Kinetics of Ferric Leaching of Copper Sulfide Ores and its Dependence on the Mineralogical Associations of Copper Minerals with Gangue Species in the Ore

摘要

Leaching of copper minerals present in copper ores is dependent on the type of associations between copper minerals and gangue species, as these can control the access of the leaching solution to the valuable metal. Understanding this dependence can help to define chemical conditions which optimize dissolution of copper minerals occluded in gangue species. This work reports the study the ferric leaching of a copper ore in which copper is present as covellite and chalcocite mainly associated to quartz and sericite. Pre-treatment of the ore with HF was used as a tool to alter the gangue composition of the ore and assess its influence on copper leaching. Leaching was conducted on small flooded ore beds with solutions containing 10 g/L H_2SO_4 and 3 g/L Fe~(3+). Monitoring of leaching progress was conducted through analysis of Cu, Fe, Si, Al, K and Mg in solution. Chemical and physical transformations in the ore were characterized by XRD and SEM. Results showed that ore pre-treatment with HF concentrations of 0,2 M and 2 M resulted in copper recoveries of 47 % and 60 %, respectively. Without this pre-treatment, only 44 % copper dissolution was obtained. The dissolution percentage of gangue elements with pre-treatment was: 18 % Si and 45 % Al, whereas in the absence of pre-treatment they reached values close to 0,1 %. Analysis of untreated and leached particles with SEM showed physical and chemical transformations of gangue species caused by pre-treatment with HF prior to leaching. Results showed that partial dissolution of the gangue species compounds could help to gain access of the leach solution to copper sulphide ores occluded within the ore particle. This selective acid attack of gangue species could provide a new porosity that increase the kinetics of copper dissolution presumably due to liberation of copper sulphide particles encapsulated in the gangue.