Copper Recovery from Copper Sulfide Ore by Combined Method of Collectorless Flotation and Additive Roasting Followed by Acid Leaching

Copper sulfide ores often contain significant amounts of silica and sulfur-bearing gangue minerals, complicating flotation efficiency. However, these challenges can be mitigated through collectorless flotation, which exploits the natural floatability of chalcopyrite and the hydrophilicity of silica minerals. Pyrite, the main sulfur gangue mineral, is also depressed under these conditions, improving concentrate quality by reducing the sulfur and iron content. Air exposure and pulp pre-aeration techniques can enhance chalcopyrite floatability, resulting in high recovery and grade. However, further processing of chalcopyrite concentrate using direct leaching remains challenging due to sulfur passivating layers. To overcome this, additive roasting is used as a pretreatment to improve the leachability of chalcopyrite. This study explored a combined collectorless flotation and additive roasting-leaching method using copper sulfide ore with chalcopyrite, quartz, and pyrite as the main minerals. Collectorless flotation achieved 94.5% recovery and a concentrate of 7.12% Cu from an initial 0.94%. Roasting this concentrate with additives like KCl and NaOH at 600 °C for 1 h, followed by leaching in 0.1 M H2SO4 at 25 °C with a hydrogen peroxide (H2O2) addition, resulted in copper dissolutions of 97% and 96.5%, respectively, with low iron dissolution. The proposed process achieved an overall copper recovery of 92%, demonstrating the effectiveness of combining collectorless flotation with additive roasting and atmospheric leaching.