The effect of thermal pre-treatment on the dissolution of chalcopyrite (CuFeS2) in sulfuric acid media

Chalcopyrite ore was roasted at 200, 550 and 800 °C in reducing (5%H2/95%Ar) and inert (N2) atmospheres to examine the effects of the thermal pre-treatment on the phase mineralogy and on subsequent copper extraction using sulfuric acid media. No mineralogical changes occurred in the pre-leached samples heated to 200 °C under both inert and reducing conditions while at 550 °C partial decomposition of chalcopyrite resulted forming bornite and metal-rich derivatives talnakhite and mooihoekite. Further heating to 800 °C saw differences in chalcopyrite decomposition according to the atmosphere. In the inert atmosphere chalcopyrite decomposed to the metal-rich derivatives and minor bornite and geerite while in the reduced atmosphere copper metal, bornite, troilite, cubanite and chalcocite formed. Leaching at 50 °C of the chalcopyrite pre-treated in an inert atmosphere saw a slight increase in %Cu extraction with increasing temperature of treatment. A maximum copper extraction of 16%Cu was measured in the sample treated at 800 °C. Leaching of the chalcopyrite pre-treated in a reduced atmosphere led to modest increases in copper extraction between the 200 °C and 550 °C samples with 21%Cu and 24%Cu leached. Treatment at 800 °C resulted in a significant increase reaching 78%Cu extraction.