Leaching of bornite in acidified ferric chloride solutions
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I.
INTRODUCTION
B O R N I T E , CusFeS4, is associated with several of the copper sulfide minerals and may be found in equilibrium with the two most common such minerals, chalcopyrite and chalcocite.~'2 Consequently, bornite is often found in copper-ore bodies with these and other minerals. It ranks in economic importance after chalcopyrite and chalcocite, but it is second only to chalcopyrite in economic importance at the largest copper mine in the United States, the Bingham mine in Utah. The leaching behavior of specific minerals such as bornite is important in gaining a better understanding of an overall ore body containing given minerals of importance. Bornite has not been studied as extensively as has chalcopyrite, 4-s covellite, 9-~2 and chalcocite. 3'~~ The studies of bornite leaching have been primarily in acidified ferric sulfate solutions, s'~4 23 though other solutions have been used. 24'25'26 The authors have studied bornite leaching in which oxygen is the oxidant both in sulfuric acid 27'28 and in hydrochloric acidfl 9 Chloride leaching o f bornite has not been carefully studied though Sullivan 16 recognized it as a superior leachant over half a century ago. The authors selected ferric chloride as the lixiviant for bornite leaching studies because of (1) the relative importance of bornite as a mineral, (2) the need for specific mineral kinetic data in modeling of processes, (3) increased interest in chloride leaching, and (4) the fact that no one has reported studies for ferric chloride leaching of bornite. The leaching study was conducted in two specific but closely related aspects, mineral dissolution and residue
B. PESIC is Assistant Professor of Metallurgy, Department of Metallurgical and Mining Engineering, University of Idaho, Moscow, ID 83843. F. A. OLSON is Professor of Metallurgy, 412 Browning Building, University of Utah, Salt Lake City, UT 84112. Manuscript submitted March 10, 1983. METALLURGICALTRANSACTIONS B
analysis. On the basis of these results, a mechanism for the leaching of bornite with ferric chloride is presented.
II.
EXPERIMENTAL
A. Dissolution Study Bornite from Pinal, Arizona of about 80 pct purity used in a previous study 27 was carefully recleaned using a Franz magnetic separator. It was separated into monosized samples (size range - 8 0 to +325 mesh) and the average analysis was 63.35 pct Cu and 11.14 pct Fe, very close to the theoretical values of 63.33 pct Cu and 11.12 pct Fe. Mineralogical and X-ray analysis indicated high purity but showed traces of chalcopyrite, chalcocite, and quartz. The bornite purity after recleaning was estimated minerallogically as 96 pct. The leaching study was conducted in an apparatus previously described 27 consisting of a one-liter glass reactor with baffles, into which 500 ml of solution was admitted and heated to equilibrium temperature ( + 0.1 ~ and then half-gram bornite samples were admitted to initiate copper dissolution. Aliquot portions (3 ml) were withdrawn at appropriate time intervals for copper analysis using an atomic absorp
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