Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 418-432). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Daene C. McKinney and Gary A. Pope. Vita. Includes bibliographical references.

Excess molar volumes have been determined for four ternary chlorobenzene + dibutyl ether + alkane mixtures at 25°C. Results of these measurements are used to test the applications and limitations of BAB, Redlich-Kister, Kohler and Hwang et al. cubic models. For the systems studied, Redlich- Kister, Kohler and Cubic models were found to provide reasonable predictions. Differences between experimental and predicted ΔV^ex_123 values were about ±0.020 cm^3mol^-1 or less at most ternary compositions. Solubilities are reported for anthracene in binary mixtures containing propanol and butanol with alkanes at 25°C. Results of these measurements are used to test the NIBS/Redlich-Kister expression. The three-parameter form of this expression is found to provide reasonable mathematical representation with deviations between experimental and back-calculated values being less than ±1%.

The purpose of this Master's Project was to develop an Acid-Base Titration Simulator. It was also to be a part of the California State University - San Bernardino's GTSS, Generic Tutorial System for the Sciences, project. The main benefit is that students will be able to conduct titration experiments over the Internet without being in the laboratory and without costly equipment or dangerous chemicals. Instructors at the high school and college level can demonstrate the key principles of titration.

No description available.

Dans la synthèse des matériaux catalytiques, deux aspects orientent en particulier les recherches actuelles: le contrôle de taille afin d’obtenir des nanoparticules finement divisées et le contrôle précis de la morphologie. Dans cette étude, nous avons utilisé les milieux non aqueux pour élaborer des matériaux catalytiques à base d’oxydes des métaux de transition (Ti, Zr, Mn). Trois méthodologies ont été employées pour la préparation des solides à base de TiO2. La synthèse dans les nitrates fondus dopés avec différents anions permet un boncontrôle des propriétés texturales des matériaux et de la nature des plans cristallins exposés. Les préparations utilisant le nitrate d’ammonium stabilisé avec des molécules organiques azotées conduit à des solides présentant des tailles et des formes de particules variables en fonction de la nature du stabilisateur. Le traitement à reflux dans des solvants organiques polaires conduit à l’obtention des supports TiO2 de grandes surfaces spécifiques. Pour la valorisation catalytique de ces matériaux, deux réactions appliquées au domaine de la photocatalyse ont été employées: la production d’H2 par déshydrogénation du méthanol etl’oxydation photocatalytique de l’acide formique. La réaction modèle de décomposition del’isopropanol a été utilisée comme test de caractérisation des propriétés acido-basiques de nossystèmes. La technique de nitrates fondus a été également appliqué avec succès pourl’obtention en une seule étape des catalyseurs supportés Mn-Zr et Mn-Ti. Ces catalyseursmontrent une excellente activité pour l’oxydation totale de composés organiques volatils(COV). / Two major challenges are particularly important for current research in the catalytic materials synthesis: preparation of finely divided particles and control of their shape. In this work we used non aqueous solvents to prepare catalytic materials containing transition metals oxides (Ti, Mn, Zr). Three techniques were applied to prepare TiO2-based solids. Reactions in molten alkali metal nitrates doped with different anions offered good control of textural properties and of the nature of exposed facets of nanocrystalline particles. Synthesis in molten ammonium nitrate stabilized with organic nitrogen-containing compounds provided TiO2 solids with variable size and shape as a function of stabilizer used. The reflux treatment in polar organic solvents leads to titania supports having high specific surface area. Two reactions from the field of photocatalysis were employed to valorize the obtained catalysts: H2 production by methanol dehydrogenation and photocatalytic oxidation of formic acid. Isopropanol decomposition has been used to determine the acid-base properties of the solids. Molten nitrate technique was then successfully applied in order to obtain in one-step highly dispersed Mn-Zr and Mn-Ti supported oxide catalysts. These systems showed excellent activity for the total oxidation of volatile organic compounds (VOC).

No description available.

