Chemistry Commons^™

Benthic Algal And Macroinvertebrate Response To The Removal Of Dreissenid Mussels In The Nearshore Zone Of Lake Michigan, Tyler Alexander Kunze

Theses and Dissertations

Dreissenid mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) have changed the fundamental community structure and biogeochemical processes of the Lake Michigan nearshore zone. There is evidence that dreissenids promote the nuisance growth of benthic algae, especially Cladophora sp. In addition, benthic macroinvertebrates have benefitted from the presence of dreissenid mussels due to the increased structural complexity along with greater nutrient availability in the benthos. These effects of the dreissenid mussel invasion are well documented; however, little is known about how these systems respond to the removal of dreissenid mussels from a once-populated area. Therefore, it is important to further our …

From Waste To Energy: The Electrochemical Reduction Of Co2 Using Recycled Nanostructured Catalysts, Ibrahim Badawy

Theses and Dissertations

The reduction of carbon dioxide (CO₂RR) using electrochemistry is a promising solution for the burgeoning global energy crisis. The overall vision of its implementation relies on renewable energy sources to power the reaction creating carbon neutral products and effectively closing the carbon cycle. Research in this field has come a long way since its inception in the mid-1900s. However, there remain significant hurdles and important considerations to overcome in order to reach full commercialization. Most electrocatalysts tested for CO₂RR have been designed solely for maximum performance while ignoring the environmental consequences if such a material were …

Synthesis And Application Of Redox-Active Covalent Organic Frameworks In Rechargeable Batteries, Mohammad K. Shehab

Theses and Dissertations

Synthesis and Application of Redox-Active Covalent Organic Frameworks in Rechargeable Batteries

Mohammad K. Shehab

Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States

Abstract

In recent years, lithium-ion batteries (LIBs) have been considered the dominant energy storage devices for portable electronics and electric vehicles due to their high energy density, low self-discharge rate, and long cycle life. In LIBs, the traditional positive electrodes employed are mainly derived from metal-containing inorganic compounds composed of cobalt, iron, nickel, or manganese (LiCoO₂, LiMn₂O₄, and LiFePO₄) coupled with graphite as the negative electrode. Despite …

Molecular Insights Into The Redox Of Atmospheric Mercury Through Laser Spectroscopy, Rongrong Wu Cohen

Theses and Dissertations

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 …

Atomistic Simulation Of Na+ And Cl- Ions Binding Mechanisms To Tobermorite 14Å As A Model For Alkali Activated Cements, Ahmed Abdelkawy

Theses and Dissertations

The production of ordinary Portland cement (OPC) is responsible for ~8% of all man-made CO2 emissions. Unfortunately, due to the continuous increase in the number of construction projects, and since virtually all projects depend on hardened cement from the hydration of OPC as the main binding material, the production of OPC is not expected to decrease. Alkali-activated cement produced from the alkaline activation of byproducts of industries, such as iron and coal industries, or processed clays represents a potential substitute for OPC. However, the interaction of the reaction products of AAC with corrosive ions from the environment, such as Cl-, …

Design And Fabrication Of Nanostructured Electrodes For Complementary Electrochemical And Photoelectrochemical Water Splitting, Kholoud El Sayed Abousalem

Theses and Dissertations

Designing highly active, durable, and nonprecious electrodes for overall water splitting is of urgent scientific importance to realize sustainable hydrogen production. Accordingly, the need to search efficient energy production systems is of crucial necessity. In this thesis, two various systems for sustainable hydrogen production have been reported using electrochemical and photoelectrochemical pathways. In the first part of the thesis, electrochemical water splitting involving both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been established. To this end, an innovative approach is demonstrated to synthesize flower-like 3D homogenous trimetallic Mn, Ni, Co phosphide catalysts directly on nickel foam via …

Fullerene And Tungsten Oxide Nanostructures-Based Electrocatalysts For All-Vanadium Redox Flow Batteries, Farah Ahmed El Diwany

Theses and Dissertations

The vanadium redox flow battery (VRFB) is one of the most promising long-term energy storage solutions mainly due to its long service life and the independence of its energy capacity on power rating and vice versa. However, its relatively high capital cost limits its widespread deployment. Economic analysis reveals that a high-power density VRFB with decreased cell stack size can dramatically reduce the cost. The energy efficiency of a VRFB primarily depends on the kinetics of vanadium redox reactions that take place in the stack. Therefore, studying the effect of surface chemistry of electrodes on the kinetics of each …

