Polymeric hollow fiber sorbents were functionalized with amine moieties for improving the carbon dioxide sorption capacity from flue gas to reduce the greenhouse gas emissions from coal-fired power plants. Three different experimental pathways were studied to form the amine-functionalized hollow fiber sorbents. Aminosilane functionalized cellulose acetate (CA) fibers, polyethyleneimine (PEI) functionalized polyamide-imide (PAI, Torlon®) fibers and PEI post-infused and functionalized Torlon®-silica fibers were formed. CO2 equilibrium sorption capacity data were collected by using the pressure decay sorption cell and thermal gravimetric analyzer. Other physio-chemical properties of the amine-functionalized fiber sorbents were characterized by using fourier-transform infrared spectroscopy, elemental analysis, and scanning electronic microscopy. Different reaction conditions were studied on the effect of sorption isotherms. Aminosilane-CA fibers were the first proof-of-concept for forming the amine functionalized polymer hollow fibers. PEI-PAI fibers were designed as a new method to reach enhanced sorption capacities than Aminosilane-functionalized CA fibers. PEI post-infused and functionalized Torlon®-silica fibers have further enhanced sorption capacity; however they easily degrade with similar reaction for forming PEI-PAI fibers. Lumen-side barrier layers were created successfully via post-treatment technique of using the crosslinked Neoprene® polymer onto PEI-functionalized PAI fibers. PEI-functionalized PAI fibers also have good cyclic stability and low heat of sorption.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiv, 74 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 69-71).

Poly(1-methylpyrrol-2-ylsquaraine) (PMPS) particles are a fine blue-black insoluble powder. Scanning electron microscopy (SEM) pictures reveal that the PMPS particles are microspheres with diameters ranging from 1.3 - 4 micrometers (distribution peaking at 1.9 micrometers). The absorption capacity values of PMPS particles were studied for a large majority of the elements in the periodic table in order to establish a pattern or trend in absorption. The elements specifically targeted at the beginning of the research were the biological elements vital to sustain life and the heavy metals that pose a threat to the environment via pollution and poisoning. Fifty-four elements were investigated in total and all absorbed in varying amounts ranging from 0.01 mmol/g for caesium up to 5.66 mmol/g for phosphorous. It was found that varying the initial elemental compound, temperature and solvent concentrations vastly altered the amount of element absorbed. The majority of elements absorbed best when dissolved in hot concentrated hydrochloric acid at 50oC, some preferred cold conditions (4oC) and/or a neutral solvent (water). The freshness of the elemental compound had a huge impact on the absorption capacities, i.e. new compounds absorbed much better than old stock. A comparison between chloride salts and the hydroxides of Group 1 alkali metals revealed that the hydroxides absorbed much better than the salts, sometimes with more than a ten-fold increase. Release profiles were studied for PMPS particles containing eleven different elements when subjected to an aqueous medium. The study focused on some of the elements that are commonly utilised in industry and also the soft acids and bases primarily because they had some of the highest sorption values and the fact that the majority are known to be particularly toxic to man. The amount of ions released varied enormously ranging from 0% release for selenium up to 83% for arsenic. It was interesting to observe that arsenic had the highest percentage release despite having the lowest sorption uptake and selenium had the lowest (zero) percentage release despite having one of the highest sorption uptakes. Analysis of the release data revealed that there appears to be two types of profile emerging. In the first type of profile the metallic ions leached out of the PMPS particles slowly over a period of time until equilibrium was reached whereupon no more ions were released. This happened for the arsenic, copper, lead, mercury, cadmium, silver and gold ions. In the second type of profile all of the free ions were released as soon as water was added, in the first 2 mL aliquot. This happened for the manganese, sodium and caesium ions. It would appear that the ions that have the gradual release profile are the heavier ions on the right hand side of the periodic table, which also means that they are soft acids or bases. The ions that have the second type of profile, where release was achieved in the first aliquot are situated on the left hand side of the periodic table and were all found to be hard acids. Over-coating studies using PMPS particles containing copper and sodium were separately investigated. The results revealed that PMPS-Cu particles when overcoated with a polymer do appear to have a slow release profile.

