Ferrous Ion oxidation monitoring by using magnetic resonance imaging for bio-oxidation laboratory testing

Abstract

A non-invasive, non-destructive monitoring approach using three-dimensional (3D) Magnetic Resonance Imaging (MRI) is proposed to study the iron oxidation process driven by Ferrooxidans’ bacterial activity. This activity is related to the oxidation of Fe2+ into Fe3+. Fe3+ ion has paramagnetic properties that could be used to visualize its presence using MRI. A novel MRI methodology has been implemented to visualize Fe3+ in solution with the aim to be used as a marker of iron oxidizer bacteria activity. A proof of concept test has been performed with bacteria in solution and in two solids media: an inert vegetal material (luffa) and solid particles, both dipped in acid solutions. The samples were scanned using a clinical 1.5 T MRI scan at several time points to test the capabilities of detecting different Fe3+ concentrations in the solution in time, while Ferrous Ion oxidation is driven by Ferrroxidans. The measurements were contrasted with titration methods to account for Ferrous Ion consumption during the process. The result reveals that a characteristic parameter obtained with MRI imaging, known as R1 relaxivity time measured in Hertz, correlates with Fe2+ oxidation (increment in Fe3+ concentration). 3D images of the distribution of Fe3+ production in the samples were acquired. Results are promising and open opportunities to continue complementary laboratory research at the network porous level to capture the spatial 3D distribution of Ferric Ions as distributed inside the porous network during a bio-reaction test.