Download or read book Redox Reactions and Phase Transformation Processes at Iron Mineral Surfaces Studied by Compound Specific Isotope Analysis written by Anke Buchholz and published by . This book was released on 2009 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Redox written by J. Schüring and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Few processes are as important for environmental geochemistry as the interplay between the oxidation and reduction of dissolved and solid species. The knowledge of the redox conditions is most important to predict the geochemical behaviour of a great number of components, the mobilities of which are directly or indirectly controlled by redox processes. The understanding of the chemical mechanisms responsible for the establishment of measurable potentials is the major key for the evaluation and sensitive interpretation of data. This book is suitable for advanced undergraduates as well as for all scientists dealing with the measurement and interpretation of redox conditions in the natural environment.
Download or read book Iron Mineral Transformations and Electron Transfer Reactions in Redox Dynamic Environments written by Elizabeth J. Tomaszewski and published by . This book was released on 2017 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the abundance and redox potential of iron (Fe), the solubility and oxidation state of trace metals may be strongly influenced by redox reactions with Fe minerals. The ability of a Fe mineral to participate in electron transfer with trace metals, such as chromium (Cr), is dependent on a variety of properties and processes. These include, but are not limited to, surface area, mineral stoichiometry, and geochemical conditions, such as redox potential. This dissertation work examines Fe mineral transformations and electron transfer reactions with Cr(VI) under varying redox conditions. In the second chapter, the mineralogical transformations of ferrihydrite ((Fe10O14(OH)2)) are investigated during rapid, abiotic redox oscillations, at different concentrations of dissolved Fe(II). The stoichiometry of the secondary mineral magnetite (Fe3O4) increases overall throughout redox oscillations, despite repeated exposure to oxygen. This work demonstrates structural Fe(II) in Fe minerals may not be oxidized in the presence of oxygen and could be a source of electrons in redox dynamic environments. In the third chapter, goethite ([alpha]-FeOOH) is exposed to varying numbers of abiotic redox cycles (e.g., 1, 2, 3, or 4) and subsequently reacted with Cr(VI). The reduction of Cr(VI) to Cr(III) is observed, demonstrating that Fe(II) substituted within the goethite lattice during anoxic periods is not only preserved during oxic periods but also available for electron transfer. Regardless of the number of redox cycles to which goethite is exposed Cr consistently is associated with the (100) crystallographic face, a predicted site of electron conduction. Finally, the fourth chapter examines the electron transfer between Cr(VI) and the reduced quinone species, AH2DS in the presence and absence of goethite at three different ratios of AH2DS:Cr(VI). Goethite inhibits of the extent of Cr(VI) reduction to Cr(III) most significantly at the highest ratio of AH2DS:Cr(VI) investigated. Possible production of semi-quinone radical species may limit electron transfer and decrease the percent yields of Fe(II) and Cr(III). Additionally, solid phase characterization of Cr confirms the formation of Cr(OH)3 phases. Understanding abiotic electron transfer reactions that occur in systems with multiple redox active species is important to elucidate the contribution of abiotic redox reactions to biogeochemical cycling in natural soils.
Download or read book Investigations of Surface Redox Chemistry on Environmentally Relevant Iron Oxides and Sulfides written by Elizabeth B. Cerkez and published by . This book was released on 2016 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Important reactions in the environment often occur at the interface between a mineral surface and aqueous phase. Reactions occurring at this interface often control the uptake or release of harmful components resulting in the geochemical cycling of elements in the environment. Additionally, minerals are commonly used in the remediation of contaminated areas, where similar chemistry occurs at their interfaces. Thus, studies of the chemistry of these interfaces are essential to our understanding of complex environments. Many of these processes are controlled by electron transfer reactions between adsorbates and the mineral interface, and it is here where this research presented will concentrate. The studies in this thesis key in on redox chemistry on various environmentally relevant iron minerals, including ferrihydrite, pyrite, and amorphous iron sulfide. A large portion of this body of work is dedicated to the understanding of the surface mediated reaction between chromate (Cr(VI)) and arsenite (As(III)). Both of these species are present in the environment and are detrimental to human health. Using in- and ex-situ experiments we have monitored the coupled redox transformation of Cr(VI) and As(III) to chromite (Cr(III)) and arsenate (As(V)). Quantum mechanical modeling was used to support the experimental studies of this novel redox chemistry. The reaction was monitored in situ, using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), on the surface of the iron oxyhydroxide, ferrihydrite, at various solution pH values by following vibrational modes unique to Cr(VI), As(III), and As(V). At pH
Download or read book Understanding Redox Processes in Surface Environments from Iron Oxide Transformations and Multiple Sulfur Isotope Fractionations written by Tsubasa Otake and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxidation reduction Mechanisms in Iron bearing Phyllosilicates written by J. W. Stucki and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Reactivity and Isotopic Fractionation of Fe bearing Minerals During Sulfidation written by Alison McAnena and published by . This book was released on 2011 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aquatic Redox Chemistry written by Paul Tratnyek and published by OUP USA. This book was released on 2012-06-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume provides a comprehensive overview of aquatic redox chemistry through chapters contributed by many of the leading investigators in the field.