The recent lowering of the arsenic MCL from 50 ppb to 10 ppb in 2006 will cause many utilities to implement new technologies for arsenic removal. Most of the affected utilities are expected to use adsorption onto solid sorbents for arsenic removal, especially in the arid Southwest, where conserving and re-using water is of utmost importance. This would cause the generation of more than 6 million pounds of arsenic residuals every year, which then would be disposed of in landfills. This thesis effort focuses on the testing of different aluminum and iron (hydr)-oxide based sorbents that are likely to be used for arsenic removal and assessing the behavior of these Arsenic Bearing Solid Residuals (ABSRs) under landfill conditions. It was demonstrated that the Toxicity Characteristic Leaching Procedure (TCLP) test underestimates the arsenic mobilization in landfills. Desorption of arsenic from ABSRs was quantified as a function of the range of pH and concentrations of competitive anions like phosphate, bicarbonate, sulfate and silicate and NOM found in landfills. The effect of pH is much more significant than the anions and NOM. Arsenic release due to competition of different anions is neither additive nor purely competitive. Landfill conditions were simulated inside long-term, continuous flow-through column reactors, and arsenic mobilization from sorbents was measured under those conditions. The results indicate that under reducing conditions, and in the presence of other competitive anions and high organics, microbes reduce arsenate to arsenite, which is a much more mobile species. Fe(III) is also reduced to Fe(II) under these conditions. Arsenic is transported in the particulate phase, associated with the iron, much more than in the dissolved phase. It was also observed that the sorbent itself might leach away at a faster rate than the arsenic sorbate causing a depletion of surface sites and a sudden spike in the release rate of arsenic, after a long residence time. Finally, investigation of different solid sorbents indicate, that the rate of leaching and the form of arsenic released varies widely and is independent of the respective adsorption capacities, even under similar leaching conditions.

Hydration of neutral and ionic species at interfaces plays an important role in a wide range of natural and artificial, fundamental processes, including in energy systems as well as biological and environmental systems. Owing to the hydration water at the interface, the rate and extent of various types of chemical reactions may be significantly enhanced. The hydration of ions does not only affect the physical structure and dynamics of water molecules, but also chemical energy transfers through the formation of highly structured water complexes that form in the bulk water. Indeed, dehydration could promote the energy levels of aqueous compounds. These shifts in energy states may receive wide applications such as in energy storage with anhydrous salts, enhancement of the free energy of binding ligands to biological systems, and gas separation using a water-modified basicity of ionic sorbents. Of particular interest in this study is a novel technology for direct air capture of carbon dioxide, driven by the free energy difference between the hydrated and dehydrated states of an anionic exchange resin and its effect on the affinity of CO2 to the resin. In this dissertation, we first demonstrate an unconventional reverse chemical reaction in nano-confinement, where changes in the amount of hydration water drive the direction of an absorption/desorption reaction, and apply this novel mechanism of controlling the behavior of a sorbent to air capture of CO2. The reduction of the number of water molecules present in the pore space promotes the hydrolysis of CO32- to HCO3- and OH-. This phenomenon has led to a nano-structured CO2 sorbent that binds CO2 spontaneously in ambient air when the surrounding is dry, while releasing it when exposed to moisture. We name this phenomenon of loading and unloading a sorbent with water a hydration swing. Wide application of hydration swings to absorb CO2 requires a detailed understanding of the molecular mechanisms of the hydration induced energy change at the ion hydration/solid interface. Using atomistic simulations, the mechanism of CO2 absorption with respect to water quantity was elucidated via the explorations of the reaction free energy of carbonate ion hydrolysis in a confined nano-environment. Next, based on the understanding of the underlying driving mechanism, a systematic study of the efficiency of effective hydration-driven CO2 capture with respect to different pore sizes, hydrophobic/hydrophilic confined layers, temperatures, and distances of cations may further benefit the optimization of the CO2 capture system, in terms of the energetically favorable states of hydration ions in dry and wet conditions. This part of the research may sheds some insights on future research of designing high efficiency CO2 capture sorbent according to adjust the above described parameters. This unconventional reverse chemical reaction is not restricted to carbonate ions in nano-confined space. This is an universal phenomenon where hydrated ions carrying several water molecules in nanoscopic pores and in the natural atmosphere under low relative humidity. Such formations of hydrated ions on interfaces with the high ratio of ions to water molecules (up to 1:1) are essential in determining the energetics of many physical and chemical systems. In this dissertation, we present a quantitative analysis of the energetics of ion hydration in nanopores based on computational molecular modeling of a series of basic salts with the different quantities of water molecules. The results show that the degree of hydrolysis of basic salts with several water molecules is significantly different from the conventional degree of hydrolysis of basic salts in bulk water. The reduction of water molecules induces divalent and trivalent basic ions (S2-, CO32-, SO32-, HPO42-, SO42-, PO43-) to hydrolyze water into a larger amount of OH- ions, conversely, it inhibits monovalent basic ions (CN-, HS-) from hydrolyzing water. This finding opens a vast scope of new chemistry in nanoconfined water. Ion hydrations containing interfaces play an important role in a wide range of natural and fundamental processes, but are much less noticeable currently. This thesis sheds some lights on a vast number of chemical processes of hydrated ion pairs containing interfaces, and design possibility for more efficient energy-saving sorbents.

