Master of Science, The Ohio State University, 2019, Chemical Engineering

Fossil fuel power plants often generate sulfur species such as hydrogen sulfide or sulfur dioxide due to the sulfur content of the raw feedstocks. To combat the associated environmental, processing, and corrosion issues, facilities commonly utilize a Claus process to convert hydrogen sulfide to elemental sulfur and water. Unfortunately, the Claus process suffers in efficiency from a thermal oxidation, or combustion, step and high equilibrium reaction temperatures. In this work, two different chemical looping process configurations towards recovering sulfur and H2 are investigated: (1) 3 reactor system (SR) for sulfur recovery; (2) 2 reactor system (SHR) for sulfur and H2 recovery. Since, H2 yield and sulfur recovery in a single thermal decomposition reactor in the SHR system is limited by low H2S equilibrium conversion, a staged H2 separation approach is used to increase H2S conversion to H2 using a staged separation methodology. Steady-state simulations and optimization of process conditions are conducted in Aspen Plus v10 simulation software for the chemical looping process configurations and the Claus process. An energy and exergy analysis is done for the chemical looping and Claus processes to demonstrate the relative contribution to exergy destruction from different unit operations as well as overall exergy and energy efficiency. The two chemical looping process configurations are compared against the Claus process for similar sulfur recovery in a 629 MW integrated combined cycle gasification power plant. The SHR system is found to be the most attractive option due to a 97.11% exergy efficiency with 99.31% H2 recovery. The overall energy and exergy efficiencies of this chemical looping system are 14.74% and 21.54% points higher than the Claus process, respectively, suggesting more efficient use of total input energy.

Committee: Liang-Shih Fan PhD (Advisor); Bhavik Bakshi PhD (Committee Member) Subjects: Energy; Engineering

Bachelor of Science (BS), Ohio University, 2024, Chemistry

Petroleum-based plastic has caused devastating effects on the health of the natural world and people from its derivation from non-renewable resources and complex recycling processes. Polylactic acid (PLA) is a bio-based plastic that has the potential to alleviate these issues. In this experiment, the ring-opening polymerization of lactide to PLA is catalyzed by two organic catalysts, resulting in a low molecular weight polymer with a degradation temperature around 300 – 340 °C and glass transition temperatures between 27 and 33 °C. The polymer is successfully degraded upon exposure to 50 % aqueous ethanol at high temperatures, resulting in a decrease in theoretical number average molecular weight. With further research, PLA exhibits considerable potential for chemical recycling to close the loop of the production process and achieve a circular economy.

Committee: Lauren McMills (Advisor); Katherine Cimatu (Advisor) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2024, Chemical Engineering

Humankind is constantly engaged in the pursuit of innovative approaches to improve process efficiency, economics, and safety. Chemical looping, a novel methodology involving a reaction carried out in multiple stages facilitated by a solid intermediate called a carrier, offers additional degrees of freedom for process intensification and product optimization. This dissertation involves the development and scale-up of new alternatives for several conventional catalytic processes, leveraging the benefits offered by the chemical looping platform to enhance operational flexibility, product yields, and process safety. The first part of this dissertation focuses on the development of alternative processes for the removal of two common industrial pollutants, NOx and H2S. NOx, a harmful pollutant generated during the processing of fossil fuels, is conventionally treated using the Selective Catalytic Reduction (SCR) process, which faces challenges such as high costs and limited operational flexibility. The chemical looping process achieves over 99% NOx removal efficiency, demonstrating significant improvements of 9% and 18% in exergy and effective thermal efficiency, respectively, over the state-of-the-art SCR process. H2S, another harmful pollutant generated during the processing of fossil fuels, is conventionally removed using the Claus Process, which encounters drawbacks such as thermodynamic limitations on conversion and the loss of valuable H2 in the form of H2O. This dissertation introduces a nano-scaled iron sulfide carrier, demonstrating ~70% enhancement in reactivity over traditional bulk carriers in chemical looping H2S splitting into H2 and sulfur. Furthermore, process analyses indicate an improvement of ~22 percentage points in energy and ~8 percentage points in exergy efficiency over the Claus process. The second part of this dissertation involves the development of new processes for commodity chemical production. Formaldehyde, an essential organic chemical wit (open full item for complete abstract)

