College Park, MD: U.S. Department of the Interior, Bureau of Mines, RI 8067, 1975 Jan; :1-18
Laboratory tests on a combined nitrogen roast--two-stage leach-- electrowinning approach show promise as a possible process for recovering copper, sulfur, iron oxide, and valuable minor metals (gold, silver, and molybdenum) with a minimum impact on the environment. During the nitrogen roast at 800 deg c, 15 to 20 percent of the sulfur together with a significant fraction of the volatile elements, such as arsenic, bismuth, lead, and zinc, are removed from the chalcopyrite concentrate. The resulting calcine, consisting of b-chalcopyrite, troilite, and a bornitelike structure, is leached with hydrochloric acid to remove 70 to 85 percent of the iron. The digenite in the leach residue is dissolved in an oxygen- saturated, spent sulfate electrolyte. Using a graphite anode plus sulfur dioxide to reduce interference from ferric iron, copper of 99.9+ Purity is electrowon at current efficiences of 88 to 92 percent and a cell voltage of 0.4 to 0.5 Volt. Copper recovery for the overall process is 98 to 99 percent. Sulfur is obtained in the elemental form from the roasting and leaching steps. Iron can be recovered from the hydrochloric acid leach solution. Gold, silver, and molybdenum are concentrated in the silica residue from the spent electrolyte leach.
College Park, MD: U.S. Department of the Interior, Bureau of Mines, RI 8067