We measured the kinetics of U(VI) reduction by Shewanella oneidensisMR-1 under anaerobic conditions in the presence of variable concentrations of either EDTA or dissolved Ca. We measured both total dissolved U and U(VI) concentrations in solution as a function of time. In separate experiments, we also measured the extent of U(VI) adsorption onto S. oneidensis in order to quantify the thermodyna...

More than 50 uranyl minerals, phases containing U as the uranyl UO2 2+ cation, and hydroxide, carbonate, phosphate, and silicate anions, H2O, and alkali and alkaline earth cations, occur in nature and as corrosion products of spent nuclear fuel. Despite their importance and the need to understand their thermodynamics to predict uranium solubility, fate, and transport in the environment, reliabl...

The form of solid phase U after Fe(II) induced anaerobic remineralization of ferrihydrite in the presence of aqueous and absorbed U(VI) was investigated under both abiotic batch and biotic flow conditions. Experiments were conducted with synthetic ground waters containing 0.168 mM U(VI), 3.8 mM carbonate, and 3.0 mM Ca2+. In spite of the high solubility of U(VI) under these conditions, apprecia...

Nuclear weapons and fuel production have left many soils and sediments contaminated with toxic levels of uranium (U). Although previous short-term experiments on microbially mediated U(VI) reduction have supported the prospect of immobilizing the toxic metal through formation of insoluble U(IV) minerals, our longer-term (17 months) laboratory study showed that microbial reduction of U can be tr...

In connection with certain metabolism experiments now in progress in this Institute, the determination of the nitrogen present in the urine of a steer as ammonium compounds and ammonia has become of considerable importance. Recurring peculiarities in the results obtained in some earlier work involving ammonia determinations led to the belief that the chloroform used in the urine as a preservati...

The purpose of this study was to determine the kinetics of the dissolution of a uranium residue in ammonium carbonate media. The residue is generated in the production of medical isotopes. The effects of parameters, such as varying peroxide and carbonate concentrations, dissolution time as well as temperature on the extraction rate have been separately studied. Results indicate complete dissolu...