Engineered Nanostructured Nitrogen-Doped Carbon Network (Ndc) Electrodes With Unprecedented Cycling Stability For Water Capacitive Deionization In Harsh Conditions, Soha Essam Anwar

Theses and Dissertations

Capacitive deionization (CDI) is a feasible low-cost desalination technique for low-to-medium (brackish) salinity water. However, cycling stability and regeneration of the CDI electrodes are the bottlenecks hindering the practical application of the technology on large scale. Oxidation of the electrodes during the sequential adsorption-desorption processes is one of the most challenging problems hindering their long-term cycling performance. Herein, we demonstrated the ability to design and fabricate exceptionally stable CDI electrodes via a one-pot pyrolysis protocol. The optimized pyrolysis of nitrogen-carbon precursors at different temperatures enabled the fabrication of carbon materials with a controlled amount nitrogen dopant (NDCs) with exceptional cycling …

Optimizing Hydrogen Sulfide Removal And Biogas Production Using The Water Wash Method, Brian Leightner

Theses and Dissertations

Biogas forms from decomposing organic material in agricultural digesters, landfills, and wastewater treatment plant digesters. Biogas is mostly composed of methane, and can be used as a carbon-based fuel. Microorganisms that consume organics in these waste streams also produce hydrogen sulfide (H2S) as part of the biogas, in varying trace amounts. H2S is corrosive to engines and pipes for machinery, a human health hazard when inhaled, and an aquatic hazard when dissolved in water. Water washing is an absorption process that dissolves hydrogen sulfide and other water soluble compounds in this process and carries it away from the gas, thereby …

Development Of Photocatalysts Supported On Graphitic Carbon Nitride For The Degradation Of Organic Water Pollutants, Atanu Giri

Theses and Dissertations

Graphitic carbon nitride (g-C₃N₄) heterojunction composites with the semiconducting metal oxides, CeO₂, ZnO and TiO₂ are prepared in situ by co-calcination of the precursor materials or by a solvothermal method. The structural, morphological and the optical properties of the prepared materials are studied using various microscopy and spectroscopy techniques. The synthesized composite materials, CeO₂/g-C₃N₄, ZnO/g-C₃N₄ and TiO₂/g-C₃N₄ are more efficient in the photocatalytic degradation of the water pollutants indigo carmine (IC) and atrazine than the pure metal oxide, g-C …

Experimental Evaluation Of Uranyl Transport Into Mesoporous Silica Gel Using Fluorescence, Brandon M. Dodd

Theses and Dissertations

This research investigated parameters that can affect the use of nanoporous silica gel as a media for accumulating a detectable amount of uranium. The unique fluorescence of the Uranyl (UO₂²⁺) ion was used to evaluate the transport kinetics and accumulation within silica gel in a static fluid and under pressure driven flow. The addition of fluid flow decreased the time constant from on the order of an hour to approximately 2s with a very low fluid velocity of 0.36cm/s. The 0.36cm/s fluid velocity was found to be the critical velocity above which there was no gain in …

Corrosion Of Aluminum Current Collector In Cost Effective Rechargeable Lithium-Ion Batteries, Shengyi Li

Theses and Dissertations

Rechargeable lithium ion batteries (LIB) have been widely used as commercial energy storage systems for portable equipment, electronic devices and high power applications (e.g. electronic vehicles). One issue with the commercialized LIB is that expensive, highly toxic and flammable organic solvents are used in the electrolyte and the fabrication process of electrodes. The toxic organic based solvents increase the production cost and lead to significant safety concerns in the event of a battery overcharge or short circuit. The recent development of “green manufacturing” technology allows manufacturers to replace the organic solvents used in the cathode coating process by aqueous based …

Removal Of Perfluorooctanoic Acid From Water Using Primitive, Conventional And Novel Carbonaceous Sorbent Materials, Christopher K. Brown

Theses and Dissertations

Polyfluoroalkyl Substances (PFAS), like perfluorooctanoic acid, have been used for the last 50 years in a wide variety of industrial processes and consumer-based products, including polymer additives, lubricants, fire retardants and suppressants, pesticides, and surfactants (Buck et al. 2015). The Department of Defense (DoD) has used PFAS-based Aqueous Film Forming Foam (AFFF) at fire training facilities and aircraft hangars. AFFF has contaminated approximately 600 sites classified as fire training facilities with PFAS (Huang, 2013).

