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Kinetic study of the dissolution of chalcopyrite in the presence of a catalyst under acidic sulfate medium Rebolledo, Monserrat


The main drawback of the atmospheric pressure hydrometallurgical process to recover copper from chalcopyrite is its slow dissolution rate. The aim of this study was to gain further insight of the kinetics of the leaching of chalcopyrite in the presence of thiourea (TU), as a catalyst, in acidic sulfate media. To do so, the influence of temperature, copper, acid and catalyst concentration on the leaching of chalcopyrite were measured and quantified. Among the parameters tested, the tendency of TU to be oxidized was found to be very sensitive to the concentration of acid in solution. Besides, the rate of its oxidation was essentially dependent on the mineral surface available and only slightly dependent on the concentration of ferric ions in solution. The data from the leaching test in this study demonstrated that in the presence of TU, it is possible to achieve ~98% of copper extraction from chalcopyrite in less than 216 hours at room temperature. Chemical reaction was determined to be the rate controlling step based on an apparent activation energy of 41 kJ/mol. The reaction order of chalcopyrite was found to be 1.7 and -0.9 with respect to TU and proton concentration (H+), respectively. The shrinking sphere model, assuming surface chemical reaction as the rate-controlling step, fitted very well the changing grain topology. The development of a single mathematical expression combining the thermal, chemical, and topological functions to predict the chalcopyrite conversion as a function of the known temperature, ferric and ferrous concentration, thiourea and proton concentration, particle size and time was also performed. The present findings open a new direction of research oriented towards the development of a plausible alternative for a low-temperature processing route for chalcopyrite leaching

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