Organic acid leaching of base metals from copper granulated slag and evaluation of mechanism

A hydrometallurgical method is discussed to selectively extract base metals such as copper, cobalt, nickel and iron from the copper granulated slag (0.53% Cu) at atmospheric pressure. It involves first-stage leaching of slag with organic (citric acid) to selectively recover cobalt, nickel and iron. The residue containing high copper was subjected to second-stage leaching with inorganic (sulphuric) acid. Leaching parameters such as acid concentration, pulp density, temperature and time were optimised to extract metals from the granulated slag. A maximum recovery of 4.47% Cu, 88.3% Co, 95% Ni and 93.8% Fe were obtained in first-stage leaching with 2 N citric acid at room temperature using 10% pulp density (w/v) in 8-9h. On subjecting the leach residue to the second-stage leaching with 2 M sulphuric acid, 66-72% Cu was recovered in 4 h. The kinetics of the metal leaching from the slag was established by the XRD and SEM-EDAX studies of the residues.