Recovery of Copper Metal through Reprocessing of Residues from a Hydrometallurgical Plant

The Chemical of Africa (CHEMAF) is a hydrometallurgical plant operated in Katanga since 2001. It produces copper metal using a process comprising the sulphuric acid leaching of copper-cobalt oxide ores under reducing conditions (Na2S2O5 or SO2) followed by the leach liquor purification by solvent extraction (SX) and electrowinning of copper. The leach liquor is recovered during the thickening of pulps from the leaching section and the scavenging of residues by washing in the counter-current decanters (CCD). The process residues were anciently dumped near the plant. With the increase in the run of mine (ROM) ores sulphide minerals content related to changes in the Kalukuluku deposit mineralogy and considering that the storage of residues may result in toxic pollutants release to the environment, their reprocessing is gaining the ground as the best option. The present research aims at recovering copper metal from residues (2.01% Cu and 0.32% Co) through their reprocessing based on the sulphuric acid leaching prior to the recovery of copper metal through cementation with iron shavings. The results from the experiments have showed that the leaching of copper (≈ 90%) and cobalt (86%) was successful when conducted during 90 minutes at 75°C using 150 g of residues subjected to stirring (500 rpm) in 1 L of H2SO4 (30 g/L) in the presence of Na2S2O5 (330 mV). Consequently, one recovers satisfactorily copper metal (2.5 g of solids assaying 93% Cu recovered at 86%) when 1 g of iron shavings was stirred (400 rpm) ？during 60 minutes at constant speed and at the room temperature in 250 mL of the metalliferous solution (10.84 g/L Cu and 1.73 g/L Co) prepared by the leaching of residues.