Download or read book Kinetic and Microscopic Studies of the Reactivity of Fe II bearing Minerals in the Reductive Transformations of Organic Contaminants written by Chan Lan Chun and published by . This book was released on 2006 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2007 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Adsorption of Metals by Geomedia II written by Mark Barnett and published by Elsevier. This book was released on 2007-12-17 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adsorption of Metals by Geomedia II serves as a needed resource for this topic which has received much attention during the past 25 years. The book provides an in-depth review of the field, followed by numerous chapters that document the current status of adsorption research for a variety of metals by geomedia ranging from individual minerals to sediments and soils. Adsorption mechanisms are detailed and precipitation is presented as a distinct sorption process. Virtually all factors affecting the extent of metal adsorption are examined, including the effects of selected anions, competition among metals, pH, metal concentration, loading, variable metal adsorption capacity, ionic strength, hydrogen exchange and stoichiometry, and solids concentration. A variety of adsorption models are briefly presented and some are used to extend laboratory studies to field sites. This is a compilation of 25 peer reviewed papers from among the 60+ platform and poster presentations of the symposium "Adsorption of Metals to Geomedia II" at the American Chemical Society (ACS) Meeting, March 27-29, 2006 in Atlanta, Georgia, USA. This symposium is a follow-up to the original held in 1996.* Learn the tools and techniques from leading academics and industry experts * One stop practical resource and guide for those in the field* Keep informed and up to date on all the latest advancements in technology

Download or read book Handbook of Soil Sciences Two Volume Set written by Pan Ming Huang and published by CRC Press. This book was released on 2018-10-03 with total page 2249 pages. Available in PDF, EPUB and Kindle. Book excerpt: An evolving, living organic/inorganic covering, soil is in dynamic equilibrium with the atmosphere above, the biosphere within, and the geology below. It acts as an anchor for roots, a purveyor of water and nutrients, a residence for a vast community of microorganisms and animals, a sanitizer of the environment, and a source of raw materials for co

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 Kinetics of Fe II catalyzed Transformation of 6 line Ferrihydrite Under Anaerobic Flow Conditions written by and published by . This book was released on 2010 with total page 5469 pages. Available in PDF, EPUB and Kindle. Book excerpt: The readsorption of ferrous ions produced by the abiotic and microbially-mediated reductive dissolution of iron oxy-hydroxides drives a series of transformations of the host minerals. To further understand the mechanisms by which these transformations occur and their kinetics within a microporous flow environment, flow-through experiments were conducted in which capillary tubes packed with ferrihydrite-coated glass spheres were injected with inorganic Fe(II) solutions under circumneutral pH conditions at 25 C. Synchrotron X-ray diffraction was used to identify the secondary phase(s) formed and to provide data for quantitative kinetic analysis. At concentrations at and above 1.8 mM Fe(II) in the injection solution, magnetite was the only secondary phase formed (no intermediates were detected), with complete transformation following a nonlinear rate law requiring 28 hours and 150 hours of reaction at 18 and 1.8 mM Fe(II), respectively. However, when the injection solution consisted of 0.36 mM Fe(II), goethite was the predominant reaction product and formed much more slowly according to a linear rate law, while only minor magnetite was formed. When the rates are normalized based on the time to react half of the ferrihydrite on a reduced time plot, it is apparent that the 1.8 mM and 18 mM input Fe(II) experiments can be described by the same reaction mechanism, while the 0.36 input Fe(II) experiment is distinct. The analysis of the transformation kinetics suggest that the transformations involved an electron transfer reaction between the aqueous as well as sorbed Fe(II) and ferrihydrite acting as a semiconductor, rather than a simple dissolution and recrystallization mechanism. A transformation mechanism involving sorbed inner sphere Fe(II) alone is not supported, since the essentially equal coverage of sorption sites in the 18 mM and 1.8 mM Fe(II) injections cannot explain the difference in the transformation rates observed.

Download or read book Molecular level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides 1997 Annual Progress Report written by and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central tenet of this proposal is that a fundamental understanding of specific mineral surface-site reactivities will substantially improve reactive transport models of contaminants in geologic systems, and will allow more effective remediation schemes to be devised. Most large-scale, macroscopic models employ global chemical reaction kinetics and thermochemistry. However, such models do not incorporate molecular-level input critical to the detailed prediction of how contaminants interact with minerals in the subsurface. A first step leading to the incorporation of molecular-level processes in large-scale macroscopic models is the ability to understand which molecular-level processes will dominate the chemistry at the microscopic grain level of minerals. To this end, the research focuses on the fundamental mechanisms of redox chemistry at mineral surfaces. As much of this chemistry in sediments involves the Fe(III)/Fe(II) and Mn(IV)/Mn(II) couples, the authors focus on mineral phases containing these species. Of particular interest is the effect of the local coordination environment of Fe and Mn atoms on their reactivity toward contaminant species. Studies of the impact of local atomic structure on reactivity in combination with knowledge about the types and amounts of various surfaces on natural grain- size minerals provide the data for statistical models. These models in turn form the basis of the larger-scale macroscopic descriptions of reactivity that are needed for reactive transport models. A molecular-level understanding of these mechanisms will enhance the ability to design much greater performance efficiency, cost effectiveness, and remediation strategies that have minimal negative impact on the local environment. For instance, a comprehensive understanding of how minerals that contain Fe(II) reduce oxyanions and chlorinated organics should enable the design of other Fe(II)-containing remediation materials in a way that is synergistic with existing minerals in the subsurface environment.

