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

This study presents the results of oxidative leaching of chalcopyrite (CuFeS₂) and pyrite (FeS₂) in a sulfuric acid medium at low temperature in the presence of copper (Cu²⁺) and iron (Fe³⁺) 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/dm³), Fe³⁺ ions (2–10 g/dm³), Cu²⁺ ions (1–3 g/dm³), 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: O₂ partial pressure of 0.25 MPa, initial concentrations of H₂SO₄ – 50 g/dm³, Cu²⁺ – 1 g/dm³, Fe³⁺ – 2.5 g/dm³, and leaching time – 240 min. The maximum degree of pyrite oxidation (56 %) was obtained at an O₂ partial pressure of 0.75 MPa, initial concentrations of H₂SO₄ – 50 g/dm³, Cu²⁺ – 2 g/dm³, and Fe³⁺ – 10 g/dm³. The results showed that leaching time and oxygen pressure have the greatest effect on chalcopyrite and pyrite decomposition (p < 0.05). The interaction between Fe³⁺ and Cu²⁺ ions was also established: excess Fe³⁺ (>10 g/dm³) leads to hydrolysis and decreases chalcopyrite leaching efficiency, whereas Cu²⁺ promotes partial formation of secondary copper sulfides. Regression equations (R² = 0.98 for chalcopyrite and R² = 0.96 for pyrite) were derived, providing an adequate description of the process.

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