, 4 g argentite (Ag₂S) and 20 g Ag–C, per kilogram of ore after 20-day bioleaching in shake flasks. The bioleaching tests for a column charged with 18 kg chalcopyrite-containing waste rock showed that the copper extraction increased from 3.4% to 21.7% and 16.5%, respectively, by using 0.21 g Ag₂S and 15 g Ag–C per kilogram of rock. The results indicated the possibility of using silver-bearing concentrate as an effective and cheap catalyst for bioleaching of chalcopyrite ore instead of the expensive silver. The mechanism of enhancement of chalcopyrite bioleaching in these systems was discussed, based on the “mixed potential model”, the mineralogy of silver-bearing concentrate as well as by using X-ray diffraction and electrochemical measurement.