Optimization of low-temperature sulfuric acid leaching of chalcopyrite and pyrite

This study presents the results of oxidative leaching of chalcopyrite (CuFeS 2 ) and pyrite (FeS 2 ) in a sulfuric acid medium at low temperature in the presence of copper (Cu 2+ ) and iron (Fe 3+ ) ions. Using orthogonal experimental design, the optimal conditions were identified to maximize sulfide matrix decomposition and valuable metal recovery. Experiments were conducted at a constant temperature of 100 °C. The parameters investigated included partial oxygen pressure (0.2–0.75 MPa), concentrations of sulfuric acid (10–50 g/dm 3 ), Fe 3+ ions (2–10 g/dm 3 ), Cu 2+ ions (1–3 g/dm 3 ), and leaching time (60–240 min). The composition of the feed minerals and leach products was analyzed by X -ray fluorescence (XRF) analysis, X -ray diffraction (XRD) analysis, and atomic absorption spectrometry (AAS). Maximum copper recovery from chalcopyrite (55 %) was achieved under the following conditions: O 2 partial pressure of 0.25 MPa, initial concentrations of H 2 SO 4 – 50 g/dm 3 , Cu 2+ – 1 g/dm 3 , Fe 3+ – 2.5 g/dm 3 , and leaching time – 240 min. The maximum degree of pyrite oxidation (56 %) was obtained at an O 2 partial pressure of 0.75 MPa, initial concentrations of H 2 SO 4 – 50 g/dm 3 , Cu 2+ – 2 g/dm 3 , and Fe 3+ – 10 g/dm 3 . The results showed that leaching time and oxygen pressure have the greatest effect on chalcopyrite and pyrite decomposition ( p < 0.05). The interaction between Fe 3+ and Cu 2+ ions was also established: excess Fe 3+ (>10 g/dm 3 ) leads to hydrolysis and decreases chalcopyrite leaching efficiency, whereas Cu 2+ promotes partial formation of secondary copper sulfides. Regression equations ( R 2 = 0.98 for chalcopyrite and R 2 = 0.96 for pyrite) were derived, providing an adequate description of the process.