Committee: Prof. Liang-Shih Fan (Advisor); Prof. Jeffrey Chalmers (Committee Member); Prof. Lisa Hall (Committee Member); Prof. Dawn Anderson-Butcher (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Chemical Engineering

Hydrogen has gained significant attraction nowadays as a clean energy source to prevent the greenhouse effect mainly caused by CO2. Currently, industrial hydrogen production is mainly based on thermal-chemical methods for economic reasons, including steam methane reforming (SMR) and auto-thermal reforming of methane (ATR). Chemical looping, as a versatile technology platform, has emerged as a promising technology to produce pure hydrogen with CO2 capture in a simple and efficient manner. In this study, two novel chemical looping processes are introduced and studied for hydrogen production with natural gas as the feedstock. Firstly, new schemes for the chemical looping water splitting scheme (CLWS) characterized by integrated turbines combined CLWS systems (ITC-CLWS) are introduced to accomplish a co-generation of hydrogen and electric power. With natural gas as a feedstock, the ITC-CLWS processes under ambient and pressurized operating conditions are simulated and analyzed based on desired riser gas velocities that transport solid particles from the combustor to the reducer. The reactors for the ITC-CLWS processes are designed by considering the gas-solid reaction kinetics and multiphase flow properties. Moreover, a novel operating strategy is conceived to yield hydrogen and electric power in varied proportions in response to their respective fluctuating needs. Secondly, using natural gas as the feedstock, another new scheme -- chemical looping combustion with a moving bed reducer coupled with the steam methane reforming (MCLC-SMR), is proposed and simulated for hydrogen production. In the new scheme, the stage injection strategy can efficiently reduce the chemical looping particle requirements. The performance results of the ITC-CLWS and MCLC-SMR processes are compared with other chemical looping processes and conventional industrial processes, including SMR and ATR, for hydrogen production. This study reveals that ITC-CLWS and MCLC-SMR can efficiently enhance ther (open full item for complete abstract)

Committee: Liang-Shih Fan (Advisor); Isamu Kusaka (Committee Member); Shang Zhai (Committee Member); Ellen Thompson (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2022, College of Sciences and Health Professions

Poly-l-lactic acid has been of great interest to the medical profession in recent years because of its biodegradability and biocompatibility. The biodegradation rate can be controlled by its crystallinity content. One method to modify its crystallinity content is by cold drawing. Raman spectroscopy is utilized to distinguish between the different crystalline content on the sample. However, a chemical imaging method is needed to characterize the polymer on the macro level. Chemical imaging using Raman spectroscopy is an important method of characterization that is non-invasive and non-destructive. The emphasis of my research has been to develop a method to characterize the crystalline content of poly-l-lactic acid using Raman chemical imaging and multivariate analysis to construct a robust image of the crystalline map. No Technique exists for this purpose. Multivariate analysis has been beneficial for reducing the time spent on finding correlations in a vast amount of data. Principal component analysis has been one of the most common methods for reducing the data dimensions to those that are the most responsible for the observed variation in the data. However, the method is scale variant and blends qualitative and quantitative information in a way that can render misleading results. Classical least squares has also been used in chemical imaging, but it requires substantial training data. In this document, we introduce a modified version of reduction of spectral images (ROSI), a multivariate analysis method that heavily modifies principal component analysis to reduce the amount of data while still prioritizing the minority pixel population on the image data to retain more of the analytically meaningful characters of the data. Preprocessing of the data is an important step to obtaining robust results and can involve multiple steps depending on the application. It often serves as an essential step for removing irrelevant information from the raw data. One important pr (open full item for complete abstract)

Committee: John Turner II (Advisor); Warren Boyd (Committee Member); Baochuan Guo (Committee Member); Xue-Long Sun (Committee Member); Petru Fodor (Committee Member) Subjects: Biomedical Engineering; Chemistry; Materials Science; Plastics

