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Enhancing the kinetics of pyrite catalyzed leaching of chalcopyrite

University of British Columbia

An investigation has been conducted into the kinetics of chalcopyrite leaching in acidic ferric/ferrous sulfate media at atmospheric pressure and low temperature in the presence of pyrite. It has been found that pyrite samples from different sources affect the rate of chalcopyrite leaching differently. Some pyrite samples accelerate the rate significantly while others have little or no influence. The effectiveness of pyrite has a strong correlation with the level of silver occurring in the pyrite. In this study, the use of silver-enhanced pyrite in the Galvanox™ process to improve the extraction of copper from chalcopyrite was investigated. The catalytic properties of pyrite have been improved such that all pyrite samples accelerate the rate of copper extraction regardless of their sources. Under appropriate conditions, complete copper extraction can be obtained in the presence of silver-enhanced pyrite in 10 to 15 hours. Silver-enhanced pyrite can also be effectively recycled with minimal loss of effectiveness. A comprehensive understanding of the mechanisms involved in the process of chalcopyrite leaching in the presence of silver-enhanced pyrite was developed. It has been found that the acceleration of the rate of chalcopyrite leaching is due to the galvanic interaction between pyrite and chalcopyrite particles. An important factor in any galvanic process is maintaining electrical contact between two minerals to ensure the transport of electrons from the anode to the cathode. As chalcopyrite leaching proceeds, layers of extremely high electrical resistivity form around chalcopyrite particles, which limit the transport of electrons from chalcopyrite to pyrite and inhibit the galvanic interaction between these two minerals. However, in this study, it has been shown that, in the presence of silver-enhanced pyrite, around 10% of the added silver gradually leaves pyrite during leaching and reacts with the elemental sulfur layer on chalcopyrite to form silver sulfide. Although the amount of silver sulfide is very low and the sulfur layer does not become very conductive, it does become conductive enough to allow the transport of electrons at a rate sufficient to support the leaching reactions at rates observed in the process. With a conductive path between pyrite and chalcopyrite, the galvanic interaction between these two minerals can now occur.

Text

2012-04-10

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/41937

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/