MS, University of Cincinnati, 0, Engineering and Applied Science: Environmental Science

An innovative method of recovering carbon dioxide from flue gas has been studied whereby reclaimed magnesium hydroxide is used as the scrubbing agent. A slurry of magnesium hydroxide (Mg(OH)2) was used to separate carbon dioxide (CO2) from flue gas in an absorber. Thermodynamic equilibrium calculations indicate that by scrubbing flue gas already cleaned of its sulfur dioxide (SO2) concentration, 99% of the CO2will react to form more soluble magnesite (MgCO3) and hydromagnesite ((Mg4(CO3)3(OH)2) in the scrubber, and that CO2 will be released when the resulting solution is heated. Turbine waste heat can be used to heat the CO2-laden slurry, creating a rich stream of CO2 gas for further processing. The Mg(OH)2 slurry can then be recycled for further CO2 absorption.

This project established proof of concept of this model by studying the reaction characteristics of the absorption of CO2 by solutions containing Mg(OH)2 in a bench-scale bubble column operated under realistic conditions. An NDIR analyzer measured the CO2 concentration in the exit gas. From this data, the steady state reaction characteristics have been determined using a simulated flue gas of 5%, 10%, and 20% CO2, Mg(OH)2 slurry concentrations of 0.027, 0.068, and 0.14 moles per liter at temperatures of 25, 45, and 65oC. Both commercially available Mg(OH)2 and reclaimed Mg(OH)2 were used. Finally, the mass transfer coefficient K'AG was calculated for the system.

Committee: Timothy Keener Ph.D. (Committee Chair); Sumana Udom Keener Ph.D. (Committee Member); Soon Jai Khang Ph.D. (Committee Member) Subjects: Environmental Science

PHD, Kent State University, 2017, College of Arts and Sciences / Department of Chemistry

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 oC) and elevated(60-120 oC) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 oC via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60- 120 oC. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per (open full item for complete abstract)

Committee: Mietek Jaroniec Prof (Advisor); Anatoly Khitrin Prof (Committee Member); Songping Huang Dr (Committee Member); Qi-Huo Wei Dr (Committee Member); Oleg Laverentovich Dr (Committee Chair) Subjects: Chemical Engineering; Chemistry; Climate Change; Earth; Ecology; Energy; Environmental Engineering; Environmental Science; Environmental Studies; Inorganic Chemistry; Materials Science; Nanoscience; Nanotechnology; Polymer Chemistry; Water Resource Management

Doctor of Philosophy, The Ohio State University, 2008, Chemical Engineering

Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area for both mobile and stationary applications, particularly for fuel cell vehicles. Compared to inner combustion engines, PEMFCs can decrease pollution and increase the energy efficiency. New proton-exchange membrane (PEM) materials and new technologies for fuel processing are the most important and challenging parts in this research field.Nafion® and other perfluorinated sulfonic acid membranes are still the only commercial PEM materials so far. However, their high cost and low performance at high temperatures significantly limit their applications. In this research, new five-member ring and six-member ring soft segment-containing sulfonated polyimide (SPI)-based membranes and new sulfonated polybenzimidazole (SPBI)-based membranes were successfully synthesized. The resulting membranes could outperform Nafion® at various conditions, particularly at high temperatures and low relative humidities (RHs). Moreover, the new membrane materials should be much more cost-effective since the starting materials are more than two orders of magnitude less expensive than those for Nafion® membranes. In the research on fuel processing, amine carriers were successfully incorporated into the SPBI copolymer or the crosslinked poly(vinyl alcohol) (PVA) matrix, which could react reversibly with acid gases, such as CO2. Thus, the resulting membranes have shown very promising CO2 selectivity vs. the other gas molecules, such as H2 and CH4, by the facilitated transport mechanism. These newly synthesized membranes have many applications in the field of gas separations, including the low pressure synthesis gas purification for fuel cell applications, the high pressure synthesis gas purification for refinery industrial applications, and the high pressure natural gas purification to obtain high purity CH4.

Committee: W.S. Winston Ho PhD (Advisor); L. James Lee PhD (Committee Member); Kurt Koelling PhD (Committee Member); Isil Erel PhD (Committee Member) Subjects: Chemical Engineering; Energy; Polymers

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

In this work, new CO2-selective membranes were synthesized and their applications for fuel cell fuel processing and synthesis gas purification were investigated. In order to enhance CO2transport across membranes, the synthesized membranes contained both mobile and fixed site carriers in crosslinked poly(vinyl alcohol). The effects of crosslinking, membrane composition, feed pressure, water content, and temperature on transport properties were investigated. The membranes have shown a high permeability and a good CO2/H2 selectivity and maintained their separation performance up to 170°C. One type of these membranes showed a permeability of 8000 Barrers and a CO2/H2selectivity of 290 at 110°C. The applications of the synthesized membranes were demonstrated in a CO2-removal experiment, in which the CO2 concentration in retentate was decreased from 17% to < 10 ppm. With such membranes, there are several options to reduce the CO concentration of synthesis gas. One option is to develop a water gas shift (WGS) membrane reactor, in which both WGS reaction and CO2-removal take place. Another option is to use a proposed process consisting of a CO2-removal membrane followed by a conventional WGS reactor. In the membrane reactor, a CO concentration of less than 10 ppm and a H 2concentration of greater than 50% (on dry basis) were achieved at various flow rates of a simulated autothermal reformate. In the proposed CO2-removal/WGS process, with more than 99.5% CO2 removed from the synthesis gas, the CO concentration was decreased from 1.2% to less than 10 ppm (dry), which is the requirement for fuel cells. The WGS reactor had a gas hourly space velocity of 7650 h-1 at 150°C and the H2 concentration in the outlet was more than 54.7% (dry). The applications of the synthesized CO2-selective membranes for high-pressure synthesis gas purification were also studied. We studied the synthesized membranes at feed pressures > 200 psia and temperatures ranging from 100-150 °C. The effects of (open full item for complete abstract)

Committee: W.S. Winston Ho (Advisor) Subjects: