The study of copper leaching from conichalcite and chalcopyrite using alternative lixiviants

This project investigated alternative lixiviants for leaching copper from chalcopyrite and conichalcite, two highly refractory Cu ore minerals. Chalcopyrite (CuFeS₂) is the most abundant of the copper sulfide minerals; conichalcite (CaCuAsO₄OH) is less well known but contributes to supergene Cu inventory in high-As deposits. Neither leaches well in sulfuric acid. Sulfurous acid, glycine, methanesulfonic acid (MSA), and thiourea (for conichalcite leaching test) were tested as lixiviants for chalcopyrite- and conichalcite-bearing ores with ferric sulfate or hydrogen peroxide as oxidant. The highest Cu extraction from chalcopyrite was obtained by MSA (47% Cu recovery in 30 g/L of MSA with 5 g/L Fe³⁺ at 75 °C within 96 h; nearly 100% Cu extraction in 30 g/L MSA with 3% hydrogen peroxide at 75 °C within 72 h). Glycine recovered 20.7% of copper from chalcopyrite at room temperature within 96 h. All these compare favorably to the results of sulfuric acid leaching of chalcopyrite (1.5% recovery at 96 h). Conichalcite proved less refractory to sulfuric acid (46–71% extraction in 10 g/L H₂SO₄ with 3 g/L Fe³⁺ in 24 h) and leached almost as well in MSA (45–67% extraction in 20 g/L MSA with 3 g/L Fe³⁺ in 24 h), but glycine, thiourea, and sulfurous acid did not effectively leach conichalcite.