Doctor of Philosophy, The Ohio State University, 2022, Chemistry

As Analytical Chemists we are constantly demanding more of our methods: greater selectivity, lower detection limits, wider utility, reduced complexity, etc. We are frequently tasked with meeting the ever-changing demands of the many evolving fields that require analytical expertise including the medical, environmental, forensic, and consumer industries. In many cases, new techniques are introduced, or old methods are refined and matured to tackle these challenges. However, there are still times when the development of new and improved instrumentation lags behind demand, and traditional chemical principles must be used to bolster current methods. Chemical derivatization is a well-established approach to overcoming the limitations of available instrumentation and methods. It is commonly used to expand detectability into adjacent areas in the chemical space, to drive signal enhancement for analytes that exhibit low sensitivity, and to improve selectivity in separations. However, conventional protocols can be resource intensive, complex, and time-consuming. The overarching aim of this dissertation is to leverage the virtues of derivatization while mitigating its shortcomings by shifting the procedure from the benchtop to the analytical platform. We do this using a specialized electrospray platform that allows us to carry out chemical reactions rapidly and online during the analysis. Although this approach can be useful for a wide range of compounds, we focus on saccharides due to their broad physiological importance. Recent potential applications in disease diagnosis and monitoring have brought about a need for new analytical tools capable of detecting saccharides at low concentrations and/or for volume-limited samples. Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (LC-ESI-MS) is the preferred methodology for these compounds due its inherent specificity. However, saccharides generally exhibit limited sensitivity in LC-ESI-MS because they are not (open full item for complete abstract)

Committee: Abraham Badu-Tawiah (Advisor) Subjects: Analytical Chemistry; Chemistry

Doctor of Philosophy, The Ohio State University, 2021, Translational Plant Sciences

Enzyme catalyzed reactions can be started, stopped, and throttled by regulating ion concentration in solution. The flow of charge through solution is related to the flow of electrons through an electric circuit using electrochemistry. However, current electrochemical methods to vary ionic concentration have been largely limited to the electrode surface, making it impractical to exploit ionic concentration as a control variable in traditional enzyme assays. This dissertation presents an electrochemical cell, termed a programmable chemical actuator (PCA), that uses selective electrochemical REDOX reactions to regulate the spatiotemporal concentration of ions that control enzyme catalyzed reaction kinetics. Polypyrrole was polymerized and equilibrated to impart H+, Na+, K+, Ca2+, Mg2+, Mn2+, OH-, HPO4-, or Cl- ion selectivity to working electrodes. PCA selectivity persisted when cycled in complex electrolyte. Duplex pulse amperometry overcame the ion transport limitations observed when using single step amperometry to control PCAs. The spatial distribution of the electrochemical gradient within the PCA control volume was tuned between 0.5% and 87% of the electrochemical cell's volume by controlling the distance between the reference electrode and the working electrode. The magnitude of the ion motive force was maximized when the working electrode's aerial charge density was 0.5 C*cm-2. Reversible control over pH, ranging from 3.9 to 10.2, is demonstrated by H+ actuators (pH 3.9 - pH 7.8) and OH- actuators (pH 6.1 - pH 10.2) as measured by pH indicating dyes. PCAs were used to reversibly control the pH-dependent kinetics of alkaline phosphatase during a spectrophotometric enzyme assay. A 50% reduction duty cycle increased dephosphorylation rate 1.5 times the initial rate and an 80% oxidation duty cycle halted the dephosphorylation reaction. The mean activity prior to REDOX cycling did not differ significantly (p=0.05) from the mean after REDOX cycling, indicating the PC (open full item for complete abstract)

Committee: Vishnu Sundaresan Ph.D. (Advisor); Katrina Cornish Ph.D. (Committee Co-Chair); Tom Mitchell Ph.D. (Committee Member); Jon Parquette Ph.D. (Committee Member); Chandan Sen Ph.D. (Committee Member); Katelyn Swindle-Reilly Ph.D. (Committee Member) Subjects: Biology; Engineering; Materials Science; Mechanical Engineering; Molecular Biology

