Enhanced leaching of copper from refractory oxidized copper ore by calcium fluoride: Behavior and mechanism

Abstract

The Luanshya area of Zambia is rich in copper oxide resources. However, copper mainly exists in biotite and phlogopite, which presents challenges for efficient extraction. To improve the leaching rate of copper from these ores, local hydrometallurgical plants use heating and stirring; however, the leaching rate is not high. To address the issue in this work, CaF2 was introduced as a leaching aid, and the effects of various parameters on leaching were systematically studied. The results revealed that when the dosage of CaF2 is 5wt% of raw ore mass, the dosage of sulfuric acid is 120 kg/t, the leaching temperature is 60 °C, and the leaching time is 200 min with a slurry concentration of 30wt%, the leaching rate of copper can reach 80.44%. Compared with regular heating stirring acid leaching, the copper leaching rate was found to increase by 8.76%, while the leaching temperature decreased by 5 °C and the leaching time shortened by 40 min. The results of the HSC Chemistry 6.0 thermodynamic calculations and mechanism analysis indicated that F can promote the fracture of Si–O and Al–O bonds in the crystal structure of biotite and phlogopite in sulfuric acid solution, enabling a direct reaction between the acid and copper. The proposed method can be applied not only to the treatment of cupriferous mica ores but also to the processing of other copper ores. This process is more efficient and cost-effective than the regular heating–stirring acid leaching process.