Physical and chemical transformations of gangue materials during leaching of copper sulphides, and their influence on copper leaching kinetics

Abstract

This work reports preliminary results from investigations of the chemical and physical transformations of gangue materials during ferric leaching of a copper sulphide ore in sulphuric acid solutions, and their effect on copper leachability. Experiments were conducted with sulphide ore containing 0.6% Cu, consisting mainly of chalcopyrite, chalcocite, and covellite particles in the size range -3/8 +1/4 inches (6.3-9.5 mm). Leaching was conducted on small flooded ore beds using solutions containing 10 g/L H2SO4 and 3 g/L Fe3+. Leaching solutions were maintained at a constant pH (pH = 1) and at a constant Eh (0.75 V/NHE) during the experiments. Leaching progress was monitored through analysis of Cu, Fe, Si, Al, Ca, and Mg in solution. Chemical transformations in the ore were characterized by XRD and changes in the internal porosity of ore particles were characterized by measuring nitrogen adsorption with a sorptometer. The results showed a fivefold increase in internal porous area of the ore particles due to selective leaching of gangue species under acid attack. Variation in ore porosity influences the kinetics of copper dissolution, presumably due to the liberation of sulphide particles occluded in the gangue.