Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.Sc.(Civil Engineering))--University of Pretoria, 2002. / Summary in English. Includes bibliographical references.

Thesis (M.A.)--University of New Brunswick, 2003. / Copyright (2003) held by author. Includes bibliographical references (p. 97-100).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250 - 300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 - C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

In this study, coal combustion by-products mainly fly ash, commercial fibers and a natural fiber i.e., human hair were applied to stabilize the kaolinite clay and local Carbondale soil i.e., silty clay. During recent decades, the demand for infrastructures such as highways, buildings, bridges have greatly increased, especially in the areas where population was growing rapidly. All of these infrastructures need a stable foundation and in many cases the original land couldn't sustain the load from the infrastructures. In such situation, soil stabilization becomes an essential step before the foundation is laid. There are several ways to stabilize soil, viz., mechanical stabilization, chemical stabilization, stabilization by inclusion and confinement etc. It has been reported by several researchers that fly ash and fibers can significantly improve the strength of soil. Fly ash and natural fiber i.e., human hair are both waste materials, and commercial fibers are low-cost compared to other soil stabilizers. In this study, class C fly ash was used to stabilize commercially available clay i.e., Kaolinite; while both human hair and commercially available fibers (e.g., glass fiber and plastic fiber) were used to stabilize Kaolinite and Carbondale local soil. Based on this research, it could be concluded that the class C fly ash can improve the Unconfined Compressive Strength (UCS) value of Kaolinite clay significantly; fibers also could increase the UCS value of both Kaolinite and Carbondale local soil. While, the tensile strength of Kaolinite and Carbondale local soil sometimes increases or decreases depending on the percentages of fiber content used into Kaolinite and Carbondale local soil. The current research on soil stabilization by fly ash and those fibers may provide a new possibility for soil stabilization.

The main theme of this research was to investigate the durability of concrete made using waste materials as a cement replacement. This is a method to produce green sustainable concrete. The objective was to use locally available wastes to produce a concrete that could be used by the local authority. The mechanical, physical and chemical properties of concrete made predominantly with IFA as a partial cement replacement have been tested. The IFA was won locally from the domestic waste incinerator at Coventry, UK. The other materials used in the mixes included Ground Granulated Blast Furnace Slag (GGBS), silica fume and by-pass dust, which was used as an activator and was also won locally from the Rugby cement plant. Compressive strength and tensile strength, workability, corrosion of embedded steel, shrinkage and expansion, freeze and thaw, corrosion and chloride ingress were studied. Water permeability was studied by the author on mortar samples during one year and on concrete samples during the following. Carbonation was studied on concrete samples and finally mechanical experiments were carried out on concrete beams and slabs. Two further experiments were carried out to complete the study of durability of concrete made with waste materials being, the ASR (Alkaline Silica Reaction) and sulphate attack experiments. One main physical experiment, in the form of a trial mix, was carried out in one of the waste recycling sites of Warwickshire in September 2013. Subsequent to observations during the site trial, the author compared results of setting time, heat of hydration and strength of the trial mix and control mixes. The outcome of this research was a novel mix that had more than 30 percent waste material and a further 40 percent of secondary materials, making it as sustainable as possible. Both laboratory and site trial results have achieved compressive strength which are higher than 30 MPa, indicating that the novel mix concrete could be used for structural purposes. Most of the durability results of the novel mix were comparable with the control OPC mix and the novel mix concrete, in terms of transport properties, induced less electrical current seepage. Furthermore the tensile strength of the novel mix concrete was higher than the control OPC concrete and this is due to the higher ductility index of the novel mix.

Ultramarine pigments are aluminosilicate-based and contain sulphur-based chromophores. Several samples from two batches of fine fly ash, a predominantly aluminosilicate waste product of coal combustion, were used successfully to synthesise ultramarine blue. This was confirmed by infrared, Raman and X-ray diffraction results. Fly ash had the advantage of being amorphous, whereas the traditional starting reagent, kaolin, needed to be heat-treated before the ultramarine synthesis to weaken its structure. A comparison of the scanning electron micrographs of fly ash, fly ash treated at 1 000°C, fly ash reacted with sodium carbonate at 860°C and the ultramarine products showed that sulphur had a structure-directing effect. The sulphur clusters found in ultramarine pigments were studied by Self-Consistent-Field Hartree-Fock theory extended by Møller-Plesset second order perturbation theory at the minimum energy with the 6-311G** basis set to determine the relative stability of S2 , S2-• , S22-, and S3, S3-•, S32-. The singly charged species were the most stable in both sets, supporting the hypothesis that the exothermic transition from green to blue ultramarine was the transformation of the doubly charged species to the singly charged species. The open, C2v, isomer was most stable for the S3-• molecule - the blue ultramarine chromophore. The S4 molecule was a likely chromophore in ultramarine red. A Woodward-Hoffmann analysis supported the concerted formation of the puckered square S4 , pyramidal S4 , and gauche S4 chain isomers. Other possible species for the red chromophore were S4 -, S3 , S3 Cl, S3 Cl-, S2 Cl, S2 O, and S2 O-. On the basis of their calculated vibrational spectra most of the species could be discounted as possible red chromophores. The best candidate chromophore was the cis S4 chain based on the computed electronic spectrum. / Thesis (PhD(Chemistry))--University of Pretoria, 2005. / Chemistry / unrestricted

