Kinetics of chalcopyrite dissolution in ammonia solution under sealed conditions and controlled redox potential

Abstract

To provide optimization strategies for chalcopyrite ammonia heap leaching processes, the key factors influencing chalcopyrite ammonia leaching kinetics were investigated under sealed reactor and controlled redox potential at ambient temperature. The results indicated that redox potential, particle size, and pH significantly affected chalcopyrite dissolution rates. The reaction orders with respect to particle size and hydroxyl ion concentration c(OH⁻) were determined to be −2.39 and 0.55, respectively. Temperature exhibited a marginal effect on chalcopyrite dissolution within the range of 25−45 °C. The ammonium carbonate medium proved more favorable for chalcopyrite leaching than ammonium chloride and ammonium sulfate systems. Surface deposits on the residues were identified as porous iron oxides, predominantly hematite and ferrihydrite, which produced diffusion barriers during leaching. Shrinking core model analysis revealed that the second stage of reaction was controlled by product-layer diffusion, which was further confirmed by the low activation energy (10.18 kJ/mol).