XPS study of MnO2 minerals treated by bioleaching

XPS has been used to follow the change of the ore surface composition during bioleaching with a mixed culture of microorganisms. In the original sample, the presence of MnO2 together with silica and alumina is observed. During bioleaching, Mn(IV) is progressively reduced to Mn(II) and signals due to the presence of the microogranisms appear in the C 1s and N 1s spectra. In the residual sample, a considerable amount of Mn associated with the cells of the microorganisms or reprecipitated in the form of the Mn(OH)2 is present on the surface of the ore. This Mn species can be removed completely by treatment with a dilute solution of HCl.