Effectiveness of iron reducing bacteria for the removal of iron from bauxite ores

Current study investigates the possibility of obtaining the removal of iron from bauxite ores, by exploiting the metabolism of iron reducing microorganisms. The experiments were carried out using the microorganism Desulfuromonas palmitatis. The effectiveness of the treatment was evaluated on six different bauxite samples, containing the alumina oxide in the form of diaspore or boehmite. The Fe2O3 content of the samples varied between 16.3% and 22.3% and occurred mainly in the form of goethite or hematite, with one sample containing also chamosite. For comparison reasons the same treatment was also applied on three samples of synthetic Fe(III)-oxides, namely ferrihydrite, goethite and hematite. The removal of iron from the six bauxite samples was found to vary between 7% and 29% and the highest extraction corresponded to the sample containing the Fe(II) rich compound, chamosite. The bioavailability of Fe in the three synthetic oxides was highly dependant on their crystallinity. The amorphous ferrihydrite was almost completely dissolved, up to 95%, whereas dissolution of crystalline goethite and hematite did not exceed 9% and 1.2% respectively.