Recovery of copper and cobalt from ancient slag

About 2.5 million tonnes of copper smelter slag are available in Küre, northern part of Turkey. This slag contains large amounts of metallic values such as copper and cobalt. A representative slag sample containing 0.98% Cu, 0.49% Co and 51.47% Fe was used in the experimental studies. Two different methods, direct acid leaching and acid baking followed by hot water leaching were used for recovering Cu and Co from the slag. The effects of leaching time, temperature and acid concentration on Cu- and Co-dissolving efficiencies were investigated in the direct acid leaching tests. The optimum leaching conditions were found to be a leaching time of 2 h, acid concentration of 120 g L^-1, and temperature of 60°C. Under these conditions, 78% Cu and 90% Co were extracted. In the acid baking + hot water leaching tests, 74% Co was dissolved after 1 h of roasting at 200°C using a 3: 1 acid: slag ratio, whereas the Cu-dissolving efficiency was 79% and the total slag weight loss was approximately 50%.