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Kinetic Studies Of The Oxidation Pathways Of Gaseous Elemental Mercury
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Book Synopsis Kinetic Studies of the Oxidation Pathways of Gaseous Elemental Mercury by : Deanna L. Donohoue
Download or read book Kinetic Studies of the Oxidation Pathways of Gaseous Elemental Mercury written by Deanna L. Donohoue and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work is the first direct measurement of a kinetic rate coefficient for these reactions, and the first work which employed one photon LIF to monitor the HgCl and HgBr products. The second aspect of this work was the development of new laser based techniques to detect atmospheric mercury and its oxidation products for both laboratory and field application. In this work a LIF technique was develop to detect HgCl and HgBr. In addition, a two photon LIF technique initially developed by Bauer et al., 2002 was verified and expanded. The two photon LIF technique was used to directly monitor Hg(0) atoms in-situ, to monitor Hg(0) evolving form a gold tube, and to monitor the Hg(0) evolving from the thermal decomposition of reactive gaseous mercury collected on a KCl coated or uncoated denuder. This work represents a significant advance in the development of a viable method the detect mercury and the mercury oxidation products in the laboratory and in the field and is the first study to observe clear differences in the characteristic desorption profiles of HgO and HgX2. This work has broad implications, it enhanced our current knowledge concerning the biogeochemical cycling of mercury, broadened our understanding of the mercury chemistry in high halogen environment, and provided new techniques which can be applied in future field and laboratory studies.
Book Synopsis Oxidation of Elemental Mercury by Chlorine by :
Download or read book Oxidation of Elemental Mercury by Chlorine written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate oxidation rate constants of mercury gas are needed for determining its dispersion and lifetime in the atmosphere. They would also help in developing a technology for the control of mercury emissions from coal-fired power plants. However, it is difficult to establish the accurate rate constants primarily due to the fact that mercury easily adsorbs on solid surface and its reactions can be catalyzed by the surface. We have demonstrated a procedure that allows the determination of gas phase, surface-induced, and photo-induced contributions in the kinetic study of the oxidation of mercury by chlorine gas. The kinetics was studied using reactors with various surface to volume ratios. The effect of the surface and the photo irradiation on the reaction was taken into consideration. The pressure dependent study revealed that the gas phase oxidation was a three-body collision process. The third order rate constant was determined to be 7.5(±0.2) x 10−39 mL2 molecules−2s−1 with N2 as the third body at 297 ± 1 K. The surface induced reaction on quartz window was second order and the rate constant was 2.7 x 10−17 mL2 molecules−1 cm−2 sec. Meanwhile, the 253.7 nm photon employed for mercury detection was found to accelerate the reaction. The utilization efficiency of 253.7 nm photon for Hg° oxidation was 6.7 x 10−4 molecules photon−1 under the conditions employed in this study.
Book Synopsis Molecular Insights Into the Redox of Atmospheric Mercury Through Laser Spectroscopy by : Rongrong Wu Cohen
Download or read book Molecular Insights Into the Redox of Atmospheric Mercury Through Laser Spectroscopy written by Rongrong Wu Cohen and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The widespread pollution of mercury motivates research into its atmospheric chemistry and transport. Gaseous elemental mercury (Hg(0)) dominates mercury emission to the atmosphere, but the rate of its oxidation to mercury compound (Hg(II)) plays a significant role in controlling where and when mercury deposits to ecosystems. Atomic bromine is regarded as the main oxidant for Hg(0) oxidation, known to initiate the oxidation via a two-step process in the atmosphere – formation of BrHg (R1) and subsequent reactions of BrHg with abundant free radicals Y, i.e., NO2, HOO, etc. (R2), where the reaction of BrHg +Y could also lead to the reduction of Hg(I) to Hg(0) (R3). A different oxidation pathway of BrHg + O3 (R4) is currently regarded as the dominant Hg(II) oxidation pathway in the atmosphere. Hg + Br + M → BrHg + M (R1) BrHg + Y + M → BrHgY + M (R2) BrHg + Y → BrY +Hg (R3) BrHg + O3 → BrHgO + O2 (R4) While the rate constants of R1 have been experimentally measured a decade ago, this research focuses on the experimental kinetic studies on the reaction of R2-R4 to better assist the efforts to predict how emission reductions impact the spatial distribution of mercury entry into ecosystems. The kinetic studies of BrHg redox chemistry are conducted by utilizing laser photolysis-laser induced fluorescence-cavity ringdown spectroscopy (LP-LIF-CRDS) systems, where BrHg radicals are generated via laser photolysis and monitored in the reaction via LIF and CRDS measurements. We report mainly on our experimental kinetic studies of the redox reactions of BrHg with relatively abundant trace gases such as NO2, NO, O3, O2, and VOCs, especially on the temperature and pressure dependence of the reaction rate constants using our LP-LIF system. We present the development and the characterization of a novel LP-CRDS system, which is a powerful tool to study reactions during which fluorescence quenching interferes with LIF measurement, and to study the spectroscopy of Hg(I) and Hg(II) compounds.
