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Carbon dioxide transport and uptake in concrete during accelerated carbonation curingKashef Haghighi, Sormeh January 2012 (has links)
Carbon dioxide (CO2) is the dominant greenhouse gas resulting from many anthropogenic activities, mainly combustion of fossil fuels. One of the strategies to mitigate CO2 emissions is considered to be carbon dioxide capture and storage (CCS). The current storage methods focus on enhanced oil recovery, underground geological storage, disposal in deep oceans, and ex situ mineral carbonation of abundant metal oxide minerals such as olivine, serpentinite and wollastonite.During mineral carbonation, a gas stream rich in CO2 is reacted with mineral metal oxides to form thermodynamically stable carbonates. These carbonated minerals, however, store CO2 but do not produce any materials that are of value. Accelerated carbonation curing of concrete can be used as a mineral sequestration method with the advantage of producing a value-added concrete product. During accelerated carbonation curing of concrete, CO2 is reacted with cement and stored as a solid calcium carbonate in concrete construction products. Among the concrete products, non-reinforced precast concrete, such as blocks and bricks, can be used for carbonation curing. In previous studies, pressurized chambers have been used for accelerated CO2 curing of concrete, where a high pressure of CO2 is required for sufficient gas diffusion in concrete and homogeneous carbonation. In this research, a flow-through carbonation reactor was used for concrete curing and the rate and extent of CO2 uptake by concrete was studied. One of the advantages of the carbonation reactor applied in this study is that significantly less energy for gas mixture compression is required compared to a CO2 pressure chamber.The overall objective of this thesis was to develop and assess the performance of an accelerated carbonation curing reactor for concrete using an advective flow of flue gas. The rate and extent of CO2 uptake by concrete in a 1-D flow-through carbonation reactor were studied and compared with the published results on CO2 uptake in pressurized chambers using diffusive flow of CO2. The factors limiting the CO2 uptake were studied through experimental observation as well as mathematical modeling of CO2 transport and reaction in concrete during accelerated carbonation curing. Carbonation efficiencies of 16-20% attained in the flow-through reactor were comparable to those obtained for static CO2 pressure chambers. The extent of CO2 uptake was limited by formation of solid calcium carbonate in micro-scale pores. Intermittent carbonation experiments showed that the carbonation efficiency was limited in part by slow dissolution and/or diffusion of dissolved reactive components in the concrete matrix. The electron microprobe imaging technique used in this study also confirmed formation of solid calcium carbonate which filled up the narrow pores (<4 µm). The uptake efficiency reached 67% when cement was carbonated in an aqueous suspension in a completely mixed flow-through reactor where the effect of pore blockage was eliminated and a higher percentage of reacting surface area was exposed to dissolved CO2. However, formation of a calcium carbonate layer still inhibited diffusion of dissolved calcium and CO2 through this layer. In the presence of the calcium carbonate layer and other carbonation products like silica (SiO2 gel), and at partial pressure of CO2 used for carbonation, the aqueous solution reached a chemical equilibrium and carbonation ceased before the maximum theoretical uptake could be achieved. The effect of physico-chemical processes on CO2 uptake during carbonation curing was also studied using a mathematical model. Equations describing the CO2 transport by advection and dispersion in concrete pore space, dissolution in pore water and reaction with reactive cement species were solved numerically. The initial concentration of cement species were calculated based on a hydration model which was developed to simulate the 4 hours of hydration time before carbonation starts. / Le dioxyde de carbone (CO2) est le gaz d'effet de serre dominant, résultat des plusieurs activités anthropogènes, dont le plus important est la combustion des combustibles fossiles. Une des stratégies qui a pour but d'atténuer des émissions de CO2 est le captage et le stockage du dioxyde de carbone (CCS en anglais). Les méthodes courantes de stockages incluent la récupération assistée du pétrole, le stockage géologique souterrain, la disposition sous les océans profonds, et la carbonatation minérale ex situ des gisements abondants des oxydes métalliques, comme l'olivine, la serpentinite et la wollastonite. Pendant la carbonatation minérale, un jet de gaz riche en CO2 est mis à réagir avec les oxydes des métaux minéraux pour former des carbonates thermodynamiquement stables. L'élimination des minerais carbonatés, cependant, stocke le CO2 mais ne produit pas des matériaux de valeurs ajoutées. La carbonatation accélérée pour murir du béton peut être employée comme une méthode de la séquestration minérale avec l'avantage de produire un produit de béton à valeur ajoutée. Pendant la carbonatation accélérée pour murir du béton, le CO2 est mis à réagir avec le ciment et stocké comme carbonate de calcium solide dans les produits de béton utilisés en construction. Les produits en béton non-armés et préfabriqués tel que les blocs et les briques sont ceux qui peuvent être faits avec la méthode carbonatation pour murir le béton. Lors des études précédentes, des chambres sous pression ont été employées pour accélérer le durcissement du CO2 au béton, où une haute pression de CO2 est exigée pour une diffusion suffisante de gaz et une carbonatation homogène. Dans cette recherche, un écoulement à travers le réacteur de carbonatation a été utilisé pour le durcissement du béton; le taux et l'ampleur de la prise de CO2 par le béton ont été également étudiés. Un des avantages du réacteur de carbonatation appliqué dans cette étude est que l'énergie exigée est nettement inférieure, comparé à une chambre sous pression de CO2. L'objectif global de cette thèse est de développer et d'évaluer la performance de l'exécution d'une carbonation accélérée traitant le réacteur pour le béton en utilisant un flux advectif des émissions gazeuses. Le taux et l'ampleur de la prise de CO2 par le béton dans un écoulement unidimensionnel (1-D) à travers le réacteur de carbonation ont été étudiés et comparés aux résultats publiés sur la prise de CO2 dans les chambres pressurisées en utilisant l'écoulement diffusif du CO2. Les facteurs limitant la prise de CO2 ont été étudiés à travers l'observation expérimentale ainsi que la modélisation mathématique du transport et de la réaction du CO2 dans le béton durant le traitement accéléré de la carbonation. Les efficacités de carbonatation de 16-20% atteintes dans l'écoulement à travers le réacteur sont comparables à celles obtenues pour les chambres de pression statiques de CO2. L'ampleur de la prise de CO2 a été limitée par la formation du carbonate de calcium solide dans des micro et macro-pores. Les expériences intermittentes de carbonatation ont prouvé que l'efficacité de carbonatation a été limitée en partie par la dissolution et/ou la diffusion lente des composants réactifs dissous dans la matrice de béton. La technique d'imagerie du micro-probe d'électron utilisé dans cette étude a également confirmé la formation du carbonate de calcium pendant la carbonatation, qui a rempli les micropores. L'efficacité de prise a atteint 67% quand le ciment a été carbonaté sous la forme de boue dans un réacteur qui contienne un mélange de suspension aqueux (à travers du quel écoule le CO2), où l'effet du colmatage des pores a été éliminé et un pourcentage plus élevé de la superficie de surface de réaction a été exposé au CO2 dissous. Cependant, la formation d'une couche de carbonate de calcium empêchait encore la diffusion du calcium dissous et du CO2 à travers cette couche.
