Surface catalysis of uranium(VI) reduction by iron(II)
TL;DR: In this article, the authors investigated the kinetic effect of specific adsorption interactions on the chemical reduction of uranyl (UVIO22+) by ferrous iron, and derived a rate law for surface-catalyzed U(VI) reduction by Fe(II), d[U(VI)] dt =−k[≡ Fe III OFe II OH 0 ][U( VI)] ads where the bimolecular rate constant k has a value of 399 ± 25 M−1 min−1 at 25°C.
About: This article is published in Geochimica et Cosmochimica Acta.The article was published on 1999-10-01. It has received 647 citations till now. The article focuses on the topics: Uranyl & Reaction rate constant.
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TL;DR: The sorption data indicate that, under most of the chemical conditions investigated in this study, reduction of As(V) in the presence of HFO or goethite would have only minor effects on or even decrease its mobility in the environment at near-neutral pH conditions.
Abstract: Arsenic derived from natural sources occurs in groundwater in many countries, affecting the health of millions of people. The combined effects of As(V) reduction and diagenesis of iron oxide minerals on arsenic mobility are investigated in this study by comparing As(V) and As(III) sorption onto amorphous iron oxide (HFO), goethite, and magnetite at varying solution compositions. Experimental data are modeled with a diffuse double layer surface complexation model, and the extracted model parameters are used to examine the consistency of our results with those previously reported. Sorption of As(V) onto HFO and goethite is more favorable than that of As(III) below pH 5−6, whereas, above pH 7−8, As(III) has a higher affinity for the solids. The pH at which As(V) and As(III) are equally sorbed depends on the solid-to-solution ratio and type and specific surface area of the minerals and is shifted to lower pH values in the presence of phosphate, which competes for sorption sites. The sorption data indicate tha...
2,115 citations
TL;DR: Recent advances in the understanding of biogeochemical redox processes are highlighted and their impact on contaminant fate and transport, including future research needs are highlighted.
Abstract: Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of biogeochemical redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms coupled to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe, Mn, C, P, N, S, Cr, Cu, Co, As, Sb, Se, Hg, Tc, a...
1,029 citations
TL;DR: Model calculations confirm that sorption of particularly carbonate at common soil and groundwater concentrations reduces the sorption capacity of arsenic on ferrihydrite significantly, a cause for the high concentrations of arsenic in groundwater in Bangladesh.
Abstract: Surface complexation models are commonly used to predict the mobility of trace metals in aquifers. For arsenic in groundwater, surface complexation models cannot be used because the database is incomplete. Both carbonate and ferrous iron are often present at a high concentration in groundwater and will influence the sorption of arsenic, but the surface complexation constants are absent in the database of Dzombak and Morel. This paper presents the surface complexation constants for carbonate and ferrous iron on ferrihydrite as derived for the double-layer model. For ferrous iron the constants were obtained from published data supplemented by new experiments to determine the sorption on the strong sites of ferrihydrite. For carbonate the constants were derived from experiments by Zachara et al., who employed relatively low concentrations of carbonate. The double-layer model, optimized for low concentrations, was tested against sorption experiments of carbonate on goethite at higher concentration by Villalobos and Leckie, and reasonable agreement was found. Sorption was also estimated using linear free energy relations (LFER), and results compared well with our derived constants. Model calculations confirm that sorption of particularly carbonate at common soil and groundwater concentrations reduces the sorption capacity of arsenic on ferrihydrite significantly. The displacing effect of carbonate on sorbed arsenate and arsenite has been overlooked in many studies. It may be an important cause for the high concentrations of arsenic in groundwater in Bangladesh. Sediments containing high amounts of sorbed arsenic are deposited in surface water with low carbonate concentrations. Subsequently the sediments become exposed to groundwater with a high dissolved carbonate content, and arsenic is mobilized by displacement from the sediment surface.
639 citations
638 citations
TL;DR: This is the first comprehensive microarray currently available for studying biogeochemical processes and functional activities of microbial communities important to human health, agriculture, energy, global climate change, ecosystem management, and environmental cleanup and restoration.
Abstract: Owing to their vast diversity and as-yet uncultivated status, detection, characterization and quantification of microorganisms in natural settings are very challenging, and linking microbial diversity to ecosystem processes and functions is even more difficult. Microarray-based genomic technology for detecting functional genes and processes has a great promise of overcoming such obstacles. Here, a novel comprehensive microarray, termed GeoChip, has been developed, containing 24 243 oligonucleotide (50 mer) probes and covering 410 000 genes in 4150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance, and organic contaminant degradation. The developed GeoChip was successfully used for tracking the dynamics of metal-reducing bacteria and associated communities for an in situ bioremediation study. This is the first comprehensive microarray currently available for studying biogeochemical processes and functional activities of microbial communities important to human health, agriculture, energy, global climate change, ecosystem management, and environmental cleanup and restoration. It is particularly useful for providing direct linkages of microbial genes/populations to ecosystem processes and functions.
