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 FeII 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).