BACTERIAL LEACHING KINETICS FOR COPPER DISSOLUTION FROM A LOW-GRADE INDIAN CHALCOPYRITE ORE

摘要

Bio-leaching of copper (0.3%) from a low grade Indian chalcopyrite ore of Malanjkhand copper mines using a native mesophilic isolate, Acidithiobacillus ferrooxidans (A.femoxidans) is reported. A bio-recovery of 72% Cu was recorded in the presence of the enriched culture of native isolate, which increased to 75% with the adapted culture in 35 days at 35°C and pH 2,0 with <50|im particles. The kinetic data showed best fit to the diffusion controlled shrinking core model exhibiting linear plots for [1- 2/3X- (1-X)~(2/3)] vs time (X - fraction leached). The role of bacteria appeared to convert ferrous ion to the ferric state which oxidised chalcopyrite to dissolve copper maintaining a high redox potential. The value of activation energy (E_a) was calculated to be 96 and 108kJ/mol with the pure isolate and the ore adapted isolate respectively in the temperature range 25-35°C. The mechanism of leaching was corroborated by XRD phase identification and SEM studies of the leach residue.