Inducing magnetite formation by microbial Fe(II) oxidation in the presence of mineral nucleation sites: Evaluating a novel approach to heavy metal remediation in the environment.

• Applicant: Professor Dr. Andreas Kappler
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256797843

Biogenic magnetite (Fe3O4) nanoparticles are mixed Fe(II)/Fe(III) minerals produced in the environment by Fe(III)-reducing bacteria with small size (<50 nm), a highly reactive Fe(II) surface layer and an organic coating. All of these properties make biogenic magnetite suitable for potential remediation strategies. Fe(II)-oxidizing bacteria are not ordinarily found associated with the formation of magnetite, instead Fe(III) oxyhydroxides such as goethite (alpha-FeOOH) and ferrihydrite (simplified as Fe(OH)3) are more commonly produced. Recent work by our group has shown that the presence of small amounts of magnetite nanoparticles during microbial Fe(II) oxidation can act as nucleation sites and lead to the formation of additional magnetite. It is not known if this new magnetite consists of spontaneously created nuclei or larger particles growing from the added nucleation sites. To apply microbially derived biogenic magnetite for remediation purposes, the mechanism of magnetite formation and its reactivity need to be known. We therefore propose experiments with Fe(II)-oxidizing bacteria to study the impact of nucleation sites in detail, with a number of variables including specific surface area and concentration of nucleation sites chosen to observe changes in the rate of magnetite formation and in the final mineral phases produced. Additionally, we propose batch experiments to test the biogenic magnetite for remediation of the toxic metal(loid)s arsenic and chromium to effectively lock-in the ions into the magnetite with sediment from the hyporheic zone of a river. This will be aimed towards developing strategies for remediation of contaminated land and water that pose serious health risks to millions of people around the world.

• DFG Programme: Research Grants
• Participating Person: Dr. James Byrne