The characteristics and kinetics of redox transformation of a redox mediator, anthraquinone-2-sulfonate (AQS), during microbial goethite reduction by Shewanella decolorationis S12, a dissimilatory iron reduction bacterium (DIRB), were investigated to provide insights into "redox mediator-iron oxide" interaction in the presence of DIRB. Two pre-incubation reaction systems of the "strain S12- goe...

Little information is available concerning cosorbing oxyanion and metal contaminants in the environment, yet in most metal-contaminated areas, cocontamination by arsenate [AsO4, As(V)] is common. This study investigated the cosorption of As(V) and Zn on goethite at pH 4 and 7 as a function of final solution concentration. Complimentary extended X-ray absorption fine structure (EXAFS) spectrosco...

Oxide surface coatings are ubiquitous in the environment, but their effect on the intrinsic metal uptake mechanism by the underlying mineral surface is poorly understood. In this study, the zinc (Zn) sorption complexes formed at the kaolinite, goethite, and goethite-coated kaolinite surfaces, were systematically studied as a function of pH, aging time, surface loading, and the extent of goethit...

To investigate the influence of carbonate on the formation of goethite and lepidocrocite, ~200 samples were synthesized by oxidizing FeC12 solutions with air/CO2 gas mixtures at ambient temperature and pH 6 and 7. The proportion of lepidocrocite in the lepidocrocite/goethite mixtures (Lp/(Lp+ GO) decreased from 100 to 0% with increasing [HCO~] in solution and with decreasing average oxidation r...

The kinetics of dissimilatory reduction of goethite (alpha-FeOOH) was studied in batch cultures of a groundwater bacterium, Shewanella putrefaciens, strain CN32 in pH 7 bicarbonate buffer. The rate and extent of goethite reduction were measured as a function of electron acceptor (goethite) and donor (lactate) concentrations. Increasing goethite concentrations increased both the rate and extent ...

This study investigated the partitioning of uranyl within a quaternary system made up of uranyl, citrate, goethite, and the bacterium Pseudomonas fluorescens. In the absence of cells, uranyl was sorbed to goethite as a complex involving surface groups and/or citrate. Measurements of the evolution of CO2 indicated that the addition of bacterial cells lead to the gradual biodegradation of citrate...

[1] The discovery of sulfate-rich layered deposits with hematite spherules at the landing site of the Opportunity rover is consistent with mineral deposition in an aqueous environment. We evaluate conditions responsible for the formation of a jarosite-goethite-gypsum assemblage with speciation calculations. The results show that the assemblage could have precipitated from acidic solutions forme...

Abstraet~Storage of ferrihydrite in aqueous suspensions at 24~ and pHs between 2.5 and 12 for as long as three years resulted in the formation of goethite and hematite. The proportions and crystallinity of these products varied widely with the pH. Maximum hematite was formed between pH 7 and 8, and maximum goethite at pH 4 and at pH 12. The crystallinity of both products, as indicated by X-ray ...

This paper reports experimental results on the low-temperature (<100 oC) 18O and  2H fractionation of goethite (hematite)-water in a closed system. Both goethite (-FeOOH) and hematite (-Fe2O3) exhibited closer fractionation factor values but the Hematite-Water value is slightly higher (~0.9932) than the Goethite-Water (~0.9924) for the 18O isotope. The average fractionation factor (1000ln...

We used a combination of in situ attenuated total reflectance Fourier transform infrared (ATRFTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy to conduct molecular scale studies on Pb(II)-sulfate interactions at the solid-water interface of goethite at pH 4.5, 5.0, and 6.0. Both the ATR-FTIR studies (probing sorbed SO4 in a flow cell setup as a function of the Pb concen...