Probing the reactivity of bio-engineered magnetic magnetite nanoparticles with metals and metalloids
Final Report Abstract
The use of heavy metals and metalloids in various industries is leading to major global challenges such as access to clean water for drinking and agriculture. These challenges have the potential to increase in severity in decades to come as industrialization continues to grow. Alternative strategies are required to either remove pollutants from water supplies after they have entered, or prevent them from getting into the ecosystem. Adsorption remains one of the most effective, particularly when using iron minerals such as ferrihydrite of magnetite as an adsorbent. Magnetite is a mixed-valent, magnetic mineral which contains both Fe(II) and Fe(III) and can be produced through a number of different pathways. Microbial strategies to producing magnetite nanoparticles have the potential to produce highly magnetic particles with narrow size distributions corresponding to high surface to volume ratios in addition to high Fe(II) content. Furthermore, those magnetite particles are associated with reactive organic compounds and offer a cost effective, and environmentally benign solution which could offer a sustainable approach to toxic metal or metalloid remediation. In this project, we scaled up the development of chemically synthesized magnetite nanoparticles (WP1) and subjected the mineral to microbial reduction/oxidation to modify surface properties. The magnetite nanoparticles showed excellent sorption behavior to several metals including Cu and Cd. To overcome potential issues with contaminated nanoparticles becoming loose and eventually being transported into water sources, we coated quartz sand with magnetite nanoparticles (WP2). This material kept the magnetite tightly bound to the surface of the sand, but without significantly impacting its performance as an adsorbent material. This technique was used to develop biogenic and abiogenic magnetite nanoparticles to remove As, Mo, V, and Cr from solution. Based on the outcome of WP2, we prepared columns containing magnetite coated sand and developed a reactive transport model (WP3) outlining the reaction between magnetite nanoparticles and Cr(VI) in solution. Overall, this work demonstrates the remarkable capacity for magnetite to bind heavy metals, and suggests it could be used as a suitable adsorption material for treating drinking water.
Publications
- (2021) Chromium (VI) removal kinetics by magnetite-coated sand: Small-scale flow-through column experiments. Journal of Hazardous Materials. 415, 125648
Sorwat J., Mellage A., Maisch M., Kappler A., Cirpka O. A., Byrne J. M.
(See online at https://doi.org/10.1016/j.jhazmat.2021.125648)
