Download or read book Sequential Transformation of Carbon Tetrachloride Perchloroethylene and 1 1 1 Trichloroethane Using Methanogenic and Methanotrophic Conditions written by Sarah Jane Christ and published by . This book was released on 1996 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: A methanogenic-methanotrophic system has been established to assess the capability of sequential treatment to transform the chlorinated aliphatics perchloroethylene (PCE), carbon tetrachloride (CT) and 1,1,1-trichloroethane (1, 1,1-TCA). Experiments compared the transformation of PCE alone and in a mixture of the target compounds. A comparison of acetate and iron as electron donors was also made. Data from the anaerobic systems have shown that PCE transformation is inhibited when in a mixture with CT and 1,1,1-TCA compared to when it is fed alone. When iron is the electron donor, PCE and 1,1,1-TCA are transformed without an acclimation period. CT was completely transformed regardless of the electron donor used. The acetate-fed system required approximately 60 days to acclimate to 1,1,1-TCA and 70 days for acclimation to PCE. Although the sequential system has been constructed, sampling from the aerobic column was not done before the thesis project ended. More investigation is required to determine the ability of the sequential system to degrade PCE, CT, and 1,1,1- TCA.
Download or read book Biotransformation of Mixtures of Carbon Tetrachloride Perchloroethene and 1 1 1 trichloroethane written by David Temple Adamson and published by . This book was released on 1996 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metabolism of Perchloroethylene and 1 1 1 2 Tetrachloroethane After Carbon Tetrachloride Pretreatment in B6C3F1 Mice written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Risk assessments for chlorinated solvents are typically only done for single chemicals, and clean up costs are based on these assessments. However, groundwater and drinking water supplies are usually contaminated with multiple compounds. The most commonly used approach for assessing risks to multiple chemical exposures assumes additivity of response. This study investigates the effect of exposure to mixtures of carbon tetrachloride and 2 other chlorinated solvents, perchloroethylene and 1,1,1,2-tetrachloroethane. Metabolite formation, which is the process thought to be responsible for toxicity is affect carbon tetrachloride. By understanding the alteration in metabolic outcome for perchlorethylene and 1,1,1,2-tetrachloroethane the assessment of risk associated with exposures to these types of mixtures may be more science-based.
Download or read book Enhanced Biotransformations of Carbon Tetrachloride Tetrachloroethene and 1 1 1 trichloroethane Using Elemental Iron written by Kelvin Bolton Gregory and published by . This book was released on 1997 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Biotransformation of 1 1 1 trichloroethane and Carbon Tetrachloride by Denitrifying Bacterial Consortia written by Juli Lynn Sherwood and published by . This book was released on 1998 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Methyl Chloroform and Trichloroethylene in the Environment written by D. M. Aviado and published by CRC Press. This book was released on 2018-01-18 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present and subsequent volumes of this book, critical coverage of the literature will be combined with the fruits of original and highly relevant research carried out by Dr. D.M Aviado and his colleagues. The total effort constitutes an authoritative up-to-date appraisal of the knowledge needed to understand the inhalational toxicity and other biological effects of an important and ubiquitous class of chemical agents.
Download or read book Biological and Metallic Iron promoted Transformations of Carbon Tetrachloride and Chloroform Under Methanogenic Conditions written by Lenly Joseph Weathers and published by . This book was released on 1995 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Review of the Chemical Use of 1 1 1 trichloroethane and Carbon Tetrachloride as Well as the Options for Replacing and Phasing Out the Substances written by Kemikalieinspektionen and published by . This book was released on 1990 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transformation of Carbon Tetrachloride and Chloroform by Trichloroethene Respiring Anaerobic Mixed Cultures and Supernatant written by Kyle E. Vickstrom and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon tetrachloride (CT) and chloroform (CF) were transformed in batch reactor experiments conducted with anaerobic dechlorinating cultures and supernatant (ADC+S) harvested from continuous flow reactors. The Evanite (EV-5L) and Victoria/Stanford (VS-5L) cultures capable of respiring trichloroethene (TCE), 1,2-cis-dichloroethene (cDCE), and vinyl chloride (VC) to ethene (ETH) were grown in continuous flow reactors receiving an influent feed of saturated TCE (10 mM; 60 mEq) and formate (45 mM; 90 mEq) but no CT or CF. In all experiments, cells and supernatant were harvested from the chemostats and inoculated into batch reactors. Transformation of various concentrations of CT (0.86, 2.6, or 8.6 [micro]M), CF (2.1 or 21.1 [micro]M), dichloromethane (DCM; 23.1 [micro]M), and TCE (50 [micro]M) was examined. CT transformation was complete and exhibited pseudo-first order kinetics with CF as the primary measured transformation product in all treatments. Lesser amounts of DCM and carbon disulfide (CS2) were measured leading to an overall mass balance of 20-40% of the original mass as CT accounted for. An analytical first order solution was developed to model CT degradation and product formation under multiple conditions. Cells poisoned with 50 mM sodium azide (NaN3) catalyzed rapid and complete CT transformation suggesting a greater importance of redox active cofactors than live cells in the abiotic and cometabolic transformation. DCM and CS2 however were not produced in the poisoned treatments. TCE and CT simultaneous transformation occurred with an approximately two-fold increase in the CT degradation rate while maintaining complete TCE respiration to ETH. During