Over the last decade, the miniaturization of analytical systems has become an increasingly important and interesting research area. Miniaturized systems offer many advantages, including reduced reagent and sample consumption, shorter analysis times, portability and disposability. This dissertation describes novel approaches in this direction, focusing on two areas: the miniaturization of existing column chromatographic systems and the development of microfluidic systems in which the separation is performed in a channel on a microchip. A new type of methacrylate-based monolithic capillary columns for liquid chromatography and capillary electrochromatography were prepared within the confines of fused-silica tubing using Starburst dendrimers to affect porosity. The polyamidoamine (PAMAM) dendrimers were incorporated into a solution of functionalized monomer, cross-linker, solvents, and polymerization initiator. Thermal polymerization, followed by the removal of solvent and dendrimers, produced a continuous rod of polymer with uniform porosity. Different column porosities were obtained by varying the amount of the dendrimer template. The chromatographic performance of these monolithic columns was evaluated using a peptides mixture obtained by tryptic digestion of chicken egg lysozyme. A distinct advantage of polymer monolithic stationary phases over conventional packed chromatographic beds is the ability to prepare them easily and rapidly via free radical polymerization within the channels of a microfluidic device. In this work, continuous polymeric beds were prepared within a channel of three different microchip substrates: glass, poly(dimethylsiloxane) and polycarbonate. The methacrylate-based monolith was cast in-situ via UV-initiated polymerization. The functionalization of the inner wall of the channel with methacryloyl groups enabled the covalent binding of the monolith to the wall. The morphology of the wall-anchored monolith was studied by SEM of chip sections, and by SEM of an extruded segment of non-anchored monolith from a separate chip. / Graduation date: 2005

No description available.

Direct capture of CO2 from ambient air is a developing technology, which is capable of removing CO2 directly from the atmosphere. Moreover, this technology is independent from sources of CO2 emissions. Hence, it can be set up at locations where pure stream of CO2 is needed such as in enhanced oil recovery. In this research, the performance of pelletized and natural limestone for CO2 capture from air in a fixed bed is studied. To compare the performance of sorbents for air capture, the effects of particle type (natural limestone and pelletized limestone), particle size (250-425 µm and 425-600 µm), gas flowrate (0.5 L/min and 1 L/min), and relative humidity, on the breakthrough time, breakthrough shape, and the global reaction rate are examined. Moreover, carbonation decay of sorbents over series of capture and regeneration cycles is studied. If the inlet stream (air) is humidified at 50% relative humidity, but the lime sorbents are not pre-hydrated, an axially non-uniform carbonated bed results. This phenomenon is due to the partial carbonation of sorbents at the first layers of the bed. While there is a competition between CO2 and water to react with CaO, partial carbonation reaction on the surface of the sorbents not only prevents further hydration, but also decreases the reaction rate at the surface. However, in comparison with a dry system where relative humidity was negligible and sorbents were not pre-hydrated, the observed carbonation conversion was higher. The best results were seen from experiments with pre-hydrated sorbents and humidified inlet stream. The smaller sorbent particles had a better performance (sharper breakthrough curve and longer breakthrough time) due to their greater surface area. A gas-solid reaction model was fitted to the breakthrough curves. Since at the beginning of carbonation there is no resistance of the product layer, it can be assumed that the process is reaction controlled. While after formation of the product layer (CaCO3), it becomes diffusion controlled. Results from fitted data also confirmed these conclusions. Moreover, each of sorbent went through 9 cycles and after each cycle the carbonation conversion of the sorbents was measured by TGA and the surface area by BET.

Polymeric hollow fiber sorbents were functionalized with amine moieties for improving the carbon dioxide sorption capacity from flue gas to reduce the greenhouse gas emissions from coal-fired power plants. Three different experimental pathways were studied to form the amine-functionalized hollow fiber sorbents. Aminosilane functionalized cellulose acetate (CA) fibers, polyethyleneimine (PEI) functionalized polyamide-imide (PAI, Torlon® fibers and PEI post-infused and functionalized Torlon®-silica fibers were formed. CO₂ equilibrium sorption capacity data were collected by using the pressure decay sorption cell and thermal gravimetric analyzer. Other physio-chemical properties of the amine-functionalized fiber sorbents were characterized by using fourier-transform infrared spectroscopy, elemental analysis, and scanning electronic microscopy. Different reaction conditions were studied on the effect of sorption isotherms. Aminosilane-CA fibers were the first proof-of-concept for forming the amine functionalized polymer hollow fibers. PEI-PAI fibers were designed as a new method to reach enhanced sorption capacities than Aminosilane-functionalized CA fibers. PEI post-infused and functionalized Torlon®-silica fibers have further enhanced sorption capacity; however they easily degrade with similar reaction for forming PEI-PAI fibers. Lumen-side barrier layers were created successfully via post-treatment technique of using the crosslinked Neoprene® polymer onto PEI-functionalized PAI fibers. PEI-functionalized PAI fibers also have good cyclic stability and low heat of sorption.

Thesis (Ph. D.)--Ohio University, November, 1993. / Title from PDF t.p.