Book Synopsis Homogeneous and Heterogeneous Oxidation of Gaseous Elemental Mercury by : Graydon Snider
Download or read book Homogeneous and Heterogeneous Oxidation of Gaseous Elemental Mercury written by Graydon Snider and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury is an atmospheric global pollutant with complex cycling behavior. Two-thirds of the mercury present in our atmosphere is anthropogenic in origin. Chemical oxidation of gaseous elemental mercury governs the deposition rate of mercury over most lakes, land, and oceans. A major uncertainty comes from the effect of atmospheric surfaces such as aerosols. Much research is devoted to mercury capture technologies to be used in coal fire power plants, which are the major source of anthropogenic emissions.This thesis is a report on oxidation kinetics and mechanistic studies relevant to mercury-scavenging reactions. It provides an overview of the mechanisms of mercury oxidation by ozone, nitrogen dioxide, and titanium dioxide (exposed to ultra-violet light). The role of surfaces was quantified, as appropriate for each system. Crossover effects between gaseous co-pollutants (e.g. CO, SO2) and surfaces (SiO2, TiO2) are discussed. Rate constants were measured for each...
Book Synopsis Atmospheric Mercury by : Robert W. Talbot
Download or read book Atmospheric Mercury written by Robert W. Talbot and published by MDPI. This book was released on 2018-09-27 with total page 307 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Atmospheric Mercury" that was published in Atmosphere
Book Synopsis Environmental Chemistry and Toxicology of Mercury by : Guangliang Liu
Download or read book Environmental Chemistry and Toxicology of Mercury written by Guangliang Liu and published by John Wiley & Sons. This book was released on 2011-11-07 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides the fundamentals, recent developments, and future research needs for critical mercury transformation and transport processes, as well as the experimental methods that have been employed in recent studies. The coverage discusses the environmental behavior and toxicological effects of mercury on organisms, including humans, and provides case studies at the end of each chapter. Bringing together information normally spread across several books, this text is unique in covering the entire mercury cycle and providing a baseline for what is known and what uncertainties remain in respect to mercury cycling.
