A kinetic study of the leaching of chalcopyrite with Sulfolobus metallicus

Batch chalcopyrite leaching experiments have been performed in the presence and absence of Sulfolobus metallicus. The effect of varying the initial co ncentration of ferric ions and the effect of the presence of medium in the leaching solution was investigated. The range of concentrations of ferric i ons investigated in the absence of microorganisms was between 0.001 and 0.5 0 M. Leaching experiments with Sulfolobus metallicus were performed over th e range of initial concentrations of ferric ions of 0.01 to 0.50 M. The rate of leaching of chalcopyrite was found to increase as the initial c oncentration of ferric ions was increased over the range of 0.001 to 0.05 M . However, the rate decreases with increasing concentration of ferric ions in the range of 0.05 to 0.50 M. This is due to the precipitation of basic f erric sulphates on the surface of the chalcopyrite particles at higher conc entrations of ferric ions, which resulted in an increasing diffusional cons traint. The maximum initial leaching rate of chalcopyrite in the absence of Sulfolo bus metallicus was 1.76 mg/L.hr and the order of the surface reaction with respect to the concentration of ferric ions was found to be 0.34. The maxim um conversion of approximately 4 percent was achieved after approximately 4 5 hours. The batch leach experiments performed in the presence of Sulfolobus metalli cus showed similar trends as experiments performed in the absence of organi sms. Complete conversion of the chalcopyrite was achieved after approximate ly 300 hours when an initial concentration of ferric ions of 0.05 M was use d. The maximum rate of chalcopyrite leaching attained at an initial ferric ion concentration of 0.05 M was 24.6 mg/L.hr. The calculated initial rates were similar to those for the leaching experiments in the absence of microo rganisms. The maximum initial rate of leaching of chalcopyrite was 2.30 mg/ L.hr in the presence of Sulfolobus metallicus with an initial concentration of ferric ions of 0.10 M. The calculated order of the reaction with respec t to the concentration of ferric ions was 0.21.