576 citations
Cites background from "Surface catalysis of uranium(VI) re..."
..., 2006c) and/or indirect chemical mechanisms (Mohagheghi et al., 1985; Liger et al., 1999), we have focused on the analysis of the dynamics of FeRB and SRB....
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...…both direct enzymatic (Lovley et al., 1993a, b; Lovley, 1995; Truex et al., 1996; Tebo and Obraztsova, 1998; Petrie et al., 2003; Wu et al., 2006c) and/or indirect chemical mechanisms (Mohagheghi et al., 1985; Liger et al., 1999), we have focused on the analysis of the dynamics of FeRB and SRB....
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References
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Book•
09 Oct 2011
TL;DR: Erratum to: Aminocarboxylic Acids to: Iminodiacetic Acid Derivatives to: Peptides to: Aliphatic Amines to: Protonation Values for other Ligands.
Abstract: Aminocarboxylic Acids.- Iminodiacetic Acid Derivatives.- Peptides.- Anilinecarboxylic Acids.- Pyrrolecarboxylic Acid.- Pyrazlinecarboxylic Acid.- Pyridinecarboxylic Acids.- Aliphatic Amines.- Azoles.- Azines.- Aminophosphonic Acids.- Carboxylic Acids.- Phosphorus Acids.- Phenols.- Carbonyl Ligands.- Alcohols.- Polyethers.- Thioethers.- Thiols.- Phosphines.- Hydroxamic Acids.- Oximes.- Amides.- Inorganic Ligands.- Protonation Values for other Ligands.- Ligands Considered But Not Included.- Erratum to: Aminocarboxylic Acids.- Erratum to: Iminodiacetic Acid Derivatives.- Erratum to: Peptides.- Erratum to: Aliphatic Amines.- Erratum to: Azoles.- Erratum to: Azines.- Erratum to: Carboxylic Acids.- Erratum to: Phosphorus Acids.- Erratum to: Phenols.- Erratum to: Carbonyl Ligands.- Erratum to: Alcohols.- Erratum to: Polyethers.- Erratum to: Thioethers.- Erratum to: Hydroxamic Acids.- Erratum to: Oximes.- Erratum to: Amides.- Erratum to: Inorganic Ligands.- Erratum to: Protonation Values for other Ligands.- Erratum to: Bibliography.
6,389 citations
Book•
01 Jan 1965
TL;DR: In this article, the authors provide a thorough, up-to-date coverage of controls on the chemical quality of surface and ocean waters. But they do not provide a detailed analysis of the results of their experiments.
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2,462 citations
Book•
08 May 2007TL;DR: The theory and instrumentation for Fourier transform infrared spectrometry are discussed, and important areas of chemistry include atmospheric monitoring, surface chemistry, and on-line identification of chromatographically separated materials.
Abstract: The theory and instrumentation for Fourier transform infrared spectrometry are discussed. These instruments measure infrared spectra of the same quality as spectra measured on grating spectrometers in about one thousandth of the time. Their sensitivity advantage for spectra measured in equal times is between a factor of 10 and 100. Commercial spectrometers are now available from nine vendors in North America. Important areas of chemistry include atmospheric monitoring, surface chemistry, and on-line identification of chromatographically separated materials. Many new biochemical and biomedical applications are also becoming apparent, including investigations of phase transitions in lipids and studies of the biocompatibility of implant polymers.
2,244 citations
Book•
01 Jan 1989
TL;DR: In this paper, the principles of reaction in solution are discussed and the basis of separarative methods are discussed, as well as the safety units of Reagent Purity and Reagent Reactions in Solution.
Abstract: 1. Preface to First Edition. 2. Preface to Sixth Edition. 3. Safety Units. 4. Reagent Purity. 5. Introduction. 6. Fundamental Theoretical Principles of Reactions in Solution. 7. Common Apparatus & Basic Techniques. 8. Statistics, Introduction to Chemometrics. 9. Sampling. 10. The Basis of Separative Methods. 11. Thin Layer Chromatography. 12. Liquid Chromatography. 13. Gas Chromatography. 14. Titrimetric Analysis. 15. Gravimetric Analysis. 16. Thermal Analysis. 17. Direct Electroanalytical Methods. 18. Nuclear Magnetic Resonance Spectroscopy. 19. Atomic Absorption Spectroscopy. 20. Atomic Emission Spectroscopy. 21. Molecular Electronic Spectroscopy. 22. Vibrational Spectroscopy. 23. Mass Spectrometry. Appendices.
2,161 citations
TL;DR: The Gibbs free energies, enthalpies and entropies of 42 dissolved uranium species and 30 uranium-bearing solid phases have been critically evaluated from the literature and estimated when necessary for 25°C.
2,019 citations