AQUEOUS OXIDATION OF CHALCOPYRITE IN HYDROCHLORIC-ACID

The aqueous oxidation of chalcopyrite flotation concentrate is faster in HC1 than in H2SO4. Under certain conditions, FeCl2 formed during reaction undergoes oxidation and hydrolysis (or vice versa) yielding α-Fe2O3 or β-FeOOH depending on the initial acidity, O2 pressure, and temperature. A small fraction of sulfur oxidizes to soluble SO 4 2- and a part precipitates as Fe(OH)SO4. The precipitation of FeOOH is more enhanced in HC1 than in H2SO4 solution. Optimum leaching conditions are 110°C, 2010 kPaO2, 2 N HC1, molar ratio CuFeS2/HCl 0.8 to 0.9, and time of reaction 45 min. Under these conditions practically all the iron precipitates and the reaction can be described by the equations: CuFeS2 + 2 HCl + 5/4 O2 → CuCl2 + FeOOH + 1/2H2O + 2S and CuFeS2 + HC1 + O2 → CuCl + FeOOH + 2S. Copper ferrite, CuFe2O4, precipitates if the final pH of the leach solution is ≥2.2, while CuCl precipitates if the initial acidity is increased to 3 N HC1. © 1979 American Society for Metals and fhe Metallurgical Society of Aime.