Leaching and Kinetic Study on Pressure Oxidation of Chalcopyrite in H2SO4 Solution and the Effect of Pyrite on Chalcopyrite Leaching

Abstract

The leaching of copper from chalcopyrite in H2SO4 solution under pressure-oxidative conditions and its kinetics were investigated in this study. Leaching variables that affect the rate of copper dissolution from chalcopyrite are agitation speed (300–900 rpm), total pressure (0.8–2.0 MPa), temperature (160–180 °C), and sulfuric acid concentration (0.1–2.0 M). Results showed that dissolution of chalcopyrite increases with increasing agitation speed, total pressure, and temperature, whereas it decreases with the increasing sulfuric acid concentration. Under the optimal conditions, copper extraction of 94.5% was achieved after 90-min leaching, while a dissolution of iron at 4.2% was obtained. The kinetic study showed that the dissolution of chalcopyrite is represented by a shrinking core model with chemical reaction controlling mechanism given as (1 − (1 − α)1/3). The activation energy (E a) for the leaching reaction was calculated to be 42.4 kJ/mol. The reaction order with respect to total pressure was about 8.0, which indicates that total pressure, i.e., oxygen partial pressure, in an autoclave is the most important factor in controlling the dissolution of chalcopyrite in H2SO4 solution under pressure-oxidative leaching conditions. The effect of Fe/Cu mole ratio (1–20 mol/mol, adjusted by addition of pyrite) on chalcopyrite leaching from a copper ore was investigated. The results show that the sulfuric acid produced during pyrite oxidation promotes the chalcopyrite dissolution.