Effect of Carbon Black on Copper Ore Leaching in Sulfuric Acid Media at 50°C

In this study, we examined the effect of carbon black on the sulfuric acid leaching of a copper ore containing 1.1% Cu occurring as CuFeS2 (chalcopyrite). Leaching experiments were performed in Erlenmeyer flasks containing 200 mL of the sulfuric acid medium while agitated with a magnetic stirrer at 50°C. The addition of carbon black enhanced the kinetics of chalcopyrite leaching at an initial pH of 1.2. The extraction yield of Cu was 97% in 98 h in the presence of 0.2 g of carbon black, compared with 18% in the absence of carbon black. The acceleration of chalcopyrite dissolution did not occur without direct contact between the ore and the carbon black, suggesting that a galvanic interaction between the two materials plays a role in the improvement of the leaching rate. In the presence of carbon black, the redox potential fell below 600 mV vs. SHE with a decrease in the ratio of Fe(III) to Fe(II), and the leaching rate of chalcopyrite increased markedly. The enhanced kinetics of chalcopyrite leaching in the copper ore could be attributed to dissolution reactions at a low redox potential and to the galvanic interaction between the chalcopyrite and the carbon black.