BACKGROUND Goethite is a common and reactive mineral in the environment. The transport of contaminants and anaerobic respiration of microbes are significantly affected by adsorption and reduction reactions involving goethite. An understanding of the mineral-water interface of goethite is critical for determining the molecular-scale mechanisms of adsorption and reduction reactions. In this study...

Many physical and chemical processes control the extent of Fe(III) oxyhydroxide reduction by dissimilatory Fe(III)-reducing bacteria. The surface precipitation of secondary Fe minerals on Fe(III) oxyhydroxides limits the extent of microbial Fe(III) reduction, but this phenomenon has not yet been observed in nature. This paper reports the observation of secondary Fe-mineral (goethite) encrustati...

Uranium retention processes (adsorption, precipitation, and incorporation into host minerals) exert strong controls on U mobility in the environment, and understanding U retention is therefore crucial for predicting the migration of U within surface and groundwater. Uranium can be incorporated into Fe (hydr)oxides during Fe(ii)-induced transformation of ferrihydrite to goethite. However, ferrih...

Sorption of dissolved strontium on kaolinite, amorphous silica, and goethite was studied as a function of pH, aqueous strontium concentration, the presence or absence of atmospheric CO(2) or dissolved phosphate, and aging over a 57-day period. Selected sorption samples ([Sr(aq)](i) approximately 0.5-1x10(-3) m) were examined with synchrotron X-ray absorption spectroscopy (XAS) at low (13-23 K) ...

We used X-ray diffraction (XRD), scanning force microscopy (SFM), transmission electron microscopy (TEM), and color to investigate the effect of phosphate on the crystallization rate, nature, and morphology of iron oxides prepared from ferrihydrite in the laboratory. Synthesis was performed at two temperatures (323 and 373 K) and two pH values (9 and 12) from ferric nitrate, for P/Fe atomic rat...

Iron (hydr)oxides not only serve as potent sorbents and repositories for nutrients and contaminants but also provide a terminal electron acceptor for microbial respiration. The microbial reduction of Fe (hydr)oxides and the subsequent secondary solid-phase transformations will, therefore, have a profound influence on the biogeochemical cycling of Fe as well as associated metals. Here we elucida...

Force microscopy has been used to quantitatively measure the infinitesimal forces that characterize interactions between Shewanella oneidensis (a dissimilatory metal-reducing bacterium) and goethite (alpha-FeOOH), both commonly found in Earth near-surface environments. Force measurements with subnanonewton resolution were made in real time with living cells under aerobic and anaerobic solutions...

Abstract Goethite/hematite ratios in soils are widely used to reconstruct past climatic changes, but their accurate measurements have remained challenging due the matrix effect. Here we present a new method for measuring soil goethite/hematite by characterizing band position of electron pair transition (EPT) based on diffuse reflectance spectra processed continuum removal. We introduce “half‐ba...

We demonstrate the suitability of polarization microscopy to study the recently discovered (parallel) nematic-(perpendicular) nematic phase separation. This novel type of phase transition is induced by applying an external magnetic field to a nematic liquid crystal of boardlike colloidal goethite and is due to an interplay between the intrinsic magnetic properties of goethite and the collective...

Chemodenitrification-the abiotic (chemical) reduction of nitrite (NO2?) by iron (II)-plays an important role in nitrogen cycling due part to this process serving as a source nitrous oxide (N2O). Questions remain about the fate NO2? presence mineral surfaces formed during chemodenitrification, such iron(III) (hydr) oxides, particularly relative dissolved iron(II). In study, stirred-batch kinetic...