Philosophiae Doctor - PhD / Coal fly ash has been studied extensively to understand the environmental impacts associated with its disposal, management and reuse. Although several beneficiation processes have been proposed, there has been little or no emphasis on the environmental safety of such processes, products and wastes. Elemental analysis has revealed that toxic elements and radionuclides are present in coal fly ash. Rare earth elements (REE) such as La, Ce and Y are also present in significant amounts in coal fly ash. The aims of this study were to determine the total elemental composition of coal fly ash using different analytical techniques; to validate the application potentials of fly ash beneficiation processes in terms of their environmental safety; and to valorise coal fly ash with a view of recovering REE either by concentrating or leaching the REE in the coal fly ash, products or waste from the beneficiation processes. The beneficiation processes studied were treatment of acid mine drainage (AMD) with fly ash; and the synthesis of geopolymer from fly ash. The fresh fly ash sample used in this study was collected directly from the hoppers at Matla power station and the AMD sample was collected from Carletonville goldmine. A total of 54 major, trace and REE were accurately determined in the ash using different analytical techniques. It was shown that the elemental content of Matla fly ash was of the same order as the SRM NIST coal fly ash 1633b. The comparative study of the four analytical techniques established that ENAA can accurately determine the major, minor and trace elements; that XRF is best suited for the determination of the major and minor elements, whilst the LA ICP-MS is reliable for trace elements determination. The solid residue (AMD/FA) resulting from the AMD interaction with fly ash was characterized with fly ash and the results compared. The results revealed that the amounts of La (141.09 ± 3.85 mg/kg), Ce (27.45 ± 2.04 mg/kg), and Nd (63.73 ± 0.05 mg/kg) in AMD/FA residue was considerably higher than their average abundance in the earth crust that varies from 66 mg/kg in Ce and 40 mg/kg in Nd to 35 mg/kg in La. The results also showed that the AMD/FA residue contained As (11.39 ± 1.21 mg/kg), Cd (3.77 ± 0.02 mg/kg), Cr (72.43 ± 1.27 mg/kg), Hg (10.50 ± 0.85 mg/kg), Ni (124.15 ± 1.6 mg/kg) and Pb (22.46 ± 1.43 mg/kg) which are potentially harmful if leached in to the environment in excessive amounts.

Bibliography: pages 119-126. / Graphite Furnace Atomic Absorption Spectrometry (GFAAS) was used for the determination of cadmium and beryllium in coal and fly ash slurries. Sample preparation involved grinding the sample to a fine powder and slurrying it in a suitable solvent. Stable slurries were maintained by magnetic stirring during sampling. Pyrolytically coated graphite tubes were used for cadmium determinations, while beryllium was determined with platform atomisation. Ammonium dihydrogen orthophosphate and magnesium nitrate matrix modifiers were used for cadmium and beryllium determinations respectively. Calibration graphs constructed with aqueous standards containing the appropriate matrix modifier were rectilinear to at least 100 pg cadmium and 45 pg beryllium. Results were calculated with integrated peak area measurements. The detection limits were 2.9 pg for cadmium and 0.7pg for beryllium. Beryllium determinations were performed with semi-automatic sample introduction. The novel semi-automatic sampling unit utilised magnetic stirring for· the maintenance of stable slurries and operated with the standard Perkin-Elmer AS-40 autosampler. The principles of this unit were extended to the development of a fully automatic auto-sampling unit. The design and operation of both units are described. The accuracy of the methods was evaluated by analysing standard reference materials and in some cases, comparisons with acid digestion procedures. Data are presented for the analysis of South African coal and fly ash samples. The slurry methods had acceptable accuracy and precision. In comparison with the conventional acid digestion procedures using high pressure bombs, a time-saving advantage was realised.