Abstract
Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain.
Highlights
The depletion of reserves of high-quality raw materials of non-ferrous metals is an increasingly significant problem around the globe today
The aim of this work is to investigate the kinetics and mechanisms of the ammonia pressure leaching of low-grade sulfide raw materials containing copper and silver, in order to study the effects of Si-containing minerals on the kinetics of Cu and Ag leaching
The pressure leaching of sulfide copper concentrate in an ammonia environment is possible only recovery will strongly depend on the process temperature
Summary
The depletion of reserves of high-quality raw materials of non-ferrous metals is an increasingly significant problem around the globe today. Low-grade ores and concentrates are involved in processing [1,2], and enterprises have to sacrifice recovery and quality to maintain the required levels of productivity. The deterioration of technological parameters and indicators is due to a decrease in the content of valuable components and an increase in harmful impurities, along with the fact that non-ferrous and noble metals often exist in minerals as fine impregnations in gangue with mutual intergrowth and the presence of nanodispersed, colloidal grains, etc. The deterioration of technological parameters and indicators is due to a decrease in the content of valuable components and an increase in harmful impurities, along with the fact that non-ferrous and noble metals often exist in minerals as fine impregnations in gangue with mutual intergrowth and the presence of nanodispersed, colloidal grains, etc. [3,4]
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