Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the
most refractory for leaching. Several processing routes have been proposed to
overcome drawbacks associated with environmental problems related to copper
extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as
being particularly attractive over other hydrometallurgical systems. However, the
challenge has been to overcome the problem of slow extraction rates due to passivity
encountered at high solution potentials in this system. This highlights the need to
investigate better operating conditions to optimize copper extraction and prevent the
problem of passivation, and to develop suitable modeling tools to assess and diagnose
leaching performance.
In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate
media is proposed accounting for effects in the active and passive regions under
potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk
solution elucidates the idea of passivation caused by precipitation of ferric species and
their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on
massive samples of chalcopyrite involving characterization and modeling of the anodic
and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential
considerations lead to the development of the mathematical expression for dissolution rate.
The mathematical model was calibrated with electrochemical parameters and results
are in good agreement with real leaching data from batch tests for solution potential
regions where passivity is not observed. On the other hand, the passive region was
modeled by means of adjusting parameters related to adsorption energies of the
passivating species. Results of the model for this region deviate from real data as
potential becomes higher probably due to diffusion resistance through a layer
composed of ferric complexes.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU./240 |
| Date | 05 1900 |
| Creators | Trejo-Gallardo, Jaime |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | 805267 bytes, application/pdf |
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