Formation of cuprous acetate in the leaching of chalcopyrite concentrate with acetic acid

Abstract Currently, the main copper reserves are found in the ore chalcopyrite (CuFeS 2 ). This metal is currently extracted mainly by pyrometallurgical processes, but this method presents several drawbacks: high energy costs and the generation of polluting byproducts, such as SO 2 and PM10 and PM 5 particles. Furthermore, environmental regulations have become stricter, restricting the amount of these substances emitted and limiting the use of pyrometallurgical processes. Therefore, the hydrometallurgical process is proposed as an alternative for obtaining copper from chalcopyrite concentrate. However, there are limitations to its implementation on an industrial scale, the most important being its passivity under ambient conditions. In this regard, organic solvents such as acetone, methanol, ethylene glycol, 2-propanol, and chlorides have been shown to favor the dissolution of chalcopyrite due to the stabilization of the cuprous ion (Cu + ). Another substance proposed as a Cu + stabilizer is acetic acid, which can form the cuprous acetate complex. Therefore, a study was conducted on its use in the leaching of chalcopyrite concentrate in combination with H 2 O 2 as an oxidizing agent in an acidic medium. The concentrations of both acetic acid and H 2 O 2 were varied. Furthermore, under optimal conditions, a kinetic analysis of the leaching process was performed. It was found that one of the leaching products is the cuprous acetate complex, and its concentration and the percentage of copper extraction are directly proportional to the amount of acetic acid and the concentration of H 2 O 2 , achieving copper extraction percentages of approximately 100 % in 120 min. The leaching reaction was then proposed. Kinetic analysis was performed at three temperatures: 20, 30, and 40 °C. The fit of the shrinking core model to the leaching results was assessed, considering control by the diffusion of reactants into the core, by reaction, and by diffusion of the products formed in the film. The latter showed the best fit. The activation energy was 78.12 kJ/mol, corresponding to reaction control, but it was found that the rate-determining step could change with increasing temperature, therefore, mixed kinetic control the leaching rate.