Selective impurity removal and Cu upgrading of copper flotation concentrate by a spontaneously oxidative H2SO4 leaching process

The gradual decrease of global copper resources is among the most urgent challenges for the mining industry. Sustainable utilization of copper sulphide flotation concentrate from iron oxide copper gold (IOCG) deposits is often constrained by the impurity elements (e.g. U, Th and F) and high levels of gangue minerals (e.g. iron oxide/hematite, U-bearing minerals and fluorite). Herein, a spontaneous oxidative H₂SO₄ leach process (<100 °C) is proposed to selectively remove the penalty elements and upgrade copper sulphide concentrate from IOCG deposits. During H₂SO₄ leach, 87–92% of F element in the fluorite mineral was extracted and the dissolution of iron oxide/hematite minerals were enhanced by the elevated temperature at 60–90 °C. The released Fe³⁺ ions from iron oxide/hematite minerals worked as the spontaneous oxidant for dissolving U-bearing minerals and upgrading copper minerals. The results reveal that the H₂SO₄ leach in presence of dissolved Fe³⁺ effectively removed 88–97% U and 89–90% Th from U-bearing minerals. Meanwhile, the elevated temperature at 60–90 °C plays a critical role in the phase transformation of bornite to covellite in the presence of Fe³⁺. Another phase transformation of chalcopyrite to bornite was also significant at the higher temperature of 90 °C through the non-oxidative dissolution mechanism. During the spontaneous oxidative H₂SO₄ leach, the dissolution of gangue minerals and phase transformations of copper minerals successfully upgraded copper concentrate from 41.1 to 50.5 wt% at 90 °C, while copper dissolution was maintained at less than 7.7%.