Optimization of copper recovery from oxide-sulfide ores through gravity separation and flotation techniques

Copper oxide ores with high clay content and fine particle size distribution pose major challenges for conventional flotation. In this study, a low-grade copper ore (0.5% Cu) obtained from drill core samples was investigated. Through a combination of mineralogical analyses, including X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM), the mineral composition and degree of copper liberation were identified. The ore is characterized by mixed chalcopyrite malachite mineralization, significant amounts of clay minerals (kaolinite and smectite), and a fine liberation size (d80 = 74 μm). the analysis revealed complex associations between copper minerals, iron oxides, and clay-rich gangue, which negatively affect sulfidation flotation performance. To overcome these constraints, a combined gravity separation–sulfidation flotation flowsheet was developed. The flotation process was optimized by adjusting parameters such as pH, collector concentration, sulfidation type, and sulfidation concentration. Sodium hydrosulfide (NaHS) was found to be the most effective sulfidation agent, significantly improving copper recovery. Optimal flotation conditions were determined to be a pH of 9.5, a combined collector concentration of 500 g/t, and 500 g/t of NaHS, yielding a copper grade of 22.5% and recovery of 94.25%. A two-stage process combining gravity separation and flotation achieved a final concentrate with a copper grade of 27.1% and a recovery of 69.94%. The findings provide valuable insights for improving the recovery of copper from complex oxide-sulfide ores, with implications for the future of copper extraction and processing.