This study focused on testing the most likely carbonaceous adsorbent compounds to remediate PFAS-contaminated sites on Air Force installations. Batch tests were performed to determine the …

Systematic Postsynthetic Modification Of Nanoporous Organic Frameworks And Their Performance Evaluation For Selective Co2 Capture, Timur Islamoglu

Theses and Dissertations

Porous organic polymers (POPs) with high physicochemical stability have attracted significant attention from the scientific community as promising platforms for small gas separation adsorbents. Although POPs have amorphous morphology in general, with the help of organic chemistry toolbox, ultrahigh surface area materials can be synthesized. In particular, nitrogen-rich POPs have been studied intensively due to their enhanced framework-CO₂ interactions. Postsynthetic modification (PSM) of POPs has been instrumental for incorporating different functional groups into the pores of POPs which would increase the CO₂ capture properties. We have shown that functionalizing the surface of POPs with nitro and amine groups …

Comparing Three Methods For Estimating Ozone Depleting Substance Substitute Greenhouse Gases: Case Study Of The New York City Region, Wallace A. Murray Iii

Theses and Dissertations

This thesis evaluates the United States Environmental Protection Agency (EPA) method for estimating emissions from one source, Ozone Depleting Substances Substitutes (ODS substitutes) by comparing results for the New York City Metropolitan Statistical Area (NYC-MSA) with results from two other methodologies. The EPA’s method utilizes population data and GDP data to estimate and geographically allocate emissions, with little regard for the geographies of industrial activity. The two alternative methods use data for industrial employment and activity to provide results for comparison and perhaps a more accurate accounting and allocation of emissions throughout the NYC-MSA.

Traceability Implementation In Organic Farming: Case Study, Chamomile Tea Production, Shaima Ibrahim

Theses and Dissertations

Implementing a traceability plan in an herbal production plant is a complex task. In this study an attempt to integrate food safety, quality and traceability through the different stages of the organic German Chamomile (Matricaria recutita) production chain was made. First, all the current relevant international laws, regulations and standards regarding traceability, safety and quality, with emphasis on how and why they are necessary for any food production chain, were set forward. Second, physico-chemical and microbiological analyses were run throughout the different processing stages of production, for four different Chamomile batches produced over the same season using the same farming …

Molecular Characterization Of Wetland Soil Bacterial Community In Constructed Mesocosms, Ethan C. Bishop

Theses and Dissertations

The use of wetlands to effectively remediate aquifers contaminated with chlorinated solvents is an emerging technique, which shows high promise. In order to better understand this process and test its legitimacy, a treatment wetland was constructed at Wright-Patterson AFB, Dayton, Ohio and, in a joint effort with Wright State University (WSU), has previously shown the effective removal of PCE. The purpose of this research was to characterize the soil bacterial community, pre-PCE injection, among three wetland plant species from the sedge family (Cyperaceae) within constructed wetland mesocosms and to identify any bacterial dominance. Carex comosa, Scirpus atrovirens, and Eleocharis erythropoda …

Evaluation Of Chlorinated Solvent Removal Efficiency Among Three Wetland Plant Species: A Mesocom Study, Jun Yan

Theses and Dissertations

Different species of plants need to be studied individually to compare the remediation efficiency of each species. This research will study three different wetland plants species and an unplanted control, under a laboratory setting. Each plant has a different characteristic favorable for chlorinated solvent degradation. Eleocharis erythropoda (Spike Rush) are plants with thin tube like leaves and large root mass. Carex comosa (Bearded Sedge) has broad leaves and Scirpus atrovirens (Green Bulrush) are broad leafed wetland plants with a long flowering stem during reproduction. PCE will be injected into the plant mesocosm and any possible PCE degradation will be observed. …