Book Synopsis Mercury as a Global Pollutant by : Donald B. Porcella
Download or read book Mercury as a Global Pollutant written by Donald B. Porcella and published by Springer. This book was released on 2014-08-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: ACKNOWLEDGEMENTS xiv PART I MERCURY AND HUMAN HEALTH B. WHEATLEY and S. PARADIS I Exposure of Canadian Aboriginal Peoples to Methylmercury 3-11 M. GIRARD and C. DUMONT I Exposure of James Bay Cree to Methylmercury during Pregnancy for the Years 1983-91 13-19 M. RICHARDSON, M. MITCHELL, S. COAD and R. RAPHAEL I Exposure to Mercury in Canada: A Multimedia Analysis 21-30 M. RICHARDSON, M. EGYED and D. J. CURRIE I Human Exposure to Mercury may Decrease as Acidic Deposition Increases 31-39 L. E. FLEMING, S. WATKINS, R. KADERMAN, B. LEVIN, D. R. AVYAR, M. BIZZIO, D. STEPHENS and J. A. BEAN I Mercury Exposure in Humans through Food Consumption from the Everglades of Florida 41-48 J. M. GEARHART, H. J. CLEWELL III, K. S. CRUMP, A. M. SHIPP and A. SILVERS I Pharmacokinetic Dose Estimates of Mercury in Children and Dose-Response Curves of Performance Tests in a Large Epidemiological Study 49-58 I. SKARE I Mass Balance and Systemic Uptake of Mercury Released from Dental Amalgam Fillings 59-67 J. DELLINGER, N. KMIECIK, S. GERSTENBERGER and H. NGU I Mercury Contamina tion of Fish in the Ojibwa Diet: I. Walleye Fillets and Skin-On versus Skin-Off Sampling 69-76 J. DELLINGER, L. MALEK and M. BEATTIE I Mercury Contamination of Fish in the Ojibwa Diet: II. Sensory Evoked Responses in Rats Fed Walleye 77-83 H. AKAGI, O. MALM, F. J. P. BRANCHES, Y. KINJO, Y. KASHIMA, J. R. D. GUIMARAES, R. B. OLIVEIRA, K. HARAGUCHI, W. C. PFEIFFER, Y.
Book Synopsis The Forcing of Mercury Oxidation as a Means of Promoting Low-Cost Capture by : John C. Kramlich
Download or read book The Forcing of Mercury Oxidation as a Means of Promoting Low-Cost Capture written by John C. Kramlich and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace amounts of mercury are found in all coals. During combustion this mercury is vaporized and can be released to the atmosphere. This has been a cause for concern for a number of years, and has resulted in a determination by the EPA to regulate and control these emissions. Present technology does not, however, provide inexpensive ways to capture or remove mercury from flue gases. The mercury that exits the furnace in the oxidized form (HgCl{sub 2}) is known to much more easily captured in existing wet pollution control equipment (e.g., wet FGD for SO{sub 2}), principally due to its high solubility in water. Until recently, however, nobody knew what caused this oxidation, or how to promote it. Recent DOE-funded research in our group, along with work by others, has identified the gas phase mechanism responsible for this oxidation. The scenario is as follows. In the flame the mercury is quantitatively vaporized as elemental mercury. Also, the chlorine in the fuel is released as HCl. The direct reaction Hg+HCl is, however, far too slow to be of practical consequence in oxidation. The high temperature region does supports a small concentration of atomic chlorine due to disassociation of HCl. As the gases cool (either in the furnace convective passes, in the quench prior to cold gas cleanup, or within a sample probe), the decay in Cl atom is constrained by the slowness of the principal recombination reaction, Cl+Cl+M {yields} Cl{sub 2}+M. This allows chlorine atom to hold a temporary, local superequilibrium concentration. Once the gases drop below about 550 C, the mercury equilibrium shifts to favor HgCl{sub 2} over Hg, and this superequilibrium chlorine atom promotes oxidation via the fast reactions Hg+Cl+M {yields} HgCl+M, HgCl+Cl+M {yields} HgCl{sub 2}+M, and HgCl+Cl{sub 2} {yields} HgCl{sub 2}+Cl. Thus, the high temperature region provides the Cl needed for the reaction, while the quench region allows the Cl to persist and oxidize the mercury in the absence of decomposition reactions that would destroy the HgCl{sub 2}. Promoting mercury oxidation is one means of getting high-efficiency, ''free'' mercury capture when wet gas cleanup systems are already in place. The chemical kinetic model we developed to describe the oxidation process suggests that oxidation can be promoted by introducing trace amounts of H{sub 2} and/or CO within the quench region. The reaction of these fuels leads to free radicals that promote the selective conversion of HCl to Cl, which can then subsequently react with Hg. The work reported here from our Phase I Innovative Concept grant demonstrated this phenomenon, but it also showed that the process must be applied carefully to avoid promoting the recombination of Cl back to HCl. For example, addition of H{sub 2} at too high a temperature is predicted to actually decrease Cl concentrations via Cl+H{sub 2} {yields} HCl+H. At lower temperatures this reaction is slowed due to its activation energy. Thus, within the correct window, the process becomes selective for Cl promotion. Key parameters are the injection temperature of the promoter, the amount of the fuel added. A successful process based on this research will add a powerful tool to the mercury control arsenal. Presently, fractional oxidation in flue gases varies widely, but averages about 50%. The amounts of promoter needed to obtain quantitative oxidation are predicted to be small ({approx}50 ppm). The H{sub 2}/CO could be supplied by conventional natural gas reformer on site, and the low expected fuel concentration would require only a relatively trivial amount of natural gas, even for a large power plant. For example, a 600 MW{sub e} plant would require the order of only 1 MW thermal equivalent of natural gas. If the mercury in the stream approaching a FGD system is highly oxidized, then high captures could be achieved without any additional cost, even for fuels of low chlorine.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine by : Andrew Rodger Fry
