An investigation into bacterial cell, ferrous iron, pH and E h interactions during thermophilic leaching of copper concentrates

Abstract

The release of ferrous iron into solution during the dissolution of copper concentrates with thermophile Sulfolobus BC65 was noted. The concentration of ferrous iron released and its final disappearance was controlled by the pH maintained during batch leaching. The effect of additions of biomass appeared to depend on the previous growth history of the cells but never resulted in the reduced release of ferrous iron nor an increase in the rate of its oxidation. Neither the control of pH nor the additions of biomass had any effect on the pulp potentials observed. The appearance of ferrous iron, relative to copper release, varied with the mineralogy of the concentrates used. Tests using a copper/zinc concentrate gave evidence of preferential release of the zinc due to galvanic interaction at high temperature. The release of ferrous iron into solution was largely absent during leaching by mesophilic cultures. The onset of leaching was itself controlled by the concentration of ferrous iron initially in solution.