Research was performed on behalf of Revett Minerals, Inc. to evaluate silver extraction from samples of bornite flotation concentrate provide by the Troy Mine. Sulfation roasting experiments were performed in a rotary tube furnace, fluidized bed reactor, and static bed muffle furnace. Roasting experiments were hindered by rapid, low-temperature calcine sintering, apparently related to the presence of organic matter in the flotation concentrate. Copper was extracted from calcine using a weak sulfuric acid media, and silver was extracted from the weak acid leach residue with a lixiviant composed of ferric chloride and hydrochloric acid. Copper extraction efficiencies in excess of 90% were attained in the weak acid leach; silver extractions approached 90% in ferric chloride leaching experiments, along with copper and lead extractions in excess of 93% and 99%, respectively. The two-stage leaching process produced cumulative extraction efficiencies of 99% and 90% for copper and silver, respectively.
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