Download or read book Experimental and Kinetic Modeling Investigation of Gas-phase Mercury Oxidation Reactions with Chlorine written by Andrew Rodger Fry and published by . This book was released on 2008 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mercury study report to Congress by :
Download or read book Mercury study report to Congress written by and published by DIANE Publishing. This book was released on with total page 1811 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis High Temperature Mercury Oxidation Kinetics Via Bromine Mechanisms by : Terumi Okano
Download or read book High Temperature Mercury Oxidation Kinetics Via Bromine Mechanisms written by Terumi Okano and published by . This book was released on 2009 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: As the foremost production of electricity in the United State comes from coal-fired plants, there is much more to learn on the topic of mercury which is a common component in coal. The speciation of mercury in the flue gas determines the best control technology for a given system. Because of the difficulty in measuring mercury at different stages of the process, it is practical to use mercury reaction kinetics to theoretically determine mercury speciation based upon coal composition, plant equipment and operating conditions. Elemental mercury cannot be captured in wet scrubbers; however, its oxidized forms can. Chlorine is a reasonable oxidizing agent and is naturally found in bituminous coal, but bromine is an even better oxidizing agent because of its larger size, it has stronger London dispersion force interactions with mercury. Bromine additive technologies have recently been implemented in several companies to enhance mercury oxidation. Because capture technologies are highly dependent upon the form of mercury that is present, investigations into their speciation are extremely important. Though there have been numerous efforts to study mercury compounds as relevant to atmospheric studies, there is little data currently available for mercury compounds found in combustion flue gases. It would be particularly beneficial to obtain kinetic rate constants at various high temperature and pressure conditions typical for a combustion system. Prevalent species of mercury containing bromine in coal combustion flue gases were studied using density functional theory (DFT) and a broad range of ab initio methods. Reaction enthalpies, equilibrium bond distances, and vibrational frequencies were all predicted using DFT as well as coupled cluster (CC) methods. All electronic calculations were carried out using the Gaussian03 or MOLPRO software programs. Kinetic predictions of three first-stage and three second-stage oxidation reactions involving the formation of oxidized mercury via bromine containing compounds are presented. Understanding the speciation of mercury in the flue gases of coal combustion is paramount in developing efficient technologies to ensure its capture.
Book Synopsis Mercury study report to Congress Vol. 8 by :
Download or read book Mercury study report to Congress Vol. 8 written by and published by DIANE Publishing. This book was released on with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Elemental Mercury and Inorganic Mercury Compounds by : J. Risher
Download or read book Elemental Mercury and Inorganic Mercury Compounds written by J. Risher and published by WHO. This book was released on 2003 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: On cover: IPCS International Programme on Chemical Safety. Published under the joint sponsorship of WHO, the United Nations Environment Programme, and the International Labour Organization and produced within the framework of the Inter-organization Programme for the Sound Management of Chemicals (IPCS).
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781723538780 Total Pages :274 pages Book Rating :4.5/5 (387 download)
Book Synopsis Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling by : National Aeronautics and Space Administration (NASA)
Download or read book Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-23 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the eleventh in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. Demore, W. B. and Sander, S. P. and Golden, D. M. and Hampson, R. F. and Kurylo, M. J. and Howard, C. J. and Ravishankara, A. R. and Kolb, C. E. and Molina, M. J. Jet Propulsion Laboratory NASA-CR-198863, JPL-PUBL-94-26, NAS 1.26:198863 NAS7-1260; RTOP 464-41-04-01-00...