Analysis Of Anion Distributions In The Developing Strata Of A Constructed Wetland Used For Chlorinated Ethene Remediation, Joshua D. Kovacic

Theses and Dissertations

Perchloroethene (PCE), Trichloroethene (TCE) and their degradation products are among the most common organic groundwater contaminants in the United States. Constructed wetlands utilizing upward flow harbor reduction-oxidation conditions that have demonstrated the potential to promote both partial and total mineralization of PCE and TCE through the process of natural attenuation. Organic acid and inorganic anion concentrations are indicative of reduction-oxidation processes that drive chlorinated ethene degradation. These analytes were investigated to assess their development within three vertically stratified regions of a constructed wetland cell at Wright-Patterson Air Force Base fed by groundwater contaminated with PCE and TCE. Data collected during …

An Anion Characterization Of A Constructed Wetland Used For Chlorinated Ethene Remediation, Bradley M. Bugg

Theses and Dissertations

Chlorinated ethenes physical properties as well as its ubiquitous state at DOD installations makes it a priority for innovative remediation efforts. Current techniques are expensive and time consuming to maintain. Constructed wetlands suggest an inexpensive and operational alternative to conventional technologies. Sub-surface flow wetlands provide the anaerobic zones necessary to reduce the recalcitrant chlorinated solvents prior to anaerobic or aerobic mineralization of its daughter products. A vertical flow cell to include sequential sedimentary layers of two hydric soil lifts and a mix of hydric soil and woody compost was the subject of this investigation. This study focused on the statistical …

Application Of Horizontal Flow Treatment Wells For In Situ Treatment Of Perchlorate Contaminated Groundwater, Jeffrey C. Parr

Theses and Dissertations

Groundwater contamination by perchlorate has recently been recognized as a significant environmental problem across the United States, and especially at Department of Defense facilities. In this study, a model is used to evaluate the potential of a innovative in situ bioremediation technology using Horizontal Flow Treatment Wells (HFTWs) to manage perchlorate-contaminated groundwater. The technology uses HFTWs to mix an electron donor into perchlorate-contaminated groundwater in order to promote reduction of the perchlorate by indigenous microorganisms in bioactive zones within the aquifer, as well as recirculate the contaminated water between treatment well pairs to achieve multiple passes of contaminated water through …

Dissolution Of Chromium From Inhalable Primer Paint Particles Into A Simulated Lung Fluid, David A. Kauth

Theses and Dissertations

The use of chromate as a corrosion inhibitor in primer paint is an essential component for the protection of aluminum-skinned aircraft and the primary source of hexavalent chromium (Cr (VI)) exposure to USAF aircraft painters. The objective of this research was to quantify the dissolution of chromate from freshly sprayed paint particles into a simulated lung fluid (SLF). Two primer paints were sprayed with a paint spray gun to generate overspray particles for collection into impingers filled with SLF. Particles were allowed to soak in SLF for 24 and 48 hours and then the particles were removed by centrifugation. The …

Optimization Of Palladium-Catalyzed In Situ Destruction Of Trichloroethylene-Contaminated Groundwater Using A Genetic Algorithm, Manuel Fernandez

Theses and Dissertations

Conventional technologies for the treatment of groundwater contaminated with chlorinated solvents have limitations that have motivated development of innovative technologies. One such technology currently under development involves using palladium-on-alumina (Pd/Al) as a catalyst to promote dechlorination. Pd/Al catalyst may be used in-well as part of a re-circulating horizontal flow treatment well (HFTW) system. An HFTW system involves two or more dual-screened wells, with in-well reactors, to capture and treat contaminated groundwater without the need to pump the water to the surface. In this study, objective and fitness functions, based on system costs and TCE concentration requirements, were developed to optimize …

In Situ Treatment Of Chlorinated Ethene-Contaminated Groundwater Using Horizontal Flow Treatment Wells, Derek R. Ferland

Theses and Dissertations

The limitations of conventional containment technologies for groundwater contaminated with chlorinated solvents have motivated development of innovative technologies to achieve national groundwater remediation objectives. One inn9vative technology that is currently under development involves metal reductants or catalysts to chemically destroy the dissolved chlorinated solvent. Models are important tools that can be used to help transition this technology to the field. Model studies can be used to gain understanding about the technology, help determine when the prospective technology might work for a given site, and design full-scale field applications.