Download or read book INTERFACIAL OXIDATION REACTIONS AND FILM NUCLEATION ON IRON SURFACES IN COMPLEX ENVIRONMENTS USING SPECTROSCOPY AT THE LIQUID SOLID AND GAS SOLID INTERFACE written by and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Iron (Fe) and its oxides are known heterogeneous catalysts in both industrial and laboratory experiments. Fe is shown to undergo oxidation forming mineral scales based on its chemical environment. A surface science approach was used to investigate chemical processes occurring at liquid/solid and gas/solid interfaces under various chemical environments to understand how Fe oxidation impacts the quality of drinking water, the catalytic ability of iron derivatives, and geological mineral formation processes. Polarized Modulated Infrared Reflection Absorption Spectroscopy (PM-IRRAS) is a surface-sensitive vibrational spectroscopic technique that is used to identify the adsorbed molecules on a reflective surface. A new PM-IRRAS method was developed to observe in situ adsorption of molecules at the air/liquid/solid interface, using 1-octadecanethiol adsorption on gold as a model system. A three-phase model was used to estimate the liquid layer thickness at the air/ethanol/Au interface. This new method was applied for investigating interfacial oxidation, corrosion, and mineral formation for understanding environmental science and heterogeneous catalytic reactions at the air/electrolyte/Fe interfaces. These studies revealed the impact of the electrolyte pH, anion concentration, effect of cations (Na+, K+, Mg2+, Ca2+, and Fe2+), and adsorption of atmospheric gases (O2, CO2) on the rate of corrosion, mineral formation, and composition of the corrosion products. The results obtained by PM-IRRAS were corroborated by the in situ liquid atomic force microscope (AFM), ex situ AFM, attenuated total reflectance Fourier transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. The initial stages of Fe surface corrosion were studied under the influence of alkali salt (NaCl) with controlled H2O and O2 pressure. Adventitious hydrocarbon on the Fe surface was found to transform into surface adsorbed carbonates in the initial stages of Fe surface oxidation. The added anions (Cl−) on the surface migrated into the bulk during oxidation in the presence of O2 and H2O pressure. Iron catalyzes the decomposition of disinfectant by-products (DBP). Halohydrocarbons can lead to severe health hazards from consumption above the threshold limits. CDCl3 was used as a model halohydrocarbon to investigate the ability to use Fe as a heterogeneous catalyst for the dehalogenation of CDCl3. The adsorption of CDCl3(g)on Fe(111) at both cryogenic and room temperatures was measured by infrared reflection absorption spectroscopy (IRRAS) and Auger Electron Spectroscopy (AES). The dissociative chemisorption of CDCl3 on the Fe(111) surface occurs and OH groups from water block adsorption sites on Fe(111) for adsorption of CDCl3. CDCl3 adsorption at the liquid/Fe interface was not observed under the applied conditions and unexpected plastic contamination may have blocked the adsorption sites on polycrystalline Fe. Spontaneous selective deposition and growth of iron oxide nanoparticles in the tailored defects on highly oriented pyrolytic graphite (HOPG) were investigated to provide seed sites for further reactions. It was found that electroless deposition using the FeCl2(aq) precursor and subsequent annealing in air at 400 °C lead to the nucleation and growth of semi-crystalline (amorphous) Fe3O4 and Fe2O3 in the tailored defects and step edges of HOPG. The research in this dissertation impacts chemical processes at complex gas/liquid/solid interfaces under ambient conditions and will have applications in designing materials for CO2 sequestration, designing heterogeneous catalysts for industrial applications, and understanding mineral formation in geological processes.