Master of Science, The Ohio State University, 2020, Environment and Natural Resources

Aminomethylphosphonic acid (AMPA) is a microbial degradation product of the herbicide glyphosate, and industrial phosphonates. In addition to possible negative effects on human health, AMPA may inhibit soil microbial growth and alter the soil microbial community composition. Strong soil adsorption causes AMPA to persist in the environment, slowing degradation, and making AMPA a possible long-term environmental contaminant. Review of the research literature in Chapter 1 revealed knowledge gaps concerning the effects of AMPA on soil microorganisms in different soil types and in isolation from glyphosate. Although there have been many studies on the behavior and effects of glyphosate in different soil types, there is scarce data that isolates the effects of AMPA. Therefore, the research objectives were to (1) study the effects of AMPA on soil microorganisms, (2) investigate how soil type affects AMPA bioavailability, (3) determine if chemical extractability can be used to predict AMPA bioavailability, and (4) investigate AMPA in isolation from glyphosate. Based on the literature, the hypotheses were that (1) a higher concentration of AMPA would be found to have a greater effect on soil microorganisms, and (2) bioavailability would be less in soils with high clay, high iron and aluminum oxides, and low pH. Chapter 2 describes a 139-day incubation study on three diverse soils with no exposure to glyphosate. These soils included a sandy soil, and two high clay soils with different mineralogy. Three field relevant concentrations of AMPA, including the control, were applied directly to soil, and the effects of AMPA on soil microbial respiration and phospholipid fatty acids were analyzed. Chapter 3 describes an investigation of AMPA bioavailability using chemical extraction, and correlations of extractable AMPA with microbial responses. Total soil carbon and pH appeared to be the most important soil factors affecting response to AMPA. Based on PLFA results, AMPA w (open full item for complete abstract)

Committee: Richard Dick PhD (Advisor); Jeffory Hattey PhD (Committee Member); Roman Lanno PhD (Committee Member) Subjects: Environmental Health; Environmental Science; Microbiology; Soil Sciences

MA, University of Cincinnati, 2019, Arts and Sciences: Anthropology

This thesis examines the role ceramic raw materials play in the technological development of pottery in two geographically separated regions, the Middle Woodland Hopewell in the Ohio River Valley and the Preclassic Maya in Lowland Belize. To this end, a suite of physical, mineralogical, and chemical analytical techniques including scanning electron microscopy, energy dispersive spectrometry, X-ray fluorescence spectrometry, and X-ray diffractometry is used to examine the ceramic raw material composition of pottery sherds from the Hopewell Twin Mounds Village site in southwestern Ohio and the Preclassic Maya Colha site in northeastern Belize. The Preclassic Maya pottery from the Colha site is technologically more advanced than Hopewell pottery from the Twin Mounds Village site in terms of hardness, porosity, and refractory properties such as thermal conductivity, resistance to thermal shock, and thermal decomposition. These ceramic properties result from the use of locally available volcanogenic clays at the Colha site. Comparable ceramic raw materials were unavailable to the Hopewell at the Twin Mounds Village site, which resulted in poorer quality pottery.

Committee: Kenneth Tankersley Ph.D. (Committee Chair); Sarah Jackson Ph.D. (Committee Member) Subjects: Archaeology

Doctor of Philosophy, The Ohio State University, 2018, Materials Science and Engineering