Modeling Chlorinated Ethene Removal In Constructed Wetlands: A System Dynamics Approach, Colby D. Hoefar

Theses and Dissertations

The purpose of this study is to gain understanding of the dynamics of the processes that degrade Perchloroethene (PCE) to ethylene, or carbon dioxide (CO₂), within the confines of a constructed wetland. A system dynamics approach will be used. This model is focused on identifying and optimizing the naturally occurring processes in stratified wetland sediment that reduce mass, toxicity, mobility, volume or concentration of contaminants in groundwater. Contaminant fate and transport within a wetland system is extremely complex and the mechanisms that drive wetland behavior are dynamic. Confidence in the model was built through verification and testing. Reasonable …

A Modeling Study For The Implementation Of In Situ Cometabolic Bioremediation Of Trichloroethylene-Contaminated Groundwater., John A. Christ

Theses and Dissertations

The limitations of conventional groundwater remediation technologies have led to the development of innovative technologies which may achieve national hazardous waste site remediation goals. Before an innovative technology can be implemented in the field, remedial project managers, regulators and other stakeholders require adequate modeling tools to help assess the applicability of the technology at a particular site. This modeling study investigates how an innovative technology, in situ cometabolic bioremediation, might be implemented to remediate a TCE-contaminated site, under different site conditions. A steady-state model is developed which couples an analytical expression to simulate the effect of flow between multiple pumping …

Modeling The Uptake And Transpiration Of Tce Using Phreatophytic Trees, Douglas P. Wise

Theses and Dissertations

Phytoremediation is a recent addition to the numerous methods used today to remediate ground water contaminants. It is proving more effective and efficient compared to existing remediation techniques. The use of phreatophytes, or water seeking trees, has great potential for phytoremediation. These trees are fast growing, long lived, grow their roots down to the ground water table, transpire large amounts of water, and are proven to actively remove contaminants from the soil horizon. The purpose of this research is to develop quantitative concepts for understanding the dynamics of TCE uptake and transpiration by phreatophytic trees over a short rotation woody …

Mass Transport Of Volatile Organic Compounds Between The Saturated And Vadose Zones, Monte S. Harner

Theses and Dissertations

Volatile organic compounds (VOCs) dissolved in the saturated zone are transported into the vadose zone primarily by gaseous phase diffusion. If the saturated zone is remediated, VOCs present in the vadose zone may become a secondary source of contamination for the groundwater. The amount of VOCs that remain in the vadose zone is dependent on site hydrology, soil properties, and the chemical properties of the contaminants. The purpose of this study was to determine what conditions caused VOC concentrations in the vadose zone to significantly recontaminate the saturated zone. A one-dimensional numerical model was developed to investigate the transport of …

The Biodegradation Characteristics Of Proposed Fuel Systems Icing Inhibitors (Fsii), Charles E. Meshako

Theses and Dissertations

The biodegradation characteristics of three fuel system icing ihhibitors (FSII) were evaluated. FSII are jet fuel additives that partition into water readily and are present in the water drained from storage tank bottoms in concentrations approaching 40%. These concentrations raise concerns as to the disposal and handling of these wastes. The current FSII, DiEGME was evaluated along with two new candidates, dipropylene glycol and glycerol formal. DiEGME appeared to be moderately but not completely biodegradable. It is likely that much of it would be removed in a wastewater treatment plant. Dipropylene glycol only showed signs of degradation after more than …

Modeling Marine Exposure To Polychlorinated Biphenyls From Sunken Ships, Charles N. Wendt

Theses and Dissertations

In the past, the U.S. Navy has routinely conducted SINKing EXercises (SINKEX) for training, weapon effectiveness tests, and economic disposal of aging assets. Recent concern over polychlorinated biphenyl (PCB) chemicals aboard such target vessels has resulted in a suspension of SINKEX. The U.S. Navy has approximately 200 vessels currently requiring such disposal. Environmental legislation and health concerns preclude selling such vessels to foreign governments or scrapping. This work attempted to model the fate and transport of these PCBs by examining their transport to coastal water and their accumulation in the marine food chain. The model includes biodegradation, upwelling, partitioning of …