Use of Glycine as an Alternative Lixiviant to Leach Copper from Chalcopyrite

"Many alternative leaching systems including bacterial leaching have been introduced to avoid passivation on the surface of chalcopyrite and to increase the leaching efficiency of copper from chalcopyrite. Recently, glycine, one of the simplest amino acids, has been emerging as an efficient and environmental-friendly lixiviant to recover copper. In the present study, an alkaline glycine–peroxide lixiviant system was used to leach copper from chalcopyrite concentrate and the leaching mechanisms were also investigated by a suite of kinetic studies under different conditions. The chalcopyrite concentrate contains 28.8% copper with 30.8% sulfide sulfur. The effect of concentration of glycine and hydrogen peroxide of the leaching solution was investigated. Glycine concentration was varied from 0.5 to 1.0 M and the hydrogen peroxide concentration was changed between 3 to 5%. Leaching time and pulp density were also varied. Hydrogen peroxide is an oxidant of the system and the leaching efficiency with periodic additions of the peroxide was also studied. A mineralogical study was performed using XRD and SEM. To investigate the surface of the residue materials, XPS was used to see if any passivating layer was formed during the leaching. Detailed results from mineralogical, chemical, and metallurgical studies will be presented and discussed.INTRODUCTION The greatest global resource of copper is low-grade chalcopyrite and heap bioleaching may be the only economic option for its processing. However, formation of a passivating layer on the surface of chalcopyrite slows down the oxidation reaction and reduces the efficiency of the process."