Kinetic study of copper leaching from chalcopyrite concentrate in alkaline glycine solution

Recently, glycine, one of the simplest amino acids, has been emerging as an efficient and environmental-friendly lixiviant for copper leaching. In the present study, an alkaline glycine–peroxide lixiviant system was used to leach copper from chalcopyrite concentrate by a suite of kinetic studies under different conditions. The particle size of the concentrate was P80 40 μm. Glycine concentration was varied from 0.5 to 3.0 M (glycine to copper molar ratio of 1.1 to 6.6:1) and the pH was maintained at 11 during the experiment. The copper extraction within 96 h was observed from 13 to 14% with glycine concentrations from 0.5 to 2 M, while the copper extraction decreased at 3 M of glycine. By reconstituting the glycine concentration during the leach test and adding hydrogen peroxide periodically, the copper extraction with 1 M glycine at 96 h increased from 14 to 21%, respectively. By changing the glycine and hydrogen peroxide solution every 24 h, 42% of copper extraction was achieved within 168 h. With increasing temperature, copper extraction decreased, while iron dissolution increased. Copper sulfide and copper sulfate precipitates were found in the leaching liquor at 22 °C test. Poorly crystalline copper-iron sulfate phase was observed in the leaching liquor at 35 and 45 °C. This precipitation is believed to be one of the factors to decrease the copper recovery from chalcopyrite.