Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Pavlostathis, Spyros G.; Committee Member: Huang, Ching-Hua; Committee Member: Hughes, Joseph B.; Committee Member: Sobecky, Patricia A.; Committee Member: Spain, Jim C.

No description available.

Thesis (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Spyros G. Pavlostathis; Committee Member: Ching-Hua Huang; Committee Member: John A. Pierson.

In this work, electrolytes for secondary batteries and fuel cells were investigated. Ionic liquids (ILs), for use as battery electrolytes, were formed using quaternary ammonium salts (Quats) and aluminum chloride. The room temperature (RT) carbonate fuel cell was demonstrated by modifying a commercially available anion exchange membrane, utilizing positive quaternary ammonium fixed sites, to transport carbonate. The charge density on the nitrogen and the symmetry of the Quat were demonstrated to be the dominant factors in determining the IL melting point (MP). The introduction of a benzyl ring was found to lower the MP of the ILs by increasing the size of the Quat, while disrupting its symmetry. ILs formed from asymmetric quaternary ammonium salts having three distinct groups were found to have lower melting points than those formed using Quats with two groups. Replacement of an alkyl group with a rigid ether linkage can lower the IL melting point. Assymetric alkyl substituted Quats were found to form more electrochemically stable, less viscous ILs than their benzyl substituted counterparts. The increased electrochemical stability is due to the smaller butyl chain being a worse leaving group than the benzyl group. Similarly, the smaller size of the alkyl substituted Quats results in the lower viscosities. Lithium and sodium can be reversibly deposited from neutral ILs following the addition of an additive (such as SOCl2). The additive disrupts the strong coordination between Na+, or Li+, and AlCl4-. Chlorinated compounds, such as chloroform-D and carbon tetrachloride, were demonstrated to catalyze the reversible reduction of sodium. When neutralized with lithium and sodium, reversible Li-Na alloys were deposited. The Li-Na alloy appears to suppress dendrite formation and could potentially be used as a metal based anode in a rechargeable Li battery. A novel room temperature carbonate fuel cell was constructed. The alkaline environment could eliminate the need for water in the oxidation of methanol. Cells were operated on hydrogen, 1M methanol, and pure methanol fuels. CO2 was produced at the anode and O2 and CO2 were necessary at the cathode for operation, indicating that carbonate was the conducting ion.

Quaternary ammonium compounds (QACs) are widely used in commercial and consumer applications as disinfectants, fabric softeners, hair conditioners, and emulsifying agents. The massive production and utilization of QACs has led to their extensive discharge into the environment, raising concerns globally. Several studies have reported on potential risks and detrimental effects of QACs on the natural environment and public wastewater treatment plants. Biological treatment has been found to be an effective way to remove QACs and especially aerobic treatment processes can provide rapid biodegradation via a consortium of bacteria. Although extensive research has been conducted on the fate and effect of QACs, relatively little is known about their effect on aerobic biological treatment processes, especially on nitrification. Research was conducted on the fate and effect of alkyl benzyl dimethyl ammonium chloride (AB), a QAC widely used as disinfectant, in mixed aerobic and nitrifying cultures. The results of this study demonstrated that up to 50 mg/L AB was efficiently degraded in a mixed aerobic culture fed with dextrin and peptone, although trace residual AB levels were observed. Nitrification of the produced ammonia was complete at an AB concentration of 20 mg/L after an acclimation period, but was almost completely inhibited at 50 mg/L. Mixed aerobic cultures maintained only with AB as external nitrogen and carbon source achieved a high degree of AB degradation at both 20 and 50 mg/L. Ammonia oxidation by a nitrifying culture, enriched with ammonium chloride and sodium bicarbonate, was inhibited with increasing AB concentration and completely ceased at 15 mg/L AB. Degradation or utilization of AB was not observed for all tested AB concentrations between 2 to 20 mg/L. Based on these experimental results, and assuming non-competitive inhibition, a relatively low value of the AB inhibition coefficient was obtained, which indicates a relatively high susceptibility of the ammonia oxidizers to AB. The results of this study have significant implications for both engineered and natural systems relative to the fate and effect of QACs.

Quaternary ammonium compounds (QACs) are ubiquitous contaminants found worldwide in both engineered and natural systems. QACs are toxic to aquatic organisms and cause co-selection for antibiotic resistance, thus providing a reservoir of antibiotic-resistant bacteria, as well as antibiotic resistance genes in QAC-polluted environments. The objectives of the research presented here were to: a) systematically assess the fate and toxicity of QACs using quantitative structure-activity relationships (QSAR); b) evaluate the biotransformation potential of QACs under aerobic, anoxic and anaerobic conditions; and c) assess the potential toxicity of QACs biotransformation products. Nine QACs, belonging to three homologous groups -- monoalkonium, dialkonium and benzalkonium chlorides -- were the target QACs. The QACs critical micelle concentration (CMC) was determined. Then, the CMC was used as a descriptor to derive relationships between QAC structure and partitioning to biosolids as well as acute Microtox® toxicity. QACs with low CMCs had a relatively high adsorption affinity for biosolids and a lower toxicity than QACs with higher CMCs, which suggests that QACs that are more mobile and more (bio)available are more toxic. The biotransformation potential of benzalkonium chlorides (BAC) -- the most commonly used QACs found in engineered and natural biological systems -- under aerobic, methanogenic, nitrate reducing, and fermentative conditions was evaluated using bioenergetics and batch bioassays. The aerobic BAC biotransformation involved sequential dealkylation and debenzylation steps resulting in the formation of benzyl dimethyl amine, and dimethyl amine, respectively. The bacterial community involved in the aerobic BAC degradation was mainly composed of species belonging to the Pseudomonas genus. All QACs tested were recalcitrant under methanogenic conditions and inhibited methanogenesis at and above 25 mg QAC/L. Under nitrate reducing and fermentative conditions, BAC was transformed to alkyldimethyl amines via an abiotic reaction known as modified Hofmann degradation and a biotic reaction known as fumarate addition, respectively. Both reactions are based on a mechanism known as nucleophilic substitution. The discovery of BAC transformation by the above mentioned two reactions is the first ever report to document QAC transformation under anoxic/anaerobic conditions and delineate the transformation pathway.