the initial round of TCE respiration, the rate limiting step was VC to ETH, which was impacted by the presence of CT and CF. A subsequent addition of 50 [micro]M TCE showed a substantial decline in the rates of reductive dechlorination owing to the inhibitory effects of long term exposure to CF. The results clearly demonstrate that transformation can be promoted by anaerobic dechlorinating cultures and supernatant not previously acclimated to CT and CF. However, abiotic reactions account for much of the observed transformation. The role of CF inhibition on H2 utilization by the culture was also explored. Sodium formate was provided as a rapid release substrate, providing H2 as an electron donor. H2 partial pressures were tracked throughout the course of the kinetic experiments. The rapid transformation of CT to CF made it not possible to determine if CT inhibited H2 use by the anaerobic dechlorinating cultures. However, the rapid buildup and subsequent slow transformation of CF was found to reversibly inhibit H2 consumption for homoacetogenesis. It was found that an aqueous CF concentration above 0.4 [micro]M or 0.6 [micro]M inhibited H2 consumption by the EV-5L and VS-5L cultures, respectively. This result differed for the VS-5L culture when metabolizing TCE in the presence of CT and CF. The VS-5L culture consumed H2 at CF concentrations as high as 1.3 [micro]M. The culture may have been partially inhibited at CF concentrations greater than 0.6 [micro]M, which is shown by slower consumption of H2 than controls that did not contain CF. The results demonstrate that CF reversibly inhibits the consumption of H2 by the anaerobic dechlorinating cultures, and that more research is required to determine if it is through a chemical inhibition or toxicity.
Download or read book Understanding Environmental Reactions of Carbon Tetrachloride Trichloroethylene Perchloroethylene and Arsenic Applying Computational Chemistry Methods written by and published by . This book was released on 2006 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, as the progress of computational abilities has increased, computational chemistry has become an interesting tool for researchers for investigating mechanisms of environmental reactions when results of experimental explorations are not sufficiently clear. In this research, several environmental reactions have been investigated using ab initio and density functional theory (DFT) methods. This research investigated the effect of the reaction energy on the reaction pathway for C-Cl bond cleavage in carbon tetrachloride (CT). Ab initio and density functional theories were used to study adiabatic electron transfer to aqueous phase CT. The potential energies associated with fragmentation of the CT anion radical into a trichloromethyl radical and a chloride ion were explored as a function of the C-Cl bond distance during cleavage. The effect of aqueous solvation was simulated using a continuum conductor-like screening model. Solvation significantly lowered the energies of the reaction products, indicating that the dissociative electron transfer was enhanced by solvation. It was found that reductive dissociation electron transfer of CT undergoes a change from an inner-sphere to an outer-sphere mechanism as the reaction energy is increased. The results showed a liner relationship between the activation energy for the dissociation and the overall energy change, which is in good agreement with the results of the Marcus model. This research also investigated the thermodynamic favorability and resulting structures for chemisorption of trichloroethylene (TCE) and perchloroethylene (PCE) on iron surfaces using periodic DFT with the non-local Perdew-Burke-Enzerhof (PBE) functional. Chemisorption structures were obtained for four physically adsorbed initial configurations. An initial configuration with two carbons (C-bridge) physicallyadsorbed at bridge sites between adjacent iron atoms was shown to be the most stable configuration for TCE, while the mode with two carbons (C-hollow) physically adsorbed at hollow site was verified to be the most stable configuration for PCE. C-Fe bonds were formed via sigma or pi bonds in the complexes formed at C-bridge, top and hollow site. Upon binding with the iron surface, the interaction of the C=C bond still remained as sp2 hybridization. Moreover, the strong chemisorption induced dissociations of C-Cl bonds and formation of Cl-Fe bonds. For both TCE and PCE, modes with two Cl atoms (Cl-bridge) physically adsorbed at bridge sites were found to be the least favorable configuration, in which only two Cl atoms formed bonds with the Fe surface and no C-Fe bonds were formed. Negative net Mulliken charges on TCE and PCE indicated they are reduced upon adsorption to the iron surface. Finally, in this research, we evaluated the accuracies and costs of several DFT methods including Harris, PWC LDA, and BLYP GGA functionals for interaction of arsenite with ferric hydroxides by comparison to calculated and experimental properties of surface complexes. It was found that the approach of using low-level structures coupled with high level single-point energies was much less expensive than the approach of using high level functionals for both structures and energies and could obtain similar computed binding energies. Further work has been done to investigate the appropriate models for interaction of arsenite with ferric hydroxide between pH values of -4 through +4. The effect of solvation on single point energy was calculated using COSMO models. The bidentate corner-sharing complexes were more energetically favorable than monodentate corner-sharing complexes for the entire pH range. Lower binding energies at some pH values indicated monodentate binding may contribute to adsorption at low pH values and at high pH values. Adsorbed arsenite species were found to be fully protonated at low pH values and partly protonated at high pH values for the most favorable complex. Models for the interaction of arsenite with ferric hydroxide provided a relationship of adsorption and pH values that the adsorption of arsenite increased as pH value increased and there was a maximum point around pH 8.5-9.