[Truncated abstract] To date, many subsurface contaminant modelling studies have focused on increasing model complexity and measurement requirements to improve model accuracy and widen model application. However, due to the highly complex and heterogeneous nature of flow in the subsurface, the greater benefit in model development may lie in decreasing complexity by identifying key processes and parameters, simplifying the relationships that exist between them, and incorporating these relationships into simple models that recognise or quantify the inherent complexity and uncertainty. To address this need, this study aims to identify and isolate the key processes and parameters that control dense nonaqueous phase liquid (DNAPL) and aqueous phase migration through single, onedimensional fractures. This is a theoretical representation which allows the study of processes through conceptual and mathematical models. Fracture systems typically consist of multiple two-dimensional fractures in a three-dimensional network; however, these systems are computationally and conceptually demanding to investigate and were outside of the scope of this study. This work initially focuses on DNAPL migration in single, one-dimensional fractures. The similitude techniques of dimensional and inspectional analysis are performed to simplify the system and to develop breakthrough time scale factors. This approach relies heavily on the limitations of the equation used for the analysis and on the difficulty in representing variable aperture scenarios. The complexity of the conceptual model is then increased by embedding the fracture in a two-dimensional, porous matrix. ... These tools can be readily applied by the field investigator or computer modeller to make order-of-magnitude estimates of breakthrough times, reduce or target measurement requirements, and lessen the need to employ numerical multiphase flow models. To determine the implications of the results found in the one-dimensional studies to applications at the field scale, the complexity of the conceptual model was increased to a single, two-dimensional, planar fracture embedded in a three-dimensional porous matrix. The focus of this study was not DNAPL breakthrough times but the relative importance and interaction of different mass transport processes and parameters on plume migration and evolution. Observations clearly show that estimates of the size, location and concentration of the plume is highly dependent on the geologic media, the temporal and spatial location and resolution of measurements, and on the history, mass and location of the DNAPL source. In addition, the processes controlling mass transport (especially matrix diffusion and back diffusion) act in combination at the field scale in ways not always expected from an analysis of processes acting individually at smaller spatial and temporal scales. Serious concerns over the application of the common '1% Rule of Thumb' to predict DNAPL presence and the use of remediation efforts that rely largely on natural attenuation are raised. These findings have major implications for the field worker and computer modeller, and any characterisation, monitoring or remediation program development needs to be sensitive to these findings.