Download or read book Kinetics of Oxidation reduction Reactions on the Surface of Birnessite written by Rebecca Vanderspiegel and published by . This book was released on 2008 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microbial Mineral Transformations at the Fe II written by and published by . This book was released on 1997 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of the project remain the same as those stated in the original proposal. Specifically, to determine microbiological and geochemical controls on carbonate mineral precipitation reactions that are caused by bacterial reduction of Fe(III)-oxides, and identify contributions of these processes to solid phase capture of strontium and other metal/radionuclide contaminants. The project on microbial mineral transformations at the Fe(II)/Fe(III) redox boundary for the solid phase capture of strontium is progressing well. Thus far, the authors have been able to demonstrate that: pH and DIC concentrations increase during microbial reduction of HFO in batch culture experiments with G. metallireducens lasting 30 days with high concentrations of strontium (1.0 \265m) and calcium (10 \265m) do not inhibit microbial HFO reduction, the extent of change in pH and DIC concentrations brings about supersaturation with respect to carbonate minerals including siderite (FeCO3), strontianite (SrCO3), and calcite/aragonite (CaCO3); in addition, precipitation of siderite has been documented in cultures of HFO reducing bacteria significant amounts of strontium and calcium (40 to 50% of the total initial concentration) sorb to particulate solids (i.e., HFO and bacteria cells)-in batch culture experiments l sorption of strontium to HFO conforms with Langmuir single site sorption models derived from corresponding mass action and mass balance relationships anticipated from thermodynamic equilibrium considerations the sorption behavior of strontium with S. alga is more complex and seems to involve two sets of reactive surface sites on the bacterial cells; a high affinity site of low total sorption capacity, and a low affinity site with high sorption capacity the total strontium sorption capacities of S. alga and HFO are comparable the observed solid phase partioning of strontium in the culture experiments is in excellent agreement with sorption characteristics measured with HFO and S. alga.