Download or read book Still Oxides Run Deep written by Robert Michael Handler and published by . This book was released on 2009 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Evolution of aqueous Fe(II)-Mn(IV) redox reactions was examined using complementary techniques. After pyrolusite particles were exposed to aqueous Fe(II), aqueous Fe and Mn were analyzed, and X-ray diffraction was utilized with electron microscopy to assess solid phase evolution during continued exposure to Fe(II). Selective use of Fe isotopes during Fe(II) resuspensions allowed us to track chemical changes occurring to one particular Fe addition using 57 Fe Mössbauer spectroscopy.
Download or read book In Situ Studies of Promoted Catalytic Surfaces and Redox Active Mineral Surfaces written by Alexander David Gordon and published by . This book was released on 2011 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation the in situ technique, attenuated total reflection-Fourier transform infrared spectroscopy, will be utilized to probe reaction chemistry on two sets of surfaces; the first, a silicon-copper alloy surface where copper acts as a catalyst in the synthesis of methylchlorosilanes, and the second, a redox active iron-sulfur surface. Spectroscopic information obtained in situ will be combined with kinetic batch reaction results to elucidate details of the reaction mechanism that gives information regarding product formation in real time under real experimental conditions, without the need for modifying the experimental conditions to fit the analysis as is the case in traditional surface science techniques.
Download or read book Tracing Redox Cycles During Microbe clay Interactions Using Stable Iron Isotopes written by Bingjie Shi and published by . This book was released on 2018 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Iron redox cycling, especially Fe(III) reduction, is mostly driven by microbial activity in the shallow subsurface. A wide range of bacteria, archaea, and fungi reduce Fe(III) to acquire energy with soil organic compounds as the electron donors. Iron isotope signatures in ancient rocks (3.1-2.4 Ga) associated with dissimilatory Fe reduction (DIR) have been interpreted in terms of global changes in oceanic redox condition. Iron isotopes have also been used as indicators of redox processes involving Fe minerals such as Fe(III) (oxyhydr)oxides and pyrite. Clay minerals, however, contain approximately the same amount of Fe as all other Fe minerals combined, thereby playing a key role in Fe redox cycling. There have been numerous studies focusing on the mineralogical changes of clays during microbially, chemically, and electrochemically mediated redox cycles, and linking these changes to the bioavailability and reversibility of clay, including processes such as layer collapse, structural Fe migration, and dehydroxylation and water fixation. I used Fe isotopes, for the first time, to trace the redox cycling of clay minerals.
Download or read book Metals Abstracts Index written by and published by . This book was released on 1978 with total page 1010 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bioavailability of Contaminants in Soils and Sediments written by National Research Council and published by National Academies Press. This book was released on 2003-05-03 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioavailability refers to the extent to which humans and ecological receptors are exposed to contaminants in soil or sediment. The concept of bioavailability has recently piqued the interest of the hazardous waste industry as an important consideration in deciding how much waste to clean up. The rationale is that if contaminants in soil and sediment are not bioavailable, then more contaminant mass can be left in place without creating additional risk. A new NRC report notes that the potential for the consideration of bioavailability to influence decision-making is greatest where certain chemical, environmental, and regulatory factors align. The current use of bioavailability in risk assessment and hazardous waste cleanup regulations is demystified, and acceptable tools and models for bioavailability assessment are discussed and ranked according to seven criteria. Finally, the intimate link between bioavailability and bioremediation is explored. The report concludes with suggestions for moving bioavailability forward in the regulatory arena for both soil and sediment cleanup.
Download or read book Phase Transformations and Surface Chemistry of Secondary Iron Minerals Formed from Acid Mine Drainage written by Jörgen Jönsson and published by . This book was released on 2003 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monitored Natural Attenuation of Inorganic Contaminants in Ground Water written by and published by . This book was released on 2007 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: V.3 ... consists of individual chapters that describe 1) the conceptual background for radionuclides, including tritium, radon, strontium, technetium, uranium, iodine, radium, thorium, cesium, plutonium-americium and 2) data requirements to be met during site characterization.
