Mixed-control kinetics of oxygen leaching of chalcopyrite and pyrite from porous primary ore fragments

The leaching of individual copper ore fragments was investigated under oxygen pressure of 690 to 3100 kPa. After 500 hours of leaching at 90°C under 3100 kPa oxygen pressure, 50 pct of copper was extracted from an ore particle of 0.57 cm size, while 1300 hours were needed to extract 90 pct of copper under the same experimental conditions. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains and the pore diffusion of dissolved oxygen within the ore fragment was formulated to interpret the experimental results. Both chemical reaction and diffusion were found to be important to the overall leaching rate in the particle size range tested. The model can also be used to predict the leaching behavior of particles of different sizes at different temperatures and oxygen partial pressures. H. K. LIN, formerly Graduate Student in the Department of Metallurgy and Metallurgical Engineering, University of Utah