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 The Impact of Small Organic Acids on Iron and Manganese Mineral Transformations and the Fate of Trace Metals written by Elaine Denise Flynn and published by . This book was released on 2018 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Iron and manganese oxides are ubiquitous in soils and sediments and play a critical role in the geochemical distribution of trace elements and heavy metals through adsorption and coprecipitation. At redox interfaces, biogeochemical processes generate conditions with coexisting dissolved Fe(II) and solid-phase Fe(III). In such systems, Fe(II) induces the recrystallization of iron oxides through coupled mineral growth and dissolution due to electron transfer as oxidative adsorption of Fe(II) and reductive dissolution of Fe(III) occur. Aqueous Mn(II) adsorption onto Mn(III/IV) oxides also likely involves oxidation although likely through different mechanisms than that of the Fe system because of the potential for Mn(II)-Mn(IV) comproportionation reactions. During reactions between reduced and oxidized forms of Fe and Mn, trace metals may be redistributed among the mineral bulk, mineral surface, and aqueous solution. Many metals, including Ni and Zn, are important micronutrients but are also toxic at higher concentrations. It is important to identify the processes controlling the fate and availability of trace metals in the environment and this requires understanding the behavior and stability of Fe and Mn oxides. Small organic acids, produced as root exudates or by decomposition of organic matter in aerated soils, may potentially alter reactions involving Fe and Mn oxide minerals and trace metals through a series of cooperative or competitive processes: solution complexation, ternary surface complexation, surface site competition, ligand-promoted dissolution, and reductive dissolution. The effects of organic acids on trace metal fate in such systems is unclear because these processes may involve both trace metals and Fe or Mn oxides, and multiple processes may co-occur. The main objective of this dissertation is to determine how organic acids interacting with Fe and Mn oxides affect structural transformations of these minerals, including dissolution and recrystallization, and the resulting impact on trace metals micronutrient and contaminant fate. Three main research projects were conducted to meet this objective. First, the cooperative and competitive interactions between oxalate and Ni during adsorption to Fe oxide minerals were identified. Next, the effects of oxalate on Ni incorporation into and release from Fe oxides at pH 4 and 7 was investigated during Fe(II)-promoted recrystallization of these minerals. Finally, reductive transformations of layered Mn oxides by oxalate, citrate, and 4-hydroxybenzoate at pH 4, 5.5, and 7 were characterized as well as the associated changes in Ni and Zn adsorption extent and mechanisms. The addition of oxalate in macroscopic adsorption studies suppresses Ni uptake by goethite and hematite at pH 7. Aqueous speciation modelling indicates that this is dominantly the result of oxalate complexing and solubilizing Ni. Comparison of the Ni surface coverage to the concentration of free (uncomplexed) Ni2+ in solution suggests that oxalate also alters Ni adsorption affinity. Extended X-ray absorption fine structure and attenuated total reflectance Fourier transform infrared spectroscopies indicate that these changes in binding affinity are due to the formation of Ni-oxalate ternary surface complexes. When Ni is initially structurally-incorporated into hematite and goethite, oxalate and dissolved Fe(II) each promote the release of Ni to aqueous solution at pH 4 and 7. With the co-addition of both species, the effects on Ni release are synergistic at pH 7 but inhibitory at pH 4. This suggests that cooperative and competitive interactions vary with pH. In contrast, oxalate suppresses Ni incorporation into goethite and hematite during Fe(II)-induced recrystallization. Mn oxides may undergo redox and structural changes which can weaken trace metal binding and promote metal mobility. The conditions studied to date involve Mn(II) and are most similar to those found at redox interfaces which are limited in spatial extent in nature. Aging e-MnO2 and hexagonal birnessite in the presence of small organic acids was investigated using powder X-ray diffraction and X-ray absorption fine structure spectroscopic measurements. Organic acids caused partial Mn reduction but did not substantially alter the phyllomanganates sheet structure nor result in transformations to Mn(III) oxyhydroxides or mixed-valent minerals. All organic acids were fully consumed, producing solid-phase Mn(II) and Mn(III) as well as dissolved Mn(II), the latter favored under acidic pH conditions. Citrate caused the greatest reduction, with its oxidation products continuing to react and near-complete mineralization observed at pH 4. These redox reactions improved stacking of the phyllomanganate sheets for e-MnO2 at pH 7 and enhanced capping of vacancy sites by cations occurred for both minerals under all conditions studied. As a result of this mineral alteration, Ni and Zn adsorption behaviors were also modified. Net metal uptake did not change substantially at pH 7 where nearly all of the Ni and Zn in the system were adsorbed to the mineral surface. However, at pH 4, adsorption of Ni and Zn decreased in the presence of the organic acids. Ni adsorption mechanisms transitioned from binding above vacancy sites to at sheet edges in the presence of citrate and 4-hydroxybenzoate, while oxalate increased binding above and in vacancy sites; citrate inhibited Ni incorporation into vacancies. Zn adsorption also transitioned to binding at weaker sites on the particle edges. The adsorption behaviors of Ni and Zn suggest that during reaction with organic acids, phyllomanganate mineral reactivities towards metals are altered by organic acids via a decrease in the vacancy content of Mn oxides. This work improves our understanding of the effect of Fe and Mn oxides in soils and aquatic systems on micronutrient availability and heavy metals sequestration. Oxalate largely enhances trace metal mobility through multiple processes occurring in solution and on Fe oxide surfaces. Similarly, phyllomanganates structural changes in the presence of oxalic, citric, and 4-hydroxybenzoate alter the reactivity of Mn oxides through Mn reduction and subtle structural changes. Overall, this dissertation demonstrates that complex interactions at Fe and Mn oxide surfaces with organic acids must be considered when evaluating micronutrient availability and contaminant sequestration in the environment.

Download or read book Iron Oxides written by Damien Faivre and published by John Wiley & Sons. This book was released on 2016-08-08 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alle relevanten Informationen zu Eisenoxiden, von der Struktur und Transformation über Charakterisierungsverfahren bis hin zu den neuesten AnwendungEN. Ein Muss für alle, die in dem Fachgebiet arbeiten.

Download or read book Microbial Fe II Oxidation at Circumneutral PH written by S. Vollrath and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic Evidence for Interfacial Fe II Fe III Electron Transfer in Clay Minerals written by and published by . This book was released on 2010 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although interfacial electron transfer has been shown to occur for sorbed Fe(II) and Fe-oxides, it is unclear if a similar reaction occurs between sorbed Fe(II) and Fe(III)-bearing clay minerals. Here, we use the isotope specificity of 57Fe Mössbauer spectroscopy to demonstrate electron transfer between sorbed Fe(II) and structural Fe(III) in a nontronite clay mineral (NAu-2). Appearance of an Fe(II) doublet in the NAu-2 spectra after reaction with aqueous 56Fe(II) (56Fe is transparent in Mössbauer spectra) provided evidence for reduction of structural Fe(III). Mössbauer spectra using enriched 57Fe(II) reveal that Fe(II) is oxidized upon sorption to NAu-2, and the oxidation product of this reaction is a ferric oxide with spectral parameters similar to lepidocrocite. The reduction of structural Fe(III) by Fe(II) induces electron delocalization in the clay structure, which we observe by variable-temperature Mössbauer spectra and macroscopic color change indicative of Fe(II)-Fe(III) pairs. The extent of structural Fe(III) reduction in NAu-2 is equal to the amount of Fe(II) sorbed until approximately 15% reduction, after which point reduction is no longer concomitant with the amount of sorbed Fe(II).

