Contaminant reduction by iron oxide nanoparticles: Environmental variables and evolving reactivity

Abstract

Iron oxide nanoparticles are a promising resource for solving some of today’s most pressing global challenges in the developed and developing world, including the removal of toxins from drinking water resources, treatment of mining wastes, and remediation of groundwater contaminated by industrial activity. There is still much to be understood, however, about the reactivity of iron oxide nanoparticles in actual groundwater systems, where mineralogy and solution conditions are complex and variable over time. In this thesis, iron oxide nanoparticle reactivity was measured as a function of environmental variables, including pH, ionic strength, and the presence of organic matter or secondary mineral phases. The chosen variables simulate severe and impacted environments, such as pesticide-polluted groundwater and acid mine drainage. Additionally, kinetic studies paired with complementary solid-state characterization were used to elucidate evolving reactivity (changes in reactivity and iron oxide properties over time) as a function of environmental variables. This interdisciplinary research incorporated analytical quantification, diffraction, magnetism, microscopy, statistical analyses, cryogenic microscopy, and fluorescence spectroscopy. The overall result of this thesis demonstrated that the reactivity of iron oxide nanoparticles towards contaminants in aqueous systems is dynamic with respect to environmental variables and reaction extent. By increasing our understanding of how iron oxide nanoparticles will react in the subsurface, predictions of efficiency and expected outcome of environmental remediation will improve.