Kinetics of the sulfidation of chalcopyrite with gaseous sulfur
- PDF / 516,544 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 10 Downloads / 235 Views
THE reaction of chalcopyrite with sulfur at moderate temperatures (350 ⬚C to 550 ⬚C) has been studied by several investigators[1–5] in order to transform the chalcopyrite into a material more reactive to leaching. The products of this thermal treatment were found to vary with the temperature, reaction time, and chalcopyrite-to-sulfur ratio. While the formation of pyrite was reported in all cases, the copperbearing sulfide was reported as covellite (CuS), idaite (Cu5FeS6), or bornite (Cu5FeS4). This discrepancy in the reported nature of the copper-bearing species was due to the different experimental conditions used in each case. Since these investigations were aimed principally to produce copper by leaching the treated chalcopyrite, more attention was paid to the leaching step than to the sulfidation step. In a systematic study of the sulfidation of chalcopyrite with elemental sulfur in the temperature range of 300 ⬚C to 500 ⬚C, as carried out by two of the present authors,[6] it was determined that chalcopyrite reacts with gaseous sulfur to produce, depending on the temperature, covellite or idaite as the copper-bearing compound and pyrite as the iron compound. Thus, the following reactions can be written for the sulfidation of chalcopyrite with gaseous sulfur: CuFeS2 ⫹ 1/2S2 (g) ⫽ CuS ⫹ FeS2
[1]
in the temperature range of 300 ⬚C to 400 ⬚C, and 5CuFeS2 ⫹ 2S2 ⫽ Cu5FeS6 ⫹ 4FeS2
[2]
for temperatures above 400 ⬚C. The reaction products can be leached with acidic solutions to dissolve copper and produce elemental sulfur, which can be extracted from the leached residues and recycled to the sulfidation of chalcopyrite. R. PADILLA, Associate Professor, E. OLIVARES, Student, and M.C. RUIZ, Professor, are with the Department of Metallurgical Engineering, University of Concepcio´n, Concepcio´n, Chile. Contact e-mail: rpadilla@ udec.cl H.Y. SOHN, Professor, is with the Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112-1183. Manuscript submitted December 14, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS B
In practice, even though both Reactions [1] and [2] produce relatively hard-to-leach pyrite, the desirable reaction for the selective leaching of copper is Reaction [1], because the copper-bearing sulfide does not contain iron; therefore, the leaching of the products in an acidic solution (i.e., the H2SO4-NaCl-O2 system) would yield a copper solution with little iron and a residue composed primarily of pyrite and elemental sulfur. Since Reaction [1] is the key reaction in the sulfidation of chalcopyrite, the study of the kinetics of this reaction was the main objective of this research. II. EXPERIMENTAL METHOD Chalcopyrite concentrate from the Andina Division of CODELCO (Andina, Chile) was used in this investigation. This material was a flotation concentrate, which was further treated with 0.5 M of sulfuric acid solution to assure that the chalcopyrite was an oxide-free material. The mineralogical analysis of the concentrate, with size fraction ⫺53 ⫹45 m, showed that the major consti
Data Loading...