In this study, the formation, evolution, and failure of dissimilar metal welds (DMWs) involving Grade 91 steel using nickel based filler metals were evaluated. First, the curiosity of stable d ferrite found in the heat affected zone (HAZ) of Grade 91 DMWs was investigated since this phase was not present in the HAZ of matching filler metal welds. This difference could have signified a change in the thermal histories of the weld, a change in the chemical potential gradients present, or a combination of both. In the first investigation, it was found that the thermo-mechanical properties of the nickel based filler metal contributed to longer dwell times within the temperature range of stable d ferrite within the HAZ as compared to the autogenous and matching filler metal welds. This occurred because solidification temperature range of nickel based filler metals overlaps the stable d ferrite temperature range and because of the lower thermal conductivity of the nickel based filler metal. These factors enabled carbide dissolution and carbon diffusion, if the presence of a chemical potential gradient existed. Since these welds involved steel base metal and nickel based filler metals, the chemical potential gradients were relevant and were also investigated. The effect of the chemical potential gradient across the dissimilar fusion boundary was also investigated. It was found that there was a strong carbon chemical potential gradient between the Grade 91 base material and the nickel based filler metal caused by a difference in carbon concentration and carbide forming elements. A diffusion simulation was used to predict the magnitude of carbon migration during welding, which resulted in a carbon depleted HAZ. Carbon depletion in the HAZ stabilized the d ferrite phase, shown through statistical analysis of the hardness distribution and a strong correlation between the carbon concentration and amount of d ferrite found in the HAZ. A mechanism was proposed for the (open full item for complete abstract)

Committee: Boian Alexandrov (Advisor); Michael Mills (Advisor); Stephen Niezgoda (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2017, College of Sciences and Health Professions

A hyperspectral image is a dataset consisting of both spectra and spatial information. It can be thought of either as a full spectrum taken at many pixel locations on a sample or many images of the same sample, each at a different wavelength. In recent decades, hyperspectral imaging has become a routine analytical method due to rapid advances in instrumentation and technique. Advances such as the speed of data acquisition, improved signal-to-noise-ratio, improved spatial resolution, and miniaturization of the instrumentation have all occurred, making chemical imaging methods more robust and more widely used. The work presented here deals with three issues in the field of hyperspectral imaging: unassisted data processing that is chemically meaningful and allows for subsequent chemometric analyses, visualization of the data that utilizes the full colorspace of modern red, green, blue (RGB) displays, and data collection with improved signal-to-noise ratios and comparably short acquisition times. Hyperspectral image data processing is a fundamental challenge in the field. There is a need for reliable processing techniques that can operate on the large amount of data in a hyperspectral image dataset. Because of the large quantity of data, currently-used methods for data processing are problematic because of how time-consuming and calculation-intensive they are or because of increased error that is observed in the less-intensive methods. The work presented here includes a user-unassisted method for rapidly generating chemical-based image contrast from hyperspectral image data. Our method, reduction of spectral images (ROSI), is an effective hyperspectral image processing method. A full theoretical description of the method is given along with performance metrics. The description has been generalized to work with any number of wavelength dimensions and spectra. A concise protocol is put forth that will enable other researchers to utilize this method by f (open full item for complete abstract)

Committee: John Turner II, Ph.D. (Advisor); David Ball Ph.D. (Committee Member); Petru Fodor Ph.D. (Committee Member); Xue-Long Sun Ph.D. (Committee Member); Yan Xu Ph.D. (Committee Member); Aimin Zhou Ph.D. (Committee Member) Subjects: Analytical Chemistry; Chemistry; Scientific Imaging

Doctor of Philosophy, The Ohio State University, 2016, Chemical Engineering

The following study entails process simulations and techno-economic analysis based investigations of novel chemical looping partial oxidation processes. The moving bed reactor system analyzed in this dissertation provides chemical looping technologies several intrinsic advantages over conventional energy processing schemes. Chapter 2 focusses on optimizing the counter-current moving bed chemical looping system for H2 production from natural gas. The chemical looping process for H2 production from natural gas is optimized based on isothermal thermodynamic limits of an iron-based counter-current moving bed reactor system. The iso-thermal analysis is followed by a parametric sensitivity for energy balance for satisfying the auto-thermal heat balance. This is completed by computing temperature swings based on a net heat duty calculation for individual chemical looping reactors. Overall the chemical looping process is shown to have a cold gas efficiency of 77.6% (HHV basis) and an effective thermal efficiency of 75.1% (HHV basis), both of which are significantly higher than the baseline case. Chapter 3 discusses the Shale gas to Syngas process for integration into a Gas to Liquid fuel (GTL) plant. Following the methodology for an isothermal and an adiabatic analysis from Chapter 2, Chapter 3 identifies a suitable auto-thermal operating condition for the chemical looping reactors. The process simulation model is used to derive cost estimates based on standard engineering assumptions and completes a sensitivity analysis for several important economic parameters. The STS process is shown to require significantly lower natural gas feedstock than the conventional process baseline for producing the same amount of liquid fuels. The STS process lowers the capital cost investment for the syngas production section of a GTL plant by over 50% and if commercialized can be disruptive to liquid fuel production markets. Chapter 4 discusses the Coal to syngas (CTS) process for its techn (open full item for complete abstract)