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007. / Kohl, Paul, Committee Chair ; Bottomley, Lawrence, Committee Member ; Eckert, Charles, Committee Member ; Fuller, Tom, Committee Member ; Teja, Amyn, Committee Member.

Quaternary ammonium salts are surface active bactericides. A mechanism of their biological activity has been well studied experimentally, and it encompasses two stages. The first stage involves electrostatic interactions of polar functional groups of the salts with oppositely charged functional groups on a bacterial cell surface, and the second stage includes incorporation of their lipophilic groups into a bacterial cell membrane. However, despite numerous experimental studies, computational modelling of this mechanism with the aim to support experimental observations with theoretical conclusions, to the author's knowledge, has not yet been reported. In the current study, linear regression models correlating theoretical descriptors of lipophilicity and electronic properties of mono- and disubstituted imidazolium carboxylates with their biological activity towards Escherichia coli have been developed. These models established that biological activity of these salts is governed by the chemical structures of imidazolium cations, and that the centre of this biological activity is located in the long alkyl side chains of the cations. It was also found that these side chains have an intrinsic electronic potential to form internal C-H- -H-C electrostatic interactions when their lengths reach seven carbon atoms. Additionally, the nature of the C-H- -O-C inter-ionic electrostatic interactions in imidazolium carboxylates has been explored via a topological analysis of these interactions in 1-ethyl-3-methylimidazolium acetate. Thus, it was established that these electrostatic interactions are hydrogen bonds.

Para aumentar os volumes de extração de petróleo, resolver e prevenir problemas nas operações de produção são utilizados diversos produtos químicos, dentre os quais se destacam os inibidores de corrosão, que são utilizados em toda cadeia produtiva do petróleo visando proteger o sistema da deterioração por corrosão. Os sais de amônio quaternário são uma das classes de inibidores mais utilizadas pela indústria do petróleo devido a sua grande eficiência. Entretanto, sua solubilidade em água faz com que estejam presentes na água produzida representando um risco para contaminação ambiental, visto que possuem baixa biodegrabilidade e potencial de bioacumulação. Como se encontram misturados a outros produtos químicos e sob efeitos das variações do ambiente em que são aplicados, definir um método de análise confiável e viável para monitoramento em linha representa um desafio para os laboratórios de campos de produção. Neste trabalho, foi estudado o emprego da fluorescência de ultravioleta na quantificação de um inibidor de corrosão do tipo sal de amônio quaternário em água. Foram obtidos espectros de emissão do produto comercial em água, além do estudo de variáveis instrumentais e interferentes presentes na água produzida. A comparação com padrões de sal de amônio quaternário permitiu identificar como principal fluorófilo, um sal alquil-aril de amônio quaternário. Estudos de estabilidade revelaram que a adsorção do inibidor de corrosão nas superfícies dos frascos plásticos provoca a queda do sinal fluorescente e que a adição de isopropanol reduz este efeito de 40 para 24%. Foram obtidas curvas de calibração com a formulação comercial e com o cloreto de 2-metil-4-dodecil-benzil-trimetil amônio com uma boa correlação. Amostras sintéticas do inibidor foram determinadas com um erro relativo de 2,70 a 13,32%. O método de adição padrão foi avaliado usando uma amostra de água produzida, e os resultados não foram satisfatórios, devido à interferência, principalmente, de compostos orgânicos aromáticos presentes / In order to increase the volume of oil extraction, solve and prevent problems in oil production, several chemical products are used. Corrosion inhibitors are the main chemical products used in the whole oil production chain, whose objective is to protect the system from deterioration caused by corrosion. The quaternary ammonium salts are the kind of inhibitor which is more frequently used by the oil industry due to its great efficiency. However, its solubility in water allows them to remain in the produced water representing a risk of environmental contamination, since they have low biodegrability and tendency to bioaccumulation. Once they are mixed to other chemical products and affected by the variations of the environment where they are applied, it becomes a challenge to production field laboratories to select a reliable and viable analysis method for on-line monitoring. This essay tends to focus on the use of the ultraviolet fluorescence in the quantification of an inhibitor of corrosion of the quaternary ammonium salt type in water. There has been obtained emission spectra of the commercial product in water besides the study of instrumental variables and interference of chemical substances in the produced water. The comparison with quaternary ammonium salt standards allow identifying an alkyl-aryl quaternary ammonium salt as the main fluorophore. Tests of stability have demonstrated that the addition of isopropyl alcohol reduces the fall of the fluorescent signal from 40 to 24% in three days time. This fall is caused by the adsorption of corrosion inhibitor in the surface of plastic containers. Good correlation curves of calibration have been obtained with commercial formularization and methyldodecylbenzyl trimethyl ammonium chloride. Synthetic samples of inhibitor have been determined with a relative error from 2,70 to 13,32%. One produced water sample from a production field has been used to evaluate the standard addition method. Satisfactory results have not been successfully achieved, principally, due to the interference of aromatics organic compounds found in the water sample