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.

Download or read book Fe III Reduction in Clay Minerals and Its Application to Technetium Immobilization written by Deb Prasad Jaisi and published by . This book was released on 2007 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: The iron redox biogeochemistry, especially in clay minerals, is poorly understood. As a result, applicability of this redox reaction or the products to environmental problems such as remediation of metal contaminants is largely unexplored. This dissertation, therefore, seeks to develop a fundamental understanding of bacterial Fe(III) reduction in clay minerals and reactivity of resulting Fe(II) in reducing and immobilizing technetium (99Tc). The first subproject involves research on iron biogeochemistry in different clay minerals [nontronite (NAu-1, NAu-2), Muloorina illite (Mu-Il) and chlorite (CCa-2)]. The results reveal that the extent of Fe(III) reduction depends on the difference in the crystal structure, layer charge and Fe(III) content. Among different Fe(III) species, Fe(III) in the tetrahedral site is the most reducible and that in the cis-octahedral sites the least. Fe(II) produced from Fe(III) reduction speciates into four chemical environments in clay minerals: aqueous, structural, complexed to amphoteric surface sites and at exchangeable sites. The Fe(II) sorbed both to cell and mineral surfaces exerts a strong inhibitory effect for further Fe(III) reduction. The interplay of these factors can be modeled by considering the reactive surface site concentration, surface saturation, Fe(II) production and its surface inhibition. The second subproject involves the use of Fe(II), produced from microbial and chemical reduction of Fe(III) in nontronite, for the long-term immobilization of technetium, a significant contaminant in several U.S. DOE sites. The Fe(II) at different chemical environments in reduced nontronite (NAu-2) is found to reduce Tc(VII) into Tc(IV) with the following order of decreasing relative reactivity: Fe(II) at surface complexation sites” Fe(II) at exchangeable sites> Fe(II) at structural sites. EXAFS results suggest that ~70% of Tc(IV) is surface precipitated and the rest forms surface complex with NAu-2. Because the reduced Tc(IV) is associated with clay particle aggregates, it is very recalcitrant to reoxidation in the presence of thermodynamically more favorable electron acceptors/oxidants such as oxygen, nitrate, Fe(III) and Mn(III/IV) oxides. Since the clay aggregates are relatively stable and are less likely perturbed by any transient changes in the aquifer geo-, hydro- and biochemistry, these findings may provide an important step toward the long term immobilization of Tc.

Download or read book Formation of Mixed Fe Fe Oxides and Their Reactivity to Catalyze Chemical Oxidation written by Muhammad Usman and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main theme of this research is the use of reactive iron minerals in the remediation of hydrocarbon contaminated soils via chemical oxidation treatments at circumneutral pH. The contribution of this thesis is two-fold including the abiotic synthesis of mixed FeII-FeIII oxides considered as reactive iron minerals (magnetite and green rust) and their use to catalyze chemical oxidation. Oxidation methods tested in this study include Fenton-like (FL) and activated persulfate oxidation (AP). The formation of magnetite and green rust was studied by abiotic FeII-induced transformations of various ferric oxides like ferrihydrite, goethite, hematite and lepidocrocite. Then, the ability of magnetite was tested to catalyze chemical oxidation (FL and AP) for the degradation of aliphatic and polycyclic aromatic hydrocarbons (PAHs) at circumneutral pH. Significant degradation of oil hydrocarbons occurring in weathered as well as in crude oil was obtained by both oxidants. Magnetite catalyzed oxidation was also effective for remediation of two PAHs contaminated soils from ancient coking plant sites. No by-products were observed in all batch slurry oxidation systems. Very low hydrocarbon degradation was observed when soluble FeII was used as catalyst under the same experimental conditions. Magnetite also exhibited high reactivity to catalyze chemical oxidation in column experiments under flow through conditions. Oxidation studies revealed the importance of catalyst type for oxidation, PAHs availability in soils and the soil matrix effect. Results of this study suggest that magnetite can be used as iron source to activate both Fenton-like and persulfate oxidation at circumneutral pH. This study has important implications in the remediation of hydrocarbon polluted soils through in-situ chemical oxidation.