Effects of Particle Sizes on Reductive Dissolution of Iron Oxides from IImenite Ores by Shewanella oneidensis MR-1

Ilmenite is the most common reserve of titanium in nature. Extracting titanium from ilmenite ore (FeTi03) by using the conventional methods require usage of hash chemicals and excessive heating, which are not environmentally friendly. Iron oxide is the most common impurities contained in Ilmenite ores. Separating iron impurities from ilmenite ore remains as a challenging part in titanium extraction proses. In this study, we explored the application of iron-reducing bacterium, Shewanella oneidensis MR-1 to leach out iron from ilmenite ore. S. oneidensis MR-1 is known for its capability to reduce various metal oxides during anaerobic respiration. Reduction of iron oxides contained in ilmenite ore by respiration activity of S. oneidensis MR-1 transform insoluble iron (III) to soluble iron (I1), which can leach out from the ilmenite ore. Different particle sizes of raw ilmenite were incubated with S. oneidensis MR-1 under anaerobic conditions for 30 days. Reductive dissolution of iron (I) from ilmenite ore were determine by monitoring iron (I) accumulation in the growth media by Ferrozine method every 3-4 days. Transformations of ilmenite ore after 30 days of S. oneidensis MR-1 treatment were further analysis by Scanning Electron Microscope/Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and X-Ray diffraction (XRD) analyses.
Incubation of S.oneidensis MR-1 with 32mm of ilmenite ore showed the highest iron(III) reductive dissolution activity, with 0.754mM, of iron(II) was leached out from ilmenite ore after 30 days. The XRD and SEM-EDS analyses indicated chemical composition and structural changes in the ilmenite incubated with S. oneidensis MR-1. The SEM demonstrated pore like corroded spots occurred after the ilmenite ores were treated with S. oneidensis MR-1, meanwhile XRD analysis produced results indicating the presence of Ti mineral crystals such as Anatase, Rutile and Brookite. The findings of this study show that reductive dissolution of iron (III) by S. oneidensis MR-1 is a promising environmentally friendly an‹ low-cost bioleaching strategy in removing iron impurity from ilmenite.