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Surfactant effects on solubilization, dissolution and biodegradation of polycyclic aromatic hydrocarbons from non-aqueous phase liquidsBernardez, Leticia Alonso January 2005 (has links)
The objective of the thesis was to investigate the effects of nonionic surfactants on the dissolution and biodegradation of polycyclic aromatics hydrocarbons (PAHs) from a multicomponent non-aqueous phase liquids (NAPLs). / The extent of solubilization of the PAHs in the surfactant micelles increased linearly with the PAH mole fraction in the NAPL. The micelle-water equilibrium partition coefficient of both PAHs was found to increase with the size of the polar shell region of the micelle rather than the hydrophobic core of the micelle and the presence of PAHs in the shell region of the micelles was confirmed by 1H-NMR analysis. Competitive solubilization effects were also observed. / The process of dissolution of the PAHs in surfactant aqueous solutions was investigated with particular emphasis on the influence of the surfactant molecular structure and dose on the kinetics of the solubilization process. The solubilization of both PAHs was limited by the rates of desorption of mixed micelles from NAPL and their rates of diffusion at high concentrations of surfactant. It was found that the dissolution rates were directly related to the length of the alkyl portion of the surfactant. The micellar volume also seemed to affect the rates. The addition of surfactants resulted in an enhancement of biodegradation rates at the initial stages because of the rapid partitioning of PAHs from micelles into the aqueous phase where uptake occurs. But at latter period, biodegradation was severely limited by the dissolution of PAHs into the true aqueous phase.
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Organic phosphorus pollution the fate of phytate in the Chesapeake Bay watershed.Hill, Jane Emily. Unknown Date (has links)
Thesis (Ph.D.)--Yale University, 2006. / (UnM)AAI3214223. Adviser: Menachem Elimelech. Source: Dissertation Abstracts International, Volume: 67-04, Section: B, page: 2171.
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Zero-valent iron (ZVI) nanoparticles: The core-shell structure and surface chemistry.Li, Xiaoqin. January 2007 (has links)
Thesis (Ph. D.)--Lehigh University, 2007. / Adviser: Wei-xian Zhang.
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Environmentally benign synthesis of sodium hydroxide and hardness removal using ion exchange fibers.Greenleaf, John E. January 2007 (has links)
Thesis (Ph.D.)--Lehigh University, 2007. / Adviser: Arup K. SenGupta.
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The role of wind-waves and currents on vertical mixing in shallow water bodies: Implications for phytoplankton distributionJones, Nicole Louise. Unknown Date (has links)
Thesis (Ph.D.)--Stanford University, 2007. / (UMI)AAI3253498. Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1212. Advisers: Stephen Monismith; Janet Thompson.
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Roles of background compound molecular size and adsorbent pore size distribution in competitive adsorption on activated carbon /Tang, George Chun Chung. January 2007 (has links)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1245. Advisers: Benito J. Marinas; Vernon L. Snoeyink. Includes bibliographical references (leaves 80-86) Available on microfilm from Pro Quest Information and Learning.
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Nature's sensors : using plants as an alternative monitoring approach for subsurface contamination /Gopalakrishnan, Gayathri. January 2008 (has links)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3201. Adviser: Barbara S. Minsker. Includes bibliographical references (leaves 124-135) Available on microfilm from Pro Quest Information and Learning.
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Desorption of trace contaminants from activated carbon : effect of strongly-competing and pore-blocking background organic matter on desorption kinetics /To, Priscilla Chu-Wai. January 2008 (has links)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3206. Adviser: Vernon L. Snoeyink. Includes bibliographical references (leaves 81-90) Available on microfilm from Pro Quest Information and Learning.
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Optical remote sensing of airborne particulate matter to quantify opacity and mass emissions /Du, Ke, January 2007 (has links)
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7580. Adviser: Mark J. Rood. Includes bibliographical references (leaves 119-126) Available on microfilm from Pro Quest Information and Learning.
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