Book Synopsis Removal of Elemental Mercury from a Gas Stream Facilitated by a Non-Thermal Plasma Device by : Charles Mones
Download or read book Removal of Elemental Mercury from a Gas Stream Facilitated by a Non-Thermal Plasma Device written by Charles Mones and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury generated from anthropogenic sources presents a difficult environmental problem. In comparison to other toxic metals, mercury has a low vaporization temperature. Mercury and mercury compounds are highly toxic, and organic forms such as methyl mercury can be bio-accumulated. Exposure pathways include inhalation and transport to surface waters. Mercury poisoning can result in both acute and chronic effects. Most commonly, chronic exposure to mercury vapor affects the central nervous system and brain, resulting in neurological damage. The CRE technology employs a series of non-thermal, plasma-jet devices to provide a method for elemental mercury removal from a gas phase by targeting relevant chemical reactions. The technology couples the known chemistry of converting elemental mercury to ionic compounds by mercury-chlorine-oxygen reactions with the generation of highly reactive species in a non-thermal, atmospheric, plasma device. The generation of highly reactive metastable species in a non-thermal plasma device is well known. The introduction of plasma using a jet-injection device provides a means to contact highly reactive species with elemental mercury in a manner to overcome the kinetic and mass-transfer limitations encountered by previous researchers. To demonstrate this technology, WRI has constructed a plasma test facility that includes plasma reactors capable of using up to four plasma jets, flow control instrumentation, an integrated control panel to operate the facility, a mercury generation system that employs a temperature controlled oven and permeation tube, combustible and mercury gas analyzers, and a ductless fume hood designed to capture fugitive mercury emissions. Continental Research and Engineering (CR & E) and Western Research Institute (WRI) successfully demonstrated that non-thermal plasma containing oxygen and chlorine-oxygen reagents could completely convert elemental mercury to an ionic form. These results demonstrate potential the application of this technology for removing elemental mercury from flue gas streams generated by utility boilers. On an absolute basis, the quantity of reagent required to accomplish the oxidation was small. For example, complete oxidation of mercury was accomplished using a 1% volume fraction of oxygen in a nitrogen stream. Overall, the tests with mercury validated the most useful aspect of the CR & E technology: Providing a method for elemental mercury removal from a gas phase by employing a specific plasma reagent to either increase reaction kinetics or promote reactions that would not have occurred under normal circumstances.
Book Synopsis Mercury Fate and Transport in the Global Atmosphere by : Nicola Pirrone
Download or read book Mercury Fate and Transport in the Global Atmosphere written by Nicola Pirrone and published by Springer Science & Business Media. This book was released on 2009-06-15 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mercury, primarily because of its existence and bioaccumulation as methylmercury in aquatic organisms, is a concern for the health of higher trophic level organisms, or to their consumers. This is the major factor driving current research in mercury globally and in environmental regulation, and is the driver for the current UNEP Global Partnership for Mercury Transport and Fate Research (UNEP F&T) initiative. The overall focus of the UNEP F&T report is to assess the relative importance of different processes/mechanisms affecting the transfer of mercury (Hg) from emission sources to aquatic and terrestrial receptors and provide possible source-receptor relationships. This transfer occurs through atmospheric transport, chemical transformations and subsequent deposition, and involves the intermittent recycling between reservoirs that occurs prior to ultimate removal of Hg from the atmosphere. Understanding the sources, the global Hg transport and fate, and the impact of human activity on the biosphere, requires improved knowledge of Hg movement and transformation in the atmosphere. An improved understanding of Hg emission sources, fate and transport is important if there is to be a focused and concerted effort to set priorities and goals for Hg emission management and reduction at the national, regional and global levels; and to develop and implement such policies and strategies. To achieve this, a series of coordinated scientific endeavors focused on the estimation of sources, measurement and validation of concentrations and processes, and modeling, coupled with interpretation of the results within a policy framework, is likely to be required.
