This paper presents and validates a new paradigm for modeling complex biogeochemical systems using a diagonalized reaction-based approach. The bioreduction kinetics of hematite ( -Fe2O3) by the dissimilatory metal-reducing bacterium (DMRB) Shewanella putrefaciens strain CN32 in the presence of the soluble electron shuttling compound anthraquinone-2,6-disulfonate (AQDS) is used for presentation/...

A series of mixed iron and titanium oxide coprecipitates ranging in composition between 0 < Ti/Ti + Fe < 1 was synthesized and aged under varying conditions of pH, temperature and time in order to establish a working model for pedogenic titanium and titano-ferric oxides. X-ray powder diffraction (XRD), selective chemical dissolution, magnetic susceptibility, charge distribution and electron opt...

*Correspondence: Ondra Sracek, Department of Geology, Faculty of Science, Palacký University in Olomouc, 17. Listopadu 1192/12, 771 46 Olomouc, Czech Republic e-mail: [email protected] Mine tailings in African countries Zambia and Namibia have been investigated with an objective to determine the role of secondary hematite in immobilization of contaminants. Two sites, Chambishi and Mindolo, are ...

Arsenic is present at relatively high concentrations in surface water and groundwater as a result of both natural impacts and anthropogenic discharge, which requires proper treatment before use. The present study describes As adsorption on a siderite-hematite filter as a function of activating condition, empty bed contact time, and As species. Hydrogen peroxide activating increased As adsorptio...

We examined the reduction of nitrobenzene by Shewanella putrefaciens CN32 in the presence of natural organic matter (NOM) and hematite. Bioreduction experiments were conducted with combinations and varied concentrations of nitrobenzene, soil humic acid, Georgetown NOM, hematite, and CN32. Abiotic experiments were conducted to quantify nitrobenzene reduction by biogenic Fe(II) and by bioreduced ...

Plutonium (Pu) adsorption to and desorption from mineral phases plays a key role in controlling the environmental mobility of Pu. Here we assess whether the adsorption behavior of Pu at concentrations used in typical laboratory studies (≥10(-10) [Pu] ≤ 10(-6) M) are representative of adsorption behavior at concentrations measured in natural subsurface waters (generally <10(-12) M). Pu(V) sorpti...

It has been discovered that magnetite ( Fe304 ) is rapidly oxidized to hematite (o<-Fe 0 ), upon illumination ( X<.310p1 ) in an 02-bear~ni atmosphere. A laboratory investigation has been carried out to determine the kinetics and mechanism of this rapid oxidation process. It has been found that the process consists of a series of constituent reactions which are common to most oxidation mechanis...

Introduction: Meridiani Planum was chosen as the landing site for the Mars Exploration Rover Opportunity partially based on Mars Global Surveyor Thermal Emission Spectrometer data indicating an abundance of hematite [1]. Hematite often forms through processes that involve water, so the site was a promising one to determine whether conditions on Mars were ever suitable for life [1,2]. Opportunit...

The sorption of uranyl onto hydrous ferric oxide (HFO) or hematite was measured by discontinuously titrating the suspensions with uranyl at pH 5.9, 6.8, and 7.8 under Pco2 = 10(-35)atm (sorption isotherms). Batch reactors were used with equilibration times up to 48 days. Sorption of 1 microM uranyl onto HFO was also measured versus pH (sorption edge). A diffuse double layer surface complexation...