Committee: Liang-Shih Fan (Advisor); Jacques Zakin (Committee Member); Andre Palmer (Committee Member); Melvin Pascall (Committee Member) Subjects: Chemical Engineering

Master of Science (MS), Wright State University, 2009, Chemistry

Quantum chemical analysis was used to examine nucleophilic aromatic substitution reactions of fluorinated benzophenones, diphenyl sulfones, and triphenylphosphine oxides. Some experimental results for these compounds were contrary to conventional wisdom, which holds that calculated atomic charges for the aromatic sites and 13C-NMR and 19F-NMR chemical shifts should allow prediction of the preferred sites for aromatic substitution. Density functional theory (B3LYP/6-31+G*//RM1) and semi-empirical (RM1) quantum chemical calculations were employed to study the intermediates in the reaction pathways in order to identify the preferred paths for aromatic substitution. In most cases studied para substitution pathways had the lower energy intermediates and were favored. Experimental acid dissociation pKa's for a set of 41 aliphatic carboxylic acids were compared with quantum chemical indices for the compounds in an attempt to find correlations that might help explain how the electronic structures of the compounds influence their tendencies to dissociate. The quantum chemical indices included the charges on atoms and groups of atoms, calculated vibrational frequencies, calculated nuclear magnetic resonance (NMR) chemical shifts, and reaction energy differences both in vacuum and in an aqueous phase solvent model. Several of these calculated quantities yielded respectable correlations, with the vibrational frequency of the carboxylic acid proton (R2 = 0.874) and the vibrational frequency of the carbonyl stretch of the carboxylate anion (R2 = 0.852) giving the best results. As was observed in earlier work, the RM1 semi-empirical calculations yielded better correlations than the more sophisticated density functional theory approach.

Committee: Paul Seybold PhD (Advisor); David Dolson PhD (Committee Chair); Eric Fossum PhD (Committee Member) Subjects: Chemistry

PhD, University of Cincinnati, 2006, Engineering : Materials Science

High-temperature electronics and MEMS (Micro-Electro-Mechanical Systems) based on polycrystalline diamond (PCD) are promising because of its wide band gap, high thermal conductivity, and large carrier mobility. To take advantage of this opportunity, research was undertaken to develop techniques for the synthesis of both undoped and doped high quality PCD films with good surface flatness suitable for the fabrication of high temperature electronics and MEMS devices. One way to fabricate smooth films is to decrease the grain size because diamond films with large grain size bring forth problems in contact formation and device fabrication due to the large surface roughness. Consequently, there is a need to fabricate nanocrystalline films with small grain size and good smoothness. In addition, the electrical properties and conduction mechanisms in nanocrystalline diamond (NCD) films have not been sufficiently analyzed. This study also aims at achieving high resistivity nanocrystalline diamond films and to study the electrical conduction mechanism. Several approaches have been used in our research to achieve these goals. Initially microcrystalline diamond (MCD) films were grown on silicon (100) substrates by the microwave plasma enhanced chemical vapor deposition (MPCVD) method using methane in a hydrogen plasma environment. Introduction of small amounts of argon into the Argon / Hydrogen plasma was used to deposit diamond films with a range of microstructures from microcrystalline to nanocrystalline grains. A detailed quantitative study of the sp3, sp2 content in the films grown with varying amounts of argon in the plasma was done using Raman spectroscopy. The optimum gas composition that gave the best quality diamond film consisting of 1.6 µm grains was 60% Ar/ 39% H2/ 1% CH4. The optimum gas composition that gave nanocrystalline grains of size in the order of <50 nm was 95% Ar/ 4% H2/ 1% CH4. A change in the cross-sectional microstructure from the columnar to grain-like (open full item for complete abstract)

