Sites contaminated with polyaromatic hydrocarbons (PAHs) pose serious health and safety risks to the surrounding environment due to their toxicity, persistence and accumulation in the environment. Because certain members of this class have been demonstrated to be both carcinogenic and mutagenic, PAHs are considered as environmental priority pollutants (US EPA). The studies in this thesis provide an efficient, economical and environmentally benign technique for the remediation of PAH contaminated soil/sediment by means of PAH mobilization with surfactant followed with a catalytic hydrogenation in supercritical carbon dioxide (scCO2). / Catalytic hydrogenation of naphthalene, acenaphthylene, ancenaphthene, anthracene, phenanthrene, chrysene and benzo[a]pyrene over alumina supported palladium (5% Pd0/gammaAl2O3) commercial catalyst were investigated in either a batch reaction mode or a continuous reaction system in H2-scCO2 (∼5% v/v). The hydrocarbon compounds were efficiently reduced to their corresponding fully saturated polycyclic hydrocarbon homologs with mild conditions of temperature (90°C) and pressure (60 psi H2 or 3000 psi H2-scCO2). The bacterial reverse mutation assay demonstrated that both the fully and partially hydrogenated products of chrysene and benzo[a]pyrene were devoid of mutagenic activity. / A laboratory study was conducted on the surfactant-assisted mobilization of PAH compounds combined with reagent regeneration and detoxification steps to generate innocuous products. Five minutes of ultrasonication of field contaminated soil with a 3% (w/v) surfactant suspension mobilized appreciable quantities of all PAH compounds. Formulating the Brij 98 surfactant in 0.1 M phosphate buffer (pH 8.0) mobilized the largest quantities of PAH compounds and the recovery of surfactant (>90%) but soil residues exceeded permissible maxima for five- and six-ring analytes. Five successive washes were required to reduce the residual fraction to permissible levels. The mobilized PAH compounds were then detoxified at line by catalytic hydrogenation in a 5% H2-scCO2 (v/v) atmosphere. / New palladium hydrogenation catalysts were fabricated in the laboratory with specific processes on various supports. The hydrogenation of phenanthrene and benzo[a]pyrene in a fixed bed micro reactor demonstrated that the catalyst that was fabricated from organosoluble precursor loaded on aluminum oxide (2.5% Pd0/gammaAl2O3) was four times more efficient than the commercial catalyst that was used for PAH hydrogenations.

Ligand I- along with nonionic surfactant, Triton X-100 or anionic surfactant, sodium dodecyl sulfate (SDS) were applied as soil washing agents to desorb Cd from both naturally and artificially contaminated soils. After seven consecutive washings, up to 90% of Cd was desorbed from both soils. Triton X-100 with I- showed a higher capacity to desorbing Cd than did SDS with I-. The increase of ligand concentration was a critical factor for increasing leaching capacity. Without the ligand, surfactant alone could not desorb Cd effectively from either soil. After seven consecutive washings, a sequential extraction experiment was performed for soil residuals to define the soil fraction of Cd removed by the washing agent. Among the washing agents, only Triton X-100/I- could remove Cd from the exchangeable fraction of both soils. / Various ligands including I-, SCN-, and I-/SCN- in combination with Triton X-100 were tested for their efficacy in desorbing heavy metals such as Cd, Zn, Cu, and Pb from a field contaminated soil. Cadmium was preferentially desorbed by Triton X-100/I- whereas Zn and Cu were preferentially desorbed by Triton X-100/SCN-. The mixture of I- and SCN- with Triton X-100 desorbed the most Cd and Cu, but not for Zn, as I- inhibited Zn desorption. Sequential extraction experiments after seven washings showed that metals held in the exchangeable fraction can be desorbed only by a combination of ligand and surfactant. / Nonionic surfactants having different alkyl chain lengths in combination with ligand I- were tested for the desorption of Cd and PCBs from soil. Cadmium desorption was increased at the lower surfactant concentration and higher ligand concentration. The increase in the hydrophilic alkyl chain length of the surfactant adversely affected Cd desorption. Up to 100% of PCBs were successfully removed by most of surfactant-ligand combinations and the desorption was less dependent, compared to heavy metals, on the concentration of washing agents and length of alkyl chain. The linear relationships between number of washings and Cd desorption, and between alkyl chain length and Cd desorption was defined. (Abstract shortened by UMI.)

The ever-increasing detection of harmful organic and inorganic compounds in habitable areas throughout the world has led to mounting research into applications and techniques for the treatment of contaminated soils, surface and groundwaters, and chemical and industrial wastewaters. Chemical oxidation technologies, in particular Fenton-based remediation systems, have exhibited considerable potential for the effective treatment and remediation of such contaminated waters and soils. The use of Fenton-based oxidation systems for the treatment of contaminated waters and wastewaters warrants the development of kinetic models capable of accurately simulating system behaviour. In this thesis, the kinetics of Fenton-mediated oxidation systems and kinetic models based on its governing reaction mechanism are investigated in order to highlight those parameters and conditions that effect Fenton chemistry and oxidation performance, and to demonstrate the application of such kinetic models to design and improve treatment systems. Experimental and simulated data describing the oxidation of formic acid by Fenton's reagent at low pH (3 to 4) and under a variety of initial conditions, operating regimes, and solution environments supports a proposed reaction mechanism that nominates the hydroxyl radical (OH) as the active oxidizing intermediate in Fenton-based oxidation systems. Laboratory experiments demonstrate that formic acid oxidation is inhibited in the presence of oxygen, and model simulations of these systems reveals that such behaviour is due to the effect organic radical intermediates and/or by-products have in assisting or hindering the redox cycling of the catalytic iron species. The critical role that iron redox cycling plays in affecting oxidation performance is further highlighted by experimental and simulated studies at alternate pHs and using different target organics, including those that react directly with iron in a redox capacity. Experiments at pH 4 reveal an increase in the redox cycling of iron and improved oxidation performance compared to pH 3 as the higher pH favours the superoxide radical, a stronger reductant than the hydroperoxyl radical that predominates at pH 3. Other laboratory and modelling studies on the Fenton-mediated oxidation of certain aromatic compounds highlight the manner in which quinone and quinone-like compounds, being added directly or generated as oxidation by-products, can improve oxidation performance via redox reactions with iron. Further simulations reveal the type of practical design and operating information kinetic models can provide for treatment processes, though it is noted an appropriate understanding of the oxidation mechanism of the target species is necessary for the accurate application of the model.

Thesis (Ph.D.) -- University of Western Sydney, Macarthur, 2001. / A thesis presented to the University of Western Sydney, in partial fulfillment of the requirements for the degree of Doctor of Philosophy, December, 2001. Bibliography : leaves 163-173.

Thesis (Ph.D.)--University of Western Sydney, Macarthur, Faculty of Informatics, Science and Technology, 1999. / References: p. 210-233.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 148-160). Also available in electronic format on the Internet.

Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Joseph B. Hughes; Committee Member: Dr. Jian Luo; Committee Member: Dr. Jim C. Spain; Committee Member: Dr. Patricia Sobecky; Committee Member: Dr. Spyros G. Pavlostathis

Thesis (M.S.) -- Mississippi State University. Dave C. Swalm School of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Restricted until May 2003. Bibliography: leaves 110-115.

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.