Copper Recovery from Conglomerative-type Native Copper Ore by Ammonia Leaching, Solvent Extraction, and Electrowinning.
To help maintain an adequate supply of minerals to meet national, economic, and strategic needs, the Bureau of Mines investigated the feasibility of extracting copper from coarse native copper ore with ammoniacal ammonium carbonate solution by a simulated in situ leaching procedure. A 5.9-Metric-ton (6.5-Ton) sample of minus 30.5- Centimeter (12-inch) conglomerate-type ore analyzing 1.96 percent copper was leached in a column for 556 days with a solution that contained, in grams per liter, 2.2 Nh3 and 1.9 Co3=. The copper extraction was 71.4 percent, and reagent consumptions were, in kilograms per metric ton of ore, 1.1 Nh3 and 0.85 Co3 (in pounds per ton of ore, 2.2 Nh3 and 1.7 Co3=). The pregnant leach solutions contained about 1.4 Grams per liter copper, which was readily extracted from these low-tenor liquors with a 1:19 mixture of an organic extractant and kerosine. Copper was stripped from the loaded organic with depleted electrolyte containing 150 grams per liter h2so4, and the copper was recovered by electrowinning with antimonial lead anodes. Conditions also were established for minimal lead transfer to the cathode copper.