Download or read book Phase Equilibria of Three Chlorinated Hydrocarbons with Near critical and Supercritical Carbon Dioxide written by Cherell Moneak Carr and published by . This book was released on 1997 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seeks to determine solubility values for three chlorinated hydrocarbons: carbon tetrachloride, 1,1,1-trichloroethane, and trichloroethylene in carbon dioxide mixtures.
Download or read book Toxicological Profile for Trichloroethylene written by and published by . This book was released on 1997 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dehalogenation written by Max M. Häggblom and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt: Halogenated organic compounds constitute one of the largest groups of environmental chemicals. The industrial production of new halogenated organic compounds has increased throughout the last century peaking in the 1960s, and continuing in widespread use today. Organohalides are integral to a variety of industrial applications, including use as solvents, degreasing agents, biocides, pharmaceuticals, plasticizers, hydraulic and heat transfer fluids, and intermediates for chemical synthesis, to name a few. It is important to recognize the beneficial aspects of halogenated organic compounds, as well as their potentially deleterious impact on the environment and health. Recognition ofthe adverse environmental effects ofmanytypes oforganohalide compounds has led to efforts to reduce or eliminate the most problematic ones. Although organohalide compounds are typically considered to be anthropogenic industrial compounds, they have their counterpart in several thousands of natural biogenic and geogenic organohalides, representing most classes of organic chemicals. Natural sources account for a significant portion of the global organohalogen budget. This volume authored by recognized experts in the field provides a current perspective on how both natural and synthetic organohalides are formed and degraded, and how these processes are incorporated into a global halogen cycle. The focus is on microbial processes, since these play a major role both in the production and degradation, i. e. , cycling of halogenated organic compounds inthe environment. This book is organized into five parts. Part I, Introduction, provides a global perspective on the issues of organohalides and their fate in the environment.
Download or read book In Situ Bioremediation of Ground Water and Geological Material written by Robert D. Norris and published by DIANE Publishing. This book was released on 1995-08 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a detailed background of the technologies available for the bioremediation of contaminated soil & ground water. Prepared for scientists, consultants, regulatory personnel, & others who are associated in some way with the restoration of soil & ground water at hazardous waste sites. Also provides insights to emerging technologies which are at the research level of formation, ranging from theoretical concepts, through bench scale inquiries, to limited field-scale investigations. 95 tables & figures.
Download or read book Alternatives for Ground Water Cleanup written by National Research Council and published by National Academies Press. This book was released on 1994-02-01 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: There may be nearly 300,000 waste sites in the United States where ground water and soil are contaminated. Yet recent studies question whether existing technologies can restore contaminated ground water to drinking water standards, which is the goal for most sites and the result expected by the public. How can the nation balance public health, technological realities, and cost when addressing ground water cleanup? This new volume offers specific conclusions, outlines research needs, and recommends policies that are technologically sound while still protecting health and the environment. Authored by the top experts from industry and academia, this volume: Examines how the physical, chemical, and biological characteristics of the subsurface environment, as well as the properties of contaminants, complicate the cleanup task. Reviews the limitations of widely used conventional pump-and-treat cleanup systems, including detailed case studies. Evaluates a range of innovative cleanup technologies and the barriers to their full implementation. Presents specific recommendations for policies and practices in evaluating contamination sites, in choosing remediation technologies, and in setting appropriate cleanup goals.
Download or read book Toxicological Profile for 1 1 dichloroethene written by and published by . This book was released on 1994 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical and Chemical Processes in the Aquatic Environment written by Erik R. Christensen and published by John Wiley & Sons. This book was released on 2014-09-15 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is need in environmental research for a book on fresh waters including rivers and lakes. Compared with other books on the topic, this book has a unique outline in that it follows pollution from sources to impact. Included in the text is the treatment of various tracers, ranging from pathogens to stable isotopes of elements and providing a comprehensive discussion which is lacking in many other books on pollution control of natural waters. Geophysical processes are discussed emphasizing mixing of water, interaction between water and the atmosphere, and sedimentation processes. Important geochemistry processes occurring in natural waters are described as are the processes specific to nutrients, organic pollutants, metals, and pathogens in subsequent chapters. Each of these chapters includes an introduction on the selected groups, followed by the physicochemical properties which are the most relevant to their behavior in natural waters, and the theories and models to describe their speciation, transport and transformation. The book also includes the most up to date information including a discussion on emerging pollutants such as brominated and phosphate flame retardants, perflurochemicals, and pharmaceutical and personal care products. Due to its importance an ecotoxicology chapter has been included featuring molecular biological methods, nanoparticles, and comparison of the basis of biotic ligand model with the Weibull dose-response model. Finally, the last chapter briefly summarizes the regulations on ambient water quality.
