Ferric chloride leaching of mechanically activated chalcopyrite

Mechanical activation is a means of accelerating the leaching process. Contributing to the success of this technique are (1) increased surface area; (2) increased surface reactivity; and (3) the microstructural modifications stemming from the deformation. Previous studies have focused on gaining a fundamental understanding of these factors. Tl-is study represents a divergence from this approach, as we set out to determine the effectiveness of the technique when applied on a scale more reflective of how the process might actually be practised. To this end, chalcopyrite was autogenously milled in a horizontal mill, and leaching was conducted using a 5 M chloride leach solution. Leaching of as-received concentrate resulted in copper extractions of 75% in 5 h of leaching, whereas leaching mechanically activated concentrates resulted in copper extractions over 95% after 3 h of leaching. This study investigated the critical parameters affecting the efficiency of mechanical activation as a means of accelerating the oxidative leaching of sulfide minerals. The processes of attrition and fragmentation enhance reaction rates by increasing both the surface area and the density of defects. A small laboratory shaker mill and a small tumbling mill were used to mechanically process chalcopyrite; the former using steel grinding media, the latter using sized ore. The increase in surface area was determined using BET; and X-ray diffraction analysis was utilized to determine the full width at half maximum (FWHM) for chalcopyrite, which is subsequently used as a marker of the relative deformation. Leaching experiments were conducted with as-received concentrate and with processed concentrate. The contributions of the increased surface area and the deformed structure were correlated with the leaching kinetics. (C) 1998 Elsevier Science B.V. All rights reserved.