Committee: Dr. Raj Singh (Advisor) Subjects: Engineering, Materials Science

Doctor of Philosophy in Engineering, University of Toledo, 2011, College of Engineering

To address drinking water quality concerns, membrane separation technologies have been developed, resulting in the continuous reduction of their cost and rapid extension of their application possibilities. Despite the remarkable advantages of membrane separation technologies, the drastic reduction of water flow due to membrane fouling and the high cost of membrane replacement pose a significant problem in water separation applications. This research investigated the impact of feed water characteristics (i.e., conductivity and pH), conditioning layer formed on biofilms, and presence and activity level of a biofoulant on the membrane-solute interaction forces (i.e. hydrophobic attraction) and membrane morphology. Experiments were performed on cellulose acetate ultrafiltration (CAUF) membranes (MWCO 20,000 D) in crossflow filtration for up to 53 hours. Fouled membrane characterization from the macro- to nano-scale was effectively carried out using existing and emerging techniques including fluorescence microscopy for cell activity, image analysis for biofilm surface coverage and intensity, ATR-FTIR for biofilm chemical composition, AFM for fouled membrane surface roughness and skewness, and CFM for its relationship to adhesion forces. As the feed water conductivity increased and the membrane surface roughness increased, the magnitude and range of the adhesion force increased and, subsequently, the permeate flux decline increased suggesting that feed water chemistry impacted membrane potential for fouling. Comprehensive biofilm characterization, specifically AFM, revealed that bacterial cells deposited, and then formed a consolidated biofilm, on the low shear rate areas of the membrane surface. And, as expected, the rate of biofilm formation was higher in the presence of a carbon source and active cells. Additional experiments were carried out to determine the contribution of abiotic fouling (conditioning layer) to cell activity and built up resistance on CAUF memb (open full item for complete abstract)

Committee: Cyndee Gruden (Committee Chair); Isabel Escobar (Committee Member); Ashok Kumar (Committee Member); Defne Apul (Committee Member); Youngwoo Seo (Committee Member) Subjects: Civil Engineering; Environmental Engineering

Master of Science (MS), Bowling Green State University, 2012, Chemistry

One mechanism to achieve photon upconversion, the frequency conversion of low energy photons to those of higher energy, is sensitized triplet-triplet annihilation, a non-coherent (lasers not required) process. In this scheme, a triplet sensitizer is selectively excited at long wavelengths, eventually transferring its triplet energy to an appropriate acceptor molecule in a bimolecular energy transfer reaction. Finally, a second bimolecular energy transfer reaction occurring between two excited triplet acceptors pools the combined energy onto one molecule, producing the fluorescent excited singlet state of the acceptor molecule. This energized molecule radiatively decays back to its ground state releasing photon energies in excess of that of the excitation source, i.e. upconverted with respect to the incident light. This phenomenon has become realized in various combinations of chromophores resulting in wavelength shifting properties that range from the UV to the near-IR. Recently, the upconversion process has become a viable solution to drive fuel-forming chemistry in photoelectrochemical cells and for display applications in polymer host films. The concepts and experiments related to photon upconversion are facile and readily present an opportunity to educate young chemists in this field. Related to established green-to-blue upconversion systems, [Ru(bpy)3](PF6)2 and 9,10-diphenylanthracene (DPA) in deoxygenated dichloromethane is demonstrated here to be a suitable composition for an undergraduate laboratory experiment in physical and/or inorganic chemistry using a conventional fluorimeter. Quadratic incident light power dependence is displayed from the singlet fluorescence of DPA (λem max = 430 nm) resulting from selective excitation of [Ru(bpy)3]2+ at 500 nm using a conventional single photon counting fluorimeter equipped with a 75 W Xe arc lamp. This is easily justified by the fact that two sensitized triplets must be formed in order to ultimately generate the si (open full item for complete abstract)

Committee: Felix Castellano PhD (Advisor); Ksenija Glusac PhD (Committee Member); Peter Lu PhD (Committee Member) Subjects: Chemistry