Pressure leaching of copper minerals in perchloric acid solutions |
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Authors: | E Peters F Loewen |
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Affiliation: | (1) University of British Columbia, Vancouver, British Columbia, Canada;(2) The International Nickel Company of Canada Limited, Copper Cliff, Ontario, Canada |
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Abstract: | The leaching of covellite (CuS), chalcocite (Cu2S), bornite (Cu5FeS4), and chalcopyrite (CuFeS2) was carried out in a small, shaking autoclave in perchloric acid solutions using moderate pressures of oxygen. The temperature
range of investigation was 105° to 140°C. It was found that covellite, chalcocite, and bornite leach at approximately similar
rates, with chalcopyrite being an order of magnitude slower. It was found that chalcocite leaching can be divided into two
stages; first, the rapid transformation to covellite with an activation energy of 1.8 kcal/mole, followed by a slower oxidation
stage identified as covelite dissolution with an activation energy of 11.4 kcal/mole. These two stages of leaching were also
observed in bornite with chalcocite (or digenite) and covellite appearing as an intermediate step. No such transformations
were observed in covellite or chalcopyrite. Two separate reactions were recognized as occurring simultaneously for all four
minerals during the oxidation process; an electrochemical reaction yielding elemental sulfur and probably accounting for pits
produced on the mineral surface, and a chemical reaction producing sulfate. The first reaction dominates in strongly acidic
conditions, being responsible for about 85 pct of the sulfur released from the mineral, but the ratio of sulfate to elemental
sulfur formed increases with decreasing acidity. Above 120°C the general oxidation process appears to be inhibited by molten
sulfur coating the mineral particles; the sulfate producing reaction, however, is not noticeably affected above this temperature.
For chalcopyrite, activation energies were determined separately for the oxygen consumption reaction and for the production
of sulfate, with values of 11.3 and 16.0 kcal/mole respectively.
This paper is based upon a thesis submitted by F. LOEWEN in partial fulfillment of the requirements of the degree of M.A.
Sc. in Metallurgical Engineering at The University of British Columbia. |
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