Reactivity of Fe^III oxyhydroxides with Fe^II in batch and dynamic flow systems

Ferrihydrite is a poorly crystallized mineral and one of the most abundant iron minerals found in soils and sediments. The mineralogical transformation of ferrihydrite into Fe^II bearing minerals represents a potential way to improve the soil self-remediation capacity. Indeed, reduction by Fe^II may be a significant abiotic pathway in the natural attenuation of environmental contaminants including organic and inorganic pollutants. The aim of this laboratory study was to investigate the Fe^II induced mineralogical transformations of three matrices: ferrihydrite, ferrihydrite-rich sand and a pristine soil under static batch and flow through conditions. Since sorbed or structural Fe^II is more reactive than minerals bearing only Fe^III to promote the remediation of various soil pollutants, generation of Fe^II bearing minerals in soil-packed columns was optimized. The starting and resulting solids were characterized by X-ray diffraction (XRD), Mössbauer spectrometry, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM).