Recovery of copper from smelting slag by sulphation roasting and water leaching

In this work extraction of copper and iron from a reverberatory furnace slag was studied. A two-step extraction procedure was followed. The first step was roasting of the slag in the presence of sulphuric acid at temperatures between 150 and 800^oC. The second step was leaching of the resulting calcine with distilled water. The maximum copper extraction of about 94% was achieved. In this case, the slag was roasted at 250^oC with sulphuric acid higher of about 33% than that stoichiometrically required, followed by water leaching of calcine at 50^oC. About 55% of iron was also dissolved under these conditions. On the other hand, for the calcine obtained at sulphation temperature of 600^oC, extraction of copper in a water leaching stage was still relatively high (about 79%), whereas that of iron was comparatively low (about 6%). Dissolution of copper and iron from the calcine was found to be very fast and was complete within the first few minutes. The water temperature in the leaching step was found to have no effect on extraction of copper and iron from the calcine in the range of 30 to 85^oC.