Kinetics of chalcopyrite dissolution in ammonia solution under sealed conditions and controlled redox potential
(1. Key Laboratory of Separation and Processing of Symbiotic-Associated Mineral Resources in Non-ferrous Metal Industry, Engineering Technology Research Center for Comprehensive Utilization of Rare Earth - Rare Metal - Rare Scattered in Non-ferrous Metal Industry, School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China;
2. National Engineering Research Center for Green Recycling of Strategic Metal Resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
3. Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
4. Inner Mongolia Research Institute, China University of Mining and Technology (Beijing), Ordos 017001, China)
2. National Engineering Research Center for Green Recycling of Strategic Metal Resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
3. Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;
4. Inner Mongolia Research Institute, China University of Mining and Technology (Beijing), Ordos 017001, China)
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).
Key words: chalcopyrite; leaching kinetics; redox potential; ammoniacal leaching; surface deposits