Oxidation Leaching of Copper Sulfides in Ammoniacal Pulps at Elevated Temperatures and Pressures

The Bureau of Mines investigated leaching of selected copper sulfide minerals and a composite of impure flotation concentrates at elevated temperatures and pressures with ammoniacal solutions. Copper extractions of 96 percent were obtained by leaching chalcopyrite at 75° C under oxidizing conditions for 60 minutes. An extraction of 99 percent of the copper contained in the composite concentrate was obtained by leaching the product for 90 minutes at 75° C. In tests of bornite, chalcocite, and covellite, 90 to 97 percent of the copper was extracted at 20° C provided an 8-hour reaction period was used. At 75° C essentially complete dissolution of the copper from these three minerals was accomplished in 60 minutes.