<p dir="ltr">As the demand for energy rises and the threat of climate change looms, the need for clean, reliable, and affordable energy solutions like renewable energies has been more crucial. Energy storage systems (ESSs) are indispensable in addressing the intermittent nature of renewable energies and optimizing grid efficiency. Redox flow batteries (RFBs), thanks to their scalability, independent energy and power, swift response time, and minimal environmental impact, are a particularly promising ESS technology for long-duration storage applications. Despite the technological maturity of aqueous RFBs, nonaqueous organic RFBs (NAORFBs) are a prospective solution due to their wider operational voltage, potentially higher energy density, and larger pool of redox-active materials. However, the current state-of-the-art NAORFBs face challenges due to the lack of suitable organic redox-active materials (ORMs).</p><p dir="ltr">Despite the development of new materials, how their variables influence the total system cost of RFBs remains an unsolved challenge. With this regard, we established a techno-economic (TE) model to calculate the capital cost of nonaqueous hybrid RFBs (NAHRFBs). Prior to this work, NAHRFBs, which employs lithium metal as the anode, were regarded as an RFB system with the highest energy density. However, the correlation between their features and the system cost remained unclear, leaving a research gap for new ORMs. In our model, we selected a state-of-the-art NAHRFB system where 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) serves as the catholyte and lithium metal functions as the anode. Thereafter, sensitivity analyses identified several key factors that determine the system cost, including operational current density, area-specific resistance, cell voltage, electrolyte composition, and both the price and equivalent molecular weight of the ORM. To enhance the cost-competitiveness of current NAHRFBs, it is advised to increase the current density by 10 times and modulate the ORM-related characteristics. The virtually optimized condition manifests that the system cost of NAHRFB can meet the long-term cost target set by the U. S. Department of Energy.</p><p dir="ltr">Informed by the TE model, we discovered that elevating the oxidation potential of catholyte ORMs is instrumental in reducing the system cost of RFBs. To explore this possibility, we incorporated fluorine atoms, a potent electron-withdrawing group (EWG), into a dimethoxybenzene (DMB) derivative, yielding a new ORM (ANL-C46) with an oxidation potential enhanced by ~0.41 V. Surprisingly, ANL-C46 demonstrated superior kinetic and electrochemical stability compared to its parent molecule, as indicated by electron paramagnetic resonance (EPR) study and bulk electrolysis. In particular, the cycling performance of ANL-46 during the bulk electrolysis outperformed most reported high-potential (> 1 V vs. Ag/Ag⁺) ORMs. Density functional theory (DFT) calculations reveals that the introduced fluorine substituents suppress the typical side reaction pathways of the DMB series. These findings offer valuable insights into molecular engineering strategies that concurrently improve multiple desired ORM properties.</p><p dir="ltr">The stability of ORMs is critical for ensuring the extended lifetime of RFBs. We conducted a systematic exploration of the conjugation effect, which potentially stabilizes the ORMs by facilitating a more homogeneous distribution of delocalized charges. This was applied to tailor the electrochemical and physical properties of several DMB derivatives with varying aromatic ring counts. As we extended the aromatic core from 1,4-dimethoxybenzene (1,4-DMB) to 1,4-dimethoxynaphthalene (1,4-DMN), we noted a decrease in oxidation potential, enhanced kinetic stability, and an extended cycling life. However, further extending the aromatic core to 2-ethyl-9,10-dimethyanthracene (EDMA) results in rapid dealkylation of the radical cation due to increased strain in the methoxy substituents. Additionally, 1,4-DMN shows cross-reactions between radical cations, likely via disproportionation. This study demonstrates that extending the π-conjugation changes reactivity in multiple ways. Therefore, attempts to lower oxidation potential and improve ORMs stability through π-conjugation should be pursued with caution.</p>

Light Non-Aqueous Phase Liquids (LNAPLs) are used throughout the world for numerous applications, the most well-known being automotive fuels, such as petrol and diesel. The widespread production, distribution, storage and use of LNAPLs results in the ubiquitous occurrence of spillage to ground (Geller et al, 2000). Considering the hazardous nature of most LNAPLs due to their explosive and toxic characteristics, releases of LNAPLs to ground have well documented human health and ecological consequences. The occurrence of leaking underground and above-ground storage tanks at service stations and consumer installations is a common cause of contamination; and is described in literature for various countries of the world (Dietz et. al., 1986; Moschini et al, 2005; Mulroy and Ou, 1997; Harris, 1989; The Institute of Petroleum, 2002). Little failure data are however available for the South African context. In addition to this, data concerning the location and characteristics of sites storing LNAPLs in South Africa is similarly scarce. The study analysed data from three sources, namely the eThekwini Fire and Emergency Services data, GIS data and data from a local consultancy, in order to determine whether certain factors increased contamination risk posed by these facilities. The results indicated that contamination may be a result of numerous factors, but primarily line and tank failure. The type of installation was also found to have a significant influence on whether a site would be contaminated or not. In addition to the above, the results indicated that certain circumstances increase the severity of loss. The results indicated the need for more investigation to be performed into contamination as a result of LNAPL loss to ground, and the need for protective measures to be implemented for high risk sites where the likelihood and severity of a potential loss is high. Focus should then be centred on the probability of failure of non-ferrous pipework and GRP tanks to ensure adequate protective mechanisms are in place in the event of a failure of this newer infrastructure. In addition, a review of regulatory control of LNAPL storage in South Africa and the eThekwini Municipality, with reference to the international context, indicated the need for a specific department within the local government structure that manages LNAPLs with the objective of reducing contamination incidents. The continued use of underground storage of LNAPLs will always present a risk of failure/contamination due to the unseen nature of the installations and related infrastructure. It is this risk that requires regulatory management. Details of contaminated sites in South Africa should be within the public domain. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.